XPS study of the process of apatite formation on bioactive Ti—6Al—4V alloy in simulated body fluid

Bioactive Ti—6Al—4V alloy, which spontaneously forms a bonelike apatite layer on its surface in the body and bonds to living bone through this apatite layer, can be prepared by producing an amorphous sodium titanate on its surface by NaOH and heat treatments. In this study, the process of apatite formation on the bioactive Ti—6Al—4V alloy was investigated in vitro, by analyzing its surface with X-ray photoelectron spectroscopy as a function of soaking time in a simulated body fluid 4SBF). Thin-film X-ray diffractometry of the alloy surface and atomic emission spectroscopy of the fluid were also performed complementarily. It was found that immediately after immersion in the SBF,the alloy exchanged Na¹ ions from the surface sodium titanate with H₃O¹ ions in the fluid to form Ti-OH groups on its surface. The Ti-OH groups, immediately after their formation,incorporated the calcium ions in the fluid to form calcium titanate. The calcium titanate thereafter incorporated the phosphate ions in the fluid to form an amorphous calcium phosphate, which was later crystallized into bonelike apatite. This process of apatite formation on the alloy was the same as on the pure titanium metal, because the alloy formed the sodium titanate free of Al and V by the NaOH and heat treatments. The initial formation of the calcium titanate is proposed to be a consequence of the electrostatic interaction of negatively charged units of titania dissociated from the Ti-OH groups with the positively charged calcium ions in the fluid. The calcium titanate is postulated to gain a positive charge and interact with the negatively charged phosphate ions in the fluid to form amorphous calcium phosphate, which eventually stabilizes into crystalline apatite.     

Optimising the bioactivity of alkaline-treated titanium alloy

A layer of sodium titanate hydrogel on titanium alloy (Ti6Al4V) induces apatite formation in simulated body fluid (SBF). This paper seeks to determine the parameters of alkaline-treated and subsequent heat treatment which lead to the most rapid formation of apatite. Specimens were soaked in 3, 5, 10 or 15 M solutions of NaOH at temperatures of 60 or 80 °C for 1, 3 or 7 days. It was found that the optimum treatment for the Ti6Al4V alloy was a 3-day soak in 5 M NaOH solution at 80 °C. Specimens treated under these optimum conditions were subsequently heat-treated at 500, 600, and 700 °C for 1 h so as to consolidate the sodium titanate hydrogel layer and improve its bonding to the substrate. Treatment at 600 °C resulted in the best bonding and the optimum rate of apatite formation. On soaking in simulated body fluid (SBF), apatite formed within 3 days, as compared to the 7-day formation, which was the best rate previously reported. The acceleration in the rate of apatite formation is significant, as it should allow for earlier load bearing of prostheses following implantation.     

A new method for deposition of nano sized titanium nitride on steels

Active screen plasma nitriding is a new and common method for deposition of Iron nitride. Since techniques such as Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD) and Plasma Assisted Chemical Vapor Deposition (PACVD) are usually applied in order to deposit the titanium nitride and each of these methods has its own problems, in this research active screen plasma nitriding method was introduced as a novel approach for deposition of nano sized titanium nitride. H11 tool steel samples were coated by plasma nitriding method at 550 °C for 5, 7.5 and 10 h, using three gas mixtures consisted of H₂/N₂ = 3, 1 and 1/3. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) were employed to investigate the coating properties such as grain size, layer thickness and chemical composition. Results showed that the proportion of H₂ in the gas mixture was a crucial point in order to obtain a perfect coating. By increasing the coating time, the grain size and the layer thickness increased. XPS results showed that the coating was mainly consisted of TiN + TiN_0.1 together with a small amount of TiO₄.     

Reactive sputtering of titanium in Ar/CH4 gas mixture: Target poisoning and film characteristics

Reactive sputtering of titanium target in the presence of Ar/CH₄ gas mixture has been investigated. With the addition of methane gas to above 1.5% of the process gas a transition from the metallic sputtering mode to the poison mode was observed as indicated by the change in cathode current. As the methane gas flow concentration increased up to 10%, the target was gradually poisoned. The hysteresis in the cathode current could be plotted by first increasing and then subsequently decreasing the methane concentration. X-ray diffraction and X-ray photoelectron spectroscopy analyses of the deposited films confirmed the formation of carbide phases and the transition of the process from the metallic to compound sputtering mode as the methane concentration in the sputtering gas is increased. The paper discusses a sputtering model that gives a rational explanation of the target poisoning phenomenon and shows an agreement between the experimental observations and calculated results.     

