Study on the hydrogen storage property of (TiZr0.1)xCr1.7-yFeyMn0.3 (1.05

Jigang Li  Li Xu  Xiaojing Jiang  Xingguo Li 《自然科学进展(英文版)》2018,28(4):470-477

Hydrogen absorption-desorption characteristic of (Ti0.85Zr0.15)1.1Cr1-xMoxMn based alloys with C14 Laves phase

The microstructure and hydrogen absorption-desorption characteristic of (Ti_0.85Zr_0.15)_1.1Cr_1-xMo_xMn (x ?= ?0.05, 0.1, 0.15, 0.2 ?at.%) alloys were investigated. The results showed that the corresponding alloys were determined as a single phase of C14-type Laves structure. With the increase of Mo content, the maximum and reversible hydrogen absorption capacity decreased, the slope factor H_f increased. Among the studied alloys, (Ti_0.85Zr_0.15)_1.1Cr_0.95Mo_0.05Mn had the best overall properties for practical application of hydrogen storage materials. The maximum and reversible hydrogen storage capacity were 1.76 ?wt% and 1.09 ?wt%, the slope factor H_f was 0.51, and its dissociation enthalpy (ΔH_d) and entropy change (ΔS_d) were 23.1 ?kJ ?mol^?1H₂, 93.8J ?K^?1mol^?1H₂ at 303K, respectively. By studying the dissociation pressures of the synthesized metal hydrides, it was found that Mo had a special effect on the dissociation pressure of Ti–Zr–Cr–Mo–Mn alloys. Among the four alloys, (Ti_0.85Zr_0.15)_1.1Cr_0.95Mo_0.05Mn alloy had the largest hydrogen absorption capacity and the fastest hydrogen desorption rate, which can meet the commercialization demand of hydrogen fuel cell hydrogen supply system.     

Centimeter-sized Ti-based bulk metallic glass with high specific strength

Based on the quaternary Ti₄₁Zr₂₅Be₂₉Al₅ glassy alloy with a critical diameter of 7 mm reported not long ago, an obvious enhancement of glass-forming ability (GFA) has been realized in this alloy by the addition of Cu element. A series of (Ti₄₁Zr₂₅Be₂₉Al₅)_100?xCu_x (x=0, 2, 5, 7, 9, 11 at%) glassy alloys have been developed and some of them can be cast into one-centimeter diameter fully glassy rods by copper mold suction casting. It has been found that Cu addition could stabilize the liquid phase and suppress the crystallization, resulting in improvement of the GFA of the alloy. The addition of Cu also increases the compressive strength of the alloy and the (Ti₄₁Zr₂₅Be₂₉Al₅)₉₁Cu₉ glassy alloy possesses a specific strength (defined as yield strength/density) of 4.13×10⁵ Nm/kg, which is much higher than most other reported centimeter-sized bulk metallic glasses. The present result suggests that the newly developed (Ti₄₁Zr₂₅Be₂₉Al₅)₉₁Cu₉ glassy alloy is a good candidate for structural applications because of its good glass-forming ability and mechanical properties.     

Composition design of superhigh strength maraging stainless steels using a cluster model

The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe–Ni–Cr corresponds to the cluster formula [NiFe12]Cr3,where NiFe12is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe12](Cr2Ni) with surplus Ni was then determined to ensure the second phase(Ni3M) precipitation,based on which new multicomponent alloys [(Ni,Cu)16Fe192](Cr32(Ni,Mo,Ti,Nb,Al,V)16) were designed. These alloys were prepared by copper mould suction casting method,then solid-solution treated at 1273 K for 1 h followed by water-quenching,and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni3M precipitation on the martensite,which enhances the strengths of alloys sharply after ageing treatment. Among them,the aged [(Cu4Ni12)Fe192](Cr32(Ni8.5Mo2Ti2Nb0.5Al1V1)) alloy(Fe74.91Ni8.82Cr11.62Mo1.34Ti0.67Nb0.32Al0.19V0.36Cu1.78wt%) has higher tensile strengths with YS?1456 MPa and UTS?1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.     

