JONES型电导池测量的LCR电桥等效电路选择

JONES电导池系统的交流阻抗由电极过程的相关阻抗和电极间溶液的电阻两部分组成,可用适当的等效电路模拟。采用LCR电桥测量JONES电导池中溶液的电阻时需要选择合适的等效电路为模型解析测量的交流阻抗。通过等效电路的分析发现,选择串联电路作为LCR电桥的解析等效电路测量JONES型电导池中溶液的电阻时引入的误差比并联电路小。     

电化学测量中的欧姆电压降补偿问题

对工作电极与参比电极之间的溶液电阻(Ru)进行准确的欧姆电压降补偿是获取可靠的电化学实验结果的前提,但测量中该如何进行补偿尚未建立规范的操作流程.本文首先探究了工作电极与Luggin毛细管末端距离对Ru的影响.随后对比了 Autolab PGSTAT 302N、CHI系列恒电位仪的交流阻抗法与CHI系列恒电位仪所测得R...     

恒电量瞬态扰动测量Tafel斜率及数据积分处理

提出了一个三参数积分法拟合恒电量强极化数据以测定Tafel斜率的新方法.实验证明,恒电量瞬态扰动测量碳钢在酸溶液中的腐蚀,获得的Tafel斜率与消除了溶液电阻影响的Tafel外推结果有很好的一致性,说明恒电量法有效地消除了溶液电阻对该体系测量结果的影响,并且通过电化学和失重实验验证表明,这种快速测量可以获得准确的腐蚀速率.这种新的恒电量强极化积分算法相对微分法的优势体现在算法简捷和用于数值计算的数据具有较高的信噪比,因此能够提高测量精度.     

水质自动采样器的校准方法及不确定度评定

建立水质自动采样器的校准方法。介绍水质自动采样器的工作原理,提出了校准项目与技术指标:单次采样量测量相对误差为±10%,等比例采样量测量相对误差为±15%,时间控制测量相对误差为±0.5%,温度控制测量误差为±2℃,绝缘电阻不低于20 MΩ。对单次采样量测量误差的测量不确定度进行了评定,相对扩展不确定度U=3.0%(k=2)。该校准方法可用于计量技术机构对水质自动采样器的校准,保证测量数据的准确可靠。     

新型耗散型电化学石英晶体微天平的研制

针对目前商品化的石英晶体微天平(Quartz crystal microbalance,QCM)仪器存在的功能单一、耗材昂贵等问题,基于正交解调法阻抗分析原理,本研究搭建了新型QCM仪器系统。在此仪器系统中,通过嵌入式软件和硬件电路的深度结合,实现了较宽的频率范围内石英晶体谐振频率自动匹配和精确测量,并引入了电容补偿电路对石英晶体谐振片的静态电容进行实时补偿,从而消除了较高弹性负载情况下谐振频率的测量误差。通过对不同粘弹性负载环境、连续小质量负载添加、电化学联用测试等多个实验对所搭建仪器的功能和性能进行了验证和测试。实验结果表明,研制的QCM仪器系统适用的石英晶体频率范围较宽,可对石英晶体谐振片的静态电容进行自动补偿,频率测量精度可达0.1 Hz,并且能够实时、连续地测量耗散因子,能与多种电化学方法联用,具有功能丰富、耗材成本低等优点。     

快扫循环伏安曲线的单纯形优化-数值模拟拟合方法

采用Gl算法改进了快扫伏安曲线的数值模拟,提高了模拟计算的速度.使用单纯形优化-数值模拟方法,以电流、峰电位误差的加权值作为拟合参数的评价函数,对二茂铁在0,3mm直径铂盘电极上,不同扫速下的循环伏安图进行了拟合.在拟合过程中自动进行伏安图基线的校正,同时拟合出标准非均相速度常数k~0,未补偿溶液电阻R_u以及双电层电容C_(dl)等重要的参数值,所得k~0值与文献报道结果一致.     

分光光度法测定铝合金中锰的不确定度评定

对分光光度法测量铝合金中锰含量的测量不确定度进行评定,分析了测量过程中不确定度的主要来源,如测量重复性、溶液浓度、溶液体积、试样溶液定容体积、分取溶液体积等,并对各不确定度分量进行了量化.对锰含量为0.80%～2.00%的铝合金,置信水平为95%时,测量结果的扩展不确定度为0.02%.     

