• 자원리싸이클링
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• 제13권6호
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• pp.16-25
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• 2004

인듐 성분을 포함하는 원료용액을 분무열분해 시켜서 평균 입자크기 100 nm 이하의 인듐 산화물 나노 분말을 제조하였으며, 용액의 농도, nozzle tip 크기 및 공기의 유입속도 변화에 따른 생성된 분말들의 특성 변화를 파악하였다. 본 연구는 폐 ITO로부터 나노 크기의 ITO 분말을 제조하기 위한 전 단계 연구로 수행되었다. 원료용액 내의 인듐 성분의 농도가 40 g/l로부터 350 g/l로 증가됨에 따라 생성된 분말의 평균 입자크기는 20~30 nm로부터 50~60 nm로 점점 증가하는 반면 입도분포는 더욱 불균일하게 나타나고 있었으며, XRD peak의 강도는 점점 증가하고 비표면적은 감소되었다. Nozzle tip의 크기가 1 mm로부터 5 mm로 증가함에 따라 분말들의 평균 입자크기는 40 nm 정도로부터 100 nm 정도까지 점점 증가하고 입도분포는 더욱 불균일하게 나타나고 있었으며, XRD peak 강도는 증가하는 반면 비표면적은 감소되었다. 반응로 내로 유입되는 공기의 압력이 0.1 kg/cm$^2$로부터 0.5 kg/cm$^2$로 증가되는 경우, 분말의 평균 입자크기는 90~100 nm로 현저한 변화를 나타내지 않았다. 반면 공기압력이 1 kg/cm$^2$ 및 3 kg/cm$^2$로 증가하는 경우에는 평균 입자크기가 50~60 nm 정도까지 감소하였으며, XRD peak 강도는 감소하고 비표면적은 증가되었다.

• 한국전기전자재료학회논문지
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• 제33권3호
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• pp.208-213
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• 2020

Four types of BaTiO₃ powders are prepared and successfully deposited on glass and Pt/Si substrates using the aerosol deposition process. Particles with sizes of 0.45 ㎛ and 0.3 ㎛ are selected as the starting powder, while those powders are treated using a different milling method. The jet-milled and ball-milled powders not only showed a smaller particle-size distribution, but compared with the non-milled powder, it also had a higher deposition rate using the uniformly generated aerosol. Although the films deposited using particles with size 0.45 ㎛ exhibited some craters on the surface, significantly flat film surfaces were obtained. However, particles with size 0.3 ㎛ create a slightly rough film surface, but the dielectric constant was greater than in the case involving particles with size 0.45 ㎛. Consequently, a suitably large particle size significantly influences the deposition rate and improvement in the surface roughness, and a uniform particle size distribution appears to contribute to an improved dielectric constant. Therefore, it is believed that the dielectric properties along with the growth characteristics can be enhanced by limiting particle size and shape.

• 한국세라믹학회지
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• 제35권10호
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• pp.1055-1060
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• 1998

고주파 저손실 재질로 사용되는 Mn-Zn ferrites의 제조공정 중 입도분포제어가 전자기적 물성에 미치는 효과에 관하여 연구하였다. 입도분포는 분쇄시간을 변화시켜 제어하였으며 철의 유입을 막기위하여 지르코니아볼을 사용하였다. 분쇄시간이 증가함에 따라 입자크기는 2.1 $\mu\textrm{m}$에서 1.0$\mu\textrm{m}$로 감소하였으며, 비표면적은 0.55에서 3.21m2/g으로 증가하였다. 비표면적 값이 증가할수록 소결체의 밀도는 증가하였으며, 높은 비표면적을 가진 분말의 경우 1300$^{\circ}C$ 이 상의 고온에서 소결할 때 불균일한 미세구조와 과대입성장이 발생하였으며, 전자기적 물성감소가 나타났다.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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• pp.87-89
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• 1997

The BaTiO$_3$ fine powder was prepared by hydrthermal method using titanium tetrahydoxide (Ti(OH)$_4$) and barium dihydroxide (Ba(OH)$_2$.8$H_2O$) as raw materials. The fine powder was obtained at temperatures as low as 160 to 185$^{\circ}C$. The properties of the BaTiO$_3$ powder were studied as a function of various parameters (reaction temperature, reaction time, Ba/Ti=ratio, etc). The average particle size of the BaTiO$_3$ increased with increasing reaction temperature. After hydrothermal treatment at 17$0^{\circ}C$ for 8 h, the average particle size of the BaTiO$_3$ powder was about 30 nm and the particle size distribution was narrow.

