Dynamic mechanical analysis (DMA) has the advantage of high sensitivity, excellent cooling system, flexible rotation testing part, multiple deformation mode, and continuous frequency and temperature scanning mode. DMA is able to characterize the strain response under alternating stress, creep, stress relaxation, and thermomechanical properties, which has application in the investigation of plastic, thermoset, composite, high elastomer, coating, alloy and ceramic. This paper briefly introduced the fundamental and method about DMA, the application of DMA in the investigation of ferroelectric-paraelectric phase transformation, low frequency relaxation, ferroelectric fatigue, and ferroelectric composite damping. In the measurement of relaxation behavior of PZT ceramics and single crystals, and BaTiO₃ ceramics, DMA tended to be more sensitive than dielectric characterization especially in the low frequency range. DMA has been one of the critical instruments for ferroelecric investigation.

Lead-based complex perovskite ferroelectric materials have been widely used as electromechanical sensors, actuators, and transducers. Among them, Pb(Ni_1/3Nb_2/3)O₃-PbTiO₃ (PNN-PT) based solid solution has been drawn much attentions of scientists for its excellent dielectric and piezoelectric properties near morphotropic phase boundary (MPB) region. However, the relatively high dielectric loss and low Curie temperature near MPB region limited its application in high temperature and high power devices. In this work, Pb(In_1/2Nb_1/2)O₃ (PIN) was introduced into PNN-PT ceramics for improving their electrical properties and Curie temperature. The ternary ferroelectric ceramics Pb(In_1/2Nb_1/2)O₃-Pb(Ni_1/3Nb_2/3)O₃-PbTiO₃ were successfully prepared by a two-step synthesis process. All samples exhibited pure perovskite phase without any secondary phase. The structure transferred from rhombohedral to tetragonal phase with increasing PT content. The MPB phase diagram of ternary system at room temperature was established based on XRD results. The values of Curie temperature were improved significantly after PIN added into PNN-PT system. Importantly, the introduction of PIN into PNN-PT system can effectively reduce dielectric loss and conductivity. The ceramics in the MPB region exhibited excellent properties. 0.30PIN-0.33PNN-0.37PT ceramic was found to have optimal properties with d₃₃=417 pC/N, T_C=200 ℃, ε′= 3206, tanδ=0.033, P_r=33.5 μC/cm² and E_c=14.1 kV/cm at room temperature, respectively. The Curie temperature and piezoelectric coefficient were improved while dielectric loss and conductivity were reduced after the introduction of PIN into PNN-PT. The enhancements of piezoelectric properties and high Curie temperature make this ternary system a promising material for high power and high temperature transducer applications.

Co-TiO₂ nanocomposite film is a novel spin electron material with good biocompatibility, attracting wordwide attention in recent years. However, during the preparation process, the magnetic metal is exposed to the oxidizing atmosphere, which tends to form partial oxidation, thus affecting the properties of the tunnel magnetoresistance. In order to inhibit the oxidation of magnetic metal and improve the metal state, Co-TiO₂ nanocomposite films were prepared by strong magnetic target co-sputtering. In this method, the strong magnetic target head has the characteristics of high magnetic field intensity and uniform distribution, which can significantly improve the sputtering particle energy and sputtering rate. This process could reduce the probability of oxidation caused by high energy particle collision during sputtering. Therefore, the method can inhibit the oxidation of metal Co, improve the spin polarizability of nanocomposite films. The Co-TiO₂ nanocomposite film is mainly composed of amorphous TiO₂ matrix and dispersed Co particles. By adjusting the particle size and distribution of Co particles, the electrical properties of the films show the transition from metal state to insulated state. Moreover, the magnetic properties of the films show the transition from ferromagnetic state to superparamagnetic state. When the Co content is 51.3at%, the Co-TiO₂ nanocomposite films exhibit high metal state and high resistivity, and room temperature tunneling magnetoresistance up to 8.25%. By strong magnetic target co-sputtering, the room temperature magnetoresistance performance is improved in Co-TiO₂ nanocomposite films, which is valuable for the study of magnetic metal-oxide nanocomposite films.

As an important transition metal oxide, manganese dioxide (MnO₂) has attracted more and more attention due to its abundant reserves, varied crystal types and excellent material properties. Nanostructured MnO₂ has smaller size and larger specific surface area, that makes it can further optimize its material properties and expand its application fields. In the introduction, this article starts with the introduction of the application of manganese dioxide, and points out that nanostructuring and variability in crystal form have an important influence on the structure and properties of manganese dioxide. The main text summarizes and reviews the research progress in recent years from two aspects: the preparation methods and the applications of nanostructured MnO₂. (1) This paper introduces the progress in the preparation methods of nanostructured MnO₂ including hydrothermal, Sol-Gel, chemical precipitation, solid-phase synthesis. Then the advantages and disadvantages of preparation methods, the morphologies and properties of nanostructured MnO₂ are summarized. (2) The applications of nanostructured MnO₂ including energy-storage electrodes, electrochromic devices, catalysts and bio-sensors are reviewed. Nanostructured MnO₂ can be used as the cathode material of batteries and the electrode material of supercapacitors. Manganese- containing composite oxides prepared by adjusting the crystal form of MnO₂ and compounding are used as the cathode material of the lithium ion batteries, which can increase the capacities and improve the cycle stability of batteries. It has been industrialized as a cathode material for lithium-ion power batteries, and has good application prospects in the field of new energy vehicles. As the electrode material of electrochromic devices, MnO₂ is usually used by combining with other materials with large optical modulations since the color of pure MnO₂ mainly changes between brown and yellow and its optical modulation is small. For example, polyaniline/MnO₂ hybrid electrochromic film has a great difference in morphology, structure and electrochromic performance compared with pure polyaniline film, showing higher optical modulation, coloration efficiency and cycle stability. Nanostructured MnO₂ plays important roles in the catalytic conversion of ethylbenzene and the catalytic elimination of air pollutants. Nanostructured MnO₂ can increase the current response, reduce the detection limit, and greatly improve the sensitivity of detection. In recent years, it has been gradually paid attention to and widely used in the field of biosensors. For example, MnO₂ nanosheets assisted fluorescence polarization biosensors can be effective in detection of Ag⁺ in environmental water samples, PtAu-MnO₂ binary nanostructures modified graphene paper show good sensing performance in non-enzymatic glucose detection. In conclusion part, current existing problems are analyzed. The development direction of nanostructured MnO₂ applied in lithium-ion battery cathode materials and electrochromic devices are pointed out. The future prospects for development of nanostructured MnO₂ are discussed.

