Abstract:Ink jet printing techniques are used for an increasing number of materials and applications. Properties of the used inks have great influence on process stability and accuracy as well as the resulting part properties. Inks containing ceramic particles have been applied in various studies and applications. The criteria identifying suitable inks vary depending on the applied printing technology. In this study, inks for application in a piezoelectric print head were investigated. Alumina inks with solid loadings … Show more
“…Compared to most commonly printed colloidal suspensions, boehmite gels have a significantly lower solids loading, and surface tension forces contribute more to deformation in the few seconds following printing. Studies usually insist on the importance of yield stress to prevent gravitational slumping 4, 18, 19 , but very few reported surface tension’s relevance in DIW suspensions 20, 21 , as it is considered to be more important for droplet based techniques 17, 19 .Figure 7Frame superposition of 45 wt% boehmite gel printed after 1 h, 5 h, and 10 h of aging, with a 500 μm nozzle.
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Direct ink writing of dense and strong ceramic objects remains an important open challenge. We develop a universal dimensionless criterion for printing such objects. Boehmite, an Al2O3 precursor, was used to assess the rheological properties leading to dense structures in ceramics manufactured by direct ink writing. Boehmite suspensions undergo time dependent gelation, thus providing a rheological laboratory of flow behaviours that can be correlated with printability requirements. We measured the evolution of rheological properties over several days and quantified the deformation of simple printed shapes at different aging times. We then identified the relevant physical parameters leading to printable suspensions. We defined a dimensionless number, Ξ, based on measured rheological properties, that predicts deformation of the printed object and determines the printability criterion. An important difference with this criterion is that Ξ necessarily accounts for capillary forces and gravitational slumping. We show that boehmite inks reach a printed shape fidelity > 90% when Ξ > 1, and that Al2O3 bars printed under these conditions can be sintered to 97% density, without printing defects, and have flexural strengths (500–600 MPa) competitive with commercial aluminas. Using Ξ, researchers can rationally design inks for printing dense materials by tailoring their rheological properties such that Ξ ≈ 1.
“…Compared to most commonly printed colloidal suspensions, boehmite gels have a significantly lower solids loading, and surface tension forces contribute more to deformation in the few seconds following printing. Studies usually insist on the importance of yield stress to prevent gravitational slumping 4, 18, 19 , but very few reported surface tension’s relevance in DIW suspensions 20, 21 , as it is considered to be more important for droplet based techniques 17, 19 .Figure 7Frame superposition of 45 wt% boehmite gel printed after 1 h, 5 h, and 10 h of aging, with a 500 μm nozzle.
…”
Direct ink writing of dense and strong ceramic objects remains an important open challenge. We develop a universal dimensionless criterion for printing such objects. Boehmite, an Al2O3 precursor, was used to assess the rheological properties leading to dense structures in ceramics manufactured by direct ink writing. Boehmite suspensions undergo time dependent gelation, thus providing a rheological laboratory of flow behaviours that can be correlated with printability requirements. We measured the evolution of rheological properties over several days and quantified the deformation of simple printed shapes at different aging times. We then identified the relevant physical parameters leading to printable suspensions. We defined a dimensionless number, Ξ, based on measured rheological properties, that predicts deformation of the printed object and determines the printability criterion. An important difference with this criterion is that Ξ necessarily accounts for capillary forces and gravitational slumping. We show that boehmite inks reach a printed shape fidelity > 90% when Ξ > 1, and that Al2O3 bars printed under these conditions can be sintered to 97% density, without printing defects, and have flexural strengths (500–600 MPa) competitive with commercial aluminas. Using Ξ, researchers can rationally design inks for printing dense materials by tailoring their rheological properties such that Ξ ≈ 1.
“…Notably, some printers equipped with industrial PTZ printheads (i.e., Xaar1003, Xaar Nitrox, Konica KM1800i, and GALAXY series) and advanced recirculation systems allow functional inks with viscosities up to 80 mPa·s. The appropriate surface tension is in the range of 35–60 mN/m [ 69 ]. Unwanted dripping and ink spreading over the orifice plate that affects the jettability occur when surface tension is too low, whereas the jet stream may not split into individual droplets when surface tension is too high.…”
Section: Multi-materials 3d Printing Methodsmentioning
In recent years, functional ceramic devices have become smaller, thinner, more refined, and highly integrated, which makes it difficult to realize their rapid prototyping and low-cost manufacturing using traditional processing. As an emerging technology, multi-material 3D printing offers increased complexity and greater freedom in the design of functional ceramic devices because of its unique ability to directly construct arbitrary 3D parts that incorporate multiple material constituents without an intricate process or expensive tools. Here, the latest advances in multi-material 3D printing methods are reviewed, providing a comprehensive study on 3D-printable functional ceramic materials and processes for various functional ceramic devices, including capacitors, multilayer substrates, and microstrip antennas. Furthermore, the key challenges and prospects of multi-material 3D-printed functional ceramic devices are identified, and future directions are discussed.
“…A high powder content increases the viscosity of the feedstock, thus increasing the risk of clogging the 3D printer nozzle. The alumina powder used was Al 2 O 3 (CT 3000 LS SG, Almatis GmbH) with a mass median diameter (D50) of 0.5 m m. CT 3000 LS SG is an oxide material widely used in ceramic research (Beresnev et al, 2014;Chovanec et al, 2012;Károly et al, 2014;Lauria et al, 2016;Melcher et al, 2011;Polsakiewicz and Kollenberg, 2011;Río et al, 2017;Zorzi et al, 2002). The binder consisted of EVA co-polymer (Elvax 420 TM , Du Pont International SARL) with a melting point of 73°C and a melt flow rate of 150 g/10 min.…”
PurposeThis study aims to fabricate complex ceramic tetrahedron structures, which are challenging to produce by more conventional methods such as injection molding. To achieve this aim, thermoplastic-ceramic composite filaments were developed and printed with unmodified, consumer-grade, fused deposition modelling (FDM) printers instead.Design/methodology/approachAl2O3 ceramic powder was mixed with ethylene vinyl acetate polymer as a binder (50 Vol.- per cent) to form a filament with a constant diameter of 1.75 mm. After the printing and thermal treatment stages, the shrinkage and mechanical properties of cuboid and tetrahedron structures were investigated.FindingsThe shrinkage of the parts was found to be anisotropic, depending on the orientation of the printing pattern, with an increase of 2.4 per cent in the (vertical) printing direction compared to the (horizontal) printing layer direction. The alignment of the ceramic particle orientations introduced by FDM printing was identified as a potential cause of the anisotropy. This study further demonstrates that using a powder bed during the thermal debinding process yields sintered structures that can withstand twice the compressive force.Originality/valueCeramic FDM had previously been used primarily for simple scaffold structures. In this study, the applicability of ceramic FDM was extended from simple scaffolds to more complex geometries such as hollow tetrahedra. The structures produced in this study contain dense parts printed from multiple contiguous layers, as compared to the open structures usually found in scaffolds. The mechanical properties of the complex ceramic parts made by using this FDM technique were also subjected to investigation.
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