PLASMA SPRAYED Ti AND HA COATINGS： A COMPARATIVE STUDY BETWEEN APS AND VPS

Titanium (Ti) and hydroxyapatite (HA) coatings have been prepared via air (APS) and vacuum plasma spraying (VPS), and then their composition, structure, bonding strength and bioactivity were examined. The results obtained reveal that in APS process many of Ti were oxidized, but in VPS the oxidization was avoided. VPS Ti coating possesses better bonding condition than APS Ti coating. As for HA coating, higher crystallinity has been obtained while the coating was deposited by VPS as compared with APS. The simulated body fluid (SBF) tests show that both of APS and VPS HA coatings possess good bioactivity. As compared with APS, VPS is recommended as a better method to deposit Ti and HA coatings that can be applied as hard tissue replacement implants.     

(Zr,Ti)CN coatings as potential candidates for biomedical applications

(Zr,Ti)CN hard coatings, deposited by DC magnetron sputtering on Ti6Al4V alloy and Si substrates, were investigated as possible candidates to be used as protective layers for medical implants. Two coating types, with different non-metal/metal ratios, were prepared. The films were analyzed for elemental and phase composition, crystallographic structure, mechanical properties, corrosion behavior, surface wettability and cell viability. The coatings were found to have composite structures, in which a (Zr,Ti)CN crystalline phase coexists with an amorphous a-C(N) one. Film thickness and hardness in the ranges 1.8-2.1 μm and 25-29 GPa, respectively, were measured. The coated samples exhibited an improved corrosion resistance as compared with the Ti6Al4V alloy. Both coating types were found to be hydrophobic, the contact angles being higher than 100°. Cell viability measurements proved that the osteosarcoma cells are adherent to the coating surface, the highest viability (90.5%) after one week incubation being found for the film with high non-metal content.     

Preparation and characterization of silicon-substituted hydroxyapatite coating by a biomimetic process on titanium substrate

A biomimetic method has been used to prepare silicon-substituted hydroxyapatite coatings on titanium substrates. The surface structures of the coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR). Si substituted hydroxyapatite (Si-HA) coatings with different Si contents were deposited successfully on the titanium substrate by immersing the pretreated titanium substrate into silicon containing supersaturated solutions (SSS) with different SiO₃²⁻ concentrations. The pretreatment of the Ti substrate in a mixed alkaline (NaOH + Ca(OH₂)) followed by a heat treatment produced a 3D porous surface structure with rutile and CaTiO₃ as main phases, which contributed mainly to the fast precipitation and deposition of Si-HA. FTIR results showed that Si in the Si-HA coating existed in the form of SiO₄⁴⁻ groups. The cross-section microstructure was observed by scanning electronic microscopy and the shear strength was tested. The coating was about 5-10 μm in thickness and no interval was observed at the interface between the coating and the substrate. Shear strength testing showed that Si-HA/Ti exhibited higher shear strength than HA/Ti due to the existence of the SiO₄⁴⁻ group in the coating.     

New method for hydroxyapatite coating of titanium by the hydrothermal hot isostatic pressing technique

A new hydrothermal method is proposed, which enables us to prepare thin hydroxyapatite (HA) ceramic coatings on Ti substrates with a curved surface at low temperatures. The method uses double layered capsules in order to produce a suitable hydrothermal condition; the inner capsule encapsulates the coating materials and a Ti substrate, and the outer capsule is subjected to isostatic pressing under the hydrothermal condition. In this study, it is demonstrated that a pure HA ceramic layer with the thickness of 50 μm could be coated to a Ti cylindrical rod at the low temperature as low as 135 °C under the confining pressure of 40 MPa. The HA coating layer had a porous microstructure with the relative density of approximately 60%. Pull-out tests were conducted to obtain an estimate for the adhesion properties of the HA coating prepared by the double capsule method. The shear strength obtained from the pull-out tests was in the range of 4.0–5.5 MPa. It was also shown that the crack propagation occurred within the HA coating layer, not along the HA/Ti interface in the pull-out tests. This observation suggests that the fracture property of the HA/Ti interface was close to or higher than that of the HA ceramics only. It is expected that the low temperature double capsule method may provide a useful method for producing bioactive HA ceramic coatings on curved prostheses surfaces.     

