Chromium(III) boride explained

Chromium(III) boride, also known as chromium monoboride (CrB), is an inorganic compound with the chemical formula CrB.[1] It is one of the six stable binary borides of chromium, which also include Cr2B, Cr5B3, Cr3B4, CrB2, and CrB4.[2] Like many other transition metal borides, it is extremely hard (21-23 GPa),[3] [4] has high strength (690 MPa bending strength),[4] conducts heat and electricity as well as many metallic alloys,[5] [6] and has a high melting point (~2100 °C).[7] [2] Unlike pure chromium, CrB is known to be a paramagnetic, with a magnetic susceptibility that is only weakly dependent on temperature.[8] [9] Due to these properties, among others, CrB has been considered as a candidate material for wear resistant coatings and high-temperature diffusion barriers.

It can be synthesized as powders by many methods including direct reaction of the constituent elemental powders,[10] self-propagating high-temperature synthesis (SHS), borothermic reduction,[11] [12] and molten salt growth.[13] Slow-cooling of molten aluminum solutions from high-temperatures has been used to grow large single crystals, with a maximum size of 0.6 mm x 0.6 mm x 8.3 mm.

CrB has an orthorhombic crystal structure (space group Cmcm) that was first discovered in 1951,[14] and subsequently confirmed by later work using single crystals.[15] The crystal structure can be visualized as slabs face-sharing BCr6 trigonal prisms, in the ac-plane, that are stacked parallel to the <010> crystallographic direction. Similar to Cr3B4 and Cr2B3, the B atoms in the structure form covalent bonds with each other and are characterized by unidirectional B-B- chains parallel to the <001> crystallographic direction. The transition metal monoborides VB, NbB, TaB, and NiB have the same crystal structure.

Notes and References

  1. 10.1016/0022-5088(67)90188-9. On the preparation of some chromium, molybdenum and tungsten borides. 1967. Peshev. P.. Bliznakov. G.. Leyarovska. L.. Journal of the Less Common Metals. 13. 2. 241.
  2. Liao. P. K.. Spear. K. E.. June 1986. The B−Cr (Boron-Chromium) system. Bulletin of Alloy Phase Diagrams. 7. 3. 232–237. 10.1007/BF02868996. 0197-0216.
  3. Okada. Shigeru. Kudou. Kunio. Iizumi. Kiyokata. Kudaka. Katsuya. Higashi. Iwami. Lundström. Torsten. September 1996. Single-crystal growth and properties of CrB, Cr3B4, Cr2B3 and CrB2 from high-temperature aluminum solutions. Journal of Crystal Growth. 166. 1–4. 429–435. 10.1016/0022-0248(95)00890-X. 1996JCrGr.166..429O.
  4. Hiroki. Yuji. Yoshinaka. Masaru. Hirota. Ken. Yamaguchi. Osamu. 2003. Hot Isostatic Pressing of CrB Prepared by Self-propagating High-temperature Synthesis. Journal of the Japan Society of Powder and Powder Metallurgy. 50. 5. 367–371. 10.2497/jjspm.50.367. 0532-8799. free.
  5. L'vov. S. N.. Nemchenko. V. F.. Kislyi. P. S.. Verkhoglyadova. T. S.. Kosolapova. T. Ya.. 1964. The electrical properties of chromium borides, carbides, and nitrides. Soviet Powder Metallurgy and Metal Ceramics. 1. 4. 243–247. 10.1007/BF00774426. 137007220. 0038-5735.
  6. Ohishi. Yuji. Sugizaki. Mitsuyuki. Sun. Yifan. Muta. Hiroaki. Kurosaki. Ken. 2019-03-22. Thermophysical and mechanical properties of CrB and FeB. Journal of Nuclear Science and Technology. 56. 9–10. 859–865. 10.1080/00223131.2019.1593893. 2019JNST...56..859O . 109795656. 0022-3131.
  7. Kislyi. P. S.. L'vov. S. N.. Nemchenko. V. F.. Samsonov. G. V.. 1964. Physical properties of the boride phases of chromium. Soviet Powder Metallurgy and Metal Ceramics. 1. 6. 441–443. 10.1007/BF00773921. 137532121. 0038-5735.
  8. Guy. C.N.. 1976. The electronic properties of chromium borides. Journal of Physics and Chemistry of Solids. 37. 11. 1005–1009. 10.1016/0022-3697(76)90123-2. 1976JPCS...37.1005G.
  9. Kota. Sankalp. Wang. Wenzhen. Lu. Jun. Natu. Varun. Opagiste. Christine. Ying. Guobing. Hultman. Lars. May. Steven J.. Barsoum. Michel W.. October 2018. Magnetic properties of Cr2AlB2, Cr3AlB4, and CrB powders. Journal of Alloys and Compounds. 767. 474–482. 10.1016/j.jallcom.2018.07.031. 103421636. free.
  10. Lundquist. N.. Myers. H. P.. Westin. R.. July 1962. The paramagnetic properties of the monoborides of V, Cr, Mn, Fe, Co and Ni. Philosophical Magazine. 7. 79. 1187–1195. 10.1080/14786436208209119. 0031-8086. 1962PMag....7.1187L.
  11. Okada. Shigeru. Iizumi. Kiyokata. Ogino. Tomoyuki. Kudaka. Katsuya. Kudou. Kunio. 1996. Preparation of CrB Single Crystals by the Reaction between Chromium Oxide and Amorphous Boron Powders.. Nippon Kagaku Kaishi. 1996. 3. 260–263. 10.1246/nikkashi.1996.260. 2185-0925. free.
  12. Iizumi. Kiyokata. Kudaka. Katsuya. Okada. Shigeru. 1998. Synthesis of Chromium Borides by Solid-State Reaction between Chromium Oxide (III) and Amorphous Boron Powders. Journal of the Ceramic Society of Japan. 106. 1237. 931–934. 10.2109/jcersj.106.931. 1882-1022. free.
  13. Cao. Weixiao. Wei. Ya'nan. Meng. Xin. Ji. Yuexia. Ran. Songlin. 2017-04-13. A general method towards transition metal monoboride nanopowders. International Journal of Materials Research. 108. 4. 335–338. 10.3139/146.111484. 2017IJMR..108..335C . 136085434. 1862-5282.
  14. Frueh. A. J.. 1951-01-01. Confirmation of the structure of chromium boride, CrB. Acta Crystallographica. 4. 1. 66–67. 10.1107/S0365110X51000118. 0365-110X. free. 1951AcCry...4...66F .
  15. Okada. Shigeru. Atoda. Tetsuzo. Higashi. Iwami. May 1987. Structural investigation of Cr2B3, Cr3B4, and CrB by single-crystal diffractometry. Journal of Solid State Chemistry. 68. 1. 61–67. 10.1016/0022-4596(87)90285-4. 1987JSSCh..68...61O.

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