Materials最新文献

Phononic band gap crystals are characterized by periodic scatterers embedded within a matrix, which enable precise modulation of acoustic or elastic waves. Conventional optimization prioritizes bandwidth maximization, yet practical engineering often requires band gaps at specified frequencies. This requirement creates a significant design challenge. To this end, we develop a topology optimization strategy capable of maximizing elastic wave band gaps around prescribed target frequencies. The approach utilizes Material-Field Series Expansion (MFSE) for unit cell representation and a gradient-free Kriging-based algorithm to tackle the complex optimization problems. This strategy is systematically applied to optimize the band gaps of out-of-plane, in-plane, and complete wave modes, and is further extended to more complex scenarios involving dual-target frequencies. A variety of numerical results demonstrate the method's effectiveness in engineering phononic crystals for bespoke frequency specifications.

The growing emphasis on sustainable material design has intensified interest in bio-based additives as environmentally friendly alternatives to conventional synthetic modifiers. This study evaluates the effects of four natural compounds-cetyl alcohol, thymol, lanolin, and lecithin-on the thermal, rheological, mechanical, surface, and aging properties of regranulated low-density polyethylene (RLDPE). Post-consumer polyethylene waste was used as the polymer matrix, while biochar served as a sustainable reinforcing filler replacing carbon black. Differential scanning calorimetry, melt flow index measurements, rheological behavior, surface energy analysis, mechanical testing and thermo-oxidative aging assessments were conducted to assess structure-property relationships. Biochar increased stiffness, hardness, and impact resistance but reduced ductility and melt flow due to restricted chain mobility. The addition of natural compounds partially compensated for these effects by improving melt flow, modifying crystallization behavior, and enhancing resistance to thermo-oxidative degradation without severely diminishing mechanical performance. Cetyl alcohol promoted the highest crystallinity and flexural properties, lanolin exhibited the strongest plasticizing effect and improved post-aging ductility, while lecithin and thymol produced intermediate changes, with lecithin significantly increasing surface energy. These results indicate that selected natural additives can act as effective ecological plasticizers or processing aids in biochar-filled recycled polyethylene composites.

In this study, a comprehensive derivatization strategy for biogenic amines based on the formation of volatile carbamate derivatives using 2,2,2-trifluoroethyl chloroformate (TFECF) was successfully developed and evaluated. A series of biogenic amine derivatives was obtained in excellent yields (94-99%) and structurally confirmed using NMR, MS, and crystal structure analysis. The reagent demonstrated high reactivity toward primary and secondary amines, providing derivatives of excellent purity and satisfactory volatility. The applicability of the proposed procedure to real food matrices was demonstrated using GC-MS. The obtained results were compared with the corresponding ethyl chloroformate (ECF) derivatives. TFECF derivatives exhibited significantly improved volatility, reflected in shorter retention times and enhanced analytical performance.

The aim was to evaluate the interface zone between glass hybrid (GH), high-viscosity (HV), and resin-modified (RM) glass-ionomer cements (GIC) and sound (SD) and artificially created caries-affected (ACAD) primary dentin. Occlusal cavities were prepared in 120 extracted primary molars and randomly assigned to SD or ACAD. Samples were restored with GH (Equia Forte HT-EF), HV-GIC (Equia Fill-E; Ketac Molar-KM), or RM-GIC (Fuji-II LC-FII; Photac Fill-PF) and exposed to thermal aging. Microleakage (methylene-blue) was analyzed using an optical digital microscope. The interface between dental tissues and restorative materials was analyzed using a scanning electron (SE) microscope. SE microphotographs were manually annotated for intimate contact and cracks/gaps at the material-enamel/dentin interface and analyzed using a custom Python-based algorithm to quantify the respective percentages. No microleakage was noted only in the SD group for EF (50%), FII (42%), and E (33%). All materials showed higher microleakage in ACAD than SD (p < 0.05). No continuous intimate contact between restorative material and dental tissues was observed along the entire interface. The mean proportion of intimate contact between the material and SD was EF (76%) > KM (55%) > E (38%) > FII (7%) > PF (4%), and EF (32%) > KM (24%) > E (16%) > FII (15%) > PF (0%) for ACAD (p < 0.05). Caries-induced demineralization affects the quality of the material-dentin interface. GH are likely to provide better sealing compared to the previous generations of GI materials.

