Electrical Conductivity Properties Research Articles

Targeting inerratic deposition behaviour via interface regulation toward dendrite-free zinc metal anodes

Aqueous zinc ion batteries are of interest due to their inherent safety, low cost and high energy density. Nevertheless, critical issues such as uncontrollable dendrite growth, hydrogen evolution reaction and corrosion have dramatically impeded the widespread utilization. To tackle above issues, the versatile artificial protective layer strategy consisting of Zn-friendly, porous and conductive carbon shells is presented for yolk-shell SiO2@void@C (SVC) nanospheres for guiding rapid and homogeneous Zn plating/stripping. On the one hand, the highly zincophilic SiO2 and pore structure interacted significantly with low nucleation overpotential and uniform Zn2+ flux, which favored homogeneous zinc deposition and ionic migration, thereby dramatically aiding in inhibition of Zn dendrites and interruption of interfacial side reactions. On the other hand, SVC nanospheres confer excellent electrical conductivity and mechanical properties, which play an important role in accelerating ion diffusion and boosting structural stability. Consequently, the SVC@Zn electrode exhibits high reversibility and electrochemical stability with a long cycling stability of 1800 h at 5 mA cm−2/1.25 mAh cm−2 and average CE of 99 %. The good properties associated with composition simplicity and abundant yield affords a feasible scheme for high-performance AZIBs.

Studies on cytocompatibility of human dermal fibroblasts on carbon nanofiber nanoparticle-containing bioprinted constructs

Functional nanocomposite-based printable inks impart strength, mechanical stability, and bioactivity to the printed matrix due to the presence of nanomaterials or nanostructures. Carbonaceous nanomaterials are known to improve the electrical conductivity, osteoconductivity, mechanical, and thermal properties of printed materials. In the current work, we have incorporated carbon nanofiber nanoparticles (CNF NPs) into methacrylated gelatin (GelMA) to investigate whether the resulting nanocomposite printable ink constructs (GelMA-CNF NPs) promote cell proliferation. Two kinds of printable constructs, cell-laden bioink and biomaterial ink, were prepared by incorporating various concentrations of CNF NPs (50, 100, and 150 µg/mL). The CNF NPs improved the mechanical strength and dielectric properties of the printed constructs. The in vitro cell line studies using normal human dermal fibroblasts (nHDF) demonstrated that CNF NPs are involved in cell-material interaction without affecting cellular morphology. Though the presence of NPs did not affect cellular viability on the initial days of treatment, it caused cytotoxicity to the cells on days 4 and 7 of the treatment. A significant level of cytotoxicity was observed in the highly CNF-concentrated bioink scaffolds (100 and 150 µg/mL). The unfavorable outcomes of the current work necessitate further study of employing functionalized CNF NPs to achieve enhanced cell proliferation in GelMA-CNF NPs-based bioprinted constructs and advance the application of skin tissue regeneration.Graphical abstract

High-speed laser cladding (Fe,Cu)-dopped Ni-Co protective coatings for SOFC MICs: From long-term oxidation behavior to mechanical stability

The long-term operation of intermediate temperature-solid oxide fuel cells (IT-SOFCs) could be significantly influenced by the stability of the interconnect itself, especially, its oxidation resistance under the cathode environment. To effectively prevent Cr-volatilization and improve the interconnector performance, application of highly dense and stable protective coatings over the interconnector is indispensable. In this work, Ni-Co-based alloy protective coatings doped with Fe and Cu were applied onto the 441 interconnector via a novel high-speed laser cladding technology. The microstructure evolution, phase composition, oxidation resistance, electrical conductivity and mechanical properties of the coated steels were investigated at different oxidation stages at 800 °C. It was found that the Ni33.8Co34Fe32.2-coated steel shows the best oxidation resistance and electrical properties. The oxidation rate (kp) and ASR of Ni33.8Co34Fe32.2-coated steel is respectively 4.44 × 10−13 g2 cm−4 s−1 and 25.55 mΩ cm2, significantly lower than the uncoated steel and Ni44.6Co44.7Cu10.7-coated steel at the end of 1000-h test cycle. The resultant conductivity of the Ni44.6Co44.7Cu10.7 and Ni33.8Co34Fe32.2-coated steels is approximately 7.8 and 4.1 S cm−1, respectively, which could meet the requirement for SOFC stacks. In addition, the nano-hardness of the Ni33.8Co34Fe32.2 and Ni44.6Co44.7Cu10.7-coated steels was found to be 8.3 GPa and 8.8 GPa, respectively, through nanoindentation testing. The improved surface hardness is attributed to grain refinement and increased oxide content on the coating surface. The results indicated that the Ni-Co-based alloy coatings effectively improved the long-term stability and mechanical property of the 441 interconnector under the SOFC cathode environment.

