We developed a green scalable approach for the synthesis of titania quantum dots, corroborated by HR-TEM. XRD and Raman confirmed the major formation of anatase. PALS analysis revealed a ratio of 1.37–1.39, consistent with annihilation in small vacancy-type defects, for both precursors, and strongly correlates with the presence of triple-vacancy complexes such as (245.5 ps) or (239.3 ps). The defect type is the same in both samples, although their concentration differs, with a higher value for TBOT.

TiO2 nanoparticles (TiO2 NPs) are widely valued for their versatile properties across catalysis, optoelectronics, cosmetics, and biomedicine. Using a modified Pechini method, we synthesized white and black TiO2 NPs (W-TiO2 and B-TiO2) via heat treatment at different temperatures in air and argon, respectively. Our study reveals distinct phase transitions: rutile appeared in W-TiO2 at 400 degrees C and anatase fully transformed by 700 degrees C, whereas in B-TiO2, the transition from anatase to rutile began at 500 degrees C. Synthesis under argon suppressed grain coarsening, yielding smaller rutile crystallites (18 nm) at 700 degrees C compared to air-synthesized sample (55 nm). This structural difference was further reflected in the BET analysis, where W-TiO2 exhibited a significant surface area reduction from 57 to 3 m2/g due to particle enlargement, while B-TiO2 showed an increase from 17 to 142 m2/g, indicating finer particles and microporosity. Carbon incorporation in B-TiO2 enhanced sub-bandgap absorption without altering the intrinsic bandgap energy, highlighting the impact of synthesis conditions on TiO2's structural and optical properties.

This research investigates the effects of crystalline (chamotte), amorphous (nano-clay), and functionalized particulate additives on the performance of metakaolin-based geopolymer (MK-GP) composites under diverse curing protocols, including temperatures of 21 degrees C and 150 degrees C and pressures of 0.1 MPa and 40 MPa. Key performance metrics-flexural and compressive strength, porosity, and thermal stability-were evaluated alongside microstructural evolution analyzed via Environment Scanning Electron Microscopy (ESEM). Results indicate that all additives improved geopolymer performance, with chamotte acting as a filler and dehydration regulator, nano-clay providing an additional aluminosilicate source, and carbon nanotubes modifying setting behavior. Each additive reduced pore size, enhancing the composite's properties. The hybrid combination of additives showed a synergistic effect, significantly enhancing compressive and flexural strength, with improvements of up to 350 % compared to plain geopolymers under similar curing conditions. Additionally, the mechanical performance was minimally affected under high pressure (40 MPa), emphasizing the potential of hybrid reinforcements for extreme environments. These findings highlight the critical role of optimizing particle size, composition, and chemical compatibility to develop high-performance geopolymer composites for challenging applications.

This work presents the design of air-stable core-shell zero-valent iron-nickel nanofilaments supported on silica and zeolite, developed to overcome the oxidation limitations of nano zero-valent iron in environmental catalysis. The nanofilaments feature similar to 100 nm iron-nickel cores surrounded by ultrafine iron-rich threads embedded with aluminates and silicates, originating from partial support dissolution during synthesis. By varying the iron reduction time, three catalysts were prepared: one on silica reduced for 30 min, and two on zeolite reduced for 30 and 15 min. They were thoroughly characterized using nitrogen physisorption, X-ray diffraction, electron microscopy with elemental analysis, M & ouml;ssbauer spectroscopy, and small-angle Xray scattering. The zeolite-supported catalyst reduced for 15 min showed the highest activity for hexavalent chromium reduction (rate constant 8.054 min-1), attributed to a higher fraction of reactive iron-nickel phases formed under shorter reduction. Its tailored core-shell structure improves air stability and surface reactivity, highlighting its potential as a next-generation zero-valent iron nanocatalyst for aqueous remediation.

