• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.58.2-58.2
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• 2000

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.586-591
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• 2010

Solar cells have been more intensely studied as part of the effort to find alternatives to fossil fuels as power sources. The progression of the first two generations of solar cells has seen a sacrifice of higher efficiency for more economic use of materials. The use of a single junction makes both these types of cells lose power in two major ways: by the non-absorption of incident light of energy below the band gap; and by the dissipation by heat loss of light energy in excess of the band gap. Therefore, multi junction solar cells have been proposed as a solution to this problem. However, the $1^{st}$ and $2^{nd}$ generation solar cells have efficiency limits because a photon makes just one electron-hole pair. Fabrication of all-silicon tandem cells using an Si quantum dot superlattice structure (QD SLS) is one possible suggestion. In this study, an $SiO_x$ matrix system was investigated and analyzed for potential use as an all-silicon multi-junction solar cell. Si quantum dots with a super lattice structure (Si QD SLS) were prepared by alternating deposition of Si rich oxide (SRO; $SiO_x$ (x = 0.8, 1.12)) and $SiO_2$ layers using RF magnetron co-sputtering and subsequent annealing at temperatures between 800 and $1,100^{\circ}C$ under nitrogen ambient. Annealing temperatures and times affected the formation of Si QDs in the SRO film. Fourier transform infrared spectroscopy (FTIR) spectra and x-ray photoelectron spectroscopy (XPS) revealed that nanocrystalline Si QDs started to precipitate after annealing at $1,100^{\circ}C$ for one hour. Transmission electron microscopy (TEM) images clearly showed SRO/$SiO_2$ SLS and Si QDs formation in each 4, 6, and 8 nm SRO layer after annealing at $1,100^{\circ}C$ for two hours. The systematic investigation of precipitation behavior of Si QDs in $SiO_2$ matrices is presented.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.18-19
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• 2002

Si 웨이퍼제조 시 나오는 페슬러지에서 SiC 연마재와 절삭유를 분리해내면 Si 분말을 얻을 수 있다. 본 연구에서의 SiC는 폐슬러지 Si 분말에 C 분말을 혼합하여 제조할 수 있다. Si-C-O 3성분계는 Si, $SiO_2$, SiC, C 4개의 응축상과 CO, SiO, $CO_2$, $O_2$ 4개의 기체상이 가능하고 생성물들 간의 평형관계를 깁스 자유에너지에 의해 평형 반응식이 계산되어질 수 있다. 계산된 평형 반응식은 2개의 SiO, CO 분압이 각각 X, Y 좌표평면에 나타나는 상안정도를 그려볼 수 있다. 상안정도에서 자유도가 2인 경우는, $SiO_2$가 불안정하므로 SiC와 C가 공존하는 영역에서 온도를 독립 변수로 놓으면 나머지 독립 변수는 SiO 나 CO 기체 분압 둘 중 하나가 되어 하나의 직선으로 나타낼 수 있다. 직선을 경계로 각 응축상들의 안정영역을 하나의 좌표평면에 나타낸 후 온도에 따른 SiC의 안정영역을 알아본다.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1570-1576
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• 1994

Effect of Na2O/SiO2 molar ratio, calcining temperature and addition of NaCl were investigated on the hydrothermal formation of X-type zeolite from the natural mordenite, which is a kind of rock deposited abundantly in kuryong po. Pulverized mordenite was first mixed with NaOH or NaOH-NaCl solution, and crystallized under hydrothermal condition at 90~10$0^{\circ}C$ for 10 hrs. Optimum condition for synthesis of the X-type zeolite were \circled1 the ratio Na2O/SiO2, NaCl/Al2O3 and H2O/Na2O:0.68, 11.4 and 40, respectively, \circled2 calcining temperature of starting materials: 90$0^{\circ}C$, \circled3 aging time: 48 hrs. and \circled4 crystallization temperature: 10$0^{\circ}C$. The yield of X-type zeolite under the optimum condition was about 55~60%, and the major crystallized X-type zeolite was faujasite phase. Zeolite of then type X was crystallized when NaCl was added to treating solution with in the limit 14.25 of NaCl/Al2O3 molar ratio. As the calcination temperature (from 50$0^{\circ}C$ to 95$0^{\circ}C$) of starting materials increases, yield of zeolite x increase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.309-313
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• 1997

(Ba$_{x}$Sr$_{l-x}$)TiO$_3$(BST) thin fi1ms with various Ba/Sr ratios were deposited on Pt(80nm)/SiO$_2$(100nm)/Si by RF magnetron sputtering. BST thin films which have x=0.6, 0.5, 0.4 were studied dielectric properties with temperature variation. The frequency was used from 100Hz to 1MHz for measuring dielectric constant. The measurement conditions of dielectric constant with Temperature Variation were 1KHz and 2$0^{\circ}C$. As a result, the dielectric constant of BST thin film was about 425 and loss factor was 0.013. Also, with increasing Temperature, the dielectric constants of BST thin films were gradually decreased.sed.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.34-42
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• 1996

