Papers by Keyword: Gamma Irradiation

Abstract: This study aims to assess the morphological, thermal, chemical structure and mechanical properties of the gamma-irradiated and conventional (unirradiated) test specimens that were 3D printed using a methacrylate-based photo-curable resin and a stereolithography (SLA) 3D printer. The irradiated test specimens were exposed to 50 kGy gamma-ray dose. The morphological, thermal, chemical structure and mechanical properties of the irradiated and unirradiated test specimens were characterized using the Atomic Force Microscope (AFM), Differential scanning calorimeter (DSC), Thermogravimetric analyzer (TGA), Fourier Transform Infrared Spectrometer (FTIR) and Universal Testing Machine (UTM). Results showed that irradiated test specimens exhibited lower surface roughness compared to the unirradiated specimens. Gamma-irradiated specimens also showed improved tensile strength and modulus of elasticity by 12.2% and 12.4 %, respectively. FTIR, DSC and TGA results showed no significant changes in the chemical structure and thermal properties of the 3D printed methacrylate-based resin after subjecting to gamma irradiation.

Abstract: 3D printing is now being applied in various research areas due to its ability to produce highly complex parts whenever needed. This is highly helpful in the fields of robotics; radiation environment monitoring and space applications where stand-alone equipment are usually required. In this work, FDM 3D-printed polycarbonate acrylonitrile butadiene styrene (PCABS) samples were subjected to 1 kGy to 9 kGy of gamma irradiation from a Cobalt-60 irradiator. Parameters such as infill density and dose rate were modified to determine the best setting to improve the mechanical characteristics of the 3D-printed thermoplastic. Results show that samples with lower infill density obtain higher ultimate strength when exposed to higher doses of radiation.

Abstract: Activated carbons (ACs) are a versatile group of adsorbents for water pollution control, especially organic dyes. Harsh chemicals and high temperatures are required for the activation process of ACs, which becomes a significant concern due to their toxicity and harmful effects on human health and the environment. Gamma irradiation, an alternative green technique, is a promising strategy for pretreatment and escalates the nitrogen or oxygen functional group of ACs. The current study provides the modification of ACs by the gamma irradiation in the various pH (5-11) of urea solution. The modified ACs were characterized by scanning electron microscopy (SEM), nitrogen gas adsorption-desorption analysts (BET), temperature program desorption (TPD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray diffraction spectroscopy (XRD). The point of zero charges and dye adsorption capacities were determined. This finding demonstrates that the ACs can be modified by gamma irradiation at 25 kGy in the urea solution media. The degree of graphitization enhanced significantly at pH 11(AC-pH11). The oxygen-rich functional groups created by radiation assists could enhance the electrostatic attraction between acid gases or cationic dyes. AC-pH11 also was able to adsorb methylene blue (160.73 ± 1.70 mg/g) greater than methyl orange (127.57 ± 2.22 mg/g).

Abstract: The influence of mechanical activation and gamma-irradiation on the structural-phase state of Ti-Al-C powder reagents was studied. The following compositions were used for research: 1) 78% Ti + 14% Al + 8% C; 2) 80% Ti + 12% Al + 8% C; 3) 81% Ti + 10% Al + 9% C. Mechanical activation of these compositions leads to an increase in the diffuse background, a decrease in the intensity of diffraction reflections of mixture components and a broadening of peaks, as well as micro-deformations. Depending on the ratio of components, the structural parameters can either increase in comparison with the initial ones, or decrease. The effect of gamma radiation with a dose rate of 1 Gy/s and accumulated dose of 3·10⁴ Gy on the mechanocomposites of the Ti-Al-C system causes unsystematic change in crystal lattices of elements, which can be explained by radiation-stimulated diffusion. Gamma-irradiation also reduces micro-deformations that occur after mechanical activation, while crystallites of the components remain nanoscale.

Abstract: The Study on synthesis of chitosan prepared by gamma irradiation and multi-stage deacetylation as chitosan-silica membrane has been carried out. Synthesis of chitosan is carried out by deproteination with papain, demineralization, and deacetylation. Deacetylation of chitosan using gamma irradiation with 0, 5, 10, 15, 20, and 25 kGy and two and multi-stage deacetyllation. The synthesis of chitosan silica composite using sol gel method with the ratio of 1:1; 1:2; and 1:3. Based on the study, gamma irradiation increase deacetylation degree of chitosan and minimize the sodium hydroxide needed for deacetylation chitosan. The multi stage deacetylation increase the efficiency procedure for increase deacetylation degree of chitosan. Chitosan-silica composite has been synthesized by sol gel method. The gamma radiation doses have significantly influence on the deacetylation degree of chitosan. Gamma irradiation and multi stage deacetylation increase the efficiency procedure for preparation chitosan and chitosan-silica composite.

