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A1₂O₂/CuO 혼합분말의 수소환원 거동 및 미세조직 특성
오승탁 서울産業大學校 2005 논문집 Vol.54 No.1
분산상Cu3 CuO 및 Cu-nitrate로 선택하여 제조한 Al₂0₃/Cu0 혼합분말에서의 나노금속 입자 형성기구를 정량적으로 해석하여, 분말제조 공정과 산화물 환원거동의 관계 및 이러한 거동이 최종 소결체의 미세조직과 특성에 미치는 영향에 대하여 고찰하였다. Al₂O₃/Cu-nitrate를 원료분말로 사용한 경우에서, 수소환원 후에 미세한 Cu 입자의 균일한 분포를 갖는 복합분말을 제조할 수 있었으며, 최종 소결체에서도 증가된 파괴강도를 나타내었다. 이러한 차이는 주로 원료분말의 환원특성에 따른 것으로 해석하였다.
Oh, Sung-Tag,Lee, Sung-Il American Scientific Publishers 2010 Journal of nanoscience and nanotechnology Vol.10 No.1
<P>The processing conditions to prepare nano-sized Cu and Mo dispersed Al2O3 (Al2O3/Cu and Al2O3/Mo) composites by pressureless sintering were explored. The composite powders of Al2O3/Cu and Al2O3/Mo were obtained by the hydrogen reduction of Al2O3/CuO and Al2O3/MoO3 powder mixtures and consolidated by pressureless sintering using infrared heating furnace with a heating rate of 200 degrees C/min. SEM and TEM analyses for the composite showed that the nano-sized metal particles were well distributed and situated on the grain boundaries of the Al2O3 matrix. The nanocomposites, sintered at 1300 to 1500 degrees C for 4 min, showed the relative density of above 90%. Maximum hardness of 16.1 GPa was obtained in Al2O3/Cu nanocomposites with sintering additive of 1 wt% MgO. The sintered nanocomposites exhibited the enhanced fracture toughness of above 4.5 MPa x m(1/2), compared with monolithic Al2O3. The mechanical properties were discussed in terms of observed microstructural characteristics.</P>
Wear Behavior of Nano-Sized Metal Particle Dispersed Al<sub>2</sub>O<sub>3</sub> Nanocomposites
Oh, Sung Tag,Yoon, Se Joong,Choa, Yong Ho,Jeong, Young Keun,Niihara, Koichi Trans Tech Publications, Ltd. 2006 Key Engineering Materials Vol.317 No.-
<P>The microstructure and mechanical properties including wear resistance of Al2O3-based nanocomposites with 5 vol% of Cu and Ni-Co dispersions were investigated. Al2O3/Cu and Al2O3/ Ni-Co nanocomposites were fabricated by hydrogen reduction and sintering process using metal oxide and metal nitrates. The composites showed homogeneous microstructures with nano-sized metal dispersions and enhanced fracture strength and toughness compared with monolithic Al2O3. In particular, high toughness and hardness were measured for the Al2O3/Ni-Co nanocomposite consolidated by PECS. A minimum wear coefficient of 2.33 x 10-5 mm3/Nm was obtained for the Al2O3/Ni-Co nanocomposite, while the monolithic Al2O3 showed a value of 2.0 x 10-5 mm3/Nm. Wear behavior is discussed in terms of microstructure and mechanical properties of the nanocomposites.</P>
Fabrication of Nanocomposites by Atmosphere-controlled Sintering and Their Properties
Oh Sung-Tag,Kim Young-Do,Lee Jeong-Keun 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
The microstructure and mechanical property of hot-pressed nanocomposites with a different temperature for atmosphere changing from to Ar have been studied. When the atmosphere changed from to Ar gas at , the hot-pressed composite was characterized by inhomogeneous microstructure and low fracture strength. On the contrary, when the atmosphere changed at a lower temperature of , a more homogeneous microstructure and higher fracture strength was observed.
Synthesis of Fe(Ni) nanoparticles by calcination and hydrogen reduction of metal nitrate powders
Oh, Sung-Tag,Joo, Min-Hee,Choa, Yong-Ho,Kim, Ki Hyeon,Lee, Sang-Kwan Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>The calcination and hydrogen reduction behavior of Fe- and Ni-nitrate powders has been investigated by using thermal analysis and microstructure observation. Fe-oxide/NiO composite powder was prepared by calcination at 350 °C for 2 h of Fe- and Ni-nitrate. Microstructural observation revealed that FeNi<SUB>3</SUB> particles with an average size of 40 nm were formed by hydrogen reduction at 320 ° C of calcined powders. Changes of the DSC curve and the XRD pattern with the increase in reduction temperature were explained as presumably due to the phase transformation of Fe(Ni) powders.</P>
Processing of Nano-Sized Metal Alloy Dispersed Nanocomposites
Oh Sung-Tag,Seok Namkung,Lee Jai-Sung,Kim Hyoung-Seop,Tohru Sekino 한국분말야금학회 2001 한국분말야금학회지 Vol.8 No.3
An optimum route to fabricate the ferrous alloy dispersed nanocomposites such as /Fe-Ni and /Fe-Co with sound microstructure and desired properties was investigated. The composites were fabricated by the sintering of powder mixtures of and nano-sized ferrous alloy, in which the alloy was prepared by solution-chemistry routes using metal nitrates powders and a subsequent hydorgen reduction process. Microstructural observation of reduced powder mixture revealed that the Fe-Ni or Fe-Co alloy particles of about 20 nm in size homogeneously surrounded , forming nanocomposite powder. The sintered /Fe-Ni composite showed the formation of Fe phase, while the reaction phases were not observed in /Fe-Co composite. Hot-pressed /Fe-Ni composite showed improved mechanical properties and magnetic response. The properties are discussed in terms of microstructural characteristics such as the distribution and size of alloy particles.
Microstructure and Properties of Nano-Sized Ni-Co Particulate Dispersed Matrix Nanocomposites
Oh Sung-Tag,Mutsuo Sando,Koichi Niihara 한국분말야금학회 1998 한국분말야금학회지 Vol.5 No.4
In purpose of introducing the inverse magnetostrictive properties into the structural ceramics, based nanocomposites dispersed with nano-sized Ni-Co particles were studied. The composites were fabricated by the hydrogen reduction and hot-pressing of and NiO-CoO mixed powders. The mixtures were prepared by using Ni- and Co-nitrate as source materials for the Ni-Co particles. Microstructural observations revealed that nano-sized Ni-Co particles were dispersed homogeneously at grain boundaries. High strength above 1 GPa was obtained for the wt% Ni-Co nanocomposite fabricated by a controlled powder preparation process. The inverse magnetostrictive response to applied stress was obtained due to the presence of dispersed Ni-Co particles, which indicates a possibility to incorporate new functions into the structural ceramics without loosing the mechanical properties.