Radiation Defects Research Articles

ASO Author Reflections: Early Postoperative Mobilization as a New Standard Approach in the Reconstruction of Irradiated Perineal Defects with Internal Pudendal Artery Perforator Flap

ASO Author Reflections: Early Postoperative Mobilization as a New Standard Approach in the Reconstruction of Irradiated Perineal Defects with Internal Pudendal Artery Perforator Flap

Effect of Early Postoperative Mobilization on Functional Recovery, Hospital Length of Stay, and Postoperative Complications After Immediate Internal Pudendal Artery Perforator Flap Reconstruction for Irradiated Abdominoperineal Resection Defects: A Prospective, Randomized Controlled Trial

Effect of Early Postoperative Mobilization on Functional Recovery, Hospital Length of Stay, and Postoperative Complications After Immediate Internal Pudendal Artery Perforator Flap Reconstruction for Irradiated Abdominoperineal Resection Defects: A Prospective, Randomized Controlled Trial

Effects of Neoadjuvant Radiation and Recipient Vessel Characteristics on Microvascular Complication Rates in Reconstruction of Lower Extremity Soft-Tissue Sarcoma Defects.

The treatment approach for soft-tissue sarcomas (STS) of the lower extremity has shifted toward the use of neoadjuvant radiation combined with limb-sparing surgery (LSS). The resulting defects often require reconstruction with free tissue transfer for adequate outcomes. Data has demonstrated a potential increased risk of microvascular complications for free flaps performed using irradiated recipient vessels. Similarly, certain anatomic areas of the lower extremity have a high proportion of unnamed perforators that are available as recipient vessels, increasing the technical difficulty. We aimed to determine if the characteristics of recipient vessels that were used for reconstruction of STS defects influenced rates of microvascular complications in our patients. A retrospective chart review of all patients who underwent reconstruction of lower extremity STS defects with free tissue transfer from 2009-2020 was conducted. Data regarding recipient vessel type (axial vessel vs. unnamed perforator), radiation status of the recipient vessels (irradiated vs. non-irradiated), and microvascular complications was compared across groups. A total of 204 free flaps were included. The overall microvascular complication rate was 13.7% (28 cases). Most microvascular complications were detected postoperatively (82.1%) rather than intraoperatively, with the majority involving venous congestion/thrombosis (20 cases, 71.4%). While there was a trend toward increased microvascular complications with the use of irradiated recipient vessels (27 cases, 96.4%), this did not reach statistical significance (OR = 1.98, p = 0.52). The use of perforating branches as recipient vessels did not confer increased risk of microvascular complications (OR = 0.87, p = 0.75). Reconstruction of irradiated lower extremity STS defects represents a particularly challenging issue. This analysis demonstrates that free tissue transfer can be safely performed using irradiated vessels without significant increased risk of microvascular complications. Furthermore, unnamed perforating branches can also be successfully used for reconstruction in anatomically challenging areas of the lower extremity.

Effect of impurity and radiation defects on the scattering of normal and fluctuation carriers in YBa2Cu3O7–δ and Y1–zPrzBa2Cu3O7–δ single crystals

Effect of impurity and radiation defects on the scattering of normal and fluctuation carriers in YBa2Cu3O7–δ and Y1–<i>z</i>Pr<i>z</i>Ba2Cu3O7–δ single crystals

Effect of thermal annealing on the luminescent and structural properties of the SiOxCy thin films by organic catalytic chemical vapor deposition

Photoluminescent silicon oxycarbide (SiOxCy) thin films were deposited on n-type (100) silicon substrates using the organic catalytic chemical vapor deposition (O-Cat-CVD) technique employing tetra-ethyl orthosilicate (TEOS) as an organic-based precursor. These films were annealed at a temperature of 500, 800 and 1000°C for 30 minutes in a nitrogen (N2) environment. The as-deposited and annealed SiOxCy films were analyzed using optical and structural characterizations, such as photoluminescence (PL), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Secondary ion mass spectrometry (SIMS) and scanning electron microscopy (SEM). The PL spectrum of the as-deposited film showed emission in the blue-green region, while the annealed SiOxCy films showed strong emission from blue to near-infrared. The PL in all the films was attributed to different structural defects related to oxygen and carbon that act as radiative centers in the SiOxCy network. The annealed films showed an increase in the emission intensity, where the annealed film at 800°C displayed the highest emission intensity. This is related to an increase in the amount of radiative defects in the films due to structural and compositional changes after the thermal annealing (TA). XPS and SIMS measurements showed an oxygen incorporation with the TA, increasing from 54.59 at. % to 63.5 at. % for the as-deposited and annealed at 1000°C films, respectively. FTIR spectra showed an increase in the Si-O-C and Si-O-Si bonds and the hydrogen and other radicals desorption. These results support the creation of radiative centers due to structural changes in the films after the thermal annealing.

