Decrease In Conductivity Research Articles

A straw-soy protein composite (SSPC) material: preparation, physical properties and wetting drying stability

The use of bio-based biomass construction materials has the advantage of helping to reduce fossil energy demand, protecting the environment from carbon dioxide emission and reducing the production of non-degradable waste. This paper used resin-modified soy protein (SP) adhesive to combine rice straw stalks, and made straw-soy protein composites (SSPC) material. The physical properties, compressive behavior and stability during wetting drying cycles of SSPC were measured. Due to water evaporation, the SP matrix is full of connected pores, resulting to its physical properties of small density, high shrinkage ratio and low thermal conductivity, which are 0.24 g/cm3, 16.2%, and 0.065 W/(m•K), respectively. Adding straw is helpful to the physical properties of SP matrix, leading to an obvious decrease in shrinkage ratio and thermal conductivity of SSPC, which are 8.51% and 0.075 W/m•K. Furthermore, the compressive load–displacement curves of SSPC groups divide into two types: divergent and convergent. The compressive strength of divergent samples is decided by the critical displacement determined according to the convergent specimens. It shows that straw stalk proves the positive effect on the compressive property of SP matrix. As to the mass of SSPC samples during the wetting drying cycles, it drops apparently in the initial three cycles, and becomes negligible from the fifth cycle, meaning that the stability of SSPC during wetting drying cyclic process is quite good. The research result would be helpful for using SSPC as building material, especially as thermal insulation material.

Effect of Artificial Humic Acids Derived from Municipal Sludge on Plant Growth, Soil Fertility, and Dissolved Organic Matter

Due to its high nutrient utilization efficiency, liquid organic fertilizer has become a research hotspot in the field of agricultural planting. Artificial humic acids, which are near-nature products, can be deemed as a green liquid organic fertilizer, but few studies have been reported, which has limited their further application. In this study, artificial humic acids were derived from municipal sludge, and their effect on rice growth, soil fertility, and dissolved organic matter was investigated using multi-chamber root box experiments. The shoot and root biomass of rice can be significantly enhanced by artificial humic acids, and the heavy metal concentration in rice was within safe limits. Artificial humic acids can limit the decrease in soil pH, especially in the far-rhizosphere zone, and improve the distribution of nutrients in the rhizosphere, near-rhizosphere, and far-rhizosphere zones. The use of artificial humic acids led to a significant decrease in soil electrical conductivity. The dissolved organic carbon content in the root zone was significantly increased, and the fluorescence intensity of dissolved organic matter in the rhizosphere was significantly increased. The proportion of specific components of dissolved organic matter was just slightly changed in the rhizosphere and near-rhizosphere zones. Artificial humic acids promoted the humification of dissolved organic matter in the near-rhizosphere and far-rhizosphere zones. The findings indicate that the environmental impact of artificial humic acids is significantly different from conventional chemical fertilizers, and they show huge potential in the agriculture field.

The study of micellar transitions in mixed systems of dibranched cationic/nonionic fluorinated surfactants using various physicochemical methods

AbstractIn this study, a new method was introduced to induce micellar transitions by using vesicles formed from mixed surfactants, which offer enhanced stability. Different physicochemical analysis methods were used to study the transition mechanism and the aggregation behavior of the mixed aqueous system composed of the double‐chain cationic didodecyldimethylammonium bromide (DDAB) and a single‐chain nonionic fluorinated surfactant undecafluoro n‐pentyl decaoxyethylene ether (C5F11(EO)10), by varying the fraction of DDAB, then the total surfactant concentration of DDAB/C5F11(EO)10 mixed system at XDDAB = 0.9. The obtained results indicated that the addition of the fluorinated surfactant C5F11(EO)10 to the mixed system resulted in a reduction of the surface tension (γ) and a decrease in the Electrical conductivity (K). Furthermore, even at high total concentrations of the mixed system, the conductivity and charge density at the surface remained stable. As XDDAB values increased, a higher degree of dissociation (α) was observed, along with negative values in the thermodynamic parameters of micellization (Δ, Δ, and Δ), confirming the transition from micelles to vesicles. The dynamic light scattering (DLS) analysis revealed the formation of two stable types of aggregates at both low and high concentrations, as supported by the zeta potential (ζ). Upon increasing the concentration of surfactants, UV–Vis absorption measurements indicated that small spherical micelles grow into large multilamellar vesicles, as evidenced by an increase in turbidity and confirmed transmission electron microscopy images.

