查看更多>>摘要：Functionalization of aniline molecules on zinc oxide(ZnO)nanoparticles is reported using a simple impregnation technique.Functionalized ZnO samples were systematically characterized based on mor-phology,surface and optical properties,and photocatalytic performance towards methyl orange(MO).Aniline functionalization increased the surface charge of the modified ZnO.Compared to pristine ZnO,the aniline-functionalized ZnO yielded faster photodegradation of MO,degrading 98.29％ of MO in 60 min and superoxide radicals were the major species during the MO photodegradation reaction.These results indi-cate that the improvement of photocatalytic degradation could be attributed to opposite charge-induced surface adsorption.Hence,protonated amine as a positively charged molecule was expected to increase the surface adsorption of MO(as an anionic dye)on ZnO nanoparticles surfaces,thereby increasing their photocatalvtic degradation performance.
查看更多>>摘要：Starch has a wide range of sources and can be used as a high-quality precursor for sodium-ion battery anode materials.However,the carbonization yield and specific capacity of carbon materials obtained by directly pyrolyzing starch are low.Herein,starch is used as the carbon source,and ammonium polyphos-phate(APP)is used as the cross-linking agent and dopant to prepare a nitrogen and phosphorus co-doped porous carbon(NPPC).As the anode for sodium-ion batteries,NPPC-2 exhibits a high reversible capacity of 385.8 mA hg-1 at 50 mA g-1.Even after 1000 cycles at a large current density of 5 A g-1,the reversible capacity can still be maintained at 126.9 mA h g-1.Based on detailed data and first-principles calculations,the excellent performance of NPPC is due to the effective doping of nitrogen and phosphorus elements,which distorts the graphite sheet,introduces defects,and increases the graphite layer spacing,thereby enhancing the adsorption capacity of the carbon material for sodium ions,reducing the diffusion barrier of sodium ions.This work provides a new idea for heteroatom doping and carbon material modification.
查看更多>>摘要：The strength and plasticity of Fe39Ni39B12.82Si2.75Nb2.3P4.13 bulk metallic glass(BMG)are improved simul-taneously by modulating atomic-scale structure through fluxing treatment.The compression strength increases from 3074 to 4220 MPa,and the plastic strain is enlarged from 10.7％ to more than 50％.The increased mechanical properties of the fluxed FeNiBSiNbP BMG originate from the optimization of atomic-scale structure.More icosahedral-like clusters(ILCs)and crystal-like clusters(CLCs)are found in this FeNi-based BMG with fluxing treatment,and the ILCs are usually surrounded by CLCs.Furthermore,phase separation and a sandwich-like heterogeneous structure of SB are also observed during deforma-tion,indicating the multiscale deformation mechanism and a stable shear-band evolution.The unique"ILC surrounded by CLCs"structure and phase separation lead to a stable plastic deformation process with strong interactions of multiple shear bands,thereby the improved plasticity and strength.This work provides useful guidelines to develop strong and plastic Fe-based BMGs from a structural aspect.
查看更多>>摘要：A new self-powered/self-cleaned atmosphere monitoring system has been fabricated from TiO2 nanopar-ticles through combining hydrovoltaic,gas sensing and photocatalytic effects.The TiO2 nanoparticle film can convert natural thermal energy into electricity(hydrovoltaic effect)by the spontaneous water evaporation.The hydrovoltaic/gas-sensing coupling effect of TiO2 nanoparticle offers the water-evaporation-powered gas detection performance,and the outputting voltage/current has a good response to the surrounding gas atmosphere,directly acting as the gas sensing signal.The zeta potential of TiO2 is changed by the surface adsorption of gas molecules,and thus affects the electricity output of the system.The outputting electricity can directly power a wireless transmitter for transmitting the sensing infor-mation to external platform,and the whole system can work independently without electricity power supply.The rainwater can be used as the fuel of the system,and thus the system can be used outdoors without scheduled maintenance.Moreover,the photocatalytic activity of TiO2 can effectively degrade the organic pollutants on the film under photo illumination,leading to a self-clean behavior of the system.The system can probably promote the development of green sensing techniques with evaporation-induced ability.