Microstructure evolution of CdZnTe crystals irradiated by heavy ions

Consideration of irradiation effects is important for in-orbit operation and radiation protection in aerospace applications. The configuration of irradiation defects and their impact on deteriorating the carrier transport properties of CZT crystals need to be clarified. In this study, the microdefect evolution mechanism of CdZnTe (CZT) crystals under 10 MeV Chlorine (Cl) ion irradiation at flux of 1×1010∼1×1012 n·cm-2 are investigated. The stacking faults first appear in the CZT crystal at 4.5×10-4 displacement per atom (dpa), which are categorized into slip-type, gap-type and vacancy-type. In order to hinder the further expansion of stacking fault, S-shaped stacking fault dipole appears. When the dpa reaches 4.5×10-2, the local phase transition occurs in the damage zone to form CuPt-A ordered phase with ZnTe/CdTe periodic arrangement because the fluctuation in local composition and strain caused by cascade collisions. The deterioration of electric field distribution and charge collection caused by irradiation damage layer leads to the decrease of γ-ray detection ability. The energy resolution (ER) of the CZT detector for γ-ray can be maintained at 30.6% when the ion flux accumulates to 1×1012 n·cm-2, revealing high irradiation hardness. Consequently, these findings provide a theoretical basis for the radiation damage recovery of CZT detectors, further demonstrating that CZT crystals are the most competitive new generation of room-temperature nuclear radiation detection materials, and can provide radiation protection strategies for similar compound semiconductor materials.

A study on initial formation stage of proton irradiation defects in reactor pressure vessel steel

A study on initial formation stage of proton irradiation defects in reactor pressure vessel steel

Multiscale-informed irradiation growth model of Zr-Sn-Nb alloys

A systematic multiscale-informed model is developed to predict the irradiation growth behavior of Zr-Sn-Nb alloys, which considers the anisotropy and temperature dependence of both plasticity and irradiation, as well as the alloying effect of Zr alloys. This model consists of a cluster dynamics submodel to consider the kinetics of irradiation defect, an alloying effect submodel informed by atomic simulations and experiments, a microstructure transition submodel derived from discrete dislocation dynamics, and a continuous irradiation growth submodel based on crystal plasticity. It effectively captures the irradiation-induced coevolution of multiple microstructures, including point defects, mobile clusters, dislocation lines and irradiation loops on the prismatic and basal plane, as well as Nb-induced precipitates. It is suitable for high-dose irradiation conditions as it reasonably considers the transition from high-density irradiation loops to tangled dislocation network. The predicted irradiation growth strain, as well as the density and size of irradiation loops, are in good agreement with almost all the available experiments for pure Zr, Zr-Sn, Zr- Nb, and Zr-Sn-Nb alloys at different irradiation doses in the temperature range of 473 - 673 K. This work is hoped to provide a powerful tool for developing irradiation resistance cladding materials.

On Prognosis of Manufacturing of P-N-Heterojunctions in the Framework of a Multilevel Inverter with Reduced Number of Switches to Increase Their Integration Rate. On Influence Mismatch-Induced Stress

In this paper we introduce an approach to increase density of p-n-heterojunctions in the framework of a multilevel inverter with reduced number of switches. Framework the approach we consider manufacturing the inverter in heterostructure with specific configuration. Several required areas of the heterostructure should be doped by diffusion or ion implantation. After that dopant and radiation defects should by annealed in the framework od an optimized scheme. We also consider an approach to decrease value of mismatch-induced stress in the considered heterostructure. We introduce an analytical approach to analyze mass and heat transport in heterostructures during manufacturing of integrated circuits with account mismatch-induced stress.

