Recent Advances on the Soluble Carbon Nanotubes

Summary form given only. Pulsed power technology has been used in many applications such as control of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> from exhaust gases, treatment of dioxins, removal of volatile organic compounds, generation of ozone and excitation of excimer laser. Since pulse duration of applied voltage to discharge reactor has a strong influence on energy efficiency of pollutants removal, the development of short pulse generator is paramount important for practical applications. The discharge observation of the short duration pulse voltage is an essential aspect for understanding plasma physics of this new field. In the present work, the characteristics of the developed nano-seconds (ns) pulse generator, which has the pulse duration of 5 ns, and the observation results of nano-second (ns) pulsed streamer discharges in atmospheric air are presented. The developed ns pulse generator consists of a high pressure spark gap as a lower inductance self-closing switch, a triaxial Blumlein line as a pulse forming line, a coaxial energy transmission line as a connection between the Blumlein and a load, and a pulse charging source. The triaxial Blumlein line is filled up with transformer oil as insulation and dielectric medium. The ns pulse generator outputs the positive voltage, having 2 ns of rise time and 5 ns of pulse duration. The maximum output voltage reaches up to 100 kV. The propagations of the positive and the negative ns pulsed streamer discharges in a coaxial electrode were observed using a high speed gated ICCD camera and a high dynamic range streak camera. During the both polarities of ns pulsed streamer discharges, the primary and the secondary streamers propagated from inner wire to outer cylinder electrodes. This phenomenon has good agreement to the previous works which are observed in the cases of sub-frac14s pulsed streamer discharges. However, the propagation velocity of the primary streamers in the present work is approximately 6 times faster than the previous one. This is because that the velocity of primary streamers dependent on applied voltage to electrode and ns pulse generator is able to apply the higher voltage to electrode than sub-frac14s pulse generator.

Recently industrial applications of ozone have increased in widely different areas including oxidation, sterilization, deodorization, bleaching and others. Especially, a demand of movable ozonizer for treatment of diesel exhaust gas has been growing up. Generally, a generation of ozone has been attained using ultra violet irradiation, electrolysis and electrical discharges such as a dielectric barrier discharge, a surface discharge, a pulsed streamer discharge and a superimposed silent and surface discharge. In the present situation, a ozonizer based on a dielectric barrier discharge has been commonly utilized in the world. However, a ozonizer based on a dielectric barrier discharge has disadvantages as a movable ozonizer since a discharge electrode, having a breakable dielectric layer and a sensitive gap separation, does not have enough resistance to vibration stress. In this study, the characteristics of ozonizer based on a pulsed streamer discharge were measured using a magnetic pulse compressor (MPC), which has a maximum output voltage of 60 kV, a maximum pulse repetition rate of 500 pulses per second and a pulse duration of about 130 ns, and discharge reactors with coaxial geometry. For the reactor of pulsed streamer discharges, an anode and a cathode electrodes are made by metallic material and a gap separation between electrodes has a little influence on a discharge condition. Therefore, this type of ozonizer has a merit to apply mobile situation. As the results, the ozonizer based on the pulsed streamer discharges has the better production yield of 150 g/kWh in the concentration range of 10 to 20 g/m

The plasma radiation from a pulsed streamer discharge at 0.2–2 Torr in the air has been studied. Pulsed discharges at these pressures at a distance from the electrodes consist of diffuse ionization waves and, therefore, are widely studied, including within the framework of modeling high-altitude atmospheric discharges, in particular, columnar sprites. Two setups with different excitation parameters were used to excite air at low pressures. When plasma was formed using a capacitive single-barrier discharge feeding by voltage pulses with an amplitude of up to 7 kV, diffuse red-colored ionization waves up to 120 cm long were formed. Due to the formation of an ionization wave by a discharge forming by voltage pulses with an amplitude of up to 33 kV between two electrodes, X-ray and runaway electron beam were recorded.

