多壁碳纳米管增强铝基复合材料的高温力学性能EI北大核心CSCD

采用搅拌摩擦加工技术制备不同含量多壁碳纳米管增强铝基复合材料,并对复合材料高温力学性能进行研究。结果表明:多壁碳纳米管的添加使得铝基体材料微观组织更加细小,并形成了少量纳米晶;铝基体中有较高密度位错,并在局部呈位错缠结状分布。与未添加多壁碳纳米管的铝基体相比,复合材料的高温拉伸强度明显增强,且随着碳纳米管含量的增加,复合材料强度逐渐提高,而高温塑性不断降低,350℃时,6.6%(体积分数)MWCNTs/Al复合材料的抗拉强度达到78MPa,为未添加多壁碳纳米管铝基材强度的3.9倍;断口分析表明,随着测试温度的提高,韧窝逐渐变小,呈脆性断裂特征。     

CNTs含量对CNTs/Al微观组织及力学性能的影响

为增加碳纳米管(CNTs)在铝基体中的分散性,利用机械球磨-真空热压烧结工艺制备碳纳米管/铝(CNTs/Al)复合材料,采用扫描电子显微镜(SEM)、电子万能试验机和万能摩擦磨损实验机,研究了CNTs质量分数对CNTs/Al复合材料微观组织、力学性能及摩擦磨损性能的影响.结果表明:CNTs经超声波预先分散后分散性增加;当CNTs质量分数为2.0%时,复合材料中CNTs与Al粉之间表现出较好的相容性;随着CNTs含量进一步增加,CNTs团聚现象严重;热压烧结温度600℃时,随着CNTs添加量的增加,铝基复合材料的屈服强度和抗拉强度呈现出明显的先增大后降低的趋势,同时,CNTs/Al复合材料的摩擦因数和磨损率随CNTs含量的增大先减小后增加;CNTs质量分数为2.0%时,复合材料的屈服强度最大值为116 MPa,抗拉强度最大值为245 MPa,与纯Al基体相比,分别提高了78%和1.9倍.2.0%CNTs/Al复合材料可获得较好的摩擦磨损性能,其摩擦系数和磨损率呈现平缓趋势,复合材料的磨痕最浅.     

旋转摩擦挤压制备MWCNTs/Al复合材料的组织及磨损性能EI北大核心CSCD

采用旋转摩擦挤压(RFE)法制备多壁碳纳米管增强铝基(MWCNTs/Al)复合材料,分析MWCNTs/Al复合材料的显微组织、硬度和磨损性能。结果表明:用RFE法可制备具有一定形状尺寸的块体MWCNTs/Al复合材料;复合材料的成形质量好,显微组织为经动态再结晶后的细小等轴晶,MWCNTs在铝合金基体中分布均匀。复合材料的硬度随着MWCNTs体积分数增加先增加后降低,当MWCNTs体积分数为4%时,硬度是经RFE加工后基材的1.2倍。MWCNTs在复合材料磨损过程中起润滑作用,有助于降低MWCNTs/Al复合材料的磨损量提高复合材料的耐磨性。随MWCNTs体积分数的增加,复合材料的磨损率降低,当MWCNTs体积分数大于3%后磨损率变化较小。这是由于MWCNTs体积分数的增加,磨损机制发生变化,即由黏着磨损和轻微磨粒磨损转变为剥层磨损和磨粒磨损。     

电场诱导多壁碳纳米管有序排列对多壁碳纳米管/环氧树脂复合材料性能的影响

采用交流（AC）电场诱导法制备了多壁碳纳米管（MWCNTs）均匀分散且定向有序排列的MWCNTs/环氧树脂复合材料。采用SEM、偏振拉曼光谱等研究了电场强度、MWCNTs含量、加电时间及温度（黏度）等因素对MWCNTs定向排列的影响,讨论了MWCNTs有序排列对MWCNTs/环氧树脂复合材料电学和力学性能的影响。结果表明：MWCNTs沿电场方向有序排列;MWCNTs/环氧树脂复合材料施加AC电场后的拉曼强度明显高于未施加电场的情况;当MWCNTs含量从0wt%增加到0.025wt%时,MWCNTs/环氧树脂复合材料导电率从2.3×10^-12 S/cm增加到1.3×10^-8 S/cm,增加了约4个数量级;MWCNTs含量为2.5wt%时,MWCNTs/环氧树脂复合材料拉伸强度提高了26.3%。     

