Student Abstracts: Materials Sciences at LBNL

In-situ Electrochemical Experiments at the Synchrotron: Applications in Battery Research. BOPAMO OSAISAI (San Francisco State University, San Francisco, CA 94564) ARTUR BRAUN (Ernest Orlando Lawrence Berkley National Laboratory, Berkley, CA 94720) .
Synchrotron radiation is more and more used nowadays to study advanced materials, including battery electrodes. We are investigating the fundamental mechanisms of battery failure using electrochemical and X-ray techniques at synchrotron radiation sources. Techniques used in this project include battery cycling (the charging and discharging of batteries at a constant current), and X-ray absorption spectroscopy. X-ray absorption spectroscopy is the probing of electrodes with X-rays of various wavelengths to obtain an entire spectrum of Manganese (Mn), a major constituent studied in our battery electrodes. From these spectra we can observe the chemical shift in Mn during battery operation (oxidation state) and determine the changes in the bonding lengths and coordination of atoms in manganese oxide. From battery cycling, we can determine the capacity and power density of the batteries, cycle life of the batteries, and degradation of the electrodes in the batteries. To assign structural and electronic changes in the electrodes as obtained by the X-ray techniques and to the charge and discharge conditions, experiments have to be made under strict potential control by an accurate data acquisition system. A computer controlled portable data acquisition system was built entirely for this purpose with LabVIEW. This research is an ongoing process and as of now, we are at the stage of establishing novel techniques.

A Facile Wet Synthesis of Litharge, the Tetragonal Form of Pbo. ERIK SPILLER (Fresno City College, Fresno, CA 93741) DALE L. PERRY (Ernest Orlando Lawrence Berkley National Laboratory, Berkley, CA 94720) .
Lead(II) oxide exists in several structural polymorphs. The phase being produced by previous synthetic techniques is dependent on experimental parameters such as temperature, pH, and concentration of the lead(II) starting solution. Additionally, micro structural phase changes that are different from the two principal phases normally reported result as a consequence of the synthetic route used to prepare the material. The resulting phase is also highly dependent on contaminant species of various other elements present in the reaction solution in addition to the lead(II) ion itself. In the present work, the red, tetragonal form of PbO, litharge, has been synthesized by a quick and easy reaction sequence using water as the reaction medium by which, unlike previously reported syntheses, the litharge phase is repeatably produced with no major side products or contaminating phases. The product was characterized by powder x-ray diffraction and compared to published data. Experimental parameters are discussed that lead to both other PbO forms being produced in the wet syntheses and to micro structural alterations of both the litharge and other phases. Motivations for working in the chemistry and technology of PbO include scintillator, thin-film, large crystal, and powder technology applications.