Boron Nitride Nanosheets Strengthened PVA/Borax Hydrogels with Highly Efficient Self-Healing and Rapid pH-Driven Shape Memory Effect

Self-healing hydrogels often possess poor mechanical properties which largely limits their applications in many fields. In this work, boron nitride nanosheets are introduced into a network of the poly(vinyl alcohol)/borax (PVA/borax) hydrogels to enhance the mechanical properties of the hydrogel without compromising the self-healing abilities. The obtained hydrogels exhibit excellent mechanical properties with a tensile strength of 0.410 ± 0.007 MPa, an elongation at break of 1712%, a Young's Modulus of 0.860 ± 0.023 MPa, and a toughness of 3.860 ± 0.075 MJ m⁻³. In addition, the self-healing efficiency of the hydrogels is higher than 90% within 10 min at room temperature. Benefiting from the excellent self-healing properties, the shapeability of the hydrogel fragments is observed using different molds. In addition, the hydrogels display rapid pH-driven shape memory effects and can recover to their original shape within 260 s. Overall, this work provides a new approach to hydrogels with integrated excellent mechanical properties, self-healing abilities, and rapid pH-driven shape memory effects.     

Natural Polysaccharides as Multifunctional Components for One-Step 3D Printing Tough Hydrogels

Natural polysaccharides (NPS) are regarded as biomolecular and structural components for preparing high-performance tough hydrogels. But the one-step fabrication of NPS-containing hydrogels in seconds and the template-free design of complicated high-resolution structures are still significant challenges in this field. To meet these requirements, various NPS-containing tough hydrogels are fabricated and processed into 2D/3D structures via the combination of Ru(bpy)₃²⁺-mediated photochemistry and extrusion 3D printing technique. The whole fabrication process is one-step, completed in tens of seconds under visible light irradiation. It is found that the used NPS plays a key role in achieving the fabrication of high-performance structured tough hydrogels. The high reactivity of functional groups in the used NPS can shorten their gelation times. Long rigid chains of the used NPS, their hierarchical assemblies, and contrasting multinetworks benefit from the efficient dissipation of mechanical energy and enhancement of its operational stability. Strong supramolecular interactions enable hydrogel precursors to have high viscosities, therefore providing good controllability to design high-resolution and complicated tough hydrogel structures via extrusion 3D printing. It is anticipated that this straightforward fabrication strategy and findings will open new horizons for NPS-containing materials.     

PAN/FPU Composite Nanofiber Membrane with Superhydrophobic and Superoleophobic Surface as a Filter Element for High-Efficiency Protective Masks

Recently, because of the outbreak of COVID-19, the demand for various types of filter elements in protective materials has increased globally. Furthermore, new requirements for the filtration performance of PM2.5 liquid (oil) particles have been put forward. In this work, Superhydrophobic and superoleophobic composite nanofibers with excellent filtration capacity for oil and salt particles are developed through the modification of polyacrylonitrile (PAN) by fluoro-polyurethane (FPU) doping. The results show that the PAN/FPU composite nanofibers doped with 9 wt% FPU has a uniform fiber morphology with a diameter of 240 ± 30 nm. Compared to the pure PAN nanofibers, the water-based contact angle of PAN/FPU increases from 90 ± 5° to 151 ± 5°, and the oil-based contact angle increases from 58 ± 2° to 152 ± 3°. Importantly, at a high flow rate of 95 L min⁻¹, the filtration efficiency of the PAN/FPU nanofiber membrane for 0.3 µm oil particles increases from 92 ± 1% to 99.2 ± 0.1%. After cyclic loading, the filtration efficiency of 0.3 µm oil particles remains above 98%. Meanwhile, the filtration efficiency for 0.3 µm salt particles remains at 98.23 ± 0.1%. The PAN/FPU nanofiber membrane developed in this work is effective in applications and has good market prospects as a protective filtration material.     

