Non-conducting Particles Research Articles

Commercially Applicable One-Step Method to Construct Homogeneous Anode/Electrolyte Interface and Cathode/Electrolyte Interface Layers in All-Solid-State Lithium-Sulfur Batteries.

Using a solid electrolyte is considered to be the most effective strategy to solve the shuttle effect in lithium-sulfur batteries. However, the practical application of solid-state lithium-sulfur batteries (SLSBs) is still far from being realized. This is because SLSBs, like all other solid-state battery systems, also face the dilemma of interface degradation (including both the anode and cathode interfaces), in addition to terrible kinetics due to the nonliquid solid-state electrolytes infiltrating the nonconductive sulfur particles inside the cathode. It is necessary to consider the factors associated with the cathode, anode, electrolyte, and all the interfaces in an integrated manner to solve the problems existing in SLSBs. Similar to the anode/electrolyte interface formation in a liquid electrolyte, this work simultaneously synthesized the in situ anode/electrolyte and cathode/electrolyte interfaces by one-step electrochemically inducing the polymerization of thiophene monomers in the poly(ethylene oxide) electrolyte. By screening and adjustment of the thiophene polymerization process, a dual ion-electron conductive layer on both sides of the electrolyte as well as the inner surface of the sulfur cathode was synthesized. As a result of these improvements, an ionic conductivity of 1.1 × 10-4 S cm-1 was achieved by the composited electrolyte at 40 °C while maintaining a specific capacity of 1166.6 mAh g-1 after 50 cycles by the SLSBs assembled. This study regulated the dual ion-electron conductive interface on both sides of the electrolyte in a one-step manner and emphasized the important role of the homogeneity inner cathode surface and cathode/electrolyte interface in SLSBs. It might be extended to production applications because of its competitiveness in both technology and economy.

Electrophoresis analysis of a hydrophobic spherical particle in a micropolar electrolyte solution

AbstractThe general expression for the time‐independent electrophoretic velocity of a spherical colloidal particle with a slippage surface in a microstructure electrolyte solution is derived. The two extreme cases of nonconducting and perfect conducting particles are investigated. The derived expression is valid for arbitrary Debye length and low particle zeta potentials. The concept of velocity spin slip is incorporated with the usual velocity slip at the particle's surface. The effect of the microstructure of fluid particles on the electrophoresis phenomena is discussed based on a micropolar fluid model. The influences of velocity slip and velocity spin slip are shown through various plots of electrophoretic velocity. The limiting case of electrolyte viscous solution is recovered. The principal findings of this research can be summarized as follows: As the micropolarity parameter increases, the normalized electrophoretic velocity decreases and reaches its peak in the case of Newtonian fluids. Additionally, the velocity slip acts as a counteracting factor that promotes an increase in the electrophoretic velocity. In the context of nonconducting particles, the normalized electrophoretic velocity rises as the spin slip parameter and Debye length decrease. Conversely, for perfectly conducting particles, it increases as the spin slip parameter and Debye length increase.

Semi-continuous dielectrophoretic separation at high throughput using printed circuit boards

Particle separation is an essential part of many processes. One mechanism to separate particles according to size, shape, or material properties is dielectrophoresis (DEP). DEP arises when a polarizable particle is immersed in an inhomogeneous electric field. DEP can attract microparticles toward the local field maxima or repulse them from these locations. In biotechnology and microfluidic devices, this is a well-described and established method to separate (bio-)particles. Increasing the throughput of DEP separators while maintaining their selectivity is a field of current research. In this study, we investigate two approaches to increase the overall throughput of an electrode-based DEP separator that uses selective trapping of particles. We studied how particle concentration affects the separation process by using two differently-sized graphite particles. We showed that concentrations up to 800 mg/L can be processed without decreasing the collection rate depending on the particle size. As a second approach to increase the throughput, parallelization in combination with two four-way valves, relays, and stepper motors was presented and successfully tested to continuously separate conducting from non-conducting particles. By demonstrating possible concentrations and enabling a semi-continuous process, this study brings the low-cost DEP setup based on printed circuit boards one step closer to real-world applications. The principle for semi-continuous processing is also applicable for other DEP devices that use trapping DEP.

