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A compact ultra-wideband (UWB) and triband patch antenna with the partial ground plane is presented in this paper. Initially, the antenna is designed for UWB applications, operating at the UWB portion of the spectrum ranging from 3.1 GHz to 10.6 GHz, then it is modified to operate at three distinct frequencies of 2.45 GHz, 5 GHz, and 10.2 GHz. The proposed antenna is inspired by a classic rectangular patch antenna in which slots, stubs, and defected ground structure (DGS) were introduced to increase its operational bandwidth. Good results in terms of return loss are found in all resonant frequencies as well as for the single wideband. In addition, the proposed antenna has been compared with related works in the literature, to highlight its potential for future UWB and multiband portable devices.

We study here the underlying factors that govern the stability of austenite in a medium Mn (Fe–0.18C–11Mn–3.8Al) (wt-%) steel. In this regard, a novel heat treatment involving intercritical quenchi...

In the double cold rolling process, oil film thickness in the deformation zone is a key parameter for evaluating rolling lubricity. This study investigated the formation and variation mechanism of ...

The perovskite structure of manganate yields a series of intriguing physical properties. Based on the results of first-principles calculations, strontium manganate appears to undergo a magnetic phase transition and a metal-insulator transition-from antiferromagnetic insulator to ferromagnetic metal and then to ferromagnetic insulator-under isotropic volume expansion combined with oxygen octahedral distortions. Interestingly, the results show that increasing the Mn-O bond length and adding rotation of the oxygen octahedra can soften the breathing distortion and account for the insulator phase. We further build a simple model to explain such transitions. Due to electron transfer and the favoring of a hole state of ligandporbitals, the electron state transfer from2(t2g3)to2(eg1+t2g2)and then tot2g3eg1+(t2g3L1). Such rearrangement of charges is responsible for the transitions of its magnetic order and electronic structure. Furthermore, we calculate spin susceptibility under the bare conditions and random phase approximation. The magnetic order of the intermediate metal state of itinerant electrons behaves as a ferromagnetic.

Synchrotron-basedL2,3-edge absorption spectra show strong sensitivities to the local electronic structure and chemical environment. However, detailed physical information cannot be extracted easily without computational aids. Here, using the experimental TiL2,3-edges absorption spectrum of SrTiO3as a fingerprint and considering full multiplet effects, calculations yield different energy parameters characterizing local ground state properties. The peak splitting and intensity ratios of theL3andL2set of peaks are carefully analyzed quantitatively, giving rise to a small hybridization energy around 1.2 eV, and the different hybridization energy values reported in the literature are further addressed. Finally, absorption spectra with different linearly polarized photons under various tetragonal crystal fields are investigated, revealing a non-linear orbital–lattice interaction, and a theoretical guidance for material engineering of SrTiO3-based thin films and heterostructures is offered. Detailed analysis of spectrum shifts with different tetragonal crystal fields suggests that theegcrystal field splitting is a necessary parameter for a thorough analysis of the spectra, even though it is not relevant for the ground state properties.

Take the wear parts of coupler knuckle as an example, the “Modeling—Slicing — Stacking” mode remanufacturing process is studied. First, the 3D model of the of the worn coupler knuckle surface is acquired by structured light 3D detection. The remanufacturing model of the failure part is built by Boolean operation between the original model and the acquired 3D model. Second, the user can slice layer of the remanufacturing model according to the remanufacturing stacking parameters. The zone that surrounded by the contour of each sliced layer is the robotic GMAW remanufacturing stack region. Third, the robotic GMAW remanufacturing path is planed within the region mentioned above and the executable program is generated to carry out the remanufacturing task layer by layer. Moreover, the worn coupler knuckle was repaired by adopting Robotic GMAW Process. The mechanical performances of component were tested, the results indicate that the remanufactured coupler knuckle satisfying the operating requirements.

