• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.893-900
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• 1999

Silica films were prepared on Si single crystal substrates by sol-gel process using TEOS as starting materials. Films were fabricated by a spin coating technique. Sol solutions were prepared by varying the compositions of CH3OH, H2O and DMF with fixed molar ratio of TEOS=1, HCl=0.05(mol). Wetting behavior viscosity of solutions gelation time thickness of films and cracking behavior were investigated with the various solution compositions. Wetting behaviors of solutions depended on the solution compositions mixing method and mixing rate. The optimum composition of sol was TEOS : DMF ; CH3OH: H2O :HCl=1:2:4:4:0.05(mol) and the mixing rate of solution was optimized at 1 ml/min. Viscosity of solutions were controlled by choosing a reaction time(elapsed time after mixing) at a room temperature so that we could get up to 800nm thick film The surface roughness was getting poor when thickness of films was thicker than 500nm. Thickness of coated films were increased with decreasing amount of CH3OH. The best surface roughness was obtained at the content of CH3OH 4 mol. The shortest gelation time was obtained with the content of CH3OH 8 mol. Crack-free filkms were fabricated when sintered at 500$^{\circ}C$ for 1 hr with heating rate of 0.6$^{\circ}C$/min.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.159-159
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• 2009

RF 스퍼터링법을 이용하여 유리기판위에 ZnO:Al 박막을 증착하고 다양한 조건 하에서 후 열처리를 실시하여 이에 따른 박막의 구조적, 전기적 및 광학적 특성과 HCl 습식 식각 후의 표면형상 변화를 조사하였다. ZnO:Al 투명전도막은 우수한 전기적, 광학적 특성, 수소 플라즈마 안정성 및 저 비용 등으로 실리콘 박막 태양전지 전면 전극용으로 많은 관심을 받고 있다. 기존의 비정질 실리콘 박막 태양전지용으로 많이 사용되고 있는 상용 Asahi-U형 ($SnO_2:F$) 투명전도막의 경우는 수소 플라즈마에 대한 안정성이 낮고 입사광의 장파장 대역에서의 낮은 산란특성으로 인하여 실리콘 박막 태양전지의 고효율화를 위한 적용에 한계를 나타내고 있다. 이를 개선하기 위하여 스퍼터링법으로 우수한 전기적 특성을 갖는 ZnO:Al 박막을 제조한 후 습식 식각을 통한 표면형상 변화를 통하여 입사광의 산란특성을 향상시키는 방법이 개발되어 많은 연구가 이루어지고 있다. 본 연구에서는 2.5 wt%의 $Al_2O_3$가 함유된 ZnO 타겟을 이용하여 ZnO:Al 박막을 RF 스퍼터링으로 증착한 후 $N_2$ 분위기와 진공 분위기 하에서 다양한 시간과 온도에 따라 후열처리를 하여 열처리 전 박막과의 물질 특성을 상호 비교하고 1%로 희석된 HCl로 습식 식각하여 열처리 전 박막의 구조적 특성이 습식 식각 후의 박막 표면형상 변화에 미치는 영향을 조사하였다. 이로부터 후열처리를 통한 ZnO:Al 투명전도막의 특성을 최적화하고 Asahi-U형 투명전도막과의 특성 비교를 통하여 실리콘 박막 태양전지용 전면전극으로의 적용 가능성을 조사하였다.

• Journal of the Korean institute of surface engineering
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• v.49 no.6
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• pp.567-574
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• 2016

We have analyzed chemical properties of polysiloxane and polysilazane films, respectively, as sealing materials for electrostatic chuck (ESC) and have investigated the possibility of polysilazane as an alternative sealant to polysiloxane. It has been revealed that Si-O with organic bonding ($Si-CH_3$) existed in polysiloxane films compared to only pure Si-O bonding in polysilazane films. The sealing property of polysilazane has been found outstanding even in a short time of application. In the polysiloxane films containing $H_2O$, pin holes have been found possibly due to $CO_2$ gas evolution, and low adhesion with Si substrate has been observed after heat stress test in connection with the existence of organic bonding. After acid resistance test in 0.5 vol.% HF, 68 wt.% $HNO_3$, and 37 wt.% HCl solution, polyilazane films have shown a longer survival times. Compared to the conventional polysiloxane sealant, polysilazane is expected as a new sealing material because of good thermal and chemical stability.

