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• The decoupling model of three-dimensional crystal orientation is invented in this paper, which is an effective tool for crystal orientation research in the industry. • A large amount of orientation deviation data and its distribution pattern for single crystal turbine blades are presented for the first time. • The reliability analysis system for the orientation-dependent fatigue life of single-crystal blades is developed by the GRNNs-MCS method. • The fatigue lifetime reliability of single-crystal blades has been significantly improved by crystal orientation design technology. The uncertainty in the casting orientation of single-crystal aeroengine turbine blades is an intractable engineering problem, and breaking through the crystal orientation design technology is vitally important to enhance the fatigue lifetime reliability of the blade. In this paper, a three-dimensional decoupling model for casting orientation is established according to the crystallographic characteristics of single-crystal blade, and the distribution information and statistical features of the orientation deviation angle of single-crystal turbine blades are obtained for the first time according to this decoupling model. Subsequently, the orientation-dependent models and generalized regression neural networks (GRNNs) analysis system of reliability are established, and the analysis of fatigue life response for single-crystal blades in four quadrants is carried out based on the neural network analysis system. Finally, three orientation design schemes are developed, and the improvement effect of each scheme on lifetime reliability are investigated. For the secondary orientation design scheme, the lifetime reliability is improved from 62 % to more than 95 % at the design life of 15,000 cycles; For the integrated orientation design scheme, the life reliability is improved from 50 % to more than 95 % at the design life of 20,000 cycles. The results show that the orientation design can effectively improve the fatigue life reliability of the product, especially in the long-life design interval of 10,000 to 20,000 cycles. Therefore, the orientation design should be highly emphasized in the design of single-crystal turbine blades for aeroengine. [ABSTRACT FROM AUTHOR]

• Thermal fatigue behavior of Ni-based single crystal superalloy at 25–900 °C are investigated. • The cracks only initiate at the direction of 45° from [0 0 1] direction in hot corrosion environment, which is different from the multi-point initiation of cracks in air environment. • The invisibility of crack morphology in hot corrosion environment deserves to be highlighted. • The influence mechanism of hot corrosion on the thermal fatigue behavior of Ni-based single crystal superalloy is proposed. As an important failure model for single crystal materials in service, with the increasing complexity of working environments, the thermal corrosion fatigue failure needs to be studied urgently. In this study, the thermal corrosion fatigue crack initiation and propagation behaviors of an Ni-based single crystal superalloy in both air and hot corrosion environments at 25–900 °C were studied by using a designed precise thermal fatigue test device. The microstructure characteristics and crack composition were analyzed by SEM, TEM and EDS, and the internal stress and recrystallization during thermal fatigue were characterized by EBSD. Moreover, the detailed and comprehensive crack morphology was characterized with different surface treatments. The results showed that the crack morphology was invisible in the hot corrosion environment, which is worthy of being highlighted. The initiation and propagation of thermal fatigue cracks were also accelerated in the hot corrosion environment, which contributed to the sufficient thermal stress, the accelerated material degradation of the inner/outer layers in the crack region, and the rapid forward diffusion of O 2 in the inner crack layer. Finally, the influence mechanism of hot corrosion on the thermal fatigue behavior of the Ni-based single crystal superalloy is proposed. [ABSTRACT FROM AUTHOR]

The accelerated creep failure of Ni-based single crystal superalloy by hot corrosion is confirmed by creep tests at 900 °C/550 MPa–400MPa in air and salt environments. The analysis of creep curve, microstructure and fracture type shows that there are obvious differences in hot corrosion-creep behavior under high, middle and low creep stress conditions, indicating that there is the stress dependence between the influence of hot corrosion on the creep properties of the alloy. Hot corrosion accelerates creep failure of Ni-based single crystal superalloy by decreasing the deformation resistance, reducing the effective stress area, and affecting the creep fracture mode. [ABSTRACT FROM AUTHOR]

Hot corrosion behaviour of Ni-base single crystal at 900 ℃ is investigated under three different mixed salts. The result shows that hot corrosion degree in Na 2 SO 4 +NaCl+NaVO 3 is the most serious, followed by Na 2 SO 4 + NaVO 3 , and Na 2 SO 4 +NaCl is the least. The hot corrosion mechanism of superalloy in Na 2 SO 4 +NaCl+NaVO 3 salts is proposed. More importantly, the interaction of Na 2 SO 4 , NaCl and NaVO 3 is a synergistic relationship in which Na 2 SO 4 causes a basic corrosion attack, and NaCl with NaVO 3 strengthen this attack. Therefore, in hot corrosion protection, the type of corrosive salt should be reduced to avoid the synergistic effect caused by multiple salts. [Display omitted] • Hot corrosion behavior of Ni-based single crystal superalloys at 900 ℃ under three different mixed salts was investigated. • Sulfides in γ′-depleted layer are mainly affected by critical oxygen partial pressure and standard free energy of sulfide. • NaCl and NaVO 3 consume the protective oxides and prolong the time of internal sulfidation-oxidation cycle reaction. • There is a synergistic relationship between the corrosion salts of Na 2 SO 4 , NaCl and NaVO 3. [ABSTRACT FROM AUTHOR]

The twin relationships of the A–C type non-modulated martensitic variant pair in Ni 54 Mn 25 Ga 21 ferromagnetic shape memory alloy were investigated in detail through experimental observations and theoretical calculations. Variants A and C are microtwins connected by intervariant interface, while the lamellae in each variant are nanotwins separated by twin boundaries. The nanotwins with different thicknesses in each variant have two types: the major lamella and the minor lamella. The orientation relationships between the lamellae across an intervariant interface vary with the volume fraction of the minor lamella. The twin relationships between the nanotwins were identified experimentally and theoretically. Specifically, the lamellae in a variant have a {1 1 2} compound twin relationship, the major lamellae (or minor lamellae) are twin related with a twinning plane of high indices, but the major and minor lamellae across the A–C interface are not twin related. The mobility of various interfaces, such as the twin boundary in a variant and intervariant interface is discussed, based on the identified twin relationships. [ABSTRACT FROM AUTHOR]

