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Carbide
About: Carbide is a research topic. Over the lifetime, 36331 publications have been published within this topic receiving 503586 citations.
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TL;DR: The first attempts to introduce carbon into glass date back to 1951 as mentioned in this paper, and the use of carbon or carbide raw materials, and the oxidation, volatilization and decomposition that accompany high temperature melting, have limited the synthesis of true silicon oxycarbide glasses.
Abstract: The first attempts to introduce carbon into glass date back to 1951. But up until recently, the use of carbon or carbide raw materials, and the oxidation, volatilization and decomposition that accompany high temperature melting, have limited the synthesis of true silicon oxycarbide glasses. Here, the term silicon-oxycarbide refers specifically to a carbon-containing silicate glass wherein oxygen and carbon atoms share bonds with silicon in the amorphous, network structure. Thus, there is a distinction between black glass, which contains only a second-phase dispersion of elemental carbon, and oxycarbide glasses which usually contain both network carbon and elemental carbon. In addition to exploring the unique properties and applications of these glasses, per se, they are also of interest for developing models of the residual amorphous phases in polymer-derived silicon-carbide and silicon-nitride ceramics. The application of sol/gel techniques to glass synthesis has significantly advanced the development and characterization of silicon oxycarbide glasses. In this approach, alkyl-substituted silicon alkoxides, which are molecular precursors containing oxygen and carbon functionalities on the silicon, can be hydrolyzed and condensed without decomposition or loss of the carbon functional group. A low-temperature (<1000°C) heat-treatment of the gel creates a glassy silicate material whose molecular structure consists of an oxygen/carbon anionic network. In addition, there is always a blackening of the material due to elemental carbon, which forms during pyrolysis and densification of the gel. The nature of the network carbon, and especially the distribution and form of the elemental carbon, are fundamental to the structure and properties of these novel materials. Their chemical and physical characteristics as revealed by NMR, Raman and TEM are discussed in the overview. In addition, the high temperature stability of these glasses (up to 1750°C), and the effect of hot-pressing, are described. It will be shown that the silicon oxycarbide network is stable up to 1000–1200°C. The network carbon is terminated with hydrogen (i.e., CH, =CH2 and –CH3), and with polyaromatic carbon (i.e., nC6Hx) wherein most of the elemental carbon resides. These glasses can be described as molecular composites of polyaromatic graphene-rings dispersed in a silicon oxycarbide network. After heating to temperatures in excess of 1000–1200°C, the oxycarbide network decomposes through the loss of hydrogen, and a two- or three-phase glass-ceramic consisting of nanocrystalline graphite, silicon carbide, and amorphous silica or cristobalite, is created. Some of the properties and applications of these glasses/glass-ceramics for coatings, composites and porous solids are summarized.
385 citations
TL;DR: In this paper, a study was made of the catalytic graphitization of carbons by 22 kinds of metals, and the relationships between some properties of the metals, their catalytic abilities and the kind of catalytic effects were discussed.
382 citations
TL;DR: In this paper, a new ab initio entropy descriptor was developed to assist in selection of candidate compositions for synthesis of high entropy and entropy stabilized carbides. But the proposed descriptor is not suitable for high-energy ball milling and spark plasma sintering.
380 citations
TL;DR: In this article, a temperature-programmed reaction between MoO3 of low specific surface area Sg and a CH 4 H 2 mixture produces unsupported powders of hexagonal Mo2C with Sg from 50 to 100 m2 g− and CO uptake number density of up to 5.0 × 1014 cm−2.
380 citations
TL;DR: In this paper, a systematic experimental investigation of a large number of carbide-derived carbons with controlled pore size distributions and specific surface area (SSA) was conducted to investigate the effect of small pore sizes on the heat and volume of adsorbed H2.
Abstract: Cryoadsorption is a promising method of enhancing gravimetric and volumetric onboard H2 storage capacity for future trans- portation needs. Inexpensive carbide-derived carbons (CDCs), produced by chlorination of metal carbides, have up to 80% open-pore volume with tunable pore size and specific surface area (SSA). Tuning the carbon structure and pore size with high sensitivity by using different starting carbides and chlorination temperatures allows rational design of carbon materials with en- hanced C-H2 interaction and thus increased H2 storage capacity. A systematic experimental investigation of a large number of CDCs with controlled pore size distributions and SSAs shows how smaller pores increase both the heat of adsorption and the total volume of adsorbed H2. It has been demonstrated that increasing the average heat of H2 adsorption above 6.6 kJmol -1 substantially enhances H2 uptake at 1 atm (1 atm=101325 Pa) and -196°C. The heats of adsorption up to 11 kJmol -1 exceed values reported for metal-organic framework compounds and carbon nanotubes.
377 citations