Preparation of magnetic Fe3O4/TiO2/Ag composite microspheres with enhanced photocatalytic activity

The novel three-component Fe₃O₄/TiO₂/Ag composite mircospheres were prepared via a facile chemical deposition route. The Fe₃O₄/TiO₂ mircospheres were first prepared by the solvothermal method, and then Ag nanoparticles were anchored onto the out-layer of TiO₂ by the tyrosine-reduced method. The as-prepared magnetic Fe₃O₄/TiO₂/Ag composite mircospheres were applied as photocatalysis for the photocatalytic degradation of methylene blue. The results indicate that the photocatalytic activity of Fe₃O₄/TiO₂/Ag composite microspheres is superior to that of Fe₃O₄/TiO₂ due to the dual effects of the enhanced light absorption and reduction of photoelectron–hole pair recombination in TiO₂ with the introduction of Ag NPs. Moreover, these magnetic Fe₃O₄/TiO₂/Ag composite microspheres can be completely removed from the dispersion with the help of magnetic separation and reused with little or no loss of catalytic activity.     

Malononitrile-involved Michael addition polymerization: An efficient and facile route for cyano-rich polyesters with programmable thermal and mechanical properties

An efficient, atom-economic, oxygen-tolerant, and water-tolerant strategy has been established to synthesize cyano-rich polyesters. Four kinds of organic bases, 1,1,3,3-tetramethylguanidine (TMG), 4-dimethylaminopyridine, triethylamine, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were explored for accelerating Michael addition polymerization of malononitrile and 1,4-butandiol diacrylate. TMG can promote the polymerization efficiently under mild conditions to quantitatively afford polyester with high-molecular weight and moderate polydispersity. The comparison of the kinetic studies of TMG and TBD reveals that TMG shows better catalytic performance, while the catalysis of TBD brings about oligomers in spite of the higher efficiency at early age of the polymerization. Moreover, other diacrylate compounds could also be quantitatively polymerized to afford polyesters with high molecular weight. When dimethacrylate is chose as the monomer, the polymerization becomes sluggish. All the afforded polyesters display programmable thermal and mechanical properties that are closely related to their chemical structures.     

Novel alternating copolyoxamides with high crystallinity and heat resistance

Two series of novel alternating copolyoxamides (PAnT-alt-n2 and PAn2-alt-62) are synthesized via solution/solid-state polycondensation (SSP). The alternating structures are analyzed carefully with ¹H NMR and ¹³C NMR spectra. The melting behaviors, thermal stabilities, crystal structures and crystallinities are systematically evaluated by DSC, TGA and WAXD. The results reveal that these alternating copolyoxamides possess almost perfect alternating chain structures and have high melting temperature (T_m > 270 °C), high crystallinity (X_c > 32%) and high decomposition temperature (T₅ > 405 °C) as well as low saturated water absorption (<3.5 wt%), which suggests that they have high potential as engineering plastic of high heat resistant.     

Zn2+@Polyvinylpyrrolidone and Urushiol Preparation of Nanofibrous Membranes and Their Synergistic Effect

In this study, lacquer is gathered from a lacquer tree and rotary evaporation is used to remove impurities to obtain urushiol. Next, 10 mL of anhydrous ethanol serves as the solvent for blending polyvinylpyrrolidone (PVP) at a specified content (0.7 g and 0.2–0.7 g urushiol) to form an electrospinning solution. Electrospinning is carried out with a voltage of 18 kV to prepare PVP/urushiol nanofibrous membranes. At a ratio of 7/4, the PVP/urushiol nanofibrous membranes are not eroded in 98% sulfuric acid and these membranes also demonstrate a 50–60% antibacterial effect against Staphylococcus aureus and Escherichia coli. Moreover, the antibacterial effect can be boosted to 98% with the incorporation of zinc ions. The results indicate that anhydrous ethanol can remove the sensitization of urushiol from PVP/urushiol membranes. Furthermore, animal test results indicate that when rats are in contact with PVP/urushiol anhydrous ethanol for 48 h, their skins are free from dark brown skin allergy. The presence of PVP eliminates the sensitization of urushiol, and the nanofibrous membranes demonstrate low toxicity. Hence, urushiol is the only natural material that enables PVP to withstand 98% sulfuric acid as well as acquire hydrolyzability, thereby qualify PVP as a medical material.     

