Ion charge influence on the molecular structure of polyethylene terephthalate films after irradiation with swift heavy ions

We report here experimental results investigating the influence of the initial swift heavy ion charge on the structure of polyethylene terephthalate (PET) film after irradiation, using a structurally sensitive X-ray diffraction method. Kr ions with an energy of 100 MeV and charges of 13+, 14+, and 15+ were each used at irradiation fluences of 5 × 1010, 7.5 × 1010, 1 × 1011, 2.5 × 1011 and 5 × 1011 ions/cm2 . At constant energy and irradiation fluence, the post-irradiation structural changes in PET film show a clear dependence on the initial ion charge. As either the fluence or ion charge increase, the latent tracks begin to overlap, leading to cross-linking of PET chain molecules to form rotational isomers (rotamers). We use the fluence corresponding to the onset of overlapping to estimate the size of latent tracks for different ion charges. At the highest fluences, the latent tracks become entirely overlapped, and the interchain cross-linking extends throughout the whole film. Since this cross-linking is due to the dipole–dipole interaction of subunits of repeat units of PET chain molecules, it is reversible, in contrast to the well-known chemical cross-linking of polymer chain molecules under irradiation. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Induced spirals in polyethylene terephthalate films irradiated with ar ions with an energy of 70 MeV

This paper presents the results of a study of the ordering in polyethylene terephthalate (PET) film induced by Ar8+ ions with an irradiation fluence of 2 × 1012 ions/cm2, and of the temporal stability of the induced ordering in the irradiated sample, over a three month period. Immediately after irradiation, sharp new reflections not seen at lower fluences were observed in X-ray diffraction patterns, with angular positions of 2 θ = 9–10° and 19° and variable azimuthal intensities. X-ray reflections, previously observed at lower fluences, were also seen: at 2 θ = 26° and 23°, associated with PET crystallites, and at 2 θ = 5–12°, associated with induced ordering in the amorphous zone. Aging of the irradiated sample led to significant growth of the ordering region in the amorphous zone for angles up to 2 θ < 15°, as well as to dissipation and blurring of the new diffraction reflections at 2 θ = 9–10° and 2 θ = 19° and the formation of a new diffraction ring reflection in the range 2 θ = 11–16°. The azimuthal distribution of diffraction reflection intensities immediately after irradiation displays a clear oblique cross located predominantly along lines at angles of π/4 with respect to the direction of the texture of the PET film, indicating the formation of spiral structures based on the molecular strands of PET. Our experimental results lead us to conclude that the formation of coherent scattering areas in the amorphous region at 2 θ < 15° is due to intra-chain rotations of benzene-carboxyl subunits of repeat units of the PET chain molecules interacting with the residual electric field of a single latent track; whereas the formation of spiral structures is due to the inter-chain interaction of these preordered asymmetric subunits under the influence of the electric fields from overlapping latent tracks. © 2020 by the authors

Assessment of the irradiation exposure of pet film with swift heavy ions using the interference-free transmission UV-VIS transmission spectra

This paper presents the results of a study of polyethylene terephthalate (PET) films irradiated with Ar and Kr ions at both normal orientation and an angle of 40° to the normal. Normal irradiation was performed using Ar8+ and Kr15+ ions with an energy of 1.75 MeV/au and fluences in the range (2-500) x1010 cm-2 for Ar8+ ions and (1.6-6.5) x1010 cm-2 for Kr15+ ions. Kr ions with an energy of 1.2 MeV/au and charges of 13+, 14+, and 15+ were used for angled irradiation. For each Kr ion charge value, three fluence values were used: 5x1010, 1x1011, and 2.5x1011 cm-2. It is well known that irradiation of PET films by swift heavy ions results in a red shift of the UV-vis transmission spectra absorption edge. The experimental transmission spectra exhibit well-defined interference fringes, which obscure the underlying transmission response. Using an existing technique to obtain inter-ference-free transmission curves Tα(λ) for both pristine and irradiated PET film samples, we found that S, the total radiation-induced absorption of light by the PET film, is proportional to the loga-rithm of the fluence F. In addition to this dependence on the irradiating fluence, we also found that the charge of the irradiating ion has a significant influence on the position of the absorption edge in the UV-vis spectra. This provides experimentally independent evidence to confirm our previous results showing that ion charge has an effect on the post-irradiation state of PET films. We present a physical interpretation of the observed absorption edge red shift in irradiated PET films as being due to the growth of extended conjugated systems via the formation of intermolecular helical structures. Our investigations into the stability of irradiation-induced effects in PET films show that comparison of UV-vis transmission spectra before and after annealing can provide information about the structure of deep traps in PET. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Urbach Rule in the Red-Shifted Absorption Edge of PET Films Irradiated with Swift Heavy Ions