Laser Powder Bed Fusion of Multifunctional Bio-inspired Vertical Honeycomb Sandwich Structures: For the Application of Lightweight Bipolar Plates of Proton Exchange Membrane Fuel Cells

The bipolar plate (BPP) is a crucial component of proton exchange membrane fuel cells (PEMFC). However, the weight of BPPs can account for around 80% of a PEMFC stack, posing a hindrance to the commercialization of PEMFCs. Therefore, the lightweight design of BPPs should be considered as a priority. Honeycomb sandwich structures meet some requirements for bipolar plates, such as high mechanical strength and lightweight. Animals and plants in nature provide many excellent structures with characteristics such as low density and high energy absorption capacity. In this work, inspired by the microstructures of the Cybister elytra, a novel bio-inspired vertical honeycomb sandwich (BVHS) structure was designed and manufactured by laser powder bed fusion (LPBF) for the application of lightweight BPPs. Compared with the conventional vertical honeycomb sandwich (CVHS) structure formed by LPBF under the same process parameters setting, the introduction of fractal thin walls enabled self-supporting and thus improved LPBF formability. In addition, the BVHS structure exhibited superior energy absorption (EA) capability and bending properties. It is worth noting that, compared with the CVHS structure, the specific energy absorption (SEA) and specific bending strength of the BVHS structure increased by 56.99% and 46.91%, respectively. Finite element analysis (FEA) was employed to study stress distributions in structures during bending and analyze the influence mechanism of the fractal feature on the mechanical properties of BVHS structures. The electrical conductivity of structures were also studied in this work, the BVHS structures were slightly lower than the CVHS structure. FEA was also conducted to analyze the current flow direction and current density distribution of BVHS structures under a constant voltage, illustrating the influence mechanism of fractal angles on electrical conductivity properties. Finally, in order to solve the problem of trapped powder inside the enclosed unit cells, a droplet-shaped powder outlet was designed for LPBF-processed components. The number of powder outlets was optimized based on bending properties. Results of this work could provide guidelines for the design of lightweight BPPs with high mechanical strength and high electrical conductivity.

Boosting Electrochemical Nitrate Reduction to Ammonia by Fe Doped CuO/Co3O4 Nanosheet/Nanowire Heterostructures.

The electrochemical nitrate reduction reaction (NO3-RR) is a novel green method for ammonia synthesis. The development of outstanding NO3-RR performance is based on reasonable catalyst. Metal oxides have garnered significant attention due to their exceptional electrical conductivity and catalytic properties. Doping serves as an effective strategy for enhancing catalyst performance due to its ability to change the electron cloud distribution and energy levels. In this study, we develop a heterojunction catalyst Fe doped copper oxide nanosheet and cobalt tetroxide nanowire growing on carbon cloth simultaneously (Fe-CuO@Co3O4/CC) via hydrothermal method. The well-designed Fe-CuO@Co3O4/CC has excellent NH3 yield (470.9 μmol h-1 cm-2) and Faraday efficiency (FE: 84.4%) at -1.2 V versus reversible hydrogen electrode (vs. RHE). The heterostructure increases the specific surface area of the catalyst, and the possibility of contact between the catalyst and NO3- ions, enhances the catalytic efficiency. In addition, the catalyst has excellent stability and can stably carry out the electrocatalytic nitrate reduction reaction (NO3-RR), which provides a way for further research on the high-efficiency reduction of nitrate.

