Saturday, September 12, 2009

Glass

A.4.1 Glass

Image by Qizhi Chen, PhD.
Internal Structure of a Bioglass
A.4.2: What is glass?

Glass is an organic, inorganic, or metallic material that is transformed through a temperature behavior state or a chemical state. Glass is an essential element used throughout a vast majority of buildings to practical uses such as a cup, to a magnify glass. In fact, most of these research images were magnified through powerful lenses using crystallized components.

A.4.3: Brief History:

Glass is everywhere! The presence of glass can be traced back to the early cave dwellers. According to J.E.Shelby, cave dwellers “…relied on chipped pieces of obsidian, a natural volcanic glass, for tools and weapons”[1] The first trace of manufactured glass can be dated back to the Egyptian empire, 7000 B.C. Evidence reveals that pharaohs would wear glass beads in their tombs to carry with them into the afterlife. These glass elements were produced by combing sea salt (NaC1) and bones (CaO) into the coals of fire, submerged in sand (SiO2) where the melting of salt and bones produce small particles of glass beads. Later, this method would be further developed by surrounding winding glass ribbons around compacted sand to produce glass bottles. Once manufacturers were able to control the shape of glass particles, glass sheets soon became available but primarily for the upper class. Today, glass is produce on a wide scale from various sizes to multiple applications; such as windows, monitors, televisions, and recently optical fibers!

A.4.4: How glass is formed?

Glass is formed by a variety of elements from silica, salt, sand, and non-metallic compounds. Silica is not a required component of glass because there are a number of inorganic glasses that contain crystalline materials. The properties of glass, regardless of their process, share a familiar behavior, glass transformation behavior; defining the temperature behavior of melting to solidification of the atomic structure. Melting particles elements is not a required process to produce glass due to advanced methods such as sol-gel processing of solutions and neutron irradiation.[2]


 Glass Materials


Look here for more information regarding the types of glass used and their molecular atomic structure altered to achieve their component development.


A.4.5: What is glass transformation behavior?

Glass is produced through a transition of temperature state based on enthalpy. The combined components go through a liquid state set at a temperature above the melting point. During this step, the liquid is cooled to transform the atomic structure, while preventing enthalpy to decrease. The liquid must be cooled below the melting temperature without crystallization so that the atoms can rearrange until the viscosity increase, slowing down atomic re-construction. As the liquid gradually cools, it enters a state of glass transformation region, where the liquid will become fixed meeting equilibrium of the liquid to a frozen solid; known as glass. (Refer to diagram)




Image by J.E.Shelby
Effect of temperature on the enthalpy of a glass forming melt


A.4.6: Components of Glass
     A. Internal Structure
  • The internal structure of glass is a composition of several properties. While most glass produce prior to the industrial revolution contained silica (SiO2), present-day glass contains multiple ingredients for multiple purposes. These elements range from but are not limited to sodium carbonate (Na2CO3), soda-lime, lead, boron, barium, thorium oxide, lanthanum oxide, iron, and cerium (IV) oxide. Other ingredients can be found in glass as a standard rule for production such as; calamite, “cullet” (recycled glass), sodium sulfate, sodium chloride, and/or antimony oxide. The image below demonstrates the internal structure of glass.



Internal structure of glass.
Courtesy of J.E. Shelby























Internal structure of silicate glass.
Source: Catalyzed Crystallization of Glass

 B. Atomic and Molecular Structure
  • Although glass has a variety of components, its atomic and molecular structure defines the generic make-up of the system.















Schematic drawing of a 2-dimensional structure for a glass.
Courtesy of J.E. Shelby
Source: An Introduction to Glass Science and Technology





















Schematic drawing of a 3-dimensional structure for a glass.
Arthor: Scientific American
Source: Materials




















Schematic drawing of a 3-dimensional structure for a glass when crystallizations occurs.
Arthor: Scientific American
Source: Materials

  C. Bonding Force
  • There are three primary subatomic particles that make up the atom known as electrons, protons, and neutrons. While each particle revolves around the other or charges the other, these molecules become electronically stable to hold larger structures together. The process of bond forces among the subatomic particles is divided into Ionic bonds, Covalent bonds, and Metallic bonds. Ionic bonds are usually associated with glass because of the ionic properties that form into “compounds composed of crystalline,” and sodium chloride (NaC1). Adding a different ingredient to the glass equation alter the material surface, texture, physical properties, and durability. The following are examples that changed the atomic structure of glass.

        • Boron
            o Changes the thermal and electrical properties

        • Lanthanum Oxide
            o High refractive, used among eyes glasses

        • Iron
            o Used to absorb infrared energy

        • Cerium (IV) Oxide
            o Helps absorbs UV wavelengths
    .




















Schematic drawing of a 3-dimensional structure for metallic glass.
Source: NanoScale



    D. Conventional Usage












Glass Pavilion at the Summer Academy in Rheinbach, Germany, 2000.

Source: Construction Materials Manual








[i][1] Shelby, J. E. Introduction to Glass Sciene and Technology. Cambridge: The Royal Society of Chemistry, 2005. Pp1-3.[2] Shelby, J. E. Introduction to Glass Sciene and Technology. Cambridge: The Royal Society of Chemistry, 2005. Pg. 3.[i] Shelby, J. E. Introduction to Glass Sciene and Technology. Cambridge: The Royal Society of Chemistry, 2005. Pp 4-5.

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