bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Blistering and Flaking of Sintered Uranium Dioxide Samples under High Dose Gas Implantation and Annealing
Authors: Martin Guillaume , Carlot Gaëlle , Desgardin Pierre , Vayer Marylène , Ramboz Claire , Sauvage Thierry , Moretto Philippe , Khodja Hicham , Garcia Philippe
Published: April 2012

High helium contents will be generated within minor actinide doped uranium dioxide blankets which could be used in fourth generation reactors. In this framework, it is essential to improve our understanding of the type of damage which a pellet could incur as a result of extensive helium build-up. This paper is an attempt at tackling this issue. Sintered uranium dioxide disks have been implanted with helium ions then annealed at various temperatures. Above a concentration of 0.4 at.% and above 1000°C, optical images of the sample surface revealed swollen grains and extensive areas which have exfoliated. Nuclear reaction microanalyses and atomic force microscopy observations were performed to demonstrate that helium has substantially precipitated within the swollen grains. Massive precipitation of the gas leads under these conditions to sample surface blistering which appears to precede flaking. Deuterium ion irradiations have also been performed at ambient and a direct flaking of the sample surface was observed, but for this phenomenon to be observed required much higher doses than in the He study, indicating that temperature could be an essential ingredient for gas to migrate and cause extensive precipitation. Such phenomena could possibly lead to degradation of the fuel.
Diffusion Aspects in High Temperature Corrosion and in the Development of Protective Coatings
Authors: Schütze Michael
Published: April 2012

The paper reviews the advantages of diffusion coating and the parameters deciding an optimum coating performance. Furthermore, innovative coating approaches are presented which have a significant potential beyond existing diffusion coating solutions.
Towards Measuring the Pu Self-Diffusion Coefficient in Polycrystalline U0.55Pu0.45O2±x
Authors: Noyau S. , Garcia Philippe , Pasquet B. , Roure I. , Audubert Fabienne , Maître Alexandre
Published: April 2012

This paper describes an original method to measure the plutonium self-diffusion coefficient in the mixed oxide U0.55Pu0.45O2±x. This method is based on using 242Pu as a tracer atom. A thin film of the tracer was deposited on the well-polished surface of the samples and then diffusion annealings were performed from 1500°C to 1700°C, in an Ar-H2 5% atmosphere. The oxygen potential was fixed at-395 kJ.mol-1. After annealing, the 242Pu self-diffusion profiles were established by means of secondary ion mass spectrometry (SIMS). The 242Pu concentration profiles were determined by assessing the relative U, Am and Pu ionisation yields according to the experimental parameters. The choice of favourable experimental conditions and the relevance of the resulting concentration profiles are discussed at length.
Development of Diffusion Coatings to Optimise the High Temperature Corrosion Resistance of Fuel Cell Reformer Materials
Authors: Naji Ammar , Schütze Michael
Published: April 2012

Reformer materials are exposed to severe operating conditions at high temperature in aggressive catalyzer and combustion atmospheres. Therefore, materials used for the construction of the reformer reactor have to possess appropriate high temperature resistance. Diffusion coatings improve the high temperature resistance of materials by enrichment of the alloy surface with thermodynamically stable oxide formers. Beside conventional mono-element diffusion coatings (e.g. Al coating), multi-element diffusion coatings can be developed in a single process step. In this work we developed Al diffusion and Al-Si and Al-Si-RE (RE: reactive element Y, Ce) co-diffusion coatings on a low cost austenitic 18Cr10Ni-steel. The high temperature resistance of coated and uncoated 18Cr10Ni-steel, 20Cr31Ni-steel and 23Cr18Fe-Ni base alloy was tested in catalyzer and combustion atmosphere under cyclic operation conditions.
Influence of Carbonation and Chemical Activity of Water on Coupled Moisture-Ion Transport in Cementitious Materials
Authors: Wang Xiao Meng , Thiéry Mickaël , Baroghel-Bouny Véronique
Published: April 2012

The influence of the chemical activity effects on moisture transport in the presence of ions in cementitious materials is studied. Wetting-drying tests are carried out on various hardened concretes (sound and fully carbonated) with water. Moisture profiles are experimentally assessed by gamma-ray attenuation. A multispecies and multiphase numerical model, in which the Lin and Lee approach is applied to compute the chemical activity coefficients of water in presence of ions, is used to simulate the transport of ions and moisture. The drying kinetics is analyzed to assess the intrinsic permeability of the material by inverse analysis. Experimental profiles are compared to the simulations to illustrate the relevance of the modeling.
The Transition from Internal to External Oxidation of Ni - X Wt.% Cr at 950°C
Authors: Nicolas A. , Aublant E. , Feulvarch E. , Wolski Krzysztof
Published: April 2012

The papers focus is to establish the criterion for the transition from internal to external oxidation. This criterion is a simple value of oxide volume fraction where the coalescence of the nodular oxide in the continuous layer is considered as inevitable. It is obtained by the Wagners analytical solution and by the data of Giggins et al. [1], which give the experimental transition from internal to external oxidation between 10 and 11 weight percent of chromium in the initial alloy. This paper also enables to obtain the oxygen diffusion coefficient in pure nickel thanks to the experimental results of oxidation at 950 °C during 10 hours on Ni-0.2Cr, Ni-1Cr and Ni-5Cr model alloys.
Corrosion Behaviour of Ti-48Al-2Nb-2Cr Alloys
Authors: Pelic B. , Rafaja D. , Masset Patrick J. , Seifert Hans Jürgen , Bortolotto L. , Schütze Michael , Wolf G. , Loeh I.
Published: April 2012

