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EN
The article presents the results of research on the impact of structural changes in polyether ether ketone (PEEK) on its mechanical properties. The polymer was exposed to gamma radiation at a dose of 50 and 150 kGy, and the radiation energy was 4 MeV. Changes in the degree of crystallinity and the related changes in the glass transition and melting temperature for the polymer were determined by differential scanning calorimetry (DSC). Mechanical properties were determined using the micro-mentoring method. The tests showed a change in the degree of crystallinity in the range of several degrees and a significant increase in the glass transition temperature. In terms of mechanical properties, the reduction of hardness and Young’s modulus was observed. Observed changes, especially in terms of changes in the structure of the polymer under the influence of radiation, are difficult to explain, which requires conducting further research, especially in the range of irradiation parameters used. Further research is important because PEEK is used in many fields, especially in conditions conducive to corrosion and the influence of radiation.
PL
W artykule przedstawiono wyniki badań wpływu zmian strukturalnych w polieteroeteroketonie (PEEK) na jego właściwości mechaniczne. Polimer został poddany działaniu promieniowania gamma w dawce 50 i 150 kGy, energia promieniowania wynosiła 4 MeV. Zmiany stopnia krystaliczności podobnie jak zmiany temperatury zeszklenia i topnienia dla polimeru zostały wyznaczone za pomocą różnicowej kalorymetrii skaningowej (DSC). Właściwości mechaniczne wyznaczono za pomocą metody mikrointendacji. Badania wykazały zmianę stopnia krystaliczności w zakresie kilku stopni oraz znaczne zwiększenie temperatury zeszklenia. Pod kątem właściwości mechanicznych zaobserwowano zmniejszenie twardości i modułu Younga. Zaobserwowane zmiany, szczególnie pod kątem zmian w strukturze polimeru pod wpływem promieniowania, są trudne do wyjaśnienia, co wymaga prowadzenia dalszych badań szczególnie w zakresie zastosowanych parametrów napromieniowania. Dalsze badania są o tyle istotne, że PEEK znajduje zastosowanie w wielu dziedzinach, szczególnie w warunkach sprzyjających korozji oraz wpływu promieniowania.
EN
The paper presents the results of studies on the effects of gamma irradiation on the static friction coefficient of thermoplastic polymer – polysulfone. These polar polymers belong to the group of amorphous thermoplastics and are widely used for various applications, e.g., automotive and electronic industries (dielectrics in capacitors), waste water recovery, medical uses (hemodialysis membranes), requiring autoclave, and steam sterilization. Polysufones are known for their toughness and stability at high temperatures. The aim of this study is to analysed changes in the static coefficient of friction in association with a contact pressure (in the range 0.2 – 0.8 MPa) depending on the ionizing radiation dose of PSU (in the range 50-150 kGy). Additionally, microhardness, and wear intensity were measured, because tribological properties of polymers as well as mechanical properties that influence their durability and applications. The studies confirmed that the static coefficient of friction increases with an increase in contact pressure (in the test range). The research has shown that mechanical (microhardness) and tribological (static coefficient of friction and tribological wear) improve as the radiation dose of irradiated material increase. Moreover, the tribological wear increases with increasing the sliding velocity. This gamma irradiated polymer is characterized by higher microhardness, a static coefficient of friction, and a higher wear rate compared to PSU in the initial state, because of changes in structure. It requires further research.
