Solid-state reactions in the system Li<Subscript>2</Subscript>CO<Subscript>3</Subscript>-Na<Subscript>2</Subscript>CO<Subscript>3</Subscript>-Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript>

The formation mechanisms of Li _x Na_{1 ?x} Ta _y Nb_{1 ? y} O₃ perovskite solid solutions in the Li₂CO₃-Na₂CO₃-Nb₂O₅-Ta₂O₅ system have been studied by x-ray diffraction, differential thermal analysis, thermogravimetry, IR spectroscopy, and mass spectrometry at temperatures from 300 to 1100°C. The results indicate that the synthesis of Li _x Na_{1 ? x} Ta _y Nb_{1 ? y} O₃ solid solutions involves a complex sequence of consecutive and parallel solid-state reactions. An optimized synthesis procedure for Li _x Na_{1 ? x} Ta _y Nb_{1 ? y} O₃ solid solutions is proposed.     

Aging of ITO anodes treated by supercritical CO<Subscript>2</Subscript>/H<Subscript>2</Subscript>O<Subscript>2</Subscript> fluids for OLEDs

The aging behaviors of indium tin oxide (ITO) anodes treated by supercritical CO₂/H₂O₂ (SCCO₂/H₂O₂) fluids were investigated. As the SCCO₂/H₂O₂-treated ITO anodes were aged, the contact angle and surface energy were analyzed and compared with those of the ITO anodes treated by oxygen plasma. The SCCO₂/H₂O₂ pretreatment yielded a stable polar component of the ITO surfaces after 48 h of aging. The energy reduction in the polar component of the oxygen-plasma-treated ITO due to aging was 20 %, as compared with the 1.1 % decrease in ITO treated with the SCCO₂/H₂O₂ fluids at 4000 psi for 15 min. The X-ray photoelectron spectroscopy analysis revealed that the oxygen content of the ITO surfaces with the SCCO₂/H₂O₂ pretreatment was significantly higher than that of the ITO treated by oxygen plasma. This could result from the formation of hydroxyl products that functioned as a stable buffer layer against further contamination during aging. In addition, the correlated dependence of the OLED performance on the aged ITO anodes was also studied. The OLEDs with the SCCO₂/H₂O₂ pretreatment showed an improved degradation of I–V characteristics and brightness in comparison with those of the devices treated with oxygen plasma after aging the treated ITO anodes for 6 and 12 h. The obtained results suggested that the ITO anodes treated by the SCCO₂/H₂O₂ fluids exhibited a stable surface chemistry and could be useful for OLED applications.     

Physicochemical simulation of fusion processes of basalt and diabase with Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> and Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> + CaO

Fusion processes of basalt and diabase with sodium carbonate and its mixture with calcium oxide are investigated by methods of physicochemical simulation. Equilibrium compositions of the Si-Al-Fe-Ca-Mg-Na system are calculated at various ratios Na₂CO₃: basalt (diabase) and (Na₂CO₃ + CaO): basalt (diabase) in the temperature range of 1270–1470 K. It is shown that, on fusion with sodium carbonate, depending on conditions, the main components of fusion products are sodium metasilicate (Na₂SiO₃) and sodium metaaluminate (NaAlO₂), magnesium orthosilicate (CaMgSiO₄), sodium ferrite(III) (NaFeO₂), iron(III) oxide (Fe₂O₃), and sodium-aluminum orthosilicate (Na₂AlSiO₄). On fusion with the mixture of sodium carbonate and calcium oxide, respectively, the products are sodium metaaluminate, calcium pyrosilicate (Ca₃Si₂O₇), calcium-magnesium orthosilicate, and calcium ferrite (CaFe₂O₄).     

