• Title/Summary/Keyword: Pores/Porosity

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Effects of Interface Porosity on Dielectric and Piezoelectric Properties of BaTiO3-Polymer Composites of O-3 Type Connectivity (O-3형 BaTiO3-폴리머 복합체의 계면기공율 변화에 따른 유전 및 압전특성)

  • 이형규;김호기
    • Journal of the Korean Ceramic Society
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    • v.26 no.5
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    • pp.617-624
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    • 1989
  • Piezoelectric composites of O-3 connectivity were prepared by thermosetting barium titanate-phenolic resin composite under various cruing pressure. Among three kinds of pore in O-3 type ceramic-polymer composite, such as matrix pores, particle pores, and ceramic-polymer interface pores, the effect of interface porosity on the dielectric and piezoelectric constant was investigated. In pure barium titanate ceramics, the porosity factor of dielectric and piezoelectric constants were 5.7 and 5.0, respectively. However, in BaTiO3-polymer composite, the interface porosity factor of the piezoelectric constant was greater than that of the dielectric constant, interface porosity factor b in d33 was 9.8 and in r 4.6. On the other, piezoelectric voltage constant g33 was independent of the porosity of barium titanate ceramics. But in composite system, the piezoelectric voltage constant g33 was decreased with interface porosity.

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AN EXPERIMENTAL STUDY ON THE PORCELAIN POROCITY EXERTED BY THE CONTAMINATION OF THE CERAMO-METAL ALLOY AND LIQUID (도재소부전장금관용 합금과 용액의 오염이 기포발생에 미치는 영향에 관한 실험적 연구)

  • Jeun, Young-Chan;Lee, Ho-Yong
    • The Journal of Korean Academy of Prosthodontics
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    • v.20 no.1
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    • pp.33-49
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    • 1982
  • This study was undertaken to observe the porcelain porosity exerted by the contamination of the alloy and liquid. The alloy used in this study was Jelstar; liquids were Ceramco Sta-Wet liquid, distilled water and tap water; and Ceramco vacuum porcelain powder was used. The measurements with photomicroscope (x200, Olympus) were made on the porosity, the diameter (mm) of the pores and the numbers of the pores ($No/mm^2$) The results of this study were obtained as follows: 1. In the porosity, the opaque layer contained over 70% of the total porosity, and the porosity was increased about twice in every porcelain layer by the tap water. 2. The contamination of the alloy and liquid caused porosity to increase markedly at the interface of the metal-porcelain. 3. The diameter of the pores were increased about 1.5 times larger by the contaimination of the liquid, and only a slight increase in the opaque layer due to the contamination of the alloy. 4. In the numbers of the pores, there were significant differences according to the contamination of the alloy and the porcelain layer. And the contamination of the liquid caused significant differences only in the opaque layer.

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The influence of fine particle migration on pore structure of overlying ballast under cyclic loading

  • Yu Ding;Yu Jia;Zhongling Zong;Xuan Wang;Jiasheng Zhang;Min Ni
    • Geomechanics and Engineering
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    • v.35 no.6
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    • pp.627-636
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    • 2023
  • The essence of subgrade mud pumping under train load is the migration of fine particles in subgrade soil. The migration of fine particles will change the pore structure of overlying ballast, thus affecting the mechanical properties and hydraulic properties of ballast layer. It is of great theoretical significance and engineering value to study the effect of fine particle migration on the pore structure of ballast layer under cyclic loading. In this paper, a tailor-made subgrade mud pumping test model and an X-ray computed tomography (CT) scanning equipment were used to study the influence of migration of fine particles in subgrade soil on the pore parameters (plane porosity, volume porosity, pore distribution and pore connectivity) of overlying ballast under cyclic loading. The results show that the compression of ballast pores and the blockage of migrated fine particles make the porosity of ballast layer decreases gradually. And the percentage of small pores in ballast layer increases, while the percentage of large pores decreases; the connectivity of pores also gradually decreases. Based on the test results, an empirical model of ballast porosity evolution under cyclic loading is established and verified.

Measurement of Porosity by EPMA-EDS Image Processing

  • Hung, Minhui;Li, Xiangting;Xia, Jiyu;Ding, Chuanxian
    • Journal of the Korean Vacuum Society
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    • v.6 no.S1
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    • pp.66-69
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    • 1997
  • Porosity is one important characteristic feature and structural index of sprayed coatings. A method of measurement of porosity, EPMA-EDS image processing is developed in the paper. The characteristics of pores can be determined by processing of the image obtained from an electron microscope via VISTA, Not only the porosity can be presented but also the statistical result of pore size distribution. Finally it can be drawn from this paper that EPMA-EDS is a quite effective method to completely characterize the pores in plasma sprayed coatings.

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CHARACTERISTICS OF RESIDUAL CARBON DERIVED FROM THE COMBUSTION OF VACUUM RESIDUE IN A TEST FURNACE

  • Park, Ho-Young;Seo, Sang-Il
    • Environmental Engineering Research
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    • v.12 no.3
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    • pp.109-117
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    • 2007
  • The characteristics of carbonaceous particles collected from the combustion of Vacuum Residue (VR) in a test furnace have been investigated. The physical and chemical characterization includes particle size, scanning electron microscopy of the surface structure, measurement of porosity, surface area and density, EDX/XRD analyses and measurement of chemical composition. The studies show that the carbonaceous VR particles are very porous and spheroidal, and have many blow-holes on the surface. The particles become smaller and more sponge-like as the reaction proceeds. The present porosity of VR particles is similar to that of cenospheres from the combustion of heavy oil, and the majority of pores are distributed in macro-pores above $0.03\;{\mu}m$ in diameter. Measurements of pore distribution and surface area showed that the macro-pores contributed most to total pore volume, whereas the micro-pores contributed to total surface area.

