Controlled surface modification of boron nitride nanotubes

Controlled surface modification of boron nitride nanotubes has been achieved by gentle plasma treatment. Firstly, it was shown that an amorphous surface layer found on the outside of the nanotubes can be removed without damaging the nanotube structure. Secondly, it was shown that an oxygen plasma creates nitrogen vacancies that then allow oxygen atoms to be successfully substituted onto the surface of BNNTs. The percentage of oxygen atoms can be controlled by changing the input plasma energy and by the Ar plasma pre-treatment time. Finally, it has been demonstrated that nitrogen functional groups can be introduced onto the surface of BNNTs using an N(2) + H(2) plasma. The N(2) + H(2) plasma also created nitrogen vacancies, some of which led to surface functionalization while some underwent oxygen healing.     

Wear resistant and anti-corrosive treatment for TI-6AL-4V using metal vapor vacuum arc source in comparison with plasma immersion ion implantation

This study utilizes two ion-implantation methods, plasma immersion ion implantation (PIII) and metal vapor vacuum arc (MeVVA), to prepare Ti-N phases on the surface of Ti-6Al-4V. By the nitrogen PIII method, both nitrogen and minor oxygen species are simultaneously attracted by the negatively charged substrate. The penetration of N and O interstitial elements to an extensible depth is possible owing to the effect from the negatively charged target. The nitrogen PIII treatment does not produce a novel Ti-N phase. As a result, the modified surface does not behave anticorrosive. The H_n and the E determined by nanoindentation also remain unchanged. It is still potential to apply this non-directional treatment by increasing bias voltage of the target, coating pure titanium on Ti-6Al-4V, and adjusting the regeneration process of nitrogen ions. The MeVVA treatment creates a novel αTiN_0.3 (011) phase on Ti-6Al-4V in present study. It signifies that the interactions between kinetic Ti ions of varied energies and minor nitrogen molecules, with minor participation of oxygen, are highly feasible. The novel ion-implanted Ti-N phase is corrosion resistant, which is capable to reduce passivation current density by forming a passive film. Moreover, the MeVVA-treated surface is surface-hardened; the E is simultaneously increased. The increase of nano mechanical properties can be visualized by 3D images using Nano Vision and determined by analyzing the tip/surface impact structure on the indentation site.     

Plasma modification of viscose textile

A study on plasma treatment of a textile is presented. Samples of pure viscose textile were exposed to RF oxygen, nitrogen or hydrogen plasma for 5 s. The gas pressure was 75 Pa and the RF power was 250 W. In all cases plasma treatment induced chemical changes in the samples' surface, which were determined by using high-resolution XPS (X-ray photoelectron spectrometer). Treatments in oxygen and nitrogen plasma increased the concentration of existing as well as formation of oxygen functional groups, while hydrogen plasma caused a substantial decrease of these groups. SEM (Scanning electron microscopy) analysis of the surface of the textile fibres was performed as well. The results showed that the fibres' surface treated in nitrogen plasma was similar to the untreated surface, while after treatment in hydrogen or oxygen plasma, the surface became rougher.     

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.     

Analysis of the mechanical and shape memory behaviour of nitrogen ion-implanted NiTi alloy

Experimental results of an accumulation and return strain behaviour of the modified surface of NiTi alloy, as well as mechanical and shape memory behaviour, are shown in this paper.Surface of equiatomic NiTi shape memory alloy (in martensitic form) has been modified by high-dose ion-implantation technique using nitrogen ion beam. The low-energy (65 keV) and following high doses have been used: 1×10¹⁷, 5×10¹⁷ and 1×10¹⁸ J/cm². Correlation between subsurface layers elemental composition of NiTi alloy, microstructure and shape memory properties is shown.     

