Pulsed Power Techniques Research Articles

Achieving excellent energy storage performance with thermal stability in lead-free AgNbO3 ceramics.

Large hysteresis and low energy density of pure AgNbO3 ceramics limit their further application in pulsed power techniques. Here, less-harmful Sm2O3-modified AgNbO3 antiferroelectric ceramics were synthesized by a rolling process, in order to improve the energy storage performance. All the Sm2O3-doped samples display reduced hysteresis due to disrupted long-range order, as certified by Raman spectra. As expected, due to the large dielectric breakdown strength and reduced hysteresis, an improved energy storage density, Wrec, of 5.85 J cm-3 and satisfactory energy efficiency, η, of 77% can be simultaneously achieved in the studied antiferroelectric ceramics, showing great superiority over other bulk electronic ceramics. Along with excellent temperature stability within the range of 20-150 °C at 320 kV cm-1 (Wrec > 4.3 J cm-3, with minimal variation of ≤4%) in the studied samples, this shows that AgNbO3-based environmentally friendly ceramics are promising materials for pulsed power techniques.

Extraction of Mycosporine-like Amino Acids and Proteins from the Agarophyte Gelidium corneum Using Pulsed Power Techniques

Gelidium corneum (syn. sesquipedale) is an industrially and ecologically important species of red alga used for the production of high-quality agar. However, the species is also of growing interest for the production of other valuable compounds, such as mycosporine-like amino acids (MAAs), with potential cosmeceutical and biomedical applications. Novel methods using two pulsed power techniques, high-voltage electrical discharges (HVED) and pulsed electrical fields (PEF), were evaluated for efficacy of MAA extraction. Algal suspensions were prepared at two ratios (1:20 and 1:40 w:v). Four different extraction protocols were compared: (i) high-voltage electrical discharges, (ii) pulsed electric fields, (iii) maceration at room temperature, and (iv) maceration at 50 °C. The algae were treated in three states: freshly harvested, dried, and powdered. HVED and PEF treatments were effective when performed on fresh algae, and in particular the HVED treatment resulted in yields of MAAs twenty times higher than the control: 0.81 ± 0.05 mg/gDry Weight (DW) vs. 0.037 ± 0.002 mg/gDW. This effect was not observed to the same extent when the algae were dried or powdered, although HVED remained the most selective method overall.

Excellent energy storage performance achieved in novel PbHfO3-based antiferroelectric ceramics via grain size engineering

• All ceramics were prepared by rolling process. • A very high W rec of 12.2 J cm −3 and efficiency of 92% can be achieved in the Pb 0.98 La 0.02 (Hf 0.65 Sn 0.35 ) 0.995 O 3 ceramic. • The Pb 0.98 La 0.02 (Hf 0.65 Sn 0.35 ) 0.995 O 3 ceramic exhibits thermal stability over a wide temperature range. • The Pb 0.98 La 0.02 (Hf 0.65 Sn 0.35 ) 0.995 O 3 ceramic displays a high W D of 5.3 J cm −3 and a discharge speed of 103 ns. • The energy storage performance of AFEs can be improved by the approach of grain size engineering. Incremental attention has been paid to the PbHfO 3 -based antiferroelectric ceramics for its giant potential in dielectric capacitors and pulsed power techniques. Here, ultrahigh energy storage properties (W rec = 12.2 J cm −3 , η = 92%) and satisfied charge–discharge property (W D = 5.3 J cm −3 , t 0.9 = 103 ns, P D = 245 MW cm −3 ) are achieved in the Pb 0.98 La 0.02 (Hf 0.65 Sn 0.35 ) 0.995 O 3 antiferroelectric ceramics. In addition, the studied ceramics also exhibited superior thermal stability within 20–120 °C (W rec > 8 J cm −3 , with minimal variation < 0.5 %). Outstanding energy storage properties can be explained by refined grain size, disrupted local structure, which is confirmed by ceramic morphology, Raman spectrum and polarization hysteresis. All these features greatly promote the application of PbHfO 3 -based ceramics in energy storage fields.

