• 한국분말재료학회지
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• 제22권1호
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• pp.46-51
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• 2015

A precipitation behavior of nano-oxide particle in Fe-$5Y_2O_3$ alloy powders is studied. The mechanically alloyed Fe-$5Y_2O_3$ powders are pressed at $750^{\circ}C$ for 1h, $850^{\circ}C$ for 1h and $1150^{\circ}C$ for 1h, respectively. The results of Xray diffraction pattern analysis indicate that the $Y_2O_3$ diffraction peak disappear after mechanically alloying process, but $Y_2O_3$ and $YFe_2O_4$ complex oxide precipitates peak are observed in the powders pressed at $1150^{\circ}C$. The differential scanning calorimetry study results reveal that the formation of precipitates occur at around $1054^{\circ}C$. Based on the transmission electron microscopy analysis result, the oxide particles with a composition of Y-Fe-O are found in the Fe-$5Y_2O_3$ alloy powders pressed at 1150oC. It is thus conclude that the mechanically alloyed Fe-$5Y_2O_3$ powders have no precipitates and the oxide particles in the powders are formed by a high temperature heat-treatment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
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• pp.55-61
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• 2002

Ultra-fine particles of $SnO_{2}$ was synthersized by the sol-gel powder processing using tin(II) chloride dihydrate$(SnCl_{2}{\cdot}2H_{2}O)$ and ethanol$(C_{2}H_{5}OH)$ as raw materials. Gel powders can be obtained by drying of sol at $120^{\circ}C$ after aging 72hrs and 168hrs. The amount of $SnO_{2}$ phase was increased with temperature because of the evaporation of volatile components, and the creation of $SnO_{2}$ phase was almost done by the heat treatment at $700^{\circ}C/30min$ The grain sizes after firing are about 20-30nm, and it showed the narrow distribution of grain size. The specimens to measure electrical properties were fabricated by the thick film screen printing technique on the alumina substrates. The conductance of $SnO_{2}$ was increased with temperature up to $380^{\circ}C$ by the typical conduction mechanism of semiconducting ceramics. There was a region of constant conductance between about $200^{\circ}C$ and $380^{\circ}C$ due to the increment of electron concentration with temperature and the annihilation of conduction carriers by the absorption and electron trapped-ionization of oxygen on the surface of $SnO_{2}$, It was finally showed the intrinsic behaviors above $450^{\circ}C$. The sensing properties of response time, recovery, and sensitivity of CO were improved with aging time.

• 한국결정성장학회지
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• 제21권5호
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• pp.214-217
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• 2011

Fresnoite 결정화 유리는 최근 비선형 광학특성으로 인하여 널리 연구되어 지고 있다. 그러나, 이전 연구 결과를 통하여 투명결정화 유리의 화학 조성으로는 정량적으로 Fresnoite 구조에 유사한 조성을 조절하는 것에 한계가 있음을 확인 할 수 있다. 본 연구에서는 $K_2O-TiO_2-SiO_2$ glass의 제조한 후, 제조된 유리를 $Sr(NO_3)_2$ 용융염에 담지하여 모유리의 표면에 Fresnoite 결정을 형성시키는 방법으로 투명결정화 유리를 제조하고, 이 때 Sr 이온이 비선형광학효과에 미치는 영향을 살펴보았다. XRD를 통하여 담지 시간에 따른 결정상 변화와 열처리를 통한 결정상 변화를 관찰하였으며, FE-SEM을 사용하여 생성된 결정의 미세구조와 Nd : YAG laser를 사용하여 2차비선형특성의 유무를 관찰하였다.

