放射性废物焚烧技术的发展历程和展望

焚烧是放射性废物的主要处理技术之一,同常规废物焚烧技术相比,放射性废物焚烧技术更关注对放射性核素的截留效果、系统的辐射安全和对废物的适应能力。随着废物特性的变化、环保要求的日益严格,焚烧技术也在不断的革新和改进,对塑料、橡胶和树脂等高分子聚合物适应性更强的第三代焚烧技术已成为主流,包括热解焚烧、蒸汽重整焚烧以及等离子体焚烧,分别适用于不同的废物类型。未来放射性废物焚烧技术的发展趋势以整体经济性和满足环保要求为前提,尽量提高废物的整体减容效果,对多种废物的兼容处理,并为满足特殊废物的处理要求开发针对性的焚烧技术。     

Reaction environment self-modification on low-coordination Ni2+ octahedra atomic interface for superior electrocatalytic overall water splitting

Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion. In this regard, meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary. Herein, a coordination environment inheriting strategy is presented for designing low-coordination Ni²⁺ octahedra (L-Ni-8) atomic interface at a high concentration (4.6 at.%). Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode. To improve the efficiency of using the self-modification reaction environment at L-Ni-8, all of the structural features, including high atom economy, mass transfer, and electron transfer, are integrated together from atomic-scale to macro-scale. At high current density of 500 mA/cm², the samples synthesized at gram-scale can deliver low hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) overpotentials of 262 and 348 mV, respectively.

     

预时效对Al-5.2Mg-0.45Cu-2.0Zn合金室温稳定性的影响

本文详细研究了预时效对Al-5.2Mg-0.45Cu-2.0Zn合金时效析出行为的影响。预时效不仅提高了合金的室温稳定性,避免了合金烤漆软化,同时提高了合金的烤漆时效响应速度。合金经T4处理后,再峰时效处理后的组织包括粗大的T-Mg₃₂(AlZn)₄₉相以及针状的S-Al₂MgCu相。然而合金经T4P处理后,再峰时效处理的组织只含有细小而高密度的T-Mg₃₂(AlZn)₄₉相而不包括S-Al₂MgCu相。自然时效后不稳定的原子团簇在180℃时效后会回溶到基体中, 从而抑制了合金的时效析出强化。而预时效后生成的稳定的原子团簇会成为180℃时效的形核点,显著提高了合金的时效响应速度。     

Site occupancy and enhanced luminescence of broadband NIR gallogermanate phosphors by energy transfer

Super broadband near-infrared (NIR) La₃Ga₅GeO₁₄(LGGO): Cr³⁺ phosphor is in urgent needs for food testing. Unfortunately, it suffers from poor luminescence intensity in applications. Herein, the enhanced NIR luminescence performance can be realized in LGGO: Pr³⁺, Cr³⁺. The preferential crystallographic site of Cr³⁺ is validated on the basis of EPR spectrum, Rietveld refinement, and the first-principles DFT calculations. It is of great importance that the as-prepared phosphors can be excited by blue light (460 nm), which is beneficial to the application of blue-pumped LEDs. The critical distance of Pr³⁺ in LGGO host has been calculated by concentration-quenching method. For co-doped sample, it is observed that Cr³⁺ luminescence intensity enhancement by a factor of 3 can be achieved by doping Pr³⁺ owing to the energy transfer from Pr³⁺ to Cr³⁺. In addition, the introduction of Pr³⁺ can also improve the Cr³⁺ luminescence intensity at elevated temperature. Furthermore, using the optimized phosphor, a blue-based NIR phosphor-converted LEDs (NIR pc- LEDs) is fabricated, the forward voltage and the intensity of LED hardly change after thermal aging for 500 hours under high temperature/ high humidity condition, indicating its great reliability for NIR pc-LEDs. Therefore, LGGO:Pr³⁺, Cr³⁺ has great potential to serve as an attractive candidate in the application of blue light-excited NIR pc-LEDs in view of its capability for blue to enhanced broadband NIR conversion.     