查看更多>>摘要：The corrosion behavior of mild steel in a simulated coastal atmosphere environment has been investigated by the indoor accelerated wet/dry cyclic corrosion acceleration test(CCT),scanning electron microscopy(SEM),Raman spectroscopy and electrochemical measurements.During the CCT test of 60 cycles,the evolution of logarithmic(corrosion rate)vs.logarithmic(CCT cycles)presents a turning point at the 5th cycle,presenting a tendency to increase first and then decrease to gradually stabilize as the CCT cycle prolonged.Before the 5th cycle,γ-FeOOH and β-FeOOH and Fe3O4 were detected,respectively.And then,α-FeOOH as a new chemical composition was detected in the subsequent corrosion cycles.It is found that,after long term corrosion,the rust separated into a relatively dense inner layer rich with α-FeOOH and a loose outer layer rich with γ-FeOOH,both of which have poor electrical conductivity.The rapid increase of corrosion rate in the early stage since reducible corrosion products are involved in the reduction process of the cathode which promotes the dissolution of the anodic metal substrate.Afterward,as the rust layer thickens,the resistance of the rust increases,and the aggressive ions diffusion is blocked,gradually suppressing the electrochemical corrosion process.At last,when the composition and distribution of the rust layer remain stable,the corrosion presents a fluctuating speed around a certain value during the cracking and self-repairing process of the rust layer.
查看更多>>摘要：The effect of a high magnetic field on the microstructural evolution of a peritectic Al-18 at.％Ni alloy during directional solidification and its dependence on pulling speed were investigated.At a low pulling speed,the application of a 2 T magnetic field triggered the appearance of a primary Al3Ni2 phase.At higher pulling speeds,a high magnetic field application induced primary Al3Ni2 phase segregation that formed close to the central alloy regions.For all pulling speeds,the application of a high magnetic field induced bulk Al3Ni/Al eutectic formation on the upper and lower parts of the alloys,and promoted elongated growth of the peritectic Al3 Ni phase along the magnetic field direction.Microstructural analysis indicated that microstructural evolution that was induced by high magnetic fields can be attributed to solute migration and melt flow that is regulated by magnetic,Lorentz,and thermoelectric magnetic forces and their coupling effects during peritectic solidification.
查看更多>>摘要：Luminescent materials show great potential in various applications.Traditional aggregation-induced emission(AIE)luminogens are mostly produced by complex organic synthesis and have poor hydrophilic-ity and biocompatibility,which limit their practical applications.Therefore,it is of great significance to develop fluorescent materials with good hydrophilicity and biocompatibility,and biomacromolecules with these properties have attracted our attention.Partial biomacromolecules can generate unique new fluorophores during the gelation process to obtain hydrogels with good fluorescence properties.In addi-tion,biomacromolecules can be modified with fluorescent groups to obtain fluorescent materials with excellent performance,thus improving the hydrophilicity and biocompatibility of fluorophore.In par-ticular,grafting aggregation-caused quenching(ACQ)luminogens onto biomacromolecules can even effectively inhibit the aggregation and self-quenching of luminogens.It is well known that aromatic biological macromolecules such as green fluorescent protein have intrinsic fluorescence.Intrinsic fluo-rescence is also observed in nonaromatic biological macromolecules without traditional chromophores such as chitosan,cellulose and sodium alginate.The luminescence of nonaromatic biomacromolecule can be rationalized by the clustering-triggered emission(CTE)mechanism,namely,clustering of nonconven-tional chromophores and subsequent electron overlap and conformation rigidification are accountable for the emssion.In this review,fluorescence gels obtained from biomacromolecules,biomacromolecules modified with fluorophores,and the intrinsic luminescence of biomacromolecular luminogens are assessed.This review will help to develop low-cost,biocompatible luminescent materials and has great significance for comprehending the luminescence of nonconventional luminophores and expanding the application of luminescent compounds.