Surface modification of an aramid fibre treated in a low-temperature microwave plasma

The surface modification of an aramid fibre treated in a low-temperature microwave (mw) plasma was investigated. Three different plasma gases, oxygen, argon and ammonia, were used to achieve different surface modifications during fibre treatment. The modification of the fibre surface was analysed with electron spectroscopy and electron microscopy. The influence of the surface modification on the fibre-matrix interaction was inspected by measuring the interlamellar shear strength of the composites and the pull-out strength of a fibre bundle in model composites. The process gas and thus the kind of plasma has no significant influence on the fibre modification resulting from plasma treatment. It was shown that a fibre cleaning with subsequent surface ablation is the dominate modification process during mw plasma treatment, independent of the process gas. The degree of surface cleaning and removal of a contamination layer strongly depended on the treatment range. No incorporation of oxygen or nitrogen containing functional groups was observed. This was explained with the composition of the process gas. The improvements of the composite properties demonstrate the advantage of the mw plasma treatment as a fast, environmentprotected, cost-efficient process for fibre modification.     

Immobilization of protein streptavidin to the surface of PMMA polymer

Immobilization of the protein streptavidin to the surface of polymethyl methacrylate (PMMA) polymer was studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Different protocols were used to attach streptavidin to the PMMA surface: physical adsorption and chemical coupling. The influence of oxygen plasma treatment on the efficiency of streptavidin binding was studied. The presence of streptavidin coating on the PMMA surface was demonstrated by the appearance of N1s signal in the XPS spectra of coated PMMA samples. The XPS results have shown that oxygen plasma treatment improves binding of streptavidin to the PMMA surface. XPS results also showed that chemical coupling is more efficient than physical adsorption. In the case of physical adsorption, rinsing of the sample with water caused noticeable decrease of nitrogen concentration, while in the case of chemical coupling the nitrogen concentration was stable. AFM measurements showed that after deposition of streptavidin coating the originally smooth surface changed to dendrite structure.     

硅中氮离子注入的研究进展

综述了硅中氮离子注入的应用和研究进展。主要讨论了氮离子注入形成SOI层的原理、质量的影响因素和电学性能；介绍了氮离子注入在制备超薄氧化栅极及其抑制掺杂杂质原子特别是硼原子扩散等方面的研究和应用。     

Control of interfacial adhesion in continuous carbon and kevlar fiber reinforced polymer composites

Carbon fiber surfaces were treated by cold plasmas of oxygen, nitrogen, argon, ammonia, and propylene. A two-component bismaleimide, an epoxy, and a model thermoplastic resin polypropylene were used as the matrices for composites. The effectiveness of various plasmas in improving the interfacial adhesion between carbon fibers and matrix resins was demonstrated. Predominant adhesion promotion mechanisms as influenced by various plasma treatments were determined. Oxygen and argon plasmas were found to promote mechanical keying by increasing the level of fiber surface roughness and porosity. The wettability of carbon fiber surface by the matrix resin was also enhanced by oxygen plasmas and argon plasmas (to a lesser extent), as evidenced by the increased total surface energies and their polar components. These surface energy increases are mainly due to the various oxygen-containing functional groups observed on the oxygen plasma-treated surface. For the cases of ammonia and combined ammonia/argon plasma treatments, possible chemical bonding between bismaleimide and the plasma-deposited amine groups is one important promoter of interfacial bonding. In these cases increased wettability was also observed. Ammonia and ammonia/argon plasmas appear to be the more appropriate treatments for carbon-fiber/thermoset resin composites considering that they generally do not induce any appreciable reduction in fiber strength. In contrast, excessively prolonged exposure of carbon fibers to oxygen, nitrogen or argon plasma could lead to a significant reduction in fiber strength. The plasma-polymerized polypropylene deposited on the fiber surface was capable of improving the compatibility and adhesion between the fiber and the polypropylene matrix.     

