Pd-C高温共晶点复现技术研究

设计了Pd-C高温共晶点复现装置,包括复现用高温均热炉炉体、温度控制系统、真空泵、充气保护装置、水冷系统、复现用的石墨坩埚、二等B型标准热电偶和Pt-Pd热电偶等。在此基础上进行了石墨坩埚的灌注和共晶点复现,并对复现的试验数据进行了相应的分析。结果表明本装置温度复现性可以达到0.2℃以下。     

Co-C共晶点研制及评价

根据国际温度咨询委员会辐射测温工作组(CCT-WG5)对世界各国计量机构开展Co-C共晶点研制工作的相关要求,设计并搭建了Co-C共晶点灌注系统,采用直接共晶法成功灌注了满足复现实验要求的Co-C共晶点坩埚。针对直接共晶灌注法效率低、坩埚破裂风险大的缺陷,提出了对灌注方法的改进方案,并依据该方案成功灌注了2个Co-C共晶点坩埚。对灌注的Co-C-2#共晶点进行了复现试验,结果显示:拐点温度的不确定度为5.3 mK,满足小于10 mK的CCT要求;短期重复性为9.6 mK,满足小于20 mK的CCT要求。     

Pd-C高温共晶点复现装置研制

主要针对Pd-C高温共晶点复现装置的组成进行介绍,其中包括复现用高温均热炉炉体、温度控制系统、真空泵、充气保护装置、水冷系统、复现用的石墨坩埚、二等B型标准热电偶和Pt-Pd热电偶等。针对石墨坩埚的灌注和共晶点复现过程进行了描述,根据复现的试验数据进行了相应的分析。     

300℃以上热电偶量传体系问题分析及对策

针对目前300℃以上热电偶量传体系存在不确定度过大、计量能力不满足要求等问题,分析了高温共晶点和实用型固定点温度复现、纯金属热电偶温度测量和1500℃以上高温热电偶校准等技术的最新进展,提出基于固定点温度复现方法的新的量值传递体系设想,可大大减小热电偶量值传递的不确定度,使各级计量标准装置不确定度分布更为合理,能保证热电偶量值的逐级量传,满足科研生产对热电偶的溯源要求。     

高温共晶固定点的建立与复现

金属(碳)-碳(M-C和M(C)-C)高温共晶固定点(以下简称高温固定点)的出现给温标复现方法带来了一次变革,并有可能成为下届温标新的定义固定点.文中介绍了目前常见的高温固定点坩埚的典型结构,描述了高温固定点的灌注工艺及灌注方法.为对固定点的不同灌注方法及其效果进行研究,使用石墨衬套和碳纤维石墨材料作内衬,灌注了Co-C和Pt-C高温固定点.对灌注的高温固定点初步的复现实验结果显示,Co-C、Pt-C的短期复现重复性均优于50 mK,进一步证明了高温固定点作为新温标定义固定点的可行性.     

Fe-C共晶点的复现与温坪特性的研究

在温度量传体系中,铜凝固点(1084.62 ℃)以上目前还没有其他纯金属固定点,而金属-碳共晶点作为新兴的固定点具备良好的复现性,可补充铜点以上的温度固定点,拓展现有的高温温度量值传递水平。尽管Fe-C共晶点非常接近铜凝固点,但其仍有较高的使用价值,可为更高温共晶点灌注及复现提供宝贵的经验。用一等标准S偶对Fe-C共晶点的温坪进行测量,其共晶点温度为1152.4 ~1152.5 ℃。     

一种三段加热的立式高温均热炉的研制

介绍了一种用于Fe-C高温共晶点装置复现的三段加热立式高温均热炉, 包括炉体的设计结构、 温度控制系统、 复现用腔体的密封结构设计和冷却水与充气保护系统等. 对炉体温场的测试结果表明: 该炉体能够满足设计的预期要求, 实现Fe-C高温共晶点的复现.     

