Electrical Conductivity Of Composites Research Articles

Enhancement of ultimate tensile strength and ductility of copper matrix composites using a low content of single-wall carbon nanotubes

Single-wall carbon nanotube (SWCNT) reinforced copper (Cu) matrix composites were fabricated by a simple procedure of rotating mixing and then spark plasma sintering (SPS). It was found that addition of SWCNTs as low as 0.05 wt% can increase the ultimate tensile strength (223.5 MPa) and elongation rate (48.0%) of composites by 20.8% and 57.9%, respectively, relative to those (185 MPa and 30.4%) of pure Cu material, while the composite electrical conductivity retained a high value of 94.3% International Annealed Copper Standard (IACS). Mechanism analyses revealed that there are nanometer Ni particles tightly attached to SWCNTs, which were formed in situ during SWCNT growth by arc discharge method. These nanometer Ni particles promoted the bonding between SWCNTs and Cu matrix, leading to a fracture-mode change from intergranular in pure Cu material to ductile in the composites. The related factors to influence the microstructure of composites were discussed as well.

Self-assembly of MXene V2CTx/Ag/rGO layered multiscale structure nanocomposite

Two-dimensional MXene materials exhibit excellent performance in various fields, especially in fuel cells and energy storage due to their two-dimensional atomic thickness topology. However, the MXene material is prone to aggregation, and its defects such as collapse seriously affect its electrochemical performance and severely limit its range of application. In this paper, V2CTx + Ag + rGO composite electrode materials were prepared with classical hydrothermal method. The doping of Ag+ and rGO consumes the negative charge on the surface of V2CTx, prevents the delamination from collapse and stacking overlap, and accelerates the penetration of electrolyte ions. The entry of Ag particles and reduced graphene oxide can provide support sites for the layered structure, widen the interlayer spacing and provide a more active contact area for the electrolyte ions, thus opening up a green channel for ion transport. The entry of rGO plays a bridging role in making the contact between Ag particles, rGO and V2CTx closer and the cross-border transport of carriers more convenient. With the incorporation of rGO and Ag particles, the capacitance contribution rate of V2CTx + Ag + rGO composite can reach 63% while the transfer charge resistance is only 17.5 Ω, and the specific capacitance decreases very little with the increase of scanning time. The reason for this is that the rGO and Ag particles transform the original two-dimensional structure of V2CTx into a sandwich structure, which gives the V2CTx + Ag + rGO composite excellent electrical conductivity. The rGO and Ag particles synergize with each other to build an excellent conductive three-dimensional network that accelerates the transfer of ions and charges, resulting in excellent electrochemical performance of the V2CTx + Ag + rGO composite electrode material.

Stepwise percolation behavior induced by nano-interconnection in electrical conductivity of polymer composites

The electrical conductivity of polymer composites incorporating a continuous nanocarbon network is reported to be 1–2 logarithmic orders higher than that of the saturation region in a typical percolation model, indicating the existence of an undiscovered region. In this study, polymer composites with high filler content (∼50 vol%) are fabricated by powder mixing and in situ polymerization including sophisticated humidity control by promoting heat convection using an air fryer. Stepwise percolation behavior is observed, wherein the electrical conductivity of the composite with a high filler content exceeds that of the percolation plateau and further increases (3828% increase at 40 vol% multi-walled carbon nanotube (MWCNT) compared to 35 vol%), and the stepwise behavior is caused by the connected filler network (nano-interconnection). A novel stepwise percolation model that describes the behavior by considering both the tunneling resistance and the nano-interconnection is proposed. In addition, the stepwise percolation behavior induces high levels of electromagnetic interference shielding (236.36% increase at 50 vol% graphene nanoplatelet relative to 40 vol%) and humidity sensing (55.59% improvement at 40 vol% MWCNT compared to 35 vol%) properties. Therefore, derivation of the stepwise percolation behavior based on the nano-interconnection can be a new breakthrough in applications of conductive composites.

