Yttria stabilized Zirconia (YSZ) pellets with different crystallite sizes were irradiated with 80 MeV Ag$^{6+}$ ions at room temperature and 1000 K to understand the role of crystallite size/material microstructure and irradiation temperature on the radiation tolerance against high electronic energy loss (S$_e$). X-ray diffraction and Raman spectroscopy measurements reveal that, irrespective of the irradiation temperature, the nano-crystalline samples suffered more damage as compared to the bulk-like sample. A reduction in the irradiation damage i.e. improvement in the radiation tolerance, was observed for all the samples irradiated at 1000 K. The reduction in the damage, however, was remarkably higher for the two nano-crystalline samples compared to the bulk-like sample, and hence the difference in the damage between the bulk-like and nano-crystalline samples was also significantly lower at 1000 K than that at room temperature. The irradiation damage, against S$_e$, was thus found to be critically dependent on the interplay between the irradiation temperature and crystallite size. These results are explained with the help of detailed theoretical calculations/simulations based on the 'in-elastic thermal spike' model by taking into consideration the combined effect of crystallite size and environmental (irradiation) temperature on the electron-phonon coupling factor and lattice thermal conductivity (and hence on the resulting thermal spike). Our results are crucial from the fundamental perspective of comprehending the size and temperature dependent radiation damage against S$_e$ ; and also for a number of applications, in various radiation environments, where nano-materials are being envisioned for use.
To investigate the variation in the radiation stability of ceria with microstructure under the electronic excitation regime, ceria samples sintered under different conditions were irradiated with high energy 100 MeV Ag ions. The ceria nanopowders were synthesized and sintered at 800 °C (S800), 1000 °C (S1000) and 1300 °C (S1300), respectively. The samples with widely varying grain size, densities and microstructure were obtained. The pristine and irradiated samples were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). None of the samples amorphized up to the highest fluence of 1 × 10(14) ions per cm(2) employed in this study. XRD and Raman studies showed that the sample with lowest grain size suffered maximum damage while the sample with largest grain size was most stable and showed little change in crystallinity. Raman spectroscopy indicated the enhanced formation of Ce(3+) and related defects in the sample with larger grain size after irradiation. The most intriguing result was the absence of Ce(3+)-related defects in the sample with lowest grain size which actually showed maximum damage upon irradiation. The XPS studies on S800 and S1300 provided concrete evidence for the presence of Ce(3+) and oxygen ion vacancies in S1300. The grain boundaries and grain size dependent stability have been discussed.
Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) is the main inorganic component of hard tissues like bone and teeth. HAp incorporated with magnetic ions, play an important role in cell separation, magnetic resonance imaging (MRI), targeted drug delivery and in hyperthermia treatment of cancer. In this study, the effect of 60 MeV Si 5+ ion on the hydrothermally synthesized Fe 3+ doped hydroxyapatite (Fe-HAp, 33 nm) was investigated. At higher fluences, partial amorphization with an increase in the cluster size and surface roughness was observed. Depending on the ion fluence, pores ranging from 300 to 360 nm in size were produced. Irradiated Fe-HAp samples showed enhanced haemocompatibility and bioactivity. The drug (amoxycillin, AMX) loaded irradiated samples exhibited high antimicrobial activity.
Poly(vinylidene fluoride-co-hexafluoropropylene) (HFP) nanocomposites with layered silicate have been synthesized via the melt extrusion route. The intriguing nanostructure, crystalline structure, morphology, and thermal and mechanical properties of the nanocomposites have been studied and compared critically with pristine polymer. HFP forms intercalated or partially exfoliated nanostructure (or both) in the presence of nanoclay, depending on its concentration. The bombardment of high-energy swift, heavy ions (SHI) on HFP and its nanocomposites has been explored in a wide range of fluence. The nanoclay induces the piezoelectric beta-phase in bulk HFP, and the structure remains intact upon SHI irradiation. SHI irradiation degrades pure polymer, but the degradation is suppressed radically in nanocomposites. The heat of fusion of pristine HFP has drastically been reduced upon SHI irradiation, whereas there are relatively minute changes in nanocomposites. The coarsening on the surface and bulk of HFP and its nanocomposite films upon SHI irradiation has been measured quantitatively by using atomic force microscopy. The degradation has been considerably suppressed in nanocomposites through cross-linking of polymer chains, providing a suitable high-energy, radiation-resistant polymeric material. A mechanism for this behavior originating from the swelling test and gel fraction (chemical cross-linking) as a result of SHI irradiation has been illustrated.
Abstract MXenes, specifically Ti3C2Tx having peculiar structural and electronic characteristics display not only high surface area, excellent thermal and electrical conductivity, but also have the potential for functionalization. The primary focus of this research is to control the decay time of Au NP-decorated multilayer Ti3C2Tx MXene (Au-Ti3C2Tx) synthesized by a simple two-step selective etching technique. Incorporation of Au NPs in the multilayer Ti3C2Tx MXene leads to lattice expansion, reduction in the micro-strain, and improvement in the crystallinity, as confirmed by XRD analysis. Observation of a well-developed G band in the Au-Ti3C2Tx MXene across different Au concentrations by Raman spectroscopy investigations suggests the accumulation of graphitic carbon on the MXene surface which has greatly improved the charge transfer characteristic of the carbide layer. Furthermore, the Au-Ti3C2Tx MXene also exhibits promising optical properties for different concentrations of gold. The time-resolved photoluminescence spectroscopy studies displayed a reduction in the average decay time (τav) to ~ 30 % with increasing gold concentration from 100 μL to 150 μL in Au NPs solution which is explained on the basis of Au NPs induced surface plasmon resonance. Au NPs decoration is also assisted in the accumulation of carbon on the MXene surface which leads to improvement in the crystallinity and reduction micro-strain as well as decay time. Thus, engineering decay time through noble metal NPs decoration onto the MXene enables the fabrication of highly efficient photodetectors and imaging devices, particularly beneficial in applications where shorter decay times are preferred.
Important correlation between valence band spectra and hydrogenation properties in Pd alloy nanoparticles is established by studying the properties of size selected and monocrystalline Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles. The X-ray photoelectron spectroscopy and elastic recoil detection analysis show that size induced Pd4d centroid shift is related to enhanced hydrogenation with H/Pd ratio of 0.57 and 0.49 in Pd-Ag and Pd-Cu nanoparticles in comparison to reported bulk values of 0.2 and 0.1, respectively. Pd-alloy nanoparticles show lower hydrogen induced lattice distortion. The reduced distortion and higher hydrogen reactivity of Pd-alloy nanoparticles is important for numerous hydrogen related applications.
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