Academic literature on the topic 'Graphite|act'
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Journal articles on the topic "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.
Dissertations / Theses on the topic "Graphite|act"
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Angerand, François. "Étude thermodynamique et structurale des changements de phase bidimensionnels dans des films de molécules physisorbées sur le graphite : Rôle de l'ordre orientationnel dans les phénomènes de mouillage et de transition rugueuse." Nancy 1, 1987. http://www.theses.fr/1987NAN10268.
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Cochet, Jean-Marc. "Etude voltamperometrique des graphites noirs de carbone et charbons actives : application a l'etude des superconducteurs." Paris 6, 1988. http://www.theses.fr/1988PA066154.
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Muller, Michel. "Etude de reactions d'isomerisation, de cracking et d'alkylation d'hydrocarbures en presence de divers superacides." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13022.
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Adhoum, Nafaâ. "Insertion du sodium et pénétration de l’électrolyte dans le carbone en milieu NaF fondu à 1025°C." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0185.
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Pendant l’électro-élaboration de l’aluminium par le procédé Hall-Héroult en milieu de cryolite fondue, il y a production parasite de sodium qui imprègne le carbone du bloc cathodique, suivi de près par l’électrolyte. Ceci provoque le gonflement du carbone et conduit à la limitation de la durée de vie de la cellule d’électrolyse. Dans l’objectif d’élucider les mécanismes d’interaction entre le sodium et le carbone, nous avons mené une étude de cinétique électrochimique en milieu NaF pur fondu à 1025°C. L’utilisation de diverses techniques électrochimiques (voltampérométrie, chronopotentiométrie et coulométrie) a mis en évidence l’existence d’une interaction complexe entre le sodium et le carbone. En effet, le métal alcalin est distribué entre deux types de sites correspondant à deux activités différentes. La forme la moins fortement liée au carbone correspond au sodium piégé dans la micro-porosité, alors que la forme plus stable est attribuée au sodium inséré entre les plans de graphène. Nous avons aussi montré l’existence d’un transfert lent et irréversible des espèces piégées vers les sites normaux d’insertion. De plus, en raison de l’évaporation du sodium à partir de l’interface, le produit Na-C subit une décomposition. Le transport du métal alcalin dans le réseau hôte est limité par une transition de phase du premier ordre. En tenant compte de toutes ces observations expérimentales, nous avons proposé un mécanisme réactionnel, construit le modèle mathématique associé et résolu le système d’équations différentielles, ainsi obtenu, en utilisant la méthode des différences finies. Les résultats obtenus montrent un bon accord entre les courbes théoriques et les résultats expérimentaux et permettent l’estimation des différents paramètres cinétiques des processus d’interaction Na-C. Enfin, nous avons montré que la pénétration du sodium provoque un changement de la tension interfaciale NaF-C et induit la progression du bain fondu par capillarité à partir d’une fraction molaire minimale en sodium (XNa=1,4. 10-2)One of the most important factors causing the failure of carbon cathode, during aluminum electrolysis by Hall-Héroult process, is the uptake of sodium which leads to a macroscopic swelling of cathode. To understand the fundamental mechanism of sodium-carbon interaction, we carried our electrochemical kinetic study in a pure molten NaF electrolyte at 1025°C. We proved the occurrence of a complex interaction between sodium and carbon. Indeed, sodium is showed to be distributed between two kinds of sites in the host material : normal sites in the Van der Wals gap between the carbon’s plans and traps which are located at microporosity and dislocations. We also showed the occurrence of a slow and irreversible transfer of sodium from traps to normal intercalation sites. Moreover, sodium transport in carbon matrix is found to be limited by a first order phase transition. Taking into account all these experimental observations, we suggested a complete mechanism scheme and developed a mathematical model which allowed the recovery, with a good accuracy of the experimental results
Book chapters on the topic "Graphite|act"
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Dispinar, Derya. "Melt Quality Assessment." In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-120052503.
