Carbon Science and Technology E-Book

Pierre Delhaes

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 262

Veröffentlichungsjahr: 2012

Beschreibung

Carbon solids have been utilized by man since prehistoric times, first as a source of heat and then for other purposes; these are used as key markers for different civilizations. The essential role played by the use of coal mines during the industrial revolution as a main source of energy is a crucial point, which was then expanded through the development of carbochemistry. This book begins by describing the use of solid carbons as traditional materials, for example in the steel industry and for ceramics, then moving on to their technological uses such as active carbons and carbon fibers, etc., before discussing nanocarbons, the jewel in the crown of contemporary technological science. The final chapter analyzes the current economic and social impact of carbon solids.

Leseprobe

Table of Contents

Introduction

Chemical Glossary

Chapter 1. From the Chemical Element to Solids

1.1. Carbon on Earth

1.2. A brief history of the chemistry of carbon

1.3. Presentation of carbon solids

1.4. Conclusion and perspectives

1.5. Bibliography

Chapter 2. The Polymorphism of Carbon

2.1. The carbon atom and its chemical bonds

2.2. A thermodynamic approach

2.3. New molecular phases

2.4. Non-crystalline carbons

2.5. From solids to materials

2.6. Bibliography

Chapter 3. Natural Carbons: Energy Source and Carbochemistry

3.1. Primary energy sources

3.2. Carbochemistry

3.3. Use of coal resources

3.4. Summation and essential points

3.5. Bibliography

Chapter 4. The Role of Carbon in Metallurgy

4.1. Principles and evolution of the steel industry

4.2. The manufacturing of aluminum

4.3. Silicon production

4.4. Metallic carbides

4.5. Summary and essential points

4.6. Bibliography

Chapter 5. Black and White Ceramics

5.1. Graphites and isotropic carbons

5.2. Pyrocarbons and pyrographites

5.3. Films of diamond

5.4. Summary and essential points

5.5. Bibliography

Chapter 6. Dispersed and Porous Carbons

6.1. Carbon blacks

6.2. Shaping and fields of application

6.3. Porous and adsorbent carbons

6.4. Summary and essential points

6.5. Bibliography

Chapter 7. Fibers and Composites

7.1. Carbon filaments

7.2. Composite materials

7.3. Summary and essential points

7.4. Bibliography

Chapter 8. Molecular Carbons and Nanocarbons

8.1. Synthesis and production

8.2. Transport and nanoelectronic properties

8.3. Physical chemistry of interface and sensors

8.4. Conclusion and prospective

8.5. Bibliography

Chapter 9. Carbon Techniques and Innovation

9.1. Evolution of carbon materials

9.2. Socio-economic aspects

9.3. Epilogue

9.4. Bibliography

Index

First published 2012 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

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Library of Congress Control Number: 2012946443

British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library ISBN 978-1-84821-431-6

To all those who are dear to me. For my grandchildren, may they live on a hospitable planet.

Introduction

The key role of the carbon atom on Earth, where it occupies a singular place, has been described by P. Levi [LEV 84]. It can form several types of chemical bonds with other atoms, but it can also self-combine in order to create a carbon skeleton; characteristics which form the basis of organic chemistry, biochemistry, and life itself. This ability to bond in various ways also gives great flexibility and fullness to solids formed solely of carbon, both natural and artificial. Carbon solids have been utilized by man since prehistoric times, first as a source of heat and then for other purposes; these are used as markers for different civilizations. This is what we will show, referring to scientific and technological history and, firstly, reminding the reader of some general definitions.

Science, in the current sense of the term, is part of the representation of a body of knowledge that seeks to answer the question: why? The corresponding material technology tends to answer the question: how is it done? This combination, also called discovery and invention, is the keystone: a scientific discovery is the determination gleaned from an experimental phenomenon or concept, while an invention is the action of creating a machine, a new device, or a new manufacturing procedure. The former is a cognitive science, while the latter, referred to as productivist, includes applications and innovations since new things and activities are created.

