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Graphene has attained a considerable amount of popularity as an attractive ultra-thin reinforcement for nickel (Ni) matrix composites in recent years. However, its excellent reinforcement efficiency is suffered from the agglomeration of graphene nanosheets in manufacturing process and the poor bonding strength of graphene with Ni matrix. To overcome these two problems, one of the efficient strategies is to in-situ grow graphene reinforcements on Ni particles for powder metallurgy. This work aims to synthesize uniform graphene@Ni composite particles by using polymethyl methacrylate (PMMA) as the solid sources for chemical vapor deposition (CVD) process. The results demonstrate that few-layer or multilayer graphene with different morphologies can be grown on the particles by controlling the PMMA content and annealed temperature, respectively. The optimum condition for the formation of high-quality few-layer graphene is 1.0 mg·ml−1 PMMA and 900 °C. A competition mechanism rises from the growth kinetic, and the spatial confinement effect has led to the formation of graphene with different microstructures and morphologies.

Using the first-principles methods, the effects of different alloying elements M (M = Fe, Ni, Mn, Si, Mo, Cu, Y) on Cr2O3 with Cl adsorption are studied. The results show that the layer distance of all doped models has been widened to different degrees with Cl adsorption. When Mo or Y is doped into the passive film, the difference of layer distance is reduced to a certain extent. The interaction between alloying elements and Cl is studied by calculating the adsorption height, bond population and electron density difference. The results show that Mo and Y can inhibit Cl erosion and improve the corrosion resistance of passive film. Furthermore, we investigate the CrMoFe and CrMoY co-doped system with Cl adsorption. The calculations point out that when Mo and Y are doped together in the passive film, the corrosion resistance of the system is more prominent than that of CrMo, CrY and CrMoFe co-doping systems.

Engineering multicomponent active materials as an advanced electrode with the rational designed core-shell structure is an effective way to enhance the electrochemical performances for supercapacitors. Herein, three-dimensional self-supported hierarchical CoMoO4@CoS core-shell heterostructures supported on reduced graphene oxide/Ni foam have been rationally designed and prepared via a facile approach. The unique structure and the synergistic effects between two different materials, as well as excellent electronic conductivity of the reduced graphene oxide, contribute to the increased electrochemically active site and enhanced capacitance. The core-shell CoMoO4@CoS composite displays the superior specific capacitance of 3380.3 F g−1 (1 A g−1) in the three-electrode system and 81.1% retention of the initial capacitance even after 6000 cycles. Moreover, an asymmetric device was successfully prepared using CoMoO4@CoS and activated carbon as positive/negative electrodes. It is worth mentioning that the device delivered the high energy density of 59.2 W h kg−1 at the power density of 799.8 W kg−1 and the excellent cycle performance (about 91.5% capacitance retention over 6000 cycles). These results indicate that the core-shell CoMoO4@CoS composites offers the novelty strategy for preparation of electrodes for energy conversion and storage devices.

The effects of B on microstructure, pitting and intergranular corrosion in solution-annealed S31254 super austenitic stainless steels were systemically investigated. After solid solution treatment at 1200 °C for different time, the precipitation and grain size of S31254 with and without B steels were analyzed. Addition of B to S31254 promotes the redissolution of detrimental sigma (σ) phases, and the optimum solid solution condition for B-containing S31254 is at 1200 °C for 2 h. The S31254 steels with B after solid solution treatment exhibited much better corrosion resistance than that without B, which is relative to the elimination of destructional σ precipitates and the decrease of chromium-depleted region near the grain boundary. Moreover, the passive films of samples with B have increased Cr2O3 and Mo-rich oxides, which may be responsible for the improvement of corrosion resistance.

Zintl phase compounds Ca9Zn4+xSb9 have promising thermoelectric properties due to their complex crystal structure and tunable interstitial Zn. In this work, we prepared nominal Ca9Zn4+xSb9 (x = 0.5...

The precipitation of the σ phase at the grain boundary (GB) has an important effect on the properties of super austenitic stainless steel. This study used density functional theory (DFT) calculations to assess the segregation of Mo and B atoms at the GB and their effects on GB strength. The results demonstrated that Mo and B atoms tend to converge to grain boundary positions and B atoms are easier to segregate than Mo atoms. In addition, B can restrain the segregation of Mo to grain boundary positions, making it difficult for the positions to form an σ phase. An analysis of the inhibitory effect of different contents of B on Mo indicated that higher B content is better for restraining Mo segregation to grain boundary sites. These results are beneficial for improving the shortcomings of super austenitic stainless steel. B can also increase the GB strength while inhibiting the segregation of Mo to grain boundary sites and a charge density analysis demonstrated the results.

Purpose The purpose of this study is to investigate the effect of iron content on the friction and wear performances of Cu–Fe-based friction materials under dry sliding friction and wear test condition. Design/methodology/approach Cu–Fe-based friction materials with different iron content were prepared by powder metallurgy route. The tribological properties of Cu–Fe-based friction materials against GCr15 steel balls were studied at different applied loads and sliding speeds. Meanwhile, microstructure and phases of Cu–Fe-based friction materials were investigated. Findings Cu–Fe-based friction materials with different iron content are suitable for specific applied load and sliding speed, respectively. Low iron content Cu–Fe-based friction material is suitable for a high load 60 N and low sliding speed 70 mm/min and high iron content Cu–Fe-based friction material will be more suitable for a high load 60 N and high sliding speed 150 mm/min. The abrasive wear is the main wear mechanism for two kinds of Cu–Fe-based friction materials. Originality/value The friction and wear properties of Cu–Fe-based friction materials with different iron content were determined at different applied loads and sliding speeds, providing a direction and theoretical basis for the future development of Cu–Fe-based friction materials.