Groundwater-surface water interactions in a semi-arid irrigated agricultural valley: A hydrometric and tracer-aided approach

The purpose of this study was to assess hydrological controls (e.g., rainfall, irrigation practices, river discharge, dam operation, evaporation) on surface (SW)- ground water (GW) interactions in an irrigated valley within semi-arid Patagonia Argentina (−65.49 W, −43.29 S). We combined different sampling designs (watershed/sub-watershed scales, longitudinal and monthly samplings) from 2015 to 2019 to investigate the temporal and spatial variation of hydrometrics, electrical conductivity (EC) and stable isotope composition of surface and ground water. Results showed that plant transpiration in the upper basin, evaporation in the middle basin and the reservoir dynamics modified water salinity and left an imprint in stable isotopes. Water tables in the irrigated valley were high (0.5–2 m level from soil surface) and presented higher salinity than river water. Groundwater salinity, temporal variation of water table levels and stable isotopes suggested that groundwater is subjected to evaporation, is recharged from field seepage and, at a lesser extent, from local rainwater. River salinity increased downstream of the irrigated valley during the whole study period (3 years), showing the effects of agriculture and urbanization. EC also responded to the opening and closing of irrigation channels. EC and daily discharge statistical analysis revealed that groundwater recharge the stream below a threshold discharge of 26 m.s−1; with river salinity increasing linearly as daily discharge decrease. This study illustrates the deep modifications that agricultural systems, mainly surface irrigation, produce on semiarid watersheds. Given that SW and GW components are currently not isolated and flow regulation and irrigation practices are playing a critical role in soil quality and river chemistry at low flow conditions, a conjunctive water management strategy must be implemented in order to prevent further land and water quality degradation.

Conducting polymer encrusted Cu/Mn-MOF-CNDs: A facile synthesis, characterization and its hydrogen evolution activity in alkaline media and seawater

The Composites of polyaniline-bimetallic metal-organic framework with carbon nanodots (PANI/bi-MOF@CNDs) were fabricated by chemically oxidising aniline monomer for the hydrogen evolution process (HER). In this investigation, the composite structure, topography, and characteristics were analysed. The Fourier transform infrared spectroscopy analyses found evidence of electrostatic interaction between the CNDs@MOF and the backbone of the PANI matrix. Investigations using scanning electron microscopy and transmission electron microscopy showed that the CNDs@MOF exhibited uneven crystals with an additional enveloping PANI material. In an alkaline medium, the produced PANI composite (PANI/bi-MOF@CNDs) electrocatalyst showed a small overpotential and significant Tafel slope (110 mV and 180 mV/dec at 10 mA/cm2), as well as the RCT value of about 12.26 Ω, determined from Nyquist plot. PANI composite structural characteristics and electrical conductivity have also resulted in a faster rate of electron charge transfer and more accessible surface edge active sites. In addition, the catalyst is stable for 48 h at the specified operating conditions, and no further buffered electrolytes are required. As a result of the enhanced electrochemical performance, a strategic approach for the development of low-priced electrocatalysts for power conversion has been discovered.

Effect of the Type of a High-Temperature Polymer Matrix on the Morphology and Electrical Conductivity of Composites with SWCNTs

Effect of the Type of a High-Temperature Polymer Matrix on the Morphology and Electrical Conductivity of Composites with SWCNTs

Multidisciplinary Study of Mud Emissions Following the 2016 Norcia Earthquake

We report composition, grain size, and rheological data related to the mud emitted as a consequence of the maximum moment magnitude (Mw max = 6.5) on 30 October 2016, commonly referred to as the Norcia earthquake (central Italy), and on the activity of pre-existent mud volcanoes affected by the central Italy seismic sequence started on 24 August 2016. The emission sites were located at Monteleone di Fermo and Santa Vittoria in Matenano, two municipalities near the town of Fermo (Marche Region, Italy). We sampled, measured, and analyzed the products of mud emissions 3 days after the mainshock to characterize the mud by geochemical, mineralogical, and rheological analyses. The muds’ geochemical composition and low electrical conductivity suggest a continental origin, likely belonging to the Colombacci Formation. The collected muds are silt–sand–water-rich suspensions characterized by a Bigham rheology with viscosity values between 6.3∙107 and 6.9∙105 Pa∙s. The calculated minimum fluidization velocity of the mud suspensions is between 0.05 m/s (grain size of 2 μm) and 0.74 m/s (grain size of 8 μm). Water-rich mud suspensions flowing on a slope move faster as the water content increases up to 30 wt.%. At higher values, the velocity remains almost constant due to the disaggregation of bonds among the solid particles in the mixtures.

