Gamma-irradiated Samples Research Articles

Studying some properties of CR-39 detector under the effect of different gamma doses

In the present study the bulk etch rate, the bulk activation energy, the track density and the degree of crystallinity percentage have been examined for gamma irradiated samples with 60Co source at doses ranging from 0 to 200kGy. After gamma irradiation the samples were exposed to zirconium sand to collect α-particle tracks. Samples were etched at 60, 65, 70, 75 and 80°C in 6.25N NaOH solution for 4h. Results indicated that, the bulk etch rate increases with the increase of gamma absorbed dose at different etching temperatures. The bulk activation energy and the track density decreased with the increase of the gamma absorbed dose. The degree of crystallinity percentage for un-etched and etched samples also has been studied for different gamma doses. The increase in bulk etch rate and the decrease in both of bulk activation energy and track density with increase in the gamma dose may be due to the degradation in CR-39 polymeric material.

Effect of europium doping levels on photoluminescence and thermoluminescence of strontium yttrium oxide phosphor

The present paper deals with the effect of europium (Eu3+) doping concentration (0.1–2.5mol%) on photoluminescence (PL) and thermoluminescence (TL) of strontium yttrium oxide (SrY2O4) phosphor. The sample was prepared by the modified solid state reaction method, which is the most suitable method for large-scale production. The prepared phosphor sample was characterized by using X-ray Diffraction (XRD), field emission gun scanning electron microscopy, fourier transform infrared spectroscopy, high resolution transmission electron microscopy, photoluminescence, thermoluminescence and commission internationale de I׳Eclairage techniques. The PL emission was observed in the range of 410–630nm for the SrY2O4 phosphor doped with Eu3+. Excitation spectrum was found at 254 and 325nm, sharp peaks were found around 593, 615 and 625nm with high intensity. From the XRD data, using Scherrer׳s formula, calculated average crystallite size of Eu3+ doped SrY2O4 phosphor is around 32nm. Thermoluminescence study was carried out for the phosphor with UV and gamma irradiation. The TL response of SrY2O4:Eu3+ phosphor for two different radiations was compared and studied in detail. The present phosphor can act as a single host for white light emission in display devices. The detailed process and possible mechanisms for PL and TL are studied and discussed. For the variable concentration of Eu3+ on PL studies the PL intensity increases with increasing the concentration of dopant and the concentration quenching found after 2mol% of Eu3+ the optimized concentration was 2mol%, which is suitable for the display device application. In TL glow curve the optimized concentration was 1mol% for the UV irradiated sample and 0.2mol% of Eu3+ for the gamma irradiated sample and beta irradiated sample for 10 Gy dose. The kinetic parameters were calculated by the computerized glow curve deconvolution (CGCD) technique.

Dielectric relaxation of gamma irradiated muscovite mica

In the present research, the dielectric relaxation of gamma irradiated muscovite mica was studied in the frequency range of 0.1Hz–10MHz and temperature range of 653–853K, using the dielectric permittivity, electric modulus and conductivity formalisms. The dielectric constants (ϵ′ and ϵ′′) are found to be high for gamma irradiated muscovite mica as compared to the pristine sample. The frequency dependence of the imaginary part of complex electric modulus (M′′) and dc conductivity data conforms Arrhenius law with single value of activation energy for pristine sample and two values of activation energy for gamma irradiated mica sample. The experimentally assessed electric modulus and conductivity information have been interpreted by the Havriliak–Negami dielectric relaxation explanation. Using the Cole–Cole framework, an analysis of real and imaginary characters of the electric modulus for pristine and gamma irradiated sample was executed which reflects the non-Debye relaxation mechanism.

