Since 2010, China's economic growth has stagnated due to an unbalanced regional industrial structure and lack of sufficient qualified technical personnel. A nonlinear autoregressive distributed lag ...(NARDL) model has been used in this study to examine the asymmetric effects of secondary vocational education and training (SVET) and higher vocational education and training (HVET) and their interaction with high-tech industries on economic growth over the period 1980-2020. The findings show that an increase in secondary vocational education and training (SVET) significantly boosts long-term economic growth, while a decrease in secondary vocational education and training (SVET) insignificantly reduces long-term China economic growth. Likewise, the upward change in higher vocational education and training (HVET) promotes and the downward fluctuation in higher vocational education and training (HVET) significantly reduces China's long-term economic growth. The moderating role of secondary vocational education in the impact of high-tech industries on China's economic growth is positive, but not significant. However, higher vocational education plays a significant positive moderating role in high technology industries impact on economic growth. Strategically, the study analysis suggests that economic transition prosperity can be achieved by encouraging higher vocational education and the equal development of high-tech industries in all regions. In addition, this study also proposes to cultivate high-quality talents related to high-tech development and modern industrial innovation and upgrading through higher vocational education, improve productivity, and promote the country's intensive development.
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•Microstructural studies of 2524-T3 Al alloy welded by FSW were performed.•Corrosion resistance of the base material and nugget zone was assessed by EIS and SVET.•Base material and ...nugget zone possess a cathodic behaviour.•The influence of FSW process on FCG curves in nugget and base material was studied.
The corrosion processes and its influence on the FCG curves of the 2524-T3 alloy joined by FSW was studied in the nugget and BM. To assess the corrosion process, SVET, pH micro-potentiometry and EIS were used. The localised corrosion results showed similar BM and nugget zone electrochemical behaviour, while the TMAZ/HAZ region was electrochemically the weakest zone, susceptible to anodic dissolution. The FSW process and saline environment was found to modify the BM and nugget FCG resistance, being more detrimental for the BM due to the primary IM particles that are not present in the nugget, making it chemically more homogeneous.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The co-polymerization of aniline with p-nitroaniline has been synthesized in oxalic acid medium, here ammonium persulfate (APS) acts as an oxidant. TGA analysis was used to study the thermal ...stability of the copolymer, as well as FTIR, UV–Vis spectroscopy, and XRD. The synthetic poly (aniline-co-p-nitroaniline) (PANA) is used as a barrier/redox pigment for PANA coatings. The anti-corrosion study on PANA coatings was performed with a 3% NaCl solution for up to 35 days. The coating resistance of PANA coatings is three orders of magnitude more than that of pure epoxy coatings, according to the results of electrochemical impedance spectroscopy (EIS). The scanning vibrating electrode method (SVET) was used to investigate the self-healing characteristics of this PANA coating.
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•The poly (aniline–co-p-nitroaniline) (PANA) is prepared by a chemical oxidation route.•The PANA doped oxalate ion acts as an inhibitor at the onset of corrosion.•The corrosion protector of PANA was studied by EIS.•The imitated corrosion process of PANA was studied by SVET.•The superior corrosion protection of PANA is better than epoxy coating.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The physico-chemical model of galvanic corrosion AA2024-Ti was developed.•Local corrosion effects and formation of porous corrosion products were considered.•The diffusion layer for O2 was ...introduced, although convection was not considered.•A qualitative agreement was found between the model and experiment.
This study focuses on the development of a physico-chemical model based on mechanistic and kinetics understanding of the corrosion process in galvanic couple Ti6Al4V-AA2024. Proposed model provides deeper insights at macro level for initiation and propagation of localized corrosion of AA2024 in galvanically coupled multi-material assemblies. The model is able to reveal the localized corrosion, related to heterogeneity of AA2024 microstructure, including local pH changes, the deposition of the reaction products, and emphasizes the important role of AA2024 self-corrosion in galvanic assemblies. The validation of the developed model was performed using relevant data collected by advanced in situ localized techniques.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•GO with different aspect ratios were prepared and the uniform GO/epoxy composite coatings were fabricated.•Anti-corrosion performance of composite coatings containing GO sheets with ...different aspect ratio were investigated.•Anti-corrosion mechanism of different GO/epoxy composite coatings were studied.•The aspect ratio of GO sheets was a significant factor for enhancing corrosion resistance of GO/epoxy coatings.
