Comparison of Pyrometric Co-C and Re-C Eutectic-Point Cells Between VNIIM and LNE-Cnam

VNIIM and LNE-Cnam have collaborated for several years in the field of metal-carbon eutectic points. The first action was the construction of a Pt-C cell at VNIIM using the LNE-Cnam technique and cell design. The Pt-C cells constructed in each of the laboratories were studied and compared in the past. The two laboratories have followed their collaboration work by studying and comparing Co-C and Re-C cells. Different designs and filling techniques were applied. The melting and freezing temperatures observed on the Re-C cells from the two laboratories were measured at VNIIM. The Re-C and Co-C cells were compared at LNE-Cnam in the high-temperature blackbody furnace HTBB 3200pg which was thermally optimized before the measurements. The results of the comparison showed that the Co-C cells were comparable at the level of 0.03 K while the Re-C cells showed a large difference of melting temperatures of about 0.7 K. In this article, the cells used and the methodology of the comparison will be described. The temperature differences that were obtained at the highest temperature will be examined to propose an explanation for this temperature difference.     

Experience of Construction and Study of Pt–C Eutectic in VNIIM and Cooperation with LNE-INM

A new high-temperature furnace was developed in VNIIM and manufactured by the Omsk plant “Etalon.” This furnace is intended for the realization of various fixed points of pure metals and high-temperature metal–carbon eutectics up to a temperature of 3000°C. The construction of the furnace allows measurements to be carried out either with or without the protective window, in a protective atmosphere of argon. The furnace will be described in this article. Cooperation with LNE-INM was initiated with the aim of sharing experience in metal–carbon eutectic cell construction and comparing two Pt–C cells (one cell was made by each partner) as a means of comparing scale realizations around 1740°C. The filling technique used in each laboratory will be described. The average melting temperature of the VNIIM Pt–C eutectic cell, characterized and studied at VNIIM, was 1738.4°C with a standard uncertainty of about 0.13 K. The repeatability of the melting temperature with various measurements was estimated to be within the limits of (0.02–0.2) K. The cell supplied by LNE-INM is the one that was constructed and studied in the framework of the HIMERT European project and described elsewhere. The difference in the melting temperatures of the fixed points (VNIIM—LNE-INM) is about 0.4 K with a standard uncertainty not exceeding 0.18 K. The cells constructed and characterized by each partner were exchanged and measured by the other partner. The results of the study of the melting and freezing of the Pt–C cells carried out by VNIIM and LNE-INM will be presented. The reasons for the difference in the melting temperatures of the two cells are analyzed, and the steps preceding the comparison of the scale realizations of the two laboratories are presented.     

State Primary Standard of Temperature Unit in the Range 0–3200°C GET 34-2020: Practical Implementation of the New Definition of Kelvin

Measurement Techniques - We consider the necessity and means of modernizing the State primary standard GET 34-2007 of the unit of temperature in the range of 0–3000°С. The problem...     

The initial kinetics of hydrolysis by cellobiohydrolases I and II is consistent with a cellulose surface-erosion model

Introduction of a novel method for the quantification of the cellobiose released made it possible to follow the initial stage of hydrolysis of bacterial microcrystalline cellulose (BMCC) by cellobiohydrolases 1,4-beta-D-glucan-cellobiohydrolase I (CBH I) and 1,4-beta-D-glucan-cellobiohydrolase II (CBH II) from Trichoderma reesei. A drastic retardation of the rate of the hydrolysis was observed already at a very low degree of conversion. Earlier-suggested retardation factors, such as product inhibition by cellobiose or enzyme inactivation, could be discounted as primary causes for the pattern. A model including steric hindrance by non-productive binding and erosion of the cellulose surface during the processive action of exoenzymes was proposed to describe the rate retardation observed. Simultaneous action of CBH I and CBH II on cellulose was not a prerequisite for synergy between them.     

Thermoelectric Characteristic of High-Temperature Thermocouples W5%RE/W20%RE

In the temperature range (900 to 2800) K, there has been confirmed compliance with the existing national standards for thermocouple wires W5% Re/W20%Re (type A) produced in Russia. The homogeneity within a lot of wires was evaluated by measuring the emf deviations from the corresponding reference function of thermocouples constructed from the front and the rear sections of paired coils of wires. The diameter of the wires amounted to 0.35 mm and 0.5 mm. Stability indicators were thermal emf changes after annealing for 2 hours at 1773 K. It was found that the inhomogeneity of thermoelements did not exceed (4 to 5) K for paired wire coils with a thermoelectric stability within a temperature equivalent of (1.0 to 1.5) K. EMF deviations from the reference table values for the thermocouples investigated did not exceed 1 % in the temperature range of (900 to 2773) K. Such deviations meet the requirements of the new draft of IEC standards 60584-1 and 2. Thermocouples were calibrated in four laboratories by comparison with various standard temperature gauges (type B thermocouple, radiation pyrometer, standard specimens of thermoelements). Measurements were carried out under vacuum, argon, and hydrogen. Depending on the calibration method, the expanded uncertainty of the measurements at 1773 K varied from (2.8 to 8) K.