杂质对复现金属碳共晶及包晶高温固定点影响研究

The International Temperature Scale (ITS) is an equipment calibration standard for making accurate measurements on the temperature and compatibility of temperature measurements internationally. The ITS is also the headwater of the temperature and playing a vital role in guaranteeing temperature's consistency of China. . .With the evolution of science and technology, accurate measurement of high temperature is vitally and imminently required. However, the uncertainty in high temperature measurement increases rapidly with increasing temperature, since the currently implemented international temperature scale (ITS-90), relying upon radiation thermometry above the silver point (962 ?C) is in lack of reference fixed points above the copper point (1084 ?C). With the establishment of high-temperature fixed points (HTFPs) based upon metal-carbon eutectics and peritectics, and further be adopted by the new ITS will drastically change the situation. In fact, before the ITS employing HTFPs as reference fixed points, HTFPs must demonstrate their abilities, i.e. the HTFP must be extremely stable and reproducible. However, impurity is one main non-ideal source that affect the reproducibility when realizing the HTFPs. In this proposal, the theories of the thermodynamic and eutectic/peritectic will be used to demonstrate the physical mechanism of the impurity effect. Then a practical and accurate model to correct such effect will be constructed...Due to the lack of suitable reference artefacts, comparisons are not able to probe the equivalence of local realizations of the ITS-90 to the uncertainty levels claimed by NMIs. So in this proposal, the doping experiments will be carried out to shift the HTFPs' temperature which is imminently required by the consultative committee for temperature (CCT). Finally, the artefacts for comparing high temperature scales will be demonstrated.

国际温标是保证温度量值准确可靠、国际一致的基础，是温度量值的源头，同样对保证我国温度量值的国际等效性起着不可或缺的作用。随着科技的发展，高温测量的准确性越发重要。然而，由于现行的温标在铜点以上缺乏参考固定点，导致高温测量的不确定度随温度升高迅速增大。建立基于金属和碳共晶和包晶相变的高温固定点并推动其被温标采用为定义参考点是解决这一问题的有效途径。高温固定点成为温标定义固定点的前提是具备良好的复现性。杂质是影响高温固定点复现性的主要非理想性因素。本项目的研究将结合现有的热力学理论、共晶和包晶相变理论来描述杂质影响的物理机制，进而建立具有普适性、实用性和较高精度的杂质影响修正理论模型。基于高温区国际温标关键比对缺乏可靠的传递标准这一现状，有针对性地开展掺杂实验研究，提供目前国际温度计量界所急需的高温固定点掺杂实验基础数据，进而探索未来高温区温标国际关键比对基于掺杂高温固定点这一技术的可行性。

国际温标是保证温度量值准确可靠、国际一致的基础，是温度量值的源头，同样对保证我国温度量值的国际等效性起着不可或缺的作用。随着科技的发展，高温测量的准确性越发重要。然而，由于现行的温标在铜点以上缺乏参考固定点，导致高温测量的不确定度随温度升高迅速增大。建立基于金属和碳共晶和包晶相变的高温固定点并推动其被温标采用为定义参考点是解决这一问题的有效途径。高温固定点成为温标定义固定点的前提是具备良好的复现性。杂质是影响高温固定点复现性的主要非理想性因素。本项目的研究紧密围绕杂质对复现金属碳共晶和包晶高温固定点的影响这一关键的科学问题，理论探索和实验研究相结合来开展。研究内容主要概况如下：(1) 基于高温固定点的灌注和复现系统，发展了新型的混合式坩埚结构设计，提出了基于预先共晶模型的灌注方法，研制了耐用稳定、具备优良计量特性的Co-C、 Pt-C、Re-C、WC-C系列高温固定点。（2）结合了现有的热力学理论、共晶和包晶相变理论来描述杂质影响的物理机制，理论上研究了杂质对共晶相变温度的作用机理，建立了具有普适性、实用性和较高精度的杂质影响修正理论模型。（3）研究了高温固定点相变温度赋值模型及关键影响因素。建立了基于凝固实验的外推至0速率的平衡相变温度理论模型，选择Pt-C进行了实验验证，理论与实验吻合良好。本模型已被国际温度计量委员会采用，用于高温固定点的热力学温度赋值。（4）针对高温区国际温标关键比对缺乏可靠的传递标准这一现状，有针对性地开展掺杂实验研究，实验研究了本文研制的一系列掺杂新型高温固定点的稳定性，取得了新型掺杂高温固定点的稳定性优于0.02K的良好结果。并利用掺杂固定点开展了中英两国高温温标国际比对盲比原型比对，两国温标的差异在Pt-C-Xi小于0.1 ℃。良好的一致性验证了掺杂型高温固定点技术将成为未来高温区关键比对盲比的可靠技术。