This article reports the first instance of exploring a chemically Zn(II) preinserted organic−inorganic hybrid material [vanadyl ethylene glycolate or VEG, (VO(CH 2 O) 2 )] as an efficient cathode for rechargeable zinc-ion batteries (ZIBs). The control VEG electrode synthesized by a glycothermal process showed a modest specific capacity of 157 mAh/g at 0.1 A/g current density, however, suffered from poor rate capability and cycle stability due to structural dissolution. Chemically Zn(II) preinsertion into VEG (Zn-VEG) catalyzed the Zn 2+ intercalation in the Zn-VEG cathode with a significantly decreased charge transfer resistance, resulting in high discharge capacity of 217 mAh/g (at 0.1 A/g) accompanied by excellent rate capability with ∼50% capacity retention on increasing the current by 50 times. A first-principles-based hybrid densityfunctional theory (DFT) study revealed that the electronic structure of the Zn-intercalated VEG is thermodynamically stable, indicating an energetically favorable Zn-ion intercalation process. The Zn(II) preinserted VEG cathode allowed faster ionic diffusion (D Zn 2+ in the order of 10 −9 cm 2 /s), and the diffusion controlled process was the major contributor (∼66.9%) to the overall capacity at low scan rate (0.1 mV/s) and remained significant (43.8%) even at high scan rate of 0.8 mV/s. Furthermore, the Zn(II) preinsertion in the VEG could act as a bridge to hold the VEG layers firmly. This provides the desired structural stability to the Zn-VEG cathode during a continuous Zn 2+ insertion/deinsertion process, resulting in excellent cycle stability with only ∼0.005% capacity loss per cycle over 2000 cycles (at 4 A/g) while maintaining a high columbic efficiency of 99.9% throughout the cycles. The high capacity accompanied by excellent rate capability and cycle stability supports the as-prepared Zn(II) preinserted organo-vanadyl hybrid electrode to be a potential cathode material for ZIBs.

A rechargeable zinc ion capacitor (ZIC) employing a metallic anode, nature-abundant materials-derived high-performance cathode, and an aqueous electrolyte represents an interesting combination of high capacitance, high power, safety operation, and overall a sustainable and economic system, which make them a leading power source to portable consumer electronics. However, it is often a challenge to fabricate a large-area flexible device with a metallic anode due to the characteristic rigidity of the metal. Herein we present a high-performance aqueous ZIC based on abundant agricultural waste biomass (Areca Catechu sheath)-derived highsurface-area (2760 m 2 /g) mesoporous multilayer-stacked carbon sheets as the capacitive electrode in 1 M ZnSO 4 electrolyte. In coin cell configuration, the ZIC showed a high specific capacitance of 208 F/g at 0.1 A/g, a good rate capability, and an outstanding cyclic stability with 84.5% capacitance retention after 10 000 cycles at a current density of 5 A/g. We also demonstrate an easy and scalable strategy to fabricate a large-area flexible zinc ion capacitor with laser-scribed carbon (LSC@PI), scribed on a polyimide film with customizable area as the flexible current collector for both anode and cathode. Electrodeposition of zinc onto LSC@PI as anode showed a very low plating stripping overpotential, and the flexible sandwich-type ZIC with an electrolyte-soaked paper separator exhibited excellent flexibility and a high areal capacitance of 128.7 mF/cm 2 at 100 mA/cm 2 current when bended at an angle of 110°, corresponding to an energy density of 32.6 μW h/cm 2 . When the current was increased by 20 times, the flexible device under bending condition could provide an energy density of 11 μW h/cm 2 at a high power density of 1.906 W/cm 2 . The synthesized materials were characterized by X-ray diffraction (XRD), RAMAN, Field Emission Scanning Electron Microscope (FESEM), and Brunauer−Emmett−Teller (BET) analysis, whereas the electrochemical performances were measured in terms of cyclic voltammetry (CV), galvanostatic charge−discharge (GCD), and Electrochemical impedance spectroscopy (EIS) analysis.