Modular solid‐state pulse generator based on multi‐turn LTD

A modular solid-state pulse generator based on a multi-turn linear transformer driver (LTD) is designed for the application of pulse power techniques with a high voltage, large current and wide pulse width. The LTD adopts the method of multi-turn winding on the magnetic core, which can help to output pulses of wide width. The isolation of the power supply with windings in the same direction of the LTD modules is designed, and the isolation voltage of the magnetic cores is the working voltage of the LTD modules. A modular solid-state pulse generator based on the multi-turn LTD is developed, which is composed of 10 LTD modules. Each module consists of 18 energy storage capacitors, metal-oxide-semiconductor field-effect transistors and their driving circuits connected in parallel. The pulse generator can output pulses with parameters including a voltage ranging from 0 to 5000 V, a pulse current up to −500 A, and a pulse width ranging from 200 ns to 5 μs. When all modules work in synchronisation, rectangular pulses can be produced with a rise time of 30 ns and a fall time of 16 ns. If all modules are asynchronised, trapezoidal pulses are produced with adjustable step-like rising and falling edges. Moreover, a higher-voltage pulse can be achieved by increasing the number of LTD modules.

Finite-Element Simulation and Experiments on Plastic Heating in the Process of Electromagnetic Pulse Forming

Electromagnetic pulse forming (EMPF) is an attractive manufacturing method using pulse power techniques. Temperature rise of the work piece is usually neglected in previous studies because the forming process is regarded as a cold process. Nevertheless, the temperature rise (if not high) also has influence on the forming process. It is important to study the temperature rise for exploring the related law in the process of EMPF. In this paper, the thermal effect in the process of EMPF, caused by the joule heating generated by the high current and the plastic work produced by the plastic deformation of the work piece in the forming process, is discussed though simulations and experiments. A finite-element simulation coupled with the electromagnetic field, plastic mechanics, deformed geometry, heat transfer, and thermal expansion based on COMSOL multiphysics is established to show the detailed thermal effect in this process. The relationship between parameters of work piece and the thermal effect has been analyzed by comparing different materials and thicknesses of work pieces. The simulation results show that the temperature of work piece has changed because of the thermal effect. A high-current pulse generator has been developed for the experiment of EMPF to verify the results of simulations. This paper describes the forming experiments of different materials and thicknesses. And the experimental results verify that the materials and thickness of work piece affect thermal effect during the process of EMPF. Compared with the Joule heating, the plastic work is the main cause of the thermal effect. Moreover, the thermal expansion caused by temperature rise could affect the forming results and material property.

Technique: effect of recycling ros on dye degradation

The objective of the present study is to be adapt pulse power technique for water treatment where an attempt has been made for recycling of the Reactive Oxygen Species (ROS) present in gaseous phase to aqueous phase and further to improve the pollutant degradation. Methylene blue (MB) was used as a model pollutant and its degradation was compared by recycling and non-recycling of ROS in the reactor. The study showed better degradation of pollutants (MB) while recycling the ROS as compared to the non-recycling condition. To support the results the different ROS such as hydrogen peroxide, Ozone and hydroxyl radicals were quantified in both conditions. We observed that the concentration of ROS present in the aqueous solution was higher in recycling conditions as compared to that of non recycled condition.

Applicability of pulsed power technique for the degradation of methylene blue

Present study evaluated the efficiency of pulsed power technique (PPT) for the degradation of methylene blue (MB) under different operating and environmental conditions. Various reactive oxygen species (ROS) such as hydroxyl radicals, hydrogen peroxide, ozone and superoxide radical were quantified. The maximum concentrations generated were found to be 63mg/L, 28mg/L, 1mg/L and 18mg/L for hydroxyl radicals, hydrogen peroxide, ozone and superoxide radical, respectively for 12min of pulsed streamer discharge at 23kV applied voltage and 25Hz frequency. It was observed that magnitude of applied voltage, frequency (pulses/sec), pH, alkalinity and natural organic matter (NOM) present in the water had a significant effect on hydroxyl radical and hydrogen peroxide generation. MB degradation efficiency and ROS formation increased with applied voltage and frequency. An initial MB concentration of 50mg/L was completely degraded within 10min at 23kV input voltage and 25Hz frequency. Acidic pH favoured ROS formation whereas high alkalinity and NOM reduced the MB degradation efficiency and ROS formation. Treatment time for the 100% degradation of 10mg/L of MB was increased from 6min to 8min in presence of 150mg/L of alkalinity. The MB degradation efficiency was further decreased to 95.6% when alkalinity was increased to 300mg/L for 10min streamer discharge. Mineralization of dye during treatment was confirmed by total organic carbon and inorganic ions analyses and IR spectra. Energy efficiency of ROS formation in the reactor was also evaluated.

