Characterization of plasma-sprayed hydroxyapatite/TiO2 composite coatings

To enhance the bonding between hydroxyapatite (HA) coating and titanium alloy substrate, HA/TiO₂ composite coatings have been fabricatedvia plasma spraying. Bonding strength evaluation, simulated body fluid tests, and cell culturein vitro were carried out to characterize the composite coatings. The results obtained showed that the addition of TiO₂ to HA coating improved the bonding strength of the coating significantly. After being immersed in simulated body fluid (SBF) for a period, the surfaces of HA/TiO₂ composite coatings were completely covered by carbonate-containing apatite, which indicated that the coatings possess good bioactivity. Thein vitro cell culture indicated good cytocompatibility for HA/TiO₂ composite coatings.     

Carbo-oxidising of titanium by diffusion treatment in carbon–oxygen containing media

Abstract

The surface engineering of titanium with TiC_xO_1?x coatings through diffusion carbo-oxidising from graphite in oxygen containing media is investigated. The effect of oxygen partial pressure on phase composition of coatings during carbo-oxidising is evaluated. The interval of oxygen partial pressure allowing the carbo-oxide TiC_xO_1?x to form is defined as 10^?2–10³ Pa. The effects of process temperature and time on evolution of TiC_xO_1?x composition and morphology of surface layer have been investigated. It is determined that increases in temperature and process time favour an increase in carbon content in TiC_xO_1?x. It is revealed that at temperatures above the transformation temperature T_α?β, TiC_xO_1?x is formed not only in coating but also throughout grain boundaries of diffusion layer. The stages of carbo-oxide formation during diffusion carbo-oxidising of commercially pure titanium are explained as follows: surface saturation with oxygen; formation of TiO₂ film; oxide dissolution and formation of diffusion layer; formation of non-stoichiometric TiC_x and TiO_x and their interaction resulting in TiC_xO_1?x formation. Corrosion properties of carbo-oxide coatings tested in 80%H₂SO₄ are compared with nitride and oxide coatings. It is revealed that carbo-oxide coating demonstrates better corrosion resistance. The tribological properties of carbo-oxide, nitride and oxide coatings tested with bronze counterbody are compared, and carbo-oxide coating demonstrates better wear resistance.     

不同wCa/wP对宽带激光熔覆生物陶瓷涂层性能的影响

目的 对不同wCa/wP的宽带激光熔覆生物陶瓷涂层性能进行研究，探究wCa/wP对涂层硬度、生物相容性及生物活性的影响规律，寻求最优试验参数，为以后制备性能优良的涂层提供参考。方法 运用梯度设计思想，采用宽带激光熔覆技术，在钛合金表面分别制备wCa/wP为1.35、1.40、1.45的梯度生物陶瓷涂层。利用X射线衍射仪(XRD)、扫描电镜(SEM)、金相显微镜、显微硬度仪、模拟体液浸泡试验、体外细胞试验，研究不同wCa/wP对生物陶瓷涂层组织结构、生物相容性以及生物活性的影响。结果 XRD结果表明，涂层主要由CaTiO3、HA、Ca2SiO4、CaO、TCP等相组成。硬度测试表明，wCa/wP=1.45的涂层平均显微硬度最高，而wCa/wP=1.35的涂层平均硬度最低。体外细胞试验表明，所有涂层上的MG63分布均匀，细胞形态良好，wCa/wP=1.40的涂层上的OD值增长较快，共同培养至第5天时，测得的OD值远高于其他涂层，相较于第1天的OD值增加最多。SBF浸泡试验表明，3种wCa/wP的陶瓷涂层都在表面覆盖了类骨磷灰石，wCa/wP=1.40的涂层，经浸泡后表面覆盖了最多的类骨磷灰石。观察细胞生长形态，细胞的许多丝状伪足紧贴在涂层上，使得细胞可以粘附在涂层上并生长，呈现出正常的梭形形态，具备较完整的细胞膜，wCa/wP=1.40的涂层上粘附的细胞数量更多、分布更为均匀。结论 当wCa/wP=1.40时，Ca-P生物陶瓷涂层不仅拥有良好的生物矿化能力，能够形成更多类骨磷灰石，而且涂层上增殖吸附的细胞数量最多，涂层表现出良好的生物相容性和生物活性。     

Preparation and cell-materials interactions of plasma sprayed strontium-containing hydroxyapatite coating

