Uranium Carbide Fibers with Nano-Grains as Starting Materials for ISOL Targets

Abstract

This paper presents an experimental study about the preparation, by electrospinning, of uranium carbide fibers with nanometric grain size. Viscous solutions of cellulose acetate and uranyl salts (acetate, acetylacetonate, and formate) on acetic acid and 2,4-pentanedione, adjusted to three different polymer concentrations, 10, 12.5, and 15 weight %, were used for electrospinning. Good quality precursor fibers were obtained from solutions with a 15% cellulose acetate concentration, the best ones being produced from the uranyl acetate solution. As-spun precursor fibers were then decomposed by slow heating until 823 K under argon, resulting in a mixture of nano-grained UO2 and C fibers. A last carboreduction was then carried out under vacuum at 2073 K for 2 h. The final material displayed UC2−y as the major phase, with grain sizes in the 4 nm–10 nm range. UO2+x was still present in moderate concentrations (~30 vol.%). This is due to uncomplete carboreduction that can be explained by the fiber morphology, limiting the effective contact between C and UO2 grains.

Laser Heating Study of the High-Temperature Interactions in Nanograined Uranium Carbides

“…The refinement of the UO 2 lattice parameter ( a = 0.5469(1) nm) points to an oxide composition very close to the 1:2 stoichiometry [ 25 ], in contrast with previous results that indicate a hyperstoichiometric oxygen composition for these types of impurities in carbo-reduced materials [ 17 ]. On the other hand, the UC 2−y lattice parameters ( a = 0.35149(2) nm, c = 0.5976(1) nm) are very close to the results obtained for UC 2−y fibers prepared using a similar procedure [ 17 ] and are in agreement with the published data [ 26 ]. The Raman spectrum of the as-fabricated material ( Figure 5 a) shows two broad bands centered at 1321 cm −1 and 1596 cm −1 , which correspond to the D-peak of defective and disordered graphite and to the G-peaks of graphite, respectively [ 27 ].…”

“…Although the initial molar ratio of U/C was 1/4, no significant diffracted signal from carbon (graphite) was observed, probably due not only to the light nature of this element but also to disorder, as suggested by the Raman analysis reported in Figure 5 a. The refinement of the UO 2 lattice parameter ( a = 0.5469(1) nm) points to an oxide composition very close to the 1:2 stoichiometry [ 25 ], in contrast with previous results that indicate a hyperstoichiometric oxygen composition for these types of impurities in carbo-reduced materials [ 17 ]. On the other hand, the UC 2−y lattice parameters ( a = 0.35149(2) nm, c = 0.5976(1) nm) are very close to the results obtained for UC 2−y fibers prepared using a similar procedure [ 17 ] and are in agreement with the published data [ 26 ].…”

“…UC 2−y materials with nanometric grain size were prepared by (i) electrospinning a solution containing uranyl acetate and cellulose acetate with a 15% concentration ( w / v ) of U/C = 1/4, followed by (ii) rapid decomposition under an argon gas flow atmosphere (by inserting the sample inside a furnace pre-heated at 550 °C for 1 h) and (iii) carboreduction under vacuum at 1800 °C for 2 h in a radioinduction furnace, as described in [ 17 ]. The prepared material was mixed with a very small proportion of zirconia glue (ZrO 2 suspended in ethanol), which was kept at 80 °C overnight in order to evaporate the solvent.…”

Nanofibers of solid-solution thorium(IV)-uranium(IV) oxides by electrospinning

“…Recently, we introduced the electrospinning route to nanofibrous uranium [18] and thorium [19] oxides. Others used the same method to prepare nanofibers containing uranium carbide [20] . Based on the experience with electrospinning processing of thoria and urania, we present here a facile preparation route to atomically mixed ThO 2 /UO 2 oxides to enlarge the family of nanocrystalline nuclear materials.…”

Interaction of Fibromodulin and Myostatin to Regulate Skeletal Muscle Aging: An Opposite Regulation in Muscle Aging, Diabetes, and Intracellular Lipid Accumulation

“…FMOD also plays critical roles during collagen fibrillogenesis, cell adhesion, in the modulation of cytokine activity, the suppression of tumor growth, and the inhibition of apoptosis [28][29][30]. Interestingly, FMOD up-regulation also promotes proliferation and migration of pancreatic stellate cells [31].…”