Papers by Keyword: γ-Irradiation

Abstract: Cd_1-0.06Mn_0.06Te epitaxial thin films were synthesis on glass substrates by the Molecular Beam Condensation (MBC) method in the vacuum evaporation equipment УВН-71-ПЗ with steam-oil pumping and nitrogen trap at working pressure of residual gas (1÷2)x10^-4 Pa. By using additional source of Te vapor and controlling temperature, it has been determined the optimum conditions for obtaining Cd_1-0.06Mn_0.06Te epitaxial films with a perfect structure, clean and smooth surface, without of second phase inclusions. XRD investigations showed that Cd_1-0.06Mn_0.06Te epitaxial films grow on glass substrates on the (111) plane of the face-centered cubic lattice with the lattice parameter of a = 6.481 Å. Effect of γ-irradiation on XRD spectra of Cd_1-0.06Mn_0.06Te epitaxial films reveals that, XRD patterns of initial and γ-irradiated samples did not show any phase transformations, however there is a variation in relative intensities of diffraction peaks. It has been found that Cd_1-0.06Mn_0.06Te epitaxial films with a film thickness of d=15 µm, absorb light up to a wavelength of λ=765 nm and at λ>765 nm the absorption begins to gradually decrease and then the material becomes transparent. The obtained results indicate that Cd_1-0.06Mn_0.06Te epitaxial films absorb light quanta in the visible and infrared spectral regions. Iirradiation of Cd_1-0.06Mn_0.06Te epitaxial films with γ rays at low irradiation doses leads to a change in the optical parameters, the profile of the spectrum curves and the intrinsic absorption edge. In additions to experimental studies, a theoretical ab initio calculations of band structure (BS) of ideal and defective semiconductors of Cd_1-0.06Mn_0.06Te has been also carried out by using Density Functional Theory (DFT) method via Atomistix ToolKit computer program. The band gap energy has been calculated as E_g = 1.6 eV for ferromagnetic (FM) and E_g = 1.7 eV for antiferromagnetic (AFM) state of Cd_1-0.06Mn_0.06Te compound. The results of theoretical calculations on the band gap energy of ideal and defective Cd_1-0.06Mn_0.06Te semiconductors are in a good agreement with experimental findings.

Abstract: This paper highlights a study on the effects of medium dose gamma (γ) irradiation towards physical properties of TiO₂ nanoparticles. Doses applied for gamma irradiation are 60, 100 and 150 kGy. Structural and morphological results show that gamma radiation did not change the crystallinity and shapes of TiO₂ nanostructures. Ratio percentages of anatase:rutile for irradiated samples is around 89:11. Agglomerated samples shown in morphology images is support with the existence of binodial shapes peak from particles size distribution analysis.

Abstract: Hydrogel dressings for biomedical application were obtained by γ-irradiation of poly-N-vinipirrolidon (PVP), agar-agar, polyethylene glycol and silver nitrate solution. Influence of irradiation doses (range from 25 kGy to 75 kGy), silver nitrate concentration and PVP concentration in initial monomer mixture on properties of obtained material were investigated. Presence and distribution of silver nanoparticles in obtained bandages is confirmed by optical microscopy and atomic force spectroscopy. Antimicrobial activity study in vitro showed antimicrobial activity, flexibility, high sorption capacity to water and biological fluids.

Abstract: This study investigated the influence of ⁶⁰Co-γ-irradiation on the structure and properties of Cu-Al-Ni shape memory alloys. The phase transformation temperatures were evaluated by differential scanning calorimeter (DSC). It was found that the γ-irradiation had a complex influence on the phase transformation parameters of Cu-Al-Ni SMAs. However, the transformation temperatures were shifted and a new curve was obtained after exposure to different irradiation doses. The thermodynamic parameters such as enthalpy and entropy tended to increase/decrease depending on the amount of the exposure. The structural properties of the exposed samples were studied by using optical microscopy and hardness measurements at room temperature. It was also found that the structural-properties of the Cu-Al-Ni SMAs were completely affected by the amount of the applied γ-irradiation dose.

Abstract: In this work, the effect of γ-irradiation on neat polypropylene (PP) and PP with the stabilizers have been studied by means of wide-angle X-ray diffraction (WAXD) and tensile properties. There is a new reflex 300, β-phase, appeared in irradiated neat PP sample, compared with non-irradiated neat PP sample. When T/S ratio are 0.1 wt%/0.1 wt% and 0.1 wt%/0.3 wt% of PP, the reflex 300 of irradiated PP with different radiation doses all increased. However T/S content is 0.1 wt%/0.5 wt% of PP, the reflex 300 is not appeared. Among the samples which contain stabilizers, the stabilization of PP against γ-irradiation increased, compared with neat PP.

Abstract: Different sterilization techniques such as Co(60) gamma irradiation and autoclaving were used to treat the regenerated Bombyx mori silk fibroin (RSF) in aqueous solutions. The effect of the two above mentioned sterilization methods on the conformational changes and gelation rate of RSF was studied. According to the analysis of circular dichroism spectroscopy, gamma irradiation may initiate the conformational transition from random coil to β-sheet for RSF, while autoclaving shows less significant influence on the structure changes of RSF in aqueous solutions. The results also indicate that gelation time decreased to 5 days after γ-irradiation treatment while gelation time increased to 31 days after autoclave treatment. Moreover, particles of RSF in solutions changed larger and gelation time increased when autoclaving treatment time extended. However, no detectable changes of RSF secondary structure were found investigated by XRD and FTIR. Which indicated that under both sterilization methods, the RSF structure was transformed from random coil to β-sheet structure after gelation.

Abstract: The influence of sterilization with γ-irradiation in the properties of plasma sprayed hydroxyapatite (HAp) coatings used for medical implants is investigated in this work. HAp coatings were applied on titanium alloy substrates by plasma spraying and then submitted to 1 and 10 cycles of sterilization with γ-irradiation. As-applied HAp coatings were used as control samples. Afterwards, the modifications on the samples, induced by the irradiation process, were evaluated by X-ray diffraction and X-ray photoelectron spectroscopy (XPS). Water contact angle measurements as well as adhesion tests were also carried out in order to evaluate the influence of the irradiation process on the wettability and mechanical behaviour of the HAp coatings. No microstructural modifications were detected by X-ray diffraction after sterilization. However, the results show that sterilization with γ-irradiation originates modifications of the surface of HAp, as detected by a change of color of the coatings and by the XPS analysis. Nevertheless, these modifications do not result in significant changes in the wettability and mechanical behaviour of the HAp coatings.

Abstract: Silver nanoparticles were synthesized by irradiating silver nitrate solution (10-4 M) (methanol:water as a solvent) with different concentrations of aniline as a stabilizer in a 60Co g-ray source at a dose rate of 1.1 kGy. The particles exhibiting maximum stability up to a period of 7 days were obtained at the concentration of 0.1M aniline. The average particle size of the nanoparticles as estimated from XRD and TEM was found to be ~23 nm. Silver-Polyaniline (Ag-Pani) nanocomposite was prepared by oxidative polymerization of aniline. The applicability of synthesized nanocomposite as a sensor was tested by exposing the same to different chemical vapors viz. alcohols, amines, ammonia, chloroform etc. The results revealed its selectivity towards ammonia vapors and a long term stability of response is observed up to a period of two months. The above results are well supported by FT-IR spectroscopy.