Inspired Fluorinated BDD Film for Multifunctional Protection of Downhole Sensor Electrodes

Effects of addition of rare-earth element on electrochemical characteristics of ZrNi 1.1Mn 0.5V 0.3Cr 0.1 hydrogen storage alloy electrodes

Electrode pitting was investigated in resistance spot welding of 1.5-mm-thick sheet aluminum alloy 5182 using a medium-frequency direct-current welder and electrodes with a tip face curvature radius of 50 mm and tip face diameter of 10 mm. Detailed investigation of the metallurgical interactions between the copper electrode and aluminum alloy sheet was carried out using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD). The results indicated that electrode degradation, which eventually leads to weld failure, proceeded in four basic steps: aluminum pickup, electrode alloying with aluminum, electrode tip face pitting, and cavitation. Since pitting and cavitation result from Al pickup and alloying, periodic electrode cleaning could extend electrode tip life by limiting the buildup of Al on the tip face. This work is part of the effort to improve electrode tip life in resistance spot welding of aluminum alloys for automotive applications.

Plasma-sprayed wear-resistant ceramic and cermet coating materials

Summary Oilwell leakage poses significant environmental, economic, and operational challenges to the oil and gas industry. Remedial operations in oil and gas wells are quite challenging, especially for narrow apertures, and often require treatment materials tailored to specific challenges encountered in downhole environments. Geopolymers represent a low-carbon and environmentally friendly alternative to conventional cement, which can be explored for remedial operations. This paper presents the development, characterization, and comparative analysis of Geoseal, a metakaolin-based geopolymer, as a candidate treatment material for remedial operations. In this study, laboratory experiments were carried out to evaluate the rheological, mechanical, and sealing performance of Geoseal at the sealant-casing interface. Microannuli sealing performance was evaluated by injecting the treatment fluids under simulated downhole conditions into naturally formed microannuli at the sealant-casing interface. Three sealant materials, neat G cement (S1), granite-based geopolymer (S2), and expansive cement (S3), were considered. The effectiveness of Geoseal in sealing narrow microannuli apertures was also compared with that of conventional remedial materials like thermosetting resin and silicate solution. The comparative assessments focused on injectivity, sealing integrity, and material compatibility with the existing set sealants at the microannuli interface. While each treatment fluid exhibited unique advantages and limitations, the results highlight the potential of Geoseal for effective microannuli remediation. However, its adoption in apertures narrower than 6 µm presented notable injectivity issues. The findings of this paper provide practical insights for industry practitioners and researchers seeking to enhance the effectiveness of remedial interventions of cementitious sealants in oil and gas wells. Keywords Oil well leakage, geopolymers, well remediation, well integrity

Description of the capacity degradation mechanism in LaNi5-based alloy electrodes

Electrochemical investigations of activation and degradation of hydrogen storage alloy electrodes in sealed Ni/MH battery

To establish hydrogen-based sustainable society, we need to change our primary energy from fossil fuels to renewable energy by water electrolysis. Among practical water electrolysis, alkaline water electrolysis is advantageous to the cost of materials, though the degradation of electrode under intermittent operation must be solved.[1] In this presentation, we will introduce our recent advancements on the developments of evaluation techniques for durability of oxygen evolution reaction (OER) electrodes and novel materials to improve their durability.(1) Accelerated durability test protocol for OER electrodes It is known that the degradation of OER electrodes proceeds rapidly under intermittent operation. Reverse current is generated by discharge of the electrodes upon suspension of electrolysis. To mimic the charge–discharge cycles, we have proposed an accelerated durability test (ADT) protocol shown in Figure 1.[2] The ADT protocol consists of cycles of constant current electrolysis, potential sweep, and potential hold. The OER electrode is charged during the electrolysis and discharged during the potential hold. Potential hold is essential to fully discharge the electrode instead of potential sweep only. Using the ADT protocol, we analyzed the degradation mechanism of NiCoOx-coated Ni electrodes in a 7 M KOH electrolyte. The electrode exhibited stable OER overpotential up to 600 cycles and increase in the overpotential after that, showing immediate degradation. The chemical analyses showed that Co is dissolved from the catalyst quickly within the first 200 cycles without significant degradation, which rather increased the active surface area. After that thinning of the catalyst layer occurs with the dissolution of Ni. The Ni substrate is finally exposed to the electrolyte. The significant degradation proceeds together with the delamination of the catalyst layer and corrosion of the substrate.(2) Hybrid cobalt hydroxide nanosheets as self-repairing catalystsThe detachment of catalyst from the electrode substrate causes significant degradation; thus, we developed repairing technology of OER electrodes. Hybrid cobalt hydroxide nanosheets (Co-ns),[3] Co(OH)2 nanosheets modified with tris(hydroxymethyl)aminomethane (Tris-NH2), are unique materials that possesses OER activity of Co(OH)2 and functionalities due to Tris-NH2. When Co-ns are dispersed in an electrolyte (1 M KOH), Co-ns are deposited to be CoOOH nanosheets, forming a catalyst layer on Ni electrodes, during constant current electrolysis. If the catalyst layer is detached by degradation, fresh Co-ns can be deposited during electrolysis to repair the defects. Therefore, this system achieves quite a long lifetime under the ADT condition (Figure 2).[4,5] The concept of the self-repairing catalysts could be extended to other hybrid metal hydroxides, such as NiFe layered double hydroxides with higher OER activities, and the design of composite catalysts that enables to utilize highly active catalysts with poor self-repairing properties as self-repairing catalysts.[6] In conclusion, the durability of OER electrodes for alkaline water electrolysis under intermittent operation can be evaluated by the newly proposed ADT protocol. The ADT protocol is useful to reveal the degradation mechanism of catalysts and also to accelerate the development of novel catalytic materials with high durability like self-repairing catalysts. This work was supported by the JSPS KAKENHI (grant number 24K01580).