Novel binder-free vanadium-based molten salt (NMPV) with low-cost as anode materials of lithium-ion batteries

Molten salt NMPV material is synthesised using a one-step method and applied to binder-free anodes for lithium-ion batteries (LIBs). In this work, simple, low-cost and highly active coordination molten salt electrode materials (NMPV and NMPV-C) were prepared, which overcame the drawbacks of cumbersome and costly preparation of the existing electrode materials. NMPV is formed by the lone pair of electrons of N-methyl pyrrolidone (NMP) molecules coordinated with vanadium ion. The synergistic effect produced by these two and the excellent electrical conductivity and electrochemical properties of the molten salt material itself exhibits satisfactory lithium storage results. The discharge capacities of NMPV-C and NMPV in the second discharge cycle are 669 and 345 mAh g−1, respectively. After 100 cycles, the capacity is maintained at 923 and 549 mAh g−1, respectively. And the capacity retention is 137.97 % and 159.13 %, respectively. In addition, the NMPV-C electrode maintains a stable reversible capacity of 450 mAh g−1 at 2000 mAh g−1 after 220 cycles. Density-functional theory (DFT) calculations revealed that Li+ is more likely to attack H on methyl nitrogen, which is the optimal reaction site for NMPV since the lone pair of electrons of N effectively stabilises the carbon cation after the reaction of Li with H.

Unlocking the potential of low-melting-point alloys integrated extrusion additive manufacturing: insights into mechanical behavior, energy absorption, and electrical conductivity

AbstractAdditive manufacturing is a commonly used manufacturing method in complex part fabrication, instant assemblies, part consolidation, mass customization and personalization, on-demand manufacturing, lightweight, and topological optimization due to its advantage of lower costs, flexibility to learn and use, reduced raw material wastage, digital design integration, high efficiency, environmental-friendliness. However, the current metal 3D printing, which is mainly fabricated layer by layer using laser, is expensive to manufacture metal parts. Therefore, in this paper, a low-cost high-quality metal manufacturing process called low-melting-point alloys (LMPAs) integrated extrusion additive manufacturing will be examined. This manufacturing process can fabricate complex metal structures and integrated circuits with simple fused deposition modeling, which is a cost-effective method for producing these objects. LMPAs with different melting points are used for performance comparison to find out the optimized mechanical behavior, energy absorption properties, and electrical conductivity. Our investigation into LMPAs integrated extrusion additive manufacturing has revealed significant findings. Tensile tests conducted on LMPAs with varying melting points have illuminated distinct mechanical behaviors. Notably, lower melting points contribute to increased ductility but reduced stiffness, while higher melting points result in greater stiffness but diminished ductility. These results emphasize the importance of tailoring LMPA selection based on specific application requirements. Furthermore, our examination of lattice and triply periodic minimal surface structures has demonstrated consistent energy absorption properties across different manufacturing temperatures, highlighting the adaptability and versatility of LMPAs for energy absorption applications. Additionally, our electrical conductivity assessments have shown that LMPAs with melting points of $${{47}^{\circ }C}$$ 47 ∘ C and $${{120}^{\circ }}\hbox {C}$$ 120 ∘ C exhibit higher electrical conductivity, making them suitable for applications requiring good electrical conduction properties. These findings collectively underscore the significance of LMPAs in additive manufacturing, offering valuable insights for material selection and applications in various domains.

Lignin hydrogel sensor with anti-dehydration, anti-freezing, and reproducible adhesion prepared based on the room-temperature induction of zinc chloride-lignin redox system

In recent years, flexible sensors constructed mainly from hydrogels have received increasing attention. However, conventional hydrogels need to be prepared by high-temperature or radiation-induced polymerization reactions, which limits their practical applications due to their suboptimal electrical conductivity and weak mechanical properties. In this paper, using sodium lignosulfonate as the raw material, a dynamic catechol-quinone redox system formed by lignin‑zinc ions was constructed to initiate rapid free radical polymerization of acrylamide (AM) monomer at room temperature. In addition, Deep eutectic solvent (DES) can form a strong hydrogen bonding network within the molecules and between the molecules of the hydrogel, resulting in a hydrogel with good tensile properties (hydrogel elongation at break of 727.19 %, breaking strength of 84.09 kPa), and provides the hydrogel with high electrical conductivity, anti-dehydration, anti-freezing, and anti-bacterial properties. Meanwhile, the addition of lignin also improved the adhesion and UV resistance of the hydrogel. This hydrogel assembled into a flexible sensor can sense various small and large amplitude movements such as nodding, smiling, frowning, etc., and has a wide range of applications in flexible sensors.

