Graphene-based hybrid materials and their applications in energy storage and conversion

Graphene attracts more and more scientists and researchers owing to its superior electronic,thermal,and mechanical properties.For material scientists,graphene is a kind of versatile building blocks,and considerable progress has been made in recent years.Graphene-based hybrid materials have been prepared by incorporating inorganic species and/or cross-linking of organic species through covalent and/or noncovalent interactions.The graphene-based hybrid materials show improved or excellent performance in various fields.In this review,we summarize the synthesis of graphene and graphene-based hybrid materials,and their applications in energy storage and conversion.     

低成本消除相变储热材料分层的方法

通过对各种增稠剂的试验研究,选出白炭黑、凹凸棒土、水溶性聚合物CA—5三种增稠剂,可有效的防止相变储热材料分层。其中以水溶性聚合物CA—5效果最好,经热循环1500次后储热能力仅衰减27.16%。     

Hydrogen storage properties of MgH<Subscript>2</Subscript> co-catalyzed by LaH<Subscript>3</Subscript> and NbH

To improve the hydrogen storage properties of Mg-based alloys, a composite material of MgH₂ + 10wt%LaH₃ + 10wt%NbH was prepared by a mechanical milling method. The composite exhibited favorable hydrogen desorption properties, releasing 0.67wt% H₂ within 20 min at 548 K, which was ascribed to the co-catalytic effect of LaH₃ and NbH upon dehydriding of MgH₂. By contrast, pure MgH₂, an MgH₂ + 20wt%LaH₃ composite, and an MgH₂ + 20wt%NbH composite only released 0.1wt%, 0.28wt%, and 0.57wt% H₂, respectively, under the same conditions. Analyses by X-ray diffraction and scanning electron microscopy showed that the composite particle size was small. Energy-dispersive X-ray spectroscopic mapping demonstrated that La and Nb were distributed homogeneously in the matrix. Differential thermal analysis revealed that the dehydriding peak temperature of the MgH₂ + 10wt%LaH₃ + 10wt%NbH composite was 595.03 K, which was 94.26 K lower than that of pure MgH₂. The introduction of LaH₃ and NbH was beneficial to the hydrogen storage performance of MgH₂.     

Mica-stabilized polyethylene glycol composite phase change materials for thermal energy storage

Mica was used as a supporting matrix for composite phase change materials(PCMs) in this work because of its distinctive morphology and structure.Composite PCMs were prepared using the vacuum impregnation method,in which mica served as the supporting material and polyethylene glycol(PEG) served as the PCM.Fourier transform infrared and X-ray diffraction analysis confirmed that the addition of PEG had no effect on the crystal structure of mica.Moreover,no chemical reaction occurred between PEG and...     

A rapid response photochromic diarylethene material for rewritable holographic data storage

A novel diarylethene,namely 4,5-(2,5-dimethyl thiophene) phthalimide,was synthesized and successfully introduced to rewritable holographic data storage.Upon the alternative illumination of UV and visible light(>400 nm),this compound underwent rapid,reversible inter-conversion between colorless open-ring isomer and yellow-green ring-closed form in both solution and polymethyl methacrylate(PMMA) film.Subsequently,we investigated the characteristics of volume homographic recording of the diarylethene-doped PMMA film(1 m thick).The maximum refractive index modulation(0.87‰) of the film during recording could be reached within just 120 s which gave the ability of fast recording.The high quality reconstruction after 50 write/erase cycles demonstrated its excellent fatigue-resistance and high resolution.All those results indicated that this molecule was a reliable fast write/erase holographic storage material.     

Investigation into the energy consumption of a data center with a thermosyphon heat exchanger

A data center test model was used to analyze the energy dissipation characteristics and energy consumption of a data center.The results indicate that adequate heat dissipation from a data center cannot be achieved only from heat dissipation through the building envelope during Beijing winter conditions.This is because heat dissipation through the building envelope covers about 19.5% of the total data center heat load.The average energy consumption for an air conditioner is 4 to 5 kW over a 24-h period.The temperature difference between the indoor and outdoor air for the data center with a thermosyphon heat exchanger is less than 20°C.The energy consumption of the thermosyphon heat exchanger is only 41% of that of an air conditioner.The annual energy consumption can be reduced by 35.4% with a thermosyphon system.In addition,the effect of the outdoor temperature on the en-ergy consumption of an air conditioner is greater than the indoor room temperature.The energy consumption of an air conditioner system increases by 5%to 6%for every 1°C rise in the outdoor temperature.     

