• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.65-66
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• 2000

Various fluoride films on a glass substrate were prepared and characterized to provide a seed layer for crystalline Si film growth. The XRD analysis on $CaF_2/glass$ illustrated (220) preferential orientation and showed lattice mismatch less than 5 % with Si. We achieved a fluoride film with breakdown electric field of 1.27 MV/cm, leakage current density about $10^{-6}$ $A/cm^2$, and relative dielectric constant less than 5.6. This paper demonstrates microcrystalline silicon $({\mu}c-Si)$ film growth by using a $CaF_2/glass$ substrate. The ${\mu}c-Si$ films exhibited crystallization in (111) and (220) planes, grain size of $700\;{\AA}$, crystalline volume fraction over 65 %, dark- and photo-conductivity ratio of 124, activation energy of 0.49 eV, and dark conductivity less than $4{\times}10^{-7}$ S/cm.

• 한국세라믹학회지
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• 제18권2호
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• pp.105-111
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• 1981

The iron precipitates were prepared by adding sodium carbonate solution to ferrous chloride and ferric chloride solutions to pH=9 and pH=4.5, respectively. The thermal reaction of the iron precipitates was investigated by means of TGA, DTA and X-ray diffraction. In the former the crystallization of $\alpha$-$Fe_2O_3$ begins at about 35$0^{\circ}C$, while in the latter at about 30$0^{\circ}C$, during the calclnation in air. In the iron precipitate from ferrous chloride solution, the activation energy for the crystallite-growth or $\alpha$-TEX>$Fe_2O_3$ in air is about 7.6$\times$104J/mole between 800 and 100$0^{\circ}C$. As the result of X-ray diffration for the reduction product of hematite, it was found that maghemite, magnetite and wustite are formed and that hematite is transformed to magnetite through maghemite.

• 마이크로전자및패키징학회지
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• 제12권2호
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• pp.161-166
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• 2005

Fresnoite($Ba_2TiSi_2O_8$)결정을 갖는 $xK_2O-(33.3-x)BaO-16.7TiO_2-50SiO_2(mole\%)$ 유리조성에서 BaO를 $K_2O$로 대체함에 따른 유리화, 열적특성 및 결정화 거풍에 관하여 관찰하였다. x(0$\le$x$\le$20)의 함량이 증가함에 따라 유리화가 용이하였으며, 유리 전이온도 및 결정화 온도가 저온부로 이동하였다. $Ba_2TiSi_2O_8$결정상의 생성을 XRD분석을 통하여 확인하였으며, x의 함량증가가 이질상의 생성과는 무관함을 보였다. 결정화 거동을 DTA를 이용한 비등온법에 의하여 조사하였으며, x의 함량증가에 따라 avrami 지수(n)가 $2.26 {\pm}0.1,\;2.03 {\pm}0.1,\;1.93{\pm}0.15$로, 활성화 에너지는 약 $279 {\pm}12kJ/mole,\;302{\pm}7kJ/ mole,\;319{\pm}1kJ/mole$ 로 변화하였으며, SEM분석결과 x의 함량 증가 시 결정의 방향성이 두드러짐이 관찰되었다.

• 한국세라믹학회지
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• 제20권4호
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• pp.333-339
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• 1983

Semiconducting glaxe of iron system for the recent use as high Voltage porcelain insulators often showed the tendancy of unstable thermal properties. Thus the development of frit including magnetite was studied to cover the defect. In the experimental process melted and quenched frits were ground pelletized and heat-treated at various temperatures in the range of 800-1 $300^{\circ}C$ for various soaking time within 4 hours and then crystallized specimens were obtained. The speciment were studied with optical and electron microscope DTA x-ray diffractometer and electrometer The results obtained were as follows : 1) The optimum condition for the crystal growth of magnetite in the frite was the heat-treatment of $1300^{\circ}C$ for 3hrs and in this case the range of crystal size was $10-11\mu\textrm{m}$ 2) The activation energy for the crystal growth of magnetite was 21.1 kcal/mole. 3) The heat-treament at $1, 250^{\circ}C$ and $1, 300^{\circ}C$ resulted in the good thermal stability and the range of surface resistivity was $3.5{\times}10^4-4.0{\times}10^7$, /TEX> $\Omega$/$cm^2$ which was adguate to semiconducting frit. 4) The conduction mechanism seems to be due to the electron mobility rather than ion mobility and the activa-tion energy for the conduction was 0.07-0.15eV/mole for the heat-treated specimes in the range of 1, 250-1, 300C

