Influence of Impurities and Filling Protocol on the Aluminum Fixed Point

Abstract

To improve the uncertainty of the aluminum fixed point, a study was launched by LNE-INM/CNAM in the framework of the EUROMET Project 732 "Toward more accurate temperature fixed points" (Coordinating laboratory: LNE-INM/CNAM, 17 partner countries). A new open cell was filled with aluminum of 99.99995% purity. A French laboratory carried out elemental analysis of the sample using glow discharge-mass spectrometry (GD-MS). The values of the equilibrium distribution coefficient k and of the derivative δT l /δc i l of the temperature of the liquidus line with respect to the concentration of impurity i will be obtained through collaboration with a French physical and chemical laboratory. In the past, some aluminum cells were opened after several melts and freezes. The aluminum ingot was sticking to the graphite crucible, indicating that physicochemical reactions had likely occurred between Al and C. To avoid this reaction, an effort was made to draw benefit from the Al 2 O 3 film that appears immediately on the surface of the aluminum ingot when it is exposed to oxygen. The open aluminum cell was tested in different furnaces and with different thermal insulator arrangements inside the fixed-point assembly. The observed drifts of the plateaux were always larger than the expected values. The cell was opened to inspect the aluminum ingot. The ingot was extracted easily, since no sticking to the crucible had occurred. The aluminum showed a very bright surface, but the presence of many "craters" throughout the thickness of the ingot was surprising. In some cases, the thermometer well was even apparent.

Uncertainties in the SPRT Subranges of ITS-90: Topics for Further Research

“…While many of these sources of impurity are understood for the cryogenic fixed points, the high mobility of potential contaminants at temperatures above 600 • C makes the high-temperature fixed points particularly prone to contamination, and at present our knowledge of the origins of the impurities, the effects of particular impurities in the fixed point, and means of preventing the migration of impurities, is weak. Significant progress has been made with investigations of impurity effects in aluminum (e.g., [15][16][17][18]), but more work is required.…”

Penerapan Iso 9001 Sebagai Dasar Pelayanan Publik Di Unit Pelayanan Pemerintah Daerah Dan Kota

“…Efek Impuritas Suhu terukur pada saat kondisi perubahan fasa pada material murni ditentukan oleh koefisien sensitivitas dan kemurnian material tersebut sesuai dengan persamaan yang diberikan oleh E. Renaot (2008).…”

Use of a phenomenological chemical scale for the identification of high distribution coefficient impurities within the ITS-90

“…The effect of impurities on the measured freezing temperature of temperature fixed-points is often the single largest component in the uncertainty of realisation of the International Temperature Scale of 1990 (ITS-90) [1] and can cause problems when it comes to confirming international equivalence of scales [2]. The solidification behaviour of Ga, In, Sn, Zn, Al, Ag, Au and Cu is of interest.…”