• 한국세라믹학회지
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• 제39권10호
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• pp.1001-1006
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• 2002

은이 피복된 Bi(2223) 단심 초전도 선재에 절연층으로 $SrZrO_3$ 피막을 졸-겔과 딥-코팅법으로 제조하여 $SrZrO_3$ 코팅층과 초전도 선재간 접착력 특성을 조사하였다. 실험인자로는 출발원료의 몰비, 유기화합물 첨가량, 건조온도 및 시간, 열처리 온도 및 시간이었으며 다구찌법의 망대특성과 $L_18(2^1{\times}3^7)$ 직교배열표를 이용하여 코팅층의 최적조건인 인자와 수준 조합의 최적화를 접착강도를 측정하여 분석하였다. 최적의 접착 특성을 가진 코팅조건은 Sr/Zr의 몰비가 0.3/0.7, 유기화합물 첨가량이 5wt%, 건조온도 및 시간은 160${\circ}C$ 10분, 열처리 온도 및 시간은 500${\circ}C$ 20분이었다. 분산분석 결과, 유의수준이 ${\alpha}$=0.1인 통계적으로 90% 신뢰공정이었다.

• 대한치과보철학회지
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• 제26권1호
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• pp.51-61
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• 1988

The recently introduced castable glass ceramics incorporate properties characteristic of natural teeth and they are regarded as an ideal material to restore lost tooth structure. The purpose of this study was to compare the marginal fit of castable ceramic crown with that of the metal-ceramic crown in the process of heat treatment. Two master dies for castable ceramic crowns and metal-ceramic crowns were fabricated from being cast with the base metal. Each master die was duplicated with addition silicone and hard stone. Ten castable ceramic crowns were made on each hard stone die and their marginal openings were measured three times first, after casting; second, after ceramming; third, after shading. The other ten metal-ceramic crowns were made on each hard stone die and their marginal openings were measured three times : first, after casting; second, after degassing; third, after porcelain veneering. Each crown was seated on its master die with the constant force delivered by loading jig. And then, marginal openings were measured on four locations by optical projector at X50 magnification. The results were as follows: 1. The mean marginal openings of castable ceramic crowns were $31.1{\pm}12.7{\mu}m$ after casting; $44.6{\pm}12.8{\mu}m$ after ceramming; $51.2{\pm}16.8{\mu}m$ after shading. 2. The mean marginal openings of the metal-ceramic crowns were $26.2{\pm}13.8{\mu}m$ after casting; $29.8{\pm}10.3{\mu}m$ after degassing; $38.0{\pm}14.5{\mu}m$ after porcelain veneering. 3. There was significant increase in the marginal opening of castable ceramic crowns after ceramming, while metal-ceramic crowns sho(wed significant increase after porcelain veneering (p<0.05). 4. Marginal fit of metal-ceramic crown was better than that of castable ceramic crown (p<0.01).

• Asian-Australasian Journal of Animal Sciences
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• 제26권11호
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• pp.1622-1629
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• 2013

The objective of this study was to develop a new method to separate phosvitin from egg yolk without using organic solvents. Phosvitin was extracted from yolk granules using 10% NaCl or 10% $(NH_4)_2SO_4$ (final concentration) and then treated with heat to precipitate the lipoproteins from the extracted solution. The optimal pH for the phosvitin extraction from yolk granules was determined, and the iron-binding ability of the extracted phosvitin (final product) was tested. Adding 10% $(NH_4)_2SO_4$ disrupted the granules, and the subsequent thermal treatment at $90^{\circ}C$ for 1 h precipitated low density and high density lipoproteins, which enabled separation of phosvitin by centrifugation. The phosvitin concentration in the extract was significantly higher when the pH of the solution was adjusted to pH ${\geq}9$. The purity and recovery rate of phosvitin at the end of the separation process were approximately 78% and 56%, respectively. The separated phosvitin was confirmed to have ferrous and ferric iron binding ability. The advantages of this new method compared with the traditional methods include no organic solvents and high-priced equipment are needed for the separation. Also, this method is more environment and consumer friendly than that of the traditional methods.