High silica SSZ-13 zeolite was synthesized by an efficient and green steam-assisted crystallization (SAC) method under a low alkalinity and low organic templates amount system. The as-prepared samples were characterized by XRD, SEM, N2 adsorption–desorption, TG–DTG and NH3-TPD. The results showed that the SAC method can not only remarkably improve zeolite yield but also enhance the crystallization rate of SSZ-13 zeolite compare to conventional hydrothermal route. Meanwhile, it was also found that the various content of the organic structure directing agent (N,N,N-trimethyladamantammonium hydroxide, TMAdaOH) in the dry gel can adjust flexibly the crystal size, morphology and acidity of samples. The zeolite samples with smaller particles and more strong acidity amount were more likely obtained under the higher TMAdaOH/SiO2 ratio (0.2) condition. In addition, the catalytic evaluation in methanol-to-olefins (MTO) reaction showed that the high silica SSZ-13 catalysts synthesized by SAC method exhibited longer lifetime and comparative selectivity to ethylene and propene than those of the SSZ-13s obtained by conventional hydrothermal route. Thus, the SAC route is believed to be a competitive strategy to synthesize high silica SSZ-13 zeolites with improved MTO catalytic performance.

The transition metal oxides with multiple oxidation states and large electrical conductivity have been extensively studied in energy storage capacitors. Herein, the core-shell cobalt sulfide/manganese molybdate composites grown on reduced graphene oxide/Ni foam (CoS/MMO/rGO/NF) have been successfully prepared via hydrothermal and followed by electrodeposition methods. It is found that the deposition mass of CoS has a significant effect on the morphologies and electrochemical properties of CoS/MMO/rGO/NF electrodes. When the mass of CoS is 0.4 mg cm−2 (CoS-0.4/MMO/rGO/NF), the composite yields a remarkable specific capacitance of 3074.5 F g−1 (1 A g−1) and a good cycling performance of 87% through 5000 cycles. Moreover, an asymmetric device based on the CoS-0.4/MMO/rGO/NF composite shows a maximum energy density (50.3 W h kg−1 at 415.8 W kg−1) and a good long-term stability (retention 96% even after 8000 cycles). These characteristics of CoS-0.4/MMO/rGO/NF are mainly attributed to the high conductivity of reduced graphene oxide and the synergistic effects of MnMoO4 and CoS, as well as its unique morphology. These superior properties of CoS-0.4/MMO/rGO/NF demonstrate its potential application as electrode material in energy storage capacitors.

Graphene characterized with ultrahigh intrinsic strength and excellent electronic properties is an ideal material to reinforce metals without despairing their thermal and electrical properties. Here, the electronic and mechanical properties of graphene intercalated copper (graphene/Cu) composites are investigated using density functional theory calculations. Graphene/Cu systems present an excellent electrical conductivity and increasing Debye temperature from 335 K for pure Cu to over 535 K in regardless of stacking models. In addition to greatly enhanced Young's modulus (149%), shear modulus (156%) and bulk modulus (108%) compared to copper, the ultimate strength of graphene/Cu composites are enhanced by 174% and 162%, in x and y directions, respectively. The strengthening and toughening effects of graphene in the composites is originated from strain strengthening and load transfer, which is consistent with the experimental results. Based on this calculation, the strengthening mechanism can be understood, which explains many experimental observations and also provides us a guide to improve graphene/metal composites quality.

In this work, we focus on the magnetic properties and martensitic transformation behaviors in Ni40Mn44-xCoxAl16 (x = 5, 7) Heusler alloys. By partial substitution of Co for Mn, the martensitic transformation (MT) can be tuned in a wide temperature range and shifts to the higher temperature with the increase of Co content in these alloys. The reverse MT can be induced by magnetic field from the weak-magnetic martensite phase to ferromagnetic austenite phase in these alloys. The large magnetoresistance effect of −46.39% and −41.75% are acquired under 90 kOe for Ni40Co5Mn39Al16 and Ni40Co7Mn39Al16 alloys, respectively. The Ni40Mn44-xCoxAl16 alloys with large low-field magnetoresistance and low cost show promising applications for multifunctional materials.

SSZ-13 zeolite with a SiO2/Al2O3 ratio in the range of 26–183 was synthesized by adding zeolite L in the synthesis gel absent from additional aluminum source, and the effects of SiO2/Al2O3 and N,N,N-trimethyladamantammonium hydroxide (TMAdaOH)/SiO2 ratios on the crystallization were investigated. The crystallization mechanism was studied with X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy and 29Si and 27Al MAS NMR spectroscopy techniques. It is shown that the SiO2/Al2O3 and TMAdaOH/SiO2 ratios have a significant effect on the acidity, and thus, the methanol-to-olefins (MTO) performance of SSZ-13. The co-presence of TMAdaOH, NaOH and extra silica source (SiO2) is necessary for formation of SSZ-13. The crystallization of SSZ-13 occurs by decomposing structure of zeolite L into double six- and four-membered rings that subsequently restructure into CHA topology under the direction of TMAdaOH, and further induce the nucleation and crystal growth. It is noteworthy that the Al species in zeolite L directly transform into those of SSZ-13 without forming monomeric species. The prepared SSZ-13 shows higher catalytic stability and selectivity to ethylene and proplyene than the conventionally synthesized sample from amorphous aluminosilicate gel in MTO reaction.

The corrosion behavior of Ti62Zr12V13Cu4Be9 metallic glass matrix composites (MGMCs) in chloride-containing (NaCl and HCl) and chloride-free (NaOH and H2SO4) solutions was studied. As a result, Ti62Zr12V13Cu4Be9 MGMCs exhibits better corrosion resistance in chloride-free solutions due to the formation of oxide layer. In comparison, the oxide layer formed in NaOH solution is superior to that formed in H2SO4 solution according to the analysis results of XPS and EIS. The irregularity of elemental and phase distribution in this Ti-based MGMCs material is considered the driving force of the corrosion process. With the inclusion of other factors such as the different pH values and the cathodic reaction, rather reasonable interpretation about the difference of corrosion behaviors of Ti-based MGMCs samples in various media is proposed.

