TY - THES

T1 - Tape casting of Cr2AlC MAX phase for multi-material designs

AU - Prötsch, Tobias

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - MAX phases are a material class which has gained interest due to its combination of properties from both metallic and ceramic materials. The ¿M¿ in MAX represents a transition metal, ¿A¿ an element from the A-group and ¿X¿ carbon and/or nitrogen. A well-studied MAX phase is Cr2AlC, which shows a high resistance against high-temperature oxidation and a unique fracture behavior. In comparison, technical ceramics are known for properties such as high hardness, strength, and stiffness as well as low density and thermal expansion. Cr2AlC can be processed using various sintering methods, such as hot-pressing, spark plasma sintering (SPS) or pressure-less sintering. To fabricate bulk MAX phases, powders or powder mixtures are commonly sintered directly. In this work, a relatively new approach is explored by sintering MAX phases which have been previously tape casted, thus offering the possibility to realize laminated structures, combining different materials layer by layer. Multi-material approaches are emerging topics in today¿s research with the aim to benefit from properties of different materials. The combination of different materials with distinct thermo-physical properties (e.g. coefficient of thermal expansion or Young¿s modulus) may cause residual stresses, which can be used to enhance mechanical properties. For instance, embedding layers with in-plane compressive residual stresses may lead to an improvement of the damage tolerance of ceramics. In this work, monolithic Cr2AlC and Al2O3 are fabricated using the tape casting process and characterized according to their thermo-physical and mechanical properties. First, ceramic tapes are casted from slurries, consisting of powder, a binder system, and organic solvents. Then, the microstructural and thermo-physical properties of the sintered monoliths are evaluated. In a next step, a multi-material design is realized, combining Cr2AlC and Al2O3 in a layered architectural design. Finally, the fracture behavior of the laminate design is studied and compared to bulk MAX phase monoliths.

AB - MAX phases are a material class which has gained interest due to its combination of properties from both metallic and ceramic materials. The ¿M¿ in MAX represents a transition metal, ¿A¿ an element from the A-group and ¿X¿ carbon and/or nitrogen. A well-studied MAX phase is Cr2AlC, which shows a high resistance against high-temperature oxidation and a unique fracture behavior. In comparison, technical ceramics are known for properties such as high hardness, strength, and stiffness as well as low density and thermal expansion. Cr2AlC can be processed using various sintering methods, such as hot-pressing, spark plasma sintering (SPS) or pressure-less sintering. To fabricate bulk MAX phases, powders or powder mixtures are commonly sintered directly. In this work, a relatively new approach is explored by sintering MAX phases which have been previously tape casted, thus offering the possibility to realize laminated structures, combining different materials layer by layer. Multi-material approaches are emerging topics in today¿s research with the aim to benefit from properties of different materials. The combination of different materials with distinct thermo-physical properties (e.g. coefficient of thermal expansion or Young¿s modulus) may cause residual stresses, which can be used to enhance mechanical properties. For instance, embedding layers with in-plane compressive residual stresses may lead to an improvement of the damage tolerance of ceramics. In this work, monolithic Cr2AlC and Al2O3 are fabricated using the tape casting process and characterized according to their thermo-physical and mechanical properties. First, ceramic tapes are casted from slurries, consisting of powder, a binder system, and organic solvents. Then, the microstructural and thermo-physical properties of the sintered monoliths are evaluated. In a next step, a multi-material design is realized, combining Cr2AlC and Al2O3 in a layered architectural design. Finally, the fracture behavior of the laminate design is studied and compared to bulk MAX phase monoliths.

KW - Cr2AlC

KW - MAX-Phase

KW - Tape Casting

KW - Spark Plasma Sintern

KW - Laminate

KW - Schadenstoleranz

KW - Cr2AlC

KW - MAX phase

KW - tape casting

KW - spark plasma sintering

KW - laminates

KW - damage tolerance

M3 - Master's Thesis

ER -