Low-temperature Oxygen Plasma Research Articles

Methane Adsorption and Desorption on Continental Shaly Matrix: Implications for Shale Gas Condensate Exploration and Production.

Shale gas condensate is a burgeoning unconventional resource with adsorbed methane (CH4) as its dominant component. Successful evaluation of marine shale gas gives limited insights into the evaluation of continental shale gas condensate due to their different occurrence patterns of organic matter and inorganic minerals and resultant contributions to pore development and CH4 ad-/desorption capability. To address this issue, we employed an advanced low-temperature oxygen plasma (LTOP) technology to extract organic matter from the continental shaly matrix. Results showed that the continental shaly matrix contains more clay minerals and less quartz, and develops fewer pores and fractures than typical marine shaly matrix. The organic matter-hosted pores instead of inorganic mineral-hosted pores are more weighted to the pore development in the continental shaly matrix. However, the inorganic minerals of the continental shaly matrix contribute more to CH4 adsorption capability than the organic matter, which could be attributed to the higher density of available adsorption sites toward CH4. Besides, the CH4 ad-/desorption hysteresis is more pronounced for the organic matter-free continental shaly matrix than the raw continental shaly matrix, which is attributed to the remarkable CH4 adsorption-induced clay mineral swelling. Overall, the effects of inorganic minerals in CH4 adsorption and desorption, particularly clay minerals, are crucial for continental shale gas condensate exploration and production.

Impact of plasma-modified pretreatment on the tensile properties of carbon fiber-reinforced epoxy composites

Abstract Low-temperature jet plasma modification technology is a surface treatment method designed to enhance the surface properties of materials without causing severe thermal damage. This technique modifies surface characteristics by creating plasma and utilizing ions and reactive groups within the plasma to chemically interact with the material’s surface. In this study, surface modification of carbon fibers was carried out by using low-temperature jet mixed oxygen plasma technology at treatment speeds of 25 mm/s, 50 mm/s, 100 mm/s, and 200 mm/s. Following the modification process, carbon fiber-reinforced epoxy composites were fabricated by using a hand-lay-up technique. Subsequently, the tensile properties of the carbon fiber composites were tested to evaluate the impact of the plasma treatment on their mechanical performance. The experimental results demonstrated a significant enhancement in the tensile properties of the composites when the carbon fibers were pretreated at a rate of 50 mm/s. This enhancement was evidenced by an impressive increase of 82.38% in tensile strength and 30.96% in tensile modulus compared to untreated samples. This signifies that low-temperature plasma treatment has a beneficial effect on enhancing the surface properties of carbon fibers and improving the performance of composites. This finding provides substantial support for the extensive application of carbon fiber composites.

ZnO Nanoparticles Enhance the Antimicrobial Properties of Two-Sided-Coated Cotton Textile.

Cotton textiles improved with metal oxide nanoparticles acquire additional features that may enhance their action against antimicrobial-resistant pathogens due to the unique properties and characteristics of the nanoparticles. The main objective of this work is to evaluate the antimicrobial features of two-sided-coated cotton textiles with ZnO nanoparticles. Nanoparticles were deposited using green chemistry technology with low-temperature oxygen plasma. ZnO particles formed stable structures on textile fibers. The optimal deposition parameters (150 W plasma power, 120 min immersion time) achieved the best effects against Gram-negative and Gram-positive bacteria and microscopic fungi. Two-sided-coated cotton with ZnO nanoparticles showed high antibacterial action on Gram-negative and Gram-positive bacteria. Modification with zinc oxide inhibited the growth of Candida albicans by more than half.

