TY - BOOK

T1 - Processing of ceramic materials with tailored microstructures deploying tape casting and stereolithographic 3D-printing

AU - Hofer, Anna-Katharina

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - Ceramics, often the selection when materials from other classes reach their limits. Their outstanding properties as e.g. low density, wear resistance, biocompatibility, thermal and/or electrical resistance/conductivity are in the first place determined by the ionic and partially covalent bonding. Besides, the polycrystalline grain structure may have a significant effect on structural as well as functional properties. As versatile the properties and application of ceramics as different the polycrystalline microstructures may be: large/small grains; anisotropic/isotropic crystallographic orientation of grains; high/low porosity; monolithic/composite. Regarding structural properties for example, small grain sizes in a defect free microstructure may be beneficial for improving the mechanical strength, whereas large as well as oriented grains may enhance the fracture resistance. Whether certain microstructural properties develop depends on the materials diffusivity throughout the sintering process. Ceramic powder size and shape, powder preparation, shaping method, green density, impurities, present sintering additives, dopants and sintering parameters are all exemplary factors which can have an impact on the diffusivity of matter. In this thesis different shaping methods as well as conventional and non-conventional sintering technologies were investigated to tailor microstructural and consequently mechanical as well as optical properties of alumina ceramics. Tape casting and a stereolithographic 3D-printing technology were used to texture alumina microstructures according to the method of templated grain growth. Monolithic textured alumina ceramics as well as the effect of a second phase were investigated regarding damage tolerance. The sintering of templated samples within a spark plasma sintering furnace with applied pressure was explored in order to obtain highly textured, fully densified and translucent alumina microstructures. For simple shapes several non-conventional sintering technologies, often combined with applied pressures, are available to optimize microstructural properties. Ceramic components of high complexity, as fabricated with additive manufacturing, are limited to conventional sintering. Here, a pressure-less spark plasma sintering set-up with a heating rate of ~ 450 °C/min was used to tailor the microstructure of stereolithographic 3D-printed alumina ceramics regarding (i) submicron grain sizes and (ii) texture. The obtained results of the rapid sintered samples have demonstrated that this non-conventional sintering technology could open the path to tailor microstructural and mechanical properties of highly complex shaped ceramics with reduced sintering times (minutes) and energy consumption.

AB - Ceramics, often the selection when materials from other classes reach their limits. Their outstanding properties as e.g. low density, wear resistance, biocompatibility, thermal and/or electrical resistance/conductivity are in the first place determined by the ionic and partially covalent bonding. Besides, the polycrystalline grain structure may have a significant effect on structural as well as functional properties. As versatile the properties and application of ceramics as different the polycrystalline microstructures may be: large/small grains; anisotropic/isotropic crystallographic orientation of grains; high/low porosity; monolithic/composite. Regarding structural properties for example, small grain sizes in a defect free microstructure may be beneficial for improving the mechanical strength, whereas large as well as oriented grains may enhance the fracture resistance. Whether certain microstructural properties develop depends on the materials diffusivity throughout the sintering process. Ceramic powder size and shape, powder preparation, shaping method, green density, impurities, present sintering additives, dopants and sintering parameters are all exemplary factors which can have an impact on the diffusivity of matter. In this thesis different shaping methods as well as conventional and non-conventional sintering technologies were investigated to tailor microstructural and consequently mechanical as well as optical properties of alumina ceramics. Tape casting and a stereolithographic 3D-printing technology were used to texture alumina microstructures according to the method of templated grain growth. Monolithic textured alumina ceramics as well as the effect of a second phase were investigated regarding damage tolerance. The sintering of templated samples within a spark plasma sintering furnace with applied pressure was explored in order to obtain highly textured, fully densified and translucent alumina microstructures. For simple shapes several non-conventional sintering technologies, often combined with applied pressures, are available to optimize microstructural properties. Ceramic components of high complexity, as fabricated with additive manufacturing, are limited to conventional sintering. Here, a pressure-less spark plasma sintering set-up with a heating rate of ~ 450 °C/min was used to tailor the microstructure of stereolithographic 3D-printed alumina ceramics regarding (i) submicron grain sizes and (ii) texture. The obtained results of the rapid sintered samples have demonstrated that this non-conventional sintering technology could open the path to tailor microstructural and mechanical properties of highly complex shaped ceramics with reduced sintering times (minutes) and energy consumption.

KW - Tape Casting

KW - Textur

KW - Alumina

KW - Additive Fertigung

KW - Vat Photopolymerisation

KW - 3D-Druck

KW - Stereolithographie

KW - tape casting

KW - texture

KW - alumina

KW - additive manufacturing

KW - vat photopolymerization

KW - 3D-printing

KW - stereolithography

U2 - 10.34901/mul.pub.2023.198

DO - 10.34901/mul.pub.2023.198

M3 - Doctoral Thesis

ER -