This paper presents a new analysis of the experimental transmission spectra of polyethylene terephthalate (PET) films before and after irradiation with swift heavy ions (SHI) films, as reported previously by the authors. It is shown that the absorption edge red shift for irradiated films contains two regions of exponential form, one of which is located in the UV region and the other at lower energy, mainly in the visible part of the spectrum. The behaviour of the transmission curves under different irradiating fluences demonstrates that these two regions reflect respectively the electron-enriched core of the latent track and its electron-depleted peripheral halo. The focal point method yields a bandgap energy of 4.1 eV for the electron-enriched core of the latent track, which is similar to n-doped semiconductors, and a bandgap of about 1.3–1.5 eV for the electron-depleted halo, similar to p-doped semiconductors. The boundary between the latent track cores and halos corresponds to a conventional semiconductor p-n junction. The values of the characteristic Urbach energy determined from experimental data correspond to the nonradiative transition energy between the excited singlet and triplet levels of benzene-carboxyl complexes in repeat units of the PET chain molecule. A parallel is drawn between the SHI-induced redistribution of electrons held in structural traps in the PET film and chemical redox reactions, which involve the redistribution of electrons in chemical bonds. It is suggested that alkali etching triggers the release of excess electrons in the latent track cores, which act as a catalyst for the fragmentation of PET chain molecules along the latent tracks of the SHI irradiation. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Сформированные наночастицами сплавы V–Cd: получение, фазовый состав и структура

The results of the study of targeted sputtering and deposition of ultrafine vanadium and cadmium particles on substrates that are not heated and shifted with respect to the substrate plasma currents are revealed. As a result of the conducted studies, coatings were obtained in the range with a concentration of cadmium from 9.6 to 88.6 at.%. The critical size of vanadium particles capable of forming alloys with cadmium is 0.6 nm. The concentration limit for the presence of solid solutions of cadmium in vanadium is the cadmium content of ~37 at.%, at a higher cadmium content the film coating is represented by a mixture of cadmium phases and a solid solution of cadmium in vanadium. The dependence of the lattice parameter of α-vanadium on the content of cadmium in it corresponds to the expression: а [nm] = 8·10–4СCd + 0.3707, where СCd is the concentration of cadmium, at.%. On the surface of the sample in the region of solid solutions (31.6 at.% Cd), the presence of threadlike crystals of cadmium was found, the reason for the appearance of which is the lattice pressure of the matrix metal. Annealing of films rich in cadmium (69.5 at.%) in vacuum is accompanied by cracking of the coating and the formation of pores. The latter can be used as a method for obtaining porous vanadium.Приведены результаты исследований распыления и осаждения ультрадисперсных частиц ванадия и кадмия на необогреваемые и перемещаемые относительно потоков плазмы подложки. Были получены покрытия в интервале концентраций кадмия от 9,6 до 88,6 ат.%. Критическим размером частиц ванадия, способных к образованию сплавов с кадмием, определена величина 0,6 нм. Концентрационной границей существования твердых растворов кадмия в ванадии является содержание кадмия ~37 ат.%, при большей его доли пленочное покрытие представлено смесью фаз кадмия и твердого раствора кадмия в ванадии. Зависимость параметра решетки α-ванадия от содержания кадмия в нем соответствует следующему выражению: а [нм] = 8·10–4СCd + + 0,3707, где СCd – концентрация кадмия, ат.%. На поверхности образца в области твердых растворов (31,6 ат.% Cd) обнаружено наличие нитевидных кристаллов кадмия, причиной появления которых является решеточное давление матричного металла. Отжиг богатых по содержанию кадмия пленок (69,5 ат.%) в вакууме сопровождается растрескиванием покрытия и образованием пор. Последнее может быть использовано как метод получения пористого ванадия

Some Insights into Cluster Structure of 9Be from 3He + 9Be Reaction

The study of inelastic scattering and multi-nucleon transfer reactions was performed by bombarding a 9Be target with a 3He beam at the incident energy of 30 MeV. Angular distributions for 9Be(3He, 3He) 9Be, 9Be (3He, 3He) 8Be, 9Be (3He, 7Be) 5He, 9Be (3He, 6Li) 6Li and 9Be (3He, 7Li) 5Li reaction channels were measured. Experimental angular distributions for the corresponding ground states (g.s.) were analyzed within the framework of the optical model, the coupled-channel approach and the distorted-wave Born approximation. Cross sections for channels leading to unbound 5Heg.s., 5Lig.s. and 8Be systems were obtained from singles measurements where the relationship between the energy and the scattering angle of the observed stable ejectile was constrained by two-body kinematics. Information on the cluster structure of 9Be was obtained from the transfer channels. It was concluded that cluster transfer was an important mechanism in the investigated nuclear reaction channels. In the present work an attempt was made to estimate the relative strengths of the interesting (n + 8Be) and (α + 5He) cluster configurations in 9Be. The contributions of different exit channels have been determined confirming that the (α + 5He) configuration plays an important role. The configuration of 8Be consisting of two bound helium clusters (5He + 6He) is significantly suppressed, whereas the two-body configurations (n + 8Be) and (α + 5He) including unbound 8Be and 5He are found more probable