Increasing Gamma Radiation Dose Research Articles

Investigating the Suitability of Cu2ZnSnS4 Thin Films for Gamma Radiation Dosimetry Applications in Non-Medical Environments

Abstract The need for the replacement of cadmium, indium, and tellurium in their compounds for sensor applications is a novel study. The Cu2ZnSnS4 thin films were synthesized from Cu (99.99%), Sn (99.99%), and Zn (99.99%) using thermal evaporation method. The same volumetric parameters were maintained throughout the synthesis process. The films were further irradiated using an isotope of cesium-137 from a gamma source at different doses (0–0.6 kGy) and dose rates of 0.1007 kGy/hr at room temperature. Both the pristine and irradiated films were characterized with Raman spectroscopy, field emission scanning electron microscope (FESEM), energy dispersive X-rays (EDX), UV-Vis spectroscopy, and four-point probe techniques. The Raman results confirmed that all the films for both pristine and irradiated films have a main and secondary phases. The EDX results showed the pristine and 0.1 kGy films were Cu-rich film, while the 0.3 kGy and 0.6 kGy films turned out to be Zn-rich films with an increase in gamma dose. The optical property of all the films showed that the band gap decreased from 1.6 eV to 1.48 eV for the pristine and irradiated films. While the electrical resistivity results decreased after irradiation dose. The structural, optical, and electrical properties results responded linearly with the increasing gamma radiation dose, which suggested the possibility of using films as a new solid-state sensor to replace CdTe and CIGS thin films.

Investigation of structural and TL kinetic parameters of smartphone screen protector glasses for applications in retrospective dosimetry

The study evaluated the structural and thermoluminescence (TL) kinetic parameters of smartphone screen protector glasses in order to use them for post-accident dose reconstruction from unplanned nuclear events. The fact that most individuals use mobile phones in working environments including nuclear power plant sites, served as the impetus for the study. The TL glow curves indicate the physical properties of the defects involved in the luminescence process; therefore, they have been analyzed to study the TL kinetic parameters by employing peak shape, initial rise and glow curve deconvolution method within the dose ranges from 2 to 50 Gy. The geometric factor (μg) ranges between 0.46 and 0.56, suggesting that Chen's general-order method can be used to compute the kinetic parameters, including activation energy (E), frequency factor (s) and trap lifetime (τ). The examined trapping parameters (E = 0.33–0.57 eV, s = 5.22E+03–8.65E+06 s−1 for peak shape and E = 0.36–0.96 eV, s = 2.90E+04–1.88E+11 s−1 for initial rise methods) suggest promise for TL dosimetry applications. Additionally, the observed lifetime (τ = 4.88E+5 s) implies the feasibility of dose reconstruction even several days after an accident, making it suitable for retrospective dosimetry. Micro-Raman spectroscopy revealed a clear correlation between increasing gamma radiation dose and microstructural damage. The analysis of intensity ratio (ID/ISi) for other components to silica, along with the area of deconvoluted micro-Raman spectra in high-frequency regions, indicated dose-dependent structural modifications and internal defect annealing. Further confirmation of structural alterations within the studied dose range was obtained through the analysis of crystallite size (Lc), dislocation density (δ), lattice strain (ɛ) and FWHM (Full Width at Half Maximum) from XRD (X-ray diffraction) patterns. These findings collectively suggest the potential of smartphone screen protector glass as a viable material for emergency dosimetry applications.

Impact of high energy photons on physical, structural and magnetic properties of Mn0.65Zn0.35Fe2-xNdxO4 nanoparticles

Ultrafine powders of Nd+3 doped Mn–Zn ferrite powders with composition Mn0.65Zn0.35Fe2-xNdxO4 (x = 0.04, 0.06, 0.08) were prepared using the combustion method of preparation. Monophasic nanoparticle formation was confirmed by X-ray diffraction. The particle size was determined using a Transmission electron microscope (TEM). The nanopowders were investigated for their physical, structural, and magnetic properties and then radiated with gamma photons obtained from Co60 source with a dose of 500Gy, 750Gy and 1000Gy. The characterization of radiated powders showed preservation of spinel structure with breaking down of crystallites into finer crystals with increment in amorphous content. Structural and physical parameters were drastically altered due to high-energy photon exposure. The breaking down of larger particles was observed as a result of photon energy impact on the samples. The Saturation magnetization of ferrite nanoparticles was observed to increase with increasing gamma radiation dose. Mössbaure spectra showed the dominance of Fe+3 in the high spin state.

