M. M. Mikhailov

Proton and electron irradiation induced changes in the optical properties of ZnO pigments modified with ZrO2 and Al2O3 nanopowders

The effect of the modification of ZnO powders by ZrO2 and Al2O3 nanoparticles with a concentration of 1–30 wt % is investigated by diffuse reflectance spectra within the wavelength range 0.2 to 2.5 μm before and after 100 keV proton and electron irradiation. It has been established that the introduction of nanoparticles enhances the optical stability of the pigments under proton irradiation, but reduces it under electron irradiation. Samples modified by 5 wt % of ZrO2 nanoparticles have the highest stability of optical properties after proton exposure. The degradation of optical properties under electron irradiation is not high for this concentration of nanoparticles. A decrease in the absorption of pigments modified with nanoparticles after proton exposure is determined by a decrease in the intensity of bands located in the UV and visible regions. After electron exposure the absorption bands have a high intensity in the whole spectrum range.

Radiation stability of ZnO pigment modified by ZrO2 · Y2O3 nanopowders

The effect of the zinc oxide’s powder modification by ZrO2 · Y2O3 nanoparticles on the spectra of diffuse reflectance and their changes after irradiation with 100-keV protons was studied at concentrations of 1, 3, 5, 7, 10, 15, and 30 wt % and T = 650 and 800 °C. Induced absorption spectra of irradiated powders were decomposed into bands of elementary defects. The effect of temperature on the band area and a change in the total absorbance of ZnO powders during nanoparticle modification and concentration was demonstrated.

Radiation stability of powders in mixtures with Al2O3 nanoparticles

A comparative research was conducted to investigate the absorption spectra of barium titanate powders mixtures with aluminum oxide micro- or nanopowders irradiated by electrons. It was established that the addition of aluminum oxide nanopowder enhances the radiation stability of mixtures, which increases with the concentration of nanoparticles. Stability augmentation of mixtures under irradiation is caused by the decrease in the concentration of radiation defects in the anion sublattice of barium titanate.

Comparative analysis of emission and absorption spectra of zinc oxide powders

AbstractsPhotoluminescence and optical absorption spectra induced by proton and electron irradiation in zinc oxide powders have been investigated. It has been found that the emission band in a visible region with a maximum of about 2.3 eV is a superposition of three bands with 2.55, 2.34, 2.12 eV, respectively, caused by oxygen vacancies VO+, interstitial oxygen Oi−, and zinc vacancies VZn− absorbing in the 3.03-, 2.83-, and 2.64-eV bands.

Dependence of optical properties and radiation resistance on the granule size of zinc oxide powders

The influence of the granule size of zinc oxide powders on the diffuse reflection spectra and their modifications caused by electron irradiation are investigated in the size range of 70–630 μm. It is ascertained that the reflection coefficient before irradiation and the coefficient of absorption induced by irradiation vary along the curves with maxima near approximately 130 μm as a function of the ZnO granule size.

Photoluminescence of Zinc Oxide Modified by Nanopowders

The modifying effect of Al2O3, Al2O3 · CeO2, ZrO2, ZrO2 · Y2O3 nanopowders on the photoluminescence spectra of ZnO powder in the 360–660 nm range is investigated. It is found that the introduction of nanoparticles causes a decrease in the ultraviolet band intensity and an increase in the visual spectral band intensity. The change in the intensity of elementary components of the visible range band during modification seems to be explained by the emergence of oxygen and zinc vacancies (VO+ and VZn−) and interstitial oxygen ions (Oi−).

Qualitative and quantitative differences in the absorption spectra of electron-irradiated reflective coatings based on mixtures of BaTio3 powder with ZrO2 micro- or nanopowder of different concentrations

The effect of the concentration and size (micro- or nanoparticles) of zirconium dioxide powders, heated in mixtures with barium titanate powder, on the radiation resistance of reflecting coatings on their basis is analyzed during accelerated electron irradiation. It is shown that nanoparticles provide increased radiation resistance of the coatings compared to microparticles.

Features of degradation and recovery of the optical properties of coatings based on ZnO powder modified with nanoparticles after irradiation

ABSTRACT The effect of electron irradiation with energy of 30u2009keV and fluence up to 7u2009×u20091016u2009cm−2 on diffuse reflection spectra in situ of coatings based on ZnO powders unmodified and modified with zirconium dioxide and aluminum oxide nanopowders was investigated. The higher radiation stability of coatings based on modified pigments in comparison to unmodified pigments has been established. A significant recovery of the reflection spectra of irradiated coatings after exposure to residual vacuum and air was shown.

Features of radiation-induced changes in the diffuse reflectance spectra of modified titanium-dioxide powders

Changes in the diffuse reflectance spectra of titanium-dioxide micropowders (initial, modified by nanoparticles, treated with oxidants such as potassium peroxoborate and sodium peroxide, or ultraviolet irradiated in an oxygen atmosphere) in the range 0.3–2.1 μm after irradiation with ultraviolet light, electrons, or protons are analyzed. The general and distinctive features of changes in the spectra in the visible and near infrared regions are revealed and an explanation of the obtained data is proposed.

The effect of heating on optical properties and radiation resistance of coatings based on micro- and nanosized aluminum oxide powders

Comparative analysis of the effect of heating in air (at T = 800°C for 2 h) on the diffuse reflectance spectra in the range of 360–2100 nm and on the integrated coefficient of the solar radiation absorption of coatings based on Al2O3 micro- and nanopowders has been carried out. Their variation under electron irradiation has been studied. It is established that the heating of powders deteriorates the optical properties and radiation resistance of coatings.