MINERALS AT THE NANOSCALE: A NOVEL, GENERALIZED METHOD TO SYNTHESIS A NEARLY UNLIMITED ARRAY OF METAL AND MIXED-METAL OXIDE NANOPARTICLES

When investigating the fundamental properties of geologically relevant materials in the nano regime, often a limiting or time consuming step in the project is the ability to synthesis nanomaterials that are both phase and chemically pure. Nanoscale synthetic methods available in the literature are many and varied, however each material system seems to have a specialized procedure, and complicated mixed-metal materials are often challenging. At Brigham Young University we have recently discovered a simple, generalized two-step method for synthesizing a vast array of metal and mixed-metal oxide nanoparticles that can be used to study geologically relevant materials. Over the past two years we have synthesized over 50 unique nanoscale materials using the same two-step process. The process involves mixing a common metal salt with a base in a solvent deficient environment to form a solid precursor material followed by calcination at temperatures near 300°C for approximately one hour. Beyond the basic processing method, control of atmosphere, precursor treatment, and calcination temperature leads to control of phase, oxidation state, crystallite size, and allows oxides to be reduced to metals. For example, using this one method we have produced 7 nm hematite, 15 nm nickel ferrite, 13 nm magnetite, and 2 nm ferrihydride. The process also allows for control of size with a tight size distribution. For example we have synthesized Fe2O3 at sizes from 7-40 nm with uniform morphology and a size distribution of ±10%. Using this process we can also control the phase of the material, such as 4 nm rutile or 8 nm anatase. The metal oxides produced by the method include most of the metals and semi-metals found in the periodic table, including but not limited to the transition metals, rare earth metals, and the Groups I, II, and III metals of the Periodic Table. The mixed-metal oxides can be produced any combination of the aforementioned metals with any stoichiometry. In this talk, we will discuss the details of the method, outline the proposed mechanism of the reaction, and show examples of the vast array of materials we have synthesized. We will also briefly show some preliminary heat capacity results of natural and synthetic ferrihydride, the synthetic ferrihydride having been produced using our method.