Corrosion resistance of cerium-doped zinc calcium phosphate chemical conversion coatings on AZ31 magnesium alloy

Zinc calcium phosphate （Zn-Ca-P） coating and cerium-doped zinc calcium phosphate （Zn-Ca-Ce-P） coating were prepared on AZ31 magnesium alloy. The chemical compositions, morphologies and corrosion resistance of coatings were investigated through energy-dispersive X-ray spectroscopy （EDS）, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, electron probe micro-analysis （EPMA） and scanning electron microscopy （SEM） together with hydrogen volumetric and electrochemical tests. The results indicate that both coatings predominately contain crystalline hopeite （Zn3（PO4）2·4H2O）, Mg3（PO4）2 and Ca3（PO4）2, and traces of non-crystalline MgF2 and CaF2. The Zn-Ca-Ce-P coating is more compact than the Zn-Ca-P coating due to the formation of CePO4, and displays better corrosion resistance than the Zn-Ca-P coating. Both coatings protect the AZ31 Mg substrate only during an initial immersion period. The micro-galvanic corrosion between the coatings and their substrates leads to an increase of hydrogen evolution rate （HER） with extending the immersion time. The addition of Ce promotes the homogenous distribution of Ca and formation of hopeite. The Zn-Ca-Ce-P coating has the potential for the primer coating on magnesium alloys.

Preparation and Performance of Rare Earths Chemical Conversion Film on Magnesium Alloy

Golden yellow cerium conversion film was obtained on magnesium alloys surface by immersion method and the preparation parameters were established. The influence of different process parameters on the surface morphology and performance of the conversion film were analyzed by means of SEM and electrochemical method. Formation dynamics about cerium conversion film on magnesium alloy in solution containing cerium salt and the anti-corrosion behavior of the conversion film in 3.5% NaCl solution were studied by electrochemical method respectively. The results shows that the conversion film is more compact at room temperature when concentration of cerium sulfate is 10 g·L-1 in the solution; the open circuit potential of the magnesium sample moves up to positive direction about 100 mV, the surface of conversion film becomes even and lustrous, and the adhesion intensity of conversion film increases when adding aluminum nitrate into the solution containing cerium salt. The pH value of the solution and immersion time of the sample in the solution also affect the surface morphology and anti-corrosion property of the conversion film. After covered by rare earths conversion film, the anti-corrosion property of magnesium alloy is obviously improved. Rare earth conversion film has self-repairing capability in corrosion medium.

Chemical conversion coating on AZ31B magnesium alloy and its corrosion tendency

The morphology change of the magnesium matrix after pre-treatment and the morphology as well as the phase composition of chemical conversion coating formed by phosphate were studied using scanning electron microscope and X-ray diffraction. The corrosion resistance of the coating was studied by salt spray and damp test, and the corrosion tendency during salt immersion test was analyzed. The results show that the phase composition before and after pre-treatment is almost changeless, and the deep microflaw appears between a andβ phases during acidic pickling. The phosphate conversion coating is mainly composed of Mg, MgO, and some amorphous phase, and it can provide a good protection for the AZ31B alloy. Results from corrosive morphology indicate that the growth and the corrosion resistance of the phosphate conversion coating are related to the forming process of the AZ31B matrix.

Cerium Chemical Conversion Coating on a Novel Mg-Li Alloy

A novel Mg-Li alloy was treated in a cerium nitrate solution and cerium chemical conversion coating was obtained on the alloy. Then the forming process, structure and corrosion resistance of the coating were investigated. The influential factors of cerium conversion coating were discussed through orthogonal experiments, and the optimum processing parameters were confirmed. XPS spectra displayed that the conversion coating consisted of cerium compounds, and the major component of the protective layer was a mixture of Ce （IV） oxide and Ce （IV） hydroxide. In addition, XRD pattern illustrated that there was crystalline CeO2 in the conversion coating. Analysis by SEM showed that the cerium conversion coating was uniform with a fiber-like morphology. The thickness of the conversion coating was 12 μm. The results of electrochemical potentiodynamic polarization and hydrogen evolution measurement indicated that the cerium conversion coating provided effective protection to the novel Mg-Li alloy.

