氧化锆陶瓷注射成型无毒性溶剂脱脂粘结剂体系研究

发布时间：2018-05-08 07:09

本文选题：注射成型 + 大分子粘结剂　；参考：《北京科技大学》2017年博士论文

【摘要】：与其他传统的成型技术相比,陶瓷注射成型(CIM)具有原材料利用率高、机械化程度高、特别适于大规模生产体积小、形状复杂、尺寸精度高等元件的优点,使其在高效制备复杂形状陶瓷部件领域得以广泛应用。有机粘结剂作为其工艺流程中重要一环将直接影响CIM制品的性能;然而目前常用的粘结剂体系存在喂料均匀度差(聚乙二醇粘结剂体系喂料易发生粘结剂偏析)、脱脂阶段易对环境产生污染(石蜡基粘结剂体系脱脂常使用有毒性溶剂)等问题。鉴于环保及喂料均匀度考虑,本论文一方面以石蜡基粘结剂体系为研究对象,采用无毒性溶剂(煤油)脱除粘结剂,从大分子粘结剂类型、粘结剂组成角度,确定最适于煤油萃取脱脂的大分子粘结剂及获得性能优异CIM制品的粘结剂配比;另一方面以聚乙二醇基水溶性粘结剂体系为研究对象,针对粘结剂偏析的问题,从粉体及粘结剂角度展开研究。本论文首先研究了不同类型(单相/复相)大分子粘结剂对注射成型氧化锆陶瓷性能的影响,发现复相大分子粘结剂的使用可使注射喂料更为均匀;混合使用高密度聚乙烯(HDPE)和低密度聚乙烯(LDPE)大分子粘结剂的坯体经煤油萃取后气孔均匀、细小,经烧结后展现出很高的致密度(相对密度98.9%)及优异的力学性能(抗弯强度949MPa),表明L/H粘结剂体系更适于氧化锆陶瓷的注射成型。粘结剂组成是影响注射喂料均匀度的内部因素。研究表明,合理调控粘结剂组成比例可使粘结剂最大程度填充于陶瓷颗粒之间,最终提高喂料的均匀度;通过直接及间接方法推测出均匀喂料的粘结剂组成,通过烧结后性能对比进一步验证了几种均匀度判定法的准确性。粘结剂偏析是聚乙二醇基水溶性粘结剂体系广泛应用的阻碍,从粉体角度来看,喂料粘结剂偏析是由纳米陶瓷颗粒易团聚及与粘结剂相容性差引起的;采用球磨预改性引入油酸可明显改善这一情况,研究表明油酸可通过酯化或离子交换反应吸附在氧化锆颗粒表面,形成一层无定形膜,改变粉体表面极性,从而减少团聚,得到均匀、缺陷少的喂料,气孔分布集中的脱脂素坯,且在烧结后展现出优异的力学性能及致密度。从粘结剂角度来看,喂料粘结剂偏析是由聚乙二醇结晶温度与聚甲基丙烯酸甲酯玻璃化温度差异过大,由聚乙二醇收缩产生的不一致收缩引起的;采用引入适量聚乙烯吡咯烷酮的方法可减少粘结剂偏析引发的缺陷,研究表明聚乙烯吡咯烷酮的引入可有效抑制聚乙二醇的结晶,提高生坯均匀度,降低热脱后坯体气孔尺寸,促进烧结致密化进行,显著减少烧结缺陷及提高烧结体力学性能。
[Abstract]:Compared with other traditional molding technologies, ceramic injection molding (CIM) has the advantages of high utilization of raw materials, high degree of mechanization, especially suitable for large scale production of small volume, complex shape, high dimensional precision and so on. It has been widely used in the field of efficient preparation of complex shape ceramic components. As an important part of the process, organic binder will directly affect the properties of CIM products. However, the commonly used binder system has some problems such as poor feed uniformity (the segregation of binder is easy to occur in the feed system of polyethylene glycol binder system, and the environment is easily polluted in degreasing stage (toxic solvent is often used in degreasing of paraffin based binder system). In view of environmental protection and feed uniformity, on the one hand, in this paper, paraffin based binder system was studied, nontoxic solvent (kerosene) was used to remove binder, from the point of view of the type of macromolecular binder and the composition of binder, The macromolecular binder that is most suitable for kerosene extraction and degreasing and the ratio of binder for obtaining excellent performance CIM products are determined. On the other hand, the water soluble binder system based on polyethylene glycol is taken as the research object, aiming at the problem of binder segregation. The study was carried out from the point of view of powder and binder. In this paper, the effects of different kinds of macromolecular binders on the properties of zirconia ceramics were studied. It was found that the use of multiphase macromolecular binders could make the injection feeding more uniform. The billet with high density polyethylene (HDPE) and low density polyethylene (LDPE) binder was extracted by kerosene and its porosity was uniform and fine. After sintering, high densification (relative density 98.9) and excellent mechanical properties (bending strength 949 MPA) showed that the L / H binder system was more suitable for the injection molding of zirconia ceramics. The composition of binder is the internal factor that affects the uniformity of injection feed. The results show that reasonable control of the proportion of binder can make the binder fill the ceramic particles to the maximum extent, and finally improve the uniformity of the feed, the binder composition of the uniform feed can be inferred by direct and indirect methods. The accuracy of several homogeneity determination methods is further verified by the comparison of sintering performance. The segregation of binder is an obstacle to the wide application of water-soluble binder system based on polyethylene glycol. From the point of view of powder, the segregation of binder is caused by the agglomeration of nano-ceramic particles and the poor compatibility with binder. It was found that oleic acid could be adsorbed on the surface of zirconia particles by esterification or ion exchange reaction, forming an amorphous film, changing the polarity of powder surface and reducing agglomeration. The degreasing billets with uniform feed, less defects and concentrated pore distribution were obtained, and the excellent mechanical properties and densification were obtained after sintering. From the point of view of binder, the segregation of feed binder is caused by the excessive difference between the crystallization temperature of polyethylene glycol and the glass transition temperature of poly (methyl methacrylate), and the inconsistent shrinkage caused by the shrinkage of polyethylene glycol. The method of introducing proper amount of polyvinylpyrrolidone can reduce the defects caused by the segregation of binder. The results show that the introduction of polyvinylpyrrolidone can effectively inhibit the crystallization of polyethylene glycol, increase the evenness of green, and reduce the pore size of green body after thermal desorption. Promote sintering densification, reduce sintering defects and improve sintering physical properties.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ174.62;TQ430.1

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