Ceramic Matrix Nanocomposites

Effects of various carbon nanofillers on the thermal conductivity and energy storage properties of paraffin-based nanocomposite phase change materials

In industrial settings, thermoplastics are frequently employed as the base materials for composites and often enhanced with micron-sized additives such as glass fibers for improved performance. This study employed twin-screw extrusion as the processing method to compound a common thermoplastic – polycarbonate (PC) with one dimensional (1D) multi-walled carbon nanotubes (MWCNTs), carbon nanofibers (CNFs) and two dimensional (2D) graphene nanoplatelets (GNPs). In the PC matrix, GNPs were found to relatively uniformly dispersed, MWCNTs were seen to have two states of dispersion, and CNFs were much shortened with many defects caused by the extrusion. At 10.0 wt%, MWCNTs reduced the electrical resistivity of PC from 4.2 × 1015 to 4.6 × 107 Ω·cm, and GNPs improved the thermal conductivity from 0.13 to 0.38 W·m−1·K−1. GNPs, MWCNTs and CNFs at 1.0 wt% all improved the mechanical properties of PC, i.e. increments of 13.8%, 5.7% and 13.8% for Young's modulus, 6.2%, 11.7% and 21.2% for tensile strength, and 9.6%, 10.2% and 5.7% for impact strength. At 10.0 wt%, the PC/GNP nanocomposite displayed the least reduction of tensile strength of PC whilst the PC/CNF nanocomposite slightly increased the un-notched Charpy impact strength from 161 to 186 kJ/m2. The structure-property relationship of these nanocompsoites was analysed, with the relavent mechanisms proposed. Overall, twin-screw extrusion proved effective for dispersing various carbon nanomaterials in PC. This work provides a guide for industry to design and manufacture thermoplastic/carbon nanomaterial composites using the extrusion method.

The one‐dimensional (1D) carbon nanotubes (CNTs) and two‐dimensional (2D) graphene nanoplatelets (GNPs) were adopted to enhance the thermal conductivity (K) of polymer‐bonded explosives (PBX). Seven 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB)‐based PBX formulations without or with 1.31 vf % carbon materials were designed and fabricated. The results indicated that, the K was only slightly improved by pure GNPs or CNTs. However, a remarkable synergetic effect between GNPs and CNTs in improving the K of PBX was demonstrated. The K of PBX with hybrid GNPs and CNTs was obviously higher than that of PBX with pure GNPs or CNTs. The bridging interactions between GNPs and CNTs could lead to the formation of a more efficient 3D percolating network. Moreover, the presence of CNTs triggered the percolation effect in the GNPs as the enhanced K was more pronounced with increasing GNPs. Additionally, the nonlinear dependence of the K of PBX on GNPs content was fitted by an analytical model which incorporated the percolation effect. The theoretical results were found to be in reasonably good agreement with the experimental data. Finally, the thermal shock resistance of PBX with hybrid CNT/GNP was significantly enhanced. POLYM. COMPOS., 39:E1452–E1462, 2018. © 2017 Society of Plastics Engineers

Enhanced antimicrobial activity of Cu-decorated graphene nanoplatelets and carbon nanotubes

The role of the geometry of nanofillers on the mechanical properties of polymer nanocomposites, such as Young's modulus and toughness, has been reviewed based on published data in the literature. The fillers considered include carbon black (CB), carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), reinforcing either elastomers or epoxy resins that act respectively as examples of flexible and rigid polymers. The Young's modulus of nanocomposites reinforced by CB is revealed to follow the classical theories on particulate reinforcement. The Young's modulus of nanocomposites reinforced by GNPs and CNTs are analysed using composite micromechanics theories, i.e. a combination of the shear lag theory and rule of mixtures. A surprising finding is that if the Young's modulus of the nanofillers is considerably higher than that of the matrix, the Young's modulus of the nanocomposite is only dependent on the aspect ratio, volume fraction and orientation of the nanofiller, and is independent of its mechanical properties. The failure of the nanocomposites by crack propagation is analysed regarding the fracture toughness of the epoxy nanocomposites and the tear strength of elastomer nanocomposites. The addition of nanoparticles is found to improve the crack resistance through crack pinning whereby the crack front length increases by pinning at individual particles. It is revealed that the tear strength of the elastomer nanocomposites and the fracture toughness of the epoxy nanocomposites filled with either GNPs or CNTs is dominated by the pull-out of nanoparticles, while for elastomers other toughening mechanisms may also occur, such as cavitation.

