• 한국결정성장학회지
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• 제9권2호
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• pp.191-196
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• 1999

수열합성법을 이용한 $\alpha$-$SiO_2$ 단결정 분말 제조시 교반의 추가와 승온속도의 변화가 입자의 결정성, 입도분포 및 평균입경에 미치는 영향을 조사하였다. KOH를 광화제로 사용하였으며, $350^{\circ}C$에서 3시간 동안 반응을 시켜 평균입자 크기가 1~3.2$\mu\textrm{m}$인 결정 분말을 제조하였다. 실험결과 반응초기부터 교반을 한 경우에는 교반속도가 증가함에 따라 평균입경이 감소했으나, 결정성은 나빠지다가 150r/min 이상에서는 다시 좋아졌다. 또한 반응 도중에 교반을 추가하면 반응초기부터 교반을 한 경우보다 입자의 크기가 커졌다. 그러나 교반속도를 일정하게 한 후 승온속도를 느리게 하면 입자의 크기가 작아졌다.

• The Korean Journal of Ceramics
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• 제2권4호
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• pp.251-256
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• 1996

Effect of mixed grinding with a planetary ball mill of starting materials before heat treatment on the crystal structure and superconduction properties in the YBaCu composite oxide was studied. The size reduction of powders too place in the early stage of grinding, followed by aggregation of the resultant fine particles. The uniformity of the composition in the mixture was improved with grinding, which later decreased in the crystal grain size and well distribution of twin phase in the sintered bodies. The critical current density of the sintered bodies obtained from the mixture ground for 60 minutes showed the maximum value about 150 A/$\textrm{cm}^2$, while critical temperatures were around 90K and were independent of the grinding time.

• 한국응용과학기술학회지
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• 제26권4호
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• pp.385-393
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• 2009

Different types magnesium hydroxide groups have been obtained using the hydrothermal precipitation technique from magnesium sulfate and calcium carbonate solution. The Mg atom coordinated around O atom of ${SO_4}^{2-}$ in another layer to form a multi-layer structure crystal. The influence of synthesis parameters on the morphological characteristics and size of magnesium hydroxide groups precipitated in aqueous were investigated such as different of additive and pH. Magnesium hydroxide groups were decomposed gradually and converted finally to MgO particles after heated in air temperature up to $1050^{\circ}C$. The particle size and it's distribution morphology, crystal phase and thermal behavior of the samples were characterized through XRD, SEM, EDS, and TG/DTA.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.684-685
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• 2006

In the present study, the powder metallurgical fabrication of $Bi_{0.4}Te_3Sb_{1.6}$ thermoelectric materials has been studied with specific interest to control the microstructure by the mechanical grinding process. The $Bi_{0.4}Te_3Sb_{1.6}$ thermoelectric powders with a various particle size distribution were prepared by the combination of the mechanical milling and blending processes. The specific electric resistivity of the $Bi_{0.4}Te_3Sb_{1.6}$ sintered bodies mainly depended on the orientation of the crystal structure rather than the particle size of the raw powders.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 2000년도 Proceedings of 2000 International Nano Crystals/Ceramics Forum and International Symposium on Intermaterials
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• pp.127-142
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• 2000

The charged cluster model states that chemical vapor deposition (CVD) begins with gas phase nucleation of charged clusters followed by cluster deposition on a substrate surface to form a thin film. A two-chambered CVD system, separated by a 1-mm orifice, was used to study gold deposition by thermal evaporation in order to determine if the CCM applies in this case. At a filament temperature of 1523 and 1773 K, the presence of nano-meter sized gold clusters was found to be positive and the cluster size and size distribution increased with increasing temperature. Small clusters were found to be amorphous and they combined with clusters already deposited on a substrate surface to form larger amorphous clusters on the surface. This work revealed that gold thin films deposited on a mica surface are the result of the sticking of 4-10 nm clusters. The topography of these films was similar to those reported previously under similar conditions.

• 반도체디스플레이기술학회지
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• 제6권1호
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• pp.59-64
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• 2007

Non-contact transportation of a large-sized glass plate using air cushion for the vertical sputtering system of liquid crystal display (LCD) panel was considered. The objective of the study was to design an air pad unit which was composed of multiple injection and exhaust holes and mass flow supplying pipe. The gas was injected through multiple small holes to maintain the force for levitating glass plate. After hitting the plate, the air was vented through exhaust holes. Complex flow field and resulting pressure distribution on the glass surface were numerically studied to design the air injection pad. The exhaust hole size was varied to obtain evenly distributed pressure distribution at fixed diameter of the injection hole. Considering the force for levitating glass plate, the diameter of the exhaust hole of 30 to 40 times of the gas injection hole was recommended.

