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Using the method of evaporation by pulsed electron beam in vacuum the mesoporous nanopowder of CaF 2 with a specific surface area up to 91.5 m2/g was produced. The effect of annealing in different media and irradiation with a nanosecond electron beam (700 keV) on the evolution of the magnetic, luminescent and textural properties of CaF 2 nanoparticles have been studied. For the first time, a joint effect of the annealing medium and the absorbed dose of a relativistic electron beam irradiation on the specific surface area and magnetization of mesoporous nanopowders of the CaF 2 was discovered, which confirms the defective nature of ferromagnetism at room temperature of CaF 2 nanopowders. The effect of nanopowder surface properties on ferromagnetism at room temperature after annealing in different media is shown, a parameter for assessing this influence is proposed. It was found that annealing and irradiation caused a significant change only in the visible range, of the pulse cathodoluminescence spectra of the CaF 2 nanopowder, with the temperature and medium of the nanopowder pre-annealing as well as the irradiation dose being important. The relationship between luminescent and magnetic properties of nanopowder was shown. [ABSTRACT FROM AUTHOR]

ZrO 2 and Ag doped ZrO 2 powders were prepared from mixtures of ZrO 2 and AgNO 3 commercial powders (99:1 and 95:5 wt %) by pulsed electron beam evaporation (PEBE) in vacuum. Samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), textural and magnetic analysis, photocatalytic test, photoluminescence spectroscopy (PL) and cell cytology (Vero and Hela). XRD analysis confirmed the presence of monoclinic ZrO 2 phase and cubic Ag phase in the final product. НRTEM pictures showed a large range of particle sizes approximately from 10 to 500 nm; the spherical silver nanoparticles (NPles) (10 nm) were observed on the ZrO 2 particle surfaces. Ferromagnetic contribution in pure ZrO 2 powder was 0,002 emu/g, and in Ag doped ZrO 2 powders it reached 0,016 emu/g. It was found that Ag doped ZrO 2 powders showed increased photocatalytic activity in methyl orange (MO) compared with pure ZrO 2 NPles. The produced powders can be used to kill Hela cancer cells, as low (<0.1 wt) Ag photocatalysts and in other applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Mesoporous multiphase amorphous–crystalline Bi2O3 nanopowder with the specific surface area of 23 m2/g is obtained using pulsed electron beam evaporation in vacuum. The influence of thermal annealing (200–300°C) of the powder in air has been investigated. Droplets 2–5 nm in size are formed on the surface of all large nanoparticles comprising the framework of 3D agglomerates of the nanopowder due to extrusion of liquid bismuth from bulk upon cooling. [ABSTRACT FROM AUTHOR]

The technology for manufacturing large size shielded metal-ceramic cold cathodes is described. It has been shown that the use of a shielded metal-ceramic cathode allows to significantly increase the impedance of the vacuum diode and to form an electron beam of constant cross-sectional size or of the required size (up to 400 mm wide) with a fairly uniform electron beam current density distribution (≤15%). It has been found that the emission decline of the shielded metal-ceramic cathode, like that of the metal-dielectric cathode operating at a high repetition rate (≥100 pps), is significant at the beginning of the process and then slows down, allowing continuous operation for up to 40 h. Both cathodes require periodic cleaning of the plates, which is more difficult for metal-ceramic plates. At the same time, a metal-ceramic cathode works better at low vacuum, allowing twice as much current to be generated (in the same geometry) as a metal-dielectric cathode, while reducing the accelerating voltage by ∼15%. However, metal-ceramic plates are about 100 times more expensive to manufacture than dielectric plates for a metal-dielectric cathode. Therefore, the choice of cathode type for vacuum diode accelerators is not a trivial problem, but depends on many factors that must be taken into account in each case and for each radiation technology. • A shielded cathode has been designed to produce an electron beam with a cross-section of up to 400 mm. • It is possible to have a fairly uniform electron beam current density distribution (≤15%). • The beam size of the shielded metal-ceramic cathode can be practically constant. • The shielded metal-ceramic cathode works better at low vacuum than a metal-dielectric cathode. [ABSTRACT FROM AUTHOR]

The crystallophores of the composition Sr2La8(1x-y)ErxYbyGe6O26 (x = 0.01, 0.05, 0.075, 0.1, 0.15) were synthesized. Nanophosphores in the amorphous state were obtained for the first time by the method of pulsed electron beam evaporation using a phosphor of the composition Sr2La7.85Er0.075Yb0.075Ge6O26 with the structure of oxyapatites as a target. DSC-TGA analysis was performed to determine the temperature stability and the onset of crystallization of the nanosample. A change in the Raman spectra of the samples with a decrease in the particle dimension from the bulk to nanoscale state was found. The spectral characteristics of the upconversion photoluminescence of samples in polycrystalline and nano-amorphous states are studied. It has been shown that luminescence is influenced by nonradiative processes between different transitions of Er3+ ions. There is a threshold population of the Er3+ and Yb3+ levels (level 2F5/2) in the region of relatively low pumping powers of nanosamples by laser radiation with a wavelength of λex = 980 nm. Above this threshold a sharp increase in the intensity of upconversion photoluminescence occurs. [ABSTRACT FROM AUTHOR]

Using vacuum evaporation by a pulsed electron beam, mesoporous CaF2 nanopowders with a specific surface area of up to 91.5 m2/g were obtained. The effect of nanosecond electron beam irradiation in air on the magnetic and texture properties of the obtained nanopowders was studied. For the first time, the effect of irradiation on the specific surface and magnetization of CaF2 nanopowders was revealed. [ABSTRACT FROM AUTHOR]

We present results of the investigation of a metal-ceramic cathode suitable for technological applications. The cathode was tested in electron diodes powered by two different high-voltage generators (500 kV, 50 ns, 300 Ω, ≤200 Hz and 300 kV, 250 ns, 84 Ω, ≤5 Hz). The metal-ceramic cathode which was made in a form of a disk was composed of TiO[sub 2] ceramics with stainless steel spherical particles uniformly inserted inside. It was shown that already at relatively low accelerating fields (E ≤ 5 kV/cm) fast cathode plasma formation occurs as a result of surface flashover. This surface flashover is initiated in triple points located in micropores which were formed during the process of cathode preparation due to the different thermal expansion coefficients of the ceramic and the metal. Experimental data concerning the uniformity of the light emission from the cathode surface and inside the anode-cathode gap and divergence of the generated electron beams are presented. Also, it is shown that the uniformity of the generated electron beam depends strongly on the duration of the accelerating pulse. [ABSTRACT FROM AUTHOR]

Mesoporous crystalline BaF 2 nanopowder with a specific surface area of up to 34.8 m2/g was produced by a pulsed electron beam through the evaporation of targets of micro-sized BaF 2 powder with optical purity (S red = 0.38 m2/g). The texture and thermal features of the BaF 2 nanopowder (before and after annealing in air at a temperature of 200 °C) and some properties of compacts made of the BaF 2 nanopowder by magnetic-pulse compaction and static pressing were studied. Glassy, opaque, and black compacts, which are promising materials for use as scintillators and dosimeters, were produced by magnetic-pulse compaction in a vacuum at a temperature of about 425 °C. It was found that heating up to 425 °C is sufficient for removing defects in nanopowders. The effect of pressing methods on the pulsed cathodoluminescence and photoluminescence spectra of the compacts was studied. Luminescent properties were found to depend on pressing technology. It was also determined that surface color centers, the number of which decreases during heating, are responsible for the pulsed cathodoluminescence band near ∼560 nm. [ABSTRACT FROM AUTHOR]

Mesoporous amorphous-crystalline nanopowders of BaF2 with the specific surface area up to 34.8 m2/g were obtained using evaporation by a pulsed electron beam in vacuum. Influence of the thermal annealing of the BaF2 nanoparticles in air at the temperatures from 200 to 900°C on the size and morphology of the particles and changes in their magnetic and luminescent properties was studied. The paramagnetic response of the BaF2 nanopowder was found to transform to the ferromagnetic response after annealing at 900°C. The appearance and transformation of the magnetic response in nanopowders made of BaF2, which is diamagnetic as the bulk material, are ascribed to the appearance of radiation-induced and structural defects during the synthesis process by pulsed electron-beam evaporation. [ABSTRACT FROM AUTHOR]

With the help of electron beam evaporation of mechanical mixtures of nonmagnetic micron powders ZnO and carbon in vacuum with the subsequent annealing of evaporation products in air at the temperature of 773 K, single-phase crystal nanopowders ZnO-C were produced with the hexagonal wurtzite structure and low content of the carbon dopant not exceeding 0.25 wt%. It was established that doping ZnO with carbon stimulates primary growth of nanoparticles along the direction 0001 in the coatings. Nanocrystal growth in coatings occurs in the same way as crystal growth in thin films, with growth anisotropy in the c-axis direction in wurtzite ZnO. Element mapping has confirmed homogeneous distribution of carbon in ZnO lattice. Ferromagnetism of single-phase crystal nanopowders ZnO-C with the hexagonal wurtzite structure and low content of the carbon dopant not exceeding 0.25 wt% was produced at room temperature. Ferromagnetic response of the doped NP ZnO-C has exceeded the ferromagnetic response of pure NP ZnO 5 times. The anhysteretic form of magnetization curves NP ZnO-C indicates aspiration of samples to superparamagnetism manifestation. [ABSTRACT FROM AUTHOR]

The nanopowders (NPs) ZnO-Zn-Fe and ZnO-Fe with the various concentrations of Fe (xFe) (0≤xFe≤0.619 mass.%) were prepared by the pulsed electron beam evaporation method. The influence of doping Fe on structural and magnetic properties of NPs was investigated. X-ray diffraction showed that powders contain fine-crystalline and coarse-crystalline ZnO fractions with wurtzite structure and an amorphous component. Secondary phases were not found. The magnetic measurements made at room temperature, using the vibration magnetometer and Faraday’s scales, showed ferromagnetic behavior for all powders. Magnetization growth of NPs ZnO-Zn and ZnO-Zn-Fe was detected after their short-term annealing on air at temperatures of 300–500°C. The growth of magnetization is connected with the increase in the concentration of the phase ZnO with a defective structure as the result of oxidation nanoparticles (NPles) of Zn. The scanning transmission electron microscopy (STEM) showed a lack of Fe clusters and uniform distribution of atoms dopant in the initial powder ZnO-Zn-Fe. A lack of logical correlation between magnetization and concentration of a magnetic dopant of Fe in powders is shown. [ABSTRACT FROM AUTHOR]

Frequency nanosecond electron accelerators type URT has been developed for use in radiation technologies. The accelerator includes a thyratron, a pulse transformer and a semiconductor opening switch. The accelerating voltage is up to 0.9 MV, FWHM pulse length is up to 60 ns, and the repetition rate is up to 250 Hz. A metal ceramic cathode, which is used in the accelerator, provides an electron beam cross section up to 16 cm in diameter or rectangular with the dimensions of 45 * 5cm2at a maximum density of the pulse current equal to 2 A/cm2. Thus, a family of nanosecond electron accelerators has been developed for use in radiation technologies applied to layers up to 0.4 g/cm2thick, such as production of nanopowders from gas and liquid precursors. Experiments on the irradiation of silver nitrate solutions in various liquids by a URT-0.5 accelerator facilitated the development of technology for producing silver nanopowders (NPs). The powder yield and particle size as a function of the irradiation mode has been established. An increase in the adsorbed dose results in an increased powder yield; however, the particle size decreases and the powder agglomeration rate increases. Therefore, the targeted production of silver NPs with a mean particle size in the range of 90–1100 nm is possible. Besides to produce TiO2and SiO2NPs the gas precursors were used. [ABSTRACT FROM AUTHOR]

Nanopowders of pure and doped oxides with high specific surface area were produced by a method of pulsed electron beam evaporation in vacuum. Characteristics nanopowders were studied by methods of XRD, high resolution transmission electron microscopy, electronography, DSC-ТG, inductively coupled plasma and pulsed cathodeluminescence. For the first time was established ferromagnetism at room temperature in nanopowders ZrO2. ZnO-Zn-Cu and СeO2-C which can be connected with high deficiency produced nanopowders. [ABSTRACT FROM AUTHOR]

Methods for the synthesis of new chelating chitosan derivatives containing 2-carboxyethyl groups were developed. Their macromolecules were cross-linked by the irradiation with a nanosecond electron beam, which gave for the first time sorbents with a high sorption capacity for CuII ions. The maximum sorption capacity, which is achieved in the pH range 6.5–7.2. and the Langmuir adsorption constant of Cu2+ ions on the sorbent with the degree of substitution 0.91 are 1.37 mmol g−1 and 152.51 L mol−1, respectively. The structures of the formed complexes in the sorbent phase were characterized by ESR spectroscopy. [ABSTRACT FROM AUTHOR]

The development of radiation processing methods for food and agricultural products increases the demand for methods of control over the processing and circulation of products. ESR spectrometry is a promising method for monitoring and detecting, which is already being used to control products containing bones, cellulose and crystalline sugar. This research presents the results of a study of the radiation-induced ESR signal in eggshells and the kinetics of radicals over time. The samples were irradiated using the URT-0.5 (0.5 MeV) and UELR-10-10S2 (10 MeV) electron accelerators. The ESR signal spectra were obtained on an ELEXSYSE500 ESR spectrometer. The dependencies of the ESR signal intensity on the value of the absorbed dose were obtained, and a comparative analysis of the irradiation of chicken eggs with different energies was carried out. • The samples were irradiated using the URT-0.5 (0.5 MeV) and UELR-10-10S2 (10 MeV) electron accelerators. • ESR signal was measured at ELEXSYSE500 ESR spectrometer. • The dependences of the ESR signal intensity on the absorbed dose in eggshell were obtained in the range from 1 to 40 kGy. [ABSTRACT FROM AUTHOR]

A vacuum diode for the two-sided electron irradiation of objects makes it possible to reduce the irradiation nonuniformity and increase the thickness of the irradiated layer of the object with a uniform distribution of the absorbed dose over the layer thickness. The cathode holder of the diode is constructed in the form of two symmetrical arms connected to a common current lead. Two cathodes are attached to the arms' ends opposite each other. The electron beam is extracted to the atmosphere through two windows–anodes positioned across from one another. The vacuum diode with metal–dielectric cathodes was tested on a УРТ-0.5 nanosecond electron accelerator (the electron energy is ∼0.5 MeV and the output beam power is ∼1 kW). The results obtained have shown that the diode ensures the two-sided irradiation of objects. Depending on the irradiated surface, the irradiation conditions can be varied by changing the cathode–anode distance in one of the arms of the diode. [ABSTRACT FROM AUTHOR]

The magnetic properties of oxide nanopowders obtained by pulsed electron beam evaporation of targets in a low-pressure gas phase have been studied. Using this method, we obtained Zn-ZnO and ZnO nanopowders with the specific magnetization amounting to 2.8 × 10−2 and 2 G cm3/g, respectively. Significant room-temperature ferromagnetism has been observed for the fist time in a nanopowder of yttria-stabilized zirconia, where the specific magnetization reached ∼6.7 × 10−2 G cm3/g. [ABSTRACT FROM AUTHOR]

Magnetic nanopowders of oxides Al 2 O 3 , SiO 2 , CeO 2 and YSZ (ZrO 2 -8% Y 2 O 3 ) with a high specific surface area irradiated in air by electrons with energy of 700 keV, pulse duration 100 ns, using the repetitively pulsed accelerator URT-1 within 15 and 30 min. The magnetic, thermal, and cathode luminescence characteristics of NPs were measured before and after irradiation. It was established that the electron irradiation non-monotonically changes the magnetization of the pristine samples. On the contrary, a clear correlation between the intensity of cathode luminescence and the irradiation dose is found in the most of the oxides. Thermal stability and phase transformations of unirradiated and irradiated CeO 2 and YSZ oxides were analyzed with the aid of synchronous analysis, using the methods of thermogravimetry and differential scanning calorimetry. The luminescent and thermal properties reflect the transformation of structural defects in NPs more strongly after exposure to a pulsed electron beam in comparison with corresponding changes of the NP's magnetic response. [ABSTRACT FROM AUTHOR]

The present paper studies the pathways of phase transformation of heterophasic nanopowder (NP) Bi 2 O 3 produced by pulsed electron beam evaporation (PEBE) in vacuum (4 Pa) when annealing in air. The phase transformation after annealing in air of heterophase bismuth oxide NPs leads to the formation of bismuth carbonate at an annealing temperature of 200–300 °C. The effect of NP aging in storage under normal conditions was investigated. [Display omitted] • The heterophase amorphous-crystalline NP Bi 2 O 3 was obtained by means of PEBE. • (α + β + amorph) → 200 0 c (β + Bi 2 O 2 CO 2) → 300 0 c (α+β + Bi 2 O 2 CO 2) → 500 0 c (α) → 750 0 c (γ+α). • The effect of aging of the samples during their storage under normal conditions. [ABSTRACT FROM AUTHOR]

A mesoporous amorphous crystalline nanopowder (NP) Si–SiO 2 with a specific surface area (SSA) of 35 m2/g was produced by pulsed electron beam evaporation (PEBE) of a compact of micron commercial SiO 2 powder (0.9 m2/g). Si semimetal nanoparticles (NPles) reduced in for vacuum (≈4 Pa) had a marked effect on the thermal and luminescent properties of the Si–SiO 2 nanoparticles compared to the properties of amorphous SiO 2 NPles produced earlier by PEBE evaporation of a target compound made from NP Aerosil 90 (Degussa). Photocatalytic capabilities of Si–SiO 2 nanoparticles were evaluated. NPles Si–SiO 2 showed high antioxidant activity on HELA cancer cells. • The PEBE method applied to the synthesis of NP Si–SiO2 from cheap commercial powder. • XRD analysis showed the presence of silicon nanocrystals in the synthesized product. • HRTEM directly confirmed the presence of crystalline Si nanoparticles in NP Si–SiO 2. • XPS analysis showed the presence of Si–OH bonds on the surface of SiO 2 particles. • The Si–SiO 2 nanopowder showed high antioxidant activity. [ABSTRACT FROM AUTHOR]

