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The silicon vertical multi-junction (VMJ) solar cell has low costs and low series resistance, thus it has a good potential in concentration photovoltaics. However, there were few discussions about the thermal and electrical performance of silicon VMJ cell under non-uniform illumination. In this work, the thermal performance of silicon VMJ cell under 1D non-uniform illumination of 500 suns was calculated using finite element method first, and then the electrical performance of the cell was calculated using SPICE software based on the thermal simulation results. It was found that the mean temperature of the cell increased with the degree of non-uniform illumination when the area ratio of the sink to the cell was 500X, and the mean temperature changed few when the area ratio was 2500X. The efficiency of the cell did not decrease with the increase of the degree of non-uniform illumination when the area ratio was 500X, and the efficiency increased with the degree of non-uniform illumination when the area ratio was 2500X. Thus, the silicon VMJ cell had better performance than silicon planar junction cell under 1D non-uniform illumination of 500 suns.

A theoretical investigation on the esterification mechanism of free fatty acid (FFA) in waste cooking oils (WCOs) has been carried out using DMol(3) module based on the density functional theory (DFT). Three potential pathways of FFA esterification reaction are designed to achieve the formation of fatty acid methyl ester (FAME), and calculated results show that the energy barrier can be efficiently reduced from 88.597kcal/mol to 15.318kcal/mol by acid catalyst. The molar enthalpy changes (ΔrHm°) of designed pathways are negative, indicating that FFA esterification reaction is an exothermic process. The obtained favorable energy pathway is: H(+) firstly activates FFA, then the intermediate combines with methanol to form a tetrahedral structure, and finally, producing FAME after removing a water molecule. The rate-determining step is the combination of the activated FFA with methanol, and the activation energy is about 11.513kcal/mol at 298.15K. Our results should provide basic and reliable theoretical data for further understanding the elimination mechanism of FFA over acid catalyst in the conversion of WCOs to biodiesel products.

MoO3 and MoO2 materials have been successfully synthesized by thermal decomposition of ammonium paramolybdate in air and a sealed quartz tube, respectively. The microstructure of as-synthesized MoO3 is composed of irregular lamellar plates with a plate thickness around 100 nm and MoO2 has the larger grain size with lamellar plates connected with each other. A maximum specific capacitance of 318 F/g at 0.5 A/g is obtained for MoO2 prepared in a closed environment. On the other hand, the sample MoO3 exhibits excellent rate capacity with specific capacitances of 218, 209, 196, 188, 176, and 160 F/g at current densities of 0.5, 1, 2, 3, 4, and 5 A/g, respectively. These results pave the way to consider MoO3 and MoO2 as prospective materials for energy-storage applications.

To get the atomic scale understanding of impurities induced intergranular embrittlement or enhancement and the control of these effects on austenitic stainless steels, behavior of impurities B and S at gamma-Fe grain boundary (GB) and effects of alloying elements (Cr, Ni, Mn, Co, Mo) additions on the cohesive properties of the gamma-Fe GB doped by impurities are investigated by performing density functional theory (DFT) calculations. The results showed that, as the GB enhancer and embrittler respectively, impurities B and S tend to stay at the interstitial sites of gamma-Fe GB, while alloying elements also can segregate at the GB studied. The presence of all the alloying elements considered can inhibit B GB segregation to some extent due to the higher segregation energies and can impair the enhancement effect of B on GB cohesion. However, these elements almost have no impact on GB segregation and embrittlement effect of S, except for Ni, Mn and Mo: Ni and Mo inhibit and improve S GB segregation, respectively; Mn and Mo strongly enhance and reduce S-induced GB embrittlement, respectively. Moreover, the remedial effect of (Cr + Ni), (Cr + Mn) on S-induced GB embrittlement is also discussed. Additional atomic structure and total valence charge density analysis demonstrated and explained our conclusions. (C) 2015 Elsevier B.V. All rights reserved.

The influences of current density and saccharin concentration on nanocrystalline nickel coatings synthesized by direct current electrodeposition were analyzed. Results show that in the current density range from 0.5 A/dm2 to 1.5 A/dm2, nanocrystalline nickel coatings with broad microhardness HV distribution from 4150 MPa to 6030 MPa can be synthesized by adjusting saccharin concentration. The preferred orientation in the deposits exists at 0.5 A/dm2, (111), (200) double orientation texture changes to a (200) orientation texture as saccharin concentration and (200) intensity increase. The internal stresses of the samples prepared at 0.5 A/dm2 decrease to nearly 0 MPa as saccharin concentration increases to 1.2 g/L. The results of DSC curves show that the grains start to grow until 600 °C and keep the thermal stability near to bulk nickel when grain sizes are in the range from 28 nm to 98 nm. However, when the grain size is 10 nm, the grains grow abnormally at 317 °C, and their thermal stability decrease sharply.

The adsorption, dissociation, and desorption of O 2 on Cu(111), Cu(110), and Cu(100) surfaces at different coverages were studied at the molecular level. The dissociation energies of O 2 molecules increase with the increase in coverage of adsorbed O 2 . The saturated coverage of O atoms from dissociation of O 2 molecules on Cu(111), Cu(110), and Cu(100) surfaces are 0.25, 0.75, and 0.375 ML, respectively. Based on the computed Gibbs free energies, the relationships between O atoms/O 2 molecules and temperature, as well as O 2 partial pressure, on these surfaces are established. Cu(111), Cu(110), and Cu(100) surfaces are covered by O atoms under ultra-high vacuum at 298 K, with O atom coverage of 0.25, 0.625, and 0.375 ML, respectively. Phase diagrams provide useful information on phase transition from Cu to Cu 2 O in terms of temperature and O 2 partial pressure. Results of this study may provide guidance in investigating the interaction between O 2 and transition metals.

