•The green synthesis of CeO2/Ti3C2 nanocomposites.•The synthetic strategy is based on the electrostatic attraction.•The CeO2/Ti3C2 nanocomposites shows the enhanced photocatalytic activity.In this study, CeO2/Ti3C2 nanocomposites were successfully synthesized by a one-step hydrothermal method with well-dispersed CeO2 nano-rods on Ti3C2 sheets. The synthetic strategy is based on the electrostatic attraction. The structure and morphology of as-prepared samples were characterized by XRD, TEM and SEM. The photocatalytic results showed that nanocomposites exhibited enhanced photocatalytic activity for the photodegradation of Rhodamine B under UV-light irradiation compared with pure CeO2 semiconductors and Ti3C2. The enhancement of photocatalytic activity can be attributed to the enhanced utilization of solar energy.

•A three-stage evolution mechanism between AlMgGaInSn alloys and water is proposed.•Raised heat treatment temperature and time on aluminum alloys accompanies with higher hydrogen production.•The reaction induction time is controlled by the initial corrosion stage under low temperature.The composition, microstructure and corrosion behavior of AlMgGaInSn alloy in cast and heat-treatment were investigated by XRD (X-ray diffraction), SEM (scanning electron microscope) and EDS (energy dispersive spectrometer). The hydrogen evolution parameters, and the electrochemical properties based on different heat-treatment parameters conditions and immersion temperature were also tested. As the heat-treated temperature increased, the second phases were found to be spheroidizing or ellipsoidal shape due to the diffusion and solid solution. The reaction can be divided into three stages: i) the amalgamation initial stage; ii) the micro-galvanic reaction for propagation corrosion; iii) the dissolution-precipitation reaction for uniform corrosion. The hydrolysis rate reached the maximum value when the sample was annealed at temperature of 500 °C for 9 h. The hydrogen generation rate and the open electrochemical potential of the activated aluminum under water are both depending on heat treatment time, heat treatment temperature, and reaction temperature. A corrosion mechanism was also proposed in which Mg2Sn and eutectic phase acted as the induction reaction stage during hydrolysis reaction.Download high-res image (267KB)Download full-size imageThe left graphic is the corrosion microstructure for the heat treatment aluminum alloy, and the right graphic is the hydrogen evolution curves about samples with different heat treatment temperatures and soaking time under 70 °C when immersed in water.

A hierarchical structure of PANI@TiO2/Ti3C2Tx ternary composite for high performance electrochemical capacitors was prepared by a hydrothermal treatment combining with in situ polymerization process. Layered Ti3C2Tx was used as both an active material with large surface area and a framework providing more paths for ion insertion/extraction. The introduction of PANI nanoflakes and TiO2 nanoparticles can offer an enhanced performance due to their good pseudocapacitance behavior and increased surface area of active materials. The hierarchical PANI@TiO2/Ti3C2Tx ternary composite exhibits high specific capacitance of 188.3 F g−1 at 10 mV s−1, which is about twice higher than that of TiO2/Ti3C2Tx, and 435.4 F cm−2 at 0.5 A g−1 in KOH solution. Furthermore, it also shows remarkable cycle stability, remaining at 94% of the initial value even after 8000 cycles at a current density of 1 A g−1. The enhanced electrochemical performance can be attributed to the hierarchical architecture and the synergistic effect of combining PANI nanoflakes with TiO2/Ti3C2Tx composite. This work propels a novel way of using MXene matrix to prepare hierarchical structure composite for next-generation electrochemical capacitors electrode.Download high-res image (148KB)Download full-size image

•A controllable preparation method was obtained to synthesize Ti3C2Tx@CNTs 3D composites.•The integrity of Ti3C2Tx structure is essential for the preparation of Ti3C2Tx@CNTs composites.•The areal capacitance of Ti3C2Tx@CNTs6.0 is as high as 924.9 mF cm-2 at 2 mV s-1.A novel two–step method has been proposed to synthesize Ti3C2Tx@CNTs three–dimensional composites. At the outset, the thin layer of polydopamine (PDA) was coated on Ti3C2Tx and served as protective cover to achieve the structural stability and integrity of Ti3C2Tx. CNTs were then in situ grown on Ti3C2Tx layers via a simple pyrolysis process using urea as carbon source, and the length and density of the grown CNTs can be effectively controlled by altering the amount of urea in the synthesis process. The vertically−aligned CNTs not only provided channels for electrolyte transport, but also greatly expanded the interlayer space of Ti3C2Tx sheets. When applied as electrode materials for supercapacitor energy storage, the Ti3C2Tx@CNTs6.0 composites revealed a high areal capacity of 924.9 mF cm-2 at 2 mV s-1 and an advantageous retentive capacity of 78.1% at 1 A g-1 after 10,000 cycles.Download high-res image (314KB)Download full-size image

