MA-SEBS对超高分子量聚乙烯/碳纳米管复合材料结晶和熔融行为的影响

以马来酸酐接枝SEBS (MA-SEBS)作相容剂,采用溶液共混的方法制备超高分子量聚乙烯(UHMWPE)/碳纳米管(CNTs)复合材料.熔融结晶的UHMWPE/CNT复合材料是将其熔体以20℃/分的速率降温结晶而成.采用差示扫描量热法(DSC)研究了以不同方式结晶制备的UHMWPE/CNT复合材料的结晶和熔融行为.结果表明UHMWPE/CNT复合材料中UHMWPE相在溶液态结晶比在熔融态结晶形成的晶片厚,因而表现出更高的熔点(Tm)和结晶度(Xc).随着CNTs含量增加,UHMWPE/CNT复合材料中UHMWPE相的结晶温度(Tc)趋于提高.而且MA-SEBS的加入降低了UHMWPE/CNT复合材料中UHMWPE相的Tm 和 Tc. 此外UHMWPE/CNT复合材料中UHMWPE相的结晶速率随CNTs的引入而提高; MA-SEBS起相容剂的作用,改善了CNTs在UHMWPE基体中的分散性,使UHMWPE相的结晶速率进一步提高.     

二氧化锰/碳纳米管/聚吡咯复合材料的制备及性能

为了进一步实现其他材料与聚吡咯的性能互补与优化,先以甲基橙为掺杂剂,过硫酸铵为氧化剂,采用软模板法制备具有一维纳米结构的聚吡咯,再利用水热法制备二氧化锰/碳纳米管复合材料,最后将二氧化锰/碳纳米管复合材料与聚吡咯进行混合处理,改变复合材料中二氧化锰/碳纳米管复合材料和聚吡咯微米管的含量,得到了3种不同比例的二氧化锰/碳纳米管/聚吡咯复合材料. 采用扫描电子显微镜测试观察所得产物的微观形貌,通过X-射线粉末衍射仪测试其结构与组成,最后通过电化学工作站测试分析复合物的电化学性能与循环稳定性. 结果表明,二氧化锰/碳纳米管/聚吡咯复合材料在微观上复合均匀,电容性能比单独的聚吡咯或二氧化锰/碳纳米管复合材料量有显著改善.     

Wear behavior of the raw and pre-smashed carbon nanotubes reinforced 6061Al composites fabricated by powder metallurgy

Science China Technological Sciences - The raw and pre-smashed (PS) carbon nanotube (CNT) reinforced 6061Al composites (CNT/6061Al) with different CNT contents were respectively fabricated by...     

Effects of size and surface modification of multi-walled carbon nanotubes on mechanical properties of polyurethane-based nanocomposites

Polyurethanes/multi-walled carbon nanotube (PU/CNT) composites were prepared with a help of ultrasonically dispersing CNT in the traditional procedure of synthesizing polyurethane. In this case, the various loading levels, sizes and surface-modified groups were considered to regulate the mechanical performances of the PU/CNT nanocomposites. Moreover, the structure and mechanical properties of all the PU/CNT nanocomposites were investigated by attenuated total reflection-Fourier transform infrared spectroscopy, dynamic mechanical analysis, scanning electron microscope, transmission electron microscope, and tensile testing. The experimental results showed that a moderate loading-level of 0.1wt% and a diameter of 10-15 nm for CNT could produce the maximum tensile strength and elongation while it was worth noting that the surface carboxylation of CNT could further enhance the tensile strength and elongation of the PU/CNT nanocomposites.     

制备工艺对CNTs/EP复合材料性能的影响

采用溶液共混法制备碳纳米管(CNTs)/环氧树脂(EP)复合材料,主要研究丙酮用量、混合方式、超声时间、CNTs含量等制备工艺对复合材料的热性能和导电性能的影响.通过用SEM、DSC,TGA以及万用表对复合材料进行分析表征,结果表明,丙酮的加入量越多,超声时间越长,CNTs/EP的复合材料的导电性越好,CNTs在复合材料中分散性也好,而随着CNTs含量增加,复合材料的导电性按照逾渗理论的规律提高,且逾渗闶值出现在0.5 0A～1%范围内.利用超声处理伴随着搅拌这种混合方式所得复合材料的导电性最好,加入碳纳米管的复合材料玻璃转化温度Tg和热稳定性能较纯EP有显著提高.     

