Surface chemistry and structural properties of proton-beam irradiated graphene oxide paper

Graphene oxide (GO) is a promising material for the futuregraphene-based electronics where the surface chemistry and structural properties of GO may play an important role. One of the unique methods with great potentialfor controllable modification of materials’ properties is the ion beam irradiation. In the present study, GO paper was irradiated with 15 keV proton- beam to a fluences from 5×10 16 to 2×1017 ionscm-2 , while Fourier-transform infrared spectroscopy (ATR-FTIR), X-ray photoelectronspectroscopy (XPS) and Raman spectroscopy (RS)were used for the examination of surface chemistry and structural properties of the irradiated material. It was shown that proton beam irradiation leads to a partial reduction of GOwith the preferential removal of the alkoxy and epoxy groups. With the increasing fluence, the oxygen content from the XPS method and the intensity ratioof D and G Raman bandsboth showed decreasing trends. When oxygen content was compared to relative areas of specific functional groups and parameters of Raman peaks an interesting correlation was found that suggest optimal fluences for tuning the surface chemistry and structural properties of GO. The observed effects on surface chemistry and structural propertiescan be ascribed to physical and chemical effectsof ion beam irradiation. The interaction of functional groups with H-atom was investigated using DFT andsemi-empirical (SE) approach. SE calculations revealed that the reduction of the epoxy group appears at H-atom energies below 1.5 eV. This work identifies ion beam irradiation as a preferable technique for selective removal of surface oxygen groups and structural modification of GO where the applied fluence can be used for tuning the degree of change.IX Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 20-21, 2021; Belgrad

Modification of surface oxygen groups of graphene oxide by ion beam irradiation for supercapacitor applications

Surface oxygen groups may have a significant impact on the electrochemical charge storage properties of graphene oxide (GO). The presence of these groups on GO should be properly balanced so that electronic conductivity is optimized, while only the groups that are beneficial to capacitance are preserved. Ion beam irradiation can be identified as a technique where a controllable change of surface chemistry and structure of GO is possible through varying the energy and the fluence of an ion beam. In the present study, the influence of proton-beam irradiation on the surface chemistry and structural properties of GO paper was investigated. GO paper was irradiated with 15 keV proton-beam to fluences from 5×1016 to 2×1017 ions cm-2, while Fourier-transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy (RS) were used for the analysis of the surface chemistry and structural properties. Results indicate increasing reduction of surface oxygen groups and the preferential removal of the alkoxy and epoxy groups as fluence increased. Desorption of these basal plane groups was outlined in our previous work as important for charge storage capacity, probably due to conductivity increase [1]. When oxygen content was compared to: 1) relative areas of specific functional groups from FTIR and XPS and 2) parameters of Raman peaks, an interesting correlation was found that suggest optimal fluences for tuning the surface chemistry and structural properties of GO. Modification of surface chemistry originates from the physical and chemical effects of ion beam irradiation which were also investigated theoretically. The interaction of functional groups with H-atom was investigated using DFT and semi-empirical (SE) approach. SE calculations revealed that the chemical reduction of the epoxy group appears at H-atom energies below 1.5 eV. Results indicate that ion-beam irradiation can be used for controllable modification of surface chemistry of GO where the applied fluence can be used for tuning the degree of change, which may have implications to electrochemical charge storage properties.4th International Meeting on Materials Science for Energy Related Applications, September 22-23, 2021, Belgrade, Serbi

Simultaneous characterization of cross- and in-plane thermal transport in insulator patterned by directionally aligned nano-channels

Anisotropic thermal transport behavior was investigated in a single crystal sapphire patterned by vertically aligned few-nanometer diameter and several micrometer long cylindrical ion tracks. These ion tracks were introduced by exposing the sapphire to energetic ions of xenon accelerated to 167 MeV with fluences ranging from 1012 to 1014 ions/cm2. It was found that, in the low ion-track density regime, cross-plane thermal conductivity is larger, whereas in the high track density regime, the trend reverses and in-plane conductivity becomes larger. The crossover between these regimes is attributed to the interplay between phonon scattering with ion track boundaries and phonon confinement effects. In the low track density regime, the material is described by bulk phonon dispersion and anisotropy in thermal transport is attributed to the aligned nature of tracks that effectively reduce the mean free path of phonons traveling in the in-plane direction more than in the cross-plane direction. In the high-density regime, larger conductivity reduction in the cross-plane direction is consistent with previous observations, where the anisotropic reduction in thermal conductivity is owed to the anisotropic reduction of acoustic velocity caused by phonon confinement. Our results are further supported by an analytical model describing phonon mediated thermal transport