Influence of Atmospheric Gas Species on an Argyrodite-Type Sulfide Solid Electrolyte During Moisture Exposure.

Sulfide solid electrolytes have potential in practical all-solid-state batteries owing to their high formability and ionic conductivity. However, sulfide solid electrolytes are limited by the generation of toxic hydrogen sulfide and conductivity deterioration upon moisture exposure. Although numerous studies have investigated the hydrolysis degradation induced by "moisture," the influence of "atmospheric gases" during moisture exposure has not been extensively investigated despite the importance for practical fabrication. Therefore, in this study, we investigated the impact of atmospheric gases during moisture exposure on an argyrodite-type Li6PS5Cl via electrochemical impedance spectroscopy, X-ray diffraction, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. The electrolyte powder was exposed to various atmospheric gases, namely Ar, Ar + 500 ppm CO2, O2, and O2 + 500 ppm CO2, with moisture at a dew point of -20 °C, and H2S gas generation was monitored. As a result, the amount of H2S gas did not depend on the atmospheric gases. However, the atmospheric gases had a significant effect on the decrease in conductivity. Spectroscopic analyses revealed that CO2 facilitates the formation of carbonates and that O2 promotes the formation of phosphates and sulfonates. The formation of these compounds leads to surface degradation, which further decreases the conductivity.

Mitigating effects of Nigeria seaweed phytonutrients on biochemical and physiological conditions of Lycopersicon esculentum under heavy metal-induced abiotic stress

Abiotic stress has become a significant issue in recent years, affecting various physiological and biochemical aspects of crops and threatening food security. This study aimed to investigate the effects of seaweed on the biochemical and physiological conditions of Lycopersicon esculentum under heavy metal-induced abiotic stress. Lycopersicon esculentum plants were grown in greenhouse bags for four weeks and then exposed to 0.10M Pb Nitrate. They were divided into six groups: one control group sprayed with tap water and five experimental groups sprayed with different seaweed concentrations (0%, 20%, 40%, 60%, and 80%). Results showed that abiotic stress led to notable decreases in root length, shoot length, chlorophyll a, chlorophyll b, stomatal conductance, photosynthetic rate, Rubisco activity, and carotenoids by 48%, 47% 38%, 65%, 61%, 77%, 75%, and 68%, respectively. Seaweed treatment improved these indices, with the 80% seaweed group showing increases of 27%, 21%, 44%, 36%, 56%, and 48%, 54% after 21 days. Additionally, seaweed application enhanced antioxidant activities in the roots (SOD by 71%, CAT by 45%, POD by 51%, and APX by 92%) and in the leaves (SOD by 18%, CAT by 26%, POD by 34%, APX by 58%) compared to the control. The study concluded that seaweeds significantly mitigated oxidative stress in plants, boosting growth, antioxidant potential, mineral absorption, and osmotic protection. Nigeria seaweeds could be a promising tool to enhance food production by reducing oxidative stress in crops.

The Electrical Conductivity Mechanisms and Dielectric Properties of Multiphase Co-synthesized CuV2O6–MnV2O6

AbstractMany research studies on photodegradation, energy storage applications, and biosensing have focused on single and mixed Cu and Mn divanadates (MV2O6, M2+ = Cu2+ and/or Mn2+). In this work, MV2O6 was synthesized, and its electrical conductivity and dielectric properties were studied. The electrical and dielectric properties were investigated in a frequency range of 0.1-300 kHz and a temperature range of 298 K to 573 K. The results indicate that the DC conductivity, AC conductivity, dielectric constant, dielectric loss factor, and loss tangent of the investigated materials increase with temperature, which support the contribution of grains and grain boundaries to the electrical properties. The materials exhibit non-Debye type relaxation, as indicated by the progression of the relaxation frequency. As frequency increases, the activation energy of AC conduction decreases, indicating that hopping conduction is the dominant mechanism. In all samples, the DC conduction activation energy is higher than the AC conduction activation energy. The circuit model was used to estimate the relaxation times. The results revealed remarkable dielectric characteristics, notably higher dielectric loss tangent values at frequencies below 1 kHz. Consequently, these materials can be used as electromagnetic attenuation absorbers. Graphical Abstract

