• Journal of Korea Foundry Society
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• v.22 no.1
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• pp.42-48
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• 2002

Effects of coating treatment of metallic Cu, Ni-P film on $SiC_p$, for $SiC_p$/iron aluminide composites were studied. Porous hybrid preforms were fabricated by reactive sintering after mixing the coated $SiC_p$, Fe and Al powders. Then the final composites were manufactured by squeeze casting after pouring AC4C Al alloy melts in preforms. The change of reactive temperature, density, microstructure of the preforms and microstructure of the composites were investigated. The exprimental results were summarized as follows. The thickness of Cu and Ni-P metallic layer formed on $SiC_p$ by electroless plating method were about $0.5{\mu}m$ and coated uniformly. There was no remakable change in the ignition temperature with variation of the mixing ratio of Fe and Al powder while in the case of coated $SiC_p$ it was lower about $20^{\circ}C$ than in the non-coated $SiC_p$. The maximum reaction temperature increased with increasing Al contents, but decreased with increasing $SiC_p$ contents. Expansion ratio of preform after reactive sintering increased with amount of Cu coated $SiC_p$. In the case of Fe-70at.%Al, the expansion ratio was about 7% up to 8wt.% of $SiC_p$, addition but further addition of $SiC_p$, increased the ratio significantly. And in the case of Fe-50 and 60at.%Al, it was about 20% up to 16wt.% of $SiC_p$ addition and about 28% in 24wt.% of $SiC_p$, addition. The microstructures of compounds showed that the grains became finer as amount of $SiC_p$, and mixing ratio of iron powder increased and the shape of compounds was changed gradually from irregular to spheroidal.

• Composites Research
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• v.21 no.2
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• pp.31-35
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• 2008

In order to design light weight and high efficient electromagnetic wave absorbing materials, hollow magnetic particles have been introduced in this study. The electroless plating method has been utilized to coat Ni and Fe on the substrates of synthesized polystyrene particles of submicron size. Removing polystyrene particles by heat treatment resulted in hollow structures. Observation by SEM, TEM and EDS confirmed the surface morphology and coating thickness of Ni and Fe. Polymeric composites containing hollow particles were tested in order to compare the electromagnetic properties between Ni coated and Fe costed particles. The composite of 30 wt% Fe hollow particles showed the higher complex permeability than Ni hollow particles or the conventional barium ferrite particles.

• Progress in Superconductivity
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• v.6 no.2
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• pp.133-137
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• 2005

We fabricated the Au/Ni template for YBCO coated conductors and evaluated texture formation and the microstructural evolution. The cube textured Ni substrate was fabricated by rolling and recrystallization annealing, and subsequently Au layer formed on the substrate by electroless-plating method. The texture was evaluated by pole-figure with x-ray goniometer with orientation distribution function (ODF) analysis. The surface roughness and grain boundary morphology of template were characterized by atomic force microscopy (AFM) We observed that Au layer deposited epitaxially on Ni substrate and formed a strong cube texture when plating time was optimized. The full-width at half-maximum (FWHM) was $8.4^{\circ}$ for out-of-plane and $9.98^{\circ}$ for in-plane texture for plating time of 30 min. Microstructural observation showed that the Au layer was homogeneous and dense without formation of crack/microcrack. In addition, we observed that root-mean-square (RMS) and depth of grain boundary were 14.6 nm and 160 $\AA$ for the Au layer, respectively, while those were 27.0 nm and 800 $\AA$ for the Ni substrate, indicating that the electoless-plated Au layer had relatively smooth surface and effectively mollified grain groove.

• Journal of Welding and Joining
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• v.23 no.3
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• pp.61-67
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• 2005

Since lead (Pb)-free solders for electronics have higher melting points than that of eutectic Sn-Pb solder, they need higher soldering temperatures. In order to decrease the soldering temperature we tried to coat Sn-Bi layer on $Sn-3.5\%Ag$ solder by electroplating, which applies the mechanism of transient liquid phase bonding to soldering. During heating Bi will diffuse into the $Sn-3.5\%Ag$ solder and this results in decreasing soldering temperature. As bonding samples, the 1608 capacitor electroplated with Sn, and PCB, its surface was finished with electroless-plated Ni/Au, were selected. The $Sn-95.7\%Bi$ coated Sn-3.5Ag was supplied as a solder between the capacitor and PCB land. The samples were reflowed at $220^{\circ}C$, which was lower than that of normal reflow temperature, $240\~250^{\circ}C$, for the Pb-free. As experimental result, the joint of $Sn-95.7\%Bi$ coated Sn-3.5Ag showed high shear strength. In the as-reflowed state, the shear strength of the coated solder showed 58.8N, whereas those of commercial ones were 37.2N (Sn-37Pb), 31.4N (Sn-3Ag-0.5Cu), and 40.2N (Sn-8Zn-3Bi). After thermal shock of 1000 cycles between $-40^{\circ}C$ and $+125^{\circ}C$, shear strength of the coated solder showed 56.8N, whereas the previous commercial solders were in the range of 32.3N and 45.1N. As the microstructures, in the solder $Ag_3Sn$ intermetallic compound (IMC), and along the bonded interface $Ni_3Sn_4$ IMC were observed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.5
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• pp.433-437
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• 2004