A recapitulation of important historical periods can allow us to specify these developments, including definitions of the terms to be used later. We have drawn inspiration from the works of J. Ellul on the progressive concept of technology [ELL 80]:

Prehistory: technological activity is a constant characteristic of humanity. The development of simple tools was crucial for “Homo faber”, and the mastery of fire was undoubtedly a key stage in this evolution.

Antiquity is the period during which, with the invention of writing, consistent scientific activity emerged in Greece; presenting the first distinction between mathematical and physical technology and science, which are associated with the birth of philosophy. Great civilizations such as those of Egypt and China were already developing through the technical applications that characterized their evolution.

The late Middle Ages and the Renaissance: this period witnessed a scientific renewal introduced by Arab cultures, and a blossoming of art and technology in 15th and 16th Century Europe. One example of this is the career of Leonardo da Vinci as an engineer and inventor of machines based on his in-depth observations of natural phenomena and subsequent experimentations. The transmission of knowledge, which increased greatly thanks to the invention of the printing press, played a decisive role.

The first Industrial Revolution, in the late 18th and early 19th Centuries, was preceded by the birth of scientific experimentation and of discoveries that laid the foundations for the physical sciences. Significant industrial development ushered in the reign of machines and their combination to create coherent and complex systems described as “technological” systems.

The modern period, which began in the 20th Century, has seen an explosion in this complementarity between scientific discoveries and technological inventions, one which is overlapping more and more closely. This is technoscience, as described by B. Bensaude-Vincent [BEN 09], in which the knowledge society and its economy are intimately mingled and considered as the main foundation of society and the driving force of the economy; the key word, then, is innovation.

This brief outline of the successive periods shows that the history of science and technology is dependent on the means of transmission of knowledge. The development of writing in antiquity, the invention of the printing press during the Renaissance and finally the digital revolution at the end of the last century, are pivotal events. This ushered the appearance in Europe of industrial and commercial protection, concomitant with that of scientific books and articles. The transmission of information became common with the recognition of commercial protection in 15th Century Venice, and also in London and Paris with the granting of monopolies by letters patent. These were the ancestors of the patents on inventions standardized from the beginning of the 18th Century in Europe and then the United States, followed by the creation of patent filing offices. The first scientific journals, summarizing the results of basic research, appeared later. This scientific press first emerged in 1665 in England, with The Philosophical Transactions of the Royal Society, and in France with Le journal des savants (“The Scholars’ News”). During this period, scholars drew together with the foundation of the Royal Society in England and the Académie des Sciences in France, indicating a sociological recognition of this activity. As the encyclopedia published by D. Diderot and J. Le Rond D’Alembert (1751–1771) — an ordered dictionary of the sciences of arts and crafts — bears witness, the global development of technology had a growing influence on the global economy and the evolution of society. The exponential proliferation of scientific publications during the past two centuries is a testament to the growth of knowledge. Finally, the recent legal concept of intellectual property in a continually evolving industrial and commercial context has become a major element of modern society.

Through the prism of the carbon element, heir to archaic techniques and developing constantly until the creation of ultramodern materials, we may analyze a textbook case. The scientific and technological explosion of the past two centuries brings up the problem of the possible precedence of discovery and its influence on invention, along with the question of its permanence. Certainly, a look at the recent Nobel Prize winners in chemistry and physics shows it to be in evidence with the discoveries of W.F. Libby in 1961 for carbon-14 isotopic dating; of R.F. Curl, R.E. Smalley and H.W. Kroto in 1996 for the discovery of fullerenes; and of A. Geim and K.S. Novolesov for that of graphene in 2010. These examples underline the existence of totally new varieties of carbon with novel properties, giving rise to new innovations that bring up the problem of the lifespan of inventions associated with increasingly rapid technological innovation. To address this, we have chosen to examine the main areas of chemistry and physics in which carbon plays a central role, following a more or less chronological order. Chapter 1 is concerned with coals in their natural state, used as a source of energy, followed by their use and transformation into industrial products. This first stage will firstly be discussed within the context of the history of alchemy, and within the context of the establishment of the corpus of modern chemistry.

