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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: 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]

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]

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]

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]

• The thermal fatigue failure mechanism of Ni-based single crystal superalloys with hole structure has been revealed. • The strain–stress constitutive equation under transient thermal shock based on the crystallographic theory was established. • The thermal stress location and evolution around the hole at different temperatures was obtained by FEM. • A thermal fatigue crack initiation life model considering transient thermal stress and cyclic oxidation has been proposed. • There is good consistency between the experimental results and the simulation results. The transient thermal fatigue behavior of Ni-based single crystal superalloys with film cooling holes under different peak temperatures (25 °C → 980 °C and 25 °C → 1050 °C) were investigated by a combination of test and finite element simulation. The initiation position and propagation direction of thermal fatigue cracks in both single hole and multi-hole specimens exhibit the angles of ± 45° with respect to the horizontal direction at the four corners of the holes. Octahedral slip failure mainly occurred at the crack initiation location and crack tip. The cyclic oxidation around the film cooling hole promotes the initiation and propagation of cracks. Based on the crystallographic theory, the strain–stress constitutive equation of the Ni-based single crystal superalloy under transient thermal shock was established. The location and evolution of thermal stress around the hole at different temperatures were obtained by finite element calculation. The kinetic behavior of cyclic oxidation has been quantitatively characterized. A thermal fatigue crack initiation life model considering heating temperature, transient thermal stress, and cyclic oxidation has been established. The simulation results are in good agreement with the tests. [ABSTRACT FROM AUTHOR]

Abstract: The relaxation behaviors of Ce65Al10Cu20Co5 and Zr46.75Ti8.25Cu7.5Ni10Be27.5 (Vit4) bulk glass-forming supercooled liquids were investigated by frequency-dependent heat capacity measurements on a temperature-modulated differential scanning calorimetry (TMDSC) apparatus. The relaxation behaviors of the investigated samples were well described by Kohlrausch–Williams–Watts (KWW) function. The temperature dependences of characteristic relaxation time of the glass-forming liquids were fitted by Vogel–Fulcher–Tamman (VFT) equation. The derived fragility index m shows that Ce65Al10Cu20Co5 (m =31) liquid is a stronger liquid than Vit4 (m =42). The sizes of cooperatively rearranging region (CRR) for Ce65Al10Cu20Co5 and Vit4 liquids were estimated to be 1.6 and 1.4nm, respectively. [ABSTRACT FROM AUTHOR]