Increased response of Vero cells to PHBV matrices treated by plasma

The copolymers poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) are being intensely studied as a tissue engineering substrate. It is known that poly 3-hydroxybutyric acids (PHBs) and their copolymers are quite hydrophobic polyesters. Plasma-surface modification is an effective and economical surface treatment technique for many materials and of growing interest in biomedical engineering. In this study we investigate the advantages of oxygen and nitrogen plasma treatment to modify the PHBV surface to enable the acceleration of Vero cell adhesion and proliferation. PHBV was dissolved in methylene chloride at room temperature. The PHBV membranes were modified by oxygen or nitrogen-plasma treatments using a plasma generator. The membranes were sterilized by UV irradiation for 30 min and placed in 96-well plates. Vero cells were seeded onto the membranes and their proliferation onto the matrices was also determined by cytotoxicity and cell adhesion assay. After 2, 24, 48 and 120 h of incubation, growth of fibroblasts on matrices was observed by scanning electron microscopy (SEM). The analyses of the membranes indicated that the plasma treatment decreased the contact angle and increased the surface roughness; it also changed surface morphology, and consequently, enhanced the hydrophilic behavior of PHBV polymers. SEM analysis of Vero cells adhered to PHBV treated by plasma showed that the modified surface had allowed better cell attachment, spreading and growth than the untreated membrane. This combination of surface treatment and polymer chemistry is a valuable guide to prepare an appropriate surface for tissue engineering application.     

Numerical analysis of ion-implantation in target with a rectangular groove

Ion dynamics of pulsed plasma sheath during the plasma source ion-implantation (PSII) affects the resultant surface properties and structures. In this work, a two-dimensional fluid model is applied to the problem of computing ion dynamics in the sheath of a target with a rectangular groove. The evolution of sheath edge, x and y components of ion velocity on the target surface are simulated to describe the physics of sheath in PSII.     

Effect of oxygen plasma treatment on bonding states for columnar structured a-CNx thin films prepared by reactive sputtering

Amorphous carbon nitride (a-CN) thin films were deposited on silicon single crystal substrates by rf-reactive sputtering method using a graphite target and nitrogen gas. The substrate temperature was varied from room temperature (RT) to 853 K. After deposition, the effect of oxygen plasma treatment on bonding structures of the film surface has been studied by using an oxygen discharge at 16 Pa and rf power of 85 W. The chemical bonding states and film composition were analyzed by X-ray photoelectron spectroscopy (XPS), while film thickness was obtained from scanning electron microscopy (SEM) and ellipsometer. XPS study revealed that the films have NO₂ and NO₃ bonding structures when the films are deposited at temperatures higher than 673 K. After exposure to oxygen plasma, carbon in the film surface was etched selectively and this phenomenon was observed in all films. In contrast, the surface concentration of nitrogen was ket at constant values before and after oxygen plasma treatment. The NO₃ bonding state had dramatically increased after oxygen plasma treatment for films deposited at higher deposition temperatures. The film surfaces have been observed to change the function from hydrophobic to hydrophilic after oxygen plasma treatment.     

Development of bio/blood compatible polypropylene through low pressure nitrogen plasma surface modification

Surface modification of polypropylene by nitrogen containing plasma was performed in this work in order to improve the wettability which resulted in enhanced biocompatibility and blood compatibility. Various nitrogen containing functional groups as well as oxygen containing functional groups were found to be incorporated to the polymer surface during plasma treatment and post plasma reaction respectively. Wettability of the polymers was evaluated by static contact angle measurement to show the improvement in hydrophilicity of plasma treated polypropylene. Cross linking and surface modification were reported to be dominating in the case of nitrogen plasma treatment compared to degradation. The effect of various process variables namely power, pressure, flow rate and treatment time on surface energy and weight loss was studied at various levels according to the central composite design of response surface methodology (RSM). Except pressure the other variables resulted in increased weight loss due to etching whereas with increasing pressure weight loss was found to increase and then decrease. The effect of process variables on surface morphology of polymers was evaluated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Well spread fibroblast cells on nitrogen plasma treated polypropylene due to the presence of CO, NH²⁺ and NH⁺ was observed. Reduced platelet adhesion and increased partial thromboplastin time evidenced the increased blood compatibility.     

