Conductive Particles Research Articles

Підвищення ефективності запалювання вакуумно-дугового розряду в джерелах плазми

The analysis of the existing vacuum-arc discharge ignition systems showed the following ways to improve their efficiency: development of new design solutions for both individual units and the entire ignition system as a whole; the use of composite materials to fill the discharge gaps of starting devices; creation of new circuit solutions for power supplies of starting discharges; the use of non-traditional methods of ignition of a vacuum-arc discharge - the transition of a glow discharge into an arc one; using laser radiation to ignite the arc. Criteria for evaluating the reliability and durability of vacuum-arc discharge initiation systems in technological plasma sources are proposed, based on which complex studies of contact-type arc excitation systems with spark surface breakdown and two-stage launch systems with an autonomous plasma injector. Based on the performed studies, designs of vacuum-arc plasma sources with contact-type systems have been developed that ensure their performance in a certain range of technological parameters; The design of the ignition system turned out to be the most effective, in which the ignition electrode and the auxiliary anode are made as a single structural element in the form of a cut cone-shaped spiral. These design features, firstly, do not prevent the condensation on the surface of the starting discharge gap of a part of the metal evaporated by the cathode spot (CS) of the arc during the operation of the device, and secondly, they greatly facilitate the output of the CS from the place of initiation to the working end of the cathode. Here, the magnetic field, under the action of the CS moves, created by the current of the starting discharge itself, flows along with the turns of the cone-shaped spiral. This ignition system does not require a separate power supply and can operate in an automatic mode from the arc power source. To implement a non-contact method of arc excitation using a plasma injector, various designs of it were studied, when the discharge gap was filled with different materials; it was found that the resource of starting injectors when filling the discharge gap with M-7 ceramics does not exceed 104 operations, with 22XC ceramics at the level of 105 operations, and when using a composite material (CM), it exceeds 106 operations at ignition energy of 5 J, an operating pulse frequency of 1 Hz and arc duration 2 s. The developed composite materials are distinguished by increasing resistance to electric discharges and low surface breakdown voltage (up to 100…200 V/mm). Such characteristics are provided by the features of the CM structure, which is a dielectric glassy matrix filled with finely dispersed conductive particles and semiconductor components. The theoretical and experimental dependence of the arc ignition probability on the ignition energy during the operation of the injector in the electric film explosion mode are compared, showing satisfactory agreement between the results.

High-efficiency, self-grinding exfoliation of small graphene nanosheets from microcrystalline graphite driven by microbead milling as conductive additives

Direct mass exfoliation of graphene from bulk graphite with high yield and productivity for commercial applications is challenging. This work proposes self-grinding exfoliation using the mutual shear friction of graphite particles to fabricate graphene from microcrystalline graphite. The concept is implemented using microbeads as the grinding medium to drive the shear friction between graphite nanocrystals in a high-concentration paste. The proposed approach substantially improves graphene yield from 6.3% to 100% and simultaneously generates a record productivity of 7.5 g h−1 L−1, achieving total graphite-to-graphene conversion on the kilogram scale. The as-prepared graphene nanosheets have an average lateral size of 298 nm and the same C/O atomic ratio as the pristine graphite. In addition, the well-exfoliated, small nanosheets display good electrical conductivity and exhibit significant potential as conductive additives that improve the specific capacity and cyclic stability of Li-ion batteries better than commercial carbon-based conductive particles.

Digital Microfluidic Mixing via Reciprocating Motions of Droplets Driven by Contact Charge Electrophoresis.

Contact charge electrophoresis (CCEP) is an electrically controllable manipulation technique of conductive droplets and particles by charging and discharging when in contact with the electrode. Given its straightforward operation mechanism, low cost, and ease of system construction, it has gained traction as a versatile and potential strategy for the realistic establishment of lab-on-a-chip (LOC) in various engineering applications. We present a CCEP-based digital microfluidics (DMF) platform with two parallel electrode modules comprising assembled conventional pin header sockets, allowing for efficient mixing through horizontal and vertical shaking via droplet reciprocating motions. The temporal chromic change caused by the chemical reaction between the pH indicator and base solutions within the shaking droplets is quantitatively analyzed under various CCEP actuation conditions to evaluate the mixing performance in shaking droplets by vertical and horizontal reciprocating motions on the DMF platform. Furthermore, mixing flow patterns within shaking droplets are successfully visualized by a high-speed camera system. The suggested techniques can mix samples and reagents rapidly and efficiently in droplet-based microreactors for DMF applications, such as biochemical analysis and medical diagnostics.

