• Title, Summary, Keyword: Porous material

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Effects of Material Properties on Optimal Configuration Design of Absorbing Porous Materials (흡음을 위한 다공성 물질의 최적형상설계에서 물성치의 영향)

  • Lee, Joong-Seok;Kim, Yoon-Young;Kang, Yeon-June
    • Proceedings of the KSME Conference
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    • pp.622-624
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    • 2008
  • This investigation studies the effects of material properties and corresponding propagation wave types on optimal configurations of sound absorbing porous materials in maximizing the absorption performance by topology optimization. The acoustic behavior of porous materials is characterized by their material properties which determine motions of the frame and the air. When the frame has a motion, two types of compressional wave propagate in the porous material. Because each wave in the material make different influence on the absorption performance, it is important to understand the relative contribution of each wave to the sound absorption. The relative contribution of the propagating waves in a porous material is determined by the material properties, therefore, an optimal configuration of a porous material to maximize the absorption performance is apparently affected by the material properties. In fact, virtually different optimal configurations were obtained for absorption coefficient maximization when the topology optimization method developed by the authors was applied to porous materials having different material properties. In this investigation, some preliminary results to explain the findings are presented. Although several factors should be considered, the present investigation is focused on the effects of the material properties and corresponding propagation waves on the optimized configurations.

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Thermoelastic Properties of Porous Metals After Material Forming Processes (다공성 금속의 성형공정 후 열탄성 계수)

  • 이종원;김진원
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.217-220
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    • 2003
  • The effective thermoelastic properties of porous metals are discussed herein after each material forming process such as hot pressing or extrusion. The voids in metal matrix are assumed to be initially spherical in shape and to be distributed randomly. Once the porous material deforms plastically due to each material forming process, the voids change their shape from a sphere to an ellipsoid and align in one direction. Since the voids are compressible in nature, the void volume fraction is assumed to be decreasing during each material forming process.

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A Study on the Acoustic Properties of Porous Material by Using Acoustic Transfer Matrix (전달행렬법에 의한 다공질 흡음재의 음향특성 연구)

  • 박철희;주재만;염창훈
    • Journal of KSNVE
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    • v.6 no.5
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    • pp.635-644
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    • 1996
  • In this paper, Allard's modelling method which employs the method of acoustic transfer matrix(ATM) is applied to yield more precise results in the analysis of porous sound absorbing material. The method of ATM, based on Biot's theory, is known to play an important role in the estimation of the sound absorption when a sound projects onto the material. In the case of a single layered porous sound absorbing material, the surface impedance and the absorption coefficient by using the method of ATM are estimated. With the variation of the material properties, sound absorption characteristics and analyzed. Transmission Loss in a combination of the porous sound absorbing material with a thin plate is predicted.

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Evaluation of Humidity Control Ceramic Board Using Gypsum Binder (석고계 바인더를 활용한 습도도절 세라믹 보드의 특성 평가)

  • Lee, Jong-Kyu;Kim, Tae-Yeon
    • Korean Journal of Materials Research
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    • v.28 no.1
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    • pp.62-67
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    • 2018
  • Active clay, bentonite and zeolite were used as porous materials for humidity controlling ceramic boards. The specific area and the pore volume of active clay were higher than bentonite and zeolite. The flexible strength of the gypsum board decreased with an increasing amount of porous material, and the flexible strength was lowest when active clay with a higher specific surface area than others porous materials was added. The specific surface area and total pore volume of ceramic boards containing porous material were highest at $102.25m^2/g$, $0.142cm^3/g$, respectively, when the active clay was added. In addition, as the amount of added porous materials increased, the specific surface area and total pore volume of the ceramic board increased, but the average pore diameter decreased. The addition of s porous materials with a high specific area and a large pore volume improved the moisture absorptive and desorptive performance of the ceramic board. Therefore, in this experiment, the moisture absorptive and desorptive properties were the best when active clay was added. Furthermore, as the amount of added porous materials increased, the moisture absorptive and desorptive properties improved. When 70 mass% of active clay was added to ${\alpha}$-type gypsum, the hygroscopicity was the highest, about $300g/m^2$, in this experiment.