Hydrogen absorption properties of amorphous (Ni0.6Nb0.4−yTay)100−xZrx membranes

Ni based amorphous materials have great potential as hydrogen purification membranes. In the present work the melt spun(Ni_(0.6)Nb_(0.4-y)Ta_y)_(100-x)Zr_x with y=0, 0.1 and x=20, 30 was studied. The result of X-ray diffraction spectra of the ribbons showed an amorphous nature of the alloys. Heating these ribbons below T 400 °C, even in a hydrogen atmosphere(1-10 bar), the amorphous structure was retained. The crystallization process was characterized by differential thermal analysis and the activation energy of such process was obtained. The hydrogen absorption properties of the samples in their amorphous state were studied by the volumetric method,and the results showed that the addition of Ta did not significantly influence the absorption properties, a clear change of the hydrogen solubility was observed with the variation of the Zr content. The values of the hydrogenation enthalpy changed from ~37 k J/mol for x=30 to ~9 k J/mol for x=20. The analysis of the volumetric data provides the indications about the hydrogen occupation sites during hydrogenation, suggesting that at the beginning of the absorption process the deepest energy levels are occupied, while only shallower energy levels are available at higher hydrogen content, with the available interstitial sites forming a continuum of energy levels.     

A Ti–Zr–Cu–Ni–Co–Fe–Al–Sn amorphous filler metal for improving the strength of Ti–6Al–4V alloy brazing joint

Ti_(50)Zr_(27)Cu_8Ni_4Co_3Fe_2Al_3Sn_3(at%) amorphous filler metal with low Cu and Ni contents in a melt-spun ribbon form was developed for improving mechanical properties of Ti–6Al–4V alloy brazing joint through decreasing brittle intermetallics in the braze zone. Investigation on the crystallization behavior of the multicomponent Ti–Zr–Cu–Ni–Co–Fe–Al–Sn amorphous alloy indicates the high stability of the supercooled liquid against crystallization that favors the formation of amorphous structure. The Ti–6Al–4V joint brazed with this Ti-based amorphous filler metal with low total content of Cu and Ni at 1203K for 900s mainly consists of α-Ti, β-Ti,minor Ti–Zr-rich phase and only a small amount of Ti_3Cu intermetallics, leading to the high shear strength of the joint of about 460 MPa. Multicomponent composition design of amorphous alloys is an effective way of tailoring filler metals for improving the joint strength.     

Synthesis and characterization of spinel Li_(1.05)Cr_(0.1)Mn_(1.9)O_(4-z)F_z as cathode materials for lithium-ion batteries

Samples with the nominal stoichiometry Li_1.05Cr_0.1Mn_1.9O_4−z F _z (z=0, 0.05, 0.1, 0.15, and 0.2) were synthesized via the solid-state reaction method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge/discharge, and slow rate cyclic voltammetry (SSCV) techniques. The results show that the pure spinel phase indexed to Fd3m can be obtained when z=0, 0.05, and 0.1. The substitution of F for O with z≤0.1 contributes to the increase of initial capacity compared with Li_1.05Cr_0.1Mn_1.9O₄ spinels. However, when the F-dopant content is designed to be 0.15 and 0.2, the Li_1.05Cr_0.1Mn_1.9O_4−z F _z samples deliver relatively low capacity and poor cycling properties at 55°C.     

Synthesis of spherical Li1.167Ni0.2Co0.1Mn0.533O2 as cathode material for lithium-ion battery via co-precipitation

xLi2MnO3·(1-x)LiNi0.4Co0.2Mn0.4O2(x=0.5) powders were synthesized from co-precipitated spherical metal carbonate,Ni0.2Co0.1Mn0.533(CO3)x.It has been found that the preparation of metal carbonate was si...     

