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Determining the thermophysical properties of Al-doped ZnO nanoparticles by the photoacoustic technique

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Chinese Physics B 2013年第7期22卷 280-285页

作者： t. A. El-Brolossy O. saber s. s. Ibrahim Department of Physicsh Faculty of ScienceKing Faisal University Department of Physics Faculty of ScienceAin Shams University Egyptian Petroleum Research Institute Department of Physics Faculty of ScienceCairo University

the thermal conductivity and specific heat capacity of undoped and Al-doped （1–10 at.%） ZnO nanoparticles prepared using the solvent thermal method are determined by measuring both thermal diffusivity and thermal effusivity of a pressed powder compact of the prepared nanoparticles by using the laser-induced photoacoustic technique. the impact of Al doping versus the microstructure of the samples on such thermal parameters has been investigated. the results reveal an obvious enhancement in the specific heat capacity when decreasing the particle size, while the effect of Al doping on the specific heat capacity is minor. the measured thermal conductivities are about one order of magnitude smaller than that of the bulk ZnO due to several nested reducing heat transfer mechanisms. the results also show that Al doping significantly influences the thermal resistance. Using a simple thermal impedance model, the added thermal resistance due to Al dopant has been estimated.

关键词： ZnO nanoparticles microstructure specific heat thermal conductivity

Flow of Casson nanofluid with viscous dissipation and convective conditions: A mathematical model

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Journal of Central south University 2015年第3期22卷 1132-1140页

作者： t.HUssAIN s.A.sHEHZAD A.ALsAEDI t.HAYAt M.RAMZAN Department of Mathematics Faculty of Computing Mohammad Ali Jinnah University Department of Mathematics Comsats Institute of Information Technology Department of Mathematics Faculty of Science King Abdulaziz University Department of Mathematics Quaid-i-Azam University

the magnetohydrodynamic(MHD) boundary layer flow of Casson fluid in the presence of nanoparticles is *** conditions of temperature and nanoparticle concentration are employed in the formulation. the flow is generated due to exponentially stretching surface. the governing boundary layer equations are reduced into the ordinary differential equations. series solutions are presented to analyze the velocity, temperature and nanoparticle concentration fields. temperature and nanoparticle concentration fields decrease when the values of Casson parameter enhance. It is found that the Biot numbers arising due to thermal and concentration convective conditions yield an enhancement in the temperature and concentration fields. Further, we observed that both the thermal and nanoparticle concentration boundary layer thicknesses are higher for the larger values of thermophoresis parameter. the effects of Brownian motion parameter on the temperature and nanoparticle concentration are reverse.

关键词： nanoparticles Casson fluid concentration convective condition

Development of calcium stabilized nitrogen rich α-sialon ceramics along the si_(3)N_(4):1/2Ca_(3)N_(2):3AlN line using spark plasma sintering

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Journal of Advanced Ceramics 2020年第5期9卷 606-616页

作者： B.A.AHMED t.LAOUI A.s.HAKEEM Department of Mechanical Engineering College of Electrical and Mechanical EngineeringNational University of Sciences and TechnologyIslamabad 44000Pakistan Department of Mechanical and Nuclear Engineering University of SharjahSharjah 27272United Arab Emitates Center for Advanced Materials Research Research Institute of Sciences and EngineeringUniversity of SharjahSharjah 27272United Arab Emitates Center of Excellence in Nanotechnology King Fahd University of Petroleum and MineralsDhahran 31261Saudi Arabia

