Titanium nitride

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Crystal structure
Crystal structure of titanium nitride
__ Ti 3+      __ N 3−
General
Surname Titanium nitride
Ratio formula TiN
Brief description

golden yellow crystals

External identifiers / databases
CAS number 25583-20-4
EC number 247-117-5
ECHA InfoCard 100,042,819
PubChem 93091
ChemSpider 84040
Wikidata Q415638
properties
Molar mass 61.91 g · mol -1
Physical state

firmly

density

5.22 g cm −3

Melting point

2950 ° C

solubility

almost insoluble in water

safety instructions
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Titanium nitride is a chemical compound of the two elements titanium and nitrogen with the ratio formula TiN. It is a metallic hard material with a typical golden yellow color. The ceramic material is characterized by its very high hardness and corrosion resistance , which results in a number of technical applications.

In nature, titanium nitride is known as the rare meteorite mineral osbornite .

Extraction and presentation

Titanium nitride is usually produced in the form of micrometer-thin coatings, less often as a ceramic body or as a powder . Manufacture from the elements is possible at temperatures above 1200 ° C, whereby care must be taken to exclude air, oxygen and moisture, which is complex in terms of process technology. This process of direct nitriding of titanium is described by the following reaction equation:

Another possibility for producing titanium nitride is gas phase ammonolysis at temperatures above 900 ° C. Here, the in is titanium tetrachloride contained titanium by the oxidation state +4 to +3 reduced in titanium nitride. The nitrogen from ammonia serves as the electron supplier . Similar to the direct nitriding of titanium, care must be taken to exclude oxygen and moisture. Gas phase ammonolysis can be described by the following reaction equation:

Ammonium chloride is formed in excess of ammonia .

The following procedures relate to the production of TiN for coating purposes
  • The direct nitriding of titanium is performed in a KCN / K 2 CO 3 - molten salt . Common processes are case hardening in a cyanide salt bath (TIDURAN process), high pressure nitriding (TIDUNIT process) and plasma nitriding in a hydrogen / nitrogen atmosphere. A protective layer obtained by nitriding usually consists of an approx. 10 μm thick connecting layer and a 50–200 μm thick diffusion layer. With plasma nitriding it is possible to obtain a layer structure without a connecting layer.
  • Synthesis from titanium chloride and nitrogen by hydrogen plasma coating (thin layers) according to the reaction equation :
Titanium nitride layers produced by sputtering with increasing nitrogen content
  • Thin layers can also be deposited on metals and some polymers , primarily by physical deposition from the gas phase ( PVD process ), e.g. B. by sputtering . A titanium plate is bombarded with noble gas ions ( argon ), whereupon titanium atoms and nitrogen from the sputtering atmosphere are deposited on the substrates. The concentration of nitrogen in the atmosphere determines the subsequent concentration in the resulting layer. From pure titanium to epsilon-Ti 2 N and the stoichiometric TiN, layers with more nitrogen than titanium can also be deposited. Depending on the nitrogen content, the physical properties alternate between the values ​​of pure titanium and TiN. Overstoichiometric layers have a bronze-brown color and only about half the hardness of TiN.

The production of ceramic bodies is difficult because pure TiN has only a low sintering activity due to its high covalent bond character . Therefore, compression of the TiN moldings, the use of sintering additives and external pressure are required. Without this pressure, the ceramics will not achieve the theoretical density and other advantageous properties. However, processes are known which avoid these high press pressures by using extremely fine, so-called nanoscale powders as the starting material.

properties

Physical Properties

Titanium nitride as powder

TiN has a storage structure and crystallizes in the salt lattice, wherein the titanium atoms form a face-centered cubic lattice and small nitrogen atoms in the octahedral holes are stored the base structure. The crystal structure that characterizes this metallic hard material exists only in the composite and not in the form of individual molecules, which is reflected in its insolubility in almost all, even aggressive solvents. The high hardness is higher than that of most metallic materials, but is exceeded by titanium carbide . The hardness is 2450 HV (for comparison aluminum oxide 2100 HV, titanium carbide up to 4000 HV). TiN has a very high melting point , but no boiling point, because it decomposes prematurely. The material has good friction properties and is therefore of interest for systems with special requirements for low wear . The adhesion to other materials is very low. In contrast to non-metallic hard materials such as diamond, B 4 C 3 or silicon carbide , TiN shows pronounced metallic behavior, such as conductivity for electrical current. The temperature coefficient of the electrical resistance is positive and the magnetic behavior is characterized by a weak paramagnetism , which is dependent on the temperature . At a temperature of T = 4.86 K, TiN is superconducting . At temperatures between 20 and 70 millikelvin and an external magnetic field of 0.9 Tesla, however, the superconductivity breaks down and changes to a super-insulating state , which only breaks down at higher electrical field strengths. TiN has a high reflectivity for infrared radiation , its reflection spectrum is similar to that of gold .