The use of strontium-containing hydroxyapatite (Sr-HA) as a biomaterial has been reported recently. In vitro and in vivo studies have shown that Sr-HA promotes osteoblast response and stimulates new bone formation. In order to extend its usage to major load-bearing applications, such as artificial hip replacement, it has been proposed that the material could be used in the form of a coating on implant surfaces. This paper reports a preliminary study of biocompatibility of plasma sprayed Sr-HA coatings on a metallic substrate. Coatings of Sr-HA containing 10 mol% Sr²⁺ was produced on titanium alloy substrates. The coating exhibited good bonding with the substrate. The bioactivity of Sr-HA coating was evaluated in vitro by immersion in simulated body fluid (SBF). After immersion in SBF, Sr-HA coating exhibited great ability to induce apatite precipitation on its surface. The possible effects of cell-materials interactions of Sr-HA coating were examined by culturing osteoprecursor cells (OPC1) on coating surfaces. The effect of Sr-HA was also compared to a hydroxyapatite (HA) coating, which is widely used in orthopedics and dentistry. The results indicated that Sr-HA coating had good biocompatibility with human osteoblasts. OPC1 cells survived and proliferated well on the surface of coating. Sr-HA coating promoted OPC1 cells attachment, and more local contacts were produced on the surface. The presence of Sr stimulated OPC1 cell differentiation and ALP expression. No deleterious effect on ECM formation and mineralization was found with Sr-HA coating. The results indicated that Sr-HA coating had good mechanical properties and bioactivity in vitro.     

甘油磷酸钙浓度对钛合金MAO涂层性能的影响

目的 提高医用钛合金的生物活性。方法 在含葡萄糖酸钙(Ca Glu₂)、葡萄糖酸镁(MgGlu₂)、植酸钠(Na₁₂Phy)和磷酸(H₃PO₄)的基本溶液中,分别添加8、10、12 g/L甘油磷酸钙(Ca-GP),采用MAO方法在Ti-6Al-4V表面制备3种涂层。使用SEM、EDS、XRD、XPS和AFM检测涂层表面形貌、化学成分、物相结构、元素存在状态和表面粗糙度,并测试涂层的接触角、结合强度以及体外生物活性。结果 经过MAO处理后,钛合金表面可成功生长出多孔陶瓷涂层,Ca-GP参与了MAO涂层形成。当Ca-GP的质量浓度为8 g/L时,涂层非常粗糙,Ca和Mg的原子数分数分别为7.56%和1.74%。随着Ca-GP浓度的增加,微孔均匀性变好,表面微裂纹减少,且钙磷原子比(Ca/P)显著提高。在含8、10 g/L的Ca-GP溶液中,制备的涂层以Ti、锐钛矿和金红石型Ti O2组成为主;在12g/L的Ca-GP溶液中生成的涂层,Ca/P原子比可达1.77,含有Ti P     

钛植入体表面构建具有抗菌活性和生物相容性的PDA/RGDC/氧化锌量子点复合涂层

传统的抗生素治疗细菌感染往往会导致细菌对抗生素产生耐药性,导致耐药细菌的形成,从而对人类健康产生更大的危害。设计了一种新颖的表面系统,其可在不使用抗生素的情况下为钛植入体提供一种可靠的自抗菌平台。这一特性的实现依靠于钛植入体表面PDA（polydopamine）/RGDC（arginine-glycine-aspartic acid-cysteine）/氧化锌量子点（ZnO QDs）复合涂层的构建,通过粒子生长法得到的ZnO QDs经RGDC修饰后连接到覆盖于钛植入物表面的PDA。用不同的细菌和小鼠成骨细胞对此涂层进行了测试,结果表明,文中设计的复合涂层对大肠杆菌的抗菌率高达98.95%,同时具有优异的生物相容性。因此,该表面涂层在生物医用植入材料领域将有着广泛的应用前景。     

Antifouling properties of micro arc oxidation coatings containing Cu2O/ZnO nanoparticles on Ti6Al4V

Micro arc oxidation (MAO), as a new special surface treatment method, has been introduced to the marine antifouling field for titanium alloys because of the anatase and rutile TiO₂ with antibacterial effects obtained during the oxidation process. Despite this, metallic oxide antifouling additives have been added into MAO coatings to improve the antibacterial and antifouling abilities of titanium alloy. In this study, MAO coatings containing nanometer particles were obtained by adding nano Cu₂O and nano ZnO into the electrolyte. Structure, morphology, phase constitution and chemical composition of the MAO coating film were studied by SEM, XRD and EDS. The antibacterial properties of the film were evaluated by exposing the specimens to Escherichia coli and comparing the Ti-MAO and Ti-bared controls. The results showed that the MAO process on Ti6Al4V has an outstanding antibacterial property which can be further enhanced by nano Cu₂O and nano ZnO. The Ti-MAO–Cu₂O group had the best antibacterial ability. These findings indicate that by means of this process adding nanometer metallic oxide into an MAO coating film via an electrolyte is useful for enhancing the antibacterial and antifouling abilities of titanium.     

