Bulletin of Materials Science最新文献

The successful preparation of Tb³⁺-doped NaCaVO₄ green-emitting phosphor powders via combustion synthesis is presented in this report. X-ray diffraction technique was used to confirm the orthorhombic phase of the prepared samples. Modified Debye–Scherrer analysis was employed for calculating crystallite size. Using X-ray photoelectron spectroscopy, the elemental composition and oxidation states of several elements present in the sample were examined. Four emission bands were identified using photoluminescence spectroscopy, and the strongest band located at 545 nm due to the transition ⁵D₄→⁷F₅ is ascribed to green emission out of the phosphor material with enhanced colour purity when excited by near-UV. Using diffuse reflectance spectra, optical parameters including bandgap, metallization criterion and refractive index were also calculated for all concentrations of Tb³⁺ ions (ranging from x = 0–0.055). For the optimum molar concentration, numerical values of these parameters were estimated to be 3.41 eV, 0.412 and 2.294. Based on the above findings, it was concluded that the title phosphor may be explored as green-emitting component near-UV pumped phosphor for white light-emitting diodes.

In this research study, the ability of a boron nitride nanocluster (hereafter B₂₄N₂₄ NC) to detect osmium tetroxide (hereafter OT) after the decoration of Ni into the B₂₄N₂₄ is investigated through the density functionals B3LYP, M06-2X and B97D. The results revealed that the interaction of the pure B₂₄N₂₄ was a physical adhesion or adsorption and the sensing response (SR) of B₂₄N₂₄ is approximately 5.2. The adsorption energy of OT becomes more negative by changing from −5.0 to −20.9 kcal mol⁻¹ after the decoration of the Ni metal on the surface of B₂₄N₂₄, which also leads to a noticeable increase in the corresponding SR to 76.2, indicating that the sensitivity of Ni-decorated B₂₄N₂₄ (Ni@B₂₄N₂₄) is increased. Based on energy decomposition analysis, the nature of the interaction between OT and Ni@B₂₄N₂₄ is mostly an electrostatic cation–lone pair interaction. The theoretically obtained results further confirmed that Ni@BN-based nanostructures can be used for practical purposes.

In the present work, α-MnO₂ thin films are deposited on a stainless steel substrate using the hydrothermal method by varying hydrothermal temperature. The impact of different hydrothermal temperatures on the structural, morphological and electrochemical performance of prepared thin films is investigated. The XRD studies confirm the tetragonal crystal structure of prepared MnO₂ thin films. The electrochemical behaviour was studied using three-electrode system in 1 M KOH electrolyte. The high electrochemical performance with a maximum specific capacitance of 442 F g⁻¹ at a scan rate 5 mV s⁻¹ and energy density of 62 Wh kg⁻¹ at a power density of 5.2 kW kg⁻¹ has been obtained. The specific capacitance shows 90% capacitance retention after 2000 GCD cycles.

Solid polymer electrolytes play a vital role in energy storage devices, especially in the battery industry, to improve compatibility and portability. Natural polymers made from biowaste material are biodegradable and have been utilized for electrolyte preparation. Biopolymer-based electrolyte leads to sustainability due to their low cost, eco-friendly nature and non-toxicity. This work pertains to the preparation of one such natural polymer electrolyte based on guar gum as the host polymer, sodium iodide as an ionic dopant and 1,2 dimethoxy ethane as the plasticizer. Traditional Solution casting technique has been used for the preparation of electrolytes. The complexation between guar gum (GG) and NaI has been revealed by Fourier transform infrared spectra. The biopolymer electrolyte is stable up to 300–350°C and was assessed by thermogravimetric analysis. The surface roughness factor (R_a) was measured by 3D-optical profilometry. The transference number was determined by the chronoamperometry technique. AC impedance spectroscopy exhibited that the biopolymer electrolyte containing 0.4 g GG: 0.75 wt% NaI has the highest ionic conductivity of 7 × 10^–3 S cm^–1. Hence with suitable electrodes, the prepared electrolyte may be used in the fabrication of coin cells.

