Graphite Brush Research Articles

Effect of Humid Tropical Climate and Electrical Current on the Electrical Sliding Wear Behavior of Graphite Brush in Motor

Abstract The commutator and brush of the motor are often worn during operation. The wear of commutator—brushes is influenced by various factors: current density, material, sliding speed, contact force, temperature, and environmental humidity, especially by humid tropical climate conditions. This affects directly wear, long life, and the reliability of commutator—brushes. This paper presents the results of the electrical sliding wear behavior of the graphite brushes when the temperature, the humidity of the humid tropical environment, and current change. According to experimental planning, the studies were conducted on graphite brushes with three input factors: the temperature of 25 °C, 40 °C, and 55 °C, relative humidity (RH) of 51%, 75%, and 99%, and current 5 A, 7.5 A, and 10 A. The results show that the specific wear-rate Ws increases when relative humidity, temperature, and current increase. When the brush works in extreme conditions, the specific wear-rate Ws will reach the maximum value and equal to about 5.37 times the Ws value in the best conditions in this experiment.

Detailed Model of the Grid-Connected Cascaded Doubly Fed Induction Machine

The Cascaded (Brushless) Doubly-Fed Induction Machine (CDFIM) is a promising substitute for the commonly used Doubly-Fed Induction Machines (DFIM) for wind power application. The CDFIM offers reliable performance and low maintenance due to the absence of slip rings and graphite brushes. In this study, a detailed analytical model for the CDFIM is proposed in order to clearly show the controllable input (i.e., current from inverter side) and output (i.e., total output torque) relationship. The proposed model is expressed in the frequency (Laplace) domain. Field oriented (i.e., vector) control approach is adopted in order to achieve a precise dynamic model for the grid connected CDFIM. The steady-state and dynamic behavior of derived torque terms are presented and explained individually. Dynamic response of the total output torque is calculated, both analytically and numerically in a simulation and the results are shown to be consistent. Next, the torque-sharing and power-sharing concepts of the CDFIM are presented to further study the system behavior under different rotor velocities. Finally, to verify the proposed model, an experimental setup, using a cascaded DFIM was used, and the results are reported.

Enhanced sulfur recovery and sulfate reduction using single-chamber bioelectrochemical system

The aim of this study was to investigate the feasibility of sulfate removal and elemental sulfur (S0) recovery in the single-chamber bioelectrochemical system (S-BES). The performance of S-BES was compared with that of dual-chamber bioelectrochemical system (D-BES). The S-BES was constructed with graphite felt as the anode and graphite brush as the cathode. The D-BES was constructed with proton exchange membrane as the separator between anode and cathode chambers. With an applied voltage of 1.0 V and 1 g/L acetate as the substrate, the S-BES and D-BES were tested by feeding with 480 mg/L SO42− in the phosphate buffer. Results showed that the maximum current density of 37.6 ± 4.5 mA/m3 was reached in the S-BES, which was higher than that in the D-BES (i.e., 22.2 ± 2.6 mA/m3). The SO42− removal was much higher in the S-BES than in the D-BES (99.5% vs. 57.2%). In the effluent and the electrodes of S-BES, S0 was identified with Raman and X- Ray diffraction analyses. The S0 recovery on the anode was 13.7 times of that on the cathode of S-BES, indicating that S0 was mainly produced on the anode. The measured total S0 recovery reached 67.5% in the S-BES. High relative abundance of Desulfurella (47.1%) and Geobacter (26.1%) dominated the community in the anode biofilm of S-BES. The excellent performance of S-BES may be attributed to the neutral pH in the solution and the synergistic reaction between the anode and cathode. Results from this study should be useful to enhance the S-BES applications in treating wastewater containing sulfate.

