共查询到16条相似文献,搜索用时 140 毫秒
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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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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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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。 相似文献
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The concept of metal–carbon eutectic temperature fixed point has been introduced in 1999 and is extensively being investigated by thermometry researchers to cover the high-temperature range above copper fixed point. Metal–carbon eutectic fixed points also helped to provide direct traceability with reduced associated uncertainty in the high temperature range for thermometry and radiometry applications. In view of this, CSIR-National Physical Laboratory, India (NPLI) has developed iron–carbon (Fe–C, 1153 °C) eutectic fixed point cell in the graphite crucible and realized by using the noble metal thermocouples. The preparation parameters such as design and fabrication of a graphite crucible, Fe:C eutectic composition and filling procedure, furnace profile, melting and freezing plateau measurements, heat flux immersion, inhomogeneity, etc. have been optimized and presented in this paper. The measurement uncertainty of the Fe–C eutectic cell realized with Type-S thermocouple was estimated to be 3.04 μV (0.25 °C) at coverage factor k = 2. 相似文献
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As another crucible material for metal–carbon eutectic points, alumina ceramic was used in the first trial to make an Fe–C eutectic point for the calibration of a thermocouple. Its melting and freezing behavior was tested 26 times with a type S thermocouple at various melting offset temperatures, namely, +4 °C, +9 °C, and +19 °C, and at a fixed freezing offset temperature of ?11 °C. The melting emf is reproducible independent of the melting offset temperatures, and the standard deviation of the 26 melting temperatures is 0.02 °C without breakage of the cell. The difference of melting emf between alumina Fe–C and graphite Fe–C fixed points is only 25 mK within an uncertainty of 0.39 °C (k = 2). The melting behaviors of an alumina cell are quite similar to a common graphite cell. Thus, alumina can be used as a crucible material in an Fe–C eutectic system without breakage, and it can be used at a higher temperature range. As possible application systems using alumina crucibles, Pd–C and Si–SiC eutectic points are suggested. 相似文献
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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. 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