Prediction of nanopowder based tape surface roughness and density from a suspension rheological data

DOI: 10.62564/M4-SI1614

Serhii Ivanchenko

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


To create a model for predicting the hydrocluster size in polymer-powder (PVB-BaTiO3) tape casting suspensions, a relation between the Peclet number and viscosity was studied. We used two suspensions with identical composition but different powder size (24 nm and 500 nm). Rheological studies of the dispersion with known-size particles make it possible to calculate the Peclet Number for this dispersion using equations [1], [2]: Pa=(6πr³ γη)/kT Where r – hydrocluster radius, γ – shear rate, η – viscosity, k – Boltzmann constant, T – temperature The relation between the Peclet number and viscosity fits a power low model Pe=$497.66\cdot x^{1,744}$ (nanopowder) and Pe= $1040557.93\cdot x^{1,425}$ (submicron powder) By applying this model to a flow curve of the tape casting suspension, where viscosity is known for each shear rate value, it is possible to calculate a hydrocluster diameter (d) using the equation: d=2∛(PekT/6πγη). Applying this model to rheological data of the nanopowder suspension showed a change in hydrocluster size from 208 to 60 nm, and for the submicron powder suspension, from 3520 to 924 nm. For a surface with the smallest possible roughness, assuming that the powder particles are spherical and tightly packed, the packing factor (φ) is 0,74. In this scenario Ra = d·(1/8), Rz = d·(1/2). In the case of non-dense packing of spheres (φ=0,68) Ra = d·(3/16), Rz = d·(3/4) [3]. The developed method was applied to compare roughness predictions based on calculated hydrocluster size with experimental data obtained from optical profilometry of the tape's surface. Predicted roughness for non-dense packing (φ=0,68) of the nanopowder tape is Ra=39 nm and Rz=156 nm. For the dense packing (φ=0,74) Ra=26 nm and Rz=104 nm. Experimental data: Ra=26 nm and Rz=100 nm. For the submicron powder tape Ra=265 nm and Rz=1062 nm (non-dense packing, φ=0,68) and Ra=177 nm, Rz=707 nm (dense packing, φ=0,74). Experimental data: Ra=261 nm and Rz=1076 nm. The error of predicted data is ranging from 1 to 4 %.

Keywords
тanopowder, tape, roughness, suspension, rheology

Acknowledgments
Not provided

References
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