Applications and Processing of Polymers/ Plastics
Plastic covers a range of synthetic or semisynthetic polymerization products. They are composed of organic condensation or addition polymers and may contain other substances to improve performance or economics. There are few natural polymers generally considered to be "plastics". Plastics can be formed into objects or films or fibers. Their name is derived from the fact that many are malleable, having the property of plasticity. Plastic can be classified in many ways but most commonly by their polymer backbone (polyvinyl chloride, polyethylene, acrylic, silicone, urethane, etc.). Other classifications include thermoplastic vs. thermoset, elastomer, engineering plastic, addition or condensation, and Glass transition temperature or Tg. A lot of plastics are partially crystalline and partially amorphous in molecular structure, giving them both a melting point (the temperature at which the attractive intermolecular forces are overcome) and one or more glass transitions (temperatures at which the degree of cross-linking is substantially reduced). Plastics are polymers: long chains of atoms bonded to one another. These chains are made up of many repeating molecular units, or "monomers". The vast majority of plastics are composed of polymers of carbon alone or with oxygen, nitrogen, chlorine or sulfur in the backbone. (Some of commercial interest are silicon based.) The backbone is that part of the chain on the main "path" linking the multitude of monomer units together. To customize the properties of a plastic, different molecular groups "hang" from the backbone (usually they are "hung" as part of the monomers…
Space Science echnology
In this chapter, we will discuss what is Space Science and how technology influences Space Science. We will focus more on the outer space, the outer space includes earth and…
Fabrication and processing of ceramics
Ceramic Synthesis Our expertise and capabilities in synthesizing ceramics are based onchemical solution techniques. Chemical solution or sol-gel approaches have beendeveloped to fabricate powders, films, and porous bodies. Materials of interest range from silica to complex, multicomponent electronic ceramics. The complexity inherent in fabricating materials with structured nanoporosity or complex chemistries requires a fundamental understanding of these chemical solution approaches. Fabrication of unique precursors for complex oxides is being done with novel metal alkoxide chemistry to produce powders and thin-film materials with carefully controlled properties. Our ability to synthesize materials with complex structures, chemistries, or both, is at the heart of numerous research and development efforts at Sandia. Ceramic Processing Sandia's fabrication of ceramic components and devices is based on a strong ceramic-processing capability. We recently have demonstrated the ability to characterize and model the powder- compaction process in detail, and to address and control density gradients in powder compacts that cause shape distortion and differential shrinkage. Proprietary 3D, finite-element code packing and compaction models, and process-control tools are now available to improve the production of ceramic components. Sandia has capabilities in the areas of hydrostatic and triaxial compaction testing to characterize materials properties, and x-ray radiography, ultrasound, and computed tomography for density characterization. In addition, expertise in slurry processing has enabled the development of direct-fabrication processes. Furthermore, we are developing phenomenological sintering models to enhance both ceramic component design and manufacturing capability.
Communication Technology
Communication is the exchange of information through different mediums. It is an activity that started even before the civilization of human beings; however, over a period of time, as technology…
Portland Cement
Portland cement is a closely controlled chemical combination of calcium, silicon, aluminum, iron and small amounts of other compounds, to which gypsum is added in the final grinding process to regulate the setting time of the concrete. Some of the raw materials used to manufacture cement are limestone, shells, and chalk or marl, combined with shale, clay, slate or blast furnace slag, silica sand, and iron ore. Lime and silica make up approximately 85 percent of the mass The term "Portland" in Portland cement originated in 1824 when an English mason obtained a patent for his product, which he named Portland Cement. This was because his cement blend produced concrete that resembled the color of the natural limestone quarried on the Isle of Portland in the English Channel. Different types of Portland cement are manufactured to meet different physical and chemical requirements for specific purposes. Common Examples Structural clay products Brick, sewer pipe, roofing tile, clay floor and wall tile (i.e., quarry tile), flue linings Whitewares Dinnerware, floor and wall tile, sanitaryware, electrical porcelain, decorative ceramics Refractories Brick and monolithic products are used in iron and steel, non-ferrous metals, glass, cements, ceramics, energy conversion, petroleum, and chemicals industries Glasses Flat glass (windows), container glass (bottles), pressed and blown glass (dinnerware), glass fibers (home insulation), and advanced/specialty glass (optical fibers) Abrasives Natural (garnet, diamond, etc.) and synthetic (silicon carbide, diamond, fused alumina, etc.) abrasives are used for grinding, cutting, polishing, lapping, or pressure blasting of materials Cements Used to produce concrete roads, bridges, buildings,…
