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1
Cvetanovska, Stojcheva Daniela, Ana Aleksandrovska, Maja Petrevska, and Bobi Micevski. "Alveolar ridge augmentation by open healing with high-density polytetrafluoroethylene membrane." International Journal of Dental Biomaterials Research 1 (March 28, 2022): 1–7. https://doi.org/10.56939/DBR22101cs.
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<strong>Abstract</strong> Non resorbable polytetrafluoroethylene membranes find great use in everyday oral surgery treatments. We aimed to verify the performance of high-density polytetrafluoroethylene (hdPTFE) membrane in open healing after alveolar ridge augmentation at two patients. For that reason, we raised full thickness flap and grafted with different xenograft granules that were covered with resorbable collagen membrane. Then the grafted area was covered with high-density polytetrafluoroethylene membrane (permamem®) and stabilized with sutures by leaving it partially exposed. Six weeks after open healing, the permamem® was removed and successful post-operative healing with no complications were observed. The newly formed soft tissue grew under the membrane and completely covered the new alveolar ridge volume. There were no signs of dehiscence or infection, and the patients had no pain or discomfort, neither after suture nor the membrane removal. Also, there were no visible signs of bacterial plaque on the membrane after its placement and during removal. After eight months implants were successfully installed, and full mouth prosthetic reconstruction was following the osseointegration. In conclusion, the high-density polytetrafluoroethylene membrane efficiently supported open healing and led to successful alveolar ridge augmentation.
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Zafiropoulos, Gregor–Georg, and Branko Trajkovski. "Socket preservation with high-density polytetrafluoroethylene barrier membrane during open healing." International Journal of Dental Biomaterials Research 1 (April 25, 2022): 13–19. https://doi.org/10.56939/DBR221013z.
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<strong>Abstract</strong> Bone volume loss appears after tooth extraction and socket preservation is the most applied procedure to prevent an alveolar resorption. The aim of this study was to retrospectively analyse three socket preservation cases with high-density polytetrafluoroethylene barrier membrane (permamem®) for open healing with and without the use of additional dental regeneration biomaterials. Here no bacterial plaque was present and the soft tissue completely re-epithelialized, which allowed new bone formation and implant treatment. The current findings indicate that the use of this membrane, leads to successful socket treatment during open healing.
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Cvetanovska Stojcheva, Daniela, Aleksandrovska Aleksandrovska, Petrevska Petrevska, and Bobi Micevski. "Alveolar ridge augmentation by open healing with high-density polytetrafluoroethylene membrane." International Journal of Dental Biomaterials Research 1 (2022): 1–7. http://dx.doi.org/10.56939/dbr22101cs.
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Zafiropoulos, Gregor–Georg, and Branko Trajkovski. "Socket preservation with high-density polytetrafluoroethylene barrier membrane during open healing." International Journal of Dental Biomaterials Research 1 (2022): 13–19. http://dx.doi.org/10.56939/dbr221013z.
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Bartee, Barry Kyle. "THE USE OF HIGH-DENSITY POLYTETRAFLUOROETHYLENE MEMBRANE TO TREAT OSSEOUS DEFECTS." Implant Dentistry 4, no. 1 (1995): 21–31. http://dx.doi.org/10.1097/00008505-199504000-00004.
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Bartee, B. K. "The use of high-density polytetrafluoroethylene membrane to treat osseous defects." Implant Dentistry 4, no. 1 (1995): 64. http://dx.doi.org/10.1097/00008505-199504000-00018.
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Zhang, Mi, Zili Zhou, Jiahao Yun, et al. "Effect of Different Membranes on Vertical Bone Regeneration: A Systematic Review and Network Meta-Analysis." BioMed Research International 2022 (July 14, 2022): 1–16. http://dx.doi.org/10.1155/2022/7742687.
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This study is aimed at performing a systematic review and a network meta-analysis of the effects of several membranes on vertical bone regeneration and clinical complications in guided bone regeneration (GBR) or guided tissue regeneration (GTR). We compared the effects of the following membranes: high-density polytetrafluoroethylene (d-PTFE), expanded polytetrafluoroethylene (e-PTFE), crosslinked collagen membrane (CCM), noncrosslinked collagen membrane (CM), titanium mesh (TM), titanium mesh plus noncrosslinked (TM + CM), titanium mesh plus crosslinked (TM + CCM), titanium-reinforced d-PTFE, titanium-reinforced e-PTFE, polylactic acid (PLA), polyethylene glycol (PEG), and polylactic acid 910 (PLA910). Using the PICOS principles to help determine inclusion criteria, articles are collected using PubMed, Web of Science, and other databases. Assess the risk of deviation and the quality of evidence using the Cochrane Evaluation Manual, and GRADE. 27 articles were finally included. 19 articles were included in a network meta-analysis with vertical bone increment as an outcome measure. The network meta-analysis includes network diagrams, paired-comparison forest diagrams, funnel diagrams, surface under the cumulative ranking curve (SUCRA) diagrams, and sensitivity analysis diagrams. SUCRA indicated that titanium-reinforced d-PTFE exhibited the highest vertical bone increment effect. Meanwhile, we analyzed the complications of 19 studies and found that soft tissue injury and membrane exposure were the most common complications.
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Korzinskas, Tadas, Ole Jung, Ralf Smeets, et al. "In Vivo Analysis of the Biocompatibility and Macrophage Response of a Non-Resorbable PTFE Membrane for Guided Bone Regeneration." International Journal of Molecular Sciences 19, no. 10 (2018): 2952. http://dx.doi.org/10.3390/ijms19102952.
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The use of non-resorbable polytetrafluoroethylene (PTFE) membranes is indicated for the treatment of large, non-self-containing bone defects, or multi-walled defects in the case of vertical augmentations. However, less is known about the molecular basis of the foreign body response to PTFE membranes. In the present study, the inflammatory tissue responses to a novel high-density PTFE (dPTFE) barrier membrane have preclinically been evaluated using the subcutaneous implantation model in BALB/c mice by means of histopathological and histomorphometrical analysis methods and immunohistochemical detection of M1- and M2-macrophages. A collagen membrane was used as the control material. The results of the present study demonstrate that the tissue response to the dPTFE membrane involves inflammatory macrophages, but comparable cell numbers were also detected in the implant beds of the control collagen membrane, which is known to be biocompatible. Although these data indicate that the analyzed dPTFE membrane is not fully bioinert, but its biocompatibility is comparable to collagen-based membranes. Based on its optimal biocompatibility, the novel dPTFE barrier membrane may optimally support bone healing within the context of guided bone regeneration (GBR).
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Song, Hyeon-Bee, Jong-Hyeok Park, Jin-Soo Park, and Moon-Sung Kang. "Pore-Filled Proton-Exchange Membranes with Fluorinated Moiety for Fuel Cell Application." Energies 14, no. 15 (2021): 4433. http://dx.doi.org/10.3390/en14154433.
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Proton-exchange membrane fuel cells (PEMFCs) are the heart of promising hydrogen-fueled electric vehicles, and should lower their price and further improve durability. Therefore, it is necessary to enhance the performances of the proton-exchange membrane (PEM), which is a key component of a PEMFC. In this study, novel pore-filled proton-exchange membranes (PFPEMs) were developed, in which a partially fluorinated ionomer with high cross-linking density is combined with a porous polytetrafluoroethylene (PTFE) substrate. By using a thin and tough porous PTFE substrate film, it was possible to easily fabricate a composite membrane possessing sufficient physical strength and low mass transfer resistance. Therefore, it was expected that the manufacturing method would be simple and suitable for a continuous process, thereby significantly reducing the membrane price. In addition, by using a tri-functional cross-linker, the cross-linking density was increased. The oxidation stability was greatly enhanced by introducing a fluorine moiety into the polymer backbone, and the compatibility with the perfluorinated ionomer binder was also improved. The prepared PFPEMs showed stable PEMFC performance (as maximum power density) equivalent to 72% of Nafion 212. It is noted that the conductivity of the PFPEMs corresponds to 58–63% of that of Nafion 212. Thus, it is expected that a higher fuel cell performance could be achieved when the membrane resistance is further lowered.
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Kim, Do-Hyeong, and Moon-Sung Kang. "Pore-Filled Anion-Exchange Membranes with Double Cross-Linking Structure for Fuel Cells and Redox Flow Batteries." Energies 13, no. 18 (2020): 4761. http://dx.doi.org/10.3390/en13184761.
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In this work, high-performance pore-filled anion-exchange membranes (PFAEMs) with double cross-linking structures have been successfully developed for application to promising electrochemical energy conversion systems, such as alkaline direct liquid fuel cells (ADLFCs) and vanadium redox flow batteries (VRFBs). Specifically, two kinds of porous polytetrafluoroethylene (PTFE) substrates, with different hydrophilicities, were utilized for the membrane fabrication. The PTFE-based PFAEMs revealed, both excellent electrochemical characteristics, and chemical stability in harsh environments. It was proven that the use of a hydrophilic porous substrate is more desirable for the efficient power generation of ADLFCs, mainly owing to the facilitated transport of hydroxyl ions through the membrane, showing an excellent maximum power density of around 400 mW cm−2 at 60 °C. In the case of VRFB, however, the battery cell employing the hydrophobic PTFE-based PFAEM exhibited the highest energy efficiency (87%, cf. AMX = 82%) among the tested membranes, because the crossover rate of vanadium redox species through the membrane most significantly affects the VRFB efficiency. The results imply that the properties of a porous substrate for preparing the membranes should match the operating environment, for successful applications to electrochemical energy conversion processes.
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Lee, Kyung Ah, Ji Hyun Lee, Chang-Kyu Hwang, Ki Ro Yoon, and Yung-Eun Sung. "Perpendicularly Stacked Array of PTFE Nanofibers As a Reinforcement for Highly Durable Composite Membrane in Proton Exchange Membrane Fuel Cells." ECS Meeting Abstracts MA2024-02, no. 67 (2024): 4684. https://doi.org/10.1149/ma2024-02674684mtgabs.
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The configuration of reinforced composite membrane (RCM), composed of porous polytetrafluoroethylene (PTFE) as a mechanical reinforcement and perfluorosulfonic acid (PFSA) as a proton conductive polymer has gained a large interest due to its promisingly high performance for polymer electrolyte membrane (PEM) fuel cells. However, the inaccessible polymeric nanocomposites in preparing RCMs are still faced with critical challenges associated with immiscible interactions between hydrophilic sulfonate groups in PFSA and the hydrophobic nanoporous PTFE matrix. Herein, we report a well-refined and facile fabrication strategy for producing a cross-aligned PTFE (CA-PTFE) framework. The electric-field guided electrospinning enables the creation of unique micron-scale, grid-type PTFE matrix, which is synthesized by annealing of electrospun conjugated polymers resulting in the removal of carrier polymer and the formation of continuous fibrious structure via fusion of PTFE particles. The CA-PTFE RCM embodying uniformly impregnated PFSA in a grid-type PTFE matrix, facilitates hydration of the membranes, with minimal swelling and efficient diffusion of protons through concentrated sulfonate groups. The CA-PTFE RCM adopted cell showed outstanding fuel cell currents during both low and high humidity operation, with a current density of 1.38 A cm−2 at 0.6 V and maximum power density of 0.85 W cm−2 under RH 100% condition. Furthermore, the CA-PTFE RCM was able to achieve a long-lasting single-cell operation with a significantly low hydrogen crossover (less than 5 mA cm−2 at 0.4 V) even after 21,000 wet/dry cycles, which surpasses the standard of membrane durability for transportation application. The rational design of fibrous PTFE reinforcements opens up new engineering opportunities for the future development of high-stability PEM fuel cells.
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Waasdorp, Jonathan, and Sylvan Feldman. "Bone Regeneration Around Immediate Implants Utilizing a Dense Polytetrafluoroethylene Membrane Without Primary Closure: A Report of 3 Cases." Journal of Oral Implantology 39, no. 3 (2013): 355–61. http://dx.doi.org/10.1563/aaid-joi-d-10-00128.
