112
Chemistry Letters 2002
A Novel B-C-N Compound Derived from Melamine Diborate
Kaoru Aoki, Susumu Tanaka, Yukiko Tomitani, Masahiro Yuda, Mio Shimada, and Kohei Oda
Department of Materials Science, Yonago National College of Technology,
Hikona-cho, Yonago, Tottori 683-8502
(Received October 18, 2001; CL-011024)
A new B-C-N compound has been synthesized by thermal
decomposition of melamine diborate mixed metal Mg powder in
Ar at 1273 K. XRD revealed that the product had turbostratic
compound was B1:1C1:1N1:0.
structure and approximate composition of that was B1:1C1:1N1:0
Properties of the B-C-N compound obtained are discussed.
.
Recently, interest in B-C-N compounds, which have the
potential applications as semiconductors and host materials, have
increased.1 Various B-C-N compounds were synthesized by
chemical vapor deposition or solid-phase pyrolysis of pre-
cursors.2 In most of the conventional research, chemical
compounds without oxygen such as BH3, BC 3l, NH3, C H,
4
melamine, and pyridine etc have been chosen as starting materials
in order to prevent the contamination of the oxygen to the B-C-N
product. Though nitrogen-rich B-C-N materials have been
prepared by the reaction between melamine and boron trichloride,
the material considerably contained hydrogen.3 The B-C-N
compound have been prepared by thermal decomposition of the
system of boric acid, saccharose, and urea by Hubacek and Sato.4
They reported that saccharose and boric acid were reduced by the
coexisting urea in this system. Melamine diborate (MDB) is the
representative material which forms turbostratic BN by the
thermal decomposition in N2 over 873 K.5 Since BN is
thermodynamically stable, B-C-N compound can not be obtained
simply by heating of MDB.
We have now found that B-C-N compound with an empirical
formula B1:1C1:1N1:0 can be produced in high yields by the
thermal decomposition of MDB mixed a metal Mg powder, which
works deoxidation material, in Ar at 1273 K.
In a typical experiment, MDB, which was precipitated by
cooling a hot solution of melamine and boric acid, and metal Mg
powder were mixed in the Mg-B mole ratio of 3 or 1, and heated
for 1 h in Ar at 1273 K. In this procedure, MgO, Mg3BN3,
Mg3B2O6, Mg3N2, and MgB12 were formed as by-products. It
was considered that the deoxidation of MDB was mainly caused
by oxidation of Mg. Since the B-C-N compound was stable for
acid, the by-products could be removed by washing with dilute
nitric acid.
Figure 1. SEM images of the B-C-N compound.
The solid-state 13CMAS NMR spectrum of the B-C-N
compound exhibited a broad peak with a maximum at about
ꢀ ¼ 120 ppm with respect to tetramethylsilane (Figure 2). The
chemical shift was in the range of sp2-hybridized carbon reported
by Jarman et al.6 The large line width might be due to the disorder
of the carbon structure and to the random distribution of C-B, C-
C, and C-N bonds, as reported by Riedel et al.7
The B-C-N compound had a density of 1.97 g cmꢀ3 and
specific surface area of 215 m2 gꢀ1. By other method, the B-C-N
The crystal shape of the B-C-N compound was the same as
MDB and the crystal size hardly changed (Figure 1). By
controlling the temperature in synthesizing MDB precisely, it is
possible to increase the crystal size of MDB. Unlike the case in
which other precursor is used, it is possible to obtain the crystal of
large size over mm order by this method.
X-ray powder diffraction of the B-C-N compound was
consistent with turbostratic structure. The diffraction pattern
revealed (hk0) and (00l) reflections, which were typical for boron
nitride precursor obtained by pyrolysis of MDB in N2.5 The
chemical analytic data in combination with the EDX analysis
confirmed that an approximate composition of the B-C-N
Figure 2. 13CMAS NMR spectrum of the B--CN
compond at a Larmore frequency of 75.468 MHz.
Copyright Ó 2002 The Chemical Society of Japan
Aoki, Kaoru