Addition of IrO2 to RuO2+TiO2 coated anodes and its effect on electrochemical performance of anodes in acid media

Ternary mixed metal oxide coatings with the nominal composition IrxRu(0.6-x)Ti0.4O2(x=0, 0.1, 0.2, 0.3) on the titanium substrate were prepared by thermal decomposition of a chloride precursor mixture. Surface morphology and microstructure of the coatings were investigated by Scanning electron microscopy(SEM), Field emission scanning electron microscopy(FE-SEM) and X-ray diffraction(XRD) analysis. Systematic study of electrochemical properties of these coatings was performed by cyclic voltammetry(CV) and polarization measurements. The corrosion behavior of the coatings was evaluated under accelerated conditions(j=2 A cm-2) in acidic electrolyte. The role of iridium oxide admixture in the change of electrocatalytic activity and stability of Ru0.6Ti0.4O2coating was discussed. Small addition of IrO2can improve the stability of the RuO2+TiO2mixed oxide, while the electrocatalytic activity for oxygen evolution reaction(OER) is decreased. The shift of redox potentials for Ru0.6Ti0.4O2electrode that is slightly activated with IrO2and improvement in the stability can be attributed to the synergetic effect of mixed oxide formation.     

DC-bias and visible light effect on dielectric characteristics of La_(0.5)Cr_(0.5)TiO_(3+δ)

La_(0.5)Cr_(0.5)TiO_(3+δ) ceramic sample was prepared via traditional solid-state reaction route. Frequency and temperature dependence of dielectric permittivity were studied in the range of 10~2~ 10~6 Hz and of 77 ~360 K, respectively. It was observed that extraordinarily high low-frequency dielectric constants appeared at room temperature, and dielectric relaxation peaks shifted to higher temperature with increasing frequency. In the dc-bias studies, it was also found that the dielectric permittivity had obviously dc-bias dependence in low frequency, but independence as the frequency above 14 kHz. Interestingly, the dielectric characteristics of the sample had obvious light dependence at room temperature within the measured frequency range. The results demonstrate that visible light improves the dielectric properties of the ceramic by means of I–V and complex impedance analysis.     

Effect of Co addition on crystallization and magnetic properties of FeSiBPCu alloy

The effects of Co addition on the microstructure,crystallization processes and soft magnetic properties of(Fe1 xCox)83Si4B8P4Cu1(x?0.35,0.5,0.65)alloys were investigated.The experimental results demonstrated that the addition of Co decreased the thermal stability against crystallization of the amorphous phase,and thus improved the heat treatment temperature of this alloy.Fe Co Si BPCu nanocrystalline alloys with a dispersedα0-Fe Co phase were obtained by appropriately annealing the as-quenched ribbons at 763 K for 10 min.Theα0-Fe Co with grains size ranging from 9 to 28 nm was identified in primary crystallization.The coercivity(Hc)markedly increased with increasing x and exhibited a minimum value at x0.35,while the saturation magnetic flux density(Bs)shows a slight decrease.The(Fe0.65Co0.35)83Si4B8P4Cu1nanocrystalline alloy exhibited a high saturation magnetic flux density Bsof 1.68 T,a low coercivity,Hcof 5.4 A/m and a high effective permeability meof 29,000 at 1 k Hz.     

Minor-alloyed Cu-Ni-Si alloys with high hardness and electric conductivity designed by a cluster formula approach

Cu-Ni-Si alloys are widely used due to their good electrical conductivities in combination with high strength and hardness. In the present work, minor-alloying with M =(Cr, Fe, Mo, Zr) was conducted for the objective of further improving their hardness while maintaining their conductivity level. A cluster-plus-glue-atom model was introduced to design the compositions of M-alloyed Cu-Ni-Si alloys, in which an ideal composition formula[(Ni,Si,M)-Cu_(12)]Cu_3(molar proportion) was proposed. To guarantee the complete precipitation of solute elements in fine δ-Ni_2 Si precipitates, the atomic ratio of(Ni,M)/Si was set as 2/1. Thus the designed alloy series of Cu_(93.75)(Ni/Zr)_(3.75)Si_(2.08)(Cr/Fe/Mo)_(0.42)(at%) were arc-melted into ingots under argon atmosphere, and solidsolutioned at 950 ℃ for 1 h plus water quenching and then aged at 450 ℃ for different hours. The experimental results showed that these designed alloys exhibit high hardness(HV 1.7 GPa) and good electrical conductivities(≥ 35% IACS). Specifically, the quinary Cu_(93.75)Ni_(3.54)Si_(2.08)(Cr/Fe)_(0.42)Zr_(0.21) alloys(Cu-3.32 Ni-0.93 Si-0.37(Cr/Fe)-0.30 Zr wt%) possess both a high hardness with HV = 2.5-2.7 GPa, comparable to the highstrength KLFA85 alloy(Cu-3.2 Ni-0.7 Si-1.1 Zn wt%,HV= 2.548 GPa),and a good electrical conductivity(35-36% IACS).     