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Case reports document successful use of a high-density polytetrafluorethylene membrane to augment horizontal defects associated with immediately placed implants. This membrane, which is designed to withstand exposure (not require primary closure) to the oral cavity because it is impervious to bacteria, reduces the need for advanced flap management to attain primary closure. Thus, the surgical aspect is less complex and the mucogingival architecture of the area can be maintained. These cases demonstrate successful use of this application and provide evidence for controlled clinical trials to further evaluate this technique.
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Pak, Chanho, Hyeon Seung Jung, Do-Hyung Kim, and Chun Hyunsoo. "Effect of Catalyst Double Layer on Performance without Micro Porous Layer in Anode for High Temperature Polymer Electrolyte Membrane Fuel Cell." ECS Meeting Abstracts MA2022-01, no. 35 (2022): 1425. http://dx.doi.org/10.1149/ma2022-01351425mtgabs.
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Catalyst double layer (CDL) structure on gas diffusion electrode (GDE) without microporous layer (MPL) is developed for the anode of high temperature polymer electrolyte membrane fuel cell (HT–PEMFC). Polytetrafluoroethylene and polyvinylidene fluoride is applied for the outer and inner layer as the hydrophobic binder for fabricating 3D electrode structure. The effect of Pt ratio in anode CDLs on the GDE performance was investigated by single cell test and electrochemical analysis using poly(benzimidazole) (PBI)–based membrane, with Pt loading under 0.3 mg/cm2 at ambient pressure air on 150℃. The results show that optimal CDL anodes present performance of 0.65V at 0.2A/cm2 and peak power density is 0.41W/cm2 at mass transfer region which is higher than conventional single layer anode with MPL. Furthermore, the 3D structure of the outer catalyst layer in anode read high catalyst utilization and preventing leakage of electrolyte with a short–term durability test shows good stability with PBI membrane.
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Cheon, Gi-Beom, Kyung Lhi Kang, Mi-Kyung Yoo, Jeoung-A. Yu, and Dong-Woon Lee. "Alveolar Ridge Preservation Using Allografts and Dense Polytetrafluoroethylene Membranes With Open Membrane Technique in Unhealthy Extraction Socket." Journal of Oral Implantology 43, no. 4 (2017): 267–73. http://dx.doi.org/10.1563/aaid-joi-d-17-00012.
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We evaluated the effectiveness of the open membrane technique using a high-density polytetrafluoroethylene (dPTFE) membrane with freeze-dried bone allografts in damaged sockets for alveolar ridge preservation (ARP). This retrospective study included 26 sites from 20 patients who had received ARP for the placement of dental implants. ARP was conducted using dPTFE membrane with allografts on the day of extraction without primary closure. When the membrane was removed after 4 weeks, the newly formed reddish tissue at the grafted site was checked (first outcome, clinical evaluation). Four months after membrane removal, a core biopsy was performed from the center of the grafted site before implant placement (second outcome, histomorphometric evaluation). Radiographic measurements of alveolar bone changes between implant prosthesis delivery and the 1-year follow-up were obtained (third outcome, radiographic evaluation). A total of 23 sites from 18 patients had no complications during the follow-up period. Three sites from two patients were excluded because of early membrane removal. Newly formed reddish tissue was found at 15 sites, and partially formed tissue was found at 8 sites. Although we were unable to harvest bone core from all sites, histomorphometric analysis in 11 patients indicated that the mean area of new bone was 28.48% ± 6.60%, that of the remaining graft particle was 27.68% ± 9.18%, and that of fibrous tissue was 43.84% ± 6.98%. The mean loss of marginal bone was 0.13 ± 0.06 mm at the mesial area and 0.15 ± 0.06 mm at the distal area, as assessed using radiographic evaluations. The results of this nonrandomized study suggest that this technique may be an appropriate procedure for ARP. Further studies with a control group and more subjectives can be designed based on this study.
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Yamaki, Tetsuya, Junichi Tsukada, Masaharu Asano, Ryoichi Katakai, and Masaru Yoshida. "Preparation of Highly Stable Ion Exchange Membranes by Radiation-Induced Graft Copolymerization of Styrene and Bis(vinyl phenyl)ethane Into Crosslinked Polytetrafluoroethylene Films." Journal of Fuel Cell Science and Technology 4, no. 1 (2006): 56–64. http://dx.doi.org/10.1115/1.2393305.
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We prepared novel ion exchange membranes for possible use in polymer electrolyte fuel cells (PEFCs) by the radiation-induced graft copolymerization of styrene and new crosslinker bis(vinyl phenyl)ethane (BVPE) into crosslinked polytetrafluoroethylene (cPTFE) films and subsequent sulfonation and then investigated their water uptake, proton conductivity, and stability in an oxidizing environment. In contrast to the conventional crosslinker, divinylbenzene (DVB), the degree of grafting of styrene∕BVPE increased in spite of high crosslinker concentrations in the reacting solution (up to 70mol%). Quantitative sulfonation of the aromatic rings in the crosslinked graft chains resulted in the preparation of membranes with a high ion exchange capacity that reached 2.9meq∕g. The bulk properties of the membranes were found to exceed those of Nafion membranes except for chemical stability. The emphasis was on the fact that the BVPE-crosslinked membranes exhibited the higher stability in the H2O2 solution at 60°C compared to the noncrosslinked and DVB-crosslinked ones, as well as decreased water uptake and reasonable proton conductivity. These results are rationalized by considering the reactivity between styrene and the crosslinker, which is an important factor determining the distribution of the crosslinks in the graft component. In the case of BVPE, the crosslinks at a high density were homogeneously incorporated even into the interior of the membrane because of its compatibility with styrene while the far too reactive DVB led to a crosslink formation only near the surface. The combination of both the cPTFE main chain and BVPE-based grafts, i.e., a perfect “double” crosslinking structure, is likely to effectively improve the membrane performances for PEFC applications.
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Tao, Guanwei, Jiajun Li, Yunyun Mu, and Xinping Zhang. "A Three-Dimensional Hydrophobic Surface-Enhanced Raman Scattering Sensor via a Silver-Coated Polytetrafluoroethylene Membrane for the Direct Trace Detection of Molecules in Water." Biosensors 14, no. 2 (2024): 88. http://dx.doi.org/10.3390/bios14020088.
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We report a three-dimensional (3D) SERS substrate consisting of a silver nanoparticle (AgNP) coating on the skeleton-fiber surfaces of a polytetrafluoroethylene (PTFE) membrane. Simple thermal evaporation was employed to deposit Ag onto the PTFE membrane to produce grape-shaped AgNPs. The 3D-distributed AgNPs exhibit not only strong localized surface plasmon resonance (LSPR) but also strong hydrophobic performance. High-density hotspots via silver nano-grape structures and nanogaps, the large 3D interaction volume, and the large total surface area, in combination with the hydrophobic enrichment of the specimen, facilitate high-sensitivity sensing performance of such a SERS substrate for the direct detection of low-concentration molecules in water. An enhancement factor of up to 1.97 × 1010 was achieved in the direct detection of R6G molecules in water with a concentration of 10−13 mol/L. The lowest detection limit of 100 ppt was reached in the detection of melamine in water. Such a SERS sensor may have potential applications in food-safety control, environmental water pollution monitoring, and biomedical analysis.
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Jung, Hyeon Seung, Dong Hee Kim, Jong Gyeong Kim, and Chanho Pak. "Characterization of Catalyst Layer Using Gas Diffusion Electrode Half-Cell System for High Temperature Polymer Electrolyte Membrane Fuel Cell." ECS Meeting Abstracts MA2023-02, no. 37 (2023): 1753. http://dx.doi.org/10.1149/ma2023-02371753mtgabs.
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High-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) is being developed for the heavy-duty vehicle which requires high power density and operation under extreme conditions. Conventional HT-PEMFC using phosphoric acid (PA) immersed PBI membranes and polytetrafluoroethylene (PTFE) binder faced issues such as unstable durability and low performance of membrane electrode assembly (MEA) due to PA leakage and uneven distribution within the catalyst layer. In recent years, ion-pair membranes and ionomers for high temperatures have been developed, which can reduce PA leakage in MEA and improve ionic conduction within the catalyst layer. Incorporation of a new material into the MEA requires further research to enhance electrode design, catalyst utilization, and performance for the appropriate ionomer, as this material exhibits different characteristics from the conventional PTFE binder. In this study, various gas diffusion electrode (GDE) was fabricated with the new ionomer, and GDE half-cell setups were introduced for rapid and efficient characterization of performance in the oxygen reduction reaction. This system serves as an intermediate step between rotating disk electrodes and single cells, providing a powerful tool for quickly screening and evaluating GDEs using small amounts of catalyst. Recent publications from Wilkinson [1] and Gasteiger [2] groups reviewed this new system, proposed new measurement protocols, and suggested improvements. Accordingly, GDE half-cell setups are designed to simulate HT-PEMFC operating conditions at 150 ℃ temperature with 85 wt.% PA electrolyte. Electrochemical characteristics were evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) following the protocols in previous papers with GDE half-cell. Resistance values obtained through EIS were further differentiated by peaks and frequency-based responses through the distribution of relaxation times transformation. Performance comparison between GDEs was carried out by measuring the voltage at 0.2 A/cm² and peak power density at 150 ℃, simulating a single cell-like environment. GDEs were fabricated with variables such as Pt loading, thickness, and porosity. And their physical properties were confirmed through mercury intrusion porosimetry and scanning electron microscopy. Ultimately, the study elucidated the correlation between the electrochemical data and physical properties. References [1] B.A. Pinaud, A. Bonakdarpour, L. Daniel, J. Sharman, D.P. Wilkinson, Key considerations for high current fuel cell catalyst testing in an electrochemical half-cell, J. Electrochem. Soc. 164 (2017) F321–F327. [2] T. Lazaridis, B.M. Stühmeier, H.A. Gasteiger, H.A. El-Sayed, Capabilities and limitations of rotating disk electrodes versus membrane electrode assemblies in the investigation of electrocatalysts, Nat. Catal. 5 (2022) 363–373.
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Seo, Chan, Joo Won Lee, Won-Kyo Jung, Yoon-Mi Lee, Seungjun Lee, and Sang Gil Lee. "Examination of Microcystin Adsorption by the Type of Plastic Materials Used during the Procedure of Microcystin Analysis." Toxins 14, no. 9 (2022): 625. http://dx.doi.org/10.3390/toxins14090625.
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The incidence of eutrophication is increasing due to fertilizer abuse and global warming. Eutrophication can induce the proliferation of cyanobacteria such as Microcystis, which produces microcystins. Microcystins are toxic to specific organs such as the liver and the heart. Thus, monitoring of microcystins is strongly required to control drinking water and agricultural product qualities. However, microcystins could be adsorbed by plastic materials during sample storage and preparation, hindering accurate analysis. Therefore, the current study examined the recovery rate of microcystins from six plastics used for containers and eight plastics used for membrane filters. Among the six plastics used for containers, polyethylene terephthalate showed the best recovery rate (≥81.3%) for 48 h. However, polypropylene, polystyrene, and high- and low-density polyethylenes showed significant adsorption after exposure for 1 hr. For membrane materials, regenerated cellulose (≥99.3%) showed the highest recovery rate of microcystins, followed by polyvinylidene fluoride (≥94.1%) and polytetrafluoroethylene (≥95.7%). The adsorption of microcystins appeared to be strongly influenced by various molecular interactions, including hydrophobic interaction, hydrogen bonding, and electrostatic interaction. In addition, microcystins’ functional residues seemed to be critical factors affecting their adsorption by plastic materials. The present study demonstrates that polyethylene terephthalate and regenerated cellulose membrane are suitable plastic materials for the analysis of microcystins.
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Pham, Huy, and Cao Thang Dinh. "Hydrophilic Separator Stables CO2-to-C2H4 Conversion at Low Cell Voltage with Non-Noble Metal Anode." ECS Meeting Abstracts MA2024-02, no. 28 (2024): 2161. https://doi.org/10.1149/ma2024-02282161mtgabs.
