查看更多>>摘要：? 2022 Elsevier B.V.Multiferroic materials have faced great interest for solar energy conversion applications due to the charge separation caused by the effective ferroelectric polarization and the photovoltage generated across the bandgap, which in principle can lead to highly efficient energy conversion. However, ferroelectric materials may show poor visible light absorption, mainly due to the large bandgap. In this work, a novel approach is adopted to effectively reduce the bandgap of a multiferroic material by doping transition metal (TM) ions, namely (Co/Fe) into the Ti site of the Bi3.25Sm0.75Ti3O12 (BSmT) lattice. The structural optimization results show that there is a difference in the lengths of the Δ(Ti(1)-O1) and Δ(Ti(2)-O5) bonds and that their value increases with increasing Co/Fe concentration, resulting in structural distortions. The optical studies showed that the BSmT band gap was successfully reduced from 3.22 eV to 2.02 eV with Co/Fe co-doping. The structural distortion explains this reduction in bandgap due to the modulation of orbital overlap and compensation mechanism. In trivalent (Fe3+/Co3+) co-doping at the titanium (Ti4+) site, oxygen vacancies are formed to maintain electroneutrality. To prove the multiferroelectricity behavior in this study, the ferromagnetism and ferroelectricity ordering of the sintered BSmT:FC2 sample was studied at room temperature. The results show unsaturated leaky P-E hysteresis loops due to domain pinning caused by the accumulation of oxygen vacancies near the domain boundaries. At the same time, distinct S-type M-H hysteresis loops were obtained, indicating typical ferromagnetic ordering. The results obtained in this work can be considered promising to promote the building of intrinsic multiferroics to develop photovoltaic devices for next-generation applications.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, Ni-Ti composite coatings were prepared using electrodeposition. Experimental results and COMSOL computer simulation revealed the effect of the Ti microparticles on the microstructure and properties of the Ni-Ti composite coating. The incorporated Ti microparticle lead to grain refinement, texture elimination which were correlated with the effect of current concentration and heterogeneous nucleation. Domains consisting of inner nano-grains and outer radial columnar grains were located around the Ti microparticles, where the Ti microparticles acted as seeds. This was closely correlated with the time-dependent plating conditions like current density and electric field lines during incorporation process of the Ti microparticles. Besides that, during the incorporation process of Ti microparticles, current density concentration on the “V”-shaped valley between closely neighboring Ti microparticles promote the presence of fine Ni grains, existing between but not belonging to the Ti microparticles. Selective deposition of Ni metal on Ti microparticle surface, local current density concentration and the aggregation of Ti microparticles were observable, contributing to the spatial heterogeneity of the microstructure. Compared with the pure Ni coating, the average hardness of the Ni-Ti composite coating increased from 2.91 ± 0.43 GPa to 3.98 ± 0.46 GPa, leading to the enhanced wear resistance. However, spatial heterogeneity of the hardness distribution was observed due to the heterogeneous microstructure of Ni-Ti composite coating, which confined the improvement of wear resistance.
查看更多>>摘要：? 2022 Elsevier B.V.It is still a great challenge to design efficient and stable photocatalysts to effectively remove organic pollution in water. A new type Bi12O15Cl6/SnO2?x Z-scheme heterojunction was successfully constructed. The best sample 30% Bi12O15Cl6/SnO2?x can degrade 86.7% TC within 90 min and 99.7% RhB within 75 min under LED light. The morphology, structure, optical and electrochemical properties of the photocatalyst were characterized by using different testing techniques. Efficient photoinduced charge transfer and separation efficiency was confirmed by photocurrent and electrochemical impedance spectra (EIS) in Bi12O15Cl6/SnO2?x structure. The active substances, intermediate product and photodegradation pathway in degradation process were revealed by capture test and mass spectrometry (MS) measurement. In photocatalytic process, h+, ?O2? and ?OH are the main active species, and h+ is the most important active substance. In addition, the photocatalytic mechanism of charge separation is also proposed, which provides a new opportunity for the construction of photocatalysts and the degradation of organic pollutants in the water environment.
