Gary P. Funkhouser

Influences of Dilute Organic Adsorbates on the Hydration of Low-Surface-Area Silicates

Competitive adsorption of dilute quantities of certain organic molecules and water at silicate surfaces strongly influence the rates of silicate dissolution, hydration, and crystallization. Here, we determine the molecular-level structures, compositions, and site-specific interactions of adsorbed organic molecules at low absolute bulk concentrations on heterogeneous silicate particle surfaces at early stages of hydration. Specifically, dilute quantities (∼0.1% by weight of solids) of the disaccharide sucrose or industrially important phosphonic acid species slow dramatically the hydration of low-surface-area (∼1 m(2)/g) silicate particles. Here, the physicochemically distinct adsorption interactions of these organic species are established by using dynamic nuclear polarization (DNP) surface-enhanced solid-state NMR techniques. These measurements provide significantly improved signal sensitivity for near-surface species that is crucial for the detection and analysis of dilute adsorbed organic molecules and silicate species on low-surface-area particles, which until now have been infeasible to characterize. DNP-enhanced 2D (29)Si{(1)H}, (13)C{(1)H}, and (31)P{(1)H} heteronuclear correlation and 1D (29)Si{(13)C} rotational-echo double-resonance NMR measurements establish hydrogen-bond-mediated adsorption of sucrose at distinct nonhydrated and hydrated silicate surface sites and electrostatic interactions with surface Ca(2+) cations. By comparison, phosphonic acid molecules are found to adsorb electrostatically at or near cationic calcium surface sites to form Ca(2+)-phosphonate complexes. Although dilute quantities of both types of organic molecules effectively inhibit hydration, they do so by adsorbing in distinct ways that depend on their specific architectures and physicochemical interactions. The results demonstrate the feasibility of using DNP-enhanced NMR techniques to measure and assess dilute adsorbed molecules and their molecular interactions on low-surface-area materials, notably for compositions that are industrially relevant.

Organogels with complexes of ions and phosphorus-containing amphiphiles as gelators. Spontaneous gelation by in situ complexation.

The properties of thermally reversible organogels that are formed spontaneously upon mixing a phosphonic acid monoester, monophosphonic acid, or bisphosphonate ester, each containing a long alkyl chain substituent, with one of several compounds of aluminum(III) and boron(III) in an organic liquid were studied by IR, NMR, optical microscopy, X-ray diffraction, and rheological techniques. Attempts to form gels with zirconium(IV) were unsuccessful. Gelation occurred at room temperature upon complexation, leading to the formation of entangled networks of elongated objects similar to giant, worm-like micelles. On the basis of the diversity of the liquids gelated, the minimum concentration of gelator required to make a gel at room temperature (typically <5 wt %), and the temporal and thermal stabilities of the gels, Al complexes of phosphonic acid monoesters were found to be better gelators than bisphosphonate complexes. Several of the gels formed from the monophosphonate-Al complexes were stable for very long periods when they were kept in sealed tubes at room temperature. When heated, they reverted to sols over wide temperature ranges. The nature of the gels and the complexes from which they were formed were correlated, especially for those with the phosphonic acid monoester. The results describe an interesting class of two-component gelators that can be made from freely flowing solutions by mixing the components at room temperature, without the need for a catalyst, radiation, or sonication. The properties of the gels can be modulated by careful choice of the structural variables in the phosphorus-containing latent gelators.

Thin polypyrrole films formed on mica and alumina with and without surfactant present: characterization by scanning probe and optical microscopy

Abstract Chemical deposition of electrically conducting polypyrrole (PPy) thin films on mica and alumina was carried out in aqueous solutions with and without surfactant. Examination of film morphology and thickness by atomic force microscopy (AFM) indicated a strong dependence of structure on the method of preparation. Films grown in the absence of surfactant were thicker than 150 nm with wrinkles present, indicating the overcoming of film–substrate adhesion by internal film cohesion. Oxidative polymerization with surfactant allowed reproducible synthesis of very thin films (50 nm thickness) with improved adhesion and suppressed formation of wrinkles. Experimental results are discussed within the context of a Stranski–Krastanov model of film growth. Film thickness and surface fractal dimensions were derived from AFM. Fractal analysis of PPy films on alumina helped discern their presence on the microscopically rough substrate and quantitatively expressed the changes in sample color by surface roughness.

