• Journal of Electrochemical Science and Technology
• /
• v.1 no.1
• /
• pp.63-68
• /
• 2010

The $Li_4Ti_5O_{12}$/AC composite was prepared by sol-gel process with ultrasonication. The prepared composite was characterized by SEM, XRD and TG analysis, and their electrochemical behaviors were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge test in 1M $LiBF_4$/PC electrolyte. From the results, the $Li_4Ti_5O_{12}$ particles coated on AC surface had an average particle size of 100 nm and showed spinel-framework structure. When the potential range of the $Li_4Ti_5O_{12}$/AC composite was extended from 0.1 to 2.5 V, redox peaks and electric double layer property were revealed. The initial discharge capacity of $Li_4Ti_5O_{12}$/AC composite was 218 mAh $g^{-1}$ at 1 C. The enhancement of discharge capacity was attributed to electric double layer of added activated carbon.

• Proceedings of the KIEE Conference
• /
• 1998.07g
• /
• pp.2501-2503
• /
• 1998

In this paper, the silicon-nitride membrane structure for IR sensor was fabricated through the etching and the direct bonding. The PTO layer as a IR detection layer was deposited on the membrane and its characteristics were measured. The attack of PTO layer during the etching of silicon wafer as well as the thermal isolation of the IR detection layer can be solved through the method of bonding/etching of silicon wafer. Because the PTO layer of c-axial orientation raised thermal polarization without polling, the more integration capability can be achieved. The surface roughness of the membrane was measured by AFM, the micro voids and the non-contacted area were inspected by IR detector, and the bonding interface was observed by SEM. The polarization characteristics and the dielectric characteristics of the PTO layer were measured, too.

• Journal of IKEEE
• /
• v.22 no.4
• /
• pp.965-969
• /
• 2018

In the dye-sensitized solar cell, the semiconductor oxide plays an important role in the generation and transport of electrons, and thus extensive research on this has been continuously carried out. In this study, the characteristics of dye-sensitized solar cell are studied by fabricating semiconductor oxide doped with $V_2O_5$. The $TiO_2$ paste with $V_2O_5$ is prepared by the screen printing method of the sol - gel process and the surface and electrical properties are measured. The addition of $V_2O_5$ increased grain size and improved the open circuit voltage, short circuit current, charge factor and conversion efficiency of the dye sensitized solar cell.

• Journal of the Mineralogical Society of Korea
• /
• v.10 no.1
• /
• pp.18-32
• /
• 1997

Analysis of geological data, relating to occurrence and formation of diamonds as well as host rocks, inclined author to have different outlook on the diamond genesis and to establish a proposition on their formation at pneumatolytic-hydrothermal conditions near superficial Earth zones. Based on that theoretical foundations and experimental works, the first low-pressure and low-temperature hydrothermal diamond synthesis from water solution in pressure autoclave was executed. As a result, the natural diamond seed crystal grew bigger ad coupling of the synthetic diamond single-crystalline grains were obtained. SEM documentation proofs that parallely paragenetic crystallization of quartz and diamond, and nucleation of new octahedral diamond crystals brush take place on the seed crystal surface. Forecast of none times growth of diamond industrial application at 2000 and seventeen times at 2010 with reference to 1995, needs technology of large and pure single-crystals diamond synthesis. Growth of the stable and destressed diamond single-crystals in the pseudo-metastable diamond plot, may be realized with processes going through the long time and with participation of free radicals catalysts admixtures only. Sol-gel colloidal processes are an example of environment which form stable crystals in thermodynamically unstable conditions through a long time. Paper critically discusses a whole way of studies on the diamond synthesis, from high-pressure and high-temperature processes through chemical vapour deposition up to hydrothermal experiments.

• Proceedings of the SCSK Conference
• /
• 2003.09a
• /
• pp.178-191
• /
• 2003

OMC is essentialiy necessary compound in sun goods as organic UV protecting products. But the skin-trouble problem is raising because of skin penetration of OMC. In this study, non-capsulated pure OMC was compared with Organic-Inorganic-Nano-hybrid OMC for skin penetration force and SPF degree. Organic- Inorganic Nano-Hybrid OMC is OMC trapped in the pore of the mesoporous silica synthesized by the sol-gel method after OMC is nanoemulsified in the system of the hydrogenated Lecithin/ Ethanol/caprylic/capric triglyceride/OMC/water. OMC- nano- emulsion was obtained by a microfluidizing process at 1000bar and then micelle size in the nanoemulsion solution is 100-200nm range. Mesoporous silica nano-hybrid OMC was prepared by the process; surfactant was added in dissolved OMC-Nanoemulsion, then the rod Micelle was formed. OMC-nanoemulsion was capsulated in this rod Micelle and then silica precursor was added in the OMC-nanoemulsion solution. Through the hydrolysis reaction of the silica precursor, mesoporous silica concluding OMC-Nanocapsulation was obtained. The nano-hybrid surface of this OMC-Nanoemulsion-Inorganic system was treated with polyalkyl-silane compound. OMC-Mesoporous silica Nano-hybrids coated with polyalkyl-silane compound show the higher sun protecting factor (SPF Analyzer: INDEX 10-15) than pure OMC and could reduce a skin penetration of OMC. The physico-chemical properties of these nano-hybrids measured on the SPF index, partical size, strcture, specific surface area, pore size, morphology, UV absorption, rate of the OMC dissolution using SPF Analyzer, Laser light scattering system, XRD, BET, SEM, chroma Meter, HPLC, Image analyzer, microfluidizer, UV/VIS. spectrometer.

