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        검색결과 13

        1.
        2012.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, fine cathode materials and were synthesized using the simple, convenient process of mechanical alloying (MA). In order to improve the cell properties, wet milling processes were conducted using low-energy ball milling to decrease the mean particle size of both materials. The cells of Na/ and Na/ show a high initial discharge capacity of 425 mAh/g and 577 mAh/g respectively using wet milled powder particles, which is much larger than commercial ones, providing some potential as new cathode materials for rechargeable sodium-ion batteries.
        4,000원
        2.
        2012.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Tool steels serve a large range of applications including hot and cold workings of metals and injection mouldings of plastics or light alloys. The high speed steels (HSS) are specifically used as cutting tools and wear parts because it has high strength, wear resistance and hardness along with appreciable toughness and fatigue resistance. From the view of HSS microstructure, it can be described as metallic matrix composites formed by a ferrous with a dispersion of hard and wear resistant carbides. The experimental specimens were manufactured using the PIM with T42 powders (50~80 vol.%) and polymer (20~50 vol.%). The green parts were debinded in n-hexane solution at for 8 hours and thermal debinded at an mixed gas atmosphere for 8 hours. Specimens were sintered in high vacuum ( Torr) and various temperatures.
        4,000원
        3.
        2011.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In order to investigate the microstructure and mechanical properties of WC-10 wt% Co insert tool alloy fabricated by PIM (Powder Injection Molding) process, the feedstock of WC-10 wt% and wax used as a kind of binder were mixed together by two blade mixer. After injection molding, the debinding process was carried out by two-steps. First, solvent extraction, in which the binder was eliminated by putting the specimen into normal hexane for 24 hrs at , and subsequently thermal debinding which was conducted at and for 6 hrs in the mixed gas of , respectively. Meantime, in order to compensate the decarburization due to hydrogen, 1.2~1.8% of carbon was added to ensure the integrity of the phase. Finally, the specimens were sintered in vacuum under different temperatures, and the relative density of 99.8% and hardness of 2100 Hv can be achieved when sintered at , even the TRS is lower than the conventional sintering process.
        4,000원
        4.
        2010.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        High speed steels (HSS) were used as cutting tools and wear parts, because of high strength, wear resistance, and hardness together with an appreciable toughness and fatigue resistance. Conventional manufacturing process for production of components with HSS was used by casting. The powder metallurgy techniques were currently developed due to second phase segregation of conventional process. The powder injection molding method (PIM) was received attention owing to shape without additional processes. The experimental specimens were manufactured with T42 HSS powders (59 vol%) and polymer (41 vol%). The metal powders were prealloyed water-atomised T42 HSS. The green parts were solvent debinded in normal n-Hexane at for 24 hours and thermal debinded at mixed gas atmosphere for 14 hours. Specimens were sintered in , gas atmosphere and vacuum condition between 1200 and . In result, polymer degradation temperatures about optimum conditions were found at and . After sintering at gas atmosphere, maximum hardness of 310Hv was observed at . Fine and well dispersed carbide were observed at this condition. But relative density was under 90%. When sintering at gas atmosphere, relative density was observed to 94.5% at . However, the low hardness was obtained due to decarbonization by hydrogen. In case of sintering at the vacuum of torr at temperature of , full density and 550Hv hardness were obtained without precipitation of MC and in grain boundary.
        4,000원
        5.
        2009.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Titanium carbides are widely used for cutting tools and grinding wheels, because of their superior physical properties such as high melting temperature, high hardness, high wear resistance, good thermal conductivity and excellent thermal shock resistance. The common synthesizing method for the titanium carbide powders is carbo-thermal reduction from the mixtures of titanium oxide() and carbon black. The purpose of the present research is to fabricate nano TiC powders using titanium salt and titanium hydride by the mechanochemical process(MCP). The initial elements used in this experiment are liquid (99.9%), (99.9%) and active carbon(<, 99.9%). Mg powders were added to the solution in order to induce the reaction with Cl-. The weight ratios of the carbon and Mg powders were theoretically calculated. The TiC and powders were milled in the planetary milling jar for 10 hours. The 40 nm TiC powders were fabricated by wet milling for 4 hours from the +C+Mg solution, and 300 nm TiC particles were obtained by using titanium hydride.
        4,000원
        6.
        2008.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper deals with the phase analysis of bulk using spark plasma sintering process after ball milling. Mg and amorphous B powders were used as raw materials, and milled by planetary-mill for 9 hours at argon atmosphere. In order to confirm formation of phase, DTA and XRD were used. The milled powders were fabricated to bulk at the various temperatures by Spark Plasma Sintering. The fabricated bulk was evaluated with XRD, EDS, FE-SEM and PPMS. In the DTA result, reaction on formation of phase started at . This means that ball milling process improves reactivity on formation of phase. The MgO and FeB phases were characterized from XRD result. MgO and FeB were undesirable phases which affect formation of phase, and it's distribution could be confirmed from EDS mapping result. Spark Plasma Sintered sample for 5 min at was relatively densified and it's density and transition temperature showing super conducting property were and 21K.
        4,000원
        7.
        2005.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, the ZnS composite powders for host material in phosphor was synthesized in situ by mechanical alloying. As the mechanical alloying time increases, particle size of ZnS decreases. ZnS powders of in a mean size was fabricated by mechanical alloying for 10h. The crystal structures of ZnS powders were investigated by X-ray diffraction and the photo-luminescence properties was evaluated with the optical spectra analyzer. The steady state condition of mechanically alloyed ZnS was obtained as a mean particle size of in 5h milling. The sphalerite and wurtize structures coexist in the ZnS mechanically alloyed for 5h. The ZnS powder mechanically alloyed for 10h grows to the sphalerite structure. And the strong emission peaks of ZnS are observed at 480 nm wave length at the powders of mechanically alloyed for 10h, but the sphalerite and wurtize structures in ZnS coexist and emission peaks are not appeared at the powders of mechanically alloyed for 10h.
        4,000원
        9.
        2005.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper deals with the fabrication of titanium carbide using fine titanium hydride. The ratio of and C (Activated carbon) was 1:1 (mol) and milled in a planetary ball mill at a ball-to-powder weight ratio of 20:1. Thereafter, TGA was performed at to observe change of weight with milling time. Titanium carbide was obtained by using tempering the milled powders at . The microstructures of titanium carbide as well as the change of the lattice parameters and particle size have been studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM).
        4,000원