Scientists discover new class of semiconducting entropy-stabilized materials

Science Daily  July 31, 2020 Almost all entropy-stabilized materials so far are either conducting metals or insulating ceramics. Researchers at the University of Michigan have experimentally synthesized and characterized a new class of the multicationic and -anionic entropy-stabilized chalcogenide alloys based on the (Ge,Sn,Pb)(S,Se,Te) formula. The configurational entropy from the disorder of both the anion and the cation sublattices reaches a record value for the equimolar composition and stabilizes the single-phase solid solution. Theoretical calculations and experiments both show that the synthesized alloys are thermodynamically stable at the growth temperature and kinetically metastable at room temperature. Doping and electronic transport […]

New fabric could help keep you cool in the summer, even without A/C

Science Daily  July 29, 2020 When interspersed in fabric the thermally conductive boron nitride has the ability to transfer heat, allow moisture to evaporate from the skin and repel water. To improve the process researchers in China enabled boron nitride to better interpenetrate and remain porous. According to the researchers the material has improved thermal conductivity, moisture permeability, and better resistance to water penetrability and repellency…read more. TECHNICAL ARTICLE

Self-healing soft material outsmarts nature

Nanowerk  July 27, 2020 Current self-healing materials have shortcomings such as low healing strength and long healing times limit their practical application. An international team of researchers (USA – State University of Pennsylvania, Germany, Turkey) studied the molecular structure and amino acid sequences of squid proteins and developed a new stretchable biosynthetic material using protein engineering. The squid takes longer to heal because the molecular structure of the proteins inside its tentacles is not perfectly intertwined. With the laboratory-developed squid-inspired material, the scientists changed the nanostructure of the molecules until they created crosslinks between all of them in such a […]

Shells and grapefruits inspire first manufactured non-cuttable material

Science Daily  July 20, 2020 An international team of researchers (UK, Germany) has created a bio-inspired metallic cellular structure (with an internal grid of large ceramic segments). It is non-cuttable by an angle grinder and a power drill, and it has only 15% steel density. The architecture derives its extreme hardness from the local resonance between the embedded ceramics in a flexible cellular matrix and the attacking tool, which produces high-frequency vibrations at the interface. The contrast between the ceramic segments and cellular material was also effective against a waterjet cutter because the convex geometry of the ceramic spheres. Shifting […]

‘Blinking’ nanocrystals may convert CO2 into fuels

Nanowerk  July 16, 2020 Using polymer‐derived mesoporous carbon (PDMC) as a template, an international team of researchers (USA- State University of New Jersey, China, Czech Republic) has synthesized mesoporous titanium dioxide comprised of small, crystalline, vacancy‐rich anatase nanoparticles that show unique optical, thermal, and electronic properties. When exposed to a slow electron beam, the nanoparticles exhibit a charge/discharge behavior, lighting up and fading away for an average period of 15 s. They show a 50 nm red‐shift in their UV/Vis absorption and long‐lived charge carriers at room temperature in the dark, even long after UV irradiation. As photocatalysts they show […]

Physics team observes extremely fast electronic changes in real time in a special material class  July 7, 2020 Topologically protected Weyl semimetal phase in the transition metal dichalcogenide Td-WTe2 can be controlled and, ultimately, destroyed upon the coherent excitation of an interlayer shear mode. An international team of researchers (Germany, China) provide direct experimental evidence that the shear mode acts on the electronic states near the phase-defining Weyl points. They observed a periodic reduction in the spin splitting of bands. Comparison with higher-frequency coherent phonon modes finally proved the shear mode-selectivity of the observed changes in the electronic structure. findings reveal direct experimental insights into electronic processes that are of vital importance for a […]

Multifunctional nanofiber protects against explosions, extreme temps

Science Daily  June 29, 2020 Current protection against both thermal and ballistic threats is a combination of multiple high-performance materials that increases equipment weight and complexity. Using para-aramid polymers as the building block researchers at Harvard University engineered precursor solutions to be fluid-like during fiber spinning and solid-like during fiber formation. This allowed for the fabrication of porous, continuous para-aramid fiber sheets (pAFS). Although exhibiting moderately reduced single-fiber mechanics, these pAFS had fragment projectile resistance comparable with commercial para-aramids, while providing 20-fold heat-insulation capability. With these synergistic properties, the nanofiber sheets act as a multifunctional material that can provide improved simultaneous protection…read more. Open […]

Synthetic materials mimic living creatures

Science Daily  June 22, 2020 Researchers at Northwestern University have developed hybrid light-responsive soft materials composed of peptide amphiphile supramolecular polymers chemically bonded to spiropyran-based networks that expel water in response to visible light. The supramolecular polymers form a reversibly deformable and water-draining skeleton that mechanically reinforces the hybrid and can also be aligned by printing methods. The noncovalent skeleton embedded in the network enables faster bending and flattening actuation of objects, as well as longer steps during the light-driven crawling motion of macroscopic films. As the material can be designed in different shapes, it could play a role in […]

A ‘hole’ lot of sponge! New technique to create super-sponges is a game changer

EurekAlert  June 10, 2020 Unlike traditional porous materials, in theory MOFs structure can be controlled through careful selection of the components of the synthesis process. But in practice, this process is challenged by the restricted synthetic conditions and high thermal and chemical sensitivity of MOFs. Researchers in South Korea introduced stable carbon-carbon bonds by converting existing carbon-hydrogen bonds using elevated temperatures and adding “electrophilic organic halides or carbonyl compounds”, allowing simultaneous introduction of the required functional groups as well as the mesoscopic holes. This technique could potentially improve the safety of workers in enclosed, gas-filled environments such as in the […]

Scientists develop the most heat-resistant material ever created  May 27, 2020 Using the method of self-propagating high-temperature synthesis, an international team of researchers (Russia, USA – University of Notre Dame) fabricated nonstoichiometric hafnium carbonitrides (HfCxNy). It had a rock-salt crystal structure with a lattice parameter of 0.4606 nm. and hardness of 21.3 GPa. The melting point of this synthesized material was experimentally shown to be higher than that of binary hafnium carbide. The nonstoichiometric hafnium carbonitride was then consolidated under a constant pressure of 50 MPa at a temperature of 2000 °C and a dwelling time of 10 min, through spark plasma sintering. The obtained bulk ceramic […]