Hydrogen bubble phenomenon is one of the key issues to be solved in the development of a long-life target system for boron neutron capture therapy (BNCT). In this study, we assessed the kinetic behaviors of H impurities in the nano-composite target from the atomic level. Firstly, two kinds of Li/Ta nanolayer models were constructed, based on the calculated lattice parameters and surface energies. The H solution energy, diffusion mechanism, and hydrogen bubbles formation in the Li/Ta nanostructured bilayer were studied, through theoretical modeling and simulation. Our results show that the Li/Ta interfaces are effective sinks of H atoms because the H solution energies in the interface are lower. Meanwhile, due to the relatively low diffusion barriers, the large-scale H transport through the interface is possible. In addition, although it is more likely to form hydrogen bubbles in the Ta layer, compared with the Li layer, the anti-blistering ability of Ta is more impressive compared with most of other candidate materials. Therefore, the Ta layer is able to act as the hydrogen absorber in the Li/Ta bilayer, and relieve the hydrogen damage of the Li layer in the large-scale proton radiations.

A series of lanthanum/beta-zeolite catalysts was prepared via hydrothermal ion exchange, and characterized by inductively coupled plasma–atomic emission spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and ammonia temperature-programmed desorption. The lanthanum-doping effect on beta-zeolite catalysts was investigated through catalytic cracking of supercritical methylcyclohexane under the system pressure of 4.0 MPa and the mass flow rate of 1.0 g/s. For lanthanum/beta catalyst of the Cat-2 type, the gas yield of 28.3% and heat sink of 3.35 MJ·kg−1 could be achieved at the temperature of 700°C, much higher than those for the pure beta zeolite without lanthanum modification and for the thermal pyrolysis. Correspondingly, Cat-2 has a better performance on coking inhibition with the reduction of 56.2 and 29.5% at 700°C compared to beta zeolite and thermal cracking. Therefore, it was indicated that beta zeolite with the suitable lanthanum content, still maintaining its high activity ...

Under part-load conditions, flow instability phenomena in a hydraulic machinery could lead to strong pressure fluctuations and vibrations, posing a great threat to the safety of the units. This paper analysed unsteady flow in a centrifugal pump (specific speed of 39 min−1·m3s− 1·m) with different inlet geometries under part-load conditions. An advanced turbulence model, PANS (partially averaged Navier-Stokes), acting as a bridge from RANS to DNS, is applied for numerical simulations. The results indicated the pump with a straight inlet pipe reached higher values of pump head and efficiency near the design point than the test pump with a non-straight inlet pipe. According to the characteristic curves, hump phenomenon was observed at 0.75ϕbep for the pump having a straight inlet pipe, while it occurred at 0.5ϕbep for the test pump. Under the condition of a low flow rate i.e. ϕ=0.5ϕbep, there is strong pre-swirling flow upstream impeller inlet for the test pump, which contributes to the propagation of rotating stall cells; But energy loss in the impeller inlet of the pump with straight inlet pipe is slightly higher than that in the test pump due to the presence of the stationary stall cells, which causes large energy loss in the impeller and the passage upstream impeller inlet. Further, rotating stall cells are captured in the impeller in both pumps under the condition of ϕ=0.75ϕbep.

This study evaluates the effect of laboratory long-term oven aging (LTOA) on the stiffness of asphalt mixture using laboratory dynamic modulus test. A large variety of materials was subjected to diverse LTOA conditions including different aging temperatures and durations with loose mixture and compacted samples. Dynamic modulus master curve and dynamic modulus ratio (DMR) data shows that the aging of loose mixture at 95 °C could be an ideal LTOA procedure with the efficiency and capability to characterize the long-term aging in the field. The variety of materials including the use of recycled asphalt pavement, warm mix asphalt technologies and asphalt binder performance grade was also found to have appreciable effect on the LTOA properties.

It is difficult to obtain film with uniform thickness and constant performance for optical components with larger diameter. It is a critical technology to improve the film uniformity during the deposition process. The ion beam sputtering system was used to prepare the film on the surface of large-aperture optical elements. The performance of film including thickness and roughness were measured by step profiler and optical profilometer instrument. The film thickness correction model was proposed in this paper. The optimized dwell time ratio was obtained by the film thickness data obtained from former experiments, and the dwell time distribution was calculated, after several iteration with the model, uniform film can be achieved on optical elements over 300mm in diameter. Taking the Si film on the surface of fused silica as an example. The research results show that, different film thickness between 100nm and 400nm can be obtained, when the film thickness is more than 200 nm, the film uniformity from more than 13% to less than 0.5%. The surface roughness variation of optical material before and after film deposition were studied, which provide stable process for obtaining high performance film on larger optical components.

