Corona Discharge Treatment Research Articles

Effect of hot water and corona discharge treatments on the bonding behavior of jute fibers in polyester matrix

Effect of hot water and corona discharge treatments on the bonding behavior of jute fibers in polyester matrix

Enhancing filter efficiency of polyimide/polyethersulfone nanofiber membranes via novel treatments of high pressure processing, thermocompression, atmospheric plasma, and corona discharge

In this study, novel post-treatments contained of high pressure processing (HPP), thermocompression, atmospheric plasma, and corona discharge were used to progress the filter quality of polyimide/polyethersulfone (PI/PES) nanofiber membranes in the conditions of 50/50 % PI/PES, 0.15 ml/hr flow rate, 22.5 kV, and 20 min. The filter quality of nanofiber membrane did not get progress after HPP and thermocompression treatments, so high temperature and pressure did not improve the filter quality. Otherwise, atmospheric plasma destroyed the morphology of fiber surface, caused loss of filter efficiency and filter quality. However, corona discharge treatment presented different result with the above three treatments, and the filter efficiency and filter quality of the fiber membrane was improved after corona discharge treatment. Furthermore, factor influence order was ranged as operational voltage, discharge time, and discharge distance from result of filter quality on comparison of S/N value and level difference via Taguchi method. The application of corona discharge resulted in fiber acquired surface electric potential of 0.315 ± 0.56 kV at the optimized conditions of operational voltage (25 kV), discharge distance (7 cm), and discharge time (60 min), and filter efficiency of fiber enhanced from 95.66 ± 0.96 % to 98.70 ± 0.36 %. Further, the optimized PI/PES nanofiber membranes with corona discharge not only had a remarkable filter quality (2.214 Pa−1) but also maintained an effective filtration efficiency of ultra-fine particles (98.70 %) and a low pressure loss of 1.961 Pa for creating a promising filter of air purification and N95 Masks of USA NIOSH Standard.

Enhancing filtration performance of submicron particle filter media through bimodal structural design

AbstractDepth filtration is a widely utilized mechanism for submicron aerosol filtration using disposable filter cartridges and facemasks. The filter media should be carefully engineered to reach high filtration efficiency and dust‐loading capacity at the expense of a low‐pressure drop (ΔP). Filter media with bimodal fiber diameter distribution enhance particle capture by creating small pores with tiny fibers, while microfibers improve airflow, reduce ΔP, and increase the effective filter area for particle retention. In this study, bimodal filters were achieved through the homogeneous distribution or layered use of nanofibers and microfibers. The impact of the bimodal design was explored using fibrous mats produced through melt‐blowing, solution‐blowing, and electroblowing methods. Keeping the basis weight of filter samples at 30 gsm, using four‐layered filters (4L) improved air permeability compared to single‐layer samples. The 4L sample exhibited the highest performance, achieving 99.52% efficiency at 148 Pa. Moreover, replacing the melt‐blown layer with bimodal mats in the 4L design increased the filtration efficiency to 99.61% keeping ΔP nearly the same. The corona discharge treatment yielded the highest efficiency (99.99%) in the 4BML sample, even after 1 month the efficiency was maintained at 99.90%, highlighting the advantage of bimodal fiber distribution in electret filters.Highlights Four‐layered filter (4L) structures resulted in improved air permeability. Bimodal layer (BL) achieved by adding SB nanofibers into the melt blowing. BL in 4L structure increased the efficiency from 99.52% to 99.61%. Modified BL sample (4BML) provides the highest QF (0.044 Pa−1) after 1 month.

Characterization of corona discharge treatment on PTFE surface for TENG applications

As for practical application of triboelectric nanogenerators (TENGs), corona discharge treatment (CDT) is often utilized further to enhance its power outputs by injecting charges. We report compositional analysis and corresponding triboelectric outputs of Poly(1,1,2,2-tetrafluoroethylene) (PTFE) based TENGs. PTFE and Al based TENGs with various PTFE film thickness are fabricated and their performances are measured with different CDT applied bias. XPS depth profile analysis reveals the relation of triboelectric outputs and depth of oxygen ions. Our discovery may give insight in the future development of high performance TENGs using CDT.

Production of Ultrafine PVDF Nanofiber-/Nanonet-Based Air Filters via the Electroblowing Technique by Employing PEG as a Pore-Forming Agent.

