Colloidal Crystal Elastic Modulus Measurement And Light Scattering Method For Measuring The Velocity Of The Colloidal Aggregation

When the colloidal system transformed the dispersed sate into the state of aggregation,nearly a great number of its features change. Therefore, the aggregation and stability of thecolloidal dispersion has profound theoretical significance. While the researching onaggregation rate constant is core of colloid aggregation and stability. This paper presents aseries of works in the following aspects:Firstly, we improve the precision of the light scattering measuring aggregation rateconstant and expand the range of large particle dispersion. We could use static lightscattering and dynamic light scattering to measure the absolutely aggregation rate constantrespectively by introducing T-matrix method, and comparing its result with dynamic andstatic light scattering method is consistent. Then in comparison with the RGD theory:Under different angles, using the RGD theory measure absolute aggregation rate constantwhich has largely difference, even the value is negative which has no physical meaning.This indicates the correctness of leading the T-matrix into light scattering. The result shows,our study simplifies the measurement skill of aggregation rate constant, and broadens therange of application of light scattering method.Secondly, in this article, we present the blind existing in the measurement of lightscattering, in the range of angle, it is inaccurate for the measurement of particleaggregation rate constant, and there is a large error between the measurement results,Through theoretical analysis, we deduct that the reasons give rise to the optical parametersof two single particle equaling the double particles. In consequence, when we use the lightscattering method to measure the aggregation rate constant, if we want to gain the accurateresults, we should avoid the angle of blind zone.Thirdly, we compare light scattering method with turbidimetric method which isintroduced the T-matrix. We find the accurate result which is measured by light scatteringmethod and turbidimetric method respectively. However, light scattering method is suitablefor a low concentration of the dispersion system, while the turbidimetric method is moresuitable for measurement of a high concentration of dispersed system. Fourthly, colloidal particles could self-assemble colloidal crystal. While the elasticmodulus of colloidal crystal is only several Pa. Conventional methods can not satisfy theneed of measuring the elastic modulus. So we built the experimental device to quicklymeasure the elastic modulus---the method of torsional resonance, and successfully measurethe elastic modulus of the crystal.