• 한국세라믹학회지
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• 제25권5호
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• pp.465-472
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• 1988

Alpha alumina powder with fine particle size and narrow particle size distribution was prepared by precipitation method using Al2(SO4)3.18H2O as a starting material. The alpha alumina powder was prepared by calcining aluminum hydroxide which was formed under various pH values. The sinterabilityof alpha alumina powder and the effect of MgO on the sinterability of alpha alumina powder were investigated. The sinterability of alpha alumina powder was the order of pH=10≒pH11>pH=7≒pH9, and alpha alumina obtained from boehmite which was prepared by precipitation method reached to 97.5% of theoretcal density by the pressureless sintering. The effect of MgO on volume shrinkage of alumina was very slight in the initial sintering stage but remarkable in the final sintering stage. It was also found that MgO controlled effectively the grain growth of alumina.

• The Korean Journal of Ceramics
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• 제3권2호
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• pp.116-123
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• 1997

A chemically stabilized $\beta$-cristobalite, which is stabilized by stuffing cations of $Ca^{2+}$ and $Al^{3+}$, was prepared by a solution-polymerization route employing Pechini resin or PVA solution as a polymeric carrier. The polymeric carrier affected the crystallization temperature, morphology of calicined powder, and particle size distribution. In case of the polyvinyl alcohol (PVA) solution process, a fine $\beta$-cristobalite powder with a narrow particle size distribution (average particle size : 0.3$\mu\textrm{m}$) and a BET specific surface area of 72 $\m^2$/g was prepared by an attrition-milling for 1 h after calcination at 110$0^{\circ}C$ for 1h. Wider particle size distribution and higher specific surface area were observed for the $\beta$-cristobalite powder derived from Pechini resin. The cubie(P1-to-tetraganalb) phase transformation in polynystalline $\beta$-cristobalite was induced at approximately 18$0^{\circ}C$. Like other materials showing transformation toughening, a critical size effect controlled the $\beta$-to-$\alpha$ transformation. Densifed cristobalite sample had some cracks in its internal texture after annealing. The cracks, occurred spontaneoulsy on cooling, were observed in the sample with an average grain sizes of 4.0 $\mu\textrm{m}$ or above. In case of the sintered cristobalite having a composition of CaO.$2Al_2O_3$.40SiO$_2$, small amount of amorphous phase and slow grain growth during annealing were observed. Shear stress-induced transformation was also observed in ground specimen. Cristobalite having a composition of CaO.2Al2O3.80SiO2 showed a more sensitive response to shear stress than the CaO.$2Al_2O_3$.40SiO$_2$ type cristobalite. Shear-induced transformation resulted in an increase of volume about 13% in $\alpha$-cristobalite phase on annealing for above 10 h in the case of the former composition.

• 한국분말재료학회지
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• 제27권4호
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• pp.325-332
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• 2020

In this study, the effects of kaolin addition on the properties of reticulated porous diatomite-kaolin composites are investigated. A reticulated porous diatomite-kaolin composite is prepared using the replica template method. The microstructure and pore characteristics of the reticulated porous diatomite-kaolin composites are analyzed by controlling the PPI value (45, 60, and 80 PPI) of the polyurethane foam (which are used as the polymer template), the ball-milling time (8 and 24 h), and the amount of kaolin (0-50 wt. %). The average pore size decreases as the amount of kaolin increases in the reticulated porous diatomite-kaolin composite. As the amount of kaolin increases, it can be determined that the amount of inter-connected pore channels is reduced because the plate-shaped kaolin particles connect the gaps between irregular diatomite particles. Consequently, a higher kaolin percentage affects the overall mechanical properties by improving the pore channel connectivity. The effect of kaolin addition on the basic properties of the reticulated porous diatomite-kaolin composite is further discussed with characterization data such as pore size distribution, scanning electron microscopy images, and compressive strength.

