Improvement of interfacial interactions in CF/PEEK composites by an s-PSF/graphene oxide compound sizing agent

The interfacial interactions of carbon fiber (CF)-reinforced polymer composites is a key factor affecting the overall performance of the material. In this work, we prepared a sulfonated poly(ether sulfone)–graphene oxide mixed sizing agent to modify the interface of CF/PEEK composites and improve the interfacial properties between the PEEK matrix and CF. Results showed that the mechanical and interfacial properties of CF/PEEK composites are improved by the sizing agent. Specifically, the flexural strength, flexural modulus and interlaminar shear strength of the materials reached 847.29 MPa, 63.77 GPa, and 73.17 MPa, respectively. Scanning electron microscopy confirmed markedly improved adhesion between the resin matrix and fibers. This work provides a simple and effective method for the preparation of high-performance CF/PEEK composites, which can improve the performance of composites without degrading the mechanical property of pristine CF.     

Effect of filler dispersion on the electrical conductivity and mechanical properties of carbon/polypropylene composites

Conducting carbon/polypropylene composites containing a mixed filler of crystalline natural graphite powder, carbon black, and multiwalled carbon nanotubes have been prepared. The effect of the filler dispersion on the electrical conductivity and mechanical properties has been studied. Keeping the graphite content constant and increasing the ratio of carbon black to nanotubes, the conductivity and the flexural modulus increased linearly at different graphite contents. Graphite aggregates on the cross sections were analyzed by optical microscopy to characterize the dispersion of graphite. The results of the optical microscopy studies showed that the dispersion of graphite is affected by the composition and amount of the nanofiller system. Based on the observations simplified morphological models were set up, that allowed to explain the change in the electrical and mechanical properties of the composites of different compositions. POLYM. COMPOS., 34:1195–1203, 2013. © 2013 Society of Plastics Engineers     

Polypropylene–Carbon black interaction in conductive composites

Interaction between polypropylene matrix and carbon black was examined by measuring physical, mechanical, and electrical properties. It has been shown that presence of carbon black influences the morphology and crystallinity of the matrix. Strong interaction was observed directly by electron microscopy and indirectly by the rise of the modulus of elasticity. The effect of carbon black on strength and physical properties of the composites is discussed. © 1993 John Wiley & Sons, Inc.     

Mechanical behavior and microstructure of cement composites incorporating surface-treated multi-walled carbon nanotubes

Multi-walled carbon nanotubes after modified by using a H₂SO₄ and HNO₃ mixture solution were added to cement matrix composites. The mechanical properties of the newly formulated composites were analyzed, and the results show that the treated nanotubes can improve the flexural strength, compressive strength, and failure strain of cement matrix composites. The porosity and pore size distribution of the composites were determined by using Mercury intrusion porosimetry, and it is observed that the addition of carbon nanotubes can fine the pore size distribution and decrease porosity. The phase composition was characterized with Fourier transform infrared spectroscopy. It is found that there are interfacial interactions between carbon nanotubes and the hydrations (such as C-S-H and calcium hydroxide) of cement, which will produce a high bonding strength between the reinforcement and cement matrix. The mineralogy and microstructure were analyzed by using scanning electron microscope. It is shown that carbon nanotubes act as bridges across cracks and voids, which guarantees the load-transfer in case of tension.     

Silicon nitride based nanocomposites produced by two different sintering methods

This research explores the use of a variety of carbon nanostructures as reinforcing agents for Si₃N₄ matrix composites. We have chosen highly promising families of carbon materials: multiwall, singlewall carbon nanotubes (MWCNTs, SWCNTs), graphene, carbon black nanograins and graphite micrograins for use as fillers. These materials were dispersed with a concentration of 3 wt% in silicon nitride matrices. A high efficiency attritor mill has also been used for effective dispersion of second phases in the matrix. In the present work the development of sintering processes (hot isostatic pressing (HIP) and spark plasma sintering (SPS)) has been performed to consolidate and tailor the microstructure of Carbon nanotube (CNT)-reinforced silicon nitride-based ceramic composites. The silicon nitride nanocomposite systems retained the mechanical robustness of the original systems. Elastic modulus measurements and micro-indentation investigations of the hardness and fracture toughness have been performed as well as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction in order to characterize the composites produced by the two sintering methods.     

