Microstructural stability and age-hardening behavior of Re-added dual two-phase Ni3Al and Ni3V intermetallic alloys

The effect of Re addition on the microstructure and hardening behaviour of the dual two-phase Ni₃Al (L1₂) and Ni₃V (D0₂₂) intermetallic alloy was investigated by scanning electron microscopy, transmission electron microscopy and Vickers hardness test. The two-phase eutectoid microstructure accompanying the Re-rich precipitates were observed in the channel region of the alloys in which Re substituted for Ni but not in those in which Re substituted for Al and V. The concomitant addition of Nb (or Ta) with Re more stabilized the two-phase eutectoid microstructure and consequently more induced the fine precipitates in the channel region. The annealing at temperatures below the eutectoid temperature was necessary to induce the fine precipitates in the channel region and thereby result in the precipitation hardening. The fine precipitation in the channel region and related hardening was attributed to the alloying feature so that Re is soluble in the A1 (fcc) phase at high temperatures and becomes less soluble in the two intermetallic phases decomposed from the A1 phase at low temperatures.     

Efficient removal of As(V) from simulated arsenic-contaminated wastewater via a novel metal–organic framework material: Synthesis,structure, and response surface methodology

A novel metal–organic framework material {[N(C₂H₅)₃][Zn₂(ptmda)₂(μ₂-H₂O)]·(H₂O)_0.5}_n { GUT-3 ; H₂ptmda is 4,4′-([p-tolylazanediyl]bis [methylene])dibenzoic acid} was successfully synthesized using the hydrothermal method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. GUT-3 has a two-dimensional network based on dinuclear [Zn₂(ptmda)₂(μ₂-H₂O)]⁻ building units which formed an eightfold interpenetration network in GUT-3 molecules. Hirshfeld surface analysis revealed that H–H, C–H, and O–H bonds accounted for the majority of intermolecular interactions. Moreover, the interactions between GUT-3 and As(V) – the form of As(V) is AsO₄³⁻ – were analyzed in aqueous solutions in a batch system to study the effect of pH, concentration, adsorbent dose, adsorption time, adsorption temperature, and shaking speed. The kinetic and isotherm data of arsenic adsorption on GUT-3 were accurately modeled by pseudo-second-order, Langmuir (q_m = 33.91 mg/g), and Freundlich models. The Box–Behnken response surface method was used to optimize the adsorption conditions of As(V) from the simulated arsenic-contaminated wastewater. The effect of various experimental parameters and optimal experimental conditions was ascertained using the quadratic model.     

On the radius of spatial analyticity for the modified Kawahara equation on the line

First, by using linear and trilinear estimates in Bourgain type analytic and Gevrey spaces, the local well‐posedness of the Cauchy problem for the modified Kawahara equation on the line is established for analytic initial data that can be extended as holomorphic functions in a strip around the x‐axis. Next we use this local result and a Gevrey approximate conservation law to prove that global solutions exist. Furthermore, we obtain explicit lower bounds for the radius of spatial analyticity given by , where can be taken arbitrarily small and c is a positive constant.     

Theoretical studies of the concentration dependences of d–d transition band,g factors,and local distortion for V4+ in Li2O–PbO–B2O3–P2O5 glasses

In this work, the g factors, d–d transition band, local distortion, and their concentration dependences for impurity V⁴⁺ in 20Li₂O–20PbO–45B₂O₃–(15 − x)P₂O₅:V₂O₅ (0 ≤ x ≤ 2.5 mol%) glasses are theoretically investigated by using perturbation formulas of g factors for a tetragonally compressed octahedral 3d¹ cluster. In the light of the cubic polynomial concentration functions for cubic field parameter D_q, covalency factor N, and relative tetragonal compression ratio ρ, the calculated concentration dependences of d–d transition band and g factors for V⁴⁺ show good agreement with the experimental data. With increasing x, N (≈0.7682–0.8165) displays the monotonously increasing trend, whereas ρ (≈6.5–4.2%) and D_q (≈1504.9–1481.1 cm⁻¹) exhibit the decreasing tendencies. The above concentration dependences can be ascribed to the modifications of the V⁴⁺–O²⁻ bonding and orbital admixtures around the impurity V⁴⁺ due to the effects of V₂O₅ doping on the stability of the glass network, the strength of local crystal fields, and the electron cloud distribution.     

Derivation of Hartreeʼs theory for generic mean-field Bose systems

In this paper we provide a novel strategy to prove the validity of Hartree?s theory for the ground state energy of bosonic quantum systems in the mean-field regime. For the known case of trapped Bose gases, this can be shown using the strong quantum de Finetti theorem, which gives the structure of infinite hierarchies of k-particles density matrices. Here we deal with the case where some particles are allowed to escape to infinity, leading to a lack of compactness. Our approach is based on two ingredients: (1) a weak version of the quantum de Finetti theorem, and (2) geometric techniques for many-body systems. Our strategy does not rely on any special property of the interaction between the particles. In particular, our results cover those of Benguria–Lieb and Lieb–Yau for, respectively, bosonic atoms and boson stars.     

