• 대한금속재료학회지
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• 제50권8호
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• pp.569-573
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• 2012

In order to understand the difference in SiC deposition between the $CH_3SiCl_3-H_2$ and $C_3H_8-SiCl_4-H_2$ systems, we calculate the phase stability among ${\beta}$-SiC, graphite and silicon. We constructed the phase-diagram of ${\beta}$-SiC over graphite and silicon via computational thermodynamic calculation considering pressure (P), temperature (T) and gas composition (C) as variables. Both P-T-C diagrams showed a very steep phase boundary between the SiC+C and SiC region perpendicular to the H/Si axis, and also showed an SiC+Si region with a H/Si value of up to 6700 in the $C_3H_8-SiCl_4-H_2$, and 5000 in the $CH_3SiCl_3-H_2$ system. This difference in phase boundaries is explained by the ratio of Cl to Si, which is 4 for the $C_3H_8-SiCl_4-H_2$ system and 3 for the $C_3H_8-SiCl_4-H_2$ system. Because the C/Si ratio is fixed at 1 in the $CH_3SiCl_3-H_2$ system while it can be variable in the $C_3H_8-SiCl_4-H_2$ system, the functionally graded material is applicable for better mechanical bonding during SiC coating on graphite substrate in the $C_3H_8-SiCl_4-H_2$ system.

• Composites Research
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• 제15권3호
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• pp.1-10
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• 2002

무가압함침법에 의해 제조된 SiCp/AC8A복합재료에 대하여 SiC 입자 크기와 부가적인 Mg의 첨가가 복합재료의 기계적 성질과 마모특성에 미치는 영향을 조사하였다. SiCp/AC8A복합재료의 경도와 굽힘강도는 입자의 크기가 작아짐에 따라 증가하였다. Mg 첨가량이 증가함에 따라 SiCP/AC8A복합재료의 경도는 경질의 반응생성물에 의해 상승하였으나 굽힘강도는 석출물의 조대화와 기공율의 증대에 의해 저하하였다. SiCp/AC8A복합재료는 AC8A 기지재에 비하여 고속의 마찰속도에서 6배의 내마모성을 나타냈으며 강화입자의 크기가 작아짐에 따라 내마모성은 향상되는 것으로 나타났다. 마모기구에 있어서 SiCp/AC8A복합재료는 마찰속도에 관계없이 연삭마모를 나타냈으나 AC8A 기지재는 마찰속도가 고속화됨에 따라 응착 및 용융마모의 마모면을 나타냈다.

• 한국세라믹학회지
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• 제19권1호
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• pp.13-18
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• 1982

The crystallization of metastable "orthorhombic" phase from the glass in the system of Na $AlSi_3O_8-CaAl_2Si_2O_8$ is studied. These crystals are crystallized in the range of composition from $Ab_80An_20$ to An100. The symmetry of these crystals show orthorhombic as a possible space group P22121. Two probable twin models are proposed. proposed.

• Journal of Advanced Marine Engineering and Technology
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• 제27권1호
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• pp.134-144
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• 2003

Reactive diffusion couples between Fe-5.8at.%Si and (Si wafer, $FeSi_2$, or FeSi alloy) were heat-treated at 1423k. The only layer of $Fe_3Si$ phase was formed in each diffusion couple. The width of $Fe_3Si$ layer was proportional to square root of diffusion time in each kind of diffusion couple. Growth rate of $Fe_3Si$ layer was relied on the concentration of Si in the supplied source of Si atoms. Interdiffusion coefficient of $Fe_3Si$ has been determined from the derived relation between growth rate constant and interdiffusion coefficient in this work. It was shown that the behavior of Kirkendall's void in $Fe_3Si$ layer was not affected by the kind of Si source. But solid solution $\alpha$ was formed in the diffusion couple between Fe-5.8 at.%Si and $Fe_3Si$ alloy. Kirkendall's voids in diffusional $\alpha$ were neglectively smaller than the case of $Fe_3Si$ phase growth.

• E2M - 전기 전자와 첨단 소재
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• 제8권1호
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• pp.71-76
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• 1995

The thermal oxidation of Ge$_{0.2}$Si$_{0.8}$ in wet ambient has been investigated by Rutherford Backscattering Spectrometry(RBS). A uniform Ge$_{0.2}$Si$_{0.8}$O$_{2}$ oxide is formed at temperatures below 650.deg. C for polycrystalline and below 700.deg. C for single crystalline substrates. At higher temperatures Ge becomes depleted from the oxide and finally SiO$_{2}$ oxide is formed with Ge piled-ub behind it. The transition between the different oxide types depends also on the crystallinity of Ge$_{0.2}$Si$_{0.8}$. When a uniform Ge$_{0.2}$Si$_{0}$8/O$_{2}$ oxide grows, its thickness is proportional to the square root of the oxidation time, which suggests that the rate noting process is the diffusive transport of oxidant across the oxide. It is believed the oxidation is controlled by the competition between the diffusion of Ge or Si in Ge$_{0.2}$Si$_{0.8}$ and the movement of oxidation front.t.oxidation front.t.