γ-TiAl intermetallics are attractive materials for high-temperature structural applications in the aerospace and automobile industries. However, they show environmental embrittlement at elevated temperatures that is mainly related to their low high-temperature corrosion resistance. One way how to improve the high-temperature corrosion resistance is the deposition of protective coatings on the surface of the base material. In this study, samples of a Ti-Al alloy with the chemical composition Ti-48Al-2Cr-2Nb (at.%) were covered by physically vapour deposited (PVD), by metalorganic chemically vapour deposited (MOCVD) and by high-velocity oxy-fuel (HVOF) sprayed coatings. All coatings were based on the Ti-Al alloys and contained different amounts of alloying elements. The corrosion experiments were performed in molten salts containing 75 wt.% Na2SO4 and 25 wt.% NaCl at 850°C up to 336 h. Both, PVD and CVD protected coatings reduced the changes in the mass of the samples over the corrosion time. Still, the formation of TiO2 could not be avoided, as it was confirmed by glancing-angle X-ray diffraction experiments.
On the Defect Structure and Transport Properties of NiS2
Authors: Grzesik Zbigniew , Poczekajło A. , Mrowec S.
Published: April 2012

Because of considerable experimental difficulties, the defect structure of NiS2 has not been elucidated so far. The first step in these investigations was to explain which sublattice of this compound is predominantly disordered. In order to solve this problem, the mechanism of sulphidation of NiS to NiS2 has been studied using marker technique. These experiments have been carried out at temperatures 823-923 K in sulphur vapors under pressure 103 105 Pa. It has been found that the predominant defects in NiS2 occur in cation sublattice. The problem then arised whether these defects are cation vacancies or interstitial cations. This phenomenon could have been explained in studying the kinetics of NiS sulphidation as a function of sulphur activity. It has been found that the parabolic rate constant of this reaction increases with sulphur activity, strongly suggesting that cation vacancies, and not cation interstitials, are the prevailing defects. If, namely, interstitial cations would prevail, the sulphidation rate would be virtually pressure independent.
Kinetics and Mechanism of High Temperature Internal Oxidation of Ni-14wt%W Alloy at 1000°C
Authors: Ganster Patrick , Pujilaksono Bagas , Wolski Krzysztof
Published: April 2012

Ni-14wt%W model-alloy has been used to study the kinetics and the mechanism of high temperature internal oxidation in presence of an external oxide scale. Oxidations have been done in air at 1000°C for different oxidation times and have allowed the evaluation of the oxidation kinetic from mass gain and from oxide thickness measurements. The oxidation kinetic which follows a parabolic oxidation rate indicates a diffusive behaviour of species during the oxide formation. Cross-section observations by Scanning Electron Microscopy (SEM) and analysis by Grazing Incidence X-Rays Diffraction (GIXRD) show a multi-layered structure of the oxide. Starting from the surface towards the bulk alloy, the scale is layered as follows : (i) a pure nickel oxide (NiO) in the outer part (ii) a porous NiO matrix containing NiWO4 second phase and (iii) an internal oxidation zone of tungsten, first forming WO3 sub-micrometer oxides that progressively transform into NiWO4 oxide precipitates in the alloy.
Oxygen Diffusion Study in Oxidation Films of the AISI 304 Austenitic Stainless Steel
Authors: Sabioni Antônio Claret Soares , Ramos Roberto Paulo Barbosa , Ji Vincent , Jomard François
Published: April 2012

Oxygen ion diffusion coefficient was measured, for the first time, in oxide films grown by the high temperature oxidation of the AISI 304 austenitic stainless steel. The steel samples were polished and then oxidized in synthetic air in order to grow the chromia oxide (Cr2O3) film. The oxygen diffusion experiments in the oxide films were performed by using the18O isotope as oxygen tracer. The isotope diffusion studies were performed from 750 to 900o C, in Ar +21%18O2 atmosphere and the oxygen ion diffusion profiles were established by secondary ion mass spectrometry (SIMS) analysis. From the18O diffusion profiles, the bulk, effective and grain boundary diffusivities were determined. Using Wagner´s theory, it is shown that, under the used experimental conditions, the oxygen ion diffusion is large enough to assure the growth rate of the chrome oxide films formed by the oxidation of the AISI 304 stainless steel.
High Temperature Corrosion Behavior of Si-Containing Alloys in the Liquid Phase of Na2SO4 25.7 Mass% NaCl
Authors: Sudiro Toto , Sano Tomonori , Kyo Shoji , Ishibashi Osamu , Nakamori Masaharu , Kurokawa Kazuya
Published: April 2012

