Bulletin of Materials Science最新文献

In this paper, the crystal structure, optical and electronic properties of two related rubidium iodide halide perovskites RbSiI₃ and RbGeI₃ are investigated and discussed thoroughly. The calculations of these properties are performed using the generalized gradient approximation under Perdew–Burke–Ernzerhof functional (GGA–PBE). Also, the structural optimizations and accurate optoelectronic properties have been achieved by exploiting full-potential linearized augmented plane wave method (FP-LAPW). Analysis of optimization results exposed that the volume per unit cell and lattice parameter (a₀ = 5.8348 Å (RbSiI₃)) and (a₀ = 5.9631 Å (RbGeI₃)) are closely in agreement with the previous results. In addition, the calculated values of tolerance factor (T_F ≈ 1.0) satisfy the creation criterion for perovskites, and the negative and small values of formation energy (ΔF_E) confirm the chemical stability of studied compounds. The results of density of states and band structures reveal that RbSiI₃ and RbGeI₃ are nonmagnetic semiconductors having a proper direct energy gap (E_g) of 0.465 and 0.953 eV, respectively, along the M–M symmetry directions in the first Brillouin zone. The 2-D distributions of charge density confirm that the chemical bonding of Rb–I and Si/Ge–I bonds obey the covalent and ionic nature. Moreover, we have calculated and discussed the optoelectronic properties, real ε₁(ω) and imaginary ε₂(ω) functions, optical absorption α(ω), reflectivity R(ω) and refractivity n(ω). The results obtained in this study like structural stability, suitable E_g and highly accurate optical absorption α(ω) of visible light waves, indicate the possible exploitation of semiconductors RbSiI₃ and RbGeI₃ and make them candidate materials for optoelectronics, such as photovoltaic solar cells, photosensors, photodetectors and photodiodes devices.

This study investigates the corrosion resistance and wear behaviour of aluminium matrix composites (AMCs) manufactured through the ultrasonic-assisted stir-casting technique. These composites were synthesized by introducing titanium carbide (TiC) and nickel (Ni) into aluminium alloys (AA6061). The X-ray diffraction results confirmed the presence of α-Al, TiC and Al₃Ni phases within the composites. Microstructural examination demonstrated an uniform dispersion of TiC particles and dispersion of Al₃Ni along grain boundaries. To evaluate the corrosion behaviour, samples were subjected to immersion tests and electrochemical techniques, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), in a 3.5 wt% NaCl solution. Immersion tests indicated that the composites exhibited slower dissolution rates than base AA6061 alloys. Potentiodynamic polarization results revealed that the inclusion of TiC and Ni reinforcements enhanced corrosion resistance, with TiC having a more pronounced influence. The EIS tests suggested that the composites had higher charge-transfer resistance than AA6061 alloys. After conducting corrosion tests, scanning electron microscope (SEM) images of the base AA6061 alloys unveiled the presence of deep pits but the inclusion of reinforcements resulted in the shallow pits. In addition, Vickers hardness tests and pin-on-disc wear tests were conducted to investigate hardness and wear properties. Notably, hybrid composites containing 3% TiC and 3% Ni exhibited a substantial 42.18% increase in hardness as compared to the base alloy. These hybrid composites also demonstrated superior wear resistance, with a wear rate that was 58.6% lower compared to AA6061 alloy and 41% less than that of the 3% Ni-reinforced composite.

In this article, we prepared europium ions (Eu³⁺) doped lithium lutetium double tungstate material using a classical solid-state reaction. X-ray diffraction (XRD), optical absorption and photoluminescence techniques were used to characterize the samples. XRD analysis and structural refinement measurements revealed that LiLu(WO₄)₂ has a monoclinic structure with a P2/n space group with a formula unit (Z = 2). Additionally, we measured, analysed, and discussed the room-temperature photoluminescence emission and excitation spectra of Eu³⁺-doped LiLu(WO4)2. The emission spectra show the intra-configurational red emission characteristic of Eu³⁺ ions, namely ⁵D₀ → ⁷F_j, J = 0–4. The quenching emission by temperature as well as the ⁵D₀ emission decay curves were measured and discussed. It was found that the quenching of luminescence is obtained for 1.5 at% Eu³⁺ concentration. Judd–Ofelt intensity parameters (Ω₂ = 5.26 × 10⁻²⁰ cm² and Ω₄ = 1.04 × 10⁻²⁰ cm²) and the ‘Commission Internationale de l’Eclairage’ (CIE) chromaticity coordinates were calculated from the emission spectrum of LiLu_1−xEu_x(WO₄)₂ for x = 0.015. The results indicate that Eu³⁺-doped LiLu(WO₄)₂ could be a suitable material for solid-state lighting applications.

Ultrahigh molecular-weight polyethylene (UHMWPE)-based composites are extensively utilized as a bearing surface in joint replacements. In the present study, due to their unique and versatile attributes halloysite nanotubes (HNTs) were used as additives in different percentages 1, 3, 5, 7 and 10 wt% to enhance the properties of UHMWPE. The effects of the weight fraction of HNT on UHMWP were investigated in terms of hardness, abrasion strength, compression strength, bulk modulus, impact resistance and biocompatibility, and the specimen showed that only a small amount of HNT (1%) optimized all the mentioned properties by 26.8, 20.77, 174.7, 351.53, 11.35 and 95%, respectively. The percentage of 5% HNT achieved the optimal content, at which the composites experienced the maximum enhancement for compression, abrasion and hardness properties. In-vitro MTT assay of UHMWPE with 1, 3 and 5% HNT nanocomposites using MG-63 cells revealed high cell viability (94.307%) after 4 days of incubation in media at concentrations of 100, 50 and 25 µg ml^–1, indicating excellent biocompatibility. These results might lay a solid basis for load bearings used in orthopaedic applications of UHMWPE-based composites.

