本文選題：可降解 + 鎂合金��； 參考：《暨南大學》2017年博士論文

【摘要】：近年來生物醫(yī)用鎂合金已成為可降解醫(yī)用金屬材料中的一個研究熱點,與植入部位匹配的力學性能及可控的腐蝕降解速率更是研究中關鍵問題,而應力與腐蝕之間相互作用導致植入材料提前失效(即應力腐蝕斷裂)的研究較少。本論文以鎂合金作為可降解骨釘、骨板和心血管支架材料為應用背景,設計出新型含鍶(Sr)可降解鎂合金—ZK40xSr(Mg-4wt.%Zn-0.6 wt.%Zr-x Sr,x=0、0.4、0.8、1.2、1.6 wt.%)。研究了Sr含量對鑄造態(tài)和鍛造態(tài)ZK40xSr合金顯微組織、腐蝕降解和應力腐蝕斷裂的影響。同時研究了微弧氧化(Micro-arc oxidation,MAO)膜層和微弧氧化/聚乳酸-羥基乙酸共聚物(Poly(lactic-co-glycolic acid),PLGA)(MAO+PLGA)復合涂層兩種表面改性方法對鍛造態(tài)ZK40-0.4Sr合金的耐腐蝕性能以及應力腐蝕降解性能的影響。研究發(fā)現(xiàn)Sr能明顯細化鑄造態(tài)ZK40x Sr合金的晶粒,在晶界形成條狀或網(wǎng)狀MgxZnySrz第二相。晶粒細化能提高鑄造態(tài)合金的抗拉強度和斷后伸長率,而晶界析出第二相與基體α-Mg之間形成的微電偶腐蝕造成合金腐蝕速率隨著Sr含量的增加而升高。同時由于條狀或網(wǎng)狀第二相沿著晶界分布,第二相與基體之間微電偶腐蝕在應力作用下,沿著晶界向基體內(nèi)加速擴展,導致鑄造態(tài)ZK40xSr合金在模擬體液中獲得的力學性能明顯下降。也即鑄造態(tài)ZK40xSr合金隨著Sr含量的增多,應力腐蝕敏感性增加。經(jīng)過鍛造塑性變形后,鍛造態(tài)ZK40xSr合金平均晶粒尺寸從幾百微米降低到幾微米,晶粒明顯得到細化,晶界第二相形態(tài)和分布也由原來的條狀或網(wǎng)狀結(jié)構(gòu)變?yōu)閸u狀或橢球狀,抗拉強度和斷后伸長率等力學性能得到明顯提高,耐腐蝕性能也得到改善。然而,晶粒細化導致鍛造態(tài)ZK40和ZK40-0.4Sr合金氫脆現(xiàn)象可能增多,應力腐蝕敏感性增加。鍛造態(tài)ZK40-1.2Sr和ZK40-1.6Sr合金由于自身依然存在均勻分布的島狀或橢球狀脆性第二相,減少了氫脆現(xiàn)象的影響,降低了合金的應力腐蝕敏感性。采用MAO和MAO+PLGA復合涂層對鍛造態(tài)ZK40-0.4Sr合金表面改性后,發(fā)現(xiàn)合金的耐腐蝕性能得到大大提高,尤其是MAO+PLGA復合涂層處理后,合金腐蝕電流密度降低了3個數(shù)量級,電化學阻抗性能明顯得到提高。采用0、20、40和60 MPa應力對鍛造態(tài)ZK40-0.4Sr裸金屬進行應力腐蝕剩余抗拉強度測試,發(fā)現(xiàn)其應力腐蝕剩余抗拉強度隨著加載應力的增加而逐漸降低,裸金屬在60 MPa應力腐蝕浸泡11 d后即發(fā)生了斷裂。由于表面MAO膜層為脆性層,生理溶液可通過MAO膜層孔洞或微裂紋向基體內(nèi)腐蝕擴展,特別是在應力作用下這些微裂紋和孔洞等缺陷被放大,導致溶液與基體接觸機會增多,膜層破壞被加速,所以MAO對合金的無應力和應力腐蝕剩余抗拉強度提高有限。而MAO+PLGA復合涂層處理中,PLGA可將MAO膜層的孔洞和微裂紋封住,同時PLGA自身具有一定的塑性,在應力作用下,仍能很好地保護基體不受液體腐蝕,合金無應力和應力腐蝕剩余抗拉強度在浸泡28 d以后分別有228.5 MPa和209 MPa,說明合金仍具有良好的力學性能。本論文對鍛造態(tài)ZK40xSr裸金屬和表面MAO,MAO+PLGA和MAO+PLGA+Vancomycin(萬古霉素)復合涂層改性樣品分別進行細胞相容性和血液相容性實驗。研究表明,經(jīng)過MAO、MAO+PLGA和MAO+PLGA+Vancomycin復合涂層表面改性后,細胞毒性評級為1級。特別是,MAO+PLGA和MAO+PLGA+Vancomycin復合涂層其表面有MC3T3-E1細胞大量粘附,血小板粘附少且形態(tài)不發(fā)生改變,抗凝血效果好,溶血率也分別為2.95%和3.91%,滿足國家標準要求,材料的體外生物相容性評級優(yōu)良。
[Abstract]:In recent years, biomedical magnesium alloys have become a research hotspot in degradable medical metal materials. The mechanical properties and controllable corrosion degradation rate matching the implanted sites are the key problems in the study. The interaction between stress and corrosion leads to less research on the early failure of implant materials (stress corrosion fracture). A new type of strontium containing (Sr) degrading magnesium alloy ZK40xSr (Mg-4wt.%Zn-0.6 wt.%Zr-x Sr, x=0,0.4,0.8,1.2,1.6 wt.%) was designed with magnesium alloy as a biodegradable bone nail, bone plate and cardiovascular scaffold. The effects of Sr content on microstructure, corrosion degradation and stress corrosion cracking of cast and forged ZK40xSr alloys were studied. At the same time, the effects of two surface modification methods on the corrosion resistance and stress corrosion degradation properties of forged ZK40-0.4Sr alloys were studied by microarc oxidation (Micro-arc oxidation, MAO) film and micro arc oxidation / poly (lactic acid hydroxyacetic acid) copolymer (Poly (lactic-co-glycolic acid), PLGA) (MAO+PLGA) composite coating. The study found that Sr can be obviously fine. The grain of the cast state ZK40x Sr alloy forms a strip or reticular MgxZnySrz second phase at the grain boundary. The grain refinement can increase the tensile strength and the elongation at the end of the cast alloy. The corrosion rate of the second phase precipitated between the grain boundary and the matrix alpha -Mg causes the alloy corrosion rate to increase with the increase of the Sr content. The second phase of the network is distributed along the grain boundary, and the micro galvanic corrosion between the second phase and the matrix Accelerates along the grain boundary to the base under stress, which