Enhanced dechlorination of 1,2-dichloropropane to propene in a bioelectrochemical system mediated by Dehalogenimonas

Bioelectrochemical systems (BES) are promising technologies to enhance the growth of organohalide-respiring bacteria and to treat chlorinated aliphatic hydrocarbons. In this study, two carbon-based cathodic electrode materials, a graphite brush and a carbon cloth, were used as hydrogen suppliers to couple growth of Dehalogenimonas and dechlorination of 1,2-DCP to nontoxic propene in the cathode vessel. The BES with graphite brush electrode consumed ~4000 µM 1,2-DCP during 110 days and exhibited a degradation rate 5.6-fold higher than the maximum value obtained with the carbon cloth electrode, with a cathode potential set at −0.7 V. Quantitative PCR confirmed that Dehalogenimonas gene copies increased by two orders of magnitude in the graphite brush BES, with an average yield of 1.2·108±5·107 cells per µmol of 1,2-DCP degraded. The use of a pulsed voltage operation (cathode potential set at −0.6 V for 16 h and −1.1 V for 8 h) increased the coulombic efficiency and degradation of 1,2-DCP when compared with a continuous voltage operation of −1.1 V. Bacterial cell aggregates were observed in the surface of the graphite brush electrodes by electron scanning microscopy, suggesting biofilm formation. This study expands the range of chlorinated compounds degradable and organohalide-respiring bacteria capable of growing in BES.

Difference in Energization Mechanism caused by Change in Brush Ag Content in Sliding Energization of Steel Slip Ring and Ag Graphite Brush

Difference in Energization Mechanism caused by Change in Brush Ag Content in Sliding Energization of Steel Slip Ring and Ag Graphite Brush

Low electrical resistance metal graphite brush reinforced with epoxy resin for electrical motor

Electrical conductive coals were invented about a hundred years. Coals often were composed of carbon materials, solid lubricants, metals, resins and etc. The main use of coal is in electric motors. In this paper Graphite, Copper and Ferromolybdenum were used as conductive carbon material, conductive metal and auxiliary material respectively. Further, epoxy resin was used as reinforcing material. Carbon brushes with resin due to suitable properties such as low resistance, conductivity and high speed are used. In this experiment first, the mixture of all materials was molded. The electrical conductivity test, FE-SEM images, Raman spectrum, and I–V diagram were carried out. FE-SEM images indicated the rate of scattering of the main materials in the samples. In this work, the electrical resistance of the optimum sample was 0.87 Ω.

Voltage Saturation Mechanism in V-I Characteristics for Natural Graphite Brush and Steel Slip-ring

Voltage Saturation Mechanism in V-I Characteristics for Natural Graphite Brush and Steel Slip-ring

Low operating cost approach in Spirulina platensis bio-photovoltaic cell

Bio-photovoltaic (BPV) cells are receiving more attention due to their clean electricity generation, utilisation of renewable energy, self-sustainability, and their ability to reduce carbon footprint by imitating the microorganism metabolism in the natural environment. This paper studied the performance of BPV using Spirulina platensis (S. platensis) as a biocatalyst in the anode compartment, under intermittent and continuous illumination with a light supply of 1500 lux. Zarrouk medium (ZM), and fertiliser medium (FM) became the anolyte, with graphite brush as electrodes. S.platensis cultured in FM showed a growth rate of 0.02285 ± 0.004 Abs/day, which was 15% less than growth in the ZM (0.02713 ± 0.006 Abs/day). The average current density normalised by the projected surface area of electrode produced by BPV with ZM under intermittent illumination at the end of the test period (≈1.654 A/m2) was higher than that of continuous illumination (≈0.391 A/m2). Meanwhile, the average current density by BPV with FM under intermittent illumination at the end of the test period (≈2.027 A/m2) was higher than that of the continuous illumination (≈0.839 A/m2). By comparison of the polarisation curve and the current density of ZM sets and FM sets, it can be deduced that the FM can be used to replace ZM in BPV operations.

A steady-state electrical model of a microbial fuel cell through multiple-cycle polarization curves

The use of Microbial Fuel Cells as power sources in rural or remote locations can solve issues related with power availability and wastewater cleaning. Furthermore, the application of such technology in wireless smart sensors applied to wastewater treatment plants can also help in water quality monitoring, increasing the process autonomy and reliability. A trustworthy power source needs to have a predictable and repeatable behavior, which cannot be achieved without adequate models and supporting hardware for energy regulation and storage. The work herein described proposes a steady-state model, represented by an electric circuit made of passive components. This model was first applied to a specific 28 mL air-cathode Microbial Fuel Cells working with artificial wastewater and using graphite brush anodes. Afterwards, the model was further validated by applying it to a larger reactor and to other bibliographic records. The goal of the study is to propose a method for finding a Microbial Fuel Cell model to be used with maximum power point tracking research, guaranteeing the best-case scenario for Microbial Fuel Cell operation as a power source. The reactors used in this study were analyzed by relating time and voltage development, both in colonization and in polarization studies. A mathematical relationship model was developed and proposed allowing to separate MFC's behavior, concerning energy production, in to meaningful components. From the experimental data the method was used to obtain a two-component circuit model that describes the power behavior of this specific Microbial Fuel Cell topology. The same method can be used to described other MFC.

