This manual is as a course of lectures for students of physical, technical, and engineering faculties, whose future field of interest is Fabrication of Nanomaterials, Nanosystems, and Nanocomposites as well as Studies of Their Properties”. The Manual also deals with relating Methods of Analysis, which are employed for Researches of above mentioned materials, as well as considers Original Works of Leading Specialists Working in the Field of Nanomaterials”.
The manual is composed of 9 Chapters. The 1st Chapter reports a general information about nanosized structures, describes mechanical, thermodynamic, electrical, and magnetic properties, and presents the structure classification. The 2ns Chapter is devoted to nanoporous materials, and presents their modern classification. The 3rd Chapter briefly describes fundamentals of amorphous material fabrication and their properties with the purpose of their comparison with nanostructured materials. The 4th Chapter considers fullerenes, fullerites, and nanotubes, as well as briefly describes their definitions and properties. The 5th Chapter briefly describes nanocomposite materials, methods of their fabrication, and properties. The 6th Chapter describes methods of nanomaterial fabrication and their classification as well as methods of nanomaterial and amorphous material fabrication, which are employed in powder metallurgy. Methods of an intensive plastic deformation, which are currently employed for a material fabrication, as well as CVD and PVD methods, which are employed for thin film fabrication, are considered. In addition, the Chapter deals with methods employed for fullerene and nanotube fabrication. It describes a particle micro-and nanoprobe applied for an analysis of the nanosized material. The Chapter 7 presents methods applied for nanomaterial researches, such as structure and chemical analysis, a mechanical testing of solids, for example, measurements of nanohardness, an elastic modulus, etc. Chapter 8 considers structure and properties of a nanostructured film and coating. This Chapter is the biggest one in its volume. It considers many problems, such as role of energy in a coating formation, effect of an ion bombardment on the formation of the nanocrystalline coating. It presents information about a mixing process, the formation of a multi-layered coating, fabrication of super-hard coatings, thermal stability, and oxidation resistance of a solid coating, as well as describes their mechanical properties. The Chapter reports why temperature and potential applied to a substrate play a crucial role in the formation of the nanocrystalline coating.
The manual is written by specialists involved for many years in researches of a material modification by particle beam and plasma, problem of new nanostructured material and combined coating fabrication, as well as all aspects of an ion implantation. The content of this eBook is well written and expressed in a compact and intelligible form. This manual is interesting not only for senior students, PhD students, but also for researchers, physicists, and chemists, whose field of interest is material science and solid, as well as for various Institutions such as Universities, Institutes, and Enterprises.
Prof. F. F. Komarov
Corresponding Member of the National Academy of Sciences of Belarus
In Recent years, a research of materials, which are composed of submicron nanosized grains and clusters, are swiftly developing due to already existing and/or potential applications in many technological fields such as electronics, catalysis, magnetic data storage, structure components, etc.
Metallic and ceramic materials with a submicron and nanocrystalline grain structure are now widely used as construction elements and functional layers in a modern microelectronics, as sites of devices in aviation and space engineering, and as hard wear resistant coatings in industry. To satisfy the technological requirements of these industrial fields, the size of structure elements is to be decreased to a submicron and a nanometer range. However, when a size of structure element decreases to a nanometer range, a material starts to demonstrate radically new physical and mechanical properties in comparison with a bulky base. Researches of these nanosized structures (nanostructures) rank among nanotechnological directions. Development and researches of nanostructured materials (further referred to as nanomaterials) and nanostructure properties obtained under various conditions are very important components of these scientific-technological directions. A material, a structure of which is composed of grains of about 0.3 to 0.04 µm size, is considered as a submicrocrystalline [1-3]. A material of smaller grain size is considered as a nanomaterial.
A nanomaterial (a nanocrystal, a nanocomposite, a material with a nanophase structure, etc.) is to be understood as a material, in which structure elements (a grain, a crystallite, a fiber, a layer, a pore) do not exceed a limit of 100 nm (1 nm = 10-9 m), at least, along one crystallographic direction. According to size of a structural unit, the nanomaterial is conventionally subdivided into a nanocluster and nanocrystalline material. A nanocluster material is subdivided into small (3 to 12 number of atoms, 100% of surface atoms, without an inside layer), big (13 to 150 number of atoms, 92 to 63% of surface atoms, including 1 to 3 inner layers), and giant nanocluster material (151 to 22000 number of atoms, 63 to 15% of surface atoms, including 4 to 18 inside layers). Conventionally, a cluster top boundary corresponds to such amount of atoms that an addition of one more atom already cannot change physical-chemical properties of this cluster. Theoretical calculations, which were confirmed by experimental researches for a cluster containing not less than 300 atoms, demonstrated that an icosahedrons structure is the most stable one. When an amount of cluster atoms increased, an elastic deformation energy quickly rouse in a proportion to their volume, and consequently, this icosahedrons structure is destabilized forming a face-centered cubic lattice .