Uranium dioxide is a potential multi-functional material as well as nuclear rod. It exhibits excellent semiconductor performance and anti-irradiation ability. It has the similar band gap (1.3 eV) of silicon crystal (1.1 eV), its Seebeck coefficient is 4 times of the commercial thermoelectric material BiTe, and it shows higher conversion efficiency of solar cells due to its nearly full absorption. These properties make it great potential applications in the fields of semiconductor, solar energy and thermoelectricity. However, the U atoms in uranium dioxide (UO_2±x) can vary from -0.5 to 1, which is called hyperstoichiometric characteristics, resulting in some problems in crystal growth and property homogeneity. In this paper, we analyzed the structure and chemical stability of uranium oxides according to U-O phase diagrams, summarized recent research progress on crystal growth and physical properties of UO₂ crystals. UO₂ is an ideal Mott insulator with a stable electric conductivity, while the hyperstoichiometric UO_2±x crystals are semiconductors, and their physical properties, including electric conductivity, thermal conductivity and diffusion coefficient, and optical properties, are closely related to x. So far, UO₂ crystals have grown via several methods, such as chemical vapor transport (CVT), sublimation, skull melting, hydrothermal and flux. The skull melting and hydrothermal techniques are expected to improve crystal dimensions and quality in future. The growth of UO₂ crystals is expected to enhance the understanding of the material and provide the possibility of great potential applications in solar cells, thermoelectric devices and future electronics.

A thin and dense high-performance T-type zeolite membrane was successfully prepared by a two-step seed crystal induction plus two-step temperature-varied hydrothermal synthesis on inexpensive and macroporous α-Al₂O₃ support. This method can fully perform nucleation of seed crystal, regulate the epitaxial growth and crystal growth direction by changing the hydrothermal crystallization temperature and time during the two-stage. Finally a continuous and defect-free a&b oriented zeolite T membrane was obtained. Effects of crystallization temperature and crystallization time of the first-stage and crystallization temperature of the second-stage on the surface structure and properties of zeolite membranes were investigated. The T-type zeolite membrane prepared under the optimal two-step crystallization condition displayed high pervaporation performance with flux over 3.84 kg·m ^-2·h ^-1 and separation factor higher than 10000 for separation of 90wt% isopropanol/water at 75 ℃.

A lightweight, environmentally-friendly thermal insulation coating was experimentally applied to the carbon fiber to reinforce epoxy resin composites. The coating is mainly composed of bonding layer, barrier layer and reflective layer, and prepared by using titanium dioxide, silica, aluminum oxide and hollow glass microspheres as function fillers. The addition of waterborne polyurethane with a thermal expansion coefficient of 120×10 ^-6 K ^-1 as a film-forming material, is to solve the problem of cracking caused by the mismatch of the thermal expansion coefficients of the coating and the substrate material. The results show that after being applied the coating, can solidify within 24 h at room temperature. When the thicknesses of the bonding layer, the heat barrier layer and the reflective layer were 80, 120, and 90 μm, the thermal insulation coating has the best performance with reflectance of the coating higher than 0.95, the thermal conductivity at 0.048 W·m ^-1·K ^-1 and the temperature difference as high as 20.1 ℃. After being subjected to thermal shock at 190 ℃ for 6 times, and the maximum weight loss rate of the coating was 3.7%, indicating the coating highly stable. When kept at 160 ℃ for 4 h, its surface turned yellow without falling off, and its nano filler particles still remained stable.

CoFe₂O₄ nanofibers with fishbone-like structure were prepared by a electrospinning method followed with high temperature calcination, using polyvinylpyrrolidone (PVP), iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O) and cobalt nitrate hexahydrate (Co(NO₃)₂·6H₂O) as raw materials. Results show that the crystallinity and grain size of nanofibers become larger with increasing calcination temperature. Meanwhile, the surface morphology of CoFe₂O₄ nanofibers changes from smooth to rough and porous. The morphology of CoFe₂O₄ nanofibers exhibits a fishbone-like structure with calcination temperature exceeding 800 ℃. The diameter of the fiber is gradually decreased with the increase of calcination temperature, and the average diameter of CoFe₂O₄ nanofibers calcined at 900 ℃ reaches 80.3 nm. By vibration sample magnetometer (VSM) test, the saturation magnetization (M_s) of CoFe₂O₄ nanofibers increases with the increase of calcination temperature, and the M_s of CoFe₂O₄ nanofibers calcined at 900 ℃ is 87.13 A·m²/kg. In a result of vector network analyzer (VNA) analysis, the microwave absorption performance is significantly different with calcination temperature changing. Among them the fibers calcined at 800 ℃ have the highest wave absorption ability. The microwave absorption mechanism of CoFe₂O₄ nanofibers mainly includes hysteresis loss and eddy current loss. The morphology of porous and fishbone-like generated by calcination can increase the reflection loss, for the reason that this morphology is beneficial for microwave reflection multiple times on the fiber surface.