Influence of thermomechanical treatment on recrystallization and softening resistance of Cu-6.5Fe-0.3Mg alloy

The recrystallization and softening resistance of a Cu-6.5Fe-0.3Mg(mass fraction,%)alloy prepared by Process 1(cold rolling heat treatment)and Process 2(hot/cold rolling heat treatment)were studied using Vickers hardness tests,tensile tests,scanning electron microscopy and transmission electron microscopy.The softening temperature,hardness and tensile strength of the alloy prepared by Process 2 were 110°C,HV 15 and 114 MPa higher,respectively,than those of the alloy prepared by Process 1 after aging at 300°C.The recrystallization activation energy of the alloys prepared by Process 1 and Process 2 were 72.83 and 98.11 kJ/mol,respectively.The pinning effects of the precipitates of the two alloys on grain boundaries and dislocations were basically the same.The softening mechanism was mainly attributed to the loss of dislocation strengthening.The higher Fe fiber density inhibited the average free migration path of dislocations and grain boundary migration in the alloy,which was the main reason for higher softening temperature of the alloy prepared by Process 2.

Formation mechanism of inherent spatial heterogeneity of microstructure and mechanical properties of NiTi SMA prepared by laser directed energy deposition

Ni51Ti49 at.%bulk was additively manufactured by laser-directed energy deposition(DED)to reveal the microstructure evolution,phase distribution,and mechanical properties.It is found that the localized remelting,reheating,and heat accumulation during DED leads to the spatial heterogeneous distribution of columnar crystal and equiaxed crystal,a gradient distribution of Ni4Ti3 precipitates along the building direction,and preferential formation of Ni4Ti3 precipitates in the columnar zone.The austenite transformation finish temperature(Af)varies from-12.65℃(Z=33 mm)to 60.35℃(Z=10 mm),corresponding to tensile yield strength(σ0.2)changed from 120±30 MPa to 570±20 MPa,and functional properties changed from shape memory effect to superelasticity at room temperature.The sample in the Z=20.4 mm height has the best plasticity of 9.6%and the best recoverable strain of 4.2%.This work provided insights and guidelines for the spatial characterization of DEDed NiTi.

Efficient and stable PtFe alloy catalyst for electrocatalytic methanol oxidation with high resistance to CO

Direct methanol fuel cells(DMFC) are widely considered to be an ideal green energy conversion device but their widespread applications are limited by the high price of the Pt-based catalysts and the instability in terms of surface CO toxicity in long-term operation.Herein,the PtFe alloy nanoparticles(NPs) with small particle size(~4.12 nm) supported on carbon black catalysts with different Pt/Fe atomic ratios(Pt_(1)Fe_(2)/C,Pt_(3)Fe_(4)/C,Pt_(1)Fe_(1)/C,and Pt_(2)Fe_(1)/C) are successfully prepared for enhanced anti-CO poisoning during methanol oxidation reaction(MOR).The optimal atomic ratio of Pt/Fe for the MOR is 1:2,and the mass activity of Pt_(1)Fe_(2)/C(5.40 A mg_(Pt)^(-1)) is 13.5 times higher than that of conventional commercial Pt/C(Pt/C-JM)(0.40 A mg_(Pt)^(-1)).The introduction of Fe into the Pt lattice forms the PtFe alloy phase,and the electron density of Pt is reduced after forming the PtFe alloy.In-situ Fourier transform infrared results indicate that the addition of oxyphilic metal Fe has reduced the adsorption of reactant molecules on Pt during the MOR.The doping of Fe atoms helps to desorb toxic intermediates and regenerate Pt active sites,promoting the cleavage of C-O bonds with good selectivity of CO_(2)(58.1%).Moreover,the Pt_(1)Fe_(2)/C catalyst exhibits higher CO tolerance,methanol electrooxidation activity,and long-term stability than other Pt_(x)Fe_(y)/C catalysts.

