Nonmetallic materials

These materials, fired clay products and glass, are still vitally important today, but to these more traditional materials, we can now add a wealth of sophisticated materials with special properties. The new superconductors mentioned in the essay on superconductivity are just one example of these new materials. More and more, high-value materials are being designed for specialized applications. 

In the following sections, we look at several nonmetallic materials with applications in modem technology. We begin with a discussion of the different allotropes or forms of carbon—diamond, graphite, and the fullerenes—where research has produced some exciting discoveries (Section 13.4). The fullerenes are recently discovraed molecular forms of the element carbon, in which the carbon atoms form hollow balls and tubes that may make them important as catalysts or possibly as drug-delivay mataials. Diamond shows promise as a material that might supersede silicon in its role as a matmal for sohd-state electronics. Silicon and diamond can act as semiconductors, which we discuss in Section 13.5. We end the chapter with sections on silicon, silica, and silicates (Section 13.6), ceramics (Section 13.7), and finally composites (Section 13.8). 

Compared to steel, other materials are of nimor importance. At low temperatures (below ca. 100°C), organic materials are increasingly being used, and at the highest temperatures exclusively inorganic materials are used, usually as composite materials 

CF-EP glass fiber reinforced epoxy resin PE-HD high-density polyethylene PF Phenol-Formaldehyde resin 

EPDM Ethylene-propylene-terpolymers PTFE Polytetrafluorethylene 

Inorganic materials such as graphite and glass are growing in popularity. Complete plants can be built of glass, although here the impact and stress sensitivity of the material must be taken into account. Furthermore, the size of such plants are severely limited. 

Plastics are mainly used in chemical plant when high resistance to aqueous acid, alkali, or salt solution at moderate temperature is required. Table 2.10-5 lists some important plastics and their chemical resistance (see also Table 2.10-1). 

CERAMICS. Tliese are brittle and corrosion resistant compounds made out of metallic and nornnetaUic elements. Some examples of ceramics are A/2O3 (alumina), SiC (silicon carbide), MgO (magnesia), Fe O (magnetite), and ZrO (zirconia). Other ceramics are made of basic ceramics and are known as bricks, clay, concrete, porcelain and the like. On the other hand, refractories are ceramics that withstand very high temperatures prior to melting, such as NhC (niobium carbide) 3615°C and MgO 2852°C In addition, ceramics are immune to corrosion by almost all environments. Those which are not dissolve by chemical oxidation. 

The forms of corrosion encounter in diverse engineering structures have a common oxidation mechanism lepiesented by an anodic reaction, such as M — M+ + ze, eq. (1.1a). Thus, corrosion may be due to chemical or electrochemical reactions. One common corrosion process is the formation of ferric hydroxide, Fe OH)3, as indicated by the sequence of reactions given by eq. (1.7. Therefore, corrosion is classified as a localized or general oxidation process. It manifests its natural or forced behavior in various forms from atmospheric corrosion of steel stmctures to oral corrosion on dental alloys due to the effect of saliva and food. 

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Among nonmetallic materials, glass, chemical stoneware, enameled steel, acid-proof brick, carbon, graphite, and wood are resistant to iodine and its solutions under suitable conditions, but carbon and graphite may be subject to attack. Polytetrafluoroethylene withstands Hquid iodine and its vapor up to 200°C although it discolors. Cloth fabrics made of Saran, a vinyHdene chloride polymer, have lasted for several years when used in the filtration of iodine recovered from oil-weU brines (64). 

Glass offers good resistance to strong acid at high temperatures. However, it is subject to thermal shock and a gradual loss in integrity as materials such as iron and siUca are leached out into the acid. Nonmetallic materials such as PTFE, PVDC, PVDF, and furan can be used for nitric acid to a limited degree, but are mainly restricted to weak acid service at ambient to moderate temperatures. 

Methyl bromide, when dry (<100 ppm water), is inert toward most materials of constmction. Carbon steel is recommended for storage vessels, piping, pumps, valves, and fittings. Copper, brass, nickel, and its alloys are sometimes used. Aluminum, magnesium, zinc, and alloys of these metals should not be used because under some conditions dangerous pyrophoric compounds may be formed. Many nonmetallic materials are also useful for handling methyl bromide, but nylon and polyvinyl chloride should be avoided. 

In many instances use of nonmetallic materials will prove to be attractive from an economic and performance standpoint. These should be considered when their strength, temperature, and design limitations are satisfactoiy. 

The lack of a well-defined specular direction for polycrystalline metal samples decreases the signal levels by 10 —10, and restricts the symmetry information on adsorbates, but many studies using these substrates have proven useful for identifying adsorbates. Charging, beam broadening, and the high probability for excitation of phonon modes of the substrate relative to modes of the adsorbate make it more difficult to carry out adsorption studies on nonmetallic materials. But, this has been done previously for a number of metal oxides and compounds, and also semicon-... 

Typical insulating materials, therefore, are usually made of nonmetallic materials and are filled with small air pockets. They include magnesium carbonate, cork, felt, cotton batting, rock or glass wool, and diatomaceous earth. Asbestos was once widely used for insulation, but it has been found to be a health hazard and has, therefore, been banned in new construction in the U.S. 

Nonmetallic materials should have the following desirable characteristics low moisture absorption, resistance to microorganisms, stability through temperature range, resistance to flame and arc, freedom from out-gassing, resistance to weathering, and compatibility with other materials. 

V01 E.L. Venturini and R.A. Graham, in Defect Properties and Processing of High Technology Nonmetallic Materials, edited by J.H. Crawford, Jr. Y. Chen and W.A. Sibley (North Holland, Amsterdam, 1984), pp. 383-389. 

