Abstract

Glass-like carbon (GLC) is a complex structure with astonishing properties: isotropic structure, low density and chemical robustness. Despite the expanded efforts to understand the structure, it remains little known. We review the different models and a physical route (pulsed laser deposition) based on a well controlled annealing of the native 2D/3D amorphous films. The many models all have compromises: neither all bad nor entirely satisfactory. Properties are understood in a single framework given by topological and geometrical properties. To do this, we present the basic tools of topology and geometry at a ground level for 2D surface, graphene being the best candidate to do this. With this in mind, special attention is paid to the hyperbolic geometry giving birth to triply periodic minimal surfaces. Such surfaces are the basic tools to understand the GLC network architecture. Using two theorems (the classification and the uniformisation), most of the GLC properties can be tackled at least at a heuristic level. All the properties presented can be extended to 2D materials. It is hoped that some researchers may find it useful for their experiments.

Highlights

  • Carbon is the most versatile element of the periodic table

  • Thanks to the uniformisation theorem and the classification one, some amazing properties of glass-like or vitreous carbon (GLC) can be understood at first glance

  • Material properties are governed by mathematics and physics

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Summary

Introduction

Carbon is the most versatile element of the periodic table. There are nearly ten million known carbon compounds, and an entire branch of chemistry, known as organic chemistry, is devoted to their study (see Figure 1). Noda and Inakagi proposed in 1964 [9] a structural model of GLC deduced from X-ray diffraction, in which tetrahedral carbon atoms form the main part of the cross-linkages which link the graphite-like layers in a random way. Harris [17] proposed a model for the structure of non-graphitising carbons, which consists of fragments of curved carbon sheets (fullerene-like), containing pentagons and heptagons as well as hexagons. Thanks to neutron and X-ray diffraction, Jurkiewicz et al [18] showed a large proportion of curved graphitic sheets The presence of these curved elements in carbon nanomaterials can be related to the formation of topological point-type defects in non-hexagonal rings (pentagons, heptagons and higher-membered rings). Other observations predict that carbon foams contain graphite-like “sp carbon” segments, connected by sp carbon atoms, resulting in porous Kagome structures [23].

Raman Spectroscopy
Other Spectroscopies
Experimental Set Up
GLC Characterisation
Algebraic Topology VERSUS Geometry
Dimension
Connection between Thermodynamics and Topology
Topology of Surfaces
Curvature
Euler Characteristic
Geometry of 2D Surface
The Classification Theorem
Planar Model
Special Points
Periodicity
The Local Gauss–Bonnet Theorem
Orientability Number
Boundary Number
Topological Invariants from Knot Theory
Electron Conductivity
Isotropy
Porosity versus Gas Diffusion
Willmore Energy
Defect Formula: “Mathematical” Stability
Constant Mean Curvature
Modified TPMS Structures
Findings
Conclusions
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