Prediction of Electrical Conductivity of Porous Composites Using a Simplified Monte Carlo 3D Equivalent Electronic Circuit Network Model: LSM-YSZ Case Study

Multiphase electric charge conductors composed of materials with various properties are widely utilized in both research and industrial applications. The composite materials include porous electrodes and other components mainly applied in fuel cell and battery technologies. In this study, a simplified Monte Carlo equivalent electronic circuit (EEC) network model is presented. In comparison to similar models, the present EEC network model allows an accurate prediction of the electrical properties of such materials, thus saving time-consuming experimental determination. The distinct feature of this EEC network model is that it requires only experimentally easily obtainable data as the input parameters: phase composition, porosity and bulk electrical conductivity of the individual constituents. During its run, the model generates a large number of artificial cubically shaped specimens based on random distribution of individual phases according to the input composition. Each of the specimens generated was modelled by a corresponding EEC network. The EEC networks were solved using Kirchhoff's laws, resulting in impedance response simulation for the prediction of composite conductivity values. The EEC network model was validated using lanthanum strontium manganite mixed with yttria-stabilized zirconia. Excellent agreement was obtained between the experimentally determined and the calculated electrical conductivity for sample porosities of 0 to 60 %. Due to its variability, the EEC network model can be suitable for a wide range of practical applications. The presented approach has high potential to save an enormous amount of experimental effort, while maintaining sufficient accuracy, when designing corresponding multiphase electrode structures.

Optimum features of wood-based biochars: A characterization study

Research on biochar is in current trend due to its vast applicability in various fields and has garnered everyone’s attention due to its unique physicochemical properties and surface structures. The favourable properties of biochar include its high surface area and porosity and ability to adsorb various compounds, including nutrients, organic contaminants, and some gases. Physical and chemical properties of biochars are dictated by the feedstock and process parameters such as pyrolysis or gasification temperature, conversion technology and pre- and post-treatment processes, if any, which vary widely across biochars produced from different biomasses. This study focuses on wood biomasses, neem and old furniture waste wood (a mixture of different woods), one natural and the other, waste, to characterise their physical and chemical properties that can signify their relevant environmental applications. Physical properties such as surface area, morphology and surface characteristics and chemical properties like organic matter and organic carbon contents, pH, and electrical conductivity, carbon, nitrogen and hydrogen (CHN) elemental composition have been analysed in this study. In addition, raw biomass analysis is also done to understand the behaviour of the biomass in producing biochar. Also, thermogravimetric analysis has been performed using three models to study the effect of process parameters on biochars. A wide range of fixed carbon (11.8–35.73%), volatile matter (58.25–82.17%), and ash contents (1.98–4.06%) were observed among tested biochars. The H/C ratio accounts for the aromaticity of the material and with temperature, the ratio decreases. Lower H/C ratios demonstrate increased aromaticity caused by pyrolysis and therefore indicate higher stability of the material than the initial feedstock. This study will pave the way for understanding the behaviour of wood biochar as a type and its efficiency as a material in utilisation as an adsorbent, in filter media, remediating water and soil amelioration.

Three-dimensional cage-like structured VOF@CNT composite material: In situ one-step synthesis and high-performance as the anode for lithium-ion batteries

Fabricating composites with three-dimensional (3D) nano-vanadium-based oxides and with carbon materials is one of the most effective ways to improve the performance of anode materials for lithium-ion batteries (LIBs). Herein, we firstly synthesized 3D V2O5 flowers (VOF) composed of interconnected ultrathin nanobelts through the surfactant-induced hydrothermal method, using vanadium pentoxide (V2O5) as vanadium source and carbon nanotubes as the carbon matrix. And then, the 3D VOF@CNT composite anode material was successfully prepared by in-situ bonding carbon nanotubes (CNT). Test results showed that the CNT can effectively inhibit the agglomeration of VOF nanoparticles, and thereby optimize the composite anode material's cycling stability and electrical conductivity. Meanwhile, as the carrier of lithium-ion (Li+), the VOF has a unique petal-like structure, which not only contributes to the Li+ diffusion and electron (e-) transport along the radial direction, but also provides sufficient space for the storage of Li+ and relieves the volume change of electrode during the cycle. Therefore, the composite electrode material still maintains at a high capacity of 417.7 mAh·g−1 after 200 cycles when the current density is 0.1 A·g−1. This work provides a method for preparing transition metal oxide electrode materials with great electrochemical performance and cycle stability.

