Dynamic Triple-Mode Sorption and Outgassing in Materials.

Moisture uptake and outgassing can be detrimental to a system by altering the chemical and mechanical properties of materials within the system over time. In this work, we conducted isotherm experiments to investigate dynamic moisture sorption and desorption in markedly different materials, i.e.

Modeling and Uncertainty Quantification of Vapor Sorption and Diffusion in Heterogeneous Polymers.

A high-fidelity model of kinetic and equilibrium sorption and diffusion is developed and exercised. The gas-diffusion model is coupled with a triple-sorption mechanism: Henry's law absorption, Langmuir adsorption, and pooling or clustering of molecules at higher partial pressures. Sorption experiments are conducted and span a range of relative humidities (0-95 %) and temperatures (30-60 °C).

A high-pressure NMR probe for aqueous geochemistry.

A non-magnetic piston-cylinder pressure cell is presented for solution-state NMR spectroscopy at geochemical pressures. The probe has been calibrated up to 20 kbar using in situ ruby fluorescence and allows for the measurement of pressure dependencies of a wide variety of NMR-active nuclei with as little as 10 μL of sample in a microcoil. Initial (11)B NMR spectroscopy of the H3BO3-catechol equilibria reveals a large pressure-driven exchange rate and a negative pressure-dependent activation volume, reflecting increased solvation and electrostriction upon boron-catecholate formation.

Advances in modeling sorption and diffusion of moisture in porous reactive materials.

Water-vapor-uptake experiments were performed on a silica-filled poly(dimethylsiloxane) (PDMS) network and modeled by using two different approaches. The data was modeled by using established methods and the model parameters were used to predict moisture uptake in a sample. The predictions are reasonably good, but not outstanding; many of the shortcomings of the modeling are discussed.

Kinetic studies of the [NpO(2)(CO(3))(3)](4-) ion at alkaline conditions using (13)C NMR.

Carbonate ligand-exchange rates on the [NpO2(CO3)3]4– ion were determined using a saturation-transfer 13C nuclear magnetic resonance (NMR) pulse sequence in the pH range of 8.1 ≤ pH ≤ 10.5.

Thermodynamic study on dynamic water vapor sorption in Sylgard-184.

The dynamic and equilibrium water vapor sorption properties of Sylgard-184, a commercially available poly(dimethylsiloxane) elastomer (PDMS), were determined via gravimetric analysis from 30 to 70 °C. Described here is a methodology for quantitatively assessing how water vapor diffuses and ad/absorbs into polymeric materials that are traditionally considered hydrophobic. PDMS materials are frequently chosen for their moisture barrier properties; our results, however, demonstrate that moisture is able to penetrate the material over a range of temperatures and humidities.

A (31) P NMR investigation of the CoPi water-oxidation catalyst.

Beneath the sheets: (31) P NMR data suggests that phosphates are liberated freely in the interlayer of a cobalt-hydroxide water-oxidation catalyst. The cobalt-hydroxide sheets are separated by an interlayer region with water, counterions and phosphate, which help to shuttle protons as the layer develops charge.

Rates of water exchange on the [Fe4(OH)2(hpdta)2(H2O)4]0 molecule and its implications for geochemistry.

The ammonium salt of [Fe(4)O(OH)(hpdta)(2)(H(2)O)(4)](-) is soluble and makes a monospecific solution of [Fe(4)(OH)(2)(hpdta)(2)(H(2)O)(4)](0)(aq) in acidic solutions (hpdta = 2-hydroxypropane-1,3-diamino-N,N,N',N'-tetraacetate). This tetramer is a diprotic acid with pK(a)(1) estimated at 5.7 ± 0.

Probing the surface structure of divalent transition metals using surface specific solid-state NMR spectroscopy.

Environmental and geochemical systems containing paramagnetic species could benefit by using nuclear magnetic resonance (NMR) spectroscopy due to the sensitivity of the spectral response to small amounts paramagnetic interactions. In this study, we apply commonly used solid-state NMR spectroscopic methods combined with chemometrics analysis to probe sorption behavior of the paramagnetic cations Cu(2+) and Ni(2+)at the amorphous silica surface. We exploit the unique properties of paramagnets to derive meaningful structural information in these systems at low, environmentally relevant cation surface loadings by comparing the NMR response of sorption samples to paramagnetic free samples.

Rates of water exchange for two cobalt(II) heteropolyoxotungstate compounds in aqueous solution.

Polyoxometalate ions are used as ligands in water-oxidation processes related to solar energy production. An important step in these reactions is the association and dissociation of water from the catalytic sites, the rates of which are unknown. Here we report the exchange rates of water ligated to Co(II) atoms in two polyoxotungstate sandwich molecules using the (17)O-NMR-based Swift-Connick method.