A structure unit with a higher amount of atoms and 3 to 40 nm grain size ranks among a nanocrystal. This nanocrystalline material has various forms and demonstrates unique chemical, physical, and mechanical properties. A grain size is limited by the maximum size of the nanostructure elements and depends on some critical parameters (a size effect): a free range length of carriers participating in an energy transfer, a size of a domain/a domain wall, a diameter of a Frank-Reed loop, a de Broglie wave length, etc. This size effect sharply changes quality and properties of the nanostructured system and indicates a special condensed material state, which exists only in the nanostructured material. Today, the nanostructured material can be formed on the basis of various metals and alloys, and with the help of specially developed technological methods.
In recent years, a definite progress had been achieved in physical researches and technologies of the nanostructured material fabrication. In particular, an important stage of these researches is a systematic study of microprocesses occurring in a phase interface in the course of nanostructured system formation. This systematic study stimulated an appearance of calculation methods, which are employed to predict optimal technological parameters and promising ways of the nanostructured material formation.
A whole number of publications, monographs, and papers [5-11] report about technologies, structures, properties, and applications of the nanomaterial and the nanostructure. Here, we present only a description of individual representatives and classes and do not reflect, to a full extent, features of this modern direction. Why is there this modern interest in a nanotechnology, in general, and in a nanostructure study, in particular?
On one hand, nanotechnologies allow formation of a principally new material, which can find its application in future, since it is compact and functionable. It plays an important role in the formation of principally new elements for future nanodevices, which are dependent on physical principles employed for their functioning.
On the other hand, the nanotechnology is an extremely wide interdisciplinary direction, uniting specialists working in a field of physics, chemistry, materials science, biology, technology, directions of intellectual/self-organized systems, high-technological computer engineering, etc.
Finally, solving problems arising in the field of nanotechnologies, and, first of all, in the process of researches, scientists find many gaps existing both in fundamental and technological knowledge. All above mentioned excites a concentrated interest of a scientific and engineering society to this direction [12-21].
In many technologically advanced countries such as USA, United Kingdom, Japan, China, Russia, national programs, which are specified at an intensive development of various directions of the nanotechnology and formation of new nanostructures, are accepted and have started to be actively introduced into a practice.
Now, several basic types of the nanomaterials are known [1, 4].
VARIETY OF NANOMATERIALS
A nanomaterial has a number of structure characteristic features, which are the parameters relating to a structure as a whole and those identifying its individual elements. In their turn, the structure characteristic features of the nanomaterials are reflected in an unusual display of their properties. Since the nanomaterial is a basic unit of a nanosystem, properties of the nanosystem to a considerable degree depend on the nanomaterial properties.
Variety of nanomaterials is immense and every type is characterized by a specific structure and, as a consequence, specific properties. The characteristic features of the nanomaterial and the system formed on its basis, first of all are manifested in a size effect, among which a quantum effect takes a special place.
According to degree of their structure complexity, the variety of nanomaterials is subdivided into materials composed of individual nanoparticles and those composed of nanostructures (Fig. 1).
A nanoparticle is a nanosized complex of atoms and molecules, which are interrelated in a definite way.
Figure 1: A classification of nanomaterials according to their structure characteristic features.
The following types of the nanoparticles are identified:
Nanocluster, which is sorted as an ordered cluster characterized by a definite order in an arrangement of atoms and molecules and a strong chemical bond and a non-ordered nanocluster characterized by a disordered arrangement of atoms and molecules and a weak chemical bond;
Nanocrystal (a crystalline nanoparticle), characterized by the ordered arrangement of atoms and molecules and the strong chemical bond like a bulky crystal (a macrocrystal);
Fullerene, which is composed of carbon atoms (or atoms of another element) forming a structure looking like a spherical carcass;
Nanotube, which is composed of carbon atoms (or atoms of another element) forming a structure looking like a cylindrical carcass closed at its both ends;
Supermolecule, which is composed of “a host molecule” with a three-dimensional structure, in a cavity of which a “guest molecule” is arranged;
Biomolecule, which is a complicated molecule of biological origin characterized by a polymer structure(DNA, a protein);
Micelle, which is composed of molecules of a surface-active matter forming a sphere-like structure;
Liposome, which are composed of molecules of a special organic compound like a phospholipid forming a spherical structure;
A nanostructured material is an ensemble of nanoparticles. Nanoparticles play a role of a structure element in such material. A type of the nanostructured material depends on a character of interrelation existing between nanoparticles: a consolidated material and a nanodispersed one.
