Titanium diboride

Last updated
Titanium diboride
Magnesium-diboride-3D-balls.png
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.771 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 234-961-4
PubChem CID
  • InChI=1S/B2.Ti/c1-2;
    Key: TXVDUUNOLJOZCR-UHFFFAOYSA-N
  • [B].[Ti].[B]
Properties
TiB2
Molar mass 69.489 g/mol
Appearancenon lustrous metallic grey
Density 4.52 g/cm3
Melting point 3,230 °C (5,850 °F; 3,500 K)
Structure
Hexagonal, hP1
P6/mmm
a = 302.36 pm, c = 322.04 pm
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Titanium diboride (TiB2) is an extremely hard ceramic which has excellent heat conductivity, oxidation stability and wear resistance. TiB2 is also a reasonable electrical conductor, [1] so it can be used as a cathode material in aluminium smelting and can be shaped by electrical discharge machining.

Contents

Physical properties

TiB2 shares some properties with boron carbide and titanium carbide, but many of its properties are superior to those of B4C & TiC: [2]

Exceptional hardness at extreme temperature

Advantages over other borides

Other advantages

Drawbacks

Chemical properties

With respect to chemical stability, TiB2 is more stable in contact with pure iron than tungsten carbide or silicon nitride. [2]

TiB2 is resistant to oxidation in air at temperatures up to 1100 °C, [2] and to hydrochloric and hydrofluoric acids, but reacts with alkalis, nitric acid and sulfuric acid.

Production

TiB2 does not occur naturally in the earth. Titanium diboride powder can be prepared by a variety of high-temperature methods, such as the direct reactions of titanium or its oxides/hydrides, with elemental boron over 1000 °C, carbothermal reduction by thermite reaction of titanium oxide and boron oxide, or hydrogen reduction of boron halides in the presence of the metal or its halides. Among various synthesis routes, electrochemical synthesis and solid state reactions have been developed to prepare finer titanium diboride in large quantity. An example of solid state reaction is the borothermic reduction, which can be illustrated by the following reactions:

(1) 2 TiO2 + B4C + 3C → 2 TiB2 + 4 CO

(2) TiO2 + 3NaBH4 → TiB2 + 2Na(g,l) + NaBO2 + 6H2(g) [3]

The first synthesis route (1), however, cannot produce nanosized powders. Nanocrystalline (5–100 nm) TiB2 was synthesized using the reaction (2) or the following techniques:

TiCl4 + 2 B + 4 Na → TiB2 + 4 NaCl

Many TiB2 applications are inhibited by economic factors, particularly the costs of densifying a high melting point material - the melting point is about 2970 °C, and, thanks to a layer of titanium dioxide that forms on the surface of the particles of a powder, it is very resistant to sintering. Admixture of about 10% silicon nitride facilitates the sintering, [9] though sintering without silicon nitride has been demonstrated as well. [1]

Thin films of TiB2 can be produced by several techniques. The electroplating of TiB2 layers possess two main advantages compared with physical vapor deposition or chemical vapor deposition: the growing rate of the layer is 200 times higher (up to 5 μm/s) and the inconveniences of covering complex shaped products are dramatically reduced.

Potential applications

Current use of TiB2 appears to be limited to specialized applications in such areas as impact resistant armor, cutting tools, crucibles, neutron absorbers and wear resistant coatings.

TiB2 is extensively used for evaporation boats for vapour coating of aluminium. It is an attractive material for the aluminium industry as an inoculant to refine the grain size when casting aluminium alloys, because of its wettability by and low solubility in molten aluminium and good electrical conductivity.

Thin films of TiB2 can be used to provide wear and corrosion resistance to a cheap and/or tough substrate.

Related Research Articles

<span class="mw-page-title-main">Boron nitride</span> Refractory compound of boron and nitrogen with formula BN

Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form corresponding to graphite is the most stable and soft among BN polymorphs, and is therefore used as a lubricant and an additive to cosmetic products. The cubic variety analogous to diamond is called c-BN; it is softer than diamond, but its thermal and chemical stability is superior. The rare wurtzite BN modification is similar to lonsdaleite but slightly softer than the cubic form.

