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This chapter discusses the effect of force and deformation of the tip apex and the sample surface in the operation and imaging mechanism of STM and AFM. Because the contact area is of atomic dimension, a very small force and deformation would generate a large measurable effect. Three effects are discussed. First is the stability of the STM junction, which depends on the rigidity of the material. For soft materials, hysterisis is more likely. For rigid materials, the approaching and retraction cycles are continuous and reproducible. Second is the effect of force and deformation to the STM imaging mechanism. For soft material such as graphite, force and deformation can amplify the observed corrugation. For hard materials as most metals, force and deformation can decrease the observed corrugation. Finally, the effect of force and deformation on tunneling barrier height measurements is discussed.

This chapter discusses the diffusional dynamics in intercalation compounds of graphite with alkali metals. These form two classes: stage 1 compounds like C₆Li, and stage 2 compounds like C₂₄Rb. HNO₃ has also been intercalated in graphite and studied by QENS. All these systems exhibit interesting transitions between commensurate and incommensurate structures which influences the diffusivity. A two-dimensional Chudley–Elliott model is applied. A few studies in the literature deal with ionic compounds with channels or layers. An example is the Chevrel phase Ni₂Mo₆S₈: the Q dependence of the linewidths establishes fast long-range motion of the intercalated Ni²⁺ ions.

This chapter begins with a discussion of the establishment of a phase diagram for a monolayer of ³He from heat capacity measurements. It then presents accounts of recent studies of the magnetic and thermal properties of first, second, and higher layers of ³He in graphite, together with some interactions of 2D ³He with other substrates.

This chapter describes application of the OLCAO method to the very loosely defined subject of complex crystals. These materials could also be classified under the previous chapters for insulators or metals. The common theme for the materials under this chapter is that they all have relatively complex structures or they are closely related to those crystals that have complex structures in terms of the number and variety of atoms as well as their geometric configurations. Yet, they are neither non-crystalline material nor are they crystals with defective structures that require complex structural modeling. These are considered separate issues and will be covered in chapters 8, 9, and 10.

Pure carbon was long thought to exist in only two crystalline forms: diamond and graphite. Conventional thinking has long since fixed on two other structural motifs. Creating fullerenes was an accidental pursuit that began among the stars. The technique used was laser vaporization coupled to mass spectrometry, a technique that indicates only the atomic mass of the products. When graphite was vaporized, the C60 peak stood out from a forest of others periodically separated by the mass of two carbon atoms. The mass production of fullerenes changed everything, not least by providing a crystal structure to lay to rest the skepticism that had always dogged the structural hypothesis of the 1985 paper. Carbon nanotubes have now supplanted fullerenes as the focus of research on nanoscale carbon.

Nuclear energy is one of the most significant sources of low carbon energy in use in the power sector today. In 2013, nuclear energy represented roughly 11% of the global electricity supply, with growth projected to occur in China, India, and Russia (International Atomic Energy Agency [IAEA], n.d.a; NEA, n.d.). As a stable source of electricity, nuclear energy can be a stand-alone, base-load form of electricity or complement more variable forms of low carbon energy, like wind and solar power. Among the energy technologies considered here, nuclear energy is complex not only for the science behind it, but also for its societal, environmental, and economic dimensions.This chapter explores the rapid rise of French nuclear energy in the civilian power sector. It considers what a national energy strategy looks like under conditions of high concern about energy supply security when limited domestic energy resources appear to exist. The case reveals that centralized planning with complex and equally centralized technology can be quite conducive to rapid change. However, continued public acceptance, especially for nuclear energy, matters in the durability of such a pathway. France is a traditional and currently global leader in nuclear energy, ranking the highest among countries for its share of domestic electricity derived from nuclear power at 76% of total electricity in 2015 (IAEA, n.d.b). France is highly ranked for the size of its nuclear reactor fleet and amount of nuclear generation, second only to the United States. In 2016, this nation of 67 million people and economy of $2.7 trillion had 58 nuclear power reactors (CIA, n.d.; IAEA, n.d.b). Due to the level of nuclear energy in its power mix, France has some of the lowest carbon emissions per person for electricity (IEA, 2016a). France is also one of the largest net exporters of electricity in Europe, with 61.7 TWh exported (Réseau de Transport d’électricité [RTE], 2016), producing roughly $3.3 billion in annual revenue (World Nuclear Association [WNA], n.d). This European country has the largest reprocessing capacity for spent fuel, with roughly 17% of its electricity powered from recycled fuel (WNA, n.d.).

