ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2011, Vol. 56, No. 4, pp. 506–509. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © S.E. Kravchenko, V.I. Torbov, S.P. Shilkin, 2011, published in Zhurnal Neorganicheskoi Khimii, 2011, Vol. 56, No. 4, pp. 546–549.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
Nanosized Zirconium Diboride: Synthesis and Properties
S. E. Kravchenko, V. I. Torbov, and S. P. Shilkin
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka,
Moscow oblast, Chernogolovka, Moscow oblast, Russia
eꢀmail: kgv@icp.ac.ru
Received November 26, 2009
Abstract—The thermolysis of Zr(BH4)4 vapor at 573 and 623 K in a vacuum of 1.33 ×
10–1 Pa was studied.
Nanosized zirconium diboride was produced as an Xꢀray amorphous powder and a crystalline film. According
to electron microscopy data, the Xꢀray amorphous zirconium diboride powder obtained at 573 or 623 K conꢀ
sists of spherical particles 30–40 nm in diameter, which is in quite a good agreement with the equivalent parꢀ
ticle diameter (~35 nm) calculated from the specific surface area of ZrB2. After annealing at 1273 K, the Xꢀray
amorphous zirconium diboride powder crystallizes into a hexagonal lattice with the unit cell parameters
0.3159 nm and = 0.3527 nm. The coherent scattering length Dhkl is ~27 nm. The zirconium diboride film
produced at 573 or 623 K crystallizes into a hexagonal lattice with the unit cell parameters = 0.3163–0.3168 nm
and = 0.3524–0.3531 nm. The coherent scattering length Dhkl is ~14 nm. The thickness of the ZrB2 film on
a =
c
a
c
quartz, glass ceramics, and stainless steel is 5–7
strate under a load of 20 g is 17.8 GPa.
µm. The microhardness of the film on a stainless steel subꢀ
DOI: 10.1134/S0036023611040164
Refractory compounds of Group 4 elements are did not exceed 0.0003 nm. Xꢀray powder diffraction
characterized by high hardness, high strength, wide patterns were used to estimate the coherent scattering
range of electrical properties, chemical inertness, and length Dhkl by the Scherrer equation Dhkl
other useful properties and are used in mechanical, cosθhkl (in the direction perpendicular to the plane
power, electronic, and chemical engineering indusꢀ hkl), where is a constant (in our case, we took it to be
tries. By the present time, the interest in such comꢀ unity), is the Xꢀray wavelength λCu α= 1.54178 is
pounds has increased on account of the development the diffraction angle, and is the diffraction peak halfꢀ
= kλ/βhkl
k
λ
Å, θ
K
β
of nanostructured materials on their basis, the physicꢀ width (expressed in radians). Electron microscopy
ochemical, physicomechanical, and other properties studies were conducted with an EMVꢀ100BR transꢀ
of which significantly differ from those for largeꢀcrysꢀ mission electron microscope and a Supra 25 field
tal materials (see, e.g., [1–3]).
emission scanning electron microscope.
A typical representative of nanosized refractory
compounds of Group 4 elements is ZrB2, the methods
of synthesis of which are few and mainly involve zircoꢀ
nium borohydride thermolysis [4–9]
Xꢀray photoelectron spectra were recorded on a
Varian IEEꢀ15 spectrometer equipped with a magneꢀ
sium anode (hν= 1253 eV). The positions of lines were
determined relative to the C1s line, the binding energy
for which was taken to be 285.0 eV.
T
Zr(BH4)4
ZrB2 + B2H6 + 5H2.
(1)
Thermogravimetric studies were made by synchroꢀ
nous thermal analysis with massꢀspectrometric analyꢀ
sis of decomposition products on an STA 409PC Luxx
thermal analyzer in an argon atmosphere at a heating
rate of 10 K/min. The specific surface area Ssp was
found in an experiment on lowꢀtemperature crypton
adsorption after volatile impurities were removed from
In this context, the purpose of this work was to
study the specifics of Zr(BH4)4 thermolysis.
EXPERIMENTAL
Initial reactants. Lithium borohydride (99.5%
purity) was obtained by the reaction of lithium hydride
with boron trifluoride etherate in diethyl ether.
Zr(BH4)4 was obtained by the reaction of ZrCl4 with
LiBH4 in a yield of ~50% and was purified by vacuum
distillation.
the solid phase in a vacuum of 1.33 ×
10–3 Pa at 573 K
and was calculated by the BET method. The area
occupied by an adsorbed crypton molecule was taken
to be 19
exceed 10%. Hydrogen and diborane were determined
×
10–20 m2. The determination error did not
Analysis methods. Xꢀray diffraction studies were on an LKhMꢀ8MD chromatograph with a katharomꢀ
performed on an automatic setup comprising an eter as a detector on a 1ꢀmꢀlong column 0.003 m in
ADPꢀ1 diffractometer (CuKα radiation) and a control diameter packed with tricresyl phosphate (30 wt %) on
computer. The error in the unit cell parameters of ZrB2 Celite 545 at a carrier gas (argon) rate of 30 mL/min.
506
Kravchenko
