발간논문

Home > KJMM 논문 > 발간논문

Nickel plate was siliconized with a gas mixture of SiC1₄ and H₂ in the temperature range from 1173K to 1323K. Effect of siliconizing variables on the growth behavior and microstructures of Ni -Si diffusion layera was studied. The nickel silicide layers consisted of γ-Ni_5Si₂, δ-Ni₂Si and θ-Ni₂Si phase at siliconizing temperature. During furnace cooling from siliconizing temperature to room temperature the θ-Ni₂Si phase was decomposed` to large δ-Ni₂Si, small δ-Ni₂Si, ε-Ni₃Si₂ and NiSi phase depending on the silicon concentration. After an incubation period necessary for nucleation of each phase, the growth rate of nickel silicide layers obeyed a parabolic law and was controlled by solid diffusion of nickel which was the primary diffuser in N-Si compounds leading to the void formation at the silicides-nickel interface. These was a tendency for the thickness of lower silicide layer to be a constant at the beginning of the nucleation and growth of the adjacent higher silicide layer. The growth behavior and microstructures of nickel silicide diffusion layers was dependent on the difference between the silicon flux supplied by gas siliconizing and the nickel flux supplied by solid diffusion from substrate which were controlled by siliconizing variables.

keyword :

The aim of this work is to develop the understanding of micro-pulsed plasma nitriding from the microstructural observations. In order to examine the difference of micro-pulsed plasma nitriding, pulse ratio was varied ranges from 0.1 to 1 by controlling both the pulse duration time and the pulse repetition time. Properties of the nitrified layer were analysed by using optical microscope, scanning electron microscope(SEM), atomic force microscope(AFM), X-ray diffractometer(XRD) and micro-vickers hardness tester. It was found that both the compound layer thickness and the case depth decreased with decreasing of pulse ratios and surface roughness also decreased with decreasing of pulse ratios.

keyword :

Ion beam assisted deposition was employed to improve the biological performances of Ti-6Al-4V as artificial joints. Interlayers of Ti oxide, Zr oxide, and calcium phosphate increased the adhesion strength of plasma-sprayed hydroxyapatite coatings to substrate by introducing chemical bonds at interfaces. Heat treatment also affected the adhesion strength, but changed the failure mechanism of HAp coatings from adhesive to cohesive type failure. The cytotoxicity of interlayers was measured with Swiss 3T3 fibroblasts by MTT method, and was comparable to that of the FDA approved Ti-6Al-4V. Titanium nitride was formed with evaporation of Ti and simultaneous bombardments of Ar/N₂ ion beam mixture. The stoichiometry was controlled by the arrival ratio of titanium atoms to nitrogen ions. TiN had the Vickers hardness of 2800 Hv and greatly improved the wear resistance of Ti-6Al-4V.

keyword :

The temperature dependences of the electrical and thermoelectric properties of the SbI₃-doped 33.3% Bi₂Te₃66.7% Sb₂Te₃ single crystals have been measured at temperatures ranging from 77K to 600K. The scattering parameter of the 33.3 Bi₂Te₃-66.7% Sb₂Te₃ single crystals was determined as s = 0. With increasing the amount of SbI₃ dopant, the hole concentration of the 33.3% Bi₂Te₃-66,7% Sb₂Te₃ single crystal is decreased, resulting in the increment of the Seebeck coefficient and electrical resistivity, and the temperature for the maximum figure-of-merit shifted to lower temperature. A maximum figure-of-merit of 2.3×10^(-3)/K was obtained for 0.3 wt% SbI₃-doped specimen. It has been revealed that. the addition of SbI₃ as a donor dopant is useful in controlling the hole concentration of p-type 33.3% Bi₂Te₃ 66.7% Sb₂Te₃ alloy system.

keyword :

The interfacial fracture energies, Γ, of the Cu/Cr/polyimide system were deduced using X-ray measurement method and theoretical method with variation of Cu film thickness and pretreatment conditions on polyimide surface. The two methods showed reasonably good agreement for most cases, imparting validity of both approaches. Estimated Γ were quite independent of the metal film thickness and increased with the rf plasma power density of polyimide pretreatment as expected. Estimated values of Γ were 46.8±7.8. 170.3±42.9 and 253.9±44.4 J/㎡ for the rf plasma power density of 0.03. 0.036 and 0.05 W/㎠, respectively.

keyword :

The interaction coefficient of phosphorus in carbon saturated Fe-Mn, Mn-Si alloys has been measured at temperatures of 1573 to 1673K using a chemical equilibration technique between BaO-BaF₂ fluxes and alloys. A slight decrease in the activity coefficient of phosphorus in Fe-Mn-C_(satd), alloys was observed with increasing manganese content, reflecting a stronger interaction between manganese and phosphorus than that between iron and phosphorus. We also found that interaction coefficient between silicon and phosphorus in the Mn-Si-C_(satd), alloys ε^(Si)_(P C_(satd)), was found to be 3.20, 4.16, 5.26 at 1573, 1623 and 1673K, respectively.

keyword :