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Attempts to carry out intramolecular annulation of 9,10‐diarylbenzo[h]quinolines and 9,10‐di(hetero)arylphenanthrenes to aromatics with expanded π‐conjugated systems by using different methods are described. The starting compounds (9,10‐diarylbenzo[h]quinolines and 9,10‐di(hetero)arylphenanthrenes) were prepared by C−C bond activation in 1‐azabiphenylene or biphenylene followed by insertion of internal alkynes. Interestingly, unlike in purely carbon‐based aromatics, the course of the annulation turned out to be highly dependent on the structure of maternal compounds. In a handful of cases were obtained the expected or desired products. In others, unexpected rearrangements of the basic molecular frameworks were observed. [ABSTRACT FROM AUTHOR]

This work reports a biomimetic synthesis of polyarylated fluorene derivatives. The molecules are formed via intramolecular electrophilic aromatic substitution, resembling a cyclization leading towards the natural selaginpulvilins from selaginellins. The scope of the reaction was investigated, and the products were obtained in 60–95 % yields. Some of the compounds decompose to a stable radical. We investigated the nature and the origin of the radical using experimental methods, including EPR or electrochemical measurements, as well as theoretical methods, such as DFT calculations. Based on our observations, we hypothesize, that phenoxy radicals are formed in the first instance, which however undergo internal rearrangement to thermodynamically more stable carbon‐centered radicals. The preliminary data also show the cytotoxic properties of some of the molecules. [ABSTRACT FROM AUTHOR]

Austenitic stainless steels are promising materials for next generation nuclear reactors due to their excellent mechanical properties and reasonable corrosion resistance compared to ferritic and ferritic-martensitic steels. However, they suffer from lower strength and void swelling resistance. Oxide dispersion strengthening (ODS) addresses these issues by incorporating nano-sized oxides, which pin dislocation motion and prevent grain coarsening, thus enhancing mechanical strength and creep resistance at high temperatures. Additionally, the matrix-oxide interfaces act as sinks for radiation-induced defects, improving swelling resistance. In this study the preparation of oxide dispersion-strengthened austenitic steel 316L involved mechanical alloying of the steel powder with Y2O3. Elemental Y was also introduced to dissolve within the Fe matrix as an alternative method. These powder precursors were then compacted using Spark Plasma Sintering (SPS) and analysed for their microstructure. The mechanical properties of the resulting compacts were assessed, revealing an initial formation of chromium-containing carbides, likely due to carbon diffusion from the graphite tools used. Both Y2O3 and Y were successfully incorporated into a solid solution during mechanical alloying, with precipitation occurring during compaction. The mechanical properties varied based on chemical composition and specific SPS conditions. Homogeneously distributed Y2O3 particles were successfully achieved through this powder metallurgy process. Future research will aim to optimize SPS conditions to prevent carbide formation. [ABSTRACT FROM AUTHOR]

Zinc alloys are extensively researched due to their potential as promising materials for biodegradable medical devices. This is primarily because of their remarkable biocompatibility and reasonable corrosion rate, which prevents the formation of toxic byproducts and hydrogen release. However, they often exhibit suboptimal mechanical, corrosion, and biological properties, limiting their applications. To address the limitations of zinc alloys, we developed a Zn-1Mg-1Si composite alloy, incorporating biologically compatible elements to potentially strengthen the zinc matrix. Utilizing powder metallurgy techniques, including mechanical alloying, spark plasma sintering, and extrusion, we produced alloys with uniquely fine-grained microstructures. Our systematic study demonstrated the possibility of achieving a homogeneous microstructure, enhanced by the intermetallic phase Mg2Zn11 and Si particles, resulting in high tensile strength exceeding 400 MPa and hardness over 130 HV1. Furthermore, the selected chemical compositions and processing methods led to slightly reduced wear during tribology testing and corrosion rates, along with more uniform corrosion behavior in the simulated human environment compared to pure metal. [ABSTRACT FROM AUTHOR]

The enhancement of mechanical properties in traditional materials can be achieved by introducing ultrafine oxide particles, which restrict dislocation movement and thereby enhance strength. This method is particularly applicable to austenitic steels, enhancing their strength and resistance to high temperatures. In our research, we fabricated oxide dispersion-strengthened austenitic stainless steel 316L by mechanically alloying steel powder with Y2O3. Following this, we consolidated the powder precursors using Spark Plasma Sintering (SPS). We then analyzed the microstructure of the resulting compacts and assessed their mechanical properties. Preliminary results revealed the formation of chromium-containing carbides, likely due to minor carbon diffusion from the graphite tools used during SPS. The mechanical alloying process successfully incorporated Y2O3 particles into the steel matrix. Variations in mechanical properties were observed, dependent on the chemical composition of materials and consolidation conditions. Powder metallurgy enabled the production of materials with a uniform distribution of Y2O3 particles, however the carbide content is not desirable due to the corrosion behavior. This work was supported by the Czech Science Foundation, project no. 22-04227L. [ABSTRACT FROM AUTHOR]