Dusan Lexa

Hermetic sample enclosure for simultaneous differential scanning calorimetry/synchrotron powder x-ray diffraction

A hermetic sample enclosure for performing simultaneous differential scanning calorimetry/synchrotron powder x-ray diffraction was designed, and a prototype was fabricated. The enclosure design is based upon a Perkin–Elmer DSC-2C measuring head with modifications allowing an unobstructed x-ray beam access to the sample in a controlled-atmosphere environment. The modifications to the measuring head base are limited to exposing the sample and reference platinum cups and providing a mating surface for the head cover. A completely new head cover, featuring semicylindrical beryllium x-ray windows, is hermetically attached to the base. A new graphite sample pan, addressing the conflicting requirements of differential scanning calorimetry and powder x-ray diffraction, was designed, and multiple pans were fabricated. An alternative temperature measurement and control system was developed and assembled. The complete system was tested in three experiments. No problems were encountered with diffraction data acquisit...

An improved hermetic sample enclosure for simultaneous differential scanning calorimetry/synchrotron powder X-ray diffraction

A hermetic sample enclosure for performing simultaneous differential scanning calorimetry/synchrotron powder X-ray diffraction, previously developed in our laboratory, suffered from poor calorimetric performance. A new enclosure design has been developed that addresses this problem. Like the previous design, it is based on a Perkin-Elmer DSC-2C measuring head. While the original enclosure necessitated a sample pan rather inconsistent with the requirements of DSC, more sophisticated modifications to the new measuring head made it compatible with a new sample pan that does not compromise calorimetric performance. The original alternative temperature measurement and control system was upgraded with low-noise components. In addition, water-cooling was added to the measuring head. A prototype sample enclosure has been fabricated and successfully tested in multiple experiments.

Hermetic holder for x-ray powder diffraction of air-sensitive differential scanning calorimetry samples

The design and performance of a hermetic holder for the preservation of air-sensitive differential scanning calorimetry samples during powder x-ray diffraction are described. The holder was developed specifically for the Perkin–Elmer DSC-2C type samples to be analyzed in a Rigaku D/max-2400V diffractometer. It could, however, easily be modified for use with a variety of diffractometers and larger samples. This holder provides simplicity of operation superior to previous holders at a fraction of the cost of environmental chambers.

Plutonium and uranium disposition in a sodalite/glass composite waste form via XAFS

Sodalite/glass composite waste forms are being developed at Argonne National Laboratory for disposal of radioactive fission elements in salt form from the electrometallurgical treatment of spent EBR-II nuclear reactor fuel. For the purposes of this experiment, a matrix of four sample types was created. Given the previously stated target actinide loading in the process waste form, the decision was made to utilize 3:1 and 1:3 uranium to plutonium ratios in the salt used where the total actinide loading sums to 2 mol%.