• Journal of Surface Science and Engineering
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• v.28 no.1
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• pp.3-13
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• 1995

Electroless Ni and Cu platings were conducted on $B_4C$ and SiC. In the electroless Ni plating, the deposition rate on $B_4C$ was higher than on SiC. However, the electroless Cu deposition occured with high deposition rate regardless of the carbide substrates used in this study. Uniformity of the deposits was better in the electroless Cu deposition than in the electroless Ni deposition. In the topographies of the electroless depositions, Ni deposits have grown as colony, whereas Cu deposits have grown as fine individual grains.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.65-70
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• 1998

Fine powders of $\alpha$-Fe2O3 were prepared by precipitation method using iron (III) nitrate in ethanol solvent and the thick film using this powder was made by the screen printing technology. Effects of the reaction temperature and concentration of the iron (III) nitrate on the particle size and specific surface area were studied. Also, the relationship between the powder size and properties of the thick film was discussed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.203-204
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• 2006

There is an increasing demand for PM-processes with the capability to produce parts of higher complexity than with conventional press and sinter technology in high production numbers. Warm-flow-compaction (WFC) makes use of improved flowability of powders when blended in an appropriate ratio with fine powder fractions and lubricating binders. Here the process is shown with examples of PM-Steels. General features possible with the process like pressing of undercuts and threaded bores are shown.

• Proceedings of the PSK Conference
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• 2000.04a
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• pp.208.1-208.1
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• 2000

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.393-394
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• 2000

The magnetic alloy of $Nd_{2}Fe_{14}B$-type was synthesized by a mechano-chemical method, including the processes of spray-drying, de-binding, milling, $H_{2}$- and Ca-reduction and washing. The very fine $Nd_{2}Fe_{14}B$ particles smaller than $1\mu\textrm{m}$ could be achieved without the inevitable pulverization step in conventional processes.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.441-446
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• 2003

Fine powders of ZnO were synthesized by the sol-gel method. The shape of gel powders with calcination temperatures changed into the sheet structure, the needle shape, and the spherical grain. The growth rate of grain size was slow to 700$^{\circ}C$ but high above 700$^{\circ}C$. The bigger the grain size is, the higher the degree of crystallization is. The organic element in gel powders evaporated below 300$^{\circ}C$. Temperature dependence of conductances showed the sigmoidal shape, but the temperature range of the constant conductances narrowed with the decrement of the calcination temperature of gel powders. The optimum sensing property for CO gas were observed with the specimen calcined at 500$^{\circ}C$ and degraded with the increment of calcination temperature.

• Journal of Korea Foundry Society
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• v.17 no.2
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• pp.158-163
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• 1997

Properties of $Al_{86}Ni_6Ce_4Mg_4$ alloy powder produced by helium gas atomization process were investigated by using DSC, XRD, SEM and TEM. The powders below 32 ${\mu}m$ in diameter were identified as an amorphous phase mixed with a ${\alpha}-Al$ phase. $Al_{86}Ni_6Ce_4Mg_4$ bulk alloy was manufactured by hot extruding the alloy powders at various temperatures, and the estimation of its mechanical properties was carried out subsequently. As a result, the bulk alloy extruded at the temperature below $450^{\circ}C$ exhibited the microstructure in which the near-spherical shape of some powders below 20 ${\mu}m$ were nearly unchanged and fine voids between matrix and powders were formed during extrusion process. On the other hand, the tensile strength and elongation at room temperature for $Al_{86}Ni_6Ce_4Mg_4$ bulk alloy extruded at $450^{\circ}C$ were 750 MPa and 7.5%, respectively.

• Journal of Korea Foundry Society
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• v.12 no.3
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• pp.210-219
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• 1992

The measurement of the apparent and tap density for Al-Pb-X(Sn,Sn-Si) powders produced by centrifugal atomizer showed that the larger theoretically calculated densities the larger those densities. And tap densities were not over 50% of the theoretical densities. The nip angle of Al-5wt%Pb alloy powders produced with 38000 r.p.m. of disk rotation was $3^{\circ}$ degree larger than that of Al-8.5wt%Pb-3wt%Sn(-4wt%Si, 8wt%Si) with 50000 r.p.m. The effects of roll gap and rolling speed on thickness and density of the single strips by rolling were that rolling speed increasing the thickness and density of strip decreased and roll gap increasing, the thickness of strip increased but the density decresed. The compactibility of Al-Pb-X with Al by rerolling showed that the coarse powder-strips were better than fine powder-strips. From the SEM study with EDX analysis on the sintered strips, it was found that Pb and Sn were segregated with maximum size $5{\mu}m$, and Si existed surrounding the segregation zone. After sintering the clad strips at $500^{\circ}C$, the pores, which were spherical with $5{\mu}m$ of mean diameter, partly remained around the particles of alloy powders area, while completely disappeared at clad interface. The hardness of strips of alloy powders decreased linearly with increasing sintering temperature.

• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.396-400
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• 2006

The Ti-Ni alloy nanopowders were synthesized by a levitational gas condensation (LGC) by using a micron powder feeding system and their particulate properties were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) method. The starting Ti and Ni micron powders $150{\mu}m$ were incorporated into the micron powder feeding system. An ingot type of the Ti-Ni ahoy was used as a seed material for the levitation and evaporation reactions. The collected powders were finally passivated by oxidation. The x-ray diffraction experiments have shown that the synthesized powders were completely alloyed with Ti and Ni and comprised of two different cubic and monoclinic crystalline phases. The TEM results showed that the produced powders were very fine and uniform with a spherical particle size of 18 to 32nm. The typical thickness of a passivated oxide layer on the particle surface was about 2 to 3 nm. The specific surface area of the Ti-Ni alloy nanopowders was $60m^2/g$ based on BET method.

• Journal of Surface Science and Engineering
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• v.26 no.2
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• pp.87-107
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• 1993

The grain size of the final products of WC-Co and WC-Ni composite powders is dependent on the size of the starting material and the conditions employed for the reduction and carburization. APT-Co and -Ni com-plex salts were prepared by the substitution reaction between ammonium ions in APT and the metal ions in Co(NO3)2 and Ni(NO3)2 solutions of different concentrations(0.1 to 0.7M) at $50^{\circ}C$ and the grain sizes of the com-plex salts was $0.54~0.76\mu\textrm{m}$. The complex which calcined the complex salts at $700^{\circ}$~80$0^{\circ}C$ for 60min. were 0.2~0.5$\mu\textrm{m}$. W-Co($5.92^{\circ}C$) and -Ni(6.95%) powders which reduced the complex oxides with H2d atmo-sphere(flow rate;600cc/min.) at $700^{\circ}$~$800^{\circ}C$ for 60min. were $0.5~0.6\mu\textrm{m}$. The mean grain sizes of WC-Co and WC-Ni composite powders which carburized both complex metals of W-Co and W-Ni at $800^{\circ}C$ for 60min. were $0.5~0.6\mu\textrm{m}$, and take place the coarsening of the grain above $800^{\circ}C$ and the optmium ratio of C3H8 and H2 was 0.2 for the control of the free carbon. The effect of Co contents on the particle sizes decreased from 0.4 to $0.25\mu\textrm{m}$ with increasing the content from 2.0 to 7.6w%. The activation energies on the reductions of oxides and the formations of carbides were as follows ; W-Co : Q = 8.7 kcal/mole, W-Ni : Q = 8.1 kcal/mole, WC-Co pow-der : Q = 17.8 kcal/mole, WC-Ni powder : Q = 16.6 kcal/mole.