Scalable fabrication of SnO<Subscript>2</Subscript>/eo-GO nanocomposites for the photoreduction of CO<Subscript>2</Subscript> to CH<Subscript>4</Subscript>

Artificial photosynthesis uses a catalyst to convert CO₂ into valuable hydrocarbon products by cleaving the C=O bond. However, this technology is strongly limited by two issues, namely insufficient catalytic efficiency and complicated catalyst-fabrication processes. Herein, we report the development of a novel spray-drying photocatalyst-engineering process that addresses these two issues. Through one-step spray drying, with a residence time of 1.5 s, nanocomposites composed of tin oxide (SnO₂) nanoparticles and edge-oxidized graphene oxide (eo-GO) sheets were fabricated without post-treatment. These nanocomposites exhibited 28-fold and five-fold enhancements in photocatalytic efficiency during CO₂ reduction compared to SnO₂ and commercialized TiO₂ (P25), respectively, after irradiation with simulated sunlight for 4 h. This scalable approach, based on short residence times and facile equipment setup, promotes the practical application of artificial photosynthesis through the potential mass production of efficient photocatalysts.

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Experimental evaluation of interactions in supercritical CO<Subscript>2</Subscript>/water/rock minerals system under geologic CO<Subscript>2</Subscript> sequestration conditions

The hydrothermal autoclave experiments were conducted to simulate the interactions in the scCO₂/water/rock minerals (quartz, biotite and granite) reaction systems using a Hastelloy C reaction cell at 100 °C. The dissolution characteristics of rock minerals and their surface texture alternation after hydrothermal treatment were examined by ICP-AES and SEM/EDX investigation, respectively. The results suggested that the hydrolysis of plagioclase phase should be mainly responsible for the elements dissolved from the Iidate granite samples. The dissolution was encouraged by the introduction of CO₂ in the water/granite system, and generated an unknown aluminosilicate. No distinct chemical alternations occurred in the water-free scCO₂/granite system, which indicated that rock minerals should be chemically stable in the water-free scCO₂ fluids under the current mild experimental conditions. Both the highest concentration of Ca existing in the scCO₂/vapor/granite system and the SEM observation results of calcite deposit, suggested that a meaningful CO₂ minerals trapping process should be potential in the CO₂-rich field during a short physicochemical interaction period.     

Online mass-spectrometric monitoring of O<Subscript>2</Subscript> and CO<Subscript>2</Subscript> during anesthesia

It is suggested to determine the breathing cycle duration during anesthesia by the online method based on synchronous mass-spectrometric monitoring of the concentrations of an inert gas (not involved in metabolism), CO₂, and O₂. Comparative results of determining the temporal boundaries of the breathing cycle using the proposed method with argon (Ar) and krypton (Kr) are presented. The concentrations of CO₂, O₂, and Ar (or Kr) were measured using an electron-impact ionization mass spectrometer. The gas mixture was sampled directly from the breathing circuit of an anesthesia machine during low-flow balanced inhalation anesthesia. The obtained results show the possibility of using mass-spectrometric monitoring of the CO₂/O₂ metabolism in order to assess online the adequacy of anesthesia with respect to surgical invasion during anesthesia.     

Phase modification induced drying shrinkage reduction on Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> activated slag by incorporating Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>

This paper aims to study the phase modification, reaction kinetics, mechanical properties and drying shrinkage of sodium carbonate activated slag by incorporating sodium sulfate in the activator. The results show that the reaction process is firstly controlled by CO₃ ^2? anions, and later runs similar to that of sodium sulfate activation. Besides, the relatively unstable phase gaylussite, commonly found in the sodium carbonate activation, is not observed in the reaction products upon hybrid activation, and monosulfoaluminate rather than ettringite is identified, probably caused by the reduced aluminate-to-sulfate ratio and increased pH value. The drying shrinkage is considerably reduced by up to 41% when replacing 50 wt% sodium carbonate by sodium sulfate, most possibly attributed to the induced phase modification. Furthermore, the relationships between the phase modification and drying shrinkage, and the potentially involved chemical reaction are discussed.     

Steady-state O<Subscript>2</Subscript> and CO<Subscript>2</Subscript> diffusion in carbonated mortars produced with blended cements

The diffusion coefficient \(D_{{{\text{O}}_{2} }}\), the porosity and the pore structure of mortars produced with a Portland cement and a range of blended cements containing limestone powder, microsilica, portlandite or slag were measured in the non-carbonated and the carbonated state. Additionally, the setup for measuring O₂ diffusion was adapted to measure also the CO₂ diffusion of the carbonated mortars. The diffusion coefficient \(D_{{{\text{O}}_{2} }}\) and the total porosity were increased in the mortars containing microsilica and slag, while they were decreased in the other mortars due to carbonation. Invariably, the pore structure became coarser in all samples. The relationship between diffusion coefficients \(D_{{{\text{O}}_{2} }}\) and \(D_{{{\text{CO}}_{2} }}\) in the carbonated mortars was always linear, with \(D_{{{\text{O}}_{2} }}\) systematically higher by factor of 1.37. As this factor broadly agrees with what was found in the scant literature about CO₂ diffusion, it could be used for estimating \(D_{{{\text{CO}}_{2} }}\) of carbonated mortar and concrete based on measurements of O₂ diffusion.     

