Combustion synthesis of fine particle rare earth orthoaluminates and yttrium aluminum garnet

Effectiveness of photocatalysis of MMT-supported TiO2 and TiO2 nanotubes for rhodamine B degradation

The aim of this paper is to synthesize montmorillonite/TiO₂-nanoparticles (MMT/TiO₂ and montmorillonite/TiO₂-nanotubes (MMT/TiO_2-NTs) photocatalysts through a simple wet agitation method based on TiO₂ nanoparticles and MMT. They are likely to accumulate the effect of adsorption and photodegradation. Then, the photocatalysts are applied to degrade the rhodamine B in dye effluents. The structural characterizations of photocatalysts are investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The photocatalytic activities and effectiveness of photocatalysts are evaluated through rhodamine B degradation at different concentrations under dark and UV-C irradiation conditions. The results show that the synthesized TiO_2-NTs have an average tube diameter of 5 nm and a tube length at least about 110 nm, which are intercalated into MMT sheets in MMT/TiO_2-NTs photocatalyst. Meanwhile, TiO₂ nanoparticles are immobilized on the surface of MMT sheets in the MMT/TiO₂ photocatalyst. The photocatalytic effectiveness of rhodamine B degradation of TiO_2-NTs shows a significantly enhance compared to that of TiO₂ nanoparticles. However, photocatalytic performance of MMT/TiO_2-NTs is lower than that of MMT/TiO₂. The degradation effectiveness of MMT/TiO₂ photocatalyst reaches to 100% for 3 ppm and 90% at 10 ppm of rhodamine B, while these values are 97.5% and 85.5%, respectively, recorded for MMT/TiO_2-NTs.

Solution Combustion Synthesis of Nanoscale Materials

Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol-gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual properties are outlined. To demonstrate the versatility of the approach, several application categories of SCS produced materials, such as for energy conversion and storage, optical devices, catalysts, and various important nanoceramics (e.g., bio-, electro-, magnetic), are discussed.

Energetic Materials in Ceramics Synthesis

Combustion of a proper combination of an oxidizer and a fuel can produce the exothermicity required for the simultaneous synthesis of oxide ceramic powders. Oxidizers include metal nitrates, ammonium nitrate, and ammonium perchlorate, while urea, carbohydrazide, glycine and others have been used successfully as fuels. Combustion methods are particularly well-suited to producing multicomponent metal oxides, yielding compositionally homogeneous, fine particles with low impurity content. Organic fuels, particularly those containing nitrogen, also serve as a complexant in the precursor, which inhibits inhomogeneous precipitation from occurring prior to combustion. The exothermic redox decomposition of these oxidizer-fuel mixtures is initiated at low temperatures, usually <250°C. Properties of the products are influenced by the nature of the fuel and the oxidizer/fuel ratio. Many technologically important oxide ceramics have been produced by these methods.

Synthesis of the long-persistence phosphor CaAl2O4:Eu2+, Dy3+, Nd3+ by combustion method and its luminescent properties

Calcium aluminate phosphor co-doped Eu(2+), Dy(3+), Nd(3+) is prepared by the combustion method. We study systemically the influences of the quantity of mixed Dy(3+) ion, the quantity of flux H(3)BO(3), the differences in dispersing methods between magnetic stirring and ultrasonic dispersing and the combustion temperature on the long-persistence phosphor. The analytical results indicate that Dy(3+) ion improves the properties of the phosphors CaAl(2)O(4):Eu(2+), Nd(3+). The appropriate quantity of flux H(3)BO(3 )to( )reduce the forming temperature of the sample was determined. The monoclinic single phase of CaAl(2)O(4) formed at 500 degrees C and remained steady. The calcium aluminate co-doped Eu(2+), Dy(3+), Nd(3+) was synthesized by dispersal of the raw material using the ultrasonic method, and it had better optical properties.

Nd(NH2SO3)(SO4) · 1.5 H2O: a non-centrosymmetric amidosulfate-sulfate of neodymium

The thermal decomposition of Nd(NH2SO3)3 · 2 H2O in a closed tube leads to violet single crystals of Nd(NH2SO3)(SO4) · 1.5 H2O. The compound crystallizes with the space group P1 (Z = 2, a = 689.2, b = 691.4, c = 962.0 pm, α = 109.64, β = 97.00, γ = 109.62°). The triclinic unit cell can be transformed into the respective bodycentered setting I1 (Z = 2, a = 977.9, b = 795.6, c = 1113.0 pm, α = 90.69, β = 115.06, γ = 88.98°) leading to a nearly monoclinic unit cell for the compound. In the crystal structure of Nd(NH2SO3)(SO4) · 1.5 H2O two Nd3+ ions are present. Nd(1)3+ is coordinated by four NH2SO3 – and two SO4 2– ions, and one H2O molecule. Owing to the chelating attack of the sulfate groups, the CN is nine. Nd(2)3+ is surrounded by four monodentate SO4 2– and two NH2SO3 – groups. Two H2O ligands fill up the coordination sphere and lead to a CN of eight. The linkage of the polyhedra leads to a three-dimensional network.