In situ neutron diffraction studies of single crystals and powders during microwave irradiation

Harrison, Andrew; Ibberson, R. M.; Robb, Graeme R.; Whittaker, Gavin; Wilson, Chick C.; Youngson, Douglas

doi:10.1039/b203379h

Cited by 35 publications

(27 citation statements)

References 49 publications

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“…Small-angle X-ray scattering (SAXS) measurements under conventional heating confirmed this, and showed that particle growth to 10 nm takes place followed by agglomeration. Further, Harrison et al [184] studied the microwave heating of aspirin and BaTiO 3 crystals and powders, using in situ neutron diffraction.…”

Section: Neutron and X-ray Scatteringmentioning

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: Neutron and X-ray Scatteringmentioning

confidence: 99%

Microwave Synthesis of Nanoporous Materials

2006

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“…10 This report and others that followed assigned a different setting of the same space group, that is, P2 1 /c. [11][12][13] In this setting, the largest face is (100). 14,15 A likely cause of the confusion over face indexing was then the use of alternative space group settings, exacerbated by the almost identical metrics of the a and c axes (Tab.…”

Section: Introductionmentioning

confidence: 98%

The Confusion of Indexing Aspirin Crystals

Aubrey‐Medendorp

Parkin

2008

Journal of Pharmaceutical Sciences

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“…A handful of studies on the effect of microwaves on other systems using in situ scattering have been published [13][14][15] as outlined previously. [11] X-ray scattering is a powerful yet simple technique capable of obtaining information on the particle size and structure of a material.…”

Section: Introductionmentioning

confidence: 99%

In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites

et al. 2007

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A custom waveguide apparatus is constructed to study the microwave synthesis of zeolites by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WR-284 waveguide is used to heat precursor solutions using microwaves at a frequency of 2.45 GHz. The reaction vessels are designed to include sections of thin-walled glass, which permit X-rays to pass through the precursor solutions with minimal attenuation. Slots were machined into the waveguide to provide windows for X-ray energy to enter and scatter from solutions during microwave heating. The synthesis of zeolites with conventional heating is also studied using X-ray scattering in the same reactor. SAXS studies show that the crystallization of beta zeolite and NaY zeolite is preceded by a reorganization of nanosized particles in their precursor solutions or gels. The evolution of these particles during the nucleation and crystallization stages of zeolite formation depends on the properties of the precursor solution. The synthesis of NaA and NaX zeolites and sodalite from a single zeolite precursor is studied by microwave and conventional heating. Microwave heating shifts the selectivity of this synthesis in favor of NaA and NaX over sodalite; conventional heating leads to the formation of sodalite for synthesis from the same precursor. The use of microwave heating also led to a more rapid onset of NaA zeolite product crystallization compared to conventional heating. Pulsed and continuous microwave heating are compared for zeolite synthesis. The resulting rates of formation of the zeolite products, and the relative amounts of the products determined from the WAXS spectra, are similar when either pulsed or continuous microwave heating is applied in the reactor while maintaining the same synthesis temperature. The consequences of these results in terms of zeolite synthesis are discussed.

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In situ neutron diffraction studies of single crystals and powders during microwave irradiation

Cited by 35 publications

References 49 publications

Microwave Synthesis of Nanoporous Materials

Microwave Synthesis of Nanoporous Materials

The Confusion of Indexing Aspirin Crystals

In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites

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