<span class="mw-page-title-main">Boron</span> Chemical element, symbol B and atomic number 5

Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three valence electrons for forming covalent bonds, resulting in many compounds such as boric acid, the mineral sodium borate, and the ultra-hard crystals of boron carbide and boron nitride.

In materials science, a metal matrix composite (MMC) is a composite material with fibers or particles dispersed in a metallic matrix, such as copper, aluminum, or steel. The secondary phase is typically a ceramic or another metal. They are typically classified according to the type of reinforcement: short discontinuous fibers (whiskers), continuous fibers, or particulates. There is some overlap between MMCs and cermets, with the latter typically consisting of less than 20% metal by volume. When at least three materials are present, it is called a hybrid composite. MMCs can have much higher strength-to-weight ratios, stiffness, and ductility than traditional materials, so they are often used in demanding applications. MMCs typically have lower thermal and electrical conductivity and poor resistance to radiation, limiting their use in the very harshest environments.

<span class="mw-page-title-main">Control rod</span> Device used to regulate the power of a nuclear reactor

Control rods are used in nuclear reactors to control the rate of fission of the nuclear fuel – uranium or plutonium. Their compositions include chemical elements such as boron, cadmium, silver, hafnium, or indium, that are capable of absorbing many neutrons without themselves decaying. These elements have different neutron capture cross sections for neutrons of various energies. Boiling water reactors (BWR), pressurized water reactors (PWR), and heavy-water reactors (HWR) operate with thermal neutrons, while breeder reactors operate with fast neutrons. Each reactor design can use different control rod materials based on the energy spectrum of its neutrons. Control rods have been used in nuclear aircraft engines like Project Pluto as a method of control.

A cermet is a composite material composed of ceramic and metal materials.

<span class="mw-page-title-main">Boron carbide</span> Extremely hard ceramic compound

Boron carbide (chemical formula approximately B4C) is an extremely hard boron–carbon ceramic, a covalent material used in tank armor, bulletproof vests, engine sabotage powders, as well as numerous industrial applications. With a Vickers hardness of >30 GPa, it is one of the hardest known materials, behind cubic boron nitride and diamond.

<span class="mw-page-title-main">Superhard material</span> Material with Vickers hardness exceeding 40 gigapascals

A superhard material is a material with a hardness value exceeding 40 gigapascals (GPa) when measured by the Vickers hardness test. They are virtually incompressible solids with high electron density and high bond covalency. As a result of their unique properties, these materials are of great interest in many industrial areas including, but not limited to, abrasives, polishing and cutting tools, disc brakes, and wear-resistant and protective coatings.

<span class="mw-page-title-main">Tantalum carbide</span> Chemical compound

Tantalum carbides (TaC) form a family of binary chemical compounds of tantalum and carbon with the empirical formula TaCx, where x usually varies between 0.4 and 1. They are extremely hard, brittle, refractory ceramic materials with metallic electrical conductivity. They appear as brown-gray powders, which are usually processed by sintering.

<span class="mw-page-title-main">Hafnium diboride</span> Chemical compound

Hafnium diboride is a type of ceramic composed of hafnium and boron that belongs to the class of ultra-high temperature ceramics. It has a melting temperature of about 3250 °C. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and zirconium diboride. It is a grey, metallic looking material. Hafnium diboride has a hexagonal crystal structure, a molar mass of 200.11 grams per mole, and a density of 11.2 g/cm3.

Aluminium carbide, chemical formula Al4C3, is a carbide of aluminium. It has the appearance of pale yellow to brown crystals. It is stable up to 1400 °C. It decomposes in water with the production of methane.

<span class="mw-page-title-main">Boron compounds</span>

Boron compounds are compounds containing the element boron. In the most familiar compounds, boron has the formal oxidation state +3. These include oxides, sulfides, nitrides, and halides.

<span class="mw-page-title-main">Rhenium diboride</span> Chemical compound

Rhenium diboride (ReB2) is a synthetic high-hardness material that was first synthesized in 1962. The compound is formed from a mixture of rhenium, noted for its resistance to high pressure, and boron, which forms short, strong covalent bonds with rhenium. It has regained popularity in recent times in hopes of finding a material that possesses hardness comparable to that of diamond.

