Effect of the changed electrolytic cell on the current efficiency in FFC Cambridge process

Low current efficiency of the FFC Cambridge process made it no obvious advantages in cost compared with the traditional process to produce metals. Effect of the changed electrolysis cell on the current efficiency has been studied. Put the cathode into an alumina tube with a hole can efficiently avoid short circuit and the cathode contaminated by carbon produced from graphite anode. The results show that the current efficiency can be improved greatly by reducing the electric field intensity in the electrolysis cell. The high background current is mainly caused by the electronic conductivity in the electrolysis cell. Otherwise, pollution of the cathode is avoided, the depletion of the anode sharply decreases and the deoxidation of the samples greatly improve when using the improvement electrolysis cell

Synthesis of TiC nanotube arrays and their excellent supercapacitor performance

Nanostructured metal carbides have numerous applications in catalysis and energy storage. However, directional construction remains a significant challenge. In this work, a novel strategy for the direct synthesis of nanostructured metal carbides using nanostructured metal oxides as the precursor is developed. TiO2 nanotube arrays (TiO2 NTAs) can be successfully transformed into TiC nanotube arrays (TiC NTAs) through electro-deoxidation and carbonization reactions in a low-temperature molten salt. TiC NTAs have a highly oriented and ordered array structure, which shows the advantages of large specific surface area, direct electron transport, and good chemical stability. Here, TiC NTA electrodes and PVA-H3PO4 electrolyte gel were assembled into a flexible quasi-solid-state supercapacitor to characterize their energy storage performance. The results show that the TiC NTA electrodes exhibit a high areal capacitance of 53.3 mF cm−2, excellent cycling stability, and mechanical flexibility. Moreover, the energy densities can reach 4.6 μW h cm−2 at a power density of 78.9 μW cm−2. This work provides a new strategy for the directed synthesis of nanostructured metal carbides and demonstrates the energy storage application potential of TiC NTAs. It is expected that this work will contribute to the development of the synthesis and application of nanostructured metal carbides

Preparation and Performance Evaluation of Temperature-Resistant and Salt-Resistant Gels

In order to improve the plugging performance of high-temperature and high-salt oil reservoir plugging agents, this paper utilizes a copolymer composed of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid (AM/AMPS) as the polymer, polyethyleneimine as the cross-linking agent, and nylon fiber as the stabilizer to develop a high-temperature- and high-salt-resistant gel system. This study analyzed and evaluated the temperature resistance, salt resistance and blocking performance of the gel system. The evaluation results show that the gel-forming strength of this gel system can reach an H level, and it has good thermal stability at the high temperature of 130 °C. At the high salinity of 240,720 mg/L, the syneresis rate remains below 2.5%, and the gel-forming time is greater than 15 h; the higher the temperature, the shorter the gelling time. The results of our sand-filled pipe-plugging experiment show that the gel system can adapt to sand-filled pipes with different levels of permeability, and reaching a plugging rate of 94%

Preparation and effect of vanadium addition on the mechanical properties of CoCrFeNiVx high-entropy alloy

High-entropy alloys (HEAs) have attracted considerable attention due to their unique phase structures and excellent properties. However, the existing preparation processes for HEAs involve high temperatures, lengthy procedures, and high costs, which limit their practical applications and confine them to the realm of fundamental research. Here, a novel method combining low-temperature solid-phase molten salt electrolysis and hot-press sintering was proposed to prepare CoCrFeNi HEA. Moreover, the study explored the addition of metal V, to modulate the composition of the HEA and improve its mechanical properties. The results showed that the molten salt electrolysis process could achieve the direct deoxidation of metal oxide mixtures, enabling one-step preparation of HEAs. During the early stages of deoxidation, the metals Ni and Co were obtained first and, under the influence of the mixed entropy, formed a non-stoichiometric NiCoCr alloy. As deoxidation progressed, Cr and Fe were successively reduced and further alloyed with the NiCoCr to form the non-stoichiometric CoCrFeNi HEA. Eventually, the aggregated dendritic metal Fe diffused and solid-solved into the non-stoichiometric CoCrFeNi HEA, resulting in the formation of a stoichiometric CoCrFeNi HEA. The CoCrFeNiVx (x = 0, 0.5, 1, 1.5) alloy maintained a single-phase FCC structure, where V effectively improved the hardness of the CoCrFeNi HEA, with minimal impact on its phase structure. V played a role in solid-solution strengthening, grain refinement, and reducing Cr segregation in the alloy. Additionally, the appropriate addition of V simultaneously increased the tensile strength, hardness, and ductility of the CoCrFeNi HEA

A Study of the Thin Film-Coated Swelling Retarding Particles in Fractured Carbonate Reservoirs for Water Plugging and Profile Control

T oilfield is the fractured-vuggy carbonate reservoir at a temperature of around 130 °C, with salinity of up to 22 × 104 mg/L. In order to solve the problem of the high water cut in the late development stage of T oilfield, we selected XN-T from 27 kinds of swelling retarding particles by testing their swelling capacity, and coated a thin film to improve its retarding swelling capacity. The mechanisms of strong water absorption and water-holding abilities of particles were analyzed by infrared spectrometry and SEM. In the core flow experiment, the plugging rate was found to be 98.42%. Finally, the injection parameters of the coated particles were optimized to maximize the water plugging and profile control ability, resulting in an optimal particle size of 0.4–0.6 mm and a mass fraction of 10%

Effect of Ti on Characterization and Properties of CoCrFeNiTi_x High Entropy Alloy Prepared Via Electro-Deoxidization of the Metal Oxides and Vacuum Hot Pressing Sintering Process

