• 한국주조공학회지
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• 제21권6호
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• pp.359-365
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• 2001

The superplastic behavior of whisker reinforced aluminum alloy matrix composites fabricated by squeeze casting as one of high pressure routes was investigated. The preforms of ${\alpha}-Si_3N_4$ and ${\beta}-SiC$ whiskers without any binder as a reinforcement were used. The matrix materials were 2024 and 7075 aluminum alloys. For the purpose of optimum superplastic condition, respectively, the whiskers volume fraction, extrusion temperature, tensile test temperature and initial strain rate were changed. Fracture surface of tested specimens were observed by SEM. By the results, it became possible to produce superplastic composites by applying only a hot extrusion process to composites obtained by the squeeze casting. The superplastic composites developed are ${\alpha}-Si_3N_4w/7075$, ${\alpha}-Si_3N_4w/2024$ and ${\beta}-SiCw/2024$ systems at high strain rate.

• 한국주조공학회지
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• 제14권5호
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• pp.471-479
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• 1994

Al-2%Si-2%Mg alloy containing SiC particle in 20, $70{\mu}m$ were prepared by mean of squeeze casting with various pressure 50, 100, 150 and 220MPa respectively. The specimens were made by casting into $50{\Phi}{\times}100{\ell}$ mold under various squeeze conditions(pressures, pressurizing temperature, particle sizes). Mechanical properties(hardness, tensile strength, elongation and wear characteristics) were evaluated at room temperature with those various fabrication factors. It became feasible to make favorable Al-SiCp composite free from casting defects by the injection of Ar gas during melting and 100MPa pressure squeeze casting. However, pressure of 50MPa was not sufficient to avoid completely porosity formation as a result of precessing and shrinkage during solidification. As the particle size is smaller and the squeeze pressure is higher, the hardness and tensile strength at room temperature are higher. Cell size became smaller gradually with increase of squeeze pressure. With increase of squeeze pressure(MPa), wear behaviors of those composites were changed from adhesive into abrasive wear, and the tendency of above behavior became outstanding with increasing sliding speed. The chemical reaction(4Al＋3SiC${\rightarrow}$$Al_4C_3+3Si$) is more accelerated at interface between SiCp and matrix with increase of squeeze pressure. Therefore $Al_4C_3$ intercompound and Si peak intensity is increased at interface.

• Composites Research
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• 제16권3호
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• pp.41-48
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• 2003

본 연구에서는 고온 산화분위기 하에서 탄소/탄소 복합재료의 내산화 특성 향상을 위해 사용된 이규화 몰리브덴(MoSi$_2$)의 함량(0. 4, 12. 그리고 20 wt%)에 따른 복합재료의 충격특성에 관하여 고찰하였다. 결과로서, MoSi$_2$가 함침된 탄소/탄소 복합재료는 이를 함유하지 않은 것에 비하여 충격특성 향상의 원인이 되는 탄소섬유와 매트릭스 수지간의 계면결합력 증가를 가져왔으며, 특히 12 wt% MoSi$_2$가 현재의 시스템에서 가장 우수한 충격특성을 나타내었다. 이는 복합재료 내의 탄소섬유, 필러, 그리고 매트릭스 수지간의 계면 접착력의 증가를 가져오는 90$0^{\circ}C$ 전후에서 MoSi$_2$의 취성­연성 전이(BDT) 작용 때문이라 사료된다.

• Composites Research
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• 제16권1호
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• pp.1-12
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• 2003

본 연구는 보강재의 부피분율이 49%, 56%, 63%첨가된 패키징용 SiC/Al복합재료를 가압주조법을 통해 개발하였다. SiC/Al복합재료는 0.8%의 무기성형제와 $Al_2$O$_3$섬유가 SiC입자에 비해 부피비 1:10의 비율로 첨가되었으며 새로이 고안된 몰드에서 제조되었다. 제조된 SiC/Al복합재료에 대해 30-300 구간에서 열팽창 계수를 측정하고, FEM수치해석과 비교하여 온도에 따른 특성을 분석하였다. 실험결과 SiC/Al복한재료의 열팽창계수는 혼합법칙, Turner모델의 중간값을 가졌으며 상온에서는 Turner모델에 가깝다가 온도가 높아질수록 혼합법칙에 가까와졌다. 이러한 특성은 모재의 소성변형 및 잔류응력에 의한 것으로 본 연구에서 제안한 모재와 보강재 사이에 작용하는 평균응력 차이로부터 분석이 된다. 해석결파 모재의 소성변형이 시작되는 온도에서 SiC/Al복합재료의 열팽창계수가 급격히 증가하였으며, 가공 잔류응력은 이러한 소성변형의 시작온도를 고온으로 이동시킴으로써 열팽창계수에 영향을 끼침을 밝혔다. 이러한 일련의 연구를 통해 온도에 따른 열팽창 특성은 복수입자모델에 의한 2차인 해석을 통해 성공적으로 분석됨을 보였다.