The consolidated material is a compact solid-phase material, which is composed of nanoparticles with a fixed spatial position in the material volume and rigidly-directly bound to another one. The consolidated material is:
Nanocrystalline material, which is composed of nanocrystals usually called a nanograin or a nanocrystallite;
Fullerite, which is composed of fullerenes;
Photon crystal, which is composed of ordered-in-space elements, a size of which is comparable with a half-length of a photon wave in one, two or three directions;
Layered composite material (with a superlattice), which is composed of various material layers of a nanosize thickness;
Matrix component, which is composed of a solid base (a matrix), in the volume of which nanoparticles (nanowires) are distributed;
Nanoporous material, which is characterized by the presence of nanopores;
Nanoaerogel, which is composed of an interlayer of a nanosize thickness separating pores.
A nanodispersed material is a dispersed system with a nanosized dispersion phase.
In addition to the above mentioned matrix nanocomposite materials and nanoporous materials, the nanodispersed materials cover:
Nanopowder, which is composed of contacting other nanoparticles;
Nanosuspension, which is composed of nanoparticles free-distributed in the liquid volume;
Nanoemulsion, which is composed of nanodrops of a liquid free-distributed in a volume of another liquid;
Nanoaerosol, which is composed of nanoparticles and nanodrops free-distributed in a volume of a gaseous medium.
Specimens of various nanostructured materials are often bulky, i.e. are characterized by a micro-and macro-size, whereas their structure elements are nanosized.
Effects, which are related to the small size of composing structures, may manifest themselves in a different way in various nanomaterials.
For example, a specific surface of the nanocrystalline and nanoporous material is crucially larger, i.e. a fraction of atoms arranged in a thin (about 1nm) near-surface layer radically arises. This increases the reaction ability of the nanocrystal, since atoms, which are arranged in the surface, have unsaturated bonds in contrast to atoms, which are arranged in the material bulk, since they are bound with surrounding atoms. A change in atomic ratio between the surface and the bulk atoms may result in atomic reconstruction, in particular, in a change of an atomic arrangement order, an interatomic distance, and a crystalline lattice period. The size dependence of a nanocrystalline surface energy predetermines a corresponding dependence of a melting temperature, which is lower for the nanocrystal than for the macrocrystal. As a whole, heat properties of the nanocrystal are crucially different, which is related to a character of atomic heat oscillations.
When the size of ferromagnetic particle decreases to a certain critical value, the domain separation becomes energetically disadvantageous. As a result, polidomain nanoparticles become single domain and acquire special magnetic properties, which are manifested in supermagnetism. The fullerene and the nanotube are characterized by very unusual properties due to their specific structure. This is true also for the molecular and biomolecular complex functioning according to laws of molecular chemistry and biology.
Peculiarities of a structure and properties of an individual nanoparticle affect in a definite way a structure and properties of the consolidated materials and the nanodispersion, which are formed on their basis.
A typical example is a nanocrystalline material, which is characterized by a decreased grain fraction, and, respectively, an increased fraction of interfaces occurring in the material volume. Simultaneously, a change of structure characteristics of both grains and interfaces takes place. As a result, mechanical properties of the nanocrystalline material significantly change. The material demonstrates a superhardness of a superplasticity under definite conditions.
Electron properties of the nanostructure, which are conditioned by quantum effects, are of a special interest for practical applications.
Figure 2: A classification of types of nanosystem-based devices according to their functional purposes.
The nanomaterial serves as a basis for the development of nanosystems with various functional purposes, which in their turn are subdivided into an electron, an optical, and a mechanical nanosystem, according to the principle of functioning, Fig. 2. An action of the electron nanosystem is based on transformation of an electrical signal, that of the optical one-on transformation of an optical signal (light) into the electrical one and vice versa, and the mechanical nanosystem transforms a mechanical motion.
Sets of definite characteristics of nanosystems are employed in definite fields of engineering such as nanoelectronics, nanooptics, and nanomechanics. Development of various types of nanosystems is closely interconnected and results in fabrication of more constructively complicated and integrated nanosystems, such as nanooptical-electron, nanoelectrical-mechanical, nano optical-mechanical, and nano optical-electro-mechanical systems.
The development of nanosystems is undoubtedly a new step, which will enable a future progress of microsystems. In practice, nanosystems are built-in various Microsystems forming in this way a promising direction of a modern system units (devices) such as a micronanosystem equipment.
