Autoclave synthesis and thermal transformations of the aluminophosphate molecular sieve VPI-5: an in situ X-ray diffraction study

Barnes, P.; Munn, Juliet; Turrillas, X.; Klinowski, Jacek

doi:10.1016/0009-2614(92)85966-e

Cited by 34 publications

(24 citation statements)

References 15 publications

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“…Provided that the X-ray energy is high enough to give reasonable transmission through a high-pressure vessel, similar experiments are possible for autoclave reactions. Several groups have explored this field, notably He et al (1992), who studied the synthesis and thermal transformations of an aluminophosphate under hydrothermal conditions (temperatures of 413-423 K), and Lupo et al (2004), who studied the hydrothermal crystallization of Ce-doped zirconia at temperatures of 473-523 K. Naturally, the autoclaves used for such studies were specially constructed. While perfect for studying relatively slow reactions, the intrinsically low heating rate of an autoclave makes this approach less suited for studying high-temperature kinetics.…”

Section: Introductionmentioning

confidence: 99%

Experimental setup forin situX-ray SAXS/WAXS/PDF studies of the formation and growth of nanoparticles in near- and supercritical fluids

et al. 2010

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The growing interest in inorganic nanoparticles for a wide range of applications is spurring a need for synthesis methods that allow a highly specific tailoring of material properties. Synthesis in supercritical fluids holds great promise for solving this problem, but so far the fundamental chemical processes taking place under these conditions are to a large extent unknown. Here the design, construction and application of a versatile experimental setup are reported; this setup enables in situ synchrotron small‐angle X‐ray scattering/wide‐angle X‐ray scattering/pair distribution function (SAXS/WAXS/PDF) studies of the formation and growth of nanoparticles under supercritical fluid conditions.

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Section: Introductionmentioning

confidence: 99%

Experimental setup forin situX-ray SAXS/WAXS/PDF studies of the formation and growth of nanoparticles in near- and supercritical fluids

et al. 2010

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“…[9][10][11][12][13] Briefly these are: using the continuous synchrotron x-ray spectrum at a fixed collection angle (2) simplifies the design of environmental sample cells; by using low-2 collection angles the diffraction peaks occur at high energies and this gives rise to x-ray penetrations three orders of magnitude greater than with conventional laboratory sources, enabling bulk samples to be examined ͑e.g., 8-12 mm thicknesses for cements͒; the high intensity can be harnessed to yield time-resolved diffraction patterns on time scales of seconds. These attributes are enhanced further by third generation sources: The intensity increase not only permits shorter collection times but also permits reduction of the beam size defining slits so that the pattern resolution becomes less degraded by geometrical effects.…”

mentioning

confidence: 99%

Fastin situx-ray-diffraction studies of chemical reactions: A synchrotron view of the hydration of tricalcium aluminate

Turrillas

Barnes

et al. 1996

Phys. Rev. B

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We report observations on the early hydration of tricalcium aluminate, the most reactive component of Portland cement, using rapid-energy dispersive diffraction on a high brilliance synchrotron source. In situ observations of the hydration process over short time scales, and through bulk samples, reveal an intermediate calcium aluminate hydrate appearing just prior to the formation of the final stable hydrate, demonstrating the nucleating role of this intermediate. The superior quality of the data is sufficient to yield concentration versus time plots for each phase over the whole hydration sequence. This improvement derives from being able to use smaller diffracting volumes and consequent removal of time smearing due to inhomogenetics, and thus now offers the possibility of extending the technique in terms of time resolution and diversity of system. ͓S0163-1829͑96͒51022-2͔Third generation synchrotron radiation sources are now providing intense beams of high-energy x-ray photons with collimation characteristics that can be exploited in the study of reactions within bulk solid state materials. For example, the European Synchrotron Radiation Facility ͑ESRF͒ has a source size of circa 120ϫ250 m, a very high brilliance and usable energies up to 200 keV for diffraction purposes. In the studies reported here the samples were exposed to fluxes of the order of 10 12 photons per second per mm 2 in a 0.1% bandwidth at 50 keV. This represents an increase of 50-100 compared to equivalent experimental fluxes using second generation sources.Given these features we can now use synchrotron methods to look at much faster solid-state transformations than previously. The hydration of Portland cement, the reactive binder in concretes 1 for construction and in grouts for oil field engineering, 2 at first appears to be slow, reacting with water on a time scale of hours and developing final strength over many months. 3,4 Nevertheless there is evidence, such as from adiabatic calorimetry 5 and environmental scanning electron microscopy, 6 of some intense chemical and microstructural activity over the first few minutes following the initial contact between water and the anhydrous cement. However the direct observation of critical rapid mineralogical changes in dense cement pastes on the time scale of seconds has only now become possible by use of the latest synchrotron technology.It has long been known 4,7 that the early hydration of Portland cement, i.e., the first few hours after mixing with water, is greatly influenced by the behavior of its most reactive component, tricalcium aluminate, or ''C 3 A'' for short. Its hydration reactions can be conveniently expressed using a cement chemistry shorthand ͑e.g., see Taylor 7,8 ͒ in which the various phases are written in terms of the oxides ͑CϭCaO; AϭAl 2 O 3 ; HϭH 2 O͒. Using this shorthand, we can summarize key parts of the hydration process in terms of the formation of several hydrates

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“…In the first examination of an AlPO system with EDXRD He et al 47 demonstrated from a direct examination of the crystallization profile that VPI-5 had a surprisingly short induction period, concluding that the nucleation event may take place during an aging step of the gel. Walton et al 48 have also observed 'pauses' in the crystallization curve during the formation of zeolite A from a gel and it was proposed that this was due to a periodic release of nuclei from the inhomogeneous gel (although recently 45 similar pauses have been noted in a clear solution zeolite A synthesis, indicating this change may be due to some other process).…”

Section: Waxs Intermediates and The Crystallization Curvementioning

confidence: 99%

The role of synchrotron radiation in examining the self-assembly of crystalline nanoporous framework materials: from zeolites and aluminophosphates to metal organic hybrids

2010

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This tutorial review describes the role of synchrotron-based techniques in the study of the formation of Crystalline Nanoporous Framework Materials (CNFMs), such as zeolites, aluminophosphates (AlPOs) and metal organic frameworks (MOFs). Initially, a general formation process for CNFMs is described and the 'tool kit' (including synchrotron and non-synchrotron-based techniques) used to examine this complex process is presented. The need for realistic in situ conditions and the balance between this, data quality and time resolution, are also discussed with reference to commonly utilized in situ synchrotron-based experimental cells. The experimental studies into the formation of several CNFM systems are then examined and the role of the synchrotron-based experiments, in context with those obtained from other techniques, is discussed. From this the importance of the synchrotron-based technique is demonstrated, however it is also shown that, to obtain a more complete understanding of the formation process, complementary independent measurements are still often required. During these discussions some of the most common experimental techniques and analytical methods are also discussed in detail and critically assessed.

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Autoclave synthesis and thermal transformations of the aluminophosphate molecular sieve VPI-5: an in situ X-ray diffraction study

Cited by 34 publications

References 15 publications

Experimental setup forin situX-ray SAXS/WAXS/PDF studies of the formation and growth of nanoparticles in near- and supercritical fluids

Experimental setup forin situX-ray SAXS/WAXS/PDF studies of the formation and growth of nanoparticles in near- and supercritical fluids

Fastin situx-ray-diffraction studies of chemical reactions: A synchrotron view of the hydration of tricalcium aluminate

The role of synchrotron radiation in examining the self-assembly of crystalline nanoporous framework materials: from zeolites and aluminophosphates to metal organic hybrids

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