EFFECTS OF STRUCTURAL RELAXATION ON CATIONIC TRACER DIFFUSION IN SILICATE MELTS
EFFECTS OF STRUCTURAL RELAXATION ON CATIONIC TRACER DIFFUSION IN SILICATE MELTS
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DOI：
10.1016/0009-2541(90)90082-i
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发表时间：
1990-04-25
期刊：
影响因子：
3.9
通讯作者：
DINGWELL, DB
中科院分区：
文献类型：
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作者：
DINGWELL, DB
硅酸盐熔体中的玻璃化转变是时间-温度空间中的曲线，标志着熔体结构从非松弛的不平衡玻璃转变为松弛的平衡液体。在玻璃与液体中获得的示踪剂扩散率数据不能进行比较，而不考虑这种转变的影响。对于示踪剂扩散率实验，两个时间尺度很重要，即实验持续时间（τd）和示踪剂跳跃频率的倒数（τp）。当实验持续时间达到熔体的驰豫时间尺度（τd=τs）时，发生从非驰豫基质中扩散的转变在一个实施例中，热膨胀可以是从热膨胀（经历振动热膨胀）到在松弛基质中扩散（经历平衡、构型和弹性、热膨胀）的过程。在这个过渡，观察到阳离子示踪剂扩散的温度依赖性的拐点。当温度低于拐点时，扩散系数为Arrhenius型，而当温度高于拐点时，扩散系数为非Arrhenius型，在高温时，阳离子的示踪扩散系数接近于由Eyring关系式（τp=τs）得到的扩散系数值。对比，高温，成分依赖性的Na和Li与Co，Cs，Sr，Ba，Eu，Fe和C的扩散系数可以解释的Eyring（网络O和Si）扩散系数影响后者组。Ba和Sr扩散率的对比高温与低温、成分依赖性可以类似地解释。这些后者的观察表明，所有的阳离子扩散率将在一个log 10单位的Eyring氧扩散率在熔体粘度低于10 P。
The glass transition in silicate melts is a curve in time-temperature space marking the transition of the melt structure from an unrelaxed, disequilibrium glass to a relaxed, equilibrium liquid. Tracer diffusivity data obtained in glasses vs. liquids cannot be compared without consideration of the effects of this transition. For tracer diffusivity experiments, two time scales are important, the time duration of the experiment (τd) and the inverse of the jump frequency (τp) of the tracer.When the time duration of the experiments reaches the relaxation time-scale (τd=τs) of the melt a transition occurs from diffusion in an unrelaxed matrix (undergoing vibrational thermal expansion) to diffusion in a relaxed matrix (undergoing equilibrium, configurational and elastic, thermal expansion). At this transition, an inflection is observed in the temperature dependence of cationic tracer diffusivity. At temperatures below the inflection, the diffusivity is Arrhenian whereas at temperatures above the diffusivity is non-Arrhenian.At high temperatures the tracer diffusivities of the cations approach the value of diffusivity obtained from the Eyring relation (τp=τs). The contrasting, high-temperature, composition dependence of Na and Li vs. Co, Cs, Sr, Ba, Eu, Fe and C diffusivities can be explained in terms of the Eyring (network O and Si) diffusivity influencing the latter group. The contrasting high- vs. low-temperature, composition dependence of Ba and Sr diffusivities can be similarly explained. These latter observations indicate that all cationic diffusivities will be within a log10unit of the Eyring oxygen diffusivity in melts with viscosities below 10 P.