Oxygen‐Enhanced Crystallization of Solution‐Derived 12CaO·7Al₂O₃

Abstract

12CaO . 7Al 2 O 3 (C12A7) composed of nanosize cage structure can clathrate oxygen radicals (O À ) and has a high potential to application of strong oxidizing catalysis. In the present report, we demonstrate a fabrication route to C12A7 fine powders by Chemical Solution Deposition method in order to enhance the catalytic reactivity. Aluminum sec-butoxide, calcium nitrate tetrahydrate, acetylacetone, 2-methoxyethanol, and nitric acid were used as raw materials. Precursor solution was dried and annealed at 8001-9001C in air or O 2 atmosphere. Crystalline C12A7 powders were obtained by annealing at 9001C in O 2 atmosphere. Scanning electron microscope and transmission electron microscope images of the obtained powders revealed C12A7 particles were sintered and formed several micrometer particles with many pores. BET specific surface area of the powders was 4.2 m 2 /g. Possibility for synthesizing C12A7 powder with higher specific surface area by the solution process was indicated.

Characteristics, Thermodynamics, and Preparation of Nanocaged 12CaO·7Al2O3 and Its Derivatives

“…produced nanocrystal material of C12A7:O − –Na 2 O by solgel method. Sakamoto et al . reported fabrication of C12A7 with acetyl acetone as stabilizer to avoid precipitation of aluminum hydroxide during dissolution process.…”

Facile and Massive Aluminothermic Synthesis of Mayenite Electrides from Cost-Effective Oxide and Metal Precursors

“…Given the above XRD results as well as previous reports, these exothermal peaks are attributed to the formation of the mayenite structure. 34,35 Furthermore, with the increase of the Al amount, the exothermal peak presented a slight shift to lower temperatures (Figure 4b). That is, the introduction of Al significantly enhanced the formation of the mayenite (C12A7) framework, reasonable when considering the intensively exothermic nature of aluminothermy (Figure S6).…”

Topotactic Synthesis of Mesoporous 12CaO·7Al2O3 Mesocrystalline Microcubes toward Catalytic Ammonia Synthesis

“…In this context, several approaches beyond the conventional solid-state reaction have been proposed for producing nanostructured C12A7 and its derivatives. 22,27,28 One of the common synthetic methods to obtain nanocrystals is a solution process represented by the hydrothermal synthesis and the sol−gel process. When the desired crystal phase cannot be directly obtained by the solution process, the calcination of the as-dried products at relatively low temperatures enables us to obtain the target phase without sacrificing the nanostructure significantly.…”

“…Morphological design of catalysts is of great importance because a catalytic activity can be effectively enhanced by increasing surface area and improving mass transport. , In inorganic crystals, the former is associated with reducing crystalline size whereas the latter is achieved by forming a well-defined porous architecture. In this context, several approaches beyond the conventional solid-state reaction have been proposed for producing nanostructured C12A7 and its derivatives. ,, One of the common synthetic methods to obtain nanocrystals is a solution process represented by the hydrothermal synthesis and the sol–gel process. When the desired crystal phase cannot be directly obtained by the solution process, the calcination of the as-dried products at relatively low temperatures enables us to obtain the target phase without sacrificing the nanostructure significantly.…”