Prediction of piezoresistive sensitivity and percolation probability of synergetic CNT-GNP conductive network composite

Synergetic effects of carbon nanotube and graphene addition on thermo-mechanical properties and vibrational behavior of twill carbon fiber reinforced polymer composites

Characterization and micro end milling of graphene nano platelet and carbon nanotube filled nanocomposites

Microstructure and fracture toughness of SiAlCN ceramics toughened by SiCw or GNPs

This paper provides a highly detailed experimental and predictive exploration of how to enhance flexural strength of polymer composites with the technique of bi-reinforced graphene nanoplatelets (GNP) and carbon nanotubes (CNT). One hundred and fifty hybrid combinations based on varying GNP (0-1 wt.%) and CNT (0-0.4 wt.%) contents were developed and prepared accordingly to determine the effects of hybrid fillers in flexural performance. Experimental findings showed that the un-reinforced baseline sample (0% GNP, 0% CNT) had flexural strength 68.90 MPa, whereas the strongest sample was recorded with 1% GNP and 0.3% CNT (120.20 MPa) which is an increment of 74.44 % as compared to the un-reinforced sample. Simultaneously, a regression model in the form of machine learning was trained to estimate the values of the flexural strength based on the filler contents as the input variables. The model proved very reliable with the highest strength being predicted as 100.85 MPa at the same optimum hybrid proportion, and lowest values of absolute and percent error in all specimens tested. The results of the model produced reasonably accurate results as compared to experimental data having R 2 values greater than 0.96, and an exclusively overlaying of predicted points on the 95 percent confidence interval.

Underwater sound absorption materials with broadband and resistance to high pressure are crucial for noise control in the ocean. Herein a new method is presented to synergistically improve material's resistance to high pressure with broadband by hybridizing carbon nanotubes (CNTs) with graphene nanoplatelets (GNPs) in polydimethylsiloxane (PDMS) matrix. The micro‐structure shows the geometrical synergy between the nanoplatelets (GNPs) and nanotubes (MWCNT‐COOH). Besides, GNPs also form junctions with air micro‐voids. The underwater acoustic tests reveal that, compared with equivalent nanocomposites containing only CNTs or GNPs, the hybridized materials show significantly better sound absorption performance with a high hydrostatic pressure increased from 0.4 MPa to 1.0 MPa at the frequency range of 1500 Hz to 7000 Hz. Therefore, the hybridization of one‐dimensional (1D) and two‐dimensional (2D) nano‐carbon materials provides a new route for increasing the underwater sound absorption performance at high hydrostatic pressure.

The synergetic effect of adding multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) on the thermomechanical properties and electric resistance of epoxy polymers were experimentally analyzed in this study. The total content of two employed carbon fillers were kept constant at 0.4 wt %, and seven filler ratios between two fillers (MWCNTs:GNPs), i.e., 10:0, 1:9, 3:7, 5:5, 7:3, 9:1, and 0:10, were considered in the experimental program to investigate the influences of employed nano-filler ratios on the viscoelastic and electrical properties of the studied nanocomposites. The thermomechanical properties and the sheet resistance of the nanocomposites were analyzed using a dynamic mechanical analyzer and four-point probe, respectively. Moreover, the thermogravimetric analyzer was utilized to measure the pyrolysis temperature of the nanocomposites. Experimental results show that the synergistic effect of adding two nano-fillers were clear for the improvement of the storage moduli, glass transition temperatures, and electric conductivity. Oppositely, the employment of two fillers has a slight effect on the pyrolysis temperatures of the studied nanocomposites. The composites with the MWCNT:GNP ratio of 1:9 display the most apparent enhancement of the thermomechanical properties. The improvement results from the uniform distribution and the high aspect ratio of GNPs. The addition of a small amount of MWCNTs provides more linkage in the matrix. Moreover, the specimens with the MWCNT:GNP ratio of 1:9 shows remarkable electrical properties, which result from the large contact surface areas of GNPs with each other. The employment of few MWCNTs plays an important bridging role between the layered GNPs.

