bluuebunny/crossref_metadata_2025 huggingface dataset:
The "EÖTVÖS” Program in Space Research – 1979-1986
Authors: Gyulai J. , Gyúró I.
Published: May 2010

A brief historical overview of one of Hungary's space projects on Soviet spacecrafts, the so-called "Eötvös" Project on semiconductor crystal growth, is given. Three experiments were proposed and performed: i) epitaxial growth of GaAs under flux, ii) seedless growth of GaSb, and as a control, iii) seeded growth of an InSb crystal. Because of thermal control problems of the furnace, only the growth of a structurally perfect GaSb bicrystal was a successful novelty. Results of structural and electrical analyses are briefly summarized. Finally, a list of related publications is given.
Oscillatory Structure of the Zn-Cu-Ti Single Crystals
Authors: Boczkal Grzegorz , Mikułowski Borys , Wołczyński Waldemar
Published: May 2010

Structures obtained during Zn-Cu-Ti single crystal growth by the Bridgman method were investigated. The alloys of composition Zn-Cu0.1wt.%-Ti0.1wt.% were used for single crystals growth, which were produced at rate in the range of 1.8mm/h to 16mm/h. The Zn-Cu-Ti alloys were characterized by multiphase structure; in the solute-hardened matrix by Cu atoms exists a needle-shaped intermetallic phase Zn16Ti. The strong anisotropy of the hexagonal structure gives a significant influence on a second phase distribution in the matrix volume. In the range of the low growth rates (from 1.8mm/h to 10mm/h) oscillatory structures were observed. That effect vanished at the growth rates higher than 10mm/h. The observed oscillatory structures were characterized by existing periodic layers rich in the intermetallic phase of Zn16Ti interlaid with pure matrix (alpha phase Zn with Cu solute).
Investigation on the Production of Thixotropic Semisolid Ti Alloys
Authors: Batista W.W. , Contieri R.J. , Zoqui Eugênio José , Robert Maria Helena , Caram R.
Published: May 2010

This work investigates the viability of production of thixotropic semisolid Ti-Cu alloys by controlled partial melting. Samples were submitted to different holding times at temperatures above solidus, from different initial microstructure conditions. In some cases, deformation by rolling before heating to semisolid was imposed. It is investigated the influence of deformation ratio and holding time in the obtained structure. Results show that thixotropic semisolid can be easily produced; pre-deformation leads to fine, globular primary phase in the liquid for short holding times. Therefore, thixoforming of Ti alloys is feasible, and can bring a whole new concept on forming complex shapes of these alloys, at low energy consumption, and new possibilities in engineering components with special properties.
Regular Structure Formation of Hypermonotectic Al-In Alloys
Authors: Yasuda Hideyuki , Kato S. , Shinba T. , Nagira T. , Yoshiya M. , Sugiyama Akira , Umetani K. , Uesugi Kentaro
Published: May 2010

Since the liquid / liquid separation occurs in hypermonotectic alloys and the liquid / liquid interface agitates mass transfer around solidifying front, it is rather difficult to achieve the aligned-rod structure. The high magnetic filed such as 10T achieved the aligned-rod structure in the Al-10at%In alloys. The in-situ observations of the monotectic solidification in the Al-10at%In alloys were performed using synchrotron radiation X-ray. Coarse and fine In rods coexisted during the unidirectional solidification without magnetic field. The local melt flow induced by the In-rich liquid / Al-rich liquid interface enhanced the mass transfer and consequently the coarse rods could continuously grow. The suppression of the local melt flow of which scale was several 10 m by the high static magnetic field resulted in the aligned-rod structure.
In Situ Observation of Solidification in an Organic Peritectic Alloy System
Authors: Mogeritsch J.P. , Eck Sven , Grasser Monika , Ludwig Andreas
Published: May 2010

Up to date very few organic substances have been reported that show a non-faceted/non-faceted (nf/nf) peritectic phase diagram in a temperature range suitable for direct observation in a micro Bridgman furnace setup. Sturz et al. [1] and Barrio et al. [2] studied the peritectic phase diagram for the organic model alloy TRIS (Tris(hydroxymenthyl)aminomethane) - NPG (Neopentylglycol). The phase diagram is based on thermal analysis by means of DSC measurements [1, 2] and evaluation of lattice parameters measured with x-ray diffractometry [2]. In the current work we present investigations on the system TRIS – NPG that have been obtained by optical investigations of directional solidification in a micro Bridgman-furnace with various initial alloy concentrations and pulling rates in a fixed temperature gradient. The phase diagram [1, 2] was confirmed by direct comparison of DSC measurements and optical investigations. Furthermore we present in situ observations of solidification in the peritectic region. They show a solidification behavior that was clearly distinguishable from the solidification in hyper- and hypoperitectic regions of the phase diagram.
The Development of a Microgravity Experiment Involving Columnar to Equiaxed Transition for Solidification of a Ti-Al Based Alloy
Authors: Lemoisson Fabienne , Mc Fadden S. , Rebow Marek , Browne David J. , Froyen Ludo , Voss D. , Jarvis David John , Kartavykh A.V. , Rex S. , Herfs W. , Groethe D. , Lapin Juraj , Budenkova Olga , Etay J. , Fautrelle Yves
Published: May 2010

