발간논문

Home > KJMM 논문 > 발간논문

We have studied an atomic ordering and ordered domains in Cd_(x)Zni_(1-x),Te epilayers grown by molecular beam epitaxy on ZnTe buffer layers. The composition of Cd_(x)Zni_(1-x)Te thin films was determined by X-ray diffraction patterns using the Vegard`s law. Selected area electron diffraction pattern and high-resolution transmission electron microscopy measurements were performed in order to investigate the ordered structure and ordered domains in Cd_(x)Zni_(1-x),Te thin films. The strong contrast modulations along the [001] direction parallel to the growth direction were observed in samples with composition x = 0.15~0.76. A superstructure reflection spots corresponding to a CuPt-type ordering were observed. Ordered domain regions were randomly distributed in Cd_(x)Zni_(1-x),,Te thin films. A possible atomic arrangement of and a formation mechanism for the CuPt-type ordered structure in the Cd_(x)Zni_(1-x);Te epitaxial layer are presented based on the TEM results. These results provide important information on the microstructural properties for enhancing efficiencies of the devices operating at the blue-green region of the spectrum. (Received July 12, 2004)

keyword : CuPt, Atomic ordering, CdZnTe, Transmission electron microscopy

Solvent extraction and stripping experiments were conducted to separate iron from a spent FeC13 etching solution containing nickel. In the operation of mixer-settler, 7 extraction stages with 1.0 M Alamine336 in toluene, led to 98% extraction percentage of iron at equal phase ratio, when the flow rate of organic and aqueous were 35 mL/min and 5 mL/min, respectively. At equal phase ratio of aqueous to organic, 10 stripping stages with 0.01 M HC1 solution resulted in 99% stripping percentage of iron when the flow rate of stripping solution and loaded organic were 5 mL/min and 35 mL/min, respectively. The concentration of iron in the stripped solution was 133 g/L and this solution could be reused in the etching of nickel lead frame. (Received June 15, 2004)

keyword : Etching solution, Iron, Nickel, Separation, Mixer-settler

Tape casting process was applied to the fabrication of cemented carbide thin plate with thickness below 1 mm, which is expected to reduce the production cost and to enable the mass production of thin plates. Using the tape casting process, thin plates of cemented carbide were fabricated in the various forms such as monolithic and laminated, perforated and non-perforated thin plate forms. The debinding and sintering behavior were investigated to define the related problems and the solutions were suggested. Through sequential application of sheet forming by tape casting, lamination, debinding and vacuum sintering, the flat cemented carbide thin plates of lateral dimension, the sintered thickness and its deviation of 45-75 mm, minimum 500μm and 50μm, respectively, could be fabricated. Cemented carbide thin plates of perforated forms as well as the laminated forms could also be fabricated with a similar specification. Abnormal grain growth was observed in the microstructure, which was attributed to the incorporation of the impurities during the tape casting process. It was found to be readily preventable. Sintering behavior was investigated for the laminated composite thin plates of TiC-Ni/WC-Ni, in the performance diversification perspectives. When the grain growth kinetics were different for the two layers, an asymmetric capillary force was generated to induce a different shrinkages of the layers. This induced a severe warping of the plates. When the grain growth kinetics of the two layers were made identical by addition of grain growth inhibitor, the shrinkage difference was prevented, which enabled warp-free, dense laminated plate. (Received February 13, 2004)

keyword : Cemented carbide, Tape casting, Metal matrix composite, Thin plate, Abnormal grain growth