Electrophoretic deposition of graphene oxide modified carbon paper: Enhance the interface strength and decrease the interface resistance

The gas diffusion layer (GDL) is a key component of the proton exchange membrane fuel cell (PEMFC) with the central roles of transporting electrons, supporting the electrode structure and transporting protons. However, the traditional carbon paper for GDL greatly limits the large-scale commercial application of PEMFC due to shortcomings such as low mechanical strength and poor electrical conductivity. Based on this, in this paper, ultrasound-assisted electrophoretic deposition of graphene oxide process is used to modify the primary carbon fiber paper and simultaneously improve the interfacial bond strength and interfacial conductivity of the carbon fiber paper to realize the facile preparation of phenolic resin carbon/reduced graphene oxide/carbon fiber (CFP-GO250–25) carbon-carbon composites with high mechanical and electrical conductivity properties. Compared to the unmodified carbon paper, the prepared CFP-GO250–25 shows an increase in tensile strength of about 76.5 % to 5.4 Mpa, a decrease in resistivity from 24.00 mΩ·cm to 10.21 mΩ·cm, and also has an excellent air permeability of 7.58 L/min. This study provides a reference for the facile preparation of phenolic resin carbon/reduced graphene oxide/carbon fiber carbon/carbon composites and promotes the large-scale commercial application of carbon fiber paper for low-cost GDL.

Robust and Environmentally Friendly MXene-Based Electronic Skin Enabling the Three Essential Functions of Natural Skin: Perception, Protection, and Thermoregulation.

The development of electronic skin (e-skin) emulating the human skin's three essential functions (perception, protection, and thermoregulation) has great potential for human-machine interfaces and intelligent robotics. However, existing studies mainly focus on perception. This study presents a novel, eco-friendly, mechanically robust e-skin replicating human skin's three essential functions. The e-skin is composed of Ti3C2Tx MXene, polypyrrole, and bacterial cellulose nanofibers, where the MXene nanoflakes form the matrix, the bacterial cellulose nanofibers act as the filler, and the polypyrrole serves as a conductive "cross-linker". This design allows customization of the electrical conductivity, microarchitecture, and mechanical properties, integrating sensing (perception), EMI shielding (protection), and thermal management (thermoregulation). The optimal e-skin can effectively sense various motions (including minuscule artery pulses), achieve an EMI shielding efficiency of 63.32 dB at 78 μm thickness, and regulate temperature up to 129 °C in 30 s at 2.4 V, demonstrating its potential for smart robotics in complex scenarios.

Synthesis and study of structural, electric, and dielectric behavior of La0.5Sm0.2Sr0.3Mn1-xFexO3 perovskite

In this study, the synthesized samples La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0.05, 0.15 and 0.20) were thoroughly investigated for their crystalline structure, electrical conductivity, and dielectric properties, the samples were prepared using autocombustion method. According to the X-ray diffraction study, the samples crystallized in an orthorhombic symmetry with the Pnma space group. To measure the dielectric characteristics, impedance spectroscopy was conducted over the temperature range of 100–260 K and a frequency range of 100 Hz to 1 MHz. Measurements of AC conductivity are indeed utilized to investigate the transport properties of materials being studied. The results indicated that both temperature and frequency significantly influence the conduction process. Three theoretical hypotheses were proposed to explain the hopping conduction: overlapping large polaron tunneling (OLPT), the non-overlapping small polaron tunneling (NSPT) mechanism, and correlated barrier hopping (CBH). It is also shown that the conductivity diminishes with an increase in Fe content. La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0.05, 0.15 and 0.20) can be used in electronic applications because of the high permittivity values confirmed by the dielectric measurements. With the aim of evaluating the distinct impacts of electrodes, grain boundaries, and grains on the complex impedance results, an appropriate alternative electrical circuit was utilized. Analysis of the sample's modulus indicated non-Debye characteristics and electrical relaxation phenomena. The materials exhibit good electrical properties, as well as strong chemical and thermal stability.