The lethal and sterile doses of gamma radiation on the museums pest, varied carpet beetle, Anthrenus verbasci (Coleoptera: Dermestidae)

Museums preserve historical cultural artifacts and serve as an essential resource for current and future generations seeking first-hand knowledge about the diversity of life on Earth. However, significant changes in climate from temperature and humidity cause serious biotic degradation. Despite ongoing insect control treatments, insect pests are still a major problem for museums due to the lack of suitable and unsafe environments that are provided for the storage and display of the collection. The varied carpet beetle, Anthrenus verbasci (Coleoptera: Dermestidae) is one of the major stored product pests whose larvae cause serious damage to household items and museum specimens. Therefore, this research aims to study the effect of gamma radiation on the larval, pupal and adult stages. The effects of gamma radiation have been studied on 3rd instar larvae (100, 200, 300, 400 and 500 Gy). The results showed that mortality in the larval stage significantly increased with increasing gamma radiation dose, which was reflected in the eclosion of the adult stage. The exposure of one-day-old pupae to 200, 400, 600, 800 and 1000 Gy of gamma radiation showed that the higher the dose, the lower the percentage of adult emergence. Additionally, there was a significant increase in the percentage of mortality in A. verbasci adults with increasing radiation doses when the newly emerged adults were irradiated with 200, 400, 600, 800 and 1000 Gy. The LD50 and LD90 of gamma radiation doses on larvae, pupae and adults were calculated, and the malformations in all stages were photographed. The fecundity and fertility of A. verbasci adults that were exposed to radiation as one-day-old pupae decreased gradually with increasing doses of gamma radiation and reached 100% sterility when exposed to a dose of 150 Gy. Among all the treatments, the sterile dose (150 Gy) or lethal dose (1000 Gy) showed superior performance over other treatments and was adjudged as the best treatments, which prevented the subsequent development and complete mortality of the pest.

Synthesis of Polyvinyl Alcohol (PVA)-Gelatin Hydrogel from White Snapper (Lates calcarifer, Bloch) with Gamma Irradiation and Its Characterizations

The application of nuclear technology in the health sector is increasing. One example is the use of irradiation in production of wound dressings. Research activities have been conducted to study whether polyvinyl alcohol (PVA)-gelatin-based hydrogel from white snapper scales can be processed using gamma irradiation into wound dressings. A series of PVA (10 %) solutions containing gelatin in various concentrations (0-4 %) were treated with three freeze-thaw cycles and then irradiated at doses of 10 and 20 kGy. They were subsequently characterized using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM). Gel fraction, water absorption, and percentage of hydrogel water evaporation rate were tested gravimetrically, while the elongation at break and the tensile strength of the hydrogels were tested with a universal testing meter. The evaluation showed that the hydrogel gel fraction decreased with increasing gelatin concentration from 0 % to 4 % for both irradiation doses (10 and 20 kGy). The rising gelatin concentration demonstrated that increasing gamma radiation dose improved the hydrogel's water absorption, evaporation rate, tensile strength, and elongation at break. PVA-gelatin hydrogel with irregular pore structure was observed from SEM test results. The FTIR measurement results confirmed the formation of crosslinks in the hydrogel matrix. The PVA-gelatin hydrogel produced through gamma irradiation could be used for wound dressings.

Influence of Gamma Radiation on the Damping Property of Magnetorheological Elastomer.