Selecting a drilling fluid from the learnings from conventional reservoirs can be a wrong choice when it is used for unconventional formations. Drilling fluid has a chemo-mechanical effect on the reservoir rock during exposure time; this interaction can be abrupt or imperceptible depending on minerals comprising the rock matrix and their chemical sensitivity to the fluid composition. Improper selection of drilling fluid may cause strong shale-fluid interaction and thus result in wellbore instability. This paper presents a comprehensive experimental study examining the effect of various drilling fluids on the mechanical properties of conventional and unconventional rock samples. Four drilling fluids with varying additives are selected to contact and saturate rock samples at the temperature of 230°F for 16 or 24 hours: Three of them are water-based muds (WBM) and the other one is an oil-based mud (OBM). Rock samples used are from the Berea sandstone, Mancos and Eagle Ford shale formations. For each type of rock, one plug is tested without contacting any drilling fluid and is used as a reference of geomechanical properties. Other samples are contacted and saturated with other drilling fluids before their geomechanical testing. A fluid-saturating process is conducted at a pressurized aging cell. Mechanical testing is performed in a servo-controlled triaxial apparatus in which samples are deformed at a constant confining pressure of 10 MPa and the drained condition. Experimental results show that drilling fluids have a negligible effect on the peak strength and Young's moduli of Berea sandstone. However, the peak strength of Mancos shales decreases dramatically while their Young's moduli change randomly. For Eagle Ford shales, fluids reduce both peak strength and Young's moduli. For all samples tested, their Poisson's ratios increase after samples are saturated with fluids. Compared to WBM, it is observed that OBM preserves the mechanical properties of Mancos shales much better. After optimizing the design of one high-performance water-based mud (HPWBM1), the new fluid (HPWBM2) has an improved performance (similar to OBM) in preserving shale geomechanical properties.

A zinc-ion battery (ZIB) employing an aqueous electrolyte, that is, an aqueous zinc-ion battery (AZIB), represents a unique combination of high energy and high power with much-desired safety. In this respect, vanadium oxide-based cathodes, with open frameworks and rich valence states, have shown promising characteristics toward hosting the Zn 2+ ions. Nevertheless, the degradation of the host during continuous (de-)intercalation and structural dissolution in the aqueous electrolyte affects the capacity and cycle life. Herein, we represent a high capacity and long cycle life AZIB based on an Ag 2 V 4 O 11 @reduced graphene oxide composite as a cathode in 1 M ZnSO 4 electrolyte. We demonstrate the combined effect of the intercalation−displacement mechanism and partially irreversible formation of zinc hydroxyl sulfate as the charge storage mechanism in 1 M ZnSO 4 electrolyte. We observed a comparatively quick capacity fading for the pristine Ag 2 V 4 O 11 ; however, the capacity, rate capability, and cycle stability could be dramatically improved when the Ag 2 V 4 O 11 was hydrothermally grown in situ in the presence of reduced graphene oxide (rGO). The charge storage mechanism, kinetics of charge storage, Zn 2+ diffusion coefficient, effect of cycling on the phase/crystallinity, and morphology of the electrode materials were investigated. A morphological transformation from nanorod to ultrathin sheet/micro-belt-type Ag 2 V 4 O 11 was observed with increasing rGO content. The rGO wrapped the Ag 2 V 4 O 11 sheets/microbelts and thus reduced the charge transfer resistance and provided structural integrity during continuous cycling. The favorable synergism between the Ag 2 V 4 O 11 and optimized rGO content could offer a high initial specific capacity of 328 mA h/g at 0.1 A/g, excellent rate capability with ∼150 mA h/g, specific capacity at 5 A/g, and long cycle stability with only 7% capacity loss over 3000 cycles.

