• Proceedings of the Membrane Society of Korea Conference
• /
• 2003.07a
• /
• pp.107-114
• /
• 2003

This study investigated the effect of 2-methoxy ethanol (2-Me) non-solvent as additive included in casting solution. Macroporous polymer membranes were prepared by using polyethersufone (PES)/N-methyl-2-pyrrolidone (NMP)/2-Me casting solution and water coagulant. The phase separation co-process of the vapor-induced phase separation (VIPS) and liquid-induced phase separation (LIPS) were used by means of membrane preparation method. The pore size and pore size distribution were controlled with additive (non-solvent), and measured with Automated Perm Porometer. By increasing additive (non-solvent) in the casting solution, the membranes produced changed from finger structure to sponge structure. That is due to the different diffusion rates. At slow diffusion process, sponge-like structure was formed and at fast diffusion process, finger-like structure was formed. Also relative humidity, evaporation time, temperature of casting solution and coagulation bath etc. had effects on the pore size distribution and the porosity of the membrane.

• Textile Coloration and Finishing
• /
• v.32 no.1
• /
• pp.57-64
• /
• 2020

In this study, alginate-gelatin/silk wet-laid nonwoven fabrics were prepared by using alginate gelatin fiber and silk fiber, as the main fiber, and PVA fiber as binder fiber. The characterization of pore size and mechanical property was carried out on the various weight ratios of alginate gelatin fiber and silk fibers, or the adding binder fibers. As the content of silk or binder fiber increases, the tensile strength increases from 0.70 kgf/㎠ to 5.08 kgf/㎠ and the pore size decreases 111.6 ㎛ to 51.00 ㎛. As the weight of the silk increased, the density increased, and binder fiber was added to enhance the cohesion between fibers, thereby increasing the wet-laid nonwoven fabric strength. We studied on wet-laid nonwoven fabrics that can be applied to mask sheet with adjustable pore size.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2007.11a
• /
• pp.179-186
• /
• 2007

The best way to understand paper properties is to study paper structure. Paper is composed solid materials (pulp and other additives) and air three-dimensionally, it's important to understand pore structure of the paper. There are several method to analysis pore structure of the paper. Mercury intrusion technique is frequently used for the characterization of the porous paper, giving access to parameters such as pore size and pore distribution. But some researchers indicated mercury intrusion distorts the structure due to application of high pressure. So this paper suggest new analysis technique to pore structure of the paper. New pore analysis technique with SEM does not require high pressure, gives good resolution and measures pore structure.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.711-714
• /
• 2003

Factors causing deterioration of concrete structures under marine environment are various, especially penetration and diffusion of chloride ion, carbon dioxide, and water through pore effects on the durability of concrete as well as mechanical properties of concrete. Pore of porous materials like concrete can be classified as micro-, meso-, and macro-pore. And pore of cement matrix is classified as pore which occupied by water, air void, and ITZ between cement paste and aggregates. In this study, to verify the relationship between pore of cement matrix and the property of chloride ion diffusivity, the regression analysis is producted. From the result of regression analysis, the average pore diameter more than total pore volume effects on the diffusivity of chloride ion.

• Journal of the Korean Ceramic Society
• /
• v.36 no.8
• /
• pp.813-819
• /
• 1999

Inner crack-like pores with controlled amount of Ca impurity level in the high purity alumina single crystal sapphire had been created by micro-fabrication technique which includes ion implantation photo-lithography Ar ion milling and hot press technique. The morphological change and the healing of crack-like pore in the Ca doped high purity single crystal alumina during high temperature heat treatment in vacuum were observed using optical microscopy. The hexagonal bridging ligaments were developed and the size of hexagonal bridging ligaments had been increased with temperature and Ca amount and had grown to their corner rounded. It appeared that the hexagonal bridging ligaments would have an equilbrium size with temperature and the amount of Ca addition. Three kinds of crack-like pore healing type were observed. Edge regression and ligament growth were observed from relatively low temperature in the crack-like pore. Edge regression were found in almost all of the crack-like pore but the ligament growth were found only in the several crack-like pores accelerating heating very fast. Flow type healing was observed above $1800^{\circ}C$ and It healed the crack-like pore very slowly.

• Journal of Sensor Science and Technology
• /
• v.22 no.3
• /
• pp.181-184
• /
• 2013

Highly ordered porous materials having mesopores in the walls of macropores showed improved adsorption dynamics results for VOC molecules, especially bulky molecules. These meso/macroporous mataerials were synthesized by the dual templating method, and mesopore and macropore size were controlled by adjusting the templates for each pore size regime. In the case of adsorption and desorption of small VOC molecules (toluene), although meso/macroporous MCM-41 with smaller mesopore size showed improved results, meso/macroporous SBA-15 with larger mesopore size was not improved regardless of the existence of macropores, since there was no limitation of movement through the larger mesopore. However, the adsorption dynamics of bulky VOC molecules (p-xylene) over meso/macroporous SBA-15 were drastically improved by increasing the macropore size.

