Xiaogang Li

Dual-action smart coatings with a self-healing superhydrophobic surface and anti-corrosion properties

This work introduces a new self-healing superhydrophobic coating based on dual actions by the corrosion inhibitor benzotriazole (BTA) and an epoxy-based shape memory polymer (SMP). Damage to the surface morphology (e.g., crushed areas and scratches) and the corresponding superhydrophobicity are shown to be rapidly healed through a simple heat treatment at 60 °C for 20 min. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) were used to study the anti-corrosion performance of the scratched and the healed superhydrophobic coatings immersed in a 3.5 wt% NaCl solution. The results revealed that the anti-corrosion performance of the scratched coatings was improved upon the incorporation of BTA. After the heat treatment, the scratched superhydrophobic coatings exhibited excellent recovery of their anti-corrosion performance, which is attributed to the closure of the scratch by the shape memory effect and to the improved inhibition efficiency of BTA. Furthermore, we found that the pre-existing corrosion product inside the coating scratch could hinder the scratch closure by the shape memory effect and reduce the coating adhesion in the scratched region. However, the addition of BTA effectively suppressed the formation of corrosion products and enhanced the self-healing and adhesion performance under these conditions. Importantly, we also demonstrated that these coatings can be autonomously healed within 1 h in an outdoor environment using sunlight as the heat source.

Microbiologically Influenced Corrosion of 2707 Hyper-Duplex Stainless Steel by Marine Pseudomonas aeruginosa Biofilm

Microbiologically Influenced Corrosion (MIC) is a serious problem in many industries because it causes huge economic losses. Due to its excellent resistance to chemical corrosion, 2707 hyper duplex stainless steel (2707 HDSS) has been used in the marine environment. However, its resistance to MIC was not experimentally proven. In this study, the MIC behavior of 2707 HDSS caused by the marine aerobe Pseudomonas aeruginosa was investigated. Electrochemical analyses demonstrated a positive shift in the corrosion potential and an increase in the corrosion current density in the presence of the P. aeruginosa biofilm in the 2216E medium. X-ray photoelectron spectroscopy (XPS) analysis results showed a decrease in Cr content on the coupon surface beneath the biofilm. The pit imaging analysis showed that the P. aeruginosa biofilm caused a largest pit depth of 0.69 μm in 14 days of incubation. Although this was quite small, it indicated that 2707 HDSS was not completely immune to MIC by the P. aeruginosa biofilm.

Effects of Applied Magnetic Field on Corrosion of Beryllium Copper in NaCl Solution

The effects of an applied magnetic field on the corrosion process of beryllium copper in NaCl solution have been investigated by electrochemical measurements, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that a horizontal magnetic field with 0.4 T barely shifted the open circuit potentials ( E corr ) of beryllium copper in NaCl solution with different concentrations. However, the horizontal magnetic field increased the limiting current density of beryllium copper in NaCl solution with low concentration, while decreased the limiting current density of beryllium copper in NaCl solution with high concentration. It was found that magnetic field accelerated the diffusion of CuCl 2− away from the electrode surface and delayed the formation of Cu 2 O. The results of SEM and EDS showed that the influence of magnetic field over the elements distribution of the corrosion products differed from the different concentration of the immersion solution.

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m2 g−1 present high specific capacities of the 308 and 200 F g−1 in KOH electrolyte at current densities of 0.1 and 10 A g−1, respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g−1 at 0.1 A g−1 and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry.

Corrosion mechanism of corrosion-resistant steel developed for bottom plate of cargo oil tanks

A new type of corrosion-resistant steel consisting of ferrite and bainite phases was developed for cargo oil tanks of crude oil tankers. The corrosion rate of this new steel was 0.22 mm/a, which was equivalent to ca. 1/5 of the criterion (≤ 1 mm/a) for corrosion-resistant steels. The composition and element distribution of the corrosion products were investigated by micro-Raman spectrometry and energy dispersive spectrometer. The results demonstrated that the corrosion product was composed of α-FeOOH, Fe3O4 and a continuous Cu enrichment layer. This kind of corrosion product was protective to the steel matrix and accounted for the enhancement of the corrosion resistance of the new developed steel.

Highly stable GeOx@C core–shell fibrous anodes for improved capacity in lithium-ion batteries

As a promising high capacity electrode material for lithium-ion batteries, germanium anodes are still to date restricted by the large volume change (>300%) during repeated cycling, which leads to a short cycle life and poor cycle stability in practical application. To overcome these challenges, herein a facile fabrication is reported to encapsulate GeOx nanoparticles into hollow carbon shells using co-axial electrospinning. This core–shell structure has shown remarkable improvements in alleviating the volume change of GeOx during cycling, minimizing the contact area between electrolyte and GeOx to form a stable solid electrolyte interface film, and providing enhanced electrical conductivity. In addition, Ge nanoparticles in the GeOx composite can promote the reversible capacity for the reversible utilization of Li2O. As a result, such a GeOx@C composite electrode exhibits excellent cycling ability with a reversible specific capacity of 875 mA h g−1 at 160 mA g−1 after 400 cycles, along with an improved rate capacity of 513 mA h g−1 at a high current density of 1600 mA g−1 upon 500 cycles.