Porometric Study on the Gas Diffusion Layer in PEMFCs Using Method of Standard Porosimetry (MSP 기법을 적용한 고분자 전해질 연료전지 가스확산층의 포로시메트리 연구)

  • Lee, Yongtaek
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.2
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    • pp.64-69
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    • 2013
  • The structure of pore network of gas diffusion layers (GDLs) in PEMFCs plays a critical role in determining the transport phenomena of reaction gas as well as generated water. In addition, the interactive characteristics between water and surface of pore are no less important than the structural characteristics of pore network. In this study, porometric investigation is conducted for two kinds of GDL using method of standard porosimetry which enable to distinguish hydrophobic pores from hydrophilic pores of GDLs. The porosity of TGPH-120 decreases by 6% by adding 30 wt.% of PTFE, but the porosity of hydrophilic pores decreases by 12%. The relation of $p_c-S_{nw}$ varies with the addition of PTFE, especially at low $p_c$.

Simulation of Pore Interlinkage in the Rim Region of High Burnup $UO_2$Fuel

  • Koo, Yang-Hyun;Oh, Je-Yong;Lee, Byung-Ho;Cheon, Jin-Sik;Joo, Hyung-Koo;Sohn, Dong-Seong
    • Nuclear Engineering and Technology
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    • v.35 no.1
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    • pp.55-63
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    • 2003
  • Threshold porosity above which fission gas release channels would be formed in the rim egion of high burnup UO$_2$ fuel was estimated by the Monte Carlo method and Hoshen-Kopelman algorithm. With the assumption that both rim pore and rim grain can be represented by cube, pore distribution in the rim was simulated 3-dimensionally by the Monte Carlo method according to porosity and pore size distribution. Then, using the Hoshen-Kopelman algorithm, the fraction of open rim pores interlinked to the outer surface of a fuel pellet was derived as a function of rim porosity. The simulation showed that porosity of 24-25% is the threshold above which the number of rim pores forming release channels increases very rapidly. On the other hand, channels would not be formed if the porosity is less than about 23.5%. This is consistent with the observation that, for porosity less than 23.5%, almost no fission gas is released in the rim. However, once the rim porosity reaches beyond 25%, extensive open paths would be developed and considerable fission gas release would start in the rim.

Damage evolution of red-bed soft rock: Progressive change from meso-texture to macro-deformation

  • Guangjun Cui;Cuiying Zhou;Zhen Liu;Lihai Zhang
    • Geomechanics and Engineering
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    • v.36 no.2
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    • pp.121-130
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    • 2024
  • Many foundation projects are built on red-bed soft rocks, and the damage evolution of this kind of rocks affects the safety of these projects. At present, there is insufficient research on the damage evolution of red-bed soft rocks, especially the progressive process from mesoscopic texture change to macroscopic elastoplastic deformation. Therefore, based on the dual-porosity characteristics of pores and fissures in soft rock, we adopted a cellular automata model to simulate the propagation of these voids in soft rocks under an external load. Further, we established a macro-mesoscopic damage model of red-bed soft rocks, and its reliability was verified by tests. The results indicate that the relationship between the number and voids size conformed to a quartic polynomial, whereas the relationship between the damage variable and damage porosity conformed to a logistic curve. The damage porosity was affected by dual-porosity parameters such as the fractal dimension of pores and fissures. We verified the reliability of the model by comparing the test results with an established damage model. Our research results described the progressive process from mesoscopic texture change to macroscopic elastoplastic deformation and provided a theoretical basis for the damage evolution of these rocks.

Acoustic Characteristics of Sand Sediment Slab with Water- and Air-filled Pore

  • Roh Heui-Seol;Lee Kang Il;Yoon Suk Wang
    • Proceedings of the Acoustical Society of Korea Conference
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    • autumn
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    • pp.223-226
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    • 2001
  • Acoustic pressure transmission coefficient and phase velocity are measured as the functions of water porosity and air porosity in sand sediment slabs with water- and air-filled pores. Pores in the sand sediment slab we modeled as the structure of circular cylindrical tube shape filled with water and air. The first kind(fast) wave and second kind (slow) wave, identified by Biot, in the solid and fluid mixed medium are affected by the presence of water and air pores. Acoustic characteristics of such porous medium in water are also theoretically investigated in terms of the modified Biot-Attenborough (MBA) model, which uses the separate treatment of viscosity effect and thermal effect in non-rigid porous medium with water- and air-filed pores. The information on the fast waves introduces new concepts of the generalized tortuosity factor and dynamic shape factor.

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Nondestructive Evaluation of Microstructure of SiCf/SiC Composites by X-Ray Computed Microtomography

  • Kim, Weon-Ju;Kim, Daejong;Jung, Choong Hwan;Park, Ji Yeon;Snead, Lance L.
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.378-383
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    • 2013
  • Continuous fiber-reinforced ceramic matrix composites (CFCCs) have a complex distribution of porosity, consisting of interfiber micro pores and interbundle/interply macro pores. Owing to the complex geometry of the pores and fiber architecture, it is difficult to obtain representative microstructural features throughout the specimen volume with conventional, destructive ceramographic approaches. In this study, we introduce X-ray computed microtomography (X-ray ${\mu}CT$) to nondestructively analyze the microstructures of disk shaped and tubular $SiC_f$/SiC composites fabricated by the chemical vapor infiltration (CVI) method. The disk specimen made by stacking plain-woven SiC fabrics exhibited periodic, large fluctuation of porosity in the stacking direction but much less variation of porosity perpendicular to the fabric planes. The X-ray ${\mu}CT$ evaluation of the microstructure was also effectively utilized to improve the fabrication process of the triple-layered tubular SiC composite.