• 한국세라믹학회지
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• 제30권7호
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• pp.535-542
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• 1993

It was investigated in this study that a preparation method, activation energy, surface area, pore volume, pore size distribution and DTA analysis of the dry gel in process of producing monolithic porous gel in Li2O-Al2O3-TiO2-SiO2 system by the sol-gel technique using metal alkoxides. Activation energy for gellation according to the variation of water concentration and the kind of catalysts ranged from 10 to 20kcal/mole. Monolithic dry gels were prepared after drying at 9$0^{\circ}C$ when the amount of water for gellation was 4~8 times more than the stoichiometric amount, that was necessary for the full hydrolysis of the mixed metal alkoxide. The specific surface area, the pore volume, the average pore radius of the dried gel at 18$0^{\circ}C$ according to the various kinds of catalyst were about 348~734$m^2$/g, 0.35~0.70ml/g and 10~35$\AA$, respectively. It showed that the dry gels were porous body. As a result ofthe analysis of DTA, it was confirmed that the exothermaic peaks at 715$^{\circ}C$ and 77$0^{\circ}C$ was clue to the crystallization of dried gel.

• 한국세라믹학회지
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• 제25권5호
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• pp.541-551
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• 1988

The purpose of this investigation was to prepare multicomponent monolithic Li-Al-Si gels of composition(mol%) 16.67 Li2O-16.67 Al2O3-66.67 SiO2 and to convert the gels to monolithic glass-ceramic at low temperature without melting. The hydrolysis, DTA, TGA, TMA, SEM, pore distribution, density and the activation energy for crystallization of the glass-ceramic formation with rawmaterials of which tetraethl orhosilicate of networkforming cation(Si) is partially hydrolyzed, aluminum isoproxide and lithium methoxide prepared by Li-metal react with methanol were studied. The results were as follows : 1) Monolithic gels which were added with additional water, resulting in a total water content 2.5 to 3.0 times the stoichiometric amount required to fully hydrolyze the alkoxides. 2) Specimens were dried to form crylinders 60mm in length and 40mm in diameter in about 800 hrs at 5$0^{\circ}C$. 3) $\beta$-eucryptite crystals and $\beta$-spodumene crystals were detected in samples heated above 75$0^{\circ}C$. 4) Within the temperature and range of 25-50$0^{\circ}C$ and 1,00$0^{\circ}C$ the thermal expansion coefficient for crystallized samples were shown as 2.6-5.7$\times$10-7/$^{\circ}C$ and 7.4-12.5$\times$10-7/$^{\circ}C$, respectively. 5) The activation energy for the crystal growth was 11.01kcal/mol at 794$^{\circ}C$ to 85$0^{\circ}C$.

• 한국세라믹학회지
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• 제32권4호
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• pp.507-515
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• 1995

The monolithic dry gels of the Li2O-Al2O3-TiO2-SiO2 system were prepared by the sol-gel technique using metal alkoxides as starting materials to obtain monolithic glass-ceramics at low temperature without melting. Activation energy for the crystal growth of the gel with 6.05% TiO2, nucleating ageng, for the preparation of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was 101.14kcal/mol. As a result of the analysis of DTA & XRD, it was confirmed that the crytallization of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was the most efficient when 6.05% TiO2, nucleating agent, was added. $\beta$-eucryptite solid solution crystals and $\beta$-spodumene solid solution crystals were detected in the sample heat treated above 85$0^{\circ}C$. The sintered gel heat treated at 85$0^{\circ}C$ had the specific surface area of 185$m^2$/g, the pore volume of 0.19cc/g and the average pore radius of 20.8$\AA$. This shows that the sintered gel is also comparatively porous material. In temperature range of 25~85$0^{\circ}C$ thermal expansion coefficient of the specimen which was crystallized for 10hrs at 85$0^{\circ}C$ was 6.7$\times$10-7/$^{\circ}C$, which indicated that the crystallized specimen was turned out to be the glass-ceramic with low thermal expansion.

