Plasma treatment as a method for functionalising and improving dispersion of carbon nanotubes in epoxy resins

This study reports on the results of plasma-treated carbon nanotubes (CNTs) in the presence of oxygen and ammonia which can be scaled up for relatively large quantities of nanomaterials. The plasma treatment has been shown to change the surface chemistry and energy as well as the morphology of the carbon nanotubes. X-ray photoelectron spectroscopy analysis shows increases in oxygen and nitrogen groups on the oxygen- and ammonia-treated CNTs, respectively. Titration of the enhanced oxygen plasma-treated CNTs reveals an increased presence of carboxylic acid groups at 2.97 wt% whilst bulk density decreases from 151 kg/m³ for untreated carbon nanotubes to 76 kg/m³ after the enhanced oxygen treatment. The free surface energy has also been shown to increase from 33.70 up to 53.72 mJ/m² determined using a capillary rise technique. The plasma-treated carbon nanotubes have been mixed in epoxy and have shown an improvement in dispersion, which was quantitatively evaluated using an optical coherence tomography (OCT) technique shown to be suitable for nanocomposite characterisation. This research has demonstrated that it is possible to surface functionalise large quantities of carbon nanotubes in a single process, and that this process improves the dispersion of the carbon nanotubes in epoxy.     

Effect of Plasma Treatment on Air and Water-Vapor Permeability of Bamboo Knitted Fabric

In this paper, the effects of oxygen and atmospheric plasma on air and water-vapor permeability properties of single jersey bamboo fabric have been investigated. The changes in these properties are believed to be related closely to the inter-fiber and inter-yarn friction force induced by the plasma treatments. The outcomes showed that the water-vapor permeability increased, although the air permeability decreased along with the plasma treatments. The SEM images clearly showed that the plasma modified the fiber surface outwardly. The results showed that the atmospheric plasma has an etching effect and increases the functionality of a bamboo surface, which is evident from SEM and FTIR–ATR analysis. These results reveal that atmospheric pressure plasma treatment is an effective method to improve the performance of bamboo fabric. Statistical analysis also indicates that the results are significant for air permeability and water-vapor permeability of the plasma-treated bamboo fabric.     

纳米银片/改性rGO的制备及在棉织物上的微波吸收性能

以氧化石墨烯(GO)、硝酸银和聚乙烯亚胺(PEI)为原料,制备了纳米银片/改性石墨烯(rGO-PEI-AgNPs)复合材料,并以二浸二轧的方式处理到棉织物上。通过FTIR、XPS、XRD、UV等测试手段对rGO-PEI-AgNPs材料以及rGO-PEI-AgNPs材料负载的棉织物进行结构表征,利用矢量网络分析仪(VNA)对rGO-PEI-AgNPs材料及其负载棉织物进行了微波吸收性能测试。SEM测试结果显示,GO-PEI材料表面成功生长了三角形状的纳米银片。研究表明,当rGO-PEI-AgNPs的质量分数为5 %时,材料的最小反射损耗可达到-37.8 dB,织物的最小反射损耗可达到-29 dB。本文制备的米银片/改性石墨烯(rGO-PEI-AgNPs)复合材料,能够有效赋予棉织物微波吸收性能,不仅可促进功能性纺织品发展,也拓宽了吸波材料的应用范围。     

Influence of atmospheric pressure plasma treatment on various fibrous materials: Performance properties and surface adhesion analysis

Atmospheric pressure plasma treatment using oxygen gas was applied to wool fibrous materials. The plasma-treated fibrous materials were characterised using advanced instrumental techniques including scanning electron microscopy and X-ray photoelectron spectroscopy. They were also tested for performance properties including tensile and tearing strength as well as change in yellowness using international standard testing methods. Wettability analysis was conducted to study the surface area and surface energy of the plasma-treated fibrous materials. Surface modification regarding the enhancement of their adhesion to other substance, i.e. microcapsule treatment, was investigated.     