Effect of different carbon fillers on the properties of PP composites: Comparison of carbon black with multiwalled carbon nanotubes

Polypropylene (PP)/carbon composites were prepared via melt blending PP with carbon fillers, including multiwalled carbon nanotubes (MWNTs) and carbon black (CB). Field‐emission scanning electron microscopy was used to research the morphology and dispersion of fillers in the PP matrix. The electrical properties, mechanical properties, and crystallization behaviors of PP/carbon composites were also investigated. The results show that the influence of MWNTs on the properties of PP composites is different with CB, which can be ascribed to the structure and aspect ratio difference between MWNTs and CB. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4823–4830, 2006     

In situ synthesis and characterization of poly(2,5-benzoxazole)/multiwalled carbon nanotubes composites

This article reports the synthesis of poly(2,5-benzoxazole)/multiwalled carbon nanotubes (ABPBO/MWNT) composites by in situ polycondensation and their chemical and physical properties. The functional groups yielded from the surface modification of MWNTs by hydrochloric acids have been demonstrated to participate in the polymerization and thus led to the composites with homogenous dispersion of carbon nanotubes. The chemical structures and morphology of the afforded polymer composites have been fully characterized by FTIR, WAXD, UV-vis, TGA and SEM. The ABPBO/MWNT composites exhibit excellent thermal stability and greatly improved mechanical properties. The tensile modulus and tensile strength of the composites are 47% and 83%, respectively, higher than those of the polymer matrix. The dielectric constant of the composites is also significantly enhanced from 4 of the polymer matrix to 65 with the incorporation of 5 wt% MWNTs.     

Synthesis and characterization of multi-walled carbon nanotubes reinforced polyamide 6 via in situ polymerization

Polyamide 6 (PA6)/carbon nanotubes (PA6/CNTs) composites have been prepared by in situ polymerization of ε-caprolactam in the presence of pristine and carboxylated multi-walled carbon nanotubes (MWNT and MWNTCOOH). Viscosity measurements show that adding 0.5 wt% of carbon nanotubes (CNTs) does not affect the molecular weight of PA6. Compared with pure PA6, the yield strength of PA6/CNTs composites loaded with 0.5 wt% CNTs is almost unchanged, and the tensile strength is increased slightly. Dynamic mechanical analysis (DMA) demonstrates that both the storage modulus (E′) and glass transition temperature (T_g) of the PA6/CNTs composites increase, particularly for PA6/MWNTCOOH, indicating there is some chemical bonding between PA6 and MWNTCOOH. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultra small-angle X-ray scattering (USAXS) show that MWNT and MWNTCOOH are well dispersed in PA6 matrix. Comparison of the USAXS data with a stiff-rod model and wormlike rod model reveals that the CNTs are quite flexible, regardless the degree of chemical modification. Due to the flexibility of CNTs, mechanical properties of the PA6/CNTs composites are marginally enhanced.     

炭黑对ASA/天然石墨复合材料的电磁屏蔽性能影响

通过熔融共混方法制备导电高分子复合材料丙烯腈-苯乙烯-丙烯酸酯共聚物(ASA)/天然石墨(NGR)/炭黑(CB),采用电磁屏蔽测量仪、四探针电阻率测量仪和动态热机械分析仪对复合材料的电性能和力学性能进行详细研究。结果表明,ASA/NGR复合材料的体积电阻率随着炭黑含量增加而增加;同时在30 MHz~1500 MHz范围内,复合材料的电磁屏蔽性能从28 dB提高到38 dB,符合商业要求。炭黑的加入大大改善了材料力学性能,弯曲强度从31 MPa增加到41 MPa;动态储能模量从4.6 GPa增加到14.5 GPa。     

