The corrosion resistance of nickel–titanium nitride (Ni/TiN) composites is significantly influenced by the operation parameters during the jet pulse electrodeposition (JPE) process. The effect of current density, jet rate, TiN concentration, and duty cycle impact on the anti-corrosion property of Ni/TiN composites were investigated and optimized using the response surface method (RSM). After the optimization of the operation parameters, the corrosion current of Ni/TiN composites decreased from 9.52 × 10⁻⁵ A/cm² to 4.63 × 10⁻⁵ A/cm². The corrosion current of Ni/TiN composites decreased initially and then increased with an increase in current density, jet rate, TiN concentration, and duty cycle. During the jet electrodeposition process, the influence of the duty cycle on the corrosion current of Ni/TiN composites was comparatively insignificant, whereas the concentration of TiN had a significant effect on the corrosion current. The error rate between the predicted value and the measured result from the corrosion current of Ni/TiN composites was only 0.64%, indicating the high accuracy of fitting the model. Furthermore, X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images revealed that the optimized Ni/TiN composites comprised significant Ti content, fine nickel gain, and a compact, smooth structure. In addition, the electrochemical measured results demonstrated that the optimized Ni/TiN composites possessed a low self-corrosion current and high self-corrosion potential. These findings show that the optimized composites have a substantially greater corrosion resistance compared to two other unoptimized Ni/TiN composites.

The process of molten salt CO₂ capture and electrochemical conversion provides us with a new way to close the present carbon cycle and mitigate global climate change by transforming the greenhouse gas CO₂ into carbonaceous fuels or chemicals. In this paper, carbon spheres and carbon nanotubes that can be used as a societal resource to serve mankind are synthesized from CO₂ in diverse electrolyte composites with inexpensive metallic electrodes. Carbon products, subsequent to electrolysis, are characterized by EDS, SEM, TEM, Raman, TGA, FTIR, BET and XRD to reveal the elemental composition and morphological and structural features. The results demonstrate that Li–Ca–Na and Li–Ca–K carbonate electrolytes favor carbon sphere formation rather than carbon nanotube formation, and in particular, K₂CO₃ shows enhanced interference with carbon nanotube growth. In contrast, Li–Ca–Ba and Li–Ba carbonate composites present an increase in the carbon nanotube fraction. Additionally, CNTs generated from Li–K, Li–Ba and Li–Ca–Ba present a different diameter. In this way, the CO₂-derived carbon products of carbon spheres and carbon nanotubes could be alternatively synthesized through the appropriate regulation of the electrolyte composition.

Well production rates in unconventional plays usually decline dramatically in the first year. Refracturing, which is a remedial production operation, is often done because original hydraulic fracturing failed to contribute any significant amount of flow or significant unfractured pay exists in the well. In order to maximize the fracturing fluid contact with the intact rock and to stimulate more reservoir volume in previously stimulated wells, a refracturing technology featuring a novel temporary plugging for fluid diversion is developed to enable the fracturing fluid to reach the untouched areas and to create reoriented fractures. In this paper, laboratory physical simulation tests of refracturing using fiber for effective temporary plugging is carried out to study the refracture morphology and the influencing factors of refractures. Results show that the refracture morphology is affected by the horizontal stress difference, the injection rate of initial fracturing fluid, and the natural fractures. Under condition of the different horizontal stress differences, the fracture initiation and orientation angle are different. When the horizontal stress difference is small, it is easy to form large angle fractures. The injection rate of initial fracturing fluid affects the length of initial fractures and refractures. The smaller the initial fracturing fluid injection rate is, the better the effect of temporary plugging in refracturing. The presence of natural fractures will lead to reorientation of refractures to form a complex fracture network. This study provides a theoretical guidance and technology support for refracturing operations.

Alkaline-earth-carbonate-included molten salts sustain continuous CO ₂ capture and electrochemical conversion.

Electrolysis of molten carbonates provides an effective means to achieve the direct conversion of the greenhouse gas carbon dioxide to readily available carbonaceous fuel or chemicals. In this study, CO₂ was electrolyzed in a Li–Na–K ternary carbonates mixture using galvanized Fe as the cathode and nickel as the anode. In particular, the effect of BaCO₃ on the generation of carbon was studied. The results demonstrate that BaCO₃ addition facilitates the deposition of compact carbon materials. Moreover, decreasing the temperature and increasing the current density lead to the formation of loosened carbon products. Though Li–Na–K–Ba electrolysis exhibits a higher cell voltage than that using Li–Na–K carbonates, BaCO₃ addition can significantly ease anode corrosion and the corresponding corrosion inhibiting action is discussed. In summary, a facile CO₂ absorption and a mitigatory nickel anode corrosion were observed when BaCO₃ was dissolved in Li–Na–K carbonates and further investigation is expected.

In order to study the deformation displacement and the stress field of brittle rocks under harmonic dynamic loading, a series of systematic numerical simulations are conducted in this paper. A 3D uniaxial compression simulation is carried out to calibrate and determine the property parameters of sandstone and a model of the cylindrical indenter intruding the rock is proposed to analyze the process of elastic deformation. Four main parameters are taken into account, namely the position on the rock, the frequency and the amplitude of dynamic load, the type of indenter and the loading conditions (static and static-dynamic). Based on the analysis undertaken, it can be concluded that both of the deformation displacement and stress field of the rock change in a harmonic manner under the static-dynamic loads. The frequency and the amplitude of harmonic dynamic load determine the period and the magnitude of the rock response, respectively. In addition, the existence of harmonic dynamic load can aggravate the fatigue damage of the rock and allow a reduction in static load. Our investigations confirm that the static-dynamic loads are more conducive to rock fracture than static load.