This study examines the impact of rolling direction on Barkhausen noise emission from the low-alloyed steel MC 500 during a uniaxial tensile test. The samples of gauged shape were cut along both the rolling and transverse directions to investigate the process of magnetic anisotropy alterations, as expressed in terms of Barkhausen noise and the extracted features. Barkhausen noise was studied as a function of both elastic and plastic straining (up to plastic strain 21.5%), and the role of domain wall realignment with respect to the rolling direction, as well as the direction of the tensile load, was analysed. Barkhausen noise emission is linked to both the stress state and the microstructure, and the role of external stressing is contrasted with the residual stress state. Barkhausen noise is measured directly during a tensile test (in situ) as well as after unloading (ex situ). It was found that Barkhausen noise is significantly affected by stress directly during the tensile test (in situ), whereas the contribution of residual stresses is less pronounced. Barkhausen noise measured in situ during the tensile test in the direction of the tensile load is higher (about 1100 mV) compared to the transverse direction (about 500 mV). However, this relationship is reversed for the ex situ measurements, especially for the more developed plastic strains above 15%. The influence of rolling direction on Barkhausen noise is relatively minor, and Barkhausen noise after matrix yielding is primarily affected by increasing dislocation density growing from 3 × 10¹⁵ up to 5 × 10¹⁵ m^-2.

Due to the unique microstructure and mechanical heterogeneity of austenitic stainless steel made via wire arc additive manufacturing (WAAM), its machinability differs significantly from that of rolled material. Accordingly, this study systematically investigates the influence of milling strategies on key process responses (cutting forces, surface roughness, vibration displacement, and temperature) to reveal the mechanisms of machining parameters during the milling of WAAM-fabricated austenitic stainless steel. The material used in this study is ER321 austenitic stainless steel. During deposition, the fusion zone cools more slowly than the transition zone; consequently, the fusion zone exhibits a hardness approximately 20 HV_0.1 lower than that of the transition zone. Surface roughness is primarily reduced by decreasing the primary feed per tooth. However, when the primary feed per tooth is small, ploughing is induced, which not only increases surface roughness by 25% but also causes abnormal increases in temperature and vibration displacement. Nevertheless, ploughing has little effect on the total milling force, and the feed per tooth shows a positive correlation with the total milling force. Tool run-out and an increase in the uncut chip thickness lead to a positive correlation between the radial depth of cut and the key process responses. Moreover, ploughing also occurs when the radial depth of cut is small. The axial depth of cut has almost no effect on the machining process. Moreover, a small-diameter mill leads to severe ploughing, and at a high table feed, climb milling leads to cutter offset.

Improving both the high- and low-temperature performance of asphalt is still difficult in modern pavement applications. This performance imbalance has motivated the development of new modification strategies that can enhance temperature stability while maintaining construction workability. In this research, a low-molecular-weight elastic polyolefin (POL) with inherent compatibility was introduced as a novel asphalt modifier. POL was incorporated at five dosages (0%, 2%, 4%, 6%, and 8% by weight of asphalt) to investigate its effects on the fundamental physical, rheological, and low-temperature properties of the asphalt. The rheological behavior was characterized by dynamic shear rheometer (DSR) and bending beam rheometer (BBR), while the modification mechanism and dispersion morphology were analyzed through Fourier-transform infrared spectroscopy (FT-IR) and fluorescence microscopy (FM). The results reveal that POL markedly improves the high-temperature performance and workability of asphalt, with the rutting factor increasing by two- to eightfold. POL modification improved the thermal stability of asphalt, shifting the maximum decomposition temperature from 455.2 °C for the base binder to 461-463 °C, while the total mass loss remained nearly constant at 80-83%. Microscopic observations confirm that POL forms a physically blended network within the asphalt matrix, exhibiting a green fluorescent structure that becomes progressively continuous with increasing dosage. The most homogeneous dispersion and optimal compatibility occur at a POL dosage of 6%, beyond which phase segregation emerges and low-temperature properties deteriorate. Accordingly, a 6% POL dosage is recommended for achieving balanced performance. These findings provide theoretical and practical guidance for the development of balanced performance and thermally stable POL-modified asphalt materials.