• Proceedings of the IEEK Conference
• /
• 2001.10a
• /
• pp.240-244
• /
• 2001

Recycling process involving mechanical, thermal, hydrometallurgical, and sol-gel step has been applied to recover cobalt and lithium from spent lithium ion batteries and to synthesize LiCoO$_2$from leach liquor as cathodic active materials. Electrode materials containing lithium and cobalt could be concentrated with 2-step thermal and mechanical treatment. Leaching behaviors of the lithium and cobalt in nitric acid media was investigated in terms of reaction variables. Hydrogen peroxide in 1 M HNO$_3$solution turned out to be an effective reducing agent by enhancing the leaching efficiency. O f many possible processes to produce LiCoO$_2$, the amorphous citrate precursor process (ACP) has been applied to synthesize powders with a large specific surface area and an exact stoichiometry. After leaching used LiCoO$_2$with nitric acid, the molar ratio of Li/Co in the leach liquor was adjusted at 1.1 by adding a fresh LiNO$_3$solution. Then, 1 M citric acid solution at a 100% stoichiometry was also added to prepare a gelatinous precursor. When the precursor was calcined at 95$0^{\circ}C$ for 24 hr, purely crystalline LiCoO$_2$was successfully obtained. The particle size and specific surface area of the resulting crystalline powders were 20 пm and 30 $\textrm{cm}^2$/g, respectively The LiCoO$_2$powder was proved to have good characteristics as cathode active materials in charge/discharge capacity and cyclic performance.

• Membrane Journal
• /
• v.4 no.3
• /
• pp.152-162
• /
• 1994

The photodegradation efficiency of formic acid on $TiO_2$ photocatalytic membranes was investigated. A new titania membrane reactors for purification of water combining microfiltration with photocatalytic degradation of organic compounds were developed. Titania membrane tubes(average pore size of $0.2\mu m$) were prepared by the slip casting, and porous thin films of $TiO_2$ were formed on the tube surface by the sol-gel process to increase the surface area, and consequently to increase photodegradation efficiency of organic compounds. The UV light with the wavelength of 365 nm was used as a light source for photocatalytic reactions. The photodegradation efficiency of the organic compounds was strongly dependent on the flux of the solution, the microstructure of the membrane (sol pH), and the amount of $O_2$ supplied. The effects of the primary oxidant such as $H_2O_2$ and dopants such as $Nb_2O_5$ on the photodegradation efficiency were also investigated. The results showed that more than 80% of formic acid could be degraded using membrane coated with a $TiO_2$ sol of pH 1.45. The photodegradation efficiency could be improved by about 20% when adding $H_2O_2$ in feed solution or doping $TiO_2$ membranes with $Fe_2O_3$.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.1
• /
• pp.83-91
• /
• 2014

In this study, we synthesized two different silica monoliths by using sol-gel, solvent exchange, surface modification, ambient pressure drying processes, and surfactant-based templating technique followed by calcination process. All of the prepared two silica monoliths showed crack-free appearance with fairly good transparency, and furthermore were confirmed to have extremely high porosity, specific surface area, and mean pore size below 30 nm. The silica aerogel sample exhibited finer and more homogeneous nano-sized pore structure due to spring back effect caused by surface modification, which resulted in better thermal insulation performance. Based on measured thermal conductivities and theoretical relationship, multi-layered glass window system in which silica monolith prepared in this study was inserted as a middle layer was revealed to have superior thermal insulation performance compared to conventional air-inserted glass window system.

• Korean Chemical Engineering Research
• /
• v.44 no.4
• /
• pp.399-403
• /
• 2006

There has been numerous reports for the synthesis of mesoporous $TiO_2$ thin films due to not only the high surface area and regular mesoscale pores but also wide band gap and photo activity. However, the synthesis has been restricted by the limited reproducibility mainly due to the extraordinarily fast hydrolysis and condensation rate of titania precursors. In this report, molar composition of reaction batch (HCl/Ti and Ti/P123) and exterior condition (humidity and temperature) during coating and anealing process. Thereafter, the mesoporous $TiO_2$ thin films were characterized by XRD and TEM

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.8
• /
• pp.469-473
• /
• 2017

We investigated the effect of different thin-film thicknesses (25, 30, and 40 nm) on the electrical performance of solution-processed indium-zinc-oxide (IZO) thin-film transistors (TFTs). The structural properties of the IZO thin films were investigated by atomic force microscopy (AFM). AFM images revealed that the IZO thin films with thicknesses of 25 and 40 nm exhibit an uneven distribution of grains, which deforms the thin film and degrades the performance of the IZO TFT. Further, the IZO thin film with a thickness of 30 nm exhibits a homogeneous and smooth surface with a low RMS roughness of 1.88 nm. The IZO TFTs with the 30-nm-thick IZO film exhibit excellent results, with a field-effect mobility of $3.0({\pm}0.2)cm^2/Vs$, high Ion/Ioff ratio of $1.1{\times}10^7$, threshold voltage of $0.4({\pm}0.1)V$, and subthreshold swing of $0.7({\pm}0.01)V/dec$. The optimization of oxide semiconductor thickness through analysis of the surface morphologies can thus contribute to the development of oxide TFT manufacturing technology.