Bulletin of Materials Science最新文献

Non-toxic, inorganic metal halide cubic perovskites are the standard for commercializing optoelectronic and photovoltaic devices. Owing to their major significance, a comprehensive analysis of the structural, electronic and optical properties of AlSnX₃ (X = F, Cl, Br, and I) perovskites was performed utilizing ab-initio density-functional theory. The negative formation energies verify the examined materials’ thermodynamic stability. All the compounds exhibit semiconducting behaviour, with bandgaps of 0.305, 0.205, 0.120 and 0.213 eV calculated using the GGA-PBE functional, and corresponding bandgaps of 1.034, 0.896, 0.854 and 0.902 eV obtained using the Hybrid HSE06 functional for AlSnF₃, AlSnCl₃, AlSnBr₃ and AlSnI₃, respectively. The confirmation of the semiconducting characteristics was achieved through the depiction of the density of states and the accurate assessment of atomic orbitals. All the perovskites have exceptional optical features in the visible spectrum, including excellent dielectric constant, refractive index, absorption capacities and conductivity. Additionally, AlSnF₃, AlSnCl₃, AlSnBr₃ and AlSnI₃ halides exhibit the largest absorption peak within the ultraviolet spectrum around 3.51 × 10⁵ cm^–1 at 22.7 eV, 3.51 × 10⁵ cm^–1 at 22.7 eV, 3.51 × 10⁵ cm^–1 at 22.7 eV, and 3.77 × 10⁵ cm^–1 at 19.3 eV, respectively. All of the investigated perovskites’ mechanical stability was confirmed using the bond stability standard. Moreover, its intrinsic stiffness, ductility, anisotropic characteristics and machinability are essential for enduring durability in fabrication processes. Thermodynamic evaluations confirmed the thermally stable nature of these perovskites throughout extensive ranges of temperature. This study’s findings revealed that AlSnX₃ (X = F, Cl, Br and I) perovskites could emerge as promising optical materials, and their synthesis in the upcoming days is highly anticipated.

In this study, hydrated tungsten oxide quantum dots (WO₃QDs) were synthesized using an electrochemical oxidation process, followed by thermal treatment via conventional and microwave heat treatment. The conventional and microwave treatments were carried out at 150°C for 45 and 8 min, respectively. The average heating rates of conventional and microwave heat treatment are 5.1 and 20.3°C min⁻¹, respectively. Heat treatment resulted in partial dehydration of hydrated WO₃QDs and generated oxygen vacancies in the lattice. Electrochemical response of as-synthesized, conventionally heat-treated, and microwave-treated WO₃QDs was measured using 1 M H₂SO₄ as electrolyte. In general, microwave-treated WO₃QDs showed better cyclic voltammetry characteristics as compared to conventionally heat-treated samples. Highest specific capacitance of 412.4 Fg⁻¹ was achieved for the microwave-treated sample at a scan rate of 10 mVs⁻¹. Correspondingly, high energy density (56.3 Whkg⁻¹) and high power density (3060 Wkg⁻¹) was noted for microwave-treated samples. The chronopotentiometry response of all samples dominantly exhibited diffusion-controlled behaviour with very small IR drop. These findings indicate that microwave-treated WO₃QDs are effective electrode materials and can be considered suitable for enhancing the performance of supercapacitors.

This research examines the effects of silane modifications on polyamide 12 (PA-12) to improve its mechanical and thermal properties. The study employs a reactive extrusion technique to integrate various silanes—Dynasylan^® AMEO, Dynasylan^® 1189, Dynasylan^® DAMO and Dynasylan^® VPS 4721—at different concentrations (0.25, 0.5 and 0.75%). Key findings reveal that silane modifications significantly enhance the tensile strength, impact resistance and viscoelastic behaviour of PA-12, with the Dynasylan^® DAMO formulation achieving the highest tensile strength of 38.25 MPa vis-à-vis 8.02 MPa for PA-12. The modifications also resulted in a reduction of crystallinity by over 35%, contributing to improved toughness and impact strength. Rheological assessments indicate that the flow properties of PA-12 are positively altered, enhancing its complex viscosity and storage modulus, which are crucial for applications in automotive and aerospace industries. Thermal analysis through differential scanning calorimetry and thermogravimetric analysis confirms improved thermal stability, particularly in the 0.5% Dynasylan^® AMEO-modified sample, exhibiting an onset temperature of 421.87°C. The study emphasizes the importance of the silane type and dosage in tailoring PA-12’s performance for advanced applications, suggesting future research directions to further refine silane-modification techniques for enhanced polymer performance. This research provides valuable insights into polymer-modification strategies, highlighting the potential for silane treatments to optimize the mechanical, thermal and rheological properties of PA-12 for diverse industrial applications.

