Pleasanton, CA, United States
Pleasanton, CA, United States

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Ross N.L.,Virginia Polytechnic Institute and State University | Spencer E.C.,Virginia Polytechnic Institute and State University | Levchenko A.A.,Setaram Inc. | Kolesnikov A.I.,Oak Ridge National Laboratory | And 7 more authors.
Materials Research Society Symposium Proceedings | Year: 2012

We present low-temperature inelastic neutron scattering spectra collected on two metal oxide nanoparticle systems, isostructural TiO 2 rutile and SnO 2 cassiterite, between 0-550 meV. Data were collected on samples with varying levels of water coverage, and in the case of SnO 2, particles of different sizes. This study provides a comprehensive understanding of the structure and dynamics of the water confined on the surface of these particles. The translational movement of water confined on the surface of these nanoparticles is suppressed relative to that in ice-lh and water molecules on the surface of rutile nanoparticles are more strongly restrained that molecules residing on the surface of cassiterite nanoparticles. The INS spectra also indicate that the hydrogen bond network within the hydration layers on rutile is more perturbed than for water on cassiterite. This result is indicative of stronger water-surface interactions between water on the rutile nanoparticles than for water confined on the surface of cassiterite nanoparticles. These differences are consistent with the recently reported differences in the surface energy of these two nanoparticle systems. © 2011 Materials Research Society.

Burnham A.K.,American Shale Oil LLC | Levchenko A.,Setaram Inc. | Herron M.M.,Schlumberger
Fuel | Year: 2015

The abundance of dawsonite in an exploration well in the Green River Formation oil shale has been characterized by well logging, FTIR, DSC, and wet chemistry. The four methods agree qualitatively but not quantitatively. Thermal analysis was then used to characterize changes in the dawsonite decomposition endotherm as a function of pressure. The peak temperature of the endotherm increased with pressure and the size decreased with pressure. The total endotherm at high temperature that includes dolomite and calcite reactions decreased with increased pressure, presumably due to formation of more stable silicates. © 2014 Elsevier Ltd.

Levchenko A.A.,Setaram Inc. | Kolesnikov A.I.,University of California at Davis | Trofymluk O.,Oak Ridge National Laboratory | Navrotsky A.,University of California at Davis
Carbon | Year: 2011

Bundles of (10,10) single-wall carbon nanotubes (SWCNTs) have been studied by high-temperature oxidation calorimetry and inelastic neutron scattering to obtain standard formation enthalpies and entropies at 298 K. SWCNTs are found to be only moderately less stable than graphite, and are significantly more stable than their fullerene counterparts. They are 7 kJ mol -1 metastable in terms of enthalpy relative to graphite, and just 5 kJ mol -1 less stable than diamond. Despite striking differences in vibrational dynamics of carbon atoms in SWCNTs and graphite, their thermodynamic properties at room and higher temperatures are dominated by the same set of high energy vibrations, reflected in very similar vibrational entropies. However, the energetics of SWCNTs are governed by the diameter-dependent enthalpic contributions, but not the specifics of phonon density of states. © 2010 Elsevier Ltd. All rights reserved.

Trofymluk O.,University of California at Davis | Levchenko A.A.,Setaram Inc. | Navrotsky A.,University of California at Davis
Microporous and Mesoporous Materials | Year: 2012

The thermodynamics of mesoporous silicas (MCM-41, MCM-48, SBA-15, and SBA-16) were studied by solution calorimetry at 323 K in 25% aqueous HF. The enthalpies of formation were determined for calcined mesoporous silica (MS) and organic structure-directing agent (SDA) occluded samples (SDA: n-hexadeciltrimethylammonium bromide or CTAB, Pluronic P123, and Pluronic F127). The following are the measured interaction enthalpies between the MS and SDA: MCM-41/CTAB, -6.1 kJ/mol SiO2; MCM-48/CTAB, -12.3 kJ/mol SiO 2; SBA-15/P123, -19.7 kJ/mol SiO2; SBA-16/F127, -19.9 kJ/mol SiO2. Per unit surface area, these interactions are -0.08, -0.15, -0.43, and -0.40 J/m2, respectively. Though these SDA-framework interaction energies are still small in magnitude, they are somewhat more exothermic than those in silica zeolite formation, reflecting the greater metastability of the MS materials and the role of the long chain SDA in stabilizing and space-filling the large pores. The cubic MS (SBA) show stronger SDA interactions than the hexagonal (MCM). The interaction energies confirm a complex landscape of many competing structures of similar energy; with the role of SDA kinetic in selecting a specific structure rather than energetic in strongly stabilizing a given state, as has already been noted for zeolites. The enthalpies of the calcined MS relative to quartz determined by HF solution calorimetry in this study are in excellent agreement with those determined previously by high temperature oxide melt solution calorimetry.

Levchenko A.A.,University of California at Davis | Levchenko A.A.,Setaram Inc. | Jain P.,University of California at Davis | Trofymluk O.,University of California at Davis | And 3 more authors.
Journal of Physical Chemistry B | Year: 2010

The dynamics of glass-forming liquids under nanoconfinement is key to understanding a variety of phenomena in nature and modern technology. We report a 13C NMR spectroscopic study that directly demonstrates that a-relaxation in bulk glycerol involves an isotropic rotational jump of the constituent molecules. The activation energy of this motion is ∼78 kJ mol-1 in the bulk, which abruptly changes to a low value of ∼27.5 kJ mol-1, characteristic of β-processes, upon confinement of glycerol into ∼2 nm pores in mesoporous silica. This observation implies that the molecular dynamics associated with structural relaxation near glass transition are inherently different in supercooled glycerol in the bulk and under extreme nanoconfinement. © 2010 American Chemical Society.