Plasma-electrolytic oxidation of titanium in Zr(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>-containing electrolyte

It is shown that anodic oxide coatings with a thickness of several to 300 νm can be obtained on titanium by varying the charge spent on (Q). The prevailing phase in the coatings is ZrO₂ in monoclinic and tetragonal modifications. The content of zirconium in the layers is up to 20 at %. Distributions of titanium, zirconium, and oxygen in the cross sections of the coatings are obtained, and the effect of Q on the formation and elementary and phase compositions of the coatings is studied. Tentative experiments clarifying the effects of bipolar anodic-cathodic polarization and electrolyte aging on the composition of coatings are carried out. The coatings are shown to be stable at temperature variations in the range of 20–700°C and to decrease the contact corrosion current at the (titanium + coating)—St3 steel interface by a digit of 10–15 in 3% NaCl.     

The effect of calcination on the corrosion performance of TiO2 sol–gel coatings doped with benzotriazole on steel CK45

Sol–gel method under dip coating process and tetra‐n‐butyle orthotitanate as precursor were used to produce titanium oxide coating on steel CK45. The effect of calcination at 400 °C, after drying at 120 °C, on the morphology and corrosion performance of the coatings was investigated. Benzotriazole (BTA) as an inhibitor was doped on titanium oxide coatings to improve corrosion performance of the coatings as well as its self‐healing properties. The morphology and structure of the coatings were studied by X‐ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X‐ray spectroscopy (EDS) techniques. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to study the corrosion behavior of the coatings. The results revealed that after calcination the dominant crystalline phase was anatase. The results obtained from potentiodynamic polarization curves and electrochemical impedance spectra showed that the calcinated and doped with BTA coatings possessed higher corrosion resistance than non‐calcinated although doped with BTA coatings.     

pH响应性聚合物抗菌涂层的制备及性能研究

目的 制备一种具有pH响应性的智能聚合物抗菌涂层,能按需实现涂层从防污到杀菌功能的转换.方法 以季铵盐甲基丙烯酰氧乙基二甲基辛烷基溴化铵(DMAEMA-8C)、对-(2-甲基丙烯氧乙氧基)苯甲醛(MAEBA)和甲基丙烯酸异辛酯(EHA)作为共聚单体,通过自由基聚合制备了一种季铵盐聚合物PMQE-CHO,并将其利用浸涂技术在不锈钢316L(SS)表面制备季铵盐聚合物涂层SS-PMQE-CHO.随后,使用PEG-NH2对季铵盐涂层SS-PMQE-CHO表面进行接枝改性,得到pH响应性聚合物涂层SS-PMQE-PEG.对涂层的基本性能进行了表征.通过大肠杆菌和荧光素偶联的牛血清白蛋白(FITC-BSA)的附着力测试,评估涂层的防污和抗菌性能.利用抗菌实验表征涂层在不同pH条件下的抗菌效果.进行体外细胞毒性分析和溶血试验,评估涂层的生物相容性.结果 涂层结构致密规整、机械性能优异,具有良好的生物相容性和低溶血率,并且可以有效地防止BSA和大肠杆菌的粘附.在菌液里培养10 h后,涂层SS-PMQE-PEG-30和SS-PMQE-PEG-40表面的细菌与SS表面的细菌相比,分别减少了94％和96％.此时,PEG显示出有效的防污作用.在菌液里培养24 h后,菌液的pH值降低.涂层SS-PMQE-PEG-30和SS-PMQE-PEG-40的功能从防污转化为杀菌,杀菌效率分别为93％和92％.即使是在PBS中浸泡两周后,涂层仍呈现出良好的功能转化性能.结论 在正常条件下,涂层SS-PMQE-PEG中的PEG可以有效抵抗蛋白质和细菌的粘附.当涂层附近的微环境变为弱酸性时,席夫碱键发生断裂,此时涂层底部的杀菌层暴露出来,以杀死细菌并抑制感染的发生.     

Metal finishing: enhanced performance achieved through plasma processing

Abstract

This paper provides an overview on how plasma deposited coatings can significantly enhance the surface properties of metallic components. Two plasma processing technologies known as physical vapour deposition (PVD) and plasma enhanced chemical vapour deposition (PECVD) are introduced. Examples of the coatings deposited using these two processes are discussed. Among the coating application areas outlined are their use to increase the wear life of tools, to improve decorative finish and to enhance medical device biocompatibility.     