The high temperature corrosion behavior of Si-containing alloys consisting of Cr-Si-Ni and CoNiCrAlY-Si alloys fabricated by spark plasma sintering technique was investigated in the liquid phase of Na2SO4 + 25.7 mass% NaCl at temperatures ranging from 923-1273 K. The purpose of this study is to develop excellent corrosion resistant alloys for coating applications. Our experimental results show the CrSi2 alloy with 10 mass% Ni content and the CoNiCrAlY alloy with 30 mass% Si content are the most promising materials for applications in this atmosphere. This is due to the formation of a protective SiO2 and Al2O3/SiO2 scale, respectively. The formation of a dense and continuous oxide layer composed and/or consisted of SiO2 plays a significant role in hindering the inward diffusion of chlorine and sulfur to the alloys substrate. Particularly, the corrosion mechanism of Cr-Si-Ni alloys and the influence of Ni addition on the corrosion resistance of CrSi2 alloy are discussed in the present paper.
On the Influence of a Heat Treat for an Aluminizing Progress Based on Al Microparticles Slurry for Model Ni and Ni20Cr. Experimental and Theoretical Approaches.
Authors: Rannou B. , Mollard M. , Bouchaud B. , Balmain J. , Bonnet G. , Kolarik Vladislav , Pedraza-Diaz Fernando
Published: April 2012

The use of thermal barrier coating systems allows superalloys to withstand higher operating temperatures in aeroengine turbines. Aiming at providing oxidation protection to such substrates, an aluminum-rich layer is deposited to form the α-Al2O3 scale over which a ceramic layer (i.e. YSZ layer) is applied to provide thermal insulation. A new approach is now being investigated within the FP7 European project « PARTICOAT », in which a single step process is employed by applying micro-sized aluminum particles. The particles are mixed in a binder and deposited by brushing or spraying on the substrate surface. During a heat treatment, the particles sinter and oxidize to form a top coat composed of hollow con-joint alumina spheres and simultaneously, an Al-rich diffusion zone is formed in the substrate. For a better understanding of the diffusion / growth processes, preliminary tests were carried out on pure nickel and Ni20Cr model alloys prior to further application on commercial superalloys. The effect of the heat treatment on the coating characteristics (number of layers, thickness, composition, homogeneity, etc.) was particularly investigated to emphasize the mechanisms of diffusion governing the growth of the coatings. The establishment of the diffused layers occurred very readily even at intermediate temperatures (650 and 700°C). However, the layers formed did not match perfectly with the thermodynamic modeling because of the quick incorporation of Ni into molten Al at intermediate temperatures (650°C). In contrast, at higher temperatures (700 and 1100°C) the phases predicted by Thermocalc are in good agreement with the observed thickness of the diffused layers. The incorporation of Cr as an alloying element restrained Al ingress by segregation of Cr even at very low temperatures aluminizing temperatures (625°C).
New Materials for Hydrogen Distribution Networks: Materials Development & Technico-Economic Benchmark
Authors: Klopffer Marie Hélène , Berne Philippe , Weber Mathilde , Castagnet Sylvie , Hochstetter Gilles , Espuche Eliane
Published: April 2012

In France, the steel transportation network for natural gas is connected to the distribution network which operates at lower pressure. This one (total length of 165 000 km) is mainly made of polymer pipes like polyethylene. With the introduction of hydrogen in mixture with natural gas and finally the transport of pure hydrogen, the key challenge is the high level of permeability that is to say the flow rate of hydrogen through polymer infrastructures (pipes or components like connecting parts). This high flow rate of hydrogen has to be taken into account for safety and economic requirements. Long-term behaviour must be carefully assessed: permeation/diffusion properties, thermo-mechanical behaviour and ageing. It is important to characterize the existing distribution network and to propose more innovative materials than polyethylene that could meet the targets for future hydrogen distribution applications. The aim of this project was to develop and assess material solutions to cope with today problems in term of high flow rate of hydrogen and ageing under a hydrogen environment. Polyethylene is considered as a reference material since it is used today in natural gas distribution pipes. Test benches and protocols for testing materials in term of mechanical and barrier properties were first developed. On the other hand, technical polymers (multi-layers, other thermoplastics, polymer blends) have been proposed and studied to improve gas-barrier performances compared to polyethylene. Step by step, permeation and basic mechanical tests have been performed and then more specific characterisations have been done (for long-term ageing under various conditions) in order to choose one or several materials that could meet the specifications required by hydrogen distribution. The design of a pipe prototype was also carried out at the end the project and an economic study was performed for the different potential solutions.
From Contact to Diffusion Controlled Growth of Nickel Silicides in Silicon Nanowires
Authors: Katsman A. , Yaish Y. , Beregovsky M.
Published: April 2012

Semiconducting nanowires (NW) are implemented as the active channel of field effect transistor (FET) with linear and Schottky barrier source and drain contacts. Thermally activated axial intrusion of nickel silicides into the silicon NW from pre-patterned Ni reservoirs is used in the formation of nickel silicide/silicon contacts in SiNW FETs. In the present work, the kinetics of nickel silicide axial growth in SiNWs was analyzed in the framework of the model taking into account the balance between transition of Ni atoms from the Ni reservoir to the NW surface, diffusion transport of these Ni atoms from the contact area to the interfaces between different silicides and nickel silicide/Si interface, and corresponding reactions of Ni atoms with Si and the nickel silicides formed. Simultaneous growth of mono-and nickel rich silicide was described for different kinetic and geometrical parameters of the system. Critical parameters for transition from the linear to the parabolic dependences were introduced. The model was applied to the experimental results on nickel silicide growth in SiNWs of 25÷50 nm in diameters in a temperature range of 300÷440C°. The silicide intrusions were obtained by annealing of SiNWs with pre-patterned Ni electrodes in a rapid thermal annealing machine under nitrogen atmosphere for different temperatures and times up to 120 s. In most cases the intrusions consisted of two nickel silicides, Ni-rich and mono-silicide NiSi, as was confirmed by TEM and measuring the electrical resistance of the SiNW after full silicidation. The total intrusion length, L, and particular silicide lengths, showed various time dependences, from a linear (with low growth rates (1÷4nm/s)) to a square root, diffusion-type dependence (with higher rates (10÷15 nm/s)). This behavior is well described by the model developed.
Diffusion in LanCoIn3n+2 Phases Studied by Perturbed Angular Correlation
Authors: Newhouse Randal L. , Collins Gary Scott
Published: April 2012

