• 한국세라믹학회지
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• 제43권4호
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• pp.213-219
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• 2006

A Monte Carlo simulation based on Potts model in a three dimensional lattice was studied to analyze and design microstructures in porous sintered compacts such as porosity, pore size, grain (particle) size and contiguity of grains. The effect of surface energy of particles and the content of additional fine particles to coarse particles on microstructure development were examined to obtain fundamentals for material design in porous materials. It has been found that the larger surface energy enhances sintering (necking) of particles and increases contiguity and surface energy does not change pore size and grain size. The addition of fine particles also enhances sintering of particles and increases contiguity, but it has an effect on increment of pore size and grain size. Such a simulation technique can give us important information or wisdom for design of porous materials, e.g., material system with high surface energy and fine particle audition are available for higher strength and larger porosity in porous sintered compacts with applications in an automobile.

• 한국막학회:학술대회논문집
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• 한국막학회 2001년도 제14회 심포지엄 : 제2회 분리막 표준화(The 2nd Standardization of Membranes)
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• pp.39-50
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• 2001

The performance of membranes is governed their pore struture. Pore structures of porous materials can be determined by a number of techniques. However, The novel technique, capillary folw porometry has a number of advantages. In this technique, the sample is brought in contact with a liquid that fills the pores in the membrane spontaneously. Gas under pressure is used to force the liquid from the pores and increase gas flow. Gas flow rate measured as a function of gas pressure in wet and dry samples yield data on the largest pore size, the mean flow pore size, flow distribution and permeability. Pore characteristics of a number of membranes were measured using this technique. This technique did not require the use of any toxic material and the pressure employed was low. Capillary flow porometry is a suitable technique for measurement of the pore structure of many membranes.

• Bulletin of the Korean Chemical Society
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• 제9권2호
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• pp.94-98
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• 1988

An improvement over the method of pore size distribution analysis has been made in this work. The improved method is based upon the idea of the micro pore analysis of Mikhail, Brunauer, and Bodor, and utilizes the V-t curve of nitrogen adsorption. Two pore models are assumed, and the deviation of the initial slope of the V-t plot is ascribed to the pore filling and to the adsorption on the wall of unfilled pores. The improved method of this work is very convenient in that the analysis starts from the small pore regions. The method of this work is however quite distinct from the similar V-t plot method proposed by Sellevold and Radjy. The proposed method is applied to a few adsorbents, and very satisfactory results are obtained. The cumulative surface area calculated by this method also agrees very well with those obtained by the BET plot or by the t-method.

• 한국세라믹학회지
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• 제41권1호
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• pp.62-68
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• 2004

본 연구에서는 SHS 공정에 의하여 기공의 크기를 조절함으로서 전기저항 발열 특성을 가지는 다공성 $MoSi_2$를 제조하는 공정에 관하여 연구하였다. 결함이 억제된 다공질 재료를 제조하기 위하여 Si 함량 변화 및 예열 공정을 실시하였으며, 성형체 제조에 사용되는 Mo 분말의 크기 변화에 따른 가공 형성 거동에 대하여 연구하였다. 실험 결과 합성된 $MoSi_2$ 입자의 크기는 Mo 입자의 크기와는 관계없이 연소 합성시 발열되는 발열양에 의해 좌우되었으며, 기공의 크기는 Mo 입자의 크기에 따라 결정되었다. 또한 가공 경사 $MoSi_2$ 다공질 재료를 만들기 위하여 150-300${\mu}m$ Mo 분말과 4-5${\mu}m$ Mo 분말을 단계별로 5층으로 혼합하여 합성한 결과 거시적으로 순차적인 기공 크기 분포를 나타내었으며, 이를 통하여 포집 효율등이 우수한 다공성 발열체 재료의 제조가 가능하였다.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.57.1-57.9
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• 2021

Objectives: This study aimed to compare and evaluate the porosity and pore size distribution of high-viscosity glass ionomer cements (HVGICs) and conventional glass ionomer cements (GICs) using micro-computed tomography (micro-CT). Materials and Methods: Forty cylindrical specimens (n = 10) were produced in standardized molds using HVGICs and conventional GICs (Ketac Molar Easymix, Vitro Molar, MaxxionR, and Riva Self-Cure). The specimens were prepared according to ISO 9917-1 standards, scanned in a high-energy micro-CT device, and reconstructed using specific parameters. After reconstruction, segmentation procedures, and image analysis, total porosity and pore size distribution were obtained for specimens in each group. After checking the normality of the data distribution, the Kruskal-Wallis test followed by the Student-Newman-Keuls test was used to detect differences in porosity among the experimental groups with a 5% significance level. Results: Ketac Molar Easymix showed statistically significantly lower total porosity (0.15%) than MaxxionR (0.62%), Riva (0.42%), and Vitro Molar (0.57%). The pore size in all experimental cements was within the small-size range (< 0.01 mm³), but Vitro Molar showed statistically significantly more pores/defects with a larger size (> 0.01 mm³). Conclusions: Major differences in porosity and pore size were identified among the evaluated GICs. Among these, the Ketac Molar Easymix HVGIC showed the lowest porosity and void size.

