怀柔广延大气簇射探测阵列

本文介绍了1988年投入运行的怀柔广延大气簇射(EAS)阵列的设备构成、工作原理、性能指标及原始数据的记录处理方式。各种检验和首批EAS观测数据表明,该阵列可有效地用于对能量在10~(15)—7×10~(16)eV范围的EAS的探测和研究。     

Composite phase change material based on reduced graphene oxide/expanded graphite aerogel with improved thermal properties and shape-stability

Composite phase change materials (PCMs) based on reduced graphene oxide/expanded graphite (rGO/EG) aerogel were prepared by hydrothermal self-assembly and impregnation method. The morphology, chemical structure, thermal properties, and shape-stability of the composite PCMs based on rGO/EG aerogel were examined. The results show that rGO sheets form a three-dimensional (3D) network structure and EG particles are attached to rGO sheets and uniformly interspersed in the aerogel. The oxygen-containing functional groups remaining in rGO/EG aerogel promote heterogeneous crystallization of paraffin, leading to increased latent heat. The 3D thermally conductive pathway provided by rGO/EG aerogel improves the composite PCM's thermal conductivity up to 0.79 W·m⁻¹·K⁻¹, which is about 4 times of that of pure paraffin. The leakage of composite PCMs is remarkably improved at very high percentage of paraffin. Simulative light-thermal experiments reveal that the composite PCMs have the ability of conversion and storage of light-thermal energy. In short, 3D network structure of rGO, with the aid of EG, endows the composite PCMs with improved thermal properties, good shape-stability, and light-thermal storage performance.     

A comprehensive study on thermal conductivity of the lithium-ion battery

The reliable thermal conductivity of lithium-ion battery is significant for the accurate prediction of battery thermal characteristics during the charging/discharging process. Both isotropic and anisotropic thermal conductivities are commonly employed while exploring battery thermal characteristics. However, the study on the difference between the use of two thermal conductivities is relatively scarce. In this study, the isotropic and anisotropic thermal conductivities of the four commercially available lithium-ion batteries, ie, LiCoO₂, LiMn₂O₄, LiFePO₄, and Li (NiCoMn)O₂, were reviewed and evaluated numerically through the heat conduction characteristics inside the battery. The results showed that there are significant differences in the temperature distribution in the battery caused by the isotropic and anisotropic thermal conductivities, which could affect the layout and cooling effectiveness of battery thermal management system. Furthermore, the effective thermal conductivities of porous electrodes and separator were determined to establish thermal conductivity bounds of lithium-ion batteries combined with the thicknesses of battery components. The thermal conductivity bounds could be applied to evaluate the rationality of the thermal conductivity data used in battery thermal models.     

Effect of interface morphology on the residual stress distribution in solid oxide fuel cell

Solid oxide fuel cell directly and efficiently converts chemical energy to electrical energy. However, the necessity for high operating temperatures can result in mechanical failure. Fuel cell is a multilayer system and its stress distribution is greatly affected by the interface morphology. In this work, cosine interfaces with different amplitudes are used to approximate the fluctuation of actual interface. The effects of interface morphology on stress state, energy release rate of crack and creep behavior have been investigated. The results show that if the interface is planar, the residual normal stress component is zero on the interface, while the nonplanarity of interface can cause the normal stress S_n and shear stress S_t on the interface. When the amplitude is relatively small, the max values of S_n and S_t on the interfaces vary linearly with increasing amplitudes in both anode and cathode. Above a certain value, nonlinearity of the interface becomes important. Max tensile S_n always occurs at the peak of convex interface, but the position of max compressive S_n varies. Max shear stress is prone to occur at 1/4 of the wavelength at small amplitude and moves towards 1/2 of the wavelength when the amplitude increases. Fracture mechanics analysis shows that the surface crack possibly penetrates into the anode function layer and then is constrained by the stiff electrolyte. On the other hand, the horizontal crack likely penetrates into the electrolyte layer when the interface is not planar. Creep analysis shows that 11 800 hours of continuous operation at high temperature cannot remove stress undulation introduced by nor-planar interface but can make max value of Sn and St decrease around 30%.     

Facile preparation of NaV3O8/polytriphenylamine composites as cathode materials towards high-performance sodium storage

NaV₃O₈/polytriphenylamine composites were synthesized by an in situ oxypolymerization way for the first time. Among them, the NaV₃O₈/20 wt.% polytriphenylamine composite shows better cycling and rate performance. Its discharge capacity retains at 118.9 mAh g⁻¹ after 300 cycles at 120 mA g⁻¹. It also obtains a reversible capacity of 101.7 mAh g⁻¹ at 300 mA g⁻¹ after 100 cycles. These enhanced results arise from the excellent morphology, that is, smaller particles of clear edges and uniform distribution suppress the expansion and deformation of the crystal structure, and avoid large agglomerate particles gathering during the electrochemical reaction. In addition, tight polytriphenylamine (PTPAn) coating also improves the conductivity of NaV₃O₈ cathode and suppresses the dissolution of NaV₃O₈ in electrolyte.     

