This study addresses the effects of mesopore orientation on mesostructural stability and crystallization of titania thin films during calcination based on measurements with in-situ grazing incidence small angle X-ray scattering (GISAXS). Complementary supporting information is provided by ex-situ electron microscopy. Pluronic surfactant P123 (with average structure (EO) 20 (PO) 70 (EO) 20 where EO is an ethylene oxide unit and PO is a propylene oxide unit) serves as the template to synthesize titania thin films on P123modified glass slides with 2D hexagonally close-packed cylindrical mesopores. The orientation of the pores at the top surface is controlled by sandwiching another P123modified glass slide on top of the titania thin film to completely orient the pores orthogonal to the films in some samples. This provides the opportunity to directly observe how pore orientation affects the evolution of pore order and crystallinity during calcination. The results show that when the pores are oriented parallel to the substrate at the top surface (for unsandwiched films), the pore structure is stable upon calcination at 400 °C but that the structure is quickly lost due to crystallization throughout the film during calcination at 500 °C. Films with pores oriented orthogonal to the substrate at the top surface (sandwiched films) retain their long-range pore order even after calcination at 500 °C. The reasons for this difference are ascribed to greater resistance to anisotropic stress during heating of the orthogonally oriented pores and titania crystallization nucleation at the top surface of the films with orthogonally oriented pores.

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The mechanism of forming orthogonally oriented hexagonal closepacked (o-HCP) mesostructures during aging of surfactant-templated titania thin films is elucidated using in situ grazing incidence small-angle X-ray scattering (GISAXS) in a controlled-environment chamber. To promote orthogonal orientation, glass slides are modified with cross-linked Pluronic P123, to provide surfaces chemically neutral toward both blocks of mesophase template P123. At 4 °C and 80% RH, the o-HCP mesophase emerges in thin (∼60 nm) films by a direct disorder-to-order transition, with no intermediate ordered mesophase. The Pluronic/titania o-HCP GISAXS intensity emerges only after ∼10−12 min, much slower than previously reported for smallmolecule surfactants. The Avrami model applied to the data suggests 2D growth with nucleation at the start of the process with a half-life of 39.7 min for the aging time just after the induction period of 7 min, followed by a period consistent with 1D growth kinetics. Surprisingly, films that are thicker (∼250 nm) or cast on unmodified slides form o-HCP mesophase domains, but by a different mechanism (2D growth with continuous nucleation) with faster and less complete orthogonal alignment. Thus, the o-HCP mesophase is favored not only by modifying the substrate but also by aging at 4 °C, which is below the lower consolute temperature (LCST) of the poly(propylene oxide) block of P123. Consistent with this, in situ GISAXS shows that films aged at room temperature (above the LCST of the PPO block) have a randomly oriented HCP mesostructure.

The mesostructure loss kinetics are measured as a function of the orientation of micelles in 2D hexagonal close packed (HCP) columnar mesostructured titania thin films using in situ grazing incidence small angle X-ray scattering (GISAXS). Complementary supporting information is provided by ex situ scanning electron microscopy. Pluronic surfactant P123 acts as the template to synthesize HCP structured titania thin films. When the glass substrates are modified with crosslinked P123, the micelles of the HCP mesophase align orthogonal to the films, whereas a mix of parallel and orthogonal alignment is found on unmodified glass. The rate of mesostructure loss of orthogonally oriented (o-HCP) thin films (∼60 nm thickness) prepared on modified substrate is consistently found to be less by a factor of 2.5 ± 0.35 than that measured for mixed orientation HCP films on unmodified substrates. The activation energy for mesostructure loss is only slightly greater for films on modified glass (155 ± 25 kJ mol(-1)) than on unmodified (128 kJ mol(-1)), which implies that the rate difference stems from a greater activation entropy for mesostructure loss in o-HCP titania films. Nearly perfect orthogonal orientation of micelles on modified surfaces contributes to the lower rate of mesostructure loss by supporting the anisotropic stresses that develop within the films during annealing due to continuous curing, sintering and crystallization into the anatase phase during high temperature calcination (>450 °C). Because the film thickness dictates the propagation of orientation throughout the films and the degree of confinement, thicker (∼250 nm) films cast onto P123-modified substrates have a much lower activation energy for mesostructure loss (89 ± 27 kJ mol(-1)) due to the mix of orientations found in the films. Thus, this kinetic study shows that thin P123-templated o-HCP titania films are not only better able to achieve good orthogonal alignment of the mesophase relative to thicker films or films on unmodified substrates, but that alignment of the mesophase in the films stabilizes the mesophase against thermally-induced mesostructure loss.