• Bulletin of the Korean Chemical Society
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• v.26 no.3
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• pp.418-422
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• 2005

By introducing spin-coating method to the evaporation induced self-assembly (EISA) process, a simple and reproducible route in controlling the mesophase of silica thin films has been developed for the first time in this work. When a comparatively solvent-rich Si-sol (The atomic ratio of TEOS : F127 : HCl : $H_2O$ : EtOH = 1 : 0.006 : 0.2 : 9.2 : 30) was used as coating solution, the mesophase of resultant silica films was selectively controlled by adjusting the spin-on speed. The cubic mesophase has been obtained from the coating at a low rpm, such as 600 rpm, while the 2-D hexagonal mesophase is formed at a high rpm, such as 2,500 rpm. At a medium coating speed, a mixture of cubic and hexagonal mesophase has been found in the fabricated films. The present results confirm that the evaporation rate of volatile components at initial step is critical for the determination of mesopore structures during the EISA process.

• Journal of the Korean Ceramic Society
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• v.31 no.8
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• pp.934-940
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• 1994

Fibers of ZrO2-SiO2 system were prepared from the hydrolysis and condensation of Si(OC2H5)4 and Zr(OnC3H7)4 with different H2O/alkoxide molar ratios. It was found that fibers could be drawn in the viscosity range of 1~100 poise from HCl catalyzed solutions with lower water contents of the mole ratio H2O/alkoxide, r 2. The fibrous gels were converted into the corresponding oxide glass fibers by heating at 80$0^{\circ}C$. Mechanical test was performed on E, A and 20ZrO2-80SiO2 glass fibers reinforced cement in order to investigate the flexural strength. The flexural strength value of 20ZrO2-80SiO2 glass fibers reinforced cement was greater than those of E and A. The chemical durability of the fibers in alkaline solutions increased with ZrO2 content. The weight loss due to the corrosion by 2N-NaOH solutions at $25^{\circ}C$ for 160 hours was about 0.31$\times$10-2 mg/dm2 for the 20ZrO2-80SiO2 glass fibers, which was superior to that of Vycor glass.

• Journal of the Korean institute of surface engineering
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• v.47 no.6
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• pp.354-361
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• 2014

In order to utilize silicon carbide (SiC) as an inner part of fluidized bed reactor (FBR) for manufacturing poly-silicon, we have carried out the thermodynamic calculation on the overall reactions including poly-silicon synthesis and compatibility of SiC with FBR process. The resources of silicon included $SiH_4(MS)$, $SiHCl_3(TCS)$ and $SiCl_4(STC)$ and the thermodynamic yield of the FBR with MS, TCS and STC were compared each other with variable range of temperature, pressure and hydrogen to silicon ratio. The silicon yield of MS, TCS and STC were 100%, 28% and 4%, respectively, throughout the conventional FBR conditions. Silicon carbide having high hardness and strength showed strong resistance to granule collisions during the FBR process using a lab-scale reactor. And it also showed quite good compatibility with the typical FBR processes of MS and TCS resources.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.370-378
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• 2000

The composite restorative resins have their insufficient resistance to wear. The subsurface degradation within the restoration is considered to be associated with wear. The aim of this study was to evaluate the resistance to degradation of six commercial composite resins in an alkaline solution. The brands studied were Clearfil APX(Kuraray), Heliomolar(Vivadent), Surefil(Dentsply), TPH(Dentsply), Tetric Ceram(Vivadent), and Z100(3M). Preweighed discs of each brand were exposed 0.1N NaOH solution at $60^{\circ}C$. After 14 days they were removed, neutralized with HCL, washed with water and dried to constant mass at $60^{\circ}C$. Resistance to degradation was evaluated on the basis of the following parameters: (a) mass loss(%) - determined from pre-and post-exposure specimen weights; (b) Si loss (ppm)-obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth$({\mu}m)$ - measured microscopically (SEM) from polished circular sections of exposed specimens. The results were as follows: 1. The mass loss was in descending order by Z100, TC H, S, CL, TPH and in the range of $0.45\sim3.64%$ 2. The degradation layer depth was in descending order by H, Z100, S, TC, TPH, CL and in the range of $10.85\sim73.38{\mu}m$ 3. For the Si concentration, Z100 was the highest of all 4. The highly significant correlation(r=0.81, p<0.05) was observed between mass loss and degradation depth. 5. Under scanning electronmicroscopy, the degradation of connection between resin matrix and fillers was observed 2 weeks after soaking in NaOH solution.