Chapter 2 will complete this introduction by enumerating current knowledge regarding the various types of carbon; this element shows the widest variety of identified solid forms (around half a dozen, including graphite, diamond, and the new molecular forms [DEL 09]). Our approach in the subsequent chapters will be based on modern scientific knowledge. In this vein, note that primary publications will not be given, but that most of the references will refer to books, articles, and journals available for review by the general public as bibliographic entry points. To help readers understand the text, the most frequently used chemical terms, based on international norms (IUPAC), are listed in a glossary. Key definitions in chemical language are used with their current meaning, corresponding to digital encyclopedias such as Wikipedia and Encyclopedia Britannica.

Chapters 3 to 5 will move from the traditional use of natural carbons as a fossil energy source and the basis of carbochemistry towards increasingly sophisticated materials. A reminder will be given of the abstract and protean concept of energy in the context of thermodynamics as it pertains to natural carbons. Next, carbon’s crucial role in metallurgy with the phenomenon of carboreduction, giving rise to metals and semiconductors, will be tackled and then completed in Chapter 6. If we examine their thermochemical inertia, these materials display a refractory character as black and white ceramics.

More modern aspects will be linked to the idea of solids in the divided state, moving on to new phases of a more molecular nature. These are the black carbons used in traditional materials, and the more technical active carbons related mainly to efforts against pollution. Filaments, fibers, and nanotubes, which are used in composite materials and derivatives, and finally the new forms most recently discovered and the nanotechnologies associated with them will be presented in Chapters 7 and 8. Their economic contribution as a primary energy source and in various types of materials used in various industrial sectors will be summarized in Chapter 9.

This approach will show how successive generations of carbon solids, used as materials of transformation and then devoted to structural or functional use, have progressively impacted and influenced economic and societal evolution. The ethnological description of C. Levi-Strauss [LEV 52] proposed the game of chance and the cumulative aspect of successive inventions oriented in a certain direction in order to explain successive cultural mutations. In this sense, we offer a technical/economic consideration. These transformations led to the Neolithic revolution, then to the Industrial Revolution, and finally, now, to the digital revolution — phases that we have mentioned in this historical panorama, and in which carbon has played an ever-present and crucial role.

Bibliography

[BEN 09] B. BENSAUDE-VINCENT, “Le vertige de la technoscience. Façonner le monde atome par atome”, La Découverte, Science and Society collection, 2009.

[DEL 09] P. DELHAES, Solides et matériaux carbonés, Hermès-Lavoisier, Paris, 2009.

[ELL 80] J. ELLUL, “La technique ou l’enjeu du siècle”, Economica, Paris, 1980.

[LEV 84] P. LEVI, “The periodic table”, Schocke, Books Ed., New York, 1984.

[LEV 52] C. LEVI-STRAUSS, Race et histoire, Unesco, 1952.

Chemical Glossary

These definitions are usual in current chemical physics of carbons and they belong to the modern language of chemistry. Within this context the choice of primitive words does not escape to the vicious circle of mixed or interactive definitions. We select them as operative rather than semantic words.

Following that purpose we use the international rules as defined for carbon materials in IUPAC texts1.

Activated carbons: porous carbons with a large and controlled internal surface issued from carbonization and surface treatments in order to increase its selective adsorptive properties.

Adsorption: binding of a liquid or a gaseous component on the solid surface thanks to different interactive mechanisms (physical and chemical adsorptions are usually recognized).

Allotropy: the existence of different crystalline forms for a simple element with each of them presenting particular characteristics.

Anthracites: the highest content of a fraction or rank for a natural sedimentary char, usually more than 95%.

Ashes: inorganic residues resulting from the burning of natural chars and often containing calcium impurities.

Asphaltens: heavy components of aromatic residues issued from the distillation of tars and bitumens, obtained respectively from coal and petroleum.

Basic structural units (BSU): building block entities formed by stacking two or three small aromatic molecules exhibiting a size in/or around the nanometer range.

Binder: carbon artefacts, as pitches or thermosetting resins, added for agglomerating different particles by mechanical and thermal treatments.

