等离子体表面处理对柔性导电纤维传感性能的影响

研究了具有PPy(聚吡咯)微纳米尺度涂层的XLA导电纤维的研制与应变传感性能。但由于XLA纤维的表面十分光滑,因此在用传统的化学气相沉积法进行涂层之前需要对纤维进行特殊处理。等离子体处理可以改变纤维表面粗糙度,使PPy更易于附着于纤维表面且增加其与纤维的接触强度。比较了经过不同等离子体处理时间(5和15min)的导电XLA纤维的力学及应变传感性能。实验结果表明,等离子体处理对纤维的力学性能几乎没有影响,但对导电纤维的应变传感性能影响很大。     

PAN基碳化纤维静电耗散材料的表面电阻率研究

制备了一种以氟碳树脂为基体,聚丙烯腈(PAN)基短切碳化纤维为导电填料的抗静电复合涂层。讨论了纤维的含量、长度、涂层厚度及外加电压对涂层表面电阻率的影响。结果表明表面电阻率和碳化纤维质量分数之间的关系符合逾渗理论,当纤维长度为4mm时,此体系的渗滤阈值为2.5‰(质量分数),其表面电阻率为106Ω,具有良好的抗静电性能;表面电阻率随纤维长度的增加而降低,但降低的程度愈来愈小;涂层厚度在不超过134μm的情况下,对表面电阻率的影响较小;涂层的表面电阻率在高外加电压下较低外加电压下小;碳化纤维/氟碳树脂复合涂层的导电机理是由导电通道、隧道效应和场致发射3种导电机理竞相作用的结果。     

用于电阻式柔性应变传感器的导电聚合物复合材料研究进展

作为物联网的触角,传感器迎来了新的发展机遇。而随着可穿戴行业的发展,电阻式柔性应变传感器在人体穿戴实时监测、机器人仿生皮肤、医学健康跟踪、运动肢体捕捉以及生产振动检测等领域展现出广阔的应用前景。聚合物导电复合材料是电阻式柔性应变传感器最常用的应变传感核心材料,具有柔性好、应变检测范围大以及成本低的优势。但现有的基于聚合物导电复合材料的传感器普遍存在迟滞明显、线性度低、导电网络稳定性差的缺点,此外对于某些复合材料在应变过程中的导电机理阐释也存在缺陷。因此,近年来诸多学者从聚合物导电复合材料导电机理、不同导电填料的特性、聚合物本身特性以及不同的制备工艺等方面开展了大量的研究工作。在解释聚合物导电复合材料的导电机理方面,目前多采用渗流理论解释其导电过程。目前聚合物导电复合材料所用的导电填料主要分为碳系导电填料和金属系导电填料两大类,由于碳系导电填料的导电稳定性好、价格低,是目前使用的主流。而目前使用的聚合物基体主要分为硅橡胶、天然橡胶以及聚氨酯三大类,硅橡胶主要用于小应变、高灵敏度传感器,天然橡胶主要用于大应变传感器。而聚合物导电复合材料的制备工艺主要分为填充式、夹心式、吸附式三种,填充式的传感器应变范围较大,而夹心式和吸附式传感器应变范围相对较小。本文对聚合物导电复合材料的导电机理、导电填料、聚合物基体以及不同制备工艺进行了归纳和分析,并展望了柔性应变传感用聚合物导电复合材料今后可能的研究热点和发展趋势。     

一种三层雷达吸波涂层的制备和性能

在磁性金属微粉的雷达吸波涂层中引入导电纤维层具有减轻质量和展宽吸收频带作用,本文采用磁性金属微粉和短导电纤维制备了一种三层雷达吸波材料.研究表明,三层的相对顺序对吸波涂层的带宽与峰值具有明显影响,在面密度为2.50 kg/m2的条件下,当导电纤维层位于表层时带宽最大,在8～18 GHz频段范围内反射率小于-10 dB的带宽达7 GHz.     

添加导电纤维对羰基铁粉吸波性能的影响

本文研究了在羰基铁粉(CIP)吸波涂层中添加导电纤维对涂层的电磁参数和反射率的影响规律.发现导电纤维的添加使磁性金属微粉CIP吸波涂层的介电常数增大,使得吸波涂层的吸收峰向低频移动,有利于改善低频段的吸收效果;利用分块设计的方法可以拓宽吸波材料在全波段(2～18GHz)范围内的吸收频带;同时导电纤维的加入还降低了吸波涂层的面密度.     

