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Electrolytic deposition of super-smart composite coating of Zn-V2O5-NbO2 on low carbon steel for defence application

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Defence Technology（防务技术） 2018年第5期14卷 446-450页

作者： O.s.I.Fayomi l.R.Kanyane A.P.I.Popoola s.O.Oyedepo Department of Chemical Metallurgical and Materials EngineeringTshwane University of TechnologyP.M.B.X680PretoriaSouth Africa Department of Mechanical Engineering Covenant UniversityP.M.B 1023OtaNigeria

Despite the massive usages of low carbon steel in automobile for engineering components, its corrosion and high friction coefficient in aggressive environment make it limited in service. This paper is aimed at modifying low carbon steel structural component with thin film composite for enhanced mechanical and corrosion properties. The steel structure was electrodeposited with Zn-V_2 O_5 and embedded with varied NbO_2 weight concentration of 6-12 wt % based electrolyte. scanning electron microscope(sem) and high optical microscope was used to study the microstructural evolution of the fabricated coatings. The thermal stability of the fabricated coatings was studied in an isothermal furnace at 300 ℃ and 600 ℃ and further characterized using a high tech optical microscope. Potentiodynamic polarization technique was used to investigate the corrosion behavior of the composites in 3.65% NaCl. From the result, the effect of NbO_2 on Zn-V_2 O_5-NbO_2 was massive with improved crystal grain within the coatings lattices. The coating possesses strong metallurgical bonding and good corrosion resistance properties of about 0.315 mm/yr corrosion rate compare to 4.1 mm/yr of as-received sample. No doubt the impact of thermal shock on the resilient characteristics of the composite coating was moderate owing to the stable adherent properties of the deposited coatings.

关键词： Electrodeposition low carbon steel Micro-hardness Thermal stability corrosion behavior Rare earth metal(REM)

Hazardous elements and amorphous nanoparticles in historical estuary coal mining area

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Geoscience Frontiers 2019年第3期10卷 927-939页

作者： Ana l.Duarte Kátia DaBoit Marcos l.s.Oliveira Elba C.Teixeira Ismael l.schneider luis F.O.silva Department of Civil and Environmental Universidad de la Costa Faculdade Meridional IMED FEPAM-Funda■o Estadual de Prote■o Ambiental Henrique luis Roessler

In Brazil, intense coal exploitation activities have led to environmental deterioration, including soil mortification, water contamination, loss of ecosystem, and atmospheric contamination. In addition,considerable quantities of sulfur-rich residues are left behind in the mining area; these residues pose grave environmental issues as they undergo sulfide oxidation reactions. When sulfur oxides come in contact with water, extreme acid leachate is produced with great proportions of sulfate, and hazardous elements(HEs), which are identified as coal drainage(CMD). CMD is an environmental pollution challenge, particularly in countries with historic or active coal mines. To prevent CMD formation or its migration, the source must be controlled; however, this may not be feasible at many locations. In such scenarios, the mine water should be collected, treated, and discharged. In this study, data from 2005 to2010 was gathered on the geochemistry of 11 CMD discharges from ten different mines. There are several concerns and questions on the formation of nanominerals in mine acid drainage and on their reactions and interfaces. The detailed mineralogical and geochemical data presented in this paper were derived from previous studies on the coal mine areas in Brazil. Oxyhydroxides, sulfates, and nanoparticles in these areas possibly go through structural transformations depending on their size and formation conditions. The geochemistry of Fe-precipitates(such as jarosite, goethite, and hematite) existent in the CMD-generating coal areas and those that could be considered as a potential source of hazardous elements(HEs)(e.g., Cr) were also studied because these precipitates are relatively stable in extremely low pH conditions. To simplify and improve poorly ordered iron, strontium, and aluminum phase characterization, field emission scanning electron microscopy(FE-sem), high-resolution transmission electron microscopy(HR-TEM), micro-Raman spectroscopy, and X-ray diffraction(XRD) a

关键词： Brazilian coal mining Environmental impacts Minerals

Influence of ZrO_(2)/siO_(2) nanomaterial incorporation on the properties of PEO layers on Mg-Mn-Ce alloy

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Journal of Magnesium and Alloys 2022年第2期10卷 552-566页

作者： D.V.Mashtalyar I.M.Imshinetskiy K.V.Nadaraia A.s.Gnedenkov s.l.sinebryukhov A.Yu.Ustinov A.V.samokhin s.V.Gnedenkov Institute of Chemistry Far Eastern BranchRussian Academy of SciencesVladivostok 690022Russian Federation Far Eastern Federal University Vladivostok 690922Russian Federation A.A.Baikov Institute of Metallurgy and Materials science Russian Academy of SciencesMoscow 119991Russian Federation