In the present work, mesoporous silica films with hexagonally packed perpendicular nanochannels treated as a 2D photonic crystal in extreme ultraviolet (EUV) range are explored by combining theories and experiments. The simulation results show that this film structure exhibits high reflectivities in a wide band range from 5 nm to 11 nm and at broad incidences angle range. The better reflective properties can be ascribed to its excellent photonic crystal structure corresponding to short spectral region. Experimentally, highly ordered mesoporous silica films with vertical mesochannels were fabricated by electrochemically assisted self-assembly method. Moreover, the reflectances of the fabricated film at 5–11 nm region were also tested using synchrotron radiation, which can reach up to 80.4% at 2°from grazing incidence direction. Meanwhile, a relative high reflectance can be maintained at 5–11 nm at incidence angles of 2–7°. This research results offer a new strategy to developing a promising extreme ultraviolet optical film with high reflectance and broad band range.

Composite electrodes that possess both appropriate integration and reasonable structures are needed to provide eminent electrochemical performance in energy storage devices. At this work, an innovative electrode material with a composite structure of Ni3S2/NiV-LDH nanosheets fixed on the reduced graphene oxide/Ni Foam (rGO/NF) was fabricated by a convenient two-step hydrothermal process. The intriguing compositional/componental advantages significantly facilitate the efficient penetration of the electrolytes and increase active sites of redox reactions in energy storage application. The Ni3S2/NiV-LDH/rGO/NF electrode reaches a standout specific capacitance of 3004.3 F g−1 at a current density of 1 A g−1 and a superb cycle stability with 92.2% capacitance retention after 5000 cycles. Furthermore, an asymmetric supercapacitor (Ni3S2/NiV-LDH/rGO/NF//AC) was also assembled, achieving a high energy density of 59.4 Wh kg−1 at 852.3 W kg−1 and favourable cycle life, where 98.3% of the capacitance was retained after 8000 cycles. These consequences show that Ni3S2/NiV-LDH/rGO/NF composite is a potential electrode material in the future.

Mixed transition metal sulfides with high electrochemical activity and theoretical capacitance have been investigated as promising electroactive materials for energy-related applications. Herein, a series of Ni3S2/MnS (NMS) composites with different sulfurization times were directly grown on reduced graphene oxide (rGO)-coated Ni foam (NF) via a facile and cost-effective hydrothermal method (NMS/rGO). The time-dependent experiments show that the sulfurization time exhibits a pronounced influence on the morphologies and electrochemical properties of NMS/rGO composites. Remarkably, the optimum electrochemical performance was obtained in the composite when the sulfurization time is 3 h (NMS/rGO-3h). The NMS/rGO-3h electrode exhibits a high specific capacitance of 3374.6 F g−1 at a current density of 1 A g−1 along with an outstanding cycling stability of 90.7% at 10 A g−1 through 8000 successive cycles. Furthermore, an asymmetric supercapacitor composed of NMS/rGO-3h electrode as a positive electrode and nitrogen-rich rGO as a negative electrode was assembled, which provided a maximum energy density of 58.9 W h kg−1 at 852.3 W kg−1 and a suitable cycling performance of 99% over 8000 cycles. The superior electrochemical behavior of NMS/rGO composites indicates their potential utilization as electrodes for energy conversion and storage devices.

Rational design of structures and higher electrical conductivity are two crucial routes to improving the electrochemical performances of battery-supercapacitors (SCs). In this paper, we have successfully synthesized the three-dimensional (3D) manganese-molybdenum-sulfide (Mn–Mo–S) composites with the microsphere morphology on the reduced graphene oxide/Ni foam (rGO/NF) substrate through a facile two-step hydrothermal method. The effects of sulfurization time on the morphologies and electrochemical performances were clearly identified. Benefiting from the unique microsphere structure and their synergistic effects between the composites, the 3D composite battery-type electrode has a fast ion and electron transfer, the abundant active sites and superior conductivity. As a result, the composite employed for battery-supercapacitors delivers the excellent specific capacity of 1637.1 C g−1 at 1 A g−1 when the sulfurization time is 3 h (MMS/rGO/NF-3h), and as well as the advantageous 96.5% of the original capacity through 8000 cycles. In addition, a battery-supercapacitor hybrid (BSH) device based on the MMS/rGO/NF-3h (positive) and active carbon (negative) shows a remarkable energy density of 59.8 W h kg−1 at power density of 402.4 W kg−1. With such outstanding electrochemical performances, the MMS/rGO/NF-3h//AC BSH device holds great potential in developing high-energy storage applications.

Graphene and its derivatives have attained a considerable amount of popularity as effective reinforcements in the electrodeposited nickel (Ni) matrix composites for lubrication. However, the composites suffer from certain challenges, such as the agglomeration of graphene nanosheets in the electrodeposition process and the uncertain role of graphene on the friction reduction and wear resistance during sliding. By using a polyvinylpyrrolidone assisted reduction method to improve the dispersity of reduced graphene oxide (RGO) in the electrolyte, we prepare the bulk RGO/Ni composites with different RGO adding amount and perform a complete research on the tribological behaviours. Our work reveals that although an extremely low amount of RGO nanosheets (carbon content below 0.018%) have been incorporated into the Ni matrix, it induces significant grain refinement and friction reduction effects. Compared with the RGO-free Ni deposit, the friction coefficient and wear rate of the composite is reduced by 25.6% and 27.5%, respectively. The improved tribological properties are ascribed to the fine-grain strengthening effect and the formation of a continuous easy-shear nickel oxide film on the contact surface. This finding offers a new view on the wear mechanism of graphene/Ni composites with low graphene content, for which the fine-grain strengthening rather than the formation of carbon-rich transfer layer will dominate the lubricating and anti-wear performances.