In the present study, attempts were made to manufacture innovative conducting polymer nanocomposites (CPCs) with high performance, low cost, and appropriate electrical, mechanical, and thermal properties. However, one of the main challenges in creating CPCs is the tendency of nanofillers to agglomerate and accumulate, resulting in a decrease in the electrical properties and performance of CPCs. To address this issue, the study developed an efficient and eco‐friendly CPC using carboxymethyl cellulose (CMC) as a binder and carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) as nanofillers. The study employed a chemical functionalization method to modify CNTs and enhance their compatibility and dispersion properties in the CMC matrix. The prepared CPCs were characterized using various techniques, including Fourier‐transform infrared spectroscopy, x‐ray diffraction, and field emission scanning electron microscopy. The results showed an improvement in homogeneity and surface cohesion between CMC and O‐CNTs through chemical surface modification of CNTs via carboxylic acid functional groups. The study observed good dispersion of nanofillers without any aggregation of the CMC/GNP/O‐CNT compared with the nontreated CMC/GNP/CNT composite. While a decrease in the degree of crystallinity was observed, conductivity increased for the CPC containing oxidized CNTs. The study found that the highest conductivity of ~112 S/m was obtained for D‐CMC/GNP/O‐CNT with 25 wt% of O‐CNT, while the maximum conductivity of D‐CMC/GNP/CNT was ~80 S/m with 35 wt% of CNTs. Additionally, the study observed an improvement in electrochemical properties after treatment of CNTs in the form of higher cathodic current in cyclic voltammetry and lower charge transfer resistance in impedance spectroscopy of D‐CMC/GNP/O‐CNT35 compared to untreated one. Highlights Preparation of new conductive nanocomposite consisting of CMC, CNTs, and GNPs. Carboxylation of CNTs to improve O‐CNT and CMC intermolecular interaction CMC/GNP/O‐CNT is 40% more conductive than unmodified CNT nanocomposite. Higher thermal stability and mechanical properties were observed by using O‐CNT. O‐CNT caused higher current density and lower electron transfer resistance for CPCs.

An improved three-dimensional percolation model taking into account the random dispersion of nanofillers in a polymer matrix has been developed in order to study the effect of the nanofiller shape and aspect ratio (AR) on the electrical percolation behavior characteristic of nanocomposites. In this new model, two nanofillers of different shape and AR have been considered separately—carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs)—while hybrid systems with different relative ratio of the fillers and various AR have also been investigated. The numerical model is able to predict the electrical percolation threshold assuming a perfect random dispersion and orientation of the nanofillers, while tunneling effects are also accounted for, resulting in a percolation volume of 0.023 and 1.628 vol% for CNTs and GNPs nanocomposites, respectively, showing a quantitative agreement with existing experimental observations. The percolation volume was found to decrease with the AR of CNT and GNP according to different relationships. Hybrid systems incorporating CNTs and GNPs exhibited significant synergistic effects when the two fillers were properly combined. The numerical predictions confirm the applicability of the model to predict the percolation behavior and percolating network morphology by indicating the probability of contact patterns between same and different elements.

Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) have attracted significant interest as hybrid reinforcements in epoxy (Ep) composites for enhancing mechanical performance in structural applications, such as aerospace and automotive. These 1D and 2D nanofillers possess exceptionally high aspect ratios and intrinsic mechanical properties, substantially improving composite stiffness and tensile strength. In this study, epoxy nanocomposites were fabricated with 0.1 wt.% and 0.3 wt.% of CNTs and GNPs individually, and with 1:1 CNT:GNP hybrid fillers at equivalent total loadings. Scanning electron microscopy of fracture surfaces confirmed that the CNTGNP hybrids dispersed uniformly, forming an interconnected nanostructured network. Notably, the 0.3 wt.% CNTGNP hybrid system exhibited minimal agglomeration and voids, preventing crack initiation and propagation. Mechanical testing revealed that the 0.3 wt.% CNTGNP/Ep composite achieved the highest tensile strength of approximately 84.5 MPa while maintaining a well-balanced stiffness profile (elastic modulus ≈ 4.62 GPa). The hybrid composite outperformed both due to its synergistic reinforcement mechanisms and superior dispersion despite containing only half the concentration of each nanofiller relative to the individual 0.3 wt.% CNT or GNP systems. In addition to mechanical performance, electrical conductivity analysis revealed that the 0.3 wt.% CNTGNP hybrid composite exhibited the highest conductivity of 0.025 S/m, surpassing the 0.3 wt.% CNT-only system (0.022 S/m), owing to forming a well-connected three-dimensional conductive network. The 0.1 wt.% CNT-only composite also showed enhanced conductivity (0.0004 S/m) due to better dispersion at lower filler loadings. These results highlight the dominant role of CNTs in charge transport and the effectiveness of hybrid networks in minimizing agglomeration. These findings demonstrate that CNTGNP hybrid fillers can deliver optimally balanced mechanical enhancement in epoxy matrices, offering a promising route for designing lightweight, high-performance structural composites. Further optimization of nanofiller dispersion and interfacial chemistry may yield even greater improvements.