高精度钾热管铝凝固点炉研制及性能测试

热管作为等温炉衬可提高固定点炉温场均匀性。为提高铝凝固点复现水平,研制了1套高精度钾热管铝凝固点炉。介绍了钾热管和固定点炉的研制流程,并测试了钾热管固定点炉性能。测试结果表明:采用分段升温的方式,炉子升温曲线平缓,整个升温过程中没有明显过冲现象,可有效保护铝凝固点容器的使用寿命;钾热管铝凝固点炉垂直温场均匀性为6.6mK;利用该钾热管铝凝定点炉可以实现铝凝固点温坪的复现,温坪重复性为0.02mK。     

高精度钠热管固定点炉及其等温特性

介绍了中国计量科学研究院新研制的两台高精度钠热管固定点炉(SHPF-1、SHPF-2),并测量了其垂直温场.当这两台钠热管固定点炉的炉温分别控制在比铝凝固点低约2℃、3℃时,铝点容器温度计阱底部150 mm范围内温场均匀性分别为15 mK和11 mK,并与国外同类的钠热管固定点炉的技术指标进行比较.此外,分析了影响固定点炉等温性能的因素.     

新型便携式镓熔点炉的研制

中国计量科学研究院最新研制的便携式镓熔点炉采用了先进的半导体制冷和控温技术及有效合理的制冷块分布方式,实现对镓熔点容器的冻制与复现自动化.实验结果显示:该固定点炉从底端起140mm范围内的垂直温场小于0.03℃,温坪时间达到80h以上,复现性优于0.06mK.     

钠热管炉等温性的实验研究

为高精度地复现铝凝固点,中国计量科学研究院研制了钠热管炉。本文使用S型热电偶和Agilent公司3458A精密数字表测量了新研制钠热管炉的垂直温场。实验结果表明,在未放铝凝固点容器的情况下,炉温约645℃时,钠热管腔体轴向垂直温场最大温度变化不超过0．2℃。此外,找到了理想的放置固定点容器的等温区,为铝凝固点的复现创造了好的外部等温环境。     

小型固定点装置温坪性能研究

给出了锡点、锌点和铝点三个小型固定点装置的垂直温场调节方法和温坪复现方法，并对调节前后的温屏曲线进行了比较。该小型固定点装置温坪曲线特性满足现有国家计量检定规程对于检定二等标准铂电阻温度计和精密级铂电阻温度计的要求。     

基于准绝热的锌固定点复现装置

ITS-90温标固定点温坪受到诸多方面的影响,温场是其中重要影响因素之一。为提升温场性能弥补漏热造成的影响,借鉴低温固定点中广泛采用的绝热原理,设计基于准绝热的锌固定点装置,温场梯度性能由传统固定点的100 mK提升至20 mK,固定点高纯金属使用量由2.0kg降至200 g。实验结果表明该装置的温坪可持续时间较长,复现性0.1 mK,既能大幅度提升温场性能,同时达到了装置小型化、可重复使用经济实用的目的,又为高纯金属中微量杂质对相变温度的影响评估降低温场因素的干扰提供研究基础。     

新型开口锌凝固点复现装置

介绍了中国计量科学研究院研制的新型开口锌凝固点复现装置,该装置采用99．99999％的高纯锌金属固定点灌注技术,固定点炉采用三段控温的方式,依靠精确控温及合理的结构设计获得优良的垂直温场。通过准确测量容器的内部气压,可以优化我国国家基准中气压修正的不确定度分量。实验结果显示：该装置复现的温坪时间大于30小时,复现的扩展不确定度为0．6mK（k=2）。     

便携式锡凝固点复现技术研究

以中国计量科学研究院最新研制的小型锡凝固点装置为基础,开展不同的凝固速率及诱导技术对锡凝固点温坪复现影响的研究,致力于获得适合本装置最优的复现技术.实验结果显示:两支室温下的石英诱导棒分别诱导60s左右,固定点炉温度设置在比温坪值低0.6K,能够获得较理想的温坪曲线,温坪时长约9h,复现性为0.18mk,扩展不确定度1.40mK(k =2)     

基于微型镓固定点的精密铂电阻温度计原位校准的研究

基于固定点温标传递技术,设计可在镓熔点原位校准的精密铂电阻温度计,并对微型固定点相变温坪特性进行实验分析.实验结果表明:微型镓固定点温坪可持续最大时长为1.2h,温坪在20 min内稳定性优于2.8 mK,复现性优于2.3 mK;微型固定点温坪值与加热温度之间存在线性关系,并且随着加热温度的升高,固定点温坪值越高,通过...     