The effect of Tungsten (W) on the precipitate evolution and mechanical properties of the alumina-forming austenitic stainless steels (AFAs) Fe-15Cr-25Ni-3Al-NbWCu during aging at 700 °C was systematically investigated. After aging at 700 °C, microstructural characterization revealed that both of the secondary NbC and L12-ordered Ni-Cu-Al phases were precipitated in the matrix of the two steels for strengthening alloys, but W-added AFA (AFA-W) steel exhibited a smaller average size of Ni-Cu-Al phase than AFA steel. In addition, most of the precipitates in AFA steels were δ-ferrite phase with prolonging the aging time, and few Fe2Nb-type Laves phases were observed in the 1000 h-aged AFA samples. However, the addition of W promoted the precipitation of Fe2W-type Laves phases and increased its volume fraction during the aging period. The continuity of δ-ferrite at the grain boundary of AFA-W steels was also interrupted by the co-precipitated Fe2W Laves phase and B2-NiAl phase, avoiding the formation of detrimental δ-ferrite network. Compared to AFA steels, AFA-W steels exhibited higher room temperature tensile properties at the same aging time, which may be caused by the strengthening effect of more dispersed Fe2W phases and smaller sizes of Ni-Al-Cu phases in the grain interiors. Meanwhile, the stress concentration on the triple junctions caused by δ-ferrite was decreased by Fe2W precipitates; thus, further resulting in an increased ductility compared to the AFA steels without W addition.

The hierarchical core-shell ZnCo2O4@Ni-Co-S nanosheets with microsphere structures for supercapacitors were prepared through a facile three-step method including hydrothermal reaction, subsequent annealing and electrodeposition process. The influences of deposition cycles on its structure and electrochemical performances were studied in detail. On account of a synergistic effect of the ZnCo2O4 and Ni-Co-S composite and its unique core-shell nanostructure, the as-prepared electrode reveals excellent supercapacitor properties. The ZnCo2O4@Ni-Co-S with 6 electrodeposition cycles (ZCO@NCS-6) shows high specific capacitance values of 1762.6 F g−1 at 1 A g−1, outstanding rate performance with 81.3% at 50 A g−1, and remarkable long-term stability of 18.6% capacity loss through 5000 cycles. Moreover, the asymmetric supercapacitor (ASC) device was further constructed by using of ZCO@NCS-6 and active carbon to evaluate the practical values of the fabricated composite materials. The assembled ASC device shows the maximum voltage window up to 1.7 V, high energy density of 37.1 W h kg−1 and the excellent cycling life-span (only 9.71% capacitance loss after 8000 cycles). All these results suggest that ZnCo2O4@Ni-Co-S could be the hopeful electrode materials for energy storage devices.

The development of bifunctional electrochemical active heterostructures for both hydrogen evolution reaction (HER) and supercapacitors provides the possibility to integrate energy conversion and storage into one single system. In this article, we have designed and investigated three-dimensional (3D) hybrid CoNiO2/CoO composites through simple hydrothermal and annealing processes, in which CoNiO2 nanowires layered on CoO nanowires arrays with distinctive hierarchically nanowires structure were supported on nickel foam. Specifically, the CoNiO2/CoO-140-400 composite (optimum experimental conditions: hydrothermal temperature 140 °C, annealing temperature 400 °C) can efficiently catalyse the HER in an alkaline electrolyte with a small overpotential of 70 mV at 10 mA cm−2 current density, and exhibit a beneficial kinetics and excellent long-term stability of 15 h without obvious fluctuations. Moreover, the material shows an areal capacitance of 5.37 F cm−2 at a current density of 1 mA cm−2, remarkable rate capability (83.9% capacity retention at 20 mA cm−2) and cycle stability (82.9% retention after 5000 cycles) for supercapacitor. This work reveals that the synergistic effects between CoNiO2 and CoO in CoNiO2/CoO-140-400 heterostructures are powerful for electrochemical property and provide a strategy to explore low cost and highly efficient electrocatalysts for the energy conversion and storage applications.

The addition of B can inhibit the precipitation of &sigma, phases at the grain boundary to improve the hot workability and corrosion resistance for super austenitic stainless steel with high Cr and Mo content. This study focused on the interaction between B and Mo at the Fe&ndash, Cr(111)/Cr2O3(0001) interface and its effect on interfacial adhesion by employing the first-principles method, especially the effect of B on the segregation behavior of Mo. The most stable O-terminated Fe/Cr2O3 interface was chosen as the basic configuration. The segregation energy and the work of separation were calculated for the metal/chromia interface with Fe&ndash, Cr as the substrate. It has been demonstrated that B can promote the diffusion of Mo atoms into the oxide layer to increase the content of Mo in the passive film. In addition, the interfacial adhesion is higher at the most segregated sites. However, it is more difficult for two or more Mo atoms than a single Mo atom to diffuse into the oxide part with the effect of B, indicating that B can only improve the Mo content of the passive film to a small extent. The electronic properties were also further discussed to analyze the interactions and the binding characters between doped atoms and their surrounding atoms and to explain the underlying reasons for the variation of interfacial adhesion.

This study investigated the potential effects of different alloying elements X (X=Fe, Ni, Mn, Co, Si, Nb, W, Cu, Ce, Y) in the Cr2O3 (0001) layers with water adsorption by using the first-principles method. For water adsorption, the most stable adsorption site was bridge site. By calculating the adsorption energy of the alloy element doped layer, the distances of top Cr and O layer and charge densities of Cr and O atoms, it is concluded that the vapor corrosion resistance of the oxide film was improved after doping with elements such as Fe, Ni, Mn, Co, Si, Cu, Ce and Y. In particular, the rare elements doped system can obviously enhance resistance to water vapor erosion. By adding YCo and YW, the oxidation film showed better corrosion resistance than single-element doping and CoW co-doping systems.

The density functional theory (DFT) has been employed to systematically investigate the successive adsorption performances of two NO molecules onto [FeO]1+-ZSM-5 surface and subsequent direct decomposition mechanisms by using cluster model in this paper. The adsorption results indicate that there are four stable adsorption configurations of the first NO molecule on [FeO]1+-ZSM-5, all of which are exothermic and strong chemisorption. Beginning with different adsorption configurations of first NO molecule on [FeO]1+-ZSM-5 followed by the adsorption of the second NO molecule, all four direct decomposition mechanisms are studied in which N2O molecule acts as the key reaction intermediate, N2 and O2 act as the target products. Based on thermodynamic analysis, η2-NO path that starts with adsorption of the first NO as O-down and follows the Eley-Rideal mechanism is proposed, in which ONNO species and N2O are the key catalytic intermediates. The full catalytic reaction is exothermic by 43.76 kcal/mol. The rate-determining step is the formation of N2(ads), i.e. N2O(ads) → N2(ads) + O(ads) and its barrier energy is 39.09 kcal/mol.

