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Four kinds of quinary high-entropy rare-earth (RE) monosilicates and (Y1-xYbx)2SiO5 have been synthesized by solid-state reaction method. Selected rare-earth oxides of Lu2O3 to Gd2O3 react with silica to form homogeneous monosilicate solid solutions at a sintering temperature of 1773 K for 4 h. Wherein Gd-Si-O transforms from oxy-apatite type to X2-RE2SiO5 with increasing the synthesis temperature from 1573 K to 1773 K. Increasing the rare-earth ion species changes the distortion degrees of [REOm] a little bit. However, it’s more effective to improve the distortion degrees with only introducing Yb3+ into Y3+ sites of Y2SiO5. Stronger distortion of [REOm] improves the high-temperature resistance to thermal deformation, resulting in a lower coefficient of thermal expansion (CTE). Due to the highest distortion degree of [REOm], (Y0.2Yb0.8)2SiO5 exhibits the lowest CTE of 6.78 × 10−6 K−1 at 1473 K. Meanwhile, RE-doping enhances the distortion and phonon scattering, contributing to a lower thermal conductivity.

The SiCf/SiC composites/Ni-based superalloys dissimilar joining encountered the problem of huge thermal mismatch and uncontrollable interfacial reactions. Two novel composite fillers were designed for the dissimilar joining. An AuCuTi/Mo/AuCuTi filler enabled a complete hindrance on the atomic exchange by a 50 μm Mo interlayer and an effective stress relief by multiple layers of the ductile (Au, Cu) solid solution and rigid Mo insert. Furthermore, the addition of B introduced an extra dimensionality to control the diffusion of interstitial atoms (Ni, Cr, and Si) and some TiB whispers to add extra nucleation sites for the Ni-compounds, by which way an easier and more accurate method to control the distribution of metallic atoms were obtained. The load-carrying of joints increased by 17.7% when using an AuCuTiB/Mo/AuCuTiB filler, because of the distribution of intermetallic compounds was homogenized and fined, and the interfacial region changed from Ti3SiC2 to TiC + Ni-compounds.

Uniform and fine in-situ short-fiber/particle hybrid reinforcements were obtained in a SiCf/SiC composite/Ni-based superalloy joint by using a novel AuCuTiB/Mo/AuCuTiB composite filler. The growth of in-situ phases showed a strong dependence on the numbers of nucleation sites and metal atoms on the ceramic side. Inadequate brazing conditions adversely affected the formation of indirect TiB whiskers, and excessive brazing conditions induced an accumulation of metal atoms. As a result, the in-situ phases switched from Ti5Si3 + TiC to Ti5Si3 + Ni + TiB + TiC, and to (Ni, Ti)-(Si, C) + TiB with increasing brazing conditions. The size, type, and composition of the in-situ phases were effectively controlled by adjusting the brazing conditions (B content, brazing temperature, and holding time). In light of this, the shear strength of the joint was optimized at 124.9 MPa. The excellent mechanical performance was ascribed to (i) a suitable interfacial layer and (ii) the effective stress relief of in-situ phases and ductile/rigid/ductile multiple layers. Moreover, the joint exhibited mechanical stability at 973 K because the in-situ phases can serve as a high-temperature resistant second structure.

Porous GdSmZr2O7 (GSZ) with different porosities has been prepared by the solid state reaction, and GSZ-carbonates composites have been prepared by infiltrating (Li0·52Na0.48)2CO3 (LNC) molten carbonates. Phase structure, microstructure and electrical property have been analyzed by X-ray diffractometer (XRD), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS). SEM results show that the voids in porous GSZ are uniformly distributed. The relative density of GSZ-LNC composites obtained by molten salt infiltration is above 93%. The electrical conductivity of the GSZ-LNC composites obtained by molten salt infiltration reaches the highest value of 0.50 S cm−1 at 600 °C, which is much higher than that of GSZ-LNC composites prepared by traditional mechanical mixing method. This excellent electrical property strongly indicates that the GSZ-LNC composite obtained by molten salt infiltration is a promising ionic conductor.

