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A series of (Ti0.5Nb0.5)C-x wt.% SiC (x = 0, 5, 10, 20) composites were prepared by spark plasma sintering. Dense microstructures with well‐dispersed SiC particles were obtained for all composites. With the increment of SiC content, the Vickers hardness, Young's modulus and fracture toughness increase monotonically. An optimized flexural strength of 706 MPa was achieved in (Ti0.5Nb0.5)C-5 wt.%SiC composite. (Ti0.5Nb0.5)C-20 wt%SiC composite exhibits the highest fracture toughness of 6.8 MPa m1/2. The crack deflections and the suppression of grain growth were the main strengthening and toughening mechanisms. Besides, (Ti0.5Nb0.5)C-20 wt%SiC composite exhibit the highest thermal conductivity of 45 W/m·K at 800 °C.

The garnet electrolyte Li7La3Zr2O12 with excellent electrochemical properties is one of the crucial materials in all-solid-state batteries. However, the abnormal grain growth (AGG) phenomena easily occurring during sintering process could damage the mechanical strength of the electrolyte. In this paper, a series of Ga–Ba co-doping LLZO samples, Li7-3x + yGaxLa3-yBayZr2O12 (x = 0.25 and y = 0.01, 0.03, 0.05, 0.15, 0.25, 0.35, 0.45, LGBLZO), were synthesized through sol-gel method to investigate the effects of Ba content on phase, morphology and ionic conduction in ceramics. The results demonstrated the influence mechanism of Ba ions in LGBLZO ceramics as follows. Firstly, the Ba ions as substitution of La sites could regulate the concentration of Li ions in lattice, reducing the bulk resistance. Secondly, the BaZrO3 embedded between grains could prevent abnormal growth of grains effectively. These ceramics acquired optimal relative density after sintering at 1160 °C for 15 h. When the Ba ions feed ratio reaches 0.25 pfu, the LGBLZO (y = 0.25) exhibits excellent performance with a relative density of 94.8%, an ionic conductivity of 8.30 × 10−4S/cm and an activation energy of 0.228eV. Above researches provide ideas for the preparation of compact LLZO ceramics with uniform grain size and outstanding properties.

The long application life and reliable performance of magnesium alloys have been putting forward strict requirements for both better chemical stability and functional characteristics of protective coating. Herein, a highly reliable superhydrophobic double-layer coating on AZ31 Mg with excellent anti-corrosion and electrical protection was achieved by assembling modified SiO2-based organic-inorganic hybrid films on Plasma Electrolytic Oxidation (PEO) ceramic bottom layer. The coating exhibits preferable antiwater surfaces with a barrier layer isolating the underlying substrate from the external environment, rendering a long-term active corrosion protection for the multilayer covered magnesium alloy. Remarkably, the coating achieves high electric insulation with volume resistivity of 1.7 × 1012 Ω cm, breakdown voltage of 1405.2 ± 117.1 V and dielectric strength of 40.2 ± 3.3 V/μm. Simultaneously, its dielectric properties with a low dielectric constant (e ≈ 3.75) and a low dielectric loss (tan δ ≈ 0.0058) outperform those of some current dielectric coatings with similar components. Moreover, the superhydrophobic coating displays strong mechanical robustness undergoing 50th linear abrasion, superior environmental stability (thermal shock, prolonged solution immersion, salt-spray corrosion and UV irradiation), and high adhesion strength. The excellent multifunction benefits from the introduction of ceramic bottom layer, the assembly of compact nanocomposite films, and the synergistic effect of organic-inorganic components. This study provides a new inspiration for designing advanced protective coating with a great potential for the applications of sensitive electronic devices.

