碳纳米管取向对HA/CNTs复合材料力学性能的影响

以碳纳米管为增韧材料,用原位合成法制备了羟基磷灰石/碳纳米管复合粉体,通过氮气保护热压烧结制备了羟基磷灰石/碳纳米管复合材料,并对其进行了XRD、FT-IR、SEM、致密度、抗弯强度及断裂韧性测试,同时探索了碳纳米管取向对材料力学性能的影响.结果表明,复合材料中碳纳米管择优分布在热压面内;碳纳米管取向对材料的力学性能有较大影响,随θ(材料表面与热压方向的夹角)的增大,材料的力学性能提高,垂直于热压面的方向最差,平行于热压面的方向最好.     

基于碳纳米管模板的氮化镓纳米线束合成

通过金属有机物化学气相沉积方法在碳纳米管模板上生长氮化镓纳米线束.对所生长的纳米结构进行了扫描电镜和X射线能谱分析,结果显示氮化镓纳米晶体可以与碳纳米管形成纳米线束状复合物.纳米线束状复合物直径为100～200 nm,长度为1.5～2.5μm,纳米线的两端呈现尖角状.由于氨气很容易吸附在碳纳米管表面,可知所获得的纳米结构的初始生长机制为碳纳米管的表面氮化.该研究也证明金属有机物化学气相沉积将是用于制造化合物纳米结构材料的一项有效的技术.     

碳纤维表面原位生长碳纳米管的研究

采用化学气相沉积工艺在碳纤维的表面分别制备了形貌为卷曲状和直立状的原位生长碳纳米管,利用扫描电镜和透射电镜分析了碳纤维表面原位生长碳纳米管的形貌、管径和管壁状态,借助拉曼光谱分析了原位生长碳纳米管的微观结构。结果表明,卷曲状和直立状原位生长碳纳米管都完整地包裹了碳纤维的表面。卷曲状原位生长碳纳米管主要生长在碳纤维的轴向上,呈现卷曲状形貌,其长度分布在5~20μm,管径分布在10~150nm。卷曲状碳纳米管之间互相交联,形成三维网络结构。直立状碳纳米管主要生长在碳纤维的径向上,呈现放射状形貌,其长度分布在10~30μm,直径分布在10~200nm。直立状碳纳米管在纤维表面分布均匀,碳纳米管之间形成了大量的孔隙,碳纳米管在碳纤维的表面呈现出疏松的网络结构。拉曼光谱分析发现两种碳纳米管均在1350cm-1和1580cm-1附近出现了显著的碳峰位。此外,卷曲状和直立状碳纳米管的D峰和G峰的强度比例分别为0.352和0.351,两种碳纳米管均具有较高的石墨化程度。     

MWCNT/TiO2复合材料光催化活性研究

以多壁碳纳米管(MWCNT)为基核,以钛酸丁酯为前驱体,分别用溶胶-凝胶法和水热法制备碳纳米管/二氧化钛纳米复合光催化材料.用X射线衍射仪(XRD)、透射电子显微镜(TEM)对样品进行了表征,研究了溶胶-凝胶法和水热法工艺的控制对碳纳米管/二氧化钛复合光催化剂显微组织及性能的影响.以甲基橙为目标降解物,考察了样品的自然光催化活性.结果表明,所得复合粉体中仅有碳纳米管和锐钛型二氧化钛两种物相,其中采用水热法所得样品,其纳米级的球形二氧化钛颗粒可均匀吸附在碳纳米管表面.     

填料对聚丙烯导热复合材料导电和流变性能的影响

分别制备了炭黑、碳纳米管、炭黑/碳纳米管简单共混以及炭黑碳纳米管化学键合聚丙烯复合材料,研究了不同体系的导热、导电和流变性能。研究发现,使用炭黑/碳纳米管简单共混或化学键合掺杂的复合材料热导率分别达到0.60W/mk和0.63 W/mk,而使用炭黑或碳纳米管杂化的组分热导率仅仅为0.36 W/mk和0.45 W/mk。掺杂碳纳米管或炭黑/碳纳米管简单共混填料的复合材料体积电阻下降了6个数量级,而掺杂炭黑或炭黑/碳纳米管化学键合填料的复合材料均有较好的绝缘性。掺杂杂化组分后,复合材料均出现了剪切变稀现象,在储能模量与频率曲线上低频区出现"第二平台",但掺杂炭黑/碳纳米管化学键合样品的第二平台极微弱。微观结构发现填料在基体中分散良好,填料间形成了很好的架桥。研究结果表明,简单使用炭黑、碳纳米管掺杂对复合材料的热导率改善不佳,使用炭黑/碳纳米管简单混合虽能大幅提高热导率,但影响复合材料的绝缘性能,而将炭黑/碳纳米管化学键合后可满足制备导热绝缘复合材料的要求。     