Bending behavior of carbon nanotube-reinforced composites

The multi-scale modeling method was utilized to study the bending characteristics of a carbon nanotube(CNT)and CNT-reinforced composites.Through combining molecular dynamics and continuum mechanics,the tensional and flexural modulus of a CNT were calculated by a finite element model constructed by reticulate beams with solid cylinder shape and energy equal to C-C bonds.Then,another beam element with hollow cylinder shape and equivalent stiffness was utilized in place of a CNT in a matrix,thus,a multi-scale representative volume element(RVE)model of CNT-reinforced composite was established.Using this RVE model,the bending behavior of CNT-based composites was analyzed.The influence of diameter D,length L,aspect ratio L/D,volume fraction,chiral of CNTs and shape of RVE as well as the arrangement of CNTs in matrix on the reinforcement effect of flexural modulus of resultant nanocomposites were further discussed.The obtained data provide useful information for the design of CNT-reinforced composites.     

Fabrication of high strength carbon nanotube/7055Al composite by powder metallurgy combined with subsequent hot extrusion

Bimodal carbon nanotube reinforced 7055Al(CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The effect of extrusion temperature varied from 320℃ to 420℃ on the microstructure evolution and tensile properties were investigated. Microstructure observation indicates that the elongated coarse grain bands aligned along the extrusion direction after extrusion. The width of the coarse grain bands increased, and the length of the coarse grain bands increased firstly and then decreased with the increase of extrusion temperature. The grain size of the ultra-fine grain zones changed little after hot extrusion, but the ultra-fine grains coarsened after subsequent heat treatment, especially for the composite extruded at low temperature of 320℃. By observing the CNT distribution, it was found that the higher temperature extrusion was beneficial to the CNT orientation along the extrusion direction.Furthermore, a precipitated free zone formed at the boundary between the coarse grain band and the ultra-fine grain zone as the composite extruded at high temperature of 420℃. As the result of the comprehensive influence of the above microstructure, the tensile strength of the composite extruded at moderate temperature of 370℃ reached the highest of 826 MPa.     

Effects of carbon nanotubes by electrophoretic deposition on interlaminar properties of two dimensional carbon/carbon composites

Carbon nanotubes(CNTs) were deposited uniformly on carbon cloth by electrophoretic deposition(EPD). Thereafter, CNT-doped clothes were stacked and densified by pyrocarbon via chemical vapor infiltration to fabricate two-dimensional(2 D) carbon/carbon(C/C) composites. Effects of EPD CNTs on interlaminar shear performance and mode Ⅱ interlaminar fracture toughness(GⅡc) of 2 D C/C composites were investigated. Results showed that EPD CNTs were uniformly covered on carbon fibers, acting as a porous coating. Such a CNT coating can obviously enhance the interlaminar shear strength and GⅡc of 2 D C/C composites. With increaing EPD CNTs, the interlaminar shear strength and GⅡc of 2 D C/C composites increase greatly and then decrease, both of which run up to their maximum values, i e, 13.6 MPa and 436.0 J·m-2, when the content of EPD CNTs is 0.54 wt%, 2.27 and 1.45 times of the baseline. Such improvements in interlaminar performance of 2 D C/C composites are mainly beneficial from their increased cohesion of interlaminar matrix, which is caused not only by the direct reinforcing effect of EPD CNT network but also by the capacity of EPD CNTs to refine pyrocarbon matrix and induce multilayered microstructures that greatly increase the crack propagation resistance through "crack-blocking and-deflecting mechanisms".     

