• Journal of Korea Foundry Society
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• v.18 no.6
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• pp.541-549
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• 1998

Microstructural characteristics of hypereutectic Al-Si alloys during reheating at semi-solid temperature have been investigated. The size and morphology of primary Si particles in wedge-type mold-cast ingot has been compared with hot-rolled sheet and Si particulate reinforced Al composite. Effects of P and Sr addition on the morphological changes of primary Si particles have been also investigated. Observation of the solidification microstructures of the wedge-type mold-cast ingot at different cooling rates showed that alloying elements such as P and Sr affect the morphology of Si particles, especially in the area solidified at a slow cooling rate. Negligible change in the size of primary crystals was observed after reheating experiment, but ${\alpha}-halo$ formed around the Si particles and fine particles of Si precipitated in the surrounding area of the Si particles. In addition, there seemed to be no coarsening with increasing of holding time and the region of ${\alpha}-halo$ being decreased. Nucleation and recrystallization was accelerated with addition of alloying elements during hot rolling resulting in a decrease of primary Si particle size. In the case of extruded specimens, morphological change of primary Si particles was not observed after reheating. No ${\alpha}-halo$ formation was observed in Si reinforced Al composite because of the oxide film formed on the Si particles which acted as a diffusion barrier between substrate and the primary Si particles.

• Journal of the Korean Vacuum Society
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• v.11 no.1
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• pp.50-58
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• 2002

The growth of GaN films on Si substrate has many advantages in that Si is less expensive than sapphire substrate and that integration of GaN-based devices with Si substrate is easier The difference of lattice constant and thermal expansion coefficient between GaN and Si is larger than those between GaN and sapphire. However, which results in many defects into the grown GaN. In order to obtain high duality GaN films on Si substrate, we need to reduce defects using the buffer layer such as AlN. In this study, we prepared three types of AlN buffer layer with various crystallinity on Si (111) substrate using MOCVD, Sputtering and MOMBE methods. GaN was grown by MOCVD on three types of AlN/Si substrate. Using TEM and XRD, we carried out comparative investigation of growth and properties of GaN deposited on the various AlN buffers by characterizing lattice coherency, crystallinity, growth orientation and defects formed (voids, stacking faults, dislocations, etc). It is found that the crystallinity of AlN buffer layer has strong effects on growth of GaN. The AlN buffer layers grown by MOCVD and MOMBE showed the reduction of out-of-plane misorientation of GaN at the initial growth stage.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.38.1-38.1
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• 2010

The trend to thinner crystalline silicon solar wafers in production of solar cells investigates re-evolution of back surface field (BSF) formation. We have studied mechanisms of back contact formation in Al evaporation and screen printed Al paste for Si solar cells by TEM analysis. We observed that Si diffuse into Al during heat up. The Si diffusion process made vacancies in Si wafer. The Al began to seep into the Si wafer (Al spike). During heat down, the Al spike were shrink which causes the doped region (BSF).

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.6
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• pp.886-894
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• 1990

Sinterbility, microstructure, mechenical and electrical properties of yttriastabilized zirkconiz (92 mole % ZrO2 + 8 mole % Y2O3) doped with 0.5 mole % SiO2 and 0-2.O mole% Al2O3 were studied as a functin of Al2O3 addition. Sintered density increased with increasing Al2O3 addition up to o.5 mole%but decreased up to 1.0mole% Al2O3. Vickers hardness is proportional to sintered density. The specimen added 0.5mole% Al2O3 and 0.5mole% SiO2 exhibited a maximum conductivity. And the specimen added 0.5 mole % Al2O3 and 0.5 mole% SiO2 was measured a maximum electromotive force for a characteristics of oxyzen partial pressure.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.46-49
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• 2003

Aluminum based metal matrix composites(MMCs) are well known for their high specific strength, stiffness and hardness. They are gaining further importance because of their high wear resistance. In this study, Al/Saffil-20%, Al/Saffil-5%/Al2O3(particle type)-15% and Al/Saffil-5%/SiC(particle type)-15% hybird MMCs' wear behavior were characterized by the pin-on-disk test under various normal load The superior wear resistance was exhibited at Al/Saffil-5%/SiC(particle type)-15% MMCs. And this MMCs' predominant wear mechanism is subsurface cracking in the low load wear regime. Others(Al/Saffil-20%, Al/Saffil-5%/Al2O3(particle type)-15%) showed the similar wear resistance with each other at the same test condition. In the low load & room temperature condition, the wear resistance was improved due to the high hardness of the ceramic reinforcements. As the test load increased, the wear properties were governed by the wear properties of matrix.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.610-614
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• 2016

