Improvement effect of reversible solid solutions Mg_(2)Ni(Cu)/Mg_(2)Ni(Cu)H_(4)on hydrogen storage performance of MgH_(2)

The hydrogen absorption/desorption kinetic properties of MgH_(2)can be effectively enhanced by doping specific catalysts.In this work,MOFs-derived NiCu@C nanoparticles(~15 nm)with regular core-shell structure were successfully prepared and introduced into MgH_(2)(denoted as MgH_(2)-NiCu@C).The onset and peak temperatures of hydrogen desorption of MgH_(2)-11 wt.%NiCu@C are 175.0℃and282.2℃,respectively.The apparent activation energy of dehydrogenated reaction is 77.2±4.5 kJ/mol for MgH_(2)-11 wt.%NiCu@C,which is lower than half of that of the as-milled MgH_(2).Moreover,MgH_(2)-11 wt.%NiCu@C displays great cyclic stability.The strengthening"hydrogen pumping"effect of reversible solid solutions Mg_(2)Ni(Cu)/Mg_(2)Ni(Cu)H_(4)is proposed to explain the remarkable improvement in hydrogen absorption/desorption kinetic properties of MgH_(2).This work offers a novel perspective for the design of bimetallic nanoparticles and beyond for application in hydrogen storage and other energy related fields.

Design of low-alloying and high-performance solid solution-strengthened copper alloys with element substitution for sustainable development

Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process,high mechanical and electrical comprehensive performances,and low cost;thus,they are widely used in high-speed rail contact wires,electronic component connectors,and other devices.Overcoming the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper alloys.Taking the typical solid solution-strengthened alloy Cu-4Zn-1Sn as the research object,we proposed using the element In to replace Zn and Sn to achieve low alloying in this work.Two new alloys,Cu-1.5Zn-1Sn-0.4In and Cu-1.5Zn-0.9Sn-0.6In,were designed and prepared.The total weight percentage content of alloying elements decreased by 43%and 41%,respectively,while the product of ultimate tensile strength(UTS)and electrical conductivity(EC)of the annealed state increased by 14%and 15%.After cold rolling with a 90%reduction,the UTS of the two new alloys reached 576 and 627MPa,respectively,the EC was 44.9%IACS and 42.0%IACS,and the product of UTS and EC(UTS×EC)was 97%and 99%higher than that of the annealed state alloy.The dislocations proliferated greatly in cold-rolled alloys,and the strengthening effects of dislocations reached 332 and 356 MPa,respectively,which is the main reason for the considerable improvement in mechanical properties.

Effect of two-step solid solution on microstructure andδphase precipitation of Inconel 718 alloy

Inconel 718 is the most popular nickel-based superalloy and is extensively used in aerospace,automotive,and energy indus-tries owing to its extraordinary thermomechanical properties.The effects of different two-step solid solution treatments on microstructure andδphase precipitation of Inconel 718 alloy were studied,and the transformation mechanism fromγ″metastable phase toδphase was clarified.The precipitates were statistically analyzed by X-ray diffractometry.The results show that theδphase content firstly increased,and then decreased with the temperature of the second-step solid solution.The changes in microstructure andδphase were studied by scanning electron microscopy and transmission electron microscopy.An intragranularδphase formed in Inconel 718 alloy at the second-[100]_(δ)[011]γ step solid solution temperature of 925℃,and its orientation relationship withγmatrix was determined as//and(010)_(δ)//(111)γ.Furthermore,the Vickers hardness of different heat treatment samples was measured,and the sample treated by second-step solid solution at 1010℃ reached the maximum hardness of HV 446.84.