柔性智能聚苯胺/聚氨酯导电纳米纤维的制备及性能

利用静电纺丝技术制备聚氨酯(PU)纳米纤维,采用原位聚合法在纤维表面聚合导电聚合物聚苯胺(PANI),得到具有优良导电性能的柔性PU/PANI复合纳米导电纤维。通过扫描电镜观察到表面均匀包覆聚苯胺的复合纳米纤维;红外光谱结果证明在聚氨酯纳米纤维表面成功合成了聚苯胺。通过实验可知,聚苯胺最佳聚合工艺为苯胺单体浓度为1.3 mol/L、聚合时间为120 min。导电性能测试发现,PU/PANI复合纳米纤维导电性能优良,电导率可达7.6×10-1S/cm,经聚合后力学性能较为稳定。将PU/PANI导电纳米纤维制成简易柔性传感器件,探究发现PU/PANI导电纳米纤维具有柔性应变电学性质,且反应灵敏。     

不同制备工艺对硅橡胶智能复合材料应变传感肩峰现象研究

导电聚合物复合材料通常使用弹性体作为应变传感材料的基体。然而，弹性聚合物复合材料在电阻-应变响应性能中通常表现出肩峰现象，从而限制应变传感材料的应用。以消除肩峰现象为目的，分别采用机械共混法与溶液共混法制备出多壁碳纳米管(MWCNT)/甲基乙烯基硅橡胶(VMQ)导电纳米复合材料，研究不同制备工艺对复合材料微观形貌、导电性能、应变传感性能的影响。结果表明：机械共混法制备出的复合材料，渗流阈值更低、灵敏度更高，电阻响应信号更加稳定，即使在2 500次循环加载-卸载过程保持良好的稳定性及重复性，没有出现肩峰现象，同时解释了肩峰现象的机理。明确了该应变传感器具有对大变形隔震支座进行实时应变监测的潜力。     

工艺参数对浅色复合导电涂料导电性能的影响

利用导电云母粉与醇酸树脂复合制备了一种浅色复合导电涂料,讨论了导电填料含量、偶联剂种类及含量、固化工艺以及涂层厚度等工艺参数对涂料导电性能的影响.结果表明,加入60%～65%导电云母粉,钛酸酯偶联剂NTG401用量为5%,涂层在50℃条件下烘烤2d,涂层厚度在120μm左右,涂料的导电性能较好,表面电阻率达到103Ω·cm-2.     

纤维高强混凝土的动态力学性能试验研究

为研究纤维高强混凝土材料在冲击荷载下的动态压缩性能,采用大尺寸φ75mm Hopkinson压杆,对三种纤维含量的钢纤维高强混凝土、PVA纤维高强混凝土试件进行了三种应变率范围的冲击压缩试验,得到了它们在较高应变率范围内的动态应力-应变关系。试验表明纤维高强混凝土材料为应变率敏感性材料,在较高应变率范围内纤维高强混凝土材料的动态应力-应变关系是与应变率相关的。纤维高强混凝土材料的破坏应力和破坏应变随应变率的增大而增大。钢纤维和PVA纤维对混凝土耗能能力的改善和提高表现在材料达到峰值应力后开始破坏的过程中。同时也对两种纤维高强混凝土材料的纤维增韧特性及耗能机理也进行了分析和探讨。     

纳米银-聚合物菱形剪纸薄膜应变传感特性的研究

采用银镜制备法和激光切割技术获得了纳米银颗粒/聚二甲基硅氧烷剪纸结构薄膜,并系统地研究了薄膜作为柔性应变传感器的力学及压阻特性。将数值模拟与实验相结合,测量了传感薄膜的应变比γ、压阻滞回特性、线性度及压阻敏感性,重点探讨了薄膜制备工艺、结构参数与上述薄膜传感特性的定量关系。结果表明,在给定结构下,结构薄膜整体与结构单元的应变比γ为常数,反映了结构薄膜的变形特性,是理想的力学性能表征参数。菱形剪纸结构薄膜具有量级可达200的大应变比,即在大应变下,材料的实际应变很小。这一特点极大地提升了薄膜的应变测量范围、压阻稳定性、线性度,并保持了合理的压阻灵敏度。     

