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Research Programs Directed

 
   
  Powder technology
 
Surface area and uniformity Publications 1-5, 18
    Developed a measure of the specific surface area and a measure of the non-uniformity of surface composition from the adsorption of non-reactive gases by powders over a range of partial pressures.
       
 
Particle Distributions Publications 6, 10 – 12
    Developed the analysis techniques, used to this day in various forms, to obtain particle-size distributions from the time-dependent fluctuations of scattered light. We obtained early real-time autocorrelators in the late 1980’s and used them to analyze the intensity correlation of diffusing particles.
       
    Surface energy Patents 39, 43-45
    A particle has a different energy of interaction with every medium. Predicting the magnitude of this interaction requires characterizing both the particle and the medium. Properties of liquids, polymers, and plastics have been characterized by many empirical scales. This program developed analytic techniques to measure particle properties on the same scales and hence provide the ability to predict the strength of particle-medium interactions. This project was also supported by research at The University of Chemnitz (Germany) under the guidance of Prof. Stefan Spange, 2006.
       
  Nanoparticles Patents 28-29, 32, 42
    Nanoparticles are especially interesting in dispersions because their small size create interesting changes in their aggregate properties, such as color and their small size creates new scaling relations with the matrix in which they are dispersed. For instance, nanoparticles are small compared to polymeric dimensions so that the behavior of nanoparticle dispersions are quite different that micron-sized particles of the same materials. The color of nanoparticles changes with interparticle distances. These patents and applications give some commercially important examples.
       
  Dispersions  
    Nonaqueous systems            Publications 21 – 23, 25 – 29;

Patents 9, 12 – 15, 51

    This project advanced the understanding of dispersion stabilization in nonaqueous dispersions by means of surface charges. The size- and electric charge-scaling laws and the necessary concepts for this nonaqueous ion chemistry were developed. Significant advances in printing and display technologies followed from this work. For example, commercial displays are now available that have two colors of pigment, oppositely charged, in the same dispersion, stable for years. This project was also supported by research at Yale University under the guidance of Prof. Eric Dufresne, 2005 – 2007.
       
    Flocculation and crystal growth Patents 1 – 4
    Crystallization from solution and adsorption from solution are related but often competitive processes. This project took advantage of the understanding of the differences to develop novel chemistries to control the rates of both processes.
       
    Phase transfer of particles  
    Invented a general surface-treatment technology for the phase transfer of particles between two immiscible phases, ideas particularly useful for nanoparticles. (This work continues.)
       
  Foams Publication 8
    Foaming and defoaming are challenges in their own right, but the use of foaming as a tool to study dispersion and emulsion stability is less often appreciated. Multi-component systems show a sudden increase in foaming or a sudden decrease in foaming when the solubilities of components change. Therefore the tendency to foam, or not, is an analytic tool for surface activity in complex systems.
       
  Surfactants Publications 7, 9, 15, 26
    Three surface phenomena are closely related: preferential adsorption, two-dimensional spreading pressures, and surface concentrations. All three, when carefully understood, give access to the understanding the behavior of surfactants.
       
  Capillarity                                         Publications 16, 20, 24, 30; Patents 7, 39
    Capillarity includes all those phenomena controlled by surface tension: either through Laplace pressures or Marangoni flow. Concentrating attention on the pressures generated at curved surfaces or stresses created by surface tension gradients, rather than just surface tension itself proves to be a fruitful method for analytic methods and the invention of new processes.
       
       
       

Contact: imorrison@colloidaldispersions.com 

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