Jump frequencies of 111In/Cd tracer atoms were measured for a series of layered phases LanCoIn3n+2 using the technique of perturbed angular correlation of gamma rays (PAC). The frequencies were determined by analysis of nuclear quadrupole relaxation produced by fluctuating electric field gradients. Samples were synthesized having nominal values n= 1, 2, 3, 5 and , with n= corresponding to the L12 phase LaIn3. The phases form heuristically from LaIn3 by replacing every (n+1)th (100) mixed plane of La and In atoms with a plane of Co-atoms. For the n=1 phase, LaCoIn5, jump frequencies were too small to detect. Two signals were observed, one for indium atoms next to the Co-planes and the other for more distant indium atoms. No relaxation was observed for atoms next to the Co-planes, indicating that there is no diffusion across the Co-planes. With increasing n, jump rates for the other In-atoms increased toward values observed for LaIn3. Jump frequency activation enthalpies for n= 3 and 5 were observed to be the same as for n=, suggesting the same diffusion mechanism. However, the jump-frequency prefactors were found to be smaller for small n, which is attributed to reductions in the connectivity of the diffusion sublattice. We conclude that diffusion in the layered phases is remarkably similar to diffusion in LaIn3 once the reduced connectivity is taken into account.
Growth Kinetics of Intermetallic Phases in Transient Liquid Phase Bonding Process (TLPB) in Al /Ni System
Authors: Tumminello S. , Sommadossi S.
Published: April 2012

New processes and materials are vital nowadays, since specific features of materials are essential to accomplish the more demanding technological and environmental requirements. Al/Ni system has stimulated a large number of phase equilibrium, thermodynamic, diffusion and related studies. Its relevance relays on first principle features as well as technological importance. Transient Liquid Phase Bonding (TLPB) process is presented in this work due to the advantages of this method above others. Low temperatures of processing are needed, to obtain stable intermetallic phases (IPs) suitable for high temperatures of service. The aim of this research is to investigate the impact of temperature on the IPs growth and formation mechanisms, completing previous works on microstructure and kinetics characterization of IPs in Al/Ni system at 720°C. The results of SEM-EDS/WDS analyses of the cross-sections of the bonds showed the presence of Al3Ni and Al3Ni2 at the beginning of the interaction between Al and Ni, which are consistent with the phase equilibrium diagram. The Al3Ni2 layer growth showed linear correlation with time at 800°C, whereas at 900 and 1000°C it suggested a diffusive growth. Inert markers experiments allowed distinguishing individual growth. Vickers micro-hardness was determined obtaining values for Ni and Al3Ni2 of about 100 and 800 HV/ 0.025, respectively.
Kirkendall Effect during Grain Boundary Interdiffusion in Polycrystalline Thin Films
Authors: Klinger Leonid , Rabkin Eugen
Published: April 2012

We consider the kinetics of chemical interdiffusion along the grain boundaries in stressed thin metal film attached to inert substrate. We show that the kinetics of stress relaxation in the film can be either accelerated or slowed down if compared with the same kinetics in a single-component film, depending on the difference of intrinsic GB diffusion coefficients of the two components. In the case of faster matrix atoms the tensile stress in the film significantly increases beyond its initial value at the beginning of interdiffusion process, while in the case of faster diffuser atoms the compressive stresses develop in the film at the intermediate stages of stress evolution.
Interdiffusion in the Binary Diffusion Couples under a Strong Gravitational Field
Authors: Ogata Yudai , Kondo Keisuke , Sakata Yuki , Iguchi Yusuke , Mashimo Tsutomo
Published: April 2012

nterdiffusion in the Cu|Cu30Zn diffusion couples under a strong gravitational field was investigated at 400. The Cu-Brass diffusion couples were prepared by electrolytic plating method. Two samples were centrifuged at 0.4×106 G for 60 hours. The initial contact interface was perpendicular to the gravitational force direction. The two different orientations of the samples were studied: with Cu 1) downside and 2) upside of the gravitational force direction. It was found that interdiffusion was markedly affected by the gravity field. This was caused by the sedimentation of atoms where heavy Cu atoms move in the direction of the strong gravitational field. A numerical simulation of the sedimentation process is self-consistent with experimental results.
Flux Driven Nucleation at Interfaces during Reactive Diffusion – New Solution of an Old Problem
Authors: Gusak Andriy , Schmitz Guido , Storozhuk Nadiya
Published: April 2012

