Monday, September 7, 2009

Synthesis and Stability of Iron Nanoparticles for Lunar Environment Studies

mong the hairiest problems facing the inevitable "extended human activity on the Moon" often discussed and underscored mightily in the Almighty "Scientific Context for the Exploration of the Moon" (NRC, 2007), is lunar dust. The six brief tours of the lunar surface by crews from the United States, forty years ago, definitely proved to be dusty.

However, not in the way some expected.

Neil Armstrong repelled away from the lunar module Eagle very carefully, on the first small step, playing out the slack glancing over both shoulders. It was a great relief to many serious geologists and to Armstrong when he, Aldrin and Eagle didn't suddenly sink into a loose pack of dust, perhaps many meters deep.

Those who believed the Moon's dusty surface was sufficiently packed down by micro-meteorites, etc., and additionally held together by a wide variety of chemical valences and gravity won out., though the same process of "gardening" eventually re-works the outer skin of the Moon every 2 million years, and has is patient.

Shards of rock are clipped off larger microscopic fragments and are so light, they've proven highly susceptible to charging in UV sunlight. In turn, this charge carries with it dust as it is repelled in every direction by the whole Moon's velocity through the interplanetary magnetic field, Earth's magnetic field and crustal magnetic anomalies locally embedded on the Moon with some strong enough to form their own pause in the relentless Solar Wind.

In short, a great volume of lunar dust levitates.

Not one vacuum bottle meant to remain sealed with it's lunar sample intact in a "native" environment managed to make it back to Earth intact, though the jostling of the handling of the samples by human and robotic methods before re-entry, and the forces of re-entry themselves are given most of the blaim, maintaining the integrity of things like flexible seals will prove more than a little important if human are to survive on the Moon or Mars for very long.

Coming up with a simulant has not been easy, and still eludes efforts to manufacture enough to be truly useful. Beyond that have been efforts to add microscopic divots by as would be created by random micro-meteorites and the little scars caused by the plasma flash of atomic nucleon of iron, cosmic rays of elemental metal traveling at or very near the Speed of Light.

The result is the hardest aspect of lunar dust to duplicate, a tattoo of "nanophase iron," the presense of which irritates many scientists (literally) and delights others, who see in it ubiquity on the Moon a resource with a potential not yet dreamed of.

Ching-cheh Hung and Jeremiah McNatt at NASA Glenn Research Center in Cleveland have been studying how to add the distinctive flavor of nanophase iron to lunar dust "simulant," fast enough to be of use.

Simulant of lunar dust is needed when researching the lunar environment. However, unlike the true lunar dust, today’s simulants do not contain nanophase iron. Two different processes have been developed to fabricate nanophase iron to be used as part of the lunar dust simulant:

(1) Sequentially treating a mixture of ferric chloride, fluorinated carbon, and soda lime glass beads at about 300 °C in nitrogen, at room temperature in air, and then at 1050 °C in nitrogen. The product includes glass beads that are grey in color, can be attracted by a magnet, and contain α-iron nanoparticles (which seem to slowly lose their lattice structure in ambient air during a period of 12 months). This product may have some similarity to the lunar glassy regolith that contains FeO.

(2) Heating a mixture of carbon black and a lunar simulant (a mixed metal oxide that includes iron oxide) at 1050 °C in nitrogen. This process simulates lunar dust reaction to the carbon in a micrometeorite at the time of impact. The product contains a chemically modified simulant that can be attracted by a magnet and has a surface layer whose iron concentration increased during the reaction. The iron was found to be α-iron and Fe3O4 nanoparticles, which appear to grow after the fabrication process, but stabilizes after 6 months of ambient air storage.

Introduction: Understanding the physics, chemistry, and toxicity of the lunar dust in the lunar environment is essential for lunar exploration. In order to do research on lunar dust, a few simulants that mimic the lunar dust obtained during the Apollo missions were produced. Although it is noted that the Apollo lunar dust contains chemically reactive iron nanoparticles, none of the current simulants do (Ref. 1). The goal of this research is to produce iron nanoparticles that can be used as a component of lunar dust simulants. Additional efforts were made to investigate the stability of the iron nanoparticles thus produced over a period of several months...

Read the Brief Study HERE.

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