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.

Fabrication Methods of Porous Ceramics and Their Applications in Advanced Engineering - Large Flat Precision Plate for Flat Display Industries

  • Matsumaru, Koji;Ishizaki, Kozo
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.3.1-3.1
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    • 2009
  • Normal sintering process of producing porous ceramics is not to sinter perfectly, i.e., stop sintering in middle-process. Our porous ceramic materials are a product of complete sintering. For example if one want to make a porous carborundum, raw carborundum powder is sintered at either lower temperatures than normal sintering temperature or shorter sintering periods than normal sintering time to obtain incompletely sintered materials, i.e., porous carborundum. This implies normally sintered porous ceramic materials can mot be used in high vacuum conditions due to dust coming out from uncompleted sintering. We could produce completely sintered porous ceramic materials. For example, we can produce porous carborundum material by using carborundum particles bonded by glassy material. The properties of this material are similar to carborundum. We could make quasi-zero thermal expansion porous material by using carborundum and particles of negative thermal expansion materials bonded by the glassy material. We apply to sinter them also by microwave to sinter quickly. We also use HIP process to introduce closed pores. We could sinter them in large size to produce $2.5m{\times}2.5m$ ceramic plate to use as a precision plate for flat display industries. This flat ceramic plate is the world largest artificial ceramic plate. Precision plates are basic importance to any advanced electronic industries. The produced precision plate has lower density, lower thermal expansivity, higher or similar damping properties added extra properties such as vacuum vise, air sliding capacity. These plates are highly recommended to use in flat display industries. We could produce also cylindrical porous ceramics materials, which can applied to precision roller for polymer film precision motion for also electronic industries.

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Preparation and characterization of a porous silicate material from silica fume

  • Zhang, Yinmin;Qi, Haiping;Li, Yaqiong;Zhang, Yongfeng;Sun, Junmin
    • Korean Journal of Chemical Engineering
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    • v.34 no.12
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    • pp.3185-3194
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    • 2017
  • A porous silicate material derived from silica fume was successfully prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, Thermogravimetry and Differential thermal gravity (TG-DTG), $N_2$ adsorption and desorption isotherms, and scanning electron microscopy (SEM). Raw silica fume was analyzed by XRD, FT-IR and SEM. The analysis results of silica fume indicated that $SiO_2$ in silica fume is mainly determined as amorphous state, and that the particles of raw silica fume exhibited characteristic spherical structure with a diameter of from 50 nm to 200 nm. The preparation of the porous silicate material involved two steps. The first step was the extraction of the $SiO_3^{2-}$ leachate from raw silica fume. The maximum value of $SiO_3^{2-}$ extraction yield was obtained under the following conditions: reaction temperature of $120^{\circ}C$, reaction time of 120 min, NaOH concentration of 15%, and alkali to $SiO_2$ molar ratio of 2. The second step was the preparation of the porous silicate material though the reaction of $SiO_3^{2-}$ leachate and $Ca(OH)_2$ suspension liquid. The optimum preparation conditions were as follows: preparation temperature of $90^{\circ}C$, preparation time of 1.5 h, Si/Ca molar ratio of 1 : 1, and stirring rate of 100 r/min. The BET surface area and pore size of the porous silicate material were $220.7m^2{\cdot}g^{-1}$ and $8.55cm^3/g$, respectively. The porous silicate material presented an amorphous and unordered structure. The spectroscopic results indicated that the porous silicate material was mainly composed of Si, Ca, O, C, and Na, in the form of $Ca^{2+}$, $SiO_3^{2-}$, $CO_3^{2-}$ and $Na^+$ ions, respectively, which agreed with the XRD, TG-DSC, and FT-IR data. The $N_2$ adsorption-desorption isotherm mode indicates that the porous silicate material belonged to a typical mesoporous material. The porous silicate material presented efficiency for the removal of formaldehyde: it showed a formaldehyde adsorption capacity of 8.01 mg/g for 140 min at $25^{\circ}C$.

