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Vertical Si nanowire (NW) arrays are a promising photoanode material in the photoelectrochemical (PEC) water splitting field because of their highly efficient light absorption capability and large surface areas for PEC reactions. However, Si NW arrays always suffer from high overpotential, low photocurrent density, and low applied bias photon-to-current efficiency (ABPE) due to their low surface catalytic activity and intense charge recombination. Here, we report an efficient oxygen evolution cocatalyst of optically transparent, mesoporous ultrathin (2.47 nm thick) In2O3 nanosheets, which are coupled on the top of Si NW arrays. Combined with a conformal TiO2 thin film as an intermediate protective layer, this Si NW/TiO2/In2O3 (2.47 nm) heterostructured photoanode exhibited an extremely low onset potential of 0.6 V vs reversible hydrogen electrode (RHE). The Si NW/TiO2/In2O3 (2.47 nm) photoanode also showed a high photocurrent density of 27 mA cm-2 at 1.23 V vs RHE, more than 1 order of magnitude higher than that of the Si NW/TiO2 photoanodes. This improvement in solar water splitting performance was attributed to the significantly promoted charge injection efficiency as a result of the In2O3 nanosheet coupling. This work presents a promising pathway for developing efficient Si-based photoanodes by coupling ultrathin 2D cocatalysts.

Al-Ti-C master alloy agent is currently the most promising grain refiner. This work investigates the influence of Ti3AlC2 addition (1.0–3.0 wt.%) on the microstructure of a hypoeutectic cast iron (4.7 wt.% Cr, 2.3 wt.% C). Microstructures of the samples were examined by SEM (scanning electron microscope). It was demonstrated that the added Ti3AlC2 did reduce the size of coarse primary carbides. The XRD (X-ray diffraction) pattern shows that Ti3AlC2 is decomposed into TiC in the alloy substrate. The EDS (energy dispersive spectrometer) interfacial element analysis shows that TiC combines well with the matrix interface. As the Ti3AlC2 amount was increased, the finest microstructure was achieved. When 2 wt.% Ti3AlC2 was added, the wear-resistance property of the material improved and became two times harder than the former. However, when 3% Ti3AlC2 was added, TiC gathered at the crystal boundary, which caused a decrease in the wear resistance of the material.

Semisolid rheological technology is an advanced casting process that can significantly refine the microstructure and improve the mechanical properties. However, the influences of fluid flow, solidification shrinkage and effective specific pressure on feeding distance during the semisolid forming process have not been investigated quantitatively. In this work, the one-dimensional (1D) model of limit feeding distance was developed for heterogeneous alloy melt with complex structures, and this alloy melt consisted of three phases including pure liquid phase, pure solid phase, and semisolid phase with the solid–liquid coexistence during pressurized rheoforming. The 1D model of limit feeding distance was derived from the semisolid rheological theory, and built on the basis of rheological feeding mechanism that the excess driving pressure caused sustained rheological feeding of alloy melts. Furthermore, the model covered three kinds of significant parameters including material property parameters, mold structure parameters and process parameters, so that it can be used to analyze the influence of various factors on the rheological feeding ability. In order to verify the theoretical model, the spiral samples of 6066 alloy were made at different velocities by squeeze casting. Moreover, the validity of theoretical model was verified through comparison of the numerical results and the length of samples without shrinkage porosity. The results showed that maximum relative deviation was only 6.8%. In addition, the effects of filling velocity, applied pressure, and the feeding channel initial diameter on the feeding distance were also discussed.