Structural properties and photovoltaic response of InGaN/GaN multi-quantum well (MQW) solar cells with low temperature grown GaN cap (LT-cap) layers were investigated. It is found that inserting a thin LT-cap layer (around 0.75 nm) between each InGaN quantum well (QW) and GaN quantum barrier (QB) can remarkably improve photovoltaic response of InGaN/GaN MQW solar cells. This is attributed to the increased optical absorption of InGaN QWs due to higher indium content and thicker InGaN QWs thickness when LT-cap layers are added. However, if the LT-cap layer is too thick, the localization effect is enhanced and the defect density of InGaN QW layers will increase too much. Both of them will result in a reduced photovoltaic response of InGaN/GaN MQW solar cells.

Based on highly efficient multi-point forming and highly accurate single-point incremental forming, precise and efficient digital formation of three-dimensional metal sheets can be realised. In this article, stress states during the forming process were investigated based on mechanical equilibrium theory. The results showed that contact points of the matrix were subject to vertical tensile stresses when friction coefficient between metal sheets and matrix was relatively low and the angle between metal sheets and vertical plane was small. In other cases, the contact points of matrix were subjected to compressive stresses and dimplings may occur. For the axisymmetric workpieces, radial shear stress in the deformed zone decreased with the increasing radius of tool head and decreasing feed. The theoretical formula of forming force was deducted based on the principle of conservation of energy. According to this formula, the forming force was proportional to the thickness and yield strength of metal she...

In order to investigate the temperature-dependent carrier transport property of the bilayer graphene, graphene films were synthesized on Cu foils by a home-built chemical vapor deposition (CVD) with C 2 H 2 . Samples regularity, transmittance ( T ) and layer number were analyzed by transmission electron microscope (TEM) images, transmittance spectra and Raman spectra. Van Der Pauw method was used for resistivity measurements and Hall measurements at different temperatures. The results indicated that the sheet resistance ( R s ), carrier density ( n ), and mobility ( μ ) were 1096.20 Ω/sq, 0.75×10 12 cm −2 , and 7579.66 cm 2 V −1 s −1 at room temperature, respectively. When the temperature increased from 0 °C to 240 °C, carrier density ( n ) increased from 0.66×10 12 cm −2 to 1.55×10 12 cm −2 , sheet resistance ( R s ) decreased from 1215.55 Ω/sq to 560.77 Ω/sq, and mobility ( μ ) oscillated around a constant value 7773.99 cm 2 V −1 s −1 . The decrease of the sheet resistance ( R s ) indicated that the conductive capability of the bilayer graphene film increased with the temperature. The significant cause of the increase of carrier density ( n ) was the thermal activation of carriers from defects and unconscious doping states. Because the main influence on the carrier mobility ( μ ) was the lattice defect scattering and a small amount of impurity scattering, the carrier mobility ( μ ) was temperature-independent for the bilayer graphene.

Nitrogen-doped graphene/Fe 2 O 3 composites (NGFeCs) have been synthesized by a simple hydrothermal method. The structure and morphology of the samples were analyzed by X-ray diffraction, Raman spectra, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results indicate that Fe 2 O 3 particles with size about 20–100 nm were homogenously anchored on nitrogen-doped graphene (NG) sheets. Electrochemical properties of the synthesized materials were characterized by serials of electrochemical measurements in 1 M Na 2 SO 4 electrolyte. The as-prepared NGFeCs show a better electrochemical performance than the graphene/Fe 2 O 3 composites (GFeCs). The specific capacitance of NGFeCs electrode is 260.1 F/g (150.4 F/g for GFeCs electrode) at a current density of 2 A/g. Additionally, over 82.5% (214.6 F/g) of the original capacitance is retained after 1000 cycles at a current density of 2 A/g (61.4% for GFeCs electrode). The superior electrochemical performance can be ascribed to the good electronic conductivity and more active and nucleation sites introduced by the nitrogen-doping (especially by pyrrolic N-doping).

