Intrinsic low energy bombardment of titanium chromium oxide thin films prepared by reactive sputtering

Titanium chromium oxide thin films were deposited by a DC reactive magnetron sputtering from separate Ti and Cr metallic targets in a reactive atmosphere. A constant current density J_Ti =150 A m⁻² was used to sputter the titanium target, whereas the current density on the chromium target was systematically changed from J_Cr=0–200 A m⁻². X-Ray diffraction, electron probe microanalysis and atomic force microscopy were used to investigate the effect of an increasing current density of the chromium target on the structural, compositional and morphological parameters of the coatings. A continuous evolution of the Ti_xCr_1−xO_y composition was observed (x=1–0.34 and y=2–1.7), whereas an amorphisation of the material and a maximum of the surface roughness was obtained for J_Cr=50–100 A m⁻². In the same way, energy distribution of the neutral and ionic species impinging on the surface of the growing film were determined by energy-resolved mass spectrometry. Mean energies and the relative fluxes of positive and negative ions were determined from their energy distributions. The behaviour of these species was also affected by the chromium current density especially between J_Cr=50 and 100 A m⁻². Similarities in the changes of the thin films properties and the characteristics of ionic species are discussed, so as to establish some relationships between the plasma parameters and the deposited films.     

Modification of copper surfaces with cathodic arc aluminum plasma

In the present study, surfaces of copper substrates were modified with aluminum plasma using cathodic vacuum arc (CVA) physical vapor deposition based technique. Surface treatments were carried out as a function of bias voltage for various time intervals. The effect of long and short durations of ion bombardment on the resulting microstructural features of the treated surfaces were studied and discussed. It was observed that surface alloying and diffusion processes were enhanced by the application of the ion bombardment and thick (10-15 μm) modified zones were achieved in a relatively short processing time (15-20 min). In the experiment executed with long bombardment duration, the modified zone consisted of a mixture of martensitic β₁-AlCu₃ phase and (Cu) solid solution, accompanied with a minor amount of γ₁-Al₄Cu₉ intermetallic phase, whereas, in the experiment involving short total bombardment duration, the modified surface predominantly consisted γ₁-Al₄Cu₉ intermetallic phase, accompanied with martensitic β₁-AlCu₃ phase at the copper aluminum interface.     

Low energy helium ion texturization of titanium and relevance to biomedical applications

Helium irradiation of metals has long been studied in efforts to understand the damaging aspects associated with applications in fusion reactors and tritium storage. This work examines the possibility of using low energy helium ion bombardment as a method of producing a beneficial surface texturization to promote bone growth on orthopedic implants. Using 300 eV helium ions, two unique porous titanium surfaces were created when substrates were held at temperatures of roughly 450 °C and 600 °C. The surfaces were physically characterized by scanning electron microscopy (SEM) and scanning white light interferometry. A week long hFOB 1.19 cell culture was performed using an untreated titanium control to evaluate the suitability of these surfaces for orthopedic implants. Cell health and viability were evaluated by calcein AM live cell staining, MTT assay, and SEM. The results show that helium texturizations promote cellular activity and have no detrimental effect on cell health.     

Ion tracks and microstructures in barium titanate irradiated with swift heavy ions: A combined experimental and computational study

Tetragonally structured barium titanate (BaTiO₃) single crystals were irradiated using 635 MeV ²³⁸U⁺ ions to fluences of 1 × 10⁷, 5 × 10¹⁰ and 1.4 × 10¹² ions cm^?2 at room temperature. Irradiated samples were characterized using ion channeling, X-ray diffraction, helium ion microscopy and transmission electron microscopy. The results show that the ion-entry spot on the surface has an amorphous core of up to ～10 nm in diameter, surrounded by a strained lattice structure. Satellite-like defects around smaller cores are also observed and are attributed to the imperfect epitaxial recrystallization of thermal-spike-induced amorphization. The critical value of the electronic stopping power for creating observable amorphous cores is determined to be ～22 keV nm^?1. Molecular dynamics simulations show an amorphous track of ～1.2 nm in radius under thermal energy deposition at 5 keV nm^?1; the radius increases to ～4.5 nm at 20 keV nm^?1. A linear fit of the core diameter as a function of the square root of the energy deposition rate suggests a reduction in the diameter by an average of ～8.4 nm due to thermal recrystallization if electron–phonon coupling efficiency of 100% is assumed. The simulation also reveals details of the bonding environments and shows different densities of the amorphous zones produced at different energy deposition rates.     