新型镓熔点自动复现装置

介绍了中国计量科学研究院新型镓熔点自动复现装置, 该装置的固定点炉采用半导体三段冻制及加热技术实现了镓熔点复现的自动化, 通过精密控温及合理的结构设计获得优良的温度稳定性与均匀性。该装置镓熔点使用当前最新提纯技术的99.999 99%高纯镓金属及完善的灌注技术。实验结果显示, 该固定点装置温坪持续了70 h以上,前20%～80%温坪变化小于0.15 mK,复现性为0.07 mK, 该装置的扩展不确定度为0.36 mK（k=2）。     

Thermal Analysis of the Heater-Induced Realization of the Tin Fixed Point

In this article, work concerning the thermal analysis of the tin fixed-point is reported. First, the development of a new fixed-point furnace is described. Improvements in the design of the furnace and in the control system enable measurement of the heater power during the phase change. The furnace is sufficiently thermally insulated to produce excellent uniformity and stability, leading to high quality freeze-initiation and minimal thermal influences on the freezing point. By employing the improved furnace and newly-fabricated tin fixed-point cells, the start and end of the melting plateau and the end of the freezing plateau were accurately determined, enabling reliable evaluation of the liquid fraction during the realization of the tin fixed-point compared to conventional methods. Two open-type tin fixed-point cells were fabricated using high-purity tin that was chemically analyzed for impurity content. Thermal analysis results of freezing-point depression are compared to those based on the chemical analysis.     

Thermal Effects in the HTBB-3200pg Furnace on Metal-Carbon Eutectic Point Implementation

The general statement that a temperature fixed-point cell will show better melting and freezing plateaux with better temperature uniformity along the dimensions of the fixed point is understood to be valid for metal-carbon (M-C) eutectics as well as for pure metal fixed points. In this article, it is shown that improved temperature uniformity in the central part of the high-temperature blackbody BB3200pg (HTBB), where the M-C fixed point is implemented, results in flatter and longer plateaux. Pyrolitic graphite rings, clamped together by a spring, form the heated cavity of the HTBB. As a first step, the relative electrical resistivity of each pyrolitic graphite ring was measured using a method advised by the furnace manufacturer. Next, the ring positions were optimized, taking into account their relative resistivities, in order to obtain a more homogeneous temperature distribution. Subsequent measurement of the temperature uniformity at the furnace walls confirmed the improvement. Measuring the melting plateaux of the Pt-C eutectic with different arrangements of the rings, and thereby operating the fixed-point cell in different temperature distributions, confirmed the influence of the temperature distribution on the plateau shape, with the best plateau shape corresponding to the most homogeneous temperature distribution.     

The Influence of Antimony on the Tin Point

In 2005, an agreement was reached on how to estimate uncertainties and how to correct fixed-point temperatures for the influence of chemical impurities. Although the general procedure is now specified, some problems remain. The slope of the liquidus line at very low-impurity concentrations must be extracted either from binary-phase diagrams or from doping experiments. Apart from this, there is little experimental evidence to prove that the models used to characterize the freezing and the melting plateaux are adequate, especially for impurities that increase the fixed-point temperature. Therefore, a series of measurements were carried out using a tin fixed-point cell doped with antimony. By varying the freezing and the melting conditions, some useful experimental data were collected.     

高精度复现铟凝固点

利用金属外壳密封铟点容器,采用连续热流密度法,高精度复现了铟熔化温坪和凝固温坪。通过线性拟合方法确定铟的液相温度,并将其与凝固温坪最大值之间的差异作为评判铟点容器质量的重要依据。实验结果表明:液相温度和凝固温坪最大值之间的差异在0.27mK范围内一致;距离容器温度计阱底部16cm内垂直温场均匀度为13mK。因此,该金属外壳铟点容器可以满足高精度温度量值传递需求。此外,研究了炉温设定对铟凝固温坪时长及过冷度的影响。     

Ga-In共晶固定点复现及赋值研究

次级固定点进一步分度温度计应用于温度校准已成为减小温度量值传递不确定度的重要方法.围绕Ga-In二元合金,以高复现水平为目标,详细介绍了大尺寸固定点容器研制、固定点灌注过程,开展了固定点复现性、亚配比剩余镓温坪验证实验研究;采用了切线交点法、均值法、三次多项式拟合法3种相变温度取值方法对Ga-In固定点进行了评价和分析...     

水三相点瓶自动冻制保存装置复现性研究

介绍了型号为CIMM-TH-0230的水三相点瓶自动冻制保存装置,对该装置进行水三相点温坪复现性研究,并考核装置的各项指标。实验结果显示:该装置冻制的水三相点的温坪在48 h内变化不大于0.2 m K,复现性小于0.04 m K,稳定性优于0.5 m K,不同瓶子之间复现的温度差值不大于0.4 m K。试验数据表明该装置非常适合水三相点瓶的自动冻制、保存与复现。