Conductivity Of Composite Materials Research Articles

Vitrimer Nanocomposites for Highly Thermal Conducting Materials with Sustainability.

Vitrimers, as dynamic covalent network polymers, represent a groundbreaking advancement in materials science. They excel in their applications, such as advanced thermal-conductivity composite materials, providing a sustainable alternative to traditional polymers. The incorporation of vitrimers into composite fillers enhances alignment and heat passway broadly, resulting in superior thermal conductivity compared to conventional thermosetting polymers. Their dynamic exchange reactions enable straightforward reprocessing, fostering the easy reuse of damaged composite materials and opening possibilities for recycling both matrix and filler components. We review an overview of the present advancements in utilizing vitrimers for highly thermally conductive composite materials.

Enhanced thermal conductivity in boron nitride incorporated polyethylene/polymethyl methacrylate composites via double percolation structure

AbstractDue to the miniaturization, integration and multi‐functional development of contemporary electronic devices, there is a growing need for efficient thermal conductive composite materials. This study focuses on enhancing the dispersion of modified boron nitride (mBN) within a linear low‐density polyethylene (LLDPE) phase by incorporating LLDPE‐graft‐Aminomethylpyridine (LLDPE‐g‐Py) to non‐covalently modify BN. Additionally, polymethyl methacrylate (PMMA) and LLDPE polymers were introduced to create modified BN/LLDPE/PMMA (mBN/LLDPE/PMMA) composites with a double percolation structure. The co‐continuous structure of the polymer composites was observed by using scanning electron microscopy (SEM). By selectively locating the BN modified by LLDPE‐g‐Py within the LLDPE phase, the co‐continuous structure of the LLDPE/PMMA blend was upgraded to a double percolation structure. This double percolation structure establishes a dense and optimal heat transfer network within the polymer matrix. The thermal conductivity of the mBN/LLDPE/PMMA composite with BN loading of 40 wt% was significantly increased to 1.12 Wm−1 K−1, which was 350% higher than that of pure LLDPE, 38% higher than that of the BN/LLDPE composite, and 17% higher than that of the BN/LLDPE/PMMA composite. This study offers valuable insights into non‐covalent modification techniques for BN and the design of double percolation structures in thermal conductive polymer composites.Highlights The double percolation structure was successfully constructed by simple melt blending method with LLDPE and PMMA as matrix and BN as thermal conductive filler. The double percolation structure can significantly promote the efficiency of heat transfer inside the thermal conductive composites. A novel non‐covalent modifier LLDPE‐g‐Py was prepared to modify the surface of BN, and the selective localization of modified BN (mBN) in the LLDPE phase was realized.

Enhanced thermal and electrical conductivity in epoxy nanocomposites via liquid crystal-driven alignment of graphene

There is a lack of systematic research on the use of liquid crystal-modified graphene in the production of thermally conductive composites. In this work, we utilized covalent and non-covalent interactions between 4′-allyloxy-biphenyl-4-ol (AOBPO) and graphene oxide (GO), reduced graphene oxide (rGO), and high-temperature reduced graphene oxide (GNS) to improve the compatibility and dispersion of the fillers with the silicone-cycloaliphatic epoxy resin. The thermal conductivity of GNS-AOBPO composite material significantly increases when a shear force field is applied, even at a lower filler content of 7 wt%, reaching 0.828 W/(m·K), which is 1.8 times higher than that without the field. At 9 wt% filler content, the thermal conductivity further increases to 1.161 W/(m·K), which is 10 times higher than epoxy resin. Concurrently, the electrical resistivity decreased by half. This provides a method for preparing thermal conductive composite materials by inducing the orientation of graphene through the application of a shear force field.

