喷涂功率对真空等离子喷涂羟基磷灰石涂层的影响

本文采用真空等离子喷涂设备（VacuumPlasmaSprnySystem），在不偷呐涂功率下制备了羟基磷灰石涂层，研究了热喷涂功率对羟基磷灰石涂层材料学特征的影响．实验中，使用X射线衍射仪，测定了涂层的相组成．使用扫描电子电镜，观察了羟基磷灰石涂层的表面形貌．研究结果表明，热喷涂功率对羟基磷灰石涂层的结构有着重大的影响．一方面，随着热喷涂功率的提高，涂层的非晶化加剧，涂层中非晶态的羟基磷灰石含量不断增大．另一方面，随着热喷涂功率的提高，羟基磷灰石粉末的熔化状态变好，颗粒之间的结合能力加强；涂层的显微结构明显改善．     

喷涂距离和喷涂功率对羟基磷灰石涂层的影响

本文以Ｔｉ－６Ａｌ－４Ｖ合金为基体材料,采用等离子喷涂方法,在不同喷涂距离和喷涂功率下制备羟基磷灰石（ＨＡ）涂层,研究喷涂距离和喷涂功率这两个重要的喷涂参数对涂层结构和组成的影响．使用扫描电子显微镜（ＳＥＭ）观察了羟基磷灰石涂层的形貌．涂层的相组成由Ｘ射线衍射谱仪（ＸＲＤ）分析而得．并使用Ｘ射线荧光谱仪（ＸＲＦ）测定了涂层的Ｃａ／Ｐ摩尔比．研究结果表明,喷涂距离对羟基磷灰石涂层的形貌、相组成以及Ｃａ／Ｐ摩尔比有着明显的影响．随着喷涂距离的增大,羟基磷灰石粉末的熔化状态得到改善,涂层的显微结构较为致密．然而,喷涂距离的增大使得涂层的非晶化更加严重,涂层中非晶相含量增大．在实验范围内,喷涂功率对涂层结构和相组成的影响不明显．Ｃａ／Ｐ比测定显示,等离子喷涂羟基磷灰石涂层均为缺磷涂层,Ｃａ／Ｐ比随喷涂距离的增大而降低,随喷涂功率的增大而增大．     

等离子喷涂羟基磷灰石涂层的结合强度

讨论了影响和制约等离子喷涂羟基磷灰石涂层与钛合金基底之间结合强度的主要因素,总结了提高涂层结合强度的方法及相关研究的进展。     

等离子喷涂羟基磷灰石涂层的材料学特征

采用等离子喷涂技术,在钛合金基体表面制备羟基磷灰石涂层．使用ＸＲＤ和ＳＥＭ等测试手段,对获得的涂层进行了表征．结果表明,等离子喷涂过程中,同时发生羟基磷灰石的非晶化与热分解现象．热分解产物为ＣａＯ及α－Ｃａ_３（ＰＯ_４）_２．非晶化是高温羟基磷灰石液滴急剧冷却的结果．羟基磷灰石材料的热力学不稳定性,是发生热分解的主要原因．等离子喷涂获得具有一定粗糙度的羟基磷灰石涂层．涂层的显微结构中;存在气孔以及微裂纹．它们是等离子喷涂工艺的显微结构特征．羟基磷灰石涂层内部存在着烧结现象．涂层与金属基体之间的热传递性能变差,是导致烧结的主要原因．     

空心球羟基磷灰石等离子喷涂粉体的制备

羟基磷灰石等离子喷涂粉体被广泛用于等离子喷涂方法制备的骨及牙等医用种植体表面的生物活性涂层产品中,研制高性能的羟基磷灰石喷涂粉体对提高等离子喷涂羟基磷灰石生物活性涂层的使用性能有着重要意义.本研究采用水热、喷雾造粒、等离子球化及空心化等方法制备出一种新型空心球羟基磷灰石喷涂粉体.扫描电镜照片显示该粉体外观主要呈规则球形,平均粒径约为80.4μm,内部为空心结构,空心部分呈球状位于粉体中心,其平均壳壁厚度约为13.3μm.另外,本工作探讨了团聚结构羟基磷灰石粉体在等离子焰流中的空心化过程,认为粉体的初始孔隙率、粉体在焰流中的熔化程度、熔滴内部的气密性是影响空心化效果的主要因素.最后,通过等离子喷涂方法制备了团聚结构和空心球结构两种羟基磷灰石粉体涂层,结果表明:空心球结构羟基磷灰石粉体涂层的致密性及结合强度均优于团聚结构羟基磷灰石粉体涂层.     

