• Title/Summary/Keyword: Aluminum Oxide Powder

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Study on Oxidation-Reaction Bonding of Aluminum Compact by Pressureless Powder Packing Method (무가압 분말 충전 성형법에 의한 알루미늄 성형체의 산화반응 소결체 제조에 대한 연구)

  • 박정현;홍기의;염강섭;유재영
    • Journal of the Korean Ceramic Society
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    • v.34 no.1
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    • pp.95-101
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    • 1997
  • Using aluminum powder with average particle size of 22.1 $\mu$m, aluminum compact made by Pressureless Powder Packing Method showed 52% green density. The activation energy of aluminum oxidation was cal-culated from the weight change of TG, and it was varied in the range of 16~64 kJ/mol. It was found from the variation of the activation energy and the observation of the microstructure that oxidation was de-pendent on the destruction of oxide film and the melt-out of aluminum. Aluminum compact was reaction-bonded at 1000~140$0^{\circ}C$ for 4~60hrs, and oxidation was dependent on temperature rather than time. Reac-tion-bonded aluminum oxide at 140$0^{\circ}C$ for 60hrs showed 92% oxidation percent. It was sintered at 1$600^{\circ}C$ for 15hrs and the sintered body showed 62% relative density.

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Study on Anodizing at Constant Current for Sealing Treatment of Nano-diamond Powder (나노 다이아몬드 분말 봉공처리 적용을 위한 정전류에서의 알루미늄 양극산화 제조 연구)

  • Kang, Soo Young;Lee, Dae Won
    • Journal of Powder Materials
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    • v.21 no.2
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    • pp.114-118
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    • 2014
  • In this study, an aluminum oxide layer for sealing treatment of nano-diamond powder was synthesized by anodizing under constant current. The produced pore size and oxide thickness were investigated using scanning electron microscopy. The pore size increased as the treatment time increased, current density increased, sulfuric acid concentration decreased, which is different from the results under constant voltage, due to a dissolution of the oxide layers. The oxide layer thickness by the anodizing increased as temperature, time, and current density increased. The results of this study can be applied to optimize the sealing treatment process of nano-diamond particles of 4-10 nm to enhance the resistances of corrosion and wear of the matrix.

Synthesis of Graphene Coated Aluminum Powders by Self-assemble Reaction (자기 조립 반응에 의한 그래핀이 코팅된 알루미늄 입자의 합성 방법)

  • Hwang, Jin Uk;Tak, Woo Seong;Nam, Sang Yong;Kim, Woo Sik
    • Journal of Powder Materials
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    • v.26 no.5
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    • pp.383-388
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    • 2019
  • To improve the mechanical properties of aluminum, graphene has been used as a reinforcing material, yielding graphene-reinforced aluminum matrix composites (GRAMCs). Dispersion of graphene materials is an important factor that affects the properties of GRAMCs, which are mainly manufactured by mechanical mixing methods such as ball milling. However, the use of only mechanical mixing process is limited to achieve homogeneous dispersion of graphene. To overcome this problem, in this study, we have prepared composite materials by coating aluminum particles with graphene by a self-assembly reaction using poly vinylalcohol and ethylene diamine as coupling agents. The scanning electron microscopy and Fourier-transform infrared spectroscopy results confirm the coating of graphene on the Al surface. Bulk density of the sintered composites by spark plasma sintering achieved a relative density of over 99% up to 0.5 wt.% graphene oxide content.

Fabrication and Characterization of Highly Reactive Al/CuO Nano-composite using Graphene Oxide (산화그래핀을 적용한 고반응성 Al/CuO 나노복합재 제조 및 분석)

  • Lim, YeSeul
    • Journal of Powder Materials
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    • v.26 no.3
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    • pp.220-224
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    • 2019
  • The aluminum (Al)/copper oxide (CuO) complex is known as the most promising material for thermite reactions, releasing a high heat and pressure through ignition or thermal heating. To improve the reaction rate and wettability for handling safety, nanosized primary particles are applied on Al/CuO composite for energetic materials in explosives or propellants. Herein, graphene oxide (GO) is adopted for the Al/CuO composites as the functional supporting materials, preventing a phase-separation between solvent and composites, leading to a significantly enhanced reactivity. The characterizations of Al/CuO decorated on GO(Al/CuO/GO) are performed through scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping analysis. Moreover, the functional bridging between Al/CuO and GO is suggested by identifying the chemical bonding with GO in X-ray photoelectron spectroscopy analysis. The reactivity of Al/CuO/GO composites is evaluated by comparing the maximum pressure and rate of the pressure increase of Al/CuO and Al/CuO/GO. The composites with a specific concentration of GO (10 wt%) demonstrate a well-dispersed mixture in hexane solution without phase separation.

