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Chromium-doped Alumina was synthesized via combustion technique. Nanoparticles were produced from aluminum nitrate, ammonium dichromate, and sucrose. Silver nitrate was used as catalyst. The use of sucrose (C12H22O11) as dispersion agent and ammonium dichromate both as fuel and a doping agent source are new techniques in the synthesis of Cr-doped Al2O3 nanoparticles. The heat-treated powders were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Heat treatment of the nanoparticles was performed at temperatures of 900 °C, 1000 °C, and 1100 °C, which resulted in the formation of porous agglomerated chromium-doped alumina nanoparticles. Chromium-doped alumina with an average crystalline size of 35 nm was successfully synthesized via combustion technique with sucrose as fuel. [ABSTRACT FROM AUTHOR]

Iron-doped Al2O3 nanoparticles were prepared via an aqueous combustion synthesis technique using stoichiometric amounts of aluminum nitrate [(Al9NO3 )3 .9H2O], ferric nitrate [Fe(NO3)3.9H2O], and sucrose (C12H22O11). The heat treatment of the nanoparticles at two temperatures (900 °C and 1100 °C) formed porous agglomerated iron-doped alumina nanoparticles. The heat-treated powders were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Characterization results showed existence of α-Al2O3 calcined at 1100 °C. In this study, iron-doped alumina particles with average crystallite size (38.94 nm) were successfully synthesized by using sucrose as dispersion agent and carbon source. Al2O3:Fe nanoparticles can be used in different fields as catalyst support and biocompatible material and for electrical applications. [ABSTRACT FROM AUTHOR]

Polyimide/SiO2 composite films were prepared from tetraethoxysilane (TEOS) and poly(amic acid) (PAA) based on aromatic diamine (4-aminophenyl sulfone) (4-APS) and aromatic dianhydride (3,3,4,4-benzophenonetetracarboxylic dianhydride) (BTDA) via a sol-gel process in N-methyl-2-pyrrolidinone (NMP). The prepared polyimide/SiO2 composite films were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The FTIR results confirmed the synthesis of polyimide (4-APS/BTDA) and the formation of SiO2 particles in the polyimide matrix. Meanwhile, the SEM images showed that the SiO2 particles were well dispersed in the polyimide matrix. Thermal stability and kinetic parameters of the degradation processes for the prepared polyimide/SiO2 composite films were investigated using TGA in N2 atmosphere. The activation energy of the solid-state process was calculated using Flynn-Wall-Ozawa's method without the knowledge of the reaction mechanism. The results indicated that thermal stability and the values of the calculated activation energies increased with the increase of the TEOS loading and the activation energy also varied with the percentage of weight loss for all compositions. [ABSTRACT FROM AUTHOR]

Type-II superlattices (T2SLs) are a class of artificial semiconductors that have demonstrated themselves as a viable candidate to compete with the state-of-the-art mercury-cadmium-telluride material system in the field of infrared detection and imaging. Within type-II superlattices, InAs/InAs 1-x Sb x T2SLs have been shown to have a significantly longer minority carrier lifetime. However, demonstration of high-performance dual-band photodetectors based on InAs/InAs 1-x Sb x T2SLs in the long and very long wavelength infrared (LWIR & VLWIR) regimes remains challenging. We report the demonstration of high-performance bias-selectable dual-band long-wavelength infrared photodetectors based on new InAs/InAs 1-x Sb x /AlAs 1-x Sb x type-II superlattice design. Our design uses two different bandgap absorption regions separated by an electron barrier that blocks the transport of majority carriers to reduce the dark current density of the device. As the applied bias is varied, the device exhibits well-defined cut-off wavelengths of either ∼8.7 or ∼12.5 μm at 77 K. This bias-selectable dual-band photodetector is compact, with no moving parts, and will open new opportunities for multi-spectral LWIR and VLWIR imaging and detection.