Journal articles: 'Graphite|act'

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Yu, Yizhen, and Jian Zhang. "Pencil-drawing assembly to prepare graphite/MWNT hybrids for high performance integrated paper supercapacitors." Journal of Materials Chemistry A 5, no. 9 (2017): 4719–25. http://dx.doi.org/10.1039/c6ta10076g.

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Here we demonstrate a facile and scalable method to fabricate paper-based SCs by an improved pencil drawing strategy. Multi-walled carbon nanotubes are directly assembled onto pencil graphite flakes to form controllable graphite/MWNT frameworks, which act as high-performance electrodes.

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Ariyawong, Kanaparin, Nikolaos Tsavdaris, Jean Marc Dedulle, Eirini Sarigiannidou, Thierry Ouisse, and Didier Chaussende. "Interaction between Vapor Species and Graphite Crucible during the Growth of SiC by PVT." Materials Science Forum 778-780 (February 2014): 31–34. http://dx.doi.org/10.4028/www.scientific.net/msf.778-780.31.

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Graphite crucible in seeded sublimation growth of Silicon Carbide (SiC) single crystal does not only act as a container but also as an additional carbon source. The modeling of the growth process integrated with the etching phenomenon caused by the interaction between vapor species and the graphite crucible is shown to be able to predict the shape of the crystal front during the growth. The additional fluxes produced at the graphite part are delivered to the growing crystal mainly at the crystal periphery. The results obtained from the modeling are in good agreement with the experimental ones.

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Dias, Halley Welther Jacques, Alessandra Batista Medeiros, Cristiano Binder, João Batista Rodrigue Neto, Aloísio Nelmo Klein, and José Daniel Biasoli de Mello. "Tribological Evaluation of Turbostratic 2D Graphite as Oil Additive." Lubricants 9, no. 4 (April 15, 2021): 43. http://dx.doi.org/10.3390/lubricants9040043.

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In this study, powder technology was used to obtain Fe-SiC composites in which SiC particles act as precursors to generate a large amount of turbostratic graphite dispersed in the composite matrix. The selection of the alloy composition was studied employing Thermo-Calc® software to obtain the temperature and composition range for the stabilization of the graphite phase in iron with a high yield. The extracted turbostratic 2D graphite particles were dispersed in mineral oil in order to evaluate the potential of these particles as a lubricating oil additive. The structure and morphology of the extracted graphite were examined by Raman spectroscopy and transmission electron microscopy (TEM), indicating the highly disordered nature of turbostratic graphite. Reductions in the friction coefficient and wear rate of a tribological pair were observed when compared to the pure mineral oil and mineral oil with commercial graphite particles added. The misorientation and increase in interplanar distances of turbostratic 2D graphite induce a low degree of interaction between these atomic planes, which contributes to the low-friction coefficient and the lower wear rate obtained for this system.

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Sung, James C., Ming Yi Tsai, Cheng Shiang Chou, Pei Lum Tso, and Ying Tung Chen. "The CMP by Polishing with GiP Dressed by BODD." Advanced Materials Research 126-128 (August 2010): 1013–18. http://dx.doi.org/10.4028/www.scientific.net/amr.126-128.1013.

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Due to the continual improvement of CMP technologies, and the need for polishing delicate wafers at high speed, graphite impregnated pads (GiP) dressed by brazed organic dia mond disks (BODD) can double the throughput of wafer-pass at the reduced cost of ownership (CoO). The increased polishing rate is due to the act of nano graphite particles that absorb slurry. The nano graphite particles coated with chemical and abrasive can achieve high removal rate without causing scratches on the wafer. In addition, nano graphite particles do not stick to wafer surfaces, so they can be cleaned easily. BODD can uniquely dress GiP to create slurry channels so the pore free pad is not bottlenecked by slurry supply. This paper also demonstrated the low stress polishing by applying ultrasound during the CMP process.

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BARMAN, SONALI, G. P. DAS, and Y. KAWAZOE. "FIRST PRINCIPLES DENSITY FUNCTIONAL INVESTIGATION OF SUPPORTED TUNGSTEN CLUSTER (Wn; n = 1 TO 6) ON ANCHORED GRAPHITE (0001) SURFACE." International Journal of Computational Materials Science and Engineering 02, no. 03n04 (December 2013): 1350015. http://dx.doi.org/10.1142/s2047684113500152.

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Size-selected Wn clusters can be deposited firmly on a graphite (0001) surface using a novel technique, where the positive ions (of the same metal atom species) embedded on the graphite surface by ion implantation, act as anchors. The size selected metal clusters can then soft land on this anchored surface m [Hayakawa et al., 2009]. We have carried out a systematic theoretical study of the adsorption of Wn (n = 1-6) clusters on anchored graphite (0001) surface, using state-of-art spin-polarized density functional approach. In our first-principles calculations, the graphite (0001) surface has been suitably modeled as a slab separated by large vacuum layers. Wn clusters bond on clean graphite (0001) surface with a rather weak Van-der-Waals interaction. However, on the anchored graphite (0001) surface, the Wn clusters get absorbed at the defect site with a much larger adsorption energy. We report here the results of our first-principles investigation of this supported Wn cluster system, along with their reactivity trend as a function of the cluster size (n).

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Setlur, A. A., J. Y. Dai, J. M. Lauerhaas, P. L. Washington, and R. P. H. Chang. "Formation of graphite encapsulated ferromagnetic particles and a mechanism for their growth." Journal of Materials Research 13, no. 8 (August 1998): 2139–43. http://dx.doi.org/10.1557/jmr.1998.0299.

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Graphite encapsulated nanoparticles have numerous possible applications due to their novel properties and their ability to survive rugged environments. Evaporation of Fe, Ni, or Co with graphite in a hydrogen atmosphere results in graphite encapsulated nanoparticles found on the chamber walls. Similar experiments in helium lead to nanoparticles embedded in an amorphous carbon/fullerene matrix. Comparing the experimental results in helium and hydrogen, we propose a mechanism for the formation of encapsulated nanoparticles. The hydrogen arc produces polycyclic aromatic hydrocarbon (PAH) molecules, which can act as a precursor to the graphitic layers around the nanoparticles. Direct evidence for this mechanism is given by using pyrene (C16H10), a PAH molecule, as the only carbon source to form encapsulated nanoparticles.

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Fonseca, R. W., N. J. Miller-Ihli, C. Sparks, J. A. Holcombe, and B. Shaver. "Effect of Oxygen Ashing on Analyte Transport Efficiency Using ETV-ICP-MS." Applied Spectroscopy 51, no. 12 (December 1997): 1800–1806. http://dx.doi.org/10.1366/0003702971939866.

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Oxygen ashing has been used in electrothermal atomic absorption spectroscopy to eliminate organic matrix sample components and is particularly useful when doing direct solids analysis of biologicals using ultrasonic slurry sampling. Oxygen ashing has also proven to be useful for the analysis of slurry samples using ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS). In this work, the effect of oxygen ashing on analyte transport in USS-ETV-ICP-MS was evaluated. Oxygen ashing in the presence of Pd modifier (Pd/O2) enhances analyte transport efficiency, possibly as a result of an increase in the number of carbon particles present in the graphite furnace during the vaporization step. These carbon particles act as a physical carrier, providing a surface on which the analytes can condense to be transported more efficiently. The carbon produced at earlier times, with Pd/O2, may be the result of either dissociation or fracture of the graphite during the rapid heating of the furnace. Pd, which was initially added to act as a physical carrier, also seems to be acting as a catalyst for carbon oxidation. The shift in the carbon signal toward earlier times when using oxygen ashing was observed only when Pd was present. In addition, scanning electron micrographs of a home-made graphite platform revealed that portions of the graphite substrate were missing when Pd/O2 was used and that clearly visible pits were found in the graphite. Oxygen ashing combined with 1 μg Pd improves quantitative results by removing the organic part of the matrix present in slurry samples while enhancing analyte transport efficiency by providing carbon particles that serve as a physical carrier.

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Riposan, Iulian, Mihai Chisamera, and Stelian Stan. "The Role of Compounds in Graphite Formation in Cast Iron - A Review." Materials Science Forum 925 (June 2018): 3–11. http://dx.doi.org/10.4028/www.scientific.net/msf.925.3.