Synthesis of PbS–K2La2Ti3O10 composite and its photocatalytic activity for hydrogen production

Photocatalyst, lead sulfide (PbS )-intercalated layer perovskite-type compound (K2La2Ti3O10), was synthesized via ion-exchange reaction, butylamine pillaring and sulfuration processes under the assistance of the microwave irradiation. The structure of the photoc atalysts was determined by means of powder X-ray diffraction, scanning electron microscope, ultraviolet- visible diffuse reflection spectra and photoluminescence measu rement. And the photocatalytic activity of the composite compound for hydrogen production was also investigated. The experimental results showed that the intercalation of PbS in the layered space of K2La2Ti3O10 greatly improved the absorption edge and the photocatalytic activity. Hydrogen production of the PbS–K2La2Ti3O10 was 127.19 mmol/(g cat) after 3 h irradiation of ultraviolet light.     

Microstructural characterization and hydrogenation performance of Zr_xV_5Fe(x=3-9) alloys

Zr_xV_5 Fe(x=3,5,7,8,9) alloys were designed to investigate the influence of Zr addition on hydrogenation performance.The alloys were prepared by arc melting and then annealed at 1273 K for 168 h.The results showed that the alloys were composed of α-Zr and C15-ZrV2 phases.The cell volume of C15-ZrV_2 phase firstly increased and then decreased as the content of Zr increased,while the reversed trend was found for the cell volume of α-Zr phase,which was related to the stoichiometric ratio of elements.α-Zr phase distributed in C15-ZrV2 phase matrix in Zr_xV_5 Fe(x=5,7,8,9) alloys,among which Zr7 V5 Fe alloy showed the best distribution.The PCT curves of the alloys under 623 K,673 K and 723 K showed that the hydrogen absorption plateau pressure of the phases in different alloys decreased gradually with the increasing content of Zr.However C15-ZrV2 phase in Zr7 V5 Fe alloy had the lowest hydrogen absorption plateau pressure at room temperature,which was consistent with the change tendency of the corresponding cell volume.Moreover,the kinetic curves of hydrogen absorption at 623 K revealed that Zr7 V5 Fe alloy with the smallest average particle size and the largest phase boundary area showed the fastest hydrogen absorption kinetics.Compared with other four alloys(including St707 alloy),Zr_7 V_5 Fe alloy is more suitable for the use of getter.     

Electroch emical properties and interfacial reactions of LiNi0.5Mn1.5O4-δ nanorods

LiNi0.5Mn1.5O4-δ which possesses a high voltage of 4.7 V vs.Li+/Li and stable structure has been considered as a promising cathode material for high energy Li-ion batteries.In this study,well-crystalli...     

Effect of sintering temperature on the preparation of Cu–Ti3SiC2 metal matrix composite

Ti3SiC2 has the potential to replace graphite as reinforcing particles in Cu matrix composites for applications in brush,electrical contacts and electrode materials.In this paper the fabrication of Cu-Ti3SiC2 metal matrix composites prepared by warm compaction powder metallurgy forming and spark plasma sintering(SPS) was studied.The stability of Ti3SiC2 at different sintering temperatures was also studied.The present experimental results indicate that the reinforcing particles in Cu-Ti3SiC2 composites are not stable at and above 800℃.The decomposition of Ti3SiC2 will lead to the formation of TiC and/or other carbides and TiSi2.If purity is the major concern,the processing and servicing temperatures of the Cu-Ti3SiC2 composite should be limited to 750℃ or lower.The composites prepared by warm compaction forming and SPS sintering at 750℃ have lower density when compared with the composites prepared by SPS sintering at 950℃,but their electrical resistivity values are very close to each other and even lower.     