PL
W artykule przedstawiono wyniki badań wpływu promieniowania gamma na właściwości tarcia statycznego polisulfonu. Ten polarny polimer należący do grupy termoplastów o budowie amorficznej został wybrany z uwagi na jego szerokie zastosowanie w różnych dziedzinach, w tym w przemyśle samochodowym, elektronicznym (dielektryki w kondensatorach), oczyszczaniu wody, medycynie (membrany do hemodializy), autoklawach. Polisulfony są znane ze swojej wytrzymałości i stabilności wymiarów w wysokich temperaturach. Celem przeprowadzonych badań była analiza wpływu promieniowania gamma (w zakresie 50–150 kGy) na zmiany wartości współczynnika tarcia statycznego (w zakresie 0,2÷0,8 MPa). Dodatkowo wykonano badania mikrotwardości oraz intensywności zużywania z uwagi na to, że właściwości tribologiczne polimerów takie jak właściwości mechaniczne mają wpływ na ich trwałość i właściwości użytkowe. Analiza wyników wykazała, że wraz ze wzrostem dawki promieniowania gamma zwiększała się wartość pomiarów mikrotwardości, współczynnika tarcia statycznego oraz intensywności zużywania. Wyniki wykazały wpływ prędkości poślizgu na zużycie liniowe materiału. Przyczyną zaobserwowanych zmian są zmiany zachodzące w strukturze polimeru pod wpływem promieniowania, co wymaga prowadzenie dalszych badań.
EN
Chlorophenols are compounds with high toxicity, poor biodegradability, and carcinogenic and recalcitrant properties. This work studies, for the first time, the destruction and detoxification of 2-chlorophenol (2-CP) in water using 60Co gamma radiation under different conditions including varied radiation doses, addition of hydrogen peroxide (H2O2), and varied pH values. High-performance liquid chromatography (HPLC) and ion chromatography (IC) confirmed a successful degradation of 2-CP to primarily yield phenol molecules and chloride anions. A radiation dose as low as 25 kGy achieved approximately 90% removal of 50–150 ppm of 2-CP in neutral water. However, the addition of a strong oxidizer such as H2O2 to 2-CP solutions reduced the required dose to achieve 90% removal to at least 1.3-fold. The reduction in radiation doses was also observed in acidic and alkaline media, reducing the required doses of 90% removal to at least 0.4-fold. It was imperative to study the toxicity levels of the oxidation by-products to provide directions for the potential applicability of this technology in water treatment. Toxicology Microtox® bioassay indicated a significant reduction in the toxicity of the degradation by-products and the detoxification was further enhanced by the addition of H2O2 and changing the pH to more acidic or alkaline conditions. These findings will contribute to the knowledge of the removal and detoxification of such challenging environmental contaminant and could be potentially applied to other biologically resistant compounds.
EN
The paper describes the effects of gamma radiation doses on the tribological and mechanical properties of selected thermoplastic polymers: PEEK, PEI, PET, and PA6. Samples of those polymers were irradiated with gamma rays of energy 1, 1.2, 3, 4, 5 MeV and with the intensity of the radiation beam 4, 7, 10, 30, 40 μA. With an increasing dose of radiation, properties such as microhardness, the friction coefficient of polymers, and the wear rate are changed. The chemical structure of the irradiated polymer may be changed by crosslinking but also by chain scission. The modified polymers may be used in medical science, electronics, and space technology. In this article, we report the results of steel C45 – thermoplastics (PEEK, PEI, PET, and PA6) friction couple during the slip motion. The analysis is focused on the friction coefficient, wear rate, and microhardness. Kinematic parameters of the experiment in slide movement were constant and defined by the following values: contact pressure p = 1MPa and sliding velocity v = 1m/s. The authors observed that, as gamma radiation dose increased, the microhardness and friction coefficient increased and their wear intensity decreased. Polymers change their microstructure and molecular structure when they are subjected to gamma ray irradiation, which results in modification on many important physical and chemical properties.
PL
Celem niniejszej pracy było określenie wpływu dawki promieniowania gamma na właściwości tribologiczne i mechaniczne wybranych polimerów termoplastycznych: PEEK, PEI, PET, PA6. Wraz ze wzrostem dawki tego promieniowania właściwości takie jak microhardness, współczynnik tarcia statycznego oraz intensywność zużycia ulegają zmianie. Wymienione właściwości mogą być modyfikowane na skutek zachodzących zmian w strukturze chemicznej naświetlonych polimerów poprzez sieciowanie łańcuchów polimerowych, ale także ich rozerwanie. Zmodyfikowane polimery mogą być wykorzystane m.in. w medycynie, elektronice i technologii kosmicznej. W pracy opisano badania par ślizgowych stal C45 – wybrany polimer. Analizie poddano wartości współczynnika tarcia statycznego oraz intensywności zużycia materiału. Dla wszystkich analizowanych przypadków wartości parametrów ruchowych były stałe: siła nacisku wynosiła 1 MPa, a prędkość ślizgowa 1 m/s. Eksperyment wykazał zwiększenie wartości mikrotwardości i współczynnika tarcia oraz zmniejszenie intensywności zużycia.