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The paper reviews original data obtained by the authors, from recent separate publications, specifically concerning graphite formation in the solidification pattern of industrial cast irons, focussing on grey iron versus ductile iron. Additional unpublished data and selected data from literature are represented in the paper. Complex compounds act as nucleation sites in commercial cast irons, generally in a three-stage graphite formation, but with different sequences: (1) first micro-compound formation is oxide/silicate in grey iron and sulphide in ductile iron; (2) the second compound nucleates on the first one, as complex manganese sulphide in grey iron and complex silicates in ductile iron; (3) graphite nucleation on the sides of stage 2 compounds, which have low crystallographic misfit with graphite. Resulphurization (Mn/S control), preconditioning with strong oxide forming elements (Al, Zr), more potent inoculants and inoculation enhancement with S, O and oxy-sulphide forming elements were found to be beneficial treatments especially in critical solidification conditions

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Riposan, Iulian, Mihai Chisamera, Stelian Stan, Eduard Stefan, and Cathrine Hartung. "Role of Lanthanum in Graphite Nucleation in Grey Cast Iron." Key Engineering Materials 457 (December 2010): 19–24. http://dx.doi.org/10.4028/www.scientific.net/kem.457.19.

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Specific investigations concerning La-contributions in graphite nucleation process in Ca,Al,La-FeSi inoculated grey cast irons were performed by using a scanning electron microscopy (SEM, EDS). It was re-confirmed that complex (Mn,X)S compounds act as major nucleation sites for graphite flakes. La was mainly concentrated in the first formed oxide-based micro-inclusions (similarly to Al), but also at an important level in the shell of (Mn,X)S compounds (accompanying Ca). It is assumed that La forms micro-inclusions later than Al, as La-reached phase surrounded Al-reached phase. Complex Al-La small micro-inclusions, as possible better nucleation sites for (Mn,X)S compounds and La-Ca presence in the shell/body of these sulphides, possible better nucleation sites for flake graphite, appear to be the peculiar effects of ferrosilicon based inoculants, which include these active elements, promoting type-A graphite, inclusively in low S-grey iron.

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Ren, Qin Xin, Ming You, Yun Bang Yao, Guang Min Wen, and Qi Zhou Cai. "Effect of Yttrium-Containing Nodulizer on the Microstructure Formation and Mechanical Properties of Heavy Section Ductile Iron Castings." Key Engineering Materials 457 (December 2010): 73–78. http://dx.doi.org/10.4028/www.scientific.net/kem.457.73.

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Ductile iron specimens with dimensions of 400mm×400mm ×450mm were prepared by treating the melt with an yttrium-containing nodulizer. The effect of yttrium on microstructure and mechanical properties was investigated, and the formation of degenerate graphite was discussed as well. The results show that the yttrium-containing nodulizer has good nodulization fading resistance for heavy section ductile iron, since the high melting point hexagonal oxide Y2O3 particles were formed from the nodulizer in the melt and those could act as heterogeneous nuclei for graphite nodule for a long time. Segregation of Ti and MgO at grain boundaries broke the austenite shell, resulting in graphite degeneration. When heavy section ductile iron castings with pearlite matrix were cast, graphite nodule size became finer and the nodularity of graphite nodules improved due to the addition of 0.01wt% Sb to the melt, and pearlite content in specimens increased due to alloying with Cu, Cr, Mo. The heavy section ductile iron tool bed was fabricated by treating the melt with the yttrium-containing nodulizer and Ni. The nodularity of the attached block was 85%~90%, tensile strength, elongation and impact toughness were 440MPa, 23.3% and 5.0J/cm2 respectively.

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Padmanabhan, Medini, Rachel Meyen, Kerri Houghton, and Miles St John. "Solvent Interface Trapping as an Effective Technique to Fabricate Graphite-Nanomaterial Composite Thin Films." MRS Advances 3, no. 1-2 (December 26, 2017): 19–23. http://dx.doi.org/10.1557/adv.2017.621.

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ABSTRACTNatural graphite can be exfoliated into thin films by trapping it at the interface between water and heptane [S. J Woltornist, A. J. Oyer, J-M. Y. Carrillo, A.V. Dobrynin, and D.H. Adamson, ACS Nano 7, 7062 (2013)]. In this work, we add functional elements into these graphitic thin films by introducing additives into the water phase prior to exfoliation. We report the successful incorporation of ZnO nanoparticles thereby enabling the composite films to act as effective ultraviolet photodetectors. In a similar manner, integration of silver nanowires is achieved, which results in an enhancement of the electrical conductivity of graphite.

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Wang, Guiquan, Xiang Chen, Yanxiang Li, and Zhongli Liu. "Effects of Inoculation on the Pearlitic Gray Cast Iron with High Thermal Conductivity and Tensile Strength." Materials 11, no. 10 (October 1, 2018): 1876. http://dx.doi.org/10.3390/ma11101876.

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With the aim of improving the thermal conductivity and tensile strength of pearlitic gray cast iron, the influence of inoculation on structure and properties was experimentally investigated. Three group of irons with similar compositions were inoculated by Zr-FeSi, Sr-FeSi, and SiC inoculants, respectively. The metallographic analysis was used to measure the maximum graphite length, primary dendrites amount and eutectic colonies counts. For a certain carbon equivalent, it was confirmed that the thermal conductivity of pearlitic gray cast iron has a direct correlation with the maximum graphite length while the tensile strength was influenced mainly by the primary dendrites amount. The optimal structure and highest thermal conductivity and tensile strength were obtained by Sr-FeSi inoculant. MnS particles act a pivotal part in modifying the structure of gray cast iron. It was found that providing nucleation sites both for graphite and primary austenite is important to promote the thermal conductivity and strength. However, excessive nuclei (MnS particles) results in shorter graphite flakes and thus the depressive growth of primary dendrites.

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Khammassi, S., M. Tarfaoui, and K. Lafdi. "Study of mechanical performance of polymer nanocomposites reinforced with exfoliated graphite of different mesh sizes using micro-indentation." Journal of Composite Materials 55, no. 19 (February 10, 2021): 2617–29. http://dx.doi.org/10.1177/0021998321993211.

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The first phase of this work aims to use the right additive nano-fillers choices, such as exfoliated Graphite (ExG), increasing the mechanical, electrical, and thermal performances. In this work, we are interested in quantifying the effect particles' size on a polymer matrix's performance. For this, three sets of exfoliated polymers filled with Graphite, characterized by three particle sizes, called meshes 50, 100, and 150, were investigated. In this analysis, exfoliated Graphite reinforced polymers were subjected to indentation tests to define local mechanical properties. The sample is an epoxy 862 matrix reinforced with exfoliated graphite additives. For each specific size, the additives are mixed in percentages of 0% in the act of control, 0.5%, 4%, 8%, and 16% by weight. Matching pure polymers, polymers reinforced by exfoliated Graphite have proven to have significant improvements in local elastic properties (such as modulus, hardness, stiffness, etc.). Results showed that the reinforced epoxy's local mechanical properties are affected by the size and the percentage of nano-additives. Through the inspection of the load-displacement curve, it can be concluded that the nano-additive has a significant influence on the plastic mechanical properties of the sample. Therefore, the size of nanoparticles has significantly improved in material properties.

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Nobuki, Tohru, Minoru Hatate, and Toshio Shiota. "Notch Effects on Impact and Bending Characteristics of Spheroidal Graphite and Compacted Vermicular Graphite Cast Irons with Various Matrices." Key Engineering Materials 457 (December 2010): 392–97. http://dx.doi.org/10.4028/www.scientific.net/kem.457.392.

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The object of this study is to find out and evaluate systematically how the basic factors such as graphite-shape, external notch and matrix-characteristic affect the impact and bending characteristics of cast irons. The Spheroidal Graphite (SG) and Compacted Vermicular graphite (CV) cast iron samples were prepared, and their matrixes were modified into ferritic, pearlitic and bainitic in order to make the various kinds of samples whose graphite-shape and matrix vary widely. From each sample we produced five kinds of Charpy-type specimens by adding five kinds of notches whose stress concentration factor (α) varied from 1.0 (un-notched) to 4.8. The Charpy impact value decreases greatly in the range of α from 1 to 2.3 but decreases slightly in the range of α larger than 2.3. No influence to the fracture energy in the range of α larger than 2.3. Increasing of α results in moderate elevation of transition temperature of Charpy impact value and the transition temperature of CV cast ion is lower than that of SG one. The impact value in brittle fracture region of the cast iron samples were recognized to be a little bit larger than that of cast steel sample, and it was considered to be caused by graphite which act as a kind of buffer effect against crack growth in brittle fracture.

