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Impact of the lasr wavelength and fluence on the ablation rate of aluminium

100%
Stafe M., Vladoiu I., Popescu I.
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vol. 6
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issue 2
327-331
EN
The dependence of the ablation rate of aluminium on the fluence of nanosecond laser pulses with wavelengths of 532 nm and respectively 1064 nm is investigated in atmospheric air. The fluence of the pulses is varied by changing the diameter of the irradiated area at the target surface, and the wavelength is varied by using the fundamental and the second harmonic of a Q-switched Nd-YAG laser system. The results indicate an approximately logarithmic increase of the ablation rate with the fluence for ablation rates smaller than ∼6 μm/pulse at 532 nm, and 0.3 μm/pulse at 1064 nm wavelength. The significantly smaller ablation rate at 1064 nm is due to the small optical absorptivity, the strong oxidation of the aluminium target, and to the strong attenuation of the pulses into the plasma plume at this wavelength. A jump of the ablation rate is observed at the fluence threshold value, which is ∼50 J/cm2 for the second harmonic, and ∼15 J/cm2 for the fundamental pulses. Further increasing the fluence leads to a steep increase of the ablation rate at both wavelengths, the increase of the ablation rate being approximately exponential in the case of visible pulses. The jump of the ablation rate at the threshold fluence value is due to the transition from a normal vaporization regime to a phase explosion regime, and to the change of the dimensionality of the hydrodynamics of the plasma-plume.
2
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Skład chondrytów węglistych jako wyznacznik zasobności planetoid typu C w surowce metaliczne

75%
Blutstein K., Przylibski T. A., Łuszczek K., Gruchot J.
Acta Societatis Metheoriticae Polonorum
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2022
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vol. 13
7-26
EN
The chemical composition of carbonaceous chondrites was analysed in terms of the content of selected 24 metals, including noble metals and rare-earth metals. Based on the obtained results, the abundance of C-type asteroids in metallic raw materials was estimated and compared to the concentration of terrestrial deposits and the average content in the Earth’s crust. All the analysed elements, except rare earths, showed higher concentrations in carbonaceous chondrites than in the Earth’s crust, but most of them did not match the Earth’s deposit contents. The exception is Fe and Ni, the concentrations of which in carbonaceous chondrites significantly exceed the Earth’s deposit concentrations. The profitability of mining operations on C-type asteroids is also increased by the number of accompanying mineral commodities, mainly metals (Cr, Co, Cu, Au, Pt, Pd, Ag), and water ice. In addition, the parent bodies of carbonaceous chondrites occur relatively close to the moons of Jupiter and Saturn – potential space mission targets.
3
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Zagadkowe znalezisko z elipsy spadku meteorytu Łowicz

75%
Kozłowski S.
Acta Societatis Metheoriticae Polonorum
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2023
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vol. 14
93-99
EN
The paper presents the circumstances of finding and analyses of an unusual 35 g piece of iron-like meteor-wrong collected in the strewnfield of the Łowicz meteorite (mesosiderite). While both the outer appearance of the specimen and its internal etched section closely resemble that of meteorites, as it includes pseudo-figures and pseudo-Neumann lines, the X-ray fluorescence (XRF) and scanning electron microscope (SEM) spectroscopy shows no signs of the nickel content in the iron-dominated alloy. This rules out the possibility of this specimen having outer space origin.
4
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Ciała macierzyste meteorytów żelaznych jako złoża metali

75%
Przylibski T. A., Donhefner H., Łuszczek K.
Acta Societatis Metheoriticae Polonorum
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2012
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vol. 3
71-103
EN
Some of M type asteroids, like 016 Psyche, 022 Kalliope, 055 Pandora, 110 Lydia, 250 Bettina, 347 Pariana, 678 Fredegundis, 771 Libera, 872 Holda, are probably the source of iron meteorites. The population of these asteroids is less than 10% of all minor bodies orbiting the Sun in the asteroid belt. In the paper we analyzed the concentrations of 19 selected metals in 1730 iron meteorites according to the groups. Base on it authors found out that beside Fe and Ni the parent bodies of iron meteorites are the richest in Co, Cu, Ge, Cr, and Ga. They are also rich in As, Pt, Mo, Os, Pd, and Ir. The iron meteorites of IVB group are the richest in metals. Meteorites belonging to this group contain the highest average concentrations of Ir, Co, W, Re, Pt, Os, Pd, Rh, Ru, Mo, and Ni. Meteorites from IAB group are the richest in Ge, As, Sb and Au. The parent bodies of iron meteorites, especially from IVB and IAB groups, can be recognized as very rich polymetallic deposits. The concentrations of most of 19 analyzed metals in iron meteorites are greater than the concentrations in Earth’s crust. Only tungsten and chromium according to their strong litophile character occur in lower concentrations than in Earth’s crust. Few of the M type asteroids, those that are the source of iron meteorites, are probably the most differentiated bodies in the asteroid belt. Their chemical composition considerably differs from the composition of CI carbonaceous chondrites. Among their the most differentiated (enriched in some elements and depleted in others) and differing from CI chondrites are the parent bodies of iron meteorites belonging to IVB group. However even they are far less differentiated than Earth’s crust. This is the proof of relatively long chemical evolution of IVB group parent body comparing to parent bodies of other groups of iron meteorites and CI chondrites, but from the other hand the evolution of this body is also significantly shorter than the chemical evolution of Earth’s crust.
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