EN
Ergosan contains 1% alginic acid extracted from two brown sea weeds. Little is known about the target organs and anatomical distribution of Ergosan (alginic acid) in fi sh. Therefore, feasibility of developing alginic acid nanoparticles to detect target organ in rainbow trout is interesting. To make nanoparticles, Ergosan extract (alginic acid) was irradiated at 30 kGy in a cobalt-60 irradiator and characterized by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Results from TEM images showed that particle sizes of irradiated alginic acid ranged from 30 to 70 nm. The FTIR results indicated that gamma irradiation had no signifi cant infl uence on the basic structure of alginic acid. Later, alginic acid nanoparticles were successively labelled with 67Ga-gallium chloride. The biodistribution of irradiated Ergosan in normal rainbow trout showed highest uptake in intestine and kidney and then in liver and kidney at 4- and 24-h post injection, respectively. Single-photon emission computed tomography (SPECT) images also demonstrated target specifi c binding of the tracer at 4- and 24-h post injection. In conclusion, the feed supplemented with alginic acid nanoparticles enhanced SPECT images of gastrointestinal morphology and immunity system in normal rainbow trout.
PL
Istnieje wiele metod sterylizacji wyrobów medycznych. Jednak najbardziej użytecznymi metodami sterylizacji syntetycznych, bioresorbowalnych polimerów wydają się być promieniowanie gamma oraz napromienianie wiązką elektronów (EB). Celem tej pracy było określenie wpływu wspomnianych metod na trzy rodzaje matryc - zawierających 3%, 5% paklitakselu oraz matryc bez leku. Badane matryce otrzymano z dwóch rodzajówpoli(L-laktydo-ko-węglanu trimetylenu) zsyntezowanych w 150°C (P1) oraz 120°C (P2). Nie zaobserwowano znaczących różnic w składzie komonomerów matryc sterylnych i niesterylnych, zawierających paklitaksel, jak i matryc bez leku. Spadek temperatury zeszklenia (Tg) wynikał ze zmniejszenia się średniej długości bloków laktydylowych oraz węglanowych, a także utraty Mn po procesie sterylizacji. Zauważalne były niewielkie różnice we właściwościach fizykochemicznych matryc napromienianych promieniowaniem gamma oraz wiązką elektronów. Otrzymane wyniki pokazują, iż lepszą metodą sterylizacji poli(L-laktydo-ko-węglanu trimetylenu) wydaje się być napromienianie wiązką elektronów.
EN
There are many methods of sterilization approved for medical devices. However, the most usable methods of synthetic, bioresorbable polymers sterilization seem to be gamma radiation and electron beam irradiation (EB). The aim of this work was to determine the impact of mentioned methods on three types of matrices - containing 3%, 5% of paclitaxel and also drug free matrices. The studied matrices were obtained from two poly(L-lactide-co-trimethylene-carbonates) synthesized at 150°C (P1) and 120°C (P2). No significant differences of comonomers' composition were observed in sterile and non-sterile matrices containing paclitaxel as well as drug free matrices. The decrease of the glass transition temperature (Tg) resulted from decrease of the lactidyl and carbonate units' content and the Mn loss after radiation. Small dissimilarities of physicochemical features between gamma and EB radiated matrices were noticeable. Thus, the obtained data showed that better method of sterilization of poly(L-lactide-co-trimethylene carbonates) seems to be electron beam radiation.