Effect of chemical modification on hydraulic conductivity of stratified porous media

ABSTRACT Understanding hydraulic conductivity is essential in porous media as it dictates the capacity of fluids to permeate through these substances. This research investigated the impact of chemical modification using fly ash on hydraulic conductivity. The coefficient of hydraulic conductivity along the bedding plane at different angles of orientations was predicted by employing machine learning techniques such as gene expression programming (GEP), artificial neural networks (ANNs), and regression tree (RT), considering various influencing parameters. As the amount of fly ash in the porous medium rises, the hydraulic conductivity decreases. The statistical results demonstrate that the proposed ANN model effectively forecasted the horizontal hydraulic conductivity. It achieved the highest R2 value (0.989), the lowest mean absolute percentage error value (5.772), the lowest scatter index value (0.040), and the lowest Akaike Information Criterion value (−2,359.914) compared to the GEP, RT, and previously established approaches. Moreover, a novel equation has been proposed for determining horizontal hydraulic conductivity, which can be used for any stratified medium, distinguishing this work from previous ones. These findings can inform global practices in mitigating groundwater contamination, enhancing irrigation efficiency, and improving the design of subsurface fluid flow systems, making it a valuable contribution to both academic and practical applications worldwide.

Анализ эффективности и безопасности применения CFTR-модулятора лумакафтор/ивакафтор у пациентов с муковисцидозом в разных возрастных группах

Russia’s first registered CFTR-modulator lumacaftor/ivacaftor was developed for patients with cystic fibrosis (CF) with the F508del/F508del genotype. The purpose of this research was to study the efficacy and safety of lumacaftor/ivacaftor therapy in different age groups. Materials and methods used: the data of homozygotes for F508del aged 2 to 18 y/o in the Russian CF Patient Registry who had been treated with lumacaftor/ivacaftor were analyzed. The effectiveness of therapy was evaluated in 3 age groups based on examination data, nutritional status, spirometry, sweat test at the start of therapy and after 12 months. In order to assess the safety, examination data, assessment of adverse events (AE), blood biochemical parameters, blood pressure and lens condition were taken into account in 334 pediatric patients in the first month of therapy and in 180 after 12 months. Results: decrease in sweat conductivity was noted in three age groups (p<0.001), only in the 2 to 6 y/o age group were negative values obtained in 6.8%. An increase in BMI was observed in the 6 to 12 y/o and 12 to 18 y/o age groups (р<0.001) whilst an improvement in FVC was observed only in the 12 to 18 y/o age group (p=0.015). Changes in biochemical parameters were statistically significant, both downward and upward, only in the age groups of 6 to 12 y/o and 12 to 18 y/o, changing not significantly. Withdrawal of the drug was required in only a single patient with a persistent increase in transaminase level. Fluctuations in blood pressure occurred within the normal age limits. Frequency of AE was comparable with the results of other studies, it was noted at the start in all groups and after 12 months more often in the age group of 12 to 18 y/o. The best tolerance was noted in the age group of 2 to 6 y/o. Conclusion: for the first time, the efficacy and tolerability of lumacaftor/ivacaftor in patients with CF in Russia was studied against the age aspect according to the 2022-2024 Registry. In the 2 to 6 y/o age group, the achievement of normal sweat test values and the lowest number of adverse reactions were noted, while in the 12 to 18 y/o age group, the positive dynamics were noted for a greater number of indicators, incl. an increase in FVC.

Fast dehydration reduces bundle sheath conductance in C4 maize and sorghum.