It is still highly desired to develop efficient, resource-abundant and inexpensive electrocatalysts to improve the sluggish kinetics of oxygen evolution reaction (OER) in electrochemical water splitting systems. In this work, the large-area ultrathin (2.52 nm thick) Ce-doped La

Vertical Si nanowire (NW) arrays are a promising photoanode material in the photoelectrochemical (PEC) water splitting field because of their highly efficient light absorption capability and large surface areas for PEC reactions. However, Si NW arrays always suffer from high overpotential, low photocurrent density, and low applied bias photon-to-current efficiency (ABPE) due to their low surface catalytic activity and intense charge recombination. Here, we report an efficient oxygen evolution cocatalyst of optically transparent, mesoporous ultrathin (2.47 nm thick) In

The edge sites of MoS

In squeeze casting process, the essence of mold-filling and feeding is rheological solidification of the alloy melt under pressure. Microstructure evolution is inevitable in this process, which affects the mold-filling and feeding in turn. In this work, the Archimedes spiral sample prepared by indirect squeeze casting was applied to investigate the microstructure evolution during the rheological process under pressure. The results showed that the primary α-Al phase was transformed from fine rosette-like or granular structure to coarse platelet-like structure with the increase of spiral length. However, the primary α-Al grain size of the starting point had a slight growing trend compared with that at the position of 140 mm away from the starting point. The volume fraction of the primary α-Al phase increased from 45.57% to 70.35% along the spiral length direction, demonstrating that the experimental pressure improved the rheological ability of the alloy melt to some extent. Furthermore, the eutectic Si phase was varied from a fine granular or wormlike structure to a coarse platelet-like or needle-like structure, and the dispersion of eutectic Si particles was also varied along the spiral length direction. This microstructure evolution was mainly owing to the comprehensive action of rheological solidification and pressurized solidification. More specifically, the microstructure evolution strongly depended on the pressure and rheological velocity during the rheological process, however, the effect of rheological distance was relatively small.

A high chromium cast iron (HCCI) matrix composite reinforced with zirconia-toughened alumina (ZTA) particles was fabricated via rapid–flow mixing followed by high–pressure compositing (FM-PC) technique, which required neither particle coating nor the use of preforms. The microstructure, mechanical properties and impact-abrasion wear resistance of the composite were investigated. The integrity of the composite without obvious defects was demonstrated, a uniform distribution of ZTA particles in the HCCI matrix and a tight mechanically bonded interface between particles and matrix were obtained. The composite exhibited better wear performance than HCCI under different energies, and the relative wear resistance was 2.35 to 1.74 times when the impact energy varied from 1.5 to 4.5 J. The wear mechanisms of the composite were mainly furrow, cutting and fragmentation of reinforced particles under a low impact energy (1.5 J). Conversely, when the impact energy increased to a high value (4.5 J), fragmentation and shedding of the particles, spalling pits and embedding of abrasive particles dominated the wear process.

Particle reinforced metal matrix composites have many problems such as complicated preparation process, high production costs, weak interface bonding between the ceramic and metal matrix, uneven distribution of ceramic particles and so on. To solve these problems, the method of "shoot mixing + pressure compositing" (SM-PC) and a mixed regulation model of ceramic particles with molten steel were proposed. In the shoot mixing process, the special designed die casting equipment was used to make the particles with the molten metal mixed in the runner at a certain ejection speed (150 mm·s-1). After the mixture is filled with the mold, the pressure is maintained until the end of solidification. In order to optimize this method to obtain the more uniform particle distribution, the parameters (ejection speed, preheating temperature of particles, the shape and size of runner) in the model were selected for sample preparation. Taking the distribution index of particles as the evaluation criterion, it is concluded that the uniform distribution of particles can be promoted with the increase of ejection velocity, the increase of particle preheating temperature, and the small change of gate size. When the preheating temperature of particles was 1,100 °C, and the shape of the runner was trumpet, the optimal particle distribution composite parts was obtained. Meanwhile, the particles and the matrix achieved strong interface bonding - "Class I interface " under the pressure compositing, even though they're non-wetting.