Recovery of rare earth element ytterbium(Ⅲ) by dried powdered biomass of spirulina: Adsorption isotherm, kinetic and thermodynamic study

The adsorption characteristics and mechanisms of spirulina powder were investigated when it was used as adsorbent to recover ytterbium(Ⅲ) from wastewater solution. Surface structure and element valence of the adsorbent were analyzed by SEM and XPS for the exploring of its adsorption mechanism for ytterbium(Ⅲ). The adsorption characteristics of ytterbium(Ⅲ) on spirulina powder was analyzed through assessing adsorption isotherm, kinetics and thermodynamic models. The adsorption isotherm data were best explained by Langmuir model, and the adsorption capacity of spirulina powder for ytterbium(Ⅲ) was 72.46 mg/g when adsorption temperature was 318 K. The kinetic experiment results showed that the pseudo-second order kinetic model can better simulate the adsorption process of spirulina powder to ytterbium(Ⅲ), indicating that the rate-controlling step was chemical adsorption. Spirulina can be an efficient and economical ytterbium(Ⅲ) recycling material, because it showed good adsorption stability and reusability from the adsorption-desorption cycle experiment results.

Effects of Fe content on microstructure and properties of Cu−Fe alloy

Cu−Fe alloys with different Fe contents were prepared by vacuum hot pressing.After hot rolling and aging treatment,the effects of Fe content on microstructure,mechanical properties and electrical conductivity of Cu−Fe alloys were studied.The results show that,when w(Fe)<60%,the dynamic recrystallization extent of both Cu phase and Fe phase increases.When w(Fe)≥60%,Cu phase is uniformly distributed into the Fe phase and the deformation of alloy is more uniform.With the increase of the Fe content,the tensile strength of Cu−5wt.%Fe alloy increases from 305 MPa to 736 MPa of Cu−70wt.%Fe alloy,the elongation decreases from 23%to 17%and the electrical conductivity decreases from 31%IACS to 19%IACS.These results provide a guidance for the composition and processing design of Cu−Fe alloys.

Complexation extraction of scheelite and transformation behaviour of tungsten-containing phase using H_(2)SO_(4) solution with H_(2)C_(2)O_(4) as complexing agent

The extraction of tungsten from scheelite was carried out using a sulfuric acid solution with oxalic acid as the chelating agent.Tungsten was obtained in the form of highly soluble hydrogen aqua oxalato tungstate H_(2)[WO_(3)(C_(2)O_(4))·H_(2)O] during the leaching process,while calcium remained in the residue as calcium sulfate dihydrate(CaSO4·2H2O).About 99.2%of the tungsten was leached at 70℃,1.5 mol/L sulfuric acid,1 mol/L oxalic acid,a liquid/solid ratio of 25:1(mL/g),an oxalic acid to sulfuric acid molar ratio of 1:1,a stirring speed of 300 r/min and a leaching time of 2 h.H_(2)[WO_(3)(C_(2)O_(4))·H_(2)O]was thermally decomposed into tungstic acid(H_(2)WO_(4)),and tungsten trioxide(WO_(3))was directly produced by calcining H_(2)WO_(4) at 700℃ for 2 h.The surface chemical reaction was determined to be the controlling step during tungsten leaching,and the apparent activation energy was calculated to be 51.43 kJ/mol.

Effect of crystal orientations and precipitates on corrosion behavior of Al-Cu-Li single crystals

The effect of the crystal orientations and precipitates on the corrosion behavior of Al-Cu-Li single crystals was studied by scanning electron microscopy, transmission electron microscopy, optical microscopy, immersion testing in exfoliation corrosion solution, and electrochemical testing. The results show that the corrosion rates of different orientations of the aged Al-Cu-Li alloy increase in the order of (001) 1 phase deteriorated the corrosion resistance of the Al-Cu-Li alloy, and the degree of deterioration differed in different crystal plane orientations. The severe localized corrosion of the aged alloy propagates along the crystallography and extends along the {111}Alplane in the form of corrosion bands.