Petroleum well drilling fluids are one of the most significant constituents in the subterranean drilling processes to meet an increasing global demand for oil and gas. Drilling fluids experience exceptional wellbore conditions, e.g. high temperature and high pressure that adversely affect the rheology of these fluids. Gas and oil well drilling operations have to adjourn due to changes in fluid rheology, since the drilling fluids may lose their effectiveness to suspend heavy particles and to carry drilled cuttings to the surface. The rheological properties of drilling fluids can be controlled by employing viscosifiers that should have exceptional stability in downhole environments. Here, we have developed next-generation viscosifiers—organically modified magnesium silicates (MSils)—for reservoir drilling fluids where organic functionalities are directly linked through the Si–C bond, unlike the industry’s traditional viscosifier, organoclay, that has electrostatic linkages. The successful formation of covalently-linked hexadecyl and phenyl functionalized magnesium silicates (MSil-C16 and MSil-Ph) were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). Identical drilling fluid formulations were designed for comparison using MSils and a commercial viscosifier. The rheological properties of fluids were measured at ambient conditions as well as at high temperatures (up to 150 °C) and high pressure (70 MPa). Owing to strong covalent linkages, drilling fluids that were formulated with MSils showed a 19.3% increase in yield point (YP) and a 31% decrease in apparent viscosity (AV) at 150 °C under 70 MPa pressure, as compared to drilling fluids that were formulated with traditional organoclay. The higher yield point and lower apparent viscosity are known to facilitate and increased drilling rate of penetration of the fluids and an enhanced equivalent circulation density (ECD), the dynamic density condition, for efficient oil and gas wells drilling procedures.

Electrode degradation has been studied during series-mode microresistance welding of thin-sheet nickel-plated steel to nickel. The main focus of the study was the effects of a TiC metal matrix composite coating. The results indicated that electrode degradation was caused predominantly by material loss due to pitting (as a result of the fracturing of local bonds between the electrode tip and sheet) and also by microscopic extrusion or plastic deformation (as a result of the softening of electrode tip regions). The composite coating improved tip life by about 70 pct, mainly because the TiC particles contained in the coating discouraged local bonding between the electrodes and sheets, and probably also improved the resistance to surface extrusion. It was also found that the use of an oxide-dispersion-strengthened copper alloy (Cu-Al2O3) improved tip life by only about 15 pct compared to the conventional precipitation-strengthened Cu-Cr-Zr electrode alloy.