Straightforward synthesis of magnetized activated carbon particles

To develop new sustainable processes, the production of materials with specific physico-chemical properties is highly desirable. Creating hybrid multi-functional materials by combining​ complementary components represents a suitable approach to meet the requirements of various industrial processes. In this work, a straightforward production route to synthesize magnetic (electrode) particles from low cost starting materials is presented. The particles were produced from iron(II) hydroxide and activated carbon (AC) via a microwave-assisted synthesis, creating a magnetite and AC hybrid material (PMAG/AC). SEM imaging shows that the particles are characterized by an amorphous surface structure, typical for AC. Visible cavities are covered by magnetite nanoparticles, confirming the specific surface area measurements, which show a reduction of the surface area when magnetite is added. Cyclic voltammetry shows increasing current densities, ranging from ＋0.49 to ＋1.31 mA cm−2 and from −0.58 to −1.47 mA cm−2 at ＋/−1000 mV vs. Ag/AgCl with increasing immobilized particle mass (25 to 124 mg cm−2). Finally, adsorption experiments were conducted by adding the particles to a culture of electroactive Shewanella oneidensis showing a time-dependent adsorption behavior. These findings represent a promising perspective for future applications of magnetic, conductive and biocompatible particles across a broad range of biotechnological and (bio-)electrochemical processes.

Insights into structural, thermal, electrical and mechanical properties of copper alumina reinforced chlorinated natural rubber nanocomposites

Current research intended the fabrication of highly durable conducting rubber products of low cost and wide applicability in the field of electronics. Chlorinated natural rubber (Cl-NR) reinforced with copper alumina (Cu-Al2O3) nanocomposites were fabricated by a solvent-free and economically viable industrial compounding technique with special attention to structural, morphological, rheometric curing behaviour, flame retardancy, electrical conductivity, dielectric, thermal and mechanical properties. FT-IR spectra confirmed the presence of Cu-Al2O3 in Cl-NR. The XRD investigation showed the crystalline peaks of Cu-Al2O3 in Cl-NR nanocomposites. The SEM and TEM results indicated that the nanoparticles were uniformly dispersed into the chlorinated rubber in the nano regime. The DSC results indicated that the addition of nanoparticles into the rubber matrix increased the glass transition temperature of the composites. The conductive metal oxide particles in the rubber accelerate the vulcanization process, which could be more beneficial in the industrial sector. The AC conductivity, dielectric properties, tensile strength, modulus, tear strength, heat build-up and hardness of nanocomposites were greatly increased, whereas the elongation at break, abrasion loss and resilience were decreased with the addition of nanoparticles to the chlorinated natural rubber. These increased mechanical properties of rubber nanocomposites with improved processability, controlled morphology and electrical properties are important parameters in the designing of flexible flame retardant electronic devices, electromagnetic induction shielding and conducting adhesive materials.

Self-Healing Interconnects for Hybrid Flexible Electronics

Hybrid flexible electronic systems promise high-performance user interfaces and smart surfaces. Despite progress in materials and manufacturing, the reliability of the interconnect due to open-circuit faults caused by mechanical, electrical, and environmental stress remains a concern. Here, we discuss an electric field-assisted self-healing (eFASH) technique that permits a real-time repair of open faults. The active material is a dispersion of conductive particles in an insulating fluid that is contained over the interconnect. Healing is triggered by the electric field that appears in the open gap during the occurrence of the fault. The technology is scalable and can be applied to the various feature sizes observed in hybrid flexible electronic systems. In this work, we describe the physics and characterize the healing mechanism for various operating conditions and finally demonstrate self-healing integrated circuits.