The properties of coatings formed on the MA8 magnesium alloy by the plasma electrolytic oxidation in electrolytes containing mechanical mixture of zirconia and silica nanoparticles in concentrations of 2,4 and 6 g/l have been *** has been established by sem,EDs,and XPs that ZrO_(2)/siO_(2)nanoparticles successfully were incorporated into the ***-Raman spectroscopy showed the presence of ZrO_(2)in tetragonal and monoclinic forms in the PEO-coating composition as well as Mg_(2)siO_(4) in tetrahedral configuration uniformly distributed in the outer part of *** coatings significantly reduce corrosion current density in comparison with bare Mg alloy and base PEOlayer(from 2.4×10^(–7)A/cm^(2) for base PEO layer to 0.7×10^(–7)A/cm^(2) for coatings with nanoparticles).It has been found that the presence of solid nanoparticles in the composition of coating has a positive effect on their hardness(this parameter was increased from 2.1±0.3 GPa to 3.1±0.4 GPa)and wearproof(the wear was reduced from(4.3±0.4)×10^(–5)mm^(3)/(N×m)to(3.5±0.2)×10^(–5)mm^(3)/(N×m)).

关键词： Plasma electrolytic oxidation Composite coatings Nanoparticles Zirconia silica Protective coatings

CORROsION BEHAVIORs OF THE EXPOsED sIDE AND UNDERsIDE OF lOW AllOY WEATHERING sTEEl IN QINGDAO AND WANNING FOR 18 MONTHs

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Acta Metallurgica sinica(English letters) 2008年第6期21卷 425-436页

作者： s. T. Wang s. W. Yang K. W. Gao X.l. He Department of Materials Physics and Chemistry University of Science and Technology Beijing Beijing 100083 China

For 18 months, a newly developed low alloy weathering steel has been exposed in two coastal sites （Qingdao in the north China, Wanning in the south China）. The different corrosion behaviors of the exposed side and the underside of the samples were characterized by X-ray diffraetion （XRD）, polarization curve, electrochemical impedance spectroscopy （EIs）, scanning electron microscopy （sem）, and N2 adsorption approach. It was found that the samples exhibited higher corrosion rate in Wanning than that in Qingdao. The underside of the samples corrodes more seriously than the exposed side in Qingdao, whereas the result in Wanning is just the reverse. The protection performance of rust layers mainly depends on its compactness and the enrichment of Cu and Cr is a secondary causation. The different compactness of rust layers in the exposed side and the underside originates from different corrosion conditions of the two sides.

关键词： low alloy weathering steel Temperate marine environment subtropical marine environment Exposed side Underside side

Formation of a cerium conversion coating on magnesium alloy using ascorbic acid as *** and anticorrosive properties of the formed films

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Journal of Magnesium and Alloys 2016年第4期4卷 278-285页

作者： A.P.loperena I.l.lehr s.B.saidman Instituto de Ingeniería Electroquímica y Corrosión(INIEC) Departamento de Ingeniería QuímicaUniversidad Nacional del SurAv.Alem 12538000 Bahía BlancaArgentina

Cerium-based conversion coatings were formed on AZ91D magnesium alloy by immersion of the substrate in solutions containing Ce(NO_(3))_(3),H_(2)O_(2) and ascorbic acid(HAsc).The characterisation of the films was performed by electrochemical and surface analysis techniques such as sem,EDs,X-ray diffraction and X-ray photoelectron spectroscopy(XPs).The degree of corrosion protection achieved was evaluated in simulated physiological solution by the open circuit potential monitoring,polarisation techniques and electrochemical impedance spectroscopy(EIs).The presence of HAsc in the conversion solution causes changes in the morphology,adherence and anticorrosive performance of the *** improvement in the corrosion resistance is closely associated with the corrosion inhibition properties of HAsc.

关键词： Cerium coatings AZ91D alloy Ascorbic acid Anticorrosive properties

synthesis of silver Nanoparticles from Honeybees and Its Antibacterial Potential

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Open Journal of Medical Microbiology 2024年第1期14卷 77-92页

作者： Akamu J. Ewunkem Niore’s Johnson A’lyiha F. Beard Ilunga Tshimanga Brittany Justice Jeffery Meixner Department of Biological sciences Winston Salem State University Winston Salem NC USA Department of Clinical science and laboratory science Winston Salem State University Winston Salem NC USA

Honeybees (Apis mellifera) are important pollinators of flowering plants and agricultural crops contributing annually to billions of dollars in revenues to crop production. Honeybees have an average lifespan between 8 weeks to 5 years. Dead honeybees are abundantly available in beehives and can be utilized as an alternative source to synthesize nanoparticles. In recent years, biologically synthesized nanoparticles have been preferred over their chemical counterparts. However, honeybee-based-green synthesis of nanoparticles has not been explored yet. Herein, we report the biosynthesis of silver nanoparticles from honeybees and its antibacterial activity. The synthesis of silver nanoparticles was monitored visually through a gradual change in color. Furthermore, the biosynthesized nanoparticles were confirmed and characterized by UV-visible spectroscopy. scanning Electron Microscope was utilized to analyze the average size and morphologies of the biosynthesized nanoparticles. subsequently, the antibacterial potential of the biosynthesized silver nanoparticles was tested against selected Gram-positive and Gram-negative bacterial strains. It was found that a distinct color change from yellow to brown in the reaction solution suggested the formation of silver nanoparticles. The biosynthesized nanoparticles exhibited absorption maxima at 430 nm. The sem analysis confirmed the spherical and cuboidal shape of the biosynthesized silver nanoparticles with a size range between 10 - 40 nm. Furthermore, the biosynthesized silver nanoparticles exhibited strong antimicrobial potential against tested Gram-positive and Gram-negative bacteria strains by aggregating on the cell surface. This study showcases the biomedical and agricultural applications of biosynthesized silver nanoparticles from honeybee wings. .

