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A Study on Preparing Bioactive Graded Ceramic Coating on Titanium Alloy by Electrophoresis Codeposition and Sintering Method

Author: ChenXiaoMing
Tutor: LiShiPu
School: Wuhan University of Technology
Course: Inorganic non-metallic materials
Keywords: Titanium alloy Surface Modification Electrophoretic co-deposition Bioglass Hydroxyapatite Gradient coating Composition Structure
CLC: TG174.4
Type: PhD thesis
Year: 2002
Downloads: 630
Quote: 9
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Abstract

Titanium alloy for the development of surface modification for bone implanted medical devices, such as artificial joints, root implants, artificial bone is important, is one of the topics at the forefront of today's biomedical materials research. Improve the stability of the coating of the titanium alloy surface of calcium and phosphorus biological, chemical treatment, high temperature vacuum Dutai and electrophoresis (EPCD) - sintering technology co-deposition of titanium surface modified by gradient design of the structure and composition of the coating and EPCD - sintering technology research, access to the complex shape products surface coating of calcium and phosphorus gradient coating and its low temperature the rapid sintering technology, and developed a high-performance system titanium alloy / bio-glass (BG) / hydroxyapatite (HA) gradient coating. The technology for low-cost, pollution-free environment-friendly technologies, and coating of calcium and phosphorus in the biomedical field, hoping to expand and enhance its service life. Titanium alloy surface processing with acids and bases (nitric acid and sodium hydroxide), plasma emission spectroscopy to determine the composition of the corrosion products, titanium alloy surface morphology was observed by SEM, found that nitric acid to make the titanium alloy surface uniformity corrosion therefore not selective dissolution of the titanium alloy surface V and Al elements; sodium hydroxide selective dissolution of titanium alloy surface V and Al, and Ti elements gel state form of TiO ₂ stay in the titanium alloy surface, the gel state TiO ₂ is not only good biocompatibility induced calcium and phosphorus mineral deposition, but is also beneficial to the sintering combined with bioactive glass. Therefore, it is expected that the alkali treatment method is a good surface of titanium biological coating pre-treatment method. To improve the possibility of the biocompatibility of the titanium alloy surface in order to explore the surface of titanium alloy plating layer of pure titanium, to carry out the study of high temperature the vacuum Dutai the titanium alloy surface with a scanning electron microscope (SEM) and electron probe X- ray fluorescence microanalysis (EPMA) titanium alloy surface and cross section element content distribution and change, Ti6Al4V alloy at 1000 ℃ for 2 to 4 hours of deposition saturated the Ti steam environment surface to a thickness of about 20μm and rich V elements of the metals Ti coating. The evaporation process, the the alloy internal grain dramatically grown the Ti6Al4V alloy V elements there is surface segregation of Al element is present the diffusion motion caused by the concentration difference. The Ti6Al4V alloy subjected to vacuum heat treatment at 1000 ℃ reduce its mechanical properties, and the the V elements within the alloy to the surface enrichment, therefore, the sintering temperature of the the titanium vacuum heat treatment and surface coating can not be too high, which should be less than its phase transition point; bioactive gradient coating composition and structure design, analysis and calculation of the size and distribution of the stress gradient coating, the results showed that: For this study, when the component distribution coefficient of n = 1.5, can be obtained more reasonable coating mechanical properties, that is, in the beginning of deposition, using a suspension of BG-rich particles, in order to obtain a good transition with the bottom of iCtgM'eMx * \u0026 CZ M f BG BG coating rich in titanium side; gradient coating layer interface and surface stress size, nature (compressive stress or tensile stress) of the material itself, the nature of the decisions to change the composition distribution coefficient, can only change the trend of the stress changes within the coating; thickness of the coating does not affect the coating stress distribution, but the thinner the coating, the faster the stress within the coating, but this does not mean that the coating the thicker the better, because the thicker the coating, the smaller the deformation of the coating allows for the applied bending force parts of the coating, the coating should be a little thin (50 um); For parts only pure by shear stress, such as root implant, coating may be appropriate to thicken (80100 um); through the HA and BG particles in aqueous systems and non-aqueous system in the charging characteristics, and electrophoretic deposition (EPD) of the study found that in aqueous systems, they are difficult to electrodeposition; occurs in the ethanol solution, the HA particles are positively charged, can be homogeneous electrophoretic deposition occurs on the cathode titanium sheet, and the BG particles with a negative charge; using metathesis reaction method, can be prepared from 100-300urn HA, the BG particles surface-coated By inducing HA crystallized in the BG particle surfaces, obtained by the HA coated SG particles, changing the charging characteristics of the the BG particle surface of the BG and the HA particles to impart a positive charge in anhydrous ethanol, thus realizing the HA and BG co-deposition of particles on the cathode. Therefore, it is feasible to use EPCD system each BGIHA gradient coating. Bioglass bioactive glass (8 ') high boron coating and plasma spray coatings for corrosion experimental findings: high boron phase separation in the preparation process, which is divided into the silicon-rich phase and boron-rich phase in alkaline its corrosion behavior in the environment to uniform corrosion, corrosion occurs mainly in the boron-rich phase region, BG recipe design should try to avoid rabbit corrosion of the glass phase separation occurred; plasma sprayed coatings exhibit non-uniform corrosion, corrosion occurs mainly The droplet edge of the laminate and corrosion accelerating trend, easy to cause the penetrating to the coating interface corrosion cracking, thereby causing the interface to permeate corrosion, which may be one of the main late plasma sprayed coatings shedding. Biological glass and titanium alloy thermal expansion coefficient of the test, indicating that the 2 'of biological glass and titanium alloys in the coefficient of thermal expansion match with titanium alloy sintered at a lower temperature (720C) into dense glaze layer. The biocompatibility evaluation test results show that the high boron bioactive glass (8 ') still has good biocompatibility: BG and HA particles in the ethanol solution of EPCD of its sintering process, and the results show that: through continuous change electrophoresis solution dispersed particles BG and HA concentration ratio, pulsed DC power supply (frequency 1200Hi duty cycle 114), BG / HA gradient coatings can be prepared in the titanium alloy surface; batter when HA and BG concentration was 30g / L, the two-electrode spacing is 1. scm, the better the deposition process: the deposition voltage is 30V, the deposition time of a flail 1 * s: low deposition voltage tend to obtain a dense coating tends to obtain a porous coating, while in high deposition voltage layer, by increasing deposition voltage, it is possible to control the porosity of the coating, thereby preparing a coating having a pore structure gradient; the titanium / BG / HA gradient coating sintered optimized process for the atmospheric low-temperature rapid sintering process, the process parameters for : heating rate of 50'C / min, 720t of sintering temperature, holding time of 7 mins natural AZedryX-we - x-\u0026 Ik f cooling; coating

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology
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