In the face of anthropogenic warming, drought poses an escalating threat to food production. C4 plants offer promise in addressing this threat. C4 leaves operate a biochemical CO2 concentrating mechanism that exchanges metabolites between two partially isolated compartments (mesophyll and bundle sheath), which confers high-productivity potential in hot climates boosting water use efficiency. However, when C4 leaves experience dehydration, photosynthesis plummets. This paper explores the physiological mechanisms behind this decline. In a fast dehydration experiment, we measured the fluxes and isotopic composition of water and CO2 in the gas exchanged by leaves, and we interpreted results using a novel biochemical model and analysis of elasticity. Our findings show that, while CO2 supply to the mesophyll and to the bundle sheath persisted during dehydration, there was a decrease in CO2 conductance at the bundle sheath-mesophyll interface. We interpret this as causing a slowdown of intercellular metabolite exchange - an essential feature of C4 photosynthesis. This would impede the supply of reducing power to the bundle sheath, leading to phosphoglycerate accumulation and feedback inhibition of Rubisco carboxylation. The interplay between this rapid sensitivity and the effectiveness of coping strategies that C4 plants deploy may be an overlooked driver of their competitive performance.

Enhanced Thermoelectric Performance of SnTe via Introducing Resonant Levels

SnTe has emerged as a non-toxic and environmentally friendly alternative to the high-performance thermoelectric material PbTe, attracting significant interest in sustainable energy applications. In our previous work, we successfully synthesized high-quality SnTe with reduced thermal conductivity under high-pressure conditions. Building on this, in this work, we introduced indium (In) doping to further decrease thermal conductivity under high pressure. By incorporating resonance doping into the SnTe matrix, we aimed to enhance the electrical transport properties while maintaining low thermal conductivity. This approach enhances the Seebeck coefficient to an impressive 153 μVK−1 at 735 K, marking a notable enhancement compared to undoped SnTe. Furthermore, we noted a substantial decrease in total thermal conductivity, dropping from 6.91 to 3.88 Wm−1K−1 at 325 K, primarily due to the reduction in electrical conductivity. The synergistic impact of decreased thermal conductivity and heightened Seebeck coefficient resulted in a notable improvement in the thermoelectric figure of merit (ZT) and average ZT, achieving approximately 0.5 and 0.22 in the doped samples, respectively. These advancements establish Sn1−xInxTe as a promising candidate to replace PbTe in thermoelectric applications, providing a safer and more environmentally sustainable option.

High-Temperature SHS Heat Insulators Based on Pre-Activated Mineral Raw Materials

In this paper, the results of the technological combustion of SHS heat insulators based on mineral origins are presented. It is shown that after mechanochemical treatment of minerals—diatomite—the kinetic characteristics of the combustion process change, providing targeted formation of the phase composition, structure, and properties of the SHS composite. A positive effect of using various modifiers during the MCT of diatomite—the activation of the combustion process—was established. The selection of modifiers provides an increase in the strength of the synthesized SHS composites as a result of the formation of aluminate compounds in the synthesis products, and a decrease in thermal conductivity to 0.157 W/m*K due to the formation of the ultraporous structure of the samples.

Valorization of Different Clays Used in the Treatment of Oily Wastewater in the Development of Construction Products

AbstractThe aim of this research is to study the feasibility of using clays used in the decontamination of wastewater containing olive oil wastewater (OOW), new lubricating oil (NOW) or motor oil (MOW) in the manufacture of ceramic bricks. Three types of clays were used for filtration, kaolinite type clay (KT), smectite type clay (CT) both from Tunisia and illitic chloritic clay (CS) from Jaén (Spain). These clays containing different types of oils, as well as the control clays, were used in the manufacture of bricks fired at 900 °C. These bricks were characterized by physical, mechanical and thermal tests. The sintered microstructure’s evolution was followed by tracked through scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The results indicate that the specific type of clay used influences the technological characteristics of the bricks. The use of CT clay gives rise to increase bulk density, greater compressive strength, and reduced apparent porosity and water absorption. The use of clays used in the decontamination of water containing oils produced a decrease in bulk density, compressive strength and thermal conductivity and leads to an increase in apparent porosity and water absorption in the order OOW > NOW > MOW according to the total organic carbon content (TOC). Therefore, the use of clays used in the filtration of water that contain different oils can represent a promising way of valorizing this waste, which can alleviate the environmental impact and represents economic savings for the industry of construction materials with properties of thermal insulation, getting closer to a circular economy.