The regeneration of air filter materials can extend the service life of filters, and also reduce resource waste and air pollution caused by replacements, which directly lower carbon emissions. This paper focuses on reduced graphene oxide (rGO) filter materials, investigating the effects of ultrasonic cleaning utilizing water, lemon acid, and a cleaning agent. Regeneration performances were also tested and discussed and analyzed. Results show the synergistic effect of the cleaning agent and ultrasonic cleaning yields the most optimal regeneration performance. Compared to the water and lemon acid, filtration efficiency of rGO materials for PM₁₀, PM_2.5, and PM_1.0 increased by 2.0%~12.15% and 0.42%~7.13%, 0.04%~5.67% and 0.03%~2.35%, and 0.02%~3.47% and 0.16%~2.02%, respectively. Filtration efficiency recovery rates for PM₁₀, PM_2.5, and PM_1.0 using the cleaning agent exceeded 70%. Counting filtration efficiency exhibited significant changes for particle sizes from 0.265 to 1.0 μm. The resistance after water cleaning was higher than that of cleaning agent cleaning and lemon acid cleaning. After 10 cleaning cycles, the cleaning agent exhibited QF values that were 0.0012 Pa^-1, 0.0003 Pa^-1, and 0.0001 Pa^-1 higher for PM₁₀, PM_2.5, and PM_1.0, respectively, compared to the water, and 0.0007 Pa^-1, 0.0001 Pa^-1, and 0.0001 Pa^-1 higher compared to the lemon acid. It provides data references for the efficient regeneration of rGO materials and promotes the green application of air filter materials.

This paper presents a numerical case study on the application of generative design to the shape optimisation of a spur gear body with consideration of manufacturing constraints and material properties. The presented results are obtained using numerical simulation and finite element analysis. A finite element-based generative design workflow was employed to evaluate weight reduction and stiffness performance under different manufacturing routes, including additive manufacturing, machining, and casting. The results show that the application of generative design enabled a gear-body mass reduction of up to 37.46-45.68% compared to the reference geometry while maintaining acceptable deformation levels. Designs constrained for additive manufacturing achieved the highest weight savings, whereas machining-constrained variants exhibited lower deformation values, indicating higher structural stiffness. Casting-oriented constraints resulted in more conservative geometries with locally reinforced regions. The study confirms that manufacturing constraints significantly influence the generated geometry and mechanical response, demonstrating that the manufacturing route acts as an independent design variable within the generative design process. The presented methodology provides practical guidance for the early-stage numerical optimisation of gear bodies and supports informed decision-making with respect to manufacturing technology selection.

Background: Durable bonding to zirconia remains difficult because its chemically inert surface resists acid etching. Additive manufacturing (AM) enables controlled surface morphology, which may enhance micromechanical retention without additional treatments.

Methods: Zirconia specimens with three AM-derived surface designs-(1) concave-convex hemispherical patterns, (2) concave hemispherical patterns, and (3) as-printed surfaces-were fabricated using a slurry-based 3D printing system and sintered at 1500 °C. Zirconia specimens fabricated by subtractive manufacturing using CAD/CAM systems, polished with 15 µm diamond lapping film and with or without subsequent alumina sandblasting, served as controls. Surface morphology was analyzed by FE-SEM, and shear bond strength (SBS) was tested after cementation with a resin-based luting agent.

Results: SEM revealed regular layered textures and designed hemispherical structures (~300 µm) in AM specimens, along with step-like irregularities (~40 µm) at layer boundaries. The concave-convex AM group showed significantly higher SBS than both sandblasted and polished subtractive-manufactured zirconia (p < 0.05). Vertically printed specimens demonstrated greater bonding strength than those printed parallel to the bonding surface, indicating that build orientation affects resin infiltration and interlocking.

Conclusion: AM-derived zirconia surfaces can provide superior and reproducible micromechanical retention compared with conventional treatments. Further optimization of printing parameters and evaluation of long-term durability are needed for clinical application.