低温熔盐电沉积羟基磷灰石复合涂层的研究

为了提高羟基磷灰石涂层的结合强度,在AlCl3-NaCl-TiCl3低温熔盐体系中加入HA微粒,复合电沉积制备Al-Ti/HA复合涂层,并对涂层的表面形貌、结构和结合强度进行了研究.结果表明: HA微粒均匀分散在Al-Ti合金镀层中,其共沉积量随电流密度的减小和熔盐中HA浓度的增大而增强;涂层的结合强度随HA共沉积量的增大而增强,当HA的共沉积量为40.1%(质量分数)时,Al-Ti/HA复合涂层的结合强度达到28.1 MPa.     

电沉积镍-羟基磷灰石工艺研究

采用电沉积法在1Crl8Ni9Ti基体上制备出Ni-羟基磷灰石(HA)生物陶瓷复合镀层。探讨了工艺条件对复合镀层中微粒含量的影响。结果表明，随镀液中HA粒子悬浮量增大，镀层中HA微粒含量增大；温度和搅拌速度提高，镀层中HA含量降低；随阳极电流密度增加，镀层中HA微粒含量增加，当达到一定数值(1．5A／dm^2)后，HA含量则开始降低。     

纯钛表面HA/BG生物复合涂层的组织结构研究

通过高温熔烧法在工业纯钛ＴＡ３表面制备出不同羟基磷灰石含量的羟基磷灰石与生物玻璃的复合涂层（简称ＨＡ／ＢＧ）,对复合涂层的微观组织结构进行了研究,结果表明,所制生物玻璃的高温处理的过程中会析出六方柱状的ＨＡ晶体,复合涂层具有粗糙表面,存在很多开放性气孔,随着ＨＡ原始含量的增加,复合涂层的致密度明显降低,而复合涂 ＨＡ相的衍射峰强度变化不大。     

Formation of highly oriented hydroxyapatite in hydroxyapatite/titanium composite coating by radio-frequency thermal plasma spraying

Highly oriented hydroxyapatite (HA) coatings with excellent adhesion were successfully obtained on titanium (Ti) and titanium alloy through a radio-frequency thermal plasma spraying method. The ratio of HA and Ti powders supplied into the plasma was precisely controlled by two microfeeders so as to change the composition from Ti-rich to HA-rich toward the upper layer of the formed coatings. The bond (tensile) strength of the HA/Ti composite coatings was ca. 40–50 MPa. XRD patterns showed that the topmost HA layer of the coatings had an apatite structure with (00l) preferred orientation. The degree of this orientation showed a tendency to increase with an increase in the substrate temperature during spraying.     

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.     

X-ray diffraction and fourier transform infrared analysis of nanophase apatite coatings prepared by electrocrystallization

The concept of biological fixation of artificial joint prosthesis by using bioactive calcium phosphate coatings has generated considerable interest in recent years. This paper reports an electrocrystallization process for fabricating stoichiometric and non-stoichiometric hydroxyapatite (HA) coatings with nanometer size crystals similar to biogenic apatite. X-ray diffraction and Fourier Transform Infrared (FTIR) spectroscopy were used to characterize the structure and chemical composition of the HA coatings.As-deposited coatings at 65°C were poorly crystalline, Ca-deficient HA with a crystallite size of about 35 nm and exhibited apatitic characteristics similar to bone apatite. Post-treatment of coatings in steam at 125°C followed by calcining at 425°C resulted in the transformation of the initial phase to a well-defined stoichiometric HA with a crystallite size of about 100 nm.     

