Production of superhydrophobic polytetrafluoroethylene (PTFE) by Ar plasma etching is challenging as it leads to defluorination, resulting in a hydrophilic surface. The effect of radiofrequency ...power, treatment time, impurity, and surface temperature on Ar plasma‐treated PTFE was investigated for producing a large‐area superhydrophobic PTFE surface. To avoid impurity and substrate temperature effects, a single electrode‐based arrangement with a sacrificial PTFE disc behind the specimen was used for plasma discharge. After 5 min treatment at 100 W, the surface became superhydrophobic (water contact angle = 156°) due to the formation of isotropic nanostructures. However, 30 min of plasma treatment caused severe chemical changes resulting in a hydrophilic surface (water contact angle = 14°). A yellowish layer was formed on the surface due to crosslinking, redeposition of fluorocarbon species, and iron impurities from the plasma system confirmed by X‐ray photoelectron spectroscopy analysis.
Transition from hydrophobic to superhydrophobic and hydrophilic surface upon Ar plasma treatment.
A computational fluid dynamics (CFD) model has been developed to investigate the time evolution of a helium plasma discharge at high pressures (from 2 to 8 MPa) and low electric current (0.35 A), ...including the interaction between the plasma and the electromagnetic fields, under local thermodynamic equilibrium (LTE) assumption. To account for pressure dependence, novel thermodynamic and transport properties have been calculated in a wide pressure and temperature range. The model has been further improved by considering the effect of plasma-electrode interactions and the formation of the plasma sheath. High-performance computing (HPC) was used to solve the CFD simulation, focusing on reference cases at 8 MPa and 0.35 A. Numerical results have shown that the sheath model and updated transport and thermodynamic properties have a significant impact on the electric potential, resulting in very good agreement between the simulation and experimental values.
Recent reports indicate that atmospheric cold plasma (ACP) treatment of seeds can enhance their germination, however, the mechanisms of action are not yet entirely clear. In the present work, we ...report on the effects of plasma treatment on wheat seed germination and seedling growth. Additionally, changes in the surface chemistry and characteristics of the wheat seeds exposed to plasma were investigated. Treatments of 30–60 s significantly enhanced the germination rate and showed positive effects on seedling growth. ACP resulted in changes of seed surface and chemical characteristics including water uptake and contact angle values. Changes in seed pH and total titratable acidity, as well as nitrites, nitrates, and malondialdehyde concentrations were also recorded.
In the present work, we report on a stimulative effect of plasma treatment on wheat seeds germination and seedlings growth. To provide insights into the mechanisms resulting in germination enhancement by cold plasma, changes in the surface chemistry and characteristics of the wheat seeds exposed to ACP were also investigated.
This article presents five alternative plasma equipments patented by the author, designed for specific applications like activation, cleaning, decontamination, or monomer polymerization on surfaces. ...Two equipments perform HF cold plasma treatment of highly adherent powdery materials (pigments, plastics, drugs, and so on), that are used to modify the physical-chemical characteristics of surfaces. Another HF plasma equipment is employed for the treatment of nonwoven stratified materials used as filters for gaseous media. A specially designed afterglow plasma equipment is used for decontamination and cleaning of highly fragile flat or 3-D cultural heritage items. An equipment for producing HF torch plasma is also described.
Several reaction mechanisms have been proposed for the formation of plasma polymers, such as monomer fragmentation followed by poly‐recombination into randomly structured and crosslinked films; ...fragmentation, accompanied by the formation of acetylene or other film‐forming intermediates and deposition of polystyrene‐like material; plasma‐initiation of a radical chain‐growth polymerization; and ion‐molecule reactions, as well as ionic chain‐growth polymerization. The bulk structure of plasma polymers is completely irregular, far from that of conventional polymers. The retention of functional groups during plasma polymerization tends to be greater than that of the entire monomer structure found again as an intact repeat unit in the resulting plasma polymer. An alternative method for depositing ultra‐thin, pin‐hole free coatings, ones that possess regular structures, is by electrospray ionization (ESI) of pre‐fabricated polymers.
Several reaction mechanisms have been proposed for the formation of plasma polymers, such as monomer fragmentation followed by poly‐recombination into randomly structured and crosslinked films, formation of intermediates and plasma‐initiation of a radical chain‐growth polymerization.
In this work, a discharge device is designed to realize the generation of alternative current (ac) and direction current (dc) cold atmospheric plasma (CAP) jet in the same generator for studying the ...production mechanism of H2O2 induced by plasma in water. The interaction between the plasma jets and deionized water is decomposed into three pathways by using a special reactor system, including electrochemical pathway, gaseous dissolution pathway, and the integrated pathway. Two kinds of ac plasma jets are generated by adjusting the electrode structure of the plasma generator, meanwhile two kinds of dc plasma jets are generated by adjusting the polarity of the discharge electrodes. Stable plasma jets are generated in all four configurations. The aqueous H2O2 as well as its vital precursor hydroxyl radical (OH) produced by the plasma jets is detected. The results show that the producing pathway of aqueous H2O2 depends on the position where the OH recombination reaction takes place during the treatment, and does not depend on whether the plasma is excited by ac or dc electric power.
This study demonstrates that plasma‐enhanced chemical vapor deposition of copper films can be achieved in ambient air and at low temperature. A helium dielectric barrier discharge jet with a small ...mixture of hydrogen and copper(II) acetylacetonate vapor is utilized as the nonthermal plasma source to deposit conductive copper films with low electrical resistivity (<1 × 10−7 Ω·m). The deposited film appears to have three distinct regions (reddish brown, dark blue, and yellowish) from center to edge. Copper nanograins (~50 nm) are observed in both the reddish‐brown and the dark‐blue regions, whereas the yellowish region exhibits a continuous structure containing copper oxide. The copper films are further deposited on various temperature‐sensitive substrates, including plastic, cardboard, agar, and pork skin.
Plasma‐enhanced chemical vapor deposition of copper films is achieved in ambient air and at low temperature using a helium dielectric barrier discharge jet. The deposited copper films are characterized. Film deposition is also achievable on temperature‐sensitive substrates, such as plastic, cardboard, agar, and pork skin.
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