MSE Colloquium - Prof. Olivia Graeve, Alfred University
Date: October 08, 2010 from 2:00 pm to 3:00 pm EDT
Location: Room 214 in S. W. Mudd
Contact: For further information regarding this event, please contact Wesley Hattan by sending email to wjh2121@columbia.edu or by calling 2128547860.
Info: Click Here to Visit Website.
Bookmark and Share

NEW SYNTHESIS AND SINTERING METHODS IN MATERIALS RESEARCH

Olivia A. Graeve

Associate Professor

Kazuo Inamori School of Engineering

Alfred University

2 Pine Street, Alfred, NY 14802, USA

 

 

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, combustion synthesis for the preparation of borides, and solvothermal synthesis for the preparation of carbides.  Specific examples will include the preparation of oxides such as Y-ZrO2, MgO, spinel, and Y2O3; metal hexaborides such as LaB6. EuB6, YbB6, and YB6; and carbides such as TaC and HfC.  The talk will also describe advanced sintering techniques for nanostructured materials.

 

For the preparation of carbides, we will describe the synthesis of carbide-based nanostructured powders via a unique and extremely promising solvothermal reduction technique in order to produce materials that have a direct application in aerospace applications.  Initial efforts have involved the synthesis of tantalum carbide nanopowders by using tantalum chloride and carbon powders, and metallic lithium or calcium as the reducing agents.  The powders were all mixed inside a fused quartz tube in argon and then reacted by placing them in a tube furnace.  Average crystallite sizes from X-ray line broadening ranged from 23-70 nm with a compound stoichiometry, TaCx, ranging from 0.93-0.98.  Thermogravimetric analysis was used determine the weight losses in the temperature range from room temperature to 400C.  Specific surface area was measured and ranged from 25-70 m2/g.  Dynamic light scattering was used to measure the average particle sizes, which ranged from 93-123 nm.

 

For the preparation of hexaborides, we will describe the synthesis of EuB6, YB6, and YbB6 using the solution combustion synthesis technique in air at low temperatures (~320C).  Important variables include the fuel to oxidizer ratio, ignition method, and boron source.  X-ray diffraction was used for qualitative phase analysis, morphology was studied by scanning electron microscopy, and particle size was studied using dynamic light scattering.  Phase pure EuB6 was obtained with a cubic morphology and with an average particle size ~170 nm.  In the case of YB6 and YbB6 there were significant amounts of borate and other boride phases in the as-synthesized state.  These borates can be easily removed by treating the powders with acids (HCl and H2SO4).  Cation radii is a limiting factor for the synthesis of the hexaboride materials by this technique.  There is less boride phase formed for the case of smaller cation radii (i.e., Y and Yb).