Materials

Blow spinning is a low-cost and versatile method that permits the large-scale production of fibrous membranes. However, polysaccharides that show numerous merits such as biocompatibility and biodegradability often have a low spinnability due to their high chain rigidity and low ability to form sufficient entanglements. Here, we report the fabrication of polysaccharide micro-fibrous membranes from sodium alginate/polyethylene oxide solutions formulated in solvent mixtures of water and ethanol. The shear and extensional rheological responses of the solutions are characterized, and parameters including specific shear viscosity, reptation time, extensional relaxation time, and maximum stretch ratio are correlated with the concentrations of polymer, polyethylene oxide, and ethanol. It is found that flexible polyethylene oxide and poorer solvent ethanol can synergistically delay the chain relaxation during stretch and increase the stretchability of the solutions. A processability map of the solutions for blow spinning is constructed, enabling the fabrication of fibrous membranes with a fiber diameter of ~1 μm, tensile strength of 4.89 MPa, elongation at break of 15.24%, and Young’s modulus of 45.43 MPa. This study presents a new strategy to fabricate sodium alginate-based membranes, which should provide insights into the design of other polysaccharide membranes with specific functions and applications.

In this study, an analytical model was developed to evaluate the influence of laser powder bed fusion (LPBF) process parameters on process-induced porosity during the 3D printing of stainless steel 316L. First, the temperature distribution, governed by a moving point heat source model of the laser, was used to predict the melt pool geometry during the melting stage. This prediction was then refined to account for the formation of the solidified cap. By analyzing the interaction between melt pool size and other process parameters, such as hatch spacing and layer thickness, criteria were established to distinguish between porosity caused by lack of fusion, porosity due to keyhole formation, and defect-free samples. A series of experiments were conducted, and porosity was measured using micro-CT analysis. The results showed that the porosity predicted by the model remained within an acceptable error range compared with the experimental measurements, with errors ranging from 10.5% to 24.78% and a mean error of 16.48%, demonstrating the accuracy of the developed model.

In recent years, there has been an increasing interest in studying multi-component alloys. A bulk solution-treated Ti₅₀Ni₄₁Cu₇Co₂ SMA was prepared and investigated. The functional properties, including phase transformation temperature, shape memory effect, cyclic superelasticity, and elastocaloric response, were systematically evaluated. The alloy exhibited a M_s temperature of around 250 K, which is beneficial for applications at room temperature. Shape memory effect with a maximum recoverable strain of 6.21% was obtained under a biased stress of 300 MPa. The superelasticity rapidly became stable during the cyclic test, reducing irrecoverable strain from 2.8% to 0.01% by the 10th cycle. After 250th superelastic cycles, the alloy exhibited a stable recoverable strain of 1.3%, and a lower critical stress for transformation (270 MPa, down from 405 MPa). The elastocaloric cooling effect reached −4.9 K at the 50th cycle and stabilized at −4.3 K thereafter. With an increase in operating temperature, the elastocaloric effect diminished and disappeared above 383 K, and the SMA retained a notable recoverable strain of ~0.5% up to 443 K.