低温等离子体放电电极结构的调整对碳纳米管表面改性的影响

普通的表面处理仪难以处理粉体材料,通过加装旋转滚筒,实现了粉体材料的表面改性处理.经过电极的换位、电极极间距的调整,分析了多壁碳纳米管成片料经氧、四氟化碳射频处理后的可浸润性;对粉体材料则采用XPS、红外分析手段,分析了不同状态处理条件下表面氟元素含量的变化情况.研究结果表明:有机玻璃滚筒的引入降低了碳纳米管射频处理效果,只有当电极换位到滚筒的两端后,材料的处理效果才不受影响;粉体碳纳米管处理效果不理想的根本原因在于纳米管本身的强烈团聚,只有解决了团聚问题后,射频处理方能显效.     

Optimization of the stream finishing process for mechanical surface treatment by numerical and experimental process analysis

The stream finishing process represents an efficient mass finishing process capable in mechanical surface modification. In order to generate a deeper understanding of the cause-effect relationships, normal forces, material removal and surface topography were analyzed and correlated for varied process parameters of disc-shaped AISI 4140 specimens. Local resolution of tangential velocities of the particles and normal forces on the workpiece’s surface were simulated using the discrete element method for defined process parameter configurations and were correlated with experimental results. A deep process understanding is accomplished enabling the process design for efficient surface smoothing and improved residual stress depth distribution.     

等离子体浸没离子注入(PⅢ)在材料表面改性中的应用及发展

等离子体浸没离子注入(PⅢ)是一种用于材料表面改性的新的离子注入技术.系统地分析和讨论了等离子体浸没离子注入技术的原理和特点:该技术直接将待处理材料浸没在等离子体中进行注入,保留了常规束线离子注入(CBⅡ)技术的主要特点,消除了常规束线离子注入所固有的视线限制,克服了保持剂量问题,使注入装置变得简单和价廉.综述了等离子体浸没离子注入技术在金属材料、半导体材料和高分子材料改性方面的应用.展示了等离子体浸没离子注入技术应用的发展前景.     

强束流脉冲金属离子束表面改性技术及其应用

介绍了强束流脉冲金属离子束技术的基本原理和主要优点,并用由金属蒸汽真空弧离子源(MEWA)引出的强束流脉冲Ti、Mo、W、Ta、C离子对Cr12、H21、H13钢进行了离子注入材料改性试验。注入剂量为3×1017～5×1017cm-2,引出电压为25～48kV,平均束流为25～50μA/cm2。用卢瑟福背散射谱(RBS)测量了注入样品表面的成分,借助X射线行射仪(XRD))和X射线光电子能谱仪(XPS)考察了注入样品的耐磨机理。     

A comparative study on titania layers formed on Ti, Ti-6Al-4V and NiTi shape memory alloy through a low temperature oxidation process

