• Title/Summary/Keyword: Pore-filled

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The Effect of Si3N4 Addition on Nitriding and Post-Sintering Behavior of Silicon Powder Mixtures

  • Park, Young-Jo;Ko, Jae-Woong;Lee, Jae-Wook;Kim, Hai-Doo
    • Journal of the Korean Ceramic Society
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    • v.49 no.4
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    • pp.363-368
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    • 2012
  • Nitriding and post-sintering behavior of powder mixture compacts were investigated. As mixture compacts are different from simple Si compacts, the fabrication of a sintered body with a mixture composition has engineering implications. In this research, in specimens without a pore former, the extent of nitridation increased with $Si_3N_4$ content, while the highest extent of nitridation was measured in $Si_3N_4$-free composition when a pore former was added. Large pores made from the thermal decomposition of the pore former collapsed, and they were filled with a reaction product, reaction-bonded silicon nitride (RBSN) in the $Si_3N_4$-free specimen. On the other hand, pores from the decomposed pore former were retained in the $Si_3N_4$-added specimen. Introduction of small $Si_3N_4$ particles ($d_{50}=0.3{\mu}m$) into a powder compact consisting of large silicon particles ($d_{50}=7{\mu}m$) promoted close packing in the green body compact, and resulted in a stable strut structure after decomposition of the pore former. The local packing density of the strut structure depends on silicon to $Si_3N_4$ size ratio and affected both nitriding reaction kinetics and microstructure in the post-sintered body.

Microstructure of Non-Sintered Inorganic Binder using Phosphogypsum and Waste Lime as Activator

  • Kim, Ji-Hoon;An, Yang-Jin;Mun, Kyung-Ju;Hyung, Won-Gil
    • Journal of the Korea Institute of Building Construction
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    • v.18 no.3
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    • pp.305-312
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    • 2018
  • This study is about the development of a non-sintered binder (NSB) which does not require a sintering process by using the industrial by-products Phosphogypsum (PG), Waste Lime (WL) and Granulated Blast Furnace Slag (GBFS). In this report, through SEM analysis of the NSB paste hardening body, micropore analysis of paste using the mercury press-in method and microstructure observation were executed to consider the influence of the formation of the pore structure and the distribution of pore volume on strength, and the following conclusions were reached. 1) Pore structure of NSB paste of early age is influenced by hydrate generation amount by GBFS and activator. 2) Through observing the internal microstructure of NSB binder paste, it was found that the strength expression at early age due to hydration reaction was achieved with a large amount of ettringite serving as the frame with C-S-H gel generated at the same time. It was confirmed that C-S-H gel wrapped around ettringite, and as time passed, the amount generated continually increased, and C-S-H gel tightly filled the pores of hardened paste, forming a dense network-type web structure. 3) For NSB-type cement, the degree of formation of gel pores below $10{\mu}m$ had a greater influence on strength improvement than simple pore reduction by charging capillary pores, and the pore size that had the greatest effect on strength was micropores with diameter below $10{\mu}m$.

Stability assessment of soil slopes in three dimensions: The effect of the width of failure and of tension crack

  • Pantelidis, Lysandros;Gravanis, Elias;Gkotsis, Konstantinos-Paraskevas
    • Geomechanics and Engineering
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    • v.22 no.4
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    • pp.319-328
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    • 2020
  • This paper investigates the effect of the width of failure and tension crack (TC) on the stability of cohesive-frictional soil slopes in three dimensions. Working analytically, the slip surface and the tension crack are considered to have spheroid and cylindrical shape respectively, although the case of tension crack having planar, vertical surface is also discussed; the latter was found to return higher safety factor values. Because at the initiation of a purely rotational slide along a spheroid surface no shear forces develop inside the failure mass, the rigid body concept is conveniently used; in this respect, the validity of the rigid body concept is discussed, whilst it is supported by comparison examples. Stability tables are given for fully drained and fully saturated slopes without TC, with non-filled TC as well as with fully-filled TC. Among the main findings is that, the width of failure corresponding to the minimum safety factor value is not always infinite, but it is affected by the triggering factor for failure (e.g., water acting as pore pressures and/or as hydrostatic force in the TC). More specifically, it was found that, when a slope is near its limit equilibrium and under the influence of a triggering factor, the minimum safety factor value corresponds to a near spherical failure mechanism, even if the triggering factor (e.g., pore-water pressures) acts uniformly along the third dimension. Moreover, it was found that, the effect of tension crack is much greater when the stability of slopes is studied in three dimensions; indeed, safety factor values comparable to the 2D case are obtained.

