Deposition of Nanostructured Fluorine‐Doped Hydroxyapatite Coating from Aqueous Dispersion by Suspension Plasma Spray

In this study, we prepared an aqueous dispersion of fluorine‐doped hydroxyapatite (FHA) nanoparticles by a wet chemical method. For the first time, the as‐prepared aqueous dispersion of FHA nanoparticles was directly used as suspension for depositing nanostructured FHA coating on stainless steel substrate by suspension plasma spray (SPS) method. Field‐emission scanning electron microscopy images confirm that the coating was nanostructured. X‐ray Diffraction pattern, Fourier‐transform infrared spectroscopy, and Raman spectra show that the as‐sprayed coating was FHA phases. The experimental result confirmed that OH^? and F^? ions have been well kept in FHA crystal lattice and structural integrity has been maintained during SPS process by using an aqueous dispersion of FHA nanoparticles. The potentiodynamic polarization and electrochemical impedance spectroscopy results prove that the nanostructured FHA coating can greatly enhance the anticorrosion performance of stainless steel in phosphate‐buffered saline solution.     

Hydroxyapatite Coating on Titanium Substrate by the Sol-Gel Process

Hydroxyapatite coatings on titanium were attempted by a sol-gel process combined with conventional heat treatment and with UV irradiation at ambient temperature after dipping/ withdrawing a substrate into/from the sol. X-ray diffraction data showed that a coating film prepared by heat treatment was amorphous and crystallized in Ca₅(PO₄)₃(OH) at a temperature of 773–973 K. The infrared spectra for coating films that have been prepared by heat treatment at a temperature of 573–873 K were in fair agreement with those for a coating film prepared by UV irradiation. After ethylene oxide sterilization, the cytotoxicity of coating film decreased with increasing irradiation time in UV irradiation, whereas it decreased with increasing temperature in conventional heat treatment. In comparisons between ethylene oxide sterilization and autoclave sterilization, the coating film sterilized by autoclave had much lower cytotoxicity than that sterilized by ethylene oxide. Furthermore, an animal test in the transfemoral drill hole on a rat for 4 weeks was examined using an implant prepared by heat treatment and autoclave sterilization. The sol-gel-coated titanium had slightly higher bone apposition than uncoated titanium as a control material.     

电泳沉积磷灰石生物陶瓷涂层的研究进展

羟基磷灰石(HA)生物涂层材料是最有发展前途的生物硬组织替代材料之一.电泳沉积具有装置简单,操作方便,非线性,沉积温度低等特点,可以解决传统HA生物陶瓷涂层制备工艺上的各种不足.文中探讨了电泳沉积的各种工艺影响因素,综合介绍了国内外有关电泳沉积HA复合(梯度)生物涂层和电泳沉积与其它方法复合制备HA生物涂层的研究报道,进而提出了相应的设想和展望.     

Hydroxyapatite Coating on Thermally Oxidized Titanium Substrates

Titanium substrates were oxidized in oxygen or air at temperatures of 600°–800°C, then immersed in solutions of 2.0m M – 20.7m M CaCl₂ and 1.2m M –12.4m M KH₂PO₄ for aging periods of 0.5–10 d. The titanium surface was successfully coated with hydroxyapatite (HAP) when the substrates were oxidized in oxygen gas at 610°C for 1 h and then aged in a solution of 2.00m M Ca²⁺ and 1.20m M PO₄³⁻. The Ca/P ratio of the surface coating increased toward its stoichiometric HAP value (return 10/6) as the aging time increased; the Ca/P ratio attained a value of 1.66 after 10 d.     

羟基磷灰石涂层的生物仿生法研究进展

羟基磷灰石的生物复合涂层具有很高的外科应用价值.制备羟基磷灰石复合材料的方法有很多种,其中仿生法模仿了自然界生理磷灰石的矿化机制,在类似于人体组织内环境条件的水溶液中自然沉积出磷灰石层.仿生法具有许多其它方法无可比拟的优越性.本文对近年来文献报道中出现的生物仿生法进行了综述,阐述了各种仿生法中包括对基体进行预处理使其表面官能团化,再将基体在模拟体液中浸泡从而使磷灰石自然沉积的模拟生物矿化的4个阶段的工艺过程及其仿生机理.     