一种三段加热立式高温均热炉的研制

介绍了一种用于Fe-C高温共晶点装置复现的三段加热立式高温均热炉,包括炉体的设计结构、温度控制系统、复现用腔体的密封结构设计和冷却水与充气保护系统等。对炉体温场的测试结果表明:该炉体能够满足设计的预期要求,实现Fe-C高温共晶点的复现。     

高温共晶点坩埚耐用性研究

高温共晶点坩埚因采用石墨材料制作,结构强度较低,在复现试验后易发生破裂,造成高温共晶点的损坏。坩埚耐用性问题已成为制约高温共晶点加入下一代温标的主要障碍之一。为了解决上述问题,本文依据ANSYS对坩埚受力情况进行分析,明确了坩埚主要受力点的理论位置,之后结合多种高温共晶点的实际破裂情况,分析了不同种类共晶点坩埚破裂的原因,并有针对性的提出了两种高温共晶点坩埚改进方案：改进型Hybrid结构和导流盖结构。最后使用改进结构的坩埚灌注了新的高温共晶点/包晶点,复现试验后未出现损坏问题,初步验证了方案的有效性。     

Ga-In-Sn微型共晶点相变特性研究

以Ga-In-Sn三元合金为研究对象,研制了可用于现场及在线标定的微型Ga-In-Sn共晶点容器,开展了3种不同配比对相变温度和温坪复现影响的研究。结果表明:3种配比的共晶点温坪可持续1.2~2 h,实验的复现性优于4.5 mK,合成扩展不确定度为9.3 mK(k=2),3种配比的共晶点相变温度平均值为10.748 ℃;在相同热工况下Ga-In-Sn合金发生共晶反应的相变温度不受配比的影响;改变合金熔体的降温速率可改变微型共晶点过冷度。     

Establishment of the Co-C Eutectic Fixed-Point Cell for Thermocouple Calibrations at NIMT

In 2015, NIMT first established a Co-C eutectic temperature reference (fixed-point) cell measurement capability for thermocouple calibration to support the requirements of Thailand’s heavy industries and secondary laboratories. The Co-C eutectic fixed-point cell is a facility transferred from NPL, where the design was developed through European and UK national measurement system projects. In this paper, we describe the establishment of a Co-C eutectic fixed-point cell for thermocouple calibration at NIMT. This paper demonstrates achievement of the required furnace uniformity, the Co-C plateau realization and the comparison data between NIMT and NPL Co-C cells by using the same standard Pt/Pd thermocouple, demonstrating traceability. The NIMT measurement capability for noble metal type thermocouples at the new Co-C eutectic fixed point (\(1324.06\,{^{\circ }}\hbox {C}\)) is estimated to be within \(\pm 0.60\,\hbox {K}\) (\(k=2\)). This meets the needs of Thailand’s high-temperature thermocouple users—for which previously there has been no traceable calibration facility.     

Comparative Study of Pt/Pd and Pt–Rh/Pt Thermocouples

The Pt/Pd thermocouple has demonstrated superior thermoelectric drift and homogeneity performance over conventional Pt–Rh/Pt thermocouples. Here, we present a systematic comparison of the drift and homogeneity performance of Pt/Pd and Type R thermocouples by ageing the thermocouples at 1350 °C for a total of 500 h and measuring the performance at regular intervals during this time. The thermocouples studied were one Pt/Pd thermocouple, one Type R thermocouple and one ‘special’ Type R thermocouple which was given the same preparatory annealing treatment as the Pt/Pd thermocouple prior to use. The thermoelectric stability of each thermocouple was measured at the freezing point of Ag (961.78 °C) and the melting point of Co–C eutectic (1324.29 °C). The thermoelectric homogeneity of the thermocouples was also measured. Two difference methods were used by withdrawing the thermocouple from the Ag cell and by moving a localized heat source along the thermocouple. The long-term drift of the Pt/Pd thermocouple was around 50 mK (Ag) and 65 mK (Co–C) after the first 100 h ageing at 1350 °C, followed by a further 25 mK (Ag) and 35 mK (Co–C) over the subsequent 400 h ageing. This drift performance and inhomogeneity were an order of magnitude lower than for the two Type R thermocouples. The Type R thermocouple which was given the ‘special’ preparatory treatment was about 50 % more stable than the conventional Type R thermocouple.     