For improving the bioactivity and biocompatibility of metals for medical applications, anatase titania layers were synthesized on Ti, Ti-6Al-4V and NiTi shape memory alloy (SMA) using the H₂O₂-oxidation and hot water aging treatment method at 80 °C. The thickness of the titania layers on Ti, Ti-6Al-4V and NiTi SMA was 7.43 ± 0.93 μm, 3.14 ± 0.38 μm and 4.04 ± 0.25 μm, respectively. X-ray diffraction (XRD) and transmission electron microscopic (TEM) analysis indicated that the titania layers formed were poorly crystalline anatase. Fourier transform infrared spectroscopy (FTIR) suggested that abundant Ti-OH functional groups were produced on titania, which could improve bioactivity of the metals. In addition, the titania layer formed on Ti substrate was shown to contain more molecularly chemisorbed water and Ti-OH functional groups than those on Ti-6Al-4V and NiTi SMA. Atomic force microscopic (AFM) results showed that the surface roughness values of metal samples depended on the scanning size and that surface roughness of samples significantly increased after the H₂O₂-oxidation and hot water aging treatment for all three metals. Compared to Ti-6Al-4V and NiTi SMA, the H₂O₂-treated and aged Ti samples exhibited the roughest surface. The wettability of samples was evaluated through water contact angle measurements. After the H₂O₂-oxidation treatment, the three metals exhibited high hydrophilicity. The bonding strength of titania layers on Ti, Ti-6Al-4V and NiTi was also investigated. Potentiodynamic polarization tests indicated that the corrosion resistance of H₂O₂-treated and aged Ti, Ti-6Al-4V and NiTi SMA was significantly improved due to the titania layer formation.     

Numerical and experimental study on the gravitation and surface tension effects on flow injection in center-gated disks

Flow injection in center-gated disks is numerically and experimentally studied in this paper for possible applications in the manufacturing of lightweight and high performance composite materials in space. A comprehensive three-dimensional model, which combines the Galerkin finite element method with a predictor/corrector scheme, is employed to determine the transient flow field. The effects of gravitation and surface tension on the development of flow front shape, velocity field pressure distribution, and advancement of the flow front are examined for a wide range of the governing parameters (namely, the capillary and Bonds numbers). It has been found that surface tension tends to hold the flow front in symmetric shape between disks while gravitation is to distort it. The balance of these two forces has significant effects on the front shape, front tip traveling speed and required injection pressure. Good agreement is found between the prediction and experimental measurements concerning the development of flow front shape and advancement of the flow front. The present results provide useful information in the design of resin transfer molding process in space.     

Zirconium vacuum arc operation in a mixture of Ar and O2 gases: Ar effect on the arcing characteristics,deposition rate and coating properties

The effect of oxygen and argon partial pressures (P_O2, P_Ar) in a Zr vacuum arc on plasma ion current density J_p, arc voltage V_arc, deposition rate v_d, and selected coating properties was determined. A d.c. arc current of I_arc = 100 A was initiated between a Zr cathode and a grounded anode. Cathode spots produced a plasma jet, which entered a 1/8 torus macroparticle (MP) filter. The plasma was guided by a d.c. magnetic field through an aperture to a glass substrate or a flat disk probe, mounted on a rotatable holder. J_p was measured with the probe, negatively biased to V_b = − 60 V. Coating thickness was measured using a profilometer, and coating properties were investigated using optical microscopy, energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), nano-indentation and optical analysis.     

Theoretical and experimental study of energy transportation and accumulation in femtosecond laser ablation on metals

The energy transportation and accumulation effect for femtosecond (fs) laser ablation on metal targets were studied using both theoretical and experimental methods. Using finite difference method, numerical simulation of energy transportation characteristics on copper target ablated by femtosecond laser was performed. Energy accumulation effects on metals of silver and copper ablated by an amplified Ti: sapphire femtosecond laser system were then studied experimentally. The simulated results show that the electrons and lattices have different temperature evolvement characteristics in the ablation stage. The electron temperature increases sharply and reaches the maximum in several femtoseconds while it needs thousands of femtoseconds for lattice to reach the maximum temperature. The experimental results show that uniform laser-induced periodic surface structures (PSS) can be formed with the appropriate pulsed numbers and laser energy density. Electron-phonon coupling coefficient plays an important role in PSS formation in different metals. Surface ripples of Cu are more pronounced than those of Au under the same laser energy density.     

