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• Decomposition of urea can facilitate the nucleation of 5 nm size SnO 2 particles. • Urea can prevent MXenes from oxidation during hydrothermal process. • Interaction between SnO 2 particles and MXenes is proved by XPS. • SnO 2 /MXenes shows a raise of capacity and reaches 904 mA h g−1 at 1000th cycles. [Display omitted] Commercial graphite anodes show limited capacity in lithium-ion batteries, which inhibits the development of high-energy and high-power devices. Although the theoretical capacity of SnO 2 based anodes is three times higher than that of graphite, their practical application is hindered by the poor cycling stability. In this study, we report a ball-milling assisted exfoliation method for the scalable production of delaminated MXene nanosheets, followed by the preparation of 5 nm SnO 2 nanocrystals anchored on MXene nanosheets through a hydrothermal reaction. SnO 2 /MXenes nanocomposites exhibit long cycling life up to 1000 cycles with a high capacity of 904 mA h g−1, which can be ascribed to the high conductivity of the MXene substrates, and the anchoring effect between SnO 2 nanoparticles and MXene sheets that can prevent crystal aggregation or collapse during cycling. [ABSTRACT FROM AUTHOR]

Highlights: [•] Porous BN/Si3N4 with spherical-shaped pore structure was prepared by gel casting. [•] Micro spherical pores and irregular sub-micro pores composed the pore structure. [•] Increasing pore size has an increased inhibition on α- to β-Si3N4 transformation. [•] Mechanical and dielectric properties depending on the pore size were revealed. [ABSTRACT FROM AUTHOR]

• A cordierite-based ceramic with controllable phase composition is successfully prepared via sol-gel method. • Cr3+-modified cordierite ceramic exhibits high emissivity (> 0.79) at 800 °C. • The thermophysical properties of cordierite ceramic is tailored by changing the additive amount of Cr3+. Cr3+-modified cordierite ceramic with high emissivity, low thermal conductivity, and controllable thermal expansion property was successfully prepared via the sol-gel process followed by cold isostatic pressing and sintering. And the phase composition and contents (α-cordierite, Mg(Al 2−x Cr x)O 4 spinel, cristobalite) can be regulated by changing the additive amount of Cr3+, which further influences the thermophysical properties of cordierite based ceramic. [Display omitted] The Cr3+-modified α - cordierite ceramics Mg 2 Al 4- x Cr x Si 5 O 18 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1, named MAS, MASCr 0.2 , MASCr 0.4 , MASCr 0.6 , MASCr 0.8 , and MASCr 1 , respectively) have been synthesized via the sol-gel process followed by cold isostatic pressing and sintering. The effects of trivalent chromium ion content in α-cordierite ceramic on microstructure and thermophysical properties were investigated. The MASCr 0.2 ceramic exhibits the highest average emissivity value of 0.87 across the whole infrared range of 3–20 µm at 500 °C, especially at the vital infrared wavelength of 3–5 µm, the value can reach 0.92. The emissivity will decrease with the increase of doping amount owing to the growing precipitation of cristobalite and MgAl 2 O 4 spinel phases. The lowest thermal conductivity 2.077 W/m K is discovered in MASCr 0.2 , a decrease of 23% compared to MAS. The MASCr 0.4 ceramic with a close emissivity value compared to MASCr 0.2 exhibits the TEC of 7.8 × 10−6 K−1 due to the multiphase structure. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the phase transformation and electrochemical characteristics of the as-cast and annealed La0.75Mg0.25Ni x (x= 3.0, 3.3, 3.5, 3.8) alloys were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), pressure composition isotherm (PCI) and electrochemical measurements. The as-cast alloys were composed of LaNi5, (La,Mg)2Ni7 and (La,Mg)Ni3 phases. Phase transformation of LaNi5 and (La,Mg)Ni3 phases into (La,Mg)2Ni7 phase occurred during annealing treatment, leading to the increase of the (La,Mg)2Ni7 phase and decrease or even depletion of the LaNi5 and (La,Mg)Ni3 phases. The two plateaus observed in P–C isotherms of the as-cast alloys tended to become single and the plateau pressure dropped after the phase transformation by annealing. Electrochemical study showed that for the alloy electrodes with and without annealing treatment, the maximum discharge capacity and HRD initially increased then decreased with x increasing from 3.0 to 3.8. The transformation of the LaNi5 and (La,Mg)Ni3 phases into (La,Mg)2Ni7 phase favored the maximum discharge capacity and cycling stability but suppressed the activation as well as HRD of the La0.75Mg0.25Ni x (x= 3.0, 3.3, 3.5, 3.8) alloy electrodes. The annealing treatment significantly improved the cycling stability of the alloy electrodes by alleviating the pulverization and oxidation degree of the electrode alloys. [Copyright &y& Elsevier]

