Immobilization of NPP evaporator bottom high salt-bearing liquid radioactive waste into struvite-based phosphate matrices.

The high salt-bearing liquid radioactive waste (evaporator bottoms, EB) makes up the most voluminous NPP waste and needs solidification. In the paper presented, we introduce a novel formation process study of the struvite-based phosphate matrices ((K, NH4)MgPO4·6H2O) and the developed phosphate matrix compositions for the solidification of high salt-bearing solutions. The solutions simulate the EB of nuclear power plants with pressurized water reactors (NPP PWR). The effect of the EB's composition and salt content on the matrices' mechanical strength was investigated. The cesium-selective nickel-potassium ferrocyanide sorbent or 10-20% of MgO over the reaction stoichiometry, introduced at the matrix synthesis stage, allowed the production of matrices with the average 137Сs leach rate of less than 10-3 g cm-2 day-1 and the mechanical strength over 5 MPa. The matrices obtained completely satisfied the cemented radioactive waste requirements and contained up to 17-17.5 wt% of salts, which was 1.7-2.5 times higher compared to the Portland cement-based matrices.

Engineering of Numerous Moiré Superlattices in Twisted Multilayer Graphene for Twistronics and Straintronics Applications.

Because of their unique atomic structure, 2D materials are able to create an up-to-date paradigm in fundamental science and technology on the way to engineering the band structure and electronic properties of materials on the nanoscale. One of the simplest methods along this path is the superposition of several 2D nanomaterials while simultaneously specifying the twist angle between adjacent layers (θ), which leads to the emergence of Moiré superlattices. The key challenge in 2D nanoelectronics is to obtain a nanomaterial with numerous Moiré superlattices in addition to a high carrier mobility in a stable and easy-to-fabricate material. Here, we demonstrate the possibility of synthesizing twisted multilayer graphene (tMLG) with a number of monolayers NL = 40-250 and predefined narrow ranges of θ = 3-8°, θ = 11-15°, and θ = 26-30°. A 2D nature of the electron transport is observed in the tMLG, and its carrier mobilities are close to those of twisted bilayer graphene (tBLG) (with θ = 30°) between h-BN layers. We demonstrate an undoubtful presence of numerous Moiré superlattices simultaneously throughout the entire tMLG thickness, while the periods of these superlattices are rather close to each other. This offers a challenge of producing a next generation of devices for nanoelectronics, twistronics, and neuromorphic computing for large data applications.

Magnetic levitational bioassembly of 3D tissue construct in space.

Magnetic levitational bioassembly of three-dimensional (3D) tissue constructs represents a rapidly emerging scaffold- and label-free approach and alternative conceptual advance in tissue engineering. The magnetic bioassembler has been designed, developed, and certified for life space research. To the best of our knowledge, 3D tissue constructs have been biofabricated for the first time in space under microgravity from tissue spheroids consisting of human chondrocytes. Bioassembly and sequential tissue spheroid fusion presented a good agreement with developed predictive mathematical models and computer simulations. Tissue constructs demonstrated good viability and advanced stages of tissue spheroid fusion process. Thus, our data strongly suggest that scaffold-free formative biofabrication using magnetic fields is a feasible alternative to traditional scaffold-based approaches, hinting a new perspective avenue of research that could significantly advance tissue engineering. Magnetic levitational bioassembly in space can also advance space life science and space regenerative medicine.

Fabrication and use of a nanoscale Hall probe for measurements of the magnetic field induced by MFM tips.

Extraordinary Hall effect probes with 160 nm × 160 nm working area were fabricated using photo- and electron-beam lithographic procedures with the aim of direct measurements of MFM cantilever tip magnetic properties. The magnetic field sensitivity of the probes was 35 Ω T(-1). Magnetic induction of the MFM cantilever tips coated by Co and SmCo films was measured with the probes. It was shown that the resolution of the probes was of the order of 10 nm.