Plasma-Resistant Dense Yttrium Oxide Film Prepared by Aerosol Deposition Process

Dense yttrium oxide film was prepared on a quartz substrate by the aerosol deposition process at the room temperature. The deposition rate was very high, 60 m/h. Thick film of 10 m was easily achievable on the quartz substrate. Transmission electron microscopy showed that the film was highly dense without voids and was composed of randomly oriented Y₂O₃ crystallites of sizes smaller than 20 nm. The interface between the film layer and the quartz substrate was homogeneous. The film (2-m thick) had a high transmittance (55–85%) in the wavelength region of 250-800 nm. The mechanical properties of the film were very good. The adhesion force of the interface between the Y₂O₃ layer and the quartz substrate was over 80 MPa. The Vickers hardness of the film was 7.7 GPa. The film also had an excellent plasma resistance in a gas mixture of CF₄/O₂. Outstanding results were noted in eroded depth, surface roughness, nanostructure, and transmittance change after plasma exposure of the film.     

Composition and Crystallization of Hydroxyapatite Coating Layer Formed by Electron Beam Deposition

To improve the biocompatibility of Ti-based metal implants, a hydroxyapatite (HA) coating layer was formed on the surface by electron-beam deposition. The dissolution rate of the coating layer was strongly dependent on the layer's calcium/phosphorus (Ca/P) ratio. Layers with a Ca/P ratio close to that of crystalline HA (Ca/P = 1.67) showed good stability in a physiologic saline solution. When the layer was crystallized by heat treatment in air at temperatures between 400° and 500°C, the stability was enhanced further while maintaining good interfacial bonding strength with the substrate. Preliminary in vivo tests on rabbits indicated that heat treatment and the resultant enhancement in stability are beneficial for bone attachment to the implants.     

溶胶凝胶法制备羟基磷灰石/TiO2复合生物活性涂层的研究

通过溶胶凝胶法在纯钛基体上制备了羟基磷灰石/TiO2复合生物活性涂层.HA可以提高钛基的生物活性,TiO2可以提高涂层与基体的物理、化学相容性和结合强度.HA和TiO2溶胶由前驱体制得,按不同物质的量比直接混合两种溶胶来制备复合溶胶.使用XRD、SEM研究了不同温度下热处理后涂层的组成和结构.实验结果表明HA的结晶度和晶粒随着温度的升高而提高和变大;涂层表面为连续多孔结构.粘结拉伸结果表明复合涂层与基体结合良好,较纯HA涂层与基体的结合强度有较大提高.复合涂层试样于SBF中浸泡2d、7d和14d的SEM分析结果表明复合涂层表面的磷灰石形成量较高.电位动力学曲线分析表明复合涂层可以提高基体的耐蚀性.     

纯钛表面电沉积羟基磷灰石复合涂层组织及性能

采用水热电沉积法在纯钛基体表面制备前驱体,对其进行碱液处理和真空热处理后得到羟基磷灰石(HA)复合涂层.采用XRD、SEM和激光共聚焦显微镜分析涂层物相结构、组织形貌,利用热震法和模拟体液浸泡法表征涂层结合强度和生物活性.实验结果表明:前驱体主要成分为CaHPO4·2H2O、Ca3(PO4)2和CaTiO3,经室温碱液处理10 h后,涂层物相由Ca10(PO4)6(OH)2(简称:HA)、Ca3(PO4)2和CaTiO3组成,组织形貌由前驱体的块状转变为细针状HA晶体.当温度一定时,涂层厚度在4.5 V电压下达到最大值38μm,热震次数在4 V电压下达到最大值11次;当电压一定时,涂层厚度在40℃和50℃下均为最大值35μm,热震次数在40℃下达到最大值11次.沉积电压为4 V、水浴温度为40℃工艺条件下的涂层经体外生物活性测试表明:HA复合涂层表面可在模拟体液中形成新的HA晶核,并不断长大.     