The authors are members of the integrated project Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS), funded within the European Framework (FP6). One of the aims of IMPRESS is to develop new alloys and processes for the casting of TiAl-based turbine blades for the next generation of aero and industrial gas turbine engines. Within IMPRESS, two related issues have been identified during the primary solidification stage, namely, segregation and the columnar-to-equiaxed transition (CET). The authors have set out to isolate the effects of thermo-solutal convection, by designing a microgravity experiment to be performed on a European Space Agency platform. This experiment will investigate the CET formation during solidification. It is planned to use a sounding rocket providing a microgravity time of approximately twelve minutes. The results of this microgravity solidification experiment will be used as unique benchmark data for development and validation of new computational models of TiAl solidification. This in turn will produce accurate models and ultimately new robust industrial processes by project partners in the aerospace industry. The evolution of the design of the microgravity experiment is discussed and the results of preliminary ground reference experiments are presented. Future plans and objectives for the project are also highlighted.
Effects of Composition on Solidification Microstructure of Cast Titanium Alloys
Authors: Andrade P.N. , Coelho A.A. , Afonso C.R.M. , Contieri R.J. , Robert Maria Helena , Caram R.
Published: May 2010

The high cost of processing of Ti alloys is an important limitation to their utilization in a number of applications. An approach to overcome such difficulties would be their processing by precision casting. The purpose of this work is to evaluate the centrifugal casting process of Ti-Cu and Ti-Nb alloys, analysing the influence of alloying element type and content in the obtained microstructure. Samples with different compositions were prepared in arc furnace with non-consumable tungsten electrode and water-cooled copper hearth under high purity argon atmosphere and cast in a copper mould. Microstructures were analysed by SEM, characterized by EDS and X-ray diffraction. Vickers hardness measurements helped the analysis of phases.
Phase-Field Simulations of Dendritic Orientation Selection in Mg-Alloys with Hexagonal Anisotropy
Authors: Eiken J.
Published: May 2010

A special feature of Mg solidification is the anisotropy of the hexagonal closed packed lattice, which under directional growth conditions causes a strong crystallographic texture. Although this primary growth texture is in technical processes masked by subsequent solid state processes, its understanding can be helpful for efficient microstructure optimization. The aim of the present work is to study the fundamental orientation selection mechanisms by numerical simulation. For this pur-pose, a phase-field model has been extended to allow for complex 3D anisotropic interfacial ener-gies and interfacial mobilities, calibrated by data from molecular dynamics studies. The model is first applied in 3D to Mg-6%Al, revealing two major stages of texture formation. Directly after nuc-leation, all grains with basal plane parallel to the gradient direction are selected. During further competitive growth, grains with <1120> closely aligned to the temperature gradient commonly pre-vail, but process dependent also other orientations of the basal plane (between <1120> and <1010>) may coexist. The latter phenomenon is investigated in detail in 2D for the ternary alloy AZ31.
Modelling of Dendritic Growth during Unidirectional Solidification by the Method of Cellular Automata
Authors: Burbelko Andriy A. , Fraś Edward , Kapturkiewicz Wojciech , Gurgul Daniel
Published: May 2010

Modelling was carried out to investigate the internal dendrite grains structure formation from a liquid two-component solution in the area adjacent to a mould wall. For the simulation, our own model and computer program based on CAFD (Cellular Automata Finite Differences) were used. In modelling, the effect of process conditions and material-related parameters, e.g. nucleation temperature, heat exchange rate, interfacial energy, crystal orientation with respect to the casting wall, etc. on the nature of the dendritic grain growth was examined. It was demonstrated that the profile of concentration field in a near-mould-wall zone impedes the growth of the solid phase in the direct vicinity of the wall. A local melting down of the grains of a solid phase due to the segregation of admixtures reducing the alloy point of liquidus is also possible.
CAFE Modeling of Segregation and Structure in Levitated Droplets
Authors: Mosbah Salem , Bellet Michel , Gandin Charles-André
Published: May 2010

The coupled two dimensional (2D) Cellular Automaton (CA) Finite Element (FE) model has been extended based on the recent work by Guillemot et al. [1]. Extensions concern i microsegregation at the scale of the CA cells ii macrosegregation at the scale of the FE mesh based on a remeshing technique. The model is applied to segregation taking place upon single grain nucleation and growth from the centre of a spherical domain. The simulation retrieves the prediction of Heringer et al. [2]. Application to solidification of a spherical Al-4wt%Cu droplet demonstrates its capability to deal with mass exchange by diffusion outside the grain envelope defined by the mushy zone together with back diffusion in the solid [3].
Revolution Number (RPM) Measurement of Molten Alloy by Pressure Compensation Method
Authors: Rónaföldi Arnold , Kovács Jenő , Roósz András
Published: May 2010

The melt flow has a significant effect on the structure developing during the unidirectional solidification of alloys. This phenomenon can be experienced during the solidification of melts stirred by the rotating magnetic field (RMF)-type magnetohydrodynamic (MHD) facility as well. As it would be very difficult to measure the intensity of melt flow (e.g. its revolution number, angular velocity) during solidification, it seems to be reasonable to perform the so-called "scale model" experiments applied usually in the hydrodynamics. Using the results of these measurements, conclusions can be drawn concerning the flows during solidification by means of the similarity law of hydrodynamics. The revolution number of Ga-In alloy melt placed in the rotating magnetic field can be measured by the equipment developed for performing the "scale model" experiments. The measurements were performed in crucibles with different surface roughness using melt-cylinders with different diameters located in rotating magnetic field having different frequencies and magnetic induction.
Melt Structural Self-Organization and Viscosity within the Transient Layer during a Single Crystal Growth in Microgravity
Authors: Kartavykh A.V. , Ginkin V.P.
Published: May 2010

