boron carbide

boron carbide
a black, crystalline, extremely hard, water-insoluble solid, B4C, used chiefly as a moderator in nuclear reactors, as an abrasive, and as a refractory.

* * *

      (B4C), crystalline compound of boron and carbon. It is an extremely hard, synthetically produced material that is used in abrasive and wear-resistant products, in lightweight composite materials, and in control rods for nuclear (nuclear reactor) power generation.

      With a Mohs hardness between 9 and 10, boron carbide is one of the hardest synthetic substances known, being exceeded only by cubic boron nitride and diamond. As an abrasive, it is used in powdered form in the lapping (fine abrading) of metal and ceramic products, though its low oxidation temperature of 400–500° C (750–930° F) makes it unable to withstand the heat of grinding hardened tool steels. Because of its hardness, together with its very low density, it has found application as a reinforcing agent for aluminum in military armour and high-performance bicycles, and its wear resistance has caused it to be employed in sandblasting nozzles and pump seals. A neutron absorber, boron carbide is used in powdered or solidified form to control the rate of fission in nuclear reactors.

      Boron carbide is produced by reducing boron oxide with carbon at high temperatures in an electric furnace. After grinding, the black powder is solidified by pressing at temperatures exceeding 2,000° C (3,630° F). Its melting point is approximately 2,350° C (4,260° F).

* * *


Universalium. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • boron carbide — n. a black, crystalline compound of boron and carbon, B4C, almost as hard as diamond: used as an abrasive and in control rods for nuclear reactors: see MOHS SCALE (sense 2) …   English World dictionary

  • Boron carbide — Chembox new Name = Boron carbide ImageFile = ImageSize = ImageName = Boron carbide IUPACName = Boron carbide OtherNames = Tetrabor B4 C B4C Black Diamond Section1 = Chembox Identifiers CASNo = 12069 32 8 Section2 = Chembox Properties Formula =… …   Wikipedia

  • boron carbide — noun : any binary compound of boron and carbon; especially : a refractory shiny black crystalline solid B4C ranking next to the diamond in hardness made usually by heating boric oxide and coke in an electric furnace and used chiefly as powdered… …   Useful english dictionary

  • boron carbide — a compound, B4C, slightly harder than silicon carbide (q.v.), obtained by heating boron at very high temperature to effect its union with carbon; used as a neutron absorber in nuclear reactors, and as an abrasive agent in industry and dentistry …   Medical dictionary

  • boron carbide — noun A binary compound of boron and carbon, BC, that is a very hard ceramic, and is used in tank armour, bulletproof vests etc. Syn: Tetrabor …   Wiktionary

  • boron carbide — noun Date: circa 1909 a refractory shiny black crystalline compound B4C that is one of the hardest known materials and is used especially in abrasives and as a structural reinforcing material …   New Collegiate Dictionary

  • boron carbide — /bɔrɒn ˈkabaɪd / (say bawron kahbuyd) noun a black crystalline solid, B4C, which is the hardest known substance after diamond, and which is used as an abrasive and to form control rods in nuclear reactors …  

  • Boron nitride — IUPAC name Boron nitride Identifiers …   Wikipedia

  • Boron — (pronEng|ˈbɔərɒn) is a chemical element with atomic number 5 and the chemical symbol B. Boron is a trivalent nonmetallic element which occurs abundantly in the evaporite ores borax and ulexite. Boron is never found as a free element on… …   Wikipedia

  • Boron trioxide — Other …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”