Bulletin of Materials Science最新文献

A significant scientific interest has been generated in developing chemical compounds with unique properties as colourants in security inks. A pyrene-based chalcone: (E)-1-(6-methoxynaphthalen-2-yl)-3-(pyren-1-yl) prop-2-en-1-one (PYNP) with aggregation-induced enhanced emission was prepared in search of smart fluorescent pigments and was characterized using spectral techniques. Water-based flexographic ink with PYNP pigment was formulated, and coats/prints were obtained on security printing paper and paperboards. The coated and printed substrates exhibited greenish-yellow fluorescence on excitation beneath UV light. Moreover, PYNP is an effective fluorescent pigment for security printing applications, as indicated by colourimetric values, good lightfastness, gloss and abrasion resistance of the prints.

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One of the non-traditional techniques for processing hard and electrically conductive materials is the powder-mixed electric discharge machining, which involves no physical connection between the tool and work surface. Nimonic C-263, a nickel-based superalloy, is widely used in aerospace and automobile sectors due to its improved inherent properties such as high hardness at elevated temperatures, high creep and corrosion resistance and excellent intermediate temperature tensile ductility. This study investigates aluminium powder-mixed electric discharge machining of Nimonic C-263 while using non-toxic environment friendly dielectric, deionized water. The effects of altering parameters such as peak current (I_pc), pulse-on-time (T_on), pulse-off-time (T_off) and powder concentration (C) on material removal rate (MRR), tool wear rate (TWR) and average surface roughness (R_a) have been critically analysed. The observations show a rise in MRR with the increase in I_pc, T_on and C. R_a is found to increase with an elevation in I_pc and T_on while it declines with a rise in C. Process parameter optimization through grey relational analysis reveals the best parametric combination as I_pc = 8 A, T_on = 1 µs, T_off = 5 µs and C = 9 kg m⁻³. SEM analyses depict that the surface quality deteriorates at higher values of I_pc.

Continuous fibre-reinforced thermoplastic composites possess excellent toughness, impact resistance and damage tolerance in comparison to their thermoset counterparts. Nevertheless, processing of thermoplastic composites is complex and expensive. In this investigation, commingled fabrics of E-glass and polyphenylene sulphide (PPS) are stacked and consolidated to produce composite laminates through an energy-efficient facile vacuum-forming technique. Laminates were fabricated and tested according to the requirements of ASTM specifications. Their void content has been evaluated, and interface morphology has been studied using field emission scanning electron microscopy. Laminates were also subjected to evaluation of tensile, flexural, compressive, interlaminar shear, in-plane shear and impact properties. Dielectric properties such as permittivity, dissipation factor and transmission loss in the 8.2–12.4 GHz frequency region have also been studied. The results are compared with data of E-glass/PPS composites that are manufactured using mainstream methods, and it is found that this technique of manufacturing thermoplastic composites is simple and energy efficient and in turn can replace thermoset composites in various sectors.

Due to the presence of several components in epoxy composites, monomers, crosslinking agents, fillers, reinforcements and other additives, the final properties and performance of the product depend strongly on their physicochemical properties and ratios of these components. In this work, the influence of natural polyphenolic compounds, tannins as bio-based additive on various properties of commercial epoxy resin was investigated. Tannins were isolated from the tree’s bark obtained as a byproduct from wood industries, purified, and they were utilized as sustainable fillers in epoxy composites. Different ratios of tannins (0, 5, 20 and 40 wt%) were added to the epoxy resin and hardener mixture. The curing behaviour, thermal properties and curing kinetics of tannin/epoxy composites were investigated. Also, the potential of tannins to utilization as crosslinking agent into epoxy resin were characterized by means of DSC. The results showed that the epoxy resin loaded with tannins reached 100% curing percentage and exhibited the same curing behaviour as pure epoxy resin, which is characterized by a single exothermic peak observed in the temperature range of 90–150 °C with a peak temperature of 130–140°C. An increase of 4°C was found in the glass transition temperature (Tg) in higher tannin content (40 wt%) composite. The addition of tannins without hardener has no influence on the curing process of pure epoxy. The values of activation energy (Ea) were in the range of 45–56 kJ mol^–1 and considered within the accepted ranges of most commercial epoxy composites. The results also showed that the tannins offer competitive advantage properties and have been considered one of the most promising materials as renewable fillers in epoxy-based composites.