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Liu, Wen, and Qing Sen Meng. "Studies on the Growth Mechanism of Onion-Like Fullerenes by Arc Discharge in Liquid Benzene." Advanced Materials Research 139-141 (October 2010): 47–50. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.47.

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The growth mechanism of Onion-like fullerenes (OLFs) synthesized by arc discharge in liquid benzene was discussed. HRTEM was employed to characterize the morphologies and microstructures of the products. Results showed that the typical OLFs were highly crystallized with uniform diameter of 10-30nm. The growth of OLFs depended on the appropriate temperature gradient and quenching zone provided by the bubbles. The aromatic debris could act as graphite fragments composed of hexagonal carbon rings. The reducing of dangling bonds on the edges of graphite fragments would lower the energy of the system, resulting in formation of a close-caged structure at suitable temperature gradient by the auto-curling of graphite fragments. Based on the impact of the innermost core shape, such as C60 shape, quasi-spherical or polyhedral hollow concentric OLFs was formed. Adding ferrocene, ferrocene directly influenced the morphology and yield of OLFs.

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Alshammari, Basheer A., Fahad S. Al-Mubaddel, Mohammad Rezaul Karim, Mokarram Hossain, Abdullah S. Al-Mutairi, and Arthur N. Wilkinson. "Addition of Graphite Filler to Enhance Electrical, Morphological, Thermal, and Mechanical Properties in Poly (Ethylene Terephthalate): Experimental Characterization and Material Modeling." Polymers 11, no. 9 (August 28, 2019): 1411. http://dx.doi.org/10.3390/polym11091411.

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Poly(ethylene terephthalate)/graphite (PET/G) micro-composites were fabricated by the melt compounding method using a minilab extruder. The carbon fillers were found to act as nucleating agents for the PET matrix and hence accelerated crystallization and increased the degree of crystallinity. TGA showed that carbon fillers improved the resistance to thermal and thermo-oxidative degradation under both air and nitrogen atmospheres. However, a poor agreement was observed at higher loadings of the filler where the composites displayed reduced reinforcement efficiency. The results demonstrate that the addition of graphite at loading >14.5 wt.% made electrically conductive composites. It was calculated that the electric conductivities of PET/graphite micro-composites were enhanced, above the percolation threshold values by two orders of magnitudes compared to the PET matrix. The minimum value of conductivity required to avoid electrostatic charge application of an insulating polymer was achieved, just above the threshold values. The addition of graphite also improved thermal stability of PET, accelerated its crystallization process and increased the degree of crystallinity. Microscopic results exhibit no indication of aggregations at 2 wt.% graphite, whereas more agglomeration and rolling up could be seen as the graphite content was increased in the PET matrix (in particular, above the percolation threshold value). Furthermore, based on the mechanical experimental characterization of the PET/graphite micro-composites, a large deformation-based mathematical model is proposed for material behavior predictions. The model fits well the experimental data and predicts other mechanical data that are not included in the parameter identification.

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Shen, Zhi Qing, Hong Liang Zheng, Tong Tong Li, Yan Xu, Rong Fu Xu, and Xue Lei Tian. "The Influence of the Residual Mg Content in the Ductile Cast Iron on the Formation Law of Spherodial Graphite." Advanced Materials Research 415-417 (December 2011): 907–14. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.907.

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The residual Mg content ,spherodize ratio and nuclei of spherodial graphites(abbreviated SG) were studied by casting a series of similar composition ductile iron rods and white samples with different holding time of spheroidizing. The results indicate that the residual Mg content in the ductile iron was less and less as the holding time grows ,which causing the morphology of graphites transfer from spherodial to oval. Spherodize ratio change law is not continuous as increasing the residual Mg content which is divided at the 0.02%. The morphologies of nuclei of SGs core are typical examples of the highly magnified structure of spherical and irregular polygons; the diameters are about 0.5~2μm, consisting of (Mg, Ca)S along with CeO2and MgO. Disregistry δ between the nucleus compounds and graphite are low,which indicates that nucleus compounds are good nucleating site for SGs.The Mg element in nuclei of SG just act as nucleation substrates.it is the Mg which maybe simple substance in the metallic matrix that act as the role of spherodizer determines the graphite shape.

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Faisal, M. H., S. Prabagaran, and T. S. Vishnu. "Comparison of mechanical and wearing properties between LM13 matrix and Stir cast LM13/B4C/Gr hybrid composites of various composition." International Journal of Engineering & Technology 7, no. 1.1 (December 21, 2017): 193. http://dx.doi.org/10.14419/ijet.v7i1.1.9454.

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Aluminium/graphite composites are the need of modern times for addressing the fuel saving issues. The graphite in such composites act as solid lubricant and it reduce external fuel requirements. But such composites are having degraded mechanical properties due to the graphite content in composite. In order to solve the negative effect of graphite on mechanical properties of LM13/Gr self-lubricating composite this study was conducted to find out the mechanical properties of LM13/B4C/Gr Metal Matrix Composites. Boron carbide was selected as reinforcement because of its better reinforcement properties compared to alumina and silicon carbide. The properties of the hybrid composites were compared with the LM13/Gr self-lubricating composite to study the enhancement in mechanical properties that has been caused by the boron carbide particles. Using computerized universal testing machine and rock-well hardness tester mechanical properties such as hardness and tensile strength were tested. Pin on disk testing machine was used to analyse the wear behavior. The test results indicates that by raising weight % of boron carbide particles in the LM13, tensile strength and hardness of the hybrid composites was increased compared to self-lubricating composite accompanied by better tribological properties.

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Mekhed, Alexander Anatolievich, and Vladislav Andreevich Andrushenko. "Calculation of Electronic Structure of the K-Phase Cells which are Involved in Thermobarically Induced Epitaxial Growth of Diamond Crystals in High-Carbon Fe-Al-Alloys." Solid State Phenomena 203-204 (June 2013): 402–5. http://dx.doi.org/10.4028/www.scientific.net/ssp.203-204.402.

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Modified unit cell of Fe3AlC (K-phase) that can act as a substrate for a diamond growth was proposed. Spin-polarized calculations were performed to compare electronic structure of carbon atoms in K-phase substrate, diamond and graphite. Standard enthalpies of formation of different K-phase unit cells were calculated and compared with formation enthalpy of modified unit cell of K-phase.

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Turnipseed, Andrew A., Peter C. Andersen, Craig J. Williford, Christine A. Ennis, and John W. Birks. "Use of a heated graphite scrubber as a means of reducing interferences in UV-absorbance measurements of atmospheric ozone." Atmospheric Measurement Techniques 10, no. 6 (June 15, 2017): 2253–69. http://dx.doi.org/10.5194/amt-10-2253-2017.

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Abstract. A new solid-phase scrubber for use in conventional ozone (O3) photometers was investigated as a means of reducing interferences from other UV-absorbing species and water vapor. It was found that when heated to 100–130 °C, a tubular graphite scrubber efficiently removed up to 500 ppb ozone and ozone monitors using the heated graphite scrubber were found to be less susceptible to interferences from water vapor, mercury vapor, and aromatic volatile organic compounds (VOCs) compared to conventional metal oxide scrubbers. Ambient measurements from a graphite scrubber-equipped photometer and a co-located Federal equivalent method (FEM) ozone analyzer showed excellent agreement over 38 days of measurements and indicated no loss in the scrubber's ability to remove ozone when operated at 130 °C. The use of a heated graphite scrubber was found to reduce the interference from mercury vapor to ≤ 3 % of that obtained using a packed-bed Hopcalite scrubber. For a series of substituted aromatic compounds (ranging in volatility and absorption cross section at 253.7 nm), the graphite scrubber was observed to consistently exhibit reduced levels of interference, typically by factors of 2.5 to 20 less than with Hopcalite. Conventional solid-phase scrubbers also exhibited complex VOC adsorption and desorption characteristics that were dependent upon the relative humidity (RH), volatility of the VOC, and the available surface area of the scrubber. This complex behavior involving humidity is avoided by use of a heated graphite scrubber. These results suggest that heated graphite scrubbers could be substituted in most ozone photometers as a means of reducing interferences from other UV-absorbing species found in the atmosphere. This could be particularly important in ozone monitoring for compliance with the United States (U.S.) Clean Air Act or for use in VOC-rich environments such as in smog chambers and monitoring indoor air quality.