This study evaluated geochemistry between the Utica-Point Pleasant shale and reservoir/hydraulic fracturing fluid mixtures under simulated reservoir conditions in a batch reactor system. Analytical techniques were utilized to monitor fluid composition with time along with pre-and post-trial shale microscopy and phase identification analyses. Formation of iron-based precipitate was evident through results from fluid and material analyses. Ferrous iron was the predominant iron form found in the aqueous phase, with oxidation to ferric iron and subsequent precipitate formation. Geochemical modeling further supported ferric iron was the favorable phase for precipitation. K E Y W O R D S crystallization (precipitation), geochemical, hydraulic fracturing, oil shale/tar sands, reaction kinetics 1 | INTRODUCTION U.S. tight oil has had a tremendous impact on stabilizing global oil prices and increasing energy security. Such light crude is recovered from low permeability rock formations, primarily shale, using unconventional methods such as horizontal drilling with hydraulic fracturing. As of March 2019, the Energy Information Association (EIA) reports approximately 60% total U.S. oil production comes from tight oil. 1 While unconventional wells have shown promise in terms of oil production, economic viability is still uncertain due to rapid production decline leading to shorter well life. Peak performance of an unconventional oil well occurs during the first quarter of production, with up to 74% production decline after 1 year. 2 Solutions explored to counteract production decline include refracturing or other enhanced oil recovery methods. Simulation studies have been developed to evaluate the effects of stimulation techniques on production to determine if profitable recovery is feasible. 3-5 Although simulation of refracturing and enhanced oil recovery methods have shown promise, these techniques do not fully account for phenomena encountered in unconventional wells. Various approaches have been utilized to mimic downhole phenomena. 6-8 An approach by Luo evaluated confinement effects on hydrocarbon bubble point. This study found octane and decane confined in nanoporous media possess two distinct bubble point temperatures, with lower/higher bubble point temperatures differing ±15 K in comparison to respective bulk properties. 6 By understanding various in-situ well phenomena, proper recovery analysis can be performed and modifications to hydraulic fracturing processes can be developed to increase well productivity and lifetime. 9 Aqueous phase chemical reactions are another key phenomenon occurring in shale reservoirs. Such reactions occur during well completion, when hydraulic fracturing fluid (HFF) mixes with rock and formation water, potentially causing precipitate formation, more commonly referred to as scale. Scales form when dissolved solid concentrations This contribution was identified by Rameshwar Srivastava (Department of Energy) as the Best Presentation in the session "New Technologies to Enhance the Productio...

A laboratory study was conducted on the leaching of chalcopyrite with NaOCl (sodium hypochlorite). Experiments were carried out in the following two stages: (1) Chalcopyrite was converted to CuO (cupric oxide) with a sodium hypochlorite solution, and (2) cupric oxide was dissolved to cupric ions with 1 normal sulfuric acid at room temperature. In the first-stage leaching, the initial pH varied from 12.5 to 13.7, the temperature from 35°C to 75°C, the sodium hypochlorite concentration from 0.2 to 0.85 molar, and the chalcopyrite dosage from 1 to 10 g/500 ml. The leaching conversion showed a maximum (68.3 pct) around a pH of 13.2 at 0.5 molar OCl -(hypochlorite) concentration and at 65°C in 1 hour. The reagent consumption ratio-defined as the number of moles of hypochlorite consumed to leach 1 mole of chalcopyrite-was much higher than its stoichiometric ratio of 8.5. It reached 57.6 when the solid dosage was 1 g/500 ml and decreased to 12.9 when the solid dosage was increased to 10 g/ 500 ml. The leaching rate of chalcopyrite in the first stage was controlled by a chemical reaction with the activation energy of 50.2 kJ/mol (12.0 kcal/mol). A leaching scheme was identified in which 98 pct of the chalcopyrite was leached by adding hypochlorite stock solution stepwise in less than 3 hours.

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