• 한국세라믹학회지
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• 제35권8호
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• pp.783-790
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• 1998

The characterization of the complexation reaction of PVA and Al(III) ion at different pH and the sint-ering behaviour of UO2 containing the PVA-Al(III) complexes were investigated. Compared with pure PVA powder the complexed PVA-Al(III) powder had compacter shape and lower decomposition temperature The major phase of PVA-Al(III) complex decomposed at 90$0^{\circ}C$ was $\alpha$-Al2O3 The PVA-Al(III) complex formed at pH 9 had the lowest relative viscosity the highest Al content of 36% and the smallest particle size of 19${\mu}{\textrm}{m}$ While the pure UO2 pellet appeared with bimodal one. The grain size of the pure UO2 pellet was 7${\mu}{\textrm}{m}$ but that of the PVA-Al(III) complex added UO2 pellet was increased up to 36${\mu}{\textrm}{m}$ The largest grain size was ob-tained when the PVA-Al(III) complex formed at pH9 was added and the PVA-Al(III) complex formed at pH 11 had the greatest effect on increasing pore size.

• 한국재료학회지
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• 제12권7호
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• pp.533-539
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• 2002

Porous anodic aluminum oxide layer for nano templates was prepared in acidic solutions. In order to investigate effects of 2nd anodization on ordered formation behaviors of the porous oxide layers, electrochemical and microstructural studies were performed, primarily using TEM, FE- SEM, AFM, and Ultramicrotomy. The pore diameter of the anodic oxide layer increased approximately linearly with increasing voltages, and to the contrary, the pore density decreased. It was shown that 2nd anodizing on the cell base after dissolving 1st anodic oxide layer was remarkably effective for forming ordered array of the pores, comparing with the case for 1st anodization only. And for controlling the diameter of pores, widening method by chemical dissolution seemed more practical than by electrochemical methods.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.30-31
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• 2006

In a multi-action tooling system, which is usually used for the powder compaction process to fabricate the complex multilevel parts, crack formation is crucially detrimental and should be avoided. Among various process factors, tool shape is an important factor to prevent the crack formation during powder compaction process. In this work, the effects of different tool shapes were investigated through the experimental oberservation of pore distribution in real products and the finite element analysis of residual stresses. The results were interpreted based on non-uniform powder density in the compacted parts.

• 한국토양비료학회지
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• 제46권6호
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• pp.549-555
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• 2013

Human influence on soil formation has dramatically increased as the development of human civilization and industry. Increase of anthropogenic soils induced research of those soils; classification, chemical and physical characteristics and plant growth of anthropogenic soils. However there have been no reports on soil pore properties from the anthropogenic soils so far. Therefore the objectives of this study were to test computer tomography (CT) to characterize physical properties of an anthropogenic paddy field soil and to find differences between natural and anthropogenic paddy field soils. Soil samples of a natural paddy field were taken from Ansung, Gyeonggi-do (Ansung site), and samples of an anthropogenic paddy field were from Gumi in Gyeongsangnam-do (Gasan) where paddy fields were remodeled in 2011-2012. Samples were taken at three different depths and analyzed for routine physical properties and CT scans. CT scan provided 3 dimensional images to calculate pore size, length and tortuosity of soil pores. Fractal analysis was applied to quantify pore structure within soil images. The results of measured physical properties (bulk density, porosity) did not show differences across depths and sites, but hardness and water content had differences. These differences repeated within the results of pore morphology. Top soil samples from both sites had greater pore numbers and sizes than others. Fractal analyses showed that top soils had more heterogeneous pore structures than others. The bottom layer of the Gasan site showed more degradation of pore properties than ploughpan and bottom layers from the Ansung site. These results concluded that anthropogenic soils may have more degraded pore properties as depth increases. The remodeled paddy fields may need more fundamental remediation to improve physical conditions. This study suggests that pore analyses using CT can provide important information of physical conditions from anthropogenic soils.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.588-590
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• 2008

The thermal signature of nucleation process is characterized by the induction time, the degree of supercooling, and the equilibrium temperature depression. The initiation of nucleation presents stochastic characteristics. The factors that affect nucleation are mechanical impact, ionic concentration, mineral surface characters, and pore size. Hydrate-bearing sediments behave mechanically like other cemented sediments. The data set has important implications for the calibration and interpretation of geophysical measurements and downhole logs collected in gas hydrate provinces, providing particular insight for the interpretation of P- and S-wave data and resistivity logs. In addition, laboratory formation history and ensuing pore-scale spatial distribution likely have a more pronounced effect on the macroscale mechanical properties of hydrate-bearing sediments

