As a kind of porous clay mineral material, diatomite has some advantages like rich reserves, low cost, and high specific surface area, which can be used as an excellent carrier of phase change material (PCM). Recent work on high-efficiency diatomite PCM is to improve its latent heat and thermal conductivity. This review represented recent research progress on the specific surface area modification and thermal conductivity enhancement modification of diatomite PCM and analyzed the thermal properties of diatomite with different types and contents of PCMs. In addition, some problems of diatomite PCM application were described, and the future research directions were prospected.

An one-dimensional (Ni_xZn_1-x)O composite desulfurizer for gasoline was prepared by an one-step composite method. The samples were characterized by X-ray diffraction, H₂-temperature programmed reduction measurement, scanning electron microscopy and BET specific surface area analysis. The results show that nickel is doped into the lattice of ZnO by the one-step compounding method, which increases the force between active component nickel and ZnO and improves the active component of nickel thermodynamic stability and chemical stability, thus effectively avoiding the loss in the process of reaction and accumulation by heating during regeneration. Also, at a certain amount of nickel, (Ni_xZn_1-x)O composite desulfurizer can maintain an one-dimensional nano-morphology that favors the reduction of active component nickel in the desulfurizer for the desulfurization. At a nickel amount of 8%, (Ni_xZn_1-x)O composite desulfurizer has better desulfurization and regeneration performances, and the desulfurization rate becomes 99.0%. The service life of desulfurizer can still maintain to be 90 h after regeneration for seven times.

Cu-doped Bi₂WO₆ nanomaterials (Cu/Bi₂WO₆) were prepared by a hydrothermal method. The structures of Cu/Bi₂WO₆ nanomaterials were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy and electrochemical impedance spectroscopy. The photocatalytic activities were examined through the photocatalytic reduction of U(VI) under visible light irradiation. The results show that Cu-doped Bi₂WO₆ samples exhibit much higher photocatalytic activity than pure Bi₂WO₆ for reduction of U(VI) under visible light irradiation. It is also revealed that 10% Cu/Bi₂WO₆ sample exhibits the optimum photocatalytic activities in the reduction of U(VI), The enhanced photocatalytic activity of Cu/Bi₂WO₆ materials are attributed to the increased transmission rate and reduced recombination rate of photogenerated electron-hole by Cu doping on BiWO₆. Also, Cu doping reduces the Bi₂WO₆ band gap and expands the response range to visible light, thus improving the activity of Cu/Bi₂WO₆ photocatalyst. Cu doped Bi₂WO₆ materials have considerable potential applications in solar-driven treatment of wastewater with U(VI).

In the present perspective, evolution of ferroelectric transition and dielectric properties in tungsten bronze oxides is surveyed, and the physical image of modulation structure is established to interpret the variation of ferroelectric transition and macro ferroelectric properties. Different A site cations lead to different modulation structure, and the relationship between temperatures of modulation structure change and ferroelectric transition dominates the crossover from normal to relaxor ferroelectric in tungsten bronze oxides. At low temperature, modulation structure will lock into a regular space group, while the interactions between modulation structure and ferroelectric order results in the low temperature dielectric relaxations.

Bone defects caused by trauma, bone tumor resection, traffic accidents, etc. increase the demand for bone scaffolds and additive manufacturing technology is gradually being widely used in the preparation of bone scaffolds. Three lattice-structured hydroxyapatite (Ca₁₀(PO₄)₆OH₂), HA ceramic green body such as Diamond structure, Rhombic dodecahedron structure and Octet truss structure were manufactured by Digital Light Processing technology and then successfully sintered three kinds of lattice structure HA ceramic scaffolds with a porosity of 70%, and the minimum pore size after sintering is about 200-300 μm. After being sintered at 1 300℃, the HA ceramic is partially decomposed into β-Ca₃(PO₄)₂, and the ceramic grains are tightly bound. Mechanical strength simulation matches actual results, the average compressive strength of the Octet truss structure is the largest, which is 3.16 MPa. In vitro cell experiments showed that the surface of the HA ceramic bone scaffold is beneficial to the spread and adhesion of bone mesenchymal stem cells (rBMSCs), and the HA ceramic prepared by DLP has good biocompatibility. Therefore high-precision lattice structure HA ceramic bone scaffold fabricated by DLP technology is expected to be widely used in bone tissue engineering.

