Search Results (50)

This study aims to evaluate the corrosion inhibition performance of different types of inhibitors for steel reinforcement in cement paste under accelerated carbonation conditions. Electrochemical methods, including electrochemical impedance spectroscopy EIS, linear polarization resistance LPR, and open-circuit potential OCP measurements, were utilized on specimens with various inhibitor formulations during exposure to a high-CO₂ environment. The results indicate that composite inhibitors provide the greatest protection, significantly outperforming single-component anodic or cathodic inhibitors. Among anodic inhibitors, sodium molybdate showed more effective corrosion inhibition than sodium chromate, and among cathodic inhibitors, BTA was more effective than DMEA, as evidenced by higher polarization resistance and more stable passivation. After 120 days of carbonation, the specimen with the optimal composite inhibitor remained passive with a low corrosion rate and a relatively noble steel potential, whereas the uninhibited specimen exhibited active corrosion. Full article

Drying is ubiquitous. However, its influence on surface speciation has been seldom studied. Through an in situ Attenuated Total Reflection–Infrared (ATR-IR) spectroscopy analysis of the drying of molybdate solutions on a lepidocrocite particle film, the change in surface speciation is followed. No formation polymolybdates nor precipitate are observed upon drying at pH 8. An in situ washing of the dried solid/solution interface unveils the existence of surface outer-sphere and inner-sphere complexes. Decreasing the molybdate concentration highlights a saturation effect of the surface upon drying. Moreover, the careful analysis of substrate IR bands showed non-uniform drying which is an important insight to understand dehydration chemistry. The remaining molybdate ions at the surface as inner-sphere complexes are present as binuclear monodentate complexes stabilized by sodium. Full article

With the rapid development of flexible electronic skin materials, the demand for ion-conductive hydrogels is constantly growing. Specifically, these ion-conductive hydrogels are required to simultaneously exhibit excellent mechanical properties, high conductivity, and multifunctionality. Moreover, this performance requirement needs to be met in complex environments. However, the rapid production of hydrogels that combine high conductivity and photochromic properties remains a major challenge. In this study, a simple one-pot method was employed to successfully prepare multifunctional photochromic hydrogels by incorporating ammonium molybdate (Mo₇) and lithium chloride (LiCl) into a dual-network hydrogel composed of polyacrylamide (PAAm) and sodium alginate (SA). PAAm/SA/Mo₇/LiCl (PSML) hydrogels exhibit excellent comprehensive performance, including superior conductivity (average value of 164 S/cm), rapid UV response time (<20 s), good color-changing reversibility, outstanding high stretchability (peak value of 2800%), and high transparency (>70%). The design ingeniously combines two types of synergistic effects: the synergistic effect of the dual-network structure and that of the multifunctional component functional additives (Mo₇, LiCl). Specifically, the PSML hydrogel integrates photochromic properties, excellent mechanical properties, good anti-freezing properties, and 3D printability through this design. Due to these outstanding properties, the PSML hydrogel shows broad application prospects in fields such as flexible strain sensors, information storage, and encryption devices. Full article

MoS₂, a key material for supercapacitors, batteries, photovoltaics, catalysis, and sensing applications, was synthesized using the hydrothermal method. Different precursors such as molybdenum sources (ammonium heptamolybdate tetrahydrate ((NH₄)₆Mo₇O₂₄·4H₂O) and sodium molybdate hydrate (Na₂MoO₄·2H₂O)) combined with L-cysteine, thiourea, and thioacetamide, as the sulfur source, were involved. The obtained samples were morphologically and structurally characterized by X-ray diffraction, Raman spectroscopy, N₂ adsorption/desorption measurements, and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM–EDX). Electrochemical impedance spectroscopy was involved in MoS₂ characterization as electrode materials. The objective of this study was to ascertain the impact of precursor combinations on the morphological, structural, and electrochemical characteristics of MoS₂. A thorough examination of the empirical data revealed that the MoS₂ compounds, which were synthesized using thiourea as the sulfur source, exhibited a more pronounced flower-like morphology, increased crystallite size, and enhanced electrochemical properties with potential electrochemical applications. Full article