• 한국건설순환자원학회논문집
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• 제6권2호
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• pp.103-111
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• 2011

본 연구에서는 현재 시멘트 콘크리트 혼합재로서 널리 사용되고 있는 고로수쇄 슬래그와 애쉬의 페이스트 유동특성을 파악하였다. 그 방법으로 혼합재 단독을 사용한 페이스트의 유동특성을 파악하여, 아래와 같은 결론을 얻을 수 있었다. 혼합재 단독의 페이스트 유동특성을 시험하기 위하여, 3종류의 분쇄기를 사용하여 3가지 입도로 분쇄된 분말을 제조하였다. 이 분말을 Rosin-Rammler 분포식을 사용하여 얻은 계수 n 값과 De 값을 유동특성과 비교 분석한 결과에서, 일반적으로 같은 입경 크기 일 때 Ash 분말이 Slag 분말보다 소성점도 및 항복응력이 높았으며, 또한 동일 n 값에서 Ash 분말이 Slag 분말 보다 비교적 높은 소성점도와 항복응력을 나타내었으나, 입도분포 폭의 변화에는 Slag 분말이 Ash 분말 보다 민감한 유동특성의 변화 경향을 나타내었다.

• 한국세라믹학회지
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• 제34권8호
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• pp.854-860
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• 1997

The tribological property of ceramics is very important for use in seal rings, pump parts, thread guides and mechanical seal, etc. In the present study, which RBSC/graphite composites were manufactured by adding graphite powders with different particle sizes to mixtures of SiC powder, metallic silicon, carbon black and alumina, effects on the tribological property of each RBSC/graphite composite was investigated in accordance with the particle size of the added graphite powder. The water absorption, the bending strength and the resistance for the friction and wear were measured, and the crystalline phase and the microstructure were respectively examined by using XRD and SEM. In case that the particle size of the graphite powder was fine(2${\mu}{\textrm}{m}$), the formation of $\beta$-SiC was accelerated, thereby making the increase of the bending strength and the decrease of the water absorption, but no improvement for the tribological properties. Furthermore, in case that the particle size of the graphite powder was some large(88~149${\mu}{\textrm}{m}$), the formation of $\beta$-SiC was not accelerated, to thereby make the decrease of the bending strength and the increase of the water absorption, but the improvement for the tribological property of only the composite having the graphite powder of 20 vol%. In addition, in case that the particle size distribution of the graphite powder was large (under 53 ${\mu}{\textrm}{m}$), there was no improvement for every properties. However, the composites, which the graphite powder with the particle size of 53~88 ${\mu}{\textrm}{m}$ was added in 10~15 vol%, had the most increased resistance for the friction and wear which show the worn out amount of 0.4~0.6$\times$10-3 $\textrm{cm}^2$, and the value of the bending strength is 380~520 kg/$\textrm{cm}^2$.

• 한국세라믹학회지
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• 제47권2호
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• pp.183-188
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• 2010

$Ce_{0.8}Gd_{0.2}O_{1.9}$(GDC20) powder was synthesized by milling of $CeO_2$ slurry and Gd oxalate precipitation. The mixture of $CeO_2$ powder and Gd precipitates calcined at $600^{\circ}C$ for 2 h showed the particle size distribution similar to that of $CeO_2$ powder, which had been milled during the synthesis process. Attrition milling of the calcined powder with an average particle size of $0.36\;{\mu}m$ for 2 h resulted in a decrease in the particle size to $0.24\;{\mu}m$. Although the milled powder consisted of small particles(<$1\;{\mu}m$), a small amount of fine platy $Gd_2O_3$ particles, which had been survived in the milling process, was observed. Sintering of the powder compacts for 4 h showed relative densities of 80.7% at $1300^{\circ}C$ and 97% at $1400^{\circ}C$, respectively. Densification was found to almost complete at $1500^{\circ}C$, resulting in a dense and homogeneous microstructure with a relative density of 99.5%.