감마선 조사에 의한 총목피(Aralia elata Cortex)의 추출수율 증대 및 항산화 효과

This study was designed to investigate the effects on anti-oxidative activities and increasing extraction yield of Aralia elata Cortex by gamma irradiation. Electron spin resonance (ESR) analysis as physical techniques for irradiation identification of Aralia elata showed that a pair of peak appeared on a space of 6.0 mT at the left and right of symmetric unspecific central ESR spectrums, confirming that the plant was gamma-irradiated. The optimum extracting conditions for preparing gamma irradiated samples from Aralia elata Cortex were to extract with 50% ethanol for 15 hrs after 10 kGy irradiation. DPPH scavenging activity and ABTS radical cation inhibitory activity of the water and 50% ethanol extracts from non irradiated and irradiated Aralia elata Cortex was very high as over 80% and 98%, respectively, at tested low concentration of 50 μg/mL. Antioxidant protection factor (PF) as anti-oxidation indicator of lipophilic compounds showed a very high level of activity as 2.18~2.78 PF. As for TBARs, water and ethanol extracts showed high level. Increase of TBARs inhibitory activity of water extracts was not shown by gamma-ray irradiation but ethanol extracts showed slight increasement of TBARs inhibitory activity with 10 kGy gamma-ray irradiation. These results shown confirmed increasement of extraction yield for phenolic compounds and anti-oxidative activity from Aralia elata. Thus, the treatment of gamma- irradiation can be used a way to amplify a solubility for biological active compounds and anti-oxidative activity in plants.

Radiation induced centers in irradiated SrB4O7 doped europium and their role in thermally stimulated reactions: Thermally stimulated luminescence, fluorescence and electron paramagnetic resonance studies

Polycrystalline samples of strontium tetraborate (SrB4O7: SBO) samples doped with different concentrations of europium (0%, 0.05%, 1% and 2%) were synthesized using solid state reaction in air at high temperature. These samples were characterized by X-ray diffraction (XRD), photoluminescence (PL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) techniques. X-ray diffraction studies indicated that SrB4O7 has orthorhombic structure with lattice parameters a=4.237±0.001, b=4.431±0.001, c=10.704±0.010, space group Pnm2i, Z=2. Thermally Stimulated Luminescence (TSL) investigations on the gamma irradiated sample showed an intense glow peak at 407K and a weak glow peak at 500K. The trap parameters namely activation energy (E), order of kinetics (b) and the frequency factor (s) for the main peak at 407K were determined using the glow curve method. Fluorescence studies showed weak emission at ca 367nm, which was attributed to f-d transition (4f65d-4f7) of Eu2+ ions in the host lattice, whereas an intense emission in the range 570–650nm was assigned to 5D0→7FJ, J=0,1,2,3 and 4 transition of Eu3+ in the host lattice. The large value of I(R)/I(O) suggested that Eu3+ ions are situated at sites without center of inversion (lower symmetry) in SBO matrix. EPR studies suggested the formation of boron–oxygen hole trapped center viz, BOHC, electron trapped at oxygen vacancies and some impurity radicals like NO32− and CO2− radicals in SBO on irradiation. EPR temperature variation studies in the range 300–475K on gamma irradiated europium doped samples, suggested a recombination process occurring between boronoxygen hole trapped species and electron trapped species and subsequently energy is transferred to Eu3+ ion, which on de-excitation yields thermally stimulated luminescence yielding an intense TSL glow peak at 407K.

Effect of gamma irradiation on the structural, thermal and optical properties of Makrofol BL 2–4

Makrofol BL 2–4 is an extrusion film based on Makrolon polycarbonate. It comprises excellent die-cutting performance combined with high light transmission and moderate light scattering properties. It is a class of polymeric solid state nuclear track detectors which has many applications in various radiation detection fields. In the present work, Makrofol samples were irradiated using different gamma doses ranging from 10 to 350 kGy. The structural modifications in the gamma-irradiated Makrofol samples have been studied as a function of dose using different characterization techniques such as X-ray diffraction, intrinsic viscosity, Fourier transform infrared spectroscopy, thermogravimetric analysis, refractive index and color difference studies. The gamma irradiation in the dose range 20–200 kGy led to a more compact structure of Makrofol polymer, which resulted in an improvement in its thermal stability with an enhancement in its structural and optical properties.

