单壁碳纳米管受限空间内水的分布

碳纳米管管腔作为分子物质的纳米通道,其储存或输送水的能力具有重要研究价值.为了研究碳纳米管管腔受限空间对水分子团簇结构和分布的影响,本文采用分子动力学方法探究了管径、手性和温度对单壁碳纳米管管腔内水的结构和分布的影响.结果表明:在常温下,管径尺寸范围为1.018—1.253 nm的单壁碳纳米管管内易形成有序的多元环水结构,此范围以外碳纳米管管内难以形成水的有序结构;且随着管径尺寸增大,多元环水呈现由三元环至六元环的结构变化;范德瓦耳斯势分布分析表明,在上述管径范围内,水分子趋向于贴近碳纳米管管壁分布而形成水的有序结构.对比管径尺寸差别较小的碳纳米管,其手性对多元环水结构影响不大.多元环水结构的稳定性表现出温度依赖性,管径较大的碳纳米管内的多元环水的有序结构更易随温度升高而消失.     

含超导的多层屏蔽体磁屏蔽特性的仿真研究

基于电磁辐射的严重危害性,探索有效的电磁屏蔽方案,已经成为当前国际上迫切需要解决的问题.本文根据高磁导率铁材料和高温超导材料的电磁屏蔽特性,利用Ansoft Maxwell 3D仿真软件,建立高磁导率材料铁空心圆柱体和高温超导材料YBCO空心圆柱体及其组合的屏蔽模型,对一个空心线圈产生的磁场进行被动磁屏蔽.仿真研究了铁屏蔽体和超导屏蔽体厚度和高度对低频磁场磁屏蔽效能的影响.仿真结果表明,YBCO/Fe组合结构的屏蔽体对低频交变磁场的磁屏蔽效能比单层YBCO屏蔽体的屏蔽效能高3倍,YBCO/Fe组合结构的屏蔽体对低频交变磁场的磁屏蔽效能比单层铁屏蔽体的屏蔽效能高1.5倍,最理想磁屏蔽体结构是YBCO/Fe二层组合结构,其具有最高的磁屏蔽效能.综合利用高磁导率材料和高温超导材料等电磁屏蔽材料的特点,选择最优电磁屏蔽方案,进行电磁屏蔽新技术研究,以提高电磁屏蔽效能,对电磁兼容问题的解决具有重要的理论和应用意义.     

纳米储氢材料的研究进展

储氢材料的纳米化为新型储氢材料的研究提供了新的研究方向和思路,本文详细介绍了纳米储氢材料性能提高的机理,综述了纳米碳纳米管储氢材料、镁基纳米储氢材料以及复合纳米储氢材料的最新研究进展,并对储氢材料纳米化的广阔前景进行了展望。     

碳纳米管复合吸波涂层微波吸收性能的模拟计算

如何利用碳纳米管复合吸波涂层的参数进行吸波性能优化是电磁屏蔽研究的热点之一.涂层参数对吸波性能影响的研究主要停留在实验探索阶段,而碳纳米管的结构参数对吸波性能影响的研究鲜有报道.因此,从微观结构层次研究涂层参数对吸波性能的影响有重要意义.基于多壁碳纳米管的等效电路,利用碳纳米管结构参数与等效电路各元件参数的关系,研究了碳纳米管损耗微波的机理,建立了碳纳米管结构参数与微波反射率的关系式.根据此关系式,利用Matlab软件模拟计算了碳纳米管管长、管径、涂层中碳纳米管的含量以及涂层厚度对微波反射率的影响.模拟计算结果表明:涂层的微波反射率随碳纳米管含量变化的模拟曲线与实验结果符合;碳纳米管含量和厚度是影响吸收峰位置和吸收强度的重要参量,而碳纳米管直径和长度是主要影响吸收峰强度的参量.     

