• Advances in nano research
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• 제5권4호
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• pp.393-414
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• 2017

Forced vibration behavior of porous metal foam nanoplates on elastic medium is studied via a 4-variable plate theory. Different porosity distributions called uniform, symmetric and asymmetric are considered. Nonlocal strain gradient theory (NSGT) containing two scale parameters is employed for size-dependent modeling of porous nanoplates. The present plate theory satisfies the shear deformation effect and it has lower field variables compared with first order plate theory. Hamilton's principle is employed to derive the governing equations. Obtained results from Galerkin's method are verified with those provided in the literature. The effects of nonlocal parameter, strain gradient, foundation parameters, dynamic loading, porosity distributions and porosity coefficient on dynamic deflection and resonance frequencies of metal foam nanoscale plates are examined.

• Advances in aircraft and spacecraft science
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• 제6권4호
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• pp.297-314
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• 2019

Dynamic stability of a porous metal foam nano-dimension plate on elastic substrate exposed to bi-axial time-dependent forces has been studied via a novel 3-variable plate theory. Various pore contents based on uniform and non-uniform models have been introduced. The presented plate model contains smaller number of field variables with shear deformation verification. Hamilton's principle will be utilized to deduce the governing equations. Next, the equations have been defined in the context of Mathieu-Hill equation. Correctness of presented methodology has been verified by comparison of derived results with previous data. Impacts of static and dynamical force coefficients, non-local coefficient, foundation coefficients, pore distributions and boundary edges on stability regions of metal foam nanoscale plates will be studied.

• Structural Monitoring and Maintenance
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• 제6권2호
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• pp.147-159
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• 2019

In present article, a size-dependent refined thick beam element has been established based upon nonlocal elasticity theory. Next, it is used to explore vibration response of porous metal foam nanobeams on elastic medium. The established beam element introduces ten degrees of freedom. Different porosity distributions called uniform, symmetric and asymmetric will be employed. Herein, introduced thick beam element contains shear deformations without using correction factors. Convergence and verification studies of obtained results from finite element method are also provided. The impacts of nonlocality factor, foundation factors, shear deformation, slenderness ratio, porosity kinds and porosity factor on vibration frequencies of metal foam nano-sized beams have been explored.

• Journal of Electrochemical Science and Technology
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• 제11권1호
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• pp.92-98
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• 2020

SnO₂-based high-capacity anode materials are attractive candidate for the next-generation high-performance lithium-ion batteries since the theoretical capacity of SnO₂ can be ideally extended from 781 to 1494 mAh g^-1. Here 3D etched Cu foam is applied as a current collector for electron path and simultaneously a substrate for the SnO₂ coating, for developing an integrated electrode structure. We fabricate the 3D etched Cu foam through an auto-catalytic electroless plating method, and then coat the SnO₂ onto the self-supporting substrate through a simple sol-gel method. The catalytic dissolution of Cu metal makes secondary pores of both several micrometers and several tens of micrometers at the surface of Cu foam strut, besides main channel-like interconnected pores. Especially, the additional surface pores on etched Cu foam are intended for penetrating the individual strut of Cu foam, and thereby increasing the surface area for SnO₂ coating by using even the internal of Cu foam. The increased areal capacity with high structural integrity upon cycling is demonstrated in the SnO₂-coated 3D etched Cu foam. This study not only prepares the etched Cu foam using the spontaneous chemical reactions but also demonstrates the potential for electroless plating method about surface modification on various metal substrates.

• Structural Monitoring and Maintenance
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• 제7권2호
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• pp.85-107
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• 2020

Dynamic responses of porous piezoelectric and metal foam nano-size plates have been examined via a four variables plate formulation. Diverse pore dispersions named uniform, symmetric and asymmetric have been selected. The piezoelectric nano-size plate is subjected to an external electrical voltage. Nonlocal strain gradient theory (NSGT) which includes two scale factors has been utilized to provide size-dependent model of foam nanoplate. The presented plate formulation verifies the shear deformations impacts and it gives fewer number of field components compared to first-order plate model. Hamilton's principle has been utilized for deriving the governing equations. Achieved results by differential quadrature (DQ) method have been verified with those reported in previous studies. The influences of nonlocal factor, strain gradients, electrical voltage, dynamical load frequency and pore type on forced responses of metal and piezoelectric foam nano-size plates have been researched.