Particles with diameters smaller than 2.5 μm (PM2.5) can penetrate the respiratory system and have negative impacts on human health. Filter media with a porous surface and nanofiber/nanonet structure demonstrate superior filtration performance compared to traditional nano- and microfiber-based filters. In this study, nanostructured filters were produced using the electroblowing method from solutions containing different ratios of poly(vinylidene fluoride) (PVDF) and polyethylene glycol (PEG) polymers for the first time. By increasing the water-soluble PEG ratio in PVDF/PEG blend nanofibers and employing a water bath treatment to the produced mat afterward, a more porous fibrous structure was obtained with a lower average fiber diameter. Notably, the removal of PEG from the PVDF/PEG (3-7) sample, which had the highest PEG content, exhibited clustered nanofiber-/nanonet-like structures with average diameters of 170 and 50 nm at the points where the fibers intersect. Although this process resulted in a slight decrease in the filtration efficiency (-1.3%), the significant reduction observed in pressure drop led to a 3.2% increase in the quality factor (QF). Additionally, by exploiting the polarizability of PVDF under an electric field, the filtration efficiency of the nanostructured PVDF filters enhanced with a ratio of 3.6% after corona discharge treatment leading to a 60% improvement in the QF. As a result, the PVDF/PEG (3-7) sample presented an impressive filtration efficiency of 99.57%, a pressure drop (ΔP) of 158 Pa, and a QF of 0.0345 Pa-1.

Laminating Structure for Interlayer Corona Discharge Treatment Toward Ion-Based Nanogenerators.

A corona discharge treatment (CDT) is utilized to maximize the performance of triboelectric nanogenerators (TENGs) by injecting extra electrons into the negative tribomaterials. Increased performance of CDT TENGs, however, exhibits rapid degradation due to the electron dissipation by air moisture or thermal emission. To overcome such drawbacks and circumvent such dissipation, the source of charges should be replaced with ionic charges. This study reports a Ag nanowires (NWs)-embedded laminating structure (AeLS) with a unique fabrication procedure for ionic charge injection by CDT. The injection of ions is achieved by interlayer-CDT (i-CDT), in which positive charges are dissipated by Ag NWs, and the opposite negative ions can remain on the outmost surface. The AeLS TENGs with i-CDT exhibit high performance, long-term stability, and durability. It shows voltage, current, and maximum power outputs of 380V, 15µA, and 827mW m-2 , respectively. As a practical demonstration, rotational TENG integrated with a direct discharge system is realized, and its current and voltage reach 7.4mA and 7800V, respectively. This work can pave the way for the design of ion-based TENGs with high performance and long-lasting retention of triboelectric charges.

Improving the Performance of a Triboelectric Nanogenerator by Using an Asymmetric TiO2/PDMS Composite Layer

To improve the output power of the polydimethylsiloxane (PDMS)-based triboelectric nanogenerators (TENGs), we fabricated an asymmetric TiO2/PDMS composite film in which a pure PDMS thin film was deposited as a capping layer on a TiO2 nanoparticles (NPs)-embedded PDMS composite film. Although in the absence of the capping layer, the output power decreased when the content of TiO2 NPs exceeded a certain value, the asymmetric TiO2/PDMS composite films showed that the output power increased with increasing content. The maximum output power density was approximately 0.28 W/m2 at a TiO2 content of 20 vol.%. The capping layer could be responsible not only for maintaining the high dielectric constant of the composite film but also for suppressing interfacial recombination. To further improve the output power, we applied a corona discharge treatment to the asymmetric film and measured the output power at a measurement frequency of 5 Hz. The maximum output power density was approximately 78 W/m2. The idea of the asymmetric geometry of the composite film should be applicable to various combinations of materials for TENGs.

Three sustainable polypropylene surface treatments for the compatibility optimization of PP fibers and cement matrix in fiber-reinforced concrete

Fiber-reinforced concrete (FRC) is a cementitious composite material that is gaining interest in the construction field to limit crack propagation and increase toughness. Polypropylene (PP) fibers are promising alternatives to steel fibers, primarily used in FRC, as they reduce weight and cost and are resistant to corrosion. However, the hydrophobic surface of PP inhibits a good adhesion with the surrounding cementitious matrix and so the exploitation of optimized mechanical performance. Though several chemical treatments have been studied, this work suggests more sustainable, cost-efficient, and fast surface treatments for the first time to increase the hydrophilicity of PP: UV-LED, picosecond UV-LASER, and corona discharge treatment. The treatments mainly provided a chemical functionalization without altering the surface morphology of PP, and their effectiveness in increasing PP hydrophilicity was confirmed by ATR-FTIR spectroscopy and optical contact angle measurements. The improved adhesion with the matrix was assessed by the pullout test of treated PP specimens from lime-based and cement-based matrices and by detecting the failure mode in the interphase zone through scanning electron microscopy.

