Chemical Properties
powder(s); made by reaction of the elements above 600°C; high neutron absorption; used as a nuclear shielding material [HAW93] [CIC73]
Description
Aluminum diboride (AlB2) is an inorganic compound with a cyclic structure formed by aluminum and boron, and is a high calorific value boron based fuel with high potential for application. Aluminum diboride has a very similar structure to magnesium diboride. It has low specific gravity and high mechanical properties. The longitudinal tensile strength of unidirectionally reinforced boron-aluminum composites is about 1.2~1.7GPa with different processes and raw materials, and the modulus of elasticity is about 200~240GPa. The longitudinal specific modulus of elasticity and specific strength are about 3~5 times and 3~4 times of those of titanium alloy duralumin and alloy steel respectively.
Physical properties
Aluminum diboride：
Crystal system, lattice
parameters, structure
type, Strukturbericht,
Pearson, space group,
structure type (Z): Hexagonal
a = 300.50 pm;
c = 325.30 pm
C32, hP3, P6/mmm,
AlB type (Z = 1).
Density
(ρ/kg.m–3): 3190; Specific heat capacity
(cP/J.kg–1.K–1): 897.87; Vickers or Knoop
Hardness (HV or
HK/GPa) (/HM): 9.61 HK; Other physicochemical: Temp. transition to AlB at 12
920°C. Soluble in dilute HCl.
Nuclear shielding material (uses).
Uses
Aluminum diboride is a solid material that has a high melting point and hardness. It is commonly used to make high-temperature ceramics and materials that are resistant to wear.
Preparation
Aluminum diboride, AlB2, was first synthesized from the elements, amorphous boron and aluminum powder, using an electric arc furnace in a manner similar to that previously described for ReB2. A second sample was prepared in a tube furnace reaction using aluminum metal powder and amorphous boron sealed in a quartz ampule, with a slight excess of boron (nominally AlB2.2). The ampule was placed in the tube furnace, heated to 910 C, and held at this temperature for 12 h before cooling back to ambient temperature. The synthetic preparation of the commercial sample differs from our preparations, involving a reaction between aluminum metal and boron trioxide (B2O3).