Because high-entropy alloys (HEAs) contain multiple major elements, the growth behavior of their plasma electrolytic oxidation (PEO) coatings differs significantly from that of traditional valve metals. Introducing oxide coatings can effectively compensate for insufficient wear resistance caused by elemental segregation, but the regulatory mechanism of valve metal content on the structure and properties of the HEAs-PEO coatings still needs further clarification. Therefore, this study used PEO technology to treat AlxCoCrFeNi high-entropy alloys (x = 0, 0.25, 0.5, and 1) and systematically investigated the effects of Al content on the microstructure, tribological properties, and electrochemical corrosion behavior of the PEO coating. The results show that with increasing Al content, the surface roughness of the PEO coating increases from approximately 3.3 μm (Al0) to 4.8 μm (Al1). Meanwhile, the surface porosity showed a trend of first decreasing and then increasing, with the Al0.25 sample exhibiting the lowest porosity of only 7.03%, significantly lower than the 11.59% of the Al0 sample, and its Vickers hardness reached 500 HV0.5. Tribological tests showed that under the three friction pair conditions of GCR15, ZrO2, and 304 stainless steel, the Al0.25 sample exhibited the lowest average coefficient of friction, approximately 0.41, 0.45, and 0.6, respectively, demonstrating excellent and stable wear resistance. Wear track morphology analysis indicated that it had the narrowest wear track width, and the iron oxide layer and CoAl2O4 lubricating phase formed during wear effectively reduced frictional shear stress. Electrochemical testing results showed that the corrosion resistance of the PEO coating significantly increased with increasing Al content. Among the samples, the Al1 sample exhibited the lowest corrosion current density of only 2.22 × 10−10 A cm−2, nearly 3 orders of magnitude lower than the Al0 sample (2.14 × 10−7 A cm−2). Simultaneously, its charge transfer resistance reached a high value of 1.14 × 108 Ω cm2, indicating that the thicker and denser PEO coating significantly improved its barrier ability against corrosive media. However, excessively high Al content led to increased coating porosity and the formation of CoAl2O4 impurity phases, negatively impacting wear resistance. In summary, Al content significantly modulates the structure and service performance of the AlxCoCrFeNi high-entropy alloy PEO coatings: the Al0.25 sample showed the best wear resistance, while the Al1 sample exhibited the best corrosion resistance. This study provides experimental evidence and theoretical reference for the compositional design and synergistic optimization of wear and corrosion resistance in high-entropy alloy PEO coatings.

The article presents the research results on the problem of the influence of the electric spark discharge parameters and electrode alloys, based on metal matrix materials, used for electro spark deposition (ESD) on the physicochemical and operational characteristics of the coating layer. Experimental dependences of the cathode weight gain, erosion resistance of the anode materials, mass transfer coefficient, wear resistance of the coating, and their mathematical expressions with a reliability criterion of at least R2> 0.9044, are obtained. It is established that, after steel 45 sample has been treated by ESD with metal-matrix materials, the hardness of its surface increases 6 times on the average and the wear resistance – 2 times. The best values of wear resistance at all the modes under investigation have been obtained for the anode material NiO-Zr-TiO2-Al. Data series of cathode weight gain (ƩΔc), erosion resistance of anode materials (ƩΔа), mass transfer coefficient Кmt, coating wear resistance after ESD (Ʃcwr), coating formation efficiency (γcfe), ESD energy efficiency (γeef), are also obtained. These data can be recommended for achieving the required parameters of the ESD on steels using metal-matrix materials.

The study objective is to obtain and study metal matrix alloys based on NiAl intermetallic compound with different concentrations of Ni for forming wear-resistant coatings on steel 45. 
 The problems to which the paper is devoted are: obtaining electrode materials based on NiAl intermetallic compound with different concentrations of Ni and studying their structure; studying the mass transfer during electrospark deposition on steel 45; studying the comparative wear resistance of the coatings obtained. 
 Research methods: electrode alloys are obtained by the method of liquid-phase self-propagating high-temperature synthesis; electro spark alloying is used to create wear-resistant coatings; the microstructure of the obtained alloys is studied by the method of metallographic analysis.
 The novelty of the work: for the first time, the influence of different Ni concentration values on the wear resistance of NiAl electrospark coatings on steel 45 is studied.
 Study results: the microstructure of the obtained alloys consists of doped Cr and Co grains of NiAl matrix with a different Ni/Al ratio, along the boundaries of which the compounds of all alloy components are located. When forming coatings by electrospark method, time dependences of changes in anode erosion, cathode gain and mass transfer coefficient are obtained. 
 Conclusions: NiAl metal-based alloys with different concentrations of Ni were smelted using a liquid-phase SHS method using charge consisting of metal oxides and mineral concentrates containing tungsten and zirconium; the microstructure of the obtained alloys consists of doped Cr and Co grains baseds on NiAl, along which boundaries compounds of all the constituent components of the alloy are concentrated, including Zr and W. Experimental results of anode erosion, cathode gain, and mass transfer coefficient were obtained while forming the coatings with the alloys using electrospark method, and it was found during wear resistance tests that with an increase of Ni concentration in the alloy, the wear resistance increases.

An overview of oil well cement retarders and the retardation mechanisms

Characteristics of surface-modified metal hydride electrode with flake Ni by the ball-milling process

Microstructure and electrochemical performance of Ti0.17Zr0.08V0.34Pd0.01Cr0.1Ni0.3 electrode alloy