Bitumens: natural products obtained from the hot splitting of mineral oil or heavy petroleum, equivalent to asphalts.

Carbochemistry: selective transformation by thermochemistry processes of natural chars or their derivatives for a specific use.

Carbon black: colloidal particles of spherical shape, issued from incomplete combustion or from a controlled pyrolysis; resulting from a nucleation step in vapor state with diameters ranging from a few nanometers to micronic size.

Carbon fibers: continuous filaments of diameter size issued from the thermal treatments of precursors in condensed states, either natural or synthetic.

Carbonization: a set of physico-chemical thermal processes which progressively transform an organic precursor into pure carbon; usually primary and secondary carbonizations are recognized.

Carbynes: bi-coordinated carbon atoms giving rise to polymeric chains and associated with metastable solid phases.

Cast-iron: alloys made with iron and carbon with a weight concentration larger than 2.1%, and eventually containing other impurities such as silicium.

Ceramics: inorganic compounds prepared by heating and crystallization after subsequent cooling, which present a thermostable or refractory character.

Char: traditional term for a solid containing more than 50% of carbon issued from natural organic compounds (charcoal).

Chemical vapor deposition (CVD): process of thermal decomposition of an organic precursor followed by a bulk deposit of solid carbon on a hot surface.

Coal: sedimentary form of fossils issued from plants with 75–95% of carbon, the most common among the different classes of natural chars.

Cokes: solid residues resulting from the pyrolysis and primary carbonization of natural chars. After thermal treatment around 500°C the brittle solid is called a raw or a green coke and above 1,000°C a classic coke (for example, a metallurgical coke).

Colloids: suspension of very small particles sized around a few nanometers and distributed inside a continuous medium which presents a homogeneous appearance.

Composites: solid materials with at least two distinctive phases, one being mechanical strengthening and the other a surrounding matrix; they exhibit final properties which are not resulting from just an additive law.

Coordination: number of first neighboring atoms linked with a covalent bonding. This definition is related to the hybridization concept in quantum chemistry.

Diamond: solid phase formed with tetra-coordinated carbon atoms, which gives rise to a face centered cubic structure or a hexagonal structure (called lonsladeite), metastable phases at room temperature under atmospheric pressure.

Elasticity: the behavior in continuum mechanics of bodies that deform reversibly under stress. In a linear elasticity regime the constraint is weak and the length deformation is proportional to it.

Energy: a fundamental physical quantity which can be present under different forms. It is usually defined from thermodynamics principles as the product of an intensive variable and an extensive variable.

Enthalpy: measure of the total energy for a thermodynamic system. An enthalpy variation is the heat associated with phase changes or chemical reactions which are exo- or endothermic (respectively negative or positive quantities).

Fuels: fossil products obtained from the sedimentation of living species leading to natural gas, petroleum and different chars (also used for synthetic products).

Fullerenes: carbon molecules in a closed structure such as a cage; formed with an even number of hexagons and twelve isolated pentagons. The first metastable compound is the icosahedra C60.

Glassy carbon: obtained by the controlled carbonization in solid state of various thermoset polymers (such as phenolic or furfurylic resins) yields a non-graphitizable carbon with a pseudo glassy appearance and a low permeability to gases and liquids.

Graphene: a single atomic layer of tri-coordinated carbons giving rise to a polyaromatic hexagonal network, usually of finite size and called a ribbon of graphene.

Graphite: ordered stacking of parallel graphene layers with two allotropic forms, two alternative planes in a thermodynamically stable hexagonal phase and three repetitive planes in a metastable rhombohedra phase.

Graphitization: this is the solid state transformation under heat treatment, above 2,000°C, leading to the 3D periodic structure of hexagonal graphite.

Greenhouse gases: a set of gases which absorb the infra-red solar radiations emitted by the Earth’s surface and induces the heating of the lower atmosphere and leads to weather change.

Hetero-elements: the presence of foreign elements other than carbon, removed by a progressive heat treatment; mainly hydrogen, nitrogen, oxygen and sulfur, depending on the origin of the natural or artificial precursor.