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This article is devoted to syntheses of thermoreactive benzotriazolylimide resins with the hexamethylene bridging and terminal maleimide groups and a study of their structure, as well as properties of materials based on such resins. These resins are cross-linked under the action of high temperatures into three-dimensional polymers without the release of low-molecular-weight by-products. Three-dimensional polymers of such a type are of interest from the point of view of the availability of precursor materials, the ease of the preparation of the initial thermoreactive resins in the melt and high-performance characteristics. One-step melt synthesis without the release of by-products and in the absence of organic solvents is most acceptable from the technological and environmental points of view. The structure of the resins was confirmed by the IR and NMR spectroscopy data. Model compounds were synthesized and a comprehensive study of their structure by the spectroscopic methods was carried out. This was necessary for obtaining valuable information for the synthesis of the resins and to facilitate confirmation of their chemical structure. According to thermogravimetry data, the temperatures of beginning decomposition of resins in air are 350–360°C. For compounds containing the aliphatic units, this is a fairly high indicator. This fact is explained by the formation of cross-linked polymers before the onset of thermal destruction. The long curing time of resins up to 12 h ensures that heat generated during this process has time to dissipate without causing local overheating of the material that could cause the mechanical stresses. This improves the mechanical characteristics of materials based on these resins. The resulting materials are resistant to high temperatures and acidic aggressive environments (for example, H₃PO₄). This allows them to be used as thermoreactive binders for the manufacture of high-heat-resistant adhesives, as well as structuring components of polybenzimidazole polymer matrices for the manufacture of the proton-conducting membranes for the medium-temperature fuel cells. The positive effect of introducing the benzotriazolyl fragments into the structure of the thermoreactive resins on the mechanical properties of adhesive joints between steel plates has been shown.

Glycolurils are building blocks for cucurbiturils. Poly(glycoluril-formaldehyde) produced microparticles, which were synthesized for the first time by the combination of glycoluril and formaldehyde. Poly(glycoluril-formaldehyde) microparticles were characterized by SEM, XRD and FTIR. The porosity of these microparticles were examined using N₂ absorption – desorption studies, which indicated the non-porous nature of the material. However, these microparticles behaved same as cucurbiturils with respect to dye removal studies. Unlike the cucurbiturils, these microparticles were easy to prepare with no purification steps involved. Furthermore, these microparticles facilitated to remove the environmental pollutants such as dyes, hair dyes, antibiotic drug and inorganic compounds. These microparticles also aided to purify the urine samples and eliminated the RBC cells from the cow urine samples effectively.

The Ti–Sb binary system, a critical component of half-Heusler thermoelectric alloys, remains incompletely defined due to the significant difference in melting points between Sb (630°C) and Ti (1670°C). In this work, Ti–Sb diffusion couples were prepared using argon gas-protected seal welding to prevent Sb volatilization during long-term annealing. Seven groups of samples were annealed at temperatures ranging from 400–900°C for 14 days. Eight equilibrium phases—(αTi), (βTi), (Ti₃Sb), Ti₂Sb, Ti_1.35Sb, TiSb, TiSb₂ and (Sb)—were identified based on microstructural and compositional analyses using electron probe microanalysis (EPMA). The equilibrium conjugate compositions reveal that the solubility of Sb in the hexagonal close-packed (αTi) phase is 0.33 at.%, while it significantly increases to ~7 at.% in the body-centred cubic (βTi) phase at 850°C due to its structural transformation. The detected phases (Ti₃Sb), Ti₂Sb, Ti_1.35Sb (or Ti_11−xSb_8−γ), TiSb and TiSb₂ exhibit stoichiometric compositions. Notably, the (Ti₃Sb) phase shows a low Sb content (~22.5 at.%) below 600°C but transitions to a higher Sb content (~25.5 at.%) above 700°C, a change attributed to its structural modification from cubic-(Ti₃Sb) to tetragonal-(Ti₃Sb). These findings provide critical insights into the phase equilibria and structural transformations in the Ti–Sb system, enhancing its understanding for thermoelectric applications.

