b'Feasibility Study of anLocal thermal transport properties can be used to remotely examine Optical Fiber Instrumentmicrostructure features in spark plasma sintered products.to Monitor MicrostructureS park plasma sintering is a rapid sintering technique that enables the densification and fabrication of a broad range of materials in an efficient way. of Spark PlasmaHigh heating rates of hundreds of degrees Celsius per minute can be achieved, Sintering Products allowing materials to reach target temperatures in a short time. However, the large temperature gradients generate unexpected microstructure heterogeneities, degrading product mechanical, thermal, and electrical performance. Currently, no experimental approach exists to monitor such microstructural variation. In this project, the proof-of-concept methodology of using local thermal transport property to index the microstructure features, such as density variation, inside spark plasma sintering sintered products was investigated. A few series of materials were sintered using spark plasma PROJECT NUMBER:sintering and their local thermal diffusivities were investigated using photothermal 21A1055-032 radiometry. We measured local thermal diffusivities along several radial directions TOTAL APPROVED AMOUNT:across the samples, and the results qualitatively agree with the local porosities observed $125,000 over 1 year by using scanning electron microscopy. The analytical model that quantitatively correlates porosity to thermal property that can be used to estimate local porosity PRINCIPAL INVESTIGATOR:from measuring thermal diffusivity was further investigated. This study sets up the Zilong Hua fundamental work to develop and deploy the photothermal radiometry-based system CO-INVESTIGATORS: in spark plasma sintering to monitor the microstructure evolution during sintering. Nathan Jerred, INL While thermal diffusivity can be measured in a real-time manner to estimate the bulk Robert Schley, INLporosity of sintered materials without interrupting the sintering process, it can also Troy Holland, INLexamine local porosity variation so that the sintering parameters can be dynamically adjusted to enhance desired microstructure features, such as to fabricate functionally graded materials, or avoid unexpected heterogeneities. (a) Qualitative comparison of results between local density characterized by using scanning electron microscopy and local thermal diffusivity measured by using photothermal radiometry on alumina samples; (b) quantitative relationship (the percolation model) of normalized thermal conductivity versus porosity with all samples.86'