Polycaprolactone scaffold surface modification with soft X-ray/extreme ultraviolet (SXR/EUV) radiation and low-temperature oxygen and nitrogen plasma for biomedical applications

Modification of the surfaces of polymeric scaffolds is often required to make the material suitable for specific tissue engineering applications. Physico-chemical properties of scaffolds can be altered using various methods, such as plasma treatment, laser processing, chemical modifications, grafting with nanoparticles, or surface coating. In this paper physico-chemical modification of polycaprolactone (PCL) surface fibers was performed by exposing PCL samples to simultaneous soft X-ray/extreme ultraviolet (SXR/EUV) radiation and low-temperature, SXR/EUV-induced, nitrogen, and oxygen plasmas. The physical and chemical changes on modified PCL surfaces were examined using a scanning electron microscope and X-ray photoelectron spectroscopy, respectively. The effects of physico-chemical scaffold surface changes were verified with biological tests, i.e., MTT assay and immunofluorescence on murine osteoblast cell line (7F2). It was found that exposure of scaffolds to ionizing radiation and low-temperature plasmas induced strong chemical changes on their surface, i.e., appearance of various new chemical groups. Also, smoothing of the surface of PCL fibers, i.e., disappearance or significant reduction of the size of micropores on their fibers was also observed. Increased viability and adhesion of 7F2 osteoblasts on modified PCL samples after 24 h cell culture compared to non-treated PCL was also confirmed.Graphical abstract

Performance enhancement of Ge/Si avalanche photodetector by specific sidewall passivation using remote oxygen plasma treatment

We report an obvious improvement in the performance of a separated absorption charger-layer multiplication Ge/Si avalanche photodetector, achieved by passivating the sidewalls with a low-temperature remote oxygen plasma (ROP) treatment. The dangling bonds on the Ge surface can be efficiently passivated by the formation of an ideal Ge/GeO2 interface. With ROP passivation, the leakage current of the device shows a three- to fourfold decrease at 300 K, resulting in a dark current (I dark) of 3.5 × 10−6 A at 90% avalanche voltage (V br) and 3.4 × 10−7 A at punch-through voltage (V puhch-through) for the 26 μm-diameter device. A reduction of over tenfold is demonstrated at 200 K and the passivation mechanism is revealed. In addition, a multiplication gain of 94 is obtained under 1550 nm illumination. The device with ROP passivation shows an improved gain bandwidth product of 190 GHz. The enhanced high-frequency response of the device with ROP passivation can be attributed to the alleviation of the retarding effect caused by the interface state on the sidewalls. Without using a trans-impedance amplifier, an opening eye diagram at 28 Gbps is demonstrated, indicating reliable device transmission performance.

Effect of Low-Temperature Oxygen Plasma Treatment of Titanium Alloy Surface on Tannic Acid Coating Deposition.

In this study, the effect of low-temperature oxygen plasma treatment with various powers of a titanium alloy surface on the structural and morphological properties of a substrate and the deposition of a tannic acid coating was investigated. The surface characteristics of the titanium alloy were evaluated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. Following this, the tannic acid coatings were deposited on the titanium alloy substrates and the structural and morphological properties of the tannic acid coatings deposited were subject to characterization by XPS, SEM, and spectroscopic ellipsometry (SE) measurements. The results show that the low-temperature oxygen plasma treatment of titanium alloys leads to the formation of titanium dioxides that contain -OH groups on the surface being accompanied by a reduction in carbon, which imparts hydrophilicity to the titanium substrate, and the effect increases with the applied plasma power. The performed titanium alloy substrate modification translates into the quality of the deposited tannic acid coating standing out by higher uniformity of the coating, lower number of defects indicating delamination or incomplete bonding of the coating with the substrate, lower number of cracks, thinner cracks, and higher thickness of the tannic acid coatings compared to the non-treated titanium alloy substrate. A similar effect is observed as the applied plasma power increases.

