Mark M. Disko

Adsorption and Diffusion of Pt and Au on the Stoichiometric and Reduced TiO

A comparative ab initio pseudopotential study of the adsorption and migration profiles of single neutral Pt and Au atoms on the stoichiometric and reduced

_2

\mathrm{Ti}{\mathrm{O}}_{2}

Rutile (110) Surfaces

rutile (110) surfaces is presented. Pt and Au behave similarly with respect to (i) most favorable adsorption sites, (ii) the large increase in their binding energy when the surface is reduced, and (iii) their low migration barrier on the stoichiometric surface. Pt, on the other hand, binds more strongly (by

Cryomilling of Nano-Phase Dispersion Strengthened Aluminum

\ensuremath{\sim}2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}

On the imaging of Pt atoms in zeolite frameworks

) to both surfaces. On the stoichiometric surface, Pt migration pattern is expected to be one dimensional, which is primarily influenced by interactions with O atoms. Au migration is expected to be two dimensional, with

Infrared hollow waveguide sensors for simultaneous gas phase detection of benzene, toluene, and xylenes in field environments.

\mathrm{Au}\ensuremath{-}\mathrm{Ti}

Electron energy-loss chemical imaging of polymer phases

interactions playing a more important role. On the reduced surface, the migration barrier of Pt trapped at an O vacancy site is significantly larger compared to that of Au.

Preferential growth of Pt on rutile Ti O 2

In recent years considerable effort has been expended on the development of dispersion strengthened alloys by mechanical alloying. Our research has shown that considerable improvement in microstructure control and properties can be gained by carrying out milling at cryogenic temperatures. We have found that aluminum and dilute aluminum alloys can be dispersion strengthened with aluminum oxy-nitride particles by the use of a slurry milling technique where the fluid medium is liquid nitrogen. The alloyed powders produced by this technique are strengthened by aluminum oxy-nitride particles which are typically 2–10 nm in diameter and with a mean spacing of 50–100 nm. The dispersoids are generated during the milling process by adsorption and reaction with components of the liquid nitrogen bath. On thermal treatment prior to consolidation, the alloyed powders recrystallize to a grain size which is typically in the range 0.05 to 0.3 μm. The alloys exhibit a yield stress in excess of 325 MPa at room temperature and a virtually temperature independent yield stress of about 130 MPa at temperatures greater than 375° C. The paper describes the preparation of dispersion strengthened aluminum by cryomilling, the characteristics of the microstructure and discusses some aspects of the mechanical properties.

Energy-loss near-edge fine structure and compositional profiles of cryomilled oxide-dispersion-strengthened aluminum

We compare the relative merits of high-resolution bright-field imaging in the TEM and high-angle annular-dark-field imaging (Z-contrast) in the STEM, for the detection and measurement of small ( <1 nm) noble-metal clusters in zeolites. Pt in K-zeolite L is used as an example system. It is confirmed that high-resolution bright-field imaging is better suited for resolving the zeolite framework. However, even with contrast enhancements gained from image-processing techniques, such as Fourier-filtering, bright-field images are ineffective for detecting clusters containing fewer than ∼ 20 Pt atoms in supports thicker than ∼ 10 nm. This is attributed mainly to ambiguous phase contrast speckle patterns associated with beam-damaged regions of the zeolite framework. Z-contrast images obtained with a STEM high-angle annular detector using a ∼ 0.2 nm probe are shown to be capable of detecting single Pt atoms against a ∼ 20 nm thick zeolite support. However, the precision with which atomic-sized clusters can be located relative to the unit cell is limited by the beam-damage-induced distortion of the zeolite framework.

Spatially resolved electron energy-loss spectroscopy of MoS2 platelets

Simultaneous and molecularly selective parts-per-billion detection of benzene, toluene, and xylenes (BTX) using a thermal desorption (TD)-FTIR hollow waveguide (HWG) trace gas sensor is demonstrated here for the first time combining laboratory calibration with real-world sample analysis in field. A calibration range of 100-1000 ppb analyte/N(2) was developed and applied for predicting the concentration of blinded environmental air samples within the same concentration range, and demonstrate close agreement with the validation method used here, GC-FID. The analyte concentration prediction capability of the TD-FTIR-HWG trace gas sensor also compares well with the industrial standard and other experimental techniques including GC-PID, ultrafast GC-FID, and GC-DMS, which were simultaneously operated in the field. With the advent of a quantum cascade laser with emission frequencies specifically tailored to efficiently overlap benzene absorption as the most relevant analyte, the overall sensor footprint could be considerably reduced to ultimately yield hand-held trace gas sensors facilitating direct and real-time detection of BTX in air down to low ppb levels.