The elimination of absorbance of excess dye by selective oxidation was first proposed for analytical methods using the formation of ion-association complexes (IAs). On this basis, a new sensitive and selective spectrophotometric method for the determination of phosphate in the form of the IA of 11-molybdovanadophosphate with diindodicarbocyanine (DIDC) was developed. Symmetric diindodicarbocyanine and diindotricarbocyanine dyes can be completely oxidized by sufficiently strong oxidizing agents such as permanganate, dichromate, cerium (IV), and vanadate. Of the three dyes investigated (DIDC, N,N’-dipropyldiindodicarbocyanine, and diindotricarbocyanine), the best results were obtained with DIDC. A mixture of molybdate, vanadate, and nitric acid was preferably used as an oxidizing agent. Selective decolorization of only free dye ions, as well as changes in the IA spectrum compared to the dye spectrum, were explained by the isolation of the dye due to the formation of poorly soluble IA nanoparticles and changes in the redox potential of the dye due to its aggregation. The following optimal conditions for phosphate determination were found: 0.3 M nitric acid, 0.43 mM sodium molybdate, 0.041 mM sodium vanadate, 0.015 mM DIDC, and 18 min for the reaction time. The molar absorptivity of the IA was 1.86 × 10⁵ mol⁻¹·L·cm⁻¹ at 600 nm, and the detection limit for phosphate was 0.013 µM. The developed method was applied to the determination of phosphate in natural water samples. Full article

Molybdenum is an essential trace element sourced during pregnancy from the maternal diet. Studies regarding molybdenum have primarily focused on overexposure in animal and cell culture studies. The effects of molybdenum supplementation on placental function are unknown. An immortalised trophoblast cell line was used to examine the placental cellular response to molybdenum in its bioavailable form as molybdate. Cells of the extravillous trophoblast first-trimester cell line HTR8-SVneo were cultured in complete cell media in the presence of 10 nM to 1 mM of ammonium molybdate or sodium molybdate. Following the addition of the molybdate salts, cell growth, viability, and several gene pathways were monitored. Sodium molybdate salt in doses from 10 nM to 1 mM did not affect cell growth or viability. Exposure to ammonium molybdate at a 1 mM concentration significantly decreased cell growth and viability (p < 0.05). Gene pathways involving molybdoenzyme expression, molybdenum cofactor synthesis, antioxidant response, and angiogenesis were affected following supplementation, although these effects differed depending on the dose and molybdate salt utilised. Molybdoenzyme activity was not affected by supplementation in a dose-dependent manner. The results indicate sodium molybdate is a more appropriate salt to use in vitro, as ammonium molybdate exposure reduced cell viability and growth and downregulated the expression of antioxidant genes NFE2L2 (p < 0.01), SOD1 (p < 0.001) and SOD2 (p < 0.001), suggestive of an inflammatory response. Sodium molybdate affected gene, protein, and activity levels of molybdoenzyme, antioxidant, and angiogenic molecules in vitro. This work demonstrates that sodium molybdate supplementation has pleiotropic effects in vitro and is well tolerated by placental cells at a range of nanomolar and micromolar concentrations. Full article

Molybdenum disulfide (MoS₂) is a promising catalyst for hydrogen evolution through water electrolysis with low cost and high efficiency, but its hydrogen evolution performance can be further improved. Using sodium molybdate (Na₂MoO₄·2H₂O) and thiourea (NH₂CSNH₂) as raw materials, MoS₂ was prepared by the hydrothermal method. Ni-doped MoS₂(Ni-MoS₂) was prepared by using nickel dichloride dihydrate (NiCl₂·2H₂O) as a Ni source and doping Ni into MoS₂ by the hydrothermal method. Under the conditions of different temperatures (190 °C, 200 °C, and 210 °C) and different Ni doping molar ratios (2%, 3%, and 4%), the optimum temperature and doping ratio of the prepared materials were explored by conducting a hydrogen evolution reaction (HER) by the electrolysis of water. The results showed that the optimum preparation temperature was 200 °C and the optimum molar ratio of Ni doping was 3%. Graphene oxide (GO) was obtained by oxidation of graphite (G), and then Ni-MoS₂/GO was prepared by the hydrothermal method with Ni-MoS₂ and GO. The performance of HER was tested. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectroscopy (XPS). The results show that the composite Ni-MoS₂/GO has good HER performance, which is better than that of MoS₂ or Ni-MoS₂. In 0.5 M H₂SO₄ solution, the η₁₀ is as low as 196 mV, the Tafel slope is 122 mV/dec, the C_dl is 13.98 mF/cm², and it has good stability. The enhancement of electrocatalytic activity is mainly due to the doping of a small amount of Ni, which increases the defects of the catalyst and forms more active sites. GO improves the conductivity of the material. Ni doping and GO compounding promote the HER performance of MoS₂. Full article

