Corrosion behavior of composite coatings containing hydroxyapatite particles on Mg alloys by plasma electrolytic oxidation: A review

Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite(HAp)has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO.

Electrophoretic deposition of titanium/silicon-substituted hydroxyapatite composite coating and its interaction with bovine serum albumin

Silicon-substituted hydroxyapatite (Ca10(PO4)6-x(SiO4)x(OH)2-x, Si-HA) composite coatings on a bioactive titanium substrate were prepared by electrophoretic deposition technique with the addition of triethanolamine (TEA) to enhance the ionization degree of Si-HA suspension. The surface structure was characterized by XRD, SEM, XRF, EDS and FTIR. The bond strength of the coating was investigated. The results show that the depositing thickness and the images of Si-HA coating can be changed with the variation of deposition time. The XRD spectra of Ti/Si-HA coatings show the characteristic diffraction peaks of HA, and the incorporation of silicon changes the lattice parameter of the crystal. The FTIR spectra shows that the most notable effect of silicon substitution is the decrease of intensities of —OH and PO43- groups with the silicon contents increasing. XRD and EDS element analyses present that the content of silicon in the coating increases with increasing silicon concentration in the suspension. The bioactive TiO2 coating formed may improve the bond strength of the coatings. The interaction of Ti/Si-HA coating with BSA is much greater than that of Ti/HA coating, suggesting that the incorporation of silicon in HA is significant to improve the bioactive performance of HA.

Influence of Zirconia on Hydroxyapatite Coating on Ti-Alloy by Laser Cladding

Coating titanium alloy with the bioceramic material hydroxyapatite(HAP) has been used to improve the poor osteoinductive properties of pure titanium alloy. But in clinical applications, the mechanical failure of HAP-coated titanium alloy implant suffered at the interface of the HAP coatings and titanium alloy substrate will be a potential weakness in prosthesis. Yttria-stablized zirconia (YSZ) is expected to enhance the mechanical properties of the HAP coating and reduce the coefficient of thermal expansion difference between the coated layer and the substrate. These may reinforce the bonding strength between the coatings and the substrate. In this paper, HAP/YSZ composite coatings were cladded by laser. The effects of zirconia on the microstructure, mechanical properties and formation of tricalcium phosphate (TCP, Ca 3(PO 4) 2) of the HAP/YSZ composite coatings were evaluated. XRD, SEM and TEM were used to investigate the phase composition, microstructure and morphology of the coatings. The experimental results showed that adding YSZ in coatings was favorable to the composition and stability of HAP, and to the improvement of the adhesion strength, microhardness and microtoughness. A well uniform, crack-free coating of HAP/YSZ composites was formed on Ti-alloy substrate by laser cladding.

Microstructure and high-temperature wear properties of in situ TiC composite coatings by plasma transferred arc surface alloying on gray cast iron

In this work, an in situ synthesized TiC-reinforced metal matrix composite （MMC） coating of approximately 350-400μm thickness was fabricated on a gray cast iron （GCI） substrate by plasma transferred arc （PTA） surface alloying of Ti-Fe alloy powder. Microhard- ness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy （SEM） and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual anstenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures （473 K and 623 K）, and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the sam- ples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstruc- ture and to the presence of TiC particles.

Ti-based composite coatings with gradient TiC_x reinforcements on TC4 titanium alloy prepared by laser cladding

TiCx-NiTi2/Ti cermet composite coatings C1 and C2 with gradient TiCx reinforcements were prepared on TC4 titanium alloy by laser cladding method.The microstructure and phase compositions were analyzed by means of scanning electron microscopy(SEM),energy-dispersive spectroscopy(EDS)and X-ray diffraction(XRD)meter.The TiCx exhibited a dendritic microstructure,and homogeneously dispersed in the Ti-based matrix where NiTi2 was embedded.With increasing ingredient supercooling,temperature gradient and cooling temperature,the dendrites displayed a finer morphology with longer primary trunks and intensified side branches in the dilution zone.But the smoothed,coarse columnar ones became dominant in the upper clad layer due to the repeated energy input during multi-track cladding.The Vickers microhardness presented a linear change trend through the cross-sections,which well confirmed the gradient distribution of TiCx.With more TiCx,C1 presented higher hardness than C2.

Mechanical properties of TiO_2-hydroxyapatite nanostructured coatings on Ti-6Al-4V substrates by APS method

TiO2-hydroxyapatite （HA） nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy （SEM）. It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder （212 nm） extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.