柔性可拉伸硅橡胶@多壁碳纳米管/硅橡胶可穿戴应变传感纤维

基于核-壳结构设计,采用简便、低成本的浸涂-固化法制得柔性、可拉伸、高灵敏且稳定的聚二甲基硅氧烷硅橡胶@多壁碳纳米管/聚二甲基硅氧烷硅橡胶(PDMS@MWCNTs/PDMS)压阻式应变传感纤维。通过FTIR、XRD、TG、TEM对硅烷偶联剂改性多壁碳纳米管(MWCNTs-KH570)的化学结构、热稳定性和微观形貌进行了分析,深入研究了核-壳结构与MWCNTs-KH570质量分数对PDMS@MWCNTs/PDMS复合纤维导电性能、传感性能及力学性能的影响规律与机制。结果表明:羟基化MWCNTs(MWCNTs—OH)表面接枝KH570使其在壳层PDMS基体中具有良好的分散性和界面相互作用;核-壳结构的设计使PDMS@MWCNTs/PDMS复合纤维在低填充下具有高电导率和传感性能;PDMS@MWCNTs/PDMS复合纤维的导电性能与传感性能随着MWCNTs-KH570质量分数增加而提高,且在人体关节运动监测中表现出良好的可重复性和工作稳定性。      

Functional properties of cement-matrix composites

The functional properties of cement-matrix composites are reviewed. The functions include strain sensing, damage sensing, temperature sensing, thermal control, vibration reduction and radio wave reflection. The functions are rendered by the use of admixtures, such as short carbon fibers, short steel fibers and silica fume.     

聚乳酸/杆菌肽静电纺丝纤维的体外释药研究

为探讨聚乳酸纤维结构形貌对杆菌肽药物的缓慢释放行为及作用机理,通过静电纺丝法制备了聚乳酸/杆菌肽单轴纤维、聚乳酸/杆菌肽串珠和(聚乳酸/杆菌肽)-聚乳酸同轴核-壳纤维等聚乳酸/杆菌肽药物缓释体系,并采用红外光谱法和差热分析法对其化学结构和热性能进行了表征.利用紫外分光光度计法研究了不同载药体系的体外药物释放行为,并探索了不同降解时期载药纤维的质量和形貌变化规律.研究表明:杆菌肽与聚乳酸主要为物理结合;聚乳酸单轴纤维和串珠对杆菌肽的扩散释放机理,属于纯Fick扩散;采用单轴和同轴静电纺丝技术可以获得两种不同释药特性的载药纤维.单轴纤维和串珠能够将药物快速释放,适合抗生素的治疗;同轴纤维中药物受控释放,更适合长期、小剂量的药物释放.     

Plastic bending of sapphire fibers for infrared sensing and power-delivery applications

Sapphire fibers with diameters of 325-850 mum were plastically bent by CO(2) laser beams with typical bending radii as small as 2.8 mm. The additional optical loss caused by a single bend was less than 0.1 dB (at 900 nm), the damage threshold of the bent fibers was higher than 150 MW/cm(2) for Nd:YAG laser pulses, and the high mechanical strength of the bending area was also proved. Several successful applications of bent sapphire fibers have shown that plastically bent sapphire fibers are promising for use in IR sensing and power-delivery applications.     

Orientation controlled preparation of nanoporous carbon nitride fibers and related composite for gas sensing under ambient conditions

Creating pores in suprastructures of two-dimensional (2D) materials while controlling the orientation of the 2D building blocks is important in achieving large specific surface areas and tuning the anisotropic properties of the obtained functional hierarchical structures.In this contribution,we report that arranging graphitic carbon nitride (g-C3N4) nanosheets into one-dimensional (1D) architectures with controlled orientation has been achieved by using 1D oriented melem hydrate fibers as the synthetic precursor via a polycondensation process,during which the removal of water molecules and release of ammonia gas led to the creation of pores without destroying the 1D morphology of the oriented structures.The resulting porous g-C3N4 fibers with both meso-and micro-sized pores and largely exposed edges exhibited good sensing sensitivity and selectivity towards NO2.The sensing performance was further improved by hybridization of the porous fibers with Au nanoparticles (Au NPs),leading to a detection limit of 60 ppb under ambient conditions.Our results suggest that the highly porous g-C3N4 fibers and the related hybrid structures with largely exposed graphitic layer edges are excellent sensing platforms and may also show promise in other electronic and electrochemical applications.     