Optimization of PMEDM process parameters for B4C and B4C+SiC reinforced AA7075 composites

MaterialsWith sufficient electrical conductivity can be successfully processed by applying the electrical discharge machining (EDM) method; however, due to the presence of non-conductive particles in composites, which have been produced by adding ceramics particles, problems such as unstable machining, low material removal rate, and high tool wear are observed during the EDM. This study employed powder-mixed electrical discharge machining (PMEDM) by adding electrically conductive nano-size graphite powder into the dielectric liquid to minimize these problems. Moreover, the machinability of AA7075/ B4C and AA7075/ B4C+SiC composites was evaluated using the Taguchi method. The experimental study used L18 orthogonal array (OA) (21 ×32). ANOVA was employed to obtain significant parameters and percent contributions of variable parameters on the material removal rate (MRR). Reinforcement ratio, current and sintering time applied to the workpiece were chosen as variable parameters. The optimum parameters for MRR were obtained at A1B3C3 (reinforcement ratio= 10%, current= 8 A, sintering time=150 min). According to S/N ratio graphs, increasing the reinforcement ratio leads to a decreased MRR. On the contrary, when the applied current increases, MRR increases. Additionally, analysis results show that the discharge current is the most important parameter affecting MRR. In the morphological examinations, it was understood that the amounts of B4C and SiC particles in the composite structure affect the quality of the machined surfaces. It was determined that the surface quality deteriorated with the increase in the amount of SiC and B4C in the composite structure and the increase in the discharge current.

Flexible fibrous separator asymmetrically coated by silica and MXene for high performance lithium batteries with enhanced safety

Introducing inorganic particles into separator for lithium batteries has been proven to be a very effective and facile way to improve battery safety and performance. In this work, a composite separator (PBS-M-S) was developed via asymmetrically coating the conductive MXene particles and the nonconductive silica particles onto a biodegradable poly(butylene succinate) (PBS) fibrous membrane. Such a structure and material design was able to give the produced separator exceptional all-around properties. Specifically, the PBS-M-S separator displayed great flexibility with a 250% elongation at break, high temperature sensitivity with shutdown function at 120 °C, and thermal stability with flame retardancy. Moreover, the network constructed by PBS's micro/nano fibers and the electrolyte affinity of silica allowed the separator to maintain abundant electrolyte. This, combined with the incorporation of MXene, optimized the separator with high ionic conductivity (3.386 mS cm−1), lithium ion transference number (0.51) and lithium dendrite inhibition ability, which rendered the cell with outstanding cycling stability. Therefore, taking safety and battery performance into account, the as-prepared composite membrane could be a promising separator candidate for lithium ion batteries.

An investigation of the transient electrophoresis of conducting colloidal particles in porous media using a cell model

A comprehensive analytical study of the electrophoresis of a suspension of charged spherical particles in an arbitrary electrolyte solution through a porous medium is analyzed using a unit cell model. The unsteady Brinkman equation with the term of the electric force governing the fluid velocity fields is solved by means of the Laplace transform. The porous medium is uniformly charged by fixed charge density Q, and the embedded spherical particle is conductive and charged with constant zeta potential. Two different accurate concepts of the boundary conditions at the outer virtual surface, are presented to solve the governing equations for the flow field. Steady-state electrophoretic velocity is obtained analytically and displayed graphically for different physical parameters. Also, a closed form of the transient electrophoretic velocity versus the dimensionless elapsed time is plotted and discussed for different values of the Debye length parameter, particle volume fraction, density ratio, permeability of the porous medium, and for highly- and non-conducting particles. The steady/ transient electrophoretic velocity is a monotonic decreasing function of the permeability parameter, the particle-to-fluid density ratio, and the particle volume fraction, but it increases with an increase in the Debye length parameter with constant zeta potential. In general, the Kuwabara cell model predicts a smaller value for the electrophoresis velocity than the Happel model, but the difference is not significant. On the other hand, when the transient velocity is normalized by its steady state, the Happel model has smaller values than the Kuwabara model. The effects of the relevant parameters on the transient starting electrokinetic flow in the porous medium are interesting and significant. The results are found to be in excellent agreement with the exact numerical results obtained by Lai and Keh.