Vanadium oxyhydroxide has been recently investigated as a starting material to synthesize different phases of vanadium oxides by electrochemical or thermal conversion and has been used as an aqueous zinc-ion battery (AZIB) cathode. However, the low-valent vanadium oxides have poor phase stability under ambient conditions. So far, there is no study on understanding the phase evolution of such low-valent vanadium oxides and their effect on the electrochemical performance toward hosting the Zn2+ ions. The primary goal of the work is to develop a high-performance AZIB cathode, and the highlight of the current work is the insight into the auto-oxidation-induced phase transition of VOOH to V10O24·nH2O under ambient conditions and Zn2+ intercalation behavior thereon as an aqueous zinc-ion battery cathode. Herein, we demonstrate that hydrothermally synthesized VOOH undergoes a phase transition to V10O24·nH2O during both the electrochemical cycling and aerial aging over 38–45 days. However, continued aging till 150 days at room temperature in an open atmosphere exhibited an increased interlayer water content in the V10O24·nH2O, which was associated with a morphological change with different surface area/porosity characteristics and notably reduced charge transfer/diffusion resistance as an aqueous zinc-ion battery cathode. Although the fresh VOOH cathode had impressive specific capacity at rate performance, (326 mAh/g capacity at 0.1 A/g current and 104 mAh/g capacity at 4 A/g current) the cathode suffered from a continuous capacity decay. Interestingly, the aged VOOH electrodes showed gradually decreasing specific capacity with aging at low current and however followed the reverse order at high current. At a comparable specific power of ∼64–66 W/kg, the fresh VOOH and aged VOOH after 60, 120, and 150 days of aging showed the respective energy densities of 208.3, 281.2, 269.2, and 240.6 Wh/kg. Among all the VOOH materials, the 150 day-aged VOOH cathode exhibited the highest energy density at a power density beyond 1000 W/kg. Thanks to the improved kinetics, the 150 day-aged VOOH cathode delivered a considerable energy density of 39.7 Wh/kg with a high specific power of 4466 W/kg. Also, it showed excellent cycling performance with only 0.002% capacity loss per cycle over 20 300 cycles at 10 A/g.

The use of nanoparticles has been demonstrated to enhance the rheological properties of the viscoelastic surfactant (VES) fluid. However, their influence on the rheological properties as a function of temperature is not well known. In this study, a detailed analysis of improved rheological properties and thermal stability of the VES fluid beyond their optimal working temperature was conducted. The effect of nanoparticles was also studied. A base VES fluid was prepared with the required amount of surfactant along with an ionic strength agent dissolved in sea water. The desired type of nanoparticles in required amounts were added to the base VES fluid and homogeneously dispersed. Different types of nanoparticles were added to prepare corresponding nano-VES fluid. Rheological properties of the base VES fluid and different nano-VES fluids were measured against variable shear rate. The fluids were tested at a temperature at which the base fluid shows highest gelling behavior, and at temperatures above and below that value. Results, Observations, Conclusions: The initial thermo-viscosifying effect and eventual thermo-thinning effect with temperature havebeen widely observed for viscoelastic surfactants based fluids. The effectshavebeen attributed to the effect of temperature on the structural changes of wormlike micelles. Nanoparticles being of the dimensions that are comparable with the thickness of these wormlike micelles are readily able to incorporate themselves into these structures and influence their rheological behavior. These interactions change both with respect to temperature and shear rate applied on them. Further, these interactions differ depending on whether the fluid is in the thermo-viscosifying region or the thermo-thinning region with respect to the temperature. Based on the kind of nanoparticle used, significant improvements in rheological behavior from a fracturing fluid perspective have been observed. In addition, shear rates at which a shift from Newtonian to non-Newtonian behavior with respect to shear rate occurs, has also been observed to change. A greater insight into the effect of nanoparticle additives on temperature related rheology of VES fluids has been provided. This understanding is crucial for the optimization of a VES fracturing fluid based on the well-to-well changes in temperatures.