Application of Rachinger''s method to separate overlapped doublets in the X-ray photoelectron spectrum

Rachinger's method of separating ₁ and ₂ doublets in X-ray emission spectra is applied for the first time to separate the superimposed doublets due to spin-orbit coupling. This method has been applied to separate closely lying doublets such as (Ag 4p_3/2and Ag 4p_1/2, (Ni 3p_3/2and Ni 3p_1/2) and (Cu 3p_3/2and Cu 3p_1/2). The intensities ratios of the separated peaks are measured and compared with the ratios obtained from a first-order calculation. An excellent agreement between the measured and calculated ratios are obtained. Residual background intensities compared with the estimated values are found to agree within certain uncertainties.     

Stability of ZnMgO oxide in a weak alkaline solution

Zinc oxide (ZnO) is a chemical compound of great interest used, for example, as photocatalyst in the purification of wastewater or polluted air. However, neither dissolution, nor photo-dissolution of ZnO is negligible: indeed, both processes reduce significantly the efficiency of photocatalysis and then lead to a secondary pollution by free Zn^2 +. In the present study, the stability of ZnMgO thin films in weak alkaline solution is investigated. We demonstrate that the replacement of Zn^2 + ion with Mg^2 + ion results in the production of a Zn_0.84Mg_0.16O solid solution, whose stability is higher than that of the ZnO sample. This alloy, thus, constitutes an alternative to the use of ZnO in photocatalysis applications. To gain more insights into the higher resistance of such alloys to the dissolution process, X-Ray photoelectron spectroscopy measurements were performed. They highlighted the role of OH group adsorption in the experimentally observed enhancement of ZnMgO stability.     

曝光量对DCG中Cr2P_(3/2)XPS谱的影响的研究

通过对不同曝光量的重铬酸盐明胶(DCG)中的Cr2P3／2XPS（X射线光电子能谱）的规定发现，Cr2P3／2XPS谱随曝光量呈规律性的变化：在0～195mJ／cm2曝光量范围内，它的1／5高宽度（FWFM，即：thefullwidthatfifthmaximum）和576．4eV附近的峰的相对强度先随曝光量增加而增大，到达极大值后又随曝光量的增加而减小；相反，它的579．4eV和577．4eV附近的两个峰的相时强度却是先随曝光量的增加而减小，达到极小值后又随曝光量的增加而增大。对这些不同曝光量的DCG膜定性地水洗处理后，曝光量为130mJ/cm2的全息图最均匀、明亮；曝光量为195mJ／cm2的全息图衍射效率很低，且有残余黄褐色。根据这些实验结果和固态膜反应的特点，就曝先对DCG微观结构引起的变化作了分析，确定出了贡献各峰的化合物状态并科学准确地找到了Cr2P3／2XPS谱随曝光量成规律性变化的本质原因是作为潜影中心的二氧化铬（576．4eV附近的铬）严格地受曝光量的制约。这个结论的得出，为制作理想的全息图选择合适的曝光量提供了理论依据。即：576．4eV附近的峰有最大相对强度的曝光量为最佳曝光量。     

爆轰法合成纳米石墨粉中的碳元素状态表征

纳米石墨粉具有晶粒细小、比表面积大的特点.石墨化度是重要的质量指标之一.通过对纳米石墨进行元素分析以确定碳元素的含量、X射线衍射以确定石墨化度、X射线光电子能谱分析以确定碳元素在表面的存在状态及含量,对纳米石墨中的碳原子进行了分析.结果表明纳米石墨中碳含量为90%左右,石墨化度为66%,表面碳原子以碳单质状态存在的占54%.     

模拟体液浸泡法评价生物材料的研究与问题

介绍了生物材料领域中常用的模拟体液(Simulated body fluid,SBF),重点分析了SBF的代表组成和特性,并从生物活性、生物惰性以及支架、涂层等角度,总结现阶段国内外对于SBF的研究和应用。强调SBF浸泡法评价生物材料在静态角度上(如成分、形核机理等)和动态角度上(如应力、温度及流动性等)存在的不足,以期对其改进起到参考作用。     

Ultraviolet-induced surface modification of polyurethane films in the presence of oxygen or acrylic acid vapours