The optimized preparation of HA/L-TiO2/D-TiO2 composite coating on porous titanium and its effect on the behavior osteoblasts

Various surface bioactivation technology has been confirmed to improve the osteogenic ability of porous titanium(pTi)implants effectively.In this study,a three-layered composite coating,i.e.outer layer of hydroxyapatite(HA),middle layer of loose titanium dioxide(L-TiO2)and inner layer of dense TiO2(D-TiO2),was fabricated on pTi by a combined processing procedure of pickling,alkali heat(AH),anodic oxidation(AO),electrochemical deposition(ED)and hydrothermal treatment(HT).After soaking in simulated body fluid for 48 h,the surface of the AHAOEDHT-treated pTi was completely covered by a homogeneous apatite layer.Using MC3T3-E1 pro-osteoblasts as cell model,the cell culture revealed that both the pTi without surface treatment and the AHAOEDHT sample could support the attachment,growth and proliferation of the cells.Compared to the pTi sample,the AHAOEDHT one induced higher expressions of osteogenesis-related genes in the cells,including alkaline phosphatase,Type I collagen,osteopontin,osteoclast inhibitor,osteocalcin and zinc finger structure transcription factor.As thus,besides the good corrosion resistance,the HA/L-TiO2/D-TiO2-coated pTi had good osteogenic activity,showing good potential in practical application for bone defect repair.

Microstructure and interface thermal stability of C/Mo double-coated SiC fiber reinforced γ-TiAl matrix composites

C/Mo duplex coating interfacially modified SiC fiber-reinforced γ-TiAl matrix composite （SiCf/C/Mo/γ-TiA1） was prepared by foil-fiber-foil method to investigate its interfacial modification effect. SiCf/C/TiAl composites were also prepared under the same processing condition for comparision. Both kinds of the composites were thermally exposed in vacuum at 800 and 900℃ for different durations in order to study thermal stability of the interfacial zone. With the aids of scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）, the interracial microstructures of the composites were investigated. The results reveal that, although adding the Mo coating, the interfacial reaction product of the SiCf/C/Mo/TiAl composite is the same with that of the SiCf/C/TiA1 composite, which is TiC/Ti2AlC between the coating and the matrix. However, C/Mo duplex coating is more efficient in hindering interfacial reaction than C single coating at 900 ℃ and below. In addition, a new layer of interfacial reaction product was found between Ti2AlC and the matrix after 900 ℃, 200 h thermal exposure, which is rich in V and close to the chemical composition of B2 phase.

A first look at the formation of PEO-PDA coatings on 3D titanium

Additive manufacturing has revolutionized implantology by enabling the fabrication of customized,highly porous implants.Surface modifications using electrochemical methods can significantly enhance the bioactivity and biocompatibility of biomaterials,including 3D-printed implants.This study investigates novel coatings on 3D titanium(Ti)samples.Mesh Ti samples were designed and subjected to plasma electrolytic oxidation(PEO)to form a calcium phosphate coating.Subsequently,a layer of polydopamine(PDA)was applied.The electrochemical properties and morphology of the coatings were analyzed.Scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS)revealed well-developed coatings containing calcium phosphates(including hydroxyapatite),titanium dioxide,and polymerized dopamine,suggesting promising bioactive potential.Composite layers incorporating PDA exhibited superior protective properties compared to base PEO coatings.

Preparation of Ti6Al4V/BG/HA graded coating by electrophoresis deposition in absolute alcohol medium

A codeposition of bioglass (BG) and hydroxyapatite (HA) on the substrate Ti6Al4V is realized in a nonaqueous solution system by inducing crystallization of HA on surface of the BG grain and electrophoresis deposition (EPD), and then a bioactive graded ceramic coating was obtained after sintering of the coating. This technique is a new method for making bioactive graded coating. The adhesive strength between the coating and the substrate reaches 18?MPa, and the better electrophoresis depositing parameters and optimal sintering procedure are obtained.