Influence of atmospheric pressure plasma treatment on various fibrous materials: Performance properties and surface adhesion analysis

Atmospheric pressure plasma treatment using oxygen gas was applied to wool fibrous materials. The plasma-treated fibrous materials were characterised using advanced instrumental techniques including scanning electron microscopy and X-ray photoelectron spectroscopy. They were also tested for performance properties including tensile and tearing strength as well as change in yellowness using international standard testing methods. Wettability analysis was conducted to study the surface area and surface energy of the plasma-treated fibrous materials. Surface modification regarding the enhancement of their adhesion to other substance, i.e. microcapsule treatment, was investigated.     

Effect of oxygen plasma-treated carbon fibers on the tribological behavior of oil-absorbed carbon/epoxy woven composites

In this study, woven type carbon fibers were plasma-treated using oxygen gas, and the effect of the plasma treatment on tribological behavior of oil-absorbed carbon/epoxy woven composites was investigated. Chemical changes on the surface of the woven carbon fibers due to oxygen plasma treatment were determined by XPS analysis. Ball-on-disk wear tests were performed on untreated and plasma-treated carbon/epoxy woven composites that were fully oil absorbed. It was found that carbonyl functional groups were created on the carbon fibers due to oxygen-plasma treatment. In addition, the friction coefficient and wear rate of the plasma-treated carbon/epoxy composites were lower than that of untreated carbon/epoxy composites. SEM examination of the worn surface showed that the improved wear properties of the plasma-treated carbon/epoxy composites were attributed to enhanced adhesive strength, caused by the carbonyl functional groups between the carbon fibers and epoxy.     

Effect of Air Plasma Treatment on Thermal Comfort Properties of Woven Fabric

In this study, the effect of air plasma on thermal comfort properties of cotton woven fabric has been investigated. The woven fabric samples were treated with plasma under various parameters like treatment time, the distance between fabric sample and electrode, and frequency of the plasma process. It was observed that air permeability of the fabric has a linear relationship with distance of the sample, and inversely related to time and frequency. The thermal resistance and water vapor permeability decreased with distance and increased with time and frequency.     

Effect of various shapes of ZnO nanoparticles on cotton fabric via electrospinning for UV-blocking

Various shapes of ZnO; multi-petals, rod and spherical were prepared and then applied on cotton fabric for UV-blocking. The ZnO particles were investigated by XRD and SEM. The mixture solution of ZnO with polyvinyl alcohol was applied onto cotton fabrics via electrospinning. The characteristics of the fabric coating were investigated by SEM, XRD, Tensile testing and Atomic absorption spectroscopy (AAS). UV-blocking property was determined by UV-vis spectrophotometer. The results of XRD and SEM on the ZnO powders show that we can produce various shape of ZnO. The investigation by SEM and AAS clearly revealed that ZnO in polyvinyl alcohol nanofibers was effectively deposited on the cotton surface. The sphericals-shaped ZnO coated fabrics show excellent UV-blocking properties. The shape of ZnO shows no considerable effect on the tensile strength of the samples.     

ZnO/CNTs复合材料的制备、表征及光催化性能

采用水热法制备了一系列氧化锌和碳纳米管的复合材料(ZnO/CNTs),详细考察了碳纳米管的含量对复合材料光催化性能的影响。利用X射线衍射仪、紫外-可见漫反射吸收光谱、扫描电子显微镜、X射线能谱、透射电子显微镜、X射线光电子能谱和氮气吸附-脱附等测试手段对样品的结构、形貌和光学性质进行了表征,并用亚甲基蓝溶液模拟污染物,评价了ZnO/CNTs复合材料的光催化性能。结果表明:添加CNTs提高了ZnO的比表面积,增强了ZnO的可见光吸收。ZnO/CNTs复合材料较纯ZnO具有更高的光催化活性,并且随着CNTs含量的增加,ZnO/CNTs复合材料的光催化活性呈先增加后减小的趋势。当CNTs的含量为0.3%(质量分数)时,ZnO/CNTs复合材料的光催化活性最高,经过50 min光照后,亚甲基蓝的降解率达到了96.2%。     

