• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.488-493
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• 2003

Nickel fine powders were prepared from aqueous nickel chloride solution containing organic solvents and the effect of the addition of the organic solvent on the formation of nickel powders were investigated. All products were spherical particles in the range of 0.1∼1.0 $\mu\textrm{m}$ and the agglomeration of particles did not appear. In case of containing 40 vol% of 1-propanol, the particle size reduction and homogeneity of the powders were remarkable. The average particle size and the specific surface area of the powders produced with 40 vol% of 1-propanol were 0.3 $\mu\textrm{m}$ and 16.4 m$^2$/g respectively. The reduction reaction time by hydrazine decreased with increasing of the content of 1-propanol, and was 5 min for 40 vol% of 1-propanol. The oxidation of synthesized nickel powders occurred at 320$^{\circ}C$ and weight loss at 300$^{\circ}C$ was due to dehydration of Ni(OH)$_2$.

• Journal of Powder Materials
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• v.24 no.3
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• pp.242-247
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• 2017

In this study, the electroless nickel plating method has been investigated for the coating of Ni nanoparticles onto fine Al powder as promising energetic materials. The adsorption of nickel nanoparticles onto the surface of Al powders has been studied by varying various process parameters, namely, the amounts of reducing agent, complexing agent, and pH-controller. The size of nickel nanoparticles synthesized in the process has been optimized to approximately 200 nm and they have been adsorbed on the Al powder. TGA results clearly show that the temperature at which oxidation of Al mainly occurs is lowered as the amount of Ni nanoparticles on the Al surface increases. Furthermore, the Ni-plated Al powders prepared for all conditions show improved exothermic reaction due to the self-propagating high-temperature synthesis (SHS) between Ni and Al. Therefore, Al powders fully coated by Ni nanoparticles show the highest exothermic reactivity: this demonstrates the efficiency of Ni coating in improving the energetic properties of Al powders.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.3
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• pp.117-121
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• 2003

Nickel(Ni) powders were prepared from the mixture of nickel chloride and magnesium stearate by a hydrogen reduction process, and the effect of reaction temperature and the addition of magnesium stearate on the chracteristics of the powders were investigated. The effect of size reduction of nickel particles was observed in the presence of magnesium stearate owing to the inhibition of excess growth of paricles. The size reduction and the degree of agglomeration of the particles affected by the amounts of liqiud phase, which related to the increase of magnesium stearate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.3
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• pp.139-144
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• 2003

Nickel fine powders were prepared from nickel chloride aqueous solution containing ethanol as an organic solvent, and their oxidation behaviors were investigated. The reduction reaction by hydrazine from nickel chloride aqueous solution containing ethanol depend on reaction temperature. The reduction reaction time by hydrazine decreased with the increase of reaction temperature. By controlling reaction temperature, the products could be obtained spherical particles in the range of 0.1 $\mu\textrm{m}$~1.0 $\mu\textrm{m}$. Also, As reaction temperature increased from $40^{\circ}C$ to $80^{\circ}C$, the particle size slightly increased and had a broad size distribution owing to the presence of the coarse particles. The mean particle size and specific surface area of nickel powders prepared at $60^{\circ}C$ were 0.3 $\mu\textrm{m}$ and 31.8 $\m^2$/g, respectively. Weight loss of the powders at $300^{\circ}C$ was due to composition of $_Ni(OH)2$. In case of heat treatment at $200^{\circ}C$ in air, oxidation resistance of nickel powders was remarkable than that of as-synthesized.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.268-273
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• 2017

In this study, nickel hydroxide crystalline powders were synthesized by continuous reaction in the taylor fluid flow using nickel chloride, nickel sulphate and sodium hydroxide as raw materials and compared with those prepared by a conventional batch type reaction. The crystallinity of nickel hydroxide prepared by the Taylor fluid flow reaction was higher than that of nickel hydroxide obtained by batch reaction. The particle size of nickel hydroxide decreased about 2.5 to 3.6 times, and the specific surface area was increased.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.165.2-165
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• 2003

• Journal of the Korean institute of surface engineering
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• v.28 no.2
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• pp.83-91
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• 1995

A new method for preparation of thin nickel foam for Ni-MH battery was investigated. In this method, fine graphite powders of $1\mu\textrm{m}$～$2\mu\textrm{m}$ diameter were pasted into pores of thin polyurethane foam film in order to supply electric conducting seeds for nickel deposition by electroless plating reaction. After electroless plating, remaining polyurethane foam was removed chemically by organic solvent treatment and graphite particles also removed by ultrasonic cleaning. Porosity of formed nickel foam was about 85% During electroplating, porosity of the nickel foam decreased less than 5% up to $30\mu\textrm{m}$ coating thickness. And then it was electroplated and heat-treated to improve mechanical strength and ductility. Finally, thin nickel foam for Ni electrode of Ni-MH battery with 80% porosity and $350\mu\textrm{m}$～X$400\mu\textrm{m}$ thickness was obtained.

• Journal of Powder Materials
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• v.18 no.6
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• pp.496-501
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• 2011

In this study, the effect of milling time on the microstructure and phase transformation behaviors of Ni-12 wt.%B powders was investigated using vibratory ball milling process. X-ray diffraction patterns showed that the phase transformation of mixed Ni-B elemental powder occurred after 50 hours of milling, with a formation of nickel boride phases. Through the study of microstructures in mechanical alloying process, it was considered that ball milling strongly accelerates solid-state diffusions of the Ni and B atoms during mechanical alloying process. The results of X-ray photoelectron spectroscopy showed that most of B atoms in the powder were linked to Ni with a formation of nickel boride phases after 200 hours of milling. It was finally concluded that mechanical alloying using ball milling process is feasible to synthesize fine and uniform nickel boride powders.

• Journal of Powder Materials
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• v.23 no.3
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• pp.247-253
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• 2016

In this study, solid solution heat treatment of consolidated nickel-based superalloy powders is carried out by hot isotactic pressing. The effects of the cooling rate of salt quenching, and air cooling on the microstructures and the mechanical properties of the specimens are analyzed. The specimen that is air cooled shows the formation of serrated grain boundaries due to their obstruction by the carbide particles. Moreover, the specimen that is salt quenched shows higher strength than the one that is air cooled due to the presence of fine and close-packed tertiary gamma prime phase. The tensile elongation at high temperatures improves due to the presence of grain boundary serrations in the specimen that is air cooled. On the contrary, the specimen that is salt quenched and consists of unserrated grain boundaries shows better creep properties than the air cooled specimen with the serrated grain boundaries, due to the negative creep phenomenon.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.2
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• pp.73-79
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• 2002

The polyol process which applies to cobalt, nickel. copper and precious metals is a interesting and unexpected example of such a method for preparing uniform metal powders. The reaction proceeds via dissolution, and the polyol acts simultaneously as a solvent, a reducing agent, and to some extent a protective agent. Submicrometer uniform cobalt particles can be obtained by seeding the reactive medium ($AgNO_3$) to achieve a complete substitution of homogeneous by heterogeneous nucleation. By varying the number of nuclei it is possible to control to some extent the average particle size in the submicrometer (0.5$\mu$m) range.