低压等离子喷涂氧化铝涂层的特性

以细小的氧化铝为热喷涂粉末,采用低压等离子喷涂制备了沉积率高于50%,孔隙率低于2%的氧化铝涂层.研究了不同工艺下低压等离子喷涂氧化铝涂层的沉积率、相组成和显微结构,并对低压等离子功率和真空室压力工艺参数对涂层的影响进行了分析.研究结果表明,所制备的涂层以α-Al₂O₃和γ-Al₂O₃相并存;随着功率和压力提高,涂层的孔隙率有明显的降低,但压力达到23.7kPa时功率影响较小.此外,还对等离子焰流中的粒子温度和速度进行了计算.结果表明,在23.7kPa压力下保证粒子充分熔融的前提下使粒子具有较高的运动速度.     

等离子喷涂羟基磷灰石涂层的相组成及其结构

研究纯钛表面羟基磷灰石(HA)涂层的相组成及其微观结构,为涂层性能与制备工艺优化提供依据.采用等离子喷涂法制备HA涂层,用X射线衍射仪和透射电子显微镜进行相细成与微观结构的表征.研究表明:涂层主要由晶相HA、非晶相和分解相组成,随喷涂功率的提高,非晶化加剧,CaO含量提高;在TEM下观察到HA晶体与非晶体共存区、HA与磷酸三钙徽晶的共存区,以及HA与Ti的反应产物CaTi03;除工艺原因外,羟基磷灰石复杂的结构和混合键的结合也是其形成非晶态的主要原因.     

热喷涂生物陶瓷涂层的研究进展

采用热喷涂技术在金属(合金)基材表面制备的生物陶瓷涂层, 兼具金属材料较高力学强度和陶瓷材料优良生物学性能, 作为骨植入材料的研究和应用备受关注。本文介绍骨植入涂层材料的研究概况, 重点阐述热喷涂羟基磷灰石(HA)涂层的研究现状, 并概述新型生物活性硅酸钙陶瓷涂层的研究进展。     

喷涂功率对碳/碳复合材料表面羟基磷灰石涂层的影响

采用等离子喷涂技术在碳/碳复合材料表面制备了羟基磷灰石(HA)涂层,采用电子拉伸机和自制装置测定了不同喷涂功率下涂层与基体的抗剪强度,采用扫描电镜观察了涂层表面、剪切断裂表面的形貌,采用电子探针分析了试样截面的形貌和成分线分布.结果表明:随着喷涂功率的增加,涂层中HA颗粒的熔化程度和涂层与基体的抗剪强度均增加,涂层与基体的界面属于机械结合,其剪切断裂的形式主要有界面失效和涂层内部失效两种.     

等离子体预处理的炭/炭复合材料等离子喷涂制备羟基磷灰石涂层

为了提高等离子喷涂法所制羟基磷灰石涂层与炭/炭复合材料的结合力,采用氩气等离子体预处理结合等离子体喷涂法在炭/炭基体表面制备羟基磷灰石涂层,采用扫描电镜、X射线衍射仪、红外光谱仪、划痕仪等研究羟基磷灰石涂层的形貌、相组成以及羟基磷灰石涂层与基体的结合力。结果表明:采用或不采用等离子体处理炭/炭复合材料,羟基磷灰石涂层形貌和相组成接近,羟基磷灰石涂层的临界载荷分别为14.0 N、8.9 N,前者比后者临界载荷提高了57.3%。采用等离子体处理可提高等离子体喷涂羟基磷灰石涂层与炭/炭复合材料基体的结合力。     