You already know, if you have read Reaction 6, that an electric current is a stream of electrons. If you have also read the section on redox reactions (Reaction 5), which you should, in preparation for this account, then you will also know that in a redox reaction electrons are transferred from one species to another. Although it is now far too late, had you had that information 150 or so years ago, then you might have realized that if those species were at the opposite ends of a piece of wire, the transfer of electrons would then take place in the form of an electric current travelling along the wire and you would have invented the electric battery. All the batteries that are used to generate electricity and drive portable electrical and electronic equipment, from torches, drills, phones, music players, laptops, through to electric vehicles, are driven by this kind of chemically produced flow of electrons. One of the earliest devices for producing a steady electric current was the ‘Daniell cell’, which was invented in 1836 by John Daniell (1790–1845) of King’s College, London in response to the demand in the nineteenth century of the then emerging technology of telecommunication for a steady, cheap source of electricity. I have already touched on the underlying reaction when I explained what happens when a piece of zinc, Zn, is dropped into a solution of copper sulfate (Reaction 5), and this section builds on that account. In that reaction copper is deposited on the zinc and the copper sulfate solution gradually loses its colour as blue Cu2+ ions are replaced by colourless Zn2+ ions. As this reaction takes place, electrons hop from the zinc metal onto Cu2+ ions nearby in the solution. If we were to stand there watching, we would see electrons snapping across from the zinc to the Cu2+ ions wherever the latter came within striking distance of the zinc surface. There would be electron transfer, but no net current of electricity. Daniell did what I outlined in the opening paragraph: he separated the zinc metal and copper ions, so that electrons released by zinc had to travel through an external wire to get to the Cu2+ ions.

The carbon atom is discussed in the Bohr and Schrödinger pictures. Radii and energies of core and valence states are estimated. Ionization levels of carbon are used to estimate properties at variable principal quantum numbers, n. Linear combinations of 2s and 2p wavefunctions leading to bonds are described. Two electron wavefunctions are discussed in connection with covalent and hybrid bonds. The benzene molecule is discussed in terms of sp² bonding. The number of free electrons supporting diamagnetism in the benzene ring is estimated using the diamagnetic susceptibility and NMR chemical shifts. The bonding of benzene in modern chemical terms is described. Graphane and fluorographene are described. Natural and Kish graphite are compared with highly oriented pyrolitic graphite (HOPG). Bernal stacking and the phenomenon of superlubricity are described.

This chapter focuses on three categories of organic superconductors: charge-transfer salts, doped fullerides, and graphite intercalation compounds (GICs). One of the most interesting problems with all of these materials is the nature of their superconducting state and the associated driving mechanism for electron pairing. In quasi-one-dimensional Bechgaard salts, triplet pairing resulting from magnetic fluctuations seems to be predominant, while for the quasi-two-dimensional ET salts, a spin-singlet state with d-wave symmetry is favoured. The strongest support for an unconventional superconducting state in these salts stems from their proximity to the tunable magnetic state as revealed by complex phase diagrams, and the way in which superconductivity is adversely affected by non-magnetic impurities and disorder. In sharp contrast to these low-dimensional organic salts, both doped fullerides and GICs appear to be conventional superconductors with some form of electron–phonon interaction as the driving mechanism.

