水蒸气处理对钛合金表面羟基磷灰石涂层结构的影响

目的 制备结晶度较高且裂纹较少的羟基磷灰石涂层。方法 采用等离子喷涂法，在不同功率下，于钛合金表面制备羟基磷灰石涂层。通过水蒸气处理法，在不同温度下处理羟基磷灰石涂层。使用扫描电子显微镜（SEM）和X射线衍射仪（XRD）分析羟基磷灰石的表面形貌和晶体结构。结果 当等离子喷涂功率从20 kW增大到29 kW时，羟基磷灰石涂层的沉积效率先增大后稳定，涂层结晶度先增大后减小，涂层中氧化钙的含量先增大后稳定。当喷涂功率为23 kW时，羟基磷灰石涂层结晶度较高。水蒸气处理能明显去除涂层中的α-磷酸三钙、β-磷酸三钙和氧化钙，当水蒸气处理温度从140 ℃增大到200 ℃时，羟基磷灰石涂层晶粒由棒状向颗粒状转变，涂层结晶度不断增大，涂层中磷酸四钙的含量先减小后增大，较高的温度会造成涂层表面微裂纹的产生。在模拟体液中浸泡后，经过水蒸气处理的涂层表面会诱导生成较纯的羟基磷灰石。180 ℃水蒸气处理后的涂层表面会沉积一层均匀的羟基磷灰石，生物活性较高。结论 羟基磷灰石涂层的结晶度随等离子喷涂功率的增大，先增大后减小，随水蒸气处理温度的上升而增大。在合适条件下制得的羟基磷灰石涂层具有较高的生物活性。     

微束等离子喷涂制备羟基磷灰石涂层微观结构的特征研究

目的 通过与大气等离子喷涂和超音速火焰啧涂的对比,研究微束等离子喷涂制备的羟基磷灰石涂层的微观组织特点.方法 以高结晶度的羟基磷灰石粉末为原料,采用三种不同的喷涂方法(微束等离子喷涂、大气等离子喷涂和超音速火焰喷涂),在Ti-6Al-4V基体上制备羟基磷灰石(HA)涂层.利用冷场发射扫描电子显微镜和X射线衍射仪,对三种涂层的形貌、相组成和择优取向进行分析.结果 与大气等离子喷涂及超音速火焰喷涂制备的涂层相比,应用该设备制备的羟基磷灰石涂层表面平整致密,无大量的气孔存在;涂层截面呈典型的层状结构,在近三分之一表面处观察到柱状晶;涂层中仅有少量的非晶相及分解相,结晶度高达90％以上.这些特征均有利于羟基磷灰石涂层在体液环境中的稳定性.结论 比较三种喷涂方法,采用微束等离子喷涂制备的羟基磷灰石涂层致密,结晶度高,杂相少,且存在择优取向的柱状晶.     

微束等离子喷涂制备羟基磷灰石涂层

采用微束等离子喷涂系统制备羟基磷灰石涂层,通过扫描电子显微分析(SEM)和X射线衍射分析(XRD)对涂层形貌、相组成和结晶度进行了研究.结果表明,随着喷涂电流和离子气流量的增加,羟基磷灰石粒子的熔化和撞击后的铺展更充分,在70～130 mm范围内随着喷涂距离的增加粒子熔化程度增加.适当的喷涂工艺条件下微束等离子喷涂制备羟基磷灰石涂层的结晶度可以相当或高于传统大气等离子喷涂制备的涂层,有利于涂层在体液环境中稳定性的提高.     

热处理对微束等离子喷涂羟基磷灰石涂层的影响

羟基磷灰石由于其良好的生物活性,被广泛的用作医用植入体的表面涂层材料.采用微束等离子喷涂(Microplasma Spraying,MPS)I艺在Ti-6Al-4V基体上制备羟基磷灰石涂层,通过扫描电镜(SEM)、X射线衍射(XRD)和傅里叶红外光谱(FTIR)分析了热处理对涂层相组成和表面形貌的影响规律.研究表明:微束等离子喷涂制备的羟基磷灰石涂层在经过热处理后结晶度提高,并且非晶相和杂质相转化成为HA结晶相.同时,羟基和磷酸根的完整性得到了恢复.过高的热处理温度易引起涂层裂纹等缺陷的增加,也容易造成羟基脱离造成HA分解.合理的热处理温度范围为600～700℃,保温时间为3 h.     

