A noncontact measurement technique for the density and thermal expansion coefficient of solid and liquid materials

Abstract

A noncontact measurement technique for the density and the thermal expansion coefficient of refractory materials in their molten as well as solid phases is presented. This technique is based on the video image processing of a levitated sample. Experiments were performed using the high-temperature electrostatic levitator ͑HTESL͒ at the Jet Propulsion Laboratory in which 2-3 mm diam samples can be levitated, melted, and radiatively cooled in vacuum. Due to the axisymmetric nature of the molten samples when levitated in the HTESL, a rather simple digital image analysis can be employed to accurately measure the volumetric change as a function of temperature. Density and the thermal expansion coefficient measurements were made on a pure nickel sample to test the accuracy of the technique in the temperature range of 1045-1565°C. The result for the liquid phase density can be expressed by ϭ8.848ϩ(6.730ϫ10 Ϫ4 )ϫT ͑°C͒ g/cm 3 within 0.8% accuracy, and the corresponding thermal expansion coefficient can be expressed by ␤ϭ(9.419ϫ10 Ϫ5 ) Ϫ(7.165ϫ10 Ϫ9 )ϫT ͑°C͒ K Ϫ1 within 0.2% accuracy.

Thermophysical properties of molten tungsten measured with an electrostatic levitator

“…As seen in Fig. 7(a), a molten levitated sample adopts a symmetric shape about the polar axis from which the volume can be easily obtained [10].…”

Challenges of Handling, Processing, and Studying Liquid and Supercooled Materials at Temperatures above 3000 K with Electrostatic Levitation

“…For the image analysis for density measurement [2], a constant sample/background contrast is important. The imaging technique with white back light led to erroneous data when applied to molten refractory materials due to the large blackbody output variation in the optical region.…”

“…The density was measured using a photogrammetric technique described elsewhere [2]. In short, the temperature and images of a spherical sample were simultaneously recorded.…”

“…Developments include thermophysical property measurements (density [2], surface tension [3], viscosity [3], heat capacity [4], electrical resistivity [5,6]) of high-temperature melts, and the combination of levitation with either synchrotron radiation sources [7] or neutron sources [8,9] to unveil the structure of high temperature melts. These activities and the obtained scientific results have been summarized in a few review papers [10,11].…”

Studies on Thermophysical Properties of CaO and MgO by γ-Ray Attenuation

“…In general the thermal expansion characteristics decide the choice of material for the construction of metrological instruments and the choice of container material in nuclear fuel technology. A number of methods have evolved for the determination of density and thermal expansion of solids at high temperature like Archimedean method [1][2][3], pycnometry [4][5][6][7][8], dilatometry [9][10][11][12], electromagnetic levitation [13], method of maximal pressure in gas bubble [14][15][16][17][18], method of sessile drop [19], hydrostatic weighing [20,21], high temperature electrostatic levitation [22], and gamma ray densitometry [23][24][25][26][27][28][29][30][31][32][33][34]. Using -ray attenuation technique Drotning [23] measured thermal expansion of solid materials at high temperatures.…”