Construction of three‐dimensional crumpled Ni‐Co TMOs for electrochemical energy storage

AbstractDue to excellent electrochemical performances, mixed transition metal oxides (TMOs) as electrode materials have attracted scholarly attention. However, the issues of volume expansion, unstable structure, and low electrical conductivity have limited their development for lithium battery (LIB). Drawing on the strategy of MOFs derivation synthesis combined with low temperature hydrothermal method, this study successfully synthesized the three‐dimensional (3D) NiCo2O4@Fe2O3 with a flower‐like crossing channel and a surface crumpled structure. As anode for LIBs, NiCo2O4@Fe2O3 exhibits more reliable performance than Ni−Co oxides. Our experiments verified that the Ni−Co composite electrical conductivity and cycling stability were both improved by the Fe2O3 coating. Under the high current density of 1000 mA g−1, the capacity decay rate of NiCo2O4@Fe2O3 tends to be stable after 60 cycles, and the capacity remains at 945 mAh g−1 after 400 cycles. Besides, the specific crossing porous‐channel structure mode improved the composite's carrier transport efficiency, and coulombic efficiency reached 100 % after 400 cycles. Noteworthy is the fact that the crumpled surface structure formed by the 2D Ni−Co nanosheets promotes the construction of heterostructures, further enhances the interface capacitance effect, and strengthens the rating capacity.

Synergistic Effect of Hybrid Carbon Fillers on the Thermal and Electrical Conductivity of Epdm Composites

Synergistic Effect of Hybrid Carbon Fillers on the Thermal and Electrical Conductivity of Epdm Composites

Impact of Carbon Nanotubes on the Mechanical and Electrical Properties of Silicone

Abstract This paper presents the results of a structure study of a dispersion composite on a silicone matrix with a filler in the form of multi-walled carbon nanotubes (MWCNTs). The study aims to determine the effect of the filler on the composite mechanical properties and electrical conductivity. Materials that are electrically conductive and exhibit high mechanical properties can find applications in high-strain sensors. During the study, the characteristic properties of the susceptible materials, silicone alone and silicone with different filler contents (4%, 6%, and 8% by weight), were determined after curing. Microscopic observations were performed to assess the influence of carbon fillers on the material structure and to determine the level of homogeneity of the material. Examination of mechanical properties facilitated the determination of the Shor A hardness (ShA), stiffness, and Poisson’s ratio of the cured composites, depending on the nanotubes’ content. In parallel with the study of mechanical properties, the effect of loading, and the associated deformation of the samples, on the conductivity of the composite was investigated. Based on the results obtained, a discussion was carried out on the type of conductivity characteristic of silicone with different filler content as well as depending on the level of deformation of the samples.

Application of geothermometric and hydrochemical methods to the investigation of thermal water of sources in the Northeastern of Algeria case of Setif city

Thermal water in northeastern Algeria (Setif) is a promising, sustainable resource of energy. To date, thermal water has not been used as a source of renewable energy in Algeria as no clear strategy has yet been developed for its use. In this study, eight samples of thermal water springs distributed within the area of Setif city were assessed, and their physical and chemical parameters (such as temperature, potential of hydrogen, electrical conductivity, and major ionic composition, including the K+, Na+, Ca2+, Mg2+, Cl−, SO42− and HCO3−) were measured. The results show that the temperature, potential of hydrogen and the electrical conductivity range between 30 and 52 °C (as measured in field), 6.92 and 7.35, and 1170 and 3160 µS/cm, respectively. Furthermore, the results indicate the existence of four hydrogeochemical facies dominating the hydrogeological system, which are SO4–Ca, Na–SO4, HCO3–Na and Cl–Na. The interaction with Jurassic limestone and the existence of evaporates along the upwelling system, respectively, control this. Due to the high variation of temperature, different geothermometers were used to estimate the geothermal reservoir temperature, the application of silica geothermometer (Quartz), because it is the most suitable in our case, gives temperatures estimated at the origin of the order of 80° C. It is higher than that measured at emergence, it reflects an average dissipation of 48° C. According to an analysis of these findings and the geothermal gradient in the area, two aquifer systems of the thermal complex are supplied by a reservoir that is stored in fissured Jurassic limestone that is more than 2600 m deep.