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Fan, Wei, Hao Qu, Sung Il Chang, Brian Kozak, Gregory Shaffer, Alex Galyukov, and Won Jae Lee. "Impacts of TaC Coating on SiC PVT Process Control and Crystal Quality." Materials Science Forum 963 (July 2019): 22–25. http://dx.doi.org/10.4028/www.scientific.net/msf.963.22.

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Tantalum carbide (TaC) coating, produced in an ultrahigh temperature chemical vapor deposition (CVD) process, exhibited high thermal and chemical stabilities, low emissivity, and high purity. The present research investigated through modeling the TaC emissivity and reactivity impacts on the temperature, C/Si ratio and growth rate in SiC physical vapor transport (PVT) process. The TaC coating effect was further validated by SiC crystal shape and quality through a series of growth experiments. As our study revealed, TaC coating can act as a protection and isolation layer to extend graphite component life, improve radial temperature uniformity, maintain SiC sublimation stoichiometry, suppress impurity migration, and reduce energy consumption. Ultimately a TaC-coated graphite crucible set is expected to improve SiC PVT process control and product quality.

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Marincean, Ana-Domnica, Sorin-Aurel Dorneanu, and Petru Ilea. "Hydrogen Peroxide Electrosynthesis Using Recycled Graphite Granules as 3D Cathode. Comparison with Other Commercial Materials and Optimization Studies." Revista de Chimie 71, no. 3 (January 1, 2001): 102–15. http://dx.doi.org/10.37358/rc.20.3.7978.

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This study aims to evaluate the ability of the graphite granules (GG) recycled from spent Zn-C batteries to act as 3D cathode for hydrogen peroxide (HP) electrosynthesis (HPE) in eco-friendly conditions (unbuffered 0.05 M Na2SO4 solution, air as O2 source). The performances of GG were compared to those of other usual carbonaceous cathode materials for HPE such as graphite bloc, graphite felt and reticulate vitreous carbon (RVC), using a divided filter-press electrochemical reactor. The operational parameters such as the polarization mode, electrolyte and air flow rates, applied potentials or imposed currents, and aeration mode were optimized by 1 h tests of electrosynthesized HP accumulation (EHPA). Considering as optimization criteria the best compromise between the final HP concentration, global current efficiency and electrical energy specific consumption, we find that the most efficient material for EHPA was RVC of 500 ppi, exploited in galvanostatic mode and using an original aeration system. In optimized conditions, for the GG cathode, very promising efficiency indicators were evaluated, suggesting that better results can be obtained by electrode geometry optimization and GG pretreatment.

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Cowley, J. M., and J. B. Hudis. "Atomic-focuser Imaging by Graphite Crystals in Carbon Nanoshells." Microscopy and Microanalysis 6, no. 5 (September 2000): 429–36. http://dx.doi.org/10.1007/s100050010049.

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AbstractOne of the atomic-focuser modes for ultra-high resolution electron microscopy is described theoretically and illustrated by the observation of images formed within the diffraction spots of nanodiffraction patterns of carbon nanoshells. In this mode, the specimen is illuminated by the focused probe of a scanning transmission electron microscope and is followed by a thin crystal at a Fourier-image distance. The theory shows that each diffraction spot of the crystal contains a magnified image of the illuminated area of the specimen, having a resolution depending on the width of the intensity peak of electrons channeled along atomic rows in the crystal. A thin graphite crystal, contained within one wall of a carbon nanoshell, can act as an atomic focuser to image part of the other wall of the nanoshell, or tungsten atoms deposited on this wall. Simulations of the transmission of electrons through graphite crystals show that the images formed should have a resolution of about 0.06 nm. Experimental images suggest that this resolution has been attained in the imaging of tungsten atoms or clusters of tungsten atoms.

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Meyer, Annemarie, Eva Sigmund, Friedhelm Luppertz, Gregor Schnakenburg, Immanuel Gadaczek, Thomas Bredow, Stefan-S. Jester, and Sigurd Höger. "Syntheses and properties of thienyl-substituted dithienophenazines." Beilstein Journal of Organic Chemistry 6 (December 13, 2010): 1180–87. http://dx.doi.org/10.3762/bjoc.6.135.

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A series of dithienophenazines with different lengths of the oligomeric thiophene units (quaterthiophenes and sexithiophenes) was synthesized. The thiophene and phenazine units act as electron donors and acceptors, respectively, resulting in characteristic absorption spectra. The optical spectra were calculated using time-dependent density functional theory at the B3LYP/TZVP level and verify the experimental data. Adsorption of the dithienophenazines on highly ordered pyrolytic graphite (HOPG) was investigated by scanning tunneling microscopy, showing that one of the compounds forms highly organized self-assembled monolayers.

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da Rocha, Rosa Maria, and Francisco Cristóvão Lourenço de Melo. "Synthesis of Fine B₄C Powder Using B₄C Seeding in Carbothermal Reduction Process." Materials Science Forum 660-661 (October 2010): 948–53. http://dx.doi.org/10.4028/www.scientific.net/msf.660-661.948.

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The focus of this work is to investigate the effect of seeding on the synthesis of B4C powder obtained by carbothermal reduction. B4C particles were added to act as seeds during reaction. Starting materials were boric acid (H3BO3) and two different carbon sources (graphite and carbon black). Mixtures of C, B2O3 (25 wt% B2O3 excess in relation to stoichiometric composition) and commercial B4C powder (0, 2.5 and 5.0 wt%) were prepared. The effect of 1.5 wt% of NaCl was also investigated. The powder mixtures were uniaxially die-pressed to form cylindrical shaped green bodies, then placed in a graphite crucible and heated at 1750°C/1h with a heating rate of 30°C/min, under argon-flowing atmosphere. Samples with seeds addition exhibited a decrease in particle size distribution. The particle morphology was uniform with a narrow size distribution and a medium particle size around 6 m regardless the initial concentration of seeds.

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26

Riposan, Iulian, Valentin Uta, Ciprian Firican, Stelian Stan, Mihai Chisamera, Rod Naro, and David Williams. "World Crisis of Rare Earth – Inoculants Enhancer Solution for Ductile Iron Production." Advanced Materials Research 1114 (July 2015): 100–111. http://dx.doi.org/10.4028/www.scientific.net/amr.1114.100.

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The unique properties of rare earth elements (REE) have resulted in their being crucial to a growing number of emerging technologies. As the demand for REE currently exceeds annual production, the present worldwide crisis for REE will probably continue for the foreseeable future. Hence, it is highly likely that the availability of REE used in the metallurgy of cast iron will be significantly reduced and alternatives to REE usage may have to be developed. Graphite nodules nucleate heterogeneously on particles formed in the melt, having a duplex structure (sulphide as a core and oxide/silicate as a shell). Mg, Ca and REE appear to act in the nucleation first stage, while Si, Al, Mg, REE, Ca, Sr and Ba act predominately in the second stage. Generally, REE are employed in ductile irons to accomplish the following tasks: (a) neutralize tramp elements such as Ti, Pb, Bi, As etc; (b) assist in nodulizing or provide a supplementary effect to Mg to promote spheroidal graphite shapes; (c) assist in nucleating graphite. When anti-nodularising Thielman control factors (K) are less than 0.8, REE are usually not required since there are no trace elements to neutralize. REE are useful for K factors between 0.80 to 1.20 and are mandatory for K factors greater than 1.20. Theilman factors greater than 2.0 will always require REE. When Theilman factors are less than 0.80, REEreslevels of 0.01% are usually more than sufficient for ductile iron production. Three ductile iron inoculation alloys were selected for this research: (a) a conventional Ca bearing 75% FeSi inoculant (Ca-FeSi), used at a high consumption level; (b) an improved conventional Ca-FeSi alloy that incorporated active inoculating elements, such as Ba or REE, used at a medium consumption level, and (c) a combination of a commercial inoculant, such as Ca-FeSi alloy, used with a separate oxy-sulphide inoculant enhancer alloy addition. The last inoculation variant provided the best structural parameters and the lowest consumption level.

