生物活性功能涂层的结构特征与性能

采用净能量控制的等离子喷涂技术,在钛合金基体上制备出HA-ZO2生物活性功能涂层,利用纳米硬度计(nanoindentation)、扫描电镜(SEM)、X射线衍射仪(XRD)等对生物活性功能涂层的结构特征进行分析.结果表明(1)生物活性功能涂层表面分布着不同尺寸范围的孔洞,具有典型的多孔结构特征,整个涂层沿垂直基体方向从底层致密结构向表面层多孔结构过渡,涂层表面成分为生物活性的羟基磷灰石;(2)金属基体与陶瓷界面区域的弹性模量、硬度呈梯度变化,涂层的这种结构特征有利于改善生物活性涂层的综合性能,提高涂层与基体的结合强度,其结合强度达到48.6MPa.     

双步微弧氧化技术制备纯钛梯度膜层的研究

采用微弧氧化技术,以β-甘油磷酸钠和乙酸钙混合溶液为电解液,对样品进行预微弧氧化-微弧氧化复合工艺制备出含有羟基磷灰石与梯度结构的生物活性功能膜层。采用XRD、SEM、EDS等对膜层的相组成、形貌以及成分结构进行了分析,结果表明,预微弧氧化形成较小孔径结构的致密阻挡层,可以阻止基体金属离子向体内释放;进一步采用微弧氧化技术在预处理的样品表面制备出含羟基磷灰石的多孔生物活性功能膜层,使整个膜层沿垂直基体方向从致密结构的底层向多孔结构的表面层逐渐变化,膜层的成分从生物稳定性的底层向生物活性的表面层梯度变化;膜层表面成分主要由金红石型TiO2、锐钛矿型TiO2和低结晶程度的羟基磷灰石等相构成,具有梯度结构特征的膜层既保持了膜层的生物活性,又保证了膜层与基体具有高的结合强度。     

氧化锆增韧HA/ZrO2功能梯度涂层的TEM分析

利用净能量控制的PRAXAIR4500型等离子喷涂系统,在钛合金基体上制备出HA/ZrO2功能梯度涂层,采用HTEM、XRD、SEM等对涂层过渡层ZrO2相的结构特征进行分析.结果表明:(1)富锆的过渡层存在ZrO2 3种晶型,主要以四方氧化锆为主,含有少量的立方氧化锆及微量的单斜氧化锆和CaZrO3,单斜氧化锆的出现说明材料内发生了四方氧化锆向单斜氧化锆马氏体相变,这种马氏体相变有利于提高HA材料的韧性;(2)生物活性功能涂层的富锆过渡层致密,与钛合金基体结合紧密,纯羟基磷灰石的表面层具有典型的多孔结构特征,整个涂层沿垂直基体方向从过渡层致密结构向表面层多孔结构过渡;涂层的这种结构特征有利于改善功能梯度涂层的综合性能,提高涂层与基体的结合强度,其结合强度达到48.6MPa.     

磁控溅射法制备HAF/YSZ梯度复合涂层及生物性能研究

采用射频磁控溅射技术在Ti6Al4V基体上成功制备了含氟羟基磷灰石梯度复合涂层(HAF/YSZ)。利用X射线光电子能谱(XPS)、电子探针(EDX)、扫描电镜(SEM)等对涂层的成分分布、形貌、界面结合进行表征。通过模拟体液(SBF)实验,分析和评价了HAF/YSZ涂层在模拟人体条件下的生物性能。结果表明,所制备涂层表面粗糙,呈多孔岛状结构,有利于新生骨组织的生长;涂层与基体结合紧密,各层间相互扩散,整体一致性较好;经模拟体液浸泡后,涂层表面有新生物质沉积,表现出较好的生物活性及稳定性;梯度复合涂层较氟含量单一的氟羟基磷灰石涂层具有更好的抗体液溶解能力及稳定性。     

