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2006, Vol.16, No.3

  • 1.

    Synthesis and characterizations of the non-swelling property micas by hydrothermal method

    박춘원 | 박선민 | Akira Kambayashi | 2006, 16(3) | pp.95~100 | number of Cited : 0
    Abstract PDF
    Synthesis of the non-swelling property micas was carried out by hydrothermal method. In order to artificially induce the diffusion of ions, a rotating system was attached to the hydrothermal apparatus and by adding 0.7 mm zircon beads, synthesis of the non-swelling property micas could be performed in a low temperature area. The hydrothermal conditions for the preparation of micas were a reaction temperature of 260 o C, for 72 hrs, using 1K2O, 1Al(OH)3, 4Mg(OH)2 and 6SiO2 as the starting materials and a 8M-KOH solution as the hydrothermal solvent. The micas obtained under these conditions were a plate shape with a size of 2.89 μm and showed a whiteness of over 97 %. Also, through the FT-IR analysis, because the absorption peak of the Mg3OH vibration was observed at approximately 3700 cm.1 , it could be known that it was phlogopite of non-swelling property showing the chemical composition of KMg3AlSi3O10(OH)2. This result was very consistent with the EDS analysis where O (41.34 %), Mg (3.88%), Al (11.45 %), Si (17.62 %) and K (25.71 %) elements were detected.
  • 2.

    Fabrication and sintering of nano TiNx and its composites

    Sungjin Kim | Lee Sang Woo | Woo Heung-sik and 7other persons | 2006, 16(3) | pp.101~105 | number of Cited : 1
    Abstract PDF
    We fabricated the nano TiNx by making of reaction between titanium powder and Si3N4 during planetary milling. The TiNx powder was sintered by spark plasma sintering machine after mixing with 50 wt% of titanium powder, and the sintered body was heat-treated at 850 o C in order to investigate its hardness property at the elevated temperature. We analyzed crystal structure by XRD. We observed the peaks of TiN0.26 and TiN after 10 hours milling, and we observed TiN peak mainly after 20 hours milling. The reacted particle size distribution was investigated by FE-SEM. Increase of milling time, the size of reacted particles was decreased and the 10~20 nm size of TiNx on the surface of titanium and TiNx was observed after 20 hours milling. The micro-Vickers hardness of mixed sintered body was about 1050 kgf/mm 2 .
  • 3.

    Potassium loading effects for nano-porous ACF pre-treated with phosphoric acid

    Oh Won Chun | Chang Sung Lim | 2006, 16(3) | pp.106~111 | number of Cited : 0
    Abstract PDF
    The objective of this paper is to compare the surface features of two kinds of nano-porous activated carbon fiber (NPACF) treated with potassium and the variation of their properties by phosphoric acid pre-treatment. X-ray diffraction (XRD) patterns indicate that NPACF containing potassium species show better performance for potassium and potassium salts by pre-treatment with phosphoric acid. In order to present the causes of the differences in surface properties and specific surface area after the samples were treated with phosphoric acid, pore structure and surface morphology are investigated by adsorption analysis and SEM. For the chemical composition microanalysis for potassium loading of the NPACF pre-treated with phosphoric acid, samples were analyzed by EDX. Finally, the type and quality of oxygen groups are determined from the method proposed by Boehm.
  • 4.

    Luminescence characteristics of bismuth and europium co-doped yttrium oxide red phosphor forwhite light emitting diodes

    박우정 | Seok Gyu Yoon | Yoon Dae Ho and 1other persons | 2006, 16(3) | pp.112~115 | number of Cited : 0
    Abstract PDF
    The red emission properties of Bi 3+ co-doped Y2O3 : Eu 3+ prepared by the solid-state reaction was investigated, in order to verify its potential to act as the red emitting phosphor of white LEDs. The emission spectrum consisted of a weak band at 581, 587, 5931 and 599 nm, with maximum sharp peaks occurring at about 611 nm due to the 5 D0 → 7 F2 transition of Eu 3+ , while the excitation spectrum exhibited a broad band between 290 and 430 mm with peaks occurring in the range of 310~390 nm. Also, SEM image of the sample containing 0.43 mol% H3BO3 and 2.08 mol% BaCl2·2H2O phosphor particles grew to achieve diameters of 700~800 nm.VX
  • 5.

