School of Engineering and Materials Science
Research Student Awards
PhD Thesis: Investigation into the use of a purpose-designed continuous ink jet printer for the deposition of ceramics on different substrates
Author: WILLIAMS, Susan
Supervisor(s): Mohan Edirisinghe
The use of continuous ink-jet (CIJ) printers to process ceramic suspensions was advanced in this research with the preparation and successful printing of ZrO2 and TiO2 inks on a variety of substrates.
The ink preparation was optimised using a statistically designed experiment where the order of raw material addition, the power input of the mixer and the amount of dispersant were varied. The suitability of the ink for use in CIJ printing was assessed by measuring the characteristics of the ink and examining the performance of the ink in the printer over extended periods. The quality of the printed ink was assessed by examining the appearance of the single drops, a single layer of adjacent drops and multiple over-printed layers.
It was found that the ceramic was drawn to the circumference of the drying drop leading to the formation of a ring structure or halo effect. With multiple drops, both planar and 3-dimensional, this effect was exaggerated. This was ubiquitous; independent of drying temperature, substrate surface energy or charge on the substrate. Splashing around the printed drops was seen with all ink-substrate combinations. Due to the low viscosity of the liquid and the high velocity of the impacting drop it was not possible to prevent this phenomenon.
The ZrO2 ink was printed on titanium to act as a mask in a diffusion bonding application. Due to the splashing phenomenon, ceramic CIJ printing was not considered suitable for this application as the printed mask had poor definition.
Video contact angle measuring equipment was used to estimate the surface energies of a range of substrates and to capture the shape of drops as they landed and dried. No discernible differences were seen in the splash formation or ceramic segregation across the dried drop relics on substrates with varying surface energies. The splash, ceramic distribution and drying behaviour of the drops also appeared to be independent of the substrate onto which it was printed.