Particle size control technology

Frock, H. N., and Weiss, E. L. Particle size control using light-scattering technology, Powder Technol., 35-39, (1988). 

Dispersion polymerization is a convenient procedtue to form larger solid particles. Uniform-sized polymer beads with diameters between 0.1 and 10 pm are finding an ever increasing role in a number of coatings, electronics, microelectronics, biomedical, and information technology applications. " Particle size control and nauow size distribution are key parameters for most of these applications. Dispersion polymerization is generally recognized as a type of... 

A wide variety of particle size measurement methods have evolved to meet the almost endless variabiUty of iadustrial needs. For iastance, distinct technologies are requited if in situ analysis is requited, as opposed to sampling and performing the measurement at a later time and/or in a different location. In certain cases, it is necessary to perform the measurement in real time, such as in an on-line appHcation when size information is used for process control (qv), and in other cases, analysis following the completion of the finished product is satisfactory. Some methods rapidly count and measure particles individually other methods measure numerous particles simultaneously. Some methods have been developed or adapted to measure the size distribution of dry or airborne particles, or particles dispersed inhquids. 

However, the chief purpose of introduction of fillers into PCM is to make possible the modification of polymers and thereby create materials with a prescribed set of physico-mechanical properties, and, obviously, the properties of filled materials may be controlled by, for example, varying the type of the base polymer (the matrix ) and filler, its particle size distribution and shape. It may not require a large quantity of filler [7]. Thanks to considerable advances in PCM research, their use in a broad range of industries — machine building, construction, aerospace technology, etc. — has become extensive [8 — 11]. 

The synthesis of nanoparticles has been intensively pursued not only for their fundamental scientific interest, but also for many technological applications [1]. For many of these applications, the synthesis of monodisperse nanoparticles (standard deviations a < 5%) with controlled particle sizes is of key importance, because the electrical, optical, and... 

This type of technology is a part of the group of air pollution controls collectively referred to as wet scrubbers. The removal of air pollutants is achieved by the use of condensation to increase pollutant particle size, followed by inertial interception. Condensation scrubbers are typically intended to control fine PM with an aerodynamic diameter of between approximately 0.25 and 1.0 pm. 

Using sol-gel technology combined with water-in-oil (W/O) emulsions, a number of silica-based ceramic particles with independent control over the release rate and particle size are to be commercialized by Australian company CeramiSphere (and other companies) for a range of... 

Transition-metal nanopartides are of fundamental interest and technological importance because of their applications to catalysis [22,104-107]. Synthetic routes to metal nanopartides include evaporation and condensation, and chemical or electrochemical reduction of metal salts in the presence of stabilizers [104,105,108-110]. The purpose of the stabilizers, which include polymers, ligands, and surfactants, is to control particle size and prevent agglomeration. However, stabilizers also passivate cluster surfaces. For some applications, such as catalysis, it is desirable to prepare small, stable, but not-fully-passivated, particles so that substrates can access the encapsulated clusters. Another promising method for preparing clusters and colloids involves the use of templates, such as reverse micelles [111,112] and porous membranes [106,113,114]. However, even this approach results in at least partial passivation and mass transfer limitations unless the template is removed. Unfortunately, removal of the template may re-... 

Modern Manufacturing Techniques. Manufacturing techniques for making bulk vitreous silica are for the most part improved variations of the historical processes. The main exception is the sol—gel process (see Sol-gel technology). All processes involve the fusion or viscous sintering of silica particles. The particles can be in the form of a loose powder or a porous preform. The powders can be made from natural quartz or from the decomposition of chemical precursors, such as silicon tetrachloride, and tetraethylorthosilicate (1 EOS). In some approaches, such as flame hydrolysis, the powder is produced and fused in a single step. The improvements made to these techniques deal mainly with the procedures used to prepare the powders, that is, to control purity and particle size, and the specific conditions under which the powders are consolidated. 

---