检索结果-南通市图书馆

Role of nickel alloying on anodic dissolution behavior of zinc in 3.5% NaCl *** II:Potentiodynamic,potentiostatic and galvanostatic studies

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous metals society of China 2015年第9期25卷 3152-3164页

作者： Hany m.ABD EL-LATEEF Abdel-Rahman EL-sAYED Hossnia s.mOHRAN Chemistry Department Faculty of ScienceSohag University

Zinc is common metal used for steel protection from *** addition of further element,such as Ni,can modify the corrosion rate and maintain sacrificial *** anodic dissolution behavior of Zn,Ni and Zn-Ni alloys with different Ni contents（from 0.5% to 10%,mass fraction） in 3.5% Na Cl solution was investigated using potentiodynamic,potentiostatic and galvanostatic *** composition and microstructure of the corrosion layer on Zn,Ni and Zn-Ni alloys were characterized by energy-dispersive X-ray spectroscopy analysis（EDX） and scanning electron microscopy（sEm）.The galvanostatic curves show that the anodic behavior of all investigated electrodes exhibits active/passive transition and the tendency of the alloys to passivity decreases with the increase in Ni content,except for 99.5Zn-0.5Ni *** the potentiodynamic curves exhibit active passive transition only for pure *** analysis reveals the presence of oxides,chlorides and metal hydroxide chloride in corrosion products,and very small cracks are observed for 90Zn-10 Ni alloy compared with that of Zn.

关键词： corrosion NaCl solution Ni content Zn-Ni alloy anodic behavior

There is life after coking for Ir nanocatalyst superlattices

在线全文

学校读者我要写书评

暂无评论

Nano Research 2022年第8期15卷 6969-6976页

作者： Antonio J.martínez-Galera Haojie Guo mariano D.Jiménez-sánchez stefano Franchi Kevin C.Prince José m.Gómez-Rodríguez Departamento de Física de la materia Condensada Universidad Autónoma de MadridMadrid E-28049Spain Instituto Nicolás Cabrera Universidad Autónoma de MadridMadrid E-28049Spain Elettra-sincrotrone Trieste s.C.p.A. in Area Science ParkBasovizza(Trieste)34149Italy Condensed matter Physics Center(IFImAC) Universidad Autónoma de MadridMadrid E-28049Spain

Achieving superior performance of nanoparticle systems is one of the biggest challenges in *** major phenomena,occurring during the reactions,hinder the development of the full potential of nanoparticle catalysts:sintering and contamination with carbon containing species,sometimes called ***,we demonstrate that Ir nanocrystals,arranged into periodic networks on hexagonal boron nitride(h-BN)supports,can be restored without sintering after contamination by persistent *** restoration yields the complete removal of carbon from the nanocrystals,which keep their crystalline structure,allowing operation without *** findings,together with the possibility of fine tuning the nanocrystals size,confer this nanoparticle system a great potential as a testbed to extract key information about catalysis-mediated oxidation *** the case of the CO oxidation by O2,reaction of interest in environmental science and green energy production,the existence of chemical processes not observed before in other nanoparticle systems is demonstrated.

关键词： catalysis coke nanoparticles scanning tunneling microscopy(sTm) X-ray photoemission spectroscopy(XPs)

Effect of Bagasse ash reinforcement on the wear behaviour of Al-Cu-mg/Bagasse ash particulate composites

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta metallurgica sinica(English Letters) 2010年第2期23卷 81-89页

作者： V.s. Aigbodion s.B. Hassan G.B. Nyior T. Ause Department of metallurgical and materials Engineering Ahmadu Bello University

The effect of Bagasse ash （BAp） particle reinforcement on the wear behavior of Al-Cu- mg alloy has been studied. Bagasse ash particles were varied from 0 wt pct-10 wt pct with interval of 2 wt pct. Unlubricated pin-on disc tests were conducted to examine the wear behaviour of the aluminium alloy/Bagasse ash particulate composites. The tests were conducted at varying loads, from 5 to 20 N and sliding speeds of 1.26 m/s, 2.51 m/s, 3.77 m/s and 5.02 m/s for a constant sliding distance of 5000 m. The results showed that the wear rates of the A1-Cu-mg/BAp composites are lower than that of the matrix alloy and further decrease with increasing Bagasse ash content. Wear rate increases as the sliding speed and applied load increase. The microstructure of the worn surface revealed that a large amount of plastic deformation appeared on the surface of the unreinforced alloy. While Bagasse ash reinforced Al-Cu-mg alloy showed worn out surface that is not smooth, and grooves, scratches and parallel lines were observed. A combination of adhesion and delamination wear was in operation. These results show that improve wear properties is achievable for the aluminium alloy by the addition of Bagasse ash particles as reinforcement material.

