• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.133-137
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• 2011

In this study, illite was size-reduced using a wet-ball-milling treatment to improve its dispersion. Changes in illite particle size, size distribution, and dispersion characteristics after varying the treatment period were investigated. And the dispersion and dispersion stability of illite solution after 2 h wet ball milling treatment with different pH conditions were also evaluated. The illite particle size significantly decreased as the treatment time increased and the size reduction effect of wet ball milling deteriorated above 2 h treatment time. In addition, illite particle size was more evenly distributed as the treatment time increased. X-ray diffraction (XRD) analysis showed that no crystal structural changes of illite were induced, but the characteristic peak of illite the weaker due to the size reduction and exfoliation, as the treatment time increased. Zeta potential analysis showed that the illite dispersion improved, as the treatment time increased. The illite wet-ball-mill treated at pH 2 had the lowest dispersion stability. Illite dispersion and dispersion stability increased as pH increased, due to the increase in surface ionization. Hence, the results showed that as the treatment time increased, the illite particle size decreased, and dispersion and dispersion stability improved due to the increase in surface energy and repulsion force between particles.

• The Journal of Engineering Geology
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• v.16 no.1 s.47
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• pp.15-21
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• 2006

Sandy soils obtained from the field were examined by the way of particle analyses. The hydraulic conductivity values of the disturbed soil samples were measured by the falling head method. Then the correlations between the hydraulic conductivity and particle distribution were defined. The soil which was a product of the weathering of the granitic rocks belonged to sand and loamy sand area in a sand-silt-clay triangular diagram. The measurements of hydraulic conductivity were $1.15X10^{-5}\sim7.31X10^{-4}cm/sec$ which is the range of sand and silt. It was clearly observed that the hydraulic conductivity measurements of the sandy soils showed stronger correlations with the particle variances rather than the mean grain sizes. The larger the variances, the smaller the hydraulic conductivity measurements. The sandy soil which was a product of weathered granite and whose mean grain size was $0.38\sim1.97mm$ showed regression curves of $y=6.0E-5x^{-1.4}$ in a correlations between hydraulic conductivity and particle variances. Accordingly, it is clearly concluded that making estimates with-out any consideration about particle variances can produce serious errors.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.282-282
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• 2017

모래, 실트 및 자갈과 같은 비점착성 유사는 하천에서의 이동 형태에 따라 소류사와 부유사로 구분된다. 부유사는 난류로 인해 흐름 내에서 부유 상태로 이동하는 유사로, 대부분의 자연 하천에서 유사는 부유사 형태로 이송된다. 유수동역학적 조건 하에서 이동하는 부유사의 입도 분포는 유사 입자의 부유와 퇴적에 따라 불규칙적으로 변화하기 때문에 여러 연구에서 주요한 문제로 다뤄지고 있다. 부유사의 입도 분포는 흐름 유속, 부유사의 부유 높이, 하상 재료의 특성 등에 따라 변화하며, 로그 정규분포를 따르는 것으로 알려져 있다. 이에 본 연구에서는 여러 다양한 하천 흐름 조건에서 부유사의 입도 분포를 모의할 수 있는 입도 분포 모형에 관한 개념적 틀(Framework)을 제안한다. 유사 입자의 입도 분포 모의는 추계학적 방법의 적용을 통해 얻어진다. 본래 점착성 유사의 입도 분포를 모의하기 위한 추계학적 입도 분포 모형으로부터 제안된 개념적 틀로, 다양한 흐름 조건 하에서 특정 확률 분포형을 띠는 입도 분포를 모의할 수 있다. 점착성 유사의 이동 모형에서는 점착성을 띠는 유사 입자들의 응집 현상에 따른 크기 변화를 모의하기 위한 응집 모형이 필수적이다. 시간에 따른 크기 변화를 모의하는 응집 모형에서, 흐름 내 여러 특성들에 의해 결정되는 응집 인자와 달리 파괴 인자의 경우 불규칙적 난류 운동으로 인해 무작위한 특성을 띤다. 모형에서 요구되는 파괴 인자를 특정 확률 분포형을 띠는 난수로 고려함으로써 점착성 유사의 입도 분포 모형이 개발되었다. 이 때, 점착성 유사는 프랙탈 구조를 가지는 것으로 가정하기 때문에 크기에 따라 밀도와 침강 속도가 변화한다. 반면 비점착성 유사는 크기에 따른 밀도 변화가 일어나지 않으므로, 고정된 밀도와 프랙탈 차원을 적용하여 점착성 유사의 입도 분포모형으로부터 비점착성 유사의 입도 분포 모의가 가능할 것으로 판단된다. 이러한 추계학적 방법의 적용을 통해, 하나의 경계 조건으로 대변되는 하상 특성에 따른 단점 또한 보완될 것으로 예측된다. 예를 들어 로그 정규 분포를 띤다고 가정할 때 보정을 통해 결정해야하는 변수는 평균과 분산으로 두 개가 요구된다. 유사의 평균 크기로부터 확률분포형의 평균값이 결정되면, 하상에 존재하는 유사의 특성에 따른 입도 분포의 분산은 난수의 분산을 결정함으로써 모의할 수 있다.