A sodium ion conducting gel polymer electrolyte based on poly(vinylidene difluoride-co-hexafluoropropylene) porous membrane is reported, which is prepared through a simple phase separation process. It exhibits high safety, good mechanical properties and good electrochemical stability. The gel polymer electrolyte provides the sodium ionic conductivity of 0.60 mS cm − 1 at ambient temperature, while the commercial separator (Celgard 2730) offers only 0.16 mS cm − 1 . The temperature dependence of the ionic conductivity from 25 to 75 °C is consistent with an Arrhenius-behavior. The ionic transference number of sodium ion (t Na + ) in the gel polymer electrolyte is 0.30, higher than that (0.17) in the commercial separator. This provides a new direction to improve the safety of sodium ion batteries. [ABSTRACT FROM AUTHOR]

Tension–tension fatigue properties of SiC fiber reinforced Ti–6Al–4V matrix composite (SiC f /Ti–6Al–4V) at room temperature were investigated. Fatigue tests were conducted under a load-controlled mode with a stress ratio 0.1 and a frequency 10 Hz under a maximum applied stress ranging from 600 to 1200 MPa. The relationship between the applied stress and fatigue life was determined and fracture surfaces were examined to study the fatigue damage and fracture failure mechanisms using SEM. The results show that, the fatigue life of the SiC f /Ti–6Al–4V composite decreases substantially in proportion to the increase in maximum applied stress. Moreover, in the medium and high life range, the relationship between the maximum applied stress and cycles to failure in the semi-logarithmic system could be fitted as a linear equation: S max / μ = 1.381 − 0.152 × lgN f . Fractographic analysis revealed that fatigue fracture surfaces consist of a fatigued region and a fast fracture region. The fraction of the fatigued region with respect to the total fracture surface decreases with the increase of the applied maximum stresses. [ABSTRACT FROM AUTHOR]

A composite polymer membrane is prepared by coating poly(vinylidene fluoride) (PVDF) on the surface of a membrane based on methyl cellulose (MC) which is environmentally friendly and cheap. Its characteristics are investigated by scanning electron microscopy, FT-IR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The outer PVDF layers are porous which results in high electrolyte uptake and the lithium ion transference number is much larger than that of the pure MC. Moreover, the cell based on Li//LiFePO 4 delivers high discharge capacity and good rate behavior in the range of 4.2–2.5 V when the composite membrane is used as the separator and the host of a gel polymer electrolyte, lithium as the counter and reference electrode, and LiFePO 4 as cathode. The obtained results suggest that this unique composite membrane shows great attraction in the lithium ion batteries with high safety and low cost. [ABSTRACT FROM AUTHOR]

7050 Al alloy was successfully processed by equal-channel angular pressing (ECAP) at room temperature (RT). The effect of ECAP on the subsequent aging precipitation behavior was investigated by using transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results reveal that the kinds, spatial distribution and sizes of precipitates in the unECAPed and the ECAPed samples are different. ECAP accelerates the process of aging precipitation and results in the broadening of precipitate size distribution. ECAP can produce not only deformation heat but also internal defects such as excess vacancies and high density of dislocations when the sample passes through the main deformation zone. Deformation heat can lead to pre-precipitation, forming a small amount of GPII zones during ECAP processing. Strain-induced excess vacancies make solute segregation along dislocations by the mechanism of nonequilibrium segregation. High density dislocations mainly accelerate the process of aging precipitation. Besides, dislocations also induce the competition between homogeneous precipitation and heterogeneous precipitation on dislocations due to the flow of solutes and vacancies towards dislocations. [ABSTRACT FROM AUTHOR]

In the magnetic field measurement of accelerator magnets, the precise positioning of the magnetic field measurement system and the magnet is a basic and very important part. By analyzing the mechanical structure and working principle of Hall magnetic field measurement system, a novel positioning method is proposed in this research for the high-precision and fast positioning of magnet and Hall magnetic field measurement system. By measuring the geometric elements of the magnetic field measurement system and the calibration benchmark of the magnet, the geometric relationship between the magnetic field measurement system and the magnet is established, so as to quickly locate the magnet to the position and attitude required by the magnetic field measurement. The mechanical structure of the Hall probe of the magnetic field measurement system is optimized. Two special ceramic reflectors are installed on the vertical and horizontal axes corresponding to the center of the Hall sensor, and the two ceramic reflectors installed on the Hall probe is monitored with a laser tracker. In this way the Hall sensor can be intuitively positioned at the geometric center of the magnet with an accuracy better than 0.05 mm. In the measurement process, the magnetic field measurement trajectory of Hall sensor in the magnet can also be detected by monitoring the coordinates of ceramic reflector in real time. The practical application in Space Environment Simulation and Research Infrastructure (SESRI) magnet magnetic field measurement show that, compared with the traditional positioning method, the proposed positioning method not only improves the repeatability of Hall magnetic field measurement integral field by nearly 10 times, but also improves the positioning efficiency of magnetic field measurement. These results have verified the practicability and effectiveness of the proposed positioning method. [ABSTRACT FROM AUTHOR]

