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1.
《Journal of the European Ceramic Society》2017,37(15):4821-4831
Alumina – MWCNTs composites were prepared using a novel approach. This process comprises functionalization of MWCNTs and stabilization of alumina-MWCNTs dispersion with subsequent freezing, which resulted in formation of granulated powders with homogeneous distribution of MWCNTs. The granulated powders were sintered by rapid hot pressing (RHP) at 1550 °C. Relative densities, microstructural analysis, tribological properties, fracture toughness and bending strength of prepared composites were investigated to reveal the effect of MWCNTs. Compared to pure alumina, bending strength and fracture toughness of dense alumina-5 vol.% MWCNTs composites decreased about 37% and 18%, respectively. At higher MWCNT contents, strength remained almost constant and fracture toughness slightly increased. Thus, the positive effect of CNTs on fracture toughness was demonstrated despite their counteracting effect on the refinement of the microstructure. 相似文献
2.
J. Echeberria N. Rodríguez J. Vleugels K. Vanmeensel A. Reyes-Rojas A. Garcia-Reyes C. Domínguez-Rios A. Aguilar-Elguézabal M.H. Bocanegra-Bernal 《Carbon》2012,50(2):706-717
It is demonstrated that 0.1 wt% of multi-walled carbon nanotubes (MWCNTs) or single-walled carbon nanotubes (SWCNTs) added to zirconia toughened alumina (ZTA) composites is enough to obtain high hardness and fracture toughness at indentation loads of 1, 5, and 10 kg. ZTA composites with 0.01 and 0.1 wt% of MWCNTs or SWCNTs were densified by spark plasma sintering (SPS) at 1520 °C resulting in a higher hardness and comparable fracture toughness to the ZTA matrix material. The observed toughening mechanisms include crack deflection, pullout of CNTs as well as bridged cracks leading to improved fracture toughness without evidence of transformation toughening of the ZrO2 phase. Scanning electron microscopy showed that MWCNTs rupture by a sword-in-sheath mechanism in the tensile direction contributing to an additional increase in fracture toughness. 相似文献
3.
Rheological properties and fracture toughness of epoxy resin/multi‐walled carbon nanotube composites 下载免费PDF全文
Multi‐walled carbon nanotubes (MWCNTs), surface‐treated via chemical functionalization, i.e., oxidation and amidation, were used to reinforce diglycidylether of bisphenol F (DGEBF) epoxy resin. The effects of the functionalization on the dispersion stability, rheological properties, and fracture toughness of DGEBF/MWCNT composites were investigated. The dispersion homogeneity of the MWCNTs in the epoxy matrix improved after functionalization. In addition, isothermal rheology measurements revealed that the DGEBF/dodecyl amine‐functionalized MWCNT (D‐MWCNT) composite had a longer gel time and higher activation energy of cross‐linking than the DGEBF/acid‐treated MWCNT (A‐MWCNT) composite. The fracture toughness of the former was also significantly higher than that of the latter; this resulted from the relatively high dispersion stability of the D‐MWCNTs in the epoxy matrix, owing to the presence of alkyl groups on the D‐MWCNT surface. POLYM. ENG. SCI., 55:2676–2682, 2015. © 2015 Society of Plastics Engineers 相似文献
4.
《Journal of the European Ceramic Society》2014,34(7):1845-1851
Alumina–carbon nanotubes composites were studied with respect to obtain the homogeneous distribution of nanotubes within the alumina matrix. Disaggregation and uniform dispersion of carbon nanotubes in alumina matrix are crucial requirements for improvement fracture toughness and also electrical conductivity of these composites. New approach comprises functionalisation MWCNTs by acid treatment, stabilisation of alumina/MWCNT dispersion with subsequent freezing has been used, which resulted in formation of granulated homogenous mixture. The ceramic composites were prepared by hot pressing at 1550 °C using these mixtures. Microstructural analysis as well as electrical conductivity measurements has been used for observation of distribution of nanotubes within composites. Electrical conductivity, as an indicator of homogeneity of conductive network distribution, increases from 6 to 1140 S/m when compared the conventional process and approach presented in this work at the same volume fraction of MWCNTs 10 vol.%. 相似文献
5.
