Enhancement of hydrogen storage properties in 4MgH2 Na3AlH6 composite catalyzed by TiF3

In this work, we have investigated the hydrogen release and uptake pathways storage properties of the MgH₂Na₃AlH₆ with a molar ratio of 4:1 and doped with 10 wt% of TiF₃ using a mechanical alloying method. The doped composite was found to have a significant reduction on the hydrogen release temperature compared to the un-doped composite based on the temperature-programme-desorption result. The first stage of the onset desorption temperature of MgH₂Na₃AlH₆ was reduced from 170 °C to 140 °C with the addition of the TiF₃ additive. Three dehydrogenation steps with a total of 5.3 wt% of released hydrogen were observed for the 4MgH₂Na₃AlH₆-10 wt% TiF₃ composite. The re/dehydrogenation kinetics of 4MgH₂Na₃AlH₆ system were significantly improved with the addition of TiF₃. Kissinger analyses showed that the apparent activation energy, E_A, of the 4MgH₂Na₃AlH₆ doped composite was 124 kJ/mol, 16 kJ/mol and 34 kJ/mol lower for un-doped composite and the as-milled MgH₂, respectively. It was believed that the enhancements of the MgH₂Na₃AlH₆ hydrogen storage properties with the addition of TiF₃ were due to formation of the NaF, the AlF₃ and the Al₃Ti species. These species may played a synergetic catalytic role in improving the hydrogenation properties of the MgH₂Na₃AlH₆ system.     

Effects of Nanosized PbO and MgO,Rolling, and Sintering Time on Crack and Current Density of Bi1.6Pb0.4Sr2Ca2Cu3O10/Ag Superconductor Tapes

Journal of Superconductivity and Novel Magnetism - The effects of nanoparticle additions, rolling, and sintering time on the transport critical current density, Jc, of Ag-sheathed...     

Flow visualisation studies and the effect of tongue area on the performance of volute casings of centrifugal machines

The present paper deals with flow visualization studies and the effect of tongue area on the performance of the volute casings of centrifugal machines with a swirling flow free from jets and wakes at their inlet. The flow visualization studies by wool tuft movements were conducted in the volute channel as well as in the exit diffuser and interpreted according to Moore and Kline[1]. Flow separation was observed at high inlet swirl angles near the volute tongue as well as in the exit diffuser. It was found that the volute performance was strongly dependent on the tongue area at low and high inlet swirl angles.     

Burnable absorber-integrated guide thimble (BigT) – II: application to 3D PWR core design

This paper is a companion to its immediate predecessor in the “Burnable absorber-integrated Guide Thimble” (BigT) series. It aims to demonstrate potential applications of the BigT concepts in a three-dimensional (3D) commercial pressurized water reactor core, which is based on the AP1000 first core design. The study specifically compares neutronic characteristics of the reference core against a BigT-loaded design. In this study, reactivity depletion patterns of nine fuel assembly lattices in the reference core were first evaluated. Corresponding sets of BigT-loaded assemblies that yield neutronically similar characteristics (i.e., initial reactivity suppression and depletion trend) with those of the reference assembly lattices were determined next. These BigT-loaded fuel assemblies were later loaded in place of the reference fuel assemblies for the subsequent high-fidelity 3D Monte Carlo core simulations. Results of the study clearly demonstrate that the BigT-loaded AP1000 first core performs as well as the reference core since all neutronic parameters are comparable, especially in terms of reactivity depletion, power peaking factors and shutdown margin. All simulations were completed using the Monte Carlo Serpent code with ENDF/B-VII.0 library.     

Charge-Programmable Photopolymers for 3D Electronics via Additive Manufacturing

Charge-programmed 3D printing enables the fabrication of 3D electronics with lightweight and high precision via selective patterning of metals. This selective metal deposition is catalyzed by Pd nanoparticles that are specifically immobilized onto the charged surface and promises to fabricate a myriad of complex electronic devices with self-sensing, actuation, and structural elements assembled in a designed 3D layout. However, the achievable property space and the material-performance correlation of the charge-programmed printing remain unexplored. Herein, a series of photo-curable resins are designed for unveiling how the charge and crosslink densities synergistically impact the nanocatalyst-guided selective deposition in catalytic efficiency and properties of the 3D printed charge-programmed architectures, leading to high-quality 3D patterning of solid and liquid metals. The findings offer a wide tunability of the structural properties of the printed electronics, ranging from stiff to extreme flexibility. Capitalizing on these results, the printing and successful application of an ultralight-weight and deployable 3D multi-layer antenna system operating at an ultrahigh-frequency of 19 GHz are demonstrated.     