碳纳米管和氧化铝混杂增强铝基复合材料的制备及力学性能

采用化学气相沉积结合机械球磨的方法制备了碳纳米管(CNTs)和Al_2O_3颗粒混杂增强铝基复合材料,研究了球磨时间、Al_2O_3含量对复合材料组织和力学性能的影响。结果表明:本方法可以获得CNTs和Al_2O_3颗粒在铝基体内的均匀分散。随球磨时间的增加,复合材料的硬度随之增大;当球磨时间为180min时,复合材料硬度达纯铝的2.1倍。此外,随Al_2O_3颗粒含量的增加,复合材料的硬度和压缩屈服强度均不断提高。当Al_2O_3的质量分数为4%时,CNTsAl_2O_3/Al复合材料的硬度达112.1HV,为纯铝的2.8倍;压缩屈服强度达416MPa,为纯铝的4.6倍,说明CNTs和Al_2O_3的混杂加入发挥了良好的协同增强效果。     

碳纳米管功能化改性聚偏氟乙烯介电复合材料的结构及性能

以聚偏氟乙烯(PVDF)为基体材料,再分别以酸化多壁碳纳米管(MWCNTs-COOH)和未酸化多壁碳纳米管(MWCNTs)为填料,通过熔融法制备了不同填料含量的MWCNTs-COOH/PVDF及MWCNTs/PVDF介电复合材料。分别采用红外光谱(FTIR)、扫描电镜(SEM)、X射线衍射(XRD)、拉伸性能测试、电性能测试、差示扫描量热分析(DSC)等方法系统研究了填料含量和碳纳米管酸化前后对复合材料的热性能、力学性能和电性能的影响。XRD测试表明,填料MWCNTs-COOH和MWCNTs的加入促进了PVDF中β晶的生成。力学性能分析表明,MWCNTs-COOH和PVDF形成的界面结合力更强,复合材料的力学强度更高,当MWCNTs-COOH的质量分数为12%时,复合材料的拉伸强度可达64.6 MPa,较纯PVDF提高了24%。介电性能分析表明:未酸化的多壁碳纳米管更容易在PVDF基中构成局部导电网络,促进电子位移极化,提高复合材料的介电常数,并在MWCNTs的质量分数为12%时达到渗流阈值,介电常数达到了286,是纯PVDF的36倍。DSC测试表明,随着填料的增加,介电复合材料的结晶温度、熔融温度和结晶度都相较于纯PVDF得到了提高。     

动态硫化制备多壁碳纳米管/热塑性硫化胶复合材料的相态结构及热电效应

采用动态硫化方法制备了多壁碳纳米管/热塑性硫化胶(MWCNTs/TPV)复合材料,研究了三种动态硫化工艺和MWCNTs用量对MWC-NTs/TPV复合材料的相态结构、介电、导热和物理性能的影响.MWCNTs/TPV复合材料呈现"海岛"结构,IIR橡胶相以微米级交联颗粒分散在PP相中.动态硫化工艺主要影响MWCNTs的分布,MWCNTs在两相中均匀分布的MWCNTs/TPV复合材料具有较高的热电性能.当MWC-NTs含量达到渗流阈值(3％(质量分数,下同))时,形成MWCNTs网络结构,MWCNTs/TPV复合材料的交流电导率、介电常数和热导率急剧增加.随着MWCNTs含量的增加,MWCNTs/TPV复合材料的弹性模量逐渐增大,拉伸强度先增大后减小;MWCNTs能够提高TPV基体的界面结合力,与纯TPV相比,当MWCNTs的含量为3％时,MWCNTs/TPV复合材料的拉伸强度提高39％.基于MWCNTs/TPV复合材料的相态结构以及MWCNTs的渗流阈值提出MWCNTs网络结构,分散在PP基体中和两相界面处的MWCNTs相互搭接形成MWCNTs网络结构.     