This chapter discusses the effect of force and deformation of the tip apex and the sample surface in the operation and imaging mechanism of STM and AFM. Because the contact area is of atomic dimension, a very small force and deformation would generate a large measurable effect. Three effects are discussed. First is the stability of the STM junction, which depends on the rigidity of the material. For soft materials, hysterisis is more likely. For rigid materials, the approaching and retraction cycles are continuous and reproducible. Second is the effect of force and deformation to the STM imaging mechanism. For soft material such as graphite, force and deformation can amplify the observed corrugation. For hard materials as most metals, force and deformation can decrease the observed corrugation. Finally, the effect of force and deformation on tunneling barrier height measurements is discussed.

Nanoscience and nanotechnology are introduced and compared. The physics of small systems introduces quantum dots and their applications. Carbon is discussed in terms of carbon black, graphite and graphene, and applications of graphene in chemical sensing and other fields are described. Carbon nanotubes and nanowires are discussed and illustrated. The topics in this chapter are under extensive current investigations and a number of recent developments are introduced. Graphite intercalation compounds, their structure and properties are treated, and the magnetic properties of chemical systems described in relation to nanosize materials. Nanopolymers and the fabrication of nanomaterials are outlined.

Ultrasonic material characterization or inspection for defects is conventionally performed using either liquid coupling (water, usually) or some type of gel or oil in contact-mode coupling. Mechanical waves can be transmitted only through some sound-supporting medium from their source (a transducer) to the object under study, and back again. Using distilled, degassed water to couple ultrasound to an object under test works quite well and has many technical advantages, including relatively low signal loss over laboratory or shop dimensions at typical frequencies, almost zero toxicity, and low cost. For many applications, the use of water is acceptable and preferred. There are, however, certain testing applications for which water can be a disadvantage. These situations include materials that are sensitive to contact with water, such as uncured graphite-epoxy composites or certain electronics. Large objects, whose total immersion is impractical, or objects for which rapid scanning is required might also be unsuitable for water coupling. Recent technological developments are beginning to permit the judicious replacement of water by a far more ubiquitous sound coupling medium—air. Ultrasonic testing in air has been investigated for more than 30 years, but recently there has been an upsurge in interest and application because of the availability of much more efficient sound-generating devices designed specifically for operation in air. In water- or direct-coupled ultrasonics, one typically employs piezoelectric transducers to generate sound waves because they are well suited to the generation of sound in water or in solids because of their high acoustic impedance. In air, however, we need just the opposite. Air is very compliant, so waves from a high-impedance source couple poorly into air. Much effort has been invested in finding suitable impedance matching materials that will render the familiar piezoelectric probe efficient in air-coupled (A-C) ultrasound. The problem, however, is nearly insurmountable because of the large acoustic impedance difference between air and quartz, for example. Quartz has an acoustic impedance of about 15 MRayl, while air’s impedance is about 425 Rayl, a ratio of about 35,000. The challenge is to find a material with an acoustic impedance that nearly equals the geometric average of these two widely disparate values.

In this chapter we consider elastic wave modes which propagate in composites with finite boundaries. There are those waves that exist between the two plane parallel boundaries of a homogeneous anisotropic solid. We consider that well-known problem, as well as waves in an elastic anisotropic rod, specifically an individual graphite fiber. Composite laminates seen in applications are essentially all multilayered structures, and in many cases can be considered periodically layered. So, we also take up the subject of guided waves in layered plates in later chapters. In a plate geometry, as illustrated in Fig. 5.1, we choose the propagation direction to be parallel to the x1 axis and the x3 axis to be normal to the plate surfaces. This geometry is particularly significant for composite materials since, by design, laminates are often locally planar in nature. While the solutions we find are appropriate for flat plates, with some modifications they describe wave motion in gently curved structures as well. Clear and mathematically straightforward descriptions of the characteristics of plate waves exist for isotropic media. The results obtained for isotropic media are not, however, directly applicable to most composites. We begin by considering the behavior of waves in a uniaxial composite laminate. In later chapters we generalize the calculation to layered orthotropic media, concentrating on the results and physical interpretation rather than the algebraic details. To begin a description of waves in plates, let us consider the possible polarizations of particle motion. Let the plate surfaces lie in the (x1, x2) plane of mirror symmetry with the origin dividing the plate thickness in half, as shown in Fig. 5.1. Then, we will at first assume the wave to be uniform in the x2 direction and propagating in the x1 direction, and (x1, x3) is the plane of symmetry. Particle motion can occur along any axis. Note that in this restricted symmetry, shear partial waves polarized along the x2 axis will have no component of particle motion normal to the plate surfaces. Partial waves are a concept introduced by Rayleigh to acknowledge that a superposition of both shear and longitudinal particle motion is generally needed to produce plate waves polarized in the vertical plane.

