Effect of purification treatment on corrosion resistance of Mg-Gd-Y-Zr alloy

Mg-Gd-Y-Zr alloys were purified by filtering purification with and without vacuum. The type, morphology, size distribution and volume fraction of inclusion were analyzed with OM and SEM. The effect of inclusion in Mg-Gd-Y-Zr alloys on anticorrosion ability was investigated with salt spray test and electrochemical test. The results show that the inclusions in the alloy can be removed effectively by filtering purification. The average size of inclusions in the alloys is decreased from 12.7 μm to 2.0 μm and the volume fraction of inclusions is reduced from 0.30% to 0.04%. With the decrease of the size of inclusions in the alloys, the corrosion rate of the alloys decreases dramatically from 38.8 g/（m 2 ·d） to 2.4 g/（m 2 ·d） in the salt spray test. The corrosion potential increases while the corrosion current decreases and the polarization resistance increases in the electrochemical tests, which indicates that the anticorrosion ability is improved.

Influence of Surface Treatment on the Corrosion Resistance of Stainless Steel in Simulated Human Body Environment

In the present research, the influence of chromium enrichment by surface treatment on corrosion resistance of type 316L stainless steel in body environment was investigated. For this study, weight loss test during 18 months, cyclic and liner polarization tests before and after surface treatment and metallography by electron and light microscopy were used to evaluate the effectiveness of the proposed method. In addition, X-ray photoelectron spectroscopy （XPS） method was used to determine the chromium concentration in the surface layer after surface treatment. Results show that the surface treatment has improved corrosion resistance of the type 316L stainless steel in body environment.

Parasitic source resistance at different temperatures for AlGaN/AlN/GaN heterostructure field-effect transistors

The parasitic source resistance（RS） of AlGaN/AlN/GaN heterostructure field-effect transistors（HFETs） is studied in the temperature range 300–500 K. By using the measured RSand both capacitance–voltage（C–V） and current–voltage（I–V） characteristics for the fabricated device at 300, 350, 400, 450, and 500 K, it is found that the polarization Coulomb field（PCF） scattering exhibits a significant impact on RSat the above-mentioned different temperatures. Furthermore, in the AlGaN/AlN/GaN HFETs, the interaction between the additional positive polarization charges underneath the gate contact and the additional negative polarization charges near the source Ohmic contact, which is related to the PCF scattering, is verified during the variable-temperature study of RS.

Corrosion influence on surface appearance and microstructure of compo cast ZA27/SiC_p composites in sodium chloride solution

The influence of corrosion on the surface appearance and microstructure of particulate ZA27/SiCp composites was examined after 30 d immersion in a sodium chloride solution with the access of atmospheric oxygen. The composites with different contents of SiC micro-particles were synthesized via compo casting. Microstructural studies by means of optical microscopy （OM） and scanning electron microscopy （SEM） showed that corrosion occurred in the composite matrices, preferentially in regions of the η phase, rich in zinc. The corrosion processes did not affect the silicon carbide particles incorporated in the matrix alloy. According to the results of electrochemical polarization measurements, an increase in the content of SiC particles in the composite matrice has led to the lower corrosion resistance in the composites.

Study of the Protective Capacity of Cements Regarding Corrosion of Reinforcements under Joint Action of CO2 and Chloride Ions

To examine the protection against reinforcement corrosion due to the combined action of CO2 and chlorides, experimental results of the evaluation of a study with three types of cement are presented. The study was performed observing the behavior of reinforcements which were put in samples submitted to accelerated carbonatation tests and accelerated tests under the effect of chlorides. For the evaluation, intensity corrosion measurements were used using the Pr （polarization resistance） technique, employing these measures as a deterioration indicator. Three types of cement available in the national market were used. The obtained results enabled the classification of the used cements, comparing their profile behaviors in the conditions of the proposed tests.

Study of an Ionic Fluid on the Electrochemical Test of A36 Carbon Steel Ingot

An ionic fluid based on aromatic heterocyclic family constituted by 1,3-diazole groups was investigated. The purpose is to describe their electrochemical characteristics in order to identify the strategy to avoid the A36 carbon steel surface degradation by using electrochemical measurements. We found that the linear polarization resistance reveals an increasing value when the organic unsaturated cyclic ionic fluid was added to the corrosive electrolyte. The polarization curves and Tafel Extrapolation obtained to know the slopes tafel and the inhibitor efficiency from current density (icorr) shows a high efficiency inhibition value.

