• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.3
• /
• pp.122-129
• /
• 2017

For the production of a high-density ITO target, $In_2O_3$ powders with a small particle size and low agglomeration should be synthesized. The purpose of this study is to control the size and shape of the Indium hydroxide precursor which affects the properties of the $In_2O_3$ powder. As a starting raw material, Indium metal was dissolved in a Nitric acid ($HNO_3$) solution. The effect of concentration, pH, and temperature on the properties of Indium hydroxide was investigated using ammonium hydroxide as a precipitant. Crystallite size of each sample was analyzed by X-ray diffraction and the shape and the size of the powder was analyzed by transmission electron microscopy. As a result, the particle size of Indium hydroxide was increased with increase in the concentration of $In(NO_3)_3$ and the particle size and shape of the Indium hydroxide remained unchanged with increase in the pH of the solution. The particle size increased with increase in the precipitation temperature during precipitation.

• Resources Recycling
• /
• v.29 no.5
• /
• pp.28-37
• /
• 2020

In this study, the effect of precipitation temperature, ammonium chloride amount and addition method, vanadium and sodium hydroxide content of the solution on the precipitation of ammonium metavanadate were examined by using the sodium vanadate(NaVO₃) solution in alkali region as a starting material. As the pH of solution decreased, the addition amount of ammonium chloride and the vanadium content of the solution increased, the precipitation rate of ammonium metavanadate increased. In this research condition, the basic conditions for obtaining more than 90% of precipitation yield were 10,000mg/L of vanadium content, 2equivalents of ammonium chloride addition, room temperature, and 2 hours of precipitation time. The size of precipitated particles decreased with increasing precipitation rate. Especially when liquid ammonium chloride was injected into the solution, the precipitation rate was the slowest and the particle size of the precipitate was the largest. After the primary precipitation by adding ammonium chloride as a solid, the secondary precipitation was carried out by adding new reactants. At this time, the precipitation with added ammonium chloride solid was not affected by the precipitates present in the solution. However, when liquid ammonium chloride was added, new precipitate was deposited on the surface of the precipitate present in the solution, increasing its size. Due to the difference in ammonium metavanadate solubility to temperature, the precipitation temperature at the vanadium content of 10,000mg/L in the solution affected the precipitation rate of ammonium metavanadate and the precipitation temperature did not affect the precipitation rate at a high concentration of more than 30,000mg/L vanadium content in the solution.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.660-660
• /
• 2013

나노 구조를 가지는 무기물은 입자의 형상, 크기, 분산도, 다공성, 표면적 등에 따라 광학, 전기 및 물리적인 특성에 큰 영향을 준다. 특히 희토류 금속 중 가장 풍부한 원소인 Cerium의 산화물은 착색제, 자동차배기가스 정화촉매, 화학 공업 촉매, 유리 연마재, 반도체 장치, 자외선 흡착제, 발광재료 등 다양한 분야에서 활용이 되는 중요한 소재이다. 본 연구에서는 공통 이온효과를 이용하여 시간을 조절하여 Cerium hydroxide의 성장 과정을 연구 하였고, Ammonium chloride의 농도를 조절하여 수백 나노 미터에서 수 마이크로 미터까지 막대와 같은 Cerium hydroxide를 합성하였다. 이들 입자의 형상 및 물리화학적 특성을 FE-SEM, XRD, EDS, FT-IR 분석장비를 사용하여 확인하였다.

• Journal of Environmental Health Sciences
• /
• v.18 no.2
• /
• pp.52-56
• /
• 1992

The ability of chemicals, 10% sodium hypochlorite, 28% ammonium hydroxide, 5% sodium hydroxide, 5% sodium bicarbonate, 0.1% hydrochloric acid, 5% hydrogen peroxide, and 5% acetone, to destroy aflatoxins in laboratory waste water containing 3.26 ppb of B$_{1}$ 7.64 ppb of B$_{6}$3 ppb of G$_{1}$, and 11.39 ppb of G$_{2}$ with the total of 29.11 ppb was investigated. High performance liquid chromatograph (HPLC) was used for the separation and quantitation of aflatoxins. Treatment for 2 hours by the chemicals affected the destruction of aflatoxins and the most effective chemical was 10% sodium hypochlorite (p<0.05). Sodium hypochlorite concentrations more than 1% significantly reduced aflatoxin B$_{2}$, G$_{1}$, G$_{2}$ and total aflatoxins and more than 3% reduced B$_{1}$ (p<0.05). No further significant decreases were observed above the concentration of 5% for all 4 aflatoxins. Complete destruction of aflatoxins B$_{2}$, G_{1}$, and G$_{2}$ was achieved by 5% sodium hypochlorite at 48 hours and B$_{1}$ at 72 hours.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.11
• /
• pp.1205-1211
• /
• 2004

This study has investigated radiation degradation of chloroprene rubber in the presence of some fire retardant. Ammonium polyphosphate, aluminium trihydroxide, magnesium hydroxide, calcium carbonate and antimony trioxide were selected as flame retardant. Samples were irradiated using a Co$^{60}$ ${\gamma}$ -ray and ray up to 2000 kGy at a dose rate of 5 kGy/hr in the presence of air atmosphere at room temperature. After irradiation, samples were assessed fire retardancy with electrical properties and mechanical properties. Some considerations concerning the effects of the fire retardants added to chloroprene rubber on the radiation and thermal stability of chloroprene rubber are presented. From fire retardancy with electrical and mechanical property measurements, it was found that addition of magnesium hydroxide resulted in maximum fire retardant effect.

