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- Un borure de silicium, parfois appelé siliciure de bore, est un composé chimique de formule SiBn, où n = 3, 4, 6, mais peut aussi prendre des valeurs bien plus élevées, telles que 14, 15, 40, etc. Il s'agit de céramiques légères constituées de silicium et de bore dont les premières, le triborure de silicium SiB3 et l'hexaborure de silicium SiB6, ont été publiées en 1900 par deux chimistes européens, le Français Henri Moissan et l'Allemand Alfred Stock. D'autres borures de silicium ont été caractérisés depuis, comme le tétraborure SiB4 en 1960, dont la structure cristalline est isomorphe de celle du carbure de bore B4C. Le tétraborure de silicium a été utilisé comme revêtement noir des tuiles de boucliers thermiques de certaines navettes spatiales. Tous ces composés sont des solides noirs cristallisés de masse volumique voisine : 2,52 g·cm-3 et 2,47 g·cm-3 pour le tri/tétraborure et l'hexaborure de silicium respectivement. Leur dureté sur l'échelle de Mohs se situe entre celles du rubis (9) et du diamant (10). (fr)
- Silicon borides (also known as boron silicides) are lightweight ceramic compounds formed between silicon and boron. Several stoichiometric silicon boride compounds, SiBn, have been reported: silicon triboride, SiB3, silicon tetraboride, SiB4, silicon hexaboride, SiB6, as well as SiBn (n = 14, 15, 40, etc.). The n = 3 and n = 6 phases were reported as being co-produced together as a mixture for the first time by Henri Moissan and Alfred Stock in 1900 by briefly heating silicon and boron in a clay vessel. The tetraboride was first reported as being synthesized directly from the elements in 1960 by three independent groups: Carl Cline and Donald Sands; Ervin Colton; and Cyrill Brosset and Bengt Magnusson. It has been proposed that the triboride is a silicon-rich version of the tetraboride. Hence, the stoichiometry of either compound could be expressed as SiB4 - x where x = 0 or 1. All the silicon borides are black, crystalline materials of similar density: 2.52 and 2.47 g cm−3, respectively, for the n = 3(4) and 6 compounds. On the Mohs scale of mineral hardness, SiB4 - x and SiB6 are intermediate between diamond (10) and ruby (9). The silicon borides may be grown from boron-saturated silicon in either the solid or liquid state. The SiB6 crystal structure contains interconnected icosahedra (polyhedra with 20 faces), icosihexahedra (polyhedra with 26 faces), as well as isolated silicon and boron atoms. Due to the size mismatch between the silicon and boron atoms, silicon can be substituted for boron in the B12 icosahedra up to a limiting stoichiometry corresponding to SiB2.89. The structure of the tetraboride SiB4 is isomorphous to that of boron carbide (B4C), B6P, and B6O. It is metastable with respect to the hexaboride. Nevertheless, it can be prepared due to the relative ease of crystal nucleation and growth. Both SiB4 - x and SiB6 become superficially oxidized when heated in air or oxygen and each is attacked by boiling sulfuric acid and by fluorine, chlorine, and bromine at high temperatures. The silicon borides are electrically conducting. The hexaboride has a low coefficient of thermal expansion and a high nuclear cross section for thermal neutrons. The tetraboride was used in the black coating of some of the space shuttle heat shield tiles. (en)
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- Un borure de silicium, parfois appelé siliciure de bore, est un composé chimique de formule SiBn, où n = 3, 4, 6, mais peut aussi prendre des valeurs bien plus élevées, telles que 14, 15, 40, etc. Il s'agit de céramiques légères constituées de silicium et de bore dont les premières, le triborure de silicium SiB3 et l'hexaborure de silicium SiB6, ont été publiées en 1900 par deux chimistes européens, le Français Henri Moissan et l'Allemand Alfred Stock. D'autres borures de silicium ont été caractérisés depuis, comme le tétraborure SiB4 en 1960, dont la structure cristalline est isomorphe de celle du carbure de bore B4C. Le tétraborure de silicium a été utilisé comme revêtement noir des tuiles de boucliers thermiques de certaines navettes spatiales. (fr)
- Silicon borides (also known as boron silicides) are lightweight ceramic compounds formed between silicon and boron. Several stoichiometric silicon boride compounds, SiBn, have been reported: silicon triboride, SiB3, silicon tetraboride, SiB4, silicon hexaboride, SiB6, as well as SiBn (n = 14, 15, 40, etc.). The n = 3 and n = 6 phases were reported as being co-produced together as a mixture for the first time by Henri Moissan and Alfred Stock in 1900 by briefly heating silicon and boron in a clay vessel. The tetraboride was first reported as being synthesized directly from the elements in 1960 by three independent groups: Carl Cline and Donald Sands; Ervin Colton; and Cyrill Brosset and Bengt Magnusson. It has been proposed that the triboride is a silicon-rich version of the tetraboride. He (en)
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