Reactions and surface interactions of saccharides in cement slurries.

Glucose, maltodextrin, and sucrose exhibit significant differences in their alkaline reaction properties and interactions in aluminate/silicate cement slurries that result in diverse hydration behaviors of cements. Using 1D solution- and solid-state (13)C nuclear magnetic resonance (NMR), the structures of these closely related saccharides are identified in aqueous cement slurry solutions and as adsorbed on inorganic oxide cement surfaces during the early stages of hydration. Solid-state 1D (29)Si and 2D (27)Al{(1)H} and (13)C{(1)H} NMR techniques, including the use of very high magnetic fields (18.8 T), allow the characterization of the hydrating silicate and aluminate surfaces, where interactions with adsorbed organic species influence hydration. These measurements establish the molecular features of the different saccharides that account for their different adsorption behaviors in hydrating cements. Specifically, sucrose is stable in alkaline cement slurries and exhibits selective adsorption at hydrating silicate surfaces but not at aluminate surfaces in cements. In contrast, glucose degrades into linear saccharinic or other carboxylic acids that adsorb relatively weakly and nonselectively on nonhydrated and hydrated cement particle surfaces. Maltodextrin exhibits intermediate reaction and sorption properties because of its oligomeric glucosidic structure that yields linear carboxylic acids and stable ring-containing degradation products that are similar to those of the glucose degradation products and sucrose, respectively. Such different reaction and adsorption behaviors provide insight into the factors responsible for the large differences in the rates at which aluminate and silicate cement species hydrate in the presence of otherwise closely related saccharides.

Origins of saccharide-dependent hydration at aluminate, silicate, and aluminosilicate surfaces

Sugar molecules adsorbed at hydrated inorganic oxide surfaces occur ubiquitously in nature and in technologically important materials and processes, including marine biomineralization, cement hydration, corrosion inhibition, bioadhesion, and bone resorption. Among these examples, surprisingly diverse hydration behaviors are observed for oxides in the presence of saccharides with closely related compositions and structures. Glucose, sucrose, and maltodextrin, for example, exhibit significant differences in their adsorption selectivities and alkaline reaction properties on hydrating aluminate, silicate, and aluminosilicate surfaces that are shown to be due to the molecular architectures of the saccharides. Solid-state 1H, 13C, 29Si, and 27Al nuclear magnetic resonance (NMR) spectroscopy measurements, including at very high magnetic fields (19 T), distinguish and quantify the different molecular species, their chemical transformations, and their site-specific adsorption on different aluminate and silicate moieties. Two-dimensional NMR results establish nonselective adsorption of glucose degradation products containing carboxylic acids on both hydrated silicates and aluminates. In contrast, sucrose adsorbs intact at hydrated silicate sites and selectively at anhydrous, but not hydrated, aluminate moieties. Quantitative surface force measurements establish that sucrose adsorbs strongly as multilayers on hydrated aluminosilicate surfaces. The molecular structures and physicochemical properties of the saccharides and their degradation species correlate well with their adsorption behaviors. The results explain the dramatically different effects that small amounts of different types of sugars have on the rates at which aluminate, silicate, and aluminosilicate species hydrate, with important implications for diverse materials and applications.

Rheological Comparison of Organogelators Based on Iron and Aluminum Complexes of Dodecylmethylphosphinic Acid and Methyl Dodecanephosphonic Acid

Organogels were prepared from a 1:3 molar ratio of metal/ligand complexes of iron(III) or aluminum(III) with methyl dodecanephosphonic acid or dodecylmethylphosphinic acid at a concentration of 10 mM in dodecane. Gelation occurs spontaneously upon dissolution of the solid complex. Dynamic oscillatory measurements over the temperature range of 100-150 degrees C indicate that these materials behave as living polymers. Both reptation and reversible chain scission contribute to stress relaxation. The phosphonate ester complex gels are stronger than the corresponding dialkylphosphinate complex gels. Even at 150 degrees C, the phosphonate ester complexes maintained significant structure. Zero-shear viscosity activation energies are in the range of 26.5-61.2 kJ/mol, comparable to that for typical polymer melts.