Calcium stabilized nitrogen rich sialon ceramics having a general formula of Ca_(x)si_(12-2x)Al_(2x)N_(16) with x value(x is the solubility of cation Ca in α-sialon structure)in the range of 0.2-2.2 for compositions lying along the si_(3)N_(4):1/2Ca_(3)N_(2):3AlN line were synthesized using nano/submicron size starting powder precursors and spark plasma sintering(sPs)*** development of calcium stabilized nitrogen rich sialon ceramics at a significantly low sintering temperature of 1500℃(typically reported a temperature of 1700℃ or greater)remains to be the highlight of the present *** sPs processed sialons were characterized for their microstructure,phase and compositional analysis,and physical and mechanical ***,a correlation was developed between the lattice parameters and the content(x)of the alkaline metal cation in the α-sialon ***-densified single-phase nitrogen rich α-sialon ceramics were achieved in the range of 0.53(3)≤x≤1.27(3).A nitrogen richα-sialon sample possessing a maximum hardness of 22.4 GPa and fracture toughness of 6.1 MPa·m^(1/2) was developed.

关键词： nitrogen rich sialon ceramics α-sialon calcium sialons spark plasma sintering(sPs) liquid phase sintering

Bioactivity enhancement by sr doped Zn-Ca-P coatings on biomedical magnesium alloy

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Journal of Magnesium and Alloys 2019年第4期7卷 584-596页

作者： P.Amaravathy t.s.sampath Kumar Medical Materials Laboratory Department of Metallurgical and Materials EngineeringIndian Institute of Technology MadrasChennai 600036India

the effect of strontium doped Zn-Ca-P(ZCP)coating by chemical conversion technique on the biodegradation of AZ31 alloy was *** coating formed with 1.5 wt.%sr and 20 min phosphating time at 50℃ with pH 2.5 completely covers the alloy *** sr doped coated sample also showed very low evolved hydrogen gas and pH change than the ZCP coatings suggested that the degradation of the alloy was extremely *** in vitro bioactivity studies in simulated body fluid exhibits deposition of calcium phosphate phases with Ca/P ratio of 1.55 which is close to that of hydroxyapatite,mineral component of *** evaluation with L929 cells showed higher cell viability of the sr doped coatings compared to ZCP coatings.

关键词： Magnesium alloy Zinc calcium phosphate Biocompatibility Corrosion strontium Cell viability

Bifunctional luminescent and magnetic core/shell type nanostructures Fe_3O_4@CeF_3:tb^(3+)/siO_2

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Journal of Rare Earths 2011年第12期29卷 1117-1122页

作者： M.Runowski t.Grzyb s.Lis Department of Rare Earths Faculty of ChemistryAdam Mickiewicz University

A facile co-precipitation and microemulsion methods were applied to obtain core/shell type nanoparticles. Cerium fluoride doped with terbittrn（Ⅲ） ions supplied intensive green luminescence of the system. Due to the presence of magnetite nanoparticles as cores, the prod- uct was highly sensitive to external magnetic field. Both sorts of nanostructures were encapsulated by silica shell. such external layer of inert oxide can potentially increase the resistance of prepared nanostructttres to thermal oxidation, aggressive agents, changing ofpH or destructive radiation. Morphology of the product was examined using transmission electron microscopy （tEM）. Formations of the core/shell type nanostructures were clearly seen in the tEM pictures. Powder X-ray diffraction （XRD） confirmed the structure of the products, their nanocrystallinity and amorphous nature of silica shell. Optical properties were investigated by measuring excitation and emission spectra. such multifunctional luminescent and magnetic nanoparticles coated with easily functionalized silica shell could be applied in many field of science.

关键词： bifunctional nanoparticles magnetic nanoparticles luminescence core/shell rare earths

Newtonian heating in stagnation point flow of Burgers fluid

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Applied Mathematics and Mechanics(English Edition) 2015年第1期36卷 61-68页

作者： t.HAYAt s.ALI M.AWAIs M.s.ALHUtHALI Department of Mathematics Quaid-i-Azam University Nonlinear Analysis and Applied Mathematics (NAAM) Research Group Faculty of Science King Abdulaziz University Faculty of Engineering sciences Ghulam Ishaq Khan Institute of Engineering Sciences and Technology Department of Mathematics COMSATS Institute of Information Technology

the Newtonian heating effects in the stagnation point flow of a Burgers fluid are addressed in this paper. the boundary layer flow problems are stated in the spatial domain from zero to infinity. the solution expressions for the velocity and the temperature are obtained and examined for the influential variables. the tabulated values show comparison with the previous results. It is observed that the obtained results are in good agreement with the existing results in limiting sense.

