Ultraflexible Ultrathin 3D/1D Hierarchical Interpenetrating Ni-MOF/CNT Buckypaper Composites: Microstructures and Microwave Absorption Properties.

Metal-organic frameworks (MOFs) have attracted attention due to their designable structures. However, recently reported MOF microwave-absorbing materials (MAMs) are dominated by powders. It remains a challenge to design MOF/carbon nanotube (CNT) composite structures that combine the mechanical properties of self-supporting flexibility with excellent microwave absorption. This work involves the hydrothermal approach to grow Ni-MOF of different microstructures in situ on the CNT monofilament by adjusting the molar ratio of nickel ions to organic ligands. Subsequently, an ultraflexible self-supporting Ni-MOF/CNT buckypaper (BP) is obtained by directional gas pressure filtration technology. The BP porous skeleton and the Ni-MOF with a unique porous structure provide effective impedance matching. The CNTs contribute to the conduction loss, the cross-scale heterogeneous interface generated by Ni-MOF/CNT BP provides rich interfacial polarization loss, and the porous structure complicates the microwave propagation path. All factors work together to give Ni-MOF/CNT BP an excellent microwave absorption capacity. The minimum reflection losses of Ni-MOF/CNT BPs decorated with granular-, hollow porous prism-, and porous prism-shaped Ni-MOFs reach -50.8, -57.8, and -43.3 dB, respectively. The corresponding effective absorption bandwidths are 4.5, 6.3, and 4.8 GHz, respectively. Furthermore, BPs show remarkable flexibility as they can be wound hundreds of times around a glass rod with a diameter of 4 mm without structural damage. This work presents a new concept for creating ultraflexible self-supported MOF-based MAMs with hierarchical interpenetrating porous structures, with potential application advantages in the field of flexible electronics.

Vancomycin-loaded hydrogels with thermal-responsive, self-peeling, and sustainable antibacterial properties for wound dressing.

Wound dressings play an important role in wound healing. However, many wound dressings lack antibacterial properties and are difficult to remove from newly grown tissues, causing secondary wound injuries and repeated medical treatment. This study reports a new type of thermal-responsive hydrogel dressing consisting of vancomycin-loaded gelatin nanospheres (GNs) and poly((N-isopropylacrylamide)-co-N-(methylol acrylamide)) functional components that could impart self-peeling and sustainable antibacterial properties. SEM images showed that the prepared hydrogel possessed a porous microstructure and the homogeneous distribution of GNs in its network. Excellent swelling ratios and thermal-induced self-peeling characteristics were confirmed by qualitative analysis. The GNs not only enhanced the strain at break of the hydrogel, but also acted as drug carriers to slow down the drug release from the hydrogel, achieving sustainable antibacterial properties and balanced biocompatibility. Therefore, this vancomycin-loaded hydrogel with self-peeling characteristics provides an effective way of preventing wound infection and can be used as a novel platform for wide-ranging applications of wound dressings.

The Influence of Alumina Bubbles on the Properties of Lightweight Corundum-Spinel Refractory.

The use of a lightweight corundum-spinel refractory in working lining could reduce the thermal conductivity of industrial furnaces. In this study, bubble alumina was introduced to realize a lightweight Al2O3-MgAl2O4 refractory assisted by the reactive sintering of Al2O3 and MgO. The effects of alumina bubble content and sintering temperature on the phase compositions, microstructure and properties of the lightweight refractory were investigated. The results indicated that the overall performance of the lightweight Al2O3-MgAl2O4 refractory was mainly dominated by the content of alumina bubbles. The bulk density, compressive strength and thermal conductivity all decreased when the alumina bubble content increased from 10 to 30 wt%. Meanwhile, the sintering temperature also significantly affected the properties of the obtained refractory. It is worth noting that specimens fired at 1650 °C achieved a high refractoriness under load (RUL) of more than 1700 °C when alumina bubble content was less than 30 wt%, which was comparable to that of the dense Al2O3-MgAl2O4 refractory. The thermal conductivity of the obtained samples was remarkably decreased to no more than 2.13 W/(m·K). In order to overcome the trade-off between the light weight of the refractory and overall performance, it is feasible to adjust the content of alumina bubbles and raise the sintering temperature appropriately.

