In situ observation of compressive deformation of an interconnected network of zinc oxide tetrapods

Zinc oxide tetrapods have remarkable functional and mechanical properties with potential applications in different fields including nanoelectronic and optoelectronic sensing, functional composites and coatings, as well as energy harvesting and storage. Based on the 3D shape of these microparticles, they can be assembled into highly porous (up to 98%) macroscopic ceramic framework structures that can be utilized as a versatile template for the fabrication of other multi-scaled foam-like materials. Here we investigated the three-dimensional structure of low density interconnected zinc oxide tetrapod networks by high resolution X-ray computed tomography. In situ observations during mechanical loading show inhomogeneous development of anelastic strain (damage) during compression, and homogeneous elastic recovery on unloading. Individual tetrapods are observed to deform by arm rotation to accommodate strain

In situ observation of compressive deformation of an interconnected network of zinc oxide tetrapods

Zinc oxide tetrapods have remarkable functional and mechanical properties with potential applications in different fields including nanoelectronic and optoelectronic sensing, functional composites and coatings, as well as energy harvesting and storage. Based on the 3D shape of these microparticles, they can be assembled into highly porous (up to 98%) macroscopic ceramic framework structures that can be utilized as a versatile template for the fabrication of other multi-scaled foam-like materials. Here we investigated the three-dimensional structure of low density interconnected zinc oxide tetrapod networks by high resolution X-ray computed tomography. In situ observations during mechanical loading show inhomogeneous development of anelastic strain (damage) during compression, and homogeneous elastic recovery on unloading. Individual tetrapods are observed to deform by arm rotation to accommodate strain

Electrically powered repeatable air explosions using microtubular graphene assemblies

Controllable rapid expansion and activation of gases is important for a variety of applications, including combustion engines, thrusters, actuators, catalysis, and sensors. Typically, the activation of macroscopic gas volumes is based on ultra-fast chemical reactions, which require fuel and are irreversible. An “electrically powered explosion”, i.e., the rapid increase in temperature of a macroscopic relevant gas volume induced by an electrical power pulse, is a feasible repeatable and clean alternative, providing adaptable non-chemical power on demand. Till now, the fundamental problem was to find an efficient transducer material that converts electrical energy into an immediate temperature increase of a sufficient gas volume. To overcome these limitations, we developed electrically powered repeatable air explosions (EPRAE) based on free-standing graphene layers of nanoscale thickness in the form of microtubes that are interconnected to a macroscopic framework. These low-density and highly permeable graphene foams are characterized by heat capacities comparable to air. The EPRAE process facilitates cyclic heating of cm3-sized air volumes to several 100 °C for more than 100,000 cycles, heating rates beyond 300,000 K s−1 and repetition rates of several Hz. It enables pneumatic actuators with the highest observed output power densities (>40 kW kg−1) and strains ∼100%, as well as tunable microfluidic pumps, gas flowmeters, thermophones, and micro-thrusters