Al@AlN-Al2O3高温复合相变蓄热材料的制备与性能研究

以Al作为相变材料,采用直接氮化法制备出一种核壳结构Al@Al N-Al_2O_3新型高温复合相变蓄热材料。利用X射线粉末衍射仪、扫描电子显微镜、能谱仪、拉曼光谱仪和差示扫描量热分析仪对材料进行表征。进一步研究锂盐助剂种类及反应时间对材料合成的影响,同时对材料的热循环性能进行测定。结果表明:在750℃条件下制备的复合材料达到预期的核壳结构,其相变材料含量64.6%,相变温度为662.3℃,蓄热密度高达326.3 kJ/kg。同时发现Li_2CO_3助剂的加入、反应时间的延长均可促进AlN的合成,从而使核壳结构更加稳定。经过20次热循环后,该材料仍表现出稳定的蓄热性能。     

静电纺丝法制备TMO/C复合纳米纤维在锂离子电池负极材料中的应用进展

过渡金属氧化物(TMO)因其极高的理论比容量被认为是代替石墨成为锂离子电池负极材料的最佳选择之一,但是在充放电过程中的过度体积膨胀以及较差的导电性能限制了其进一步发展.将TMO材料与碳材料复合,既能满足储锂容量需求,又能避免充放电过程中过度体积膨胀.通过对近期相关文献的调研,对以静电纺丝技术为基础制备的TMO/C混合材料纳米纤维作为锂离子电池的负极材料的研究结果进行了总结.着重介绍了多孔、核壳、中空以及混合结构的TMO/C混合材料纳米纤维的制备过程,以及这些特殊结构对锂离子电池性能的影响情况.综合分析表明,具有较大比表面积和丰富孔洞结构的纳米纤维膜在充放电循环过程中为化学反应提供更多的活性点位,为锂离子的快速扩散和电荷转移建立了良好的导电通路,对于锂离子电池的电化学性能有着较大的改善作用.最后讨论了该领域目前存在的不足和挑战,并对TMO基锂离子电池负极材料未来的发展方向做了如下展望:简化制备工艺,降低制备成本,提高制备效率,实现量产;研究发掘出更适合与TMOs复合的材料,开发出结构更加合理、性能更加优异的锂离子电池.     

TiO2纳米薄膜厚度对CdS纳米柱阵列 光电化学性能和稳定性的影响

利用水热合成法在导电玻璃表面上原位生长CdS纳米柱阵列（CdSNRA）,然后通过浸渍提拉法在其表面涂覆TiO₂纳米薄膜,制备CdSNRA@TiO₂异质结复合结构材料。利用扫描电镜、X射线衍射、紫外可见光吸收、拉曼光谱等手段对其形貌和结构进行表征。进一步考察了TiO₂薄膜厚度对CdSNRA@TiO₂复合结构光电极的光电化学性能的影响。结果表明,覆盖50 nm 厚TiO₂层的CdSNRA复合结构光电极在可见光下具有更好的光电性能和稳定性,这归因于CdSNRA核和TiO₂壳之间光生电子和空穴的有效分离。     

Sol-gel法制备Y_2O_3∶Eu~(3+)/Yb~(3+)@SiO_2太阳能上转换材料的研究

采用pechini溶胶-凝胶法制备Eu~(3+)/Yb~(3+)共掺Y_2O_3纳米颗粒,采用经典的St?ber方法制备SiO_2包覆上述纳米颗粒的核壳结构。借助X射线衍射仪和傅里叶红外光谱仪等测试手段,研究材料的结构性能。结果表明:SiO_2包覆后,Y_2O_3的晶体结构和粒子的上转换发光机制均未发生改变,Y-O-Si键的形成说明SiO_2成功包覆在Y_2O_3∶Eu~(3+)/Yb~(3+)粒子表面。紫外-可见光分光光度计和光致发光谱测试结果对比表明,SiO_2包覆后的粒子在980 nm处仍有光谱吸收,并且材料的发光强度有较大提高。     