全金属组元铁基块体非晶的制备与性能研究

3D打印成型碳纤维接枝碳纳米管增强热塑性复合材料的强度提高

王婼楠¹，吴海宏^1，2，郭子月³，刘春太²，申长雨²

（1. 河南工业大学 机电工程学院，郑州450001; 2.郑州大学 橡塑模具国家工程研究中心，郑州450002; 3.中山大学 数学学院（珠海）,珠海519082）

创新点说明：

1) 研究了碳纤维定量接枝碳纳米管对热塑性复合材料的界面性能及拉伸性能的影响。

2) 用3D打印模压成型的工艺方法制备了热塑性复合材料。

研究目的：

研究碳纤维表面接枝不同含量的碳纳米管对复合材料微观结构、界面性能和力学性能的影响。

研究方法：

1) 采用溶液法，通过控制碳纳米管接枝反应时间，制备不同含量碳纳米管接枝碳纤维，然后用硝酸刻蚀法，去除残留溶剂，验证了碳纳米管接枝的可靠性。用扫描电镜观察碳纤维的微观形貌，用FTIR测试碳纤维表面官能团并用XPS对碳纤维的表面官能团进行分析。

2) 用扫描电镜观察碳纤维与基体的结合情况并用接触角测量仪测试碳纤维与基体的接触角。

3) 通过 3D打印成型法成型了热塑性复合材料样条，并用扫描电镜观察碳纤维热塑性复合材料的界面微观形貌。

4) 采用万能试验机测试3D打印成型热塑性碳纤维复合材料的拉伸性能，并观察复合材料断口形貌。

结果：

1) 溶液法.扫描电镜观察发现碳纳米管在碳纤维表面均匀分布，表明碳纤维与碳纳米管之间存在较强的键合关系。但随着接枝时间的增加，碳纤维表面的碳纳米管含量逐渐增加，但达到0.4%时，出现分散不均匀现象。碳纤维表面含有上浆剂和去掉上浆剂的对比发现，无上浆剂的碳纤维表面沟壑明显，这些沟槽可以增加碳纤维的比表面积和表面能，增强了基体与碳纤维的机械相互作用。用FTIR测试碳纤维表面官能团并用XPS对碳纤维的表面官能团进行分析，结果表明，经偶联剂改性后，C=O键含量明显增加，碳纤维表面引入含氧官能团。C1，O1S峰增强，表明碳纳米管接枝到了碳纤维表面。

2) 扫描电镜结果表明，与表面未接枝碳纳米管的碳纤维相比，接枝碳纳米管的碳纤维与基体PA6具有更好的润湿性。接触角测试结果对比发现，接枝碳纳米管的碳纤维与基体的接触角，明显小于未接枝碳纳米管的。

3) 通过扫描电镜观察复合材料的界面微观形貌，结果表明：纤维与基体之间存在一定厚度的界面层，界面层的存在可以减轻纤维与基体之间的力学性能突变引起的应力集中，并防止界面缺陷的扩展。

4）界面结合强度测试结果表明，当碳纳米管的质量分数增加到0.25%时，复合材料的界面结合强度比未接枝碳纳米管的碳纤维增强的PA6复合材料提高了20%，比表面有环氧的碳纤维复合材料提高了41.8%。然而当碳纳米管含量大于0.4%时，界面结合强度不再继续增加。力学测试表明碳纳米管含量为0.25%的复合材料具有最高的平均模量、拉伸强度和界面剪切强度。接枝碳纳米管的碳纤维复合材料断口形貌可以观察到界面处基体中的韧窝。表明基体树脂在拔出纤维前经历了较大的塑性变形，表明纤维与基体有很好结合性。

结论：

实验结果表明，碳纳米管可以提高表面的润湿性和CF表面粗糙度。碳纳米管接枝碳纤维增强PA6与环氧上浆的碳纤维复合材料相比，当碳纳米管的质量分数达到0.25%时，复合材料的界面结合强度增加了41.8%，拉伸强度提高了130%，界面剪切强度提高了238%。然而，随着碳纳米管含量的继续增加到0.4%时，界面结合强度和力学性能就会下降。

关键词：热塑性复合材料，界面结合强度，界面剪切强度，3D打印成型

     

Aluminum matrix composites reinforced by molybdenum-coated carbon nanotubes

To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT (Mo-CNT)/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering.The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated.The results show that magnetic stirring is better tha...     

