Low-temperature Plasma Treatment Research Articles

The effect of nitrogen plasma treatment on adhesive properties of PEEK

The purpose of this study is to investigate the effect of nitrogen plasma treatment on the shear bonding strength (SBS) of polyetheretherketone (PEEK) to resin cements. A total of 240 PEEK specimens were subjected to different duration of nitrogen plasma treatment for 0 min, 15 min, 25 min, 35 min respectively. The surface topography was observed by a scanning electron microscope (SEM). In addition, X-ray photoelectron spectroscopy (XPS) was applied to study the surface element content changes before and after treatment. The adhesive specimens were bonded with Variolink in all groups. Afterwards, each group was divided into three subgroups (n = 20/group), (a) water storage for 56 h at 37 °C, (b) thermal cycling for 5000 times, (c) thermal cycling for 10000 times. Following storage shear bond strength (SBS) was tested in a universal testing machine and the failure modes were observed by stereoscopic microscope. After plasma treatment, the bonding strength between PEEK and Variolink was significantly increased. Among them, the 25 min group achieved the highest bonding strength. After thermal cycling, the SBS values were significantly decreased, compared with the group in water storage. Nitrogen low temperature plasma treatment improves SBS between PEEK and resin, and a duration of 25 min treatment group seems to be the best.

Effect of Low Temperature Plasma Treatment on Biological Characteristics and Yield Components of Wheat Seeds (Triticum aestivum L.)

The impacts of a low temperature plasma treatment on wheat seed germination and field growth were investigated using a plasma system about the first generation (T0), the second generation (T1) and the third generation (T2). Untreated wheat seeds were set as the control (CK). Plasma treatments of 80 W and 100 W were employed during the experiments. Germination characteristics, seedling growth parameters, biological characters and yield components were measured following the plasma treatments. The wheat seed germination index, plant height, tiller, growth and grain number obviously changed significantly after the low-temperature plasma treatment. Furthermore, the moderate-intensity plasma had an active impact on wheat seed germination and growth. The results showed that the theoretical yield of T0 significantly increased by 8.92% and 8.14%, while the actual yield increased by 8.12% and 6.10% compared with untreated. The theoretical yield of T1 increased by 5.69% and 6.62%, while it increased by 3.70% and 0.45% for T2. The actual yield of T1 increased by 5.75% and 4.94%, while it increased by 3.81% and 0.82% for T2. Plasma treatment exhibited the following trend of increasing: T0 > T1 > T2 > CK. We conclude that the effects of low-temperature plasma on the biological characteristics and yield components of wheat seeds exhibited a consistent trend from T0 to T1 to T2.

Surface modification on semi-coke-based activated carbon for enhanced separation of CH4/N2

Semi-coke-based activated carbons (SACs) were prepared using semi-coke powders as raw materials. They were modified by organic reagents (benzene, methyl benzoate, and ethyl acetate), low-temperature plasma (CH4 and N2 atmosphere), and organic reagent-low temperature plasma synergistic methods. FT-IR analysis showed that the corresponding functional groups were introduced to the surface of the SACs and the absorption peak intensities of the corresponding functional groups were enhanced via low-temperature plasma treatment. Low-temperature N2 adsorption tests showed that the organic reagent played an important role for regulated mesopores of the SACs. The adsorption capacities of the SACs for CH4 and N2 were measured via static volumetric method, and their separation factors of the CH4/N2 were calculated, in which the biggest separation factor (5.08) of CH4/N2 was obtained from the SAC-ben-P-N2, which was synergistic modified by benzene and low-temperature plasma (N2 atmosphere) and its breakthrough time of methane was 93s. The biggest breakthrough time of methane (112s) was acquired from the SAC-ben, which was modified by benzene and its separation factor of CH4/N2 was 4.87.