Silk fibroin (SF) composite films with electrical conductivity hold potential for fabricating artificial nerve catheters compatible with electrical stimulation. Multiwalled carbon nanotubes (MWCNTs) are considered a promising conductive material for integration into polymers due to their high electrical conductivity, excellent nanotopography, and biocompatibility. However, few studies on CNT-doped biomaterials have achieved high conductivity. In this study, to achieve a nanofibre film with high conductivity, an MWCNTs/SF composite film was fabricated through electrospinning, and then coated with a MWCNTs solution. Various tests were conducted to evaluate the composite films, including mechanical property tests, analyses of chemical structure, morphological characteristics, hydrophobicity and conductivity. The results show that the addition of MWCNTs improved the transformation of SF’s structure, enhancing spinnability and fibre uniformity. However, a continuous increase in the MWCNTs in the spinning solution led to deteriorating spinnability. The addition of MWCNTs did not significantly impact the hydrophilic properties of the films, only the film with a CNT-SF mass ratio of 1:8 exhibited hydrophobicity. Films soaked in a mixture of carbon nanotubes with a concentration of 0.5% (w/v) exhibited good electrical conductivity and biocompatibility simultaneously, indicating significant potential for synergy with electrical stimulation in tissue repair.

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In the present investigation, we have examined the structural, mechanical, electronic and optical properties of the BaScAgTe₃ material by a first-principles approach based on density functional theory as implemented in WIEN2k. The optimized structure shows that BaScAgTe₃ contains four formula units and belongs to the orthorhombic Pnma space group. The coordination environment consists of ScTe₆-distorted octahedra and AgTe₄ tetrahedra, which constitute the fundamental components of the crystal structure. Electronic properties were evaluated using the GGA–PBE and TB-mBJ functionals using band structure and density of state analysis. We found a direct bandgap at the Γ point with a value of 0.86 eV for TB-mBJ. The mechanical stability of BaScAgTe₃ was assessed using the Born criteria based on the elastic constants C_ij. This study confirms that BaScAgTe₃ is mechanically stable. Poisson’s ratio and Pugh’s ratio calculations indicate that the material is ductile. The thermoelectric properties are evaluated, including Seebeck coefficient (S), electrical conductivity (σ), thermal conductivity (k), figure of merit (ZT), and power factor analysed over a temperature range of 100 to 1100 K under the constant relaxation time approximation of 10⁻¹⁴ s. Furthermore, the frequency response of optical properties was studied, including the real (dispersive) and imaginary (absorptive) parts of the complex dielectric function, the refractive index, and the absorption coefficient. The results indicate that the material exhibits a direct bandgap within a suitable range for photovoltaic applications. Additionally, it has a high dielectric constant, a substantial absorption coefficient (α ≈ 10⁶ cm⁻¹), and a refractive index that suggests the suitability of BaScAgTe₃ as a promising solar cell absorber material.

This study provides new insights into the structure, morphology and conduction mechanisms of the La_0.8Sr_0.1Ba_0.1FeO₃ compound synthesized via the sol–gel method. A better understanding of its properties paves the way for potential applications in areas such as sensing, batteries and electrochemical devices. To examine the physical properties of the prepared sample, a variety of techniques, such as FTIR spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and impedance spectroscopy, were used. The XRD analysis confirmed that the prepared powder exhibits a single phase that correspond to the rhombohedral structure (with R(overline{3})c space group). The SEM images revealed a uniform nanometric granular morphology. The Raman spectroscopy evidenced the characteristic vibration modes of the perovskite structures. Complex impedance measurements as a function of frequency and temperature were carried out to confirm the strong correlation between the microstructure and the electrical response of the material. In the limit of the AC regime, the conductivity spectra of the compound were analyzed using Jonscher’s power law. The temperature dependence of the exponent suggests that the conductivity response at high frequencies is related to the activation of the overlapping large polaron tunneling (OLPT) and the correlated barrier hopping (CBH) conduction processes. The DC conductivity investigation indicates that La_0.8Sr_0.1Ba_0.1FeO₃ exhibits a semiconductor behaviour over a large temperature domain. This behaviour is related to the activation of the small polaron hopping (SPH) process at high temperatures, the greaves variable range hopping (VRH) process in the intermediate temperature range, and the Mott-VRH mechanism at low temperatures. The presence of relaxation phenomena is confirmed via variation of the imaginary part of the impedance spectra. Likewise, the Nyquist diagrams show the main importance of the microstructure on governing the electrical response of the ceramic compounds.