Application of Plasma Surface Modification and Slide-ring Polymer Networks for Development of Thermally Conductive Composite Materials

Application of Plasma Surface Modification and Slide-ring Polymer Networks for Development of Thermally Conductive Composite Materials

Electro-Codeposition of Composite Materials for Enhanced Thermal and Electrical Properties

State of the art cryocoolers, high powered electronic systems, semiconductor backplanes, and space platforms require next generation high conductivity composite materials that can reduce product weight while improving performance. To meet this need, Faraday Technology with the help of Universities, National Labs, and industrial partners is developing a scalable electro-codeposition method to produce high conductivity hybrid graphene/copper composite materials. Specifically, this talk will highlight two activities ongoing at Faraday and demonstrate the feasibility of fabricating either composite or laminated graphene-copper hybrid foils or direct printed composite nanowires via a pulse electro-codeposition approach. These activities indicated these composite materials can achieve a greater than 50% reduction in sheet resistance, a ~50% increase in mechanical strain, and a 100% increase in thermal conductivity compared to Cu foils. We will also discuss the opportunity to produce a wide range of material shapes by enabling a direct print apparatus that combines x,y,z control methods with an electro-codeposition printhead. If successful we envision that method to print next generation composite materials like ‘covetics’ that have the potential to meet many of the electronics and space community’s needs by enabling in space structural repairs, fabrication of new electronic components or sensors, or be utilized as heat exchanger composite materials. Finally, this activity also identified commercial partners interested in integrating these next generation into high powered electronics like laser diodes or invertors for electric vehicles.Acknowledgements: Faraday Technology acknowledges the Department of Energy and NASA SBIR activities under Contract No. DE-SC0021676 (DOE Phase II) and 80NSSC22CA099 (NASA Phase II).

In-situ growing of helical carbon fibers on graphene for high-performance flexible strain sensor

Flexible strain sensors have broad applications in the field of human health monitoring. It is essential to design and manufacture sensors with high sensitivity and stability. The aim could be achieved by constructing multi-level interface structure with non ohmic contact in the flexible three-dimensional conductive network. In this paper, helical carbon fibers (HCF) were grown in situ on the surface of 2D sheet material graphene. The prepared composite conductive material GO/HCF has an excellent 3D structure, significantly enhancing the sensor's sensitivity. PDMS and NH4HCO3 encapsulated strain sensor (GO/HCF/N) has GF values of up to 622.8. Besides, the sensor exhibits unique sensing characteristics that other sensors do not have: under low strain conditions, the resistance of the sensor increases with the increase of deformation, and when the deformation exceeds a certain value, the resistance decreases instead. Therefore, GO/HCF/N sensor has a shallow detection limit (0.1 %) and works steadily after 1000 times tensile release cycles. This flexible strain sensor can quickly and accurately identify different human movements in human health monitoring.

Flexible Piezoresistive Polystyrene Composite Sensors Filled with Hollow 3D Graphitic Shells.

The objective of this research was to develop highly effective conductive polymer composite (CPC) materials for flexible piezoresistive sensors, utilizing hollow three-dimensional graphitic shells as a highly conductive particulate component. Polystyrene (PS), a cost-effective and robust polymer widely used in various applications such as household appliances, electronics, automotive parts, packaging, and thermal insulation materials, was chosen as the polymer matrix. The hollow spherical three-dimensional graphitic shells (GS) were synthesized through chemical vapor deposition (CVD) with magnesium oxide (MgO) nanoparticles serving as a support, which was removed post-synthesis and employed as the conductive filler. Commercial multi-walled carbon nanotubes (CNTs) were used as a reference one-dimensional graphene material. The main focus of this study was to investigate the impact of the GS on the piezoresistive response of carbon/polymer composite thin films. The distribution and arrangement of GS and CNTs in the polymer matrix were analyzed using techniques such as X-ray diffraction and scanning electron microscopy, while the electrical, thermal, and mechanical properties of the composites were also evaluated. The results revealed that the PS composite films filled with GS exhibited a more pronounced piezoresistive response as compared to the CNT-based composites, despite their lower mechanical and thermal performance.