Cr doped diamond-like carbon (DLC) coating was deposited on the carburized Ti6Al4V alloy (TA) by magnetron sputtering (MS). The physical and chemical characteristics of Cr doped DLC coating were obtained using scanning electron microscope, energy dispersive spectroscope, Raman spectrometer, X-ray photoelectron spectroscopy and Fourier transform infrared, and the mechanical property and adhesion force were analyzed by nanoindenter and scratch tester. The effects of carburizing treatment on the coefficient of friction (COF) and wear mechanism of Cr doped DLC coatings were investigated on a ball-on-disk tribometer. The results show that the adhesion force and mechanical property of Cr doped DLC coating deposited on the carburized TA are higher than those deposited on the original TA. The average coefficients of friction (COFs) of Cr doped DLC coatings deposited on the original and carburized TAs under the dry-friction condition are 0.157 and 0.143, respectively, showing that the carburizing treatment has the obvious effect of friction reduction for the Cr doped DLC coating. The wear mechanism of Cr doped DLC coating deposited on the carburized TA is combined action of abrasive wear and adhesive wear, which are contributed to the enhancement of mechanical property of Cr doped DLC coating by carburization treatment. Furthermore, the average COFs of Cr doped DLC coatings deposited on the original and carburized TAs under the oil-lubrication condition are 0.152 and 0.131, respectively, which are superior to those under the dry-fiction condition. The carburizing treatment promotes the formation of self-repairing carbonyl of Cr doped DLC coating, and the oil-wet characteristic of Cr doped DLC coating with the aromatic aldehyde of C O as the functional group plays the main role of friction reduction.

Continuous carbon-fibre-reinforced Cs-geopolymer composite (Cf/CsGP) were prepared, and its in-situ conversion was investigated during high-temperature treatments. The effect of treatment temperature on the thermal evolution process and mechanical properties of the resulting products were systematically evaluated. The results indicated that the crystallization temperature of Cf/CsGP composite was considerably delayed because the amorphous structure of carbon fibres was not conducive as a nucleation substrate for pollucite derived from the CsGP matrix. Moreover, the integrity of the corresponding resulting products derived from the Cf/CsGP composite were damaged due to thermal shrinkage that occurred during the high-temperature treatment process. When treatment temperature was ≤1200oC, the mechanical properties of the corresponding products exhibited an upward trend, which was ascribed to the improvement of the densification degree of the resulting composite and well interface-bonding state between carbon fibres and pollucite. However, the mechanical properties of the resulting composites decreased with the treatment temperature continued increased from 1200 to 1400oC. This phenomenon was attributed to the impairment of fibre properties caused by interfacial reactions.

Laminated B4C–TiB2 ceramics with h-BN interface layers were successfully prepared by roll forming and tape casting, and samples with different numbers of stacked layers were obtained. Scanning electron microscopy and X-ray diffraction were used to analyze the microstructure and interlayer crystal phases of the composites, and the bending strength, fracture toughness, and work of fracture were measured. As the number of h-BN layers increased, the fracture toughness increased from 7.38 ± 0.5 MPa m1/2 to 9.01 ± 0.61 MPa m1/2, which is 2–3 times higher than that of monolithic B4C ceramics. As the fracture toughness increased, the hardness remained at a high level (31.67 GPa). Bending tests showed that cracks deflected when they encountered the h-BN interfacial layers. The toughening mechanisms included the deflection and branching of cracks and generation of new microcracks, which increased the length of the propagation path and work of fracture.

MXenes have good application prospects due to the attractive mechanical and physicochemical properties. Here, for the first time, silicoboron carbonitride (Si–B–C–N) ceramics with the integration of MXene(Ti3C2Tx) nanosheets were developed, and the influences of MXene additives (1.0–3.0 wt%) on mechanical properties and microstructures were investigated. The ceramics containing 3.0 wt% MXene(Ti3C2Tx) show better mechanical properties including fracture toughness of 7.6 MPa‧m1/2, 36% higher than ceramics without any additives. The toughening mechanisms consist of pull-out, delamination, crack bridging, and crack deflection. This work demonstrates that MXenes are good reinforcements for enhancing the fracture toughness of structural ceramics, and also paves the way for the investigation of high-temperature properties of MXene-containing ceramics.

Porous polycaprolactone (PCL)/calcium sulfate hemihydrate (CSH) composite fibers with different compositions were fabricated via electrospinning by using chloroform/dimethyl sulfoxide (volume ratio = 8:2) as the co-solvent. It was found that the incorporation of fine CSH powders greatly improved the morphology of the PCL fibers and generated continuous, bead-free PCL/CSH composite fibers with the pore diameter varying from 0.2 to 1.1 μm when 20% CSH was added. As compared with the PCL fibers, the PCL/CSH composite fibers also exhibited enhanced thermal stability and hydrophilicity. The tensile strength and elastic modulus of the PCL/CSH fibrous membranes first increased and then decreased with the increase of the CSH content, while their ductility exhibited a sustained decrease. Moreover, after immersion in water, the PCL-20%CSH composite fibers presented a much higher tensile strength than the pristine ones probably due to the self-setting of the CSH powders through the porous structure. In addition, the PCL-20%CSH composite fibers displayed a strong ability to form bone-like apatite after immersion in simulated body fluid for 3 days, which suggests their potential applications in bone tissue regeneration as a novel type of substitute.

