Phys.org July 23, 2024 The formation kinetics and nanoscale three-dimensional structure of topological defects are poorly understood. An international team of researchers (Switzerland, Japan, USA – Northwestern University, Cornell University, France, Germany, Austria) described the fabrication of a pair of topological defects in the volume of a single-diamond network templated into gold from a triblock terpolymer crystal. They resolved the three-dimensional structure of nearly 70,000 individual single-diamond unit cells with a spatial resolution of 11.2 nm, allowing analysis of the long-range order of the network. The defects observed morphologically resembled the comet and trefoil patterns of equal and opposite half-integer topological […]
Category Archives: Materials science
A new way to control the magnetic properties of rare earth elements
Phys.org July 19, 2024 Rare-earth elements with strong magneto-crystalline anisotropy (MCA) are important ingredients for magnetic devices. Control of their localized 4f magnetic moments and anisotropy is one major challenge in ultrafast spin physics. An international team of researchers (Germany, Czech Republic, France, Sweden) used time-resolved x-ray absorption and resonant inelastic scattering experiments to show that for terbium that 4f-electronic excitations out of the ground-state multiplet occurred after optical pumping. These excitations were driven by inelastic 5d-4f-electron scattering, altering the 4f-orbital state and consequently the MCA with important implications for magnetization dynamics in 4f-metals and more general for the excitation […]
A novel thermal insulation material for ultra-high temperature applications: Hierarchical porous high-entropy ceramics
Phys.org July 22, 2024 To meet the emerging demands for thermal protection materials is a critical challenge. Researchers in China developed a novel porous high-entropy carbide (PHEC) ceramic fabricated by a self-foaming method using commercially available metal chloride and furfuryl alcohol as the precursor. The PHEC ceramic was constructed by microspheres with a size of 2 µm, high porosity and an interconnected frame. The microspheres consisted of high-entropy carbide grains resulting in abundant interface and nanosized pores in the PHEC ceramic. It has outstanding compressive strength and exceptionally low thermal conductivity at room temperature. According to the researchers their work […]
Researchers zero in on the underlying mechanism that causes alloys to crack when exposed to hydrogen-rich environments
Phys.org July 19, 2024 Researchers at Texas A&M University conducted in situ tensile straining experiments to investigate the role of hydrogen and slip in crack initiation in nickel-based alloy 725. The experiments revealed no tendency for hydrogen to enhance localized slip and no necessity of slip for crack initiation. Using electrochemical charging introduced hydrogen into samples, melted extraction was used to measure hydrogen content. Image correlation analyzed localized plastic strains during in situ tensile tests. Cracks initiated both in regions with and without nearby localized slip. The fraction of cracks initiating with no nearby slip was greater at higher hydrogen […]
Scientists develop new AI method to create material ‘fingerprints’
Phys.org July 16, 2024 Understanding and interpreting dynamics of functional materials in situ is a challenge in physics and materials science due to the difficulty of experimentally probing materials at varied length and time scales. Although X-ray photon correlation spectroscopy (XPCS) is uniquely well-suited, spatial and temporal heterogeneity in material behavior can make interpretation of experimental XPCS data difficult. A team of engineers in the US (Argonne National Laboratory, University of Chicago) developed an unsupervised deep learning (DL) framework for automated classification of relaxation dynamics from experimental data without requiring any prior physical knowledge of the system. They demonstrated how […]
Can a computer chip have zero energy loss in 1.58 dimensions?
Phys.org July 1, 2024 Topological insulators are known to exist in one (wire), two (sheet) and three (cube) dimensions; all with different possible applications in electronic devices. An international team of researchers (the Netherlands, China, Sweden) discovered that topological insulators may also exist at 1.58 dimensions, and that these could be used for energy-efficient information processing. They demonstrated that topological edge and corner modes arise in fractals formed upon depositing thin layers of bismuth on an indium antimonide substrate. Their scanning tunnelling microscopy results and theoretical calculations revealed the appearance and stability of nearly zero-energy modes at the corners of […]
A chip-scale titanium-sapphire laser
Nanowerk June 26, 2024 Ti:sapphire lasers are unmatched in bandwidth and tuning range, yet their use is restricted because of their large size, cost and need for high optical pump powers. An international team of researchers (USA – Stanford University, Belgium) demonstrated a monocrystalline titanium:sapphire-on-insulator (Ti:SaOI) photonics platform that enabled dramatic miniaturization, cost reduction and scalability of Ti:sapphire technology. Through the fabrication of low-loss whispering-gallery-mode resonators, they realized a Ti:sapphire laser operating with an ultralow, sub-milliwatt lasing threshold; through orders-of-magnitude improvement in mode confinement in Ti:SaOI waveguides, they realized an integrated solid-state optical amplifier operating below 1 μm. They amplified distortion-free […]
Common plastics could passively cool and heat buildings with the seasons
Science Daily June 27, 2024 Vertical facades of buildings mostly see terrestrial features that become broadband-radiative heat sources in the summer and heat sinks in the winter. The resulting summertime terrestrial heat gain by buildings overwhelms their narrowband longwave infrared (LWIR) radiative cooling to space, while the wintertime terrestrial heat loss causes overcooling. A team of researchers in the US (Princeton University, Oak Ridge National Laboratory, UCLA, Arizona State University) showed that selective LWIR emitters on vertical building facades could exploit the differential transmittance of the atmosphere toward the sky and between terrestrial objects to achieve higher summertime cooling and […]
Inverse design method improves high-temperature performance of carbide coatings
Phys.org July 3, 2024 Researchers in China prepared the (Hf0.36Zr0.24Ti0.1Sc0.1Y0.1La0.1)C1-δ (HEC) coatings. The HEC possesses higher toughness with a higher Pugh’s ratio of 1.55 in comparison with HfC (1.30). The in-situ formed dense (Hf0.36Zr0.24Ti0.1Sc0.1Y0.1La0.1)O2-δ oxide scale during ablation benefits to improve the anti-ablation performance was attributed to its high structural adaptability with a lattice constant change not exceeding 0.19 % at 2000–2300 °C. According to the researchers the current investigation demonstrated the effectiveness of the inverse theoretical design, providing a novel optimization approach for ablation protection of high-entropy carbide coatings… read more. Open Access TECHNICAL ARTICLE
MIT researchers identify routes to stronger titanium alloys
MIT News July 2, 2024 Optimizing the properties of structural materials to involve a tradeoff between two key characteristics: strength and ductility. Mechanical properties of titanium alloys suffer from the lack of 〈c + a〉dislocations on pyramidal slip planes, failing homogeneous plastic strain accommodation. A team of researchers in the US (MIT, industry) demonstrated that such a dilemma may be overcome by meticulously tuning the c/a ratio, the simplest crystallographic parameter of the hexagonal close-packed lattice, through Sn alloying. Combining this lattice-scale design concept with a cross-rolling based polycrystal-scale design solution, they showed a facile route to bimodal (α + […]