Abstract: Cobalt oxide thin film (Co₃O₄) has been prepared from cobalt chloride with distilled water on conducting glass substrates Fluorine doped Tin Oxide (FTO) at (400^ºC) by depositing chemical spray pyrolysis, with thickness (200 nm). The structural properties are studied by XRD. Also, optical properties and electrical properties of Co₃O₄ thin film are studied by UV spectroscopy and Cyclic voltammetry (CV) respectively. The effects of gamma irradiation on optical properties are also examined. XRD results showed that the film was polycrystalline with cubic structure having preferred orientation (111). The as-prepared Co₃O₄ film exhibits a noticeable EC behaviour with reversible colour which changes from dark grey to pale yellow with bleaching time (55 s) and colouring time (40 s). After irradiation, the optical properties showed that as the transmittance decrease leads to decrease the direct optical band gap from (3.68eV) to (3.55eV)

Abstract: We tested stability of 43 selective sorbents, covering the widest range of functional groups, efficiency of sorption, method of production, and which are theoretically useful for sorption of cesium, strontium, cobalt, arsenic and actinoids. We present 3 of them: A = TiO₂, B = Al₂O₃ and C = MxH(TiO)₄(SiO4)₃ . z H₂O. In first testing, sorbents were exposed to the model solution of boric acid for 168 hours, in which they were mixed in a closed container with a rotator. After the exposure, sorbent solutions were filtered and analysed by spectroscopic techniques (Infrared Spectroscopy (IR), Raman Spectroscopy (RS) and newly by Scanning Electron Microscopy (SEM), combined with Energy Dispersive Spectroscopy (EDS)). Exposed spectra were compared with spectra of new, non-exposed sorbents. In second testing, sorbents were exposed to gamma radiation for 12 days with total dose 666 ± 43 kGy, produced by cobalt bomb and analysed by same techniques. The aim of our testing was to find out how sorbents behave in model boric acid solution and what effect has the gamma radiation on sorbent spectra and to analyse sorbents by SEM with EDX.

Abstract: Kaempferia parviflora rhizomes exposed to gamma irradiation at doses of 0, 5, and 7.5 kGy were evaluated every 3 months for their microbial loads, contents of 5,7-dimethoxyflavone (DMF), total phenolic contents, and antioxidant activities (DPPH and FRAP assays) during 12 months of storage at 25 °C. After gamma irradiation, microbial loads were reduced below acceptable limits. Phytochemical contents in irradiated samples were significantly increased as compared to those of the control (0 kGy) while DPPH radical scavenging activities were significantly decreased. However, gamma irradiation had no effect on FRAP values. During storage of irradiated samples, phytochemical contents and antioxidant activities were gradually decreased whereas microbial loads were progressively increased. Even so, microbial quality of irradiated samples was less than acceptable limits through 12 months' storage. Gamma irradiation at doses of 5 and 7.5 kGy was sufficient to control microbial growth and T. castaneum infestation of K. parviflora rhizomes within acceptable limits for at least 12 months at 25 °C. Additionally, 5 and 7.5 kGy were effective doses to retain DMF and phenolics in K. parviflora rhizomes.

Abstract: Uncontrolled hemorrhage is the leading cause of death. The efficient hemostatic dressings are needed to promote coagulation and hold ongoing hemorrhage. Hydrogels are hydrophilic polymers with three-dimensional network structures with high swelling capacity to prevent accumulation of exudates. Hydrogels prepared from polyvinyl alcohol (PVA) grafted with chitosan have attracted considerable attentions due to their biocompatibility, high moisture balance property, and transparency. In this study, alginate was utilized to improve elasticity and thermal stability, also enhance hydrophilicity and increase swelling ability. The hydrogels composed of PVA (7.5 % w/v), chitosan (0.05 % w/v), and alginate (0.2, 0.4, and 0.6 % w/v) were synthesized by gamma irradiation technique at total dose of 15 kGy. The results showed that the increasing of alginate concentration in the total reactant mixture can improve elasticity, swelling capacity and the equilibrium degree of swelling (EDS), and decrease water vapour transmitted rate/moisture vapour transmitted rate (MVTR). The hydrogel wound dressing with 0.6 % of alginate concentration was the best product in this study with 79.49 % gel content, 608.65 % swelling ratio, 628.32 % EDS in 22 hours, elasticity 62.58 KPa, evaporation rate (MVTR) 105g/m2 h, degraded at temperature of 298.89oC, and the weight loss was reached 88.84 % (w/w).

Abstract: Glass fibre reinforced epoxy (GRE) composites, used as mechanical support and thermal insulators for superconducting magnets of fusion reactors, have been exposed to gamma irradiations at both higher and lower order ranges of doses. Hand layed E-glass fibre/epoxy composite samples, exposed to gamma-irradiations of cumulative doses of both low strength (10, 20, 30, 40, 50 and 60 kGy) and high strength (0.5, 2.5, 6.5, 8.5 and 10.5 MGy) reveal a huge lowering of the ILSS (inter laminar shear strength) for its exposure to low strength dose irradiation. However, improved ILSS values are recorded for high dose exposures. At both high and low doses of exposure to irradiation the T_g (glass transition temperature) got improved initially with a decreasing trend towards the later stages of exposures. Thermo-gravimetric analysis (TGA) test reveals lowest initial decomposition temperature (IDT) for the composite sample irradiated to maximum dose (10.5 MGy). Activation energy () values of gamma-irradiated composite samples for thermal decomposition were found less compared to that for as-cured composite. FTIR spectra of irradiated samples reveal formation of oligomers confirming the trend of activation energy of irradiated composite. FESEM fractographs of the irradiated composite fracture samples reveal several modes of failure.