Microstructure and oxidation behaviour of an AlSiY/NiCrAlYSi composite coating at 1150 °C

A composite coating consisting of an outer AlSiY layer and an inner NiCrAlYSi layer has been prepared by a two-step arc ion plating method. The isothermal and cyclic oxidation behaviour of the composite coating at 1150 °C, including the growth of oxide scale and the microstructure transformation of the coatings, have been investigated comparing with the reference coating, NiCrAlYSi. The results show enhanced oxidation performance of the composite coating, which is concerned with its abundant possession of β-NiAl phase reservoirs, providing it the long term healing capacity of re-growing the α-Al₂O₃ scale.     

Tribological behavior and wear mechanisms of TiN/TiCN/TiN multilayer coatings

This work employs the PVD process to deposit coatings of single layer TiN, binary layer TiN/TiCN, multilayer TiN⇔⇔N, and sequenced TiN⇔CN⇔N multilayer coatings with variable individual TiN-layer and TiCN-layer thicknesses on tungsten carbide disks and inserts. Also investigated are the fracture mechanisms and the influence of sequence and thickness of these coatings on cylinder-on-disk, line-contact wear mode and ball-on-disk, point-contact wear mode through SRV reciprocating wear tests. Actual milling tests identify wear performance. Experimental results indicate that the coating with a total thickness of 7 Μm and layer sequence TiN/TiCN/TiN exhibits good wear resistance on SRV wear test and milling test. The thickest multilayer TiN/Ti/TiN coating, although having the highest hardness, has the worst wear resistance for all tests. No-tably zero-wear performance was observed for all coating disks under cutting fluid lubricated condition due to the transferred layers formed between the contact interface.     

Studies on the thermal spraying of apatite bioceramics

Hydroxylapatite (HA) coatings on metal substrates have been investigated for many years. These coatings have proved to be compatible with bone. The degree of crystallinity of HA changed, and sometimes dissociation was observed with respect to the plasma spray process. However, the plasma spray process hardly altered the crystallographic structure, with only line broadening visible. Thein vitro solubility is dependent on the degree of crystallinity of the coating. Tensile strength measurements on the strength of the coating-substrate interface using various adhesives revealed a significant difference between epoxy resin and methacrylate. The failure mode of this tensile test was dependent on the coating thickness and surface texture (polished versus nonpolished). In animal studies, the fixation of hydroxylapatite plasma- spray coated cylinders as well as noncoated Ti- 6A1- 4V cylinders (Ti) in cortical bone was evaluated using pushout tests. It appeared that HA- coated implants showed higher push- out strengths in the first months than the titanium implants, because of the earlier bone formation against the HA coating.     

Tribological properties of titanium aluminides coatings produced on pure Ti by laser surface alloying

Titanium aluminides coatings were in-situ synthesized on a pure Ti substrate with a preplaced Al powder layer by laser surface alloying. The friction and wear properties of the titanium aluminides coatings at different normal loads and sliding speeds were investigated. It was found that the hardness of the titanium aluminides coatings was in the following order: Ti₃Al coating > TiAl coating > TiAl₃ coating. Friction and wear tests revealed that, at a given sliding speed of 0.10 m/s, the wear volume of pure Ti and the titanium aluminum coatings all increased with increasing normal load. At a given normal load of 2 N, for pure Ti, its wear volume increased with increasing sliding speed; for the titanium aluminides coatings, the wear volume of Ti₃Al coating and TiAl coating first increased and then decreased, while the wear volume of TiAl₃ coating first decreased and then increased with increasing sliding speed. In addition, the friction coefficients of pure Ti and the titanium aluminides coating decreased drastically with increasing sliding speed. Under the same dry sliding test conditions, the wear resistance of the titanium aluminium coatings was in the following order: Ti₃Al coating > TiAl coating > TiAl₃ coating.     

In vitro biocompatibility of titanium-nickel alloy with titanium oxide film by H2O2 oxidation

Titanium oxide film with a graded interface to NiTi matrix was synthesized in situ on NiTi shape memory alloy（SMA） by oxidation in H2O2 solution. In vitro studies including contact angle measurement, hemolysis, MTT cytotoxicity and cell morphology tests were employed to investigate the biocompatibility of the H2O2-oxidized NiTi SMAs with this titanium oxide film. The results reveal that wettability, blood compatibility and fibroblasts compatibility of NiTi SMA are improved by the coating of titanium oxide film through H2O2 oxidation treatment.     