Ti6Al4V表面HAF/YSZ梯度复合涂层的制备和性能

采用射频磁控溅射技术在Ti6Al4V基体上制备含氟羟基磷灰石(HAF)梯度复合涂层,对涂层的氟含量、物相组成及形貌进行了表征,并分析了梯度复合涂层在模拟人体条件下的生物活性和稳定性。结果表明:复合涂层中的氟呈梯度分布,n(Ca)/n(P)随着涂层中氟含量的增加逐渐减小。HAF/YSZ(Y_2O_3稳定的ZrO_2,简称YSZ)复合涂层在SBF环境下生成的新物质为碳酸类骨磷灰石,氟促进磷灰石相的发育,氟含量呈梯度分布能有效提高涂层的抗体液溶解能力和与基体间的结合性能;HAF/YSZ梯度复合涂层比无氟羟基磷灰石及氟含量单一的涂层具有更好的生物活性和稳定性。     

仿生磷灰石涂层与钛基体结合强度的划痕法实验

本文采用碱热处理及SBF浸泡的方法在钛片上制备了仿生磷灰石涂层,并采用AES进行表面成分-深度分析,划痕法测定磷灰石涂层与基体的结合强度.结果显示,经碱热处理而制得的钛表面仿生磷灰石涂层与基体结合的界面为成分梯度界面,二者的结合要通过成分含量呈梯度变化的过渡层:Ca、P元素的含量从表面到基体逐渐下降,Ti元素的含量逐渐上升.热处理有利于提高涂层的基体结合强度,其原因是热处理使SBF中形成的磷灰石的晶核细小而均匀,使得表面涂层与基体之间的结合更为紧密.预钙化处理后形成的磷灰石涂层与金属之间仍为成分梯度界面,因此对涂层的基体结合强度影响不大.     

氧化锆基羟基磷灰石梯度涂层材料的研究

本文采用涂覆-烧结法制备了一种以氧化锆为基体的生物玻璃-羟基磷灰石梯度涂层材料，并对其热学、力学性能进行了测试实验发现，在生物玻璃-羟基磷灰石梯度设计时，羟基磷灰石含量对复合体材料的热膨胀性能有着较大的影响．这种影响的原因是，随着羟基磷灰石含量的变化，复合体材料的结构发生改变，从玻璃相为主晶相向羟基磷灰石为主晶相转变．文中对梯度涂层各层中的热应力进行了计算，其结果与涂层-基体的结合强度相吻合.     

两步电沉积法制备HA-Ti/HA复合涂层的研究

为了提高金属基羟基磷灰石（HA）涂层的结合强度,采用复合电沉积一电沉积两步法在含Ti粉的钙磷电解液中制备HA—Ti／HA复合涂层,对涂层的组分结构、表面形貌、热稳定性、结合强度和生物活性进行了研究．实验结果表明：两步法制备的底层为HA—Ti复合涂层,外层为纯HA涂层的HA—Ti／HA复合涂层既提高了涂层的结合强度,又保证了涂层的生物活性．当涂层中Ti粉的质量分数为51．2wt％时,涂层与基体的结合强度达到21．2MPa,约为纯HA涂层的3倍．模拟体液浸泡7天后,涂层表面即被一层球状碳磷灰石覆盖,具有良好的生物活性,与纯HA涂层相比,复合涂层具有更好的耐蚀性能．     

羟基磷灰石/生物玻璃复合涂层的研究

设计了适合在Ti6Al4V金属基体上制备涂层的生物玻璃，通过电泳沉积以及后续热处理在Ti6Al4V合金上制备了羟基磷灰石／生物玻璃复合涂层，实现了底层致密表层多孔的结构梯度。利用平底锥头法对涂层剪切强度进行了测试；利用SEM观察了其表面形貌；利用EPMA分析了复合涂层断面结构和组成。     