Hydroxyapatite-anatase-carbon nanotube nanocomposite coatings fabricated by electrophoretic codeposition for biomedical applications

In order to eliminate micro-cracks in the monolithic hydroxyapatite (HA) and composite hydroxyapatite/carbon nanotube (HA/CNT) coatings, novel HA/TiO₂/CNT nanocomposite coatings on Ti6Al4V were attempted to fabricate by a single-step electrophoretic codeposition process for biomedical applications. The electrophoretically deposited layers with difference contents of HA, TiO₂ (anatase) and CNT nanoparticles were sintered at 800°C for densification with thickness of about 7–10 μm. A dense and crack-free coating was achieved with constituents of 85 wt% HA, 10 wt% TiO₂ and 5 wt% CNT. Open-circuit potential measurements and cyclic potentiodynamic polarization tests were used to investigate the electrochemical corrosion behavior of the coatings in vitro conditions (Hanks’ solution at 37°C). The HA/TiO₂/CNT coatings possess higher corrosion resistance than that of the Ti6Al4V substrate as reflected by nobler open circuit potential and lower corrosion current density. In addition, the surface hardness and adhesion strength of the HA/TiO₂/CNT coatings are higher than that of the monolithic HA and HA/CNT coatings without compromising their apatite forming ability. The enhanced properties were attributed to the nanostructure of the coatings with the appropriate TiO₂ and CNT contents for eliminating micro-cracks and micro-pores.     

Silicon-substituted hydroxyapatite: The next generation of bioactive coatings

Silicon-substituted hydroxyapatite (Si–HA) coatings with three different Si compositions (0.8, 2.2 and 4.9 wt.%) were produced as thin films on titanium substrates by magnetron co-sputtering. Following heat-treatment, a crystalline, single-phase apatite structure was obtained for all coatings, as evidenced by the presence of characteristic peaks for HA in X-ray diffraction traces, and infrared absorption P–O and O–H bands. A human osteoblast-like (HOB) cell model was employed to assess the biocompatibility of these Si–HA coatings. Unsubstituted HA thin coatings were used as a control. The results demonstrated that Si–HA elicited a significantly more rapid growth response by the HOBs as compared to HA, although cells spread well on both coatings, with the formation of extracellular matrix. The cytoskeletons on Si–HA showed clear and distinct actin filaments that were parallel to the long axis of the cells. In contrast, a more diffuse actin cytoskeleton organisation was observed on HA. Biomineralisation was seen on both coatings after 42 days of culturing, with a higher level observed on the Si–HA samples. In conclusion, Si–HA offers great potential as a coating material for future medical applications in hard and soft tissue replacements.     

Morphology and immersion behavior of plasma-sprayed hydroxyapatite/bioactive glass coatings

A series of hydroxyapatite/bioactive glass (HA/BG) coatings have been plasma-sprayed on Ti6Al-4V substrate using HA/BG powders that were prepared by both sinter-granulation and direct mixing methods. The morphology and immersion behavior of these coatings in a simulated body fluid (SBF) were investigated. The results showed that in-house fabricated BG and sinter-granulated HA powders were irregularly shaped and dense. When 5 wt % or more BG was added in HA, the powder became rough and porous. X-ray diffraction (XRD) patterns showed that the presence of BG enhanced the decomposition of HA structure during fabrication of the powders. Reasonably high bond strengths were obtained from all coatings. The granulated type HA/BG coatings showed no significant differences in bond strength from the mixed type HA/BG coatings. The plasma spray process itself and the presence of BG enhanced the decomposition of apatite. Surface morphology of all sinter-granulated type coatings was similar to that of monolithic HA coating, that was comprised of patches of smooth and shiny glassy film and irregularly-shaped particles on its surface. The dissolution depth of plasma-sprayed coatings immersed in SBF was largely dependent on the type and composition of the coating. Granulated type HA/BG coatings were much less dissolvable than monolithic HA or mixed type HA/BG coatings. It seems that the presently used granulation method for the preparation of HA/BG powders plays a predominant role in determining the dissolution behavior of the plasma-sprayed coatings. ©©2000 Kluwer Academic Publishers     

Hydrothermal-electrochemical codeposited hydoxyapatite/yttria-stabilized zirconia composite coating