Sulfur-doped shaddock peel–derived hard carbons for enhanced surface capacity and kinetics of lithium-ion storage

Sulfur doping has been regarded an energetic route to optimize the lithium storage properties of carbon-based electrode materials. In this work, sulfur-doped shaddock peel–derived hard carbon is successfully prepared by a KOH- and C₂H₅NS-assisted pyrolysis procedure. It is demonstrated that sulfur doping has strong effect on surface activation and graphitization enhancement, which results in the significant enhancement of the surface adsorption capacity and reaction kinetics of the hard carbon materials. When employed as a lithium ion batteries (LIBs) anode, the as-obtained hard carbon demonstrates excellent cycling and rate properties, presenting a great specific capacity of 738 mAhg⁻¹ at 50 mAg⁻¹ after 200 cycles, as well as 491 mAhg⁻¹ at 200 mAg⁻¹ after 300 cycles. Even at 1000 and 2000 mAg⁻¹, the hard carbon provides a large rate capacity of 283 and 179 mAhg⁻¹, respectively. Besides, it is revealed that the Li⁺ storage process is determined by the surface-induced pseudocapacitive process, whose capacitive proportion reach 60% at 0.5 mVs⁻¹. This work suggests that the low cost and eco-friendly sulfur-doped shaddock peel–derived hard carbon is a very prospective LIB anode material.     

Nickel cobalt oxide nanowires-modified hollow carbon tubular bundles for high-performance sodium-ion hybrid capacitors

Sodium-ion hybrid capacitors are a prospective energy storage device candidate that couples the superiorities of battery-type and capacitive storage mechanisms. In this study, we fabricate a composite of NiCo₂O₄ nanowires with carbon tubular bundles (CTBs) via a facile hydrothermal and annealing procedure. The density functional theory (DFT) calculations are performed to evaluate the bonding strength between the two components of the composite, the binding energy of the NiCo₂O₄ is calculated to be −0.952 J m⁻², indicating that the NiCo₂O₄ nanowires can be stabilized on both sides of the carbon tubular bundles, which leads to a good cycling performance. Moreover, the composite in this work exhibits a metallic property because of the introduction of carbon material. As expected, when used for sodium storage, the NiCo₂O₄/CTBs shows a high capacity of 298 mA h g⁻¹ at 1 A g⁻¹ and high capacity retention of 92% after 500 cycles, which are superior than the bare NiCo₂O₄ electrode. Consequently, the sodium-ion hybrid capacitor is also assembled with NiCo₂O₄/carbon tubular bundles and commercial activated carbon, which achieves high energy density of 99 Wh kg⁻¹ in a wide potential range from 0.5 V to 4.0 V.     

Sub-channel-based multiscale thermal-hydraulic analysis of a medium-power,lead-cooled fast reactor

The lead-cooled fast reactor (LFR) offers enhanced safety and reliability with the fine properties of liquid lead and lead alloy. To study accurately the thermal characteristics of fast reactors, the multiscale thermal-hydraulic coupling simulation is an effective way. Multiscale coupling based on the sub-channel code has evident advantages on the analysis of fuel assemblies. In this study, a multiscale thermal-hydraulic analysis of a forced-circulation, medium-power LFR under steady-state and transient conditions is performed with the system code ATHLET and sub-channel code KMC-SUBtraC which was developed based on the previous version by modifying the pressure drop correlations and adding the assembly-level calculation. The codes are one-way-coupled, with good efficiency and precision. Transient verification of the sub-channel code is conducted with the CFD code. In the steady-state analysis of M²LFR-1000, mass flow and temperature distributions of the assemblies, sub-channels, and fuel rods in the hottest assembly are analyzed and the safety performance is investigated. In the transient analysis, two typical DECs (unprotected overpower transient and ULOF+ULOHS) are simulated and the multiscale thermal-hydraulic characteristics are analyzed. With the negative reactivity feedback, the variations of the temperatures of the coolant and fuel rods are within the safe limits, which shows the inherent safety of the reactor. And the results indicate that the loss of primary flow could increase the risk of cladding corrosion.     

小粒径油雾发生装置研制

针对现有的油雾发生装置油雾粒径(7~40 μm)不符合中国船级社《钢制海船入级规范》关于油雾发生装置油雾粒径不得超过5 μm的规范要求,研制了一种小粒径油雾发生装置。经测量验证:所研制的油雾发生装置油雾粒径可控制在5 μm以内,并能控制油雾浓度、雾化温度及油雾流量,可为油雾探测器研制提供平台试验条件。