Modeling and simulation of neodymium oxide dissolution in molten fluorides

By combining the mass transfer mechanism of neodymium oxide with dissolution kinetics,a solution strategy for neodymium oxide dissolution was proposed to predict the dissolved neodymium oxide concentration during the process under complex flow field conditions.The factors affecting neodymium oxide dissolution were analyzed in detail.Aiming at the pulse feeding and continuous feeding modes in industrial practice,the characteristics of the dissolution process under the two feeding modes were compared.Simulation results showed that pulse feeding took shorter time to distribute evenly than continuous feeding.Finally,the dissolution time of single-particle neodymium oxide under static flow field conditions was compared with the literature results.Except for only one set of data with a maximum error of about 10%,the errors of other data are all within 5%.

Preparation and Electrorheological Response of PAL/TiO_(2)/PANI Nanorods

Using palygorskite(PAL)as template,the PAL/TiO_(2)/PANI nano-rods were synthesized by heterogeneous precipitation and in-situ polymerization.The synthesized PAL/TiO_(2)/PANI nanorods were used as a novel electrorheological(ER)fluid by mixing with silicone oil,which showed excellent ER effect.The yield stress of the PAL/TiO_(2)/PANI based ER fluid(15 vol%)reached 8.8 kPa under 4 kV mm^(−1) electric field.The dynamic shear stress of the PAL/TiO_(2)/PANI based ER fluid could maintain a stable level in the shear rate range of 0.1–100 s^(−1).Furthermore,the PAL/TiO_(2)/PANI ER fluid exhibited excellent suspension stability.

Effect of cerium alloying on microstructure,texture and mechanical properties of magnesium during cold-rolling process

Hot-extrusion and cold-rolling were conducted on Mg-Ce binary alloys to explore the effect of cerium(Ce)on microstructure,texture and mechanical properties of Mg alloys.The addition of Ce results in significant grain refinement both in as-cast and hot-extruded samples.The basal texture is also weakened after extrusion and an inclined basal texture is formed with Ce addition.The strength and elongation of the Mg-Ce alloys are improved simultaneously due to such grain refinement and texture weakening effect.After cold-rolling,plenty of twins are found in the pure Mg and AZ31 plates while grains in the Mg-0.3Ce plate deform more uniformly without lamellar twin structure.Furthermore,Mg-0.3Ce alloys own strong and continuous strain hardening because Ce atoms and Mg-Ce precipitated phases serve as obstacles for dislocation slip.

Attaining synergetic equilibrium of electrical conductivity and tensile strength in GQDs@GN/Cu composites through multi-scale intragranular and intergranular reinforcements

The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength in metal matrix composites. In this study, citric acid was employed as the precursor for synthesizing multiscale carbon nanomaterials(graphene quantum dots and graphene, abbreviated as GQDs and GN). The GQDs@GN/Cu composites were fabricated through a segmented ball milling process in conjunction with subsequent spark plasma sintering(SPS). The intragranular GQDs and intergranular GQDs@GN had synergistically reinforced Cu composites through Orowan strengthening, load transfer strengthening and refinement strengthening. Furthermore,the robust interface bonding between GQDs@GN and Cu effectively mitigated interfacial impedance stemming from electron-boundary scattering. The yield strength and ultimate tensile strength of the GQDs@GN/Cu composites were recorded as 270 and 314 MPa, respectively, representing an improvement of 92 and 28% over pure Cu, while maintaining electrical conductivity at a level comparable to that of pure Cu. This study advances the understanding of the possibility of realizing a synergistic compatibility between electrical conductivity and mechanical strength in Cu composites.