One of the biggest challenges when drilling in deep water is the excessive dependence of drilling fluid rheological properties on temperature. Conventional drilling fluids often have high viscosity at the seabed temperature, which increases the Equivalent Circulating Density (ECD) and surge pressures when running pipe or initiating circulation, elevating the risk of fracturing the wellbore. This paper describes the development of a drilling fluid for deep-water applications, with minimum viscosity variation with temperature. Multiple laboratory formulations were evaluated during the development of the new, non-aqueous based drilling fluid that meets deep-water's challenging rheological and barite suspension requirements. CaCl2 brine was used as the internal emulsion phase, and synthetic isomerized olefin as the base oil. The testing followed the API Recommended Practice for Field Testing Oil-based Drilling Fluids. Samples were aged at dynamic conditions for 16 hours at several temperatures. Then, rheological properties and high-pressure high-temperature (HPHT) fluid loss, emulsion stability, and dynamic sagging were tested. Static sag experiments were also carried out for up to seven days together with improved step down rheology tests. A low-impact, non-aqueous drilling fluid (LIDF) was designed to minimize ECD increases by reducing the effect of cold temperature on the fluid viscosity. The fluid offers a superior low viscosity profile and rapid-set, easy-break gel strengths, while maintaining low shear rate viscosity at high temperatures with optimal weight material suspension. The fluid is also compatible with all contaminants usually found during the drilling operation and meets all the regulatory requirements for the Gulf of Mexico and other deep-water operational areas. Field application demonstrated that LIDF reduced the effect of temperature on the fluid rheological properties and minimized the risk of induced formation losses. These same rheological features reduced non-productive time associated with cement displacement and barite sagging. Supporting laboratory and field data are presented to demonstrate the superior performance of the fluid in maintaining rheological and barite suspension properties over a wide range of temperatures. The properties of the LIDF are achieved by matching the effects of emulsifier, organophilic clay, and rheological modifiers to maintain correct rheological properties at low and high temperatures.

This work presents new surface modified nanoparticles (SMN) that act as internal breakers for viscoelastic surfactant (VES) based fluids. Breaking profile is a key performance feature of a fracturing fluid. In addition to providing greater application latitude at high temperatures, the proposed solution is suited for gas wells or where there is less likelihood of encountering formation crude oil, which could also act as breaker for VES fluids. The SMNs were prepared by organically modifying nanoparticles with specific surface capping agents that have functional groups with the ability to bind on to their surfaces by chemical or physical interactions. The base VES fluid was prepared from a mixture of sea water, ionic strength agents and a viscoelastic surfactant formulation. Varying amounts of SMNs were added to the base fluid and mixed vigorously to form a homogeneously dispersed fluid. The viscosities of the base fluid without SMNs and with varying amount of SMNs were monitored over time at fixed temperature to observe the breaking profile. The base fluid consisting of VES dispersed in sea water with ionic strength agent exhibits stable viscosity for prolonged times. Compared to base fluid, addition of bare nanoparticles marginally improves the fluid's viscosity, although, the fluid does not break down to very low viscosity within desired time for convenient flowback operations. Slow viscosity drop is ideal from a fracturing fluid point of view that helps in efficiently placing the proppants inside of created fractures and eventual fluid cleanup. However, without the organically modified nanoparticles, the viscosity is too stable causing the post fracturing cleanup to be too slow. With the SMN the viscosity drop could be controlled and achieved in relatively shorter time. Further, with these breaker control over breaking time is also achievable. The SMN internal breakers interact with the worm like micelles and disrupt the gel formed by these elongated micellar structures. The surface modified nanoparticles with a functional capping agent alters the way the nanoparticles interact with the wormlike micelles from electrostatic interactions to hydrophobic-hydrophobic interactions. This change provides an efficient mechanism for breaking the VES base fluids in absence of any external breaker with high temperature latitude.