• 한국재료학회지
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• 제27권5호
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• pp.281-288
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• 2017

In this study, Fe-Ni slag, converter slag and dephosphorization slag generated from the steel industry, and fly ash or bottom ash from a power plant, were mixed at an appropriate mixing ratio and melted in a melting furnace in a mass-production process for glass ceramics. Then, glass-ceramic products, having a basalt composition with $SiO_2$, $Al_2O_3$, CaO, MgO, and $Fe_2O_3$ components, were fabricated through casting and heat treatment process. Comparison was made of the samples before and after the modification of the process conditions. Glass-ceramic samples before and after the process modification were similar in chemical composition, but $Al_2O_3$ and $Na_2O$ contents were slightly higher in the samples before the modification. Before and after the process modification, it was confirmed that the sample had a melting temperature below $1250^{\circ}C$, and that pyroxene and diopside are the primary phases of the product. The crystallization temperature in the sample after modification was found to be higher than that in the sample before modification. The activation energy for crystallization was evaluated and found to be 467 kJ/mol for the sample before the process modification, and 337 kJ/mol for the sample after the process modification. The degree of crystallinity was evaluated and found to be 82 % before the process change and 87 % after the process change. Mechanical properties such as compressive strength and bending strength were evaluated and found to be excellent for the sample after process modification. In conclusion, the samples after the process modification were evaluated and found to have superior characteristics compared to those before the modification.

• 한국분말재료학회지
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• 제16권5호
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• pp.363-369
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• 2009

The amorphization process and the thermal properties of amorphous Ti$_{40}$Cu$_{40}$Ni$_{10}$Al$_{10}$ powder during milling by mechanical alloying were examined by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The chemical composition of the samples was examined by an energy dispersive X-ray spectrometry (EDX) facility attached to the scanning electron microscope (SEM). The as-milled powders showed a broad peak (2$\theta$ = 42.4$^{\circ}$) with crystalline size of about 5.0 nm in the XRD patterns. The entire milling process could be divided into three different stages: agglomeration (0 < t$_m$ $\leq$ 3 h), disintegration (3 h < t$_m$ $\leq$ 20 h), and homogenization (20 h < t$_m$ $\leq$ 40 h) (t$_m$: milling time). In the DSC experiment, the peak temperature T$_p$ and crystallization temperature T$_x$ were 466.9$^{\circ}C$ and 444.3$^{\circ}C$, respectively, and the values of T$_p$, and T$_x$ increased with a heating rate (HR). The activation energies of crystallization for the as-milled powder was 291.5 kJ/mol for T$_p$.

• 한국재료학회지
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• 제21권5호
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• pp.277-282
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• 2011

Negative temperature coefficient (NTC) materials have been widely studied for industrial applications, such as sensors and temperature compensation devices. NTC thermistor thick films of $Ni_{1+x}Mn_{2-x}O_{4+{\delta}}$ (x = 0.05, 0, -0.05) were fabricated on a glass substrate using the aerosol deposition method at room temperature. Resistance verse temperature (R-T) characteristics of the as-deposited films showed that the B constant ranged from 3900 to 4200 K between $25^{\circ}C$ and $85^{\circ}C$ without heat treatment. When the film was annealed at $600^{\circ}C$ 1h, the resistivity of the film gradually decreased due to crystallization and grain growth. The resistivity and the activation energy of films annealed at $600^{\circ}C$ for 1 h were 5.203, 5.95, and 4.772 $K{\Omega}{\cdot}cm$ and 351, 326, and 299 meV for $Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$, $NiMn_2O_4$, and $Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$, respectively. The annealing process induced insulating $Mn_2O_3$ in the Ni deficient $Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$ composition resulting in large resistivity and activation energy. Meanwhile, excess Ni in $Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$ suppressed the abnormal grain growth and changed $Mn^{3+}$ to $Mn^{4+}$, giving lower resistivity and activation energy.