Characterization and Evaluation of Novel Maglev EDM with Existing EDM

At present, the machining performance of the existing EDM technology depends upon the commonly used pulsed power supply and gap control mechanism. The complexity and the higher cost of the above said vital components, reflected in the product cost. A simple electrical circuit has been applied to control the voltage and the electric magnet so that the tool electrode can levitate over the workpiece at the desired distance (electrode gap). A prototype is fabricated with the DC power supply and the maglev levitation mechanism. To evaluate novel maglev EDM technology with the existing EDM technology, experiments were conducted on Ti-6Al-4V alloy with a brass tool. The discharge waveform of maglev EDM has shown the discharge voltage and current and the absence of short-circuit at high duty factor. A predictive model is formulated by dimensional analysis based on MRR and average surface roughness. The experimental result of conventional EDM from the literature were used to prepare the model. The maglev EDM is showing higher MRR and surface roughness than the prediction. Surface morphology showed similar surfaces as formed in EDM. The specific energy analysis showed that the developed maglev EDM performs in reported data range. It is noted that the proposed technology is in its early stage and the performance is significantly comparable with the existing technology. Therefore, it is expected that the research in this area may help to develop an economically sustainable alternative to the existing costly and complex EDM technology.

Electrochemical Deposition of Lead for Water Quality Sensing

Lead contamination in drinking water can pose serious health risks to humans, and can often go undetected as a result of corrosion of lead infrastructure installed in buildings constructed prior to 1986. Thus, there is an unmet need for timely, cost-effective, and onsite monitoring of lead in drinking water. Here, we have designed a four-electrode system to reliably respond to electrodeposited lead oxide that provides a near real-time indication of lead presence. To better understand this detection mechanism, we investigated the temporal and spatial electrochemical deposition of lead using potential response data, scanning electron microscopy (SEM), fractal dimension (fD), and COMSOL Multiphysics® finite element analysis. Our results suggest that the deposition of lead oxide on the sensor is diffusion limited. Such fundamental understanding of the detection mechanism is critical to improve and shorten the detection time of the sensor. We used this information to improve the detection time and reliability of the signal by reducing the electrode gap distance and agitating the solution. This study provides a path for further optimization of a continuous electrochemical sensor for onsite monitoring of lead in drinking water.

The Nanosecond Impulsive Breakdown Characteristics of Air, N2 and CO2 in a Sub-mm Gap

The present paper investigates the breakdown characteristics—breakdown voltage, with breakdown occurring on the rising edge of the applied HV impulses, and time to breakdown—for gases of significance that are present in the atmosphere: air, N2 and CO2. These breakdown characteristics have been obtained in a 100 µm gap between an HV needle and plane ground electrode, when stressed with sub-µs impulses of both polarities, with a rise time up to ~50 ns. The scaling relationships between the reduced breakdown field Etip/N and the product of the gas number density and inter-electrode gap, Nd, were obtained for all tested gases over a wide range of Nd values, from ~1020 m−2 to ~1025 m−2. The breakdown field-time to breakdown characteristics obtained at different gas pressures are presented as scaling relationships of Etip/N, Nd, and Ntbr for each gas, and compared with data from the literature.

Approach to setting the mode parameters in combined electro-erosive - electrochemical processing during piercing the deep holes of small diameter

The article considers the problem of forming the deep holes of small diameter by using the combined electro-erosive and electrochemical machining based on the electrochemical and electro-erosive processes. The approach to setting the mode parameters during piercing the deep holes with a diameter of less than 1 mm is suggested. The approach takes into consideration the influence of hydrodynamic losses in the inter-electrode gap on the limitation of the mode parameters of the electrochemical and electro-erosive components in the combined processing. It also takes into account the interrelation between the magnitude of the inter-electrode gap and the linear velocities of the removal of the processed material in each of the components during the combined processing. The validity of the approach to setting the mode parameters in the combined electro-erosive -electrochemical processing during piercing the deep holes with a diameter from 0.3 mm to 1 mm in the range of the inter-electrode gap from 0.025 mm to 1 mm is experimentally confirmed.

Design, fabrication, and testing of microelectromechanical system spark gap switch based on streamer theory

In order to realize that the fuze micro system has both high security and miniaturization characteristics, the spark gap research of Micro-Electro-Mechanical System safety system is carried out. So that to solve the safe and reliable function of the spark gap switch under the low power supply voltage (35 V) of the fuze micro system, the gas gap size and electrode radius are shown to significantly affect the gas breakdown voltage using streamer theory. Based on these results, a spark gap switch with triggering electrodes is designed. The triggering electrode gap is 2 μm and the main electrode gap is 10 μm. A spark gap switch test circuit is designed based on the RLC circuit. Through finite element simulation, it is verified that the gas breakdown voltage increases nonlinearly with increasing gap size. Pre-breakdown spark gap switches were fabricated based on the surface silicon process and tested. The test results show that the conduction voltage values of the triggering electrode and the main electrode are basically consistent with the simulation and calculation results. The breakdown voltage of the main electrode can be greatly reduced by applying a certain voltage to the triggering electrode, realize the reliable function in the micro fuze system.

