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Hafnium diboride
Identifiers
CAS Number
12007-23-7Y
3D model (JSmol)
Interactive image
ChemSpider
21241816Y
ECHA InfoCard
100.031.351
PubChem CID
6336857
CompTox Dashboard (EPA)
DTXSID10893925
InChI
InChI=1S/B2.Hf/c1-2;/q+2;-2Y
Key: MELCCCHYSRGEEL-UHFFFAOYSA-NY
InChI=1/B2.Hf/c1-2;/q+2;-2/rB2Hf/c1-2-3-1
Key: MELCCCHYSRGEEL-KRVKJWMQAC
SMILES
B\1=B\[Hf]/1
Properties
Chemical formula
HfB2
Molar mass
200.11 g/mol
Density
11.2 g/cm3[1]
Melting point
ca. 3,250 °C (5,880 °F; 3,520 K)
Structure
Crystal structure
Hexagonal, hP3
Space group
P6/mmm, No. 191
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
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.
Hafnium diboride is often combined with carbon, boron, silicon, silicon carbide, and/or nickel to improve the consolidation of the hafnium diboride powder (sintering). It is commonly formed into a solid by a process called hot pressing, where the powders are pressed together using both heat and pressure.
The material has potential for use in hypervelocity reentry vehicles such as ICBM heat shields or aerodynamic leading-edges, due to its strength and thermal properties. Unlike polymer and composite material, HfB2 can be formed into aerodynamic shapes that will not ablate during reentry.
Hafnium diboride is also investigated as a possible new material for nuclear reactor control rods.
It is also being investigated as a microchip diffusion barrier. If synthesized correctly, the barrier can be less than 7 nm in thickness.
Nanocrystals of HfB2 with rose-like morphology were obtained combining HfO2 and NaBH4 at 700-900°C under argon flow:[2]
HfO2 + 3NaBH4 → HfB2 + 2Na(g,l) + NaBO2 + 6H2(g)
^Fahrenholtz, William (10 May 2007). "Refractory diborides of zirconium and hafnium". Journal of the American Ceramic Society. 90 (5): 1347–1364. doi:10.1111/j.1551-2916.2007.01583.x.
^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.
Hafniumdiboride 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...
Diboride may refer to: Aluminium diboride, compound of aluminium and boron Hafniumdiboride, ultra-high temperature ceramic composed of hafnium and boron...
conductivities, properties it shares with isostructural titanium diboride and hafniumdiboride. ZrB2 parts are usually hot pressed (pressure applied to the...
hafnium oxide. Hafnium diboride belongs to the class of ultra-high temperature ceramics, a type of refractory ceramic composed of hafnium and boron. It has...
compounds such as molybdenum boride, hafniumdiboride, titanium diboride, dysprosium titanate and gadolinium titanate. Hafnium absorbs neutrons avidly and it...
zirconium diboride ZrB2 and hafniumdiboride HfB2 can be prepared through CVD of the zirconium(IV) tetrahydroborate Zr[BH4]4 and hafnium(IV) tetrahydroborate...
materials, referred to as SHARP materials (typically zirconium diboride and hafniumdiboride) have been used on steering vanes for ICBM reentry vehicles...
based on ultra-high temperature ceramics such as zirconium diboride (ZrB2) and hafniumdiboride (HfB2). The thermal protection system based on these materials...
borides of transition metals, e.g. zirconium carbide, hafnium carbide, tantalum carbide, hafniumdiboride, and their mixtures. Metals from groups IIIB (scandium...
properties it shares with isostructural titanium diboride, zirconium diboride, hafniumdiboride and tantalum diboride. NbB2 parts are usually hot pressed or spark...
Research Probe (SHARP). These TPS materials are based on zirconium diboride and hafniumdiboride. SHARP TPS have suggested performance improvements allowing...
Rhenium diboride (ReB2) is a hard compound having a hardness similar to that of tungsten carbide, silicon carbide, titanium diboride or zirconium diboride. Dirhenium...
comparable to that of tungsten carbide, silicon carbide, titanium diboride or zirconium diboride. Similarly, AlMgB14 + TiB2 composites possess high hardness...
additive during the liquid-phase sintering of silicon nitride and zirconium diboride. Small amounts of lanthanum added to steel improves its malleability, resistance...
name Thule, and the immediately-following group 4 element (number 72) hafnium is named for the Latin name of the city of Copenhagen. The properties of...
be obtained by heating an oxide or halide of americium with magnesium diboride in vacuum or inert atmosphere. Analogous to uranocene, americium forms...
dark-gray solids with the hardness increasing with the boron content. Samarium diboride is too volatile to be produced with these methods and requires high pressure...
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