电化学阻抗谱法研究环氧膜的渗水机理

本工作测量了覆盖环氧膜的铝电极在NaCl溶液中的电化学阻抗谱, 并求得了该膜的膜电阻、膜电容和环氧膜与底金属间的腐蚀电阻及双电层电容。由膜电容求得该膜的介电常数为5.2。此种膜未浸入NaCl溶液前的介电常数为4.9。将上述数据与未覆盖环氧膜的铝电极的电化学阻抗数据比较, 可认为溶液是经上述膜中的化学通道而渗入膜内的。     

快扫循环伏安曲线的单纯形优化—数值模拟合方法

采用Ｇ１算法改进了快扫伏安曲线的数值模拟,提高了模拟计算的速度。使用单纯形优化－数值模拟方法,以电流、峰电位误差的加权值作为拟合参数的评价函数,对二茂铁在０．３ｍｍ直径铂盘电极上,不同扫速下的循环伏安图进行了拟合。在拟合过程中自动进行伏安图基线的校正,同时拟合出标准非均相速度常数ｋ＾０,未补偿溶液电阻Ｒｕ以及又电层电容Ｃｄｌ等重要的参数值,所得ｋ＾０值民文献报道结果一致。     

微电极的稳态可逆极化曲线

微电极具备一些常规尺寸电极所没有的优点,例如:(1)半径很小的微电极在不对溶液进行搅拌的情况下就具备与高速旋转的圆盘电极类似的性质,即在电位扫描速率较低时,可获得稳态伏安曲线.这一特点使微电极能方便地用于稳态测量.与暂态测量相比,稳态测量精度较高(实验曲线几乎不受充电电流干扰),实验方法较简单,实验结果的数学处理较容易.(2)微电极体系的时间常数(溶液电阻和双层电容的乘积)正比于电极面积的平方根.若在     

Combined kinetic analysis of solid-state reactions: a powerful tool for the simultaneous determination of kinetic parameters and the kinetic model without previous assumptions on the reaction mechanism

The combined kinetic analysis implies a simultaneous analysis of experimental data representative of the forward solid-state reaction obtained under any experimental conditions. The analysis is based on the fact that when a solid-state reaction is described by a single activation energy, preexponetial factor and kinetic model, every experimental T-alpha-dalpha/dt triplet should fit the general differential equation independently of the experimental conditions used for recording such a triplet. Thus, only the correct kinetic model would fit all of the experimental data yielding a unique activation energy and preexponential factor. Nevertheless, a limitation of the method should be considered; thus, the proposed solid-state kinetic models have been derived by supposing ideal conditions, such as unique particle size and morphology. In real systems, deviations from such ideal conditions are expected, and therefore, experimental data might deviate from ideal equations. In this paper, we propose a modification in the combined kinetic analysis by using an empirical equation that fits every f(alpha) of the ideal kinetic models most extensively used in the literature and even their deviations produced by particle size distributions or heterogeneities in particle morphologies. The procedure here proposed allows the combined kinetic analysis of data obtained under any experimental conditions without any previous assumption about the kinetic model followed by the reaction. The procedure has been verified with simulated and experimental data.     

A fully consistent experimental and molecular simulation study of methane adsorption on activated carbon

The adsorption of pure methane in activated carbon Ecosorb was studied by combining grand canonical ensemble Monte Carlo molecular simulations and an experimental approach based on a gravimetric device. Experimental and calculated adsorption isotherms of methane were determined in supercritical conditions at 303.15 and 353.15 K and pressures up to 10 MPa. The comparison between both experimental and estimated data proves the consistency of the methodology used in this work, starting from the characterization of the porous media in terms of pore size distribution, the determination of the experimental adsorption isotherms, and the final estimation of computational results through estimated isotherms determination. Moreover, additional differential enthalpy of adsorption calculations were compared with experimental values obtained by means of a manometric/calorimetric technique. The good agreement shows the strength and the originality of this paper by combining experimental and computational homemade results allowing a complete characterization of the activated carbon substrate and its methane storage capacity.     