Microwave processing has attracted much attention in the field of cereal processing due to its positive effect on improving the nutritional quality of cereals and prolonging the shelf life of cereal food. Microwave (MW) treatment (600 W, 6 min) was studied to evaluate its effect on the physicochemical properties and in vitro digestibility of three kinds of sorghum (Sorghum bicolor [L.] Moench) starch, including Longmiliang No. 1 (LML1), Longza No. 13 (LZ13), and Hongnuo (HN). After microwave treatment, the contents of insoluble dietary fiber, soluble dietary fiber and total dietary fiber of the three kinds of sorghum were significantly increased by 3.72–7.45 g/100 g, 0.33–0.64 g/100 g, and 4.36–7.78 g/100 g, respectively. Microwave treatment also resulted in sorghum starch granules with rough surfaces, an increase in pasting temperature and pasting time, and a decrease in pasting viscosity and transition enthalpy (p &lt; .05). However, Fourier transform near infrared spectroscopy showed that microwaves did not change the chemical groups of sorghum starch. Additionally, after microwave treatment, the in vitro digestibility of sorghum starch was significantly reduced by 3.21–6.61%, the rapidly digestible starch content decreased by 5.88–9.24%, the slowly digestible starch and resistant starch contents increased by 4.63–6.65% and 1.03%–2.41%, and the hydrolysis index (HI) and glycemic index (GI) decreased by 4.98–5.74% and 2.73–3.15%, respectively. These results indicate that microwave treatment is an effective method for decreasing the in vitro digestibility and improving the physicochemical properties of starch.Practical applicationsSorghum, as an important raw material in the food industry, plays an irreplaceable role in the development of cereal food. Additionally, microwaves have been used as a novel approach for improving the edible quality and functional characteristics of cereals. A comparative study of the microstructure, pasting properties, thermal properties, and in vitro digestion of sorghum starch was performed. The results showed that compared with the original starch, microwave treatment changed the physicochemical properties of sorghum starch and decreased the GI. The results can be used to improve the properties of sorghum starch and provide a theoretical basis for the development of sorghum food.

In pre-ionized pulsed streamer discharge, regulating the seed-electron density and its spatial distribution during the pre-ionization stage provides an effective approach to control streamer development and plasma chemical activity. Using electrical measurements, optical diagnostics, and a two-dimensional axisymmetric fluid model, this study systematically analyzes the behavior of pulsed streamer discharges under seed-electron pre-ionization and quantitatively clarifies how seed-electron density and spatial distribution govern the evolution of the primary streamer (PS), the secondary streamer (SS), as well as the generation of reactive species. The results show that UV pre-ionization enhances the discharge intensity and promotes streamer development. Under the same experimental conditions, simulations indicate that the minimum seed-electron densities required to initiate the development of PS and SS are 10 10 m -3 and 10 12 m -3 , respectively. When the seed-electron density exceeds 10 10 m -3 , PS development is enhanced, leading to increased formation of N 2 (C), N 2 + and O 2 + . Once the density exceeds 10 12 m -3 , SS development is accelerated, and the generation of N and O increases markedly. The spatial distribution of seed electrons is also critical to discharge development. Placing electrons near the anode region accelerates breakdown and promotes PS development, whereas electrons near the cathode region favor SS development, intensifies the radial electric field and electron density near the cathode region, and ultimately leads to a large discharge volume. These findings clarify how seed electrons regulate pulsed streamers and provide guidance for tailoring pre-ionization strategies to optimize plasma reactivity.

Pulsed streamer discharges have been extensively used in many applications such as control of NO/sub X/ and SO/sub 2/ from exhaust gases, treatment of dioxins, removal of volatile organic compounds, generation of ozone, and laser excitation. An operation with a high energy efficiency is necessary for practical applications. It is very important to know the propagation mechanism of streamer discharges in order to improve the energy efficiency of pulsed discharge systems. In this paper, the emission from pulsed streamer discharges in a coaxial electrode system in air at 0.1 MPa was observed using a high-speed gated intensified charge-coupled display camera. A concentric wire-cylinder electrodes configuration was used. A positive pulsed voltage having a width of about 100 ns was applied to the central electrode. The streamer discharges were initiated at the inner electrode and terminated at the outer electrode. The propagation velocity of the streamer discharges was 1.8-3.3 mm/ns.

Axisymmetric two-dimensional (2D) simulation is often used in case of streamer discharge in atmospheric-pressure air. To validate the 2D simulation of streamer discharge, the simulation has to be compared with the measurement results. However, there is difficulty in performing the comparison because the streamer is not a 2D phenomenon but a three-dimensional phenomenon. In this study, a pseudo-2D axisymmetric single-filament pulsed positive streamer discharge was generated in atmospheric-pressure air and compared with our 2D simulation. The propagation, emission intensity, shape, and cathode current of the streamer were compared. The ozone density was also measured using laser spectroscopy and compared with the simulation because our simulation intends to simulate the dynamics of reactive species. The measurements and simulations exhibited some agreements and disagreements. The measurement also showed a cathode fall and other cathode phenomena, which were not considered in the simulation.