• 약학회지
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• 제29권4호
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• pp.176-182
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• 1985

As a part of the studies on adsorptive properties of Korean halloysite clays, Hadong white clays of premium grade were examined for geometric pore structured by mercury porosimetry and for specific surface areas by nitrogen adsorption according to the BET procedure. Three size fractions of the native clay sample were derived from passage BS #100, #200 and #325 meshes, respectively. Several parameters lhus observed in relation to the pore structures are shown below: 1. The size fraction of BS #100, #200 and #325 show internal pore volumes of 25.3, 30.2 and $35.0m^2g^{-1}$, respectively. 2. In the distribution curves of the cumulative pore volume against pore diameter, it has been shown that the larticle sizes, the steeper the distribution over the larger ranges of pore diameters. The converse is true the smaller particles. 3. Internal pore areas increase with decrease in pore sizes. It follows that the pores having diameters of $\leq$0.1$\mu\textrm{m}$ are responsible for more than 90% of the total pore area. 4. The behaviour of nitrogen adsorption can be best described by BET type IV isotherm. Further, the hysteresis loops of the adsorptiondesorption curves become narrower with decresing particle sizes. 5. The specific surface areas observed for the fractions of BS #100, BS #200 and BS #325 are 34.6, 35.4 and 43.2m $^2g^{-1}$, respectively. and the calcined clay of BS #325 has a specific surface area near $30.4m^2g^{-1}$.

• 한국염색가공학회지
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• 제12권6호
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• pp.380-388
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• 2000

The porosity of polyester fibers treated with sodium hydroxide aqueous solution was investigated using a nitrogen porosimeter, and the dyeability of the treated fibers was discussed in terms of the porosity. In pore distribution, the polyester fibers treated with sodium hydroxide aqueous solution were characterized by higher amount of pores below $10\AA$ than those of the untreated fibers, and by shift of the pore size having maximum accumulated volume from $10\AA$ for the untreated fibers to $5~6\AA$. As the weight loss of the polyester fibers treated with sodium hydroxide aqueous solution increased, BET surface area and total pore volume increased linearly, but average pore size, showing some different aspect, increased steeply at earlier stage and then approached the maximum value. The dye uptakes of the polyester fibers treated with sodium hydroxide aqueous solution increased with the BET surface area, the total pore volume and the average pore size. The alkali treatment increased the surface area of polyester fibers, so that the chance of contact between the fiber and dye molecules increased. In addition, the pores created on the surface of polyester fibers by alkali treatment might act as pathways for dye molecules into the polyester fibers.

• 한국세라믹학회지
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• 제51권1호
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• pp.11-18
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• 2014

Onggi, which is described as a breathing pottery, has strongly influenced the traditional food culture in Korea. In this study Onggi is compared to porcelains including celadon and white porcelain to analyze the sources of pore formation. The differences in starting materials are examined for chemical and mineralogical compositions, particle size and distribution. The gas permeability of the fired samples is correlated to the matrix microstructure. The broad particle size distribution and high iron oxide content of Onggi are revealed as the major cause for the pore formation. Open pores are formed with large particles in the Onggi body while closed pores have a high iron oxide concentration. The Onggi body with increased open pores leads to the high gas permeability.

• 한국막학회:학술대회논문집
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• 한국막학회 1994년도 춘계 총회 및 학술발표회
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• pp.38-38
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• 1994

일반적으로 다공성 비대칭막은 상분리법에 의하여 제조하는데, 분리막을 구성하는 고분자를 적절한 용매에 녹인 제막용액을 일정한 두께로 casting하고 이를 비용매에 담가서 binodal/spinodal decomposition이 일어나도록 하여 제조한다. 이 방법으로 제조된 다공성 분리막의 성능은 표면층에 존재하는 pore의 크기와 그 분포 및 porosity에 의해 결정된다. 표면층의 pore size와 분포를 조절하기 위하여 그간 고분자 용액내의 고분자 농도조절, 첨가제의 사용, 비용매의 조성을 바꾸는 등의 여러가지 방법에 대한 연구가 진행되어 왔다. Casting된 고분자 용액을 비용매에 침잠시켜 다공성막을 형성시킬 경우 막의 표면과 비용매 사이의 계면에서 용매와 비용매의 교환이 일어난다. 용매-비용매 교환이 일어나면 제막된 고분자 용액이 열역학적으로 불안정해져 상분리가 일어난다. 이 때 용매-비용매의 교환이 매우 빠른 속도로 일어나 pore-size의 분포를 조절하기가 매우 어렵다.

• The Korean Journal of Ceramics
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• 제6권3호
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• pp.209-213
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• 2000

Microstructural changes of AlOOH doped UO$_2$pellet after annealing up to 216h have been observed and they were compared with those of the standard pellet. Grain and pore size of UO$_2$pellet increased with the addition of AlOOH and its effect was still validated during annealing. Densification rate was reduced by the addition of AlOOH and it was attributed to coarsened pores with spherical shape. Grain and pore growth was stopped and density increase was the least after 144h of annealing. The variation of pore size resulting from annealing has a linear relationship with that of grain size.