• Journal of Photoscience
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• 제3권3호
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• pp.159-161
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• 1996

Photosensitivity of silver halide emulsion depends on the properties of the microcrystals. Size, shape, grain distribution and chemical composition as well as the inner structure or the topography of the latent image specks affect on the optical properties and play an important role in the photographic process. In the present paper, a study on the sensitization of emulsion containing AgBrClI core/shell grains showed that for the given size, shape, halide content and crystal habit, under the optimal conditions the photosensitivity of the heterojunction type grains are different from that of the common regular grains. The optimal photosensitivity was obtained at the iodide content of 2.0 mo1%.

• 한국표면공학회지
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• 제28권2호
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• pp.92-100
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• 1995

To increase the capacity of positive electrode materials for matching the high capacity negative electrode materials in alkaline rechargeable batteries, high-density nickel hydroxide powders were made through a continuous process from nickel sulfate reacted with ammonia and sodium hydroxidc. The effect of operating conditions on structure, shape, size distribution, apparent density and tap density of powders were investigated. Crystal structure of nickel hydroxide powder was hcp according to Bravais Lattice. The increase of mean residence time promoted the growth of (101) plane. The shape of powder was nearly spherical. Their size was in the range of $2~50\mu\textrm{m}$. The size distribution of the powders prepared was narrower than that of commercially obtained nickel hydroxide. Apparent density and tap density were 1.6~1.7g/cc and 2.0~2.1g/cc, respectively.

• 한국전기전자재료학회논문지
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• 제37권4호
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• pp.412-419
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• 2024

Mn-doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_2/3Nb_1/3)O₃-PbTiO₃ (Mn:PIN-PMN-PT) single crystals, which exhibit improved phase transition temperatures and coercive field properties compared to Pb(In_1/2Nb_1/2)O₃-Pb(Mg_2/3Nb_1/3)O₃-PbTiO₃ (PIN-PMN-PT) single crystals, are expected to be utilized in high-power acoustic transducers. Bridgeman method, growing single crystals along the axial direction from melt, is most widely used method for single crystal growth with large size and high quality. However, single crystal boules grown by the Bridgeman method demonstrate a PT compositional variation, giving rise a distribution of crystal structure and material properties along the growing axis. To employ piezoelectric single crystals grown by the Bridgeman method for acoustic transducers, it is essential to investigate their overall property distribution. In this study, the compositional distribution and property variation of Mn:PIN-PMN-PT single crystals grown by the Bridgeman method was investigated. Measured compositional distribution of PT was from 29% to 32.5% in the Rhombohedral crystal region of the boule. Two types of specimen, [011]-poled Mn:PIN-PMN-29PT and Mn:PIN-PMN-32PT single crystals, were fabricated and tested to obtain full property variation at both ends of the Rhombohedral crystal region. The properties related to the 32 directional vibration mode and the properties related to high-power driving were measured to confirm the overall distribution of properties by composition.

• 한국세라믹학회지
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• 제31권10호
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• pp.1218-1230
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• 1994

In manufacturing process of porous glass-ceramics by the filler method, the sintering behaviour of crystallizable glass powder mixed with various salts was studied and also the effects of precipitated crystal phases on the properties of porous glass-ceramics were investigated. Fine-grained crystallizable glass powder was homogeneously mixed with various slat having grain size 100~200 ${\mu}{\textrm}{m}$ and sintered for densification. After washing out the inorganic salt with distilled water, the porous sintered body was heat treated additionly for crystallization. The MgO-Al2O3-SiO2 base glass was used as crystallizable glass powder and the water soluble salts such as K2SO4 and MgSO4 were used as filler. When K2SO4 was used, leucite crystal phase was formed as a result of the ion exchange and porous glass-ceramics which exhibit high temperature resistance and high thermal expansion coefficient of 17$\times$10-6/$^{\circ}C$ could be obtained. On the contrary, when MgSO4 was used, only slight ion exchange is observed and $\mu$-cordierite and $\alpha$-cordierite crystal phases were formed and porous glass-ceramics which exhibit low thermal expansion coefficient schedule were determined with the results of DTA curves, thermal shrinkage curves and XRD patterns analysis. From DTA curves and thermal shrinkage curves, it was found that the sintering densification have been completed at the temperature range of exothermic peak for crystallization. The pore size distributions and pore diameters were measured by mercury porosimeter. The pore diameter of porous glass-ceramics was 10~15 ${\mu}{\textrm}{m}$ when 100~200${\mu}{\textrm}{m}$ grain size of K2SO4 was used and it was 25~30 ${\mu}{\textrm}{m}$ when the same grain size of MgSO4 was used. The porous glass-ceramics K2SO4 used shows bimodal pore size distribution and its porous skeleton structure was ascertained by SEM observation.