Design of Plasma Surface‐Activated,Electrospun Polylactide Non‐Wovens with Improved Cell Acceptance

Electrospinning is a versatile technique to generate tissue engineering matrices possessing structural features similar to the extracellular matrix. Biodegradable polylactides are well suited for processing by this technique, but their innate hydrophobicity impairs initial protein adsorption and cell adhesion. In this work, therefore, electrospun poly(L ‐lactide‐co‐D,L ‐lactide) (70/30) non‐wovens are modified with an ultrathin plasma‐polymerized allylamine (PPAAm) coating. Using scanning electron microsocopy (SEM), it is shown that the fiber structure of the non‐woven is not affected by the plasma treatment. X‐ray photoelectron spectroscopy (XPS) and contact angle measurements of PPAAm‐coated non‐wovens confirm the presence of nitrogen and oxygen‐functional groups in the coating and a hydrophilic nature of the coated non‐woven surface. Cell experiments in vitro demonstrate that the PPAAm‐coated surface promotes occupancy of the non‐woven by human MG‐63 osteoblasts accompanied by improved initial cell spreading and filopodia formation along and between the electrospun polylactide fibers. Overall, plasma‐assisted incorporation of amino groups into electrospun polylactone non‐wovens represents a promising approach to tissue engineering scaffolds with improved cell–material interfaces.     

Plasma pre-treatment of liquid crystal polymer and subsequent metallization by PVD

In this paper surface modification of a liquid crystal polymer (LCP) substrate by oxygen containing plasma pre-treatment and subsequent Cu/Cr deposition by physical vapour deposition (PVD) technique is described. By pre-treatment with oxygen containing plasma more volatile reaction products are generated compared to argon plasma pre-treatment as is shown by the etching rate. The small molecule fragments generated during the pre-treatment process are analyzed by mass spectrometry. After the pre-treatment metal layers with suitable adhesion strength even after 1000 cycles of thermal shock are obtained.     

Oxygen plasma modification of polyurethane membranes

Polyurethane membranes were prepared under nitrogen atmosphere by using various proportions of toluene diisocyanates (TDI) and polypropylene-ethylene glycol (P) with addition of no other ingredients such as catalysts, initiator or solvent in order to achieve medical purity. Effects of composition on mechanical properties were examined. In general, modulus and UTS values demonstrated an increase and PSBR demonstrated a decrease as the TDI/Polyol ratio of the polymer increased. Elastic modulus, ultimate tensile strength (UTS) and per cent strain before rupture (PSBR) values were found to be in the range of 1.4–5.4 MPa, 0.9–1.9 MPa, and 60.4–99.7%, respectively. Surfaces of the membranes were modified by oxygen plasma applying glow-discharge technique and the effect of applied plasma power (10 W or 100 W, 15 min) on surface hydrophilicity and on the attachment of Vero cells were studied. Water contact angle values of the plasma modified surfaces varied between 67° and 46°, demonstrating a decrease as the applied plasma power was increased. The unmodified material had 42–45 cells attached per cm². It was observed that as the applied power increased the number of attached cells first increased (60–70 cells/cm² at 10 W) and then decreased (27–40 cells/cm² at 100 W). These demonstrated that surface properties of polyurethanes can be modified by plasma-glow discharge technique to achieve the optimum levels of cell attachment.     

