[en] After NiO coating of aluminum borate whisker, the whisker-reinforced aluminum composite was fabricated by the squeeze casting technique. The effects of surface coating on the interface reaction and microstructure of the composite were investigated using transmission electronic microscope. The results indicate that the NiO on the whisker surface can react with the aluminum matrix during T4 treatment, and the degree of the reaction increases with the T4 treatment time increasing. The interfacial reaction affects obviously the tensile strength of the composite, and the suitable degree of the interfacial reaction can be found for the ultimate tensile strength

[en] Two 123 thin films grown by e-beam evaporation have been studied using Raman microscopy. The films were grown under different conditions of temperature and oxygen partial pressure and show different levels of cation disorder as determined from the c axis lattice parameter in combination with x-ray data. The oxygen stoichiometry in each film was changed by controlled anneals using a coulometric titration apparatus. As a result the authors report on the sensitivity of the 500 cm^-1 and 585 cm^-1 Raman peak to the oxygen stoichiometry and how the intensity and position of these peaks can be used to detect or confirm the presence of a small amount of cation disorder

[en] Highlights: •The fire spray system can be used as a mitigation strategy in SAMG. •The effectiveness of FSS is evaluated on three effects for severe accident mitigation. •The FSS can postpone the process of accidents for safety system recovery. •The effects of FSS are limited due to its system limitation. •Negative impacts are identified and evaluated. -- Abstract: The fire spray system (FSS) of the Advanced Passive PWR, as a part of the fire protection system, can provide a non-safety related containment spraying function for severe accident mitigation which is included in the Severe Accident Management Guidelines (SAMG) of the Advanced Passive PWR when dealing with severe accidents. The effectiveness of the FSS is investigated on three effects for severe accident mitigation which are controlling the containment condition, washing out fission product and injecting into the containment through three representative severe accident scenarios analysis with integral accident analysis code since there is no sufficient data support, besides the negative impact is also discussed. Results show that the FSS can be effective for controlling the containment condition, washing out fission product and injecting into the containment, however the effect is limited due to system limitation: the FSS can only cool the containment atmosphere for a short term; the flow rate of FSS cannot fulfill the success criteria given in the PRA report of the Advanced Passive PWR. Meanwhile, the hydrogen concentration and the containment water level should be the long-term monitored because actuating the FSS may cause hydrogen risk in the containment and containment flooding. Despite its limitation and negative impact, the FSS can be effective as an alternative severe accident mitigation measurement for postponing the process of accidents for safety system recovery.

[en] Highlights: • A passive cavity injection system is suggested for Chinese improved 1000 MWe PWR. • The system is assessed with Risk Oriented Accident Analysis Methodology. • Three factors are discussed as sensitivity study for the assessment. • Assessment result shows an acceptable high successful probability. - Abstract: After the Fukushima Daiichi accident, the Chinese National Nuclear Safety Administration requires enhancements of safety and mitigation capability under severe accidents for nuclear power plants (NPPs). In-vessel retention (IVR) strategy is proposed to mitigate the consequences of severe accidents for pressurized water reactors (PWR) to satisfy the requirements. Therefore, a proposal with passive cavity injection system (PCIS) is designed for Chinese improved 1000 MWe PWR for implementation of IVR strategy. Besides, to condense the steam generated in the cavity head, a passive heat exchange system (PHES) is also designed for passive containment cooling. To evaluate the coolability of the PCIS, a computer code is developed to assess the effectiveness of IVR strategy based on the integrated risk oriented accident analysis methodology (ROAAM) approach. In order to obtain input parameters for assessment, seven severe accident sequences are screened based on Level 1 PRA results and analyzed with integral accident analysis computer code. With the characteristics of the molten pool and key parameters gained from accident analysis, the IVR assessment program is developed with MATLAB code considering parameters of decay power, zirconium oxide fraction, the mass of stainless steel (SS). The influence of thermophysical parameters, critical heat flux (CHF) correlation and mass of metal layer on IVR effectiveness are discussed as sensitivity study for the assessment. Thermophysical parameters have the major effect. Combining the sensitivity study, assessment results show that the IVR strategy for Chinese improved 1000 MWe PWR has an acceptable high success probability. However, for engineering practice, detail system design and analysis should be evaluated in the near future

[en] Highlights: • A two-equation model was proposed to study heat transfer in MEPCM/foam composite. • Insertion of metal foam significantly enhanced heat transfer of MEPCM. • Metal foam unified internal temperature distribution and reduced temperature gradient. • Higher porosity composite had higher wall temperature and consumed less time to melt. • Higher pore density composite attained better thermal control for larger area density. -- Abstract: This article reported an efficient hybrid phase change material (PCM) for passive thermal management that integrated micro-encapsulated phase change material (MEPCM) and metal foam. This PCM composite was aimed to enhance the heat transfer of MEPCM, while avoid the leakage of molten phase change material (PCM). We proposed a two-energy equation model and experiment demonstration to investigate phase change heat transfer inside MEPCM/foam composite. The surface/internal temperatures, interface evolution and non-equilibrium heat transfer in the composite were discussed. Results showed that the pure MEPCM was not suitable for thermal management due to the low thermal conductivity. The wall temperature of the MEPCM/foam composite was only half of the pure MEPCM attributed to the latent heat absorption of MEPCM and thermal enhancement of metal foam. The higher porosity composite obtained higher surface temperature, and also consumed less time to start phase change due to the lower effective thermal conductivity. Besides, better thermal control was achieved by the MEPCM/foam composite with higher pore density attributed to its larger volumetric area. The employment of metal matrix made the internal temperature distribution more homogeneous and reduced the inside temperature gradient.

