• The Korean Journal of Ceramics
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• 제3권4호
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• pp.229-234
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• 1997

Silicon carbide-carbon fiber composites have been prepared by partially Infiltrating porous carbon fiber composites with liquid silicon at a reaction temperature of $1670^{\circ}C$. Reaction between molten silicon and the fiber preform yielded silicon carbide-carbon fiber composites composed of aggregates of loosely bonded SiC crystallites of about 10$\mu\textrm{m}$ in size and preserved the appearance of a fiber. In addition, the SiC/C fiber composites had carbon fibers coated with a dense layer consisted of SiC particles of sizes smaller than 1$\mu\textrm{m}$. The physical and mechanical properties of SiC/C fiber composites were discussed in terms of infiltrated pore volume fraction of carbon preform occupied by liquid silicon at the beginning of reaction. Lower bending strength of the SiC/C fiber composites which had a heterogeneous structure in nature, was attributed to the disruption of geometric configuration of the original carbon fiber preform and the formation of the fibrous aggregates of the loosely bonded coarse SiC particles produced by solution-precipitation mechanism.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.739-740
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• 2011

• 한국세라믹학회지
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• 제48권5호
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• pp.373-378
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• 2011

The composite added with surface-coated chopped carbon fiber showed the microstructure of a 3 dimensional discretional arrangements. The fiber reinforced reaction bonded silicon carbide composite, containing the 50 vol% carbon fiber, showed the porosity of < 1 vol%, 3-point bending strength value of 250MPa and fracture toughness of 4.5 $MPa{\cdot}m^{1/2}$. As the content of carbon fiber was increased from 0 vol% to 50 vol% in the composite, fracture strength was decreased due to the increase of carbon fiber, which has a less strength than SiC and molten Si. On the other hand, the fracture toughness was increased with increasing the amount of carbon fiber. According to the polished microstructure, carbon fiber was shown to have a random 3 dimensional arrangement. Moreover, the fiber pull-out phenomenon was observed with the fractured surface, which can explain the increased fracture toughness of the composite containing high content of carbon fiber.

• 대한금속재료학회지
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• 제50권8호
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• pp.575-582
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• 2012

Medium carbon steel was aluminized by hot dipping into molten Al or Al-1 at% Si baths. After hot-dipping in these baths, a thin Al-rich topcoat and a thick alloy layer rich in $Al_5Fe_2$ formed on the surface. A small amount of FeAl and $Al_3Fe$ was incorporated in the alloy layer. Silicon from the Al-1 at% Si bath was uniformly distributed throughout the entire coating. The hot dipping increased the microhardness of the steel by about 8 times. Heating at $700-1000^{\circ}C$, however, decreased the microhardness through interdiffusion between the coating and the substrate. The oxidation at $700-1000^{\circ}C$ in air formed a thin protective ${\alpha}-Al_2O_3$ layer, which provided good oxidation resistance. Silicon was oxidized to amorphous silica, exhibiting a glassy oxide surface.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.43.2-43.2
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• 2010

In this study, metallurgical grade (MG) silicon with 99% purity produced by arc furnace process was systematically investigated for slag refining. The most problematic impurities to remove from MG silicon are boron (B) and phosphorus (P). To remove B and P from MG-silicon, we used synthetic slag in the molten state. MG-silicon with synthetic slag of CaO, $SiO_2$, and $CaF_2$ was melted using by high-frequency induction furnace with electrical output of 50kW. Specimens prepared by various refining process conditions(holding time, mixture ratio) were inspected by combined analysis of ICP-MS and XRF. With this approach, B has been reduced to <5ppm, P to <1ppm and other impurities to 0.1~0.2% except for Calcium. Calcium has been increased from 17ppm to 1500ppm. Problem of calcium contamination will be resolved by additional refining processes.

