Compensation of Heat Effect in Dielectric Barrier Discharge (DBD) Plasma System for Radar Cross-Section (RCS) Reduction

In this study, the problems encountered in radar cross-section (RCS) measurement experiments utilizing a dielectric barrier discharge (DBD) plasma system are examined and an effective solution is proposed. A DBD plasma system generates heat due to the high bias voltage required for plasma generation. The thermal-induced structural deformation of the DBD structure caused by this high voltage and its impact on RCS measurements are analyzed. In addition, techniques for minimizing the thermal-induced deformation and compensation methods for addressing the minimized deformation are proposed. Furthermore, RCS measurements are conducted on two kinds of DBD structures using the proposed method to experimentally demonstrate the improved agreement between the simulation and measurement results. For both structures, the RCS experimental results are in very good agreement with the simulation results, which enables accurate plasma characterization. In conclusion, it can be expected that the proposed method can be used to provide more accurate RCS measurements on various DBD structures that generate high heat.

Review of Plasma Processing for Polymers and Bio-Materials Using a Commercial Frequency (50/60 Hz)-Generated Discharge

This manuscript introduces the properties and diverse applications of plasma generated using commercial frequencies of 50/60 Hz. Commercial frequency (CF) derived plasma exhibits characteristics similar to DC discharge but with an electrical polarity and a non-continuous discharge. Due to the low-frequency nature, the reactor configurations usually are capacitively coupled plasma type. The advantages of this method include its simple power structure, low-reaction temperature, and low substrate damage. The electrical polarity can prevent charge buildup on the substrates and deposited films, thereby reducing substrate damage. The simple, low-cost, and easy-to-operate power structure makes it suitable for laboratory-scale usage. Additionally, the various applications, including plasma-enhanced vapor deposition, sputtering, dielectric barrier discharge, and surface modification, and their outcomes in the CF-derived plasma processes are summarized. The conclusion drawn is that the CF-derived plasma process is useful for laboratory-scale utilization due to its simplicity, and the results of the plasma process are also outstanding.

Enrichment of Bone Tissue with Antibacterially Effective Amounts of Nitric Oxide Derivatives by Treatment with Dielectric Barrier Discharge Plasmas Optimized for Nitrogen Oxide Chemistry

Cold atmospheric plasmas (CAPs) generated by dielectric barrier discharge (DBD), particularly those containing higher amounts of nitric oxide (NO) or NO derivates (NOD), are attracting increasing interest in medical fields. In the present study, we, for the first time, evaluated DBD-CAP-induced NOD accumulation and therapeutically relevant NO release in calcified bone tissue. This knowledge is of great importance for the development of new therapies against bacterial-infectious complications during bone healing, such as osteitis or osteomyelitis. We found that by modulating the power dissipation in the discharge, it is possible (1) to significantly increase the uptake of NODs in bone tissue, even into deeper regions, (2) to significantly decrease the pH in CAP-exposed bone tissue, (3) to induce a long-lasting and modulable NO production in the bone samples as well as (4) to significantly protect the treated bone tissue against bacterial contaminations, and to induce a strong bactericidal effect in bacterially infected bone samples. Our results strongly suggest that the current DBD technology opens up effective NO-based therapy options in the treatment of local bacterial infections of the bone tissue through the possibility of a targeted modulation of the NOD content in the generated CAPs.

Modification of the physicochemical and structural characteristics of zein suspension by dielectric barrier discharge cold plasma treatment

Owing to the strong hydrophobicity of zein, improved solubility is required to enhance the recovery of bioactive peptides. Using a zein suspension prepared by the antisolvent precipitation method, the impact of varying the voltage during dielectric barrier discharge (DBD) treatment on the physicochemical and conformational properties of zein in water was investigated. Analysis of the particle size, specific surface area, and free sulfhydryl content indicated that the protein solubility was maximized by treatment at 70 V for 70 s. DBD treatment destroyed covalent bonds and introduced some hydrophilic groups onto the zein surface, thus enhancing the contact area with water molecules and leading to a more uniform dispersion. A decrease in the hydrodynamic radius of zein micelles indicated that intermolecular interactions were disrupted, thus improving dispersion stability. A more hydrophilic microenvironment was formed owing to the reduction in hydrophobic interactions. Additionally, evaluation of the secondary structure demonstrated that DBD treatment broke hydrogen bonds, resulting in a loose conformation with more exposed sites of action for water. These results are expected to facilitate the development of technologies for improving utilization of zein. PRACTICAL APPLICATION: Strong hydrophobicity limits the application of zein in the food industry. The study indicated that DBD treatment could promote loose structure, and improve dispersion stability and hydrophilicity of zein suspension prepared by antisolvent precipitation method. This work revealed the potential of cold plasma treatment for modifying zein and other insoluble proteins, which would expand their scope of application.