EN
We have performed nonlinear optical and piezoelectric studies of the Rb1-xKxTiOPO4 (RKTP) (with x = 0.01 and 0.002) single crystals irradiated by ?-quanta at power 1.23 Gy. We have found that for non-irradiated samples with x = 0.01 the effective second-order susceptibilities determined from the powder-like micrometer samples were less than for x = 0.02 and the effective values of the second-order susceptibilities for 1064 nm were equal to 3.12 pm/V (x = 0.002) and 2.56 pm/V (x = 0.01). After the gamma irradiation the corresponding values were equal to 2.45 pm/V and 2.78 pm/V, respectively. Moreover, for the samples with x = 0.01 one can observe the occurrence of the damage at laser energy density equal to about several J/cm2. Such effect is absent for the pure KTP crystals and may be a consequence of substantial role of the intrinsic defects caused by insertion of potassium ions in the positions of the rubidium cations. At the same time the piezoelectrical constants show an opposite behavior with respect to the SHG.
PL
Istnieje wiele metod sterylizacji wyrobów medycznych. Jednak najbardziej użytecznymi metodami sterylizacji syntetycznych, bioresorbowalnych polimerów wydają się być promieniowanie gamma oraz napromienianie wiązką elektronów (EB). Celem tej pracy było określenie wpływu wspomnianych metod na trzy rodzaje matryc - zawierających 3%, 5% paklitakselu oraz matryc bez leku. Badane matryce otrzymano z dwóch rodzajów poli(L-laktydo-ko-węglanu trimetylenu) zsyntezowanych w 150°C (P1) oraz 120°C (P2). Nie zaobserwowano znaczących różnic w składzie komonomerów matryc sterylnych i niesterylnych, zawierających paklitaksel, jak i matryc bez leku. Spadek temperatury zeszklenia, Tg, wynikał ze zmniejszenia się średniej długości bloków laktydylowych oraz węglanowych, a także utraty Mn po procesie sterylizacji. Zauważalne były niewielkie różnice we właściwościach fizykochemicznych matryc napromienianych promieniowaniem gamma oraz wiązką elektronów. Otrzymane wyniki pokazują, iż lepszą metodą sterylizacji poli(L-laktydo-ko-węglanu trimetylenu) wydaje się być napromienianie wiązką elektronów.
EN
There are many methods of sterilization approved for medical devices. However, the most usable methods of synthetic, bioresorbable polymers sterilization seem to be gamma radiation and electron beam irradiation (EB). The aim of this work was to determine the impact of mentioned methods on three types of matrices - containing 3%, 5% of paclitaxel and also drug free matrices. The studied matrices were obtained from two poly(L-lactide-co-trimethylene-carbonates) synthesized at 150°C (P1) and 120°C (P2). No significant differences of comonomers' composition were observed in sterile and non-sterile matrices containing paclitaxel as well as drug free matrices. The decrease of the glass transition temperature, Tg, resulted from decrease of the lactidyl and carbonate units' content and the Mn loss after radiation. Small dissimilarities of physicochemical features between gamma and EB radiated matrices were noticeable. Thus, the obtained data showed that better method of sterilization poly(L-lactide-co-trimethylene carbonates) seems to be electron beam radiation.
EN
The influence was studied of potato and wheat starch irradiation on physicochemical properties of films, prepared using either starch alone or a composition of potato starch with three surfactants: sodium laurate, sodium palmitate and cetyl-trimethyl-ammonium bromide (CTAB). The surfactants were introduced at a level of 0.038 division sign 0.075 g per 1 g of starch. This corresponds to 0.136–0.222 mmol/g, depending on the surfactant type and its amount used. Irradiations were carried out using 60Co radiation with doses of 5, 10, 20 and 30 kGy. Films were prepared with addition of glycerol (0, 20 or 30% in terms of starch mass) by means of casting from the gelatinized starch or starch-surfactant solutions. With the purpose to characterize the films, mechanical tests (using an Instron instrument) and the wetting angle measurements were performed. The effect was determined of the storage and conditioning in an atmosphere characterized by the various moisture content on the properties of films with various compositions. The results show the radiation-induced improvement of hydrophobic properties of the films prepared using potato and wheat starch, and the selected potato starch-surfactant compositions. Improvement of strength and flexibility was obtained in the case of potato starch films, while in the case of wheat starch films the increase of strength was accompanied by a decrease in flexibility. Improvement of the functional properties of potato starch films corresponds to the improvement of their structural properties, found by scanning electron microscopy (SEM). The possibilities of modification of the films properties by modification of composition and radiation treatment were discussed.