锂离子电池正极材料生产技术的发展CSCD

本文对锂离子电池正极材料生产制备技术的发展历史进行了回顾,对锂离子电池正极材料的发展方向进行了分析。20世纪末,从锂离子电池正极材料加工性能和电池性能的角度出发,清华大学研究团队提出了控制结晶制备高密度球形前驱体的技术,结合后续固相烧结工艺,提出了制备含锂电极材料的产业技术。其中,控制结晶方法制备前驱体,可以在晶胞结构、一次颗粒组成与形貌、二次颗粒粒度与形貌,以及颗粒表面化学4个层面对材料的性能进行调控与优化。利用该技术工艺生产的材料具有颗粒粒度及形貌易控制、均匀性好、批次一致性和稳定性好的特点,可以同时满足电池对于材料电化学性能和加工性能的综合要求。因材料的堆积密度高,尤其适用于高比能量电池。该技术工艺适用于多种正极材料,并适合于大规模生产,随着时间的推移,逐步被证明是锂离子电池正极材料的最佳生产技术工艺,得到了现今产业界的普遍接受和认可。这也是我国科学工作者对国际锂离子电池产业做出的重要贡献之一。     

CaO/Ca(OH)_(2)核壳结构颗粒的制备及其储热性能北大核心CSCD

热化学储热具有储热密度高,可实现跨季节储热的优点。在中高温储热领域,氧化钙/氢氧化钙储热系统目前仍存在储热材料易结块、难以流态化等问题。本文通过在氢氧化钙颗粒外包覆一层烧结的碳化硅陶瓷壳的方法,制备了一种可用于氧化钙/氢氧化钙储热系统的具有核壳结构的储热颗粒。研究表明,该核壳结构颗粒壳体和芯体的内部孔隙呈现出不同的孔径分布,壳体的孔径大于内部芯体的孔径,因此壳体的包裹对于内部氢氧化钙的储放热反应进程影响较小,相对于纯氢氧化钙,核壳结构颗粒在反应速率和力学性能方面也有所提升。表征结果显示,颗粒的壳体化学性质较为稳定,不会与氢氧化钙发生反应导致储热密度的降低。此外,该核壳结构颗粒具有较好的循环稳定性,在空气氛围下,对所制备颗粒进行了25次储放热循环,发现该颗粒储热密度的下降在20%以内且未发生开裂和破碎。颗粒储热密度的下降是由于氢氧化钙与空气中的二氧化碳反应生成了碳酸钙,经过高温煅烧除去碳酸钙后,颗粒的储热密度可恢复至初始储热密度的96.7%。综上,本工作制备储热颗粒对热化学储热技术的实际应用具有重要意义。     

含氟层包覆镁粉的制备与燃烧性能

使用聚四氟乙烯(PTFE)作为氟源，在高温电阻炉中将PTFE/Mg混合粉末加热到600℃后制备了包覆镁粉．使用XRD、SEM、EDS、TG-DSC和显微镜等对镁原料和包覆镁粉的反应特性进行了研究．结果表明：包覆镁中活性镁的含量为97.2%．在空气中反应时，其DSC上放热峰的起始反应温度比镁原料上升了233.9℃．燃烧过程中包覆镁形成了典型的壳核结构，且在燃烧后期，包覆层内的F-Mg相会转化为MgF₂相并析出多余的Mg.     

磷化工副产物磷铁制备锂电池正极材料LiFePO4的研究

本文从废物利用和可持续发展的角度出发,成功利用磷化工副产物磷铁制备了储能锂电池正极材料LiFePO4。从原料磷铁的粒度和碳包覆量两个方面对制备的LiFePO4性能进行了探究,磷铁粒度越小,制备的LiFePO4综合性能越好。当碳包覆量为6.5wt% 时,在0.1 C、0.2 C、0.5 C、1 C、2 C和5 C的倍率下,4000目磷铁制备的样品放电容量分别为153、150、143、130、115和103 mA•h/g,和传统昂贵原料制备的对应材料性能相当,表明利用磷铁制备能源材料具有良好的发展前景。     

