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The Bi 2 Te 3 -based thermoelectric crystal ingots produced by the zone-melting (ZM) are the most widely used commercially at present. However, the poor mechanical properties caused by the ZM are unfavorable to the production of miniature devices. The mechanical properties can be improved by the powder metallurgy (PM), but the PM results in performance degradation of n -type Bi 2 Te 3 -based alloys, which could be attributed to the disappearance of intrinsic anisotropy and the increased carrier concentration originated from the "donor-like" effect of grain boundary. In this paper, the Bi 2 Te 2.7 Se 0.3 + 4 wt % Te (BTST) powder was from the ground ZM ingots, and the influence of CuO doping on the thermoelectric properties of hot-pressed BTST polycrystalline bulks with a large size was investigated. It can be found that the thermoelectric properties of BTST are improved remarkably by CuO doping due to the increased Seebeck coefficient and suppressed thermal conductivity, which is caused by the synthetic effects of optimised carrier concentration, increased effective mass, and enhanced phonon scattering by the Cu 2 Te/Bi 2 Te 2.7 Se 0.3 hetero-interfaces. Finally, the dimensionless thermoelectric figure of merit (ZT) of the sample (CuO) 0.1 (Bi 2 Te 2.7 Se 0.3 + 4 wt % Te) reaches 1.32 at 408 K, which is about 65 % higher than that of the pristine BTST, and its average ZT ave value reaches 1.27 in the temperature range of 300–473 K. The large size bulks produced by this method are not only commercialized directly, but also avoid the problem of poor mechanical properties. • Effects of CuO doping on the thermoelectric properties of Bi 2 Te 2.7 Se 0.3 + 4 wt% Te. • Simultaneous optimization of power factors (S2σ) and thermal conductivity (κ). • High peak ZT max of 1.32 at 408 K, and high average ZT ave of 1.27 from 300 K to 473 K. • Large size of 30 mm*30 mm*70 mm. [ABSTRACT FROM AUTHOR]

Nano-second-phase dispersion usually improves the thermoelectric properties of thermoelectric materials through energy filtering effects and phonon scattering effects. In this paper, MXene was introduced as a new nano second phase material into the Cu 2 Se alloy bulks prepared by the hydrothermal method and the vacuum hot-pressing method. The microstructure, electrical and thermal transport properties of the samples were studied, and the results showed that the introduction of MXene can not only optimize its electrical transport properties, but also significantly suppress its thermal conductivity, thereby effectively improving its thermoelectric properties. Overall, the maximum ZT value of the Cu 2 Se + 0.20 mol % MXene sample reached 1.77 at 923 K, which was 30 % higher than that of the pristine Cu 2 Se sample. • Mxene dispersant. • Simultaneous optimization of power factors (S2σ) and thermal conductivity (κ). • Improved ZT value by 33 % compared with the pure Cu 2 Se sample. [ABSTRACT FROM AUTHOR]

We demonstrate a forming-free electrochemical metallization resistive memory device (Ag/TiO x N y /Pt) based on the nanoporous titanium oxynitride (TiO x N y ) thin film. Due to the nanoporous structure of TiO x N y , Ag atoms can migrate into the film during the Ag electrode evaporation process, resulting in a pre-formed Ag conductive filament inside the switching layer. This is responsible for the forming-free resistive switching behavior. Subsequently, resistive switching with attractive performance is achieved after a reset process, including good endurance, low operation voltages, and fast switching speed. The forming-free and reliable switching characteristics suggest that nanoporous TiO x N y thin film is one of the promising material candidates for future nonvolatile memory applications. [ABSTRACT FROM AUTHOR]

• MAPbI 3 /RGO material with high TCR and low heat capacity synthesized by composite engineering. • The hot carrier injection is introduced to enhance the bolometric effect in graphene. • The responsivity and the response time of the terahertz detector are synchronously improved. Thermal photodetectors, such as bolometers, are the most promising option for detecting infrared (IR) to terahertz (THz) radiation at room temperature. Previous studies have shown that graphene has great potential for broadband thermal photodetection because of its distinctive optical and electrical properties. However, the responsivity of graphene photodetector is limited by the weak absorption and the finite temperature coefficient of resistance (TCR). Here, we synthesize the methylamine lead iodide perovskite (MAPbI 3)/graphene oxide (RGO) composite material, exhibiting high TCR of −0.89%K−1 and low heat capacity at room temperature. The composite is designed to construct a sensitive and fast IR to THz bolometer. The MAPbI 3 /RGO detector shows significant performance breakthroughs, with the responsivity as high as 805 mA/W, the response time of about 700 μs, at 220 GHz, which are about an order of magnitude higher than those of pure RGO detector. These results suggest that compositing engineering gives a new approach to the technological innovation of THz detectors. [ABSTRACT FROM AUTHOR]

How to effectively use the structural design on poly para-phenylene terephthalamide (PPTA) fabric to provide superior electromagnetic interference (EMI) shielding performance while giving it hydrophobicity and comprehensive functions remains a significant issue. Herein, a layered assembly technique is demonstrated to construct a hollow hybrid separated structure with gradient electrical conductivity on PPTA fabric for achieving efficient electromagnetic radiation attenuation and excellent hydrophobic properties. Due to the difference in electrical conductivity between Ni and polyaniline (Pani), gradient conductivity is generated from top to bottom that highly conductive core-shell Ni provides excellent electromagnetic reflection capability, and Pani-Fe 3 O 4 forms a separated electromagnetic absorption network to achieve an "absorption-reflection-reabsorption" shielding mode. The EMI shielding effectiveness (SE) of the composite fabric is more than 65 dB, and the normalized specific SE (SSE) is as high as 2153 dB·cm2/g at a thickness of 0.221 mm, more than 20% of electromagnetic waves are absorbed, which can effectively alleviate the secondary contamination caused by reflection. The constructed hydrophobic structure enables the fabric to reach a large contact angle (CA) of 156.4° with excellent self-cleaning and antifouling properties. More, integrated functionalities are discovered in the composite fabric including flexibility, thermal stability and corrosion resistance, offering great potential for EMI shielding in complex environments. • Constructing a hollow hybrid separated structure with gradient conductivity on PPTA fabric. • Achieving an "absorption-reflection-reabsorption" EMI shielding mode. • Decreasing secondary pollution caused by reflection of electromagnetic waves. • Micro and nano columnar hydrophobic structure. [ABSTRACT FROM AUTHOR]