It is well known that alkali metal binary GICs adsorb gaseous species (H2, N2, Ar, CH4, etc.) physisorptively at low temperatures, where physisorbed gaseous molecules are accommodated in the interstitials of the alkali metal lattice within the graphitic galleries (Lagrange and Hérold, 1975; Lagrange et al., 1972, 1976; Watanabe et al., 1971, 1972, 1973). The capacity for hydrogen adsorption, which is estimated at 144 cm3/g in KC24, for example, is large and comparable to the capacity in other adsorbers such as zeolite or activated charcoal. Interestingly, the physisorption phenomenon in alkali metal GICs has different features from that in conventional adsorbents such as zeolite or activated charcoal; that is, guest molecules in alkali metal GICs are not simply bonded to the adsorbents through weak van der Waals forces without any change in the electronic structures. Here we discuss the gas physisorption phenomenon in alkali metal GICs from general aspects, in relation to their specific features. Then in subsequent sections, we will give details of actual cases. Hydrogen is a typical gaseous molecule adsorbed in alkali metal GICs. Hydrogen physisorption takes place at low temperatures below about 200 K, where hydrogen molecules are accommodated in the graphitic galleries and are not dissociated into atomic hydrogen species. When the temperature is increased to over 200 K, the alkali metal GICs work as catalysts to hydrogen, resulting in the occurrence of hydrogen chemisorption. Hydrogen physisorption will be discussed in Section 8.1.2, hydrogen chemisorption and related issues have been discussed partly in Sections 2.2.1 and 5.4.1 from the viewpoints of structure and electronic properties, and will be discussed again in Section 8.1.2. Figure 8.1 represents the composition dependence of the amount of physisorption of hydrogen molecules in KCm at 77 K (Lagrange and Hérold, 1975). The composition of 1/m = 1/8 corresponds to the stage-1 compound and the composition 1/m = 1/24 to the stage-2 compound; intermediate compositions between 1/8 and 1/24 are considered to have a mixed structure of stage-1 and stage-2 compounds. The stage-1 compound does not adsorb hydrogen at all.

Intercalation can be defined as the process of inserting atoms or molecules (guest chemical species) between layers in a host material with layered structure such as graphite. Intercalation can be achieved using a solid, liquid, or gaseous intercalate reagent, as discussed in Chapter 2. However, preparation from the vapor is the most common. When graphite is used as a host material, a high degree of three-dimensional (3D) structural ordering is generally desired. The intercalation rate and the resulting intercalate concentration are strongly dependent on the intercalation conditions, such as pressure, temperature difference between the host graphite material and the intercalate, the physical dimensions of the sample, the degree of crystalline order, and the defect density within the host graphite material. The most important factors for controlling the physicochemical properties of GICs are the host material and the types of intercalate. Compared with other host materials, fibrous materials, including vapor-grown carbon fibers (VGCFs) (Dresselhaus et al., 1988), have shown particular suitability for GIC from the viewpoint of practical applications. Fiber hosts are normally intercalated using techniques similar to those considered for HOPG-based GICs, though the specific intercalation conditions may be different with regard to intercalation temperature, time, and other conditions. It is noteworthy that the intercalation of chemical species within fiber hosts is successful at lower temperature ranges than for bulk graphite or HOPG host materials (Meschi, 1988; Meschi et al., 1986). Because of the small size of the fibrous hosts, with diameter around 10 μm , the intercalation time tends to be shorter. With regard to the kinetics, the intercalation of fibers is initiated at the free edges of the fibers and then proceeds along the fiber length, thus depending on the macroscopic structure or morphology of the host fibers (Shioya et al., 1986). Fibers prepared from polymeric precursors can be intercalated in the radial direction (Goldberg and Kalnin, 1981). However, for the case of low crystalline fibrous carbon such as PAN-based carbon fiber, it is very difficult to fully form intercalated materials. On the other hand, covalent GICs such as fluorinated graphite and graphite oxide can be synthesized (see Sections 2.3.4 and 9.1.8).