Tyranno SA (SiC-polycrystalline fiber, Ube Industries Ltd.) shows excellent heat-resistance up to $2000^{\circ}C$ with relatively high mechanical strength. This fiber is produced by the conversion process from a raw material (amorphous Si-Al-C-O fiber) into SiC-polycrystalline fiber at very high temperatures over $1500^{\circ}C$ in argon. In this conversion process, the degradation reaction of the amorphous Si-Al-C-O fiber accompanied by a release of CO gas for obtaining a stoichiometric composition and the subsequent sintering of the degraded fiber proceed. Furthermore, vaporization of gaseous SiO, phase transformation and active diffusion of the components of the Si-Al-C-O fiber competitively occur. Of these changes, vaporization of the gaseous SiO during the conversion process results in an abnormal SiC-grain growth and also leads to the non-stoichiometric composition. However, using a modified Si-Al-C-O fiber with an oxygen-rich surface, vaporization of the gaseous SiO was effectively prevented, and then consequently a nearly stoichiometric SiC composition could be obtained.

• Korean Journal of Materials Research
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• v.32 no.10
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• pp.403-407
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• 2022

This research investigated the effect of Si addition on the microstructure, mechanical properties, electric and thermal conductivity of as-extruded Al 6013 alloys. As the content of Si increased, the area fraction of the second phase increased. As the Si content increased, the average grain size decreased remarkably, from 182 (no Si addition) to 142 (1.5Si), 78 (3.0Si) and 77 ㎛ (4.5Si) due to dynamic recrystallization by the dispersed second particles in the aluminum matrix during the hot extrusion. As the Si content increased, the yield strength and ultimate tensile strength increased. The maximum values of yield strength and ultimate tensile strength were 224 MPa and 103 MPa for the 6013-4.5Si alloy. As the amount of Si added increased, the electrical and thermal conductivity decreased. The electrical and thermal conductivity of the Al6013-4.5Si alloy were 44.0 % IACS and 165.0 W/mK, respectively. The addition of Si to Al 6013 alloy had a significant effect on its thermal conductivity and mechanical properties.

• Journal of Sensor Science and Technology
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• v.16 no.6
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• pp.457-461
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• 2007

This paper describes the characteristics of poly (polycrystalline) 3C-SiC grown on $SiO_{2}$ and AlN substrates, respectively. The crystallinity and the bonding structure of poly 3C-SiC grown on each substrate were investigated according to various growth temperatures. The crystalline quality of poly 3C-SiC was improved from resulting in decrease of FWHM (full width half maximum) of XRD and FT-IR by increasing the growth temperature. The minimum growth temperature of poly 3C-SiC was $1100^{\circ}C$. The surface chemical composition and the electron mobility of poly 3C-SiC grown on each substrate were investigated by XPS and Hall Effect, respectively. The chemical compositions of surface of poly 3C-SiC films grown on $SiO_{2}$ and AlN were not different. However, their electron mobilities were $7.65{\;}cm^{2}/V.s$ and $14.8{\;}cm^{2}/V.s$, respectively. Therefore, since the electron mobility of poly 3C-SiC films grown on AlN buffer layer was two times higher than that of 3C-SiC/$SiO_{2}$, a AlN film is a suitable material, as buffer layer, for the growth of poly 3C-SiC thin films with excellent properties for M/NEMS applications.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2279-2286
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• 1992

A hypereutectic Aluminum-Silicon Alloy is widely used in the parts of autombile because of high-resistance and good strength. In this study, the cutting of a hypereutectic Al-Si alloy (A390) for extraction of Si particle was experimentally investigated. By proper selection of cutting tool materials and optimization of cutting conditions, economical machining of this alloy is achieved. The surface roughness relates closely with the feed rate and cutting speed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.160-160
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• 2012

Al과 Al합금은 경량금속으로 가공성과 내식성이 우수하여 철강제품의 부식방지, 고효율 반사체 등의 산업 분야에 널리 이용된다. 본 연구에서는 Al과 Al-3wt%Si, Al-10wt%Si의 Al 합금을 마그네트론 스퍼터링으로 코팅하였고 외부 자기장 변화와 빗각 증착에 따른 반사율과 조직 변화 등의 물성을 비교 분석하였다.