• 제목/요약/키워드: Alumina Powder

검색결과 413건 처리시간 0.032초

알루미나 단섬유 및 입자강화 알루미늄 청동기지 복합재의 마모특성 (On the Wear Properties of the Alumina Short Fiber and Particle Reinforced Aluminium Bronze Alloy Composite)

  • 이상로;허무영
    • Tribology and Lubricants
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    • 제10권3호
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    • pp.39-46
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    • 1994
  • In order to investigate the effect of the ceramic reinforcements on the wear properties of aluminum bronze composites, Cu-8wt%Al aluminum bronze alloys reinforced with the Saffil alumina short fiber were produced by the powder metallurgical method and tested by a pin-ondisc wear testing machine. The wear surfaces of the pin specimens and discs, wear debris, and the cross sections of the wear specimens were observed by SEM. The wear mechanism according to various wear conditions and the change of microstructure in the composites were also discussed. In the results, the reinforcement of the composites with alumina short fiber was very effective at the higher applied load over 10N. The material transportation to the counter disc was observed in the alloy specimens without reinforcements. However, the composites reinforced with ceramic particles and fibers showed the resistance against the material transportation.

Properties of Hot Pressed Alumina-Titanium Diboride Particulate Composites

  • Park, Dong-Soo;Han, Byung-Dong
    • The Korean Journal of Ceramics
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    • 제4권3호
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    • pp.227-230
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    • 1998
  • Alumina($Al_2O_3$)-Titanium Diboride($TiB_2) particulate composites were fabricated by hot pressing of the powder mixture that was prepared from Self-propagating High Temperature Synthesis (SHS) product and commercial powders. Their propeties were examined in order to find feasibility of using SHS for making the high performance ceramic composite. $TiB_2 particles obtained by grinding the SHS product were finer than the commercial powders. Hot pressed sample containing the SHS products exhibited higher strength than the one prepared from the commercial powders.

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Magnetic Abrasive Polishing for Internal Face of Seamless Stainless Steel Tube using Sludge Abrasive Grain

  • Kim, Hee-Nam
    • 동굴
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    • 제78호
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    • pp.23-27
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    • 2007
  • In this paper, we have investigated the characteristics of the magnetic abrasive using sludge on polishing of internal finishing of seamless stainless steel tube applying magnetic abrasive polishing. Either white alumina grain was used to resin sludge at a low temperature, and the sludge of magnetic abrasive powder was synthesized and crushed into 200 meshes. Surface roughness was measured before and after polishing, and more than 40% of improvement of surface roughness was achieved when grain was used under a specific condition. Even though some degree of surface roughness due to deeper scratches still exist, but the result showed a prospective magnetic abrasive polishing using sludge with white alumina grains.

금형온도와 탈지조건이 사출성형에 의한 알루미나 부품 제조에 미치는 영향 (EFfect of Molding Temperature and Debinding Conditions on Fabrication of Alumina Component by Injection Molding)

  • 임형택;임대순
    • 한국세라믹학회지
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    • 제32권5호
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    • pp.559-566
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    • 1995
  • Alumina powder was coated with stearic acid and then mixed with isotactic polypropylene, atactic polypropylene as binders at 15$0^{\circ}C$ for 2 hours. The mixture was then injection molded at various mold temperatures using injection molding machine to investigate the effect of the molding temperature and debinding parameters on the formation of the defects. The molded specimens were debinded in both air and nitrogen atmospheres. Wicking and solvent methods were also used to enhance debinding efficiency. The specimens were prefired at 120$0^{\circ}C$ and then sintered at 150$0^{\circ}C$ for 3 hours. Various defects were formed at mold temoperature of 3$0^{\circ}C$, 6$0^{\circ}C$ and 10$0^{\circ}C$ and any noticeable defect was not formed at 85$^{\circ}C$. The density of green body increased with mold temperature. Debinding in air atmosphere was more effective than in nitrogen atmosphere. Results also proved that wicking and solvent treatments helped minimize the number of defects.