The growing demand for petroleum and its derivatives is the main contributor to increased carbon monoxide (CO) emissions. Catalytic oxidation is considered an effective technology for CO removal since it has low-energy consumption and pollution. There is great interest in reducing the costs associated with CO oxidation catalysts replacing noble metals (platinum and gold, for example) with non-noble transition metal oxides, such as titanium and manganese oxides. This work proposes a simple controlled synthesis of titanate nanowires decorated with copper islands prepared by a wet impregnation route using various copper quantities (1, 2.5, and 5 wt %). The nanomaterials were characterized by X-ray diffraction, small angle X-ray scattering, nitrogen physisorption (BET and BJH), transmission electron microscopy, and scanning electron microscopy. The copper/titanate materials with 5% copper allowed the CO oxidation at 100 degrees C, a very low temperature for this reaction, and the hydrogenation of 4-nitrophenol by sodium borohydride with very good kinetics, indicating great potential for these and other catalytic reactions. The use of copper not only improved the catalytic efficiency but also met environmental sustainability objectives.

Black nanostructured titanium dioxide (TiO2) has garnered attention due to its potential for enhanced photocatalytic activity under visible light. One of the advantages of black TiO2 over conventional TiO2 is its extended visible light absorption, which can improve photocatalytic performance under solar light. In this study, TiO2 was synthesized using two different methods - hydrothermal (HT) and sol-gel (SG) using titanium butoxide (TBOT) and titanium isopropoxide (TTIP) as precursors, followed by heat treatment under argon atmosphere. The aimed of this study was to investigate the influence of precursors and synthesis routes on achieving an anatase/rutile ratio similar to that of commercial TiO2 (P25) after heat treatment under argon. The calcination temperatures required for anatase to rutile transformation differed significantly: HT syntheses required higher temperatures (680 degrees C for TBOT, 710 degrees C for TTIP) compared to SG syntheses (590 degrees C for TBOT, 570 degrees C for TTIP) for the same rutile range (20-25 %). Activation energies for crystal growth varied with synthesis method and precursor: TBOT-HT (193.8 kJ mol(-1) up to 670 degrees C, 11 kJ mol(-1) up to 750 degrees C); TTIP-HT (40 kJ mol(-1) up to 800 degrees C); TBOTSG (9.4 kJ mol(-1) up to 600 degrees C, 191.6 kJ mol(-1) up to 750 degrees C); TTIP-SG (129.8 kJ mol(-1) up to 570 degrees C, 17 kJ mol(-1) up to 650 degrees C). Morphological analysis by SEM showed nanoflower-like structures for HT and dendritic or massive morphologies for SG samples. Raman spectra indicated carbon presence, contributing to black color and anatase peak shifts, suggesting oxygen vacancy formation; XPS confirmed Ti4+ presence instead of Ti3+. EPR detected oxygen vacancies characteristic of black TiO2, enhancing visible light absorption and reducing electron-hole recombination for improved photocatalytic performance. The study demonstrates that both precursor and synthesis method influence the anatase to rutile transformation temperature and morphology of TiO2. The transformation of anatase to rutile occurred at a lower temperature for SG than for HT samples and the morphologies obtained varied depending on the method. It was possible to obtain black TiO2 presenting oxygen vacancies as well as carbon residues from the precursors.

Cementing is one of the most crucial operations in an oil well since it fixes the casing and prevents fluid migration across permeable zones. However, the material used in this process, Class G cement, faces exposure to various agents during and after its curing process, particularly at greater depths where temperatures and pressures are elevated. Exposure of this cement to elements like brine, H 2 S gas, and CO 2 gas tends to compromise the material 's durability and the well 's integrity. Consequently, exposure to these agents leads to modifications in the cement paste 's physical, chemical, and mechanical properties. Thus, investigations into the influence of these agents are crucial to ensure the integrity of the cement sheath. In this study, Class G cement pastes were exposed for three months in an autoclave under elevated pressure (20 MPa) and temperature (88 degrees C) in a brine-saturated environment with either H 2 S or CO 2 at different stages. The research investigated mechanical behavior through uniaxial and triaxial compression tests, physical properties through porosity and micro-computerized tomography tests, and chemical properties through X-ray diffraction and pH tests. The study demonstrates that confining pressure significantly affects the deformation of samples exposed to brine + H 2 S and brine + CO 2 , causing plastic deformations at confining pressures above 20 MPa even before applying deviatoric stresses. Exposure to acidic gases also leads to a 27% reduction in compressive strength for brine + H 2 S and a 45% reduction for brine + CO 2 , affecting the elastic moduli due to potential micro-defects originating from the curing process and chemical reactions induced by the presence of the acidic gases.