Effects of compression deformation on the sigma-phase precipitation behavior of B-containing S31254 stainless steel after solution treatment were studied using the Gleeble compression test. The cold and hot processing characteristics of B-containing S31254 stainless steel were evaluated, and the results show that the speed of compression deformation increased the precipitation rate of the sigma phase, and the location of precipitation extended from the austenite grain boundary to the original hot rolling deformation area. During cold deformation at room temperature, the precipitation rate increased when the deformation reached at 40%. Deformation at 950 °C affected precipitation more obviously. At 1074 °C, when the deformation reached 20%, the precipitated phases started increasing, and above this deformation range, precipitation began decreasing. Also, at 1074 °C, the deformation accelerated the precipitation of sigma phase; but with deformation, there was a change in critical temperature for the sigma-phase excursion. The precipitation position of the sigma phase is strongly related to the area of the original hot rolling deformation. With an increase in the deformation amount, precipitates in this region appeared as coarse-grained, skeletal, and network-like features.

Sanicro 25 austenitic heat-resistant steel is expected to be used in superheaters and reheaters for ultra-supercritical power plants above 600 &deg, C due to its excellent structural stability and high temperature mechanical properties. In this paper, the effects of Co and W on the structural stability, thermodynamic stability and mechanical properties of Sanicro 25 steel are analyzed by calculating the formation energy, binding energy, Gibbs free energy, elastic constant, Peierls stress and generalized stacking fault energy (GSFE) with first-principles calculation method. By calculating the formation energy, binding energy and Gibbs free energy, it concludes that alloying elements Co and W in Sanicro 25 steel can improve the structural stability and thermodynamic stability. It indicates that W and a small amount of Co can improve the plasticity and ductility of Sanicro 25 steel by calculating the bulk modulus (B), shear modulus (G), Young&rsquo, s modulus (E), the B/G ratio, Poisson&rsquo, s ratio and Peierls stress. It is found that when Co and W are far from the stacking fault region, it will promote the formation of partial dislocations and twins in the system, thereby improving its plastic deformation ability and mechanical properties.

2707 hyper-duplex stainless steels (HDSSs) contain high contents of alloying elements (Cr, Ni, Mo and N), which may shorten the incubation period and promote both nucleation and growth of sigma (σ) phase. 2707 HDSS was first aged at different temperatures and periods of time for drawing the time–temperature–transformation profiles. The results identified the main precipitates as σ phase, with nose temperature of about 950 °C. Also, 2707 specimen was aged at 950 °C for a short time, and the morphology, distribution and amount of σ phase were examined through the scanning electron microscope and X-ray diffraction. σ phase was initially formed at the boundaries of ferrite and austenite and then transformed through the eutectoid reaction (α → σ + γ2). Finally, the precipitation and growth of σ phase in 2707 steels aged at nose temperature for a short period reduced the corrosion resistance and deteriorated the mechanical properties, and the corresponding reason was further analyzed.

Photoelectric performance of (C, S) co-doped SnO2 was explored by an integrated strategy combining first principle calculation with experimental measurement. The exploration began with theoretical calculation upon geometry characteristic and electronic structure of pure and (C, S) co-doped SnO2, then follow by experimental measurement. Namely, pure and different ratios of (C, S) co-doped SnO2 were prepared and characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). And photoelectric performance of the prepared pure and (C, S) co-doped SnO2 electrodes was studied. Theoretical calculation result indicate that carbon and sulfur atom interact intensely to each other by lattice distortion. Fully filled energy levels are introduced to the top of the valence band, resulting effective reduction of band gap value and suppression of charged defects. Consequently, the photoelectric performance of SnO2 is improved. Double-hole-assisted coupling mechanism of dopants in SnO2 is interpreted to reveal the interaction of C and S. Besides, experimental results indicate that all samples are rutile phase with the dopants carbon and sulfur entered into SnO2 crystal by substituting oxygen. 5% co-doped sample shows the most homogeneous spherical shape and dispersed character, which is provided with the maximum photocurrent value (6.8 μA/cm2) and minimum electrochemical impedance. Theoretical calculation and experiment jointly indicate that (C, S) co-doped SnO2 possess superior photoelectric performance. The doping method of double-hole-assisted coupling may contribute to the design of highly active tin oxide-based photoelectric materials, and also pave the way for modification of other congener materials.

Herein, zinc cobalt layered double hydroxide (ZnCo-LDH) hybrid composites with different Zn/Co molar ratios are in-suit grown onto Ni foam by a simple and cost-effective hydrothermal approach. It is found that the Zn/Co molar ratios have an important influence on the morphology and electrochemical performance of the ZnCo-LDH composites. An interconnected nanowires structure and the highest specific capacitance were achieved when the Zn/Co molar ratio is 1: 2 (Zn1Co2-LDH).Moreover, interconnected Zn1Co2-LDH is further combined with reduced graphene oxide stuck onto Ni foam (Zn1Co2-LDH@rGO/NF) to improve its electrochemical properties. Benefiting from its unique structural feature and excellent electrical conductance ability, the as-prepared material exhibits an enhanced specific capacitance of 2142.0 F g−1 as supercapacitor electrode. Remarkably, the assembled asymmetric supercapacitor device based on Zn1Co2-LDH@rGO/NF and active carbon delivers a high specific capacitance (149.6 F g−1), high energy density (53.2 Wh kg−1), and excellent long cycling stability (90.9% capacitance retention after 6000 cycles at 3 A g−1), which holds huge potential for practical application in energy conversion and storage fields.