Extending the solid solution range of sodium ferric pyrophosphate:Off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)as a novel cathode for sodium‐ion batteries

Iron‐based pyrophosphates are attractive cathodes for sodium‐ion batteries due to their large framework,cost‐effectiveness,and high energy density.However,the understanding of the crystal structure is scarce and only a limited candidates have been reported so far.In this work,we found for the first time that a continuous solid solution,Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2)(0≤α≤1,could be obtained by mutual substitution of cations at center‐symmetric Na3 and Na4 sites while keeping the crystal building blocks of anionic P_(2)O_(7) unchanged.In particular,a novel off‐stoichiometric Na_(3)Fe(2.5)(P_(2)O_(7))_(2)is thus proposed,and its structure,energy storage mechanism,and electrochemical performance are extensively investigated to unveil the structure–function relationship.The as‐prepared off‐stoichiometric electrode delivers appealing performance with a reversible discharge capacity of 83 mAh g^(−1),a working voltage of 2.9 V(vs.Na^(+)/Na),the retention of 89.2%of the initial capacity after 500 cycles,and enhanced rate capability of 51 mAh g^(−1)at a current density of 1600 mA g^(−1).This research shows that sodium ferric pyrophosphate could form extended solid solution composition and promising phase is concealed in the range of Na_(4−α)Fe_(2+α)_(2)(P_(2)O_(7))_(2),offering more chances for exploration of new cathode materials for the construction of high‐performance SIBs.

Tungsten combustion in impact initiated W-Al composite based on W(Al) super-saturated solid solution

Element W can effectively improve the density of energetic structural materials. However, W is an inert element and does not combust in air. To change the reaction characteristics of W, 60 at.% Al was introduced into W through mechanical alloying. XRD analysis shows that after 50 h of ball milling, the diffraction peak of Al completely disappears and W(Al60) super-saturated solid solution powder is obtained. Further observation by HAADF and HRTEM reveals that the W(Al60) super-saturated solid solution powder is a mixture of solid solution and amorphous phase. Based on the good thermal stability of W(Al60) alloy powder below 1000℃, W(Al60)-Al composite was synthesized by hot pressing process.Impact initiation experiments suggest that the W(Al60)-Al composite has excellent reaction characteristics, and multiple types of tungsten oxides are detected in the reaction products, showing that the modified W is combustible in air. Due to the combustion of tungsten, the energy release rate of the W(Al60)-Al composite at speed of 1362 m/s reaches 2.71 kJ/g.

Structure, synthesis, and catalytic properties of nanosize cerium-zirconium-based solid solutions in environmental catalysis

Nanosize cerium-zirconium solid solution(CZO)with a special fluorite structure has received an increasing research interest due to their remarkable advantages such as excellent oxygen storage capacity and great flexibility in their composition and structure.By partial metal(including rare earth,transition,alkaline earth or other metal)doping into CZO,the physicochemical properties of these catalytic materials can be controllable adjusted for the study of specific reactions.To date,nanosize CZO has been prepared by co-precipitation,sol-gel,surfactant-assisted approach,solution combustion,micro-emulsion,high energy mechanical milling,etc.The advent of these methodologies has prompted researchers to construct well-defined networks with customized micromorphology and functionalities.In this review,we describe not only the basic structure and synthetic strategies of CZO,but also their relevant applications in environmental catalysis,such as the purification for CO,nitrogen oxides(NOx),volatile organic compounds(VOC),soot,hydrocarbon(HC),CO2 and solid particulate matters(PM),and some reaction mechanisms are also summarized.

Effect of doping elements on catalytic performance of CeO_2-ZrO_2 solid solutions

CeZr, CeYZr, LaCeZr, LaCePrZr, LaCePrYZr, and LaCePr solid solutions were prepared via the coprecipitation method, and characterized by means of X-Ray Diffraction （XRD） and Brunauer-Emmett-Teller （BET） techniques. The oxygen storage capacity （OSC） of the solid solutions was evaluated by the pulse technique and the catalytic activity was assessed using a 4-channel catalysis device. It was seen that the solid solutions presented cubic structure. The specific surface area and thermal stability could be enhanced by doping Y into the solid solutions. Doping a small amount of La had a positive effect on the thermal durability while doping a large amount of La decreased the specific surface area and the thermal stability. LaCePrZr and LaCePrYZr solid solutions synthesized using Baotou rare earth mineral residue enriched with LaCePr after Nd extraction presented a certain higher value in specific surface area and thermal stability, thereby enabling to be used as economic catalysts for automobile exhaust purification. Coating Al2O3 or SiO2 layer on the surface of ceria-zirconia solid solutions increased the specific surface area and thermal resistance.

