Smart Polymer/Carbon Nanotube Nanocomposites and Their Electrorheological Response.
Ontology highlight
ABSTRACT:
SUBMITTER: Zhang K
PROVIDER: S-EPMC5453228 | biostudies-other | 2014 Apr
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Carbon nanotubes (CNTs) are highly promising for strength reinforcement in polymer nanocomposites, but conflicting interfacial properties have been reported by single nanotube pull-out experiments. Here, we report the interfacial load transfer mechanisms during pull-out of CNTs from PMMA matrices, using massively- parallel molecular dynamics simulations. We show that the pull-out forces associated with non-bonded interactions between CNT and PMMA are generally small, and are weakly-dependent on the embedment length of the nanotube. These pull-out forces do not significantly increase with the presence of Stone Wales or vacancy defects along the nanotube. In contrast, low-density distribution of cross-links along the CNT-PMMA interface increases the pull-out forces by an order of magnitude. At each cross-linked site, mechanical unfolding and pull-out of single or pair polymer chain(s) attached to the individual cross-link bonds result in substantial interfacial strengthening and toughening, while contributing to interfacial slip between CNT and PMMA. Our interfacial shear-slip model shows that the interfacial loads are evenly-distributed among the finite number of cross-link bonds at low cross-link densities or for nanotubes with short embedment lengths. At higher cross-link densities or for nanotubes with longer embedment lengths, a no-slip zone now develops where shear-lag effects become important. Implications of these results, in the context of recent nanotube pull-out experiments, are discussed.
| S-EPMC6127397 | biostudies-literature
Project description:The interphase region around nanoparticles changes the percolation threshold of long and thin nanoparticles, such as carbon nanotubes (CNT) in polymer nanocomposites. In this paper, the effects of the interphase region on the percolation threshold of nanoparticles and the network fraction are studied. New percolation threshold (?P) is defined by the role of the interphase in the excluded volume of nanoparticles (Vex). Moreover, the influences of filler and interphase size on the percolation volume fraction, the fraction of nanoparticles in the network as well as the volume fraction and relative density of the filler network are investigated. The least ranges of "?P" are obtained by thin and long CNT. Similarly, a thick interphase increases the "Vex" parameter, which causes a positive role in the percolation occurrence. Also, thin CNT and a thick interphase cause the high fraction of the filler network in the nanocomposites.
| S-EPMC7022448 | biostudies-literature
Project description:A solid epoxy resin formulation containing 2.5 wt % carbon nanotubes is 3D printed into self-standing parts, which after thermal curing result in CNTs/epoxy nanocomposites with mechanical properties attractive for heavy-duty applications.
| S-EPMC7804968 | biostudies-literature
Project description:This work reports the nanocomposites of graphitic nanofibers (GNFs) and carbon nanotubes (CNTs) as the electrode material for supercapacitors. The hybrid CNTs/GNFs was prepared via a synthesis route that involved catalytic chemical vapor deposition (CVD) method. The structure and morphology of CNTs/GNFs can be precisely controlled by adjusting the flow rates of reactant gases. The nest shape entanglement of CNTs and GNFs which could not only have high conductivity to facilitate ion transmission, but could also increase surface area for more electrolyte ions access. When assembled in a symmetric two-electrode system, the CNTs/GNFs-based supercapacitor showed a very good cycling stability of 96% after 10 000 charge/discharge cycles. Moreover, CNTs/GNFs-based symmetric device can deliver a maximum specific energy of 72.2?Wh?kg-1 at a power density of 686.0?W?kg-1. The high performance of the hybrid performance can be attributed to the wheat like GNFs which provide sufficient accessible sites for charge storage, and the CNTs skeleton which provide channels for charge transport.
| S-EPMC5998012 | biostudies-literature
Project description:The strong structural integrity of polymer nanocomposite is influenced in the moist environment; but the fundamental mechanism is unclear, including the basis for the interactions between the absorbed water molecules and the structure, which prevents us from predicting the durability of its applications across multiple scales. In this research, a molecular dynamics model of the epoxy/single-walled carbon nanotube (SWCNT) nanocomposite is constructed to explore the mechanism of the moisture effect, and an analysis of the molecular interactions is provided by focusing on the hydrogen bond (H-bond) network inside the nanocomposite structure. The simulations show that at low moisture concentration, the water molecules affect the molecular interactions by favorably forming the water-nanocomposite H-bonds and the small cluster, while at high concentration the water molecules predominantly form the water-water H-bonds and the large cluster. The water molecules in the epoxy matrix and the epoxy-SWCNT interface disrupt the molecular interactions and deteriorate the mechanical properties. Through identifying the link between the water molecules and the nanocomposite structure and properties, it is shown that the free volume in the nanocomposite is crucial for its structural integrity, which facilitates the moisture accumulation and the distinct material deteriorations. This study provides insights into the moisture-affected structure and properties of the nanocomposite from the nanoscale perspective, which contributes to the understanding of the nanocomposite long-term performance under the moisture effect.
