Добірка наукової літератури з теми "Chemo-mechanical issues"

The materials and the structure of solid oxide fuel cells are designed to avoid thermo-mechanical damages under various operation conditions. However, inherent risk of chemo-mechanical failures are still not fully understood. This paper aims to review the recent works related to this topic, and to address some issues which have not been widely recognized. The coupling of chemistry and mechanics are classified into four types, i.e. (1) chemically driven strain, (2) chemically modified mechanical properties, (3) mechanically driven chemical reactions, and (4) mechanically modified chemical (physical) properties. Since chemical energies are much larger than mechanical energy accommodated in SOFC, the former two types (type(1) and (2)) of chemo-mechanical coupling have been recognized as more important than the others, and have been studied intensively. An example of type-1 phenomena is chemical expansion of mixed conducting oxides with e.g. (La,Sr)(Co,Fe)O3 cathode, LaCrO3 based interconnect, and CeO2 based or (La,Sr)(Ga,Mg,Co)O3 electrolytes. Since the transient behavior as well as steady state distribution of oxygen potential inside the constituent solids is essential to know the effect of the chemical strain, Terada et al. developed a computer code “SIMUDEL” of an FEM-based calculation of oxygen potential. This code considers “chemical capacitance” due to nonstoichiometry of the materials to treat the transient responses, and the results of the calculation can be transported into some of major commercial programs for structure analysis. Volume change of a nickel cermet anode is also an important feature of type-1 coupling which must be considered in determining fabrication and operation processes. The electrode shrinks on reduction and expands on re-oxidation as expected from the lattice size of the metal and the oxide. However, under certain conditions, a porous cermet was found to “shrink” upon oxidation. It took place only during light re-oxidation around 400C. Under this condition the formation of NiO was not obvious from XRD, whereas weight gain was observed by thermo-gravimetry. Careful observation of the microstructure of a porous Ni revealed that, upon shrinkage, the particle-to-particle separation changed partly due to the neck growth between the particles and to the change of the connection angle of the particles. Further study is underway to elucidate the detailed mechanism of the oxidation-induced shrinkage. The change of mechanical properties such as elastic moduli and fracture strength are also dependent on defect concentration and its motion in the lattice (type-2 coupling). Young’s modulus of nonstoichiometric oxides show dependences not only on temperature but also on pO2 through the change of defect concentration. Also, domain boundary shift of ferroelastic phase of LSCF was found to be correlated with the defect concentration. As is discussed for the anomaly of Young’s modulus of YSZ around 400˚C, the motion of oxide ion vacancies may also have correlation with the ferroelastic strain observed with Sc and Ce doped ZrO2 electrolyte above 300˚C. Another interesting type-2 coupling is with the lightly oxidized Ni cermet electrode. It was found that the creep rate of Ni-YSZ cermet at 400˚C was dramatically increased when oxygen-containing gas was introduced. This may be by a correlated mechanism with the above mentioned oxidation induced shrinkage. Several reports, including those from our group, have been published on the effect of mechanical stress on defect formation (type-3 coupling) of nonstoichiometric oxides determined by experiments or by calculation. As is expected from thermodynamic consideration, the experimentally determined effect was not large, e.g. 1G Pa stress was equivalent to 1/5 order of magnitude shift of chemical potential of oxygen for nonstoichiometry of LSCF. Similarly, only minor effect on a practical system was reported for type-4 coupling. However, those phenomena can have significant effect on long-term stability if cation mobility and their driving force are modified at a strained interfaces or grain boundaries.