Electronegative gas components and gas pressure significantly change residual charge dynamics, which are critical for pulse-periodic streamer discharge behaviors. Evolutions of repetitively pulsed positive streamer discharge and the streamer-to-spark transitions were investigated at high pressures and compared between typical weak (O2) and strong (SF6) electronegative gas mixtures. Pulse-sequence resolved electrical and optical diagnostics were implemented to capture discharge evolutions in long pulse trains. We observe that streamer inception and propagation under subsequent pulses in N2 and N2–O2 mixtures are similar, including the earlier inception of the primary streamer and the accelerated propagation of the secondary streamer. The repetitively pulsed breakdown is extended to the low pulse repetition frequency region with the addition of O2. Discharge evolutions are unexpectedly different in N2–SF6 mixtures. Subsequent discharge channels prefer to propagate around the periphery of the inception cloud region with large radial deviations. Another difference is the precursor channel identified besides multiple streamer channels. Effects of electronegative gas on streamer evolutions under positive repetitive pulses have been qualitatively analyzed. Collisional electron detachment and photo-ionization are crucial in N2–O2 mixtures. With the presence of strong electronegative gas (SF6), the leader formation is probably induced by the earlier corona inception and longer voltage stressing period under following pulses in a pulse train, which are caused by the strong electronegativity of SF6 and the small ion mobility.

In this study, spatially resolved measurements of the emission intensity of OH (A2Σ↦X2Π, 0-0) and the vibrational temperature of N2 (C) have been performed during a positive pulsed streamer discharge with a wire-plate electrode configuration at atmospheric pressure. The effects of pulse peak voltage, pulse repetition rate and the added O2 flow rate on the spatial distributions of the emission intensity of OH (A2Σ↦X2Π, 0-0) and the vibrational temperatures of N2 (C) perpendicular to the wire in the direction towards the plate (in the radial direction) are investigated. It has been found that the emission intensity of OH (A2Σ↦X2Π, 0-0) increases with increasing pulse peak voltage and pulse repetition rate and decreases with increasing the distance from the wire electrode. When the different oxygen flows are added in N2 and H2O mixture gas, the emission intensity of OH (A2Σ↦X2Π, 0-0) decreases with increasing the flow rate of oxygen. The vibrational temperature of N2 (C) is nearly independent of pulsed peak voltage and pulsed repetition rate, but increases with increasing the added O2 flow rate and keeps almost constant in the radial direction under the present experimental conditions. This measurement plays a crucial role in understanding the discharge characters of pulsed streamer discharge and establishing the molecule reaction dynamics model of pulsed streamer discharge.

Experimental investigation of HV short pulsed streamer discharges in dry air-fed ozonizers under various operating conditions are reported. Ozone concentration, energy input and ozone production yield (efficiency) were measured at various voltages (14 to 37 kV), pulse repetition rates (25 to 400 pulses per second, pps), flow rates (1.5 to 3.0 1/min) and different gap spacings (10 to 20 mm) at a pressure of 1.01/spl times/10/sup 5/ Pa in dry air. A spiral copper wire (1 mm in diameter) made to a cylindrical configuration (18 to 38 mm in diameter) in a concentric coaxial electrode system of various dimensions was employed. A magnetic pulse compressor provided the HV and current pulses. Higher voltage and higher repetition rates yielded higher concentrations of ozone at a fixed air flow rate. The present investigation was extended to assess the performance of this pulsed ozone generator using dry air under desired conditions of high concentration and high yield of ozone for industrial applications.

Corona is one of the important problems in the design and operation of transmission lines, and humidity has a significant effect on the starting voltage of the wire corona. The paper focuses on the development of positive DC corona under different humidity conditions, including the corona onset voltage, corona streamer pulse characteristics and the conversion process of streamer corona to glow corona. The paper arrives the conclusion that when a positive DC voltage is applied, a pre-initial streamer occurs first as the voltage increases, followed by glow corona. When the voltage is further increased and the ratio of the rod electrode radius to the gap distance is less than a certain value, the breakdown occurs directly. If the ratio is greater than a certain value, a pre-breakdown streamer will occur before the glow corona when the voltage rises. In addition, the corona onset voltage increases with the rise of humidity, which is related to the absorption of electrons in the electric field by water molecules. Under low humidity, there is a pulsed streamer discharge in the narrow voltage range, but under high humidity, there is always a streamer discharge in a wider voltage range. This shows that as the humidity increases, the streamer corona is more difficult to convert into a glow corona.

ABSTRACTThe influence of thermal (95°C, 5 min), pulsed light (PL, 1.64 kJ/cm2 available fluence) and microwave (MW, 2 kW, and 16 min ≈ 90°C final temperature) treatment on various quality attributes and shelf‐life of bael (Aegle marmelos) beverage was investigated. The quality parameters under consideration included microbial growth, enzyme activity, bioactive components, sensory quality, and physicochemical properties. Effects of different packaging materials (ethyl vinyl alcohol (EVOH) and multilayered (ML) pouches) and storage temperatures (25°C and 4°C) were also explored. The rate of sample deterioration, loss of bioactive components, and sensory qualities increased with higher storage temperature. MW and thermal processing showed better storage stability based on the minimum microbial counts, enzyme activities, and minimal changes in soluble solids. Least sedimentation was seen in thermally treated samples. MW treatment was better in preventing alterations in pH and titratable acidity (at 25°C), reducing sugars, browning, and sensory acceptance. On 50th day at 4°C, higher total phenolic content (59%–64%), antioxidant capacity (69%–72%), and total carotenoid content (136%–139%) were obtained with the PL treatment. For both packaging materials, a shelf‐life of 40–50 days (as per aerobic mesophile count ≤ 4.0 log CFU/mL) and 30 days (as per overall sensory acceptability &gt; 5) at 4°C was obtained for thermal and microwave. As per AM count, shelf‐life of PL irradiated beverages was 40 days, and according to sensory acceptability, it was 30 days. Overall, MW processed beverages stored in ML‐pouches and at 4°C exhibited better shelf life and storage quality.

