We present a method for calculating depolarizing fields in thin ferroelectric films within the framework of a discrete model, taking into account effects of screening by free charges of the film material itself and the electrodes. The formulas for the energy of dipole-dipole interactions were obtained from the multipole expansion of the screened Coulomb potential. Calculations were performed using the periodic Green’s function method and the Ewald method. We found that the dependence of depolarizing field on the layer number in a monodomain film can be approximated by the sum of exponential functions. We also investigated the effect of screening parameters on the domain structure.

The dielectric properties of layered two-component structures consisting of a dielectric of strontium titanate SrTiO3 and a ferroelectric of lead titanate PbTiO3 are investigated. In these structures, a ferroelectric phase transition occurs at a temperature of 544 ˚С, which significantly exceeds the phase transition temperature of ferroelectric PbTiO3. This effect may be due to the very small thickness of the PbTiO3 ferroelectric layer and the influence of the dielectric SrTiO3.

Ferroelectric and antiferroelectric phase transitions at Curie temperatures, T C, of the multiferroics, along with their magnetic phase transitions at Néel temperatures, T N, classical ferroelectric and antiferroelectric phase transitions, as well as rotational phase transitions of known perovskite oxides and fluorides ABX 3, where X = O or F, at temperatures T R are considered. The goal is to construct the dependences of their T C, T N or T R values on their corresponding interatomic bond strain values, δ AX , and determine how much the areas of changes in δ AX values for phase transitions of every nature separate from each other or where they overlap.

ZnO nanorod arrays were prepared using the sol-gel method and hydrothermal method, and ZnO/ZnSe nanorod arrays composites were fabricated using an improved CIRR (Chemical Infiltration and Reaction at Room Temperature) method. The samples have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), etc. The results show that the dark current of the ZnO nanorod arrays photoelectric device is 1.79 × 10−5 A, the photocurrent of which is 3.33 × 10−3 A, and the photocurrent response of which is 186. The current of the ZnO nanorod arrays photoelectric device does not drop sharply, and the photoelectric response and recovery process are slow, which shows the appearance of photoconductive relaxation phenomenon. The dark current of the ZnO/ZnSe nanorod arrays composite photoelectric device was 3.61 × 10−7 A, the photocurrent of which was 4.39 × 10−4 A, and the photocurrent response of which was 1216. This may be because the photogenerated electrons and holes can be quickly separated at the heterojunction interface, which provides a strong basis for optimizing the design of optoelectronic devices.

In this paper, Cu-Ti alloy powder with Ti content of 2%, 2.5%, 3% and 3.5% was prepared by mechanical alloying method, and then Cu-Ti alloy powder was formed using vacuum hot pressing sintering method to prepare Cu-Ti alloy. The results show that the complete mechanical alloying time of Cu-2%Ti, Cu-2.5%Ti, Cu-3%Ti and Cu-3.5%Ti is 1h, 1h, 1.5h and 2h, respectively. Cu-Ti alloys with different Ti contents prepared by vacuum hot pressing sintering, the comprehensive properties of Cu-2.5%Ti are better, with electrical conductivity of 33.42%IACS and tensile strength of 385 MPa, which is 193.5% higher than that of pure copper. The hardness is 201.66HV, 331.1% higher than that of pure copper.

In this paper, several new powder packing methods are proposed, and the COMSOL software is used to simulate the temperature distribution under different conditions. The influence of powder packing on the growth of SiC single crystal by physical vapor transport (PVT) is studied. The results show that the heat flux of the top region of the powder is increased by trapezoid graphite and graphite ring, the radial temperature gradient of the powder is reduced, which contributes to the improve the powder utilization rate. By covering the surface of the powder with a layer of porous graphite filter, the recrystallization on the surface of the powder is inhibited, the defects of carbon inclusion and thermal stress in the SiC crystal are reduced, and the growth quality and growth rate of the SiC crystal are obviously improved. The simulation results were verified by experiment, and the results agrees well with experiment.

ZnCo2O4/ZnO composites nanomaterials were synthesized by a hydrothermal method. The morphologies and structures of ZnCo2O4/ZnO composites nanomaterials were studied by using different reaction temperature. The results indicated that the morphology of ZnCo2O4/ZnO composites nanomaterials can be controlled and changed effectively by reaction temperature. A reasonable growth mechanism for ZnCo2O4/ZnO composites nanomaterials by hydrothermal processes was proposed. Moreover, photocatalytic degradation properties of ZnCo2O4/ZnO composites under visible light were evaluated by degradation of common organic dye Rhodamine B (RhB solution). The results showed that ZnCo2O4/ZnO composites grown at a hydrothermal temperature of 160 °C had the excellent selective catalytic ability to RhB solution with photocatalytic efficiency of 95% in 60 min. The method conducted in this work could be expanded to other composite nanomaterials with controllable morphology and structure to further improve the photocatalytic performance.

Cerium dioxide (CeO2) is an extremely versatile rare-earth oxide, which is chemically stable, nontoxic, and simple to prepare, making it of great interest in the field of photocatalysis. However, cerium dioxide has a low forbidden band width, its utilization of sunlight is not high, and the However, cerium dioxide has a low forbidden band width, its utilization of sunlight is not high, and the photogenerated carriers are very easy to compound. These problems lead to the low photocatalytic efficiency of cerium dioxide, which greatly limits the practical application of cerium dioxide photogeneration. These problems lead to the low photocatalytic efficiency of cerium dioxide, which greatly limits the practical application of cerium dioxide photocatalysts. morphologies was prepared by hydrothermal method using cerium nitrate as raw material, and then compounded with CdS to form a composite photocatalyst. The effect of morphology on the degradation efficiency of CeO2 and the change of the degradation efficiency of CeO2 with different morphologies after The effect of morphology on the degradation efficiency of CeO2 and the change of the degradation efficiency of CeO2 with different morphologies after compounding with CdS were investigated.

Three types of pinless friction stir spot welding (PFSSW) tools were designed employing Fibonacci spiral curve, involute curve, and Archimedean spiral curve to create corresponding grooves. Subsequently, PFSSW experiments were conducted on copper sheets using these three distinct tools. The surface morphology, cross-sectional macrostructure and microstructure, microhardness, joint strength, fracture type, and fracture surface morphology of the joints were analyzed under the influence of different tools. The research findings indicate that the Fibonacci spiral curve groove (FSCG) tool exhibits the highest disparity in three-dimensional morphology within the central zone of the joint, followed by the involute curve groove (ICG) tool and the Archimedean spiral curve groove (ASCG) tool. The ICG tool generates the widest stirring zone (SZ) in the joint, while the FSCG tool produces the deepest SZ. The grains of SZ under all three tools is coarser compared to the base material. The microhardness values under the ASCG tool are relatively higher, whereas those under the FSCG tool are lower. Among the welded specimens, those created using the FSCG tool exhibit the highest average tensile-shear failure load of 8.21 kN, followed by the ICG tool of 7.80 kN, and the ASCG tool yielding the lowest average tensile-shear failure load of 7.77 kN. The fracture type of the specimens welded by FSCG tool is semi-nugget pull-out fracture, while the joint specimens of ICG tool and ASCG tool are both nugget pull-out fracture. The fracture mode of the joints under all three tools is characterized as ductile fracture. The conducted research can not only enrich the variety of PFSSW tool grooves, but also enhance the comprehension of joint properties under distinct tool groove configurations.