Interface properties study of black silicon solar cells with front surface a-Si:H/c-Si heterojunction

Abstract The exceptionally low reflectance of black silicon across a broad wavelength range makes it an intriguing surface texture for solar cell applications. Silicon heterojunction (SHJ) solar cells fabricated on black silicon (Si) formed by dry reactive ion etching (RIE) using inductive coupled plasma (ICP) on n-type Si are explored. The study is focused on the properties of the a-Si:H/c-Si interface, being a key issue for the photovoltaic performance of SHJ. Deep-level transient spectroscopy (DLTS) detected no radiation defect in Si after the etching. The surface of black Si was passivated with an intrinsic a-Si:H layer, followed by the deposition of p-type and n-type a-Si:H on the front and back sides, respectively. The SHJ solar cell photovoltaic performance based on black Si is strongly influenced by defect density at the a-Si:H/Si interface. Admittance spectroscopy and effective charge carrier lifetime measurements demonstrate that interface defect density decreases with the increase of (i)a-Si:H thickness. The value of 0.75 ms effective charge carrier lifetime was reached for single (i) a-Si:H layer passivation and 0.25 ms when (p)a-Si:H was deposited over the intrinsic a-Si:H layer. The measured open circuit voltage (VOC) values for the SHJ solar cells increase with the (i)a-Si:H layer thickness reaching 658 mV. However, the fill factor decreases with increasing (i) a-Si:H layer thickness, limiting the efficiency at the maximum value below 14% due to the thickness uniformity of the a-Si:H layer. The development of conformal growth of a-Si:H is a key issue for further improvement of black Si heterojunction solar cell photovoltaic performance. &amp;#xD;

Photoluminescence Spectra of Helium Ion-Implanted Diamond.

Ion implantation in diamond crystals is widely used both for producing conducting microstructures in the bulk of the material and for creating isolated photon emitters in quantum optics, photonics, cryptography, and biosensorics. The photoluminescence (PL) spectra of helium ion-implanted diamonds are dominated by two sharp emission lines, HR1 and HR2 (from Helium-Related), at ~536 and 560 nm. Here, we report on PL studies of helium-related optical centers in diamonds. Experiments have been carried out on a (110) plate of natural single-crystal type IIa diamonds. The uniform distribution of radiation defects in a 700 nm-thick layer was obtained by ten cycles of multiple-energy (from 24 to 350 kV) helium ion implantation with a total dose of 5 × 1016 cm-2. The diamonds were annealed in steps in a vacuum oven at temperatures from 200 to 1040 °C. It is demonstrated that helium ion implantation in diamonds followed by annealing gives rise to more than a dozen various centers that are observed in the PL spectra in the range of 530-630 nm. The transformations of the PL spectra due to annealing are investigated in detail. The spectral shapes of phonon sidebands are determined for the HR1, HR2, and HR3 bands with ZPLs at ~536, 560, and 577 nm, respectively, and it is shown that these bands are attributed to interstitial-related centers in diamonds. The reported results are important for understanding the structure and properties of helium-related defects in diamonds.

Radiation defect formation and effect on mechanical property in octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine investigated by molecular dynamics method

Energetic materials (EMs) are generally used in various conditions including under the neutron irradiation environment. To understand the radiation damages and related effects on mechanical property of EMs is important and necessary for their further applications under radiation conditions. In this paper, the displacement cascades are firstly simulated with molecular dynamics method in an octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) with the maximum energy of a primary knock-on atom (PKA) up to around 5 keV. The bond breaking, formation of free radicals, new gas molecules and interstitial and vacancy clusters, are all observed after displacement cascades, which can be used to explain the change of color and release of gas after irradiation as reported in experiments. Furthermore, the effect of above defect formation on mechanical property is calculated based on tensile stress simulations on damaged HMX. The results clearly show the appearance of strong stress gradient around defect formation region, resulting in lower external stress needed to deform the system. Thus, the radiation softening can be explored according to these results, same to experimental reports. Therefore, all these results indicate the radiation damages induced by energetic particles should be considered seriously for further application of energetic materials in nuclear conditions.

Microstructural changes and irradiation hardening behavior of V-4Cr-4Ti alloys irradiated with He ions using flash-electropolishing

The flash-electropolishing of focused ion beam samples for V-4Cr-4Ti alloys is established, and the microstructures of high-purity V-4Cr-4Ti alloys after He ion irradiation are examined by transmission electron microscopy from room temperature to 700 °C. The correlation between irradiation hardening behavior and microstructural changes is clarified. During room temperature irradiation, defect clusters are formed at shallow positions in the specimens and no He bubbles are observed at the damage peak position. In contrast, 500 and 700 °C, TiCON precipitates are predominantly formed and He bubbles and voids were formed at the damage peak position. The results of nanoindentation tests and a comparison of irradiation hardening by irradiation damage indicate that the obstacle barrier strength factorαof TiCON is 0.45 while that of the irradiation defect clusters irradiated at room temperature is 0.10. Irradiation damage in the He ion range extends toward the interior of the specimens with increasing irradiation temperature.

