Molybdenum disilicide

Crystal structure
Space group	I 4 / mmm (No. 139)
General
Surname	Molybdenum disilicide
other names	Molybdenum silicides
Ratio formula	MoSi 2
Brief description	gray powder
External identifiers / databases
CAS number 12136-78-6 EC number 235-231-8 ECHA InfoCard 100.032.016 PubChem 6336985 Wikidata Q2352958
properties
Molar mass	152.12 g mol −1
Physical state	firmly
density	6.31 g cm −3 (25 ° C)
Melting point	1870-2030 ° C
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 302-312-332 P: 280
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Molybdenum disilicide is an intermetallic chemical compound of molybdenum from the group of silicides . In addition to this, other molybdenum silicides are known with Mo ₃ Si and Mo ₅ Si ₃ .

Extraction and presentation

Molybdenum disilicide can be obtained by reacting molybdenum with silicon at temperatures greater than 1400 ° C.

${\displaystyle \mathrm {Mo+2\ Si\longrightarrow MoSi_{2}} }$

Corresponding layers can be obtained by reacting molybdenum with silicon tetrachloride and hydrogen .

${\displaystyle \mathrm {Mo+2\ SiCl_{4}+4\ H_{2}\longrightarrow MoSi_{2}+8\ HCl} }$

properties

Molybdenum disilicide is a gray powder. The connection has a tetragonal crystal structure with the space group I 4 / mmm (space group no. 139) . Above 1900 ° C this changes into a hexagonal structure. In air or pure oxygen, it oxidizes at temperatures above 400 ° C, which can be delayed by using an appropriate alloy.

${\displaystyle \mathrm {2\ MoSi_{2}+7\ O_{2}\longrightarrow 2\ MoO_{3}+4\ SiO_{2}} }$

Molybdenum disilicide is resistant to acids, dilute alkalis, salt solutions and various molten salts. It also stands out from other metals and alloys in that it is corrosion-resistant to reducing and oxidizing gases at temperatures from 1350 to 700 ° C.

use

Molybdenum disilicide is used as an electrically conductive ceramic material, for example in high-temperature heating conductors. In combination with other non-oxide ceramics, it is used, for example, in glow plugs for the automotive industry.

Individual evidence

1. ↑ ^{a b c d e f g} data sheet Molybdenum disilicide, α-phase, powder, ≥99.8% trace metals basis from Sigma-Aldrich , accessed on May 24, 2015 ( PDF ).
2. ↑ ^{a b} Sam Zhang, Dongliang Zhao: Aerospace Materials Handbook . CRC Press, 2012, ISBN 978-1-4398-7330-4 , pp. 253 ( limited preview in Google Book search).
3. ↑ ^{a b} Wolfgang Kollenberg: Technical ceramic basics, materials, process engineering . Vulkan-Verlag, 2004, ISBN 978-3-8027-2927-0 , pp. 135,340,344 ( limited preview in Google Book search).
4. ↑ ER Braithwaite, J. Haber: Molybdenum An Outline of its Chemistry and Uses . Elsevier, 2013, ISBN 978-1-4832-9089-8 , pp. 83 ( limited preview in Google Book search).
5. ^ Helmut Mehrer, Hans Eckhardt Schaefer, Irina V. Belova, Graeme E. Murch: Molybdenum Disilicide - Diffusion, Defects, Diffusion Correlation, and Creep. In: Defect and Diffusion Forum. 322, 2012, p. 107, doi: 10.4028 / www.scientific.net / DDF.322.107 .
6. ↑ O. Rubisch: Molybdenum disilicide, a high temperature material for extreme chemical and thermal loads. In: Materials and Corrosion / Werkstoffe und Korrosion. 16, 1965, p. 467, doi: 10.1002 / maco.19650160604 .
7. ↑ HC Starck: Product Information Molybdenum Disilicide ( Memento of the original dated May 24, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed on May 24, 2015.