In this work, nickel-manganese metal oxide (NiMnOx) composites with different Ni to Mn molar ratios onto Ni foam (NF) were fabricated by one-pot hydrothermal method. The influence of Ni to Mn molar ratio on the electrochemical performance was investigated and the optimal value was determined to be 2/1 (Ni2Mn1Ox/NF). A Co(OH)2/Ni2Mn1Ox/NF nanocomposite with novel porous honeycomb network structure was designed by electrodeposition Co(OH)2 on the surface of Ni2Mn1Ox/NF. The specific capacity value of Co(OH)2/Ni2Mn1Ox/NF composite electrode material reaches 949.02 C g−1 at 1 A g−1, which is obviously superior to those of the Ni2Mn1Ox/NF electrode. A battery-supercapacitor hybrid (BSH) device was assembeld by developing Co(OH)2/Ni2Mn1Ox/NF with activated carbon (AC), which possesses a promising energy of 47.34 Wh kg−1 at 424.69 W kg−1 power density, cycling retention 100% even after 5000 cycles over a voltage window of up to 1.7 V. This approach generates a strategy to fabricate nanocomposite electrode materials and also provides a promising contender for battery-supercapacitor hybrid devices in energy storage.

The rational construction and synthesis of mixed composites made up of multiple components as electrode materials have shown great potential in battery-supercapacitors. Here, the hybrid structure of MnCo-layered double hydroxide onto reduced graphene oxide (MC-LDH/rGO) and NiCo2S4 (NCS) is prepared via a two-step method. The electrochemical performance of the composites were optimized systematically by the growth/deposition cycles of the NCS material. When the deposition cycle reaches 6 (MC-LDH/rGO@NCS-6), the prepared composite exhibits the superior electrochemical performance due to the compositional and structural advantages. The resulting MC-LDH/rGO@NCS-6 composite achieves an excellent specific capacity (1446.5C g−1 at 1 A g−1) and the outstanding cycling life (98% capacity retention after 5000 cycles at 10 A g−1). Besides, a battery-supercapacitor hybrid device based on MC-LDH/rGO@NCS-6 composite and active carbon electrode possesses a remarkable energy density of 55.8 Wh kg−1 at a power density of 856.2 W kg−1 and a better cycling performance (100% capacity retention after 6000 cycles at 10 A g−1), suggesting the promising candidates of MC-LDH/rGO@NCS composites for high-performance battery-supercapacitors.

Graphene with single vacancy (SV) defect is investigated as the electrode substrate for Li-S battery and its reactions towards lithium polysulfide (LiPS) molecules are investigated by DFT calculations. It is found that the presence of SV defect changes the local electronic structure of graphene and enhances the adsorption energy to Li2Sx (x = 1,2,4,8) molecule, especially for the insoluble final discharge product. When Li2S molecule approaches SV defected graphene, the S atom in Li2S directly connects to the C atom having unpaired electron in graphene. This unique S-C binding behavior is very seldom reported previously. Compared with other LiPSs, the adsorption height of Li2S on SV defected graphene is the lowest due to this strong S-C binding. At the same time, the interaction between SV defected graphene and Li2S2 molecule is also enhanced compared with pristine graphene due to the presence of unpaired electron, although the adsorption energy and adsorption height is smaller than that in the case of Li2S. Based on electronic structure analysis, covalent character bond is found between S and C atom because that the frontier orbitals of Li2S molecule and SV defected graphene have close energy and the symmetry also adapts. However, interaction between Li2S2 and SV defected graphene material is through a Li-C bond with ionic character, in which Li2S2 molecule act as an electron donor. The Li-C bond is also found when Li2S molecule is adsorbed on the pristine graphene. This work provides new insights to LiPS adsorption on carbon materials and gives inspiration to research on cathode of Li-S battery. Since it can work as the effective nucleation sites to enhance the affinity to Li2S, carbon materials with SV defect might be a good cathode substrate for Li-S battery to make Li2S particles deposit uniformly. Further theoretical and experimental research on the following growth of Li2S particle around the SV defect is still ongoing.

The present work reports on the hydrothermal conversion of Ni-Ti-O nanopores anodically grown on NiTi alloy into nanospindles and their cytocompatibility. The results show the amorphous nanopores can transform to anatase nanospindles with length concentrated at 70–110 nm and diameter at 16–24 nm upon hydrothermal treatment at 200 °C in pure water for 2 h. The nanospindles also can promote proliferation of bone marrow mesenchymal stem cells when compared with that of nanopores and bare NiTi alloy thus are promising as biomedical coatings of NiTi alloy.

Cu,N-TiO2 nanotube (Cu,N-TNT) is prepared through a novel magnetron sputtering and anodic oxidation method. Then the morphology, structure and physicochemical property of Cu,N-TNT was analyzed by XRD, SEM, TEM, EDX and UV-vis-DR. The results indicate that the evenly doped copper is beneficial to the transformation of the TNT from anatase to rutile and play a key role in the morphology of the Cu,N-TNT. The doped Cu and N in the TNT influence the growth orientation of the TiO2 crystals, which result in the lattice distortion and wider the interplanar spacing 60s-Cu,N-TNT has less band gap and stronger absorption intensity in visible region than other Cu,N-TNT samples, which make the combination rate of photogenerated electron and photogenerated hole decrease greatly, thus beneficial to its physicochemical property.