PL
Przedstawiono charakterystykę promieniowania gamma. Szczególną uwagę zwrócono na mechanizm działania promieniowania gamma na mikroorganizmy oraz wrażliwość organizmów na pośrednie produkty naświetlania. Podano przykłady instalacji do dezynfekcji ścieków miejskich za pomocą promieniowania gamma działających w skali pilotowej i technicznej.
EN
The characteristics of gamma irradiation are presented. Special attention is given to the reaction of microorganisms to particular disinfection method and sensibility of the organisms to intermediate products of irradiation. Examples of pilot-plant and commercial systems for municipal wastewater disinfection by gamma irradiation method are given.
EN
Arbuscular mycorrhizae are endogenous fungi that form symbiotic association with the vast majority of vascular plants. They help to increase the nutrient uptake, especially phosphorus and to exploit a larger area of soil. Also, they improve soil aggregation, contribute to nutrient cycling processes in plants and improve their tolerance of heavy metal contamination or drought, as well as their susceptibility to root pathogens or herbivores. These fungi colonize the root epidermis and outer cortical layers and release bioactive molecules. The transcriptome and the proteome of plants are substantially altered. They have evolved multiple mechanisms that result in improvements in plant resistance to disease and plant growth and productivity, being included in a lot of combination of biofertilizers. In order to study these mechanisms, gamma irradiation was used to create mutants that are defective in their association. Culture under in vitro conditions is presented as method for maintaining the useful mutants in pure line.
12
Content available Archives decontamination by gamma irradiation
EN
The treatment of archives with gamma irradiation is an efficient and environmental friendly alternative for biological decontamination of large volume of archives. It substitutes the use of chemicals for conservation and contributes to safer workplaces. This work is targeting documents from recent archives where the value of information is not obsolete and may become an important historical and cultural testimony. For a successful treatment, an optimal absorbed dose has to be established. An excessive dose may damage papers and an insufficient one will not reduce bioburden to the desired level. An interdisciplinary team was performing various physical and chemical tests in order to evaluate deterioration of paper at high doses. In the case of natural disaster, it is not excluded the “emergency” treatment for documents in immediate danger of total destruction.
EN
Radiation processing has been considered as a promising process for the treatment of textile industry waste effluents. In this study, the possibility of using gamma-rays to degrade and decolorize Apollofix dyes in water has been investigated. Two different Apollofix dyes, Apollofix Red (AR) and Apollofix Yellow (AY) in aqueous solutions were irradiated in air with doses from 1.0 kGy to 8.0 kGy at a 0.14 kGy/h of dose rate. The change in absorption spectra, pH, chemical oxygen demand (COD), biological oxygen demand (BOD) and the degree of decoloration (percent reduction in optical density) were examined in the presence and absence of H2O2. The absorption bands at 534 nm and 420 nm for AR and AY were observed to decrease rapidly with increasing irradiation dose. The degree of decoloration of each dye solution with irradiation dose was estimated as 100 percent for the lower concentration (50 ppm) dye solutions. The complete decoloration was observed after 2.0 kGy and 1.0 kGy doses for AR and AY dyes. The COD and BOD reduction and the change of pH for all dye solutions on irradiation showed similar behavior.