Abstract: Silicon carbide–aluminium nitride ceramic composites were prepared by gelcasting method. The effect of the solid contents of the slurry on the relative densities, mechanical properties of the green bodies and the pressureless sintered ceramic composites were investigated. When the solid contents increased from 35 to 40vol.%, the mechanical properties, such as elastic modulus, flexural strength and fracture toughness simultaneously increased due to the improving of the relative density. But when the solid contents reached to 42vol.%, the mechanical properties became noticeably worse, which caused by the sharply increase of the slurry viscosity, and many defects such as large scale and uneven pores also can be observed in the green bodies and the sintered ceramic composites. [Copyright &y& Elsevier]

Abstract: Multiferroic BiFeO3 (bismuth ferrite, BFO) ceramics were sintered using a rapid heating and quenching technique in an atmosphere of argon or oxygen. The resulting ceramics were phase pure with the space group R3c. BFO ceramics sintered under an argon atmosphere contained more oxygen vacancies and Fe2+ ions compared with those sintered under an oxygen atmosphere, which resulted in high dielectric loss and large dielectric dispersion. It confirms that the unavoidable Fe2+ ions may play a fundamental role in these special materials, such as in the evaporation of the Bi component and valence change of the Fe component. This work also discusses the dielectric response mechanism in BFO ceramics. [Copyright &y& Elsevier]

Abstract: Nano SiC/BN(C) ceramic was prepared from the mechanically-alloyed amorphous SiBCN powder, hot pressed at 1900°C under 80MPa in the nitrogen atmosphere for 30min. The microstructures and the properties of the prepared ceramic were carefully studied by XRD, TEM (SAED, HRTEM and EFTEM), EELS and property testing. Results show that the ceramic consists of β-SiC, α-SiC and BN(C). SiC has an average grain size of about 78.2±32.4nm, most of which have numerous stacking faults. BN(C) has small size, no fixed shape and turbostratic structure with heterogeneously distributed t-carbon layers, t-BN layers and B-doped t-carbon layers. It has uniform distribution in the ceramic, retarding the atomic diffusion and being responsible for the fine grains. The ceramic has room-temperature density, flexural strength, Young’s modulus and fracture toughness of 2.6g/cm3, 331.1MPa, 139.4GPa and 2.8MPam1/2, respectively. The detailed investigation of the hot-pressed SiC/BN(C) ceramic is helpful for the further study of this material and other ceramics, targeted for the high-temperature applications. [Copyright &y& Elsevier]

Abstract: This paper concentrates on the influence of gadolinia on structure and thermal expansion property of ZrO2–4.5mol%Y2O3 (YSZ) ceramics. The YSZ–xGd2O3 (0≤ x ≤7.5 in mol%) ceramics were synthesized by solid state reaction method at 1500°C for 2h in air. The relative density, phase structure and thermal expansion property of YSZ–xGd2O3 ceramics were investigated by the Archimedes method, X-ray diffraction and high-temperature dilatometer. The thermal expansion coefficients of YSZ–xGd2O3 ceramics increase with the increase in temperature. The thermal expansion coefficients of YSZ–xGd2O3 ceramics first decrease with increasing the mole fraction (x) of gadolinia from x =0 (YSZ) to x =4.5 (YSZ–4.5Gd2O3), and then increase from x =4.5 (YSZ–4.5Gd2O3) to x =7.5 (YSZ–7.5Gd2O3) in the temperature range of 50–1200°C. The YSZ–4.5Gd2O3 ceramics have the lowest thermal expansion coefficient in YSZ–xGd2O3 ceramics, which is due to formation of the () ionic vacancy clustering. [Copyright &y& Elsevier]

