Structural and physical characterization of iron-oxide based inks for inkjet printing

Iron-oxide nanopowders, hematite and magnetite, are basic compounds applied in several steps for the prepa-ration of magnetic inks. These steps included ball milling of the nanopowders in dowanol, mixing with poly-siloxane binder dissolved in pure ethanol, and final dilution in hexanol to adjust the rheological parameters of the inks applied in the inkjet printing technology under ambient conditions. Various experimental methods, carried out for the samples in all forms (powder, ink, and layer), have yielded basic data concerning morphology, chemical, and physical properties and allowed to follow their changes during individual processing steps. The phase analysis of both the pristine iron-oxides did not confirm the pure single-phase compositions. The hematite contained also a substantial amount of magnetite and maghemite contributing to its unusual high saturation magnetization, Ms, of 66 Am2kg(-1). The magnetite contained about 38 % maghemite and its Ms was 117 Am2kg? 1. The magnetic parameters of both the iron-oxides in the nanopowder and ink forms were comparable contrary to those measured in the solidified state after printing. Substantial decrease in the Ms values and changes of the remnant magnetization and coercivity were observed in both cases. The obtained results were verified by measurement of a designed magnetite core printed on the flexible foil and tested as a magnetic sensor. Nevertheless, despite the worse magnetic parameters, the relative permeability, approximately 2, was twice as high as that reported by other authors.

Automated summary

The application of iron-oxide nanopowders in the preparation of magnetic inks was studied. Basic data of samples in different forms were obtained through experimental methods and the changes during processing steps were tracked. It was found that the iron-oxides were not pure single-phase compositions, with substantial amounts of magnetite and maghemite present in hematite. The magnetic parameters of the iron-oxides were comparable in nanopowder and ink forms, but showed significant changes in the solidified state after printing.