Abstract: The interfacial reactions of B4C-coated and C-coated SiC fiber reinforced Ti–43Al–9V composites were investigated by scanning electron microscope and transmission electron microscope. The detailed microstructures as well as the chemical composition throughout the reaction zone were identified. For SiCf/B4C/TiAl composite, the reaction zone from B4C coating to TiAl matrix is composed of 4 layers, namely, a carbon-rich layer, a mixed layer of TiB2 + amorphous carbon, a TiC layer and a mixed layer of TiB + Ti2AlC. For SiCf/C/TiAl composite, the reaction zone from C coating to TiAl matrix is composed of 3 layers, namely, a fine-grained TiC layer, a coarse-grained TiC layer and a thick Ti2AlC layer. For both kinds of composites, the reaction mechanisms of the interfacial reactions were analyzed, and the corresponding reaction kinetics were calculated. The activation energies of interfacial reaction in SiCf/B4C/TiAl composite and SiCf/B4C/TiAl composite are 308.1 kJ/mol and 230.7 kJ/mol, respectively. [Copyright &y& Elsevier]

Highlights: [•] The substructures in rotation-twinned T (Al20Cu2Mn3) particles were investigated. [•] A flattened hexagonal structural subunit with 20 atomic columns was proposed. [•] The stacking mode of these subunits at APB and TB were revealed. [•] The transition structures at twin domain junctions were unraveled. [ABSTRACT FROM AUTHOR]

Abstract: The deformation and fracture process in Al–Cu–Mg alloy were investigated by using the in situ straining transmission electron microscopy (TEM) method. Some major aspects of the fracture process, including dislocation emission and migration, thinning of dislocation free zone (DFZ), crack propagation (both in continuous and discontinuous manners) and slipping/twinning deformation, can be observed. The rod-like T dispersoids, which may increase the microcrack initiation sensitivity, also can effectively prevent the fast and continuous propagation of the crack. DFZ ahead of crack tip can be thinned in a mixed mode characterized by tearing and shear deformation, while nanovoids, which are typical characteristics in DFZ during discontinuous crack propagation, may originate from the enrichment of defects such as dislocations and vacancies. Deformation twinning at crack tip can slow down crack propagation and change crack propagation path, thus may be beneficial to the fracture toughness of the alloy. [Copyright &y& Elsevier]

Abstract: The microstructural characteristics in the matrix of SiCf/Ti–6Al–4V composites prepared by consolidation of the matrix-coated fibers in the high-temperature β single-phase field were investigated using both experimental and modelling methods. Some of the critical microstructure features, like volume fraction of component phases, composition of matrix alloys and matrix morphology were systematically studied, providing valuable insight into the microstructural characteristics in the matrix of SiCf/Ti–6Al–4V composites. In order to assist in understanding the grain growth occurred in the matrix during consolidation processing, a theoretical model was developed. Excellent agreement between theoretical and experimental results was achieved. [Copyright &y& Elsevier]

Abstract: The microstructures of titanium aluminides matrix based on TiAl both in matrix-coated fiber and in fiber-reinforced composites were studied in this paper. The titanium aluminides matrix was examined by means of scanning electron microscope, X-ray diffractometer and transmission electron microscope. The results show that, in sputtering process, amorphous phase forms firstly, and α-Ti(Al) + TiAl3 form later. Subsequently, during hot isostatic pressing, the amorphous phase, α-Ti(Al) and TiAl3 in the matrix-coated fibers transform into γ-TiAl and α2-Ti3Al in the composites. [Copyright &y& Elsevier]

Abstract: Ti-43Al-9V/Ti-6Al-4V joints were fabricated by vacuum hot pressing under 920 °C/45 MPa/2 h. After fabrication the joints were thermally exposed in vacuum at 920 °C for 5 h and 17 h, and at 1100 °C for 1 h. The interfaces of both the as-prepared and the thermally exposed joints were analyzed by means of optical microscope, scanning electron microscope, electron backscatter diffraction system and energy dispersive spectrometer. The results indicate that sound joints can be achieved under 920 °C/45 MPa/2 h, and the interfacial phase sequence of the as-prepared joints was identified as Ti-43Al-9V/γ(TiAl)/B2 (the ordered form of β-Ti phase)/α 2(Ti3Al)/α(Ti)/Ti-6Al-4V. The thickness of the interfacial zone increased with the duration of thermal exposure at 920 °C. Furthermore, the interfacial zone thickened rapidly when the joints were thermally exposed at temperature above the phase transformation point (α-Ti → β-Ti) of Ti-6Al-4V. In this paper, the interface growth way was also discussed based on the locations of the refractory phase YAl2 and microvoids. The analysis of the thermally exposed joints confirmed the correctness of the interface growth way. Moreover, elemental diffusion mechanism was discussed in this paper. [Copyright &y& Elsevier]

Abstract: SiC fiber reinforced titanium aluminides matrix composites based on TiAl (Ti–43Al–9V) were fabricated by means of matrix-coated fiber method through hot isostatic pressing. Microstructure of the SiCf/Ti–43Al–9V interfacial reaction zone in the composites was identified by means of scanning electron microscopy and transmission electron microscopy. The results show that three types of reaction products TiC, Ti2AlC and (Ti,V)5(Si,Al)3 are formed between carbon coating of SiC fiber and the matrix. TiC is adjacent to the carbon coating of the SiC fiber, and (Ti,V)5(Si,Al)3 is close to the matrix. Ti2AlC layer exists as columnar grains between TiC and (Ti,V)5(Si,Al)3 layers. The TiC layer can be divided into fine-grained layer and coarse-grained layer. The fine-grained TiC layer contains amorphous carbon, and the coarse-grained TiC layer is separated from fine-grained TiC by an intermittent carbon layer. In addition, TiC particles are also formed between carbon coating and SiC. Furthermore, the formation mechanism of the interfacial reaction products was discussed. [Copyright &y& Elsevier]