椭球形金纳米棒作为癌细胞靶向探针的研究

【摘要】 目的 制备椭球形核-壳结构二氧化硅包覆的金纳米复合材料。方法 选用二氧化硅作为壳材,制备椭球形二氧化硅包覆的金纳米棒,并用硅烷耦联剂和二氧化硅耦联,将叶酸联接到二氧化硅包覆的金纳米棒（GNRs@SiO2?蛳 FA）,用罗丹明异硫氰酸酯与GNRs@SiO2?蛳 FA表面的氨基基团反应,得到罗丹明标记的GNRs@SiO2?蛳 FA。用MTT比色法研究其生物相容性。结果 表面修饰后的金纳米棒有良好的生物相容性。透射电镜观察到金纳米颗粒以细胞吞噬方式进入细胞,可靶向结合于叶酸高表达的癌细胞;激光共聚焦显微镜见GNRs@SiO2?蛳 FA能携带荧光探针进入细胞内,可作为荧光物质或药物的载体。结论 GNRs@SiO2?蛳 FA可靶向作用于癌细胞,并可作为荧光试剂或其他生物标记物的载体,应用于疾病的诊断及肿瘤125I粒子治疗等方面。     

Review of doping and surface coating of cathode materials for lithium ion batteries

随着国家政策对电动汽车的支持力度不断加大,锂离子电池的电化学性能瓶颈愈发凸显。本文综述了锂离子电池正极材料钴酸锂、锰酸锂、磷酸铁锂及三元材料在掺杂和表面包覆两种工艺对电池电化学方面的影响,并展望了掺杂和表面包覆两种工艺未来的研究方向。     

Recent insights in synthesis and energy storage applications of porous carbon derived from biomass waste: A review

In the last few decades, global warming, environmental pollution, and an energy shortage of fossil fuel may cause a severe economic crisis and health threats. Storage, conversion, and application of regenerable and dispersive energy would be a promising solution to release this crisis. The development of porous carbon materials from regenerated biomass are competent methods to store energy with high performance and limited environmental damages. In this regard, bio-carbon with abundant surface functional groups and an easily tunable three-dimensional porous structure may be a potential candidate as a sustainable and green carbon material. Up to now, although some literature has screened the biomass source, reaction temperature, and activator dosage during thermochemical synthesis, a comprehensive evaluation and a detailed discussion of the relationship between raw materials, preparation methods, and the structural and chemical properties of carbon materials are still lacking. Hence, in this review, we first assess the recent advancements in carbonization and activation process of biomass with different compositions and the activity performance in various energy storage applications including supercapacitors, lithium-ion batteries, and hydrogen storage, highlighting the mechanisms and open questions in current energy society. After that, the connections between preparation methods and porous carbon properties including specific surface area, pore volume, and surface chemistry are reviewed in detail. Importantly, we discuss the relationship between the pore structure of prepared porous carbon with surface functional groups, and the energy storage performance in various energy storage fields for different biomass sources and thermal conversion methods. Finally, the conclusion and prospective are concluded to give an outlook for the development of biomass carbon materials, and energy storage applications technologies. This review demonstrates significant potentials for energy applications of biomass materials, and it is expected to inspire new discoveries to promote practical applications of biomass materials in more energy storage and conversion fields.     

秸秆高值化综合利用研究现状

秸秆高值化综合利用是生物质化工的重要研究方向,可望成为传统石油化工的重要补充。通过化学与生物手段可以将秸秆转化为各类产品,为能源、材料、化工领域提供绿色可再生的制备路线。整合化学与生物手段是实现秸秆高值化综合利用及产业化的关键。本文介绍了典型秸秆的化学与生物转化方法,阐述了化学与生物技术集成应用于秸秆高值化转化的科学思路、研究现状与发展趋势,为秸秆高值化综合利用技术的发展提供一定的参考。     

Preparation of hollow carbon nanocages by iodine-assisted heat treatment

Carbon nanocages (CNCs) with a hollow structure and high degrees of graphitization and purity have wide applications. However, preparation of such material is still a great challenge. In this study, we report a general strategy for the preparation from iron/graphite core-shell nanoparticles. The core-shell nanoparticles are synthesized by the pyrolysis of acetylene with iron carbonyl. In order to remove the metallic core, rather than using the conventional acid oxidation, the nanoparticles are heat treated in the presence of iodine. It is found that the entrapped iron particles can be completely eliminated and hollow CNCs with good graphitization and high purity can be obtained. The purification process may involve the diffusion of iron atoms out from CNCs and their reaction with iodine molecules in the surrounding atmosphere. The reaction product FeI₂ is soluble in ethanol and could thus be easily removed. As an example of a potential application, the CNCs are demonstrated to be a superb material for supporting the Pt catalyst used in low-temperature fuel cells. The present method could be applied to the production of graphitic carbon in large scale, and the resultant material could prove to be practically relevant for fuel cell and many other technologies.     