Microstructure evolution and property characteristics in hot-pressed Mo-W-Cu refractory functional alloys with varying tungsten content

Mo-W-Cu refractory functional alloys (RFAs), combining property advantages of MoCu and WCu alloys, have great application potential in microelectronics, aerospace technology, and military equipment due to their excellent electrical and thermal conductivity, low coefficient of thermal expansion, and high-temperature properties. W content in the alloy is a key factor influencing these properties. However, there is a lack of systematic investigation on the microstructure and properties of hot pressing (HP) processed Mo-W-Cu RFAs with different W contents these days. In this study, Mo-W-20Cu alloys with varying W content of 0–50 wt% RFAs are prepared by mechanical activation (MA) followed by hot pressing. The effect of W content on the microstructure and properties of the alloy is investigated in detail. The results show that all Mo-W-Cu RFAs mainly consist of Mo phase, W phase, and Cu phase after adding W. The microstructure observation shows that the Cu powder particles undergo a plastic deformation during the HP processing, resulting in the closure of the pores and the good metallurgical bonding with Mo phase and W phase at a relatively low temperature. Transmission electron microscopy (TEM) determination indicates that the MoCu phase interface and that of WCu both possess a semi-coherent structure. The property measurements demonstrate that the electrical and thermal conductivity properties of Mo-W-Cu RFAs continuously increase with W content rising while the relative densities of all the alloys are over 94 %. This study can provide a valuable theoretical and technological guidance for the investigation on preparation, microstructure, and properties of high-performance RFAs.

Engineering multifunctionality graphene-based nanocomposites with epoxy-silane functionalized cardanol for next-generation microwave absorber

As technology advances, the demand for effective microwave-absorbing materials (MAM) to mitigate electromagnetic wave interference is growing. Two-dimensional (2D) materials are increasingly favored across various fields for their high specific surface area, electrical conductivity, low density, and dielectric loss properties. This study presents lightweight nanocomposites composed of graphene nanoplatelets blended with epoxy resin (ER) and cardanol with silane-functionalized (SFC) as a toughening agent. The resulting nanocomposites exhibit a high surface roughness of 130 nm and an enhanced hydrophobicity, as evidenced by a high contact angle. Notably, the ER/SFC/GNP sample at 3 wt% (0.075 g) achieves a minimum reflection loss value of −18 dB at a thickness of 10 mm, indicating improved impedance matching and enhanced dielectric loss capability. The increasing damping factor ratio to approximately 0.95 further augments the reflection loss performance. The research aims to develop cost-effective, efficient, lightweight graphene-based nanocomposite absorbers.

CHARACTERIZATION OF COATINGS PREPARED FROM PREVULCANIZED NR/POLYANILINE LATEX

ABSTRACT Latex consisting of a NR/polyaniline (NR/PAni) blend is used in the preparation of thin elastic films. In this study, NR/PAni latex blends with different amounts of doped PAni and surfactants (sodium dodecylbenzene sulfonate [SDBS] and sodium dodecyl sulfate [SDS]) were prepared through prevulcanization. The films were prepared from prevulcanized latexes by casting in a petri dish or with the spin coating method. The conditions suitable for prevulcanization were investigated. The effect of doped PAni amounts and the surfactants SDBS and SDS on the mechanical, electrical conductivity, and physico-chemical surface properties and morphologies of NR/PAni films were characterized. The results indicated that PAni doped with dodecylbenzene sulfonic acid (DBSA) was well dispersed in NR latex in the presence of 0.01 mol/w% of SDBS. The highest amount of doped PAni that was dispersed was 17 w/w%. The properties of the blend of NR and DBSA-doped PAni were superior to those of the other blends. The compatibility between SDBS and DBSA was the dominant factor in improving the properties of the film prepared from the prevulcanized NR/PAni latex blend.

