Study on the early surface films formed on Mg-Y molten alloy in different atmospheres

In the present study,the non-isothermal early stages of surface oxidation of liquid Mg-1%Y alloy during casting were studied under UPH argon,dry air,and air mixed with protective fluorine-bearing gases.The chemistry and morphology of the surface films were characterized by SEM and EDX analyses.The results indicate a layer of smooth and tightly coherent oxidation film composed of MgO and Y_(2)O_(3) formed on the molten Mg-Y alloy surface with 40-60 nm thickness under dry air.A dendritic/cellular microstructure is clearly visible with Y-rich second phases gathered in surface of the melt and precipitated along the grain/cell boundaries under all gas conditions.Under fluorine-bearing gas mixtures,the surface film was a mixed oxide and fluoride and more even;a flat and folded morphology can be seen under SF6 with oxide as dominated phase and under 1,1,1,2-tetra-fluoroethane,a smooth and compact surface film uniformly covering the inner surface of the bubble with equal oxide and fluoride thickness,which results in a film without any major defects.MgF_(2) phase appears to be the key characteristic of a good protective film.

Can the Prior Cathodic Polarisation Treatment Remove the Air-Formed Surface Film and Is It Necessary for the Potentiodynamic Polarisation Test?

This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisation test results. X-ray photoelectron spectroscopy analyses of fluoride ion-labelled samples show that PCPT cannot remove the surface film completely due to the low reaction rate. Potentiodynamic polarisation tests demonstrate that PCPT with proper operating parameters,-1.0 V SCE for 5 min with subsequent open circuit potential(OCP) stabilisation in this study, is necessary because it can improve the test reproducibility without affecting the corrosion parameters by unifying the initial surface state. However, PCPT with lower potentials, longer time or no OCP stabilisation has significant effects on the electrochemical corrosion parameters due to the hydrogen absorption under the conditions of this study.

Effect of Annealing Temperature on the Formation of Silicides and the Surface Morphologies of PtSi Films

The effect of annealing temperature on the formation of the PtSi phase. distribution of silicides and the surface morphologies of silicides films is investigated by XPS. AFM. It is shown that the phase sequences of the films change from Pt-Pt2Si-PtSi-Si to Pt+Pt2Si+PtSi-PtSi-Si or Pt+Pt2Si+PtSi-PtSi-st with an increase of annealing temperature and the reason for the formation of mixed layers is discussed.

Effects on the Surface Passive Film of Carbon Anode on Cell Behavior

The properties of the films formed in the electrolyte of PC/DME LiClO4 on two kinds of Carbon materials were examined by cathodic polarization measurements. The result suggested that the films on both carbon electrodes have different morphology which resulted in the different cell performance of the two carbon anodes.

A MOLECULAR BEAM INVESTIGATION ON ACTIVATED CHEMISORPTION OF N_2 ON Ni SURFACE AND La FILM

The activated chemisorption of N2 on Ni （poly） and La film was performed on a molecular beam—surface scattering apparatus. Experimental results indicate that the initial sticking probability so increases linearly from 0 to 0.03 as normal component of translational energy of the molecuar beam En increases from 11.00 to 19.91 kcal/mol for N2/Ni system and S0 from 0 to 0. 10 as En from 10. 40 to 19.91 kcal/mol for N2/La system. The apparent activation energy △E are 6.16 kcal/mol and 5.30 kcal/mol for N2/Ni and N2/La systems respectively.

Abnormal IR Spectra of CO Adsorbed on the Surface of Glass Carbon Electrode Modified with Polypyrrole Film with Platinum Microparticles

Abnormal IR spectra of CO adsorbed at the surface of glass carbon electrode modified with polypyrrole film with Pt microparticles are

Acetic acid additive in NaNO_(3)aqueous electrolyte for long-lifespan Mg-air batteries

Mg-air batteries have attracted tremendous attention as a potential next-generation power source for portable electronics and e-transportation due to their remarkable high theoretical volumetric energy density,environmental sustainability,and cost-effectiveness.However,the fast hydrogen evolution reaction(HER)in NaCl-based aqueous electrolytes impairs the performance of Mg-air batteries and leads to poor specific capacity,low energy density,and low utilization.Thus,the conventionally used NaCl solute was proposed to be replaced by NaNO_(3)and acetic acid additive as a corrosion inhibitor,therefore an electrolyte engineering for long-life time Mg-air batteries is reported.The resulting Mg-air batteries based on this optimized electrolyte demonstrate an improved discharge voltage reaching~1.8 V for initial 5 h at a current density of 0.5 mA/cm^(2) and significantly prolonged cells'operational lifetime to over 360 h,in contrast to only~17 h observed in NaCl electrolyte.X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry were employed to analyse the composition of surface film and scanning electron microscopy combined with transmission electron microscopy to clarify the morphology changes of the surface layer as a function of acetic acid addition.The thorough studies of chemical composition and morphology of corrosion products have allowed us to elucidate the working mechanism of Mg anode in this optimized electrolyte for Mg-air batteries.