热处理活性半焦的表面性质和SO2脱除活性

前驱体和表面改性过程都影响着活性半焦脱除SO2的活性.在氮气中、800℃下对原料半焦进行热处理,并在固定床反应器上测试了其脱除SO2的活性.利用酸碱滴定、工业分析和元素分析、X-射线光电子能谱(XPS)、傅立叶转换红外光谱(FTIR)等表征原料半焦和活性半焦表面化学性质.结果表明:石墨碳是原料半焦和活性半焦样品表面的主要碳功能团.表面C=O基团(酮、内酯、羰和醌类中)和吡咯-N分别是原料半焦表面的氧、氮功能团.热处理导致半焦表面含氧基团分解、表面含氧和含氮基团分布改变、表面C=O基团(酮、内酯、羰和醌类中)明显下降;而化学吸附氧和水增加,吡咯-N变成类吡啶结构.醚类和π - π* 离域基团的增加提高了活性半焦表面的碱性.热处理提高了活性半焦脱除SO2的活性.影响SO2脱除活性的表面基团可能是具有碱性性质的醚类、π - π* 离域及含氮基团.     

Factors affecting the interfacial adhesion of ultrahigh-modulus polyethylene fibre–vinylester composites using gas plasma treatment

The interfacial adhesion of ultrahigh-modulus polyethylene (UHMPE) fibre–vinylester composites was improved by the oxygen plasma treatment of the UHMPE fibre. The chemical functional group formations on the UHMPE fibre surface by oxygen plasma treatment were analysed using diffuse reflectance Fourier transform infrared spectroscopy and the morphological changes of the UHMPE fibre surface by plasma etching were observed by scanning electron microscopy. The wettability enhancement by the chemical functional group formation and the mechanical interlocking due to the micropits were important factors in improving the interfacial adhesion of the UHMPE fibre–vinylester composites by oxygen plasma treatment. In order to investigate the relative importance of the two factors, wettability enhancement and mechanical interlocking, in the improved interfacial adhesion of the UHMPE fibre–vinylester composites, nitrogen plasma treatment was also performed. Nitrogen plasma treatment of the UHMPE fibre was proved to be effective in the formation of the micropittings and ineffective in the chemical functional group formation in comparison with the oxygen plasma treatment. The interlaminar shear strengths of the nitrogen-plasma-treated UHMPE fibre–vinylester composites showed almost the same value as those of the oxygen-plasma-treated UHMPE fibre–vinylester composites. The wettability enhancement and mechanical interlocking are important in the improvement of interfacial adhesion of UHMPE fibre–vinylester composites by plasma treatment and mechanical interlocking seems to be more important.     

Fabrication and characterization of p-type In–N codoped ZnMgO films

Indium (In) and nitrogen (N) codoped ZnMgO films (ZnMgO:In–N) were fabricated on quartz substrates by radio frequency magnetron sputtering and ion-implantation technique. p-ZnMgO:In–N films were successfully achieved after post-implantation annealing at an appropriate temperature ranging from 570 to 590?°C. X-ray diffraction (XRD) indicates that severe damage in films is introduced by N ion implantation and the damaged lattice can be partially recovered after post-implantation annealing. The analysis of Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) demonstrates that post-implantation annealing can promote a reduction of donor type zinc interstitials (Zn_i) and the formation of In_Zn+2N_O acceptor complex, which mainly contribute to the realization of p-type ZnMgO:In–N films.     

Influence of oxygen and nitrogen plasma treatment on polyethylene terephthalate (PET) polymers

In this paper we present surface modification of polyethylene terephthalate (PET) polymer, which is commonly used as synthetic vascular graft. Surface modification was made by oxygen and nitrogen plasma at different treatment times. Plasma was created by means of an RF generator at a discharge power of 200 W and gas pressure fixed at 75 Pa. The surface of PET polymer was modified in order to achieve improved attachment of fucoidan, which is a bioactive coating with antithrombogenic properties. In our study we analysed chemical modification of plasma treated surfaces by X-ray photoelectron spectroscopy (XPS), while the changes in morphology and surface roughness were observed with atomic force microscopy (AFM). Our results indicate that attachment of fucoidan is improved by oxygen plasma treatment, especially due to surface roughening.