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SYNTHESIS AND CHARACTERIZATION OF HYBRID PROTON CONDUCTING MEMBRANES OF POLY(VINYL ALCOHOL) AND PHOSPHOMOLYBDIC ACID

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Chinese Journal of Polymer Science 2006年第5期24卷 449-456页

作者： Arfat Anis a.k. Banthia S. Mondal a.k. Thakur Materials Science Centre Indian Institute of TechnologyKharagpur 721302India Department of Physics & Meteorology Indian Institute of TechnologyKharagpur 721302India

Hybrid proton conducting membranes of poly（vinyl alcohol）（PVA） and phosphomolybdic acid （PMA） were prepared by solution casting method. The effect of PMA doping and PVA crosslinking density on the membrane properties and proton conductivity were investigated. The crosslinking reaction between the hydroxyl group of PVA and the aldehyde group of glutaraldehyde （GA） was characterized by IR spectroscopy. Proton conductivity of the membranes increases with an increase in concentration of the doped PMA and also with an increase in crosslinking density of the membranes. Proton conductivity results indicate that a significant amount of PMA was maintained in the membranes even after several hours of immersion in water. A maximum conductivity of 0.0101 S cm^-1 was obtained for the membrane with 33.3 wt% PMA and crosslinking density of 5.825 mol%. X-ray diffraction studies were carried out to investigate the influence of PMA doping and crosslinking density on the nature of the membranes. These properties make them very good candidates for polymer electrolyte membranes for direct methanol fuel cell application.

关键词： Polymer electrolyte membranes Proton conductor Phosphomolybdic acid Crosslinked PVA membranes.

Tensile and Impact Properties of Shielded Metal Arc Welded AISI 409M Ferritic Stainless Steel Joints

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Journal of Materials Science & Technology 2009年第2期25卷 181-186页

作者： k. Shanmugam a.k. Lakshminarayanan V. Balasubramanian Centre for Materials Joining & Research (CEMAJOR) Department of Manufacturing Engineering Annamalai UniversityAnnamalai Nagar 608 002 Tamil Nadu India

The present study is concerned with the effect of filler metals such as austenitic stainless steel, ferritic stainless steel and duplex stainless steel on tensile and impact properties of the ferritic stainless steel conforming to AISI 409M grade. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. Tensile and impact properties, microhardness, microstructure and fracture surface morphology of the joints fabricated by austenitic stainless steel, ferritic stainless steel and duplex stainless steel filler metals were evaluated and the results were reported. From this investigation, it is found that the joints fabricated by duplex stainless steel filler metal showed higher tensile strength and hardness compared to the joints fabricated by austenitic and ferritic stainless steel filler metals. Joints fabricated by austenitic stainless steel filler metal exhibited higher ductility and impact toughness compared with the joints fabricated by ferritic stainless steel and duplex stainless steel filler metals.

关键词： Ferritic stainless steel Shielded metal arc welding Tensile properties Impact toughness

Study of Dehydrocoupling Reactions of Diorganotin Dihydrides R^1R^2SnH2 with Biuret

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Chinese Journal of Chemistry 2007年第7期25卷 1036-1040页

作者： DEEP, Gagan NARULA, a.k. School of Basic and Applied Sciences Guru Gobind Singh Indraprastha University Kashmere Gate Delhi 110006India

The reaction of unsymmetrical phenylmethyltin dihydride （PhMeSnH2）, phenylethyltin dihydride （PhEtSnH2）, phenylbutyltin dihydride （PhBuSnH2） and butylmethyltin dihydride （BuMeSnH2） with biuret （HAL） proceeds via SnH/NH dehydrocoupling to afford the corresponding tetra-coordinate cyclic products. The reactions in the molar ratios of 1 ： 1, 2 ： 1 and 1 ： 2 have been studied. The yellow derivatives so isolated were soluble in polar solvents and insoluble in nonpolar solvents. It was found that 1 ： 1 reaction went to completion while 2 ： 1 and 1 ： 2 did not go to completion. The derivatives had been characterized by elemental analysis and spectroscopic techniques viz. IR, ^1H NMR, ^13C NMR, ^119Sn NMR. DSC and TGA of the reaction products have also been studied. All the derivatives were thermally stable upto （1904- 10）℃ and degradation occurred after that.