β-Si3N4 ceramics were prepared by gas pressure sintering using α-Si3N4 powders, β-Si3N4 whiskers and Re2O3–MgO (Re = Y, La, Gd, Ho, Yb) additives. The phase transformation from α-Si3N4 to β-Si3N4 was completed after sintering. The distribution of oxide particles gets more homogeneous with the increase of the atomic number of the Re element, resulting in an increase of the grain size and the formation of elongated β-Si3N4 grains, which significantly influence the fracture mode and the mechanical properties of β-Si3N4 ceramics. The thermal conductivity of β-Si3N4 ceramics is determined by both the grain size and the distribution homogeneity of oxide particles, thus showing no regular trend between different specimens.

Tris(dichloromethylsilylethyl)borane is a compound containing a B-C bond and Cl and H elements. Herein, we propose a novel method to synthesize polyborosilazanes using tris(dichloromethylsilylethyl)borane and boron trichlorosilane as boron sources and hexamethyldisilazane as a nitrogen source. The microstructure and chemical composition of the as-synthesized polyborosilazanes and as-annealed SiBCN ceramics were investigated using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, Raman spectroscopy, scanning electron microscope, and transmission electron microscope methods. The organic precursors were converted entirely into inorganic ceramics at 800 degrees C, and the ceramic yield of the polyborosilazanes was 88% at 1000 degrees C. SiBCN ceramics with irregular shapes contained chemical bonds of B-N, Si-N, and Si-C at 1500 degrees C and retained an amorphous structure below 1600 degrees C. After the first cycle, the fabricated SiBCN ceramic anodes exhibited a reversible capacity of 261.3 mA h/g, which was 2.6 times that reported in the literature (101 mA h/g). The discharge capacity decreased to 157.6 mA h/g after 30 cycles. The satisfactory electrochemical performance of the resulting SiBCN ceramic anodes can be attributed to the formation of conductive carbon species favoring the transport properties of lithium ion.

In this study, SiC whiskers (SCWS) reinforced geopolymer composites (SCWS/KGP) and their ceramic products (SCWS/leucite) were prepared, and effects of SiC whiskers contents on the microstructure and flexural strength of the SCWS/KGP and SCWS/leucite composites were investigated. The results show that the whisker addition has little influence on both phase composition and thermal shrinkage of the KGP composites, but a suitable content of whisker will result in the improved flexural strength, and when the SCWS content is 2 wt%, flexural strength of the SCWS/KGP composite is enhanced by 95% compared with the neat geopolymer. The flexural strength of the composites can be further enhanced significantly after the composites being treated at 1100 °C and 1200 °C and flexural strength of the composite with SCWS content of 2 wt% was 107% and 125% higher than the untreated counterpart, respectively. The increase in flexural strength of the composites should be attributed to the strong leucite formation, whisker debonding and pulling out from matrix during the fracturing process based on the good interfacial bonding state between whisker and leucite matrix.

The high-temperature service performance of nearly fully dense 20 wt% BNW/SiO2 ceramic was systematically investigated. The oxidation damage and strength degradation of the whiskers combined with the surface microstructures of the samples predominantly influence the flexural strength from RT to 1000 °C. In previous work, the temperature dependence of the material properties is invariably ignored when evaluating thermal stress crack initiation and propagation behaviour. In this work, modified thermal shock models that include temperature-dependent material properties were established based on thermal-shock fracture (TSF) theory and thermal-shock damage (TSD) theory. Then, the thermal shock resistance (TSR) of the BNW/SiO2 ceramic was evaluated by preforming a water quenching test. The modified models could better explain the TSR behaviour of the ceramic, indicating that considering the temperature-dependent material properties will reveal the thermal shock damage mechanism more precisely.

