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1.
氨基酸在水溶液中扩散系数的实验研究   总被引:6,自引:0,他引:6       下载免费PDF全文
氨基酸在水溶液中扩散行为的研究具有非常重要的理论及指导意义。采用实时激光全息干涉法对甘氨酸、L-丙氨酸和L-缬氨酸在298.15K水溶液中的扩散行为进行了研究,计算得到了5个不同浓度下的扩散系数,并对实验结果及扩散系数的影响因素进行了分析和讨论,为进一步研究甘氨酸、L-丙氨酸和L-缬氨酸在水溶液中的扩散行为和传质机理打下了基础。  相似文献   

2.
L-抗坏血酸水溶液扩散系数的全息干涉法测量   总被引:5,自引:0,他引:5  
设计并建立了一套用于液相扩散系数测定的激光实时全息干涉及液相扩散模拟系统。测定了25℃0.33mol/LKCl水溶液的扩散系数,结果与文献值非常接近,证明了仪器的准确性。进而利用该装置测定了不同浓度(0.0100、0.0287、0.0542、0.0822、0.1007mol/L)的L 抗坏血酸水溶液的扩散系数,得到了不同浓度L 抗坏血酸水溶液在不同位置的扩散系数以及每一浓度的平均扩散系数为13.5552、12.5230、11.4577、10.5606、10.0148×10-6cm2/s。  相似文献   

3.
为了研究维生素B6的扩散行为,采用了激光全息干涉法,得到了298.15K时不同浓度维生素B6在水溶液和生理盐水中的扩散系数。结果表明,维生素B6在水溶液中的扩散系数随着溶质浓度的增大一直下降,而在生理盐水中则呈现先上升后下降的趋势。这对维生素B6的医学应用具有重要的参考价值。  相似文献   

4.
本文扼要叙述了扩展电阻分析用以测量较低浓度砷的剖面的有效性,进而研究了较低浓度砷在硅中的扩散问题.由于通过快速热退火对样品进行预处理,排除了辐照损伤对扩散系数测定的影响,从而测得砷在硅中本来意义下,即替位扩散意义下的本征扩散系数.如所预期,这组数据比国外直至目前所测得的数据要低.浓度剖面的实验数据由非线性扩散方程的数值解进行拟合.结果表明:SUPREM III所采用的模型在较高浓度区扩散系数随浓度递增速率较小,Hu理论仍然和本实验(?)较符合.本文还求得了扣除辐照损伤增强扩散效应后,砷在硅中的激活能为4.42eV  相似文献   

5.
本文介绍自差拍光混频准弹性激光散射装置和技术,以及用该技术首次实现对几种C_8卵磷酯加盐水溶液中微团的流体力学半径,扩散系数和多散性的直接测量.  相似文献   

6.
电力电容器行业所使用的绝缘油在生产过程中会挥发产生有害气体,由于缺少其扩散系数,导致设计人员无法准确确定通风量。为了建立绝缘油混合物扩散系数的测定方法,运用拟稳态扩散方程的理论,测定出了该种绝缘油在20℃~35℃时的扩散系数。结果表明其在室温下线性度良好。最后利用气相色谱法对实验结果进行验证,给出了换气次数的参考数据。  相似文献   

7.
对丙酮-水溶液在紫外光激励下产生的荧光光谱和不同检偏角下的偏振光谱进行了实验研究,分析和讨论了其荧光产生机理和谱线特性,并计算了其偏振度和各向异性度。结果表明,丙酮-水溶液在波长为303nm左右的紫外光激励下能产生较强的荧光,其主要荧光峰位于395nm左右,荧光的发射类型为π*→n;随着浓度的增加395 nm处的荧光强度线性增强,当增至8%后发生浓度猝灭;丙酮-水溶液发射出的荧光为部分偏振光,具有确定的分子取向,偏振度和各向异性度分别为0.343和0.510。研究结果可为丙酮-水溶液的物理化学性质及团簇结构的研究提供参考。  相似文献   

8.
在实验中应用了波尔兹曼-马塔诺分析法,测定了砷扩散到硅中引起的杂质原子的分布。由此分析推断出在高的砷浓度下砷浓度同扩散系数的关系。此外,采用理论同实验相比较的方法,对砷在硅中的本征扩散率作了估价。  相似文献   

9.
以共面微带结构为基础提出了一种全新的双端口抗腐蚀复介电常数测量方法,该方法包含一种基于共面波导(CPW)结构的测量装置和由人工神经网络算法训练得到的反演算法。与传统测量方法相比,该方法具有测量性能灵敏,装置结构简单,双端口测量等优势,并且其在测量过程中不与待测溶液发生任何直接接触,因此具有良好的抗腐蚀特性,可以广泛应用于腐蚀性溶液介电常数的测量。该方法中的反演算法在进行训练时全部使用实测数据,有效避免了仿真数据与实测结果之间的差异所产生的误差。对20℃下多组不同浓度的甲醇水溶液和乙醇甲醇混合溶液在2.45 GHz频率下的介电常数进行了测量,并与理论值进行了对比,两者具有较好的一致性,证明了该介电常数测量方法的有效性和准确性。  相似文献   