搅拌摩擦加工法制备碳纳米管增强铝基复合材料

为了制备晶粒细小、 组织均匀的复合材料, 提高材料的力学性能, 用搅拌摩擦加工法制备碳纳米管增强铝基复合材料, 并对不同碳纳米管含量的复合材料的微观结构、 拉伸性能及断口形貌进行分析。结果表明: 碳纳米管添加到铝基体中, 搅拌摩擦中心区晶粒细小, 碳纳米管与基体之间结合良好, 未发现明显的缺陷; 碳纳米管对基材有明显的强化作用, 铝基复合材料抗拉强度随着碳纳米管含量的增加而提高; 碳纳米管体积分数为7%时, 抗拉强度达到201 MPa, 是基材的2.2倍; 复合材料在宏观上呈现脆性断裂特征, 微观上呈现韧性断裂特征, 其断裂机制以CNTs/Al界面脱粘、 基体撕裂和增强体断裂为主。      

原位聚合制备尼龙6/多壁碳纳米管复合材料及性能表征

用原位聚合法制备了尼龙6/多壁碳纳米管(MWCNTs)复合材料。先对多壁碳纳米管进行胺基功能化处理,再研究了多壁碳纳米管添加量对复合材料电性能和力学性能的影响,结果显示,复合材料体积电阻率和表面电阻率相对于不加碳纳米管制得的尼龙6基体降低了3个数量级,复合材料的介电常数显著增加,相对于不加碳纳米管的增加了71%;复合材料的弹性模量、弯曲模量、弯曲强度随碳纳米管加入量的增加大幅提高。     

混杂功能化多壁碳纳米管/环氧树脂复合材料的制备及性能

对多壁碳纳米管(MWCNTs)分别进行共价、非共价和混杂功能化改性, 然后采用溶液共混法, 将三种功能化类型的MWCNTs按不同质量分数分别加入环氧树脂(EP)制备MWCNTs/EP复合材料。通过拉伸试验和热重分析, 研究MWCNTs的功能化类型及含量对复合材料力学性能和热学性能的影响, 并对复合材料拉伸试件断面进行SEM观察分析。结果表明: 与共价功能化复合材料(MWCNTs-Epon828/EP)和非共价功能化复合材料(MWCNTs-PPA/EP)相比, 混杂功能化复合材料(MWCNTs-Epon828-PPA/EP)的力学性能和热学性能最佳。当MWCNTs质量分数为0.3%时, 其拉伸强度、弹性模量和断裂伸长率较纯EP分别提高30%, 62%和26%。      

Mechanical properties of porous Al2O3 composite with surface modified multi-walled carbon nanotubes (MWCNTs)

Multi-walled carbon nanotubes (MWCNTs) have been reinforced in alumina (Al2O3) matrix to overcome the inherent brittleness of the Al2O3 matrix. In this work, MWCNTs were treated by acid to provide hydrophilicity to hydrophobic MWCNTs, inducing the homogeneous dispersion of MWCNTs in an aqueous solution. Aluminum hydroxide (Al(OH)3) as a Al2O3 precursor was added in the solution with the modified MWCNTs, and then this mixture solution was filtered at room temperature. The prepared powders were calcinated at 800-1000 degrees C to reduce the gas pocket in the matrix by decomposition of Al(OH)3. Then the calcinated powders were formed, and heat-treated. The porous MWCNTs-Al2O3 composites show higher mechanical properties in flexure strength and hardness than the porous Al2O3 without the reinforcement phase, which is attributed to the high mechanical properties of MWCNTs. However, higher MWCNTs contents in the composites decrease the mechanical properties due to the aggregation of MWCNTs in the composites. Therefore, control of the MWCNTs content and its dispersibility in the matrix are key factors to be considered for the fabrication of the porous MWCNT-Al2O3 composites.     

Microstructure and mechanical properties of Al2O3 composites with surface-treated carbon nanotubes (CNTs): dispersibility of modified carbon nanotubes (CNTs) on Al2O3 matrix

Aluminum oxide (Al2O3) matrix have been reinforced by the multi-walled carbon nanotubes (MWCNTs) to overcome the inherent brittleness of Al2O3 matrix. In order to increase mechanical properties of MWCNTs-Al2O3 composites, MWCNTs need to be well dispersed and individually incorporated in Al2O3 matrix. In this work, aluminum hydroxide (Al(OH)3) used as a Al2O3 precursor and MWCNTs were mixed in an aqueous solution for the homogeneous mixing of hetero-particles, as functions of the content of MWCNTs and the potential hydrogen (pH) of Al(OH)3 suspension. Firstly, MWCNTs were purified and modified by an acid reagent, inducing that the dispersibility of MWCNTs is increased in an aqueous solution by carboxylic group given on the surface of MWCNTs. The modified MWCNTs were added in the Al(OH)3 suspension, and then the mixture was filtered at room temperature. The filtered powders were formed using an uniaxial pressing and then densified by a pressureless heat treatment. As the pH is decreased the Al(OH)3 particles are well dispersed in an aqueous solution, due to the increment of repulsive force between particles with a same surface charge. MWCNTs are individually incorporated into Al2O3 matrix up to 1 vol.% MWCNTs, whereas MWCNTs are aggregated at the composite with 3 vol.% MWCNTs. Therefore, control of the pH and the MWCNTs content are key factors to be considered for the fabrication of MWCNTs-Al2O3 composites with high functional properties.     