• Journal of Electrochemical Science and Technology
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• 제2권3호
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• pp.168-173
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• 2011

The availability, low toxicity, and high degree of technological development make silicon the most likely material to be used in solar cells, the cost of solar cells depends entirely on cost of high purity silicon production. The present work was conducted to electrodeposite of silicon from $K_2SiF_6$, an inexpensive raw material prepared from fluorosilicic acid ($H_2SiF_6$) produced in Iraqi Fertilizer plants, and using inexpensive graphite material as cathode electrode. The preparation of potassium fluorosilicate was performed at ($60^{\circ}C$) in a three necks flask provided with a stirrer, while the electro deposition was performed at $750^{\circ}C$ in a three-electrodes configuration with melt containing in graphite pot. High purity potassium fluorosilicate (99.25%) was obtained at temperature ($60^{\circ}C$), molar ratio-KCl/$H_2SiF_6$(1.4) and agitation (600 rpm). Spongy compact deposits were obtained for silicon with purity not less than (99.97%) at cathode potential (-0.8 V vs. Pt), $K_2SiF_6$ concentration (14% mole percent) with grain size (130 ${\mu}m$) and level of impurities (Cu, Fe and Ni) less than (0.02%).

• 한국세라믹학회지
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• 제31권5호
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• pp.561-571
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• 1994

For the preparation of SiC composite, the properties of reaction sintering in the SiC-C-Si-Ti system with the titanium contents variation were investigated. Either the case of titanium additions or the case of direct infiltration of titanium in SiC+C preform, the newly formed fine-grained $\beta$-SiC, which was reacted from the molten silicon with graphite, was intergranulated between the original $\alpha$-SiC particles. Also titanium disilicide (TiSi2) was discontinuously formed isolated pocket in silicon matrix. The amount of titanium disilicide was gradually increased as titanium content increase. With the results of hardness and fracture toughness measurement, SiC-titanium disilicide (TiSi2) composite represented high properties compared with the system of the infiltrated pure silicon.

• 반도체디스플레이기술학회지
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• 제21권4호
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• pp.50-52
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• 2022

Brownish rings (BRs) with white interiors are formed during the manufacture of silicon ingots in quartz glass crucibles. These BRs inhibit the yield of silicon ingots. However, the composition and mechanism of the formation of these BRs remain unclear thus far. Therefore, in this study, we analyzed the color and shape of these BRs. Raman analysis revealed that the brown and white colors appear owing to oxygen deficiency rather than crystallization from excess oxygen supply as previously assumed. Moreover, the dark shade of the brown areas depends on the degree of oxygen deficiency and the asymmetrical width of the brown areas is attributed to the direction of the molten silicon flow, which is influenced by the rotation and heat of the ingot crucible.

• 한국재료학회지
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• 제25권12호
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• pp.694-702
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• 2015

Nd-Fe-B permanent magnets have been used in a wide variety of applications because of their high magnetic flux density. So, demand for neodymium has been increasing in worldwide. In this study, an electrowinning process was performed in $LiF-NdF_3-Nd_2O_3$ high temperature molten salts. However, a corrosion resistant material for use in the molten salt must be found for stable operation because of the harsh corrosion environment of the electrowinning process. Therefore, for this paper, boron nitride(BN), aluminum nitride(AlN), and silicon nitride($Si_3N_4$) were selected as protective and structural materials in the high temperature electrolyte. To investigate the characteristics of BN, AlN, and $Si_3N_4$, in molten salts, materials were immersed in the molten salts for 24, 72, 120, and 192 hours. Also, surface condition and stability were investigated by SEM and EDS and corrosion products were calculated by HSC chemistry. As a result, among BN, AlN, and $Si_3N_4$, AlN was found to show the best protective material properties.

• 자원리싸이클링
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• 제30권4호
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• pp.20-26
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• 2021

태양전지용 실리콘은 주로 반도체급 실리콘 제조공정에서 발생하는 규격외 실리콘을 사용하여 왔다. 태양전지의 보급 활성화를 위해서는 보다 저렴한 정제 공정의 개발이 필요하다. 태양전지용 실리콘을 위한 저비용이면서 효율적인 방법은 금속급 실리콘을 정제하여 고순도화하는 것이다. 본 연구에서는 금속급 용융 실리콘 중의 Fe를 제거하기 위해 고주파 유도로 중에서 일방향 응고를 실시하였다. 실험조건과 실험결과를 유효 편석계수, Scheil 식 및 Peclet 수로 평가하였다. 시료의 하강속도가 감소함에 따라 불순물의 매크로 편석과 잉곳의 순도가 증가하였다. 이러한 결과는 시료의 하강속도 감소에 따른 유효 편석계수의 감소에 의한 것으로 생각된다.