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The paper studies the electron irradiation at an energy of 30 keV affecting the diffuse-reflectance spectra and integrated absorption coefficient of solar irradiance of the micron-sized mZnO powder modified by adding nY2O3 nanoparticles in the amount of 0.1 to 10 wt.%. The best content of nanoparticles is found to be 3 wt.%, when the diffuse-reflectance spectra and the integrated absorption coefficient of the modified powder are 1.41 times lower than in the initial powder. It is shown that free electrons forming during the powder irradiation, make the highest contribution to the powder degradation. [ABSTRACT FROM AUTHOR]

The radiation resistance and optical properties of micron-sized mCaSiO3 wollastonite powders (initial and modified by gadolinium oxide nGd2O3 nanoparticles) were studied. For this purpose, the powders were irradiated with accelerated electrons, and diffuse reflection spectra (ρλ) were recorded in high vacuum (in situ). The mCaSiO3 powder features a high reflectance throughout the measured spectrum range from 200 to 2,500 nm. The obtained value of the solar absorptance (αs = 0.117) is less compared to known powders used as pigments for reflective coatings, such as ZnO and TiO2. Depending on the concentration of nanoparticles in the range of 1–10 wt%, the radiation resistance of the modified mCaSiO3/nGd2O3 powder increases up to 1.7 times compared to the unmodified powder. The achieved increase is of great practical importance for various applications, which require high radiation resistance, such as nuclear industry (cement and ceramics fillers, dosimetry materials) and aerospace industry (pigment for thermal control coatings). [ABSTRACT FROM AUTHOR]

Abstract—The work reports on studies of the diffuse reflectance spectra in situ recorded in vacuum for SiO2-nanoparticle-modified BaSO4 micron-sized powders in the range of 0.2–2.2 μm before and after the separate solar spectrum quanta exposure and the successive irradiation after exposure to protons with energy of 5 keV. The absence of additivity upon the separate and successive solar spectrum quanta irradiation of the examined compound is established. [ABSTRACT FROM AUTHOR]

A comparative analysis of changes in the diffuse reflectance spectra (ρλ) and the integrated absorption coefficient in the range of 0.2–2.2 μm is performed after the separate and sequential irradiation of a barium-sulfate powder modified with silicon-dioxide nanoparticles (mBaSO4/nSiO2) with 5-keV protons and solar-radiation quanta. The spectra are recorded after each irradiation cycle in vacuum within the irradiation region (in situ). The integrated solar-radiation absorption coefficient of the modified mBaSO4/nSiO2 pigment before irradiation is 0.048, which is several times lower than that of ZnO pigment widely used around the world. The additivity coefficient calculated from the results of sequential and separate irradiation of the mBaSO4/nSiO2 powder decreases by a factor of 7.5–1.052 with an increase in the fluence of 5-keV protons. Assessment of the additivity changes under the action of the spectrum of charged particles in geostationary orbit (as one of the most used and with the most severe radiation conditions) shows that the nonadditivity of separate and sequential exposure to protons and solar-radiation quanta on the pigment for mBaSO4/nSiO2 thermal-control coatings will persist for 1.27 years under these irradiation parameters. [ABSTRACT FROM AUTHOR]

Comparative studies of the optical properties and photostability of pristine microsized TiO2 powder and modified with its own nano- and hollow particles have been carried out. It was established that the reflection coefficient (ρ) decreases down to 3.5% in the visible region and increases up to 3–4% in the near-IR region at a 3 wt% concentration of nano- and hollow TiO2 particles. Powders irradiation with intensive solar radiation causes an appearance of absorption bands with maxima at 420 nm and 800–1200 nm in the difference diffuse reflection spectra. In the spectra of the powder modified with hollow particles, the bands with lower intensity shift to shorter wavelengths—to 410 and 750–800 nm. An increase in irradiation time from 5 to 40 h results in the intensity increasing of such bands. It was found that a greater effect was obtained upon modification with hollow particles in comparison with TiO2 nanoparticles. Photostability of the powders modified with hollow particles is more than 4.6 times higher than for unmodified one and it was compared with powders modified with SiO2 and ZrO2 nanoparticles. An explanation of the results obtained is given. [ABSTRACT FROM AUTHOR]

