scholarly journals Corrosion Protection of 6061 Aluminum Alloys by Sol-Gel Coating Modified with ZnLaAl-LDHs

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 478
Author(s):  
Youbin Wang ◽  
Qiuyu Huang ◽  
Bingtao Zhou ◽  
Zengyin Yuan ◽  
Yuezhou Wei ◽  
...  
Keyword(s):  
Aluminum Alloys ◽  
Corrosion Protection ◽  
Sol Gel ◽  
Precipitation Method ◽  
Corrosion Mechanism ◽  
Corrosion Performance ◽  
The Stability ◽  
Co Precipitation ◽  
Double Hydroxides

In this work, ZnLaAl layered double hydroxides (LDHs) were prepared by the co-precipitation method, and the ZnLaAl-LDHs nanosheets were embedded in sol-gel coating for the corrosion protection of 6061 aluminum alloys. The structure, morphology, and long-term anti-corrosion performance of sol-gel coating modified with ZnLaAl-LDHs were investigated. The structure and morphology analysis showed that nanosheets of ZnLaAl-LDHs are finer than those of ZnAl-LDHs, with the results suggesting that the La can refine the size of LDHs’ nanosheets and improve their nucleation rate. The results of long-term corrosion tests showed that the sol-gel coating with ZnLaAl-LDHs exhibits higher corrosion resistance and better stability compared with the sol-gel coating with ZnAl-LDHs, which indicates that the addition of La enhances the anti-corrosion performance of the LDHs and improves the stability of sol-gel coating with LDHs. Finally, the formation mechanism of ZnLaAl-LDHs and the corrosion mechanism of sol-gel coating with ZnLaAl-LDHs on 6061 aluminum alloys are both discussed in detail.

Corrosion Protective Properties of Hydrotalcites Doped Hybrid Sol-Gel Coatings on Aluminium Substrates

2010 ◽  
Vol 636-637 ◽  
pp. 996-1003 ◽  
Author(s):  
D. Álvarez ◽  
A. Collazo ◽  
Miguel Hernández ◽  
Xosé R. Nóvoa ◽  
C. Pérez
Keyword(s):  
Electrochemical Impedance ◽  
Sol Gel ◽  
Dip Coating ◽  
Precipitation Method ◽  
Corrosion Performance ◽  
Protective Properties ◽  
Coating Method ◽  
Dip Coating Method ◽  
Co Precipitation ◽  
Salt Fog

Hydrotalcite-like compound that belongs to anionic clay family was prepared by classical co-precipitation method using magnesium and aluminium nitrates as precursors. Different weight percentages of hydrotalcite with Mg/Al ratio of 2.5 was added (1, 5 and 10 % wt.) to hybrid sols prepared by copolymerization of 3-Glycydoxypropyltrimethoxysilane (GPTMS) and tetra-n-propoxyzirconium (TPOZ). The aim of this work was to study the effect of the hydrotalcite incorporation to hybrid sol-gel coatings on aluminium alloys as substitution of chromate inhibitors. Hybrid sol-gel coatings were deposited by dip coating method on AA2024-T3 substrates. By Scanning Electron Microscopy (SEM) and mechanic profilometry it was possible to see the distribution of HTCP agglomerates which varies from nanometres to micrometers. The corrosion performance was evaluated by the accelerated test salt fog spray chamber (SSFC) and by Electrochemical Impedance Spectroscopy (EIS). The obtained results show the corrosion resistance improvement at higher weight percentages of HTCP.

scholarly journals Dielectric properties of Bi-substituted LDHs synthesized by co-precipitation and sol-gel methods

2019 ◽  
Vol 37 (2) ◽  
pp. 190-195 ◽  
Author(s):  
Denis Sokol ◽  
Maksim Ivanov ◽  
Andrei N. Salak ◽  
Robertas Grigalaitis ◽  
Juras Banys ◽  
...  
Keyword(s):  
Sol Gel ◽  
Xrd Analysis ◽  
Precipitation Method ◽  
Complexing Agent ◽  
Mixed Metal Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Co Precipitation ◽  
Double Hydroxides ◽  
Gel Processing

AbstractMagnesium-aluminum-bismuth layered double hydroxides (Mg3Al1−xBix; LDHs) were prepared using both coprecipitation and sol-gel methods. For the preparation of Mg/Al/Bi LDH by the co-precipitation method, the appropriate amounts of dissolved starting materials (Al(NO3)3 · 9H2O, Mg(NO3)2 · 6H2O and Bi(NO3)3 · 5H2O) were mixed with a solution of NaHCO3:NaOH. In the sol-gel processing, the precursor Mg–Al–Bi–O gels were synthesized using the same starting materials and ethylene glycol as complexing agent. The mixed-metal oxides obtained by subsequent heating of Mg–Al–Bi–O gels at 650 °C were reconstructed to Mg3Al1−xBix LDHs in water at 80 °C. All the synthesized products were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and dielectric measurements.