Co-evolution of M23C6 precipitates and cavities in a boron-free Ni-based alloy GH3617 under high-temperature He ion irradiation: Effects on cavity swelling and mechanical properties

Ni-based alloys are promising materials for advanced nuclear reactors operating at high temperatures due to their exceptional resistance to high temperatures and corrosion. Understanding the synergy of phase stability and helium effects is crucial for assessing the long-term performance and reliability of these alloys in advanced nuclear reactors. This study has investigated the co-evolution behavior of M23C6 precipitates and cavities in a boron-free solid solution strengthened Ni-based alloy GH3617 under high-temperature He ion irradiation, and its impact on alloy swelling and mechanical properties, by He ion irradiation experiments with the highest fluence of 1 × 1017 He/cm2 up to 800 °C. Transmission Electron Microscopy (TEM) and Nanoindentation are employed to investigate microstructural evolution and mechanical properties, respectively. The findings show that at room temperature and 500 °C, cavities and dislocation loops were the dominant irradiation defects, whereas at 800 °C, the density of cavities and dislocations reduced while the formation of M23C6 precipitates increased. These precipitates act as effective trapping sites for He and point defect, leading to cavity formation at the interfaces or within the precipitates. Moreover, increased irradiation fluence accelerates the co-evolution process, resulting in an increase in the density and size of both precipitates and cavities, ultimately leading to enhanced swelling. The {111} planes are favored interfaces between intragranular M23C6 precipitates and the matrix due to their minimal misfit, while the preferred interface planes between cavities with octahedral or cubo-octahedral shapes and the precipitate/matrix are also {111}, owing to their lower surface energy as well. The co-evolution of cavities and precipitates was found to influence mechanical properties, resulting in an irradiation hardening effect at lower fluences, while softening at higher fluences. This study provides novel insights into the degradation mechanisms of Ni-based alloys under coupling effect of He and high-temperature irradiation.

Excellent radiation resistance via enforced local non-directional He diffusion in a WTaCrV multicomponent alloy containing coherent ordered nanoprecipitates

We design and investigate a W15Ta15Cr35V35 (at.%) multicomponent alloy (MCA) with exceptional radiation resistance. The sintered WTaCrV alloy exhibits a body-centered cubic (BCC) matrix with dispersed coherent ordered nanoprecipitates. After ∼3-hour irradiation under 400 keV He+ at room temperature (RT) and 450°C with a fluence of 2 × 1017 ions/cm2, the irradiation hardening values of the MCA are about a quarter of those of pure tungsten counterparts irradiated at identical conditions. Besides, helium bubbles generated in the irradiated matrix of the MCA are much smaller, compared with those in the pure tungsten and other tungsten-rich alloys previously reported. The exceptional radiation resistance of the present WTaCrV alloy can be mainly attributed to two synergistic mechanisms. First, the high lattice distortion of the solid solution matrix promotes the local non-directional diffusion of irradiation defects, effectively suppressing the aggregation of irradiation defects and helium atoms along specific orientations. This facilitates more uniform nucleation of helium bubbles in the alloy matrix. Second, carbon was introduced during fast hot pressing sintering as interstitial solute to form carbon-rich coherent ordered nanoprecipitates. The carbon-vacancy complexes generated in the nanoprecipitates inhibit the nucleation and aggregation of helium atoms at the vacancies during He+ irradiation. The above two mechanisms synergistically enhance the resistance against He+ irradiation. This work thus demonstrates a design strategy for high radiation resistance alloys by introducing well-tuned ordered coherent nanoprecipitates in multicomponent alloy systems.

Effect of Electron Irradiation on the Optical Properties of Zinc Oxide Powder Modified by Magnesium Oxide Nanoparticles

The effect of modifying ZnO powders with MgO nanoparticles (with a concentration of 0.1–10 wt. %) on their diffuse reflectance spectra in the region of 0.2–2.5 μm before and after irradiation with 30 keV electrons was studied. Modification of ZnO powder was carried out by MgO nanopowder with concentrations from 0.1 to 10 wt. % using a solid-state method at 650°C heating temperature. X-ray diffraction analysis showed that this method of modification there is no formation of additional phases. It has been established that zinc oxide structure symmetry belongs to the P63mc space group, magnesium oxide – to the Fm–3m space group. The spectral reflectance of such powders in the visible region is over 90%. Under irradiating by 30 keV electrons of initial and modified ZnO powders, as well as MgO nanopowder, a decrease in their reflectance recorded in the entire studied region of the spectrum. It has been established that modification with MgO nanoparticles at a concentration of 3 wt. % leads to an increase in radiation resistance by a factor of 1.32 compared to unmodified samples. This effect is determined by the sink of radiation defects on the large specific surface area of nanoparticles.