• Advances in materials Research
• /
• v.2 no.2
• /
• pp.99-109
• /
• 2013

In the present investigation, nanocomposite films with poly(methyl methacrylate) (PMMA) as a polymer matrix and barium titanate as a filler were prepared by solution casting method. Barium titanate nano particles were prepared using Ti(IV) triethanolaminato isopropoxide and hydrated barium hydroxide as precursors and tetra methyl ammonium hydroxide (TMAH) as a base. The nanocomposite films were characterized using XRD, FTIR, SEM and dielectric spectroscopy techniques. Dielectric measurements were performed in the frequency range 100 Hz-10 MHz. Dielectric constant of nanocomposites were found to depend on the frequency, the temperature and the filler fraction. Dissipation factors were also influenced by the frequency and the temperature but not much influenced by the filler fractions. The 10 wt% of BT-PMMA nanocomposite had the lowest dielectric constant of 3.58 and dielectric loss tangent of 0.024 at 1MHz and $25^{\circ}C$. The dielectric mixing model of Modified Lichtenecker showed the close fit to the experimental data.

• Journal of Sensor Science and Technology
• /
• v.30 no.1
• /
• pp.10-14
• /
• 2021

Wet etching is more economical than dry etching and provides a uniform etching depth regardless of wafer sizes. Typically, potassium hydroxide (KOH) and tetra-methyl-ammonium hydroxide (TMAH) solutions are widely used for the wet etching of silicon. However, there is a limit to the wet etching process when a material deposited on an unetched surface reacts with an etching solution. To solve this problem, in this study, an apparatus was designed and manufactured to physically block the inflow of etchants on the surface using a rubber O-ring. The proposed apparatus includes a heater and a temperature controller to maintain a constant temperature during etching, and the hydrostatic pressure of the etchant is considered for the thin film structure. A corrugation membrane with a diameter of 800 ㎛, thickness of 600 nm, and corrugation depth of 3 ㎛ with two corrugations was successfully fabricated using the prepared device.

• Journal of Microbiology and Biotechnology
• /
• v.11 no.2
• /
• pp.229-233
• /
• 2001

Trichoderma reesei Rut C-30 produced high levels of ${\beta}$-glucosidase, endo-${\beta}$-glucosidase, endo-${\beta}$-1,4-glucanase, and exo-${\beta}$-1,4-glucanase. In pilot-scale production (50-1 fermentor), productivity and yield of CMCase (carborymethyl cellulose) and FPase (filter paper activity) were 273 U/ml and 35 U/ml, and 162 FPU/l.h and 437 FPU/g, respectively. The fed-batch techniques were used to improve enzyme activities with constant cell concentration. The acidity was an important parameter and controlled at pH 3.9 and 5.0 by automatic addition of ammonium hydroxide. Cellulase powder was prepared by ammonium sulfate precipitation and its CMCase and FPase activities were 3,631 U/g and 407 U/g, respectively.

• Journal of the Korean institute of surface engineering
• /
• v.19 no.1
• /
• pp.13-19
• /
• 1986

Manganese in the Anode slime and the paste-positive material of waste-dry cell was recovered by leaching with the hydrochloric acid solution. The impurities (Zn, Fe, Pb), co-leached with manganese were removed from the leached solution prior to electrolysis by hydrometallurgical techniques such as the neutralization with ammonium hydroxide and cementation on manganese powder. The electrodeposition of manganese from the purified chloride solution with sodium selenate was performed. Cathode current efficiency was found to be affected significantly by the concentration of sodium selenate and ammonium chloride salt, bath temperate, current density and PH. The current efficiency of about 88.7% was obtained by electrolysis manganese chloride solution with sodium selenate (0.1/g) at 10$^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.416-417
• /
• 2005

In this study, we optimized the process of Si anisotropy etching by combing tetramethyl ammonium hydroxide (TMAH) etching process with ultrasonic wave technology. New ultrasonic TMAH etching apparatus was developed and it was used for fabricating a $20{\mu}m$ thick diaphragm for Si piezoresistive pressure sensors. Based on comparison study on etch rate and surface flatness, it was observed that the Si anisotropy etching methode with new ultrasonic TMAH etching apparatus (at 40 kHz/ 500 watt) was superior to conventional etching methods with TMAH or TMAH+ammonium persulfate(AP) solutions.