Highly conductive and high-strength carbon nanotube film reinforced silicon carbide composites

Film formed by carbon nanotubes is usually called carbon nanotube film (CNT_f). In the present study, CNT_f fabricated by floating catalyst method was used to prepare CNT_f/SiC ceramic matrix composites by chemical vapor infiltration (CVI). Mechanical and electrical properties of the resulting CNT_f/SiC composites with different CVI cycles were investigated and discussed, and the results revealed that the CNT_f has a good adaptability to CVI method. Tensile test demonstrated an excellent mechanical performance of the composites with highest tensile strength of 646 MPa after 2 CVI cycles, and the strength has a decline after 3 CVI cycles for an excessively dense matrix. While, the elastic modulus of the composite increased with the CVI cycles and reached 301 GPa after 3 CVI cycles. Tensile fracture morphologies of the composites were analyzed by scanning electron microscope to study the performance change laws with the CVI cycles. With SiC ceramic matrix infiltrated into the CNT_f, enhanced electrical conductivity of the CNT_f/SiC composite compared to pure CNT_f was also obtained, from 368 S/cm to 588 S/cm. Conductivity of the SiC matrix with free carbon forming in the CVI process was considered as the reason.     

l-Phenylalanine amino acid functionalized multi walled carbon nanotube (MWCNT) as a reinforced filler for improving mechanical and morphological properties of poly(vinyl alcohol)/MWCNT composite

Carbon nanotube dispersion in polymer matrix is one of the most crucially important aspects in carbon nanotube/polymer composites. This paper is aimed to discuss the considerable improvement in dispersion of multi walled carbon nanotubes (MWNTs) in poly(vinyl alcohol) (PVA) matrix that was attained through bio-functionalization of MWCNTs. Initially, for getting better dispersion in water, pure MWCNTs have been functionalized by l-phenylalanine amino acid. The functionalized MWCNTs (f-MWCNTs) show much enhanced solubility in water. So, effects of modified MWCNT on dispersion in PVA matrix and certain properties of the resulting composites, like; mechanical, thermal and morphological properties were studied. The prepared composites were examined by Fourier transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy. Also, the mechanical and thermal properties of composite films have been investigated and revealed that incorporation of just a few percent of f-MWCNTs can improve the PVA mechanical and thermal properties significantly.     

Microstructure and elastic properties of individual components of C/C composites

Carbon fiber reinforced carbon matrix (C/C) composites are often used for structural and frictional applications at a wide range of temperatures due to their excellent mechanical and thermal properties. Tailoring of mechanical properties through optimization of microstructure is critical for achieving maximum composite performance. This article addresses the evolution of the fiber and matrix microstructure and related nano-mechanical properties in two different C/C composites after being subjected to heat treatment at temperatures between 1800 and 2400 °C. Microstructure and corresponding nano-mechanical properties of C/C composites were studied using Polarized Light Microscopy (PLM), High-Resolution Transmission Electron Microscopy (HRTEM) and nanoindentation techniques. Increased heat treatment temperature (HTT) led to formation of a better-organized microstructure of fiber and matrix and also to formation of thermal cracks. The elastic modulus of rough laminar CVI pyrocarbon decreased from 18 to 12 GPa with increased HTT. In contrast, the isotropic CVI pyrocarbon and charred resin matrix displayed only a slight change of elastic modulus. The elastic modulus of PAN fiber increased from 18 to 34 GPa, indicating the development of a better-organized microstructure in the fiber-axial direction.     

