Nitric Acid-Air Diffusion Coefficient: Experimental Determination Using a Diffusion Cell

Abstract

Trace gaseous nitric acid was generated using a diffusion cell. The determination was made by collection in cellulose filters coated with K₂CO₃ and measuring the concentration by ion chromatography. The measured HNO₃-air diffusion coefficient was 0.0404±0.0010 cm²/s (n=21) for T=298.15 K and P=1 atm. Their dependence with the temperature, over the range from 297.15 K to 318.15 K, could be expressed by D = 10^?4.7773.T^1.366 (R²=0.9467).     

平面铂电极上吸附氢原子表面扩散系数的测定

This Paper describes an experimental method that established a local Pt/Nafion interface on the Platinum Plane, so that the boundary conditions and the initial condition of the (diffusion equation about the diffusion of adsorbed hydrogen atom the platinum plane can be controlled. The average diffusion coefficient of underpotential deposition of hydrogen on a surface of platinum was obained for the first time and D=1.50 ×10-4cm2•s-1.The accuracy of the datum was discussed.     

La1-xSrxCoC3钙钛矿在碱性溶液中的析氧电催化

 稳态极化研究结果表明, La1-xSrxCoO3电极的析氧Tafel斜率为2303RT/F, OH-的反应级数近似为1, 在阳极析氧反应中, OH-的电化学脱附为速度控制步骤. 随着La1-xSrxCoO3中Sr含量的增加,氧化物表面的粗糙度提高,当x=02时,析氧反应的活化能最低,即La0.8Sr0.2CoO3表现有最高的析氧电催化活性.     

The Diffusion Coefficient of Molecular Oxygen in Macroporous Sulfocationite

An electrochemical method for experimentally estimating the diffusion flux of molecular oxygen through a spherical porous medium by taking chronoamperograms with an electrode of a special design was suggested. The corresponding mathematical apparatus based on numerically solving the molecular diffusion equation in spherical coordinates was developed, which enabled the diffusion coefficient and medium porosity to be determined from the experimental data. The method was tested by applying it to the system KU-23 15/100 macroporous sulfocationite—aqueous solution of molecular oxygen.     

电化学阻抗法测定金属氢化物电极中氢的扩散系数

应用电化学阻抗法测定了不同荷电状态 (SOC)和不同温度下MlNi3.75Co0 .65Mn0 .4 Al0 .2 金属氢化物电极中氢的扩散系数 .结果表明 :室温下该电极中氢的扩散系数随其荷电量的增大而减小 ,SOC为 5 0 %时氢的扩散系数随温度的升高而增大 ,相应的氢扩散活化能为 35kJ/mo     

Determination of Proton Diffusion Coefficient in Spherical Nickel Hydroxide Using Potential Step Measurement on Single Beads

The Potential step measurements are carried out on single beads of nickel hydroxide and the results are interpreted with a dual structure model featuring fast and slow diffusing components The intrinsic diffusion coefficients for the two components are found to be in the order of magnitude 10^-7 and 10^-13-10^-14 cm^2s^-1, respectively, with an apparent value for the slow component in the order of 10^-10 cm^2s^-1.     

锂离子在石墨化碳纤维中的扩散系数

锂电子电池;嵌入电极;锂离子在石墨化碳纤维中的扩散系数     

Oxygen Diffusion in Orthopyroxene. TG study

Oxygen partial pressure is supposed, by analogy with olivines, to influence the kinetics of the Fe-Mg exchange reaction in orthopyroxene. It has been demonstrated for olivines that the Fe−Mg interdiffusion coefficient is dependent on P(O₂), according to D _Fe−Mg ∝ P(O₂)^∼1/6 [1−3]. By means of thermogravimetric analyses performed at different P(O₂) on orthopyroxene grains from a volcanic rock it was possible to detect a certain degree of non-stoichiometry which is function of P(O₂).Oxygen moves into or out of the orthopyroxene lattice in response to a compositional gradient. Therefore, in orthopyroxene too, the Fe/Mg interdiffusion and hence the kinetics of the Fe−Mg intracrystalline exchange should be affected by P(O₂). The oxygen chemical diffusion coefficients at P(O₂)∼5⋅10⁻¹⁹atm were calculated at ∼400, 500 and 600°C. It was also verified on the orthopyroxene from the TPK-30F granulite that, at the operating conditions normally used for single-crystal annealing experiments, oxygen quickly responds to a chemical potential gradient in order to maintain the system in equilibrium conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of Gas-Vapor Binary Diffusion Coefficient by Gas Chromatography