• 한국공작기계학회논문집
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• 제15권1호
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• pp.113-118
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• 2006

In this work, we observed the changes in mass difference according to Al-foam's amount of Ca contents which depends on the viscosity control of fusion, quality of foamed addition, mixing, temperature tests. These are crucial influencing factors in determining foam-metal's size in the manufacturing process. In order to obtain the specimen, we changed the specific gravity from 0.2 to 0.3 for the study of the light weight, and obtained the optimal values of specific gravity, and then showed the mechanical characteristics of ultra-lightweight metal according to the changing mass. The optimal conditions for aluminum foam is when the addition of Ca content in $1.5wt\%~2.0wt\%$

• 한국주조공학회지
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• 제30권1호
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• pp.22-28
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• 2010

Metal foam is a porous or cellular structure material and representative property is a very high porosity. Foamed materials have very special properties such as sound, vibration, energy and impact absorption capacity. Especially this properties are widely used for safety demands of architecture, auto and aircraft industry. But metal foam need to increased its compression strength and hardness. This study were researched about Al-Si alloy foams with variation amount of Si contents for their fabrication and properties such as porosity, cell structure, microstructure and mechanical properties. The result are that the range of pore size is 2~4 $mm{\phi}$, the high porosity are 88%, high yield strength is 1.8MPa, the strain ratio is 60~70% and vickers hardness is 33.1~50.6.

• 설비공학논문집
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• 제22권7호
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• pp.448-453
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• 2010

Porous media containing complex fluid passage have especially large surface area per unit volume. This study is aimed to identify the heat transfer characteristics of high-porosity metal foams in a horizontal channel. Experiment is performed under various heat flux, velocity and pore density. Nusselt number decreases with higher pore density. Metal foams shows higher heat transfer coefficients than pin-fin structure with the same porosity. This is due to the more complex flow passage and larger heat transfer area based on the structure of the metal foams. The analysis on the pin-fin structure may not be suitable to the metal foam structure but should be identified extensively through further study.

• 한국세라믹학회지
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• 제14권4호
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• pp.248-255
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• 1977

The effect of firing temperature, soaking time and batch composition upon the glass phase and pore formation as well as their distribution in slag foamed glass was investigated. Sulfur dioxide gas produced by the oxidation and reduction of metal sulfide in waterslag was attributed to foam forming agent. Slag foamed glass matrix was mainly composed of 35~60% glas phase and melilite crystalline phase. The increment of bentonite addition in batch lowered the foam forming temperature in studied system. The result showed also that the foam size distribution was broadened as th firing temperature wa inbereased.

• 한국표면공학회지
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• 제28권2호
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• pp.83-91
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• 1995

A new method for preparation of thin nickel foam for Ni-MH battery was investigated. In this method, fine graphite powders of $1\mu\textrm{m}$～$2\mu\textrm{m}$ diameter were pasted into pores of thin polyurethane foam film in order to supply electric conducting seeds for nickel deposition by electroless plating reaction. After electroless plating, remaining polyurethane foam was removed chemically by organic solvent treatment and graphite particles also removed by ultrasonic cleaning. Porosity of formed nickel foam was about 85% During electroplating, porosity of the nickel foam decreased less than 5% up to $30\mu\textrm{m}$ coating thickness. And then it was electroplated and heat-treated to improve mechanical strength and ductility. Finally, thin nickel foam for Ni electrode of Ni-MH battery with 80% porosity and $350\mu\textrm{m}$～X$400\mu\textrm{m}$ thickness was obtained.