中等导电性材料覆盖的金属腔体的电磁屏蔽效能研究

基于传输线和波导理论, 提出了一种用于计算覆盖中等导电性材料的金属腔体电磁屏蔽效能的解析理论模型, 并通过和全波电磁模拟结果的比较检验了该模型的有效性. 计算分析了屏蔽体屏蔽效能的位置效应和谐振效应. 建议了一种评价导电材料电磁屏蔽效能的方法, 能很好的削弱谐振效应和位置效应的影响, 直接反映出材料本身的电磁屏蔽效能. 关键词： 电磁屏蔽 导电材料 金属腔体 屏蔽效能     

碳纳米流体强化传热研究

在去离子水中分别添加了单壁、多壁碳纳米管材料,通过配比一定质量的亲水性分散剂,经超声波振荡试制了水基碳纳米流体。测试分析了不同碳纳米管材料质量分数下的纳米流体热导率和动力粘度等重要热物性参数。测试结果表明:碳纳米管粒子能够强化基液工质导热性能,随着其质量分数的增加,水基单壁、多壁碳纳米流体热导率均明显提高;单壁碳纳米流体粘度显著增加,多壁碳纳米流体粘度无明显变化,多壁碳管更适用于纳米流体强化传热。     

纳米碳/氢氧化锂复合材料的低温化学蓄热性能研究

本文将氧化石墨烯(GO)、羧基化多壁碳纳米管(c-MWCNTs)等纳米碳材料通过水热的方法与氢氧化锂进行反应,得到碳基氢氧化锂化学蓄热复合材料。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射分析仪(XRD)以及热重/同步差热分析仪(TGA-DSC)等表征手段获取了复合材料的表观形貌、负载组分、蓄热密度等关键热物性参数。研究表明纳米碳材料的复合使LiOH的单体水合速率大幅度提升,与此同时蓄热密度有着不同程度地增大,其中以GO/LiOH复合材料的化学蓄放热性能最为突出。除此之外,材料整体的导热系数也由于GO的复合有着显著的提高。本研究拓展了碳材料在储能领域的应用范围,针对纳米碳化学蓄热复合材料提供了理性的设计方法。     

碳纳米流体强化传热研究

在去离子水中分别添加了单壁、多壁碳纳米管材料,通过配比一定质量的亲水性分散剂,经超声波振荡试制了水基碳纳米流体。测试分析了不同碳纳米管材料质量分数下的纳米流体热导率和动力粘度等重要热物性参数。测试结果表明:碳纳米管粒子能够强化基液工质导热性能,随着其质量分数的增加,水基单壁、多壁碳纳米流体热导率均明显提高;单壁碳纳米流体粘度显著增加,多壁碳纳米流体粘度无明显变化,多壁碳管更适用于纳米流体强化传热。     

高压退火对碳纳米管微结构转变的影响

利用高分辨电子显微镜研究了在高压退火条件下碳纳米管的微结构变化规律，发现在5.5GPa下，770℃退火后即发生了明显的结构改变；在950℃退火25min后发现形成了类碳纳米洋葱和纳米碳条带结构.碳纳米管转变成类碳纳米洋葱可以分成几个步骤，首先碳纳米管破裂，然后形成碳纳米球，最后形成类碳纳米洋葱结构.讨论了高压和退火温度对碳纳米管结构变化的影响. 关键词：     

基于超级碳点的水致荧光“纳米炸弹”

介绍了一种发光性质依赖于水接触的新型纳米发光材料--基于超级碳点的发光"纳米炸弹"。在甲苯溶液中, 这种"纳米炸弹"光致发光很弱;当遇见水后, "纳米炸弹"分解为小的碳点, 光致发光显著增强。将"纳米炸弹"与纸复合可应用在喷水荧光打印和汗孔成像。目前, 大部分智能荧光材料存在光稳定性差, 潜在的生物毒性, 制备成本高, 或与传统喷墨打印不兼容等缺点。本文报道的碳基纳米材料没有(或很少有)这些缺点, 并可实际应用在光信息存储, 司法鉴定和医疗检测等领域。     