SnO_2-based solid solutions for CH_4 deep oxidation: Quantifying the lattice capacity of SnO_2 using an X-ray diffraction extrapolation method

A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, Zr4＋, Ti4＋and Pb4＋cations are incorporated into the lattice of tetragonal rutile SnO2 to form a solid solution structure. As a consequence, the surface area and thermal stability of the catalysts are improved. Moreover, the oxygen species of the modified catalysts become easier to be reduced. Therefore, the oxidation activity over the catalysts was improved, except for the one modified by Pb oxide. Manganese oxide demonstrates the best promotional effects for SnO2. Using an X‐ray diffraction extrapolation method, the lattice capacity of SnO2 for Mn2O3 was 0.135 g Mn2O3/g SnO2, which indicates that to form stable solid solution, only 21%Sn4＋cations in the lattice can be maximally replaced by Mn3＋. If the amount of Mn3＋cations is over the capacity, Mn2O3 will be formed, which is not favorable for the activity of the catalysts. The Sn rich samples with only Sn‐Mn solid solution phase show higher activity than the ones with excess Mn2O3 species.

Hydrogen storage properties of magnesium hydride catalyzed by Ni-based solid solutions

The Ni−25%X(X=Fe,Co,Cu,molar fraction)solid solutions were prepared and then doped into MgH_(2) through high-energy ball milling.The initial dehydrogenation temperatures of MgH_(2)/Ni−25%X composites are all decreased by about 90℃relative to the as-milled pristine MgH_(2).The Ni−25%Co solid solution exhibits the most excellent catalytic effect,and the milled MgH_(2)/Ni−25%Co composite can release 5.19 wt.%hydrogen within 10 min at 300℃,while the as-milled pristine MgH_(2) can only release 1.78 wt.%hydrogen.More importantly,the dehydrogenated MgH_(2)/Ni−25%Co composite can absorb 5.39 wt.%hydrogen at 275℃within 3 min.The superior hydrogen sorption kinetics of MgH_(2)/Ni−25%Co can be ascribed to the actual catalytic effect of in-situ formed Mg_(2)Ni(Co)compounds.First-principles calculations show that the hydrogen absorption/desorption energy barriers of Mg/MgH_(2) systems decrease significantly after doping with transition metal atoms,which interprets well the improved hydrogen sorption properties of MgH_(2) catalyzed by Ni-based solid solutions.

Synthesis and thermoelectric properties of Mg_2Si_(1-x)Sn_x solid solutions by microwave irradiation

In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Sil-xSnx （x=0.2, 0.4, 0.6, 0.8） solid solutions, microwave irradiation techniques were used in preparing them as thermoelectric materials. Structure and phase composition of the obtained materials were investigated by X-ray diffraction （XRD）. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 750 K. It is found that Mg2Si1-xSnx solid solutions are well formed with excessive content of 5% （molar fraction） Mg from the stoichiometric MgESil.xSnx under microwave irradiation. A maximum dimensionless figure of merit, ZT, of about 0.26 is obtained for Mg2Si1-xSnx solid solutions at about 500 K for x=0.6.

Quantifying Solid Solution Strengthening in Nickel-Based Superalloys via High-Throughput Experiment and Machine Learning

Solid solution strengthening(SSS)is one of the main contributions to the desired tensile properties of nickel-based superalloys for turbine blades and disks.The value of SSS can be calculated by using Fleischer’s and Labusch’s theories,while the model parameters are incorporated without fitting to experimental data of complex alloys.In thiswork,four diffusionmultiples consisting of multicomponent alloys and pure Niare prepared and characterized.The composition and microhardness of singleγphase regions in samples are used to quantify the SSS.Then,Fleischer’s and Labusch’s theories are examined based on high-throughput experiments,respectively.The fitted solid solution coefficients are obtained based on Labusch’s theory and experimental data,indicating higher accuracy.Furthermore,six machine learning algorithms are established,providing a more accurate prediction compared with traditional physical models and fitted physical models.The results show that the coupling of highthroughput experiments and machine learning has great potential in the field of performance prediction and alloy design.