• Polymer(Korea)
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• v.26 no.3
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• pp.307-315
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• 2002

Major factors affecting the impact resistance of high impact polystyrene (HIPS), the rubber-toughened grade of polystyrene, are rubber-phase particle size and size distribution, molecular weight, morphology, and degree of grafting. Accordingly, it is important to control or investigate these factors. In this study, the effect of solvent content was analyzed by the morphology and particle size distribution of rubber phase, and final properties in bulk-solution polymerization of HIPS. The prepolymerization time was, first, determined by measuring the evolution of particle size distribution of dispersed phase to explain the phase inversion with time. As the solvent content increased, the size of rubber particle increased and then gradually decreased. Rubber-phase morphology was likely to have higher degree of grafting as the solvent content increased. Rheological and mechanical properties decreased as the solvent content increased because of the decrease of matrix molecular weight due to the chain transfer reaction to solvent and the existence of residual solvent. Nevertheless, the impact resistance seemed to increase when the rubber particle size increased.

• Journal of the korean Society of Automotive Engineers
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• v.6 no.2
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• pp.55-63
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• 1984

Berglund-Liu 진동방식 단분산 분체입자 발생기(Berglund-Liu vibrating orifice monodisperse aerosol generator)에 의하여 제작한 단분산 광흡수성 표준분체입자를 사용하여 레이저 산란광 분체입도 측정기 (Knollenberg active scattering aerosol spectrometer)의 반응특성을 조사하 였다. 실험결과, 기기의 반응특성은 Mie 산란이론에 의하여 계산한 이론치와 매우 잘 일치하며 특히 광흡수성 분체입자는 광통과성 분체입자가 다의적인 특성을 나타내는 것에 반하여 거의 단조증가하는 일의적인 특성을 가지고 있으며 광흡수성 분체입자의 반응특성이 제작자의 교정 치에 가까운 결과를 나타내었다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.280-280
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• 2014

본 연구에서는 유체 플라즈마 공정 (Solution plasma process; SPP)이라고 불리우는 새로운 공정법을 이용하여 ZnO 나노입자를 합성하였고 그 입도와 분산성을 평가하였다. 이 방법으로 인해 합성된 ZnO 나노입자는 10~60 nm 범위의 입도를 가지며, 플라즈마 처리시간이 길어질수록 유체 내 ZnO 나노입자의 분산성이 향상되었다.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.311-316
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• 2010