A high-entropy (TiZrNbTaMo)C ceramic has been successfully fabricated by hot pressing the newly-synthesized quinary carbide powder to investigate its microstructure and mechanical properties. The carbothermal reduction process of equimolar quinary metallic oxides at 1500 °C for 1 h generates a carbide powder mixture, which consists mainly of TaC- and ZrC-based solid solutions. The as-synthesized powder was then sintered to form a single-phase high-entropy ceramic by a two-step hot pressing at 1850 °C for 1 h and 2100 °C for 0.5 h, respectively. The high-entropy ceramic exhibits a fine grain size of about 8.8 μm, a high compositional uniformity and a high relative density of 98.6% by adding Mo as the strategic main component. The measured nanohardness values of (TiZrNbTaMo)C ceramic are 25.3 GPa at 9.8 N and 31.3 GPa at 100 mN, respectively, which are clearly higher than those of other available high-entropy carbide ceramics.

(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 .

Li7–xLa3Zr2–xTaxO12 (0 ≤ x ≤ 1) ceramics were prepared by pressureless sintering at 1230 °C in air. XRD, SEM and Impedance test were used to characterize the crystal structure, microstructure and electrical performance of Li7–xLa3Zr2–xTaxO12 ceramics. According to XRD data, the specimens with x ≥ 0.2 sintered at 1230 °C for 1 h exhibit a cubic garnet structure without impurities. The Ta-doped specimens sintered at 1230°C for 1 h show high relative density of 91.6%–93.9%. Ta doping has a certain effect on the Li vacancy concentration, lithium arrangement, movable Li+ concentration and microstructure of the LLZO ceramic. The Li6.6La3Zr1.6Ta0.4O12 ceramic sintered at 1230°C for 1 h has the highest total conductivity of 6.01 × 10–4 S·cm–1 at room temperature and the lowest activation energy of 0.27 eV.

The present work aims to provide fundamental insights into the grain size dependence and mechanical behavior of hot-pressed Al2O3-ZrO2 ceramic at its eutectic composition, and further to explore the hardening effect of laser-induced surface nanoeutectic layer. The underlying correlations between densification behavior, grain size distribution and mechanical properties were elucidated. Sintering at 1550 °C promotes the densification without extensive grain growth, and in this case the sample exhibits a critical density of 99.3 %. The average grain size is tailored into a range of 0.6–0.9 μm, and the measured flexural strength and toughness reach 1100 MPa and 11 MPa·m1/2, respectively. The metastable t-ZrO2 grains indeed play a pivotal role in energy dissipation at the crack tip through crack deflection and branching. In addition, the mechanical behavior is reasonably explained through constructing a multilevel toughening mechanism map associated with grain size distribution of ZrO2. Particularly, surface nanocrystallized Al2O3-ZrO2 eutectic layer with a thickness of 1000 μm free of pores and cracks is achieved by a rapid laser melting process. The outmost laser-modified nanoeutectic layer exhibits a fine cellular structure with an interphase spacing of only 105 nm and a hardness of as high as 26.1 GPa, which provides a promising potential in enhancing significantly the hardness and wear resistance for applications as sliding ceramic components.