Levchenko A.,Setaram Inc. | LeParlouer P.,Setaram Instrumentation | Karim S.,Setaram Inc.
10AIChE - 2010 AIChE Annual Meeting, Conference Proceedings | Year: 2010

Great efforts have been directed towards understanding the relevant phenomena and foster innovation in the field of CO2 capture and sequestration (CCS). Knowledge about the CO2 sorption properties (adsorption capacity, pressure regimes, energetics and kinetics) is essential to the design of advanced materials capable of capturing CO2 in industrial settings. A twin Calvet calorimeter coupled with a high pressure gas dosing system offers a means to characterize materials for CO2 capture and sequestration applications under critical and supercritical conditions. New and published data will be presented to illustrate capabilities and advantages of the Calvet calorimeters for high pressure research with a special focus on CO2 capture applications.

Nforbi L.-N.N.,University of Nevada, Reno | Talekar A.,University of Nevada, Reno | Lau K.H.,SRI International | Chellapa R.,Los Alamos National Laboratory | And 6 more authors.
International Journal of Hydrogen Energy | Year: 2014

The vapor pressure and molecular weight of effusing vapors of α, β, and amorphous Mg were determined by Torsion-effusion gravimetric method, under dynamic vacuum. A Cahn balance in the system yielded the rate of the weight loss. Molecular weights measured revealed if the effusion was congruent or there was disproportionation. The vaporization behavior of crystalline Mg(BH42, was measured up to 533 K at pressures of ∼10-5 torr. It was found that Mg(BH4)2 disproportionates to form predominantly H2 gas (∼95%) with a small amount of Mg(BH4) (∼5%) in the gas phase. The combined average molecular weight measured is 4.16 g/mol. The equations for vapor pressures for crystalline Mg(BH4)2 are given by: log PT (bar) = 9.2303 - 7286.2/T, logPMg(BH4)2(bar)=8.2515-7286. 2/T, and logPH2(bar)=9.1821-7286.2/T. The partial pressures of the gaseous species were determined as PMgBH4)2PT=0.105 and PH2(g)PT=0.895. Enthalpies of vaporization for the effusing gases were calculated to be ΔH = +558.0 kJ/mol H2 and ΔH = +135 kJ/mol Mg(BH4)2. The standard Gibbs free energy changes, ΔG (kJ/mol), for the complete decomposition reaction (Mg(BH4)2(s) → Mg (s) + 2B(s) + 4H2(g)), sublimation reaction (Mg(BH4)2(s) → Mg(BH4)2(g)) and the disproportionation reaction for Mg(BH4)2 are reported in this paper. The decomposition pathway of amorphous Mg(BH4) 2 was also carried out between 388.2 K and 712.8 K showing multistep decomposition of a-Mg(BH4)2 Different reaction products were obtained depending on the method used in the vaporization experiment. The behavior of the amorphous Mg(BH4)2(s) is very different from those for the two crystalline phases (α and β). The vapor pressure behavior and thermodynamics of vaporization of different phases of Mg(BH4)2 are presented. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

Levchenko A.,Setaram Inc
11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings | Year: 2011

The new hydrogen storage materials discovered in the last few years present a number of challenges to the research community from a viewpoint of materials characterization. These include both evaluation of the performance in real-world applications of hydrogen storage materials and understanding the underlying fundamental mechanisms controlling their properties. This presentation gives an overview of state-of-the-art characterization techniques for hydrogen storage materials. It covers simultaneous TPD-gas sorption/mass-spectrometry measurements, volumetric PCT isotherm measurements on thin-film and extremely small metal-hydride samples, as well as direct van't Hoff and in-situ calorimetric measurements of enthalpy of formation of hydrides. Challenges in performing measurements on particular types of materials or under demanding conditions are discussed.

Levchenko A.,Setaram Inc | Andre R.,Setaram Inc | Parken M.,Setaram Inc | Le Parlouer P.,Setaram Inc
ACS National Meeting Book of Abstracts | Year: 2011

A great deal of research is directed towards understanding the CO2 capture and sequestration (CCS) phenomena as applied to mitigation the global warming. Critical data on CO2 sorption properties (adsorption capacity, pressure regimes, energetics and kinetics) is needed to design of advanced materials capable of capturing CO2 in industrial settings. Many materials including solids such as metal organic frameworks (MOFs) and liquids (ionic liquids) are considered as prospective candidates for CCS applications. The ability to assess energetics of carbon dioxide adsorption in addition to CO2 capacity is key to the successful application of the proposed systems such ionic liquids and MOFs. In this paper we demonstrate how calorimetric data in conjunction with adsorption data render insights into and assist in the further materials development. The adsorption data for MOFs and ionic liquids have been obtained using a Sievert's apparatus. A critical analysis of volumetric technique and CO2 data is presented. The paper also discusses the calorimetric results for MOFs and ionic liquids which have been obtained in-situ with a coupled system.

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