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The exponential rise of power dissipation in electric devices has so far vastly surpassed the performance of power converter systems. New thermal management solutions are therefore in high demand to maintain devices at their optimal temperature and efficiency. Here, we present an innovative magnetically actuated thermal switch (MATS) based on nanofluids capable of controlling both the magnitude and direction of the heat flux. When in the OFF state (zero applied magnetic field), the nanofluid captures the heat being generated at the heat source. When an external magnetic field is applied (ON state), the nanofluid is transported from the heat source to the heat sink where it releases the carried heat. This work (i) provides a detailed description of the MATS operating principles, (ii) studies the effect of thickness and operation frequency in its cooling power, (iii) presents numerical simulations to forecast MATS behavior and (iv) demonstrates the MATS applicability in the thermal management of a 10 W Light Emitting Diode. The versatility, simple design, unique operating mode and high performance of the MATS suggests that the proposed approach is a promising technology to be used in a vast number of electronic devices, thermal storage systems and thermal management applications. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators are a new promising energy harvesting technology that has a simple working mechanism, produces high output power and has the ability of harvesting energy from a wide range of sources and under various conditions. Here, we present a rotary triboelectric nanogenerator (TENG) that harvests energy from water flows using polytetrafluoroethylene (PTFE) and Nylon 6.6 as triboelectric materials. The operation mechanism of the fabricated rotary TENG is a hybridization of the contact and sliding modes by using the triboelectrification and electrostatic induction effects. The optimization of the developed setup for the effective generation of electricity showed that the best configuration consists in a triboelectric structure with four Nylon and one PTFE plate for the maximum used water flow of 44 L/min. With this configuration, the rotary TENG delivers a mean voltage value of ∼102.2 V, a short-circuit current density ∼120 mA/m 2 and a maximum power density of ∼6.1 W/m 2 . Finally, with this device it was possible to light up more than 50 serial-connected light emitting diodes, fully charge a 1.0 μF capacitor with 15.2 V in just 65 s and feed a commercial temperature and humidity sensor. The developed rotary TENG can then be applied to autonomous sensors that monitor water supply systems using the energy produced by water movement in plumbing. [ABSTRACT FROM AUTHOR]

Nanoporous silica materials of regular porosity (of SBA-15 type) doped with magnetic iron oxide nanoparticles were prepared by two routes that differ essentially in the pH of the reaction medium and calcination step. Both routes produced magnetic SBA-15 materials with regular porosity and containing different loadings of iron oxide particles. The increase of the amount of iron oxide incorporated in SBA-15 was directly related with the increase of the pH during the material synthesis but the magnetic properties also showed a dependence on the type of calcination used. Two of the prepared materials showed relevant results for the catalytic degradation of acetaminophen, a pharmaceutical emerging pollutant. In the present work mild reaction conditions were used, that is, reaction conditions that do not involve imposition of low pH values, a specific radiation source nor high-pressure autoclave. [ABSTRACT FROM AUTHOR]

The implementation of processed magnetic materials onto thermoplastics can be an approach for practical use of brittle intermetallic materials on device development with the advantage of enlarging the range of applications. In this paper, we present the evaluation on the effect of blending magnetocaloric Gd 5 Si 2.4 Ge 1.6 3.4 μm particles with in different weight fractions onto a flexible, transparent and non-magnetic poly(methyl methacrylate) (PMMA). A close to homogeneous grain distribution along the polymer surface were achieved by using a simple solvent casting method for their magnetocaloric properties studies. From XRD analysis, it was found a unit cell volume shrinkage by increasing the powder concentration followed by a reduction on the amount of secondary monoclinic phase as a result of interfacial interactions. As a consequence, a weakening of secondary phases effect on the composite magnetocaloric behavior is observed as a result of the effective hydrostatic pressure from the difference between thermal expansions of matrix and filler. Unlabelled Image • Particle size reduction of Gd 5 Si 2.4 Ge 1.6 bulk to 3.4 μm increases the detection on the amount of distorted monoclinic phase. • The solvent casting technique allows a close to homogeneous dispersion of the micropowder along the composite volume. • Inclusion of the micropowder into the thermoplastic converts the monoclinic phase into an orthorhombic-I phase. • PMMA matrix works as a pressure cell for the micropowder leading to a reduction on the magnetocaloric response of the monoclinic phase. [ABSTRACT FROM AUTHOR]