GdSm(Zr1–xCex)2O7 solid solutions are successfully prepared by a conventional solid-state sintering method for intermediate-temperature solid oxide fuel cells. The effect of cerium content on the microstructure and electrical conductivity of the GdSmZr2O7 ceramic is studied. The phase composition, morphology and electrical conductivity are investigated by means of X-ray diffraction, scanning electron microscopy and electrochemical impedance spectroscopy. GdSm(Zr1–xCex)2O7 solid solutions exhibit a single phase structure. With the increase of cerium content, GdSm(Zr1–xCex)2O7 solid solutions change from pyrochlore-type structure to defect fluorite-type structure. The lattice parameters of GdSm(Zr1–xCex)2O7 solid solutions approximately linearly increase with the increase of cerium content. The relative densities of GdSm(Zr1–xCex)2O7 solid solutions are over 91%. The grains of GdSm(Zr1–xCex)2O7 solid solutions are inhomogeneous and the grain boundaries can be observed clearly. The relationship between grain conductivity of GdSm(Zr1–xCex)2O7 solid solutions and test temperature conforms to Arrhenius equation and the curve is approximately linear. The grain conductivity increases with the increase of temperature for each composition. At the same test temperature, the grain conductivity of GdSm(Zr1–xCex)2O7 solid solutions decreases firstly and then increases or maintains steady with the increase of cerium content.

In the present work, nanostructured surface layers of Al2O3-ZrO2 eutectic with a thickness of approximate 1000 μm and free of cracks and pores were produced on the surface of conventionally-sintered Al2O3-ZrO2 ceramic via the laser irradiation rapid solidification process. The molten pool geometry and microstructure were characterized by scanning electron microscopy and Raman spectroscopy. The geometrical evolution of molten pool in response to laser power and laser scanning velocity was established, where the top view of molten pool exhibits a circular shape at low velocities and gradually evolves into an oval-shaped surface at high velocities. Singular Al2O3-ZrO2 eutectic colonies with a size of 100–200 μm, which is formed around a spontaneously nucleated dendritic ZrO2 core, are found on the surface of laser-remelted layer. The eutectic colony has an interphase spacing of 190–280 nm. The variation of eutectic spacing with growth rate is essentially linear on the logarithmic scale as λ = K V - 0.4 by binary regression analysis. Predicted by the Jackson-Hunt theory on eutectic solidification (JH theory), the eutectic spacing is consistent with the inverse-square-root dependence on growth rate with a proportionality constant of 3.32. The eutectic colonies consist of α-Al2O3, t-ZrO2 and m-ZrO2 phases, where α-Al2O3 and t-ZrO2 are the dominant phases and the m-ZrO2 phase increases with the decrease of laser scanning velocity.

This work concerns the microstructure-mechanical properties relationship in Al2O3/SmAlO3 composites prepared by hot pressing at temperatures from 1450 °C to 1650 °C. Dense samples have been prepared using co-precipitated trigonal α-Al2O3 and orthorhombic SmAlO3 at the pseudo-binary eutectic composition. The overall microstructure coarsens with increasing processing temperature, but the nanoscale precipitates within α-Al2O3 and SmAlO3 grains contribute to coherency strains and distortions in Al2O3/SmAlO3 prepared at 1650 °C. The intragranular SmAlO3 precipitates in Al2O3 grains exhibit semi-coherent interface and an orientation relationship of the intragranular phase SmAlO3 and alumina matrix close to two different zone axes, namely [ 2 3 ¯ 1 ] SmAlO 3 and [ 4 ¯ 401 ] Al 2 O 3 . Consequently, significant strengthening effect is found from the measured hardness values on the sample sintered at 1650 °C. The measured flexural strength and single edged notched beam fracture toughness of the Al2O3/SmAlO3 ceramic are comparable to traditional secondary phases reinforced alumina composites. The sample sintered at 1500 °C exhibits a flexural strength of 558 MPa and a fracture toughness of 5.59 MPa⋅m1/2.

Lanthanum silicate (LSO) electrolytes doped with different valence cations are successfully synthesized by solid state reaction. Crystal structure, electrical properties, stability and compatibility with cathode materials are characterized. The measured total conductivities of LSO electrolytes doped with In3+, Nb5+ and W6+ are relatively high compared with that of undoped La10Si6O27, which is attributed to more carriers including either excessive oxygen vacancies generated when doping with In3+ or more interstitial oxide-ion O (5) generated when doping with Nb5+ and W6+. The thermal expansion coefficients of La10Si5.9A0.1O27±δ (A = In3+, Si4+, Nb5+, W6+) electrolytes vary from 8.48 to 8.83 × 10–6 K–1 at 1073 K. The doped LSO electrolytes match well with (La0.75Sr0.25)0.95MnO3±δ cathode at temperatures below 1573 K, which is highly stable, to some extent, in various atmospheres of CO2 or H2O vapour.

