共查询到17条相似文献,搜索用时 125 毫秒
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镓熔点是ITS-90国际温标中重要的定义固定点,在温度计量研究中起着重要作用。由于高纯镓从液态转化为固态时,体积膨胀约3.1%,传统玻璃外壳的镓熔点容器在冻制过程中很容易造成损坏。为了解决这一难题,设计了一种具有金属外壳的镓熔点装置,以该装置为对象,开展了2种不同镓熔点复现方法和2种不同复现装置对镓相变温坪影响方面的研究,并与国外同类型装置的性能进行了比较。实验结果表明:不同镓点容器复现的镓熔点温度在0.02 mK范围内一致,高纯镓中的微量杂质是造成差异的主要原因;外液-固界面复现方法比双液-固界面复现方法得到的温坪值低0.09 mK;不同复现装置对镓熔点温坪的影响较小。 相似文献
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本文介绍了计量院研制的新型结构的镓三相点容器及镓三相点的复现方法。并将两个镓三相点容器与镓熔点容器进行了比对 ,结果表明 :两个镓三相点容器所复现的镓三相点温度与镓熔点温度的差值分别为1 85mK、1 71mK ;通过分析认为镓三相点容器间的温差 (0 1 4mK)主要是镓样品所含杂质成分的差异引起的。 相似文献
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介绍了微型镓基共晶固定点的灌注工艺和准绝热相变特性测量系统;结合空腔黑体和非近位安装的温度传感器,研究了Ga-Sn和Ga-Zn共晶固定点的相变温坪重复性和Ga固定点的相变温坪长期稳定性;通过特定的热环境下镓及2个镓基共晶固定点三者熔化过程中温度传感器测量到的相变温坪值,对嵌入空腔黑体底部的温度传感器进行校准,其校准结果与实验室常规校准方法得到的结果差异均小于2mK。实验结果表明:在热环境保持不变的条件下,随着相变时间的增加,相变温坪值就越靠近理论上相变物质的熔化温度,即固定点与温度传感器测孔之间的异位温差越小;对于Ga-Sn和Ga-Zn共晶固定点,温度传感器测量到的相变温坪值与加热功率呈线性关系,零功率下的单点校准温度分别为20.352℃和25.187℃。 相似文献
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The triple point of gallium has been realized by a calorimetric method using capsule-type standard platinum resistance thermometers
(CSPRTs) and a small glass cell containing about 97 mmol (6.8 g) of gallium with a nominal purity of 99.99999%. The melting
curve shows a very flat and relatively linear dependence on 1/F in the region from 1/F = 1 to 1/F = 20 with a narrow width of the melting curve within 0.1 mK. Also, a large gallium triple-point cell was fabricated for the
calibration of client-owned CSPRTs. The gallium triple-point cell consists of a PTFE crucible and a PTFE cap with a re-entrant
well and a small vent. The PTFE cell contains 780 g of gallium from the same source as used for the small glass cell. The
PTFE cell is completely covered by a stainless-steel jacket with a valve to enable evacuation of the cell. The melting curve
of the large cell shows a flat plateau that remains within 0.03 mK over 10 days and that is reproducible within 0.05 mK over
8 months. The calibrated value of a CSPRT obtained using the large cell agrees with that obtained using the small glass cell
within the uncertainties of the calibrations. 相似文献
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A new model of sealed cells with three thermometer wells for calibration of capsule-type thermometers at low-temperature fixed
points of the International Temperature Scale of 1990 has been developed at the National Metrology Institute of Japan (NMIJ).
The melting curves of Ar and O2 obtained using the new cells show very flat plateaux and a linear temperature dependence as a function of the inverse liquid
fraction (1/F) over the range 1/F = 1 to 1/F = 20 with a narrow melting curve width of 0.1 mK. The melting curves of Ne obtained with the new cell also show very flat
plateaux and approximately linear temperature dependence versus 1/F and a narrow melting curve width of 0.1 mK, though with a slight concave structure at high 1/F. The melting temperatures with the new cells agree with previous NMIJ sealed cells within 10 μK, which is similar to the reproducibility of the realization of the triple points at NMIJ. The source dependence of the triple-point
temperature of Ne was investigated by filling two of the new cells from different sources of Ne. The difference in the realized
triple point temperatures between the two sources is 0.031 mK, consistent with that estimated from isotope analysis. The uncertainties
in the calibration of standard platinum resistance thermometers at the low-temperature fixed points are summarized. The uncertainty
of the calibration at the triple point of e-H2 has been reduced to about one-third of its value without the correction by making the isotopic correction on the basis of
the technical annex for the ITS-90 in the mise en pratique for the definition of the kelvin. 相似文献
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A. Merlone F. Moro T. Zandt C. Gaiser B. Fellmuth 《International Journal of Thermophysics》2010,31(7):1386-1395
A liquid-bath thermostat with a volume of about 800 L was designed to provide a suitable thermal environment for a dielectric-constant
gas thermometer (DCGT) in the range from the triple point of mercury to the melting point of gallium. In the article, results
obtained with the unique, huge thermostat without the DCGT measuring chamber are reported to demonstrate the capability of
controlling the temperature of very large systems at a metrological level. First tests showed that the bath together with
its temperature controller provide a temperature variation of less than ±0.5mK peak-to-peak. This temperature instability
could be maintained over a period of several days. In the central working volume (diameter—500mm, height—650mm), in which
the vacuum chamber containing the measuring system of the DCGT will be placed later, the temperature inhomogeneity has been
demonstrated to be also well below 1mK. 相似文献
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Davor Zvizdic Tomislav Veliki Lovorka Grgec Bermanec 《International Journal of Thermophysics》2008,29(3):984-990
This article describes the realization of the International Temperature Scale in the range from 234.3 K (mercury triple point)
to 1084.62°C (copper freezing point) at the Laboratory for Process Measurement (LPM), Faculty of Mechanical Engineering and
Naval Architecture (FSB), University of Zagreb. The system for the realization of the ITS-90 consists of the sealed fixed-point
cells (mercury triple point, water triple point and gallium melting point) and the apparatus designed for the optimal realization
of open fixed-point cells which include the gallium melting point, tin freezing point, zinc freezing point, aluminum freezing
point, and copper freezing point. The maintenance of the open fixed-point cells is described, including the system for filling
the cells with pure argon and for maintaining the pressure during the realization. 相似文献
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A concentration-saturated helium mixture at the melting pressure consists of two liquid phases and one or two solid phases. The equilibrium system is univariant, whose properties depend uniquely on temperature. Four coexisting phases can exist on singular points, which are called quadruple points. As a univariant system, the melting pressure could be used as a thermometric standard. It would provide some advantages compared to the current reference, namely pure $^3$ He, especially at the lowest temperatures below 1 mK. We have extended the melting pressure measurements of the concentration-saturated helium mixture from 10 to 460 mK. The density of the dilute liquid phase was also recorded. The effect of the equilibrium crystal structure changing from hcp to bcc was clearly seen at $T=294$ mK at the melting pressure $P=2.638$ MPa. We observed the existence of metastable solid phases around this point. No evidence was found for the presence of another, disputed, quadruple point at around 400 mK. The experimental results agree well with our previous calculations at low temperatures, but deviate above 200 mK. 相似文献