The problem of phase competition during reactive diffusion is revisited. Nucleation of an intermediate phase at an interface under external fluxes in the neighboring phases is considered in the frame of kinetic Fokker-Planck approach. Effective nucleation barrier depending on the divergence of external fluxes is introduced. New suppression/growth criteria are obtained.
Numerical Analysis of the Diffusive Field around a Growing Protein Crystal in Microgravity
Authors: Inaka Koji , Tanaka Hiroaki , Takahashi Sachiko , Sano Satoshi , Sato Masaru , Shirakawa Masateru , Yoshimura Yoshinori
Published: April 2012

t is believed that a microgravity environment may maintain ideal depletion zones of protein (PDZ) and impurity (IDZ) around growing crystals and may contribute to growing high-quality crystals. This can lead to an X-ray diffraction data collection of higher resolution with lower mosaicity, because of the better internal order and fewer defects in the crystals when compared to ground-grown crystals. The extent of these depletion zones are dependent on a competition between the diffusion of the molecules in the solution (indexed by the diffusion coefficient, D) and the adsorption of those into the growing crystal (indexed by the kinetic constant, β). If we use the D/β value as an index of the extent of PDZ and IDZ, a lower D/β value is ideal for maintaining PDZ and IDZ. Using experimental results, we could easily obtain the D/β value. When we combined the D/β value with the quality of protein crystals obtained in microgravity experiments provided by Japanese Space Agency (JAXA), we found that the effects of microgravity contributed to obtaining superior crystals especially if the D/β value was less than 3 mm. The numerical analysis of the PDZ and IDZ shows that the radius of the crystal (R) is also related to the PDZ and the IDZ. If the Rβ/D value is large, both the PDZ and the IDZ provide a filtration effect, but if the Rβ/D value is small, only the IDZ does.
Interdiffusion in InSb/Zn/InSb System
Authors: Glodán Györgyi , Iguchi Yusuke , Cserháti Csaba , Pál Gergő , Mashimo Tsutomo , Beke Dezső L.
Published: April 2012

Interdiffusion in Zn/InSb system has been investigated under high (0.59×106 G) and low (1 G) gravity conditions at 673, 593 and 573K, respectively. Samples annealed at 0.59×106 G, 673K for 60 hours, indicated the formation of a periodic reaction layer structure. Since such structures can be formed in solid state reactions of ternary systems [, the effect of high gravitational field and high hydrostatic pressure (approximately 3kbar) in the formation of periodic patterns was investigated. Systematic investigations at ambient pressure and low gravitational field were carried out at 593 and 573 K in sandwich geometry. SEM and EDX analysis had shown that there are different phases between the initial components. Starting from the Zn side of the specimen there is a very thin single-phase with high (about 90%) In content. Next to it is a thin two-phase layer, containing mainly 50-50% InSb and some elongated Zn particles and then there is a thick phase with the composition of Zn5In2Sb4 which is followed by a similar two-phase mixture (InSb+Zn) similar to the Zn side of the sample. Although the diffusion zone is not a well developed periodic structure, but every layer (clearly distinguishable form the others and was either a single-or multiphase layer) grows with the time.
Determination of Diffusion Coefficients with Quantitative X-Ray Microanalysis at High - Spatial Resolution
Authors: Gauvin Raynald , Brodusch Nicolas , Michaud Pierre
Published: April 2012

This paper present the determination of concentration profiles of an Mg Al diffusion couple that was obtained with a high resolution field emission scanning electron microscope, the Hitachi SU-8000 equipped with a SDD EDS detector. From these concentration profiles, the inter-diffusion coefficient is determined with the Boltzmann-Matano technique. The advantages and disadvantages of working at high and low beam energy for quantitative x-ray microanalysis are highlighted. The f ratio method is used in this work to convert the x-ray intensities into composition.
A SIMS Study on Li Diffusion in Single Crystalline and Amorphous LiNbO3
Authors: Rahn Johanna , Hüger E. , Dörrer E. , Ruprecht B. , Heitjans P. , Schmidt H.
Published: April 2012

We investigated lithium self-diffusion in amorphous and single crystalline lithium niobate at low temperatures of 323, 423 and 623 K. The diffusivity was studied by secondary ion mass spectrometry (SIMS), using ion beam sputtered 6LiNbO3 as a tracer source. Our intention was to get information how structural disorder influences ionic diffusivity, while chemical composition remains unchanged. The results indicate an increase of the Li diffusivity by about eight orders of magnitude in the amorphous state.
Atomistic Simulation of Clustering and Annihilation of Point Defects in Molybdenum
Authors: Yanilkin Alexey , Insepov Zeke , Norman Genri , Rest Jeff , Stegailov Vladimir
Published: April 2012

Evolution of a molybdenum system containing self-interstitials and vacancies was studied by molecular dynamics simulation using a new molybdenum interatomic potential. The potential was parameterized by using formation and migration energies of the defects. Clustering and annihilation of the defects were investigated in terms of the defect concentration changes during the calculation. The rate constants were evaluated and compared with the diffusion coefficients. Also investigated was the influence of one-dimensional diffusion on kinetics, as well as the effects of temperature and defect concentrations on the reaction rates.
The Influence of Steel Slag on Phosphorous Slag Cement
Authors: Zhao Qian , Wu You
Published: April 2012