A consolidated material-is a compact, a film, or a coating formed from a metal, an alloy, or a compound using a powder technology, an intensive plastic deformation, a controlled crystallization from an amorphous state, and various other techniques, which are currently applied for deposition of a film and a coating.
A nanosemiconductor, a nanopolymere, and a nanobiomaterial may exist in an isolated or a partially mixed (consolidated) state.
Fullerene and nanotube became an object of researches since the moment, when Sir Harold (Harry) Walter Kroto (1985) found a new carbon allotrope form-a cluster C60 and C70, which was called fullerene. This new carbon form attracted much more attention, when the carbon nanotube was revealed in a graphite product after an electrical-arc evaporation (Sumio Iijima, 1991).
Nanoparticles and nanopowder represent a quasizero grain size structure having various compositions and a size of which usually does not exceed a nanotechnological limit. A difference is that the nanoparticle is isolated, while the nanopowder is an aggregate. In a similar way, the nanoporous material is characterized by a pore size, which, as a rule, is not less than 100 nm.
A supermolecular structure is a structure, which is formed as a result of so-called non-covalent synthesis accompanied by formation of weak bonds (a Van der Waals, a hydrogen type, etc.) between molecules and their ensembles.
The nanomaterial is not a “universal” material; it is a vast class of many various materials joining different families. In addition, there exists a delusion that the nanomaterial is a material composed of very small “nano”-particles. In reality, many nanomaterials are not composed of individual particles; they are complicated micro objects nanostructured either in a surface or in a volume. Such nanomaterials are considered as a special state of matter, since properties of these materials, which are composed of nanostructured and nanosized elements, are not identical to properties of a volume material.
So, the nanomaterial is characterized by several basic features, which position it beyond any competition in comparison with other matters.
First, the nanomaterial is composed of very small objects, which cannot be seen with a naked eye. It represents a “super miniaturization”, which leads to a possibility that more and more quantity of functional nanodevices can be placed at an area unit. This is vitally important, say, for nanoelectronics or very dense magnetic information recording, which can reach 10 Tirrabit per a square centimeter.
Second, the nanomaterial has a large surface area, which promotes a hastened interaction inside and within a medium, to which it is placed in. For example, a catalytically active material can hasten a chemical and biochemical reaction by a factor of ten, thousand, and even a million [22-30].
Decomposition of water into hydrogen and oxygen for needs of a hydrogen power engineering, which is realized in the presence of titanium dioxide nanoparticles (everyone knows it as a component of titanium white paint), seems to be very interesting. A nanofilter can screen bacteria or efficiently absorb impurities and toxins.
Third, the nanomaterial has unique physical and mechanical properties, and this means that such a matter is in a specific “nanosized” state. Changes found in the nanomaterial fundamental characteristics are conditioned not only by a small grain size, but also by a quantum-mechanical effect, in which an interface plays a dominating role. The effect arises when the grain size is so “critical” that is commensurable to a so-called correlation radius or other physical parameters (for example, a free electron and a phonon range, a coherence length in superconductors, a magnetic domain or a nucleon size of solid phase, etc.). This makes, in particular, a semiconducting material to be an ideal element for a perfect energy-consuming laser and light emission. Hardness of an individual carbon nanotube exceeds that of the best steel by a factor of ten. At the same time, it has many-fold advantage in a specific mass. All above-mentioned characteristics fully explain the fact that even a gram of the nanomaterial may be much more efficient than a ton of an ordinary matter, and that its industrial production is not a problem of quantity, ton, and kilometer, but that of a human thought quality, i.e. “know-how”.
Nanotechnology is an extremely complicated, professional, interdisciplinary field, which needs joined efforts of chemists, physicists, specialists in material science, mathematicians, medics, specialists in calculation methods, etc. Deep scientific fundamentals are admirably interwoven in a field of nanomaterials with aspects of a human knowledge and practical applications.
In this eBook, we report fundamental data concerning structure, properties, and application of the modern nanomaterials. In the First Chapter, we present general information about nanomaterials, their structure features, size effect on structure formation and on physical-mechanical properties.
In Chapters 2 and 3, we present information about structure and properties of a nanoporous and an amorphous material.
In Chapter 4, we consider certain properties of fullerene and nanotube. Chapter 5 deals with a nanocomposite based on a polymer. Chapter 6 is devoted to methods, which are currently employed for the nanomaterial fabrication, since these new methods really gave rise to a violent development of this field.
Physical research methods, namely, novel methods employed for surface studies are presented in Chapter 7.
In Chapter 8, we consider mechanical and thermal properties of a nanocrystalline film and a nanocomposite coating, which are fabricated using physical deposition methods.
Chapter 9 is devoted to an application of the nanocrystalline material, which is employed in an engineering society.