Aluminum Powder Metallurgy Current Status, Recent Research and Future Directions

  • Schaffer, Graham
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2001.11a
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    • pp.7-7
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    • 2001
  • The increasing interest in light weight materials coupled to the need for cost -effective processing have combined to create a significant opportunity for aluminum P/M. particularly in the automotive industry in order to reduce fuel emissions and improve fuel economy at affordable prices. Additional potential markets for Al PIM parts include hand tools. Where moving parts against gravity represents a challenge; and office machinery, where reciprocating forces are important. Aluminum PIM adds light weight, high compressibility. low sintering temperatures. easy machinability and good corrosion resistance to all advantages of conventional iron bm;ed P/rv1. Current commercial alloys are pre-mixed of either the AI-Si-Mg or AL-Cu-Mg-Si type and contain 1.5% ethylene bis-stearamide as an internal lubricant. The powder is compacted in closed dies at pressure of 200-500Mpa and sintered in nitrogen at temperatures between $580~630^{\circ}C$ in continuous muffle furnace. For some applications no further processing is required. although most applications require one or more secondary operations such as sizing and finishing. These sccondary operations improve the dimension. properties or appearance of the finished part. Aluminum is often considered difficult to sinter because of the presence of a stable surface oxide film. Removal of the oxide in iron and copper based is usually achieved through the use of reducing atmospheres. such as hydrogen or dissociated ammonia. In aluminum. this occurs in the solid st,lte through the partial reduction of the aluminum by magncsium to form spinel. This exposcs the underlying metal and facilitates sintering. It has recently been shown that < 0.2% Mg is all that is required. It is noteworthy that most aluminum pre-mixes contain at least 0.5% Mg. The sintering of aluminum alloys can be further enhanced by selective microalloying. Just 100ppm pf tin chnnges the liquid phase sintering kinetics of the 2xxx alloys to produce a tensile strength of 375Mpa. an increilse of nearly 20% over the unmodified alloy. The ductility is unnffected. A similar but different effect occurs by the addition of 100 ppm of Pb to 7xxx alloys. The lend changes the wetting characteristics of the sintering liquid which serves to increase the tensile strength to 440 Mpa. a 40% increase over unmodified aIloys. Current research is predominantly aimed at the development of metal matrix composites. which have a high specific modulus. good wear resistance and a tailorable coefficient of thermal expnnsion. By controlling particle clustering and by engineering the ceramic/matrix interface in order to enhance sintering. very attractive properties can be achicved in the ns-sintered state. I\t an ils-sintered density ilpproaching 99%. these new experimental alloys hnve a modulus of 130 Gpa and an ultimate tensile strength of 212 Mpa in the T4 temper. In contest. unreinforcecl aluminum has a modulus of just 70 Gpa.

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Proposals for Revising the Occupational Exposure Limits for Aluminum in Korea (국내 알루미늄 노출실태 및 노출기준 개정 제안)

  • Seung Won Kim;Young Gyu Phee;Yong-Joon Baek;Taejin Chung;Hye-Sil Lee
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.34 no.1
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    • pp.85-97
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    • 2024
  • Objectives: This study was intended to investigate the revision status of the occupational exposure standards for aluminum at home and abroad; to investigate worker exposure at domestic aluminum manufacturing and handling workplaces; to conduct social and economic evaluation for the revision of domestic aluminum exposure limits. Methods: We investigated the current status of occupational exposure limits for aluminum at home and abroad, and analyzed supporting data. An exposure survey was conducted targeting domestic aluminum manufacturing and handling workplaces. Based on these, revised aluminum occupational exposure limits were proposed. Results: The major aluminum exposure limits at home and abroad show a notable difference. The toxicity of aluminum, which was revealed through animal experiments and epidemiological investigations. The average concentration of aluminum in the air at 12 workplaces was 0.016 mg/m3, and the maximum was 0.0776 mg/m3. When total dust and respiratory dust were measured side by side and simultaneously for the same process, 12.1% of the total mass concentration of aluminum dust was respiratory dust. As a result of measuring and comparing the size distribution of dust with an optical particle counter in real time, 48.1% of the total dust in the form of welding fume and pyro-powder was respiratory dust. Based on the literature review and workplace survey, three proposals for changing the aluminum exposure limit were proposed. Proposal (1): For all types, 10 mg/m3 is unified as the exposure limit except for soluble salts and alkyls. Proposal (2): 1(R) mg/m3 as the exposure limit for all forms except soluble salts and alkyl. Proposal (3): 1(R) mg/m3 for pyro-powder and welding fume, and 10 mg/m3 for metal dust, aluminum oxide, and insoluble compounds as exposure standards. A pyro-powder was defined as dry aluminum powder of 200 mesh size (74 ㎛) or smaller (larger size classified as metal dust). Reason for setting: In the workplace survey, the ratio of respiratory dust to total dust was analyzed to be about 1:10, so it was judged that the domestic standard and the ACGIH standard were compatible. Conclusions: In all scenarios according to the revision of the exposure standard, the B/C ratio was greater than 1 or only benefits existed, so it was evaluated as sufficiently reasonable as a result of the socio-economic evaluation.

