• Title/Summary/Keyword: Micro pore

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Disintegration process and micro mechanism of mudstone under dry-wet cycles

  • Ji Chen;Ruyu Huang;Xinyu Luo;Xin Liao;Qiang Tang
    • Geomechanics and Engineering
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    • v.36 no.1
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    • pp.9-18
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    • 2024
  • With the rapid development of highways and railways, series of traffic safety issues emerged because of mudstone disintegration. To research on the mechanism and further guarantee the stability and safety of transportation infrastructure built on or near mudstone formations, the mudstone disintegration test of mudstone was carried out based on mudstone and sandy mudstone. The element types, cementation characteristics and pore characteristics of the tested specimens were studied by means of Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Image Pro Plus (IPP). The disintegration index of mudstone was approximately 1%, and even some specimens were difficult to be calculated, while the disintegration index of sandy mudstone is approximately 8.7%. According to the results, the two mudstones belong to grade II and III disintegration respectively, of which the sandy stone presents more extensive disintegration than mudstone. This phenomenon was distinguished that, the clay minerals of mudstone are approximately 25% more abundant than those of sandy mudstone, and the unit pore area is 20 ㎛2 larger, which result in different microstructure and water absorption capacities. In the liquid phase, the ions in the mudstone specimens were exchanged and combined with water molecules in the environment during the whole disintegration process. This results in continuous spalling and fragmentation of clay minerals, the emergence of secondary fractures, and the deepening of primary fractures.

An Experimental Study on the Microstructure Characteristics of Cementitious Composites by MIP (MIP를 통한 혼합 시멘트계 재료의 미세구조 특성에 관한 실험적 연구)

  • Kim, Tae-Sang;Jung, Sang-Hwa;Chae, Seong-Tae;Lee, Bong-Chun;Woo, Young-Je;Song, Ha-Won
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.533-536
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    • 2008
  • Recently, in Korea, there has been an increasing number of research papers published which are to improve durability of concrete, particularly by analyzing correlation between diffusivity of chloride and porosity/pore size distribution. In these studies, such test methods as mercury intrusion porosimetry(MIP), gas adsorption or image analysis method are used to analyze the microstructure of materials while MIP is most widely used for concrete. This study analyzes the results of porosity and pore size distribution of paste and concrete adding fly ash or blast furnace slag by using MIP equipment which is widely used for determining micro-porosity structure of cementitious materials. A variation in porosity and pore size distribution at the curing day 3, 7 and 28 has been observed by using MIP equipment for cement paste 35%, 40%, 45%, 50%, 55%, 60% of W/C when using $300kg/m^3$ of cement, 35%, 45%, 55% of W/C when replaced 60% with blast-furnace slag, and 35%, 45%, 55% of W/C when replaced 30% with fly ash. For long-term water cured normal OPC concrete and mixed concrete replaced 60% with blast-furnace slag powder, micro-structure of the sample has been analyzed by using MIP equipment when W/C indicated 40%, 45%, 50% respectively and the binder varied $300kg/m^3$, $350kg/m^3$, $400kg/m^3$, and $450kg/m^3$.

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A Study on the Surface Pre-treatment of Palladium Alloy Hydrogen Membrane (팔라듐 합금 수소 분리막의 전처리에 관한 연구)

  • Park, Dong-Gun;Kim, Hyung-Ju;Kim, Hyo Jin;Kim, Dong-Won
    • Journal of the Korean institute of surface engineering
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    • v.45 no.6
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    • pp.248-256
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    • 2012
  • A Pd-based hydrogen membranes for hydrogen purification and separation need high hydrogen perm-selectivity. The surface roughness of the support is important to coat the pinholes free and thin-film membrane over it. Also, The pinholes drastically decreased the hydrogen perm-selectivity of the Pd-based composite membrane. In order to remove the pinholes, we introduced various surface pre-treatment such as alumina powder packing, nickel electro-plating and micro-polishing pre-treatment. Especially, the micro-polishing pretreatment was very effective in roughness leveling off the surface of the porous nickel support, and it almost completely plugged the pores. Fine Ni particles filled surface pinholes with could form open structure at the interface of Pd alloy coating and Ni support by their diffusion to the membrane and resintering. In this study, a $4{\mu}m$ surface pore-free Pd-Cu-Ni ternary alloy membrane on a porous nickel substrate was successfully prepared by micro-polishing, high temperature sputtering and Cu-reflow process. And $H_2$ permeation and $N_2$ leak tests showed that the Pd-Cu-Ni ternary alloy hydrogen membrane achieved both high permeability of $13.2ml{\cdot}cm^{-2}{\cdot}min^{-1}{\cdot}atm^{-1}$ permation flux and infinite selectivity.

