Electrical Conductivity Of Composites Research Articles

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.

A two-dimensional finite element model for Cu-CNT composite: The impact of interface resistances on electrical and thermal transports

Copper (Cu)-carbon nanotube (CNT) composites are considered as potential alternatives for pure Cu based on the theoretical predictions of their superior electrical, thermal, and mechanical properties. However, the conductivities of experimentally synthesized Cu-CNT composites rarely exceed those of Cu primarily due to the large inherent interface resistances. Here, this article presents a two-dimensional (2D) finite element model (FEM) which accounts for the interface resistances both at CNT-CNT and Cu-CNT contacts, random distribution of CNTs, and CNT fractions up to 80%. The model predicts that the high concentration of single-walled CNTs in Cu matrix may enhance the composite electrical and thermal conductivity by up-to ∼5 times at 27℃ only when interface resistances are highly regulated below 1 kΩ and 10−7 m2K/W. The streamlines of electrical current and heat flow reveal that the CNTs serve as an effective conduction medium only with the low levels of interface resistance. This work elucidates the importance of interface resistances for the electrical and thermal transport in Cu-CNT composites.

Nutrient dynamics under unmanaged rubber, cocoa, and oil palm plantations in a sandy soil under humid lowland tropical climatic conditions

Changes in land use are an important issue in many farms that affect soil biological, chemical, and physical properties temporarily under cropping cycles or when the land is permanently allocated to perennial tree crops, e.g., in agroforestry. This study investigated the changes in sandy soil chemistry induced by three perennial tree crops (rubber, cocoa, and oil palm) growing in 30-year-old unmanaged and abandoned plantations and the surrounding grasslands dominated by cogon grass. A disruptive approach was used to collect soil samples from the top 60 cm under all the tree crops and in the grassland soils. A 500-gram sample of each soil originating from under each tree crop and the grassland were carefully packed into pre-labeled paper bags in triplicate (n=3) and sent to the laboratory for analysis of a selected number of primary and secondary macronutrients, micronutrients, and other soil parameters. The results showed N, K, Mg, Cu, Zn, and S were generally deficient in the sandy soil. A tree crop-specific soil organic matter, organic carbon, carbon stock contents, and water holding capacity measured were high under rubber and cocoa only. The variation in pH, electrical conductivity, bulk density, total porosity, and particle composition were generally similar except that the sand composition was lower in the soils under rubber and oil palm.

An innovative ternary composite paper of graphene and Fe3O4 decorated multi-walled carbon nanotube for ultra-efficient electromagnetic interference shielding and fire-resistant properties

Herein, Fe3O4 modified multi-walled carbon nanotube (Fe3O4@MWCNTs) heterostructure has been synthesized by a one-pot simplified coprecipitation method. After introducing it into graphene oxide dispersions, Fe3O4@MWCNTs/reduced graphene oxide (RGO) composite paper was prepared by evaporation-assisted self-assembly and hydrazine hydrate vapor reduction. The composite paper's electrical conductivity, electromagnetic interference (EMI) shielding and fire-resistant properties were investigated by four-point probe method, network analysis and combustion test method, respectively. The EMI shielding effectiveness (SE) can be adjusted by the filling amount of Fe3O4@MWCNTs and paper's thickness. When the thickness of the composite paper is approximately 0.6 mm and the mass fraction of Fe3O4@MWCNTs is 2%, the total SE of the composite paper in the X-band reaches 45.9 dB, which is 31.14% higher than that of the pure RGO paper (∼35 dB). Therefore, the Fe3O4@MWCNTs/RGO composite paper prepared in this study is a promising lightweight shielding material, especially suitable for various harsh natural high temperature environments.