Disinfection of water by pulsed power technique: a mechanistic perspective

A detailed sub-cellular level bacterial disinfection mechanism and perturbation of bacterial surface potential due to ROS/RNS in pulsed plasma treatment.

Disinfection of water using pulsed power technique: Effect of system parameters and kinetic study

Present study investigated the use of pulsed power technique for disinfection of water under different operating and environmental conditions. Final concentrations of reactive oxygen species (ROS) like hydroxyl radical, hydrogen peroxide, ozone, and superoxide radicals generated in the system were found to be 56, 17, 1 and 18mg/L, respectively, for an applied voltage of 23kV, frequency of 25Hz and a streamer discharge time of 12min. It was observed that disinfection efficiency was high with sequential stress compared to continuous stress. The disinfection efficiency increased with increasing applied voltage and frequency. Disinfection efficiency was high when pH was less than 7. Presence of alkalinity, natural organic matter and turbidity reduced the disinfection efficiency significantly. For 7 log reduction of Escherichia coli, the treatment time was increased from 6 to 10min, when pH was increased from 4 to 9. Complete disinfection of E. coli was achieved in a short treatment time of 4–10min, with an energy consumption of 0.0056–0.014kWh for 50mL of contaminated water. An empirical model for optimum disinfection efficiency was developed using Box–Behnken design (BBD). As per the model, applied voltage, time of treatment and alkalinity were found to be the most significant factors affecting the disinfection efficiency. Model predicted values were in good agreement with the experimental values. Rate constant for disinfection and ROS formation was also evaluated. Rate of disinfection was between 0.59 and 1.68log(cfu/mL)/min.

PRODUCTION AND CHARACTERIZATION OF NANO COPPER POWDER USING ELECTRIC EXPLOSION PROCESS IN LIQUID MEDIA

Nanoscience and Nanotechnology are the growing fields of scientific research and commercial development. Nanosize powders are solid particles with typical size in the range of 1 to 100 nm. Nanosize powders have very large specific surface area giving rise to many special physical and chemical properties. The important objective of the present research is to produce high purity Nanopowder using pulse power technique. The advantage of the pulse power generation is that particle size could be controlled by varying the injected power and the method has high energy efficiency and high product purity. In the present study charging voltage, dielectric strength of operating medium, length and size of operating wire on the production of Nanoparticle were analysed. We exploded Cu wires of 25 mm in length and 0.08 mm in diameter in distilled water with same discharge energy /mol. The capacitance of the energy storage capacitor was 50000pF, and the charging voltage was varied from 30 kV to 40 kV. The mechanism of generation of Nanoparticles using pulsed power technique is explained in detail. Also the relationship between different control parameters on the particles were explained in detail.

The Design of Fast Pulse Power Generator with Low Voltage

In recent years, nanosecond pulse power techniques used in the millimeter-wave solid-state pulse power amplifiers attracted much attention. The rise- and fall-time of the pulse, the flatness of pulse-top and the stability of pulse-to-pulse, which have play important roles in a nanosecond pulse power generator techniques, and directly determine the system performance. In this paper, a method using the outbreak current with low-voltage to drive MOS-FETs is proposed. The measured results show that the rise- and fall-time of the output pulse is less than 1.5 ns with a pure resistance 0.5Ω, and it only needs two 12V power supply to give a output current of 20A with a pulse width of 160 ns at a repetition rate of 540 kHz in continuous mode. A flatness of 3% for the output voltage was obtained,which meet the requirements of ka-band solid-state millimeter-wave pulse power amplifier.