Multiple cracking response of plasma treated polyethylene fiber reinforced cementitious composites under flexural loading

The effects of low frequency cold plasma treatments on the microstructure and chemistry of Polyethylene (PE) have been investigated. PE plates and fibers were exposed to plasmas of argon and oxygen gases. The surface wettabilities of plasma-treated plates were monitored. Possible physical changes on fiber surfaces were observed by a scanning electron microscope (SEM) at micrometer scale and by an atomic force microscope (AFM) at nanometer scale after this process. The effects of plasma treatment on surface chemistry of PE fibers have been analyzed by using an X-ray photoemission spectroscope (XPS). The fibers modified by plasma treatments were used in prismatic cementitious composites. The flexural performance of samples were characterized at two different ages (28 days and 8 months). Results showed that plasma treatment caused significant modifications on fibers’ surface structure and composites’ performance. Proper plasma treatment conditions significantly leads to improvement of multiple cracking behavior of fiber reinforced composites.     

丙烯酸等离子体改性电池隔膜用无纺丙纶

研究了利用等离子体接枝聚合技术对电池隔膜用无纺丙纶表面处理以达到预期性能的方法,并对处理时所涉及的工作参数(放电功率、放电时间、处理压强等)进行了探讨.结果表明,通过丙烯酸等离子体处理显著提高了无纺丙纶隔膜的吸碱速率和吸碱量,同时大幅降低了隔膜的面电阻.此外还采用红外光谱、扫描电镜对处理样品表面进行了表征分析.     

New plasma surface-treated memory alloys: Towards a new generation of “smart” orthopaedic materials

This paper describes the corrosion resistance, surface mechanical properties, cyto-compatibility, and in-vivo performance of plasma-treated and untreated NiTi samples. Nickel–titanium discs containing 50.8% Ni were treated by nitrogen and carbon plasma immersion ion implantation (PIII). After nitrogen plasma treatment, a layer of stable titanium nitride is formed on the NiTi surface. Titanium carbide is also found at the surface after carbon plasma implantation. Compared to the untreated samples, the corrosion resistances of the plasma PIII samples are better by a factor of five and the surface hardness and elastic modulus are better by a factor of two. The concentration of Ni leached into the simulated body fluids from the untreated samples is 30 ppm, whereas that from the plasma-treated PIII are undetectable. Although there is no significant difference in the ability of cells to grow on either surface, bone formation is found to be better on the nitrogen and carbon PIII sample surfaces at post-operation 2 weeks. All these improvements can be attributed to the formation of titanium nitride and titanium carbide on the surface.     

Plasma treatment effects on surface morphology and field emission characteristics of carbon nanotubes

In this study, electron field-emission properties of carbon nanotube films (CNTs) grown on silicon substrate before and after tetrafluoromethane (CF₄), hydrogen (H₂) and argon (Ar) plasma etchings were investigated. The CNTs were synthesized by thermal decomposition of methane in the presence of nickel catalyst. Our research results reveal that plasma treatment can modify the surface morphology and enhance the field-emission characteristics of CNTs regardless of the plasma used. The CNTs treated by both non-reactive and reactive plasmas have a higher density of defect and a smaller average diameter reflecting the etching effects of plasma treatments. In addition, higher emission currents and lower turn-on electric fields are also obtained for the CNTs after plasma treatment. As expected, reactive plasma treatment has a more pronounced effect on the surface morphology and field-emission characteristics of the synthesized CNTs than non-reactive plasma treatment. In particular, a huge increase in emission current (more than three orders of magnitude at high electric fields) and a substantial lower turn-on electric field are found for the CNTs after H₂ plasma treatment. This huge increase in the emitted current is primarily caused by the increase in the density of field-emission sites resulting from the change of surface morphology and the –CH _x nanoparticles redeposited on the CNTs.     