Environmental variables such as temperature, matric suction and pore fluid composition are well known to influence the hydro-mechanical behavior of clays and shales. The type and the relevance of this influence depends on the mineralogical composition and on the fabric of the material. Soil activity is an engineering proxy for mineralogical composition which can be used for a preliminary characterization of the expected type of behaviour under chemical actions, if those do not imply very significant cation exchange or pH variations. Very large chemo-mechanical effects occur in highly active soils used in engineering works such as barriers for nuclear waste or landfills, however concentration changes also impact on the mechanical behavior of non – active soils and rocks, such as illitic or natural blends of clays. Such materials are widely distributed in nature and their mechanical response upon chemical changes can be problematic in many cases. Examples of engineering relevance include vast slope instabilities promoted by fabric changes due to desalinization in Scandinavian quick clays, and instability or convergence issues for boreholes drilled in shales exposed to muds with a different chemical composition from the one of the pore fluid. An elastoplastic model is formulated to simulate the volumetric behaviour of such materials along chemical and mechanical loads. In addition to the parameters of the Modified Cam Clay, it requires defining the dependency of the elasto-plastic compliance and reference void ratio on pore fluid salinity. The model performs well against experiments from literature where complex chemo-mechanical histories were imposed.

It has been shown that in the last decades nanotechnology plays a key role not only in science but more and more often in industry as well. Recent research has shown that agricultural waste is a possible feedstock to produce nanocellulose which can be used for different applications, such as a biosensor, semiconductor and reinforcing agent. The use of agro-waste as a precursor not only offers advantages for raw material costs, but also for the climate, low processing costs, availability and convenience. It also helps to address environmental issues, such as illness, foul odor and concerns with indoor use. Different processes, such as chemical treatment, mechanical treatment and chemo-mechanical treatment, have been used to extract nanocellulose from agro-waste. This article highlights the latest technologies used to acquire agro-waste nanocellulose, as well as existing advances in and applications of nanocellulose technologies.

We have analyzed the detection of microcantilevers utilized in biosensing chips. First, the primary deflection due to the chemical reaction between the analyte molecules and the receptor coating, which produces surface stresses on the receptor side is analyzed. Oscillating flow conditions, which are the main source of turbulence in cantilever based biosensing chips, are found to produce substantial deflections in the microcantilever at relatively large frequency of turbulence. Then mechanical design and optimization of piezoresistive cantilevers for biosensing applications is studied. Models are described for predicting the static behavior of cantilevers with elastic and piezoresistive layers. Chemo-mechanical binding forces have been analyzed to understand issues of saturation over the cantilever surface. Furthermore, the introduction of stress concentration regions during cantilever fabrication has been discussed which greatly enhances the detection sensitivity through increased surface stress, and novel microcantilever assemblies are presented for the first time that can increase the deflection due to chemical reaction. Finally an experiment was made to demonstrate the shift of resonant frequency of cantilever used as biosensor. The relation between resonant frequency shift and the surface stress was analyzed.

The use of reclaimed and devulcanised material in virgin rubber compounds has attracted the attention of many rubber industries due to increasing raw material costs, diminishing resources and growing awareness of environmental issues. Several methods have been developed to reclaim rubber waste, for example, thermo-and chemo-mechanical processes, microwave regeneration, microbial action and ultrasonic regeneration. However, extensive research on processes for high-quality recycling materials based on waste tyres is still lacking. In this study, optimised processing conditions for the devulcanisation of whole passenger car tyres using diphenyldisulphide (DPDS) as a devulcanisation aid will be applied. The devulcanised ground tyre rubber (D-GTR) obtained from the process was blended on top of the original tyre tread formulation at different concentrations. The results so far indicate that the addition of D-GTR influences the properties of the blend, but to a lesser extent than the commercially used powder or reclaim types do, for which loadings less than 5% can be applied. The main reason for the influence of D-GTR on the rubber properties is inhomogeneities in the D-GTR/virgin rubber blend and quality aspects of raw GTR.