A brief review is given of the results obtained and published in 2003–2007 by IChPM and IPPE during their joint study and modeling of Ge:Ga, Ge:Sb, GaSb:Te, InP:S single crystal growth from stoichiometric and non-stoichiometric melts on board the Photon satellite series. The use of microgravity is shown to be justified and holding promise for research into the structural self-organization processes (cluster forming) taking place within the transient layer of the melt during the solidification. The mathematical model of convective heat and mass transfer taking into account the dual-phase character of matter in the boundary layers near the interface has been created and used as an independent tool for the study of such processes. Prospects are discussed for this new area of space material science.
Silicon Particle Precipitation during DC Casting of Al-Si Clad Alloys
Authors: Carlberg Torbjörn
Published: May 2010

The formation of polyhedral silicon crystals in aluminium 7-9% silicon alloys has been studied both in industrial ingots and in simulation experiments in a Bridgman furnace. It was found that the nucleation temperature and the cooling rate were important factors influencing the amount and size of the polyhedral crystals. To avoid large particles in the as cast material early nucleation have to be suppressed and the phosphorous content should be kept low.
Modelling of diffusion-controlled growth of the silicon phase in this type of aluminium-silicon alloys shows how the nucleation temperature influences the morphology of the precipitated sili¬con.
Measurement of Solute Profiles by Means of Synchrotron X-Ray Radiography during Directional Solidification of Al-4 wt% Cu Alloys
Authors: Buffet Adeline , Nguyen-Thi Henri , Bogno Aziz , Schenk Thomas , Mangelinck-Noël Nathalie , Reinhart Guillaume , Bergeon Nathalie , Billia Bernard , Baruchel J.
Published: May 2010

In the present study, we report on an image analysis procedure, which enables to extract from synchrotron radiographs the long range solute profiles in the whole sample and in both phases (solid and liquid). This image analysis is based on the measurement of local density differences, and is applied to study the directional solidification of Al - 4wt% Cu alloy, from planar to onset of the initial instability. Dedicated experiments were carried out at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France). In order to validate this analysis the value of a key solidification parameter, namely the partition coefficient, was experimentally determined during the planar solidification, and a very good agreement was found with value found usually in the literature. On a further step, the evolution of the microstructure and solute profile during the initial transient of solidification was analysed in detail.
Columnar to Equiaxed Transition in Al-Cu-Ag
Authors: Nagels Els , Froyen Ludo
Published: May 2010

In this work the transition from columnar to equiaxed growth is studied during the solidification of the univariant eutectic L=> α(Al) + θ-Al2Cu in the ternary Al-Cu-Ag system. The columnar to equiaxed transition (CET) in a ternary system behaves very similar to the CET observed in binary systems [1]. It is observed that the CET occurs at lower temperature gradients when the amount of the third alloying element, in this case Ag, is increased. Another important solidification parameter is the cooling rate of the furnace. When the cooling rate is increased, the CET will occur at lower positions in the sample where the temperature gradient is lower.
The Solidification in the Presence of a Metastable Miscibility Gap: The Case of Co-Cu and Co-Cu-X Alloys
Authors: Battezzati Livio , Johnson Erik , Pryds Nini , Penna Andrea , Curiotto Stefano
Published: May 2010

Alloys displaying positive enthalpy of mixing demix below a critical temperature. In Co-Cu and related ternaries the miscibility gap is metastable, i.e. it occurs at temperatures lower than the liquidus. In order to study the liquid phase separation high melt undercooling is necessary. This was obtained via rapid solidification techniques using melt spinning and casting in moulding devices, as well as high temperature DSC experiments with samples embedded in a flux.
Results are given for Co-Cu, Co-Cu-Fe and Co-Cu-Ni systems. Phase diagrams were optimised using the DSC data. The mechanism of phase separation was investigated by comparing samples produced under different cooling conditions. The hierarchy of microstructures obtained was interpreted accounting for the processing technique and the phase diagram. They constitute a database useful for the interpretation of the thermal history of samples processed in microgravity.
Regression Model Describing the Thermal Conductivity of Various Cast Irons
Authors: Holmgren Daniel , Selin Martin
Published: May 2010

The thermal conductivity of various grades of pearlitic cast iron has been modelled with good results by means of regression analysis. The experimental thermal conductivity data, which the modelling is based on, were obtained by the laser flash method. The microstructure was investigated by digital image analysis combined with a colour etching technique. The model developed takes the carbon content, the silicon content, the nodularity as well as the fraction of cementite into consideration. The graphite morphologies of the samples investigated were lamellar, compacted and spheroidal.
Assessment of the Al Corner of the Ternary Al–Fe–Si System
Authors: Eleno Luiz , Vezelý Josef , Sundman Bo , Cieslar Miroslav , Lacaze Jacques
Published: May 2010

The present work provides a review of the information available on the Al-rich corner of the Al–Fe–Si system as well as a CALPHAD type assessment making use of the COST 507 database as a starting point. The description of the intermetallic compounds has been modiﬁed to account for substitution of Al and Si in the ternary Al-Fe-Si system and to take new experimental information into account.
Benefits of Modeling of Melting for the Understanding of Solidification Processes
Authors: Rettenmayr Markus
Published: May 2010