CHEMICAL CONVERSION OF INOSINE INTO 6-(2-METHYL PHENOXY)-PURLNENUCLEOSIDE DERIVATIVES

A 6-pyridinium salt(2)was obtalned from 2',3',5'-tri-O-acetyhnosine by use of phosphoryl chloride as the condensmg agent.The conversion of salt(2)into 6-(2- methylphenoxy)-purinenucleoside(3)denvatives under mild condition is also described.

Structures,Chemical Conversions,and Cytotoxicity of Tricholopardins C and D,Two Tricholoma Triterpenoids from the Wild Mushroom Tricholoma pardinum

Two undescribed Tricholoma triterpenoids,namely tricholopardins C(1)and D(2),were isolated from the wild mushroom Tricholoma pardinum.Their structures with absolute configurations were elucidated by spectroscopic methods,as well as the single crystal X-ray diffraction.Compounds 1 and 2 were further obtained by chemical conversions from the known analogues.Compound 1 showed significant cytotoxicity to MCF-7 and Hela cell lines with IC_(50)values of 4.7μM and 9.7μM,respectively.Its mechanism of inducing MCF-7 cell apoptosis was studied briefly.

Chemical looping conversion of methane via Fe_(2)O_(3)-LaFeO_(3)calcined from LaFe-MOF precursor

The effective utilization of natural gas resources is a promising option for the implementation of the"dual carbon"strategy.However,the capture of carbon dioxide with relatively lower concentration after the combustion of natural gas is the crucial step.Fortunately,the lattice oxygen is used for chemical cycle conversion of methane to overcome the shortcomings mentioned above.A method was proposed to synthesize perovskite for methane cycle conversion using metal organic framework as a precursor.Morphology and pore structure of Fe_(2)O_(3)-LaFeO_(3)composite oxides were regulated by precursor synthesis conditions and calcination process.Moreover,the chemical looping conversion performance of methane was evaluated.The results showed that the pure phase precursor of La[Fe(CN)_(6)]·5H_(2)O was synthesized with the specific surface area of 23.91 m^(2)·g^(-1)under the crystallization of 10 h and the pH value of10.5.Fe_(2)O_(3)-LaFeO_(3)was obtained by controlled calcination of La[Fe(CN)_(6)]·5H_(2)O and Fe_(2)O_(3)with variable mass ratio.The selectivity of CO_(2)can reach more than 99%under the optimal parameters of methane chemical looping conversion:m(Fe_(2)O_(3)):m(LaFeO_(3))=2:1,the reaction temperature is 900℃,the lattice oxygen conversion is less than 40%.Fe_(2)O_(3)-LaFeO_(3)still has good phase and structure stability after five redox reaction and regeneration cycles.

Site-specific quantification of 5-carboxylcytosine in DNA by chemical conversion coupled with ligation-based PCR

5-Methylcytosine(5mC)is the most important epigenetic modification in mammals.The active DNA demethylation could be achieved through the ten-eleven translocation(TET)protein-mediated oxidization of 5mC with the generation of 5-hydroxymethylcytosine(5hmC),5-formylcytosine(5fC)and 5-carboxylcytosine(5caC).It has been known that 5mC,5hmC and 5fC play critical roles in modulating gene expression.However,unlike the 5mC,5hmC,and 5fC,the functions of 5caC are still underexplored.Investigation of the functions of 5caC relies on the accurate quantification and localization analysis of 5caC in DNA.In the current study,we developed a method by chemical conversion in conjugation with ligation-based real-time quantitative PCR(qPCR)for the site-specific quantification of 5caC in DNA.This method depends on the selective conversion of 5caC to form dihydrouracil(DHU)by pyridine borane treatment.DHU behaves like thymine and pairs with adenine(DHU-A).Thus,the chemical conversion by pyridine borane leads to the transformation of base paring from 5caC-G to DHU-A,which is utilized to achieve the site-specific detection and quantification of 5caC in DNA.As a proof-of-concept,the developed method was successfully applied in the site-specific quantification of 5caC in synthesized DNA spiked in complex biological samples.The method is rapid,straightforward and cost-effective,and shows promising in promoting the investigation of the functional roles of 5caC in future study.

