The effects of ionizing radiation,temperature and substitutions on the thermophysical properties of La-ferrite polycrystals

Various samples of different substituted Laferrites La_1–xSm_x1 (Fe_1–x2B_x2)O₃ have been prepared by the usual ceramic procedure and firing technique. On these samples, numerous measurements have been performed, namely, thermogravimetric analysis (TGA), differential scanning calorimetry, the temperature dependence of electrical conductivity before and after -absorbed dose (4.5×10⁷ rad) and the temperature dependence of dielectric constant. Results obtained were explained, interpreted and discussed in detail on the basis of interaction of the dopant cations and ionizing radiation with La-ferrite lattice. Furthermore, the thermal stability, activation energy and energy gap for semiconduction of the investigated ferrites were evaluated before and after -absorbed dose (4.5×10⁷ rad). Finally, the activation energy for -radiation induced carrier liberation in La-ferrites was evaluated for the first time.     

The effects of ionizing radiation on the cellulose of woodfree paper

There is presently a concern because the US Postal Service now has 8 electron beam accelerators to treat mail in locations along the east coast and that a sufficient dosage to destroy Anthrax is also strong enough to darken and weaken the paper in the postal envelopes. In addition to direct photolytic scission of the cellulose chain, irradiation darkens paper, swells pulp fibres, increases hygroscopicity, and renders the cellulose more soluble in alkaline solution and more susceptible to acid hydrolysis. This report will focus on the effect of electron beam irradiation on degradation of cellulose of fine papers. Three reference papers were selected, sorted into postal envelopes and exposed to electron beam irradiation. The results have shown that irradiation at the dosage used to treat mail by the US Postal Service depolymerizes and oxidizes the cellulose. Depolymerization is responsible for a decrease of paper strength while oxidation induces darkening of the paper. Irradiating at high electron beam energy is less damaging than using lower energy. Moreover, linear relationships have been found between the number of chain scission (CSN) in cellulose and the irradiation dosage as well as between CSN and Zero-Span Breaking Length. These relationships make the strength loss predictable.     

The effect of ionizing radiation on electrophysical properties of HTSC-ceramics

The effect of ionizing radiation (γ-quanta, accelerated electrons) on electrophysical properties of superconducting ceramic materials has been studied.The effect of a gaseous medium and irradiation conditions on the change in resistance of yttrium ceramics has been investigated. It has been shown that thermal and γ-activated changes in electroconducting properties of ceramics are affected by the migration of oxygen and thermal transformations in the interface with the participation of copper-oxygen centres of the type (Cu⁺)-oxygen vacancy and (Cu³⁺, O^2-) situated near the effluents of neutral oxygen.     

Direct effects of ionizing radiation on macromolecules

In the dry or frozen states, macromolecules are damaged directly by interactions with ionizing radiation. As γ‐rays and high‐energy electrons randomly ionize orbital electrons in their path, larger molecules are more likely to suffer an interaction with these radiations. In each interaction, energy is transferred to the struck molecule, resulting in irreversibly broken covalent bonds. There is an extensive literature describing these radiation modifications in both synthetic and biopolymers. Although many different properties are measured, there emerges a similar picture of the nature of radiation damage that is common to all macromolecules. The techniques used in study of one species may be used to resolve questions raised in the other class of macromolecules. © 2011 Wiley Periodicals, Inc.? J Polym Sci Part B: Polym Phys, 2011     

Direct effects of ionizing radiation unique to macromolecules

Radiation studies of macromolecules have revealed several effects which are not describable by classical radiation physics and are not observed in radiation studies of simple diatomic gases: (1) the radiation damage to macromolecules depends on the temperature at which irradiation was performed; (2) polymeric molecules suffer radiation damage throughout the chain no matter where the primary ionization occurred; (3) there is only minimal appearance of radiation damage in other chains which are not covalently linked to the one suffering the primary ionization. These effects have been observed in radiation studies of all synthetic polymers and biologic macromolecules including proteins and nucleic acids. Data implicating free radicals in the temperature effects and studies concerning energy transfer in irradiated macromolecules provide a basis for the mechanisms involved in these effects.     

