Ceramics for Molten Materials Containment, Transfer and Handling on the Lunar Surface

As part of a project on Molten Materials Transfer and Handling on the Lunar Surface, molten materials containment samples of various ceramics were tested to determine their performance in contact with a melt of lunar regolith simulant. The test temperature was 1600 C with contact times ranging from 0 to 12 hours. Regolith simulant was pressed into cylinders with the approximate dimensions of 1.25 dia x 1.25cm height and then melted on ceramic substrates. The regolith-ceramic interface was examined after processing to determine the melt/ceramic interaction. It was found that the molten regolith wetted all oxide ceramics tested extremely well which resulted in chemical reaction between the materials in each case. Alumina substrates were identified which withstood contact at the operating temperature of a molten regolith electrolysis cell (1600 C) for eight hours with little interaction or deformation. This represents an improvement over alumina grades currently in use and will provide a lifetime adequate for electrolysis experiments lasting 24 hours or more. Two types of non-oxide ceramics were also tested. It was found that they interacted to a limited degree with the melt resulting in little corrosion. These ceramics, Sic and BN, were not wetted as well as the oxides by the melt, and so remain possible materials for molten regolith handling. Tests wing longer holding periods and larger volumes of regolith are necessary to determine the ultimate performance of the tested ceramics

Ceramics for Molten Materials Transfer

The paper reviews the main issues associated with molten materials transfer and handling on the lunar surface during the operation of a hig h temperature electrowinning cell used to produce oxygen, with molten iron and silicon as byproducts. A combination of existing technolog ies and purposely designed technologies show promise for lunar exploi tation. An important limitation that requires extensive investigation is the performance of refractory currently used for the purpose of m olten metal containment and transfer in the lunar environment associa ted with electrolytic cells. The principles of a laboratory scale uni t at a scale equivalent to the production of 1 metric ton of oxygen p er year are introduced. This implies a mass of molten materials to be transferred consistent with the equivalent of 1kg regolithlhr proces sed

Particle Engulfment and Pushing by Solidifying Interfaces

The scientific objectives of the work on Particle Engulfment and Pushing by Solidifying Interfaces (PEP) include: (1) to enhance the fundamental understanding of the physics of interaction between inert particles and the solidification interface, and (2) to investigate aspects of melt processing of particulate metal matrix composites in the unique microgravity environment that will yield some vital information for terrestrial applications. The proposal itself calls for a long-term effort on the Space Station. This paper reports on ground experiments performed to date, as well as on the results obtained from two flight opportunities, the LMS mission (1996) and the USMP-4 mission (1997)

Production of Oxygen from Lunar Regolith using Molten Oxide Electrolysis

This slide presentation reviews the possible use of molten oxide electrolysis to extract oxygen from the Lunar Regolith. The presentation asserts that molten regolith electrolysis has advanced to be a useful method for production of oxygen and metals in situ on the Moon. The work has demonstrated an 8 hour batch of electrolysis at 5 amps using Iridium inert anodes

Thin Wall Cast Iron: Phase II

The development of thin-wall technology allows the designers of energy consuming equipment to select the most appropriate material based on cost/material properties considerations, and not solely on density. The technology developed in this research project will permit the designers working for the automotive industry to make a better informed choice between competing materials and thin wall cast iron, thus decreasing the overall cost of the automobile

Recent Developments in Understanding Nucleation and Crystallization of Spheroidal Graphite in Iron-Carbon-Silicon Alloys

The last decade has witnessed significant research efforts directed to the understanding of nucleation and crystallization of graphite and associated solidification phenomena, driven in part by the ever-growing interest in the use of spheroidal graphite cast iron in the manufacture of large castings, such as wind turbine parts. These applications raised new challenges to the production of sound castings, mostly because of the exceedingly long solidification times imposed by the size of the castings. These solidification conditions resulted in many instances in graphite degeneration with subsequent decrease in mechanical properties. Obviously, the subject of graphite nucleation and crystallization in cast iron is still in need of additional answers. Over the years, many reviews of the subject have been published. The goal of this paper is to provide an update on the advances achieved in comprehending the mechanisms that govern the nucleation and crystallization of spheroidal graphite and related imperfect morphologies from iron-carbon-silicon melts. In this analysis, we examine not only the crystallization of graphite in cast iron, but also that of metamorphic graphite (natural graphite formed through transformation by heat, pressure, or other natural actions), and of other materials with similar lattice structure and crystallization morphologies

Molten Materials Transfer and Handling on the Lunar Surface

Electrolytic reduction processes as a means to provide pure elements for lunar resource utilization have many advantages. Such processes have. the potential of removing all the oxygen from the lunar soil for use in life support and for propellant. Electrochemical reduction also provides a direct path for the. production of pure metals and silicon which can be utilized for in situ manufacturing and power production. Some of the challenges encountered in the electrolytic reduction processes include the feeding of the electrolytic cell (the transfer of electrolyte containing lunar soil), the withdrawal of reactants and refined products such as the liquidiron~siliconalloy with a number of impurities, and the spent regolith slag, produced in the hot electrolytic cell for the reduction of lunar regolith. The paper will discuss some of the possible solutions to the challenges of handling molten materials on the lunar surface, as well as the path toward the construction and testing of a proof-of-concept facility

Numerical Calculation of the Morphology of a Solid/Liquid Interface Near an Insoluble Particle

A numerical mathematical model capable of accurately describing the evolution of the shape of the solid/liquid interface in the proximity of a foreign particle is presented in this paper. The model accounts for the influence of the temperature gradient and the Gibbs-Thomson and disjoining pressure effects. It shows that for the systems characterized by k(sub P) < k(sub L) the disjoining pressure causes the interface curvature to change its sign in the close-contact particle/interface region. It also shows that the increase of the temperature gradient diminishes the effect of the disjoining pressure. Calculated critical solidification velocities for the pushing/engulfment transition are compared with experimental measurements performed in microgravity conditions

Interaction of Porosity with a Planar Solid/Liquid Interface

In this article, an investigation of the interaction between gas porosity and a planar solid/liquid (SL) interface is reported. A two-dimensional numerical model able to accurately track sharp SL interfaces during solidification of pure metals and alloys is proposed. The finite-difference method and a rectangular undeformed grid are used for computation. The SL interface is described through the points of intersection with the grid lines. Its motion is determined by the thermal and solute gradients at each particular point. Changes of the interface temperature because of capillarity or solute redistribution as well as any perturbation of the thermal and solute field produced by the presence of non-metallic inclusions can be computed. To validate the model, the dynamics of the interaction between a gas pore and a solidification front in metal alloys was observed using a state of the art X-ray transmission microscope (XTM). The experiments included observation of the distortion of the SL interface near a pore, real-time measurements of the growth rate, and the change in shape of the porosity during interaction with the SL interface in pure Al and Al-0.25 wt pct Au alloy. In addition, porosity-induced solute segregation patterns surrounding a pore were also quantified