The ablation properties and mechanisms of BN-coated Cf-reinforced SiBCNZr composites under an oxyacetylene combustion torch were investigated. The mass and linear ablation rates of the Cf/SiBCNZr ceramic matrix composites were lower than those of Cf/SiBCN and SiCf/SiBCN composites, reaching 0.0022 mg/s and 0.0136 mm/s, respectively. The ablation resistance of the SiBCN ceramics was enhanced by the addition of Zr, whereas the BN-coated Cf increased the thermal shock resistance of the SiBCNZr ceramics. No macrocracks were found on the ablation surface of the Cf/SiBCNZr specimen. The ablation mechanisms based on different ablation temperatures, phase evolution during ablation, and ablation morphologies in the different ablation regions consisted of oxidation of the carbon fibre and ceramic matrix, emission of various gases, the flow of high-viscosity SiO2, and denudation of Cf under the erosion of the ablation flame.

With excellent specific capacity, superior cycle stability, safety and strong practical, Nb2O5 has been considered as one of the prospective anode materials for lithium-ion batteries (LIBs). However, current study suggests that Nb2O5 electrode materials for LIBs still face the vital issues of low electrical conductivity and poor rate performance. Therefore, carbon-coated TT-Nb2O5 materials are designed and synthesized through solid state method in this work, which present high specific capacity (228 mA h g−1 at 0.2C), satisfactory rate properties (107 mA h g−1 at 20 C). The outstanding electrochemical property can not only give the credit to the pseudocapacitance effect of TT-Nb2O5, but also attribute to introduction of carbon. The homogeneous carbon-coated materials enhance the electrical conductivity, increase the electron transmission speed and alleviate particle crushing. This research not only offers a new method for preparing excellent electrode materials, but also provides a kind of excellent anode material with prospective application for LIBs.

To improve the passive radiative heat dissipation property of aluminum alloy, a novel-structural SiC/hBN nanocomposite ceramic coating with high emissivity value (>0.86) was fabricated by one-pot liquid-phase plasma assisted electrophoresis and sintering (LPES) method. The special formation conditions of nanocomposite coating were optimized as: applied voltage was not lower than 600 V, temperature of electrolyte was ranged from 70 to 90 °C and the concentrations of SiC and hBN nanoparticles were 8 g/L and 40 g/L, respectively. The unique parameters contributed to the plasma assisted SiC and hBN nanoparticles synergistic electrophoresis and then sintering together by SiO2 based glassy phase. The infrared emissivity in the wavelength of 3–20 μm was enhanced by SiC/hBN nanocomposite coating, especially the value was up to 0.86 in 3–8 μm wavelength. The nanocomposite coating enabled the temperature drop by 10.4 °C for 1 W LED compared with the bare aluminum alloy, which leds to the cooling efficiency of 19.8%, respectively. The SiC/hBN ceramic nanocomposite coating fabricated by one-pot LPES process shows a novel strategy to design excellent radiative heat dissipation property coatings.

In this paper, we have discussed the synthesis of nanoscale silicoboron carbonitride (SiBCN) nanofibers by electrospinning of novel polyborosilazane precursor solutions, which were synthesized from boron trichloride, tris(dichloromethylsilylethyl)borane and hexamethyldisilazane using a one-pot method, followed by pyrolysis at 1000 °C under nitrogen atmosphere. The influence of the processing procedure (solution concentration, feeding rate and spinning voltage) of the electrospum fibers was also investigated. TGA and FT-IR experiments were employed to study the polymer-to-ceramic conversion and SEM was used to characterize the final materials. Combining the precursor derived ceramics route and electrospinning process enables to product SiBCN nanofibers for industrial applications.

The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock.

Li-excess cation-disordered rocksalt oxides have attracted extensive attention for their high capacity (>210 mA h g−1) and energy density. In these oxides, both cationic and anionic redox take responsibility for bringing capacity. However, anionic evolution as well as their intrinsic poor electronic conductivity raises the problem in large polarization and inferior rate performance of these oxides, especially for Ni-based ones. Herein, we report a facile strategy to synthesize a series of Li1·2Ni0·3Ti0·3Nb0·2O2 (LNTNO20) @ C using different mass ratios of carbon precursor and calcination temperatures. It is found that carbon-coated materials possess impressive electrochemical properties with both high specific capacity and rate performance. Specifically, Li1·2Ni0·3Ti0·3Nb0·2O2@C synthesized with ratio of 6:1 (LNTNO20: sucrose) and calcination temperature of 450 ○C exhibits an initial specific capacity of 268.2 mA h g−1 and a high capacity retention of 90.1% after 50 cycles. Based on multi-scale test results, we propose that carbon coating process using moderate mass ratio of carbon precursor and calcination temperature will increase tetrahedron height making Li diffuse easily. Besides, carbon coating layer reduces polarization upon cycling, protects cathode from reacting with electrolyte retarding SEI layer thickening and enhances electronic conductivity. Therefore, carbon coating is a facile and effective strategy to improve properties of Ni-based cation-disordered oxides.