I-sieve: An Inline High Performance Deduplication System Used in Cloud Storage

Data deduplication is an emerging and widely employed method for current storage systems. As this technology is gradually applied in inline scenarios such as with virtual machines and cloud storage systems, this study proposes a novel deduplication architecture called I-sieve. The goal of I-sieve is to realize a high performance data sieve system based on i SCSI in the cloud storage system. We also design the corresponding index and mapping tables and present a multi-level cache using a solid state drive to reduce RAM consumption and to optimize lookup performance. A prototype of I-sieve is implemented based on the open source i SCSI target, and many experiments have been conducted driven by virtual machine images and testing tools. The evaluation results show excellent deduplication and foreground performance. More importantly, I-sieve can co-exist with the existing deduplication systems as long as they support the i SCSI protocol.     

汽车制动能量再生方法的探讨

介绍了汽车制动能量再生原理，分析了飞轮储能、液压储能和电化学储能三种汽车制动能量再生方法．在充分比较三种储能方式的优点和技术制约问题的基础上，提出了一种新型制动能量再生系统的技术方案．该新型制动能量再生系统既可以实现汽车制动能量的回收和在车发电，也能实现发动机起动，汽车加速辅助功率等功能、在城市工况下可节油10％～30％。     

Development of Rare Earth Hydrogen Storage Alloys: Correlation Between Structure,Stability, and Hydrating Properties

The structure of β-LaNi₅H_x is mentioned. Special emphasis is laid on the influence of substitutions with metallic elements on the thermodynamic properties of the rare-earth-nickel hydrogen storage alloys. The models of the heat of hydride formation are studied attentively. The relation between the stability and the heat of formation of intermetallic compounds including with other physical properties is discussed. The relations between hydriding properties and the geometric and electronic structure of the intermetallic compounds are presented.     

基于石墨烯的功能化复合材料及其在电化学储能中的应用

能源问题是人类社会未来面临的重大挑战,从实现电能与化学能相互转换的角度而言,作为一种二维结构材料,石墨烯不仅可以构筑电子导电网络,也可实现对反应活性物种状态的设计和调控,进而改变反应的热力学和动力学,在电化学储能系统中具有十分重要的意义.本文主要介绍了石墨烯的制备方法及其在构筑电子导电网络以实现对反应活性物种状态的设计和调控方面的作用和功能,分别就其在构筑硫复合材料、氧化物复合材料、导电聚合物复合材料等方面进行了讨论,并结合相应的电化学储能系统评价这些复合材料的性能.     

Frequency and Similarity-Aware Partitioning for Cloud Storage Based on Space-Time Utility Maximization Model

With the rise of various cloud services, the problem of redundant data is more prominent in the cloud storage systems. How to assign a set of documents to a distributed file system, which can not only reduce storage space, but also ensure the access efficiency as much as possible, is an urgent problem which needs to be solved.Space-efficiency mainly uses data de-duplication technologies, while access-efficiency requires gathering the files with high similarity on a server. Based on the study of other data de-duplication technologies, especially the Similarity-Aware Partitioning(SAP) algorithm, this paper proposes the Frequency and Similarity-Aware Partitioning(FSAP) algorithm for cloud storage. The FSAP algorithm is a more reasonable data partitioning algorithm than the SAP algorithm. Meanwhile, this paper proposes the Space-Time Utility Maximization Model(STUMM), which is useful in balancing the relationship between space-efficiency and access-efficiency. Finally, this paper uses 100 web files downloaded from CNN for testing, and the results show that, relative to using the algorithms associated with the SAP algorithm(including the SAP-Space-Delta algorithm and the SAP-Space-Dedup algorithm), the FSAP algorithm based on STUMM reaches higher compression ratio and a more balanced distribution of data blocks.     

Investigation of octupole effects in superheavy nuclei with improved potential-energy-surface calculations

It has been found that high-order deformation (e.g.β6) can have important effects on the structures of superheavy nuclei. In the present work, we investigate octupole deformation effects on superheavy nuclei with an improved potential-energy-surface (PES) calculation by including reflection-asymmetric deformations in a space of (β2 ,β3 ,β4 , β5). The calculations give various deformations including highly deformed (β2 ≈ 0.4) and superdeformed (β2 ≈ 0.7) shapes. The octupole-deformation degree of freedom mainly affects the fission barrier beyond the second minimum of PES.     

A simulation study on a solar driving adsorption chiller with heat and mass recovery

Effects of the cycle time,the mass recovery time and the hot water tank capacity on the performance of the chiller had been investigated.And these results also provided a proposal for the chiller driven by solar energy to work under the optimum working conditions,such as hot water circulation mode,cycle time and mass recovery time.     

