金属粉末非水基凝胶注模成形中的浆料悬浮及凝胶化机理

Copper and aluminum base non-aqueous gelcasting system were investigated in the present study. In order to establish and perfect the existing mechanism for slurry suspension stability, the influences of species and content of solvent and dispersant, surface state of metal powder, and suspension temperature on slurry suspension stability were significantly studied. Especially, the effects of incorporation of metal powder and solvent into gelcasting system on the chain initiation, propagation and termination were investigated. In addition, the influence laws of metal powder (shape, size, volume fraction, surface state, etc.) and solvent molecules (variety, content, chemical property, etc) on in situ solidification process were revealed by means of related knowledge of molecular dynamics. The drying process of green body organic solvent removing, process of gel removing, mechanism of sintering process, as well as properties of sintering specimens were studied. In the meantime, the influences of species and content of monomer, crosslinking agent, dispersant and initiator on green body sintering process, green body properties and sintering process were also investigated. This work intent to successfully fabricate the Al and Cu based products with complex shape, narrow volume and excellent performance, according to the slurry suspension stability, gel solidification as well as green body sintering mechanism. Expanding the application area and research range of gelcasting technology was also the key aim of this research.

以铝基、铜基非水基凝胶注模成形体系为研究对象，深入探讨金属粉体的非水基凝胶体系中的溶剂、分散剂种类与含量、金属粉体表面状态、悬浮体温度等因素对非水基凝胶体系浆料悬浮稳定性的影响，建立与完善现有浆料悬浮稳定机制；重点研究凝胶化过程中金属粉体与溶剂的引入对链引发、链增长、链终止过程的影响，结合分子动力学的相关知识，揭示金属固相颗粒（形状、粒径、体积分数、表面状态等）和溶剂分子（种类、含量、化学性质等）对原位固化过程的影响规律；研究坯体有机溶剂去除的干燥过程、凝胶去除的排胶过程以及烧结过程的机理和烧结制品的性能；探讨体系中单体、交联剂、分散剂及引发剂等组分的种类和用量对坯体干燥过程、坯体性能和烧结过程的影响规律，并结合浆料悬浮稳定和凝胶固结理论，制备出形状复杂、体积收缩小、性能优异的铝基、铜基等制品，拓展凝胶注模成形的应用领域和研究范围。

凝胶注模成形工艺结合了胶体化学及材料学的工艺，可以实现近净尺寸成形，具有一系列的优势，已经在陶瓷的生产中被广泛的应用。本课题是将此工艺应用于粉末冶金领域，对金属粉末材料的成形是一项具有意义的工作，同时研究了金属粉末凝胶注模成形的机理。通过反应机理，推导出了链引发、链增长、链转移和交联反应的方程式；通过差示扫描量热法研究凝胶体系的固化反应过程，得到活化能均值为2258 KJ/mol，反应级数为0.95；通过动力学研究确定了体系的固化工艺；通过热分析和热重-红外-质谱联用系统研究反应动力学过程，发现凝胶后金属坯体的聚合物主要是由于自由基的聚合反应形成的；采用热重-差示扫描量热-红外-质谱联用技术，研究了聚合物热分解脱脂的过程，建立动力学方程，发现聚合物脱脂反应级数为1，活化能为79.86~108.63 k Jmol-1；综合红外谱图与碎片离子分析，得到了在不同温度范围聚合物的挥发、裂解、分解行为；研究了固化机理，发现在低温干燥过程中裂纹呈现多发性，而在高温干燥过程中裂纹呈现爆裂性。在上述研究的基础上总结出了各种试剂的选择原则，并自主开发了适合金属粉末凝胶注模的凝胶体系。一例：溶剂1,2-丙二醇（PBO）、甲基丙烯酸羟乙酯（HEMA）为单体；二乙二醇二丙烯酸酯（DEGDA）为交联剂；过氧化苯甲酰（BPO）和N,N-二甲基苯胺（DMA）组成的氧化还原体系为引发剂；聚乙烯吡咯烷酮（PVP）K30为分散剂。采用凝胶注模成形的铁基样品，含碳量0.72%的碳钢件，含97.2%铁、2.0％铜、0.8％碳的Fe-Cu-C合金，性能均优于普通粉末冶金方法，并且可以制备形状更为复杂的样品。最终制备出了致密度达76%，抗拉强度达205 MPa，维氏硬度达124 HV的复杂形状铜试样，成功获得了力学性能优异的铝铜合金多孔材料，孔隙率和显微硬度分别为42.8 %和48.58 HV。.出版专著1部；发表论文11篇；培养博士生2人，硕士生3人。