• Tribology and Lubricants
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• v.25 no.1
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• pp.7-12
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• 2009

Coating brittle intermetallic compounds on metal can enlarge the range of their use. It is found that intermetallic compound coating layers made by only combustion synthesis in an electric furnace have porous multi-phase structures containing several intermediate phases, even though the coating layers show good wear resistance. In this study, dense $Ni_{3}Al$ single phase layer corresponding to the initial composition of the mixed powder is coated on two different ferrous materials by the diffusing treatment after combustion synthesis. After- ward, sliding wear behaviors of the coating layer are evaluated in comparison with that of the coating layer with porous multi-phase structure made by only combustion synthesis. As a result, the wear properties of the coating layer composed of dense $Ni_{3}Al$ single phase are considerably improved at the range of low sliding speed com- pared with that of the coating layer with porous multi-phase structure, particularly in the running-in wear region. This is attributed to the fact that wear of the coating layer is progressed by shearing as a sequence of adhesion, not by occurring of pitting on the worn surface due to having dense structure without pores.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.1
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• pp.83-102
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• 2015

The present paper analyses the radiation effects of mass transfer on steady nonlinear MHD boundary layer flow of a viscous incompressible fluid over a nonlinear porous stretching surface in a porous medium in presence of heat generation. The liquid metal is assumed to be gray, emitting, and absorbing but non-scattering medium. Governing nonlinear partial differential equations are transformed to nonlinear ordinary differential equations by utilizing suitable similarity transformation. The resulting nonlinear ordinary differential equations are solved numerically using Runge-Kutta fourth order method along with shooting technique. Comparison with previously published work is obtained and good agreement is found. The effects of various governing parameters on the liquid metal fluid dimensionless velocity, dimensionless temperature, dimensionless concentration, skin-friction coefficient, Nusselt number and Sherwood number are discussed with the aid of graphs.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.814-817
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• 2015

A new ionic mass transfer correlation is derived for the fluid-saturated, horizontal porous layer. Darcy-Forchheimer model is used to explain characteristics of fluid motion. Based on the microscales of turbulence a backbone mass transfer relation is derived as a function of the Darcy-Rayleigh number, $Ra_D$ and the porous medium Schmidt number, $Sc_p$. For the Darcy's limit of $Sc_p{\gg}Ra_D$, the Sherwood number, Sh is a function of $Ra_D$ only. However, for the region of high $Ra_D$, Sh can be related with $Ra_DSc_p$. Based on the present backbone equation and the electrochemical mass transfer experiments which are electro plating or electroless plating, the new ionic mass transfer correlation is suggested in the porous media.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.494-496
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• 1996

The purpose of this study is to investigate the effect of process conditions on pore distribution in porous silicon layer prepared by electrochemical reaction. Porous silicon layers formed on p-type silicon wafer show the network structure of fine porse whose diameters are less than 100${\AA}$. In n-type porous silicon, selective growth was found on the pore surface by wet etching process after PR patterning. And numerical method showed high current density on the pore tip. With this result we confirmed that pore formation has two steps. First step is the initial attack on the surface and second step is the directional growth on the pore tip.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.235-235
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• 2010

The Anti-reflection coating(ARC) properties can be formed on silicon substrate using a simple electrochemical etching technique. This etching step can be improve solar cell efficiency for a solar cell manufacturing process. This paper is based on the removal of silicon atoms from the surface a layer of porous silicon(PSi). Porous silicon is form by anodization and can be obtained in an electrolyte with hydrofluoric. It have demonstrated the feasibility of a very efficient porous Si layer, prepared by a simple, cost effective, electrochemical etching method. We expect our research can results approaching to lower than 10% of reflectance by optimization of process parametaer.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.100-106
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• 2012

