This procedure for measuring the surface tension of molten metals or alloys utilizes electrostatic levitation and resonance to derive the values with sufficient accuracy for designing reliable metallic 3D prints. The use of 3D printing in the metals industry is growing rapidly, and analysts expect the market for metal 3D printing to be worth $10 billion by 2030. Advancements in metallic 3D printing would improve resource utilization so that unneeded tools could be melted down for 3D reprinting as other tools. Such on-site manufacturing could reduce the amount of refined metal needed for many projects, including long-term space missions. Accurate measurement of thermophysical properties like surface tension is crucial for various manufacturing methods, such as metal 3D printing and crystal growth. Traditional procedures for surface tension measurement fail when measuring high-temperature materials because of their high surface reactivity. Electrostatic levitation of liquid droplets can facilitate accurate surface tension measurement via pulse-decay analysis, but this can prove inaccurate if the droplets are highly viscous or the levitation system is noisy.
Researchers at the University of Florida and NASA have developed a system that accurately measures the surface tension of oscillating liquid droplets at high temperatures. Resonance analysis of an electrostatically levitated molten metal droplet measures its surface tension value, which enables accurate calculation of the 3D printing speed of a metal in order to eliminate aberrations in prints. This measurement system will undergo tests in microgravity, which should demonstrate its ability to determine surface tension.
Highly accurate system to measure surface tension of molten metals that can improve the quality of metallic 3D printing and crystal growth processes
The process measures the surface tension of a molten metal droplet that is electrostatically levitated in a vacuum (at least 10-7 torr). A range of continuously applied electric field oscillations causes a maximum deformation of the droplet at two distinct modes of oscillation. The droplet’s resonance then allows determination of its surface tension value at a specific temperature. The system works with high viscosity materials and remains accurate in extreme high-temperature environments . The surface tension value determines the 3D printing speed of a metal, so increased measurement accuracy can reduce or eliminate aberrations. This will improve the potential for on-site manufacturing, which would reduce the mass of metals and processing energy needed in space.