High temperature treatment (HTT): this is the highest temperature to which an organic compound is submitted; an essential parameter used to characterize both carbonization and graphitization processes.

Hybridation: a quantum effect based on the linear combination of the atomic orbitals to build up a chemical bond with the available valence electrons.

Intercalation: a mechanism induced by various chemical species, which opens the space between two graphene layers to form an ionic intercalation compound. The inverse way of leaving this space is called exfoliation.

Kerogens: a set of dispersed organic residues found in mineral rocks.

Lignite: the fossil residue of plants at the second step of sedimentation, between peat and coal, containing around 65–75% of carbon mainly of lignin origin.

Local molecular order (LMO): the microstructural organization of basic structural units, which gives rise to anisotropic domains.

Maceral: the main recognizable constituents of different natural chars and coals, depending on the vegetal origin and the sedimentation level.

Material: the constituent of a solid phase, eventually liquid, which presents a shape and a specific surface functionality, allowing it to communicate with the surroundings.

Mesophase (carbonaceous): a liquid crystal-type fluid phase constituted by polyaromatic flat molecules of discotic form and exhibiting an orientational order.

Microstructures: length characterization of a solid at a textural scale larger than the usual one in crystallographic structures and based on symmetry elements.

Nanocarbons: generic term for nanosized carbon materials constituted by three or four coordinated atoms — they include, for example, nanowires, nanodiamonds, etc., but they are different from nanostructured carbons exhibiting a large accessible surface due to porosities.

Nanotubes (single and multi-wall): the rolling and closing up of a graphene ribbon to form a single wall, open or capped; and the superposition of concentric layers for multi-wall nanotubes, which can present several other textures but always with an axial hole.

Natural expended graphite: artifact obtained from an intercalation-exfoliation chemical process enabling us to isolate a few graphene layers.

Oils: aromatic liquids issued from the distillation of coal, petroleum or bituminous shale.

Peat: obtained after the first step of partially decayed vegetation. Its carbon content is only about 55%.

Percolation: mathematical theory which allows us to describe the characteristics of heterogeneous random mediums in order to model their transport and dynamic properties.

Petroleum: natural liquid issued from the crude oil of complex mixtures constituted with liquid hydrocarbons, which are very dependent on their geological origin.

Pitch: a solid aromatic residue at room temperature obtained from tar distillation and characterized by a broad softening temperature range depending on its chemical composition.

Phase: in the thermodynamic sense, this is a collection of atoms or molecules filling a macroscopic volume in space and defined within a thermodynamic phase diagram.

Plasma: this is a state of matter similar to gas in which a part of the atoms or molecules are ionized. This unstable state is formed with charged particles, ions and electrons, and excited neutral atoms or molecules.

Polycrystalline or polygranular graphites: artificial artifacts formed with microcrystalline powders of different sizes (coarse or fine grained), randomly distributed and agglomerated with a binder to present a macroscopically isotropic behavior.

Polymorphism: the characteristics of a chemical compound to be present under different crystalline forms and associated morphologies.

Porosities: presence of an internal surface in a solid giving rise to pores characterized by their size, shape and connectivity (open and closed pores).

Pyrocarbons (PyC) and pyrographites: bulk products obtained from the chemical vapor deposition process on a bulk or porous substrate which presents a more or less graphitizable lamellar microstructure. Further temperature treatment up to 3,000°C under an uniaxial pressure of a graphitisable pyrocarbon gives a quasi-crystal called pyrographite.

Pyrolyse: the chemical decomposition of an organic matter by heating under a controlled atmosphere which is non reactive (or thermochemical process).

Resins (α, β, γ): different chemical parts of a given pitch separated by successive selective organic solvents.

Schwarzenes: infinite triperiodical structures of tri-coordinated carbon atoms, giving rise to a concave or convex curved surface depending on the cycle size; strongly metastable phases which are not experimentally proved.

Steel: this is an alloy created by combining iron and other elements, in particular carbon of between 0.2 and 2.1% by weight.