Variation of the Electrical Conductivity of PLA‐Based Composites with a Hybrid of Graphene and Carbon Black During 3D Printing

AbstractIn order to develop conductive‐biocompatible 3D parts, poly(lactic acid) (PLA) is mixed with a hybrid of carbon black (CB, 4%) and graphene (GP, 0.1–0.5%) and the change of the particle dispersion under a flow is investigated based on rheological and electrical characterizations. In CB/PLA composite, CB aggregates are rearranged and percolation structure is disrupted under the given flow, resulting in a decrease in the modulus of the composite and lower electrical conductivity. During the 3D printing process, assemblies of CB aggregates do not remain close enough to maintain the percolation structure. When CB/PLA composite is mixed with GP, CB aggregates come into contact with GP aggregates to form percolation, maintaining a durable particle percolation against a flow and realizing electrical conductivity in 3D part. Despite the orientation effect of GP, the presence of GP enhances connectivity between the aggregates under a flow and maintains electrical percolation. A cell viability test of a 3D composite part shows good adsorption and growth of the cell due to the rough surface and biocompatibility of PLA. The addition of CB and GP to PLA improves not only the electrical properties of the 3D printing part but also enhances the cell viability.

Research on the electrical conductivity and mechanical properties of copper slag multiphase nano-modified electrically conductive cementitious composite

Electrically conductive cementitious composite (ECCC) features structural material functions, electrical conductivity, and piezoresistivity properties broadly applied in snow melting, electromagnetic shielding, cathodic protection system, and structural health monitoring (SHM). Nano-graphite is an ideal ECCC functional filler since its ability to fill molecular pores, reduce concrete shrinkage and significantly improve their electrical conductivity. However, nano-graphite is high-cost and its excessive amounts can lead to particle agglomeration. Therefore, copper slag (CS) can partially replace NG to beneficially reuse the waste by-products and save energy for protecting the environment. Nevertheless, a single blend of fillers hardly exploits the potential mechanical and conductive properties. Consequently, different activation methods were adopted to obtain desirable dispersion and performances. This paper explored the influences of chemical alkali excitation, ultrasonic vibration, and combined activation on copper slag and nano-graphite wrapped ECCC. Experimental results from a total of 387 ECCC specimens with 16 design ratios demonstrated that the combined treatment of alkali excitation and ultrasonic vibration was superior to any single treatment. The optimal samples based on 3 wt% ratio of NG and 60 wt% of copper slag activated with combined treatment exhibited 44.55 MPa compressive strength, 6.65 MPa flexural strength, and 8180 Ω·cm electrical resistance. Lastly, an SEM was conducted to analyze the microstructure of the mixture and ECCC and a schematic diagram was proposed.

Carbon layer coated nickel phosphide nanoparticles embedded in three-dimensional graphene network for high-performance supercapacitor

Transition metal phosphides (TMPs) are widely used as an electrode material because of their adjustable electronic structure, variable composition, and excellent electrical conductivity, which possess a broad application prospect in supercapacitors (SCs). The participation of carbon material is capable of enhancing the conductivity and electrochemical property of TMPs. Herein, carbon layer coated Ni2P nanoparticles embedded in a three-dimensional graphene network (Ni2P@C@rGO) are elaborately designed by the chemical-blowing method and subsequently low-temperature phosphorylation. The optimal Ni2P@C@rGO exhibits excellent capacitance of 1338.8 F/g at 1 A/g with a good rate capability of 66% even up to 30 A/g. For further exploring the practical application value, asymmetric SCs (ASCs) are successfully constructed based on Ni2P@C@rGO and N-PCS (nitrogen-doped porous carbon sheet) fabricated using a one-step chemical-blowing method. As a result, the ASC shows an excellent energy density of 33.4 Wh/kg at a power density of 792.1 W/kg, and remarkable cycle stability (85.2% capacitance retention after 10,000 cycles at 10 A/g). Thus, the Ni2P@C@rGO exhibits very attractive candidate as electrode material in high-performance energy-storage devices.

