Pyromaniacs, Unltd.
Solid-Solid Pseudo-High-T Inorganic Synthesis

The conventional method of producing high-melting complex compounds from simpler high-melting precursor compounds) is to melt the starting materials together at high temperatures followed by carefully-controlled cooling to produce crystals.  For example, Lu₂O₃ and SiO₂ can be melted together at 2050ºC in an iridium (Ir) crucible by induction heating followed by highly-regulated very slow cooling to produce crystalline Lu2SiO5. The process is very expensive, time-consuming, and subject to failure.

The research of this group is focused on the production of such high-melting complex compounds by less expensive, short-time, and reliable techniques.  Using the above example, three main approaches are being made:

(1) Grinding in High-Energy Ball Mills

Lu₂O₃ and SiO₂ are placed in a very-hard ZrO₂ cup along with several small very-hard  ZrO₂ balls.  The cup is rotated at 850 rpm.  When the balls crash into the walls and into each other, very small spots of high temperature and high pressure are produced.  The energy is partially  transferred to the Lu₂O₃/SiO₂ mixture, and after 6 hours, complete transformation into Lu₂SiO₅ has occurred.  By alteration of conditions, Lu₂SiO₅ at μm or nm sizes can be made.

(2) Solution-to-Solid Internal Combustion Synthesis

Lu(NO₃)₃, amorphous fumed silica (SiO₂) and urea are mixed in water, which is then evaporated to dryness.  The resulting mixture is then heated to 300^oC, where the NO₃^– rapidly oxidizes the urea to give a temperature of 1600^oC which produces Lu₂SiO₅ at the 50-100 nm level.

(3) Liquid-Feed Spray Pyrolysis of Precursor Solutions

A solution of Lu(NO3)3 and tetraethyl orthosilicate (TEOS) in ethanol is treated with an ultrasonic atomizer and O₂, and the stream is passed through a  methane-oxygen pyrolysing flame zone. The resultant Lu₂SiO₅ particles are in the 50-100 nm size range.

Monitoring the Reactants and the Products

In all three of the above approaches, the disappearance of the precursors and the appearance of the Lu₂SiO₅ is monitored by the Powder X-ray Diffraction (PXRD) spectra of the compounds.  When irradiated with X-rays, a crystalline powder compound diffracts the X-rays at different angles from its crystal planes.  Each different crystal displays a distinctive spectrum (intensity vs. angle) which permits it to be distinguished from all other crystals.  Typical Powder X-ray Diffraction spectra for SiO₂, Lu₂O₃, and Lu₂SiO₅ follow:

Andreaco, Mark S.; Schweitzer, George K.; Stewart, Jake A.*; Quinton, Brant; Marlar, Troy, “Device for Separating Iridium Materials and a Method for Accomplishing the Same,”   U.S. Pat. Appl. Publ. (2015), US 20150115074, A1 20150430

Keefer, G.; Grant, C.; Piepke, A.; Ebihara, T.; Ikeda, H.; Kishimoto, Y.; Kibe, Y.; Koseki, Y.; Ogawa, M.; Shirai, J.; Takeuchi, S.; Mauger, C.; Zhang, C.; Schweitzer, G. K., “ Laboratory Studies on the Removal of Radon‑ born Lead from KamLAND’s Organic Liquid Scintillator ,” Nuclear Instruments & Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment (2015), 769, 79‑87.

John D. Auxier II*, Andrew N. Mabe,* Stephen A. Young, Jerrad P. Auxier, George K. Schweitzer, “Synthesis and Characterization of Ce+3-doped Amorphous Lithium Tetraborate, Journal of Nuclear Materials Management (2015) volume 18(2), 344-351.

Andrew N. Mabe, M. J. Urffer, D. Penamandu, George K. Schweitzer, and L. F. Miller, “Transparent Li-6-Loaded Terpolymer Scintillation Films for Thermal Neutron Detection,” Radiation Measurements, vol 66, pages 5-11.(2014)

L. F. Miller, M. J. Urffer, Andrew. N. Mabe, R. Uppal, D. Penumadu, and George.K. Schweitzer, “Secondary Electron Energy Deposition in Thin Polymeric Films for Neutron/Photon Discrimination,” to IEEE Transactions in Nuclear Science accepted, now online, to be published in July, issue 99 (2014).

Mabe, Andrew N.*; Auxier, John D.*, II; Urffer, Matthew J.; Penumadu, Dayakar; Schweitzer, George K.; Miller, Laurence F., “Transparent Lithiated Polymer Films for Thermal Neutron Detection,” Nuclear Instruments & Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment (2013), volume 722, 29‑33.

A. N. Mabe, J. D. Auxier, M. J. Urffer, S. A. Young, D. Penumadu, George K. Schweitzer, and L. F. Miller, “Thin-Film Polymer Scintillators for Thermal Neutron Detection,” Journal of Composites, Volume 2013, Article ID 539060, 8 pages.

L. L. Pesterfield, J. Maddox, G. K. Schweitzer, and M. Crocker, “Pourbaix Diagrams in Three Dimensions”, Journal of Chemical Education 89 (2012) 891-899.

Indraneel Sen, Rohit Uppal, Matthew Urffer, Dayakar Penumadu, Larry Miller, Stephen Young, Andrew Mabe, Polyester Composite Thermal Neutron Scintillation Films.  IEEE Trans, Nucl, Sci.. May, 2012.

Andrew Mabe, Matthew J. Urffer, Stephen A. Young, John D. Auxier II, Dayakar Penumadu, George K. Schweitzer, and Laurence F. Miller.  Thin Film Polystyrene Composite Scintillatiors for Thermal Neutron Detection and Gamma Discrimination.   Nucl. Instr. Meth., April, 2012.

I. Sen, A. D. Green, A. N. Mabe, D. Penueadu, G. K. Schweitzer, L. F. Miller, and K. Thomas, “Neutron Scintillation Detectors based on Like-Emitting Polymers, Transactions on Nuclear Science, January, 2012.

I. D. Sen, D.; Penumadi. M.Williamson, L. F. Miller, A. D. Green, A. N. Mabe,  Thermal Neutron Scintillator Detectyors Based on Poly (2-Vinylnaphthalene) Composite Films.  IEEE Trans. Nucl.  Sci. 58 (3), 1386-1393, June 2011.

George K. Schweitzer and Lester L. Pesterfield. The Aquieous Chemistry of the Elements, Oxford University Press, New York, NY, 2010.  Second printing 2011.

George K. Schweitzer and Lester L. Pesterfield, THE AQUEOUS CHEMISTRY OF THE ELEMENTS, Oxford University Press, New York, NY, 2010.  Kindle Edition.