• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.642-643
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• 2006

Direct reduction and carburization process was thought one of the best methods to make nano-sized WC powder. The oxide powders were mixed with graphite powder by ball milling in the compositions of WC-5,-10wt%Co. The mixture was heated at the temperatures of $600{\sim}800^{\circ}C$ for 5 hours in Ar. The reaction time of the reduction and carburization was decreased as heating temperatures and cobalt content increased. The mean size of WC/Co composite powders was about 260 nm after the reactions. And the mean size of WC grains in WC/Co composite powders was about 38 nm after the reaction at $800^{\circ}C$ for 5 hours.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.361-362
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• 2005

Antimony doped tin oxide(ATO) nano powders have been synthesized by homogeneous precipitation method using $SnCl_4\cdot5H_2O$ for precursor, $SbCl_3$ as doped material and urea. The hydrolysis of urea and conductive mechanism and Heat treatment was performed at the temperature from $500^{\circ}C$ to $700^{\circ}C$ in air. The ATO nano powders are characterized by means of Thermogravimetry differential thermal analyzer (TG-DTA), X-ray diffraction (XRD), Brunauer, Emmett, and Teller adsorption (BET), Scanning electron microscopy (SEM) ATO nano powders with an average size of nm and the highest surface area 129 $m^2g^{-1}$ are obtained.

• Korean Journal of Metals and Materials
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• v.48 no.6
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• pp.570-574
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• 2010

Silver conducting films were formed from nano-sized silver powders and glass frits prepared by flame spray pyrolysis. The mean sizes of the silver powders and glass frits were 73 and 63 nm, respectively. Nano-sized glass frits improved the adhesion strength of the silver conducting film to the glass substrate. The densities of the silver conducting films increased by increasing the glass contents of the films at firing temperatures of 400 and $500{^{\circ}C}$. The specific resistances of the silver conducting films with 5 wt.% glass of silver component were 7.8, 4.2 and 2.4 cm at firing temperatures of 400, 450 and $500{^{\circ}C}$.

• Journal of the Korean Ceramic Society
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• v.49 no.5
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• pp.417-422
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• 2012

Copper nano particles have been considered as the materials for conductive ink due to its good thermal, electrical conductivity and low cost. However, copper nanoparticles oxidize easily, decreasing dispersion stability and electrical conductivity. Therefore, it is important to develop a method to minimize oxidation of copper nano particles to improve its dispersion stability property in copper nano ink. In this study, copper nano particles were coated with 1-Octanethiol VSAM(Vaporized Self Assembled Multilayers) to prevent oxidation and coated copper powders were dispersed in conductive ink successfully by studying its relationship of different chain length of solvents to 1-Octanethiol coating layer to fabricate nano ink. Various alcohol solvents, such as 1-Hexanol, 1-Octanol, and 1-Decanol were used. The coating layer was observed using FESEM and TEM. Furthermore, dispersion of copper nano particles in nano inks, was characterized using Turbiscan analyzer, viscometer, and contact angle measurement tool.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1117-1123
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• 2005

In this study, our varistors based on M. Matsuoka's composition were fabricated with ZnO nano-powder whose sizes were 50 nm and 100 nm. Before fabrication of ZnO nano-powder varistors, structure and Phase were analyzed by FE-SEM and XRD with size of ZnO nano-powders to obtain manufacturing information to fabricate the first ZnO varistors using by nano-powders. As a results of these analyses, calcination and sintering temperatures were respectively designed at $600^{\circ}C\;and\;1050^{\circ}C$. ZnO nano-powder varistors were analyzed by SEM and XRD to measure the changes of microstructures and phase after sintered by out process conditions. Also, electrical properties of ZnO nano-powder varistors were obtained by capacitance-voltage, frequency-teal impedance, and current-voltage corves. Our ZnO nano-powder varistors had about 2.5 times of electric field at varistor voltage as compared with normal ZnO varistors fabricated with micro-powder. Also, leakage current and non-liner coefficient respectively had $2.0{\times}10^{-6}A/cm^{-2}$ and 41 for ZnO nano-powder varistors with 50 nm.