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Bagby, S., P. D. Barker, H. A. O. Hill, G. S. Sanghera, B. Dunbar, G. A. Ashby, R. R. Eady, and R. N. F. Thorneley. "Direct electrochemistry of two genetically distinct flavodoxins isolated from Azotobacter chroococcum grown under nitrogen-fixing conditions." Biochemical Journal 277, no. 2 (July 15, 1991): 313–19. http://dx.doi.org/10.1042/bj2770313.

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Two genetically distinct flavodoxins, designated AcFldA and AcFldB, were isolated from Azotobacter chroococcum (MCD1155) grown under nitrogen-fixing conditions. AcFldA and AcFldB differ in their midpoint potentials for the semiquinone-hydroquinone couple (Em -305 mV and -520 mV respectively). Only AcFldB was competent to act as an electron donor to the Mo-containing nitrogenase of A. chroococcum. The N-terminal amino acid sequence (20 residues) of AcFldB was identical with that predicted from the nifF DNA sequence of A. vinelandii OP [Bennett, Jacobsen & Dean (1988) J. Biol. Chem. 263, 1364-1369], suggesting that AcFldB is the nifF gene product of A. chroococcum (MCD1155). Direct fast reversible electrochemistry of these flavodoxins has been achieved at a polished edge-plane graphite electrode using the aminoglycoside neomycin as a promoter. The heterogeneous rates of electron transfer between the graphite electrode and AcFldA and AcFldB were determined to be 1.2 x 10(-3) cm.s-1 and 2.0 x 10(-3) cm.s-1 respectively. The natures of two minor species of flavodoxin designated AcFldC and AcFldD, which were resolved by f.p.l.c., are also discussed.

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Li, Chen, Heng Wen, Kun Chen, Longxiao Zhang, Ting Xie, Yaru Shi, and Junlong Zhang. "Development of a mini-tribometer for in-situ observation of subsurface and the corresponding experiments." Industrial Lubrication and Tribology 73, no. 5 (July 13, 2021): 822–29. http://dx.doi.org/10.1108/ilt-04-2021-0130.

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Purpose This paper aims to develop a Mini-Tribometer for in-situ observation of subsurface. Design/methodology/approach To observe the change of the microstructure during wear in real time, an in-situ observation mini-tribometer was developed according to the requirements of the basic frictional experiments and carried out the verification experiments. Findings The subsurface images and the tribological data obtained from the mini-tribometer clearly show that the graphite in the matrix moves to the surface and takes part in lubrication mainly in the form of extrusion and peeling off, and the migration of graphite in the copper-based composite to the frictional interface to act as lubricant and to result in the decrease of the friction coefficient. The experimental results of the developed tribometer are accurate, which can provide important references for further research on the wear mechanism of materials. Originality/value The developed in-situ observation mini-tribometer can be used to observe the dynamic wear mechanism of the frictional pairs, which is very important for optimization of material design and tribological performances.

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29

Tomiak, Florian, Angelina Schoeffel, Klaus Rathberger, and Dietmar Drummer. "A Synergistic Flame Retardant System Based on Expandable Graphite, Aluminum (Diethyl-)Polyphospinate and Melamine Polyphosphate for Polyamide 6." Polymers 13, no. 16 (August 13, 2021): 2712. http://dx.doi.org/10.3390/polym13162712.

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Expandable graphite (EG), aluminum (diethyl)polyphosphinate (AlPi) and melamine polyphophate (MPP) was used as flame retardant multi-material additive in a polyamide 6 (PA6) matrix. Flame inhabitation performances were conducted by cone calorimeter, LOI and UL-94 tests, synergisms identified analyzed by TGA-FTIR and TGA-GC/MS and effects found were comprehensively discussed. SEM images were used for char residue characterization. For PA6 containing 20 wt.% EG and 5 wt.% AlPi/MPP (3:2), a well working synergism in limiting oxygen indices could be identified exhibiting the highest oxygen index (OI) measured: 46%. The study shows that the synergism due to the partial substitution of EG by AlPi/MPP can be attributed to two effects: (1) When PA6/AlPi/MPP mixtures decompose predominantly CO2 evaporates in early decomposition stages. CO2 evaporations was found to be sensitive to the heating rate applied, whereas specifically high heating rates increased the CO2 yield measured. (2) Solid decomposition products of AlPi/MPP act as “glue” between expanded graphite and thus increase the mechanical residue stability.

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Lima Filho, Antonio de Pádua, Bruno Katsuyoshi Silama Ueda, Tales Paschoalino de Castro, and Rodrigo Alessandro Nunes de Oliveira. "Manufacture of Continuous Metal Matrix Composite Strip Reinforced by Particulate Materials from the Semisolid Processing." Solid State Phenomena 285 (January 2019): 189–96. http://dx.doi.org/10.4028/www.scientific.net/ssp.285.189.

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Strip casting is a new method of producing metal matrix composites. Two-roll melt dragged processing (TRMD-ing) and single-roll melt dragged processing (SRMD-ing) methods were used to study the manufacture of 2-mm-thick composite strips by using PbSn (≈ 11.3 g/cm3) eutectic alloy matrix reinforced with iron (≈ 7.86 g/cm3) powder (≈ 70 μm) at a rate of 0.3 m/s. The metallic powder stored in the feed hopper (≈ 90 g) was pushed during the pouring operation of the cast alloy (≈ 4 kg) at 260 oC on the cooling slope to produce a mixture of metallic slurry and particles to feed the nozzle to be dragged by the lower roll. Various surface defects occurred during processing, such as the failure of the powder particle to be embedded in the matrix by SRMD-ing with and without stirrer into the nozzle, and the rolling up of the strip into the nozzle by TRMD-ing. Graphite nanoparticles formed inside the α-Pb grain revealed a complicate eutectic structure in both the processing methods. The colloidal graphite used to coat the crucible, cooling slope, and nozzle could act as a nucleation agent for preferential centre segregation in the α-Pb grain. This suggests that the graphite nanoparticles functioned as nucleation points in the lead-rich α phase. Thus, another type of composite was formed in the presence of graphite nanoparticles within the lead-rich α-phase surrounded by β-Sn. An electron probe microanalysis and scanning electronic microscopy were used to investigate the composition and distribution and identify the different phases. Several types of particulate reinforcements may be added to the matrix to obtain composites for mechanical, electronic, and magnetic applications using these technologies.

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31

Al-Ruqeishi, Majid S., Tariq Mohiuddin, Moza Al-Moqbali, Hamyar Al-Shukaili, Said Al-Mamari, Hashim Al-Rashdi, Rahma Al-Busaidi, Vishnu Sreepal, and Rahul R. Nair. "Graphene Oxide Synthesis: Optimizing the Hummers and Marcano Methods." Nanoscience and Nanotechnology Letters 12, no. 1 (January 1, 2020): 88–95. http://dx.doi.org/10.1166/nnl.2020.3074.

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Fabricating graphene oxide (GO) in a cost-effective, efficient manner remains challenging. Some researchers manufacture GO that is comprised of a small number of layers by a modification of Hummers' method, as follows: (1) minimize use of NaNO3, a source of toxic gases; and (2) use MnO2 as the oxidizer. Other researchers fabricate GO by Marcano's method, where KMnO4 substitutes for MnO2. Here, one uses a 9:1 volume ratio of H2SO4/H3PO4. The role of KMnO4 is to diffuse slowly in the graphite interlayer and act as a peroxidation agent throughout the oxidation. For large-scale production, there is an explosion risk from using KMnO4 in H2SO4, and incomplete graphite oxidation. We overcame these challenges by growing GO sheets exhibiting an average size thickness of ∼3.1 ± 0.2 μm by optimizing the quantity of KMnO4 and H2SO4/H3PO4 as oxidizer ion sources, in modifications of both the Hummers and Marcano methods, without using NaNO3. Optimizing the reaction time and using small graphite flakes optimized oxidation to afford a high yield of GO sheets. X-ray diffraction showed an interlayer d-spacing of 5.7 Å for GO and 2.9 Å for the lesser quantity of remaining non-exfoliated graphite grains. Fourier-transform infrared spectroscopy showed no peaks for stretching vibrations within the graphitic domains, especially for GO grown via the modified Hummers method. Ultraviolet-visible and Raman spectroscopy showed that the number of layers with sp2 domains of interconnected carbon atoms, and disorder such as ripples and major defects at the edge planes, decreased compared to prior research. The Raman Id/Ig ratio of the GO sheets ranged from 1.21 to 1.75. The carbon/oxygen atomic ratio (RC/O), deduced from the C 1 s core level as per X-ray photoelectron spectroscopy, ranged from 0.43 to 6.84.