This study aimed to prepare antimony-doped tin oxide (ATO) dispersion with high stability. The methods to achieve this goal were sought by investigating the changes of ATO particle size, size distribution, dispersion property as wet ball milling treatment time increased. And the changes of wet ball milled ATO dispersion property were also investigated, as pH increased. The changes of ATO particle size and size distribution, according to wet ball milling treatment time were evaluated with laser diffraction particle size analyzer and scanning electron microscope (SEM). The changes of ATO dispersion property, as wet ball milling treatment time and pH increased, were evaluated with zeta potential analysis and Turbiscan. By 60 min wet ball milling treatment time, ATO particle size decreased and size distribution became narrower, as the treatment time increased. After 60 min milling, the ATO particle size decreased to less than 30% of the initial size and the size distribution was narrowed to $0.1{\sim}5{\mu}m$ from $1{\sim}35{\mu}m$. However, more than 60 min milling, ATO particles aggregated and the particle size increased. ATO dispersion stability also increased as the treatment time and pH increased because the reduced particle size increased particle surface energy and repulsion between particles and the increased pH enhanced particle surface ionization. Hence, after proper length of wet ball milling treatment, highly stable ATO dispersion can be prepared, as increasing pH of the dispersion.

• Polymer(Korea)
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• v.25 no.5
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• pp.744-753
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• 2001

One of the most important factors which affect the impact strength of high impact polystyrene (HIPS) is the rubber-phase particle size and size distribution. In this study, HIPS was prepared from a batch reactor to observe the influence of reaction conditions such as rubber content, agitation speed and prepolymerization time on the particle size and size distribution. Measurements concerning the particle size distribution were conducted using a particle size analyzer. Due to swelling, the particle suspended in toluene increases in size with lower heat-treatment temperature and shorter heat-treatment time, while the particle in methyl ethyl ketone shows quite reasonable size without any effort of heat-treatment. As rubber content increases, the average particle size increases substantially, but the increase in agitation speed at lower rubber contents does not have much influence on the size. However, the polystyrene-phase particles occluded in rubber-phase become more uniform as agitation speed increases. Longer prepolymerization time produces rubber-phase particles with narrower particle size distribution.

• Resources Recycling
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• v.15 no.4 s.72
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• pp.19-26
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• 2006

The preparation of Ag nano-powder from aqueous silver nitrate solution, which would be available for the recycling of silver bearing wastes, was investigated by a reductive precipitation reaction using hydrazine hydrate as a reducing agent. Silver solution was prepared by dissolving silver nitrate with distilled water, and then the dispersant, Tamol NN8906 or Tween 20, was also mixed to avoid the agglomeration of particles during the reductive reaction followed by the addition of hydrazine hydrate to prepare Ag nano-particles. Ag particles obtained from the reduction reaction from silver solution were characterized using the particle size analyzer and TEM to determine the particle size distribution and morphology. It was found that about 100% excess of hydrazine hydrate was required to reduce completely silver ions in the solution. Ag powders with very narrow distribution could be obtained when Tamol NN8906 was used as the dispersant. In case of Tween 20, the particle size distribution showed typically the bimodal or multimodal distribution and the morphology of Ag particles was found to be irregular shape in both cases.

• Journal of the Korean Geographical Society
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• v.45 no.5
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• pp.553-572
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• 2010

Grain size analysis of sediments and soils has been regarded as a one of the most important analytical methods in Earth Sciences. The results of grain size analysis by 10 different pretreatment procedures in loess-paleosol sediments are compared in the study. In spite of the most powerful effectiveness of dispersant(sodium hexametaphosphate) on the dispersions of sediments, the effects show large differences by its treatment orders with HCl. It may result from that $Na^+$ ions in the dispersant may not be able to effectively substitute $Ca^{2+}$ ions in the sediments due to the electrostatic forces between $Na^+$ and $Cl^-$ ions in the dispersant and HCl, respectively. Although $H_2O_2$ and HCl are more effective in dispersion than hot water, they do not affect greatly the dispersions. Therefore, the reliable results of grain size analysis can be obtained by selecting the adequate pretreatment procedures most suitable for the purposes of researches and characteristics of sediments.