• 한국재료학회지
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• 제14권6호
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• pp.389-393
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• 2004

The silicide layer used as a diffusion barrier in microelectronics is typically required to be below 50 nm-thick and, the same time, the silicides also need to have low contact resistance without agglomeration at high processing temperatures. We fabricated Si(100)/15 nm-Ni/15 nm-Co samples with a thermal evaporator, and annealed the samples for 40 seconds at temperatures ranging from $700^{\circ}C$ to $1100^{\circ}C$ using rapid thermal annealing. We investigated microstructural and compositional changes during annealing using transmission electron microscopy and auger electron spectroscopy. Sheet resistance of the annealed sample stack was measured with a four point probe. The sheet resistance measurements for our proposed Co/Ni composite silicide was below 8 $\Omega$/sq. even after annealing $1100^{\circ}C$, while conventional nickel-monosilicide showed abrupt phase transformation at $700^{\circ}C$. Microstructure and auger depth profiling showed that the silicides in our sample consisted of intermixed phases of $CoNiSi_{x}$ and NiSi. It was noticed that NiSi grew rapidly at the silicon interface with increasing annealing temperature without transforming into $NiSi_2$. Our results imply that Co/Ni composite silicide should have excellent high temperature stability even in post-silicidation processes.

• 한국주조공학회지
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• 제17권4호
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• pp.338-346
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• 1997

Mechanical properties of ($10%Al_2O_3{\cdot}SiO_2+5%Ni$)/Al hybrid composites fabricated by the reaction squeeze casting were compared with those of ($15%Al_2O_3{\cdot}SiO_2$)/Ai composites. Al-Ni intermetallic compounds ($10{\sim}20 {\mu}m$) formed by the reaction between nickel powder and molten aluminum were uniformly distributed in the Al matrix. These intermetallic compounds were identified as $Al_3Ni$ using X-ray diffraction analysis and they resulted in beneficial effects on room and high temperature strength and wear resistance. Microhardness values of ($10%Al_2O_3{\cdot}SiO_2+5%Ni$)/Al hybrid composite were greater by about 100Hv than those of ($15%Al_2O_3{\cdot}SiO_2$)/Al composite. Wear resistance of ($10%Al_2O_3{\cdot}SiO_2+5%Ni$)/Al hybrid composites was superior to that of ($15%Al_2O_3{\cdot}SiO_2$)/Al composites regardless of the applied load. While tensile and yield strength of ($10%Al_2O_3{\cdot}SiO_2+5%Ni$)/Al hybrid composites were greater at room temperature and $300^{\circ}C$, strength drop at high temperature was much smaller in hybrid composites.

• 한국표면공학회지
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• 제22권2호
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• pp.69-77
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• 1989

Codeposion of inert particles particles in a metallic mateix by electroless plating process involves two phenomena. Firstly, the adsorption of inercles and secondly, the adsorption of inert particles on the cathode. In the present paper the first adsorption phenomenon and in the next paper the second ane are studied in greaterdetail for the Ni-SiCc, Ni-Al2AO3 and Ni-WC systems. Measurements of the Zeta potentials for the SiC and Al2AO3 particles have been in different electrolyte solutions and the ionic species adsorbed on the Particles studied. The addition of sodium acetate, trisodium citrate and sodium phosphinate to nikel sulface sruomotes the zeta potential of SiC and Al2O3 particles, but zeta phosphinate to nickel is more positive than Al2O3 particles although the amount of nickel ion adsorbrd on the Al2O3 particles become greater than that of SiC particles. It is suggested that this is due to adsortion of Na ion onto the surface SiC particles.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.398-400
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• 2004

The three-dimensional woven fabric C/SiC composites blisk turbine rotor model was evaluated. The spin tests of the blisk model were performed to measure strain distributions at the room temperature. The rotational strength of the blisk model could be improved by the fiber addition. But, there are still more researches to be done.

• 한국항공우주학회지
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• 제48권9호
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• pp.663-670
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• 2020

2.5D C/SiC를 적용한 구조물의 거동 특성을 유한요소해석으로 근사하기 위해 기계적 물성 특성화와 모델링 기법에 관한 연구를 수행하였다. 2.5D C/SiC 소재의 거동 특성을 분석하기 위해 인장시험을 수행하였고 수학적 균질화 기법과 수정된 혼합 법칙을 적용하여 2.5D C/SiC를 구성하는 섬유와 기지의 탄성 물성을 정의하였다. 탄소성 거동을 나타내는 기지는 소성 영역의 거동을 bilinear 함수로 근사하고 시험과 해석의 오차를 최소화하여 등가 항복 강도와 등가 소성 강성을 계산하였다. 그리고 2.5D C/SiC의 RVE를 정의하고 수정된 혼합 법칙을 적용하여 유효강성행렬을 계산하는 과정을 ABAQUS의 User-defined subroutine을 통해 구성하였다. 제안된 과정을 바탕으로 정의된 섬유와 기지의 기계적 물성을 적용하여 유한요소해석을 수행한 결과는 시험의 거동을 잘 근사하고 있음을 확인하였다.

• 한국표면공학회지
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• 제22권2호
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• pp.78-87
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• 1989

Mechanism of formation of electroless composite coatings is similar to that of electrodeposited composite coating, but the amount of particles entraped in electroless coating is higher that the one of electrodeposited coatings. The methol of entrapment by the metal for SiC and Al2O3 particles is different from that for WC particles. In the former case the particles are gracually engulfed by the depositing metal, wheran with WC a metal envelope is rapidly fomed around each particles. This difference can be attributed to the difference in electrical resistivity of the particles. Inclusion density of SiC and Al2O3 particles during copeposition depend on the particle size, agitation condition, vabration conditions and electrolyte temperatures.