High-entropy metal boron carbonitride ceramic powders including (Ta0.2Nb0.2Zr0.2Hf0.2W0.2)BCN, (Ta0.2Nb0.2Zr0.2Hf0.2Ti0.2)BCN, and (Ta0.2Nb0.2Zr0.2Ti0.2W0.2)BCN, were successfully synthesized via mechanical alloying at room temperature. Results show that for the first step of 10 h milling, the amorphous BCN phases are observed. After 24 h of second step milling, the as-synthesized high-entropy ceramics exhibit a single face-centered cubic solid solution structure with high compositional uniformity from nano-scale to micron-scale. When heated to 1500 °C for 30min in flowing Ar, the as-prepared high-entropy ceramic powders still show relatively high thermal stability; however, some metals oxides like HfO2 and ZrO2 are detected due to the pre-existing oxides on sample surfaces. After heat treatment, some amorphous phases are still retained. This work suggests a new processing route on the synthesis of high-entropy metal boron carbonitride ceramics.

Porous Si2N2O ceramics strengthened by directional β-Si3N4 are fabricated by direct ink writing technique and seeding method. Slurries prepared with different contents of β-Si3N4 grains exhibited superior printing behavior. The degree of orientation of β-Si3N4 grains increased with the increase of grains content. The mechanical properties of the porous Si2N2O ceramic are effectively improved by interspersed β-Si3N4 grains and present anisotropy. This novel strategy provides a reference for fabricating high-performance anisotropic complex structure ceramics.

Study of thermal conduction process of ceramics by experimental and theoretical model analysis methods is complicated and non-intuitive. In this work, to analyze the influence mechanism of h-BN grain orientation on the thermal conduction of h-BN ceramics, new mesoscale finite element models considering the anisotropy in the thermal conductivity of h-BN grain were established based on random sequential adsorption method and periodic boundary condition. And the accuracy of the finite element models was verified by theoretical model and experimental results. The heat flux vector and temperature distributions intuitively show that the orientation of h-BN grains will significantly affect the thermal conduction process of the ceramics by affecting the heat flow path. The heat flow will propagate mainly along the “thermal conducting pathways” formed by the h-BN grains when the h-BN layer direction shows small angle with the external temperature difference direction, otherwise, h-BN grains will act as barriers to the heat conduction.

Novel BN whisker reinforced SiO2 matrix composites were achieved via hot-pressing at various temperatures, oriented to an enhanced mechanical properties of fused silica. Near full dense BNW/SiO2 composite sintered at 1350 °C presents optimal mechanical properties with bending strength of 124.8 ± 3.4 MPa and fracture toughness of 1.76 ± 0.32 MPa m1/2. The improved bending strength is mainly ascribed to the strengthening effects of BNW and crystallized nanosized α-cristobalite. Indentation crack paths indicate that the crack deflection and interface debonding are the main toughening mechanisms when BNW/SiO2 composite is dense. The desirable dielectric properties (dielectric constant of 3.93 and loss tangent of 0.46 × 10−3), the tiny mean thermal expansion coefficient (1.40 × 10−6 K−1) and thermal diffusivity (1.16 mm2/s) suggest that the BNW/SiO2 composite is definitely a promising high temperature electromagnetic wave transparent material.

In this work, we presented investigations on the microstructural, magnetic, dielectric and conductive properties of (1-x)Na0.5Bi0.5TiO3-xCoFe2O4 (NBT-CFO) composite ceramics (x = 0.1, 0.2, 0.3 and 0.5). The composites were synthesized using the in-situ sol-gel method, and the resulting CFO/NBT embedded structure was observed in the 0.9NBT–0.1CFO sample. Rietveld refinement confirmed that the embedded structure had remarkable effects on the c/a ratios of NBT-CFO composites. Increasing normalization saturation magnetizations were observed with increasing of CFO contents, thus revealing the influence of phase interfaces on magnetism. Dielectric relaxation anomalies were observed on both temperature dependent permittivity and loss spectra. Two sets of anomalies in these spectra were caused by space charges on the phase interfaces of embedded CFO grains and the NBT matrix. The conduction behavior of ceramics with and without the embedded structure obeyed the double power law and Jonscher's fraction power law, respectively, which inferred a transformation from the AC to the DC conduction mechanism with the disappearance of the embedded structure.

