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Preparation and Characterization of Porous Polymethylmethacrylate Film Showing Optical Reflectivity

  • Kim, Jihoon
    • Journal of the Chosun Natural Science
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    • v.6 no.2
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    • pp.82-86
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    • 2013
  • This paper describes a method for the preparation of porous polymethylmethacrylate showing optical reflectivity from the porous silicon template. A porous polymethylmethacrylate showing optical reflectivity was prepared by replicating porous silicon template which was obtained by applying a computer-generated periodic square current density and resulted in a mirror with high reflectivity in a specific narrow spectral region. A porous polymethylmethacrylate showing an excellent reflectivity was successfully obtained by dissolving the Porous silicon template from the porous polymethylmethacrylate composite film. A porous polymethylmethacrylate exhibited a sharp reflection resonance in the reflectivity spectrum. Surface image of the porous polymethylmethacrylate indicated that the surface of the porous polymethylmethacrylate film had a porous structure. These porous polymethylmethacrylate films in aqueous solutions were stable for several days without any degradation.

A Review of Porous Media Theory from Woltmans Work to Biots Work

  • Park, Taehyo;Jung, Sochan
    • Journal of the Korean Geoenvironmental Society
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    • v.4 no.2
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    • pp.93-104
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    • 2003
  • Porous media consist of physically and chemically different materials and have an extremely complicated behavior due to the different material properties of each of its constituents. In addition, the internal structure of porous materials has generally a complex geometry that makes the description of its mechanical behavior quite complex. Thus, classical continuum mechanics cannot explain the behavior of materials with pore spaces, such as concrete, soils and organic materials in waste landfill. For these reasons, porous media theory has been developed in the nineteenth century. Biot had the greatest influence on the development of porous media theory. Biot's work has been referred by many authors in the literature. Development of numerous fundamental equations in porous media theory were made possible due to Biot's work. His contributions made the greatest influence on porous media theory. Therefore, it is highly advantageous to review Biot's publications. This work presents a review of Biot's work. It shows how porous media theory has been developing so far and provides a chance to discuss the contribution of his work to the modern porous media theory.

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A Study of Developing Guides for the Construction Site Quality Control of Porous Concrete (투수콘크리트 현장품질관리 지침서 개발에 관한 연구)

  • Ko, Eun-Jung;Goh, Eun-Joo;Seok, Ho-Joong;Lee, Seung-Hyeok
    • Journal of the Korea Institute of Building Construction
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    • v.9 no.3
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    • pp.65-71
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    • 2009
  • General criteria for the quality of porous concrete have not been established yet in Korea. And yet, pavement and construction have been performed. In this paper, guidelines on the construction site quality control of porous concrete were developed in order to establish criteria for resolving the issues and problems of porous concrete, to establish methods for improving poor performance, and to manage porous concrete more systematically. In addition, a guide for the construction site quality control of porous concrete, which was appropriate for reality, was developed by researching several quality control guides and maintenance at construction sites. The guide consists of a total of nine chapters such as Application Range, Overview, the Structure of Porous Concrete, the Design of Package Thickness, Package Materials for Porous Concrete, Construction Methods, Quality Assurance and Inspections, Construction Site Quality Control, and Maintenance. It describes quality control guidelines in all steps such as methods for transporting porous concrete from the factory to the construction site, cautions for construction work at construction sites, maintenance, and management. The Guide for the Construction Site Quality Control of Porous Concrete is expected to ensure the quality of porous concrete, to reduce national costs for quality assurance, and to help ensure the health and safety of Korean people.

Strength and Reliability of Porous Ceramics Measured by Sphere Indentation on Bilayer Structure

  • Ha, Jang-Hoon;Kim, Jong-Ho;Kim, Do-Kyung
    • Journal of the Korean Ceramic Society
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    • v.41 no.7
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    • pp.503-507
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    • 2004
  • The importance of porous ceramics has been increasingly recognized and adequate strength of porous ceramics is now required for structural applications. Porosities of porous ceramics act as flaws in inner volume and outer surface which result in severe strength degradation. The effect of pore structure, however, on strength and reliability of porous ceramics has not been clearly understood. We investigate the relationship between pore structure and mechanical properties using a sphere indentation on bilayer structure, porous ceramic top layer with soft polymer substrate. Porous alumina and silica were prepared to characterize the isolated pore structure and interconnected pore structure, respectively. The porous ceramic with 1mm thickness were bonded to soft polycarbonate substrate and then fracture strengths were estimated from critical loads for radial cracking of porous ceramics during sphere indentation from top surface. This simple and reproducible technique provides Weibull modulus of strength of porous ceramics with different pore structure. It shows that the porous ceramics with isolated pore structure have higher strength and higher Weibull modulus as well, than those with interconnected pore structure even with the same porosity.