Melting and solidification are both phase transformations involving a liquid and a solid phase. In a simplifying procedure melting could be treated as the inverse process of solidification. However, there are substantial differences in the thermodynamics and kinetics of melting and solidification. The elaboration of a model for melting of binary alloys has lead to the possibility to also describe solidification processes more consistently. Input parameters in the model are the Gibbs Free Energy curves and the diffusion coefficients in the liquid and solid phase, respectively. Assumptions about the thermodynamic state of the interface like local equilibrium are not necessary, recently developed interface thermodynamics is coupled with the kinetic equations. Simulations results for steady-state melting and solidification are compared. The treatment of both solidification and melting yields some insight in the proper¬ties of the liquid/solid interface and its role during the phase transformation.
In Situ Produced MMC Layer by Laser Melt Injection
Authors: Kálazi Zoltán , Janó Viktória , Buza Gábor
Published: May 2010

Tungsten (W) based alloy composite layer reinforced with TiC particles has been successfully prepared on unalloyed steel sample by LMI technology. In order to obtain in situ produced TiC reinforcement, pure titanium has been introduced to the melt pool. WC powder was added for increasing the carbon content of the layer in order to avoid the softening of the matrix (with low carbon content) during TiC formation. The present study aims to investigate the optimum amount of injected WC and Ti powder to improve wear resistance and hardness of the layer. Samples were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD).
The maximum hardness of the layer has been reached ~900HV in case of 2-4wt% of titanium content. Ti has been collected all of the carbon from the matrix when titanium content was 9,6wt%, which resulted that the austenite and (Fe,W)6C phases have been disappeared. Only α-Fe and TiC phases were presented in the layer. The hardness of the layer reduced to the hardness of the base material.
Identification of Bulk Metallic Forming Compositions through Thermodynamic and Topological Models
Authors: Bhatt J. , Murty B.S.
Published: May 2010

This paper attempts to optimize the bulk metallic glass forming compositions using enthalpy of chemical mixing (DHchem) as thermodynamic, mismatch entropy (DSs/kB) as topological and configurational entropy (DSconfig/R) as statistical parameters. The product of DHchem and DSs/kB which is termed as PHS in the DSconfig/R range of 0.9 to 1.0 can be correlated strongly to glass forming ability. PHS being an important parameter has been used to design the quaternary and quinary Bulk Metallic Glass compositions from ternary compositions. This has been demonstrated for two Zr rich quaternary systems in Zr-Ti-Cu-Ni and Zr-Cu-Ni-Al based bulk metallic glasses. By weighing approach of PHS of four Zr rich quaternary systems and one non-Zr rich systems a new Zr rich quinary bulk metallic glass in Zr-Ti-Cu-Ni-Al system is designed. Mechanical alloying is used to prepare the bulk amorphous powder at the compositions predicted by the model in order to validate the model.
Effects of Barium Substitution on the Structure and Properties of PSZT Piezoelectric Ceramics
Authors: Feng Yu Hua , Pan Tie Zheng , Shen Xiang Qian , Song Hao Jie , Guo Li Ping
Published: May 2010

Piezoelectric ceramics with appropriate curie temperatures and high dielectric and piezoelectric performances are attractive for formations of ceramic/polymer piezoelectric composites. The PSZT ceramics with compositions of 0.98Pb1.0-xBaxTi0.48Zr0.52O3-0.02PbSbO3 (x=0.14~0.24) have been prepared by a conventional solid reaction process. The ceramic structures are analyzed by X-ray diffraction and the barium substitution leads to structural changes of the tetragonal and rhombohedral phases which constitute the perovskite PSZT ceramics, and lattice distortions. The curie temperature almost linearly decreases from 226 °C to 141 °C corresponding the barium content increases from 0.14 to 0.24 in the ceramics. The dielectric and piezoelectric properties are largely influenced by the barium substitution and when the barium content at vicinity of 0.22, the piezoelectric strain constant d33 exhibits a dramatic change. It is found that as the barium content around 0.22, the PSZT ceramic specimen is characterized with a low curie temperature Tc=156 °C, and satisfied dielectric and piezoelectric properties with the relative dielectric constant εr=5873, dielectric loss factor tanδ=0.0387, piezoelectric strain constant d33=578 pC/N.
A Simple Way of Pre-Doping Lithium Ion into Carbon Negative Electrode for Lithium Ion Capacitor
Authors: Wu Feng , Lu Hua Quan , Su Yue Feng , Chen Shi , Guan Yi Biao
Published: May 2010

A simple strategy of pre-doping lithium ion into carbon negative electrode for lithium ion capacitor was introduced. In this strategy, a kind of Li-containing compound was added directly into the positive electrode of the lithium ion capacitor (LIC). When the lithium ion capacitor was charging first time, the Li-containing compound releases Li+, and the pre-doping of lithium ion into the negative electrode was performed. Here, we developed a lithium ion capacitor using Meso-carbon microbeads (MCMB)/activated carbon (AC) as the negative and positive electrode materials, respectively and use the lithium iron phosphate (LiFePO4) as the Li-containing compound, which supply the Li+ ions for pre-doping. The results demonstrated that, by adding 20 percent of LiFePO4 into the positive electrode, the efficiency of the capacitor increases from lower than 60% up to higher than 90%, and the capacitor shows good capacitance characteristics and high capacity.
Effects of Conical Transition Section on Microstructure of a Ni3Al-Base Single Crystal Superalloy IC6SX
Authors: Jiang Li Wu , Li Shu Suo , Han Ya Fang
Published: May 2010

