New microbalance measurement of ceramic reactivity: a scoping study.

本文提出的范围研究的基础是申请人发现的一个新定律，该定律表明，烧制粘土陶瓷对大气水分的化学吸附引起的质量增益和相关膨胀应变都与（时间）1/4成正比。这种分数次幂定律依赖意味着在1、16、81、256等秒/天/年（对应于t = 14、24、34、44秒/天/年）之后获得的质量相等。这种渐进的化学驱动过程表明，烧制粘土发生了非常显著的再羟基化作用，这个过程非常缓慢，在所有实际的历史时间尺度上都在继续。事实上，我们在2000年前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是这些材料的基础，必须具有科学意义。这种反应的潜在机制还远未被理解。然而，质量增益必须是潜在化学吸收过程的更基本的测量，膨胀应变是其结果。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天平（CiSorp水吸附分析仪）的资助。这种新设备在质量测量和环境控制方面提供了一个全新的精度水平。我们已经获得了一些惊人的结果，这些结果使我们能够以前所未有的精度检查质量增加过程，并对使用质量增加方法研究化学吸附/再羟基化过程的动力学给予了充分的信心。在这项范围研究中，我们的目标是将重点从应变测量（除了一个例外，自20世纪20年代开始研究水分膨胀以来，应变测量一直是唯一使用的调查工具）转移到质量测量，作为研究反应过程基本原理的更好方法。迫切需要全面确定的是，这种新设备将极大地改变烧制粘土陶瓷化学吸附的研究，未来的工作重点应该转移到质量测量上。拟议的工作完全基于申请人的许多新发现，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的质量增益效应的大小。这将为烧制粘土陶瓷行为的许多现象学特征提供新的见解，这些特征尚未被探索，并将为这些材料的任何进一步科学研究奠定必要的基础。该项目的主要目标是对新烧制陶瓷的质量增益进行首次微天平测量，并确定石英转变温度（575℃）对再加热到原始烧制温度和500℃的相同材料的质量增益的重要性。这将使我们能够确定再加热是否确实可以使陶瓷恢复到其被声称的烧制状态，但从未得到证实。在以往的工作中基于应变测量。我们还将评估粉末状样品（与小批量样品相比）作为测量潜在活性低得多的材料（如瓷器和其他精制陶瓷）质量增益的手段的使用。最后，通过仔细测量不同温度下的质量增益，计算第一阶段和第二阶段反应的活化能。

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.