Nanowerk April 21, 2021 Researchers at MIT performed an experimental-theoretical investigation of the electrical conductivity and resistive heating of highly heterogeneous nanocarbon–cement-based composites (pastes and mortars). Even a small voltage — as low as 5 volts — could increase the surface temperatures of their samples (approximately 5 cm3 in size) up to 41 degrees Celsius (around 100 degrees Fahrenheit). They found that electrical conductivity is determined by the electric tortuosity of a “volumetric wiring” permeating a highly heterogeneous matrix from percolation to saturation. They showed that the electric energy dissipation at the origin of the Joule heating originates from spatial […]
Tag Archives: Materials science
Inspired by nature, the research to develop a new load-bearing material
Phys.org April 22, 2021 Researchers in the UK developed a method to fabricate interconnected macro-porous elastomers based on sintering poly(methyl methacrylate) beads. The porous elastomer imparted structural support and resilience to its composite with an infused-grafted hydrogel. The composite exhibited a load-bearing behavior that was 14–19 times greater than that of pristine hydrogel and approximately 3 times greater than that of the porous elastomer. The equilibrium elastic modulus of the composite was close to the values reported for the modulus of cartilage tested with similar experimental parameters defined in this study. The composite immediately recovers its load-bearing properties with the […]
New conductive polymer ink opens for next-generation printed electronics
Science Daily April 21, 2021 Today, the most used conducting polymer is the p-type conductor PEDOT:PSS. However, many electronic devices require a combination of p-types and n-types to function. There is no n-type equivalent to PEDOT:PSS. An international team of researchers (Sweden, South Korea) has developed a conductive n-type polymer ink, BBL:PEI which is stable in air and at high temperatures. It comes in the form of eco-friendly ink with ethanol as the solvent. The ink can be deposited by simply spraying the solution onto a surface, making organic electronic devices easier and cheaper to manufacture. Printable n-type mixed ion-electron […]
Using sound waves to make patterns that never repeat
Phys.org April 14, 2021 Crystals have been shown to be stiffer than similar periodic or disordered materials and conduct electricity. Researchers at the University of Utah have shown how ultrasound waves can organize carbon particles in water resulting in “quasicrystals” with custom magnetic or electrical properties. They experimentally demonstrated this by using ultrasound waves to assemble quasiperiodic patterns of carbon nanoparticles in water using an octagonal arrangement of ultrasound transducers, and documented good agreement between theory and experiments. The theory also applies to obtaining quasiperiodic patterns in other situations where particles move with linear waves, such as optical lattices. According […]
Anti-reflective films: What high-tech can learn from plants
EurekAlert April 13, 2021 Rose petals have a matt and at the same time rich color. The outer tissue of its petals, the epidermis, consists of densely packed microstructures, additionally ribbed by nanostructures. With these structures, the rose manages to couple all incident light into the cells – only the colored light escapes again. Researchers in Germany combined micro- and nanostructure to develop an anti-reflective film that replicates the epidermis of rose petals. The film increases the yield of solar modules by up to ten percent. Posters, display panels, traffic signs, furniture, packaging, facades, and many other applications also benefit […]
Transforming circles into squares
Science Daily April 14, 2021 The fundamental topology of cellular structures can profoundly affect their acoustic, electrical, chemical, mechanical, and optical properties, as well as heat, fluid, and particle transport. In the previous techniques the resulting structures generally preserve the defining connectivity features of the initial topology. Researchers at Harvard University have developed a two-tiered dynamic strategy that achieves systematic reversible transformations of the fundamental topology of cellular microstructures, which can be applied to a wide range of materials and geometries. The approach requires exposing the structure to a selected liquid that can first infiltrate and plasticize the material at […]
Less than a nanometer thick, stronger and more versatile than steel
Science Daily April 5, 2021 A team of researchers in the US (Northwestern University, Argonne National Laboratory, University of Florida) grew borophene on a silver substrate then exposed it to hydrogen to form the borophane and unraveled its structure by combining a scanning tunneling microscope with a computer-vision based algorithm that compares theoretical simulations of structures with experimental measurements. They found a borophane nanosheet on a silver substrate to be quite stable making it easy to integrate it with other materials in the construction of new devices for optoelectronics, it could boost performance for electronic devices, solar cells, batteries, and […]
Discovery of a mechanism for making superconductors more resistant to magnetic fields
Phys.org March 30, 2021 Researchers in Japan discovered that when the crystalline films of indium is thinned to a two-dimensional atomic layer, the spin, and the momentum of the electrons in the layer are coupled, causing the electron spins to frequently rotate. This offsets the effect of the changes in electronic energy induced by the magnetic field and thus preserves superconductivity. This mechanism can enhance the critical magnetic field up to 16-20 Tesla, which is approximately triple the generally accepted theoretical value. It is expected to have a wide range of applications as it was observed for an ordinary superconducting […]
Fast-acting, color-changing molecular probe senses when a material is about to fail
Science Daily March 25, 2021 A team of researchers at the University of Illinois have improved their previously developed mechanophores (force-sensitive molecules) where the molecules were slow to react and return to their original state. The new mechanophores, they developed produced reversible, rapid, and vibrant color change when a force was applied. The color change is the result of stress applied to the bonds that connect the mechanophores to a polymer chain. In the current work they are bonding the mechanophores to polymer chains using a different arrangement scheme, called an oxazine structure. The new structure allows for an instantaneous […]
Scientists observe complex tunable magnetism in a topological material
Science Daily March 23, 2021 An international team of researchers (USA – Ames Laboratory, Iowa State University, University of Missouri Research Reactor, Oak Ridge National Laboratory, Harvard University, Canada) discovered that EuIn2As2 has collinear antiferromagnetic order where the magnetic moment direction determines either a topological-crystalline-insulator phase supporting axion electrodynamics or a higher-order-topological-insulator phase with chiral hinge states. They used neutron diffraction, symmetry analysis, and density functional theory results to demonstrate that EuIn2As2 exhibits low-symmetry helical antiferromagnetic order which makes it a stoichiometric magnetic topological-crystalline axion insulator protected by the combination of a 180∘ rotation and time-reversal symmetries: C2×T=2′. Surfaces protected […]