Microstructure and Tensile Deformation Behavior of Ni-Cr-Al Powder Porous Block Material (블록형 Ni-Cr-Al 분말 다공성 소재의 미세조직 및 인장 변형 거동)

  • Kim, Chul-O;Bae, Jung-Suk;Lee, Kee-Ahn
    • Journal of Korean Powder Metallurgy Institute
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    • v.22 no.2
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    • pp.93-99
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    • 2015
  • This study investigated the microstructure and tensile properties of a recently made block-type Ni-Cr-Al powder porous material. The block-type powder porous material was made by stacking multiple layers of powder porous thin plates with post-processing such as additional compression and sintering. This study used block-type powder porous materials with two different cell sizes: one with an average cell size of $1,200{\mu}m$ (1200 foam) and the other with an average cell size of $3,000{\mu}m$ (3000 foam). The ${\gamma}$-Ni and ${\gamma}^{\prime}-Ni_3Al$ were identified as the main phases of both materials. However, in the case of the 1,200 foam, a ${\beta}$-NiAl phase was additionally observed. The relative density of each block-type powder porous material, with 1200 foam and 3000 foam, was measured to be 5.78% and 2.93%, respectively. Tensile tests were conducted with strain rates of $10^{-2}{\sim}10^{-4}sec^{-1}$. The test result showed that the tensile strength of the 1,200 foam was 6.0~7.1 MPa, and that of 3,000 foam was 3.0~3.3 MPa. The elongation of the 3,000 foam was higher (~9%) than that (~2%) of the 1,200 foam. This study also discussed the deformation behavior of block-type powder porous material through observations of the fracture surface, with the results above.

Application of sensitivity analyses in premixed combustion within a porous ceramic burner (다공 세라믹 연소기 속에서의 예혼합연소에 대한 민감도 해석의 적용)

  • Im, In-Gwon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.2
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    • pp.162-172
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    • 1998
  • A numerical study of premixed combustion within a porous ceramic burner (PCB) is performed to understand flame behavior with respect to various model parameters. Basic flame structure within the porous ceramic burner and species profiles such as NO and CO are examined. Sensitivity analysis of flame speed, gas and solid temperature, NO and CO emission from the burner with respect to reaction steps and various physical properties of the ceramic material is applied to find the most significant parameters in selection of porous materials for the porous ceramic burner. Effects of thermal conductivity, extinction coefficient and scattering albedo on the burner characteristics are studied through the sensitivity analysis. The results of sensitivity study reveal the order of importance in ceramic material properties to get suitable burner performance. Scattering albedo, which governs the ratio of absorbed energy by the ceramic material to total radiative energy transferred, is one of the most important parameters in the material properties since it affects the actual absorbed radiation rate and thus it largely affects the flame structure. Through the study, it is found that the sensitivity study can be used to estimate the flame behavior within the porous ceramic burner more effectively.

Thermal Diffusivity Measurement of Carbon/Epoxy and Porous Thermal Insulation Material under Vacuum Condition Using Cyclic Heating Method (주기가열법을 이용한 탄소/에폭시 및 다공성 단열재의 진공 열확산도 측정)

  • Nam, Gi-Won;Yi, Yeong-Moo;Ohnishi, Akira;Kong, Cheol-Won
    • Composites Research
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    • v.20 no.5
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    • pp.20-25
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    • 2007
  • Cyclic heating method is useful method for measuring the thermal diffusivity of porous materials. The main object of this paper is to develop and verify the thermal diffusivity measuring system of porous materials under vacuum condition. To verify this method, thermal diffusivities of the alumina ($Al_2O_3$) specimen and polystyrene foam were measured. Thermal diffusivities of these specimens were agreed with reference values. Thermal diffusivities of carbon/epoxy and porous insulation material were measured at atmospheric room temperature condition and vacuum condition respectively. Thermal diffusivities of carbon/epoxy and porous insulation material under vacuum are reduced by 66.4% and 64.9% compared to the thermal diffusivities under the atmospheric condition. These differences are considered the effect of the porous insulation material with an air.