This present work explores initially the feasibility of producing in-situ surface nanoeutectic Al2O3-ZrO2(Y2O3) (SNAZ) ceramics via the oxyacetylene flame remelting (OAFR) process. Singular cellular nanoeutectics consist of nanoscale lamellae, which prevail in the samples formed under different irradiation times. Ultrafine nanoeutectics are achieved by prolonging the irradiation time, and their formation mechanisms associated with eutectic refinement are proposed to obtain a better understanding on the melt thermal history and microstructural inheritance. The enhanced nucleation undercooling is the essential mechanism associated with the microstructural refinement. SNAZ formed by the OAFR-based rapid solidification seem to offer an inexpensive route to realize in-situ microstructure tailoring or surface shaping.

The residual stress distribution as a function of depth in a sapphire/Ti6Al4V brazing joint is non-destructively measured using Raman Spectra for the first time. A modified method that is suitable for brazing joints is developed to deconvolute the actual residual stress value in each depth from the measured averaged stress value. The measured in-plane residual stress is compressive and increases non-linearly from the surface to the interface. While the out-of-plane residual stress is compressive; it increases from the surface to the interface and peaks at a distance of 150 µm from the sample surface. Then the stress begins to decrease and becomes tensile stress, which increases to the interface. This method can also be applied to other brazing/ diffusion bonding joint with a transparent substrate.

Variations in composition, microhardness (in the thermomechanically affected zone) and texture in the tool domain of the dissimilar friction stir weld of AA5083-O and AA6082-T6 alloys were investigated. The contents of the major alloying elements in the weld zones were determined using inductively coupled plasma−atomic emission spectroscopy. It was observed that a slight drop in the content of the alloying elements results from the friction stir welding process with the Mg content being the most affected amongst the major alloying elements in the two alloys. By relating the mass fractions of the major alloying elements in the parent metals of both alloys to those of the stir zone, the relative proportions of the two alloys in the stir zone were estimated with the results showing that at least 60% of the materials in the stir zone are from the retreating side of the weld. It was also revealed that the changes in the hardness profile in the thermomechanically affected zone of the retreating side are predominantly influenced by changes in grain size in that domain. Finally, the investigation further revealed that the texture component in the tool shoulder domain is different from the texture component in the tool pin domain.

The nucleation and epitaxial growth behavior of a novel Al 2 O 3 -ZrO 2 nanoeutectic rapidly solidified from the oxyacetylene flame remelting have been investigated. The nanoeutectic ceramic consists mainly of highly textured cellular structure with an average interphase spacing of 136 nm. Especially, a singular transition mechanism associated with “ one-step cellular refining ” to “ two-step cellular refining ” is proposed in a variable region from a coarse irregular to an ultrafine lamellar structure, and the regional undercooling is estimated to be 0.57–2.86 K. The Al 2 O 3 phase nucleates as the leading phase in the rapidly solidified structure according to a quantitative calculation of nucleation rate. The cellular eutectic exhibits with a tilted feature, where its cellular growth deviates from the heat flow direction to a preferred growth orientation.

