Rapid preparation of Palygorskite/Al2O3 composite aerogels with superhydrophobicity,high-temperature thermal insulation and improved mechanical properties

Al₂O₃ aerogels are widely employed in heat insulation and flame retardancy because of their unique combination of low thermal conductivity and exceptional high-temperature stability. However, the mechanical properties of Al₂O₃ aerogel are poor, and the preparation time is considerably long. In this study, we present a simple and scalable approach to construct monolithic Pal/Al₂O₃ composite aerogels using solvothermal treatment instead of traditional solvent replacement, which remarkably shortened the preparation time. Subsequently, to obtain stable superhydrophobicity (θ > 152°), the Pal/Al₂O₃ aerogel was modified by gas-phase modification method. The obtained Pal/Al₂O₃ composite aerogels demonstrate the integrated properties of low density (0.078–0.106 g/cm³), low thermal conductivity (1000 °C, 0.143 W/(m·K)), good mechanical properties (Young's modulus, 1.6 MPa), and good heat resistance. The monolithic Pal/Al₂O₃ composite aerogels with improved mechanical performance and improved thermal stability can show great potential in the field of thermal insulation.     

In Situ Anchoring Ultra Small Au Nanoparticles by Conformal Coating of Carbon Layer within the Micro-Environments of Mesoporous Silica for Highly Efficient Catalytic Reduction of 4-nitrophenol

Catalysis Letters - For the noble-metal based catalysts, the metal dispersion and sinter resistance of the metal nanoparticles (NPs) are the most vital factors for their application in series...     

Strain properties of (1-x)Bi0.5Na0.4K0.1TiO3-xBi(Mg2/3Ta1/3)O3 electroceramics

A ternary solid solution of Bi_0.5Na_0.5TiO₃–Bi_0.5K_0.5TiO₃–Bi(Mg_2/3Ta_1/3)O₃ (BNKT-xBMT) lead-free electroceramics was synthesized by a solid-state reactive sintering technique. The electrostrain, dielectric, and ferroelectric properties as well as the impedance characteristics and the microstructure were systematically assessed. With the increase of BMT, the BNKT-xBMT ceramics gradually transformed from non-ergodic relaxor phase to ergodic relaxor phase, manifested as the ferroelectric-to-relaxor temperature (T_F-R) shifts towards below room temperature. Additionally, the ferroelectric hysteresis curves became pinched, and the strain curve changed from butterfly-shaped into sprout-shaped. At the ergodic relaxor composition of x = 0.04, a large electrostrain value (S = 0.4%; under an electric field of 60 kV/cm, d₃₃* = 632 pm/V) was achieved, which is mainly attributed to the electric-field-induced transition from the ergodic relaxor phase to the ferroelectric phase.     

Enhanced microwave absorption and electromagnetic shielding property of (1-x)K0.5Na0.5NbO3 ~ xAl2O3 nano-ceramics

(1-x) K_0.5Na_0.5NbO₃ ~ xAl₂O₃ (x = 0, 0.2, 0.4, 0.6) ceramics were prepared via a traditional solid-state reaction method. The phase structure, micro-morphology, dielectric properties and electromagnetic properties of ceramic samples were studied and analyzed. Results indicate that all the samples are similar to K_0.5Na_0.5NbO₃ (KNN) in perovskite structure. With the increase of Al₂O₃ content, the X-ray diffraction peaks move to a large angle region, suggesting the substitution of niobium ions by aluminium ions and the distortion of the KNN lattice with a new phase arising. With the increase of Al₂O₃ content the grain size reduces and the dielectric constant decrease, yielding to the decrease of the electromagnetic shielding performance of ceramic. When the x is 0.4, the minimum value of reflectivity of sample is −28 dB at the frequency of 11.6 GHz. It can be concluded that both the grain size and Al₂O₃ content can obviously affect the electromagnetic properties of ceramics, which can be easily turned through a multi-layer SiO₂ heterojunction structure.     