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점토 광물로부터 제어 침전법에 의한 고순도 알루미나의 합성 (I) 점토 광물로부터 수화 황산 알루미늄 및 알루미나의 제조 (Synthesis of High Purity Alumina by Controlled Precipitation Method from Clay Minerals (I) Preparation of Aluminum Sulfate Hydrate and Alumina from Clay Minerals)

  • 노태환;이헌수;손명모;박희찬
    • 한국재료학회지
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    • 제2권1호
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    • pp.3-11
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    • 1992
  • 점토 광물로부터 황산 처리법을 이용하여 수화 황산 알루미늄을 제조하였다. 하동 카올린 을 황산 처리하였을 때 수화 황산 알루미늄 형성에 미치는 카올린의 하소 온도와 하소 시간, 산처리 반응 온도와 반응 시간 및 황산의 농도의 영향을 조사하였다. 또한, 황산 처리된 용액으로부터 수화 황산 알루미늄이 석출되는 최적 조건을 구하였으며, 생성된 수화 황산 알루미늄을 상온에서 $1200^{\circ}C$ 까지 각각의 온도 구간에서 열처리한 분말에 대해서 XRD, TG-DTA, FT-IR, SEM, 입도 분석 및 불순물 분석을 하였다. 최적 조건 하에서, 카올린 중의 알루미나가 수화 황산 알루미늄으로 생성되는 전화율은 약 60%였고, XRD, TG-DTA, FT-IR 등의 분석 결과로 부터 생성된 수화 황산 알루미늄의 열분해 반응은 $Al_2(SO_4)_3{\cdot}18H_2O{\rightarrow}Al_2(SO_4)_3{\cdot}6H_2O{\rightarrow}Al_2(SO_4){\rightarrow}\;amorphous\;alumina{\rightarrow}{\gamma}-alumina{\rightarrow}{\delta}-alumina{\rightarrow}{\theta}-alumina{\rightarrow}{\alpha}-alumina$이었다. 또한 생성된 수화 황산 알루미늄을 $1200^{\circ}C$에서 하소 하여 얻은 알루미나 분말의 순도는 99.99%였다.

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열화학적 방법에 의한 전극용 나노 Cu/Al2O3 복합분말 합성 (Synthesis of Cu/Al2O3 Nanostructured Composite Powders for Electrode Application by Thermochemical Process)

  • 이동원;배정현;김병기
    • 한국분말재료학회지
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    • 제10권5호
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    • pp.337-343
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    • 2003
  • Nanostructured Cu-$Al_2O_3$ composite powders were synthesized by thermochemical process. The synthesis procedures are 1) preparation of precursor powder by spray drying of solution made from water-soluble copper and aluminum nitrates, 2) air heat treatments to evaporate volatile components in the precursor powder and synthesis of nano-structured CuO + $Al_2O_3$, and 3) CuO reduction by hydrogen into pure Cu. The suggested procedures stimulated the formation of the gamma-$Al_2O_3$, and different alumina formation behaviors appeared with various heat treating temperatures. The mean particle size of the final Cu/$Al_2O_3$ composite powders produced was 20 nm, and the electrical conductivity and hardness in the hot-extruded bulk were competitive with Cu/$Al_2O_3$ composite by the conventional internal oxidation process.

반응소결 SiC-graphite 복합체의 마찰마모특성 (Tribological Properties of Raction-Bonded SiC-Graphite Composites)

  • 백용혁;신종윤;곽효섭;박용갑
    • 한국세라믹학회지
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    • 제33권5호
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    • pp.479-484
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    • 1996
  • The tribological properties of ceramics are very important in the application to engineering ceramic parts such as mechanical seal slurry valve disc and so on. In this study the effect of graphite addition on the mechanical and tribological properties of RBSC/graphite composites were investigated. The composites were prepared by adding graphite powder to the mixture of SiC powder metallic siliconcarbon black and alumina. Bending strength water absorption friction coefficient the amount of worn out material at a certain time and maximum surface roughness(Rmax) of the prepared composites were measured and crystalline phases were examined with XRD. The composite containing 5 vol% graphite powder showed improved bending strength due to high green density and decreased friction coefficient and wear resistance. The friction coefficient and the wear resistance of the composite were increased by adding graphite powder up to 10 vol% They decreased however as increasing the amount of graphite powder more that 10vol% There was no linear relationship between the tribological properties and bending strength of the composites.

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알루미나 졸-겔 코팅 공정을 이용한 질화규소의 상압소결 및 물질 특성 (Application of Sol-Gel Coating Process in Pressureless Sintering of Si3N4 and Their Properties)

  • 임경란;임창섭
    • 한국세라믹학회지
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    • 제31권1호
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    • pp.69-73
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    • 1994
  • Si3N4 ceramics could be densified above 3.2g/㎤ with pressureless sintering at below 178$0^{\circ}C$ by coating Si3N4 and Y2O3 powder with an alumina sol. Substitution a portion of Al2O3 with AlN improved densification. Additional milling of the coated powder in large improvement in bending strength greater than 800 MPa (4-point).

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