Real-time stroke volume measurements for the optimization of cardiac resynchronization therapy parameters

We investigated the utility of real-time stroke volume (SV) monitoring via the arterial pulse power technique to optimize cardiac resynchronization therapy (CRT) parameters at implant and prospectively evaluated the clinical and echocardiographic results. Fifteen patients with ischaemic or non-ischaemic dilated cardiomyopathy, sinus rhythm, Class III congestive heart failure, and QRS >150 ms underwent baseline 2D echocardiogram (echo), 6 min walk distance, and quality of life (QOL) questionnaire within 1 week of implant. Following implant, 0.3 mmol lithium chloride was injected to calibrate SV via dilution curve. Atrioventricular (AV) delay (90, 120, 200 ms, baseline: atrial pacing only) and V-V delay (-80 to 80 ms in 20 ms increments) were varied every 60 s. The radial artery pulse power autocorrelation method (PulseCO algorithm, LiDCO, Ltd.) was used to monitor SV on a beat-to-beat basis (LiDCO, Ltd.). Optimal parameters were programmed and echo, 6 min walk, and QOL were repeated at 6-8 weeks post-implant. Nine patients had >5% increase in SV after optimization (Group A). Six patients had <5% improvement in SV (Group B). Compared with Group B, Group A had significant improvements in left ventricular ejection fraction (LVEF) (11.0 +/- 8.5 vs. 0.8 +/- 2.0%) and decrease in left ventricular end-diastolic dimension (LVEDD) (-0.6 +/- 0.4 vs. -0.2 +/- 0.2 cm) and 6 min walk (346 +/- 226 vs. 32 +/-271 ft, P < or = 0.05). Group A patients also tended to have greater improvement in the septal-to-posterior wall motion delay on M-mode echo (P = 0.07). Real-time SV measurements can be used to optimize CRT at the time of implant. Improvement in SV correlates with improvement in LVEF, LVEDD, and 6 min walk, and improvement in echocardiographic dyssynchrony.

Magnetic field enhancement in electromagnetic forming systems using anisotropic materials

Electromagnetic Forming (EMF) is a type of high rate forming which exploits pulsed power techniques to create high intensive pulsed magnetic fields to rapidly reshape metal parts. This technique is sometimes called magnetic pulse forming. In this technique, a metal work-piece is pushed to a die and formed by a pressure created using an intensive, transient magnetic field. This magnetic field is produced by passing a pulse of electric current through a forming coil in a pulsed power circuit. Application of field shapers has been proposed to enhance the magnetic fields and consequently to increase the applied magnetic pressure at some desired regions. In this paper, 3D Finite element simulations have been applied to study the magnetic field distribution during an electromagnetic forming process with anisotropic material. Anisotropic magnetic material is described using a permeability tensor. Elements of this tensor are obtained from different magnetization curves dependent on the direction of the magnetic field. It has been shown that application of anisotropic materials with appropriate lamination directions can result in an enhancement of the magnetic field at desired points as well as in better overall efficiencies.

An investigation of spark discharge parameters for material processing with high power ultrasound

High power ultrasound (HPU) generated using pulsed-power techniques provides an alternative method for treating ores and minerals prior to extraction processes and for the comminution of waste materials as part of a recycling process. In an earlier publication [Wilson, M.P., Balmer, L., Given, M.J., MacGregor, S.J., Mackersie, J.W., Timoshkin, I.V., 2006. Application of electric spark generated high power ultrasound to recover ferrous and non-ferrous metals from slag waste. Minerals Engineering 19, 491–499], preliminary results using the HPU technique to treat stainless steel slag and waste bottle glass were reported. This paper describes further work performed on stainless steel slag to determine the likely energy costs associated with HPU processing. In industrial applications of HPU it is important to optimise the parameters of the high-voltage (HV) spark discharge causing the shock wave in the working liquid to maximise the efficiency of the treatment. However, because of the high intensity of the shock wave it is difficult to measure its output close to the HPU source. Experiments have therefore been performed using Pinducer sensors to measure the pressure waves produced by the source at distances relatively far from the spark discharge. These measurements made in the far field have been correlated with the electrical energy provided to the discharge and treatment rates for stainless steel slag and bottle glass obtained under identical conditions.