查看更多>>摘要：? 2022 Elsevier B.V.Skutterudite (CoSb3), as a promising thermoelectric material for medium-temperature applications, has attracted considerable interest. However, improving its thermoelectric properties is still an important problem. In this work, first-principles calculations combined with semiclassical Boltzmann theory are adopted to investigate the electronic transport and thermoelectric properties of CoSb3 under external strain. It is found that both tensile strain and compressive strain reduce the bandgap of the CoSb3 system and influence the Co_d orbitals near the Fermi level. Further, the steepness of the valence band near the Fermi level along the M–G and G–R directions are changed by external strain to different extents, which directly affects the Seebeck coefficient and the ratio of conductivity to relaxation time; both of these values are optimized under tensile and compressive strain. Therefore, the power factor of CoSb3 is greatly enhanced under external strain. At 700 K, the maximum power factors under strains of ? 1% and 3% are 23.77% and 47.63% higher than those without strain, respectively. Thus, the thermoelectric properties of CoSb3 can be greatly improved by external strain.
查看更多>>摘要：? 2022 Elsevier B.V.Microstructure, crystallographic texture, and mechanical properties of pure Mg, as a model hcp metal, were compared after processing by the two severe plastic deformation (SPD) techniques of equal channel angular pressing (ECAP) and simple shear extrusion (SSE). Both processes were performed on extruded bars at 250 °C for up to four passes, where the minimum grain sizes of 13.7 and 9.8 μm were achieved in the ECAP and SSE processes, respectively. The fraction of dynamically recrystallized (DRX) grains, high angle grain boundaries (HAGBs), and the evolution of dislocation density with equivalent strain experienced the same trend in both processes with higher values after ECAP. The textural evolutions were completely different during ECAP and SSE despite their similar deformation modes. A conventional shear texture was developed after ECAP, while after SSE basal planes were aligned parallel to the processing direction. In the ECAP-processed material, texture softening and lower dislocation density counterbalanced the strengthening effect of grain refinement, resulting in a decrease in shear yield stress (SYS) and ultimate shear strength (USS), while in SSE the shear strength increased constantly with increasing number of passes. It can be deduced from the experimental results that SSE was more effective in achieving a fine-grained homogenous microstructure with high shear strengths as compared to ECAP.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, a novel TiO2@C@Prussian Blue core-shell nanorod arrays film was constructed through two-step hydrothermal and electrodeposition methods. Such a designed structure could increase the specific surface area, reactive site, and conductivity of Prussian Blue (PB) and reduce the diffusion distance of ions due to the nano-architecture arrays of TiO2 and the high conductivity of the carbon layer, thus leading to the remarkably improved storage capacity and reaction speed of ions during the electrochromic (EC) process of PB. Moreover, porous morphology and strong adhesion on the FTO substrate of the TiO2 nanorod arrays could alleviate the lattice stress and volume expansion and enhance the binding force, thus improving the cycle stability of EC. Given these benefits, the TiO2@C@PB films display a large optical modulation range (67%), fast switching speed (tc/tb = 1.25 s/2.71 s), and high coloration efficiency (129.4 cm2/C). In particular, the EC cycle stability is remarkably improved (96.3% after 5000 cycles), implying a promising application in high-performance EC devices (ECDs).
查看更多>>摘要：? 2022In this research, WE43-based nanocomposites were fabricated by addition of nano- and micro-sized particles of ZnO and Cu/ZnO, followed by friction stir processing (FSP). In addition to the effect of the size of additives, the effect of geometry of the particle insertions, groove and holes, on the evolution of microstructure and corrosion properties of Mg-based composites were studied. The grain size of the matrix of the fabricated composite was reduced after FSP. In addition, significant fragmentation and re-distribution of secondary phase particles occurred which resulted in size reduction, increased density and improved uniformity of the particles. Corrosion behavior of the composite was assessed by scrutinizing potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic polarization and immersion tests. It was found that the corrosion mechanism of Mg-based nanocomposite samples was a combination of pitting and uniform corrosion. Furthermore, the rate of electrochemical corrosive reactions reduces by performing FSP and addition of particles. The composite fabricated using hole insertion and nano-sized particles showed a more uniform distribution of additives resulting in higher corrosion resistance in comparison with groove insertion. In addition, fabricated composite sample with Cu/ZnO particles presents the highest anti-corrosion properties.