Viscosity: this is a measure of the resistance of a fluid being deformed under stress (several types of viscosity). The study of flowing matter is known as rheology which relates the deformation and flow regime under different mechanical constraints.

Volatile organic compound (VOC): any molecule, except methane, which is a gas or a vapor under standard temperature and pressure conditions.

1 See Pure and Applied Chemistry, vol. 67, pp. 473–506, 1995 and the internet site “IUPAC gold book”, available online at: http://goldbook.iupac.org/.

Chapter 1

From the Chemical Element to Solids

We will take an historical approach to the conceptual context of the history of chemistry [BEN 93]. The first part of this chapter will discuss natural carbon solids in the context of their biological cycle, in order to show, as part of the history of the sciences, that the roots of many uses have been developed empirically since the dawn of civilization. The birth of modern chemistry allowed us to clarify and further define the carbon element. Its main varieties as a pure body existing in the solid state will be discussed in the second part of the chapter. Finally, an overall presentation of several types of carbon solids, both natural and artificial in origin, will provide a broad outline of the subsequent chapters.

1.1. Carbon on Earth

The carbon atom, which is cosmic in origin, results from nucleosynthesis that occurs in the cores of stars and is subsequent to the formation of the Sun. We know that the fusion of three helium cores creates carbon (the existence of different isotopes will be discussed in Chapter 2). Since the formation of the Earth around five billion years ago, the quantity of carbon of interstellar origin is considered to have been nearly constant on our planet. It is not one of the most frequently-occurring elements, but it occupies a singular position. Through the centuries, a carbon atom will exist in a living organism; a molecule such as carbon dioxide or another more complicated molecule; or under the ground in fossilized carbon, and will thus move through what we call the carbon cycle. Its distribution has evolved across geological time periods. With the birth of life and photosynthesis, it was involved in the formation of plants, mainly in the carboniferous period (a Paleozoic era that occurred around 300 million years ago), and then stored in the form of fossils after sedimentation. In its gaseous or liquid state it can be found in the form of carbon oxides, alkanes, and hydrocarbonated compounds, as well as in many molecules resulting from bio-organic synthesis.

Figure 1.1. Schematic representation of the global cycle of carbon (adapted from L.R. Kump, J.F. Kasting and R.G. Crane [KUM 99]); the symbol GTc indicates gigatons (109 tons) of carbon equivalent

A balance sheet of sorts may be created by examining the currently-established global cycle of carbon [KUM 99]. As we have shown schematically in Figure 1.1, the distribution of carbon results from the flows identified among the four surface parts of the planet: atmosphere, biosphere, hydrosphere and lithosphere. To understand this, we must distinguish between organic and inorganic carbon, which have short and long cycles of very different durations. Short cycles with rapid exchanges concern the atmosphere, biosphere, and surface hydrosphere, with the residence time of an atom expressed in years.

It is within this context that animal and human activity leads to the emanation of greenhouse gases. These are principally carbon dioxide, methane, and carbonaceous aerosols. Annual production, currently estimated at around 8–10 gigatons, has an unavoidable effect on the atmosphere and climate. On the other hand, for the lithosphere and the deep oceans, long cycles are involved, with residence times on a geological scale expressed in millions of years. This leads to an immense reservoir of carbon with storage divided into two roughly equivalent parts; carbonates in calcareous rocks, and carbons of various organic origins. We are mainly interested in plant residues resulting from the biological cycle related to production by photosynthesis and stored in sedimentary rocks: these are kerogens. A slight fraction of this dispersed matter constitutes on the one hand the precursor of gas, mineral oils and petroleum stored in mother rocks or reservoirs, and fossil carbons on the other hand.