Hierarchical nanoarchitecture of vanadium disulfide decorated 3D porous carbon skeleton with improved electrochemical performance toward Li ion battery and supercapacitor

Vanadium disulfide (VS2) is deemed to be a competitive active material in electrochemical energy storage field in both lithium-ion battery and supercapacitor owing to its unique chemical and physical property. Nevertheless, serious aggregation and structure damage in continuous charge-discharges would result in a decreased capacity, an inferior cycling stability and a poor rate capability, which severly limits the practical application of VS2. In this current work, a hierarchical porous nanostructured composite composed of VS2 nanoparticles confined in gelatin-derived nitrogen-doped carbon network (VS2-NC) was successfully designed and synthesized via a simple freeze drying plus an annealing method. In this VS2-NC composite, porous architecture is conductive to providing high active surface areas, facilitating the access of electrolyte into active materials and ion diffusion. The confinement of carbon matrix on VS2 nanoparticles is beneficial to inhibition of the volume change, reinforcement of the structural stability and improvement of the overall electrical conductivity of composite. Benefitting from the advantages mentioned above, the as-prepared VS2-NC electrode demonstrates outstanding electrochemical performances. Employed as an anode for lithium ion battery, VS2-NC delivers a relatively high reversible capacity about ∼1061 mA h g−1 in 200-cycle test at 100 mA g−1. When applied in supercapacitor, VS2-NC electrode manifests a large pseudocapacitance of 407.3 F g−1 at a current density of 10 A g−1 and superior cycling stability.

Enhancement of Electrical Conductivity of Bismuth Oxide/Activated Carbon Composite

This study aims to synthesize bismuth oxide/activated carbon composites composed of rice husks for battery anodes and to determine the effect of bismuth nitrate pentahydrate mole variations on the characteristics of the resulting composites. The bismuth oxide/activated carbon composite synthesis was carried out using bismuth nitrate pentahydrate, sodium sulfate, and sodium hydroxide precursors which were mixed with rice husk-based activated carbon. A variation was made for the mole of bismuth nitrate pentahydrate used, while the compositions of activated carbon and other precursors were made fixed. The composites were synthesized using the hydrothermal method at a temperature of 1100C for 5 hours. The results showed that bismuth oxide was successfully formed as a composite in the 8 mmol variation with a composite electrical conductivity value of 2.40 x 10-3 S.m-1.

Using supervised machine learning methods to predict microfiber alignment and electrical conductivity of polymer matrix composite materials fabricated with ultrasound directed self-assembly and stereolithography

Engineered polymer matrix composite materials with designer electrical properties are important for a myriad of engineering applications including flexible actuators and wearable sensors. We use stereolithography in combination with ultrasound directed self-assembly to align electrically conductive microfibers in a photopolymer matrix. We relate the fabrication process parameters to the resulting filler material alignment and corresponding electrical conductivity using supervised machine learning methods and quantify the prediction accuracy of data-driven models derived from different interpretable and non-interpretable algorithms. We determine that decision tree and artificial neural network algorithms result in data-driven models with R2 scores that are 79.8% and 83.2% higher, respectively, than a traditional multivariate regression analysis benchmark model in predicting the microfiber alignment. Similarly, random forest and artificial neural network algorithms result in data-driven models that predict composite material electrical conductivity 9.1% and 13.7% more accurately, respectively, than a logistic multivariate regression benchmark model. Relating the fabrication process parameters to the resulting electrical conductivity of the material is a crucial step towards fabricating polymer matrix composite materials with designer electrical properties for use in engineering applications.

Designing a Functional CNT+PB@MXene-Coated Separator for High-Capacity and Long-Life Lithium-Sulfur Batteries.

