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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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640 citations
TL;DR: In this paper, a boron-containing silicon nitride/carbide ceramic that does not degrade at temperatures up to 2,000 °C even in nitrogen-free environments is presented.
Abstract: CERAMICS based on silicon nitride and carbide are strong and stable at high temperatures, and are therefore under investigation for the fabrication of motor and turbine parts1–3. But silicon nitride decomposes at about 1,400 °C in vacuum and 1,775 °C in 0.1 MPa nitrogen4,5, limiting the high-temperature range of its technological uses. Here we describe a boron-containing silicon nitride/carbide ceramic that does not degrade at temperatures up to 2,000 °C even in nitrogen-free environments. We synthesize the material in a polymer-to-ceramic transformation6 from a single polymeric polyborosilazane precursor. On heating at 1,000 °C in argon we obtain a ceramic with the composition Si3.0B1.0C4.3N2.0. The ceramic begins to convert to a polycrystalline composite of silicon nitride and carbide (with some non-crystalline boron nitride) at 1,700 °C, a process that is completed (without substantial change in elemental composition) at 2,000 °C.
634 citations
25 Nov 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a novel concept for the heat treatment of martensite, different to customary quenching and tempering, is described, which can be used to generate microstructures with martensites/austenite combinations giving attractive properties.
Abstract: A novel concept for the heat treatment of martensite, different to customary quenching and tempering, is described. This involves quenching to below the martensite-start temperature and directly ageing, either at, or above, the initial quench temperature. If competing reactions, principally carbide precipitation, are suppressed by appropriate alloying, the carbon partitions from the supersaturated martensite phase to the untransformed austenite phase, thereby increasing the stability of the residual austenite upon subsequent cooling to room temperature. This novel treatment has been termed ‘quenching and partitioning’ (Q&P), to distinguish it from quenching and tempering, and can be used to generate microstructures with martensite/austenite combinations giving attractive properties. Another approach that has been used to produce austenite-containing microstructures is by alloying to suppress carbide precipitation during the formation of bainitic structures, and interesting comparisons can be made between the two approaches. Moreover, formation of carbide-free bainite during the Q&P partitioning treatment may be a reaction competing for carbon, although this could also be used constructively as an additional stage of Q&P partitioning to form part of the final microstructure. Amongst the ferrous alloys examined so far are medium carbon bar steels and low carbon formable TRIP-assisted sheet steels.
618 citations
TL;DR: Carbide-derived carbons (CDCs) as discussed by the authors are a large family of carbon materials derived from carbide precursors that are transformed into pure carbon via physical (e.g., thermal decomposition) or chemical processes.
Abstract: Carbide-derived carbons (CDCs) are a large family of carbon materials derived from carbide precursors that are transformed into pure carbon via physical (e.g., thermal decomposition) or chemical (e.g., halogenation) processes. Structurally, CDC ranges from amorphous carbon to graphite, carbon nanotubes or graphene. For halogenated carbides, a high level of control over the resulting amorphous porous carbon structure is possible by changing the synthesis conditions and carbide precursor. The large number of resulting carbon structures and their tunability enables a wide range of applications, from tribological coatings for ceramics, or selective sorbents, to gas and electrical energy storage. In particular, the application of CDC in supercapacitors has recently attracted much attention. This review paper summarizes key aspects of CDC synthesis, properties, and applications. It is shown that the CDC structure and properties are sensitive to changes of the synthesis parameters. Understanding of processing–structure–properties relationships facilitates tuning of the carbon material to the requirements of a certain application.
612 citations
TL;DR: Observation of crystals of pure encapsulated α-LaC2 that were exposed to air for several days before analysis indicates that the LaC2 is protected from degradation by the carbon polyhedral shells of the nanoparticles, a new class of materials that can be protected in their pure or carbide forms and may have interesting and useful properties.
Abstract: Single-domain microcrystals of LaC2 encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observed by high-resolution transmission electron microscopy and energy dispersive spectroscopy (EDS). EDS spectra show that La and C are the only elements present. Characteristic interatomic distances of 3.39 and 2.78 angstroms identify the compound inside the nanoparticle cavities as α-LaC2, the phase of LaC2 that is stable at room temperature. Bulk α-LaC2 is metallic and hydrolytic. Observation of crystals of pure encapsulated α-LaC2 that were exposed to air for several days before analysis indicates that the LaC2 is protected from degradation bythe carbon polyhedral shells of the nanoparticles. A high percentage of the carbon nanoparticles have encapsulated LaC2 single crystals. These carbon-coated metal crystals form a new class of materials that can be protected in their pure or carbide forms and may have interesting and useful properties.
609 citations