水热处理对电化学沉积HA涂层物相的影响

采用电化学沉积在碱处理Ti6Al4V钛合金基体上生成羟基磷灰石（HA）涂层,研究了水热处理对该涂层物相的影响。结果表明,电化学沉积HA涂层结晶度低、晶粒尺寸较小,经120 ℃和160 ℃水热处理后,HA结晶度和晶粒尺寸显著增大,且随水热处理温度的增加,结晶度和晶粒尺寸增加。     

预应力热处理对羟基磷灰石涂层相组成和结合强度的影响

设计不同角度的斜面工业纯钛柱,采用等离子法制备羟基磷灰石涂层,设计工装使涂层在预加相同正应力和不同切应力条件下进行热处理.利用电子拉伸实验机进行剪切结合强度测试,利用X射线衍射仪检测涂层的相组成与结晶度,探讨应力条件下热处理对涂层组成和涂层/基体结合强度的影响.研究表明:热处理中预加应力可以提高涂层的结晶度和涂层/基体的剪切结合强度.     

利用Ca（NO3）2-P2O5乙醇溶液体系制备纳米羟基磷灰石

使用Ca（NO3）2-P2O5乙醇溶液体系制备纳米羟基磷灰石，研究了在该体系中水浴温度、煅烧温度、陈化时间等因素对粉体的相成分，粒度和结晶度的影响。结果表明：水浴温度低，合成的粉体粒度小（约20nm），颗粒均匀且具有良好的分散性，但是结晶度较低；陈化后导致粉体粒度变大，结晶度增加；随着煅烧温度的升高，粉体的结晶度增加，600℃时可以得到结晶高的单一的羟基磷灰石粉体。在800℃煅烧时，羟基磷灰石发生部分分解。     

钛基羟基磷灰石涂层的界面结构及梯度设计

羟基磷灰石是最有发展前途的生物硬组织替代材料之一,临床上采用在钛合金上涂覆HA生物活性涂层,涂基结合及涂基界面的整合是决定HA涂层性能和可靠性的关键因素.评述了钛基羟基磷灰石涂层的界面微观结构,指出界面上存在纳米氧化物薄膜是提高涂层结合强度的关键,并结合纳米多层薄膜和功能梯度膜的优点,提出改善涂基结合强度,发挥羟基磷灰石生物活性涂层的三明治式的梯度设计.     

电化学沉积法制备钛基HA涂层

在钛基材表面获得羟基磷灰石（HA）涂层以改善钛与生物体的相容性，本项工作采用电沉积的方法在阳极氧化处理过的钛基体上制备了羟基磷灰石涂层。用扫描电子显微镜（SEM）、X射线衍射（XRD）等手段对涂层进行了表征。试验结果表明：电沉积初期的羟基磷灰石涂层呈多孔层片状：随电压、时间、电解液浓度的增大，涂层变厚，层片呈花瓣状发散排列：对基体阳极氧化处理有助于提高钛基与涂层的结合强度。     

微束等离子喷涂氧化锆增韧羟基磷灰石复合涂层

采用微束等离子喷涂方法,在Ti-6Al-4V基体上制备了羟基磷灰石 氧化锆(70HA-30ZrO2,质量分数,%)复合涂层.将复合涂层置于模拟体液中分别浸泡了3,7,14,28 d并观察表面磷灰石的生长情况以评价涂层生物活性.采用扫描电镜(SEM)和X射线衍射(XRD)分析技术对涂层浸泡前后的表面形貌和相组成进行了研究.结果表明,涂层中ZrO2主要以立方相存在;喷涂过程中羟基磷灰石(HA)出现了一定的分解,产生大量的α-Ca3(PO4)2杂质相.HA涂层熔化效果很好,但涂层中有未熔化的ZrO2颗粒.涂层在模拟体液中浸泡28 d后表面可以形成磷灰石,说明涂层具有很好的生物活性.     

