离子交换氟氧化物玻璃平面光波导的制备与折射率分布

用Ag -Na 离子交换法,制备了氟氧化物玻璃平面光波导.应用棱镜耦合技术测量光波导的有效折射率,通过Inverse Wentzel-Kramer-Brillouin法计算了有效折射率对应的各阶模深度,并采用Gaussian函数对其分布进行拟合,结果显示:不同交换时间下折射率最大改变量为0.0367,离子交换扩散系数为0.012 μm2/s.探讨了交换时间对氟氧化物玻璃平面光波导性能的影响.     

Li_2O(Na_2O)-BaO-B_2O_3-Al_2O_3-SiO_2玻璃与NaNO_3熔盐之间的离子交换

用电子探针研究了在低于玻璃转变温度以下NaNO_3熔盐和(20-x)Li_2O·xNa_2O·5BaO·15B_2O_3·(10+y)Al_2O_3·(50-y)SiO_2玻璃之间的离子交换。当存在有大量NaNO_3熔盐时,玻璃表面上离子交换的动力学平衡可在极短的时间内建立,并能表达为在表面交换离子的浓度比。在玻璃应变温度以上,由Boltzmann-Matano方法得到的互扩散系数取决于玻璃中氧化钠浓度,显示类似混合碱或混合位效应,并随长时间的离子交换而降低。低于玻璃应变温度,互扩散系数几乎不依赖玻璃中的氧化钠浓度,而略随离子交换时间增加而增大。     

采用电子探针扫描电镜法确定玻璃板中交换离子的有效扩散系数

本文介绍采用电子探针扫描电镜测量离子交换的玻璃板的离子浓度分布,并根据离子的扩散深度计算其有效扩散系数和扩散速度。根据离子的扩散速率研究离子的扩散过程能获得较理想的浓度分布。因此,这种测量方法,较双光束干涉法等更精确。     

离子交换工艺对ESP玻璃的影响

使用两步离子交换法制备工程应力分布玻璃( ESP玻璃)。两步离子交换中第一步交换时间较长,第二步交换时间较短。主要研究经过不同第一步离子交换工艺制度后的ESP玻璃性能上的区别。本文对ESP玻璃测试了弯曲强度,显微硬度,K+分布状态,并根据弯曲强度,K+分布状态计算得出Weibull模量以及离子扩散系数。结果表明：第二步离子交换会降低第一步离子交换玻璃的弯曲强度,而两步离子交换后的ESP玻璃其Weibull模量有所升高。显微硬度趋势与弯曲强度趋势一致。结合抗折强度以及K+分布状态,可知第一步离子交换最佳温度为450℃,时间30 h;第二步离子交换最佳温度为400℃,时间33 min。     

新型硫卤玻璃GeS2-Ga2S3-AgX(X=Cl,Br,I)中的K+-Ag+离子交换

以油酸钾为熔盐,GeS2-Ga2S3-AgX(X=Cl,Br,I)玻璃为基玻璃,在270℃的环境温度下,以氮气作为保护气氛,成功地进行了K -Ag 离子交换。在50GeS2-25Ga2S3-25AgI玻璃中,K 离子的交换深度可达256μm,并对交换深度、离子扩散系数以及离子浓度之间的规律进行了初步研究。通过离子交换研究,为制备硫卤玻璃光波导奠定了基础,并可以进一步拓宽硫卤玻璃的应用前景。     

用混合熔盐离子交换法研制锂玻璃自聚焦透镜

本文用Na_2O-Li_2O-Al_2O_3-B_2O_3-SiO_2系统玻璃细棒在混合熔盐中进行离子交换制造自聚焦透镜。应用横向干涉法测定了透镜的折射率分布,成像法测定了分辨率、数值孔径等参数并用表面分析系统测定透镜表面Na_2O浓度。讨论了熔盐组成、离子交换时间等因数对透镜折射率分布及其他光学性能的影响。得出合适的NaNO_3与LiNO_3混合熔盐的配比及最佳离子交换时间参数,制成折射率分布接近于二次抛物线分布、具有实用价值的自聚焦透镜。     

