Phys.org March 14, 2024 MXenes are a family of 2D materials typically formed by etching the A element from a parent MAX phase. Computational screening for other 3D precursors suitable for such exfoliation is challenging because of the intricate chemical processes involved. Researchers in Sweden proposed a theoretical approach for predicting 2D materials formed through chemical exfoliation under acidic conditions by identifying 3D materials amenable for selective etching. From a dataset of 66,643 3D materials, they identified 119 potentially exfoliable candidates, within several materials families. To corroborate the method, they chose a material distinctly different from MAX phases, in terms […]
Category Archives: Materials science
Researchers achieve >99% photoluminescence quantum yield in metal nanoclusters
Phys.org March 18, 2024 Metal nanoclusters have emerged as NIR–emissive materials, but their room-temperature photoluminescence quantum yield (PLQY), especially in solution, is often low. Researchers in China studied the photophysics of Au22(tBuPhC≡C)18 (Au22) and its alloy counterpart Au16Cu6(tBuPhC≡C)18 (Au16Cu6) (where tBu is tert-butyl and Ph is phenyl) and found that copper doping suppressed the nonradiative decay and promoted intersystem crossing rate ~300-fold higher. According to the researchers their approach could enable the development of highly emissive metal cluster materials… read more. TECHNICAL ARTICLE
Researchers develop novel ‘super-tetragonal’ sacrificial layer for freestanding oxide membranes
Phys.org March 18, 2024 Freestanding oxide membranes have a variety of interesting applications, but pulling these materials off the substrate after synthesis can be challenging. An international team of researchers (China, Austria) has developed a water-soluble sacrificial layer, “super-tetragonal” Sr4Al2O7 (SAOT). The low-symmetric crystal structure enabled a superior capability to sustain epitaxial strain, allowing for broad tunability in lattice constants resulting in structural coherency and defect-free interface in perovskite ABO3/SAOT heterostructures effectively restraining crack formation during the water release of freestanding oxide membranes. For a variety of nonferroelectric oxide membranes, the crack-free areas can span up to a millimeter in […]
Researchers discover new yttrium-hydrogen compounds with implications for high-pressure superconductivity
Phys.org March 14, 2024 An international team of researchers (Germany, UK, USA – University of Chicago) used synchrotron single-crystal x-ray diffraction (SCXRD) and found (two YH3 phases) and five previously unknown yttrium hydrides. These were synthesized in diamond anvil cells by laser heating yttrium with hydrogen-rich precursors—ammonia borane or paraffin oil. The arrangements of yttrium atoms in the crystal structures of new phases were determined based on SCXRD, and the hydrogen content estimations based on empirical relations and ab initio calculations revealed the following compounds: Y3H11, Y2H9, Y4H23, Y13H75, and Y4H25. They also uncovered a carbide and two yttrium allotropes. […]
A 3D view into chaos: Researchers visualize temperature-driven turbulence in liquid metal for the first time
Phys.org March 11, 2024 Researchers in Germany conducted an experiment inside a cylinder filled with the ternary alloy GaInSn focusing on the manifestation and dynamics of the large-scale circulation (LSC) in turbulent liquid metal convection. The large-scale flow structures were classified and characterized at Rayleigh numbers by means enabling the full reconstruction of the three-dimensional flow structures in the entire convection cell. They identified the dominating modes of the turbulent convection. The analysis revealed that a single-roll structure of the LSC alternates in short succession with double-roll structures or a three-roll structure. This was accompanied by dramatic fluctuations of the […]
Materials research explores design rules and synthesis of quantum memory candidates
Phys.org March 11, 2024 Stoichiometric Eu3+ compounds have recently shown promise for building dense, optically addressable quantum memory as the cations’ long nuclear spin coherence times and shielded 4f electron optical transitions provide reliable memory platforms but finding rare linewidth behavior within a wide range of potential chemical spaces remains difficult. Researchers at the University of Illinois, Urbana─Champaign, have found density functional theory (DFT) procedures that reliably reproduce known phase diagrams and correctly predict two experimentally realized quantum memory candidates. They synthesized the double perovskite halide Cs2NaEuF6 which is an air-stable compound with a calculated band gap of 5.0 eV […]
New research on tungsten unlocks potential for improving fusion materials
Phys.org March 13, 2024 Understanding phonon scattering has remained challenging and requires detailed information on interactions between phonons and electrons. An international team of researchers (USA – SLAC National Accelerator Laboratory, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, Sweden, Italy) used an ultrafast electron diffuse scattering technique to resolve the nonequilibrium phonon dynamics in femtosecond–laser-excited tungsten in both time and momentum. They determined transient populations of phonon modes which show strong momentum dependence initiated by electron-phonon coupling. For phonons near Brillouin zone border, they observed a transient rise in their population on a timescale driven by the strong electron-phonon […]
Preventing magnet meltdowns before they can start
Science Daily March 11, 2024 Unlike conventional magnets where a normal zone expands typically quickly, and the stored energy is dissipated across a large volume of the windings, a normal zone in a High-temperature superconductor (HTS) magnet propagates slowly and, thus, can heat up quickly to high temperatures destroying the conductor. At the same time, growing experimental evidence suggests that HTS conductors can operate in a stable dissipative flux flow regime for a substantial range of operational currents before entering an irreversible thermal runaway. Researchers at Lawrence Berkeley National Laboratory proposed a simple criterion for the thermal runaway in HTS […]
You don’t need glue to hold these materials together—just electricity
Phys.org March 13, 2024 Researchers at the University of Maryland discovered that hard, electrical conductors (e.g., metals or graphite) could be adhered to soft, aqueous materials (e.g., hydrogels, fruit, or animal tissue) by a low DC electric field. They applied 5 V DC to graphite slabs spanning a tall cylindrical gel of acrylamide which resulted in a strong adhesion between the anode (+) and the gel in about 3 min. This adhesion lasted after the field was removed. They called it hard–soft electroadhesion or EA[HS]. Depending on the material, adhesion occurred at the anode (+), cathode (−), or both electrodes. […]
Better neutron mirrors can reveal the inner secrets of matter
Science Daily February 29, 2024 The state-of-the-art multilayer polarizing neutron optics has limitations, particularly low specular reflectivity and polarization at higher scattering vectors/angles, and the requirement of high external magnetic fields to saturate the polarizer magnetization. An international team of researchers (Sweden, Iceland, Switzerland, Germany) showed that, by incorporating 11B4C into Fe/Si multilayers, amorphization and smooth interfaces could be achieved, yielding higher neutron reflectivity, less diffuse scattering, and higher polarization. Magnetic coercivity was eliminated, and magnetic saturation could be reached at low external fields. According to the researchers this approach offered prospects for substantial improvement in polarizing neutron optics with […]