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Electrochemical carbon dioxide (CO2) reduction (ECR) is a promising approach for enabling the conversion of greenhouse gas CO2 into valuable products with electricity from renewable sources to achieve net-zero CO2 emission. ECR simultaneously reduces carbon emissions and dependence on fossil-based fuels and chemicals. Membrane electrode assemblies (MEAs), which often comprise an anion exchange membrane (AEM) and a precious iridium oxide (IrOx)-based anode, have been extensively studied in the last few years. However, challenges such as salt precipitation on cathodic gas diffusion electrodes (GDEs), high cell voltage and the need to use noble metal anodes have hindered ECR's practical applications. Herein, we introduce a new design of MEA cells using a low-cost hydrophilic film separator and a Nickel (Ni) foam instead of AEM and IrOx, respectively. Hydrophilic separator material with high water permeability lowers the full-cell voltage and eliminates the salt accumulation on the GDE in both alkaline and neutral-pH conditions. Using copper-sputtered polytetrafluoroethylene (Cu/PTFE) as cathodes, we demonstrated a stable conversion of CO2 to ethylene (C2H4) at current densities over 100 mA/cm2. In neutral-pH anolyte, the average C2H4 FE was sustained at around 50% for more than 200 hours with a cell voltage of 3.1 V at the current density of 110 mA/cm2. Under alkaline conditions, this system showed 500 hours of stability of CO2-to-C2H4 conversion: the C2H4 FE was maintained above 60% with the cell voltage of only 2.2 V at 110 mA/cm2 current density. Our research provides a solution for achieving stable ECR operation at a relatively high current density using Earth-abundant materials. This work opens opportunities for energy-efficient and stable CO2 conversion without needing expensive and rare elements, which are crucial for practical applications.
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Al-Hezaimi, Khalid, Giovanna Iezzi, Ivan Rudek, et al. "Histomorphometric Analysis of Bone Regeneration Using a Dual Layer of Membranes (dPTFE Placed Over Collagen) in Fresh Extraction Sites: A Canine Model." Journal of Oral Implantology 41, no. 2 (2015): 188–95. http://dx.doi.org/10.1563/aaid-joi-d-13-00027.
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In untreated extraction sockets, buccal bone remodeling compromises the alveolar ridge width. The aim of this study was to histologically assess the efficacy of using a dual layer of membranes (high-density polytetrafluoroethylene [dPTFE] placed over collagen) for ridge preservation in fresh extraction sites. Eight beagle dogs were used. After endodontic treatment of mandibular bilateral second (P2), third (P3), and fourth (P4) premolars, mandibular bilateral first premolars and distal roots of P2, P3, and P4 were extracted atraumatically. Animals were randomly divided into 4 treatment groups. group 1, the control group, received no treatment; in group 2, allograft was placed in the alveolum and the socket covered with dPTFE membrane; in group 3, allograft was placed in the alveolum, the buccal plate was overbuilt with allograft, and the socket was covered with dPTFE membrane; in group 4, allograft was placed in the alveolum and covered with dual layer of membranes (dPTFE placed over collagen). No intent of primary closure was performed for all groups. After 16 weeks, the animals were sacrificed and mandibular blocks were assessed histologically for buccolingual width of alveolar ridge, percentage of bone formation and bone marrow spaces, and the remaining bone particles. The buccolingual width of the alveolar ridge was significantly higher among sockets in group 4 than in group 1 (P &lt; .05). the amount of newly formed bone in each socket was higher in extraction sockets in group 4 than in groups 1, 2, and 3 (P &lt; .001). A significant difference was found in the percentage of bone marrow spaces among all groups (P &lt; .001). No significant difference was found in the number of nonresorbed bone particles among the groups. Using a dual layer of membrane was more effective in ridge preservation than conventional socket augmentation protocols.
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Kim, Ju-Won, You-Young Jo, Jwa-Young Kim, Ji-hyeon Oh, Byoung-Eun Yang, and Seong-Gon Kim. "Clinical Study for Silk Mat Application into Extraction Socket: A Split-Mouth, Randomized Clinical Trial." Applied Sciences 9, no. 6 (2019): 1208. http://dx.doi.org/10.3390/app9061208.
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Silk mat originates from the cocoon of the silkworm and is prepared by a simple method. The material has been used for guided bone regeneration (GBR) in animal models. In this study, the silk mat used for a clinical application was compared with a commercially available membrane for GBR. A prospective split-mouth, randomized clinical trial was conducted with 25 patients who had bilaterally impacted lower third molars. High-density polytetrafluoroethylene (dPTFE) membrane or silk mat was applied in the extraction socket randomly. Probing depth (PD), clinical attachment level (CAL), and bone gain (BG) were measured at the time of extraction (T0) and then at three months (T1) and six months after extraction (T2). There was no missing case. GBR with silk mat was non-inferior to GBR with dPTFE for PD reduction at T1 and T2 (pnon-inferiority < 0.001). PD and CAL were significantly decreased at T1 and T2 when compared with those at T0 in both membrane groups (p < 0.001). BG at T2 was 3.61 ± 3.33 mm and 3.56 ± 3.30 mm in the silk mat group and dPTFE group, respectively. There was no significant complication from the use of silk mat for the patients. The results for patients undergoing GBR with silk mat for third-molar surgery were non-inferior to GBR with dPTFE for PD reduction.
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Franović, Barbara, Marija Čandrlić, Marko Blašković, et al. "The Microbial Diversity and Biofilm Characteristics of d-PTFE Membranes Used for Socket Preservation: A Randomized Controlled Clinical Trial." Journal of Functional Biomaterials 16, no. 2 (2025): 40. https://doi.org/10.3390/jfb16020040.
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Background: Understanding microbial colonization on different membranes is critical for guided bone regeneration procedures such as socket preservation, as biofilm formation may affect healing and clinical outcomes. This randomized controlled clinical trial (RCT) investigates, for the first time, the microbiome of two different high-density polytetrafluoroethylene (d-PTFE) membranes that are used in socket preservation on a highly molecular level and in vivo. Methods: This RCT enrolled 39 participants, with a total of 48 extraction sites, requiring subsequent implant placement. Sites were assigned to two groups, each receiving socket grafting with a composite bone graft (50% autogenous bone, 50% bovine xenograft) and covered by either a permamem® (group P) or a Cytoplast™ (group C). The membranes were removed after four weeks and analyzed using scanning electron microscopy (SEM) for bacterial adherence, qPCR for bacterial species quantification, and next-generation sequencing (NGS) for microbial diversity and composition assessment. Results: The four-week healing period was uneventful in both groups. The SEM analysis revealed multispecies biofilms on both membranes, with membranes from group C showing a denser extracellular matrix compared with membranes from group P. The qPCR analysis indicated a higher overall bacterial load on group C membranes. The NGS demonstrated significantly higher alpha diversity on group C membranes, while beta diversity indicated comparable microbiota compositions between the groups. Conclusion: This study highlights the distinct microbial profiles of two d-PTFE membranes during the four-week socket preservation period. Therefore, the membrane type and design do, indeed, influence the biofilm composition and microbial diversity. These findings may have implications for healing outcomes and the risk of infection in the dental implant bed and should therefore be further explored.
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Jaouen, Frederic, Simon Amigues, Nicolas Bibent, et al. "Effect of Asymmetrically Reinforced Membrane on Anion Exchange Membrane Fuel Cell." ECS Meeting Abstracts MA2023-02, no. 41 (2023): 2033. http://dx.doi.org/10.1149/ma2023-02412033mtgabs.
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Anion Exchange Membrane Fuel Cells (AEMFCs) is promising for the generation of electric power from hydrogen, with the expected possible replacement of precious metal catalysts by Earth abundant ones.[1-2] Beyond the independent properties of core materials (AEM, anode and cathode catalysts), the water management during operation is key to achieving high power density, but also high longevity. Thin AEMs are critical to achieve high AEMFC power performance, as the back-diffusion of water from anode to cathode critically helps to mitigate anode flooding. [3] Due to the high swelling of hydrated AEMs, good mechanical durability of thin AEMs however typically requires the introduction of a reinforcement, often a porous polytetrafluoroethylene (PTFE) membrane filled with the anion exchange ionomer. Here, we investigated the structure of different commercial AEMs and their behavior in operating AEMFC. We identified that the position of the reinforced layer (PTFE or other) strongly differs from one type of AEM to another. In the case of strongly asymmetric through-plane position of the PTFE layer (Fig. 1a), the positioning of the PTFE reinforcement close to anode or to cathode has a significant impact on initial power performance (Fig. 1b). A better performance and improved stability was observed with the PTFE layer close to the anode, suggesting that the asymmetric structure can improve the water management in such configuration. The presentation will discuss the results obtained on different commercial AEMs, and whether the asymmetric structure of AEM can be combined with PTFE hydrophobized anodes for even improved performance. The effect of the reinforcement position on the water management was also studied operando by two techniques. With high energy X-ray diffraction technique on an AEMFC under current load, the water distribution profile across the MEA thickness could be obtained from phase deconvolution analysis. With the use of relative humidity sensors at the outlet of anode and cathode of a regular AEMFC setup, [4] the water balance at a given current load could be established and compared for the two different positionings of reinforced AEM. The results shed light on the importance of identifying the position of PTFE reinforcement in commercial or in-house AEM for AEMFC application, with potential implications also for AEM electrolyzers or water-CO2 co-electrolyzers. References: Ni, W; Wang, T; Heroguel, F; Krammer, A; Lee, S; Yao, L; Schuler, A; Luterbacher, J S; Yan, Y; Hu, X, Nature Mater. 2022, 21, 804-810. Adabi, H; Santori, P G ; Shakouri, A ; Peng, X ; Yassin, K; Rasin, I G; Brandon, S; Dekel, D R; Ul Hassan, N; Sougrati M-T; Zitolo, A; Varcoe, J R, Regalbuto, J R; Jaouen, F; Mustain, W E, Materials Today Advances 2021, 12, 100179. Yassin, K; Douglin, J C; Rasin, I G; Santori, P G; Eriksson, B; Bibent, N; Jaouen, F; Brandon, S; Dekel, D R, Energy Conversion and Management 2022, 270, 116203. Eriksson, B; Santori, P. G. ; Lecoeur, F ; Dupont, M ; Jaouen, F, J. Power Sources 2023, 554, 232343. Figure 1
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Shimbori, Yuma, and Kiyoshi Kanamura. "Preparation of 3DOM PI–Ion Gel Composite Electrolyte Membranes for Li Metal Batteries." ECS Meeting Abstracts MA2024-02, no. 7 (2024): 961. https://doi.org/10.1149/ma2024-027961mtgabs.