Peri-implantitis is the major cause of the failure of dental implants. Since dental implants have become one of the main therapies for teeth loss, the number of patients with peri-implant diseases has been rising. Like the periodontal diseases that affect the supporting tissues of the teeth, peri-implant diseases are also associated with the formation of dental plaque biofilm, and resulting inflammation and destruction of the gingival tissues and bone. Treatments for peri-implantitis are focused on reducing the bacterial load in the pocket around the implant, and in decontaminating surfaces once bacteria have been detached. Recently, nanoengineered titanium dental implants have been introduced to improve osteointegration and provide an osteoconductive surface; however, the increased surface roughness raises issues of biofilm formation and more challenging decontamination of the implant surface. This paper reviews treatment modalities that are carried out to eliminate bacterial biofilms and slow their regrowth in terms of their advantages and disadvantages when used on titanium dental implant surfaces with nanoscale features. Such decontamination methods include physical debridement, chemo-mechanical treatments, laser ablation and photodynamic therapy, and electrochemical processes. There is a consensus that the efficient removal of the biofilm supplemented by chemical debridement and full access to the pocket is essential for treating peri-implantitis in clinical settings. Moreover, there is the potential to create ideal nano-modified titanium implants which exert antimicrobial actions and inhibit biofilm formation. Methods to achieve this include structural and surface changes via chemical and physical processes that alter the surface morphology and confer antibacterial properties. These have shown promise in preclinical investigations.

e290 Background: There are a myriad of experiences reported from various cancer survivors, but few individuals have been involved with cancer drug development, speaking publicly to prostate cancer groups, working privately with prostate cancer survivors and studying the psychosocial aspects of post treatment patients. Methods: N/A Results: The postsurgical and post treatment issues , particularly ED are either not discussed by the patient due to embarrassment or lack of knowledgeable of the type of questions to ask, or not addressed directly by the HCP. Unlike other oncological disciplines, the prostate cancer patient is confronted with major decisions on which treatment approach to choose from which therapeutic discipline. The clinicians they are meeting are explaining their expertise on radiation, surgery, chemo, or other interventions leading the patient to become overwehlemed at these choices. There are few “neutral” voices talking to the patient on which procedure or treatment would suit him best. In addition to the treatment decisions the patient is also told about watch and wait approach. Besides the tough decision for the patient to choose the right approach for himself, he is shown data by each treatment specialty from postsurgical & other treatments relative to the percentage success rates for ED and continence that the patient may expect. These numbers through data from the participating surgical centers etc are typically very inflated. Many patients leave thinking they will return to normal function in x amount of months, only to find that they are quite dysfunctional for much longer or in some cases never gaining functionality. The last part of the discussion is what is available for these men with continuing dysfunction. Potential options exist but for many men they are met with mixed results. The treatments for ED are quite expensive to most men, and in many cases do not work. When the diesterase inhibitors fail to work for the patient, options for ED remain vary greatly-from mechanical interventions to various chemical and pharmacological approaches, and the patient has no voice to turn to get non biased information needed to help with the next steps. Conclusions: Suggestions for the HCP.

