• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.948-949
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• 2006

An infiltration technique using W-Cu composite powder has been developed to enhance microstructural uniformity of W-Cu pseudo-alloy. W-Cu composite powder, manufactured by reduction from $WO_3$ and CuO powder mixtures, were blended with W powder and then cold iso-statically pressed into a cylindrical bar under 150 MPa. The pressed samples were pre-sintered at $1300^{\circ}C$ for 1 hour under hydrogen to make a skeleton structure. This skeleton structure was more homogeneous than that formed by using W and Cu powder mixtures. The skeleton structures were infiltrated with Cu under hydrogen atmosphere. The infiltrated W-Cu pseudo-alloy showed homogeneous microstructure without Cu rich region

• Journal of Powder Materials
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• v.4 no.2
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• pp.122-132
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• 1997

Nanostructured(NS) W-Cu composite powders of about 20~30 nm grain size were synthesized by mechanical alloying. The properties of NS W-Cu powder and its sintering behavior were investigated. It was shown from X-ray diffraction and TEM analysis that the supersaturated solid solution of Cu in W was not formed by the mechanical alloying of mixed elemental powders, but the mixture of W and Cu particles with nanosize grains, i.e., the nanocomposite powder was attained. Nanocomposite W-20wt%Cu and W-30wt%Cu powders milled for 100 h were sintered to the relative density more than 96% and 98%, respectively, by sintering at 110$0^{\circ}C$ for 1 h in $H_2$. Such a high sinterability was attributed to the high homogeneous mixing and ultra-fine structure of W and Cu phases as well as activated sintering effect by impurity metal introduced during milling.

• Journal of Powder Materials
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• v.6 no.1
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• pp.36-41
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• 1999

The present work has attempted to investigate the dependence of Cu infiltration kinetics on in-situ structure modification of W powder skeleton in W-Cu system. In-situ structure modification of W skeleton by addition of 0.3wt%Ni-P eutectic alloy was designed to proceed during heat-up of the W compact for Cu infiltration process. It was found that the Ni-P added W skeleton underwent remarkable stucture change only during heating-up. its structure was composed of large necks of W particles above 0.5 in the ratio of neck to particle size and smooth pore channels. The infiltration experiment showed that the infiltration kinetics for the W-Ni-P followed well the linear relationship of h vs. $t^{1/2}$ the rate constant K of which was in good agreement with the theoretical value. On the other hand, in case of the pure W skeleton a lower K value by 20% than the theoretical one was obatined. Such discrepancy is discussed in terms of skeleton structure induced infiltration mechanics.

• Journal of Powder Materials
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• v.7 no.4
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• pp.228-236
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• 2000

An investigation was carried out on the possibility whether the ball-milling process of low energy could successfully improve the packing density and flowability for MIM application in W-20wt%Cu system. In this study, W-20wt%Cu powder mixture was prepared by ball-milling. W powder was not fractured by low mechanical impact energy used in the present work during the critical ball-milling time, but the ductile Cu powder was easily deformed to the 3 dimensional equiaxed shape, having the particle size similar to that of W powder. The ball-milled mixture of W-20wt%Cu powder had the more homogeneous distribution of each component and the higher amount of powder loading for molding than the simple mixture of W-Cu powder with an irregular shape and a different size. Accordingly, the MIM W(1.75)-20wt%Cu powder compacts were able to be sintered to the relative density of 99% by sintering at $1400^{\circ}C$ for one hour.

• Journal of Powder Materials
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• v.5 no.3
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• pp.210-219
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• 1998

The W-Cu composite powders were synthesized from W and Cu elemental powders by ball-milling process, and their microstructural changes and sintering behaviors were evaluated. The ball milling process was carried out in a 3-dimensional mixer (Turbula mixer) using zirconic ($ZrO_2$) ball and alumina ($Al_2O_3$) vial up to 300 hrs. The ball-milled W-Cu powders revealed nearly spherical shape. Microstructure of the composite powders showed onion-like structure which consists of W and Cu shells due to the moving characteristic of Turbula mixer. The W and Cu elements in the composite powders milled for 300 hrs were homogeneously distributed, and W grain size in the ball-milled powder was smaller than 0.5 $\mu\textrm{m}$. Fe impurity introduced during ball milling process was very low as of 0.001 wt%. The relative sintered density of ball-milled W-Cu specimens reached about 94% after sintering at $1100^{\circ}C$.

