Microstructure and mechanical characteristics of an in-situ synthesis of AA7075/TiB2 metal matrix composite

In the present study, AA7075/TiB2 aluminium metal matrix composite (AMCs) was prepared by stir casting method using in-situ reactions of inorganic salts KBF4 and K2TiF6. In this process AA7075 alloy is reinforced with different weighted percentages of (5 %wt, 10 %wt, and 15 %wt) Titanium Diboride (TiB2) particles. X-ray Diffraction (XRD) investigation reveals the presence of TiB2 particles without any formation of the intermediate phase. An optical microscope was used to examine the microstructure, which revealed that the TiB2 particles are equally distributed and that grain size reduces as the weighted percentage of reinforcement particles increases. When the weighted percentage of TiB2 reinforcement particles increased, the microhardness and ultimate tensile strength of the AA7075/TiB2 AMCs increased. Furthermore, the ductile mode of failure of the tensile specimen has been observed by fractography analysis.

Thermal and morphological analysis of the interaction effect of different assist gases with gas-filled closed-cell aluminium foam during laser cutting process

Closed-cell aluminium foam, a porous structure, is effectively used for insulation, structural applications, packaging and filtering. Cutting of aluminium foam with the help of fibre laser is an efficient method due to the inherent advantages of fibre laser. Laser cutting of aluminium foam was carried out using a 2-kW fibre laser system for varying process parameters and different assist gas environments. Use of different foaming agents results in the generation of gas-filled pores. During the laser cutting process, the interaction of these gas-filled pores with assist gas results in in-situ reactions, generating different kerf quality. This interaction effect of foam cutting was reported using optical, metallurgical and thermal analysis. Thermal cycles were recorded to understand the occurrence of different in-situ reactions. From the temperature signal for different assist gases, oxygen showed the highest temperature, followed by nitrogen and argon. Argon assist gas gave minimum kerf width, while nitrogen assist gas produced minimum dross. Elemental and phase analysis showed the presence of new compounds and intermetallics in the cut section that stipulated the occurrence of in-situ reactions during the cutting process. The internal pore surface showed the presence of spatter in case of oxygen, while nitrogen and argon gas environment showed relatively less pore-clogging.

Giant Polymer Compartments for Confined Reactions

In nature, various specific reactions only occur in spatially controlled environments. Cell compartment and subcompartments act as the support required to preserve the bio-specificity and functionality of the biological content, by affording absolute segregation. Inspired by this natural perfect behavior, bottom-up approaches are the focus to develop artificial cell-like structures, detrimental for understanding relevant bioprocesses and interactions or to produce tailored solutions in the field of therapeutics and diagnostics. In this review, we discuss the benefits of constructing polymer-based single and multicompartments (capsules and giant unilamellar vesicles (GUVs)), equipped with biomolecules as to mimic cells. In this respect, we outline key examples of how such structures have been designed from scratch, namely starting from the application-oriented selection and synthesis of the amphiphilic block copolymer. We then present the state-of-the-art techniques for assembling the supramolecular structure while permitting the encapsulation of active compounds and the incorporation of specific ion channels (peptides/proteins), essential to support in situ reactions, e.g., to replicate intracellular signaling cascades. Finally, we briefly discuss important features that these compartments offer and how they could be applied to engineer the next generation of microreactors, therapeutic solutions, and cell models.

Effect of In-Situ Synthesized Boride Phases on the Impact Behavior of Iron-Based Composites Reinforced by B4C Particles

The objective of this study is to investigate the impact behavior of iron-based composites reinforced with boron carbide (B4C) particles and in-situ synthesized iron borides (Fe2B/FeB). The composite specimens (Fe/B4C) were fabricated by hot-pressing under a pressure of 250 MPa at 500 °C, and sintered at a temperature of 1000 °C. The effects of the reinforcement ratio on the formation of in-situ borides and impact behavior were investigated by means of different volume fractions of B4C inside the iron matrix: 0% (un-reinforced), 5%, 10%, 20%, and 30%. Drop-weight impact tests were performed by an instrumented Charpy impactor on reinforced and un-reinforced test specimens. The results of the impact tests were supported with microstructural and fractographical analysis. As a result of in-situ reactions between the Fe matrix and B4C particles, Fe2B phases were formed in the iron matrix. The iron borides, formed in the iron matrix during sintering, heavily affected the hardness and the morphology of the fractured surface. Due to the high amount of B4C (over 10%), porosity played a major role in decreasing the contact forces and fracture energy. The results showed that the in-situ synthesized iron boride phases affect the impact properties of the Fe/B4C composites.

Al3Ti/ADC12 Composite Synthesized by Ultrasonic Chemistry in Situ Reaction

Al3Ti/ADC12 composite was synthesized in situ using Al-fluoride potassium titanate (K2TiF6) as the reaction system and an ultrasonic assisted direct melt reaction. Results indicate ultrasonic chemistry reactions are both accelerated and more complete compared to traditional in situ reactions. Al3Ti reinforced particles with a regular shape and size of 1-2 μm were well distributed and as-cast microstructures of composites were superior. Composite particles under ultrasonic assistance were also refined to a greater extent. Tensile strength and elongation rate of the composites reached 255 MPa and 2.2%, an increase of 19.1% and 37.5% respectively to those without ultrasonic aid. Cleavage surface of the composite declined and the number of dimples increased while dimples became smaller and deeper, showing obvious ductile fracture.