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32

Anca, Denisa, Mihai Chisamera, Stelian Stan, Iuliana Stan, and Iulian Riposan. "Sulfur and Oxygen Effects on High-Si Ductile Iron Casting Skin Formation." Coatings 10, no. 7 (June 29, 2020): 618. http://dx.doi.org/10.3390/coatings10070618.

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The main objective of the present paper is to evaluate by thermal (cooling curve) analysis the solidification pattern and the occurrence of the layer of degenerate graphite at the surface of ductile iron castings (3.15% Si, typically as 450-18 grade, ISO 1563/2011), with or without a mold coating, including S or O, and different agents (carbonic material, iron powder), supposed to act to block their diffusion into the iron melt. It is found that the mold coating materials temperately influence the parameters of the solidification cooling curves and, more visibly, the occurrence and the thickness of the undesired skin layer. Different graphite morphologies comparable to the casting body are present, at a large range of thicknesses, from 50 up to 200 µm. The sulfur presence in the mold coating will promote a higher skin thickness compared to oxygen (up to 50% by oxygen and 2.5–3.3 times for sulfur action), despite the fact that in the casting body, the graphite nodularity undergoes a limited decrease (from 85% up to 82%–83% level). Carbonic material or iron powder supplementary addition decreases these undesired effects, but the solidification undercooling compared to the equilibrium system is increased. It is found that carbonic material is more efficient at limiting oxygen than iron powder is at limiting the negative effects of sulfur on the casting skin thickness. More experiments are necessary to quantify their capacity to block the oxygen or sulfur transfer into the iron melt.

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33

Zhang, Jintao, Zhenhai Xia, and Liming Dai. "Carbon-based electrocatalysts for advanced energy conversion and storage." Science Advances 1, no. 7 (August 2015): e1500564. http://dx.doi.org/10.1126/sciadv.1500564.

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Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play curial roles in electrochemical energy conversion and storage, including fuel cells and metal-air batteries. Having rich multidimensional nanoarchitectures [for example, zero-dimensional (0D) fullerenes, 1D carbon nanotubes, 2D graphene, and 3D graphite] with tunable electronic and surface characteristics, various carbon nanomaterials have been demonstrated to act as efficient metal-free electrocatalysts for ORR and OER in fuel cells and batteries. We present a critical review on the recent advances in carbon-based metal-free catalysts for fuel cells and metal-air batteries, and discuss the perspectives and challenges in this rapidly developing field of practical significance.

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34

He, Yong Qiang, Na Na Zhang, Ying Long, Hong Sun, Hai Xia Qiu, and Jian Ping Gao. "Study on the Catalytic Activity of Graphene Oxide." Advanced Materials Research 430-432 (January 2012): 488–91. http://dx.doi.org/10.4028/www.scientific.net/amr.430-432.488.

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Graphene oxide (GO), an oxygen-rich carbonaceous layered material, is produced by the strong oxidation of graphite. The GO aqueous suspension is very stable and can be fabricated to porous GO aerogels by a green method, unidirectional freeze-drying technology. GO shows catalytic activities in both solution and solid state. It can also act as reductant or oxidant depending on the reaction patterns. The product of the reaction was analyzed and the component change of the graphene oxide (GO) was monitored by x-ray photoelectron spectrometer, scanning electron microscopy and transmission electron microscopy. The results confirm that GO not only acts as the reactant in the reaction, but also as the catalyst to catalyze the reaction.

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35

Alonso, Gorka, Doru Michael Ştefănescu, Esther de La Fuente, Pello Larrañaga, and Ramón Suárez. "The Influence of Trace Elements on the Nature of the Nuclei of the Graphite in Ductile Iron." Materials Science Forum 925 (June 2018): 78–85. http://dx.doi.org/10.4028/www.scientific.net/msf.925.78.

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Nucleation mechanisms and the effect of minor elements added with the inoculants are still a subject of extensive research in ductile iron. Oxides, sulfides, silicates and nitrides have been reported to be nuclei for graphite precipitation. Those compounds originate both from the nodulizing treatment and the inoculation process. Previous research works have shown that titanium nitrides or carbonitrides play an active role in graphite nucleation. In order to determine the efficiency and nature of nitrides that can act as nuclei for graphite, and the possible effect of the trace elements added with the inoculant, melts with titanium contents ranging from 0.007% to 0.036% were produced and poured into standard thermal analysis cups, with and without inoculation. Different inoculants rich in titanium, cerium, aluminum or zirconium were used. Two cups were produced with each inoculant, one cooled down to room temperature, and the other quenched in brine immediately after pouring. Nucleation sites were characterized through detector, spectrum, mapping and line scans of a FEG-SEM equipment. Most of the analyzed nuclei exhibited two or three different inclusions: magnesium sulfides or Mg-Ca oxy-sulfides, Mg or Al oxides, and Ti carbo-nitrides or Mg-Si-Al nitrides. The appearance of each type of nitrides is directly related to the titanium content in the base melt. When titanium was added in the inoculant, no titanium nitrides were noticeable. The zirconium added with the inoculant promoted more complex nitrides that appeared in higher amount. Cerium appears occasionally forming sulfides. Aluminum stimulates the formation of complex nitrides. No differences in the nature of the nuclei were observed between the samples quenched and the ones obtained at room temperature, which assures the methodology approach.

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Babu, J. S. S., and C. G. Kang. "Nanomechanical properties of magnesium-based hybrid composites with graphite nanofiber and alumina short fiber." Journal of Composite Materials 45, no. 25 (October 12, 2011): 2685–95. http://dx.doi.org/10.1177/0021998311401109.

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In this study, an attempt was made to evaluate the nanomechanical properties of magnesium-based hybrid composites with graphite nanofibers (GNFs) and alumina short fibers (Al2O3sf) by nanoindentation. The nanoindentation was performed using continuous stiffness measurement (CSM) method with an indentation depth of 2000 nm. To find out the modulus and hardness of composites of local regions, indentation tests were carried out in different locations of the sample, such as GNFs/Al2O3sf region, Al2O3sf region, GNFs cluster, and Mg matrix. The modulus and hardness values closer to the GNFs/Al2O3sf region are higher than those of the corresponding to the other regions primarily because of a higher constraint to the localized matrix deformation during indentation. Furthermore, the presence of GNFs can act as a barrier for movement of dislocations enhancing the indentation properties. The presence of MgO/Mg17Al12 also can contribute to improve the nanoindentation properties of the present composite system.

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37

Kopyciński, Dariusz, Edward Guzik, Andrzej Szczęsny, and Józef Dorula. "Influence of Iron Powder Addition on the Number of Primary Austenite Grains and Tensile Strength of Inoculated Cast Iron." Materials Science Forum 790-791 (May 2014): 59–64. http://dx.doi.org/10.4028/www.scientific.net/msf.790-791.59.

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The study proves that by introducing the iron powder to low-sulphur cast iron still before the inoculation carried out with a conventional graphitising inoculant, the mechanical properties similar to those obtained during the inoculation treatment carried out on cast iron with the recommended high sulphur content are achieved. The said operation increases the number of crystallisation nuclei for of the primary austenite dendrites. In this case, the iron particles act as substrates for the nucleation of primary austenite due to a similar crystallographic behaviour of the regular face centered cubic lattice The more numerous are the dendrites of primary austenite, the less free space is available in the interdendritic spaces for the formation of graphite eutectic grains, which makes the mechanical properties higher.