Abstract With genomic instability being a hallmark of cancer, heterogeneity within solid tumors is prevalent. Intra-tumoral heterogeneity contributes strongly to clinical outcomes. In fact, heterogeneity is often cited as a driver of therapeutic failure, chemo-resistance, and recurrence of disease. Current bulk profiling analysis of tumors is limited in its ability to provide the level of granularity necessary for uncovering aspects of heterogeneity that contribute to poor outcomes. Thus, it is imperative to gain a deeper understanding of tumors at the single-cell level. To properly analyze tumor heterogeneity at the single-cell level it is critical that quality methods for tissue dissociation and cell purification be utilized. While the most frequently used workflows rely on a combination of enzymatic and mechanical dissociation of the tissue followed by RBC lysis to remove contaminating red blood cells, these approaches tend to be harsh on cells leading to activation of cell stress pathways or even the loss of target cells due to their death during processing. The analysis of tumor heterogeneity has long been hampered by issues with low yield and sample preparation-induced alterations in cell physiology. To alleviate these issues, we present a workflow that couples Cellsonics’ SimpleFlow™ with Akadeum’s Buoyancy Activated Cell Sorting (BACS™) Microbubbles for gentle and effective tumor dissociation and clean-up that does not compromise precious samples. Cellsonics’ SimpleFlow™ system features the proprietary Bulk Lateral Ultrasonic™ (BLU™) energy to generate single cells from solid tissue with unparalleled speed, quality, and sample integrity. SimpleFlow™ is engineered to enable any lab to obtain the full spectrum of heterogeneous cell populations while maintaining the native gene expression patterns across all cell types. Single cell samples can be generated from solid tissues in 4-10 minutes under cold temperature without the use of enzymes. Akadeum’s BACS™ Microbubble technology features low-density microbubbles that are functionalized to capture an array of analytes including particular cell types. Akadeum’s BACS™ Microbubbles enable the purification of cell types of interest quickly, easily, and without sacrificing cell health and physiology. In this study, The SimpleFlow™ system was used to dissociate fresh tissues from mice to obtain a heterogeneous suspension of single cells. Following the dissociation, up to 99% of RBCs were removed from samples using Akadeum’s Mouse RBC Depletion. In subsequent studies, cancer cells were spiked into tissue samples prior to processing to assess their recovery and physiology. The novel workflow presented here combing SimpleFlow™ and microbubbles demonstrates the recovery of the full spectrum of cells and did not harm tumor cell recovery or health. Citation Format: Chananat Klomsiri, Edward Grimley, Jon Roussey, Carolina Livi, Casey Wegner, Brandon H. McNaughton, Steve Levers, Vibhu Vivek, Dan Snyder, Doug Summers, Ma Phiengsai. Novel workflow enables enhanced tissue dissociation and gentle clean-up for single cell applications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6089.

Silicon wafer thinning process is meeting great challenges to fulfill requirements of ultra-thin IGBT for automotive applications. Chemo-mechanical grinding (CMG) process is potentially emerging stress relief thinning process which combines the advantages of fixed abrasive machining and chemical mechanical polishing (CMP). A major issue in CMG of Si wafers is the relatively low material removal rate (MRR). This paper studies the influence of the wheel specifications and grinding conditions on the MRR of CMG. Two sets of three-factor two-level full factorial designs of experiment (DOE)[1] are employed to reveal the main effects and interacted effects of CMG wheel specifications and grinding parameters on MRR. The optimal combination scenarios for improving MRR of CMG are analysized and obtained. By use of the optimal CMG wheel and grinding parameters, the MRR of more than 60nm/min is achieved.

Chemo-mechanical grinding (CMG) process is a promising process for large-sized Si substrate fabrication at low cost. An encountered issue in current CMG process of Silicon (Si) wafers is metallic contaminations on ground Si wafer surface, which is attributed to the existence of sodium carbonate in wheel compounds. In this paper, four different CMG wheels were developed and grinding experiments were conducted to study the effects of exclusion of sodium carbonate and concentration of ceria abrasive on grinding performance. The grinding characteristics of the four wheels were analysized and discussed to reveal the effects of different compositions.