Doped and undoped ternary and binary Mg 2 Sn solid solutions were fabricated using high-energy ball milling followed by hot pressing according to the nominal Mg 2 Sn 1−x Y x (X = 0, 0.25 and Y= Si, Ge) composition with the addition of 20 at% of Cu 2 S. The effects of Cu 2 S addition on the thermal conductivity, Seebeck coefficient and electrical conductivity were investigated in the temperature range of 300–800 K. It was found that the Cu 2 S addition increased both the electrical conductivity and Seebeck coefficient simultaneously, which is unusual in thermoelectricity, leading to enhancement of the power factors. Additionally, the addition of Cu 2 S significantly decreases the thermal conductivity. It was also observed that the ternary compositions (i.e. compositions containing Si, Ge) results in a high power factor as a result of the combined optimized Seebeck coefficient and electrical conductivity. This is as a result of phase separations into SnS and Mg 3 Sb 2 phases, which are enhanced by the addition of Si and Ge. Overall, the ZT values significantly improved to 1.35 at 700 K and 1.3 at 750 K for Si and Ge ternary samples, respectively. [Display omitted] • Thermoelectric properties of binary Mg 2 Sn and ternary Mg 2 Sn 1−x Y x (Y = Si, Ge) with the addition of Cu 2 S. • Phase separation into SnS and Mg 3 Sb 2 in the binary Mg 2 Sn and ternary Mg 2 Sn 1−x Y x (Y = Si, Ge) /Cu 2 S solid solution. • Effect of Si and Ge addition on the phase separations. • Partial S substitution of Sn in ternary Mg 2 Sn 1−x Y x (Y = Si, Ge) solid solution, which leads to SnS phase formation. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotube (MWCNT)-reinforced Al 2 O 3 -matrix nanocomposites were obtained by wet ball milling composite powders and spark plasma sintering. The mechanical and thermal properties of the nanocomposites with five different MWCNT concentrations from 0 to 2.0 wt% were studied. Results show that the matrix grain sizes of the composites decreased after MWCNT addition. The hardness, bending strength, and fracture toughness of 0.5 wt% MWCNT nanocomposite are the highest, which are 35.7%, 55%, and 182% higher than those of monolithic alumina, respectively. Errors of fracture toughness values obtained by the single-edge notch beam method are significantly smaller than those measured by the direct crack measurement method. With the addition of MWCNTs, the thermal conductivity of the nanocomposites decreases gradually, reaching the minimum of 12 W/mK in 2.0 wt% MWCNT composite at 300 °C. The thermal conductivity decreased owing to the agglomeration of MWCNTs and changes in the porosity and grain size of the composite matrix. No distinct difference is observed in thermal expansion behaviours between the nanocomposites and monolithic Al 2 O 3 owing to the low content of MWCNTs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of Bi, Sb and Ag doping on the appropriate X-rich (i.e., Si-, sn- or Ge-rich) member in Mg 2 X ternary series. • Effect of Ni doping on Mg 2.2 Ge 0.9 Sn 0.1. solid solution. • Secondary phase formation in Mg 2.2 Ge 0.9 Sn 0.1 solid solution. • RT lattice thermal conductivity of Mg 2.2 Ge 0.9 Sn 0.1 ternary solid solution using Abeles model. Mg 2.2 (Ge 0.9 Sn 0.1) 0.94 X 0.06 (X = Ag, Bi, Ni, Sb) ternary solid solutions were synthesized using a two-step solid state reaction followed by hot pressing. The effects elemental doping on thermoelectric properties of these compounds were studied in the temperature range of 300 to 800 K. The findings demonstrate that Bi, Sb, and Ni function as useful n -type dopants, with Bi being more efficiently in the solid solution of Mg 2.2 Ge 0.9 Sn 0.1. Additionally, the findings indicate that Ag is less efficient in n -type doping. Finally, maximum ZT for the Bi-doped sample is 0.82 at 800 K because of its strong electrical conductivity and moderate Seebeck coefficient. [ABSTRACT FROM AUTHOR]

A new set of measurement system on the Experimental Advanced Superconducting Tokamak (EAST), based on voltage and current probes, is installed on transmission line between matching system and ion cyclotron range of frequencies antenna to measure the antenna input impedance. The data can be used for impedance-matching points optimizing, as well as coupling coefficient assessment by deducing the antenna coupling resistance from antenna input impedance. The measurement error of amplitude and phase difference show distinct impact on the coupling resistance. Generally, the amplitude measurement error has a small impact on coupling resistance, while the phase measurement error significantly affects the coupling resistance. Instead of using phase detectors, phases can be extract from the power measurements. Thus, the antenna input impedance and coupling resistance can be deduced from the amplitude of voltage probe, amplitude of current probe, as well as the antenna feeding power. on previous experiments, the impedance measurement technique based on voltage probes array is utilized to evaluate coupling resistances. In EAST 2016 campaign, the load coupling resistance calculated by using such two techniques were detected and the results showed agreement. [ABSTRACT FROM AUTHOR]

This paper investigates the thermal stability of nanocrystalline surface layer in an aged Al–Zn–Mg–Cu alloy fabricated by ultrasonic surface rolling process (USRP). The microstructure of the nanocrystalline surface layer and the microstructure changes of grains and precipitates in the nanocrystalline surface layer after annealing at various temperatures were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. The microhardness after annealing was also analyzed. The results show that a nanostructured lamella with a thickness of about 40 nm was prepared in the surface layer of the aged Al–Zn–Mg–Cu alloy after USRP. The granulation of the nanostructured lamellae occurs during subsequent annealing due to recovery and becomes more significant with the increase of annealing temperature. Besides, the coarsening η phases occur at the lamellae boundaries by heterogeneous nucleation. Meanwhile, the precipitate inside lamellae gradually changes from GP zone and η' phase to η phase. The thermal stability of the nanostructured lamellae is excellent below 160 °C, but it deteriorates significantly when the temperature exceeds 200 °C. The hardness variation of the nanostructured lamellae is mainly determined by the variation of lamellae thickness and the precipitation behavior plays an auxiliary role. • A nanostructured lamella was prepared in the surface layer of an aged Al–Zn–Mg–Cu alloy by USRP. • The evolutions of grains and precipitates in the nanostructured lamellae during annealing were studied. • The thermal stability of the nanostructured lamellae is excellent below 160 °C. • The hardness variation is mainly determined by the change of lamellae thickness. [ABSTRACT FROM AUTHOR]