Precipitate phases often play an important role on the corrosion resistance of 2205 Duplex stainless steels (DSS). In the present paper, the microstructure and the corrosion resistance of the hot-rolled and cold-rolled 2205 steels aged for different times at 850 &deg, C was investigated through XRD, SEM, and potentiodynamic polarization. It was discovered that the Chi(&chi, ) phase and Sigm(&sigma, ) phase were precipitated in turn following the aging treatment of the hot-rolled and cold-rolled steels, but the precipitate amount in the cold-rolled samples was significantly higher when compared to the hot-rolled samples. The corrosion resistance of the solution-annealed cold-rolled samples was similar to the hot-rolled samples, but the corrosion resistance of the cold-rolled sample with precipitate was weaker when compared to the hot-rolled sample following aging treatment. Pitting preferentially initiates in the Cr-depleted region from the &sigma, phase in the aged hot-rolled 2205, becoming increasingly severe during aging for a long lime. Adversely, the initiation of pitting corrosion might occur at the phase boundary, defects, and martensite in the aged cold-rolled 2205. The &sigma, phase was further selectively dissolved through the electrochemical method to investigate the difference in microstructure and corrosion behavior of the hot-rolled and cold-rolled 2205 duplex stainless steels.

To reduce the precipitation of &sigma, phases and to improve the hot workability of S31254 steels, boron has been added into the composition of S31254 to a concentration of 40 ppm. The precipitation behavior was investigated before and after the addition of boron in different S31254 alloys during the compression deformation, and the nose temperature at 950 &deg, C and the phase dissolution temperature at 1074 &deg, C were selected as the measurement temperature. The result showed that more &sigma, phases were precipitated at the grain boundary of S31254 alloys, compared to the boron-added alloy. Meanwhile, the addition of 40 ppm boron into the alloys has obviously prevented the &sigma, phases from the austenitic matrix, and it takes longer time for the precipitation of &sigma, phase at 950 &deg, C. The specific influence factors of boron on the precipitation of &sigma, phases were also further discussed.

The precipitate phases often play an important influence on the corrosion resistance of 2205 Duplex stainless steel (DSS). In the presented paper, the microstructure and corrosion resistance in the hot-rolled and cold-rolled 2205 DSS aging for different time at 850 °C was investigated by XRD, SEM and potentiodynamic polarization. It has been found that the Chi(χ) phase and Sigm(σ) phase were precipitated in turn after aging treatment of hot-rolled and cold-rolled materials, but the precipitate amount in cold-rolled material is much more than that of hot-rolled samples. The corrosion resistance of the solution-annealed cold-rolled material is similar to the hot-rolled material, but the corrosion resistance of cold-rolled material with precipitate is weaker than that of hot-rolled material after aging treatment. Pitting initiates preferentially in the Cr-depleted region from σ phase in aged hot-rolled 2205, and severe selective corrosion occurs on sigma/ferrite interfaces aged for a long aged lime. However, the initiation of pitting corrosion may take place at the phase boundary, defect and martensite in the aged cold-rolled 2205. The σ phase is further selectively dissolved by electrochemical method to investigate the difference of microstructure and corrosion behavior in hot-rolled and cold-rolled 2205 duplex stainless steel.

Friction stir welding (FSW) was applied to a 2.4 mm thick high nitrogen nickel-free austenitic stainless steel plate using tungsten–rhenium (W–Re) tool. The high-quality weld was successfully produced at a tool rotational speed of 400 rpm and a traveling speed of 100 mm/min. The microstructure, mechanical and corrosion properties of the weld were studied. The nitrogen content of the weld was almost identical to that of base metal (BM). FSW refined grains in the stir zone (SZ) through dynamic recrystallization and led to increase in hardness and tensile strength within the SZ, while the ductility was slightly decreased. The failure of tensile specimens occurred in the BM. TEM results revealed precipitates of Cr23C6 of size ~1 μm in the SZ, although their content was small. The precipitation of Cr23C6 and increase in δ-ferrite in the SZ led to small decrease in both pitting and intergranular corrosion resistance. Keywords: Friction stir welding, High nitrogen austenitic stainless steel, Microstructure, Mechanical properties, Corrosion resistance

This study investigated the segregation behavior of alloying additives X (X = Si, Al, V, Ti, Mo, W, Nb, Y) on the Fe(1 1 1)/Cr2O3(0 0 0 1) interface as well as the effects of these additives on the interfacial adhesive strength by using the first-principles method. The results indicated that W, Mo, and Nb atoms were easily segregated at the Fe(1 1 1)/Cr2O3(0 0 0 1) interface, however, the introduction of them would weaken the adhesive strength of the interface through weak-electron effects. Moreover, Y, Al, Si, Ti, and V were difficult to segregate at the Fe(1 1 1)/Cr2O3(0 0 0 1) interface. Comparison of separation energies and interfacial structural properties suggested that introduction of Si and Al improved the adhesive strength of the Fe(1 1 1)/Cr2O3(0 0 0 1) interface through strong interactions between Si/Al and O. Thus, Si and Al improved the adhesion of surface oxide scales and enhanced oxidation resistance.

The problems of worldwide energy shortage and environment pollution are becoming more and more serious, thus lots of attention has been paid to renewable and sustainable energy. The development of photovoltaic technology was rapid in recent years as one of the promising renewable energy, the worldwide total amount of photovoltaic power plants had reached nearly 100 GW in 2012, and about 90% of the worldwide solar cells are crystalline silicon solar cells. But there is still a large gap between the electricity costs of photovoltaic and traditional fossil energy, lots of methods have been tried to decrease the costs. The efficiency of the cell could be increased by concentration, and parts of the solar cells are replaced by cheaper optical elements in concentration photovoltaic, thus the costs of photovoltaic could be decreased by concentration. The traditional solar cells used for concentration were III–V multi-junction solar cells, their costs were high although they had high efficiency, thus people tried to use cheaper silicon solar cells for concentration to decrease the costs further. In this work, six kinds of silicon solar cells with different structures used for concentration were summarized; the device structures, manufacturing processes and efficiencies of the cells were compared. The prospects of concentrator silicon solar cells were predicted, the Si HIT cell using back contact structure, the multi-junction cell containing Si back contact cell and the Si VMJ cell used with Ge and GaP VMJ cells were considered to have good potential in low, middle, high and very high concentration photovoltaic.

