Exploration of the Exceptional Capacitive Deionization Performance of CoMn_(2)O_(4) Microspheres Electrode

The“battery type”inorganic electrode has been demonstrated the highly efficient sodium ion intercalation capacity for capacitive deionization.In this work,the CoMn_(2)O_(4)(CMO)microspheres with porous core-shell structure are prepared via co-precipitation and followed by annealing.The effects of annealing temperatures on the morphology,pore structure,valence state,and electrochemical behavior of CMO are explored.As electrode for capacitive deionization,the salt removal capacity and current efficiency of optimized AC||CMO device reaches up to 60.7 mg g^(−1) and 97.6%,respectively,and the capacity retention rate is 74.1%after 50 cycles.Remarkably,both the in-situ X-ray diffraction and ex-situ X-ray diffraction analysis features that the intercalation/de-intercalation of sodium ions are governed by(103)and(221)crystal planes of CMO.Accordingly,the density functional theory calculations realize that the adsorption energies of Na+onto(103)and(221)crystal planes are higher than that of any other crystal planes,manifesting the priorities in adsorption of sodium atoms.Furthermore,the X-ray photoelectron spectra of pristine and post-CMO electrode highlights that the reversible conversion of Mn^(3+)/Mn^(4+)couple is resulted from the intercalation/de-intercalation of Na^(+),while this is irreversible for Co^(3+)/Co^(2+)couple.Beyond that,the CMO electrode has been proven the selectivity removal of Na^(+) over K^(+)and Mg^(2+)in a multi-cation stream.

Semisolid microstructural evolution of (CNTs+Sip)/AZ91D powder compacts prepared from powders by cold pressing and remelting

The evolution of semisolid microstructure during partial remelting of(CNTs+Sip)/AZ91 D powder compacts prepared by cold pressing was studied.The results indicate that rapid grain coarsening is driven by the dissolution of eutecticβphase material during the initial heating period of 0-10 min,so the AZ91 D powders with fine equiaxed grains surrounded by intergranular eutectic phases evolve into compact particles.As the heating time proceeds,α-Mg particles were gradually separated by liquid due to the phase transformations ofα-Mg+β→L andα-Mg→L.The primary particles coarsened rather slowly and the as-received Mg powder evolved into nearly spheroidal particles surrounded by liquid phase after partial remelting.The in situ synthesized Mg2 Sip were distributed homogeneously around the CNTs with maintained structural integrity during partial remelting.Moreover,this microstructural evolution was accompanied by densification through pore filling.An ideal semisolid ingot suitable for thixoforming can therefore be obtained by partially remelting a(CNTs+Sip)/Mg powder compact.

Improving phase transition temperature of VO_(2) via Ge doping:a combined experimental and theoretical study

Enhancing the semiconductor-metal phase transition temperature(TSMT)of VO_(2) is of great consequence for further exploring the potential applications of VO_(2) at elevated temperatures.In this study,Ge^(4+)-doped VO_(2)(Ge_(x)V_(1-x)O_(2))samples were prepared by the hydrothermal and annealing approach.X-ray diffraction(XRD),high-resolution transmission electron microscopy(HRTEM),differential scanning calorimetry(DSC)and resistivity-temperature(R-T)analyses were used to investigate the influence of Ge doping on the lattice structures and phase transition properties of Ge_(x)V_(1-x)O_(2) samples.We found that the lattice parameter of Ge_(x)V_(1-x)O_(2) decreased with the Ge concentration increasing from 2 at%to 18 at%,which was further supported by density functional theory(DFT)-based first-principle simulations.TSMT firstly increased from 64.5 to 73.0℃ at 8 at% Ge and then decreased to 71.5℃ at higher Ge concentration.Furthermore,DFT analysis revealed that the impact of lattice distortion induced by Ge doping rather than the changes in electronic structure is more pronounced on modulating TSMT of Ge_(x)V_(1-x)O_(2).The present work has pointed out the direction that the TSMT could be enhanced and illustrated the physical reason behind the regulation of TSMT in ionsdoped VO_(2) systems.

Fabrication of nano-grained negative temperature coefficient thermistors with high electrical stability

Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique.Samples were sintered at 1042℃ for 30 s in the first rapid step and then at 850-950℃ for 20 h in the second soaking step.Crystal phase,microstructure and electrical properties of sintered samples were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),resistance temperature relationship and aging performance.Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density.Moreover,average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm.Meanwhile,the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises.In addition,the obtained material constant(B) ranges from 3931 to 3981 K.Ni_(0.7)Mn_(2.3)O_(4)-3(soaking at 900℃) and Ni_(0.7)Mn_(2.3O4)-4(soaking at 950℃) present little aging behavior,implying great electrical stability.

Enhanced corrosion protection of magnesium alloy via in situ Mg-Al LDH coating modified by core-shell structured Zn-Al LDH@ZIF-8

The Mg-Al layered double hydroxide(LDH)conversion coatings were first synthesized in situ to modify the AZ91 D alloy through urea hydrolysis to adjust the pH values(9.4,10.4,11.2 and 11.4).The pH 11.2 Mg-Al LDH possessed the best compactness and good crystallinity compared to other in situ LDH coatings and obtained the lowest corrosion current density(i_(corr))of(2.884×10^(-6)±0.345×10^(-6))A·cm^(-2),which was attributed to the anion-exchange reaction of LDH and the physical barrier against corrosion owing to the twisted penetration pathway of the interlaced LDH sheets.Core-shell structured Zn-Al LDH@ZIF-8 powder modified with stearic acid(SA)was further wrapped with polyvinylidene fluoride(PVDF)to prepare a hydrophobic double-layered coating on the underlying pH 11.2 Mg-Al LDH(SLLZ).The water contact angle(CA)of the SLLZ coating reached 105.6°,and its i_(corr)decreased to(3.524×10^(-7)±0.214×10^(-7))A·cm^(-2)compared with a single pH 11.2 film.The SLLZ coating exhibited high durability and corrosion protection,even after15 days of immersion in NaCl solution.The PVDF,SA and ZIF-8 nano-shells contributed to good hydrophobicity,effectively forming a physical barrier.The Zn-Al LDH core and underlying in situ Mg-Al LDH were beneficial for synergistically promoting anion-exchange reaction between the intercalated anions of LDH and chlorides in corrosive media.This work provides a promising approach that combines core-shell LDH@ZIF-8 with LDH film on a Mg alloy surface to construct a hydrophobic film with excellent longterm anti-corrosion performance.

A combined experimental and theoretical investigation of donor and acceptor interface in efficient aqueous-processed polymer/nanocrystal hybrid solar cells

As a route to improving the energy conversion of organic-inorganic hybrid-solar cells, we have tested the performance of poly(phenylene vinylene)(PPV), poly(2,5-thienylene vinylene)(PWTV) polymers and CdTe nanocrystal devices produced via aqueous-processing. It is found that small differences in the conformation of the sensitizer lead to dramatic effects on the solar cell efficiency. Using a combination of UV-Vis absorption spectroscopy and first-principles non-adiabatic molecular dynamics(NAMD) based on time-dependent density-functional theory(TDDFT), PPV is found to have a longer electron injection and recombination time despite seeming to have a better energy alignment with the substrate, which leads to a higher devices performance than PWTV. The present results shed new light on the understanding of organic-inorganic hybrid-solar cells and will trigger further experimental and theoretical investigations.