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The electrolyte used in Li metal batteries (LMBs) contributes to high cycle performance, coulombic efficiency and safety. In particular, highly flammable electrolytes limit an operating temperature of LMBs around room temperature to keep safety, so that an introduction of cooling system is necessary, resulting in a reduction of the energy density of LMBs. Therefore, a use of safer electrolytes is required. Ion gel (IG) electrolytes have attracted attention as a candidate for electrolytes with high safety. Ionic liquid (IL) electrolytes have been incorporated in a polymer matrix. A large amount of polymer matrix has been needed to prepare thinner membranes of IG electrolytes, due to achieve high mechanical strength of mebranes. In contrast, the amount of polymer matrix is minimized to achieve higher ionic conductivity. This trade-off relationship between mechanical strength and ionic conductivity of IG electrolyte membranes must be solved by different approaches. This problem may be solved by IG electrolyte membranes incorporated into a separator framework. This separator does not contributes only to mechanical strength and ionic conductivity, but also to electrochemical performance of Li metal anode, such as Li metal deposition and dissolution and its coulombic efficiency. Therefore, a selection of separator used in the composite electrolyte membrane is very important. We have developed a three-dimensionally ordered macroporous polyimide (3DOM PI) separator that has a good affinity with IL electrolytes. In this study, the mechanical strength and ionic conductivity of the IG electrolyte membranes are improved by using a 3DOM PI separator as the framework. In addition, the more uniform porous structure of the 3DOM PI separator provides a high reversibility of Li metal dissolution and deposition. Three types of electrolytes were used in this study: pristine IG electrolyte membrane, surfactant-coated polypropylene (PP 25 μm)–IG composite electrolyte membrane, and 3DOM PI (30 μm) –IG composite electrolyte membrane. Lithium bis(fluorosulfonyl)imide and N-metyl-N-Propylpyrrolidinium bis(fluorosulfonyl)imide mixture with a molar ratio 1:1 was used as the IL electrolyte. Polymeric precursor solution for IG composite electrolyte was prepared from methyl methacrylate (MMA), 5 wt% of ethylene glycol dimethacrylate (EDGMA) to MMA, and 0.2 wt.% of 2,2’-azobis(isobutyronitrile) (AIBN) to MMA. The polymeric precursor was casted on the polytetrafluoroethylene (PTFE) sheet, PP separator, or 3DOM PI separator and sandwiched between PTFE sheets and then heated at 75 °C for 12 hours for polymerization in the separator. In the case of pristine IG electrolyte, the thickness of the self-standing membrane was at least 300 μm. The 3DOM PI separator was prepared by using a colloidal template method. An ionic conductivity measurement was performed to investigate an effect of separators on ionic conductivities of membranes. Figure 1 (a) shows the Arrhenius plots of the ionic conductivity of the membranes. The pristine IG electrolyte membrane exhibited the highest ionic conductivity, followed by 3DOM–IG composite membrane and PP–IG composite membrane. There was no significant difference in the slope of Arrhenius plots, indicating that the ionic conduction mechanisms of these electrolytes were not different each other. The unique pore structure of the 3DOM PI separator provided higher ionic conductivity than the surfactant-coated PP separator. The thickness of the membrane between the anode and cathode is an important parameter for an internal resistance of cell. Therefore, a conductance of real electrolyte membranes should be discussed. Figure 1 (b) shows the Arrhenius plots of the conductance of the electrolytes. The 3DOM PI–IG composite electrolyte exhibited both higher mechanical strength and conductance compared with those of other electrolytes. In conclusion, the composite electrolyte membrane between 3DOM-PI and IG is the most promising separator. Figure 1
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Nishihara, Masamichi, Zulfi Gautama, Yang I, Yasir Hutapea, and Kazunari Sasaki. "Suppression of Chemical Degradation By Gas Barrier Polymer Electrolyte Membranes." ECS Meeting Abstracts MA2023-02, no. 39 (2023): 1923. http://dx.doi.org/10.1149/ma2023-02391923mtgabs.
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[Introduction] Polymer electrolyte fuel cell (PEFC) is one of the promising technologies for decarbonization. Especially, PEFC is suitable to power heavy-duty vehicles (HDV) because of its high efficiency and high fuel capacity. However, there are some serious technical challenges for PEFC application for HDV such as the durability. When we focus on the chemical degradation of polymer electrolyte membranes (PEMs), it happens due to attack by radical species. One of the radical formation mechanisms is the reaction at the anode side by the penetrated oxygen from cathode. Therefore, a promising mitigation strategy against chemical degradation is the suppression of oxygen permeability through the PEM. To verify this concept, we developed high gas barrier PEM. As a model gas barrier PEM, we made a sandwich type PEM with high oxygen barrier property. The sandwich PEM was prepared by depositing a thin interlayer consisting blended poly(vinyl alcohol) (PVA) as a gas barrier material and poly(vinyl sulfonic acid) (PVS) as a proton conductor in between two layers of Nafion 211 membranes. We evaluate chemical durability using the sandwich gas barrier PEM and discuss about the mechanism. [Experimental] To fabricate thin sandwich PEMs (15-20 µm), ethanol diluted Nafion dispersion solution (20 mg/ml) and PVA/PVS solution (10 mg/ml) were sprayed on a polytetrafluoroethylene (PTFE) sheet by a spray gun (Tamiya HG wide airbrush). The thickness of each layer was controlled by controlling the deposited weight. Then, membrane characterization procedures such as surface roughness, proton conductivity, and dimensional stability were performed. To evaluate fuel cell performance, the PEMs were mounted to a JARI cell with 1 cm2 active area. Chemically accelerated stress test was performed by open circuit voltage (OCV) holding test following NEDO protocol. [Results and Discussion] Several areal densities of PVA/PVS interlayer were successfully incorporated into Nafion membrane to make sandwich PEM. The sandwich PEM shows considerable fuel cell performance, and thin sandwich PEMs show higher performance than the 50 µm sandwich PEM, although it is lower than the thin sprayed Nafion. For example, the peak power density of 15 µm sandwich PEM was 0.44 W cm-2 compared to 0.30 W cm-2 and 0.50 W cm-2 for 50 µm sandwich PEM and 15 µm Nafion, respectively. Furthermore, the incorporation of interlayer to thin PEM can suppress the hydrogen crossover current density from 7.8 mA cm-2 to 5.5 mA cm-2 indicating superior gas barrier property. From the higher gas barrier property, it is predicted thin sandwich PEMs will have higher chemical durability than Nafion with similar thickness.
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Al Murisi, Mohammed, Prabhu Ganesan, Hector-Colon Mercado, and William Earl Mustain. "The Effect of PTFE Dip Coating on Enhancing the Durability and Performance of Anion Exchange Membrane Electrolyzers." ECS Meeting Abstracts MA2024-01, no. 34 (2024): 1746. http://dx.doi.org/10.1149/ma2024-01341746mtgabs.
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Anion exchange membrane electrolyzers (AEMELs) are widely regarded as one of the most promising technologies to enable low-carbon hydrogen production. AEMELs can combine the advantages the traditional alkaline electrolyzer (AEL) and proton exchange membrane electrolyzer (PEMEL) – allowing for the use of PGM free electrodes, high operating current density, environmentally friendly materials, and compact design. Although significant progress has been made in the field of AEMELs, there is still a gap in performance compared to PEMELs that can be overcome through electrode design. One of the most critical aspects affecting the overall performance of the AEMEC is the water management. It has a major influence on cell behavior, and specifically mass transfer at the anode side of the cell. To improve AEMEL anode water dynamics, our team modified its porous transport layer (PTLs) through the addition of controlled amounts of hydrophobic polytetrafluoroethylene (PTFE). This study investigated the effect of PTFE loading and coating method on the performance of AEMELs. Ni-based PTLs were used. Experimental results revealed that a low amount of PTFE not only enhanced the performance, but it also enhanced the catalyst layer attachment. On the other hand, higher PTFE content led to a reduction in water availability in the electrode, leading to increased mass transfer overpotentials. In summary, increasing the hydrophobicity of Ni-PTLs appears to improve AEMEC performance, with the best performing electrodes having a PTFE loading of ~1-2% (equivalent to 5-10 wt.% on carbon GDLs).
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Luongo, Roberto, Marco Tallarico, Elena Canciani, et al. "Histomorphometry of Bone after Intentionally Exposed Non-Resorbable d-PTFE Membrane or Guided Bone Regeneration for the Treatment of Post-Extractive Alveolar Bone Defects with Implant-Supported Restorations: A Pilot Randomized Controlled Trial." Materials 15, no. 17 (2022): 5838. http://dx.doi.org/10.3390/ma15175838.
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Aim: The aim of the present study was to investigate quantitative histological examination of bone reconstructed with non-resorbable high-density polytetrafluoroethylene membrane (d-PTFE), left intentionally exposed in post extraction sockets grafted with anorganic bone material, and removed after four weeks, versus extraction and guided bone regeneration (GBR), performed two months later. Materials and Methods: This study was designed as a multicenter randomized controlled trial of parallel-group design. Patients were selected and consecutively treated in three centers in Italy. Patients randomly received intentionally exposed non-resorbable d-PTFE membrane (group A), or guided bone regeneration (group B), to treat post-extractive alveolar bone defects with implant-supported restorations. Outcomes were: the implant failure, any mechanical and biological complications, patient satisfaction, and qualitative and histomorphometric evaluation of the collected bone samples. Results: Eighteen patients were consecutively enrolled in the trial. Of these, six out of 18 patients were male. All the included patients were treated according to the allocated interventions, and no drop out occurred. No implant failure and no complications were experienced, and all the patients were fully satisfied with the function and aesthetic of their implant-supported restoration, without difference between groups. Morphological analysis revealed no sign of tissue reaction, such as fibrosis or necrosis. Regenerated bone was well mineralized in both groups, but it seemed more mature in group B than in group A. Three samples showed a minimal number of lymphocytes. Several blood vessels of small size occupied the medullary spaces, where the tissue resulted in more maturity, indicating the activity of the tissue in progress. The histomorphometric evaluation showed no statistically significant differences in the tissue volume fractions between the two groups of patients. Conclusions: With the limitation of the present study, buccal plate reconstruction with an intentionally exposed non-resorbable membrane is an effective and easy procedure for regenerating a resorbed buccal bone plate, reducing the need for guided bone regeneration.
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Yi-Tien Tsai, Yi-Tien Tsai, Chun-Jung Chen Yi-Tien Tsai, Lian-Ping Mau Chun-Jung Chen, and Chen-Chou Tsai Lian-Ping Mau. "Alveolar Ridge Preservation with The Use of Demineralized Bone Matrix Putty: Clinical, Radiographic and Histological Observations in A Case Series." Journal of Periodontics and Implant Dentistry 6, no. 2 (2023): 077–84. http://dx.doi.org/10.53106/261634032023100602004.
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<p>Alveolar ridge preservation (ARP) can minimize alveolar ridge resorption following tooth ex&not;traction and facilitate restorative-driven implant placement. Demineralized bone matrix (DBM) comprises a human allograft that is osteoinductive and osteoconductive. This report describes radiographic, histologic and clinical findings of ARP using DBM putty and non-resorbable high-density polytetrafluoroethylene (d-PTFE) membrane in three cases. </p> <p>Materials and Methods: From January 2018 to May 2018, three patients underwent the ARP procedure. The surgery involved atraumatic extraction, socket debridement, filling the socket with DBM putty, applying a d-PTFE membrane, and suturing with 5-0 nylon. After healing for 6&ndash;7 months, an implant was placed and biopsy specimens were collected simultaneously. Using the same customized surgical stent and computed tomography, the preoperative and postoperative alveolar ridge heights and widths were measured. Histological evaluations in&not;cluding the percentage of newly formed bone, residual graft particles, and fibrous connective tissue were performed. </p> <p>Results: In all three cases, the health status of the hard and soft tissue improved (mean fol&not;low-up: 54 months). Guided bone regeneration was not required during implant placement. Radiographically, the mean change was 0.5 mm in the alveolar ridge height and 1.2, 0.87, and 0.73 mm in the alveolar ridge width at 2, 4, and 6 mm apical to the initial vertical measure&not;ment, respectively. Histologically, the mean percentage of new bone, residual graft particles, and fibrous connective tissue was 40.5&plusmn;5.9%, 10.7&plusmn;6.9%, and 48.8&plusmn;9.6%, respectively, and the voids were not included in these calculations. </p> <p>Conclusion: This case series demonstrated the effectiveness of DBM putty as a biocompatible filler in extraction sockets for ridge preservation prior to implantation. Further longitudinal studies regarding the efficacy and stability of DBM putty in ridge preservation are required.</p> <p>&nbsp;</p>
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Gao, Jianan, and Wen Zhang. "(Invited) Next Generation Electrified Membrane Technology for Simultaneous Wastewater Treatment and Production of Nitrogen Fertilizer." ECS Meeting Abstracts MA2023-01, no. 39 (2023): 2303. http://dx.doi.org/10.1149/ma2023-01392303mtgabs.