Microstructural evolution and abrasive resistance of WC7Co ceramic particle-reinforced Ti6Al4V composite coating prepared by pulse laser cladding

WC7Co/Ti6Al4V composite coatings are deposited on the pure Ti substrate by pulse laser cladding(LC).During the laser melting process,the decomposition of WC7Co particles will lead to the evolution of microstructure and phases,which is directly related to the wear resistance and mechanism of composite coating.The microstructural evolution,phase compositions and interface reaction of WC7Co/Ti6Al4V composite coating were examined by scanning electron microscopy,energydispersive spectrum and X-ray diffraction(XRD).The hardness of different structures and abrasive resistance of composite coating were measured.The results show that the typical microstructure of LC WC7Co/Ti6Al4V composite coating can be classified into dissolved WC7Co composite structure and un-dissolved WC7Co structure.According to XRD results,there are Ti solid solution,W,TiC,VC,Co3W3C and secondary W2C in composite coating.The eutectic structure formed by the dissolved WC7Co particles consisted of W,W2C,TiC and P-Ti solid solution.The mean hardness of different structures exhibits a significant gradient distribution in composite coating.A reaction layer composed of TiC,W and W2C is also generated onto the interface between un-dissolved WC7Co particles and Ti6Al4V alloy matrix.The abrasive mechanisms of WC7Co/Ti6Al4V composite coating are mainly adhesive wear and oxidation wear during the dry sliding process.

电化学沉积时间对碱预处理钛合金表面HA涂层的影响

采用碱预处理钛合金表面再电化学沉积的方法,研究了电化学沉积时间对羟基磷灰石(HA)涂层物相、形貌、生物活性及其与钛合金基体间结合强度的影响。结果表明,碱预处理钛合金表面制备的电化学沉积涂层主要由片状HA相组成,电化学沉积时间对涂层物相组成没有影响,但会影响涂层厚度;沉积时间60 min时得到的HA涂层较致密,与基体的结合强度达17.85 MPa。各沉积时间下得到的HA涂层均具有较好的生物活性,在模拟体液(SBF)中,CO_(3)^(2-)置换HA中的PO_(4)^(3-)进入磷灰石中形成类骨磷灰石CHA,呈馒头状,直径7~8μm,且在SBF中浸泡3 d,CHA可铺满HA表面。

Synthesis of Titanium Carbide Particle in Laser Melted-pool in situ

The titanium carbide phase was synthesized in laser melted-pool in situ as the reinforced particles of nickel based composite coating on Ti-6Al-4V alloy surface using the nickel and graphite blending powder by laser cladding. The microstructure investigation showed that the petals-shaped particles and granular particles were two main morphology of titanium carbide particles. And a few spiral-shaped titanium carbide pattern and eutectic titanium carbide appeared on the cross-sections of the coating. The spiral-shaped titanium carbide pattern composed of some slender arc-shape titanium carbide particles and the eutectic titanium carbide was fine. The morphology and distribution of the spiral-shaped titanium carbide patterns and eutectic titanium carbide confirmed that their growth mechanism was the dissolution-precipitation mechanism and was affected by the convection behavior of the laser melted pool. The spiral-shaped titanium carbide pattern would precipitate out the high-temperature melts under high-speed convection. The eutectic titanium carbide would precipitate out when the melts stopped convection or dropped to eutectic temperature.

冷喷涂Ti/WC复合涂层的组织与耐磨性研究

为解决钛及其合金磨损性能较差的问题,采用高压冷喷涂技术在Ti6Al4V合金基体上沉积了2种不同成分的Ti/WC复合涂层,通过室温下的干滑动摩擦磨损试验分别测试了基体与复合涂层的摩擦性能,并采用扫描电镜及拉曼光谱对磨损表面进行了观察与表征。结果表明,与Ti6Al4V基体的磨损率(4.06×10-7 mm3/(N·m))相比,复合涂层的磨损率降低了一个数量级,表现出优异的耐磨性。此外,涂层内WC含量的增加,提高了涂层的显微硬度,涂层的耐磨性也随之提升。在磨损轨迹表面,由TiO2、WO3以及WC碎片构成的摩擦膜能够有效避免磨球与涂层表面的直接接触,从而降低磨损程度。因此,冷喷涂Ti/WC复合涂层在钛合金磨损防护方面具有一定的应用前景。