Computer Simulation of Gamma Irradiation Energy Deposition in MOSFET Dosimeters

The application of MOSFETs as detectors or device components in pulse power technique requires an investigation of their characteristics in radiation fields. Computing possibilities of the renowned programs FOTELP and PENELOPE for determining the energy deposited in MOSFET structure and dose distribution within microscopic dimensions of the dosimeter sensitive volume were presented in this paper. Based on the obtained results, qualitative conclusions were drawn about the values of energy deposited in different material zones having various dimensions. The difference between the two codes used for calculations in materials physics and semiconductor technics, basically originates from the different physical models for numerical simulation of photon, positron, and electron transport through various materials

Production and Characterization of Nano Copper Powder Using Pulsed Power Technique

The nano copper particles were produced by the wire explosion process. The influence of chamber pressure on the size of the particles was analysed. The size of the particles was measured using Transmission Electron Microscope (TEM) studies and particle size distribution analysis was carried out by adopting log‐normal distribution. WAXD studies were carried out to understand the presence of copper particles. SAD studies were carried out. The mechanism of formation of nano powder by wire explosion technique was explained in detail. It is realised that the particle produced in this process is independent of polarity of the charging voltage.

Enhanced anaerobic gas production of waste activated sludge pretreated by pulse power technique

An electric pulse-power reactor consisting of one coaxial electrode and multiple ring electrodes was developed to solubilize waste activated sludge (WAS) prior to anaerobic digestion. By pretreatment of WAS, the soluble chemical oxygen demand (SCOD)/total chemical oxygen demand (TCOD) ratio and exocelluar polymers (ECP) content of WAS increased 4.5 times and 6.5 times, respectively. SEM images clearly showed that pulse-power pretreatment of WAS was found to result in destruction of sludge cells. Batch-anaerobic digestion of pulse-power treated sludge showed 2.5 times higher gas production than that of untreated sludge. Solubilized sludge cells by pulse-power pretreatment would be readily utilized for anaerobic microorganisms to produce anaerobically-digested gas. Slow or lagged gas production in the initial anaerobic digestion stage of pulse-power pretreated sludge implied that the methane-forming stage of anaerobic digestion would be the rate-limiting step for anaerobic digestion of pulse-power pretreated sludge.

Matching Repetitive Pulsed Power to Industrial Processes

Repetitive pulsed power techniques have enormous potential for a wide range of applications, such as nano-particle and hydrogen production, gas and water processing and sterilization, and generation of X-ray, EUV, and high-power acoustics. This paper presents the state of the art of our activities on repetitive ultra-short and microsecond pulsed power sources, pulsed thermal and streamer corona plasmas. Critical circuit elements are heavy-duty thyristors, transmission line transformers, and triggered spark-gap switches.

Comparison between characteristics of radio-frequency sheaths and pulse sheaths with insulating substrates

Characteristics of collisionless radio-frequency (r.f.) and pulse modulated sheaths near an insulating substrate are studied with a one-dimensional fluid model coupled to an equivalent circuit model. The fluid model includes all the time-dependent terms to ensure that it can describe the sheath dynamics over a wide range of r.f.- or pulse-frequency. In addition, the equivalent circuit model can self-consistently determine the relationship between the instantaneous sheath thickness and instantaneous surface potential at an insulting substrate placed on the r.f. or pulse biased electrode. The characteristic parameters of the two kinds of sheath, such as the time-dependent surface potential and sheath thickness as well as spatiotemporal variations of the potential, ion density and electron density are compared. Furthermore, the ion energy distributions (IEDs) arriving at insulating substrates and the charge density accumulated on insulating substrates are also calculated with the model. It is shown that the pulsed-power operation can more efficiently remedy the ‘surface charging effect’ than the r.f. technique for etching and deposition on insulators. Also, more uniform IED can be obtained by pulse-power techniques than that by r.f. ones.

Burn wave simulation in Z-pinch channel

The progress in pulsed power technique in the last decade can make the idea oftrigger the fusion reaction in the Z-pinch column. To show possibilities of burn wave propagation in this case, we used 2-D MHD code. The physical model includes: kinetics ofthermonu-clear reaction in D-T mixture, non-local deposition ofalpha particles, radiation transport and the influence ofmagnetic field on transport coefficients. We presented the results of simulation ofburn wave propagation in conical Z-pinch channel initiated fom hot, central region. These results are compared with the previous ones for the case without magnetic field.