• Journal of Integrative Natural Science
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• v.2 no.4
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• pp.289-292
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• 2009

Perchlorosilanes are useful precursors for the synthesis of hydrosilanes for the fabrication of electronic devices such as silicon thin-film transistors and silicon nanoparticles. For this solution process, requirements of precursors applicable to solution process are relatively low volatile and soluble in common organic solvents. In this work, the decaphenylcyclopentasilane has been obtained from the reaction of the lithium wire and dichlorodiphenylsilane. The reaction of decaphenylcyclopentasilane with lewis acid catalyst, HCl/$AlCl_3$, gives the perchlorocyclopentasilane. Decaphenylcyclopentasilane exhibits an unusual optical property. Its optical property was characterized by UV-vis and fluorescence spectroscopy. Absorption wavelength maxima for the decaphenylcyclopentasilane was 272 nm. Decaphenylcyclopentasilane displayed an emission band at 741 nm with excitation wavelength of 272 nm.

• Applied Chemistry for Engineering
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• v.26 no.5
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• pp.543-548
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• 2015

Si/C/CNF composites as anode materials for lithium-ion batteries were examined to improve the capacity and cycle performance. Si/C/CNF composites were prepared by the fabrication process including the synthesis and magnesiothermic reduction of SBA-15 to obtain Si/MgO by ball milling and the carbonization of phenol resin with CNF and HCl etching. Prepared Si/C/CNF composites were then analysed by BET, XRD, FE-SEM and TGA. Among SBA-15 samples synthesized at reaction temperatures between 50 and $70^{\circ}C$, the SBA-15 at $60^{\circ}C$ showed the largest specific surface area. Also the electrochemical performances of Si/C/CNF composites as an anode electrode were investigated by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of LiPF6 dissolved in mixed organic solvents (EC : DMC : EMC = 1 : 1 : 1 vol%). The coin cell using Si/C/CNF composites (Si : CNF = 97 : 3 in weight) showed better capacity (1,947 mAh/g) than that of other composition coin cells. The capacity retention ratio decreased from 84% (Si : CNF = 97 : 3 in weight) to 77% (Si : CNF = 89 : 11 in weight). It was found that the Si/C/CNF composite electrode shows an improved cycling performance and electric conductivity.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.3
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• pp.530-539
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• 2003

The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. The brands studied were Charisma, Filtek P 60, Palpique Estelite, and Spectrum. Preweighed discs of each brand were exposed to 0.1N NaOH solution at $60^{\circ}C$. After 2 weeks they were removed, neutralized with HCl, washed with water and dried. Resistance to degradation was evaluated on the basis of following parameters: (a) mass loss(%) - determined from pre-and post-exposed specimen weights; (b) Si loss(ppm) - obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation depth(${\mu}m$) - measured SEM and CLSM from polished circular sections of exposed specimens. The results were as follows: 1. The sequence of mass loss was in descending order by Palpique Estelite, Filtek P 60, Charisma, and Spectrum. 2. The sequence of the degree of degradation layer depth was in descending order by Filtek P 60, Charisma, Palpique Estelita, and Spectrum. 3. The sequence of the Si loss was in descending order by Chrisma, Spectrum, Palpique Estelite, and Filtek P 60. 4. The correlation coefficient between mass loss and degradation layer depth was relatively high(r=0.704, p<0.05). 5. When observed with SEM, destruction of bonding was observed between resin matrix and filler. 6. When observed with CLSM, degradation layer depth of composite resin surface was observed.