Microstructure and mechanical property of multi-walled carbon nanotubes reinforced aluminum matrix composites fabricated by friction stir processing

Aluminum matrix composites reinforced by different contents of multi-walled carbon nanotubes (MWCNTs) were fabricated by friction stir processing (FSP). The microstructure of nano-composites and the interface between aluminum matrix and MWCNTs were examined using optical microscopy (OM) and transmission electron microscopy (TEM). It was indicated that MWCNTs were well dispersed in the aluminum matrix throughout the FSP. Tensile tests and microhardness measurement showed that, with the increase of MWCNT content, the tensile strength and microhardness of MWCNTs/Al composites gradually increased, but on the contrary, the elongation decreased. The maximum ultimate tensile strength reached up to 190.2 MPa when 6 vol.% MWCNTs were added, and this value was two times more of that of aluminum matrix. Appearances and fracture surface micrographs of failed composite samples indicated that the composites become more and more brittle with the increase of the MWCNT content.     

The effects of the variations of carbon nanotubes on the micro-tribological behavior of carbon nanotubes/bismaleimide nanocomposite

Two kinds of original multiwalled carbon nanotubes (MWCNTs) with different diameters, and one carboxyliated MWCNTs were used to prepare three kinds of MWCNTs/bismaleimide (BMI) nanocomposites. The effects of the diameter, concentration and functional group of MWCNTs used in the composites on the micro-tribological behavior of the MWCNTs/BMI nanocomposites were investigated in this paper. The microhardness, the morphology of the worn surface, the glass transition temperature and dynamic mechanical properties of the MWCNTs/BMI nanocomposites were also measured to figure out the possible main wear mechanism of the composites. Results show that the addition of MWCNTs in BMI resin decreases the friction coefficient of the resin no matter what kind of MWCNTs is added. Moreover, the wear loss rate of all nanocomposites considerably decreases with the increasing of nanotube content until the content reaches 2.5 wt%. Functionalization of MWCNTs changes the main wear mechanism of the MWCNTs/BMI composite from adhesive wear (for pure BMI resin) to abrasive attrition by changing the self-lubricating property of the wore surface, the dispersion of MWCNTs in the BMI matrix, the interfacial strength between MWCNTs and the matrix as well as the internal strength of the materials.     

球磨工艺对原位合成碳纳米管增强铝基复合材料微观组织和力学性能的影响

将原位化学气相沉积法合成的碳纳米管(CNTs)与铝的复合粉末进行球磨混合,进而粉末冶金制备CNTs/Al复合材料,研究球磨工艺对复合材料的微观组织和力学性能的影响。结果表明:球磨过程中不添加过程控制剂所得到的复合材料力学性能优异;随着球磨时间的增加,CNTs逐步分散嵌入铝基体内部,复合材料的组织也变得更加致密均匀。CNTs/Al复合材料的硬度和抗拉强度均随球磨时间的延长持续增加,但是伸长率先增后减。经90min球磨的CNTs/Al复合材料展现了强韧兼备的特点,其硬度和抗拉强度较原始纯铝提高了1.4倍和1.7倍,并且具有17.9%的高伸长率。     

Influence of carbon nanotubes structure on the mechanical behavior of cement composites

Cement matrix composites have been prepared by adding 0.5% in weight of multi wall carbon nanotubes (MWCNTs) to plain cement paste. In order to study how the chemical–physical properties of the nanotubes can affect the mechanical behavior of the composite, we compared the specimen obtained by mixing the same cement paste with three different kinds of MWCNTs. In particular, as-grown, annealed and carboxyl functionalized MWCNTs have been used. In fact, while high temperature annealing treatments remove lattice defects from the walls of CNTs, hence improving their mechanical strength, acid oxidative treatments increase chemical reactivity of pristine material, consequently chemical bonds between the reinforcement and the cement matrix are supposed to enhance the mechanical strength.Flexural and compressive tests showed a worsening in mechanical properties with functionalized MWCNTs, while a significant improvement is obtained with both as-grown and annealed MWCNTs.The phase composition of the composites was characterized by means of thermo gravimetric analysis coupled with mass spectroscopy, while the mineralogy and microstructure were analyzed by means of an X-ray diffractometer and scanning electron microscope. The results are interpreted and discussed taking into account the chemical and physical properties of the MWCNTs by means of EDX, TGA, SEM and Raman analysis.     

