The paper presents a study of phase transformations upon heat--treatment of three titania--containing zinc aluminosilicate glasses with equal contents of ZnO and Al2O3 by small--angle X--ray ...scattering and X--ray powder diffraction methods. Additionally the glass with the lowest SiO2 content was studied by both traditional and low--frequency Raman spectroscopy. It was found that upon phase decomposition a bimodal structure is developed in glasses under study. There are two types of nanometer sized inhomogeneous regions different in composition and in dimension: small zinc aluminate regions (~6--10nm in size) and large zinc aluminotitanate ones (~10--50nm in size depending on the composition of the initial glass). In zinc aluminate regions, aluminozinc spinel, gahnite, crystallizes starting from heat--treatment at 750 deg C. Zinc aluminotitanate phase remains amorphous until the material is heat--treated at 950 deg C, whereupon on heat--treatment up to 1050 deg C, crystals of two metastable forms of TiO2, anatase and brookite, are formed in this phase. At higher temperatures they transform into a stable form of TiO2, rutile. The origin of the low--frequency Raman scattering in titania--containing zinc aluminosilicate glasses has been associated with the formation of amorphous zinc aluminate nanometer sized inhomogeneous regions. It has been found that zinc aluminotitanate inhomogeneous regions do not reveal themselves in low--frequency Raman scattering.
Transparent glass-ceramic materials based on glasses of the MgO–Al
2
O
3
–SiO
2
–TiO
2
system doped with CoO and Ga
2
O
3
are synthesized. The secondary heat treatment of the initial glasses at ...temperatures of 800–950°C leads to precipitation of nanosized (6–7 nm) crystals of magnesium aluminogallium spinel doped with cobalt ions and magnesium aluminotitanate solid solutions. The optical absorption spectra of the initial glass and glass-ceramic materials are studied. It is shown that the absorption band caused by the
4
A
2
(
4
F)→
4
T
1
(
4
F
) transitions of tetrahedrally coordinated Co
2+
ions in glass-ceramics with nanosized Co:Mg(Al,Ga)
2
O
4
crystals is shifted to longer wavelengths (up to ~1.67 µm) compared to the position of this band in materials with Co:MgAl
2
O
4
crystals. The synthesized glass-ceramics are characterized by a relatively low saturation fluence FS ~ 0.5 ± 0.1 J/cm
2
at a wavelength of 1.54 µm, as well as by a high radiation resistance to nanosecond laser pulses, which is no lower than ~15 ± 2 J/cm
2
. This explains their attractiveness as materials for saturable absorbers for erbium lasers emitting in the spectral range 1.5–1.7 µm.
The effect of the temperature of heating for quenching on the content of retained austenite and its resistance to the deformation-induced martensitic transformation, the hardening capacity, and the ...resistance to abrasive wear are studied for high-carbon tool steels 150KhNML and Kh12MFL of pearlitic and ledeburitic classes.
The effect of the Na
4
CuN(CH
2
PO
3
)
3
·
13H
2
O complex compound with a chelate structure on the corrosion-electrochemical behavior of 20# steel in a borate buffer solution at pH 7.4 and natural ...aeration was studied using the potentiodynamic method and methods of X-ray photoelectron spectroscopy and surface scanning electron microscopy with microanalysis. It was established that in the concentration range of 0.2–1.0 mM the complex under study inhibits the anodic dissolution of the metal and drives it at higher concentrations. In terms of its effect on the corrosion-electrochemical behavior of steel, the Na
4
CuN(CH
2
PO
3
)
3
·
13H
2
O complex differs significantly from the previously studied complexes Na
4
ZnN(CH
2
PO
3
)
3
·
13H
2
O and Na
4
Cd(H
2
O)N(CH
2
PO
3
)
3
·
7H
2
O. In the potential range –0.66…–0.05 V relative to the Ag,AgCl|KCl-electrode (SSCE) a layer of metallic copper is generated on the surface in the form of nano-sized crystals, shielding the surface of the steel. In the potential range of 0.05–0.13 V (SSCE), metallic copper is oxidized, and with a further increase in the potential, a layer of mixed iron and copper oxides is formed.
Transparent glass-ceramics of magnesium aluminosilicate system based on Fe2+:MgAl2O4 spinel nanocrystals nucleated by a mixture of TiO2 and ZrO2 and doped with 0.6 mol% FeO were developed. The glass ...was melted at 1580 °C with stirring and heat-treated in the temperature range from 800 to 1300 °C. The structure and spectroscopic properties of the glass and glass-ceramics were studied by DSC and XRD methods, Raman and absorption spectroscopy. ZrTiO4 nanocrystals 6 nm in size precipitate during the nucleation heat-treatment at 800 °C. Spinel nanocrystals 9-14 nm in size are formed during heat-treatments at 850- 1000 °C. Intense absorption at ~2 μm is observed due to Fe2+ ions in tetrahedral positions in these crystals. Iron-doped sapphirine crystallization in transparent glass-ceramics at 1000-1050 °C results in a decrease of absorption in this spectral range. The glass-ceramics are important for the development of saturable absorbers for the spectral range of 2-3 μm.