• Journal of Powder Materials
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• v.22 no.1
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• pp.46-51
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• 2015

A precipitation behavior of nano-oxide particle in Fe-$5Y_2O_3$ alloy powders is studied. The mechanically alloyed Fe-$5Y_2O_3$ powders are pressed at $750^{\circ}C$ for 1h, $850^{\circ}C$ for 1h and $1150^{\circ}C$ for 1h, respectively. The results of Xray diffraction pattern analysis indicate that the $Y_2O_3$ diffraction peak disappear after mechanically alloying process, but $Y_2O_3$ and $YFe_2O_4$ complex oxide precipitates peak are observed in the powders pressed at $1150^{\circ}C$. The differential scanning calorimetry study results reveal that the formation of precipitates occur at around $1054^{\circ}C$. Based on the transmission electron microscopy analysis result, the oxide particles with a composition of Y-Fe-O are found in the Fe-$5Y_2O_3$ alloy powders pressed at 1150oC. It is thus conclude that the mechanically alloyed Fe-$5Y_2O_3$ powders have no precipitates and the oxide particles in the powders are formed by a high temperature heat-treatment.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.99-102
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• 2007

The Cu oxide nano powders were synthesized by levitational gas condensation (LGC) method and their high heterogeneous catalytic effects of oxidation of 2,3,5-trimethyl-1,4-hydroquinone (TMHQ) and catalase activity were studied. The nano powders consist of mainly $Cu_2O$. The catalytic effect which was clarified by the oxidation of TMHQ and the activity of catalase, was found to depend on the amount of $Cu_2O$ phase and the particle size.

• Journal of the Korean Ceramic Society
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• v.50 no.4
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• pp.275-279
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• 2013

The purpose of this study was to prepare calcium phosphate cement [CPC] for use in artificial bone. Nano-crystalline calcium phosphate [CaP] was precipitated at $37^{\circ}C$ using highly active $Ca(OH)_2$ in DI water and an aqueous solution of $H_3PO_4$. From the XRD measurements, the nano-CaP powder was close to apatitic TCP phase and the powders fired at $800^{\circ}C$ showed a critical ${\beta}$-TCP phase. A mixture of one mole $CaCO_3$ and two moles di-calcium phosphate was calcined at $1100^{\circ}C$ to make a reference ${\beta}$-TCP material. The nano-CaP powders were added to the normal ${\beta}$-TCP matrix and fired at $900^{\circ}C$ to make a ${\beta}$-TCP block. The sintered block showed improved mechanical strength, which was caused by the solid state interaction between nano-CaP and normal ${\beta}$-TCP.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.42-48
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• 2001

Chromium carbides have the excellent wear properties as transition metal carbides. Their tribological applications were studied recently. The nano-sized ceramic could enhance the mechanical and electronical properties of materials. In this study, it was observed to test the wear of the coated surface of nano-sized chromium carbides. The nano-sized chromium carbides were produced by sol-gel processing. Coating surface of produced powders was obtained front plasma spraying. Wear test of coating surface was held increasing temperature. The friction coefficient and the wear loss were testified in dry environment. And the worn surfaces were analyzed by XRD and SEM.

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1113-1118
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• 2002

Nano sized $(Pb_{0.5}Ca_{0.5})(Fe_{0.5}Nb_{0.5})O_3$ (PCFN) powders with the stoichiometric composition and the uniform size distribution were successfully synthesized by the metal-citrate process through the calcination of the polymeric precursor which consisted of the metal ions and the organic network. The crystallization of the initial amorphous powders began at $400{\circ}$ and completed at $700{\circ}$. The pyrochlore phase was detected caused by the dissociation of PbO above $900{\circ}$. Single phase perovskite PCFN powders with 40 nm size and uniform shape were obtained through the calcination at $700{\circ}$.