Surface Analysis and Reaction Apparatus (SARA)
This facility is used for the analysis of metal surfaces, metal oxides and thin films grown in situ. Analytical techniques include Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED). Gases can be adsorbed on these surfaces through directed dosers. Surface reactions are monitored by Temperature Programmed Desorption (TPD), High Resolution Electron Energy Loss Spectroscopy (HREELS) and XPS.
Soft X-ray Photoelectron Spectroscopy (SXPS)
This system is located on Beamline U12A at the National Synchrotron Light Source . Samples are analyzed by high resolution core- and valance-level photoelectron spectroscopy. The beamline supplies monochromatic radiation from 100 - 800 eV. The emitted photoelectrons are analyzed by a multichannel electrostatic analyzer. Soft X-ray Adsorption Spectroscopy (SXAS or NEXAFS) can be performed by scanning the excitation energy and detecting the emission of electrons. Any vacuum compatible sample can be analyzed however the system is optimized for studying metals, metal oxides and thin films. Films can be grown in situ and gases dosed through directed dosers.
Surface Analysis and High Pressure Reaction Facility
This system couples an ultra high vacuum (UHV) surface analysis chamber to a high pressure reaction cell. Substrates can be prepared and characterized in the UHV chamber and then moved through a vacuum seal into the high pressure cell. Reactions can be run at pressures up to one atmosphere and products monitored by gas chromatography. Surface species can be monitored in situ by reflection - adsorption infrared spectroscopy (RAIRS). The reaction can be halted at any point and the sample retracted into the UHV chamber to analyze the substrate by XPS or TPD.
Positron Lifetime Spectroscopy
Positron annihilation spectroscopy is used to measure void structure and concentration in films and bulk materials. The advanced capabilities at ORNL include (1) DC positron beam, which provides 0.8x106 e+/sec with the positron energy tunable up to 50 keV. This energy-tunable beam is used to depth-profile the void structure. (2) Linac pulsed positron beam, which is produced at the Oak Ridge Electron Linear Accelerator (ORELA). This beam has an intensity of 108 e+/sec and a pulse width less than 500 ps. It can be used to measure void sizes and distributions as a function of depth. (3) Bulk positron lifetime spectroscopy, which uses a Na22 isotope to measure void size and concentration in bulk materials at a depth up to a few hundred microns. (4) Two-detector Doppler broadening coincidence system, which is used to detect the chemical environment of the voids. This system is one of only two in the United States.
Raman Microscope
The group
maintains a new Renshaw 2000 Raman confocal microscope with macro and micro
stages. These permit Raman images with spatial resolution down to
about 1 micron. Using different
objective lenses, images up to about 1 mm can be obtained. Three
different lasers permit variability in the excitation wavelength to avoid
interferences. The high temperature
capabilities permit Raman spectroscopic studies up to 1600 C.
This system is also being used for surface enhanced Raman spectroscopy.
It is planned also to use this for studies of catalysts and molten
glasses to study vitrification of uranium oxides.
Infrared Spectroscopy
In addition to the surface reflection absorption infra-red system (RAIRS) mentioned above, the group maintains two additional Fourier transform infra-red spectrometers. One is a Bowman high resolution spectrometer which permits FTIR at resolutions down to around 0.1 cm-1. It has three different sample compartments with three different types of interchangeable detectors. The broad range of the FTIR scan permits collecting spectra into the UV range. It is currently planed to use this for chemisorption studies on mesoporous catalysts. The group also maintains a BioRad FTIR spectrometer. This system has accessories for performing diffuse reflectance (DRIFTS), and attenuated reflectance (ATR) and also single reflection mode FTIR. This spectrometer is currently used for analysis tasks to support synthesis of nanomaterials and mesoporous structured oxides.
BET Surface Area Measurements
The group maintains two systems for routine measurement of surface area, pore volume, and pore size distributions. These are a Quantachrome Autosorb 1 and a Micromerictics 2275. These are used as an aid to synthesis and for characterization of mixed oxides, mesoporous materials and nanocatalysts.
Absorption Spectrometry
A Cary 14 H UV-visible spectrometer is modified for high temperature applications and uses phase sensitive detection techniques for removal of thermal background radiation from high temperature samples.
Synthesis Laboratories
Two complete laboratories for synthesis of nanomaterials are maintained. They include standard synthesis capabilities including autoclaves for hydrothermal synthesis, a high pressure reactor, dip and spin coaters, Schlenk lines, inert atmosphere boxes, a centrifuge, apparatus for drawing optical fibers from so-gel synthesis and a radiation contamination zone for safe handling of depleted uranium and uranium based catalysts. The labs are used for research and preparation of sol-gel materials, nanowires, mesoporous Au catalysts, co-assembled and mesoporous supported uranium oxide catalysts. A process furnace for preparation of carbon nanotubes supported in mesoporous materials is in progress.