Functionally graded carbon nanotubes/hydroxyapatite composite coating by laser cladding

Functionally graded carbon nanotubes/hydroxyapatite (CNTs/HA) composite coatings have been fabricated by laser cladding technique using CNTs/HA composite powders. As the feedstock for laser deposition, CNTs/HA composite powders were prepared by ball-milling different weight ratios (1%, 3% and 5%) of CNTs with HA powders. CNTs/HA composite coatings were fabricated with CNTs/HA composite powders and functionally graded coating was fabricated by sequentially depositing different CNTs/HA composite coatings on pure titanium. The phase composition, microstructure, micro-hardness, bonding strength and in vitro cellular responses of the composite coatings and the functionally graded composite coating were studied. The results show that the crystallinity of CNTs/HA composite coatings increased with increasing amount of CNTs in the powder mixture. The CNTs were dispersed homogeneously in the coatings to form an interconnected web and the cylinder graphic structure of CNTs was not changed after laser irradiation. Compared with pure HA coating, the maximum increase of the micro-hardness of CNTs/HA composite coatings was 46.8% and the micro-hardness of the functionally graded coating increased gradually through the thickness of this coating. Furthermore, the bonding strength of the functionally graded coating was nearly twice higher than that of pure HA coating. The in vitro cellular biocompatibility tests reveal that the functionally graded composite coating has comparable in vitro bioactivity with pure HA coating.     

Developing and studying the properties of Pb–TiO2 alloy coated lead composite anodes for zinc electrowinning

Abstract

A new anodic material for zinc electrowinning from sulphate electrolytes has been developed. This is a lead–titanium alloy coated lead composite electrode containing titanium nanoparticles. The titanium is present in the lead matrix as n-type TiO₂. It has been established that the optimal content of the Ti in the composite coatings is about 0·5 wt-%. The behaviour of the lead–titanium anodes during the zinc electrowinning has been studied by means of galvanostatic polarisation investigations. The depolarising of the anodic reaction at lead–titanium composite electrodes is attributed to the increased anode area during continued polarisation. The processes occurring on the lead–titanium anodes during zinc electrowinning have been studied by cyclic voltammetry. The surface morphology of the composite lead–titanium electrodes was investigated by scanning electron microscopy.     

TC4钛合金表面TiAlN/Ti涂层的抗冲蚀性能研究

目的 通过明晰TC4钛合金表面不同结构的TiAlN/Ti涂层的冲蚀机制,为提高TC4钛合金的抗冲蚀性能、制备具有良好冲蚀性能的涂层奠定基础.方法 采用磁过滤真空阴极弧(FCVA)与金属蒸汽真空弧(MEVVA)技术,按照一定方式在TC4钛合金表面制备相同厚度不同层数的TiAlN/Ti涂层,采用扫描电镜(SEM)、光学显微镜、纳米压痕仪,对TiAlN/Ti涂层的微观结构和力学性能进行表征和分析.采用冲蚀试验平台,通过参数的调整来模拟沙尘环境,开展TC4钛合金和TiAlN/Ti涂层的冲蚀试验,计算获得冲蚀率.采用Proto-LXRD应力仪测试分析冲蚀前后TiAlN/Ti涂层的残余应力,利用SEM对涂层的冲蚀形貌进行表征和分析,并探讨涂层冲蚀损伤机理.结果 相比于TC4基体试样,层数为4、8、12层的TiAlN/Ti涂层试件冲蚀后的质量损失分别降低了86.9％、91.3％和94.0％,残余压应力分别增加了34、135、203 MPa.对比冲蚀区表面形貌,当涂层的层数为4层时,冲蚀区涂层脱落明显;当涂层层数为8层时,冲蚀区涂层局部有脱落;当涂层层数为12层时,冲蚀区涂层脱落不明显,对基体的防护较好.结论 MEVVA离子源注入技术显著提高了涂层的致密度和涂层与基体间的结合力.TiAlN/Ti涂层能显著改善试样的表面性能.相同涂层厚度下TiAlN/Ti涂层的层数越多,H3/E2值越大,抗冲蚀性能越优异.     

Investigation of surfacing processes using aluminium-based alloys

Summary

It has been recently reported that porous Ti-N sprayed coatings can be made fine-structured by laser irradiation. This paper describes an investigation of the effects of infiltrated metal species on the wear resistance of Ti-N remelted layers.

Non-ferrous metal powders were sprayed on SS400 steel plate substrates in an argon atmosphere. The coating thickness was around 200 μm. Pure titanium was also sprayed on the non-ferrous sprayed coatings in a nitrogen atmosphere. The coating thickness was around 400 μm. Coating specimens consisting of non-ferrous and Ti-N layers were remelted by laser in a nitrogen atmosphere. The remelted layers of the coatings had a fine microstructure with a hardness value above HV1000. The wear resistance of the Ti-N coatings was appreciably improved by remelting.