• Bulletin of the Korean Chemical Society
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• 제25권3호
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• pp.351-356
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• 2004

Selected MPEG-b-PDLLA block copolymers have been synthesized by ring-opening polymerization with systematic variation of the chain lengths of the resident hydrophilic and hydrophobic blocks. The size and shape of the micelles that spontaneously form in solution are then controlled by the characteristics of the block copolymer template. All the materials prepared in this study showed the tunable pore size of 20-80 ${\AA}$ with the increase of hydrophobic chain lengths and up to 660 $m^2$/g of specific surface area. The formation mechanism of these nanoporous structures obtained by controlling the micelle size has been confirmed using both liquid and solid state $^{13}C\;and\;^{29}Si$ NMR techniques. This work verifies the formation mechanism of nanoporous structures in which the pore size and wall thickness are closely dependent on the size of hydrophobic cores and hydrophilic shells of the block copolymer templates.

• Journal of Periodontal and Implant Science
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• 제43권6호
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• pp.251-261
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• 2013

A paradigm shift is taking place in medicine and dentistry from using synthetic implants and tissue grafts to a tissue engineering approach that uses degradable porous three-dimensional (3D) material hydrogels integrated with cells and bioactive factors to regenerate tissues such as dental bone and other oral tissues. Hydrogels have been established as a biomaterial of choice for many years, as they offer diverse properties that make them ideal in regenerative medicine, including dental applications. Being highly biocompatible and similar to native extracellular matrix, hydrogels have emerged as ideal candidates in the design of 3D scaffolds for tissue regeneration and drug delivery applications. However, precise control over hydrogel properties, such as porosity, pore size, and pore interconnectivity, remains a challenge. Traditional techniques for creating conventional crosslinked polymers have demonstrated limited success in the formation of hydrogels with large pore size, thus limiting cellular infiltration, tissue ingrowth, vascularization, and matrix mineralization (in the case of bone) of tissue-engineered constructs. Emerging technologies have demonstrated the ability to control microarchitectural features in hydrogels such as the creation of large pore size, porosity, and pore interconnectivity, thus allowing the creation of engineered hydrogel scaffolds with a structure and function closely mimicking native tissues. In this review, we explore the various technologies available for the preparation of macroporous scaffolds and their potential applications.

• 한국세라믹학회지
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• 제45권2호
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• pp.132-137
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• 2008

The main purpose of this study is enhancing the filtering efficiency, performance and durability of filter by growing SiC whiskers on cordierite honeycomb substrate. The experiment was performed by Chemical Vapor Infiltration (CVI) in order to control pore morphology of substrate. Increasing the mechanical strength of porous substrate is one of important issues. The formation of "networking structure" in the pore of porous substrate increased mechanical strength. The high pressure gas injection to the specimen showed that a little of whiskers were separated from substrate but additional film coating enhanced the stability of whisker at high pressure gas injection. Particle trap test was performed. More nano-particle was trapped by whisker growth at the pore of substrate. Therefore it is expected that the porous cordierite which deposited the SiC whisker will be the promising material for the application as filter trapping the nano-particles.

• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.349-352
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• 2014

Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i.e., meshed pore, was produced.

• 대한건축학회논문집:구조계
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• 제33권12호
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• pp.63-70
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• 2017

When industrial by-products like slag and fly ash are using in concrete with cement, it improves strength and durability against external deterioration factors by densifying the structure through potential hydraulic and pozzolanic reaction. But it has been pointed out that high dependence on the quality variation and the curing condition using a admixure material for concrete. In this study, the characteristics of internal micropore structure according to curing condition were analyzed for pastes and mortar specimens under using blast furnace slag powder. As a result, the variation of compressive strength and the internal microstructure were observed according to curing conditions by binder type. Particularly, using blast furnace slag powder, decrease in compressive strength were clearly observed in indoor and carbonation curing compared with water curing. The pore structure analysis also clearly observed the decrease of the gel pore existing in the CSH hydrate layer and the increase of the capillary pore in indoor and carbonation curing compared with water curing condition.