Narrow Results

Measurements of optical transmission in the visible spectral range of N⁺ irradiated thin films of multiwall carbon nanotubes (MWCNTs) at various doses prepared by a vacuum filtration method are reported. An increase in optical transmission was observed corresponding to increase in N⁺ ion doses. Changes in Raman spectra at different ions doses ranging from 5 × 10¹⁵ ions/cm² to 1 × 10¹⁷ ions/cm² indicate that the structure of graphene evolves from a highly ordered layer to a disordered domains. These structural changes result in a dramatic increase in the optical transmission. Additionally, the increase of optical transmission of irradiated MWCNTs thin film as a function of electrical conductivity at various doses is also discussed. The optical transmission increases in irradiated MWCNT thin films is found to be a function of defects density in MWCNTs.

Radiation damage in structural materials is of major concern and a limiting factor for a wide range of engineering and scientific applications, including nuclear power production, medical applications, or components for scientific radiation sources. The usefulness of these applications is largely limited by the damage a material can sustain in the extreme environments of radiation, temperature, stress, and fatigue, over long periods of time. Although a wide range of materials has been extensively studied in nuclear reactors and neutron spallation sources since the beginning of the nuclear age, ion beam irradiations using particle accelerators are a more cost-effective alternative to study radiation damage in materials in a rather short period of time, allowing researchers to gain fundamental insights into the damage processes and to estimate the property changes due to irradiation. However, the comparison of results gained from ion beam irradiation, large-scale neutron irradiation, and a variety of experimental setups is not straightforward, and several effects have to be taken into account. It is the intention of this article to introduce the reader to the basic phenomena taking place and to point out the differences between classic reactor irradiations and ion irradiations. It will also provide an assessment of how accelerator-based ion beam irradiation is used today to gain insight into the damage in structural materials for large-scale engineering applications.

$(1-y)$(BiFe${}_{1-x}$GdxO₃)–y(PbZrO₃) composites $(y=0.5)$, having four different Gd concentrations ($x=0.05$, 0.1, 0.15, and 0.2), were synthesized and their structural, dielectric, and ferroelectric properties have been studied using different characterization techniques. In addition, to investigate the effect of ion implantation on the microstructure and dielectric properties, these composites were exposed to 2MeV He${}^{+}$-ions. Modifications of the structure, surface morphology and electrical properties of the samples before and after ion exposure were demonstrated using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) technique, and LCR meter. The compositional analysis was carried out using energy dispersive X-ray spectrometry (EDS). XRD results demonstrated a decrease in the intensity profile of the dominant peak by a factor of 6 showing a degradation of the crystallinity. Willliamson–Hall (WH) plots reveal reduction in the grain size after irradiation along with an increase in strain and dislocation density. A decrease in the dielectric constant and loss has been recorded after ion beam exposure with reduction in ac conductivity value. The contribution of grain and grain boundary effect in conduction mechanism has been addressed using Nyquist plots. All the samples demonstrate a lossy ferroelectric loop which shows a clear modification upon irradiation. The role of structural defects modifying the physical properties of the composite materials is discussed in this work.

In this paper, we present the study of the shape change on the polar surface and in the bulk of the walls of lamellar domains as a result of local switching by focused ion beam. Periodical lamellar domain structures (PDS) are created alternatively by two methods: (i) electric-field poling using photolithographically defined electrodes and (ii) ion beam poling. The dot irradiation of Z${}^{+}$ areas near the walls of lamellar domains leads to the formation of faceted or rounded hexagonal domains. For e-field PDS additional formation of nanodomain ensembles was observed. We have revealed two types of domain wall shape changes induced by irradiation: (1) merging of the hexagonal domain with the domain wall for Z${}^{+}$ areas; (2) formation of rounded distortion of the domain wall for Z⁻ areas. For Z${}^{+}$ areas irradiation, the domain wall distortion was described by a simple model of independent growth of isolated domain with its subsequent merging with a static domain wall. For Z⁻ surface irradiation, the domain wall shift increases linearly with the distance between the irradiation dot and the wall. It was revealed that the merging between the growing hexagonal pyramid domain and lamellar domain can be obtained in the bulk even for absence of merging at the surface. All obtained results have been explained within a kinetic approach to the domain wall motion by step generation. The switching field consists of inputs produced by: (i) the charges injected during dot irradiation into the photoresist layer and crystal bulk, (ii) the charges injected during the creation of i-beam PDS, (iii) the depolarization fields. The transition of the shapes of isolated domains and wall distortions from faceted to rounded ones with field increase was attributed to the transition from determined step generation to stochastic one.

Radiation damage in structural materials is of major concern and a limiting factor for a wide range of engineering and scientific applications, including nuclear power production, medical applications, or components for scientific radiation sources. The usefulness of these applications is largely limited by the damage a material can sustain in the extreme environments of radiation, temperature, stress, and fatigue, over long periods of time. Although a wide range of materials has been extensively studied in nuclear reactors and neutron spallation sources since the beginning of the nuclear age, ion beam irradiations using particle accelerators are a more cost-effective alternative to study radiation damage in materials in a rather short period of time, allowing researchers to gain fundamental insights into the damage processes and to estimate the property changes due to irradiation. However, the comparison of results gained from ion beam irradiation, large-scale neutron irradiation, and a variety of experimental setups is not straightforward, and several effects have to be taken into account. It is the intention of this article to introduce the reader to the basic phenomena taking place and to point out the differences between classic reactor irradiations and ion irradiations. It will also provide an assessment of how accelerator-based ion beam irradiation is used today to gain insight into the damage in structural materials for large-scale engineering applications.