Review of gold leaching in thiosulfate-based solutions

Numerous non-cyanide leaching lixiviants have been developed,among which thiosulfate is considered the most promising alternative to cyanide due to its non-toxicity,low price,high leaching rate and excellent characteristics in dealing with carbonaceous and copper-bearing gold ores.The traditional copper−ammonia−thiosulfate system has been studied extensively.However,with many years of process development,there are still some problems and challenges with this gold leaching system.A series of studies using nickel-,cobalt-and ferric-based catalyst to substitute copper have been conducted with the purpose of reducing the consumption of thiosulfate.A variety of non-ammonia thiosulfate leaching systems including oxygen−thiosulfate,copper−thiosulfate,copper−EDA−thiosulfate,ferric−EDTA−thiosulfate,and ferric−oxalate−thiosulfate leaching systems have been also developed to eliminate the potential side-effect of ammonia.In this review,the basic theory and process development of some main gold leaching systems based on thiosulfate solutions were systematically summarized to illustrate the research status on thiosulfate leaching process.The potential effects of various additives such as organic ligands containing amino,carboxyl or hydroxy functional groups on gold thiosulfate leaching were described in detail.The potential opportunity and challenge for promoting the industrial development of thiosulfate-based gold leaching systems were also discussed.

Effect of Mo content on the thermal stability of Ti-Mo-bearing ferritic steel

The effects of tempering holding time at 700℃on the morphology,mechanical properties,and behavior of nanoparticles in Ti-Mo ferritic steel with different Mo contents were analyzed using scanning electron microscopy and transmission electron microscopy.The equilibrium solid solution amounts of Mo,Ti,and C in ferritic steel at various temperatures were calculated,and changes in the sizes of nanoparticles over time at different Mo contents were analyzed.The experimental results and theoretical calculations were in good agreement with each other and showed that the size of nanoparticles in middle Mo content nano-ferrite(MNF)steel changed the least during aging.High Mo contents inhibited the maturation and growth of nanoparticles,but no obvious inhibitory effect was observed when the Mo content exceeded 0.37wt%.The tensile strength and yield strength continuously decreased with the tempering time.Analysis of the strengthening and toughening mechanisms showed that the different mechanical properties among the three different Mo content experiment steels were mainly determined by grain refinement strengthening(the difference range was 30-40 MPa)and precipitation strengthening(the difference range was 78-127 MPa).MNF steel displayed an ideal chemical ratio and the highest thermodynamic stability,whereas low Mo content nano-ferrite(LNF)steel and high Mo content nano-ferrite(HNF)steel displayed relatively similar thermodynamic stabilities.

Effects of long-term fast charging on a layered cathode for lithium-ion batteries

Fast charging, which aims to shorten recharge times to 10–15 min, is crucial for electric vehicles(EVs),but battery capacity usually decays rapidly if batteries are charged under such severe conditions.Revealing the failure mechanism is a prerequisite to improving the charging performance of lithium(Li)-ion batteries. Previous studies have focused less on cathode materials while also mostly focusing on their early changes. Thus, the cumulative effect of long-term fast charging on cathode materials has not been fully studied. Here, we study the changes in a layered cathode material during 1000 cycles of 6 C charging based on 1.6 Ah LiCoO_(2)/graphite pouch cells. Postmortem analysis reveals that the surface structure, charge transfer resistance and Li-ion diffusion coefficient of the cathode degenerate during repeated fast charging, causing a large increase in polarization. This polarization-induced poor utilization of the Li inventory is an important reason for the rapid capacity fading of batteries. These findings deepen the understanding of the aging mechanism for cells undergoing fast charging and can be used as benchmarks for the future development of high-capacity, fast-charging layered cathode materials.

Non-conjugated terpolymer acceptors for highly efficient and stable lager-area all-polymer solar cells