Chromium salt fillers commonly used in current anti-corrosion coatings are highly toxic. However, due to the unique high–low valence transformation and passivation mechanisms of chromium-based functional fillers and their wide applicability, chromium-free coatings find it challenging to achieve the same performance and industry acceptance. This study introduces an innovative approach that uses zinc to reduce molybdate (MoO₄²⁻) in an acidic solution, thereby forming a multivalent MoO₄²⁻ system (PMZ system), and applies it to chromium-free insulating coating for oriented silicon steel. The effects of reductant dosage on the valence composition of molybdenum in the PMZ system and the corrosion resistance of the coating were investigated. Additionally, the difference in the valence composition of molybdenum between the PMZ system and the multivalent phosphomolybdate system (PMNZ system) and its impact on corrosion resistance were studied. The results indicate that the PMZ system contains trivalent molybdenum and hexavalent molybdenum, while the PMNZ system contains pentavalent molybdenum and hexavalent molybdenum. The systems leverage the reactivity of lower-valence molybdenum to delay the corrosion by reacting with oxygen while maintaining the original mechanism of molybdenum salt fillers and forming sediment with iron ions to form a passivation layer. As the content of trivalent molybdenum in the PMZ system increases, the corrosion resistance of the insulating coating improves. When the amount of zinc added in the PMZ system is 0.006 g, the relative proportion of trivalent molybdenum reaches 20.52%, and the salt spray resistance of the coating developed with the PMZ system reaches 248 h with a corrosion area of less than 5%. When the contents of the main components and sodium molybdate in the PMZ coating and the PMNZ coating are the same, the corrosion resistance of the PMZ coating, which contains trivalent molybdenum, is better than that of the PMNZ coating, and the salt spray resistance exceeds 192 h. Full article

Semi-arid regions present edaphoclimatic limitations for forage production, primarily affecting plant growth and development. Crops adapted to such conditions, like forage sorghum, and nutritional supplementation with nitrogen and molybdenum, can increase forage production. The objective of this study was to evaluate the interaction between nitrogen and molybdenum on the bromatological and structural components of forage sorghum (SF-15) cultivated in a semi-arid environment, with the hypothesis that nitrogen fertilization combined with molybdenum would enhance nitrogen use efficiency in sorghum. The methodology involved a 5 × 2 factorial experiment in a randomized block design (RBD) with increasing doses of nitrogen (urea) (0, 50, 100, 150, 300 kg ha⁻¹) and two doses of molybdenum (sodium molybdate): 0 and 160 g ha⁻¹, conducted over three cultivation cycles. At the end of each cycle, morphological variables were evaluated, and yield of natural mass (YNM), yield of dry mass (YDM), crude protein production (CPP), and bromatological components were determined. Morphometric characteristics were influenced by the interaction between cycle x nitrogen doses (N) and molybdenum doses (Mo). For productive characteristics, there was an interaction between cycle and nitrogen doses, with the first regrowth cycle and the dosage of 100 kg ha⁻¹ N showing the highest mean. Bromatological components were influenced by the N and Mo interaction. The study confirmed the synergistic effect between nitrogen and molybdenum. It is recommended to use 100 kg ha⁻¹ nitrogen fertilization for an average production of 10 t ha⁻¹ for SF-15 sorghum. Full article

The presence of harmful oxidizing gases accelerates the oxidation of cellulose fibers in paper, resulting in reduced strength and fading ink. Therefore, the development of highly sensitive NO₂ gas sensors for monitoring and protecting books holds significant practical value. In this manuscript, ZnO/MoS₂ composites were synthesized using sodium molybdate and thiourea as raw materials through a hydrothermal method. The morphology and microstructure were characterized by X-ray diffraction analysis (XRD), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The ZnO/MoS₂ composite exhibited a flower-like structure, with ZnO nanoparticles uniformly attached to the surface of MoS₂, demonstrating advantages such as high specific surface area and good uniformity. The gas sensitivity of the ZnO/MoS₂ nanocomposites reached its peak at 260 °C, with a sensitivity value around 3.5, which represents an improvement compared to pure ZnO, while also enhancing sensitivity. The resistance of the ZnO/MoS₂ gas sensor remained relatively stable in air, exhibiting short response times during transitions between air and NO₂ environments while consistently returning to a stable state. In addition to increasing adsorption capacity and improving light utilization efficiency, the formation of hetero-junctions at the ZnO-MoS₂ interface creates an internal electric field that effectively promotes the rapid separation of photo-generated charge carriers within ZnO, thereby extending carrier lifetime. Full article

