仪器分析技术在直接甲醇燃料电池研究中的应用

介绍了仪器分析技术在直接甲醇燃料电池电催化剂及其载体结构,电池反应动力学、产物分析、固体聚合物电解质膜以及电池性能评价等各方面的应用及研究进展。     

固体核磁共振技术在锡硅分子筛表征中的应用

生物质等绿色资源的高效转化利用是催化科学的重要发展方向.锡硅分子筛因具有优良的催化性能而得到相关研究者的普遍关注.准确构建催化剂活性中心结构/酸性与催化反应性能之间的构效关系是新型高效催化剂设计与研发的基础.固体核磁共振（NMR）是研究分子筛活性中心局域结构、酸特性与催化反应机理的重要手段.本文简述了近年来固体NMR技术在锡硅分子筛研究领域的一系列主要进展,并进行了展望.     

三苯胺染料在钴电解质电池中的光伏性能

合成了4种己氧基取代的三苯胺类有机染料,制备了钴电解质的染料敏化太阳能电池,研究了染料的共轭桥结构对电池的光电压和光电流的影响．结果表明,以噻吩环为共轭桥的有机染料在钴电解质的染料敏化太阳能电池中表现良好的光伏性能,在100 mW/cm²太阳光照射下,获得6.1％的光电转换效率．同时研究了染料的构效关系．     

一种高电导率PVA聚合物电解质的制备与表征

通过溶液浇注法制备了一种polymer in salt型PVA KOH H2O聚合物电解质.对该电解质进行了X射线衍射、热性质及电化学性质测试与分析.X射线衍射显示PVA和KOH在聚合物电解质中均以非晶态存在.随着KOH含量的增加,聚合物的玻璃转化点温度逐渐上升,而电解质电导率也随之增加.该电解质的电化学窗口可达1.4V,阻抗测试显示当电解质组成PVA/KOH为1/3(质量比)时,室温电导率可达0.15S/cm,电导率与温度关系符合Arrhenius方程.该电解质热力学稳定性好,机械强度高、电化学性质优越.     

基于酪氨酸端基的ACE三肽抑制剂定量构效关系研究

固定酪氨酸为端基对ACE三肽抑制剂进行构效关系研究,采用多元线性回归方法,基于不同描述符建立模型,比较模型的可靠性和准确性.结果表明Z描述子建立的模型最好.定量构效关系研究表明ACE抑制三肽第二位氨基酸的电性参数是抑制活性的最大影响因素.     

固体氧化物燃料电池体系掺杂氧化锆的理论研究：从结构到导电性

固体氧化物燃料电池是一种将化学能(如H₂和O₂)转化为电能的清洁能源系统,它具有高效、低碳以及燃料适应性广的特点. 作为燃料电池的“心脏”,电解质决定了整个电池的性能,其中掺杂氧化锆是最为典型的燃料电池电解质材料. 氧化钇稳定氧化锆在高温下具有优良的离子电导率,广泛应用在固体燃料电池中. 电解质材料的组成和使用温度对电导率的影响在实验和理论上已得到了充分研究. 复合氧化物的原子结构的表征是阐明其导电行为的关键,本文综述了氧化钇稳定氧化锆电解质的结构和导电性研究的最新理论进展,比较了研究该材料所采用的不同的理论方法及其相应结果,并总结了各种方法的优缺点. 重点介绍了利用随机表面行走-神经网络方法取得的最新成果,这些成果和实验结果相吻合. 结果表明,采用机器学习进行原子模拟为理解固体电解质中遇到的复杂物质现象提供了一种经济、高效和准确的方法.     

聚合物纳米复合电解质(PEO)8-ZnO-LiClO4微结构及电导率研究

以聚氧化乙烯(PEO)为基质,成功制备出纳米ZnO掺杂的(PEO)₈-ZnO-LiClO₄离子导电聚合物电解质,并利用多种实验技术,包括扫描电子显微镜、X射线衍射(XRD)、傅里叶变换红外光谱和正电子湮没寿命谱(PALS),系统地研究了纳米ZnO与基质间相互作用及其对聚合物链段运动、纳米尺度自由体积、离子输运和复合电解质电导率的影响.实验结果发现,纳米ZnO的掺杂使聚合物电解质的离子电导率得到了大幅度提高,当ZnO与PEO质量比为6%时达到最大,(PEO)₈-ZnO-LiClO₄的电导率为1.82×10^-4 S ·cm^-1,比(PEO)₈-LiClO₄的电导率(6.58×10^-5 S ·cm^-1)提高了大约一个数量级.XRD结果显示,纳米ZnO的加入降低了PEO的结晶性,增加了锂离子传输的非晶相,从而提高了电导率.离散PALS测量结果表明,随着纳米ZnO的加入,复合电解质的自由体积、浓度和相对自由体积分数f_r均增加.连续PALS分析揭示了自由体积的分布由一个峰劈裂成两个峰,表明纳米ZnO的掺杂对聚合物的微结构有很大影响.基于实验测量的f_r和离子电导率,研究了离子导电机理.研究发现, f_r与电导率之间存在一个直接关系,即f_r越大,越有利于锂离子的传输,导致电导率越大.这个结果支持聚合物电解质导电的自由体积理论. 关键词： 正电子湮没寿命谱 聚合物纳米复合电解质 离子电导率 自由体积     

定量构效关系研究中图论方法:烷烃13C NMR化学位移

系统研究了图论方法在定量构效(性)关系(QSAR/QSPR)中的应用.本文研究提出了一种新的指数L,并发现它与烷烃¹³C NMR有良好线性相关性.     

基于Zview和Origin软件的交流阻抗谱的实验数据处理

以固体氧化物燃料电池(SOFC)电解质的研究为例,具体介绍了基于Zview软件和Origin8.5软件对交流阻抗实验数据进行处理和分析的方法。通过等效电路处理可区分电解质的晶粒电阻、晶界电阻以及界面电阻,获得电导率与温度的变化关系等重要的实验结果,为本科生关于氧化物电解质交流阻抗以及导电性能方面的研究项目进行数据处理和分析提供借鉴和参考。     

基于材料基因组方法的锂电池新材料开发

近年来,在锂二次电池新材料的研发过程中逐渐建立了基于材料基因组思想的高通量计算理论工具与研究平台.在该平台上,通过将不同精度的计算方法组合,实现了基于离子输运性质的材料筛选;通过将信息学中数据挖掘算法引入高通量计算数据的分析,证实了材料大数据解读的可行性.上述平台实现了在锂电池固体电解质的高通量筛选、优化和设计上进行新材料研发的示范应用,通过高通量计算筛选获得了两种可用于富锂正极包覆材料的化合物Li_2SiO_3和Li2SnO_3,有效改善了富锂正极的循环稳定性;通过对掺杂策略的高通量筛选,获得了提高固体电解质β-Li_3PS_4离子电导率和稳定性的方案;通过高通量结构预测设计了全新的氧硫化物固体电解质LiAlSO;并在零应变电极材料结构与性能的构效关系研究中进行了大数据分析的尝试,分析了零应变电极材料的设计依据.上述材料基因组方法在锂电池材料研发中的应用为在其他类型材料研发中推广这种新的研发模式提供了可能.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.