There are two important features in the structure and electronic properties of graphite: a two-dimensional (2D) layered structure and an amphoteric feature (Kelly, 1981). The basic unit of graphite, called graphene is an extreme state of condensed aromatic hydrocarbons with an infinite in-plane dimension, in which an infinite number of benzene hexagon rings are condensed to form a rigid planar sheet, as shown in Figure 1.1. In a graphene sheet, π-electrons form a 2D extended electronic structure. The top of the HOMO (highest occupied molecular orbital) level featured by the bonding π-band touches the bottom of the LUMO (lowest unoccupied molecular orbital) level featured by the π*-antibonding band at the Fermi energy EF, the zero-gap semiconductor state being stabilized as shown in Figure 1.2a. The AB stacking of graphene sheets gives graphite, as shown in Figure 1.3, in which the weak inter-sheet interaction modifies the electronic structure into a semimetallic one having a quasi-2D nature, as shown in Figure 1.2b. Graphite thus features a 2D system from both structural and electronic aspects. The amphoteric feature is characterized by the fact that graphite works not only as an oxidizer but also as a reducer in chemical reactions. This characteristic stems from the zero-gap-semiconductor-type or semimetallic electronic structure, in which the ionization potential and the electron affinity have the same value of 4.6 eV (Kelly, 1981). Here, the ionization potential is defined as the energy required when we take one electron from the top of the bonding π-band to the vacuum level, while the electron affinity is defined as the energy produced by taking an electron from the vacuum level to the bottom of the anti-bonding π*-band. The amphoteric character gives graphite (or graphene) a unique property in the charge transfer reaction with a variety of materials: namely, not only an electron donor but also an electron acceptor gives charge transfer complexes with graphite, as shown in the following reactions: . . .xC + D → D+ C+x. . . . . .(1.1). . . . . .xC + A → C+x A−. . . . . .(1.2). . . where C, D, and A are graphite, donor, and acceptor, respectively.

Pristine graphite crystallizes according to the D46h space group. There are twelve modes of vibration associated with the three degrees of freedom of the four atoms in the primitive cell. The hexagonal Brillouin zone and the phonon dispersion curves of pristine graphite, calculated by Maeda et al. (1979), are shown in Figure 4.1. The zone-center (Γ point) modes are labeled as three acoustic modes (A2u + Elu), three infrared active modes (A2u + Elu), four Raman active modes (2E2g), and two silent modes (2Blg). The first calculation of phonon dispersion for the stage-1 compounds KC8 and RbC8 was presented by Horie et al. (1980) on the basis of the model of Maeda et al. (1979) for the lattice dynamics of pristine graphite. Although the calculated phonon energies do not agree well with the experimental data, the model has most of the ingredients for describing the lattice dynamics of stage-1 GICs. A simple review of their work is presented as follows. The primitive cell of KC8, having a p(2 × 2)R0° superlattice, contains 16 carbon atoms and two K atoms. Note that only an αβ stacking sequence is assumed here (see Section 3.6.1). The primitive translation vectors are given by t1 (0, a, 0), t2 = (−√3a/2, a/2, 0), and t3 = (−√3a/4, −a/4, c), where a = 2aG = 4.91 Å and c = 5.35 × 2 = 10.70 Å. The corresponding Brillouin zone is shown in Figure 4.2b. The phonon dispersion for KC8 has been calculated by Horie et al. (1980) on the basis of the Born-von Karman force constant model. This dispersion curve is compared with that of pristine graphite by folding the dispersion curves of graphite into the first Brillouin zone of KC8. Since the side of the Brillouin zone in KC8 is not flat in two directions, as shown in Figure 4.2b, it is a little difficult to transfer the information on the dispersion curves in the first Brillouin zone of graphite into the Brillouin zone of KC8. For simplicity, nevertheless, we assume that the side of the Brillouin zone in KC8 is flat like that of graphite.