Ternary metal sulfides such as manganese-cobalt-sulfide (MCS) with the unique physical, chemical properties and high specific capacity can be used as energy storage material for supercapacitor. Herein, we prepared a MCS nanosheet array stick onto reduced graphene oxide (rGO)/Ni foam (MCS/rGO/NF) by a carefully controlled sulfurization time process. As the reaction time increased, the thickness of MCS/rGO/NF nanosheet arrays charged from thin to thick. After 3 h of sulfurization reaction (MCS/rGO/NF-3h), the nanosheets became rough due to the formation of some small sheets, and the composite showed the best electrochemical performance. The MCS/rGO/NF-3h composite exhibited a large specific capacity of 1356 C g−1 at a current density of 1 A g−1, and a long-term cyclic stability of 92.9% at a current density of 10 A g−1 through 3000 cycles. Moreover, a hybrid supercapacitor (HSC) device was assembled using MCS/rGO/NF-3h and rGO as the positive and negative electrodes, respectively. The MCS/rGO/NF-3h//rGO HSC exhibited a high energy density of 45.4 W h kg−1 at a power density of 850.2 W kg−1. The prominent electrochemical performance suggests that MCS/rGO/NF composites are promising electrode materials for energy storage applications.

The electronic structure of Sb-N co-doped SnO2 was explored by first principles calculation. The results show that Sb (donor) and N (acceptor) introduce new energy levels in the band gap, which reduce the band gap of SnO2 obviously. Besides, the carrier separation rate of the system is improved owing to the charge compensation effect of Sb and N. Consequently, the photoelectric performance of SnO2 is improved. Based on the results of theoretical calculation, the intrinsic and different ratios of Sb-N co-doped SnO2 were prepared by hydrothermal method. And the samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and x-ray photoelectron spectroscopy (XPS). The photoelectric performance of the prepared intrinsic and Sb-N co-doped SnO2 electrodes was studied. The results prove that all samples are rutile phase with the dopants Sb and N entered into SnO2 lattice by substituting Sn and O. Besides, the 5% co-doped sample has uniform spherical shape and dispersed character. The photoelectric performance tests indicate that photoelectric performance of SnO2 is enhanced by Sb-N co-doping. The maximum photocurrent value (9 μA/cm2) and minimum electrochemical impedance is achieved at the doping ratio of 5%. Theoretical calculation and experiment results indicate that Sb-N co-doped SnO2 possesses superior photoelectric performance.

High-quality amorphous NiO/C/carbon nanotubes (CNTs) composite with an irregular porous structure have been successfully synthesised by a one-step combustion process at 350°C for 2 h with a heating rate of 3°C/min in air. To fully understand the potential of NiO/C/CNTs, the phase composition, morphology and electrochemical properties of materials were investigated. Benefiting from the in situ formed carbon, the addition of the CNTs and the advantages of the porous structure, the materials have shown superior electrochemical properties for supercapacitors. The specific capacitance of the composite reaches up to 1618 F/g at a current density of 1 A/g. Furthermore, the NiO/C/CNTs||activate carbon asymmetric supercapacitor device demonstrates both a high energy density (25.9 Wh kg−1) and power density (5570 W kg−1), and delivers a better cycling stability (about 94%) after 7000 cycles, which is a potential material for further development of fabricating a supercapacitor electrode.

Nickel composites reinforced with reduced graphene oxide (rGO) nanosheets were fabricated by a direct current electrodeposition technique. The low volume fraction of graphene can promote the cathodic polarized potential, facilitate the transport of ions and electrons on electrodes, and provide a large number of nucleation sites, consequently accelerate the formation of heterogeneous microstructure features. The graphene/Ni composite with 2 mL graphene dispersions demonstrates a tensile strength of 864 MPa and a plastic elongation of 20.6%, which are 25% and 36% higher than that of the pure bulk Ni. The enhancements in strength and ductility of the composite can be ascribed to the bimodal microstructure, for which the fine grain population provides for enhanced strength, whereas the coarse grain population enhances ductility by enabling strain hardening. On the contrary, the positive role of rGO in microstructure control will be weakened due to the agglomeration of rGO sheets in a high-volume plating bath. The low adsorption quantity of rGO is unfavourable for the nucleation of Ni matrix, accordingly produces a uniform fine-grained microstructure. The tensile strength of the composite with 5 mL rGO is 750 MPa, whereas the fracture elongation is only 7.5%. It is believed that a proper addition of rGO dispersion makes a promising microstructure for advanced graphene/Ni composite.

A facile and cost-effective one-time solution combustion method is designed for the synthetic of CNTs/C/NiMoO4 and C/NiMoO4 porous composites at 300 °C for 0.5 h in the atmosphere. The characteristics of products are investigated by advanced physical property test and electrochemical analysis. The results reveal that the electrochemical performances of C/NiMoO4 composites are strongly influenced by the molar ratio of oxidizer to fuel and the largest specific capacitance of the optimized sample reaches 859 F g−1 at 1 A g−1. Moreover, the capacitance of CNTs/C/NiMoO4 composites has been further enhanced to 1037 F g−1 at 1 A g−1, in which added acid-treated CNTs into the precursor mixed solution in the combustion process. Furthermore, an asymmetric supercapacitor CNTs/C/NiMoO4||activated carbon (AC) is assembled, which the CNTs/C/NiMoO4 used as cathode and AC used as anode. Its energy density of 32.6 Wh kg−1 at power density of 150.5 W kg−1 and even retains 18.2 Wh kg−1 at 8509 W kg−1. This asymmetric device exhibits a well cycle stability, which the capacitance retain 96.5% after 1500 cycles. The excellent electrochemical behaviors indicate that CNTs/C/NiMoO4 composites have great potential for application in high capacity energy storage devices.

The electronic structures and conducting mechanism of (Mg, S) co-doped rutile SnO2 were explored through density functional theory (DFT) calculation. Results showed that the acceptor metal Mg assisted the coupling of the incorporated S with a neighbouring O in SnO2, which introduced new energy levels into the forbidden band of SnO2 and thereby improved the photoelectric performance of SnO2. Based on this result, we proposed an integrated strategy that combines DFT calculations with experiments to study the photoelectric performance of (Mg, S) co-doped SnO2 prepared through hydrothermal method. Conducting glass (FTO) was used for the preparation of (Mg, S) co-doped SnO2 electrode. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy results confirmed the incorporation of Mg and S elements into the SnO2 cell. Furthermore, photoelectric performance tests revealed that (Mg, S) co-doping can improve photoelectric performance. The maximum photocurrent (0.50 μA/cm2) and smallest impedance were obtained at a co-doping ratio of 5%. Therefore, the (Mg, S) co-doped SnO2 is a strong candidate for photoelectrocatalysis.