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It is well known that the reaction of liquid aluminum with the moisture in the environment results in two products: aluminum oxide and hydrogen gas that dissolves in aluminum. Both of these products are considered to be detrimental to the properties of aluminum alloys. Therefore, test equipment has been developed to check the levels of these defects in the melt. Many of these involve expensive and consumable tools. In addition, an experienced personnel may be required to interpret the results. Nonetheless, aluminum oxide is harmless as long as it remains on the surface. The problem begins when this oxide is entrained into the liquid aluminum such as turbulence during transfer or mold filling in a non-optimized design. This can only happen by folding of the oxide. During this action, rough surface of the oxides comes in contact to form no bonds. These defects are known as bifilms that have certain characteristics. First, they act as cracks in the cast parts since they are oxides. It is important to note that aluminum oxide has thin amorphous oxide (known as young oxides) and thick crystalline oxide (γ-Al2O3) that may be formed in a casting operation. Second, almost zero force is required to open these bifilms due to the unbonded folded oxide skins. Thus, these defects can easily form porosity by unravelling during solidification shrinkage. On the other hand, the formation of porosity by hydrogen is practically impossible. Theoretically, hydrogen has high solubility in the liquid but it has significantly low solubility in solid aluminum. Thus, it is suspected that hydrogen is rejected from the solidification front to form hydrogen gas and porosity. However, the hydrogen atom has the smallest atomic radii and high diffusibility. Therefore, segregation of hydrogen in front of the growing solid is difficult. In addition, the energy required for hydrogen atoms to segregate and form hydrogen gas molecule is around 30,000 atm. Under these conditions, porosity formation by hydrogen is not likely to be achieved. Hydrogen probably stays in a supersaturated state or diffuses homogeneously through the cast part. The effect of hydrogen can only be seen when it can diffuse into the unbonded gap between the bifilms to open them up to aid the unravelling of bifilms to form porosity. This phenomenon can be easily detected by a very simple test called reduced pressure test. When a sample is solidified under vacuum, the bifilms start to open up. Since all porosity is formed by bifilms, the cross section of the sample solidified under vacuum can be analyzed by means of image analysis software. The sum of maximum length of pores can be measured as an indication of melt quality. Since bifilms are the most detrimental defects, this value is called “bifilm index” given in millimetres, which makes this test the only test that can quantify aluminum melt quality in such detail including both the effects of bifilms and hydrogen together. Several Al-Si alloys were used at various conditions: degassing with lance, ceramic diffusers, and graphite rotary has been compared. Gravity sand casting, die casting, and low-pressure die casting methods were evaluated. The effect of grain refiners and modifiers was studied. And the evolution of the bifilm index has been presented.
Conference papers on the topic "Graphite|act"
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Ozanam, Odile, and Gerald Ouzounian. "I-Graphite Waste Management in France." In ASME 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2009. http://dx.doi.org/10.1115/icem2009-16301.
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In France about 23,000 tons of irradiated graphite waste were generated mainly from 9 nuclear gas-cooled reactors (UNGG type). All these reactors are now shut down. In France, a final disposal route has been decided for i-graphite waste management by the French Parliament in 2006. The planning act of June 28, 2006 has provisioned that a research and investigation programme shall be established with a view to developing disposal options for graphite waste. The low specific activity of these wastes means shallow disposal facilities located in a geological layer with a low permeability. The main radionuclides that need specific attention for the long term safety are Chlorine 36 and Carbon 14. This establishes the main requirements for the graphite disposal. According to these requirements, underground disposal in a clay layer, at shallow depth, offers good performance in terms of the delay and the reduction of the radionuclide release; it also offers guarantees for the cover’s hydrodynamic and transport properties. The progress of the programme makes it now necessary for a site to be found. Based on a bibliographical study, a wide-spread call for applications took place during the second semester of 2008.
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Tada, Naoya, and Takeshi Uemori. "Dimensional Changes of Graphite Flakes and Fracture in Tensile Tests of Gray Cast Iron." In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-85124.
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Gray cast iron has been used as a component in various mechanical parts, such as the blocks and heads of automobile and marine engines, cylinder liners for internal combustion engines, and machine tool bases. It is desirable because of its good castability and machinability, damping characteristics, and high ratio of performance to cost. On the other hand, the weak graphite flakes present in gray cast iron act as stress concentrators and negatively affect the strength of this material. It is therefore important to know the relationship between the distribution of graphite flakes and the strength or fracture of gray cast iron. In this study, a tensile test of gray cast iron was carried out using a plate specimen in a scanning electron microscope, and the microscopic deformation was observed on the surface of specimen. Particularly, the change in the size of graphite flakes during the tensile test was examined, and the observed trend was discussed. We found from the experimental results that the dimensional changes in the graphite flakes varied in the observed area, and that the final fracture occurred in an area where a relatively large dimensional change was observed. This suggests that the fracture location or the critical parts of gray cast iron, can be predictable from the dimensional changes of the graphite flakes at an early stage of deformation.
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Phillips, Jonathon, Zayd C. Leseman, Joseph Cordaro, Claudia Luhrs, and Marwan Al-Haik. "Novel Graphitic Structures by Design." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42977.