An analytical model of the push-out test was developed to predict the interfacial fracture toughness of fiber-reinforced matrix composites. Elastic deformation, thermal residual stress, Poisson effect, and energy dissipation due to interfacial friction are all accounted for in the model based on a fracture mechanics approach and a general solution was derived from the analysis. In addition, finite element analysis was performed to validate the analyti-cal model. The results show that the predictions from the analytical model are in good agreement with the finite element results and experimental data on SiC-reinforced Timet-al834 composites. The effects of residual stress, the friction stress, and the debonding crack length on the interfacial fracture toughness were discussed for a better understanding of the interfacial phenomena in push-out test. The analytical model could be applied to other composite systems as well. [ABSTRACT FROM AUTHOR]

Monolithic Al 2 O 3 and Al 2 O 3 -graphene-SiC hybrid composites were prepared by spark plasma sintering (SPS) under vacuum atmosphere. The results show that the hybrid composites were almost completely dense (>97%). SiC content has a significant effect on the microstructure of the composites. With the increase of SiC content, the average grain size of alumina decreased gradually. The addition of SiC to alumina changed fracture mode from inter-granular fracture to mixed fracture mode of inter-granular fracture and trans -granular fracture. The Al 2 O 3 -0.4 wt%graphene-5 wt% SiC hybrid composite has the highest bending strength and hardness, which were 57% and 19.22% higher than those of the monolithic alumina, respectively. The room temperature (RT) thermal conductivity of the monolithic Al 2 O 3 (25.5 W/m·K) was the highest. The thermal conductivity and thermal diffusivity coefficient of the composites decreased with the increase in temperature, while the specific heat of monolithic alumina and composites increased with the increase in temperature and additives. These properties were related to the microstructure of materials and the possible transport mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Abstract: The axisymmetric cell model consisting of interface, matrix and reinforced particle is used to simulate the tensile test of particle reinforced metal matrix composite for predicting the micro stress/strain field and macro tensile stress/strain curve. In simulation of the tensile test, the cohesive element model is selected to model interfacial crack growth. It mainly analyzed the effects of interfacial properties, reinforcement volume fractions and aspect ratios on the stress–strain states of particle reinforced metal matrix composite. The results show that the peak micro stress and plastic strain occur at the interface in which it is a certain angle from the tensile stress direction; with the interfacial fracture toughness and reinforcement volume fraction increasing, the flow stress increases firstly and then decreases. The tensile stress–strain properties of SiC/6064Al are good when the interfacial fracture toughness is equal to 60J/m and the reinforcement fraction volume is equal to 20%. Smaller reinforcement aspect ratio leads to smaller micro stress in composites. [Copyright &y& Elsevier]

Abstract: Effect of interfacial shear strength on longitudinal tensile properties for SiCf/Ti–6Al–4V composites is investigated by Monte Carlo finite element method. A two-parameter Weibull function is employed to describe random distribution of fiber strength. Fiber breakage, matrix cracking and interfacial debonding are simulated by killing the element when stress applied to element exceeds corresponding strength and releasing coupled nodes when shear stress exceeds shear strength at interfaces. The results show that tensile strength of SiCf/Ti–6Al–4V composites keeps unchanged for various interfacial shear strengths, but low interfacial shear strength is advantageous to reduce catastrophic failure. Moreover, with low interfacial shear strength, fiber breakage in the composites is more inclined to be non-coplanar. In addition, tensile strength obtained from finite element method is compared with those predicted by global load-sharing model (GLS), local load-sharing model (LLS) and conventional rule of mixtures (ROM) and is identical with that obtained from LLS. [Copyright &y& Elsevier]

Abstract: The characteristic of Raman scattering spectra of a carbon coating, which was modified by radio frequency argon plasma, has been investigated. The argon ion bombardment causes changes in the microstructure and amount of stress in the coating. Raman scattering spectra are discussed in terms of intensity, bandwidth and wavenumber. The evolvement of Raman spectra shows the following behavior with increasing bombardment time: the intensity changes of the disordered D band, amorphous band and graphite G band could be separated into several stages; low-energy argon ion bombardment over a short period can reduce the number of defects in the carbon coating, while a larger bombardment period can increase the number of defects; the widths of the D and G bands both increase, while that of the band decreases; the wavenumbers of all the three bands fluctuate according to the changes in electronic configuration and amount of stress in the carbon coating. [Copyright &y& Elsevier]

Abstract: The high angle annular dark field scanning transmission electron microscopy (STEM-HAADF) tomography technique was applied to understand the three dimensional (3D) morphology and distribution characteristic of grain boundary precipitate (GBP) in peak-aged Al–Cu–Mg alloy. The results indicate that GBPs show both spherical and lenticular shapes and triangularly distribute along grain boundary (GB). Based on 3D observations from various directions, the values of GBP relevant parameters such as GBP size, center to center distance, number of GBPs per unit GB area and area fraction of GB covered by GBPs are further determined. The 3D method for GBP relevant parameter determination seems an effective way to avoid misunderstandings in the conventional two dimensional (2D) methods induced by GBP overlapping and projection effect as well as curved GB surface. [Copyright &y& Elsevier]

Abstract: The heterogeneous precipitation of the S (Al2CuMg) phase along dislocations is investigated using high-resolution transmission electron microscopy various configurations of the S precipitate group form according to the initial dislocation morphology and no more than two S variants coexist along a single dislocation line. The most favorable combination of two S variants is observed to be variants 1 and 4 (or variants 2 and 3), and the variant selection criterion for S precipitate with the classic orientation relationship is proved to be that the dislocation line direction lies in the habit plane of the precipitate. The contribution of S precipitate groups to strengthening is evaluated by comparing the difference in total system energy increment induced by precipitate loop and the equivalent number of Guinier–Preston–Bagaryatsky zones and discrete S particles during plastic deformation. The results show that the average size of the precipitate loops as well as other kinds of precipitate groups has an important influence on the final strengthening effect. By keeping the precipitate groups below a critical size and increasing their density, the strength and thermal stability of the alloy are expected to be improved. [Copyright &y& Elsevier]