聚氯乙烯/埃洛石纳米管复合材料的制备与性能研究

通过熔融混炼法制备了聚氯乙烯（PVC）/埃洛石纳米管（HNTs）复合材料,通过力学性能测试和扫描电子显微镜、透射电子显微镜等方法研究了HNTs含量对复合材料形貌与性能的影响,并分析了HNTs的作用机理。结果表明,HNTs可以对PVC产生增强增韧的作用;PVC/HNTs复合材料的储能模量和玻璃化转变温度相对纯PVC均有所增加;不同含量的HNTs在PVC基体中的分散性均较好且无大面积团聚的现象;HNTs与PVC间具有较强的界面作用力,其界面作用半经验参数（B）值为4.35。     

乌兰布和沙漠砂制备高延性水泥基复合材料的力学性能

使用内蒙古乌兰布和沙漠砂完全代替微石英砂配置了高延性水泥基复合材料(ECC),并以砂胶比为变量,对其抗压强度、抗拉强度、抗剪强度以及抗弯强度四个方面的力学性能展开了全面的研究。抗拉试验后进一步对纤维断面使用扫描电镜(SEM)进行了观测,并采用X射线衍射分析(XRD)方法研究了沙漠砂的物质组成。结果表明,以沙漠砂配置的ECC,在相同骨料含量的条件下,其抗压强度、抗拉强度、抗剪强度以及抗弯强度均与微石英砂配置的ECC接近,延性约为微石英砂ECC的一半。除抗剪强度外,沙漠砂ECC其他各项性能均随砂胶比增大而提高,优化配比设计的沙漠砂ECC延性能够达到微石英砂ECC的水平。     

Formation of a carbon fiber/polyhedral oligomeric silsesquioxane/carbon nanotube hybrid reinforcement and its effect on the interfacial properties of carbon fiber/epoxy composites

A carbon fiber/polyhedral oligomeric silsesquioxane/carbon nanotube (CF–POSS–CNT) hybrid reinforcement was prepared by grafting CNTs onto the carbon fiber surface using octaglycidyldimethylsilyl POSS as the linkage in an attempt to improve the interfacial properties between carbon fibers and an epoxy matrix. X-ray photoelectron spectroscopy, scanning electron microscopy, dynamic contact angle analysis and single fiber tensile testing were performed to characterize the hybrid reinforcements. Interlaminar shear strength (ILSS), impact toughness, dynamic mechanical analysis and force modulation atomic force microscopy were carried out to investigate the interfacial properties of the composites. Experimental results show that POSS and CNTs are grafted uniformly on the fiber surface and significantly increase the fiber surface roughness. The polar functional groups and surface energy of carbon fibers are obviously increased after the modification. Single fiber tensile testing results demonstrate that the functionalization does not lead to any discernable decrease in the fiber tensile strength. Mechanical property test results indicate the ILSS and impact toughness are enhanced. The storage modulus and service temperature increase by 11 GPa and 17 °C, respectively. POSS and CNTs effectively enhance the interfacial adhesion of the composites by improving resin wettability, increasing chemical bonding and mechanical interlocking.     

机械混炼制备碳纳米管/天然橡胶复合材料特性分析

通过机械混炼方法将碳纳米管与天然橡胶复合，与炭黑补强样品相比，碳纳米管在橡胶中的混入速度快，功率消耗低，温升幅度小，混炼胶的硫化焦烧时间略有增加，硫化返原现象减轻，硫化剂用量应适当增加。加入碳纳米管后，橡胶DSC曲线中的结晶熔融峰面积减少，交联反应放热峰变宽。碳纳米管复合材料的回弹、压缩疲劳性能明显优于炭黑补强样品，耐老化性能较好，拉伸、撕裂性能水平有待提高。     

In Situ Polymerized Poly(Amide Imide)/Multiwalled Carbon Nanotube Composite: Structural,Mechanical, and Electrical Studies

Poly(amide imide)/multiwalled carbon nanotube composites were in situ polymerized through Yamazaki–Higashi phosphorylation method, and the carboxylated multiwalled carbon nanotubes are added in the post-reaction stage. The good dispersion of multiwalled carbon nanotubes in the poly(amide imide) matrix was achieved even at 20?wt% nanotube loading. The electrical conductivity reached 33?S?m^?1; meanwhile, the tensile strength and Young’s modulus were 106MPa and 2.52?GPa, respectively. These excellent properties were contributed to the good dispersion of nanotubes and strong multiwalled carbon nanotubes–poly(amide imide) interfacial adhesions. We also demonstrate that the incorporation of multiwalled carbon nanotubes depressed the crystallization characteristics of poly(amide imide) but improve its thermal stability.     

