Room Temperature Irradiation Research Articles

Electron transfer photochromism of Ln-based (Ln = Dy, Tb) coordinated polymers for reversibly switching off/on single-molecule magnetic behavior

Switching on/off single-molecule magnets (SMMs) at room temperature is still a challenge in moleculebased magnets. Herein, two photochromic Ln-based (Ln = Dy, Tb) phosphonate coordinated polymers were synthesized with regulable SMM behavior. The reversible room-temperature photo-coloration was an electron transfer process with a generation of relatively stable radicals, characterized by structural analyses, ultraviolet-visible, luminescence and electron spin resonance spectra and magnetic measurements. Importantly, owing to the antiferromagnetic coupling interactions between Ln3+ ions and photogenerated radicals, the room-temperature light irradiation surprisingly switched off the SMM behavior, showing the first example of radicalquenched SMMs in the molecule-based magnets. Moreover, the silient SMM behavior could be recovered after eliminating photogenerated radicals via heat treatment, showing a reversible off/on switch of SMMs via light and heat. This work constructs a system for switching off/on SMMs through electron transfer photochromism, providing a visual operation way via naked-eye-detectable coloration for the switchable SMMs.

Room temperature NO2 sensing properties of ZnO1-α coating prepared by hydrogen reduction method

NO2 emission is currently one of the important factors threatening the quality of life of residents. Preparing ZnO-based gas sensors to monitor the concentration of NO2 has attracted growing attention. This article reports a method for preparing ZnO1-α by hydrogen heat treatment. The ZnO coating prepared by the spin coating method is directly placed in a reduced atmosphere with 3% hydrogen for heat treatment to produce a self-doped ZnO1-α coating with oxygen vacancies, which can effectively narrow the bandgap. The article studied the influence of heat treatment time and visible light wavelength on sensing properties. The results show that under the conditions of room temperature and blue light irradiation, the coating heat-treated in a reduced atmosphere for 1 h showed the best gas-sensing properties to 1 ppm NO2 with a response of 7.0. The outstanding selectivity of ZnO1-α coating has been displayed.

The investigation of distribution on size and concentration of helium bubbles in Y-bearing ODS steel using by SAXS and GIXRD

The nucleation and growth of the helium bubble in the structure material usually were subjected to temperature in a thermodynamic environment. In this study, Y-bearing oxide dispersed strengthened (ODS) ferritic/martensitic steels were used as the research material. The Y-bearing ODS steel samples with a thickness of 30 microns were irradiated successively by helium ions with three energies of 300 keV, 400 keV and 550 keV at room temperature and 450°C respectively. Firstly, the evolution of defects caused by H e + irradiation is analyzed by using slow positron beam Doppler broadening spectroscopy (DBS) in positron annihilation spectroscopy technology (PAS). The formation and growth of helium bubbles are deduced from the changes in the concentration of vacancy-type defects. The increase in the size of the helium bubbles at high temperatures leads to a certain distortion of the crystal lattice, which is also verified by analyzing the grazing incidence X-ray diffraction (GIXRD) patterns. The characterization of radius and concentration of helium bubbles in samples irradiated at room temperature and 450°C have been studied by Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM). The results showed that the intensity (I) ~ q-vector (q) curves of samples vary with irradiation temperature over ranges of 0.13 ≤ q ≤ 4.6 nm −1 , which is attributed to the growth of helium bubbles at different irradiation temperature. It is found that the average size of helium bubbles under room temperature irradiation is about 1.78 nm, and the size distribution is narrow, while at the irradiation temperature of 450°C, the size of helium bubbles increases to 2.9 nm, and the size distribution is wider. This result is also verified from the TEM analysis. Besides, the shape of helium bubbles was assumed roughly and tends to spherical with higher temperatures.

