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  • 1
    Publication Date: 2011-05-05
    Description: Hydroxy sodalite (HS) particles were synthesized hydrothermally at 90°C for 10 h in the presence of cetyltrimethylammonium bromide (CTAB) and other aqua-based precursor materials like sodium aluminate, sodium metasilicate, and water. Crystalline phases and microstructures of the synthesized particles were studied by X-ray diffraction and field emission scanning electron microscopy, respectively. The effect of CTAB concentrations on the crystallinity and morphology of the synthesized particles was investigated. Thread-ball like HS particles along with some cube-shaped zeolite A were obtained in the presence of 0–0.5 mM CTAB while flower-like HS particles were observed in the presence of 1–5 mM of CTAB concentrations. With increase in CTAB concentration, HS phase increased significantly, and phase pure HS particles resulted for 3 and 5 mM of CTAB concentrations. A mechanism for the formation of flower-like HS particles was also proposed.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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  • 2
    Publication Date: 2011-12-13
    Description: The ZSM-5 zeolite powders were prepared through in situ extraction (extraction and conversion in single step process) of silica from rice husk ash in the presence of other aqueous-based precursors (sodium aluminate and tetrapropyl ammonium hydroxide) following a simple hydrothermal condition at 130°C–170°C. The powders were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared (FTIR) spectroscopy, N 2 physisorption measurements, and field emission scanning electron microscopy (FESEM). Crystallizations of ZSM-5 were noticed at 130°C/96 h, 150°C/24 h, and 170°C/12 h. The exothermic peak at 422°C in DTA curve indicated the removal of tetrapropyl ammonium ions (TPA + ) used as structure directing agent (SDA). The vibration bands at around 550 and 1221 cm −1 indicated the presence of double 5-ring in ZSM-5. The 150°C–170°C-treated samples exhibited higher BET surface area and pore volume compared to those of 130°C-treated powders. The FESEM images showed coffin-shaped morphology of the powders, and their sizes increased with increase in both reaction temperature and time.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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  • 3
    Publication Date: 2011-12-15
    Description: The ZSM -5 zeolite particles have been prepared using triethanol amine as structure-directing agent under static hydrothermal condition at 170°C for 7 days. The particles were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared (FTIR) spectroscopy, N 2 physisorption measurements, and field emission scanning electron microscopy (FESEM). The crystalline ZSM -5 was found at 170°C/7 days as shown by XRD. The vibration bands at around 549 and 1226 cm −1 in the FTIR spectra indicated the presence of double 5-ring in ZSM -5. The exothermic peak at 395°C in DTA curve indicated the removal of structure-directing agent. The BET surface area of the particles was 100 m 2 /g. The FESEM images showed coffin-shaped and broom-like crystals of ZSM -5.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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  • 4
    Publication Date: 2012-11-17
    Description: Zeolite Na A membranes were prepared hydrothermally by secondary crystallization process at different temperatures (55°C–75°C) on porous α-alumina-based support tubes (inner side) precoated with poly(ethyleneimine) (PEI) buffer layer and Na A seed particles. The Na A seed crystals synthesized at 65°C/2 h in the size range 100–200 nm having BET surface area of 71.57 m 2 g −1 were used for secondary crystallization of the membranes. The secondary crystallization at 65°C for (4 + 4) h (double-stage) showed highly dense Na A grains in the microstructure of the membrane with a thickness of 5 μm. It rendered the permeance values of 50.6 × 10 −8 , 2.47 × 10 −8 , and 0.55 × 10 −8  molm −2 s −1 Pa −1 for H 2 , N 2 , and CO 2 , respectively, with their permselectivity of 20.48 ( H 2 / N 2 ), 92 ( H 2 / CO 2 ), and 4.49 ( N 2 / CO 2 ). A tentative mechanism was illustrated for the interaction of PEI with the support substrate and Na A seed crystals.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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