Large AlPO4-5 crystals by microwave heating

Girnus, I.; Jancke, K.; Vetter, Roman; Richter‐Mendau, J.; Caro, Jürgen

doi:10.1016/0144-2449(94)00004-c

Cited by 165 publications

(79 citation statements)

References 24 publications

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“…3) Microwaves change the association between species within the synthesis mixture. [32,33] 4) Microwave heating superheats the synthesis mixture. [34] 5) Hot spots are created within the synthesis mixture.…”

Section: Proposed Synthesis Enhancement By Microwavesmentioning

confidence: 99%

Microwave Synthesis of Nanoporous Materials

2006

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Studies in the last decade suggest that microwave energy may have a unique ability to influence chemical processes. These include chemical and materials syntheses as well as separations. Specifically, recent studies have documented a significantly reduced time for fabricating zeolites, mixed oxide and mesoporous molecular sieves by employing microwave energy. In many cases, microwave syntheses have proven to synthesize new nanoporous structures. By reducing the times by over an order of magnitude, continuous production would be possible to replace batch synthesis. This lowering of the cost would make more nanoporous materials readily available for many chemical, environmental, and biological applications. Further, microwave syntheses have often proven to create more uniform (defect-free) products than from conventional hydrothermal synthesis. However, the mechanism and engineering for the enhanced rates of syntheses are unknown. We review the many studies that have demonstrated the enhanced syntheses of nanoporous oxides and analyze the proposals to explain differences in microwave reactions. Finally, the microwave reactor engineering is discussed, as it explains the discrepancies between many microwave studies.

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Section: Proposed Synthesis Enhancement By Microwavesmentioning

confidence: 99%

Microwave Synthesis of Nanoporous Materials

2006

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“…The most utilized source of phosphore is orthophosphoric acid, and the most studied sources of aluminum are pseudoboehmite and alkoxides [14]. Single crystals with nearly perfect morphology were grown using hydrofluoric acid [15]. With a specially prepared and aged aluminum hydroxide gel crystal sizes around 1 mm in caxis direction were obtained [16], whereas microwave heating proved to increase the crystallization rates by more than one order of magnitude [15,17].…”

Section: Host Crystalmentioning

confidence: 99%

Hexagonal microlasers based on organic dyes in nanoporous crystals

Braun

Ihlein

Laeri

et al. 2000

Applied Physics B: Lasers and Optics

137

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Molecular sieves, such as nanoporous AlPO4-5, can host a wide variety of laser active dyes. We embedded pyridine 2 molecules as a representative of a commercially available dye which fits into the channel pores of the host matrix. Many efficient dye molecules, such as rhodamines, do not fit into the pores. But modifying the structure of the dyes to appear like the used templates allows to increase the amount of encapsulated dyes. The properties of resulting microlasers depend on size and shape of the microresonators, and we discuss a model for microscopic hexagonal ring resonators. In terms of pump needed to reach lasing threshold molecular sieve microlasers are comparable to VCSELs. For dyes which fit into the pores we observed a partial regeneration of photo-induced damage.

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“…Cutting the reaction times short can, however, jeopardize the silica condensation process, leading to poorly polymerized products. Microwave heating overcomes this problem by speeding up the condensation step, allowing high quality products to form in times as short as 1 h at 150 C. [39][40][41][42] The resulting MCM-41 crystallites are very small (approximately 100 nm in diameter).…”

Section: Synthetic Aspects: Template Theory For Mesoporous Oxides Synmentioning

confidence: 99%