Developing robust functional materials with tunable nano-engineered heat flow directionality in micro-scale devices for operation in high demanding applications presents a major challenge for conventional nano-fabrication techniques. In this work, we explore the control of emergent anisotropic heat propagation in single-crystalline yttrium aluminium garnet (YAG) Y3Al5O12 nano-patterned by long amorphous cylindrical tracks induced by 167 MeV Xe ion irradiation. The resulting nano-composite layer consists of high aspect-ratio, nanoscale-thick and microscale-long amorphous tracks embedded within a YAG matrix. The formation of amorphous phase is finely tuned by varying the ion fluence, spanning from isolated tracks to the regime of their partial overlap. High-resolution scanning transmission electron microscopy (HR-STEM) reveals a uniform and directionally consistent amorphous structure across the irradiated depth. Thermal anisotropy of the resulting crystalline-amorphous nano-composite is confirmed by spatial domain thermoreflectance measurements and aligned nano-channel model based on phonon scattering from oriented tracks with the radial and axial thermal resistances. Heat is conducted primarily along the ion beam direction due to the elongated crystalline domains, while the radial transport is inhibited by increased phonon scattering on multiple crystalline-amorphous boundaries. The Klemens model considering ion track scattering terms is shown to be an effective tool to estimate the ion track cross-section area, which is confirmed by HR-STEM measurements and molecular dynamics simulations. Amorphous extended nano-patterning by swift heavy ion irradiation of robust crystalline insulators and semiconductors provides a viable path to control orientation-dependent heat flow.

Swift heavy ion irradiation induces complex, depth-dependent damage in nuclear ceramics, challenging their radiation tolerance. Using Brillouin spectroscopy and optical reflectometry, we resolve micrometer-scale elastic, photoelastic, and strain profiles in MgAl2O4 spinel irradiated with 710 MeV Bi ions at fluences of 6 x (1010-1012) ions/cm2. We discover a subsurface reversal of radiation damage characterized by a swelling-to-compression transition: while near-surface elastic (C11, C22, C44) and photoelastic (P12, P21) constants decrease with fluence, they recover at deeper regions following the tapering of ion tracks and reduction of electronic stopping power (Se). At the highest fluence, overlapping tapered tracks form a composite of acoustically mismatched nanocrystalline and nano-amorphous phases, evidenced by the emergence of confined GHz longitudinal acoustic modes. This study reveals a self-healing densification mechanism driven by tapering track morphology and electronic stopping power which provides a new strategy for engineering depth-resolved tolerance in ceramics to extreme radiation.

Magnesium fluoride has exceptional optical properties and is widely used in the production of optical components such as anti-reflective coatings, optical windows, lenses, prisms and planar waveguides. In particular cases, the production of optical components requires modification of the material's optical properties. Specifically, planar waveguides could be produced by refractive index modulation using ion implantation technique, as a consequence of damage/impurity introduction in the crystal structure during the ion implantation process. In this work, the damage and impurity depth profiles induced by 4 MeV C implantation in MgF2 single crystal were investigated. Ion implantation was performed in MgF2 (001) crystal orientation. The damage and impurity profiling were achieved by Elastic Backscattering Spectrometry/Channeling technique (EBS/C). EBS/C spectra were analyzed by in-house developed phenomenological Channeling SIMulation (CSIM) code. It was shown that CSIM obtained damage depth profiles poses gradual changing nature, suitable for refractive index modulation making ion implantation and corresponding EBS/C analysis complementary for production and control of magnesium fluoride planar waveguides.

The depth distributions of the spectral parameters of Raman and luminescence features of diamond implanted with Xe ions of an energy 167 MeV have been studied in as-irradiated state and after post-irradiation annealing. The Raman data show that the distribution of radiation defects in the as-irradiated layer follows the nuclear stopping power of the ions. It has been found that the two major mechanisms determining the distribution of intensity of the luminescence centers are the quenching due to crystal lattice damage and the instantaneous heating due to intense electronic stopping. It has been shown that the strong nuclear stopping at the end of the ion penetration produces a highly disordered buried layer. The atomic structure of this layer completely loses its crystallinity for ion fluences above 3 x 10(14) cm(-2). This atomic structure does not collapse into graphite during high temperature annealing and can be regarded as amorphous diamond. It has been shown that the postirradiation annealing produces secondary radiation defects far deeper than the depth of the ion penetration. This deep defect production is explained by the dislocations propagating from the disordered layer into the diamond bulk during heating.