Metal-pad-enhanced resistive pulse sensor reveals complex-valued Braess paradox.

A resistive pulse sensor measures the electrical impedance of an electrolyte-filled channel as particles flow through it. Ordinarily, the presence of a nonconductive particle increases the impedance of the channel. Here we report a surprising experimental result in which a microfluidic resistive pulse sensor experiences the opposite effect: The presence of a nonconductive particle decreases the channel impedance. We explain the counterintuitive phenomenon by relating to the Braess paradox from traffic network theory, and we call it the complex-valued Braess paradox (CVBP). We develop theoretical models to study the CVBP and corroborate the experimental data using finite element simulations and lumped-element circuit modeling. We then discuss implications and potential applications of the CVBP in resistive pulse sensing and beyond.

Influence of Particle Shape on Tortuosity of Non-Spherical Particle Packed Beds

Tortuosity in packed beds or porous media is of significant interest in many fields, from geoscience to the chemical industry. Tortuosity plays a significant role in the mass transport in porous media, but also in their residual thermal or electric conductivity when the particles are not conducting. Several predictive models have been proposed to evaluate tortuosity, but there is still a gap when it comes to considering various particle shapes. The preponderance of tortuosity models substantiated in the literature are porosity-dependent while only a few include shape parameters. In this work, we propose a new model with sphericity and porosity to predict the tortuosity based on thermal simulations carried out with non-conducting particles for domains with no wall effect. The beds generated from rigid body simulations are compared and studied for different particle shapes with a sphericity range of 0.65–1. Sphericity showed a significant effect on the tortuosity compared with other 3D shape parameters (numbers of faces, edges, and vertices); therefore, only sphericity has been considered in the new model. The proposed new model is well suited for the porosity range of 0.3 to 0.4. In said ranges, it is an upgrade of the classical Zehner–Bauer–Schlünder (ZBS) model for the effective thermal conductivity of packed beds, with superior performance.

Development of Electrically Conductive Thermosetting Resin Composites through Optimizing the Thermal Doping of Polyaniline and Radical Polymerization Temperature

This work developed an electrically conductive thermosetting resin composite that transitioned from a liquid to solid without using solvents in response to an increase in temperature. This material has applications as a matrix for carbon fiber reinforced plastics. The composite comprised polyaniline (PANI) together with dodecyl benzene sulfonic acid (DBSA) as a liquid dopant in addition to a radical polymerization system made of triethylene glycol dimethacrylate with a peroxide initiator. In this system, micron-sized non-conductive PANI particles combined with DBSA were dispersed in the form of conductive nano-sized particles or on the molecular level after doping induced by a temperature increase. The thermal doping temperature was successfully lowered by decreasing the PANI particle size via bead milling. Selection of an appropriate peroxide initiator also allowed the radical polymerization temperature to be adjusted such that doping occurred prior to solidification. Optimization of the thermal doping temperature and the increased radical polymerization temperature provided the material with a high electrical conductivity of 1.45 S/cm.

