MgH2粒径对2LiBH4+MgH2体系放氢动力学性能的影响

研究了MgH₂粒径对2LiBH₄+MgH₂体系放氢动力学性能的影响.采用高能球磨方式对50~100 μm 粒径的MgH₂预球磨96 h, 其粒径可减小到100~200 nm.结果表明, 对MgH₂进行预球磨可使2LiBH₄+MgH₂体系的两步放氢温度分别降低58和24℃, 并可明显提高体系的放氢动力学性能.XRD结果表明, MgH₂粒径的减小有利于放氢过程中MgB₂ 的生成, 从而提高体系放氢产物的可逆吸氢能力.     

3LiBH4/CeF3体系的放氢性能及机制

采用球磨法制备了3LiBH₄/CeF₃反应体系, 通过压力-组成-温度(PCT)测试仪、 X射线衍射仪(XRD)和傅里叶变换红外光谱仪(FTIR)研究了体系的放氢性能、 反应机制及性能改善机理. 结果表明, 3LiBH₄/CeF₃体系在295 ℃左右快速放氢, 总放氢量为4.1%(质量分数). 放氢过程中CeF₃与LiBH₄直接发生反应: 3LiBH₄+CeF₃1/2CeB₆+1/2CeH₂+3LiF+11/2H₂. 与纯LiBH₄相比, 放氢热力学稳定性和表观活化能的降低是3LiBH₄/CeF₃体系放氢温度下降的主要原因.     

硼氢化锂储氢材料研究*

车载储氢是推进氢燃料车规模化商业应用的“瓶颈”环节,开发高性能车载储氢材料/技术成为当前能源及材料领域关注的热点。近年来,随着储氢材料领域的不断拓展,以硼氢化锂（LiBH₄）为典型代表的高储量配位金属氢化物日渐成为新兴的储氢材料研究热点。本文从体系成分/反应路径调整、纳米结构调制、阴/阳离子替代及催化体系构建等方面概述了改善LiBH4综合储/放氢性能的最新研究进展,旨在明确配位硼氢化物储氢材料研究中的关键问题及可能的解决途径。     

g-C3N4光催化材料的第一性原理研究

能源短缺和环境恶化是人类社会快速发展面临的重大难题。太阳能作为一种清洁无污染的理想新型能源,具有取之不尽、用之不竭的特点,是实现可持续发展的最佳能源选择。半导体光催化可以直接利用太阳光进行催化反应,得到了广泛关注。作为一种低成本无金属光催化剂,g-C₃N₄具有独特的电子能带结构、优良的化学稳定性和热力学稳定性,在光催化领域如分解水制氢制氧、降解有机污染物、CO₂还原、抗菌和有机官能团选择性转换等方面表现出巨大的应用前景。目前g-C₃N₄光催化剂存在着如比表面积小、可见光利用率低、量子产率低和光生载流子易复合等问题,制约了其在光催化领域的应用。因此,提升g-C₃N₄光催化性能是光催化研究领域的重要课题。第一性原理具有半经验方法不可比拟的优势,已成为光催化研究领域计算和模拟的重要基础。基于密度泛函理论的第一性原理在光催化领域的广泛应用,为有效迅速地探求能够改善g-C₃N₄光催化性能的方法提供了明确的研究手段。本文从理论计算的角度综述了近年来在g-C₃N₄改性方面所取得的一些重要研究进展,主要包括元素掺杂、复合和形貌调控等改性手段。本文以g-C₃N₄改性光催化剂为研究对象,从电子性质、能带结构、光学性质和缺陷形成能的角度阐述了各种改性手段提高光催化活性的微观机理。最后,在总结前文所述各类改性研究的基础上,对g-C₃N₄改性光催化剂未来的发展趋势作出了展望。     

Pt-C3N4/BiOCl S型异质结应用于光催化CO2还原的理论计算研究(英文)