The Effect of Sintering Temperature on the Microstructures and Properties of Resin-Bonded Copper–Graphite Brush Materials

In this paper, resin-bonded copper–graphite brush materials were prepared by powder metallurgy method with sintering temperatures of 450 °C and 910 °C. The microstructures of both the prepared brush materials and their worn surfaces after current-carrying friction and wear test were characterized. The physical and mechanical properties of the brushes were tested as well. The results indicate that both open pores and MoS2 are the main factors influencing the abrasion resistance of the brushes. The porosity of the brushes sintered at 450 °C is relatively low, and there is a certain amount of MoS2 on the worn surface which provides a self-lubricating effect and reduces the wear during the current-carrying friction and wear process. Brushes sintered at 910 °C have higher porosity which leads to more serious cumulative oxidative wear effects. In the meantime, the MoS2 has decomposed during sintering process, resulting in a relatively poor lubricating effect during friction process.

Aryl Diazonium Modification for Improved Graphite Fiber Brush in Microbial Fuel Cell

Aryl diazonium salts are coupling agents that assist in molecules attachment to interfaces for sensing purposes. Despite not being fully explored and not yet widely applicable for cell-based sensors, the high stability of aryl diazonium salt formed sensing system is highly favorable in biological applications. Carbon-based electrodes are the most commonly used in aryl diazonium modification due to its post grafting stable C-C bond formation. Here, salt bridge based microbial fuel cells (MFCs) were used to study on the effect of aryl diazonium modification on the anode graphite fibre brush. Aryl diazonium salts were in situ generated by the diazonation of p-phenylenediamine with NaNO2 in HCl solution. The electrochemical performance of the aryl diazonium modified graphite brush MFC was measured and compared with the unmodified graphite brush MFC. The power output of the modified graphite brush bioanode was higher (8.33 W/m3) than the unmodified graphite brush (7.60 W/m3) after 20 days of operation with ferricyanide as the catholyte. After 70 days of operation using phosphate buffer solution as the catholyte, the Pmax of modified brush was three times higher (0.06 W/m3) than of the unmodified brush (0.02 W/m3), which indicates an enhanced binding towards the substrate that facilitates a better electron transfer between the microbial and electrode surface.

Reduced graphene oxide/polyacrylamide composite hydrogel scaffold as biocompatible anode for microbial fuel cell

In this study, a reduced graphene oxide/polyacrylamide (rGO/PAM) three-dimensional (3D) composite hydrogel coupled with current collector graphite brush (GB) was developed as anode for microbial fuel cells (MFCs). The rGO/PAM was fabricated through in-situ polymerization of acrylamide in graphene oxide dispersion, followed by reduction with ascorbic acid. The resulting macro-porous scaffold with high surface area and biocompatibility was benefit for both mass diffusion of the culture medium, microbial colonization and electron mediators. As a result, the GB/rGO/PAM anode produces a remarkably high maximum power density and volumetric power density of 758 mW m−2 and 53 W m−3 at the stable state of power generation, respectively. Moreover, the orientated rGO/PAM (O-rGO/PAM) with higher conductivity could further improve the maximum power density of MFCs, achieving 782 mW m−2. The above results are substantially higher than those of traditional GB, plain carbon cloth (CC), and the control GB/GO/PAM and CC/rGO/PAM based electrodes measured under the same conditions. The new 3D composite hydrogel electrode shows great promise for improving the power generation of MFCs devices.

