Microstructure Evolution of AS41 Magnesium Alloy in ECAP

ECAP is a continuous multi-pass extrusion process that enables the specimen to obtain considerable cumulative deformation to refine the grain. In this paper, ECAP was used to deform AS41 magnesium alloy at 350°C, and the microstructure was observed and analyzed. The results show that the ECAP process has excellent effect on grain refinement and uniform microstructure. The grain size of AS41 decreases from 200μm to 20μm, and the microstructure is more uniform than that of as-cast sample. The reason is that the original grain is broken and refined under the action of shear force, and dynamic recrystallization occurs at the same time, resulting in small recrystallized grains. The Mg2Si particles were redistributed during ECAP and uniformly distributed in the crystal in rod shape.

High-Performance Passive Plasma Separation on OSTE Pillar Forest

Plasma separation is of high interest for lateral flow tests using whole blood as sample liquids. Here, we built a passive microfluidic device for plasma separation with high performance. This device was made by blood filtration membrane and off-stoichiometry thiol–ene (OSTE) pillar forest. OSTE pillar forest was fabricated by double replica moldings of a laser-cut polymethylmethacrylate (PMMA) mold, which has a uniform microstructure. This device utilized a filtration membrane to separate plasma from whole blood samples and used hydrophilic OSTE pillar forest as the capillary pump to propel the plasma. The device can be used to separate blood plasma with high purity for later use in lateral flow tests. The device can process 45 μL of whole blood in 72 s and achieves a plasma separation yield as high as 60.0%. The protein recovery rate of separated plasma is 85.5%, which is on par with state-of-the-art technologies. This device can be further developed into lateral flow tests for biomarker detection in whole blood.

Fabrication of Y2Ti2O7 Transparent Ceramic by Spark Plasma Sintering

Y2Ti2O7 transparent ceramic was fabricated by reactive sintering using spark plasma sintering at 1673 K for 2.7 ks. The sintered body exhibited a cubic pyrochlore structure and uniform microstructure with an average grain size of 2.9 μm. The transmittance reached 73% at a wavelength of 2000 nm after annealing at 1023 K for 21.6 ks.

Joining of Carbon Nanotube Fiber by the Meniscus-Confined Electrochemical Deposited Silver

To use carbon nanotube fibers (CNT) extensively in a wide range of electrical and electronic applications, an essential key step is to produce a low-resistance, high-strength and reliable connection between the CNT fibers and other live parts in the circuit. In this study, meniscus-confined electrochemical deposition (ECD) process with silver was proven to be a practical way of joining CNT fibers together head-to-head. The whole ECD process was stable. The shape of the joints was found to depend on the shape of the tips of the CNT fibers. The deposited silver exhibited a dense and uniform microstructure and it was tightly bound to the CNT fibers, with a distinct interface between them. In the ECD process, the original morphology of the CNT network was maintained. The lowest electrical resistance of the CNT fibers joints was measured to be 8.72[Formula: see text][Formula: see text], which is 45% lower than that of the original CNT fibers. The deposited joint sustained a fracture load of 7.5cN with an elongation of 0.4%.

THE DEFORMATION OF AZ31 MAGNESIUM ALLOY DURING WARM CONSTRAINED GROOVE PRESSING

A magnesium alloy AZ31 as plate of dimensions (60 x 60 x 3) mm has been constrained groove pressed (CGP) four deformation passes (16 pressings) at 250 oC by simulation and experiments. On the basis of the analysis of calculation results about the deformation distribution in the alloy AZ31 workpieces, the mechanism for its microstructure evolution during the severe plastic deformation (SPD) process was partly clarified. On the other hand, deformation heterogeneity distribution developed in the workpieces by applying CGP caused the evolution of a non-uniform microstructure. The TEM microstructure analysis results provided clear evidence that across the plate both the banded deformed microstructure where dislocation cell structure and/or partially or fully recovered polygonized subgrain microstructure are present. The recovering dynamic and local polygonization process contributes significantly to the formation of ultra-fine materials (UFG) microstructure.

Fabrication and Characterization of Gelatin/Zein Nanofiber Films Loading Perillaldehyde for the Preservation of Chilled Chicken

Perillaldehyde is a natural antibacterial agent extracted from perilla essential oil. In our methodology, five antibacterial nanofiber packaging films are prepared by loading different concentrations of perillaldehyde (P) into gelatin/zein (G/Z) polymers. Morphology observations show that the G/Z/P film had a good uniform microstructure and nano-diameter as the weight ratio of 5:1:0.02 (G/Z/P). Fourier transform infrared spectroscopy, and X-ray indicate that these three ingredients had good compatibility and strong interaction via hydrogen bonding. Water contact angle results show that the G/Z/P films gradually change from hydrophilic to hydrophobic with the increase of perillaldehyde. Thermal analysis indicates that the G/Z/P (5:1:0.02) film has good thermal stability. Antibacterial and storage analysis indicates that G/Z/P (5:1:0.02) film is effective to inactivate Staphylococcus aureus and Salmonella enteritidis, and obviously reduces the increasing rate of total bacteria counts and volatile basic nitrogen of chicken breasts. This study indicates that the G/Z/P (5:1:0.02) is a kind of potential antibacterial food packaging film.

Effect of Substrate Plate Heating on the Microstructure and Properties of Selective Laser Melted Al-20Si-5Fe-3Cu-1Mg Alloy

The Al-20Si-5Fe-3Cu-1Mg alloy was fabricated using selective laser melting (SLM). The microstructure and properties of the as-prepared SLM, post-treated SLM, and SLM with substrate plate heating are studied. The as-prepared SLM sample shows a non-uniform microstructure with four different phases: fcc-αAl, eutectic Al-Si, Al2MgSi, and δ-Al4FeSi2. With thermal treatment, the phases become coarser and the δ-Al4FeSi2 phase transforms partially to β-Al5FeSi. The sample produced with SLM substrate plate heating shows a relatively uniform microstructure without a distinct difference between hatch overlaps and track cores. Room temperature compression test results show that an as-prepared SLM sample reaches a maximum strength (862 MPa) compared to the heat-treated (524 MPa) and substrate plate heated samples (474 MPa) due to the presence of fine microstructure and the internal stresses. The reduction in strength of the sample produced with substrate plate heating is due to the coarsening of the microstructure, but the plastic deformation shows an improvement (20%). The present observations suggest that substrate plate heating can be effectively employed not only to minimize the internal stresses (by impacting the cooling rate of the process) but can also be used to modulate the mechanical properties in a controlled fashion.