Li₂ZnGe₃O₈:Er³⁺ and Li₂ZnGe₃O₈:Er³⁺/Yb³⁺ phosphors were successfully synthesized via a high-temperature solid-state reaction method, and the upconversion luminescence properties and mechanisms of both Er³⁺-doped and Er³⁺/Yb³⁺ co-doped systems under 980 and 1550 nm excitation were systematically investigated. Additionally, the optical temperature sensing performance of the Li₂ZnGe₃O₈:Er³⁺/Yb³⁺ phosphor was explored in detail. To enhance temperature sensitivity and self-calibration features, a dual-mode temperature sensing method was designed and implemented based on fluorescence intensity ratio from thermally coupled energy levels (TCELs) and non-thermally coupled energy levels (NTCELs). Experimental results show that in the TCELs mode, the maximum absolute sensitivity under 980 nm excitation is 0.003197 K^–1 (462 K), and under 1550 nm excitation is 0.0028 K^–1 (303 K); while in the NTCELs mode, the maximum absolute sensitivity under 980 nm excitation is 0.003059 K^–1 (529 K), and under 1550 nm excitation is 0.0013 K^–1 (303 K). These findings indicate that Li₂ZnGe₃O₈:Er³⁺/Yb³⁺ phosphors exhibit excellent dual-mode optical temperature sensing potential under dual-excitation conditions.

The pursuit of nanomaterials with desirable properties including excellent reflection loss (RL), reduced thickness, wide bandwidth, facile fabrication process and low density has garnered significant attention. In this study, we explore the potential of new nanocomposite samples through the incorporation of copper oxide nanoparticles into epoxy resin matrices. The investigation further delves into the thermal, morphological and electrical characteristics of these samples. This study evaluates the electromagnetic properties of the composites, including permittivity (ε), permeability (μ), RL and shielding effectiveness. The microwave characterization and shielding effectiveness assessments were conducted across the X-band frequency range (8–12 GHz). The findings are promising where the epoxy/10% CuO composite exhibits strong absorption with a spectrum below −10 dB in the 8.5–9 GHz and 9.75–11.25 GHz ranges. Notably, the 20% CuO composite consistently achieves a spectrum below −10 dB across all frequencies, indicating a remarkable 90% absorption capability at varying thicknesses.

This study investigates the effect of nanoclay (NC) and alumina on improving the thermo-mechanical properties of high-density polyethylene (HDPE) and polypropylene (PP) blends, compatibilized with polyethylene-grafted maleic anhydride (pEMAH). The modulus of the sample containing 1.5% and 3% NC are 893 MPa and 786 MPa, respectively. The ratio of the modulus of composites to that of the matrix increase proportionally with an increase in the composition of NC for various micromechanical models studied. The fracture energy release rate for Run 1 and Run 2 start at 2.08 and 2.35 kJ m^–2 before aging, and once aged, they increase to 6.17 and 5.82 kJ m^–2. High heat on tensile samples leads to bonding in the polymer. The bonding makes a polymer firm, prevents bending and increases the tensile strength. The COMSOL models predict the tensile strength of simulated values at 27 MPa for the 1.5% NC-reinforced matrix, which is the same as the experimental tensile value. Maximum mass loss rates show an increasing trend, with heating rates for the samples containing NC. For instance, the polymer blend containing 1.5% NC has peak mass loss rates of 15% at 5°C, 26% at 10°C and 43% at 15°C as the temperature increases. Adding NC particles to the blend improves its temperature resistance. The activation energy found using Horowitz and Metzger plots for HDPE/PP is 113 kJ mol^–1, which increases to 141 kJ mol^–1 for the 1.5% NC blend.