Adhesion on polyethylene glycol and quaternary ammonium salt-grafted silicon surfaces: Influence of physicochemical properties

The aim of this work was to develop a new generation of antimicrobial materials. In order to restrict surface contamination by micro-organisms, the approach developed consisted in modifying the surface properties of a silicone wafer by grafting antimicrobial compounds such as quaternary ammonium salts (QAS) and polyethylene glycol (PEG). Under this approach, the grafted compound was endowed with a functionalised extremity which allowed it to react with the silicone wafer in order to form a covalent bond. The first part of this paper describes the synthesis of QAS and PEG molecules, and then the physicochemical characteristics of the modified silicon surfaces were determined. The second part concerned determination of the surface properties of the wafers and polystyrene beads used for adhesion tests. In line with the extended DLVO theory, it was thus possible to understand the mechanisms involved in the adhesion of polystyrene beads to the surface of QAS and PEG-modified silicon wafers.     

A theoretical and experimental investigation into five-DOF dynamic characteristics of an aerostatic bearing spindle in ultra-precision diamond turning

In ultra-precision diamond turning (UPDT), spindle vibration has great influence on machining precision of high precision optical components. However, the spindle-vibration mechanism has not been fully understood. In this study, mathematical solutions for a proposed five-degree-of-freedom (FDOF) dynamic model of an aerostatic bearing spindle are derived to explore natural mechanisms of spindle vibration. Thus, the potential benefits of the solutions are to be applied for the prediction and optimization of the effects of spindle vibration on surface generation. Its dynamic characteristics possess three translational frequencies along the radial and axial directions, a spindle rotational frequency (SRF), and a pair of coupled tilting frequencies (CTFs) around the radial directions influenced the SRF. The theoretical results are identified by the frequency characteristics of thrust cutting forces, and the periodic, concentric, spiral, radial and two-fold patterns (PCSRPs) of the machined and simulated surface topographies, respectively.     

Adhesion analysis and dry machining performance of CVD diamond coatings deposited on surface modified WC-Co turning inserts

This paper investigates the effects of different surface pretreatments on the adhesion and performance of CVD diamond coated WC-Co turning inserts for the dry machining of high silicon aluminum alloys. Different interfacial characteristics between the diamond coatings and the modified WC-Co substrate were obtained by the use of two different chemical etchings and a CrN/Cr interlayer, with the aim to produce an adherent diamond coating by increasing the interlocking effect of the diamond film, and halting the catalytic effect of the cobalt present on the cemented carbide tool. A systematic study is analyzed in terms of the initial cutting tool surface modifications, the deposition and characterization of microcrystalline diamond coatings deposited by HFCVD synthesis, the estimation of the resulting diamond adhesion by Rockwell indentations and Raman spectroscopy, and finally, the evaluation of the dry machining performance of the diamond coated tools on A390 aluminum alloys. The experiments show that chemical etching methods exceed the effect of the CrN/Cr interlayer in increasing the diamond coating adhesion under dry cutting operations. This work provided new insights about optimizing the surface characteristics of cemented carbides to produce adherent diamond coatings in the dry cutting manufacturing chain of high silicon aluminum alloys.     

Surface study of composite photocatalyst based on plasma modified activated carbon fibers with TiO2

Composite photocatalyst was prepared by the nitrogen plasma modification of active carbon fibers (ACF) loaded with TiO₂ using a tetrabutyl titanate hydrolyzing process. The surface morphology was characterized by SEM. The specific surface area and the pore size distribution of ACF were compared by N₂ adsorption before and after modification loaded TiO₂. The surface chemical functional groups and the performance of photocatalyst were investigated by XPS and formaldehyde decomposition respectively. The results show that after carrier surface nitrogen plasma modification, the surface morphology of composite photocatalyst barely changed, the surface area and pore volume decreased slightly, XPS revealed that nitrogen plasma modification could remarkably change the distribution of the oxygen functional groups on the carrier surface and adsorbing oxygen species on the surface of the composite photocatalyst increased. The efficiency of formaldehyde photocatalysis purification was improved by modification.     