纳米碳形貌对纳米碳/聚乙烯导电复合材料性能的影响

分别以纺锤形碳酸钙表面改性的二维片状石墨烯微片（CGM）和多壁碳纳米管（MWCNTs）作为导电剂填充改性聚乙烯（PE）制备导电复合材料。重点研究了二维或一维纳米碳/PE复合材料形成导电网络时力学与电学性能。CGM/PE或MWCNTs/PE复合材料达到抗静电要求时CGM的质量分数为8wt%,而MWCNTs的质量分数为1wt%。填充8wt% CGM的复合材料表现出优异的综合性能,而填充0.5wt% MWCNTs的复合材料综合力学性能达到最大值还未能达到抗静电要求,达到抗静电要求时MWCNTs/PE复合材料的综合力学性能出现下降趋势。通过形貌及流变学分析了复合材料不同的力学与电学性能的微观作用因素。CGM/PE复合材料流变渗流阈值与导电渗流阈值存在比较好的相关性,MWCNTs/PE复合材料达到流变渗流阈值还不能形成导电网络。结果表明,与二维CGM相比,一维MWCNTs不易均匀分散于聚合物基体中,并降低MWCNTs/PE复合材料的力学性能。     

碳纳米管增强镁基复合材料导热性能研究

镁及其合金是目前最轻的金属结构材料,合金化虽然提升了镁合金的力学性能,但导致其导热性能严重下降,限制了镁合金的应用。碳纳米管(CNTs)因具有优异的力学、热学等性能,是最理想的增强体之一,可以用于改善镁合金的力学性能和热学性能。采用粉末冶金法分别以纯Mg、Mg-9Al合金、Mg-6Zn合金为基体制备了不同CNTs含量的镁基复合材料,利用光学显微镜、扫描电子显微镜、透射电子显微镜对复合材料微观组织、基体与增强体界面及析出相进行表征,并对复合材料的拉伸性能和热学性能进行测试。研究结果表明,当CNTs质量分数不超过1.0%时,可提高纯镁基复合材料的导热性能,力学性能仅有稍微降低;将CNTs添加到Mg-9Al合金中,可以促进纳米尺度β-Mg 17 Al 12相在CNTs周围析出,降低了Al在Mg基体中的固溶度,使CNTs/Mg-9Al复合材料的导热性能有所提高。此外,在CNTs/Mg-6Zn复合材料界面处存在C原子和Mg原子的相互嵌入区,这种嵌入型界面不仅有利于复合材料力学性能的提高,也使CNTs起到加速电子移动的“桥”的作用,有利于该复合材料热导率的提高。当CNTs质量分数为0.6%时,CNTs/Mg-6Zn复合材料具有较为优异的热学性能和力学性能,其热导率为127.0 W/(m·K),抗拉强度为303.0 MPa,屈服强度为204.0 MPa,伸长率为5.0%。     

Al含量对漂珠/镁合金可溶复合材料组织与性能的影响

采用搅拌铸造法制备了不同Al含量下的漂珠（FAC）/镁合金可溶复合材料。采用金相显微镜、SEM及XRD观察分析了FAC/镁合金可溶复合材料的微观组织、溶解表面形貌及溶解产物的物相组成,采用力学性能试验机研究了复合材料的压缩性能,采用电化学工作站对复合材料进行电化学性能测试,在常温及水浴锅内进行复合材料在不同温度下的KCl溶液中的溶解试验。结果表明：该FAC/镁合金可溶复合材料主要由α-Mg基体相、β-Mg₁₇Al₁₂相、Mg₂Si相和MgO相组成。随着Al含量的增加,FAC/镁合金可溶复合材料的溶解速率先变快后减慢,在80℃的3wt% KCl溶液中,含15wt% Al的FAC/镁合金复合材料溶解速率最快,为56 mg/（h·cm²）。Al-FAC/镁合金可溶复合材料的抗压强度随Al含量的增加先提高后下降,四种合金的抗压强度均大于300 MPa,最高强度达到372 MPa。