In situ trace analysis of oil in water with mid-infrared fiberoptic chemical sensors

The determination of trace amounts of oil in water facilitates the forensic analysis on the presence and origin of oil in the aqueous environment. To this end, the present study focuses on direct sensing schemes for quantifying trace amounts of oil in water using mid-infrared (MIR) evanescent field absorption spectroscopy via fiberoptic chemical sensors. MIR transparent silver halide fibers were utilized as optical transducer for interrogating oil-in-water emulsions via the evanescent field emanating from the waveguide surface, and penetrating the surrounding aqueous environment by a couple of micrometers. Unmodified fibers and fibers surface-modified with grafted epoxidized polybutadiene layers enabled the direct detection of crude oil in a deionized water matrix at the ppm level to ppb concentration level, respectively. Thus, direct chemical sensing of crude oil IR signatures without any sample preparation as low as 46 ppb was achieved with a response time of a few seconds.     

Performance analysis of a fiber Bragg grating filter-based strain/temperature sensing system based on a modified Gaussian function approximation method

This paper analyzes the performance of a fiber Bragg grating (FBG) filter-based strain and/or temperature sensing system based on a modified Gaussian function (MGF) approximation method. Instead of using a conventional Gaussian function, we propose the MGF, which can capture the characteristics of the sidelobes of the reflected spectrum, to model the FBG sensor and filter. We experimentally demonstrate that, by considering the contributions of the sidelobes with the MGF approximation method, behaviors of the FBG filter-based FBG displacement and/or temperature sensing system can be predicted more accurately. The predicted behaviors include the saturation, the sensitivity, the sensing range, and the optimal initial Bragg wavelengths of the FBG sensing system.     

Structural changes of polyacrylonitrile precursor fiber induced by γ-ray irradiation

The structural changes of polyacrylonitrile precursor fibers under γ-ray irradiation were studied. The Fourier transform infrared spectroscopy (FTIR) results indicated that chemical reactions occurred in the irradiated fibers. The thermal and thermal mechanical behaviors of the fibers, which were characterized by differential scanning calorimetry (DSC), thermal gravimetry (TG) and thermal mechanical analysis (TMA), changed under irradiation, since ladder structure had formed in the fibers under irradiation prior to the heating process. The crystallinity and crystallite size were found to decrease with the increase of irradiation time, as the chemical reactions induced by γ-ray irradiation affected the crystal structure of the fibers. γ-ray irradiation may be useful in accelerating the thermal stabilization of PAN precursor fibers.     

Preparation and humidity sensing properties of Ba0.8Sr0.2TiO3 nanofibers via electrospinning

Ba_0.8Sr_0.2TiO₃/Poly (vinylpyrrolidone) (BST/PVP) composite fibers were successfully synthesized via electrospinning. The ceramic nanofibers were obtained after calcining the composite at 800 °C for 2 h. The morphology and structure of the BST fibers were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results reveal that the as-synthesized BST nanofibers show a diameter of 50-150 nm with the length over 0.1 mm, and a well-defined perovskite crystal structure. The electrical properties of the as-synthesized BST nanofibers were investigated through an impedance-type humidity sensor. The nanofibers exhibited excellent humidity sensing properties at room temperature. The possible sensing mechanism was proposed.     

Temperature and voltage sensings by mode‐mode interference in polarization‐maintaining optical fibers

Abstract

Two optic fiber sensing systems for temperature and voltage have been developed which utilize the mode‐mode interference of the two orthogonally polarized modes, HE^x _II and HE^y _II, in two commencal polarization‐maintaining fibers (bow‐tie and elliptical core fibers). A package of controlled programs in a Macintosh computer, which can record and process all related data automatically, is established for temperature sensing. The signal drifting problem in voltage sensings has been investigated, and the elimination of signal drifting is obtained by the phase tracking with direct current technology The agreement between the sensing results for temperature and dynamic voltage and those predicted by experimental principles is satisfactory, which confirms the validity of the developed sensing systems.