Oxygen plasma treatment-enhanced humidity sensing performance of MoS2 nanoparticles-anchored nitrogen-doped laser-induced graphene

The monitoring of humidity has elicited considerable interest in diverse fields. Nevertheless, the intricate nature of preparatory procedures employed for humidity sensors poses a formidable challenge in the pursuit of a streamlined, expeditious, and highly efficient technique for fabricating humidity-sensitive materials. Herein, the fundamental formation principle of polyimide (PI) film serves as the underpinning for the application of a swift and effective laser direct writing technique in creating a composite integrating MoS2 nanoparticles anchored within nitrogen-doped laser-induced graphene (MoS2@NLIG). Subsequently, a rapid low-temperature oxygen plasma treatment is administered to enhance humidity sensing capabilities of the MoS2@NLIG composite. The oxygen plasma treatment-enhanced MoS2@NLIG humidity sensor exhibits exceptional capability in detecting relative humidity (RH) with a significant sensitivity of 61,219.97 Ω/%RH across an extensive range from 11% to 95%RH, while maintaining a hysteresis as minimal as 3.72%. Moreover, the sensor exhibits outstanding response and recovery times with respective values of 9 s and 15.5 s. Additionally, the humidity sensor demonstrates the capacity to identify human exhalation, potentially serving as a valuable electronic device for monitoring clinical respiration.

Enhancing the electric charge output in LiNbO3-based piezoelectric pressure sensors.

Lithium niobate (LiNbO3) single crystals are a kind of ferroelectric material with a high piezoelectric coefficient and Curie temperature, which is suitable for the preparation of piezoelectric pressure sensors. However, there is little research reporting on the use of LiNbO3 single crystals to prepare piezoelectric pressure sensors. Therefore, in this paper, LiNbO3 was used to prepare piezoelectric pressure sensors to study the feasibility of using LiNbO3 single crystals as a sensitive material for piezoelectric pressure sensors. In addition, chemical mechanical polishing (CMP) technology was used to prepare LiNbO3 crystals with different thicknesses to study the influence of these LiNbO3 crystals on the electric charge output of the sensors. The results showed that the sensitivity of a 300 μm sample (0.218 mV kPa-1) was about 1.23 times that of a 500 μm sample (0.160 mV kPa-1). Low-temperature polymer heterogeneous integration and oxygen plasma activation technologies were used to realize the heterogeneous integration of LiNbO3 and silicon to prepare piezoelectric pressure sensors, which could significantly improve the sensitivity of the sensor by approximately 16.06 times (2.569 mV kPa-1) that of the original sample (0.160 mV kPa-1) due to an appropriate residual stress that did not shatter LiNbO3 or silicon, thus providing a possible method for integrating piezoelectric pressure sensors and integrated circuits.

Speciation of Oxygen Functional Groups on the Carbon Support Controls the Electrocatalytic Activity of Cobalt Oxide Nanoparticles in the Oxygen Evolution Reaction.

The effective use of the active phase is the main goal of the optimization of supported catalysts. However, carbon supports do not interact strongly with metal oxides, thus, oxidative treatment is often used to enhance the number of anchoring sites for deposited particles. In this study, we set out to investigate whether the oxidation pretreatment of mesoporous carbon allows the depositing of a higher loading and a more dispersed cobalt active phase. We used graphitic ordered mesoporous carbon obtained by a hard-template method as active phase support. To obtain different surface concentrations and speciation of oxygen functional groups, we used a low-temperature oxygen plasma. The main methods used to characterize the studied materials were X-ray photoelectron spectroscopy, transmission electron microscopy, and electrocatalytic tests in the oxygen evolution reaction. We have found that the oxidative pretreatment of mesoporous carbon influences the speciation of the deposited cobalt oxide phase. Moreover, the activity of the electrocatalysts in oxygen evolution is positively correlated with the relative content of the COO-type groups and negatively correlated with the C═O-type groups on the carbon support. Furthermore, the high relative content of COO-type groups on the carbon support is correlated with the presence of well-dispersed Co3O4 nanoparticles. The results obtained indicate that to achieve a better dispersed and thus more catalytically active material, it is more important to control the speciation of the oxygen functional groups rather than to maximize their total concentration.