基于蒙特卡罗方法的中子屏蔽材料设计

基于蒙特卡罗粒子输运程序MCNP,设计了一种强度高、密度低、具有优异中子屏蔽性能的新型玻璃纤维/B4C/环氧树脂复合材料,模拟计算了镅-铍（Am-Be）中子源产生中子对该材料的透射率;研究了该材料的中子屏蔽性能与传统屏蔽材料的差异以及不同B4C质量分数对该材料的屏蔽性能影响;根据模拟结果分析了该材料对不同能区中子（慢中子、中能中子、快中子）具有的不同屏蔽性能。研究发现：B4C质量分数为10%的该种新型玻璃纤维/B4C/环氧树脂复合材料的中子屏蔽性能,尤其是慢中子屏蔽性能较传统的含硼聚乙烯和Al-B4C合金材料更为优异;但随着B4C质量分数的增大,屏蔽性能提升不明显。结果验证了蒙特卡罗方法用于中子屏蔽材料优化设计的可行性。     

Effect of processing on rheological properties and structure development of EPOXY/MWCNT nanocomposites

Polymer nanocomposites of epoxy resin containing multiwall carbon nanotubes (external diameter ~30 ± 10 nm, approximate length 10–20 μm) are studied using a rheological approach to determine the stage of debundling of the nanofiller in the epoxy matrix and the development of the rheological properties and structure with time. The role of processing for nanotube dispersion and structure formation is also determined by polarized microscopy and Raman spectrometry. Functionalization with amine groups is applied for part of the samples (mixing the nanotubes in amine hardener followed by mixing in appropriate amounts of epoxy resin). Further on the experimental procedure has been optimized and samples within the concentration range from 0 to 1.0 wt% have been prepared by applying high speed mechanical mixing and ultrasonic treatment with power of 250 W. The results show that chemical functionalization with amine groups contributes to significant changes in the rheological properties and hence in the structure of the composites, as proved by Raman and POM results, indicating better deaggregation of the carbon nanotubes in the amine hardener and chemical bonding of the amine groups attached to the functionalized nanotube surface with the epoxy matrix. The evolution of the dynamic viscosity in the process of polymerization reveals some interesting aspects as retarded curing in the viscometer cell, compared to the control sample under the same conditions, prolonged polymerization time owing to the applied shear rates and carbon nanotube content.     

Conduction noise absorption by fiber-reinforced epoxy composites with carbon nanotubes

Nearly all electronic equipment is susceptible to malfunction as a result of electromagnetic interference. In this study, glass fiber, and carbon fiber as a type reinforcement and epoxy as a matrix material were used to fabricate composite materials. In an attempt to increase the conduction noise absorption, carbon nanotubes were grown on the surface of glass fibers and carbon fibers. A microstrip line with characteristic impedance of 50 Ω in connection with network analyzer was used to measure the conduction noise absorption. In comparing a glass fiber/epoxy composite with a GF-CNT/Ep composite, it was demonstrated that the CNTs significantly influence the noise absorption property mainly due to increase in electric conductivity. In the carbon fiber composites, however, the effectiveness of CNTs on the degree of electric conductivity is negligible, resulting in a small change in reflection and transmission of an electromagnetic wave.     

Preparation of vertically aligned carbon nanotube arrays grown onto carbon fiber fabric and evaluating its wettability on effect of composite

Vertically aligned carbon nanotube (CNT) arrays have been grown onto the carbon fiber fabric using a catalytic chemical vapor deposition (CCVD) method. The as-synthesized CNT arrays are about 20 μm in height, and the nanotube has a mean inner and outer diameter of 2.6 nm, 5.5 nm, respectively. The CNT-grafted carbon fabric shows a hydrophobic property with a contact angle over 145°, and the single CNT-grafted carbon fiber shows a sharp increase of dynamic contact angle in de-ionized water from original 71.70° to about 103°, but a little increase does in diiodomethane or E-51 epoxy resin. However, the total surface energy of carbon nanotube-grafted carbon fiber is almost as same as that of as-received carbon fiber. After CNTs growth, single fiber tensile tests indicated a slight tensile strength degradation within 10% for all different lengths of fibers, while the fiber modulus has not been significantly damaged. Compared with the as-received carbon fibers, a nearly 110% increase of interfacial shear strength (IFSS) from 65 to 135 MPa has been identified by single fiber pull-out tests for the micro-droplet composite, which is reinforced by as-received carbon fiber or CNT-grafted carbon fiber.     

