Thermal and stress analyses in an end-pumped Nd:YAG slab laser using finite element method

Mina Babaei Bavil,Ebrahim Safari 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8

The increasing application on high laser power in industries required studies in the portion of pump radiation absorbed by laser mediathat exchanges to heat. Heat may cause thermal stress, stress birefringence and thermal lens effects. These effects can destroy the opticalproperties of the laser medium, decrease the beam quality and may lead to medium break. In this paper, the thermal and stress analyses ofcontinuous and pulsed end-pumped Nd:YAG slab laser are studied using finite element method. Heat deposited in the slab is removed bycooling water, flowing on the largest faces of the slab, which surrounds the active media. The temperature and stress distributions of theend-pumped Nd:YAG slab are defined by coupled field methods in the ANSYS commercial finite element software. The value of maximumtemperature and stress in the slab which is affected by an end-pumping are calculated. Finally the maximum pump-power rangewhich can be applied to the slab is determined using the limit of maximum stress in the slab. The analyses are done in from transient tosteady-state regimes for continuous pumping. Results show that deposited heat due to the pulsed pumping acts like a mechanical impact.

Inhibition of corrosion of aluminum in alkaline solution by a novel azo-schiff base: Experiment and theory

Arjomandi, Jalal,Moghanni-Bavil-Olyaei, Hamed,Parvin, Mohammad Hadi,Lee, Jin Yong,Chul Ko, Kyoung,Joshaghani, Mohammad,Hamidian, Kourosh Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.746 No.-

<P><B>Abstract</B></P> <P>The inhibition effect of a Schiff base with several functional groups on the corrosion of aluminum in alkaline solution is studied by experimental techniques and density function theory (DFT) calculations. The Schiff base are characterized by <SUP>1</SUP>HNMR, <SUP>13</SUP>CNMR, FT-IR, and CHN elemental analysis. In addition, different electrochemical and corrosion techniques such as weight loss, tafel polarization, electrochemical impedance spectroscopy (EIS) and optical microscopy images are performed to analyze the inhibiting performances. In the Tafel measurements the cathodic Tafel slopes values incurred small changes with increasing the inhibitor concentration, which revealed that the inhibitor was adsorbed on the aluminum surface. The inhibition efficiencies are calculated from weight loss measurement and electrochemical tests. The adsorption of the inhibitor onto the aluminum surface follows the Langmuir adsorption isotherm with the free adsorption energy of −8.66 kJ mol<SUP>−1</SUP>. The calculated adsorption energies and the amount of charge transfer obtained by DFT calculation revealed that corrosion inhibition effectively occurs with chemisorption, where new NAl bonds are formed between of N atoms in azo (–NN–) group and Al surface atoms, which is confirmed from <I>ab initio</I> molecular dynamics (AIMD) simulation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel Schiff base were synthesized as inhibitor for Al corrosion in alkaline. </LI> <LI> The Schiff base were characterized by <SUP>1</SUP>HNMR, <SUP>13</SUP>CNMR, FT-IR, and CHN. </LI> <LI> The inhibition effect of Schiff base were studied by experimental and DFT. </LI> <LI> The adsorption of inhibitor on Al surface follows Langmuir adsorption isotherm. </LI> <LI> The corrosion inhibitions is chemisorptions which confirmed by AIMD simulation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Experimental investigation and 3D finite element prediction of the white layer thickness, heat affected zone, and surface roughness in EDM process

Mohammadreza Shabgard,Samad Nadimi Bavil Oliaei,Mirsadegh Seyedzavvar,Ahmad Najadebrahimi 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12

An axisymmetric three-dimensional model for temperature distribution in the electrical discharge machining process has been developed using the finite element method to estimate the surface integrity characteristics of AISI H13 tool steel as workpiece. White layer thickness, depth of heat affected zone, and arithmetical mean roughness consisting of the studied surface integrity features on which the effect of process parameters, including pulse on-time and pulse current were investigated. Additionally, the experiments were carried out under the designed full factorial procedure to validate the numerical results. Both numerical and experimental results show that increasing the pulse on-time leads to a higher white layer thickness, depth of heat affected zone, and the surface roughness. On the other hand,an increase in the pulse current results in a slight decrease of the white layer thickness and depth of heat affected zone, but a coarser surface roughness. Generally, there is a good agreement between the experimental and the numerical results.

Modeling and analysis of surface roughness of microchannels produced by µ-WEDM using an ANN and Taguchi method

Rahim Jafari,Müge Kahya,Samad Nadimi Bavil Oliaei,Hakkı Özgür Ünver,Tuba Okutucu Özyurt 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

Microchannel heat exchangers are used to remove the high heat fluxes generated in compact electronic devices. The roughness of the microchannels has a significant effect on the heat transfer characteristics, especially the nucleate boiling and pumping power. Therefore, development of predictive models of surface texture is of significant importance in controlling heat transfer characteristics of these devices. In this study, micro-Wire electrical discharge machining (µ-WEDM) was employed to fabricate metal-based microchannel heat sinks with different surface textures. First, experiments were conducted to achieve the desired surface roughness values. Oxygen-free copper is a common material in the cooling systems of electronic devices because of its high thermal conductivity and low cost. Design of experiment approach based on the Taguchi technique was used to find the optimum set of process parameters. An analysis of variance is also performed to determine the significance of process parameters on the surface texture. An artificial neural network model is utilized to assess the variation of the surface roughness with process parameters. The predictions are in very good agreement with results yielding a coefficient of determination of 99.5 %. The results enable to determine µ-WEDM parameters which can result in the desired surface roughness, to have a well-controlled flow and heat transfer characteristics for the microchannels.

