Bulletin of Materials Science最新文献

A highly sensitive hydrogen gas sensor operating at room temperature made of macroporous silicon (MPS) coated with a thin NiO film was developed. MPS layer was shaped by electrochemical anodization on an n-type Si surface. Thereafter, p-type NiO film was deposited onto the MPS surface by electrodeposition method. The morphology of the NiO/MPS sample was characterized by scanning electron microscopy. Al electrical contacts for further measurements were deposited onto the structure NiO/MPS by evaporation technique under vacuum. Gas sensing performances were measured to various H₂ concentrations ranging from 122 to 1342 ppm at room temperature. The results showed that the electrical behaviour of synthesized NiO/MPS sensor is similar to that of a diode, which can be used to detect H₂ gas at low concentrations, which reveals high sensitivity, fast response and recovery times working at room temperature.

Graphical Abstract

MgKPO₄·6H₂O (magnesium potassium phosphate-based cement; MKP) is an environment friendly alternative to Portland cement with potential applications in environmental remediation and radioactive nuclear waste management, particularly in the context of β-emitting Cs and Sr immobilizations. Thus, investigation of the radiation effects and temperature due to decay heat in such material is of prime importance. In this study, MgKPO₄·6H₂O powders were synthesized and subsequently annealed at 1273 K for 2 h under ambient atmosphere to form MgKPO₄. The synthesized and annealed MKP specimens were irradiated under ambient conditions with 10-MeV electron beam up to imparted doses of 20 MGy. XRD results reveal the formation of amorphous fraction in irradiated MgKPO₄·6H₂O, while the annealed MKP specimens exhibit good radiation stability without amorphization. The annealed specimens also indicated good thermal stability when compared to as-prepared MgKPO₄·6H₂O specimen both in pristine and irradiated conditions. Vibrational spectroscopic results confirm that the radiation effect resulted in distortion/removal of structural water and formation of radiolysis products in MgKPO₄·6H₂O.

This study presents the interfacial behaviour of benzoylated cellulose of different wettability from melon and moringa pods waste using Pickering emulsions systems. The benzoylated cellulose was prepared in an aqueous alkaline medium using benzoyl chloride as a modifying agent and characterized by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). The X-ray diffraction showed that crystallinity of cellulose from moringa and melon are 67.47 and 70.20%, respectively. The functionalized derivatives are thermally stable than the native counterpart. The SEM revealed that isolated cellulose suffered surface degradation upon functionalization as a result of the repeated collision between reactants. The wetting properties of the cellulose can be controlled by using different quantities of modifying agents, and the emulsions stability depend on the wettability of the emulsifiers. The higher stability recorded for the emulsions stabilized by benzoylated cellulose from moringa pod waste revealed that cellulose wettability depends on the sources.

Local structure and magnetic properties of CoMn₂O₄ nanoparticles prepared by co-precipitation method have been examined. X-ray diffraction pattern shows mixed phase of tetragonal and cubic phases at room temperature with crystallite size of 42 nm, while Fourier transform infrared spectrum shows bands corresponding to tetrahedral and octahedral sites of spinel. Pre-edge feature from XANES and Fourier transform (FT) EXAFS spectra at Co and Mn K-edges confirm that majority of Co and Mn occupy A and B sites, respectively, while small amount of Co and Mn occupies the B and A sites, respectively. The spin dynamics of these nanoparticles show the dispersion of ac susceptibility (χ″) with frequency, and confirm the spin-glass like behaviour. Surprisingly, we observe a progressive increase in vertical magnetization shift (VMS), while measuring magnetization under field-cooled condition. Remarkably, a maximum VMS of 2.45 emu g⁻¹ and exchange bias (EB) of 888.5 Oe were observed under a 10,000 Oe cooling field. Such a shift is intricately linked to the Yafet–Kittel spin structure of Mn³⁺ localized in B site and the EB could be due to the interaction between ferrimagnetic and spin-glass like phase.

Here, we assess the effect of silica and modifier ions on the biological performance of quaternary 81S bio-glass (81SiO₂–16CaO–2P₂O₅–1Na₂O mol%) against ternary 85S bio-glass (85SiO₂–10CaO–5P₂O₅ mol%) synthesized via Stober’s method. The in vitro simulated body fluid (SBF) assay confirms the deposition of a hydroxyapatite layer on 81S and 85S bio-glasses, verified by XRD, FTIR and HRSEM analyses. However, a notable difference emerges in the pH study, where a slower degradation rate has been observed in the case of 85S compared to that of 81S bio-glass, which can be attributed to the presence of high silica content. In the MTT assay, 81S bio-glass exhibits significantly higher cell viability of 130%, surpassing that of 85S bio-glass, where 114% of cell viability is detected. While both bio-glasses exhibit antibacterial properties, 81S shows a higher efficacy in inhibiting the growth of E. coli by 47% and S. aureus by 51%, whereas 85S demonstrates comparatively lower inhibition, restraining E. coli by 16% and S. aureus by 35%. The substantial difference in antibacterial activity can be attributed to a slower dissolution rate of 85S bio-glass, which results in a very small change in pH of the surrounding environment. In conclusion, 81S bio-glass demonstrates superior bioactivity, cell proliferation and antimicrobial efficacy, making it a promising candidate for biomedical applications.