The bulk of the LiNa₅Mo₉O₃₀ (LNM) crystals were successfully grown in the [010] and [001] directions without internal inclusions and cracks, using the Czochralski method with a low temperature gradient. The crystal grown in the [010] direction showed a tendency to twinning. The crystal grown in the [001] direction demonstrated high structural perfection (FWHM = 13″) for the (001) plane and high optical quality Δn ≈ 2 × 10⁻⁵. The laser-induced damage threshold was measured along a, b and c axes and was 12.2, 27.0 and 27.5 J/cm², respectively. The thermo-optical coefficient dn/dT was measured for the main crystallographic axes, which was −5.75 × 10⁻⁶, −20.2 × 10⁻⁶ and 3.65 × 10⁻⁶ K⁻¹ along the a, b and c axes, respectively. The second harmonic generation (SHG) was conducted in the crystalline LNM sample. The maximum efficiency value of 3.5% at a pump power of 12 W was achieved. Full article

The service performance of chromium-free zinc–aluminum coatings exhibits characteristics from multiple perspectives. Fully considering the physical properties, corrosion resistance, and economic viability of the coatings, this study incorporates the concepts of “domain” and “degree” from extenics theory into the analytic hierarchy process to optimize the formulation of chromium-free zinc–aluminum coatings. The findings reveal that the extension analytic hierarchy process takes into account the diversity of evaluation indicators, enhancing the objectivity and accuracy of the comprehensive evaluation results. Nine formulations were developed using a four-factor, three-level orthogonal experiment to evaluate the effects of metal powder, PEG-400, KH-560, and sodium molybdate on the service performance of chromium-free zinc–aluminum coatings. Utilizing an extensible hierarchical sorting weight system alongside a performance index grading and scoring method, 3# emerged with the highest score, indicating the best overall performance. The research outcomes offer innovative insights and technical support for optimizing the formulations of chromium-free zinc–aluminum coatings and other coatings. Full article

Calcium molybdate (CaMoO₄) is of significant interest due to its unique properties and numerous industrial applications, such as catalysis, electrochemistry, and optoelectronics. In this study, we developed an economical and environmentally friendly method to synthesize calcium molybdate from Moroccan phosphogypsum (PG) industrial waste and sodium molybdate, all at room temperature. Comprehensive analysis through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman vibrational spectroscopy, and scanning electron microscopy (SEM) revealed the high purity of the synthesized calcium molybdate, with particle sizes of only 12 nm. Additionally, optical characteristics were studied using ultraviolet-visible spectroscopy (UV-vis), which showed an optical band gap of Egap = 3.96 eV for CaMoO₄. These results confirm the successful synthesis of calcium molybdate nanoparticles from Moroccan phosphogypsum, demonstrating an effective pathway to valorize this industrial waste into a valuable material. This approach contributes to environmental sustainability by reducing dependence on rare chemicals while offering innovative solutions for the industry’s sustainable development. Full article

Most crops are fertilized with high amounts of nitrogen, and have an alarmingly low utilization efficiency. For this reason, the coordination between the fertilizer contribution and the nitrogen requirements of the crop is very important. Therefore, the objective of the present study was to establish new indices to determine nitrogen use efficiency (NUE), and to define the amount of assimilated nitrogen, which is used for the formation of green bean plant organs, fertilized with molybdenum nanofertilizer applied foliarly, and combined with edaphic fertilization of ammonium nitrate. The plants were grown in a greenhouse covered with anti-aphid mesh and irrigated with nutrient solution. Three sources of foliar molybdenum (Nanofertilizer, molybdenum Chelate and Sodium Molybdate) were applied in four doses of 0, 5, 10 and 20 ppm Mo, complemented with edaphic fertilization of NH₄NO₃ (0, 3, 6 and 12 mM of N). As results, the NUE indices showed that with the application of the nanofertilizer, the total biomass production increased 41.65% more than with the application of the chelate, and 36.84% more than with the application of molybdate. In summary, the dose that presented the highest efficiency was 6 mM-N with 10 ppm-Mo. Finally, it is concluded that the use of NUE indices is an important approach that evaluates the fate of nitrogen and accurately estimates plant yield. Full article

Molybdenum (Mo) is a rare and important element extensively utilised in aerospace, radar communications, optoelectronic devices, and the military. This study proposes an environmentally friendly physical method based on photon–phonon resonance absorption for the separation of Mo from sodium molybdate (Na₂MoO₄). We examined the vibrational spectrum of Na₂MoO₄ using the CASTEP code, employing first-principles density functional theory. Through dynamic process analysis, we analysed the vibrational modes and assigned peaks corresponding to experimental infrared (IR) and Raman data. We focused on the vibrational modes associated with Mo and identified that the highest-intensity IR-active peak at 858 cm⁻¹ corresponded to Mo–O bond asymmetric stretching. Therefore, we propose the use of a high-power terahertz laser at ~25 THz to facilitate the separation of Mo from Na₂MoO₄. Experimental investigations are expected in the future. Full article