Materials Today Advances最新文献

The non-equiatomic FeNiCoAlTaB high-entropy alloy exhibits outstanding quasi-static mechanical properties. Here, we investigate the microstructural evolution and mechanical response of this alloy subjected to dynamic loading, which has not been done before. A novel strategy combining extensive microbanding and martensitic transformation improves the resistance to the plastic instability by deterring the formation of adiabatic shear bands, that only occur beyond a critical shear strain larger than 4. The aged alloy, with grain sizes up to 400 μm, exhibits a dynamic yield stress over 1300 MPa with good deformability in this regime. This investigation sheds light on potential strategies for the enhancement of dynamic mechanical properties of structural materials through the use of a stress-induced martensitic transformation.

Three major complications often occur after osteosarcoma resection: large bone defects, infectious wounds, and tumor recurrence. In addition to conventional internal fixation and auto- or allografts, multifunctional supportive treatments are needed for limb reconstruction after tumor removal. With inspiration from the "organic-inorganic" hybrid concept, we developed a freestanding polyelectrolyte membrane (PEM) using a layer-by-layer (LBL) deposition of quaternized chitosan (QCS) and hyaluronic acid (HA), and with copper-doped laponite (CuLAP) intercalation. The CuLAP demonstrated photothermal conversion capabilities under near-infrared (NIR) light irradiation, and displayed glutathione (GSH)-depleted Fenton-like catalytic activity. The further engineered PEM possesses a "brick and mortar" structure with enhanced surface roughness and stiffness. The fusion of CuLAP-mediated GSH-depleted chemodynamic treatment (CDT) and moderate photothermal therapy (PTT) facilitated tumor ablation and bactericidal effects. Moreover, the continuous release of copper ions and silicates aided angiogenesis and osteogenesis, supporting the regeneration of both soft (skin) and hard (bone) tissues. This all-in-one platform offers a promising clinical tool for assisting tissue reconstruction after osteosarcoma resection.

This work investigates the influence of heat treatments on a pseudo-binary Ti₃₀Zr₁₀Hf₁₀Ni₃₅Cu₁₅ high-entropy shape memory alloy. Heat treatments on the alloy resulted in the formation of second phases and thus were able to adjust its transformation temperatures. This phenomenon results from the formation of H-phase and (Zr,Hf)₇Cu₁₀ phase during low-temperature and high-temperature aging, respectively. The superelasticity of solution-treated, 500 °C-aged and 700 °C-aged samples was tested under compression, and all samples exhibited nearly 5 % recoverable strain and 15 °C elastocaloric cooling capacity. Further cyclic compression tests confirmed their stability, with up to 75 % of the initial cooling capacity retained after 5000 compression cycles. Due to its high yield strength, the Ti₃₀Zr₁₀Hf₁₀Ni₃₅Cu₁₅ high-entropy shape memory alloy showed great superelasticity and elastocaloric performance at various testing temperatures. Furthermore, with heat treatments, the austenitic transformation finishing temperature (A_f) of the alloy was tunable to between −10 °C (furnace-cooled) and 60 °C (700 °C-aged) with promising functional performance. These features expand the application range of TiZrHfNiCu high-entropy shape memory alloys as potential superelastic and elastocaloric materials.

We report a novel electro-nano-pulsing (ENP) processing method to achieve localized engineering of grain boundary (GB) morphology in polycrystalline metallic materials. ENP is extraordinarily capable of generating intense nanopulse electric current with a current density greater than a few to several hundreds of 10¹⁰A/m² and a pulse duration on the order of a few 100ns. Such a level of current density is ∼3–5 magnitudes higher than that is usually achieved during the Spark Plasma Sintering process. Using the Nichrome-80 superalloy as a model material, we observed a variety of GB roughening phenomena at multiple length scales, resulting in the generation of diverse forms of atomistic facets, nanoscale serrations, and nanoscale step-like GB morphologies after the ENP processing. We think that the excessive GB heat localization and electron wind force or stress are the main factors contributing to the GB morphological changes during the ENP processing. The ENP processing provides a new unique grain boundary engineering strategy to manipulate the GBs with the changes localized at the GB region, without altering its adjacent grains.

With the increase in studies on high-entropy alloys and their impressive structural properties, the preparation processes and applications of high-entropy alloys have become a popular research topic in metallic materials. In this paper, the preparation of FeCrNiCoMnSi_0.1 high-entropy alloy coatings was carried out by the follow-welding high-frequency power ultrasonic impact composite TIG arc melting process, the effects of different power ultrasonic impacts on the microstructure and properties of the coatings are investigated. The results showed that the average grain size is reduced by 74 % (from 278 μm to 72 μm), the average microhardness is increased by 41 % from 568 HV₁ to 807 HV₁, the abrasion resistance is improved by 68 % under the effect of ultrasonic impact. The ultrasonic impact treatment process can effectively refine the microstructure of the coatings and improve the strength of grain boundaries. The corrosion resistance of the coating in 3.5 wt% NaCl solution is enhanced by 65 %, the corrosion type was changed from intergranular corrosion to uniform corrosion. This is mainly caused by the ultrasonic impact treatment which suppresses the elemental segregation of Cr and Mn and improves the grain boundary strength.