Preparation and Optical Characterization of DBR/Host Dual Porous Silicon Containing DBR and Host Structures (DBR 다공성 실리콘과 Host 다공성 실리콘으로 이루어진 이중 다공성 실리콘의 제조와 광학적 특성)

  • Choi, Tae-Eun;Yang, Jinseok;Um, Sungyong;Jin, Sunghoon;Cho, Bomin;Cho, Sungdong;Sohn, Honglae
    • Journal of the Chosun Natural Science
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    • v.3 no.2
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    • pp.78-83
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    • 2010
  • DBR/Host dual porous silicons containing DBR and host structure were prepared and their optical properties were characterized using Ocean Optics spectrometer. In this dual porous silicon, single porous silicon layer was used as host layer for possible biomolecule and drug materials and DBR porous silicon layer was used for signal transduction due to the recognition of molecules. Optical reflection spectrum of dual porous silicon displayed only DBR reflection but Fabry-Perot fringe pattern. DBR reflection band of dual porous silicon shifted to the shorter wavelength as the etching time of host layer increased. Cross-sectional FE-SEM image of dual porous silicon displayed a thickness of about 20 micrometer for DBR porous silicon layer. Developed etching technology could be useful to prepare DBR porous silicon which exhibited specific reflection resonance at the required wavelength and to provide an label-free biosensors and drug delivery materials.

Fabrication and Properties of Bioactive Porous Ceramics for Bone Substitution (뼈 대체용 생체활성 다공질 세라믹스의 제조 및 특성)

  • Lee, Lak-Hyoung;Ha, Jung-Soo
    • Journal of the Korean Ceramic Society
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    • v.45 no.10
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    • pp.584-588
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    • 2008
  • Porous hydroxyapatite(HA) and HA-coated porous $Al_2O_3$ possessing pore characteristics required for bone substitutes were prepared by a slurry foaming method combined with gelcasting. The HA coating was deposited by heating porous $Al_2O_3$ substrates in an aqueous solution containing $Ca^{2+}$ and ${PO_4}^{3-}$ ions at $65{\sim}95^{\circ}C$ under ambient pressure. The pore characteristic, microstructure, and compressive strength were investigated and compared for the two kinds of samples. The porosity of the samples was about 81% and 80% for HA and $Al_2O_3$, respectively with a highly interconnected network of spherical pores with size ranging from 50 to $250{\mu}m$. The porous $Al_2O_3$ sample showed much higher compressive strength(25 MPa) than the porous HA sample(10 MPa). Fairly dense and uniform HA coating(about $2{\mu}m$ thick) was deposited on the porous $Al_2O_3$ sample. Since the compressive strength of cancellous bone is $2{\sim}12$ MPa, both the porous HA and HA-coated porous $Al_2O_3$ samples could be successfully utilized as scaffolds for bone repair. Especially the latter is expected suitable for load bearing bone substitutes due to its excellent strength.

Electrical Characteristics of Porous Carbon Electrode According to NaCl Electrolyte Concentration (NaCl 전해질 농도 변화에 따른 다공질 탄소전극의 전기적 특성)

  • Kim, Yong-Hyuk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.10
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    • pp.814-819
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    • 2010
  • Porous carbon electrodes with wooden materials are manufactured by molding carbonized wood powder. Electrical properties of the interface for electrolyte and porous carbon electrode are investigated from viewpoint of NaCl electrolyte concentration, capacitance and complex impedance. Density of porous carbon materials is 0.47~0.61 g/$cm^3$. NaCl electrolytic absorptance of the porous carbon materials is 5~30%. As the electrolyte concentration increased, capacitance is increased and electric resistance is decrease with electric double layer effect of the interface. The electric current of the porous carbon electrode compared in the copper and the high density carbon electrode was improved on a large scale, due to a increase in surface area. The circuit current increased as the distance between of the porous carbon electrode and the zinc electrode decreased, due to increase in electric field. Experimental results indicated that the current properties of galvanic cell could be improved by using porous carbon electrode.