Selective electro-oxidation of phenol to benzoquinone/hydroquinone on polyaniline enhances capacitance and cycling stability of polyaniline electrodes

Polyaniline (PANI)-based conductive polymers are promising electrode candidates for energy storage, but they suffer the common hurdle of poor cycling stability due to structural rupture during the doping and de-doping processes. Electro-oxidation of phenol is an attractive method for removing phenol from contaminated wastewaters, but the method usually suffers from electrode fouling due to formation of non-conductive polymers on the anode. Here, we propose an environmentally benign strategy that addresses these two issues simultaneously, which can substantially enhance the cycling stability of PANI and prevent passivation of the electrode. We show that, in comparison with the bare graphite brush (GB) electrode, the PANI-GB electrode (aniline electropolymerized on GB) enables high selectivity of phenol conversion to the redox-active benzoquinone (BQ)/hydroquinone (HQ). These species are largely immobilized on the electrode, as evidenced via chemical identification and physicochemical characterization. Meanwhile, the P/40-PANI-GB electrode (obtained from CV scans of phenol on PANI-GB over 40 cycles) achieves a larger specific capacitance and, more importantly, a remarkably higher capacitance retention rate compared to the PANI-GB electrode. Such improvements are demonstrated to be caused by the availability of a second BQ/HQ redox system and the strong affinity between PANI and BQ/HQ via the interactions of π–π stacking, hydrogen bonding, and chemical doping.

Preparation of carbon discs using petroleum-based binder pitch reformed with carbon black

Carbon materials are widely used in various industry applications, such as a carbon fibers, graphite brushes, aluminum engineering and binders,...

Electricity generation using continuously recirculated flow electrodes in reverse electrodialysis

Abstract Capacitive flow electrode systems that generate electricity from salinity gradients are limited by low power densities, inefficient electrical current collection, and complex system operation. We show here the proof-of-concept that a single reverse electrodialysis cell using continuously recirculated activated carbon flow electrodes can generate uninterrupted electricity from an artificial sea/river water gradient. Power densities reached 61 ± 5.7 mW m −2 (normalized to total membrane surface area) and current densities 2.4 ± 0.13 A m −2 when a 10% by weight carbon loading was used with graphite plate current collectors. Using high-surface area graphite brush current collectors, maximum power densities increased more than 320% to 260 ± 8.7 mW m −2 and maximum current densities more than 400% to 14 ± 0.59 A m −2 . The performance improvements were attributed to a more than 80% decrease in electrode resistances when brushes were used instead of plates. A control static capacitive electrode system obtained slightly higher average power densities (290 ± 8.7 mW m −2 ), but could not produce it continuously, highlighting the operational advantage of the recirculated flow electrode design.

Electrical contact resistance and wear of a dynamically excited metal–graphite brush

The wear and contact resistance of sliding contacts are typically researched with a pin-on-disk experiment that prevents dynamic excitation. However, in electrical machines, the brush clearance enables dynamic excitation, resulting in flexible body dynamics. To research the wear and contact resistance during dynamical excitation, an in-situ experimental approach is introduced here, with the influences of rotational speed, electrical current, and temperature being assessed. This research shows that a small wear rate and contact resistance are possible at 10,000 and 5000 RPM if the electrical current is higher than 3 A. It was also found that the contact resistance decreased with an increased ambient temperature, electrical current, and rotating speed, whereas the wear rate increased with the rotating speed at low current density and low ambient temperature.

Sacrificing power for more cost-effective treatment: A techno-economic approach for engineering microbial fuel cells

Microbial fuel cells (MFCs) are a promising energy-positive wastewater treatment technology, however, the system’s cost-effectiveness has been overlooked. In this study, two new anode materials – hard felt (HF) and carbon foam (CF) – were evaluated against the standard graphite brush (GB) to determine if using inexpensive materials with less than ideal properties can achieve more cost-effective treatment than high-cost, high-performing materials. Using domestic wastewater as the substrate, power densities for the GB, HF and CF-MFCs were 393, 339 and 291 mW m−2 normalized by cathodic surface area, respectively. Higher power densities correlated with larger anodic surface areas and anodic current densities but not with electrical conductivity. Cyclic voltammetry revealed that redox systems used for extracellular electron transport in the GB, HF and CF-MFCs were similar (−0.143 ± 0.046, −0.158 ± 0.004 and −0.100 ± 0.014 V vs. Ag/AgCl) and that the electrochemical kinetics of the MFCs showed no correlation with their respective electrical conductivity. 16S rRNA sequencing showed the GB, HF and CF microbial community compositions were not statistically different while organic removal rates were nearly identical for all MFCs. The HF-MFC generated a power output to electrode cost (W $−1) 1.9 times greater than the GB-MFC, despite producing 14% less power and 15% less anodic current, while having 2.6 times less anodic surface area, 2.1 times larger charge transfer resistance and an electrical conductivity three orders of magnitude lower. The results demonstrate that inexpensive materials are capable of achieving more cost-effective treatment than high-performing materials despite generating lower power when treating real wastewater.

