Radiotracer diffusion and conductivity of sodium and potassium in alkali feldspar

碱长石中钠和钾的放射性示踪扩散和电导率

• 批准号: 275110401
• 负责人: Professor Dr.-Ing. Gerhard Wilde, since 6/2017
• 金额: --
• 依托单位: Department für Lithosphärenforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/275110401?language=en
• 关键词: Radiotracer; diffusion; conductivity; sodium; potassium

The proposal is an interdisciplinary, bilateral initiative between a material science group (Münster, Germany) and a geoscience group (Vienna, Austria), which aims at investigating alkali transport in alkali feldspar crystals of different composition and in different orientations as a function of temperature. The ultimate goal is to identify the underlying diffusion mechanisms and to characterize the point defects involved. Achievement of this goal will greatly help to understand the retention of major- and trace-element composition and isotope record in alkali feldspar, one of the most abundant phases in the Earth´s crust, over geological time scales. Moreover, evaluation of the experimental data is expected to shed light on fundamental issues of materials science not yet sufficiently dealt with, such as Frenkel pair formation and diffusion via interstitialcy defects on a binary (sub)lattice, diffusion correlation factors and their relevance to mixed alkali effects, and a possible composition-dependent changeover from vacancy- to interstitialcy-controlled diffusion. The project goals will be achieved by performing 22Na and 43K radiotracer diffusion experiments on gem quality alkali feldspars from the Eifel and Madagascar differing in composition. Additional compositions can be prepared by cation exchange, so that a wide range can be investigated covering relative K contents XOr between 0.65 and 1.00. The resulting tracer diffusion coefficients will be compared with ion conductivity data obtained by frequency-dependent impedance measurements on samples of the same composition and crystallographic direction using the Nernst-Einstein equation. Data analysis will involve a continuum approach based on the numerical solution of coupled diffusion-reaction equations. Monte Carlo simulations will be performed for testing theoretical models of alkali transport in the monocline feldspar structure.

该提案是一个材料科学小组（德国明斯特）和一个地球科学小组（奥地利维也纳）之间的跨学科双边倡议，旨在研究不同成分和不同取向的碱性长石晶体中的碱迁移随温度的变化。最终的目标是确定潜在的扩散机制，并描述所涉及的点缺陷。这一目标的实现将大大有助于了解在地质时间尺度上碱性长石中主要和微量元素组成和同位素记录的保留，碱性长石是地壳中最丰富的相之一。此外，实验数据的评估预计将揭示材料科学的基本问题尚未充分处理，如弗伦克尔对形成和扩散通过二元（子）晶格上的双金属缺陷，扩散相关因子及其相关性的混合碱效应，以及可能的组合物依赖于从空位到双金属控制扩散的转换。该项目的目标将通过对来自艾弗尔和马达加斯加的不同成分的宝石级碱性长石进行22 Na和43 K放射性示踪剂扩散实验来实现。可以通过阳离子交换制备另外的组合物，使得可以研究覆盖0.65和1.00之间的相对K含量XOr的宽范围。将所得示踪剂扩散系数与使用能斯特-爱因斯坦方程对相同组成和结晶方向的样品进行频率依赖性阻抗测量获得的离子电导率数据进行比较。数据分析将涉及基于耦合扩散-反应方程数值解的连续方法。将进行蒙特卡罗模拟，以测试单斜长石结构中碱传输的理论模型。

项目成果

Monte Carlo simulation of diffusion and ionic conductivity in a simple cubic random alloy via the interstitialcy mechanism

通过间隙机制对简单立方随机合金中的扩散和离子电导率进行蒙特卡罗模拟

• DOI: 10.1088/0953-8984/27/50/505401
• 发表时间: 2015
• 期刊: Journal of Physics: Condensed Matter
• 作者: F. Wilangowski;N. A. Stolwijk
• 通讯作者: N. A. Stolwijk

Potassium self-diffusion in a K-rich single-crystal alkali feldspar

富钾单晶碱长石中钾的自扩散

• DOI: 10.1007/s00269-016-0862-1
• 发表时间: 2017
• 期刊: Physics and Chemistry of Minerals
• 影响因子: 1.4
• 作者: F. Hergemöller;M. Wegner;M. Deicher;H. Wolf;F. Brenner;H. Hutter;R. Abart;N. A. Stolwijk
• 通讯作者: N. A. Stolwijk

Vacancy-related diffusion correlation effects in a simple cubic random alloy and on the Na–K sublattice of alkali feldspar

• DOI: 10.1080/14786435.2015.1054918
• 发表时间: 2015-06
• 期刊: Philosophical Magazine
• 影响因子: 1.6
• 作者: F. Wilangowski;N. Stolwijk

Ionic conductivity in gem-quality single-crystal alkali feldspar from the Eifel: temperature, orientation and composition dependence

• DOI: 10.1007/s00269-015-0797-y
• 发表时间: 2016-01
• 期刊: Physics and Chemistry of Minerals
• 影响因子: 1.4
• 作者: H. El Maanaoui;F. Wilangowski;Aditya Maheshwari;H. Wiemhöfer;R. Abart;N. Stolwijk

Radiotracer Experiments and Monte Carlo Simulations of Sodium Diffusion in Alkali Feldspar: Evidence against the Vacancy Mechanism

• DOI: 10.4028/www.scientific.net/ddf.363.79
• 发表时间: 2015-05
• 期刊: Defect and Diffusion Forum
• 作者: F. Wilangowski;R. Abart;S. Divinski;N. Stolwijk