14
Content available remote Gamma irradiation effect on polystyrene + SBR blends: morphology and microhardness
EN
Blends with 0, 5, 10 and 13 weight % of styrene/butadiene (SBR) copolymer embedded in a rigid polystyrene matrix were prepared. Microhardness was determined and morphology evaluated by scanning electron microscopy (SEM) before and after gamma irradiation. We relate the morphology to chemical structure and to composition of the SBRs as well as to irradiation dosages. We also connect the microhardness to the impact strength determined previously.
PL
Praca stanowi kontynuację badań opisanych w [5] i dotyczy takich samych kompozycji zawierających 5, 10 lub 13 % masowych kopolimeru styren/butadien (SBR) w matrycy polistyrenu (PS); stosowany SBR różnił się przy tym składem (57-75 % mas. butadienu) i charakterem struktury (gwiaździsta - S, liniowa - L, multiblokowa - MB - por. tabela 1). Wyniki badań mikrotwardości (rys. l i 2) i wcześniejszych pomiarów udarności [5] powiązano z ocenianą metodą elektronowej mikroskopii skaningowej (SEM) morfologią powierzchni próbek (rys. 3-12). Badano próbki nienapromieniane oraz napromieniane różnymi dawkami promieniowania g (do 250 kGy). Ustalono, że zwiększanie zawartości SBR w kompozycji oraz wzrost udziału butadienu w SBR (co polepszało udarność) na ogół pogarsza mikrotwardość. Interpretacja wyników badania morfologii powierzchni próbek przed i po napromienianiu pozwoliła na wyjaśnienie zaobserwowanego uprzednio wpływu struktury SBR, zawartości w nim butadienu oraz dawki promieniowania na udarność.
EN
Effects of chemical structure, composition, thermal stability and molecular weights of the rubber phase in amorphous polystyrene + styrene/butadiene rubber (SBR) blends on impact behavior were investigated. Blends with 5, 10 and 13 wt. % of SBR embedded into a rigid polystyrene matrix were prepared as well as the samples without SBR. For all blends the Izod impact tests were performed and those with the best impact strength values were submitted to gamma irradiation. The Izod impact tests of the irradiated samples were then performed. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) runs were made for both irradiated and not-irradiated blends. Blends compositions with the highest impact energies have been defined. Gamma irradiation initially enhances the impact energies but then reaches a maximum around 150 kGy above which the impact strength eventually becomes lower than in the samples not subjected to irradiation.
PL
Przedstawiono wyniki badań wpływu promieniowania gamma na udarność, stabilność termiczną i temperaturę zeszklenia różniących się składem mieszanin polistyren + kauczuk styrenowo-butadienowy (SBR). Udział SBR w mieszaninach wynosił do 13 % mas. Stosowano SBR o różnej strukturze (gwiaździsta, liniowa oraz multiblokowa) i różnej zawartości butadienu (57-75 % mas., tabela 1). Określono wpływ na udarność zarówno zawartości SBR w mieszaninach, jak i stężenia butadienu w SBR (rys. 1 i 2). Następnie zbadano zmiany udarności pod wpływem różnych dawek promieniowania gamma (do 250 kGy) dotyczące rozmaitych typów SBR (rys. 3-6). Największy wzrost udarności wykazały próbki PS zawierające SBR-4 (70 % butadienu, budowa liniowa). Nienapromieniane i napromieniane próbki mieszanin badano metodami TGA (tabela 2 i 4) oraz DSC (tabela 3 i 5). Stwierdzono nieznaczną poprawę stabilności termicznej napromienionych mieszanin oraz pewne podwyższenie wartości ich Tg ze wzrostem udziału SBR; zwiększanie dawki promieniowania w bardzo niewielkim stopniu wpływa na spadek Tg.