Formation of tracks of swift heavy ions decelerating in the electronic stopping regime in CeO2 was studied, combining the Monte Carlo code TREKIS with molecular dynamics. We show that strong lattice disordering (melting) followed by structure recovery form finally a damaged ion track consisting of a discontinuous crystalline region in CeO2. Normal ion impacts result in appearance of spherical crystalline hillocks on CeO2 surface. The solid-vacuum interface strongly suppresses the recrystallization of the near-surface layers, forming conically shaped tracks with several tens of nanometers lengths. Grazing ion irradiation induces intensive material expulsion from the surface forming finally grooves surrounded by nanohillocks. The processes of surface nanostructures formation is similar to those observed previously in CaF2 which has the similar crystalline structure, however requires much longer recrystallization time. Recent experimental data confirm the simulation results.

The article presents results of the transmission electron microscopy examination of nanocrystalline TiO2 irradiated with swift Kr, Xe and Bi ions in a wide electron energy loss range. Threshold energy loss for a formation of amorphous tracks were estimated between 9.5 +/- 1.5 and 11.5 +/- 0.5 keV/nm. At Se lower than 5.2 +/- 0.9 keV/nm no tracks were detected. Comparative analysis of tracks in nanocrystalline and bulk TiO2 suggests that there is an insignificant influence of grain size on their structural stability during ion irradiation.

Studies of radiation effects in nuclear reactor materials using ion irradiation in accelerators, instead of effort and time-consuming neutron irradiation are limited, in addition to the high dose rate effect, by the strictly peak nature of ion damage and implantation. To overcome the limitation of fixed ion ranges, a new methodology for uniform bulk ion irradiation of material samples using a software-controlled tilting target was developed and tested. For the verification experiment, a heat-resistant austenitic steel sample was uniformly irradiated with 3 MeV He2+ ions to a dose of 0.1 dpa and a helium doping level of 1100 appm in the depth range from 1.8 to 4.5 mu m. The dislocation-loop structure and gas porosity obtained as a result of irradiation and post-irradiation annealing were studied using TEM in cross-section geometry. The homogeneity of helium doping of the sample was verified by determining the specific surface area of helium porosity as a function of depth based on measurements of gas bubble diameters and foil thickness.

Swift heavy ion (SHI) irradiation (Xe ions, 150 MeV, 5 x 109 to 5 x 1011 ions per cm2) is utilized to engineer the defect landscape in hydrothermally synthesized BiVO4 (BVO) thin films, aiming to understand its role in photoelectrochemical (PEC) performance toward the oxygen evolution reaction (OER). Our findings show that SHI irradiation, from individual to overlapping ion tracks, induces residual stress and amorphization in BVO, accompanied by the formation of bismuth-rich hillocks above oxygen-depleted ion tracks. While high fluence irradiation results in the irreversible reduction of PEC activity, the lower fluences (5 x 109 ions per cm2 and 1 x 1010 ions per cm2) induce defects that initially trap charge carriers, but over time lead to a 58.6% and 25.2% increase in the photocurrent density, respectively. Detailed post-PEC morphological analysis reveals opening of ion tracks and the formation of nanoscale holes, reaching up to 30 nm in diameter and up to 200 nm in depth. Our study establishes a link between defect creation and PEC performance in BVO thin films, paving the way for innovative approaches to its morpho-structural manipulation and nano-structuring while simultaneously contributing to the fundamental understanding of SHI-induced phenomena in BVO films.

High-energy (710 MeV) Bi ion track morphology in polycrystalline silicon nitride was investigated during post-irradiation annealing. Using both in-situ and ex-situ transmission electron microscopy, we monitored the recovery of crystallinity within initially amorphous ion track regions. In-situ annealing involved heating samples from room temperature to 1000 °C in 50 °C increments, each held for 10 s. We observed a steady decrease in both the size and number of tracks, with only a small number of residual crystalline defects remaining at 1000 °C. Ex-situ annealing experiments were conducted at 400 °C, 700 °C, and 1000 °C for durations of 10, 20, and 30 min. Complete restoration of the crystalline lattice occurred after 30 min at 700 °C and 20 min at 1000 °C. Due to inherent differences in geometry, heat flow, and stress conditions between thin lamella and bulk specimens, in-situ and ex-situ results cannot be compared. Molecular dynamics simulations further revealed that track shrinkage begins in cells within picoseconds, supporting the notion that recrystallization can start on very short timescales. Overall, these findings demonstrate that thermal recrystallization of damage induced by swift heavy ion irradiation in polycrystalline Si3N4 is possible. This study provides a foundation for future research aimed at better understanding radiation damage recovery in this material.