Design and synthesis of NiS@CoS@CC with abundant heterointerfaces as high-efficiency hydrogen evolution electrocatalyst

Rational design and construct heterointerfaces of noble-metal-free materals is of very important to prepare high-performance electrocatalysts for hydrogen evolution reactions (HER). Herein, a novel 3D core-shell NiS@CoS@CC with abundant heterointerfaces is synthesized via a three-step strategy. The three-steps involve the rectangular Co(OH)₂ nanosheet arrays were grown on the CC, Ni(OH)₂ nanowires further grown on the Co(OH)₂ nanosheets to form a novel core-shell architecture (that is, nanosheets wrapped with nanowires), and the conversion of hydroxides to sulfides. In the 3D NiS@CoS@CC heterostructure, NiS are dispersively distributed on the surface of rectangular CoS nanosheets to form abundant heterointerface active sites, meanwhile, a large number of tiny pores are uniformly distributed over the core-shell structure due to the conversion of hydroxides to sulfides. The abundant NiS@CoS core-shell heterointerfaces can decrease the free energy of adsorption of H_ads and enhance electronic conductivity through electronic coupling effects between different components, facilitate the electron transfer from the CoS nanosheets to the surrounding NiS. Furthermore, 3D porous structure can provide abundant edge sites and more electroactive surface area, and can accelerate the diffusion of gaseous products. Consequently, the as-prepared NiS@CoS@CC electrocatalyst presents remarkably enhanced performance for the HER in alkaline medium. The overpotential for HER is as low as 30 mV at a current density of 10 mA cm⁻². Correspondingly, the Tafel slope of the electrode reaction is 97 mV dec⁻¹. Particularly, the catalyst maintained a high stability (the final polarization curves suffer negligible degradation in comparison with the initial after taking 1000 continuous CV). The work provides a viable technical solution for fabricating heterostructure materials with excellent performances for future energy storage and conversion devices.     

Review on core-shell structured cathode for intermediate temperature solid oxide fuel cells

Lowing the operating temperature can greatly promote the commercialization of solid oxide fuel cells (SOFCs), however it also results in a significant increase in cell impedance, which is the bottleneck for the development of intermediate temperature SOFCs (IT-SOFCs). Major hurdles in developing conventional single-phase cathode materials for IT-SOFCs are poor electrochemical performance or durability. The investigation of new cathode materials or the optimization of the existing cathodes is imminent for the development of IT-SOFCs. Among them, core-shell structured cathode can combine the advantages of multiple components, and has been demonstrated with excellent oxygen reduction reaction (ORR) catalytic activity and long-term stability. This review summarizes the recent research progress on core-shell structured cathode for enhanced electrochemical performance, long-term stability, CO₂ tolerance and Cr tolerance. Furthermore, the future directions are discussed from a perspective of materials design, preparation and characterization. Core-shell structured cathodes are expected to play an increasingly critical role in the commercialization of IT-SOFCs.     

Crosslinked poly(vinyl alcohol)/sulfonated poly(ether ether ketone) blend membranes for fuel cell applications—Surface energy characteristics and proton conductivity

Ionic polymers, their blends and composites are considered potential candidates for application as electrolytes in fuel cells. While developing new materials for membranes, it is important to understand the interactions of these electrolytic materials with electrodes/catalysts and with reactants/products. Some of these interactions can be understood by estimating the surface energy and wettability of the membrane materials. In this work, polyvinyl alcohol with varying degrees of sulfonation and its blend with sulfonated poly(ether ether ketone) are prepared and studied for their wettability characteristics using goniometry. The surface energy and its components are estimated using different approaches and compared. Properties such as the ion-exchange capacity, the proton conductivity and the water sorption/desorption behaviour are also investigated to understand the relationship with wettability and surface energy and its components. Among the different methods, the van Oss acid-base and the modified Berthelot approaches yield comparable estimates for the total surface energy.     