Cu, Zn, and Al-based catalysts were prepared, characterized, and tested in order to describe the role of Al in the CO2 hydrogenation to methanol. This work shows that Al3+ replaces Zn2+ in the ZnO lattice, promoting the generation of oxygen vacancies (Vo) on the oxide surface. When the Al and Vo concentration increases, the rate of methanol formation also increases. Once Al3+ solubility in ZnO is reached this rate decreases. An Al-based compound is formed which occludes a portion of the catalyst’s surface, changing the behavior of the catalyst. DFT calculations highlight the role of Al in methanol formation by lowering the energy required for the formation of Vo. This species promotes the adsorption of CO2 on the interface between ZnO and Cu0. Thus, both Al and Vo show a pivotal role in the catalytic behavior of Cu/ZnO/Al.

Summary Limiting the fluid loss from the cement slurry to the adjacent formation by using additives is essential for maintaining the slurry’s water/cement ratio. The present work focuses on the effect of noncrosslinked polyvinyl alcohol additive (PVOH), a widely used fluid loss additive (FLA), on the compression strength and rheological behavior of Class G cement pastes. Results of the current study show that the PVOH surfactant characteristic and its absorptive mechanism interfere not only with the hydration process but also with the physical properties and compressive strength of cement pastes, such as porosity, permeability, and early age strength, which revealed the importance of using a defoamer when PVOH is present in the mixture. In the absence of a defoamer, the PVOH additive generates foam in the mixed cement paste samples, which results in increased porosity and reduced compressive strength of the hardened cement paste. Moreover, regarding rheology, increasing the PVOH concentration increased the effective viscosity when evaluating flow curves. Therefore, this study demonstrates a systematic method for assessing the possible effects of cement paste additives, such as PVOH and defoamer, providing a physical and mechanical approach rather than just chemical to evaluate additives’ influence on the mixtures. This method should consider different additives in combination with PVOH to test cement paste stability and to obtain specific working recipes.

Recent research on the use of physical mixtures In2O3-ZrO2 has raised interesting questions as to how their combination enhances catalytic activity and selectivity. Specifically, the relationship between oxygen diffusion and defect formation and the epitaxial tension in the mixture should be further investigated. In this study, we aim to clarify some of these relationships through a molecular dynamics approach. Various potentials for the two oxides are compared and selected to describe the physical mixture of In2O3 and ZrO2. Different configurations of each single crystal and their physical mixture are simulated, and oxygen defect formation and diffusion are measured and compared. Significant oxygen defect formation is found in both crystals. In2O3 seems to be stabilized by the mixture, while ZrO2 is destabilized. Similar results were found for the ZrO2 doping with In and ln2O3 doping with Zr. The results explain the high activity and selectivity catalyst activity of the mixture for the production of isobutylene from ethanol.

Nanocrystals' surface area and shape significantly impact their activities in fuel cells. On the other hand, additional parameters that may affect their activities cannot be neglected. Here, we demonstrate that the presence of crystalline defects (such as oxygen vacancies) and the relative concentration of CuI/CuII may also vary with the decrease of CuxO nanocubes sizes, contributing to the observed activities as noble metal-free anodes for methanol fuel cells. However, such differences did not follow the size as expected, showing that this parameter does not play a critical role in determining materials' properties. To this end, CuxO nanocubes having controllable sizes (50, 65, and 85 nm) were synthesized by a simple and similar protocol, leading to nanocrystals enclosed by {100} surfaces. When the catalytic activity of the different-sized CuxO nanocubes was performed toward the electrooxidation of methanol in alkaline media, the observed performances decreased as follows: 50 nm > 85 nm > 65 nm-CuxO nanocubes, in which 50 nm-CuxO nanocubes led to the best electrocatalytic results. Interestingly, our results showed that the differences in the catalytic activities of CuxO nanocubes displaying different sizes could not only be assigned to a gain of surface area with a decrease in particle size. More specifically, XPS results indicated that the reduction of particle size led to an increase in both Os/OL and Cu(I)/Cu(II) ratios, demonstrating the enrichment of oxygen vacancies at the surface of CuxO nanocubes, which also contributed for the observed catalytic activities.