Size-manipulat ion, compacti on and electrical properties of barium manganite nanorods synthesized via the CHM method

A composite-hydroxide mediated method was employed to synthesize barium manganite nanorods.Diameter,surface smoothness and uniformity of these nanorods were optimized by varying reaction temperature and reaction time.The rods with an average diameter of 200 nm and length of1–1.5 μm were obtained at optimum conditions of 200 1C/48 h.The dielectric study of these rods reveals that they have higher value of dielectric constant at lower frequencies which was attributed to the interfacial and rotational type polarizations.Similarly,the increase in dielectric constant with temperature was attributed to the thermal activation of such polarizations.Furthermore,the analysis of ln(J) vs.E1/2characteristics in the temperature range of 300–400 K shows that possible operative conduction mechanism was of Poole–Frenkel type.The value of βexp was found to be 4.85 times greater than the expected theoretical value of feld lowering coeffcient with an internal feld enhancement factor ofα2 23.5.This high value of βexp may be due to some localized electric felds existing inside the sample.     

Mn0.8Zn0.2Fe2O4 nanoparticulates spinel ferrites:An approach to enhance the antenna field strength for improved magnitude versus offset（MVO）

Electromagnetic signals in deep reservoir are very weak so that it is difficult to predict about the presence of hydrocarbon in seabed logging(SBL) environment.In the present work,Mn0.8Zn0.2Fe2O4 nanoferrites were prepared by a sol–gel technique at different sintering temperatures of450 °C,650 °C and 850 °C to increase the strength of electromagnetic(EM) antenna.XRD,FESEM,Raman spectroscopy and HRTEM were used to analyze the phase,surface morphology and size of the nanoferrites.Magnetic properties of the nanoferrites were also measured using an impedance network analyzer.However,nanoferrites sintered at 850 °C with initial permeability of 200 and Q factor of 50 were used as magnetic feeders with the EM antenna.Lab scale experiments were performed to investigate the effect of magnetic field strength in scale tank.SPSS and MATLAB softwares were also used to confirm the oil presence in scale tank.It was observed that the magnitude of the EM waves for the antenna was increased up to 233%.Finally,the correlation values also show 208% increase in the magnetic field strength with the presence of the oil.Therefore,antenna with Mn0.8Zn0.2Fe2O4 nanoferrites based magnetic feeders can be used for deep water and deep target hydrocarbon exploration.     

Fabrication of fine spongy nanoporous Ag-Au alloys with improved catalysis properties

Fine NP-AgAu(nanoporous AgAu) alloys with spongy structure was fabricated by chemical dealloying from rapidly solidified amorphous precursors Ag_(38.75-x)Cu_(38.75)Si_(22.5)Au_x(x=0, 0.5, 1 and 5). The results indicate that the addition of small content Au in precursor can refine both the ligaments and pores obviously. Among the present components of the precursors, NP-AgAu alloys dealloying from Ag_(37.75)Cu_(38.75)Si_(22.5)Au_1 had the finest spongy structure. The size of pores was 5–10 nm and the grain size of ligaments was 10–20 nm. It also had the highest surface area of 106.83 m~2g~(-1) and the best catalytic activity towards electro-oxidation of formaldehyde with the peak current of 665 mA mg~(-1).     

Preparation of Cu（In,Ga）Se2 thin film by sputtering from Cu（In,Ga）Se2 quaternary target

Cu(In,Ga)Se2 (CIGS) thin films were prepared by directly sputtering Cu(In,Ga)Se2 quaternary target consisting of Cu:In:Ga:Se 25:17.5:7.5:50 at%. The composition and structure of CIGS layers have been investigated after annealing at 550 ℃ under vacuum and a Se-containing atmosphere. The results show that recrystallization of the CIGS thin film occurs and a chalcopyrite structure with a preferred orientation in the (112) direction was obtained. The CIGS thin film annealed under vacuum exhibits a loss of a portion of Se, while the film annealed under Se-containing atmosphere reveals compensation of Se. Several solar cells with three different absorber thicknesses were fabricated using a soda lime glass/Mo/CIGS/CdS/i-ZnO/ZnO:Al/Al grid stack structure. The highest conversion efficiency of 9.65% with an open circuit voltage of 452.42 mV, short circuit current density of 32.16 mA cm2 and fill factor of 66.32% was obtained on a 0.755 cm2 cell area.