ZnO-based ultraviolet (UV) light-emitting diodes (LEDs) are attractive for potential applications. In the study, ZnO-based UV LEDs were numerically investigated to determine the effects of the different step graded Mg compositions in multiple quantum barriers (QBs) on their electrical and optical properties. With the increase of Mg composition for QBs from n -side to p -side, the maximum internal quantum efficiency of various LEDs increase from 32.6% to 91.9%. These improvements can be explained in terms of the modified energy band structures which improve hole injection from p- side to the active region and change the carrier-concentration distributions in multiple quantum wells, then lead to an improvement of radiative recombination rates. One can expect that by the elaborate design of device structure, the performance of ZnO-based LEDs can be further improved. [ABSTRACT FROM AUTHOR]

Mg 2.18 (Si 0.3 Ge 0.1 Sn 0.6) 1-y X y (X ​= ​Bi, Sb; y ​= ​0, 0.02, 0.06) quaternary solid solutions were synthesized via solid state reaction after ball milling followed by hot-pressing. The influences of Bi and Sb doping on its thermoelectric (TE) properties, such as thermal conductivity, Seebeck coefficient, and electrical conductivity were discussed in the temperature range of 300–800 ​K. Our results show that Bi and Sb are effective in n-type doping. The results illustrate that the Seebeck coefficient decreases, whereas electrical conductivity increases with increasing temperature for undoped compositions. However, the electrical conductivity decreases in a metal-like behavior for the doped sample. Additionally, the samples doped with Bi 0.02 and Sb 0.02 show enhanced TE properties as compared to those doped with Bi 0.06 and Sb 0.06 , respectively. A maximum ZT of 1.28 is achieved in the sample doped with Sb 0.02. [Display omitted] • The effect of Bi and Sb doping on the appropriate X-rich (i.e., Si-, Sn- or Ge-rich) member in Mg 2 X quaternary series. • Effect of doping content on quaternary Mg 2.18 Si 0.3 Ge 0.1 Sn 0.6 solid solutions. • Secondary phase formation in Mg 2.18 Si 0.3 Ge 0.1 Sn 0.6 solid solutions. [ABSTRACT FROM AUTHOR]

This paper systematically investigates the microstructural evolution of Al-Zn-Mg-Cu alloy during ultrasonic surface rolling process (USRP). Al-Zn-Mg-Cu alloys with different gradient deformation degrees were prepared by USRP conducted with 1, 2, 6, 8, 10 and, 12 processing cycles, respectively, and then the deformation structures from the surface of samples with different deformation degrees were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. The results indicated that with the increase of processing cycle, the microstructural evolution at different depths of surface deformation layer is basically the same. But the closer to the surface, the faster microstructure evolves. The basic microstructural evolution order of Al-Zn-Mg-Cu alloy during USRP is scattered dislocation, dislocation cells (DCs), elongated dense dislocation cell walls (DDWs), thick laminated structure and nanolaminated structure. According to results of crystallography and atomic level analysis, the microstructural evolution was described in detail. Scattered dislocation structure is formed by dislocation proliferation. According to the low energy dislocation structures (LEDS) principle, the scattered dislocation structure is transformed into DCs structure through dislocation movement. Under the action of large shear stress, DCs structure is elongated along the direction of shear stress to form elongated DDWs structure. The transformation of elongated DDWs into thick laminated structure and the continuous refinement of laminated structure are mainly achieved by the formation of the low angle grain boundaries (LAGBs) and the transformation from LAGBs to high angle grain boundaries (HAGBs). In some nanolaminated structure regions, the laminated structure is further refined by twin deformation. Our work provides a theoretical basis for the adjustment of the actual processing technology. • Different gradient deformation degrees- were prepared by 1, 2, 6, 8, 10 and 12 cycles of USRP. • The deformation structures in the same distance from the surface of different treated samples were compared. • The microstructural evolution details were analyzed from the crystallographic perspective and at atomic level. • The roles of dislocation movement and twin deformation on microstructural evolution is comprehensively considered. [ABSTRACT FROM AUTHOR]