Corrosion prevention of sintered Nd-Fe-B magnet by a phosphate chemical conversion treatment

The corrosion-resistant coating formed on the surface of sintered Nd-Fe-B magnet by a phosphate chemical conversion(PCC)treatment was studied.The morphology,phase composition and thickness of the coating were investigated by field emission scanning electron microscopy(FE-SEM),energy-dispersive spectrometer(EDS),Fourier transform infrared(FTIR)spectrometer and coating thickness gauge.The corrosion behaviour of the phosphated magnet was evaluated by copper sulphate spot test,neutral salt spray test and electrochemical potentiodynamic polarization experiment.The magnetic properties of the phosphated magnet were also tested.The experimental results show that the phosphate coating has such characteristics as dense granular growth,uniform distribution and thickness range of 10-18μm.The corrosion resistance of the magnet is significantly improved by phosphate coating without losing magnetic properties.Therefore,this highly efficient PCC was a good way for increasing the corrosion resistance of the sintered Nd-Fe-B magnets.

Self-catalytic degradation of iron-bearing chemical conversion coating on magnesium alloys — Influence of Fe content

A number of industrial and biomedical fields,such as hydraulic fracturing balls for gas and petroleum exploitation and implant materials,require Mg alloys with rapid dissolution.An iron-bearing phosphate chemical conversion(PCC)coating with self-catalytic degradation function was fabricated on the Mg alloy AZ31.Surface morphologies,chemical compositions and degradation behaviors of the PCC coating were investigated through FE-SEM,XPS,XRD,FTIR,electrochemical and hydrogen evolution tests.Results indicated that the PCC coating was characterized by iron,its phosphates and hydroxides,amorphous Mg(OH)2 and Mg3-n(HnPO4)2.The self-catalytic degradation effects were predominately concerned with the Fe concentration,chemical composition and microstructure of the PCC coating,which were ascribed to the galvanic corrosion between Fe in the PCC coating and the Mg substrate.The coating with higher Fe content and porous microstructure exhibited a higher degradation rate than that of the AZ31 substrate,while the coating with a trace of Fe and compact surface disclosed a slightly enhanced corrosion resistance for the AZ31 substrate.

Chemical Conversion Film of Mischmetal on Zinc Deposit

A conversion film was obtained on zinc deposit by immersing zinc coated specimens in a mischmetal salt solution. Several factors affecting the anticorrosive efficiency of the conversion film were studied. The suitable technological conditions were established. The composition and the thickness of the conversion film were determined by Auger electron spectroscopy(AES).

Reaction of perfluoroalkanesulfonyl halide——3. The reactions of perfluoroalkanesulfonyl bromide with α,β-un-saturated esters and chemical conversions of the products

The reactions of perfluoroalkanesulfonyl bromide with a,β-unsaturated esters were studied in detail. The reaction products were further converted to a series of perfluoroalkyl-substituted a, β-unsaturated acids or esters, a-amino acids and γ-lactones. A peculiar peak (M+15)was found to appear in the mass spectra of some perfluoroalkyl-substituted methyl esters. It was interpreted to be the result of a CH_3 group transfer to the molecular ion. Magnetic nonequivalence was observed in the ^(19)F NMR spectra of CF_2 group linked to CH_2 in compounds 2t, g and 3t', g which showed a typical AB pattern, and was attributed to the effect of steric hindrance.

Improvement of Bonding Strength of AZ31B Magnesium Alloy by Anodizing and Chromium-free Conversion Treatments

The influences of chromium-free chemical conversion treatment and anodizing treatment on bonding strength of AZ31 magnesium alloy were studied by lap-shear test, SEM and electrochemical methods. Both chemical conversion treatment and anodizing can increase the bonding strength. The anodizing treatment gives higher bonding strength and better corrosion resistance than chemical conversion treatment. The increase of bonding strength by the treatmetlts may be attributed to the uneven surface structures with micro-pores, resulting in increased bonding areas and the embedding effect.