固溶-冷速-时效对TC4-DT合金力学性能的影响

本文以Ti6Al4V-DT (TC4-DT)为研究对象，分别对其进行不同方式的固溶、冷却和时效处理，利用金相显微镜、拉伸试验机研究其显微组织、强度和塑性的变化，结果表明：强度和塑性的主要影响因素为固溶温度和冷却方式。在α+β两相区和单相区固溶并在580℃时效8小时，可以分别得到双态组织和片层组织，相变点以下随着固溶温度的提高，初生α相含量明显减少，且强度和塑性在两相区固溶更优；相变点以上固溶时，冷却速率降低会使α相片层粗化，抗拉强度和屈服强度逐渐降低；在两相区固溶α相尺寸随着时效温度升高而增大，在低温时效时，由于α相的弥散强化作用使得合金强度较高。TC4-DT合金在α+β两相区860℃/1.5h固溶，550℃/8h时效处理，在空冷的状态下，可获得合金强度（1017MPa）、塑性（伸长率22%）匹配良好的综合性能。     

Shale gas pad development planning under price uncertainty

In this article, we study shale gas pad development under natural gas price uncertainty. We optimize the sequence of operations, gas curtailment, and storage on a single pad to maximize the net present value. The optimization problem is formulated as an mixed-integer linear programming model, which is similar to the one proposed by Ondeck et al. We investigate how natural gas price uncertainty affects the operation strategy in the pad development. Both two-stage and multistage stochastic programming are used as the mathematical framework to hedge against uncertainty. Our case study shows that there is value of using stochastic programming when the price variance is high. However, when the variance of the price is low, solving the stochastic programming problems does not create additional value compared with solving the deterministic problem.     

SMDP-based sleep policy for base stations in heterogeneous cellular networks

A dense heterogeneous cellular network can effectively increase the system capacity and enhance the network coverage. It is a key technology for the new generation of the mobile communication system. The dense deployment of small base stations not only improves the quality of network service, but also brings about a significant increase in network energy consumption. This paper mainly studies the energy efficiency optimization of the Macro-Femto heterogeneous cellular network. Considering the dynamic random changes of the access users in the network, the sleep process of the Femto Base Stations (FBSs) is modeled as a Semi-Markov Decision Process (SMDP) model in order to save the network energy consumption. And further, this paper gives the dynamic sleep algorithm of the FBS based on the value iteration. The simulation results show that the proposed SMDP-based adaptive sleep strategy of the FBS can effectively reduce the network energy consumption.     

Effect of boron addition on microstructure,mechanical properties and oxidation resistance of TaC ceramics

TaC ceramics with 0.03–0.60?wt% of boron additions were prepared by hot pressing at 2100?°C for 1?h under a pressure of 40?MPa. Effects of boron content on densification, phase composition, microstructure, mechanical properties and oxidation resistance of the TaC ceramics were investigated. When the boron content was 0.12?wt% and above, full density was obtained due to reactions between boron and oxygen impurity at presence of TaC. Minor phases of TaB₂ and C were formed in the 0.24 and 0.60?wt% B compositions after gas-out of the oxygen impurity. Microstructure of the TaC ceramics was refined with increasing in boron content. The TaC ceramic with 0.24?wt% of boron showed the best mechanical properties with a Vickers hardness, flexural strength and fracture toughness of 17.7?GPa, 534?MPa and 4.6?MPa?m^1/2, respectively. When more boron was added, interfacial bonding of the TaC grains was strengthened causing a decrease in fracture toughness. Oxidation resistance of the TaC ceramics increased with boron content. Particularly, the 0.60?wt% B composition showed a weight gain of 0.0018?g/cm² after oxidization at 800?°C in air for 3?h.     

Single metal atom decorated photocatalysts:Progress and challenges

Photocatalysis has attracted intense attention due to its potential to solve the energy resource problem and environmental issues.The single metal atom decorated photocatalysts as a rising star become more and more popular because of the unique advantages of superior catalytic activities and ultrahigh atom utilization efficiency.The key function of single metal atom catalysts in photocatalytic reactions is boosting surface redox reactions by utilizing photogenerated charges,and has been verified by various spectroscopic and microscopic techniques.Nevertheless,the activities of the single metal atoms highly depend on the binding environment in the host photocatalyst that affect the adsorption and activation of reactants as well as the reaction energy barrier.Herein,this mini review summarizes recent progress on single metal atom decorated photocatalysts,and discusses the roles of the single metal atom catalysts in different types of host photocatalysts including organic,carbon-based and inorganic materials.The remaining challenges and future perspectives on the stability and activities of single atom catalysts in photocatalytic processes are elaborated in the end.We believe that this mini review will provide valuable overview on synthetic methods of different single atom photocatalysts for researchers towards future development of highly efficient photocatalysts.