The purpose of the paper is to study the efficiency of modification with CeO2 nanoparticles (average particle size — 20–30 nm) in a concentration range from 0.1 to 10 wt.% aimed at improving the optical features and radiation stability of micron-sized ZnO powders. The optimal concentration of CeO2 nanoparticles, 3 wt.%, was determined. The change of the solar absorptance in a range of 0.2 to 2.2 µm after electron irradiation of the modified powder (E = 30 keV, F = 2·1016 cm−2) is 1.41 less compared to the unmodified powder. The paper demonstrates that the increase in radiation stability of zinc oxide powders modified with cerium dioxide nanoparticles is provided by two mechanisms: relaxation of primary defects on nanoparticles and capture of formed free electrons by cations of a rare-earth element. [ABSTRACT FROM AUTHOR]

It has been shown experimentally that the flameless combustion of RDX mixtures with iron precursors, nitrogen-containing additives, and a polymer binder can lead to the formation of iron nitrides. Nanosized particles of iron nitride (Fe3N) were obtained by optimizing the ratio of initial components and the conditions of flameless combustion of RDX. The method developed for obtaining iron nitrides in this way can be used to obtain nanosized particles of nitrides of other elements. [ABSTRACT FROM AUTHOR]

The influence of the time of irradiation with solar spectrum quanta (SSQ) on the diffuse reflectance spectra (ρλ) and the integral solar radiation absorption coefficient (as) of the zinc oxide powders without and with modification with silicon dioxide nanoparticles has been studied. A comparison of changes in the absorption coefficient as have shown that after 3 h irradiation, they decreased by a factor of 2.89, whereas after 15 h irradiation with SSQ the intensity of which was 3 times higher than the solar radiation intensity they decreased by a factor of 1.28. [ABSTRACT FROM AUTHOR]

The composition, structure, and diffuse reflectance spectra of ZnO powder modified with SiO2 nanoparticles have been investigated in the range of 0.2−2.2 μm and in the IR range together with the radiation stability under irradiation with electrons at 30 keV and fluence up to 9∙1016 cm−2. It has been found that after modification and irradiation, new compounds are not formed, the intensity of some bands in the IR spectra decreases, and the reflectivity in the range from 0.4 to 2.2 μm decreases. An absorption band appears in the visible range with a maximum at 420 nm caused by intrinsic ZnO point defects; its intensity increases with increasing electron fluence. After irradiation, the induced absorption appears in the near-IR range due to free electrons. A comparison with unmodified ZnO powder showed the effectiveness of modification to increase the radiation stability. [ABSTRACT FROM AUTHOR]

BaZrxTi(1 − x)O3 powders were solid-state synthesized from mixtures of BaCO3 and ZrO2 powders of micron sizes and TiO2 nanopowder at a concentration of substituting zirconium atoms of 10–50 wt%. The dependencies of the grain-size distribution and phase composition, diffuse reflection spectra in the UV, visible, near IR, and IR regions, as well as the solar absorptance (as), on zirconium atom concentration were studied. It was stated that the maximal yield of the main phase of the powder was 88.5%. The high reflective capacity in the visible region of the spectrum and the low value of the solar absorptance as is determined by the presence of unreacted TiO2 nanoparticles in a quantity of up to 7.3% in the phase composition and small sizes of grains and granules of the powder. [ABSTRACT FROM AUTHOR]

Changes in the in-situ measured diffuse reflection spectra and the integrated absorption coefficient of a barium-sulfate powder modified by silicon-dioxide nanoparticles are analyzed comparatively after separate and simultaneous events of irradiation with 30-keV electrons and solar-spectrum quanta. Two kinetic regions on the curves of degradation of the optical properties are found. Simultaneous irradiation is additive with respect to separate irradiation in the first region. In the second region, the changes caused by simultaneous irradiation are smaller than the sum of changes caused by separate irradiation. [ABSTRACT FROM AUTHOR]

The effect on optical properties of modifying KO-921 organosilicon compound with Al2O3 nanoparticles in the concentration range of 0.5 – 7 wt.% after irradiation with electrons is studied. Optimum values of nanoparticle concentration in order to improve compound radiation properties are established. [ABSTRACT FROM AUTHOR]

