Bulletin of Materials Science最新文献

The present work focuses on synthesis, characterization and applicability of green carbon quantum dots (CQDs) from leaves of Plumeria obtusa plant as a fluorescent metal ion sensor. These precursors undergo hydrothermal treatment, which produces fluorescent CQDs. The morphological and optical studies of synthesized CQDs have been studied by FESEM image analysis, XRD, UV–Vis absorption, photoluminescence and FTIR spectroscopy. The average size of prepared green CQDs estimated was ~ 4 nm, which matches with the result from FESEM image analysis. Based on absorption data, the direct band gap of 3.4 eV has been determined for the prepared CQDs. ‘Turn off’ fluorescence is observed in the presence of Fe³⁺ ions. High sensitivity and low detection limit of our synthesized CQDs for metal ions sensing have established their prominent candidature to be used as good efficient biocompatible fluorescent sensor.

Combustion process was used to synthesize the dysprosium (Dy³⁺)-doped sodium calcium vanadate (NaCaVO₄) phosphor. The structural, optical and morphological investigations were carried out with the dopant concentrations ranging from x = 0–3 mol% for which X-ray diffraction, photoluminescence spectroscopy, SEM and UV–Vis spectroscopy were used. We have explored that the XRD results indicate vibrant, clear and well-defined peaks that are matched to the NaCaVO₄ standard card confirming that the phosphor powder crystallized in the orthorhombic phase with space group C_mcm. From the FESEM pictures, the particles had an agglomerated morphology with irregular shapes and sizes in the nm range. The PL properties of undoped and Dy³⁺-doped NaCaVO₄ were investigated using a 310 nm excitation source to determine the suitability for use in displays. The emission spectrum exhibited two sharp peaks at 450–500 and 550–600 nm and a weak peak at 650–700 nm, which is assigned to Dy³⁺-emission transitions of ⁴F_9/2 → ⁶H_15/2 (blue), ⁴F_9/2 → ⁶H_13/2 (yellow) and ⁴F_9/2 → ⁶H_11/2 (red). Doping of NaCaVO₄ with Dy³⁺ for x = 0.25–3 mol% concentrations resulted in band gap modifications in the range of 3.341–3.866 eV. The material that we have taken up might be investigated as a new phosphor that could be activated by UV light-emitting diode (LED) light for solid-state lighting and display applications.

The synthesis of bioactive magnetic glass ceramics for hyperthermia treatment is still far from optimization due to the variable performance of many nanostructured systems. ({0.2}{text{SiO}}_{{2}} {-}{0.5}{text{FeO}}{-}{0.3}{text{CaO}}) glass ceramics were synthesized by sol–gel method at room temperature with a precursor to solvent ratio 1:5. The effect of adding polyethylene glycol 4000 (PEG4000) with 2, 4, 8, 12 and 16 wt% in the final stage of the sol preparation, on the magnetic and phase properties of the samples was studied. Heat treatment of the samples was done at 680 and 760°C. Phase analysis showed that maghemite and hematite phases have crystallized. By adding PEG4000 from 2 to 12 wt%, the saturation magnetization of the samples increased from 6.9 to 14.95 emu g^–1. Further increase of PEG did not have much effect on improving the magnetic properties. It was also seen that heat treatment at higher temperatures led to a decrease in magnetic properties.

Recent achievements in engineering include the development and production of hybrid aluminium metal matrix composites (AMMCs), which are widely employed in all automotive applications due to their significant weight reduction and better strength compared to the base metal used in various manufacturing processes. The present work used burnt sugarcane bagasse powder (SCBP) as the filler material in aluminum–alumina composite. This filler material is inexpensive, low in density, accessible and widely available, renewable and ecologically innocuous. The fabrication of various AMMCs has been implemented using SCBP and alumina at different weight percentage ratios by powder metallurgy process. The validity of elemental composition is tested using energy-dispersive X-ray analysis, X-ray fluorescence, X-ray diffraction and CHNS studies. The specimens are made using an Instron machine at a pressure of 474 MPa and sintered for various lengths of time and temperatures. All specimens were checked for microhardness, uniaxial compression and fractography using the FMV1-MC-AT model, the Instron 8801 MT model, and the JEOL JSM-7001F model, respectively. The outcomes were compared with the base composite. At 600°C and for 2.5 h with 3 wt% burned SCBP, it was observed that relative density, microhardness and ultimate compression strength improved by 1.98, 28.18 and 24.27%, respectively.

Titanium dioxide/multi-walled carbon nanotubes (TiO₂/MWCNTs) are nanocomposites (NCs) prepared via click reaction of TiO₂ nanoparticles (TiO₂ NPs) with azide groups (TiO₂–N₃) on the surface and MWCNTs with alkynyl groups (MWCNTs–ALK) on the surface. The phase structure, graphitization degree, structure, elemental composition, the microstructure of TiO₂/MWCNTs NCs were characterized by XRD, Raman, IR, XPS and SEM, and their electromagnetic (EM) parameters were determined by the vector network analyser. For TiO₂/MWCNTs NCs with click reaction, the minimum reflection loss (RL_min) is up to −47.87 dB at 12.02 GHz, the matching thickness is 2.0 mm, and the bandwidth is lower than −10 dB in the range of 7.7–12.48 GHz. Compared with the physically mixed TiO₂/MWCNTs composites, TiO₂/MWCNTs NCs prepared by click reaction show more excellent EM absorption properties, which is mainly due to the binding of covalent bonds between the two kinds of materials that lead to the enhancement of interfacial effects, the improvement of impedance matching and the increase of electron migration.