退火温度及TiO_2结构对羟基磷灰石的沉积诱导作用

采用阳极氧化法在钛金属表面制备TiO2薄膜,将表面改性的钛金属在过饱和钙化溶液中浸泡,在其表面沉积羟基磷灰石,研究了退火处理温度对TiO2薄膜晶型转变的影响以及TiO2的晶型结构对羟基磷灰石的诱导沉积作用。研究表明,300℃退火处理,TiO2薄膜为板钛矿相,500℃退火处理转变为锐钛矿相,高于500℃退火处理,锐钛矿相开始向金红石相转变。其中锐钛矿相的TiO2对羟基磷灰石的沉积具有最好诱导作用,沉积物分布均匀,板钛矿相对羟基磷灰石的诱导作用最差,所形成的沉积层是由片状的羟基磷灰石围成的多孔结构。     

溶液钙浓度和水热合成条件对微弧氧化TiO2／羟基磷灰石复合膜层形貌和组成的影响

钛在含钙磷的溶液中微弧氧化，表面形成含有钙磷元素的，均匀多孔的氧化膜层，水热合成后转化为含羟基磷灰石晶体的复合氧化膜。研究表明：钙离子浓度未使膜层的形貌和相组成发生明显变化；仅在较低的浓度下增加溶液Ca^2 的浓度，膜层中Ca，P元素的相对含量和Ca／P比都会增加；在不同的水热温度和溶液钙浓度下，得到的羟基磷灰石具有不同的晶体形貌，相对含量和Ca／P比；缩短恒温时间可以使HA晶粒细化。这为优化生物医用钛表面TiO2／羟基磷灰石复合膜层的成分和形貌提供了依据。     

Novel hydroxyapatite coating on new porous titanium and titanium-HDPE composite for hip implant

Porous titanium (Ti) and Ti-high density polyethylene (Ti-HDPE) composite were investigated as new hip implant materials to increase the biomechanical compatibility by promoting a matching modulus of elasticity between hip stem and human bone. Surfaces of both materials were modified to increase its bioactivity and biocompatibility through electrochemical activation treatment and deposition of hydroxyapatite (HA) coating. The electrochemical activation treatment of both materials in 10 M NaOH solution created a bone-like porous nanostructure across the surfaces, thus enhancing the growth of natural bone. A top layer with nanometer-pores and TiO₂ was formed during the activation process, creating a favorable and prerequisite condition conducive to the formation of hydroxyapatite coating. Furthermore, a layer of hydroxyapatite, a bioactive and biocompatible bioceramics that is the main component of natural bone, was deposited on the porous Ti and Ti-HDPE composite through a novel chemo-biomimetic method. The formed coating was characterized through TEM as a nanometer scale crystalline.     

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.     

Preparation and in vitro biocompatibility of hybrid oxide layer on titanium surface

A new technique combining microarc oxidation (MAO) and electrophoresis was introduced to develop a biocompatible oxide layer on pure titanium implant surface. Originally developed alkaline electrolyte containing nano-scale hydroxyapatite powder suspension was used in the new technique. In the electric field, nano-scale hydroxyapatite powder was electrophoretically moved and sintered into the gradually-formed oxide layer on titanium anode. Physio-chemical properties and in vitro biological performance of the newly-formed surface were examined and evaluated. A 8.5-μm thick oxide layer with high surface energy and roughness, which was composed of titanium dioxide and calcium phosphates as well as hydroxyapatite, was formed on titanium surface by the modified MAO technique. Osteoblasts cultured on the modified MAO titanium surface showed significantly increased alkaline phosphatase (ALP) activity comparing to machined and MAO titanium surface. Natural oxide surface of titanium could be transformed into a hybrid oxide layer by modified MAO treatment. The modified titanium surface, which is rough and porous, contains calcium phosphates and proved to be more biocompatible in vitro.     