The thermal relaxation behaviour of compressive residual stress (CRS) in the gradient nanostructure of TC11 titanium alloy treated with ultrasonic surface rolling process (USRP) was investigated by X-ray residual stress test, transmission electron microscope (TEM) and high-resolution TEM (HRTEM). The Zener-Wert-Avrami (ZWA) model was successfully used to simulate the CRS relaxation behaviour in nanocrystalline and non-nanocrystalline regions at different temperatures. The results show that the relaxation of CRS is thorough and fast at higher temperature (650 ºC). There are two distinct relaxation stages at lower temperatures, and the relaxation rate in the first stage is much faster, dominated by the annihilation of lattice defects through short-range diffusion. The relaxation in the second stage is slow and dominated by dislocation rearrangement. In contrast to the situation at low temperatures, the nanocrystals appear to be a negative factor in stabilizing the CRS at high temperatures, as the unstable sub-grain boundaries act as sources of stress relaxation and the multiple grain boundaries act as high-speed diffusion channels and accelerate the annihilation of dislocations. • CRS relaxation in the surface gradient nanostructures of TC11 titanium alloy at different temperatures was revealed. • Two stages of CRS relaxation at temperatures below 0.3 Tm were identified and simulated by the Zener-Wert-Avrami model. • The evolution of microstructure and element distribution of nanostructures after annealing was characterised by TEM. • Nanostructure induced by SPD is a negative factor for the residual stress stability at high temperature. [ABSTRACT FROM AUTHOR]

Developing sulfur hosts with reasonable structure and effective catalyst is essential for lithium-sulfur (Li-S) batteries. Herein, a novel multifunctional sulfur host composed of hollow carbon spheres with mesoporous channels (MHCS) coupled with few ultrathin Mo 2 C/C nanosheets embedded with Mo 2 C nanocrystals (MHCS@Mo 2 C/C) has been prepared via one-pot self-assembly and in-situ grown strategies. The Mo 2 C/C nanosheets with heterostructure can shorten the electron/ion transport path, and ultra-small Mo 2 C nanocrystals with abundant active sites contribute to enhancing chemical adsorption towards polysulfides and propel their conversion. Meanwhile, the MHCS facilitates physical adsorption towards polysulfides, effective sulfur/electrolyte permeation, fast electron/ion transportation, and sufficient buffering for volume change. Given these, the multifunctional MHCS@Mo 2 C/C-S cathode demonstrates an initial specific capacity of 1316.8 mAh g−1 at 0.1 C and outstanding cycling stability with an average capacity decay rate of 0.045 % for 500 cycles at 0.5 C. Moreover, MHCS@Mo 2 C/C-S cathode with high areal sulfur loading of 4.5 mg cm−2 can deliver a high initial discharge specific capacity of 797.4 mAh g−1, and a reversible capacity of 542.7 mAh g−1 after 500 cycles at 0.5 C. It is expected this work could provide a new perspective to the rational design of sulfur hosts for Li-S batteries with enhanced performance. [Display omitted] • MHCS@Mo 2 C/C are reasonably designed and prepared as a multifunctional sulfur host. • Synergy is achieved by combining reasonable structure and abundant catalytic sites. • Shuttle effect is suppressed by enhanced adsorption and catalytic conversion. • MHCS@Mo 2 C/C-S with sulfur loading of 4.5 mg cm−2 delivers excellent performance. [ABSTRACT FROM AUTHOR]

Defects in grain boundaries and at the surface of perovskite polycrystalline film lead to nonradiative recombination losses and ion migration, which seriously affects the performance and stability of optoelectronic devices. However, the process of passivation by using functional groups in polymers is expected to solve the problem. In this work, a tandem-like perovskite photodetector (PD) is developed, and an improved solution process is proposed to promote perovskite crystal growth and reduce the horizontal grain boundaries by using excess poly(methyl methacrylate) (PMMA) as anti-solvent. In addition, PMMA retained in perovskite grains acts as an interlayer for storing photocarriers, reducing the dark current and enhancing the PD gain. As a result, optimal perovskite PD exhibits a peak specific detectivity of 3.38 × 1012 Jones, a high responsivity of 5.65 A/W, a linear dynamic range of 80 dB, and an external quantum efficiency of 1321% under 532 nm illumination at the small bias of − 1 V. In addition, the PD has a fast response (5.90 μs rise time, 6.75 μs decay time). These results combine to provide a low-cost method for designing high-performance, ultrafast-response perovskite optoelectronic devices with low power consumption. • An improved one-step process for preparing large grain perovskite. • CH 3 NH 3 PbI 3 /PMMA composite photodetector with enhanced responsivity and detectivity. • Photocurrent gain is achieved by Fowler-Nordheim tunneling effect. • Performance of perovskite photodetector with different concentration of PMMA antisolvent. [ABSTRACT FROM AUTHOR]