The electrokinetic process seems to be interesting to the earthwork portion on the construction of buildings, and transportation projects since this simple, fast, yet reliable technique could expedite dehydrating of soil and reduce delays in the construction schedule. This paper examined the technical feasibility and a brief cost analysis of using plastic electrodes for electrokinetically dehydrating clayey soils with high moisture content were also carried out. The results from the experimental program carried out on a marine clayey soil with copper and plastic electrodes showed a great deal of soil improvement since positive changes in undrained shear strength occur due to the free water dehydration process induced by electroosmosis and to the adsorbed water dehydration process induced by electromigration. It was also observed that values of the undrained shear strength remained stable at the final stages of the electrokinetic process indicating a permanent soil improvement. Finally, it was noticed that dehydrating could be achieved at lower costs by employing plastic electrodes.

This work studies the crystallinity and rheology of HDPE/PA12 blends compatibilized with 2 wt% of HDPE-alt-MAH. Specimens of HDPE/PA12 blends were extruded and injected into a mold with 75/25, 50/50, and 25/75 HDPE/PA ratios. The Fourier-transform infrared spectroscopy (FTIR) analysis showed that no oxidation reaction occurred in the high-temperature processing and that stronger interactions between the components of the blends occurred in the polyamide's functional groups. The x-ray diffraction (XRD) analysis showed that the crystallinity degree of the blends and the mean crystallite sizes decreased with the addition of PA12 for both blends. The HDPE's lattice parameters were consistent with the values in the literature, whereas for the PA12, it was not possible to fit its lattice parameters. The rheology analysis evaluated the relationship between the shear stress and viscosity and found that the HDPE/PA 75/25 blend was the most pseudoplastic, presenting the best processability under high shear rates.

The crystal structure of a novel bis(ligand)copper(II) complex of the pyridine-2-carboxaldehyde 2-furoyl hydrazone (HPCFur) metallophore is described, altogether with its Hirshfeld surface analysis. The isolated compound crystallizes in the monoclinic system, space group P21/c, with four [Cu(PCFur)2] molecules in the asymmetric unit. Symmetry around copper is distorted octahedral. HPCFur coordinates in its deprotonated, iminolate form, which impacts the O1−C7 and N2−N3 distances in both ligand units. The complex exhibits a variety of weak, non-conventional intermolecular hydrogen bonds. Hirshfeld analysis and fingerprint plots indicate that, overall, hydrogen bond interactions are responsible for almost 50

A low-temperature sintering process was used to produce pellets at different temperatures using TiO2 anatase (Vetec) and P25 (Evonik) commercial powders. The initial powder was mixed with 75% acetic acid aqueous solution and pressed under 375 MPa. The temperature was applied after the pelletization in a conventional furnace for 4 hours. The best sintering temperature for anatase was 800 degrees C, which is higher than typical cold sintering temperatures but below conventional ones. However, the optimal temperature was 450 degrees C for P25 due to its density and SEM results. The sintered pellets' maximum densities were 70% (anatase, 800 degrees C) and 66% (P25, 450 degrees C). It was not possible to measure the anatase pellets treated under 800 degrees C because they disintegrated in water. This work studied the effects of the applied pressure, solvent concentration, particle size, and sintering temperature on the properties of sintered pellets, such as integrity, density, and presence of porous. It also evaluated the electrochemical activity measured by cyclic voltammetry (CV), which indicated that the sintered TiO2 pellets are porous with a partial capacitive response.

CO2 methanation – TPSR profiles of the Ni/ZrO2, Ni/Mg(Al)O, and Ni/SiO2 catalysts.

