Synthesis of Uniform Diameter Boron-Based Nanostructures Using a Mesoporous Mg-Al2O3 Template and Tests for Superconductivity
Mg incorporated mesoporous alumina with high surface area and narrow pore size distribution was prepared by the sol-gel method to use as a template for the synthesis of boron-based nanostructures by the CVD method. The mesoporous nature of the Mg-Al{sub 2}O{sub 3} was confirmed by low-angle XRD and N{sub 2} adsorption analyses. The randomly ordered pores were observed by TEM. The growth of boron-based nanostructures, such as nanowires and nanotubes, over Mg-Al{sub 2}O{sub 3} is evidenced by TEM analysis. Use of BCl{sub 3} as the boron source resulted in nanowires of around 20 nm in diameter and several micrometers in length. When using B{sub 2}H{sub 6} as the boron source, the diameter of the obtained nanostructures was in the range 3-4 nm, reflective of the pore diameter of Mg-Al{sub 2}O{sub 3}. Further loading of Mg in the form of Rieke Mg by sonication over 1% Mg-Al{sub 2}O{sub 3} resulted in the growth of straight nanotubes with a uniform diameter of 3-4 nm. The NEXAFS of the boron K-edge of purified boron-based nanostructures shows characteristic peaks for the existence of Mg-B and Al-B bonding. The STEM and EELS of the obtained individual nanostructures confirm the presence of B, Mg, and Al in the nanostructures. The appearance of a boron prepeak at 186 eV in EELS indicates that the boron hole states are not filled by the aluminum present in the nanostructures. Both field dependent DC magnetization (SQUID) and AC magnetic susceptibility measurements of Mg{sub x}B{sub y} nanostructures grown over 2 wt % Rieke Mg sonicated 1% Mg-Al{sub 2}O{sub 3} using B{sub 2}H{sub 6} as the boron source show evidence of a diamagnetic transition at about 80 K. The diamagnetic nature of Mg{sub x}B{sub y} nanostructures is suppressed significantly when the grown Mg{sub x}B{sub y} nanostructures are washed with NaOH solution to remove the template.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- DOE - OFFICE OF SCIENCE
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 1020140
- Report Number(s):
- BNL-95990-2011-JA; TRN: US201116%%121
- Journal Information:
- Journal of Physical Chemistry C, Vol. 113, Issue 41; ISSN 1932-7447
- Country of Publication:
- United States
- Language:
- English
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