A rapid determination of the diffusion coefficients of some gas-vapor binary systems was studied with a method similar to the operation of gas chromatograpic techniques. The diffusion coefficients of some hydrocarbons and alcohols in hydrogen atmosphere were determined. Then, detailed comparisons of these data with the available experimental values obtained by other methods and with the theoretical values calculated from the equations of Gilliland, Arnold, Hirschfeder, Slattery, Othmer, and Giddings respectively were discussed. The diffusion coefficients at various temperatures and flow rates of the carier gas were studied and their correlations to the different types of tubes were also discussed. The temperature power dependences of their diffusion coefficients were found experimentally for several gas-vapor binary systems.     

MH电极中氢扩散系数的测定及其应用

利用恒流放电法测定了金属氢化物(MH)电极中氢原子扩散系数的平均值. 通过恒电位法测定了MH电极中氢原子的扩散系数与其荷电态(SOC)的关系. 根据MH电极模型可知, 增大氢原子扩散系数或减小储氢合金粒径均能提高MH电极的快速充电性能, 并能计算出MH电极在不同的初始荷电态、不同充电倍率下, 表面氢原子浓度达到最大值所需的时间.     

Time-dependent Diffusion Coefficient and Conventional Diffusion Constant of Nanoparticles in Polymer Melts by Mode-coupling Theory (cited: 2)

Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts. A generalized Langevin equa-tion is adopted to describe the diffusion dynamics. Mode-coupling theory is employed to calculate the memory kernel of friction. For simplicity, only microscopic terms arising from binary collision and coupling to the solvent density fluctuation are included in the formalism. The equilibrium structural information functions of the polymer nanocomposites required by mode-coupling theory are calculated on the basis of polymer reference interaction site modelwith Percus-Yevick closure. The effect of nanoparticle size and that of the polymer size are clarified explicitly. The structural functions, the friction kernel, as well as the diffusion coefficient show a rich variety with varying nanoparticle radius and polymer chain length. We find that for small nanoparticles or short chain polymers, the characteristic short time non-Markov diffusion dynamics becomes more prominent, and the diffusion coefficient takes longer time to approach asymptotically the conventional diffusion constant. This constant due to the microscopic contributions will decrease with the increase of nanoparticle size, while increase with polymer size. Furthermore, our result of diffusion constant from mode-coupling theory is compared with the value predicted from the Stokes-Einstein relation. It shows that the microscopic contributions to the diffusion constant are dominant for small nanoparticles or long chain polymers. Inversely, when nanonparticle is big, or polymer chain is short, the hydrodynamic contribution might play a significant role.     

计时安培法测定镧在汞中的扩散系数

计时安培法测定镧在汞中的扩散系数徐逸心，牟兰，张长庚（贵州大学化学系，贵阳，５５００２５）关键词镧，镧汞齐，扩散系数，计时安培法金属在汞中的扩散系数与离子在溶液中的扩散系数一样，是电化学研究中的重要基础数据。目前已用各种方法测定过３２种金属元素和１种...     

尖晶石Li4Ti5O12中锂离子的化学扩散系数的研究

A relatively simple galvanostatic method was used for the evaluation on the average chemical diffusion coefficient of lithium-ion in spinel Li₄Ti₅O₁₂ prepared by solid-state reaction technique. The diffusion coefficient of lithium-ion was estimated to be 2.8×10^-13 cm²·s^-1 and 1.3×10^-13 cm²·s^-1 for charge and discharge， respectively.     

由扩散阻抗过渡区求金属氢化物电极中氢扩散系数的不确定性

本文参照文献[1] 报导的利用扩散阻抗过渡区求金属氢化物电极中氢扩散系数的方法测定了MlNi3.75Co0 .6 5Mn0 .4 Al0 .2 电极中氢的扩散系数 .结果发现 :运算过程中由于所用到的一些函数具有周期性 ,使计算结果变为多解 ,而且这些解之间存在着数量级上的差别 ;对同一组实验数据 ,过渡区内依据不同频率点求得的扩散系数也很不同 .总之 ,该方法尚不成熟 ,有待于进一步完善     