Recyclable, healable, and stretchable thermoset shape memory polythiourethane/carbon nanotube composite with segregated conductive structure for strain sensing

AbstractSegregated conductive polymer composites (CPCs) show high conductivity at low loading of filler. However, the weak interactions between fillers and polymer matrix may destroy the mechanical property of the segregated CPCs. Moreover, even with the introduction of dynamic bonds in thermoset polymers, the preparation of thermosetting CPCs remains a big challenge, as most crosslinked polymers should be ground into granules or crushed into powder with liquid nitrogen before mixing with fillers. Herein, the dynamic crosslinked polythiourethane microspheres (PTUM) are designed and synthesized. Then, a special mixing method (the mixing temperature is higher than melting temperature of soft segments of PTUM) is used to make the carbon nanotubes (CNTs) adhering closely to the surface of the crosslinked PTUM, promoting the formation of compacted conductive network. The CNT‐3%/PTUM shows the electrical conductivity of 21.9 S/m and an elongation at break of 472%. Additionally, the CNT/PTUM composites exhibit good self‐healing property, reprocessability, and close‐loop recycling property. The construction of dynamic crosslinked microspheres and compacted segregated conductive network in this work supplies a new approach to prepare thermoset CPCs with simultaneous high electrical conductivity and mechanical property, which is expected to be applied to wearable strain sensors.

The Effect of Rubber-Metal Interactions on the Mechanical, Magneto-Mechanical, and Electrical Properties of Iron, Aluminum, and Hybrid Filler-Based Styrene-Butadiene Rubber Composites.

Multifunctional stretchable rubber composites are gaining attention due to their unique electrical, mechanical, and magnetic properties. However, their high production costs pose economic challenges. This study explores the use of cost-effective metal powders-iron, aluminum, and their 1:1 (vol/vol) hybrid filler-in styrene-butadiene rubber composites, varying from 10 to 20 vol%. The effects of these metal particles on the mechanical, electrical, morphological, and swelling properties were investigated. Metal particles generally act as non-reinforcing fillers but can significantly enhance the mechanical modulus, electrical, and magnetic properties based on the filler structure and the filler-rubber interactions. Iron-based composites exhibit significant electrical conductivity and excellent magnetic properties. Aluminum enhances the modulus, while the combination yields average mechanical properties with added magnetic characteristics. Iron demonstrates higher reactivity with sulfur-based crosslinking ingredients, adversely affecting the rubber matrix's crosslinks, as shown by swelling tests. This reactivity is attributed to iron's transition metal characteristics. At 20 vol%, iron-filled composites display the highest magnetic anisotropic effect on toughness (~25%) under a magnetic field by permanent magnets and excellent electrical conductivity (1.5 × 10-2 S/m). While iron significantly boosts the electrical and magnetic properties, higher filler amounts degrade the mechanical properties. These composites are currently suitable for electrical and smart mechanical applications, but incorporating reinforcing fillers could enhance their robustness for broader applications.

Impact of annealing on the characteristics of 3D-printed graphene-reinforced PLA composite

Manufacturing through additive techniques, especially utilizing the fused filament fabrication (FFF) method, is a transformative technology revolutionizing design and manufacturing. FFF builds parts layer by layer using thermoplastic polymer and polymer composite filaments. However, weak interlayer connections often lead to low interlaminar resistance in printed structures. Recent studies suggest that post-deposition heat treatments can mitigate this issue by reducing internal thermal stresses and enhancing layer adhesion, thereby improving part properties. This research delves into the impact of annealing heat treatment on a composite of Polylactic Acid (PLA) reinforced with graphene. The annealing process was conducted at temperatures of 90, 100, and 120 °C for durations of 60, 120, and 240 min. The annealing response of the graphene-reinforced PLA composite is compared to that of natural PLA for reference, analyzing its effects on electrical, thermal, chemical, and mechanical properties. Chemical characterization was performed using X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). Thermal properties were analyzed via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Electrical properties were assessed by measuring resistance, resistivity, and conductivity. Mechanical properties were evaluated through tensile, flexural, notch sensitivity, impact tests, and hardness measurements. The results demonstrated that annealing of graphene-reinforced PLA and natural PLA did not alter their functional groups but increased their crystallinity. This treatment improved thermal stability, electrical conductivity, and mechanical properties, including tensile strength, flexural strength, and Shore D hardness. However, it reduced impact and notch sensitivity resistances. The increased crystallinity had a greater beneficial impact on some properties than the graphene reinforcement. These findings have potential applications in the automotive, aerospace, electronics, and medical sectors, given the increasing use of PLA in these industries.

Highly Sensitive, Degradable, and Rapid Self-Healing Hydrogel Sensor with Semi-Interpenetrating Network for Recognition of Micro-Expressions.