Designing a novel, efficient and cost-effective nanocomposite with the advantage of robust structure and outstanding conductivity is highly promising for the electrode materials of high-performance supercapacitors. Herein, we designed and synthesized a hierarchical structured NiMoO4@rGO/NF via a facile and scalable approach by growing NiMoO4 nanowires onto the skeleton of reduced graphene oxide (rGO)/Ni foam (NF). The as-made NiMoO4@rGO/NF exhibits a superior electrochemical behavior owing to the coupling effect of homogeneous NiMoO4 nanowires and high conductivity of rGO, and it exhibits a superb capacitance value of 1877 F g−1 at 1 A g−1 and shows a ultralong life span with over 98% capacitance retention after 4000 cycles at 5 A g−1 in 2 M KOH electrolyte. Moreover, an asymmetric device employing NiMoO4@rGO/NF composite and activated carbon is assembled with an aqueous electrolyte, and it displays a maximum energy density of 40 Wh kg−1 at a specific power 218.2 W kg−1. Interestingly, the asymmetric device can remain 111.2% of its initial value even after 8000 charge/discharge cycles. These results demonstrate that the NiMoO4@rGO/NF binder-free electrode provides greatly enhanced electrochemical performance and shows promising application as an anode for energy storage.

First-principles calculations have been carried out to investigate the effects of alloying elements (Zn, Li, Y and Sc) on the electronic structure, elastic and thermal properties of Mg solid solution. The calculated cohesive energies show that Mg-Sc has the highest structural stability. The calculations of the densities of states (DOS) and electronic charge density difference indicate that Mg-Y (Sc) alloys have very strong covalent bonding due to a very strong Mg p-Y(Sc) d hybridization. The bulk modulus B, shear modulus G, Young's modulus E and Poisson ratio ν are derived using Voigt-Reuss-Hill (VRH) approximation. The results show that all the alloys can exhibit ductile properties at 2.77 at% R, and Mg-Zn(Li) alloys have the better ductility and plasticity. In the end, the Debye temperature and isochoric heat capacity are also calculated and discussed.

To evaluate the suitability of HR3C and 22Cr–25Ni–2.5Al AFA steels as the heat-resistant alloys, the oxidation behavior of them was investigated in air at 700, 800, 900 and 1000 °C. The evolution of oxide layer on the surface and subsurface was investigated using a combination of compositional/elemental (SEM, EDS) and structural (XRD, GDOES) techniques. A dense and continuous Cr2O3 healing layer on the HR3C was formed at the temperature of 700 or 800 °C, but the Cr2O3 oxide film on HR3C was unstable and partly converted into a less protective MnCr2O4 with the increase in temperature to 900 or 1000 °C. The composition and structure of oxide film of 22Cr–25Ni–2.5Al AFA steels are significantly different to the HR3C alloys. The outer layer oxides transformed from Cr2O3 to Al-containing oxides, leading to a better oxidation resistance at 700 or 800 °C compared to HR3C. Further, the oxide films consist of internal Al2O3 and AlN underneath the outer loose layer after 22Cr–25Ni–2.5Al AFA oxidized at 900 or 1000 °C. It can be proved that the internal oxidation and nitrogen would make 22Cr–25Ni–2.5Al AFA steels have worse oxidation resistance than HR3C alloys at 900 or 1000 °C.

The tetragonal distortion, magnetic and electronic properties of full Heusler compounds Ni2XAl (X = Cr, Fe, Co) have been studied by first-principles calculations based on density functional theory. The obtained lattice parameters, magnetic moments and bulk modulus are well consistent with available data of references. The ferromagnetic Ni2XAl compounds are more favorable than non-magnetic compounds. The resistance to volume deformation increases as the order of Ni2CrAl

The adsorptions of fixed groups −COOH, −OH, −CN, −NH2 and −SH of dye molecules on three kinds of SnO2 (110) surfaces were systematically investigated by first principle calculations. It is found that the adsorptions of five fixed groups on three kinds of SnO2 (110) surfaces are chemical adsorption which includes both dissociative adsorption and non-dissociative adsorption. The most stable adsorption configuration of the five fixed groups on three kinds of SnO2 (110) surfaces is bidentate chelate adsorption configuration of COOH group on Pt-doped SnO2 (110) surface with adsorption energy of −3.265 eV. Thus, −COOH group is a promising fixed group of dye molecules for the preparation of dye-sensitized solar cells (DSSCS). At the same time, the Pt-doped SnO2 photo-anode shows optimal adsorption performance, which provides theoretical basis for the design and application of SnO2 dye-sensitized cells.

CO hydrogenation to higher alcohols (C 2 + OH) was examined in a slurry bed reactor. CuZnAl samples without promoters were prepared by a complete liquid-phase method at different pH value (pH = 7–10), with the aim of studying the influence of pH value on the catalytic performance in this catalytic reaction. The pH value had significantly influence on the Cu 0 crystallite size, the amount of reducible Cu + , surface Cu/Zn atomic ratios and the acidity, which led to the diverse activities toward C 2 + OH synthesis. Characterization results showed that relatively larger crystallite size of Cu 0 and a suitable amount of acid sites was beneficial to the formation of C 2 + OH. Activity results indicated that the sample prepared at pH = 8 exhibited the best catalytic performance compared with other samples. In addition, the catalytic performance of pH = 8 sample showed that increasing temperature favored to the formation of C 2 + OH.

