The temperature dependences of the heat capacity
C
p
(
T
) and thermal expansion coefficient α(
T
) of NaNbO
3
ceramic samples have been investigated in the temperature range from 2 to 800 K. In ...addition to the anomalies associated with the known phase transitions at temperatures
T
6
≈ 265 K,
T
5
≈ 638 K,
T
4
≈ 760 K, and
T
3
≈ 793 K, anomalies in the behavior of
C
p
(
T
) and α(
T
) have been observed near
T
5″
≈ 500 K and
T
5′
≈ 600 K. It has been found that all the observed structural transformations, according to the values of the entropy change, are not related to the ordering of structural elements. It has been shown that, with an increase in the temperature, the unit cell volume during the phase transitions near 265, 515, 604, and 638 K decreases. The specific features of the transition to the phase
R
3
c
have been examined. Two possible scenarios of the sequence of phase transformations in the temperature range between
T
5
and
T
6
have been analyzed.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The effect of Zr and O incorporation on the structure and properties of TiC(N) coatings deposited by DC magnetron sputtering of composite TiC0.5+|>xZrO2(x=10 and 20wt.%) and (Ti,Zr)C0.5+10%ZrO2 ...targets in an argon atmosphere or reactively in a gaseous mixture of Ar+N2 is presented. The structure, elemental and phase composition of the coatings were studied by means of X-ray diffraction, scanning electron microscopy, and glow discharge optical emission spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery using the load-depth-sensing nanoindentation method. Tribological properties were investigated using ball-on-disk tests against cemented carbide at 25 degree C and alumina in the temperature range of 25-500 degree C. To evaluate the oxidation resistance, the coatings were annealed in air at 400, 550, and 600 degree C for 1h. The obtained results show that the TiZrCO(N) coatings exhibit a peak hardness versus nitrogen partial pressure. The coatings with maximum hardness tested at room temperature against WC+Co and Al2O3 counterparts showed low friction coefficients below 0.25. At higher temperatures 300-500 degree C, the friction coefficient against an Al2O3 ball was recorded to be 0.6. The tribological tests of the coatings demonstrated their high wear resistance at moderate temperatures 25-300 degree C (wear rate, k~10-6mm3N-1m-1) . Moreover, the coatings with high Zr content were the most wear resistant. The oxidation resistance of the Zr-doped TiCON coatings was not as high as expected and restricted by 600 degree C. The combination of high hardness about 40GPa with low friction coefficient and superior wear resistance makes the TiZrCON coatings promising candidates for various dry tribological applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The equation of state of a face-centered cubic phase has been quantitatively analyzed in terms of the statistical theory of crystals. It has been shown that, for xenon at room temperature, the ...pressure equal to 1.5 GPa determines the instability point where the condition of the positive bulk modulus of a face-centered cubic crystal is violated. A “universal line” bounding the thermodynamic stability region of the face-centered cubic phase of van der Waals crystals has been constructed. An analysis of the data available in the literature allows the conclusion that the revealed transition of face-centered cubic xenon to the martensitic phase at a pressure of 1.5 GPa and a temperature of 300 K can be considered a manifestation of the predicted instability. In this respect, it is important to perform detailed experiments on polymorphic transformations of real xenon (and also krypton). Another aspect of the proposed theory is that it provides a means for quantitatively predicting the characteristics of the so-called “cold” (at negative pressures) melting, which recently has become accessible for experimental observation.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The inhibitory potency of the series of inhibitors of the soluble epoxide hydrolase (sEH) based on the selenourea moiety and containing adamantane and aromatic lipophilic groups ranges from 34.3 nM ...to 1.2 μM. The most active compound 5d possesses aliphatic spacers between the selenourea group and lipophilic fragments. Synthesized compounds were tested against the LPS-induced activation of primary murine macrophages. The most prominent anti-inflammatory activity, defined as a suppression of nitric oxide synthesis by LPS-stimulated macrophages, was demonstrated for compounds 4a and 5b. The cytotoxicity of the obtained substances was studied using human neuroblastoma and fibroblast cell cultures. Using these cell assays, the cytotoxic concentration for 4a was 4.7–18.4 times higher than the effective anti-inflammatory concentration. The genotoxicity and the ability to induce oxidative stress was studied using bacterial lux-biosensors. Substance 4a does not exhibit genotoxic properties, but it can cause oxidative stress at concentrations above 50 µM. Put together, the data showed the efficacy and safety of compound 4a.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this work, the wear resistance and fracture characteristics of (Ti,Al)N-Cu, (Ti,Al)N-Ni, and (Ti,Al)N coatings deposited onto a carbide substrate by the filtered cathodic vacuum arc deposition ...method were investigated comparatively under various loading and friction conditions. The (Ti,Al)N-Cu and (Ti,Al)N-Ni metal-ceramic coatings showed an equiaxial structure with a ceramic phase grain size of about 15–20 nm. The coatings showed a hardness of about 50 GPa and maintained their fracture toughness (the relative work of plastic deformation was ~65%). The (Ti,Al)N ceramic coating showed a columnar structure having elements with a diameter of about 120 nm. This coating exhibited a hardness of about 27 GPa and was characterized by a significantly lower fracture toughness (the relative work of plastic deformation was ~45%).
The tribological properties of these coatings were examined at 20 and 500 °C. It was found that the metal-ceramic coatings showed significantly lower friction coefficient values (~0.56 and 0.61) than the ceramic coatings (~0.68 and 0.70).
The fracture pattern of the metal-ceramic coatings was obtained by simulating their abrasive wear during a scratch test. Complete abrasion of the coatings was not observed until 90 N. Under similar tests, the (Ti,Al) N coating showed adhesive destruction by the separation of large fragments from the substrate. Complete coating wear was observed at a load of ~70 N.
The erosion of the coatings during hydroabrasive treatment under multicycle impact loading was investigated. It was found that the nanostructured (Ti,Al) N-Cu and (Ti,Al)N-Ni coatings were 1.5 and 2 times less susceptible to wear than the (Ti,Al) N coating, respectively.
The wear characteristics of the coatings were analysed on the basis of their structures and physical and mechanical properties, including their H/E and H3/E2 parameters, which denote the resistance of a material to elastic and plastic deformation respectively.
•(Ti,Al,)N-Cu/Ni coatings with different Cu and Ni contents were deposited.•(Ti,Al,)N-Cu/Ni coatings are characterized by high resistance to abrasive wear.•(Ti,Al,)N-Cu/Ni durability was 3–4 fold as high as that of the (Ti,Al)N coating.•Cu/Ni-containing nitride coatings exhibit absence of complete wearing up to ~90 N.•(Ti,Al)N–Cu/Ni coatings perform as materials with high ductility and safety factor.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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