关键词： butylnmethylti dihydride biuret synthesis spectroscopic analysis thermal behaviour

Effect of (Ba_(0.6)Sr_(0.4))TiO_3(BST) Doping on Dielectric Properties of CaCu_3Ti_4O_(12)(CCTO)

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Journal of Materials Science & Technology 2012年第12期28卷 1137-1144页

作者： I. Norezan a.k. Yahya M.k. Talari Faculty of Applied Sciences Universiti Teknologi MARAShah Alam Selangor Malaysia

The effect of （Ba（0.6）Sr（0.4））TiO3（BST） addition on dielectric properties of CaCu3Ti4O（12）（CCTO） ceramic was investigated. Ceramic samples with the chemical formula （1-x）CaCu3Ti4O（12）＋ x（Ba（0.6）,Sr（0.4））TiO3 （x=0, 0.05, 0.1, and 0.2） were synthesized from high purity oxide powders by the conventional solid-state synthesis method. X-ray diffraction （XRD） analysis showed the existence of BST as a secondary phase alongside CCTO. Scanning electron microscopy （SEM） investigation showed a slight decrease in grain size of doped CCTO samples. Density measurements showed that porosity content increased with increasing BST addition indicating low densification due to high melting point secondary phase addition. Dielectric constant of undoped CCTO （x=0） showed la.k.of stability with frequency which dropped drastically between 104 and 105Hz and accompanied by high dielectric loss. Addition of BST into CCTO caused the dielectric constant to slightly decrease but improved stability with frequency compared to the undoped sample. The decrease in dielectric constant of doped CCTO samples was suggested to be partly due to the decrease in average grain size and increase in porosity with BST addition. Nevertheless, a high value of dielectric constant was still maintained around ～104 range for all doped samples. The dielectric loss （tanδ） of all BST-doped samples was lower than that of pure CCTO sample at the frequency range of 103 to 105 Hz probably due to the increase of grains boundary resistivity. The activation energy of grains boundary （E（gb）） showed higher values as compared to the activation energy of grains （Eg ） for all samples and conforms to the internal barrier layer capacitor （IBLC） model.

关键词： CaCu3Ti4O(12)(CCTO) Dielectric properties (Ba(0.6)Sr(0.4))TiO3(BST)

Effect of orientation on the drag of a cone settling in a Bingham plastic fluid

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Particuology 2019年第2期17卷 157-170页

作者： Pragya Mishra a.k. Tiwari R.P. Chhabra Department of Chemical Engineering. Indian Institute of Technology Kanpur 208016 India M2NeT Laboratory Wilfrid Laurier University 75 University Avenue West Waterloo ON N2L 3C5 Canada

Effects of the orientation and apex angle on the settling velocity of conical particles in Bingham plas-tic fluids are numerically investigated over a Reynolds number range of 1 ≤Re ≤100, Bingham number range of 0 ≤ Bn ≤ 100, and cone angle range of 20 ≤α≤ 150°. Governing equations (of continuity and momentum) are solved numerically using the finite element method to obtain velocity and pressure fields that are postprocessed to obtain values of the drag ***, the effect of cone ori-entation on the flow field is visualized and explored in terms of streamline contours and the morphology of yielded/uny ielded regions. Finally, the obtai ned values of drag are correlated via a simple predictive expression in terms of the modified Reynolds number. The effect of the cone angle on drag is found to be moderate because the drag force acting on the lateral surface is a small fraction of the overall drag.

关键词： Bingham number Reynolds number Yielded/unyielded regions Drag

Processing of rare earth concentrates

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Rare Metals 2005年第3期24卷 210-215页

作者： Pamela Alex R.C. Hubli a.k. Suri Material Processing Division Bhabha Atomic Research Centre Trombay Mumbai-400085 IndiaMaterial Processing Division Bhabha Atomic Research Centre Trombay Mumbai-400085 IndiaMaterial Processing Division Bhabha Atomic Research Centre Trombay Mumbai-400085 India

The paper describes process details for extraction of rare earths from an intermediate grade concentrate of Madhya Pradesh region in India and a South African slag. The xenodme concentrate obtained from the former place was an intermediate grade （47%） rare earth phosphate containing both monazite and xenotime. The South African slag was a low-grade waste product typically containing only 4% of rare earths. The rare earth resource concentrates have been treated individually by different methods such as a.k.li fusion and a.k.li leaching to convert them into their mixed oxides. Both types of materials have been processed and greater than 98% solubilization of metal values has been achieved in the intermediate grade xenotime and 80% from the South African slag. The residue of xenotime hydroxide has been washed thoroughly to collect the sodium phosphate, as by-product and the slurry pH have been adjusted to separate rare earths from thorium effectively. Other impurities such as uranium and iron have been removed by precipitation of rare earths by oxalic acid. It has been possible to recover 〉95% yttrium along with other rare earth oxides.

