纤度和预氧化处理对酚醛纤维性能的影响

将热塑性酚醛树脂通过熔融纺丝的方法制备了不同纤度的酚醛纤维原丝,并经后固化处理得到了交联的酚醛纤维,考察了酚醛纤维纤度与纤维拉伸强度和溶失率之间的关系,以及预氧化处理对酚醛纤维残碳率和耐热性的影响。研究结果表明,在一定范围内,经同样固化工艺处理的酚醛纤维的拉伸强度随纤度的减小而明显增大,而溶失率随纤度的减小而减小;经过预氧化处理过的酚醛纤维结构上引入更多交联点,当纤维在220℃处理30 min后,其强度和残碳率均达到最大值,并且纤维的耐热性能得到显著提高。     

含孔CFRP正交层合板的双轴拉伸力学行为

采用加载臂开槽的中心开孔等厚度十字形试样,实验研究了正交对称铺层碳纤维增强聚合物基复合材料（CFRP）层合板在双轴拉伸载荷作用下的力学行为,分析了3种双轴加载比对其拉伸强度和破坏行为的影响。研究表明:纤维被切断的铺层部分在拉伸作用下容易与其相邻铺层脱粘,导致层合板承载力下降;等双轴加载时,在孔边的被切断纤维与连续纤维间基体在横向拉伸和纵向剪切组合作用下首先开裂;非等双轴加载时,在垂直于快速拉伸方向的铺层中沿孔边应力集中处先出现基体裂纹;随着加载比的增大,快速拉伸方向的细观结构损伤随载荷的增大发展更快,刚度下降更快,破坏时主裂纹的扩展方向更趋于垂直于快速拉伸方向;强度包络线的分析表明快速拉伸方向的拉伸强度随加载比的增大呈缓慢增大的趋势。      

拉伸热定型对PPS纤维结构与性能的影响

以国产聚苯硫醚(PPS)为原料,采用熔融法纺丝制备PPS纤维,测定了拉伸倍数、拉伸温度和热定型温度对纤维结构与性能的影响。结果表明,PPS纤维的断裂强度和整体取向随拉伸倍数的变化趋势一致,收缩率随拉伸倍数的增大而增大;随着拉伸温度的升高,纤维收缩率减小,而断裂强度和取向呈先增大后减小的趋势;随热定型温度升高,纤维断裂强度增大,收缩率减小。     

聚乙烯中空纤维膜制备及微孔结构的控制

通过熔纺-拉伸(MS)法制备了聚乙烯(PE)中空纤维微孔膜,并研究了纺丝牵伸比、拉伸速率及拉比率等对膜结构和性能的影响.研究结果表明PE中空纤维的结晶度和弹性回复率(ER,%)随纺丝牵伸比的增加而增大,且随着纺丝牵伸比的增大,PE中空纤维膜的微孔结构也增大;拉伸工艺对膜的结构和性能也有很大的影响,随着拉伸速率和拉伸比率的增加,PE中空纤维膜的透气率和孔隙率均增加.     

凝固条件对PBO初生纤维孔结构及拉伸强度的影响

研究了凝固浴条件对PBO初生纤维孔结构及拉伸强度的影响。结果表明：在考察范围内,随凝固浴温度的降低、凝固浴浓度的增大,初生纤维的孔体积总量减小,孔径分布范围变窄,优势孔的孔径分布峰数量减少,初生纤维的强度增大。随着凝固牵伸倍率（2～10）的增加,孔体积减小、优势孔的孔径分布峰数量减少;但当牵伸倍率大于10倍时,总孔体积和优势孔的孔径分布峰数量开始增加;初生纤维的强度则随牵伸倍率的增大而增长。     

辐射接枝改性对UHMWPE纤维性能的影响

采用预辐射接枝聚合方法制备了丙烯酸甲酯(MA)接枝改性的超高分子量聚乙烯(UHMWPE-g-PMA)纤维。研究了接枝率对UHMWPE纤维结构和力学性能的影响。红外光谱(FT-IR)和扫描电镜(SEM)测试显示,UHMWPE纤维上接枝了PMA分子链。UHMWPE-g-PMA纤维结晶度随接枝率增大而降低;PMA接枝链对UHMWPE纤维的正交晶相无影响,但对单斜晶相和中间相影响明显。UHMWPE-g-PMA纤维的拉伸断裂强度随吸收剂量增大而减小,但不随接枝率变化;拉伸断裂伸长率随吸收剂量增大而减小,随接枝率升高而增大。接枝前后UHMWPE纤维的水接触角测试结果显示,随着接枝率的增加,UHMWPE-g-PMA纤维与水的接触角减小。     