宏观超长定向碳纳米管阵列的制备

采用二甲苯和二茂铁作为碳源和催化剂的化学气相沉积法连续制备定向碳纳米管阵列,在反应6h内获得长度为6mm的宏观定向碳纳米管阵列。当反应时间超过6h后,定向碳纳米管阵列的生长速度明显下降,并有停止生长的趋势,反应16h,定向碳纳米管阵列的厚度仅为6．7mm。本文研究了采用多次连续进给碳源和催化剂的方式制备定向碳纳米管阵列,成功的制备了8．9mm厚的定向碳纳米管阵列,阵列中的碳纳米管具有高的定向性和良好的界面结合。     

镀银碳纳米管的抗菌性研究

用离子束辅助沉积(IBAD)方法在碳纳米管表面制备银膜.用琼脂平板法测试了抗菌率,测试菌种为革兰氏阴性大肠杆菌(E.coil)和革兰氏阳性金黄色葡萄球菌(S.aureus);用扫描电子显微镜(SEM) 观测了镀银碳纳米管的微观形貌;用能量散射X射线谱(EDX)分析了镀银碳纳米管表面元素的原子百分比;用X射线光电子能谱(XPS) 分析了镀银碳纳米管的表面元素的价态.研究结果表明,镀银碳纳米管具有优良的抗菌性能,且比在热解碳上镀银样品的抗菌性强.     

原位生长碳纳米管增强复合材料风机叶片性能预测

本文采用均匀化理论,结合有限元方法,预测了碳纤维表面原位生长碳纳米管增强复合材料风机叶片的等效性能。根据实验分析,将碳纳米管/碳纤维增强复合材料风机叶片内部结构分别用宏观、细观和纳观三个层次来描述。利用APDL编写的均匀化计算程序,分析了碳纳米管的长度、直径以及弹性模量对复合材料等效性能的影响。计算结果表明,随着碳纳米管长度的增加,复合材料的等效性能增加;当长度一定时,增加碳纳米管的直径和弹性模量,也能提高复合材料的性能。本文结果对复合材料风机叶片的制备有一定的指导作用。     

碳纳米管镀铜薄膜的抗菌性研究

本文用离子束辅助沉积（mAD）方法在碳纳米管薄膜表面制备铜薄膜。用琼脂平板法测试了抗菌率，测试菌种为革兰氏阴性大肠杆菌（E．coil）和革兰氏阳性金黄色葡萄球菌（S．aureus）；用扫描电子显微镜（SEM）观测了镀铜碳纳米管薄膜的微观形貌；用能量散射X射线谱（EDX）分析了镀铜碳纳米管薄膜表面元素的原子百分比；用X射线光电子能谱（XPS）分析了镀铜碳纳米管薄膜的表面元素的价态。研究结果表明，镀铜膜碳纳米管薄膜具有优良的抗菌性能，且比在热解碳上镀铜膜样品的抗菌性强。     

氨基改性碳纳米管的制备及对聚氨酯泡沫材料的影响

在碳纳米管表面引入大量氨基后,将其加入水为发泡剂的聚氨酯发泡体系,研究了碳纳米管对聚氨酯泡沫泡孔结构和力学性能的影响。实验结果表明,氨基表面改性碳纳米管的引入有助于提高聚氨酯泡沫孔壁结构的完整性,并且泡孔分布更加均匀。随着体系中碳纳米管含量的增加,泡沫孔径尺寸先减小后增大,当填充量为0.75%时,泡沫材料具有最小平均孔径(0.23mm)。扫描电子显微镜观察发现该条件下泡孔分布均匀,结构最为完整。同时,材料的力学性能也表现出相同的规律,当碳纳米管含量为0.75%时,材料具有最大压缩强度和压缩模量,分别为0.14 MPa和2.09 MPa,与纯聚氨酯的泡沫材料相比分别提高了100%和161%。     

螺旋状碳纳米管的热传导系数

分析了螺旋状碳纳米管沿其轴向的热传导特性,给出了螺旋碳纳米管轴向热传导系数ks的经验表达式。为验证ks公式的有效性,还将螺旋碳纳米管ks的理论解和相应的有限元结果进行了比较。结果发现,螺旋碳纳米管的ks理论解和有限元结果较为接近。本文螺旋碳纳米管的轴向热传导系数ks表达式对人们进一步研究螺旋碳纳米管的热学特性具有重要的参考意义。     

