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Chemistry Letters Vol.36, No.4 (2007)
Synthesis of Ni3C Nano-whisker from NiSO4 and Sucrose by Means of Spray Pyrolysis
Takeshi Kashiwagi, Naohisa Suzuki, Masashi Niina, Hiroyasu Nishiguchi, Katsutoshi Nagaoka, and Yusaku TakitaÃ
Department of Applied Chemistry, Faculty of Engineering, Oita University, 700 Dannoharu, Oita 870-1192
(Received December 15, 2006; CL-061472; E-mail: takita@cc.oita-u.ac.jp)
Ni particles and Ni3C whiskers with a novel morphology,
spheres. In this way, spray pyrolysis of sucrose and metal salts is
a novel, safe, and easy method of the synthesis of carbon–metal
composites. Since these composite was composed of amorphous
carbon, electro conductivity seems to be small.
grew on the Ni–carbon composite by heat treatment at 1073 K
in Ar. Ni–carbon composites were prepared by spray pyrolysis
of a solution of sucrose and NiSO4 in Ar at 1073 K.
When post treating of these composites was carried out in
Ar flow, particles of Ni metals and fibers of Ni3C were formed
on the spheres. We report these novel composites for practical
utilization.
Formation of Ni3C have been reported in various situations
such as alloy formation1 and diamond synthesis,2 and some in-
vestigations of their physical properties were reported.3,4 Forma-
tion of Ni3C appeared in many catalytic reactions using Ni metal
such as the formation of symmetric helical carbon filaments
from Ni–Cu/MgO-catalyzed 1,3-butadiene decomposition,5
Fischer–Tropsch reaction over Ni/SiO2,6 production of methane
from a mixture of CO and H2 over Ni(111) surface,7 partial
oxidation of methane to synthesis gas over Ni/La2O3 and Ni/
Al2O3 catalysts,8 hydrogen treatment of Ni/SiO2 thin films
prepared from the deposition of carbon from acetylene,9 and
the hydrodehalogenation of CCl2F2 and CHClF2 over Ni–Al2O3
catalyst supported on activated carbon.10 However, no formation
of single crystal of Ni3C has been reported so far.
Sucrose (Wako pure chem., reagent grade) and nickel salts
(Wako, Pure grade) were used. An aqueous solution containing
sucrose and NiSO4 was fed by a spray into a reactor made of
stainless steel with 10 cm in diameter. Feed rates of the liquid
and Ar as a carrier gas were 300 cm3/h and 3 L/h, respectively.
A schematic diagram of the reaction system appears elsewhere.11
The length of an electric heater for reaction chamber was 40 cm.
The product was collected by a water trap. The recovered water,
containing products, was filtered, washed with pure water and
dried at 343 K for one night. The sample was treated at 1073 K
in an Ar flow. Then, the products were supplied to analysis by
XRD, TG-DTA, and SEM and TEM observations.
The products from a solution of 0.05 M NiSO4 and 0.50 M
sucrose at 1073 K were composed of veritable and slightly dis-
torted spheres of 1–15 mm in diameter. Amount of non uniform
particles was very small. According to TEM observation of
sphere of 400 nm in size, 6–12 nm Ni particles were well
dispersed in the spheres. SEM observation showed that there
are many white spots of 28–40 nm on the surface. These sizes
are somewhat larger than that of Ni particles observed by
We have studied the spray pyrolysis of a solution composed
of sucrose in the presence of nickel salts at 873–1173 K
in an inert gas flow and reported novel methods of the synthesis
.
of a kind of Hofmann complex, Ni(CN)2(NH3) 0.25H2O and
carbon–Ni composites with several different shapes such as
spheres, broken spheres, and sheets.11,12 Hofmann complex
crystals of rectangular body were formed at 973 and 1073 K.
Carbon–Ni composites are composed of amorphous carbon
and mainly Ni metal. No product was obtained by the spray
decomposition of Ni-free sucrose and spheres of NiO were
obtained from sucrose free Ni(NO3)2 solution. Therefore,
.
Ni(NO3)2 catalyzed the formation of Ni(CN)2(NH3) 0.25H2O
and carbon–Ni composites. Spherical Ni–carbon composite
was obtained from a solution composed of Ni(CH3COO)2
and sucrose at 973–1073 K. When the concentration of
Ni(CH3COO)2 was much high as 0.50 M, formation of CNT
on the small composite less than 1 mm in diameter was observed
at 1073 K. In case of 0.005 M NiSO4, genuine spherical Ni–
carbon composites were obtained at 873–973 K. The optimum
temperature for CNT formation depended on the concentration
of NiSO4; 973 K for low NiSO4 concentration (0.005 M) and
1073 K for high NiSO4 concentration (0.05 M). Ni particles with
7–17 nm were well dispersed in the obtained Ni–carbon compo-
site. In the spray pyrolysis of solutions containing sucrose and
metal salts, cubic crystal of Co2(CN)5(NH3) was obtained from
only a solution of Co(NO3)2 and sucrose at 1073 K. Amorphous
carbon–Co metal composites or carbon–Fe oxide composites
were obtained from solutions of sucrose and Co or Fe salts such
as acetate, sulfate, and chloride. The shapes of major products
were spheres that have filled or egg shell structures and particles
of broken large spheres. Small particles of Co metal with 7–
22 nm or Fe3O4 with 6–22 nm were well dispersed in the formed
1 µm
Figure 1. SEM image of the Ni–carbon composite after heat
treatment at 1073 K for 3 h.
Copyright ꢀ 2007 The Chemical Society of Japan
Kashiwagi, Takeshi
