Glycine Combustion Research Articles

Experimental study on preparation of LaMO 3 (M = Fe, Co, Ni) nanocrystals and their catalytic activity

The perovskite-type oxides LaMO 3 (M = Fe, Co, Ni) were prepared by a glycine combustion method using La (NO 3) 3·6H 2O and Fe (NO 3) 3·9H 2O, Co (NO 3) 2·6H 2O, Ni (NO 3) 2·6H 2O as the raw materials, respectively, and C 2H 5NO 2 as gelating agent. The products were characterized by XRD, TEM, HRTEM, SEM and BET. The catalytic activity of LaMO 3 (M = Fe, Co, Ni) nanocrystals on thermal decomposition of NH 4CIO 4 (AP) were carried out by DTA and TG. The burning rate of the propellant modified by obtained LaCoO 3 was measured by strand burner method. The experimental results showed that the obtained products can play a catalytic role in the thermal decomposition of AP and combustion of AP-based propellant. The order of the catalytic performance of obtained products on AP thermal decomposition is LaCoO 3 > LaNiO 3 ≈ LaFeO 3. Adding 2% of LaCoO 3 nanocrystals to AP decreases the decomposition temperature by 134 °C and increases the heat of decomposition by 0.8 kJ g −1. Compared with basic propellant, the burning rate of propellant modified by 1% LaCoO 3 nanocrystals increases around 8%.

Thermal decomposition behavior of precursors for yttrium aluminum garnet

Precursor powders for yttrium aluminum garnet (YAG) were synthesized by solution combustion reactions (nitrate–glycine reaction with stoichiometric and sub-stoichiometric amount of fuel) and simple decomposition of nitrate solution. The TG-DTA, FTIR and XRD analyses of the precursors and the typical heat-treated samples were carried out to understand the processes occurring at various stages during heating to obtain phase pure YAG. Precursors from all the reactions exhibited dehydration of adsorbed moisture in the temperature range of 30 to 300°C. The precursor from nitrate–glycine reaction with stoichiometric amount of fuel (precursor- A) contained entrapped oxides of carbon (CO and CO2) and a carbonaceous contaminant. It exhibited burning away of the carbonaceous contaminant and crystallization to pure YAG accompanied by loss of oxides of carbon in the temperature ranges of 400 to 600 and 880 to 1050°C. The precursor from simple decomposition of nitrates (precursor-B) exhibited denitration cum dehydroxylation and crystallization in the temperature ranges of 300 to 600 and 850 to 1050°C. The precursor from nitrate–glycine reaction with sub-stoichiometric amount of fuel (precursor-C) contained entrapped carbon dioxide and exhibited its release during crystallization in the temperature range of 850 to 1050°C. This study established that, in case of metal nitrate–glycine combustion reactions, crystalline YAG formation occurs from an amorphous compound with entrapped oxides of carbon. In case of simple decomposition of metal nitrates, formation of crystalline YAG occurs from an amorphous oxide intermediate.

Preparation and characterization of perovskite LaFeO3 nanocrystals

Orthorhombic structure perovskite LaFeO3 nanocrystals with size of 59 nm were prepared by glycine combustion method. The as-prepared LaFeO3 nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high reaction transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometer (EDS), scanning electron microscope (SEM), UV–Visible absorption spectroscopy, Laser Raman Spectroscopy (LRS) and Brunauer–Emmett–Teller (BET) nitrogen adsorption. The preparation process can be also applied to synthesize other complex oxides such as NdFeO3, LaCoO3 and LaNiO3.

Preparation and characterization of LaNiO 3 nanocrystals

Ten to twenty-three nanometers of LaNiO 3 nanocrystals were prepared by glycine combustion method using nickel nitrate and lanthanum nitrate as raw materials, glycine as gelating agent and fuel. The preparation process was monitored by thermogravimetric analysis and differential thermal analysis (TG-DTA); the final products were characterized by X-ray diffraction (XRD), electron diffraction (ED), high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The effect of thermal treatment temperature on crystal size of the nanocrystals was studied and the activation energy of LaNiO 3 nanocrystals formation during calcinations was calculated to be 41.9 kJ/mol. Moreover, the interplanar distances of d 110 and d 101 measured from the TEM images were 0.272 and 0.363 nm, respectively, coinciding with the theoretical values.

Processing and characterisation of fine crystalline ceria gadolinia–yttria stabilized zirconia powders

For low temperature SOFCs the yttria stabilized zirconia (YSZ)-coated ceria is a promising candidate for replacing YSZ-electrolyte. An important requirement for the co-firing feasibility of such a configuration is the densification of ceria at low temperatures (<1400°C). Fine crystalline gadolinia doped ceria (CGO)-powder readily sinterable at 1250°C was synthesized by co-precipitation with oxalic acid of 0·05 M and crystallization in methanol at 200°C for 6 h. The fabrication and characterisation of solid solution phases with a graded composition (CGO) x (YSZ) 1− x , to be used as an interlayer between YSZ and CGO, in order to avoid delamination, were also studied and discussed. CGO x YSZ 1− x powders, prepared by the glycine combustion method, required higher sintering temperatures (1500°C) to densify, while they showed significantly lower ionic conductivity than YSZ and CGO, attributed to the large lattice deformation and scattering of oxygen ions.

Structural and electrochemical properties of LiNi0.3Co0.7O2 synthesized by different low-temperature techniques

Single phase LiNi1−yCoyO2 (y=0.7) with fine particles were prepared by two different low-temperature methods, namely sol–gel and combustion techniques. It was found that bulk quantities of submicron-sized particles of layered LiNi0.3Co0.7O2 can be obtained at temperatures below 400°C by these solution techniques. The methods involved the mixing of either acetates or nitrates of the metals, Ni and Co, with a chelating agent, carboxylic acid (sol–gel method) or a complexing agent, glycine (combustion method) in an aqueous medium. Both carboxylic acid and glycine acted as fuels, decomposed the homogeneous precipitate of metal complexes at low temperature, and yielded the free impurity LiNi0.3Co0.7O2 compound. The synthesized products were characterized by structural (XRD, SEM), spectroscopic (FTIR) and thermal (DTA-TG) analyses. The electrochemical performance of the synthesized products in rechargeable Lithium cells were evaluated using a non-aqueous organic electrolyte mixture of 1M LiPF6 in EC+DMC. The electrochemical behavior of synthesized LiNi0.7Co0.3O2 is discussed in relation with its synthesis procedures.