Crude Wax Extracted from Rice Bran Oil Improves Oleogel Properties and Oxidative Stability

Crude wax extracted from rice bran oil (RBO) is used to improve the oleogel properties and oxidative stability of RBO. The effect of crude rice bran wax (CrBW) on the formation characteristics and oxidative stability of oleogels is discussed. The results show that oleogels can be formed with 7.0 wt% CrBW at 20 °C. As the concentration of CrBW increases from 7.0 to 11.0 wt%, the hardness and solid fat content (SFC) of the oleogels increase significantly, and the oleogels are primarily β' crystals. Moreover, oleogel crystals formed with 5 and 7 wt% CrBW are flocculent; when the amount included is 9%, the oleogel crystals are transformed into long dendrites, and the density rises. After 90 days of storage at 20 °C, the peroxide value of oleogels formed with 9.0 wt% CrBW slowly rises from 3.21 to 6.52 mmol kg⁻¹. Practical Applications: Oleogels prepared here by CrBW and RBO are an innovative structural lipid without trans fats. Useful information on the rich fats and nutrients in CrBW is provided, which reduces the production cost and improves the industrial production capacity.     

基于ANSYS Workbench下芯片的耦合研究

为了研究电子设备在温度较高的环境下电路板元器件散热和在温度载荷下引起的变形,通过ANSYS数值模拟的方法建立流热耦合的电路芯片散热模型,对芯片与电路板表面形成冲击压力进而导致热疲劳进行研究,分析与讨论温度对流场与静力学结构的影响.通过数值模拟分析得出:电路板为铝材质的变形很大,变形从中间凸起;而PCB材料电路板的变形不是局部变形,属于扩散式变形.     

10.5/0.4kV干式变压器承受短路冲击电流能力的分析与研究

本文主要针对AP1000核电机组10.5/0.4kV低压厂用干式变压器的设计规格书与实际设备存在的技术参数偏差,根据GB 1094.5-2008和IEC 60076.5-2005中的相关理论要求,来分析该变压器承受短路冲击电流的能力是否满足要求,为后续项目变压器短路耐受能力验算提供借鉴意义,并提出了后续项目变压器采购过程中的关注点.     

Structure and Properties of Explosion-Welded Joints of Carbon Steels

The structure and mechanical properties of bimetallic joints of the same and different types, i.e., iron and steels St3, 45, and 85, are studied after explosion welding and subsequent heating. The cladding and the base layer have a thickness of 2.5 and 12 mm, respectively. It is shown that bending of explosion-welded joints from same-type and different-type steels is accompanied by an anomalous phenomenon of local softening of the near-weld zone in the region of residual deformation with degree ε = 2 – 9%.     

Viscosity of Conventional Cryolite-Alumina Melts

Russian Journal of Non-Ferrous Metals - Viscosity of conventional cryolite-alumina melts NaF–AlF3–CaF2–Al2O3 with a cryolite ratio (xNaF/xAlF3, mol/mol) 2.3 was studied in...     

从改革中求发展 从改革中求效益

总结了解放４５年来上海钢铁工业所取得的成就，重点阐述了技术、工艺、装备方面的现状和不足以及发展目标，指出：只有实行改革开放，加快技术改造，才能提高上海钢铁工业的总体水平，提高经济效益，也才能使老企业焕发青春，步入现代化钢铁工业之林。     

充填型单缝煤岩水力脉动解堵试验研究

利用室内自行研制的可调频脉动水力压裂系统及预制充填型单缝的煤岩,开展不同频率条件下水力脉动解堵试验,研究脉动作用下解堵水压演化过程和解堵效果。试验结果表明,水力脉动解堵压力演化过程可分为三个阶段:压力上升阶段、压力下降阶段和压力波动稳定阶段。在疲劳损伤和脉动波的双重作用下,脉动作用下的煤岩解堵表现出解堵压力阀值比定常流作用下更低、压降持续时间更短、压降幅值更小的特点。定常流作用下煤粉运移集中在压力下降阶段;脉动压力作用下煤粉在压力下降阶段和压力波动稳定阶段均有运移,且压力下降时间与运移煤粉总量成正相关关系,但煤粉总的运移量和定常流作用下的相当。脉动作用和定常流作用下径向渗透主要发生在压力上升至压力峰值阶段,但脉动流的解堵时间短,则滤液渗透半径小对储层的伤害小。综合考虑解堵压力、煤粉运移、解堵渗透路径和解堵渗流深度,特别是解堵压力和解堵渗流深度作为主要评价因素,在3 Hz条件下解堵效果最好,其具有较低的解堵压力和最小的解堵渗流深度。