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New microbalance measurement of ceramic reactivity: a scoping study.

陶瓷反应性的新微天平测量：范围研究。

基本信息

批准号：
EP/G009694/1
负责人：
Moira Wilson
金额：
$ 7.83万
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FG009694%2F1
关键词：
New microbalance measurement ceramic reactivity

项目摘要

The basis for the scoping study proposed here is a new law, discovered by the applicants, which shows that the mass gain and associated expansive strain caused by the chemisorption of atmospheric moisture by fired clay ceramics are both proportional to (time)1/4. This fractional power law dependence means that equal amounts of mass will be gained after 1, 16, 81, 256 etc seconds/ days/ years (corresponding to t = 14, 24, 34, 44 seconds/ days/ years). This progressive chemically driven process indicates a very remarkable rehydroxylation of the fired clay which is so slow that it continues certainly over all practical historical timescales. Indeed we have found residual reactivity in 2000 year old ceramic. The extremely slow progress of the reaction appears to be fundamental to these materials and must be scientifically significant. The underlying mechanisms of this reaction are as yet far from understood. However, mass gain must be the more fundamental measure of the underlying chemisorptive process, with expansive strain being a consequence of this. In support of this approach, we have recently been successful in obtaining funding from EPSRC for an ultra-high accuracy recording microbalance (CiSorp Water Sorption Analyser). This new equipment provides an entirely new level of precision in mass measurement and environmental control. We have already obtained some spectacular results using this equipment which have enabled us to examine the mass gain process with an unprecedented level of precision and which give full confidence in the use of the mass gain approach to study the kinetics of the chemisorption/rehydroxylation process. In this scoping study we aim to shift the emphasis from strain measurement (which, with one exception, has been the only investigative tool employed since studies of moisture expansion began in the 1920s) to mass measurement as the better methodology for studying the fundamentals of the reaction process. It is urgent to establish comprehensively that this new equipment will so greatly revolutionise the study of chemisorption in fired clay ceramics that the focus of future work should be transferred to mass measurement. The proposed work, which is entirely based on a number of new discoveries made by the applicants, is a contained and focussed study to assess the magnitude of the mass gain effect in a wide range of ceramic types that have not yet been examined using this technique. This will give new insights into a number of phenomenological features of fired clay ceramic behaviour which have yet to be explored and will form an essential basis for any further scientific examination of these materials. The main objectives of the project are to carry out the first microbalance measurements of mass gain in freshly fired ceramic and to establish the significance of the quartz transition temperature (575 deg C) on mass gain in the same materials that have been reheated to both the original firing temperature and 500 deg C. This will allow us to establish whether reheating can indeed return the ceramic to its as fired state as has been claimed, but never proven, in previous work based on strain measurement. We will also assess the use of powdered samples (compared to small bulk samples) as a means of measuring mass gain in potentially much less reactive materials such as porcelain and other refined ceramics. Finally, from careful measurements of mass gain at different temperatures, to calculate the activation energies of the Stage I and Stage II reactions.

本文提出的范围研究的基础是申请人发现的新规律，其表明由烧制的粘土陶瓷对大气水分的化学吸附引起的质量增加和相关的膨胀应变都与（时间）1/4成比例。这种分数幂律依赖性意味着在1、16、81、256等秒/天/年（对应于t = 14、24、34、44秒/天/年）之后将获得等量的质量。这种渐进的化学驱动过程表明烧制粘土的非常显著的再羟基化，其是如此缓慢，以至于在所有实际的历史时间尺度上肯定会继续。事实上，我们已经在2000年的陶瓷中发现了残留的反应性。反应的极其缓慢的进展似乎对这些材料至关重要，并且必须具有科学意义。这种反应的基本机制还远未被理解。然而，质量增加必须是基本的化学吸附过程的更基本的措施，与膨胀应变是一个后果。为了支持这种方法，我们最近成功地从EPSRC获得了超高精度记录微量天平（CiSorp水吸附分析仪）的资金。这种新设备在质量测量和环境控制方面提供了全新的精度水平。我们已经获得了一些壮观的结果，使用这种设备，使我们能够检查的质量增益过程与前所未有的精度水平，并给予充分的信心，在使用的质量增益的方法来研究化学吸附/再羟基化过程的动力学。在这个范围研究中，我们的目标是将重点从应变测量（其中，有一个例外，一直是唯一的调查工具，因为水分膨胀的研究开始于20世纪20年代），质量测量作为更好的方法来研究反应过程的基本原理。这是迫切需要全面建立，这种新的设备将大大革命性的研究化学吸附在烧制粘土陶瓷，未来的工作重点应转移到质量测量。所提出的工作完全基于申请人的一些新发现，是一项包含和集中的研究，以评估尚未使用该技术检查的各种陶瓷类型中的质量增加效应的大小。这将提供新的见解，一些现象学特征的烧制粘土陶瓷的行为，尚未被探索，并将形成一个重要的基础上，任何进一步的科学检查这些材料。该项目的主要目标是对新烧制陶瓷的质量增加进行首次微量天平测量，并确定石英转变温度（575摄氏度）对重新加热到原始烧制温度和500摄氏度的相同材料的质量增加的重要性。这将使我们能够确定重新加热是否真的可以使陶瓷返回到它的烧制状态，就像以前的工作中基于应变测量所声称的那样，但从未得到证实。我们还将评估使用粉末样品（与小批量样品相比）作为测量潜在反应性低得多的材料（如瓷器和其他精制陶瓷）质量增加的一种手段。最后，通过在不同温度下的质量增加的仔细测量，计算第一阶段和第二阶段反应的活化能。