Hydroxyapatite(HA)/yttria-stabilized zirconia(YSZ) composite coatings were deposited on titanium substrates using a hydrothermal electrochemical method in an electrolyte containing calcium, phosphate ions and YSZ particles. HA/YSZ composite coatings were prepared in different conditions with different electrolyte temperatures(100 ∼ 200°C), current densities(0.1 ∼ 10.0 mA/cm²), and particles content in bath(0 ∼ 100 g/L). The effect of YSZ additions on the phase composition, microstructure, thermal stability, corrosion behavior and the bonding strength of HA/YSZ composite coatings were studied. The results show that crystallinity of HA in HA/YSZ composite coatings increase continuously with the electrolyte temperature and close to stoichiometric HA. The n(Ca)/n(P) ratio at 200°C is about 1.67 according with stoichiometric HA. YSZ particles are imbedded uniformly between the HA crystals. The average HA crystal size are reduced owing to the additions of YSZ particles. After annealing at 1200°C, tetragonal phase YSZ tend to react with the released CaO to form cubic phase YSZ and CaZrO₃, which cause destabilization of HA to decompose into more α-TCP phase. The bonding strength between HA/YSZ composite coatings and titanium substrates increase with increasing volume content of YSZ in the composite coatings (V %). HA/YSZ composite coatings exhibit a better electrochemical behavior than pure HA coatings and uncoated Ti metals.     

Coatings of needle/stripe-like fluoridated hydroxyapatite on H2O2-treated carbon/carbon composites prepared by induction heating and hydrothermal methods

A hydroxyapatite (HA) coating was achieved on H₂O₂-treated carbon/carbon (C/C) composite through hydrothermally treating and induction heating deposited CaHPO₄ coating in an ammonia solution under ultrasonic water bath. Then, this HA coating was placed in a NH₄F solution and hydrothermally treated again to fabricate fluorinated hydroxyapatite (FHA) coatings for 24 h at 353, 373, 393 and 413 K, respectively. The structure, morphology and chemical composition of the HA and FHA coatings were characterized by SEM, XRD, EDS and FTIR, and the adhesiveness and chemical stability of these FHA coatings were examined by a scratch test and an immersion test, respectively. The results showed that the as-prepared FHA coatings contained needle-like or stripe-like crystals, different from those of the HA coating. As the fluoridation temperature rose, the adhesiveness of the FHA coating first increased from 34.8 to 40.9 N at a temperature between 353 and 393 K, and then decreased to 24.2 N at 413 K, while the dissolution rate of the FHA coating decreased steadily. The reasons for the property variation of the FHA coatings were proposed by analyzing the morphology, composition and structure of the coatings.     

Surface microstructure and cell biocompatibility of silicon-substituted hydroxyapatite coating on titanium substrate prepared by a biomimetic process

Silicon-substituted hydroxyapatite (Si-HA) coatings with 0.14 to 1.14 at.% Si on pure titanium were prepared by a biomimetic process. The microstructure characterization and the cell compatibility of the Si-HA coatings were studied in comparison with that of hydroxyapatite (HA) coating prepared in the same way. The prepared Si-HA coatings and HA coating were only partially crystallized or in nano-scaled crystals. The introduction of Si element in HA significantly reduced P and Ca content, but densified the coating. The atom ratio of Ca to (P + Si) in the Si-HA coatings was in a range of 1.61–1.73, increasing slightly with an increase in the Si content. FTIR results displayed that Si entered HA in a form of SiO₄ unit by substituting for PO₄ unit. The cell attachment test showed that the HA and Si-HA coatings exhibited better cell response than the uncoated titanium, but no difference was observed in the cell response between the HA coating and the Si-HA coatings. Both the HA coating and the Si-HA coatings demonstrated a significantly higher cell growth rate than the uncoated pure titanium (p < 0.05) in all incubation periods while the Si-HA coating exhibited a significantly higher cell growth rate than the HA coating (p < 0.05). Si-HA with 0.42 at.% Si presented the best cell biocompatibility in all of the incubation periods. It was suggested that the synthesis mode of HA and Si-HA coatings in a simulated body environment in the biomimetic process contribute significantly to good cell biocompatibility.     