Garnet electrolytes have been approved widespread as one of the most competitive candidates in all solid state lithium batteries (ASSLBs). Herein, dense Li6.4La3Zr1.4Ta0.6O12 (LLZTO) ceramics were successfully produced via liquid sintering method by introducing 1 wt% 3Li2O-2GeO2 additive at reduced sintering temperatures for a shortened process period compared to solid method in air atmosphere. Relationships among sintering temperature, microstructure, densities, mechanical properties and electrical performance of the ceramics were explored concretely. The ceramics can be well densified and modified microstructurally at the appropriate sintering temperature, making the ionic conductivity significantly promoted. Mechanical properties would be enhanced as well, resulted to a compact and tough ceramic surface. Hence, a good-contacted, homogeneous and electrochemically stable electrolyte/Li interface can be fabricated. The LLZTO-1 wt% (3Li2O-2GeO2) composite electrolyte sintered at 1160 °C for 3 h exhibits the best comprehensive properties, the ionic conductivity and critical current density (CCD) of which reach 6.27 × 10−4 S·cm−1 and 0.5 mA·cm−2 at 25 °C. The improved interfacial performance enables the Li|LLZTO-1 wt% (3Li2O-2GeO2)|Li symmetrical cells and the LiFePO4|LLZTO-1 wt% (3Li2O-2GeO2)|Li cells a good cycling performance at different current densities.

The practical applications of ZrC are restricted by its low fracture toughness and resistance to sintering densification. This study reports the in-situ precipitation behavior of (Zr,W)C solid solution precipitates induced by Ti. The (Zr0.7W0.3)C solid solution powder was prepared via carbothermic reduction using pressureless sintering at 2200 °C for 1 h. Varying quantities of TiH2 were reacted with the (Zr0.7W0.3)C matrix, to precipitate the second phase in-situ, via hot-pressing sintering (50 MPa) at 1600 °C for 1 h. When the content of TiH2 was 10 mol%, W and W2C were the second phases precipitated. As the TiH2 concentration increased, the precipitates converted into W2C and the (Ti,Zr)C solid solution. Furthermore, nano-scale dot-like W precipitates gradually increased inside the crystal grains of the (Zr,W,Ti)C matrix. The optimized comprehensive mechanical properties of (Zr,W,Ti)C-based multiphase ceramics were obtained by adding 40 mol% TiH2; the relative density was 99.7%, the Vickers hardness was 24.68 GPa, and the fracture toughness was 5.76 MPa·m1/2. The precipitates (of varying type and concentration) exhibited distinct toughening effects relative to the (Zr,W)C solid solution.

A novel GdSmZr2O7–(Li0.52Na0.48)2CO3 composite electrolyte material is successfully developed by pressureless-sintering for intermediate temperature solid oxide fuel cells. GdSmZr2O7 nanopowders are synthesized by a low cost chemical coprecipitation and calcination method. The phase structure and morphology as a function of the calcination temperature are investigated by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The resulting GdSmZr2O7 nanopowders after calcination at 800 °C for 5 h exhibit good crystallization and uniform particle morphology with an average size of 50 nm. The GdSmZr2O7–40 wt.% (Li0.52Na0.48)2CO3 composite sintered at 600 °C for 1 h has a high conductivity of 0.54 S cm−1 at a temperature of 600 °C. From the Arrhenius curve of the composite, the activation energy has different temperature behaviors around the knee region of 480 °C, where the slope changes and separates the intrinsic oxygen vacancy conduction dominated region from the ‘superionic highway’ region. For GdSmZr2O7–40 wt.% (Li0.52Na0.48)2CO3 composite at temperatures above 480 °C, there is good correlation between ionic diffusivity and conductivity. The introduction of (Li0.52Na0.48)2CO3 carbonate into GdSmZr2O7 ceramics significantly promotes the enhancement of its conductivity by one or two orders of magnitude at the intermediate temperatures, especially above 480 °C. A maximum power density of 221 mW cm−2 at 650 °C was achieved for excellent performance of fuel cell based on GSZ–40LN composite electrolyte.