This paper described a comprehensive DFT + U investigation on the general trends in structural stability, electronic and optical absorption properties, photocatalytic activity of BiOCl doped with 3d transition metals (TMs = Sc, V, Cr, Ti, Fe, Co, Ni, Cu, Zn). We find that it is rather difficult for Sc, V, Ti, Ni atoms to substitute Bi into BiOCl crystal lattice in experiments due to their positive formation energies, but the negative formation energies for Cr-, Mn-, Fe-, Co-, Ni-, Cu-, Zn-doped BiOCl systems exhibit the thermodynamic structure stability. Most of TMs doping could narrow the band gap of BiOCl and lead to the changes in conduction band minimum and valance band maximum as well as the formation of several impurity energy levels within the forbidden band of BiOCl, achieving the photoactivity improvement and simultaneously maintaining the stronger redox potential. With 3d TMs doping, the optical absorption intensity of BiOCl around 350 nm increased and exhibited a redshift to the different extents, in good agreement with reported experimental data. Our theoretical calculations should provide meaningful guidance for the experimentalists to design and develop more thermodynamically stable and highly effective visible light response photocatalysts.

The crystal structure, phase stability, mechanical and thermodynamic properties of the Al2Cu (θ), Al2Cu (θ′) and Al2Cu (Ω) phases are studied by the first-principles method. The predicted lattice constants are consistent with the available literature data. θ, θ′ and Ω phases are thermodynamically stable, and do not undergo any phase transition under pressure. The values of B for Ω are larger than that for θ and θ′ phases, while the values of G for θ are smaller than that for Ω and θ′ phases. The studies also reveal that pressure can improve the elastic anisotropy of the θ, θ′ and Ω phases. The Debye temperature, heat capacity and thermal expansion coefficient for the phases are determined by the quasi-harmonic Debye model. Under identical conditions, the values of ΘD from high to low is in the following order: θ′>Ω>θ. The heat capacity and thermal expansion coefficient for θ, θ′ and Ω phases decrease with pressure when the temperature is kept constant. In contrast, thermal expansion coefficient α is more sensitive to any changes in pressure than any temperature change in the temperature range, 300–800 K.

Three-dimensional hierarchical hybrid composites incorporating both CoAl-layered double hydroxide and Ni3S2 grown onto the framework of reduced graphene oxide (rGO) on Ni foam were successfully fabricated by hydrothermal procedure combined with electrodeposition method (Ni3S2/CoAl-LDH/rGO). The Ni3S2 nanoplates was anchored on the surface of the CoAl-LDH/rGO nanosheets, forming a cross linked core-shell structure. Electrochemical measurements demonstrate that the outer Ni3S2 layer can significantly influence the morphology and electrochemical properties of the hybrid electrodes. Benefiting from its attractive structural feature and strong synergy of multiple components, excellent results were obtained in the composite with the optimal mass loading of Ni3S2 layer, which exhibited an excellent specific capacitance of 2457.5 F g−1 at 1 A g−1 and a desirable cycling behavior of 90.0% retention over 5000 cycles. The assembled asymmetric supercapacitor using Ni3S2/CoAl-LDH/rGO as positive electrode and active carbon as negative electrode delivers a high energy density of 59.8 W h kg−1 at a power density of 402.8 W kg−1 and a good cycling property (91% capacitance retention after 8000 cycles). These encouraging results demonstrate that such hybrid nanostructure provides great potential as electrode material for the energy storage devices.

A series of P-promoted non-noble metal Cu-based catalysts without alkalis and Fischer-Tropsch elements were prepared by a complete liquid-phase method and tested for the synthesis of higher alcohols (C2+OH) from syngas in slurry bed reactor. The catalysts were characterized by XRD, 27Al-MAS-NMR, N2 adsorption, XPS, H2-TPR and NH3-TPD techniques. Results showed that the incorporation of an appropriate amount of phosphorus into the non-noble metal Cu-based catalyst could increase the surface Cu content, the amount of weak acid and improved the Cu+ reducibility, which promoted the synergistic effect between Cu and Al, and thus enhanced both stability and selectivity towards to higher alcohols formation. Activity results showed that the production of alcohols and hydrocarbons over this kind of catalyst followed A-S-F distributions, similar with conventional CuFe and CuCo based catalysts. The catalysts with Cu:Zn:Al:P = 2:1:0.8:0.05 showed the best catalytic performance with long-term stability toward CO conversion and C2+OH selectivity (reaching 55%) during the lifetime test for 120 h. It was speculated that AlOOH favored CO dissociation, and the synergism of Cu0, Cu+ and AlOOH was beneficial to the formation of higher alcohols. This work provided a new sight that alkalis and F-T elements were not indispensable for direct synthesis of higher alcohols from syngas over non-noble metal Cu-based catalysts.

A series of CuZnSiAl catalysts with Si/Al molar ratios from 0 to 1 were prepared by a complete liquid-phase method and tested for syngas to higher alcohols (C 2+ OH) in slurry bed reactor. The catalysts were characterized by XRD, H 2 -TPR, NH 3 -TPD, N 2 adsorption, FT-IR and XPS techniques. Activity results showed that the mass fractions of C 2+ OH in the total alcohols reached approximately 40.8% over CuZnAl catalyst without promoters. With increased Si/Al ratio, the crystallite size of Cu 0 first increased until Si/Al = 0.5 and then decreased, However, the total number of weak acid on catalysts surface increased continuously and the surface Cu content gradually decreased. In addition, compared with the acidic Si sol, the catalysts promoted by alkaline Si sol exhibited better performance in terms of both stability and selectivity to C 2+ OH. It was found that AlOOH functioned for CO dissociation and C 2+ OH synthesis simultaneously required relative larger Cu particles, more number of weak acid and higher Cu content on catalyst surface. The incorporation of a suitable amount of alkaline Si sol was beneficial for both the stability as well as C 2+ OH selectivity, and the best catalytic performance was obtained when the Si/Al atomic ratio was 0.5.