十八烷基胺处理在热力设备停用保护中的应用研究

对不同浓度十八烷基胺（ＯＤＡ）处理铁电极的交流阻抗研究显示，电极阻抗值先随ＯＤＡ浓度的增加而增大，在ＯＤＡ为２５ｍｇ／Ｌ时阻抗值最大，之后，随ＯＤＡ浓度增加而减小；用俄歇电子能谱对成膜电极进行表面分析，发现ＯＤＡ处理后膜表面具有如下结构：铁│氧化铁层│含氧化铁的ＯＤＡＷ层│ＯＤＡ层；ＯＤＡ层在乙醇中溶解后电极阻抗值减小。     

FeCoSiB/Cu/FeCoSiB多层膜的应力阻抗效应研究

采用直流磁控溅射法在柔性Kapton基片上制备了三明治结构的FeCoSiB/Cu/FeCoSiB多层膜,研究了多层膜的交流阻抗随外加应力变化的规律.测试结果表明,三明治结构多层膜的阻抗随外加应力的增大而增大,应力阻抗效应随中间导电层厚度以及铁磁层厚度的增加而增强,同时应力阻抗效应也与测试频率密切相关.     

超拉伸UHMWPE纤维的超分子结构变化

用WAXD、DSC、SAXS及拉曼光谱等测试手段,研究了拉伸过程中UHMWPE纤维的超分子结构变化。结果表明,随拉伸的进行,纤维非晶区中分子链逐渐参与了结晶,超分子结构逐渐变得紧密规整,其SAXS强度逐渐减弱;纤维结晶度及熔融峰温随拉伸倍数的增加而增大,并逐渐趋于平衡,高倍拉伸后纤维WAXD结晶度为67．5％,DSC结晶度为96．1％,熔点为155．4℃;纤维横向晶粒平均尺寸随拉伸倍数的增加而变小,并逐渐趋于平衡,而纤维轴向晶粒尺寸随拉伸倍数的增加而变大,高倍拉伸后纤维结晶长周期为50nm左右。     

氯盐环境下纤维编织网增强混凝土拉伸性能

通过拉伸试验研究了氯盐干湿、氯盐冻融循环和常规环境下纤维编织网层数、种类以及氯盐浓度和循环次数等因素对纤维编织网增强混凝土（纤维/混凝土）拉伸性能的影响。结果表明：三种环境下,增加纤维编织网层数均可提高纤维/混凝土的拉伸性能,且碳纤维编织网较玄武岩纤维编织网的增强作用更明显;氯盐浓度、干湿或冻融循环次数对纤维/混凝土拉伸极限荷载影响不明显;常规环境和氯盐干湿循环下,掺入短切聚乙烯醇（PVA）纤维和耐碱玻璃（AR-glass）纤维均可以提高纤维/混凝土的拉伸极限荷载;氯盐冻融循环下,掺入短切PVA纤维的纤维/混凝土的拉伸极限荷载未有提高,而掺入短切AR-glass纤维的纤维/混凝土的拉伸极限荷载增大。     

基于自组织神经网络的军用车辆装备涂层腐蚀行为研究

为探究军用车辆有机涂层在全浸泡条件下的腐蚀行为特征,寻找评价涂层腐蚀防护性能的有效方法,通过对某型军绿有机涂层全浸泡条件下腐蚀行为电化学阻抗谱(EIS)特征的研究,提取并研究了低频阻抗模值Z0.1Hz、高频相位角θ10 k Hz和高频阻抗模值变化率k这3种特征参数的变化规律,并结合自组织神经网络(SOM)对涂层防护性能变化进行了辅助分析。特征参数变化规律与SOM分析结果均证明涂层在1 330 d浸泡过程中出现4个阶段的性能变化,反映了SOM神经网络辅助分析有机涂层浸泡性能的有效性。     

