Sm³⁺ doped SrBi_8-xSm_xTi₇O₂₇(SBT-BIT-xSm³⁺, 0≤x≤0.50) inter-growth bismuth layer-structured ceramics were prepared by a conventional solid-state method. The effect of Sm³⁺ doping on the structural, electrical and photoluminescence properties of SBT-BIT-xSm³⁺ ceramics were investigated. All the samples show a single inter-growth bismuth layer-structure. Based on the results by the Rietveld analysis and Raman spectroscopy, the lattice distortion decreases. The dielectric loss (tanδ) decreases and piezoelectric constant (d₃₃) increases with the increase of Sm³⁺ doping content. SBT-BIT-xSm³⁺ ceramic with x of 0.30 exhibits an optimum electrical behavior, i.e., d₃₃=16.3 pC/N, and tanδ=0.90%. Moreover, Under a near ultraviolet excitation at 407 nm, a most intense red orange emission appears at 598 nm in SBT-BIT-xSm³⁺ ceramics. The optimized emission intensity was obtained when x=0.15 for SBT-BIT-xSm³⁺ ceramic. The results show that Sm³⁺ doped SBT-BIT-xSm³⁺ inter-growth bismuth layer-structured ceramics have potential applications in the field of optoelectronic multifunctional devices.

Na_0.5Bi_4.5-x(Sm_0.5Ce_0.5)_xTi₄O₁₅ (NBT-x(Sm, Ce) bismuth-layered lead-free piezoelectric ceramics were fabricated by a solid-state synthesis method, and the influence of (Sm_0.5Ce_0.5)³⁺ additive on the structure and electrical/photoluminescence properties of samples was investigated. For the ceramics modified by (Sm_0.5Ce_0.5)³⁺ dopants, the phase structure and microstructure have little changes. The electrical properties of ceramics are enhanced. As x=0.008, the remnant polarization 2P_r reaches 13.33 μC/cm², and a high Curitemperature T_C is 640 ℃. After (Sm_0.5Ce_0.5)³⁺ doping, the ceramics show a bright orange photoluminescence. The more intense emission band at 597 nm appears under an excitation at 407 nm, corresponding to the ⁴G_5/2→⁶H_7/2 energy level transition. As a multifunctional material, (Sm_0.5Ce_0.5)³⁺-modified NBT piezoelectric ceramics have promising application prospects in optoelectronic devices, sensors, etc..

The ZnO-Pr₆O₁₁-Co₂O₃-Cr₂O₃-La₂O₃ varistors were prepared by solid state sintering method. The effect of La₂O₃ doping on the microstructure, varistor property, and dielectric characteristics of the ZnO varistor ceramics were studied in detail. The results show that the ZnO varistor has the best overall performance with La₂O₃ content of 1.5% (in mole fraction), the grain size is the smallest and uniform, the breakdown voltage E_1Ma is the highest (752 V/mm), the nonlinear coefficient is large (12), the grain boundary capacitance is the largest (276 pF), and the loss tangent is relatively low.

In order to evaluate the absorbing properties of B₄C ceramic absorber, B₄C powder was fabricated via combustion synthesis with carbon black and boron oxide as raw materials, and Mg as a reductant. The microstructure of the products was characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The samples for dielectric test were prepared with B₄C powder as an absorber and paraffin as a binder, respectively. The complex permittivity of samples containing different amount of B₄C absorber was tested by a rectangular waveguide method at X band (8.2 GHz-12.4 GHz), and the reflection loss values were calculated based on the transmission line theory. The results show that the impurities such as MgO and Mg₃B₂O₆ can be removed by pickling. The grain size of the product is 0.4-1.0 μm with an oblique hexagonal structure. The real and imaginary parts of the complex permittivity increase with the increase of the content of B₄C powder. When the content is 50% (mass fraction), the real and imaginary parts are 19.33 and 10.40, respectively. The calculated results show that the optimum electromagnetic wave absorption performance can be obtained at B₄C powder content of 33%. The minimum reflection loss value is -21.1 dB when the thickness is 2.3 mm, and the effective bandwidth reaches 2.95 GHz. It is indicated that B₄C powder could be a promising candidate as a high-temperature microwave absorber.