关键词： Al-Cu-mg alloy Bagasse ash Composites Load sliding speed and Wear

First-principles calculations of structural, electronic, and thermodynamic properties of ZnO_(1-x)s_x alloys

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第10期23卷 394-400页

作者： muhammad Zafar shabbir Ahmed m.shakil m.A.Choudhary simulation Laboratory Department of Physics The Islamia University of Bahawalpur

In this study the pseudo-potential method is used to investigate the structural, electronic, and thermodynamic proper- ties of ZnOl_xsx semiconductor materials. The results show that the electronic properties are found to be improved when calculated by using LDA ~ U functional as compared with local density approximation （LDA）. At various concentrations the ground-state properties are determined for bulk materials ZnO, Zns, and their tertiary alloys in cubic zinc-blende phase. From the results, a minor difference is observed between the lattice parameters from Vegard＇s law and other calculated results, which may be due to the large mismatch between lattice parameters of binary compounds ZnO and Zns. A small deviation in the bulk modulus from linear concentration dependence is also observed for each of these alloys. The ther- modynamic properties, including the phonon contribution to Helmholtz free energy △F, phonon contribution to internal energy △E, and specific iheat at constant-volume Cv, are calculated within quasi-harmonic approximation based on the calculated phonon dispersion relations.

关键词： first principles calculations density functional theory (DFT) semiconductor materials structural,electronic, and thermal properties

Effects of Ni doping on the structural properties and collapse of magnetic ordering in NdFe_(1-x)Ni_xO_3(0.1 ≤x≤ 0.7) orthoferrites

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第2期25卷 496-503页

作者： I.Ahmad m.J.Akhtar m.siddique Department of metallurgy and materials Engineering PIEAS Physics Division PINSTECH

Nd Fe_（1-x）Ni_xO_3（0.1 ≤ x ≤ 0.7） orthoferrites are synthesized by solid state reaction method, and the structural properties of these materials are investigated by employing x-ray diffraction（XRD）, scanning electron microscopy（sEm） and m o¨ssbauer spectroscopy. The orthorhombic structure is observed in all systems; however, with the increase in Ni doping,the increase in tolerance factor and the decrease in the cell volume are observed. Orthorhombic distortion decreases with Ni content increasing up to 50%, while above 50% Ni doping it increases. sEm examination indicates the increases in grain size and intermixing of grains with increase in Ni concentration. Comparison between bulk and theoretical densities shows that in each of all samples porosity is less than 2%. m？ssbauer spectroscopic investigations are performed to explain local structure, Fe oxidation states and collapse of the magnetic ordering. In these samples the Fe oxidation state remains＋3 and there is no considerable increase in hole states observed; however due to mismatch of the ionic radii between Fe^（3＋） and Ni^（3＋）, octahedral distortions, sagging and distribution of hyperfine parameters increase with increase in Ni concentration. The major factors behind the collapse of magnetic ordering in the Ni-doped systems are the weakening of the super-exchange interactions, decrease in the Neel temperature, increase in spin–spin relaxation frequency and high spin to low spin transition.

关键词： ceramic crystal structure electron microscopy mossbauer spectroscopy

Physical properties of hematite α-Fe_2O_3 thin films:application to photoelectrochemical solar cells

在线全文

学校读者我要写书评

暂无评论

Journal of semiconductors 2011年第1期32卷 9-16页

作者： s.s.shinde R.A.Bansode C.H.Bhosale K.Y.Rajpure Electrochemical materials Laboratory Department of Physics Shivaji University

The physical properties and photoelectrochemical characterization of aluminium doped hematite α-Fe2O3, synthesized by spray pyrolysis, have been investigated in regard to solar energy conversion. stable Al-doped iron （Ⅲ） oxide thin films synthesized by a spray pyrolysis technique reveals an oxygen deficiency, and the oxide exhibits n-type conductivity confirmed by anodic photocurrent generation. The preparative parameters have been optimized to obtain good quality thin films which are uniform and well adherent to the substrate. The deposited iron oxide thin films show the single hematite phase with polycrystalline rhombohedral crystal structure with crystallite size 20-40 nm. Optical analysis enabled to point out the increase in direct band-gap energy from 2.2 to 2.25 eV with doping concentration which is attributed to a blue shift. The dielectric constant and dielectric loss are studied as a function of frequency. To understand the conduction mechanism in the films, AC conductivity is measured. The conduction occurs by small polaron hopping through mixed valences Fe2＋/3＋ with an electron mobility 300 K of 1.08 cma/（V.s）. The oe-Fe203 exhibits long term chemical stability in neutral solution and has been characterized photoelectrochemically to assess its activity as a photoanode for various electrolytes using white light to obtain I- V characteristics. The Al-doped hematite exhibited a higher photocurrent response when compared with undoped films achieving a power conversion efficiency of 2.37% at 10 at% Al：Fe2O3 thin films along with fill factor 0.38 in NaOH electrolyte. The flat band potential Vfb （-0.87 VscE） is determined by extrapolating the linear part to C-2 = 0 and the slope of the mott-schottky plot.