Bis(2-hydroxyethyl) terephthalate from depolymerized waste polyester modified graphene as a novel functional crosslinker for electrical and thermal conductive polyurethane composites

Bis(2-hydroxyethyl) terephthalate (BHET) with active hydroxyl group derived from waste polyester can be applied as a polyurethane chain extender and an organic modifier for graphene oxide (GO). Herein, functionalized reduced GO (BHET-rGO) with single-layer was obtained by modifying GO with BHET, and then reduced by hydrazine hydrate. Waterborne polyurethane (WPU) nanocomposites with excellent mechanical performance, electrical and thermal conductivities were prepared via in-situ polymerization using the novel functional crosslinker BHET-rGO. Compared with the same content of rGO (7.41 wt%), WPU/BHET-rGO composites exhibit better properties containing equivalent BHET content. For example, BHET-rGO endows the WPU composites with higher tensile strength of 39.1 MPa (enhanced by 454.6%), electrical conductivity of 8×10−3 S/m (improved by 15 times), and thermal conductivity of 0.551 W m−1 K−1 (increased by 21.1%). Meanwhile, the sensitivity of WPU/BHET-rGO composite is well recovered during a large-strain stretching/shrinking cycle, and its resistance is stable under complex deformation. Besides, significant thermal stability ensures the durable of polyurethane to resist high-temperature. Hence, BHET-rGO have greater potential for fabricating high-performance elastomer composites, especially for conductive elastomer composites.

Electrical Conductivity of Composites from Polymer Poly(Ethylene Oxide) and Nematic Liquid Crystals E8


 
 
 The electrical conductivity of thin films (150 μm) of composites produced from polymer poly(ethylene oxide) (PEO) and nematic liquid crystals E8 (in compositional ratio PEO:E8 = 70:30 wt%) was studied by means of complex electrical impedance spectroscopy in the range from 1 Hz to 1 MHz. Both ion conductivity and alternating-current conductivity of PEO/E8 films were determined as depending on temperature in the room-temperature region 25–50◦C. The results show that the ion-conductive PEO/E8 composite is a promising material for electronic applications.
 
 

Properties of CNTs‐modified lead‐free BCTS ceramic–Portland fly ash cement composites

AbstractFly ash (FA) is widely used as a supplementary cementitious material in the production of Portland cement concrete. The effect of addition of carbon nanotubes (CNTs) and FA on the properties of barium calcium stannate titanate (BCTS) ceramic–Portland FA cement composites was investigated. These composites have potential for use as sensors and transducers in the monitoring of structural health in concrete structures containing FA. CNTs were found to have filled the pores of the composites. All composites showed good compatibility with the concrete mix. The dielectric constant and electrical conductivity of composites were in the range 200–257 and 1.04 × 10–6 to 1.66 × 10−6 S/m, respectively. The presence of FA in composites increased the piezoelectric voltage coefficient (g33). Adding CNTs increased the piezoelectric charge coefficient (d33), thickness electromechanical coupling coefficient (Kt), and also g33 but decreased mechanical quality factor (Qm), which is related to good for the receiving sensor and transducer application. CNTs can improve the properties of these composites and composite with FA content at 10 vol.%, and CNTs at 1 vol.% exhibited the highest compressive strength and piezoelectric values (d33 = 44 pC/N, g33 = 20.21×10–3 V m/N, and Kt = 18.9%), along with higher g33 values, than pure BCTS ceramic.