Performance of thermally conductive NR composites reinforced with stearic acid‐modified microcrystalline cellulose: A combined experimental and molecular dynamic simulation study

AbstractWith the increasing environmental requirements for improving products and materials using renewable and sustainable resources, cellulose has been seen as one of the most attractive and promising alternatives to traditional inorganic fillers. We developed a new modification method to improve the interface compatibility between natural rubber and sisal cellulose, to improve the mechanical and thermal conductivity properties of rubber composite. Microcrystalline cellulose (MCC) was extracted from sisal cellulose and then the hydrophobic cellulose (SA‐MCC) was prepared by grafting stearic acid on the surface of MCC. MCC and SA‐MCC were added to the thermal conductivity composite material composed of natural rubber and boron nitride. The results showed that the thermal conductivity and tensile properties of the natural rubber composites increased by 17.3% and 20%, respectively, under the addition of 1.8 wt% SA‐MCC. Furthermore, the interfacial interaction between the components in the composite was studied by molecular dynamics simulation. The solubility parameters, free volume fraction, and molecular binding energy were calculated to verify the effectiveness of the modification. This work is expected to provide a theoretical basis for the design and preparation of high‐performance natural rubber composite materials.Highlights Cellulose microcrystals were successfully extracted from sisal fiber and modified. Through the combination of boron nitride and the modified cellulose microcrystals, the thermal conductivity and tensile properties of thermal rubber were successfully improved synchronously. A reasonable molecular simulation model was established to analysis the strengthening mechanism from the microscopic point of view. The molecular simulation conclusions on interface enhancement are in good agreement with the experimental properties.

Universal Approach to Integrating Reduced Graphene Oxide into Polymer Electronics.

Flexible electronics have sparked significant interest in the development of electrically conductive polymer-based composite materials. While efforts are being made to fabricate these composites through laser integration techniques, a versatile methodology applicable to a broad range of thermoplastic polymers remains elusive. Moreover, the underlying mechanisms driving the formation of such composites are not thoroughly understood. Addressing this knowledge gap, our research focuses on the core processes determining the integration of reduced graphene oxide (rGO) with polymers to engineer coatings that are not only flexible and robust but also exhibit electrical conductivity. Notably, we have identified a particular range of laser power densities (between 0.8 and 1.83 kW/cm2), which enables obtaining graphene polymer composite coatings for a large set of thermoplastic polymers. These laser parameters are primarily defined by the thermal properties of the polymers as confirmed by thermal analysis as well as numerical simulations. Scanning electron microscopy with elemental analysis and X-ray photoelectron spectroscopy showed that conductivity can be achieved by two mechanisms-rGO integration and polymer carbonization. Additionally, high-speed videos allowed us to capture the graphene oxide (GO) modification and melt pool formation during laser processing. The cross-sectional analysis of the laser-processed samples showed that the convective flows are present in the polymer substrate explaining the observed behavior. Moreover, the practical application of our research is exemplified through the successful assembly of a conductive wristband for wearable devices. Our study not only fills a critical knowledge gap but also offers a tangible illustration of the potential impact of laser-induced rGO-polymer integration in materials science and engineering applications.

Development of electrically conductive wood‐based composites using carbon nets

AbstractA novel conductive composite material was developed using woven carbon nets. For this purpose, carbon nets with different mesh sizes of 25, 100, 225, and 400 mm2 were woven, using two different carbon yarns with widths of 2 and 0.5 mm. The woven carbon nets were used before and after the core layer formation during mat forming of the particleboard. It was found that the insertion of carbon nets into the panel structure not only transforms insulated particleboard into a highly conductive composite but also significantly improves the flexural properties of the composite. However, the internal bond strength and physical properties of the composites were negatively affected by the presence of carbon nets in the panel structure, although their values were still above the minimum requirements of the standard values. Increasing the mesh area of the carbon nets and using thinner carbon yarns to weave the nets had a negative effect on the electrical and mechanical properties of the composites. In addition, a demonstration object was made of conductive composites to integrate lighting and a smartphone charging port into the object and prove the applicability of the developed composites for the furniture industry.Highlights Composites with carbon nets with smaller mesh area showed higher conductivity. The smaller the width of the carbon yarn, the higher the electrical resistance. The carbon net in the composites led to a decrease in internal bond strength. The carbon nets improved the flexural properties of the composites. Thickness swelling was significantly reduced by the use of carbon nets.