Failure investigation of carbon nanotube/3Y-TZP nanocomposites 总被引:1,自引:0,他引:1
Jing Sun Lian Gao Mikio Iwasa Tadachika Nakayama Koichi Niihara 《Ceramics International》2005,31(8):1131-1134
3Y-TZP matrix composites containing 0.1–1 wt.% of multi-wall (MWCNT) and single-wall (SWCNT) carbon nanotubes were fabricated by spark plasma sintering technique. The sintered composites reached full density. Hardness and fracture toughness were measured using Vickers indention method. The hardness of the composite decreased with increasing weight content of the MWNT. The fracture toughness was 5.52 MPa m0.5 when the amount of MWCNTs was 0.5 wt.%, however it decreased to 4.5 MPa m0.5 when the content was raised to 1.0 wt.%. The composite containing 0.5 wt.% SWCNTs showed similar fracture toughness as that of matrix. The incorporation of CNTs into 3Y-TZP matrix led to no prominent improvement on the mechanical properties. The failure mechanism was analyzed finally. 相似文献
6.
M.H. Bocanegra-Bernal J. Echeberria J. Ollo A. Garcia-Reyes C. Domínguez-Rios A. Reyes-Rojas A. Aguilar-Elguezabal 《Carbon》2011,49(5):1599-1607
The use of multi-wall carbon nanotubes (MWCNTs) or single-wall carbon nanotubes (SWCNTs) as filler in ceramic matrices could create composites with exceptional mechanical properties. We have prepared dense monolithic alumina (Al2O3) and zirconia-toughened alumina (ZTA) composites with additions of 0.01 wt% of MWCNTs or 0.01 wt% of SWCNTs by conventional sintering and have demonstrated that the mechanical properties depend on (a) the distribution of CNTs in the matrix and (b) the interaction between the ceramic phases and CNTs. The fracture toughness of Al2O3 ceramics reinforced with SWCNTs was significantly better than those reinforced with MWCNTs. However, fracture toughness in MWCNT-reinforced ZTA increased 41% over ZTA free of the toughening agent and 44% over ZTA reinforced with SWCNTs. A well dispersed and small amount of MWCNTs was enough to produce an increase of fracture toughness in ZTA composites. 相似文献
7.
We present a simple, out-of-autoclave approach to improve the delamination toughness of fiber-reinforced composites using epoxy interlayers containing 20 wt.% polyamide-12 (PA) particles and 1 wt.% multi-walled carbon nanotubes (MWCNTs). Composites were prepared by integrating partially cured thin films at the laminate mid-plane using vacuum-assisted resin transfer molding. The introduction of epoxy/PA interlayers increased fracture toughness due to the ductile deformation and crack bridging of PA particles within an interlaminar damage zone with uniform thickness of about 20 μm. Composites interlayered with epoxy/PA/MWCNT exhibited nearly 2.5 and 1.5 times higher fracture toughness than composites containing neat epoxy and epoxy/PA interlayers, respectively, without an observable increase in interlaminar thickness. The fracture surface was analyzed to identify failure modes responsible for the fracture toughness improvement. The MWCNTs are proposed to inhibit critical loading of defects by minimizing stress concentration within the interlaminar region, thereby enabling greater deformation of the PA particles during fracture. 相似文献
8.
《Journal of the European Ceramic Society》2014,34(14):3329-3337
Multi-walled carbon nanotubes (MWCNTs) are often reported as additives improving mechanical and functional properties of ceramic composites. However, despite tremendous efforts in the field in the past 20 years, the results are still inconclusive. This paper studies room temperature properties of the composites with polycrystalline alumina matrix reinforced with 0.5–2 vol.% MWCNTs (composites AC) and zirconia toughened alumina with 5 vol.% of yttria partially stabilised zirconia (3Y-PSZ) containing 0.5–2 vol.% of MWCNTs (composites AZC). Dense composites were prepared through wet mixing of the respective powders with functionalised MWCNTs, followed by freeze granulation, and hot-pressing of granulated powders. Room temperature bending strength, Young's modulus, indentation fracture toughness, thermal and electrical conductivity of the composites were studied, and related to their composition and microstructure. Slight increase of Young's modulus, indentation fracture toughness, bending strength, and thermal conductivity was observed at the MWCNTs contents ≤1 vol.%. At higher MWCNTs contents the properties were impaired by agglomeration of the MWCNTs. The DC electrical conductivity increased with increasing volume fraction of the MWCNTs. 相似文献
9.