两种连续SiC纤维的高温介电及吸波性能对比

采用XPS、XRD、Raman光谱等方法分析了两种典型SiC纤维的微观结构, 研究了微观结构对纤维电导性能的影响, 并揭示了其高温介电性能和吸波性能的演变规律, 对高温结构吸波复合材料的研究具有重要意义。研究表明: KD-I SiC纤维表面富碳, 而SLF SiC纤维以Si-C-O结构为主, 前者具有较高的电导率和复介电常数, 从而导致KD-I纤维与空气阻抗匹配差, 而SLF纤维的损耗较小, 因此两者在X波段的室温反射率仅为-3.2 dB和-0.3 dB。KD-I纤维的复介电常数随着温度的升高显著增大, SLF纤维的实部增幅较大而虚部略小, 两者在700℃时的复介电常数分别达到20.9-j25.0和5.0-j0.37, 高温条件下由于阻抗匹配均变差, 吸波性能无明显改善。     

Thermoelectric power and AC electrical properties of PAN-based carbon fiber composites

The thermoelectric power and AC electrical properties of conductive polymer composites made of polycarbonate filled with randomly distributed PAN-based carbon fibers of different concentration: 0, 5, 10, 18, and 30 wt% were studied. The thermoelectric power was measured as a function of temperature in the frequency range from 200 kHz to 12 MHz. It was found that the observed Seebeck coefficient and thermoelectric activation energy depend on temperature, frequency and fiber concentration. The Seebeck coefficient calculated using the electrical transport theory of semiconductors decreases with both increasing temperature and carbon fiber content. The thermoelectric power results revealed that the composites function electrically as semiconductors. Dielectric constants and AC conductivity were calculated from impedance and phase angle measurements. It was found that both increase with increasing temperature. The activation energy and relaxation time decrease with increasing temperature measured and applied frequency. The thermoelectric power results indicated that electrical conduction in bulk composites is produced from a combination of transport processes involving: electrons, holes, ions and charged impurity motion in addition to protonic migration.     

以中间相沥青为粘结剂的低密度高导热炭纤维网络体的研究

以中间相沥青为粘结剂, 采用500 ℃低温炭化炭纤维, 经低压模压成型、炭化和石墨化后得到低密度高导热炭纤维网络体。与以1300 ℃炭化炭纤维为原料和以酚醛为粘结剂制备的炭纤维网络体进行了比较。对粘结剂炭收率(热重分析)、样品微观形貌(扫描电子显微分析)、石墨化度及微晶尺寸(X射线衍射分析)等进行了表征。研究结果表明: 由于高炭收率和高片层取向度的中间相沥青与500 ℃低温炭化处理炭纤维共同经历后续热处理时呈现出相近的热收缩率, 因而具备良好的相互粘结性和石墨片层铆接效应, 其制备的炭纤维网络体经石墨化后密度为0.317 g?cm ^-3, 由此制备的相变复合材料的面内热导率为19.30 W·m ^-1·K ^-1, 较纯相变材料(石蜡)提升了80倍, 明显高于以1300 ℃炭化炭纤维为原料, 以中间相沥青和酚醛分别为粘结剂制备样品的面内热导率(17.03和14.47 W·m ^-1·K ^-1)。     

Near-ohmic behavior for conducting polymers: extension beyond PEDOT on gold-plated platinum to other polymer-counterion/substrate combinations

Conducting polymers constitute a class of materials for which electrochemical and electron transport properties are a function not only of their chemical identity but also of their complex morphology. In this paper, we investigate and compare the frequency dependence behavior of the impedance of poly(3,4-ethylenedioxythiophene), or PEDOT, and that of poly(3,4-ethylenedioxypyrrole), or PEDOP, which are doped with a series of polyatomic anions during electrodeposition. We also contrast the behavior of PEDOT on Pt|Au, Pt, glassy carbon, and gold. Initial results for polycarbazole, PCz, electrodes are, in addition, included. Deposition parameters were adjusted to produce morphologically similar films for PEDOT, PEDOP, and PCz. In doing so, we have been successful in producing frequency-independent impedance behavior similar to that previously reported for PEDOT on Pt|Au. Although the impedance behavior of these polymers appears to be primarily determined by morphological features, the impact of counterion identity (beyond ionic charge transport) is also discussed. These studies suggest that choice of polymer/dopant combination and electrodeposition parameters can be manipulated to tune the impedance characteristics of electrodes, thereby optimizing them for capacitive or faradaic charge injection, or some combination of the two.     

