Method for the synthesis of para‐aramid nanofibers

The synthesis and electrospinning of novel N‐substituted aramid nanofibers (ANFs) prepared from basic dispersions of commercial microscale Kevlar fibers are herein reported. The functionalized ANFs were characterized via Fourier transform infrared spectroscopy, ¹³C solid‐state nuclear magnetic resonance spectroscopy, and X‐ray diffraction to confirm proper N‐substitution of the side groups and to determine changes to the polymer crystallinity and stability. These analyses suggested that the electrospun ANFs consisted of numerous crystalline domains in the transverse fiber direction with large amorphous regions that were void of defects commonly found in commercial Kevlar fibers. A semi‐empirical study of the variations in the solubility parameter due to various side chain moieties was conducted to facilitate solvent selection and to elucidate the enhanced solubility effects with selected organic solvents. These initial findings suggest a promising route for obtaining a new class of nanofibers with ultrahigh strength and stiffness. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44082.     

Structure–Property Relationships in Aligned Electrospun Barium Titanate Nanofibers

Barium titanate nanofibers were uniaxially aligned by electrospinning onto a rotating copper wire drum and alignment was maintained during calcination of the fibers. Two methods for maintaining alignment during calcination were tested, by either using carbon tape or a peeling off method to remove the aligned fibers from the mandrel followed by calcination. The carbon tape removal method led to the formation of shorter aligned nanowires while the peeling off method resulted in longer nanofibers. Additionally, the effects of calcination temperature and time on crystal structure were also examined. The degree of tetragonality in the barium titanate nanofibers increased at higher calcination temperatures and times. Piezoelectricity was confirmed in the nanofibers calcined using piezoeresponse force microscopy, yielding a d₃₃ value of 15.5 pm/V. Using the methods presented here, large quantities of aligned piezoelectric barium titanate and other ceramic fibers or wires can be produced to fulfill their demand in novel microelectronics.     

Fabrication of polymer/drug‐loaded hydroxyapatite particle composite fibers for drug sustained release

The aim of this study is to fabricate polymer/hydroxyapatite (HA) particle composite fibers for drug encapsulation and sustained release. Firstly, drug‐loaded hydroxyapatite particles are synthesized in one step, then by electrospinning of the blends of drug‐loaded hydroxyapatite particles and polymer solution the drug‐loaded polymer/hydroxyapatite particle composite fibers are successfully prepared. Effect of loading ratio of drug‐loaded hydroxyapatite particles in the fibers and pH value of the release medium on the drug release kinetics are both investigated, and the results demonstrate that, as compared with the polymer/drug electrospun fibers, the drug in the polymer/drug‐loaded hydroxyapatite particle composite fibers shows a sustained release manner, and the drug release rate can be regulated by both the loading ratio of drug‐loaded hydroxyapatite particles in the composite fibers and pH value of the buffer solution. The results indicate that the developed drug‐loaded polymer/hydroxyapatite particle composite fibers show great potential in bone regeneration and other related biomedical fields. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42871.     

Electrospun biodegradable nanofibers scaffolds for bone tissue engineering

Many polymeric materials have been developed and introduced for bone regeneration. Especially, their nanofibrous forms are mostly applied for artificial extracellular matrices. Polymeric materials in their nanofibrous form show some potent properties such as high surface‐to‐volume ratio, tunable porosity, and ease of surface functionalization. Benefiting from the properties of their main polymer and additives, they can provide new opportunities for cell seeding, proliferation, and new 3D‐tissue formation. This article focuses on most cited polymeric nanofibrous scaffolds fabricated by electrospinning and recent achievements. They were divided into two main categories: natural (collagen, silk, keratin, gelatin, chitosan, and alginate) and synthetic (e.g., polycaprolactone, polylactic acid, and polyglycolic acid) polymers. The role of several additives like hydroxyapatite, bone morphogenetic proteins (BMPs), tricalcium phosphate, and collagen type I in improving the adhesion, differentiation, and tissue formation of stem cells were discussed. Finally, the osteogenic capacity and ability of nanofibrous scaffolds to support the growth of clinically relevant bone tissue were briefly studied. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42883.     