Investigating the Effect of Plasma Treatment and Amine-Based Surfactants on Quality of Sheepskin Dyeing

The paper presents the results of studying the effect of non-equilibrium low-temperature plasma (LTP) and synthesized non-ionic and cation-active amine-based surfactants on the quality of acid dyeing of wool and leather sides of sheepskins. The plasma treatment conditions, which led to high quality in colour intensity and uniformity of dyeing along both the height of a wool fiber and sheepskin surface area, were determined (U=3.0 кV; I=0.8 A; Wp=2.15 kW; τ=5.0 min; G =0.04 g/s; plasma gas – argon). The study showed that the application of surfactants for the dyeing process led to an increase in dye selectivity ranging from 90% to 100%. A significant increase in dye resistance to dry friction of sheepskins as well as in their strength and elastic characteristics after low temperature plasma treatment was observed (grayscale level was 5; the tensile strength at breaking increased by 10%, the tensile elongation of a leather fabric after dyeing increased by 15%). The study proved the efficiency of the technology which combined plasma treatment and dyeing of sheepskins in the presence of synthesized surfactants used as dye-leveling agents.

Nonequilibrium low temperature plasma in process of collagen containing polymer materials electrical properties modification

The process of treatment with nonequilibrium low temperature plasma allows to reduce collagen materials electric potential due to charges dissipating along leather surface. Under certain conditions the main reason for the generation and accumulation of static electricity is the high hydrophilicity of the material. Leather surface hydrophobization is achieved through water repellent application and bulk nonequilibrium low temperature plasma treatment. Despite material surface hydrophobization nonequilibrium low temperature plasma processing parameters for genuine collagen containing polymer materials hygroscopicity increasement are determined. Collagen containing polymer materials plasma treatment also increases its biological compatibility and antimicrobial properties, improves mechanical characteristics by changing the internal structure of the material.

Realization of electrical signal monitoring of metal surface modification by means of low-temperature plasma treatment

The paper shows good prospects of modifying the working surfaces of metal products by low-temperature plasma treatment. We suggest a treatment monitoring method based on the recording of signals that arise in the electrical circuit of the processing unit and present the results of this approach realization. The study substantiates the expediency, assesses possibility, and shows the efficiency of controlling the low-temperature plasma modification based on the correction of its operating parameters according to monitoring data.

Performance Enhancement of Vanadium Redox Flow Battery by Treated Carbon Felt Electrodes of Polyacrylonitrile using Atmospheric Pressure Plasma.

A high-performance carbon felt electrode for all-vanadium redox flow battery (VRFB) systems is prepared via low-temperature atmospheric pressure plasma treatment in air to improve the hydrophilicity and surface area of bare carbon felt of polyacrylonitrile and increase the contact potential between vanadium ions, so as to reduce the overpotential generated by the electrochemical reaction gap. Brunauer-Emmett-Teller (BET) surface area of the modified carbon felt is, significantly, five times higher than that of the pristine felt. The modified carbon felt exhibits higher energy efficiency (EE) and voltage efficiency (VE) in a single cell VRFB test at the constant current density of 160 mA cm−2, and also maintains good performance at low temperatures. Moreover, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis results show that the resistance between electrolyte and carbon felt electrode decreased. As a result, owing to the increased reactivity of the vanadium ion on the treated carbon felt, the efficiency of the VRFB with the plasma-modified carbon felt is much higher and demonstrates better capacity under a 100-cycle constant current charge-discharge test.

Amorphous Iridium Oxide Nanoparticle Films Prepared by Low-temperature Annealing and Plasma Treatment as Highly Efficient Oxygen Evolution Electrocatalysts

This study reports a facile strategy to prepare IrOx nanoparticle films on FTO substrates through simple spin-coating, annealing, and plasma treatment, which act as efficient electrocatalysts towar...

Effects of plasma treatment on properties of carbon fiber and its reinforced resin composites

The influence of plasma treatment on the wettability of carbon fiber was studied using the vacuum assisted resin transfer molding (VARTM) process. The influence of plasma treatment on the mechanical properties of carbon fiber-reinforced polymer (CFRP) composites, including interlaminar shear strength and tensile properties, were investigated. The carbon fiber surface chemistry analysis was carried out by Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). Results showed that low-temperature plasma treatment had little effect on the surface morphology of the carbon fiber; however, it changed the chemical surface state of the carbon fiber, which contributed to enhance the wettability of the carbon fiber by increasing the perfusion speed of the resin to be more than two times of the original speed. The fiber wettability improvements are of great significance to the preparation of the CFRP composite by the VARTM process. Compared to untreated carbon fiber, the plasma treatment caused an acceptable decrease in tensile properties and offered an increase in the interlaminar shear strength of the CFRP composite. Low-temperature plasma treatment played an important role in the effective preparation and application of the CFRP composite.

