Electromagnetic and microwave absorbing properties of FeCoB powder composites

The electromagnetic and microwave absorbing properties of FeCoB powder composites prepared by sin- gle-roller melt-spinning and mechanical milling processes were investigated in this paper. The result indicates that the flake-like powders are obtained. As milling time increases, the flake-like powder particles tend to agglomerate, causing the flake-like powders decrease gradually. The milling time plays an important role in the electromagnetic parameters which relates to the shape and size of the powder particles. The calculation shows that the sample milled for 6 h could achieve an optimal reflection loss of -11.5 dB at 5.8 GHz, with mass fraction of 83 % and a matching thickness of 1.8 mm. The result also indicates that the microwave absorbing properties of the FeCoB powder composites are adjustable by changing their thickness, and can be applied as a thinner microwave absorbing material in the range of 2-8 GHz.

Localized Electrochemical Impedance Spectroscopy Study on the Corrosion Behavior of Fe-Cr Alloy in the Solution with Cl^- and SO_4^(2-)

The corrosion behaviors of Fe-Cr alloy under three different pH values solutions with C1- and SO42- were investigated by localized electrochemical impedance spectroscopy （LEIS） measurements and the corrosion products were analyzed by laser Raman spectrometry. The results show that the high corrosion resistance of Fe-Cr Alloy is attributed to a passive film which is formed more easily when the alloy contains a large quantity of Cr element. However, its corrosion resistance varies in the solutions with different pH values, especially in the initial corrosion. The average impedance values in neutral and alkaline solution are much higher than that in acidic solution because the passive film is more likely to dissolve in the acidic condition. Moreover, the destructive effect of C1- and SO42 ions on the passive film is also demonstrated in corrosion process through the change of the impedance value with the steeping time.

Effect of cerium content on microstructure and hydrogen storage performance of Ti_(24)Cr_(17.5)V_(50)Fe_(8.5)Ce_x(x=0-1.0) alloys

Effect of Ce addition on microstructure and hydrogen storage performance of Ti24Cr17.5V50Fe8.5Cex（x=0, 0.5at.%, 0.8at.% and 1.0at.%） alloys was studied by X-ray diffraction, scanning electron microscopy and P-C-isotherm measurements.The results indicated that Ce addition was a useful way to improve the flatness of the plateau and increase hydrogen storage capacity of Ti24Cr17.5V50Fe8.5 alloy.It was indicated that both homogenization of composition and increase of hydrogen diffusion coefficient were the main reasons for improving the hydrogen storage performance of Ti24Cr17.5V50Fe8.5Cex alloys.

Structural characteristics and mechanism of hydrogen-induced disproportionation of the ZrCo alloy

The intermetallic compound ZrCo was prepared, and its hydrogen-induced disproportionation in hydrogen desorption processes was investigated. The hydrogenation-dehydrogenation thermodynamics of the ZrCo alloy was evaluated by pressure-composition isotherm measurements at different temperatures. The kinetic processes of hydrogen-induced disproportionation at different temperatures under certain pressures were detailedly studied. The disproportionation rate of the ZrCo alloy increased with the increases of temperature and initial hy- drogen pressure under experimental conditions. However, the maximum attainable extent of disproportionation did not change much with an increase in temperature or initial hydrogen pressure. The crystallographic structure analysis of the ZrCo alloy combining with its corre- sponding dehydrogenation kinetic curves under the conditions of an initial hydrogen pressure of 0.2 MPa and a temperature of 723 K indi- cated that the basic process of disproportionation reactions was composed of four stages： rapid dehydrogenation of ZrCoH3, equilibrium of dehydrogenation, simultaneity of dehydrogenation and disproportionation, and completion of disproportionation.

Formation potentials of typical disinfection byproducts and changes of genotoxicity for chlorinated tertiary effluent pretreated by ozone

The effects of ozonation on the formation potential of typical disinfection byproducts （DBPs） and the changes of genotoxicity during post chlorination of tertiary effluent from a sewage treatment plant were investigated. Ozonation enhanced the yields of all detected chlorine DBPs except CHCI3. At a chlorine dose of 5 mg/L, the three brominated THMs and five HAAs increased, while chloroform decreased with the increase of ozone dose from 0 to 10 mg/L （ozone dose in consumption base）. At a chlorine dose of 10 mg/L, the two mixed bromochloro species THMs and two dominant HAAs （DCAA and TCAA） increased firstly and then decreased with the increase of ozone dose, with the turning point approximately occurring at an ozone dose of 5 mg/L. The genotoxicity detected using umu test, on the other hand, was removed from 7 Ixg 4-NQO/L to a negligible level by ozonation under an ozone dose of 5 mg/L. Chlorination could further remove the genotoxicity to some extent. It was found that SUVA （UV absorbance divided by DOC concentration） might be used as an indicative parameter for monitoring the removal of genotoxicity during the oxidation.

