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2011, Vol.21, No.2

  • 1.

    Characterization of dark core and blue patch in Mong Hsu ruby

    P. Maneeratanasarn | P. Wathanakul | Kim, Young-chool and 3other persons | 2011, 21(2) | pp.55~59 | number of Cited : 0
    Abstract PDF
    Mong Hsu rubies from Myanmar include typically the dark core and blue patch but most of the previous research has merely focused on the dark core. This work is aimed to understanding clearly the characteristic of the dark core and blue patch of Mong Hsu rubies. It was found from the FTIR analysis that the dark core and blue patch region showed the absorption peaks of boehmite (1986 cm−1), diaspore (2115 cm−1) and water (3400~3900 cm−1) but the absorption peaks of O-H stretching (3309 cm−1and 3078 cm−1) were found only in blue patch region. The UV-VIS-NIR analysis of the dark core region revealed the stronger absorption of Cr 3+at 405 and 554 nm compared to the blue patch region. In range of 600~800 nm, the UV absorption characteristic at 659, 675 and 693 nm assigned to Cr 3+of core group samples is distinct from that of blue patch. The SEM-EDS examinations disclosed the existence of lots of micro-cracks and pores in the core regions compared to blue patch region.
  • 2.

    Optoelectronic properties of the Metal-dielectric complex thin films for applying high sensitivity IR image sensors

    김예나 | 권순우 | 박승준 and 4other persons | 2011, 21(2) | pp.60~64 | number of Cited : 0
    Abstract PDF
    High sensitivity IR image sensors require materials characteristics with temperature coefficient of resistance (TCR)and IR range absorption. In this study, the metal-dielectric thermo sensitive films (MDTF) based on (SiO2)x-(Ti)y composition were deposited on substrates of germanium and glass by thermal evaporator. The SiO2 : Ti mixture was made from the ratio of 9 : 1, 8 : 2, 7 : 3, 6 : 4, respectively. (SiO2)x-(Ti)y mixture powder was loaded on tungsten boat in evaporator and was 15.5 cm from the substrate. Resistance of (SiO2)x-(Ti)y in the range of 273~333 K were measured as a function of temperature. Temperature coefficient of resistance (TCR) was calculated by the resistance variation. Under the various mixture ratios condition, it is possible to obtain SiO2-Ti layers with resistance from units kilo-ohm to hundreds kilo-ohm. Finally, our results showed that Temperature coefficient of resistance (TCR) of these films varies from −1.4 to −2.6 %K−1.
  • 3.

    Characterizations of TiO2 thin films with atmosphere control of the RF magnetron sputtering

    Park Ju-Hoon | 김봉수 | 김병훈 | 2011, 21(2) | pp.65~69 | number of Cited : 3
    Abstract PDF
    The TiO2 films were prepared on glass, silicon and quartz substrate at different temperature by radio frequency reactive magnetron sputtering under different flow ratios of Ar and O2 gases. The films were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and UV-VIS spectrophotometer. Only the anatase phase was observed in films and their diffaction peaks increased with temprature of substrate. The size of crystallites decreased with higher concentration of oxygen. Refractive index and optical absorption of thin films decreased with higher concentration of oxygen. The thin films which have good transmittance spectra and smooth surface, deposited in the sputtering ambient with 10 % of O2 at the temperature from 300oC to 400oC.
  • 4.

    Preparation and properties of porous (Ca,Mg)0.15Zr0.7O1.7 ceramics

    김복희 | 김상희 | 최은실 | 2011, 21(2) | pp.70~74 | number of Cited : 0
    Abstract PDF
    (Ca,Mg)0.15Zr0.7O1.7 ceramics was investigated for the application to SOFC ceramic supporter with high porosity and mechanical strength. ZrO2 powder was prepared by combustion method with glycine using the solution of ZrO(NO3)2 ·2H2O dissolved into deionized water and calcination at 800oC. Porous (Ca,Mg)0.15Zr0.7O1.7 ceramics was prepared by sintering the mixture of prepared ZrO2 powder, dolomite and carbon black at 1200~1400oC for 1 h. The open porosity of the (Ca,Mg)0.15Zr0.7O1.7 ceramics sintered at 1300oC was over 30 % and increased linearly with the amount of carbon black. The crystal structure of (Ca,Mg)0.15Zr0.7O1.7 ceramics consisted of single cubic phase. The open pore of this ceramics was connected continuously and distributed well on the whole. This ceramics sintered at 1300oC showed the porosity from 32to 55 % and mechanical strength from 90 MPa to 30 MPa with increasing the content of added carbon black.
  • 5.