Computational Modeling and Analysis of Ablative Composites Using Micro-tomographic Images (미세 단층 영상을 이용한 삭마 복합재료의 전산 모델링 및 해석)

  • Cheon, Jae Hee;Roh, Kyung Uk;Shin, Eui Sup
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.9
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    • pp.642-648
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    • 2019
  • In this study, Image-based computational analysis using the developed models was performed to predict the degradation of effective properties by ablation. The ablation tests of carbon/phenolic composites were performed using a 0.4 MW arc-heated wind tunnel. The carbon/phenolic composite samples were scanned using the micro-computed tomography (Micro-CT) to analyze the ablation characteristics according to a duration time of the ablation test. By calibrating the scanned images, computational models were developed that reflect the actual microstructure of the ablation composites. Also, nine computational models that reflect the actual pore shape were developed using the created cross-sectional images. Image-based computational analysis using the developed models was performed to predict the degradation of effective properties by ablation and the decrease of effective properties was confirmed with increase of porosity.

Experimental Study on the Setting Time and Compressive Strength of Nano-Micro Pozzolanic Binders as Cement Composites (포졸란 혼화재의 입자 크기 및 비표면적에 따른 응결시간 발현 및 압축강도 특성 평가)

  • Kim, Won-Woo;Yang, Keun-Hyeok
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.10 no.3
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    • pp.269-275
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    • 2022
  • In this study, the setting time and compressive strength of cement paste composites applied with nano-micro pozzolanic binders were experimental analyzed. The pozzolanic binder was reduced initial and final setting time and the compressive strength was increased. Micro silica was effective in decrease the initial setting and final setting time and impressing the compressive strength. When two or more cement binders were used, the using of silica fume and a small amount of nano silica at reduced the setting time to 62-64 % to OPC cement and the compressive strength was increased to 117 %. A small amount of mixing the nano silica was effect to pore filling and pozzolanic activation. However, the addition of a chemical admixture should be considered when mixing table design because pozzolanic binders high specific surface area causes a decrease in cement composites flow.

Pore Gradient Nickel-Copper Nanostructured Foam Electrode (기공 경사화된 나노 구조의 니켈-구리 거품 전극)

  • Choi, Woo-Sung;Shin, Heon-Cheol
    • Journal of the Korean Electrochemical Society
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    • v.13 no.4
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    • pp.270-276
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    • 2010
  • Nickel-copper foam electrodes with pore gradient micro framework and nano-ramified wall have been prepared by using an electrochemical deposition process. Growth habit of nickel-copper co-deposits was quite different from that of pure nickel deposit. In particular, the ramified structure of the individual particles was getting clear with chloride ion content in the electrolyte. The ratio of nickel to copper in the deposits decreased with the distance away from the substrate and the more chloride ions in the electrolyte led to the more nickel content throughout the deposits. Compositional analysis for the cross section of a ramified branch, together with tactical selective copper etching, proved that the copper content increased with approaching central region of the cross section. Such a composition gradient actually disappeared after heat treatment. It is anticipated that the pore gradient nickel-copper nanostructured foams presented in this work might be a promising option for the high-performance electrode in functional electrochemical devices.

Silver Coating on the Porous Pellets from Porphyry Rock and Application to an Antibacterial Media (반암(맥반석)으로 제조한 다공성 펠렛의 Ag 담지 및 항균 메디아로서의 적용)

  • Han, Yo-Sep;Kim, Hyun-Jung;Shin, Young-Seop;Park, Jai-Koo;Ko, Jae-Churl
    • Journal of the Korean Ceramic Society
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    • v.46 no.1
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    • pp.16-23
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    • 2009
  • The porous pellets were prepared from porphyry by slurry foaming method. The effect of sintering temperatures on pore structure of porous porphyry pellets with different extension ratio ($E_R$) was investigated by specific surface area, water absorption and porosity, which changed with sintering temperatures. When the sintering temperatures increased from $975^{\circ}C$ to $1075^{\circ}C$, specific surface area and water absorption of the all samples decreased. In case of the sample with an equal sintering temperature, $E_R=3.0$ pellets had little influence on pore structure compared to the $E_R=2.0$ pellets. As a results, it was shown by SEM that facilitated formation of micro pores at $E_R=2.0$ pellets shrunk increasingly after sintering process. At $E_R=3.0$ and sintering temperature at $1025^{\circ}C$, optimum conditions of the porous porphyry porous pellets was found. Also, Escherichia coli removal efficiency of the silver-containing porphoyry porous pellets was measured for the feasibility as a antibacterial media. The antibacterial activity of prepared silver-containing sample was maintained above 90% for 40 days.