The SSC-LINAC project is launched at Institute of Modern Physics in China to develop one new linear accelerator (LINAC) injector for separated sector cyclotron (SSC). It includes a high charge state ion source, a CW RFQ and a DTL section, and is designed to accelerate ions up to 580 keV/u. Now the ion source and the RFQ cavity have been installed in the main hall and the beam commissioning has been carried out. Two kinds of ions have been tested, 16 O 5+ and 40 Ar 8+ . The experiment result of 16 O 5+ is: the measured beam current is 180 μA at entrance of RFQ and 150 μA at exit of RFQ. The output energy of 16 O 5+ is 141.89 keV/u. The measured beam current is 210 μA at entrance of RFQ and 198 μA at exit of RFQ for 40 Ar 8+ . The output energy of 40 Ar 8+ is 142.78 keV/u. The experiment results agree with the design parameters of RFQ very well. This paper presents: the design consideration of beam dynamics, RF and cooling structure design; measurement of the cold model; high power test of RFQ and beam commissioning result. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nanowire K0.19MnO2•0.2H2O is prepared by a hydrothermal method. [•] It presents better electrochemical behavior than K0.45MnO2•0.3H2O from the solid-state method. [•] Its capacitance is 148 F g−1 its cycling performance is excellent. [•] A supercapacitor based on activated carbon and nanowire K0.19MnO2•0.2H2O is assembled. [•] The supercapacitor delivers an energy density 41.3 Wh kg−1 based on the mass of the active electrode materials. [ABSTRACT FROM AUTHOR]

Abstract: Nanowire Na0.35MnO2 was prepared by a simple and low energy consumption hydrothermal method; its electrochemical performance as a cathode material for aqueous asymmetric supercapacitors in Na2SO4 solution was investigated. Due to the nanowire structure its capacitance (157 F g−1) is much higher than that of the rod-like Na0.95MnO2 (92 F g−1) from solid phase reaction although its sodium content is lower. When it is assembled into an asymmetric aqueous supercapacitor using activated carbon as the counter electrode and aqueous 0.5 mol L−1 Na2SO4 electrolyte solution, the nanowire Na0.35MnO2 shows an energy density of 42.6 Wh kg−1 at a power density of 129.8 W kg−1 based on the total weight of the two electrode material, higher than those for the rod-like Na0.95MnO2, with an energy density of 27.3 Wh kg−1 at a power density of 74.8 W kg−1, and that of LiMn2O4. The new material presents excellent cycling behavior even when dissolved oxygen is not removed from the electrolyte solution. The results hold great promise for practical applications of this cathode material since sodium is much cheaper than lithium and its natural resources are rich. [Copyright &y& Elsevier]

Cryorolling (CR) can effectively avoid room temperature rolling cracking of high-strength aluminum alloy. In this work, solution-treated bulk Al 7085 alloy samples were subjected to CR and room temperature rolling (RTR), respectively. When the deformation was 70%, the RTR sample was broken, while the CR one still had no cracks when the deformation was up to 90%. Consequently, the microstructure and mechanical properties of the CR samples before and after ageing treatment were investigated. The results show that after the solution-treated bulk Al 7085 alloy samples were cryorolled, the yield strength (YS) and the ultimate tensile strength (UTS) were increased by 74% and 31%, respectively. However, the elongation to failure (EtF) was decreased. After the subsequent 100 °C/20 h peak ageing (PA) treatment, the YS and UTS can be further increased by 14% and 10%, respectively, and the EtF was increased by 39% compared with that of the CR samples. After PA treatment, nanosized GP zones and η′ precipitates were precipitated. Precipitation strengthening is the main contributor to the strength enhancement of CR samples after PA treatment, which can not only compensate for the reduction caused by the decrease in dislocation density but also improve the strength of the material. • Al 7085 alloy was processed by cryorolling and subsequent ageing treatment. • Strength and ductility of the cryorolled sample can be simultaneously improved after peak ageing treatment. • The aged sample contains nanosized GP zone and η′ precipitates. • Precipitation strengthening is the main contributor for strength enhancement of the cryolled + peak aged sample. [ABSTRACT FROM AUTHOR]