The MmSH is a process of injecting ABS to produce innovated physical properties compared to the conventional injection process. Physical properties such as thickness and adhesion strength of Ni plate electrolessly coated on a conventional and a MmSH injected ABS have been studied in the pH range 4~8. Thickness of the plate on the MmSH and the conventionally injected ABS appeared to be directly proportional to pH. The ABS processed by the conventional injection showed adhesion strength corresponded to ASTM 4B above pH 5. On the other hand, the ABS processed by the MmSH injection showed a superior adhesion strength corresponded to ASTM 5B above pH 6. It was calculated the shielding effectiveness of above 50 dB in all conditions.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.794-801
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• 1995

To connect the driver IC and Al coated glass, a method has been developed to plate electrolessly Ni on Al/PR system. It Is necessary to pretreat Al to remove oxide film before plating. In order to find pretreatment process which does not damage photoresist or glass, alkaline and fluoride zincate process have been investigated. Because photoresist and aluminum thin film can easily dissolve in alkaline solution, it is considered that the fluoride zincate process was a suitable one. After immersion in the zincate solution containing 1.5 g/$\ell$ ammonium bifluoride and 100 g/$\ell$ zinc sulfate, electroless nickel plating could be performed. The additive in the zincate solution and thiourea in the plating solution increased smoothness of the plated surface. Acld dip could improve the uniformit of the surface.

• Korean Journal of Materials Research
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• v.15 no.11
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• pp.735-740
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• 2005

The phase transformation of Ni-B diffusion barrier by Cu diffusion was studied. The Ni-B diffusion barrier, thickness of 10(Inn, was electrolessly deposited on the electroplated Cu interconnect. The specimens were annealed either in Ar atmosphere or in $H_2$ atmosphere from $300^{\circ}C\;to\;800^{\circ}C$ for 30min, respectively. Although the Ni-B coated specimens showed the decomposition of $Ni_3B$ above $400^{\circ}C$ in both Ar atmosphere and $H_2$ atmosphere, Ni-B powders did not show the decomposition of $Ni_3B$. The $Ni_3B$ was decomposed to Ni and B in hi atmospherr: and the metallic Ni formed the solid solution with Cu and the free B was oxidized to $B_2O_3$. However, both the boron hydride and free B were not observed in the diffusion barrier after the annealing in $H_2$ atmos There. These results revealed that the decomposition of $Ni_3B$ by Cu made the Cu diffusion continued toward the Ni-B diffusion barrier.

• Composites Research
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• v.25 no.4
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• pp.93-97
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• 2012

Carbon nano fibers (CNFs) reinforced magnesium alloy (AZ91) matrix composites have been fabricated by liquid pressing process. In order to improve the dispersibility of CNFs and the wettability with magnesium alloy melt, CNFs were mixed with submicron sized SiC particles ($SiC_p$). Also, the mixture of CNFs and $SiC_p$ were coated with Ni by electroless plating. In liquid pressing process, AZ91 melts have been pressed hydrostatically and infiltrated into three reinforcement preforms of only CNFs, the mixture of CNFs and $SiC_p$ (CNF+$SiC_p$), and Ni coated CNFs and $SiC_p$ ((CNF+$SiC_p$)/Ni). Some CNFs agglomerates were observed in only CNFs reinforced composite. In cases of the composites reinforce with CNF+$SiC_p$ and (CNF+$SiC_p$)/Ni, CNFs were dispersed homogeneously in the matrix, which resulted in the improvement of mechanical properties. The compressive strengths of CNF+$SiC_p$ and (CNF+$SiC_p$)/Ni reinforced composites were 38% and 28% higher than that of only CNFs composite.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.161-167
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• 1998

It has been investigated the effects of alloying elements and binders on the corrosion behavior of metal hydride electrodes for anode of Ni/MH secondary battery. The $AB_5$-type alloys, $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ and $(LM)Ni_{3.6}Co_{0.7}Mn_{0.3}Al_{0.4}$, were used for the experiments. The electrodes were prepared by mixing and cold-pressing of alloy powders with Si sealent or PTFE powders, or cold-pressing the electroless copper coated alloy powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

• Carbon letters
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• v.9 no.2
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• pp.105-107
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• 2008

In this work, we employed an electroless nickel plating on glass fibers in order to enhance the electric conductivity of fibers. And the effects of metal content and plating time on the conductivity of fibers were investigated. From the results, island-like metal clusters were found on the fiber surfaces in initial plating state, and perfect metallic layers were observed after 10 min of plating time. The thickness of metallic layers on fiber surfaces was proportion to plating time, and the electric conductivity showed similar trends. The nickel cluster sizes on fibers decreased with increasing plating time, indicating that surface energetics of the fibers could become more homogeneous and make well-packed metallic layers, resulting in the high conductivity of Ni/glass fibers.