Abstract: Thermodynamics, kinetics and structural relaxation of Ce-based bulk metallic glass-forming liquid were investigated in the glass transition region by calorimetric measurements. The differences in thermodynamic functions were calculated between the supercooled liquid and crystalline state of the Ce-based alloys. Structural relaxation was studied by heating rate dependence of glass transition temperature. In terms of fragility parameter m, the Ce-based alloys were stronger liquid than other metallic glass-forming liquids. The correlation of the excellent glass-forming ability of Ce-based alloys with the thermodynamic property (Gibbs free energy) and the kinetic property (m) was discussed. The structural relaxation from glass state to the equilibrium supercooled state was well described by Tool–Narayanaswamy–Moynihan (TNM) model using the parameters derived from the calorimetric measurements. [Copyright &y& Elsevier]

Abstract: A two-dimensional finite element model is created to investigate the effects of temperature and residual stress on transverse tensile behaviors for SiC/Ti–6Al–4V composites with square fiber array. The spring elements are used to simulate interfacial debonding when interfacial radial stress, composed of residual radial stress and radial stress introduced by the applied transverse tensile stress, reaches interfacial bonding strength. The results indicate that temperature has an obvious influence on the collapse stress of composites due to the change of matrix strength with temperature. And the higher temperature is, the lower collapse stress is. Residual radial stress can increase the applied stress required to cause interfacial debonding, but has a little influence on the collapse stress of the composites. [Copyright &y& Elsevier]

Abstract: The plasticity of AZ31 and ZK60 magnesium alloys was studied by means of hot compression deformation tests on Gleeble 1500D machines at different temperatures and strain rates. The results indicate that the thermal simulation curves of AZ31 and ZK60 have different forms under the same deformation condition. The general curves of AZ31 have the character of dynamic recrystallization that the flow stress increases to a peak and then decreases to a steady state. Most deformation curves of ZK60 have the obvious character that around 0.2 in strain the stress reaches the peak and declines rapidly to the lowest, while the other curves have the character of dynamic recrystallization. From the analysis, a deformation temperature should reasonably be selected from 250°C to 400°C for AZ31, while it was concluded to be 200°C or 400°C for ZK60. [Copyright &y& Elsevier]

Abstract: A three-dimension atomic-scale model with kinetic Monte Carlo method was used to simulate the evolution of microstructure, surface morphology and internal defects of {111}- and {100}-oriented planes of SiC film prepared by chemical vapor deposition, and the growth rate and growth velocity ratio of the two orientations were analyzed. Additionally, a two-dimension grain-scale model with Potts Monte Carlo method was used to simulate the process of competitive growth on the two orientations. The effect of different growth velocity ratio and nuclear density on SiC film morphology was discussed. Furthermore, the reason why the preferred orientations were {111} and {110} is analyzed by combining the above two scale models. It is proved that the morphology and preferred orientation of the film, simulated under actual experimental conditions, are consistent with those obtained by actual experiment. [Copyright &y& Elsevier]

Abstract: An improved interphase layer model, which combines the interphase layer model and the spring layer model, is presented to describe the interphase of composites. The finite element model consists of the fiber, the matrix, the interphase and the spring element. The finite element model is used to model the push-out test and evaluate interface properties of composites. The results show that the interfacial shear strength of SiC/Timetal-834 is about 500 MPa. Moreover, the effects of the interphase thickness and interfacial shear strength on the peak load of the push-out test are analyzed in detail. Evaluation of interfacial properties in SiC fiber reinforced titanium matrix composites using an improved finite element model [Copyright &y& Elsevier]

Abstract: Radio-frequency magnetron sputtering technique is used to deposit Ba0.65Sr0.35TiO3 (BST) thin films on fused quartz substrates. In order to prepare the high-quality BST thin films, the crystallization and microstructure of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). More intense characteristic diffraction peaks and better crystallization can be observed in BST thin films deposited at 600°C and subsequently annealed at 700°C. The refractive index of the films is determined from the measured transmission spectra. The dependences of the refractive index on the deposition parameters of BST thin films are different. The refractive index of the films increases with the substrate temperature. At lower sputtering pressure, the refractive index increases from 1.797 to 2.197 with pressure increase. However, when the pressure increases up to 3.9Pa, the refractive index reduces to 1.86. The oxygen to argon ratio also plays an important effect on the refractive index of the films. It has been found that the refractive index increases with increase in the ratio of oxygen to argon. The refractive index of BST thin films is strongly dependent on the annealing temperature, which also increases as the annealing temperature ascends. In a word, the refractive index of BST thin films is finally affected by the films’ microstructure and texture. [Copyright &y& Elsevier]

Abstract: SiC fiber reinforced copper matrix composites were prepared by foil-fiber-foil method (FFF) and, fiber-coating method (MCF) with and without a Ti6Al4V interlayer, respectively. The copper coating was prepared by different electroplating processes and the Ti6Al4V interlayer by magnetron sputtering. The results show that the tensile strengths of specimens without Ti6Al4V interlayer are nearly identical and poor, between 250 and 290MPa, while the ones of specimen with Ti6Al4V interlayer can be greatly improved, over 500MPa. This great increase attributes to the improvement of the SiC/Cu interfacial bonding strength because the interfacial reactions occur at Cu/Ti6Al4V interface and Ti6Al4V/SiC interface. Additionally, there are generally many micropores produced by hydrogen and oxygen in the electroplated coating, which would influence the density of the matrix. Therefore, the densification of the matrix was worth investigating since it would influence the thermal and electrical conductivity of the composite, though it has only a little contribution to the tensile strength. Experiments indicate that proper heat-treatment before hot pressing could improve the densification of the matrix. [Copyright &y& Elsevier]