Corrosion behavior of low alloy steels in a wet–dry acid humid environment

The corrosion behavior of corrosion resistant steel（CRS） in a simulated wet–dry acid humid environment was investigated and compared with carbon steel（CS） using corrosion loss, polarization curves, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, electron probe micro-analysis（EPMA）, N2 adsorption, and X-ray photoelectron spectroscopy（XPS）. The results show that the corrosion kinetics of both steels were closely related to the composition and compactness of the rust, and the electrochemical properties of rusted steel. Small amounts of Cu, Cr, and Ni in CRS increased the amount of amorphous phases and decreased the content of γ-Fe OOH in the rust, resulting in higher compactness and electrochemical stability of the CRS rust. The elements Cu, Cr, and Ni were uniformly distributed in the CRS rust and formed CuFeO2, Cu2O, CrOOH, NiFe2O4, and Ni2O3, which enhanced the corrosion resistance of CRS in the wet–dry acid humid environment.

Influences of Ca and Y Addition on the Microstructure and Corrosion Resistance of Vacuum Die-Cast AZ91 Alloy

The influences of Ca and Y additions on the microstructure and corrosion resistance of vacuum die-cast AZ91 alloys were investigated by optical microscope,electron scanning microscope,weight-loss test,and electrochemical corrosion experiment.The results indicate that the Ca or Ca and Y additions refined the microstructure and decreased the amount of Mg17Al12 phase on grain boundaries in the alloys.Meanwhile,the addition of Ca and Y led to the formation of network Al2 Ca phase and rod-like Al2 Y phase,improved the corrosion resistance of AZ91 magnesium alloy.Compared with AZ91 alloy,the corrosion rate of AZ91–1.5Ca–1.0Y alloy was decreased to 16.2%,and its corrosion current density was dropped by one order of magnitude after immersion in 3.5 wt% NaCl solution for 24 h.

Influence of Microstructures on Polarization Resistance and Hydrogen-Induced Cracking of a Micro-Alloyed Steel Submitted to Different Cooling Rates

The effect of different microstructures on the polarization resistance (Rp) and the hydrogen-induced cracking (HIC) of a micro-alloyed steel austenitized and submitted to different cooling rates was studied.Samples 19.1 x 6 x 2 mm,containing the whole thickness of the plate were extracted from a 20 mm plate and heat treated on a quenching dilatometer,were submitted to Rp and HIC corrosion tests.Both Rp and HIC tests followed as close as possible ASTM G59 and NACE standard TM0284-2003,in this case,modified only with regard to the size of the samples.Steel samples transformed from austenite by a slow cooling (cooling rate of 0.5℃.s-1) showed higher susceptibility to hydrogen-induced cracking,with large cracks in the middle of the sample propagating along segregation bands,corresponding to the centerline of the plate thickness.For cooling rates of 10℃.s-1,only small cracks were found in the matrix and micro cracks nucleated at non-metallic inclusions.For higher cooling rates (40℃.s-1) very few small cracks were detected,linked to non-metallic inclusions.This result suggests that structures formed by polygonal structures and segregation bands (were eutectoid microconstituents predominate) have higher susceptibility to HIC.Structures predominantly formed by acicular ferrite make it difficult to propagate the cracks among non-oriented and interlaced acicular ferrite crystals.Smaller segregation bands containing eutectoid products also help inhibit cracking and crack propagation;segregation bands can function as pipelines for hydrogen diffusion and offer a path of stress concentration for the propagation of cracks,frequently associated to non-metallic inclusions.Polarization resistance essays performed on the steel in theas received condition,prior to any heat treatment,showed larger differences between the regions of the plate,with a considerably lower Rp in the centerline.The austenitization heat treatments followed by cooling rates of 0.5 e 10℃.s-1 made more uniform the corrosion resistance along the thickness of the plate.The effects of heat treatments on the corrosion resistance are probably related to the microconstituent formed,allied to the chemical homogenization of the impurities concentrated on the centerline of the plate.