In order to study the influence of process parameters of femtosecond laser helical machining on the formation of micro-holes, we selected main parameters of the femtosecond laser helical drilling process, used 304 stainless steel as the target material, designed a 5-factor and 5-level orthogonal experiment based on the L 25 (56) orthogonal table, and analyzed the significance levels of the impacts of single pulse energy, repetition rate, rotation rate, rate of focus downward movement, and air-blowing pressure on the ablation depth. Based on back propagation (BP) neural network, we established the relationship model between five factors and the material ablation depth, and trained the network with orthogonal experiment data. We used the data of the additional drilling experiments to test the generalization ability of the established network, and the results show that the prediction error of the model is within 3%. We designed a single-factor experiment for the characteristic parameter of the helical drilling--the rate of focus downward movement--and obtained the effect of the rate of focus downward movement on the formation of the micro-holes during the process of femtosecond laser helical drilling.

During its converter extraction process, vanadium is oxidised into vanadium slag and forms spinel crystals. The spinel crystallisation process is one of the most decisive factors in the subsequent extraction and hence is worth exploration and discussion. The classical crystallisation kinetic model presented by Turnbull and Uhlmann was employed to analyse the crystallisation processes of vanadium, chromium and titanium spinel crystals in the vanadium slag. The crystallisation abilities of the three kinds of spinels were quantified and found to follow the order FeCr2O4>FeV2O4>Fe2TiO4. Furthermore, the precipitation sequence of spinels in the vanadium slag during cooling was achieved as FeCr2O4→FeV2O4→Fe2TiO4, and a suitable heat treatment condition on the vanadium slag was proposed. Finally, the optimum temperature range that benefits the precipitation of spinels was obtained as 1507–1557 K by both theoretical calculation and experiment.

This work reports the functionalization of multi-walled carbon nanotubes (MWCNTs) with crystalline poly(4- vinylpyridine) (P4VP) in CO2-expanded liquids (CXLs). The structure and morphology of MWCNT-induced polymer crys- tallization are examined, with the focus on molecular weight of P4VP (MW-P4VP), the pressure of CXLs and the concentration of P4VP. First, it is observed that the crystallization morphologies for the P4VP/MWCNTs composite with a low molecular weight P4VP (LMW-P4VP) matrix could be finely controlled in CXLs, and it is surprising to find that the P4VP8700 wrapping patterns undergo a morphological evolution from dot crystals to dotted helical wrappings, and then to dense helical patterns by facile pressure tuning under lower polymer concentration. In other words, the CXLs method enables superior control of the P4VP crystallization patternings on MWCNTs, particularly efficient for LMW-P4VP at lower polymer concentration. Meanwhile, the CXL-assisted P4VP crystal growth mechanism on MWCNT is investigated, and the dominating growth mechanism is attributed to 'normal epitaxy' at lower P4VP concentration rather than 'soft epi- taxy' at higher concentration. We believe that this work reports a new crystalline polymer wrapping approach in CXLs to noncovalent engineering of MWCNTs surfaces.

Nanostructured polycrystalline titanium dioxides are produced by gas-phase detonation and pyrohydrolysis. Titanium tetrachloride (TiCl4) is used as a precursor in the gas phase, and a premixed gas (O2 and H2) is used as a source of energy. The product is a mixture of TiO2 crystals in the rutile phase (80%) and anatase phase (20%).

Nanosized TiO2 powders were prepared for the first time by gaseous detonation method. The structure, composition and size distribution of the detonation product were systematically characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicate the powders are a mixed crystal of rutile and anatase exhibiting non-spherical grains, and the average size of particles was between 20 and 40 nm. The results of detonation pressure measurement show that the reaction took place under a deflagration-to-detonation transition (DDT) course.