Oxygen plasma modulates the interfacial impedance of microwave reduced graphene oxide for enhanced microwave absorption

As a classic two-dimensional material, graphene has attracted worldwide attention in the fields of electromagnetic shielding and microwave absorption. However, the excellent electrical conductivity makes it challenging to achieve impedance matching, which significantly limits its application microwave absorption. Here, we propose a strategy for the modification of graphene by low-temperature oxygen plasma that precisely regulates the electromagnetic parameters of the graphene material by adjusting the plasma irradiation time. This approach controls the electrical conductivity of graphene for impedance matching and creates enriched defects that effectively improve the material permittivity loss capability. Owing to these advantages, the sample (O-MW-rGO-60) irradiated by plasma for 60 min showed excellent microwave absorption properties with a minimum reflection loss of −54.11 dB at a matched thickness of 1.7 mm and an effective absorption bandwidth of 5.68 GHz at a thin thickness of 2.0 mm. In addition, CST simulation is used as an intelligent design strategy to verify a product's radar wave absorption capability under realistic conditions. The RCS values of the model covered with the O-MW-rGO-60 sample coating are significantly lower than those of the metal substrate, which confirms its excellent microwave absorption properties and provides new insights into the future development of microwave absorbing materials.

Microscopic Characterisation of the Effect of Low Temperature Oxygen Plasma Treatment on Recycled Polyethylene Terephthalate (Pet)

Microscopic Characterisation of the Effect of Low Temperature Oxygen Plasma Treatment on Recycled Polyethylene Terephthalate (Pet)

Multi-functional Calotropis gigantea fabric using self-assembly silk fibroin, chitosan and nano-silver microspheres with oxygen low-temperature plasma treatment

The present paper describes a novel multi-functional Calotropis gigantea (CG) fabric with durable antibacterial property and comfortable wearability for various applications. First, antibacterial microspheres (AMs) were prepared by self-assembly of silk fibroin (SF), chitosan (CS) and nano-silver microspheres (NSMs). Oxygen low-temperature plasma (OLTP) treatment was used to improve the adhesion between AMs and CG yarn. The AMs modified CG fabric has soft hand feeling, high moisture regain (10.37 ± 1.87%), good breathability, strong wrinkle resistance, and durable antibacterial properties. The antibacterial rate of the modified CG fabric against Escherichia coli (E. Coil) and Staphylococcus aureus (S. Aureus) is as high as 99.9 ± 0.1%, and it still has an antibacterial activity after washing 20 times (90.24 ± 0.65% and 80.25 ± 1.14%, respectively). The in vivo biocompatibility test showed clear signs of angiogenesis at the implantation site in the rats. Thus, this study offers the foundation for the development of functional CG fiber-based biomedical textiles.

Tailoring the surface chemistry of hard carbon towards high-efficiency sodium ion storage.

Hard carbon (HC) is most likely to be a commercialized anode material for sodium-ion batteries (SIBs). However, its low initial coulombic efficiency (ICE) impedes its further large-scale industrialization. Since the ICE is greatly related to the side reactions of the electrolyte on the HC surface, herein, we focus on tailoring the surface chemistry of HC via a facile low-temperature oxygen plasma (LTOP) treatment technique. The modified HC after a suitable treatment time possesses a highly ordered and low defect surface without a negligible change in layer spacing, thus facilitating Na+ deinsertion/insertion and reducing the HC/electrolyte side reactions. Moreover, LTOP treatment also brings oxygen functional groups (CO) to the HC surface to enrich Na+ storage active sites. Consequently, the modified HC reveals a higher ICE of 80.9% compared to 60.6% in the bare HC. Also, the modified HC delivers an ultrahigh specific capacity of 331.0 mA h g-1 at 0.1 A g-1 and exhibits superior rate performance with a high specific capacity of 211.0 mA h g-1 at 5 A g-1. This work provides a feasible strategy to tailor the surface chemistry of HC for high-efficiency Na-storage and provides a novel avenue to construct high-efficiency SIBs.

Plasma Modification of Carbon Coating Produced by RF CVD on Oxidized NiTi Shape Memory Alloy under Glow-Discharge Conditions.