Ordered Semantic Hyper Tableaux

A family of tableau methods, called ordered semantic hyper (OSH) tableau methods for first-order theories with function symbols, is presented. These methods permit semantic information to guide the search for a proof. They also may make use of orderings on literals, clauses, and interpretations to guide the search. In a typical tableau, the branches represent conjunctions of literals, and the tableau represents the disjunction of the branches. An OSH tableau is as usual except that each branch B has an interpretation I ₀[B] associated with it, where I ₀ is an interpretation supplied at the beginning and I ₀[B] is the interpretation most like I ₀ that satisfies B. Only clauses that I ₀[B] falsifies may be used to expand the branch B, thus restricting the kinds of tableau that can be constructed. This restriction guarantees the goal sensitivity of these methods if I ₀ is properly chosen. Certain choices of I ₀ may produce a purely bottom-up tableau construction, while others may result in goal-oriented evaluation for a given query. The choices of which branch is selected for expansion and which clause is used to expand this branch are examined and their effects on the OSH tableau methods considered. A branch reordering method is also studied, as well as a branch pruning technique called complement modification, that adds additional literals to branches in a soundness-preserving manner. All members of the family of OSH tableaux are shown to be sound, complete, and proof convergent for refutations. Proof convergence means that any allowable sequence of operations will eventually find a proof, if one exists. OSH tableaux are powerful enough to be treated as a generalization of several classes of tableau discussed in the literature, including forward chaining and backward chaining procedures. Therefore, they can be used for efficient query processing.     

Influence of Ce Substitution at Sr-Site on Superconducting Fluctuation Behavior and Infrared Absorption of Tl0.9Bi0.1Sr2?x Ce x Ca0.9Y0.1Cu1.99Fe0.01O7?δ (x=0–0.20) Ceramics

Ce substituted Tl_0.9Bi_0.1Sr_2?x Ce _x Ca_0.9Y_0.1Cu_1.99Fe_0.01O_7??? (x=0?C0.20) samples were synthesized to determine the effects of the higher valence ion substitution on superconductivity and structure of the Fe-doped Tl1212 derivatives. The normal state behavior for x=0 showed semiconductor-like behavior which gradually turned to metallic behavior with increasing Ce at x=0.05?C0.15. However, further substitution of Ce for x>0.15 turned the normal state to insulating behavior. The zero critical temperature, T _{c zero} increased from 65.4?K (x=0.05) to 71.0?K (x=0.10), but slightly decreased for x>0.10 indicating the optimum value of average copper valence was achieved at x=0.10. Excess conductivity analysis using the Aslamazov Larkin, AL and Lawrence?CDoniach, LD models revealed two-dimensional, 2D to three-dimensional, 3D transition of superconducting fluctuation behavior, SFB with the highest transition temperature, $T_{\mathrm{2D}\mbox{-}\mathrm{3D}}$ at x=0.10. FTIR analysis in conjunction with XRD results showed softening of FeO₂/CuO₂ planar oxygen mode from 610.5?cm^?1(x=0) to 605?cm^?1(x=0.20) which is suggested to be related to possible increase of inter plane coupling, J and this is supported by computed results based on the LD model. The enhanced J increases superconducting coherence length along c-axis, ?? _c (0), and hence lowers anisotropy, ?? resulting in enhanced superconducting properties.     

Effect of V2O5–TeO2 Glass Addition on Dielectric Properties of CaCu3Ti4O12 Ceramics Prepared by Solid State Method

CaCu₃Ti₄O₁₂ (CCTO) is well known to have colossal dielectric constant in the range of 10⁵. However, CCTO has considerably high dielectric loss values (tanδ > 0.1) at room temperature and 1 kHz. In this work, addition of glass to CCTO was suggested in order to improve its dielectric properties. The effect of V₂O₅–TeO₂ (VT) glass addition on microstructure and dielectric properties of CCTO ceramics were investigated. Dielectric measurements were carried out for (1 ? x) CCTO-(x) V₂O₅–TeO₂ (x = 0, 0.03, 0.05, 0.10) samples in the frequency range of 10²–10⁶ Hz using impedance spectrometer. Electron micrographs showed that low melting VT glass addition facilitated the grain growth of CCTO. As VT glass amount increased, dielectric constant decreased. The drop, though within reasonable values (~10⁵), may related to the presence of grain boundary glassy phase which itself has low dielectric constant. However, the dielectric loss of the composite has decreased after VT glass addition. The low melting V₂O₅–TeO₂ glass aided in liquid phase sintering and improved the grain boundary resistance which resulted in decreased leakage currents.