Spinel oxides are a type of material that can be used in a wide range of applications, such as photocatalysis, hydrogen production and environmental protection. In this respect, calcium aluminate (CaAl₂O₄) and chromate (CaCr₂O₄) spinels were synthesized in this study by the coprecipitation method using potash solution as a precipitant. CaAl₂O₄ and CaCr₂O₄ spinels were annealed at 900 and 1100°C, respectively, for different periods. The obtained spinels were first characterized by thermal analysis, and the phase composition of the oxides was analysed using X-ray diffraction. Hydroxyl groups and absorbed water in the obtained precipitates disappeared after calcination and were observed via Fourier transform infrared spectroscopy. BET and SEM/EDS analyses were also used to determine the total surface area of the powder particles, the size of the grains and the morphology of the powders of the synthesized nanoparticles, respectively. The structural and morphological analyses revealed the formation of single-phase CaAl₂O₄ and dual-phase CaCr₂O₄, with specific surfaces for each spinel of 44.2165 and 5.7190 m² g⁻¹, respectively. Moreover, DFT calculations were performed on the materials, and the direct bandgaps of these spinels were found to be 4.365 eV for CaAl₂O₄ and 2.256 eV for CaCr₂O₄. The results indicated that different compositions led to different optical bandgaps. Finally, the results indicate that due to the suitable characteristics and properties of the produced spinel oxides, they are among the promising materials that may be employed as semiconductors for various applications.

Many researchers are working on graphene production at a cost-effective level with less number of layers and lower defects. To achieve this goal, this research is performed by numerical and experimental methods to optimize graphene production utilizing sonication via a probe in a liquid medium. Theoretical prediction of the pressure distribution in a liquid medium can aid in the easier optimization of geometry and operating parameters. This liquid-phase-exfoliation study includes a parametric investigation of alter in; the probe diameter (D_P), the probe immersion depth (d) and the cylindrical reactor geometry. The numerical simulation is validated by experiments studied by sonicating graphite powder in a water–ethanol medium to produce graphene. From a comparison between simulation and experimentation, our results from the UV–visible spectra, FESEM, TEM images and Raman spectrum indicate that the bilayer graphene is produced in this experimentation. Sonicating graphite in a cylindrical reactor by the ratio of height H to diameter D of the cylinder being 2 with a probe of 40 mm in diameter, the probe immersion depth of 15 mm, results in the production of pure graphene with minimum defect bilayer. This happens when the simulation shows that maximum differential pressure (Δp) in the solution has reached.

Organometallic halide perovskites have shown significant promise for applications in optoelectronics and photovoltaics in recent years. This research looks into the performance of bulk heterojunction-based photodetectors (PDs) based on the active layer of a CH₃NH₃PbI₃:PCBM bulk heterojunction (BHJ). We assessed the impact of PCBM concentration in CH₃NH₃PbI₃:PCBM BHJ on the electrical performance of the PDs. We found that the BHJ PD with a 4% PCBM concentration had the strongest capability to reject noise, as demonstrated by its superior ratio of photocurrent to dark current. Moreover, the PD with a 4% PCBM concentration in the active layer outperforms pristine CH₃NH₃PbI₃-based PDs in terms of optoelectronic performance, showing greater responsivity and detectivity. The improved optoelectronic performance of BHJ PD is due to increased interfacial area, higher electron extraction and a decrease in traps and defects. The analysis of dark current–voltage curves reveals a significant reduction in charge recombination for BHJ devices, supporting the elimination of traps and defects by the inclusion of PCBM. The PD’s impedance study unveils that the incorporation of PCBM enhances charge transfer and effectively suppresses charge recombination, leading to enhanced optoelectronic performance.

Sealant properties of CaO- and SrO-containing BaO–B₂O₃–SiO₂ and BaO–ZnO–B₂O₃–SiO₂ glasses were first reported in this work. CaO and SrO were used as glass modifiers to improve thermal properties and optimize CTE value and possess a good joining interface between SOFC components. Addition of CaO and SrO enhanced the glass transition and softening temperature due to the higher ionic field strength of Ca and Sr ions promoting the boroxol ring formation and a denser glass network. IR spectra confirmed a less significant effect of CaO and SrO in the glass structures. Addition of doubled CaO and SrO retained the compatibility of CTE to that of SDC electrolyte and Crofer22APU interconnect. Crystalline phases with compatible CTE were formed in the CaO- and SrO-containing glass ceramics. This provided good adhesion without defects at the interface, which is close to the electrolyte and interconnect after prolonged operation at 800°C for 50 h.