[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.

Intrinsic ripples in graphene

More than 1000× uranium exists in the oceans than exists in terrestrial ores. With nuclear power generation expected to increase over the coming decades, access to this unconventional reserve is a matter of energy security. With origins in the mid-1950s, materials have been developed for the selective recovery of seawater uranium for more than six decades, with a renewed interest in particular since 2010. This review comprehensively surveys materials developed from 2000–2016 for recovery of seawater uranium, in particular including recent developments in inorganic materials; polymer adsorbents and related research pertaining to amidoxime; and nanostructured materials such as metal–organic frameworks, porous-organic polymers, and mesoporous carbons. Challenges of performing reliable and reproducible uranium adsorption studies are also discussed, as well as the standardization of parameters necessary to ensure valid comparisons between different adsorbents.

Materials for the Recovery of Uranium from Seawater

Emerging natural and tailored materials for uranium-contaminated water treatment and environmental remediation

Facile preparation of amino functionalized graphene oxide decorated with Fe 3 O 4 nanoparticles for the adsorption of Cr(VI)

Adsorption of U(VI) from aqueous solution by the carboxyl-mesoporous carbon

Ordered mesoporous polymer–carbon composites containing amidoxime groups for uranium removal from aqueous solutions

Synthesis of ultralight phosphorylated carbon aerogel for efficient removal of U(VI): Batch and fixed-bed column studies

Synthesis of flower-like MoS2/g-C3N4 nanosheet heterojunctions with enhanced photocatalytic reduction activity of uranium(VI)

Removal of uranium from aqueous solution by a low cost and high-efficient adsorbent

Youqun Wang

Papers

Adsorption of U(VI) from aqueous solution by the carboxyl-mesoporous carbon

Ordered mesoporous polymer–carbon composites containing amidoxime groups for uranium removal from aqueous solutions

Synthesis of ultralight phosphorylated carbon aerogel for efficient removal of U(VI): Batch and fixed-bed column studies

Synthesis of flower-like MoS2/g-C3N4 nanosheet heterojunctions with enhanced photocatalytic reduction activity of uranium(VI)

Removal of uranium from aqueous solution by a low cost and high-efficient adsorbent