Liquid Petroleum Gas Fracturing Fluids for Unconventional Gas Reservoirs

Unconventional gas reservoirs, including tight gas, shale gas and coalbed methane, are becoming a critically important component of the current and future gas supply. However, these reservoirs often present unique stimulation challenges. The use of water-based fracturing fluids in low permeability reservoirs may result in loss of effective frac half-length caused by phase trapping associated with the retention of the introduced water into the formation. This problem is increased by the water-wet nature of most tight gas reservoirs (where no initial liquid hydrocarbon saturation is, or ever has been, present) because of the strong spreading coefficient of water in such a situation. The retention of increased water saturation in the pore system can restrict the flow of produced gaseous hydrocarbons such as methane. Capillary pressures of 10 to 20 MPa or higher can be present in low permeability formations at low water saturation levels. The inability to generate sufficient capillary drawdown force using the natural reservoir drawdown pressure can result in extended fluid recovery times, or permanent loss of effective fracture half-length. Furthermore, use of water in subnormally saturated reservoirs may also reduce permeability and associated gas flow through a permanent increase in water saturation of the reservoir. Secondary costs, such as rig time for swabbing, can add to the negative economic impact. Gelled liquid petroleum gas-based fracturing fluids are designed to address phase trapping concerns by replacement of water with a mixture of liquid petroleum gas (LPG) and a volatile hydrocarbon fluid. Once the well is drawn down for flowback, some of the LPG portion of the fluid may be produced back as a gas, dependent upon temperature and pressure. The remaining LPG remains dissolved in the hydrocarbon fluid and is produced back as a miscible mixture using a methane drive mechanism. By eliminating water and having LPG as up to 80 - 90% of the total fluid system, cleanup is greatly facilitated, even in wells having very low permeability and reservoir pressure. The effects of fracturing fluid retention on gas flow in the fracture face can be as important as fracture conductivity when designing a treatment. It is possible to have a conductive fracture with good half-length in the desired productive zone and still not realize economic or optimum gas production if phase trapping and/or relative permeability effects are restricting gas flow.

Modeling the Effect of Curing Temperature and Pressure on Cement Hydration Kinetics

This study shows that chemical shrinkage tests can be used to evaluate the hydration kinetics of cement cured under different temperatures and pressures. Test results suggest that the effect of curing condition on cement hydration is represented by a scale factor on hydration rate as a function of degree of hydration. Therefore, the hydration kinetic curves of cement at any curing condition can be predicted from those of a reference condition by simple coordinate transformations (that is, scaling the x- and/or y-axis using the scale factor). The dependence of the scale factor on curing temperature and curing pressure is related to the activation energy and the activation volume of the cement, respectively. Test results of five different types of oil well cements in this study give an apparent activation energy ranging from 42.5 to 52.6 kJ/mol and an apparent activation volume ranging from –22.3 to –29.5 cm3/mol.

Strength improvement via coating of a cylindrical hole by layer-by-layer assembled polymer particles.

Negatively charged colloidal poly(methyl methacrylate-co-butyl acrylate) (P(MMA-BA)) particles and positively charged dissolved poly(ethyleneimine) (PEI) were adsorbed onto a cement block using a layer-by-layer (LBL) assembly technique. The block was fashioned so as to have a cylindrical hole running from one face to another along the long axis of the rectangular block, and a fluid containing either of the two charged materials was pumped through the block. The result was a film tens of micrometers thick, and the pressure required to crack the cement block was measured after one end of the hole was sealed. Latex particles with a T(g) near the use temperature showed the maximum improvement in the cracking stress of the blocks. In a multilayer coating with identically sized particles, the cracking stress of the blocks increased to an improvement of 25% and then dropped off with increasing number of layers, even though the relationship between film thickness and the number of layers was linear. An improvement of about 30% in the cracking stress of the coated blocks was obtained when using multiple layers with different particle sizes. The effects of the number of layers and particle size on the cracking stress suggest that both the morphology and the thickness of the film play a role in performance. Tests done under confinement, e.g., with an external stress applied to the outside of the blocks, suggest that not only does a film-forming mechanism contribute to performance but that filling of microcracks in the rock may also play a role.

Mechanical properties and rheology of polyalkenoate cements using various low-cost fillers

The Publisher apologizes for a misprint that appeared on the Journal of Materials Science webpage for “Mechanical properties and rheology of polyalkenoate cements using various low-cost fillers” by Diego A. Acosta, Gary P. Funkhouser and Brian P.Grady. The last author’s name was spelled incorrectly.