关键词： Burgers fluid Newtonian heating series solutions

Genotypic,size and morphological diversity of virioplankton in a deep oligomesotrophic freshwater lake(Lac Pavin,France)

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Journal of Environmental sciences 2017年第3期29卷 48-59页

作者： Jonathan Colombet Agnès Robin télesphore sime-Ngando Laboratory Microorganisms:Oenome and Environment Clermont University Blaise PascalUMR CNRS 602324 avenue des LandaisBP 80026F-63171 AubiereFrance CIRAD UMR Eco&Sols2 place Viala34060 Montpellier Cedex 1France

We examined changes in morphological and genomic diversities of viruses by means of transmission electronic microscopy and pulsed field gel electrophoresis （PFGE） over a nine-month period （April-December 2005） at four different depths in the oligomesotrophic Lac Pavin. We found that the majority of viruses in this lake belonged to the family of siphouiridae or were untailed, with capsid sizes ranging from 30 to 60 nm, and exhibited genome sizes ranging from 15 to 45 kb. On average, 12 different genotypes dominated each of the PFGE fingerprints. the highest genomic viral richness was recorded in summer （mean = 14 bands per PFGE fingerprint） and in the epilimnion （mean = 13 bands per PFGE fingerprint）. Among the physico-chemical and biological variables considered, the availability of the hosts appeared to be the main factor regulating the variations in the viral diversity.

关键词： VirusLac PavinDynamicMorphological diversity Genomic diversity

MHD three-dimensional flow of Jeffrey fluid with Newtonian heating

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Journal of Central south University 2014年第4期21卷 1428-1433页

作者： s.A.shehzad t.Hayat M.s.Alhuthali s.Asghar Department of Mathematics Quaid-i-Azam University Nonlinear Analysis and Applied Mathematics (NAAM) Research Group Faculty of ScienceKing Abdulaziz University Department of Mathematics Comsats Institute of Information Technology

the magnetohydrodynamic(MHD) three-dimensional flow of Jeffrey fluid in the presence of Newtonian heating is investigated. Flow is caused by a bidirectional stretching surface. series solutions are constructed for the velocity and temperature fields. Convergence of series solutions is ensured graphically and numerically. the variations of key parameters on the physical quantities are shown and discussed in detail. Constructed series solutions are compared with the existing solutions in the limiting case and an excellent agreement is noticed. Nusselt numbers are computed with and without magnetic fields. It is observed that the Nusselt number decreases in the presence of magnetic field.

关键词： three-dimensional flow Jeffrey fluid Newtonian heating

Mixed Convection stagnation Point Flow of Casson Fluid with Convective Boundary Conditions

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Chinese Physics Letters 2012年第11期29卷 148-151页

作者： t.Hayat s.A.shehzad A.Alsaedi M.s.Alhothuali Department of Mathematics Quaid-i-Azam University 45320 Islamabad 44000Pakistan Department of Mathematics Faculty of ScienceKing Abdulaziz UniversityJeddah 21589Saudi Arabia

the mixed convection stagnation-point flow of an incompressible non-Newtonian fluid over a stretching sheet under convective boundary conditions is *** formulation is presented for a Casson *** resulting partial differential equations are converted into the ordinary differential equations by the suitable *** velocity and temperature profiles are computed by employing the homotopy analysis *** plotted graphs illustrate the flow and heat transfer characteristics and their dependence upon the embedded *** values of skin-friction coefficient and Nusselt number are given and *** of the present results with the existing solution is also given.

关键词： method stretching ordinary