• 한국재료학회지
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• 제8권6호
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• pp.477-483
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• 1998

$SiC_{4}$$C_{3}$$H_{ 8}$$H_{2}$와 $C_{3}$$H_{8}$ $H_{2}$, $CH_{3}$$SiCI_{3}$$CH_{4}$$H_{2}$계를 사용하여 흑연기판 위에 SiC와 SiC/C FGM을 CVD법에 의해 코팅하였다. $SiCI_{4}$$C_{3}$$H_{8}$ $H_{2}$ 계에서 SiC 증착 시 바람직한 수소의 비는 10-30사이였고 결정 배향성은 입력가스의 탄소비에 따라 여러번의 대 반전이 일어났다. 성장조건을 {111} 배향성을 갖도록 조절하는 것이 FGM층간 접착상태를 증진시킬 수 있는 방법으로 판단되었다. $CH_{3}$$SiCI_{3}$C$_{3}$$H_{8}$ $H_{2}$ 계에서는 SiC와 C의 비율을 조절하기가 $SiCI_{4}$$C_{3}$$H_{8} $H_{2}$계를 사용했을 때 보다 용이하였고, FGM 단면 관찰에서 층간의 뚜렷한 경계를 발견할 수 없을 정도로 우수한 층간 접착상태를 보였다.

• 한국재료학회지
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• 제28권8호
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• pp.474-477
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• 2018

$Ca_3MgSi_2O_8:Eu^{2+}$(x = 0.003, 0.005, 0.007, 0.01, 0.03 mol) white phosphors for Light Emitting Diodes(LED) are synthesized with different concentrations of $Eu^{2+}$ ions using a solid state reaction method. The crystal structures, surface and optical properties of the phosphors are investigated using X-Ray Diffraction(XRD), Scanning Electron Microscope(SEM) and photoluminescence(PL). The X-Ray Diffraction results reveals that the crystal structure of the $Ca_3MgSi_2O_8:Eu^{2+}$ is a monoclinic system. The particle size of $Ca_3MgSi_2O_8:Eu^{2+}$ white phosphors is about $1{\sim}5{\mu}m$, as confirmed by SEM images. The maximum emission spectra of the phosphors are observed at 0.01 mol $Eu^{2+}$ concentration. The decrease in PL intensity in the $Ca_3MgSi_2O_8:Eu^{2+}$ white phosphors with $Eu^{2+}$ concentration is interpreted by concentration quenching. The International Commission on Illumination(CIE) coordinate of 0.01 mol Eu doped $Ca_3MgSi_2O_8$ is X = 0.2136, Y = 0.3771.

• 한국주조공학회지
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• 제17권1호
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• pp.28-35
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• 1997

SiC whisker and $Al_2O_3-SiO_2$ short fiber reinforced AC8A, AC8B and AC8B(J) marix composites were fabricated by squeeze casting method. Preform deformation, change of reinforcement volumefraction and formation of macro-segregation in two composites were investigated by using micro Vickers hardness test, analysis of macro and micro structures with OM, SEM and EDAX. $Al_2O_3-SiO_2$ short fiber preform manufactured with 5% $SiO_2$ binder in this study was considerably deformed and cracked, nevertheless, the short fibers were distributed homogeneously in the composites. In SiC whisker reinforced composites, on the other hand, preform deforming and cracking were not occurred, however, macro segregation zone formed along the infiltration routes by interface reaction during infiltration of molten metal into the preform was observed at center-low area in the composites. The decrease of hardness in the macro segregation zone resulted from the depletion of Si and Mg atoms.

• ETRI Journal
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• 제25권3호
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• pp.203-209
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• 2003

This paper reports on our investigation of DC and RF characteristics of p-channel metal oxide semiconductor field effect transistors (pMOSFETs) with a compressively strained $Si_{0.8}Ge_{0.2}$ channel. Because of enhanced hole mobility in the $Si_{0.8}Ge_{0.2}$ buried layer, the $Si_{0.8}Ge_{0.2}$ pMOSFET showed improved DC and RF characteristics. We demonstrate that the 1/f noise in the $Si_{0.8}Ge_{0.2}$ pMOSFET was much lower than that in the all-Si counterpart, regardless of gate-oxide degradation by electrical stress. These results suggest that the $Si_{0.8}Ge_{0.2}$ pMOSFET is suitable for RF applications that require high speed and low 1/f noise.

• 한국분말재료학회지
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• 제4권3호
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• pp.179-187
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• 1997

Milling media of steel and zirconia were used to produce $MoSi_2$ by mechanical alloying (MA) of Mo and Si powders. The effect of milling media on MA of Mo-65.8at%Si powder mixture has been investigated by SEM, XRD, DTh and in-situ thermal analysis. The powders mechanically alloyed by milling medium of steel for 8 hours showed the structure of fine mixture of Mo and Si, and those mechanically alloyed by milling medium of zirconia for longer milling time showed the structure of fine mixture of Mo and Si. The tetragonal $\alpha$-$MoSi_2$ Phase and the tetragonal $Mo_5Si_3$ phase appeared with small Mo peaks in the powders milled by milling medium of steel for 4 and 8 hours. The $\alpha$-$MoSi_2$ phase and the hexagonal $\beta$-$MoSi_2$ phase were formed after longer milling time. The $\alpha$-$MoSi_2$ phase appeared with large Mo peaks in the powders milled by milling medium of zirconia for 4 hours. The phases, $\alpha$-$MoSi_2$ and $\beta$-$MoSi_2$. were formed in the powders milled for longer milling time. DTA and annealing results showed that Mo and Si were transformed into $\alpha$-$MoSi_2$ and $Mo_5Si_3$, while $\beta$-$MoSi_2$ into $\alpha$-$MoSi_2$. In-situ thermal analysis results demonstrated that there were a sudden temperature rise at 212 min and a gradual increase in temperature in case of milling media of steel and zirconia, respectively. The results indicate that MA can be influenced by materials of milling medium which can give either impact energy on powders or thermal energy accumulated in vial.