Supercritical carbon dioxide was employed as the solvent for the functionalization of multi-walled carbon nanotubes (MWCNTs) with an epoxy-capped silane. The silanization protocol was found to be a suitable green alternative to traditional routes that rely on organic solvents for grafting nearly monolayers of silane molecules onto the nanotube surfaces. The addition of silanized MWCNTs to a model epoxy markedly increased its Tg, and measurements of the network cooperativity length scale linked this change to a reduction in polymer segment mobility. Composites filled with low loading levels of both pristine and silanized MWCNTs exhibited significantly higher strain at break and toughness than the neat epoxy, and the greatest improvements were observed at low loading levels. SEM analysis of the composite fracture surfaces revealed that nanotube pullout was the primary failure mechanism in epoxy loaded with pristine MWCNTs while crack bridging predominated in composites containing silanized MWCNTs as the result of strong interfacial bonding with the matrix. The elevated Tg and toughness achieved with small additions of silanized MWCNTs promise to extend the engineering applications of the epoxy resin. 相似文献
10.
Tufail Mustafa Jilong Huang Jie Gao Peng Yan Yongping Liu Karla Hernandez Ruiz Shikuan Sun Jishi Du Yuchi Fan Wan Jiang 《Journal of the European Ceramic Society》2021,41(11):5541-5547
Although the strengthening and toughening effects on ceramic composites are expected to be maximized by alignment of multi-walled carbon nanotubes (MWCNTs) in matrices, this concept has been rarely realized in practice due to the lack of convenient processing strategy. Here, the alignment of MWCNTs in alumina composite can be readily obtained by using α-Al2O3 nanoplates as raw powder. With the assistance of vacuum filtration and pressure in sintering, the highly aligned MWCNTs in alumina matrix are formed in in-plane direction. Accordingly, the strength and toughness in 1.5 wt% MWCNTs/alumina composite are improved by 58 % and 66 % with respect to monolithic alumina, respectively. Transmission electron microscopy observation reveals that the MWCNTs under great compressive residual stress are mainly embedded inside the grains, leading to much stronger grain boundaries. Meanwhile, the toughening effect is mainly attributed to the highly energy dissipating bridging and pullout, owing to the very effective load transfer. 相似文献
11.
《Carbon》2014
Fracture properties of both carbon nanotube (CNT) and carbon nanoscroll (CNS) reinforced silicon (Si) matrix composites under tension are investigated by molecular dynamics simulations. It is found that either a single-wall CNT or a multi-wall one (MWCNT) will be pulled out if the length of the CNT is short, while brittle fracture of CNT will happen for a relatively long one. It is interesting to find that the “sword-in-sheath” fracture mode observed experimentally in a long MWCNT reinforced alumina matrix composite is verified well by our simulations. Furthermore, comparing to a CNT reinforced Si matrix composite, fracture toughness of a CNS reinforced one can be significantly enhanced by both the length and the layer of the CNS. Crack in CNS propagates along its circumference and moves inward layer by layer so that large parts of the fracture energy are dissipated. The results provide a direct understanding of the fracture strength observed experimentally and an insight for improving the fracture toughness of some novel composites. 相似文献
12.
The polypropylene‐grafted multiwalled carbon nanotubes (PP‐MWCNTs) were produced from the reaction of PP containing the hydroxyl groups and MWCNTs having 2‐bromoisobutyryl groups. The PP‐MWCNTs had a significantly rougher surface than the original MWCNTs. PP‐MWCNTs had PP layers of thickness 10–15 nm on the outer walls of the MWCNTs. PP/PP‐MWCNT composites and PP/MWCNT composites were prepared by solution mixing in o‐xylene. Unlike PP/MWCNT composites, PP‐MWCNTs were homogeneously dispersed in the PP matrix. As a consequence, the thermal stability and conductivity of PP/PP‐MWCNT composites were dramatically improved even if only 1 wt % of PP‐MWNTs was added to the PP matrix. The good miscibility of PP and PP‐MWCNTs plays a critical role in the formation of the homogeneous composites and leads the high thermal stability and conductivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
13.