High-performance wearable flexible strain sensors based on an AgNWs/rGO/TPU electrospun nanofiber film for monitoring human activities

Abstract Wearable flexible strain sensors have attracted considerable attention in recent years, while it is still a significant challenge to fabricate wearable flexible strain sensors with high sensitivity and wide sensing range simultaneously. In this work, a high-performance wearable flexible strain sensor based on a thermoplastic polyurethane electrospun nanofibers (TPUNFs) film embedded with a silver nanowires/reduced graphene oxide (AgNWs/rGO) composite conductive material was fabricated via a simple drop-coating technique. The effect of the amount of AgNWs/rGO composite conductive material on the strain sensing range of the AgNWs/rGO/TPUNFs film flexible strain sensor was investigated, the strain sensing range of AgNWs/rGO/TPUNFs film flexible strain sensor was compared with that of the AgNWs/TPUNFs and GO/TPUNFs film flexible strain sensor, and the strain sensing properties of the AgNWs/rGO/TPUNFs film flexible strain sensor were measured. The results showed that the AgNWs/rGO/TPUNFs film flexible strain sensor with high sensitivity and wide sensing range simultaneously was achieved by compounding AgNWs and the reduced graphene oxide (rGO) conductive material. The strain sensing range of the AgNWs/rGO/TPUNFs film flexible strain sensor could be improved by increasing the amount of the AgNWs/rGO composite conductive material, and it was obviously better than that of AgNWs/TPUNFs and the rGO/TPUNFs film flexible strain sensor. The obtained AgNWs/rGO/TPUNFs film flexible strain sensor possessed high sensitivity (the gauge factor could reach a maximum of 2513.23.) as well as a wide sensing range (∼187%). Furthermore, the obtained AgNWs/rGO/TPUNFs film flexible strain sensor had a fast response/recovery time (200 ms/300 ms) and good cycling stability (∼3,000 cycles). Benefitting from the outstanding strain sensing performance, the AgNWs/rGO/TPUNFs film flexible strain sensor could detect large human motions such as finger, wrist, and knee bending as well as expression, which demonstrates great potential applications in wearable devices.

Synthesis and dynamic crosslinking of a hydroxyl-functionalized ethylene-propylene copolymer: Preparation of an elastomer with reprocessability and shape memory properties

The ternary copolymers of ethylene, propylene and 10-undecen-1-ol were prepared using a vanadium catalyst bearing an 8-anilide-5,6,7-trihydroquinoline ligand. By adjusting the concentration of 10-undecen-1-ol and polymerization temperature, the insertion rate of polar monomers was modulated with a maximum value of 3.8% achieved for 10-undecen-1-ol. With an increase in the hydroxyl insertion rate, the water contact angle of hydroxyfunctionalized ethylene-propylene copolymers decreased from 112.3° to 95.3°, indicating that the incorporation of 10-undecen-1-ol enhanced the hydrophilicity of the copolymers. Subsequently, a reprocessable ethylene-propylene rubber (EPR) with double dynamic bonds was synthesized through reaction between the hydroxyl group on functionalized ethylene-propylene copolymer and the crosslinking agent using isocyanate as chain end. The strength of functionalized ethylene-propylene copolymers was significantly improved through dynamic crosslinking. Significantly, the tensile strength of sample EP6-V-0.5 reached 14 MPa, which was 27 times higher than that of un-crosslinked EP6. The prepared functionalized ethylene-propylene rubber prepared exhibited not only reprocessability, but also remarkable shape memory and reshaping properties. Moreover, the conductive composite materials based on this rubber displayed great potential for application in motion sensors.

