Nanomaterials
_Fundamental Concept_
_Size Concerns_
_Materials Used_
_Chemical Processing of Ceramics_
In the treatment of fine ceramic, the irregular particle sizes and types in a typical powder often lead to uneven packing morphologies that result in packing density variations in the powder compact. Uncontrolled agglomeration of powders due to attractive van der Waals forces may also give rise to micro structural inhomogeneities.
_Fundamental Concept_
_Size Concerns_
_Materials Used_
_Chemical Processing of Ceramics_
In the treatment of fine ceramic, the irregular particle sizes and types in a typical powder often lead to uneven packing morphologies that result in packing density variations in the powder compact. Uncontrolled agglomeration of powders due to attractive van der Waals forces may also give rise to micro structural inhomogeneities.
Differential stresses that develop as a result of non-uniform drying shrinkage is directly related to the rate at which the solvent can be removed, and therefore heavily dependent on the distribution of porosity. Such stresses have been associated with a plastic-to-brittle transition in consolidated entities, and can provide the crack propagating material in unfired body, if not relieved.
Furthermore, any fluctuation in packing density of the compact as it is prepared for the oven frequently is amplified during the sintering process which gives inhomogeneous densification. Some pores and other structural defects associated with density variations have been shown to play a negative role in the sintering process of growing and reducing the end-point densities.Differential stresses arising from inhomogeneous densification has also been shown to result in the propagation of internal cracks, and thus is the strength-controlling defects.
It would therefore be desirable to treat a material in a way that is physically consistent in terms of distribution of components and porosity instead of using the particle size distributions that will maximize the green density. Containment of a uniformly dispersed collection of strongly interacting particles in suspension requires complete control of particle-bound particle size interactions. Monodisperse colloids offer this potential.
Furthermore, any fluctuation in packing density of the compact as it is prepared for the oven frequently is amplified during the sintering process which gives inhomogeneous densification. Some pores and other structural defects associated with density variations have been shown to play a negative role in the sintering process of growing and reducing the end-point densities.Differential stresses arising from inhomogeneous densification has also been shown to result in the propagation of internal cracks, and thus is the strength-controlling defects.
It would therefore be desirable to treat a material in a way that is physically consistent in terms of distribution of components and porosity instead of using the particle size distributions that will maximize the green density. Containment of a uniformly dispersed collection of strongly interacting particles in suspension requires complete control of particle-bound particle size interactions. Monodisperse colloids offer this potential.
