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Mingwei Chen – One of the best experts on this subject based on the ideXlab platform.

  • structure and mechanical properties of Boron rich Boron carbides
    Journal of The European Ceramic Society, 2017
    Co-Authors: Chun Cheng, Mingwei Chen, Kolan Madhav Reddy, Akihiko Hirata, Takeshi Fujita
    Abstract:

    Abstract A series of Boron-rich Boron carbides are investigated to explore the effect of Boron/carbon ratios on the microstructure and mechanical properties of the complex material. It has been found that excess Boron substitution gives rise to expanded lattice constants, orientational asymmetry of the chain structure and distortion of the icosahedra of rhombohedra B 4 C units in comparison with conventional carbon-rich Boron carbides. Microstructure characterization reveals a high density of stacking faults and growth twins in Boron-rich Boron carbides. Nanoindentation measurements demonstrate that the hardness and modulus of Boron-rich Boron carbides decrease with the increase of Boron content while the B 10.2 C sample with the highest Boron substitution shows relatively high hardness and modulus. This study suggests that the structure of single-phase covalent materials could be tailored by self-alloying for improved mechanical properties.

Mafra Luís – One of the best experts on this subject based on the ideXlab platform.

  • Boron removal and reinsertion studies in 10B–11B exchanged HAMS-1B (H-[B]-ZSM-5) borosilicate molecular sieves using solid-state NMR
    Elsevier, 1
    Co-Authors: Hough Andrea, Routh, Alexande F., Clarke, Stua M., Wipe Paul, Amelse, Jeffrey A., Mafra Luís
    Abstract:

    Novel atomic level insight in Boron removal and reinsertion into the framework of a HAMS 1B (H [B] ZSM 5) borosilicate molecular sieve was obtained by a combination of wet chemistry and one /two dimensional 11B solid state NMR (SSNMR) spectroscopy. Uncalcined HAMS 1B shows only tetrahedral Boron. However, three Boron species are observed in 11B SSNMR spectra of as prepared and then calcined HAMS 1B: tetrahedral framework Boron ([4]Bfr), trigonal framework Boron ([3]Bfr), and non framework trigonal Boron ([3]BNF). A picture has emerged as to the origins of these three species. Trigonal Boron spe cies are formed via hydrolysis by reaction with the water formed from water release and water formed by oxidation and removal of the template during calcination. The trigonal Boron species are readily removed from the framework by slurrying in water or mild acid solutions. Tetrahedral Boron remains at a concen tration about equal to that in the calcined sieve not slurried, indicating that it is more difficult to remove. The extent of Boron removal and reinsertion is pH dependent. We demonstrate that Boron is removed to a greater extent at low pH and can be reinserted when pH is increased. Boron reinsertion into the frame work is proven by 11B SSNMR on a series of 10B 11B exchanged borosilicate zeolites. We found that when Boron is reinserted it enters at higher concentrations ( 40% more) as tetrahedral Boron, not trigonal Boron, thus reversing partial hydrolysis and removal during calcination

  • Boron removal and reinsertion studies in B-10-B-11 exchanged HAMS-1B (H-[B]-ZSM-5) borosilicate molecular sieves using solid-state NMR
    ACADEMIC PRESS INC ELSEVIER SCIENCE, 1
    Co-Authors: Hough Andrea, Routh, Alexande F., Clarke, Stua M., Wipe Paul, Amelse, Jeffrey A., Mafra Luís
    Abstract:

    Novel atomic-level insight in Boron removal and reinsertion into the framework of a HAMS-1B (H-[B]-ZSM-5) borosilicate molecular sieve was obtained by a combination of wet chemistry and one-/twodimensional B-11 solid-state NMR (SSNMR) spectroscopy. Uncalcined HAMS-1B shows only tetrahedral Boron. However, three Boron species are observed in B-11 SSNMR spectra of as-prepared and then calcined HAMS-1B: tetrahedral framework Boron (B-[4](fr)), trigonal framework Boron (B-[3](fr)), and non-framework trigonal Boron (B-[3](NF)). A picture has emerged as to the origins of these three species. Trigonal Boron species are formed via hydrolysis by reaction with the water formed from water release and water formed by oxidation and removal of the template during calcination. The trigonal Boron species are readily removed from the framework by slurrying in water or mild acid solutions. Tetrahedral Boron remains at a concentration about equal to that in the calcined sieve not slurried, indicating that it is more difficult to remove. The extent of Boron removal and reinsertion is pH dependent. We demonstrate that Boron is removed to a greater extent at low pH and can be reinserted when pH is increased. Boron reinsertion into the framework is proven by B-11 SSNMR on a series of B-10-B-11 exchanged borosilicate zeolites. We found that when Boron is reinserted it enters at higher concentrations (similar to 40% more) as tetrahedral Boron, not trigonal Boron, thus reversing partial hydrolysis and removal during calcination. (C) 2015 Elsevier Inc. All rights reserved

Chun Cheng – One of the best experts on this subject based on the ideXlab platform.

