Materials Letters最新文献

In this study, the microstructure evolution, mechanical properties and thermal conductivity of laser powder bed fused tungsten subjected to the subsequent hot isostatic pressing (HIP) processes with natural cooling (NC) and ultra-rapid quenching (URQ) were investigated. The results showed that the relative density was significantly improved after HIPping regardless of the cooling rates. The HIP-URQ treatment led to a near defect-free component with increased recrystallization and reduced dislocation density. The enhanced comprehensive mechanical properties, including the ultimate compressive strength of 1180 MPa without sacrificing microhardness was achieved for the HIP-URQ sample. Furthermore, the highest thermal conductivity of 168.6 W/(m·K) related to the densification behaviour and microstructure evolution during the HIP treatments was reported.

The P. syringae bacteria is one of the most relevant pathogens for agriculture due to the large number of agricultural species it infects. At this point, the formation of biofilms contributes to determining its virulence and fitness. In agriculture, the ZnO nanoparticles are recognized for their potential use as nanofertilizers and antimicrobial compounds. In this sense, this work aimed to study the effect of ZnO nanorods (ZnONRs) on biofilms and in the planktonic state of different pathovars of the plant pathogen P. syringae. In contrast with the literature, our results showed that the tested pathovars are highly resistant to shaped-rod ZnO with tiny sizes because they showed no inhibitory effect in mature biofilms exposed to high concentrations of up to 500 µg/mL of nanoparticles.

This paper aims to investigate the fatigue crack propagation behavior of quenching and partitioning 980 steel (as base metal) and its welded joint at low-temperature environments. The fatigue crack propagation tests are carried out at 25°C, −40°C and −80°C under R=0.1, 0.3 and 0.5. The results show that the fatigue crack propagation threshold value increases and fatigue crack propagation rate decrease of base metal, whereas welded joint behaved opposite results as the temperature decreases. The fatigue ductility to brittle transition temperature of base metal is lower than that of welded joint. Compared with the welded joint, the base metal has higher fatigue resistance.

Nowadays harmful bloom tides affect greatly the economy of coastal states. For this reason, the present communication reports on a practical method for synthesizing SiO₂ and γ-alumina nanospheres, immobilized by sonochemistry on low-density porous foams and perlite granules, as a solution to this problem. A biostatic AgNP effect was incorporated into both materials, achieving AgSi and AgAl. The green-tide inactivation was performed by using Tetraselmis suecica under aqueous conditions. AgAl/FWGS displayed the best inactivation efficiency performance (94 %). Additionally, foams have significant buoyancy and are easy to handle, being an option for T. suecica inactivation for their easy recovering.

This paper presents processing and characterization of hydrochar derived from bamboo via hydrothermal carbonization at 200 °C for 4 h followed by activation at 600 °C for 2 h. The hydrochar contains hierarchical pores. The BET surface area of the hydrochar activated by KOH reached 4.5506 m²/g. KOH enhanced pore and nanofiber formation. All the bamboo-derived hydrochars can effectively harvest solar energy to evaporate seawater. The KOH-activated one showed the best performance with the maximum evaporation rate of 3.057 kg/(m²∙h).

This work shows a new way to grow 1-D Silicon Nanowires (SiNWs) over pyramidal black silicon used as substrates. These nanostructures are grown by the plasma-assisted vapor–liquid-solid (VLS) as a bottom-up process, using tin thin films as a catalytic metal and dichlorosilane gas as a silicon precursor. SiNWs were obtained with diameters from 300-600 nm and 4–6 µm lengths on the black silicon surface. Due to the pyramid-shaped and porous nature of the black silicon surface, SiNWs form a complex mesh nanostructure. This network has a large surface area and exhibits intense and effective photoluminescence with a peak in the green spectrum, which is attributed to the quantum confinement effect that occurred in small nc-Si embedded inside SiNWs. These structural configurations hold significant promise for applications in optical biosensors, solar cells, and other prospective fields.

In this study, the influence of post-annealing at 800 °C and cryogenic heat treatment at −196 °C of as-print laser powder bed fusioned Ti64-ELI alloy on the microstructure and corrosion behavior is investigated and its performance was compared with that of as-cast Ti64-ELI alloy. The acicular martensitic phase of the as-print sample degraded into alpha and beta phase upon heat treatment. The Tafel curve was obtained after electrochemical corrosion analysis and it was observed that the as-print sample had a higher corrosion rate due to the increased martensitic phase content present in the sample. The degradation of the unstable martensitic(α’) phase and the increased presence of β-phase content after post processing (annealing and cryogenic treatment) significantly improved the corrosion resistance of as-print sample.

The dissolution reaction kinetics were determined by differential scanning calorimetry (DSC) analysis for Mg-0.6Gd (wt.%) in an as-cast condition and after processing by high-pressure torsion (HPT) at room temperature for 20 turns. For the as-cast condition, the dissolution temperature was in the range of 634–658 K with an activation energy of 135 ± 9 kJ/mol. After HPT, the range of dissolution temperature decreased to 601–633 K, with a lower activation energy of 118 ± 10 kJ/mol. In both conditions, the Avrami and growth exponents are around 1.5, which suggests that the dissolved precipitates exhibit polyhedron-like morphology and that the dissolution process is dominated by bulk dissolution with a constant rate controlled by diffusion.

In order to solve the electromagnetic pollution problem, NiCo-MOFs-74 material was used as the parent material, and the new NiCo/C composite was prepared by high temperature carbonization method. The results show that the wave absorbing properties of NiCo/C composites change significantly with the change of the molar ratio of Ni/Co. When the molar ratio of Ni/Co is 1:1, the absorption performance of Ni₁Co₁/C composite is the best at the frequency of 16.75 GHz, the best reflection loss at 2.5 mm thickness is −51.5 dB, and the effective absorption bandwidth is 3.39 GHz.

Biodegradable Mg-based scaffolds are regarded as potential bone tissue engineering materials for a promising approach to bone repair. In this work, the spherical/cubic hybrid pore-forming agents were introduced to prepare a porous Mg-based alloy scaffold by the negative salt pattern molding method. The porous Mg-Zn-Ca alloy scaffold containing spherical/cubic hybrid pores exhibited a porosity of about 68.60 % and a surface area ratio of about 7.88 cm²/cm³. The compressive elastic modulus was about 0.32 GPa and the compressive strength was about 4.22 MPa, close to cancellous bone. However, the rapid degradation of Mg alloy scaffold was inadaptive to orthopedic repair. Thus, a calcium phytate coating was prepared on the Mg-based scaffold for surface modification to retard rapid corrosion.