Recommended practice for applying statistics to analysis of corrosion data Practice for operating light- and water-exposure apparatus (carbon-arc Type) for exposure of nonmetallic materials Method for detecting susceptibility to intergranular attack in wrought nickel-rich, chromium-bearing alloys... 

High thermal conductivity. Heat is carried through metals by collisions between electrons, which occur frequently. Saucepans used for cooking commonly contain aluminum, copper, or stainless steel their handles are made of a nonmetallic material that is a good thermal insulator. 

ASM engineered materials reference book , 2nd edition, Michael L. Bauc-cio., ASM International (1994) ISBN 0871705028 (www. asm-intl.org). Compact compilation of numeric data for metals, polymers, ceramics and composites. This is an excellent reference for persons involved in nonmetallic materials selection, design, and manufacturing. Sections include ... 

For additional information about the x-ray emission electron-microprobe, the reader will do well to consult Birks and Brooks,11 who built a simplified probe that gave satisfactory results. They examined both metallic and nonmetallic materials, the surface of the latter being covered by evaporation with about 50 A of manganese or copper to provide sufficient electrical conductivity. Figure 9-15 illustrates an application... 

Mine cases, at first made largely of steel, were later made from all sorts of nonmetallic materials. Today, many of the metallic and nonmetallic bodied mines are equipped with improved contact fuzes and influence fuzes that do not require direct contact with the target, and are thus difficult if not almost impossible to detect and disarm... 

What Do We Need to Know Already It would be a good idea to review the information on periodic trends in Sections 1.15-1.22 and 14.1-14.2. Because the nonmetals form molecular compounds, it would also be helpful to review Lewis structures, electronegativity, and covalent bonding in Chapters 2 and 3. The bulk properties of nonmetallic materials are affected by intermolecular forces (Sections 5.1-5.5). 

Nomnetallics As stated, corrosion of metals apphes specifically to chemical or electrochemical attack. The deterioration of plastics and other nonmetallic materials, which are susceptible to sweUing crazing, cracking, softening, and so on, is essentially physiochemical rather than electrochemical in nature. Nonmetallic materials can either be rapidly deteriorated when exposed to a particular enviromnent or, at the other extreme, be practicidly unaffected. Under some conditions, a nonmetallic may show evidence of gradual deterioration. However, it is seldom possible to evaluate its chemical resistance by measurements of weight loss alone, as is most generally done for metals. 

Crevice Corrosion Crevice corrosion occurs within or adjacent to a crevice formed by contact with another piece of the same or another metal or with a nonmetallic material. When this occurs, the intensity of attack is usually more severe than on surrounding areas of the same surface. 

Nistor RA, Polihronov JG, Muser MH, Mosey NJ (2006) A generalization of the charge equilibration method for nonmetallic materials. J Chem Phys 125(9) 094108... 

Paralleling the corrosion problem is one involving compatibility of any well fluid with nonmetallic materials used in well completion apparatus. All injection wells and many producing wells are equipped with packers to isolate the casing annulus from the high temperature, pressure, and salinity characteristic of the petroleum reservoir environment. Conventional packers, as well as other well tools, utilize elastomeric materials to mechanically seal appropriate locations. 

M. Meissner-.Nonmetallic Materials and Composites at Low Temperatures, vol. 2, Plenum Press, New York and London (1982)... 

Dislocations occur profusely in nonmetallic materials. As mentioned above, ceramics are brittle at ordinary temperatures, not because of a lack of dislocations but because these cannot easily glide due to strong bonding between the component atoms. Organic crystals, which are usually composed of molecules consisting of strongly bound atoms, linked by weak external bonds, usually glide by movement of molecules rather than atoms, and dislocations can be referred to the molecular array rather than the atom array. 

Nonmetallic Materials Division, Air Force Materials Laboratory, Wright-Patterson Air Force Base, OH 45433... 

Most nonmetallic materials, such as salts, oxides, and ceramics deform also in such a linear fashion, although in a very small range if the applied force is further increased the compound fractures in a catastrophic manner. 

Push-on Joints These joints (Fig. 10-140) require diametral control of the end of the pipe. They are used for brittle and nonmetallic materials. Pipe, fittings, and valves are furnished with the bells on one or more ends. 

Plastic pipe or tubing may be used for a wide variety of services. As with all nonmetallic materials, code restrictions limit the applications in which their use is permitted. In general, their use in flammable or toxic service is limited. Plastic tubing of various types may be used for instrument air-signal connections however, as is the case with all nonmetallic applications, the need for fire resistance must be considered. When used)in specialized applications such as potable water or underground fire water, care should be taken to ensure that the specified products are certified by appropriate agencies such as the National Sanitation Foundation and Factory Mutual. 

Now let us turn to a brief examination of flotation. Virtually all nonferrous metallic ores are concentrated by the flotation process. Sulfide ores have been studied particularly extensively, although the method has been used with oxides and carbonates as well as such nonmetallic materials as coal, graphite, sulfur, silica, and clay. Something on the order of a billion tons of ore a year are processed in this way. 

Combustion is an oxidation-reduction reaction between a nonmetallic material and molecular oxygen. Combustion reactions are characteristically exothermic (energy releasing). A violent combustion reaction is the formation of water from hydrogen and oxygen. As discussed in Section 9.5, the energy from this reaction is used to power rockets into space. More common examples of combustion include the burning of wood and fossil fuels. The combustion of these and other carbon-based chemicals forms carbon dioxide and water. Consider, for example, the combustion of methane, the major component of natural gas ... 

Combustion An exothermic oxidation-reduction reaction between a nonmetallic material and molecular oxygen. 

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