Ni-doped ZnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> atomic layers to boost the selectivity in solar-driven reduction of CO<Subscript>2</Subscript>

Regulating the selectivity of CO₂ photoreduction is particularly challenging. Herein, we propose ideal models of atomic layers with/without element doping to investigate the effect of doping engineering to tune the selectivity of CO₂ photoreduction. Prototypical ZnCo₂O₄ atomic layers with/without Ni-doping were first synthesized. Density functional theory calculations reveal that introducing Ni atoms creates several new energy levels and increases the density-of-states at the conduction band minimum. Synchrotron radiation photoemission spectroscopy demonstrates that the band structures are suitable for CO₂ photoreduction, while the surface photovoltage spectra demonstrate that Ni doping increases the carrier separation efficiency. In situ diffuse reflectance Fourier transform infrared spectra disclose that the CO₂^·? radical is the main intermediate, while temperature-programed desorption curves reveal that the ZnCo₂O₄ atomic layers with/without Ni doping favor the respective CO and CH₄ desorption. The Ni-doped ZnCo₂O₄ atomic layers exhibit a 3.5-time higher CO selectivity than the ZnCo₂O₄ atomic layers. This work establishes a clear correlation between elemental doping and selectivity regulation for CO₂ photoreduction, opening new possibilities for tailoring solar-driven photocatalytic behaviors.

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Photocatalytic reduction of CO<Subscript>2</Subscript> with H<Subscript>2</Subscript>O over modified TiO<Subscript>2</Subscript> nanofibers: Understanding the reduction pathway

Nanosized metal (Pt or Pd)-decorated TiO₂ nanofibers (NFs) were synthesized by a wet impregnation method. CdSe quantum dots (QDs) were then anchored onto the metal-decorated TiO₂ NFs. The photocatalytic performance of these catalysts was tested for activation and reduction of CO₂ under UV-B light. Gas chromatographic analysis indicated the formation of methanol, formic acid, and methyl formate as the primary products. In the absence of CdSe QDs, Pd-decorated TiO₂ NFs were found to exhibit enhanced performance compared to Pt-decorated TiO₂ NFs for methanol production. However, in the presence of CdSe, Pt-decorated TiO₂ NFs exhibited higher selectivity for methanol, typically producing ～90 ppmg^?1·h^?1 methanol. The CO₂ photoreduction mechanism is proposed to take place via a hydrogenation pathway from first principles calculations, which complement the experimental observations.

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Ultrasonic-assisted synthesis of amorphous Bi<Subscript>2</Subscript>S<Subscript>3</Subscript> coupled (BiO)<Subscript>2</Subscript>CO<Subscript>3</Subscript> catalyst with improved visible light-responsive photocatalytic activity

A series of Bi₂S₃/(BiO)₂CO₃ composite photocatalysts with different loadings of amorphous Bi₂S₃ were successfully synthesized through an ultrasonic-assisted ion-exchange reaction between thioacetamide (CH₃CSNH₂) and (BiO)₂CO₃, and characterized by XRD, XPS, BET, EELS, EDX, SEM, TEM/HRTEM, UV–Vis, and photoluminescence (PL) techniques. The results of TEM/HRTEM, EELS, and EDX indicate that the composite catalyst Bi₂S₃/(BiO)₂CO₃ has been successfully synthesized with the deposited Bi₂S₃ present in amorphous state on the surface of (BiO)₂CO₃. The activities of the catalysts for RhB degradation under visible light show that the catalyst prepared under ultrasonic is more active than the one synthesized without ultrasonic. The optimized sample Bi₂S₃/(BiO)₂CO₃ (U5.0) exhibits a much higher activity, about 4.8 times to that of pure (BiO)₂CO₃. Based upon the band structures of Bi₂S₃/(BiO)₂CO₃, it is deduced that the migration of the visible light-induced electrons from the conduction band of Bi₂S₃ to that of (BiO)₂CO₃ should have facilitated the separation of photogenerated carriers, as confirmed by the suppressed photoluminescence spectra. Using different scavengers, the ·O₂ ^? and holes are clearly identified as the main oxidative species for RhB photodegradation. In light of these observations, a potential photocatalytic mechanism of RhB degradation over Bi₂S₃/(BiO)₂CO₃ is proposed.     