Some recent progress in study of gravity and cosmology

We briefly review some progress made in the areas of gravity and cosmology.Only a small portion of the work done in China is covered.     

Mechanical properties and kinetics of thermally aged Z3CN20.09M cast duplex stainless steel

Cast stainless steels used in nuclear power plants suffer from fracture toughness losses owing to thermal aging after long-term service at temperatures ranging from 280-320℃. To study the thermal aging embrittlement of Z3CN20.09M duplex stainless steel produced in China, accelerated thermal aging experiments were carried out at 350, 380, and 400℃ for up to 10000 h. Microhardness and Charpy impact energies were measured at different aging times. The microhardness of ferrite increased drastically over the initial aging time of 2000 h at 380 and 400℃ and then slowly reached HV_0.01 560. In contrast to this observed change in microhardness, Charpy impact energies sharply decreased after initial aging and then gradually reached a minimum value. Taking the microhardness of the ferrite phase as the parameter describing the thermal kinetics of the stainless steel samples, the activation energy of thermal aging was calculated to be 51 kJ/mol. Correlations between the thermal aging parameter, P, and ferrite microhardness and between P and Charpy impact energy were also analyzed. The results showed that the activation energy calculated from the ferrite microhardness is much more reasonable than that obtained using other parameters, such as chemical composition and impact energy.     

储能压力对液态压缩空气储能系统特性的影响

为了探究液态压缩空气储能系统工作参数对系统性能的内在作用机理及系统能效提升方法,建立了该系统的热力学模型。应用Aspen Plus软件进行流程仿真,对系统进行了热力学特性分析,并深入研究了液态空气储能压力对系统各单元及系统能效的影响规律。研究结果表明:较高品位的压缩余热和较小的循环空气流量可有效提升系统余热再利用率,显著提升系统性能;当储能压力由0.86 MPa提升至1.67 MPa时,系统压缩热的品位得以提升,膨胀机级间再热温度由114℃提升至160℃,同时可降低循环空气流量约0.5%,使得压缩机耗功降低,同时膨胀机输出总功增加,系统效率由31.61%提升至42.54%;储能压力的提升有利于降低低温储罐漏热,并减少制冷膨胀机出口带液量,可进一步改善系统的整体性能。     

Electrochemical properties and structure of MlNi5-xSnx system

The electrochemical properties and structure of MlNiSnx (x=0-0.5) hydrogen storage alloys were investigated by pressure-composition isotherms, electrochemical measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic parameters. With a small amount of tin substitution, the cycle life increases by 52% (0.5C) and 42% (1.0C), but maximum discharge capacity decreases only by 3.0% and 3.5%, respectively. The cycle life is obviously improved by the low volume expansion and the formed SnO2 surface layers upon electrochemical cycling. The substitution of Ni by Sn leads to an increase of theunit cell volume and charge-discharge cycle life and decrease of the plateau pressure, hysteresis and the hydrogen storage capacity. The standard enthalpy of hydride formation decreases with increasing tin substitution. The main factor that influences the standard enthalpy of the hydriding reaction is the number of the outer orbit electrons and not the atomic size factor.     

Seismic considerations for spent nuclear fuel storage in dry casks

o aid the United States’ Nuclear Regulatory Commission, Sandia National Laboratories (SNL) was contracted to investigate the seismic behavior of typical dry cask storage systems. Parametric evaluations characterized the sensitivity of calculated cask response characteristics to input parameters. The parametric evaluation investigated two generic cask design (cylindrical and rectangular), three different foundation types (soft soil, hard soil, and rock), and three different cask to pad coefficients of friction (0.2, 0.55, 0.8) for earthquakes with peak ground accelerations of 0.25g, 0.6g, 1.0g and 1.25g. A total of 1 165 analyses were completed, with regression analyses being performed on the resulting cask response data to determine relationships relating the mean (and 16 % and 84 % confidence intervals on the mean) to peak ground acceleration, peak ground velocity, and pseudo-spectral acceleration at 1 Hz and 5 % damping. In general, the cylindrical casks experienced significantly larger responses in comparison to the rectangular cask. The cylindrical cask experienced larger top of cask displacements, larger cask rotations (rocking), and more occurrences of cask toppling (the rectangular cask never toppled over). The cylindrical cask was also susceptible to rolling once rocking had been initiated, a behavior not observed in the rectangular cask. Cask response was not overly sensitive to foundation type, but was significantly dependent on the response spectrum employed.