Electric and mechanical performances of Bi_(0.5)Sb_(1.5)Te_(3) prepared by spark plasma sintering

Thermoelectric(TE)materials are a kind of functional materials which can be used to convert directly heat energy to electricity or reversely.The thermoelectric effects hold great potential for application in power generation and refrigeration.Bi_(2)Te_(3)and its alloys are well known as best TE materials currently available near room temperature.This paper studies respectively the effects of spark plasma sintering(SPS)on electric performance of Bi_(0.5)Sb_(1.5)Te_(3)thermoelectric materials that are prepared through vacuum melting and ball milling.Through X-ray Diffraction and cold field emission scanning electric microscope s4800,the phase constituent and microstructure of the TE materials samples were analyzed.Electric conductivity and power factor can be improved with the rise of Spark Plasma Sintering temperature(from 300 to 500℃)and pressure(from 30 to 60 MPa),and the density and mechanical strength of Bi_(0.5)Sb_(1.5)Te_(3)thermoelectric material increase,too.

Preparation and hydrogen sorption properties of Mg-Cu-Y-H systems

Mg-xwt.%CuY(x=15,20,25)composites were successfully prepared by reactive mechanical alloying(RMA).X-ray diffraction(XRD)measurement shows that main phases of the as milled composites are MgH_(2) and Mg_(2)Cu,and they converted into Mg and MgCu_(2) after dehydrogenation,respectively.Pressure-Composition-Isotherm(PCI)test shows that the composites exhibit double pressure plateau at each isothermal desorption process.The hydrogen absorption and desorption kinetics of the composites become worse with increasing x content,indicating that Mg-Cu phase has a negative effect on the hydrogen sorption properties of the composites.It is supposed that the good hydrogen sorption properties of the composites attribute to the catalyst effect of yttrium hydride distributed in Mg substrate and the particles size reduction and crystal defects formed by RMA.

Low-temperature performance and high-rate discharge capability of AB_5-type non-stoichiometric hydrogen storage alloy

Low-temperature performance and high-rate discharge capability of AB5-type non-stoichiometric hydrogen storage are studied. X-ray diffraction(XRD),pressure-composition-temperature(PCT) curves and electrochemical impedance spectroscopy(EIS) are applied to characterize the electrochemical properties of ABx(x=4.8,4.9,5.0,5.1,5.2) alloys. The results show that the non-stoichiometric alloys exhibit better electrochemical properties compared with that of the AB5 alloy.

Remote Tracking Gas Molecular via the Standalone-Like Nanosensor-Based Tele-Monitoring System

Remote tracking the variation of air quality in an effective way will be highly helpful to decrease the health risk of human short-and long-term exposures to air pollution.However,high power consumption and poor sensing performance remain the concerned issues,thereby limiting the scale-up in deploying air quality tracking networks.Herein,we report a standalone-like smart device that can remotely track the variation of air pollutants in a power-saving way.Brevity,the created smart device demonstrated satisfactory selectivity(against six kinds of representative exhaust gases or air pollutants),desirable response magnitude(164–100 ppm),and acceptable response/recovery rate(52.0/50.5 s),as well as linear response relationship to NO2.After aging for 2 weeks,the created device exhibited relatively stable sensing performance more than 3 months.Moreover,a photoluminescence-enhanced light fidelity(Li-Fi)telecommunication technique is proposed and the Li-Fi communication distance is significantly extended.Conclusively,our reported standalone-like smart device would sever as a powerful sensing platform to construct high-performance and low-power consumption air quality wireless sensor networks and to prevent air pollutant-induced diseases via a more effective and low-cost approach.

Microstructure and properties of p-type (Bi_(0.25)Sb_(0.75))_2Te_3 fabricated by spark plasma sintering

P-type thermoelectric material(Bi0.25Sb0.75)2Te3 was sintered by spark plasma sintering(SPS) process in the temperature range of 320-420 ℃. The microstructures of sintered materials were found to be well aligned,particularly when sintered at lower sintering temperatures. The electrical conductivity of the material became larger as the sintering temperature increased. The Seebeck coefficient showed a general decreasing tendency with an increase in sintering temperature. In terms of the power factor,the optimum sintering temperature was found to be 380 ℃ for a maximum value of around 2.6 mW/K.