It is still highly desired to develop efficient, resource-abundant and inexpensive electrocatalysts to improve the sluggish kinetics of oxygen evolution reaction (OER) in electrochemical water splitting systems. In this work, the large-area ultrathin (2.52 nm thick) Ce-doped La2O3 nanofilms were developed via a facile and reliable ionic layer epitaxy method with different Ce content. The ultrathin Ce-doped La2O3 nanofilm with optimum composition of La1.22Ce0.78O3 exhibited an excellent OER performance with a very low overpotential of 221 mV at 10 mA cm−2 and a small Tafel slope of 33.7 mV dec−1. A remarkable high mass activity of 6263.2 A g−1 was also obtained from ultrathin La1.22Ce0.78O3 nanofilm at the overpotential of 221 mV. Such a high mass activity was three orders of magnitude higher than state-of-the-art commercial IrO2 powders (3.8 A g−1) and more than 30 times higher than La2O3 nanofilm (196.7 A g−1) without Ce doping at the same overpotential. This high mass activity was even significantly higher than other recently reported typical OER catalysts. The substantial OER performance gain by the Ce doping was attributed to the improved conductivity and electrochemical active surface areas of nanofilms as a result of favorable tuning on the charge transfer and electronic structures. This work provides a promising approach to develop high-performance two-dimensional (2D) electrocatalysts by effective heteroatom doping strategy.

There were some errors in Tables 1, 2 and 3, and in Figure 9b in the initial online publication. The original article has been corrected.

The hollow structure commonly used in aerospace field is generally formed by the SPF/DB, but its disadvantages lead to surface groove and complex internal structure difficult to form. In this paper, the method of milling combined with diffusion bonding is used to improve the defect. Diffusion bonding of TC4 titanium alloy hollow structure was carried out at temperature ranging from 800 °C to 900 °C for 10 ~ 30 min. The interfacial bonding ratio, deformation ratio, microstructures, microhardness and mechanical properties of the diffusion bonded joints were investigated. The results show that joints with high bonding quality can be obtained when bonded at 850 °C and 900 °C for 20 ~ 30 min. The joint bonding ratio is more than 92%, the tensile strength is 952 MPa, and the deformation ratio is maintained at about 10%. The microhardness of the TC4 alloy hollow structural joint increases with the increase in bonding temperature, showing a trend of "high in the middle and low on both sides", and it has a peak value (HV472) when bonding time is prolonged up to 30 min. The findings indicate that qualified workpiece can be obtained by the process.

An electron water calorimeter is described and is used to experimentally determine beam quality dependent conversion factors, kQ, for two ionization chamber types in high-energy electron beams. The current water calorimeter was upgraded to obtain reproducible measurements in electron beams from 10 MeV to 22 MeV (corresponding beam quality index R50 ranging over 4.20–8.97 g cm−2). Measurements of radiation induced temperature rise are made using a plane-parallel glass vessel with calibrated thermistor probes in a 4 °C water phantom. Three types of plane-parallel chambers (PTW Roos, IBA PPC40 and SNC 1045) and two types of cylindrical chambers (PTW30013 and IBA FC65-G) are measured to directly derive beam quality correction factors in the same water phantom. Relative combined standard uncertainty for kQ factors of 0.56% for 10 MeV beams and above were achieved. General agreement is obtained between the relative electron energy dependencies of the kQ factors measured in this work and those derived from TRS-398 of the IAEA and recent other experimental investigations. Furthermore, the experimental kQ values obtained here will impact future updates of reference dosimetry protocols, and the current standard uncertainties in electron reference dosimetry can be reduced by the method proposed in this work.

A ZrO2-toughened Al2O3 (ZTA) particle-reinforced high chromium cast iron (HCCI) composite was prepared by pressure bonding following flow mixing (PB-FM). Its microstructure, mechanical properties, and impact abrasive wear behavior were investigated and compared with a similar commercially available composite (Xwin® composite), which is prepared by infiltration casting. The PB-FM composite exhibited better wear performances under high impact energies. The wear mechanisms of the investigated composites at low impact energies were mainly ploughing and cutting of the matrix and slight breaking of the reinforcements, whereas at high impact energies, they were dominated by the breaking and detachment of the reinforced particles, embedded abrasives, and spalling pits.