Fabrication and Thermophysical Properties of Nickel-coated Aluminum Powder by Electroless Plating (비전해 방법을 이용한 니켈 코팅 알루미늄 분말 제조 및 열물성 평가)

  • Lee, Sanghyup;Lim, Jihwan;Noh, Kwanyoung;Yoon, Woongsup
    • Journal of the Korean Society of Propulsion Engineers
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    • v.18 no.4
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    • pp.9-17
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    • 2014
  • In this study, in order to improve the ignitability of high energy aluminum powder, natural oxide films (alumina) were chemically removed, and instead nickel coat was applied. We used an electroless plating for nickel coating and confirmed quantitatively and qualitatively a time-dependent degree of nickel coating through analysis of surface by SEM/EDS. We also conducted element analysis by XRD and thermal properties by TGA/DSC in air oxidizer environment. There results explained the ignition enhancement mechanism of the nickel-coated aluminum powder in air. The difference between coated and un-coated aluminum powder, the effectiveness of coated powder has better ignitability.

Effect of Fillers on the Mechanical and Thermal Properties of Glass/Novolac Composites (충전재의 종류에 따른 유리/노볼락 복합재료의 기계적 및 열적 성질 연구)

  • Lee, Soo;Lee, In-Kyu;Park, Sang-Hee
    • Journal of the Korean Applied Science and Technology
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    • v.25 no.1
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    • pp.15-22
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    • 2008
  • The effects of fillers on the mechanical and thermal properties of glass/novolac composites have been studied. The matrix polymer and reinforcement were novolac type phenolic resin and milled glass fiber, respectively. Three different fillers, such as calcium carbonate, aluminum oxide, and wood powder were used for glass fiber reinforced plastic(GFRP) manufacture. Gravity, moisture content, tensile and flexural strength were measured to analyze the mechanical properties of GFRP and the final composites was burned in the electronic furnace at $1000^{\circ}C$ to confirm thermal properties GFRP containing aluminium oxide shows the highest thermal stability with 32% of weight loss at $1000^{\circ}C$ for one hour. GFRP containing calcium carbonate shows the maximum flexural strength (146 MPa), but that containing wood powder dose the highest tensile strength (65 MPa). Conclusively, we found that the characteristics of final composites strongly depend on several factors, such as types of materials, contents and chemical affinity of fillers. Therefore, it is very important to set up the combination of fillers for GFRP manufacturing to improve both mechanical and thermal properties at the same time.

The Study on the Production of Reaction Bonded Aluminum Oxide by Using Microwave Energy (마이크로파 에너지를 이용한 저수축 반응소결 알루미나의 제조에 관한 연구)

  • 박정현;안주삼
    • Journal of the Korean Ceramic Society
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    • v.32 no.2
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    • pp.227-233
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    • 1995
  • By using homestyle microwave oven, Al-Al2O3 powder mixture could be oxidized and sintered into Al2O3 body. The differences in powder characteristics among the differently processed raw materials affect the oxidation and sintering behaviours, and these effects were more pronounced in case of microwave oven than of conventional furnace. Al-Al2O3 powder mixture was oxidized and sintered within 2hrs, which could save both processing time and energy.

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The studies on synthesis of aluminum oxide and boron oxide co-doped zinc oxide(AZOB) powder by spray pyrolysis (분무열분해법(Spray Pyrolysis)에 의한 알루미늄 산화물과 보론 산화물이 함께 도핑된 산화아연(AZOB: $Al_2O_3$ and $B_2O_3$ Co-doped Zinc Oxide)의 분말 제조에 대한 연구)

  • Kim, Sang Hern
    • Journal of the Korean Applied Science and Technology
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    • v.31 no.4
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    • pp.731-739
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    • 2014
  • Aluminum and boron co-doped zinc-oxide(AZOB) powders as transparent conducting oxide(TCO) were prepared by spray pyrolysis at $900^{\circ}C$. The micron-sized AZOB particles were prepared by spray pyrolysis from aqueous precursor solutions for aluminium, boron, and zinc. The micron-sized AZOB particle after the spray pyrloysis underwent post-heat treatment at $700^{\circ}C$ for 2 hours and it was changed fully to nano-sized AZOB particle by ball milling for 24 hours. The size of primary AZOB particle by Debye-Scherrer Equation and surface resistance of AZOB pellet were measured.