Design and development of ultra-sensitive, dynamically stable, multi-modal GnP@MXene nanohybrid electrospun strain sensors

Electrospun fiber-based strain sensors are widely used in biomonitoring due to their network construction and tailorable design. However, poor cycling stability and lack of multi-modality remain major issues. In this study, a 3-component material system consisting of MXene, graphene nanoplatelets (GnPs), and cellulose nanocrystals (CNCs) was employed to address multi-modality and sensitivity shortcomings. The hybrid synergetic interactions between MXene and graphene nanoplatelets (GnPs) provided high gauge factors (400 at 100% and 76.1 at 10% strains). Smaller and more conductive MXene particles provided higher electrical conductivity and sensitivity at lower strain ranges (with a low detection limit of 0.25% and a short response time of 100 ms) by forming localized brittle regions. Synergistically, GnP flakes with large laterial sizes promoted network connectivity, easy sliding across larger strains, and lubricity. On the other hand, the CNC binder enhances the uniformity and interfacial hydrogen bonding between the constituents, leading to desirable cycling capabilities for over 2,000 cycles. An in-situ ultrasonic atomization process was used to decorate the poly(styrene–butadienestyrene) (SBS) substrate with the electrically conductive additives, which remarkably enhanced the uniformity of the conductive coating. With the simultaneous vacuum-assisted filtration, this technique provided more conformal and in-depth fiber decoration, promoting multi-modality and sensitivity. The developed strategies proved to be effective in creating sensors with ideal body integration and successful recording of various body motions.

Fruit ripeness sensors based on poly(lactic acid)/polyaniline solution blow‐spun fibrous membranes

AbstractReal‐time ripening monitoring stands as an attractive way to guarantee quality control and prediction of shelf life during transport and prolonged storage of fruits and vegetables. Herein, we investigate the use of poly(lactic acid)/polyaniline (PLA/PANI) solution blow‐spun nanofibrous membranes as gas sensors for fruit ripening monitoring. PLA/PANI with different blend ratios was prepared by dissolving PANI in dichloroethane (DCE) for further mixing with PLA and spinning onto interdigitated microelectrode (IME). The ripening process of four different fruits (apple, orange, banana, and cashew peduncle), climacteric, and non‐climacteric fruits, was assessed over 72 h by real‐time monitoring changes in volatile organic compounds (VOCs) released during fruit ripening. Since adsorption of VOCs onto sensor surface causes changes in electrical response, which is directly related to the fruit ripening process, PANI addition was essential to monitor the ripening. However, higher concentrations (2% PANI in PLA) impair sensor conductivity and sensitivity because of the agglomeration of conductive polymer particles, which directly influences the sensitivity and the average fiber diameter. One of the main findings, here, was the clear distinction between different patterns of monitoring curves according to the category of the analyzed fruit (climacteric or non‐climacteric).

Fabrication of Conductive, High Strength and Electromagnetic Interference (EMI) Shielded Green Composites Based on Waste Materials.

Conventional conductive homopolymers such as polypyrrole and poly-3,4-ethylenedioxythiophene (PEDOT) have poor mechanical properties, for the solution to this problem, we tried to construct hybrid composites with higher electrical properties coupled with high mechanical strength. For this purpose, Kevlar fibrous waste, conductive carbon particles, and epoxy were used to make the conductive composites. Kevlar waste was used to accomplish the need for economics and to enhance the mechanical properties. At first, Kevlar fibrous waste was converted into a nonwoven web and subjected to different pretreatments (chemical, plasma) to enhance the bonding between fiber-matrix interfaces. Similarly, conductive carbon particles were converted into nanofillers by the action of ball milling to make them homogeneous in size and structure. The size and morphological structures of ball-milled particles were analyzed by Malvern zetasizer and scanning electron microscopy. In the second phase of the study, the conductive paste was made by adding the different concentrations of ball-milled carbon particles into green epoxy. Subsequently, composite samples were fabricated via a combination of prepared conductive pastes and a pretreated Kevlar fibers web. The influence of different concentrations of carbon particles into green epoxy resin for electrical conductivity was studied. Additionally, the electrical conductivity and electromagnetic shielding ability of conductive composites were analyzed. The waveguide method at high frequency (i.e., at 2.45 GHz) was used to investigate the EMI shielding. Furthermore, the joule heating response was studied by measuring the change in temperature at the surface of the conductive composite samples, while applying a different range of voltages. The maximum temperature of 55 °C was observed when the applied voltage was 10 V. Moreover, to estimate the durability and activity in service the ageing performance (mechanical strength and moisture regain) of developed composite samples were also analyzed.

