Particle morphology shape factors

Impression Plasters. Impression plasters are prepared by mixing with water. Types I and II plasters are weaker than dental stone (types III and IV) because of particle morphology and void content. There are two factors that contribute to the weakness of plaster compared to that of dental stone. First, the porosity of the particles makes it necessary to use more water for a mix, and second, the irregular shapes of the particles prevent them from fitting together tightly. Thus, for equally pourable consistencies, less gypsum per unit volume is present in plaster than in dental stone, and the plaster is considerably weaker. 

The morphology of zeolites can also be strongly influenced by the variation in different synthesis parameters. Aluminium content, template/silica ratio, water content, nature of cations present, alkalinity and degree of polymerization of the silica are all major factors which can influence the crystallization and hence the morphology of zeolites [5 - 7]. These particle morphological types can generally be characterized as either spherulitic (polycrystalline spherical) or lath-shaped (polyhedral) in nature. In both cases... 

The physical and chemical properties of magnesium oxide are primarily governed by the source of the precursor, that is, derived from magnesite or precipitated from brine or seawater. Other important factors include time and temperature of calcination and the presence of trace impurities. Electron microscope studies have revealed that the precursor particle morphology has a large impact on the morphology of the final MgO particle. It has been shown that when brucite and magnesite crystals are thermally decomposed at low temperatures, pseudomorphs of a size and shape similar to the parent crystal are formed. 

Various theories and empirical expressions are available (14. 16) for estimating K for special situations. Obviously, this factor will depend on the volume fraction of impermeable particles, their shape, and their arrangement in space, that is, morphology. Crystalline polymers are much better barriers to permeation than are equivalent amorphous polymers by virtue of the obstruction to transport caused by their crystallites. Often their resistance to permeation can be further improved by stretching or drawing so that the crystals are converted from a random arrangement to a more ordered array such as that illustrated in Figure 4. 

Although not yet taking into account the structural chemistry of the surfaces, this case study shows that the crystalline morphology can have an effect on the rate of dissolution, that is dissolution rate is faster when the shape factor which is greater. This model is robust and can be applied to compare the dissolution rates of different morphologies and extended to examine different polymorphs. The approach can also take into account the polydisperse nature of particles. Ultimately, this will allow the formulator and process chemist to examine the link between the evolving chemical route and API particles and the dissolution rate. 

The nature of the carbon used as an electronic conductor may vary carbon black from different sources with particle size distributions (PSDs) of 30-40 nm and specific surface areas of 100-2,000 mVg (BET surface), activated carbons, carbon fibers or indeed carbon nanotubes (CNTs). The type of carbon, its morphology and its mode of dispersion or coating play a part in the resulting electrical properties of the electrode. For instance, carbon fibers or CNTs improve the electronic conductivity of thick electrodes, because their high shape factor enables them to form a good electronic percolation lattice.In the presence of CNTs, a capacity of 900 mAh/gs in the first cycle and 75% retention of capacity after 60 cycles (with a charge/discharge current density of 100 mA/g and 68% sulfur in the... 

The miscibility on the molecular level is not necessarily desirable for all properties of blend. For example, for the impact strength of PC/ABS blends, the morphology (shape or structure), size distribution, and average size of rubber particles are key factors. However, the miscibility may be necessary for some specific properties of blends. For example, the optical clarity of PC-rich blends such as PC/PMMA requires the critical minimum size of well dispersed PMMA particles. ... 

The shape, content, size, and size distribution of dispersed rubber particles are important factors affecting the toughening effect of PP impact modified copolymer, which relate to the micromorphological structure of the material. A wide range of characterization methods has been applied to study these rTPOs. A number of these techniques are suited to providing information on the morphology of PP copolymers where the EPR domains typically extend form a few hundred nanometers to a few micrometers in size. 

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