碱处理法制备钛合金表面羟基磷灰石涂层

采用碱处理法制备钛基羟基磷灰石涂层,考察了碱液处理中有关钛合金表面活化参数对其诱导羟基磷灰石沉积速度的影响,采用X射线衍射和扫描电镜对样品的化学组成、结构和性能进行了表征,确定了钛合金表面活化处理的最优参数.结果表明,钛基体经10 mol/L氢氧化钠,饱和硝酸钙预钙化处理,模拟体液中培养后,羟基磷灰石沉积速度快,14 d就可形成致密﹑均匀﹑裂纹少的涂层;碱液处理后饱和硝酸钙溶液预钙化可得到片状的羟基磷灰石生物矿化层;且钛基体在600 ℃的热处理是HAP涂层沉积的重要条件之一.与相关研究相比较,该方法的优点在于可在形状复杂的植入体上形成均匀的涂层,工艺简单,并且涂层与基体结合牢固.     

溶胶凝胶法制备钛基羟基磷灰石涂层的研究

混合硝酸钙乙醇溶液和磷酸三甲酯水溶液作为羟基磷灰石(HA)前驱体,利用旋转涂膜技术在钛片表面制备羟基磷灰石涂层.研究了溶胶陈化时间和凝胶热处理温度对涂膜的影响,同时对涂层的生物活性进行了研究.样品利用X射线衍射仪(XRD)和扫描电子显微镜(ESEM)进行表征.结果表明:利用经过24 h陈化的溶胶涂膜的样品在500℃热处...     

Oxidation Behavior of Ferritic Steel Alloy Coated with Highly Dense Conducting Ceramics by Aerosol Deposition

Conducting La_0.8Sr_0.2MnO₃ (LSM) ceramic layers with a thickness of ∼10 μm were deposited on ferritic stainless steel (SS) by aerosol deposition for use as an oxidation resistance coating layer in the metallic interconnects of solid oxide fuel cell. The microstructural evolution and electrical properties of the LSM-coated SS were observed. The coated layers were fairly dense without pores or cracks, and maintained good adhesion even after oxidation at 800°C for 1000 h in air atmosphere. The surface of the bare SS after heat treatment at 800°C for 1000 h was covered with Cr-containing oxide scales, and the electrical conductivity was sharply decreased. However, the LSM-coated SS alloy showed a surface microstructure with almost no chromic oxide formation and maintained good electrical conductivity after the heat treatment. Close observation of the interface between LSM and SS indicated the presence of ∼500-nm-thick Cr₂O₃ and MnCr₂O₄ spinel phase, which may have caused the long-time deterioration of the interconnector performance. The area-specific resistance of the LSM-coated alloy after heat treatment at 800°C for 1000 h was 10.4 mΩ·cm².     

Improvement of Hydroxyapatite Sol–Gel Coating on Titanium with Ammonium Hydroxide Addition

Small amounts (1–5 vol%) of ammonium hydroxide (NH₄OH) were added to the ethanol–water-based hydroxyapatite (HA) sol–gel solution. After aging the sol, a Ti substrate was dip-coated and heat-treated at 500°C for 1 h in air. The sol properties were monitored in terms of pH, viscosity, and structure changes with aging time; also, the coating phase and structure on Ti were investigated. During aging, the viscosity of the sol increased while the pH decreased, confirming the polymerization and gelation of the sol. The addition of NH₄OH altered the sol properties significantly. Increase in the NH₄OH concentration increased the pH and viscosity of the sol considerably, especially at short aging period, followed by a saturation with further aging. The Fourier transformed-infrared analysis also confirmed a gradual structure change of the sol with NH₄OH addition. Such changes in pH, viscosity, and structure bands of the sol driven by the NH₄OH addition were attributed to the improved polymerization and gelation of the sol. The improved gelation shortened the aging time needed for crystallization of the apatite coating, i.e., increase in the NH₄OH addition improved the crystallization of the coatings. Within 24 h aging time, the coatings on Ti containing over 3.5 vol% NH₄OH showed characteristic HA phase and structure bands, at which period no apatite peaks were observed on the HA coating obtained without NH₄OH addition.     

Deposition Via Dip Coating Technique of Dense Yttrium Stabilized Zirconia Layers

A deposition of yttrium stabilized zirconia layer for its use as an electrolyte in solid oxide fuel cell was performed using dip coating technique. Two commercially available surfactant systems were evaluated; nonionic surfactant which stabilizes only by steric repulsion and anionic surfactant which provides both steric and electrostatic repulsion. Dip coating process was optimized to two step deposition process. Uniform 10–15 μm thick yttria stabilized zirconia (YSZ) electrolyte layer is obtained after the final sintering step at 1400°C. Impedance spectroscopy measurements showed that selected phosphate ester based surfactant has negligible effect on the performance of the YSZ material as electrolyte.     

