Aggregated diamond nanorods, or ADNRs, are an allotrope of carbon believed to be the hardest and least compressible known material, as measured by its isothermal bulk modulus; aggregated diamond nanorods have a modulus of 491 gigapascals (GPa), while a conventional diamond has a modulus of 442 GPa. ADNRs are also 0.3
enser than regular diamond. The ADNR material is also harder than type IIa diamond and ultrahard fullerite.
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