Hydroxyapatite coating on pretreated CoNiCrMo prosthesis

1 INTRODUCTIONCo-alloys arei mportant metallic medical mate-rials for tribologically loaded knee , hip joints andtheir fixation parts ,as shownin Fig.1 ,due to ex-cellent mechanical , tribological and corrosion-resistant properties[1]. A bioactive ceramic coat-ings ,especially hydroxyapatite( HA) coating, onmetallic prostheses is a promising approachfor i m-proving its osteoconductivity and bone-bondingability[2 11]. Nowadays ,some plasma sprayed HAand other bioceramic coatings on metall…     

Adhesion of sol-gel derived hydroxyapatite nanocoatings on anodised pure titanium and titanium (Ti6Al4V) alloy substrates

The mechanical properties and adhesion behaviour of sol-gel derived hydroxyapatite (HA) nanocoatings on commercially pure (cp) titanium (Ti) and Ti6Al4V alloy have been determined and related to anodising treatment. The surface roughness, wetting and coating characteristics were examined using profilometry, contact angle, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Nano-indentation was used to determine the Young's modulus and hardness of the coatings, while microtensile tests were used to introduce controlled strains in the coatings through the cp Ti and TiAl6V4 alloy substrates, from which the strength, fracture toughness and adhesion behaviour could be ascertained based on multiple cracking and delamination events. The toughness of the HA coatings is found to be slightly lower to that of equivalent bulk pure HA ceramics. The substrate and the anodized layer thickness have the most influence on the interfacial adhesion of HA, with nanocoatings on Ti6Al4V exhibiting superior interfacial bonding in comparison to cp Ti.     

钛合金表面GO/HA/MAO复合膜层的制备及其性能

为了改善钛合金种植体在体液中的腐蚀及摩擦腐蚀行为,延长其在人体环境中的服役时间,在微弧氧化 (MAO)膜层上采用溶胶凝胶(Sol-gel)法于羟基磷灰石(HA)和氧化石墨烯(GO)的混合溶胶中浸渍提拉成膜,从而在 Ti6Al4V 合金表面成功地制备了 GO/ HA/ MAO 复合膜层。 结果表明,MAO 膜层表面的微孔及微球被 GO/ HA 薄膜有效的覆盖且较为致密;膜层的物相组成主要为金红石相及锐钛矿相的 TiO₂、HA、SiO₂ 和GO;根据电化学腐蚀和摩擦腐蚀结果分析知,GO/ HA/ MAO 复合膜层在模拟体液(SBF)中的耐蚀性及耐摩擦腐蚀性相比于 MAO 膜层和 Ti6Al4V 基体均得到了显著提高。     

超音速氧焰喷涂HA/BG涂层的制备及表征

利用超音速氧焰喷涂(HVOF)在Ti6A14V基体上制备了羟基磷灰石(HA)/生物玻璃(BG)涂层,考察了涂层的相组成、表面形貌及生物活性.XRD显示:涂层的结晶相为HA,未检测到HA分解产物,添加生物玻璃不影响涂层的相组成;SEM结果表明:HA颗粒熔化较少,计算熔化比例为13%,BG颗粒以球形方式镶嵌在涂层表面,含量小于粉末中的比例:涂层浸泡在模拟体液中7天后发现:添加20%BG的涂层表面有类骨类磷灰石涂层生成,说明添加BG可以提高涂层的生物活性.     

Influence of Alkali Treatment on Ti6Al4V Alloy and the HA Coating Deposited by Hydrothermal-Electrochemical Methods

Ti6Al4V基体经NaOH溶液恒温预处理不同的时间(12、24、36、48、60 h),然后分析了不同的碱预处理时间对Ti6Al4V基体及羟基磷灰石(HA)形态、物相的影响。经碱预处理后Ti6Al4V表面呈现三维网状结构,并检测到了钛酸钠凝胶的存在。随后采用水热电化学方法得到了HA涂层,水热反应电解质包括NaCl、K2HPO4·3H2O、CaCl2,在恒温120℃、电流密度为1.25 mA/cm2的条件下保持120 min。结果表明:HA的生长模式及形态均受预处理时间的影响:当基体经过12 h的预处理后,水热反应形成一层针状HA及少量蒲公英状HA。而蒲公英状HA的数量随预处理时间的增加而增多。但预处理时间大于48 h时,其数量稍有减小。HA在(002)晶面的取向指数、结晶度在预处理时间为48 h时分别达到了最小值、最大值。     