Hydrogen storage properties of Zr_(1-x)Ti_xCo intermetallic compound

The intermetallic compound Zr1-xTixCo was prepared and its suitability for hydrogen storage was investigated. The alloys obtained by magnetic levitation melting with the composition of Zr1-xTixCo (x=0, 0.1, 0.2 and 0.3, at.%) show single cubic phase by X-ray diffraction. A single sloping plateau was observed on each isothermal, and pressure-composition-temperature (PCT) measurement results show that the equilibrium hydrogen desorption pressure of Zr1-xTixCo alloy increases with increasing Ti content. The desorption temperatures for supplying 100 kPa hydrogen are about 665, 642, 621 and 614 K for ZrCo, Zr0.9Ti0.1Co, Zr0.8Ti0.2Co and Zr0.7Ti0.3Co alloy, respectively. Repeated hydrogen absorption and desorption cycles do not generate separated ZrCo, TiCo and ZrH2 phases, indicating that alloys have good thermal and hydrogen stabilization.

Graphite-polypyrrole coated 316L stainless steel as bipolar plates for proton exchange membrane fuel cells

316L stainless steel（SS 316L） is quite attractive as bipolar plates in proton exchange membrane fuel cells（PEMFC）.In this study,graphite-polypyrrole was coated on SS 316L by the method of cyclic voltammetry.The surface morphology and chemical composition of the graphite-polypyrrole composite coating were investigated by scanning electron microscopy（SEM） and X-ray photoelectron spectroscopy（XPS）.A simulated working environment of PEMFC was applied for testing the corrosion properties of graphite-polypyrrole coated SS 316L.The current densities in the simulated PEMFC anode and cathode conditions are around 3×10-9 and 9×10-5 A·cm-2,respectively.In addition,the interfacial contact resistance（ICR） was also investigated.The ICR value of graphite-polypyrrole coated SS 316L is much lower than that of bare SS 316L.Therefore,graphite-polypyrrole coated SS 316L indicates a great potential for the application in PEMFC.

Laves phase hydrogen storage alloys for super-high-pressure metal hydride hydrogen compressors

Ti-Cr- and Ti-Mn-based alloys were prepared to be low- and high-pressure stage metals for a double-stage super-high-pressure metal hydride hydrogen compressor. Their crystallographic characteristics and hydrogen storage properties were investigated. The alloy pair Ti0.9Zr0.1Mn1.4- Cr0.35V0.2Fe0.05/TiCr1.55Mn0.2Fe0.2 was optimized based on the comprehensive performance of the studied alloys. The product hydrogen with a pressure of 100 MPa could be produced from 4 MPa feed gas when hot oil was used as a heat reservoir.

Strontium ferrite powders prepared from oily cold rolling mill sludge by solid-state reaction method

Oily cold rolling mill （CRM） sludge is one of the pollutants emitted by iron and steel plants. Recycling oily CRM sludge can not only reduce pollution but also bring social and environmental benefits. In this study, using oily CRM sludge as sources of iron oxide, the strontium ferrite powders were synthesized in multiple steps including vacuum distillation, magnetic separation, oxidizing roasting, and solidstate reaction. The optimal technological conditions of vacuum distillation and oxidizing roasting were studied carefully. To consider the effects of Fe203/ SrCO3 tool ratio, calcination temperature, milling time and calcination time on magnetic properties of prepared strontium ferrite powders, the orthogonal experimental method was adopted. The maximum saturation magneti- zation （62.6 mA-m2.g-1） of the synthesized strontium ferrite powders was achieved at the Fe203/SrCO3 mol ratio of 6, 5 h milling time, 1250 ~C calcination temperature, and 1 h calcination time. Strontium ferrite powders syn- thesis method not only provides a cheap, high quality raw material for the production of strontium ferrite powders, but also effectively prevents the environmental pollution.

Effects of flaky rare earth oxide additives on the high temperature performance of nickel electrodes

Effects of flaky rare earth oxide additives including Er2O3,Tm2O3,and Yb2O3,Lu2O3 on high temperature and high rate discharge performance of nickel electrodes were investigated.The discharge efficiency at 0.2C reached 96% at 60 oC for electrodes with 1 at.% flaky rare earth oxides.The high rate discharge performance for electrodes with flaky rare earth oxides were improved significantly,for example,discharge efficiency at 5C improved from 50% to 70%.The results showed that the end charging potential of the ...

