Catalyst-free synthesis of copper oxide composites as solar radiative filters.

Copper oxide composites were successfully synthesized by a catalyst-free method, plasma arc technology. The as-synthesized composites were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. The analysis revealed a mixture of crystalline copper oxide (CuO), cuprous oxide (Cu2O) and copper (Cu) phases of the copper oxide composites constitute of irregularly spheroidal particlesµ with nanoparticles aggregate on the surface. Gas pressure during plasma arc process noticeably influences the composition and solar radiative properties of the composite materials. Among the samples studied, the composites synthesized with an arc current of 80 A and a pressure of 300 Torr exhibited the highest near infrared diffuse reflectance, providing a total solar reflectance of 22.96%. The mixed phase composition together with the nanostructures among the composites are considered to contribute to the excellent near infrared reflectance of copper oxide composites. Low reflectance in the visible region combined with high reflectance in the near infrared region make this composite material a good candidate for solar reflective coating which will demonstrate black appearance but keep a cool surface under solar irradiation.

Enhanced Power Factor and Increased Conductivity of Aluminum Doped Zinc Oxide Thin Films for Thermoelectric Applications.

We report the structural, electrical and thermopower properties of un-doped and Al doped zinc oxide (ZnO) thin films. Al doping was carried out using 25 keV Al+ implantation with 0.1, 1 and 2% Al into ZnO. X-ray diffraction measurements showed that the lattice parameters were larger than the bulk values, which is consistent with the incorporation of Al atoms at interstitials. Al doping increased the electrical conductivity from 100 (Ωcm)-1 in the un-doped ZnO film to 598 (Ωcm)-1 in the 2% Al doped ZnO film. Electron doping by Al resulted in an increase in the carrier concentration and it had an advantageous effect on the mobility where it was highest for 2% doping. The absolute value of the Seebeck coefficient systematically increased for un-doped, 1% and 2% Al doped ZnO films where the room temperature values were -50.8, -60.9 and -66.3 µV/K, respectively. The power factor increased significantly from 2.58 × 10-5 W/mK2 in un-doped ZnO film to 2.63 × 10-4 W/mK2 in 2% Al doped ZnO film. Our results suggest that the ion beam method is a suitable technique to enhance the thermoelectric properties of ZnO.

Ironsand (Titanomagnetite-Titanohematite): Chemistry, Magnetic Properties and Direct Applications for Wireless Power Transfer.

Ironsand is an abundant and inexpensive magnetic mineral resource. However, the magnetic properties of unprocessed ironsand are often inadequate for any practical applications. In this work, the applicability of ironsand for use as a component in a soft magnetic composite for large-scale inductive power transfer applications was investigated. After magnetic separation, the chemical, structural and magnetic properties of ironsand sourced from different locations were compared. Differences observed in the DC magnetic properties were consistent with changes in the chemical compositions obtained from X-ray Absorption Near-Edge Spectroscopy (XANES), which suggests varying the titanohematite to titanomagnetite content. Increased content in titanomagnetite and magnetic permeability correlated well with the total Fe content in the materials. The best-performing ironsand with the highest permeability and lowest core losses was used alongside Mn,Zn-Ferrite particles (ranging from ∼100 µm to 2 mm) to fabricate toroid cores with varying magnetic material loading. It was shown that ironsand can be used to replace up to 15 wt.% of the magnetic materials with minimal impact on the composite magnetic performance, thus reducing the cost. Ironsand was also used as a supporting material in a single-rail wireless power transfer system, effectively increasing the power transfer, demonstrating potential applications to reduce flux leakage.