EN
Dried humic acid and its aqueous solution in 0.1 M Na2CO3 were gamma-irradiated with 1 90 kGy from 60Co. Thereafter, a secondary ultraweak radiation in the spectral range of gamma = 340 650 nm from aqueous solutions was recorded as long-lived chemiluminescence (CL). Only for absorbed doses lower than 10 kGy low intensity signals of the CL decay were measurable. For absorbed doses higher than 40 kGy residual flat and weak signals are observed. Humic acid irradiated in the dry form did not reveal statistically significant CL. Absorption spectra (gamma = 240 800 nm) of irradiated solutions indicated the occurrence of a dominant degradation process of the humic acid macromolecular components. The effect of H2O2 and CL enhancers (luminol and lucigenin) on the intensity and kinetics of CL proved the participation of reactive oxygen species and the free radical mechanism in the CL and degradation processes. The dose-effect relationship (i.e. gamma-radiation absorbed dose vs. intensity of gamma-radiation-induced CL) showes a non-linear shape, especially in the range of 1-10 kGy, which suggests complex radical mechanisms. A possible ecological significance of the observed phenomena is briefly discussed.
EN
The formation and stabilization of reduced silver species in the regularly interstratified clay minerals, trioctahedral smectite/chlorite (tri-Sm/Ch) and dioctahedral smectite/mica (di-Sm/M), have been studied by electron paramagnetic resonance (EPR) spectroscopy. Both minerals loaded with Ag+ cations after degassing and dehydration were g-irradiated at 77 K and monitored by EPR as the temperature increased. Some samples were exposed to water or methanol vapor after dehydration. In both hydrated and dehydrated samples only the doublets assigned to Ag0 atoms were observed with no evidence of the formation of Ag clusters. However, the EPR parameters of silver atoms in both matrices are different. In tri-Sm/Ch the narrow anisotropic EPR lines overlap with the broader isotropic lines, whereas in di-Sm/M only broad lines are recorded. The hyperfine splitting - Aiso(Ag0) is larger in tri-Sm/Ch than in di-Sm/M. Also the stability of Ag0 in both clay minerals is distinctly different. Ag0 doublet in di-Sm/M disappears completely above 230 K, whereas in tri-Sm/Ch it is still recorded at 310 K. It is proposed, basing on the EPR results that Ag0 atoms appear at different sites in both matrices: - in tri-Sm/Ch in the middle of smectite interlayer and in hexagonal cavities in the silicate sheets of tetrahedron layer and in di-Sm/M in hexagonal cavities only. When samples had been exposed to methanol before irradiation, the silver clusters become stabilized in the interlayer sites. In tri- Sm/Ch matrix the silver dimer Ag2+ formed by g-irradiation at 77 K is transformed to tetrameric cluster, Ag43+ at 150 K. In di-Sm/M the radiation-induced silver agglomeration proceeds in a similar way, but with a slower rate and Ag tetramer is formed only above 190 K. In both clay minerals, Ag43+ clusters decay above 250 K.
EN
Positron annihilation Iifetime spectroscopy is applied to the study of gamma irradiation effect on polymers based on the acrylate oligomers. The gamma irradiation of Co60 was carried out in air, with a flux of 20 Gy s-1. The measurements were made on specimens with different absorbed dose in the range 10-100 kGy. The longest lifetime, τ3, in three-component analyses of the spectra was associated with the pickoff annihilation of ortopositronium trapped in voids. After irradiation changes in the lifetimes are observed. The intensity of the longest-Iived component, I3, increases in comparison with the as-received sample. These results are discussed on the basis of free volume model.
19
Content available remote Radiation-induced paramagnetic centers in Bioglass(R).
EN
The X-band (v=9.4 GHz) electron spin resonance (ESR) and thermally stimulated luminescence (TSL) spectra of the UV-, X-, and gamma -irradiated Bioglass(R) samples of different composition (Bioglass(R) I and Bioglass(R) II) have been investigated. The efficiency of generation of electron and hole centers strongly depends on basic Bioglass(R) composition and is almost independent of ionizing radiation type and presence of Fe/sup 3+/ non-controlled impurity in the glass network. The spin Hamiltonian parameters (g and a values) and thermal stability of the radiation-induced centers have been evaluated. The results of TSL measurements show good agreement with ESR data. The energetic structure, formation peculiarities and specific models of the radiation-induced paramagnetic centers in the Bioglass(R) network are discussed.
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