The strategy of rare-earth elements addition into Mg alloys has been successfully developed and applied to enhance the mechanical performance and corrosion resistance of Mg alloys. Although this strategy has also been applied to enhance their high-temperature oxidation resistance, the mechanistic understanding of the beneficial effects remains elusive. Here, the oxidation of Mg–4Nd and Mg-4Nd–1Y alloys in Ar–20%O₂ at 500 °C was studied and compared. It was found that even though a continuous layer of Nd₂O₃ did not form, the Nd addition could still enhance the oxidation tolerance of Mg–4Nd alloy by facilitating the generation of a more continuous and intact oxide scale and working as oxygen sinks to delay the violent oxidation of Mg. The formation of a continuous Y₂O₃ layer on Mg-4Nd–1Y alloy suggests that Y was more capable of facilitating the external oxidation due to its much faster diffusion rate in Mg matrix than that of Nd. However, the Nd addition could decrease the critical content of Y necessary for the oxidation transition from internal to external because of the synergistic effect of the Nd and Y addition. The dissolution of the thermal unstable Mg₁₂Nd precipitates resulted in a localized increase of Nd content, accelerating the oxidation by increasing the preferential oxidation of Nd. Hence, in the design of oxidation-resistant Mg alloys, the addition of RE elements with faster diffusion rate and the addition of multiple alloy elements are preferred. In addition, the number of thermal unstable precipitates needs to be strictly controlled.

Antibacterial properties are critical for implants, while general pure titanium implants are bioinert. Adding nano Ag to metals is an effective strategy to obtain antibacterial properties. However, the comprehensive properties of Ti–Ag alloy prepared by traditional methods are not satisfactory. In this paper, Ti–5Ag alloy with an antibacterial rate close to 100 % was synthesized in situ by laser powder bed fusion (LPBF), and its microstructure and properties were studied systematically. Phase analysis demonstrated the existence of Ti₂Ag which played an important role in gaining excellent antibacterial properties. Benefiting from in situ laser alloying, the elements were homogeneously distributed, which endowed the Ti–5Ag alloy with excellent mechanical properties and corrosion resistance. The tensile strength and elongation reached 716 MPa and 33.51 %, respectively. Furthermore, through the design of triply periodic minimal surface (TPMS) structures, mechanical properties matching human bone were obtained. Based on LPBF-printed Ti–5Ag alloy and TPMS structures, this paper provides a feasible method for the manufacturing of bone implants with excellent comprehensive properties.

Mycoplasma contamination in cell/tissue cultures significantly affects cell characteristics, susceptibility to infectious pathogens, and drug reactions without obvious morphological changes and noticeable changes in cell growth rates. Although the technology for screening mycoplasma is essential, conventional technologies have limitations in the selection of a quick and easy manner. Here, we introduce an innovative screening system for mycoplasma based on electrochemical methods. In the electrochemical screening, a newly designed electrode, consisting of a sandwich-DNA hybridization for high selectivity and a nano-amplifier to improve the sensitivity, has implemented a realistic screening system by presenting detection capability at extremely low (ng/μL) levels and detection potential in real samples. Therefore, this system offers rapid screening, data accuracy, temporal effectiveness, and affordable-and-portable installation, enabling timely elimination of Mycoplasma contamination and facilitating progress in biomedical and pharmaceutical research.

Emerging technologies such as neuromorphic computing and nonvolatile memories based on floating gate field-effect transistors (FETs) hold promise for addressing a wide range of artificial intelligence tasks. For example, neuromorphic computing seeks to emulate the human brain's functionality and employs a device that mimics the role of a synapse in the brain. However, achieving a high current ON/OFF ratio for the program and erase states of nonvolatile memory and neuromorphic computing device with a metal gate is necessary. This study demonstrates a multi-functional device based on heterostructures of transition metal dichalcogenides (TMDCs) with a metal floating gate. Five different channel materials (SnS₂, WSe₂, MoS₂, WS₂, and MoTe₂) were employed, and hexagonal boron nitride (h-BN) was used as a tunneling layer. The study found that n-type SnS₂ exhibits high endurance (15,000 cycles), good retention (2.4 × 10⁵ s), and the highest current ON/OFF ratio (∼2.58 × 10⁸) among the materials for the program and erase states. Moreover, the SnS₂ device exhibits synaptic behavior and offers highly stable operation at room temperature. Furthermore, the device shows high linearity in both potentiation and depression, with good retention time and repeatable results with low cycle-to-cycle variations. Additionally, the study used an artificial neural network (ANN) for MNIST simulation of image recognition and achieved the highest accuracy of ∼92 % based on the SnS₂ synaptic device experimental results. These findings pave the way for developing nonvolatile memory devices and their applications in brain-inspired neuromorphic computing and artificial intelligence systems.

Controlled immune response, enhanced osteogenesis, and antibacterial effect are essential for successful implanted biomaterials in the long-term. However, the previous research only considers one of the above-mentioned materials’ properties, and the potential synergetic effects are still unknown. Inspired by the mussel adhesion-mediated ions-coordinated strategy, a multifunctional coating integrated with bioactive Sr²⁺ and antibacterial Cu²⁺ was fabricated the multifunctional PEEK implants (PEEK-PDA-Sr/Cu). Compared to the uncoating PEEK, the PEEK implants with a multifunctional coating can regulate the M1 subtypes of macrophages to M2 subtypes due to the presence of Sr²⁺, which further promote the osteogenic differentiation of BMSCs. Even under the bacterial infection environment, the PEEK implants with a multifunctional coating can still enhance the osseointegration of bone implants due to the antibacterial properties of Cu²⁺. Taken together, PEEK implants with a multifunctional coating can provide an osteogenic immune microenvironment with enhanced osteogenesis and antibacterial property, which is essential for successful implantation in the long-term.