Tantalum carbide

Crystal structure
__ Ta 4+      __ C 4−
Crystal system	cubic
Space group	Fm 3 m (No. 225)
Lattice parameters	445 pm (corresponds to 4.45  Å )
General
Surname	Tantalum carbide
Ratio formula	TaC
Brief description	brown powder or gold colored crystalline solid
External identifiers / databases
CAS number 12070-06-3 EC number 235-118-3 ECHA InfoCard 100,031,914 Wikidata Q426498
properties
Molar mass	192.959 g mol −1
Physical state	firmly
density	13.9 g cm −3
Melting point	3880 ° C
boiling point	5500 ° C
solubility	almost insoluble in water
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 228 P: 210
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Tantalum carbide is an intermetallic compound made of tantalum and carbon with the empirical formula TaC.

Occurrence

Tantalum was completed only once as a natural formation in the "Aurorinsky Mine" (Avrorinskii, Avorinskiy) on the river Aktai in Barantschinski massif in the Russian Sverdlovsk Oblast discovered (Ural) and 1962 Clifford Frondel described. Hugo Strunz changed its original name “Tantalum carbide” in 1966 to the form tantalum carbide, which is still valid today.

Tantalum carbide as a mineral

Natural occurrences of tantalum carbide were already known before the International Mineralogical Association (IMA) was founded. Tantalum carbide is therefore recognized as a so-called grandfathered mineral as an independent type of mineral.

According to the systematics of minerals according to Strunz (9th edition) , tantalum carbide is used under system number 1.BA.20 (elements - metallic carbon, nitrogen and phosphorus compounds - carbides - tantalum carbide group) or in the outdated 8th edition under I / A.09 ( Metals and intermetallic alloys (excluding semimetals) ). The systematics of minerals according to Dana , which is mainly used in English-speaking countries , lists the element mineral under the system no. 01.01.19.04 ( elements: metallic elements other than the platinum group - osbornite group, carbides and nitrides ).

So far, tantalum carbide could only be found in nature in the form of microcrystalline grains .

Extraction and presentation

Tantalum carbide is made by reacting tantalum powder with flame black

${\displaystyle \mathrm {Ta+C\longrightarrow TaC} }$

or reduction of tantalum pentoxide with carbon. For this reason metallic tantalum must be produced by reduction with hydrogen , alkali or alkaline earth metals .

Small amounts of tantalum carbide can be obtained from tantalum wires at temperatures above 2500 ° C in a hydrogen atmosphere with the addition of small amounts of hydrocarbons (e.g. toluene , methane , acetylene ).

properties

Crystal structure and shape

Tantalum carbide crystallizes isostructurally with niobocarbide in the cubic crystal system in the space group Fm 3 m (space group no. 225) with the lattice parameter a  = 4.45  Å and 4 formula units per unit cell . The crystal structure of tantalum carbide corresponds to the sodium chloride structure .

The carbide is opaque and develops yellowish-gray to bronze-colored, cubic crystals with a metallic sheen .

Physical Properties

Tantalum carbide is chemically inert and only dissolves in hydrofluoric or sulfuric acid . It has one of the highest melting points of all known substances with 3880 ° C - only tantalum hafnium carbide has an even higher melting point. If the material is substoichiometric with the formula TaC _0.89 , the melting point rises to just under 4270 K (4000 ° C) and is thus again higher than that of hafnium carbide .

The data on the hardness of tantalum carbide are contradictory. Depending on the source, the TaC compound has either a Mohs hardness of 6 or 6.5 to 7 or 9 to 10. According to other sources, tantalum carbide has a Vickers hardness (micro hardness HV _0.05 ) of 1800, which is a Mohs hardness of around 8.5 to 9 would correspond.

With a density of 13.9 g · cm ⁻³ , tantalum carbide is almost twice as dense as steel .

In addition to TaC, the intermetallic phase Ta ₂ C is also known, which has a melting temperature of 3500 ° C and a density of 15 g · cm ⁻³ .

use

Due to its high hardness, tantalum carbide is one of the hard metals and is mainly used for the manufacture of cutting tools and the coating of engine nozzles.

Individual evidence

1. ^ ^{A b c} Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  47 .
2. ^ Heinrich Remy: Textbook of Inorganic Chemistry Volume I + II, Leipzig 1973.
3. ↑ ^{a b c d e f g} data sheet Tantalum carbide, 99.5% (metals basis) from AlfaAesar, accessed on December 6, 2019 ( PDF )(JavaScript required) .
4. ↑ Find location list for Tantalum Carbide Mineralienatlas and Mindat
5. ^ MH Hey: Twenty-fourth list of new mineral names . In: Mineralogical Magazine . tape 36 , December 1966, p. 1126–1164 ( minersoc.org [PDF; 1.9 MB ; accessed on February 24, 2018] Tantalum carbide p. 29, Tantalum carbide p. 30).
6. ^ IMA / CNMNC List of Mineral Names; November 2017 (PDF 1.67 MB).
7. ^ IMA / CNMNC List of Mineral Names; 2009 (PDF 1.8 MB, tantalum carbides see p. 276).
8. ↑ Webmineral - Minerals Arranged by the New Dana classification. 01/01/19 Osbornite group carbides and nitrides
9. ↑ ^{a b} Georg Brauer (Ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1475.
10. ↑ Mindat - Tantalum Carbide .
11. ↑ Mineral Atlas: Tantalum Carbide
12. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  398 (first edition: 1891).
13. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
14. ↑ Tantalum carbide in the Lexikon der Chemie on Spektrum.de
15. ↑ Martin Bertau, Armin Müller, Peter Fröhlich, Michael Katzberg: Industrielle Inorganische Chemie . 4th, completely revised and updated edition. John Wiley & Sons, Weinheim 2013, ISBN 978-3-527-33019-5 , pp. 623 ( 6.5.4 Carbides of subgroup IV. (Table 6.28: Properties of metallic carbides) in the Google book search).