Investigation into phase transformations and structural and luminescent properties of multiphase coatings and aluminum oxide nanopowder prepared by evaporation with a pulsed electron beam

Multiphase nanopowder and amorphous/amorphous-nanocrystal coatings on the basis of Al2O3 have been produced on a glass substrate by the method of pulsed electron-beam evaporation in vacuum. Their characteristics are studied by XRD, BET, pulsed cathodoluminescence, and differential scanning calorimetry (DSC)/thermogravimetric analysis. The effect of the deposition time of nanoparticles (NPs) on the phase composition of coatings and nanopowders is established. The correlation of luminescent properties with the phase composition of coatings and nanopowders is detected. Amorphous-nanocrystal coatings and nanopowders containing an Al2O3γ phase with a defective cubic spinel structure are promising materials for the dosimetry of different types of ionizing radiation. © 2013 Pleiades Publishing, Ltd

Physical properties of fluorides barium and calcium nanopowders produced by the pulsed electron beam evaporation method

The mesoporous nanocrystal powders BaF 2 and CaF 2 with a specific surface up to 34.8 and 88.7 sq.m/g, respectively, are produced by the pulsed electron beam evaporation method in vacuum. The influence of thermal annealing of nanoparticles on air in the range of temperature from 200 to 900°C on the size, morphology of particles and change of their magnetic and luminescent properties investigated have been investigared. The essential stoichiometric impurity (overage of metals) and significant growth in a specific surface of nanopowders (NP) BaF 2 and CaF 2 after annealing at the temperature of 200°C have been detected. It is established that the synthesized NP BaF 2 is a paramagnetic while initial material in the bulk state is diamagnetic. After annealing at 900°C appears the small ferromagnetic contribution at NP BaF 2 . Produced NP CaF 2 showed ferromagnetic behavior. In literature there is no information about the ferromagnetism of CaF 2 . Appearance of the ferromagnetic response can be explained with formation of structural and radiation defects (F-centers, etc.). The analysis of PCL and magnetization curves of samples BaF 2 and CaF 2 allows drawing conclusions about their connection. © Published under licence by IOP Publishing Ltd.The authors are grateful to Pryanichnikov S.V., a researcher of the shared equipment center “Ural” of the Institute of Metallurgy of the Ural division of RAS, for the X-ray phase analysis; to the researchers of the Institute of Electrophysics of the Ural division of RAS Demina T.M. for the texture analysis, Murzakayev A.M. and Timashenkova O.R. for the microscopic analysis, Spirina A.V. for the PCL analysis. This work has been carried out within the scope of government order No. 0389-2015-0026 and with partial support of RFBR project No. 18-08-00514. The magnetic measurements were carried out within the scope of government order under the topic MAGNIT, state registration No. AAAA-A18-118020290129-5

Properties of the amorphous-nanocrystalline Gd2O3 powder prepared by pulsed electron beam evaporation

An amorphous-nanocrystalline Gd2O3 powder with a specific surface area of 155 m2/g has been prepared using pulsed electron beam evaporation in vacuum. The nanopowder consists of 20- to 500-nm agglomerates formed by crystalline nanoparticles (3-12 nm in diameter) connected by amorphous-nanocrystalline strands. At room temperature, the Gd2O3 nanopowder exhibits a paramagnetic behavior. The phase transformations occurring in the powder have been investigated using differential scanning calorimetry and thermogravimetry (40-1400°C). The amorphous phase of the nanopowder is thermally stable up to a temperature of 1080°C. It has been found that the amorphous phase has an inhibitory effect on the temperature of the polymorphic transformation from the cubic phase into the monoclinic phase. It has been revealed that, compared with the microcrystalline powder, the Gd2O3 nanopowder is characterized by a complete quenching of photoluminescence. © 2013 Pleiades Publishing, Ltd

Structural and Magnetic Properties of Nanopowders and Coatings of Carbon-Doped Zinc Oxide Prepared by Pulsed Electron Beam Evaporation

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

Luminescent and dosimetric properties of thin nanostructured layers of aluminum oxide obtained using evaporation of a target by a pulsed electron beam