In this paper, the influence of steel slag and its pretreatment method on properties of phosphorus slag cement has been studied. The hydration process and microstructure were studied by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). Results show that, the problem of long setting time of high content phosphorous slag cement can be effectively solved by adding steel slag and pretreated steel slag. About 6% content of steel slag could promote the early hydration of phosphorus slag cement and reduced the initial setting time 2 hours. Grinding phosphorous slag and steel slag with different water content, the initial set time of phosphorus slag cement for 6 hours has reduced to 2.5 hours without changing the strength. Ageing the mixed grinding power of phosphorous slag and steel slag and keeping 2.5 hours of the initial set time, the early cement strength can increase 3 MPa.
Effect of Polycarboxylate Superplasticizer on Properties of Phosphogypsum-Based Cement
Authors: Lin Zong Shou , Shi Hua Dong , Beguedou Essossinam
Published: April 2012

By using XRD、SEM and other experimental methods, some details of polycarboxylate superplasticizer on the hydration products and performance of phosphogypsum-based cement(PBC) can be obtained. It can be found that the polycarboxylate superplasticizer makes the structure of the cement stone more compact, and significantly increases the strength of the cement. Besides, it can also improve the anti-carbonation and degradation properties of that cement.
Mechanical Properties of Asphalt Mixture Reinforced with Cellulose-Polyester Hybrid Fibers
Authors: Chen Zheng , Ma Deng Cheng
Published: April 2012

With regards of discussing cellulose and polyester fibers reinforced asphalt mixtures, the contribution of cellulose (CEL) and polyester (PET) fibers had therefore been experimented. And on the basis of different reinforcement mechanisms, this research focused on the cellulose (CEL) - polyester (PET) hybrid fibers reinforced system, consequently determined the feasibility of utilizing CEL-PET hybrid fibers in asphalt mixture. Asphalt mixtures had been prepared, according to the specifications, following both the SHRP procedure and the traditional one. Mechanical characteristics of the mixtures were evaluated with Marshall stability (MS), indirect tensile strength (ITS), moisture sensitivity, high temperature rutting test and fatigue test. This study compared the performance of mixtures containing hybrid fibers with mixes made with and without commonly used cellulose and polyester fibers produced specifically for use in hot mix asphalt (HMA). The research results showed that no significant differences in MS, ITS or moisture susceptibility were found in mixtures containing hybrid fibers compared to cellulose or polyester. Also, the hybrid fibers significantly improved the permanent deformation resistance of the mixtures compared to cellulose fibers, say nothing of the control one without fibers.
A Novel Way to Change Color of Allphatle Sulfonated Resin
Authors: Liu Qiang , Guo Hong Xia , Wang Zi Ming , Yang Peng , Cui Su Ping
Published: April 2012

The color of allphatle sulfonated acetone-formaldehyde resin has been changed by a novel way of mixing with blue and green dye. The UV spectroscopy and colorimeter were used to characterize the color change. And the water reducing performance of the resin was investigated. The results indicated that the ratio of SAF water reducer to blue dye was 10:5, and that to green dye was 10:4, the color of the SAF water reducer can be efficiently changed. The fluidity of cement paste of SAF water reducer added the blue dye was improved, and the water-reducing rate was almost not influenced by addition of dyes.
Experimental Research on AZ31 Magnesium Alloy Sheet with Electromagnetic Forming and Quasi-Static Forming
Authors: Feng Fei , Meng Zheng Hua , Huang Shang Yu , Hu Jian Hua , He Zhi Lei
Published: April 2012

Forming Limit Diagram of AZ31 magnesium alloy in different forming methods was researched in this paper. Experiment equipment and processes were improved successfully. Some tests and experiments (including tensile test, punch test and electromagnetic forming experiment) of AZ31 magnesium alloy sheet were done. Forming Limit Diagram of electromagnetic forming was established successfully. It could promote the application of magnesium alloy sheet in electromagnetic forming. Forming Limit Diagram of static forming was established successfully. It was very useful for the application of magnesium alloy sheet in other forming methods. The difference between these Forming Limit Diagram showed that electromagnetic forming obviously improve forming ability of the magnesium alloy sheet.
Light Scattering by Textured Al-Doped Zinc Oxide Film for Thin Film Silicon Solar Cells Coated on Glass Substrates
Authors: Miao Deng Kui , Zhao Qing Nan , Dong Yu Hong , Yuan Wen Hui , Wu Lei , Liang Hong Yu , Wang Bin , Lu Xiu Qiang
Published: April 2012

ZnO:Al thin films were deposited on low-iron glass substrates (size: 1100×1400 mm2 ) in an in-line sputtering system, using ZnO:Al ceramic targets. The initially smooth films exhibit high transparencies (T≥85% for visible light) and excellent electrical properties (carrier concentration N=3.810×1020cm-3, mobility μ=20.47 cm2/V•s). The films, etched by diluted HCl for different time, appear roughness morphology with suitable angles and crater structure, used for controlling the light scattering properties of the textured ZnO:Al films. Moreover, the electrical properties are not affected by the etching process. Thus, it is possible to optimize separately the electro-optical and light trapping properties. The textured ZnO:Al films (haze 21.2%, 550 nm) were used as front contacts for amorphous silicon thin film solar cells prepared by PECVD, 6.5% conversion efficiency were obtained.
Optimization of Optical Properties of SiO2/TiO2/SiO2 Multilayer Films
Authors: Ni Jia Miao , Gu Qi Bin
Published: April 2012

