共查询到18条相似文献,搜索用时 125 毫秒
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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. 相似文献
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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。 相似文献
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本文叙述用精密直流光电温度计昨现纯金属铝凝固点的实验装置和实验方法,复现铝凝固点的总不确定度小于50mK,置信度为99%。实验中对3个铝点黑体石墨坩埚容器的凝固温度进行了多次测量,3个容器的铝凝固点温度之差不大于10mK。在8个月的时间内,对同一铝点坩埚容器的铝凝固点温度进行了11次测量,其标准偏差为15mK,长期重复性也很好。 相似文献
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TiC–C eutectic (2,761°C) and WC–C peritectic (2,749°C) fixed points were investigated to compare their potential as high-temperature
thermometric reference points. Two TiC–C and three WC–C fixed-point cells were constructed, and the melting and freezing plateaux
were evaluated by means of radiation thermometry. The repeatability of the TiC–C eutectic within a day was 60 mK with a melting
range roughly 200 mK. The repeatability of the melting temperature of the WC–C peritectic within 1 day was 17 mK with a melting
range of ∼70 mK. The repeatability of the freezing temperature of the WC–C peritectic was 21 mK with a freezing range less
than 20 mK. One of the TiC–C cells was constructed from a TiC and graphite powder mixture. The filling showed the reaction
with the graphite crucible was suppressed and the ingot contained less voids, although the lack of high-purity TiC powder
poses a problem. The WC–C cells were easily constructed, like metal–carbon eutectic cells, without any evident reaction with
the crucible. From these results, it is concluded that the WC–C peritectic has more potential than the TiC–C eutectic as a
high-temperature reference point. The investigation of the purification of the TiC–C cell during filling and the plateau observation
are also reported. 相似文献
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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. 相似文献
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N. Sasajima D. Lowe C. Bai Y. Yamada C. Ara 《International Journal of Thermophysics》2011,32(11-12):2696-2707
The Cr3C2?C peritectic fixed point was investigated to test its capability to serve as a practical high-temperature fixed point. An improved filling technique where C/C sheet works as a wick and graphite paper as a hopper was applied successfully, and the long-term stability of the peritectic cell was evaluated by means of radiation thermometry. The repeatability of the melting point in one day was 7 mK with a melting range of approximately 100 mK. The cell was aged for 7 days, and the evaluated 56 melting temperatures during this period all fall within 90 mK, with a standard deviation of 19 mK. X-ray transmission photos showed that the ingot was filled uniformly in the crucible. After the evaluation of long-term stability, no clear degradation of the ingot shape and no leakage of molten metal were observed. From these results, it can be concluded that the Cr3C2?C peritectic cell has good stability and robustness, and the new filling technique was established. The impurity effect on the Cr3C2?C peritectic cell was also investigated by adding tungsten powder to another cell as the impurity component. After the observation of melting and freezing plateaux, the cell was cut in half to analyze the microstructure by means of electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS). The high concentration of impurity was observed in the area of the chromium-rich domain (eutectic mixture of Cr7C3 and Cr3C2), which suggests that impurities were rejected from the Cr3C2 peritectic phase during the peritectic freezing and were accumulated in the Cr7C3?Cr3C2 eutectic phase. This explains why the impurity effect is more severe for the Cr7C3?Cr3C2 eutectic point than for the Cr3C2?C peritectic point. 相似文献
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National Institute of Metrology (NIM) (China) and National Physical Laboratory (NPL) (UK) have collaborated to construct metal-carbon
eutectic alloy fixed points at NPL. A modified NPL Thermogauge furnace was vertically used to construct fixed points of Pd–C,
Pt–C, Ru–C, and Ir–C. Breakage of Pd–C and Ru–C cells was traced to changes in furnace temperature gradients resulting from
changing from horizontal to vertical operation. Subsequently, it was found that positioning the cell being filled so that
the metal melting always starts from the top and freezing from the bottom to solve this problem. The constructed Pt–C cell
was then compared to a Pt–C fixed point previously constructed by NIM. The results indicate that the two cells made independently
agreed to be better than 40 mK. 相似文献