Hydrogen adsorption on zinc-terminated ZnO(0001) surface at varying coverages and its effects on electronic and optical properties: A DFT+U Study

Abstract Spin-polarized density functional theory implementing Hubbard corrections (DFT+U) were utilized to study H adsorption of different coverages on Zn-terminated ZnO(0001) surface. Changes in electronic and optical properties were observed upon H adsorption of varying coverages, namely with 0.25 monolayer (ML), 0.50 ML, 1 ML, and 2 ML coverage. In terms of surface structure, H atoms were found to adsorb on top of Zn forming Zn-H bond lengths ranging from 1.54-1.73 Å for certain coverages. On the other hand, O-H bond length values are 2.41 Å and 2.37 Å for 0.50 ML and 2 ML coverage respectively. Additionally, for 0.50 ML, the most stable configuration is when one H atom adsorbs on top of Zn and the other near the hollow site. At low coverage (0.25 ML and 0.50 ML), H prefers to interact with topmost layer Zn atoms resulting to shifts in the electronic bands relative to the pristine surface’s. In addition, at high coverage (1 ML and 2 ML), shifting of bands are observed and are mainly guided by Zn-H atom interaction for 1 ML and weak H-O atom interaction for 2 ML. The observed decrease in band gap as the coverage was increased from 1 ML to 2 ML is supported by the red shift in the absorption plot. However, for low H coverage adsorption, the optical plots deviate due to emergence of flat bands. Changes in electronic properties such as shifts in conduction band minimum (CBM) and decrease in measured band gap occur as guided by the interaction of adsorbed H atoms with the surface atoms and are supported with obtained optical plots. These findings present the tunability of Zn-terminated ZnO(0001) polar surface properties depending on H coverage.

Binder Jetting Additive Manufacturing of Inconel 718/TiC Metal Matrix Composites: Influence of TiC Content on Processing, Microstructure, Mechanical and Tribological Properties.

This paper investigated the influence of titanium carbide (TiC) content on the processing, microstructure, mechanical and tribological properties of Inconel 718/TiC composites produced by binder jetting additive manufacturing. It was found that increasing the amount of TiC required an increase of the drying intensity during printing due to a decrease in the thermal conductivity of the powder mixture. The sintering process also depended on the TiC content. The most optimal modes were 1270 °C for 10 h for samples with 0 and 3% TiC and 1280 °C for 5 h for samples with 5 and 10% TiC. The hardness of the materials increased as the proportion of reinforcement increased. The best tensile properties, also at high temperatures, were possessed by samples with 3% TiC, showing high strength and, in addition, satisfactory plasticity. The maximum wear resistance was achieved by the composite material containing 5% TiC.

INVESTIGATION OF FLUORINATED DOUBLE-WALL CARBON NANOTUBES

Experimental results of investigation of the original and fluorinated ultra-long double-walled carbon nanotubes (DWCNTs) with a length of at least 1000 μm are presented. The degree of fluoridation did not exceed 27 at.%. It has been shown that the process of fluorination of samples of double-walled carbon nanotubes deforms the outer surface of the nanotube wall although does not destroy its internal concentric structure, while the diameter of the fluorinated nanotube increases by 1.5-2 times. In addition, the fluorinated samples, which were thermochemically purified from iron particles and other forms of carbon before fluorination, demonstrated many split/cut ends of nanotubes. The effect of fluorination on the electrical properties of initial and purified samples of double-walled carbon nanotubes was studied. It was revealed that with an increase in temperature from 80 to 300 K for non-fluorinated and fluorinated purified nanotube samples, the resistivity decreases, which corresponds to the semiconductor nature of the conductivity. It was also revealed that when a sample of initial DWNT is fluorinated, a change in the nature of conductivity from semiconductor to metallic is observed. With an increase in temperature from 80 to 300 K, the resistance of the non-fluorinated sample of the original DWNTs decreased by 45%, while the resistance of the fluorinated sample increased by 11%. Despite the decrease in electrical conductivity as a result of fluorination of the purified samples, all samples remained conductors, which presumably indicates partial fluorination of the outer wall of the DWNTs while maintaining the structure of the inner wall. Thus, fluorination of double-walled carbon nanotubes with a well-aligned and concentric structure leads to the formation of fluorocarbon nanostructures, which can be promising materials for electronic nanodevices. For citation: Karaeva A.R., Khaskov M.A., Kurzhumbaev D.Zh., Kulnitskiy B.A., Mordkovich V.Z. Investigation of fluorinated double-wall carbon nanotubes. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 10. P. 38-48. DOI: 10.6060/ivkkt.20246710.4y.