Improved cell performance and sulphur tolerance using A-site substituted Sr_(2)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)anodes for solid-oxide fuel cells

Solid-oxide fuel cells(SOFCs)offer great promise for producing electricity using a wide variety of fuels such as natural gas,coal gas and gasified carbonaceous solids;however,conventional nickel-based anodes face great challenges due to contaminants in readily available fuels,especially sulphur-containing compounds.Thus,the development of new anode materials that can suppress sulphur poisoning is crucial to the realization of fuel-flexible and cost-effective SOFCs.In this work,La_(0.1)Sr_(1.9)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)(LSFNM)and Pr_(0.1)Sr_(1.9)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)(PSFNM)materials have been synthesized using a sol-gel method in air and investigated as anode mater-ials for SOFCs.Metallic nanoparticle-decorated ceramic anodes were obtained by the reduction of LSFNM and PSFNM in H_(2)at 850℃,forming a Ruddlesden-Popper oxide with exsolved FeNi3 bimetallic nanoparticles.The electrochemical performance of the Sr_(2)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)ceramic anode was greatly enhanced by La doping of A-sites,resulting in a 44%decrease in the polarization resistance in reducing atmosphere.The maximum power densities of Sr-and Mg-doped LaGaO_(3)(LSGM)(300μm)electrolyte-supported single cells with LSFNM as the anode reached 1.371 W cm^(-2)in H_(2)and 1.306 W cm^(-2)in 50 ppm H_(2)S-H_(2)at 850℃.Meanwhile,PSFNM showed improved sulphur tolerance,which could be fully recovered after six cycles from H_(2)to 50 ppm H_(2)S-H_(2)operation.This study indicates that LSFNM and PSFNM are promising high-performance anodes for SOFCs.

Frequency synchronization for TD-LTE-A downlink receiver

A high accuracy frequency synchronization method is proposed for the 3rd generation partnership project （3GPP） long term evolution advanced （LTE-A） downlink receiver in time division duplexing （TDD） mode. In general, cyclic prefix （CP） correlation based fractional frequency offset （FFO） estimation method and primary synchronization signal （PSS） differential correlation based integer frequency offset （IFO） estimation method are applied for LTE-A frequency synchronization. However, the polarity of CP based FFO estimation result may get reversed when system FFO is closer to the edge of frequency estimation range on account of noise interference; PSS based IFO estimation has performance degradation in low signal noise ratio （SNR）. We propose polarity detection aided CP based FFO estimation and frequency domain enhanced differential correlation based IFO estimation to obtain higher accuracy of frequency synchronization. Computer simulation shows that the proposed method greatly outperforms the conventional methods, especially in low SNR scenario.

Removal of Ni（ll） ions from wastewater by micellar enhanced ultrafiltration using mixed surfactants

Ni（II） ions were removed from aqueous waste using micellar enhanced ultrafiltration （MEUF） with a mixture of surfactants. The surfactant mixture was the nonionic surfactant Tween 80 （TW80） mixed with the anionic surfactant sodium dodecyl sulfate （SDS） in different molar ratios ranging from 0.1-1.5. The opera- tional variables of the MEUF process such as pH, applied pressure, surfactant to metal ion ratio and nonionic to ionic surfactant molar ratio （α） were evaluated. Rejection of Ni and TW80 was 99% and 98% respectively whereas that for SDS was 65%. The flux and all resistances （fouling resistance, resistance due to concentration polarization） were measured and calculated for entire range of α respectively. A calculated flux was found to be declined with time, which was mainly attributed to concentration polarization rather than resistance from membrane fouling.

Corrosion property of copperized layer on Zr formed by double glow plasma surface alloying technique

Zr and its alloys have excellent mechanical properties as new structural material,but in specific application environment,its corrosion resistance still needs to be further explored.In this work,double glow plasma surface alloying technique was used for copperizing on pure Zr surface.Besides,X-ray diffraction（XRD）,scanning electron microscope（SEM） and energy dispersion spectrum（EDS） were employed to characterize the samples.Furthermore,research was also conducted on the polarization curve of the samples in different solutions.Copperizing on surface can improve corrosion resistance of pure Zr in 3.5 % Na Cl and 0.5 moláL-1Na OH solutions.Especially in 0.5 moláL-1Na OH solution,the corrosion resistance can achieve significant improvement.However,copperizing has no influence on the improvement of corrosion resistance of pure Zr in 0.5 moláL-1H2SO4 solution.The results may provide new insight into way for improving the corrosion property of zirconium alloys.