MgO-Al2O3-SiO2 (MAS) glass ceramic was used as liquid sintering aid to densify h-BN ceramics, and effects of sintering temperature on the phase composition of MAS, texture behavior of h-BN grains and properties of the composite ceramics were studied. h-BN grains will react with MAS by forming N-M (Al3+ and Si4+) coordinate-covalent bonds and inhibit the crystallization of glass phase. The h-BN grains will rotate parallel to the pressure direction due to the joint action of the liquid sintering aid and the pressure. The sintering temperature will significantly affect the properties of the composite ceramics by effecting the texture behavior of h-BN grains. And higher sintering temperature of 1900 °C will result in the decline of mechanical properties and increase of thermal conductivity due to the decrease of texture degree caused by the grain growth of h-BN.

In this work, SiBCN–TaC composite ceramics were prepared by a combination of mechanical alloying and reactive hot-pressing sintering techniques. The effects of TaC addition on microstructure, mechanical properties and oxidation resistance of the resulting composite ceramics were studied in detail. Results suggested that the as-sintered SiBCN–TaC composite ceramics composed of three phases: SiC, BN (C) and TaC. Some TaC~10–20 nm dispersed randomly within the ceramic matrix while others ~3–5 nm were scattered in turbostratic BN(C). The introduction of nanocrystalline TaC can effectively improve the flexural strength and fracture toughness of SiBCN ceramics. The incorporation of 10 wt% TaC showed the optimized mechanical properties with flexural strength and fracture toughness reaching to 399.5 MPa and 4.26 MPa m1/2 respectively. The TG-DTA analysis confirmed the oxidation damage of BN (C) phase can be effectively alleviated by the introduction of TaC nanocrystals.

In this paper, bulk and porous AlN/SiC based ceramics were in-situ prepared from graphite/geopolymer composites based on the carbon thermal reduction reaction under high temperatures. Thermal evolution of graphite/geopolymer composites were systematically investigated by XRD, TG/DTA, DIL, SEM, and TEM. The results show that graphite co-exists with amorphous geopolymer below 900 °C, whereas leucite crystallizes from geopolymer matrix and thus results in graphite/leucite composites in the temperature range of 1000 °C–1400 °C. After being treated at 1500 °C, h-AlN emerges due to the carbon thermal reduction reaction. By further increasing the heating temperature to 1700 °C, h-AlN or SiC with flocculent structures dominate the resulting high-temperature products, depending on the sintering atmosphere. It has been proved that h-AlN is the predominant phase of the resulting products after being treated at 1700 °C in N2 atmosphere. Nevertheless, SiC becomes the dominant one in Ar atmosphere, ceteris paribus. Moreover, both h-AlN and SiC ceramics derived by this technique show porous features, with the porosity of 61% and 68% and considerable compressive strength of 0.76 MPa and 0.63 MPa, respectively.

(Ti, W)C–W composites have been successfully synthesized by in-situ precipitation of multiscale W-rich particles in (Ti, W)C solid solution incorporated with TiH 2 as inducer. The microstructure of (Ti, W)C–W composites is characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The variations in lattice parameter of (Ti, W)C solid solution with increasing the sintering temperature are dependent upon the in-situ precipitation process of W-rich phase. The low temperature sintering route is beneficial to the precipitation of W-rich phase due to high concentration gradient in (Ti, W)C solid solution. The intragranular W-rich precipitates in the (Ti, W)C matrix exhibit semi-coherent interface and an orientation relationship of [111] W //[011] (Ti, W)C . The in-situ precipitation of multiscale W-rich particles have a positive influence on the fracture toughness, and the value of (Ti, W)C–W composite obtained at 1700 °C is 4.23 MPa m 1/2 .

The processing of 3D carbon fiber reinforced SiCN ceramic matrix composites prepared by polymer impregnation and pyrolysis (PIP) route was improved, and factors that determined the mechanical performance of the resulting composites were discussed. 3D Cf/SiCN composites with a relative density of ∼81% and uniform microstructure were obtained after 6 PIP cycles. The optimum bending strength, Young's modulus and fracture toughness of the composites were 75.2 MPa, 66.3 GPa and 1.65 MPa m1/2, respectively. The residual strength retention rate of the as-pyrolyzed composites was 93.3% after thermal shock test at ΔT = 780 °C. It further degraded to 14.6% when the thermal shock temperature difference reached to 1180 °C. The bending strength of the composites was 35.6 MPa after annealing at 1000 °C in static air. The deterioration of the bending strength should be attributed to the strength degradation of carbon fibers and decomposition of interfacial structure.