Results of a study of optically and thermally stimulated luminescence (OSL and TL) of thin nanostructured aluminum oxide coatings obtained with evaporation of the target by a pulsed electron beam and deposited on quartz glass, Al, steel, Cu, Ta, and graphite wafers are presented. It follows from data of X-ray phase analysis that the obtained Al2O3 layers have an amorphous nanocrystal structure with different contents of the γ phase depending on the geometry of the wafer location on evaporation and annealing temperature of the samples. It is established that the material of the wafer and the ratio of the amorphous and γ phase in Al2O3 layers affect the yields of OSL and TL. Annealing at up to 970 K results in an increase of γ-phase concentration and OSL and TL responses. It was found that the yields of OSL and TL for the most emission-effective coating samples are comparable with those for the detectors on the basis of anion-defective corundum. The dose-dependence for β radiation, which was linear in the range 20-5000 mGy, was investigated. © 2013 Pleiades Publishing, Ltd

Production and Investigation of Biological and Photocatalytic Activit Multimodal Nanopowders Produced by Pulsed Electron Beam Evaporation in Vacuum

Nanopowders doped with silver were produced by the methode pulsed electron beam evaporation. © Journal of Physics: Conference Series 2021.The study was carried out with the financial support of RFFI and the Sverdlovsk region as part of the scientific project No. 20-48-660019. For assistance in research, we thank students of the Ural Federal University Troshina Anastasia and Tairov Yevgeny

Effect of iron doping on the properties of nanopowders and coatings on the basis of Al2O3 produced by pulsed electron beam evaporation

Multiphase nanopowders (NPs) and amorphous/amorphous-nanocrystalline coatings (A-NC) have been prepared by the evaporation of ceramic targets of Al2O3-Fe2O3 (0.1, 3, 5 Fe2O3 mass %) by a pulsed electron beam in vacuum. The specific surface area of NP Al2O3-Fe2O3 reached 277 m2/g. The α and γ phases Al2O3 and other nonidentified phases have been found in the composition of NP Al2O3-Fe2O3. All coatings contained an insignificant fraction of the crystalline γ phase. No secondary phases on the basis of iron have been revealed. According to transmission electron microscopy, the fine fraction of NP Al2O3-Fe2O3 consists of amorphous nanoparticles of an irregular and quasispherical shape no more than 10 nm in size which form agglomerates reaching 1.5 μm. A large fraction of NPs consists of crystal spherical nanoparticles with preferential sizes of about 10-20 nm. All NP Al2O3-Fe2O3 showed ferromagnetic behavior at room temperature. The maximum magnetic response has been established in NPs with a minimum iron content (1.1 mass %). The pulsed cathode luminescence spectra of coatings and NP Al2O3-Fe2O3 have been presented by a wide band in the wavelength range of 300-900 nm regardless of their phase composition. Phase transformations into NP AL2O3-1.1% Fe and coatings from undoped Al2O3 heated to 1400°C occur according to the following scheme: amorphous phase → γ → δ → θ → α, regardless of their initial phase composition. The threshold of thermal stability of the Γ phase in NPs and the coating of undoped Al2O3 does not exceed 830°C. For the first time, the increased thermo and optically stimulated luminescent response comparable with the response of the leading TLD-500K thermoluminescent dosimeter has been reached in A-NC coatings of undoped Al2O3. © 2013 Pleiades Publishing, Ltd

Physical properties of calcium fluoride nanopowder produced by the method of evaporation by pulsed electron beam in a low-pressure gas

Mesoporous CaF2 nanopowders with the specific surface area up to 88.7 m2/g have been produced by the evaporation by a pulsed electron beam in vacuum. The influence of thermal annealing in air on the size and morphology of CaF2 nanoparticles and their magnetic, luminescence, and texture characteristics has been studied. Ferromagnetism of CaF2 nanopowders was discovered for the first time. The influence of radiation defects (CaF2 dye centers) on magnetic properties of CaF2 nanoparticles has been examined. © Published under licence by IOP Publishing Ltd.Russian Foundation for Basic Research, RFBR: 18-08-00514This work was performed within the subject of the state task [0389-2015-0026]; was partial supported by the Russian Foundation for Basic Research [18-08-00514]

Physical properties of calcium fluoride nanopowder after irradiation by relativistic electrons

Mesoporous CaF2 nanopowders with specific surface area up to 91.5 m2/g have been obtained through evaporation by electron beam in vacuum. The effect of relativistic e-beam irradiation in air on magnetic and texture properties of CaF2 nanoparticles has been studied. The influence of annealing and irradiation on the specific surface area and magnetization of CaF2 nanopowder has been discovered for the first time. © Published under licence by IOP Publishing Ltd.Russian Foundation for Basic Research, RFBR: 18-08-00514This work was performed within the subject of the state task [0389-2015-0026]; was partial supported by the Russian Foundation for Basic Research [18-08-00514]