Morphologies of carbon micro-coils grown by chemical vapor deposition

The carbon micro-coils were obtained by the Ni-catalyzed pyrolysis of acetylene. The carbon micro-coils with various coiling morphology: regular double coils, coils built up by circular or flat fibers, super helix coils, single coils, etc. can be observed. The carbon coils with various coil diameters and coil pitches were obtained by controlling reaction conditions, such as reaction temperature, source gas flow rate of sulfur-impurity, acetylene or hydrogen.     

螺旋形手征碳纤维的微波介电特性

研究了线圈状和麻花状两种典型螺旋形手征碳纤维以及直线形碳纳米管在8.2-12.4GHz的微波介电特性.螺旋形手征碳纤维通过催化化学气相沉积法制备,直线形碳纳米管用催化裂解浮游法以苯为碳源制备.螺旋形手征碳纤维与石蜡复合体的介电常数的实部(ε′)和虚部(ε″)比直线形碳纳米管与石蜡复合体的小,但线圈状螺旋形碳纤维的介电损耗角正切(tgδ=ε″/ε′)却明显偏大,线圈状和麻花状螺旋形碳纤维的tgδ分别为0.77—0.80和0.47—0.53,直线形碳纳米管的tgδ为0.45-0.77.螺旋形碳纤维与微波作用时的手征特性是导致其tgδ增大的主要原因,螺旋形手征碳纤维对微波的吸收与其自身的形状和尺寸密切相关,所以线圈状螺旋形碳纤维的tgδ比麻花状的大得多,探讨了螺旋形手征碳纤维与微波的作用机理,螺旋形手征碳纤维是一种非常有发展前景的微波吸收材料.     

Calculation of self- and mutual impedances in planar sandwichinductors

High-frequency planar magnetic components, employing thin film and thick film technology, have become important components in applications, such as filters and switching converters, due to their ease of manufacture and reliability. In a previous paper, the authors established a frequency dependent impedance formula for planar coils on a magnetic substrate that is infinitely thick. In this paper, two new impedance models are described: the first is for planar coils on a magnetic substrate of finite thickness, and the second represents a planar coil sandwiched between two substrates. The models include the electrical conductivity of the magnetic material so that the effects of eddy currents, particularly at high frequencies, are taken into account. The eddy currents reduce the inductance and increase the losses associated with the device. The new impedance formulas are derived from Maxwell's equations. Simulations were carried out on a typical device, using finite element analysis, and the results validate the new formulas. This paper establishes the frequency limitations of lossy magnetic substrates     

沉积条件对CVD碳纤维生长的影响

用CH4、H2或包含NH3的混合气体为反应气体,利用负偏压增强热丝化学气相沉积方法在沉积有过渡层(Ta或Ti)和催化剂层(NiFe)的Si衬底上制备碳纤维,并用扫描电子显微镜研究了它们的生长和结构,结果发现不同的沉积条件对碳纤维的生长和结构有很大的影响。在无辉光放电的条件下,衬底温度较低时碳纳米管或纤维生长困难;提高衬底温度,能够弯曲生长;在辉光放电的条件下,则呈现定向生长的特点。     

磁共振成像交替阻抗微带线射频线圈仿真分析

为研究改变交替阻抗微带线射频线圈的几何尺寸对感兴趣区内磁场分布的影响,保持微带线射频线圈总长度不变,改变宽带与窄带的长度比例和宽度比例,在HFSS中建立交替阻抗微带线射频线圈的仿真模型,与传统微带线射频线圈进行比较,利用ADS与HFSS的协同仿真实现线圈的调谐和匹配.仿真结果表明交替阻抗微带线射频线圈感兴趣区内的磁场均值比传统微带线射频线圈的提高了一倍以上.调整交替阻抗微带线射频线圈的宽带与窄带的长度比例和宽度比例,可以提高感兴趣区内的磁场强度,同时改善磁场分布的均匀性.