• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.75-78
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• 2009

Si-doped GaAs single crystals were grown by vertical gradient freeze using PBN crucibles. The amount of oxide layer $B_{2}O_{3}$ in PBN crucible was changed($0{\sim}0.2wt%$) and measured the concentration of carriers. The segregation coefficients of Si in GaAs melt decreased rapidly from initial 0.1 to 0.01 as the amount of $B_{2}O_{3}$ increases. At the same time, concentration of carriers was shown to decrease. It is likely that the reaction between dopant Si and $B_{2}O_{3}$ in GaAs melt results in the reduction of Si dopants(donor) while increase in the amount of boron(acceptor). The thin layer of $B_{2}O_{3}$ glass in PBN crucible was proved to be a better way to reduce defect formation rather than the total amount of $B_{2}O_{3}$.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.861-862
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• 2009

Precipitated iron-based catalysts are highly promising for the Fischer-Tropsch synthesis (FTS), in particular for the low temperature FTS below $280^{\circ}C$, because of their high activity and low cost. $SiO_2$ is an essential promoter for the precipitated iron-based catalysts to improve the attrition strength and physical stability. In this study, we carried out FTS over precipitated iron-based catalysts with and without $SiO_2$ in a fixed-bed reactor. The catalysts were prepared by a conventional co-precipitation method. In case of the catalysts with $SiO_2$, we used two comparative preparation methods, i.e., incorporation of $SiO_2$ before precipitation (denoted as precipitated $SiO_2$) and after precipitation (denoted as binder $SiO_2$), respectively. The addition of $SiO_2$ crucially affects both physico-chemical properties and catalytic peformance of precipitated iron-based catalysts.

• Journal of Welding and Joining
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• v.22 no.5
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• pp.46-52
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• 2004

AlSi-Al$_2$O$_3$ composite layer was prepared by plasma spray on steel substrate. The composite powder for plasma spray was prepared by simple mechanical blending. The wear resistance of the composite layers and matrix aluminum alloy were performed in terms of size distribution of ceramic particles. Friction coefficients of AlSi were decreased with incorporation of $Al_2$O$_3$. The tribological properties of coated layers were affected by the size of incorporated $Al_2$O$_3$ particle. The reinforcement of $Al_2$O$_3$ particle into aluminum alloy matrix decreased the friction coefficient as well as wear loss.

• Journal of the Korean Ceramic Society
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• v.28 no.7
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• pp.517-524
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• 1991

The CVD process of BPSG (BoroPhosphoSilicate Glass) and its thin film properties were studied. B2H6, PH3, SiH4 and O2 gases were reacted in a AP (Atmospheric Pressure) CVD system in the temperature range of 300℃ and 460℃. The interaction of B2H6 and PH3 was studied from the deposition rate and dopant incorporation change point of view. The dependency of BPSG step coverage on the temperature was changed with different O2/(B2H6+PH3+SiH4) ratio. Finally, the boundary which distinguishes the stable BPSG's from the ones that react with Di (Deionized) water or cleaning chemicals such as H2SO4, HCl, H2O2, NH4OH etc could be defined.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.799-804
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• 1999

Composites of SiC-Si3N4 consisted of uniformly distributed elongated $\beta$-Si3N4 grains and equiaxed $\beta$-SiC grains were fabricated with $\beta$-SiC,. $\alpha$-Si3N4 Al2O3 and Y2O3 powders. By hot-pressing and subsequent annelaing elongated $\beta$-Si3N4 grains were grown via$\alpha$longrightarrow$\beta$ phase transformation and equiaxed $\beta$-Si3N4 composites increased with increasing the Si3N4 content owing to the reduced defect size and enhanced crack deflection by elongated $\beta$-Si3N4 grains and the grain boundary strengthening by nitrogen incorporation. Typical flexural strength and fracture toughness of SiC-40 wt% Si3N4 composites were 783 MPa and 4.2 MPa.m1/2 respectively.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.298-302
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• 2010