Influence of experimental parameters on spatial phase distribution in as-sprayed and incubated hydroxyapatite coatings

In the present study, the behavior and properties of plasma-sprayed hydroxyapatite coatings [Ca(10)(PO(4))(6)(OH)(2), HAp] were investigated in relation to the spraying process. The experiments were focused on the influence of type of feedstock and spray power on the phase composition and distribution within the coatings. Depth profiles of the coatings were investigated before and after incubation in revised simulated body fluid (SBF) by X-ray diffraction and infrared spectroscopy. Besides HAp, the coatings contain oxyapatite (OAp) and carbonate apatite (CAp). Additionally, tricalcium phosphate (TCP), tetracalcium phosphate (TTCP), CaO, and an amorphous phase were detected in the coatings. The HAp content directly depends on the used spray powder and spray power, where the influence of spray powder is much higher than the influence of the spray power. The grain size range of the spray powder strongly influences the HAp content in the coating and the formation of CaO. The in vitro behavior of the coatings in simulated body fluid mainly depends on the contents of CaO and amorphous calcium phosphate, respectively. The formation of portlandite due to the reaction of the coating with the SBF is strongly influenced by the porosity of the coatings and can be used as an indicator for the depth of interaction between fluid and coating.     

Prozeßidentifikation beim Plasmaspritzen temperatursensitiver Werkstoffe mit Hilfe einer Infrarot-Hochtemperatur-Thermokamera

Process-Identification at Plasma Spraying Thermally Sensitive Materials Using an Infra-red Thermal Imaging System Nowadays so called thermally sensitive materials are deposited by thermal spray techniques. Due to the high temperature process an undesired alteration (evaporation, chemical decomposition) of the material could occur. Therefore, optimisation of the deposition based only on empirical methods may be deremental with respect to the coating properties. This study shows the potential of an IR thermal imaging technique as a process control for evaluation and optimisation of the deposition through better understanding of the thermal spray process. The spray trials presented are based on preliminary examinations carried out with diagnostic tools. Therefore it was possible to achieve defined air plasma sprayed coatings of hydroxyapatite with different coating and component properties. This is particularly of interest, since there exists only a standard for hydroxyapatite as starting material but not for plasma sprayed coatings. Hence the coatings had either high or low contents of undesired phases, different degrees of cristallinity and bond strengths-varying from 5 to 42 MPa. Besides the power levels and the way to obtain the power the carrier gas flow significantly influences the properties of the coatings.     

氟化钠处理对炭/炭复合材料磷灰石生物活性涂层的影响

通过声电沉积工艺在炭/炭复合材料表面制备钙磷生物活性涂层, 采用扫描电镜、 X射线能谱仪、 X射线衍射仪、 红外光谱等方法研究了氟化钠处理前后钙磷生物活性涂层的形貌、 结构和组成。实验结果表明: 氟化钠能促进磷酸三钙转化为含氟羟基磷灰石(FHA), 并提高涂层结晶度; 经氟化钠处理后, 羟基磷灰石(HA)的(112)、 (300)衍射峰明显增强, 涂层是HA和FHA的混合物。氟化钠处理前后涂层表面形貌均为片状晶体, 但处理后其颗粒尺寸增大; 氟化钠处理后涂层与基体的结合强度略有增强, 结合强度可达4.08MPa, 涂层氟的含量为4.59wt％。分析了炭/炭复合材料表面HA转变为FHA的反应机制。采用氟化处理HA制备FHA涂层时, 应加入磷酸盐保持整个反应过程的pH值不变。      

Optimization of Dielectric Properties of Suspension Plasma Sprayed Hydroxyapatite Coatings

Conventional plasma torch was adapted to spray very fine Ca₅ (PO₄)₃OH (hydroxyapatite, HA) precursors having sizes ranging from a few hundreds of nanometers to a few micrometers. The powders were put in suspension with distilled water and antidispersive agent. A home made suspension feeder, including two peristaltic pumps, delivered the suspension into atomizer and therefrom injected into plasma jet. The suspension flow rate was electronically controlled. The resulting coatings had the thickness of a few tenths of μm. The electrical properties of the coatings including breakdown voltage and loss factor of suspension sprayed hydroxyapatite coatings sprayed onto aluminium substrates were also tested. The influence of such experimental factors as power input to plasma, pressure of atomizing gas, spray distance and suspension feed rate on the responses being the electrical properties was investigated using a 2⁴ design of experiments (DOE). The mathematical models relating the responses with the factors were created and the significant factors were selected.     