In this study, Fe–Al was developed through multiple rolling passes followed by heat treatment at 500 and 1050°C using the accumulative roll bonding technique (ARB). The study gives insights of their microstructural and intermetallic formation along with interfacial integrity. The microstructure establishes the progressive diffusion of Al into Fe. The phase analysis confirmed the formation of FeAl, Fe₂Al₅, Al₁₃Fe₄ and oxides. The microhardness of the as-rolled specimens exhibited a lower hardness of 152.3 HV due to strain hardening, while heat treatment at 500 and 1050°C showed high hardness of 291.1 and 264 HV. However, precipitate coarsening and reduced dislocation density lead to a slight decrease in hardness at 1050°C. The morphology and line mapping studies established the distribution of Fe–Al phases and oxidation effects. The results revealed that 500°C heat treatment optimizes hardness, while 1050°C leads to embrittlement.

It is well-reported that the synthesis of cancrinite zeolite via hydrothermal process requires long treatment reaching up to several days; also, the resulting zeolite is commonly phase impure and has weak mechanical strength. In the current work, cancrinite zeolite was synthesized using a simple hydrothermal method utilizing metakaolin-based geopolymer as a template and 5 M aqueous solution of sodium hydroxide as a medium for the hydrothermal process. The time and the temperature effects on the hydrothermal treatment were investigated. X-ray diffraction, scanning electron microscopy, and infrared spectroscopy techniques were used to analyse the structure, morphological properties, and functional groups of the synthesized cancrinite zeolite. It has been found that phase-pure cancrinite zeolite can be obtained via the treatment at 220°C for 6 h in NaOH solution. The findings not only establish the viability of geopolymer as a starting material for cancrinite zeolite synthesis but also contribute valuable insights into the key factors influencing the process. This research advances the understanding of zeolite synthesis pathways and expands the potential applications of geopolymers in the realm of zeolite materials.

Over the years, research related to Bismuth ferrite (BiFeO₃ or BFO) has gained pace, as it is one of the few materials that exhibit single-phase multiferroicity. Researchers have consistently endeavoured to optimize processing techniques, stabilize crystal symmetry and microstructure, enhance magnetoelectric coupling, and thereby expand the range of applications of BFO via doping or creating solid solutions. In this study, strontium (Sr) and titanium (Ti) are chosen and concurrently doped at the A- and B-sites of BFO to develop the (Bi_0.5Sr_0.5)(Fe_0.5Ti_0.5)O₃ ceramic. A PC-controlled impedance analyzer is used to assess the electrical parameters of the sample as a function of frequency (1 kHz–5 MHz) at multiple temperatures (room temperature 500°C). A thorough examination of complex impedance and complex modulus parameters reveals that the sample goes through a relaxation phenomenon that deviates from the ideal Debye-like behaviour. The role of bulk/grain and grain boundary effects on the impedance parameter is visualized by the Nyquist plot. The AC conductivity response of the sample aligns well with Jonscher’s power law. The disparity amongst the calculated activation values through the relaxation time plot and the DC conductivity plot indicates that separate charge carriers are involved in the conduction and relaxation phenomena. Additionally, the negative temperature coefficient of resistance property of the sample is disclosed, indicating its applicability for semiconducting usages.

Graphene oxide (GO), as a 2D membrane, exhibits outstanding molecular sieving properties for gas separation. The gas permeation mechanism in GO sheets is quite different from that of traditional polymer membranes due to their multilayer nature. It is still a challenge to directly and accurately measure gas diffusion coefficients in ultrathin multilayer membranes. In this work, we applied a well-proven experimental method to determine the diffusivities for H₂, He, CH₄, N₂, O₂, Ar and CO₂. Unlike polymer membranes, the diffusivity for all gases in 2D membranes depends exponentially on the path length and diffusing time. This study is important for both characterizing and standardizing the gas transport properties of thin GO sheets, designing novel membranes based on carbon materials, and for gas mixture separation or toxic gas removal processes. Some applications of the present investigation are discussed.

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