• Journal of Powder Materials
• /
• v.22 no.2
• /
• pp.100-104
• /
• 2015

The porous metals are known as relatively excellent characteristic such as large surface area, light, lower heat capacity, high toughness and permeability. The Fe-Cr-Al alloys have high corrosion resistance, heat resistance and chemical stability for high temperature applications. And then many researches are developed the Fe-Cr-Al porous metals for exhaust gas filter, hydrogen reformer catalyst support and chemical filter. In this study, the Fe-Cr-Al porous metals are developed with Fe-22Cr-6Al(wt) powder using powder compaction method. The mean size of Fe-22Cr-6Al(wt) powders is about $42.69{\mu}m$. In order to control pore size and porosity, Fe-Cr-Al powders are sintered at $1200{\sim}1450^{\circ}C$ and different sintering maintenance as 1~4 hours. The powders are pressed on disk shapes of 3 mm thickness using uniaxial press machine and sintered in high vacuum condition. The pore properties are evaluated using capillary flow porometer. As sintering temperature increased, relative density is increased from 73% to 96% and porosity, pore size are decreased from 27 to 3.3%, from 3.1 to $1.8{\mu}m$ respectively. When the sintering time is increased, the relative density is also increased from 76.5% to 84.7% and porosity, pore size are decreased from 23.5% to 15.3%, from 2.7 to $2.08{\mu}m$ respectively.

• Elastomers and Composites
• /
• v.42 no.2
• /
• pp.86-92
• /
• 2007

A few of polytetrafluoroethylene(PTFE) membranes and PTFE fine powders were analyzed to chooce an optimum resin. The bi-axial stretching process was developed to set up the foundation of the preparation process and control the pore size and porosity of PTFE membrane. The pretreatment of PTFE fine powder used in the preparation process for PTFE was needed. The mixing of additives, the ripening of mixture, paste extrusion process of ripening powder, calendering process and the bi-axial process were conducted for controlling pore size, porosity and thckness of membrane. The aftertreatment which strengthened the mechanical properties was necessary. The control of pore size and porosity of the membrane were determined. The ratio of PTFE fine powder and additives at the paste extrusion process, the ripening time, the ripening temperature and the parameters of temperature and pressure at the paste extrusion process were optimized.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.8
• /
• pp.106-114
• /
• 2015

Nowadays, cameras embedded in smartphones can take high resolution photographs that can be used to analyze skin conditions without using specialized equipments. In shooting photographs with a smartphone, it is difficult to maintain a uniform shooting distance. Therefore, it is essential to adapt a skin analysis method to the shooting distance. In this paper, we focus on a pore detection algorithm that is adaptive to the camera distance. We develop a relationship model between the shooting distance and the appropriate size of the pore detection mask. In addition, we propose a method to estimate the normalized pore size (i. e. pore size at a standard shooting distance). We conducted experiments on skin images taken from different shooting distances. It was verified that the proposed method can achieve more accurate pore detection result, close to those from skin images taken at a standard shooting distance.

• Journal of Soil and Groundwater Environment
• /
• v.20 no.4
• /
• pp.31-40
• /
• 2015

Various types of inorganic and organic colloids are present in natural water including groundwater. Previous studies showed that Fe, Mn and Al are colloid-forming elements and dissolved concentrations can be erroneous for these elements if water samples are not properly filtered. Dissolved concentrations of elements including Ca, Na, Mg, K, Fe, Mn, Si and Al in groundwater from alluvial and bedrock aquifers, and surface water near Nakdong River were determined to evaluate effects of colloids on dissolved concentrations in natural water samples using various pore sizes of filters. Groundwater is mostly anoxic and have elevated concentrations of Fe and Mn, which provides a unique opportunity to observe the effects of colloids on dissolved concentrations of colloid-forming elements. Membrane filters with four kinds of pore sizes of 1000 nm, 450 nm, 100 nm, and 15 nm were used for filtration of water samples. Concentrations of dissolved concentrations in each filtrate did not show significant differences from 1000 nm to 100 nm. However, concentrations of all elements considered were decreased in the filtrates obtained using 15 nm pore size filters by 10 to 15% compared to those using 450 nm except for bedrock groundwater. Al in surface water showed a distinct linear decrease with the decrease of filter pore sizes. These results showed that 100 nm pore size had little effect to remove colloidal particles in alluvial groundwater and surface water in our study. In contrast, significant concentration decreases in 15 nm pore size filtrates indicate that the presence of 15 to 100 nm colloidal particles may affect determination of dissolved concentrations of elements in natural water.