Low-temperature synthesis of nanocrystalline ZrB2 via co-reduction of ZrCl4 and BBr3

Article abstract of DOI:10.1246/bcsj.77.1423

Nanocrystalline zirconium diboride (ZrB₂) has been synthesized via a sodium co-reduction of ZrCl₄ and BBr₃ at 400 °C. The XRD patterns can be indexed as hexagonal ZrB₂ with the lattice constants a = 3.167 and c = 3.527 A. The TEM image indicates the product has particle morphology, with size of about 20 nm.

Full text of DOI:10.1246/bcsj.77.1423

Short Articles
Bull. Chem. Soc. Jpn., 77, 1423–1424 (2004) 1423
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3
ZrO2 and B4C (1400 C) and the mechano-chemistry treat-
ment of a mixture of zirconia powder and amorphous boron fol-
Low-Temperature Synthesis
of Nanocrystalline ZrB via
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4
lowed by annealing (1100 C). In addition, other methods have
been developed to prepare zirconium diboride. Andrievskii et
al. obtained amorphous powder of ZrB2:76 with mean particle
2
Co-reduction of ZrCl and BBr3
4
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5
size 40 nm by thermolysis of Zr(BH4)4 at 573–623 C;
Berthon et al. synthesized ZrB2 by CVD from a mixture of
6
1
1
1
ZrCl4, BCl3, and H2; Devyatkin researched electrosynthesis
from cryolite–alumina melts containing zirconium and boron
Luyang Chen, Yunle Gu, Liang Shi,
1
1
ꢀ;1;2
Jianhua Ma, Zeheng Yang, and Yitai Qian
7
oxides; Reich et al. synthesized zirconium boride by plasma
8
enhanced chemical vapor deposition; Otani et al. prepared
ZrB2 single crystals by the floating zone method.9
Herein, we report a low-temperature route to nanocrystalline
1Department of Chemistry, University of Science and
Technology of China, Hefei, Anhui 230026, P. R. China
2Structure Research Laboratory, University of Science and
ZrB by co-reduction of ZrCl and BBr using metallic sodium
4
2
3
as reductant and solvent. The reaction can be described as
follows:
Technology of China, Hefei, Anhui 230026, P. R. China
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4
00
C
Received September 9, 2003; E-mail: chendavy@mail.ustc.
edu.cn
ZrCl4 þ 2BBr3 þ 10Na ꢂꢂꢂ! ZrB2 þ 4NaCl þ 6NaBr: ð1Þ
In this reaction, nascent zirconium and boron are generated in
ꢁ
the reaction of ZrCl4 (boiling point = 331 C) and BBr3 (boil-
ꢁ
ꢁ
Nanocrystalline zirconium diboride (ZrB2) has been
synthesized via a sodium co-reduction of ZrCl4 and BBr3 at
ing point = 90 C) by metallic sodium (melting point = 98 C),
and they combine to form nanocrystalline ZrB2.
In the typical process, 0.01 mol ZrCl4 (analytical pure
ꢁ
4
00 C. The XRD patterns can be indexed as hexagonal ZrB2
ꢀ
with the lattice constants a ¼ 3:167 and c ¼ 3:527 A. The
TEM image indicates the product has particle morphology,
with size of about 20 nm.
grade), 0.02 mol BBr (99.99%, shanghai pharmaceutical cor-
3
poration), and 0.1 mol sodium were placed into a stainless steel
autoclave with a quartz liner. And then, the autoclave was
ꢁ
sealed and heated at 400 C for 6 h, followed by naturally cool-
ing to room temperature. The product in the quartz liner was
washed with distilled water and absolute ethanol for several
times to remove the impurities. The final product was vacu-
um-dried at 60 C for 2 h. Black powders were obtained.
X-ray powder diffraction (XRD) pattern was carried out on a
Zirconium diboride (ZrB2) is a potential advanced ceramic
material for use at high temperatures requiring resistance to
wear, oxidation, and corrosion. It has a very good thermal
and electrical conductivity.1 However, there have been few re-
ports on the composition, structure, and physical properties of
the ZrB2 nanocrystallites, indicating that there is a great chal-
lenge in synthesis and characterization of nanocrystalline ZrB2.
Traditionally, ZrB2 powder was synthesized by various high
temperature methods, such as the carbothermal reduction of
ꢁ
,2
Rigaku Dmax-ꢀA X-ray diffractometer with Cu Kꢁ radiation
ꢀ
(ꢂ ¼ 1:54178 A). The morphology of nanocrystalline ZrB2
was observed from transmission electron microscopy (TEM)
images taken with a Hitachi H-800 transmission electron
microscope.
Fig. 1. XRD pattern of nanocrystalline ZrB2 obtained from co-reduction of ZrCl4 and BBr3 using metallic sodium.
Published on the web July 9, 2004; DOI 10.1246/bcsj.77.1423

1
424 Bull. Chem. Soc. Jpn., 77, No. 7 (2004)
Ó 2004 The Chemical Society of Japan
Fig. 2. TEM image (a) and ED pattern (b) of nanocrystalline ZrB2 obtained from co-reduction of ZrCl4 and BBr3 using metallic
sodium.
Figure 1 shows the XRD pattern of the sample. In Fig. 1, all
of the nine peaks at d-spacings can be indexed as hexagonal
In summary, nanocrystalline hexagonal ZrB2 has been suc-
cessfully synthesized via a sodium co-reduction of ZrCl4 and
BBr3 at 400 C for 6 h. The present route allows the fabrication
of ZrB2 powder with higher crystallinity and a narrow particle-
size distribution. This route described may be extended to syn-
thesize other transition metal boride, which may offer opportu-
nity for technological applications.
ꢁ
ꢀ
ZrB2. The lattice constants are a ¼ 3:167 and c ¼ 3:527 A,
ꢀ
in good agreement with a ¼ 3:170 and c ¼ 3:530 A (JCPDS
card# 75-1050). No evidence of crystalline Zr, ZrO2, NaCl,
and other impurities are observed.
TEM image and selected area electron diffraction (ED) pat-
tern of crystalline ZrB2 are shown in Fig. 2. In Fig. 2a, the ma-
terial exhibits uniform particle with about 20 nm in size. In Fig.
This work is supported by the Chinese National Science
Research Foundation.
2
3
b, the diffraction rings from inner to outer, at d-spacings of
ꢀ
.53, 2.74, 2.17, 1.76, and 1.58 A, match hexagonal ZrB2
(001), (100), (101), (002), and (110) planes, in good agreement
with the XRD results.
References
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1
ꢂ1
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ꢂ1 10
ꢂ2881:29 kJ mol ). It was found that an optimum reaction
(
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ꢁ
4
5
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ꢁ
3
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ꢁ
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6
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8
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ꢁ
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ꢁ
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ꢁ
6
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9
tallinity and the yield (90%). However, when reaction time was
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