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Purpose This paper aims to investigate the anti-biocorrosion performance and mechanism of the Cu-bearing carbon steel in the environment containing sulfate-reducing bacterial (SRB). Design/methodology/approach The biocorrosion behavior of specimens with Cu concentration of 0 Wt.%, 0.1 Wt.%, 0.3 Wt.% and 0.6 Wt.% were investigated by immersion test in SRB solution. By examining the prepared cross-section of the biofilm using focused ion beam microscopy, SRB distribution, bacterial morphology, biofilm structure and composition were determined. The ion selectivity of the biofilm was also obtained by membrane potential measurement. Moreover, the anti-biocorrosion performance of the Cu-bearing carbon steel pipeline was tested in a shale gas field in Chongqing, China. Findings Both the results of the laboratory test and shale gas field test indicate that Cu-bearing carbon steel possesses obvious resistance to microbiologically influenced corrosion (MIC). The SRB, corrosion rate and pitting depth decreased dramatically with Cu concentration in the substrate. The local acidification caused by hydrolyze of ferric ion coming from SRB metabolism and furtherly aggravated by anion selectivity biofilm promoted the pitting corrosion. Anti-biocorrosion of Cu-bearing carbon steel was attributed to the accumulation of Cu compounds in the biofilm and the weaker anion selectivity of the biofilm. This research results provide an approach to the development of economical antibacterial metallic material. Originality/value MIC occurs extensively and has become one of the most frequent reasons for corrosion-induced failure in the oil and gas industry. In this study, Cu-bearing carbon steel was obtained by Cu addition in carbon steel and possessed excellent anti-biocorrosion property both in the laboratory and shale gas field. This study provides an approach to the development of an economical antibacterial carbon steel pipeline to resist MIC.

ZnO nanopowders with hexagonal wurtzite structure were synthesized by hydrothermal method with different concentrations of Fe. X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spe...

The field emission cathode coating of nano-diamond on titanium substrate was prepared by electrophoretic deposition, the hydrogen plasma process was carried out after heat treatment, and then the microstructure, field emission properties and the luminescence performance of the samples were characterized. The results show that the adsorption of H + and the etching of H + collectively affect the morphology of diamond coating. Deficient hydrogen treatment can't reach the requirement and excessive hydrogen treatment can lead to serious etching for the diamond coating, resulting in worse field emission properties of the coating and luminescence effect. The appropriate hydrogen treatment is helpful to improve the field emission properties and luminescence effect. Finally, the field emission mechanism of nano-diamond coating on titanium substrate was discussed, and the reasons of luminescence effect difference were explained.

The sustained casing pressure (SCP) threatens the wellbore safety significantly. Generally, the effects of factors that cause casing pressure cannot be quantified. Some vague terms are often used to describe the risk degree. Considering the serious SCP situation in XX gas field in the southwest of China, a SCP risk evaluation model was proposed based on the fuzzy comprehensive evaluation method. Three risk indicators (annulus pressure, cementing quality, and formation leakage) were used to describe the SCP risk. The indicators' weight was determined with the application of Delphi method, and the membership matrix was established based on the trapezoidal distribution membership function and the gas field testing data. Then the evaluation model was used to calculate the risk values and risk degrees of 27 SCP wells in XX gas field. Electronic sensors installing and real-time monitoring were recommended to enhance the safety annulus pressure management. The proposed model provides an important technical basis for the production and management of SCP gas wells.

Field emission characteristics of metal-doped nano-diamond on titanium substrate were studied, wherein metals—Ti and Hf were mixed with nano-diamond separately, and cathode samples were prepared by electrophoresis. Then the structures and morphologies of cathode samples were characterized by SEM and XRD; finally, field emission tests were conducted. Results show that the morphology of 5 mg Ti-doped sample is more uniform and dense, but the morphologies of Hf-doped samples become worse. Meanwhile, compared with the undoped sample, field emission characteristics of Ti-doped samples improve, while those of Hf-doped samples decrease. From the comparison between Ti-doped samples, it is found that the amount of Ti mixed with nano-diamond should not be too much; a moderate amount of Ti can improve field emission characteristics of nano-diamond on Ti substrate. It is determined by the nature of metal Ti and Hf, which influences the bonding reaction between nano-diamond and substrate Ti, thus affecting, field emission characteristics of doped nano-diamond on Ti substrate.

Cathode samples of nano-diamond by graphitization pretreatment with different temperatures were fabricated by electrophoresis, then the structures and morphologies of the cathode samples were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), and the field emission tests were conducted. The effects of graphitization pretreatment on the field emission characteristics of nano-diamond cathode surface on titanium substrate are studied. The results indicate that the surface morphologies of nano-diamond cathode samples after graphitization pretreatment change a lot, and the field emission characteristics in low-voltage area are improved obviously. However, in high-voltage area, the curve distortion happens, and it doesn’t conform the mechanism of field emission characteristics.

Microbiologically influenced corrosion (MIC) and CO2 corrosion are the common types of corrosion in shale gas fields. In this study, the effect of quaternized polyacrylamide inhibitor on MIC was studied in the produced water from a shale gas field using a circulating loop system with CO2. The result shows that polyacrylamide can inhibit CO2 corrosion. However, in the presence of microorganisms, polyacrylamide failed to inhibit MIC. Microorganisms formed biofilm on the coupon surface. Pitting nucleated underneath the biofilm and developed into cavity-type due to the local acidification. According to crystal structure and chemical composition of matters in the biofilm, the mechanism of microbial acidification leading to pitting corrosion was proposed. The prevention and control strategy for MIC in CO2 environment was discussed.

The bacterial distribution in biofilm and the longitudinal element distribution of MIC pitting by an SRB consortium were investigated using focused ion beam-scanning electron microscope (FIB-SEM). Results show that bacteria were surrounded by shells, and the bacterial distribution in the biofilm varied depending on the corrosion morphology. At the pitting corrosion area, cells gathered at the bottom of biofilm, while at the general corrosion area, cells distributed at the outer side of biofilm. The membrane potential measurement result shows that the biofilm has an anion selectivity. MIC pitting mechanism was proposed considering the bacterial distribution and the biofilm ion selectivity.

Chrysanthemum-like ZnO nanowire clusters were prepared by hydrothermal process, then were transferred to Ti substrate by electrophoresis method, and uniform ZnO nano-film with certain thickness was formed. Finally ZnO field emission cathode sample was fabricated after vacuum heat treatment. The microstructure and the morphology of chrysanthemum-like ZnO nanowire clusters were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Field emission tests were conducted for cathode samples after heat treatment, results reveal that the low turn-on field is 2.0 V/μm for the chrysanthemum-like ZnO, and the threshold field is 5.5 V/μm. Moreover, the field emission current density is 200 μA/cm2 under the condition of electric field of 7.5 V/μm, and the field emission current density and its stability can be effectively improved by appropriate enlarging the thickness of the ZnO coating. The field emission mechanism was also explored.

In order to solve the problem of high voltage driving of nano-diamond coating field emission display, a driving circuit with gray-scale modulation and high-low voltage conversion is designed. Hardware circuits are based on assembled data driving chips of HV632PG and HV5308, which form the framework of gray-scale modulation and scanning display circuit; as well as, the framework of before and after low-level high-low voltage isolated and converted circuit is assembled based on half-bridge driving chip IR2235. Test the whole characteristics of software and hardware circuits, the dynamic display of simple image and character is realized on the screen of LED, which lays a certain foundation of theory and experiment for developing the application of nano-diamond coating FED of large screen.