In-situ ion irradiation study of alloy 709 stainless steels with different processing histories

Alloy 709 stainless steel (A709 SS) has gained an increased interest in nuclear applications due to its advanced properties at high temperatures over the widely used Type 316 SS. However, how this alloy behaves under irradiation with concurrent environmental factors, such as mechanical deformation and/or thermal annealing, has not been studied. In this work, we used in-situ ion irradiation inside a transmission electron microscope (TEM) to investigate the effects of irradiation on the microstructures of A709 SS samples with different prior processing histories, including as-received, annealed, and creep-deformed. It was found that, compared to room temperature irradiation, 600°C irradiation led to larger dislocation loop sizes and lower loop densities. With 600°C irradiation, the creep-deformed sample, which had the highest precipitate density and the highest dislocation density, had the smallest loop size and the lowest loop density compared to others. This observation has been rationalized with quantitative evaluation of the sink strength factors in each sample. This study shows that in-service deformation can significantly affect the irradiation performance in structural materials at reactor operating conditions.

Photocross-Linked Antimicrobial Amino-Siloxane Elastomers.

Mechanically robust bulk antimicrobial polymers are one way to address disease transmission via contaminated surfaces. Here, we demonstrate the visible light photo-oxidative cross-linking of amine-containing PDMS using a single-component, solvent-free system where amines have a dual role as antimicrobial functionalities and cross-linking sites. Rose Bengal, a xanthene dye used as a fluorescent stain, is thermally reacted with the polymer to give a solvent-free liquid siloxane that can generate reactive singlet oxygen upon aerobic green light irradiation, coupling the amine functionalities into imine cross-links. Photorheological experiments demonstrate that light intensity is the largest kinetic factor in the photo-oxidative curing of these polymers. Room temperature irradiation under an ambient atmosphere results in free-standing elastic materials with mechanical properties that depend on the amount of Rose Bengal present. An ultimate elongation strain of 117% and Young's modulus of 2.15 MPa were observed for the highest dye loading, with both mechanical properties found to be higher than those for the same solution-based dye amounts. We demonstrate that the solvent-free nature of the material can be exploited to generate 3D structures using low-temperature deposition as well as direct-write patterning and photolithography on glass substrates. The antimicrobial activity was investigated, with the cross-linked material demonstrating greater efficacy against E. coli (Gram negative) compared with MRSA (Gram positive) bacterial strains and inducing complete cell lysis of incubated CHO-K1 mammalian cells, demonstrating applicability as a mechanically robust single-component antimicrobial elastomer.

Regeneration of Fiber Bragg Gratings and Their Responses Under X-Rays

Fiber Bragg gratings (FBGs)-based temperature sensors present numerous advantages such as small packaging, fast acquisition rate, and accuracy for structural health-monitoring applications in nuclear environments. Among the various classes of FBGs, Type I FBGs are inscribed with a UV continuous or pulsed laser on a photosensitive fiber or with femtosecond laser even in nonphotosensitive fibers. These gratings, however, cannot survive at temperatures exceeding 400 °C. Regenerated FBG (RFBG) gratings, instead, are derivative from type I grating: when a high thermal treatment (> 650 °C) is applied after the inscription on a prehydrogenated fiber, a new grating (RFBG) appears with different thermal properties. It withstands temperatures as high as 1000 °C, opening the way to new application fields such as the temperature monitoring of the nuclear reactor cores. This work investigates the radiation response of RFBGs originated from type I seed FBGs inscribed with an argon laser (244 nm) in two different fibers (SMF-28e fiber or in a B/Ge co-doped fiber), loaded with either H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> or D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> before the inscription to enhance the fiber photosensitivity. Regeneration was achieved at 650 °C or 900 °C depending on the fiber type. After this, the RFBGs were irradiated under 40-keV X-rays at two different dose rates [1 Gy(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )/s or 10 Gy/s] and at two temperatures of irradiation-25 °C or 250 °C. At room-temperature (RT) irradiation, a Bragg Wavelength Shift (BWS) of about 35 pm was observed for the SMF-28e and more than 130 pm for the B/Ge fiber at 400-kGy dose, and the combined temperature and radiation constraints reveal that the RFBGs are radiation-tolerant. Indeed, no BWS is observed anymore, at the highest temperature of irradiation.