Ti2AlC has been investigated for several decades, but much less attention has been paid to its delamination and potential energy storage applications, mainly due to the difficulty of delamination and its oxidation features. Herein, a new path to enhance exfoliation and delamination of two-dimensional (2D) Ti2CTx MXene is used. By using an etchant of HCl + LiF, multilayer Ti2CTx is easy to obtain. With only the assistance of mild sonication for 1.5 h without any additional intercalation, two-dimensional (2D) Ti2CTx flake suspensions are produced. Subsequently, the as-fabricated stable suspensions of delaminated Ti2CTx flakes are combined with carbon nanotubes. After filtration, a two-dimensional layered Ti2CTx/carbon nanotube (CNT) nanocomposite “paper” is prepared. Owing to the larger specific area of MXene flakes, which is caused by the complete exfoliation of MXene, with carbon nanotubes assisting with structural support between layers to prevent restacking, this structure provides a rapid charge transfer path during electrochemical reactions. When the nanocomposite paper is used as a lithium ion battery anode, it exhibits a higher capacitance and better cycling stability (a reversible capacity of 155.5 mA h g−1 at 100 mA g−1 after 200 cycles). Moreover, the “paper” can be directly used for electrodes in supercapacitors; the calculated capacitances are 515.3 F g−1 and 694 F cm−3 at a scanning rate of 2 mV s−1. The facile synthesis of layered Ti2C MXene/carbon nanotube nanocomposite paper provides a more secure and easy way to fabricate promising energy storage materials, and creates wider opportunities for exploiting the potential of other MXenes.

The separative-phase fancy glaze was successfully prepared by using the iron ore residue as the ceramic colorant. A possible coloring mechanism was proposed to explain the variation of glaze colors and patterns with the increasing of firing temperature. Effects of the firing temperature on the chromaticity, precipitated phase and microstructure of separative-phase fancy glaze were investigated. The results indicated that with increasing the firing temperature, the content of whitlockite decreased while the size of phase separation droplets in glazes increased. The residual whitlockite weakened coloring of Fe2O3 and formed glaze patterns. In addition, the increased size of phase separation droplets weakened the structural color, which increased the L* and b* value of glazes. Therefore, the color of separative-phase fancy glaze got more yellow and brown gradually.

The effect of Cr2O3 addition on the properties of (Co, Nb)-doped SnO2 varistors were investigated. The samples with different Cr2O3 concentrations were fabricated by the conventional ceramic method and sintered at 1,250, 1,300, 1,350 and 1,400 °C for 2 h. It was found that the nonlinear coefficient present a peak value when 0.05 mol % Cr2O3 was added. The leakage current density decreases with increasing Cr2O3 from 0 to 0.05 mol %, but increases when the concentrations increase from 0.05 to 0.07 mol %. The breakdown electrical field increased from 337 to 866 V/mm with increasing Cr2O3 from 0 to 0.07 mol %. The optimal samples obtained by doping Cr2O3 with 0.05 mol % and sintered at 1,300 °C have the highest nonlinear coefficient value of 27 and lowest leakage current density of 9 μA/cm2.

(Ti,Nb)2AlC/Al2O3 in-situ solid solution composites were successfully synthesized from the elemental powder mixtures of Nb2O5, Ti, Al and carbon black using hot-press-aided reaction synthesis. The reaction path was investigated by differential scanning calorimetry (DSC) and X-ray diffractometry (XRD), and a possible reaction mechanism was proposed to explain the formation of (Ti,Nb)2AlC/Al2O3 composites in which the thermite reaction between Al and Nb2O5 formed Al2O3 and Nb, and the latter together with TiAl and TiC reacted to form (Ti,Nb)2AlC. The synthesized composites show plate-like grains packed in a laminated structure typical of Ti2AlC, and the fine Al2O3 particles formed in-situ tend to disperse on the matrix grain boundaries. Compared with the monolithic Ti2AlC synthesized using an identical process, the Vickers hardness, maximum compressive stress, flexural strength and fracture toughness of (Ti0.96,Nb0.04)2AlC/5 wt% Al2O3 were enhanced by 33.8%, 12.1%, 118.4% and 111.8%, respectively. The mechanisms by which Al2O3 increases the strength and toughness of the material were also discussed.

The microstructure and electrical properties of ZnO-Bi2O3-based varistor ceramics doped by Pr6O11 in the content range of 0–5.49 wt% were investigated at different sintering temperatures (1,100, 1,150, 1,175, 1,200 °C). The increase of sintering temperature leads to more dense ceramics, which increases the nonlinear property, whereas it decreases the voltage-gradient and leakage current. With increasing Pr6O11 content, the breakdown voltage increases because of the decreases of ZnO grain size. The improvement of non linear coefficient together with the decrease of leakage current are related to the uniformly distribution of secondary phases along the grain boundaries of the ZnO. The varistors sintered at 1,175 °C with the 3.37 wt% Pr6O11 doping possess the best electrical properties: the varistor voltage, nonlinear coefficient, and leakage current are 340 V/mm, 46 and 0.63 μA, respectively.