Physical Properties of Carbon Prepared from a Coconut Shell by Steam Activation and Chemical Activation and the Influence of Prepared and Activated Carbon on the Delivery of Mainstream Smoke

  • Ko, Dong-Kyun;Shin, Chang-Ho;Jang, Hang-Hyun;Lee, Young-Taeg;Rhee, Moon-Soo
    • Journal of the Korean Society of Tobacco Science
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    • v.30 no.1
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    • pp.8-13
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    • 2008
  • Several activated carbon in different specific surface area was prepared by steam and chemical activation of coconut shell. Products were characterized by BET ($N_2$) at 77K, and probed to be highly specific surface area of $1580m^2/g$ and pore volume that had increased with activating conditions. And also we have analyzed the adsorption efficiency of vapor phase components in cigarette mainstream smoke in order to evaluate the relationship between thesmoke components and the physicochemical properties of activated carbons. As a result of this study, the delivery of mainstream smoke was directly affected by the specific surface area and the pore size of activated carbon. The activated carbon prepared by steam activation exhibited better adsorption efficiency on the vapor phase components in mainstream smoke compared with activated carbon prepared by $ZnCl_2$, due to the higher micro-pore area of 66%. But the adsorption efficiency of semi-volatile matters such as phenolic components in a main stream smoke by the activated mesoporous carbon prepared by $ZnCl_2$ is more effective. From the these results, we can conclude that specific surface area by the micropore area increased the adsorption efficiency of activated carbon on vapour phase components, but semi-volatiles or particulate matter was affected by the ratio of mesopore area in total specific surface area.

Fabrication of BCP/Silica Scaffolds with Dual-Pore by Combining Fused Deposition Modeling and the Particle Leaching Method (압출 적층 조형법과 입자 추출법을 결합한 이중 공극 BCP/Silica 인공지지체의 제작)

  • Sa, Min-Woo;Kim, Jong Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.10
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    • pp.865-871
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    • 2016
  • In recent years, traditional scaffold fabrication techniques such as gas foaming, salt leaching, sponge replica, and freeze casting in tissue engineering have significantly limited sufficient mechanical property and cell interaction effect due to only random pores. Fused deposition modeling is the most apposite technology for fabricating the 3D scaffolds using the polymeric materials in tissue engineering application. In this study, 3D slurry mould was fabricated with a blended biphasic calcium phosphate (BCP)/Silica/Alginic acid sodium salt slurry in PCL mould and heated for two hours at $100^{\circ}C$ to harden the blended slurry. 3D dual-pore BCP/Silica scaffold, composed of macro pores interconnected with micro pores, was successfully fabricated by sintering at furnace of $1100^{\circ}C$. Surface morphology and 3D shape of dual-pore BCP/Silica scaffold from scanning electron microscopy were observed. Also, the mechanical properties of 3D BCP/Silica scaffold, according to blending ratio of alginic acid sodium salt, were evaluated through compression test.

Effect of KOH Addition on Pore Structure of Glassy Carbon Prepared by Polymerization of Phenolic Resin (KOH 첨가에 의한 페놀수지로 제조된 유리상탄소의 미세구조제어)

  • 김지현;박세민;임연수;박홍수;김명수
    • Polymer(Korea)
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    • v.26 no.4
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    • pp.477-482
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    • 2002
  • In order to control the micro-pore structure of glassy carbon (GC), an activation agent of KOH was introduced as the glassy carbon was prepared from phenolic resin with a curing agent of phosphoric acid. The yield and properties of GC were investigated as a function of KOH content. Although the GC produced without KOH had nonporous structure except the trace of bubble formation, the GC with KOH had very porous structure. The surface area of GC with KOH increased continuously up to 870 $m^2$/g with the increase of KOH content. The carbonization yield and apparent density measured in water reduced from 40 to 15% and iron 1.5 to 0.9 g/$cm^3$, respectively, and the electrical resistivity increased from $50{\times}10^{-4}$ to $60{\times}10^{-4}$$\Omega$.cm with the increase of KOH content.