Texturing was employed to tailor the mechanical properties of h-BN ceramic with MAS as liquid texturing aid. Effects of MAS content on the texture behavior, densification behavior, bending strength, fracture toughness and the fracture behavior of the h-BN ceramics were studied. Moderate MAS of 30 wt% can significantly facilitate the orientation of h-BN grains in the direction perpendicular to the hot-pressing direction. MAS is also in favor of the densification behavior of h-BN as sintering aid. In-situ mechanical testing shows that texturing can greatly improve the mechanical properties and avoid the catastrophic fracture of the h-BN ceramics, and the textured h-BN ceramics exhibit distinct rising R-curve behavior, which is primarily attributed to the effect of parallel-aligned h-BN grains to the crack propagation under loading.

The lead-free KNN (K0.5Na0.5NbO3) films were co-doped with Mn-Ta and Mn-Ti via the Sol-Gel method. With Mn doping, the leakage behavior in the KNN films is significantly weakened. Annealed at 700 °C, the KNNM film shows good crystallinity, dense morphology and better energy storage performance. With Mn-Ta and Mn-Ti co-doping, the KNNM4R (K0.5Na0.5Nb0.96-xMn0.04RxO3, R = Ta, Ti) films still show tetragonal phase and the smoothest surface morphology at 6mol% Ta or Ti content, with about 200 nm in thickness. Under the breakdown field strength of 2700 kV/cm and 2800 kV/cm, the (Pm-Pr) of Ta6 and Ti6 films are 20.7 μC/cm2 and 22.4 μC/cm2, the Wrec and η are up to 20.7 J/cm3, 23.9 J/cm3 and 57%, respectively.

Barium aluminosilicate (BAS) matrix composite ceramics containing 10, 30 and 50 wt% h-BN and monolithic BAS have been prepared by hot pressing. Results showed that the incorporation of h-BN has a remarkable effect on thermal properties and thermal shock resistance of the composites. The addition of h-BN promoted the thermal conductivity but deceased the average coefficient of thermal expansion. The retained strength rate of sample achieved 42.9% (temperature difference ΔT = 1000 °C) when the content of h-BN was 50 wt%. The residual strength of the BAS-BN composites declined rapidly with increasing ΔT from 400 °C to 600 °C, which is mainly due to the gradual growth of cracks derived from the thermal stress damage. However, the retained strength ratio of the composites rose slightly as ΔT increased from 800 °C to 1000 °C. This strengthening is ascribed to the formation of the compressive stress layer. These results revealed that the thermal shock resistance of the BAS-BN composites could be enhanced by the introduction of h-BN.

Various x NiFe 2 O 4 –(1- x )SrTiO 3 ( x = 0.04, 0.05, 0.1, 0.2) composite ceramics were prepared using sol–gel method and two-step calcination. The composite ceramics possessed no impurities and exhibited obvious magnetic properties (22.8 emu/g at x = 0.2). The magnetic second phase imposed strain effects on the SrTiO 3 matrix to induce ferroelectricity. Strain values of (001) and (110) crystal planes were ~2.9% and ~1.3%. The tetragonal phase transition was evident in the Raman spectra. The remanent and maximum polarizations were 1.4 and 15.8 μC/cm 2 , respectively, in ceramic with 10 mol% NiFe 2 O 4 . The dielectric permittivity was tuned with 1.6% change rate at 50 kHz and 10,000 Oe.