Higher energy density of MoSe2/polyaniline capsule nanospheres for enhanced performance supercapacitor.

It is very important to develop novel nanocomposites as electrode materials for supercapacitors (SCs). MoSe2porous nanospheres were prepared by one-step hydrothermal method, and polyaniline (PANI) nanosheets were grownin situto obtain MoSe2/PANI capsule nanospheres (CNs). By changing the amount of aniline, it was found that MoSe2/PANI-16 CNs had the best electrochemical performance, and a high specific capacitance of 753.2 F g-1was obtained at a current density of 1 A g-1. In addition, the interface electron transport path was clarified that a C-Mo-Se bridge bonds may be formed for rapid electron transfer. The reaction kinetics was also explored. The large specific surface areas of MoSe2/PANI CNs provided more reactive sites, so that the contribution of pseudocapacitance was much larger than diffusion capacitance. The assembled MoSe2/PANI//activated carbon asymmetric supercapacitor has a energy density of 20.1 Wh kg-1at a power density of 650 W kg-1. These results indicate that the MoSe2/PANI CNs are a promising electrode material.

Low Temperature Thermal Treatment of Incineration Fly Ash under Different Atmospheres and Its Recovery as Cement Admixture.

Municipal solid waste incineration fly ash is classified as hazardous waste because it contains dioxins and a variety of heavy metals. It is not allowed to be directly landfilled without curing pretreatment, but the increasing production of fly ash and scarce land resources has triggered consideration of the rational disposal of fly ash. In this study, solidification treatment and resource utilization were combined, and the detoxified fly ash was used as cement admixture. The effects of thermal treatment in different atmospheres on the physical and chemical properties of fly ash and the effects of fly ash as admixture on cement properties were investigated. The results indicated that the mass of fly ash increased due to the capture of CO2 after thermal treatment in CO2 atmosphere. When the temperature was 500 °C, the weight gain reached the maximum. After thermal treatment (500 °C + 1 h) in air, CO2, and N2 atmospheres, the toxic equivalent quantities of dioxins in fly ash decreased to 17.12 ng TEQ/kg, 0.25 ng TEQ/kg, and 0.14 ng TEQ/kg, and the degradation rates were 69.95%, 99.56%, and 99.75%, respectively. The direct use of fly ash as admixture would increase the water consumption of standard consistency of cement and reduce the fluidity and 28 d strength of mortar. Thermal treatment in three atmospheres could inhibit the negative effect of fly ash, and the inhibition effect of thermal treatment in CO2 atmosphere was the best. The fly ash after thermal treatment in CO2 atmosphere had the possibility of being used as admixture for resource utilization. Because the dioxins in the fly ash were effectively degraded, the prepared cement did not have the risk of heavy metal leaching, and the performance of the cement also met the requirements.

Mn- and Yb-Doped BaTiO3-(Na0.5Bi0.5)TiO3 Ferroelectric Relaxor with Low Dielectric Loss.

In this work, a Mn-and Yb-doped BaTiO3-(Na0.5Bi0.5)TiO3 ferroelectric relaxor was designed and prepared. The effects of Mn on the microstructures, dielectric and electrical properties of the ceramics were investigated. The X-ray structural analysis shows a perovskite structure. The SEM images show the homogeneous microstructure of ceramics with an average grain size of about 1 µm. The temperature-dependent permittivity shows relaxor characteristics as Mn-doped. Mn at a low level (x ≤ 0.005) is beneficial for low dielectric loss and high resistivity. The maximum resistivity of ≥3 × 1012 Ω cm and minimum dielectric loss of ≤0.06 can be achieved at x ≤ 0.005. The resistivity of the ceramics follows the Arrhenius law with activation energy decreasing from ~1.31 to 1.01 eV as x increases. With lower Mn dopant, oxygen vacancies and charge carrier concentration partially decrease with Mn doping, which is helpful to improve the insulation resistance and decrease the dielectric loss.