All-polymer solar cells(all-PSCs)have made significant progress recently,but few studies have been conducted to investigate the lab-to-manufacturing translation from the spin-coating method to the printing process.Here,the random copolymerization method and non-conjugated backbone approach are integrated to manipulate the morphology and photoelectric properties of the active layer for large-area printed all-PSCs.A series of non-conjugated terpolymer acceptors PYSe-TC_(6)T(x)(x=5,10,and 20,refers to the molar ratio of TC_(6)T unit)are developed by covalently introducing non-conjugated unit TC_(6)T into the PYSe host bipolymer by random copolymerization.The spin-coated PYSe-TC_(6)T(10)-based all-PSC demonstrates the best power conversion efficiency(PCE)of 13.54%,superior to the PYSe-based one(12.45%).More intriguingly,morphological studies reveal that a combination of the random polymerization and non-conjugated backbone strategy can effectively prevent the active layer from overaggregation and improve the film quality during the printing process,thereby minimizing the efficiency and technology gap between spin-coated small-area devices and blade-coated large-area devices.By directly using the same preparation condition of spin-coating,the blade-coated small-area(0.04 cm^(2))delivers a PCE of 12.83%and the large-area(1.21 cm^(2))device achieves a PCE of 11.96%with a small PCE loss.Both PCE value and PCE loss are one of the most outstanding performances of the bladecoated all-PSCs.These findings reveal that a combination of the non-conjugated flexible backbone with random copolymerization to develop non-conjugated terpolymers is an attractive design concept to smoothly realize the lab-to-manufacturing translation.

First principles study of post-boron carbide phases with icosahedra broken

Boron carbide (B4C) is a rhombic structure composed of icosahedra and atomic chains, which has an important application in armored materials. The application of B4C under super high pressure without failure is a hot spot of research. Previous studies have unmasked the essential cause of B4C failure, i.e., its structure will change subjected to impact, especially under the non-hydrostatic pressure and shear stress. However, the change of structure has not been clearly understood nor accurately determined. Here in this paper, we propose several B4C polymorphs including B4C high pressure phases with non-icosahedra, which are denoted as post-B4C and their structures are formed due to icosahedra broken and may be obtained through high pressure and high temperature (HPHT). The research of their physical properties indicates that these B4C polymorphs have outstanding mechanical and electrical properties. For instance, aP10, mC10, mP20, and oP10-B4C are conductive superhard materials. We hope that our research will enrich the cognition of high pressure structural deformation of B4C and broaden the application scope of B4C.

Theoretical study of novel B–C–O compounds with non-diamond isoelectronic

Two novel non-isoelectronic with diamond(non-IED)B–C–O phases(tI16-B_(8)C_(6)O_(2)and mP16-B_(8)C_(5)O_(3))have been unmasked.The research of the phonon scattering spectra and the independent elastic constants under ambient pressure(AP)and high pressure(HP)proves the stability of these non-IED B–C–O phases.Respective to the common compounds,the research of the formation enthalpies and the relationship with pressure of all non-IED B–C–O phases suggests that HP technology performed in the diamond anvil cell(DAC)or large volume press(LVP)is an important technology for synthesis.Both tI16-B_(8)C_(6)O_(2)and tI12-B_(6)C_(4)O_(2)possess electrical conductivity.mP16-B_(8)C_(5)O_(3)is a small bandgap semiconductor with a 0.530 eV gap.For aP13-B_(6)C_(2)O_(5),mC20-B_(2)CO_(2)and tI18-B_(4)CO_(4)are all large gap semiconductors with gaps of 5.643 eV,6.113 eV,and 7.105 eV,respectively.The study on the relationship between band gap values and pressure of these six non-IED B–C–O phases states that tI16-B_(8)C_(6)O_(2)and tI12-B_(6)C_(4)O_(2)maintain electrical conductivity,mC20-B_(2)CO_(2)and tI18-B_(4)CO_(4)have good bandgap stability and are less affected by pressure.The stress-strain simulation reveals that the max strain and stress of 0.4 GPa and 141.9 GPa respectively,can be sustained by tI16-B_(8)C_(6)O_(2).Studies on their mechanical properties shows that they all possess elasticity moduli and hard character.And pressure has an obvious effect on their mechanical properties,therein toughness of tI12-B_(6)C_(4)O_(2),aP13-B_(6)C_(2)O_(5),mC20-B_(2)CO_(2)and tI18-B4CO4 all increases,and hardness of mP16-B_(8)C_(5)O_(3)continue to strengthen during the compression.With abundant hardness characteristics and tunable band gaps,extensive attention will be focused on the scientific research of non-IED B–C–O compounds.