The utilization of titanium dioxide (TiO₂) as a photocatalyst is widespread in materials chemistry; however, handling this material in powder form poses significant challenges. Therefore, it becomes imperative to process TiO₂ into inorganic sheets with improved stability and ease of handling. In this study, a glass fibre cloth was utilized as an inorganic support, and TiO₂ nanoparticles were integrated onto the glass fibre surface without employing binders. This integration was accomplished by treating the fibre with a sodium hydroxide (NaOH) solution at 60°C for 24 h. The NaOH treatment dissolved the fibre surface, forming a flower-like structure that facilitated the integration of TiO₂ nanoparticles. The resulting glass fibre cloth, embedded with TiO₂ nanoparticles, efficiently adsorbed and decomposed acetaldehyde gas. Further enhancement was achieved by subjecting the glass fibre cloth to heat treatment after the ammonium chloride treatment, leading to improved crystallinity and photocatalytic activity of TiO₂. Using the glass fibre cloth as an inorganic substrate for TiO₂ nanoparticles is promising for the fabrication of durable and high-performance photocatalysts with superior adsorption properties. Moreover, this technique offers a practical solution to the challenges associated with handling and processing TiO₂ in its powdered form.

This study highlights the effect of high-pressure torsion (HPT), a severe plastic deformation technique, on the magnetic properties of equiatomic FeNi alloys prepared from mechanical alloying. The prime objective of this study is to increase the interdiffusion of FeNi and accelerate the formation of L1₀ ordering. HPT processing on FeNi alloy was carried out at room temperature under 6 GPa for 5, 10 and 20 turns. Subsequently, the samples were subjected to heat treatment in a vacuum at 593 K for 1000 h without any magnetic field. Further heat treatment of 4 h was also performed at 593 K in the presence of a 1.5 T magnetic field. It is observed that HPT processing first increases the lattice strain; however, further processing causes strain relaxation due to dynamic recrystallization. Initially, for 5 turns of HPT, the saturation magnetization decreases. However, after 10 and 20 turns of HPT, the saturation magnetization increases due to recrystallization and formation of L1₀ ordering. After 5 turns, the coercivity increases by ~175% due to lattice strain. With further processing, the coercivity decreases by ~50% due to recrystallization. Heat treatment on the HPT-processed samples shows increased coercivity and remanence due to the annihilation of defects and formation of short-range L1₀ ordering.

Utilization of waste pollution to solve electromagnetic waves pollution is a good strategy towards a green future. In this study, we have used two different biowastes, wheat stubble and peanut hulls, as biocarbon sources to obtain two diverse inherited morphologies, i.e., sheet-like morphology from wheat stubble and distorted/ripped biocarbon morphology from peanut hulls. Detailed microwave absorption characterization analysis shows that the distorted/ripped morphology has better reflection loss and effective absorption bandwidth (EAB) as compared to the sheet-like morphology. Furthermore, ({{text{MnFe}}}_{2}{{text{O}}}_{4}) particles are also used to get composites with both types of biocarbon. The minimum reflection loss (RL_mini) value achieved by the ripped biocarbon/({{text{MnFe}}}_{2}{{text{O}}}_{4}) is − 40.6 dB, with EAB being 5.6 GHz (13.2–7.6 GHz). Our findings show that better microwave absorption performance is attributed to the distorted/ripped morphology and by biocarbon–({{text{MnFe}}}_{2}{{text{O}}}_{4}) synergetic influence. These findings open a route for biowaste and magnetic waste to be used in controllable microwave absorption applications.

Noble metal like Pt or Au deposited on reducible oxides like TiO₂ is one of the promising catalysts for CO oxidation, which has many applications including developing long-life sealed-off CO₂ lasers, pollution control, etc. Catalytic oxidation of CO is pre-requisite for sealed-off CO₂ lasers, because dissociation of lasing CO₂ molecules in gas discharge decreases the laser power and may kill laser action in few minutes. Hence, this study was aimed to investigate the CO oxidation efficiency of in-house prepared Pt–TiO₂ and Au–TiO₂ catalysts, both at room temperature and under discharge conditions. The results of XPS and CO₂ conversion measurements revealed that the post-reduction of catalyst plays a very important role for increasing the Pt⁰ and efficiency of CO oxidation to about 80%. Importantly, in the presence of gas discharge, considerably higher catalytic performance was observed for Pt–TiO₂ catalyst with respect to their performance at room temperature and commercial gold (Au)-coated catalyst present in CO₂ laser tubes.

In this work, a series of materials composed of Ba_1−xY_xTi_1−x/4O₃ noted as BYT with x = 0, 0.025, 0.05, 0.075, 0.1 and 0.15 were prepared by hydrothermal route at 200°C for 24 h. Pressure, temperature and pH of the environment are essential factors for obtaining a pure phase. The effect of yttrium (Y³⁺) on the structural and dielectric properties of barium titanate was studied. Pure phases of the perovskite structure without secondary phases were confirmed by X-ray diffraction analysis. Raman spectroscopy analysis of the obtained samples confirms the presence of different vibration modes characteristic of the pure quadratic phase. Using a scanning electron microscope, the texture, morphology and microstructure of Ba_1−xY_xTi_1−x/4O₃ ceramics were observed. The study of dielectric properties was examined by impedance spectroscopy of dielectric measurements in the frequency range from 1 kHz to 2 MHz as a function of temperature, confirming the incorporation of yttrium and highlighting its influence on Curie temperature (T_c) and permittivity value (ε_r).