Abstract: High-energy ball milling and spark plasma sintering were adopted to prepare ZrC–SiC composite. Zirconium carbide, silicon, and graphite powders were used as raw materials. ZrC–30vol.%SiC was sintered to a relative density of >96.1% at 1800°C. The composite showed a fine microstructure. The fracture strength reached up to 523.4MPa, Vickers’ hardness 18.8GPa, fracture toughness 4.0MPam1/2, and elastic modulus 390.5GPa. [Copyright &y& Elsevier]

Abstract: Ferroelectric Bi3.25La0.75Ti3O12 (BLT) nanotubes were synthesized by sol–gel technique using nanochannel porous anodic aluminum oxide (AAO) templates, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). BLT nanotubes with diameter of around 240nm and the wall thickness of about 25nm exhibited a single orthorhombic perovskite structure and highly preferential crystal growth along the [117] orientation, which have smooth wall morphologies and well-defined diameters corresponding to the diameter of the applied template. The formation mechanism of BLT nanotubes was discussed. [Copyright &y& Elsevier]

Abstract: A chemical co-precipitation method is proposed for the synthesis of nano-sized multiferroic BiFeO3 powders. Pure phase can be obtained by controlling the chemical co-precipitation process, pH level, Bi content, and calcination temperature. The evolutions of phase constitution and structural characteristic of BiFeO3 powders were investigated by XRD, FT-IR, SEM, and TEM techniques. The slight excess in Bi content plays an important role in the synthesis. The resultant BiFeO3 powders are of pure phase and have the R3c crystal structure under optimized conditions. The grain size of the BiFeO3 powders with weak magnetism ranges from 30–40nm. [ABSTRACT FROM AUTHOR]

Abstract: We report the synthesis of perovskite ferroelectric nanowire strontium bismuth tantalate (SrBi2Ta2O9, SBT). Sol–gel techniques have been used. The morphology and structures are analyzed via SEM, TEM and XRD. The XRD and TEM analysis show that the structure of SBT nanowires is single orthorhombic perovskite with A2 1 am structure space group. The obtained SBT nanowires with an average length of 35μm and a diameter of 200nm are c-axis preferred orientation in the templates. The formation mechanism of SBT nanowires with complex crystal structure was discussed. [ABSTRACT FROM AUTHOR]

Abstract: The effects of the excess Lu2O3 addition and post heat treatment on the phase composition, morphology of α-SiAlON grains and mechanical properties of Lu-α-SiAlON were investigated. The results show that incorporation of excess Lu2O3 facilitates the formation of elongated α-SiAlON grains. Post heat treatment not only further promotes the growth of α-SiAlON grains with a larger aspect ratio, but also results in the adjustment of phase compositions and eliminates the residual glass phases between α-SiAlON grains. [Copyright &y& Elsevier]

Abstract: Bismuth ferrite (BiFeO3) nanopowders were synthesized by a sol–gel method at the temperature as low as 450°C. The obtained sol was transparent and homogenous when the mixture ionic concentration was properly controlled with the help of ethylene alcohol. The preparation process of crystalline BiFeO3 could be divided into three stages: (i) the evaporation of organics and decomposition of nitrogen-containing organics below 200°C; (ii) the collapse of Bi–Fe gel network in the temperature range of 200–300°C and (iii) the formation of BiFeO3 nanopowders by the solid-state reaction between Bi2CO3O2 and Fe2O3. [Copyright &y& Elsevier]

Abstract: Ceramic powders of Nd x Zr1−x O2−x/2 (x =0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by chemical-coprecipitation followed by calcination method. The ceramic powders of Nd x Zr1−x O2−x/2 were pressureless-sintered at 1600°C for 15h in air to fabricate dense bulk ceramics. The relative density of sintered samples was measured by the Archimedes method. Structures of the synthesized powders and sintered ceramics were identified by X-ray diffractometer. The morphologies of ceramic powders were observed by transmission electron microscope. Various thermal analysis methods were used for thermal expansion coefficient, specific heat, thermal diffusion coefficient and DSC measurements in a temperature range of room temperature to 1400°C. The thermal conductivity was calculated from thermal diffusivity, density and specific heat. Nd0.1Zr0.9O1.95 ceramics consist of both monoclinic and tetragonal structures. However, Nd0.2Zr0.8O1.9 and Nd0.3Zr0.7O1.85 ceramics only exhibit a single fluorite structure. Nd0.4Zr0.6O1.8 and Nd0.5Zr0.5O1.75 ceramics have a pyrochlore-type lattice. With the increase of Nd2O3 concentration, the thermal expansion coefficients of Nd x Zr1−x O2−x/2 ceramics increase. The thermal conductivities of Nd x Zr1−x O2−x/2 ceramics were located in the range of 1.50–2.01Wm−1 K−1 from room temperature to 1400°C. [Copyright &y& Elsevier]