The present work concentrated on a novel one-step pulse discharge plasma melting method for in situ fabricating Al2O3-ZrO2 binary eutectic in a short processing time. Al2O3-ZrO2 eutectic exhibited well-aligned fibrous and colonial structure with a minimum lamellar spacing of ∼250 nm at the growth rate of ∼176.0 μm/s. The lamellar spacing was well consistent with the inverse-square-root dependence on the growth rate as λ = 2.90 × v − 1 / 2 , and the constant of proportionality of 2.90 was close to 3.32 predicted by the JH eutectic theory. The formation mechanism of Al2O3-ZrO2 eutectic on primary faceted-alumina crystals was also proposed. The Al2O3-ZrO2 eutectic originated from the faceted Al2O3 primary crystals, which played the leading role in the coupled growth process. The interfacial fracture behavior across the coarse intercolony regions was explored, and the fracture toughness of Al2O3-ZrO2 eutectic ceramics was comparable to those achieved by traditional directional solidification.

In the present work, Al 2 O 3 -GdAlO 3 oxide nanopowders with eutectic composition of 77:23 (in molar ratio) were prepared via a chemical co-precipitation method. α-SiC particles were then incorporated with different volume fractions of 10, 15 and 20 vol% into the oxide powders. Al 2 O 3 -GdAlO 3 –SiC ceramics were hot-pressed at different sintering temperatures to obtain fully densified bulk ceramics. The as-sintered composites consist mainly of α-Al 2 O 3 , GdAlO 3 and α-SiC phases, and exhibit a dense and uniform microstructure. The GdAlO 3 grains are entangled with α-Al 2 O 3 grains as indicated by SEM observations. SiC nanoparticles are found within the interior of both α-Al 2 O 3 and GdAlO 3 grains or at the interfaces between entangled α-Al 2 O 3 and GdAlO 3 . With increasing the SiC content from 10 to 20 vol%, the high-temperature flexural strength of Al 2 O 3 -GdAlO 3 -SiC ceramics increases from 567 to 616 MPa, and the Vickers hardness increases from 17.5 to 19.5 GPa, while the fracture toughness of Al 2 O 3 -GdAlO 3 -SiC ceramics increases from 8.20 to 9.28 MPa m 1/2 , which is significantly improved with respect to that (7.5 MPa m 1/2 ) of unmodified Al 2 O 3 -GdAlO 3 ceramic. The toughening mechanisms of Al 2 O 3 -GdAlO 3 -SiC ceramics are attributed to crack deflection, pinning and bridging, and bifurcation due to the presence of SiC nanophases observed from the indentation.

Plasma electrolytic oxidation (PEO) ceramic coatings were formed on Ti2AlNb alloy in various NaAlO2 electrolytes containing 2 g L−1, 4 g L−1, and 6 g −1 Na2CrO4 additive, respectively. The influence of Na2CrO4 additive in NaAlO2 electrolyte on structure and high-temperature oxidation behavior at 800 °C was investigated. The Na2CrO4 additive in the NaAlO2 electrolyte not only promotes the formation of γ-Al2O3 phase and densification of ceramic coatings, but also participates directly in the growth of ceramic coating to form new Cr3O and (Al0.948Cr0.052)2O3 phases. The PEO ceramic coatings formed in NaAlO2 electrolytes with 2 g L−1 and 4 g L−1 Na2CrO4 additive show better oxidation resistance than those PEO coatings formed in a NaAlO2 basic electrolyte based on isothermal oxidation tests at 800 °C up to 150 h. A thin and uniform isothermally oxidized layer is formed in the interlayer adjacent the substrate, which protects the substrate from the inward diffusion of oxygen and the outward diffusion of metallic elements. The PEO ceramic coatings formed in NaAlO2 electrolyte with 4 g L−1 Na2CrO4 additive exhibit the least mass gain among all the specimens, which is only a half of the ceramic coating formed in a NaAlO2 basic electrolyte without any Na2CrO4 additive.