Novel Al 2 O 3 nanoparticle-reinforced heterogeneous CrCoNi-matrix composites (CrCoNi–Al 2 O 3P) with 10–30 wt% of coarse grain (CG) matrix were prepared by multi-step mechanical milling plus hot pressing sintering. The relationships between microstructure and mechanical properties of the composites were studied in detail. The results reveal that the heterogeneous structure in CrCoNi–Al 2 O 3P composites is composed of CG region and ultrafine grain (UFG) region with uniform distribution of Al 2 O 3 nanoparticles. With increasing content of CG matrix in the nanocomposite, the hardness first decreases but then increases, and the increase of hardness may be due to the formation of carbides. Compared with homogeneous CrCoNi–Al 2 O 3P composite, the compressive fracture strain of heterogenous composite increases by 53.2% at most, while sacrificing a small amount of strength, among which the 20 wt% CG heterogeneous composite exhibits an excellent strength-ductility synergy. For the mechanisms of strengthening and toughening, hetero-deformation induced (HDI) hardening makes the heterogeneous composites almost as strong as the homogeneous composite. Meanwhile, the CrCoNi matrix with low stacking fault energy can be deformed by dislocation slipping and twinning at room temperature, which improves the plasticity of the composite. Furthermore, the heterogeneous structure with soft and hard domains increases the work hardening ability of the composite. ● Heterogeneous matrix of CrCoNi–Al 2 O 3 composites was successfully prepared via multi-step mechanical milling plus hot pressing sintering. ● The composites contain CG region, UFG region with Al 2 O 3 nanoparticles and annealed twins in the matrix grains. ● The fracture strain of 20 CG heterogeneous composite increases distinctly and the strength remains high. [ABSTRACT FROM AUTHOR]

Abstract: Ag-DLC different films with six Ag contents on AISI 440 steel substrate were deposited with a multi-ion beam assisted deposition, and attempt to correlate the incorporation of silver with the sliding tribological behavior was performed. Results show that: (i) increasing Ag content leading to an upward tendency of Ag of nanocrystallite size; (ii) superior tribological behaviors for the films with Ag content ranging between 4.3 and 10.6 at%; and (iii) the best tribological behaviors for the film of 8.3 at% Ag and 12.9 grain size. It also confirms that the evolution of the tribological properties is closely related to the level of the interaction of incorporated silver in forming sp3 hybridization in the DLC films. These phenomena imply that the energetic particles may induce a balance between the recombination of particles and the change of internal stress in the DLC films. [Copyright &y& Elsevier]

Abstract: Crystal structure of the compounds Co40V60−2x La x has been investigated by means of X-ray powder diffraction (XRD). The compounds crystallize in the tetragonal σ phase structure with the space group P42/mnm and form a solid solution with a solubility limit of x =9.52. The lattice parameters a, c and the unit cell volume V of the compounds decrease linearly with the La content. A structure model with a preferential substitution of La for V atoms on the 8j sites accompanied by the presence of vacancies on these sites is proposed for Co40V44La8. The proposal structure model gives a satisfactory fitting to the XRD data and a reasonable La content close to the nominal composition as well as a coincidence of the calculated density with the experimentally measured one. The preferential occupation of La atoms on the 8j site is discussed based on a consideration of geometric constrain and thermodynamics. [Copyright &y& Elsevier]

Abstract: A refined method for analysing X-ray diffraction spectrum was used to determine the carbon content of bainite ferrite in 40CrMnSiMoV steel. The supersaturated carbon concentration linearly decreases with increase of isothermal holding time at 310°C due to the carbon repartition and carbide precipitation. The deduced carbon content of lower bainite embryo in the steel is 0.36wt%, which agrees well with the prediction from the mechanism that bainite forms in carbon depleted regions in supercooling austenite through martensitic shear. [Copyright &y& Elsevier]

Abstract: The coherence transfer between stretching vibration modes of C–H bonds in the ethanol is detected by time-resolved multiplex CARS technique and it occurs via “through-bond transfer” pathway. The time scale and velocity of coherence transfer are estimated at 90fs and 1670m/s. Moreover, coherence transfer process requires vibrational modes of acceptor and donor are different. [Copyright &y& Elsevier]