碳纳米管/四针状纳米氧化锌复合涂层的电磁波吸收特性

以碳纳米管(CNT)和四针状纳米氧化锌(NT-ZnO)混合物作为吸收剂、环氧树脂(EP)为黏结剂制备吸波涂层,研究不同CNT和NT-ZnO含量对吸波性能的影响.采用三次刷涂后,发现当CNT含量达到12%,NT-ZnO的含量为8%、涂层厚度为1·5mm时,吸波涂层的最小反射率为-23·07dB,小于-10dB的吸波带宽为5GHz,涂层的面密度2kg/m2·复合涂层的吸波性能比纯CNT和纯NT-ZnO涂层有显著的提高,并对其吸波机理进行了分析.     

Electromagnetic shielding of multiwalled,bamboo-like carbon nanotube/methyl vinyl silicone composite prepared by liquid blending

Multiwalled, bamboo-like carbon nanotube (BCNT)/methyl vinyl silicone (MVQ) composites with different concentrations of BCNT were fabricated by liquid blending method with an aim to investigate the behavior of such composites as effective electromagnetic interference shielding material in the frequency range of 1–6?GHz. The morphology and structure of BCNT were characterized and elucidated. Scanning electron microscopy examination showed that the BCNTs homogeneously dispersed in MVQ. The electrical conductivity (σ) and shielding effectiveness (SE) of the composite were measured and discussed. The results showed that the BCNTs/MVQ composites had a relatively low percolation threshold at 0.92?wt. % BCNT, and the σ showed a decreasing linear relation with temperature, i.e., the σ slightly decreased with increasing temperature. The BCNTs/MVQ composites with SE of 33–38?dB were obtained at 7?wt. % BCNT loading. Shielding mechanism was studied by resolving the total incident energy into absorbed, reflected, and transmitted contribution, and the result showed that the dominated shielding mechanism was reflection loss.     

单壁碳纳米管膜及其三聚氰胺甲醛树脂复合材料的光电特性

单壁碳纳米管能够强烈吸收光线,尤其是在近红外区域,并能将光能转换成热能.同时,单壁碳纳米管还具有相当大的将热能转换成电能的能力.通过真空过滤方法,将由化学气相沉积生成的单壁碳纳米管阵列制备成单壁碳纳米管膜.根据研究的需要设计了一个简单的单壁碳纳米管膜光伏性质测试实验装置,并在其两端成功地实现了由红外光转换为电压输出.通过功能化步骤,制备了单壁碳纳米管/三聚氰胺甲醛树脂复合材料膜,实验结果表明该复合材料能产生符号相反的输出电压.这预示着单壁碳纳米管及其三聚氰胺甲醛树脂复合材料在光电领域具有良好的应用前景.     

Study on the Structure and Properties of UHMWPE/Epoxy Resin Composite Fiber

The preparation, crystallization behavior, and fiber structure and properties of ultrahigh molecular weight polyethylene (UHMWPE) epoxy resin composite fiber were studied by means of differential scanning calorimeter (DSC), X‐ray diffraction (XRD), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and tensile testing. The morphology showed a different behavior from pure polyethylene (PE) fiber. The fiber mechanical properties, creep behavior, and thermal properties of UHMWPE fiber can be improved by adding epoxy resin. It's believed that the epoxy can serve as a physical cross‐linking agent to limit the motion or migration of PE molecules and consequently improve the fiber creep property. However, when the content of epoxy resin is higher than 5 wt%, all of the behavior and properties deteriorate.     

四针状纳米氧化锌电磁波吸收特性

将四针状纳米ZnO作为吸收剂、环氧树脂为粘结剂制备成吸波涂层,分析了吸波涂层中的四针状纳米氧化锌含量及涂层厚度对吸波性能的影响,当涂层厚度为15mm时,吸收主要集中在15—18GHz波段;当涂层厚度增加到35mm后,样品的吸波性能提高明显,特别在6—11GHz之间的吸波性能提高显著,样品反射率小于-5dB的频率宽度达到136GHz(44—18GHz),其吸波性能相比较微米级ZnO有显著提高. 最后对四针状纳米氧化锌的吸波机理进行了讨论. 所研究的涂层在电磁波屏蔽方面具有较大的应用价值. 关键词： 四针状纳米ZnO 吸波性能 反射率 吸波机理