Jöns Jacob Berzelius (1779–1848), discoverer of the elements selenium, thorium, cerium, and silicon and deviser of the chemical symbols we use today, was one of the last in a long list of Swedish mineralogists and chemists active during the eighteenth century. Berzelius himself regarded one of his predecessors, Axel Fredrik Cronstedt (1722–65), as the founder of chemical mineralogy. We met Cronstedt in Chapter 2 as the discoverer of the element nickel, isolated from the ore kupfernickel. But another of Cronstedt’s achievements was perhaps of even greater significance: his development of a classification of minerals based not on their physical appearances, as had been common up to this time, but on their chemical compositions. He first published his scheme anonymously in Swedish in 1758, but it was later translated into English as An Essay towards a System of Mineralogy. Cronstedt recognized four general classes of minerals: earths, bitumens, salts, and metals. As their name suggests, the bitumens were flammable substances that might dissolve in oil but not in water. The main difference between the salts and the earths was that the former, which included the ‘alcaline mineral salt’ natron, could be dissolved in water and recrystallized from it. The earths he defined as ‘those substances which are not ductile, are mostly indissoluble in water or oil, and preserve their constitution in a strong heat’. Cronstedt initially recognized nine different classes of earth. By the time of Torbern Bergman (1735–84), these had been reduced to five which ‘cannot be derived from each other or from anything simpler’. Lavoisier and his collaborators included these five in their great work on nomenclature even though they suspected that, like soda and potash, they were most likely not simple substances, but species that contained new metals. In the 1788 English translation of the nomenclature these were called silice, alumina, barytes, lime, and magnesia. The first two eventually, in the early nineteenth century, yielded the elements silicon and aluminium. The word ‘silicon’ derives from the Latin ‘silex’ (meaning ‘flint’—a form of silicon dioxide), with the ending ‘-on’ reflecting its resemblance to the other non-metals carbon and boron.

Words are our enemies, words are our friends. In science, we think that words are just an expedient for describing some inner truth, one that is perhaps ideally represented by a mathematical equation. Oh, the words matter, but they are not essential for science. We might admit there is a real question as to whether a poem is translatable, but we argue that it is irrelevant whether the directions for the synthesis of a molecule are in Japanese or Arabic or English—if the synthesis is described in sufficient detail, the same molecule will come out of the pot in any laboratory in the world. Yet words are all we have, and all our precious ideas must be described in these history- and value-laden signifiers. Furthermore, most productive discussion in science takes place on the colloquial level, in simple conversation. Even if we know that a concept signaled by a word has a carefully defined and circumscribed meaning, we may still use that word colloquially. In fact, the more important the argument is to us, the more we want to be convincing, the more likely we are to use simple words. Those words, even more than technical terms, are unconsciously shaped by our experience—which may not be the experience of others. I was led to reflect on this by the reaction of a friend of mine, a physicist, to my use of the word “stable.” I had said that an as yet unmade form of carbon was unstable with respect to diamond or graphite by some large amount of energy. Still, I thought it could be made. My friend said, “Why bother thinking about it at all, if it’s unstable?” I said, “Why not?,” and there we were off arguing. Perhaps we should have pondered why the simple English word “stable” has different meanings for a physicist and a chemist. First, a little background. Diamond and graphite are the two well-known modifications, or allotropes, of carbon.