TY - THES

T1 - Thermal shock behavior of 3D-printed alumina ceramics with spatially tailored porosity

AU - Bastos Mateus, Luisa

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - Ceramic materials are known for their outstanding properties, such as high-temperature stability and corrosion resistance. However, ceramics are inherently brittle and exhibit large scatter in mechanical strength. The initiation of damage depends on the type of loading, components' geometry, among other factors. In particular, thermal shock associated with rapid temperature changes is one of the main critical loading scenarios for ceramic components, due to the high elastic modulus and low thermal conductivity of ceramic materials. Finding alternative strategies to increase the resistance to damage in ceramic parts is crucial for industrial applications, where components may be subjected to rapid temperature changes. Introducing porosity in a ceramic material has been proven as a positive way to improve its thermal shock resistance. A strategy to increase the structural integrity of porous ceramics may be through designing with gradients. Porosity-graded alumina ceramics have shown potential in applications such as filters, membranes, coatings, and others. A new up-and-coming technique that enables the introduction of gradient porosity in alumina without limitations in design-complexity is Lithography-based Ceramic Manufacturing (LCM). In this work, novel alumina-based laminates with embedded porous layer regions as well as porosity-graded alumina samples are additive manufactured and thermo-mechanically characterized. A novel approach is explored in this thesis, which utilizes the layer-by-layer printing process to introduce porosity to achieve new 3D-printed alumina-based materials with spatially tailored porosity. The layered samples with varied designs together with the (reference) monolithic samples are fabricated using the LCM -technology. The different sample designs are tested under biaxial bending and the strength parameters (i.e. characteristic strength and Weibull modulus) are determined. Subsequently, thermal shock tests are performed at selected temperature differences and the corresponding strength degradation of the layered porous designs are investigated and compared to the reference (monolithic) samples. The experimental findings show that the addition of porous layer regions may increase the specific strength, thermal shock resistance, and crack deflection of 3D-printed ceramics. The advantages of the LCM technology together with the capability of tailoring the porosities are discussed, which may open new (lightweight) application fields for alumina-based ceramic parts.

AB - Ceramic materials are known for their outstanding properties, such as high-temperature stability and corrosion resistance. However, ceramics are inherently brittle and exhibit large scatter in mechanical strength. The initiation of damage depends on the type of loading, components' geometry, among other factors. In particular, thermal shock associated with rapid temperature changes is one of the main critical loading scenarios for ceramic components, due to the high elastic modulus and low thermal conductivity of ceramic materials. Finding alternative strategies to increase the resistance to damage in ceramic parts is crucial for industrial applications, where components may be subjected to rapid temperature changes. Introducing porosity in a ceramic material has been proven as a positive way to improve its thermal shock resistance. A strategy to increase the structural integrity of porous ceramics may be through designing with gradients. Porosity-graded alumina ceramics have shown potential in applications such as filters, membranes, coatings, and others. A new up-and-coming technique that enables the introduction of gradient porosity in alumina without limitations in design-complexity is Lithography-based Ceramic Manufacturing (LCM). In this work, novel alumina-based laminates with embedded porous layer regions as well as porosity-graded alumina samples are additive manufactured and thermo-mechanically characterized. A novel approach is explored in this thesis, which utilizes the layer-by-layer printing process to introduce porosity to achieve new 3D-printed alumina-based materials with spatially tailored porosity. The layered samples with varied designs together with the (reference) monolithic samples are fabricated using the LCM -technology. The different sample designs are tested under biaxial bending and the strength parameters (i.e. characteristic strength and Weibull modulus) are determined. Subsequently, thermal shock tests are performed at selected temperature differences and the corresponding strength degradation of the layered porous designs are investigated and compared to the reference (monolithic) samples. The experimental findings show that the addition of porous layer regions may increase the specific strength, thermal shock resistance, and crack deflection of 3D-printed ceramics. The advantages of the LCM technology together with the capability of tailoring the porosities are discussed, which may open new (lightweight) application fields for alumina-based ceramic parts.

KW - Additive Fertigung

KW - Aluminiumoxid

KW - Porosität

KW - Thermoschock

KW - Mechanische Eigenschaften

KW - additive manufacturing

KW - alumina

KW - porosity

KW - thermal shock

KW - mechanical properties

M3 - Master's Thesis

ER -