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, pointed out that in the extraction of quinine (the main component of antimalarial drugs), quinine obtained from quinoline tincture mainly exists in the form of amorphous [11]. It does not affect its medical value but can greatly enhance the natural quinoline. In 1862, G. Gore pointed out in On the Properties of Electro-Deposited Antimony that when antimony was electrodeposited, different deposition conditions would lead to two kinds of antimony monomers with different structures, i.e. crystalline antimony and amorphous antimony [12]. He also reported that amorphous antimony showed different physical and chemical properties.
Before the twentieth century, the research on amorphous materials was still in the enlightenment stage. The amorphous materials were mainly found in the preparation of traditional crystal materials. The morphology and properties of this “novel” material were fully compared with traditional crystal materials. Because X-ray has not been discovered and modern crystallography has not been developed, the essential characteristics of the disordered structure have not been discovered. However, these studies are very important for the development of amorphous and crystal. For example, in the study of amorphous sulfur, Liebig argued that the softness of amorphous sulfur proved a remarkable fact that the smallest particles that make up a solid are movable to some extent and not perfectly connected. Modern X-ray crystallography verified that the structure of amorphous sulfur should be a spiral chain structure changed from the S8 ring of crystal sulfur, endowed it with the same elasticity as rubber. There is no doubt that, the recognition at that time has a great significance in the research of solid science.
The amorphous state of phosphorus is the same as that of sulfur. Similar to the octahedral ring structural unit of sulfur crystal, the structural unit of phosphorus crystal is a regular tetrahedral structure composed of phosphorus atoms (P4). When the crystal of white phosphorus is melted at a high temperature, P4 tetrahedron transforms into a chain-connected structure. Then, the amorphous red phosphorus could be obtained by quenching, maintaining its chain-like structure. Recently, amorphous phosphorus has showed great applications in lithium-ion batteries and sodium-ion batteries because of their superhigh theoretical capacity. Similarly, in some polymer materials, when the asymmetry of the atoms connected changes irregularly, the polymer will form a random stereomer, which will behave as an amorphous state. Because of the complexity of the molecular structure of ultralong chains, the atomic arrangement modes of amorphous nonmetallic elements such as amorphous sulfur, red phosphorus, and amorphous polymers are not clear yet. However, they all have glass transition temperatures similar to those of glass, so they belong to the category of amorphous.
1.3.4 Modern Amorphous Materials 2-Metallic Glass
Metallic glass is the most abundant and widely used material in modern amorphous scientific research. Because its main synthetic process and property are similar to traditional glass, it is usually just named as glass.
Learn from the quenching technology in glass and smelt, the earliest attempts were made to condense high-temperature metal vapors (Bi, Ga, Sn, etc.) on ultra-low-temperature (2–4 K) substrates and use large instantaneous temperature differences to stabilize disorder structure. In 1934, German scientist Krammer used vapor deposition to obtain the first systematic preparation of amorphous alloys. Subsequently, a variety of metals, including semiconductors such as As and Te, were produced by gas-phase quenching [13]. However, these reports have not attract much attention to amorphous materials because the preparation process is more limited and cannot be extended to other materials.
For metals and alloys, the traditional manufacturing process has long been melting and colling. Because the difference of local structure and density between metal liquids and their solids is very small, it has been thought that metal liquids cannot be overcooled. However, in 1952, Turnbull David discovered that metals can be supercooled to 20% of their melting temperature, breaking this conclusion and providing a theoretical basis for the development of amorphous alloys [14]. In 1960, Pol Duwez et al. [15] reported in Nature that a band-shaped amorphous Au–Si alloy was synthesized by quenching for the first time. He improved the rapid quenching process with a quenching rate of 106 K s−1, made the disordered atoms in the metal melt unable to rearrange to crystal, and obtain amorphous material. Since then, metallic glass has quickly attracted widespread attention, and quenching has also become a basic method for synthesizing amorphous materials.
Especially since 1988, Inoue et al. [16] summarized three experimental rules for obtaining bulk amorphous alloys:
1 (1) The alloy should be composed of more than three alloy elements;
2 (2) There should be more than 12% atomic size difference between the main elements;
3 (3) The mixing heat between the elements should be negative.
The preparation of metallic glass were then promoted from low-dimensional materials to bulk amorphous materials. Many excellent characteristics are fully utilized, so it has become a research field with important application prospects.
Metallic glass showes a unique disordered structure, without defects such as dislocations and grain boundaries in the crystal, endowing them with many unique superior properties. For example, in terms of mechanical properties, metallic glasses exhibit high strength, high hardness, high wear resistance and corrosion resistance, high fatigue resistance, low elastic modulus, large elastic strain limit, etc. Thus, metallic glass possesses broad potential applications in the fields of engineering mechanics, biological sciences, and aerospace. For example, the amorphous alloys in almost every alloy system have achieved several times higher strength than the crystalline material. In 2011, Zhang Tao et al. [17] developed a CoTaB ternary alloy with