An efficient surface functionalization of polyurethane (PU) films has been obtained by ultraviolet (UV)-assisted modification in the presence of oxygen or acrylic acid (AA) vapours. Film analyses were carried out by water contact angle measurements, X-ray photoelectron spectroscopy (XPS) and Near-edge X-ray absorption fine structure (NEXAFS). Film hydrophilicity increased with photolysis time in the presence of oxygen or AA vapours. Incorporation of COO and CO functional groups at the polymer surface after the UV-assisted treatments was observed. In addition, High resolution XPS and NEXAFS results showed that a thin film of poly (acrylic acid) (PAA) is formed over the PU films during the UV irradiation with AA vapours. The obtained results are compared with previous published oxygen and AA low-power plasma treatments. Similarity between both treatment methodologies is shown. UV surface functionalization and polymerization of PAA can be used instead of a traditional plasma treatment with the advantage of set-up simplicity and lower costs.     

A study of titanium thin films in transmission laser micro-joining of titanium-coated glass to polyimide

Electron beam evaporation (EB-PVD) and cathodic arc physical vapor deposition (CA-PVD) techniques were used for the preparation of titanium (Ti) thin films onto Pyrex borosilicate 7740 glass wafers and the deposited films were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The microstructure and surface morphology of the films were studied as a function of the film deposition techniques. Film properties such as, adherence, microstructure and roughness were interconnected to the laser joint strength between Ti coated glass wafers and polyimide films. Ti thin films on glass had a natural oxide layer on the surface as found from XPS. AFM study showed the formation of a uniform Ti coating consisted of packed crystallites with average size of 35 nm by EB-PVD. The root-mean-square surface roughness of the films was 1-2 nm. Whereas, films prepared by CA-PVD had crystallites with an average size of 120 nm and defects in the form of macro-particles which is a common attribute of this deposition system. The surface roughness of the film was 125 nm. The laser joint strength was found to be influenced by the Ti film quality on the glass substrate.     

Surface oxygen in the growth of plasma polymerised thin films

Three different types of non-oxygen containing monomers were plasma polymerised into thin films and then studied using X-ray photoelectron spectroscopy (XPS) to determine the surface oxygen content. These three monomers were benzene, ferrocene, and octafluorocyclobutane. Depth profiling was also used to investigate the oxygen content into the bulk of the films by analysing the newly formed film surfaces after different amounts of argon ion sputtering. The initial oxygen concentration on the surface of the ferrocene films was the largest of the three (>20 at.%) while octafluorocyclobutane films had only a small concentration at the surface (∼0.4 at.%). The benzene films had an intermediate concentration (∼4 at.%). Affinity for oxygen on the benzene films is due to residual activated species including free radicals and dangling bond sites on the film surface. Depth profiling showed a rapid reduction of oxygen (to ∼0.2 at.%) a short distance into the benzene films, indicating that the oxygen adsorbed on the surface after film deposition and exposure to the ambient. For the ferrocene films, a substantial amount of oxygen remained with depth, indicating that oxygen was incorporated into the film during deposition. Due to the chemical nature of fluorine, the as-deposited octafluorocyclobutane films did not exhibit significant affinity towards oxygen.     

Influence of dopant concentration and type of substrate on the local organization of low-pressure chemical vapour deposition in situ boron doped silicon films from silane and boron trichloride

The deposition of in situ boron doped silicon films from boron trichloride BCl₃ and silane SiH₄ in a conventional low-pressure chemical vapour deposition reactor has been studied for high boron doping levels and two kinds of substrates (SiO₂ and Si₃N₄). On the basis of transmission electron microscopy and X-ray photoelectron spectroscopy results, these films appear to be highly sensitive to the local electronic environment of both substrate and deposited atoms. Indeed, beyond a critical doping level, this material becomes more and more amorphous, due to the occurrence of a particular organization of boron atoms in the silicon matrix. This behaviour results in a lowering of the well-known boron enhancement effect for deposition rate and crystalline fraction.     

Molecular dynamic simulation of heterogeneity and chemical states of fluorine in amorphous alkaline earth silicate systems

Chemical states of fluorine in fluorosilicate glasses in the system MF₂-MO-SiO₂ (M = Ca, Sr and Ba; SiO₂ content < 60 mol%) have been investigated by molecular dynamic (MD) simulations with a perfect ionic two-body potential. Comparison of the results with those derived by X-ray photoelectron spectra of the actual glasses demonstrates that MD simulations reproduce well the bonding states of fluorine in the systems as well as the formation of M-F clusters. The MD generated structure of imaginary glasses, or glasses not obtained by the conventional melt-quench technique, with 70 mol% SiO₂ indicates that an acidic environment induces a greater amount of F---Si bonds. Their M-F pair correlation functions plotted against normalized M-F distances suggest that relative ion positions in the clusters are very similar.     