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Recovery and repurposing of wastewater nitrogen such as nitrate (NO3 −) and nitrite (NO2 −) receive increasing attention as the current approaches of biological nitrogen removal or conversion into nitrogen gas (N2) renders high energy footprints. This study reported the first electrified membrane upcycling of NO3 − into NH3 that further converted into ammonia sulfate (NH4SO4), a liquid fertilizer readily for use. Paired electrolysis was used to couple simultaneous cathodic and anodic electrochemical half-reactions to enable nitrate reduction and eliminate the external acid/base consumption. Under a partial current density of 63.8±4.4 mA·cm−2 on a cathodic membrane made of a mixed-valence copper oxide and a polytetrafluoroethylene (PTFE) hydrophobic substrate, a recovery rate and energy consumption of 3100±91 g-(NH4)2SO4·m−2·d−1 and 21.8±3.8 kWh·kg−1-(NH4)2SO4 were achieved with the synthetic feed solution (150 mM NO3 −) flowing into the cathode chamber and the produced NH3 migrating across the cathodic membrane into a trap and anode chambers filled with the flowing 0.5 M Na2SO4 solution. 99.9% NO3 − was removed in the feed after 5 h operation with a NH3 recovery rate of 99.5%. This electrified membrane process was demonstrated to achieve comparable performances of synergistic nitrate decontamination and nutrient recovery using real nitrate wastewater with durable catalytic activity and stability. Specifically, the required electricity cost for converting 10 to 100 mM NO3 − to (NH4)2SO4 was $675 to $408 ton−1, respectively. The obtained (NH4)2SO4 may be sold as fertilizer at a price of 533 $·ton−1 (according to USDA) and further offset the cost of the NO3 − removal. According to the International Fertilizer Association, in 2018 the U.S. ranked second in nitrogen production, representing 11.6% of global production. However, it still requires the importation of nitrogen fertilizer, to fully meet the national demand. The US Environmental Protection Agency reports that in 2013, ~38 kg of nitrogen per acre per year was used for fertilization, and in 2016, 94 million acres of corn were planted in the US, representing ~40% of US fertilizer demand. Roughly, this equates to ~8.9 billion kg of nitrogen per year needed to meet total US fertilization demand. The nitrogen available in drinking water sources is roughly 65 million kg per year, and the nitrogen available in wastewater sources is roughly 2.4 billion kg per year. Thus, by fully recovering the nitrogen from wastewater 34.3% of the US nitrogen fertilizer requirement could be met. This could also further mitigate the increase in nitrogen fertilizer prices due to blocked nitrogen fertilizer imports and even free the US from nitrogen fertilizer imports. According to U.S. Department of Agriculture, the average U.S. farm price of sulfate of ammonium fertilizers is $533 per ton. Even leaving aside the revenue generated by the treatment of nitrogen-containing sewage, the market size of nitrogen fertilizer produced through sewage is as high as $12.8 billion.
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Schweiss, Ruediger, Magnus Herb, Raj Earla, and Christian Meiser. "On the Importance of MPL Structural Characteristics for PEM Fuel Cell Performance." ECS Meeting Abstracts MA2023-02, no. 37 (2023): 1764. http://dx.doi.org/10.1149/ma2023-02371764mtgabs.
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Gas diffusions layers (GDLs) constitute vital subcomponents of proton exchange membrane fuel cells (PEMFCs) since they participate in all relevant transport processes (gases, vapor, liquid water, electricity and heat).Meanwhile, state-of-the-art GDLs are produced on commercial scale using high volume reel-to-reel (R2R) processes. In almost any case, GDLs are designed as dual-layer structures with a macro-porous carbon fiber-based substrate (backing) and a micro-porous layer (MPL) consisting of carbon particulates bonded with polytetrafluoroethylene (PTFE) binder. A body of scientific work has verified that different aspects of the MPL microstructure and the MPL/macroporous substrate interface play a substantial role in the water management of PEMFCs [1-6]. A systematic study was performed based on a singular backing using different MPL types and penetration levels.A simple method to estimate the micro-porous layer penetration in gas diffusion layers based on data obtained from force-deflection behavior of backings and MPL-coated GDLs is proposed. Comparison with SEM and previously published tomographic studies shows that a good estimate for the extent of MPL intrusion into the backing is obtained. MPL loading and penetration is shown to affect different ex-situ GDL properties (in-plane gas permeability, electrical and thermal conductivity) as well as the GDL single cell performance characteristics with respect to humification and high current density operation. Keywords: Gas diffusion layers, Microporous Layer, PEMFC fuel cells Weber, and J. Newman, “Effects of microporous layers in polymer electrolyte fuel cells”, J. Electrochem. Soc. 152, A677-A688 (2005). Lee, R. Yip, P. Antonacci, N. Ge, T. Kotaka, Y. Tabuchi, and A. Bazylak, Synchrotron investigation of microporous layer thickness on liquid water distribution in a PEM fuel cell, J. Electrochem. Soc. 162, F669-F676 (2015). Zhou, S. Shukla, A. Putz, and M. Secanell, “Analysis of the role of the microporous layer in improving polymer electrolyte fuel cell performance”, Electrochim. Acta. 268, 366-382 (2018). Cho, J. Park, H. Oh, K. Min, E. Lee, and J.Y. Jyoung, “Analysis of the transient response and durability characteristics of a proton exchange membrane fuel cell with different micro-porous layer penetration thicknesses”, Appl. Energy 111, 300-309 (2013). T. Gostick, M. A. Ioannidis, M. W. Fowler, and M. D. Pritzker, “On the role of the microporous layer in PEMFC operation.”, Electrochem. Comm. 11, 576-579 (2009). P. Ramasamy, E. C. Kumbur, M. M. Mench, W. Liu, D. Moore, and M. Murthy, “Investigation of macro- and micro-porous layer interaction in polymer electrolyte fuel cells”, Int. J. Hydrogen Energy 33, 3351-3367 (2008).
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Yoshikawa, Makoto, Zhiyun Noda, Masahiro Yasutake, et al. "Self-Supporting Microporous Layer for Polymer Electrolyte Fuel Cells Using Thin Carbon Mesh Gas Diffusion Layer." ECS Meeting Abstracts MA2024-02, no. 44 (2024): 3059. https://doi.org/10.1149/ma2024-02443059mtgabs.
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Introduction Research and development of polymer electrolyte fuel cells (PEFC) have been conducted extensively to improve power density. The gas diffusion layer (GDL) and microporous layer (MPL) used in PEFCs are much thicker than the electrocatalyst layer and electrolyte membrane. Down-thinning GDL and MPL to 50 μm or less is desirable to reduce gas diffusion resistance and to increase the power density per volume of the cell stack [1]. However, while both the electrocatalyst layer and electrolyte membrane have been thinned down to about 10 μm, the GDL with MPL is still thick at about 150 to 200 μm. Previous studies have considered the possibilities and technical issues in using porous metals as GDLs, which can make GDL thinner with high mechanical strength [2]. In addition, a composite MPL with both hydrophobic and hydrophilic channels was developed and its effect on oxygen transport resistance was investigated [3]. Based on these findings, the aim of this study is to develop a self-supporting thin MPL/GDL using carbon mesh as a GDL, which is relatively stable and thinner than carbon paper, and commercially available. In addition, contact resistance is reduced by printing thinner MPL, for improving power density. Experimental In this study, the MPL/GDL was fabricated by printing MPL on a carbon mesh (50 µm thick, Cosmotech, Japan) as a GDL using a screen-printing method. Cells were fabricated by using these materials. Current-voltage characteristics, microstructural observation, and gas diffusion resistance measurements were conducted. The MPLs were composed of carbon black, carbon nanotubes (CNT), polytetrafluoroethylene (PTFE), and solvent (a mixture of polyethylene glycol 600, and pure water). After mixing, the first MPL “layer” was printed on a dense PTFE sheet using a 30-µm-thick screen and dried at 150°C for 30 min. Afterwards, this first MPL “layer” on the PTFE sheet was transferred to the porous GDL by pressing the MPL/PTFE sheet and the porous GDL together. The second MPL “layer” was then directly screen-printed by using a 10-µm-thick screen and then heat-treated at 300°C for 30 min to prepare the MPL/GDL. A standard Pt/C electrocatalyst (TEC10E50E, Tanaka Kikinzoku, Japan) was used for preparing membrane-electrode assemblies (MEAs). As the electrochemical characterization in this study, current-voltage characteristics were evaluated using an electrochemical impedance analyzer (SAS SP-240, Bio-Logic Science Instruments, France) and various overvoltages were separated. Results and discussion Figure 1 shows the current-voltage characteristics of the cells using various MPL/GDLs. The thickness of MPL/GDLs fabricated was ranging from 80 to 100 µm. For comparison, the characteristics of a cell using a standard, commercially-available MPL/GDL (22BB, SGL Carbon, Germany) are also shown. These results show that the use of MPL significantly improves cell performance even with thin GDLs. The cells with carbon mesh but without MPL exhibited particularly high concentration overvoltage and low I-V characteristics compared to the cells with an MPL. Without MPL, the contact resistance between the carbon mesh and the electrocatalyst layer was high due in part to the limited contact area, and water flooding may occur at high current densities. In contrast, when the MPLs with highly conductive materials were printed, cell performance was improved, and comparable results to the standard MPL/GDL were obtained. The presence of the highly conductive MPL improves conductivity and current collection, resulting in lower ohmic overvoltage. The hydrophobicity of the PTFE-containing MPL suppresses an increase in concentration overvoltage. In addition, the addition of CNTs may increase the porosity at a nanometer level and improve the drainage of generated water (Figure 2). These suggest that the self-supporting thin MPL/GDL has a potential to improve the power density per cell stack volume. Acknowledgements This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). An educational part for young scientists was supported by the Japan Science and Technology Agency (JST) as a part of Adopting Sustainable Partnerships for Innovative Research Ecosystem (ASPIRE), Grant Number JPMJAP2307. References New Energy and Industrial Technology Development Organization (NEDO), Roadmap of Fuel Cells for Heavy-Duty Vehicles, 2022 (in Japanese). Yamamoto, M. Yasutake, Z. Noda, S. M. Lyth, J. Matsuda, M. Nishihara, A. Hayashi, and K. Sasaki, ECS Trans., 109 (9),265 (2022). Wang, H. Nakajima, and T. Kitahara, J. Electrochem, Soc., 171, 014501 (2024). Larminie and A. Dicks, Fuel Cell Systems Explained, 2nd ed., John Wiley & Sons, England, 2003. T. Kitahara, T. Konomi, H. Nakajima, and J. Shiraishi, Kikai B, 76 (761), 101 (2010). Figure 1
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Wang, Peng, Hironori Nakajima, and Tatsumi Kitahara. "(Digital Presentation) Effect of the Hydrophilic Layer in Double Microporous Layer Coated Gas Diffusion Layer on PEFC Performance." ECS Meeting Abstracts MA2022-02, no. 39 (2022): 1383. http://dx.doi.org/10.1149/ma2022-02391383mtgabs.
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The polymer electrolyte fuel cells (PEFCs) are commonly used in the vehicle industry, but the relatively higher costs of power generation limit the potential for further application. The PEFCs output power can be mainly undermined by the water management of the membrane electrode assembly (MEA). If the water content balance in the MEA is broken by fast water expelling, the dehydrated membrane significantly raises the proton transport resistance, which results in severe ohmic resistance loss. Oppositely, the slow water removal pace makes the production water stay at the catalyst layer (CL) surface, and the reactants are prohibited from accessing the reaction area and causing high reactants concentration overpotential during the high current density range. To elongate the limiting current density and raise the output power, beneficial water management should keep the MEA from dehydration by using the water generated from electrochemical reactions and can expel additional water from the CL and gas diffusion layer (GDL) interface. To implement the favorable water balance in the cell, the GDL with the microporous layer (MPL) is necessary. Traditional MPL mainly contains carbon black and hydrophobic binder Polytetrafluoroethylene (PTFE), which can guarantee water-unoccupied pathways for gas transport. The produced water can be expelled by the relatively large pores, and the water transportability is mainly controlled by the pore size and hydrophobicity. When the pore size is excessively narrow, the easily gathered water creates flooding between the CL and GDL. Large pores can solve this issue but bring the water stored in the MPL. Thus, a double MPL is developed to achieve better water management when it cannot forwardly enlarge the pore sizes under low and high humidity conditions. A commercially available hydrophobic MPL coated GDL (SGL 22BB) is the standard sample in this study. As for double MPL coated GDL, the hydrophilic layer is coated on the hydrophobic MPL coated GDL. One candidate composition uses Nafion as the hydrophilic binder, TiO2 as the hydrophilicity improvement particles, and the rest of the part is carbon black; the other way applies only Polyvinyl alcohol (PVA) as the hydrophilic binder and mixes with carbon black. Both types of hydrophilic slurry are directly coated on the 22BB, and the maximum pore diameter slightly changed from 45um (SGL 22BB) to a smaller size. These very thin hydrophilic layers modify the surface properties, which can help reduce the surface contact angle and make water easier to be introduced into the hydrophobic MPL. According to the tests, the performance of the double MPL containing PVA binder becomes worse than the Nafion-TiO2 double MPL, even than standard hydrophobic MPL. Due to the strong hydrophilicity of the PVA binder, even though a tiny amount of it is added to the top layer, water accumulation still occurs in the MPL, so the PVA binder is not suitable for the MPL property modification. The double MPL, which applied a Nafion-TiO2 hydrophilic layer, achieves lower oxygen transport resistance under high humidity conditions than the standard hydrophobic MPL. Besides, the appropriate composition of the hydrophilic contents is determined. With the increase of the TiO2 and Nafion content, the significantly enhanced hydrophilicity leads to more water absorption. However, it blocks the gas pathways, showing terrible reactants transport and high concentration over-potential. When the hydrophilic content becomes overly low, it is not enough to afford the water expelling, and water still occupies the MPL and CL interface. The thickness of the top hydrophilic MPL is another critical design parameter. A too thick hydrophilic layer can hold more water and cause a high risk of hampering reactants supply. The moderate thickness of the hydrophilic layer should be less than 5μm, which guarantees the function of the water transport and keeps away from severe water absorption.
