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Transformation of amorphous TiO2 to a hydronium oxofluorotitanate and applications as an HF sensor

Sensors and Actuators, B: Chemical

Appelhans, Leah A.; Finnegan, Patrick S.; Massey, Lee T.; Luk, Ting S.; Rodriguez, Mark A.; Brumbach, Michael T.; McKenzie, Bonnie B.; Craven, Julia M.

Amorphous titania thin films were examined for use as the active material in a polarimetry based HF sensor. The amorphous titania films were found to be sensitive to vapor phase HF and the reaction product was identified as a hydronium oxofluorotitanate phase, which has previously only been synthesized in aqueous solution. The extent of reaction varied both with vapor phase HF concentration, relative humidity, and the exposure time. HF concentrations as low as 1 ppm could be detected for exposure times of 120 h.

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TYPE Journal Article YEAR 2016
ScopusOSTIDOI

Monitoring of CoS2 reactions using high-temperature XRD coupled with gas chromatography (GC)

Powder Diffraction

Rodriguez, Mark A.; Coker, Eric N.; Griego, James J.M.; Mowry, Curtis D.; Pimentel, Adam S.; Anderson, Travis M.

High-temperature X-ray diffraction with concurrent gas chromatography (GC) was used to study cobalt disulfide cathode pellets disassembled from thermal batteries. When CoS2 cathode materials were analyzed in an air environment, oxidation of the K(Br, Cl) salt phase in the cathode led to the formation of K2SO4 that subsequently reacted with the pyrite-type CoS2 phase leading to cathode decomposition between ∼260 and 450 °C. Independent thermal analysis experiments, i.e. simultaneous thermogravimetric analysis/differential scanning calorimetry/mass spectrometry (MS), augmented the diffraction results and support the overall picture of CoS2 decomposition. Both gas analysis measurements (i.e. GC and MS) from the independent experiments confirmed the formation of SO2 off-gas species during breakdown of the CoS2. In contrast, characterization of the same cathode material under inert conditions showed the presence of CoS2 throughout the entire temperature range of analysis.

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TYPE Journal Article YEAR 2016
ScopusOSTIDOI

4,4'-([4,4'-Bipyridine]-1,1'-diium-1,1'-diyl)dibenzoate dihydrate

IUCrData

Rodriguez, Mark A.; Sava Gallis, Dorina F.; Chavez, James S.; Klivansky, Liana M.; Liu, Yi L.

We report here the synthesis of a neutral viologen derivative, C24H16N2O4·2H2O. The non-solvent portion of the structure (Z-Lig) is a zwitterion, consisting of two positively charged pyridinium cations and two negatively charged carboxylate anions. The carboxylate group is almost coplanar [dihedral angle = 2.04 (11)°] with the benzene ring, whereas the dihedral angle between pyridine and benzene rings is 46.28 (5)°. TheZ-Lig molecule is positioned on a center of inversion (Fig. 1). The presence of the twofold axis perpendicular to thec-glide plane in space groupC2/c generates a screw-axis parallel to thebaxis that is shifted from the origin by 1/4 in theaandcdirections. This screw-axis replicates the molecule (and solvent water molecules) through space. TheZ-Lig molecule links to adjacent moleculesviaO—H...O hydrogen bonds involving solvent water molecules as well as intermolecular C—H...O interactions. There are also π–π interactions between benzene rings on adjacent molecules.

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TYPE Journal Article YEAR 2016
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Selective O2 Sorption at Ambient Temperatures via Node Distortions in Sc-MIL-100

Chemistry of Materials

Sava Gallis, Dorina F.; Chapman, Karena W.; Rodriguez, Mark A.; Greathouse, Jeffery A.; Parkes, Marie V.; Nenoff, T.M.

An open pored metal-organic framework (MOF) with oxygen selectivity at exceptionally high temperatures is confirmed by synthesis, sorption, and synchrotron structural analyses. The large-pore MIL-100 framework with access to the metal center (e.g., Sc and Fe) resulted in preferential O2 over N2 gas uptake at temperatures ranging from 77 K to ambient temperatures (258, 298, and 313 K). Most notably, Sc-MIL-100 shows exceptional O2 sorption; pair distribution function analyses indicate that this is due to distortions in the framework owing to the size of Sc atoms, in particular in the trimer metal cluster. Experimental studies also correlate very well with GCMC simulations, confirming more favorable O2-framework interactions at pressures up to 1 bar, due to the close proximity of O2 to the high density of metal centers in the small tetrahedral cages. Both materials maintain their crystallinity upon gas adsorption cycling, are regenerable, and show exceptional promise for use in energy efficient oxygen purification processes, such as Pressure Swing Adsorption.

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TYPE Journal Article YEAR 2016
ScopusOSTIDOI

Scaling effects in sodium zirconium silicate phosphate (Na1+xZr2SixP3-xO12) ion-conducting thin films

Journal of the American Ceramic Society

Ihlefeld, Jon I.; Jones, Brad H.; Wheeler, David R.; Rodriguez, Mark A.; McDaniel, Anthony H.; Gurniak, Emily G.

Preparation of sodium zirconium silicate phosphate (NaSICon), Na1+xZr2SixP3–xO12 (0.25 ≤ x ≤ 1.0), thin films has been investigated via a chemical solution approach on platinized silicon substrates. Increasing the silicon content resulted in a reduction in the crystallite size and a reduction in the measured ionic conductivity. Processing temperature was also found to affect microstructure and ionic conductivity with higher processing temperatures resulting in larger crystallite sizes and higher ionic conductivities. The highest room temperature sodium ion conductivity was measured for an x = 0.25 composition at 2.3 × 10–5 S/cm. In conclusion, the decreasing ionic conductivity trends with increasing silicon content and decreasing processing temperature are consistent with grain boundary and defect scattering of conducting ions.

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TYPE Journal Article YEAR 2016
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Results 126–150 of 193
Results 126–150 of 193