铝及其合金表面改性技术的研究与发展

铝及其合金材料具有质量轻、易加工、比强度高等优良特性,随着现代经济的高速发展,它在产量和用途上已成为仅次于钢铁的第二大金属材料.为了更好地体现其巨大价值,必须解决其硬度低、耐磨性差等缺点.因此铝及其合金的表面改性显得格外重要.综合了国内外近年来对铝及其合金表面改性技术的研究与应用情况,从电化学氧化法、化学转化技术、微弧氧化技术、等离子注入、冷喷涂技术和激光处理这几个方面对铝及其合金表面改性技术的发展状况进行了简要的综述,并展望了其研究前景.     

Preparation and in vitro biocompatibility of hybrid oxide layer on titanium surface

A new technique combining microarc oxidation (MAO) and electrophoresis was introduced to develop a biocompatible oxide layer on pure titanium implant surface. Originally developed alkaline electrolyte containing nano-scale hydroxyapatite powder suspension was used in the new technique. In the electric field, nano-scale hydroxyapatite powder was electrophoretically moved and sintered into the gradually-formed oxide layer on titanium anode. Physio-chemical properties and in vitro biological performance of the newly-formed surface were examined and evaluated. A 8.5-μm thick oxide layer with high surface energy and roughness, which was composed of titanium dioxide and calcium phosphates as well as hydroxyapatite, was formed on titanium surface by the modified MAO technique. Osteoblasts cultured on the modified MAO titanium surface showed significantly increased alkaline phosphatase (ALP) activity comparing to machined and MAO titanium surface. Natural oxide surface of titanium could be transformed into a hybrid oxide layer by modified MAO treatment. The modified titanium surface, which is rough and porous, contains calcium phosphates and proved to be more biocompatible in vitro.     

Computational study and experimental comparison of the in-flight particle behavior for an external injection plasma spray process

A three-dimensional computational fluid dynamic (CFD) analysis using Fluent V5.4 was conducted on the in-flight particle behavior during the plasma spraying process with external injection. The spray process was modeled as a steady jet issuing from the torch nozzle via the heating of the are gas by an electric are within the nozzle. The stochastic discrete model was used for the particle distribution. The particle temperature, velocity, and size inside the plasma plume at a specified standoff distance have been investigated. The results show that carrier gas flow rate variation from 2 standard liters per minute (slm) to 4.0 slm can increase the centerline particle mean temperature and mean velocity by 10% and 16%, respectively, at the specified standoff distance. A further increase of the carrier gas flow rate to 6 slm did not change the particle temperature, but the particle velocity was decreased by 20%. It was also found that an increase in the total arc gas flow rate from 52 slm to 61 slm, with all other process parameters unchanged, resulted in a 17% higher particle velocity, but 6% lower particle temperature. Some of these computational findings were experimentally confirmed by Kucuk et al. For a given process parameter setting, the kinetic and thermal energy extracted by the particles reached a maximum for carrier gas flow rate of about 3.5–4.0 slm.     

Effects of the electric conditions of AC-type microarc oxidation and hydrothermal treatment solution on the characteristics of hydroxyapatite formed on titanium

This study examined the effects of the conditions for AC-type microarc oxidation (MAO) and the type of hydrothermal treatment solution on the characteristics of hydroxyapatite(HAp)-containing oxide films deposited on commercially pure titanium (CP-Ti). The MAO treatments were carried out in an electrolyte containing 0.2 M calcium acetate monohydrate and 0.02 M β-glycerophosphoric acid disodium salt pentahydrate (β-GP) using AC-type rectangular electric pulses at different voltages and frequencies. HAp formation on the surface of the MAO-treated group was induced by a hydrothermal treatment in either an alkaline solution to form HT-treated groups or a 0.002 M β-GP solution (pH = 11.0) to produce HTP-treated groups. A mixed crystalline structure consisting of anatase TiO₂, rutile TiO₂ and CaTiO₃ was observed on the MAO-treated groups treated with a low frequency and voltage. When the AC frequency was increased, anatase TiO₂ became the dominant crystalline structure and there was an even distribution of pores. HAp particles were formed more densely on the HTP-treated groups than on the HT-treated groups. Among the HTP groups, the groups fabricated at higher frequencies contained more evenly distributed and crystallized HAp crystallites.