Interfacial potassium induced enhanced Raman spectroscopy for single-crystal TiO2 nanowhisker

Structural control and element doping are two popular strategies to produce semiconductors with surface enhanced Raman spectroscopy(SERS) properties. For TiO_2 based SERS substrates, maintaining a good crystallinity is critical to achieve excellent Raman scattering. At elevated temperatures(N600 °C), the phase transition from anatase to rutile TiO_2 could result in a poor SERS performance. In this work, we report the successful synthesis of TiO_2 nanowhiskers with excellent SERS properties. The enhancement factor, an index of SERS performance, is 4.96 × 10~6 for methylene blue molecule detecting, with a detection sensitivity around 10~(-7) mol·L~(-1).Characterizations, such as XRD, Raman, TEM, UV–vis and Zeta potential measurement, have been performed to decrypt structural and chemical characteristics of the newly synthesized TiO_2 nanowhiskers. The photo absorption onset of MB adsorbed TiO_2 nanowhiskers was similar to that of bare TiO_2 nanowhiskers. In addition, no new band was observed from the UV–vis of MB modified TiO_2 nanowhiskers. Both results suggest that the high enhancement factor cannot be explained by the charge-transfer mechanism. With the support of ab initio density functional theory calculations, we reveal that interfacial potassium is critical to maintain thermal stability of the anatase phase up to 900 °C. In addition, the deposition of potassium results in a negatively charged TiO_2 nanowhisker surface, which favors specific adsorption of methylene blue molecules and significantly improves SERS performance via the electrostatic adsorption effect.     

Integrating coral-like morphology into cyano-containing carbon nitride towards efficient photocatalytic H2 evolution and Cr(Ⅵ) reduction

The incomplete polymerization of graphite carbon nitride (g-C₃N₄) due to the kinetic problems resulted in its high recombination rate of photo-generated electron-hole pairs. Hence, cyano-containing carbon nitride with coral-like morphology (CCCN) was prepared by the molten salt method with heptazine-based melem as precursor, which presented excellent separation rate of photo-generated electron-hole pairs. SEM exhibited that CCCN owned coral-like morphology which exposed ample active sites and enhanced the capture ability of visible light while FT-IR and XPS demonstrated that cyano groups appearing in coral-like carbon nitride enhanced the separation rate of photo-induced charge carriers. The synergistic effect of coral-like morphology and cyano groups endowed CCCN-15% with superior performance of both the photocatalytic H₂ evolution (4207 μmol h^?1 g^?1) and Cr (Ⅵ) reduction (k = 0.059 min^?1), approximately 16.8 and 6.0 times that of g-C₃N₄, which was comparable among the similar materials. Density functional theory calculation (DFT) revealed that cyano groups decreased the bandgap and strengthened the activation degree of reaction substrate, which enhanced the thermodynamic driving force and the interaction between catalyst and substrate. This work provided a potential strategy for both the renewable energy generation and environmental restoration.     

Two-dimensional graphitic carbon nitride for membrane separation

Recent years, membrane separation technology has attracted significant research attention because of the efficient and environmentally friendly operation. The selection of suitable materials to improve the membrane selectivity, permeability and other properties has become a topic of vital research relevance. Two-dimensional (2D) materials, a novel family of multifunctional materials, are widely used in membrane separation due to their unique structure and properties. In this respect, as a novel 2D material, graphitic carbon nitride (g-C₃N₄) have found specific attention in membrane separation. This study reviews the application of carbon nitride in gas separation membranes, pervaporation membranes, nanofiltration membranes, reverse osmosis membranes, ion exchange membranes and catalytic membranes, along with describing the separation mechanisms.     

Chemically dealloyed MgCuGd metallic glass with enhanced catalytic activity in degradation of phenol

Nanoporous Cu with tunable pore size (20–50 nm) are synthesized through chemical dealloying of the Mg₆₅Cu₂₅Gd₁₀ metallic glass in sulfuric acid solution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) demonstrated the formation of mixing structures consisting of amorphous matrix and fcc-Cu ligaments with nanoporous structure in the dealloyed samples. The nanoporous alloy obtained shows superior catalytic activity in degrading phenol-containing wastewater, e.g., the degradation rate increases by 2–4 times as compared to the un-dealloyed Mg-based metallic glass. It was also found that surface wettability plays an important role in degradation, which results in a better catalytic performance in the sample with coarser nanoporous structure although it has relatively less specific surface area as compared to the samples with finer pores. Finally, the mechanism for degradation of phenol is discussed.     

Advances in biofilm control for food and beverage industry using organo-silane technology: A review

Cell adhesion can be a potential problem as well as a valuable tool for microbiological engineering. It can lead to biofouling, contamination of product and corrosion. On the other hand, cell adhesion is purposely employed in fermenters and bioreactors to influence reactor performance. This paper presents an overview of organo-functional silanes – their chemistry, properties, use, and the main laboratory experiments that can be of interest to the food and beverage industry. The purpose is to introduce and explore possibilities for using organo-silane combinations to enhance or reduce microbial adhesion.