Electronic and thermoelectric properties of Mg2GexSn1-x(x=0.25,0.50,0.75) solid solutions by first-principles calculations

The electronic structure and thermoelectric（TE） properties of Mg2GexSn1-x（x = 0.25, 0.50, 0.75） solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special quasi-random structure（SQS） is used to model the solid solutions, which can produce reasonable band gaps with respect to experimental results.The n-type solid solutions have an excellent thermoelectric performance with maximum zT values exceeding 2.0, where the combination of low lattice thermal conductivity and high power factor（PF） plays an important role. These values are higher than those of pure Mg2Sn and Mg2Ge. The p-type solid solutions are inferior to the n-type ones, mainly due to the much lower PF. The maximum zT value of 0.62 is predicted for p-type Mg2Ge（0.25）Sn（0.75） at 800K. The results suggest that the n-type Mg2GexSn1-x solid solutions are promising mid-temperature TE materials.

Preparation and Characterization of Ce_x Th_(1-x)O_2 Solid Solutions Prepared by Sol-Gel Method

The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x = 0.2, 0.5, 0.8) Ce_xTh_(1-x)O_2. Raman spectrum showsthat Ce-Th complex oxides can promote the formation of oxygen vacancies. Two reduction peaks appearin the TPR profiles of Ce_xTh_(1-x)O_2 solid solution. The a peak is attributed to the reduction ofCe^(4+) on the surface, and the β peak is attributed to the reduction of bulk CeO_2. Theincorporation of Th atom into CeO_2 improves the reduction of CeO_2. Ce_xTh_(1-x)O_2 mixed oxidesare promising materials for oxygen vacancies produced, as well as catalysts for many reactionsinvolved oxygen, such as the catalysts for three-way reactions for reducing the releasing pollutantsor combustion of VOCs.

Hydrothermal Synthesis and Characterization of Ce_(1-x)Mn_xO_(2-δ) Solid Solutions

Nanocrystals of Ce1-xMnxO2-δ（x=0.00,0.05,0.10,0.15,and 0.20） were synthesized by a hydrothermal reaction route.The solid solutions crystallized in a cubic fluorite structure with a particle size in the range of 11～15 nm.The incorporation of Mn ions in CeO2 resulted in a lattice volume reduction.Mn ions showed a mixed valence state of ＋2,＋3 and ＋4 in CeO2 lattice.An obvious red-shift of the absorption threshold edge was observed from the UV-visible spectrum.Compared with the bulk CeO2,Ce1-xMnxO2-δ nanocrystals exhibited a lower releasing oxygen temperature as indicated by TPR technique.

The Precise Inner Solutions of Gravity Field Equations of Hollow and Solid Spheres and the Theorem of Singularity

The precise inner solutions of gravity field equations of hollow and solid spheres are calculated in this paper. To avoid space curvature infinite at the center of solid sphere, we set an integral constant to be zero directly at present. However, according to the theory of differential equation, the integral constant should be determined by the known boundary conditions of spherical surface, in stead of the metric at the spherical center. By considering that fact that the volumes of three dimensional hollow and solid spheres in curved space are different from that in flat space, the integral constants are proved to be nonzero. The results indicate that no matter what the masses and densities of hollow sphere and solid sphere are, there exist space-time singularities at the centers of hollow sphere and solid spheres. Meanwhile, the intensity of pressure at the center point of solid sphere can not be infinite. That is to say, the material can not collapse towards the center of so-called black hole. At the center and its neighboring region of solid sphere, pressure intensities become negative values. There may be a region for hollow sphere in which pressure intensities may become negative values too. The common hollow and solid spheres in daily live can not have such impenetrable characteristics. The results only indicate that the singularity black holes predicated by general relativity are caused by the descriptive method of curved space-time actually. If black holes exist really in the universe, they can only be the Newtonian black holes, not the Einstein’s black holes. The results revealed in the paper are consistent with the Hawking theorem of singularity actually. They can be considered as the practical examples of the theorem.