Charge transfer in graphene/polymer interfaces for CO<Subscript>2</Subscript> detection

Understanding charge transfer processes between graphene and functional materials is crucial from the perspectives of fundamental sciences and potential applications, including electronic devices, photonic devices, and sensors. In this study, we present the charge transfer behavior of graphene and amine-rich polyethyleneimine (PEI) upon CO₂ exposure, which was significantly improved after introduction of hygroscopic polyethylene glycol (PEG) in humid air. By blending PEI and PEG, the number of protonated amine groups in PEI was remarkably increased in the presence of water molecules, leading to a strong electron doping effect on graphene. The presence of CO₂ gas resulted in a large change in the resistance of PEI/PEG-co-functionalized graphene because of the dramatic reduction of said doping effect, reaching a maximum sensitivity of 32% at 5,000 ppm CO₂ and an applied bias of 0.1 V in air with 60% relative humidity at room temperature. This charge transfer correlation will facilitate the development of portable graphene-based sensors for real-time gas detection and the extension of the applications of graphene-based electronic and photonic devices.

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Supercritical CO<Subscript>2</Subscript>-assisted,silicone-modified wood for enhanced fire resistance

A composite fabrication method is reported that incorporates silicones into bulk aspen substrates and subsequently crosslinks the additives in situ. This process utilizes supercritical CO₂, a non-toxic and easily recoverable solvent, as a transport and reaction medium resulting in aspen composites that have been uniformly infused with silicone. Flexure properties of aspen–silicone composites were determined to be indistinguishable from those of aspen. However, after thermal degradation, the residual flexure properties of the composite char were significantly improved compared to the virgin aspen char. Energy release rate, total energy released, and char yield of aspen and aspen–silicone composites were measured and a significant improvement in all three of these fire-resistance parameters was observed after the incorporation of silicone. Samples were also exposed to a controlled thermo-oxidative environment under an applied stress to measure lifetimes of each sample at given temperatures and stress levels. This data were subjected to an Arrhenius analysis and show a good linear correlation. Composite systems demonstrate significantly longer lifetimes than virgin aspen and the slopes of all lines are nearly identical, suggesting that no change in the chemical degradation mechanism has occurred.     

The unstructured two-dimensional grid-based computation of selective thermal radiation in CO<Subscript>2</Subscript>-N<Subscript>2</Subscript> mixture flows

The possibility of applying the P ₁ approximation of the spherical harmonics method to the computation of the radiant heat transfer in heterogeneous volumes of complicated geometry is investigated. This approximation is used to evaluate the radiant heating of the surface of a spacecraft descending in the Martian atmosphere. The chemical composition of the gas heated behind the shock wave is calculated by using a kinetic model including 79 chemical reactions and ten components, such as CO₂, CO, C, O, O₂, C₂, N, N₂, CN, and NO. The optical properties are set by a spectral multigroup model computed with the help of the ASTEROID computer code with averaging over the rotational molecular spectrum structure in each group. The mechanisms of the radiant heating of the surface of descent space vehicles in the Martian atmosphere are studied.     

Solid–Liquid Equilibria for the CO<Subscript>2</Subscript> + R23 and N<Subscript>2</Subscript>O + R23 Systems

A recently built experimental setup was employed for the estimation of the solid–liquid equilibria of alternative refrigerant systems. In this paper two binaries, i.e., carbon dioxide + trifluoromethane (CO₂ + R23) and nitrous oxide + trifluoromethane (N₂O + R23), were studied down to temperatures of 117 K. In order to check the reliability of the apparatus, the triple points of the pure fluids contained in the mixture were measured, revealing good consistency with the literature. The results obtained for the mixtures were interpreted by means of the Schröder equation.     