Compositional and structural control in bone regenerative coatings

The development of a low-temperature method of producing bioactive coatings for medical implants has been shown to bypass the problems associated with high temperature processing routes, in particular the appearance of amorphous phases and non-stoichiometric hydroxyapatite (HA), and delamination of the coating from the substrate. An electric field/aqueous solution technique for producing adherent, crack-free calcium phosphate coatings on titanium and stainless steel substrates is described. The characteristics of the coating are a function of electrode spacing, supersaturation, temperature and current and voltage conditions. Scanning electron microscopy (SEM) characterized the surface morphology of the coatings, which were shown to be HA. The possibility of producing a coating of carbonate-substituted HA having the same chemical composition as bone apatite, and forming at physiological temperatures, has also been demonstrated. The size of the microstructure decreased and the morphology changed as the carbonate ion concentration in the calcium and phosphate ion solution increased. © 1999 Kluwer Academic Publishers     

Electrospray deposition of nanohydroxyapatite coatings: A strategy to mimic bone apatite mineral

The biological performance of orthopaedic and oral metallic implants can be enhanced significantly by the application of bioactive coatings. In this work, a cost-efficient alternative to the traditional technique to produce a hydroxyapatite (HA) coating with a nanostructured feature onto a metallic implant surface at room temperature via electrospray deposition, is presented. To evaluate the bioactive capacity of these nanoHA (nHA) coatings in vitro, an acellular simulated body fluid soaking experiment and a human osteoblast (HOB) cell culture work were conducted. Under these physiological conditions, the accelerated apatite precipitation process occurred on the nHA-coated titanium surfaces as compared to the uncoated titanium surfaces. HOB cells developed mature cytoskeletons with distinct evidence of actin stress fibres and vinculin adhesion plaques, on these nHA coatings. Hence, this deposition technique holds great potential in producing high quality nHA coatings for biomedical applications.     

牛血清环境下等离子喷涂ZrO_2增强羟基磷灰石涂层的摩擦磨损性能

为了研究ZrO_2增强羟基磷灰石(HA)复合涂层在牛血清润滑环境下的摩擦磨损性能,首先,采用等离子喷涂技术在钛合金基体上制备了ZrO_2含量分别为0、15wt%和30wt%的HA生物陶瓷涂层;然后,分析了ZrO_2/HA复合涂层的物相成分和结合强度;最后,采用UMT-3销盘摩擦试验机研究了ZrO_2/HA复合涂层在牛血清润滑环境下的摩擦磨损性能,观察涂层磨损表面微观形貌并分析了磨损机制。结果表明:HA涂层的主要物相为HA,15wt%ZrO_2/HA复合涂层和30wt%ZrO_2/HA复合涂层中的ZrO_2以立方相形式存在,并且衍射峰强度高于HA的。随着ZrO_2含量增大,涂层的结合强度明显增大。ZrO_2/HA复合涂层与纯HA涂层相比,有更好的耐磨性和更低的摩擦系数。纯HA涂层的磨损机制以犁沟效应和磨粒磨损为主,而15wt%ZrO_2/HA复合涂层和30wt%ZrO_2/HA复合涂层的磨损机制为脆性剥落磨损。     

Silicon–hydroxyapatite bioactive coatings (Si–HA) from diatomaceous earth and silica. Study of adhesion and proliferation of osteoblast-like cells

The aim of this study consisted on investigating the influence of silicon substituted hydroxyapatite (Si–HA) coatings over the human osteoblast-like cell line (SaOS-2) behaviour. Diatomaceous earth and silica, together with commercial hydroxyapatite were respectively the silicon and HA sources used to produce the Si–HA coatings. HA coatings with 0 wt% of silicon were used as control of the experiment. Pulsed laser deposition (PLD) was the selected technique to deposit the coatings. The Si–HA thin films were characterized by Fourier Transformed Infrared Spectroscopy (FTIR) demonstrating the efficient transfer of Si to the HA structure. The in vitro cell culture was established to assess the cell attachment, proliferation and osteoblastic activity respectively by, Scanning Electron Microscopy (SEM), DNA and alkaline phosphatase (ALP) quantification. The SEM analysis demonstrated a similar adhesion behaviour of the cells on the tested materials and the maintenance of the typical osteoblastic morphology along the time of culture. The Si–HA coatings did not evidence any type of cytotoxic behaviour when compared with HA coatings. Moreover, both the proliferation rate and osteoblastic activity results showed a slightly better performance on the Si–HA coatings from diatoms than on the Si–HA from silica.     

