Vaterite compacts that undergo cold

Vaterite compacts that undergo cold sintering exhibit a multiscale structure, consisting of an assembly of interconnected nanoparticles inside individual agglomerates and the assembly of agglomerates into a macroscopic sample of well-defined geometry (Fig. 1). The deformation of the assembly of nanoparticles and the assembly of agglomerates under the imposed uniaxial stress determines the creep rate, the final relative density, and the possible build-up of density gradients within the compacts. To shed light on the contribution of these multiscale deformation processes on the cold sintering of vaterite compacts we employ in-situ X-Ray tomography during uniaxial pressing and instrumented mechanical indentation on compacted samples at two different length scales. In-situ X-Ray tomography was used to quantify the deformation of agglomerates throughout the mechanically loaded compact by measuring the evolution of local displacement in stress relaxation experiments. Instrumented mechanical indentations were performed on compacted specimens to measure the deformation of the assembly of nanoparticles and of the assembly of agglomerates at the micro- and nano-scales, respectively, and their contributions to the overall creep rate of the macroscopic vaterite sample.