Ni3Al based single crystal alloy IC6SX was prepared by election spiral crystal method. The effect of the conical transition section of the single crystal on the microstructure of the single crystal was studied in this work. The results showed that, in the crystal growth process, the effect of the conical transition section on the orientation of single crystal was significant. The yield ratio of the single crystal alloy specimen with <001> orientation could be improved significantly by adding cone transition section. With the angle of the cone transition section increasing from 20 º to 43 º, the dendrite arm spacing increased gradually, and dendrite morphology was coarsened and the third dendrite arm appeared.
Synthesis and Characterization of TiO2 Nanoparticles Doped with Cu2+ by Microemulsion Method
Authors: Long Jian Xin , Chen Yong Jun
Published: May 2010

Copper doped TiO2 nanoparticles were synthesized by hydrolysis of tetrabutyl titanate (Ti(OBu)4) and copper nitrate (Cu(NO3)2) in water-in-oil (W/O) microemulsions, consisting of water, Triton X-100, n-hexanol, cyclohexane and water. In this W/O system, Trinton X-100, n-hexanol and cyclohexane were used as surfactant, co-surfactant and organic solvent, respectively. The prepared nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The results show that the Cu-doped TiO2 nanoparticles synthesized by this method have a good dispersion character and relatively small sizes of about 80 nm. The XRD results show that the calcination temperature greatly influences the crystallization transformation. When calcined below 550 °C, the prepared sample is composed of anatase structure. When the calcination temperature increases to 650 °C, rutile phase appears besides the anatase phase. While doping amount has little effects on crystal phase. FTIR analysis indicates that most of the contained water and the residual organic surfactants can be removed by calcination.
Application of Regression Analysis to Optimize Hot Compaction Processing in an Indirect Solid-State Recycling of Mg Alloy
Authors: Peng Tao , Wang Qu Dong
Published: May 2010

An appropriate hot compaction technology is applied not only to obtain high-density blocks from chips, but to consume relatively low energy. In this paper, regression analysis is used to optimize hot compaction processing of machined chips in an indirect solid-state recycling. The nonlinear relation of the temperature, the press and deformation velocity was established according to the rheology of the matrix material using MRA. The lowest energy consumption as criterion is also introduced to further optimize hot compaction parameters in the solid-state recycling. The results based on MRA show that high-density (93%) blocks are obtained according to the built model and that effect of work velocity of the hydrostatic machine on total energy consumption is negligible. During hot compaction, the higher temperature, the more total energy consumption. Besides, void and interface between chips in these hot compaction blocks will be disappeared by extrusion deformation.
Effects of Particle-Reinforcement on Elastic Modulus of Metal-Matrix Composites
Authors: Huang J.Y. , Ling Z.H. , Wu Guo Qing
Published: May 2010

To study the influence of particle’s characteristics on mechanical properties of the metal-matrix composites (MMCs), A two-dimensional randomly-distributed ellipsoidal particles finite element model was proposed and the tensile process of composites was simulated. The effects of adding proportion, geometrical parameters and attribute features of the particle-reinforcement on elastic modulus of composite were investigated and analyzed. The results show that there are several factors affect elastic modulus of the composite, including the adding proportion, elastic modulus, shape, size and tilt angle of the particles, etc. Among them, the elastic modulus and adding proportion of the reinforcement can primarily enhance the elastic modulus of the composite by 25% - 40% and 50% or more respectively, while the effects of particle shape, size and tilt angle on composite’s elastic modulus is relatively minor.
Dynamic Recrystallization of 7055 Aluminum Alloy during Hot Deformation
Authors: Yan Liang Ming , Shen Jian , Li Ju Peng , Li Zhou Bing , Tang Zhen Lei
Published: May 2010

Compression tests were performed at temperatures from 350 to 450 °C with different strain rates of 1.0×10−2 and 1.0×10−1 s−1. The microstructures of deformed samples were investigated by electron backscatter diffraction (EBSD). Microstructure observations indicated that under present deformation conditions, fraction of new grains increases with the Z value. It was found that different nucleation mechanisms for DRX were operated in hot deformed 7055 alloy, which was closely related to deformation condition. DRX nucleation and development were discussed in consideration of bulging of original grain boundaries and occasional subgrain rotation near the grain boundaries. Discontinuous dynamic recrystallization (DDRX) which occurred in a local area was also proved to be a nucleation mechanism at higher Z value for 7055 alloy.
Thermal Properties of the FCC Al3Zr : First-Principles Study
Authors: Li Dong Lin , Chen Ping , Yi Jian Xiong , Tang Bi Yu , Peng Li Ming , Ding Wen Jiang
Published: May 2010

Ab inito density functional theory (DFT) and density function perturbation theory (DFPT) have been applied to investigate the thermal properties of the face-center-cubic (fcc) Al3Zr alloy over a wide range of pressure and temperature. Phonon dispersions were obtained at equilibrium and strained configurations by density functional perturbation theory. Using the quasiharmonic approximation for the free energy, several interesting physical quantities such as thermal Grüneisen parameter, heat capacity at constant pressure and volume, thermal expansion coefficient and entropy, as well as adiabatic bulk modulus and isothermal bulk modulus, were calculated as a function of temperature and pressure, and the variation features of these quantities were discussed in details.
Molecular Dynamics Investigation of Relaxation and Local Structure Changes in a Quenched Molten TiAl Alloy Film
Authors: Zhang Lin , Fan Qin Na , Zhang Cai Bei , Wang Shao Qing
Published: May 2010

