Reasonable construction of proton conducting channel via biomimetic caterpillar-like alumina fiber to improve the properties of its composite proton exchange membrane

In this paper, we prepare a novel biomimetic caterpillar-like alumina fiber with the characteristic of continuous alumina backbone and fine needle whiskers spine. Then the high-performance caterpillar-like alumina fiber composite proton exchange membrane (CAPEM) is obtained by introducing the amino modified biomimetic caterpillar-like alumina fiber into sulfonated polysulfone (SPSF) matrix, which successfully reasonable construction of the proton conducting channels in both vertical and horizontal orientation. The properties of CAPEM, including proton conductivity, methanol permeability, etc. Are systematically studied. The results show that the proton conductivity of CAPEM increases with rising the temperature, which reaches the maximum of 0.263 S/cm at 80 °C and 100% RH, respectively. The excellent proton conductivity of CAPEM is attributed to the long-range continuous proton conducting channel formed by the horizontal continuous alumina skeleton in the in-plane direction and the vertical overlapped fine needle whiskers spine in the through-plane direction. In addition, the interfacial compatibility between amino modified caterpillar-like alumina fiber and SPSF matrix is enhanced through the reasonable construction of proton conducting channels, which effectively inhibits the methanol permeation of the composite membrane with 4.18 × 10^?7 cm² s^?1 and improves the comprehensive performance of the CAPEM.     

Facile synthesis of Ti3C2 MXene-modified Bi2.15WO6 nanosheets with enhanced reactivity for photocatalytic reduction of Cr(VI)

Through a facile hydrothermal method, we have successfully prepared Ti₃C₂/Bi_2.15WO₆ (TC/BWO) composite, and systematically investigated their reactivity for the photocatalytic reduction of Cr(VI) under visible light. X-ray diffraction and Raman analysis confirm the formation of heterostructure between Bi_2.15WO₆ and Ti₃C₂. The resultant 7TC/BWO composite exhibits enhanced photoactivity toward Cr(VI) reduction. After 120 min irradiation, the conversion of Cr(VI) reaches 92.5% with the quasi-first-order kinetic constant of k = 0.0145 min^?1, which is higher than that of pure BWO (30% and k = 0.0005 min^?1). The electrochemical and photoluminescent characterization confirm that the introduction of Ti₃C₂ is conducive to the separation of carriers, thus significantly improves the photocatalytic performance of TC/BWO. Furthermore, the radical capture experiments verify that the electrons are important for enhancing reduction of Cr(VI) to Cr(III). As a result, this research provides a comprehensive understanding of the reduction of Cr(VI) by TC/BWO composite under visible light.     

Genipin-crosslinking polyvinyl alcohol hollow braids degradable tissue engineering scaffolds: Manufacturing techniques and property evaluations

Tissue engineering has been developed with the aim of improving the regeneration and recovery of impaired tissues and organs. Biodegraded scaffolds serve the aforementioned functions and can also be decomposed by means of metabolism. They have no biological toxicity and save patients from injuries by the second surgery, which makes biodegradable scaffolds a new development trend in the tissue engineering. In this study, the textile engineering and chemical crosslinking techniques are employed to produce biodegradable polyvinyl alcohol (PVA) hollow braids, serving as the tissue engineering scaffolds. The process involves two types of products, including the twisted yarns and hollow braids. The twist number of PVA twisted yarns is changed to form different PVA twisted yarns, which are then used to braided into hollow braids via the braiding technology. Therefore, the hollow braids are basically composed three types of PVA twisted yarns. Next, the surface observation, mechanical properties, and degradation of the products are then evaluated. The test results indicate that PVA twisted yarns exhibit the optimal mechanical properties when being twisted with 3 turns/inch. Any higher twist counts result in over twist in the twisted yarns. The optimal hollow braids are composed of PVA twisted yarns with a twist counts being 3 turns/inch. Afterwards, hollow braids are crosslinking with genipin, thereby obtaining greater mechanical strength of 23.6 N and higher decomposition rate of 0.8. The specified hollow braids are suitable for the use as tissue engineering scaffolds.     