海上油田含聚污水用清水剂性能评价方法

海上聚合物驱采油污水成分复杂、乳化程度高、处理难度大,对清水剂的性能提出了更高要求,传统的清水剂性能评价方法已无法满足要求。分析了传统清水剂性能评价方法中存在的不足,结合海上油田现场采出液处理问题,分别从评价条件、水质性能、絮体性能、溶解及配伍性能方面探讨了海上油田含聚污水用清水剂的评价指标及方法,并提出对清水剂的絮体黏附性和流动性等应给予关注。     

基于方差分析法的C-276合金脉冲电流自动化钨极气体保护电弧焊参数优化

优化C-276合金脉冲电流自动化钨极气体保护电弧焊参数有着重要的意义。采用田口方法,设计了拥有4个焊接参数(脉冲电流、基值电流、脉冲电流占空比和脉冲频率),3个水平等级,9组实验方案的正交实验,利用方差分析每个焊接参数的贡献百分比。实验结果表明,当脉冲电流、基值电流、脉冲电流占空比和脉冲频率分别为165 A、77 A、60%和5 Hz时,焊件具有最大的熔深。     

带有刷直流电机的家电产品骚扰功率应对策略

针对带有刷直流电机的家电产品因电机换向而引起电磁兼容项目骚扰功率测试不合格问题,分析了电机换向时火花的成因,指出了当前电子滤波理论设计在抑制骚扰功率时的局限性以及建立电机骚扰功率电路模型的复杂性。综合考虑了骚扰功率测试时遇到的多种场合下的频点和测试幅值超标情况,提出了相对应的控制策略,并对控制策略进行了理论分析。最后,通过实际试验给出了采用该策略后家电产品骚扰功率抑制的改善效果。研究结果表明,通过采用所提出的控制策略对家电产品设计人员快速、有针对性地改进电机电磁兼容设计、降低骚扰辐射具有指导作用。     

基于田口正交法的小计量称重配料系统优化设计

针对小计量称重配料过程中人工配料效率低、精度低的问题,对小计量称重配料系统的电磁振动供电电压、落料口高度和出料口大小方面进行了研究,提出了一种自动称重配料系统。通过称重配料实验平台,得出了电磁振动供电电压、落料口高度和出料口大小3个参数的实验数据,利用田口正交实验对称重系统的这三个参数进行了望目特性分析,获得了影响称重精度的因子贡献率以及因子间的交互作用。研究结果表明,田口正交实验法在材料颗粒较均匀的条件下可以优化称重配料系统参数,提高了计量准确度,为小计量称重配料系统的设计提供了参考依据。     

电纺压电聚偏二氟乙烯有序纳米纤维及其在压力传感器中的应用

针对传统静电纺丝法制备聚偏二氟乙烯(PVDF)压电纤维工艺复杂和效率低等问题,提出了采用滚筒收集方式制备PVDF有序纳米纤维的方法。通过改变滚筒转速收集纤维,得到了有序程度不同的PVDF纤维膜。用傅立叶变换红外光谱(FTIR)分析了有序纤维膜β晶相的含量,并利用NI数据采集卡在相同条件下测试了纤维膜的压电特性。结果表明:随着滚筒转速提高,纤维有序度增强,β相的含量提高,压电电压输出也明显增大,由此得知滚筒转速变化对β晶相的含量及压电输出电压的影响规律基本一致。基于得到的结果,设计制作了利用该有序PVDF纤维膜的压力传感器,并在不同气压下进行了动态响应测试。结果显示:所制备的PVDF有序纤维压力传感器在0.145~0.165 MPa下的电压输出随气压的增加呈线性增大,表现出了良好的线性度,其灵敏度达179mV/kPa。采用该种方法制备PVDF纤维对研制动态压力传感器极有意义。     

Structure and dielectric characteristics of continuous composition spread Ba1−xSrxTiO3 thin films by combinatorial pulsed laser deposition

Ba_1−xSr_xTiO₃ (0≤x≤1, BST-x) continuous composition spread thin films were grown on SrTiO₃ substrates buffered by La_0.9Sr_1.1NiO₄ (LSNO) electrodes using combinatorial pulsed laser deposition. The effects of Sr concentration on the structure and dielectric properties of the Au/BST-x/LSNO capacitors were investigated. X-ray diffraction patterns and reciprocal space maps revealed that both the in-plane and out-of-plane BST-x lattice parameters decreased with the increment of Sr content. Impedance measurements showed that the dielectric constant and tunability simultaneously changed with Sr concentration and reached the maximum at about x=0.5, which is comparable to that of BST-x individual thin films or bulks. Our results showed the large potential of combinatorial method in optimizing materials properties and even finding new materials.