Relaxation and local structure changes of a molten TiAl alloy film during quenching have been investigated by molecular dynamics simulations within the framework of embedded atom method (EAM). The details of atom motions are analyzed using mean square displacement (MSD). Accompanying with massive atom rearrangement at a certain quenched temperature and time, local structural patterns are identified by decomposing peaks of pair distribution functions (PDFs) according to the pair analysis(PA) technique. The relaxation factor clearly reveals two relaxation processes involving in slow relaxation and fast relaxation of the quenched liquid TiAl film. Concerning the studied film, the obtained results reveal how quenched temperatures affect local structure changes.
Effect of Curing Temperature on Morphology and Properties of Polyureas Based on Polyaspartic Esters
Authors: Lu Ping , Huang Wei Bo , Shi Hui , Zhu Li
Published: May 2010

In this paper the effect of curing temperature on the morphology and properties of PAE based polyureas were evaluated using FTIR, AFM and electrochemical impedance spectroscopy (EIS). The PAE based polyureas were prepared from synthesized PAE chain extenders and hexamethylene diisocyanate（HDI）trimer/polytetramethylene ether glycol (PTMG) prepolymer. The morphology and properties were investigated through FTIR, EIS and atomic force microscope(AFM). The results indicated that curing temperature has a great influence on morphology and properties of the polyureas. FTIR studies showed that hydrogen-bonded urea carbonyl are increased from 74.3% to 82.1%, and the length of hydrogen bonding were decreased from 0.307 nm to 0.303 nm while curing temperature were increased from 20°C to 80°C. FTIR experimental studies indicated that the degree of hydrogen-bonded –NH groups and urea carbonyl groups increased while curing temperature increased, as a consequence, intermolecular force enhanced. The AFM was applied to study the topography of PAE based polyureas for the first time,and the microphase separation phenomenon of the PAE based polyureas were observed directly through AFM topography studies. AFM studies confirmed that the compatibility of soft and hard segment decreased and microphase separation degree increased while the curing temperature increased. The EIS studies indicated that during 90 days immersion, the resistance of 20°C cured samples changed obviously higher than 80°C cured ones. The results showed that much corrosion medium permeated into the coatings, and the corrosion resistance of 80°C cured PAE based polyureas exhibited a higher EIS features and a better corrosion resistance than the 20°C cured ones. The effect of curing temperature on EIS properties of PAE based polyureas could be confirmed by FTIR and AFM morphology studies.
The Mössbauer Spectrum Research of the Lanthanon Compound Tb3Fe29-xCrx
Authors: Liu Hong Li , Huang Min , Feng Qiu
Published: May 2010

A systematic investigation on the isomer shift, quadrupole split, hyperfine field and the preferential occupation of Cr atom of the crystal site at different temperatures of the novel compounds Tb3Fe29-xCrx (x=1.0,1.2,2.0,3.0)has been performed. Our research method is to use ATOM process to protract the crystal site structure map and every sit near neighbor configuration map of the Tb3Fe26.0Cr3.0, and calculate the bond length of neighboring atoms. At the base of the careful research of the Tb3Fe26.0Cr3.0 crystal structure, we establish the Mössbauer Spectroscopy fitting program.The result of the research indicates that the Cr substitutes the Fe in 4i crystal site priority when the content of the Cr atom in the Tb3Fe29-xCrx is x=1.0, 1.5, the Cr substitutes the Fe in 8j crystal site priority when the content of Cr atom is x=2.0, 3.0, Tb3Fe29-xCrx hyperfine field reduces as x adds up from 1.0 to 3.0.
The Influence of Degree of Polymerization on Precursor-Derived Si-B-C-N Ceramics
Authors: Geng Xiang , Huang X. , Li Ya Jing , Li Song , Shi Xiao Bin
Published: May 2010

Precursor derived Si-B-C-N ceramic is a kind of amorphous materials with high hardness, low density, durability at extremely high temperature. The materials show a great potential to be used in the field of the Thermal Protective System (TPS). The physical states and chemical properties of the amorphous materials greatly depend on the starting materials. The effect of degree of polymerization (DP) of the precursor on the pyrolysis process and the characteristics of the amorphous Si-B-C-N materials are studied. The SiBCN-based preceramic polymer synthesized by dichloromethylvinylsilane, ammonia and BH3•SMe2. Dichloromethylvinylsilane reacted with ammonia and BH3•SMe2 in toluene or tetrahydrofuran (THF) as solvent in the presence of catalytic amounts of pyridine. The polymeric precursors were cured at low temperature to obtain solid-state precursors. Pyrolysis process of the solid-state precursors under various temperatures and carried out in nitrogen atmosphere. The results showed that DP of the precursor influences the pyrolysis process and the high temperature stability of the Si-B-C-N amorphous ceramics.
Synthesis of a New Semiconductor Compound [(C5S5H3CH2O)4Ni](FeCp2)0.84
Authors: Zhang Yan Bing , Zhang Ting , Yang Xian Li , Zhang Wen Tao , Wang Xiao Jing
Published: May 2010