The feasibility of bonding amorphous ribbons via explosive welding (EW) is demonstrated. With 20–120 layers of Fe78B13Si9 and Fe40Ni40P14B6 amorphous ribbons 25 µm thick and 10 cm wide, the plate samples are bonded by using two setups with a collision point velocity of 3900–4800 m/sec and a flyer plate velocity of 570–900 m/sec. The largest area of the bonded sample is 30 cm2. The microstructures of the samples are observed by optical microscopy and X-ray diffractometry. Based on the formation characteristics of amorphous alloys and heat-exchange characteristics during the EW process, a square-wave model for the temperature distribution across the interface is proposed. It can be used to explain the reasons for the samples keeping the amorphous state across the interface after explosive welding. The calculated results are in good agreement with the experiments.

The operating conditions of cast steel staves at Masteel blast furnace have been simulated to generate the temperature distribution under different operating conditions. The influence of the temperature and velocity of cooling water as well as the gas temperature of blast furnace on the temperature distribution of the cast steel stave was obtained. The main cause of stave damage is discussed. The result shows that cast steel staves possess better heat transfer ability and a lower temperature distribution field than nodular cast iron staves, but their performance is much less satisfactory than that of copper staves.

The morphology development of an immiscible polymer blend along a single screw extruder was investigated, concentrating on the effect of screw geometry. Three different screw geometries were evaluated: one with conventional screw elements; the other two with a fluted and Pineapple mixing element, respectively. The experiments were conducted using a polypropylene/polyamide-6 (PP/PA 6) blend. The blend samples were collected from four different positions using specially designed sampling device along the extruder online during blending and were then examined using scanning electron microscopy. The experimentally observed morphology evolution was evaluated both qualitatively, in terms of spatial distribution of dispersed phase, as well as quantitatively, by analysis for the size of the dispersed phase. The morphology development was interpreted with the aid of the flow fields occurring along screw elements. The results showed that the screw with conventional screw elements produce the coarsest and most non-uniform morphology whereas the screw with a fluted mixing element appears to produce the finest and most uniform morphology at the end of the extruder. The Pineapple mixing element, with a characteristic of chaotic mixing, facilitates to form thinner laminar layers of dispersed phase. The experimentally observed morphology difference between the conventional and fluted mixing element was demonstrated by the simulation.

The effects of the combined substitution of Y and Ga on the crystallographic structure of Nd 2− x Y x Fe 17− y Ga y compounds with x = 0, 0.5, 1.0, 1.5 and y = 0, 1, 2, 3 have been investigated using X-ray and neutron powder diffractions. Rietveld refinements of the diffraction data indicate that all the samples crystallize in the rhombohedral Th 2 Zn 17 -type structure with only small amounts of alpha iron. It is found that the addition of Ga atoms lessens the decreasing rates of the a -axis and unit cell volume V on the Y content but almost does not affect the decreasing rates of the c -axis. However, the substitution of Y has a positive effect on the increasing rates of the a -axis and unit cell volume V on the Ga content but has a very slight effect on the increasing rate of the c -axis. The c / a ratio of Nd 2− x Y x Fe 17− y Ga y as a function of Ga content exhibits a different increase for different Y content owe to the combined effects of Y and Ga on the crystallographic structure. The substitution of Y is found to have little effect on the site occupancy of Ga in Nd 2− x Y x Fe 17− y Ga y . The combined effects of Y and Ga on the bond lengths and ASBL of Nd 2− x Y x Fe 17− y Ga y indicate that more bonds detrimental to ferromagnetic exchange can be modulated into the desirable ferromagnetic exchange distance range through suitable combined substitution, which provides a valuable way to improve the magnetic properties of rare earth-transition intermetallic compounds.

GaN-based magnetic semiconductors are expected to exhibit ferromagnetism even at high temperatures. We have studied the magnetic and optical properties of transition-metal- and rare-earth-doped GaN. GaCrN showed ferromagnetic characteristics at 7–400 K. Clear hysteresis and clear saturation were observed in the magnetization versus magnetic field (M–H) curves at all measuring temperatures. We observed photoluminescence (PL) emission from GaCrN layers. GaGdN also showed ferromagnetic characteristics at 7–400 K. Sharp PL emission was observed for GaGdN. X-ray diffraction and EXAFS measurements showed no phase separation, and that the Cr and Gd atoms substitute Ga sites. Applications to novel devices controlling charges (electrons and holes), spins and photons are expected.