光催化CO₂还原制备可再生的碳氢燃料为缓解温室效应、解决能源短缺问题提供了一个可行的办法。然而,单一组分光催化剂的CO₂还原活性非常低。一是因为光生载流子的快速复合导致光子效率很低。二是因为CO₂的活化需要较高的能垒。对此,研究人员作出了许多改进以提高CO₂还原性能。例如,发展S型异质结可以增强载流子的分离和光催化剂的氧化还原能力,引入金属单原子助催化剂可以优化反应热力学。因此,协同利用S型异质结和金属单原子修饰将能同时促进载流子的转移和CO₂还原反应过程。本文构建了由单原子Pt负载的g-C₃N₄和BiOCl组成的Pt-C₃N₄/BiOCl异质结模型。用密度泛函理论计算研究了其光催化性能,包括几何结构和电子性质的探索、CO₂转化过程的模拟。差分电荷密度结果表明g-C₃N₄中的电子转移至BiOCl,这是由于g-C₃     

ZnCl2、KOH和HNO3改性MWCNT对苯酚的吸附行为研究

通过扫描电子显微镜、X射线衍射仪、N₂吸附分析仪及Boehm滴定法获得ZnCl₂、KOH和HNO₃化学处理对高纯多壁碳纳米管的结构和表面含氧官能团的影响,通过批处理实验考察吸附条件（吸附时间、初始浓度、温度）对处理前后的碳纳米管吸附苯酚行为的影响,并采用准一级、准二级、Evolich动力学模型和热力学方程拟合其吸附数据,分析其动力学行为、热力学行为和吸附机理。结果表明,虽然ZnCl₂、KOH和HNO₃化学处理法均未对碳纳米管BET比表面积产生显著影响,但会影响其表面化学性质（即,对于ZnCl₂和KOH化学处理降低表面羧基、内酯基含量和增大碱性官能团量,而对于HNO₃化学处理可以增大表面羧基、内酯基含量,而碱性官能团略有增加）;改性处理影响碳纳米管去除苯酚效率：由于ZnCl₂和KOH改性处理降低碳纳米管表面羧基量,故其提高了苯酚去除率,而HNO₃处理则略减小碳纳米管的苯酚去除率,可能是由于碳纳米管结构和表面化学性质共同影响所致;碳纳米管的苯酚去除率均随苯酚溶液初始浓度的增大而减小;高温不利于吸附;热力学研究发现碳纳米管吸附苯酚过程是自发的和放热的,属于物理吸附;动力学研究表明,吸附过程符合准二级动力学方程。通过ZnCl₂和KOH化学处理,可以显著提高碳纳米管对苯酚的吸附性能。     

铁与氯气反应的产物分析

应用高温传感器测定了铁在氯气中燃烧时的温度;基于实际反应温度、压强与物质状态,对铁与氯气的相关反应进行了热力学分析,发现FeCl₃(Fe₂Cl₆)是铁与氯气反应过程中绝大多数情况下的热力学稳定产物,而铁与氯气反应生成FeCl₂的条件则较为苛刻;反应的动力学分析,FeCl₂和FeCl₃的结构分析,也表明铁与氯气反应生成FeCl₃更加有利。     

具有18电子结构的镁基过渡金属氢化物*

本文综述了近年来备受关注的具有18电子结构和高储氢容量的镁基过渡金属氢化物Mg₂NiH₄、Mg₂CoH₅和Mg₂FeH₆的研究进展,特别从材料组成、制备工艺、热力学及动力学性能等方面进行了综合评述。提出了该类金属氢化物在实际应用中存在的一些问题,如吸/放氢温度均较高,反应动力学性能较差,对于Mg₂CoH₅和Mg₂FeH₆的制备较困难,且可逆性不好。最后展望了对于具有18电子结构的镁基过渡金属氢化物在今后研究中的发展方向。     

钐钴永磁合金吸放氢特性及应用研究进展

钐钴永磁合金因卓越的磁性能、优异的高温性能和耐蚀性得到了广泛应用。随着在航空航天,风力发电等行业对高性能钐钴永磁合金需求加强,开发高性能钐钴永磁合金一直是本领域的研究热点。采用吸氢破碎制备单晶磁粉为制备高性能钐钴永磁合金的发展提供了新思路,同时,为了满足氢气服役环境对钐钴永磁合金高温耐氢能力的要求,开发强耐氢钐钴永磁合金的需求日趋迫切,因此需加强钐钴永磁材料吸放氢动力学与热力学机制的认识与了解,以指导研究钐钴合金吸氢破碎和强耐氢合金。本文首先介绍了合金吸放氢动力学与热力学研究中常用的检测与分析方法,然后综述了SmCo₅, Sm₂Co₇和Sm₂Co₁₇合金吸放氢过程中的结构变化和动力学与热力学研究进展,接着对近年来钐钴永磁材料吸氢破碎应用的研究成果进行了总结与讨论,最后对开发易氢破和强耐氢钐钴永磁合金作了展望。     