10.
基于滤纸富集技术的LIBS污水检测   总被引:1,自引:0,他引:1  
将滤纸作为基底用于LIBS测定水溶液中的金属元素,分析了不同的滤纸浸泡时间对LIBS信号的影响,以及在不同质量浓度的情况下,分析浸泡时间与信号的关系.以实验室配置的不同浓度的偏砷酸钠溶液为研究对象,对浸泡时间为10s和60s的As元素和Na元素做了探测分析并得到了其定标曲线,初步确定了在As元素和Na元素在不同时间下的检测限分别为:As元素0.379g/L(10s)、0.224g/L(60s);Na元素0.021g/L(10s)、0.018g/L(60s).实验所得的结果为探测工业废水中金属元素的含量提供依据.  相似文献   

11.
Doping profiles in bipolar devices are numerically calculated taking into account the actual space charge produced during the diffusion process, which is described by standard models based upon effective diffusivities. The influence of this charge on the diffusion of dopants was examined for arsenic/boron double diffusion in order to evaluate the errors on profiles obtained using the well-known approximation of space-charge neutrality. Numerical results show that this approximation satisfactorily predicts practical doping profiles except for short-time low-temperature diffusion  相似文献   

12.
The recently developed Arrhenius formula of the modified Sutherland equation was first employed to calculate the self- and impurity diffusivities in liquid Sn, Bi, and Pb. The reliability of the calculated results was validated in comparison with the critically reviewed literature data. Based on the reliable tracer and chemical diffusivities available in the literature, the atomic mobility parameters in both Sn-Bi and Sn-Pb melts were then evaluated by the DICTRA (DIffusion-Controlled TRAnsformations) software package with the aid of thermodynamic parameters. Comprehensive comparisons show that most of the measured and theoretical diffusivities in Sn-Bi and Sn-Pb melts can be reasonably reproduced by the currently obtained atomic mobilities. Moreover, the atomic mobilities were further verified by comparing the model-predicted concentration profiles and the measured ones in various liquid Sn-Bi and Sn-Pb diffusion couples.  相似文献   

13.
14.
A network defect model suitable for use in process simulation is presented for the diffusion of B in SiO2 and, in particular, B in the presence of F and H2. We find that B diffuses via a peroxy linkage defect the concentration in the oxide of which changes under different processing conditions. From random walk theory it is possible then to calculate the resulting diffusion coefficients. These results are compared with measured diffusivities and empirical adjustments are made  相似文献   

15.
The out-diffusion of an impurity by the kick-out mechanism during gettering is analyzed by the numerical solution to the set of diffusion-kinetic equations. On the example of the Au impurity in silicon, the effect of the degree of gettering and the dislocation density on the concentration profiles of the impurity and self-interstitials is investigated. It is shown that the usually used approximation based on the solution to diffusion equations for a substitutional impurity with effective diffusivities can lead to an underestimation of the gettering time. In the absence of dislocations, this underestimation is caused by modifying the expression for effective diffusivity in the case of gettering and violating the local-equilibrium condition at the gettering front. For a high dislocation density, the process of lowering the impurity-concentration level is caused by the kinetics of generation of self-interstitials on dislocations instead of the impurity diffusion.  相似文献   

16.
The mechanism of Cu diffusion over a clean Si(110) surface was studied by Auger electron spectroscopy and low-energy electron diffraction in the temperature range from 500 to 650°C. It is shown that the Cu transport over the Si(110) surface proceeds by Cu atom diffusion through the Si bulk and Cu atom segregation at the surface during diffusion. The temperature dependence of the effective Cu diffusivities at the clean Si(110) surface was found. The results were compared to those previously found for a Si(111) surface.  相似文献   

17.
The existence of interfacial states and fixed charges between the silicon and sapphire films create an electric field that affects the diffusion of impurities near the interface. The effect of this field is modeled as a new term in the diffusion equation. A computer program was written to numerically integrate the diffusion equation for a one-dimensional model. The results were correlated with SIMS data for high-concentration phosphorus profiles. A predicted peak in the phosphorus concentration at the silicon-sapphire interface, due to the effect of negative charges at that interface, was confirmed. A pipe diffusion model was incorporated to account for the higher (than bulk silicon) diffusivities observed. New values of skewness were also needed to match implanted profiles with Pearson-IV type distributions.  相似文献   

18.
The ZnSe:Ni single crystals doped by diffusion are investigated. The diffusion is carried out from metallic nickel in helium and argon atmosphere. The optical-density spectra are investigated in the wave-length range of 0.4–3 μm. From the value of the absorption-edge shift, the nickel concentration in crystals under investigation is determined. The optical-density and luminescence spectra of ZnSe:Ni are identified. The nickel-impurity diffusion profile is determined by measuring the relative optical density of crystals in the visible spectral region. The diffusivities of nickel in ZnSe crystals are calculated at temperatures of 1073–1273 K.  相似文献   

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