The effect of aging temperature and holding time on the precipitation of secondary phases and pitting corrosion resistance of SAF2906 super duplex stainless steel was examined. Chromium nitride and σ phase were observed to preferentially precipitate at the ferrite/austenite interface. An amount of nitrides was also observed within the ferrite grain. The precipitation of chromium nitride occurred before the σ phase. The increase in aging temperature and holding time did not affect the concentration of the nitrides but increased the area fraction of the σ phase at a faster rate. The Cr2N precipitation in SAF2906 is more evident than that of the other duplex stainless steels. The variation tendency of the precipitation concentrations is primarily consistent with the prediction results of Thermo-Calc software. The electrochemical results showed that Cr2N and σ phase significantly reduced the pitting potential. Scanning electron microscope observations revealed that pits appear mainly in regions adjacent to sigma phase and Cr2N.

First-principles calculations within density functional theory have been carried out to investigate α2 phase in the Ti3Al based alloy with Zr, Hf, and Sn (6.25at%) elements doped. The lattice constants, total energies and elastic constants were calculated for the supercells. The formation enthalpies, bulk modulus, shear modulus, Young’s modulus, and intrinsic hardness were investigated. The ductility of the doped α2 phases was analyzed by the Cauchy pressure, G/B and Poisson’s ratio. The results show that the substitution of Ti(6 h) by Zr, Hf, and the substitution of Al(2n) by Sn can make the doped α2 phase more stable. The inflexibility and hardness of α2 phase can be enhanced by doping with Zr and Hf, while Sn brings the opposite effect. Sn is more powerful to improve the ductility of the doped α2 phase than Hf, but Zr can increase the brittleness. The densities of states (DOS and PDOS) and the difference charge density are obtained to reveal the underlying mechanism of the effect of alloying elements.

This work aims to use surfactant-assisted direct current electrodeposition technique to prepare four types of bimodal nickel, under different current densities. Bimodal Ni is obtained with different grain size and spatial distribution of CG and UFG areas showing a big disparity in mechanical properties. As a result of small population of coarse-grained surrounded by quite a lot of ultrafine-grained forming a unique shell-and-core bimodal structure, bimodal one present the best comprehensive mechanical properties with an ultrahigh tensile strength (~847 MPa) and a considerable plastic strain (~16.7%). Deformation initial, bimodal structures display more positive strain hardening to meaningful strains than unimodal structure of UFG and CG. Particularly bimodal one work-hardening rate is the highest thanks to its structure (UFG occupy 76.7% in total number fraction) and the distribution of growth twins. Growth twins in this article are referred to Σ3(111) coherent twins playing an important role in improving high strength, enhancing uniform plastic deformation ability.

We report herein the influence of various pressures on the crystal structure, mechanical and electronic properties and Debye temperature of Al 7 Cu 2 Fe alloy determined from the first-principles calculations. The lattice constants at 0 GPa are in good agreement with the data previously reported. We have also employed DOS and computational studies ( i.e. enthalpy of formation and elastic constants), which have revealed its mechanically stable nature. We have found that parameters B , G , E , Θ D , and H have proportionally enhanced with the pressure. The B /G ratio has indicated its ductile behavior at 30 GPa, suggesting that pressure favorably influences the ductile materials.

A combined experimental and first-principle study on the oxidation mechanism of super austenitic stainless steel S32654 at 900 °C for a short time period (1, 3, and 5 h) in air is presented. The samples exhibit excellent oxidation resistance because of the initial and gradual formation of the denser Fe- and Cr-rich layer with increasing oxidation time. Meanwhile, the Mo-rich layer gradually forms because of the Mo diffusion, which results in the formation of the oxide layer with two distinct regions: an inner Fe- and Cr-rich layer and an outer Mo-rich layer. Density functional theory is applied to investigate the diffusion behaviour of Mo atom in the Fe-Cr-Ni/Cr2O3 interface and the effects of alloying elements (Fe, Ni, and Mn) on the Mo diffusion. The Mo originating from the alloy matrix tends to diffuse into the Cr2O3 part, thereby resulting in the formation of the continuous Mo-rich layer, which is consistent with the experimental behaviour. Moreover, the introduction of Ni to the Cr2O3 part can promote the Mo diffusion and the formation of the Mo-rich oxide layer, whereas Fe and Mn can hinder the Mo diffusion. The calculated results provide a microcosmic explanation of the experimental results.

The pressure dependence behaviors of structural and mechanical properties as well as the effect of temperature on thermodynamic properties of Ni-Al ordered intermetallic compounds (i. e. Ni 3 Al, Ni 5 Al 3 , NiAl, Ni 2 Al 3 and NiAl 3 ) are investigated in details by implementing first-principles calculations. The calculated lattice parameters, bulk modulus and its pressure derivative are well in agreement with available experimental and theoretical values at zero pressure. All the compounds are mechanically stable with pressure going up to 50 GPa, and the volume change resistance of nickel aluminum alloys can be improved by increasing pressure and Ni concentration. The shear deformation resistance, elastic stiffness and microhardness of nickel aluminum alloys can be strengthened by increasing the content of Ni 5 Al 3 and Ni 2 Al 3 , and pressure can also enhance these properties of Ni 5 Al 3 , NiAl and Ni 2 Al 3 . The ductility of Ni 3 Al, Ni 5 Al 3 and NiAl can be improved by increasing pressure, while brittle nature turns into ductile nature in 20–30 GPa and 10–20 GPa for Ni 2 Al 3 and NiAl 3 , respectively. Furthermore, the elastic anisotropy of Ni 3 Al, Ni 5 Al 3 , Ni 2 Al 3 and NiAl 3 enhances with pressure, while NiAl shows few change with pressure increasing. In addition, Ni 3 Al is the most sensitive to pressure change among considered compounds. Finally, the Debye temperature, linear thermal expansion coefficient and heat capacity of these compounds are calculated using the quasi-harmonic Debye model in pressure ranging from 0 to 50 GPa and temperature ranging from 0 to 1200 K to elucidate the relationships between thermodynamic parameters and temperature under various pressure. The results are helpful insights into the study of nickel aluminum alloys.