Optimizing electrophoretic deposition conditions for enhancement in electrical conductivity of carbon fiber/carbon nanotube/epoxy hybrid composites

The effectiveness of optimizing electrical conductivity of carbon fiber/carbon nanotube (CNT)/epoxy hybrid composites via Taguchi method was demonstrated.CNTs were induced on carbon fabric by electrophoretic deposition (EPD) technique.The essential deposition parameters were identified as 1) the deposition time,2) the deposition voltage,3) the mass fraction of CNTs in suspension,and 4) the distance between the electrodes.An experimental design was then performed to establish the appropriate levels for each factor.An orthogonal array of L9 (34) was designed to conduct the experiments.Electrical conductivity results were collected as the response.The relative influences of design parameters on the response were discussed.Using the model,signal to noise (S/N) ratio and response characteristics for the optimized deposition parameter combination were predicted.The results show clearly that the optimum condition of electrophoretic deposition (EPD) process improves the electrical conductivity of carbon/epoxy hybrid composites.     

聚吡咯/磺化石墨烯/磺化碳纳米管复合材料的界面合成

对氧化石墨烯（GO）和碳纳米管（CNT）进行磺化处理,得到的磺化石墨烯（SG）和磺化碳纳米管（SCNT）在溶液中有良好的分散性。将SG、SCNT和氧化剂溶于水中形成水相,聚吡咯（PPy）单体溶于有机溶剂中形成有机相。有机相与水相之间发生界面反应,得到PPy/SG/SCNT复合材料。采用扫描电子显微镜、X射线衍射、电化学工作站对复合材料进行表征与测试。结果表明:PPy/SG/SCNT复合材料组分复合均匀,是无定形材料,其电化学性能较单独的PPy、SG或SCNT更优越,而且当正己烷作为有机溶剂时,所得到的三组分复合材料更适合作为超级电容器电极材料。     

Fluxing Agents on Ceramification of Composites of MgO-Al_2O_3-SiO_2/Boron Phenolic Resin

Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al_2O_3-SiO_2/boron phenol formaldehyde resin(MAS/BPF) composites to lower the formation temperature of eutectic liquid phase and promote the ceramification of ceramifiable composites. The effects of fluxing agents on the thermogravimetric properties, phase evolution, and microstructure evolution of MAS/BPF composites were characterized by TG-DSC, XRD and SEM analyses. The results reveal that the addition of a fluxing agent highly reduces the decomposition rate of MAS/BPF composites. Fluxing agents lower the formation temperatures of liquid phases of ceramifiable MAS/BPF composites obviously, and then promote the ceramification and densification process. The final residues of composites are ceramic surrounded by large amount of glass phases.     

Fractal characterization of pore microstructure evolution in carbon/carbon composites

A fractal characterization approach was proposed to research pore microstructure evolution in carbon/carbon (C/C) composites during the chemical vapor infiltration process. The data obtained from mercury porosimetry determinations were analyzed using the sponge fractal model and the thermodynamics relation fractal model, respectively. The fractal dimensions of C/C composites at different densification stages were evaluated. The pore microstructure evolution with densification time was studied by fractal dimension analysis. The results showed that C/C composites belong to porous fractal structure. The fractal dimensions increase on the whole with decreasing porosity as the densification proceeds. The fractal dimensions are influenced by the texture of pyrocarbon and decrease with increasing anisotropy from isotropic pyrocarbon to high textural one. Both the complicacy of pore structure and the textural morphology of pyrocarbon can be represented simultaneously by the fractal dimension. The pore evolution of C/C composites in the densification process can be monitored using fractal dimension. Supported by the National Natural Science Foundation of China (Grant No. 50742008)     

Fluxing Agents on Ceramification of Composites of MgO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>/Boron Phenolic Resin

Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al₂O₃-SiO₂/boron phenol formaldehyde resin (MAS/BPF) composites to lower the formation temperature of eutectic liquid phase and promote the ceramification of ceramifiable composites. The effects of fluxing agents on the thermogravimetric properties, phase evolution, and microstructure evolution of MAS / BPF composites were characterized by TG-DSC, XRD and SEM analyses. The results reveal that the addition of a fluxing agent highly reduces the decomposition rate of MAS / BPF composites. Fluxing agents lower the formation temperatures of liquid phases of ceramifiable MAS / BPF composites obviously, and then promote the ceramification and densification process. The final residues of composites are ceramic surrounded by large amount of glass phases.     

