Bulletin of Materials Science最新文献

To address the corrosion of mild steel in aggressive mine water environments, nickel-chromium-iron (Hastelloy^® G30), copper-nickel-tin (ToughMet^® 3), and cobalt-chromium-tungsten (Stellite^® 6B) alloys were evaluated for their corrosion resistance. The study examined their behaviour in synthetic mine water at pH levels 6, 3 and 1 using potentiodynamic polarisation, alongside microstructural, hardness, and X-ray diffraction (XRD) analyses. Hastelloy^® G30 had equiaxed γ grains with Cr₃C₂ precipitates, ToughMet^® 3 displayed large, irregular grains, and Stellite^® 6B showed γ grains with Cr₃C₂ at boundaries and twinning. Hastelloy^® G30 and Stellite^® 6B demonstrated active-passive transitions with localized corrosion, while ToughMet^® 3 showed pseudo-passivation with severe pitting across all pH levels. Hastelloy^® G30 achieved the lowest corrosion rates at pH 6 (0.63 ± 0.01 µm·y^–1) and pH 3 (0.74 ± 0.05 µm·y^–1) but performed poorly at pH 1 (7.75 ± 0.64 µm·y^–1), with a hardness of 180 ± 10 HV₂. Stellite^® 6B had low corrosion rates at pH 3 (1.32 ± 0.34 µm·y^–1) and pH 1 (5.61 ± 1.13 µm·y^–1), with a hardness of 368 ± 13 HV₂. ToughMet^® 3 showed high corrosion rates, particularly at pH 1 (118.78 ± 8.00 µm·y^–1). Stellite^® 6B is the most promising alternative for harsh mining environments, offering optimal hardness and corrosion resistance.

The growth of the pre-immersion and anodic surface oxide films on titanium was found to be influenced by the pH of the saliva using open-circuit potential (E_ocp), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. It was found that the titanium's E_ocp increased with time as the metal was immersed in saliva with different pH values, from acidic to alkaline. This suggests that the titanium's pre-immersion oxide coating grew in these solutions. Furthermore, the EIS data showed that the oxide film resistances of both anodic and pre-immersion films increased with the saliva's pH, although anodic films did so faster than the pre-immersion films. Even though titanium's pre-immersion coating grows in neutral saliva that contains fluoride ions (F^– ions), the corrosion resistance of the metal diminishes as the concentration of these ions rises because of their aggression. The results of potentiodynamic polarization demonstrated that the rate of corrosion of the titanium surface was reduced by both an increase in pH and a decrease in fluoride ion concentration in saliva. The resistance of titanium's pre-immersion layer increased when the immersion period was raised to 17 days in saliva containing 0.005 M F^– ions at pH 6.34. The titanium surface was examined using scanning electron microscopy (SEM), and it was shown that when the pH of saliva increases, a greater percentage of the faults and notches on the growing pre-immersion oxide layer are repaired and healed. Additionally, the atomic force microscopy (AFM) data demonstrated that the titanium's surface roughness increases with the concentration of F^– ions in saliva due to their corrosive action. Energy dispersive spectroscopy (EDS) revealed that a titanium oxide layer was formed when titanium was submerged in artificial saliva.

The doubly ordered perovskites, NaYFeWO₆ and NaHoFeWO₆, have been synthesized by high pressure (4.5 GPa) and high temperature (1000ºC) methods. Powder X-ray diffraction (PXRD) analysis has confirmed that these compounds crystallize in the monoclinic structure with the space group P2₁. These materials exhibit distinct layer ordering of A-site cations (Na and Ln) and a common rock-salt ordering of cations (Fe, W) in B-site. Magnetic, heat capacity and dielectric data, reveal antiferromagnetic ordering of NaYFeWO₆ (T_N ~ 13 K), and NaHoFeWO₆ (T_N ~ 15 K) accompanied by a dielectric anomaly. Although pyroelectric and DC-bias current measurements were impacted by leakage currents, variations in these currents were detected near the magnetic ordering temperatures. The dependence of dielectric, pyrocurrent and DC-bias anomalies on the magnetic field suggests that these compounds exhibit multiferroic behaviour.

Sensing of explosive molecules for defence application was done using freely positionable and fibre coupled Raman probe. We developed the highly sensitive Ag-based array of surface enhanced Raman substrate (SERS) using a nanoimprint lithography. A limit of detection (LOD) as low as 10^–9 M for Cyclotetramethylene-tetranitramine (HMX) was achieved with long distance detection of 10 m. The optical fibre length could be customized from 1 to 10 m. This is the upcoming remote technique for sensing, using fibre coupled Raman probe, containing 20x objective present just in front of the optical fibre, so that the background signal does not dominates. An enhancement factor of 3.11 × 10⁶ was achieved with the limit of detection as 10^–9 M and it finds useful application in defence and medical field.

