Events Calendar

New Synthesis and Sintering Methods in Materials Research

Olivia A. Graeve Associate Professor Kazuo Inamori School of Engineering Alfred University2 Pine Street Alfred, NY 14802 ABSTRACT:This talk will present an overview of leading precipitation processes for the synthesis of nanostructured ceramic and metallic powders, with special emphasis placed on reverse micelle synthesis for the preparation of oxides and combustion synthesis for the preparation of borides. Specific examples will include the preparation of yttria-doped zirconia (Y-ZrO2) and lanthanum hexaboride (LaB6). The talk will also describe advanced sintering techniques for nanostructured materials. For the case of Y-ZrO2, the thermal stability of the synthesized particles will be described. Transmission electron microscopy and Williamson-Hall analysis from x-ray diffraction have shown that the crystallite size ranges from 5-50 nm. A detailed study on the level of agglomeration and the particle size of the nanopowders will be described and corroborated using dynamic light scattering. Reaction parameters such as precursor concentration, aging time, and water-to-surfactant ratio were varied to optimize the synthesis process. Some of the powders were subsequently sintered using spark plasma sintering (SPS). Dense compacts of >98% density were obtained in 20 minutes. The feasibility of preparing nanocrystalline LaB6 powders via a controlled combustion synthesis process will also be presented. These powders are extraordinarily strong electron emitters with applications in micro- and nano-satellite propulsions systems, where they can serve as substitutes for chemical propellants, such that the electrons being emitted by the material are the source of propulsion. The synthesis reaction for the preparation of the powders is described below. During this process, controlled amounts of lanthanum nitrate (oxidizer) and boron were reacted with carbohydrazide (fuel) in a muffle furnace at 320°C. As the reactants were heated, the oxidizer and fuel reacted to form a fine violet powder that contains both nanocrystalline LaB6 and unreacted boron. After synthesis, the unreacted boron was removed from the powders using a controlled acid wash. The resulting phase-pure and faceted LaB6 powders were then characterized using x-ray diffraction for phase purity and crystallite size, and scanning electron microscopy for particle morphology.

Location: Seaver Science Library, SSL Room 150

Audiences: Everyone Is Invited

Contact: April Mundy