Production of Layered Double Hydroxides for Anion Capture and Storage

2009 ◽  
Vol 1215 ◽  
Author(s):  
Jonathan Phillips ◽  
Luc Vandeperre
Keyword(s):  
Liquid Waste ◽  
Precipitation Method ◽  
Long Term Storage ◽  
Trivalent Cations ◽  
Co Precipitation ◽  
Double Hydroxide ◽  
Double Hydroxides ◽  
And Storage ◽  
Positively Charged

AbstractTechnetium has a long half life of up to 2.13×105 years. It is separated from liquid waste streams with tetraphenylphosphonium bromide [1], which upon degradation releases Tc as the pertechnetate anion, TcO4−. Pertechnetate is highly mobile in groundwater and it is therefore highly desirable to capture and immobilise this anion within a solid for interim and ultimately long term storage. Layered Double Hydroxide (LDH) materials are known to possess excellent anion sorption capabilities due to their structure which consists of ordered positively charged sheets intercalated with interchangeable hydrated anions. The composition can be tailored to produce suitable precursors for ceramic phases by varying the divalent and trivalent cations and the anions. LDHs with the general formula Ca1-x (Fe1-y, Aly)x (OH)2 (NO3)x . nH2O were produced by a co-precipitation method from a solution of mixed nitrates. Calcination leads to the formation of Brownmillerite Ca2(Al,Fe)2O5 like compounds for temperatures as low as 400°C, this is close to the lowest temperature at which Tc is known to volatilise (310.6 °C Tc2O7). It was shown that after calcining up to 600°C, the LDH structure is recovered in water allowing rapid ion capture to occur. This suggests that these materials have potential for both capture and as a storage medium for Tc.

scholarly journals Mixed Oxide Layered Double Hydroxide Materials: Synthesis, Characterization and Efficient Application for Mn2+ Removal from Synthetic Wastewater

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4089
Author(s):  
Cristina Modrogan ◽  
Simona Cǎprǎrescu ◽  
Annette Madelene Dǎncilǎ ◽  
Oanamari Daniela Orbuleț ◽  
Eugeniu Vasile ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Layered Double Hydroxides ◽  
Synthetic Wastewater ◽  
Precipitation Method ◽  
Metallic Ions ◽  
Materials Synthesis ◽  
Experimental Conditions ◽  
Edx Analysis ◽  
Co Precipitation ◽  
Double Hydroxides

Magnesium–aluminum (Mg-Al) and magnesium–aluminum–nickel (Mg-Al-Ni) layered double hydroxides (LDHs) were synthesized by the co-precipitation method. The adsorption process of Mn2+ from synthetic wastewater was investigated. Formation of the layered double hydroxides and adsorption of Mn2+ on both Mg-Al and Mg-Ni-Al LDHs were observed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDX) analysis. XRD patterns for prepared LDHs presented sharp and symmetrical peaks. SEM studies revealed that Mg-Al LDH and Mg-Al-Ni LDH exhibit a non-porous structure. EDX analysis showed that the prepared LDHs present uniformly spread elements. The adsorption equilibrium on these LDHs was investigated at different experimental conditions such as: Shaking time, initial Mn2+ concentration, and temperatures (10 and 20 °C). The parameters were controlled and optimized to remove the Mn2+ from synthetic wastewater. Adsorption isotherms of Mn2+ were fitted by Langmuir and Freundlich models. The obtained results indicated that the isotherm data fitted better into the Freundlich model than the Langmuir model. Adsorption capacity of Mn2+ gradually increased with temperature. The Langmuir constant (KL) value of Mg-Al LDH (0.9529 ± 0.007 L/mg) was higher than Mg-Al-Ni LDH (0.1819 ± 0.004 L/mg), at 20 °C. The final adsorption capacity was higher for Mg-Al LDH (91.85 ± 0.087%) in comparison with Mg-Al-Ni LDH (35.97 ± 0.093%), at 20 °C. It was found that the adsorption kinetics is best described by the pseudo-second-order model. The results indicated that LDHs can be considered as a potential material for adsorption of other metallic ions from wastewater.

scholarly journals Crystallographic, Energy Gap, Photoluminescence and Photo-Catalytic Investigation of Cu Doped Cd0.9Zn0.1S Nanostructures by Co-Precipitation Method

2021 ◽  
Author(s):  
P. Raju ◽  
Joseph Prince Jesuraj ◽  
S. Muthukumaran
Keyword(s):  
Crystallite Size ◽  
Energy Gap ◽  
Wavelength Region ◽  
Lattice Parameter ◽  
Precipitation Method ◽  
Optical Absorbance ◽  
Stability Measurement ◽  
Cubic Structure ◽  
The Stability ◽  
Co Precipitation