Graphene oxide (GO) has a wide application prospect in the field of metal protection due to its good dispersion, chemical activity and physical barrier property. Herein, graphene oxide sheets with different aspect ratio were first prepared by simply controlling the procedure of chemical exfoliation and then used to fabricate GO/epoxy composite coatings. The morphology and structural features of as-prepared GO sheets were characterized by Raman spectroscopy, X-ray diffraction and atomic force microscopy. The dispersion and anticorrosive performances of GO with different aspect ratios incorporated in epoxy-based waterborne composite coatings were investigated by Raman spectroscopic mapping, electrochemical measurements and scanning vibrating electrode technique. The results demonstrated that the different types of GO showed homogeneous dispersion in epoxy resin and GO with higher aspect ratio exhibited larger corrosion protection potential. Furthermore, the anti-corrosion mechanisms for composite coatings enhanced via GO with different aspect ratio were tentatively proposed, which indicating that the GO sheets with higher aspect ratio provided a more tortuous permeation path for corroding medium and thus displayed better corrosion resistance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In order to study the effect of defects on the corrosion behavior of MAO coatings, global electrochemical method including potentiodynamic polarization (PDP) and electrochemical impedance ...spectroscopy (EIS) was used to measure the corrosion resistance of MAO coatings. Local electrochemical measurements including local impedance spectroscopy (LEIS) and scanning vibrating electrode technique (SVET) were used to study the local corrosion mechanism. The confocal microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to observe the microstructure and phases of the samples. Results of global electrochemical measurement demonstrate that the scratches cause the reduction of the impedance and the increase of the corrosion current density. LEIS results show the impedance value distribution of the coating with the scratch. With the changes over time, the minimum impedance value of the scratch decreases first and then increases from the third hour. SVET results show the corrosion current density distribution of the scratched coating. The maximum corrosion current density at the scratch increases first and then decreases. The results of local electrochemical measurements show that the corrosion rate at the scratch decreases when the reaction lasted 3 h. Confocal microscopy found that the scratch is expanding with increasing time, and the depth and cross-sectional area of the coating is 5 times deeper and 10 times larger than that of 7075Al with scratch at the first 6 h. The 6-day immersion test proved that the scratch coating still has the protective effect on the substrate. The main corrosion product is Al(OH)3. A physical model reflecting the mechanism of the scratch propagation and the formation of the corrosion product film is proposed.
•Global and local electrochemical corrosion of scratched MAO coating on Al Alloy was studied.•The electrochemical impedance and current distribution of scratches were analyzed by LEIS and SVET.•A phenomenological model for the influence of scratch on the local corrosion of the MAO coated Al alloy was proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•pH-dependent electrochemical behaviour of Al3Mg2 has been confirmed.•Galvanic corrosion currents versus pH of coupled Al3Mg2/Al were studied by SVET.•Dealloying element changes from ...Al to Mg as pH deviates from strong alkaline.•Three models were proposed to depict the corrosion process of Al3Mg2 at pH 2–12.