溶胶-凝胶生物活性玻璃纤维的制备及其体外矿化性能研究

采用溶胶-凝胶法制备出CaO-P2O5-SiO2系统生物活性玻璃纤维．通过倒置相差显微镜、SEM、FTIR等测试手段考察了生物活性玻璃纤维的微观形貌和显微结构；采用生物材料的体外实验方法以及XRD、SEM、FTIR等测试手段研究了生物活性玻璃纤维在模拟生理体液（SBF）中浸泡后的表面反应产物的形成机理、结晶程度和微观形貌．结果表明，这种生物活性玻璃纤维是一种不连续的短纤维，具有较好的纤维形态和较高的生物活性，在短时间内即可在模拟生理体液（SBF）中形成茸毛状A类碳酸羟基磷灰石（HCA）层．     

模拟混凝土孔隙液中钢筋电化学腐蚀行为及pH值的影响作用

应用极化曲线法和电化学阻抗技术,结合扫描电子显微镜方法,测试钢筋在模拟混凝土孔隙液中的钝化与去钝化行为,以及溶液pH值对钢筋电化学腐蚀行为的影响作用.结果表明,钢筋在pH值为12.50的模拟液中处于钝态,随着溶液pH值的降低,钢筋的耐蚀性下降.钢筋表面去钝化发生腐蚀的临界PH值在11.12-11.05范围内.     

CaO-P2O5-SiO2系统溶胶-凝胶玻璃的生物矿化行为

利用体外实验方法(in vitro)以及XBD、SEM、FTIR、BET、ICP等手段研究了两种溶胶一凝胶生物活性玻璃的显微结构及其在模拟生理溶液(SBF)中的降解过程、表面反应产物和生物矿化机理．结果表明,两种生物活性玻璃都具有较高的生物活性,均具有由纳米尺寸颗粒相互连接而成的微孔结构和较大的比表面积,在模拟生理溶液(SBF)中浸泡后可形成表面类似天然骨中无机矿物的碳酸经基磷灰石层(HCA),说明两者均具有较高的生物活性和生理环境相应特性．材料表面的硅酸凝胶层及其硅经基团的形成对碳酸经基磷灰石(HCA)微晶的成核有重要作用。     

Apatite formation from simulated body fluid on various phases of TiO2 thin films prepared by filtered cathodic vacuum arc deposition

Hydroxyl (OH⁻)-free TiO₂ thin films with amorphous and crystalline phases were deposited onto (100) silicon substrates using filtered cathodic vacuum arc deposition in order to investigate the in vitro apatite formation in simulated body fluid (SBF). The surface morphology, composition and structure of the TiO₂ thin films were characterized. The X-ray photoelectron spectroscopy results confirmed the presence of calcium and phosphorus on all TiO₂ thin film surfaces after immersion in SBF at 37 °C. Fourier transform infra red results showed the presence of carbonated apatite on the surface of these films. Amorphous structured TiO₂ thin film showed poor ability to form apatite on its surface in SBF. Apatite formation was more pronounced on the surfaces of the anatase films in comparison to those of rutile. The carbonated apatite deposition rate increased significantly when the TiO₂ film was illuminated with UV light prior to immersing in the SBF. In particular, the UV-treated anatase and rutile films showed increased rates of carbonated apatite formation on their surfaces in comparison to samples not treated with radiation. The increase in hydrophilicity due to UV treatment appears beneficial for the apatite growth on these surfaces.     

The effect of de-ionized water rinsing after immersion in hydrofluoric acid on the electrical conductivity of silicon nanomembranes

Electrical conductivity of 28 and 220-nm thick silicon membranes was measured by the van der Pauw method in dry air (relative humidity < 5%) at room temperature (around 20 °C). Immediately after hydrofluoric acid immersion the conductivity increases several orders of magnitude because of surface-induced band bending; it then drops and reaches the level of samples with a native oxide surface in several weeks due to the surface's re-oxidation. The oxidation rate is found to increase with the de-ionized water rinsing time, which is confirmed by X-ray photo electron spectroscopy measurements.