基于动电学研究磁流变抛光液中双相颗粒的分散行为

发布时间：2018-05-28 17:05

本文选题：磁流变抛光液 + Zeta电位　；参考：《中国工程物理研究院》2015年硕士论文

【摘要】：磁流变抛光技术是一种确定性的超精密光学元件加工技术,是强激光光学元件表面无缺陷加工的主要手段。磁流变抛光液是磁流变抛光技术的关键和基础,它直接作用于光学元件表面并决定抛光去除过程与效果。目前,多通过抛光工艺试验研究磁流变抛光液的工艺性能,对其中的基本材料学和材料物理化学性能问题涉及较少,尤其对其中的双相颗粒的聚集-分散行为缺乏有效的认识。这直接制约了磁流变抛光液和抛光技术的发展。本文提出以颗粒动电学特征为核心建立多尺度的方法,研究双相颗粒的聚集-分散行为,将为磁流变抛光液的设计和表征提供相应的理论支持和表征方法。首先分析了双相颗粒之间的主要相互作用并推导了其表达式,即范德华作用、空间位阻作用、双电层作用。基于扩展的DLVO理论,建立了磁流变抛光液中双相颗粒之间相互作用的物理模型；在深入分析模型的基础上,得出了双电层作用是影响磁流变抛光液中双相颗粒之间分散行为的主要因素；进一步理论分析发现,双相颗粒之间的表面电位之比是影响双电层作用的主要因素。通过理论计算发现,双相颗粒表面电位即使较大,但是在双相颗粒表面电位差异越大的情况下,也有可能发生类电荷吸引所致的异质聚集。在理论分析计算的基础上,通过实验研究了磁流变抛光液中颗粒的分散行为,并提出了适合表征单相抛光粉颗粒悬浮液的方法和适合表征双相颗粒之间分散状态的方法。首先,对单相纳米抛光粉颗粒悬浮液的表征,提出了Zeta电位,流变性能和粒度分布等多尺度的表征方法,其中最核心的是Zeta电位的分析表征；其次,基于电声振幅(ESA)效应的电声方法研究发现,带同种电荷双相颗粒之间的表面电位差异较大时易发生类电荷吸引所致的异质聚集,很好地验证了前面理论分析的结论。实验发现,由于动电学差异的因素,单相颗粒悬浮液与双相颗粒悬浮液的分散性差异较大。通过改进的ESA方法可以定性判断磁流变抛光液中双相颗粒的分散状态。采用磁场环境下固化的方式研究了异质聚集的微观结构,实验结果很好的验证了上述结论。最后,分析了磁场对磁流变抛光液异质聚集和流变性能的影响。结果表明,只有当异质聚集体界面处的实际接触半径小于临界接触半径的时候,界面处的磁致冲击力才有可能使聚集体重新解聚。双相颗粒之间的异质聚集对磁流变抛光液的零场流变性能影响显著,但是对磁场作用下的流变性能影响有限。
[Abstract]:Magnetorheological polishing (MRF) is a kind of deterministic ultra-precision optical element machining technology, which is the main method of non-defect machining on the surface of high-power laser optical element. Magnetorheological polishing fluid is the key and foundation of magnetorheological polishing technology. It acts directly on the surface of optical elements and determines the polishing process and effect. At present, the process performance of magnetorheological polishing liquid is mostly studied by polishing process test. There is little concern about the basic material science and physical and chemical properties of materials, especially for the agglomeration and dispersion behavior of biphasic particles. This directly restricts the development of magnetorheological polishing fluid and polishing technology. In this paper, a multi-scale method is proposed to study the agglomeration and dispersion behavior of biphasic particles, which will provide theoretical support and characterization methods for the design and characterization of magnetorheological polishing fluids. Firstly, the main interactions between the two phase particles are analyzed and their expressions are derived, that is, van der Waals interaction, spatial steric hindrance, and double electric layer interaction. Based on the extended DLVO theory, a physical model of the interaction between two-phase particles in magnetorheological polishing fluid is established. It is concluded that the action of double layer is the main factor to influence the dispersion behavior of duplex particles in the magnetorheological polishing fluid, and further theoretical analysis shows that the ratio of surface potential between biphasic particles is the main factor affecting the action of double layer. It is found by theoretical calculation that even if the surface potential of biphasic particles is larger, the heterogeneity aggregation caused by charge-like attraction may also occur when the surface potential of biphasic particles is greater than that of biphasic particles. On the basis of theoretical analysis and calculation, the dispersion behavior of particles in magnetorheological polishing solution was studied experimentally, and a suitable method for characterizing the suspension of single-phase polishing powder and the method for characterizing the dispersion state between two-phase particles was put forward. Firstly, the multi-scale characterization methods such as Zeta potential, rheological properties and particle size distribution are proposed for the characterization of single-phase nano-polishing powder suspension, in which the core is the analysis and characterization of Zeta potential. The electroacoustic method based on the electroacoustic amplitude (ESA) effect shows that the heterogeneity aggregation caused by charge-like attraction is easy to occur when the surface potential difference between particles with the same charge is large, which verifies the conclusion of the previous theoretical analysis. It is found that the dispersion of single-phase and dual-phase granular suspensions is different from that of biphasic suspension due to the difference of dynamic electricity. The dispersion state of biphasic particles in magnetorheological polishing fluid can be qualitatively determined by the improved ESA method. The microstructure of heterogeneous aggregation was studied by solidification in magnetic field. Finally, the effect of magnetic field on the heterogeneous aggregation and rheological properties of magnetorheological polishing liquid is analyzed. The results show that only when the actual contact radius at the interface of heterogeneous aggregates is less than the critical contact radius, can the magnetic impact force at the interface make the aggregates depolymerize again. The effect of heterogeneous aggregation between two-phase particles on the zero-field rheological properties of magnetorheological polishing fluids is significant, but the effect on the rheological properties of magnetorheological polishing fluids is limited.
【学位授予单位】：中国工程物理研究院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB306

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