Nanowerk July 13, 2023 Contrary to topological insulators, topological semimetals possess a nontrivial chiral anomaly that leads to negative magnetoresistance and host to both conductive bulk states and topological surface states with intriguing transport properties for spintronics. Researchers at the University of Minnesota fabricated highly ordered metallic Pt3Sn and Pt3SnxFe1-x thin films via sputtering technology. Systematic angular dependence (both in-plane and out-of-plane) study of magnetoresistance presented surprisingly robust quadratic and linear negative longitudinal magnetoresistance features for Pt3Sn and Pt3SnxFe1-x, respectively. They attributed the anomalous negative longitudinal magnetoresistance to the type-II Dirac semimetal phase (pristine Pt3Sn) and/or the formation of tunable […]
Category Archives: Materials science
Researchers achieve interdimensional superconductivity
Nanowerk July 19, 2023 Spatial disorder has been shown to drive two-dimensional (2D) superconductors to an insulating phase through a superconductor–insulator transition (SIT). Numerical calculations predict that with increasing disorder, emergent electronic granularity is expected in these materials—a phenomenon where superconducting (SC) domains on the scale of the material’s coherence length are embedded in an insulating matrix and coherently coupled by Josephson tunneling. An international team of researchers (USA – SLAC National Accelerator Laboratory, Colombia) has shown spatially resolved scanning tunneling spectroscopy (STS) measurements of the three-dimensional (3D) superconductor BaPb1−xBixO3 (BPBO), which surprisingly demonstrated three key signatures of emergent electronic […]
Physicists develop a metamaterial that can count
Phys.org July 3, 2023 Researchers in the Netherlands have designed irreversible metamaterials that count mechanical driving cycles and store the result into easily interpretable internal states. They extended the designs to aperiodic metamaterials that were sensitive to the order of different driving magnitudes and realized “lock and key” metamaterials that only reach a specific state for a given target driving sequence. The metamaterials were robust, scalable, and extendable, gave insight into the transient memories of complex media, and opened new routes towards smart sensing, soft robotics, and mechanical information processing. Video https://youtu.be/soO2OzbdRzU… read more. TECHNICAL ARTICLE
Scientists develop highly porous materials for electronic and photocatalytic applications
Phys.org July 3, 2023 Porous poly(aryl thioether)s offer stability and electronic tunability by robust sulfur-aryl conjugated architecture, but synthetic access is hindered due to limited control over the nucleophilic nature of sulfides and the air sensitivity of aromatic thiols. An international team of researchers (South Korea, Saudi Arabia) has developed a regioselective synthesis of highly porous poly(aryl thioether)s through polycondensation of perfluoroaromatic compounds with sodium sulfide. The temperature-dependent para-directing formation of thioether linkages led to a stepwise transition of the polymer extension into a network, thereby allowing fine control of the porosity and optical band gaps. The resulting porous organic […]
Surprise! Weaker bonds can make polymers stronger
MIT News June 22, 2023 Tough materials can sustain substantial subcritical damage without complete failure of the material, but trying to improve toughness can often lead to the degradation of other mechanical properties. Researchers at Duke University developed cyclobutane-based mechanophore cross-linkers that broke through force-triggered cycloreversion led to networks that were up to nine times as tough as conventional analogs. The response was attributed to a combination of long, strong primary polymer strands and cross-linker scission forces that were approximately fivefold smaller than control cross-linkers at the same timescales. According to the researchers the enhanced toughness comes without the hysteresis […]
Researchers develop an extreme environment-resistant nanopaper
Phys.org June 21, 23 Researchers in China developed a kind of nacre-inspired bacterial cellulose (BC)/synthetic mica (S-Mica) nanopaper with excellent mechanical and electrical insulating properties that has excellent tolerance to extreme conditions. The nanopaper exhibited excellent mechanical properties, including high tensile strength (375 MPa), outstanding foldability, and bending fatigue resistance. S-Mica arranged in layers endowed the nanopaper with remarkable dielectric strength (145.7 kV mm−1) and ultralong corona resistance life. The nanopaper was highly resistant to alternating high and low temperatures, UV light, and atomic oxygen… read more. TECHNICAL ARTICLE
Treatment creates steel alloys with superior strength and plasticity
Science Daily June 14, 2023 Nanostructured metallic materials with abundant high-angle grain boundaries exhibit high strength and good radiation resistance. While the nanoscale grains induce high strength, they also degrade tensile ductility. A team of researchers in the US (Purdue University, Sandia National Laboratory) showed that a gradient nanostructured ferritic steel exhibited simultaneous improvement in yield strength by 36% and uniform elongation by 50% compared to the homogenously structured counterpart. In situ tension studies coupled with electron backscattered diffraction analyses revealed intricate coordinated deformation mechanisms in the gradient structures. The outermost nanolaminate grains sustained a substantial plastic strain via a […]
Liquid metal sticks to surfaces without a binding agent
Science Daily June 9, 2023 Origami’s performance is limited by the properties of the constituent materials, including long-term bending, electrical, and thermal conductivity. Researchers in China reported a new method for directly adhering liquid metal onto non-wetting substrates on a large scale, allowing for the regulation of the mechanical and electrical properties of the enhanced paper by controlling the applied force during fabrication. The mechanism of adhesion between different liquid metals (eGaIn and BiInSn) and non-wetting substrates through force was explained. Multifunctional origami structures based on the enhanced paper could switch between several deformation modes and include a shape memory […]
Multifunctional self-healing liquid metal hydrogel developed for human-computer interaction
Phys.org June 8, 2023 Researchers in China used gallium indium alloy (EGaIn) to initiate the polymerization and simultaneously serve as flexible fillers to construct a super-stretchable and self-healing liquid metal/polyvinyl alcohol/p(acrylamide-co-octadecyl methacrylate) (liquid metal/PVA/P(AAm-co-SMA)) double network hydrogel (LM hydrogel). These together with the ionic coordination and hydrogen bonds between polymer networks (multiple physical cross-links) made LM hydrogel super-stretchable, tough, notch resistant, and self-healing. The LM hydrogel exhibited sensitive strain sensing behavior, allowing human–computer interaction to achieve motion recognition and health monitoring because of the photothermal effect and low infrared emissivity of EGaIn. The LM hydrogel showed potential in infrared camouflage. […]
New material transforms light, creating new possibilities for sensors
Phys.org June 12, 2023 Hybrid structures formed between organic molecules and inorganic quantum dots can accomplish unique photophysical transformations by taking advantage of their disparate properties. However ,the electronic coupling is typically weak, leading photoexcited charge carriers to spatially localize to the dot or to a molecule at its surface. A team of researchers in the US (University of Utah, University of Colorado, UC Riverside, UT Austin) has shown that by converting a chemical linker that covalently binds anthracene molecules to silicon quantum dots from a carbon–carbon single bond to a double bond, they accessed a strong coupling regime where […]