Artificial Intelligence
Artificial Intelligence or simply AI is an experimental science being developed with the purpose to understand the nature of intelligent thought and subsequent action. It is presented by machines or…
Types and applications of ceramics
Ceramics offer a high temperature range. However, ceramics are not very strong. To compensate for their lack of strength ceramics are usually combined with some other material to form a ceramic composite. 1) Glasses and glass ceramics- The glasses are a familiar group of ceramics; containers, windows, lenses and fiberglass represent typical applications. The properties of standard vitrified products are insufficient for architectural applications and structural building components, insulation or other specialized applications. Yet there is an effective way to improve these properties without major alterations to the process itself - the introduction of a controlled crystallization process through a subsequent heat treatment, i.e. by forming a glass-ceramic. Production of Glass-Ceramics Glass-ceramic articles may be produced by three routes: • The heat treatment of solid glass (the traditional route) • The controlled cooling of a molten glass, known as the petrurgic method • The sintering and crystallisation of glass powders. In the latter case, the powders are densified at relatively low temperatures by exploiting a viscous flow sintering mechanism. After densification, the material is subjected to a crystallisation heat- treatment to obtain the required glass-ceramic microstructure. Alternatively, both densification and crystallisation may take place during a single sintering step. Along with the economic advantage of using relatively low processing temperatures, the powder technology route is suitable for the production of a range of advanced materials, including glass-ceramics with specified porosities and glass-ceramic matrix composites. Using the petrurgic method, the slow cooling from the molten state causes nucleation and growth of certain crystalline phases. Therefore, the final microstructure, and hence the properties, depends mainly on the composition and the cooling rate.…
Ceramics (Applications and Processing)
Ceramics encompass such a vast array of materials that a concise definition is almost impossible. However, one workable definition is: Ceramics can be defined as inorganic, nonmetallic materials. They are typically crystalline in nature and are compounds formed between metallic and nonmetallic elements such as aluminum and oxygen (alumina-Al2O3), calcium and oxygen (calcia - CaO), and silicon and nitrogen (silicon nitride-Si3N4). Ceramics is a refractory, inorganic, and nonmetallic material. Ceramics can be divided into two classes: traditional and advanced. Traditional ceramics include clay products, silicate glass and cement; while advanced ceramics consist of carbides (SiC), pure oxides (Al2O3), nitrides (Si3N4), non-silicate glasses and many others. Ceramics offer many advantages compared to other materials. They are harder and stiffer than steel; more heat and corrosion resistant than metals or polymers; less dense than most metals and their alloys; and their raw materials are both plentiful and inexpensive. Ceramic materials display a wide range of properties which facilitate their use in many different product areas. In general, most ceramics are: - hard, - wear-resistant, - brittle, - refractory, - thermal insulators, - electrical insulators, - nonmagnetic, - oxidation resistant, - prone to thermal shock, and - Chemically stable. Of course there are many exceptions to these generalizations. For example, borosilicate glasses (glasses that contain silica and boron as major ingredients) and certain glass ceramics (glasses that contain a crystalline phase) and NZP ceramics are very resistant to thermal…
E-Infrastructure in India
In today’s world, e-infrastructure is the key element for the development of a society. E-infrastructure facilitates competent equipment and favorable resources and opportunities that are essentially needed to for the…
Meissner Effect & Superconductor Types
The Meissner effect is an expulsion of a magnetic field from a superconductor during its transition to the superconducting state. T he German physicists Walther Meissner and Robert Ochsenfeld discovered the phenomenon in 1933 by measuring the magnetic field distribution outsidesuperconducting tin and lead samples. The interior of a bulk superconductor cannot be penetrated by a weak magnetic field, a phenomenon known as the Meissner effect. When the applied magnetic field becomes too large, superconductivity breaks down. Superconductors can be divided into two types according to how thisbreakdown occurs. In type-I superconductors, superconductivity is abruptly destroyed via a first order phase transition when the strength of the applied field rises above a critical value Hc. Type-II superconductor is characterized by the formation of magnetic vortices in an applied magnetic field. This occurs above a certain critical field strength Hc1. The vortex density increases with increasing field strength. At a higher critical field Hc2, superconductivity is completely destroyed.