This study presents an experimental and numerical investigation of the dynamic behaviour of sandwich plate consists of  jute fibre-reinforced face layers and TiO₂-incorporated tea waste epoxy core layers. The core layers are reinforced with varying amounts of weight percentages of TiO₂ nanofiller (0%, 1%, 1.5% and 2%) to assess their impact on the tensile strength and free vibration responses. Tensile properties are evaluated using uniaxial tensile tests according to the ASTM D 3039 standard. The natural frequencies of the sandwich plates are obtained experimentally through experimental modal analysis using a fast fourier transform (FFT) analyser with PULSE Lab software (Bruel & Kjaer). These experimental findings are validated against numerical results obtained from the finite element software ABAQUS, where material properties are derived from the tensile tests are used as inputs. Additionally, numerical simulations are conducted to explore the effects of varying boundary conditions, aspect ratios, core thicknesses, face l ayer thickness ratios, and ply orientations (symmetric and antisymmetric) on the dynamic behaviour of the sandwich plates. Comparison with published literature confirms the accuracy and reliability of the proposed sandwich structures. The results provide insights into optimizing the dynamic performance of jute fibre-reinforced composite structures with sustainable tea waste-based epoxy cores for lightweight engineering applications. The optimum performance was observed at 2 wt% TiO₂ loading, which showed the best compromise between improved tensile strength and enhanced vibration damping without agglomeration effects seen at higher concentrations.

The fused filament fabrication (FFF) is a widely used technique for 3D printing of thermoplastics. The mechanical properties of 3D-printed samples may decrease with an increase in operating temperature. In this study, the degradation of the mechanical properties of 3D-printed polyethylene terephthalate glycol samples has been studied using dynamic mechanical analysis. The effect of process parameters such as layer thickness and operating frequency has been analysed in detail. The storage and loss modulus at the glass transition temperature decrease with an increase in layer thickness. Temperature and frequency-dependent analytical models and machine-learning (ML) algorithms, such as K-nearest neighbours, random forest (RF) and gradient boosting, are used to estimate the modulus variation as a function of temperature and loading frequency. The predictability of analytical models and ML models has been assessed. The fitting coefficients of the analytical model are evaluated as a function of temperature and frequency. Also, it is observed that the RF algorithm predicts the dynamic mechanical behaviour of 3D-printed samples with better accuracy at known frequencies as well as at unknown frequencies. For a layer thickness of 0.17 mm at 1 Hz frequency (known frequency), the RF algorithm demonstrated better performance indices with the highest R²-value of 0.983 compared to other ML algorithms. Similarly, for a layer thickness of 0.17 mm at 9 Hz frequency (unknown frequency), the RF algorithm predicted the modulus values with the highest R²-value of 0.967 compared to other ML algorithms.

Shear thickening fluid (STF) is a novel nanosuspension, formed by the uniform dispersion of micro- and nano-silicon within a specific dispersant. This study presents a review of the research on the applications of STF in impact protection, with a focus on two forms: composite fabrics and sandwich panels. The first section presents an initial overview of the impact protection performance of various STF-treated fabrics made from different fibres. Subsequently, methods for optimizing performance and potential application directions for composite fabrics are analysed. For STF sandwich panels, the enhancement of impact resistance in protective structures due to STF is highlighted, along with an evaluation of its application prospects in protective gear, aerospace and other fields. Finally, this study outlines the potential problems and challenges that STF may encounter in impact protection applications, drawing on the current status and developmental trajectory of STF’s applications.

The present study uses electrochemical approaches, such as linear and cyclic polarization, to examine the effects of immersion time (7, 14, 21 and 28 days) on the corrosion behaviour of X70 and X80 line pipe steels in a simulated concrete pore solution (SCPS) contaminated with 3.5 wt% NaCl (pH ~ 12 to 13.8). The results show that the corrosion resistance of the X70 line pipe steel decreases from 7 to 21 days, and then increases significantly after 28 days. For the X80 line pipe steel, corrosion resistance improves from 7 to 14 days due to the preferential dissolution of the bainitic phase, which enables the building of a passive film. However, corrosion resistance declines after 21 days before improving again after 28 days. This occurrence can be ascribed to the formation of stable passive film on both the steels after extended immersion periods (beyond 28 days), driven by the elevated phase fraction of α/γ* in corrosion products, where α signifies the stable α-FeOOH phase and γ* encompasses the less stable phases, such as γ-FeOOH, β-FeOOH and Fe₃O₄.

In the current study, the polymer composites are prepared by blending varied percentages of high-density polyethylene (HDPE) and polycarbonate (PC) along with fixed amounts of coir fibre (reinforcement) and f-MWCNT (nanofiller) and then compressed into thin sheets. The influence of changing the HDPE/PC ratio with fixed levels of reinforcement and nanofiller on the mechanical and tribological properties has been looked into using tensilometer and pin-on-disc test setup, respectively. They were also characterized for density, hardness, surface roughness and functional group identification (Fourier transform infrared spectroscopy), respectively. It is observed that the composite with HDPE/PC matrix ratio of 70/19 with 10 wt% coir fibre and 1 wt% f-MWCNT yielded improved results in terms of higher strength (21.1%) and modulus (4.5%) as well as good slide wear resistance and low friction characteristics (0.14) as compared to other composites. The results obtained have been assessed with the fractured and wear damage morphology using scanning electron microscope. Thus the prepared composites could be a choice for manufacturing of tyres, bumpers and panels, etc. in automotive sectors, as it possesses appropriate degree of mechanical and tribological properties.