Growth of synthetic emerald [($(BeO)_3(Al_{2-x}Cr_xO_3)(SiO_2)_6$] single crystals was carried out by flux method. In this study, the starting materials were prepared by stoichiometric mixing of BeO, $Al_2O_3$ and $SiO_2$ as reaching components. The conditions for the growth of synthetic emerald single crystals are as follows : temperature range ; $1150{\sim}900^{\circ}C$, cooling rate ; 2, 4, $10^{\circ}C/hr$, flux ; $Li_2CO_3$, $V_2O_5$, dopant ; $Cr_2O_3$. The sizes of $Cr_2O_3$emerald single crystals depending on 2, 4, $10^{\circ}C/hr$ cooling rates. The obtained emerald single crystal was characterized and the following results were obtained : lattice parameter : a=0.921nm, c=0.917nm, crystal system ; hexagonal, crystal size ; max. $0.80{\times}0.95mm^2(c{\times}m)$, orientation ; (1000), $m(10{\bar{1}}0)$.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.808-815
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• 1995

The magnetic states of nonstoichiometric substituted ferrite Fe$_{}1.429$(Al$_{4-x}$ Ga$_{x}$)$_{0.286}$ Si$_{0.143}$ /O$_4$ system have been investigated using Mossbauer spectroscopy and SQUID. The Mossbauer spectra at room temperature show well-defined two Zeeman patterns for x=0.2, superpositions of two Zeeman patterns and a doublet for x=0.4. The doublet peak seems to be originated from the superparamagnetic clusters. The system shows significant departures from the Neel's collinear model and seems to be the diluted ferrites. The Mossbauer spectra below R.T show various and complicated patterns, which can be explained by freezing of the superparamagnetic clusters. On cooling, magnetic states of the system may be various and multicritical, Resulting from SQUID measurements, there was an unexpected dip in magnetization curves below 50K. It was interpreted as an effect of spin canting including spin freezing or collective spin behavior.

• Journal of the Korean Chemical Society
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• v.61 no.4
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• pp.179-184
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• 2017

In this paper, a $ZnO/SiO_2$ nano-composite was prepared by a simple chemical method at room temperature. For the synthesis of ZnO nanoparticles (NPs), a sonochemical method was used, and $SiO_2$ NPs were prepared by precipitation method. The formation of $ZnO/SiO_2$ NCs was characterized by X-ray diffractometer (XRD) and confirmed by field-emission scanning electron microscopy (FE-SEM) and Fourier transform infra-red spectroscopy(FT-IR). The photocatalytic properties of $ZnO/SiO_2$ NCs formed at different concentrations of $SiO_2$ were evaluated by rhodamine-B dye. It was confirmed that increasing $SiO_2$ concentration resulted in an increase in the photocatalytic property. In addition, the antibacterial activity of $ZnO/SiO_2$ NCs was conducted against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). As a result, the antibacterial activities of E.coli and S. aureus were increased in the presence of thick SiO NPs layer.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.714-722
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• 2019

Catalysts were prepared by using incipient wetness impregnation method with 17 wt% Ni on a support ($SiO_2-Y_2O_3$, $Al_2O_3$, $SiO_2-ZrO_2$, $SiO_2$, $TiO_2$, MgO) and the catalytic activity in the reductive amination of ethanol with ammonia in the presence of hydrogen was compared and evaluated. The catalysts used before and after the reaction were characterized using X-ray diffraction, nitrogen adsorption, ethanol-temperature programmed desorption (EtOH-TPD), isopropanol-temperature programmed desorption (IPA-TPD), and hydrogen chemisorption etc. In the case of preparing $ZrO_2$ and $Y_2O_3$ supports, the small amount of Si dissolution from the Pyrex reactor surface provoked the formation of mixed oxides $SiO_2-ZrO_2$ and $SiO_2-Y_2O_3$. Among the catalysts used, $Ni/SiO_2-Y_2O_3$ catalyst showed the best activity, and this good activity was closely related to the highest nickel dispersion, and low desorption temperature in EtOH-TPD and IPA-TPD. The low catalytic activity on Ni/MgO catalysts showed low activity due to the formation of NiO-MgO solid-solutions. In the case of $Ni/TiO_2$, the reactivity was low due to the low nickel metal phase due to strong metal-support interaction. In the case of using a support as $SiO_2-Y_2O_3$, $Al_2O_3$, $SiO_2-ZrO_2$, and $SiO_2$, the selectivities of ethylamines and acetonitrile were not significantly different at similar ethanol conversion.

• Journal of Electrochemical Science and Technology
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• v.4 no.3
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• pp.108-112
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• 2013

Lithium diffusivity of the silicon (Si)-based materials of Si-Cu and $SiO_x$ (x = 0.4, 0.85) with improved interfacial stability to electrolyte have been determined, using variable rate cyclic voltammetry with film model electrodes. Lithium diffusivity is found to depend on the intrinsic properties of anode material and electrolyte; the fraction of oxygen for $SiO_x$ (x = 0.4, 0.85), which is directly related to electrical conductivity, and the electrolyte type with different ionic conductivity and viscosity, carbonate-based liquid electrolyte or ionic liquid-based electrolyte, affect the lithium diffusivity.