氧化石墨烯/羟基磷灰石复合涂层对RAW264.7巨噬细胞免疫活性的影响

背景:纯钛种植体植入机体后存在骨融合失败或者种植体周围感染等问题,因此对钛种植体表面进行改良已成研究的热门话题。巨噬细胞是机体应对外界刺激的一道免疫防线,任何生物材料植入体内后的相关免疫反应均与巨噬细胞相关。目的:采用电化学沉积法在纯钛片表面制备氧化石墨烯/羟基磷灰石复合涂层,分析涂层的表面特征及对RAW264.7巨噬细胞生长、极化的影响。方法:采用电化学沉积法在纯钛片表面分别制备单纯氧化石墨烯涂层、氧化石墨烯/羟基磷灰石复合涂层,表征涂层的物理性能。将纯钛片(空白组)、沉积单纯氧化石墨烯涂层的钛片(对照组)、沉积氧化石墨烯/羟基磷灰石复合涂层的钛片(实验组)分别与RAW264.7巨噬细胞共培养,采用CCK-8法、DAPI染色检测细胞增殖,扫描电镜观察细胞在钛片表面的黏附,流式细胞仪检测细胞极化表型。结果与结论:(1)扫描电镜下可见纯钛片有定向划痕与少量点状凹陷;沉积单纯氧化石墨烯涂层后,钛片表面可见较多裂纹沟壑和大小不均匀的颗粒状物,以及氧化石墨烯特征的褶皱样结构;沉积复合涂层后,钛片表面较光滑,可见团状颗粒,颗粒大小较为均匀。沉积复合涂层钛片的水接触接角小于纯钛片、沉积单纯氧化石墨烯涂层的钛片(P <0.05)。(2)CCK-8检测与DAPI染色显示,相较于空白组、对照组,实验组细胞增殖更快。扫描电镜下可见RAW264.7细胞均黏附于3组钛片表面,随着培养时间的延长细胞形态发生改变,由圆形向梭形转变,至培养7 d时,空白组细胞伸出的伪足短而少,对照组细胞伸出长而多的伪足,实验组细胞伸出短而多的伪足,并且实验组细胞整体饱满度最优。流式细胞仪检测显示,实验组细胞更高比例向抗炎方向M2型极化。(3)结果表明,氧化石墨烯/羟基磷灰石复合涂层具有良好的理化性能及生物学性能。

钛合金钙磷涂层电沉积技术研究进展

钛合金表面电沉积钙磷涂层技术具有处理温度低、组织结构易控和经济高效等优势,在保持植体优良机械性能的同时提高生物活性,有望替代等离子喷涂技术。为了促进钛合金表面电沉积钙磷涂层技术的临床转化,首先简述钛合金表面电沉积钙磷涂层机理,然后详述近年来在电解液参数(钙磷比、添加剂、p H值和气氛)、外场条件(电场、温度、磁场、超声波)和沉积时间对钛合金表面电沉积钙磷涂层影响的研究进展。其中,钙磷比改变电解液中钙源和磷源离子的临界浓度;p H值调节电解液中磷源离子的存在形式,直接影响涂层的物相种类;添加剂通过与钙源、磷源、溶剂或沉积晶体发生静电吸引、配位或特征吸附等作用,能够进一步调控涂层的种类和形态;控制气氛可有效防止空气中CO_(2)对涂层物相产生影响;进一步通过电场、温度、磁场、超声波和沉积时间的调控,可以优化涂层的结构形态和性能。最后,阐述了钛合金表面电沉积钙磷涂层技术的现存问题,并对其未来发展方向做了展望。

3D打印钛合金多孔支架表面构建羟基磷灰石涂层促进骨生长

为了解决人工关节假体的应力屏蔽问题,基于3D打印技术设计了70%孔隙率的X型多孔钛合金支架,并在支架表面构建羟基磷灰石(HA)涂层,探究了反应时间及不同预处理方法对HA涂层沉积效果的影响。发现水热反应12 h,且经酸蚀+预碱化+预钙化处理后HA涂层效果最好。将涂覆HA涂层的X型结构多孔Ti6Al4V合金支架与小鼠的MC3T3-E1细胞共同培养,评价其细胞毒性、生物相容性、细胞增殖行为以及成骨能力。结果表明,HA涂层可以增强多孔Ti6Al4V合金支架的生物相容性,使得MC3T3-E1细胞在多孔Ti6Al4V合金支架上更易于粘附和铺展,有利于钙、磷等元素的沉积,使支架矿化能力增强,骨整合能力提高。