Abstract: Ti6Al4V/TA1 diffusion couples were fabricated and then heat-treated in vacuum under different conditions. The metallographic structure, morphologies and the composition distribution in diffusion bonding zone were investigated by means of OPM, SEM and EDS. The results indicate that the diffusion couples are bonded well; the alloying elements Al and V diffuse from Ti6Al4V to TA1, and Ti atoms diffuse in the opposite direction. The transition zone of the alloying elements obeys a rule of parabolic rate. At the same time, based on Koher''s ternary solution model and Miedema''s model for calculating the thermodynamical interaction coefficients, the theoretical diffusion profiles of Ti and alloying elements are obtained according to the inter-diffusion coefficients of the alloying elements and the numerical solution of the phenomenological equation. Moreover, the calculated values are well fitted to the experimental data. So the distribution of the diffusion atoms can be predicted at the diffusion bonding interface. [Copyright &y& Elsevier]

Abstract: Laser spray cladding in N2-rich atmosphere is a competitive technique for manufacture of porous NiTi shape memory alloy (SMA) and TiN surface film. In order to gain expected porous coating and porosity size, TiH2 powder was considered to be used as porosity initiating agent, and nitrogen was used for shielding and active nitriding gas. A 2 kW continuous wave Nd:YAG laser equipped with a 3-way coaxial nozzle was used for laser spraying. NiTi alloy powder and TiH2 powder were used as additive materials. The mixed powder of NiTi and TiH2 was conveyed by a powder feeder, congregated at the laser interacting zone and sprayed onto the substrate with molten droplets. In order to improve the corrosion resistance of the surface of coating layer, a gas nitriding process is facilitated simultaneously during the laser spraying and cladding process in nitrogen-rich atmosphere. A gradient porous coating of NiTi alloy had been manufactured by laser spraying. The investigation shows that there are pores with size of 100–200 μm near the surface. XRD analysis shows that the coating consists of intermetallic compounds NiTi, NiTi2 and nitrides TiN, Ti2N. Corrosion test was carried out in Hank''s balanced salt solution (H9269) by potentiostat/galvanostat model 273A. The polarization curves of the test result demonstrates the porous coating with TiN presents better corrosion resistance than NiTi substrate. [Copyright &y& Elsevier]

The consolidation process of composites, the specimen preparation process and the push-out test were simulated by the finite element method in this paper. A special subroutine was introduced while modeling the push-out test in order to control the interfacial failure. The results show that the shear strength evaluated from the push-out test is only a reference value. In addition, interfacial frictional shear stresses evaluated from the push-out test are reliable and play a key role in the mechanical performance of composites. [Copyright &y& Elsevier]

Abstract: This work reports a ceria solid and Pd/ceria catalyst prepared through a surfactant-templated synthesis route used for simultaneous abasement of NO and CO emissions. The surface features, textural properties and crystalline structure of ceria and Pd/ceria catalyst were studied by means of thermogravimetric analysis (TGA), N2 physisorption isotherms and in situ Fourier transform infrared (FT-IR) spectroscopy, high resolution electron transmission microscopy (TEM) and X-ray diffraction (XRD) techniques. In the calcination procedure, part of the adsorbed water on the surface of the solid was derived into unidentate and bidentate hydroxyls associated with surface cationic ions of ceria. The surfactant cations were strongly interacted with the solid during the preparation, which induces defects formation in the crystalline structure of the annealed ceria. The retained surfactant in the solid could be combusted to yield CO2, water and organic molecules with a small amount of coke-like deposits. The resultant ceria showed mesoporous texture and cubic phase containing lattice defects in the crystalline structure. The Pd/CeO2 catalyst was very active for NO reduction via CO with a high selectivity to N2. A 100% NO conversion with a selectivity to 100% N2 was achieved over the Pd/ceria catalyst at a reaction temperature of 300°C. The catalytic activity and selectivity of this catalyst are much superior to the catalysts of Pt or Rh supported on TiO2, Al2O3, TiO2–Al2O3 and ZrO2–Al2O3 prepared by a sol–gel method. A possible reaction mechanism of NO reduction by CO over the Pd/CeO2 catalyst was discussed. [Copyright &y& Elsevier]

The interfacial reaction zone of SCS-6 SiC/Ti2AlNb composites consists of two TiC layers with fine and large grains, respectively, and a layer of Ti3Si separating the large grained TiC layer with matrix. A discontinuous layer of Ti5Si3 was identified between the two TiC layers. Some Ti3AlC particles distribute within the Ti2AlNb matrix in thermally exposed composites. The formation mechanism of the reaction products was discussed. [Copyright &y& Elsevier]

Most laser clad surface layers on aluminium alloys consist of a hard carbide phase and an aluminium alloy matrix phase. The distribution of the carbide phase and the strength of the matrix phase are not always satisfactory. The paper describes a method to fabricate a metal matrix composite layer on Al 6061 by adopting the laser induced reaction synthesis technique. Powder of pure titanium, pure carbon, pure tungsten or tungsten carbide are mixed at various proportions and then pasted on an Al 6061 surface. Laser cladding with Ni–Al powders delivered by a coaxial nozzle onto the above pasted surface using a 2 kW Nd:YAG laser was carried out. During laser cladding, exothermic reactions of Ti–C, W–C and Ni–Al expedite the melting and alloying of the coatings. X-Ray diffraction and scanning electronic microscopy results show that TiC and WC phases were in situ synthesized during the cladding process and they appear in a Ni–Al matrix. The microstructure, hardness and pin-on-disk wear of the coatings are investigated and discussed. [Copyright &y& Elsevier]

