Phase formation and crystal-chemical characterization of low- and high-alumina mullite-type compounds

低铝和高铝莫来石型化合物的相形成和晶体化学表征

基本信息

批准号：
283003582
负责人：
Professor Dr. Reinhard X. Fischer
金额：
--
依托单位：
Fachbereich 05: Geowissenschaften
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/283003582?language=en
关键词：
Phase formation crystal chemical characterization

项目摘要

It is the aim of this project to understand the complete structural evolution of the phases in the alumino-silicate system of mullite-type compounds with the endmembers sillimanite (Al2O3 . SiO2, x=0) and jota-alumina (Al2O3, x=1) in the compositional series Al4+2xSi2-2xO10-x. While sillimanite and synthetic mullite with its most abundant phases 2:1-mullite (2Al2O3 . SiO2, x=0.4) and 3:2-mullite (3Al2O3 . 2SiO2, x=0.25) have been studied extensively within the last decades, there is essentially no information on the crystal structures of these compounds at the low (x < 0.2) and high-alumina (x > 0.8) side of the series. Minerals (usually containing some Fe) are known to exist in the low-alumina range, but there are no crystal-structure investigations available. The existence or nonexistence of jota-alumina is still a matter of debate. In hypothetical models derived from DFT calculations a highly disordered structure was proposed (Aryal et al., Phys. Rev. B84, 2011, 174123) with AlO6 and AlO5 polyhedra forming the polyhedral chain crosslinked by di-, tri-, and tetraclusters of AlO4 tetrahedra. Instead, we suggest that it could consist of AlO6 octahedra and of AlO4 forming tetrahedral tetraclusters only. However, experimental proof is still missing. We propose to study a series of natural mullites already available and to be collected in the Eifel area as members of the low-alumina compounds. Since we have shown just recently (Fischer et al., Amer. Mineral. 2015, in press) that a mineral exists which has structural features from both sillimanite (Si/Al ordering) and mullite (O vacancies) it will be especially interesting to characterize these Eifel minerals structurally and microchemically. It is also planned to synthesize these intermediate low-alumina phases by annealing sillimanite at high temperatures and pressures in a piston cylinder apparatus. High-alumina compounds including jota-alumina will be synthesized in a microwave system following known routes. It will be the first time that crystal-structure investigations are performed on these compounds. Since mullite-type materials are most important ceramic constituents it will be extremely important to extend our knowledge on these compounds towards the hitherto unknown crystal structures of the low- (x<0.2) and high- (x>0.8) alumina mullites and mullite-type phases.

该项目的目的是了解与Endmembers sillimanite（Al2O3。Sio2，X = 0）和Jota-Alumina（Al2O3，X = 1）中的Mullite型化合物的铝硅酸盐系统的完整结构演变（Al2O3。Sio2，X = 0）。虽然sillimanite和合成的mullite具有最丰富的阶段2：1-毛石（2al2o3。Sio2，x = 0.4）和3：2-硫酸盐（3Al2O3。2SIO2，x = 0.25），在过去的几十年中已经广泛地研究了这些综合（x.2）。系列的一面。已知矿物质（通常包含一些Fe）存在于低铝范围内，但没有可用的晶体结构研究。 Jota-Alumina的存在或不存在仍然是一个争论的问题。在从DFT计算得出的假设模型中，提出了高度无序的结构（Aryal等，Phys。Rev.B84，2011，174123），Alo6和Alo5 Polyhedra由DI-，Tri-和Tri-和Tetraclusters的Alo4 tetrahedra的Tetraclusters交联的多面体链。取而代之的是，我们建议它只能由Alo6八面体和Alo4组成，而Alo4仅形成四面体四簇。但是，实验证明仍然缺失。我们建议研究一系列已经可用的天然穆特岩，并将作为低铝制化合物的成员在Eifel区域收集。由于我们最近展示了（Fischer等人，Amer。Miner。2015，印刷中），存在具有sillimanite（Si/Al Ordering）和Mullite（o空位）的结构特征的矿物质，在结构和微生物学上表征这些Eifel矿物质会特别有趣。还计划通过在高温和活塞缸设备中的高温和压力下退火，通过在高温和压力下退火来合成这些中间的低铝制相。包括JOTA-ALUMINA在内的高铝化合物将在已知途径的微波系统中合成。这是第一次在这些化合物上进行晶体结构研究。由于mullite型材料是最重要的陶瓷成分，因此将我们对这些化合物的知识扩展到低 - （x <0.2）和高 - （x> 0.8）氧化铝mullites和mullite型相位将非常重要。