This grant supports the acquisition and development of equipment for sintering and in-sintering non-destructive characterization of functionally graded materials (FGM) at San Diego State University. The new instrumentation will augment modeling efforts in the area of the continuum theory of sintering. This theory is becoming the basis for macroscopic analysis of technological processes of sintering including both conventional powder thermo-processing and novel areas such as microwave sintering. The continuum approach enables the prediction of shape distortions and density distributions under sintering which are critical in modeling net-shape processing of powder materials. Thereby one of the most important problems of powder treatment - dimension control can be successfully resolved. In processing of FGM, sintering rates differ with position and uneven shrinkage may lead to defect formation and damage of a powder specimen. Without advances in the predictive modeling and experimentation, the cost of FGM may remain too high. The new instrumentation will enable the utilization and comparative assessment of two main approaches for the sintering of FGM: conventional sintering by external heating and microwave sintering. While conventional sintering by external heating is usually applied to already graded green specimens, in microwave sintering, porosity gradients appear due to a non-uniform temperature distribution within powder specimens. In sintering of FGM, shape distortions and damage are two most significant known problems. We will also develop a unique dilatometric-ultrasonic testing device. This device will incorporate both dilatometry and nondestructive ultrasonic characterization of powder materials during the sintering process. For this system, we will acquire a Confocal Fabry-Perot Interferometer. This is an innovative experimental technique that will enable a comprehensive integrated and comparative examination of both conventional and microwave sintering kinetics (including shrinkage and surface area reduction) and damage detection. Integration of modeling and experiments should provide the basis for on-line process control for a wide range of sintering operations. %%% Broader impacts of the project include the growing industrial importance of the functionally graded materials, which are used in joining of dissimilar materials, in micro-electronic devices, bioimplants, etc. Furthermore, the acquired and developed equipment will contribute to the research programs of multiple San Diego State University faculty members. Currently active research programs in powder processing and non-destructive materials evaluation will benefit. The new instrumentation will also contribute to the research program in the area of fabrication and in-processing characterization of magnetic materials. The development part of this project assumes considerable involvement of undergraduate students who will be able to explore new experimental capabilities in the framework of their senior design projects.
