Ultrahigh-Temperature Ceramic Aerogels

Journal Article · Mon May 13 00:00:00 UTC 2019 · Chemistry of Materials

DOI:https://doi.org/10.1021/acs.chemmater.9b00496· OSTI ID:1542117

Cahill, James T. ^[1]; Turner, Sally ^[2]; Ye, Jianchao ^[1]; Shevitski, Brian ^[3]; Aloni, Shaul ^[3]; Baumann, Theodore F. ^[1]; Zettl, Alex ^[3]; Kuntz, Joshua D. ^[1]; Worsley, Marcus A. ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Univ. of California, Berkeley, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
3. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

In this work, we demonstrate the synthesis of high-surface-area, low-density refractory aerogels. The monolithic hafnium boride (HfB₂) and zirconium boride (ZrB₂) aerogels are prepared via borothermal reduction of precursor hafnia and zirconia aerogels, respectively, consisting of a fine mixture of boron nanoparticles and the metal oxide. This precursor boron–metal oxide (B–MO₂) composite aerogel was synthesized by modifying the pure ethanol solvent typically used in the epoxide-initiated sol–gel synthesis of metal oxide aerogels with an ethanolic boron nanoparticle suspension. After reduction, precursor aerogels are converted to metal boride aerogels containing primary particles in the sub-100 nm regime. The relative densities of the HfB₂ and ZrB₂ aerogels are 3 and 7%, respectively, and could be tailored by simply changing the density of the precursor aerogels via modifying the reagent concentrations or the drying conditions. Thermal conductivities of the ZrB₂ monoliths ranged from 0.18 to 0.33 W/(m K). The surface areas of the HfB₂ and ZrB₂ aerogels were 10 and 19 m²/g, respectively. Lastly, successful reduction of the aerogels to the diboride phase was confirmed by X-ray diffraction.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
• Grant/Contract Number: AC02-05CH11231; AC52-07NA27344
• OSTI ID: 1542117
• Report Number(s): LLNL-JRNL--763511; 953337
• Journal Information: Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 10 Vol. 31; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY