Thermoelectric Performance of Polypropylene/Carbon Nanotube/Ionic Liquid Composites and Its Dependence on Electron Beam Irradiation

The thermoelectric behavior of polypropylene (PP) based nanocomposites containing single walled carbon nanotubes (SWCNTs) and five kinds of ionic liquids (Ils) dependent on composite composition and electron beam irradiation (EB) was studied. Therefore, several samples were melt-mixed in a micro compounder, while five Ils with sufficiently different anions and/or cations were incorporated into the PP/SWCNT composites followed by an EB treatment for selected composites. Extensive investigations were carried out considering the electrical, thermal, mechanical, rheological, morphological and, most significantly, thermoelectric properties. It was found that it is possible to prepare n-type melt-mixed polymer composites from p-type commercial SWCNTs with relatively high Seebeck coefficients when adding four of the selected Ils. The highest Seebeck coefficients achieved in this study were +49.3 µV/K (PP/2 wt.% SWCNT) for p-type composites and −27.6 µV/K (PP/2 wt.% SWCNT/4 wt.% IL type AMIM Cl) for n-type composites. Generally, the type of IL is decisive whether p- or n-type thermoelectric behavior is achieved. After IL addition higher volume conductivity could be reached. Electron beam treatment of PP/SWCNT leads to increased values of the Seebeck coefficient, whereas the EB treated sample with IL (AMIM Cl) shows a less negative Seebeck coefficient value.

Electron Beam-Treated Enzymatically Mineralized Gelatin Hydrogels for Bone Tissue Engineering

Biological hydrogels are highly promising materials for bone tissue engineering (BTE) due to their high biocompatibility and biomimetic characteristics. However, for advanced and customized BTE, precise tools for material stabilization and tuning material properties are desired while optimal mineralisation must be ensured. Therefore, reagent-free crosslinking techniques such as high energy electron beam treatment promise effective material modifications without formation of cytotoxic by-products. In the case of the hydrogel gelatin, electron beam crosslinking further induces thermal stability enabling biomedical application at physiological temperatures. In the case of enzymatic mineralisation, induced by Alkaline Phosphatase (ALP) and mediated by Calcium Glycerophosphate (CaGP), it is necessary to investigate if electron beam treatment before mineralisation has an influence on the enzymatic activity and thus affects the mineralisation process. The presented study investigates electron beam-treated gelatin hydrogels with previously incorporated ALP and successive mineralisation via incubation in a medium containing CaGP. It could be shown that electron beam treatment optimally maintains enzymatic activity of ALP which allows mineralisation. Furthermore, the precise tuning of material properties such as increasing compressive modulus is possible. This study characterizes the mineralised hydrogels in terms of mineral formation and demonstrates the formation of CaP in dependence of ALP concentration and electron dose. Furthermore, investigations of uniaxial compression stability indicate increased compression moduli for mineralised electron beam-treated gelatin hydrogels. In summary, electron beam-treated mineralized gelatin hydrogels reveal good cytocompatibility for MG-63 osteoblast like cells indicating a high potential for BTE applications.

Synthesis of ZnS:Cu,Br radioluminescent phosphors using the electron-beam treatment and studying their characteristics

ZnS:Cu radioluminescent phosphors find their applications in medicine nondestructive testing, safety control and can be used as a part of the solid-state radioluminescent light sources (SRLS). This devices are very promising technology due to their independence longevity and safety compared to the gas-filled RLS. Because of the fact that tritium (the most popular radioisotope for RLS) has a very short range in substances, the improving the operating performances of radiophosphors is a crucial task for SRLS. In our study we used the electron-beam treatment to increase the brightness of radioluminescence of ZnS:Cu phosphors. It was found that bombardment of the phosphors initial charge with electrons of 900 kEv energy improves the brightness of radioluminescence by 15 – 20%. Double modifying of the initial charge and ready phosphor cause the 80% increase of brightness. The effect of electron-beam treatment on the phase content and the surface properties was studied at varying the content of activator (Cu) in the range of 0 – 0.6 % mass. As a result the model describing structure of the acid-base sites on the ZnS:Cu phosphor surface was suggested.

Structural Phase States and Surface Properties of Steel 45 after Electroexplosive Borocoppering and Electron-Beam Treatment

The paper concerns improving the microhardness and wear resistance of steel 45 by the combined treatment of electroexplosive borocoppering with the subsequent electron-beam treatment. It is found that surface roughness at the area of the electroexplosive treatment increases along with the absorbed power density and the mass of boron powder. The electron-beam treatment leads to a decrease of roughness and appearance of craters instead of radial melt flow traces. The depth structure of the electroexplosive alloying area with a thickness of 25 µm includes a coating layer, near-surface, intermediate, and boundary layers. The surface microhardness and the depth of the hardening zone after the electroexlosive alloying increase along with the absorbed power density and boron concentration and reach the values of 1400 HV The electron-beam treatment causes merging of the coating and the surface layers and increases the hardening zone depth up to 80 µm. A cellular or dendritic crystallization structure is formed near the surface, and a grain structure is formed in the depth. The inhomogeneous distribution of alloying elements over the volume of the alloying area and its adjustment during the electron-beam treatment are established. The inter-dendritic distances and grain diameters increase as the absorbed power density becomes higher with the increase of the electron-beam treatment exposure time. Also, the size of martensite needles increases in the depth. The combined treatment produces the sub microcrystalline strengthening phases-borides FeB, Fe2B, FeB2, carboboride Fe23 (C, B)6 , and carbide B4C. The microhardness level is reduced to 800 HV, and the wear resistance increases up to five times when compared to the wear resistance of the base.