h-BN composite ceramics were prepared by hot-pressing using La 2 O 3 and Al 2 O 3 as additives to form liquid phases during sintering. The effect of the amorphization/nanocrystallization of raw h-BN powders by high-energy ball-milling on the microstructure evolution of h-BN composite ceramics was investigated. The amorphization/nanocrystallization of raw h-BN powders significantly promotes grain growth during liquid-phase sintering. The specimen prepared using ball-milled h-BN powders possesses a higher crystallization degree, larger grain size, higher texture degree and more significant anisotropic thermal conductivity than the specimen prepared using raw h-BN powders. Image 1 [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries engage widespread attention due to their high theoretical capacity in recent years. However, the shuttle effect and some other issues are not thoroughly solved at present. Here, VO 2 nanotubes with relatively higher redox potential (than sulfur) are in situ compounded with graphene (G) for constructing an effective VO 2 /G binary sulfur host. In such a binary host, VO 2 nanotubes are able to chemically adsorb soluble lithium polysulfides (LiPSs) and optimize their electrochemical conversion kinetics, thereby, inhibiting the shuttle effect of LiPSs. In addition, the presence of graphene can be capable of improving the electronic conductivity of the cathode material and reducing the polarization of the whole electrode. Impressively, the final fabricated VO 2 /G/S electrode delivers large specific capacity, good rate performance and stable cycling performance, which holds great potential for different applications. One-step hydrothermal method has been used to synthesis VO 2 nanotubes grown on graphene (VO 2 /G), in which, VO 2 nanotubes with strong chemical polarity and high electrochemical redox potential play the key roles for chemically adsorption of soluble lithium polysulfide and accelerating the conversion process between long-chain lithium polysulfide and short-chain Li 2 S 2 /Li 2 S, and thus effectively inhibit the "shuttle effect" during charge and discharge process. Image 1 [ABSTRACT FROM AUTHOR]

A facile heat treatment strategy suitable for TiB reinforced titanium matrix composites (TMCs) fabricated by selective laser melting (SLM) is proposed. The effects of boron modification and heat treatment on the microstructure and mechanical properties of the selective laser melted TMC samples were systematically investigated. The ultrafine ∼2 vol% TiB whiskers that formed in situ exhibited a much more homogeneous distribution in the matrix compared to that of conventionally processed composites containing similar volume fractions, further promoting the formation of fine equiaxed α-Ti grains throughout the matrix. An excellent combination of strength and fracture strain of 1428 MPa and 43.6%, respectively, was simultaneously achieved for the heat-treated TMC, in which the plasticity was improved by 126% over that of the as-fabricated composite (19.3%). This finding provides significant guidance for tailoring the microstructure in selective laser melted TMCs to achieve the desired mechanical properties. [ABSTRACT FROM AUTHOR]

