A hundred years on, the energy‐intensive Haber–Bosch process continues to turn the N2 in air into fertilizer, nourishing billions of people while causing pollution and greenhouse gas emissions. The ...urgency of mitigating climate change motivates society to progress toward a more sustainable method for fixing N2 that is based on clean energy. Surface oxygen vacancies (surface Ovac) hold great potential for N2 adsorption and activation, but introducing Ovac on the very surface without affecting bulk properties remains a great challenge. Fine tuning of the surface Ovac by atomic layer deposition is described, forming a thin amorphous TiO2 layer on plasmon‐enhanced rutile TiO2/Au nanorods. Surface Ovac in the outer amorphous TiO2 thin layer promote the adsorption and activation of N2, which facilitates N2 reduction to ammonia by excited electrons from ultraviolet‐light‐driven TiO2 and visible‐light‐driven Au surface plasmons. The findings offer a new approach to N2 photofixation under ambient conditions (that is, room temperature and atmospheric pressure).
Surface oxygen vacancies play a promotional role in the outer amorphous TiO2 (a‐TiO2) thin layer during the adsorption and activation of N2. The process facilitates N2 reduction to ammonia by excited electrons derived from UV‐light‐driven rutile TiO2 nanorod arrays and visible‐light‐driven gold surface plasmons.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Absorption and luminescence of nickel-containing ZnO–Al2O3–SiO2 glasses and glass–ceramics nucleated by TiO2 and ZrO2 were investigated for variable NiO content and heat-treatment conditions. Ni2+ ...ions in the as-cast glasses are predominately five-fold coordinated. Heat-treatment of glasses containing 1–3mol.% NiO at 730–800°C results in precipitation of nickel titanate–zirconate xNiO·yTiO2·zZrO2 nanocrystals with Ni2+ ions entering octahedral sites. Optical absorption of samples treated at 800–1100°C is determined by precipitation of gahnite nanophase with Ni2+ ions entering both octahedral and tetrahedral sites and minor fraction of ions remaining in the residual glass phase. These samples are characterized by strong near-IR luminescence associated with 3T2g(3F)→3A2g(3F) transition of 6Ni2+ ions (FWHM more than 200nm, centered at ~1.2μm) in gahnite nanocrystals. Luminescence intensity increases substantially with the increase of heat-treatment temperature due to increase of volume fraction of gahnite nanophase and size of gahnite nanocrystals (which in turn causes decrease of relative fraction of Ni2+ ions located near the nanocrystal surface and suppresses the non-radiative relaxation path), the second factor is the dominant one. Concentration of NiO has dramatic effect on the luminescence efficiency of glass–ceramics due to a strong temperature and concentration quenching.
•Nickel-containing ZnO–Al2O3–SiO2 glass and glass–ceramics nucleated by TiO2 and ZrO2•Influence of heat-treatment and NiO content on absorption and luminescence spectra•Structural state of Ni2+ in gahnite and titanate–zirconate crystalline nanophase•Discussion of physical mechanisms governing photoluminescence intensity
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This article is devoted to the evaluation of additional power losses that occur in an asynchronous traction motor operating from a frequency converter. An algorithm for calculating additional losses ...arising in electric-machine windings is proposed. The influence of pulse-width modulation parameters on the change in additional losses is studied. The influence of the number of elementary conductors along the slot height on additional losses is considered. The insignificant influence of additional core losses on the reduction in the asynchronous motor efficiency is shown.