This study was performed to fabricate porous titanium foam by three-dimensional layer manufacturing process, and to evaluate the porosities, compressive stress, Young's modulus and fracture pattern. Porous titanium foam was made of CP(Commercial Pure) titanium powder (${\leq}5{\mu}m$). Total porosities of titanium foam were in the range of 55-68%. Pore size distribution was $200-440{\mu}m$ for coarse pores, $50-100{\mu}m$ for intermediate pores and $5-10{\mu}m$ for fine pores. Compression elastic modulus and compression stress were decreased with increasing porosity. Young's modulus ranged from 1.04-5.62 GPa and maximum stress ranged from 20-241 MPa. Regarding the mechanical properties, 3D(Three Demensional) porous titanium fabricated layer manufacturing is a promising material for human bone replacement.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.9
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• pp.31-36
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• 1999

A capacitance-type sensor using porous silicon layer is developed to measure aqueous alcohol concentration. Since alcohol, so called ethanol, is very permeable into the silicon wafer, it is often used to help chemical reaction when the silicon wafer is processed under some aqueous solution. In this work, the sensing property was measured for the alcohol concentration from zero to near 100 percent with two types of samples with porous silicon layer formed in 25 and 35% HF solution, respectively. Good reliability as well as fast response time and good linearity were shown over 10kHz and the measured capacitance was observed to be inverse to alcohol concentration due to the decrease of the whole dielectric constant in porous silicon layer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.8
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• pp.617-623
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• 2008

The membrane filter adhered with nanostructured porous layer was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto a conventional micron-fibrous metal filter as a substrate filter. The Sintered-Nanoparticle-Agglomerates-coated NanoStructured porous layer Membrane Filter (SNA-NSMF), whose the filtration performance was improved compared with the conventional metal membrane filters, was developed by adhesion of nanoparticle-agglomerates of dendrite structure sintered onto the micron-fibrous metal filter. The size of nanoparticle-agglomerates of dendrite structure decreased with increasing the sintering temperature because nanoparticle-agglomerates shrank. When shrinking nanoparticle-agglomerates were deposited and treated with heat onto the conventional micron-fibrous metal filter, pore size of nanostructured porous layer decreased. Therefore, pressure drops of SNA-NSMFs increased from 0.3 to 0.516 kPa and filtration efficiencies remarkably increased from 95.612 to 99.9993%.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.417-422
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• 2015

In this study, we investigate the effect of porous $Al_2O_3$ substrate on the strengths of asymmetric structures after we prepare such a structure consisting of a dense $Li_2ZrO_3$ top layer and porous $Al_2O_3$ substrate layer. The porosity and elastic modulus of the substrate layer are controlled by sintering temperature, which has three values of 1150, 1250 and $1350^{\circ}C$. The porosity is controlled in the range of ~ 30-50 vol%, elastic modulus is ~80-120 GPa and elastic mismatch $E_s/E_c$ is ~ 0.6-1.0. Indentation stress-strain curves are obtained and analyzed to evaluate the yield stress of the asymmetric structure by concentrated local loading of WC balls. Conventional flexural strengths are also obtained to evaluate the strength of the asymmetric structure. The results indicate that the local yield strength of the asymmetric structure has mid-values between the top and the substrate layer; however, the flexural strength of the asymmetric structure are mainly influenced by elastic modulus and strength of the substrate.

• Structural Engineering and Mechanics
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• v.72 no.6
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• pp.763-774
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• 2019

The main aim of this paper is enhancing design of traditional laminated composite plates subjected to static loads. In this regard, this paper suggests embedding a lightweight porous layer in the middle of laminated composite as the core layer of the resulted sandwich plate. The static responses of the suggested structures with uniform, symmetric and non-symmetric porosity distributions are compared to optimize their design. Using the first order shear deformation theories, the static governing equations of the suggested laminated composite plates with a porous layer (LCPPL) rested on two-parameter foundation are obtained. A finite element method is also utilized to solve the governing equations of LCPPLs. Effects of laminated composite and porosity characteristics as well as geometry dimension, edges' boundary conditions and foundation coefficients on the static deflection and stress distribution of the suggested composite plates have been investigated. The results reveal that the use of core between the layers of laminated composites leads to a sharp reduction in the static deflections of LCPPLs. Furthermore, in compare with perfect cores, the use of porous core between the layers of laminated composite plates can offer a considerable reduction in structural weight without a significant difference in their static responses.