Magnetorheological elastomer (MRE) is a kind of smart material, whose mechanical property can be controlled by the external magnetic field quickly and reversibly. The damping property of MRE is one of the most concerned properties when designing MRE based devices. In this work, the influence of gamma radiation on the damping property of MRE was investigated. Six different exposures of gamma radiation were applied to the MRE samples. The highest gamma radiation dose was up to 1 × 105 Gy(Si), which can cover most of the engineering application scenarios. The influence of gamma radiation on the damping-strain relation and the damping-magnetic-field relation were studied. The probable mechanisms were discussed in detail. It is found that the gamma radiation does not affect the variation trend of loss factor of MRE with increasing strain amplitude or magnetic flux density. But it affects the variation trend of the maximum change of strain-induced or magnetic-field-induced loss factor of MRE. Besides, with constant strain and constant magnetic flux density, the loss factor of MRE shows w-shape variation trend with increasing gamma radiation dose. It is considered to be resulted from the combined action of the intrinsic damping and the interfacial friction damping of MRE.

THE GENETIC VARIATION ASSESSMENT OF IN VITRO IRRADIATED TOMATO (Lycopersicon esculentum Mill) BY SCoT AND ISSR MARKERS

Tomato (Lycopersicon esculentum Mill.) are considered major and important globally vegetable crops and in Egypt in particular. Tissue culture techniques have encouraged the utilization of mutation methods in crop improvement. The mutation induction in vegetative crops through tissue culture may be the optimal method to improve these crops. Induced genetic variation in tomato plantlets by using gamma radiation and identified these changes through SCoT and ISSR markers. Egyptian tomato cultivar Idkawy explant was cultured onto MS medium supplemented with 0.2 mg-l BAP. The resulted plantlets were irradiated with γ radiation doses (50, 100, 150, 200 or 250 Gy). The survival, growth rate, and mean of shoot length were decreased with increasing gamma radiation dose. The irradiated plantlets survival percentages were ranged from 78.75% to (50 Gy) and 18.75% to (250 Gy), whereas, the shoot length decreased by a rate of 2.71 cm for the dose (50 Gy) and 1.2 cm for dose (250 Gy). Genetic diversity was evaluated by SCoT and ISSR markers using ten primers for each. It was noticed that the polymorphism percentage mean of SCoT marker (60.53%) is higher than the ISSR marker (39.6). The PIC values average for both markers SCoT and ISSR were 0.429 and 0.347, as well, MI values were 0.345 and 0.156, respectively. On the other hand, the effective no. of alleles (Ne), Nei’s genetic diversity (H) and Shannon’s information index (I) parameters, it was found that the dose 100 Gy caused the highest genetic variation compared with other doses using SCoT marker, however, in ISSR marker was dose of 150 Gy the highest dose for induced genetic variation. The obtained results demonstrate that SCoT marker was more accurate and efficient than ISSR marker for distinguishing and genetic variation analysis of irradiated tomato plantlets. The relationships within treatments were assessed through cluster analysis (UPGMA) based on SCoT and ISSR analysis.

Effects of gamma irradiation under vacuum and air packaging atmospheres on the phytochemical contents, biological activities, and microbial loads of Kaempferia parviflora rhizomes

Kaempferia parviflora is a traditional herb for health promotion and therapy attributed to its methoxyflavone and phenolic constituents. This study was performed to determine the effects of gamma irradiation (0, 5, 7.5, and 10 kGy) under vacuum and air packaging atmospheres on the phytochemical contents, biological activities, and microbial loads of K. parviflora rhizomes. The optimal extraction condition for achieving high antioxidant activity was: ethanolic concentration, 40% v/v; solid/solvent ratio, 1 : 10 g/ml; extraction temperature, 30 °C; and extraction time, 1 h. This condition was used to prepare extracts of K. parviflora rhizomes for further determination. The high performance liquid chromatography-diode array detector method was employed for the determination of methoxyflavones in rhizome extracts. The contents of methoxyflavones and phenolic compounds were found to increase with increasing gamma irradiation dose. In contrast, the antioxidant activities decreased with increasing gamma radiation dose. However, all three doses applied did not affect total flavonoid contents and albumin denaturation inhibitory activities in all extracts. The highest contents of methoxyflavones and phenolic compounds were observed in 7.5 kGy irradiated rhizomes packaged under air atmosphere. Irradiation treatment at doses of 5–10 kGy was sufficient to control microbial contamination and Tribolium castaneum infestation in dried rhizomes. This study suggests that 7.5 kGy irradiation is the effective treatment to improve the quality of K. parviflora rhizomes.