Surface oxidation study of molten Mg–Al alloys by oxide/metal/oxide sandwich method

The dynamic oxidation of molten Mg–Al alloy was investigated via the oxide/metal/oxide(OMO)sandwich method.The characteristics of sandwiches were explored using optical microscopy,scanning electron microscopy,X-ray energy dispersive spectroscopy,and X-ray diffraction analyses.The results showed the formation of porous oxide films with varying thicknesses from 0.43 to 16.7 mm.Both the measurements and calculations confirmed the literature findings that the oxidation product consists mainly of MgO and Mg Al_(2)O_(4)compounds.The increase in thickness and amount of folds formed on the oxide films implies the significant effect of aluminum in reducing the oxidation resistance of magnesium.

Effect of Al addition on corrosion behavior of high-purity Mg in terms of processing history

In this study,the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history.The results revealed that the corrosion behavior of high-purity Mg-Al alloys is strongly related to changes in the microstructure,including theβphase and Al-Mn or Al-Fe phases,and the protectiveness of the surface film according to the Al content and processing history.In the as-cast alloys,the corrosion rate increased due to the increase ofβphase as the Al content increased,but in the as-extruded alloys,the corrosion rate,which was high due to intermetallic compounds caused by impurities in the low Al alloy,decreased as the Al content increased,and then increased again.This is due to the combined effect of the increase of theβphase and decrease of the impurity effect,and the increase of the dissolved Al content.The results suggest that it is necessary to analyze the effect of alloying elements on the corrosion behavior of pure Mg with information concerning the impurity content and processing history.

Effect of phosphate conversion film on fatigue and corrosion fatigue behavior of an as-rolled Mg–3.08Zn–0.83Al(in wt.%)alloy

Through investigating and comparing the fatigue behavior of an as-rolled Mg–3.08Zn–0.83Al(in wt.%)alloy performing surface phosphate conversion film treatment,it revealed that the determined fatigue strength of surface treated samples at 106 cycles in air was 65 MPa,whereas the fatigue strength was only 35 MPa when tested in 3.5 wt.%NaCl solution.Failure analysis demonstrated that in air,the fatigue crack initiation was mainly dominated by the interaction between the retarding effect of phosphate conversion film on cyclic slips occurring in the underneath substrate.When the matrix cannot endure the accumulated stress concentration due to the irreversibility of cyclic slips,the fatigue crack will preferentially initiate at sample subsurface.Since the phosphate conversion film cracked easily under the cyclic loading and lost its protectiveness on the substrate in 3.5 wt.%NaCl solution,fatigue cracks were preferentially nucleated at the localized corrosion pits.

On Radar Signatures of Upwelling

In studies of upwelling,usually data from infrared and optical sensors is used which provides information on the sea surface temperature(SST)and the chlorophyll-a(Chl-a)concentration.In this paper,we show that also synthetic aperture radars(SAR)images can give valuable contribution to such studies.Upwelling regions become detectable by SAR because they are associated with a reduction of the radar backscatter due to(1)the change of the stability of the air-sea interface or/and(2)the presence of biogenic slicks.Furthermore,the boundary of upwelling regions consists of a line of increased radar backscatter due to the presence of convergent surface flow.

Surface configurations during annealing of sputter-deposited NiTi thin films

SPUTTER-DEPOSITED NiTi thin films are becoming more and more important because of their po-tential applications to the intelligent thin-film systems. The as-deposited NiTi thin films pre-pared by magnetron sputtering are generally amorphous. Because the amorphous NiTi thinfilms cannot show shape memory effect, they should be crystallized under appropriate anneal-

Design and experiment of an upper-side-discharge straw-returning and bundle self-unloading integrated corn residual film recycling machine