Magnetically induced robust anisotropic structure of multi-walled carbon nanotubes/Ni for high-performance flexible strain sensor

Multi-walled carbon nanotubes (MWCNTs) are widely used as functional nanomaterials in flexible strain sensing polymer composites. They are expected to exhibit high anisotropy when aligned along a certain direction due to their unique one-dimensional structure, which has a positive effect on enhancing the sensing performance of the original polymer composites. Here, we used a weak curing magnetic field (less than 0.7 T) to induce the self-assembly of MWCNTs in polymer composites to obtain a novel flexible strain sensor with anisotropic structure (MAPC). To further optimize the comprehensive sensing performance, the synergistic effect between MWCNTs and conductive particles was utilized to enhance the sensitivity of MAPC to tensile strain by filling a small amount of nickel nanoparticles (MAPCN). The sensor can measure the tensile strain range up to 720%, with high sensitivity (GF=1768.7, 90%–100% strain), fast response (loading delay time τ1 = 92.2 ms and unloading delay time τ2 = 143.6 ms, 0–10% strain), and high durability (1050 cycles at 10% strain). These important properties allowed MAPCN to accurately monitor human physiological activities, and a gesture recognition system was designed to demonstrate its practical value and potential application prospect in wearable devices.

Low-voltage and controllable-developed actuator with bilayer structure based on triple-shape actuation

Multiple-Shape memory polymers containing conductive particles are seen as potential soft actuators due to their superiority in remote operation and simple equipment. Though abundant conductive particles can reduce the actuating voltage, it has a risk of reducing the shape-memory effect. Bilayer structure is a good strategy to solve the above contradictions. Herein, a low-voltage, controllable-developed, and triple-shape actuator with bilayer structure is prepared successfully. The dense and thin conductive layer brings excellent electrical heating performance to the triple-shape carbon nanotubes (CNTs)/poly(ethyl vinyl acetate) (EVA)/polycaprolactone (PCL) composite without degradation of the actuation. Therefore, low voltages (15–18 V) can heat the CNT/EVA/PCL composite up to 60–100 °C to actuate multiple-shape transition. Various desired patterns upon actuation based on controllable and programming performance can be easily designed based on the resultant composite, such as retrorse and stepwise actuation. Moreover, the actuator could be designed into a “flower” shape to imitate blooming and withering. The low-voltage, controllable-developed and triple-shape actuator based on bilayer structure make it be potential in applications of soft robots and spaceflight fields.

Thermal and optical performance characterization of bare and phosphor converted LEDs through package level immersion cooling

Increased demand for high flux electronics requires creative and affordable thermal management approaches to meet the performance and lifetime expectations. In the present study, optical and thermal improvements of a new package level liquid coolant encapsulation that directly targets heat generation zones are studied for bare and phosphor converted LEDs. As heat both at chip and phosphor composite regions are being generated, a series of detailed experimental and theoretical characterization is performed in order to examine the capability of the new cooling method. The findings can be used to extend the application of precisely controlled liquid packing on the heat source region of optoelectronic components. This method has shown a 15% reduction in thermal resistance and a 7% increase in power conversion efficiency of LED packages. The capacity of this method is mainly limited to the thermal conductivity of the coolant while a significant ability for improvement can be expected by utilizing thermally conductive particles such as hexagonal boron nitride inside the coolant.

The effective thermal conductivity of polymer composites filled with high conductive particles and the shell structure

AbstractThe addition of fillers with high thermal properties to polymer matrices increases the thermal conductivity of the composites in comparison with pure polymers. In the literature, various models have been proposed for predicting the thermal conductivity of polymer composites, where, in order to agree with the experimental data, some control parameters are introduced, the physical meaning of which is sometimes in doubt. In the present paper, a new effective thermal conductivity model of polymers filled with highly conductive particles is proposed. According to this model, the structure of a polymer composite is represented as the sum of two different parts: a structure with uniformly dispersed in polymer and not in contact with each other filler particles, and a structure with randomly distributed polymer particles, completely covered by monolayers of aggregated filler particles (“shell structure”). The comparison shows good agreement between the results of the proposed model and experimental data, in contrast to the results of the Lichtenecker and Mamunya models. Based on the proposed model, the aggregation abilities of filler particles for some polymer composites have been determined.