Luminescence modulation of the Eu3+ doped Srn+1SnnO3n+1 (n=1, 2, 5, ∞) ceramics based on photochromism and its application in anti-counterfeiting technology

The structure and optical properties of Sr_n+1Sn_nO_3n+1 ceramics greatly depend on the n value. Thus, we fabricated four compositions, namely Sr_n+1Sn_nO_3n+1:Eu³⁺ (n = 1, 2, 5, ∞) ceramics, and their crystal structure, photoluminescence, photochromism and luminesce modulation properties have been investigated. It is found that excellent photochromism and luminesce modulation properties are found in Sr₂SnO₄:Eu³⁺ and Sr₃Sn₂O₇:Eu³⁺ ceramics. After 280-nm light irradiation, the Sr₂SnO₄:Eu³⁺ ceramics transform into gray purple from primal white. Meanwhile, luminescence intensity decrement ratio ΔI_dec of the colored Sr₂SnO₄:Eu³⁺ reaches a high value of 80.8% under optimized irradiation wavelength. The decreased luminescence intensity of Eu³⁺ can be completely recovered via 450-nm light irradiation. The ΔI_dec of Sr₃Sn₂O₇:Eu³⁺ ceramic reaches 53.1%, and the decreased luminesce intensity can not be covered by light irradiation, only can be covered by a high temperature stimulus at 400 °C. Finally, we successfully fabricated a flexible membrane using Sr₂SnO₄:Eu³⁺ and PDMS for anti-counterfeiting applications.     

罗布麻抑菌物质及其作用机制的研究进展

为阐明罗布麻抑菌功能的物质基础,促进罗布麻纤维在医疗保健用纺织品领域的开发和应用,综述了罗布麻韧皮和精干麻纤维中存在的主要抑菌物质,包括:黄酮类化合物、鞣质、甾体及其苷类、香豆素类化合物、酚酸类和苯甲醛类化合物、脂肪酸以及挥发油。分析了各类抑菌物质的化学成分和抑菌活性,并着重从抑制核酸合成、破坏细胞膜、抑制能量代谢、影响脂肪酸合成、抑制运动性、阻断电子传递链、抑制酶活性、减弱营养物质的吸收以及通过过氧化和自氧化形成具有毒性的降解产物等方面介绍了抑菌作用机制。最后针对精干麻纤维抑菌物质的来源问题,指出韧皮中功能性成分在脱胶过程中的演化行为应成为未来研究的一个重要方向。     

季铵型改性壳聚糖的制备及其在兔毛织物抗菌整理中的应用

以三乙胺和环氧氯丙烷为原料，合成醚化剂3-氯-2-羟丙基三乙基氯化铵。以甲壳素为原料通过醚化反应合成了季铵型甲壳素（CCT），再经脱乙酰得到季铵型阳离子改性壳聚糖（CCTS）。采用红外光谱（FTIR）、核磁碳谱（¹³C NMR）对其化学结构进行了表征，运用黏度法和分光光度法测定了黏均分子量和溶解性等理化性能。采用最小抑菌法对CCTS的抗菌活性进行了测定，得到其对大肠杆菌的最低有效抑菌浓度（MIC）为0.2g/L，优于天然壳聚糖的MIC值。以柠檬酸为交联剂、次磷酸钠为催化剂，用CCTS对兔毛织物进行抑菌整理，考察织物经整理的抑菌效果和耐洗性。经5次洗涤后结果表明，CCTS对大肠杆菌的抑菌率达99.9%以上，抑菌率高于CCT和天然壳聚糖，是一种针对动物毛织物良好的天然高分子长效抑菌整理剂。     