Simultaneous Contact and Non-contact Measurements of the Melting Temperature of a Ni–C Fixed-Point Cell

A novel fixed-point cell design that allows simultaneous measurements using contact and non-contact thermometers was developed and investigated at PTB to realize the nickel-carbon (Ni–C) fixed-point. The melting temperature indicated by the LP3 radiation thermometer amounted to (1328.86 ± 0.52)°C (k = 2). The melting temperature of the Ni–C fixed-point cell was also calculated by extrapolating the emf-temperature characteristics of two Pt/Pd thermocouples based on their calibrations at conventional fixed points of the ITS-90. The melting temperature of the Ni–C eutectic amounts to (1328.44 ± 0.45)°C using thermocouple Pt/Pd 01/04, and to (1328.53 ± 0.46)°C using thermocouple Pt/Pd 01/05, with uncertainties for k = 2. The contact and non-contact thermometers agree well within the combined uncertainties.     

Relating Composition and Thermoelectric Stability of Pt–Rh Alloy Thermocouples

A simple model is presented which relates the electromotive force drift rate of Pt–Rh thermoelements to dS/dc, the sensitivity of the Seebeck coefficient, S, to rhodium mass fraction, c. The model has been tested by repeated measurements of a Pt–Rh thermocouple assembly consisting of five thermoelements, using a Co-C high-temperature fixed point (\(1324{\,}^{\circ }{\mathrm{C}}\)) for a total duration of 500 h. By considering various thermocouples from the assembly, it is demonstrated that in this case, remarkably, there is a linear relationship between the measured drift rate and the combined dS/dc, where the combination is determined by addition of the individual values for each wire. Particular emphasis is placed on evaluation of the uncertainties associated with the calculations. This result supports previous findings that the thermoelectric stability of Pt–Rh thermoelements improves as the rhodium mass fraction increases. Within this paradigm, it is shown that for a selected Pt–Rh thermoelement of any given composition, there exists a second thermoelement having a composition that yields a minimum drift when combined with the first to form a thermocouple.     

Evaluation of Cobalt–Carbon and Palladium–Carbon Eutectic Point Cells for Thermocouple Calibration

Two cobalt–carbon (Co–C) eutectic point (1,324 °C) cells and one palladium–carbon (Pd–C) eutectic point (1,492 °C) cell were constructed for thermocouple calibration. The lengths of the Co–C and Pd–C cells were 297 mm, 140 mm, and 140 mm, respectively. The melting and freezing plateaux at the Co–C and Pd–C eutectic points were observed using Pt/Pd thermocouples. The repeatability of the plateau, the effect of the surrounding temperature, and the temperature profile in the cell were measured, and the heat flux effect along the thermometer well was evaluated. When the plateaux of Co–C (297 mm height), Co–C (140 mm height), and Pd–C cells, were measured three times, seven times, and six times, respectively, the standard deviations of the melting points were 0.1 μV, 0.1 μV, and 0.4 μV, respectively. According to the temperature profiles along the thermometer well during the melting plateaux, it was found that the Pt/Pd thermocouple should be inserted at least 9.5 cm, 5 cm, and 6 cm below the surface of the eutectic alloys in the Co–C (297 mm height), Co–C (140 mm height), and Pd–C cells with the furnace set-point 16 °C above the melting point.     