钛表面微弧氧化结构和成分对其润湿性的影响

通过改变微弧氧化过程中的电压及电流在钛表面分别制备了羟基磷灰石(HA)和TiO_2涂层,为分析表面不同结构和成分对材料润湿性的影响,利用超声清洗制备了具有多孔结构的HA。结果表明:对于不同形貌的HA涂层,花瓣状结构HA的润湿性优于多孔结构,且HA的花瓣越大、致密性越高,其润湿性越好;而与多孔结构的TiO_2相比,HA涂层的接触角更小,润湿性更好。     

Thermal Treatment Optimization of Electrodeposited Hydroxyapatite Coatings on Ti6Al4V Substrate

Thermal behavior of electrodeposited hydroxyapatite (HAP) coating on a titanium alloy (Ti6Al4V) is investigated in order to optimize the heat treatment conditions for this prosthetic material. The synthesized coatings are annealed in air atmosphere at 400, 600, 800, and 1000 °C, and then characterized by X‐ray diffraction (XRD) and selected area electron diffraction (SAED) for structure and phases analysis. Scanning and transmission electron microscopy associated to energy dispersive X‐ray microanalysis (SEM‐EDXS and STEM) are used for morphology and composition analysis. The results show that when the electrodeposited coating is annealed at temperatures greater than 600 °C, a well‐crystallized HAP is obtained with a notable change of its morphology. However, at these temperatures the surface of Ti6Al4V alloy (uncoated zones of the implant) is deteriorated by the formation of a thick surface oxide layer. Therefore, we limit the heat treatment temperature for the electrodeposited coatings on a Ti6Al4V alloy at 550 °C. At this optimized temperature it is demonstrated that the link between the coating and the substrate is improved and the crystallinity of the coating is controlled which make it well bioactive.     

Porous Titanium Coatings Through Electrophoretic Deposition of TiH2 Suspensions

In the biomedical field, modification of titanium surfaces to improve the osteoinductive and antibacterial behavior is widely investigated. This functionalization can be further ameliorated by providing a porous coating with high loading capacity for bioactive materials and drug delivery carriers at the implant surface. In this work, a new powder metallurgical processing route used to deposit such porous pure titanium coatings on Ti based substrates is presented. The coatings were prepared by electrophoretic deposition (EPD) of TiH₂ powder suspensions followed by dehydrogenation and sintering in vacuum. The use of hydrides allowed to lower the sintering temperature below that of the α–β transition of the Ti6Al4V substrate. Measurement of the tensile bond strength confirmed a strong adhesion of the porous coating. Deposition of powders with different grain sizes resulted in porous titanium coatings with varying thickness, pore morphology, and surface roughness. The possibility to extend this coating technique to complex shaped implants is highlighted.     

Laser surface coating of Mo–WC metal matrix composite on Ti6Al4V alloy

Laser surface alloying of Mo, WC and Mo–WC powders on the surface of Ti6Al4V alloys using a 2 kW Nd-YAG laser was performed. The dilution effect upon the microstructure, microhardness and wear resistance of the surface metal matrix composite (MMC) coating was investigated. With a constant thickness of pre-placed powder, the dilution levels of the alloyed layers were found to increase with the incident laser power. The fabricated surface MMC layer was metallurgically bonded to the Ti6Al4V substrate. The microhardness of the fabricated surface layer was found to be inversely proportional to the dilution level. The EDAX and XRD spectra results show that new intermetallic compounds and alloy phases were formed in the MMC layer. With the existence of Mo content in the pre-placed powder, the β-phase of Ti in the MMC coating can be retained at the quenching process. With increasing weight percentage content of WC particles in the Mo–WC pre-pasted powder, the microhardness and sliding wear resistance of the laser surface coating were increased by 87% and 150 times, respectively, as compared with the Ti6Al4V alloy. The surface friction of the laser-fabricated MMC coatings was also decreased as compared with the worn Ti6Al4V substrate.     

