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[en] A composite material was developed as sorbent for sorption thermal energy storage (TES) which was used to recycle the low-temperature heat in industry and life fields in this study. The composite sorbent was formed by strontium bromide (SrBr_2) and the additive of expanded natural graphite treated with sulfuric acid (ENG-TSA). Sorption characteristics, kinetic sorption performance, thermal conductivity and permeability of 15 samples were studied. The material test results indicated the following: (1) the composite SrBr_2 is of high energy density and good mass transfer performance; (2) it can be regenerated below 100 °C; (3) the additive of ENG-TSA greatly improves the heat transfer performance, while no degradation is observed on sorption water uptake; (4) the optimal composite sorbent is of 743 kg/m"3 and with 10 wt% ENG-TSA. An lab-scale sorption TES system with 1 kWh design capacity was established and investigated. Under the conditions in winter seasons: charging temperature T_c_h_a is 80 °C, discharging temperature T_d_i_s is 35 °C, condensing temperature T_c is 15 °C, evaporating temperature T_e is 15 °C, the heat storage capacity can reach 1.02 kWh. The heat storage density obtained is 242 Wh/kg composite sorbent and the heat discharging power is 67.4 kW/m"3 composite sorbent. - Highlights: • A new type of consolidated composite SrBr_2 sorbent was developed. • We tested the thermal properties and sorption performance of samples. • The optimal composite sorbent was chosen for thermal energy storage. • A 1 kWh sorption thermal energy prototype was investigated.
[en] The exotic nonstrange ΔΔ dibaryon with I(J"P) = 0(3"+) has been confirmed by the experimental data reported by WASA-at-COSY Collaboration, and the result is consistent with our theoretical prediction in the chiral SU(3) quark model and extended chiral SU(3) quark model, showing that the effect from hidden-color channel (CC) is important. In the present work, we further investigate another exotic nonstrange ΔΔ dibaryon with I(J"P) = 3(0"+) in the chiral SU(3) quark model that describes the energies of baryon ground states and the nucleon-nucleon (NN) scattering data satisfactorily. We perform a dynamical coupled-channel study of the ΔΔ-CC system with I(J"P) = 3(0"+) within the framework of resonating group method (RGM). We find that the binding energy of I(J"P) = 3(0"+) state is about 22.3 MeV and a root-mean-square radius (RMS) of 1.03 fm in single-channel calculation. Then we extend the model to include the CC channel to further study the I(J"P) = 3(0"+) state and find that the binding energy is about 31.3 MeV and RMS is 0.97 fm in coupled-channel calculation. We can see that the CC channel coupling has a relatively large effect on this state. The color screening effect is further considered and we find that the bound state property will not change much. It is shown that the binding energy of this state is stably ranged around several tens of MeV; it means that its mass is always lower than the threshold of the ΔΔ channel and higher than the mass of NΔπ. (orig.)
[en] An electron paramagnetic resonance absorption study is conduced on four separately prepared single crystal groups of the superconductor YBa2Cu3O7-δ, each group consisting of from four to six crystalline platelets. This investigation confirms conclusions reached by others regarding the EPR silence of this superconducting oxide while demonstrating that EPR spectroscopy can be used to determine certain properties of suerconducting oxides. Such determinations include detection of paramagnetic impurity phases, noninvasive means for determining Tc, and estimating the depth of penetration of a microwave radiation field in these materials. Some comments are provided on the nonresonant, zero field absorption in both, the powders and single crystal platelets. (author)
[en] The binary Cu-Cr and Cu-Zr and ternary Cu-Cr-Zr copper-base alloys are successfully prepared by the conventional metallurgy. Electrochemical measurements are used for examining the effect of single and binary addition of chromium and zirconium metals on the corrosion resistance of pure copper in 0.01-1 M NaCl solutions. Significant reduction in the corrosion resistance is observed when chromium and zirconium are added simultaneously to copper instead of single addition of chromium or zirconium metals. Meanwhile, the results of cyclic voltammetry show that the element Cr plays an offsetting role to the Cu2O film while the element Zr plays a deteriorated role. Finally, the corrosion mechanism for element Cr and Zr is suggested
[en] Highlights: ► Ca–Mg–Zn Metallic glasses were prepared using the melt-spinning technique. ► The crystallization was characterized by DSC, XRD and electrical resistivity. ► The glass transition, crystallization and activation energy were determined by DSC. ► The phases from each crystallization stage were identified by Rietveld analysis. ► The composition showing the best glass-forming ability and thermal stability was determined. -- Abstract: Metallic glasses in the composition range of Ca4Mg72−xZn24+x (x = 0–12, Δx = 2) were successfully prepared using the melt-spinning technique. The crystallization characteristics of the alloys were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and electrical resistance measurements. All samples show a complex crystallization process with four exothermic events. The phases resulting from each crystallization stage were identified by XRD. The crystallization was initiated at lower temperatures by the precipitation of Mg51Zn20 crystals. Mg-hcp and Ca16.7Mg38.2Zn45.1 (IM1) ternary compound precipitated from the retained amorphous phase during the second crystallization event. After that, Ca1.5Mg55.3Zn43.2 (IM4) ternary compound formed at higher temperatures and the crystallization event terminated via IM4 transforming to Ca2Mg5Zn13 (IM3) before melting. All crystallization reactions were found to be in qualitative agreement with the equilibrium phase diagram. The activation energy for each stage of crystallization was determined from DSC analysis and calculated by Kissinger method. The temperature dependence of electrical resistance shows good consistency with DSC and XRD results