Physical mechanism of gettering of impurity Ni atom clusters in Si lattice

This article presents the gettering mechanism and the physical model of impurity Ni atom clusters in the Si crystal lattice. The study finds out that the formed Ni atom clusters lead to gettering various rapidly diffusing impurities, both present in the Si lattice and introduced, as well as oxygen atoms, by stimulating generation of recombination centers of thermal and radiation defects.

Luminescence and dielectric investigations of crystalline niobate nanoceramics prepared through aqueous chemical process

The present study reflects the synthesis of MgNb2O6 using hydrofluoric acid via a wet chemical approach, followed by characterizations involving XRD, electron microscopy, Raman spectroscopy, optical analyses, and impedance spectroscopy. The crystallite size of the synthesized material was determined to be 44 nm through XRD analysis. The lattice parameters of MgNb2O6 a, b, and c, were found to be 14.1998 Å, 5.6844 Å, and 4.9813 Å, respectively. Raman spectroscopy identified molecular bonds ranging from 253 to 1011 cm−1, mainly indicating the presence of metal oxide bonds. EDX spectra confirmed the presence of Mg, Nb, and O atoms in the prepared ceramics, indicating phase purity. FESEM analysis revealed a grain size of approximately 48 nm, with the presence of agglomerated grains. Bright spots in the SAED pattern observed by HRTEM confirmed the crystallinity of the prepared niobate materials, with the HRTEM microstructure showing a particle size near 49 nm. The crystallite size by XRD, grain size by FESEM, and particle size by HRTEM are in accordance with each other. The direct band gap was determined to be approximately 2.76 eV using UV-Visible spectroscopy. Additionally, MgNb2O6 materials exhibited a broad and strong photoluminescence emission near 445 nm with excitation at 270 nm, possibly indicating the presence of radiative defects in the crystalline nanostructure. Furthermore, impedance studies conducted between 40 and 110 MHz demonstrated a decrease in the dielectric constant at higher frequencies, reaching 21.06 at 110 MHz. A low dielectric loss was also observed at 110 MHz. The moderate band gap and strong room-temperature photoluminescence in the visible range make magnesium niobates suitable for possible applications in optical devices. This investigation shows that a dielectric constant near 21 and low dielectric loss can be achieved in the high-frequency range around 110 MHz.

The evolution of irradiation defects and hardening of CVD-SiC induced by He ions irradiation at 800°C

In this study, 500 keV He ions were used to irradiate CVD-SiC samples at 800 °C. The influence of doses on the microstructural evolution and hardness of the irradiated samples were investigated by TEM, Raman, and nanoindentation. TEM results show that He bubbles and dislocation loops appeared after irradiation, and their number densities increased with doses, resulting in the gradual decrease of the intensity of the TO peak in Raman spectra. Moreover, He platelets with strain field were observed in both stacking faults and matrixes. Nanoindentation results indicated that the irradiation hardening occurred, and the hardening degree was positively correlated with the irradiation dose.

Radiation Effects in Tungsten and Tungsten-Copper Alloys Treated with Compression Plasma Flows and Irradiated with He Ions.

The paper presents the results of studying the structure and phase state of tungsten and tungsten-copper alloy after pulsed action of compression plasma flows and irradiation with helium ions. The compression plasma flows were used to modify the surface layer of tungsten, as well as to create an alloy based on tungsten and copper. Using scanning electron microscopy and X-ray structural analysis, the formation of radiation defects on the tungsten surface was detected in the form of local areas of exfoliation and destruction, which begin to form at helium ion irradiation doses of 2 × 1017 cm-2. It is shown that preliminary plasma treatment of the surface in the melting mode leads to the complete disappearance of surface radiation defects up to a dose of 2 × 1017 cm-2, which may be associated with the formation of a fine-crystalline grain structure, the intergranular boundaries of which serve as effective sinks for primary radiation defects.