  • structure and mechanical properties of Boron rich Boron carbides
    Journal of The European Ceramic Society, 2017
    Co-Authors: Chun Cheng, Mingwei Chen, Kolan Madhav Reddy, Akihiko Hirata, Takeshi Fujita
    Abstract:

    Abstract A series of Boron-rich Boron carbides are investigated to explore the effect of Boron/carbon ratios on the microstructure and mechanical properties of the complex material. It has been found that excess Boron substitution gives rise to expanded lattice constants, orientational asymmetry of the chain structure and distortion of the icosahedra of rhombohedra B 4 C units in comparison with conventional carbon-rich Boron carbides. Microstructure characterization reveals a high density of stacking faults and growth twins in Boron-rich Boron carbides. Nanoindentation measurements demonstrate that the hardness and modulus of Boron-rich Boron carbides decrease with the increase of Boron content while the B 10.2 C sample with the highest Boron substitution shows relatively high hardness and modulus. This study suggests that the structure of single-phase covalent materials could be tailored by self-alloying for improved mechanical properties.

Rene Vacher – One of the best experts on this subject based on the ideXlab platform.

Hough Andrea – One of the best experts on this subject based on the ideXlab platform.

  • Boron removal and reinsertion studies in 10B–11B exchanged HAMS-1B (H-[B]-ZSM-5) borosilicate molecular sieves using solid-state NMR
    Elsevier, 1
    Co-Authors: Hough Andrea, Routh, Alexande F., Clarke, Stua M., Wipe Paul, Amelse, Jeffrey A., Mafra Luís
    Abstract:

    Novel atomic level insight in Boron removal and reinsertion into the framework of a HAMS 1B (H [B] ZSM 5) borosilicate molecular sieve was obtained by a combination of wet chemistry and one /two dimensional 11B solid state NMR (SSNMR) spectroscopy. Uncalcined HAMS 1B shows only tetrahedral Boron. However, three Boron species are observed in 11B SSNMR spectra of as prepared and then calcined HAMS 1B: tetrahedral framework Boron ([4]Bfr), trigonal framework Boron ([3]Bfr), and non framework trigonal Boron ([3]BNF). A picture has emerged as to the origins of these three species. Trigonal Boron spe cies are formed via hydrolysis by reaction with the water formed from water release and water formed by oxidation and removal of the template during calcination. The trigonal Boron species are readily removed from the framework by slurrying in water or mild acid solutions. Tetrahedral Boron remains at a concen tration about equal to that in the calcined sieve not slurried, indicating that it is more difficult to remove. The extent of Boron removal and reinsertion is pH dependent. We demonstrate that Boron is removed to a greater extent at low pH and can be reinserted when pH is increased. Boron reinsertion into the frame work is proven by 11B SSNMR on a series of 10B 11B exchanged borosilicate zeolites. We found that when Boron is reinserted it enters at higher concentrations ( 40% more) as tetrahedral Boron, not trigonal Boron, thus reversing partial hydrolysis and removal during calcination

  • Boron removal and reinsertion studies in B-10-B-11 exchanged HAMS-1B (H-[B]-ZSM-5) borosilicate molecular sieves using solid-state NMR
    ACADEMIC PRESS INC ELSEVIER SCIENCE, 1
    Co-Authors: Hough Andrea, Routh, Alexande F., Clarke, Stua M., Wipe Paul, Amelse, Jeffrey A., Mafra Luís
    Abstract:

    Novel atomic-level insight in Boron removal and reinsertion into the framework of a HAMS-1B (H-[B]-ZSM-5) borosilicate molecular sieve was obtained by a combination of wet chemistry and one-/twodimensional B-11 solid-state NMR (SSNMR) spectroscopy. Uncalcined HAMS-1B shows only tetrahedral Boron. However, three Boron species are observed in B-11 SSNMR spectra of as-prepared and then calcined HAMS-1B: tetrahedral framework Boron (B-[4](fr)), trigonal framework Boron (B-[3](fr)), and non-framework trigonal Boron (B-[3](NF)). A picture has emerged as to the origins of these three species. Trigonal Boron species are formed via hydrolysis by reaction with the water formed from water release and water formed by oxidation and removal of the template during calcination. The trigonal Boron species are readily removed from the framework by slurrying in water or mild acid solutions. Tetrahedral Boron remains at a concentration about equal to that in the calcined sieve not slurried, indicating that it is more difficult to remove. The extent of Boron removal and reinsertion is pH dependent. We demonstrate that Boron is removed to a greater extent at low pH and can be reinserted when pH is increased. Boron reinsertion into the framework is proven by B-11 SSNMR on a series of B-10-B-11 exchanged borosilicate zeolites. We found that when Boron is reinserted it enters at higher concentrations (similar to 40% more) as tetrahedral Boron, not trigonal Boron, thus reversing partial hydrolysis and removal during calcination. (C) 2015 Elsevier Inc. All rights reserved