[en] Novel EVM/SrBr_2 composite sorbents with different salt contents were developed for low-temperature thermal energy storage (TES). Simulative sorption experiment was conducted to obtain the sorption kinetics diagram and identify threshold salt content that composite sorbents can hold without solution leakage. Distribution of salt embedded in EVM was observed by extreme-resolution scanning electron microscopy (ER-SEM). Thermochemical characterizations including desorption performance and desorption heat were fully investigated by analyzing simultaneous thermal analyzer (STA) results. Results reveal that sorption process of composite sorbents is divided into three parts: water adsorption of EVM, water adsorption of SrBr_2 crystal and liquid-gas absorption of SrBr_2 solution. Since SrBr_2 solution can be hold in macrospores of EVM, water uptake and energy storage density are greatly increased. It appears that the composite sorbent of EVMSrBr_240 is a promising material for thermal energy storage, with water uptake of 0.53 g/g, mass energy storage density of 0.46 kWh/kg and volume energy storage density of 105.36 kWh/m"3. - Highlights: • Vermiculite/SrBr_2 composite sorbents were developed for thermal energy storage. • Water uptake of composite sorbents is divided into three phases. • Energy storage density of each sorption phase is evaluated via calculations. • EVMSrBr_240 is chosen as optimal sorbent without solution leakage.
[en] In this Letter, the effects of shear rate on structural properties of liquid Al in quenching process were investigated via molecular dynamics (MD) simulations based on the EAM potential. Analyses in internal energy and pair correlation functions (PCF) reveal an increasing structural transition temperature as the shear rate is enhanced in the liquid. Results of pair analysis indicate that for liquid Al under normal condition, face center cubic (FCC) structure is clearly detected upon cooling; while in sheared liquid, structural transition from FCC to body center cubic (BCC) at temperature of 800 K is manifested, leading to the dominance of BCC structural order at low temperatures
[en] A continuous-wave 5 kW fiber laser welding system was used in conduction mode to deposit Inconel® alloy 718 (IN718) by employing filler wire on as-serviced IN718 parent material (PM) substrates. The direct laser deposited (DLD) coupons and as-serviced IN718 PM were then evaluated through tensile testing. To understand the failure mechanisms, the tensile fracture surfaces of the as-serviced IN718 PM, DLD and DLD-PM samples were analyzed using scanning electron microscopy. The fracture surfaces revealed the presence of both Al2O3 and Cr2O3 films, although the latter was reasoned to be the main oxide in IN718. Both the experimental observations and thermodynamic analysis indicated that oxidation of some alloying elements in IN718 cannot be completely avoided during manufacturing, whether in the liquid state under vacuum (for casting, the electron beam melting, welding and/or deposition) or with inert gas protection (for welding or laser deposition). The exposed surface of the oxide film on the fracture surface has poor wetting with the metal and thus can constitute a lack of bonding or a crack with either the metal and/or another non-wetted side of the oxide film. On the other hand, the wetted face of the oxide film has good atom-to-atom contact with the metal and may nucleate some intermetallic compounds, such as Laves, Ni3Nb-δ, Nb-rich MC and γ′ compounds. The potential of their nucleation on Cr2O3 was assessed using planar disregistry. Coherent planes were found between these intermetallics and Cr2O3
[en] The dynamic evolution of the lamellar eutectic of binary alloys in directional solidifications was studied in detail using the Monte-Carlo technique. In our simulation, the solidification is executed by individual A and B atoms (Case I) and individual A atoms and AB dimers (Case II). We can find: (1) the off coupled eutectic pattern occurs easily in Case II by introducing the cluster deposition; (2) the fluctuation of branching degree (D b) of the lamella in Case II is larger than Case I; (3) the simulated tendency for the formation of the off-coupled and branched structures accords with the experimental results in the Al-Cu alloys and Al-Si alloy
[en] In this work, we studied the magneto-optical properties of ZnMnTe/ZnMgTe spin superlattices by using photoluminescence (PL) spectroscopy at low temperature. The circularly polarized PL measurements in an increasing magnetic field were performed. Detailed characteristics of the level crossing behavior for the spin-polarized excitonic states due to the giant Zeeman splitting were observed. The results show that an increase of the magnetic field transfers the spin superlattices from direct band gap system to indirect band gap system, and spatially separates the electrons and the holes by changing type-I band alignment to type-II band alignment. These features are confirmed by the behavior of the PL intensity in magnetic field, and agree well with the theoretical expectation basing on the sp-d exchange interaction