Comparison of the colloidal stability of 10wt.% suspensions of three commercial alpha alumina powders (Taimei dv50=132nm and Nanotek dv50=93nm, Degussa C dv50=40nm), suspended in 0.01M KNO3 (pH=3, zeta potential =53mV). The curves show the interaction potentials as a function of distance, whereas the horizontal lines present the barrier required for the suspension to remain stable for a given time (dashed line=1h, solid line=5h).
As shown in the figure, the bigger the particle size the easier it is to obtain the required repulsive barrier for stability. The extremely fine Degussa C powder will agglomerate almost instantly under the chosen conditions while the Nanotek will agglomerate after more than one hour. This lack of stability would lead to green bodies with lower density, less homogeneous pore structure and poorer sintering properties than the stable powder suspension.
This example shows that the software can be used to choose powders and suspension conditions for a given application with specific processing limitations, a task being especially tricky on the nanometer range. This approach will guide experimentalists in the nanometer regime where little experience and literature is available.
A new version currently being developed will allow for dissimilar particles (size and material), the integration of plug-in modules for additional forces, as user input for specific requirements (e.g magnetic forces or other steric models) as well as an advanced plotting facility. A web driven database of Hamaker constants as well as a wizard allowing the inexperienced user to quickly create a model suitable for their specific problem are also planned.
The software is written in Java and will thus run on all major operating systems (tested on Microsoft Windows, Mac OS, Linux). For more information please visit the Nanoker website, which contains a link to the software.