化学发光-化学需氧量测定新方法

根据重铬酸钾消解废水后其最终还原产物Cr3+ 浓度与COD值成正比关系 ,以及在碱性条件下 ,Luminol H2 O2 Cr3+ 体系产生很强的化学发光的原理 ,提出了一种用光电二极管做检测器测定水体的化学需氧量的新方法。本方法线性范围为 2 .1～ 60 0mg L,r2 =0 .9974;检出限为 2 .1mg L ;回收率为 1 0 0 %± 1 0 % ;RSD≤ 5 % (n =6)。用于实际样品测定 ,结果满意。     

掺杂Ni(OH)_2的质子扩散系数

利用粉末微电极恒电位阶跃法 ,研究了掺杂元素对球形 Ni(OH) 2 阳极过程和阴极过程质子扩散系数的影响 .结果表明 ,与纯 Ni(OH) 2 相比 ,掺 Co、Co Zn、Ca后镍微电极的阳极过程质子扩散系数稍有增大 ,掺 Zn、Fe、Mg后则有所降低 ,而掺杂 Co、Ca后的阴极过程质子扩散系数增大约 1倍 ,掺杂 Fe、Mg后则减少约 3/4倍 ;掺 Cd对阳极和阴极过程的质子扩散系数影响均不大 .尽管掺杂元素对扩散层厚度的影响不大 ,但阴极过程扩散系数比阳极过程小约 2个数量级 ,将是影响阴、阳极电极电化学过程的重要因素 .     

Operation of an Oxygen Gas Diffusion Electrode in a Hybride Fuel Cell

The paper is devoted to the operation of a hybride fuel cell (i.e. in the course of simultaneous electrosynthesis of a chemical product), in particular, the polarization characteristic of an oxygen electrode and the ratio of the produced electric energy to the amount of the produced target product. An equation for the dependence of the polarization of an oxygen gas diffusion hydrophobized electrode of a hydrogen-oxygen fuel cell on the concentration of the produced electroactive soluble product H₂O₂ in an inner-kinetic regime is suggested. It is established that the polarization variation does not depend on its initial magnitude but does depend on the concentration of the target product and the ratio between currents of the side and target reactions. The ratio of the produced electric energy to the amount of the produced target product is found to depend on the concentration of the produced target product, the electrode polarization, and the ratio between exchange currents of the side and target reactions.     

气体扩散耦合顺序注射分光光度法测定葡萄酒中的二氧化硫

依据在微碱性条件下,亚硫酸根离子可与孔雀绿溶液发生加成反应并使其褪色的原理,建立了气体扩散耦合顺序注射分光光度法测定葡萄酒中二氧化硫的新方法。当接收液流速为1.2mL/min和4.2mL/min时,方法的线性响应范围分别为1.0~5.0μg/mL和5.0~50.0μg/mL,方法的检出限为0.33μg/mL,相对标准偏差(RSD)≤0.43%,对葡萄酒样中二氧化硫测定的加标回收率为98.7%~104.7%。     

组合氧化法测空气中的氧气含量

“空气中氧气体积含量的测定”是人教版初三《化学》上册和浙教版《科学》八年级下册的一个重要的定量实验,课本中的设计方案有明显缺陷,测定结果不够准确。用烧杯和水槽组装成水封,消除了反应容器内外气体交换的可能性;烧杯上的体积刻度可以直观地反映出反应前后的气体体积变化;活性铁粉缓慢氧化提供热量,使白磷达到着火点燃烧,用组合氧化(白磷燃烧+活性铁粉缓慢氧化)耗尽烧杯中的氧气,该设计方案更为周密、完善。测定过程中现象明显,结果更准确。     

快速消解分光光度法测定高氯废水中低浓度化学需氧量

建立快速消解分光光度法检测高氯废水中低浓度化学需氧量(COD)的方法。通过提高催化液中硫酸银的浓度(46 g/L)充分络合氯离子,同时降低消解液中重铬酸钾的浓度至0.061 2 mol/L来抑制重铬酸钾与氯离子的反应,达到有效消除Cl~–干扰的目的。水样在165℃消解30 min,于600 nm波长检测吸光度,标准曲线法计算COD。实验结果表明,水样中COD质量浓度为20 mg/L时,2 000 mg/L的Cl~–不干扰COD的测定(相对误差小于10%),并且随着COD质量浓度的增加,Cl~–产生的干扰误差逐渐降低。对国家环境保护部标准样品进行了测定,COD测定值与标准值一致。样品加标回收率为97.0%~103.7%,测定结果的相对标准偏差为2.01%~6.33%(n=6)。该法快速,有毒试剂用量小,成本低,具有较高的准确度和良好的精密度,可以用于多数工业废水中COD的测定。