The computer aid simulation of optical properties of thin films has been used to optimize SiO2/TiO2/SiO2 multilayer films to obtain high transparent films in this paper. The maximum transmittance at the visible light wavelength range is proper criteria for optical films optimizing design. The effect of design parameters (film thickness and refractive index) on optical properties of SiO2/TiO2/SiO2 multilayer films were also discussed in detail. According to the result of optimization, high quality SiO2/TiO2/SiO2 multilayer film with a maximum of > 99% at visible light wavelength range can be achieved on the glass.
Synthesis and Properties of SnS Thin Films by Chemical Bath Deposition
Authors: Xia Dong Lin , Xu Jun , Shi Wen Qing , Lei Pan , Zhao Xiu Jian
Published: April 2012

Tin sulphide (SnS) thin films have been deposited on glass substrate by chemical bath deposition. The precursor solution was prepared from tin (II) chloride dihydrate, thioacetamide. Triethanolamine, ammonia and ammonium chloride were used as complexant, solvent and buffer solution, respectively. The crystallographic structure, morphology and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy and UV-Vis spectrophotometer. XRD analysis shows that SnS thin films were polycrystalline and had orthorhombic structure, and SEM micrographs reveal that SnS thin films were densely packed surface coverage and consists of large flowerlike grains. SnS thin films with the optical bandgap of 1.3 eV were achieved at 300 °C.
The Effect of Fluorine on the Viscosity and Crystallization of Lithium Aluminosilicate Glasses
Authors: Zheng Wei Hong , Dai Yang , Lin Mo Zhou , Yang Kun , Wu Hao
Published: April 2012

Lithium aluminosilicate glasses have high viscosities, resulting in high melting temperatures and processing temperatures. In this study, F was added to the LAS glasses to reduce the melting temperature and viscosity for float process. The effects of fluorine content on the viscosity and crystallization of the parent glasses were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA) and rotation viscometer. It was found that the addition of F was useful in reducing the melting temperature and viscosity. The main crystalline phase of resulting glass-ceramics was β-spodumene. The activation energy (E) of LAS glasses was decreased from 460.3 KJ/mol to 417.7 KJ/mol with the addition of 2.63 wt% F, which accelerated the crystallization and enhanced the crystallinity of specimens.
Physico-Mechanical Properties of Rubberized Lightweight Aggregate Concrete for Tunnel Pavements
Authors: Wang Ji , Li Yue , Fan Xiao Chun
Published: April 2012

Both asphalt concrete (AC) and Portland cement concrete (PCC) are limited in applications in tunnel pavements, due to special conditions in tunnel. To improve the fire resistance, durability and comfort of the tunnel pavements material, rubber particles, lightweight aggregate and polymer were added into PCC. Experimental results showed that physico-mechanical properties such as strength, rigidity, shrinkage and abrasion resistance got worse when rubber particles and lightweight aggregate were added, but when polymer was mixed, the physico-mechanical properties were enhanced dramatically. Microstructure analysis indicated that the interface transition zone (ITZ) influenced the physico-mechanical properties of concrete directly; the ITZ bondage between rubber particles or lightweight aggregate and cement matrix was very poor, which was the main reason for the decline of physico-mechanical properties; when polymer was mixed into the concrete, the ITZ structure were improved, which made the strain energy absorbing function of rubber particles can be exerted entirely, the flexibility and the strength of ITZ were boosted, thereby the physico-mechanical properties of concrete were improved.
Solid Phase Synthesis of S-Doped TiO2 Nanomaterials with Visible Light Degradation Property
Authors: Gao Ya Li , Liu Shao You , Zhang Fei , Feng Qing Ge
Published: April 2012

S-doped TiO2 nanomaterials (S-TiO2) synthesized by solid state and liquid state reaction route were used for the visible light degradation of Rhodamine B. The results show that at 20°C，pH=5, the rule of pseudo-first-order reaction and high catalytic activity were found in the visible light degradation of RhB on the S-TiO2 nanomaterials and pure TiO2. Within 80 min, the visible light degradation ratio of RhB is 97.9%, which is 6.6 times for pure TiO2. The reaction conditions such as the initial concentration, pH value, the sorts of metal ions, and consumption of catalyst affect the reaction rate constant of S-TiO2 material. The addition of Cu2+ enhances the visible light degradation rate of 28.6%, but Cr3+ decreases greatly the reaction rate of RhB.
The Effect of Layered Double Hydroxides on the Concrete Resistance of Chloride-Ion Penetration
Authors: Shui Zhong He , Ma Jun Tao , Chen Wei , Gao Xu
Published: April 2012

Layered double hydroxides (LDH) can provide the ion-exchange ability and the addition of LDH can affect the chloride-ion transfer in the concrete. The effect of LDH on the chloride-ion penetration is investigated in this study. Concrete samples contained different addition of LDH are designed in the experiment and tested by electric flux method and NT Build 443 method. The experimental results show that the addition of LDH can solidify the chloride-ion in concrete and slow down the transfer of chloride-ion, which enhanced the concrete resistance of chloride-ion penetration.
Grain Coarsening – Insights from Curvature Modeling Cyril Stanley Smith Lecture
Authors: Doherty Roger D.
Published: April 2012