On the photo and thermally stimulated luminescence properties of U doped SrBPO5

Un-doped and uranium doped SrBPO5 samples were synthesized using solid-state reaction route and investigated for their photo and luminescence properties. Photoluminescence (PL) spectrum of uranium doped sample showed five peaks at 502, 524, 547, 569 and 597nm. The average frequency of symmetric stretching of O=U=O in the ground electronic state was found to be about 757cm−1. PL decay time measurements on the system confirmed the stabilization of uranium as UO22+ in the matrix. Thermally stimulated luminescence (TSL) measurements carried out on gamma irradiated SrBPO5:U sample showed a glow peak at 390°K, whose spectral characteristics was found to be typical of UO22+. The trap parameters were evaluated using different heating rate method. Room temperature EPR data suggested the formation of borate and oxygen based radical centers in the gamma-irradiated sample. Detailed EPR-TSL correlation studies confirmed the destruction of the oxygen radical to be responsible for the observed glow peak.

UV and gamma ray induced thermoluminescence properties of cubic Gd2O3:Er3+ phosphor

This paper reports the thermoluminescence properties of Er3+ doped gadolinium oxide nanophosphor. The phosphor is prepared by high temperature solid state reaction method. The method is suitable for large scale production. Starting materials used for sample preparation were Gd2O3, Er2O3 (0.5–2.5mol%) and fixed concentration of boric acid using as a flux. The prepared samples were characterized by X-ray diffraction technique and the particle size calculated by Scherer's formula. The surface morphology of prepared phosphor is determined by scanning electron microscopic (SEM) technique. Functional group analysis was done by Fourier transform infra-red spectroscopy (FTIR) analysis. The elemental analysis of prepared sample was determined by energy dispersive X-ray analysis (EDX) and the exact particle size of prepared phosphor for the different concentration of dopant (Er3+) was evaluated by transmission electron microscopy (TEM) technique. The prepared phosphors for different concentration of Er3+ were examined by thermoluminescence (TL) glow curve for UV and gamma irradiation. The UV 254 nm source was used for UV irradiation and Co60 source was used for gamma irradiation. The samples show well resolved broad peak covered the temperature range 50–250 °C and the peak temperature found at 126 °C for UV irradiation and higher temperature peak at 214 °C for gamma irradiation. The effect of heating rate on TL studies was presented for optimized sample. Here UV irradiated sample shows the formation of shallow trap (surface trapping) and the gamma irradiated sample shows the formation of deep trapping. The estimation of trap formation was evaluated by knowledge of trapping parameters. The trapping parameters such as activation energy, order of kinetics and frequency factor were calculated by peak shape method. Here most of the peak shows second order of kinetics. The effect of gamma and UV exposure on TL studies was also examined and it shows linear and sublinear response with dose which indicates that the sample may be useful for TL dosimetry.

Verification of a new biocompatible single-use film formulation with optimized additive content for multiple bioprocess applications.

Single-use bioprocessing bags and bioreactors gained significant importance in the industry as they offer a number of advantages over traditional stainless steel solutions. However, there is continued concern that the plastic materials might release potentially toxic substances negatively impacting cell growth and product titers, or even compromise drug safety when using single-use bags for intermediate or drug substance storage. In this study, we have focused on the in vitro detection of potentially cytotoxic leachables originating from the recently developed new polyethylene (PE) multilayer film called S80. This new film was developed to guarantee biocompatibility for multiple bioprocess applications, for example, storage of process fluids, mixing, and cell culture bioreactors. For this purpose, we examined a protein-free cell culture medium that had been used to extract leachables from freshly gamma-irradiated sample bags in a standardized cell culture assay. We investigated sample bags from films generated to establish the operating ranges of the film extrusion process. Further, we studied sample bags of different age after gamma-irradiation and finally, we performed extended media extraction trials at cold room conditions using sample bags. In contrast to a nonoptimized film formulation, our data demonstrate no cytotoxic effect of the S80 polymer film formulation under any of the investigated conditions. The S80 film formulation is based on an optimized PE polymer composition and additive package. Full traceability alongside specifications and controls of all critical raw materials, and process controls of the manufacturing process, that is, film extrusion and gamma-irradiation, have been established to ensure lot-to-lot consistency. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1171–1176, 2014

Gamma radiation roused lattice contraction effects investigated by Mössbauer spectroscopy in nanoparticle Mn–Zn ferrite