钛基材上电化学沉积羟基磷灰石

通过电沉积法在经过阳极氧化的钛基材表面沉积磷酸钙盐涂层,再经碱热处理使磷酸钙涂层转变为羟基磷灰石涂层。扫描电镜(SEM)观察了阳极氧化后生成的TiO2纳米管的微观结构,以及生成的羟基磷灰石的形貌。X射线衍射仪(XRD)分析了涂层的相组成,同时测定了涂层与基体的结合强度。试验结果表明:电沉积涂层CaHPO4·2H2O经碱处理后转变为羟基磷灰石;电沉积添加双氧水与钛基材经过阳极氧化后使得涂层与基体结合强度有所提高。模拟体液浸泡试验表明涂层具有良好的生物活性。     

New generation hopeite coating on Ti6Al4V (TC4) by radio frequency magnetron sputtering for prosthetic-orthopaedic implant applications: synthesis and characterisation

ABSTRACT

Bioceramic coatings with multifunctionality have emerged as an effective alternative to conventional coatings, owing to their combination of various properties that are essential for bio-implants, such as osseointegration and antibacterial character. In the present study, thin hopeite coatings were synthesised by radio frequency magnetron sputtering on TC4 substrates. The obtained hopeite coatings were thermally treated at 500°C in ambient air and characterised in terms of surface morphology, phase composition, surface roughness, adhesion strength, antibacterial efficacy, apatite forming ability, surface wettability and corrosion resistance by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Atomic Force Microscopy(AFM), Tensometer, Fluorescence-Activated Cell Sorting (FACS), Simulated Body Fluid (SBF) immersion, Contact Angle Goniometer and potentiostatic polarisation respectively. It was observed that the post-deposition annealing increases the crystallinity of the synthesised hopeite coatings. SEM analysis showed deposited particles are spherical in shape and small in dimensions (<1?μm in diameter). XRD results confirm the deposited coating is crystalline in nature. AFM analysis reveals deposited hopeite coating has an average surface roughness value of 8.66?nm. Tensile pullout experiments indicated that the adhesive strength of the hopeite coating is 21.75?±?2.1?MPa. FACS study confirms the deposited hopeite coating possesses antibacterial character. SBF immersion experiments clearly demonstrate apatite growth on the surface of the deposited hopeite coating. The surface wettability test showed that the deposited coatings are hydrophobic in character having an average contact angle value of 136.65°. Potentiodynamic polarisation experiments in SBF showed a significant improvement in corrosion resistance (R_p?=?7945.87?Ω?cm²) of hopeite coated samples. In summary, it can be concluded that the new generation multifunctional hopeite coating synthesised by an alternative new process route of radio frequency magnetron sputtering on TC4 substrates is an effective alternative to conventional coatings. This is largely attributed to the strong osseointegration and antibacterial character of deposited hopeite coating ensuring the overall stability of metallic orthopaedic implants.     

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.     

Atomic structure studies of chrome alloy coatings and their abrasion resistance

In this study, thin chrome alloy reflective coatings of less than 50 nm are prepared by magnetron co-sputtering chrome and a dopant material onto coated polymeric substrates. This report shows that the lattice parameter of the alloy of chrome and dopant can be used to control the macroscopic abrasion resistance of the coating. These alloy structures are not predicted by thermodynamic equilibrium phase diagrams, illustrating the ability of physical vapour deposition to generate novel coatings. As these coatings are deposited on substrates having a glass transition temperature below 150 °C, the structure after deposition but without post processing is critical because conventional post processing (high temperature annealing) cannot be applied.     