电热蒸发电感耦合等离子体质谱(ETV-ICP-MS)技术中气溶胶传输效率研究进展

蒸发效率和传输效率是影响电热蒸发电感耦合等离子体质谱技术分析性能的关键因素。本文综述了有关气溶胶传输效率的研究进展,在归纳常用的传输系统评价方法的基础上,重点对影响气溶胶传输效率的电热蒸发装置的改进、蒸发过程的探讨、基体改进剂的选择等研究现状进行了评述。但有关ETV 蒸发过程中基体干扰的作用机制仍有待进一步地系统研究,这对于校正策略的优化、新型校正技术的创新与集成具有重要的理论指导意义,可推动ETV-ICP-MS在地质、环境、生物等学科的更广泛应用。     

Improved thermal and mechanical properties of bacterial cellulose with the introduction of collagen

Composite films comprised of bacterial cellulose (BC) and collagen (COL) were developed using BC hydrogel membranes as the base material and COL as the reinforcing material. Glutaraldehyde (GT) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC·HCl) were then used as cross-linking agents to prepare cross-linked BC/COL composite films by a wet chemical method. The effects of chemical cross-linking on the thermal and mechanical properties of composite films were investigated in detail. The COL molecules were adsorbed and deposited inside of 3D nanofiber networks of BC, coated on the surface of BC fibers. Chemical bonds formed between BC molecules, and between BC and COL molecules after cross-linking. Compared with BC, the obtained composite films showed 57.9 and 70.8% improvement in tensile strength after being cross-linked by GT and EDC·HCl, respectively. Cross-linking also enhanced the thermal stability of the specimens.     

Transient deformation and heat generation of solid polyurethane under impact compression

This investigation examines the transient deformation and heat generation of a solid polyurethane subjected to dynamic compression. A special method is presented to prepare the solid polyurethane from raw materials which are commonly used to make polyurethane foams. Testing methods including infrared spectrum, differential scanning calorimetry, quasi-static and dynamic compression were applied to study the basic physical properties of the solid polyurethane. High-speed optical and infrared imaging systems are used to obtain visual and thermo-graphic images during impact tests. Under quasi-static compression, the solid polyurethane presents a good performance in toughness. This is confirmed by its Poisson's ratio. Under impact compression, the adiabatic heat generation are identified statistically. Temperature distribution confirms the fact of transient heat generation in specimens. Adiabatic self-heating mechanism provides a consideration to understand the negative strain-rate effect and post-yield softening effect found in the solid polyurethane. Mechanical properties including quasi-static and dynamic responses are related with the composition of molecular and structure of polymer.     

Determination of reliable fatigue life predictors for magnetorheological elastomers under dynamic equi-biaxial loading

Fatigue life prediction is of great significance in ensuring magnetorheological elastomer (MRE) based rubber components exhibit reliability and do not compromise safety under complex loading, and this necessitates the development of plausible fatigue life predictors for MREs. In this research, silicone rubber based MREs were fabricated by incorporating soft carbonyl iron magnetic particles. Equi-biaxial fatigue behaviour of the fabricated MREs was investigated by using the bubble inflation method. The relationship between fatigue life and maximum engineering stress, maximum strain and strain energy density were studied. The results showed that maximum engineering stress and stored energy density can be used as reliable fatigue life predictors for SR based MREs when they are subjected to dynamic equi-biaxial loading. General equations based on maximum engineering stress and strain energy density were developed for fatigue life prediction of MREs.     

Effects of solar irradiation on the properties of ethylene-norbornene composites containing solvent dyes

This study investigates the effects of irradiation with artificial solar light on the resistance to aging of ethylene-norbornene (EN) copolymer with different solvent dyes and commercial stabilizers. The mechanical properties of the samples were measured before and after ageing using tensile tests. FTIR spectroscopy was used to evaluate the carbonyl index as a measure of photooxidation after irradiation. It was found that the carbonyl index of the samples depended on the type of additive in the composite. Secondary ion mass spectrometry (TOF-SIMS) was used to analyze the chemical composition of the sample surfaces. The degree of oxidative aging was evaluated by measuring the intensities of secondary C_xH_yO_z⁺ type ions. Samples containing anthraquinone solvent dyes, such as Solvent Blue 97 or Solvent Green 28, showed the most significant improvements in durability in an aging test. Some of the applied solvent dyes showed much greater ability than the studied stabilizers to protect EN films exposed to the full solar spectrum.     

Influence of hybridization on in-plane shear properties of 2D & 3D thermoplastic composites reinforced with Kevlar/basalt fabrics

This paper investigates the characterization of in-plane shear properties of thermoplastic composites reinforced with Kevlar/basalt fabrics. Different fabrics had architectures of two dimensional plain woven (2D-P) and three dimensional angle-interlock (3D-A). Intralayer hybridization was performed during the weaving of the fabrics with the combination of Kevlar and basalt yarns. Five 2D-P and three 3D-A composite laminates were manufactured with polypropylene (PP) as a matrix, using compression molding. Iosipescu shear tests were carried out to evaluate the in-plane shear properties. The experimental results revealed that the shear properties including shear modulus, shear strength and shear failure strain of homogeneous composites were improved by 6.5–14.9%, 4.3–19.7%, and 3.2–46.7%, respectively. Similarly, change in the fabric architecture from 2D-P to 3D-A also enhanced the shear strength and shear failure strain by 32.0–41.6% and 7.2–22.5%, respectively. Intralayer hybrid composites had better in-plane shear properties than the interlayer hybrid composites. The fracture morphologies of the specimens were examined by scanning electron microscopy (SEM).