Abstract Nanopowders and coatings of pure and Cu-doped ZnO were prepared by the pulsed electron beam evaporation method. The results of X-ray diffraction demonstrated that all samples have a single-phase ZnO hexagonal wurtzite type structure. The SEM images highlighted that pure and Cu-doped ZnO samples have bimodal nanoparticle shapes with an average particle size of 40 nm-5 μm. The magnetic hysteresis loop of pure ZnO nanoparticles at room temperature revealed a saturation magnetization of 0.044 emu/g in a vacuum and 0.027emu/g in air. The hysteresis loops of Zn0.9978Cu0.0022O and Zn0.9965Cu0.0035O samples indicated similar magnetic properties with the saturation magnetization of 0.037 and 0.012 emu/g and coercivity of about zero and ∼100 Oe, respectively. The correlation between the concentration of structural defects (oxygen vacancies) and the ferromagnetic behavior of nanopowders are presented. The dependences of the integral intensity of the green and the orange bands of photoluminescence spectra and the magnetization on the copperdoping level are considered and their correlation is established. Graphical abstract Image 1 Highlights • Nanopowders and coatings of pure and weakly Cu-doped ZnO have been prepared by pulsed electron beam evaporation. • Room temperature ferromagnetism has been achieved in nanostructured pure and Cu doped ZnO. • Investigate the structure of Cu-doped ZnO by XRD, SEM, HRTEM, PCL, PL, DSC-TG, FTIR and VSM measurements. [ABSTRACT FROM AUTHOR]

Radiation processing applications for food and agricultural products require to control the applied doses values. This investigation shows the potential of using electron paramagnetic resonance (EPR) spectrometry for dosimetric control of wheat seeds irradiated at the URT-0.5 (0.5 MeV) linear electron accelerator. The general view of the wheat EPR spectra in the dose range 0–20 kGy is presented. The temporal kinetics of the entire spectrum and separated peaks has been studied. The EPR signal integral intensity dependences on the absorbed dose were obtained. • Wheat seeds were irradiated at electron accelerator URT-0.5 with 500 keV beam energy. • The EPR signal was evaluated to identify processing by low energy electron beam. • The dependences of the EPR signal on the absorbed dose in wheat seeds were obtained in the range from 1 to 20.4 kGy. [ABSTRACT FROM AUTHOR]

• Formation of R-phase Bi 2 O 3 in vacuum. • Reduction of heterophase Bi 2 O 3 NPs in argon atmosphere with formation of metallic Bi. • Formation of uniform nanoparticles (droplets) of metallic Bi with a size of 3–5 nm. • Absence of cathodoluminescence in powders annealed in air. • Extrusion of liquid Bi onto the surface of Bi 2 O 3 3D nanostructures leads to the formation of droplets. [Display omitted] In this work the method of pulsed electron beam evaporation (PEBE) in vacuum (4 Pa) was used to produce the mesoporous multiphase (α, β and amorphous) amorphocrystalline nanopowder (ACN) of Bi 2 O 3 with specific surface area (SSA) up to 23 m2/g. The effect of thermal annealing on the properties of Bi 2 O 3 ACN was investigated in vacuum and in air. Using the HTXRD method in a vacuum (10−4 mbar) in the RT-510 °С temperature range, the phase transformation of the NP was established according to the scheme (α + β + amorph) ⟶ 200 ° C (α + β + R) ⟶ 280 ° C (α + R) ⟶ 510 ° C (α). The formation of uniform Bi amorphocrystalline nanoparticles (droplets) with a size of 3–5 nm was observed on the surface of all bismuth oxide samples (S200, S300 and S500) that were annealed in air in the temperature range of 200–500 °С, respectively, due to extrusion of liquid Bi from the volume to the surface of large nanoparticles (NPles) forming the framework of 3D nanoparticle agglomerates during the cooling of the annealed NPs. The presence of NPles of metallic Bi in the original sample was confirmed directly by HRTEM and indirectly by RS, DSC and PCL. The magnetic behavior of annealed samples confirmed their diamagnetic nature. The weak ferromagnetic response (3–4 memu/g) in the as prepared sample was associated with its very defective structure. The photocatalytic activity of NPs was confirmed in decomposition of MO colorant during UV irradiation. [ABSTRACT FROM AUTHOR]