Synthesis and characterization of copper hydroxynitrate salt (Cu2(OH)3NO3): Effect of gamma radiation absorbed doses on thermal stability

Thermal stability is one of the main preferred material properties for industrial applications. Gamma radiation has a high ability to deeply penetrate in structure of materials and develop their physical properties. This work is devoted to sensitize copper hydroxynitrate Cu2(OH)3NO3, and study the effect of different doses of gamma rays on its thermal stability. The sample was prepared by co-precipitation technique and identified using X-ray diffraction and Fourier-transform infrared spectroscopy. The prepared sample was divided to seven subsamples, six of them were irradiated by different doses from 10 KGy up to 300 KGy while the seventh one used as a reference sample. The obtained results showed significant enhancement of thermal stability which represented by shifts of onset temperature to higher values for the irradiated samples from 10 to 100 kGy. Also, temperature corresponding to the residual masses 5%, 15% and 25% increased with increasing gamma radiation dose. However, the thermal stability reduced for the sample irradiated with high dose (300 KGy). The obtained data could be explained in terms of the principle of free radicals formation beside the interaction of these free radicals with each other. The obtained results shed light on the positive effect of the selective dose of gamma radiation for enhancement of the thermal stability of chemical structures.

Effect of gamma irradiation dose on the structure and pH sensitivity of ITO thin films in extended gate field effect transistor

Abstract Even though several studies have demonstrated the use of Indium Tin Oxides (ITO) as an extended gate field effect transistor (EGFET), the effect of different doses of gamma radiation on the intrinsic properties of the ITO films has not been considered. This study investigates the effect of gamma irradiation on the structural, optical, morphological and electrical properties as well as pH sensitivity (as an extended gate field effect transistor) of ITO thin films. ITO thin films with thickness of 400 nm were prepared using a radio frequency sputtering technique. The samples were then subjected to various doses of gamma radiation from a Co-60 radio-isotope (0.5 kGy, 1 kGy, 1.5 kGy, and 2 kGy). The structural and morphological changes as well as transmission and absorption of the thin films were analyzed using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field-Emission Scanning Electron Microscope (FESEM) and UV–Vis spectrophotometry, before and after irradiation. The irradiated ITO thin films were then used as an extended gate field effect transistor to determine its ability to improve sensitivity as pH sensors. The grain size and transmittance in the range 300–900 nm of the ITO films were found to decrease with increasing gamma irradiation dose. In contrast, the uniformity and surface roughness of ITO thin films increased with increasing gamma radiation dose due to the formation of lattice defects. Moreover, the electrical resistance of the thin films increased with increasing dose because of the low current density and high number of surface defects associated with irradiation. The pH sensitivity of the ITO thin films improved after irradiation, possibly due to the concomitant increase in surface roughness with increasing radiation dose. The improvements in the pH sensitivity of ITO thin films after irradiation justify their potential use as pH sensors.

Effect of Gamma Radiation Induced on Structural, Electrical, and Optical Properties of N, N′-Dimethyl-3,4,9, 10-Perylenedicarboximide Nanostructure Films

N,N′-Dimethyl-3,4,9,10-perylenedicarboximide (PTCDI-C1) thin films were first prepared by thermal evaporation technique. Then, the prepared films were irradiated with gamma rays at room temperature with different absorbed doses. The structure of PTCDI-C1 films at different doses of gamma radiation was elucidated by x-ray diffraction. The results confirmed that PTCDI-C1 film has a nanostructure morphology. The grain size was observed to decrease slightly with increasing the gamma radiation doses. The temperature dependence of the electrical conductivity was measured in the temperature range of 293–423 K. It was found that the obtained activation energy of PTCDI-C1 films decreased with increasing gamma radiation dose. The optical parameters were obtained using spectrophotometric measurements. The single oscillator model of Wemple–Didomenico was adopted to study the normal dispersion of refractive index. The optical dispersion parameters of PTCDI-C1 films such as dispersion energy, oscillator energy and the high frequency dielectric constant were calculated. Furthermore, the nonlinear susceptibility values of PTCDI-C1 films at different gamma radiation dose were calculated. Also, the dielectric constants of the films were investigated in a large range of frequencies. The fundamental band gap energy values (3.91 eV Eg2 > 50 kGy).