To endow the insulation shielding of electromechanical devices, a TiO2 based ceramic coating with high voltage resistance was fabricated on titanium alloy by plasma electrolytic oxidation (PEO). The effects of PEO coatings with different phase composition and microstructure on insulation performance were determined. The results show that the ceramic coating formed in the silicate-based solution was mainly composed of rutile, anatase TiO2 and Al2TiO5. As the coating thickens from 10 to 36 µm, the increasing cross-sectional porosity enables the dielectric strength decrease from 32.94 ± 2.1 V/μm to 11.9 ± 0.71 V/μm and the electric resistivity drop from 1.17 × 108 Ω cm to 0.99 × 108 Ω cm respectively. With 2 g/L KOH added into the basic electrolyte, the thickness of coating significantly increased to 50.0 ± 2.1 µm, accompanied by the enhanced crystalline degree of rutile TiO2 phase and the decreasing of internal defects. In this way, the optimum coating with preferable resistivity of 1.08 × 1010 Ω cm, high breakdown voltage of 617.78 ± 26.31 V and dielectric strength of 12.36 ± 0.53 V/μm was achieved.

TiB2–40 wt% TiC composites were prepared by pressureless sintering. Prior to the conventional heating at 2000 °C for 1 h for final densification, addition of a low temperature hold at 1500 °C for 4 h was found effective in densification of the composite, refining the microstructure and promoting the anisotropic growth of TiB2 grains. The TiB2-TiC composite prepared by two-step sintering had better mechanical properties with flexural strength of 776 MPa and fracture toughness of 7.43 MPa m1/2, in comparison with the values of 419 MPa and 4.81 MPa m1/2 for composite by conventional one-step sintering.

Lead-free 0.9Na0.5Bi0.5TiO3 − 0.1CoFe2O4 (0.9NBT-0.1CFO) composite ceramics with novel embedded microstructures were synthesized by an in-situ sol-gel method. The structural evolution, ferroelectricities and dielectricities were studied. The embedded structures were formed around 1000 °C − 1100 °C with contributions of the strong grain boundary mobility and small size of CFO grains, and then were destroyed at 1150 °C. The 0.9NBT-0.1CFO ceramic sintered at 1100 °C showed the optimal ferroelectric hysteresis loop with a remanent polarization of ~ 52 μC/cm2. Anomaly peaks in the temperature dependent permittivity curves were observed in all ceramics with embedded structures. These Debye-like type peaks generated by the interface effects of NBT and CFO appeared around ~620 °C, and could reach relatively large values of ~15000 at 100 kHz. The change rate of permittivity between zero magnetic field and 500 Oe reached 2.4%, indicating a noteworthy magnetoelectric effect.

Effects of three different heat treatment conditions (air, vacuum and nitrogen) on the structure, magnetic, electrical transport and low-field magnetoresistance behaviors of La0.67Sr0.33MnO3 manganite coatings synthesized by sol-gel and screen printing methods have been systematically investigated. The detailed crystallographic analyses revealed that the diffraction peak positions of the samples subjected to annealing in vacuum and nitrogen ambients shifted to lower-angle regions, and lattice parameters and structure distortion increased as compared with those of the sample annealed in air, which were due to the introduction of oxygen deficiency under the annealing conditions of vacuum and nitrogen. The content of oxygen deficiency of the samples could be determined by the change of lattice parameters. Furthermore, the vacuum and nitrogen annealed samples exhibited a dramatic increase in the resistivity, accompanied by the reduction in ferromagnetism, the resistivity peak temperature and the ferromagnetism transition temperature. These phenomena were attributed to the decrease of average manganese oxidation state, as a result the mobile charge carriers were reduced, the ferromagnetic coupling and the double exchange effect between manganese ions decreased while the magnetic inhomogeneity increased. In the meanwhile, magnetoresistance ratios of the oxygen-deficient samples were enhanced around the percolation threshold.

In this paper, a high temperature treatment procedure was designed to evaluate the effect of holding temperature on thermal evolution process of Li + substituted Cs-based geopolymer (Cs 0.7 Li 0.3 GP), including the thermal analysis, phase composition and microstructure evolution. With rising of holding temperature, amorphous unheated Cs 0.7 Li 0.3 GP gradually transformed into a multiphase system during the high temperature treatment process, which consisted of pollucite (CsAlSi 2 O 6 ), spodumene (LiAlSi 2 O 6 ) and amorphous glass phase. In the multiphase system, Cs + ions were in the form of pollucite grains, while Li + ions were in the form of spodumene nanocrystallines distributed in amorphous matrix. The pollucite grains gradually coarsened with rise in holding temperature, and the densification of the resulting products were also improved synchronously, which were related to the presence of amorphous glass phases. The amorphous glass phase would be in a molten state when holding temperature over 800 °C. And the presence of molten amorphous phase would make the mass transfer process easier, which could contribute to the growth of the crystal grains and the elimination of the pores.