Controlling Water Splitting Characteristics of Anion-Exchange Membranes by Coating Imidazolium Polymer (이미다졸륨 고분자 코팅을 통한 음이온교환막의 물분해 특성 제어)

  • Kim, Do-Hyeong;Park, Jin-Soo;Kang, Moon-Sung
    • Membrane Journal
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    • v.25 no.2
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    • pp.152-161
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    • 2015
  • In this study, novel pore-filled anion-exchange membranes (PFAEMs) with low electrical resistance, high permselectivity, and low water-splitting flux property under a concentration polarization condition have been developed for the enhancement in the efficiency of electrochemical water treatment processes. The base membranes have been prepared by filling a copolymer containing quaternary ammonium groups with an excellent ion-exchange capability into a porous polyolefin substrate, showing a high performance superior to that of a commercial membrane. In addition, it was confirmed that the electrochemical membrane performances are preserved while the water-splitting flux is effectively controlled by coating an imidazolium polymer onto the surface of the base membrane. The prepared PFAEMs revealed remarkably low electrical resistances of about 1/6~1/8 compared to those of a commercial membrane, and simultaneously low water-splitting flux comparable with that of cation-exchange membranes under a concentration polarization condition.

The Estimation of the Loss Possibility of Zeolite in Sandy Soil (사질토양(砂質土壤)에서의 Zeolite 유실(流失) 가능성(可能性)의 추정(推定))

  • Kang, Shin-Jyung;Choi, Jyung
    • Applied Biological Chemistry
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    • v.29 no.3
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    • pp.311-317
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    • 1986
  • This experiment was conducted to find out the minimum size of pores through that Zeolite particles moved vertically out with percolated solution in the sand column and to estimate whether they were lost through the pores in the field sandy soil. The results were as follows. 1. The amount of Zeolite loss through sand columns was increased in the order of the columns filled with $2{\sim}1>1{\sim}0.5>0.5>0.25mm$ sand particles. 2. The Zeolite particles lost through columns filled with $1{\sim}0.5$ and $0.5{\sim}0.25mm$ sand were clay fraction. 3. The pore sire that clay fraction of Zeolite mineral could migrate through was determined to be above $150{\mu}m$ and Jangchon subsoil was presumed to have possibility of Zeolite loss in consideration of its pore size distribution. 4. The suitable particle size of Zeolite for application in sandy soil was presumed to be above $2{\mu}m$.

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Wave-Induced Response of Unsaturated and Multi-layered Seabed; A Semi-analytical Method (파랑으로 인한 불포화된 다층 해저지반의 거동;준해석적 방법)

  • ;Rahman, M. S.
    • Journal of the Korean Geotechnical Society
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    • v.15 no.6
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    • pp.45-55
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    • 1999
  • Wave-induced response, liquefaction and stability of unsaturated seabed are studied. The unsaturated seabed is modeled as a fluid-filled polo-elastic medium. The coupled process of fluid flow and the deformation of soil skeleton is formulated in the framework of Biot's theory. The resulting governing equations are solved using a semi-analytical method to evaluate the stresses and pore water pressure of unsaturated and multi-layered seabed. The semi-analytical method can be applied to calculate a pore pressure and the stresses of in anisotropic inhomogeneous seabed. The results indicate that the degree of saturation influences mostly on the magnitudes of a pore pressure and the stresses of unsaturated and multi-layed seabed. Based on the pore pressure and stresses in seabed, the analysis on the possibilities of liquefaction and shear failure was performed. The results show that the maximum depth of shear failure occurrence is deeper than the maximum liquefaction depth.

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Pressure Loss and Enhancement of Heat Transfer in an Annulus Filled with Aluminum Foam

  • Noh, Joo-Suk;Han, Young-Hee;Lee, Kye-Bock;Lee, Chung-Gu
    • International Journal of Air-Conditioning and Refrigeration
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    • v.15 no.1
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    • pp.17-24
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    • 2007
  • An experimental investigation was carried out for 4 different types of the aluminum foam heat sinks which were inserted into the annulus. The purpose of this study is to examine the feasibility of a heat sink with high performance forced convective water cooling in the annulus. The local wall temperature distribution, inlet and outlet pressures and temperatures, and heat transfer coefficients were measured for heat flux of 13.6, 18.9, 25.1, 31.4 $kW/m^2$ and Reynolds number ranged from 120 to 9,000. Experimental results show that the departure from the Darcy's law is evident from the pressure loss and the friction factor is much higher while the significant enhancement in Nusselt number is obtained, and average Nusselt number of aluminum foam with high pore density is much higher than that of aluminum foam with low pore density. Correlations for the friction factor is proposed and used for design of thermal applications.