Measurement of the Intrinsic Thermal Conductivity of a Multiwalled Carbon Nanotube and Its Contact Thermal Resistance with the Substrate

The intrinsic thermal conductivity of an individual carbon nanotube and its contact thermal resistance with the heat source/sink can be extracted simultaneously through multiple measurements with different lengths of the tube between the heat source and the heat sink. Experimental results on a 66‐nm‐diameter multiwalled carbon nanotube show that above 100 K, contact thermal resistance can contribute up to 50% of the total measured thermal resistance; therefore, the intrinsic thermal conductivity of the nanotube can be significantly higher than the effective thermal conductivity derived from a single measurement without eliminating the contact thermal resistance. At 300 K, the contact thermal resistance between the tube and the substrate for a unit area is 2.2 × 10^?8 m² K W^?1, which is on the lower end among several published data. Results also indicate that for nanotubes of relatively high thermal conductance, electron‐beam‐induced gold deposition at the tube–substrate contacts may not reduce the contact thermal resistance to a negligible level. These results provide insights into the long‐lasting issue of the contact thermal resistance in nanotube/nanowire thermal conductity measurements and have important implications for further understanding thermal transport through carbon nanotubes and using carbon nanotube arrays as thermal interface materials.     

低温聚苯胺/碳纳米管复合材料的制备

采用原位聚合法合成出了具有较高导电性的聚苯胺及聚苯胺 /碳纳米管复合材料 ,考察了不同碳纳米管添加量对聚苯胺 /碳纳米管复合材料表面形态、材料结构及导电性的影响并进行了表征。结果证实 ,制备出的复合聚苯胺的电导率比所见报道值提高了 1～ 2个数量级 ,为高电导率聚苯胺的合成开辟了更广阔的前景。     

太阳能建筑用石蜡/CNTs相变乳液的制备及光-热性能研究

结合建筑结构在太阳能领域的蓄热控温特点,采用"两步法"制备出适用于太阳能蓄热的新型石蜡/CNTs相变乳液,通过纳米粒度电位仪和布鲁克旋转黏度仪分析了CNTs掺量对相变乳液技术性能的影响,确定最佳CNTs掺量;再采用差示扫描量热仪、导热系数测定仪、自制太阳光-热转换装置及紫外/可见/近红外分光光度计探究相变乳液的热物性能和光-热转换性能。结果表明,随着CNTs掺量的增大,相变液滴的粒径分布和运动黏度发生较为明显的变化,综合考虑相变乳液的稳定性及泵送性,推荐石蜡相变乳液中CNTs的最佳掺量控制为0.6%。由于石蜡具有较高的相变储热性能及CNTs具有较大的导热系数,掺加石蜡/CNTs能够显著增强相变乳液的导热性能和光-热转换能力,完全可用于建筑结构中以达到对太阳光辐射的蓄热与调温作用。     

Measurement of Thermal Transport Properties with an Improved Transient Plane Source Technique

The transient plane source (TPS) technique has been revised with the aim of developing a simple and fast system to measure the thermal transport properties of materials at low temperatures, especially high-T _c superconductors. To ensure reliable results, any new system should be tested with known samples. Fused silica, 0.9% carbon steel (215/3), and halide crystals (silver chloride) were studied with the new setup to check its performance. Data were taken from room temperature down to liquid nitrogen temperature. The assembly was designed for cryogenic (79 to 300 K) measurements in an atmosphere free of humidity. Dry nitrogen gas was used as a heat transfer medium around the sample holder assembly. The measured values for thermal conductivity and thermal diffusivity of these samples are in excellent agreement with values reported earlier. The thermal conductivity and thermal diffusivity for silver chloride crystals are extended down to 80 K although recommended data were available only down to 220 K. A Ba-doped, Bi-based, high-T _c superconductor was prepared by a solid-state reaction method. The nominal composition used was Bi_1.6Pb_0.4Sr_1.6Ba_0.4Ca₂Cu₃O_y. Large-sized samples (diameter 28mm and length 11mm) are investigated for thermal transport properties.     