Spherical Shell with CNTs Network Structuring Fe-Based Alluaudite Na2+2 δ Fe2- δ (SO4 )3 Cathode and Novel Phase Transition Mechanism for Sodium-Ion Battery.

Iron-based sulfate cathodes of alluaudite Na2+2 δ Fe2- δ (SO4 )3 (NFS) in sodium-ion batteries with low cost, steady cycling performance, and high voltage are promising for grid-scale energy storage systems. However, the poor electronic conductivity and the limited understanding of the phase-evolution of precursors hinder obtaining high-rate capacity and the pure phase. Distinctive NFS@C@n%CNTs (n = 1, 2, 5, 10) sphere-shell conductive networks composite cathode materials are constructed creatively, which exhibit superior reversible capacity and rate performance. In detail, the designed NFS@C@2%CNTs cathode delivers an initial discharge capacity of 95.9 mAh g-1 at 0.05 C and up to 60 mAh g-1 at a high rate of 10 C. The full NFS@C@2%CNTs//HC cell delivers a practical operating voltage of 3.5V and mass-energy density of 140Wh kg-1 at 0.1 C, and it can also retain 67.37 mAh g-1 with a capacity retention rate of 96.4% after 200 cycles at 2 C. On the other hand, a novel combination reaction mechanism is first revealed for forming NFS from the mixtures of Na2 Fe(SO4 )2 ·nH2 O (n = 2, 4) and FeSO4 ·H2 O during the sintering process. The inspiring results would provide a novel perspective to synthesize high-performance alluaudite sulfate and analogs by aqueous methods.

High Antileakage and Thermal Conductivity Composite Phase-Change Material with Anisotropy Expanded Graphite for Battery Thermal Management

High Antileakage and Thermal Conductivity Composite Phase-Change Material with Anisotropy Expanded Graphite for Battery Thermal Management

Data-Driven Framework toward Accurate Prediction of Interfacial Thermal Resistance in Particulate-Filled Composites.

The interfacial thermal resistance (ITR) inside the particulate-filled polymer composite is a bottleneck for improving the thermal conductivity (TC) of the material. Getting full knowledge of the ITR is crucial to the material design as well as to a faithful prediction of TC of the composite. However, a method fully taking into account the local circumstances inside the composite is yet to be developed to precisely characterize the ITR. Here, we propose a comprehensive framework combining high-throughput numerical simulations, machine learning and optimization algorithms, and experiments, which is demonstrated to be robust for the accurate determination of ITRs inside the particulate-filled composites. The strategy extracts as much information as possible about the structure and heat transfer characteristics of the composite based on simple experiments, which lays the foundation for the method to be effective. We show that the polymer-filler ITRs and the effective filler-filler contact ITRs predicted with the method faithfully represent the true characteristics inside the composite materials; they also provide the exact effective parameters, which cannot be obtained from experiments, for accurate numerical prediction of TCs of composite materials with high efficiency. As a result, the framework not only provides a robust tool for accurate characterization of ITRs inside composites but also paves the way for virtual high-throughput formula screening of thermally conductive composite materials that could be used in industrial product design.

Experimental investigation on mitigation of thermal runaway propagation of lithium-ion battery module with flame retardant phase change materials

In the application of lithium-ion battery (LIB) modules, the pivotal factor in ensuring battery safety performance lies in enhancing thermal management effectiveness and adeptly curbing the thermal runaway propagation (TRP). This paper synthesizes the innovative type of high thermal conductivity composite phase change material (CPCM) and flame retardant phase change material (RPCM) with the inclusion of intumescent flame retardant (IFR). The structural and thermal attributes of these phase change materials (PCMs) are meticulously examined. The findings reveal that the RPCM, fortified with 10% SiC and 10% IFR, attains a peak thermal conductivity of 4.022 W/(m·K) and latent heat of 112.9 J/g. Diverse PCMs are then employed to scrutinize the thermal management of single cell and the mitigation of TRP in battery modules. The outcomes of charging and discharging cycles demonstrate that PCM cooling effectively curbs maximum temperature elevation. The most efficient PCMs reduce the maximum temperature by around 7.8 ℃ and 7.4 ℃. The impact of RPCMs and aerogel on curtailing TRP unveils that their amalgamation notably diminishes the risk of TRP and prolongs the propagation time. This research contributes a novel approach by exploring advanced PCMs potential to tackle heat dissipation optimization and TRP suppression for LIB modules simultaneously, and these findings proffer valuable information into enhancing battery operational safety.