leads to the obvious decrease of the mechanical properties of the cast ZK40xSr alloy in the simulated body fluid. That is, the stress corrosion sensitivity of the cast ZK40xSr alloy increases with the increase of the Sr content. After the forging plastic deformation, the average grain size of the forged ZK40xSr alloy decreased from several hundred microns to a few microns. The grain size was obviously refined. The morphology and distribution of the second phase of the grain boundary were changed from the original strip or reticulate structure to the island or ellipsoid, and the tensile strength and the elongation at the post fracture were obviously improved, and the corrosion resistance was also obtained. However, the grain refinement leads to the increase of hydrogen brittleness in the forged ZK40 and ZK40-0.4Sr alloys, and the increase in the susceptibility to stress corrosion. The forging state and ZK40-1.6Sr alloys have reduced the effect of the hydrogen embrittlement image and reduce the stress corrosion sensitivity of the alloys because of their still uniform distribution of island or ellipsoidal brittle second phase. After the MAO and MAO+PLGA composite coatings were used to modify the surface of the forged ZK40-0.4Sr alloy, it was found that the corrosion resistance of the alloy was greatly improved. Especially after the MAO+PLGA composite coating treatment, the corrosion current density of the alloy was reduced by 3 orders of magnitude and the electrochemical impedance properties were obviously improved. 0,20,40 and 60 MPa stress were applied to the forging state ZK40. -0.4Sr bare metal is tested for residual tensile strength of stress corrosion, and it is found that the residual tensile strength of stress corrosion gradually decreases with the increase of loading stress, and fracture occurs when bare metal is immersed in 60 MPa stress corrosion for 11 d. Because the surface MAO film is a brittle layer, the physiological solution can be rotted to the matrix through the pores of the MAO layer or the micro crack. Corrosion expansion, especially under stress, these micro cracks and holes are magnified, resulting in increased contact opportunities of the solution with the matrix and the accelerated failure of the film, so MAO has limited stress and stress corrosion residual tensile strength of the alloy. In the treatment of MAO+PLGA composite coatings, PLGA can seal holes and microcracks in the MAO film, At the same time, PLGA itself has a certain plasticity. Under stress, it can still protect the matrix from liquid corrosion. The residual tensile strength of the alloy without stress and stress corrosion is 228.5 MPa and 209 MPa respectively after soaking 28 d, indicating that the alloy still has good mechanical properties. This paper is on the forging state ZK40xSr bare metal and the surface MAO, MAO+PLG A and MAO+PLGA+Vancomycin (vancomycin) composite coating modified samples were tested for cytocompatibility and blood compatibility respectively. The study showed that after the surface modification of MAO, MAO+PLGA and MAO+PLGA+Vancomycin composite coatings, the cytotoxicity rating was 1. In particular, the surface of MAO+PLGA and MAO+PLGA+Vancomycin composite coatings had MC3T3-E1 cells on the surface. A large number of adherent, platelet adhesion and morphology do not change, anticoagulant effect is good, the hemolysis rate is 2.95% and 3.91% respectively, meet the national standard requirements, the material in vitro biocompatibility rating is excellent.

【學位授予單位】：暨南大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：R318.08

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