Les batteries, qui constituent l'une des technologies de stockage d'énergie les plus polyvalentes, sont essentielles dans un large spectre d'applications telles que les réseaux électriques, l'aérospatiale, la robotique, et les véhicules électriques. Cette dépendance rend la qualité, la fiabilité, la durée de vie et la sécurité des batteries immensément plus importantes que jamais. Cela confirme la nécessité de surveiller avec précision l'état fonctionnel des batteries et appelle donc au développement de techniques de détection intelligente dans ces dispositifs. Cette thèse vise à explorer ce sujet en utilisant des capteurs à fibre optique à réseau de Bragg (FBG). Pour commencer, nous donnons un aperçu historique de l'évolution de la surveillance des batteries, avant de nous concentrer sur la détection optique. Ensuite, nous démontrons la faisabilité de l'incorporation de capteurs FBG à l'intérieur de cellules cylindriques et de poches commerciales pour effectuer une calorimétrie optique. Ensuite, en utilisant le même capteur optique, on étudie la contrainte chimico-mécanique qui se produit au niveau de l'électrode dans des cellules contenant un électrolyte liquide ou solide. Pour la validation du concept, des électrodes en alliage de Li qui présentent d'importants changements de volume lors de l'insertion ou du retrait de Li sont sélectionnées. Au cours de cette thèse, le signal optique surveillé pendant le cyclage de la batterie est traduit soit en température, pression ou stress et corrélé avec le profil de voltage. Enfin, ce travail propose une technique operando avec une utilisation potentiellement efficace pour le diagnostic des cellules et le design des batteries
Rechargeable batteries, as one of the most versatile energy storage technologies, are essential in a broad range of applications such as power grids, aerospace, robotics, consumer electronics, and electric vehicles. Such dependence makes battery quality, reliability, lifetime, and safety (QRLS) immensely more important than ever before. This underlines the need to accurately monitor the batteries’ functional status and therefore calls for the development of non-invasive operando techniques that could inject smart sensing functionalities into these dynamic electrochemical devices directly from inside. This is exactly what this thesis aims to explore by using optical fiber Bragg grating (FBG) sensors. To begin with, we first provide an historical overview of the evolution of battery monitoring, before focusing on optical sensing. Then, we demonstrate the feasibility of incorporating FBG sensors inside commercial pouch and cylindrical cells to perform optical calorimetry, hence assessing chemical events such as solid electrolyte interphase formation or thermodynamic parameters. Next, by using the same optical sensor, the chemo-mechanical stress occurring at the electrode level in cells containing either liquid or solid-state electrolyte is investigated. For proof-of-concept, Li-alloying electrodes that undergo large volume changes upon Li uptake or removal are selected. More specifically, throughout this thesis the optical signal monitored during battery cycling is translated into either temperature, pressure or stress and correlated with the voltage profile. To sum up, this work proposes an operando technique with potential use in cell diagnosis and battery designs

La thèse qui suit est organisée en deux volets: un premier volet portant sur les modèles de masse de galaxies et un second volet sur la conception de revêtements optiques et le contrôle de leurs propriétés mécaniques. Les modèles de masse présentés dans cette thèse ont été réalisés sur un sous-échantillon de dix galaxies de l'étude SINGS comprenant neuf galaxies normales et une galaxie naine. Ce travail visait à fixer le rapport masse-luminosité du disque à tout rayon en utilisant les résultats de modèles d'évolution galactique chimio-spectrophotométriques ajustés spécifiquement à chaque galaxie grâce à son profil de photométrie multi-bandes. Les résultats montrent que les disques stellaires tels que normalisés par les rapports masse-luminosité issus des modèles ont des masses cohérentes dans toutes les bandes étudiées de l'ultra-violet, du visible ainsi que du proche infrarouge (bandes FUV à IRAC2). Ces disques peuvent être considérés comme maximaux par rapport aux données cinématiques des galaxies étudiées. Ceci est dû au fait que le rapport M/L est plus élevé au centre que sur les bords. Les disques étant maximaux et physiquement justifiés, on ne peut dès lors ignorer les effets de composants tels que les bulbes ou les barres et les corrections nécessaires doivent être apportées aux profils de luminosité et de vitesses de rotation de la galaxie. Dans les travaux de la seconde partie, le logiciel en développement libre OpenFilters a été modifié afin de tenir compte des contraintes mécaniques dans la conception numérique de revêtements optiques. Les contraintes mécaniques dans les couches minces ont un effet délétère sur leurs performances optiques. Un revêtement destiné à rendre réflectives les lames d'un étalon Fabry-Perot utilisé en astronomie a été conçu et fabriqué afin d'évaluer les performances réelles de la méthode. Ce cas a été choisi à cause de la diminution de la finesse d'un étalon Fabry-Perot apporté par la courbure des lames sous l'effet des contraintes. Les résultats montrent que les mesures concordent avec les modèles numériques et qu'il est donc possible à l'aide de ce logiciel d'optimiser les revêtements pour leur comportement mécanique autant que pour leurs propriétés optiques.
The following thesis includes two parts: the first concentrates on mass models of galaxies while the second concerns the design of broadband optical coatings and the control of their mechanical properties. Mass models presented here were performed on a subsample of ten galaxies from the SINGS survey. It includes nine late-type regular galaxies as well as a dwarf galaxy. The work consisted in the determination at all radii of M/L ratio of galactic discs by choosing, amongst a grid of chemospectrophotometric galactic evolution models, the one that fits better the galaxy's multi-band photometric profile. Results from this work show that stellar discs weighted by the model's mass-to-luminosity ratio display consistent masses in all studied bands from the ultraviolet to the near-infrared (FUV to IRAC2 bands). The resulting discs are physically motivated and maximal, due to their mass-to-luminosity ratio being higher in the center of the galaxies than at their outskirts. In this maximal-disc situation, bars and bulges of galaxies can no longer be ignored and the appropriate corrections need to be made on the luminosity or circular velocity profiles of the galaxy. In the second part, an additional module of the open source software Open Filters was written in order to take into account the mechanical properties of thin films in the design of optical coatings. The mechanical stresses arising in optical coatings can have a deleterious effect on the optical performances of coatings, and this tool was meant to provide design capacities to minimize this effect. Broadband reflective coatings for Fabry-Perot plates were designed and fabricated as a proof of concept of the method. This specific case was interesting because the curvature induced by mechanical stresses induces decrease of the finesse of Fabry-Perot etalons. Actual curvature of the deposited samples are coherent with the numerical calculations and undergo a substantial reduction for the two strategies devised here with this new design too. We therefore conclude that it is possible with this new software module to optimize coatings for their mechanical behaviour as well as for their optical properties.