Retracted: Application of Polypyrrole Cellulose Nanocrystalline Composite Conductive Material in Garment Design

Retracted: Application of Polypyrrole Cellulose Nanocrystalline Composite Conductive Material in Garment Design

Self-Assembled CNF/rGO/Tannin Composite: Study of the Physicochemical and Wound Healing Properties.

In this study, a conductive composite material, based on graphene oxide (GO), nanocellulose (CNF), and tannins (TA) from pine bark, reduced using polydopamine (PDA), was developed for wound dressing. The amount of CNF and TA was varied in the composite material, and a complete characterization including SEM, FTIR, XRD, XPS, and TGA was performed. Additionally, the conductivity, mechanical properties, cytotoxicity, and in vitro wound healing of the materials were evaluated. A successful physical interaction between CNF, TA, and GO was achieved. Increasing CNF amount in the composite reduced the thermal properties, surface charge, and conductivity, but its strength, cytotoxicity, and wound healing performance were improved. The TA incorporation slightly reduced the cell viability and migration, which may be associated with the doses used and the extract's chemical composition. However, the in-vitro-obtained results demonstrated that these composite materials can be suitable for wound healing.

3D Printed Supercapacitor Exploiting PEDOT-Based Resin and Polymer Gel Electrolyte.

Renewable energy-based technologies and increasing IoT (Internet of Things) objects population necessarily require proper energy storage devices to exist. In the view of customized and portable devices, Additive Manufacturing (AM) techniques offer the possibility to fabricate 2D to 3D features for functional applications. Among the different AM techniques extensively explored to produce energy storage devices, direct ink writing is one of the most investigated, despite the poor achievable resolution. Herein, we present the development and characterization of an innovative resin which can be employed in a micrometric precision stereolithography (SL) 3D printing process for the fabrication of a supercapacitor (SC). Poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive polymer, was mixed with poly(ethylene glycol) diacrylate (PEGDA), to get a printable and UV curable conductive composite material. The 3D printed electrodes were electrically and electrochemically investigated in an interdigitated device architecture. The electrical conductivity of the resin falls within the range of conductive polymers with 200 mS/cm and the 0.68 µWh/cm2 printed device energy density falls within the literature range.

Multifunctional composite foam with high strength and sound‐absorbing based on step assembly strategy for high performance electromagnetic shielding

AbstractSoft polyurethane (PU) materials exhibit excellent structural stability, sound absorption and heat insulation, and they can be used to prepare multifunctional conductive composites with electromagnetic interference (EMI) shielding function. On the basis of a multistep assembly strategy, our study constructed composite foams with sound absorption and EMI shielding properties by designing different functional layers and expanded the application field of PU foam. First, carbon black particles are compounded with PU foam to improve the mechanical properties and conductivity of pure foam. Then, an aluminum layer and a knitted fabric layer were introduced to construct composite foam samples with a sandwich structure, endowing the materials with excellent EMI shielding performance. The resultant composite foam material exhibits effective EMI shielding performance and good sound absorption performance, which are 58.33 dB and >0.3, respectively. Moreover, the composite foam material demonstrates high bursting strength and compression resistance, suggesting that it can be used under different conditions. The employment of the multistep assembly strategy provides PU foam with a flexible range of applications, offering an innovative approach for preparing multifunctional conductive composite materials.