By adding a few atomic percent of amorphous silicon to titanium nitride, extreme changes in the mechanical properties (increase in hardness and fracture toughness) can be achieved.

The many outstanding technical properties of the material are offset by its brittleness , which is why it is mainly used in the form of the finest coatings.

other physical properties

Chemical properties

Titanium nitride is generally extremely inert. The substance is only gradually attacked at temperatures above 600 ° C in air and only oxidized rapidly at 1200 ° C in O 2 or CO 2 atmospheres. In hot alkaline lye , it decomposes with the formation of ammonia .

use

Titanium nitride coating on HSS drill
Punching tool
Indexable insert

Often the focus of titanium nitride coatings is on increasing the service life of products and thus their profitability . These gold-colored layers, which are generally used for product finishing, are usually very thin. Typical technical coatings are not thicker than 4  µm - thicker layers would be prone to cracking. The base material must also be stable (high compressive strength ) so that the layer does not collapse in the event of a point load.

  • TiN is used to coat tool materials , especially high-speed steel and weapons, in order to increase their wear protection and scratch resistance. Above all, tools for cutting materials such as drills , punching tools and milling cutters are coated .
  • Its resilience, low wear and tear, paired with good dissipation of frictional heat, qualify the material for use as a bearing material in precision machine bearings and roller bearings.
  • Its non-stick properties enable it to be used as a high-temperature release agent .
  • Due to its good sliding properties and its low breakaway torque , TiN is also used as a coating for sliding tubes in shock absorber technology and in hydraulics.
  • The excellent temperature resistance enables the sintering of hard metal powders .
  • Because of its biocompatibility, it can be used in medical and surgical instruments. This material property also comes into play with implants (cardiac pacemaker electrodes are mentioned as an example).
  • As a wear protection layer, TiN is very scratch-resistant and is therefore also used decoratively on consumer goods. Examples are glasses frames, watches and bracelets, cutlery.
  • TiN can be used as an additive to increase the electrical conductivity of technical ceramics .
  • The material is used in semiconductor technology as a barrier material, since it is able to prevent metal atoms from penetrating into silicon, but at the same time it maintains a certain electrical conduction between two components to be separated.
  • TiN precipitates play an important role in the production of micro-alloyed steels. Due to the high melting point of TiN, such precipitates can inhibit austenite grain growth even at high temperatures.

Titanium nitride in additive manufacturing and powder metallurgy

If powders of alloys containing titanium are thermally processed, titanium nitride is formed in the presence of nitrogen. This is undesirable as it can lead to micro-cracks. Therefore, on the one hand, work is always carried out under an argon protective gas atmosphere and, on the other hand, the nitrogen content of the powder itself should be reduced.

safety instructions

There is practically no danger from titanium nitride because it is non-flammable, non-toxic and, moreover, biocompatible. Titanium nitride is not a hazardous substance in the sense of the EC guidelines and does not require labeling. It is classified as not hazardous to water. As fine dust , TiN - like all other substances - would be problematic. Here, a value of 15 mg / m 3 is considered tolerable ( OSHA ).