Synthesis and characterization of cadmium-calcium hydroxyapatite solid solutions

A series of cadmium-calcium hydroxyapatite solid solutions was prepared by an aqueous precipitation method. By various means, the characterizations confirmed the formation of continuous solid solutions over all ranges of Cd/（Cd＋Ca） atomic ratio. In the results, both lattice parameters a and c display slight deviations from Vegard’s rule when the Cd/（Cd＋Ca） atomic ratio is greater than 0.6. The particles change from smaller acicular to larger hexagonal columnar crystals as the Cd/（Cd＋Ca） atomic ratio increases from 0-0.60 to 0.60-1.00. The area of the phosphate peak for symmetric P-O stretching decreases with the increase in Cd/（Cd＋Ca） atomic ratio, and the peak disappears when the Cd/（Cd＋Ca） atomic ratio is greater than 0.6; the two phosphate peaks of P-O stretching gradually merge together for the Cd/（Cd＋Ca） atomic ratio near 0.60. These variations can be explained by a slight tendency of larger Cd ions to occupy M（2） sites and smaller Ca ions to prefer M（1） sites in the structure.

Electrophysical propertis of solid solutions of Zn_2–x(Ti_aZr_b)_1–xFe_2xО₄

Electrophysical properties of multicomponent system Zn2TiO4–Zn2ZrO4–ZnFe2O4 were investigated. The electrical conductivity, band gap, dielectric permittivity, and molar polarizability of formed solid solutions –Zn2-x(TiaZrb)1-xFe2xO4 (x = 0 - 1.0 are defined;Δх = 0.05;a + b = 1;a:b = 1:5;1:4;1:3;1:2;1:1;2:1;3:1;4:1) were defined. Electrophysical properties of samples are in linear dependence on their composition. All the synthesized samples are semiconductors with high electrical resistivity. Was confirmed the formation of two phases of variable composition with a wide homogeneity range.

Density Functional Theory and Electrochemistry Studies on LiFexMn1-xPO4 Solid Solutions

The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4, and the two forms may co-exist in the actual LiFexMn1-xPO4 materials. The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method. The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.

Composition-tunable ZnS1-xSex nanobelt solid solutions for efficient solar-fuel production

Band engineering based on the construction of solid solutions is an effective approach to enhance the efficiency of semiconductor photocatalysts, via which the balance between light absorption and driving force can be well achieved by continuously tuning the band structure. Here the ZnS1–xSex nanobelt solid solutions have been prepared via thermal treatment of ZnS1–xSex(en)0.5 precursors. The compositions are adjusted by changing the mole ratio of Se to S powder in the starting materials, resulting in continuously modulating the alignment of energy levels of the obtained solid solutions. The band structure is also studied via theoretical calculation. Accordingly, the light harvesting can be tuned too, as confirmed by the UV-vis absorption spectra. XPS valence spectra are used to determine the valence band maximum. Transient photoluminescence spectra are employed to study the separation of photogenerated charge carriers. BET specific surface area and CO2 adsorption isotherms of different catalysts are measured. The obtained ZnS1–xSex nanobelts exhibit different photocatalytic activity for solar-fuel production, dependent on many factors like the light harvesting and alignment of energy levels. The related mechanism is studied in detail.

ADSORPTION OF SULFOXIDES ON SOLID FROM AQUEOUS SOLUTIONS——Ⅲ.THE ADSORPTION ON CARBON BLACK

The adsorption of decylmethylsulfoxide(DEMS)onto carbon black and the effects of temperature,salt(NaCl)and acid (HCl)have been measured.Typical two plateaux type adsorption isotherms were obtained.Applying the two step model of surfactant adsorption on solid/liquld interface and the general adsorption isotherm equation[9]the experimental results were interpreted qualitatively and quantitatively.