• Archives of Pharmacal Research
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• 제18권5호
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• pp.314-319
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• 1995

Antacid granules were prepared by agglomeration and powder method in high speed agitation type granulator. The copmositions of the test antacids were sodium bicarbonate nad magnesium carbonate nad a coating material was powder of polyvinylacetal diethyl-aminocacetate (AEA) and an additive material was talc powder. The dissolution characteristics of base from the antacid granules were investigated to evaluate neutralization capacity of hydrochloric profile of base and neutralization behavior, the following results were obtained : The prepared granules showed a pH-dependent dissolution pattern of a base. The dissolution profile of a base was varied with addition of talc powder as well as coating amount of AEA. The relationship between the ratio of dissolution retarded time for 20% and 10% AEA. The relationship between the ratio of dissolution retarded time for 20% AEA coated granules $\theta_{20}/\theta_{10}$ and the diameter reduction of the granules was explained by the rate process of neutralization of hydrochloric acid.

• 한국결정성장학회지
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• 제13권3호
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• pp.117-121
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• 2003

염화 니켈과 마그네슘 스테아린산 혼합 분말로부터 수소환원 공정에 의하여 니켈 분말을 제조하고 반응온도 및 마그네슘스테아린산의 첨가에 따른 분말의 특성을 검토하였다. 마그네슘 스테아린산을 함유한 경우 과도한 입자 성장의 억제로 인하여 입경 감소 효과가 있었다. 마그네슘 스테아린산의 함유량이 증가함에 따라 이에 따른 액상량의 증가로 인하여 입경 감소와 입자들간의 응집 정도에도 영향을 주었다.

• 한국세라믹학회지
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• 제32권10호
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• pp.1123-1130
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• 1995

In the preparation of manganese zinc ferrite powders by alcoholic dehydration of citrate/formate solution. The effect of pH change on precipitation was investigated. The pH range for obtaining stable precipitates was studied. The glassy phase was obtained when the pH value of solution is higher than 5, and the formation mechanism of glassy phase was suggested. Below pH 5, the stable precipitates were formed, and the optimal pH was 2. Formation of glassy phase was accounted for the change of surface charge by pH change. The change of surface charge is caused by the interparticular agglomeration. The precipitate was redissolved into the water on the surface of precipitate itself and through the polymerization, it agglomerated. This mechanism is tought to be similar to that of viscous flow.

• 한국재료학회지
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• 제17권10호
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• pp.532-537
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• 2007

A series of wet grinding experiments have been carried out using a stirred ball mill to systematically investigate consideration of grinding characteristics. The particle size distribution and median diameter of the grinding consumption power for a given grinding time were considered. Also, the effect of grinding aids on particle size and grinding consumption energy defined as the summation of grinding power was investigated. The grinding aids had influence on the smaller products size and decrease grinding consumption energy because the function of grinding aids were to be attribute to the prevention of agglomeration and ball and grinding chamber wall coating of sample powder. The grinding process seemed to be controlled by the force of agglomeration of the ground products. It was demonstrated that the particle size and grinding consumption energy could be more decreased by the addition of grinding aids.

• 한국결정성장학회지
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• 제2권1호
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• pp.51-59
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• 1992

일차입경이 동일한 $Nb_20_5$분체의 응집 상태가 $Pb(Mg_{1/3}Nb_{2/3})O_3$의 생성 반응 및 소결에 미치는 영향을 조사하였다. 합성 방법으로는 고체 반응법과 용융염법으로 나누어 각각 실험하였다. 고체 반응법의 경우에는 perovskite 상의 생성 반응이 $Nb_20_5$의 응집도가 낮을수록 크게 영향을 받았으나, 용융법시에는 거의 영향을 받지 않았다. 그 이유는 고상 반응법시에는 perovskite 상의 생성이 중간생성물인 perovskite 상의 분포의 균일성, 즉 $Nb_20_5$의 응집도에 지배를 받게되나, 용해, 석출 과정에 의해 진행되는 용융염법에서는 반응물의 비표면적에 의존하므로, 응집도에는 그다지 영향을 받지않는 것으로 사료된다.