The preparation of calcium phosphate coatings on titanium and nickel–titanium by rf-magnetron-sputtered deposition: Composition, structure and micromechanical properties

Thin calcium phosphate coatings with a thickness of 0.09 to 2.7 µm were prepared by radio-frequency magnetron sputtering deposition on NiTi and Ti substrates at a substrate temperature of 500 °C in argon atmosphere. Scanning electron microscopy (SEM) showed that the surface structure is uniform and dense without visible defects (pores and microcracks). Rutherford backscattering spectroscopy (RBS) and energy-dispersive X-ray spectroscopy (EDX) confirmed that the coating contains calcium, phosphorus, and oxygen with a uniform composition. Crystallographically, the coating consists of crystalline hydroxyapatite which is also supported by infrared spectroscopy. The mechanical characteristics of the coating were measured by nanoindentation (Vickers indenter), giving a nanohardness of 10 GPa and a Young's modulus of 110 GPa. The strength of adhesion of the calcium phosphate coating to the metallic substrates depended on the coating's thickness and decreased for a thickness larger than 1.6 µm. No difference was observed between NiTi and Ti substrates.     

Mg-4Zn合金表面掺锶羟基磷灰石涂层：物理化学性质及体外细胞响应

生物可降解镁合金由于具有高比强度、低弹性模量和优良生物相容性而受到广泛关注。然而,其过高的腐蚀速率却限制了其潜在的临床应用。因此,具有高生物相容性的羟基磷灰石(HA)涂层常被用于阻碍镁基体和周围生物环境的相互作用。采用电化学沉积法在Mg-4Zn合金表面制备了HA和掺锶(Sr)HA涂层。利用扫描电子显微镜(SEM)、能谱(EDS)、透射电子显微镜(TEM)、三维激光扫描显微镜(3D LSM)和亲水角监测系统对材料表面性质进行表征。本研究还探讨了材料动态离子释放、蛋白吸附、细胞吸附、增殖与成骨分化行为。结果显示,HA中引入Sr导致了晶格畸变和结晶度下降。涂覆掺SrHA的样品中镁离子释放量比其他样品更低,说明耐腐蚀性更好。掺Sr样品表面蛋白吸附与初始细胞吸附的改善是由于其具有更高的表面粗糙度和亲水性。Sr的引入并未显著改变细胞的增殖,却明显提高了成骨分化效果。综上所述,掺SrHA涂层是一种非常有前景的镁合金保护性生物相容涂层。     

Surface morphology and in vitro bioactivity of biocompatible hydroxyapatite coatings on medical grade S31254 steel by RF magnetron sputtering deposition

Hydroxyapatite (HA) is popularly used as a biocompatible coating material for metallic implants, in view of its improved bone fixation property, leading to an increased life of the implant. However, the deposition of HA on medical grade UNS S31254 stainless steel (SS254) for orthopaedic implant applications by the radio-frequency magnetron sputtering technique is unreported in the literature so far. The surface morphology of the deposited HA coatings was characterised using scanning electron microscopy and atomic force microscopy, while their phase composition was determined using X-ray diffraction. The thickness and adhesive strength of the HA coatings were determined using an ellipsometer and a tensometer, respectively. Finally, the antibacterial efficacy and bioactivity of the deposited coatings were confirmed using fluorescence activated cell sorting and immersion testing in simulated body fluid environment. The results obtained showed that the HA coatings grown on SS254 using magnetron sputtering possess desirable surface properties as well as good adhesion and biocompatibility properties, ideally suited for potential applications in orthopaedic implants.     

Fabrication and Characterization of Suspension Plasma-Sprayed Fluoridated Hydroxyapatite Coatings for Biomedical Applications

Fluoridated hydroxyapatite (FHA) coatings were prepared on a Ti substrate using a suspension plasma spraying technique. The crystalline phases and chemical compositions of the coatings were characterized using x-ray diffraction, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. The analysis confirmed that the coating consisted of an FHA phase. The corrosion behavior in simulated body fluid was studied using potentiodynamic polarization tests, and the results indicated that the FHA coating greatly enhanced the corrosion resistance of the Ti substrate. The chemical stability of the FHA coatings was assessed by evaluating the release of Ca²⁺ ions. The results indicated that the substitution of fluorine into the hydroxyapatite (HA) structure had a positive effect on the dissolution resistance of the HA. The antibacterial activity was investigated using a surface-plating method; the results revealed that the antibacterial activity of the FHA coating was greater than that of the pure HA coatings. During cell culture tests, the FHA coating did not exhibit cytotoxicity toward the osteoblast cell line, and the cell proliferation was comparable with that of the HA coatings. The antibacterial activity and cell culture results suggested that the plasma-sprayed FHA coating possesses good antibacterial qualities, but is biocompatible with osteoblasts. The promising features of the FHA coating render it suitable for orthopedic and dental applications.     