关键词： xenotime slag fusion leaching calcining solubilization

Finite element model for linear-elastic mixed mode loading using adaptive mesh strategy

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第1期9卷 32-37页

作者： Miloud SOUIYAH Abdulnaser ALSHOAIBI A. MUCHTAR a.k. ARIFFIN Department of Mechanical & Materials Engineering Universiti Kebangsaan Malaysia Bangi Selangor 43600 Malaysia

An adaptive mesh finite element model has been developed to predict the cra.k.propagation direction as well as to calculate the stress intensity factors （SIFs）, under linear-elastic assumption for mixed mode loading application. The finite element mesh is generated using the advancing front method. In order to suit the requirements of the fracture analysis, the generation of the ba.k.round mesh and the construction of singular elements have been added to the developed program. The adaptive remeshing process is carried out based on the posteriori stress error norm scheme to obtain an optimal mesh. Previous works of the authors have proposed techniques for adaptive mesh generation of 2D cra.k.d models. Facilitated by the singular elements, the displacement extrapolation technique is employed to calculate the SIk The fracture is modeled by the splitting node approach and the trajectory follows the successive linear extensions of each cra.k.increment. The SlFs values for two different case studies were estimated and validated by direct comparisons with other researchers work.

关键词： Linear-elastic fracture mechanics Adaptive refinement Stress intensity factors (SIFs) Cra.k.propagation

Study on mixing and segregation behaviors in particulate fluidized bed system for mineral processing

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International Journal of Mining Science and Technology 2015年第3期25卷 459-464页

作者： Sahu S.N. Sahu a.k. Biswal S.k. Mineral Processing Department CSIR-Institute of Minerals and Materials Technology

In order to identify the mixing and segregation behaviors in a mineral processing operation, present study aimed on the hydrodynamics of solid–liquid fluidization. The study was carried out in a fluidization column with tapings at different height of the bed to collect the sample. The binary particles considered in this study are hematite(4800 kg/m3) and quartz(2600 kg/m3) at different size fractions in the range of average size 87×10^(-6)m to 400×10^(-6)m. It is observed that for various binary mixtures, both quartz and hematite particles share the equal composition by mass(50%) at a particular height of fluidized bed, referred as ‘‘locus point'' of mixing. Study indicates that the mixing zone volume will increase for a continuous fluidized bed plant operation. It is observed that the number of locus points varies from 1 to 3 signifying their dependency on the size ratios of binary mixture. Whenever, the difference in terminal velocity between quartz and hematite particles approaches to zero, mixing is ***, the present study is extended to find the segregation index for the different size ratios of quartz and hematite particles. It is evident that depending on the size ratios, various regions such as complete segregation, partial mixing and complete mixing can be observed.

关键词： Liquid-solid fluidization Mixing Segregation Locus point Mineral processing

Effects of irregularity and initial stresses on the dynamic response of viscoelastic half-space due to a moving load

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Acta Mechanica Solida Sinica 2017年第3期30卷 306-317页

作者： a.k. Singh A. Das A. Lakshman A. Negi A. Chattopadhyay Department of Applied Mathematics Indian Institute of Technology (Indian School of Mines) Dhanbad 826004 Jharkhand India

The present article deals with the stresses developed in an initially stressed irregular viscoelastic half-space clue to a load moving with a constant velocity at a rough free surface. Expressions for normal and shear stresses are obtained in closed form. The substantial effects of influence parameters, viz., depth （from the free surface）, irregularity factor, maximum depth of irregularity, viscoelastic parameter, horizontal and vertical initial stresses, and frictional coefficient, on normal and shear stresses are investigated. Moreover, comparative study is carried out for three different cases of irregularity, viz., rectangular irregularity, parabolic irregulariW and no irregularity, which is manifested through graphs.

关键词： Viscoelastic Irregularity Moving load Frictional coefficient Stresses