• 한국재료학회지
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• 제11권5호
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• pp.345-353
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• 2001

본 연구에서는 MA 방법을 사용하여 $Al_3$Nb 금속간화합물의 조성에 Zr을 첨가하여 $Al_3$(Nb$_{1-x}$ )Zr$_{x}$ 합금분말을 제조한 후 이에 따른 상변화 거동 및 미세구조특성을 분석하였다. MA는Al$_3$(Nb$_{1-x}$ )Zr$_{x}$의 조성으로 Al, Nb, Zr 원료분말과 arc meltinly된 $Al_3$Nb, $Al_3$Zr 금속간화합물 분말을 사용하여 300rpm의 회전속도로 20시간 동안 MA하였다. 이때의 정상상태의 원료분말은 약 4$\mu\textrm{m}$의 평균입도와 약 12~18nm의 결정립크기를 가졌으며, arc melting된 분말은 약 2$\mu\textrm{m}$의 평균입도와 약 14nm의 결정립크기를 가지는 분말을 얻을 수 있었다 원료분말과 금속간화합물 분말의 MA 기구는 상이한 거동을 나타내었으며, 분말의 내부변형량은 원료분말이 금속간화합 분말보다 내부변형량이 더 많이 축적되었다. 이는 원료분말의 MA 경우 냉간 압접과 파괴가 반복적으로 진행되었지만 금속간화합물 분말은 취약한 화합물상이어서 냉간압접 보다는 파괴가 지배적으로 진행되었기 때문이다. 원료분말을 MA하였을 경우에는 Al (Nb.Zr)$_2$상이 형성되었으나 금속간화합물 분말로 MA하였을 경우에는 3원계 화합물상이나 비정질상으로 상변태 되지 않고 단지 두 합금상이 분쇄되어 나노복합화 되었다. 후속 열처리에 의해 원료분말인 경우에는 $Al_3$(Nb.Zr)의 화합물상이 쉽게 형성되었으나, 금속간화합물 분말의 경우에는 새로운 상 생성은 얼었고 단지 열처리 전의 분말내부에 쌓여있던 내부변형에너지가 약 60% 정도 감소하였다.

• Journal of Magnetics
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• 제21권3호
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• pp.303-307
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• 2016

$Y_{3-x}R_xFe_5O_{12}$ (R = La, Nd, and Gd) powder were fabricated using a sol-gel pyrolysis method. Their magnetic properties and crystalline structures were investigated using x-ray diffraction (XRD), a vibrating sample magnetometer (VSM), and $M{\ddot{o}}ssbauer$ Spectrometer. The $M{\ddot{o}}ssbauer$ spectra for the powders were taken at various temperatures ranging from 12 K to Curie temperature (Tc). The isomer shifts indicated that the valence states of Fe ions for the 16(a) and 24(d) sites have a ferric character. The saturation magnetization (Ms) increases from 32 to 34 (emu/g) for the YIG, and Nd-YIG, respectively. However, Ms decreases to 27 (emu/g) at Gd-YIG.

• 한국정밀공학회지
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• 제21권8호
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• pp.34-42
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• 2004

A new polishing technique for three dimensional micro/meso-scale parts is suggested using a micro quill and a magnetic chain structure. The principle of this method is to polish the target surface with the collected magnetic brushes at a micro tool by the non-uniform magnetic field generated around the tool. In a typical magnetic abrasive finishing process magnetic particles and abrasive particles are unbonded each other. But, to finish the three dimensional small parts bonded magnetic abrasive have to be used. Bonded magnetic abrasives are made from direct bonding, and their polishing characteristics are also examined. Alumina, silicon carbide and diamond micro powders are used as abrasives. Base metal matrix is carbonyl iron powder. It is found that bonded magnetic abrasives are superior to unbonded one by experiment. finally, the polished surface roughness is evaluated by atomic force microscope.