The receptor activator of nuclear factor kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG), are important bone metabolism molecules, which directly control osteoclastogenesis. Periodontal ligament (PDL) cells play a vital role in maintaining the homeostasis of periodontal tissues, releasing cytokines to affect bone metabolism. The purpose of this study was to investigate the expression of OPG and RANKL in cultured human periodontal ligament cells (hPDLCs) derived from permanent teeth and the expression change after stimulation by 1α,25-dihydroxyvitamin D3 (1α,25(OH)2vitD3), a kind of bone resorption promoter. HPDLCs were cultured in the presence or absence of 10−8 M 1α,25(OH)2vitD3 in vitro. The expression of mRNA for OPG and RANKL in hPDLCs during 6 days’ culture was examined using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). The level of secreted OPG protein in the culture medium during 6 days’ culture was detected by enzyme-linked immunoabsorbent assay (ELISA). The result showed that OPG and RANKL were expressed by hPDLCs. OPG expression was down-regulated by 10−8 M 1α,25(OH)2vitD3 in a time-dependent manner, while RANKL mRNA was up-regulated. The ratio of OPG/RANKL was decreased. In conclusion, our findings suggest that hPDLCs may regulate the alveolar bone metabolism through the OPG/RANKL system. [Copyright &y& Elsevier]

Structure activity relationship (SAR) has been playing a more and more important role in medicine design. We presented here a preliminary investigation on the relationship between the structure of different phosphonates and the preparation of corresponding complexes labeled with 153Sm. By study of seven complexes, it was found that the number of -PO3H2 groups, the stereoscopic distance between them and the existence of strong electron-providing groups in the ligand molecule affected the preparation of 153Sm-complex. [ABSTRACT FROM AUTHOR]

Proposes a stochastic averaging method to predict approximately the response of multi-degree-of-freedom quasi-nonintegrable-Hamiltonian systems. Constructibility of a one-dimensional approximate Fokker-Planck-Komogorov equation for the transition probability density of the Hamiltonian; Comparison with an equivalent nonlinear system method.

Shows that the structure and property of the exact stationary solution of a stochastically excited and dissipated n-degree-of-freedom Hamiltonian system depend upon the integrability and resonant property of the Hamiltonian system modified by the Wong-Zakai correct terms. Reduced Fokker-Planck-Kolmogorov equation for Hamiltonian systems.

Although deformation processes in single-phase nano-polycrystalline alloys at different temperatures are well described, the deformation mechanism in two-phase nano-polycrystalline alloys at different temperatures is still unclear. Here, the deformation behaviour of the two-phase TiAl+Ti 3 Al nano-polycrystalline alloys is investigated at different temperatures by molecular dynamic simulation. For a comprehensive understanding of the processes, mechanical properties of the single-phase TiAl and Ti 3 Al nano-polycrystalline alloys are explored as well. The results of numerical simulations indicate that temperature has a strong influence on the deformation mechanism of the alloys. When temperature is below 800 K, the critical grain size (~8.3 nm) becomes a dominant factor controlling the deformation process in the single-phase TiAl. In the two-phase TiAl+Ti 3 Al nano-polycrystalline alloys, the motion of dislocations in the TiAl phase with the grain size smaller than the critical size dominates the deformation process. On the other hand, no obvious phenomena linked with the critical size occur in the Ti 3 Al phase. Once the strain exceeds 18.0%, the dislocation emission is observed in the Ti 3 Al grains. At high temperatures (≥800 K), in the two-phase nano-polycrystalline alloy, the deformation mechanism changes from the plastic deformation to the boundary slip and recrystallization. Unlabelled Image • Deformation behaviour of two-phase TiAl+Ti 3 Al nanopolycrystalline alloys is described using molecular dynamic simulations. • The displacement of dislocations in TiAl grains smaller than ~ 8.3 nm dominates the deformation processes below 800 K. • The deformation mechanism changes from the plastic deformation (< 800 K) to the boundary slip and recrystallization at 800 K. [ABSTRACT FROM AUTHOR]

The Heavy Ion Medical Machine (HIMM) is China's first heavy ion accelerator specifically for cancer treatment. To minimize the uncontrollable beam orbit and beam loss, the HIMM accelerator magnets require the condition of stringent field uniformity. The best way to examine whether the actual field is consistent with the design or not is to perform an accurate and reliable measurement on the magnetic field, which requires the accurate alignment of the magnetic field measurement system as the prerequisite. This research adopts the alignment of a Hall probe mapping system, long coil integral system and harmonic coils system. Firstly, the preliminary test launched at the HIMM is described. Then, a new alignment method is developed to improve the positioning accuracy and performance of magnetic field measurement system. The experimental results show that the alignment accuracy (maximum deviations) of all components of each magnetic field measurement system is higher than 0.1 mm, which satisfies the requirements for the positioning accuracy of high-precision magnetic field measurement system. [ABSTRACT FROM AUTHOR]

SiC fiber-reinforced Ti-21Al-29Nb matrix composites with either C and C/Mo duplex coatings were prepared by the foil-fiber-foil (FFF) method, in order to comparatively study the effects of C/Mo duplex coatings on the interface and mechanical properties of the composites. The longitudinal tensile strength of the as-prepared composites was measured at room temperature. In order to study the interfacial thermal stability and microstructure evolution characteristics of the composites, vacuum thermal exposures of the composites were carried out at 800, 900 or 940 °C for different durations. The interfacial microstructures of the as-prepared and thermally-exposed composites were investigated by means of scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The results indicate that the C/Mo duplex coating does not only have better thermal stability, but also can further slow down the interfacial reaction of the composites in comparison with the C single coating. The diffusion of a small amount of Mo atoms made the matrix close to the interface have better plasticity, so the tensile strength of the composites can be further improved. The interface of the composite with the C/Mo duplex coating was nearly intact after the 940 °C/50 h thermal exposure while that of the composite with the C single coating was not intact, as the C/Mo duplex coating can better relax the thermal residual stresses than the C single coating. [ABSTRACT FROM AUTHOR]