Tungsten carbide coatings with different binders prepared by low power plasma spray system

Thermal spraying of cermet coatings is widely used for protection of machining parts against wear and corrosion. These coatings consist of WC particles in metal binders such as Co, Cr and Ni. Three kinds of WC powders with different metal binders (Co, NiCr and CoCr) were sprayed by low power plasma spray system on Al-Si-Cu alloy substrate. Fundamental aspects of sprayed cermet coatings, including (i) the effects of binder type on the coating structure, (ii) the hardness and (iii) the microstructure, were investigated. All cermet coatings have the same phase structure such as WC and W2 C. However, the intensities of these phases are different in each coating, mainly due to the difference in solidification rate in each case. Moreover, the hardness measurements are found to be different in each coating. The results show that, binder type has a significant effect on the physical and mechanical properties of the sprayed coatings.

Growth of high quality InSb thin films on GaAs substrates by molecular beam epitaxy method with AlInSb/GaSb as compound buffer layers

A series of In Sb thin films were grown on Ga As substrates by molecular beam epitaxy(MBE).Ga Sb/Al In Sb is used as a compound buffer layer to release the strain caused by the lattice mismatch between the substrate and the epitaxial layer,so as to reduce the system defects.At the same time,the influence of different interface structures of Al In Sb on the surface morphology of buffer layer is explored.The propagation mechanism of defects with the growth of buffer layer is compared and analyzed.The relationship between the quality of In Sb thin films and the structure of buffer layer is summarized.Finally,the growth of high quality In Sb thin films is realized.

Effects of erbium additions on high temperature performance of high power Ni-MH batteries

The Co(Ⅲ)-coated spherical nickel hydroxide powder is optimum as positive electrode of high power Ni-MH battery because of its excellent property. But the performances at high temperature(above 50 ℃) is still not satisfied. In the present paper,the effect of element erbium,used as additive by different methods to prepare positive electrode,on the high temperature performances of the Ni-MH batteries is studied. It is found that the charge acceptance ability of the spherical Ni(OH)2 electrode with element erbium as additive is improved. The discharge capacities of Ni(OH)2 coated with 1%(atomic fraction) Er(OH)3 and mechanically added with 1%(atomic fraction) Er2O3 at 1C are 12.6% and 11.7%,respectively,higher than those of the samples without erbium at 70 ℃.

Fabrication of zirconia separator for nickel-hydrogen battery

Zirconia separator is one of the key materials of nickel-hydrogen battery,thereby zirconia separators are prepared by precursor process in which cellulose textiles immersed with zirconium salts are oxidized,infrared spectra show that viscose textile is an excellent precursor for preparing zirconia separator. The dominant factors in immersion are studied,it is revealed that the solution concentration and the temperature are the most important factors with regard to the area density of zirconia separator. The main reactions of immersed textiles during heat treatment are investigated by TG-DSC. The prepared zirconia separators are analyzed by SEM,XRD and infrared spectroscopy,which lead to kown that the separators maintain the same morphology of precursor textiles and contain little organic components,the main phase of the separators is tetragonal zirconia,the rate and the amount of alkaline absorption are about 5 cm/min and 220% respectively.

Magnetic skyrmions:materials,manipulation,detection,and applications in spintronic devices

Magnetic skyrmions are vortex-like spin configurations that possess nanometric dimensions,topological stability,and high controllability through various external stimuli.Since their first experimental observation in helimagnet MnSi in 2009,magnetic skyrmions have emerged as a highly promising candidate for carrying information in future high-performance,low-energy-consumption,non-volatile information storage,and logical calculation.In this article,we provide a comprehensive review of the progress made in the field of magnetic skyrmions,specifically in materials,manipulation,detection,and application in spintronic devices.Firstly,we introduce several representative skyrmion material systems,including chiral magnets,magnetic thin films,centrosymmetric materials,and Van der Waals materials.We then discuss various methods for manipulating magnetic skyrmions,such as electric current and electric field,as well as detecting them,mainly through electrical means such as the magnetoresistance effect.Furthermore,we explore device applications based on magnetic skyrmions,such as track memory,logic computing,and neuromorphic devices.Finally,we summarize the challenges faced in skyrmion research and provide future perspectives.