Flexible conductive hydrogels have revolutionized the lives and are widely applied in health monitoring and wearable electronics as a new generation of sensing materials. However, the inherent low mechanical strength, sensitivity, and lack of rapid self-healing capacity results in their short life, poor detection accuracy, and environmental pollution. Inspired by the molecular structure of bone and its chemical characteristics, a novel fully physically cross-linked conductive hydrogel is fabricated by the introduction of nanohydroxyapatite (HAp) as the dynamic junction points. In detail, the dynamically cross-linked network, including multiple physical interactions, provides it with rapid self-healing ability and excellent mechanical properties (elongation at break (>1200%), tensile strength (174kPa), and resilience (92.61%)). Besides, the ions (Cl-, Li+, Ca2+) that move freely within the system impart outstanding electrical conductivity (2.46±0.15 S m-1), high sensitivity (gauge factor, GF>8), good antifreeze (-40.2°C), and humidity properties. The assembled sensor can be employed to sensitively detect various large human motions and subtle changes in behavior (facial expressions, speech recognition). Meanwhile, the hydrogel sensor can also degrade in phosphate-buffered saline solution without causing any environmental pollution. Therefore, the designed hydrogels may become a promising candidate material in the future potential applications for smart wearable sensors and electronic skin.

Effect of melt‐processing conditions on the electrical conductivity and microwave absorbing properties of composites based on clean scrap poly(vinylidene fluoride/ethylene vinyl acetate copolymer and graphene nanoplatelets

AbstractClean scrap polyvinylidene fluoride (rPVDF) from industrial reject was compounded with ethylene vinyl acetate (EVA) copolymer and graphene nanoplatelets (GNP) to produce low cost and scalable conductive composites. The effect of the melt processing conditions (temperature, time, and rotor speed) on the electrical conductivity and microwave absorbing (MWA) properties was investigated. All systems presented co‐continuous morphology indicated by scanning electron microscopy (SEM) and selective extraction experiments. The preferential localization of GNP in the EVA phase was evidenced by selective extraction and thermogravimetric analysis (TGA). Higher conductivity value was observed for the composite processed at 210°C for 3 min at a rotor speed of 200 rpm. The MWA performance of monolayer and bilayer composite structures with 2 mm thickness was investigated in terms of minimum reflection loss (RL) and effective absorption bandwidth (EAB). The bilayer system provided the best MWA response with RL = − 43.1 dB (>99.99% of EM attenuation) when prepared at 190°C for 3 min at a rotor speed of 200 rpm. The ecological and environmental importance of finding new applications for plastic waste, and the low cost of the materials and processing make this composite an interesting candidate for MWA purpose.Highlights Promising application of clean scrap polyvinylidene fluoride (PVDF) in microwave absorbing materials; Conductivity and absorbing performance are affected by processing conditions; Co‐continuous structure of rPVDF/EVA blend influenced by graphene nanoplatelets (GNP); Selective localization of GNP in EVA phase; Outstanding microwave absorption properties achieved with bi‐layer structure.

Photo‐responsive systems based on anisotropic composites of poly(N‐vinyl formamide) and active fillers using directional freezing combined with gamma irradiation crosslinking

AbstractThis study deals with the fabrication of smart anisotropic composite systems capable of reacting to light stimulus and reversibly providing significant change in the length. Surface‐modified carbon nanotubes (CNTs) and poly(pyrrole) (PPy) nanotubes were used as photoactive fillers. Anisotropic composites containing these fillers and poly(N‐vinyl formamide) (PNVF) matrix were fabricated using a directional freezing technique with freezable monomer, N‐vinyl formamide (NVF), as structure guiding medium and subsequent gamma irradiation polymerization and crosslinking technique. The dielectric properties showed that there is the presence of both relaxation processes α and β, which are significantly influenced by the presence of photoactive filler. The anisotropic distribution of fillers in samples was confirmed using microscopical, electrical conductivity and mechanical properties analysis. Finally, the photoactuation capabilities were investigated and showed enhanced photoactive response for the anisotropic system in the change in the length up to 54 μm after irradiation at 627 nm with a very low light intensity of 6 mW cm−2 in a fully reversible and repeatable manner. The simple, affordable, and industrially scalable fabrication technique opens an avenue for smart anisotropic photoactive composite systems.