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38

Murakami, H., and A. Akiyama. "A Mixture Theory for Wave Propagation in Angle-Ply Laminates, Part 2: Application." Journal of Applied Mechanics 52, no. 2 (June 1, 1985): 338–44. http://dx.doi.org/10.1115/1.3169050.

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A binary mixture theory with microstructure is constructed for symmetric angle-ply laminates with orthotropic laminas for wave motion in arbitrary directions. A numerical study of phase-velocity spectra associated with the resulting theory reveals that dispersion is most prominent in waveguide propagation. Further, it is directionally dependent and may be strong depending on the propagation direction and lay-up angle. Typical results are presented for a graphite/epoxy composite. To assess the accuracy of the mixture model, a finite element eigenvalue analysis has been carried out. The comparisons of exact versus mixture phase-velocity spectra imply that the theory provides a tool with which one may efficiently study the rather extraordinary capability of angle-ply laminates to act as “shock absorbers.”

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39

Nishimura, K., Y. A. Kim, T. Matushita, T. Hayashi, M. Endo, and M. S. Dresselhaus. "Structural Characterization of Boron-doped Submicron Vapor-grown Carbon Fibers and Their Anode Performance." Journal of Materials Research 15, no. 6 (June 2000): 1303–13. http://dx.doi.org/10.1557/jmr.2000.0189.

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Structural evolution of undoped and boron-doped submicron vapor-grown carbon fibers (S-VGCFs) was monitored as a function of heat-treatment temperature (HTT). Based on x-ray and Raman data, over the range of HTT from 1800 to 2600 °C, it was found that boron atoms act as catalysts to promote graphitization due to boron's higher diffusivity. For the range of HTT from 2600 to 2800 °C, the process of boron out-diffusion from the host material induces defects, such as tilt boundaries; this process would be related with the improved capacity and Coulombic efficiency of boron-doped S-VGCFs. When 10 wt% S-VGCFs was used as an additive to synthetic graphite, the cyclic efficiency of the capacities was improved to almost 100%.

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Pedersen, Karl Martin, and Niels Tiedje. "Solidification of Hypereutectic Thin Wall Ductile Cast Iron." Materials Science Forum 508 (March 2006): 63–68. http://dx.doi.org/10.4028/www.scientific.net/msf.508.63.

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Hypereutectic ductile iron was cast in green sand moulds with four plates with thickness of 1.5, 2, 3 and 4 mm in each mould. Temperatures were measured in the 3 and 4 mm plate. The temperature curves showed that eutectic solidification was divided into two stages: primary and secondary eutectic solidification. The first stage, which was relatively short, had none or very little recalescence. Further under cooling, followed by reheating during recalescence, was necessary to initiate the second part of the eutectic solidification. Both the secondary under cooling and recalescence was larger in the 3 mm plates than in the 4 mm plates. All 1.5 mm plates contained carbides but the other plates solidified without carbides. Metallographic examination showed two populations of graphite nodules. A small group of nodules was larger than rest of the nodules. Color etching revealing the segregation of Si showed a higher Si content in the ferrite around the larger nodules compared to the ferrite around the rest of the nodules. This indicates that solidification took place along the following path: The solidification starts with nucleation and growth of primary graphite nodules. This probably starts during the filling of the mould. The primary nodules act as nuclei for austenite. As austenite easily nucleates on graphite the temperature will be the same for the 3 and 4 mm plate for the first part of the eutectic solidification. This first part of the solidification ends when concentration of carbon around austenite dendrites is too large and new nodules have to nucleate and grow. The larger under cooling for the 3 mm plates compared to the 4 mm indicates that the nucleation of new nodules is governed by kinetics even in very well inoculated melts.

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Chen, Zhe, Arash Khajeh, Ashlie Martini, and Seong H. Kim. "Chemical and physical origins of friction on surfaces with atomic steps." Science Advances 5, no. 8 (August 2019): eaaw0513. http://dx.doi.org/10.1126/sciadv.aaw0513.

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Friction occurs through a complex set of processes that act together to resist relative motion. However, despite this complexity, friction is typically described using a simple phenomenological expression that relates normal and lateral forces via a coefficient, the friction coefficient. This one parameter encompasses multiple, sometimes competing, effects. To better understand the origins of friction, here, we study a chemically and topographically well-defined interface between silica and graphite with a single-layer graphene step edge. We identify the separate contributions of physical and chemical processes to friction and show that a single friction coefficient can be separated into two terms corresponding to these effects. The findings provide insight into the chemical and topographic origins of friction and suggest means of tuning surfaces by leveraging competing frictional processes.

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42

NING, JIANG, S. XU, J. W. CHAI, L. K. CHEN, ALEX SEE, and J. AHN. "AMORPHOUS CARBON NITRIDE THIN FILM AS A BARRIER AGAINST COPPER DIFFUSION." International Journal of Modern Physics B 16, no. 06n07 (March 20, 2002): 1127–31. http://dx.doi.org/10.1142/s0217979202010981.

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The application of carbon nitride as a barrier against copper diffusion was investigated. Amorphous carbon nitride (a-CN) thin films were prepared on Si(100) substrates by rf magnetron sputtering of graphite target in N2 plasma. A thin Cu layer was then deposited in-situ atop of the a-CN film. Annealing process was carried out in nitrogen (N2) ambient at the temperature of 400°C and 600°C respectively. The as-deposited and annealed films were characterized by x-ray photoelectron spectroscopy (XPS). The measurements show that both sp2C-N and sp3-N bonds were formed in the as-deposited carbon nitride films. The compositional analyses indicate that the deposited a-CN thin film is able to act as an effective diffusion barrier against copper at annealing temperature up to 400°C.

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43

Brancato, Vincenza, Elpida Piperopoulos, Emanuela Mastronardo, Luigi Calabrese, Candida Milone, and Edoardo Proverbio. "Synthesis and Characterization of Graphite Composite Foams for Oil Spill Recovery Application." Journal of Composites Science 4, no. 4 (October 19, 2020): 154. http://dx.doi.org/10.3390/jcs4040154.

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The aim of this paper is the synthesis and characterization of a composite silicone foam filled with expanded graphite (EG) for oil spill recovery applications. The EG foams were obtained using a foaming slurry consisting of a mixture of siloxane compounds as the matrix with an EG filler. The effect of the filler content’s performance on an innovative composite silicone-based foam was investigated. All the obtained samples exhibited an open cell morphology. Each foam was evaluated in four commonly used oils (kerosene, pump oil, naphtha and crude oil). Additionally, kinetics was studied in order to investigate the physical, chemical and mass transport mechanisms that act during the absorption phenomenon and uptake evolution of the contaminants. Foam filled with 3% of EG exhibited the highest absorption capacity, particularly with light oils kerosene and virgin naphtha (854 and 1016 wt.%, respectively). Furthermore, the kinetic study showed that pseudo-second order mechanisms better fitted the composite absorption performances, suggesting that the oil sorption into EG filled polydimethylsiloxane (PDMS) foams could be related to chemisorption mechanism. The results evidenced a good oil sorption capability and water/oil selectivity indicating this class of materials as a potentially applicable material for oil spill remediation.

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Homaeigohar, Shahin. "Amphiphilic Oxygenated Amorphous Carbon-Graphite Buckypapers with Gas Sensitivity to Polar and Non-Polar VOCs." Nanomaterials 9, no. 9 (September 19, 2019): 1343. http://dx.doi.org/10.3390/nano9091343.

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To precisely control the emission limit of volatile organic compounds (VOCs) even at trace amounts, reactive nanomaterials of, e.g., carbon are demanded. Particularly, considering the polar/non-polar nature of VOCs, amphiphilic carbon nanomaterials with a huge surface area could act as multipurpose VOC sensors. Here, for the first time, a buckypaper sensor composed of oxygenated amorphous carbon (a-COx)/graphite (G) nanofilaments is developed. Presence of the oxygen-containing groups rises the selectivity of the sensor to polar VOCs, such as ethanol and acetone through formation of hydrogen bonding, affecting the electron withdrawing ability of the group, the hole carrier density, and, thus, the resistivity. On the other hand, the electrostatic interactions between the toluene aromatic ring and the π electrons of the graphitic crystals cause a formation of charge-transfer complexes, which could be the main mechanism of high responsiveness of the sensor towards non-polar toluene. To the best of my knowledge, an amphiphilic carbon nanofilamentous buckypaper has never been reported for gas sensing, and my device sensing polar/non-polar VOCs is state of the art for environmental control.