查看更多>>摘要：? 2022The photo-Fenton technology has shown widespread application potential in the degradation of wastewater. Herein, solid waste coal fly ash magnetospheres (MS) composed of a large amount of Fe3O4 and Fe2O3 were used as raw materials to prepare a novel photo-Fenton catalyst MS@C/g-C3N4. The SEM characterization results showed MS@C had a special core@shell structure with many micro-cracks, and for MS@C/g-C3N4, the g-C3N4 nanosheets not only intersperse in the cracks of MS@C, but also adhere to the surface of MS@C. The FTIR characterization results showed the little changes of the peaks corresponding to -CN heterocycles in MS@C/g-C3N4 may be caused by the interaction between g-C3N4 and MS@C. The photo-Fenton performance of MS@C/g-C3N4 composites was evaluated by degrading of Rh B. MS@C/g-C3N4 composites displayed the highest rate constant (0.1532 min?1) than MS@C (0.0671 min?1) and pure g-C3N4 (0.0018 min?1)as well as samples of mixture of MS@C and g-C3N4 (0.0745 min?1) due to the presence of the synergistic effect between photocatalysis and Fenton reaction. The effects of carbon shells thickness, H2O2 concentration, Rh B concentration and pH value on the photo-Fenton degradation of Rh B by MS@C/g-C3N4 were studied. The ICP results showed that the carbon shells had an inhibitory effect on the leaching of iron ions, and the optimal photo-Fenton degradation conditions were H2O2 concentration of 50 mmol/L, Rh B concentration of 100 mg/L and pH = 3. The recycle experiment showed that the degradation rate of MS@C/g-C3N4 composites was only slightly decreased about 5% after four cycles, and the XRD results for the fresh MS@C/g-C3N4 and used MS@C/g-C3N4 showed that there were no obvious changes occurred in the crystal structure after fourth cycle, which indicated that MS@C/g-C3N4 possessed excellent stability. The main active species were ?OH and h+ in this system, and a possible photo-Fenton mechanism was proposed. The carbon shells (coated on MS) could enhance the separation efficiency of photogenerated electron-hole pairs of g-C3N4. In addition, the leached iron ions in MS@C/g-C3N4 could be anchored to the surface by the pyridine nitrogen in g-C3N4 to form Fe-N bonds, which could accelerate the transfer of electrons and be regarded as the active site in the Fenton reaction.
查看更多>>摘要：? 2022 Elsevier B.V.Novel thermal barrier coatings (TBCs) based on Mg2SiO4/8YSZ double-ceramic-layer (DCL) were prepared by atmospheric plasma spraying (APS). Thermal cycling tests of the TBC specimens were performed at 1373 K. Results indicate that the DCL coating has a much longer lifetime compared to the single layer Mg2SiO4 coating. This is attributed to the fact that DCL Mg2SiO4/8YSZ TBCs further enhances the thermal insulation effect, improves sintering resistance and relieves thermal mismatch between ceramic layer and bond coat (BC). It can be concluded that this DCL coating structure design is ideal to optimize the performance of single layer Mg2SiO4 TBC and shows the Mg2SiO4 exhibiting a promising potential as new TBC materials.
查看更多>>摘要：? 2022 Elsevier B.V.The controlled growth of needle-like Co3O4 and composite formation with highly graphitic carbons such as N-CNOs is critically essential for obtaining high-performance energy storage supercapacitors. In this study, the needle-like Co3O4 and graphitic N-CNOs are synthesized by the simple solvothermal and pyrolysis methods, respectively. The Co3O4/N-CNO composite enhances the fast charge transfer by reducing ion diffusion. The Co3O4/N-CNO composite demonstrated an improved specific capacitance (3066 F g?1) than the needle-like structure of Co3O4 (2068 F g?1). The Co3O4/N-CNO composite exhibited very good rate capability and high capacitance retention of 82% at a high current density of 8 A g?1 meanwhile the Co3O4/N-CNO//AC ASC device shows high power and energy densities with capacitance retention of 78% and Coulombic efficiency of 100% over 2000 cycles. This attractive electrochemical performance of Co3O4/N-CNO composite makes it a favorable device for practical applications of supercapacitors.
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