Our previous work has shown that for cardiac applications, combining low-temperature plasma oxidation with an amorphous carbon coating (a-C:N:H type) constitutes a prospective solution. In this study, a short-term modification by low-temperature oxygen plasma is proposed as an example and a method for shaping the topography and surface energy of the outer amorphous carbon coating, produced via the Radio-Frequency Chemical Vapour Deposition (RFCVD) method on NiTi alloy oxidized under glow-discharge conditions. This treatment alters the chemical composition of the outer zone of the surface layer. A slight increase is also noted in the surface roughness at the nanoscale. The contact angles were shown to increase by about 20% for water and 30% for diiodomethane, while the surface free energy decreased by ca. 11%. The obtained results indicate that even short-term contact with low-temperature plasma can shape the surface properties of the carbon coating, an outcome which shows potential in terms of its use in medical applications.

Сорбция и удерживающая способность модифицированных волокнисто-пористых материалов по отношению к нефти и нефтепродуктам

Purpose. Investigation of the effect of electric polarization of polymeric fibrous materials on the sorption of oil and petroleum products. Methods. Melt blowing of Borealis brand polypropylene. Polarization of samples in a corona discharge field of positive and negative polarity with a strength of 25 kV/cm. Sample processing in low-temperature oxygen plasma of a glow discharge with a frequency of 35 kHz. Weighting method for determining sorption characteristics. Scanning electron microscopy method. Electret thermal analysis method. Findings. The dependence of sorption parameters of materials on the type of physical modification – corona discharge of different polarity and low-temperature plasma of a glow discharge – has been established. It is shown that the modification of fibrous-porous materials in a corona discharge field to impart electret properties to them somewhat reduces the sorption characteristics of these materials in relation to oil. In the manufacture of sorption materials for the collection of crude oil, the original unmodified fibrous-porous material should be used. It has been experimentally established that in the manufacture of sorption materials for the collection of light oil fractions, the preferred method is the modification of fibers in a corona discharge field of negative polarity. Electrization has a significant effect on the processes of sorption by fibers of its lipophilic components. A physical model of the sorption of petroleum products by electret samples of polymeric fibrous-porous materials is proposed. Application field of research. Fibrous-porous polymeric materials subjected to physical modification with the formation of an electret state can be used for: sorption of some oil fractions, filtration of liquids from contaminants of a dielectric nature, purification of air from ionized dust containing radioactive particles, targeted separation of biological fluids containing dielectric and (or) electret components.

Investigation of the properties of knitted woolen fabrics treated with oxygen low-temperature plasma for sportswear applications

Nine groups of knitted woolen fabrics for sportswear with different technical characteristics were treated with oxygen low-temperature plasma, and the changes in the surface morphology and chemical composition of wool fibers before and after plasma treatment, as well as the changes in the applicability indexes of knitted woolen fabrics, were studied. Finally, the comfort performance of the fabrics was evaluated by combining the concentration mapping method and the function evaluation value method. The analysis found that the surface scales of wool fibers were seriously etched after oxygen low-temperature plasma treatment, and the anti-felting, bursting strength and moisture absorption of the knitted woolen fabrics were improved. At the same time, the quick-drying index of the fabric has also been improved to a certain extent. This research provides a basis for the development of knitted woolen fabric for sportswear with excellent performance.

Surface modification of activated carbon fiber by low-temperature oxygen plasma: Textural property, surface chemistry, and the effect of water vapor adsorption

The effects of adsorbent characteristics on its water adsorption performance were investigated using low-temperature oxygen plasma technology (LTOP) as a surface modification method. A series of activated carbon fiber (ACF)-based adsorbents was prepared to get further insight into the functions of water vapor adsorption behavior with textural property and surface chemistry. The result shows that LTOP treatment does not alter drastically the physical surface properties and simultaneously functionalize oxygen-containing functional groups (OFGs) especially carboxyl groups on the ACF surface when the treatment time and effective output voltage are 15 min and 8–9 kV, respectively. Meanwhile, the carbon atoms with unpaired electrons are found to be increased during the process of plasma treatment and used as active sites for chemical adsorption. Both OFGs and carbon atoms with unpaired electrons on the carbon surface play a vitally important role for water vapor adsorption. The surface functionalities and chemical adsorption may govern the adsorption–desorption behavior of water vapor at low relative humidity (RH less than 40%). Adsorption mechanism of water vapor on the carbon surface before and after LTOP treatment is proposed. After several adsorption and desorption cycles, the adsorption capacity of LTOP-treated ACFs is still higher than that of ACF-raw. Therefore, this technology may shed light on the potential application of LTOP-treated ACFs in harvesting water from air at low relative humidity.