Nanopowders of MnxZn1−xFe2O4 with x=0.4, 0.5 and 0.6 were synthesized using a combustion synthesis method. X-ray diffraction (XRD) patterns obtained on samples confirmed formation of monophasic cubic phase material. Lattice parameters and X-ray densities were obtained from rietvield refinement of the XRD patterns. All samples were radiated with gamma radiation with a dose of 200Gy obtained from 60Co source. Structural and physical parameters, such as lattice constant, X-ray density and particle size, determined for as prepared samples (SA) and gamma irradiated samples (SR), showed extraordinary variations in their values. Saturation magnetizations (MS), remnant magnetization (MR) and coercive field (HC) for both sets of samples illustrated an enhancement in their values for SR samples. Investigations were carried out using Mössbauer spectroscopy to divulge structural and magnetic information of all samples. Room temperature Mössbauer spectra were fitted with five magnetic sextets and a symmetric paramagnetic doublet for the data obtained on samples except for x=0.4, SA sample. The presence of well defined doublets in the spectra of SA and SR samples is attributes of superparamagnetism, indicating the reduction in A–B superexchange interaction due to dilution of sub-lattice by Zn ions. Cation distribution at A site and B site, estimated from Mössbauer data exhibited amazing alterations which were highly stable. The variations in physical, structural and magnetic properties observed are attributed to change of Fe2+/Fe3+ and Mn+2/Mn+3 ratios in gamma-irradiated samples.

(Invited) Effect of Annealing on Electronic Carrier Transport Properties of Gamma-Irradiated AlGaN/GaN High Electron Mobility Transistors

AlGaN/GaN High Electron Mobility Transistors (HEMTs) are the most advanced electronic nitride devices to be used at high temperatures and in harshly radiated environments. A clear understanding of radiation effects on these devices is essential in order to predict their behavior in space and terrestrial applications including military, nuclear and high energy physics. Only a limited amount of insight exists into the behavior of III-N based junction transistor after exposure to gamma irradiation. Investigation of gamma-irradiated device properties will provide important information about the defects in semiconductor heterostructures. Therefore, it is important to understand how defects are created by gamma-rays and how they can be healed by annealing. Here we present the impact of gamma-irradiation on AlGaN/GaN heterostructures fundamental properties including carrier transport and recombination. We also report the effect of annealing at 200o C over 25 min on gamma-irradiated samples through monitoring of minority carrier diffusion length using Electron Beam Induced Current (EBIC) method.We found the relationship between dose, diffusion length and its activation energy after gamma-irradiation and after annealing treatment. Temperature dependent EBIC measurements yielded a decrease in diffusion length with corresponding increase in activation energy after the gamma-irradiation.The increase in activation energy is likely an indication of the creation of deeper gamma irradiation induced defect traps due to nitrogen vacancies. These deep traps reduce the carrier concentration and mobility and increase the activation energy related to carrier recombination. It is evident from our results that annealing of HEMTs that were gamma-irradiated with moderate dose leads to the recovery (depending on dose) of minority carrier diffusion length. The recovery is also reflected in the activation energy returning to its pre-irradiated value. The level of recovery of gamma-irradiated devices after annealing treatment depends on the dose of irradiation. Increase in diffusion length after annealing had been attributed to a reduction in point defects (nitrogen vacancies) induced in AlGaN/GaN by gamma-irradiation.

Effect of heat treatment on some properties of CR-39 nuclear track detector irradiated by gamma ray

The present study aims to determine the effect of heat treatment on the bulk etch rate of un-irradiated and gamma irradiated CR-39 detector. Track density and the damage in samples surface due to the heat treatment have also studied for the un-irradiated and gamma irradiated CR-39 detector. The samples of CR-39 polymer track detector has been exposed to γ-ray from 60Co source with doses 0, 10, 50, and 100 kGy then exposed to α-particles from the air radon gas. These samples have been annealed at 50, 100 and 150 °C for different annealing times then etched in 6.25 N NaOH solution at 70 °C for 6 h. The variation of bulk etch rate and the track density as a function of annealing temperature have been studied. The bulk etch rate increases with gamma dose and with increasing both of the annealing time and the annealing temperature. The decrease of track density with increasing the annealing time and the damage of annealed gamma irradiated CR-39 samples clarify serious degradation under the effect of heat treatment.