Investigation of magnetite concentrate utilization as reinforcement in aluminum matrix composites

The utilization of harder particles with magnetic properties as reinforcement in aluminum matrix composites (AMCs) enhances the mechanical and magnetic properties of aluminum. Present study investigates the utilization of magnetite concentrate (MC), which is composed of mainly Fe3O4, as reinforcement in AMCs. To achieve this goal, commercially pure Al and MC powders were blended (0–40 wt.% of MC) and ground by high energy ball milling, pressed, and sintered at 600°C for 30 min under an argon atmosphere. The products were characterized by XRD, and SEM analyses. Also, the density and porosity of the samples were determined by Archimedes’ principle. According to the results, it was observed that with the increasing reinforcement amount, agglomeration of the MC particles inside the Al matrix, as well as the porosities of the samples, increased. 10–20 wt. % of MC containing samples, the porosity values were obtained around 12 vol. %, however higher reinforcement amounts, raised the porosity values to 17.33 vol. % linearly. With the increment in both nonconductive MC particles and pores, the electrical conductivity of the samples decreased linearly. On the other hand, hard reinforcement particles played a positive role in both hardness and wear properties and a 43.37 HB of hardness value and 0.197 m3/N.m × 10−12 specific wear rate was obtained for the sample containing 40 wt. %, MC. In addition, an increase in magnetic properties was observed in direct proportion to the amount of MC particles added, up to 31 Am2.kg−1 of saturation magnetization.

Experimental study on dressing concave trapezoidal diamond grinding wheel by electrical discharge grinding method

Electrical discharge grinding (EDG) method is proposed for dressing bronze bonded diamond grinding wheel for the first time. The advantage of this dressing method is that it can realize the discharge removal of non-conductive diamond abrasive particles and greatly improve the dressing efficiency. It is suitable for dressing coarse-grained complex forming grinding wheel. The material removal mechanism in EDG dressing is deeply analyzed, and a three-dimensional heat conduction model in the discharge process is established. The temperature field distribution in bronze and diamond under corresponding discharge parameters is obtained by numerical simulation, and the grinding depth is optimized based on the softening depth of diamond. The dressing scheme of quickly removing the rectangular block area first and then approaching layer by layer according to the design profile is formulated. The high-precision concave isosceles trapezoidal grinding wheel is dressed by using the optimized machining parameters. Finally, the dressing accuracy is evaluated by grinding the graphite plate. The detection results show that the dimensional errors of the upper and lower lines are all within 5 μm, the dimensional error of the height is 9 μm. The maximum error of the angle between the two waist is 0.33°. The minimum transition arc radius between waist and lower line is 202 μm. The straightness errors of the lower line and the two waist oblique lines are less than 7 μm. The profile error at the transition between waist and lower line is less than 62 μm.

Effective thermal conductivity of packed beds made of cubical particles

This work addresses the parameterization of the Zehner-Bauer-Schlünder model (ZBS), a standard model for the determination of the effective thermal conductivity of packed beds, based on thermal simulations in ANSYS. Data are presented for the effective thermal conductivity of packed beds of cubical particles, obtained from simulations of heat conduction in particle systems generated by rigid body dynamics using the open-source software Blender. The particle-to-gas thermal conductivity ratio is varied over many orders of magnitude in these simulations. Punctual validation is provided by heat conduction measurements with cubes made of plastic and aluminum in air. Structural results are validated by micro-computed X-ray tomography. Emphasis is set on bed porosity and on the relative interparticle contact area. Comparisons elucidate ZBS behavior at the limit of non-conducting particles. In the region of medium particle-to-fluid conductance, ZBS shape factor is for the first time evaluated for cubes. At high solid conductance, the effective thermal conductivity of the bed is dominated by areal contacts between particles. Such contacts are large with cubes, but they are also shown not to be thermally perfect. Contact imperfection limits the increase in bed conductivity with increasing particle conductivity and requires the introduction of an additional empirical parameter in the ZBS model. In total, a full parametric setting of ZBS is provided for cubical particles. Several sets of this kind would help to generalize the model for applicability to particles of arbitrary shape.