Biocompatible and mechanical properties of low temperature deposited quaternary (Ti, Al, V) N coatings on Ti6Al4V titanium alloy substrates

A series of quaternary (Ti, Al, V) N coating layers were obtained by low temperature reactive plasma sputtering in differing deposition conditions to improve the wear resistance and the biocompatibility of a titanium surgical alloy, specifically Ti-6Al-4V. Characterization of the mechanical properties, structure and the chemical composition of the coating layer was explored by microhardness test, ball against flat wear test, scanning electron microscopy and X-ray diffraction. The biocompatibility of the optimum coating layer (as determined by mechanical performance) was examined by a modified MTT toxicity test and by monitoring cell growth assessed by quantitative stereological analysis. The experimental results are encouraging, indicating that this low temperature deposited, dense, quaternary (Ti, Al, V) N coating layer exhibits improved mechanical properties such as high hardness and excellent adhesion to a Ti alloy substrate and is highly biocompatible.     

Self-assembled right handed helical ribbons of the bone mineral hydroxyapatite

Osteointegration of titanium or its alloy with bone can be greatly improved by calcium phosphate coatings, and further enhanced by an extracellular matrix protein layer such as collagen. In this study, an octacalcium phosphate (OCP)/collagen composite coating layer on Ti6Al4V substrate was prepared using electrolytic deposition method. A layer of OCP mineral consisting of flake-like crystals was first formed on the Ti6Al4V substrate. Subsequently, mineralized collagen fibrils were deposited on the former OCP layer. These collagen fibrils were interconnected and well adhered on the OCP layer so that they were immobilized. The microstructure of the composite coating varied with collagen concentration in the electrolyte. This study could offer a possibility of fabricating a desired surface matrix on orthopedic implants to enhance bone formation and fixation of implants.     

Fabrication of nano-structured HA/CNT coatings on Ti6Al4V by electrophoretic deposition for biomedical applications

In order to improve the bone bioactivity and osteointegration of metallic implants, hydroxyapatite (HA) is often coated on their surface so that a real bond with the surrounding bone tissue can be formed. In the present study, cathodic electrophoretic deposition (EPD) has been attempted for depositing nanostructured HA coatings on titanium alloy Ti6Al4V followed by sintering at 800 degrees C. Nano-sized HA powder was used in the EPD process to produce dense coatings. Moreover, multiwalled carbon nanotubes (CNTs) were also used to reinforce the HA coating for enhancing its mechanical strength. The surface morphology, compositions and microstructure of the monolithic coating of HA and nanocomposite coatings of HA with different CNT contents (4 to 25%) on Ti6Al4V were investigated by scanning-electron microscopy, energy-dispersive X-ray spectroscopy and Xray diffractometry, respectively. Electrochemical corrosion behavior of the various coatings in Hanks' solution at 37 degrees C was investigated by means of open-circuit potential measurement and cyclic potentiodynamic polarization tests. Surface hardness, adhesion strength and bone bioactivity of the coatings were also studied. The HA and HA/CNT coatings had a thickness of about 10 microm, with corrosion resistance higher than that of the substrate and adhesion strength higher than that of plasma sprayed HA coating. The properties of the composite coatings were optimized by varying the CNT contents. The enhanced properties could be attributed to the use of nano-sized HA particles and CNTs. Compared with the monolithic HA coating, the CNT-reinforced HA coating markedly increased the coating hardness without deteriorating the corrosion resistance or adhesion strength.     

钛合金表面激光熔覆Ni基梯度涂层的研究

为了改善Ti6Al4V钛合金表面耐磨性能和抗高温氧化性能,采用CO2激光在Ti6Al4V钛合金表面进行激光熔覆Ni基梯度涂层试验.利用扫描电镜和显微硬度计等手段分析了熔覆层组织,测试了基体和熔覆层的显微硬度.结果表明,采用适当的工艺参数,可以在钛合金表面获得连续、均匀、无裂纹和气孔的熔覆层.熔覆层组织由树枝晶和晶间共晶组织构成,并与基体形成牢固的冶金结合.由基体到表面,显微硬度过渡平稳,呈明显梯度渐变特征.