The influence of nanomechanical tensile behavior on electron transport is especially interesting for ultra-thin SiC nanowires (NWs) with different diameters. Our studies theoretically show that these NWs can hold stable electron transmission in some strain ranges and that stretching can enhance the electron transmission around the Fermi level (EF) at the strains over 0.5 without fracture for a single-atom SiC chain and at the strains not over 0.5 for thicker SiC NWs. For each size of SiC NW, the tensile strain has a tiny effect on the number of device density of states (DDOSs) peaks but can increase the values. Freshly broken SiC NWs also show certain values of DDOSs around EF. The maximum DDOS increases significantly with the diameter, but interestingly, the DDOS at EF shows little difference among the three sizes of devices in the late stage of the stretching. Essentially, high electron transmission is influenced by high DDOSs and delocalized electronic states. Analysis of electron localization functions (ELFs) indicates that appropriate tensile stress can promote continuous electronic distributions to contribute electron transport, while excessively large stretching deformation of SiC NWs would split electronic distributions and consequently hinder the movement of electrons. These results provide strong theoretical support for the use of ultra-thin SiC NWs in nano-sensors for functional and controllable electronic devices.

Zirconium dioxide shows great potential for use in the nuclear power industry. It exhibits high radiation stability (neutron and heavy ions) and can withstand harsh environments. The paper presents a study on the effects of 710 MeV Bi ion irradiation on polycrystalline partially yttria-stabilized zirconia using the combination of experimental techniques-X-ray diffraction, transmission electron microscopy and Raman spectroscopy. It was revealed that bismuth ion induced tracks retain their crystalline structure and their density tends to saturate at similar to 1 x 10(12) cm(-2). As a result of dense ionization stimulated structural modification a t -> t" phase transformation was observed. The radiation stability of t" phase against swift heavy ion impact was found to be higher compared to the t phase. No amorphization was detected up to Bi ion fluence of 2 x 10(13) cm(-2).

Ion implantation is frequently used method for the simulation of material damage caused by its exposure to harsh environments. The induced material damage and impurities accumulation will exhibit strong depth dependency in the case of its exposure to charged particles due to particle energy losses mechanisms. In presented study, we have performed an ion implantation of 4 MeV C3+ ions with three different fluences (1.5, 5 and 10 x 10(-15) cm(-2)) in the MgO [100] crystal in order to simulate structural damage induced by energetic particles. The damage depth profiles have been obtained by Elastic Backscattering Spectrometry in channeling orientation (EBS/C) using 1.86 MeV protons. EBS/C spectra were analyzed with the in house developed phenomenological Channeling SIMulation (CSIM) code. In addition to the damage depth profiles, with the new upgraded version of CSIM, concentration depth profile of implanted atoms (impurities) have also been determined. EBS/C spectra obtained profiles have been compared with the results of depth-resolved (micro) Photoluminescence spectroscopy (mu PL) of the implanted MgO crystal cross-section. EBS/C and mu PL obtained profiles for all investigated samples show very good consistency. This opens up the possibility for usage of EBS/C method in material analysis of lighter than bulk impurity concentration profiling.

Near-surface nanoscale thermal conductivity (k) variation of ion-irradiated single-crystalline ZnO was studied by time-domain thermoreflectance. ZnO was irradiated by 710 MeV Bi swift heavy ions (SHI) in the 1010-1013 ion/cm2 fluence range to investigate the progression of radiation damage both from single ion impacts and ion path overlapping regimes. Structural characterization using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy indicated the absence of amorphization. The degradation in k was attributed primarily due to phonon scattering on point defects. The results of measured k were used to validate several models including the semi-analytical Klemens-Callaway model, and a novel hybrid modeling approach based on the Monte-Carlo code TREKIS coupled with molecular dynamics simulations which captures the effects of single ion and ion path overlapping regimes, respectively. The findings promote a novel approach to developing radiation-controlled thermally functional materials.

57Fe transmission Mossbauer (TMS) spectroscopy and powder X-ray diffractometry (XRD), as well as scanning electron microscopy (SEM-EDX) measurements were used to study the effect of swift heavy ion irradiation on powdered hematite mixed with epoxy resin. TMS, XRD and EDX of the samples indicated no significant changes neither in the crystal structure nor in the composition of hematite irradiated with 148 MeV Xe ions with a fluence of 1 x 1013 cm-2 as compared to those of non-irradiated ones. However, about a quarter of the total iron content of the hematite detected by TMS was converted to w & uuml;stite and to magnetite superparamagnetic at room temperature upon irradiation with a fluence of 5 x 1013 cm-2. The presence of w & uuml;stite was evidenced by XRD in agreement with TMS measurements. Temperature dependence of the hematite TMS measurements indicated a significant change in the Morin transition after irradiation with a fluence of 5 x 1013 cm-2. The results are discussed in terms of the defects produced by irradiation and corresponding changes in the Morin transition and for the hematite to w & uuml;stite and magnetite transformation. (c) 2017 Elsevier Inc. All rights reserved.