共价有机框架材料在光催化CO2还原中的应用

全球范围内化石燃料的大量消耗导致了能源危机,同时其所排放的CO₂等温室气体使环境问题日渐突出。将CO₂等废气进一步转化为高附加值燃料是解决能源与环境问题的理想方案。利用取之不尽的太阳能作为能源实现光催化CO₂还原为能源化合物被认为是有效解决此问题的最佳途径之一。共价有机框架材料(COFs)是一类新型晶态多孔有机聚合物材料,具有结构稳定性、可设计性和结构多样化的特征,因此在光催化CO₂还原领域表现出了巨大潜力。本文概述了近年来COFs在光催化CO₂还原领域中的催化应用研究进展,包括引入不同金属离子提供活性位点、增加光敏性官能团提高其对可见光利用率等方法。最后对以COFs材料为光催化CO₂还原催化剂的研究进行了总结和展望,我们认为更进一步的新材料合成、修饰与催化机理研究仍是前景广阔的研究领域。     

A new nonempirical tuning scheme with single self‐consistent field calculation: Comparison with global and IP‐tuned range‐separated functional

System‐dependent nonempirical tuning of range‐separated functional provides a way to minimize the delocalization error of the system. However, existing nonempirical tuning method requires the computation of several ΔSCF calculations to determine the optimal μ value. In this article, we have defined a scheme to evaluate the optimal μ value with single self‐consistent field calculation. Our method is based on the evaluation of the spherically symmetric average Electron localization function (ELF) region. According to this scheme, the radius of the spherically symmetric average ELF region gives is a measure of the distance at which the long‐range part of the range‐separated functional becomes dominant. Numerical results indicate that our method improves the reproduction of HOMO energies and HOMO‐LUMO gap in comparison to global and IP‐tuned range‐separated functional. Moreover, in case of HOMO energies, maximum error of the ELF‐tuned functional is considerably smaller than the global and IP‐tuned functional. Furthermore, our method gives considerably smaller deviation of HOMO energies from ΔSCF IP than global range‐separated functional. © 2017 Wiley Periodicals, Inc.     

Synthesis,characterization, and application of light‐emitting copolyfluorenes slightly doped with distyrylbenzene derivatives

Copolyfluorenes PFG1～PFG4 slightly doped with 0.006–0.5 mol % of 2,5‐dihexyloxy‐1,4‐bis(2‐phenyl‐2‐cyanovinyl)benzene (green chromophore) were synthesized by the Suzuki coupling reaction to be evaluated as hosts for white‐light electroluminescent (EL) devices. Their optical, thermal and electrochemical properties were almost identical to those of polyfluorene ( PF ) due to minimal chromophore content. However, the electroluminescent (EL) spectra of the PFGn were very different from photoluminescence spectra in film state. Relative intensity of green emission (ca. 521 nm) in EL spectra are much stronger than those in PL spectra, which can be attributed to charges trapping in the chromophores due to its narrow band gap (E_g ≈ 2.56 eV). The performance of EL devices [ITO/PEDOT:PSS/polymer/Ca (50 nm)/Al (100 nm)] were improved with an increase in chromophore content. The PFG4 device revealed the best performance (6790 cd/m², 1.69 cd/A), and the PFG1 and PFG2 devices exhibited comparable intensity in blue and green emissions. Blend EL devices were fabricated by using the PFGn as the hosts and a red iridium complex [Ir(piq)₂(acac)] as dopant. By controlling the amount of the iridium complex, the white‐light emitting device was achieved with PFG2 , with maximum brightness and CIE coordinate being 4120 cd/m² and (0.31, 0.28), respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 149–160, 2009     

A New Software to Show The Behaviour of The PID Controller. Part II. Influence of the setting parameters of DSCs