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Graphitic Structures by Design (GSD) is a novel technology for growing graphite in precise patterns from the nano to the macroscale, rapidly (>1 layer/sec), at low temperatures (ca. 500°C), and in a single step using ordinary laboratory equipment. The GSD process consists of exposing particular metals (Ni, Pd, Pt, Co), which act as ‘templates’, to a fuel rich combustion environment. As an example, we have thoroughly characterized graphite growth on nickel in a mixture of ethylene and oxygen (O2/C2H4 ratio<3), and found that it grows in a geometry remarkably consistent with the shape of the metal template at a rate of the order one graphene layer/second at temperatures between about 500 and 700°C. Graphite structures created with GSD to date include two dimensional ‘screens’ that are inches in extent, yet are composed of micron scale squares graphite foam, hollow nanoparticles, and micron scale particles. All alternative technologies for graphite growth require specialty equipment, such as 2000 °C + ovens, and multiple steps. The alternatives are also not suited for a wide variety of pattern growth in either two or three dimensions. We propose to change focus from demonstrating GSD to determination of the mechanism of graphite growth. GSD could meet a number of recognized technological needs for future generation integrated circuits (IC). Precise patterns of oriented graphite are envisioned as: i) replacements of carbon fibers as structural elements in some aerospace and transport applications, ii) as heat conductive pathways aiding thermal management in ICs iii) as electrical conduits in ICs, iv) as the basic elements of nano-scale logic circuits. GSD graphite is arguably superior to the older and more broadly studied carbon nanotubes technology for all these IC applications for many reasons: only GSD be grown in any pattern on any surface, GSD is far cleaner (no metal residue in the graphite structure, in contrast to nanotubes), GSD structures can be formed consistently and cheaply, at low temperature, and only GSD can be readily grown into large designed macrostructures required for some heat transfer applications.
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Rajaram, Gukan, Salil Desai, Zhigang Xu, Devdas M. Pai, and Jag Sankar. "Process Optimization Studies on Ni-YSZ Anode Material for Solid Oxide Fuel Cell Applications." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43592.
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The characteristics of the Ni/YSZ anode material for the solid oxide fuel cells (SOFCs) were investigated in order to study the relation between the porosity and the conductivity of the cell. The nano-sized Yittria Stabilized Zirconia (YSZ) (∼ 60 nm), Nickel Oxide (NiO) (∼ 40 nm) and graphite (∼ 40 nm) particles were used as the raw materials. The graphite particles act as a pore former. The experiments were planned based on a response surface design (central composite design matrix). The graphite content and the sintering temperatures were varied based on the design chart, while the other variables like NiO/YSZ ratio, ball milling time, powder compaction pressure and reduction temperature values were fixed. Porosity and conductivity measurements were performed on the sintered and reduced anode material. The results indicated that the porosity values got decreased by increasing sintering temperature values, while the conductivity values were on the reverse scale. The conductivity values increase with increasing temperature. The scanning electron microscope (SEM) images showed that the sintering temperature had a visible impact on the microstructure. At elevated temperature, the microstructure showed visible particle growth and it formed a better Ni-network along the structure, compared to samples sintered at lower temperature. It is believed that the enhanced Ni-network at elevated temperature helps to increase the electrical conductivity of the Ni-YSZ anode cermet.
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Kockelmann, H., and R. Hahn. "High Grade Performance Proof on Gaskets for Bolted Flange Connections With Organic Fluids." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93634.
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For the “high grade performance proof” on gaskets for bolted flange connections according to TA Luft (German Clean Air Act) and VDI guideline 2440 “Emission Reduction - Mineral Oil Refineries” the pressure increase method was developed as an alternative method based on simple physical laws. The comparison of measuring results with results of the usual Helium mass spectrometry did show rather good agreement of both methods validating the pressure increase method. The advantage of the pressure increase method is the fact that a lot of volatile organic fluids can be used as test medium. It was shown that with Methanol and Ethanol the leakage rate criterion of VDI guideline 2200 for 40 bar internal pressure for a Graphite based sheet gasket often in use in chemical plants is met.
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Shahinpoor, Mohsen. "Smart Thin Sheet Batteries Made With Ionic Polymer Metal Composites (IPMC’s)." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60954.
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Presented is some experimental results and theoretical modeling pertaining to thin (30 microns) paper-like sheets of ionic polymer metal composites (IPMC’s) as paper batteries. These materials can generate electrical power by means of mechanical flexing, normal pressure and motion in general and they are smart because they are self-powered but rechargeable by moisture. Thin sheets or paper-like labels of IPMC’s can be bonded, glued or attached to any flexible or rigid substrate or can be laminated and can generate power by the motion of that substrate or any normal or oblique pressure exerted on that substrate through the IPMC sheet, label or laminate. A good example of these materials is perfluorinated sulfonic or carboxylic ionic polymers, which are suitably made into a functionally graded composite with a conductive phase such as graphite, conductive polymers or metals. These materials can also act as distributed nanosensors and distributed nanoactuators if moderate electrical field strength of about 10 volts per millimeter (10V/mm) is imposed on them through printed or interdigitated electrodes.