The CoCrFeNi system is one of the most important high entropy alloys (HEAs) systems. By adding and adjusting the alloy element components and using different synthesis methods, different phases, organization and microstructure can be obtained, thus improving their properties. In this study, CoCrFeNiTix HEAs with various Ti contents (x in molar ratio, x = 0, 0.5, 1.0, 1.5) were fabricated by an electrochemical process by virtue of different oxides. The impacts of different Ti contents on the structure, distribution of elements, mechanical properties and corrosion behavior were researched using XRD, EDX and other testing methods. The bulk CoCrFeNiTix (x = 0, 0.5, 1.0, 1.5) HEAs could be obtained through vacuum hot pressing sintering process (VHPS), which had a single-phase FCC structure. The results of the study showed that the bulk CoCrFeNiTix exhibited superior ultimate tensile strength (UTS) and hardness, with the UTS of CoCrFeNiTi as high as 783 MPa and the hardness of CoCrFeNiTi1.5 reaching 669 HV. The corrosion behavior of CoCrFeNiTix (x = 0, 0.5, 1.0, 1.5) HEAs in 0.5 M H2SO4, 1 M KOH and 3.5 wt% NaCl was improved with addition of Ti. CoCrFeNiTix (x = 0, 0.5, 1.0, 1.5) HEAs have great potential for application in the fields of biomedical coating and aerospace, as well as extreme military industry, etc

Experimental Study on SiO₂ Nanoparticles-Assisted Alpha-Olefin Sulfonate Sodium (AOS) and Hydrolyzed Polyacrylamide (HPAM) Synergistically Enhanced Oil Recovery

The purpose of this study is to investigate the use of SiO2 nanoparticles in assisting with surfactants and polymers for tertiary oil recovery, with the aim of enhancing oil recovery. The article characterizes the performance of SiO2 nanoparticles, including particle size, dispersion stability, and zeta potential, evaluates the synergistic effects of nanoparticles with alpha-olefin sulfonate sodium (AOS) surfactants and hydrolyzed polyacrylamide (HPAM) on reducing interfacial tension and altering wettability, and conducts core flooding experiments in rock cores with varying permeabilities. The findings demonstrate that the particle size decreased from 191 nm to 125 nm upon the addition of SiO2 nanoparticles to AOS surfactant, but increased to 389 nm upon the addition of SiO2 nanoparticles to HPAM. The dispersibility experiment showed that the SiO2 nanoparticle solution did not precipitate over 10 days. After adding 0.05% SiO2 nanoparticles to AOS surfactant, the zeta potential was −40.2 mV, while adding 0.05% SiO2 nanoparticles to 0.1% HPAM resulted in a decrease in the zeta potential to −25.03. The addition of SiO2 nanoparticles to AOS surfactant further reduced the IFT value to 0.19 mN/m, altering the rock wettability from oil-wet to strongly water-wet, with the contact angle decreasing from 110° to 18°. In low-permeability rock core oil displacement experiments, the use of AOS surfactants and HPAM for enhanced oil recovery increased the recovery rate by 24.5% over water flooding. The recovery rate increased by 21.6% over water flooding in low-permeability rock core experiments after SiO2 nanoparticles were added and surfactants and polymers were utilized for oil displacement. This is because the nanoparticles blocked small pore throats, resulting in increased resistance and hindered free fluid flow. The main causes of this plugging are mutual interference and mechanical entrapment, which cause the pressure differential to rise quickly. In high-permeability rock core oil displacement experiments, the use of AOS surfactants and HPAM for oil recovery increased the recovery rate by 34.6% over water flooding. Additionally, the recovery rate increased by 39.4% over water flooding with the addition of SiO2 nanoparticles and the use of AOS surfactants and HPAM for oil displacement. Because SiO2 nanoparticles create wedge-shaped structures inside highly permeable rock cores, they create structural separation pressure, which drives crude oil forward and aids in diffusion. This results in a comparatively small increase in pressure differential. Simultaneously, the nanoparticles change the rock surfaces’ wettability, which lowers the amount of crude oil that adsorbs and improves oil recovery

Preparation and Performance Evaluation of a Self-Crosslinking Emulsion-Type Fracturing Fluid for Quasi-Dry CO₂ Fracturing

Quasi-dry CO2 fracturing technology is a new CO2 fracturing technology that combines liquid CO2 fracturing (dry CO2 fracturing) and water-based fracturing. It uses a liquid CO2 system containing a small amount of water-based fracturing fluid to carry sand, and it is characterized by sand blending at normal pressure, convenient preparation, the integrated application of resistance reduction and sand carrying, and no dedicated closed sand blender requirement. We developed a self-crosslinking emulsion-type water-based fracturing fluid (ZJL-1), which contained ionic bonds, hydrogen bonds, van der Waals forces, and hydrophobic associations, for quasi-dry CO2 fracturing, and the comprehensive properties of the ZJL-1 fracturing fluid were evaluated. The results showed that the ZJL-1 fracturing fluid had obvious viscoelastic characteristics, a heat loss rate of less than 10% at 200 °C, a good thermal stability, sufficient rheology under high temperature and high shear conditions, and a good thermal stability. The resistance reduction rate reached 70%, which demonstrates a good resistance reduction performance. Compared with conventional guar fracturing fluid, ZJL-1 can carry more sand and has a lower core damage rate. The on-site use of quasi-dry fracturing showed that optimizing the mixing ratio of liquid CO2 fracturing fluid and ZJL-1 fracturing fluid effectively enhanced oil and gas recovery. This can be used to optimize quasi-dry fracturing and can be used as a reference