Rational design of hierarchical core-shell structured CoMoO4@CoS composites on reduced graphene oxide for supercapacitors with enhanced electrochemical performance

Engineering multicomponent active materials as an advanced electrode with the rational designed core-shell structure is an effective way to enhance the electrochemical performances for supercapacitors. Herein, three-dimensional self-supported hierarchical CoMoO₄@CoS core-shell heterostructures supported on reduced graphene oxide/Ni foam have been rationally designed and prepared via a facile approach. The unique structure and the synergistic effects between two different materials, as well as excellent electronic conductivity of the reduced graphene oxide, contribute to the increased electrochemically active site and enhanced capacitance. The core-shell CoMoO₄@CoS composite displays the superior specific capacitance of 3380.3 F g⁻¹ (1 A g⁻¹) in the three-electrode system and 81.1% retention of the initial capacitance even after 6000 cycles. Moreover, an asymmetric device was successfully prepared using CoMoO₄@CoS and activated carbon as positive/negative electrodes. It is worth mentioning that the device delivered the high energy density of 59.2 W h kg⁻¹ at the power density of 799.8 W kg⁻¹ and the excellent cycle performance (about 91.5% capacitance retention over 6000 cycles). These results indicate that the core-shell CoMoO₄@CoS composites offers the novelty strategy for preparation of electrodes for energy conversion and storage devices.     

Preparation and characterization of active and cost-effective nickel/platinum electrocatalysts for hydrogen evolution electrocatalysis

Designing active and cost-effective electrocatalysts is important in the field of energy economics, particularly for hydrogen production, which is at the core of many energy conversion technologies. This investigation reports on the preparation of nickel-based materials targeting electrocatalytic hydrogen evolution in either alkali or physiological solutions. Nickel-based metallic nanoparticles were synthesized via the bromide anion exchange method, and their performance was compared with the performances of a homemade nickel mesh and a high-purity nickel foil. The Ni₉₉Pt₀₁/C electrocatalyst performed the best in terms of overpotential and generated current density, notably in physiological conditions. In addition, the homemade electroformed nickel mesh behaved as well as a commercial high-purity nickel foil in alkaline medium and even better in buffered solution at pH 7. Both materials are environmentally friendly and economically viable candidates for technologies that require large cathode materials, especially when hydrogen production in neutral electrolytes is sought.     

Overview of current and future energy storage technologies for electric power applications

In today's world, there is a continuous global need for more energy which, at the same time, has to be cleaner than the energy produced from the traditional generation technologies. This need has facilitated the increasing penetration of distributed generation (DG) technologies and primarily of renewable energy sources (RES). The extensive use of such energy sources in today's electricity networks can indisputably minimize the threat of global warming and climate change. However, the power output of these energy sources is not as reliable and as easy to adjust to changing demand cycles as the output from the traditional power sources. This disadvantage can only be effectively overcome by the storing of the excess power produced by DG-RES. Therefore, in order for these new sources to become completely reliable as primary sources of energy, energy storage is a crucial factor. In this work, an overview of the current and future energy storage technologies used for electric power applications is carried out. Most of the technologies are in use today while others are still under intensive research and development. A comparison between the various technologies is presented in terms of the most important technological characteristics of each technology. The comparison shows that each storage technology is different in terms of its ideal network application environment and energy storage scale. This means that in order to achieve optimum results, the unique network environment and the specifications of the storage device have to be studied thoroughly, before a decision for the ideal storage technology to be selected is taken.     

Superconducting magnetic energy storage

Superconducting magnetic energy storage (SMES) is an energy storage technology that stores energy in the form of DC electricity that is the source of a DC magnetic field. The conductor for carrying the current operates at cryogenic temperatures where it is a superconductor and thus has virtually no resistive losses as it produces the magnetic field. The overall technology of cryogenics and superconductivity today is such that the components of a SMES device are defined and can be constructed. The integrated unit appears to be feasible for some utility applications at a cost that is competitive with other technologies. SMES is the only technology based on superconductivity that is applicable to the electric utilities and is commercially available today. In addition to today's power quality application, the historical development of SMES starting with the concept of very large plants that would store hundreds of megawatt hours of energy and were intended for diurnal load leveling are described.