Ceramic/metal nanocomposites by lyophilization: Processing and HRTEM study

Abstract

This work describes a wet-processing route based on spray-freezing and subsequent lyophilization designed to obtain nanostructured ceramic/metal powders. Starting from the ceramic powder and the corresponding metal salt, a water-based suspension is sprayed on liquid nitrogen. The frozen powders are subsequently freeze-dried, calcined and reduced. The material was analyzed using X-ray diffraction analysis at all stages. High Resolution Transmission Electron Microscopy studies showed a uniform distribution of metal nanoparticles on the ceramic grain surfaces, good interfaces and high crystallinity, with an average metal particle size in the nanometric range.

Selective Oxidation of HMF via Catalytic and Photocatalytic Processes Using Metal-Supported Catalysts

“…Magnesia ceramics prepared with the spray-freeze drying technique made it possible to prepare high-thermal-strength materials, which were also characterized by a large surface area [ 50 ]. The spray-freeze drying (SFD) technique is an industrial process which consists of removing water from frozen samples by sublimation and desorption under a vacuum; it has also been applied to the preparation of nanostructured materials because it made it possible to maintain the nanometric size of the phase, while avoiding the agglomeration and segregation of components [ 51 ], while at the same time, increasing the stability of the system [ 52 , 53 ]. Moreover, this technique can be used for the homogeneous embedding of active phases into the support, minimizing the possibility of phase separation on a molecular scale.…”