Separators, as indispensable parts of LSBs (lithium–sulfur batteries), play a cucial role in inhibiting dendrite growth and suppressing the shuttle of lithium polysulfide (LiPSs). Herein, we prepared a functional carbon nanotube (CNT) and Fe-based Prussian blue (PB)@MXene/polypropylene (PP) composite separator using a facile vacuum filtration approach. The CNTs and MXene nanosheets are excellent electronic conductors that can enhance the composite separator electrical conductivity, while Fe-based Prussian blue with a rich pore structure can effectively suppress the migration by providing physical space to anchor soluble LiPSs and retain it as cathode active material. Additionally, MXene nanosheets can be well attached to Fe-based Prussian blue by an electrostatic interaction and contribute to the physical barriers that inhibit the shuttle of long-chain soluble Li2Sn (4 ≤ n ≤ 8). When used as a lithium–sulfur (Li–S) cell membrane with a functional coating layer of CNT+PB@MXene facing the cathode side, the batteries reveal a high initial discharge capacity (1042.6 mAh g−1 at 0.2 C), outstanding rate capability (90% retention of capacity at 1.0 C) and high reversible capacity (674.1 mAh g−1 after 200 cycles at 1.0 V). Of note, separator modification is a feasible method to improve the electrochemical performance of LSBs.

Evaluation of the health status of mammary glands and compositional changes in udder-half milk obtained from dairy goats for milk quality management.

This study evaluated the health status of the mammary glands and milk composition of dairy goats. The California mastitis test (CMT) score, somatic cell counts (SCCs), somatic cell type, electrical conductivity (EC), N-acetyl-β-d-glucosaminidase (NAGase) activity, mastitis-causing pathogens, and milk composition in 121 udder-half milk samples from 62 crossbreed goats (1-3years old) at 23-45 days postpartum were compared in four categories with SCCs of <200 × 103 , <300 × 103 , 301-1000 × 103 , and >1010 × 103 cells/ml. The SCC, CMT score, EC, and NAGase activity were significantly lower (p < 0.05) in udder-half milk with SCCs of <200 × 103 and <300 × 103 cells/ml than those in milk with SCCs of 301-1000 × 103 and >1010 × 103 cells/ml. The protein, lactose/ash, and solids-not-fat (SNF) in milk with an SCC of <300 × 103 cells/ml were similar to the previously reported values. The proportion of polymorphonuclear neutrophils was significantly higher (p < 0.05) in milk with SCCs of 301-1000 and >1010 × 103 cells/ml than in milk with an SCC of <300 × 103 cells/ml. Assessing mammary gland health and milk composition based on categorization of udder-half milk by SCC may be useful for milk quality control on goat farms.

Properties of TiCp/Cu composites fabricated by powder metallurgy and electrodeless copper plating

In situ spherical TiCp-reinforced copper matrix composites were prepared via hot-pressing sintering assisted with copper plating. Brinell hardness and electrical conductivity of composites with various contents were investigated, room temperature compression properties and fractography of optimal TiCp/Cu composites and sintered pure copper were analysed. It was found that with the increase of TiCp content, Brinell hardness of composites was increased, while electrical conductivity decreased. When TiCp content was 1.0 wt-%, the Brinell hardness increased significantly and the conductivity was maintained at a high level. Compared with sintered pure copper, the yield strength and ultimate compressive strength of the composites were improved, while the fracture strain was reduced.

Association of Lameness with Body Condition Score, Udder Health and Milk Quality in Sahiwal Dairy Cows

Background: Bovine lameness predominantly due to foot disorders is a severe herd health concern instigating substantial influence on dairy economics owing to increased odds of mastitis and reduced fertility. Timely diagnosis and treatment of lameness can save these economic losses. The current study was aimed to evaluate lameness and its effect on animal health in terms of body condition score and on udder health in Sahiwal cows. Methods: 204 lactating Sahiwal dairy cows in different lactation lengths and parities, from local Sahiwal farms in Punjab were evaluated for lameness. Cows were scored for body condition and lameness. Quarter foremilk used to determine the quarter health status of the cows by California mastitis test (CMT) and bacteriological culture and cow composite milk samples for estimation of somatic cell count (SCC), electrical conductivity, pH and milk composition, in terms of fat, solids not fat, protein and lactose were collected maintaining aseptic conditions. Result: 34 per cent had asymmetry in gait or mild lame, 5 per cent had moderate lameness and 1 per cent had severe lameness. Lameness had no significant effect on the body condition scores of Sahiwal cows. Subclinical mastitis was found in 40.2 per cent of Sahiwal dairy cows. It was concluded that incidence of mastitis was higher in the lame group as revealed by CMT and bacteriological culture and the lame group had significantly (P less than 0.05) more SCC and electrical conductivity than healthy cows. However, milk composition was not affected by lameness.

