Advanced Engineering Materials最新文献

Fused filament fabrication (FFF) offers great potential to fabricate patient-specific implants to treat large size defects resulting from craniectomy. Such cranial implants impose critical requirements on material and design. So far, the field has focused on printing cranial implants from polyetheretherketone (PEEK), which is semicrystalline in nature and, therefore, not ideal for FFF because of warping and nonhomogeneous crystallization. Consequently, this work aims at exploring alternative amorphous high-performance polymers. The tensile and flexural mechanical properties of printed samples from PEEK, polyetherketoneketone (PEKK), and polyphenylsulfone (PPSU) according to ISO standards are compared. Testing of specimens obtained from three orthogonal build directions reveals nearly isotropic mechanical behavior (e.g. ultimate tensile strength differed no more than 8% between print orientations). This enables printing of patient-specific cranial implants in vertical orientation with minimal support structures, which result in dimensional accuracies in the clinically acceptable range for craniofacial reconstructions. Mechanical assessment via an in-house designed indentation set-up shows that both PEKK and PPSU should be considered valid alternatives to PEEK for cranial implants. This work showcases the maturity of FFF for high-performance polymers and leverages it for complex patient-specific geometries such as a cranial implant.

Composites comprising conductive polymers and metal particles have garnered considerable interest in sensor technology due to their excellent electrical conductivity. However, producing controllable pressure sensors that retain high sensitivity under microstress remains challenging. Polyimide (PI) sponge exhibits excellent chemical and thermal stability and a porous structure that facilitates considerable deformation under low stress levels and results in good sensitivity to external forces. Herein, a conductive polymer–metal composite conductive phase, polypyrrole–silver (PPy–Ag), is directly fabricated on the PI surface through incipient network conformal growth. This method ensures that the PPy–Ag composite maintains optimal performance within its original temperature range, thereby enhancing detection sensitivity at low stress levels. The maximum conductivity of the fabricated PPy–Ag/PI composite sponge-based flexible piezoresistive sensor is 2.42 × 10⁻⁴ S m⁻¹, and the sensitivity is recorded at 16.31 kPa⁻¹ within a stress range of 0–80 Pa. After undergoing 1000 compression cycles, the sensor exhibits commendable stability and reproducibility.

The friction lining is a critical component of the friction hoist, serving as the driving force for lifting through its interaction with the wire rope. Monitoring the friction state between the wire rope and the friction lining is crucial as it directly impacts lifting capacity, work efficiency, and overall safety. By employing finite element simulation and creating surface microstructures on triboelectric nanogenerators (TENG) using ultraviolet laser, this study demonstrats that microstructure can improve voltage output. Compared with TENG without morphology, the voltage is increased by nearly seven times, reaching 2.28 V. Moreover, experiments revealed that embedding TENG at the optimal standard point of the friction lining enables effective monitoring of friction transmission under varied conditions, with the voltage signal showing synchronization with friction force. Notably, the voltage reached 520 mV under increasing specific pressures and stabilized around 670 mV with rising sliding speeds. This research represents a significant step toward real-time monitoring of intelligent mining systems by dynamically observing friction transmission in mine hoists.

In this study, forming palladium germano-silicide on Si_0.8Ge_0.2-based complementary metal-oxide semiconductor (CMOS) transistors by high-pressure annealing compared to microwave annealing is investigated. Boron-doped Si_0.8Ge_0.2 layers are epitaxially grown on n-type Si wafers, achieving an initial boron concentration of 5 × 10¹⁵ cm⁻³, which increase to ≈6 × 10²⁰ cm⁻³ after microwave annealing, reducing sheet resistance. Palladium is deposited using electron beam evaporation to form a 15 nm layer on Si_0.8Ge_0.2 (200 nm)/Si (100) substrates. High-pressure annealing is conducted from 300 to 500 °C in N₂ ambiance at 5 kg cm⁻³, while microwave annealing is performed at 5.8 GHz and 1800–3000 W for 100 s. X-ray diffractometer confirms high-intensity Pd₂Si phase formation, but scanning electron microscope and atomic force microscope reveal increased surface roughness and clustering after annealing. Sheet resistance increases from 10.35 Ω sq⁻¹ (unannealed) to 131.8 Ω sq⁻¹ (high-pressure annealing at 300 °C) and 85.8 Ω sq⁻¹ (microwave annealing at 1800 W). In these results, the trade-offs between annealing methods and metal choices for achieving low contact resistance and Schottky barrier heights in p-type Si_0.8Ge_0.2 CMOS circuits are highlighted.

The poor corrosion resistance of magnesium and its alloys can be overcome by developing appropriate surface treatments of these materials. The article explores the impact of using a current density of 15 mA cm⁻², lower than those considered so far for the plasma electrolytic oxidation treatment of the WE43 earth rare-based magnesium alloy, on process energy consumption as well as on microstructure and corrosion properties of oxide coatings grown on the magnesium alloy. Using a low current density during the treatment certainly means significant energy savings, but also good corrosion resistance compared to the untreated alloy, as demonstrated by electrochemical analyses and a through-hole morphology of the oxide coating, which could be useful for all the applications in which beyond good corrosion resistance a specific surface area is essential.

