Effect of fuel type on morphology and reactivity of combustion synthesised MgAl₂O₄powders

Abstract

bustion depends in turn mainly on the type and quantity the Institute of M aterials, M inerals and M ining.of fuel used (i.e. the higher the molecular size and weight of the fuel the greater the generation of gas). As the distance between adjacent metal ions in the solution increases as a result of the larger size of the fuel molecule, the interaction of the hydrolysed metal ions will decrease, resulting in

Effect of Urea Excess on the Properties of the MgAl2O4 Obtained by Microwave-Assisted Combustion

“…This technique basically consists of using aluminum and magnesium nitrates as oxidants and an organic compound (urea, glycine, sorbitol, citric acid, among others) as fuel. It is the heat generated during the combustion reaction between oxidant and fuel (reducing agent) that promotes the formation of the material 28,29,32 . A large amount of gases (CO 2 , NO x , N 2 , H 2 O, CO) are also released during the process, and is responsible for the destruction of agglomerates and the formation of micropores in the material, facilitating the access of reagents to the active sites 31,32 , if the spinel is used as catalyst support.…”

“…However, many of those are complex, expensive, have several steps, require long time for synthesis, require high temperatures and produce nonhomogeneous and generally low surface area solids 28 . In the case of solution combustion method, it has been extensively used recently, due to its several advantages, such as simplicity, low cost, short synthesis time and less amount of external energy required, also it produce powders of oxides more homogeneous, more crystalline and of higher purity [29][30][31] . This technique basically consists of using aluminum and magnesium nitrates as oxidants and an organic compound (urea, glycine, sorbitol, citric acid, among others) as fuel.…”

Preparação e caracterização de espinélio MgAl2O4 nanoestruturado através de síntese por combustão em solução

“…O alto ponto de fusão (2135 °C), a resistência mecânica em altas temperaturas, inércia química e boa resistência ao choque térmico são propriedades consideráveis que conferem a aplicabilidade do MA na metalurgia, eletroquímica, radiotecnologia e outros campos industriais [4,5], como os relatados na literatura: material transparente ao infravermelho (infrared window material), variedade de aplicações na indústria nuclear, incluindo novos tipos de reatores nucleares, potencial de acomodar resíduos de cerâmica, e placas cerâmicas de circuitos integrados em compósitos de vidro de borossilicato [6]. Trabalhos recentes têm investigado a incorporação de espinélio MA nanoestruturado, com o objetivo de diminuir a oxidação dos refratários MgO-C durante o seu aquecimento, além de aumentar a resistência ao ataque de escória em serviço [7,8].…”

Synthesis, characterization and ionic conductivity of MgAl2O4

“…The impedance data are used to evaluate the relaxation time (τ) of the electrical phenomena in MgAl2O4 using the following relation: ( 4 ) where fmax is the relaxation frequency. The variation of τ with temperature is shown in Figure 7.…”

“…Thanks to its high thermal stability (melting point at 2135 °C), high hardness (16 GPa), high mechanical resistance, high resistance against chemical attack, wide band gap energy, high electrical resistivity, relatively low thermal expansion coefficient (9.10 -6 1/°C) between 30 and 1400 °C, low dielectric constant (ε = 7.5), low density 3.58 g/cm 3 , high thermal shock resistance, hydrophobicity and low surface acidity, MgAl2O4 has been widely used in various applications such as in metallurgical, electrochemical, radiotechnical and chemical industrial fields [3][4][5][6][7][8][9][10].…”