Development of PZT Suspensions for Ceramic Ink-Jet Printing
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Development of PZT Suspensions for Ceramic Ink-Jet Printing
B. Derby, D.H. Lee, T. Wang and D. Hall Manchester Materials Science Centre, UMIST and the University of Manchester, Grosvenor St., Manchester, M1 7HS, UK ABSTRACT The direct ink-jet printing of ceramic powders requires the development of highly fluid suspensions of ceramic particles with viscosity < 40 mPas. Here we describe the development of two such ceramic suspensions, which contain up to 30% by volume of PZT particles in either an azeotropic mixture of MEK and ethanol or in an alkane wax at 120 °C. The influence of various processing parameters on fluid rheology are investigated and trial fluids have been passed through an ink-jet printing head. INTRODUCTION Ink-jet printing is now a mature technology and has widespread applications in the fields of printing, product marking and microdosing. Initial work combining ink-jet printing and layered manufacturing for the production of ceramic parts was undertaken by Sachs and co-workers, using a process of selectively printing binders onto powder beds [1]. Evans and co-workers extended this concept by pioneering the direct printing of ceramic suspensions using ink-jet printers [2-4]. Direct ink-jet printing is a very attractive route for the freeform fabrication of ceramics as fabrication of an object by droplet deposition allows the composition of each voxel of a design to be individually determined. This extends the fabrication method to components requiring multiple materials or materials of graded composition. Initial studies of direct ink-jet printing used commercial ink-jet printers optimised for text printing, and thus the volume of ceramic powder available in suspension was relatively low (< 10 volume%). This was because the viscosity of the suspensions had to be low to allow printing using the unmodified printers available. Evans’ work used ceramic suspensions in aqueous or alcohol-based media. The liquid carrier or solvent is removed by evaporation from the deposit after printing. Solid objects can be fabricated by overprinting, however the combination of low solid volume, and the need to remove the solvent before deposition of subsequent layers, resulted in a relatively low rate of growth in the direction normal to the printed plane. Our earlier work on ceramic ink-jet printing used alumina powders suspended in low melting point alkane (paraffin) waxes [5,6]. These suspensions solidify on impact and build up a thickness more rapidly than do deposits that solidify by evaporation. Both these methods have their advantages and disadvantages. Suspending fluids that evaporate allow dilute, low viscosity ceramic particle suspensions to be used. However solid distribution during drying is affected by Marangoni convection and the resulting deposit may show an irregular packing density. Phasechange fluids that solidify on impact result in more uniform particle distributions but now the solidified fluid must be removed from the object by an additional processing step prior to firing. Whichever rout
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