Hydrodynamic arc moving mechanism in EDM of polycrystalline diamond

ABSTRACT Polycrystalline diamonds (PCD) are difficult-to-cut materials due to their ultra-hardness caused by the diamond particles sintered in the materials’ structure. Electrical discharge machining is a universal nontraditional method to process electrically conductive hard-to-cut materials by using electro-thermal energy without considering the workpiece’s hardness and strength. However, due to the high electrical resistivity caused by the non-conductive diamond particles, EDM machining characteristics of PCD are different from those of metals. Dielectric flushing can disturb the position and shape of the plasma channel, resulting in predictable movements of the sparking spot, which provides the possibility of preventing the discharge from being trapped between the non-conductive particles during each single discharge. This paper explored the potential of improving the processability of PCD by utilizing the moving electric arcs formed by dielectric flushing. Mathematical models were established and simulated to investigate the movement behavior of plasma channels in one single-pulse discharge for the first time. A series of experiments were conducted to investigate the theory and validate the assumptions. The results showed that dielectric flushing stretched the plasma channel and changed the spots of the arcs, which increased the material removal rate and improved the consistency of the processed surface topography.

Interactions between conducting surfaces in salt solutions.

In this work, we simulate interactions between two perfectly conducting surfaces, immersed in a salt solution. We demonstrate that these forces are quantitatively different from those between (equally charged) non-conducting surfaces. There is, for instance, a significant repulsion between net neutral surfaces. On the other hand, there are also qualitative similarities, with behaviours found with non-conducting surfaces. For instance, there is a non-monotonic dependence of the free energy barrier height, on the salt concentration, and the minimum essentially coincides with a flat profile of the apparent surface charge density (i.e. the effective net surface charge density, some distance away from the surface, when accounting for ion neutralization), outside the so-called Stern layer. These conditions can be described as "perfect surface charge neutralization". Despite observed quantitative differences, we demonstrate that it might be possible to mimic a dispersion containing charged colloidal metal particles by a simpler model system with charged non-conducting particles, using modified particle-ion interactions.

High-Sensitivity Large-Throughput Broadband Tunable Microwave Wear Debris Sensing System

A highly sensitive, large throughput and wide dynamic range (in the aspect of size and material type) broadband tunable microwave interferometer based rectangular waveguide wear debris detection system is presented. Passing of (non)ferrous and (non)conductive particles through the sensor, which causes inductance and/or capacitance changes, are detected as transmission signal variations of the system. We first demonstrate the sensing principle with the aluminum particle of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$800~\mu \text{m}$ </tex-math></inline-formula> and epoxy resin particle of 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 6 GHz. Then, the effects of particle size and flow speed are tested with aluminum particles ranging from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~\mu \text{m}$ </tex-math></inline-formula> to 1.8 mm. The measurement results show that the system is able to measure particle sizes with known material and differentiate nonconductive particles from conductive ones. With the proposed data processing techniques, this system is capable of detecting as small as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$76~\mu \text{m}$ </tex-math></inline-formula> particles within an 8 mm outer diameter tube. And with future improvements on sensitivity and particle material characterization, the proposed system has the potential to differentiate (non)ferrous and (non)conductive particles and measure their sizes as a real-time wear debris sensing devices for rotating and reciprocating machines.

Effect of applied vertical stress on the electrical conductivity of particulate mixtures containing both electrically conductive and nonconductive particles: experimental study on recovered carbon black

Effect of applied vertical stress on the electrical conductivity of particulate mixtures containing both electrically conductive and nonconductive particles: experimental study on recovered carbon black

A New Evaluation Method of Total Organic Carbon for Shale Source Rock Based on the Effective Medium Conductivity Theory

In the evaluation of source rocks, the total organic carbon (TOC) is an important indicator to evaluate the hydrocarbon generation potential of source rocks. At present, the commonly used methods for assessing TOC include △ log R and neural network method. However, practice shows that these methods have limitations in the application of unconventional intervals of sand-shale interbeds, and they cannot sufficiently reflect the variation of TOC in the vertical direction. Therefore, a total organic carbon (TOC) evaluation model suitable for shale and tight sandstone was established based on the effective medium symmetrical conduction theory. The model consists of four components: nonconductive matrix particles, clay minerals, organic components (solid organic matter and hydrocarbons), and pore water. The conductive phase in the model includes clay minerals and pore water, and other components are treated as nonconductive phases. When describing the conductivity of rock, each component in the model is completely symmetrical, and anisotropic characteristics of each component are considered. The model parameters are determined through the optimization method, and the bisection iteration method is used to solve the model equation. Compared with the classic TOC calculation method, the new model can evaluate the abundance of organic matter in shale and tight sandstone, which provides a new option to assess the TOC of rocks based on logging methods.