The results of studies of optical properties in UV, visible and IR spectral regions, and radiation resistance of nanocomposites based on polypropylene modified with nanoparticles of oxide compounds (ZrO 2 , Al 2 O 3 , SiO 2 , MgO, TiO 2 , ZnO) are presented. Diffuse reflectance spectra were recorded under 2 ∙ 10−6 torr vacuum before and after electron irradiation (in situ, Е = 30 keV, F = 2 ∙ 1016 cm−2). According to research findings, modification of polypropylene with nanoparticles leads to an increase in radiation resistance, which depends on the structure of the nanopowders, their size and specific surface area. The SiO 2 nanopowder, characterized by its amorphous nature, the largest specific surface area, and the smallest particle size, stands as the most effective modifier for enhancing radiation resistance. The IR-Fourier spectra of electron-irradiated samples are similar to the original spectra. A slight decrease in transmission across all characteristic bands compared to the non-irradiated samples indicates minor structural changes as a result of irradiation. [Display omitted] • Modification of polypropylene (PP) with oxide nanoparticles was carried out. • Modification makes it possible to increase the radiation resistance of the optical properties of PP. • Mechanisms for such an increase in stability upon irradiation of PP by modification with nanoparticles have been proposed. • The best modifier was selected to increase the radiation resistance of the optical properties of PP. [ABSTRACT FROM AUTHOR]

Photoluminescence spectra in the range of 3.4–1.8 eV and X-ray photoelectron spectra are analyzed comparatively after the 100-keV proton and electron irradiation of ZnO micropowder and nanopowder. A blue shift of the ultraviolet (UV) luminescence band of ZnO nanoparticles compared with microparticles is established. Exposure to ionizing radiation leads to quenching of the luminescence bands of the ZnO micropowder and nanopowder, which is related to an increase in the concentration of interstitial oxygen. [ABSTRACT FROM AUTHOR]

The paper studies the absorption spectrum and the integrated absorption coefficient of organosilicic KO-859 enamel samples modified by silicon dioxide nanoparticles and exposed to solar radiation. It is shown that nanomodification improves the radiation resistance of thermal control coatings and provides stability of their optical properties. [ABSTRACT FROM AUTHOR]

It has been experimentally proven for the first time that nanoparticles deposited on the surface of a micropowder perform the role of relaxation centers for the primary defects induced by radiation. This article focuses on the results of studying the radiation stability of ZnO powders modified with TiO 2 nanoparticles. The study shows the presence of the three processes that pre-determine the change of diffuse reflectance spectra and solar absorptance: 1) TiO 2 powders deposited on the surface of micropowder grains perform the role of a protective layer by absorbing a part of incident radiation; 2) when exposed to radiation, primary defects are formed inside a micropowder, that is, electron – hole pairs transforming into intrinsic defects; 3) the nanoparticles act as relaxation centers for primary defects formed inside the grains and granules of micron-size particles, which reduces the concentration of the former. • Optical properties stability while irradiating nano-TiO 2 is lower than that for micro-/nano-ZnO. • Modifying ZnO micropowders with nano-TiO 2 leads to an increase in radiation stability. • Nanoparticles act as relaxation centers for the post-irradiation primary defects. • Sample irradiation and diffuse reflectance spectra measurement were conducted in vacuum. [ABSTRACT FROM AUTHOR]

The combustion of cellulose nitrate in ballasted mixtures containing an organic binder and nickel hydroxycarbonate or silver carbonate as precursors resulted Ni or Ag nanoparticles. The formation of Ni and Ag nanoparticles from flameless combustion of cellulose nitrate was monitored by time-resolved X-ray diffraction. During the formation of the Ag nanoparticles, the diffraction patterns exhibited only signals from decreasing amounts of the precursor and newly simultaneously formed 20-30 nm silver particles. It was detected that in the systems with Ni precursor the formation of the Ni 5-10 nm crystals proceeded by some 2-3 s diffraction-silent intermediate states of the whole system. [ABSTRACT FROM AUTHOR]