<span class="mw-page-title-main">Boron suboxide</span> Chemical compound

Boron suboxide (chemical formula B6O) is a solid compound with a structure built of eight icosahedra at the apexes of the rhombohedral unit cell. Each icosahedron is composed of twelve boron atoms. Two oxygen atoms are located in the interstices along the [111] rhombohedral direction. Due to its short interatomic bond lengths and strongly covalent character, B6O displays a range of outstanding physical and chemical properties such as great hardness (close to that of rhenium diboride and boron nitride), low mass density, high thermal conductivity, high chemical inertness, and excellent wear resistance.

<span class="mw-page-title-main">Zirconium diboride</span> Chemical compound

Zirconium diboride (ZrB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB2 is an ultra-high temperature ceramic (UHTC) with a melting point of 3246 °C. This along with its relatively low density of ~6.09 g/cm3 (measured density may be higher due to hafnium impurities) and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and hafnium diboride.

Aluminium magnesium boride or Al3Mg3B56, colloquially known as BAM, is a chemical compound of aluminium, magnesium and boron. Whereas its nominal formula is AlMgB14, the chemical composition is closer to Al0.75Mg0.75B14. It is a ceramic alloy that is highly resistive to wear and has an extremely low coefficient of sliding friction, reaching a record value of 0.04 in unlubricated and 0.02 in lubricated AlMgB14−TiB2 composites. First reported in 1970, BAM has an orthorhombic structure with four icosahedral B12 units per unit cell. This ultrahard material has a coefficient of thermal expansion comparable to that of other widely used materials such as steel and concrete.

An inclusion is a solid particle in liquid aluminium alloy. It is usually non-metallic and can be of different nature depending on its source.

Ultra-high-temperature ceramics (UHTCs) are a type of refractory ceramics that can withstand extremely high temperatures without degrading, often above 2,000 °C. They also often have high thermal conductivities and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking. Chemically, they are usually borides, carbides, nitrides, and oxides of early transition metals.

<span class="mw-page-title-main">Niobium diboride</span> Chemical compound

Niobium diboride (NbB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure.

Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known.

References

  1. 1 2 J. Schmidt et al. "Preparation of titanium diboride TiB2 by spark plasma sintering at slow heating rate" Sci. Technol. Adv. Mater. 8 (2007) 376 free download
  2. 1 2 3 Basu, B.; Raju, G. B.; Suri, A. K. (2006-12-01). "Processing and properties of monolithic TiB2 based materials". International Materials Reviews. 51 (6): 352–374. Bibcode:2006IMRv...51..352B. doi:10.1179/174328006X102529. ISSN   0950-6608. S2CID   137562554.
  3. Zoli, Luca; Galizia, Pietro; Silvestroni, Laura; Sciti, Diletta (23 January 2018). "Synthesis of group IV and V metal diboride nanocrystals via borothermal reduction with sodium borohydride". Journal of the American Ceramic Society. 101 (6): 2627–2637. doi: 10.1111/jace.15401 .
  4. S. E. Bates et al. "Synthesis of titanium boride (TiB)2 nanocrystallites by solution-phase processing" J. Mater. Res. 10 (1995) 2599
  5. A. Y. Hwang and J. K. Lee "Preparation of TiB2 powders by mechanical alloying " Mater. Lett. 54 (2002) 1
  6. A. K. Khanra et al. "Effect of NaCl on the synthesis of TiB2 powder by a self-propagating high-temperature synthesis technique" Mater. Lett. 58 (2004) 733
  7. Amin Nozari; et al. (2012). "Synthesis and characterization of nano-structured TiB2 processed by milling assisted SHS route". Materials Characterization. 73: 96–103. doi:10.1016/j.matchar.2012.08.003.
  8. Y. Gu et al. "A mild solvothermal route to nanocrystalline titanium diboride" J. Alloy. Compd. 352 (2003) 325
  9. Titanium diboride sintered body with silicon nitride as a sintering aid and a method for manufacture thereof

Compare

See also