Chromium(III) boride

Chromium(III) boride, also known as chromium monoboride (CrB), is an inorganic compound with the chemical formula CrB.[2] It is one of the six stable binary borides of chromium, which also include Cr2B, Cr5B3, Cr3B4, CrB2, and CrB4.[3] Like many other transition metal borides, it is extremely hard (21-23 GPa),[4][5] has high strength (690 MPa bending strength),[5] conducts heat and electricity as well as many metallic alloys,[4][6][7] and has a high melting point (~2100 °C).[8][3] Unlike pure chromium, CrB is known to be a paramagnetic, with a magnetic susceptibility that is only weakly dependent on temperature.[9][10] Due to these properties, among others, CrB has been considered as a candidate material for wear resistant coatings and high-temperature diffusion barriers.

Chromium(III) boride
Names
IUPAC name
boranylidynechromium
Other names
Chromium monoboride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.339
EC Number
  • 234-487-8
  • InChI=1S/Cr.B
    Key: NUEWEVRJMWXXFB-UHFFFAOYSA-N
  • B#[Cr]
Properties
CrB
Molar mass 62.81 g/mol
Appearance silver, ceramic material
Density 6.17 g/cm3
Melting point 1,950 to 2,050 °C (3,540 to 3,720 °F; 2,220 to 2,320 K)
insoluble
Structure
orthorhombic (space group Cmcm)
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
0
0
0
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 1 mg/m3[1]
REL (Recommended)
 TWA 0.5 mg/m3[1]
IDLH (Immediate danger)
 250 mg/m3[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

It can be synthesized as powders by many methods including direct reaction of the constituent elemental powders,[11] self-propagating high-temperature synthesis (SHS),[5] borothermic reduction,[12][13] and molten salt growth.[14] 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.[4]

CrB has an orthorhombic crystal structure (space group Cmcm) that was first discovered in 1951,[15] and subsequently confirmed by later work using single crystals.[16] 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.

Crystal Structure of CrB in the space group Cmcm

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0141". National Institute for Occupational Safety and Health (NIOSH).
  2. Peshev, P.; Bliznakov, G.; Leyarovska, L. (1967). "On the preparation of some chromium, molybdenum and tungsten borides". Journal of the Less Common Metals. 13 (2): 241. doi:10.1016/0022-5088(67)90188-9.
  3. Liao, P. K.; Spear, K. E. (June 1986). "The B−Cr (Boron-Chromium) system". Bulletin of Alloy Phase Diagrams. 7 (3): 232–237. doi:10.1007/BF02868996. ISSN 0197-0216.
  4. 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. Bibcode:1996JCrGr.166..429O. doi:10.1016/0022-0248(95)00890-X.
  5. 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. doi:10.2497/jjspm.50.367. ISSN 0532-8799.
  6. 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. doi:10.1007/BF00774426. ISSN 0038-5735. S2CID 137007220.
  7. 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. doi:10.1080/00223131.2019.1593893. ISSN 0022-3131. S2CID 109795656.
  8. 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. doi:10.1007/BF00773921. ISSN 0038-5735. S2CID 137532121.
  9. Guy, C.N. (1976). "The electronic properties of chromium borides". Journal of Physics and Chemistry of Solids. 37 (11): 1005–1009. Bibcode:1976JPCS...37.1005G. doi:10.1016/0022-3697(76)90123-2.
  10. 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. doi:10.1016/j.jallcom.2018.07.031. S2CID 103421636.
  11. 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. Bibcode:1962PMag....7.1187L. doi:10.1080/14786436208209119. ISSN 0031-8086.
  12. 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. doi:10.1246/nikkashi.1996.260. ISSN 2185-0925.
  13. 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. doi:10.2109/jcersj.106.931. ISSN 1882-1022.
  14. 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. doi:10.3139/146.111484. ISSN 1862-5282. S2CID 136085434.
  15. Frueh, A. J. (1951-01-01). "Confirmation of the structure of chromium boride, CrB". Acta Crystallographica. 4 (1): 66–67. doi:10.1107/S0365110X51000118. ISSN 0365-110X.
  16. 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. Bibcode:1987JSSCh..68...61O. doi:10.1016/0022-4596(87)90285-4.
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