Introduction to Materials - Sample Preparation Topic for Transmission Electron Microscopy - page 8

The recognition of a specific site by a molecule enables a highly specific type
of bond called an immunological reaction. This type of bond occurs in antigen-
antibody reactions. The antigen-antibody reaction (Ag-Ab) is due to the interaction
between the epitopes of the antigen and the paratopes of the antibody. The reac-
tion involves four types of non-covalent bonds: hydrogen bonds, electrostatic bonds,
hydrophobic bonds, and van der Waals forces.
2.2 Type of Materials and Chemical Bonds
The different types of materials (metal, semiconductor, ceramic, mineral, polymer,
biological material, and mixed-composite material) contain one or more different
types of chemical bonds or electronic structures, giving them their specific physical
properties. These different types of materials can be divided into five classes based
on the nature of the chemical bonds of which they are composed.
Metallic Materials : These are pure metals and their mixtures or alloys. They
essentially contain metallic bonds. Metallic bonds are characterized by an electronic
structure with free electrons in the conduction band and no forbidden bands.
Semiconducting Materials : Their name is directly related to their electronic prop-
erty, which differs from that of metals by the presence of a forbidden band and an
unoccupied conduction band. This electronic structure, or band structure, is at the
origin of the effects of impurities or dopants on the electronic, optical, and mechan-
ical properties of semiconductors, which will either raise or lower the Fermi level
(the last electronic level occupied by the valence electrons).
Mineral Materials : These are rocks, oxides, mineral glasses, and ceramics. They
contain ionic and/or covalent bonds and may be attached to biological materials
such as bones, teeth, shells which are of biological origin but with mineral compo-
sitions. Ceramics are compounds with covalent and/or ionic bonds that are either
natural or synthetic. Among them are the families of oxides, carbides, nitrides, etc.,
which are either simple or complex. In the oxide family, the structures and prop-
erties can vary widely depending on their oxygen stoichiometry. Compounds with
mixed cationic valences are very sensitive to the effects of radiation, which could
result in the formation of non-stoichiometric compounds.
Organic Matter (Polymers, Biological Materials) : This includes C-, H-, and
O-based compounds of organic or synthetic origin. These are molecular systems
composed of a high number of atoms that contain covalent, ionic, and weak bonds.
Composite Materials : Composites combine different materials at different scales,
forming a new material with specific properties. These materials contain a mixture
of materials from the four preceding classes.
2.3 Chemical Bonds and Mechanical Properties
The mechanical behavior of materials is related to the nature of the chemical bonds,
but especially to crystal structure and organization. This will be an important factor