Metal Matrix Composites (MMCs) are potential candidate materials in the aerospace and automobile industries because of its attractive properties, in particular, their high specific properties, and Superplastic forming (SPF) is a good solution to the problems in the forming process of MMCs due to their low ductility resulting from the incorporation of reinforcement. High strain rate superplasticity (HSRS) is attractive for industrial applications because superplastic forming at high strain rates can reduce forming time greatly. The strength of P/M 6061 Al and 6061 Al/SiCp (3 μm) composites during superplastic deformation at temperatures of 853 K–871 K and a high strain rate of 0.1 s−1 has been studied in this paper. Experimental results presented a softening effect by the SiCp reinforcement. Mechanical and microstructural analyses show that the decrease in the strength during high strain rate superlastic (HSRS) deformation is associated with the decreased grain size of the Al matrix with increase of the SiCp volume fraction or the extrusion ratio, and the occurrence of liquid phase. The formation of the liquid phase was related to segregation of the solute atom during HSRS deformation.

Metal matrix composites (MMCs) are candidate materials in the aerospace and automobile industries and have found increasing use in recent years. However, their low ductility resulting from the incorporation of reinforcement particles produces a lot of problems in forming process and limits their applications. A good solution to this problem in processing is to adopt superplastic forming (SPF). High strain rate superplasticity (HSRS) is attractive for industrial applications because SPF at high strain rates can reduce forming time greatly. High strain rate superplasticity and deformation mechanisms of powder metallurgy (PM) 6061 Al/SiCp (3 νm) composites have been investigated in this study. The extrusion ratios were 20 and 47. High temperature tensile tests were conducted over a temperature range of 853-871 K at initial strain rates of 0.001-1 s–1. Experiments show that PM 6061 Al/SiC (3 νm) composites exhibit good high strain rate superplasticity at temperatures of 853-871 K and high strain rates...

The hole distribution and electroluminescence property improvement by adjusting the relative position between quantum wells and p-doped region in InGaN/GaN multiple-quantum-well structures are experimentally and theoretically investigated. Five designed samples with different barrier layer parameters of multiple-quantum-well structure are grown by MOCVD and then fabricated into devices. The electroluminescence properties of these samples are measured and compared. It is found that the output electroluminescence intensity of samples is enhanced if the position of quantum wells shifts towards p-side, while the output power is reduced if their position is shifted towards the n-side. The theoretical calculation of characteristics of these devices using the simulation program APSYS agrees well with the experimental data, illustrating that the effect of relative position between p-doped region and quantum wells on the improvement of hole distribution and electroluminescence performance is significant, especially for InGaN/GaN multiple-quantum-well devices operated under high injection condition.

Light emitting porous silicon (PS) was prepared by hydrothermal etching of P-type singlecrystal silicon. Red (690 nm), blue (430 nm) photolumiaescence (PL) samples can be obtained respectively by controlling etching condition. Scanning Tunneling Microscopy (STM) image of the PS layer shows individual uniform columns exist throughout the structure. High-resolution Electron Microscopy (HREM) image further shows these columns are amorphous phase with nanocrystallites (5nm) embedded, conlimed to be SiO2 and silicon nanocrystallites, respectively. X-ray diffraction (XRD) study shows these silicon nanocrystallites have lattice distortion. Photoluminescence in PS is suggested to be aroused from quantum confinement in these distorted nanocrystallites, and PL wavelength variation with preparation was interpreted on the basis of microstructure studies. Nondegrading PL in PS can be obtained by iron-passivat-ing of surface of silicon nanocrystallites, confirmed to be the formation of Fe—Si bonds on the surfa...

