• Title, Summary, Keyword: Composite granule

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Hybrid Composite Nano-sized WC-Co Cemented Carbide

  • Park, Sun-Yong;Lee, Wan-Jae
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.640-641
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    • 2006
  • To improve the mechanical properties of WC-Co cemented carbides, the dual composite was studied. The compositions of granule and matrix were nano-sized WC-6 wt% Co(granule) and normal sized WC-20 wt% Co(matrix), respectively. The granules were grouped 50, 100 and $150\;{\mu}m$ and mixed with WC and Co powders as the volume fractions of granule to matrix were 50 to 50, 40 to 60 and 30 to 70. These compacts were sintered at $1380^{\circ}C$ for 10 minutes in vacuum. The microstructure, transverse rupture strength and wear resistance were investigated.

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Study on the Granulation Behavior of TiO2-PVA Composite Powders Prepared Via Spray Drying Technique

  • Avcioglu, Celal;Ozkal, Burak
    • Journal of the Korean Ceramic Society
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    • v.56 no.5
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    • pp.443-452
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    • 2019
  • In this study, TiO2-polyvinyl alcohol (PVA) composite granules were prepared via spray drying technique. To investigate the effects of solid content and binder/powder ratio in the slurry on the granulation behavior of TiO2 powders, the feed compositions were designed to vary over a wide range. The morphology, actual densities, and average granule size and size distribution of the TiO2-PVA composite granules were characterized by using scanning electron microscopy technique, a gas pycnometer, and an image analyzing program (Image-J), respectively. The results indicate that solid content and the amount of PVA in the feedstock slurry are the dominant factors determining the granule morphology, size, and size distribution of TiO2-PVA composite. Moreover, it was observed that increasing the solid content and the amount of PVA in the slurry improved the granulation process and reduced the granule defects. For the preparation of spherical TiO2-PVA composite granules with the minimum amount of non-granulated powders, the optimized composition of the feedstock slurry was found to be 35 wt.% solid and 3 wt.% PVA.

Production of Porous Metallic Glass Granule by Optimizing Chemical Processing

  • Kim, Song-Yi;Guem, Bo-Kyung;Lee, Min-Ha;Kim, Taek-Soo;Eckert, Jurgen;Kim, Bum-Sung
    • Journal of Korean Powder Metallurgy Institute
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    • v.21 no.4
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    • pp.251-255
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    • 2014
  • In this study, we optimized dissolution the dissolution conditions of porous amorphous powder to have high specific surface area. Porous metallic glass(MG) granules were fabricated by selective phase dissolution, in which brass is removed from a composite powder consisting of MG and 40 vol.% brass. Dissolution was achieved through various concentrations of $H_2SO_4$ and $HNO_3$, with $HNO_3$ proving to have the faster reaction kinetics. Porous powders were analyzed by differential scanning calorimetry to observe crystallization behavior. The Microstructure of milled powder and dissolved powder was analyzed by scanning electron microscope. To check for residual in the dissolved powder after dissolution, energy dispersive X-ray spectroscory and elemental mapping was conducted. It was confirmed that the MG/brass composite powder dissolved in 10% $HNO_3$ produced a porous MG granule with a relatively high specific surface area of $19.60m^2/g$. This proved to be the optimum dissolution condition in which both a porous internal granule structure and amorphous phase were maintained. Consequently, porous MG granules were effectively fabricated and applications of such structures can be expanded.

Development of Fe/$Al_2O_3$ Composite Granules and Activation Conditions for Fischer-Tropsch Synthesis (구형 철-알루미나 입자 제조 및 피셔-트롭시 반응을 위안 전처리 조건 확립)

  • Yoo, Kye-Sang;Lee, Dong-Joon;Jung, Kwang-Deog
    • Transactions of the Korean hydrogen and new energy society
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    • v.19 no.6
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    • pp.545-551
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    • 2008
  • Fe/$Al_2O_3$ composite granules were prepared by combining sol-gel/oil drop method. The shape of granules were mainly determined by composition and concentration of aluminum precursor. The composite granule with the lowest aluminum concentration was synthesized with 0.75M boehmite solution. The prepared granules were tested as a catalyst in the plug-flow reactor for Fischer-Tropsch synthesis. Before the reaction, catalysts were activated by hydrogen reduction and synthesis gas treatment. The activation conditions and aluminum concentration have affected catalytic performance significantly.