A study of loading property of the bioactive materials in porous Ti implants (다공성 티타늄 임플란트의 생리활성물질 담지특성에 관한 연구)

  • Kim, Yung-Hoon
    • The Journal of Korean Academy of Dental Technology
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    • v.35 no.4
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    • pp.281-286
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    • 2013
  • Purpose: Surface modification is important techniques in modern dental and orthopedic implants. This study was performed to try embedding of bioactive materials in porous Ti implants. Methods: Porous Ti implant samples were fabricated by sintering of spherical Ti powders in a high vacuum furnace. It's diameter and height were 4mm and 20mm. Embedding process was used to suction and vacuum chamber. Loading properties of porous Ti implants were evaluated by scanning electron microscope(SEM), confocal laser scanning microscope(CLSM), and UV-Vis-NIR spectrophotometer. Results: Internal pore structure was formed fully open pore. Average pore size and porosity were $10.253{\mu}m$ and 17.506%. Conclusion: Porous Ti implant was fabricated successfully by sintering method. Particles are necking strongly each other and others portions were vacancy. This porous structure can be embedded to bioactive materials. Therefore bioactive materials will be able to embedding to porous Ti implants. Bioactive materials embedding in the porous Ti implant will induced new bone faster.

Oxidation Behaviors of Porous Ferritic Stainless Steel Support for Metal-supported SOFC

  • Moon, I.J.;Lee, J.W.;Cho, H.J.;Choi, G.M.;Sohn, H.K.
    • Corrosion Science and Technology
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    • v.9 no.5
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    • pp.196-200
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    • 2010
  • Recently porous metal has been used as supporting metal in planar type SOFC. In order to search optimum alloys for porous metal support and estimate the stability of metal-supported SOFC at high temperature, it is necessary to investigate the oxidation behaviors of porous material for metal support in comparison with dense material. Oxidation tests of porous and dense stainless steels were conducted at $600^{\circ}C$ and $800^{\circ}C$. Since the specific surface area of porous material is much larger than that of dense material, surface area should be considered in order to compare the oxidation rate of porous stainless steel with that of dense stainless steel. The specific surface area of porous body was measured using image analyzer. The weight gain of porous stainless steel was much greater than those of dense stainless steels due to its larger specific surface area. considering the specific surface area, the oxidation rate of porous stainless steel is likely to be the same as that of dense stainless steel with the same surface area. The change in chromium content in stainless steel during oxidation was also investigated. The experimental result in chromium content in stainless steel during oxidation corresponded with the calculated value. While the change in chromium content in dense stainless steel during oxidation is negligible, chromium content in porous stainless steel rapidly decreases with oxidation time due to its large specific surface area. The significant decrease in chromium content in porous stainless steel during oxidation may affect the oxidation resistance of porous stainless steel support and long term stability of metal-supported SOFC.

Detection of Organic Vapors Using Change of Fabry-Perot Fringe Pattern of Surface Functionalized Porous Silicon (표면 기능성을 가진 다공성 실리콘의 Fabry-Perot fringe pattern의 변화를 이용한 유기 화합물의 감지)

  • Hwang, Minwoo;Cho, Sungdong
    • Journal of the Chosun Natural Science
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    • v.3 no.3
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    • pp.168-173
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    • 2010
  • Novel porous silicon chip exhibiting dual optical properties, both Frbry-Perot fringe (optical reflectivity) and photoluminescence had been developed and used as chemical sensors. Porous silicon samples were prepared by an electrochemical etch of p-type sillicon wafer (boron-doped, <100> orientation, resistivity 1 - 10 ${\Omega}$). The ething solution was prepared by adding an equal volume of pure ethanol to an aqueous solution of HF (48% by weight). The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Ething was carried out as a two-electrode Kithley 2420 preocedure at an anodic current. The surface of porous silicon was characterized by FT-IR instrument. The porosity of samples was about 80%. Three different types of porous silicon, fresh porous silicon (Si-H termianated), oxidized porous silicon (Si-OH terminated), and surface-derivatized porous silicon (Si-R terminated), were prepared by the thermal oxidation and hydrosilylation. Then the samples were exposed to the wapor of various organics vapors. such as chloroform, hexane, methanol, benzene, isopropanol, and toluene. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organic wapors.