A finite-size effect leads to more electrons to occupy high-energy states in a graphene nanoribbon. Therefore, the thermionic-emission (TE) current density of a metal/graphene nanoribbon changes with its width when the graphene nanoribbon is a semiconductor. This letter demonstrates that the TE current density increases rapidly with the decreasing width of the graphene nanoribbon. It is also found that the finite-size effect on TE current density is more significant at low temperatures.

The mixtures of mesogen-jacketed liquid crystalline polymers (MJLCP) and epoxy resin (E-51) have been prepared in a certain proportion. The category of the MJLCP is poly{2, 5-bis[(4-butoxyphenyl) oxycarbonyl] styrenes} (PBPCS). Methyl tetrahydro phthalic anhydride (MeTHPA) is served as a curing agent, and N, N-dimethylbenzylamine plays the role of catalyst. Then, based on the curing process, the modified materials have been acquired by casting molding. The effect of PBPCS's improvement has been researched through the mechanical properties test, dynamic thermal mechanical test and scanning electron microscope (SEM). The results indicated that PBPCS could apparently improve the mechanical properties of resin E-51. Compared with unmodified materials, the elongation at break and the tensile strength of PBPCS have been improved remarkably through modification. Both mechanical properties of the 4wt% PBPCS/E-51/MeTHPA were enhanced by 48% and 153% separately, and the characteristics of the 3wt% one were raised by 47% and 19% respectively. Also, the ductile fracture morphology of the resins was exhibited in SEM photograph clearly.

The optical and structural properties of InGaN/GaN multi-quantum wells (MQWs) with different thicknesses of low temperature grown GaN cap layers are investigated. It is found that the MQW emission energy red-shifts and the peak intensity decreases with increasing GaN cap layer thickness, which may be partly caused by increased floating indium atoms accumulated at quantum well (QW) surface. They will result in the increased interface roughness, higher defect density, and even lead to a thermal degradation of QW layers. An extra growth interruption introduced before the growth of GaN cap layer can help with evaporating the floating indium atoms, and therefore is an effective method to improve the optical properties of high indium content InGaN/GaN MQWs.

The influence of unintentionally doped carbon impurities on electrical resistivity and yellow luminescence (YL) of low-temperature (LT) grown Mg doped GaN films is investigated. It is found that the resistivity of Mg doped GaN films are closely related to the residual carbon impurity concentration, which may be attributed to the compensation effect of carbon impurities. The carbon impurity may preferentially form deep donor complex CN-ON resulting from its relatively low formation energy. This complex is an effective compensate center for MgGa acceptors as well as inducing YL in photoluminescence spectra. Thus, the low resistivity LT grown p-type GaN films can be obtained only when the residual carbon impurity concentration is sufficiently low, which can explain why LT P-GaN films with lower resistivity were obtained more easily when relatively higher pressure, temperature, or NH3/TMGa flow rate ratio were used in the LT grown Mg doped GaN films reported in earlier reports.

The effect of quantum barrier (QB) thickness on performances of InGaN/GaN multiple-quantum-well light-emitting diodes (MQW LEDs) with relatively large barrier layer thicknesses has been investigated. It is found that the density and averaged size of V-defects increases with QB thickness, resulting in larger reverse- and forward-bias current in LEDs. Electroluminescence measurement shows that LED with thinner QB has higher internal quantum efficiency but lower efficiency droop-onset current density, which should be ascribed to the faster saturation of carrier leakage into V-defects. Correspondingly, above the droop-onset current density, severer Auger recombination and carrier overflow are induced by higher carrier density due to the less V-defect related carrier leakage, leading to the more serious droop phenomenon in LEDs with thinner QB.

The high-order modes and the moving wave characteristics of rotating thin shell are investigated in this paper based on transfer matrix method when the damping effects of the hard-coating layers are applied on the shell. Firstly, the dynamic model of the thin shell is obtained based on the Love theory, with introducing centrifugal force and Coriolis force. Then, the transfer matrix formulas of the shell with partially coated layers at different segments are obtained under the clamped-free boundary condition, in which the mechanical property of the hard-coating material is simplified to be linear and isotropic. The modal characteristics of the shell are calculated numerically. The obtained higher order modal frequencies of the partially coated shells are compared with those of the bare shell. The effects of the material parameters and locations of the hard-coating layers are also illustrated based on the different modal characteristics., great care should be taken in constructing both.