Chemical, Thermo-Mechanical and Antimicrobial Properties of DBD Plasma Treated Disinfectant-Impregnated Wipes during Storage

Disinfectant-impregnated wipes are broadly used in hospitals, as an important approach for infection prevention and control. But their ageing performance has rarely been studied. Untreated and Dielectric Barrier Discharge (DBD) plasma pre-treated wiping materials made of nonwoven 100% polyester (W1), nonwoven 55% cellulose/45% polyester (W2) and woven cotton (W3) were impregnated with a quaternary ammonium compound solution (ADBAC) for 30 min, 3, 7, 15, and 30 days of storage time and characterized in term of chemical, thermo-mechanical and antimicrobial efficacy. X-ray photoelectron spectroscopy analysis on the plasma-treated polyester wipes demonstrates the incorporation of reactive oxygen species on the fiber surface. Laser scanning microscopy demonstrates the plasma etching effect in smoothing the surface of the cotton wipe reducing the adsorption of ADBAC. The result showed no significant changes in breaking force and elongation during storage for W1 and W2. However, plasma treatment affects W3 in weft direction reducing the force at break in water and ADBAC treated wipes. Dynamic mechanical analysis results show that ADBAC and plasma treatment have a significant influence in W1 and W3 viscoelastic properties improving the elastic response limiting the polymeric chains mobility and the non-elastic response due to the etching effect, respectively. Overall, the plasma pre-treatment of ADBAC-impregnated wipes is able to enhance the antimicrobial performance and the storage time of polyester-containing wipes.

Effect of Argon Plasma Treatment on Tribological Properties of UHMWPE/MWCNT Nanocomposites

Ultra-high molecular weight polyethylene (UHMWPE) is widely used in artificial joints in the replacement of knee, hip and shoulder that has been impaired as a result of arthritis or other degenerative joint diseases. The UHMWPE made plastic cup is placed in the joint socket in contact with a metal or ceramic ball affixed to a metal stem. Effective reinforcement of multi-walled carbon nanotubes (MWCNTs) in UHMWPE results in improved mechanical and tribological properties. The hydrophobic nature of the nanocomposites surface results in lesser contact with biological fluids during the physiological interaction. In this project, we investigate the UHMWPE/MWCNTs nanocomposites reinforced with MWCNTs at different concentrations. The samples were treated with cold argon plasma at different exposure times. The water contact angles for 60 min plasma-treated nanocomposites with 0.0, 0.5, 1.0, 1.5, and 2.0 wt % MWCNTs were found to be 55.65°, 52.51°, 48.01°, 43.72°, and 37.18° respectively. Increasing the treatment time of nanocomposites has shown transformation from a hydrophobic to a hydrophilic nature due to carboxyl groups being bonded on the surface for treated nanocomposites. Wear analysis was performed under dry, and also under biological lubrication, conditions of all treated samples. The wear factor of untreated pure UHMWPE sample was reduced by 68% and 80%, under dry and lubricated conditions, respectively, as compared to 2 wt % 60 min-treated sample. The kinetic friction co-efficient was also noted under both conditions. The hardness of nanocomposites increased with both MWCNTs loading and plasma treatment time. Similarly, the surface roughness of the nanocomposites was reduced.

Spectroscopic Study of Plasma Polymerized a-C:H Films Deposited by a Dielectric Barrier Discharge

Plasma polymerized a-C:H thin films have been deposited on Si (100) and aluminum coated glass substrates by a dielectric barrier discharge (DBD) operated at medium pressure using C₂H_m/Ar (m = 2, 4, 6) gas mixtures. The deposited films were characterized by Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS), Raman spectroscopy, and ellipsometry. FT-IRRAS revealed the presence of sp³ and sp² C–H stretching and C–H bending vibrations of bonds in the films. The presence of D and G bands was confirmed by Raman spectroscopy. Thin films obtained from C₂H₄/Ar and C₂H₆/Ar gas mixtures have I_D/I_G ratios of 0.45 and 0.3, respectively. The refractive indices were 2.8 and 3.1 for C₂H₄/Ar and C₂H₆/Ar films, respectively, at a photon energy of 2 eV.

Efficient Flame Retardant Thin Films Synthesized by Atmospheric Pressure PECVD through the High Co-deposition Rate of Hexamethyldisiloxane and Triethylphosphate on Polycarbonate and Polyamide-6 Substrates

An innovative approach to produce high-performance and halogen-free flame-retardant thin films at atmospheric pressure is reported. PDMS-based coatings with embedded dopant-rich polyphosphates are elaborated thanks to a straightforward approach, using an atmospheric pressure dielectric barrier discharge (AP-DBD). Deposition conditions have been tailored to elaborate various thin films that can match the fire performance requirements. Morphology, chemical composition, and structure are investigated, and results show that the coatings performances are increased by taking advantage of the synergistic effect of P and Si flame retardant compounds. More specifically, this study relates the possibility to obtain flame retardant properties on PolyCarbonate and PolyAmide-6 thanks to their covering by a 5 μm thick coating, i.e. very thin films for this field of application, yet quite substantial for plasma processes. Hence, this approach enables deposition of flame retardant coatings onto different polymer substrates, providing a versatile fireproofing solution for different natures of polymer substrates. The presence of an expanded charred layer at the surface acts as a protective barrier limiting heat and mass transfer. This latter retains and consumes a part of the PC or PA-6 degradation byproducts and then minimizes the released flammable gases. It may also insulate the substrate from the flame and limit mass transfers of remaining volatile gases. Moreover, reactions in the condensed phase have also been highlighted despite the relatively thin thickness of the deposited layers. As a result of these phenomena, excellent performances are obtained, illustrated by a decrease of the peak of the heat release rate (pHRR) and an increase of the time to ignition (TTI).