The results are presented on changes in the parameters of pseudo-MOS transistors based on silicon-on-sapphire (SOS) mesastructures upon irradiation with swift heavy ions (SHIs) of Xe ^+26 (150 MeV) and Bi ^+51 (670 MeV) to a fluence of 2 × 10^11 cm ^-2 , indicating the accumulation of mechanical stresses and charges in the intermediate ferroelectric (Fe) layers of HfO _2 films (HO) with a thickness of 20 nm and Hf _0.5 Zr _0.5 O _2 (HZO) laminated with inserts of Al _2 O _3 monolayers (HA, HZA) or without them. SOS heterostructures are formed by direct bonding and hydrogen transfer of a silicon film (500 nm) with HA and HZA nanolayers pre-applied by plasma-stimulated atomic layer deposition onto sapphire. Electrophysical parameters are determined from the drain current—gate voltage characteristics ( I_ds – V_g) of pseudo-MOS transistors with tungsten drain/source electrodes (100 nm) deposited by magnetron sputtering on SOS mesastructures through a lithographic mask. Comparison of the characteristics with Raman scattering analysis showed the correspondence of the mechanical compressive stresses introduced by SHI irradiation in silicon with the ratios of the Xe and Bi track volumes in the HA ferroelectric and sapphire.

Ni60A/WC in-situ reinforced composite coatings are prepared on Inconel 718 alloy by laser cladding. The reinforcements/matrix micro-interface evolution, microhardness, and corrosion resistance are investigated. The phases in the coatings are mainly composed of γ-Ni, M23C6, M7C3 and NbC. The reinforcements/matrix micro-interfaces concerned in the coatings mainly include WC/matrix micro-interface and M23C6/matrix micro-interface. The WC/matrix micro-interface evolution is divided into five stages, namely, WC enters the molten pool, the micro-interface begins to grow, the reinforcements enriched at the tip, the reinforcements fall off and the formation of the stable micro-interface. The microhardness of the coatings increases with increasing WC content. On one hand, the increase in WC content promotes the generation of in-situ reinforcements, and the large lattice mismatch between dispersed reinforcement particles and matrix hinders dislocation motion. On the other hand, the two-dimensional mismatch degree of WC and γ-matrix calculated by Bramfitt's two-dimensional mismatch degree formula is 9.77 %, indicating that WC particles can serve as particles for γ heterogeneous nucleation. The increase of WC particles plays the role of fine grain strengthening, so the microhardness of the coating increases. The effect of WC on the corrosion resistance is also analyzed. The reinforcements are mainly distributed in the grain boundaries, and the HRTEM results indicate that a large degree of lattice mismatch exists in the micro-interface of reinforcements and γ-matrix. The large degree of mismatch shows that the interface between the two phases is relatively weak, and the weak interface is easy to become the channel for corrosive ion (Cl−) diffusion.

We report a detailed study about the correlation between the physicochemical properties of solvothermally synthesized pristine and 1 %, 2.5 %, and 5 % Cu, Mo, and W-doped bismuth vanadate (BiVO4, BVO) with its phase composition. The effect of the dopant and the duration of synthesis (8 h and 20 h) on the physicochemical properties of BVO allowed us to tune the ratio of monoclinic scheelite to tetragonal zircon phase in BVO powders. This approach helped us to establish the relationship between the presence of monoclinic scheelite or tetragonal zircon phase with structural, morphological and optical properties of BVO powders, obtained by different physicochemical methods (e.g. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence spectroscopy (PL)). The results indicated that, in addition to XRD, Raman, and DRS, several other methods could distinguish between the two phases. For example, SEM analysis revealed that monoclinic scheelite BVO exhibits either elongated assemblies of cube-like particles or prismatic particles with sizes similar to 500 nm. In contrast, tetragonal zircon BVO exclusively exhibited porous spherical particles with diameter similar to 2 mu m. DRS and Raman spectroscopy indicated that there is a possibility of distinguishing between the two phases if their shares are large enough. For instance, monoclinic BVO showed band gap values in the range of 2.35-2.52 eV, while tetragonal zircon BVO exhibited values in the range of 2.80-3.00 eV. XPS showed a correlation between phase composition and surface chemistry of BVO only for Cu-doped samples, revealing the presence of Cu+ in monoclinic BVO and the presence of both Cu+ and Cu2+ in tetragonal zircon BVO. PL showed that monoclinic scheelite BVO displayed decreased charge recombination compared to tetragonal zircon BVO. Deeper insight into the correlation between the physicochemical properties and phase composition of Cu, Mo, and W-doped bismuth vanadate (BiVO4, BVO) was based on water/pentanol medium (2:1 vol%) as a novel synthesis pathway. This may open new avenues for the broader methodological exploration of surface chemistry, particle size, and morphology of BVO particles through the use of diverse functionalization agents. Finally, the established links between phase composition and structural, morphological, and other physicochemical properties provide new and more predictable opportunities for further improvement of BVO properties for various applications.