Ilmenite-type A TiO 3 ( A =Fe, Co, Ni) crystals have been investigated via Generalized Gradient Approximation (GGA) in the scheme of Revised Perdew-Burke-Ernzerhof (RPBE) using the first-principles method. The band structures, densities of states, bond orders and charge populations, optical properties including the dielectric function e ( ω ), absorption coefficient I ( ω ), refractive index n ( ω ), extinction coefficient k ( ω ), electron energy loss function L ( ω ) and reflectivity function R ( ω ), are calculated. The results show that the GGA-optimized geometries agree well with the experimental data. FeTiO 3 has a direct band gap, but both CoTiO 3 and NiTiO 3 exhibit indirect band gap. The analysis for densities of states and atomic charge populations exhibits that Ti O bonds possess the stronger covalent bonding strength than A O bonds. The calculated optical properties along [100], [010] and [001] as well as polycrystalline directions demonstrate the significant optical anisotropy parallel and perpendicular to c -axis for A TiO 3 . Finally, the origins of main peaks for optical spectra are presented based on electron transitions. Theoretical insights into the microscopic intrinsic properties of A TiO 3 should provide fundamental investigations for further understanding the Ilmenite A TiO 3 materials and improving their practical applications.

First-principles calculations were performed to study the structural, elastic, electronic properties and Debye temperature of D022-Ni3V under pressure. The obtained structural parameters are in accord with previous data. The calculated elastic constants manifest that Ni3V binary compound is mechanically stable. Using the Voigt–Reuss–Hill method, elastic properties such as bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio υ are calculated. And results indicate that pressure can improve the hardness of Ni3V compound. Moreover, the density of states as a function of pressure is analyzed, and Population analysis explain the improvement of hardness by pressure from the view of chemical bonds. The Debye temperature ΘD calculated from elastic constants goes up with the increasing pressure.

High active BN/CdS composite photocatalysts were prepared by the ball milling method. The prepared BN/CdS composites were characterized by the X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV–vis absorption spectra (UV–vis) and fluorescence emission spectra (PL). The effects of the loading amounts of BN and the ball milling time on the H2-evolution rate were investigated. The results indicated that the tight contact of CdS with h-BN can be achieved, and the photocatalytic activity of CdS could be improved substantially by coupling with a proper amount of milled h-BN. The optimal loading amount of h-BN was found to be 5 wt% and the milling time was 1 h. In the Pt/CdS/BN photocatalytic system, both the Pt as the electron acceptor and the BN as the hole transfer may cause the improvement of the CdS activity. The highest H2-evolution rate over the Pt/BN/CdS photocatalyst can reach as high as ∼17.563 mmol g−1 h−1.

The first-principles calculations were conducted to investigate the effect of Fe doping in different positions on the electronic structure, chemical bonds and dielectric properties of o-Mn7C3. In contrast with pure o-Mn7C3, the reduced density of states at the Fermi level and the increased peak separation between both sides of the Fermi level are observed in Fe-doped o-Mn7C3, suggesting that Fe doping enhances the covalency of CMn bonds and yet weakens the metallicity of o-Mn7C3. Moreover, Fe doping causes a red shift of the dielectric properties. In microwave field, the interband transition of 3d electrons is apt to take place.

Hierarchical mordenite with micropores and mesopores was one-pot synthesized through a soft-templating method using a special diquaternary ammonium-type surfactant as a mesoporogen. The obtained samples were characterized by XRD, N2 physisorption, SEM, TEM, TG-DTG, 27Al and 29Si NMR spectroscopy, and NH3-TPD techniques. The catalytic performance of the hierarchical mordenite compared to that of conventional mordenite and mesoporous AlMCM-41 material was evaluated in the benzylation of benzene with benzyl alcohol. The results show that the hierarchical mordenite is highly crystalline and possesses large mesopore volume and strong acidity. Moreover, the prepared hierarchical mordenite catalyst is high-efficiency for the conversion of benzyl alcohol into diphenylmethane due to the superior mass transfer ability and largely accessible acid sites. The apparent reaction rate constant for HMOR is 23 times that for CMOR and 8 times that for AlMCM-41. These results suggest that hierarchical zeolites with mesoporosity and strong acidity may be the ideal catalysts in reactions involving large molecules.

The rapidly solidified Ni41.98Mn42.97V2.08Sn12.97 ribbons are prepared by the melt-spinning technique. The microstructure, martensitic transformation (MT), and magnetocaloric effect of the ribbons are greatly affected by annealing treatment. The equiaxed crystallized grains with the relatively homogeneous size distribution are observed for these ribbons. After annealing, the grain size becomes obviously large, the lattice constants decreases, and the exchange bias effect gets improved. The MT temperatures increase obviously for the annealed ribbons. Large magnetic entropy change (ΔS) is obtained in the annealed Ni–Mn–V–Sn ribbons. The peak values of ΔS in the annealed ribbons are 41.6 and −2.3 J kg−1 K−1 in the vicinity of MT temperature and Curie temperature of austenite, respectively, for the field change of 30 kOe.

Hierarchical mesoporous zeolites with different levels of micro- and mesoporosity were prepared by dissolution and reassembling processes of MOR zeolite in the presence of mesoscale cationic surfactant cethyltrimethylammonium bromide. The obtained materials were characterized by X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, Fourier transform infrared, Nitrogen (N2) adsorption/desorption, Temperature programmed desorption of NH3 (NH3-TPD) and Nuclear magnetic resonance techniques. Moreover, these hierarchical zeolites were tested as hydrocarbon traps using toluene as probe molecule and the temperature programmed desorption method. The results showed that the amount of microstructure and mesostructure in the composite was able to be favorably tuned by varying dissolution time at the first stage. The hierarchical materials displayed remarkably high desorption temperature in toluene-TPD, which is an expected performance of hydrocarbon trap in automobile tailpipes. The effect is due to the easier transport of bulky molecules provided by mesopores and increasing the number of available active sites via a fragmentation of the microporous framework. Therefore, the synthesized composite molecular sieve may be a novel catalyst for hydrocarbon trap in automobile tailpipes.