Influence of the Small Sc and Zr Additions on the As-Cast Microstructure of Al–Mg–Si Alloys with Excess Silicon

This research is devoted to the study effects of complex alloying of Al-0.3 wt. % Mg-1 wt. % Si and Al-0.5 wt. % Mg-1.3 wt. % Si alloys by small additions of Sc and Zr on the microstructure in the as-cast condition. The effect of small additions of these elements on the microhardness, electrical conductivity, grain size and phase composition of the indicated alloy systems was studied. The methods of optical and electron microscopy were used for the study. Moreover, the phase composition was calculated using the Thermo-Calc software package. The study showed a strong effect of the chemical composition of investigated alloys on the size of the grains, which, with a certain combination of additives, can decrease several times. Grain refinement occurs both due to supercooling and formation of primary Al3Sc particles in the liquid phase. Alloys based on Al-0.5 wt. % Mg-1.3 wt. % Si are more prone to the formation of this phase since a lower concentration of Sc is required for it to occur. In addition, more silicon interacts with other elements. At the same time, Al-0.3 wt. % Mg-1 wt. % Si requires lower temperature for complete dissolution of Mg2Si, which can contribute to more efficient heat treatment, which includes reducing the number of steps. TEM data show that during ingot cooling (AlSi)3ScZr dispersoid precipitates. This dispersoid could precipitate as coherent and semi-coherent particles with L12 structure as well as needle-shaped particles. The precipitation of coherent and semi-coherent particles during cooling of the ingot indicates that they can be obtained during subsequent multistage heat treatment. In addition, in the Al0.5Mg1.3Si0.3Sc alloy, metastable β″ (Mg5Si6) are precipitated.

Macro copper-graphene composites with enhanced electrical conductivity

Composites demonstrating enhanced electrical conductivity compared to copper have been highly sought after for their advantages in efficient energy transport behavior. While such conductors have been demonstrated in 1D (nanowires) and 2D (films) samples, achieving similar behavior in 3D has been challenging owing to the limitations of the synthesis techniques used. In this paper, novel macro-scale 3D copper conductors were demonstrated with increased electrical conductivity through the addition of graphene. Hot extrusion was used to manufacture 12 AWG copper-graphene composite wires with varying graphene content and defect density. Graphene defect density was measured using Raman spectroscopy. Results showed that the electrical conductivity of composites with low defect density graphene increased as a function of graphene content. Comparatively composites with high defect density graphene demonstrated lower electrical conductivity. This study provides first-of-its-kind evidence of 3D metal composites whose bulk electrical performance has been enhanced using graphene additive in minute quantities (15 ppm). Further developments in this area are essential to achieve high performance composite conductors that can improve energy transport efficiency and pave way for industrial adoption of such materials in the future.

Fabrication of actiniae-like atomically thin hydroxylation boron nitride@polyaniline hierarchical composites with adjustable high thermal conductivity and electrical conductivity

Polyaniline (PANI) has been studied as soft electronic materials, which is still subject to performance obstacles such as low thermal conductivity and undesirable electrical conductivity. Herein, we report the in situ preparation of an atomically thin hydroxylated boron nitride (HO-BNNS)@PANI actiniae-like layered composite. HO-BNNS@PANI composite obtains brilliant electrical and thermal conductivity without destroying the pH sensitivity of PANI. In this case, the test results show that when the HO-BNNS content is 15 wt%, the conductivity of the HO-BNNS@PANI composite is 10.8 S cm−1, and the thermal conductivity is 1.21 W m−1·K−1 (≈520% that of pure PANI). More strikingly, the HO-BNNS@PANI composite maintains the pH responsiveness of the intrinsic PANI. This greatly improves the application range of composite materials. Meanwhile, since actiniae-like structural factors simultaneously improve ion diffusion capability and optimize reaction area, after five times of doping and dedoping, the conductivity of the HO-BNNS@PANI composite can still be maintained above 60%.