Impact of high temperature electron irradiation on characteristics of power SiC Schottky diodes

Impact of high temperature electron irradiation on the characteristics of power silicon carbide-based semiconductor devices was studied for the first time. Commercial 4H–SiC integrated Schottky diodes (JBS) with blocking voltage of 1700 V were irradiated with 0.9 MeV electrons at temperatures from 23 to 5000С in the fluence range Φ from 1 × 1016 cm−2 to 1.3 × 1017 cm−2. It was shown that ruggedness of the diodes during high temperature (“hot”) irradiation significantly exceeds the ruggedness of diodes at room temperature (“cold”) irradiation. With an increase in the irradiation temperature from 23 to 500 °C, the change in the base resistance at a fluence of 1.3 × 1017 cm−2 decreases by 6 orders of magnitude. In the entire investigated range of irradiation temperatures and fluences, irradiation does not change the height of the metal-semiconductor barrier even at the maximum fluence Φ.

Creation of pure non-crystalline diamond nanostructures via room-temperature ion irradiation and subsequent thermal annealing

Carbon exhibits a remarkable range of structural forms, due to the availability of sp3, sp2 and sp1 chemical bonds. Contrarily to other group IV elements such as silicon and germanium, the formation of an amorphous phase based exclusively on sp3 bonds is extremely challenging due to the strongly favored formation of graphitic-like structures at room temperature and pressure. As such, the formation of a fully sp3-bonded carbon phase requires an extremely careful (and largely unexplored) definition of the pressure and temperature across the phase diagram. Here, we report on the possibility of creating full-sp3 amorphous nanostructures within the bulk crystal of diamond with room-temperature ion-beam irradiation, followed by an annealing process that does not involve the application of any external mechanical pressure. As confirmed by numerical simulations, the (previously unreported) radiation-damage-induced formation of an amorphous sp2-free phase in diamond is determined by the buildup of extremely high internal stresses from the surrounding lattice, which (in the case of nanometer-scale regions) fully prevent the graphitization process. Besides the relevance of understanding the formation of exotic carbon phases, the use of focused/collimated ion beams discloses appealing perspectives for the direct fabrication of such nanostructures in complex three-dimensional geometries.

Hardening behavior and deformation microstructure beneath indentation in heavy ion irradiated 12Cr-ODS steel at elevated temperature

Hardness behavior and deformation of the microstructure beneath the indentation in 12Cr-ODS steel after exposure to heavy ion irradiation at 573 K were investigated with combined applications of nano-indentation tests, EBSD analysis, and TEM observation. The inhomogeneous nano-indentation hardness behavior was firstly investigated in both non-irradiated and irradiated specimens and compared to those at room temperature (RT) irradiation. Subsequently, TEM observations were performed to understand the deformation behaviors beneath the indentation tested at typical low-indexed orientations. Obvious irradiation hardening was confirmed in both the normal direction (ND) and rolling direction (RD) specimens, and the hardening effect intensified with an increase in irradiation dose. Meanwhile, various anisotropic hardness behaviors were observed such as a lower hardness value and a weaker hardening effect in the RD specimen compared to the ND specimen, and a lower hardness value but a greater hardening effect in [001] orientation relative to [111] orientation. Furthermore, results from 573 K irradiation showed similar anisotropic hardness behaviors with those obtained from RT irradiation, despite the fact that irradiation at 573 K exhibited a weakened irradiation hardening effect in this steel. TEM observation of the deformation microstructure beneath the indentation reveals that (i) the depth of the deformation affected zone varied with orientation, ranging from ~6-9 times that of the indent depth, and (ii) distinct dislocation-grain boundary (GB) interactions beneath the indentations was confirmed to exhibit dependence on the geometric relation between GB and indenter impression direction. Correlation between the anisotropic hardness behavior and microstructural features is discussed based on Schmid factor analysis, comparison of geometric favorability between indenter and possible slip planes, and TEM observation of deformation microstructure. The results conclude that the anisotropic hardness behaviors in the present 12Cr-ODS steel are ascribed to the combined effect of crystal orientation and the non-uniform grain morphology with the existence of the elongated grains having low aspect ratio in the ND plane and nano-layered grains in the RD plane.