Oxidation Resistance Coating of LSM and LSCF on SOFC Metallic Interconnects by the Aerosol Deposition Process

Conductive La_0.8Sr_0.2MnO₃ (LSM) and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) layers with a thickness of ∼10 μm were deposited on ferritic stainless steel (SS) by the aerosol deposition method, for use as an oxidation resistance-coating layer in the metallic interconnector of a solid oxide fuel cell. The coated layers were fairly dense without pores or cracks, and maintained good adhesion even after oxidation at 800°C for 100 h. The surface of the bare SS after annealing at 800°C for 100 h was covered with Cr₂O₃ and Fe₃O₄ oxide scales, and the electrical conductivity was sharply decreased. However, the LSM- and LSCF-coated SSs showed a surface microstructure with almost no oxidation and maintained good electrical conductivity after annealing at 800°C for 100 h. The area-specific resistance (ASR) of LSM- and LSCF-coated alloys after 100 h of oxidation at 800°C was 20.6 and 11.7 mΩ·cm², respectively.     

Surface Characterization and Biocompatibility of Selenium‐Doped Hydroxyapatite Coating on Titanium Alloy

Selenium‐doped hydroxyapatite (HA) was biomimetically coated on Ti6Al4V plates with the aim of combining the anticancer and antibacterial properties of selenium with the biocompatibility and bioactivity of HA. For the coating process, the composition of 1.5 × SBF (solution with ion concentrations at 1.5 times that of simulated body fluid, SBF) was modified to include 0.15 mM selenate (SeO₄^2?) ion. The selenium‐doped HA coating was characterized by several methods, such as scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy. The cytotoxicity of selenium on osteoblast and osteosarcoma cells was determined. The coating was shown to inhibit the growth of Staphylococcus epidermidis.     

Preparation of Highly Dense PZN–PZT Thick Films by the Aerosol Deposition Method Using Excess-PbO Powder

Lead zinc niobate–lead zirconate titanate thick films with a thickness of 50–100 μm were deposited on silicon and alumina substrates using the aerosol deposition method. The effects of excess lead oxide (PbO) on stress relaxation during postannealing were studied. Excess PbO content was varied from 0 to 5 mol%. The as-deposited film had a fairly dense microstructure with nanosized grains. The films deposited on silicon were annealed at temperatures of 700°C, and the films deposited on sapphire were annealed at 900°C in an electrical furnace. The annealed film was detached and cracks were generated due to the high residual compressive stress and thermal stress induced by thermal expansion coefficient mismatch. However, the film deposited using powder containing 2% of excess PbO showed no cracking or detachment from the substrate after the postannealing process. The PbO evaporation at elevated temperature during the postannealing process seemed to have reduced the residual compressive stress. The remanent polarization and relative dielectric constant of the 50 μm thick films annealed at 900°C were 43.1 μC/cm² and 1400, respectively, which were comparable with the values of a bulk specimen prepared by a powder sintering process.     

共沉淀法制备羟基磷灰石影响因素的研究

论述了共沉淀法制备羟基磷灰石粉体的过程,以Ca(OH)2和H3PO4为原料,控制适当Ca/P的比、H3PO4的滴加速率、溶液的pH值、反应温度和时间以及煅烧温度等条件,采用电子显微镜、X射线衍射仪和红外光谱仪对目标产物的结构和粒度进行了分析。结果表明,溶液在40℃下反应6 h,煅烧温度为900℃,产物用无水乙醇洗涤可获得纯度、结晶度、颗粒度和分散性均较好的羟基磷灰石粉体。     

羟基磷灰石涂层的制备

本文以五氧化二磷、无水乙醇、硝酸钙为原料,通过溶胶-凝胶法制备羟基磷石灰涂层。选用2mm/s的速度浸渍提拉载玻片,在载玻片上进行涂膜,经60℃干燥后在650℃烧结保温3h,可在载玻片上得到羟基磷灰石涂层。研究结果表明:制备溶胶合适的配比为Ca(NO3)22·4H2O:P2O5(摩尔比)=10:3,即Ca/P原子比=5:3(约等于1.67)。