• 한국공작기계학회논문집
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• 제14권2호
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• pp.33-41
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• 2005

ZnO epilayer was synthesized by the pulsed laser deposition(PLD) process on Al$_2$O$_3$ subsorte after irradiating the surface of ZnO sintered pellet by ArF(193nm) excimer laser. The epilayers of ZnO were achieved on sapphire(A1203) substrate at the 境mperature of 400$^{circ}$C. The crystalline structure of epilayer was investigated by the Photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of ZnO epilayer measure with Hall effect by van der Pauw mothod are $8.27\times$1016cm$^{-3}$ and 299 cm$^{2}$/V$\cdot$s at 293 K respectively, The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, E$_g$(T)= 3.3973 eV - ($2.69\times$ 10$^{-4}$ eV/K)T$^{2}$/(T + 463K). After the as-grown ZnO epilayer was annealed in Zn atmospheres, oxygen and vaccum the origin of point defects of ZnO atmospheres has been investigated by the photoluminescence(PL) at 10K. The native defects of V$_{Zn}$, V$_{O}$, Zn$_{int}$, and O$_{int}$ obtained by PL measurements were classified as a donor or acceptor type. In addition we concluded that the heat-treatment in the oxygen atmosphere converted ZnO thin films to an optical p-type. Also, we confirmed that vacuum in ZnO/Al$_2$O$_3$ did not firm the native defects because vacuum in ZnO thin films existed in the form of stable bonds.

• 한국작물학회지
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• 제47권6호
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• pp.475-478
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• 2002

보리의 산물처리 확대를 위한 기초자료를 제공하고자 미곡종합처리장을 이용한 보리 산물처리시 품질변화와 생력효과를 조사 분석한 결과는 다음과 같았다. 1. 정립율은 2.5-2.2mm의 비율이 가장 많았으며, 건조방식에 따른 차이는 없었다. 2. 경도는 건조방식에 따른 차이는 없었고, 색도는 산물건조와 관행인 천일건조와 차이는 없었다. 3. 흡수율은, 고형용출물, 퍼짐성 등의 취반특성은 건조방식에 따른 차이는 없었다. 4. 산물처리에 의하여 관행의 ha당 46시간에 비하여 21시간으로 54.3%의 생력효과가 있었고, 수확 후 관리는 54.3% 생력화되었다. 5. 산물처리로 수확 후 관리노력이 관행에 비하여 ha당 25시간이 절감되어 101,83원의 경영비 절감효과가 있었다.

• 한국염색가공학회지
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• 제29권4호
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• pp.231-238
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• 2017

There are many kinds of elements and processes for the development of high quality bedding products like fiber, high-temperature heat treatment, dyeing process, tenter drying with softening agent and multiple final finishing. Especially we examined the mechanical characteristic properties of fabrics according to different yarn types. The critical physical properties of the yarn consisting the pile knitted fabrics were obtained for the development of the hi-grade bedding items. The material property and the exhaustion behaviour of the developed pile knitted fabrics composing of different yarns were measured and observed. The physical properties of the developed fabric were evaluated through the material property analysis of the yarn, the physical nature of the pile knitted fabrics and the data of the exhaustion performance; tensile strength, tensile elongation, tearing strength, cross section of yarn types, dyeing properties etc. And then high-class of bedding items were knitted using the double raschel machine to make the pile knitted fabrics.

• Tribology and Lubricants
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• 제33권3호
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• pp.106-111
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• 2017

Sapphire is an anisotropic material with excellent physical and chemical properties and is used as a substrate material in various fields such as LED (light emitting diode), power semiconductor, superconductor, sensor, and optical devices. Sapphire is processed into the final substrate through multi-wire saw, double-side lapping, heat treatment, diamond mechanical polishing, and chemical mechanical polishing. Among these, chemical mechanical polishing is the key process that determines the final surface quality of the substrate. Recent studies have reported that the material removal characteristics during chemical mechanical polishing changes according to the crystal orientations, however, detailed analysis of this phenomenon has not reported. In this work, we carried out chemical mechanical polishing of C(0001), R($1{\bar{1}}02$), and A($11{\bar{2}}0$) substrates with different sapphire crystal planes, and analyzed the effect of crystal orientation on the material removal characteristics and their correlations. We measured the material removal rate and frictional force to determine the material removal phenomenon, and performed nano-indentation to evaluate the material characteristics before and after the reaction. Our findings show that the material removal rate and frictional force depend on the crystal orientation, and the chemical reaction between the sapphire substrate and the slurry accelerates the material removal rate during chemical mechanical polishing.