Barium hexaaluminate nanowhiskers synthesized by novel sol–gel process in reverse micellar media

Abstract

Barium hexaaluminate (BHA) synthesized by coupling of sol-gel process in reverse microemulsions shows a unique nanowhisker morphology and high surface area, which are retained after calcination at 1300 degrees C.

Reverse microemulsion mediated sol–gel synthesis of lithium silicate nanoparticles under ambient conditions: Scope for CO2 sequestration

“…These surfactantcovered water pools offer a confined microenviornment for the formation of nanoparticles and inhibit their excess growth and agglomeration. Synthesis of nanoparticles by coupling of sol-gel process in reverse microemulsions has proved to be very efficient in controlling the diffusion rates of the different alkoxides for getting non-agglomerated, high surface area nanoparticles (Sahu et al, 2003).…”

Structure–Activity Relationships of Nickel–Hexaaluminates in Reforming Reactions Part I: Controlling Nickel Nanoparticle Growth and Phase Formation

“…Additionally, carbon selectivity is widely believed to depend on Ni nanoparticle size, with a prerequisite for larger particles to favor growth of carbon deposits such as carbon whiskers. [24][25][26][27] The potential very high specific surface area of Ba-hexaaluminates recently reported at 70-100 m 2 g À1 [28][29][30] and up to 160 m 2 g À1 [31] with calcination temperatures up to 1300 8C can offer a sufficiently large specific surface for the stabilization of Ni nanoparticles. Therefore, the influence of the mirror plane cation as well as the substitution cation concentration was investigated with four series of Ni-hexaaluminates ANi y Al 12Ày O 19Àd (A = Sr, La, Ba, and y = 0.25, 0.5, 1) that were prepared by a convenient impregnation.…”

Catalytic combustion of methane over mixed oxides derived from Co–Mg/Al ternary hydrotalcites

“…However, perovskites and pyrochlores and solid solution oxide catalysts suffer from gas diffusion limitation in combustion due to their low specific surface areas (SSAs) [15,[17][18][19]24]. The activity of most hexaaluminates is very low for igniting methane combustion and these are difficult to synthesize [7,10,[20][21][22]. Most recently, transition metal composite oxides derived from hydrotalcites have shown great potential as novel combustion catalysts due to their excellent catalytic activity and stability, high SSAs and dispersion of active sites [26][27][28].…”

“…Generally, supported noble metal oxides, particularly palladium oxide, are excellent catalysts for lower temperature combustion, but noble metals are expensive and prone to deactivation owing to sintering, decomposition and undesirable interaction with supports under hydrothermal situations encountered in combustion [3,6,[8][9][10]. A variety of inexpensive transition metal oxide catalysts, such as solid solution oxides [11][12][13], perovskites [14][15][16], pyrochlores [17][18][19] and hexaaluminates [7,[20][21][22] have been explored for catalytic combustion of methane. Unfortunately, no single catalyst, so far, can tolerate the stringent hydrothermal conditions existing in methane combustion.…”