Significantly improved stability of n-octadecyltrichlorosilane self-assembled monolayer by plasma pretreatment on mica

It has been well known that plasma pretreatment can stabilize the hydrocarbon silane monolayer self-assembled on a mica surface. However, the extent of this improvement is not well known. To explore this issue, n-octadecyltrichlorosilane (OTS) monolayers were self-assembled on both untreated and plasma-treated mica surfaces, and their interfacial properties were investigated and compared at various physical conditions (temperature, relative humidity, contact time, high stress, and contact repetition) through the use of surface force measurements. This study revealed that in highly humid conditions (> 90% relative humidity) there is a substantial difference of stability between untreated and plasma-treated surfaces, the OTS monolayer on plasma-treated mica surface being much more stable. In particular, protrusion behavior in the monolayer was always observed in untreated samples, but never in plasma-treated samples during contact repetition experiments. This directly demonstrates that the significantly improved stability directly comes from extensive chemical bonds between OTS molecules and the plasma-treated mica surface.     

Plasma processing for surface optical modifications of PET films

The plasma interaction with the surface produces modifications of its chemical structure or morphology. Surface modifications through cold plasma occur, thanks to the high plasma reactivity and ability to affect the surface of materials.The present work shows the surface modification of polyethylene terephthalate (PET) films after the exposure both to low-pressure plasma (film deposition by plasma enhanced chemical vapour deposition) and to an atmospheric pressure dielectric barrier discharge (surface etching). After plasma treatment we have analysed the effect on the PET surface.For the atmospheric pressure plasma-treated samples, contact angle and atomic force microscope analysis enable us to determine roughness changes. For the low-pressure plasma samples, contact angles and Fourier transform infrared absorption spectroscopy analysis are used to estimate the chemical composition of the deposition and focused ion beam analysis to collect the image and calculate the thickness of plasma deposition.Both plasma treatments (film deposition and etching) cause changes in optical properties as indicated by reflectivity measurements.     

Functional finishing of cotton fabrics using silver nanoparticles

We have reported a novel in situ synthesis protocol for silver nanoparticles onto cotton fabrics. Here, cotton fabric immersed in silver nitrate solution is autoclaved at 15 psi, 121 degrees C for 15 min. At this temperature and pressure, the aldehyde terminal of starch (residual size material on cotton fabric) reduced the silver nitrate to silver metal and simultaneously stabilized the nanoparticles on fabric itself. The UV-visible absorption spectrum of both cotton fabrics and bath solution showed a typical absorption peak at 420 nm corresponding to the surface plasmon resonance of silver nanoparticles. With the help of transmission electron micrographs, the average size of the dislodged silver nanoparticles in water is calculated to be 20.9 +/- 13.7 nm. This silver nanoparticles impregnated cotton fabrics showed excellent antibacterial activity against Staphylococcus aureus and bacteriostasis activity against Klebsiella pneumoniae. Also, silver nanoparticles impregnated fabrics expressed significant UV-protection capability in comparison with the untreated fabrics.     

Surface properties and in vitro analyses of immobilized chitosan onto polypropylene non-woven fabric surface using antenna-coupling microwave plasma

Antenna coupling microwave plasma enables a highly efficient and oxidative treatment of the outermost surface of polypropylene (PP) non-woven fabric within a short time period. Subsequently, grafting copolymerization with acrylic acid (AAc) makes the plasma-treated fabric durably hydrophilic and excellent in water absorbency. With high grafting density and strong water affinity, the pAAc-grafted fabric greatly becomes feasible as an intensive absorbent and as a support to promote chitosan-immobilization through amide bonds. Experimental result demonstrated that surface analyses by FTIR-ATR have shown that R–CONH–R', amide binding were emerged between pAAc and chitosan. The XPS measurements on C_1s 286.0 eV (C–OH), 286.5 eV (C–N) and 288.1 eV (O=C–NH) also could be found. Bioactivity assessments on the chitosan-immobilized surfaces were anticipated by activated partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen concentration. By means of cell counter we counted the ratio of blood cell adhesion on the modified fabric matrix. After human plasma incubated with the chitosan-immobilized PP fabrics, the required time for aPTT and blood cell adhesion increased significantly, while fibrinogen concentration and TT did not change. Due to the capability of anticoagulation and cell adhesion, the chitosan-immobilized PP fabric can be used as the substrate for cell culturing and then developed the wound-dressing substitute for second-degree burn.     