Self-reduction is a pyrometallurgical treating process that aims to valuable metal recovery from mining-metallurgical industry wastes, mainly from steelmaking industries. Electric Arc Furnace Dusts (EAFD) are still the most attractive materials to be tested in using this technique, due to their high magnetite and franklinite/zinc ferrite contents. This research will address the reuse of these co-products in steel plants, providing added value to this material that until now is constituted as an environmental liability of considerable economic importance in steelmaking industries. Chemical and microstructural analysis has determined high contents of iron and zinc from magnetite and franklinite/zinc ferrite. Iron was present in the non-stoichiometric form of “hapkeite” (Fe1.34Si0.06) in both EAFD 1 and EAFD 2. A rare appearance of Moissanite CSi –2H was also found in EAFD 1. Thermogravimetric evaluations allowed elimination of almost 15% of volatile matter at 1000 °C in EAFD 1. EAFDs were partially reduced and showed a high porosity, which would make it possible for the recovery of its main metal content by carbothermic self-reduction. Proximate analysis and carbon dioxide reactivity of two reductants were tested for evaluating the behavior of selected reductants in carbothermic self-reduction of EAFDs using a procedure given by the Steelmaking and Ironmaking Group of DEQM PUC/RJ. This mixture included 85% (EAFD + coal), 6% CPV ARI, and 9% water. Operational Diagram of Phase Predominance (ODPP) from the Zn–Fe–C–O system was used to calculate the required carbon and to guarantee the occurrence of the global chemical reactions of carbothermic reduction either in franklinite/zinc ferrite as in magnetite by 100% CO and temperatures between 1000 and 1100 °C. In these conditions, self-reducing briquettes of EADF 2 lost more weight so reacted faster than EAFD 1. Finally, reactions rates of carbothermic self-reducing briquettes EAFDs were very fast during the first 5 min and retarded from 5 to 40 min.

We describe the synthesis of Pd nanoflowers in a single reaction step by reducing PdCl4 2-(aq) with hydroquinone. Simply by controlling the reaction temperature, we could obtain monodisperse Pd nanoflowers with well-defined shapes and sizes. Based on the detected product morphology, crystallinity, and several control experiments, a novel non-classical mechanism based on both LaMer and DLVO theories was established. Specifically, Pd nanoclusters were produced at the initial stages of the reaction, followed by their fusion to form larger poly-crystalline Pd nanoparticles. These polycrystalline Pd nanoparticles served as seeds for further Pd deposition and attachment of Pd nanoclusters to generate Pd nanoflowers. In this procedure, the control over the temperature enabled us to tune the ionic strength of the solution (control over the fraction of PdCl42-and K+ ions present in the solution), which affected the attachment and aggregation steps, leading to Pd nanoflowers with controlled sizes and morphologies. When these nanomaterials were employed as nanocatalysts for electrooxidation of ethanol, the 12 nm-Pd nanoflowers were the best catalyst in terms of both activity and peak potential.

Zirconia oxide (ZrO2) is a material that has aroused great interest in the scientific community for its general use in various technological applications, such as fuel cells, solar cells, electronic devices, catalysis, dental biomaterial and ceramics. When it is applied as a catalyst, the doping and vacancy effects of their crystalline phases are important properties to guide new developments. This work investigates tetragonal and monoclinic crystalline phases of the Zn-doped ZrO2 by periodic density functional calculations. Changes in the electronic and acid-basic properties were performed by Bader charge analysis, the density of states calculations (DOS) and the projected density of states (PDOS). The formation of oxygen vacancies was also evaluated. The calculated oxygen vacancy formation energies indicate that it is much easier to generate oxygen vacancy in the Zn-doped ZrO2 than in the pure material; in addition, oxygen vacancy formation is favored in the monoclinic phase. Bader charge analyses and projected density of states indicated that the doping of ZrO2 with Zn creates more basic and acid sites. The most stable material is the Zn-doped 3-fold coordinated Zr atom of the m-ZrO2, which can be used for future developments and applications.