《Carbon》2014
The fracture behaviors of graphene oxide (GO) and GO/multi-walled carbon nanotube (MWCNT) hybrid papers are studied in both quasi-static mode-I opening and mode-III tearing fracture. Large GO papers give rise to a higher energy release rate and tearing toughness than those made from small GO sheets: about 36% and 70% enhancements are shown for the large GO papers due to a more compact structure and better GO sheet alignment. Hybridization of GO papers with MWCNTs also improves these properties when up to 5 wt.% of MWCNTs is incorporated, attributed to the stronger GO interlayer bonds through π–π interactions with intercalated MWCNTs. Fracture surface examination indicates that cleavage failure prevails in mode-I fracture depending on the size of GO sheets: the unsorted and large GO papers fail mainly by brittle cleavage of GO sheets whereas small GO papers fail by combined brittle cleavage and minor pullout following debonding of GO bundles. In contrast, combination of cleavage and debonding failures is dominant in mode-III fracture of GO papers, regardless of GO size. The torn edges present typical characteristics of a saw-tooth wave with disordered oscillation where the large GO papers exhibit generally higher amplitude peaks than the small GO papers. 相似文献
14.
Nere Garmendia Isabel Santacruz Rodrigo Moreno Isabel Obieta 《Journal of the European Ceramic Society》2009,29(10):1939-1945
The addition of carbon nanotubes (CNTs) is expected to increase the fracture toughness of ceramic matrix composites, but an uniform dispersion of the nanotubes in the matrix is essential. This is a complex issue in aqueous medium because of the nanotubes hydrophobicity. In this work, the stability and rheological behaviour of nanozirconia concentrated suspensions, from 20 to 33 vol% solids, with and without multiwall carbon nanotubes (MWCNTs) was optimised in order to obtain homogeneous green samples by slip casting. The manufacture of nanozirconia/MWCNTs composites was performed using a heterocoagulation process in which the CNTs were homogeneously coated by the ceramic particles through strong electrostatic attractive forces between the two phases and further consolidation by a slip casting route. After sintering, the effect of the MWCNT on the hardness and fracture toughness of the nanostructured zirconia samples was evaluated. 相似文献
15.
《Ceramics International》2020,46(12):19723-19730
Multiwalled carbon nanotubes (MWCNTs) have been widely considered for mechanical reinforcement of ceramic matrix composites. Nevertheless, the efficiency of this reinforcement strategy is under debate due to fabrication issues, such as a good homogenization or the location of the MWCNTs inside the matrix composite. Regarding this, the intragranular location of the MWCNTs has been deemed a crucial feature for optimizing the reinforcement compared to the typical intergranular placement achieved by conventional procedures. Recently, the sol-gel method has been reconsidered, as it promotes the intragranular placement of the MWCNTs. This work presents the mechanical characterization of these composites synthesized by the sol-gel method, where crack-bridging has been revealed as toughening mechanism. Finally, the conventional use of the bibliographical Young's modulus of pure alumina for the estimation of the fracture toughness is discussed, obtaining significant improvements of the fracture toughness when indentation measurements are treated by considering elastic moduli obtained by nanoindentation. 相似文献
16.
Poly(ethylene terephthalate) (PET)/multiwalled carbon nanotube (MWCNT) composites were prepared by in situ polymerization. To improve the dispersion of MWCNTs in the PET matrix, functionalized MWCNTs having acid groups (acid‐MWCNTs) and acetic groups (acetic‐MWCNTs) on their surfaces were used. The functional groups were confirmed by infrared spectrometry. Scanning electron microscopy showed that acetic‐MWCNTs had a better dispersion in the PET matrix than pristine MWCNTs and acid‐MWCNTs. A reaction between PET and acetic‐MWCNTs was confirmed by a shift of the Raman G band to a higher frequency and an increase of the complex viscosity in the rheological properties. The composites containing functionalized MWCNTs showed a large increase in their tensile strengths and moduli. The values of the strengths and moduli of the PET/acetic‐MWCNT composites were higher than those of the PET/acid‐MWCNT composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
17.
Synergetic effects of graphene platelets and carbon nanotubes on the mechanical and thermal properties of epoxy composites 总被引:4,自引:0,他引:4
Shin-Yi Yang Wei-Ning Lin Yuan-Li Huang Hsi-Wen Tien Jeng-Yu Wang Chen-Chi M. Ma Shin-Ming Li Yu-Sheng Wang 《Carbon》2011,(3):793-803
A remarkable synergetic effect between the multi-graphene platelets (MGPs) and multi-walled carbon nanotubes (MWCNTs) in improving the mechanical properties and thermal conductivity of epoxy composites is demonstrated. Stacking of individual two-dimensional MGPs is effectively inhibited by introducing one-dimensional MWCNTs. Long and tortuous MWCNTs can bridge adjacent MGPs and inhibit their aggregation, resulting in a high contact area between the MGP/MWCNT structures and the polymer matrix. Scanning electron microscope images of the fracture surfaces of the epoxy matrix showed that MWCNT/MGP hybrid nanofillers exhibited higher solubility and better compatibility than individual MWCNTs and MGPs did. The tensile strength of GD400-MWCNT/MGP/epoxy composites was 35.4% higher than that of the epoxy alone, compared to only a 0.9% increase in tensile strength for MGP/epoxy composites over the epoxy compound. Thermal conductivity increased by 146.9% using GD400-MWCNT/MGP hybrid fillers and 23.9% for MGP fillers, compared to non-derivatised epoxy. 相似文献
18.