The formation of hydrocarbons is a long and complex phenomenon characterized by a biodegradation caused by micro-organisms leading to natural gases and then to oils and bitumen collected in mother rocks. Under the influence of a terrestrial thermal gradient, solid residues in the massive state and fossil carbons of different so-called ranks are obtained. These constitute only a small fraction of all of the trapped carbon, but they are an important source of fossil energy (see Figure 1.1). Therefore, all carbon products come from carbon of biological origin through the progressive burying of living matter, its fermentation in an aerobic environment, and then an anaerobic transformation. Under the effect of the geothermal gradient, this living matter becomes progressively richer in carbon, to become at last mineral coal. This is classified into different ranks according to the origin and the carbon content, based on the earliest works of V. Regnault beginning in 1837.

Figure 1.2. Example of a Van Krevelen diagram [VAN 61] showing the categories of kerogens indicated in the text leading to natural carbons, showing the main products during the three principal stages of biochemical evolution: diagenesis, catagenesis, and metagenesis

Kerogens and natural coal are usually grouped according to their ultimate analysis, as proposed by D.W. Van Krevelen [VAN 61], who created a diagram of evolution using the atomic ratio [H/C] in terms of [O/C], with hydrogen and oxygen being the main hetero-elements present. He distinguished three main types of kerogens, depending on the origin of organic residue (see Figure 1.2):

– series I contains products that are very rich in hydrogen, resulting from plankton in fresh or brackish water;

– series II corresponds to sea organisms; the [H/C] ratio remains high, but [O/C] increases significantly;

– series III comes from land plants that are low in hydrogen but rich in oxygen.

During the degradation of these molecules, two developmental stages are characteristic: diagenesis, which includes the main output of oxygen and the elimination of carbon dioxide and water; then a stage of maturation called catagenesis, marked especially by a subsequent release of hydrogen and the formation of polyaromatic groups. In all cases, the deep burial of an accumulated phase leads to the formation of carbon solids that are increasingly rich in carbon; for growing carbon content, we distinguish the following major categories: peat, lignites, bituminous coal, and anthracite, with increasing carbon weights ranging from 50% to more than 90%, and with increasingly higher calorific powers. Ores also undergo complete metamorphic transitions under the influence of temperature and pressure, which lead to pure crystallized bodies such as graphite and diamond, formed in the deepest, oldest rocks.

1.2. A brief history of the chemistry of carbon

We will turn now to a brief recapitulation of the four principal stages in the history of chemistry as analyzed by B. Bensaude-Vincent and I. Stengers [BEN 93], which justify the historical periods given in the introduction. This approach will serve as a methodological framework to observe, define, and categorize the successive contributions that will be made on the bases of the theoretical concepts of modern chemistry.

In antiquity, the philosophical question of how to represent matter and its transformations first appeared in Greece between the 6th and 4th Centuries BC [BAU 04]. Plato proposed a rather geometrical approach, based on the attribution of regular polyhedra to primordial substances already cited by Empedocles: water, air, earth, and fire. Later, Aristotle, as part of his philosophy of nature, proposed a more substantialist concept by assigning a crucial role to the associated qualities: hot, cold, moist and dry. As the chemist and historian M. Berthelot remarked [BER 75], this concept involves the chemistry of properties rather than substances; if the compositions are not known, it is their qualities that are used to classify them. As J. Baudet says [BAU 04], it should be noted that during this same period, more atomist views of discontinuous matter were suggested, particularly by Democritus, but these were not taken up again until much later.

In the Middle Ages, Arab scholars used Greek cultural sources to deepen their studies of alchemy (“al-kimya”) with an experimental approach to the transformations they observed in the laboratory. Between the 8th and 10th Centuries AD, Jabir ibn Hayyan (or Geber) and his successors developed apparatuses and laboratory techniques associated with operations such as the fusion and distillation of natural bodies [BRI 99]. This resulted in a classification of substances based on their origin — mineral, vegetable, or animal — as well as a new way of grouping the artificial compounds that resulted from progressively codified manipulations. Interest in Arab alchemy found its way to medieval Europe, extending from the work of Bacon in the 13th Century to that of Paracelsus 300 years later, particularly with work regarding the characterization and transformation of metals, including research on transmutation into gold using the Philosopher’s Stone [BER 75].

The beginnings of modern science in Europe with the work of Galileo, Boyle, and Newton in the 17th