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Washington, Brian, Gabriel Goenaga, and Thomas A. Zawodzinski. "(Digital Presentation) Evaluating the Performance of Multi-Walled Carbon Nanotube Composite Microporous Layers Deposited on Carbon Felt Gas Diffusion Layers." ECS Meeting Abstracts MA2022-02, no. 1 (2022): 15. http://dx.doi.org/10.1149/ma2022-02115mtgabs.
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Electrochemical energy storage devices (EESDs) such as metal-air batteries (MABs) and alkaline electrolyte membrane fuel cells (AEMFCs) have begun to gain vast amounts of attention due to their high theoretical energy densities and open-circuit voltage values. Although these devices present promising aspects for the environment and sustainability, they suffer from the slow reaction kinetics and degradation effects that occur at the catalyst layer interface of the air electrode. Typically, these effects are due to the accumulation of molecular species such as water or oxygen at catalyst active sites because of poor electrode hydrophobicity and fluid management. Herein, we perform experimentation to mitigate these effects by implementing mixed carbon composite microporous layers onto porous carbon felt based air electrodes. This adaptation of the air cathode was predominantly based on the aforementioned downfalls and the lack of availability of commercial carbon felts that have adequate wet proofing and conductivity like some of the related carbon paper gas diffusion layers. Microporous layers (MPLs) enhance electrical conductivity, surface area, and adhesion at the catalyst layer and gas diffusion layer interface. These layers typically consist of a hydrophobic polymer such as polytetrafluoroethylene (PTFE) and a conductive carbon black substrate such as Ketjen Black 600JD (KJB). The incorporation of multi-walled carbon nanotube (MWCNT) and carbon black composites into the structure of the MPLs drastically decreases ohmic polarization with minimal increases in specific resistance. The electrical resistance of the synthesized carbon substrate decreases at high rates of MWCNT dispersion, which corresponds directly to a low MWCNT weight percentage within the composite. The MPL increases the mass transport through the electrode by mitigating flooding effects that typically occur within the pores near the surface of the catalyst layer, ultimately aiding in charge transfer between the gas diffusion layer and catalyst active sites. Preliminary data from AEMFC symmetric cell tests suggests that a microporous layer consisting of a 10 wt.% MWCNT/KJB (m/m) substrate is the optimal loading of carbon nanotubes and leads to better cell performance. There is an increase in current density of 60 mA/cm2 compared to an air electrode with no MPL within the ohmic region of the polarization curve corresponding to approximately 0.7 V, while only an increase of 18 mA/cm2 is seen for an MPL consisting of a 30 wt.% MWCNT/KJB (m/m) carbon substrate. The increase of charge transfer by the 10 wt.% synthesized carbon substrate MPL was attributed to the ability of the nanotubes at high rates of dispersion to act as molecular wires within the electrode. Additionally, zinc-air battery tests using the optimally configured air electrode, determined from previous experiments, show that the current density at an operating voltage of 1.1 V was increased by 2.3 times that of an electrode without an MPL using the same catalyst material and loading. Significantly, this research will lead to a better understanding of optimization of the air electrode used within electrochemical devices and how to eliminate some of the adverse effects associated with it. Figure 1
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Yoshikawa, Makoto, Kotaro Yamamoto, Zhiyun Noda, et al. "Self-Supporting Microporous Layer for Polymer Electrolyte Fuel Cells." ECS Meeting Abstracts MA2023-02, no. 37 (2023): 1734. http://dx.doi.org/10.1149/ma2023-02371734mtgabs.
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Introduction Improving power density is desired in research and development of polymer electrolyte fuel cells (PEFC) [1-5]. A reduction of gas diffusion resistance by down-thinning the gas diffusion layer (GDL) less than 50 μm is desirable [2]. Whilst both the electrocatalyst layers and electrolyte membrane are around 10 μm, the GDL is still relatively thick at about 150 μm [1]. The previous study investigated the possibility and technical issues in using high-strength and thin, porous metallic GDLs [3]. Based on such previous studies, this study aims to develop a self-supporting thin MPL/GDL with improved power density by creating conductive paths and reducing contact resistance with microporous layer (MPL) deposited on various GDLs. Experimental In this study, MPL was screen-printed on various mesh GDLs as substrates. Cells were fabricated by using these materials, and current-voltage characteristics and microstructural observations were performed. Stainless steel (SUS316 977mesh, 28 μm thick), titanium (200mesh, 152 μm thick), and carbon fiber (45 μm thick) were used as mesh GDL materials. The MPLs were composed of carbon black, carbon nanotubes, polytetrafluoroethylene (PTFE), and solvent (a mixture of polyethylene glycol 600 and pure water), which were mixed, screen printed, and heat treated at 300°C for 30 min to fabricate the MPL/GDL. Conventional materials such as Pt/C (TEC10E50E, Tanaka Kikinzoku, Japan) were used for preparing membrane-electrode-assemblies (MEAs). In the electrochemical characterization of this study, current-voltage characteristics were evaluated using an electrochemical impedance analyzer (SAS SP-240, Bio-Logic Science Instruments, France), and various overvoltages were separated. Results and discussion Figure 1 shows the current-voltage characteristics of cells using various MPL/GDLs. The thickness of MPL/GDLs fabricated was ranging from 62 to 180 μm. For comparison, the characteristics of a cell using a standard material, commercially available MPL/GDL (22BB, SGL Carbon, Germany), are also shown. The results indicate that the use of any kind of these MPLs improves cell performance. The electrochemical performance with metallic GDLs was considerably improved by applying MPLs. In particular, GDLs with metallic meshes made of SUS316 show a significant improvement in current-voltage characteristics by depositing MPLs. The activation overvoltage and ohmic overvoltage were comparable to those of 22BB, the commercial GDL/MPL. This is because the contact resistance between the GDL and the catalyst layer is reduced by the carbon component in the MPL, and the electrical conductivity is improved. The concentration overvoltage was also suppressed by depositing the MPL. The cell performance with MPL3/SUS316 977mesh was comparable to that of 22BB. In the future, we aim to further reduce the concentration overvoltage by optimizing e.g., the content of hydrophilic components in MPLs. Acknowledgment This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References Takahashi, T. Ikeda, K. Murata, O. Hotaka, S. Hasegawa, Y. Tachikawa, M. Nishihara, J. Matsuda, T. Kitahara, M. Lyth, A. Hayashi, and K. Sasaki, J. Electrochem. Soc., 169, 044523, (2022). New Energy and Industrial Technology Development Organization (NEDO), Roadmap of Fuel Cells for Heavy-Duty Vehicles, 48, (2022), (in Japanese), https://www.nedo.go.jp/content/100944011.pdf Yamamoto, M. Yasutake, Z. Noda, S. M. Lyth, J. Matsuda, M. Nishihara, A. Hayashi, and K. Sasaki, ECS Trans., 109 (9),265 (2022). Larminie and A. Dicks, Fuel Cell Systems Explained, 2nd ed., John Wiley & Sons, England, 2003. Kitahara, T. Konomi, H. Nakajima, and J. Shiraishi, Kikai B, 76 (761), 101, (2010). Figure 1
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Zhang, Tianyu, Max Pupucevski, Shuo Ding, and Judith Lattimer. "Large-Scale and Highly Selective Electrochemical CO2 to C2H4 Conversion Based on the Giner Water Management GDL." ECS Meeting Abstracts MA2023-01, no. 26 (2023): 1713. http://dx.doi.org/10.1149/ma2023-01261713mtgabs.
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C2H4 is a key building block in the chemical industry to produce a wide range of plastics, solvents, cosmetics, etc. On average, the production of 1 MMT of C2H4 generates 1.5 MMT of CO2, coming from fuel combustion, decoking, and utilities. Globally, C2H4 production by steam cracking is ranked as the second-largest contributor of energy consumption (2.8 EJ/year) and greenhouse gas emissions (300 MMT of CO2-e/year) in the chemical industry. Electrochemical CO2 reduction reaction (CO2RR) to produce C2H4 at ambient conditions, when coupled with renewable electricity, could reduce dependence on fossil fuels and decarbonize the chemical sector associated with C2H4 production. However, more efforts are needed to improve selectivity, productivity, and durability before the CO2 electrolyzer can be deployed commercially. State-of-the-art continuous CO2 electrolyzers utilize gas diffusion electrodes (GDEs) to achieve CO2-to-C2H4 conversion at industrially relevant current density. However, managing the flooding of liquid electrolytes into the porous structure of GDE remains a critical practical challenge for stable and efficient CO2 transport. To date, most CO2 electrolyzers used commercial gas diffusion layer (GDLs) designed for polymer electrolyte membrane fuel cells (PEMFC), which operate under different conditions than CO2RR. The conventional GDL is generally made of carbon paper coated with 5-30 wt.% of polytetrafluoroethylene (PTFE) to protect against flooding. These GDLs still lose hydrophobicity fast during CO2 electrolysis at highly negative potentials due to the electrowetting of carbon materials, salt precipitation, and chemical degradation. As a result, the electrolyte even penetrates the micropores of the GDL, blocking CO2 transport to catalyst sites. Giner has designed an innovative structure, the water management GDL (WM-GDL), providing a breakthrough solution for water management under the operational conditions of a CO2 electrolyzer. The WM-GDL has dedicated mass transport pathways for gas and electrolyte, which allows durable and efficient mass transport of both over long-term operation. The utilization of WM-GDL will assist in the scale-up of electrochemical CO2-to-C2H4 conversion. Currently, the state-of-the-art WM-GDL achieved 60% C2H4 selectivity at 500 mA cm-2 and 3 V in a 50 cm2 MEA electrolyzer. Larger-scale demonstration of the CO2-to-C2H4 conversion with high selectivity and durability will be carried out in stacks. Acknowledgment: The project is financially supported by the Department of Energy’s Office of EERE under the Grant DE-EE000942l
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Carbonell, J. M., I. Sanz Martín, A. Santos, A. Pujol, J. D. Sanz-Moliner, and J. Nart. "High-density polytetrafluoroethylene membranes in guided bone and tissue regeneration procedures: a literature review." International Journal of Oral and Maxillofacial Surgery 43, no. 1 (2014): 75–84. http://dx.doi.org/10.1016/j.ijom.2013.05.017.
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Al-Kattan, Reem. "An update on the utilization of high-density polytetrafluoroethylene (d-PTFE) membranes for guided bone regeneration." International Journal of Oral Care and Research 8, no. 4 (2020): 91. http://dx.doi.org/10.4103/injo.injo_51_20.