A new charge-transfer coordination compound [(C5S5H3CH2O)4Ni](FeCp2)0.84 was synthesized in this work. The molecular formula of the coordination compound was confirmed by elementary analysis and ICP. The structure of this compound was defined by 1HNMR, IR and UV-Vis. Electrochemical properties of the new compound were studied by cyclic voltammetry (CV). Electrical property was tested by four probe methods with R-T curve.
Analysis of Influencing Factors of CO2 Emissions from Integrated Steelworks Based on LCA
Authors: Huang Zhi Jia , Ding Xiao , Sun Hao , Liu Si Yue
Published: May 2010

The amount of CO2 emissions from steelworks accounts for a great share of the total CO2 emissions from industry in China. Thus, reducing CO2 emissions from steelworks is urgent for China’s environmental protection and sustainable development. This study aims at identifying factors that influence CO2 emissions from steelworks and proposing measures to reduce CO2 emissions. The life cycle inventory (LCI) of iron and steel products implies the relationship between the CO2 emissions of the steelworks and the input variables of the LCI. The Tornado Chart Tool is utilized to calculate the variation of CO2 emissions caused by the change of each input variables of LCI. Then, mean sensitivity of each input variable is calculated and the ranking criterion developed is used to identify the main factors influencing the integrated steelworks. Subsequently, measures for reducing CO2 emissions are proposed. The results indicate that the very important influencing factors of CO2 emissions in steelworks are the CO2 emission factor of Blast Furnace Gas (BFG), liquid steel unit consumption of continuous casting, continuous casting slab unit consumption of hot rolling and hot metal ratio of steelmaking. Consequently, many efficient measures for reducing CO2 emissions have been proposed, such as removing CO2 contained in BFG, decreasing the hot metal ratio of Basic Oxygen Furnace (BOF), recycling BFG, optimizing the products’ structure, etc.
Cu-Ni-Ti Composite Diffusion Coating on Si3N4 Ceramic Surface
Authors: Zhang Hong Xia , Wei Ying Hui , Wang Wen Xian
Published: May 2010

Si3N4 ceramic surface was metallized using multi-ionic composite coating technology. The obtained Cu-Ni-Ti composite coating was examined and evaluated by energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffusion (XRD) and sound emissive scratch test (SEST). The composite coating composition, the element distribution, the phase structure of the deposited coating, and the jointing mechanism of steel/ceramics were analyzed. It was found that the obtained alloy coating layer contained elements such as Cu, Ti, Ni and Fe, etc, and no element segregation was observed. XRD result showed that the diffusion coating alloy layer was composed of Cu2Ti4O, Cu, NiTi and CuTi2. Sound emissive scratch test (SEST) results revealed a good adhesion between the diffusion coating alloy layer and ceramic, and no spallation occurred under the maximum load of 100N.
The Immune Enhancement of Sodium Lauryl Sulfoacetate in Chickens
Authors: Cheng DaRong , Zhu ShanYuan , Sun HuaiChang
Published: May 2010

The purpose of this study is to investigate feasibility of sodium lauryl sulfoacetate (SLS) as an immunoadjuvant in chickens. After treating with 62.5, 125, 250, or 500 μg/mL SLS in vitro, lymphocyte proliferation assay of chicken peripheral blood mononuclear cells showed that theOD570values of all experimental groups, as well as Con A-stimulated group, were significantly higher than that of the untreated control group. After injection with 1.0, 2.0, or 4.0 mg/kg of SLS for 3 consecutive days, chickens were vaccinated with an attenuated vaccine againstNewcastle disease virus(NDV), and the immunoadjuvant effects of SLS were evaluated on the basis of immune organ index, antibody response, andCD4+/CD8+T-cell ratio. The results confirmed that SLS could enhance NDV-specific antibody response and increaseCD4+/CD8+T-cell ratio in vivo. Furthermore, SLS could improve NDV-specific antibody response in thiamphenicol-treated chickens. These data indicate that SLS not only can improve humoral immune response but also reverse the immunosuppressive effect of thiamphenicol in chickens.
Japanese Encephalitis in Travelers from Non-Endemic Countries, 1973–2008
Authors: Hills Susan L. , Griggs Anne C. , Fischer Marc
Published: May 2010

Japanese encephalitis (JE) is a severe disease and a risk for travelers who visit JE-endemic countries. We reviewed all published JE cases in travelers from non-endemic areas from 1973 through 2008, and assessed factors related to risk of infection. There were 55 cases that occurred in citizens of 17 countries. Age range of case-patients was 1–91 years (median = 34 years). Ten (18%) persons died and 24 (44%) had mild to severe sequelae. In a detailed risk assessment of 37 case-patients, 24 (65%) had spent ≥ 1 month in JE-endemic areas, and most had factors identified that may have increased infection risk. The estimate of overall JE risk was low, < 1 case/1 million travelers to JE-endemic countries. Nonetheless, for each traveler, a careful assessment of itinerary and activities, a decision on vaccination, and information on mosquito precautions are needed to reduce the risk of this disease.
Modelling hourly rates of lake evaporation
Authors: Granger R. J. , Hedstrom N.
Published: May 2010