Segregated polylactide/poly(butylene adipate‐co‐terephthalate)/MWCNTsnanocomposites with excellent electrical conductivity and electromagnetic interference shielding

AbstractAs plastic pollution becomes more serious, we need to find out eco‐friendly materials to alleviate the pollution. Polylactide (PLA) and poly (butylene adipate‐co‐terephthalate) (PBAT) will be one of the most attractive materials to replace those undegradable materials. However, few studies research the segregated conductive PLA/PBAT/MWCNTs nanocomposites. Herein, PLA/PBAT/MWCNTs nanocomposites with the segregated structure were successfully fabricated firstly. The MWCNTs are selectively dispersed in the continuous PBAT phase. The nanocomposite with segregated structure owns excellent electric conductivity. When the content of MWCNTs is 0.41 vol%, the electrical conductivity of composites with segregated structure is 9.43 × 10−4 S/m, which is about 5 orders higher than the nanocomposites without the segregated structure (1.75 × 10−10 S/m). The segregated nanocomposite with 2 wt% (1.18 vol%) MWCNTs owns excellent electromagnetic interference (EMI) of 24 dB, while the ordinary structure of composite is only 17 dB.

Influence of solution electrical conductivity and ionic composition on the performance of a gas–liquid pulsed spark discharge reactor for water treatment

The influence of solution electrical conductivity and ion composition on the performance of plasma reactors for water treatment applications is only partially understood. This study uses a point–point discharge over the surface of water in argon gas to determine the influence of solution conductivity, in the range of 0.3–45 mS/cm, on the physiochemical properties of spark discharges and the removal of two organic contaminants: perfluorooctanoic acid (PFOA) and Rhodamine B dye. The influence of various ions was also explored using chlorine and non-chlorine salts to adjust solution conductivity. The removal of PFOA increased with conductivity regardless of the salt type due to the salting out effect which increased PFOA's interfacial concentration. The removal of Rhodamine B dye depended on both salt type and solution electrical conductivity. In the presence of non-chorine salts, UV photolysis was the main mechanism for the dye degradation and its removal rate did not change with conductivity. The dye removal rate was the highest in the presence of chloride-based salts at the highest values of solution conductivities. In the presence of chorine salts, OH radicals are produced by the discharge generated hypochlorous acid, which is mixed into the bulk solution to react with the Rhodamine B dye. The generation rate of hydroxyl radicals appears to decrease with increasing solution conductivity, and these species are not directly involved in the degradation of the two compounds investigated in this study.

Enhanced positive temperature coefficient effect by crosslinking reaction for silicone rubber/carbon black composites with high pressure sensitivity

AbstractPositive temperature coefficient (PTC) composites are usually made of crystalline plastics and conductive fillers, but they are not suitable for flexible electronic devices because of their high rigidity. Rubber‐based PTC composites are flexible but their PTC intensity is low. In this work, based on the effect of crosslinking reaction on the electrical conductivity of silicone rubber composites, silicone rubber/conductive carbon black composites with an obvious PTC effect were prepared. Compared with the hydrosilylation crosslinking reaction, the peroxide crosslinking reaction has much more obvious decrease in electrical conductivity of the composites. The conductive percolation threshold of the composites was 4.98%. A composite filled with 5.98% conductive carbon black showed obvious PTC effect at circa 150°C, which can be attributed to the re‐aggregation of conductive carbon black in silicone rubber during the crosslinking process. The composite with an obvious PTC effect was well used in an overheating protection device. The composite exhibited an excellent pressure‐sensitivity of conductivity.