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Tandava, Venkata S.R.K., Mayra S. Tovar-Oliva, Martí Biset-Peiró, et al. "Modulating the surface interface of PTFE/Cu-based GDEs to boost the electrochemical conversion of CO2 to C2H4 at ultra-low overpotential." Applied Catalysis B: Environment and Energy 371 (August 15, 2025): 125276. https://doi.org/10.1016/j.apcatb.2025.125276.
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The electrochemical CO<sub>2</sub> reduction to multi-carbon products has received significant attention with the successful implementation of gas diffusion electrodes (GDEs) in flow electrolysers. In this work, we present the convenience of systematically modulating the surface interface of copper-based catalyst layers. Tailored GDEs fabricated by sputtering copper on polytetrafluoroethylene porous membranes and applying additive layers prove to be very effective in boosting selectivity towards C<sub>2</sub>H<sub>4</sub> and other C<sub>2+</sub> products. A comparative study of sputtered copper with additive layers (i.e. carbon black and/or catalyst-ionomer) allows to understand the role of the catalyst/catalyst-additive heterojunction. The additive layer aids not only in tuning the selectivity towards C<sub>2</sub>H<sub>4</sub> as the prime product, but also significantly lowers the cathodic overpotential required to achieve high current densities. PTFE/Cu GDE with an appropriate additive layer loading (i.e. mixed copper oxide in a carbon black matrix) converts CO<sub>2</sub> to C<sub>2</sub>H<sub>4</sub> with a faradaic efficiency of ≥ 70 % (combined faradaic efficiency of ≥90 % for C<sub>2+</sub> products) at industrially relevant current density of 250 mA·cm<sup>−2</sup> with an <em>iR</em>-corrected potential of −0.55 V <em>vs</em> RHE. The PTFE/Cu/Cu<sub>x</sub>O-C GDE exhibits excellent stability, delivering a consistently high yield of C<sub>2</sub>H<sub>4</sub> over 25 h while effectively suppressing the competitive hydrogen evolution reaction.
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Palkovics, Daniel, Fanni Bolya-Orosz, Csaba Pinter, Balint Molnar, and Peter Windisch. "Reconstruction of vertical alveolar ridge deficiencies utilizing a high-density polytetrafluoroethylene membrane /clinical impact of flap dehiscence on treatment outcomes: case series/." BMC Oral Health 22, no. 1 (2022). http://dx.doi.org/10.1186/s12903-022-02513-7.
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Abstract Objectives The aim of this study was to evaluate the effects of membrane exposure during vertical ridge augmentation (VRA) utilizing guided bone regeneration with a dense polytetrafluoroethylene (d-PTFE) membrane and a tent-pole space maintaining approach by registering radiographic volumetric, linear and morphological changes. Methods In 8 cases alveolar ridge defects were accessed utilizing a split-thickness flap design. Following flap elevation VRA was performed with tent-pole space maintaining approach utilizing the combination of a non-reinforced d-PTFE membrane and a composite graft (1:1 ratio of autogenous bone chips and bovine derived xenografts). Three-dimensional radiographic evaluation of hard tissue changes was carried out with the sequence of cone-beam computed tomography (CBCT) image segmentation, spatial registration and 3D subtraction analysis. Results Class I or class II membrane exposure was observed in four cases. Average hard tissue gain was found to be 0.70 cm3 ± 0.31 cm3 and 0.82 cm3 ± 0.40 cm3 with and without membrane exposure resulting in a 17% difference. Vertical hard tissue gain averaged 4.06 mm ± 0.56 mm and 3.55 mm ± 0.43 mm in case of submerged and open healing, respectively. Difference in this regard was 14% between the two groups. Horizontal ridge width at 9-month follow-up was 5.89 mm ± 0.51 mm and 5.61 mm ± 1.21 mm with and without a membrane exposure respectively, resulting in a 5% difference. Conclusions With the help of the currently reported 3D radiographic evaluation method, it can be concluded that exposure of the new-generation d-PTFE membrane had less negative impact on clinical results compared to literature data reporting on expanded polytetrafluoroethylene membranes.
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He, Chengmiao, Chengwei Gao, Jiahui Zhang, et al. "Air‐stable, flexible Na3SbS4 thin membrane prepared via a dry‐film strategy." Journal of the American Ceramic Society, September 2023. http://dx.doi.org/10.1111/jace.19404.
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AbstractAll‐solid‐state sodium ion batteries (ASSIBs) attract growing attention as the next generation of batteries due to their high energy density, excellent safety, and the abundance of sodium resources. As a vital component of ASSIBs, chalcogenide Na‐ion solid‐state electrolytes (SSEs) have been widely studied due to their high ionic conductivity and outstanding ductility. However, due to the susceptibility to organic solvents and moisture, no chalcogenide Na‐ion SSEs membrane has been reported while only thick SSEs pellets have been investigated, which introduces abundant “dead” weight and lowers the energy density of ASSIBs. Herein, utilizing the excellent air stability of Na3SbS4, a thin (∼220 μm) Na3SbS4 membrane is prepared in air via a facile dry‐film method with polytetrafluoroethylene fibrillation, which exhibits a high ionic conductivity of 0.19 mS cm and an excellent critical current density of 0.6 mA/cm2. In summary, the chalcogenide Na‐ion SSEs membranes with high ionic conductivity and the simple preparation process could be readily adopted by pragmatic high‐performance ASSIBs.
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Zhao, Xue Jiao, Zhi Hao Zhao, Zhong Lin Wang, Guang Zhu, and Jie Wang. "High Tribo‐Charge Density Composite Nanofiber Membrane for Motion Sensing and Water Wave Energy Harvesting." Small, December 17, 2024. https://doi.org/10.1002/smll.202408929.
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AbstractTriboelectric nanogenerators (TENGs), among the most simple and efficient means to harvest mechanical energy, have great potential in renewable energy utilization. While the output performance of TENGs is still not high enough, which limits its practical application. Here, a poly(vinylidene fluoride) (PVDF)/fluorinated ethylene propylene nanoparticles (FEP NPs) porous nanofiber (PFPN) membrane with waterproof, breathable, surface superhydrophobic and high tribo‐negative properties is proposed for achieving high‐performance of TENGs. The PFPN‐based solid–solid contact PFPN‐TENG achieved an optimal electric output with a net tribo‐charge density of 294 µC m−2, which is 42.2% more than that of polytetrafluoroethylene (PTFE) film. The PFNP membrane can maintain the best performance with almost no attenuation after 142680 working cycles. Based on its excellent triboelectric characteristics, the PFPN membrane shows its excellent performance for self‐powered body motion sensing and mechanical energy harvesting. A flexible solid–liquid contact PFPN‐TENG can achieve high electrical output with an average volume power density of ≈544.1 W m−3 by harvesting water wave energy. Such excellent performance of the PFPN membrane makes it a potential candidate to promote the power density of TENGs in harvesting blue water wave energy.
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Luo, Cong, Qingsheng Guo, Cong Feng, Yun Wang, Pingwen Ming, and Cunman Zhang. "Proton Transport, Electroosmotic Drag and Oxygen Permeation in Polytetrafluoroethylene Reinforced Ionomer Membranes and Their Effects on Fuel Cell Performance." Journal of The Electrochemical Society, March 18, 2024. http://dx.doi.org/10.1149/1945-7111/ad34fe.
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Abstract With the increasing need for high power density of proton exchange membrane fuel cells, new composite membranes have been explored for superior proton transport and gas impermeability. These membranes’ physicochemical properties usually deviate from existing empirical formulas, which are poorly understood, especially when mechanical deformation occurs. This poor understanding hinders development of novelty membranes and their fuel cell applications. Here, using polytetrafluoroethylene reinforced ionomer membrane as an example, we conducted extensive water absorption experiments to determine hydration levels at different water activities. Molecular dynamics simulations and electrochemical impedance spectroscopy were used to investigate the impacts of hydration level, external electric field strength, and tensile deformation on proton transport and electroosmotic drag coefficient, as well as the impact of hydration level and free volume ratio on oxygen permeability. We proposed mathematical correlations for these impacts and incorporated them into a single-cell voltage model to analyze their effects on fuel cell performance. Results show that an increase in the electric field strength alters the proton transport pattern, but has minimal impact on the electro-osmosis coefficient. The oxygen permeability coefficient of a deformed membrane with a free volume ratio of 28.57% is more than two orders of magnitude higher than that of a non-deformed membrane. The electro-osmatic drag coefficient imposes a larger influence on fuel cell performance than oxygen permeability
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Gu, Yueyuan, Jucai Wei, Xu Wu, and Xiaoteng Liu. "A study on improving the current density performances of CO2 electrolysers." Scientific Reports 11, no. 1 (2021). http://dx.doi.org/10.1038/s41598-021-90581-0.
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AbstractElectrochemical CO2 reduction reaction (CO2RR) technology can reduce CO2 emission with converting excess electrical energy to high-value-added chemicals, which however needs further improvement on the electrolyser cell performance. In this work, extensive factors were explored in continuous CO2 electrolysers. Gold, one of the benchmark materials for CO2RR to produce CO, was used as the catalyst. Electrolyser configurations and membrane types have significant influences on cell performance. Compact MEA-constructed gas-phase electrolyser showed better catalytic performance and lower energy consumption. The gas diffusion electrode with a 7:1 mass ratio of total-catalyst-to-polytetrafluoroethylene (PTFE) ionomer exhibited the best performance. At a low total cell voltage of 2.2 V, the partial current density of CO production achieved 196.8 mA cm−2, with 90.6% current efficiency and 60.4% energy efficiency for CO producing respectively. Higher CO selectivity can be achieved using anion exchange membranes, while higher selectivity for hydrogen and formate products can be achieved with cation exchange membranes. This research has pointed out a way on how to improve the CO2RR catalytic performance in flow cells, leaving aside the characteristics of the catalyst itself.
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Al-Hezaimi, Khalid, Giovanna Iezzi, Ivan Rudek, et al. "Histomorphometric Analysis of Bone Regeneration Using a Dual Layer of Membranes (dPTFE Placed Over Collagen) in Fresh Extraction Sites: A Canine Model." May 28, 2013. https://doi.org/10.1563/aaid-joi-d-13-00027.
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In untreated extraction sockets, buccal bone remodeling compromises the alveolar ridge width. The aim of this study was to histologically assess the efficacy of using a dual layer of membranes (high-density polytetrafluoroethylene [dPTFE] placed over collagen) for ridge preservation in fresh extraction sites. Eight beagle dogs were used. After endodontic treatment of mandibular bilateral second (P2), third (P3), and fourth (P4) premolars, mandibular bilateral first premolars and distal roots of P2, P3, and P4 were extracted atraumatically. Animals were randomly divided into 4 treatment groups. group 1, the control group, received no treatment; in group 2, allograft was placed in the alveolum and the socket covered with dPTFE membrane; in group 3, allograft was placed in the alveolum, the buccal plate was overbuilt with allograft, and the socket was covered with dPTFE membrane; in group 4, allograft was placed in the alveolum and covered with dual layer of membranes (dPTFE placed over collagen). No intent of primary closure was performed for all groups. After 16 weeks, the animals were sacrificed and mandibular blocks were assessed histologically for buccolingual width of alveolar ridge, percentage of bone formation and bone marrow spaces, and the remaining bone particles. The buccolingual width of the alveolar ridge was significantly higher among sockets in group 4 than in group 1 (P &lt; .05). the amount of newly formed bone in each socket was higher in extraction sockets in group 4 than in groups 1, 2, and 3 (P &lt; .001). A significant difference was found in the percentage of bone marrow spaces among all groups (P &lt; .001). No significant difference was found in the number of nonresorbed bone particles among the groups. Using a dual layer of membrane was more effective in ridge preservation than conventional socket augmentation protocols.
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Amaral Valladão, Carlos Alberto, Mabelle Freitas Monteiro, and Julio Cesar Joly. "Guided bone regeneration in staged vertical and horizontal bone augmentation using platelet-rich fibrin associated with bone grafts: a retrospective clinical study." International Journal of Implant Dentistry 6, no. 1 (2020). http://dx.doi.org/10.1186/s40729-020-00266-y.