| S-EPMC5666489 | biostudies-literature
Project description:Bionic composites are an emerging class of materials produced exploiting living organisms as reactors to include synthetic functional materials in their native and highly performing structures. In this work, single wall carboxylated carbon nanotubes (SWCNT-COOH) were incorporated within the roots of living plants of Arabidopsis thaliana. This biogenic synthetic route produced a bionic composite material made of root components and SWCNT-COOH. The synthesis was possible exploiting the transport processes existing in the plant roots. Scanning electrochemical microscopy (SECM) measurements showed that SWCNT-COOH entered the vascular bundles of A. thaliana roots localizing within xylem vessels. SWCNT-COOH preserved their electrical properties when embedded inside the root matrix, both at a microscopic level and a macroscopic level, and did not significantly affect the mechanical properties of A. thaliana roots.
| S-EPMC7676904 | biostudies-literature
Project description:The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region.
| S-EPMC4180807 | biostudies-other
Project description:Recent advances in fabricating controlled-morphology vertically aligned carbon nanotubes (VA-CNTs) with ultrahigh volume fraction create unique opportunities for markedly improving the electromechanical performance of ionic polymer conductor network composite (IPCNC) actuators. Continuous paths through inter-VA-CNT channels allow fast ion transport, and high electrical conduction of the aligned CNTs in the composite electrodes lead to fast device actuation speed (>10% strain/second). One critical issue in developing advanced actuator materials is how to suppress the strain that does not contribute to the actuation (unwanted strain) thereby reducing actuation efficiency. Here our experiments demonstrate that the VA-CNTs give an anisotropic elastic response in the composite electrodes, which suppresses the unwanted strain and markedly enhances the actuation strain (>8% strain under 4 volts). The results reported here suggest pathways for optimizing the electrode morphology in IPCNCs using ultra-high volume fraction VA-CNTs to further enhanced performance.
| S-EPMC3134233 | biostudies-literature
Project description:Our work introduces a class of stimuli-responsive expanding polymer composites with the ability to unidirectionally transform their physical dimensions, elastic modulus, density, and electrical resistance. Carbon nanotubes and core-shell acrylic microspheres were dispersed in polydimethylsiloxane, resulting in composites that exhibit a binary set of material properties. Upon thermal or infrared stimuli, the liquid cores encapsulated within the microspheres vaporize, expanding the surrounding shells and stretching the matrix. The microsphere expansion results in visible dimensional changes, regions of reduced polymeric chain mobility, nanotube tensioning, and overall elastic to plastic-like transformation of the composite. Here, we show composite transformations including macroscopic volume expansion (>500%), density reduction (>80%), and elastic modulus increase (>675%). Additionally, conductive nanotubes allow for remote expansion monitoring and exhibit distinct loading-dependent electrical responses. With the ability to pattern regions of tailorable expansion, strength, and electrical resistance into a single polymer skin, these composites present opportunities as structural and electrical building blocks in smart systems.
| S-EPMC3697066 | biostudies-literature
Project description:It is well known the thermal properties of three-dimensional (3-D) hybrid graphene (GR)-carbon nanotube (CNT) structures are not superior to that of the individual GR and CNT, however, the 3-D hybrid GR-CNT structures can effectively improve the thermal properties of polymer matrix. Therefore, understanding the thermal energy transport in the interface between polymer matrix and 3-D hybrid GR-CNT structure is essential. Here, the enhancement mechanism of interfacial thermal transport of hybrid GR-CNT structure was explored by applying non-equilibrium molecular dynamics (NEMD) simulations. Three different types of hybrid GR-CNT structures were built. The influences of CNT radius and CNT type for the hybrid GR-CNT on the interfacial thermal properties were also analyzed. Computational results show that among the three different types of hybrid GR-CNT structures, the Model-I, i.e., the covalent bond hybrid GR-CNT structures are of the best interfacial thermal properties. Meanwhile, the CNT radius of hybrid GR-CNT structure has a great influence on the interfacial thermal properties.
| S-EPMC5666017 | biostudies-literature