查看更多>>摘要：A two-dimensional(2-D)multi-component and multi-phase cellular automaton(CA)model coupled with the Calphad method and finite difference method(FDM)is proposed to simulate the gas pore for-mation and microstructures in solidification process of hypoeutectic Al-Si-Mg alloys.In this model,the pore growth,and dendritic and eutectic solidification are simulated using a CA technique.To achieve the equilibrium among multiple phases during ternary Al-based alloy solidification,the phase transition thermodynamics and kinetics are evaluated by adopting the Calphad method.The diffusion equations of hydrogen and two solutes are solved by FDM.The developed CA-FDM coupled model can be used for sim-ulating the evolution of gas microporosity and microstructures,involving dendrites and irregular binary and ternary eutectics,of ternary hypoeutectic Al-Si-Mg alloys.It has the capability of reproducing the interactions between the hydrogen microporosity formation and the growth of dendrites and eutectics,the competitive growth among the growing gas pores of different sizes,together with the time-evolving concentration fields of hydrogen and solutes.The simulated morphology of gas pore and microstructure has a good agreement with the experimental observation.The influences of the initial hydrogen concen-tration and cooling rate on the microporosity formation are investigated.It is found that the main portion of porosity formation occurs in the eutectic solidification stage through analyzing the profiles of porosity percentage and solid fraction varying with solidification time.The varying features of simulated porosity percentage,the maximum and average pores radii indicate that increasing initial hydrogen concentration promotes the formation of higher final porosity percentage and larger pores,while the size of gas pores will significantly reduce with increasing cooling rate,leading to a lower final porosity percentage.
查看更多>>摘要：Hydroisomerization of linear alkanes to branched isomers is an important petrochemical process for production of gasoline with high octane number.Non-noble metal bifunctional catalysts used in this process always suffer from low metal dispersion and poor metal-acid synergy.Herein,a facile one-pot synthesis method was used to simultaneously regulate metal particle sizes and acidity of the Ni-SAPO-11 hydroisomerization catalyst.The physicochemical properties are investigated using XANES,EXAFS,TEM/STEM,FT-1R,XPS,UV-vis and NH3-TPD.Apart from the highly dispersed nickel nanoparticles with an average diameter of 8 nm,the framework Ni2+ions are generated via substituting framework Al3+ions of the SAPO-11.The formed NiP-OH structures have lower deprotonation energy(DPE)than the SiAl-OH ones,contributing more and stronger acid sites to the Ni-SAPO-11 catalyst.The great metal-acid synergy including high metal to acid sites ratio(nNi/nA)and close intimacy is obtained for the Ni-SAPO-11 catalyst.The Ni-SAPO-11 catalyst outperforms the counterpart prepared by the impregnation method and exhibits comparable activity and isomers selectivity to the Pt/SAPO-11 catalyst in the n-hexane hydroisomerization.
查看更多>>摘要：The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior.The as-built microstructure showed fine cell and columnar structure due to high cooling rate.Ti element segrega-tion was observed in inter-cell/inter-columnar area.After post heat-treatment,the initially-observed cell structure disappeared,instead bimodal Ni3(Al,Ti)particles formed.High temperature(1273 K and 1373 K)oxidation test results showed parabolic oxidation curves regardless of temperature and initial microstructure.The as-built IN738LC fabricated via the selective laser melting process displayed oxida-tion resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast process.Heat-treated SLM IN738LC,although had similar oxidation weight-gain values to those of the SLM as-built material at 1273 K,showed relatively better oxidation resistance at 1373 K.Bimodal Ni3(Al,Ti)precipitate formed in the post heat treatment changed the local chemical composition,thereby led to changes in alumina former/chromia former location and fraction on the alloy surface.It was concluded that in heat-treated IN738LC increased alumina former fraction was found,and this resulted in excellent oxidation resistance and relatively low weight-gain.
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