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•A new design of the SAW UV is proposed, in which the sensitive element is located outside the acoustic channel and does not affect the propagation of SAW, which makes it possible to ...use such a sensor wireless in the frequency range 2400–2483 MHz, where wireless sensors have compact antennas.•It It is proposed to connect the impedance sensitive to UV radiation not to reflective, but to the transceiver IDT, which made it possible to increase the sensitivity of the sensor to 8000 ppm/(μW/cm2).•New sensor design allowed us to obtain 8000 ppm/μW cm2 sensitivity, measure UV radiation intensity from some units μW/cm2 to 4 mW/cm2 and to reduce the response time.•The theoretical and experimental studies of reflection coefficient UV dependence can also be used for the development of passive wireless UV radiation sensors.
An investigation of impedance-loaded surface acoustic waves (SAW) UV sensor is presented in this paper. New sensor design allowed us to obtain 8000 ppm/μW·cm2 sensitivity, measure UV radiation intensity from some units μW/cm2 to 4 mW/cm2 and to reduce the response time. The photosensitive film is located outside the acoustic channel in our design of the sensor, which makes it possible to avoids SAW damping by the surface of the film. The theoretical and experimental studies of reflection coefficient UV dependence can also be used for the development of passive wireless UV radiation sensors.
To assess the significance of metals in biota of the Barents Sea, preliminary information is presented on concentrations of Cu, Zn, Ni, Cr, Mn, Co, Pb, Fe, Cd and As in livers and muscle tissues of 3 ...commercial fish species collected in winter 2011. Generally, our results are within the reported literature range for regarding some commercially important species like cod and flounders indicating that metal levels are not elevated. The interspecific variability is not substantial; we only found significant difference for Fe concentrations for muscle, with the highest concentrations measured in long rough dab and the lowest in cod. To assess whether metal levels found in fish samples from the Barents Sea are safe for human consumption, a comparison is made to reference values for fish muscle and fish liver. Available data suggest that all muscle and liver of fish analysed in this study may be regarded as safe, since they are far below these thresholds.
•Transparent glass-ceramics (GCs) of K2O–ZnO–Al2O3–SiO2 system with 1.5 mol% Er2O3.•Light scattering coefficient of GCs is a power function of the inverse wavelength.•The values 5.3−7.0 of the ...exponent in the power function were observed.•The conclusion about the anomalous light scattering in GСs was made.
Potassium zinc aluminosilicate glass doped with 1.5 mol% Er2O3 was subjected to successive heat treatments at 720 and 750 °C resulted in precipitation of ZnO nanocrystals. After each hold, the volume fraction and size of crystals in transparent glass-ceramics were determined, and optical density spectrum was recorded. Analysis of optical spectra revealed that: the surrounding of Er3+ ions differs in the initial glass and glass-ceramics; a strong absorption band is observed in glass-ceramics at wavelengths longer than 1000 nm, which is caused by localized surface plasmon resonance in semiconducting ZnO nanocrystals; the so-called “anomalous light scattering” is observed, i.e., scattering coefficient of glass-ceramics in the spectral range 480−800 nm is a power function of the inverse wavelength, and the exponent (“the scattering exponent”) is appreciably greater than the Rayleigh value 4. The experimental scattering coefficient of one glass-ceramic is compared with that calculated for the model proposed earlier.
Saturation of optical density for thick sample is caused by contribution of scattered light to detector signal.
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•Effect of light scattering on optical density measurement is ...studied.•Acceptance angle of the spectrophotometer is estimated to be 6°.•Glass-ceramics are used as model objects for measurements.•Spectral behavior of glass-ceramics optical density is used to study the effect.•If optical density is less than 2, effect of light scattering is negligible.
In determination of the extinction coefficient for light-scattering materials from transmission experiments, a problem arises, which is connected with unwanted contribution from the scattered light to readings of the detector of a spectrophotometer. In this paper, the problem is discussed for the case of nanostructured nonabsorbing glass-ceramics. For the detector of the spectrophotometer Shimadzu UV 3600, the acceptance angle was determined to be about 6°. The methods are proposed for determination of the critical value of optical density, exceeding of which leads to an appreciable measurement error associated with falling the scattered light into a detector. The methods are based on study of the spectral behavior of the optical density or extinction coefficient. If the acceptance angle of the detector is about 6° and the refractive index of the nanostructured material exceeds 1.6, the critical value of optical density was experimentally found to be approximately 2.
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