Temperature dependence of bipolar junction transistor current-voltage characteristics after low dose rate irradiation

Temperature variation on board can have a significant impact on electronic circuit parameters. In this paper, we investigate and model how both irradiated NPN and PNP-Bipolar Junction Transistors (BJTs) at room temperature respond electrically to temperature variation. A temperature-dependent analytical model for total-ionizing-dose-induced excess base current in BJTs is proposed. Our model captures base current dependence on temperature on irradiated parts. To do so, the devices under test are irradiated at room temperature with all terminals grounded. After irradiation, base currents are obtained, and the concentrations of oxide defects (i.e., oxide trapped charge and interface traps) created during irradiation are calculated. At the end, results from our analytical model and experimental data are compared to SPICE simulations. Both base current and defect densities resulting from room temperature irradiations are used as inputs to SPICE simulations and the analytical model. Experimental data obtained from measurements at both low and high temperatures on parts irradiated at room temperature are shown to compare well to the simulation results and analytical model over a range of temperatures. The modeling work shows that SPICE simulations can support qualification for commercial-off-the-shelf (COTS) linear bipolar components with temperature for space applications.

Heterostructured Fe2O3/BiVO4 nano-photocatalyst for the reduction of nitroarenes into amines

Nitro-reduction of aromatic nitro compounds into anilines has vast opportunities in synthetic chemistry. The catalytic systems used earlier operated under harsh conditions, which was very expensive to achieve end products. Visible light has advantages over the catalytic system due to the easy availability, low cost, and abundance. The present methodology describes the efficient reduction of a variety of aromatic nitro compounds into the corresponding anilines using a Z-scheme Fe2O3/BiVO4 photocatalyst under visible light illuminance. The photocatalyst demonstrated excellent activity up to 99% conversion of the nitrobenzene into aniline and for a series of nitroarenes as well at room temperature and atmospheric pressure visible light irradiation. The catalytic system has the advantage due to no leaching in the recycling experiments and high stability up to six cycles. The use of low-cost transition and p-block metal enhances the applicability of the catalytic system for aromatic nitro compounds reduction into the corresponding amines.

He ion irradiation response of a gradient T91 steel

Metallic materials with a gradient microstructure usually exhibit excellent mechanical properties. However, the radiation response of gradient structural materials is less well understood. Here, room-temperature He ion irradiation up to ~4.5 dpa with ~10 at% He injection was performed on a gradient T91 steel processed by surface severe plastic deformation. In comparison to the coarse-grained ferritic T91, the gradient T91 with the nanocrystalline layers shows improved radiation tolerance in terms of less bubble swelling and radiation hardening. Additionally, bubble distribution along grain boundaries depends on misorientation angle suggesting a strong capacity of non-equilibrium grain boundaries in storing He atoms. The present study provides insight into the design of radiation tolerant gradient steels for nuclear industry applications.

GREEN SYNTHESIS OF NEW SULFANYL DERIVATIVES OF AMPYRONE AND PREDICTION OF THEIR ANTI-INFLAMMATORY ACTIVITY

A selective method was developed for the synthesis of acyclic sulfanyl derivatives of ampyrone by thiomethylation reaction of 4-amino- 2,3-dimethyl-1-phenyl-3-pyrazolin-5-one with formaldehyde and thiols in aqueous medium under various conditions (room temperature, 80°C, ultrasonication or microwave irradiation). A series of the synthesized sulfanyl derivatives of ampyrone were characterized with regard to their anti-inflammatory activity by molecular docking method using the AutoDock 4.2 and AutoDock Vina software. The steric complementarity with the active sites of cyclooxygenase isoforms (COX-1 and COX-2) was explored.