Low-Temperature Plasma Suppresses Proliferation and Induces Apoptosis in Lung Cancer Cells by Regulating the miR-203a/BIRC5 Axis.

AimLow-temperature plasma (LTP) has potential applications in cancer therapy. Herein, we explored the molecular mechanisms of proliferation inhibition induced by LTP.MethodsLTP was generated by a helium atmospheric-pressure plasma jet and used to treat A549 and H1299 cells. CCK-8 and cell apoptosis assays were performed to evaluate the effects of LTP treatment on A549 and H1299 cells. The qRT-PCR was performed to measure the expression of miR-203a after treating with LTP. CCK-8, colony formation, cell apoptosis assays, and Western blotting were performed to analyse the function of miR-203a in the development of lung cancer. Dual-luciferase assay and Western blotting were used to probe the relationship between miR-203a and BIRC5, and gene silencing using si-BIRC5 was carried out to explore the effect of knocking down BIRC5 on lung cancer cells.ResultsWe found that LTP significantly suppressed proliferation and promoted apoptosis in A549 and H1299 cells. The miR-203a expression was increased after cells were treated with LTP. The miR-203a expression was downregulated among lung cancer tissue samples, and overexpression of miR-203a suppressed cell growth and induced apoptosis in lung cancer cells. We showed that miR-203a targeted BIRC5. Moreover, silencing of BIRC5 caused proliferation inhibition and induced apoptosis in lung cancer cells.ConclusionOur study revealed that LTP inhibited proliferation and induced apoptosis in A549 and H1299 cells through the miR-203a/BIRC5 axis. These findings showed that LTP could potentially be used to treat lung cancer.

Relationship between Metallurgical States and Corrosion Resistance of Nitrided Martensitic Steels in Marine Environment

The objective is focused on the comprehension of the relationship between the metallurgical state and the functional properties of nitrided martensitic stainless steels.Nitriding is performed by a low temperature plasma treatment (Direct Current mode) in various conditions. Metallurgy of the nitrided layer was characterized at different scales, from the macroscopic to the nanometric ones. An increase of the thickness of the nitrided layer with temperature of the plasma treatment is observed. Precipitation of CrN and others nitrided phases in relation with crystallographic defects is observed. Moreover, the TEM analyses on FIB samples extracted from the surface highlight the formation of a succession of different nitrided layers depending on the nitrogen content : expanded martensite, iron-nitride phases [2].The electrochemical properties of nitrided samples are also assessed by voltammetry test and extended immersion test. Results highlight differences on the corrosion behaviour of the nitrided X17CrNi16-2 steels with temperature of the plasma treatment. The reactivity evolution is linked to the formation of a “composite” system composed of different layers. SECM was used to understand the reactivity evolution through these layers, and successive surface grinding permits to corroborate the reactivity evolution and to understand the origin of the corrosion resistance evolution after nitriding process.[1] H.E. Boyer, T.L. Gall. Metal Handbook, Desk edition, ASM, Ohio, USA, 1986[2] J. Yang &al. Materials and Design, Vol. 32 (2011) 808-814

Low-Temperature Plasma Modification of Styrene-Butadiene Block Copolymer Surfaces for Improved Adhesion-A Kinetic Approach.

This paper proposed a kinetic model that can describe the changes in the adhesion properties of styrene–butadiene (SBS) block copolymer surfaces under the influence of low-temperature plasma treatment. As a measure of these changes, the peel strength of joints formed between the copolymer surface and the polyurethane adhesive was chosen. Five types of low-temperature low-pressure RF plasma, two inert plasmas (Ar and He), and three reactive plasmas (O2, CO2, and CCl4) were tested. It was found that for all these types of plasma, the peel strength with the plasma treatment time first increases rapidly reaching a maximum value, and then there is a visible decrease in peel strength, after which the peel strength increases again. This dependence of the peel strength on the plasma treatment time is very well described by the proposed model, which considers three processes: (1) the generation of radical states followed by the creation of functional groups involved in the adhesive bonding process, (2) the surface cross-linking that decreases the concentration of these functional groups, and (3) the formation of nano-roughness. The model analysis revealed differences between the action of reactive and inert plasmas in the SBS surface cross-linking mechanism and preferential etching process, as well as differences in the generation of radical states between the O2 plasma (electron process) and other plasmas tested (ionic processes).