With the help of first principles method based on density functional theory, the structural, elastic, electronic properties and Debye temperature of Ni 3 Mo binary compound under pressure are investigated. Our calculated structural parameters are in good agreement with experimental and previous theoretical results. The obtained elastic constants show that Ni 3 Mo compound is mechanically stable. Elastic properties such as bulk modulus B , shear modulus G , Young’s modulus E and Poisson’s ratio υ are calculated by the Voigt–Reuss–Hill method. The results of B/G under various pressures show that proper pressure can improve the ductility of Ni 3 Mo but excess pressure will make the ductility decrease. In addition, the density of states as a function of pressure is analyzed. The Debye temperature Θ D calculated from elastic constants increases along with the pressure.

The martensitic transformation (MT) and magnetic properties have been investigated in a series of Ni50−x Fe x Mn32Al18 ferromagnetic shape memory alloys. The substitution of Fe for Ni reduces the MT temperature of Ni–Fe–Mn–Al alloys effectively, and the magnetization of the austenite was significantly enhanced in these high-doped alloys. The Fe introduction converts antiferromagnetic austenite to ferrimagnetic state, and therefore, the unique MT occurs between ferrimagnetic and antiferromagnetic state in these alloys. The MT temperatures decreased by about 15 K under the magnetic field of 30 kOe for x = 8 alloy. The positive value of magnetic entropy change was determined to 3.35 J/kg K around the MT in the field change of 30 kOe for x = 6 alloy. These results suggest that Ni50−x Fe x Mn32Al18 alloys would be the promising candidates for magnetic multifunctional materials.

The effect of variation in Ni/Sn ratio on martensitic transformation (MT) and magnetic properties was investigated in high-Mn content Mn2Ni1.64−xSn0.36+x alloys. With the increase of Sn content, the MT temperature shifts substantially towards lower temperature, while the Curie temperature of austenite remains almost unchanged. The reverse MT temperature decreases from 268 to around 80 K for Mn2Ni1.64−xSn0.36+x alloys as x increases from 0.02 to 0.08. Under the low field of 1.2 T, the peak values of magnetic entropy changes are 9.8 J/kg K, 10.1 J/kg K, 10.3 J/kg K, and 6.1 J/kg K for x = 0.02, 0.04, 0.06, and 0.08, respectively. The abrupt changes in magnetization around MT temperatures and the field-induced metamagnetism should account for the large magnetic entropy changes. Incorporating the advantages of inexpensive and non-toxic raw materials, these high-Mn content alloys exhibit very promising prospects for the applications in magnetic refrigeration.

One-dimensional β-SiC nano-whiskers are synthesized from two-dimensional graphene by a facile catalyst-free carbothermal reaction. Comparing with closed or semi-closed carbon sources, the large exterior surface area and exposed rich edge render graphene an ideal carbon source for the scale-up production of carbide materials.

Ti/SnO 2 -Sb 2 O 4 -Pr 2 O 3 /PbO 2 anodes are prepared by electrodepositing method. The electrodes are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The degradation of phenol experiment and accelerated life test of the electrode are carried out. Futhermore, the formation energy, band structure and density of states (DOS) are calculated by first principles calculations. The results show that Pr doping can change the phase of SnO 2 and prevent the spread of the oxygen to the substrate, lower the interfacial resistance. The catalytic degradation of phenol rate is 58.3% when the doping ratio is 100:8. The service life of electrode reaches the maximum of 121 hours under a high current density of 4 A cm −2 in 1 mol L −1 of H 2 SO 4 solution at 60 °C when the doping ratio is 100:8. Moreover, at the same doping ratio, the formation energy and band gap reach the minimums of -15.59 eV and 0.656 eV respectively. The experiments are consistent well with the theories. Thus, we conclude that the praseodymium doped tin oxide electrode is one promising acid-proof anode.

The adsorption energies, geometric structures, electronic properties, work functions and surface dipole moments of monatomic Ag adsorption on the (2 × 2) BiOCl (0 0 1) surfaces, including the 1Cl-, BiO- and 2Cl-terminated BiOCl (0 0 1) surfaces, have been investigated using first-principles calculations based on density functional theory. The most energetically favorable adsorption configuration of single Ag atom is at the fourfold hollow site, with the minimum adsorption energies of −0.465, −2.954 and −8.080 eV for the 1Cl-, BiO- and 2Cl-terminated BiOCl (0 0 1) surfaces, respectively. The analysis results of electronic properties indicate that there are new intermediate energy states mainly contributed to Ag 4d and Cl 3p states for 2Cl-terminated (0 0 1) surface, and Ag 5s states for 1Cl- and BiO-terminations. In addition, Ag adsorption can induce the formation of surface dipole moment and change in work function by the interfacial charge transfer. Combined with the previously reported experiments, the charge transport mechanism and effective separation processes of photo-induced electron–hole pairs of Ag/BiOCl photocatalytic system are built up and discussed. More importantly, our calculated findings could afford the theoretical basic knowledge for further understanding the microscopic structures, electronic properties, and photocatalytic reaction mechanism of Ag/BiOCl photocatalyst, providing a new analysis calculation for potential application in the investigation on the Ag/BiOBr and Ag/BiOI as well as other noble metals/BiOCl catalytic systems.

The Ni43.3Mn31.5Fe11.7Al13.5 ribbon was obtained by melt-spinning method and the microstructure, magnetic and magnetoresistance properties of these ribbons were studied by scanning electron microscope and vibration sample magnetometer. The reverse martensitic transformation from the weak-magnetic martensite phase to the ferromagnetic austenite was confirmed in these ribbons. A moderate negative magnetoresistance in the magnetic field of 30 kOe was obtained around the martensitic transformation, which would mainly owing to the field-induced reverse martensitic transformation. Taking into account of various properties, the present Ni–Fe–Mn–Al ribbons provide an impetus for further research.

