Inductively Coupled Nonthermal Plasma Synthesis of Size-Controlled γ-Al2O3 Nanocrystals

Abstract

Gamma alumina (γ-Al2O3) is widely used as a catalyst and catalytic support due to its high specific surface area and porosity. However, synthesis of γ-Al2O3 nanocrystals is often a complicated process requiring high temperatures or additional post-synthetic steps. Here, we report a single-step synthesis of size-controlled and monodisperse, facetted γ-Al2O3 nanocrystals in an inductively coupled nonthermal plasma reactor using trimethylaluminum and oxygen as precursors. Under optimized conditions, we observed phase-pure, cuboctahedral γ-Al2O3 nanocrystals with defined surface facets. Nuclear magnetic resonance studies revealed that nanocrystal surfaces are populated with AlO6, AlO5 and AlO4 units with clusters of hydroxyl groups. Nanocrystal size tuning was achieved by varying the total reactor pressure yielding particles as small as 3.5 nm, below the predicted thermodynamic stability limit for γ-Al2O3.

半导体纳米晶体的冷等离子体合成：原理、进展和展望

“…Gresback等 人 [47] 研究了硅和锗纳米颗粒尺寸与停留时间的对应关 系, 发现当停留时间从30 ms增加到860 ms时, 硅纳米颗 粒的尺寸从3.4 nm逐渐增加到了10 nm; 而当停留时间 从30 ms增加到440 ms时, 锗纳米颗粒尺寸可以在 4~50 nm之间变化 [48] . 同样的方法也适用于氧化铝纳米 颗粒 [24] . 在更大的尺寸范围内, Eslamisaray等人 .…”

“…电感耦合等离子体 主要是通过流经线圈的射频电流引起的振荡电场产生 (图1(b)). 在电感耦合等离子体系统中, 等离子体具有很 高的离子密度, 导致晶核在形成后立即离解, 因而对于 晶体尺寸和形貌的控制较差 [23,24] . 电容耦合等离子体 则是通过电容效应将射频电场耦合到等离子体中, 其 反应腔体(石英、玻璃等)通常使用两个电极环绕介电 管(图1(c)).…”

Efficient simultaneous removal of diesel particulate matter and hydrocarbons from diesel exhaust gas at low temperatures over Cu–CeO2/Al2O3 coupling with dielectric barrier discharge plasma

“…Furthermore, Cu-CeO 2 catalyst with an Cu/Ce atomic ratio of 1 is most active in catalyzing the combustion of diesel soot [21]. γ-Al 2 O 3 is extensively used as a catalyst support in the automotive industries due to its high specific surface area, high porosity and excellent thermal stability [22,23]. The common methods for preparation of supported catalysts are impregnation, deposition-precipitation and mechanical grinding, among which the grinding method has the advantages of simplicity, rapidity, no usage of solvent, environmental friendliness and energy conservation [24].…”