Effect of mechanical activation of Al(OH)<Subscript>3</Subscript> on its reaction with Li<Subscript>2</Subscript>CO<Subscript>3</Subscript>

The effect of preliminary mechanical activation of Al(OH)₃ on its solid-state reaction with Li₂CO₃ at temperatures above 800°C has been studied by thermogravimetry, X-ray diffraction, in situ X-ray diffraction, electron microscopy, and specific surface area and particle size measurements. The results demonstrate that preliminary mechanical activation of Al(OH)₃ in an AGO-2 planetary mill at 40g for 1 min allows phase-pure γ-LiAlO₂ to be obtained. The composition of the lithium aluminates resulting from mechanical activation and heat treatment depends on the phase composition of the aluminum oxides resulting from the thermal decomposition of Al(OH)₃. The particle size and specific surface area of the forming γ-LiAlO₂ have been determined.     

Synthesis and crystal structure of [UO<Subscript>2</Subscript>(OH)(CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>)<Subscript>3</Subscript>]<Subscript>2</Subscript>(ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The complex [UO₂(OH)(CO(NH₂)₂)₃]₂(ClO₄)₂ (I) was synthesized. A single crystal X-ray diffraction study showed that compound I crystallizes in the triclinic system with the unit cell parameters a = 7.1410(2), b = 10.1097(2), c = 11.0240(4) Å, α = 104.648(1)°, β = 103.088(1)°, γ = 108.549(1)°, space group \(P\bar 1\), Z = 1, R = 0.0193. The uranium-containing structural units of the crystals are binuclear groups [UO₂(OH)· (CO(NH₂)₂)₃] ₂ ²⁺ belonging to crystal-chemical group AM²M ₃ ¹ [A = UO ₂ ²⁺ , M² = OH^?, M¹ = CO(NH₂)₂] of uranyl complexes. The crystal-chemical analysis of nonvalent interactions using the method of molecular Voronoi-Dirichlet polyhedra was performed, and the IR spectra of crystals of I were analyzed.     

Properties of nanocrystalline ZrO<Subscript>2</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-CeO<Subscript>2</Subscript>-CoO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> powders

We have studied the properties of nanocrystalline ZrO₂-Y₂O₃-CeO₂-CoO-Al₂O₃ powders prepared via hydrothermal treatment of a mixture of coprecipitated hydroxides at 210°C. A number of general trends are identified in the variation of the properties of the synthesized powders during heat treatment at temperatures from 500 to 1200°C. Our results demonstrate that the addition of 0.3 mol % CoO to nanocrystalline ZrO₂-based powders containing 1 to 5 mol % Al₂O₃ allows one to obtain composites with good sinterability at a reduced temperature (1200°C).     

Ceramics Based on Powder Mixtures Containing Calcium Hydrogen Phosphates and Sodium Salts (Na<Subscript>2</Subscript>CO<Subscript>3</Subscript>, Na<Subscript>4</Subscript>P<Subscript>2</Subscript>O<Subscript>7</Subscript>, and NaPO<Subscript>3</Subscript>)

Ceramic materials in the Na₂O–CaO–P₂O₅ system have been produced using powder mixtures containing calcium hydrogen phosphates (monetite/brushite: CaHPO₄/CaHPO₄ ? 2H₂O) and sodium salts (Na₂CO₃ ? H₂O, Na₄P₂O₇ ? 10H,O, and NaPO₃). These salts were used as precursors to the following high-temperature phases: Сa₂P₂O₇, Na₂O, Na₄P₂O₇, and NaPO₃. The amount of the salts in the powder mixtures was such that the oxide composition of the ceramics corresponded to 10 mol % sodium oxide for each mixture in the Na₂O–CaO–P₂O₅ system. The powder mixtures were prepared using mechanical activation in acetone, which was accompanied by monetite rehydration to brushite. X-ray diffraction characterization showed that, after firing, the phase composition of the ceramics produced from the powder mixtures thus prepared lay in the Сa₂P₂O₇–NaCaPO₄–Na₂СaP₂O₇–Са(РО₃)₂ phase field. The resultant ceramic materials contain biocompatible and bioresorbable phases and can be recommended for bone implant fabrication.