微弧氧化—水热合成生物活性二氧化钛层的结构与性能

在钛合金基体上通过微弧氧化形成含钙和磷的二氧化钛层，再经过水热合成转化为含羟基磷灰石的生物活性二氧化钛层，该膜层结合强度高，而且是多孔和均匀的。因此，该方法很适合钛合金植入体的生物活性表面改性。     

Synthesis of nanocrystalline hydroxyapatite by using precipitation method

In this investigation, hydroxyapatite powder has been synthesized from the calcium nitrate hydrated and di-ammonium hydrogen phosphate solution by precipitation method and heat treatment of hydroxyapatite powders. In order to study the structural evolution, the Fourier transform infrared spectroscopy (FTIR), the X-ray diffraction (XRD) and simultaneous thermal analysis (STA) were used. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to estimate the particle size of the powder and observe the morphology and agglomeration state of the powder. Results show that hydroxyapatite nanocrystalline can successfully be produced by precipitation technique from raw materials. Hydroxyapatite grain gradually increased in size when temperature increased from 100 to 1200 °C, and the hydroxyapatite hexagonal-dipyramidal phase was not transformed to the other calcium phosphates phases up to 1200 °C.     

Enhancement of adhesion bonding between titanium metal and electrodeposited calcium phosphate

A novel hydroxyapatite/rutile coating was prepared on a titanium substrate. Initially, an amorphous calcium phosphate coating layer was electrochemically deposited on a Ti substrate. The surface morphology, chemical composition and phase identification of the coatings were investigated by the X-ray diffraction and scanning electron microscopy associated with an energy dispersive spectrometer. Annealing at 700°C for 3 hrs. transforms the amorphous calcium phosphate layer into well-crystallized hydroxyapatite (HAP) and the Ti metal surface into rutile. The developed HAP/rutile composite surface layer became denser and better adhering with the substrate than the initially formed amorphous calcium phosphate. The adhesion bond strength and the hardness of the coating were extremely raised by thermal annealing.     

Characterization and Corrosion Behavior of Functional Gradient Hydroxyapatite Coating

The aim of the present work is to examine the characterization and corrosion behavior of functional gradient hydroxyapatite coating deposited on titanium-based alloy by plasma spray coating process. The functionally graded coating is designed to provide the crystalline hydroxyapatite at the interface with metallic substrate and the amorphous hydroxyapatite at the outer surface. It is considered that the top amorphous layer of hydroxyapatite has higher bioactivity, and its initial dissolution will lead to bone tissue growth enhancement and bonding, whereas the underneath crystalline hydroxyapatite coating after heat treatment is expected to enhance the long-term stability of coating at the interface with metal. The heat treatment of the underneath as-sprayed coating for crystallization was performed at 700 °C for 1 h. The characterization of the coatings was performed by various techniques such as scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction analysis, surface roughness, and microhardness. It was observed from potentiodynamic scan that heat-treated coating exhibited better dissolution resistance as compared to the as-sprayed coating. Heat treatment of the hydroxyapatite coating resulted in improved crystallinity of the coating which may provide long-term stability to the coating.     

Extraction of pure natural hydroxyapatite from the bovine bones bio waste by three different methods

In the present study, natural hydroxyapatite has been extracted from bio-waste; namely the bovine bones. Three different processes have been applied to extract the natural hydroxyapatite: thermal decomposition, subcritical water and alkaline hydrothermal processes. The results obtained by many physiochemical analyses have indicated that all the utilized methods have the ability to eliminate the organic compounds present in the bovine bones and produce pure hydroxyapatite bioceramic with average yield of 65%. Nanorod shape hydroxyapatite with an average length of 300 nm was obtained by the thermal process at temperature of 750 °C and holding time of 6 h. For the alkaline hydrothermal process, pure hydroxyapatite nanoparticles were produced at sodium hydroxide concentration of 25 wt%, temperature of 250 °C and holding time of 5 h. The subcritical water plucks out the collagen present in the bovine bones, so pure hydroxyapatite nanoflakes have been obtained at temperature of 275 °C and holding time 1 h. Selected area electron diffraction pattern images have signified that the thermal process produces good crystallinity hydroxyapatite. However, the subcritical water and alkaline processes produce small nanoparticles hydroxyapatite.