Super-austenitic stainless steel S32654 sheets with 2.4 mm thickness were successfully welded by friction stir welding (FSW) at the rotational speeds of 300 and 400 rpm with a constant traverse speed of 100 mm/min using W-Re tool. The sound joints with almost no nitrogen loss were successfully produced. The microstructure evolution was characterized by optical digital microscope (ODM), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), electron backscatter diffraction (EBSD) and transmission electron spectroscopy (TEM). The results suggest that the grain structure evolution in stir zone (SZ) is dominated by continuous dynamic recrystallization (CDRX). The strain rate plays a dominated effect on obvious grain refinement. The band structures containing W and Re are generated due to the wear between tool probe and steel in SZ. Furthermore, the microhardness measurements and transverse tensile tests indicate that the grain refinement combining with high density dislocations and substructures improves the hardness and strength, but greatly reduces the plastic deformation capacity of joints. The more suitable welding parameters are determined as 300 rpm and 100 mm/min for this steel. Keywords: Friction stir welding, Super-austenitic stainless steel, S32654, Microstructure evolution, Recrystallization, Mechanical properties

The oxidation resistance of austenitic stainless steels modified with various aluminum contents was investigated. The weight gain per unit area is in parabolic relation to oxidation time, and the oxidation rate significantly decreases with increased aluminum content. Outer layer oxides of austenitic stainless steel transform from Cr2O3 to a composite oxide layer comprising Cr and Al, and more dense Al-containing oxides formed with increasing the added Al contents. Since the diffusion of element Al is enhanced and the diffusion of element Cr is inhibited, the oxides enriched in Al dramatically contribute to the improved oxidation resistance of austenitic stainless steels at high temperature. The possible oxidation mechanisms are also proposed based on microstructural observations.

In this study, theoretical calculations and experiments have been carried out to investigate the photoelectric performance of (2Al, S) co-doped rutile SnO2. The electronic structures are studied by density functional theory (DFT). It is found that the metal Al can assist the bonding of the incorporated S with the neighboring O in SnO2, introducing new energy levels in the forbidden band of SnO2, which enhance the photoelectric performance. Meanwhile, the experiments are conducted to verify this. The (2Al, S) co-doped SnO2 with different doping ratios are prepared by a hydrothermal method. The samples are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that all the samples have rutile structure without any extra phase, and the dopant S2− ion was implanted into the crystalline lattice of (2Al, S) co-doped SnO2 and Al dopants replaced Sn atoms. The photoelectric performance tests show Al and S co-doping can improve the photoelectric performance, especially with a doping ratio of 5%, when the photocurrent reaches maximum of 3.0 μA cm−2 which is almost twice as much as pure SnO2, and the impedance is the smallest. The experiments results are consistent with our theoretical calculations. These findings are expected to be helpful for the design of highly active tin oxide-based photoelectric materials.

Adding antireflection and light trapping structures to the solar cell can decrease the optical losses and increase the efficiency of the cell effectively, the nanocone antireflection structure was paid lots of attention because of its simple manufacture processes and low reflectance. In this work, the effect of the height and diameter of the periodic unit on the reflectance, transmittance and absorptance of the parabolic-shaped nanocone (PSNC) arrays was calculated using finite-difference time-domain method. It was found that the average reflectance decreased and the average absorptance increased with the increase of height in our calculation range. The average reflectance could be decreased to 0.13% by optimizing the diameter even when the height decreased to 1 μm, thus the PSNC arrays had good antireflection character. The average absorptance could reach 81.16% by optimizing the diameter when the height increased to 7 μm.

A combination of experiment and first-principles research on the formation of the Al2O3 layer in alumina-forming austenitic stainless steel is presented. The results show that the oxide layer has a multilayer structure with an outer oxidized Cr2O3 and an inner Al2O3. Further, theoretical simulation using the first principles method is applied to research the formation process of the Al2O3 layer in the Fe/Cr2O3 interface as well as the impact of four alloying elements (Cr, Ni, Mn, and Si) on the formation of Al2O3. Results indicate that the Al atom originating from the Fe-based matrix prefers to diffuse into the Cr2O3 slab, thereby resulting in the formation of the Fe/Al2O3/Cr2O3 construction, which agrees with the experimental behaviour. Moreover, the introduction of Cr, Ni, Mn, and Si can slow down the diffusion of Al and result in a slower growth rate of Al2O3. The effects of Cr–Y (Ni, Mn, and Si) co-doping are more significant than those of X (Cr, Ni, Mn, and Si) single doping. Furthermore, Si can improve the adhesion of the Fe/Al2O3/Cr2O3 interface, thus can improve the adhesion of the oxide scales.

The effect of pressure on structural and mechanical properties as well as the temperature dependence of thermodynamic properties, such as enthalpies of formation, elastic moduli, anisotropy, heat capacity and thermal expansion coefficient et al., of Ni2XAl (X = Sc, Ti, V) Heusler compounds are investigated implementing first-principles calculations. The influence of pressure on lattice parameters decreases as the increase of atomic number X (Sc, Ti, V). The Ni2XAl (X = Sc, Ti, V) show mechanically stable, ductility and anisotropy in 0–50 GPa, and appropriate pressure can improve their mechanical properties because the bulk modulus B, shear modulus G, Young's modulus E, G/B and microhardness H almost linearly increase with pressure. The influence of pressure on B, G, E and H gradually decreases as the order of Ni2ScAl > Ni2TiAl > Ni2VAl, while it has an inverse effect on ductility and anisotropy. In addition, the resistance to volume deformation of NiAl alloys can be improved by second-phase strengthening with Ni2VAl and Ni2TiAl precipitates. Finally, the temperature and pressure dependences of bulk modulus, Debye temperature, heat capacity as well as thermal expansion coefficient of these compounds are elucidated using the quasi-harmonic Debye model. It is inverse for the effect of temperature and pressure on thermodynamic parameters. Keywords: Heusler compounds, L21-type Ni2XAl, Mechanical properties, Thermodynamic properties, First-principles