[en] Mn-doped ZnO nanocrystal have been synthesized by the hydrothermal method under a 4 T pulsed magnetic field. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations reveal the samples are nano-columns with a hexagonal wurtzite ZnO structure. Raman measurement indicates that internal stress and structure defects of the samples increase due to the Mn atoms intercalate into the ZnO crystal lattice. Vibrating sample magnetometer (VSM) detection reveals well room-temperature ferromagnetism for our Mn-doping samples. The origin of room-temperature ferromagnetism may arise from the exchange interaction between Mn²⁺ ions and defects in ZnO. Combined with XRD, Raman and VSM measurement, it can also find that high pulsed magnetic field introduces more defects into Mn-doped ZnO samples, thus leads to the enhancement of their saturation magnetization.

[en] Highlights: • Sc addition promoted the grain refinement of the Al-35Zn alloys. • A dynamic precipitation was observed in Al-35Zn(-0.5Sc) alloys during rolling. • Al-35Zn-0.5Sc alloy shows well damping and mechanical properties. • A strategy of preparing Al with well damping and mechanical properties. Al-35Zn and Al-35Zn-0.5Sc alloys were fabricated in this study. The addition of 0.5 Sc promoted the grain refinement of the Al-35Zn alloys during solidification, heat treatment, and hot rolling. Dynamic precipitation also occurred in the Al-35Zn and Al-35Zn-0.5Sc alloys during rolling. The damping capacity and mechanical properties of the Al-35Zn alloy were improved by the Sc addition and hot rolling. The rolled Al-35Zn-0.5Sc alloy with 90% reduction demonstrated better damping capacity than those of commercial Al alloys and some metallic materials with high damping capacity, which is mainly attributed to the high interface sliding capacity. Compared with the commercial Al alloys, the rolled Al-35Zn-0.5Sc alloy with 90% reduction showed balanced mechanical properties, including high strength and reasonable ductility. This work provided an effective strategy for preparing Al alloys with excellent damping capacity and mechanical properties.

[en] Highlights: •Surface barrier effects on AC loss were studied by simulations. •Surface and bulk region is characterized by different critical current density. •Simulation results are similar to the experimental results. -- Abstract: Influences of surface barrier in Ag–Bi2223 tapes on AC loss are studied. The Ag–Bi2223 tape is described by a surface region (near to the silver) and a bulk region, which are depicted by different critical current densities j_cs and j_cb, respectively. Simulations using the flux creep model indicate that with surface barrier increasing, a kink then a dip appear in the AC loss and the peak and dip positions move to higher magnetic fields. The results can be used as an effective method to qualitatively estimate the surface barrier strength

[en] Highlights: ► We investigated electronic structure and impurity states of different S-doping levels in cBN crystal theoretically using LDA approach in the frame of DFT. ► Both theory and experiment indicate that S is more likely to be substituted for a B atom than an N atom. ► S substituted for an N atom creates shallow electron levels merged to the states at the conduction band edge, and S substituted for a B atom creates deep levels within the band gap, both forming n-type cBN. - Abstract: The electronic structure and impurity states of S-doped cBN were investigated by first-principle approaches. Our calculation shows that S substituted for an N atom creates shallow donor levels merged to the states at the conduction band edge, S substituted for a B atom creates deep donor levels within the band gap, both forming n-type cBN, and band gap of S-doped cBN decreases with the increase of dopant concentration. Moreover, from the view of energy, S is more likely to be substituted for a B atom than an N atom.

[en] The influence of Cu substitution for Ni on magnetic properties and magnetic entropy change has been investigated in the Ni_49-xCu_xMn₃₉Sb₁₂ alloys with x = 0, 1 and 2. With increasing Cu content from x = 0 to 2, a decreasing dependence of the martensitic transformation temperature (T_M) on the number of valence electrons per atom (e/a) is observed, which cannot be explained by the size factor or the number of valence electrons per atom. An inverse magnetocaloric effect was observed in the vicinity of the first order martensitic transition. The maximum value of -ΔS_M^max in the nominal Ni₄₈Cu₁Mn₃₉Sb₁₂ alloy is 9.38 J kg^-1 K^-1 at 291 K for a magnetic field change from 0 to 5 T, with the refrigerant capacity of 25.9 J kg^-1. The large ΔS_M indicate that nominal Ni₄₈Cu₁Mn₃₉Sb₁₂ alloy may be a promising candidate for magnetic refrigeration at room temperatures.