仿生梯度多孔镍钛合金共凝胶注模成形过程基础研究

In order to solve the processing difficulty and high manufacture cost of porous NiTi parts with complex shape, the project put forward a new research idea to directly prepare gradient porous NiTi alloys and its parts with biomimetic bone porous structure using co-gel casting technology with different type of slurries based on the design of biomimetic structure through combination of CT scanning and image processing technology. The effects of all kinds of factors such as the characteristics of powder, pore forming agent types, morphology and content, solid content and process parameters on the rheological properties and casting process of slurry, the mechanical properties and pore structure of the porous materials are studied. By means of the ANSYS simulation of the co-gel casting process, the cooperative rheological behavior, the evolution of the interface microstructure and morphological among different slurries during co-gel casting are revealed. The evolution law of microstructure and pore morphology and structure during the microwave reaction sintering process between Ni and Ti powders is clarified. Combining co-sintering numerical simulation and sintering experiment, the co-densification behavior of different slurries are studied and the co-sintering model is determined, to solve the problem of the precise regulation of gradient pore structure of NiTi porous alloys. On this basis, the relate theory and technology combined the co-gel casting and the microwave sintering of different slurries of Ni and Ti powders to prepare the biomimetic gradient porous NiTi implant materials matching with the human bone are established. The research results not only enrich and develop the theory of gel casting, but also have an important role in promoting the preparation and wide application of gradient porous medical implant materials.

针对复杂形状多孔NiTi合金难加工成形及高成本难题，项目提出结合CT扫描及图像处理构建仿生骨多孔结构基础上，采用不同浆料共凝胶注模成形直接制备仿生梯度多孔NiTi合金及制品的研究思路。研究粉末特性、造孔剂类型、形态及用量、固相含量、工艺参数等因素对浆料流变性能、注模工艺以及多孔材料孔隙结构和力学性能的影响，借助共注模过程的ANSYS模拟，揭示不同浆料在共注模过程中的协同流变行为及其界面结构、形态演变规律，阐明Ni、Ti粉末在微波烧结中的组织和孔隙结构演变规律与不同浆料的共致密化行为，结合数值模拟方法确定共烧结模型，解决材料孔隙形态及梯度结构的精确调控问题，建立一种共凝胶注模成形-微波烧结直接制备力学性能及孔隙结构与人体骨匹配的仿生梯度多孔NiTi合金及零部件的相关理论及技术。研究成果不仅丰富并发展了凝胶注模成形相关理论，也对梯度多孔医用植入材料的制备及广泛应用具有重要的促进作用。

多孔NiTi合金具有优异的力学性能和生物相容性，广泛应用于医用植入材料。针对复杂形状多孔NiTi合金难加工成形及高成本的难题，项目发展了共凝胶注模成形-微波烧结新技术。根据钛粉、镍粉易氧化特点，设计了一种非水溶性凝胶体系，即以正辛醇为溶剂，甲基丙烯酸羟乙酯为单体，1，6-己二醇二丙烯酸酯为交联剂，过氧化苯甲酸叔丁酯为引发剂，N,N-二甲基苯胺DMA为催化剂；在分析各种分散剂分散机理和分散效果之后，优选兼具静电阻止及位阻效应的silok7456作为分散剂；研究了分散剂、单体及固相体积分数等因素对浆料流变行为及其固化过程影响规律，建立了可控固化手段，揭示了HEMA-HDDA-TBPB-DMA凝胶体系固化动力学方程，其固化反应表观活化能为61.52 kJ/mol，反应级数为0.91，以保证浆料的顺利注模及坯体均匀性。研究了镍钛合金的致密化过程及微观结构演变规律，证实了微波对 Ni、Ti 反应烧结体系中原子扩散与致密化的促进作用。通过固相体积分数、原料粉末粒度、造孔剂的粒径及用量，烧结工艺等因素的控制可以实现多孔NiTi合金孔隙结构及性能在一个较大范围内进行精确调控，明确了粉末-工艺-孔隙结构-性能的内在关系，其抗压强度与孔隙率关系符合 Eudier方程，即σb=492.15(1-1.3θ2/3)。通过对多浆料的个性化梯次设计及烧结升温工艺的精确控制，采用共凝胶注模-微波烧结制备出孔隙率从10%至65%的呈梯度连续变化的轴向或径向梯度多孔 NiTi 合金，其综合性能优良，匹配人体骨的力学性能，为低成本快速制备复杂形状移植骨提供了新技术及新方法；针对造孔剂加入导致浆料粘度急剧增大及充模困难的难题，发展了一种凝胶注模发泡成形新工艺，该技术可以制备高孔隙率的多孔镍钛合金；开发了一种微量掺杂铜及硒的高抗菌性多孔NiTiCuxSey（x,y<1.5%）合金，进一步提升NiTi合金的耐腐蚀性能及抗菌性能。研究成果不仅丰富了凝胶注模成形技术相关理论及应用，而且对仿生多孔NiTi医用植入材料的广泛应用具有重要的促进作用。