Determination of the Anisotropic Thermal Conductivity of a Carbon Aerogel–Fiber Composite by a Non-contact Thermographic Technique

The carbon-composite under investigation consists of a felt of carbon fibers infiltrated by a nanoporous sol-gel derived carbon aerogel; in addition, cracks caused by the shrinkage of the gel upon drying are present within the composite. Due to the anisotropic structure of the felt, consisting of a pinned stack of fiber mats, the thermal conductivity of the compound is anisotropic. The components of the thermal conductivity in the different directions were measured at room temperature using a non-contact technique, which was formerly established for fibers and foils. Here, a high-power laser diode is used for non-contact heating and a thermographic system for non-contact detection of the surface temperature of the samples. The stationary profile of the surface temperature next to the laser focus was evaluated with respect to the lateral thermal conductivity. Using a line-shaped laser focus, a one-dimensional heat flow within the samples was established and the two relevant components of the thermal conductivity in the different directions could be separated by investigating slices of the composite with different orientation to the main fiber orientation of the felt. The anisotropy of the thermal conductivity, i.e., the ratio of the components perpendicular and parallel to the felt surface, was determined to be about two under vacuum conditions. This relatively small thermal anisotropy was in qualitative agreement with preliminary tests of the electrical conductivity. In addition, local inhomogeneities due to macroscopic voids within the samples influenced the observed temperature profile. As alternative measurement variants, point-shaped laser-heating of sample discs was used and evaluated in terms of a two-dimensional heat flow and periodic, i.e., dynamical heating of the sample slices with a line-shaped laser focus was used. The reliability of the results was also tested by comparing them to data derived with a guarded-hot-plate measurement of a (1.1 × 15 × 15) cm³ large tile. Paper presented at the Seventeenth European Conference on Thermophysical Properties, 1 September 5–8, 2005, Bratislava, Slovak Republic.     

铜基碳纳米管复合薄膜电沉积制备工艺

为获得碳纳米管分布均匀且导电性良好的铜基碳纳米管复合材料,用超声辅助搅拌复合电沉积方法制备了Cu/MWCNT复合薄膜.采用扫描电子显微镜(SEM)、四探针电阻率仪等研究了电沉积过程中复合电镀液中碳纳米管浓度、电镀液p H值、脉冲电流密度等各项电沉积工艺参数以及不同退火温度对复合薄膜的组织形貌和电阻率的影响规律.结果表明:改变镀液中碳纳米管含量和电镀液的p H值可以改变镀层中碳纳米管的含量及分布,MWCNTs质量浓度升高到2 g/L时,复合薄膜中MWCNTs的质量分数达2.17%;改变电流密度可以细化镀层组织并改善碳纳米管在镀层中的分布,从而提高镀膜的致密度并降低镀层的电阻率;合适的热处理温度可以改善薄膜结晶度和致密度,并提高导电性.镀液中MWCNTs质量浓度为2 g/L,电镀液p H为2,电流密度为20 A/dm2,电镀时温度在25℃且加入超声辅助搅拌时,所得到的复合镀膜经400℃退火后电阻率最低.     

碳纳米管/聚乙烯复合物分子动力学模拟研究

采用分子动力学方法模拟了碳纳米管/聚乙烯复合物的结构、热力学和力学特性,分析其随模拟温度和碳纳米管填充率的变化。模拟结果表明,碳纳米管/聚乙烯复合物为各向同性的无定形结构,聚乙烯和碳纳米管通过较强的范德华作用结合在一起,在聚乙烯基体作用下,碳纳米管壁上的碳原子排列的周期性下降,出现弯曲和褶皱。从能量上看,填充率较高的复合物更加稳定。碳纳米管/聚乙烯复合物具有比聚乙烯体系更高的等容热容和与聚乙烯体系相反的负值热压力系数,热容随碳纳米管填充率的变化较小,但随温度的升高而明显减小,具有显著的温度效应;热压力系数随温度的变化较小,温度稳定性比聚乙烯更好,但随填充率增加而减小。碳纳米管/聚乙烯复合物的力学特性表现出各向同性材料的弹性常数张量,弹性模量和泊松比比纯聚乙烯体系高得多,并且都随温度的升高和碳纳米管含量的降低而减小,说明加入碳纳米管可显著改善聚乙烯的力学性质。     

碳纳米管/导热硅脂复合材料的导热性能

为了提高导热硅脂的导热性能,本文研究了一种新型的碳纳米管/导热硅脂复合材料。研究结果表明,酯化处理后的碳纳米管有利于其在导热硅脂中的分散,并由此在导热硅脂中形成一个有效的导热网络,达到提高导热硅脂导热性能的目的。     

导热型碳纤维增强聚合物基复合材料的研究进展

综述了导热型连续碳纤维增强聚合物基复合材料(CFRP)的研究与应用现状和进展,阐述了CFRP的声子导热和光子导热机理,介绍了不同铺层角度和铺层比的CFRP面内和厚度方向热导率计算模型及测试方法,分析了环氧树脂、氰酸酯、双马来酰亚胺等3类树脂体系和聚丙烯腈基(PAN)碳纤维、中间相沥青基碳纤维、气相生长碳纤维、碳纳米管纤维等4类增强体以及工艺方法等因素对CFRP热导率的影响。