In this paper, new lead-free luminescent ferroelectric materials, (Bi_0.5Na_0.5)_0.935-xSm_xBa_0.065Ti_1-xSb_xO₃ (BNT-0.065BT-xSmSb) ceramics, were prepared by introducing Sm/Sb. The influence of Sm/Sb on the phase structure, microstructure and electrical functions of BNT-0.065BT was systematically studied. BNT-0.065BT-xSmSb ceramics presented a pure perovskite phase structure. Doping with Sm/Sb induced a ferroelectric to relaxor phase transformation and thus promoted strain improvement. When x=0.004, the unipolar strain was 0.31% (70 kV/cm), equivalent to a large signal d₃₃^*(S_max/E_max) of 443 pm/V. Moreover, studies on the luminescence properties showed that BNT-0.065BT-xSmSb ceramics exhibited bright orange-red luminescence under 407 nm excitation. The luminescence intensity increased as the Sm/Sb doping concentration increased. The main emission peak was a strong red emission peak located near 599 nm, corresponding to the ⁴G_5/2→⁶H_7/2 transition. As multifunctional materials, BNT-0.065BT-xSmSb ceramics showed great latent capacity for optical-electrical integration and coupling device applications.

B₄C-TiB₂ multi-phase ceramics were prepared in a pressureless vacuum sintering-furnace at different temperatures with TiB₂ added into B₄C matrix as a second phase substance, and C and Si as sintering aids. The density, hardness, bending strength and fracture toughness of the samples were determined. The influences of composition ratio of B₄C-TiB₂ and sintering temperature on the microstructure and mechanical properties of the multiphase ceramics were investigated by X-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. The toughening mechanism of ceramics was discussed. The results show that the optimum density and comprehensive mechanical properties of the multiphase ceramics (i.e., the relative density of 94.59%, the Rockwell hardness of 87.62, the bending strength of 182 MPa, and the fracture toughness of 3.97 MPa·m^1/2 can be obtained at a sintering temperature of 2 200 ℃ and TiB₂ content of 30%. The TiB₂ particles can effectively nail the grain boundary, inhibit the growth of B₄C grains and play a role in fine-grain strengthening. The TiB₂ and laminated graphite phase hinder the crack growth, thus improving the fracture toughness.

A Si₃N₄ ceramic foam having a shell with the thickness of 500 μm and the thickest portion of 693 μm was prepared by a reaction sintering method with a pre-embedding powder. The shell sintered at 1 400 ℃ for 6 h appears a staggered crystal columnar structure. The length of the crystal column in the shell increases slightly when the nitriding temperature is 1 450 ℃. Prolonging the nitriding time to 10 h can transform the microstructure of shell into a coarse crystalline column structure, thus reducing an aspect ratio of the crystal column. The shell has a ceramic foam with a certain degree of elasticity (i.e., Young's modulus of elasticity is 117-352 MPa), and increases the compressive strength of the sample by 47%. In addition, the presence of shell has little effect on the porosity, density and thermal conductivity of ceramic foam.

Alumina (Al₂O₃) porous ceramics green bodies were prepared by a gel-foaming method with sodium alginate as a gelation reagent and sodium alcohol ether sulphate (AES) as a foaming agent, and Al₂O₃ porous ceramics were sintered by a pressure-less sintering technique. The relationship between the solid content/foaming agent content and the porosity/compressive strength of Al₂O₃ green bodies was investigated. The effect of sintering temperature on the microstructure and mechanical property of Al₂O₃ porous ceramics and the curing mechanism of sodium alginate were analyzed. The result show that alumina particles are solidified by a network formed due to the reaction between sodium alginate and free calcium ions. Al₂O₃ porous green body with a high porosity and a uniform aperture can be obtained under the optimum condition (i.e., solid content of 25% and foaming agent content of 3.0%). The porosity of Al₂O₃ porous ceramics decreases and the compressive strength increases with the increase of sintering additive content. Excessive sintering temperature leads to the abnormal growth of Al₂O₃ grain, thus reducing the compressive strength.

The effect of TiN source (i.e., TiN powder, TiO₂ powder and TiO₂ sol) on the phase compositions, microstructures and mechanical properties of hot-pressed Si₃N₄-TiN ceramics was investigated. The results show that only β-Si₃N₄ and TiN phases are detected for the sample with TiN powder. The sizes of β-Si₃N₄ and TiN grains are large, the Vickers hardness, flexure strength, and fracture toughness are (15.6±0.3) GPa, (1 058±78) MPa, and (11.2±0.6) MPa·m^1/2, respectively. However, the O′-Sialon phase appears in the sample with TiO₂ powder in addition to β-Si₃N₄ and TiN phases, and the content of O′-Sialon is 8.7wt%. Due to the relatively fine grains of β-Si₃N₄ and TiN, the Vickers hardness increases to (16.7±0.4) GPa, and the flexure strength and fracture toughness are (986±76) MPa and (11.3±0.4) MPa·m^1/2, respectively. Moreover, the O′-Sialon phase appears in the sample with TiO₂ sol, the content of O′-Sialon is 12.5wt%, and the size of β-Si₃N₄ and TiN grains is finer, having a higher Vickers hardness (i.e., 16.6±0.5 GPa), and relatively lower flexure strength (i.e., 788±94 MPa) and fracture toughness (i.e., 10.2±1.0 MPa·m^1/2). Si₃N₄-TiN ceramics with uniformly fine microstructures and good mechanical properties can be thus obtained with TiO₂ powder.