A hybrid method is proposed to study atomic diffusion behavior in Cu-Al explosive welding process. The method combines molecular dynamics simulation and classical diffusion theory. Cu-Al explosive welding and scanning electron microscope experiments are done to verify the method. Using the method, we find that the atomic diffusion mostly takes place in the unloading stage of the welding process. The diffusion coefficients are collision velocity-dependent, with higher velocities generating larger coefficients. When there is no transverse velocity, the diffusion coefficient is directly proportional to the longitudinal velocity. With the longitudinal velocity fixed, the diffusion coefficient is proportional to the square of the transverse velocity. The thickness of the diffusion layer is calculated from the simulation result, and it is in good agreement with the experiment result. Published version

A Ti40Zr25Cu12Ni3Be20 bulk metallic glass (BMG) was welded to a crystalline aluminum by the parallel plate explosive welding method. Experimental evidence and numerical simulation show that atomic-scale bonding between the BMG and the crystalline aluminum can be achieved, and the weldment on the BMG side can retain its amorphous state without any indication of crystallization in the welding process. Nanoindentation tests reveal that the interface of the explosive joints exhibits a significant increase in hardness compared to the matrix on its two sides. The joining of BMG and crystalline materials opens a window to the applications of BMGs in engineering.

A series of compounds Nd3−xYxFe23−yCo6Moy (x=0.36–3.0) has been synthesized and studied by x-ray powder diffraction and neutron diffraction. Rietveld analyses of the diffraction data indicate that all the compounds crystallize in A2∕m. The lattice parameters a, b, and c and unit-cell volume V decreased monotonically with the increase of Y content. Neutron-diffraction results show that Mo atoms occupy three sites, two 4i sites and one 4g site, while Co atoms are found to occupy all the Fe sites not shared with the Mo atoms. However, the most preferential sites for Co are Fe1(2c), Fe8(8j), and Fe11(4e). It is also observed that those sites preferred by Mo have the long average bond length, while sites preferred by Co have short average bond lengths.

Recrystallization texture evolution of rolled V-4Cr-4Ti alloy has been investigated by quasi-in-situ EBSD (electron back-scattering diffraction) method. Concurrently, the precipitates were characterized by SEM (Scanning Electron Microscopy). It was found that both the initial rolling textures and the distribution of the precipitates affected the formation of the recrystallization texture. It was revealed that the texture transformations of {558} 〈110〉 + {665} 〈110〉 to {334} 〈483〉 + {665} 〈1 1 2.4〉 were possibly attributed to the selective drag induced by the sparsely dispersed Ti-rich precipitates. While the densely distributed Ti-rich precipitates were responsible for the randomized recrystallization texture. Finally, when the precipitates were absent, the orientation changes from {112} 〈110〉 and {558} 〈110〉 to {111} 〈112〉 and {001} 〈110〉 to {001} 〈520〉 were observed.

The formation of precipitates and its effect on the grain structure in V-4Cr-4Ti alloys with and without yttrium addition have been investigated. As-cast and recrystallized grain structure and the secondphase particles were studied via OM (Optical Microscopy), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), and EBSD (Electron Back-scattering Diffraction). It was found that yttrium oxides inclusions with size of micrometer level existed in all yttriumcontaining V-4Cr-4Ti alloys including as-cast, rolled, annealed and forged states. It was revealed that fine yttrium-enriched particles, less than 200 nm in size, were frequently observed in V-4Cr-4Ti-0.3Y alloys annealed or forged above 1000 °C. Yttrium addition was observed to have refining effect on the as-cast grains and homogenization effect on the annealed grain structure of rolled sheets. Yttrium addition mitigated the inhomogeneity of recrystallized grain structure in rolled V-4Cr-4Ti sheets due to the enormous reduction of nonuniform Ti(C, N, O) particles, and inhibited the abnormal growth of grains at relatively high annealing temperatures because of the formation of the finer yttrium-enriched precipitates.