Effects of fabrication processes on the properties of SiC/SiC composites

Precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI) were used to fabricate SiC/SiC composites on a four-step 3D SiC fibre preform deposited with a pyrolytic carbon interface. The effects of fabrication processes on the microstructure and mechanical properties of the SiC/SiC composites were studied. Results showed the presence of irregular cracks in the matrix of the SiC/SiC composites prepared through PIP, and the crystal structure was amorphous. The room temperature flexural strength and modulus were 873.62 MPa and 98.16 GPa, respectively. The matrix of the SiC/SiC composites prepared through CVI was tightly bonded without cracks, the crystal structure had high crystallinity, and the room temperature bending strength and modulus were 790.79 MPa and 150.32 GPa, respectively. After heat treatment at 1300 °C for 50 h, the flexural strength and modulus retention rate of the SiC/SiC composites prepared through PIP were 50.01% and 61.87%, and those of the composites prepared through CVI were 99.24% and 96.18%, respectively. The mechanism of the evolution of the mechanical properties after heat treatment was examined, and the analysis revealed that it was caused by the different fabrication processes of the SiC matrix. After heat treatment, the SiC crystallites prepared through PIP greatly increased, and the SiOxCy in the matrix decomposed to produce volatile gases SiO and/or CO, ultimately leading to an increase in the number of cracks and porosity in the material and a decrease in the material load-bearing capacity. However, the size of the SiC crystallites prepared through CVI hardly changed, the SiC matrix was tightly bonded without cracks, and the load-bearing capacity only slightly changed.     

Functionalization of multi-walled carbon nanotubes grafted with self-generated functional groups and their polyamide 6 composites

Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were applied in this study to demonstrate that multi-walled carbon nanotubes synthesized from ethanol flames (F-MWCNTs) inherently have functional groups on their surfaces. This finding clearly indicates that the covalent functionalization of carbon nanotubes can be achieved without oxidation as pretreatment. Thus, n-hexadecylamine functionalized F-MWCNTs (H-MWCNTs) can be synthesized simply, without disrupting the primary structures of the nanotubes. The melt-compounding method was used to fabricate polyamide 6/MWCNTs composites. Scanning electron microscope results confirmed that both F-MWCNTs and H-MWCNTs have much better nanoscopic dispersion in PA6 matrix than commercial MWCNTs, and the tensile strength, Young’s modulus, dynamic mechanical properties, and thermal behavior of their PA6 composites are considerably improved.     

Facile way to disperse single‐walled carbon nanotubes using a noncovalent method and their reinforcing effect in poly(methyl methacrylate) composites

In this work, a noncovalent method was used to functionalize and thereby disperse single‐walled carbon nanotubes (SWCNTs) in dimethylformamide with poly[methyl methacrylate‐co‐(fluorescein O‐acrylate)] as a surfactant, and then the resultant poly(methyl methacrylate) (PMMA)‐based nanocomposites were fabricated via solution casting. The dispersion level of carbon nanotubes in the solvent was investigated by means of scanning electron microscopy and atomic force microscopy. The results showed that carbon nanotubes were well wrapped by the surfactant, and small carbon nanotube bundles several nanometers or less in diameter and several micrometers in length were obtained. Both scanning electron microscopy and transmission electron microscopy confirmed the uniform dispersion of SWCNTs in the PMMA matrix. The mechanical properties of the composites were determined with a universal tension tester. The PMMA composite containing 2 wt % SWCNTs showed improved tensile properties versus neat PMMA, showing 56 and 30% enhancements of the tensile modulus and tensile stress, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009