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The need to increase the precision with which the form of the pulse of the rapidly varying current of powerful plasma radiation is recorded under the conditions of powerful electromagnetic induction ...is considered. It is suggested that that a polarimetric fiber-optic current sensor based on a Spun-type light guide should be used to record powerful pulsed discharges. With the use of this type of current sensor it becomes possible to implement a technique of recording powerful pulse discharges of a plasma radiator in a regime of time profiling of the current pulse of two high-voltage capacitative storage devices with total energy up to 1800 kJ. The discharge chamber, power circuit, and evolution of the plasma discharge are described. The design and operating principle of a prototype of a two-pass polarimetric fiber-optic sensor with Spun-type optical cable and Faraday compensator that exhibits mutual optical anisotropy are presented. The general scheme of current measurements and the calibration circuit of the sensor are presented and experience gained from the use of a prototype of a sensor for measurement of powerful current pulses is described. Features of pre-calibration of the sensor are discussed. Results of a measurement of current by optical and traditional methods of recording based on the use of a Rogowski coil and Hall sensors are compared and a significant increase in the precision of reproduction of the shape of the current pulse by the optical method of recording is noted. Different modes of modernization of a fiber-optic sensor for expanding the range of recording current are considered.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Binary metal hydrides can act as low-temperature reducing agents for complex oxides in the solid state, facilitating the synthesis of anion-deficient oxide or oxyhydride phases. The reaction of ...LaSrCoRuO6, with CaH2 in a sealed tube yields the face-centered cubic phase LaSrCoRuO3.2H1.9. The reaction with LiH under similar conditions converts LaSrCoRuO6 to a mixture of tetragonal LaSrCoRuO4.8H1.2 and cubic LaSrCoRuO3.3H2.13. The formation of the LaSrCoRuOxHy oxyhydride phases proceeds directly from the parent oxide, with no evidence for anion-deficient LaSrCoRuO6-x intermediates, in contrast with many other topochemically synthesized transition-metal oxyhydrides. However, the reaction between LaSrCoRuO6 and LiH under flowing argon yields a mixture of LaSrCoRuO5 and the infinite layer phase LaSrCoRuO4. The change to all-oxide products when reactions are performed under flowing argon is attributed to the lower hydrogen partial pressure under these conditions. The implications for the reaction mechanism of these topochemical transformations is discussed along with the role of the hydrogen partial pressure in oxyhydride synthesis. Magnetization measurements indicate the LaSrCoRuOxHy phases exhibit local moments on Co and Ru centers, which are coupled antiferromagnetically. In contrast, LaSrCoRuO4 exhibits ferromagnetic behavior with a Curie temperature above 350 K, which can be rationalized on the basis of superexchange coupling between the Co1+ and Ru2+ centers.Binary metal hydrides can act as low-temperature reducing agents for complex oxides in the solid state, facilitating the synthesis of anion-deficient oxide or oxyhydride phases. The reaction of LaSrCoRuO6, with CaH2 in a sealed tube yields the face-centered cubic phase LaSrCoRuO3.2H1.9. The reaction with LiH under similar conditions converts LaSrCoRuO6 to a mixture of tetragonal LaSrCoRuO4.8H1.2 and cubic LaSrCoRuO3.3H2.13. The formation of the LaSrCoRuOxHy oxyhydride phases proceeds directly from the parent oxide, with no evidence for anion-deficient LaSrCoRuO6-x intermediates, in contrast with many other topochemically synthesized transition-metal oxyhydrides. However, the reaction between LaSrCoRuO6 and LiH under flowing argon yields a mixture of LaSrCoRuO5 and the infinite layer phase LaSrCoRuO4. The change to all-oxide products when reactions are performed under flowing argon is attributed to the lower hydrogen partial pressure under these conditions. The implications for the reaction mechanism of these topochemical transformations is discussed along with the role of the hydrogen partial pressure in oxyhydride synthesis. Magnetization measurements indicate the LaSrCoRuOxHy phases exhibit local moments on Co and Ru centers, which are coupled antiferromagnetically. In contrast, LaSrCoRuO4 exhibits ferromagnetic behavior with a Curie temperature above 350 K, which can be rationalized on the basis of superexchange coupling between the Co1+ and Ru2+ centers.