Confined Porous Graphene/SnOx Frameworks within Polyaniline-Derived Carbon as Highly Stable Lithium-Ion Battery Anodes

Tin oxides are promising anode materials for their high theoretical capacities in rechargeable lithium-ion batteries (LIBs). However, poor stability usually limits the practical application owing to the large volume variation during the cycling process. Herein, a novel carbon confined porous graphene/SnOx framework was designed using a silica template assisted nanocasting method followed by a polyaniline-derived carbon coating process. In this process, silica served as a template to anchor SnOx nanoparticles on porous framework and polyaniline was used as the carbon source for coating on the porous graphene/SnOx framework. The synthesized carbon confined porous graphene/SnOx frameworks demonstrate substantially improved rate capacities and enhanced cycling stability as the anode materials in LIBs, showing a high reversible capacity of 907 mAh g(-1) after 100 cycles at 100 mA g(-1) and 555 mAh g(-1) after 400 cycles at 1000 mA g(-1). The remarkably improved electrochemical performance could be assigned to the unique porous architecture, which effectively solves the drawbacks of SnOx including poor electrical conductivity and undesirable volume expansion during cycling process. Consequently, such design concept for promoting SnOx performance could provide a novel stage for improving anode stability in LIBs.

Preparation and characterization of bimodal porous alumina–silica and its application to removal of basic nitrogen compounds from light oil

Aluminium nitrate and aluminium isopropoxide were used as aluminium precursors to prepare bimodal porous alumina–silica mixed oxides via the sol–gel method with the addition of nonionic surfactant C16EO10 as the structure-directing agent. The characterization of the mixed oxides was performed using scanning electron microscopy (SEM), nitrogen adsorption/desorption measurements, chemical composition measured by X-ray fluorescence (XRF), and surface acidity was investigated by the Hammett indicator method and Fourier transform infrared spectroscopy (FT-IR) of adsorbed pyridine. It is found that the resultant mixed oxides possess micrometer-range interconnected macropores and nanometer-range mesopores. Studies have shown that relatively large mesopore size materials can be obtained with aluminium nitrate precursor, but relatively high Al content materials can be synthesized using aluminium alkoxide as aluminium precursor. Surface acidity analysis results indicate that the alumina–silica mixed oxides synthesized by present sol-gel method have Lewis acid sites and Bronsted acid sites, and these acid sites exhibit mild strong acidity. Moreover, two different synthesis pathways have little influence on the acidity of alumina–silica prepared by the present method. In addition, the adsorption capacity of such acidic mixed oxides, with bimodal pore structures, for pyridine from diesel oil was studied. The adsorption experiments indicate that these mild strong acidic adsorbents with high surface areas and large macropores are effective in removing basic nitrogen compounds (BNC) such as pyridine from diesel oil, and are easily regenerated by washing with polar solvents.

Extracellular Electron Transfer Is a Bottleneck in the Microbiologically Influenced Corrosion of C1018 Carbon Steel by the Biofilm of Sulfate-Reducing Bacterium Desulfovibrio vulgaris

Carbon steels are widely used in the oil and gas industry from downhole tubing to transport trunk lines. Microbes form biofilms, some of which cause the so-called microbiologically influenced corrosion (MIC) of carbon steels. MIC by sulfate reducing bacteria (SRB) is often a leading cause in MIC failures. Electrogenic SRB sessile cells harvest extracellular electrons from elemental iron oxidation for energy production in their metabolism. A previous study suggested that electron mediators riboflavin and flavin adenine dinucleotide (FAD) both accelerated the MIC of 304 stainless steel by the Desulfovibrio vulgaris biofilm that is a corrosive SRB biofilm. Compared with stainless steels, carbon steels are usually far more prone to SRB attacks because SRB biofilms form much denser biofilms on carbon steel surfaces with a sessile cell density that is two orders of magnitude higher. In this work, C1018 carbon steel coupons were used in tests of MIC by D. vulgaris with and without an electron mediator. Experimental weight loss and pit depth data conclusively confirmed that both riboflavin and FAD were able to accelerate D. vulgaris attack against the carbon steel considerably. It has important implications in MIC failure analysis and MIC mitigation in the oil and gas industry.

Effect of pH Value on Stress Corrosion Cracking of X70 Pipeline Steel in Acidic Soil Environment

The effect of pH value on the stress corrosion cracking (SCC) of API X70 pipeline steel in simulated acidic soil solutions was investigated by using slow strain rate test, electrochemical polarization curves, electrochemical impedance spectroscopy, and scanning electron microscopy. pH plays an important role in the susceptibility and electrochemical mechanism of SCC. The pH higher than 5 has no significant effect on electrochemical processes. By contrast, the pH lower than 5 intensifies cathodic hydrogen evolution reactions, thus increasing the cathodic current and corrosion potential. Under different pH values, the SCC mechanism of X70 pipeline steel varies among anodic dissolution (AD), hydrogen embrittlement (HE), and the combination of AD and HE (AD + HE) with variations of applied potential. At −850 mVSCE, the SCC mechanism is HE if pH is less than 4 or AD + HE if pH value is more positive.