Nanoarchitectonics of Niobium-Doped,Lead-Free BLT (Ba0.97La0.02Ti0.98Nb0.016O3) for Electrical Properties with Unusual d.c Bias Voltage Independence

Polycrystalline sample of Ba_0.97La_0.02Ti_0.98Nb_0.016O₃ (distinguished as BLTi_0.98Nb_0.016) has been prepared through Molten-Salt-Flux reaction route. The XRD, surface morphology, absorption spectra, impedance, and dielectric behaviors were employed to typify the prepared polycrystalline ceramic. The XRD analysis reflects that obtained perovskite having the pure-tetragonal structure with space group P4/mmm. As of the absorption spectra, the optical band gap (Eg), Urbach energy (Eu), and refractive index values have designed. The electrical properties of synthesized compound have been inspected via complex impedance spectroscopy vs. frequency (f) (10² Hz–10⁶ Hz) within the d.c-bias voltage range [0.5 V–5 V]. The fitting of the Nyquist plot exposes that both intra- and intra grains contribute to relaxation and the grain limits are more resistive and capacitive than the grains. Modulus analysis confirms that relaxation in our sample is of non-Debye nature and d.c-bias voltages dependent. Depending on the frequency, the change of ε′ can be discussed founded on the principle of interfacial polarization of the Maxwell–Wagner category. BLTi_0.98Nb_0.016 shows notable frequency independent relative studied properties, it is a potential candidate for devices.

     

提高小型VRLA电池充电接受能力方法的研究

目前对使用中的小型VRLA电池提出了具备适应快速充电能力的要求 ,因此 ,对能够提高该类电池充电接受能力的方法进行了研究与实践。这些方法是基于改变正负极活性物质添加剂和电解液添加剂的组分及配比来实现的。某些方法有实际推广应用的价值。     

A priori characterization of criticity and of dynamic thermal behaviour of a storage of cork powder

The new dispositions of the recent French law, called “Lois Risques” present some difficulties of application to qualify and quantify the new notion of dynamics of a hazardous process such as a thermal runaway. Many steady models predicting the thermal runaway (Semenov, Frank–Kamenetskii, Thomas, etc.) are proposed in literature. Due to their simplifying hypotheses, even if these models are widely used, they do not provide any information on the history of the self-heating of the system enabling to predict the necessary time to urgently react to a drift. The analysis of the transient thermal behaviour turns out to be necessary to complete the previous classical results, to estimate the profile of the adiabatic temperature rise and the time of induction for reaching the maximum adiabatic temperature and thus to better characterize the ability of the system to runaway, whose prediction fiability must be presently improved to respond to the new needs of the hazard study. The present work shows that the consideration of the influence of temperature on the heat transfer parameters and of more realistic boundary conditions during the numerical solution of the heat balances describing the storage behaviour allows us to better predict the criticity and the dynamics of appearance and of evolution of the runaway concerning the example of a cork storage.     

Co‐doped ZnO thin films grown by pulsed electron beam ablation as model nano‐catalysts in fischer‐tropsch synthesis

A single‐step deposition of cobalt‐doped zinc oxide (Co‐ZnO) thin film nano‐composites on three different crystalline substrates, viz., Al₂O₃ (c‐sapphire), silicon (100) (Si), and SiO₂ (quartz) is reported, using pulsed electron beam ablation (PEBA). The results indicate that the type of substrate has no effect on Co‐ZnO films stoichiometry, morphology, microstructure, and film thickness. The findings show the presence of hexagonal close‐packed metallic Co whose content increases in the films deposited on Al₂O₃ and Si substrates relatively to SiO₂ substrate. The potential of the films as model nano‐catalysts has been evaluated in the context of the Fischer‐Tropsch (FT) process. Fuel fractions, which have been observed in FT liquid products, are rich in diesel and waxes. Specifically, Co‐ZnO/Al₂O₃ nano‐catalyst shows a selectivity of ～4%, 31%, and 65% towards gasoline, diesel, and waxes, respectively, while Co‐ZnO/SiO₂ nano‐catalyst shows a selectivity of ～12%, 51%, and 37%, for gasoline, diesel, and waxes, respectively. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3332–3340, 2018     

Eccentric counts,connectivity and chordality

Let $e_j$ denote the number of vertices of eccentricity j in a graph. We provide sharp lower bounds on $e_j$ in graphs of given connectivity and in chordal graphs of given connectivity.     

GFM型VRLA电池正极汇流排腐蚀机理研究

从 Ｐｂ－Ｃａ－Ｓｎ合金的结构和性能、铅在不同环境中的腐蚀倾向、结合实际使用情况,得出ＧＦＭ型ＶＲＬＡ电池正极汇流排腐蚀是在中性或弱碱性条件下产生的强烈晶间腐蚀的看法,其腐蚀产物主要是 ＰｂＯ·ＰｂＳＯ４,并提出了一些避免正极汇流排腐蚀的途径。