New Experimental Cross-Section Measurements for Cr and Cu and Comparison with Model Predictions

 In order to obtain more accurate experimental values of X-ray emission cross sections, resulting from the interaction of ion with atoms, we have measured them for the K-inner-shell of Cr and Cu elements using a proton beam of energy range 1–2.3 MeV. The experimental data obtained in the present work are compared with the theoretical calculations given by the two models BEA (binary encounter approximation) and ECPSSR (energy coulombian perturbed stationary state relativistic). Also, the present experimental results are compared with those obtained by Paul and Sachert. The comparison shows a good agreement between the previous and the present data with a slight improvement in the measurement accuracy for Cr. From the theoretical point of view, agreement with the experimental data is observed only for the ECPSSR predictions, while the BEA’s cross section calculations at higher energies are approximately 20% lower than the present experimental values.     

New micro-structure designs of a wide band reflective polarizer with a pitch gradient

New microstructure designs for fabricating a wide band reflective polarizer (WBRP) from cholesteric liquid crystals are reported. The pitch difference in the WBRP is formed by orienting a single layer consisting of different glassy siloxane cyclic side chain oligomer powders on a heater. The molecular arrangement obtained is frozen by quenching. The experimental results show that various micro-areas exhibiting different reflection wavelengths and pitch gradients are formed in the WBRP. A WBRP exhibiting the reflection properties of the original cholesteric liquid crystals is fabricated by a novel experimental process and the experimental results are in accordance with the microstructure designs of the WBRP.     

Use of equations for the description of experimental dependence of the height equivalent to a theoretical plate on carrier gas velocity in capillary gas-liquid chromatography

Optimal equation for fitting the experimental data on the height equivalent to a theoretical plate (HETP) versus carrier gas velocity in GLC was determined. The data obtained by authors and the literary data by other investigators were used for the comparative study of Van Deemter, Golay and the little known Golay-Guiochon equations. The Golay-Guiochon equation takes into account instrumental contribution and other sources of additional band broadening. Correlation coefficient R and Pirson's criterion chi2 were used as a criterion of the data correspondence to the equations. The Golay-Guiochon equation is the best for fitting of the experimental data in 71% considered examples, 19% experimental data may be fitted very precisely by the Van Deemter equation, the Golay equation is preferable for 7% experimental data only. Three percent experimental data may be fitted with the same precision by the Golay and the Van Deemter equations. The results obtained are of theoretical and practical interest. The Golay-Guiochon equation must be used more widely in analytical practice and physicochemical measurements.     

Hierarchical classification designs for the estimation of different sources of variability in proficiency testing experiments

An approach to the estimation of possible different sources of variation found in proficiency testing experiments is described. Four errors namely, technique, analyst, laboratory and geographical location are considered and calculated by using a rational experimental design based on hierarchical classification. The treatment of the confidence of the design over different experimental arrangements is explored and visualised by calculating a function that depends only on the design and not on the experimental response. An illustrative example based on simulated data is used to show how the theory could be applied in practice.     

新型PVT性质测试系统的研制

研制了一套新型压力-温度-体积（PVT）性质测试系统．该系统由自行开发的测控软件实时测控,温度测量精度可达±10mK,压力测量系统最大不确定度为±1．2KPa．利用新的测试系统对294～351K温度区间的Hydrofluorocarbons（HFC）-245fa饱和蒸气压进行了研究．实验结果表明,HFC-245fa的测量值与公认文献值的平均偏差小于0．03％,最大偏差小于0．484％,结果与文献值吻合较好．     

Dynamics of the Rydberg electron in H*+D2-->D*+HD reactive collisions

Experimental crossed-beam studies carried out previously have indicated that the dynamics of the Rydberg-atom-molecule reaction H*+D2-->D*+HD are very similar to those of the corresponding ion-molecule reaction H++D2-->D++HD. The equivalence of the cross sections for these related systems would open up a new approach to the experimental study of ion-molecule reactions. However, a recent experimental and theoretical study has brought to light some important qualitative differences between the Rydberg-atom reaction and the ion-molecule reaction; in particular, the experimental cross section for the Rydberg-atom reaction exhibits a higher degree of forward-backward scattering asymmetry than predicted by a quasiclassical trajectory study of the ion-molecule reaction. In this paper, the authors consider the dynamics of the Rydberg-electron over the course of a reactive collision and the implications of these dynamics for the Rydberg-atom-molecule crossed-beam experiment. Using an approach based on perturbation theory, they estimate the attenuation of the experimental signal due to the Rydberg-electron dynamics as a function of the scattering angle. They show that at least part of the experimental asymmetry can be ascribed to this angle dependent attenuation. Their results offer general insight into the practical aspects of the experimental study of ion-molecule reactions by means of their Rydberg-atom counterparts.