Sputter deposition of calcium phosphate/titanium dioxide hybrid thin films

The application of either hydroxyapatite (HA) or titanium dioxide (TiO₂) as coatings onto existing bioinert materials has been explored as the key route for enhancing the surface properties of hard tissue implant devices. However, it has been proposed that composite HA/TiO₂ coatings may provide significant advantages for the application of such surfaces. This work reports on the surface properties of such composite HA/TiO₂ surfaces produced by the sputter deposition of HA onto a titanium surface and their subsequent thermal processing using either post deposition (PDA) or in situ annealing (ISA). For both the PDA and ISA coatings, a hybrid nature was only achieved in the uppermost surface region after annealing at 700 °C. It was observed that the Ca/P ratio decreased with increasing annealing temperature for the PDA coatings and that the coating annealed to 700 °C had a value of 1.82 ± 0.07, which was closest to stoichiometric HA. In comparison, the Ca/P ratio of the ISA samples increased with increasing annealing temperature. It has been shown that the resultant coatings have surface properties that are dependent on the annealing profiles employed, and that a temperature of 700 °C is required in order to create a Ca–P/TiO₂ hybrid surface.     

Pulsed laser deposition of hydroxyapatite on titanium substrate with titania interlayer

Pulsed laser deposition (PLD) has been used to deposit hydroxyapatite (HA) ceramic over titanium substrate with an interlayer of titania. PLD has been identified as a potential candidate for bioceramic coatings over metallic substrates to be used as orthopedic and dental implants because of better process control and preservation of phase identity of the coating component. However, direct deposition of hydroxyapatite on titanium at elevated temperature results in the formation of natural oxide layer along with some perovskites like calcium titanate at the interface. This leads to easy debonding of ceramic layer from the metal and thereby affecting the adhesion strength. In the present study, adherent and stable HA coating over Ti6Al4V was achieved with the help of an interlayer of titania. The interlayer was made to a submicron level and HA was deposited consecutively to a thickness of around one micron by exposing to laser ablation at a substrate temperature of 400°C. The deposited phase was identified to be phase pure HA by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and inductively coupled plasma spectrometry. The mechanical behavior of coating evaluated by scratch test indicates that the adhesion strength of HA coating was improved with the presence of titania interlayer.     

炭/炭复合材料表面等离子体喷涂羟基磷灰石涂层的生物学性能

采用等离子体喷涂法在炭/炭复合材料基体上制备了羟基磷灰石涂层,并对所制材料开展体外模拟和试验.结果表明:在体外模拟生理环境的Ringer溶液中,涂层组成相随浸泡时间发生变化.涂层表面有新生羟基磷灰石结晶析出并聚集长大.骨内种植试验期间,动物末出现排异和炎症反应,涂层与基体结合良好.组织学观察发现,涂层与骨界面处有明显的组织改建和新骨形成形态.炭/炭复合材料表面等离子体喷涂羟基磷灰石涂层作为一种潜在的骨组织修复材料具有良好的应用前景.     

微束等离子喷涂羟基磷灰石涂层

采用微束等离子喷涂(MPS) 在Ti6Al4V基体上制备了羟基磷灰石(HA)涂层, 并以大气等离子喷涂(APS)为对照. 利用光学显微镜、SEM和XRD分析技术对MPS涂层形貌、相组成和结晶度进行了研究. 结果表明: 在微束等离子喷涂过程中, HA 的分解程度比大气等离子喷涂有显著降低, 除了HA相, 仅形成β-TCP相和非晶相. MPS涂层的结晶度主要受喷涂距离的影响. 喷涂距离较短(<80mm)时, 涂层结晶度高于APS方法制备的涂层. 喷涂距离在130mm时, 涂层结晶度低. 大气等离子喷涂层含有β-TCP、α-TCP、TTCP、CaO和非晶. MPS涂层分解较APS少的主要原因是喷涂过程中HA粒子过热不严重.