Fatigue crack propagation behaviors of the as-prepared and thermally exposed (700 °C/196 h, 800 °C/196 h) C/Mo double-coated SiC fiber-reinforced Ti6Al4V composites were investigated. The results show that interfacial microstructure evolution has significant effect on fatigue crack propagation behaviors. As for the as-prepared and 700 °C/196-h thermally exposed composites, fiber-bridging accompanied with interfacial debonding can decrease the crack growth rate significantly, while the latter one has lower crack growth rate at the early fatigue crack propagation stage, as the diffusion of Mo atoms makes the matrix close to the interface have more ductileβ-Ti. However, fiber-bridging phenomena disappeared with the altered interface in the composite after 800 °C/196-h thermal exposure. Fatigue fracture analysis further reveals that multistep deflections of crack in interface contribute to the improvement of interface toughness. The formation of ductileβ-Ti layer resulted from the diffusion of Mo atoms is beneficial to blunt the crack tip. [ABSTRACT FROM AUTHOR]

The model based on fracture mechanics is developed to evaluate the fracture toughness Γ of the fiber/matrix interface in titanium alloys reinforced by SiC monofilaments. Theoretical model for single fiber push-out testing is obtained by shear-lag method. The influences of several key factors (such as the applied stress needed for crack advance, crack length, and interfacial frictional shear stress) are discussed. Using the model, the interfacial toughness of typical composites including Sigma1240/Ti-6-4, SCS-6/Ti-6-4, SCS-6/Timetal 834, SCS-6/Timetal 21s, SCS-6/Ti-24-11 and SCS-6/Ti-15-3 are successfully predicted compared with previous results of these composites. It is verified that the model can reliably predict the interfacial toughness of the titanium matrix composites as well as other metal matrix composites, due to interfacial debonding usually occurs at the bottom face of the samples in such composites. [ABSTRACT FROM AUTHOR]

Based on shear-lag method, two models for a single fiber push-out test are proposed to evaluate the interfacial shear strength of SiC fiber-reinforced titanium-matrix composites (TMCs). In the models, the effects of specimen parameters (such as specimen thickness and fiber volume fraction) on the interfacial shear strength are considered. The interfacial shear strengths of SCS-6/Ti-24-11 and SCS-6/Ti-15-3 composites are predicted using the model. The predicted results indicate that the models can be reliably used to predict interfacial shear stress of TMCs. [ABSTRACT FROM AUTHOR]

Experimental analysis of single-fiber push-out for SiC fiber-reinforced titanium matrix composites (TMCs) is complicated by the incorporation of large thermal residual stresses, strong chemical bond of the fiber/matrix interface and matrix plastic deformation. This paper summarizes the development of push-out test and the characteristics of push-out test for TMCs such as crack initiating at the bottom face and theoretical analysis of the test. Moreover, it deeply analyzes the progresses of interfacial shear strength and fracture toughness, and work focus is pointed out in future. [ABSTRACT FROM AUTHOR]

A dense instead of porous gel polymer electrolyte for lithium ion batteries is reported for the first time. Its host is a renewable and environment friendly polymer, hydroxyethyl cellulose (HEC). The preparation of HEC membrane is very simple. The membrane is stable up to 280 °C, much higher than the melting points of those commercial separators based on polyolefin. The evaporation temperature of the organic electrolyte in the prepared gel polymer electrolytes is up to 75 °C. In addition, the gel polymer electrolyte shows good electrochemical performance including high ionic conductivity at room temperature, and a high lithium ion transference number. When tested as separator and electrolyte, a LiFePO 4 positive electrode displays satisfactory electrochemical properties including high discharge capacity and stable cycling. These results indicate a very promising direction for a low cost and renewable gel polymer electrolyte for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Pt group metals display lower HER activity in alkaline solution than in acidic solution, because they are inefficient in the water dissociation step (Volmer step). Compared with Pt, the activity difference of Rh in alkaline and acidic media is much smaller. Meanwhile, Ni(OH) 2 is proved to be an effective catalyst for water dissociation. Therefore, Rh–Ni(OH) 2 /C nanocomposites with different Rh:Ni(OH) 2 ratios were synthesized by a co-deposition/partial reduction method, and their microstructures as well as electrocatalytic properties were studied. The results show that Rh and Ni(OH) 2 display synergistic effect in Rh–Ni(OH) 2 /C nanocomposites. The Rh–Ni(OH) 2 /C nanocomposite with a molar ratio of Rh to Ni(OH) 2 of 1:1 exhibits the highest activity. It shows an overpotential of 36 mV at 10 mA cm−2 and a Tafel slope of 32 mV dec−1 for HER in alkaline media, which is superior to commercial Pt/C. In addition, the Rh–Ni(OH) 2 /C (1:1) nanocomposite shows excellent durability in alkaline media as well. • A set of Rh–Ni(OH) 2 /C nanocomposite catalysts were synthesized by a co-deposition/partial reduction method. • The degree of dispersion of Rh and Ni(OH) 2 nanoparticles on carbon spheres was influenced by Ni(OH) 2 content. • Rh and Ni(OH) 2 display synergistic effect in Rh–Ni(OH) 2 /C nanocomposites in alkaline solution. • The Rh–Ni(OH) 2 /C nanocomposite with a molar ratio of Rh to Ni(OH) 2 of 1:1 exhibits superior HER catalytic activity. • The combined use of Ni(OH) 2 and Rh provides a way of designing low-cost and high efficient HER electrocatalysts. [ABSTRACT FROM AUTHOR]