The poor mechanical and electrical properties and single function of conventional conductive hydrogels severely limit their application in flexible sensors. Here, a multifunctional nanomaterial composite high-strength hydrogel strain sensor was prepared by incorporating α-zirconium phosphate (α-ZrP) nanosheets with hydroxyl functional groups on the surface and cellulose nanofibers (CNFs) into a poly(vinyl alcohol) (PVA)matrix simultaneously, using a binary glycerol/water solution as the dispersion medium and a strategy of cyclic freeze-thawing followed by sodium chloride immersion. The experiments showed that CNFs and α-ZrP nanosheets can form hydrogen bonding interactions with PVA chains, which can synergistically improve the mechanical and electrical properties of the gels with little effect on its transparency, and the tensile strength and elongation at break of the gels can reach 2.42 MPa and 541%, respectively, and the ionic conductivity exceeds 7.65 mS/cm, while possessing a transmission rate of 87% at 600 nm visible light wavelength. In addition, the introduction of glycerol imparts the gel with remodeling, anti-freezing, and long-term stability. As a strain sensor, it has a linear sensing range of 0%-350% and high sensitivity (GF = 2.46), and the sensing gloves prepared based on it can accurately and stably recognize letters written by hand.
Zirconium is one of the most commonly used crosslinkers for guar gum‐based fracturing fluid. Nevertheless, it is difficult for zirconium crosslinkers applied in fracturing to possess both high temperature resistance and adjustable crosslinking time. Meanwhile, few people did systematical research on the crosslinking process of fracturing fluid. In this study, an organic zirconium crosslinker with high temperature resistance and controllable crosslinking time was synthesized. The seawater‐based fracturing fluid gel prepared with the crosslinker could perform well under 170°C. Oscillatory shear experiments were conducted to analyze the rheology of the gelation process. Moreover, steady‐state shear and micro‐rheological tests were conducted to analyze the dynamic and static crosslinking process of the fracturing fluid, respectively. Meanwhile, rheo‐kinetic equation was used to fit the data and the effects that various factors had on the gelation process were illustrated thoroughly. This study not only prepared an organic zirconium crosslinker with good performances, but also explored the crosslinking process of fracturing fluid gel, which could improve its further application in oilfields.
Polyacrylamide nanospheres are widely applied enhancing oil recovery polymers in low‐permeability oilfields. However, it is difficult to detect polyacrylamide nanospheres concentration in the produced fluid. In this study, fluorescent polyacrylamide nanospheres were synthesized via a reverse phase microemulsion method by the copolymerization of acrylamide and pyranine derivative. The structure, fluorescence properties, and oil displacement mechanisms of fluorescent polyacrylamide nanospheres were researched. The results indicated that the fluorescence intensity of the nanospheres had a distinct linear relationship with the concentration at a certain concentration range. The relative error of standard curve method was less than 1%. Alkaline conditions and aging process could diminish fluorescence intensity while temperature and ionic species had slightly effect on it. The oil displacement phenomenon of the nanospheres in T‐shaped microchannel, oil–water interface, and glass plate were observed clearly. This work provides support for the practical applications of fluorescent polyacrylamide nanospheres in oilfields.
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