Conductive Particles in Anisotropic Conductive Films

Polymer Science: Peer Review Journal Conductive Particles in Anisotropic Conductive Films Federico Trupp1, Roberto Cibils2 and Silvia Goyanes1* 1Physics Department, University of Buenos Aires, Argentina 2INVAP, Argentina *Corresponding author: Silvia Goyanes, Physics Department, University of Buenos Aires, Int Güiraldes 2160, Ciudad Autónoma de Buenos Aires, Argentina Submission: January 26, 2022;Published: February 17, 2022 DOI: 10.31031/PSPRJ.2022.03.000554 ISSN: 2770-6613 Volume3 Issue1

Revised Manuscript with Corrections: Polyurethane-Based Conductive Composites: From Synthesis to Applications.

The purpose of this review article is to outline the extended applications of polyurethane (PU)-based nanocomposites incorporated with conductive polymeric particles as well as to condense an outline on the chemistry and fabrication of polyurethanes (PUs). Additionally, we discuss related research trends of PU-based conducting materials for EMI shielding, sensors, coating, films, and foams, in particular those from the past 10 years. PU is generally an electrical insulator and behaves as a dielectric material. The electrical conductivity of PU is imparted by the addition of metal nanoparticles, and increases with the enhancing aspect ratio and ordering in structure, as happens in the case of conducting polymer fibrils or reduced graphene oxide (rGO). Nanocomposites with good electrical conductivity exhibit noticeable changes based on the remarkable electric properties of nanomaterials such as graphene, RGO, and multi-walled carbon nanotubes (MWCNTs). Recently, conducting polymers, including PANI, PPY, PTh, and their derivatives, have been popularly engaged as incorporated fillers into PU substrates. This review also discusses additional challenges and future-oriented perspectives combined with here-and-now practicableness.

Resistivity Signature of Graphene-Based Fiber-Reinforced Composite Subjected to Mechanical Loading

The paper reports on a piezoresistivity response of fiber-reinforced cement mortar with graphene nano-platelets. The use of a small quantity (0.25% by the weight of cement) of nano-sized conductive particles of graphene turned conventional portland cement-based composite into a semiconductive stress-sensing material. The resistivity was measured using a surface resistivity tester, well accepted by the concrete industry, which employs an alternative current through four electrodes. Tension and compression tests of standard specimens were used to establish the relationship between the resistivity and the applied strain. Finite element analyses were employed to predict the resistivity of the slab specimen under three-point bending. The tests results and simulation indicate that the electrical resistivity of the graphene-cement composite material can be used for structural health monitoring and damage detection.

Long-term performance of granular activated carbon electrode system for the removal of amoxicillin

Three-dimensional electrode reactor, packed with conductive particles, is more cost-effective than traditional two-dimensional electrode reactor. In this study, granular activated carbon (GAC) was applied as particle electrode, then the long-term performance on amoxicillin (AMX) removal and activated carbon regeneration of the GAC particle electrode oxidation process (GAC EOP) was investigated, and the GAC adsorption process (GAC ADS) was carried out for comparison. Both of them ran continuously to remove AMX. Because of the regeneration effect of electrochemical action, the GAC EOP showed a more stable physisorption capacity than GAC ADS, with less change in micropore volume, pore size distribution and surface morphology of GAC. The result of XPS revealed the AMX chemisorption mechanism: the carbonyl (CO) and phenolic hydroxyl (OH) on activated carbon combined with carboxyl (COOH) and ammonium group (NH3+) on AMX, respectively. Correspondingly, the content of CO and OH on GAC fell significantly during the GAC ADS. However, due to the chemical bond regeneration effect of electrolysis, noticeable declines were not observed in GAC EOP, which ensured the stable chemisorption capacity of this system. It was shown that during the 50 consecutive runs, the AMX removal in GAC EOP was always higher than 60%. Even the removal efficiency showed an upward tendency, with the average value reached 86.1% and 99.1% in the 31–40 and 41–50 run times respectively. It was because of the rising specific surface area of GAC and the effect of electro-polarization, which made it more meaningful to explore the long-term performance of three-dimensional electrode reactor.