We report the effect of surface morphology on the conductivity of the poly-N-vinylcarbazole (PVK)/silica gel ($SiO_2$) nanocomposites as a function of $SiO_2$ weight percentage (%).The polymerization of PVK was initiated by a free-radical polymerization. The surface morphology of the prepared composite shows the incorporation of $SiO_2$ in the prepared PVK-$SiO_2$ (PS) nanocomposites. The conductivity increased from $9.2{\times}10^{-5}S\;cm^{-1}$ to $9.6{\times}10^{-4}S\;cm^{-1}$ with the increase in the percentage of silica gel from 5 to 30%. The nanocomposites show a percolation behavior having a threshold value between 15 and 20%.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.304-310
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• 2010

The FTS(Fischer-Tropsch synthesis) was carried out over precipitated iron-based catalysts with or without $SiO_2$ in a fixed-bed reactor at $250^{\circ}C$ and 1.5 MPa. The catalysts with $SiO_2$ showed much higher catalytic activity for the FTS than those without $SiO_2$, displaying excellent stability during 144 h of reaction. The X-ray diffraction and $N_2$ physisorption revealed that the catalysts with $SiO_2$ showed enhanced dispersion of $Fe_2O_3$ compared with those without $SiO_2$. Also, the results of temperature-programmed reduction by $H_2$ showed that the addition of $SiO_2$ markedly promoted the reduction of $Fe_2O_3$ into $Fe_3O_4$ and FeO at low temperatures below $260^{\circ}C$. In contrast, surface basicity of the catalysts, which was analyzed by temperature-programmed desorption of $CO_2$, decreased as a result of $SiO_2$ addition. We attribute the high and stable performance of the catalysts with $SiO_2$ to the improved dispersion and reducibility by the $SiO_2$ addition.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.2
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• pp.128-135
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• 2019

In this study, the mesoporous $SiO_2$ (5, 10, or 15 wt%) was incorporated into the polybenzimidazole matrix in order to improve the proton conduction as well as physiochemical properties of composite membrane. The chemical structure of mesoporous $SiO_2$ and crystallinity of as-prepared membranes were analyzed by Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis, respectively. The thermal stability of the pristine $X_1Y_9$ and composite membranes were evaluated by thermogravimetric analyzer (TGA). On other side, the physical and chemical properties of the pristine $X_1Y_9$ and composite membranes were also determined by acid uptake and oxidative stability tests, respectively. With the incorporation of 15 wt% $SiO_2$, the composite membrane exhibits the higher proton conductivity that may be applicable for non-humidified high temperature fuel cell applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.690-693
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• 2003

An Si substrate (100) was oxidized at $400^{\circ}C$ in inductively coupled oxygen plasma. Interstitial oxygen was found in the Si substrate at the initial stage of oxidation by IR measurements. An x-ray rocking curve of Si substrates showed a lower peak intensity due to lattice distortion by the interstitial oxygen. The refractive index of thin oxides, below which interstitial oxygen existed in the Si substrate, was smaller than the refractive index of thick oxides, below which no interstitial oxygen existed. The interstitial oxygen was found by plasma oxidation using $O_{2}$ gas and $N_{2}O$ gas. The inductively coupled plasma oxidation using $N_{2}O$ gas was performed by atomic oxygen, not by molecular oxygen, indicating that atomic oxygen in plasma is responsible for the incorporation of interstitial oxygen.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.69-72
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• 2012

In this study, deposition of low-dielectric constant SiOC(H) films by conventional plasma-enhanced chemical vapor deposition (PECVD) were investigated through various characterization techniques. The results show that, with an increase in the plasma power density, the relative dielectric constant (k) of the deposited films decreases whereas the refractive index increases. This is mainly due to the incorporation of organic molecules with $CH_3$ group into the Si-O-Si cage structure. It is as confirmed by FT-IR measurements in which the absorption peak at 1,129 $cm^{-1}$ corresponding to Si-O-Si cage structure increases with power plasma density. Electrical characterization reveals that even after fast thermal annealing process, the leakage current density of the deposited films is in the order of $10^{-11}$ A/cm at 1.5 MV/cm. The reliability of the SiOC(H) film is also further characterized by using BTS test.