Low-temperature plasma applications in chemical fungicide treatment reduction

Abstract In order to reduce the environmental burden of chemicals, various new alternatives to seed protection are being sought. Our aim was to find an environmentally acceptable solution leading to the inactivation of seed-borne phytopathogenic fungi Fusarium culmorum on the surface of wheat and barley seeds with a positive effect on their germination. As a low-temperature plasma (LTP) source, a Diffuse Coplanar Surface Barrier Discharge (DCSBD) was used. Plasma generated by DCSBD is non-equilibrium, cold, diffuse, macroscopically homogeneous even in ambient air at atmospheric pressure. Experimental results showed that LTP treatment in the range of 120—300 s significantly inhibits the growth of F. culmorum on the surface of the seeds. The efficiency of LTP treatment was compared with traditional seed protection processes using chemical fungicide and also with combined seed pretreatment by plasma and subsequent application of chemical fungicide. No growth of F. culmorum was observed after the combination of Vitavax 2000 fungicide application in the dose of 10 % and 60 s of LTP treatment even on the 5th day of incubation. Better wettability of seeds with the chemical fungicide was related to the change on seed surface, which becomes hydrophilic after 10 s of LTP application. Short LTP exposure times did not affect germination and improved the growth parameter of cereal seeds. By combining physical (LTP) and chemical (Vitavax 2000) treatments of cereal seeds, it is possible to effectively reduce the required amount of chemical fungicide and to stimulate germination and early growth seed parameters.

Photocatalytic activity of spinel ferrites CoxFe3−xO4 (0.25 < x < 1) obtained by treatment contact low-temperature non-equilibrium plasma

CoxFe3−xO4 (0.25 < x < 1) spinel ferrite nanocrystalline powder was synthesized by co-precipitation method and low-temperature contact nonequilibrium plasma treatment. Structural characterization of the samples was performed using powder X-ray diffraction. The results show the presence of mixed-type spinel with a cubic structure. It is established that the distribution of cations and structural parameters strongly depends on the ratio of cations. It is determined that the photocatalytic activity in the decomposition reaction 4-nitrophenol decreases with increasing x.

Enhanced interfacial strength of plasma treated polyethylene and glass

Low-temperature plasma treatment represents an important technology to influence surface properties of polymers. Less financially demanding and environmentally friendly way leads to a significant enhancement of adhesion to another type of surfaces. The article describes the influence of plasma treatment time of polyethylene (PE) powder leading to the increase of interfacial strength to glass substrate. This strength was quantified by the tensile test and compared with the industrially used chemical products, maleic anhydride or silane. The maximum value of the interfacial strength was achieved by plasma treatment with an exposure time of 60 s and is at least by 150 % higher than in the case of the interphase created by silane. The results of the research, also proven by ESCA measurement, represent the potential of using plasma treatment of powder semi-products for the preparation of fibre-reinforced composites with a thermoplastic matrix processed only at atmospheric pressures. Keywords: Plastics; Glass; Surface treatment; Interface/interphase

Antibacterial effects of low-temperature plasma generated by atmospheric-pressure plasma jet are\xa0mediated by reactive oxygen species

Emergence and spread of antibiotic resistance calls for development of non-chemical treatment options for bacterial infections. Plasma medicine applies low-temperature plasma (LTP) physics to address biomedical problems such as wound healing and tumor suppression. LTP has also been used for surface disinfection. However, there is still much to be learned regarding the effectiveness of LTP on bacteria in suspension in liquids, and especially on porous surfaces. We investigated the efficacy of LTP treatments against bacteria using an atmospheric-pressure plasma jet and show that LTP treatments have the ability to inhibit both gram-positive (S. aureus) and gram-negative (E. coli) bacteria on solid and porous surfaces. Additionally, both direct LTP treatment and plasma-activated media were effective against the bacteria suspended in liquid culture. Our data indicate that reactive oxygen species are the key mediators of the bactericidal effects of LTP and hydrogen peroxide is necessary but not sufficient for antibacterial effects. In addition, our data suggests that bacteria exposed to LTP do not develop resistance to further treatment with LTP. These findings suggest that this novel atmospheric-pressure plasma jet could be used as a potential alternative to antibiotic treatments in vivo.