• Journal of Powder Materials
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• v.5 no.2
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• pp.145-153
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• 1998

W-Cu alloy is attractive to thermal managing materials in microelectronic devices because of its good thermal properties. The metal injection molding (MIM) of W-Cu systems can satisfy the need for mass production of the complex shaped W-Cu parts in semiconductor devices. In this study, the application of MIM process of the mechanically alloyed (MA) W-Cu composite powders, which had higher sinterability were investigated. The MA W-Cu powders and reduction treated (RT) powders were injected by using of the multicomponent binder system. The multi-stage debinding cycles were adopted in $N_2$ and $H_2$ atmosphere. The isostatic repressing treatment was carried out in order to improve the relative density of brown parts. The brown part of RT W-Cu composite powder sintered at 110$0^{\circ}C$ had shown the higher sinterability compared to that of MA powder. The relative sintered density of all specimens increased to 96% by sintering at 120$0^{\circ}C$ for 1 hour. The relationship between green density and the sintering behavior of MA W-Cu composite powder was analyzed and discussed on the basis of the nanostructured characteristics of the MA W-Cu composite powder.

• Journal of the Korean Magnetics Society
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• v.5 no.3
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• pp.191-196
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• 1995

NiCuZn ferrites were prepared by a solid-state reaction and sintered at $900^{\circ}C$ for 5 hours. Its properties were investigated by controlling the ferrite composition and processing. NiCuZn ferrite with a composition of ${(Ni_{0.2}Cu_{0.2}Zn_{0.6}O)}_{1.02}{(Fe_{2}O_{3})}_{0.98}$ was found to have the maximum initial permeability as a result of the variation of Cu content and the (Ni+Cu)/Zn ratio. Curie temperature($T_{c}$) of NiCuZn ferrite was decreased with the larger Cu content and increased with the larger Ni content. NiCuZn ferrites of ${(Ni_{0.2}Cu_{0.2}Zn_{0.6}O)}_{1-w}{(Fe_{2}O_{3})}_{1+w}$ composition milled for 20~80 hours had the maximum initial permeability at w=-0.015 and Curie temperature ($T_{c}$) was decreased with the increasing of $Fe_{2}O_{3}$ deficiency(w).

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.761-762
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• 2006

W-Cu alloy was very useful material for a heat sink, high electric contact and EDM electrode. Powder injection molding (PIM) is the optimum manufacturing technology to provide W-Cu components with low-cost and high-volume. We used various compositions of tungsten coated copper powders (W-Cu with 10 to 80 wt-% of copper) to manufacture W-Cu components by PIM. The optimum mixing, injection molding, debinding and sintering conditions to provide the high performance W-Cu components were investigated. The thermal and mechanical properties of W-Cu parts by PIM were measured. Finally, we can verify the high performance of W-Cu components by PIM with the tungsten coated copper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.05a
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• pp.43-45
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• 1988

Four W/Cu system(60wt%W-40wt%Cu, -0.lwt%Ni, -0.5wt%Ni, -0.lwt%C) and four WC/Cu system(60wt%WC-40wt%Cu, -0.lwt%Ni, -0.5wt%Ni, 0.lwt%C) electrical contacts were prepared by a press-sinter-infiltration process to compare with their properties. Hardness and electrical conductivity are proportional to the refractory metal(W or WC) properties and showed the effect of additives. Arc erosion trend of switch test is changed by current level. High currant test at 1kA showed a different crack formation pattern and erosion mode between W/Cu system and WC/Cu system contacts.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.16-16
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• 2001