High emissivity coatings have been widely used in thermal protection systems and high heat efficiency devices in furnaces. In the present work, high emissivity ceramic coatings incorporated with different SiC contents have been prepared on Ti2AlNb alloy by microarc oxidation (MAO) method. The addition of different SiC contents into the Na2SiO3 electrolyte has a distinct influence on the microstructure and normal spectral emissivity of composite coatings. Microstructure of MAO coatings was investigated by using a glancing incidence X-ray diffractometer, a scanning electron microscope, an eddy current thickness meter and a contact surface profiler. A two-step voltage-controlled technology was also used to tailor the microstructure by adjusting the microarc oxidation duration. The composite coatings formed on Ti2AlNb alloy exhibit a porous structure, and consist of R-TiO2, A-TiO2, Al2SiO5, SiC as well as amorphous phase. The normal spectral emissivity of both coated and bared Ti2AlNb samples was measured at 600 °C in the infrared wavelength range of 3–20 μm. The S-10C composite coating incorporated with a 10 g/L of SiC in the Na2SiO3 electrolyte has a much higher emissivity in the wavelength range of 3–20 μm than the bared Ti2AlNb alloy. High emissivity of the S-10C coating is attributed to its porous structure and chemical composition, especially SiC content.

The cubic Li7La3Zr2O12 (LLZO) electrolytes co-doped with Ca2+ and Ta5+ dopants were produced successfully through solid method at 1230 °C for 1 h in ambient air atmosphere. The crystal structure, morphology, density and electrical performance of the Li6.4+xLa3–xCaxZr1.4Ta0.6O12 (0 ≤ x ≤ 0.08) and Li6.6+xLa3–xCaxZr1.6Ta0.4O12 (0 ≤ x ≤ 0.08) ceramics were characterized in detail. The synergistic effects of Ca2+ and Ta5+ dopants were explored. Attributed to the gaps of valence and ion radius between Ca2+ and La3+, the increasing concentration of transferable Li+ and the broader Li+ conduction pathway could be obtained in LLCZTO ceramics. A significantly improved electrical performance was achieved in the Li6.4+xLa3–xCaxZr1.4Ta0.6O12 (0 ≤ x ≤ 0.08) ceramics. Particularly, the specimen with the constituent of Li6.42La2.98Ca0.02Zr1.4Ta0.6O12 exhibited the highest ionic conductivity of 5.69 × 10 4 S·cm 1 as well as the lowest activation energy of 0.27 eV. Nevertheless, the excessively high Li+ concentration would result to inferior ionic conductivities instead ascribed to the serious abnormal grain growth inside the ceramics.

Laser surface melting (LSM) was carried out on the SiCp/Al metal matrix composite (MMC) using a KrF excimer laser with a fluence of 7 J/cm2. The re-solidification microstructure was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray detector, and X-ray diffraction (XRD) analysis. It was found that a 2.5 μm thick melted layer was formed in the near-surface region, in which dissolution of the intermetallics and removal of the SiC particles occurred. The thermal and material response upon laser irradiation was simulated using three models, i.e. analytical model, finite element model (FEM) and smoothed-particle hydrodynamics (SPH) model. The effect of SiC particles on the LSM process, the mechanism of the SiC removal and the re-solidification microstructures in the melted layer were discussed. The simulation results were in good agreement with the experimental results and contributed to the generic understanding of the re-solidification microstructures induced by ns-pulsed lasers.

An efficient and flexible chemical co-precipitation method has been used to synthesize nanoscale Al 2 O 3 -GdAlO 3 powders with eutectic composition. The as-synthesized powders exhibit a highly dispersive and homogeneous distribution with an average particle size of 50 nm. The phase transition in the resulting powders strongly depends upon the calcination temperature. GdAlO 3 undergoes complete crystallization after calcination at 1050 °C, however, the diffraction peaks of α-Al 2 O 3 are found at a relatively high calcination temperature of at least 1300 °C. The fully-densified Al 2 O 3 -GdAlO 3 ceramic with eutectic composition obtained by hot pressing the nanoscale powders at 1500 °C exhibits a room temperature flexural strength of 556 MPa, a Vickers hardness of 17.3 GPa and a fracture toughness of 7.5 MPa m 1/2 . The high temperature flexural strength of the as-sintered Al 2 O 3 -GdAlO 3 ceramic is measured to be 515 MPa after bending tests at 1000 °C.