    Structural characterization of Al2O3 layer coated with plasma sprayed method

    Jwayeon Kim | JaeKeun Yu | Sul Yong Tae | 2006, 16(3) | pp.116~120 | number of Cited : 0
    Abstract PDF
    We have investigated plasma spray coated Al2O3 layers on Al-60 series substrates for development of wafer electrostatic chuck in semiconductor dry etching system. Samples were prepared without/with cooling bar on backside of samples, at various distances, and with different powder feed rates. There were many cracks and pores in the Al2O3 layers coated on Al-60 series substrates without cooling bar on the backside of samples. But the cracks and pores were almost disappeared in the Al2O3 layers on Al-60 series substrates coated with cooling bar on the back side of samples, 15 g/min. powder feed rate and various 60, 70, 80 mm working distances. Then the surface morphology was not changed with various working distances of 60, 70, 80 mm. When the powder feed rate was changed from 15 g/min to 20 g/min, the crack did not appear, but few pores appeared. Also the Al2O3 layer was coated with many small splats compared with Al2O3 layer coated with 15 g/min powder feed rate. The deposited rate of Al2O3 layer was higher when the process was done without cooling bar on the back side of sample than that with cooling bar on the back side of sample.
  • 6.

    Wear behaviors of HVOF spray coating of Co-alloy T800

    TONG YUL CHO | Chun Hui Gon | Jaehong Yoon and 4other persons | 2006, 16(3) | pp.121~126 | number of Cited : 3
    Abstract PDF
    HVOF thermal spray coating of Co-alloy T800 is progressively replacing the classical hard coatings such as chrome plating because of the very toxic Cr 6+ ion known as carcinogen causing lung cancer. For the study of the possibility of replacing of chrome plating, the wear properties of HVOF Co-alloy T800 coatings are investigated using the reciprocating sliding tester both at room and at an elevated temperature of 1000 o F (538 o C). The possibility as durability improvement coating is studied for the application to the high speed spindles vulnerable to frictional heat and wear. Wear mechanisms at the reciprocating sliding wear test are studied for the application to the systems similar to the sliding test such as high speed spindles. Wear debris and frictional coefficients of T800 coatings both at room and at an elevated temperature of 1000 o F (538 o C) are drastically reduced compared to those of non-coated surface of parent substrate Inconel 718. This study shows that the coating is recommendable for the durablity improvement coatings on the surfaces vulnerable to frictional heat. The sliding surfaces are weared by the mixed mechanisms such as oxidative wear, abrasion by the sliding ball, slurry erosion by the mixture of solid particles and small drops of the melts and semi-melts of the attrited particles, cavitation by the relative motions among the coating, sliding ball, the melts and semi-melts. and corrosive wear. The oxide particles and the melts and semi-melts play roles as solid and liquid lubricant reducing the wear and friction coefficient.0
  • 7.

    Analysis of Ca-rich efflorescence in ceramic bodies

    Lee,Ki-Gang | 2006, 16(3) | pp.127~131 | number of Cited : 1
    Abstract PDF
    The efflorescence mechanism of ceramic bodies with diferent sintering temperature was studied by quantitativeanalysis for the efect of various metal ions and anions. SEM and EDS characterization for efflorescence formed on thesurface of the ceramic body showed that the main components of the efflorescence were Ca and S atoms. Leachingwere evaluated by ICP and IC analysis. The results of leaching test showed that the concentration of Ca ion at pH 7 bodywas eight times more than that of pH 10 body. Ca-rich efflorescence was not formed on the surface of ceramic bodywhich prepared at pH 10 and sintered over 10oC.Key words Eflorescence, Ca ion, S ion, Ceramic body