Abstract
The thermal and radiation stability of free-standing ceramic nanoparticles that are under consideration as potential fillers for the improved thermal and radiation stability of polymeric matrices were investigated by a set of transmission electron microscopy (TEM) studies. A series of lanthanide-doped ceria (Ln:CeOx; Ln = Nd, Er, Eu, Lu) nanocubes/nanoparticles was characterized as synthesized prior to inclusion into the polymers. The Ln:CeOx were synthesized from different solution precipitation (oleylamine (ON), hexamethylenetetramine (HMTA) and solvothermal (t-butylamine (TBA)) routes. The dopants were selected to explore the impact that the cation has on the final properties of the resultant nanoparticles. The baseline CeOx and the subsequent Ln:CeOx particles were isolated as: (i) ON-Ce (not applicable), Nd (34.2 nm), Er (27.8 nm), Eu (42.4 nm), and Lu (287.4 nm); (ii) HMTA-Ce (5.8 nm), Nd (6.6 nm), Er (370.0 nm), Eu (340.6 nm), and Lu (287.4 nm); and (iii) TBA-Ce (4.1 nm), Nd (5.0 nm), Er (3.8 nm), Eu (7.3 nm), and Lu (3.8 nm). The resulting Ln:CeOx nanomaterials were characterized using a variety of analytical tools, including: X-ray fluorescence (XRF), powder X-ray diffraction (pXRD), TEM with selected area electron diffraction (SAED), and energy dispersive X-ray spectroscopy (EDS) for nanoscale elemental mapping. From these samples, the Eu:CeOx (ON, HMTA, and TBA) series were selected for stability studies due to the uniformity of the nanocubes. Through the focus on the nanoparticle properties, the thermal and radiation stability of these nanocubes were determined through in situ TEM heating and ex situ TEM irradiation. These results were coupled with data analysis to calculate the changes in size and aerial density. The particles were generally found to exhibit strong thermal stability but underwent amorphization as a result of heavy ion irradiation at high fluences.
Highlights
Lanthanum oxide (LnOx ) nanomaterials are of interest as potential fillers in polymeric coatings to protect internal electronic components and circuits from high temperature and ionization exposure
In Figure 10ii(a–c), the Eu-doped that at higher fluences, the ion irradiation appeared to deplete the SiOx layer beneath particles remained separated at higher fluences and displayed a small amount of crystalline the nanoparticles, while simultaneously forcing the aggregation of the particle
The poor irradiation stabilityand observed in this work is similar to that particles separated at higher fluences displayed a small amount of crystalseenbehavior in crystalline nanoparticles withnanoparticle heavy ions [23,24]
Summary
Lanthanum oxide (LnOx ) nanomaterials are of interest as potential fillers in polymeric coatings to protect internal electronic components and circuits from high temperature and ionization exposure (i.e., rad-hard) This is mainly due to their high Z number, which helps to prevent the ionization of energy and variable oxidation state, which can be accessed when exposed to ionizing radiation-reducing Compton and Auger effects [1]. This is in direct contrast to 2.5 MeV electron beam irradiations, where elastic collisions produced isolated defects that were repaired by thermal annealing [7] This suggests that dopant atoms within CeO2 may be warranted to enhance radiation stability and prevent significant lattice disorder upon interaction with external stimuli. The results of the synthesis route, ligand, dopant, and resulting particulates were evaluated
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