关键词： photoelectrochemical hematite spray photoanode

The oscillatory behavior, static and dynamic analyses of a micro/nano gyroscope considering geometric nonlinearities and intermolecular forces

在线全文

学校读者我要写书评

暂无评论

Acta mechanica sinica 2013年第6期29卷 851-863页

作者： m.mojahedi m.T.Ahmadian K.Firoozbakhsh school of mechanical Engineering Sharif University of Technology Center of Excellence in Design Robotics and AutomationDepartment of Mechanical EngineeringSharif University of Technology

The nonlinear dynamic and static deflection of a micro/nano gyroscope under DC voltages and base rotation are investigated. The gyroscope undertakes two cou- pled bending motions along the drive and sense directions and subjected to electrostatic actuations and intermolecular forces. The nonlinear governing equations of motion for the system with the effect of electrostatic force, intermolecular tractions and base rotation are derived using extended Hamilton principle. Under constant voltage, the gyroscope finds the preformed shape. First, the deflection of the rnicro/nano gyroscope under electrostatic forces is obtained by static and dynamic analyses. Furthermore, the static and dynamic in- stability of the system are investigated. Afterward the oscillatory behavior of the pre-deformed micro/nano gyroscope around equilibrium is studied. The effects of intermolecular and nonlinear parameters on the static and dynamic de- flection, natural frequencies and instability of the micro/nano gyroscope are studied. The presented model can be used to exactly determine static and the dynamic behavior of vibratory micro/nano gyroscopes.

关键词： Nano-structures microstructures static dynamic

sorption and Fractionation of a Peat Derived Humic Acid by Kaolinite, montmorillonite, and Goethite

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2009年第1期19卷 21-30页

作者： s. GHOsH WANG Zhen-Yu s. KANG P. C. BHOWmIK B. s. XING Department of Plant Soil and Insect Sciences University of Massachusetts Amherst MA 01003 （USA）. College of Environmental science and Engineering Ocean University of China Qingdao 266100 （China）

sorption of humic acid （HA） on mineral surfaces has a profound interest regarding the fate of hydrophobic organic contaminants （HOCs） and carbon sequestration in soils. The objective of our study is to determine the fractionation behavior of HA upon sorption on mineral surfaces with varying surface properties. HA was coated sequentially on kaolinite （1：1 clay）, montmorillonite （2：1 clay）, and goethite （iron oxide） for four times. The unadsorbed HA fractions were characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy （DRIFT）, and solid state 13C nuclear magnetic resonance spectroscopy （NmR）. The mineral-HA complexes were characterized by DRIFT. Polarity index [（N＋O）/C] revealed higher polarity of the unadsorbed HA fractions after coating on kaolinite, reflecting that relatively higher polarity fractions of HA remain unadsorbed. sorption of aiiphatic alcohol fraction along with carbohydrate was prominent on kaolinite surface. DRIFT results of the unadsorbed HA fractions indicated more sorption of aiiphatic moieties on both kaolinite and montmorillonite. DRIFT results of the unadsorbed HA fractions after sorption on kaolinite and goethite showed the sorption of the proteinaceons fractions of HA. The HA fractions obtained after coating on goethite showed significant sorption of carboxylic moieties. The results mentioned above comply reasonably well with the DRIFT spectra of the minerai-HA complexes. ^13C NmR results showed higher sorption of anomeric C on kaolinite surface. Higher sorption of paraffinic fraction was observed on montmorillonite. NmR data inferred the sorption of carboxylic moieties on goethite surface. Overall, this study showed that aliphatic moieties of HA preferentially sorbed on kaolinite and montmorillonite, while carboxylic functional groups play a significant role in sorption of HA on goethite. The sorbed fractions of HA may modify the mineral surface properties, and thus, the interaction with organic cont

关键词： carboxylic group DRIFT hydrophobic NmR sequential coating

Effect of pH on Crystal size and Photoluminescence Property of ZnO Nanoparticles Prepared by Chemical Precipitation method

在线全文

学校读者我要写书评

暂无评论

Acta metallurgica sinica(English Letters) 2015年第3期28卷 394-404页

作者： m.Jay Chithra m.sathya K.Pushpanathan PG & Research Department of Physics Government Arts College

The effects of pH value on crystal size and optical property of zinc oxide nanoparticles prepared by chemical precipitation method were *** samples have been characterized by means of X-ray diffraction,scanning electron microscopy,ultraviolet-visible spectrometer and photoluminescence *** X-ray diffraction profile,it is found that the particle size of sample increases from 13.8 to 33 nm when the pH value of the solution was increased from 6 to *** study also shows that the particle size increases with pH *** shape of the zinc oxide nanoparticle has been confirmed by the scanning electron microscopy *** recorded ultraviolet-visible spectrum shows excitonic absorption peaks around 381 *** energy gap of the prepared samples has been determined from the ultraviolet-visible absorption spectrum,effective mass model equation and Tauc＇s *** was found that the energy gap of the prepared samples decreases with increase in pH *** recorded blue shift confirmed the quantum confinement effect in the prepared zinc oxide *** spectrum infers that the increase in pH value shifts the ultraviolet-visible emission but not the violet and green emissions.

关键词： Zinc oxide nanoparticles pH value Crystal structure microstructure Energy gap Photoluminescence