MAX-phase coatings produced by thermal spraying

This paper presents a comparative study on the Ti₂AlC coatings produced by different thermal spray methods, as Ti₂AlC is one of the most studied materials from the MAX-phase family. Microstructural analysis of coatings produced by High Velocity Air Fuel (HVAF), Cold Spray and High Velocity Oxygen Fuel (HVOF) has been carried out by means of the scanning electron microscopy equipped with an energy dispersive spectrometer (EDS). The volume fraction of porosity was determined using the ASTM standard E562. The phase characterization of the as-received powder and as-sprayed coatings was conducted using the X-ray diffraction with CrKα radiation. Impact of the spray parameters on the porosity and the mechanical properties of the coatings are discussed. The results show that the spraying temperature and velocity play a crucial role in coatings characteristics.     

Nanocrystalline structure of the surface layer of plasma-sprayed hydroxyapatite coatings obtained upon preliminary induction heat treatment of metal base

Biocompatible nanocrystalline hydroxyapatite (HA) coatings for intrabone titanium implants have been obtained by plasma spraying. The HA coatings have an average grain size within 10–30 nm and are characterized by improved characteristics of morphological heterogeneity that is acquired due to the induction heat treatment (IHT) of substrates prior to plasma spray deposition. Based on the data of scanning electron microscopy with computer-aided processing of images, it is established that the average grain size depends on the IHT temperature.     

Preparation and characterization of bioactive monolayer and functionally graded coatings

Hydroxyapatite powders were made by reacting orthophosphoric acid with calcium hydroxide and dense bioactive coatings were subsequently produced by the plasma spray technique. Three types of hydroxyapatite (flame spheroidized) monolayer coatings and three types of functionally graded coatings were manufactured. It was found that average microhardness values of monolayer coatings decreased as the indentation load increased. The relationship between indentation load and indent diagonal length observed Meyer's law. Microhardness and fracture toughness of coatings were affected by characteristics of feedstock powders for plasma spraying. The indentation fracture toughness of coatings could be significantly increased by incorporating a toughening phase. ©1999 Kluwer Academic Publishers     

Post-deposition treatment effects on hydroxyapatite vacuum plasma spray coatings

The purpose of this work is to evaluate the effects of post-deposition heat treatments on high and low crystallinity hydroxyapatite coatings on Ti6Al4V alloy. HA layers were produced by the vacuum plasma spray (VPS) technique, and the desired degrees of crystallinity were obtained by changing the deposition parameters. An analysis of the mechanical properties of the coatings and their adhesion to the substrate has been done by shear strength test. X-ray diffraction analysis was used to detect the structure and the chemical components in which HA dissociates during the deposition process and heat treatments. The data obtained indicates that heat treatments can increase the crystallinity of HA, but they also introduce a mechanical degradation of the coatings. After heat treatments, it was also observed that a large amount of tetracalcium phosphate was formed.     

Solution precursor plasma sprayed tungsten oxide particles and coatings

Solution precursor plasma spray process was used to deposit single particles and coatings of tungsten oxide (WO₃), and the microstructures of single particles and coatings were characterized by field emission scanning electron microscopy. The effects of substrate temperature and spraying distance on the microstructure of single particles and coatings were studied. In the case of WO₃ particles, the particle spheroidization degree became better as the increase in substrate temperature. When the substrate temperature increased up to 200°C, bubble-like morphologies appeared. For the deposited WO₃ coatings, a highly porous structure was obtained when a 100?mm spraying distance was used. Besides, the grain size of coatings decreased through increasing the spraying distance from 60 to 100?mm.