Strong Impact of Particle Size Polydispersity on the Thermal Conductivity of Yukawa Crystals

Control of thermal transport in colloidal crystals plays an important role in modern technologies. A deeper understanding of the governing heat transport processes in various systems, such as polydisperse colloidal crystals, is required. This study shows how strongly the particle size polydispersity of a model colloidal crystal influences the thermal conductivity. The thermal conductivity of model colloidal crystals has been calculated using molecular dynamics simulations. The model crystals created by particles interacting through Yukawa (screened-Coulomb) interaction are assumed to have a face-centered cubic structure. The influence of the Debye screening length, contact potential, and particle size polydispersity on the thermal conductivity of Yukawa crystals was investigated. It was found that an increase in particle size polydispersity causes a strong—almost fivefold—decrease in the thermal conductivity of Yukawa crystals. In addition, the obtained results showed that the effect of the particle size polydispersity on reducing the thermal conductivity of Yukawa crystals is stronger than changes in values of the Debye screening length or the contact potential.

Enhanced relationship between seasonal soil moisture droughts and vegetation under climate change over China

Climate change could intensify seasonal soil moisture droughts and subsequently degrade vegetation, but it can also facilitate vegetation growth with the rising temperature and CO2 concentrations. Therefore, the change of the vegetation-drought relationship under climate change remains elusive. Here, we investigate the effects of vegetation greening (i.e., increasing leaf area index (LAI)) on seasonal soil moisture drought trends by performing a set of land surface model simulations with the Conjunctive Surface-Subsurface Process model version 2 (CSSPv2), as well as the impact of seasonal soil moisture drought change on vegetation productivity via a statistical fitting model. Our results indicate that both the impact of increasing LAI on exacerbating seasonal droughts and the impact of increasing seasonal droughts on reducing vegetation productivity have been enhanced over China during 1961–2018. Specifically, increased LAI accounts for 48 % of the rising drought frequency through escalated evapotranspiration losses, with more pronounced effects in northern semiarid regions. The decrease in vegetation stomatal conductance caused by rising CO2 concentrations limits transpiration and alleviates 11 % of the increase in drought frequency, but it cannot fully offset the drought aggravation induced by increased vegetation water consumption under climate warming. Meanwhile, increased drought frequency and intensity have reduced the upward trend in vegetation productivity by 5 % over China, and by 8 % in water-limited northern regions. Our study shows the relationship between seasonal soil moisture droughts and vegetation over China has strengthened, indicating that vegetation greening will lead to increased water shortages and further impact vegetation growth and carbon sequestration. This challenges water resources management and environmental sustainability, especially in semiarid regions.

A theoretical study of thermal properties and structural evolution in binary carbonates phase change material: Machine learning-enhanced sampling strategy.

