Bulletin of Materials Science最新文献

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.

The compound, mercury bismuth sulphide (HgBi₂S₃), represents a promising semiconductor within the II–V–VI group, demonstrating potential as a solar cell absorber layer. However, its synthesis and investigation through the successive ionic layer adsorption and reaction (SILAR) method have remained unexplored. This study focuses on the successful synthesis of HgBi₂S₃ nanoparticles using the SILAR technique atop wide band gap n-type semiconducting titanium dioxide (TiO₂) thin films. Characterization via X-ray diffraction (XRD) confirmed the synthesis, revealing an average crystallite size of 93.83 nm. The lattice strain percentage was measured at 0.1467 with a dislocation density of 1.13 × 10⁻⁴ 1/nm². Scanning electron microscopy (SEM) analysis showcased the spherical morphology of the nanoparticles, exhibiting average sizes of 169, 238 and 329 nm corresponding to 5, 10 and 15 SILAR cycles, respectively. The thickness of the TiO₂/HgBi₂S₃ composite thin film ranged from 12 to 18 µm. Notably, sensitizing the TiO₂ film with HgBi₂S₃ nanoparticles resulted in a substantial reduction in the contact angle by ~24°. Optical studies demonstrated a significant decrease in the energy band gap of TiO₂ from 3.06 to 1.6 eV post-sensitization with HgBi₂S₃ nanoparticles, indicating enhanced light absorption capabilities. Interestingly, the energy band gap of the TiO₂/HgBi₂S₃ composite thin film remained consistent across different SILAR cycles. Moreover, electrochemical impedance spectroscopy and photoelectrochemical analyses revealed the intriguing performance characteristics of the TiO₂/HgBi₂S₃ composite thin film, showcasing promising yet marginal enhancements.

Polypropylene multifilament yarns produced with flame-retardant (FR) additives have a significant place in the technical textile market. Determination of the technical performances of these multifilaments is very important. In addition, effects of the additive in the filament structure on the thermal and structural properties of the filament must be examined. In this study, new polypropylene polymer (PP) filament yarns having FR properties were produced and their thermal properties and crystallization data were determined and results are interpreted. Thermal properties and crystallization data of the PP multifilament yarns were determined by DSC analysis. Further, values of crystalline region ratio were determined and thermogram graphs of all samples were interpreted. As can be seen from the graphs, PP filaments had two consecutive melting points because PP has a double melting peak due to its structural character. Also, it has been observed that there is a direct proportionality between the melting enthalpy values of PP filaments and crystalline region ratios (%). The melting point was not significantly affected by the amount of FR additive. The addition of FR granule to PP filament further increases the enthalpy (∆H_m) required to melt the filament but there was no effect on melting temperature due to loading of FR additive to the PP filament yarns. Also, mechanical properties (tenacity and breaking elongation) and unevenness values were determined.

The present work investigated the effect of Ni-doping on the structural and dielectric properties of Ni-doped zinc oxide (ZnO) prepared by a solvothermal route. The substitution of nickel at Zn sites was confirmed via X-ray diffraction and Rietveld refinement, which revealed a hexagonal crystal structure. Morphological characterization was performed with the help of SEM, in which a significant variation in morphology was observed with increasing nickel doping concentration. The dielectric properties of all the compositions were measured as a function of frequency (1 Hz–10 MHz) and temperature (100–350°C). A temperature-dependent dielectric study of the compositions showed negative values for the dielectric constant in the low-frequency and high-temperature regimes. A decrease in the dielectric constant is observed for ZnO ceramics with increasing nickel doping percentage and is explained with the Penn model. Finally, an attempt is made to discuss the possible mechanism for the emergence of a negative dielectric constant. Additionally, a detailed structural analysis was performed to understand the conductivity behaviour of the nickel-doped zinc oxide ceramics. For ZnO samples with higher nickel doping, epsilon-near-zero behaviour is achieved, which is necessary for developing waveguides and coil-free resonators.