镁合金及复合材料表面钙磷膜层的制备与腐蚀降解行为研究

发布时间：2018-01-23 02:52

本文关键词： 镁合金镁基复合材料钙磷膜层化学转化膜溶胶凝胶膜层羟基磷灰石氟羟基磷灰石生物可降解　出处：《吉林大学》2016年博士论文　论文类型：学位论文

【摘要】：与临床应用的不锈钢、钛合金和钴铬合金等金属植入材料相比,镁及镁合金作为潜在的生物医用植入材料,具有良好的力学相容性、生物相容性和体内可降解性。但是,镁合金作为骨植入材料,在人体中腐蚀降解过快,导致植入体在骨组织尚未完全修复前就失去其机械完整性,而且腐蚀过程中产生的过量氢气会导致植入体和骨组织之间的连接松动,这些都限制了镁及镁合金作为骨植入材料的临床应用。为了降低镁的腐蚀降解速率,通常采用高纯化、合金化、复合材料及表面改性等技术手段提高镁的耐蚀性能。与其他技术手段相比,在镁合金表面制备生物相容性膜层,不仅可以使植入体在植入初期减缓降解速率,保持良好的机械完整性,而且在骨修复即将完成时膜层失效使植入体较快降解,还能有效改善植入体与骨组织的界面关系,加速骨骼修复愈合。由于Ca和P是骨骼矿物质的主要组成元素,钙系磷酸盐(Ca P),例如二水磷酸氢钙(DCPD,Ca HPO_4·2H2O)、羟基磷灰石(HA,Ca10(PO_4)_6(OH)_2),都具有天然的生物活性和生物相容性。本文通过化学转化法和溶胶凝胶旋涂法等简单易控方法,在镁合金及复合材料表面制备多种不同结构与形貌的钙磷膜层,然后通过在模拟体液(SBF)中的电化学和浸泡矿化试验、体外细胞培养试验以及体内植入试验等对其腐蚀降解行为、生物矿化行为及细胞相容性等进行系统研究。本文的主要研究工作如下:1.采用简单易控的化学转化法,在镁合金表面制备具有复合膜层结构的钙磷化学转化(calcium phosphate chemical conversion,CPCC)膜层。研究分析了膜层生长过程、膜层横截面元素含量变化、log[Mg~(2+)]-p H热力学稳定相图以及镁基体电化学反应产生的Mg~(2+)对CPCC膜层成膜的影响。结果表明,CPCC膜层具有三层复合结构:内层为三水磷酸氢镁(MHPT,Mg HPO_4?3H2O),厚度约为1.2μm;中间层由DCPD、磷镁钙矿(MWH,Ca9Mg(HPO_4)(PO_4)_6)和MHPT组成,厚度约为1.5μm;外层由DCPD和MWH组成,厚度约为2.5μm。研究了成膜时间对CPCC膜层的表面形貌及电化学行为的影响,成膜时间为20 min时的膜层具有最佳的耐腐蚀性能。体外浸泡试验、细胞培养试验以及体内植入试验结果表明,CPCC膜层具有良好的细胞粘附能力与细胞相容性,膜层涂覆镁合金试样的体内外腐蚀降解速率明显降低。2.由于CPCC膜层中的DCPD成分在碱性环境中很容易转化为更稳定的HA,因此,采用一种简单的碱热处理方法将CPCC膜层转化为HA膜层。研究了碱热处理时间对膜层组织形貌及电化学行为的影响,结果表明,碱热处理1 h形成的HA膜层具有较为均匀致密的膜层结构和明显改善的耐蚀性能,在SBF中表现出较好的生物矿化能力。3.为了制备组织更加稳定的氟掺杂HA(fluor-hydroxyapatite,FHA)膜层,在上述碱热处理溶液中加入氟化物,探索一种新的氟热处理方法。分析了氟热处理溶液的p H值和处理时间对膜层形貌和电化学耐蚀性能的影响,确定最佳的氟热处理工艺参数为p H=12,时间为2 h。经过氟热处理后,镁合金表面的CPCC膜层转化为主要由FHA、MWH和Mg F2组成的复合膜层。电化学和浸泡矿化试验结果表明,氟化处理后的膜层具有比CPCC膜层和HA膜层更高的耐蚀性能和生物矿化能力。4.采用溶胶凝胶旋涂法在镁合金CPCC多孔膜层表面制备了HA、FHA、FA三种溶胶凝胶膜层,膜层表面均匀致密,对镁合金表面CPCC膜层具有良好的封孔效果。研究了溶胶凝胶膜层中的氟含量和溶胶凝胶层数对复合膜层的形貌和电化学耐蚀性能的影响,结果表明,5层的FA溶胶凝胶膜层具有最佳的封孔效果和最优的电化学耐蚀性能。电化学和浸泡试验结果表明,结构稳定无空隙的溶胶凝胶膜层显著降低了镁合金的腐蚀降解速率。5.采用粉末冶金法制备了不同质量分数的微米级HA颗粒增强镁基复合材料。电化学试验结果表明,20%HA/Mg复合材料的腐蚀电流密度约为纯镁的五分之一,而10%HA/Mg的腐蚀电流密度约为纯镁的2倍。为了控制复合材料的腐蚀降解速度,将化学转化方法和后续碱热处理应用到复合材料的表面处理上,在10%HA/Mg复合材料表面制备了CPCC膜层和HA膜层。通过与纯镁和AZ60镁合金表面CPCC膜层沉积过程的对比,发现复合材料在膜层沉积过程中表面活化更快,形核率和生长速度明显提高。电化学和浸泡试验表明这两种膜层,尤其是HA膜层,显著提高了HA/Mg复合材料在SBF中的耐腐蚀性能和表面生物矿化能力。
[Abstract]:With the clinical application compared with stainless steel, titanium alloy and cobalt chromium alloy and other metal implant materials, magnesium and magnesium alloys as biomedical implant materials potential, has good mechanical compatibility, biocompatibility and biodegradability. However, magnesium alloy used as bone implant materials, corrosion and degradation in the body is too fast, resulting in the implants in bone tissue has not been fully repaired before it loses its mechanical integrity, but also produce excess hydrogen corrosion process would result in a loose connection between the implant and bone tissue, which limits the clinical application of magnesium and magnesium alloys as implant materials. In order to reduce the corrosion degradation rate of magnesium, usually high purification, alloying, composite materials and surface modification techniques to improve the corrosion resistance of magnesium. Compared with other techniques, on the surface of magnesium alloy for preparing biocompatible coating, can not only make the implant in The early implantation slow degradation rate, maintain good mechanical integrity, but the film in bone repair is complete failure to implant rapid degradation, can effectively improve the interface between the implant and bone tissue, accelerate bone healing. Because Ca and P are the main elements of bone mineral, calcium phosphate (Ca P) for example, two water (DCPD, Ca HPO_4, dicalcium phosphate, hydroxyapatite (2H2O) HA, Ca10 (PO_4) _6 (OH) _2), are compatible with natural biological activity and biological. Through chemical conversion method and sol-gel spin coating method is simple and easy to control method, preparation of calcium phosphate coating of different structure and in the morphology of magnesium alloy and composite surface, and then in a simulated body fluid (SBF) immersion test and electrochemical mineralization in the in vitro and in vivo implantation test on the corrosion behavior, the behavior of biomineralization and cell Compatibility was studied. The main research work is as follows: 1. using the chemical transformation method is simple and easy to control, on the surface of magnesium alloy prepared with calcium and phosphorus chemical compound layer structure transformation (calcium phosphate chemical conversion, CPCC) coatings. Research and analysis of the film growth process, the cross-sectional variation in element content of log[Mg~ film. (2+)]-p H thermodynamically stable phase diagram and the electrochemical reaction of magnesium matrix Mg~ (2+) film on the impact of CPCC film. The results show that the CPCC film has a composite structure of three layers: the inner layer is magnesium hydrogen phosphate trihydrate (MHPT, Mg HPO_4? 