$SO_3$ decomposition over Cu/Fe/$Al_2O_3$ granules with controlled size for hydrogen production in SI thermochemical cycle (황-요오도 열화학 수소제조 공정에서 다양한 크기의 Cu/Fe/$Al_2O_3$ 구형 촉매를 이용한 삼산화항 분해)

  • Yoo, Kye-Sang;Jung, Kwang-Deog
    • Transactions of the Korean hydrogen and new energy society
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    • v.19 no.3
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    • pp.226-231
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    • 2008
  • Cu/Fe/$Al_2O_3$ granules with various sizes have been prepared by a combination of sol-gel and oil drop method for the use in sulfur trioxide decomposition, a subcycle in thermochemical sulfur-iodine cycle to split water in the hydrogen and oxygen. The size of composite granules have been mainly changed by the flow-rate of the gel mixture before dropping in the synthesis. The structural properties of the samples were comparable with granule size. In the reaction, the catalytic activity was enhanced by decreasing size in the entire reaction temperature ranges.

Spray Drying of Zirconia/Alumina Composite Powder Using PVP as a Binder (PVP 결합제를 이용한 지르코니아/알루미나 복합분말의 분무건조)

  • Shim, Hyung-Bo;Moon, Joo-Ho;Kim, Dae-Joon
    • Journal of the Korean Ceramic Society
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    • v.39 no.5
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    • pp.446-451
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    • 2002
  • Zirconia/alumina mixture powder was spray-dried various degree of dispersion, type of dispersants and powder content in the slurry. The quality of the granule was determined by observation of the granule shapes after spray drying and fracture of intergranular boundaries during pressing. Defect-free granules were obtained from the powders that formed weak flocs in the slurry. The granules, spray-dried from the slurry containing 32.5 vol% powder mixture and PVP as binder, were fractured completely during shaping and the sintered specimens showed a density of 99.7% and a flexural strength of 850 MPa.

Preparation and Dielectric Properties of Ceramic(BNT)-Polymer(LCP) Composite (세라믹(BNT)-폴리머(LCP) 복합체 제조 및 유전특성)

  • Park, Myoung-Sung;Chun, Myoung-Pyo;Cho, Jung-Ho;Nam, Joong-Hee;Choi, Byung-Hyun;Nahm, Sahn
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.11
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    • pp.935-940
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    • 2009
  • In this research, the composites (100-x)LCP-xBNT (x = 0, 10, 20, 30, 40 vol.%) were fabricated with thermoplastic LCP(Liquid Crystal Polymer) and BNT($BaNd_2Ti_4O_{12}$) which is a high frequency dielectric material. Their dielectric properties, mechanical strength and microstructure were investigated by Impedance analyser, Instron and SEM. In order to fabricate LCP-BNT composites, LCP resin was put into the twin screw type mixer($310^{\circ}C$), melted by keeping for 10 min. After that, BNT filler was dispersed with melted LCP resin for 15 min. in the mixer. For measuring the dielectric properties and mechanical strength, Composite specimens were made by pressing composite granule (LCP-BNT) with 7 ton in the mold at $310^{\circ}C$. With increasing the BNT content (0~40 vol.%) of the composite, Its dielectric constant increased, dielectric loss and flexural strength decreased. The dielectric constant and flexural strength of composites with 20~30 vol.% of BNT filler are 4.1~6.0 and 35~55 MPa respectively. BNT/LCP composite is the potential substrate material for the high frequency application.

