Narrow Results

A hot spot model, involving interaction of pulse laser with nanoparticles where heat diffusion and exothermic chemical reaction are considered and spread out of heat and chemical reaction, is developed to model the thermal reaction dynamic process of Al/NC (nitrocellulose) nanothermites excited by pulse laser for the purpose of verifying the experimental ablation criterion proposed recently and providing a microscopic insight into different physical pathways leading to ablation. In this model, the spatial position and conversion of matters taking place in chemical reactions are regarded as the functions of time, space, and temperature. An exact expression of power density absorbed by nanoparticles in matrix is incorporated to calculate the diameters of chemical reaction region. Calculation results justify experimental ablation criterion, and show that thermal decomposition mechanism predominates the nanosecond pulse-excited process before ablation but it is not suitable for the 100 ps regime which is qualitatively attributed to shock pressure. The effects of pulse duration and nanoparticle size on ablation threshold are examined.

The thermal decomposition pathway and desorption of diethylamido of tetrakis(diethylamido)zirconium [TDEAZr, Zr(N(C₂H₅)₂)₄] on Si(100) were studied using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). During TPD experiments, ethylethyleneimine (C₂H₅N=CHCH₃), diethylamine [NH(C₂H₅)₂], acetonitrile (CH₃CN), ethylene (C₂H₄) and hydrogen (H₂) desorbed as the main decomposition products of diethylamido, which was chemisorbed on Si(100) through the scission of the zirconium–diethylamido bond in TDEAZr. After TPD runs, the formation of silicon carbide and silicon nitride was observed on the surface by XPS, indicating that a complete decomposition of diethylamido proceeded. This could be a reaction pathway of C, N incorporation in the thin film growth using TDEAZr as a Zr precursor.

The decomposition of goethite and goethite/siderite concentrates into hematite with thermal modification was studied through the measurements of X-ray diffraction (XRD), scanning electronic microscope (SEM) and thermal gravimetric analysis (TGA). The experimental results showed that goethite decomposed into hematite directly at around 300°C without any intermediate phase and the decomposition of siderite completed at 500°C. Nanoscale granular structures were observed in the thermally treated products. It deserves highlighting that the decomposition processes proceeded from surfaces into bulks.

Cu nanoparticles have been synthesized by thermal decomposition of Cu-oleate complex, which was prepared by the reaction with CuCl₂ and sodium oleate in water solution. The monodispersed Cu nanoparticles were produced by controlling temperature (290°C). TEM images of the nanoparticles showed two-dimensional assembly of particles with diameter of 16.2 ± 2.9 nm, demonstrating the uniformity of these nanoparticles. EDX spectrum and XRD peaks of the nanoparticles showed the highly crystalline nature of the Cu structures. The decomposition of Cu-oleate complex was analyzed with TGA and the crystallization of Cu nanoparticles was observed with XRD.

Mn₃O₄ nanocrystals have been prepared using [bis(2-hydroxyacetophenato)manganese(II)] as precursor. Transmission electron microscopy analysis demonstrated nanocrystals Mn₃O₄ with an average diameter of about 20 nm. The structural study by X-ray diffraction indicates that these nanocrystals have pure tetragonal phase. The phase pure samples were characterized using X-ray Photoelectron Spectroscopy for Mn 2p level. The values of binding energies are consistent with the relative values reported in the literature.

Ceria (CeO₂) nanoparticles (NPs) have been produced from cerium nitrate and walnut shell as a worthless agricultural waste by a thermal decomposition method followed by open air calcination. These NPs further were characterized using powder X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy, energy dispersive X-ray spectroscope and Fourier transform infrared spectroscopy. Moreover, particle sizes can be tuned by changing cerium source/biomass ratio. To test the catalytic activity of cerium NPs as a heterogeneous catalyst, we selected three-component synthesis of 3,4-dihydroquinoxalin-2-amine. Also, the efficiency of CeO₂ NPs as a support for palladium NPs and subsequent use in aerobic oxidation of alcohols has been investigated. TEM image of a recovered catalyst indicates the formation of 12 nm sized palladium NPs within the cerium oxide NPs. The catalyst is quite effective for the oxidation of primary and secondary benzylic alcohols into their corresponding aldehydes and ketones under atmospheric pressure of air. Oxidation of secondary aliphatic alcohols is performed in oxygen atmosphere.

Nanostructured CuO has been successfully synthesized via Thermal decomposition method at 700^∘C. Prepared CuO was characterized using IR spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM). IR spectra confirm the metal–oxygen bonding in these nanoparticles. The XRD pattern confirms a single-phase crystalline nature of the nanoparticles. The synthesized CuO was demonstrated as an efficient catalyst in degradation of Rhodamine B in the presence of light through oxidation. More than 93% of the Rhodamine B dye was degraded after 150min. It was observed that photocatalytic degradation of dyes follows pseudo-first-order kinetics. A tentative mechanism has also been proposed for the photocatalytic degradation of dyes in the presence of copper oxide semiconductor.

Three-dimensionally ordered macroporous (3DOM) CuO is prepared by colloidal crystal templated method. The obtained 3DOM structure with about 230nm pore diameter is composed of small CuO windows. The special structured CuO is used as a catalyst for thermal decomposition of ammonium perchlorate (AP) and its catalytic activity is measured by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) techniques. Test results show that thermal decomposition performance is significantly improved after adding 2wt.% 3DOM CuO.