高精度金-铂热电偶的制作和热电稳定性研究

金-铂热电偶是采用纯金和纯铂电极制成,长期使用过程中是否能够保持温度与热电势关系稳定是其准确测温的关键.首先,对热电极丝材进行剪切、清洗、退火并焊接组装成热电偶;然后,再对制作成的热电偶进行退火实验,热电偶在其使用上限965℃附近累计退火时间700 h,在银凝固点的稳定性达到±0.02℃.在制造热电偶过程中,采取了传统...     

Melting Temperature of High-Temperature Fixed Points for Thermocouple Calibrations

Thermocouples can be calibrated at pure metal ingot-based fixed points at temperatures up to the freezing point of copper (1084.62 °C). For Pt/Pd thermocouples, the deviation from the accepted reference function very often takes an approximately linear form up to the copper fixed point. The calibration of Pt/Pd thermocouples may therefore be more amenable to extrapolation than that of Pt/Pt-Rh thermocouples. Here, the melting temperatures of a Co?CC and a Pd?CC eutectic fixed point are determined by extrapolating the deviation functions of several Pt/Pd thermocouples, after the fashion of Edler et al. The results are compared with the melting temperatures measured using non-contact radiation thermometry. The expanded uncertainty (k = 2) of the melting temperatures determined by extrapolation of the Pt/Pd thermocouple calibrations is ±0.32 °C for the Co?CC fixed point, and ±0.49 °C for the Pd?CC fixed point. For both fixed points, these uncertainties are comparable to those of non-contact radiation thermometry measurements. While a number of assumptions are made in performing the extrapolation of the calibrations, the method does appear to offer a useful complement to non-contact radiation thermometry measurements.     

标准铂铑10-铂热电偶热电势约束公式探讨

铂铑10-铂热电偶可以通过3个固定点的热电势与温度之间的关系反映其特性。在ITPS-68温标中,铂铑10-铂热电偶作为温标内插仪器,其3个固定点热电势必须满足一定的约束公式。介绍了从其约束公式推导出现行检定规程使用的3个不同的温度固定点的新约束公式,以规范标准铂铑10-铂热电偶的热电特性;通过对大量源于中国计量科学研究院热电偶校准实验室的标准热电偶的实际数据的计算,验证了新约束公式的有效性。新公式在锌固定点的不合格检出率从0% 提升到3%左右。     

Comparison of Co�CC and Pd�CC Eutectic-Point Cells for Thermocouple Calibration Between LNE-Cnam and NMIJ

Evaluation of the melting temperatures of two Co?CC and two Pd?CC eutectic-point cells were performed using three Pt/Pd thermocouples constructed at LNE-Cnam and NMIJ. During the comparison of cells, Pt/Pd thermocouples were evaluated at the Ag fixed point, at which their drifts and inhomogeneity represented differences within 0.03 °C and 0.14 °C, respectively. One Co?CC cell and one Pd?CC cell were designed and constructed at LNE-Cnam, while one Co?CC cell and one Pd?CC cell were designed and constructed at NMIJ. In spite of differences in cell design and in materials sources, melting points of Co?CC and Pd?CC eutectic-point cells realized using LNE-Cnam high-temperature furnace agreed within approximately 0.02 °C and 0.01 °C, respectively. Furthermore, the realizations of the Pd?CC eutectic point at LNE-Cnam and NMIJ agreed within a temperature equivalent of approximately 0.11 °C. The uncertainty of the realization was estimated to be approximately 0.14 °C (k = 2), with a major contribution from the inhomogeneity of the thermocouple.     

溴苯熔点研制及复现方法研究

研制了可用于工业铂电阻温度计现场校准的溴苯熔点.对溴苯过冷度、熔点复现性进行了实验研究,并比较了基于曲线拟合法和切线交点法的两种熔点取值方法,最后对溴苯熔化温坪用于现场校准的实用性进行分析,提出了溴苯熔点的使用建议.实验表明:溴苯凝固前的保温温度越接近其凝固点温度,过冷度越小;溴苯熔化时保温温度越高,升温速率越大,熔化...