In this paper, a two-step method, rapid-flow mixing followed by high-pressure compositing was used to prepare a macro-ZTA (ZrO2-toughened Al2O3) particles reinforced high chromium cast iron (HCCI) matrix composite. The method is based on the squeeze casting process without general casting pollution problems. The microstructure, mechanical properties and dry sliding wear performance of the fabricated composite were investigated. The results showed that the particles were distributed uniformly throughout the iron matrix and a tightly bonded interface was obtained. Under dry sliding wear conditions, the wear resistance of the composite was significantly improved in comparison with the HCCI alloy, and the relative wear resistance was 1.8 and 2.9 times at the applied load of 300 and 900 N, respectively. When the load increased from 300 N to 900 N, the wear characteristics of the composite changed from shallow and narrow grooves and scratches to damages in the form of fragmentation of particles, transfer layer and interface cracking.

The microstructure and mechanical properties of nodular cast iron produced by the melted metal die forging process (MMDF for short) were experimentally researched. The main obtained results are: the nodular cast iron produced by this process can be machined as easy as traditional one only if holding at the remained temperature for 4 h; its strength and plasticity are obviously higher than those of traditional ones; the graphite size arrived at grade 8, and the graphite spheroidizing arrived at grade 1 or 2, but a streamline molded distribution of the graphite slightly appeared. Both of the strength and plasticity increased with the pressure when the pressure holding time was larger than its critical value. A new way to produce high properties nodular cast iron was provided.

A traditional semisolid processing based on the rheological properties of semisolid alloy is very difficult in manufacturing the semisolid slurry because of the chase for spherical, fine and high solid fraction of the primary solid in the slurry. Through many experiments, it is found that it is not very necessary to excessively emphasize the glomeration and high solid fraction considering of the facts that the rheological properties of the semisolid slurry is controlled by not only the microstructure of the primary solid but also the rheological conditions. The manufacturing slurry can be simply regarded as preparing the semisolid alloy melt, therefore, a modified semisolid processing technology is presented. Its procedure consists of three basic steps, such as preparing slurry, filling mould cavity and solidification with pressure. The basic aim of the preparing slurry is to obtain the slurry containing 5%-20% (volume fraction) primary solid with particle or stick instead of spherical morphology. The experiment results show that, with the modified rheological processing technology, many steel and nonferrous alloy products are industrially produced.

To evaluate the flow stress of the twin-roll casting magnesium sheet in high temperature forming processes, a new analytical model was proposed by analyzing stress-strain curves measured under various temperatures and strain rates. The model can be parameterized to reflect the volume fraction of semi-sold grain and sold grains undergoing twinning. By applying the new model, the result showed that the simulated stress-strain curves fit the experiment data very well. Such curve fitting can be employed for any magnesium sheet when the deformation conditions are known. Microstructure evolution indicated that it affected the stress-strain curves directly. The mechanisms of dynamic recrystallization (DRX) depended on the operating deformation mechanisms, which changed with temperatures. And the volume fraction and grain size of DRX changed with the Zener-Hollomon parameter and temperatures.

High temperature tensile properties and microstructure evolutions of twin-roll-cast AZ31B magnesium alloy were investigated over a strain rate range from 10−3 to 1 s−1. It is suggested that the dominant deformation mechanism in the lower strain rate regimes is dislocation creep controlled by grain boundary diffusion at lower temperature and by lattice diffusion at higher temperatures, respectively. Furthermore, dislocation glide and twinning are dominant deformation mechanisms at higher strain-rate. The processing map, the effective diffusion coefficient and activation energy map of the alloy were established. The relations of microstructure evolutions to the transition temperature of dominant diffusion process, the activation energy platform and the occurrence of the full dynamic recrystallization with the maximum peak efficiency were analyzed. It is revealed that the optimum conditions for thermo-mechanical processing of the alloy are at a temperature range from 553 to 593 K, and a strain rate range from 7×10−3 to 2×10−3 s−1.

On the basis of the analysis of solidification interval and temperature distribution of components manufactured by the squeeze casting method, formulas for calculating the solidification interval and compaction pressure were deduced according to the principal request that the compaction pressure should be equal to or greater than the plastic deformation resistance of the forming component when solidification ended. The solidification interval was proven to be associated with many factors, such as weight of the component, specific heat of the alloy, latent heat, pouring temperature, component temperature at the end of solidification and heat-transfer coefficients. The compaction pressure was related to the strain rate, deformation temperature, and dimension of the deforming component. The solidification interval and compaction pressure calculated by the formulas deduced in this article were adopted in the production of 45 steel bidirectional chapiter valves, and components with excellent performance were manufactured.