Abstract. The paper presents the initial results of a field study of open water evaporation carried out on three small- to medium-sized lakes in Western and Northern Canada. Lake evaporation was measured directly using eddy covariance equipment; profiles of wind speed, air temperature and humidity were also obtained over the water surfaces. Observations were made as well over the upwind land surface. Relationships were developed between the hourly rates of lake evaporation and those significant parameters (wind speed, land-water temperature and humidity contrasts, and the downwind distance from shore). The result is a relatively simple versatile model for estimating the hourly lake evaporation rates. The model was tested using two independent datasets. Results show that the modelled evaporation follows the observed values very well; the model follows the diurnal trends and responds correctly to sudden changes in environmental conditions.
Fabrication of Density Gradients of Biodegradable Polymer Microparticles and Their Use in Guiding Neurite Outgrowth
Authors: Li Xiaoran , MacEwan Matthew R. , Xie Jingwei , Siewe Daku , Yuan Xiaoyan , Xia Younan
Published: May 2010

A new method for generating both continuous and discrete density gradients in microparticles of biodegradable polymers via an electrospray technique is reported. The gradients are generated by spatially varying the deposition time of electrosprayed microparticles. The substrate coated with a density gradient of microparticles has varying surface roughness, offering a unique system for studying the effect of physical cues on neurite outgrowth from dorsal root ganglia. An optimal surface roughness for promoting neuron adhesion and neurite extension in vitro is obtained. Furthermore, this capability of approach is extended to generate a gradient of fluorescein isothiocyanate labeled bovine serum albumin by encapsulating it in the polymer microparticles in situ during electrospray. Taken together, this new class of substrates with gradients of microparticle density can potentially be used in various biomedical applications such as neural tissue engineering.
Applying soft computing methods to fluorescence modeling of the polydimethylsiloxane/silica composites containing lanthanum
Authors: Curteanu Silvia , Nistor Alexandra , Curteanu Neculai , Airinei Anton , Cazacu Maria
Published: May 2010

Lanthanum, as a fluorescent element, was encapsulated in complexing silica xerogel by using a one‐pot procedure: silica formation from tetraethyl‐orthosilicate and 3‐aminopropyltriethoxysilane, its chemical modification by reacting with 2,4‐dihydroxybenzaldehyde, and lanthanum complexation through the formed hydroxy‐azomethine groups occurred in the same reaction system. A polydimethylsiloxane‐α,ω‐diol with average number molecular weight of 20,000 was added in the sol–gel system to facilitate obtaining the flexible, free‐standing films. Using different molar ratios among the reactants, a series of experiments was performed and the fluorescence of the resulted compounds was evaluated, since the photophysical properties of the prepared compounds strongly depend on the composition. The acquired data have been used for fluorescence modeling based on soft computing instruments. Neural network models, individually or aggregated in stacks, were developed to estimate the fluorescence intensity depending on the reaction mixture composition: tetraethyl‐orthosilicate, 3‐aminopropyltriethoxysilane, 2,4‐dihydroxybenzaldehyde, lanthanum acetate, and polydimethylsiloxane‐α,ω‐diol amounts. A procedure based on genetic algorithms was used to design simple neural networks. Two main goals are pointed out in this article: developing a general methodology for modeling the complex processes with simple or stacked neural networks, and demonstrating the improvement of the modeling performance by combining different neural networks. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Evaluation of properties of unsaturated polyester/acetylated hydroxypropyl guar gum composites
Authors: Shenoy M. A. , D'Melo D. J.
Published: May 2010

Guar gum is a naturally occurring galactomannan, which is extremely hydrophilic in nature. Hydroxypropyl guar gum (HPG) was subjected to acetylation using acetic anhydride and pyridine. The effect of the reduction in the hydrophilic nature of the polymer on its filler properties was studied by using the derivatized guar gum as filler in an unsaturated polyester composite. The effect of degree of substitution and the concentration of filler on the rheological, chemical, and mechanical properties of the composites were studied. Results indicated that an increase in the acetate content in the HPG resulted in an increased polymer–filler interaction. However, the composites resulting from these derivatized HPGs showed reduced mechanical properties. This decrease in the mechanical properties were attributed to the decrease in the hydrogen bonding in the filler particles, thus reducing the cohesiveness and strength of the filler particles themselves. Thus, polysaccharides can be used as fillers but chemically modifying them results in a change in the basic nature of the filler itself and is not just restricted to surface modification as is the case of inorganic fillers and fibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Investigation of the phase morphology of dynamically vulcanized PVC/NBR blends using atomic force microscopy
Authors: Gheno S. M. , Passador F. R. , Pessan L. A.
Published: May 2010

Dynamic vulcanization is a mixing process employed in the melt state of elastomers with thermoplastics. This process may result in the formation of thermoplastic vulcanized (TPV) materials with improved properties such as mechanical strength, Young's modulus, hardness, and abrasion fatigue. In this study, a vulcanized thermoplastic was obtained by the dynamic vulcanization of poly(vinyl chloride)/acrylonitrile butadiene rubber (PVC/NBR) blends using a curative system based on sulfur (S)/tetramethylthiuram disulfide (TMTD) and mercaptobenzothiazyl disulfide (MBTS). The formation of crosslinks was characterized by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The mechanical properties were analyzed by tensile tests and the phase morphology was investigated using atomic force microscopy (AFM) operating in the tapping mode‐AFM. The phase images of the dynamically vulcanized blends showed an elongated morphology, which can be associated to the formation of crosslinks that give the material its excellent mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010