This study investigates the microstructure, mechanical properties, and corrosion resistance of a friction-stir-welded joint of the hyper duplex stainless steel SAF2707. Friction stir welding (FSW) is performed at a tool rotation rate of 400 rpm and a welding speed of 100 mm/min. The microstructure of the joints is examined using scanning electron microscopy and X-ray diffraction. Tensile test and fractography are subsequently employed to evaluate the mechanical properties of the joints. Results show that the grain size of the stir zone (SZ) is smaller than that of the base metal (BM). Electron back-scattered diffraction analysis reveals that fine-equiaxed grains form in the SZ because of the dynamic recrystallization during the FSW. These grains become increasingly pronounced in the austenite phase. The tensile specimens consistently fail in the BM, implying that the welded joint is an overmatch to the BM. Moreover, the welded joints consist of finer grains and thus display higher tensile strength than their BMs. Potentiodynamic polarization curves and impedance spectroscopy both demonstrate that the corrosion resistance of the SZ is superior to that of the base material.

Metallofullerenes of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 encapsulating mixed-metal nitride clusters were synthesized. Spectroscopic characterization of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 was employed to reveal their structural and vibrational properties. The structural properties of these species were analyzed by using theoretical calculations. The studies of Gdx Ho3-x N@C80 and Gdx Lu3-x N@C80 laid the foundations for these species to be used as multifunctional molecules.

The effects of Cu substitution on the phase transitions and magnetocaloric effect of Mn 50 Ni 40− x Cu x Sn 10 Heusler alloys were investigated. With the increase of Cu content, the martensitic transformation (MT) temperature shifts substantially towards lower temperature, while the Curie temperature of austenite remains almost unchanged. The reverse MT temperature decreases from 180 to 171 K for Mn 50 Ni 39 Cu 1 Sn 10 alloy as the magnetic field increases from 1 to 30 kOe. Under an applied magnetic field of 30 kOe, the maximum values of magnetic field induced entropy changes are 19.6, 28.9, and 14.2 J/kg K for x = 0, 1, and 2, respectively. The effective refrigerant capacities and hysteresis losses for these alloys were discussed in this paper.

During solid-phase decarburization, the changes of the electromagnetic properties can reflect the variation degree of material components. High-carbon ferrochrome powders (HCFCP) with addition of CaCO3 were decarburized in solid phase by microwave heating and the electromagnetic properties of the decarburized materials were investigated. With increasing in heating temperature from 1173 to 1473 K, the relative permittivity of the decarburized materials increases initially and then decreases, whereas the relative permeability exhibits an opposite change trend. As holding time ranges from 40 to 60 min at 1273 K, the relative permittivity and dielectric loss factor tend to decrease while the relative permeability and magnetic loss factor tend to increase, corresponding to the maximum mean velocity of decarburization. In microwave fields, electromagnetic properties of the decarburized materials principally vary with carbon content, C-vacancies and crystal structure, and their changes in turn affect the interaction of microwaves with the decarburized materials.

First-principles calculations have been carried out to investigate the structural stabilities, electronic structures and elastic properties of Mg17Al12, Al2Ca and Al4Sr phases. The optimized structural parameters are in good agreement with the experimental and other theoretical values. The calculated formation enthalpies and cohesive energies show that Al2Ca has the strongest alloying ability, and Al4Sr has the highest structural stability. The densities of states (DOS), Mulliken electronic populations, and electronic charge density difference are obtained to reveal the underlying mechanism of structural stability. The bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio are estimated from the calculated elastic constants. The mechanical properties of these phases are further analyzed and discussed. The Gibbs free energy and Debye temperature are also calculated and discussed.

To better understand the autoxidation mechanism of Cu-based catalysts, we studied the oxidation of Cu sheet exposed to ultrahigh vacuum and air at ambient temperature using X-ray photoelectron spectroscopy (XPS) and density functional theory. Six main stages of Cu autoxidation are revealed: (1) dissociative adsorption of O2, (2) coexistence of nondissociative and dissociative H2O adsorption, (3) diffusion of O and OH into Cu bulk, (4) formation of metastable Cu2O layer, (5) further oxidation and formation of metastable Cu(OH)2 and CuO layer, and (6) transformation phase of the metastable Cu(OH)2 to CuO. The formation of Cu(OH)2 depends on the relative humidity of air and the concentration of adsorbed OH of the Cu sheet. On the basis of these results, we propose that the preservation time of the Cu-based catalysts should be decreased or the catalysts should be preserved in a high vacuum and at low relative humidity. Considering the time of the sample preparation before ex situ XPS analysis and other surfac...

The aim of the present work was to evaluate initial secondary austenite phase microstructural changes (δ → γ′) in 2205 duplex stainless steel with N content of 0.36 wt% during hot tensile test. The results showed there is no secondary austenite microstructural change in zero deformation degree. The secondary austenite (γ2) phase transformation occurred only in the cooling process and under hot deformation condition. Initial secondary austenite (γ′) occurred within the ferrite matrix at the temperature range of 950–1150 °C. The precipitation of initial γ′ increased with the increase in aging time and deformation degree. With increasing time, a progressive transformation of initial γ′ to γ2 occurred. The orientation relationship between the initial γ′ phase and the δ matrix was different at varying high temperatures. A significant change in the hot deformation condition has been observed as a consequence of secondary austenite reformation. These results indicated the importance of control over the shape and volume fraction of secondary austenite phases on high nitrogen duplex stainless steels to improve hot ductility.

We theoretically analyze the improvement in light extraction efficiency (LEE) of GaN-based LEDs with transmission grating. Light propagation and extraction was simulated using the finite-difference time-domain (FDTD) method for conical, cylindrical, and hemispherical grating. The simulations show that the use of transmission grating leads to increase in the LEE of GaN-based LEDs. The enhancement in LEE is attributed to the decrease in the Fresnel reflection and the effective increase in the photon escape cone. The maximum LEE enhancement of 2.3 times was achieved by employing hemispherical grating. The directional emission pattern converged by employing conical grating.