Crystal structure of tetrapropylammonium fluoride-containing precursor to fluoride silicalite

Price, G. D.; Pluth, J. J.; Smith, J. V.; Bennett, J. M.; Patton, R. L.

doi:10.1021/ja00386a023

Cited by 154 publications

(111 citation statements)

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“…This model consists of two central and four side pyramidal subunits (Figure 1 a). This model was proposed on the basis of an early XRD study [22] and was further corroborated by optical microscopy results [7,23] and by experiments in which the crystals were disassembled into single crystalline fragments by ultrasonic treatment. [24] In the so-called three-component model (Figure 1 b), the crystallographic axes maintain the same orientation across the entire crystal.…”

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confidence: 73%

Intergrowth Structure of Zeolite Crystals and Pore Orientation of Individual Subunits Revealed by Electron Backscatter Diffraction/Focused Ion Beam Experiments

et al. 2008

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confidence: 73%

Intergrowth Structure of Zeolite Crystals and Pore Orientation of Individual Subunits Revealed by Electron Backscatter Diffraction/Focused Ion Beam Experiments

et al. 2008

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“…With this model, the crystal face that was probed contains straight and zigzag channels, channels aligned parallel to the a and b direction, respectively (Figure 3 a). [23][24][25] Based on the light-polarization dependence of the optical absorption, only straight channels of ZSM-5 were found to host the oligomerization products. [4] In the present case, the intensity of the IR band associated with the dimer is higher with the light polarized along the c direction, implying that the transition moment associated with the vibrational mode is likely to be directed perpendicular to the long molecular axis of the dimeric carbocation.…”

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confidence: 99%

“…The spatial map of the 1534 cm À1 band is shown in Figure 4 b. UV/ Vis microspectroscopy results have suggested that dimeric carbocations are exclusively formed in the case of 4-fluorostyrene, [5] with lower concentrations at the edges of the crystals compared to that in the center. The intergrowth structure of ZSM-5 [23][24][25] entails that the two-dimensional channel network is oriented nonuniformly, i.e., at the edges of the crystal straight pores, open to the top surface of the crystal are accessible. On the contrary, in the center region of the crystals zigzag pores are accessible.…”

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confidence: 99%

In Situ Synchrotron‐Based IR Microspectroscopy To Study Catalytic Reactions in Zeolite Crystals

et al. 2008

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“…Samples were oriented with a four-circle x-ray diffractometer before the Brillouin experiments. Although twinning is commonly found in silicalite crystals, [28][29][30] no evidence of twins was indicated by the x-ray in polished crystals used in our measurements.…”

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confidence: 54%

“…The sample was shown to be phase pure by powder x-ray diffraction. The orthorhombic symmetry of silicalite, space group Pmna, 28 was verified by using single-crystal x-ray diffraction, from which unit-cell parameters of a = 20.019͑5͒ Å, b = 19.963͑9͒ Å, and c = 13.388͑5͒ Å and V = 5350.4͑6͒ Å 3 were obtained. As-synthesized TPAcontaining silicalite was determined to have the formula ͉͑C 3 H 7 ͒ 4 NF͉ 4 ͓Si 96 O 192 ͔ by thermogravimetric and carbon, hydrogen, and nitrogen elemental analyses.…”

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confidence: 99%

Negative Poisson’s ratios in siliceous zeolite MFI-silicalite

Sanchez-Valle

Lethbridge

Sinogeikin

et al. 2008

The Journal of Chemical Physics

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Brillouin scattering measurements of the single-crystal elastic properties of the as-made zeolite silicalite ͉͑C 3 H 7 ͒ 4 NF͉ 4 ͓Si 96 O 192 ͔-MFI provides the first experimental evidence for on-axis negative Poisson's ratios ͑auxeticity͒ in a synthetic zeolite structure. MFI laterally contracts when compressed and laterally expands when stretched along x 1 and x 2 directions in the ͑001͒ plane ͑ 12 = −0.061, 21 = −0.051͒. The aggregate Poisson's ratio of MFI, although positive, has an anomalously low value = 0.175͑3͒ compared to other silicate materials. These results suggest that the template-free MFI-silicalite ͓Si 96 O 192 ͔ might have potential applications as tunable sieve where molecular discriminating characteristics are adjusted by application of stress along specific axes. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2912061͔ Materials with a negative Poisson's ratio known as auxetics are solids that exhibit the unusual property of laterally expanding under uniaxial tension and laterally shrinking under uniaxial compression. 1,2 Far from being a mere scientific curiosity, these materials have important applications in various technologies and are of interest to a range of scientific communities, from chemistry to material engineering. Their unusual mechanical properties, indeed, give rise to a long list of measured and predicted technological enhancements, such as improved plane-strain fracture toughness, and increased indentation resistance, 2 improved honeycomb dielectric properties, 3 self-adaptative vibrational damping properties, 4 increased shear modulus, improved sound and shock absorption, and the ability to form dome-shaped surfaces. 5 The identification of auxetic behavior on an atomic level has also opened up the possibility of molecular-scale amplifiers and other nanoscale devices. 6 Given the widespread potential applications of these materials, experimental and theoretical investigations have focused for the past few years into the identification and refinement of new auxetic materials and understanding the physical basis of this unusual property. Negative Poisson's ratios have been experimentally identified in a number of organic and inorganic materials, both in crystalline and amorphous forms, including polymers, foams, elemental cubic metals and alloys, and the silica polymorph ␣-cristobalite. 5,[7][8][9][10][11][12] The latter is, in fact, the only known crystalline silicate possessing an aggregate negative Poisson's ratio ͑ = −0.16͒, which has been interpreted as arising from the concurrent rotation of the SiO 4 -tetrahedral building units 13,14 under an applied stress. The search for auxetic materials has targeted other related low-density openframework SiO 2 -based structures, and recent simulations performed by Grima et al. have predicted negative Poisson's ratios in a number of idealized siliceous zeolites. 15 However, the lack of accurate experimental data on the elastic properties of zeolites has precluded confirmation of these predictions for many years.To address th...

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Crystal structure of tetrapropylammonium fluoride-containing precursor to fluoride silicalite

Cited by 154 publications

References 0 publications

Intergrowth Structure of Zeolite Crystals and Pore Orientation of Individual Subunits Revealed by Electron Backscatter Diffraction/Focused Ion Beam Experiments

Intergrowth Structure of Zeolite Crystals and Pore Orientation of Individual Subunits Revealed by Electron Backscatter Diffraction/Focused Ion Beam Experiments

In Situ Synchrotron‐Based IR Microspectroscopy To Study Catalytic Reactions in Zeolite Crystals

Negative Poisson’s ratios in siliceous zeolite MFI-silicalite

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