Designing and exploring efficient and stable Fe-based nanostructures catalyst is playing a critical role in the industrial application of water splitting. Herein, amorphous Fe–Ni bimetallic hydroxides film on the conductive FeS nanosheets supported by three-dimensional iron foam (IF) (denoted as FeNi(OH) x /FeS/IF) has been successfully synthesized by an ultrafast surface modification process (30 s). The fast surface reaction using FeS/IF as substrate in nickel nitrate solution facilitates the formation of bimetallic ultrathin film of FeNi(OH) x with enhanced performance oxygen evolution reaction (OER). Owing to the excellent conductivity, FeS nanosheets supported by IF may improve the dispersion and conductivity of FeNi(OH) x as active sites for OER. The physical characterizations confirm the closed interaction of FeNi(OH) x /FeS/IF, which suggests the validity of this facile surface modification. The electrochemical measurements show that FeNi(OH) x /FeS/IF only need a low overpotential of 273 mV to reach the 100 mA cm−2 (geometric current density) towards OER. The excellent catalytic performance can be attributed to the improved conductivity of substrate, a greater number of active sites and strong the synergistic effect of the Fe–Ni bimetallic hydroxides. The great long-term stability has been obtained. This work provides a simple route to produce advanced hierarchical nanostructure as electrocatalysts for OER. Image 1 • Amorphous Fe–Ni bimetallic hydroxides film on the conductive FeS nanosheets was prepared. • The fast surface reaction using FeS/IF as substrate is the key for amorphous hydroxides. • The bimetallic ultrathin amorphous film of FeNi(OH) x has the enhanced intrinsic activity. • This work provides a simple route for hierarchical nanostructure for OER. [ABSTRACT FROM AUTHOR]

The plastic deformation mode and slip transfer between the α and β phases of Ti–5Al-2.5Cr-0.5Fe-4.5Mo–1Sn–2Zr–3Zn titanium alloy were investigated using a combination of ex-situ scanning electron microscopy tensile tests and electron backscatter diffraction characterization. With increasing tensile strain, local orientation changes (which lead to the sub-grain boundary generation and migration) occurred in the α phase, resulting in grain subdivision/coalescence. Afterward, the elongated α grains were subdivided (in general) into small equiaxed grains. Abrupt changes in the crystal orientation of the continuous β-matrix were, however, rare. Three primary slip systems (prismatic and basal slip: α phase and {110}<111> slip: β phase) accounted for more than 70% of the total slip system activity at each strain level. These systems could be activated with very low Schmid factors (<0.1) at high strains. The compatible deformation between the α and β phases was realized mainly through the slip transfer correlated with the three primary slip systems, and the prismatic slip system was the most active system. In general, the α phase underwent plastic deformation first and compelled plastic deformation of the separated β grains. Subsequently, the deformed β grains transmitted the strain between an adjacent α grain and other α grains, leading to deviations from the uniaxial stress state in the local region. This resulted in wide distributions of the activated slip systems with various Schmid factors, and considerable strain concentration and failure in the α phase near the phase boundaries. Image 1 • Compatible deformation mode between α and β phases of a new Ti alloy was revealed. • Slip activations/transfers in two phases were identified and quantitatively analyzed. • Separated β transmitted strains but abrupt orientation changes were found to be rare. • Slip transfers from α phase played a dominant role in the slip activation in β phase. [ABSTRACT FROM AUTHOR]

In this work, in situ ZrC/Si-B-C-N monoliths prepared by sol-gel and reactive hot-pressing techniques were developed. The fine ZrC powders were synthesized by decomposition of zirconium propanol and furfuryl alcohol using as the source of zirconium and carbon, respectively. The as-sintered ZrC/Si-B-C-N monoliths composed of ZrC, SiC and BN(C) with a very fine and homogenous microstructure. The in situ formed ZrC and SiC were equiaxed, whereas the in situ BN(C) was graphic hexagonal with a fake-like structure. Due to the poor sinterability of ZrC, the as-sintered monoliths with relative low densities of <80% were obtained, which was primarily responsible for the poor mechanical performance. ZrC/Si-B-C-N monoliths oxidized at 1500 °C for different time possessed the same oxidation products of ZrO 2 and ZrSiO 4. SiC and BN(C) oxidation are predicted thermodynamically more strongly than ZrC, which resulted in a thick, uneven, heterogenous and porous oxide scale. The introduction of ZrC weakens the oxidation resistance of Si-B-C-N matrix leading to a continuous weight gain. • A novel method combination of sol-gel and mechanical alloying to prepare ZrC/Si-B-C-N mixed powders with fine microstructure was proposed. • Full densification of ZrC/Si-B-C-N monoliths by reactive hot-pressing at relatively low sintering temperature was unfeasible. • A porous oxide scale composed of ZrO2 and ZrSiO4 was primarily responsible for the degradation of oxidation resistance. [ABSTRACT FROM AUTHOR]