Fecal sludge (FS) requires effective management to mitigate environmental and public health risks and enable resource recovery. This study evaluated the effects of microwave (MW) treatment on FS characteristics and subsequent anaerobic digestion (AD) performance. MW treatment raised FS temperatures to ~96 °C, reducing FS volume by 50% and inducing three thermal phases. Soluble chemical oxygen demand (sCOD) showed a multi-phase pattern, with a maximum solubilization of 29.8% during initial heating due to the solubilization of proteins and carbohydrates. Scanning electron microscopy (SEM) revealed morphological changes, while Fourier transform infrared (FTIR) spectroscopy confirmed that core functional groups remained unchanged. MW-pretreated FS enhanced AD performance, achieving a 17% increase in cumulative methane yield, alongside 18% and 33% improvements in organic loading and methane production rates, respectively. MW treatment influenced the phase distribution of digestate components, showing a shift in nutrient portioning towards the liquid fraction. These results suggest that integrating MW pretreatment into FS management systems can improve energy recovery, reduce treatment costs, and support resource-efficient sanitation solutions.

Summary form only given. Whereas bacterial decontamination of gases by means of pulsed corona discharges is now a firmly established method, efforts to use pulsed corona or streamer discharges in liquids for decontamination have only begun recently. This is due to the extremely high electric fields intensities required to initiate plasma formation in liquids. Using a wire anode and a planar cathode, experimental studies have shown that electric field intensities of approximately 2.5 MV/cm at the wire surface are needed to obtain pulsed corona discharges in tap water. By using a tungsten wire with 75 /spl mu/m diameter, two cm apart from a plane cathode, and applying a 600 ns, 135 kV square wave pulse, we were able to obtain a water corona discharge (PWC) without glow-to-arc transition. The effect of these discharges on bacteria was studied using water contaminated with Escherichia coli and Bacillus subtilis, the latter in both the vegetative and spore state. The strongest effect was obtained on E. coli. The concentration of E. coli could be reduced by two orders of magnitude after applying 3 corona discharges to the water. The corresponding energy expenditure is 4 J/ml. The decontamination rate had the largest values at the beginning, and decreased considerably after 15 electrical discharges, an effect which has also been observed in experiments using pulsed electric fields (PEF), and is assumed to be due to bacterial cell adhesion to and release from the chamber walls. For B. subtilis in the vegetative state, it took 20 discharges to reach the same result, corresponding to an energy expenditure of 28 J/ml. There was no effect on B. subtilis spores. Comparisons with the PEF method, a widely explored electro-technology used for bacterial decontamination, indicate that the decontamination efficiency of the PWC method is slightly higher than that of the PEF method.

Biomass is the only solid, carbon-rich, renewable resource that is abundantly available, geographically diverse, and inherently eco-friendly. As a sustainable precursor, it offers significant potential for the development of high-performance carbon-based nanomaterials, particularly carbon nanotubes (CNTs). This review provides a comprehensive overview of various biomass feedstocks utilized for CNT synthesis, emphasizing their physicochemical properties and suitability as carbon sources for CNT synthesis. It further explores multiple thermochemical conversion techniques, such as pyrolysis, microwave-assisted pyrolysis, and gasification, which generate intermediate carbon-rich materials. Special focus is given to the synthesis pathways of CNTs from bio-waste using the solid–solid–solid (SSS) two-step method, solid–gas–solid (SGS) method, microwave-assisted pyrolysis, and chemical vapor deposition (CVD) methods. Advanced characterization techniques are discussed in detail to assess the morphology, crystallinity, purity, and structural integrity of the biomass-derived CNTs. This review also highlights the intrinsic physical, chemical, and structural properties of CNTs that govern their functionality. Finally, emerging and established applications of biomass-derived CNTs are critically analyzed across diverse domains, such as environmental remediation, adsorption, energy storage devices, catalysis, sensors, and biomedical engineering. This review underscores the promising role of bio-waste-derived CNTs in advancing sustainable nanotechnology and contributing to the circular carbon economy.