Results regarding the fabrication of SiC coating layers and other SiC-related materials for nuclear reactor applications are reported herein. A fluidized bed chemical vapor deposition (FB-CVD) method was used to prepare the SiC coatings, and the coating process was simulated using the newly proposed multiscale coupling model to enhance the coating uniformity. Different kinds of SiC series products, such as dense SiC layers, fine-grained SiC coating layers, SiC/C/Si mixed coating layers, porous SiC coating layers, SiC nanowires and SiC nanoparticles, were developed for nuclear energy applications. Postulated accident conditions, such as air ingress, wereconsideredto evaluate the reliability of the SiC coating layer. An irradiation test was also performed in ahigh-flux nuclear reactor, and the results validated the high performance of SiC coating materials in nuclear reactor applications.

The use of zirconia ceramics in humid environments is limited by the phase transformation from the tetragonal phase to the monoclinic phase. In this study, an oscillatory pressure sintering (OPS) technique was developed for the preparation of zirconia ceramics that were characterized by high density, fine grain size and excellent mechanical properties. The hydrothermal aging behaviors of the oscillatory pressure sintered and hot-pressed zirconia were investigated. The Raman analysis showed strong peaks at 178 and 189 cm^-1 in both the oscillatory pressure sintered and the hot-pressed specimens, but the peak intensities of the oscillatory pressure sintered specimen were much weaker than those of the hot-pressed specimen. When the specimens were aged for 18 h, the flexural strength of the oscillatory pressure sintered zirconia reached approximately 1 216 MPa, which is much higher than that of the hot-pressed zirconia. Therefore, the OPS technique is promising for the preparation of zirconia ceramics that are used in the biomedical field.

A preparation method to improve the dispersion of zirconia particles in the slurry and the strength of the ceramic body was proposed. The physicochemical properties of the slurry were analyzed. The ceramic slurry was extruded via micro-flow extrusion forming, and the mechanical properties of the printed body were analyzed. The results show that the size of zirconia particle reaches a minimum value and the zeta potential is maximum after ball milling at 600 r/min for 12 h. The slurry with 5%-6% sodium polyacrylate has the lowest viscosity at pH 8.5. Zirconia slurry prepared under the optimized conditions (i.e., grinding parameters and dispersant content) is smooth in the extrusion process and meets the requirements of micro-flow extrusion. The surface roughness and mechanical properties of sintered printed blank are satisfactory, thus meeting the mechanical performance requirements of denture.

To solve thermal mismatch problem in the bonding process of RB-SiC ceramic using borosilicate glass braze (BS), β-eucryptite/BS composite braze (BSL) was designed. The effect of β-eucryptite addition on a) the characteristic temperature, thermal expansion coefficient and wettability of composite glass braze, as well as b) the microstructure and mechanical properties of joints was investigated. The thermal expansion coefficient of BSL decreases and its rate increases with the increase of β-eucryptite amount. Also, the characteristic temperature of BSL and its rate both increase with the increase of β-eucryptite amount. The apparent contact angle of BSL increases at the same temperature, and the variation of apparent contact angle along with temperature becomes slow. The RB-SiC/composite glass solder (BSL3)/RB-SiC joint has the similar interface to the RB-SiC/BS/RB-SiC joint bonded at 850 ℃ for 10 min. However, in the glass seam, β-eucryptite turns into massive gray KAlSiO₄ crystals (i.e., kaliophilite). The massive KAlSiO₄ crystals with a negative expansion characteristic can reduce the thermal expansion coefficient and prevent the crack propagation, thus strengthing the joint. The shear strength of the joint after reinforcement increases from 5.2 MPa to 10.9 MPa.

The insulating ceramic plate was sintered and surface-decorated using molybdenum tailings as the main raw material (55%) with kaolin, red sludge, feldspar, glass powder and blowing agent incorporated. The water absorption, bulk density, compressive strength and thermal conductivity of the insulating ceramic plate were measured, and the microstructure was observed and the pore diameter was counted. The effects of firing temperature, slurry fineness and addition of blowing agent on the pore size of insulating ceramic plates were studied. The results show that the addition of blowing agent has the most significant influence on the pore structure, pore size and distribution of the insulating ceramic plate, and is the key to obtain low thermal conductivity. In this study, the prepared molybdenum mine tailings-based insulating ceramic plate has high solid content, excellent thermal insulation performance and light weight, and is surely a new building insulation material with broad market prospects.