Zirconium nitride (ZrN) has attracted scientific interest due to its diverse physical and functional properties. Despite the energetic favourability of room-temperature synthesis of ZrN_x, only a handful attempts have been made to understand the low-temperature synthesis protocols. In the present work, we synthesized a series of Zr–N thin films by varying partial N₂ gas flow (RN₂) at room temperature (300 K). The structural and compositional characteristics of resulting Zr–N films were studied. The investigation combines X-ray reflectivity (XRR), X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) measurements, which includes X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and variable angle spectroscopic ellipsometer (VASE). XRR results reveal the effects of varying RN₂ on deposition rate, providing insights into the formation of ZrN phase. XRD patterns reveal the structural evolution from the hcp Zr to fcc ZrN phase. Further, structural parameters, including lattice parameter and crystallite size are systematically examined, revealing high-quality nature of the films, with optimal results observed in RN₂ = 5–10% samples. XAFS measurements, particularly XANES of N and Zr K-edges, provide insights into the local environment, showing a centrosymmetric structure with octahedral symmetry within the ZrN films. Shifting of pre-edge features in the XANES spectra suggests variations in the oxidation state, implying a complex interplay between Zr and N atoms within the films. Emphasizing the importance of EXAFS, this study showcases its reliability for quantitative analyses. The technique unravels atomic coordination and bond lengths within the Zr–N films, which is crucial for a comprehensive understanding of the film’s structural characteristics. VASE measurement was done to understand the optical behaviour from the real and imaginary parts of permittivity spectra.

Tremendous potential in the field of anti-biofouling coatings to prevent stainless steel (SS)-based underwater pipelines, sea vessels and other marine structures have been recognized to protect from biofouling, which is often initiated by algae attachment over the surface. In this work, hydrophobicity in spray-pyrolysed tungsten oxide (TO) coating on SS-316 substrate has been reported for the first time, via post-processing treatment using octadecyltrimethoxysilane (ODTMS) to induce self-assembled monolayer (SAM). Initially, structural and vibrational characteristics of ODTMS and ODTMS-treated TO (OTO) coating on SS were analysed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies. OTO-coating depicted a water contact angle (WCA) of 121°, revealing its hydrophobic nature, with further affirmation from X-ray photoelectron spectroscopy (XPS). Durability of the TO-coating was explored using the scratch hardness (H_s) test at different loading conditions (5, 10 and 15 N). Biofouling study was conducted by culturing blue-green algae (BGA, Phormidium sp.) in an in-house laboratory setup for 40 days, using seawater (collected from the Arabian Sea, Karnataka). The SS, TO- and OTO-coatings were immersed for 14 days in a controlled sea-water environment in the laboratory with the presence of BGA. A comparative study on the areal-algae attachment was keenly analysed over SS-, TO- and OTO-coatings. This work can be projected as a promising application providing multi-dimensional solutions in creating scratch-resistant and anti-biofouling coatings on SS in the shipbuilding industry.

This study presents the modelling of magnetocaloric effect of Pr_0.67Sr_0.33MnO₃ nanoparticles by using the mean-field theory (MFT). Theoretical calculations were used around the Curie temperature (T_C) to simulate the temperature dependence of magnetic entropy change under several applied magnetic fields. The obtained results were compared with experimental data computed using the Maxwell relation. Discrepancy between the two methods confirm the invalidity of MFT for modelling the magnetocaloric properties of Pr_0.67Sr_0.33MnO₃ nanoparticles. This invalidity suggests the presence of critical fluctuations near the T_C, which can be attributed to the presence of disordered surface and/or magnetic frustration, and highlights the limitation of the used model.

B3LYP was employed as a density functional to inspect the impact of Mn doping on the ability of graphyne (Gr) in the delivery of the propylthiouracil (PTU) drug. The interaction between the pure Gr and PTU was weak. Doping of the Mn metal into the Gr surface raised the PTU adhesion energy from −6.1 to −28.3 kcal mol⁻¹, and PTU prefers to attach through its O atom to an Mn of the Mn-doped Gr (Mn@Gr). The analysis of partial density-of-states demonstrated that Mn substantially contributes to generating the virtual orbitals of Mn@Gr. It indicates the suitability of Mn, in contrast to the C atoms of Gr, for the nucleophilic attack. In addition to substantial energy release, the electronic properties of Mn@Gr were appreciably sensitive to the attachment of PTU, making it possible for recognizing the trajectory of the drug. A drug release mechanism was provided in cancer tissues, demonstrating that in cancer cells with a low pH, PTU and Mn@Gr were protonated significantly, thus separating PTU from the surface of Gr. Finally, there was a change in the reaction mechanism of PTU with Mn@Gr from covalent bonding in the natural environment to the H-bonding in the acidic environment of cancerous cells.

An easily industrialized method for the synthesis of LiNi_1/3Co_1/3Mn_1/3O₂ from waste lithium-ion batteries (LIBs) is developed in this study. The positive electrode-active material is recycled by N-methyl-pyrrolidone (NMP) and calcination without using organic acid to leach metal. The recycling process parameters, including reaction time, reaction temperatures and solid–liquid ratios, are used to optimize the recycling process. The results show that the reaction time of 20 min, the temperature of 60°C and the solid–liquid ratio of 80 g l^–1 lead to a recovery rate of 82%. Carbonates are added to the recycled material to adjust the metal ion ratios and the structures to re-synthesize LiNi_xCo_yMn_zO₂ (LNCMO). The structure of the re-synthesized LNCMO is characterized by X-ray diffraction analysis and scanning electron microscopy. Electrochemical tests suggest that the waste LIBs can be recycled to re-synthesize new cathode materials with good electrochemical performance, which is comparable to the cathode materials prepared with commercial chemicals.