Theoretical Studies On Nm-Sizer

Particle sizing, especially for nano-particles, is of crucial importance due to their special characters. PCS (Photon Correlation Spectroscopy), also called DLS (dynamic light scattering), is almost exclusively employed in nano-particle sizing. The related theory is based on the Brownian motion. This dissertation tackles the basic issues of nm-sizer and its developments and the principle and instrumentation of nm-sizer using PCS. The thesis pays great attention towards some related theories for data processing and particle size distribution retrieval, which is the key point of the present research work.The section of theories on data processing and particle size distribution retrieval is further detailed into three parts:1. Mono-disperse system: It is simple for data processing for this kind of particulate system, it is proven that polynomial fitting method can simply give the target results even for noisy simulation data.2. Model poly-disperse system: Parameter-searching method works great. We use Rosin-Rammler distribution function to describe the nano-particle system. This distribution model is reliable in practice and can simplify data processing. We have discussed a lot about the errors associated with this method and the ways to reduce them.3. Omni poly-disperse system: The retrieving method for arbitrarily distributed system presents the greatest challenge. This is, therefore, the key point and innovation of this dissertation. Our vast discussions range from basic physical principles, to basic mathematical theory, and to computer programming. In contrary to parameter searching method, this algorithm makes no pre-assumptions on size distribution of the particle system. Theoretically, our method can retrieve particle size distribution for any system, it is, however, pretty hard to obtain acceptable results in practice. To that end, we cast the integration equation to be solved into a linear equation system. The non-negativity of the solution to this equation system can be ensured by deploying the constrained least squares criteria. Our vast numerical simulation corroborates this theoretical footing by fairly successfully restoring particle size distributions of the target systems, with a really good control over the error and stability.In the last chapter, we introduce a circuit design scheme for a real sizer's data acquisition system, and made some certain progress.In conclusion, this dissertation talked the related theories for data processing and particle size retrieval for nm-sizer, made extensive numerical simulation, and obtained fairly good results.