The thermal stability of the stack repeating unit and short stacks was investigated for a flat tube anode-supported solid oxide fuel cell based on double-sided cathodes under rapid cycling condition from room temperature to operating temperature. The cell can experience a secondary pressure on cathode sides due to its anti-destructive characteristics, and the performance of the stack repeating unit and short stack can be improved slightly or keep stable during rapid thermal cycles. The cell characteristics of experiencing rapid thermal cycling and secondary pressure give a foundation for its rapid start-up and reuse, indicating a new feature of large-scale solid oxide fuel cell and having broad potential applications.

Hard carbon material was extracted from an expired composite donkey-hide gelatin pulp via hydrothermal carbonization pelletizing and subsequent pyrolysis reaction. The corresponding micro-morphology, element composition, structure and Na-storage performances were investigated. The results show that the obtained carbon material manifests a smooth microsphere-like morphology with the mean diameter of 4.3 μm, and N and S elements evenly distribute in carbon micro-spheres with a low degree of graphitization. The reversible discharge specific capacities are 225 and 180 mAh/g at 0.5 and 1.0 A/g for 500 cycles, respectively, and the reversible discharge specific capacity remains 108 mAh/g even at 2.0 A/g for 1 000 cycles, indicating the electrochemical Na-storage cycling performances at the large current density. The results could facilitate to promote the development of the circular economy mode of expired waste medicine and the green energy.

Two kinds of CuS counter electrodes with different morphologies applied to QDSC were prepared by a solvothermal method and an in-situ method, respectively. The prepared counter electrodes were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy (EIS) and current-voltage (J-V) curve measurement, respectively. According to the results by morphology analysis, CuS nanoparticles with a size of 20 nm can be agglomerated into larger and irregular particles in CuS counter electrode prepared by the in-situ method, and CuS counter electrode prepared by the solvothermal method consists of nanorods and nanoparticles in microstructrue. The results reveal that two kinds of CuS counter electrodes are superior to Pt counter electrode in the electrical performance. CuS counter electrode prepared by the in-situ method yields the maximum power conversion efficiency (i.e., 1.840%) and the charge transfer resistance R_ct is 3.346 Ω. CuS counter electrode prepared by the solvothermal method yields a power conversion efficiency of 1.450% and R_ct is 2.609 Ω. The corresponding parameters of Pt counter electrode are 0.940% and 11.680 Ω, respectively.

The performance of direct internal reforming of ethanol as a fuel in a flat tube solid oxide fuel cell based on double-sided cathodes was investigated. The results show that the cell can operate stably for 100 hours with a power density of 0.137 W/cm²@0.8 V when ethanol is injected into the cell at a constant water to carbon ratio. A slight carbon deposition only occurs inside the cell. The structure cell can be applied for direct internal reforming of carbon-containing fuels, indicating a promising potential for use.

A series of orange red-emitting NaLa_1-xSm_xMgWO₆ phosphors were synthesized by a conventional solid-state reaction method. The crystal structure, microstructure, luminescence properties and thermal stability were investigated. The results show that NaLa_1-xSm_xMgWO₆ crystals form in a monoclinic structure with a space group of C2/m. Under an excitation at 406 nm, the emission spectra of NaLa_1-xSm_xMgWO₆ phosphors exhibit a most intense red emission peak at 645 nm, corresponding to the ⁴G_5/2→⁶H_9/2 transition of Sm³⁺. The photoluminescence intensity of the sample firstly increases and then decreases with the increase of Sm³⁺ doping concentration. The optimal concentration of Sm³⁺ appears at x=0.05. The mechanism of energy transfer between Sm³⁺ is proved to be dipole-dipole interaction based on the analysis of the concentration quenching curve. In addition, the temperature quenching behavior was also investigated according to the Arrhenius equation, and the results reveal that the quenching process of ⁴G_5/2 can be ascribed to the crossover process, and the calculated activation energy is 0.326 eV.

ZIF-67 as one kind of zeolitic imidazolate frameworks was synthesized by a conventional precipitation method, and the mother liquor was concentrated and crystallized to recover cobalt-based compounds. For AB hydrolysis, two kinds of Co₃O₄ catalyst precursors (i.e., Co₃O₄-S and Co₃O₄-L) were prepared from the ZIF-67 and recovered compounds via calcination treatment, respectively. The morphology and phase composition of the samples were characterized by field-emission scanning electron microscopy and X-ray diffraction, respectively. Effects of AB and catalyst concentration and reaction temperature on the hydrogen generation rates and kinetics were investigated. The results show that Co₃O₄-S has a porous and polyhedral structure, and Co₃O₄-L is composed of nanoparticles. In addition, increasing AB and catalyst concentration can enhance the hydrogen generation rates. The maximum hydrogen production rates do not decline in the presence of Co₃O₄-S, but decrease to 78% of the initial level in the presence of Co₃O₄-L after recycling for four times.