Nickel-based superalloys are extensively utilized in the aerospace industry due to their exceptional corrosion resistance. Laser cladding as an advanced and effective technology has applied in the field of surface modification and additive manufacturing of nickel-based superalloys. However, crack is a challenging problem for nickel-based superalloys during laser cladding and crack issue has limited its specific application. This paper reviewed various types and mechanisms of cracks (solidification cracks, liquefaction cracks, ductility-dip cracks, etc.) in nickel-based superalloys during laser cladding. Some effective methods to suppress these cracks were also provided from two perspectives. On one hand, technological optimization can be considered from optimizing laser cladding process parameter and adopting heat treatment before laser cladding. On the other hand, metallurgical measure is also helpful and more attention can be paid on optimization of alloy composition and microstructure. Some suggestions for the further research direction on the cracking of nickel-based superalloys during laser claddings were also proposed so as to promote the development of laser cladding and widen its application.

Submicron-grade Y2.5Nd0.5Al5O12 oxide (YAG:Nd) powder with garnet structure was synthesised by the co-precipitation method. YAG:Nd ceramics with a relative density of similar to 99 % were obtained by Spark Plasma Sintering. The ceramics had a fine-grained microstructure and low YAlO3 impurity phase content. The radiation resistance of the ceramics was investigated with irradiation with accelerated Xe ions (E = 148 MeV) and Ar ions (E = 46 MeV), with the fluences ranging from 6 x 10(11) to 1 x 10(13) cm(-2). The phase composition, microstructure and microhardness of the irradiated ceramics were studied. X-ray diffraction (XRD) analysis in the symmetric mode and grazing incidence XRD were used to study the irradiated layer structure. A gradient-defect structure was shown to be formed in the YAG:Nd ceramics under irradiation: amorphous phase, deformed garnet phase and non-deformed garnet phase. The dependencies of the volume fraction of the amorphous phase and of the amorphisation structure on the fluence were analysed. The calculated value of the critical fluence was 1 x 10(13) cm(-2), corresponding to 0.044 displacements per atom (dpa). The microhardness Hv of the surface layer decreased with increasing ion fluence.

In this study, the effect of swift heavy ions (SHIs) irradiation in the recrystallization of polycrystalline SiC pre-implanted with selenium (Se) ions and migration of Se was investigated. The main objective of this study is to investigate the role of SHIs with the maximum electronic energy loss greater than 20 keV/nm on structural evolution of initially amorphized pre-implanted SiC and the migration of pre-implanted fission products (FPs). The pristine SiC samples were first implanted with 200 keV Se ions to a fluence of 1×1016 cm−2 at room temperature (RT) and at 350 °C. Some of the pre-implanted samples were then irradiated with bismuth (Bi) ions of 710 MeV to a fluence of 1×1013 cm−2 at RT. The characterization of both the implanted and implanted then irradiated SiC was conducted using techniques such as transmission electron microscopy (TEM), Raman spectroscopy, scanning electron microscopy (SEM), and Rutherford backscattering spectrometry (RBS). At RT, Se ions implantation caused the amorphization of SiC to a depth of about 187 nm beneath the surface. In contrast, when implanted at 350 °C, the SiC retained its crystalline structure with some defects (i.e., point defects, point defect clusters and some dislocation loops). The SHIs irradiation of the RT implanted SiC resulted in the reduction of the amorphous layer thickness from 187 nm to around 178 nm and led to the formation of nanocrystalline SiC in the amorphous layer. Irradiation of the SiC implanted at 350 °C induced some crystallization of defects. Notably, no evidence of Se ions migration was observed in both the irradiated RT-implanted and the hot-implanted SiC.