Highly efficient nanofibrous sterile membrane with anti-BSA/RNA-fouling surface via plasma-assisted carboxylation process

Constructing a functional porous membrane scaffold for the efficient separation of bacteria from protein and nucleic acid drug stock solution remains a great challenge due to the permeability-selectivity trade-off and fouling propensity of membranes. Here, we adopted the nanofiber suspension coating approach to prepare sterile membrane with nanofiber coverage density of 6 g/m2. The carboxylation surface was further achieved through a facile route including alkaline solution activation and low temperature plasma treatment in sequence. As indicated by experimental and theoretical model analysis, nanofibrous membrane treated by alkali and plasma (NFM-APT) possess an ultrathin nanofiber active layer (about 4.7 μm), narrow pore size distribution (average size: 0.1 μm) and high hydrophilicity, which is beneficial for the absolute interception of E. coli, S. aureus and B. diminuta as well as a relative high and stable permeability (7400.4 L/(m2h), 0.2 MPa). Moreover, NFM-APT presents ultralow adsorption of BSA and RNA in the test of continue-flow and static-immersion modes with an excellent reusability after back-washing process, which is superior to the nascent nanofibrous membrane and commercially available PES membrane. The extraordinary anti-BSA/RNA-fouling performance can be attributed to the excellent hydrophilicity of membrane as well as the robust repulsive interaction between the negatively charged carboxyl group grafted on the surface of fiber and the negatively charged BSA&RNA. The NFM-APT also possesses outstanding performance stability, easy operation, and excellent recoverability. This work may provide a new avenue to design and develop next-generation high-performance sterile membrane for bio-separation.

Stimulation of biomass and astaxanthin accumulation in Haematococcus pluvialis using low-temperature plasma (LTP)

Increasing biomass of H. pluvialis can improve astaxanthin production. In this work, we employed low-temperature plasma (LTP) to explore new ways of improving biomass and astaxanthin production in H. pluvialis. We optimized the LTP treatment conditions, analyzed the growth, photosynthetic efficiency and transcriptome of H. pluvialis. We found that LTP at proper condition could effectively improve the growth of H. pluvialis and affect the processes of synthetic and metabolic production of the phytohormones beneficial for the stimulation of H. pluvialis biomass and astaxanthin accumulation. This study therefore not only provides a novel approach for promoting the growth of H. pluvialis and its production of astaxanthin, but also gives some new insights into the mechanism of LTP-induced stimulation effect on H. pluvialis.

Effect of Low-Temperature Plasma Treatment on Surface Modification of Polycaprolactone Pellets and Thermal Properties of Extruded Filaments

Polycaprolactone (PCL) polymer has been surface modified using oxygen low-temperature plasma and melt extruded into single filaments. Oxygen plasma was generated using a radiofrequency source with power of 150 W. The PCL polymer samples were treated with plasma for various durations of 5 min, 10 min, and 20 min. Water contact angle measurements were carried out to assess the wettability, revealing that the treatments reduced the contact angle by up to 11°. Changes in the chemical bonding and surface compositions were characterized by using x-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy, revealing a high concentration of oxygen functionalities on the surface. Crystallinity changes were studied by using x-ray diffraction analysis. The surface morphology of the polymer was investigated using field-emission scanning electron microscopy. The thermal degradation and melting behavior was studied using thermogravimetric analysis and differential scanning calorimetry, respectively.

Study on the process of knitted woolen fabric treatment based on oxygen low-temperature plasma

The oxygen low-temperature plasma (LTP) treatment on knitted woolen fabric was carried out to investigate the changes of shrinkage resistance, bursting strength and moisture absorption of knitted woolen fabric after treatment. In addition, the effects of different levels of exposure time, treatment power and gas flow rate on the change of felting rate, bursting strength and moisture absorption of knitted woolen fabric in the process of LTP were investigated. The results show that LTP treatment can improve the anti-felt, bursting strength, moisture absorption of knitted woolen fabric. According to the analysis of variance, in the process of LTP treatment, the exposure time is the primary factor that affects the degree of change in the hygroscopicity of knitted woolen fabric, and treatment power is the main factor that affects the degree of change in the shrinkage resistance of knitted woolen fabric. Finally, under the experimental conditions, the best treatment process of knitted woolen fabric by oxygen low-temperature plasma is 20 min, 150 sccm and 400 w.