Due to the arid climate,flat terrain,certain irrigation sources and high popularization of mechanical harvest in Hexi Irrigation Area of Gansu Province,the widely adopted half film-flat-mulching for corn cultivation faces serious adverse situations,such as high soil compactness,strong film-soil adhesion,significant straw stubble and thick covering accumulation on film.Therefore,a new kind of segmented combination upper-side-discharge straw-returning and bundle self-unloading integrated corn residual film recycling machine was proposed.The scheme was characterized by small volume,low resistance,low complexity and film-impurities twice separation.It is constructed based on the concept of module subsection combination.It was composed of film surface straw cleaning device and the followed residual film recycling machine,in terms of function,any usage requirements of separate and joint operations can be satisfied.The film surface straw cleaning device is responsible for the removal of vertical corn straw and ground covering beyond the film.Although its stubble cutter roller obtuse-angle Lshaped blades paired single-helix arrangement is simple,it runs smoothly and the straw crushing effect is good enough.The layout that upper-side-discharge straw-returning cross-range screw conveyor auger is back and beyond the stubble cutter roller,eliminates the common connecting transportation mechanism between crushing and straw-returning section,so that,the system structure can be optimized and the efficiency has been significantly improved.The integrated residual film recycling machine is composed of triangular pyramid arc two-stage wing(TPATSW)type film lifting shovel,rod-tooth-belt type film-impurities separation device and semi-enclosed shaftless bundle film collector.Among them,TPATSW type film lifting shovel has good corn root whisker cutting effect,low soil contact resistance and small soil congestion area,but its ability to lift film is strong,more importantly,the special segmented configuration of shovel handle and the body,shortens the overall machine length significantly.For semi-enclosed shaftless bundle film collector,however,a new scheme of eight sub-rolls rotate in the same direction,to roll the residual film into a bundle is innovatively adopted.Under its own parameters,the system has the lowest sub-roll rotation speed that can bundle the residual film without shaft inside the film collecting chamber,rather than on any subroll itself.The gap between the sub-rolls can separate impurities for the second time.After the film collection reaches the standard,the film collector can dump the residual film directly,which is simple and efficient.The field orthogonal test data of the prototype show that,the optimal parameter combination is:film lifting shovel earth angle is 30°,its operation depth is 50 mm and the machine forward speed is 5.0 km/h.The average residual film recycling rate and the crushed straw qualified rate under the optimal parameters are 84.9%and 90.3%respectively,which meet the requirements of the national and industrial standards.The research solved the passive situation that there was no matching equipment for the recycle of residual film in corn field in Hexi Irrigation Area effectively.

内层锌锂成核位点和外层富含氟化锂保护组织的混合表面膜提高锂阳极循环性能

锂金属阳极具有高活性,易与电解液反应并产生锂枝晶,因而很难实际应用.本文提出在锂阳极表面构建表面膜的解决方案.将含三氟甲烷磺酸锌(Zn(OTF)_(2))和氟代碳酸乙烯酯(FEC)的溶液滴加到锂阳极表面,形成化学组成与结构独特的表面膜(由内层活性成核位点的锌锂合金和外层起保护作用的氟化锂/聚合物组成的复合膜).内层锌锂合金由金属锂与Zn(OTF)_(2)反应形成,为锂沉积/溶解提供了低极化的成核活性位点;外层氟化锂/聚合物由金属锂与FEC反应形成,对锂阳极底层的锌锂合金和金属锂起保护作用,同时对锂阳极充放电过程中产生的体积变化起缓冲作用.锂-锂对称电池和锂-磷酸亚铁锂全电池充放电测试表明,这种独特的表面膜能够显著提高锂金属阳极的循环稳定性,同时降低沉积/溶解过电位.

Research on ZnO/Si heterojunction solar cells

We put forward an n-ZnO/p-Si heterojunction solar cell model based on AFORS-HET simulations and provide experimental support in this article.ZnO:B(B-doped ZnO) thin films deposited by metal-organic chemical vapor deposition(MOCVD) are planned to act as electrical emitter layer on p-type c-Si substrate for photovoltaic applications.We investigate the effects of thickness,buffer layer,ZnO:B affinity and work function of electrodes on performances of solar cells through computer simulations using AFORS-HET software package.The energy conversion efficiency of the ZnO:B(n)/ZnO/c-Si(p) solar cell can achieve 17.16%(V_(oc):675.8 mV,J_(sc):30.24 mA/cm^2,FF:83.96%) via simulation.On a basis of optimized conditions in simulation,we carry out some experiments,which testify that the ZnO buffer layer of 20 nm contributes to improving performances of solar cells.The influences of growth temperature,thickness and diborane(B_2H_6) flow rates are also discussed.We achieve an appropriate condition for the fabrication of the solar cells using the MOCVD technique.The obtained conversion efficiency reaches2.82%(V_(oc):294.4 mV,J_(sc):26.108 mA/cm^2,FF:36.66%).