Out-of-Plane Compressive Behavior for UHMWPE/ Polyurethane Composites after Hygrothermal Treatment

Quasi-static and high strain rate compressive behaviors and failure mechanisms of hygrothermal treated ultra-high molecular weight polyethylene/polyurethane (UHMWPE/PU) composites have been studied in this paper. Firstly, the UHMWPE composites were immersed in water at 70 ℃. The out-of-plane compression test was then performed on the dry/wet state specimens at quasi-static states (0.001-0.01 s^-1) and high strain rate states (800-2 400s^-1). The split Hopkinson pressure bar (SHPB) was adopted in the dynamic tests and waveform shapers were used to smooth and control the incident pulse. The results show that there are two platforms for the water absorption curve of UHMWPE composites. The absorption of moisture reduces the quasi-static compressive strength of the material while initially increasing, then decreasing the dynamic compressive strength. Matrix plasticization, fiber/matrix interface degradation and void expansion are the main factors affecting the irregular change of static/dynamic compressive strength of UHMWPE composites.     

硅烷接枝聚丙烯对聚丙烯复合材料性能的影响

目的研究硅烷接枝聚丙烯（PP－g－Si）对不同填料如滑石粉（Ta）、碳酸钙和硫酸钡填充的PP复合材料性能的影响,方法分别制备经PP－g－Si偶联的滑石粉、CaCO3和BaSO4填充的PP复合材料,并测试其机械性能和结晶熔融行为,结果与未经偶联的体系相比,在一定PP－g－Si含量范围内,PP－g－Si可使T3／PP体系力学性能提高,但拉伸模量降低;而对PP／CaCO3和PP／BaSO4体系的力学性能影响不大或使其性能有所降低,同时,PP－g－Si对这3种填料填充的PP体系中PP的结晶熔融行为也有较大影响,结论在实验范围内,PP－g－Si对聚丙烯和滑石粉界面有增容作用,可作为PP／Ta材料的大分子偶联剂,而对PP／CaCO3和PP／BaSO4体系则没有增容作用。     

Strain rate response of a Zr-based composite fabricated by Bridgman solidification

Zr_(58.5)Ti_(14.3)Nb_(5.2)Cu_(6.1)Ni_(4.9)Be_(11.0) bulk metallic glass matrix composites,containingβ-Zr dendrites,were fabricated by Bridgman solidification at the withdrawal velocity of 1.0 mm/s through a temperature gradient of～45 K/mm.Subjected to the increasing compressive strain rates,the monotonic increasing and decreasing were obtained for the maximum strength and the fracture strain,respectively.The results show that high strain rate may induce the insufficient time for the interaction between s...     

The hot compressive deformation behavior of the metal matrix composites with the large whisker orientation

Metal matrix composites are often subjected to ahot compressive plastic forming.During the thermome-chanical process the reinforcements are misaligned fromthe loading axis and rotate toward a more stable posi-tion.Meanwhile,the strain softening can be observedduring the hot compression of the metal matrix compos-ites reinforced with discontinuous reinforcements suchas the randomly oriented whiskers[1-3],the whiskersparallel to the applied loading[4-5]and the whiskerstilted away from the applie…     

编织5D复合材料轴向压缩力学性能统计特性分析

采用概率统计方法,研究编织5D复合材料轴向压缩力学性能.分析了给定应变条件下,应力的统计分布特性;给定应力条件下,应变的统计分布特性.提出了描述编织5D复合材料轴向压缩应力—应变关系统计特性的随机变量方法.为编织5D复合材料可靠性分析提供了试验基础.