Indirectly probing the structural change in ion-irradiated Zr-Based metallic glasses from small scale mechanical tests

Ion irradiation was applied to tailor the structural heterogeneities in Zr-based metallic glasses at room temperature. Experimental methods of X-ray diffraction, nanoindentation, and micropillar compression were conducted to examine the irradiation effects on their structural and mechanical property changes. It is found that the irradiated materials retained amorphous structure after room-temperature Ni ion irradiation. The reduction of elastic modulus and hardness measured by nanoindentation indicated the irradiation-induced mechanical degradation. A unified statistic model was employed to quantitatively predict the density and strength of irradiation defects, although their specific structural and physical nature is not explicitly included in this model. The transition of non-intersecting shear bands to multiple intersecting shear bands was observed on compression tests of irradiated micropillars with the increase of irradiation dose. The analysis of the displacement excursion of micropillar compression tests indicated a different deformation mode from the unirradiated state. These results from nanoindentation pop-in and micro-pillar compression tests suggested that irradiation eventually leads to a new state with different types and characteristics of structural heterogeneities from violent displacement cascades and non-equilibrium energy deposition/dissipation processes, which also proves ion irradiation as an effective method to tune the structure and mechanical properties of metallic glasses.

Green synthesis of new sulfanyl derivatives of ampyrone and prediction of their anti-inflammatory activity

A selective method was developed for the synthesis of acyclic sulfanyl derivatives of ampyrone by thiomethylation reaction of 4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one with formaldehyde and thiols in aqueous medium under various conditions (room temperature, 80°C, ultrasonication or microwave irradiation). A series of the synthesized sulfanyl derivatives of ampyrone were characterized with regard to their anti-inflammatory activity by molecular docking method using the AutoDock 4.2 and AutoDock Vina software. The steric complementarity with the active sites of cyclooxygenase isoforms (COX-1 and COX-2) was explored.

Defect evolution in Ni and solid-solution alloys of NiFe and NiFeCoCr under ion irradiation at 16 and 300 K

Single-phase concentrated solid-solution alloys (SP-CSAs) have shown unique chemical complexity at the levels of electrons and atoms, and their defect evolution is expected to be different from conventional dilute alloys. Single crystals of Ni, NiFe and NiFeCoCr are chosen as model systems to understand the chemical complexity on defect formation and damage accumulation in SP-CSAs under ion irradiation. The high-quality crystals were irradiated at 16 and 300 K to different ion fluences, to form irradiated region with little to heavy damages. The ion-induced damage was determined using Rutherford backscattering spectrometry technique along a channeling direction (RBS/C) and the level of lattice damage in irradiated Ni and SP-CSAs was quantified from Monte Carlo (MC) simulations. The results are interpreted using the Multi Step Damage Accumulation model to reveal material damage accumulation kinetics. Key findings of the study are that in case of room temperature irradiations the damage level measured for complex alloys at the highest irradiation fluence of 2 × 1015 cm−2 (∼3 dpa) is significantly higher than that obtained for pure nickel samples and suggest two-step damage accumulation process with a defect transformation taking place at a fluence of about 1.5 × 1015 cm−2. Moreover, structural and damage kinetic differences clearly imply that, with increasing degree of chemical complexity and high solid-solution strengthening effects from Ni to NiFe and to NiFeCoCr, the enhanced lattice stiffness resists to randomization of atomic configurations and inhibits the growth of extended defects.

Investigation on interlaminar properties of photopolymerizable resin repaired GFRPs during long-term acid ageing

Fiber reinforced plastics (FRPs) are extensively utilized in various applications due to their excellent comprehensive properties. However, the weak interlaminar property and durability of FRPs have been repeatedly mentioned as limitations in applications that include complex loading conditions. The remediation of FRPs has recently become a research focus for lifetime extension and strength reversion. Photopolymerizable resins, as a novel matrix material and an alternative for thermal polymerizable resins, have the advantages of short operation time, low price, and low equipment requirements. This study investigated the durability in long-term acid atmosphere exposure environment of photo and thermal polymerizable resin repaired GFRP. External glass fabric patches impregnated with the photo or thermal polymerizable resins were attached to pre-damaged fundamental specimens to conduct the remediation, followed by room temperature (RT) or UV irradiation for curing processing. The repaired specimens were positioned in the laboratory-fabricated hermetically-sealed condensation device. The 10 vol.% sulphuric acid (pH[Formula: see text][Formula: see text][Formula: see text]0.76) was chosen as the source to generate the acidic atmosphere. The total ageing time was sustained for eight weeks (over 1300 h), and ILSS and DCB tests were performed every seven days, together with morphology observation. Better interlaminar properties retention and stability were revealed after eight weeks ageing for UV repaired specimens. The hardener is a factor that tends to increase the acid penetration rate, which is thought of as the mechanism of the better acid resistance of the UV repaired specimens.