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IJS, KILJ, NUK, PNG, UL, UM
The influence of NiO addition (from 0.1 up to 3mol%) on structure and phase transformations of zinc aluminosilicate glasses nucleated by a mixture of TiO2 and ZrO2 has been studied using small angle ...X-ray scattering (SAXS), X-ray diffraction (XRD) analysis, Raman scattering and optical absorption spectroscopy. All parent glasses were X-ray amorphous and according to SAXS data inhomogeneous. Though SAXS intensity increased with increasing the NiO content in parent glasses, the distance between the inhomogeneous regions was independent of the NiO content implying that NiO does not play a role of additional nucleating agent. The processes of phase transformations were different for glasses doped with 0–0.1 and 1–3mol% NiO. In glasses containing 0–0.1mol% NiO, ZrTiO4 and Ni,Ti-doped gahnite crystals precipitated simultaneously starting from heat-treatment at above 730°C; traces of ZrO2 tetragonal crystals were found in glass-ceramics prepared at 1000–1200°C. In glasses doped with 1–3mol% NiO, metastable nickel titanate-zirconate crystals with fluorite-type structure and size of 4–5nm appeared during heat-treatments in the temperature range of 730–800°C, the fraction of this phase increased with the increase of the NiO content in the parent glass. Nickel titanate-zirconate crystals with fluorite structure decomposed during annealing at above 800°C. Ni,Ti-doped gahnite crystals precipitated starting from heat-treatment at 800°C; ZrO2 tetragonal crystals were formed at 900–1200°C.
•Zinc-aluminosilicate glass-ceramics based on Ni,Ti-doped gahnite nanosized crystals•Inhomogeneity of parent glasses according to SAXS and Raman spectroscopy•Metastable nickel titanate-zirconate nanophase with fluorite-type structure•Sequence of phase transformations in glasses doped with low and high concentrations of NiO
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Complex transition-metal oxides exhibit a wide variety of chemical and physical properties which are a strong function the local electronic states of the transition-metal centres, as determined by a ...combination of metal oxidation state and local coordination environment. Topochemical reduction of the double perovskite oxide, LaSrCoRuO
, using Zr, yields LaSrCoRuO
. This reduced phase contains an ordered array of apex-linked square-based pyramidal Ru
O
, square-planar Co
O
and octahedral Co
O
units, consistent with the coordination-geometry driven disproportionation of Co
. Coordination-geometry driven disproportionation of d
transition-metal cations (e.g. Rh
, Pd
, Pt
) is common in complex oxides containing 4d and 5d metals. However, the weak ligand field experienced by a 3d transition-metal such as cobalt leads to the expectation that d
Co
should be stable to disproportionation in oxide environments, so the presence of Co
O
and Co
O
units in LaSrCoRuO
is surprising. Low-temperature measurements indicate LaSrCoRuO
adopts a ferromagnetically ordered state below 120 K due to couplings between S=
/
Ru
and S=1 Co
.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This paper describes the outcomes of practical experiments in the validation of a technology for welding of the Al-Al2O3 metal-matrix composite material produced by the internal oxidation method. ...Technological capabilities are herein considered for argon-arc welding (Tungsten Inert Gas/ TIG) with filler wire and arc welding in a protective inert/active gas medium using a melting electrode (Metal Inert Gas/ MIG) for joining sheets of A6 aluminum alloy-based metal-matrix composite material (MMC). Mechanical properties of welded joints are determined and the fracture macrostructure is investigated. Fracture patterns and tensile strength are shown for different modes of welding procedure for alloy plates of 5, 8 mm in thickness by the TIG method and 25 mm by the MIG method. The macrostructural and mechanical heterogeneity of welded joints is shown. Welds made under optimal conditions are free of any macrodefects. The welded joint strength is up to 96% of the base material strength.
Climate change (global warming) is leading to an increase in heat extremes and coupled with increasing water shortage, provides a perfect storm for a new era of environmental crises and potentially, ...new diseases. We use a comparative physiologic approach to show that one of the primary mechanisms by which animals protect themselves against water shortage is to increase fat mass as a means for providing metabolic water. Strong evidence suggests that certain hormones (vasopressin), foods (fructose), and metabolic products (uric acid) function as survival signals to help reduce water loss and store fat (which also provides a source of metabolic water). These mechanisms are intricately linked with each other and stimulated by dehydration and hyperosmolarity. Although these mechanisms were protective in the setting of low sugar and low salt intake in our past, today, the combination of diets high in fructose and salty foods, increasing temperatures, and decreasing available water places these survival signals in overdrive and may be accelerating the obesity and diabetes epidemics. The recent discovery of multiple epidemics of CKD occurring in agricultural workers in hot and humid environments may represent harbingers of the detrimental consequences of the combination of climate change and overactivation of survival pathways.
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