The effects of pH on the electrochemical behaviour of β-phase (Al3Mg2) and its role in corrosion of AA5000 series alloys in NaCl solution were investigated. The galvanic corrosion behaviour of synthesized Al3Mg2 intermetallic particle coupled with Al in 0.01 M NaCl solution over a wide pH window of 2–12 was studied using the scanning vibrating electrode technique (SVET). The results show that bulk Al3Mg2 acts as anode at pH 2–10.5, while cathode at pH 12. The corrosion resistance properties of bulk Al3Mg2 were then evaluated via potentiodynamic polarization and electrochemical impedance spectroscopy tests. Surface characterization were carried out by confocal laser scanning microscope (CLSM), scanning electron microscope (SEM) and X-ray photoelectron spectrometry (XPS). These results indicate that Al3Mg2 exhibits active dissolution of both Al and Mg elements at pH 2, while selective dissolution occurs at pH 3.5–12. At pH 3.5–10.5, any deviation from neutral pH causes a significant increase in the selective dissolution rate of Mg element, which results in a rough outer layer and a relatively compact inner layer of corrosive surface. At pH 12, the selective dissolution of Al element becomes dominant and the formation of compact Mg(OH)2 achieves complete passivity on the surface of Al3Mg2. This work contributes to further understanding of the electrochemical behaviour of β-phase in AA5000 series alloys.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Synthesis of microcapsules (5−20 μm) containing isophorone diisocyanate using tris (p-isocyanatophenyl) thiophosphate as a shell forming agent.•Microcapsules show high encapsulation ...efficiency and high thermal and chemical resistance.•Microcapsules show high compatibility with epoxy coating formulations.•Electrochemical studies confirmed important healing ability of the microcapsules- containing coating.
This work aims at investigating the self-healing ability of epoxy coatings, modified with microcapsules containing highly reactive isocyanate in their core. Highly efficient, thermally and chemically stable isophorone diisocyanate microcapsules were prepared via emulsification followed by interfacial polymerization at the surface of oil droplets of the oil-in-water (O/W) emulsion. The microcapsules were incorporated into an epoxy coating to protect carbon steel from corrosion. Scanning Electron Microscopy (SEM) was used to assess the microcapsules̕ and coating morphology. The physico-chemical characterization of the microcapsules was studied by Fourier Transformed Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate the protective performance of coated steel samples and results confirmed that the barrier properties of modified coatings increased over time. The self-healing ability was studied via Localized Impedance Spectroscopy (LEIS), Scanning Vibrating Electrode Technique (SVET) and Scanning Ion-Selective Electrode Techniques (SIET) on coated steel samples containing artificial defects. This comprehensive study confirmed the ability of the capsules to heal damaged areas in the coating and to mitigate corrosion thanks to the formation of a protective polymeric barrier layer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of cerium salts on the cut-edge of zinc-based sacrificial coated steel was investigated by theoretical approach (based on individual polarization curves on the top surface and by Scanning ...Vibrating Electrochemical Technique (SVET). In both approaches, cerium salts increase the galvanic corrosion of zinc-based sacrificial layer coupled with steel. Furthermore, the anion parts of cerium salts exhibited a synergistic accelerated effect of galvanic activity on the cross-section. The SVET results indicated that the addition of Al, Mg alloying elements promotes localized corrosion and influences the formation and distribution of corrosion products.
•Effect of CeCl3 and Ce(NO3)3 on the cut-edge of steel coated by zinc alloyed (HDG, ZnAl, and ZAM).•Cerium salts accelerated the corrosion of zinc coated steel on the cut-edge.•NO3- ion exhibited a synergistic accelerating effect on galvanic corrosion.•The presence of Al and Mg alloying elements promotes localized corrosion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Cerium malate was synthesized.•The corrosion inhibition on Al2Cu-Al2CuMg-Al, Al2CuMg-Al and Al2Cu-Al was studied.•Cerium malate is effective in corrosion inhibition of AA 2024-T3.
A new corrosion ...inhibitor, cerium malate, was synthesized. Its inhibiting behaviour on coupled Al2Cu-Al2CuMg-Al, Al2CuMg-Al and Al2Cu-Al was studied. Cerium malate is effective in corrosion inhibition of the three coupled systems. The inhibition mechanism of cerium malate on pitting corrosion of Al2CuMg and Al2Cu phases in AA 2024-T3 was analyzed by scanning vibrating electrode technique (SVET), atomic force microscopy (AFM) and scanning kelvin probe force microscopy (SKPFM). The results indicate that cerium malate has good inhibiting effect on AA 2024-T3.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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