Influence of Solution Composition on Formation of Golden Yellow Rare Earth Conversion Film on Magnesium Alloy

Cerium sulfate was used as main composite in solution to prepare golden yellow chemical conversion film on magnesium alloy. The influence of solution composition on the surface morphology of golden yellow rare earth conversion film on magnesium alloy was studied by means of SEM; potential-time curves in the formation process of rare earth conversion film and the anti-corrosion property of the conversion film were tested through ECT. The results show that, when there is no other component in the solution besides cerium sulfate, yellow film can be obtained on magnesium alloy, but there are some dusts on the film surface and the solution is not stable. The stability of cerium sulfate solution increases with adding hydrogen peroxide, while the film is thin and its color turn light. After adding combination additive containing Al 3+, smooth and compact golden yellow film was obtained on magnesium alloy. The polarization curves tested in 3.5% NaCl solution show that the anti-corrosion property of magnesium alloy is increased obviously by rare earth conversion film, and the film has self-repairing capability in the corrosion process.

Liquid chemical looping gasification of biomass:Thermodynamic analysis on cellulose

Liquid chemical looping technology is an innovation of chemical looping conversion technology.Using liquid metal oxide as the oxygen carrier during gasification process could prolong the service life of oxygen carrier and improve the process efficiency.In this paper,based on Gibbs minimum free energy method,the thermodynamic characteristics of biomass liquid chemical looping gasification were studied.Cellulose and lignin,the main components of biomass,were taken as the research objects.Bismuth oxide and antimony oxide were selected as liquid oxygen carriers.The results showed that when the temperature increased from 600℃to 900℃,the output of H_(2)and CO in the products of cellulose gasification increased from 0.5 and 0.3 kmol to 1.3 and 2.6 kmol respectively.Different ratios of oxygen carriers to gasification raw materials had the best molar ratio.The addition of steam in the system was beneficial to the increase of H_(2)content and the increase of H_(2)/CO molar ratio.Bi_(2)O_(3)and Sb_(2)O_(3)with different mass ratios were used as mixed oxygen carriers.The simulation results showed that the gasification temperature of biomass with different mixed oxygen carriers had the same equilibrium trend products.It could be seen from the results of product distribution that the influence of the mixing ratio of Bi_(2)O_(3)and Sb_(2)O_(3)on gas product distribution could be neglected.These results could provide simulation reference and data basis for subsequent research on liquid chemical looping gasification.

Progress of electroplating and electroless plating on magnesium alloy

The current research processes of electroplating and electroless Ni-P alloy plating on magnesium alloys were reviewed. Theoretically,the reason for difficulties in electroplating and electroless plating on magnesium alloys was given.The zinc immersion, copper immersion,direct electroless Ni-P alloy plating and electroplating and electroless plating on magnesium alloys prepared by chemical conversion coating were presented in detail.Especially,the research development of magnesium alloy AZ91 and AZ31 was discussed briefly.Based on the analysis,the existing problems and future research directions were then given.

ZnO/ZnS core-shell composites for low-temperature-processed perovskite solar cells

Electron transport layers （ETLs） in perovskite solar cells （PSCs） are a key factor to determine the photo- voltaic performance. Herein, we demonstrate preparation of ZnO/ZnS core-shell composites through di- rectly synthesizing ZnS on the ZnO nanoparticles in solution. We confirmed the formation of ZnO/ZnS core-shell composites by the uses of X-ray diffraction patterns and the Fourier transform infrared spec- troscopy. ZnO/ZnS composites exhibit much homogeneous surface morphology as compared with the bare ZnO as revealed in the scanning electronic microscopy. Moreover, the upper shift of conduction band level upon composition of the ZnO/ZnS film results in a better alignment of energy level, which facilitates cas- cade charge extraction and thus improves the current density of perovskite solar cell. The shift of conduc- tion band also improves the voltage of the PSCs. The photoluminescence （PL） spectroscopies measured in both steady and transient states were carried out to characterize the charge extraction at the interface between CH_3NH_3Pbl_3 and the electron transport layers of either ZnO or ZnO/ZnS composite. The ZnO/ZnS composite can more efficiently quench the PL signal of perovskite absorber than bare ZnO resulting in enhanced photocurrent generation in PSCs.