Sericin Grafting onto Cashmere Fiber and Its Properties Investigation

ABSTRACT Cashmere fiber is pretreated with oxygen low temperature plasma to increase the content of polar groups (-OH, -COOH) on the surface. Then by using aziridine crosslinker and polycarbodiimide crosslinker, the sericin with health-care function is grafted onto the surface of the pretreated cashmere fiber. Plasma treatment is optimized after the assessing of methylene blue staining and fiber tensile strength. The grafting rate of sericin indicates that both aziridine and polycarbodiimide crosslinker could play a bridging role. Compared with untreated fiber, oxygen plasma treatment can improve the grafting rate significantly. The chemical changes and morphological structures of the fiber surface are analyzed by infrared spectroscopy and scanning electron microscope. After modification, cashmere exhibited good antibacterial and antioxidant properties. In addition, the fiber still has excellent dyeability while its crimp property and whiteness are slightly reduced.

Study on the Interfacial Shear Strength of a Polyamide 66/Epoxy Resin Composite

In this work, the interfacial shear strength (IFSS) of polyamide 66/epoxy resin composite was improved through the surface modification of polyamide 66 by low-temperature oxygen and nitrogen plasma. Microbond test was used to study the IFSS of the composite. In addition, the composition, microstructures and deboned morphology of the fiber were investigated using the methods of XPS, AFM and SEM. The results show that the polar functional group, such as -NH2, -COOH, and -OH, were successfully introduced on the surface of the polyamide 66 fiber by plasma treatment. Meanwhile, the surface roughness of the polyamide 66 also increased. After oxygen and nitrogen plasma treatment, the interfacial shear strength of the composite increased to 3.52 MPa and 4.89 MPa, respectively, which is 2 times and 3 times higher than that of the untreated composite. Nitrogen plasma treatment showed better results than oxygen plasma treatment.

Effects of oxygen plasma ashing treatment on carbonate clumped isotopes.

For clumped isotope analysis (Δ47 ), hydrocarbon and organic molecules present an important contaminant that cannot always be removed by CO2 purification through a Porapak-Q trap. Low-temperature oxygen plasma ashing (OPA) is a quick and easy approach for treatment; however, the impact of this treatment on the original carbonate clumped isotope values has never been fully studied. We tested the isotopic impact of OPA using three natural samples with a large range of initial Δ47 values. Crushed and sieved (125 μm mesh) samples were placed into a Henniker Plasma HPT-100 plasma system and treated at a flow rate of 46 mL/min and a power of 100 W at a vacuum of 0.2 mbar for 10, 20, 30 and 60 min before clumped isotope analysis using two MAT 253 isotope ratio mass spectrometers modified to measure masses 44-49. OPA treatment for 30 min or more on calcite powder samples has the potential to alter the clumped isotopic composition of the samples beyond analytical error. A systematic positive offset is observed in all samples. The magnitude of this alteration translates to a temperature offset from known values ranging from 4°C to 13°C. We postulate that the observed positive offset in Δ47 occurs because the bonds within lighter isotopologues are preferentially broken by plasma treatment, leading to an artificial increase in the 'clumping' value of the sample. We recommend that any laboratory performing OPA treatments should reduce the runs to 10-20 min or carry out successive runs of 10 min followed by sample stirring, as this procedure showed no alteration in the initial Δ47 values. Our results validate the use of OPA for clumped isotope applications and will allow future research to use clumped isotopes for challenging samples such as oil-stained carbonates, bituminous shales or host rocks with very high organic carbon content.