Reliability of equivalent-dose determination and age-models in the OSL dating of historical and modern palaeoflood sediments

The challenge of accurately estimating the deposition age of incompletely-bleached samples in luminescence dating has motivated developments in the analysis of single grain dose distributions, and a number of statistical approaches have been proposed over the last few years. In this study, we compare the behaviour of the arithmetic average, so-called ‘robust statistics’, the Central Age Model (CAM), the Minimum Age Model (MAM) and the Internal–External Consistency Criterion (IEU) and lowest 5% method, when applied to single-grain dose distributions from a sequence of eight recent (40–1000 years) flash-flood deposits. These sediments are expected to be incompletely bleached, but all have age control from historical records. Modifications were made to allow the use of the standard CAM and MAM models with dose distributions containing near zero and negative dose values. An assessment of minimum over-dispersion (OD) is based on dose recovery tests based on gamma-irradiated samples. We then present a detailed analysis of the effect of an additional uncertainty added to the individual dose estimates on the burial dose estimates from the MAM and the IEU approach. The results of the various models are discussed in terms of the accuracy of the resulting age, and we conclude that, overall, the IEU approach generates the most accurate ages. We also demonstrate that accurate doses can be obtained for those older samples for which uncertainties of ∼40 years are unimportant by applying the IEU model to small aliquot (∼30 grains) dose distributions. From our study we conclude that these and similar young slack-water flood deposits can be accurately dated using quartz OSL, opening up the possibility of establishing time series of flood discharge in catchments for which no instrumental or historical record exists.

The Influence of Gamma Irradiation on Repeated Recycling and Accelerated Acrylonitrile Butadiene Styrene Terpolymer Aging

Electronic waste also referred to as waste electrical and electronic equipment (WEEE) is the fastest growing waste stream in Europe today. The fast exchange pace of mobile phones, television sets and computers create an important need to develop recycling areas to take care of, reuse and recycle all the materials they contain. One common plastic in WEEE is acrylonitrile butadiene styrene terpolymer (ABS). Repeated recycling of plastic causes it to chemically degrade and one of the unwanted effects is the shortening of the polymer chains. Gamma irradiation is known to be able to crosslink polymers and thus reverse the chain shortening. Therefore, the hypothesis of this study is that gamma irradiation of ABS would have a beneficial effect when recycling plastic. Comparative experiments of gamma irradiation has been done according to two methods: A single gamma irradiation (40 kGy) before the extrusion and aging cycles, and the effect of four 10 kGy doses delivered before each of the re-extrusion steps were completed. The results show that gamma irradiation has an impact on the mechanical and rheological properties of ABS. The yield stress increased with irradiation doses of 0, 10, 50 and 400 kGy. The viscosity also increased in the test samples with irradiation doses of 0, 10, 100 and 200 kGy. In the multi-recycling and accelerated aging test, there was a significant reduction in stiffness for the gamma irradiated samples after the second out of four cycles which cannot be fully explained.

Kinetic parameters and TL mechanism in cadmium tetra borate phosphor

Polycrystalline powder samples of cadmium tetra borate were synthesized by a simple solid state sintering technique and gamma irradiated sample showed a simple Thermoluminescence (TL) glow peak around 460K. The TL kinetic parameters of gamma irradiated phosphor were determined by initial rise (IR), isothermal decay (ID), peak shape (PS), variable heating rate (VHR) and glow curve de-convolution method. The kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics (b) were calculated by IR, ID, PS and VHR methods are in the order of ~1.05eV, 109–1012s−1 and 1.58, respectively. From the results of TL and PL emission studies carried out on the phosphor revealed that the defect centers related to TL is different from that for PL. EPR measurements were carried out to identify the defect centers formed in cadmium tetra borate phosphor on gamma irradiation. Based on EPR studies the mechanism for TL process in cadmium tetra borate is proposed in this paper

Discriminating gamma-irradiated soybean seeds by 1H NMR-based metabonomics

Gamma irradiation has been paramount for enhancing the quality of grain production, mainly in terms of distribution and storage. Gamma irradiation classification models for soybeans, however, are still in development. In this paper, we present a metabonomic model able to distinguish between gamma-irradiated and non-irradiated soybeans. The metabonomic model works on 1H NMR spectra of chloroform extracts and makes use of PCA and PLS-DA formalisms to classify the samples and to investigate which spectral bins are discriminatory. The model has presented an accuracy of 100% in the face of a real dataset involving 49 samples from diverse cultivars. In turn, the most important chemical shifts (δ) for discriminating among the samples were δ 1.57 and 1.62 ppm, which are assigned to β-carboxyl methylene groups of aliphatic chains of fatty acids. Besides, the gamma-irradiated samples showed an increasing in the integration areas at δ 1.57 ppm (assigned to free fatty acid) whilst non-irradiated samples showed an increasing in the integration areas at δ 1.62 ppm (assigned to fatty acids linked to glycerol as esters).