A review on the effects of ionizing radiation on blood and blood components

The major application of blood irradiation is for the prevention of graft-versus-host disease on immunodeficient patients by the abrogation of T-lymphocytes. Despite screening of blood donations, transfusion associated transmission of infections due to contaminated blood products is common. Hence, there is potential for the application of irradiation for the inactivation of pathogenic microbes in blood products. Literature on the effect of radiation on blood components is reviewed in order to make a rational decision on the feasibility of their irradiation.     

Study of ionizing radiation on the properties of polyamide 6 with fiberglass reinforcement

The use of polymers reinforced with fiberglass is becoming more and more common in the switches for household industries. These compounds perform a good tension resistance to the impact and the humidity absorption being used at the present time and also are in the automobile industry in parts underneath the hood, especially in the radiator frames. The aim of this work is to study the effect of ionizing radiation on the properties of polyamide 6 with fiberglass reinforcement and undergone to different irradiation doses. Samples were prepared and irradiated on JOB 188 accelerator with an electron beam energy of 1.5 MeV in air with different doses and a dose rate of 27.99 kGy/h. Afterward, the properties of the non-irradiated and irradiated polyamide 6 with fiberglass reinforcement were evaluated.     

The influence of fillers on thermophysical properties of adhesives

The influence of powder fillers (boron nitride, aluminum powder, processed asbestos) on the thermal conductivity and linear thermal-expansion coefficient of epoxy adhesives has been investigated. It has been shown that the use of powder fillers makes it possible to develop polymer compositions with a high thermal conductivity.     

VUV absorption and its relation to the effects of ionizing corpuscular radiation

Elements of the physics of photoabsorption as well as of energy transfer from fast charged particles are discussed. Among the key notions there are oscillator-strength spectra, quantum yields, and action spectra. Throughout the discussion, emphasis is put on the important role of soft X-rays and VUV light as obtained from a synchrotron radiation source in the understanding of actions of ionizing radiations in general.     

Influence of ionizing radiation on physical properties of native and chemically modified starches

Cationic and anionic starches (chemically modified) and native starch (non-modified) were exposed to electron-beam irradiation at doses of 25, 75 and 150 kGy. The increasing solubility in water, due to chain scission and creation of polar groups as already mentioned in the literature, has been confirmed using several physical methodologies. Impedance Spectroscopy (IS) on water solutions was carried out in order to calculate the relaxation parameters of the Cole–Cole model and α and β parameters of the Jones–Dole equation, which show the influence of radiation dose on increasing polarity, decreasing of molecular mass and increasing of electrostatic attraction between chains. Infra-red spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) confirm the formation of polar groups that retain water. The aim of this work was to confirm that the control of chain scission and functionalization of starches with irradiation could then be used in a future work to create nanoparticles by complex coacervation in an aqueous base.     

The effects of ionizing irradiation on Salmonella inoculated on almonds and changes in sensory properties

The goal of this study was to test the efficacy of irradiation on destroying Salmonella on raw almonds and evaluating the resultant sensory changes in the almonds. Raw almonds inoculated with various strains of Salmonella were irradiated at 5 dose levels up to 3 kGy and the D value was determined. The strain SEPT30 was the most resistant strain with a D value of 1.25 kGy indicating that a 4 log CFU/g reduction would require a dose of 5.0 kGy. Irradiation at 2.98 and 5.25 kGy induced significant sensory changes in almond nuts as manifested by intensity of chemical/metallic/rancid flavor ranked by a trained panel. A consumer panel found that samples treated with 5.25 kGy irradiation rendered the almonds unacceptable. Thus, irradiation by itself is unlikely to be a feasible method to eliminate Salmonella from raw almonds.     