Synthesis and Characterization of Hydroxyapatite/TiO<Subscript>2</Subscript> Coatings on the β-Type Titanium Alloys with Different Sintering Parameters using Sol-Gel Method

In this study, hydroxyapatite (HA) based composite films were successfully syntheses on the β-type Ti29Nb13Ta4.6Zr (TNTZ). The solutionized TNTZ substrates coated with HA and HA/Titania (TiO₂) bioactive composite coatings by sol-gel method under various sintering parameters related to sintering temperatures and heating ramp rates. Microstructural observations of the coatings revealed that apatite was formed on the substrates. The hardness values of the coatings increase with increasing both the sintering temperature and the TiO₂ concentration in the coatings layer. However, it was found that the heating ramp rate of the sintering was not affecting the hardness values so much. Also, the hardness values of the HA/TiO₂ composite coatings at all sintering temperatures were higher than only HA coated TNTZ samples due to the existence TiO₂ phases in the HA matrix. Results indicating that the doping of HA with TiO₂, improve the physical consistency between the coating layer and the substrates and provide a better inter-particle bonding due to the existence TiO₂ phases in the HA.     

Effect of Magnesium and Osteoblast Cell Presence on Hydroxyapatite Formation on (Ti,Mg)N Thin Film Coatings

TiN and (Ti,Mg)N thin film coatings were deposited on Ti substrates by an arc-physical vapor deposition technique. The effect of cell presence on hydroxyapatite (HA) formation was investigated using surfaces with four different Mg contents (0, 8.1, 11.31, and 28.49 at.%). Accelerated corrosion above 10 at.% Mg had a negative effect on the performance in terms of both cell proliferation and mineralization. In the absence of cells, Mg-free TiN coatings and low-Mg (8.1 at.%)-doped (Ti,Mg)N surfaces led to an early HA deposition (after 7 days and 14 days, respectively) in cell culture medium (DMEM), but the crystallinity was low. More crystalline HA structures were obtained in the presence of the cells. HA deposits with an ideal Ca/P ratio were obtained at least a week earlier, at day 14, in TiN and low-Mg (8.1 at.%)-doped (Ti,Mg)N compared with that of high-Mg-containing surfaces (>10 at.%). A thicker mineralized matrix was formed on low-Mg (8.1 at.%)-doped (Ti,Mg)N relative to that of the TiN sample. Low-Mg doping (<10 at.%) into TiN coatings resulted in better cell proliferation and thicker mineralized matrix formation, so it could be a promising alternative for hard tissue applications.     

Interface activation and surface characteristics of Ti/TiN/HA coated sintered stainless steels

Interface activation and surface characteristics of Ti/TiN/HA film coated sintered stainless steels (SSS) have been investigated by electrochemical and biocompatibility tests. HA (hydroxyapatite), Ti, and Ti/TiN film coatings were applied using electron-beam deposition method (EB-PVD). Ti, Ti/TiN, and Ti/TiN/HA film coated surfaces and layers were investigated by SEM and XPS. The coated films showed micro-columnar structure, and Ti/TiN/HA films were denser than Ti or HA-only film. The corrosion resistance of the HA coating was similar to that of Ti/TiN/HA film coating when Cu content reached 4 wt.%, but the corrosion resistance of the HA coating decreased when Cu content increased from 4 wt.% in 0.9% NaCl solution. Therefore, HA-only coating could ensure corrosion resistance when Cu content does not exceed 4 wt.%. The results of biocompatibility tests of SSS on dogs showed that bone formation and biocompatibility were favorable when Cu content did not exceed 4 wt.%. The biocompatibility with bone was generally favorable in Ti/TiN/HA film coating and HA-only coating, while bone formation was somewhat faster for the HA film coated surface than for the Ti/TiN/HA film coating. Also, good cell growth and osseointegration without toxicity were observed.