Quantitative analysis of changes in antioxidant in crosslinked polyethylene (XLPE) cable insulation material exposed to heat and gamma radiation

Quantitative analysis of the antioxidant poly(1,2-dihydro-2,2,4-trimethylquinoline) (pTMQ) was conducted on pristine, thermally-aged, and gamma radiation-aged commercial cross-linked polyethylene-(XLPE-)based cable insulation material aged at temperatures 60, 90, and 115 °C, with gamma radiation exposure dose rates of 0, 120, 300, and 540 Gy/h for 15 days. The quantification of antioxidant was performed using pyrolysis gas chromatography-mass spectrometry (Py-GCMS). Oxidation induction time (OIT) was measured using differential scanning calorimetry (DSC) and correlation was made between the quantified depletion of antioxidant and measured OIT. It was observed that, in the case of isothermal aging, the quantity of antioxidant and OIT decreased with increasing gamma radiation dose. In the case of samples exposed to the same gamma radiation dose, the quantity of antioxidant and OIT were observed to decrease with increasing aging temperature. Depletion in the quantity of antioxidant relative to that in the pristine material ranged from 7 to 93% for differently aged samples. The measured decline in OIT ranged from 0 to 80%. Change in the quantity of antioxidant in the material was observed to follow the same trend as the change in OIT when the samples were aged under various conditions. The observations are explained in terms of the reaction between the antioxidant and free radicals created during exposure of the samples to thermal and gamma radiation.

Molecular Diversity Analysis of Two Irradiated Potato Varieties in vitro Revealed by Random Amplified Polymorphic DNA

Potato buds cvs. Spunta and Valor were cultured in vitro on MS solid medium supplemented with 0.2 mg -1 BAP. The resulting plantlets were irradiated with gamma radiation doses 10, 20, 30 and 40Gy. Irradiated single node pieces were transferred onto fresh MS with BAP. Plantlets survival percentage calculated after eight weeks, gamma radiation caused decrease in the survival percentage of micropropagated buds in both Spunta and Valor cultivars ranging from 91.4 % to 28.5% in cv. Spunta and 93.3% to 30.47% in cv. Valor, comparing with the values of the two non-irradiated cultivares 95.2% and 96.2% respectively. Microtubers produced from irradiated plantlets were decreased with increasing gamma radiation doses with changes in size and numbers. The estimated proline content in irradiated plantlets was increased with increasing gamma radiation dose. The genomic DNA of non-irradiated (control) in two cultivars and eight radiation treatments was amplified with 10 RAPD primers that generated 54 polymorphic bands. The highest number of genetic similarity was 0.9672 showed between irradiated plantlets with dose 20 and 30Gy in cv. Valor. However, the highest genetic distance was 0.3995 observed between irradiated plantlets with dose 20Gy in cv. Valor and 30Gy in cv. Spunta. The dendrogram generated by cluster analysis distinguished the irradiated plantlets genetically.

High level gamma radiation effects on Cernox™ cryogenic temperature sensors

Cryogenic temperature sensors are used in high energy particle colliders to monitor the temperatures of superconducting magnets, superconducting RF cavities, and cryogen infrastructure. While not intentional, these components are irradiated by leakage radiation during operation of the collider. A common type of cryogenic thermometer used in these applications is the Cernox™ resistance thermometer (CxRT) manufactured by Lake Shore Cryotronics, Inc. This work examines the radiation-induced calibration offsets on CxRT models CX-1050-SD-HT and CX-1080-SD-HT resulting from exposure to very high levels of gamma radiation. Samples from two different wafers of each of the two models tested were subjected to a gamma radiation dose ranging from 10 kGy to 5 MGy. Data were analysed in terms of the temperature-equivalent resistance change between pre- and post-irradiation calibrations. The data show that the resistance of these devices decreased following irradiation resulting in positive temperature offsets across the 1.4 K to 330 K temperature range. Variations in response were observed between wafers of the same CxRT model. Overall, the offsets increased with increasing temperature and increasing gamma radiation dose. At 1.8 K, the average offset increased from 0 mK to +13 mK as total dose increased from 10 kGy to 5 MGy. At 4.2 K, the average offset increased from +4 mK to +33 mK as total dose increased from 10 kGy to 5 MGy. Equivalent temperature offset data are presented over the 1.4 K to 330 K temperature range by CxRT model, wafer, and total gamma dose.