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Cabet, Celine, Fabien Rouillard, Gouenou Girardin, and Martine Blat. "Corrosion Issues of HTR Structural Metallic Materials." In Fourth International Topical Meeting on High Temperature Reactor Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/htr2008-58152.
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Cooling helium of HTRs is expected to contain a low level of impurities: oxidizing gasses and carbon-bearing species. Reference structural materials for pipes and heat exchangers are chromia-former nickel base alloys — typically alloys 617 and 230 — and, as is generally the case in any high temperature process, their long term corrosion resistance relies on the growth of a surface chromium-oxide that can act as a barrier against corrosive species. This implies that the HTR environment must allow for oxidation of these alloys to occur, while it remains not too oxidizing against in-core graphite. First, studies on the surface reactivity under various impure helium containing low partial pressures of H2, H2O, CO and CH4 show that alloys 617 and 230 oxidize in many atmospheres from intermediate temperatures up to 890–970°C, depending on the exact gas composition. However when heated above a critical temperature, the surface oxide becomes unstable: it was demonstrated that at the scale/alloy interface the surface oxide interacts with the carbon from the material. These investigations have established an environmental area that promotes oxidation. When expose in oxidizing HTR helium, alloys 617 and 230 actually develop a sustainable surface scale over thousands of hours. On the other hand if the scale is destabilized by reaction with the carbon, the oxide is not protective anymore and the alloy surface interacts with gaseous impurities. In the case of CH4-containg atmospheres, this causes rapid carburization in the form of precipitation of coarse carbides on the surface and in the bulk. Carburization was shown to induce an extensive embrittlement of the alloys. In CH4-free helium mixtures, alloys decarburize with a global loss of carbon and dissolution of the pre-existing carbides. As carbides take part to the alloy strengthening at high temperature, it is expected that decarburization impacts the creep properties. Carburization and decarburization degrade rapidly the alloy properties and thus result in an unacceptably high risk on the material integrity at high temperature. Therefore, the purification system shall control the gas composition in order to make this unique helium atmosphere compatible with the in-core graphite as well as with structural materials. This paper reviews the data on the corrosion behavior of structural material in HTR and draws some conclusion on appropriate helium chemistry regarding the material compatibility at high temperature.
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Hasib, A. M. M. G., Rambod Rayegan, and Yong X. Tao. "Investigation of Using Dispersed Particle and Branching Heat Exchnager in Medium Temperature Thermal Energy Storage System to Achieve Maximum Utilization of Solar Power." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65646.
Full textAbstract:
Maximum utilization of solar energy is very critical to achieve, because a significant portion of solar energy is lost in the form of heat. In that case Thermal Energy Storage (TES) can play a significant role by capturing the energy in the form of heat and later on can be used as a backup source of energy for utilizing it in critical time. On the other side, from the view point of conservation of energy, energy cannot be created or destroyed, but surprisingly a significant amount of energy cannot be utilized due to the instantaneous nature of conventional power generation. So storing Energy is the most unique idea that can act as a strong backup for the instantaneous nature of power generation as it not only adds up to the power generation capacity but also serves to be the most reliable medium of supplying power when the energy demand is at peak. In the authors’ previous work a phase change material (molten solar salt comprised of 60% NaNO3+40%KNO3) and a system design for thermal energy storage (TES) system integrated with a solar Organic Rankine Cycle (ORC) has been proposed. The associated research problems investigated for phase change material (PCM) are the low thermal conductivity and low rate of heat transfer from heat transfer fluid to PCM. In this study a detailed numerical modeling of the proposed design using MATLAB code and the relevant calculation and results are discussed. The numerical model is based on 1-D finite difference explicit technique using the fixed grid enthalpy method. To overcome the research problem highly conductive nano-particle graphite is used to enhance the effective thermal conductivity of the PCM material in theoretical calculation. In the later part of the study results from the numerical computation have been utilized to demonstrate a comparison between a conventional heating system (with a simple single tube as a heat exchanger) and a branching heat exchanger in PCM thermal energy storage system using NTU-Effectiveness method. The comparison results show a significant amount of improvement using branching network and mixing nano-particle in terms of heat transfer, thermal conductivity enhancement, charging time minimization and pressure drop decrease. The results of this study can convince us that the proposed medium temperature TES system coupled with solar ORC can be a stepping-stone for energy efficient and sustainable future in small-scale power generation as the system proves to be better in terms of enhanced heat transfer, increased thermal conductivity and overall sustainability.