Normal and abnormal grain coarsening, NGC and AGC, are briefly reviewed and discussed in the light of grain curvature and kinetic models - notably those of Mullins. The critical importance of the log-normal grain size distribution determined by Hull and the grain shapes measured by Rhines and Craig are reviewed. It is shown that in NGC, as in particle coarsening, the largest grains or particles in their respective distributions grow at the rates, larger by a factor of the ratio of the largest to average size, required to maintain the size distributions during coarsening. The particle curvature removal model for NGC anchorage, giving = 0.2 r/f, developed here, matches surprisingly well the data reviewed by Manohar et al. Finally the need is indicated for further experimental and modeling studies to test the current ideas and to answer the many remaining questions.
Grain Growth Control in Grain Boundary Engineered Microstructures
Authors: Randle Valerie , Coleman Mark
Published: April 2012

Grain boundary engineering (GBE) to promote degradation-resistant interfaces in the microstructure usually requires that the grain size remains small so that strength is not compromised. Aspects of grain size measurement and control will be reviewed and discussed for a variety of GBE materials such as copper, nickel, nickel-based alloys and austenitic stainless steels, particularly in the light of the high proportion of annealing twins that constitute the GBE microstructure.
An Investigation of the Dynamic Recrystallisation Behaviour of Magnesium AZ31 Alloy at 450°C Using Plane Strain Compression Testing as a Tool
Authors: Wynne Bradley P. , Bhattacharya R. , Davis Bruce , Rainforth W.M.
Published: April 2012

The dynamic recrystallisation (DRX) behaviour of magnesium AZ31 is investigated using a plane strain compression (PSC) testing machine at 450°C. The variables included strain rate, double hit including intermittent anneal and double hits with different strain rate at each hit. The alloy shows higher peak stress and strain with increasing strain rates. Predominant basal texture with different intensities are observed at different strain rates. The annealing treatment between double tests leads to strong basal texture. Reversal of strain rate during double hit results in similar flow curves. This shows that in AZ31 alloy, DRX mechanism is independent of the initial microstructure and only depends on the test condition viz. temperature, strain rate and total equivalent strain.
Simulation of Grain Growth under the Effect of Stress
Authors: Uyar F. , Wilson S. , Winning Myrjam , Rollett Anthony D.
Published: April 2012

Abstract.are preferentially eliminated, thus leading to interface texture development and a higher pop-ulation of low energy grain boundaries. However, when stress is introduced as an additionaldriving force, the dynamics of grain growth change. To model these eﬀects, a three dimensionalanisotropic multi-level set model was modiﬁed in order to account for the eﬀect of stress ﬁeld ongrain growth. For this mesoscale study, grain boundaries were treated as dislocation structuresand their associated net Burgers vectors were calculated using the misorientation informationand boundary inclinations. Using these net Burgers vectors and their associated densities, ad-ditional forces due to stress ﬁeld were calculated via the Peach-Koehler equation. Qualitativecomparisons of 5 parameter grain boundary character distribution will be carried out in orderto analyze the diﬀerences in texture evolution during grain growth.
Advances in Grain Growth Theory
Authors: Rios Paulo Rangel , Glicksman Martin E. , Lewis Daniel
Published: April 2012

The theoretical description of grain growth was based for many years on the so-calledspherical model. The spherical model represents a polyhedral grain with N faces and a volume, V ,by a sphere with an equal volume having the equivalent grain radius, R. That model leads to severalinteresting results concerning normal and abnormal grain growth as well as grain size distribution.Nevertheless, representation of grains by spheres entails a fundamental limitation: namely, all topo-logical information of the polyhedral grain is forsaken. The rich variety of grain shapes occurringin three-dimensional polycrystalline networks, however, makes their energetic and kinetic analysesextremely difficult. To simplify analyses of isotropic polycrystals, average N-hedra and generalizedN-hedra ANHs or GNHs .N D 3; 4; 5;1/ were created as a set of regular polyhedra, consisting ofN identical faces that act as topological proxies for analyzing irregular grains containing N mixedfaces. The adoption of ANH/GNH as representations of polyhedral grains led to further progress inour understanding of grain growth, particularly those aspects related to topological behavior. This pa-per summarizes some recent advances of representing polyhedral grains by ANHs/GNHs rather thanby spheres.
The Role of Deformation Microstructure in Recovery and Recrystallization of Heavily Strained Metals
Authors: Hansen Niels
Published: April 2012

Metals deformed to high and ultrahigh strains are characterized by a nanoscale microstructure, a large fraction of high angle boundaries and a high dislocation density. Another characteristic of such a microstructure is a large stored energy that combines elastic energy due to dislocations and boundary energy. Parameters of the deformed microstructure significantly affect annealing processes such as recovery and recrystallization. For example, the recovery rate can be significantly increased after high strain deformation and restoration may occur as either discontinuous recrystallization or structural coarsening. A characterization and analysis of deformed and annealed microstructures presented in this work covers Al, Ni, Cu and Fe heavily deformed by rolling, accumulative roll bonding (ARB), equal channel angular extrusion (ECAE) and high pressure torsion (HPT). The important effect of recovery on subsequent restoration processes is discussed along with the effect of heterogeneities both on the local scale and on the sample scale.