关键词： Honeybee Bacteria Green synthesis Nanoparticles Antimicrobial

Eco-friendly reduced graphene oxide for the determination of mycophenolate mofetil in pharmaceutical formulations

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Journal of Pharmaceutical Analysis 2018年第2期8卷 131-137页

作者： Prashanth s.Narayan Nagappa l.Teradal seetharamappa Jaldappagari Ashis K.satpati Department of Chemistry Karnatak University Analytical Chemistry Division Bhabha Atomic Research Centre

Graphene oxide(GO) was synthesized and characterized by scanning electron microscopy(sem), energy dispersive X-ray spectroscopy(EDX), atomic force microscopy(AFM), X-ray diffraction(XRD), Fourier transform-infrared spectroscopy(FT-IR) and thermogravimetric analysis(TGA). GO was then electrochemically reduced and used for electrochemical study of mycophenolate mofetil(MMF). The electrochemically reduced graphene oxide(ERGO) film on glassy carbon electrode(GCE) showed enhanced peak current for electrooxidation of MMF. MMF exhibited two irreversible oxidation peaks at 0.84 V(peak a_1)and 1.1 V(peak a_2). Effects of accumulation time, pH and scan rate were studied and various electrochemical parameters were calculated. A differential pulse voltammetric method was developed for the determination of MMF in bulk samples and pharmaceutical formulations. linear relationship was observed between the peak current and concentration of MMF in the range of 40 nM–15 μM with a limit of detection of 11.3 nM. The proposed method is simple, sensitive and inexpensive and, hence, could be readily adopted in clinical and quality control laboratories.

关键词： Mycophenolate mofetil Electroreduced graphene oxide Electrochemical sensor Analytical application

MICROsTRUCTURAl CHARACTERIsTICs AssOCIATED WITH HIGH- sTRAIN-RATE PlAsTIC DEFORMATION IN THE ElECTROFORMED COPPER lINER OF sHAPED CHARGEs

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Acta Metallurgica sinica(English letters) 2005年第5期18卷 620-626页

作者： A.l. Fan W.H. Tian Q. suns B.s. Wang Department of Materials Physics and Chemistry University of Science and Technology Beijing Beijing 100083 China Taiyuan University of science and Technology Taiyuan 030024 China 210 Institute The Chinese Ordnance Industry Institute Beijing 100081 China

The microstructures of electroformed copper liners of shaped charges that had undergone high-strain-rate deformation were observed by optical microscopy （OM） and scanning electron microscopy （sem）. Meanwhile, the orientation distribution of the grains in the recovered jet was examined by electron backscattering Kikuchi pattern （EBsP） technique. EBsP analysis reveals that the fibrous texture observed in the as-electroformed copper liners disappeared after explosive detonation deformation. OM observation shows that the microstructure evolves system- atically from the jet center to its perimeter during cooling from high temperatures after explosive detonation deformation. This microstructural characteristic is similar to that of solidification, i.e. there exist equiaxed grains in the center of the jet and significant columnar grains around the equiaxed grains. The result reveals that there is melting-related phenomenon in the jet center. Corresponding microhardness variations from the jet center to its perimeter is also determined. All the phenomena can be explained by a strong gradient of temperature across the section of the jet during plastic deformation at high-strain-rate.

关键词： jetting electroformation microstructure hardness,ultra-high strain rate deformation

MICROsTRUCTURAl sTUDIEs OF FRICTION sTIR WElDED AZ31 MAGNEsIUM AllOY

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Acta Metallurgica sinica(English letters) 2004年第5期17卷 747-753页

作者： H.Zhang s.B.lin l.Wu J.C.Feng stateKeylab.ofAdvancedWeldingProductionTechnology HarbinInstituteofTechnologyHarbin150001China

Friction stir welding achieves the weld in solid phase by locally introducing frictional heating and plastic flow arising from rotation of the welding tool, which results in changes in the local microstructure of magnesium alloy. The purpose in the paper is to study the microstructures of friction stir welded AZ31 magnesium alloy. Residual microstructures, including dynamic re-crystallization zone and nugget structures have been systematically investigated utilizing optical microscopy (OM), scanning electric microscopy (sem), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDs), X-ray diffraction (XRD) and micro-hardness. AZ31 magnesium alloy has been successfully friction stir welded and exhibits the variations of microstructure including dynamically recrystallized, equaxied grains in the weld nugget. Residual hardness in the nugget was found slightly lower than the parent but not too obvious.

关键词： friction stir welding AZ31magnesium alloy weld nugget thermo- mechanically affected zone microstructure