Copper‐doped zinc sulfide nanoframes with three‐dimensional photocatalytic surfaces for enhanced solar driven H_(2) production

Solar‐to‐chemical energy conversion is perceived as one of the most potential solutions to the current energy and environmental crisis,yet requires major scientific endeavors on the development of efficient and sustainable photocatalysts.Remolding the composition and morphology of a semiconductor jointly for the purpose of improving photocatalysis efficiency remains challenging.Herein,we rationally fabricated Cu‐doped ZnS nanoframes via a simple conjunct strategy of substitutional doping,chemical acidic etching,and sulfidation,aiming at enhancing the light utilization and charge separation/transfer efficiency for solar‐light‐driven hydrogen generation.Cu‐doped zeolitic imidazolate framework‐8(ZIF‐8)rhombic dodecahedrons are transformed to hollow Cu‐ZIF‐8 nanoframes converted to Cu‐ZnS nanoframes with three‐dimensional photocatalytic active surfaces via anisotropic chemical etching,which is further converted to Cu‐ZnS nanoframes.By combining the merits of optimal heteroatom doping and frame‐like open architecture,the obtained 1%Cu‐doped ZnS nanoframe exhibits high photocatalytic activity under solar light irradiation with improved hydrogen production rate up to 8.30 mmol h^(–1) g^(–1) and excellent stability in the absence of cocatalysts,which is significantly improved in comparison with those of the bare ZnS and Cu‐ZnS with different morphologies.This work inspired by merging the merits of metal doping and anisotropic chemical etching may shed light on the rational design and fabrication of advanced photocatalysts.

Truth and False-carbon Dioxide Mitigation Technologies

Research progress is required to be enhanced for those storage technologies which store CO_(2)fast and permanently.However,temporary storage technologies importance cannot be denied to immediately reduce global warming and reduce higher CO_(2)concentration in the atmosphere.Continuous CO_(2)storage facilities,semi-batch and batch pilot plants deemed necessary to build for future survival of the earth planet.Membranes can be used to separate CO_(2)from common flue gases followed by mineral carbonation to convert CO_(2)into stable carbonates.Modifications in cement industry,coal fired power plants,fertilizer industries and other chemical process industries appears essential.

Interfaced Ag/Cu nanostructures derived from metal thiolate nanoplates:A highly selective catalyst for electrochemical reduction of CO_(2) to ethanol

Selective reduction of CO_(2) into liquid products such as ethanol through electrochemical catalysis is promising in storing renewable energy in more deliverable chemicals and balancing the carbon footprint in the environment.However,the lack of efficient catalysts for electrochemical CO_(2) reduction reaction(eCO_(2)RR)makes the promise challenging because the formation of C2+alcohols requires coupling reactions between the shallow reduction intermediates and deep reduction intermediates that are usually difficult to form on uniform catalyst surfaces simultaneously with appropriate transient kinetics.Herein,we report a new strategy for synthesizing bimetallic nanostructures with high densities of interfaced Ag/Cu boundaries,which facilitate the coupling reaction of the high‐oxidation‐number intermediates(CO)formed on the Ag surface and the low‐oxidation‐number intermediates(CHx)formed on the Cu surface.The synthesis relies on the electrochemical reduction of bilayered nanoplates made of silver thiolate and copper thiolate,resulting in Ag/Cu nanostructures exposing Ag surface,Cu surface,and the Ag/Cu interfaced boundaries.Balancing the accessible surface areas of the Ag surface,Cu surface,and Ag/Cu boundaries is beneficial for maximizing the activity and selectivity of eCO_(2)RR towards ethanol production.Faradaic efficiency of forming ethanol has been observed as high as about 50%using the Ag/Cu nanostructure catalyst with molar ratio nAg:nCu of 1:1.Moreover,the promoted coupling reaction at the Ag/Cu boundaries and surface modification with thiolate anions significantly suppress the undesirable hydrogen evolution reaction,particularly at high cathodic potentials,maintaining high energy efficiency for eCO_(2)RR.