Plasma surface modification of polylactic acid to promote interaction with fibroblasts

In this work, medium pressure plasma treatment of polylactic acid (PLA) is investigated. PLA is a biocompatible aliphatic polymer, which can be used for bone fixation devices and tissue engineering scaffolds. Due to inadequate surface properties, cell adhesion and proliferation are far less than optimal and a surface modification is required for most biomedical applications. By using a dielectric barrier discharge (DBD) operating at medium pressure in different atmospheres, the surface properties of a PLA foil are modified. After plasma treatment, water contact angle measurements showed an increased hydrophilic character of the foil surface. X-ray photoelectron spectroscopy (XPS) revealed an increased oxygen content. Cell culture tests showed that plasma modification of PLA films increased the initial cell attachment both quantitatively and qualitatively. After 1 day, cells on plasma-treated PLA showed a superior cell morphology in comparison with unmodified PLA samples. However, after 7 days of culture, no significant differences were observed between untreated and plasma-modified PLA samples. While plasma treatment improves the initial cell attachment, it does not seem to influence cell proliferation. It has also been observed that the difference between the 3 discharge gases is negligible when looking at the improved cell-material interactions. From economical point of view, plasma treatments in air are thus the best choice.     

Using low-pressure plasma for Carthamus tinctorium L. seed surface modification

Low-pressure RF argon gas discharge was used for surface modification of Safflower (Carthamus tinctorium L. semen) to increase the germination rate and activity and reduce the germination time. The results showed that plasma-treated C. tinctorium L. semen has 50% higher germination rate, 100% increase in the activity and 24 h reduction in germination time relativeto untreated. The effect of two different pressure plasma treatments at constant power and exposure time were also investigated. The result showed that the low-pressure plasma treatment was a more effective way to increase the germination rate at a smaller plasma treatment time. Using scanning electron microscope (SEM), the surface structure of plasma-treated and untreated C. tinctorium L. semen has been characterised. The SEM observations of Carthamii pericarpium and Hilum showed a change in the surface structure after plasma treatment. The physical structure of Carthamii pericarpium after plasma treatment looks softer relative to untreated. The Hilum of untreated C. tinctorium L. semen showed a very nice structure and boundary layer whereas after plasma treatment the structure was modified.     

Coating effects on mid-infrared reflection spectra of fabrics

Polymer films of varying thicknesses were deposited onto cotton and polyester fabric samples by dip-coating from solution. Scanning electron microscopy (SEM) images of the coated fabric samples were used to evaluate the quality of the polymer coating. The samples were analyzed by infrared diffuse reflection spectroscopy to determine the relationship between film thickness and the effect of the coating on the spectroscopy of the two fabrics. Effects observed in four limiting cases are examined: (Case I) weak coating absorption on a fabric with weak absorption at the same frequency; (Case II) strong coating absorption in a spectral region of weak fabric absorption; (Case III) weak coating absorption in a spectral region of strong fabric absorption; and (Case IV) strong coating absorption in a spectral region of strong fabric absorption. In the first case, effects were dominated by reduced scattering as the coating is added. In the second case, the strong coating absorption that was observed at low coverages plateaus at higher coverage due to depth of penetration effects. In the third and fourth cases, reduced Fresnel diffuse reflection is measured as the coating is added, consistent with the reduction of scattering observed in the first case.