Enhanced Barrier Performance of Engineered Paper by Atomic Layer Deposited Al2O3 Thin Films.

Surface modification of cellulosic paper is demonstrated by employing plasma assisted atomic layer deposition. Al2O3 thin films are deposited on paper substrates, prepared with different fiber sizes, to improve their barrier properties. Thus, a hydrophobic paper is created with low gas permeability by combining the control of fiber size (and structure) with atomic layer deposition of Al2O3 films.

High-Performance Supercapacitors from Niobium Nanowire Yarns.

The large-ion-accessible surface area of carbon nanotubes (CNTs) and graphene sheets formed as yarns, forests, and films enables miniature high-performance supercapacitors with power densities exceeding those of electrolytics while achieving energy densities equaling those of batteries. Capacitance and energy density can be enhanced by depositing highly pseudocapacitive materials such as conductive polymers on them. Yarns formed from carbon nanotubes are proposed for use in wearable supercapacitors.

Formation of methane nano-bubbles during hydrate decomposition and their effect on hydrate growth.

Molecular dynamic simulations are performed to study the conditions for methane nano-bubble formation during methane hydrate dissociation in the presence of water and a methane gas reservoir. Hydrate dissociation leads to the quick release of methane into the liquid phase which can cause methane supersaturation. If the diffusion of methane molecules out of the liquid phase is not fast enough, the methane molecules agglomerate and form bubbles.

Why ice-binding type I antifreeze protein acts as a gas hydrate crystal inhibitor.

Antifreeze proteins (AFPs) prevent ice growth by binding to a specific ice plane. Some AFPs have been found to inhibit the formation of gas hydrates which are a serious safety and operational challenge for the oil and gas industry. Molecular dynamics simulations are used to determine the mechanism of action of the winter flounder AFP (wf-AFP) in inhibiting methane hydrate growth.

Contact angle hysteresis of non-flattened-top micro/nanostructures.

A two-dimensional (2D) thermodynamic model is proposed to predict the contact angle (CA) and contact angle hysteresis (CAH) of different types of surface geometries, particularly those with asperities having nonflattened tops. The model is evaluated by micro/nano sinusoidal and parabolic patterns fabricated by laser ablation. These microstructures are analyzed thermodynamically through the use of the Gibbs free energy to obtain the equilibrium contact angle (CA) and contact angle hysteresis (CAH).

Femtosecond laser irradiation of metallic surfaces: effects of laser parameters on superhydrophobicity.

This work studies in detail the effect of femtosecond laser irradiation process parameters (fluence and scanning speed) on the hydrophobicity of the resulting micro/nano-patterned morphologies on stainless steel. Depending on the laser parameters, four distinctly different nano-patterns were produced, namely nano-rippled, parabolic-pillared, elongated sinusoidal-pillared and triple roughness nano-structures. All of the produced structures were classified according to a newly defined parameter, the laser intensity factor (LIF); by increasing the LIF, the ablation rate and periodicity of the asperities increase.

Superhydrophobic lignocellulosic wood fiber/mineral networks.

Lignocellulosic wood fibers and mineral fillers (calcium carbonate, talc, or clay) were used to prepare paper samples (handsheets), which were then subjected to a fluorocarbon plasma treatment. The plasma treatment was performed in two steps: first using oxygen plasma to create nanoscale roughness on the surface of the handsheet, and second fluorocarbon deposition plasma to add a layer of low surface energy material. The wetting behavior of the resulting fiber/mineral network (handsheet) was determined.

Molecular modeling of the dissociation of methane hydrate in contact with a silica surface.

We use constant energy, constant volume (NVE) molecular dynamics simulations to study the dissociation of the fully occupied structure I methane hydrate in a confined geometry between two hydroxylated silica surfaces between 36 and 41 Å apart, at initial temperatures of 283, 293, and 303 K. Simulations of the two-phase hydrate/water system are performed in the presence of silica, with and without a 3 Å thick buffering water layer between the hydrate phase and silica surfaces. Faster decomposition is observed in the presence of silica, where the hydrate phase is prone to decomposition from four surfaces, as compared to only two sides in the case of the hydrate/water simulations.

Application of the ATR-IR spectroscopic technique to the characterization of hydrates formed by CO(2), CO(2)/H(2) and CO(2)/H(2)/C(3)H(8).