Controllable Synthesis of Mo3C2 Encapsulated by N-Doped Carbon Microspheres to Achieve Highly Efficient Microwave Absorption at Full Wavebands: From Lemon-like to Fig-like Morphologies.

Mo3C2@N-doped carbon microspheres (Mo3C2@NC) have been discovered to be a family of superior microwave absorbing materials. Herein, Mo3C2@NC was synthesized through a simple high-temperature carbonization process by evaporating a graphite anode and Mo wire in Ar and N2 atmospheres with an N-doping content of 6.4 at. %. Attributing to the self-assembly mechanism, the number of Mo wires inserted into the graphite anode determined the morphologies of Mo3C2@NC, which were the unique lemon-like (1- and 2-Mo3C2@NC) and fig-like (3-, 4-, and 5-Mo3C2@NC) microstructures. 1- and 2-Mo3C2@NC exhibited powerful reflection losses (RLs) of -45.60, -45.59, and -47.11 dB at the S, C and X bands, respectively, which corresponded to thinner thicknesses. 3-, 4-, and 5-Mo3C2@NC showed outstanding absorption performance at the C, X, and Ku bands, respectively, with each value of a minimum RL less than -43.00 dB. In particular, the strongest RL (-43.56 dB) for 5-Mo3C2@NC corresponded to an ultrathin thickness of 1.3 mm. In addition, the maximum effective absorption bandwidth was 6.3 GHz for 4-Mo3C2@NC. After analysis, all Mo3C2@NC samples showed well-matched impedance due to the enhanced dielectric loss caused by the unique carbon structure and moderate magnetic loss derived from the weak magnetic property of Mo3C2. More importantly, the unique lemon-like and fig-like microstructures created sufficient interfaces and differentiated multiple reflection paths, which greatly contributed to the strong microwave absorptions at full wavebands. In full consideration of the simple preparation method and tunable absorption properties, Mo3C2@NC composites can be regarded as excellent electromagnetic wave absorption materials.

All-yarn triboelectric nanogenerator and supercapacitor based self-charging power cloth for wearable applications.

Despite rapid developments, multifunctional wearable electronics are still not significant in practical applications as compared to portable and stretchable power devices. In this paper, we present the flexible and easy large-scale production of single-electrode mode triboelectric nanogenerator (TENG) and supercapacitor yarn-based self-charging power fabric, for simultaneously converting and storing biomechanical energy. Fabricated using traditional knitting technologies, the self-charging power fabric can adapt to complex mechanical deformations owing to its high flexibility and stretchability. Additionally, the output characteristics of the TENG fabric were systematically investigated with the purpose of energy generation. The TENG fabric can generate a maximum peak power density of ∼90 mW·m-2using nylon as the contact material, with an operating frequency of 4 Hz. The as-prepared yarn-based supercapacitor exhibited high capacitance, good cycling stability, and flexibility, making it an appropriate wearable energy-storage device. Moreover, the proposed design uses energy harvested from biomechanical motions to sustainably power portable electronic devices. The results of this study indicate that the proposed design is a promising sustainable power source for wearable electronic devices.

Anchoring of Formamidinium Lead Bromide Quantum Dots on Ti3C2 Nanosheets for Efficient Photocatalytic Reduction of CO2.

Metal halide perovskite with a suitable energy band structure and excellent visible-light response is a prospective photocatalyst for CO2 reduction. However, the reported inorganic halide perovskites have undesirable catalytic performances due to phase-sensitive and severe charge carrier recombination. Herein, we anchor the FAPbBr3 quantum dots (QDs) on Ti3C2 nanosheets to form a FAPbBr3/Ti3C2 composite within a Schottky heterojunction for photocatalytic CO2 reduction. Upon visible-light illumination, the FAPbBr3/Ti3C2 composite photocatalyst exhibits an appealing photocatalytic performance in the presence of deionized water. The Ti3C2 nanosheet acts as an electron acceptor to promote the rapid separation of excitons and supply specific catalytic sites. An optimal electron consumption rate of 717.18 µmol/g·h is obtained by the FAPbBr3/0.2-Ti3C2 composite, which has a 2.08-fold improvement over the pristine FAPbBr3 QDs (343.90 µmol/g·h). Meanwhile, the FAPbBr3/Ti3C2 photocatalyst also displays a superior stability during photocatalytic reaction. This work expands a new insight and platform for designing superb perovskite/MXene-based photocatalysts for CO2 reduction.