Li_2O-(LiCl)_2-B_2O_3-Al_2O_3系玻璃在水溶液中的Li~+-H~+离子交换

在锂卤铝硼酸盐玻璃与缓冲水溶液作用下,测量了溶液pH值随时间的变化,分析了玻璃在水溶液中的反应过程和玻璃的离子交换能力随组成的变化,发现Li~+-H~+离子交换能力与玻璃的离子电导率有很好的对应关系,说明离子电导率主要取决于锂离子与阴离子或阴离子团即定域体的相互作用力,从而支持了玻璃离子电导的弱电解质理论。     

磷酸盐激光玻璃离子交换动力学研究

对Li2O质量分数不同的磷酸盐激光玻璃进行了离子交换实验,并研究了熔盐中K+及Na+在玻璃中的扩散动力学。使用波分散光谱(WDS)技术分析了K+及Na+在玻璃中的扩散深度,并研究了两种离子在玻璃中的离子扩散系数和扩散活化能。实验结果表明,玻璃中Li2O质量分数较高时,K+及Na+在玻璃中的扩散深度较大;混合碱效应导致离子的扩散系数降低。     

电渗析脱盐过程离子传递现象的数值模拟

建立了电渗析脱盐过程离子传递稳态模型,研究了离子电荷数、离子扩散系数和离子交换膜电导率对脱盐过程传质的影响,描述了离子浓度分布、电势分布和离子传递通量分布的变化情况。研究表明：相较于一价离子,二价离子在电渗析过程中膜两侧浓度差较小,跨膜电压降较高,各项传递通量较小;当离子扩散系数增大时,膜两侧浓度差减小,跨膜电压降升高,总传递通量和电迁移通量增大;当离子交换膜电导率增大时,膜两侧浓度差增大,跨膜电压降降低,各项传递通量均增大。     

物理气相沉积对离子交换玻璃中钾离子浓度的影响(英文)

采用真空烘烤热蒸发沉积和离子束辅助沉积两种方法在离子交换玻璃上分别镀制ZnS薄膜,用扫描电镜和电子探针线扫描分析了物理气相沉积对离子交换玻璃中K＋浓度的影响,并测量了经不同方法镀膜玻璃的抗弯强度。结果表明：镀膜的离子交换玻璃中K＋的分布峰值减小并从玻璃表面向玻璃内部移动;与真空烘烤热蒸发沉积相比,离子束辅助沉积ZnS薄膜的离子交换玻璃中K＋的分布峰值增大且继续向玻璃内部移动,K＋浓度分布也随之移动,并导致离子交换玻璃力学性能下降。     

Theoretical Aspects of the Ion Exchange in the Fabrication of Focusing Gradient-Index Lenses

An expression relating the refractive index at different points of the gradient region of an axially symmetric ion-exchanged gradient-index element to the concentration of the component incorporated into the glass from the salt melt is derived and analyzed. It is demonstrated that the radial distribution of the refractive index gradient in a focusing gradient-index element is described by an even function symmetric about the ordinate axis with a local minimum on it and two side maxima in the surface region of the cylinder. This provides an explanation for the origin of the surface “tails.” A theoretical relationship is obtained using the metric of the equilibrium chemical diagram. The correctness of this relationship is verified for the case of the exchange between lithium ions from an alkali borosilicate glass and sodium ions from the salt melt, as well as for the case of the exchange between thallium ions from a thallium borosilicate glass and potassium ions from the salt melt.     

Coupling of diffusion and chemical stress: The case of ion exchange in glass

The chemical strengthening of glass results from an ion exchange process in which smaller alkali ions in a glass are replaced with larger alkali ions from a molten salt bath. This interdiffusion process leads to a buildup of chemical stress in the glass. However, traditional modeling of the ion exchange process has not fully accounted for interaction effects between mass diffusion and the chemical stress developed during the process. In this study, we develop the general theory of coupling between diffusion and stress, resulting in a single flux equation with a concentration- and stress-dependent interdiffusion coefficient. We apply the theory to the specific cases of chemically strengthened soda lime silicate and aluminosilicate glasses, demonstrating the impact of interaction terms on concentration profiles and interdiffusion coefficient. Following a phenomenological approach, this study demonstrates the effect of the interdiffusion on stress generation and vice versa to account for deviations from the simple expressions published hitherto in the literature.     