Pipeline Processing via the Combination of Heat and Corona Treatments for Improving the Poly(p-phenylene benzobisoxazole) Fiber Surface and Anti-Aging Performances.

Although many strategies have been reported for modified poly(p-phenylene benzobisoxazole) (PBO) fiber surfaces, the absence of approaches with the potential of applications in industries limits the further applications of the fibers in a wide field. Herein, PBO fibers are modified by heat treatment combined with corona discharge treatment, which is a continuous industrialized method. Then, the surface morphology, wettability, orientation, and crystallinity of the PBO fibers are characterized in detail. Systematic experiments demonstrate that the high thermal treatment can improve the orientation and crystallization degree of the fibers, as well as the degradation resistance. In addition, owing to the synergistic mechanism of ozone and high-frequency shock, the corona discharge treatment increases the contents of O and N elements on the surfaces, which improves the superficial properties of the fibers. Based on the modification of PBO fibers, the inter-laminar shear strength between the fiber and the resin for the composite increases to 94.8%, and the tensile strength of the composite increases to 29.2%, compared to those using untreated fibers. In general, the proposed modification strategy not only easily improves the surface properties and the mechanical properties of composites but also can be used with great potential in industrial production.

Bilayer biocomposites of PVOH/WPI/nano‐silica treated with corona discharge

AbstractIn order to evaluate the influence of a different assembly of biocomposites of polyvinyl alcohol (PVOH), whey protein isolates (WPI), and nano‐silica (NS), a bilayer film treated with corona discharge was produced through a two‐step lamination. The first layer of PVOH/NS, treated with up to 90 s of discharge, and the second layer of WPI/NS, the bilayer films had their morphology, tensile strength, and water barrier investigated and compared to a single layer PVOH/WPI/NS film. Corona discharge increased the wettability of the first layer, improving the ability to interact with the second layer, thus increasing the adherence between these layers. Films treated with higher times of discharge showed a homogeneous transition between phases, suggesting compatibility, and adherence between layers. At 90 s of corona discharge treatment, bilayer films showed a tensile strength 72% higher than the bilayer film not treated and also 23% more resistant and 7.4 times more ductile than the single‐layer film. The lamination process and corona treatment increase the affinity of water with film constituents, thus leading to a higher permeability. The use of corona discharge associated with the lamination of PVOH/WPI/NS biocomposites provides a bilayer film and produces a more resistant, flexible, and ductile biocomposite film for packaging.

Influence of Crosslinking Extent on Free Volumes of Silicone Rubber and Water Diffusion after Corona Discharge.

Silicone rubber is widely used as an insulating material. In this article, silicone rubber samples were prepared by varying the content of crosslinker (2,5-bis(tert-butyl-peroxy)-2,5-dimethylhexane, DBPMH), and the free volume holes in the samples were investigated by means of positron annihilation lifetime spectroscopy (PALS) measurement. The surface chemical structure, surface micromorphology and water diffusion of the samples after corona discharge treatment were studied by FTIR, SEM and EIS measurements, respectively. As the crosslinker weight ratio increased from 0.2 wt.% to 1.5 wt.%, the mean free volume hole size first decreased and then remained unchanged. However, the concentration of free volume holes did not vary as the crosslinker weight ratio increased. SEM morphologies show that surface cracks were produced on samples having high crosslinking levels after corona treatment. The water diffusion coefficient of samples after corona treatment increased from 3.13 × 10−10 cm2 s−1 to 17.68 × 10−10 cm2 s−1 in the initial immersion period, as the crosslinker weight ratio increased from 0.2 wt.% to 3.0 wt.%. The results indicated that deterioration of samples with high crosslinking levels were more serious and water repellency more easily lost. The corona resistance ability of low crosslinking level silicone rubber stems from internal low molecular weight molecules.

Effect of corona discharge treatment on the polyethersulfone microfiltration membrane surfaces to reduce fouling phenomenon during tomato juice clarification

Tomato juice with high molecular weight components (high foulants) creates a turbid appearance as well as high fouling and a substantial flux decline in membrane applications. For this purpose, the surface modification of polyethersulfone (PES) microfiltration (MF) membranes was investigated by corona discharge to improve fouling propensities for clarifying tomato juice. The results revealed that corona discharge changed the surface hydrophilicity, morphology, and antifouling performance of the membranes. However, it has not made any substantial changes to mechanical properties. The hydrophilicity of the modified membranes with the reduction of contact angle (CA) from 53° to 10°, increased. Accordingly, the tomato juice flux of the modified membranes increased from 11 to 26 kg m−2 h−1 (∼2.4 times). Moreover, the reduction of the cake resistance as the main fouling mechanism (1.81 × 1012 m−1) was 1.4 times, and the enhancement of the flux recovery ratio (27%) was 2 times higher than of the neat PES membrane.