Influence of High-Temperature Liquid on Phase Composition and Morphology of Carbothermal Reduction-Nitridation Products from Coal Gasification Slag.

In this paper, the products using three kinds of coal gasification slags as starting materials were obtained via carbothermal reduction-nitridation at 1450 °C. The effects of high-temperature liquid on the phase composition and morphology of the samples were investigated by XRD and SEM, while the content of high-temperature liquid was calculated by the computer software package FactSage. The results show that: (1) the existence of high-temperature liquid phase is beneficial to the formation and growth of Ca-α-SiAlON phase; (2) The formation of long-columnar Ca-α-SiAlON were greatly affected by the content and viscosity of liquid phase, which is in non-linear relationship with aspect ratios of Ca-α-SiAlON. Among the three kinds of slags, the HT slag with relatively high liquid phase content and the lowest viscosity is the most favorable to the growth of elongated Ca-α-SiAlON grain; the aspect ratio of the formed Ca-α-SiAlON is the largest; Compared to the SH slag with the highest liquid phase content and viscosity, Ca-α-SiAlON prepared from TE slag possesses the smallest aspect ratio, which exhibits equiaxed grain morphology.

Role of Ammonium Derivative Ligands on Optical Properties of CH3NH3PbBr3 Perovskite Nanocrystals.

Amines, ammonium salts, and their combination with organic acids are commonly employed ligands during the synthesis of colloidal perovskite nanocrystals (PNCs). However, the role of surface coordination, derived from different ammonium derivative ligands, on the optical properties of PNCs remains poorly understood. In this study, octylamine (OA), octylammonium bromide (OABr), and oleic acid (OAc) were applied, standing for amine, ammonium salt, and organic acid, respectively. The effects of four different types of ligands, including OA, OABr, OA-OAc, and OABr-OAc, on the surface coordination and subsequently optical properties of CH3NH3PbBr3 PNCs were comparatively investigated. Compared to amine ligand, the ammonium salt could coordinate to both surface cations and anions of PNCs to passivate their surface defects more effectively, leading to enhanced optical properties including higher photoluminescence (PL) spectral intensities and PL quantum yield. Moreover, the combination of OAc with amine rather than ammonium salt ligand could trigger the protonation-deprotonation reaction to further improve their coordination effect on a PNC's surface, thus leading to significantly enhanced optical properties of PNCs. This study clarified the surface coordination of different ammonium derivative ligands and their role on the optical properties of PNCs, which could guide the design of ligands during the synthesis of PNCs.

Fabrication of TiO2 Nanostructures on Ti3SiC2 Substrate by Anodic Oxidation.

A TiO2 nanostructure was prepared on a Ti3SiC2 substrate with different water and NH4F concentrations in a fluoride-containing ethylene glycol electrolyte via an anodization process using the same constant-anodization potentials, anodization duration and temperature. The as-prepared samples were characterized by a field-emission scanning electron microscope equipped with an energy dispersive X-ray spectroscope, as well as by X-ray diffraction and X-ray photoelectron spectroscopy. The influence of the anodizing parameters and annealing temperature on the morphology of the nanostructure and the phase structure was studied. The results showed that the scattered TiO2 nanotubes and TiO2 nanoporous films were successfully fabricated in the glycol electrolyte containing (3.0 wt%) NH4F +(5.0 vol%) H2O. The as-prepared samples before calcination were amorphous and could transform to the anatase phase at temperatures higher than 500 °C. As the annealing temperature increased, the crystallization of the anatase phase was enhanced, and the rutile phase appeared at 600 °C. The as-prepared samples mainly consisted of oxides. Ti2O3 and SiO2 oxides were present in addition to TiO2.