Improving antistatic and mechanical properties of glass fiber reinforced polypropylene composites through polar adsorption and anchoring effect of organic salt

Matrix toughness and viscosity, fiber length, interface bonding, and crystalline structure play significant roles in tuning the antistatic and mechanical properties of polypropylene (PP) composites. However, there is no report available concerning the development of antistatic PP composites by considering all these factors. In this study, we fabricate antistatic long glass fiber reinforced polypropylene random copolymer composites filled with Li-TFSI (LGF/PPR/Li-TFSI) and explore how crystallization behavior due to Li-TFSI affects the interfacial strength and conductive mechanism. It is found that the polar effect promotes the adsorption of Li-TFSI on the surface of LGF to form a conductive track, and consequently, the three-dimensional conductive network formed by intertwined LGF effectively reduces the percolation threshold (i.e., 0.15 wt/wt%). Besides, the heterogeneous nucleation induced by Li-TFSI promotes the nucleation and crystal growth of PPR molecular chains on the surface of Li-TFS. Thus, Li-TFSI wrapped by spherulites improves the anchoring effect of the LGF on the PPR matrix. However, the anchorage degree is related to the close proximity of conductive particles, specifically, 0.05 wt/wt% Li-TFSI results in the highest level of stress transfer. Meanwhile, although the addition of 0.15 wt/wt% Li-TFSI causes a slight decrease in the interface strength, it leads to competitive nucleation between Li-TFSI and LGF, thereby generating thicker lamellae, which makes LGF/PPR/Li-TFSI the largest modulus. This study provides some new insights into the tailoring of material properties using Li-TFSI for antistatic PP composites.

Carbon Black/PDMS Based Flexible Capacitive Tactile Sensor for Multi-Directional Force Sensing.

Flexible sensing tends to be widely exploited in the process of human–computer interactions of intelligent robots for its contact compliance and environmental adaptability. A novel flexible capacitive tactile sensor was proposed for multi-directional force sensing, which is based on carbon black/polydimethylsiloxane (PDMS) composite dielectric layer and upper and lower electrodes of carbon nanotubes/polydimethylsiloxane (CNTs/PDMS) composite layer. By changing the ratio of carbon black, the resolution of carbon black/PDMS composite layer increases at 4 wt%, and then decreases, which was explained according to the percolation theory of the conductive particles in the polymer matrix. Mathematical model of force and capacitance variance was established, which can be used to predict the value of the applied force. Then, the prototype with carbon black/PDMS composite dielectric layer was fabricated and characterized. SEM observation was conducted and a ratio was introduced in the composites material design. It was concluded that the resolution of carbon sensor can reach 0.1 N within 50 N in normal direction and 0.2 N in 0–10 N in tangential direction with good stability. Finally, the multi-directional force results were obtained. Compared with the individual directional force results, the output capacitance value of multi-directional force was lower, which indicated the amplitude decrease in capacity change in the normal and tangential direction. This might be caused by the deformation distribution in the normal and tangential direction under multi-directional force.

Thermoelectrical properties of graphene knife-coated cellulosic fabrics for defect monitoring in Joule-heated textiles

Knife-coating can confer new properties on different textile substrates efficiently by integrating various compounds into the coating paste. Graphene nanoplatelets (GNP) is one of the most used elements for the functionalization of fabrics in recent years, providing electrical and thermal conductivity to fabrics, later used to develop products such as sensors or heated garments. This paper reports thermoelectrically conductive textiles fabrication through knife-coating of cellulosic fabrics with a GNP load from 0.4 to 2 wt% within an acrylic coating paste. The fabric doped with the highest GNP content reaches a temperature increase of 100°C in few seconds. Besides, it is found out that the thermographic images obtained during the electrical voltage application provide maps of irregularities in the dispersion of conductive particles of the coating and defects produced throughout their useful life. Therefore, the application of a low voltage on the coated fabrics allows fast and effective heating by Joule’s effect, whose thermographic images, in turn, can be used as structural maps to check the quality of the GNP doped coating. The temperature values and the heating rate obtained make these fabrics suitable for heating devices, anti-ice and de-ice systems, and protective equipment, which would be of great interest for industrial applications.