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45

Zaldívar Santamaría, Elvira, David Molina Dagá, and Antonio T. Palacios García. "Statistical Modelization of the Descriptor “Minerality” Based on the Sensory Properties and Chemical Composition of Wine." Beverages 5, no. 4 (November 22, 2019): 66. http://dx.doi.org/10.3390/beverages5040066.

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When speaking of “minerality” in wines, it is common to find descriptive terms in the vocabulary of wine tasters such as flint, match smoke, kerosene, rubber eraser, slate, granite, limestone, earthy, tar, charcoal, graphite, rock dust, wet stones, salty, metallic, steel, ferrous, etc. These are just a few of the descriptors that are commonly found in the tasting notes of wines that show this sensory profile. However, not all wines show this mineral trace at the aromatic and gustatory level. This study has used the statistical tool partial least squares regression (PLS) to mathematically model the attribute of “minerality” of wine, thereby obtaining formulas where the chemical composition and sensory attributes act jointly as the predictor variables, both for white wines and red wines, so as to help understand the term and to devise a winemaking approach able to endow wines with this attribute if desired.

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Fournier, P., Ph Reynaud, F. Platon, and J. Absi. "Tribological behaviour of carbon-fibre-reinforced SiC matrix composites." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 214, no. 3 (March 1, 2000): 291–306. http://dx.doi.org/10.1243/1350650001543188.

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Reinforcement of monolithic ceramics by carbon fibres improves the tribological behaviour of ceramic materials. The lamellar graphite of carbon fibres can act as a natural third body, leading to low friction. The tribological behaviour of carbon-fibre (M40)-reinforced SiC matrix composites under different experimental conditions (velocity, load and temperature) is discussed in this paper. C-SiC composites are tested in sliding contact using a disc-on-disc tribometer. The results show that the behaviour of the contact is highly dependent on friction conditions. Friction transitions can occur during tests. The purpose of this paper is to identify the mechanisms which lead to these transitions. The main hypothesis concerns the mechanical and thermal fatigue phenomena. Under restrictive experimental conditions the C-SiC composites can be considered as self-lubricating materials. Self-lubricating conditions are experimentally given by a curve according to test temperature and pv parameter.

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Hsieh, Chien-Te, Bing-Hao Yang, and Wei-Yu Chen. "Dye-Sensitized Solar Cells Using Mesocarbon Microbead-Based Counter Electrodes." International Journal of Photoenergy 2012 (2012): 1–6. http://dx.doi.org/10.1155/2012/709581.

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The dye-sensitized solar cells (DSCs) equipped with mesocarbon microbead (MCMB)-based counter electrodes were explored to examine their cell performance. Three types of nanosized additives including platinum, carbon nanotubes (CNTs), and carbon black (CB) are well dispersed and coated over microscaled MCMB powders. In the design of the counter electrodes, the MCMB graphite offers an excellent medium that allows charge transfer from the ITO substrate to the dye molecule. The active materials such as Pt, CNT, and nanosize CB act as an active site provider for the redox reaction. Among these counter electrodes, the DSCs fabricated with CB electrode exhibit the highest power conversion efficiency. This improved efficiency can be attributed to the fact that the CB nanoparticles not only offer a large number of catalytic sites but also low charge transfer resistance, facilitating a rapid reaction kinetics. Such design of carbon counter electrode has been confirmed to be a promising candidate for replacing Pt electrodes.

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Mustafa, Dalia M. T., and Sarkawt Rostam. "Friction and Wear Resistance for Polyetheretherketone Filled with Different Filler Materials: A Comparative Study." Kurdistan Journal of Applied Research 2, no. 3 (August 27, 2017): 335–40. http://dx.doi.org/10.24017/science.2017.3.55.

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Friction and wear behavior of Polyetheretherketone (PEEK) filled with different filler composites were compared. The comparisons were made for different scholar research works which were published between 1987 – 2017.The comparison took place between different filler composites such as carbon fiber (CF) reinforced Polyetheretherketone, nanometer Al2O3, nanometer SiC, polytetrafluoroethylene (PTFE) filled PEEK, nanometer ZrO2, nanometer SiO2, nanometer Si3N4, CuS, short fiber reinforced PEEK composites, PEEK-CF30, GO-Si and Graphite composites.The friction and wear were studied according to different factors of the filler composites such as plasma treated PEEK, volume percentage, weight percentage, sliding distance, surface of roughness, and size of particles.By this work we can understand the effect of some nanometer particles which act as fillers in polyetheretherketone, and by this comparison study we conclude that friction and wear properties can be decreased or increased or stay unchanged by increasing and decreasing the amount of fillers but it can be improved by adding different fillers with certain properties to obtain optimal results.

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De Stefano, R., B. Pérot, C. Carasco, and E. Simon. "Simulation of delayed gamma rays from neutron-induced fissions using MCNP 6.1." EPJ Web of Conferences 225 (2020): 06007. http://dx.doi.org/10.1051/epjconf/202022506007.

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As part of its R&xD activities in the fields of radioactivewaste drum storage and homeland security, the NuclearMeasurement Laboratory of CEA Cadarache has started studiesrelated to the detection of induced delayed fission gamma rays asa signature of U/Pu presence either in radioactive wastes or incargo containers and luggage. The study described in the presentpaper explores the feasibility of detecting fission delayed gammarays of nuclear materials interrogated by a pulsed neutrongenerator. For this purpose, Monte Carlo simulations have beenperformed with ACT, the MNCP6 Activation Control Card.Simulated results have been compared with experimental data tovalidate the numerical model. Samples of uranium andplutonium have been irradiated for 2 hours with a pulsed D-Tneutron generator delivering 14 MeV neutrons with an averageemission of 8.107 n/s, which are thermalised in a graphite cellcalled REGAIN. At the end of irradiation, activated nuclearmaterials were placed in a low-background, high-resolutiongamma spectroscopy station in order to detect delayed gammarays emitted by fission products. Anomalies have been observedin the calculated time decay curve of fission delayed gamma rayswith MCNP6 ACT card, but the time behavior is correct for non-fission activated materials like aluminum or copper. On the otherhand, the number of counts recorded in the main simulatedgamma ray lines from activated nuclear material fission productsis consistent with the experimental results, thus validating thesimulation scheme in view of further studies on thecharacterization of radioactive waste drums or special nuclearmaterial detection in cargo containers.

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Ferrás, Luís Lima, Célio Fernandes, Denis Semyonov, João Miguel Nóbrega, and José António Covas. "Dispersion of Graphite Nanoplates in Polypropylene by Melt Mixing: The Effects of Hydrodynamic Stresses and Residence Time." Polymers 13, no. 1 (December 29, 2020): 102. http://dx.doi.org/10.3390/polym13010102.

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This work combines experimental and numerical (computational fluid dynamics) data to better understand the kinetics of the dispersion of graphite nanoplates in a polypropylene melt, using a mixing device that consists of a series of stacked rings with an equal outer diameter and alternating larger and smaller inner diameters, thereby creating a series of converging/diverging flows. Numerical simulation of the flow assuming both inelastic and viscoelastic responses predicted the velocity, streamlines, flow type and shear and normal stress fields for the mixer. Experimental and computed data were combined to determine the trade-off between the local degree of dispersion of the PP/GnP nanocomposite, measured as area ratio, and the absolute average value of the hydrodynamic stresses multiplied by the local cumulative residence time. A strong quasi-linear relationship between the evolution of dispersion measured experimentally and the computational data was obtained. Theory was used to interpret experimental data, and the results obtained confirmed the hypotheses previously put forward by various authors that the dispersion of solid agglomerates requires not only sufficiently high hydrodynamic stresses, but also that these act during sufficient time. Based on these considerations, it was estimated that the cohesive strength of the GnP agglomerates is in the range of 5–50 kPa.

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Journal articles on the topic 'Graphite|act'

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