Hafnium diboride

Crystal structure
	__ Hf __ B
General
Surname	Hafnium diboride
Ratio formula	HfB 2
Brief description	gray solid
External identifiers / databases
EC number	234-500-7
ECHA InfoCard	100.031.351
PubChem	6336857
Wikidata	Q4161099
properties
Molar mass	200.11 g mol −1
Physical state	firmly
density	10.5 g / cm³ (25 ° C)
Melting point	3100 ° C
solubility	practically insoluble in water
safety instructions
GHS labeling of hazardous substances Caution
H and P phrases	H: 315-319-335
	P: 261-305 + 351 + 338
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Hafnium diboride is an inorganic chemical compound of hafnium from the group of borides . In addition to this, two other hafnium borides are known: hafnium monoboride HfB and hafnium dodecaboride HfB ₁₂ .

Extraction and presentation

Hafnium diboride can be obtained by reacting hafnium dioxide with carbon and boron trioxide or boron carbide . It can also be produced by reacting mixtures of hafnium tetrachloride , boron trichloride and hydrogen at temperatures above 2000 ° C or directly from the elements.

{\ displaystyle {\ ce {HfO2 + B2O3 + 5 C -> HfB2 + 5 CO}}}

Electrochemical processes are known for the deposition of thin layers of hafnium diboride.

properties

Hafnium diboride is a gray solid that is practically insoluble in water. The compound is attacked by hydrofluoric acid , but is resistant to almost all other reagents at room temperature. It only oxidizes at temperatures above 1500 ° C. The Vickers hardness is between 2200 and 2900. Hafnium diboride has a hexagonal crystal structure of the aluminum diboride type C32 with the space group P 6 / mmm (space group no. 191) . Its specific resistance is 15 µΩ · cm and its hardness is 29 GPa. Template: room group / 191

use

Hafnium diboride is used in wear-resistant coatings. It is also used as a material for control rods in nuclear reactors and as a material for ICBM - heat shields or aerodynamic leading edges. It is also a component of high-temperature composite materials in conjunction with silicon carbide . It is also used as a material for heating elements in nozzles in inkjet printers.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f Data sheet Hafnium boride, powder, −325 mesh, 99% trace metals basis from Sigma-Aldrich , accessed on February 26, 2018 ( PDF ).
↑ ^a ^b ^c Data sheet Hafnium boride, 99.5% (metals basis excluding Zr), Zr <2% from AlfaAesar, accessed on February 26, 2018 ( PDF )(JavaScript required) .
↑ ^a ^b ^c Eula Bingham, Barbara Cohrssen: Patty's Toxicology . John Wiley & Sons, 2012, ISBN 0-470-41081-7 , pp. 463 ( limited preview in Google Book search).
↑ Marcelle GAUNE-Escard, Kenneth R. Seddon: Molten Salts and Ionic Liquids Never the Twain? John Wiley & Sons, 2012, ISBN 0-470-94776-4 , pp. 197 ( limited preview in Google Book search).
↑ Michael McNallan: High Temperature Corrosion and Materials Chemistry Proceedings of the Per Kofstad Memorial Symposium . The Electrochemical Society, 2000, ISBN 978-1-56677-261-7 , pp. 490 ( limited preview in Google Book search).
↑ Ian Hutchings, Philip Shipway: Tribology Friction and Wear of Engineering Materials . Butterworth-Heinemann, 2017, ISBN 978-0-08-100951-2 , pp. 171 ( limited preview in Google Book search).
^ John W. Lawson, Murray S. Daw, Charles W. Bauschlicher: Lattice thermal conductivity of ultra high temperature ceramics ZrB ₂ and HfB ₂ from atomistic simulations. In: Journal of Applied Physics. 110, 2011, p. 083507, doi : 10.1063 / 1.3647754 .
↑ ^a ^b Sreenivas Jayaraman, Y. u. Yang, Do Young Kim, Gregory S. Girolami, John R. Abelson: Hafnium diboride thin films by chemical vapor deposition from a single source precursor. In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films. 23, 2005, p. 1619, doi : 10.1116 / 1.2049307 .
↑ Loehman, RE. (2004). Ultra-high-temperature ceramics for hypersonic vehicle applications . 71.
↑ DS Wuu, ML Lee, TY Lin, RH Horng: Characterization of hafnium diboride thin film resistors by rf magnetron sputtering. In: Materials Chemistry and Physics. 45, 1996, p. 163, doi : 10.1016 / 0254-0584 (96) 80096-4 .

[Sigma-1] ↑ ^a ^b ^c ^d ^e ^f Data sheet Hafnium boride, powder, −325 mesh, 99% trace metals basis from Sigma-Aldrich , accessed on February 26, 2018 ( PDF ).

[Alfa-2] Data sheet Hafnium boride, 99.5% (metals basis excluding Zr), Zr <2% from AlfaAesar, accessed on February 26, 2018 ( PDF )(JavaScript required) .

[Eula_Bingham,_Barbara_Cohrssen-3] Eula Bingham, Barbara Cohrssen: Patty's Toxicology . John Wiley & Sons, 2012, ISBN 0-470-41081-7 , pp. 463 ( limited preview in Google Book search).

[Marcelle_Gaune-Escard,_Kenneth_R._Seddon-4] Marcelle GAUNE-Escard, Kenneth R. Seddon: Molten Salts and Ionic Liquids Never the Twain? John Wiley & Sons, 2012, ISBN 0-470-94776-4 , pp. 197 ( limited preview in Google Book search).

[Michael_McNallan-5] Michael McNallan: High Temperature Corrosion and Materials Chemistry Proceedings of the Per Kofstad Memorial Symposium . The Electrochemical Society, 2000, ISBN 978-1-56677-261-7 , pp. 490 ( limited preview in Google Book search).

[Ian_Hutchings,_Philip_Shipway-6] Ian Hutchings, Philip Shipway: Tribology Friction and Wear of Engineering Materials . Butterworth-Heinemann, 2017, ISBN 978-0-08-100951-2 , pp. 171 ( limited preview in Google Book search).

[DOI10.1063/1.3647754-7] John W. Lawson, Murray S. Daw, Charles W. Bauschlicher: Lattice thermal conductivity of ultra high temperature ceramics ZrB ₂ and HfB ₂ from atomistic simulations. In: Journal of Applied Physics. 110, 2011, p. 083507, doi : 10.1063 / 1.3647754 .

[DOI10.1116/1.2049307-8] Sreenivas Jayaraman, Y. u. Yang, Do Young Kim, Gregory S. Girolami, John R. Abelson: Hafnium diboride thin films by chemical vapor deposition from a single source precursor. In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films. 23, 2005, p. 1619, doi : 10.1116 / 1.2049307 .

[9] Loehman, RE. (2004). Ultra-high-temperature ceramics for hypersonic vehicle applications . 71.

[DOI10.1016/0254-0584(96)80096-4-10] DS Wuu, ML Lee, TY Lin, RH Horng: Characterization of hafnium diboride thin film resistors by rf magnetron sputtering. In: Materials Chemistry and Physics. 45, 1996, p. 163, doi : 10.1016 / 0254-0584 (96) 80096-4 .