The December 2001 [1, 2] edition of the International Technology Roadmap for Semiconductors [3] (ITRS-2001) identifies several challenges for the manufacturing of silicon and silicon-on-insulator (SOI) wafers. For silicon, edge exclusion, site flatness and nanotopography1 requirements will become extremely challenging. For SOI, requirements for the control of the top silicon layer and its associated uniformity are pushing the limits of metrology. Keeping ± 5% tolerances on thicknesses, gradually decreasing from more than 100nm to less than 20nm for partially depleted devices (let alone from 30 to 3nm for fully depleted devices) is exceeding the capabilities of traditional chemo-mechanical-polishing (CMP) processes [5]. This paper will briefly describe magnetorheological finishing (MRF) and its suitability for prime silicon and SOI wafer polishing. Particular emphasis will be placed on MRF’s ability to improve the global flatness and the total thickness variation (TTV) on prime silicon wafers, and to reduce the nominal thickness of the top silicon layer, while improving thickness uniformity on SOI wafers. The paper will also touch upon the process qualification issues associated with the tight requirements of the semiconductor industry.

Abstract The warpage of thermoset composite structures during the manufacturing process is a direct consequence of residual stress development. The capability to predict residual stresses is crucial to the manufacture of dimensionally accurate composite structures. This paper is focused on understanding the fundamental issues leading to residual stresses in thermoset polymer composites and their effect on the dimensional accuracy of the manufactured components. Special emphasis is placed on the simulation of autoclave curing and hot pressing. A three-dimensional coupled thermo-chemo-viscoelastic model is developed to simulate the heat transfer, curing, residual stresses and deformation of a composite part during the entire cure cycle. The predicted values of curvature for cross-ply graphite-epoxy laminates agree well with experimental observations. The numerical result indicates that a significant fraction of the residual stress develops before cooldown. Detailed studies are also performed to examine the springforward phenomenon in L-shaped composite parts. The finite element results show that mold design (male vs. female mold), mold thermal expansion, and part thickness all play an important role on the final shape of the parts.