Properties of ABS/Organic-Attapulgite Nanocomposites Parts Fabricated by Fused Deposition Modeling

The paper discusses the mechanical and thermal performance manifested in natural nanorods attapulgite(ATP)reinforced Acrylonitrile butadiene styrene(ABS)nanocomposites in the process of fused deposition modeling(FDM).Molten extrusion technique was taken to manufacture the filaments of ABS/organic-attapulgite(OAT)nanocomposites with different mass fraction and the printing operation was made by one commercial FDM three-dimensional(3D)printer.Results indicate that the mechanical performance of these FDM 3D printed specimens are improved obviously via the introduction of OAT,and tensile strength of the ABS/OAT nanocomposites parts with only 2 wt%OAT addition is enhanced by 48.1%.At the same time,the addition OAT can reduce the linear expansion coefficient and creep flexibility,and improve the thermal stability and dimensional accuracy of these FDM 3D printed parts.

Effect of roasting activation of rare earth molten salt slag on extraction of rare earth,lithium and fluorine

A new process was proposed to extract rare earth elements(REEs),Li and F from electrolytic slag of rare earth molten salt by synergistic roasting and acid leaching.Firstly,the thermodynamic analysis of roasting reaction was carried out,then the effects of roasting factors on leaching REEs,Li and F in slag were investigated.In additions,the mineral phase and morphology of molten salt slag,roasting slag and acid leaching slag were characterized,and the migration mechanism of REES,Li and F minerals in roasting and leaching process was analyzed.The results show that the synergistic roasting and activation of molten salt slag by CaO and Al_(2)(SO_(4))_(3)are thermodynamically feasible.The optimum roasting conditions are as follows:molten salt slag of 20 g,Al_(2)(SO_(4))_(3)of 31.25 g and CaO of 6.25 g,roasting temperature of 1173.15 K and reaction time of 2 h,under this condition,the leaching rates of Nd,Pr,Gd,Li and F are 92.47%,91.56%,91.08%,96.69%and 96.8%,respectively.X-ray powder diffraction(XRD)and scanning electron microscopy-energy dispersive X-ray spectroscopy(SEM-EDS)analysis show that the rare earth fluoride(REF3)in molten salt slag transforms into soluble rare earth oxide(REO)after roasting and activation.After leaching,the leaching residue is mainly strip CaSO4,indicating that REES,Li and F can be fully extracted from molten salt slag.

Co_(3)O_(4)/stainless steel catalyst with synergistic effect of oxygen vacancies and phosphorus doping for overall water splitting

The electrolysis of water into hydrogen and oxygen provides an effective means of storing electrical energy indirectly.The current challenge is to design an optimal catalyst that exhibits low overpotentials,long-term stability,universal availability,and only uses inexpensive materials.Herein,a Co3O4nanoflower/stainless steel(P-Ov-CO_(3)O_(4)/SS) catalyst with both oxygen vacancies(Ovs) and phosphorus doping was perfectly prepared via a simple three-step method.The Ovs promoted charge transfer and accelerated the electrocatalysis,while P finely tuned the surface charge state.This resulted in numerous active sites for catalysis,and the synergistic effect of phosphorus doping and oxygen vacancies was finely demonstrated.The resultant electrocatalyst exhibited low hydrogen evolution overpotentials of 118 mV(-10 mA·cm^(-2)) and 242(-200 mA·cm^(-2)),as well as oxygen evolution overpotentials of 327 mV(100 mA·cm^(-2)) and 370 mV(200 mA·cm^(-2)),owing to the excellent synergistic effect of the Ovs and low-temperature phosphating.Moreover,P-Ov-Co_(3)O_(4)/SS//P-Ov-Co_(3)O_(4)/SS exhibited a low water splitting voltage of 1.681 V at 20 mA.cm-2.These findings will enable the synthesis of novel high-performance electrocatalysts for overall water splitting.