基于神经网络和遗传算法的锭子弹性管性能优化

为得到减振弹性管对下锭胆的支承弹性和锭子高速运动下的稳定性等性能的最优匹配效率,依据减振弹性管的等效抗弯刚度及底部等效刚度系数公式,利用MatLab数值分析软件构建弹性管抗弯刚度和底部挠度数学模型。首先,结合Isight优化软件基于径向基神经网络构建其近似模型,且使精度达到可接受水平,并以模型的关键结构参数弹性模量、螺距、槽宽、壁厚为设计变量,结合遗传算法对弹性管抗弯刚度和底部挠度进行多目标优化设计,得到Pareto最优解集和Pareto前沿图,确定出减振弹性管结构工艺参数的优化方案。通过对优化数据进行分析发现,该方案在保证减振弹性管弹性的同时,其底部振幅明显减弱。     

Phase transition and interface evolution of Al2O3/ZrO2 particles in plasma-sprayed coatings

Alumina and zirconia ceramic particles exhibit high hardness and excellent wear resistance at high temperature, and hence are used as ceramic reinforcement phases in some plasma sprayed coatings. In this study, the interface evolution of a zirconia/alumina eutectic ceramic and the phase transition of zirconia in a plasma-sprayed coating were investigated. Scanning electron microscopy and transmission electron microscopy combined with focused-ion beam and energy dispersive X-ray were used to analyze the microstructure and composition of the ceramic interface. The results showed that the eutectic ceramic particles consisted of alumina (outer) and columnar zirconia (inner) before and after the plasma spraying process. The inner zirconia part showed the martensitic transformation of t-type zirconia to stripe-like m-type zirconia. After the plasma spraying, the interface between alumina and zirconia changed significantly, which formed a new oxide layer. The phase transition mechanism in the ceramic particle and oxide layer formation mechanism at the alumina/zirconia interface were investigated.     

Preparation of mixed matrix composite membrane for hydrogen purification by incorporating ZIF-8 nanoparticles modified with tannic acid

The incompatibility between nanofillers and polymer, caused by the agglomeration of nanoparticles and their weak interaction with each other, is still a challenge to develop mixed matrix composite membrane. Herein, we introduced the ZIF-8-TA nanoparticles synthesized by in situ hydrophilic modification into the hydrophilic poly(vinylamine) (PVAm) matrix to prepare composite membranes for H₂ purification. The dispersion of ZIF-8 in water was improved by tannic acid modification, and the compatibility between ZIF-8 particles and PVAm matrix was enhanced by chemical crosslinking between the quinone groups in oxidized tannic acid (TA) and the amino groups in PVAm. Moreover, the compatibility between hydrophobic polydimethylsiloxane (PDMS) gutter layer and hydrophilic separation layer was achieved by the adhesion of TA-Fe³⁺ complex to the surface of PDMS layer during membrane preparation. The interlayer hydrophilic modification and the formation of separation layer were accomplished in one step, which simplified the preparation process. The experimental results indicated that when the TA addition used for modification was 0.5 g and the ZIF-8-TA_0.5 content in membrane was 12 wt%, the prepared membrane showed the best separation performance with the CO₂ permeance of 987 GPU and the CO₂/H₂ selectivity of 31, under the feed gas pressure of 0.12 MPa.     

Pairing effect and tensile properties of laminated high-performance hybrid composites prepared using carbon/glass and carbon/aramid fibers

Many attempts have been made to fabricate lightweight, high-performance, and low-cost polymeric composites. To improve the mechanical performance of the same material compared to conventional composites, paired hybrid materials were manufactured with different lamination structures. Each of six types of hybrid composite was designed by lamination pairing of carbon/aramid fabric and carbon/glass fabric using VARTM. The dependence of the mechanical properties of the samples on the pairing effects of the lamination structures was investigated. All pairing materials did not lead to a large increase of tensile strength due to the domination of carbon fiber, but the mechanical properties of specific laminates were clearly changed by the particular pairing sequence used. Using the limited material, the design of an effective structure was the central laminating condition with a good tensile and bending properties. Laminating position of the carbon fiber was found to play an important role in the stacking design of hybrid composites.