Synthesis,properties and effect of ionizing radiation on sorption behavior of iron silico-antimonate

Incorporation of iron oxide into silico-antimonate of different Si/Sb molar ratios introduced a class of dual salts ion exchangers with advanced ion exchange properties. Physicochemical and equilibrium studies have been carried out to understand the ion exchange properties of these materials. Apparent investigation indicated that iron incorporation into silico-antimonate yields materials having excellent mechanical properties. On the basis of distribution studies, the materials were found to be highly selective for Sr²⁺ or Ce³⁺ depending on their Si/Sb molar ratios. Diffractogram, thermogram, IR spectra and sorption performance of crystalline FeSiSb (114) indicated that no detectable structural changes after an exposure up to 100 kGy of γ-rays. Effect of reaction temperature on the exchange process was investigated and the respective thermodynamic parameters were calculated.     

Effect of ionizing radiation on polyaniline solutions

This communication presents the optical studies associated with transition doped (metallic)-neutral (semiconductor or insulator) state for conducting polymers. Special attention is focused on the electronic properties of polyaniline. The interconversion of different oxidation states of polyanilines has been studied by chemical and radiolytic methods. The polyaniline system is described by three sets of chromophores of three different oxidation states: fully reduced leucoemeraldine base (LB), partially oxidized emeraldine base (EB), and fully oxidized pernigraniline (PB). Each oxidation state can exist in its protonated form by treatment with an acid. All members of polyaniline family are spectroscopically distinguishable. The radiolytic study presents evidence that the polyaniline can exist in a continuum of oxidation states. The highly conducting form of polymer, i.e. emeraldine salt can be converted by using ionizing radiation into leucoemeraldine salt. The leucoemeraldine base is the final product of radiolysis of emeraldine base solution. The fully oxidized form of polyaniline can also be obtained by the irradiation of EB in the presence of CCl₄ or chlorobenzene.     

Crosslinking of rigid PVC by ionizing radiation to improve its thermal properties

Rigid PVC formulations containing two different stabilizer systems (tin and Ca/Zn) and TMPTMA as a crosslinking agent were treated with ionizing radiation (gamma and electron beam) at different doses and irradiation atmospheres. The objective was to increase thermal and mechanical properties of this material. Polyene formation was followed through the yellowing index (YI), the extent of crosslinking by gel percentage, thermal resistance by Vicat temperature and the mechanical properties by DMA. Both formulations became colored with irradiation, especially with gamma as a result of a longer treatment time; the gel formation and the Vicat temperature were also higher for gamma treated samples, suggesting that values were enhanced by oxidation. However, DMA elastic modulus traces were almost similar for both treatments. The main difference observed for Ca/Zn samples compared with traditional tin samples was the lower ability of the former system in protecting the material against processing conditions.     

Temporary changes in electrical properties of polymer dielectrics due to ionizing radiation

Measurements of conductivity, permittivity, and dissipation factor on polystyrene, low-density polyethylene, poly(ethylene terephthalate), and polytetrafluoroethylene under irradiation with x-rays at exposure rates from 0.004 to 400 r/sec. are presented. The radiation-induced anomalous conductivity as well as the induced dielectric loss are interpreted by Maxwell-Wagner polarization due to radiation imbalance in surface layers of the specimen. The nature of radiation-induced steady-state conductivity is also discussed.     

Further investigations on the thermophysical properties of gamma-irradiated urania-doped orthoferrites

(Y_1.85?U_0.15) FeO₃ orthoferrite was carefully prepared using the solid-state high temperature ceramic and sintering technique. On this orthoferrite, numerous measurements have been undertaken before and after 1.24 Mrad γ-absorbed dose, namely X-ray diffraction (XRD), DC-electrical conductivity versus temperature, UV/Vis. absorption, IR absorption, Mössbauer effect (ME) and EPR. In the present work the results obtained were explained, interpreted and discussed in details on the basis of lattice structure of the new perovskite investigated and the interaction of γ-radiation with the orthoferrite lattice.     

The Influence ofγ-irradiation on the thermophysical properties of potassium ammonium sulphate crystals

The effect ofγ-irradiation on the thermal properties of KNH₄SO₄ single crystals in the temperature range 300–600 K is investigated. The variation ofC _P as a function of radiation dose is determined. Analysis of the results indicates that changes induced in the thermal behaviour of KNH₄SO₄ crystal byγ-irradiation might be due to direct collision with lattice atom and multiple atom displacement.