Improvement of Liquid Wetting and Retention Properties of Wool Fabric in Nonionic Surfactant Solutions (비이온계 계면활성제 수용액에서 모직물의 표면적심과 액체보유력 향상)

  • Kim, Chun-Hee
    • Textile Coloration and Finishing
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    • v.21 no.2
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    • pp.7-13
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    • 2009
  • The effects of 0.1g/dl nonionic surfactant solutions on liquid wetting and retention properties of wool fabric are reported. The 10 different nonionic surfactants (Span 20, Tween 20, 40, 60, 80, 21, 61, 81, 65, 85), wool cloth (EMPA 217), and wool soiled cloth (EMPA 107) are used in the study. Both EMPA 217 and 107 have water contact angle($\Theta$)>$90^{\circ}$, which indicates that water spreading over a fabric surface and penetration into the fabric rarely occur. However, EMPA 217 and 107 are easily wetted with perchloroethylene(PCE) having very low values of $\Theta$'s and high values of liquid retention. Water wetting properties are greatly improved by adding nonionic surfactants into the system. Generally, hydrophilic surfactants which have low number of carbon atoms or unsaturated hydrophobic structures are effective in improving water wetting of wool fabrics. The water retention of EMPA 217 and 107 in surfactant solutions have positive relations with $cos{\Theta}$, adhesion tension, and work of adhesion. 40.3% pore volume of EMPA 217 and 26.1% pore volume of EMPA 217 can be filled with water even when we assume $cos{\Theta}=1$ (${\Theta}=0^{\circ}$).

AN EXPERIMENTAL STUDY ON THE CYTOTOXICITY OF SEVERAL COMPOSITE RESINS (수종(數種) 치과(齒科) 수복용(修復用) 복합(複合)레진의 세포독성(細胞毒性)에 관(關)한 실험적(實驗的) 연구(硏究))

  • Myoung, Jae-Keun;Lee, Myoung-Jong
    • Restorative Dentistry and Endodontics
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    • v.14 no.1
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    • pp.25-40
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    • 1989
  • This study was conducted to evaluate the influence of 5 microfilled composite resin to fibroblast cultivated from human pulp (age 13). Each composite resin was manually mixed and filled in cylinder. Resin filled cylinders were placed in dishes (35mm in diameter) containing 3 ml of ${\alpha}$-MEM. Filters (pore size 0.22 ${\mu}m$) to simulate dentin were also placed between the bottom of cylinder and the dish floor. Then stored in 5% $CO_2$ containing incubator for 1 and 2 weeks at the temperature 36.6 C. The results analysed after 1 and 2 weeks were as follows: 1. Experimental group except group 2, 2 weeks incubation cases showed the cytotoxicity compared to the control group in cell count. 2. After 2 week-incubation of group 1 and group 4, cell count was more decreased than 1 week cases and cytotoxicity seemed to be constantly influenced to the cell multiplication. 3. The cell growth rate of 1 week incubation in group 3 and group 5 was similar to the control group and recognized the cytotoxicities of these groups were mild. 4. The cell multiplication rate of 2 week incubation cases in group 2 was greater than control group.

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Analysis of Seepage Behavior of Bottom Protection Layer by Filed Monitoring (계측관리를 통한 방조제 바닥보호공의 침투거동분석)

  • Kang, Byung-Yoon;Oh, Young-In;Kim, Ki-Nyeon;Kim, Hyun-Tae
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.806-813
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    • 2008
  • In this research, mainly research about the structural and functional stability of sea dyke with variation of seepage condition after final closure. The piezometric head (water head in embankment) monitoring system was installed at two representative final closure section. The dredged fine sand filling condition was evaluated by in-situ test results. Also, the numerical analysis was performed to determine the permeability of bottom protection layer filled with dredged fine sand by monitoring results. According to numerical back analysis results, the coefficient of permeability of bottom protection section of is $7.6{\times}10^{-6}$ m/sec. These results are noted that the bottom protection layer of sea dyke was strong and intensively filled with dredged sand. Also, based on the seepage analysis, the seepage flux of this sea dyke was calculated about $2.42m^3$/day/m which is 29% decreased value compare with adjacent sea dyke.

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