Lattice structures, as integrated structure-function engineering materials, have developed rapidly in industrial fields. In this study, the in situ integrated solid/hollow aluminum lattice structure filled tubes are designed and manufactured by a selective laser melting technique. The effects of structure parameters on compressive properties, energy absorption, and sound absorption are analyzed. The in situ integrated aluminum lattice structure filled tubes with hollow lattice structure and strengthened hollow lattice structure can achieve a wide adjustment of compressive property (31.04–185.64 MPa) and energy absorption density (11.21–51.70 MJ m⁻³) in a narrow density range. The compressive property and energy absorption are superior compared with ex situ aluminum lattice structure filled tubes due to the interaction and metallurgical bonding between the thin-walled tubes and the aluminum lattice structures. The hollow structure design and altering its structure parameters can regulate the sound absorption coefficient and the corresponding peak frequency (the highest absorption peak is 0.723 at 2098 Hz). In addition, the hollow structure design can realize double absorption peaks (0.360 at 1462 Hz and 0.503 at 2122 Hz), presenting the potential for broadband sound absorption. Eventually, superior integrated energy/sound absorption structures can be obtained by the hollow structure design and its corresponding optimization.

Developing thermoplastic polyimide (TPI), capable of handling space conditions, through 4D printing is challenging due to its high melting temperature and inherent viscosity. This study presents 4D printing of TPI for shape memory investigation under repetitive cycles for the first time, exploring its potential for self-deployable hinges in space devices. 4D-printed TPI exhibits outstanding shape memory effect (SME) with shape fixity (R_f) up to 100% and shape recovery (R_r) of 100% in first cycle. R_f is noted to be increasing up to third cycle and then fixed to 100% up to tenth cycle, while R_r shows a decreasing trend in subsequent cycle with a drop of 37% in tenth cycle. Moreover, it exhibits extremely high glass-transition temperature, T_g = 263.10 °C, degradation temperature, T_d = 520 °C, and storage modulus of 1600 MPa. Among existing high-performance (HP) and conventional shape memory polymers (SMPs), 3D-printed TPI exhibits superior performance. T_g of the TPI is found to be 66.52%, 107.16%, and 62.41%, higher than existing HP-SMPs, polyether ether ketone (T_g = 158 °C), polyamide (T_g = 127 °C), and polyether ketone ketone (T_g = 162 °C), respectively. This investigation reveals a novel characteristic, the SME, of 4D-printed TPI with ultra-high T_g and T_d, demonstrating suitability for self-deployable hinges, contributing to materials engineering and 4D printing.

The in situ WC-reinforced Ni60 laser cladding layer-assisted electromagnetic field is prepared on the H13 steel surface. The microstructure and phase of the cladding layer are analyzed by scanning electron microscope, energy disperse spectroscopy, and X-ray diffractometry, the hardness and wear resistance of the coating are tested by microhardness tester and ring-block friction and wear tester. The results indicate that more WC particles are generated with the increase in the magnetic field strength and current value, and many uniformly distributed eutectic carbides are formed in the coating, which makes the structure more uniform and dense. The average microhardness of the coating reaches 786.5HV when the electromagnetic intensity is 20 mT-9 A, and the wear amount after 90 min is 35.2 mg, which is 65.7% of the nonelectromagnetic-assisted WC/Ni60 coating and only 28.6% of the substrate, the wear resistance is obviously improved. The change in the structure and the improvement in microhardness and wear resistance are the result of the combined action of the directional Lorentz force generated by the electric field and the inductive Lorentz force generated by the magnetic field.

Surface-enhanced Raman spectroscopy (SERS) has a wide range of applications in molecular recognition, environmental pollutant detection, and other fields. However, the intensity and number of “hot spots” in 1D and 2D nanostructures are limited due to the scale-dependent localized plasmonic effect of nanostructures, making it difficult to increase the detection limit. Herein, a kind of 3D substrate called Au@Ag double-layer nanoarray (Au@Ag DLA) is prepared using rapid thermal annealing and chemical replacement methods. The energy-dispersive spectrometer spectra confirm the successful growth of AgNPs on the gold nanoarray (Au SLA) by showing no presence of the copper element, indicating complete replacement of the Cu film deposited on Au SLA by Ag atoms. The detection limit of malachite green in Au@Ag DLA is 10⁻⁸ mol L⁻¹, four and three orders of magnitude higher than that of Au SLA and AgNPs, respectively. This stronger SERS effect of Au@Ag DLA arises from the larger number of intense hot spots generated not only on the horizontal surface but also in the vertical direction. This finding provides a method for developing efficient and stable 3D SERS substrate, which can be utilized for the trace detection of water pollutants and pesticide residue.

The shift from traditional, single-component metals and alloys continues, and researchers are currently investigating alternative materials. This evolution has led to the creation of innovative materials, including hybrid metal-matrix composites. The present study aims to investigate the microstructural, surface morphological, and thermal properties of a novel Al7075/TiO₂/Kaoline hybrid metal-matrix composite prepared using high-energy ball milling and sintering methods. In this study, phases related to the composite components are formed depending on the milling time, no undesirable phase is formed, but the peak intensities decreas as the milling time increases. Particle size increases from 63 to 215 μm with increasing milling time. Increasing the kaoline reinforcement ratio and sintering temperature increases the microhardness from 62.27 ± 2 to 75.83 ± 2 HV, and reduces the friction coefficient from 0.82 ± 0.01 to 0.62 ± 0.01. The wear rate of the composite without kaoline addition is 2.1 (mm³ m⁻¹) × 10⁻³, while with 6 wt% kaoline addition, it decreases to 1.5 (mm³ m⁻¹) × 10⁻³. There are no cracks in the composite other than plastic deformation due to sintering and wear. Peaks indicating endothermic and exothermic reactions during continuous heating occurr in the 635–750 °C temperature range.