Low-energy electron beam has severe impact on seedling development compared to cold atmospheric pressure plasma

Sprouts are germinated seeds that are often consumed due to their high nutritional content and health benefits. However, the conditions for germination strongly support the proliferation of present bacteria, including foodborne pathogens. Since sprouts are consumed raw or minimally processed, they are frequently linked to cases of food poisoning. Therefore, a seed decontamination method that provides efficient inactivation of microbial pathogens, while maintaining the germination capacity and quality of the seeds is in high demand. This study aimed to investigate and compare seed decontamination by cold atmospheric-pressure plasma and low-energy electron beam with respect to their impact on seed and seedling quality. The results show that both technologies provide great potential for inactivation of microorganisms on seeds, while cold plasma yielded a higher efficiency with 5 log units compared to a maximum of 3 log units after electron beam treatment. Both techniques accelerated seed germination, defined by the percentage of hypocotyl and leaf emergence at 3 days, with short plasma treatment (< 120 s) and all applied doses of electron beam treatment (8–60 kGy). However, even the lowest dose of electron beam treatment at 8 kGy in this study caused root abnormalities in seedlings, suggesting a detrimental effect on the seed tissue. Seeds treated with cold plasma had an eroded seed coat and increased seed wettability compared to electron beam treated seeds. However, these effects cannot explain the increase in the germination capacity of seeds as this was observed for both techniques. Future studies should focus on the investigation of the mechanisms causing accelerated seed germination and root abnormalities by characterizing the molecular and physiological impact of cold plasma and electron beam on seed tissue.

Synthesis and Electron-Beam Modification of Zinc-Sulphide Phosphors for Solid-State Radioluminescent Light Sources (SRLS)

Radioluminescence technologies are at the front line of the optic and electronic studies. Effective, self-contained and safe radioluminescent light sources can find their application in space industry, in medicine and in military technologies. The question of the performance improvement of the solid-state radioluminescent light sources (SRLS) without raising the included activity of working radionuclide can be solved by upgrading the phosphor crystalline structure. The electron-beam treatment for zinc-sulphide phosphors initial batch has been studied in a wide range of concentrations of the activating agent (Cu) for improving the radioluminescent performances of the phosphors, for creating the structural defects that form centers of luminescence. The changes of the phase composition were investigated under different synthesis conditions. It is revealed that electron-beam treatment of the initial batch leads to the growth of the wurtzite phase content in zinc-sulphide phosphors synthesized below the phase transition temperature. The changes of the phase content promote the spectral redistribution under the tritium beta-excitation. It is obviously the reflection of the fact of «green» luminescence centers rearrangement between the volume of the crystal and its surface. The correlations between structural configuration and performances of ionizing luminescence were found. Electron beam treatment gave the 20% increase of brightness of the radioluminescence. The achieved enhancement of luminescence performances allows the development of advanced tight-packed SRLS with minimal radioactivity and high energy-light conversion.

Effect of CeO2 on Corrosion Resistance of High-Current Pulsed Electron Beam Treated Pressureless Sintering Al-20SiC Composites

In this paper, the effect of rare earth Ce on the corrosion resistance of Al-20SiC composites treated with high-current pulsed electron beams is investigated, and the corresponding corrosion mechanism is proposed. The scanning electron microscope (SEM) results show that cracks arise on the surface of Al-20SiC composites prepared by pressureless sintering. After electron beam treatment, the pores on the surface are reduced because of the filling of Al liquid. After adding CeO2 to Al-20SiC composites, the wettability between Al and SiC phases is improved, thus realizing metallurgical bonding of the two phases, and microcracks generated after HCPEB treatment are significantly eliminated. Glancing X-ray diffraction (GIXRD) results show that after electron beam treatment, aluminum grains tend to grow more favorably with the stable and dense crystal plane of Al(111), thus improving corrosion resistance. The electrochemical test results show that the corrosion current density decreases by one order of magnitude with increase in the number of pulses because of rare earth Ce compared to the initial Al-20SiC composite specimens, indicating that the corrosion resistance of the Al-20SiC-0.3CeO2 composite is improved. This is because rare earth not only eliminates microcracks, but also changes the type of corrosion from localized to uniform, thus improving corrosion resistance. The Al-based composite material modified by electron beam and rare earth has many potential applications and development prospects.