Sulfonimide-Based Dendrimers: Progress in Synthesis, Characterization, and Potential Applications

There are more than 50 families of dendrimers, and some of which, such as polyamidoamine PAMAM, are well studied, and some are just starting to attract the attention of researchers. One promising type of dendrimers is sulfonimide-based dendrimers (SBDs). To date, SBDs are used in organic synthesis as starting reagents for the convergent synthesis of higher generations dendrimers, in materials science as alternative electrolyte solutions for fuel cells, and in medicinal chemistry as potential substances for drug transfer procedures. Despite the fact that most dendrimers are amorphous substances among the SBDs, several structures are distinguished that are prone to the formation of crystalline solids with melting points in the range of 120–250 °C. Similar to those of other dendrimers, the chemical and physical properties of SBDs depend on their outer shell, which is formed by functional groups. To date, SBDs decorated with end groups such as naphthyl, nitro, methyl, and methoxy have been successfully synthesized, and each of these groups gives the dendrimers specific properties. Analysis of the structure of SBD, their synthesis methods, and applications currently available in the literature reveals that these dendrimers have not yet been fully explored

Very High Cycle Fatigue Behavior of Additively Manufactured 316L Stainless Steel

The present paper is focused on an experimental study of the damage-to-failure mechanism of additively manufactured 316L stainless steel specimens subjected to very high cycle fatigue (VHCF) loading. Ultrasonic axial tension-compression tests were carried out on specimens for up to 109 cycles, and fracture surface analysis was performed. A fine granular area (FGA) surrounding internal defects was observed and formed a “fish-eye” fracture type. Nonmetallic inclusions and the lack of fusion within the fracture surfaces that were observed with SEM were assumed to be sources of damage initiation and growth of the FGAs. The characteristic diameter of the FGAs was ≈500 μm on the fracture surface and were induced by nonmetallic inclusions; this characteristic diameter was the same as that for the fracture surface induced by a lack of fusion. Fracture surfaces corresponding to the high cycle fatigue (HCF) regime were discussed as well to emphasize damage features related to the VHCF regime

Mechanical Behavior of a Medium-Entropy Fe₆₅(CoNi)₂₅Cr_9.5C_0.5 Alloy Produced by Selective Laser Melting

Specimens of a medium-entropy Fe65(CoNi)25Cr9.5C0.5 (in at.%) alloy were produced using additive manufacturing (selective laser melting, SLM). The selected parameters of SLM resulted in a very high density in the specimens with a residual porosity of less than 0.5%. The structure and mechanical behavior of the alloy were studied under tension at room and cryogenic temperatures. The microstructure of the alloy produced by SLM comprised an elongated substructure, inside which cells with a size of ~300 nm were observed. The as-produced alloy demonstrated high yield strength and ultimate tensile strength (YS = 680 MPa; UTS = 1800 MPa) along with good ductility (tensile elongation = 26%) at a cryogenic temperature (77 K) that was associated with the development of transformation-induced plasticity (TRIP) effect. At room temperature, the TRIP effect was less pronounced. Consequently, the alloy demonstrated lower strain hardening and a YS/UTS of 560/640 MPa. The deformation mechanisms of the alloy are discussed

Anisotropy of Mechanical Properties and Residual Stress in Additively Manufactured 316L Specimens

In the presented study, LPBF 316L stainless steel tensile specimens were manufactured in three different orientations for the analysis of anisotropy. The first set of specimens was built vertically on the build platform, and two other sets were oriented horizontally perpendicular to each other. Tensile test results show that mean Young’s modulus of vertically built specimens is significantly less then horizontal ones (158.7 GPa versus 198 GPa), as well as yield strength and elongation. A role of residual stress in a deviation of tensile loading diagrams is investigated as a possible explanation. Simulation of the build process on the basis of ABAQUS FEA software was used to predict residual stress in 316L cylindrical specimens. Virtual tensile test results show that residual stress affects the initial stage of the loading curve with a tendency to reduce apparent Young’s modulus, measured according to standard mechanical test methods

Chemical Space Mapping for Multicomponent Gas Mixtures

In our manuscript, we present our protocol for data processing to mitigate the effects of interfering analytes on the identification of the chemical species detected by sensors. Considering NO2 and CO2, we designed electrochemical sensors whose response yielded the cyclic voltammetry data that we analyzed to classify single-species components and their mixtures using a data-driven approach to generate a chemical space where their mixtures can be deconvoluted.<br /

Design and Fabrication of Complex-Shaped Ceramic Bone Implants via 3D Printing Based on Laser Stereolithography

3D printing allows the fabrication of ceramic implants, making a personalized approach to patients&rsquo; treatment a reality. In this work, we have tested the applicability of the Function Representation (FRep) method for geometric simulation of implants with complex cellular microstructure. For this study, we have built several parametric 3D models of 4 mm diameter cylindrical bone implant specimens of four different types of cellular structure. The 9.5 mm long implants are designed to fill hole defects in the trabecular bone. Specimens of designed ceramic implants were fabricated at a Ceramaker 900 stereolithographic 3D printer, using a commercial 3D Mix alumina (Al2O3) ceramic paste. Then, a single-axis compression test was performed on fabricated specimens. According to the test results, the maximum load for tested specimens constituted from 93.0 to 817.5 N, depending on the size of the unit cell and the thickness of the ribs. This demonstrates the possibility of fabricating implants for a wide range of loads, making the choice of the right structure for each patient much easier

Effect of Glass Filler Geometry on the Mechanical and Optical Properties of Highly Transparent Polymer Composite

In this work, we studied the influence of the geometry and degree of filling of glass dispersed particles on the optical and mechanical properties of flexible high-transmission composites, based on thermoplastic polyurethane. Glass spheres, glass flake and milling glass fiber were used as fillers. Studies of mechanical properties have shown that the introduction of any filler leads to a decrease in tensile strength and an increase in the elastic modulus of the composite material, however, with the introduction of glass flakes and milling glass fiber, a significant increase in the yield strength of the material is observed. The optical properties of composites with glass spheres decrease exponentially with an increase in the volume fraction of the filler. With an increase in the concentration of glass flakes and milling glass fiber to 10 vol.%, a sharp decrease in transmission is observed. With a further increase in concentration, the orientation of the filler along the film occurs, due to which the transmission in the visible range increases to values close to those of a pure polymer