Effect of Gamma Radiation on the Properties of Jute Reinforced Polyester Matrix Composites

The interest in fiber-reinforced polymer composites is growing rapidly due to its high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost, and low density. In the present work, hessian jute cloth, were used to prepare jute-polyester composites by hand lay-up and heat press molding techniques. The Jute fabrics were also treated with irradiated under gamma radiation (The source strength 50 kCi Cobalt-60) of various doses (2 kGy to 9 kGy). It was found that by using gamma radiation, the mechanical properties of these composites were improved and at 5 kGy doses all the composite structures shows the best mechanical properties. The increase in tensile properties of jute with increasing gamma radiation dose may be due to the intercross-linking between the neighboring cellulose molecules, which resulted in the strength of natural fibre. It was observed that tensile properties increase with gamma pretreatment up to a certain limit and then decrease due to the two opposing phenomena, namely, photocross-linking and photodegradation that took place simultaneously under gamma radiation.

Androgenesis Induced in <i>Nicotiana alata</i> and the Effect of Gamma Irradiation

Nicotiana alata anthers cultured on different modified media based on MS, MT and N were used to obtain haploid plants through direct and indirect ways. The haploid plants resulting on MS medium ranged from 52% - 80%, on MT medium ranged from 32% - 52% and on N medium ranged from 28% - 44%. Accordingly, the best medium used for haploid induction was MS supplemented with 0.2 mgl-l NAA + 0.5 mgl-l KIN. On the other hand, MS medium supplemented with 0.4 mgl-l NAA + 0.5 mgl-l KIN or 1.0 mgl-l BAP + 0.5 mgl-l NAA were the best mediums for callus induction and plant regeneration, respectively. Morphologically, the leaf size, stem highest and diameter, flower size and diameter, anther length and number were about 67% of the diploid plants growth. Irradiated anthers with doses of 0, 2.5, 5, 7.5, 10, 15, 20 and 25 Gy caused reducing the number of haploid plants with increasing gamma radiation dose. For the haploid plants irradiated with same doses, the mortality percentage of bud survival was increasing with increasing gamma radiation dose. The irradiated callus with doses of 0, 5, 10, 15 and 20 Gy was affected negatively on growth rate and morphology. Proline content in irradiated plantlets increased with increasing gamma radiation dose. As well, total soluble protein content was increased with gamma irradiation up to 10 Gy. However, the higher doses caused a severe decrease of total soluble proteins. The production of proline and total soluble proteins in haploid plants were 48.6% and 69.5%, respectively comparing with diploid plants.

Androgenesis Induced in <i>Nicotiana alata</i> and the Effect of Gamma Irradiation

Nicotiana alata anthers cultured on different modified media based on MS, MT and N were used to obtain haploid plants through direct and indirect ways. The haploid plants resulting on MS medium ranged from 52% - 80%, on MT medium ranged from 32% - 52% and on N medium ranged from 28% - 44%. Accordingly, the best medium used for haploid induction was MS supplemented with 0.2 mgl-l NAA + 0.5 mgl-l KIN. On the other hand, MS medium supplemented with 0.4 mgl-l NAA + 0.5 mgl-l KIN or 1.0 mgl-l BAP + 0.5 mgl-l NAA were the best mediums for callus induction and plant regeneration, respectively. Morphologically, the leaf size, stem highest and diameter, flower size and diameter, anther length and number were about 67% of the diploid plants growth. Irradiated anthers with doses of 0, 2.5, 5, 7.5, 10, 15, 20 and 25 Gy caused reducing the number of haploid plants with increasing gamma radiation dose. For the haploid plants irradiated with same doses, the mortality percentage of bud survival was increasing with increasing gamma radiation dose. The irradiated callus with doses of 0, 5, 10, 15 and 20 Gy was affected negatively on growth rate and morphology. Proline content in irradiated plantlets increased with increasing gamma radiation dose. As well, total soluble protein content was increased with gamma irradiation up to 10 Gy. However, the higher doses caused a severe decrease of total soluble proteins. The production of proline and total soluble proteins in haploid plants were 48.6% and 69.5%, respectively comparing with diploid plants.