The flow trends of gas mainstream and coolant ejection in the blade fluid domain are closely related to the non-uniform profile characteristics of gases before the turbine stage. The validity of the non-uniform pressure and temperature profile for the mainstream was determined under the typical working conditions of a torsion blade by comparing the differences between the experimental and numerical simulation results of the leading-edge Mach numbers for various mainstream cases. Then, the film cooling effectiveness of the showerhead holes at the leading edge of the gas turbine twisted blade under the non-uniform mainstream was analyzed. The influence mechanism and rule of the radial angle and streamwise torsion angle on the cooling effectiveness of the leading-edge showerhead were analyzed using the jet characteristics of single film and the spanwise average film cooling effectiveness, respectively. Finally, analyzing the influence of different coupling angles on the cooling effectiveness of the leading-edge region provided the optimal angle arrangement scheme. The results show that the reasonable coupling angle arrangement of showerhead holes can enhance the cooling effectiveness in the leading-edge region. Thus, the coupling angle arrangement should be considered in the engineering design for the leading edge of gas turbine blades. [ABSTRACT FROM AUTHOR]

[Display omitted] • A low concentration of graphene (less than 0.4 wt%) was well dispersed into alumina matrix by physical dispersion method. • The hardness, bending strength and fracture toughness were increased significantly by 19.2%, 84.7% and 49.5%, respectively at low graphene contents. • Different types of toughening mechanisms are observed. • With the increase of graphene contents and temperature, thermal conductivity of the nanocomposites decreases. Graphene/CNTs-reinforced alumina ceramic composites were prepared by spark plasma sintering (SPS) method at 1500 °C. The distribution behaviors of graphene/CNTs reinforcements in alumina matrix composite were studied and mechanical properties of the composite were tested. The structural integrity of the graphene after sintering was analyzed by Raman spectroscopy. The composites show inter and trans-granular fracture behaviors. Many toughening mechanisms such as graphene and CNTs necking, crack bridging, crack deflection and crack branching were observed. The experiment-based calculation of heat capacity of the composite was presented in details. The thermal diffusivity and thermal conductivity of the nanocomposites were discussed. The thermal conductivity increased with the increase of grain size. The pure alumina had the highest thermal conductivity, which was 23.9 Wm−1 K−1. [ABSTRACT FROM AUTHOR]

Improving surface properties can effectively expand the industrial application of aluminum alloys. In this study, a gradient nanostructured surface layer was successfully fabricated in an aged Al–Zn–Mg–Cu alloy by ultrasonic surface rolling processing (USRP). The microstructure and microhardness of the gradient nanostructured surface layer were investigated. The results show that a perfect gradient lamellae structure was fabricated in the surface layer. The average structural size in the topmost surface layer is approximately 41 nm, and the depth of nanostructure lamellae layer is up to 50 μm. After the USRP and two years of natural aging, the gradient distribution of precipitates was formed in gradient lamellae structure. A large number of discontinuous coarse η phase are formed on the lamellae boundary throughout the lamellae structure. However, the precipitates inside the lamellae have gradient distribution. The volume fractions of precipitates increase gradually from nanostructure to ultrafine-grained structure, and the main precipitates are GPII zones. The microhardness in the topmost surface is increased by 40% and gradually decreases from the surface to the matrix. The increase in microhardness is attributed to the fact that the enhancement of the hardness by the grain refinement is greater than the decrease due to the reduction of the precipitates inside the gradient lamellae structure from the surface to the matrix. This study provides technical method and theoretical basis for improving the surface hardness of Al–Zn–Mg–Cu alloy. [ABSTRACT FROM AUTHOR]