Fracture resistance of imperfect filler particles within nuclear graphite during irradiation

Although there have been many in-reactor experiments of nuclear graphite in history, its microstructure evolution during irradiation have not been well studied. One filler particle within nuclear graphite was investigated during ion irradiation. Remarkable dimensional changes and distortion of graphite filler were observed. Different from the well-known Mrozowski crack, cracks formed by graphite sheets fracture were found in filler and showed continuous opening during irradiation, resulting in porosity increase and decline in integrity of nuclear graphite. But evidences show that these cracks did not grow along the c-axis, indicating a strong resistance to irradiation-induced fracture of un-fractured graphite sheets. Although the dimensional evolution of graphite crystallite continues at the highest dose of 10 dpa, the Raman spectra showed that the structure of damaged graphite lattice became very stable at doses above 0.84 dpa during room-temperature irradiation.

Selective Sensors of Nitrogen Dioxide Based on Thin Tungsten Oxide Films under Optical Irradiation

It is shown that NO2 present in air, beginning at a concentration of 1 ppm, can be selectively detected by sensors based on Au/WO3:Au thin films activated by laser diode radiation with maximum intensity at 400 nm instead of constant heating. The radiation-activated photodesorption reduces the time of sensor response to NO2. A high humidity of air under conditions of room-temperature irradiation additionally increases the device sensitivity to NO2 due to the appearance of additional adsorption sites. The absence of a sensor response to reducing gases and varying oxygen concentration in the atmosphere is caused by the photodesorption of chemisorbed $${\text{O}}_{2}^{ - }$$ species during their interaction with holes generated in intrinsic optical transitions in the near-surface region of WO3 film.

Phenomenological model of aluminium-hole ([AlO4/h+]0) defect formation in sedimentary quartz upon room temperature irradiation: electron spin resonance (ESR) study

The mechanism governing the production of the paramagnetic [AlO4/h+]0 centres (denoted also as Al-hole or Al-h) in quartz as a function of given dose is of great importance in electron spin resonance (ESR) dating, as the analytical function used to characterise the evolution of this centre with accumulated dose is used to derive the equivalent dose by extrapolation to the abscissa-axis. The single saturating exponential model fails to accurately represent the dose response curve especially at high doses, and consequently, empirical functions, such as a saturating exponential plus a linear term, are widely used in the dating community. Herein, a physical phenomenological model is presented to describe the Al-hole formation under gamma irradiation in sedimentary quartz. Based on previous studies it is known that the Al-hole centre is formed via the dissociation of the Al centres compensated with alkali ions [AlO4/M+]0 (generally denoted as Al-M) where M+ could be Li+, Na+ or K+, as well as by the dissociation of Al compensated with hydrogen ions [AlO4/H+]0, (denoted as Al–H). When irradiation moves interstitial alkali ions away from the aluminium ions, they can be replaced by H+ ions beside the conversion to Al-hole centres. By assuming that the rate of the dissociation process is proportional to the concentration of the defects themselves, a sum of saturating exponential functions is obtained for describing the growth of Al-hole with dose. The model is applied on data obtained on sedimentary quartz specimens of different origins for describing the dose response of the paramagnetic Al-hole ESR signal. We are showing that the signal of Al-hole does not reach full saturation at doses even as high as 100 kGy and can it be well represented by two exponential components as predicted by the model. As such, the additional linear term reported by other works when describing the dose response is just a first order approximation of one of the saturating exponential functions.