The spectroscopic investigation of CO(2)-containing clathrate hydrates is complicated because techniques such as Raman spectroscopy cannot distinguish cage populations. (13)C NMR spectroscopy also has some complications as the isotropic chemical shifts do not change for the different CO(2) cage populations. It is known that CO(2) molecules in the different phases relevant to hydrates give unique infrared vibrational frequencies; however, so far only thin cryogenic films prepared at low pressure have been studied with IR transmission spectroscopy.

Patterned superhydrophobic metallic surfaces.

This work shows that after creating certain dual scale roughness structures by femtosecond laser irradiation different metal alloys initially show superhydrophilic behavior with complete wetting of the structured surface. However, over time, these surfaces become nearly superhydrophobic with contact angles in the vicinity of 150 degrees and superhydrophobic with contact angles above 150 degrees. The contact angle hysteresis was found to lie between 2 and 6 degrees.

Guest-host hydrogen bonding in structure H clathrate hydrates.

The formation of guest-host hydrogen bonds in structure H (sH) clathrate hydrates is studied herein. We contrast the structure and guest dynamics of the tert-butylmethylether (TBME) and neohexane (NH) sH clathrates by performing molecular dynamics simulations on these two clathrates and measuring (1)H and (13)C NMR relaxation times of the guests. These two guests are isoelectronic and differ with respect to the presence of the ether oxygen atom in TBME and a CH(2) group in NH.

Surfactant effects on SF6 hydrate formation.

Sulfur hexafluoride (SF(6)) has been widely used in a variety of industrial processes, but it is one of the most potent greenhouse gases. For this reason, it is necessary to separate or collect it from waste gas streams. One separation method is through hydrate crystal formation.

Molecular dynamics study of structure H clathrate hydrates of methane and large guest molecules.

Methane storage in structure H (sH) clathrate hydrates is attractive due to the relatively higher stability of sH as compared to structure I methane hydrate. The additional stability is gained without losing a significant amount of gas storage density as happens in the case of structure II (sII) methane clathrate. Our previous work has showed that the selection of a specific large molecule guest substance (LMGS) as the sH hydrate former is critical in obtaining the optimum conditions for crystallization kinetics, hydrate stability, and methane content.

Medium-pressure clathrate hydrate/membrane hybrid process for postcombustion capture of carbon dioxide.

This study presents a medium-pressure CO2 capture process based on hydrate crystallization in the presence of tetrahydrofuran (THF). THF reduces the incipient equilibrium hydrate formation conditions from a CO2/N2 gas mixture. Relevant thermodynamic data at 0.

The clathrate hydrate process for post and pre-combustion capture of carbon dioxide.

One of the new approaches for capturing carbon dioxide from treated flue gases (post-combustion capture) is based on gas hydrate crystallization. The basis for the separation or capture of the CO(2) is the fact that the carbon dioxide content of gas hydrate crystals is different than that of the flue gas. When a gas mixture of CO(2) and H(2) forms gas hydrates the CO(2) prefers to partition in the hydrate phase.

Hydrate kinetics study in the presence of nonaqueous liquid by nuclear magnetic resonance spectroscopy and imaging.

The dynamics of methane hydrate growth and decomposition were studied by nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI). Three well-known large molecule guest substances (LMGS) were used as structure H hydrate formers: 2,2-dimethylbutane (NH), methylcyclohexane (MCH), tert-butyl methyl ether (TBME). In addition, the impact of a non-hydrate former (n-heptane/nC7) was studied.

Application of the NICA-Donnan approach to calculate equilibrium between proton and metal ions with lignocellulosic materials.

The NICA (nonideal competitive adsorption)-Donnan model is employed to describe the interactions between Cu2+, Pb2+, Cd2+, Mn2+, and Fe3+ ions and the lignins extracted from wheat bran (lignocellulosic substrate, LS) and from kraft pulp (residual kraft lignin, RKL), and between Cu2+, Mn2+, and Fe3+ ions and wood fibers from kraft pulps. The charge of the LS and the fiber charge need to be obtained from potentiometric titration data for the LS, and by use of Donnan equilibrium, mass balance, and electroneutrality equations for the kraft fiber. The proton binding parameters for the LS and the kraft fiber, the total site densities (Qmax,1 and Qmax,2), the median protonation constants (K1 and K2), and nonideality-generic heterogeneity parameters (m1 and m2) (subscripts 1 and 2 refer to the carboxyl and phenolic functional groups) are obtained by fitting these charge data.