In this study, novel CrCoNi–Al 2 O 3 composites with 2.5–7.5 wt% Al 2 O 3 were prepared by mechanical alloying (MA) plus rapid spark plasma sintering (SPS) method, and their microstructure and mechanical properties were systematically investigated. The results demonstrate that the Al 2 O 3 nanoparticles are distributed homogeneously in the CrCoNi medium entropy alloy (MEA) matrix with ultra-fine grain size (≤0.37 μm). Moreover, the composites have clean, regular and well bonded matrix/α-Al 2 O 3 interfaces. Interestingly, a large number of nano twin bundles, large-scale 9R phase and geometrically necessary dislocations (GNDs) were formed near the matrix/α-Al 2 O 3 interfaces. The Vickers hardnesses of the 2.5–7.5 wt% Al 2 O 3 composites reach 521–603 HV 0.3 , and the compressive yield strength is 1877–2359 MPa with fracture strains of 9.3–31.6%. The yield strength of the composites is by 65.4–107.8% higher than that of the pure CrCoNi matrix, meanwhile they still have considerable ductility, which indicates composite strengthening is a feasible method to improve mechanical properties of high/medium entropy alloys. The composite includes multiply strengthening mechanisms, namely grain refinement strengthening, twin strengthening, Orowan strengthening and dislocation strengthening. The contributions of various strengthening mechanisms were quantitatively analyzed, which were well consistent with the experimental values. • CrCoNi–Al 2 O 3 composites with different Al 2 O 3 contents were successfully prepared via powder metallurgy route. • The grain size of CrCoNi-matrix was effectively refined by Al 2 O 3 nanoparticles uniformly distributed in the matrix. • Nano twin bundles, broad 9R phase and geometrically necessary dislocations were formed near CrCoNi/α-Al 2 O 3 interfaces. • CrCoNi–Al 2 O 3 composites possess remarkable strength due to the synergy of multiply strengthening mechanisms. [ABSTRACT FROM AUTHOR]

HIAF-BRing, the main synchrotron accelerator of the High Intensity Heavy-Ion Accelerator Facility, requires an average pressure lower than 1 × 10−9 Pa and the magnetic field increase rate no less than 12 T/s to fulfill radioactive beam physics and high energy density physics experiments. To reduce the eddy current effect and the gap size of dipoles compared to the thin-wall stainless steel vacuum chamber with reinforced ribs, a new design of ceramic-lined vacuum chamber with wall thickness 0.3 mm has been proposed by IMP. In order to effectively reduce the beam impedance and the desorption rate of ceramic materials, Au coating on ceramic (Yttria stabilized zirconia) by magnetron sputtering has been carried out. The adhesive force of Au film is 28.1 MPa measured by scratch test while the crystalline size of Au particle is in the range of 15.7–21.4 nm by X-ray diffraction (XRD). The longitudinal impedances of four types of round-ring-lined 0.6-m-long straight stainless-steel tubes and the ultimate pressure of the new designed vacuum chamber (uncoated vs Au-coated) have been measured to verify the feasibility of this method. • A new design of ceramic-lined vacuum chamber with wall thickness 0.3 mm has been proposed to reduce the eddy current effect and the gap size of dipoles, where the ceramic rings are Au-coated and a prototype has been designed and manufactured to test the concept. The ceramic ring is made by yttrium stabilized zirconia, which has very good mechanical strength and toughness. •Compared to the thin-walled stainless steel vacuum chamber with reinforced ribs, the gap size of the dipole decreases significantly and therefore the magnets manufacturing and operating cost reduce accordingly. •In order to reduce the beam impedance and the desorption rate of the ceramic surface, the ceramic rings have been coated with a 1 μm Au film. The Au coating has been characterized by several surface analysis technologies. Film quality proved to be good and adhesion was tested to be 28.1 MPa. [ABSTRACT FROM AUTHOR]

• Graphene were excellently dispersed into alumina matrix by physical dispersion method. • The structural stability of graphene was analyzed by Raman spectroscopy. • The fracture toughness of the material was measured by the method of single edge notched beam (SENB). • The bending strength and the fracture toughness of the nanocomposites increased significantly at low graphene contents. • Different types of toughening mechanisms are observed. Monolithic Al 2 O 3 and graphene-reinforced Al 2 O 3 ceramic-matrix nanocomposites were fabricated with the help of spark plasma sintering (SPS). Density, hardness, bending strength, fracture toughness and microstructure of the sintered samples were studied. The contents of graphene were 0–1.6 wt%. The strengthening and toughening mechanisms of the composites were discussed in detail. The results showed that the density of the composites varied from 99.7% to 98.7%. 0.4–1.6 wt% of graphene was homogeneously distributed in the matrix. The structural stability of graphene was analyzed by Raman spectroscopy. The bending strength of the nanocomposite reached the maximum when graphene content was 0.4 wt%. The fracture toughness of the composites also increased when the addition of graphene was between 0.4 and 1.6 wt% as compared to monolithic alumina. Different types of toughening mechanisms were observed including; micro-cracks, graphene pull-out, crack deflection and crack bridging. [ABSTRACT FROM AUTHOR]