There is significant interest in the utilization of inorganic materials with low thermal conductivity (κ) in thermoelectric applications. A key strategy for reducing thermal conductivity through phonon scattering is the formation of synthetic nanostructures. In this study, we synthesized pure SnTe and Bi–Mg co-doped SnTe materials via the solvothermal method. We report very low thermal conductivity of ~2.17 W m⁻¹ K⁻¹ at room temperature in pure SnTe. The notable low thermal conductivity in SnTe is mostly attributable to its nanometre-sized crystallites. Bi and Mg substitution in SnTe significantly lowers κ value from 2.17 to 0.5 W m⁻¹ K⁻¹ for Sn_0.94Bi_0.03Mg_0.03Te sample at 300 K, reducing it by ~4 times compared to pure SnTe. Point defect scattering of phonons due to Bi–Mg co-doping may also lower thermal conductivity. This study reveals a potential novel approach to achieve low thermal conductivities in SnTe through nanoscale engineering.

Graphene has intriguing electrical, mechanical, thermal and biological properties that are being investigated for use in composites, modern electronics, membranes, and in the industry. Also, graphene has huge biological applications. Hydroxypropyl methylcellulose (HPMC) is a widely used bio-polymer effective for various biomedical applications. As a filler in this polymer matrix, graphene oxide (GO), reduced graphene oxide (RGO) and silver (Ag) nanoparticles (NPs) can be used to improve various properties of the matrix. They are also beneficial for bio-applications like drug delivery, the production of reactive oxygen species (ROS) and the antimicrobial properties of nanocomposite films. Here we synthesize a series of polymer nanocomposites taking GO, RGO and Ag NPs as a filler by the solution mixing method and explore the comparative biological application of such composites. We choose Ag NPs as it has the superior potential for multiple drug resistance. X-ray diffraction, Fourier-transform infrared and scanning electron microscope studies are used to describe how nanocomposites are formed. Energy-dispersive X-ray and dynamic mechanical analyzer analyses were also done to check elemental percentage in nanocomposite films and mechanical properties, respectively. To check several fruitful applications, antimicrobial properties, ROS generation and in-vitro drug release study of nanocomposite films with the loading of Ketorolac Tromethamine were also performed.

Monoclinic tungsten trioxide (WO₃) thin films have been successfully synthesized on the glass substrate in a reactive environment (Ar/O₂) using DC magnetron sputtering. Effect of substrate temperature (RT–450°C) on wetting and other physical properties of the films was investigated comprehensively. Various standard techniques, such as XRD, XPS and FESEM were employed to examine the physical properties of deposited films, while the sessile drop method-based contact angle measurement was employed to examine the wetting properties. The important findings of our study demonstrated the significant role played by the substrate temperature in enhancing the film properties. The WO₃ thin film synthesized at 450°C shows the preferred (020) orientation with a large crystallite size of about 68.2 nm. Further, this film showed high porosity and displayed a hydrophobic nature comparable to others, which makes it highly suitable for applications in sensing and water-repellent fields.

Titanium dioxide (TiO₂) nanotubes were obtained by the anodization process, applying a potential of 30 V for 2 h in an electrolyte composed of NH₄F, H₂O and ethylene glycol. The nitrogen doping of the obtained nanostructures was studied and the influence of the use of different temperatures during the thermal treatments 400, 500 and 600°C, on the formed nanotubes were evaluated. The morphology and crystalline structure of the obtained materials were determined by field emission gun scanning electron microscopy and X-ray diffraction. The optical properties were evaluated by UV–Vis diffuse reflectance spectroscopy and the photoelectrochemical properties by linear sweep voltammetry curves. The photocatalytic activity of nanotubes was evaluated by degradation of glycerol in aqueous medium using UV and visible radiation. TiO₂ nanotubes developed photoactivity, photoelectrochemical behaviour and presented catalytic activity for glycerol degradation, which is more evident with UV radiation. The sample thermally treated at 500°C was the one that presented superior photoelectrochemical behaviour and superior photocatalytic activity when exposed to both UV and visible radiation.

In this work, we studied the preparation of graphene dispersions by liquid-phase ultrasound exfoliation in aqueous solutions, using amphiphilic stabilizers, such as Pluronic F108 (Plu) and polyvinylpyrrolidone (PVP), as well as in N-MP. The resulting dispersions were characterized by TEM, dynamic light scattering, UV spectroscopy. Optimal conditions for ultrasonic treatment of few-layer graphene dispersions were established, which make it possible to obtain stable concentrated graphene dispersions (1–4 layers) with lateral dimensions of 50–2000 nm. Based on the developed graphene dispersions, composite films with various polymer matrices (polylactide, collagen, chitosan), using graphene as nano-filler, were obtained. The presence of the latter provided electrical conductivity up to 0.9 S cm⁻¹, a change in electrical resistance during deformation with a strain sensitivity coefficient of 1.3–5.7, as well as an increase in breaking stress up to 97.1 ± 1.6 MPa and in elastic modulus up to 3.99 GPa. The designed films possess a wide variety of properties and are promising for use as flexible biosensors for biomechanical studies and electrically conductive matrices for tissue engineering.

In vitro biomineralization, carried out under laboratory conditions, provides scope for highly controlled crystallization events, at different stages of the formation reaction. This crystallization control is exerted using foreign substances or additives, which are usually organic compounds. Here, we have shown how with the use of homeopathic medicine Symphytum Q, the morphology of calcium carbonate is changed from its rhombohedral, the most stable morphology to spherical morphology, while the phase remains the same. A study has also been done on the formation of gypsum with varying parameters.