Ehsan Moaseri Behnaz Bazubandi Majid Baniadam Morteza Maghrebi 《Polymer Engineering and Science》2019,59(9):1905-1910
In this study, the effect of diamine molecular structure, attached to the multiwalled carbon nanotubes (MWCNTs), on the interfacial interactions of the MWCNTs and the epoxy matrix was studied. Pristine MWCNTs were successfully functionalized with multiple aliphatic and aromatic diamines. It has been found that, compared to aliphatic molecules, aromatic diamines can yield higher functionalization degree, due to higher activity and longer half‐life of aromatic intermediates. However, at the same functionalization degree, the aliphatic ligands were more successful in reacting with epoxy chains and forming covalent bonds between the MWCNTs and the matrix. Considerable improvements were achieved in the mechanical properties of functionalized MWCNT‐reinforced epoxy composites in comparison with the pristine MWCNT‐reinforced composites. Fractography observations revealed distinct differences in the failure modes of reinforced composites after functionalization of the MWCNTs with diamines. POLYM. ENG. SCI., 59:1905–1910, 2019. © 2019 Society of Plastics Engineers 相似文献
19.
Shinichi Kawasaki Masahiro Yamada Kana Kobori Fengzhe Jin Toshikazu Takata 《应用聚合物科学杂志》2010,118(5):2690-2695
The high compatibility of fluorene‐based polyester (FBP‐HX) as a polymer matrix for multiwalled carbon nanotubes (MWCNTs) is discussed. A low surface resistivity due to the fine dispersion of MWCNTs in FBP‐HX and polycarbonate (PC) is reported. With a solution‐casting method, a percolation threshold with the addition of between 0.5 and 1.0 wt % MWCNTs was observed in the MWCNT/PC and MWCNT/FBP‐HX composites. Because of the coverage of FBP‐HX on the MWCNTs, a higher surface resistivity and a higher percolation ratio of the MWCNT/FBP‐HX composites were achieved compared with the values for the MWCNT/PC composites. In the MWCNT/FBP‐HX composites, MWCNTs covered with FBP‐HX were observed by scanning electronic microscopy. Because of the coverage of FBP‐HX on the MWCNTs, FBP‐HX interfered with the electrical pathway between the MWCNTs. The MWCNTs in FBP‐HX were covered with a 5‐nm layer of FBP‐HX, but the MWCNTs in the MWCNT/PC composites were in their naked state. MWCNT/PC sheets demonstrated the specific Raman absorption of the MWCNTs only with the addition of MWCNTs of 1 wt % or above because of the coverage of the surface of the composite sheet by naked MWCNTs. In contrast, MWCNT/FBP‐HX retained the behavior of the matrix resin until a 3 wt % addition of MWCNTs was reached because of the coverage of MWCNTs by the FBP‐HX resin, induced by its high wettability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
20.
Strength and Toughness of Continuous-Alumina-Fiber-Reinforced Glass-Matrix Composites 总被引:1,自引:0,他引:1
Unidirectional, continuous-fiber composites were fabricated using polycrystalline alumina fibers and four different silicate glass matrices of differing thermal expansion. Fracture toughness measurements, strength measurements, and fractographic analysis of failed specimens are used to identify the failure mechanism. Results show that the elastic modulus mismatch between the matrix and the fibers shields the reinforcing fibers from matrix crack extension, thereby increasing composite toughness without fiber pullout. Fractographic analysis shows that fiber shielding leads to fiber failure ahead of matrix crack. Composite toughness increases linearly with increases in the residual compressive stress in the matrix phase. Ultimate composite strengths are dependent upon thermal-expansion-induced residual stresses and fiber strength. 相似文献