3H2O), the thickness is about 1.2 m; the middle layer is composed of DCPD stanfieldite, (MWH, Ca9Mg (HPO_4) (PO_4) _6) and MHPT, the thickness is about 1.5 m; the outer layer by DCPD and MWH. The effect of thickness is about 2.5 M. of the film time on the CPCC film surface morphology and electrochemical behavior, film forming time is 20 mi N coating has the best corrosion resistance. In vitro immersion test, cell culture test and in vivo test results show that the CPCC film has the ability of cell adhesion and cell compatibility, corrosion rate in vivo degradation of film coating of magnesium alloy.2. decreased significantly due to the DCPD component in CPCC coatings in alkaline environments easily converted into more stable HA, therefore, using a simple alkali heat treatment methods CPCC film into HA film. The alkali heat treatment time effect on morphology and electrochemical behavior of films, the results show that the alkali heat treatment 1 h formation of the HA film has more uniform and compact film structure corrosion resistance was significantly improved, showing fluorine doped HA good biological mineralization ability of.3. in order to prepare the organization more stable in SBF (fluor-hydroxyapatite, FHA) in the treatment of alkali heat film Fluoride solution, to explore a new treatment method of fluorine heat. The fluorine heat treatment solution P H value and the effect of treatment time on film morphology and electrochemical corrosion resistance, determine the parameters f the best heat treatment process for P H=12, time of 2 h. After fluoride after heat treatment, the surface of the magnesium alloy CPCC film into mainly by FHA, MWH and Mg composite film composed of F2. The electrochemical and immersion mineralization test results showed that the fluoride treated film is better than that of CPCC film and HA film corrosion resistance and biological mineralization of.4. by sol-gel spin coating method on CPCC magnesium alloy surface preparation of HA porous film FHA, FA, three kinds of sol gel coatings, uniform coating surface is compact, has good sealing effect on the surface of CPCC magnesium alloy film by sol-gel film. The fluorine content and sol gel layers on the film morphology and electrical Effect of chemical corrosion resistance, the results show that the electrochemical corrosion resistance of FA coating by sol gel layer 5 has the best sealing effect and optimal. The electrochemical and immersion test results show that the sol gel film structure stable void free significantly reduces the corrosion degradation rate of.5. magnesium alloy by powder metallurgy method of micron HA particles of different quality the fraction of reinforced magnesium matrix composites were prepared. The electrochemical test results show that the corrosion current density of 20%HA/Mg composite is about 1/5 mg, while the corrosion current density of 10%HA/Mg is about 2 times that of pure magnesium corrosion. In order to control the degradation speed of composite materials, the chemical conversion method and subsequent alkali heat treatment is applied to the surface processing of composite materials, on the surface of 10%HA/Mg composite material prepared CPCC film and HA film. With pure magnesium and CPCC magnesium alloy AZ60 surface film deposition process In contrast, the composite film deposition process of surface activation faster, the nucleation rate and growth rate was significantly improved. The electrochemical and immersion test showed that the two kinds of films, especially HA film, HA/Mg was significantly increased in SBF composite corrosion resistance and surface biological mineralization ability.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG174.4

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