PISCES Geology & Materials Science technicians Kyla Edison and Kye Harford (shown above) have been researching various basalt sintering methods for novel uses on Earth and other planets. Their current focus is tile production using basalt of varying grain sizes to produce an extremely durable product resembling marble countertop.

By: Kye Harford

As much as we want to expand and try different things with our sintering technology, we have been facing a problem where the basalt crystallizes to the surface of its casting mold. When this happens, it becomes nearly impossible to scrape or chip away the sintered fines without destroying the mold—and the product.

Two sections of sintered basalt blocks made with varying grain size distribution. The slab on the left was polished.

Two sections of sintered basalt blocks made with varying grain size distribution. The slab on the left was polished.

To solve this challenge, we first tried a different material for the mold that we hoped would not create adhesion with the sintered basalt. We conducted two trial bakes using plates made of vitreous alumina. One plate was polished using a wet polisher with 3000 grit, the other was left in its original condition. One sample each of crushed and sieved basalt were placed in the middle of these plates and baked. Unfortunately, the results were unsuccessful and the crystallization between the basalt and mold actually strengthened. Next, we looked at an alternative mold release agent to prevent surface crystallization: yttrium oxide aerosol. We tested this rare, earth metal oxide agent in a high-temperature bake, but once again found the results to be unsuccessful.

With two failed attempts, Kyla decided we should instead alter the physical properties of the mold rather than its chemical composition. She designed a free-floating mold with sealed corners to allow the basalt to compress and expand more. We also altered the grain size distribution of basalt fines by arranging them from coarse to fine layers in the mold, bottom to top. The resulting sintered basalt brick released from the mold without any chipping.

Now that we have this problem solved, we are working on baking ½-inch thick tiles using various grain sizes. Our most recent bake incorporated four different grain sizes, layered from bottom to top and baked under high heat. The resulting tile (pictured left) was then polished with a wet polisher creating a solid and glossy finish like a marble countertop. We’re excited to see what kind of applications this product might have. It is extremely durable and could be used for in-situ construction on Earth, or places like the Moon and Mars using surface regolith to build infrastructure.