Some DSC calorimeters, such as the model DSC 111, built by the society Setaram, allow the user to set the temperature programming parameters. Usually default values furnished by the constructor are often used, but it is very interesting to study the thermal behaviour of the regulation of the calorimeter under different conditions and with different kinds of set point temperatures. For this research, we have developed in C language a set of software in order to demonstrate the behaviour of the (proportional integral derivative) PID controller of the DSC. It can help the user to choose correct values for P, I and D parameters according to the kind of experiment conducted. The software allows studies of extra parameters, such as the sampling rate of the computerized PID controller or the determination of filtering of the correction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Emission Color Tuning with Polymer Molecular Weight for Dyes of 4‐Dicyanomethylene‐2‐methyl‐6‐{4‐[(2‐hydroxyethyl)(methyl)amino]styryl}‐4H‐pyran

A series of novel polylactide (PLA) polymers were synthesized initiated by 4‐dicyanomethylene‐2‐methyl‐6‐{4‐[(2‐hydroxyethyl)(methyl)amino]styryl}‐4H‐pyran (DCM) with Sn(Oct)₂ as catalyst. The color and emission of the polymer can be tuned just with polymer molecular weight.     

Selectivity and selectivity tuning in capillary gas chromatography

The selection of stationary phases in capillary gas chromatography is discussed. Methyl silicone, phenyl methyl silicone, trifluoropropylmethyl silicone, biscyanopropyl silicone, and high molecular weight (HMW) polyethylene glycol are considered to be the basic phases. Selectivities and polarities between these phases are obtained by selectivity tuning. Selectivity tuning can be performed in three different ways, namely by synthesizing a tuned stationary phase, by mixing the basic phases, or by coupling capillary columns of different selectivities. In coupling capillary columns the variables are column length, β-value, temperature, and/or pressure.     

A New Software to Show the Behaviour of the PID Controller. Influence of the setting parameters of DSCs. Part I

Some DSC calorimeters such as the model Setaram DSC 111 allow the user to set the parameters of temperature programming. Default values furnished by the constructor are often used, but it is very interesting to study the thermal behaviour of the regulation of the calorimeter under different conditions and kinds of set point temperatures. For this research we have developed in C a set of softwares in order to show the behaviour of the proportional integral derivative (PID) controller of the DSC. It can help the user to choose correct values for P, I and D parameters according to the kind of experiment conducted. The software allows studies for extra parameters such as the sampling rate of the computerized PID controller or the determination of filtering of the correction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tuning Optical and Electron Donor Properties by Peripheral Thio–Aryl Substitution of Subphthalocyanine: A New Series of Donor–Acceptor Hybrids for Photoinduced Charge Separation

Subphthalocyanine (SubPc), a unique ring‐reduced member of the common phthalocyanines family, although known for its higher absorptivity, reveals narrow absorption with peak maxima around 570 nm thus limiting its utility in light‐energy‐harvesting applications. In the present study, by peripheral thio–aryl substitution of SubPc macrocycle, the spectral properties have been modulated to extend the absorption and emission well into the visible/near‐IR region. Additionally, for α‐ring‐substituted derivatives, facile oxidation of SubPc was witnessed, thus making these derivatives better electron donors. Next, the preparation of donor–acceptor dyads containing the well‐known electron acceptor C₆₀ connected to the central boron atom of SubPc was accomplished by making use of the 1,3‐dipolar cycloaddition reaction. Control experiments and free‐energy calculations using the redox and spectral data suggested that the observed fluorescence quenching of SubPc in these dyads is due to electron transfer. Accordingly, transient spectral studies performed both in polar and nonpolar solvents conclusively proved electron transfer to be the quenching mechanism in these dyads. The measured rate constants by fitting kinetic data revealed efficient charge separation and charge recombination processes, suggesting that these dyads could be useful materials for the construction of light‐to‐electricity or light‐to‐fuel production devices.     

EXTENDED GABOR FUNCTION MODEL AND SIMULATION OF SOME CHARACTERISTIC CURVES OF RECEPTIVE FIELD

In this paper we propose a family of extended Gabor functions as weight functions of the primary information processing in the visual system. The orientation tuning curve, the length tuning curve and spatial frequency tuning characteristics of simple cells, complex cells and some hypercomplex cells were simulated by means of our model. The results calculated by this model coincide closely with the experimental data. It has been shown that the extended Gabor function model can reasonably describe the main properties of receptive fields several levels of the visual system.