Polyaniline/aluminum and iron oxide nanocomposites supercapacitor electrodes with high specific capacitance and surface area

Arjomandi, Jalal,Lee, Jin Yong,Movafagh, Raheleh,Moghanni-Bavil-Olyaei, Hamed,Parvin, Mohammad Hadi Elsevier 2018 Journal of electroanalytical chemistry Vol.810 No.-

<P><B>Abstract</B></P> <P>We introduce high-performance polyaniline (PANI) nanocomposite supercapacitors based on gamma aluminum oxide (γ-Al<SUB>2</SUB>O<SUB>3</SUB>) and gamma iron (III) oxide (γ-Fe<SUB>2</SUB>O<SUB>3</SUB>) nanoparticles with a high specific surface area. PANI and its polymer nanocomposites are synthesized <I>via in situ</I> electropolymerization on gold electrodes. The structures and morphologies are characterized by cyclic voltammetry, FT-IR spectroscopy, SEM, TEM, and EDX. The electrochemical properties and specific surface area of the electrodes are investigated by galvanostatic charge–discharge, electrochemical impedance spectroscopy (EIS) and BET theory. The enhanced specific capacitance with higher surface area and conductivities is observed in PANI/γ-Fe<SUB>2</SUB>O<SUB>3</SUB> (342F/g), PANI/γ-Al<SUB>2</SUB>O<SUB>3</SUB> (292F/g) and PANI (180F/g) electrodes with a constant current density of 1A/g. The cyclic performance of the PANI electrodes following 8000cycles of operations were at 87% (PANI), 91% (PANI/γ-Al<SUB>2</SUB>O<SUB>3</SUB>), and 93% (PANI/γ-Fe<SUB>2</SUB>O<SUB>3</SUB>) of their initial capacitance. In addition, higher specific capacitances, higher conductivity and cyclic self-stabilities observed for the PANI/nanocomposite electrodes can provide new opportunities in the field of energy storage and supercapacitor applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PANI with γ-Al<SUB>2</SUB>O<SUB>3</SUB> and γ-Fe<SUB>2</SUB>O<SUB>3</SUB> supercapacitors were fabricated. </LI> <LI> Samples were characterized by <I>in situ</I> method, FT-IR, SEM, EDX, TEM, BET and EIS. </LI> <LI> Charging-discharging behavior of the electrodes was investigated. </LI> <LI> The specific capacitance values of PANI/nanocomposites were higher than that of PANI. </LI> <LI> Polymer nanocomposites show higher surface area and stability with long cycle life. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Spectroelectrochemistry and electrosynthesis of polypyrrole supercapacitor electrodes based on gamma aluminum oxide and gamma iron (III) oxide nanocomposites

Arjomandi, Jalal,Lee, Jin Yong,Ahmadi, Fatemeh,Parvin, Mohammad Hadi,Moghanni-Bavil-Olyaei, Hamed Elsevier 2017 ELECTROCHIMICA ACTA Vol.251 No.-

<P><B>Abstract</B></P> <P>Polypyrrole (PPy) and polypyrrole-based gamma aluminum oxide (γ-Al<SUB>2</SUB>O<SUB>3</SUB>) and gamma iron (III) oxide (γ-Fe<SUB>2</SUB>O<SUB>3</SUB>) nanocomposites were synthesized via <I>in situ</I> electropolymerization methods Films were characterized via cyclic voltammetry (CV) and <I>in situ</I> spectroelectrochemistry methods such as <I>in situ</I> UV–Visible spectroscopy and <I>in situ</I> conductivity measurements. Polymer nanocomposite structures and morphologies were studied and characterized via Fourier transform infrared (FT-IR) spectroscopy, electrochemical impedance spectroscopy (EIS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). According to the CV results of the nanocomposites, the separation of anodic and cathodic peak potential of the redox couples (ΔE) exhibited good reversibility with a positive potential shift compared with PPy during redox sweeps. The electrochemical properties of PPy, PPy/γ-Fe<SUB>2</SUB>O<SUB>3,</SUB> and PPy/γ-Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite electrodes in a solution of H<SUB>2</SUB>SO<SUB>4</SUB> were studied via CV, galvanostatic charge–discharge, and EIS measurements to understand the pseudocapacitance that formed due to oxidation and reduction reactions over the double layer capacitance. Results for the nanocomposites revealed that they were very good candidates for supercapacitor applications, with higher specific capacitances, cyclic self-stabilities, and better rate capabilities than those of PPy films. The specific capacitance values of PPy/γ-Fe<SUB>2</SUB>O<SUB>3</SUB> (106F/g) and PPy/γ-Al<SUB>2</SUB>O<SUB>3</SUB> (92F/g) nanocomposites based on a three-electrode cell configuration from galvanostatic charge–discharge at a constant current density of 1A/g were higher than that for PPy (75F/g).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Polypyrrole based γ-Al<SUB>2</SUB>O<SUB>3</SUB> and γ-Fe<SUB>2</SUB>O<SUB>3</SUB> nanocomposites were synthesized. </LI> <LI> The structure and morphology of the polymer nanocomposites were studied. </LI> <LI> Nanocomposites were characterized by <I>in situ</I> spectroelectrochemistry methods. </LI> <LI> PPy and polymer nanocomposites were applied as supercapacitor materials. </LI> <LI> The specific capacitance values of nanocomposites were higher than that of PPy. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>