Super hydrophilic modified biaxially oriented polypropylene microporous membrane for excellent gravity-driven oil/water emulsion separation

Considering the protection of our natural environment from oily wastewater toxicity, the biaxially orientated polypropylene (PP) microporous membrane is taken as a suitable substrate to prepare a super hydrophilic and underwater superoleophobic membrane for oily wastewater separation. It is designed as a large-scale, cost-effective, and stable technology with the minimum possible environmental pollution to prepare the membrane for oily wastewater emulsion separation. The hydrophobic PP membrane is initially treated via corona discharge treatment followed by a grafting reaction with hydrophilic acrylamide monomer to generate rough micro-nano structures and polar functional groups. The permanent super hydrophilicity and underwater oleophobicity properties are accomplished by measuring the water contact angle (∼ 0°) and the underwater-oil contact angle (∼ 153°) over 10 weeks. Due to its excellent mechanical properties with a uniform modified micro-nano porous structure, significant separation flux with high efficiency is achieved for layered mixtures, surfactant-free, and surfactant-stabilized emulsions over 10 times reusability. Consequently, all separation processes are handled by the energy-saving gravity-driven separation method. Overall, this study demonstrated the super hydrophilic and underwater superoleophobic biaxially oriented polypropylene membrane, prepared in a stable and large-scale approach with outstanding separation performance, which can be widely used in emulsion separation and practically as an excellent solution for water separation from oily wastewater.

Oxidation of aqueous p-Nitroaniline by pulsed corona discharge

Toxic and potentially carcinogenic aromatic amines widely used in industry find their way to the aquatic environment. Gas-phase pulsed corona discharge (PCD) treatment of recalcitrant organic pollutants is a promising energy-efficient advanced oxidation process. The study assessed the energy efficiency of PCD in oxidation of p-nitroaniline (PNA), a persistent and ubiquitous pollutant of the aquatic environment. The effect of process control parameters on the energy efficiency of PNA degradation was studied including pH, gas–liquid contact surface and applied pulse repetition frequency. The results showed that PCD surpasses the commercially available competitor, Fenton reagent, for about three times. The reaction intermediates were analysed by HPLC-MS(ESI ± ) resulting in proposal of two transformation products. The PNA oxidation process followed the second-order kinetics showing the reaction rate coefficient moderately increasing with the contact surface and decreasing with the pulse repetition frequency. The acute toxicity of PNA solutions decreased substantially on the course of PCD treatment.

Mutation of Bacillus velezensis Using Corona Discharge

Bacillus velezensis is a kind of beneficial bacteria that is widely used in agriculture industry. Bacillus velezensis was irradiated with corona discharge generated by a needle-array high-voltage electrode. The results showed an improvement of activity of Bacillus velezensis by the corona discharge treatment was confirmed at an optimum input energy. Mutation of the Bacillus velezensis by the corona discharge treatment was also confirmed through an rRNA sequence alignment analysis. The enzyme activity of the mutated bacteria was greatly improved, which was a positive effect that can meet the production demand.

New in vitro SPF Evaluation Method for Hydrophilic Sunscreen Samples.

A new method was developed for the in vitro sun protection factor (SPF) evaluation of sunscreen samples. A new type of substrate, a hydroxyalkyl cellulose-coated plate, was also prepared specifically for hydrophilic samples. This new substrate was required because hydrophilic samples would be unlikely to wet the surface of the standard cosmetic PMMA UV evaluation plate. A super-hydrophilic quartz plate was prepared by corona-discharge treatment before an aqueous solution of hydroxyalkyl cellulose was spread on it. A flat and uniform hydroxyalkyl cellulose film was subsequently formed through the evaporation of water. Special care was taken to inhibit the generation of spatial non-uniformity. Six hydrophilic sunscreen samples with in vivo SPF values of 56, 55, 52, 25, 15, and 4, were then applied to the prepared hydroxyalkyl cellulose-coated plate, as well as a super-hydrophilic quartz plate and a flat hydrophobic PMMA plate. The thicknesses of the applied layers were determined using a wheel-shaped wet film thickness gauge immediately after the application, and UV transmission was measured using an SPF analyzer. The value of in vitro SPF was calculated from the UV absorbance and the thickness of the layer. For two out of the six samples, PMMA plate could not be available, as the samples were unable to wet the PMMA surface. Relatively small differences were observed between the in vitro SPF values when the super-hydrophilic and hydroxyalkyl cellulose-coated plates were used. Samples exhibiting higher in vivo SPF were also associated with higher in vitro SPF values, although a linear relationship was not observed. In contrast to the super-hydrophilic plate whose half-life of the super-hydrophilicity is only approximately five days, the hydrophilicity of the hydroxyalkyl cellulose-coated plate scarcely varied during six months of storage. Finally, a simplified evaluation method was also proposed. The validity of the method was verified through a ring test where three researchers employed this method in different laboratories at three independent organizations.