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Abstract Background The use of guided bone regeneration (GBR) for vertical and horizontal bone gain is a predictable approach to correct the bone defects before implant installation; however, the use of different protocols is associated with different clinical results. It is suggested that platelet-rich fibrin (PRF) could improve the outcomes of regenerative procedures. Thus, this study aimed to describe the bone gain associated with GBR procedures combining membranes, bone grafts, and PRF for vertical and horizontal bone augmentation. Materials and methods Eighteen patients who needed vertical or horizontal bone regeneration before installing dental implants were included in the study. The horizontal bone defects were treated with a GBR protocol that includes the use of a mixture of particulate autogenous and xenogenous grafts in the proportion of 1:1, injectable form of PRF (i-PRF) to agglutinate the graft, an absorbable collagen membrane covering the regenerated region, and leukocyte PRF (L-PRF) membrane covering the GBR membrane. The vertical bone defects were treated with the same grafted mixture protected by a titanium-reinforced non-resorbable high-density polytetrafluoroethylene (d-PTFE-Ti) membrane and covered by L-PRF. The bone gain was measured using a cone-beam computed tomography at baseline and after a period of 7.5 (± 1.0) months. Results All patients underwent surgery to install implants after this regenerative protocol. The GBR produces an increase in bone thickness (p < 0.001) and height (p < 0.005) after treatment, with a bone gain of 5.9 ± 2.4 for horizontal defects and 5.6 ± 2.6 for vertical defects. In horizontal defects, the gain was higher in the maxilla than in mandible (p = 0.014) and in anterior than the posterior region (p = 0.033). No differences related to GBR location were observed in vertical defects (p > 0.05). Conclusion GBR associated with a mixture of particulate autogenous and xenogenous grafts and i-PRF is effective for vertical and horizontal bone augmentation in maxillary and mandibular regions, permitting sufficient bone gain to future implant placement. Trial registration REBEC, RBR-3CSG3J. Date of registration—19 July 2019, retrospectively registered. http://www.ensaiosclinicos.gov.br/rg/RBR-3csg3j/
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Fatima, Masoom, Yohannes Kiros, Robina Farooq, and Rakel W. Lindström. "Low-Cost Single Chamber MFC Integrated With Novel Lignin-Based Carbon Fiber Felt Bioanode for Treatment of Recalcitrant Azo Dye." Frontiers in Energy Research 9 (June 21, 2021). http://dx.doi.org/10.3389/fenrg.2021.672817.
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A flow through anaerobic microbial fuel cell (MFC) was designed and optimized for efficient treatment of recalcitrant textile wastewater. The membrane-less MFC was first time fabricated with a unique combination of electrodes, a novel bioanode of synthesized lignin-based electrospun carbon fiber supporting a biofilm of Geobacter sulfurreducens for acetate oxidation and an air-breathing cathode, consisting of a pyrolyzed macrocycle catalyst mixture on carbon bonded by polytetrafluoroethylene (PTFE). The effects of different organic loadings of acetate along with Acid Orange (AO5), operation time and ionic strength of auxiliary salts (conductivity enhancers) were investigated and responses in terms of polarization and degradation were studied. In addition, the decomposition of the organic species and the degradation of AO5 along with its metabolites and degraded products (2-aminobenzenesulfonic acid) were determined by chemical oxygen demand (COD) analysis, UV-Vis spectrophotometry and high-performance liquid chromatography (UV-HPLC) techniques. SEM and TEM images were also used to find out the biocompatibility of the microbes on lignin-based electrospun carbon felt anode and the morphology of the cathode. Reduction and breakage of the azo bond of AO5 occurs presumably as a side reaction, resulting in the formation of 2-aminobenzenesulfonic acid and unidentified aromatic amines. Maximum current density of anode 0.59 Am−2 and power density of 0.12 Wm−2 were obtained under optimized conditions. As a result, decolouration of AO5 and chemical oxygen demand (COD) removal efficiency was 81 and 58%, respectively. These results revealed that the low-cost MFC assembly can offer significant potential for anaerobic decolouration of recalcitrant textile wastewater.
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Windisch, Peter, Kristof Orban, Giovanni E. Salvi, Anton Sculean, and Balint Molnar. "Vertical-guided bone regeneration with a titanium-reinforced d-PTFE membrane utilizing a novel split-thickness flap design: a prospective case series." Clinical Oral Investigations, October 10, 2020. http://dx.doi.org/10.1007/s00784-020-03617-6.
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Abstract Objectives To evaluate the feasibility of a newly proposed minimally invasive split-thickness flap design without vertical-releasing incisions for vertical bone regeneration performed in either a simultaneous or staged approach and to analyze the prevalence of adverse events during postoperative healing. Materials and methods Following preparation of a split-thickness flap and bilaminar elevation of the mucosa and underlying periosteum, the alveolar bone was exposed over the defects, vertical GBR was performed by means of a titanium-reinforced high-density polytetrafluoroethylene membrane combined with particulated autogenous bone (AP) and bovine-derived xenograft (BDX) in 1:1 ratio. At 9 months after reconstructive surgery, vertical and horizontal hard tissue gain was evaluated based on clinical and radiographic examination. Results Twenty-four vertical alveolar ridge defects in 19 patients were treated with vertical GBR. In case of 6 surgical sites, implant placement was performed at the time of the GBR (simultaneous group); in the remaining 18 surgical, sites implant placement was performed 9 months after the ridge augmentation (staged group). After uneventful healing in 23 cases, hard tissue fill was detected in each site. Direct clinical measurements confirmed vertical and horizontal hard tissue gain averaging 3.2 ± 1.9 mm and 6.5 ± 0.5 mm respectively, in the simultaneous group and 4.5 ± 2.2 mm and 8.7 ± 2.3 mm respectively, in the staged group. Additional radiographic evaluation based on CBCT data sets in the staged group revealed mean vertical and horizontal hard tissue fill of 4.2 ± 2.0 mm and 8.5 ± 2.4 mm. Radiographic volume gain was 1.1 ± 0.4 cm3. Conclusion Vertical GBR consisting of a split-thickness flap and using titanium-reinforced non-resorbable membrane in conjunction with a 1:1 mixture of AP+BDX may lead to a predictable vertical and horizontal hard tissue reconstruction. Clinical relevance The used split-thickness flap design may represent a valuable approach to increase the success rate of vertical GBR, resulting in predicable hard tissue regeneration, and favorable wound healing with low rate of membrane exposure.
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Kwon, Sung Hyun, So Young Lee, Hyoung-Juhn Kim, Sung-Dae Yim, Young-Jun Sohn, and Seung Geol Lee. "Multiscale simulation approach to investigate the binder distribution in catalyst layers of high-temperature polymer electrolyte membrane fuel cells." Scientific Reports 12, no. 1 (2022). http://dx.doi.org/10.1038/s41598-021-04711-9.
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AbstractA multiscale approach involving both density functional theory (DFT) and molecular dynamics (MD) simulations was used to deduce an appropriate binder for Pt/C in the catalyst layers of high-temperature polymer electrolyte membrane fuel cells. The DFT calculations showed that the sulfonic acid (SO3−) group has higher adsorption energy than the other functional groups of the binders, as indicated by its normalized adsorption area on Pt (− 0.1078 eV/Å2) and carbon (− 0.0608 eV/Å2) surfaces. Consequently, MD simulations were performed with Nafion binders as well as polytetrafluoroethylene (PTFE) binders at binder contents ranging from 14.2 to 25.0 wt% on a Pt/C model with H3PO4 at room temperature (298.15 K) and operating temperature (433.15 K). The pair correlation function analysis showed that the intensity of phosphorus atoms in phosphoric acid around Pt ($${\rho }_{\mathrm{P}}{g}_{\mathrm{Pt}-\mathrm{P}}\left(r\right)$$ ρ P g Pt - P r ) increased with increasing temperature because of the greater mobility and miscibility of H3PO4 at 433.15 K than at 298.15 K. The coordination numbers (CNs) of Pt–P(H3PO4) gradually decreased with increasing ratio of the Nafion binders until the Nafion binder ratio reached 50%, indicating that the adsorption of H3PO4 onto the Pt surface decreased because of the high adsorption energy of SO3− groups with Pt. However, the CNs of Pt–P(H3PO4) gradually increased when the Nafion binder ratio was greater than 50% because excess Nafion binder agglomerated with itself via its SO3− groups. Surface coverage analysis showed that the carbon surface coverage by H3PO4 decreased as the overall binder content was increased to 20.0 wt% at both 298.15 and 433.15 K. The Pt surface coverage by H3PO4 at 433.15 K reached its lowest value when the PTFE and Nafion binders were present in equal ratios and at an overall binder content of 25.0 wt%. At the Pt (lower part) surface covered by H3PO4 at 433.15 K, an overall binder content of at least 20.0 wt% and equal proportions of PTFE and Nafion binder are needed to minimize H3PO4 contact with the Pt.
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Shao, Runze, Guilong Wang, Jialong Chai, Guizhen Wang, and Guoqun Zhao. "Flexible, Reliable, and Lightweight Multiwalled Carbon Nanotube/Polytetrafluoroethylene Membranes with Dual‐Nanofibrous Structure for Outstanding EMI Shielding and Multifunctional Applications." Small, January 4, 2024. http://dx.doi.org/10.1002/smll.202308992.
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AbstractIn this study, lightweight, flexible, and environmentally robust dual‐nanofibrous membranes made of carbon nanotube (CNT) and polytetrafluoroethylene (PTFE) are fabricated using a novel shear‐induced in situ fibrillation method for electromagnetic interference (EMI) shielding. The unique spiderweb‐like network, constructed from fine CNTs and PTFE fibrils, integrates the inherent characteristics of these two materials to achieve high conductivity, superhydrophobicity, and extraordinary chemical resistance. The dual‐nanofibrous membranes demonstrate a high EMI shielding effectiveness (SE) of 25.7–42.2 dB at a thickness range of 100–520 µm and the normalized surface‐specific SE can reach up to 9931.1 dB·cm2·g−1, while maintaining reliability even under extremely harsh conditions. In addition, distinct electrothermal and photothermal conversion properties can be achieved easily. Under the stimulation of a modest electrical voltage (5 V) and light power density (400 mW·cm−2), the surface temperatures of the CNT/PTFE membranes can reach up to 135.1 and 147.8 °C, respectively. Moreover, the CNT/PTFE membranes exhibit swift, stable, and highly efficient thermal conversion capabilities, endowing them with self‐heating and de‐icing performance. These versatile, flexible, and breathable membranes, coupled with their efficient and facile fabrication process, showcase tremendous application potential in aerospace, the Internet of Things, and the fabrication of wearable electronic equipment for extreme environments.
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Huang, Jing, Travis Ward, and Amir Faghri. "Optimizing the Anode Structure of a Passive Tubular-Shaped Direct Methanol Fuel Cell to Operate With High Concentration Methanol." Journal of Fuel Cell Science and Technology 9, no. 5 (2012). http://dx.doi.org/10.1115/1.4007274.
Full textAbstract:
In order to take full advantage of the high energy density available in methanol fuel, one must use high concentration methanol in direct methanol fuel cells (DMFCs). However, this causes severe methanol crossover and leads to low power density and fuel efficiency. In this work, a tubular shape is adopted to generate higher volumetric power density; porous polytetrafluoroethylen (PTFE) membranes at the anode are used to control methanol transport with a high concentration fuel. A novel passive tubular-shaped DMFC is improved to achieve stable operation with methanol concentrations up to 20 M. It is observed that a balance between fuel transport resistance, power density, energy density, and fuel efficiency exists. Increased resistance enhances fuel efficiency, hence, energy density, but limits the fuel supply and causes low power density. With the improved anode structure and higher concentration fuel (1 M to 15 M), the energy output of the tubular DMFC increases 591%, from 0.094 Wh to 0.65 Wh with 2 ml fuel. The power densitymaintains the same level as 16 mW/cm2. For different fuel concentrations, there exists an optimum structure to generate the highest power density, which is a result of minimizing the methanol crossover while also providing sufficient fuel. The discharge characteristic at constant voltage and its effect on fuel efficiency are also discussed.