• 한국재료학회지
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• 제13권1호
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• pp.53-58
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• 2003

For the rib materials in PDP(plasma display panel), an effective method to improve the mechanical properties is to form a composite material by reinforcing a glass matrix with rigid fillers, such as alumina and titania powders. In this study, two types of ribs with different volume percent of fillers and with different glass matrix were tested for hardness, Young's modulus with the Berkovich indentation. As a result, cracks appeared around at the load of 1345 mN for the dense type of rib, while porous one endured until 2427 mN without any crack formation. Young's modulus and hardness decreased at the range: 90∼65 GPa, 9∼4 GPa, respectively as a function of indent load. Thus, a new method with nanoindenter represents a possible evaluation method for mechanical properties of barrier ribs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.138-138
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• 2013

Ni-CeO2 및 Ni-MgO와 같이 Ni이 포함된 나노복합물질을 고주파 유도결합 플라즈마를 이용하여 합성하였다. 이를 위해, 먼저, 1~100 ${\mu}m$ 크기의 가상 Ni 입자와 고융점 세라믹 입자가 플라즈마 유동 내에서 겪는 열전달 과정을 수치해석을 통해 묘사하였다. 묘사 결과로부터, 완전 기화한 Ni 증기가, 채 기화하지 못하고 고체 형태로 남은 세라믹 입자 위에서 균일하게 응축된 형태를 갖는 Ni-세라믹 나노입자 합성을 예측하고, 실제 합성 실험을 25 kW 급 고주파 유도결합 플라즈마에 0.1~10 ${\mu}m$ 크기의 Ni, CeO2 및 MgO 분말을 주입하여 수행하였다. 마지막으로, 실험을 통해 합성된 Ni 계 복합나노물질에 대해, FE-SEM 및 TEM 사진 분석과 EDS 및 ICP-AES 성분 분석을 진행하고, 수치해석을 통해 예측된 결과와 비교 검토하였다.

• 한국분말재료학회지
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• 제11권6호
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• pp.522-527
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• 2004

Nano sized FeAl intermetallic particles were successfully synthesized by plasma arc discharge pro-cess. The synthesized powders shouted core-shell structures with the particle size of 10-20 nm. The core was metallic FeAl and shell was composed of amorphous $AI_{2}O_{3}\;and\;a\;little\;amount\;of\;metallic\;Fe_{3}O_{4}.$ Because of the difference of Fe and Al vapor pressure during synthesis, the Al contents in the nanoparticles depended on the Al contents of master alloy.

• 한국분말재료학회지
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• 제9권3호
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• pp.161-166
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• 2002

Processing and properties of $Al_2O_3$ composites with Ni-Fe content of 10 and 15 wt% were investigated. Homogeneous powder mixtures of $Al_2O_3$/Ni-Fe alloy were prepared by the solution-chemistry route using $Al_2O_3$, $Ni(NO_3)_2{\cdot}6H_2O$ and $Fe(NO_3)_3{\cdot}9H_2O$ powders. Microstructural observation of composite powder revealed that Ni-Fe alloy particles with a size of 20nm were homogeneously dispersed on $Al_2O_3$ powder surfaces. Hot-pressed composites showed enhanced fracture toughness and magnetic response. The properties are discussed based on the observed microstructural characteristics.

• 한국분말재료학회지
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• 제11권4호
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• pp.328-332
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• 2004

Fe nanopowders were successfully synthesized by plasma arc discharge (PAD) process using Fe rod. The influence of chamber pressure on the microstructure was investigated by means of X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The prepared particles had nearly spherical shapes and consisted of metallic cores (a-Fe) and oxide shells (Fe$_{3}$O$_{4}$), The powder size increased with increasing chamber pressure due to the higher dissolution and ejection rate of H$_2$ and gas density in the molten metal.

• Transactions on Electrical and Electronic Materials
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• 제4권3호
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• pp.15-18
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• 2003

Aluminum oxide ($Al_2O_3$) materials were coated conformally on ZnO nanorods by atomic layer deposition (ALD). The ZnO nanorods were first synthesized on a Si(100) substrate from ball-milled ZnO powders by a thermal evaporation procedure. $Al_2O_3$ films were then deposited on these ZnO nanorods by ALD at a substrate temperature of $300^{\circ}C$ using trimethylaluminum (TMA) and distilled water ($H_2O$). Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of the deposited ZnO nanorods revealed that amorphous $Al_2O_3$ cylindrical shells surround the ZnO nanorods. These TEM images illustrate that ALD has an excellent capability to coat any shape of nanorods conformally.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.989-992
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• 2008

X-ray lithography is one of the most powerful processes in the fabrication of nano/micro structures with a high aspect ratio. This process enables the fabrication of ultra-thin barrier ribs for PDP using X-ray sensitive paste. In this paper, organic material including photo-monomers, photo-oligomers, binder polymer and additives as well as inorganic powders with different size were optimized to fabricate high aspect ratio barrier rib pattern for PDP.