Salicylic Acid Elimination by Pulsed Corona Discharge Treatment of Wastewater

AbstractElimination of salicylic acid by pulsed corona discharge in a multipin‐plate reactor was investigated. Corona discharge is an alternative technique that produces highly active species such as HO• that degrade salicylic acid. Salicylic acid was totally eliminated in 60 min of treatment with 200 stainless steel needles. Variables such as pH, initial concentration, conductivity, and Na2SO4 dosage were studied to elucidate their influence on salicylic acid elimination. Salicylic acid elimination increased with decreasing pH, initial concentration, and conductivity of the liquid.

Effect of DC Corona Discharge onAmmopiptanthus MongolicusSeeds

In this study, a direct-current multineedle-plate corona discharge with different parameters was used to treat <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ammopiptanthus mongolicus</i> (Maxim. ex Kom. Cheng f.) seeds and study the effect of corona discharge physicochemical etching on these seeds. Results showed that the surface of the seed coat of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A. mongolicus</i> had wind erosion after corona discharge treatment, a large number of small ravines were generated and the surface crack of the seed coat was serious. Analysis of Fourier transform infrared spectroscopy revealed that the hydrophilic functional groups increased and corona discharge changed the chemical structure of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A. mongolicus</i> seed coat. The apparent contact angle decreased significantly from 99.82° ± 4.86° to 60.11° ± 8.44°, suggesting that corona discharge could significantly improve the hydrophilicity of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A. mongolicus</i> seeds. All the corona discharge treatment groups had seed germination at 24 h, whilst the control group had zero germination. This finding suggested that corona discharge treatment could significantly affect the structure and properties of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A. mongolicus</i> seed coat, improve the seed hydrophilicity and water absorption rate and promote the germination and growth of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A. mongolicus</i> seeds. This study provided ideas and experimental data support for the analysis of the mechanism of corona discharge biotechnology and seed-surface modification.

Electrocharging face masks with corona discharge treatment.

We detail an experimental method to electrocharge N95 facepiece respirators and face masks (FMs) made from a variety of fabrics (including non-woven polymer and knitted cloth) using corona discharge treatment (CDT). We present practical designs to construct a CDT system from commonly available parts and detail calibrations performed on different fabrics to study their electrocharging characteristics. After confirming the post-CDT structural integrity of fabrics, measurements showed that all non-woven polymer electret and only some knitted cloth fabrics are capable of charge retention. Whereas polymeric fabrics follow the well-known isothermal charging route, ion adsorption causes electrocharging in knitted cloth fabrics. Filtration tests demonstrate improved steady filtration efficiency in non-woven polymer electret filters. On the other hand, knitted cloth fabric filters capable of charge retention start with improved filtration efficiency which decays in time over up to 7 h depending on the fabric type, with filtration efficiency tracking the electric discharge. A rapid recharge for a few seconds ensures FM reuse over multiple cycles without degradation.

IMPACT OF CORONA DISCHARGE ON ASPERGILLUS NIGER SPORES AND CYATHUS OLLA MYCELIUM GROWTH

The article presents an investigation of the influence of the corona discharge with needle-ring electrode configuration on the efficiency of Aspergillus niger spore germination and Cyathus olla mycelium development. Current-voltage characteristics were measured for different distances between the needle and the metal ring. The plot of the dependence of conductance on voltage was built and the corona discharge breakthrough voltage was determined to be (2.7±0.1) kV. The treatment of Aspergillus niger spores was conducted at different development stages: at the germination stage (corona discharge treatment 1 day after the seeding) and dormant state (corona discharge treatment on the day of seeding). The growth rate of Cyathus olla mycelium in samples treated by corona discharge and in control group samples was investigated. The influence of the corona discharge on the potato dextrose agar growth medium before the seeding of Cyathus olla was studied. The pure cultures were obtained from the Culture Collection of Fungi at Kyiv University (FCKU) at the «Institute of Biology and Medicine» Educational and Scientific Centre of the Taras Shevchenko National University of Kyiv.