The effect of He and swift heavy ions on nanocrystalline zirconium nitride

Recent studies have shown that swift heavy ion irradiation may significantly modulate hydrogen and helium behaviour in some materials. This phenomenon is of considerable practical interest for ceramics in general and also for candidate materials for use as inert matrix fuel hosts. These materials will accumulate helium via (n, alpha) reactions and will also be subjected to irradiation by fission fragments. Cross-sectional transmission electron microscopy and scanning electron microscopy was used to study nanocrystalline ZrN irradiated with 30 keV He to fluences between 10(16) and 5 x 10(16) cm(-2), 167 MeV Xe to fluences between 5 x 10(13) and 10(14) cm(-2) and also 695 MeV Bi to a fluence of 1.5 x 10(13) cm(-2). He/Bi and He/Xe irradiated samples were annealed at temperatures between 600 and 1000 degrees C and were analysed using SEM, XTEM and selected area diffraction. The results indicated that post irradiation heat treatment induces exfoliation at a depth that corresponds to the end-of-range of 30 keV He ions. SEM and XTEM analysis of He/Xe irradiated samples revealed that electronic excitation effects, due to Xe ions, suppress helium blister formation and consequently the exfoliation processes. He/Bi samples however do not show the same effects. This suggests that nanocrystalline ZrN is prone to the formation of He blisters which may ultimately lead material failure. These effects may however be mitigated by electronic excitation effects from certain SHIs. (C) 2014 Elsevier B.V. All rights reserved

Effect of swift heavy ion irradiation in the migration behavior of Xe implanted into TiN

Sintered TiN were implanted with Xe ions of 360 keV to a fluence of 1.1 × 10 16 cm −2 at room temperature (RT) and others were co-irradiated with Xe ions of 167 MeV to a fluence of 3.4 × 10 14 cm −2 and Xe ions of 360 keV to a fluence of 1.1 × 10 16 cm −2 also at RT, successively. Both samples were isochronally annealed at temperatures ranging from 1100 to 1500 °C. Both irradiations caused no amorphization of the sintered TiN, however more defects were retained in the samples implanted with only Xe (360 keV) ions. Annealing of defects retained after irradiations were found to be faster in the co-irradiated samples. The migration behavior of implanted Xe was explained by trapping and de-trapping by defects at temperatures below 1200 °C while at temperatures above 1200 °C, it was dominated by grain boundary diffusion, in the un-irradiated samples. In the co-irradiated samples, Xe migrated via fast grain boundaries. © 2019 Elsevier Lt

Thermal stability of nanocrystalline (Ti,Zr)(0.54)Al0.46N films implanted by He+ ions

The influence of irradiation with He+ ions on the thermal stability of TiZrN and (Ti,Zr)(0.54)Al0.46N nanocrystalline films was studied. The TiZrN and (Ti,Zr)(0.54)Al0.46N films were prepared by reactive magnetron sputtering. XRD research showed that the TiZrN and (Ti,Zr)(0.54)Al0.6N films were single-phase systems (based on cubic c-(Ti,Zr)N and cubic c-(Ti,Zr,AI)N solid solutions) with nanocrystalline (grain size 30 and 21 nm, respectively) structure. The irradiation with He ions and thermal annealing up to 800 degrees C do not affect the structure and phase composition of the (Ti,Zr)(0.54)Al0.46N film. The prior irradiation of the (Ti,Zr)(0.54)Al0.46N film with He+ ions activates spinodal decomposition of the c-(Ti,Zr,Al)N solid solution after thermal annealing at 1000 degrees C due to redistribution of the components of the solid solution inside the grains. (C) 2014 Elsevier B.V. All rights reserved

Characterization of 167 MeV Xe ion irradiated n-type 4H-SiC

Please read abstract in the article.The National Research Foundation of South Africa (NRF) via iThemba LABS Materials Research Department (MRD).http://www.elsevier.com/locate/apsusc2020-11-01hj2019Physic

A comparison of Ar ion implantation and swift heavy Xe ion irradiation effects on immiscible AlN/TiN multilayered nanostructures

We have compared the effects of 200 keV Ar-40(1+) ion implantation and 166 MeV Xe-132(27+) ion irradiation on immiscible (AlN/TiN) x 5 multilayers grown on Si(1 0 0) wafers. The layers were deposited by reactive sputtering, individual layer thickness was similar to 22 nm (AlN) and similar to 32 nm (TiN), the stoichiometry Al:N similar to 45:55 and Ti:N similar to 50:50 at%. Argon was implanted to 4 x 10(16) ions cm(-2), and xenon to 5 x 10(14) ions cm(-2). The projected Ar range is around mid depth of the multilayered structure, while swift Xe ions are buried deep into the Si substrate. Upon irradiation the structures remain essentially stable and unmixed; although in both cases we observed detectable effects. The use of wide range of irradiation parameters (S-e/S-n = 1.2-1.4, dpa = 42-63 for Ar; and S-e/S-n = 249-258, dpa = 0.03-0.05 for Xe) enabled to distinguish between the contribution of nuclear and electronic stopping. In case of Ar implantation both atomic collisions and electronic excitations contribute to the induced structural modifications, and in case of Xe only electronic excitations. It was deduced that electronic excitations generate local heating which influences lateral grain growth within individual layers, but no elemental redistribution. On the other hand, atomic collisions facilitate a low level of Ti migration into the under-stoichiometric AlN layers, in the vicinity of the implanted Ar ion range. Energy transfer and temperature distribution were evaluated and compared to the effects produced in the structures. The presented results can be interesting towards developing radiation tolerant materials. (C) 2012 Elsevier B.V. All rights reserved