1.3 History of Amorphous Materials
Throughout the history of human science and technology, the breakthrough of new technologies is always accompanied by the discovery of new materials. From ancient bone, stone, porcelain, metal materials to modern high-performance plastics, alloys, micro–nanomaterials, which are still developing, all of them have left a deep imprint in the history of science development. Along with the progressing of scientific theory, the ways of exploring new materials have changed significantly (Figure 1.5). For example, it took thousands of years for human beings to distinguish and adjust the composition of substances. From original bone and stone tools to synthetic bronze and iron tools, we finally obtained engineering materials based on precisely controlled alloys and composites. All of them provide the strong support for the industrialization process of human beings. On the other hand, it took decades to achieve material design and control from macroscale to nanoscale, then to atomic scale, laying a structural foundation for discovery of modern high performance energy storage and conversion materials. This accelerated proceeding was strongly supported by various physical and chemical theories and methods and also supported by the rapid development of characterization methods. On the basis of these development, scientists continue to focus on atomic ordering of the materials, which was expected to further improve the mechanical or catalytic properties of traditional crystal materials. With the help of the most advanced characterization methods, such as spherical AC-TEM and synchrotron radiation X-ray fine absorption spectroscopy, scientists try to adjust the atomic arrangement to obtain new structural materials, such as metastable materials, high-entropy alloys, metallic glass, and amorphous materials.
Figure 1.5 The development of materials research in different research orientations.
1.3.1 Establishment of Crystallography
The concept of amorphous is defined in the comparison of crystallography in solid physics. Therefore, the history of amorphous materials should be compared with that of crystallography.
On 25 June 2012, the General Assembly of the United Nations adopted a resolution, which proclaiming the year 2014 as the International Year of Crystallography. It was named to commemorate Max von Laue, who won the Nobel Prize in Physics of 1917, about 100 years ago for characterizing the crystal structure by X-ray. At the same time, it was also commemorated Johannes Kepler proposed the famous article A New Year’s Gift of Hexagonal Snow 400 years ago (1611). He was regarded as the first one to conceptualize the symmetry of crystals which were formed by a regular accumulation of spherical elements. It was considered to be the beginning of the establishment of traditional crystallography.
In 1699, Nicolas Steno observed a large number of ores and proposed that the angle between two identical crystal planes of a crystal is always constant, regardless of the size and shape of the crystal plane [9]. It was called the law of constant angles of the crystal plane, which was generally recognized as the first law of crystals. Prior to the discovery of X-ray, the law laid the foundation for crystal identification, and the word Crystal began to be used to describe substances with regular morphologies and fixed angles.
In 1784, Rene Just Hayuy proposed that each crystal plane was simply composed of blocks of the same size and shape. The crystal structure was described as a regular three-dimensional arrangement, which was an infinite repetition of cells in the three-dimensional directions. On this basis, William Hallowes Miller proposed in 1839 that each crystal plane can be described by three simple integers (h, l, k). That was the Miller Index, as was still used today.
At the end of the nineteenth century, from a mathematical point of view, scientists put forward 32-point groups to describe the symmetry of crystal shape and 230 space groups to nominate the symmetry of microelements. Until now, all the geometric structure characteristics of crystallography have been basically perfected.
In 1912, on the basis of Laue’s work, William Lawrence Bragg proposed the famous Bragg Formula, which laid the foundation for the establishment of modern crystallography and the characterization of crystal structure. Later, together with his father William Henry Bragg, he quickly characterized the crystal structure of various substances, and established modern crystallography soon [10].
From the development history of crystallography, we can find that the confirmation of crystal structure characteristics depends on the discovery of X-ray, but the establishment of geometric theory in crystallography was far before the characterization of its crystal structure. All the elements in the definition of crystals (crystals are solids with regular periodic repetitive arrangement of internal particles in three-dimensional space) are determined before X-ray discovery. The establishment of crystallography depends more on the mathematics-induced theoretical system and physics-drove technique.
1.3.2 Enlightenment of Amorphous Materials
The use of natural amorphous materials can be traced back to prehistoric times when Obsidian was used as a cutting tool. It was a kind of natural glass, formed by the sudden cooling of magma from volcanic lava. With a sharp fracture surface, people used it for cutting as knives.
Because of the simplicity of preparation, glass has become the first amorphous material to be prepared on a large scale. The history of glass preparation can be traced back to the ancient Babylonians and Greeks 5000 years ago, but it was not until the twelfth century that glass began to be manufactured in batches as an industrial material. Subsequently, the large-scale preparation of transparent glass rapidly promoted the development of science and technology at that time. For example, Galileo Galilei’s home-made telescope discovered the uneven surface of the moon in 1609, refuted Aristotle’s theory of perfect celestial bodies, and opened the curtain of modern astronomy; Isaac Newton observed the dispersion of light with a prism in 1666. A year later in 1676, Antonie van Leeuwenhoek, the father of the microscope, reported observations of red blood cells and microbes, which laid the foundation of modern bacteriology and protozoology in biology. This transparent, stable, and processable material provided fully technical support for the development in many disciplines.
1.3.3 Modern Amorphous Materials 1-Disordered Elementary Substance
The research on amorphous materials is still centered on the comparison with crystals. There are three most used names of disorder materials. Amorphous is the earliest and most widely used expression approach. Glass is another name of disorder material, especially in the metallic glass field. Non-crystal is used in the field of biomineralization.
Amorphous, the most common English expression of disordered materials, originated from Greek, where a is a prefix, indicating no; morphous comes from morph, referring to morphology. The original meaning of this word is material without morphology. It can be seen that before the establishment of modern crystallography, people have known the morphological differences between amorphous materials and crystalline materials to distinguish them.
In 1840, Justus von Liebig, the German organic chemist and father of mineral nutrition, described in his classic book Organic Chemistry in its Application to Agriculture and Physiology that when sulfur is heated to 160 °C, and then quickly pouring into cold water, sulfur does not crystallize but turns soft and transparent. In this chapter, he wrote “such solid bodies are called amorphous”. This may be the earliest report that compared morphologies between amorphous and crystalline materials. Liebig then published in the famous medical journal Provincial Medical and Surgical Journal in 1840,