Structural investigations of bismuth lead borosilicate glasses under the influence of gamma irradiation through ultrasonic studies

The ultrasonic velocity measurements for different compositions of irradiated bismuth lead borosilicate glasses xBi2O3–(50–x)PbO–20B2O3–30SiO2 (x=2, 4, 6, 8, and 10 mol.%) were performed at room temperature using pulse-echo technique. Densities of glass samples were measured by Archimedes’ principle using n-hexane as the immersion liquid. The results from the studies show that ultrasonic velocity, elastic moduli, Poisson's ratio, microhardness, and the Debye temperature increase with increasing bismuth oxide content and increasing gamma-radiation dose (3–12 Gy).

Advanced Carbon-based Material as Space Radiation Shields

ABSTRACTCarbon-based materials including microcrystalline diamond, nanocrystalline diamond, and carbon nanotubes films were prepared by microwave plasma-assisted chemical vapor deposition (MWCVD) technique. While the former were submitted to gamma radiation doses of 1, 5, and 20 Mrad, the latter to low energy electron beam of 30 keV or to 30 GeV/cm2) to study the radiation-induced structural transformation. The characterizations were performed prior to and after irradiation using Raman spectroscopy, scanning electron microscopy, and X-ray diffraction, techniques. Microcrystalline diamond showed a dramatic modification in the structural properties only after a cumulative dose of 26 Mrad (2 Grad/cm2), while nanocrystalline carbon showed a relatively small but systematic transformation with increasing gamma radiation dose. The results indicate that nanocrystalline carbon tends to reach a state of saturation when submitted to 26 Mrad doses of gamma radiation, suggesting the possibility of fabricating radiation buffer materials that would undergo internal sp3 ⇔ sp2 inter-conversion while absorbing ionizing radiation without changing their average microstructure and protecting the device/material underneath. Single- and multi-walled nanotubes exhibited structural modifications after 5.5–8 hrs of continuous exposure to electron beam. The variation in the characteristic X-ray peaks for multi-walled and single-walled corresponding to intertube spacing and the high frequency Raman band around 1580 cm−1 (G band) are reflected in their corresponding spectra. The results indicate that there is an increase in the intertube spacing for multi-walled nanotubes due to electron irradiation. While single-wall nanotubes tends to ‘collapse’ after > 8 hours of exposure forming multi-wall nanotubes analyzed using scanning electron microscopy and Raman spectroscopy. These C materials can be employed for preventing space radiation from reaching sensitive materials and electronic devices at least for short term experiments and entitled them as ‘space radiation shields’.

Electron field emission properties of gamma irradiated microcrystalline diamond and nanocrystalline carbon thin films

Microcrystalline diamond and nanocrystalline carbon thin films prepared by microwave plasma assisted chemical vapor deposition were submitted to gamma radiation in order to study the radiation-induced structural transformation and the corresponding changes in the electron field emission properties. Electron field emission measurements and microstructural characterizations, which included Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and x-ray photoelectron spectroscopy, were performed before and after gamma radiation doses of 1, 5, and 20 Mrads. Microcrystalline diamond showed a dramatic improvement in the emission properties only after a cumulative dose of 26 Mrad, while nanocrystalline carbon showed a relatively small but systematic decrease in turn-on field from 9 to 4 V/μm with increasing gamma radiation dose. The enhancement in emission characteristics associated with the radiation-induced microstructural transformation shows the critical role of defects with their associated electronic defect states, and of sp2-bonded carbon channels in the electron field emission mechanism of nanocomposite carbon materials. The results also indicate that nanocrystalline carbon tends to reach a state of damage saturation when submitted to Mrad doses of gamma radiation, suggesting the possibility of fabricating radiation buffer materials that would undergo internal sp3–sp2 interconversions while absorbing ionizing radiation without changing their average microstructure, which can be employed for preventing radiation from reaching sensitive materials.