• 한국결정성장학회지
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• 제15권6호
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• pp.244-251
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• 2005

수열합성법에 의해 제조된 티탄산바륨 (BT01, BT02, BT03, BT04, BT05)의 입자크기와 분체특성과의 상관관계를 비표면적, 제타전위, XPS, XRD 및 SEM에 의해 조사하였다. 레이져광산법에 의해 측정된 입자의 크기는 비표면적과 XRD를 통해 결정된 격자이방성과 밀접한 관계가 있음을 보였다. 분말의 비표면적은 입자의 크기가 증가함에 따라 감소하였으며, BT03 시료는 동일한 입자크기의 BT04에 비하여 큰 비표면적을 보였으며, 이는 입자들의 응집에 기인하는 것으로 SEM사진 및 XRD 분석을 통하여 밝혀졌다. 입자의 크기가 증가함에 따라 제타전위는 증가하는 경향을 보였으며, BT02와 BT03 분말은 다른 분말에 비하여 제타전위가 큰 음의 값을 나타내었다. XPS 분석결과 분쇄시 티탄산바륨과 물 사이의 반응에 의한 $Ba^{2+}$ 이온의 용출과 관련이 있는 것으로 분석되었다.

• 한국재료학회지
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• 제14권10호
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• pp.725-730
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• 2004

Nickel ultrafine powder have been synthesized by chemical reduction of aqueous $NiSO_4$ with hydrazine at various reaction conditions. The effect of reaction conditions such as the amount of surfactant and reductor, and reaction temperature on the particle size and shape was investigated by the mean of XRD, SEM and SEM-PSA. Experiments showed that the ratio of $N_{2}H_4/Ni$ and the reaction temperature were affected on the particle size of the nickel powder. The average particle size of synthesized nickel powder increased with increasing reaction temperature regardless of the ratio of $N_{2}H_4/Ni$. Also the surfactant could influence the size and agglomeration of ultrafine powder with the reaction temperature.

• 한국분말재료학회지
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• 제24권6호
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• pp.444-449
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• 2017

Aluminum nitride (AlN) powder specimens are treated by high-energy bead milling and then sintered at various temperatures. Depending on the solvent and milling time, the oxygen content in the AlN powder varies significantly. When isopropyl alcohol is used, the oxygen content increases with the milling time. In contrast, hexane is very effective at suppressing the oxygen content increase in the AlN powder, although severe particle sedimentation after the milling process is observed in the AlN slurry. With an increase in the milling time, the primary particle size remains nearly constant, but the particle agglomeration is reduced. After spark plasma sintering at $1400^{\circ}C$, the second crystalline phase changes to compounds containing more $Al_2O_3$ when the AlN raw material with an increased milling time is used. When the sintering temperature is decreased from $1750^{\circ}C$ to $1400^{\circ}C$, the DC resistivity increases by approximately two orders of magnitude, which implies that controlling the sintering temperature is a very effective way to improve the DC resistivity of AlN ceramics.

• 한국세라믹학회지
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• 제44권3호
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• pp.152-156
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• 2007

Tungsten carbide powder was synthesized by SHS (self-propagating high-temperature synthesis). Except $WO_{3}$, each concentration of raw material ($WO_{3},\;Mg,\;NaCl,\;Na_{2}CO_{3},\;C$) was investigated. Final product was characterized by XRD and SEM. X-ray data demonstrated that the $NaCl+Na_{2}CO_{3}$ combined mixture has superiority in the WC formation process. Single phase and submicrometer WC powder was synthesized at the temperature below $1600^{\circ}C$. The role of sodium salts in combustion process was discussed, and chemical mechanism of WC formation was proposed. WC powder prepared by salt-assisted combustion synthesis has a size $0.2{\sim}3\;{\mu}m$ and low agglomeration degree.

• 한국결정학회지
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• 제11권1호
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• pp.52-57
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• 2000

Hydrothermal synthesis of find CeO₂ powder has been investigated. Synthesis was performed with Ce(NO₃)₃·6H₂O, in ethanol and water solution. Mineralizer were NH₄OH and KOH and reaction for the powder synthesis has performed at 130℃. The morphology of CeO₂ was nearly spherical in using NH₄OH and cubic form in KOH. Particle size increased with addition of NH₄OH. Ethanol solution was effective to reduced the agglomeration.