This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

With this award from the Major Research Instrumentation (MRI) program Professor Christoph Geiss and colleagues Jonathan R. Gourley, Ralph O. Moyer, and Maria Parr from the Departments of Chemistry, Physics and Environmental Science at Trinity College will acquire a powder X-ray diffractometer which will be capable of providing good quality structural (Rietveld) analyses which can also be used as an analytical instrument for classroom use. The instrument will be used to support research activities such as: 1) characterization of iron-minerals in sediments and soil; 2) fault zone fluid migration pathways; 3) trace metal sediment concentrations in impaired watersheds; 4) synthesis, structure and characterization of ternary metal hydrides and hydrogen storage; 5) structure and characterization of Yb2RuH6(D6); 6) high pressure X-ray diffraction of A2RuH6 compounds; and 7) characterization of transition metal complexes and archaeological materials.

An X-ray diffractometer allows accurate and precise measurements of the full three dimensional structure of a molecule, including bond distances and angles, and provides accurate information about the spatial arrangement of a molecule relative to neighboring molecules. A powder diffractometer allows diffraction studies in powdered crystalline materials. The studies described here will impact a number of areas, including chemistry, materials chemistry, geology, archeology and the environment. This instrument will be an integral part of teaching as well as research.

Project Report

Funds were used to purchase a new Powder X-ray diffractometer for research and classroom use at Trinity College, Hartford, CT. In X-ray diffraction (XRD) a sample is exposed to X-rays. These X-rays interact with the sample and the modified X-ray signal can be used to analyze the sample’s crystalline structure. By comparing the recorded PXRD signal of an unknown sample with a database of known substances a PXRD experiment can reveal the mineralogical composition of natural and man-made substances. In the case of new substances, PXRD experiments can also elucidate the crystal structure of that substance. At Trinity College PXRD is used throughout the year in the Chemistry, Engineering, Environmental Science and Physics Departments. Trinity has owned and operated PXRD instruments since the early 1960’s, but our last instrument had become unreliable, and its slow measuring speed made it poorly suited for class-projects. Using NSF funds we purchased a PANalytical X’pert Pro XRD system which was during the summer of 2010. The new system has the following advantages: The instrument is highly accurate, allowing for the identification of minor mineral phases. The instrument is fast, allowing for the analysis of large number of samples, or live measurements during class periods. The instrument is modular, allowing it to be adapted to specific research needs. Over the past two years the instrument has been used for the following research projects: Characterization of newly synthesized ternary metal solid state hydrides and mixed crystal compounds, and the search for new ternary metal hydrides (Moyer) Identification of iron-oxide phases in soils and sediments to investigate the climatic history recorded in these sites. (Geiss) Clay mineral identification in sheared mudstones from Taiwan to constrain the thermal history of these fault rocks. (Gourley) Measurements of the quartz / calcite ratio in lake sediments to reconstruct the frequencies of major storm events over the past few thousand years. (Geiss) Analysis of archeological samples to determine the composition and origin of ancient pottery (Parr) Additional faculty have used the instrument to elucidate the structure of Cd-substituted apatite through the Rietveld method and to analyze inorganic pigments for art conservation research. These projects involved both faculty and students, and over twenty students conducted experiments using the instrument. The instrument was also used in various courses offered by the Chemistry, Engineering and Environmental Science Departments, introducing more than 70 students to the XRD analyses. It also is presented at campus tours to attract more incoming students to the sciences.

National Science Foundation (NSF)
Division of Chemistry (CHE)
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Carlos A. Murillo
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Trinity College
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