Dynamic electrical conductivity induced by isothermal crystallization in aluminum hydroxide filled silicone rubber

In this paper, taking aluminum hydroxide (ATH) filled silicone rubber as a model composite, we report the “n-shape” dynamic electrical conductivity during isothermal crystallization in nonconductive particles filled insulating polymers. During the initial crystallization, rapid growth of dominant lamellae blocks the transport path of impurity ions, contributing to the remarkable reduction of conductivity. Addition of ATH fillers could reduce the silicone rubber content and randomness of crystals formation, lessening the amplitude of decreased conductivity. Afterward, the silicone rubber composites further shrink due to the development of subsidiary lamellae. It results in low activation energy of ion migration and thereby enhances conductivity, whose amplitude is positively related to the crystalline phase. Finally, continuous growth of rigid amorphous fraction with reduced chain mobility impedes the ions transport, decreasing the conductivity again. The growth of rigid amorphous fraction is accelerated in silicone rubber with more ATH fillers because of more constraint of ATH on molecular chains. Our findings afford a simple means to manipulate insulation performance of nonconductive particles filled semi-crystalline polymers and provide a guideline for their use in real operation.

Transient electrophoresis of a conducting spherical particle embedded in an electrolyte-saturated Brinkman medium.

In this study, the time-dependent electrophoretic motion of a conducting spherical particle embedded in an arbitrary electrolyte solution saturated porous medium is investigated. The porous medium is uniformly charged and the embedded hard particle is charged with constant -potential or constant surface charge density. The unsteady modified Brinkman equation with an electric force term, which governs the fluid velocity field, is used to model the porous medium and is solved by Laplace's transform technique. An analytical expression for the electrophoretic velocity of the spherical particle is obtained in Laplace transform domain as a function of the relevant parameters, and its inversion is obtained through numerical techniques. Also, in this study, the steady-state electrophoretic velocity is obtained analytically as linear functions of -potential (or surface density charge) and the fixed charge density. The steady-state electrophoretic velocity is displayed graphically for various relevant parameters and compered with the available data in the literature. Also, the numerical values of the transient electrophoretic velocity are plotted versus the nondimensional elapsed time and discussed for different values of the Debye length parameter, density ratio, permeability of the porous medium, and for high and nonconducting particles.

Corrosion protection of electrogalvanised steel by application of non-conducting polyaniline-silica particles

ABSTRACT The authors have demonstrated that incorporation of poly(ethyleneimine) (PEI) coated polyaniline-silica (PANI-SiO2) particles into the zinc coating matrix improves the corrosion resistance of low carbon steel in a 5% NaCl solution compared to the bare zinc coating. The zinc and hybrid coatings were electrodeposited on a steel cathode surface at pH 5.5 when PANI manifests itself as non-conductive emeraldine base. Scanning electron microscopy showed that the hybrid coating consists of particle agglomerates in size 50–100 μm, mixed with smooth formations and smaller needle-like particles. The influence of PEI is suggested to cause the appearance of the smooth formations. The influence of PANI-SiO2 particles on the cathodic deposition and anodic dissolution has been checked with cyclic voltammetry. The protective properties of the coatings were characterised by potentiodynamic polarisation and polarisation resistance studies. X-ray diffraction and X-ray photoelectron spectroscopy were also applied to investigate the metallographic structure and chemical composition of the coatings.