Excimer UV laser radiation sources have recently employed for surface modification of aluminium alloys to provide melted layers with highly refined microstructure and superior pitting corrosion resistance. Moreover, the resultant rough appearance might be an excellent base for the later paint application. Unfortunately, during the paint baking process and depending on the exposure time, the temperature of the alloy may raise up to 200 °C, thus affecting the stability of the melted film. In the present work, the excimer KrF laser source was employed to create a melted film on the aerospace AA2024-T351 aluminium alloy, which was subsequently evaluated under different heat treatments with the aim to evaluate its thermal stability in terms of microstructure and corrosion performance. Microstructural modification was analysed by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), whereas the corrosion performance was evaluated by anodic polarisation and immersion testing in deaerated 0.1 M NaCl solution. The experimental results showed that above 160 °C, heat treatment of the melted layer resulted in the precipitation of the strengthening Al2CuMg phase as well as the nucleation and coarsening of the Al(Cu,Fe,Mn) secondary phase from the solute segregation bands originally formed during laser surface melting (LSM). The formation of these particles influenced the pitting corrosion resistance in two different ways: diminishing the pitting potential (Epit), and increasing both corrosion and passivation current densities. Nevertheless, this reduction was relatively negligible for all the heat treatment conditions studied, when compared to the parent alloy.

A series of garnet-type electrolytes with the compositions of Li6.6+yLa3–yBayZr1.6Ta0.4O12 (0 ≤ y ≤ 0.08) and Li6.4+yLa3–yBayZr1.4Ta0.6O12 (0 ≤ y ≤ 0.08) were obtained through pressureless sintering method at 1230 °C for 1 h successfully. The microstructure and electr0.4O12performance of the electrolytes were characterized and the co-doping effects of Ba2+ and Ta5+ were investigated. The substantially promoted ionic conductivity was achieved by doping Ba2+ into the Li6.4La3Zr1.4Ta0.6O12 ceramic. Ba2+ dopant made the LLZTO electrolyte a higher Li+ concentration ascribed to the valence gap between Ba2+ and La3+. This facilitated the grain growth so that the electrolytes could be sintered densely in a relatively short sintering time. Meanwhile. The Li+ transportation channel would be enlarged due to the larger ion radius of Ba2+ compared to that of La3+. The higher Li+ concentration and the broader Li+ transportation channel contributed primarily to the improvement of the electrical performance of LLZTO electrolytes. The specimen with the constituent of Li6.46La2.94Ba0.06Zr1.4Ta0.6O12 exhibited the highest conductivity of 6.04 × 10−4 S cm−1 and the lowest activation energy of 0.27 eV.

Perovskite-structured Sn- or Ta-doped Li0.24–(q–4)xLa0.587Ti1–xMxO3 (LLTMxO, M = Sn or Ta, q is equal to the valence of M, x = 0, 0.02, 0.04, 0.06, 0.08) solid electrolytes are prepared by the pressureless sintering method for Li ion batteries. The phase composition, microstructure and electrical performance as a function of the type of doping elements and the amounts corresponding are studied by XRD, Raman spectrometer, SEM and electrochemical impedance spectroscopy. The LLTMxO pellets sintered at 1350 °C for 12 h have high relative densities (96.2%–97.9%) and high conductivities, where the total conductivity of LLTTa0.04O and LLTSn0.02O reach 4.09 × 10−4 S cm−1 and 2.98 × 10−4 S cm−1 at room temperature (RT) respectively. Compared with the pure specimen (1.52 × 10−4 S cm−1), the total conductivities of the doped specimens are more than doubled. In addition, Sn or Ta doping can significantly reduce the activation energy, with LLTTa0.04O exhibiting the low activation energy of 0.31 eV. The improvement in the total conductivity is attributed to the expansion of the Li ion transmission channels, the improvement of the relative density and the rise in the Li ion vacancy concentration, which are all resulted from the effect of dopant.