N-dimensional Schrödinger equation at finite temperature using the Nikiforov–Uvarov method

The N-radial Schrödinger equation is analytically solved. The Cornell potential is extended to finite temperature. The energy eigenvalues and the wave functions are calculated in the N-dimensional form using the Nikiforov–Uvarov (NV) method. At zero temperature, the energy eigenvalues and the wave functions are obtained in good agreement with other works. The present results are applied on the charmonium and bottomonium masses at finite temperature. The effect of dimensionality number is investigated on the quarkonium masses. A comparison is discussed with other works, which use the QCD sum rules and lattice QCD. The present approach successfully generalizes the energy eigenvalues and corresponding wave functions at finite temperature in the N-dimensional representation. In addition, the present approach can successfully be applied to the quarkonium systems at finite temperature.     

Manipulating OH−-Mediated Anode-Cathode Cross-Communication Toward Long-Life Aqueous Zinc-Vanadium Batteries

The anode-cathode interplay is an important but rarely considered factor that initiates the degradation of aqueous zinc ion batteries (AZIBs). Herein, to address the limited cyclability issue of V-based AZIBs, Al₂(SO₄)₃ is proposed as decent electrolyte additive to manipulate OH⁻-mediated cross-communication between Zn anode and NaV₃O₈ ⋅ 1.5H₂O (NVO) cathode. The hydrolysis of Al³⁺ creates a pH≈0.9 strong acidic environment, which unexpectedly prolongs the anode lifespan from 200 to 1000 h. Such impressive improvement is assigned to the alleviation of interfacial OH⁻ accumulation by Al³⁺ adsorption and solid electrolyte interphase formation. Accordingly, the strongly acidified electrolyte, associated with the sedated crossover of anodic OH⁻ toward NVO, remarkably mitigate its undesired dissolution and phase transition. The interrupted OH⁻-mediated communication between the two electrodes endows Zn||NVO batteries with superb cycling stability, at both low and high scan rates.     

Aryl groups,supplement of amino protecting group chemistry!

Amino group protective strategy has consequently emerged in multistep organic synthesis. Easy and selective deprotection procedures are crucial to facilitate the chemical transformation. Recently, Zhang's group from Henan Normal University collaborating with Chen's group of Nankai University developed a novel strategy for the regiospecific cleavage of inert aryl C-N bonds in N-aryl amides by hypervalent iodine(V) reagents. These procedures allow removal of sort of aryl groups under mild conditions to give primary amides in high efficiency. It bestows these aryl groups with the characteristics of amino protecting groups that might be the supplement of amino protecting group chemistry.     

V2O5纳米片固载Pt纳米粒子催化剂的构建及其增强催化空气氧化脱硫性能

以铂系金属为代表的贵金属催化剂在工业反应中通常表现出优异的催化性能,这是因为其具有独特的d带电子结构和较高的价电子比.近年来,由于大气排放法规愈发严苛,铂系贵金属催化剂在催化空气氧化燃油脱硫方面的研究引起了广泛关注.在该催化反应中,铂系金属纳米粒子可以有效活化空气中的氧气,产生的活性氧物种可以将油品中的噻吩类硫化物氧化为其对应的强极性砜类物质,从而可以将其从非极性的油品中分离出来,有效实现油品中硫化物的深度氧化脱除.然而,在反应过程中铂系贵金属纳米粒子易发生流失和烧结,从而导致催化剂的失活.因此,急需寻找一类可以有效固载铂系贵金属纳米粒子的载体.在目前已报道的众多载体中,以ZrO₂、TiO₂、CeO₂、ZnO等为代表的过渡金属氧化物引起了广泛的关注.通常认为,铂系贵金属纳米粒子的d轨道电子和过渡金属氧化物之间可形成金属-载体强相互作用.然而,目前所使用的过渡金属氧化物载体的比表面积较小,从而导致铂系贵金属纳米粒子难以有效且均匀地分散于其表面.本文采用热膨胀气相剥离法制备了超薄V2O5纳米片,并通过超声辅助沉积法将Pt纳米粒子固载于其表面,从而得到一系列可高效活化空气氧化脱硫的催化剂(Pt NPs-n/V₂O₅纳米片).通过电感耦合等离子体光谱、高倍透射电镜、原子力显微镜、X射线光电子能谱、X射线衍射、拉曼光谱和氮气吸附脱附等方法对催化剂的结构和形貌进行了表征.结果表明,尺寸为4-5 nm的Pt纳米粒子可有效均匀分散于层数约为6层的V2O5纳米片表面;在空气氧化脱硫反应中,当催化剂中Pt理论负载量为2 wt%时,反应5 h后,油品的脱硫率可达99.1%,实现了硫化物的深度氧化脱除.该反应体系对不同硫浓度、不同含硫底物的油品均有较好的脱除效果,但对含有烯烃、芳烃的油品脱除效果较差.此外,催化剂循环使用7次后,其脱硫活性仍无明显下降,表现出优异的重复使用性能.对反应后的催化剂进行表征,发现Pt几乎不发生流失,这可能是由于Pt纳米粒子和V₂O₅纳米片之间形成了金属-载体强相互作用.该结果为其他空气氧化反应的有效进行提供了新思路.