Analysis on the Reduction of Phosphorus Release in River and Lake Sediments through Application of Capping Technology (Capping 기술을 이용한 하천 및 호소 퇴적토의 인 용출 저감 효과 분석)

  • Kim, Seog-Ku;Yun, Sang-Leen
    • Journal of Korean Society of Environmental Engineers
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    • v.36 no.11
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    • pp.781-790
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    • 2014
  • Contaminants such as organic matters, nutrients and toxic chemicals in rivers and lakes with a weak flow rate are first removed from the water and accumulated in the sediments. Subsequently, they are released into the water column again, posing direct/indirect adverse effects on the water quality and aquatic ecosystems. In particular, phosphorus is known to accelerate the eutrophication phenomenon when it is released into the water column via physical disturbance and biological/chemical actions as one of important materials that determine the primary production of aquatic ecosystems and an element that is stored mainly in the sediments in the process of material circulation in the body of water. In this study, the effect on reducing phosphorus release in sediments was analyzed by applying different capping materials to lake water, where the effect of aquatic microorganisms is taken into account, and to distilled water, where the effect of microorganisms is excluded. The experimental results showed that capping with chemical materials such as Fe-gypsum and $SiO_2$-gypsum further reduced the phosphorus release by at least 40% compared to the control case. Composite materials like granule gypsum+Sand showed over 50% phosphorus release reduction effect. Therefore, it is determined that capping with chemical materials such as granule-gypsum and eco-friendly materials such as sand is effective in reducing phosphorus release. The changes in phosphorus properties in the sediments before and after capping treatment showed that gypsum input helped to change the phosphorus that is present in lake sediments into apatite-P, a stable form that makes phosphorus release difficult. Based on the above results, it is expected that the application of capping technology will contribute to improving the efficiency of reducing phosphorus release that occurs in river and lake sediments.

Properties and Structure of High Frequency Soft Magnetic Nano-composite Films

  • Ohnuma, Shigehiro;Masumoto, Hiroshi
    • Journal of Magnetics
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    • v.16 no.4
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    • pp.403-407
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    • 2011
  • Metal-insulator type, nano-granular soft magnetic films have been reviewed from the viewpoint of high frequency magnetic materials. The formation of nano-granular structure is related to the magnitude of heat of formation of intergranule materials. Variation of the ratio of granule phase to intergranule phase in the film is found to produce various characteristics in the magnetic properties of the film. The HRTEM observation reveals that neighboring granules in the film with above 60 at.% Co, contact at considerable points and the films show soft magnetic properties which are explainable in terms of the random anisotropy model for nano-crystalline materials. Addition of Ni group elements in Co-O based films enhances their anisotropy field up to 400 Oe and they exhibit excellent frequency response of permeability. Also, large electromagnetic noise suppression effect is demonstrated as one of their potential applications.

A study on the characteristics and noodle structure made from pea starch-wheat composite flour using a scanning electron microscopy (Scanning Electron Microscopy을 이용한 완두 전분 복합면의 반죽구조 및 특성연구)

  • 김은주;윤재영;김희섭
    • Korean journal of food and cookery science
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    • v.15 no.5
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    • pp.500-506
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    • 1999
  • Scanning electron microscopy was used to study changes in granule shape, dough and cooked noodle structure of pea starch-wheat composite flour with 20% and 30% pea starch substitution. The granule shape of pea starch with low swelling power and solubility was oval, irregular and smooth, which had more a deep groove than corn starch and wheat flour. During gelatinization, pea starch after swelling was partially collapsed but it still held its main shape. The dough microstructure of 20% pea starch substitution showed compact structure distributed with more small starch granules than wheat dough and was held in discontinuous network. When cooked, more open filamentous network where starch gelatinization was complete were noticed. Swollen but partially collapsed large starch granules maintaining their shape were appeared in noodle structure after 30 min soaking in soup. In farinograph studies, 20% pea starch substitution to wheat flour showed that MTI value was as same as wheat flour even though stability was slightly decreased so that it was considered that it has proper property of noodle making.

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