The mold-filling ability of alloy melt in squeeze casting process was evaluated by means of the maximum length of Archimedes spiral line. A theoretical evaluating model to predict the maximum filling length was built based on the flowing theory of the incompressible viscous fluid. It was proved by experiments and calculations that the mold-filling pressure and velocity are prominent influencing factors on the mold-filling ability of alloy melt. The mold-filling ability increases with the increase of the mold-filling pressure and the decrease of the proper mold-filling velocity. Moreover, the pouring temperature relatively has less effect on the mold-filling ability under the experimental conditions. The maximum deviation of theoretical calculating values with experimental results is less than 15%. The model can quantitatively estimate the effect of every factor on the mold-filling ability.

Zirconia toughened alumina (ZTA) particles reinforced high chromium cast iron composites (ZTA/Iron composites) were prepared by a two-step processing method, i.e. mixing particles by the molten metal and cohering by high pressure, which based on the squeeze casting process. The impact wear resistance under different impact energies were investigated using dynamically loaded abrasive wear tester at room temperature. For comparison, the wear tests of high chromium cast iron were also carried out under the same conditions. Worn surfaces of the samples were observed under scanning electron microscopy equipped with an energy dispersive detector. The results showed that the composites have better impact wear resistance than that of high Cr cast iron regardless of impact energy level, and the wear resistance of the two materials all decrease with the increase of the impact energy. The main wear mechanisms of the high Cr cast iron were micro-cutting and fatigue peeling, while the wear of composites occurred through micro-cutting of the matrix (lower impact energy) and breaking and shedding of the reinforced particles (higher impact energy).

Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated. M2 cast ingots of non-dendritic primary austenite and fine eutectic ledeburite network carbide structure were obtained, with the casting temperature, slope length and angle of 1480 °C, 500 mm and 60° respectively. Meanwhile, the microstructure of cast samples was quantitatively assessed by Image tool software. Results show that optimum mean equivalent diameter of primary austenite crystal grain is 50.8 µm, shape factor is 0.83, and mean thickness of network carbide is 5.21 µm.

A new equation of load curve of critical wrinkles variable blank holder force (VBHF) during the warm deep-drawing of twin-roll cast Mg sheets was derived, which based on correlative energy conservation theorem. Experiments of limited drawing ratio (LDR) suggested that calculated load curve of minimum wrinkles using the new formulas fit to the tested data very well. The LDR was improved from 1.75 to 1.92 by using a new three segments way of load VBHF applied in the warm deep-drawing, at the forming temperature of 523 K and punch velocity of 45 mm/min. Finally, the VBHF warm deep-drawing process is also simulated by the finite element method, and a new technique of variable punch velocity (VPV) is applied in the simulation. The simulation indicated that the VPV technology can improve the LDR from 1.86 to 2.26 and gain the whole cylinder part, at the forming temperature of 523 K, when the punch velocity varied gradually from 30 to 5 mm/s.

This paper described a novel method to fabricate aluminum foam precursor. High viscosity character of semi-solid melt as well as stirring technique were used in this method, the blowing agents were homogeneously distributed without adding thicken additions, aluminum foam precursor embedded with distributed blowing agents were fabricated directly and efficiently through this method. This paper investigated the effects of main parameters in the fabricating process such as solid phase fraction, stirring speed, stirring time and stirring blade angle. And it was proved that when solid fraction was lower than 30%, the distribution effects would increase with stirring time and speed. The great amounts of aluminum solid-phases in the semi-solid melt would not lead to more nucleation and harmful initial gas bubbles. The growing behavior of initial gas bubbles in semi-solid melt was closely related to the melt temperature and cluster size of blowing agents. Lower temperature and smaller size of blowing agent cluster were the key factors to better precursors. The distribution behavior would be affected by the melt viscosity and stirring speed. The useful lag in melt transportation would perform greater with increase of the viscosity and would be weaken when the stirring speed was too high.