Ion Exchange of Soda-Lime Glass with Univalent Cations

Fhdeld-assisted and ordinary diffusion ion exchange of K⁺, Rb⁺hd Cs⁺, and Ag⁺ from nitrate salts with Na⁺ in soda-lime glass tubes were investigated between 700 and 735 K by application of various currents between 0 and 20.0 mA. An analysis of the field-assisted process with both a forward and a reverse field allowed calculation of the conductivity of the exchanged layer from the change of potential difference with time. Good agreement with experiment was found in both directions but anomalously high conductivities were observed in the Rb and Cs layers. Photoelastic measurements on rings sliced from the ion-exchanged tubes were used to calculate the residual stress arising from the ion exchange with the different cations. These results showed that other factors in addition to the ion size influence the magnitude of residual stress after exchange. The voltage-current relation during field-assisted ion exchange, along with the Nernst-Einstein equation, permitted calculation of the self-discussion coefficient of the exchanged cation in the exchanged layer. The self-diffusion coefficient was also estimated by applying the Nernst-Planck equation to results from unassisted ion-exchange experiments.     

Strengthening of Class Fibers: 11, Ion Exchange *

Soda-alumina-silica glass fibers were ion-exchanged in potassium nitrate at 400°C; their strength was measured before and after exchange. The potassium concentration distribution and the optical retardation were also measured. The results for unetched fibers are consistent with the premise that the kinetics of exchange are controlled by diffusion with D⋍×10⁻¹¹ cm²/s) and with the predictions of thermal stress analysis with a dilation coefficient of 2.8×10⁻⁴ (wt fraction potassium)⁻¹. The existence of a broad maximum in the plot of strengthening of unetched fibers vs time may be explained by the existence of Griffith flaws about 2 μm deep in the unexchanged glass. A deleterious effect from ion exchange was noted with etched fibers, in which even a short (½ h) exchange caused significant weakening.     

Ion Concentration and Stress in a Chemically Tempered Glass

Diffusion and stress profiles were determined in an Na-for-Li exchanged Li₂O-Al₂O₃-SiO₂ glass as a function of the time of reheating in air. Comparison of the two sets of data by a thermal-stress analogy gave a fair correlation, although the depth of the compressive layer was overestimated by about 16%. Stress data alone were used to obtain an interdiffusion coefficient at 400°C which agreed well with the diffusivity obtained directly. The stress and concentration fractions were related graphically; the relation suggests that there is a slight accommodation of the larger ion by the glass structure without stress buildup during the early stages of exchange. These results led to a method of predicting the modulus of rupture of an exchanged glass after it is reheated in air     

Influence of Strain Energy on Kinetics of Ion Exchange in Glass

The kinetics of the K⁺⇌ Na⁺ exchange in Na₂O·3SiO₂ glass at 350°C were studied. The distribution of K in the glass specimens after exchange in molten KNO₃ was determined with an electron microprobe. The calculated interdiffusion coefficients, which varied with the local composition in the glass, were compared with those obtained using the Nernst-Planck equation and Fleming and Day's self-diffusion data for xNa₂O. (1-x)K₂O·3SiO₂ glasses. Deviations of the observed interdiffusion coefficient from the Nernst-Planck formula were noted. These deviations are explained on the basis of changes in the average size of the alkali ion sites and in the strain energy that occur during ion exchange.     

Model for Ion-Exchanged Waveguides in Glass

An analytical model describing refractive index profiles in ion-exchanged glass waveguides is presented. Polarizability, volume, and stress-state changes are accounted for. Index distribution is given in terms of known or measurable physical parameters. Model predictions compare favorably with experimental results of field-assisted ion-exchanged waveguides fabricated in 7740 borosilicate glass. Experimental characterization of the index changes includes prism coupling, microprobe, and photoelastic measurements.