The amorphous structure of glassy Silica (SiO₂). No long range order is present, however there is local ordering with respect to the tetrahedral arrangement of Oxygen (O) atoms around the Silicon (Si) atoms. A tetrahedron (plural tetrahedra) is a Polyhedron composed of four triangular faces three of which meet at each vertex.

An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. In Physics, long-range order characterizes physical Systems in which remote portions of the same sample exhibit correlated behavior History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny (Solids in which there is long-range atomic order are called crystalline solids or morphous). In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Most classes of solid materials can be found or prepared in an amorphous form. For instance, common window glass is an amorphous ceramic, many polymers (such as polystyrene) are amorphous, and even foods such as cotton candy are amorphous solids. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many The word ceramic is derived from the Greek word κεραμικός ( keramikos) A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Polystyrene ˌpɒliˈstaɪriːn ( IUPAC Polyphenylethene is an aromatic Polymer made from the aromatic Monomer Styrene

In principle, given a sufficiently high cooling rate, any liquid can be made into an amorphous solid. Cooling reduces molecular mobility. If the cooling rate is faster than the rate at which molecules can organize into a more thermodynamically favorable crystalline state, then an amorphous solid will be formed. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " Because of entropy considerations, many polymers can be made amorphous solids by cooling even at slow rates. In contrast, if molecules have sufficient time to organize into a structure with two- or three-dimensional order, then a crystalline (or semi-crystalline) solid will be formed. Water is one example. Because of its small molecular size and ability to quickly rearrange, it cannot be made amorphous without resorting to specialized hyperquenching techniques.

Amorphous materials can also be produced by additives which interfere with the ability of the primary constituent to crystallize. For example, addition of soda to silicon dioxide results in window glass, and the addition of glycols to water results in a vitrified solid. Sodium carbonate (also known as washing soda or soda ash), is a Sodium Salt of Carbonic acid. The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide A diol or glycol is a Chemical compound containing two Hydroxyl groups (-OH groups Vicinal diols have hydroxyl groups attached to adjacent atoms Water is a common Chemical substance that is essential for the survival of all known forms of Life. Vitrification is a process of converting a material into a Glass -like Amorphous solid that is free from any Crystalline structure either by the quick removal

Some materials, such as metals, are difficult to prepare in an amorphous state. Unless a material has a high melting temperature (as ceramics do) or a low crystallization energy (as polymers tend to), cooling must be done extremely rapidly. As the cooling is performed, the material changes from a supercooled liquid, with properties one would expect from a liquid state material, to a solid. Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter The temperature at which this transition occurs is called the glass transition temperature or T_g. The glass transition temperature, T g is the temperature at which an Amorphous solid, such as Glass or a Polymer, becomes brittle

Toward a strict definition

It is difficult to make a distinction between truly amorphous solids and crystalline solids in which the size of the crystals is very small. Even amorphous materials have some short-range order at the atomic length scale due the nature of chemical bonding. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic Furthermore, in very small crystals a large fraction of the atoms are located at or near the surface of the crystal; relaxation of the surface and interfacial effects distort the atomic positions, decreasing the structural order. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Even the most advanced structural characterization techniques, such as x-ray diffraction and transmission electron microscopy, have difficulty in distinguishing between amorphous and crystalline structures on these length scales.

The transition from the liquid state to the glass, at a temperature below the equilibrium melting point of the material, is called the glass transition. The glass transition temperature, T g is the temperature at which an Amorphous solid, such as Glass or a Polymer, becomes brittle It was found that the topology of bonds changes at glass transition from 3D below to fractal (<3) above the glass transition^[1]. This change characterises the glass transition as a percolation transition in the system of broken bonds assotiated by a decrease of Hausdorff dimension. In Mathematics, the Hausdorff dimension (also known as the Hausdorff–Besicovitch dimension) is an extended non-negative Real number associated From a practical point of view, the glass transition temperature is approximately the temperature at which the viscosity of the liquid exceeds a certain value (about 10¹² Pa·s). Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. The transition temperature depends on cooling rate, with the glass transition occurring at higher temperatures for faster cooling rates. The precise nature of the glass transition is the subject of ongoing research. While it is clear that the glass transition is not a first-order thermodynamic transition (such as melting), there is debate as to whether it is a higher-order transition, or merely a kinetic effect.

See also

• Fused silica
• Glass
• Glass-liquid transition
• Amorphous ice
• Amorphous silicon
• Amorphous metal
• Supercooling
• Vitrification
• Paracrystalline

References

1. ^ M. Fused quartz and fused silica are types of Glass containing primarily Silica in amorphous (non- Crystalline form Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many Glass-liquid transition: The glass-liquid transition is a pseudo second order phase transition in which a solid amorphous material ( Glass) transforms on heating into Amorphous ice is an Amorphous solid form of water meaning it consists of Water molecules that are randomly arranged like the atoms of common Glass. Amorphous silicon (a-Si is the non-crystalline Allotropic form of Silicon. An amorphous metal is a Metallic material with a disordered atomic-scale structure Vitrification is a process of converting a material into a Glass -like Amorphous solid that is free from any Crystalline structure either by the quick removal Paracrystalline materials are defined as having short and medium range ordering in their lattice (similar to the Liquid crystal phases but lacking long range order I. Ojovan, W. E. Lee. Topologically disordered systems at the glass transition. J. Phys. : Condensed Matter, 18, 11507-11520 (2006). http://eprints.whiterose.ac.uk/1958/

External links

• Vogel-Tammann-Fulcher Equation Parameters
• Fragility thy name is glass