Abstract The controlled synthesis of Cd0.9Zn0.1S, Cd0.89Zn0.1Cu0.01S and Cd0.87Zn0.1Cu0.03S nanostructures by simple chemical co-precipitation technique was reported. The XRD investigation confirmed the basic CdS cubic structure on Zn-doped CdS and also Zn, Cu dual doped CdS with no secondary/impurity related phases. No modification in cubic structure was detected during the addition of Zn/Cu into CdS. The reduction of crystallite size from 63 Å to 40 Å and the changes in lattice parameter confirmed the incorporation of Cu into Cd0.9Zn0.1S and generation of Cu related defects. The shift of absorption edge along upper wavelength region and elevated absorption intensity by Cu doping can be accredited to the collective consequence of quantization and the generation of defect associated states. The enhanced optical absorbance and the reduced energy gap recommended that Cd0.87Zn0.1Cu0.03S nanostructure is useful to enhance the efficiency of opto-electronic devices. The presence of Cd-S / Zn-Cd-S /Zn/Cu-Cd-S chemical bonding were confirmed by Fourier transform infrared investigation. The elevated green emissions by Cu incorporation was explained by decrease of crystallite size and creation of more defects. Zn, Cu dual doped CdS nanostructures are recognized as the possible and also efficient photo-catalyst for the removal dyes like methylene blue. The enhanced photo-catalytic behaviour of Zn, Cu dual doped CdS is the collective consequences of high density electron-hole pairs creation, enhanced absorbance in the visible wavelength, surface area enhancement, reduced energy gap and the formation of novel defect associated states. The stability measurement signified that Cu doped Cd0.9Zn0.1S exhibits superior dye removal ability and better stability even after 6 repetitive runs with limited photo-corrosion.

Enhanced catalytic phenol hydroxylation by CuZnFeAl layered double hydroxides: synergistic effects of Cu+ and oxygen vacancies

2021 ◽  
Vol 45 (1) ◽  
pp. 179-188
Author(s):  
Yong Jiang ◽  
Wenlong Xu ◽  
Jinhua Liang ◽  
Jiecan Shen ◽  
Xiaomin Fu ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Oxygen Vacancies ◽  
Synergistic Effects ◽  
Phenol Oxidation ◽  
Precipitation Method ◽  
Phenol Hydroxylation ◽  
Co Precipitation ◽  
Double Hydroxides

In this work, a series of CuZnFeAl-LDH catalysts for phenol oxidation to dihydroxybenzene have been prepared through a co-precipitation method.

scholarly journals Gas-Phase Hydrogenation of Furfural to Furfuryl Alcohol over Cu-ZnO-Al2O3 Catalysts Prepared from Layered Double Hydroxides

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 486
Author(s):  
Guillermo R. Bertolini ◽  
Carmen P. Jiménez-Gómez ◽  
Juan Antonio Cecilia ◽  
Pedro Maireles-Torres
Keyword(s):  
Gas Phase ◽  
Aging Time ◽  
Layered Double Hydroxides ◽  
Furfuryl Alcohol ◽  
Precipitation Method ◽  
Molar Ratio ◽  
X Ray ◽  
General Chemical ◽  
Co Precipitation ◽  
Double Hydroxides

Several layered double hydroxides (LDHs) with general chemical composition (Cu,Zn)1−xAlx(OH)2(CO3)x/2·mH2O have been synthesized by the co-precipitation method, maintaining a (M2+/M3+) molar ratio of 3, and varying the Cu2+/Zn2+ molar ratio between 0.2 and 6.0. After calcination and reduction steps, Cu/ZnO/Al2O3 catalysts were synthesized. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), H2 thermoprogrammed reduction (H2-TPR), N2 adsorption-desorption at −196 °C, N2O titration, X-ray photoelectron miscroscopy (XPS), NH3-thermoprogramed desorption (NH3-TPD) and CO2- thermoprogrammed desorption (CO2-TPD). The characterization data revealed that these catalysts are mainly meso-and macroporous, where Cu, ZnO and Al2O3 are well dispersed. The catalytic results show that these catalysts are active in the gas-phase hydrogenation of furfural, being highly selective to furfuryl alcohol (FOL) and reaching the highest FOL yield for the catalyst with a Cu2+/Zn2+ molar ratio of 1. In an additional study, the influence of the aging time on the synthesis of the LDHs was also evaluated. The catalytic data revealed that the use of shorter aging time in the formation of the LDH has a beneficial effect on the catalytic behavior, since more disordered structures with a higher amount of available Cu sites is obtained, leading to a higher yield towards FOL (71% after 5 h of time-on-stream at 210 °C).

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