The perovskite and perovskite-like microwave dielectric ceramics have some excellent dielectric properties due to their unique crystal structure. They play an important role in microwave communication technology and can be widely used in satellite communications, radar, and civil mobile communication. In this review, we summarized recent work on the microwave dielectric properties of perovskite and perovskite-like microwave dielectric ceramics. The crystal structure and microwave dielectric properties of a series of perovskite and perovskite-like compounds were discussed. The effects of ion substitution, combined modification and low-temperature sintering on the dielectric properties of the ceramics were analyzed. Finally, the existing main problems were summarized and the future development direction was prospected.

The microstructure of layer perovskite La_0.9Sr_0.1TiO_3+δ was investigated by high-resolution transmission electron microscopy and high angle annular dark field image analysis. The mechanism of oxygen vacancy on the lattice structure was revealed. Based on the results by X-ray diffraction, the oxygen-difficient environment effect on the lattice structure leads to the change of axial length and volume contraction in the material. The partial atomic plane rearrangement and dislocation caused by oxygen vacancy and continuous lattice distortion are identified based on high-resolution microscopic and Z-contrast atomic images, respectively. The effective regulation of oxygen vacancy defect shows a great significance on changing the microstructure of materials and further preparation of high-performance perovskite materials.

A lead-free piezoelectric ceramic (NaBi)_0.5-x(KCe)_xBi₂Ta₂O₉(NBTO-x, 0≤x≤0.15) was prepared by a solid-state reaction method. The influence of K/Ce ions co-doping content on the structure and electrical properties of NBTO ceramic was investigated. Based on the results by X-ray diffraction, a bismuth layered structure compound with m=2 is formed in all the ceramic samples. The Curie temperature T_C of the samples decreases gradually with the increase of K/Ce ions co-doping content. The piezoelectric properties of the samples are improved due to K/Ce ions co-doping, The piezoelectric constant d₃₃ initially increases and then decreases with the increase of K/Ce ions co-doping content. The ceramic with x of 0.075 exhibits the optimal properties, i.e., d₃₃ of 19.0 pC/N, the Curie temperature T_C of 735℃, dielectric loss tanδ of 0.137%, and volume density ρ of 9.113 g·cm^-3. The piezoelectric constant d₃₃ of NBTO (x of 0.075) ceramic has a good temperature stability, and the d₃₃ of NBTO ceramic annealed at 600℃ for 2 h is still as high as 17.8 pC/N, which is 93.7% of the original value (i.e., d₃₃=19.0 pC/N).

La³⁺-doped Ca_1-xLa_xBi₂Nb₂O₉(CBN-xLa, x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10) piezoceramics were synthesized by a solid-state reaction method. The crystal structure, microstructure, dielectric, piezoelectric and ferroelectric properties as well as high-temperature conductive mechanism of La³⁺-doped CBN ceramics were investigated. The results show that an appropriate amount of La³⁺ donor ion substituted for Ca²⁺ ion can optimize the crystal structure, decrease the grain size, reduce the oxygen vacancy, and effectively improve the electrical properties of CBN ceramics. The Ca_0.92La_0.08Bi₂Nb₂O₉ ceramics with the optimal performance (high piezoelectric coefficient (d₃₃=11.7 pC/N) and the Curie temperature (T_C=905℃), remanent polarization (2P_r=9.51 μC/cm²) and low dielectric loss, (tanδ=3.87% at 550℃)). After annealing, the piezoelectric properties of all the samples remain stable at 800℃. According to the complex impedance plots, the grain boundary and grain both contribute the impedance, and the conduction mechanism is closely related to oxygen vacancies. Moreover, La³⁺-doping can effectively improve the resistivity of CBN ceramics at high temperatures, indicating a potential application in high-temperature sensors.

A gradient structure piezoelectric fiber composite dynamic simulation model for energy harvesting was built using a multiphasics simulation software, and the effects of the interdigitated electrode structure, applied load and piezoelectric active layer parameter on the energy harvesting behavior were studied. The results show that under the same active layer structure parameters, gradient structure piezoelectric fiber composites can obtain larger output voltage than traditional structures. Under the fixed gradient structure parameters, the polymer elastic modulus is smaller, the higher the output voltage. And the output voltage increases first and then decreases as the volume fraction of the piezoelectric fiber increases. The larger the elastic modulus of the polymer, the higher the volume fraction of the piezoelectric fiber when the maximum output voltage is obtained. Reasonable adjustment of the mechanical load frequency and load resistance of the system can effectively enhance the electrical output performance of the energy harvesting model.