Recovery of Nanoparticles of Metal Values from Spent Metallized Graphite Brushes and Slip Rings

This work provides a method to recover monolayer metal values having nanoparticle in size from spent metalized graphite brushes. The recovered metals are supported on porous glassy carbon substrate by chemical or electro deposition process. The chemical method involves crushing and grinding of the spent brushes to pass 200 mesh. Magnetic separation removed magnetic susceptible metals such as iron. Nonferrous metals were leached using 3N nitric acid in hot conditions. Hydroxide gel of the dissolved metals generated with 1N ammonium hydroxide. The carbon substrate was multi-impregnated with metals hydroxide 3-4 times. In each time, the loaded carbon was dried. Free metals on the carbon substrate are obtained by reducing the hydroxide with hydrazine hydrate or by thermal reduction using hydrogen gas at 900°C. In the electro deposition process, ground spent brushes were packed in a polyethylene cloth used as anode. The electrolyte is 3M of sulfate salt of the metal of concern. Pulse current cyclic voltmetric technique was applied to control the particle diameter and thickness of the deposited metal. Results revealed that monolayer silver and copper of nanoparticles has been successfully prepared from spent metalized graphite brushes. Electro deposition is more friendly environment procedure and more convenient, less cost and more precise.

Real-time monitoring of subsurface microbial metabolism with graphite electrodes.

Monitoring in situ microbial activity in anoxic submerged soils and aquatic sediments can be labor intensive and technically difficult, especially in dynamic environments in which a record of changes in microbial activity over time is desired. Microbial fuel cell concepts have previously been adapted to detect changes in the availability of relatively high concentrations of organic compounds in waste water but, in most soils and sediments, rates of microbial activity are not linked to the concentrations of labile substrates, but rather to the turnover rates of the substrate pools with steady state concentrations in the nM–μM range. In order to determine whether levels of current produced at a graphite anode would correspond to the rates of microbial metabolism in anoxic sediments, small graphite anodes were inserted in sediment cores and connected to graphite brush cathodes in the overlying water. Currents produced were compared with the rates of [2-14C]-acetate metabolism. There was a direct correlation between current production and the rate that [2-14C]-acetate was metabolized to 14CO2 and 14CH4 in sediments in which Fe(III) reduction, sulfate reduction, or methane production was the predominant terminal electron-accepting process. At comparable acetate turnover rates, currents were higher in the sediments in which sulfate-reduction or Fe(III) reduction predominated than in methanogenic sediments. This was attributed to reduced products (Fe(II), sulfide) produced at distance from the anode contributing to current production in addition to the current that was produced from microbial oxidation of organic substrates with electron transfer to the anode surface in all three sediment types. The results demonstrate that inexpensive graphite electrodes may provide a simple strategy for real-time monitoring of microbial activity in a diversity of anoxic soils and sediments.

Effect of hydrogen producing mixed culture on performance of microbial fuel cells

This study examined the influence of H2-producing mixed cultures on improving power generation using air-cathode microbial fuel cells (MFCs) inoculated with heat-treated anaerobic sludge. The MFCs installed with graphite brush anode generated higher power than the MFCs with carbon cloth anode, regardless heat treatment of anaerobic sludge. When the graphite brush anode-MFCs were inoculated selectively with H2-producing bacteria by heat treatment, power production was not improved (about 490 mW/m2) in batch mode operation, but for slightly increased in carbon cloth anode-MFCs (from 0.16 to 2.0 mW/m2). Although H+/H2 produced from H2-producing bacteria can contribute to the performance of MFCs, suspended biomass did not affect the power density or potential, but the Coulombic efficiency (CE) increased. A batch test shows that propionate and acetate were used effectively for electricity generation, whereas butyrate made a minor contribution. H2-producing mixed cultures do not affect the improvement in power generation and seed sludge, regardless of the pretreatment, can be used directly for the MFC performance.