Rare Earth Oxide Nanopowder (RE = Nd, Eu, Gd, Ho, Y, Yb) by Combustion Synthesis, Sulfation and Calcination: Role of the Initial Structure
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
A novel method for synthesising rare earth oxide (RE2O3) nanopowder was applied to several rare earths including Nd, Eu, Gd, Ho, Y and Yb. The process was successful in producing homogeneous, fine dispersed and deagglomerated powder particles with uniform morphology for all rare earth oxides, except neodymia. In the first process step, rare earth nitrate solutions were mixed with glycine and subsequently heated in a furnace. Glycine acted as fuel to initiate the combustion synthesis (SHS) in order to obtain nanocrystalline and weakly agglomerated particles. Powder samples were produced at three different glycine-to-nitrate ratios (G/N), involving stoichiometric ratio (G/N = 0.56) and two fuel lean ratios (0.32 and 0.25). As a consequence of low combustion temperature at fuel lean ratios were carbonate structures found and their formation was correlated to the size of the rare earth cation. Resulting cellular structures were analysed by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The cellular structure is unsuitable to be processed to a final product. The resulting powder has a very large specific volume and is comprised of strongly agglomerated crystallites, which renders pressing and sintering of these structures difficult. Therefore an additional synthesis step was employed with the addition of ammonium sulfate and calcination for 4 h in a tube furnace at 1100°C. In order to understand the influence of the initial, cellular structure on the morphological and microstructural powder properties different sulfate concentrations were used. Samples were characterized by XRD and scanning electron microscopy (SEM). The average crystallite size increased during calcination from below 15 nm in the initial structure to 50 nm in the final product. However, the resulting particles were loosely agglomerated. A benefit of sulfate-doped rare earth compounds under heat treatment is the formation of nearly isotropic surfaces, which might be related to the promotion of surface diffusion and partial inhibition of densifying transport mechanisms such as volume diffusion.
Place, publisher, year, edition, pages
2011. , 43 p.
Physics Chemistry Maths, rare earth, neodymia, europia, gadolinia, holmia, yttria, ytterbia, neodymium oxide, europium oxide, gadolinium oxide, holmium oxide, yttrium oxide, ytterbium oxide, powder, combustion, synthesis, glycine, nitrate, shs, sulfation, sulfate, calcination, nano, particles, rare earth oxide, Nd, Eu, Gd, Ho, Y, Yb, Nd2O3, Eu2O3, Gd2O3, Ho2O3, Y2O3, Yb2O3, RE2O3, oxide
Fysik, Kemi, Matematik
IdentifiersURN: urn:nbn:se:ltu:diva-59471Local ID: ffc153f2-7939-432b-acb0-6bb0415a21c7OAI: oai:DiVA.org:ltu-59471DiVA: diva2:1032859
Subject / course
Student thesis, at least 30 credits
Chemical Engineering, master's level
Validerat; 20110923 (anonymous)2016-10-042016-10-04Bibliographically approved