Mechanical properties and electrical conductivity of oriented-SiC-whisker-reinforced Al2O3/Cu composites

Oriented SiC whisker-reinforced Al2O3/Cu composites were fabricated by powder metallurgy and hot extrusion. The microstructure of the composites was characterized by scanning electron microscopy. The mechanical properties and electrical conductivity of the composites were measured. The results indicated that the SiC whiskers aligned along the extrusion direction, and the nano Al2O3 particles were uniformly dispersed in the Cu matrix with ideal interfacial bonding. Particle and whisker hybrid reinforcement significantly enhanced the mechanical properties. The yield strength and elongation of (1 vol.%SiCw + Al2O3)/Cu composites were 6% and 15.6% higher than those of the Al2O3/Cu composites, respectively. The experimental yield strength was consistent with the theoretical value associated with different strengthening mechanisms. The main strengthening mechanisms were fine grain strengthening, Orowan strengthening and load transfer strengthening. The electrical conductivity of all the composites was higher than 82.8% IACS; however, the SiC whiskers led to electrical conductivity anisotropy. In general, the electrical conductivity of composites is related to the volume fraction and type of reinforcement. Therefore, the influence of the hybrid composition on the electrical conductivity was studied, and an analytical model for the electrical conductivity of hybrid-reinforced copper matrix composites was established, including the characteristic parameters of the particles and whiskers. The model and presented findings can provide a design basis for hybrid-reinforced composites.

Rational design of graphene/polymer composites with excellent electromagnetic interference shielding effectiveness and high thermal conductivity: a mini review

• This review concludes the works of composites using graphene as filler loadings to improve the thermal conductivity enhancement and EMI shielding performance • It was found that the graphene frameworks with the anisotropic orientation can achieve higher thermal conductivity enhancement efficiency and EMI SE at lower filler loading • This review also makes prospect for the development trend of graphene/polymer composites with high thermal conductivity and EMI shielding performance in the future The integration and miniaturization of chips lead to inevitable overheating and increasing electromagnetic interference (EMI) problems, which threaten the performance, stability, and lifetime of electronic components. Therefore, it is important to improve the heat dissipation and EMI shielding performance in device packaging for the steady operation of electronic products. In recent years, due to its intrinsic superior thermal conductivity, proper electrical conductivity, light-weight, and structural adjustability, graphene has been widely used as high thermal and conductive fillers incorporated in the polymer matrix to improve the thermal conductivity and electrical conductivity of composites. This review concludes the recent development of graphene/polymer composites by using graphene as fillers to improve the thermal conductivity and EMI shielding effectiveness (EMI SE). The structure of graphene embedded in the composites varies from zero-dimension (0D), one-dimension (1D) to two-dimensions (2D). Moreover, highly thermally and electrically conductive fillers with different dimensions were also modified on the graphene to improve the composite performance. Finally, this review also makes prospects for the development trend of graphene/polymer composites with high thermal conductivity and EMI SE in the future.

Tetramethylammonium hydroxide modified MXene as a functional nanofiller for electrical and thermal conductive rubber composites

Ti3C2 MXene with super conductivities can be used in polymer nanocomposites. However, MXene is difficult to disperse uniformly in polymer matrics due to their high surface energy, weakening the filler-rubber interfacial interaction. Herein, functional Ti3C2 (ƒ-Ti3C2) with single-layer and high surface charge loading was prepared by modifying Ti3C2 with tetramethylammonium hydroxide (TMAOH). A novel mechanical mixing and freeze-drying method was provided to fabricate styrene-butadiene rubber (SBR)/ƒ-Ti3C2 nanocomposites. Compared with the same content of Ti3C2 (3.85 wt%), SBR/ƒ-Ti3C2 exhibited better properties. For instance, ƒ-Ti3C2 endows the SBR composites with high tensile strength of 13.7 MPa (enhanced by 479%), electrical conductivity of 3.74 × 10-4 S/m (improved by 116%), and thermal conductivity of 0.659 W m-1·k-1. Besides, the wet skid resistance of SBR/ƒ-Ti3C2 nanocomposites was remarkably enhanced and the rolling resistance was decreased. Hence, ƒ-Ti3C2 has more potential for fabricating high-performance elastomer nanocomposites, especially for conductive elastomer composites.