literature

  • Florian Kauffmann: Microstructure and properties of titanium nitride-silicon nitride layers (= Max Planck Institute for Metal Research. Report. No. 140). Max Planck Institute for Metal Research, Stuttgart 2003 (also: Stuttgart, University, dissertation, 2003).
  • Sener Albayrak: Colloidal processing and sintering of nanoscale TiN powder. Saarbrücken 1997, published 2002 (Saarbrücken, Universität des Saarlandes, dissertation, 1997).
  • M. Diserensa, J. Patscheider, F. Lévy: Mechanical Properties and Oxidation Resistance of Nanocomposite TiN-SiNx Physical-Vapor-Deposited Thin Films. In: Surface and Coatings Technology. Volume 120/121, November 1999, ISSN  0257-8972 , pp. 158-165, doi: 10.1016 / S0257-8972 (99) 00481-8 .
  • DE Wolfe, J. Singh: Microstructural Evolution of Titanium Nitride (TiN) coatings produced by reactive ion beam-assisted, electron beam physical vapor deposition (RIBA, EB-PVD). In: Journal of Materials Science. Volume 34, No. 12, 1999, ISSN  0022-2461 , pp. 2997-3006, doi: 10.1023 / A: 1004668325924 .
  • Jürgen Crummenauer: TiN coatings using plasma CVD. Aachen, Shaker 1995, ISBN 3-8265-0732-0 (also: Bremen, University, dissertation 1994).
  • Blagica Bliznakovska, Milosav Miloševski: Analysis methods and techniques for hard thin layer coatings characterization in particular on Titanium Nitride (= Scientific series of the International Bureau. Volume 15). Research Center, Central Library, Jülich 1993, ISBN 3-89336-109-X .
  • Wolfram Kamke: Stimulation and perception properties of new pacemaker electrodes made of iridium nitride and titanium nitride and their importance for extending the service life of pacemakers. Berlin 1993 (Berlin, Humboldt University, dissertation, 1994).
  • Minoru Moriyama, Hiroo Aoki, Yoshikazu Kobayashi, Kiichiro Kamata: The Mechanical Properties of Hot-Pressed TiN Ceramics with Various Additives. In: Journal of the Ceramic Society of Japan. Volume 101, No. 3 = No. 1171, 1993, ISSN  0914-5400 , pp. 279-284.
  • F. Preißer, P. Minarski, P. Mayr, F. Hoffmann: High pressure nitriding of titanium materials. In: Härterei-Technische Mitteilungen. Volume 46, No. 6, 1991, ISSN  0017-6583 , pp. 361-366.
  • Rishi Pal Singh, Roger D. Doherty: Synthesis of Titanium Nitride Powders under Glow Discharge Plasma. In: Materials Letters. Volume 9, No. 2/3, 1990, ISSN  0167-577X , pp. 87-89, doi: 10.1016 / 0167-577X (90) 90158-I .
  • M. Desmaison-Brut, L. Themelin, F. Valin, M. Boncoeur: Mechanical Properties of Hot-Isostatic-Pressed Titanium Nitride. In: G. de With, RA Terpstra, R. Metselaar (eds.): Euro-Ceramics. Volume 3: Engineering ceramics. Elsevier Applied Science, London et al. 1989, ISBN 1-85166-432-7 , pp. 258-262.
  • Joachim Droese: Titanium nitride-coated HSS twist drills. Performance and wear mechanisms. Aachen 1987 (Aachen, Technical University, dissertation 1987).
  • K. Uematsu, N. Mizutani, O. Sakural, M. Kato: Effect of Nonstoichiometry on the Sintering of TiNx. In: Journal of the Ceramic Society of Japan. International edition. Volume 90, 1982, ISSN  0912-9200 , pp. 597-603.
  • Reimar Gehrke: Reactions of titanium nitride at high temperatures. Clausthal 1967 (Clausthal, Technical University, dissertation, 1967).
  • A. Münster: Properties and application of titanium nitride and titanium carbide. In: Angewandte Chemie . Volume 69, No. 9, 1957, pp. 281-290, doi: 10.1002 / anie.19570690902 .

Web links

Individual evidence

  1. ↑ a b Entry on titanium nitride. In: Römpp Online . Georg Thieme Verlag, accessed on June 1, 2014.
  2. ↑ a b c d data sheet Titanium nitride, 99.7% (metals basis) from AlfaAesar, accessed on December 6, 2019 ( PDF )(JavaScript required) .
  3. ↑ Osbornite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( PDF 60 kB )
  4. ↑ Benedikt Martin: Production and characterization of sputtered TiN layers on copper materials (=  reports from production technology ). Shaker, Aachen 1994, ISBN 3-86111-950-1 (also: Stuttgart, Universität, Dissertation, 1994).
  5. ↑ maschinenmarkt.vogel.de , accessed on December 1, 2015.