    Effects of EDTA on morphology of hydroxyapatite prepared by hydrothermal method

    최봉석 | 김동현 | Taewan Kim and 2other persons | 2011, 21(2) | pp.75~81 | number of Cited : 0
    Abstract PDF
    Hydroxyapatite (HAP) crystals with hexagonal structure have been successfully synthesized by using EDTA (ethylene diamine tetraacetic acid) as chelate under hydrothermal condition. The as-prepared HAp powders were characterized by XRD and SEM. The XRD result indicated that the products were preferentially oriented along c-axis. The SEM photographs showed that the morphology of the HAp crystals was well controlled by the reaction parameters such as temperature, pH value, and the molar ratio of EDTA/Ca.
  • 6.

    Water absorption characteristics of artificial lightweight aggregates prepared by pre-wetting

    KIM, YOOTAEK | Changsub Jang | 류유광 | 2011, 21(2) | pp.82~86 | number of Cited : 2
    Abstract PDF
    Lightweight aggregate which is composed of sintered polycrystalline materials usually has a certain portion of pores inside of it. Because of such a structural characteristics, it tends to that movement of water in aggregate shows an abnormal behavior against the change of outside environment. In general, water movement behavior is controlled by porosity, distribution of pore size; however, dense surface layer will also affect water movement behavior in case of artificially sintered aggregates. Factors affecting water movement behavior in the aggregate are pore distribution, pore shape, pre-wetting method, etc. In this study, absorption characteristics of aggregate under the pressure and absorption rate according to water dipping time are analyzed for the basis of pressure pumping of lightweight concrete. Two kinds of aggregates were used for the test: one is made by ‘L’ company in Germany and the other is of our own made at the pilot plant in Kyonggi University. Absorption rate of aggregate is measured according to water dipping time, vacuum pressure,and quenching condition. Absorption rate of aggregate with 300oC quenching is higher than that of aggregate with 24 hr water dipping. Generally the more vacuum the higher water absorption rate. Water absorption rate of ‘L’ aggregate under −300 mmHg is 54 % higher than that of aggregate with 24 hr water dipping; however, only 2 % increase in water absorption was measured for the K622 and K73 which were of our own.
  • 7.

    Development of ceramic glazes utilizing wasted porcelains

    이제일 | 이병하 | 2011, 21(2) | pp.87~91 | number of Cited : 1
    Abstract PDF
    The purpose of this study is to develop ceramic glazes for the pottery production by utilizing wasted white porcelain, celadon porcelain and bone china thrown away from the areas of Icheon and Yeoju. Most of Korean pottery manufacturers are located in the both areas. According to the XRF analysis, the wasted white porcelain contains over 67 %of silica. It is enough to make a transparent glaze without adding silica. The wasted celadon porcelain contains much Fe2O3, which is suitable for producing a celadon glaze. The wasted bone china contains 22 % of P2O5, which is suitable for making a milky white bone china glaze. As a result, it is expected that production of pottery glaze using the wasted porcelains will reduce pollution problems comes from the landfill, and obtain economic effects in terms of resources recycling. It is also expected to be utilized as alternative materials of imported ones.
  • 8.

    Characterization of interfacial chemistry on the coal bottom ash

    Lee,Ki-Gang | 2011, 21(2) | pp.92~97 | number of Cited : 0
    Abstract PDF
    Landfill is the main treatment method for bottom-ash because it has not only an irregular particle size and ingredients but also not proper recycling treatment. The aim of this study is to raise recycling rate of bottom-ash (nonplasticity pulverulent) and for the purpose of alternatives of clay to investigate the properties of Bottom-ash (B/A)-Hard Clay (H/C) bodies with controlled interfacial chemistry properties. After investigating the sedimentation height of suspensions with controlled pH, it was discovered that there was no hetero-polar aggregation for mixed slips because hard clay and bottom-ash had similar interfacial chemistry properties. Also, bulk density, water absorption, and microstructure properties of each pellet was observed that made by silp casting method and manufactured at 50oC intervals between 1000~1250oC. As a result, dispersed slip of clay and bottom ash are possible for slip casting and plastic forming process because they exhibit Bingham plastic behavior. Products that made by slip with dispersed clay and bottom ash are not only suitable for KS L 4201 and KS L 1001 at 1250oC, but it is also possible to apply for ceramic and sanitary ware because specific gravity was about 15 % lighter than general ceramic materials.