Spatiotemporal control of femtosecond laser filament-triggered discharge and its application in diagnosing gas flow fields

Precise control of the discharge in space and time is of great significance for better applications of discharge plasma. Here, we used a femtosecond laser filament to trigger and guide a high-voltage DC pulse discharge to achieve spatiotemporal control of the discharge plasma. In space, the discharge plasma is distributed strictly along the channel generated by the femtosecond laser filament. The breakdown voltage threshold is reduced, and the discharge length is extended. In time, the electrical parameters such as the electrode voltage and the electrode gap affect discharge delay time and jitter. By optimizing the parameters, we can achieve sub-nanosecond jitter of the discharge. Based on the spatiotemporal control of the discharge, we applied filament-triggered discharge for one-dimensional composition measurements of the gas flow field. Besides, the technique shows great potential in studying the spatiotemporal evolution of discharge plasma.

Effects of Radio Frequency Tempering on the Texture of Frozen Tilapia Fillets

Radio frequency (RF) tempering has been proposed as a new alternative method for tempering frozen products because of its advantages of rapid and volumetric heating. In this study, the texture of RF-tempered frozen tilapia fillets was determined under different RF conditions, the effects of related factors on the texture were analyzed, and the mechanisms by which RF tempering affected the texture of the tempered fillets were evaluated. The results show that the springiness (from 0.84 mm to 0.79 mm), cohesiveness (from 0.64 mm to 0.57 mm), and resilience (from 0.33 mm to 0.25 mm) decreased as the electrode gap was increased and the power remained at 600 W, while the shear force increased as the power was increased for the 12 cm electrode gap (from 15.18 N to 16.98 N), and the myofibril fragmentation index (MFI) values were markedly higher at 600 W than at 300 W or 900 W (p < 0.05). In addition, the tempering uniformity had a positive effect on hardness and chewiness. The statistical analysis showed that the texture after RF tempering under different RF conditions correlated relatively strongly with the free water content, cooking loss, and migration of bound water to immobilized water. The decrease in free water and bound water migration to immobilized water resulted in a significant increase in cohesiveness and resilience.

Detection of oscillatory solutions in a vacuum diode with total electron reflection

Stability features of steady-state solutions for a vacuum diode with complete deceleration of electron beam is studied. A boundary line on the (inter-electrode gap, external voltage)-plane separating stable solutions from unstable ones is built up. An instability development is shown to end in a state with non-linear oscillations of the electric field but with no virtual cathode in a plasma. Existence of non-linear oscillations of the electric field in a vacuum diode with total reflection of an electron beam points out that such a diode can be a basis to create microwave generator.

The Effect of Cobalt Catalyst Loading at Very High Pressure Plasma-Catalysis in Fischer-Tropsch Synthesis

The influence of different catalyst cobalt loadings on the C1-C3 hydrocarbon product yields and energy consumption in plasma-catalytic Fischer-Tropsch synthesis (FTS) was investigated from the standpoint of various reactor operating conditions: pressure (0.5 to 10 MPa), current (250 to 450 mA) and inter-electrode gap (0.5 to 2 mm). This was accomplished by introducing a mullite substrate, coated with 2 wt%-Co/5 wt%-Al2O3, 6 wt%-Co/5 wt%-Al2O3 or 0 wt%-Co/5 wt%-Al2O3 (blank catalyst), into a recently developed high pressure arc discharge reactor. The blank catalyst was ineffective in synthesizing hydrocarbons. Between the blank catalyst, 2 wt%, and the 6 wt% Co catalyst, the 6 wt% improved C1-C3 hydrocarbon production at all conditions, with higher yields and relatively lower energy consumption at (i) 10 MPa at 10 s, and 2 MPa at 60 s, for the pressure variation study; (ii) 250 mA for the current variation study; and (iii) 2 mm for the inter-electrode gap variation study. The inter-electrode gap of 2 mm, using the 6 wt% Co catalyst, led to the overall highest methane, ethane, ethylene, propane and propylene yields of 22 424, 517, 101, 79 and 19 ppm, respectively, compared to 40 ppm of methane and < 1 ppm of C1-C3 hydrocarbons for the blank catalyst, while consuming 660 times less energy for the production of a mole of methane. Furthermore, the 6 wt% Co catalyst produced carbon nanotubes (CNTs), detected via transmission electron microscopy (TEM). In addition, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD) showed that the cobalt catalyst was modified by plasma treatment.