Thermal energy storage and utilization has been widely concerned due to the intermittency, renewability, and economy of renewable energy. In this paper, the potential energy function of binary Na2CO3-K2CO3 salt was first constructed using the Deep Potential GENerator (DPGEN) enhanced sampling method. Deep potential molecular dynamics simulations were performed to calculate the thermal properties and structural evolution of binary carbonates. The results show that as the temperature increases from 1073 to 1273K, the viscosity and thermal conductivity decrease from 5.011 mPa s and 0.502 W/(m K) to 2.526 mPa s and 0.481 W/(m K), respectively. The decrease in viscosity is related to the distance and interaction between the molten salt ions. In addition, the diffusion coefficients, energy barriers, ionic radius, angular distribution function, and coordination number of molten salt were calculated and analyzed. The CO32- exhibits a stable planar triangular structure. The ionic radius of Na+ is smaller than that of K+, which makes Na+ suffer less spatial hindrance during motion and has a higher diffusion coefficient. The energy barriers that Na+ needs to overcome to escape the Coulomb force is greater than that of K+ ions, so molten salt containing Na+ may possess greater heat storage potential. We believe that the potential function constructed with DPGEN enhanced sampling strategy can provide more convincing results for predicting the thermal properties of molten salts. This paper aims to provide a technical route to develop the novel complex molten salt phase change material for thermal energy storage.

Influence of morphology, crystal structures on the enhanced photoluminescence dynamics, zeta potential, and AC resistance of disc shaped cesium oxidex@cobalt oxide nanostructures

In the present study, cesium oxidex@cobalt oxide (Cs2Ox@Co3O4) (x = 5, 10 and 12 wt%) nanostructures (NS) were successfully synthesized by chemical precipitation method and characterized by XRD (X-ray diffraction), SEM (scanning electron microscope), EDX (energy dispersive X-ray), XPS (X-ray photoelectron spectroscopy), BET (Brunauer-Emmett-Teller), Raman, and UV–visible analytical techniques. XRD studies revealed the formation of the mixed phase of orthorhombic/monoclinic crystal structure. Disc shaped morphology of the cesium oxidex@cobalt oxide NS was noticed from SEM images. Redshift in optical absorbance and decrease in optical band gap (Eg) resulted in increase in Cs1+ concentration. Room temperature photoluminescence (RTPL) studies of cesium oxidex@cobalt oxide NS at various excitation wavelengths showed sharp and broad emission peaks located at 668.2 nm (red), 675.1 nm (red), 561.8 nm (yellow-green), 834.5 nm (near infrared region), 594 nm (yellow). Steady state photoluminescence (SSPL) studies revealed a sharp emission peak at ∼ 428.0 nm (violet) with large stoke’s shift (21.1 to 590.0 eV). The zeta potential studies showed a decrease in conductance from 62 to 57 μs with an increase in mobility of the charge carriers (0.4 to 1.08 μ/s V/cm) and an increase in zeta potential (31.90 to 82.92 mV). AC resistance studies at various temperatures showed inducting coupling phenomenon in cesium oxidex@cobalt oxide NS with DC resistance of cesium oxide5 wt.%@cobalt oxide was found to be 8.2 × 10–4 Sm–1. The relaxation frequency of cesium oxide12 wt.%@cobalt oxide NS was found be 1.2 × 105 Hz. The synthesized NS is a promising candidate for optoelectronics and photonic applications.

Study on thermoelectric properties and atomic-scale mechanism of B-site molybdenum-modified La0.1Sr0.9TiO3

Extensive studies on strontium titanate thermoelectric materials have shown that their poor conductivity results in a low ZT value. However, elemental doping can effectively improve the thermoelectric properties of these materials. In this study, a two-step sintering process was applied, using physical mixing to introduce 1 % molybdenum powder as a modification to the lanthanum-doped strontium titanate solid powder (La0.1Sr0.9TiO3). The obtained sample exhibited a maximum conductivity of 7830 S/m, with a maximum ZT of 0.12. Furthermore, this study combined experimental data with first-principles simulation calculations to elucidate the mechanism at the atomic scale. The incorporation of Mo6+ in place of Ti4+ at the B-site by molybdenum (Mo) adds two free electrons, leading to an elevated carrier concentration. This change concurrently reduces the Fermi level of the material and improves mobility, collectively resulting in a substantial increase in electrical conductivity. Phonon simulation indicated that Mo doping increased structural defects, thereby reducing lattice thermal conductivity. This significant enhancement in electrical conductivity and decrease in lattice thermal conductivity collectively increased the ZT value of the material.