Radiation Stimulated Permanent Alterations in Structural and Electrical Properties of Core-Shell Mn-Zn Ferrite Nanoparticles

A series of core-shell type nanoparticle samples of MnxZn1-xFe2O4were prepared by auto-combustion technique with x=0.3, 0.5, 0.7, 1.0. Subsequent to the structural and electrical property investigation the samples were irradiated with gamma radiation for different time intervals using60Co source. A significant decrease in lattice parameter and particle size was observed in gamma irradiated samples. Electrical resistivity of irradiated samples was found to decrease with the increase in γ-radiation dose. Frequency and temperature dependent dielectric constant and dissipation constant measurements carried out showed multifold enhancement of dielectric constant with pragmatic increase in dielectric loss, in γ-irradiated samples.

Effect of gamma irradiation on physicochemical properties of stored pigeon pea (Cajanus cajan) flour.

The effect of gamma irradiation at various doses (5, 10, 15, 20 kGy) was observed on pigeon pea flour stored for 3 months on proximate composition, functional properties, and peroxide value. Sensory evaluation was also carried out on bean cake (moinmoin) made from nonirradiated and irradiated pigeon pea flour. The results showed that stored gamma-irradiated samples had significantly lower (P < 0.05) value of protein and little or no effect on moisture content. There were slight decreases in crude fiber and ash content of the irradiated samples compared with the control sample. The result of functional properties of the irradiated flours showed slight increase in water absorption capacity, swelling capacity and bulk density. The peroxide value of crude oil increased significantly with dose increases for the period of storage. The sensory evaluation of moinmoin samples prepared from irradiated pigeon pea flour showed no significant difference from the moinmoin sample prepared from nonirradiated flour. It can be concluded that gamma irradiation can extend the shelf life of pigeon pea flour.

Gamma-induced augmentation in EBHA: A dielectric and electro-optical study

The gamma irradiation technique has been used to alter the dielectric and electro-optical properties of a liquid crystal material. The present paper reports a comparative study of dielectric and electro-optical properties of unirradiated EBHA nematic liquid crystal (NLC) with gamma-irradiated EBHA NLC. The dielectric measurement has been performed with variation in voltage and temperature within the frequency range 100 Hz - 10 MHz. Variations in response time for both gamma-irradiated and unirradiated samples have also been measured and are well explained in the present paper.

Modification induced by gamma irradiation in Bayfol CR 1-4 polycarbonate

Bayfol CR 1-4 polycarbonate is a class of polymeric solid state nuclear track detector which has many applications in various radiation detection fields. Samples from sheets of Bayfol have been irradiated with gamma doses ranging from 100 to 620 kGy. The structural modifications in the gamma-irradiated Bayfol samples have been studied as a function of dose, using different characterization techniques such as X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, intrinsic viscosity and refractive index. The results indicate that the carbonyl group (C˭O) degraded under irradiation up to 200 kGy. This degradation, reported by FTIR spectroscopy enhanced the degree of ordering in the degraded samples as revealed by the XRD technique. Above 200 and up to 620 kGy, cross-linking is achieved, leading to an increase in the intrinsic viscosity from 0.41 to 0.78 at 35°C, indicating an increase in the average molecular mass. On the other hand, the resultant effect of gamma irradiation on the thermal properties of Bayfol has been investigated using thermo-gravimetric analysis, results indicating that the gamma irradiation in the dose range 200–620 kGy led to a more compact structure of Bayfol polymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition due to cross-linking. In addition, the V–I characteristics of the polymer samples were performed, results indicated that at higher voltage, the conduction mechanism of Bayfol CR 1-4 was identified as the Poole–Frenkel type.