TLM钛合金表层TiN/Sn复合涂层的制备及磨损行为研究

为了提高Ti-25Nb-3Zr-2Sn-3Mo(TLM)钛合金的耐磨性能,采用表面机械复合强化(SMCS)工艺在合金表层制备了复合涂层并研究了复合涂层的显微组织、微观力学性能和摩擦学性能。结果表明:采用表面机械复合强化技术可在合金表层成功制备TiN/Sn复合涂层,随着Sn含量的增加,复合涂层的厚度和粗糙度不断增大,10%、20%、30%、40%Sn涂层的厚度分别为9.08、14.05、18.33、23.55μm;10%、20%、30%、40%Sn涂层的表面硬度分别为590、529、465、400 HV,相比基体硬度(~230 HV)有所提高。复合涂层的磨损量随Sn含量的增加先减小后增大,20%Sn样品具有最低的磨损量;在干磨损试验中,原样的磨损机制以黏着磨损为主,同时伴随磨粒磨损,复合强化样的磨损机制为磨粒磨损、黏着磨损,同时伴随氧化磨损。

钛合金脉冲电沉积Cu-WC复合镀层的硬度与摩擦磨损性能

为有效提高钛合金的抗摩擦磨损性能,在钛合金表面脉冲电沉积Cu-WC复合镀层。分别研究了平均电流密度、脉冲占空比对复合镀层的微观形貌、WC颗粒含量、硬度以及摩擦磨损性能的影响。结果表明:当平均电流密度为1.5 A/dm^(2)、脉冲占空比为20%时,电沉积的Cu-WC复合镀层致密性最好,WC颗粒含量接近2.4%,其硬度(240.4 HV)约为纯Cu镀层的2倍,还表现出良好的抗摩擦磨损性能,平均摩擦系数较钛合金降低约38%。适当增大平均电流密度(0.5~1.5 A/dm^(2))或提高脉冲占空比(10~20%)能使较多WC颗粒参与电沉积过程,起到明显细化晶粒作用和弥散强化作用,促进形成结构致密的Cu-WC复合镀层,因而具有较高硬度和良好的抗摩擦磨损性能。

铜锶二元掺杂硅酸钙涂层改性钛合金的促成骨和抗菌效应

背景:钛合金作为骨科植入物时缺乏生物活性,可导致种植体松动和假体周围感染,因此,研究一种兼顾促成骨和抗感染复合功能的钛合金表面改性方法具有重要意义。目的:研究铜、锶二元掺杂硅酸钙复合涂层改性钛合金的理化性质,评估其促成骨和抗菌方面的潜能。方法:采用球磨、造粒方法制备含有氧化铜、氧化锶及硅酸钙的复合粉末,采用大气等离子喷涂技术在钛合金(Ti6Al4V)表面制备铜锶二元掺杂硅酸钙复合涂层,对复合涂层进行表征。将钛合金浸提液、硅酸钙涂层改性钛合金浸提液、铜掺杂硅酸钙复合涂层改性钛合金浸提液、铜锶二元掺杂硅酸钙复合涂层改性钛合金浸提液分别与MC3T3-E1细胞共培养,检测材料的生物安全性与促成骨性能。将金黄色葡萄球菌(或大肠埃希菌)分别与钛合金、硅酸钙涂层改性钛合金、铜掺杂硅酸钙复合涂层改性钛合金、铜锶二元掺杂硅酸钙复合涂层改性钛合金共培养,扫描电镜、平板计数法检测材料的体外抗菌性能。结果与结论:(1)扫描电子显微镜下可见铜锶二元掺杂硅酸钙复合涂层粗糙表面存在大量的纳米结构,该复合涂层成功喷涂在钛合金表面,在体外可缓释Sr^(2+)和Cu^(2+),并且Sr^(2+)的释放浓度大于Cu^(2+);(2)CCK-8和细胞活死染色结果显示,铜掺杂硅酸钙复合涂层改性钛合金具有一定的细胞毒性,硅酸钙涂层与铜锶二元掺杂硅酸钙复合涂层改性钛合金具有良好的生物相容性;碱性磷酸酶与茜素红染色结果显示,相较于钛合金、硅酸钙涂层改性钛合金,铜锶二元掺杂硅酸钙复合涂层改性钛合金表现出更优的促成骨性能;(3)扫描电镜观察、细菌涂布和细菌计数法结果表明,相较于钛合金、硅酸钙涂层改性钛合金,铜掺杂硅酸钙复合涂层与铜锶二元掺杂硅酸钙复合涂层改性钛合金能有效抑制金黄色葡萄球菌和大肠埃希菌的生长,表现出抗菌潜能;(4)结果表明,铜锶二元掺杂硅酸钙复合涂层改性钛片具备良好的生物相容性、促成骨性能与抗菌性能。