Elevated temperature solid

Certain materials are transported at elevated temperatures. They may have been intentionally heated or have undergone self-heating exothermic reactions (e.g., oxidation, radiation, bacterial decay). Primarily, though, applied heat controls viscosity as the molecules absorb the heat as kinetic energy and move more actively in relation to one another or as the intramolecular and intermolecular bonds vibrate more. Heat turns certain solids into liquids, viscous liquids into less viscous liquids, and liquids into gases. Examples of materials that are transported at elevated temperatures include the following  

Other materials are shipped hot because unwanted chemical or physical changes would take place if they were allowed to cool or solidify. 

Elevated temperature materials present a number of hazards in transportation  

Liquid, see Terminology, Liquid, p.241 Solid, see Terminology, Solid, p.lM 

This class also includes (a) Liquids offered for transport at temperatures at or above their flash point and (b) Substances that are transported or offered for transport at elevated temperatures in a liquid state and which give off a flammable vapour at a temperature at or below the maximum transport temperature. UN 2.3.1.1 

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Aspartame is the most widely used artificial sweetener in the world. It was approved by the FDA for use in the USA in 1981, and now is approved for use in several other countries of the world. One of the drawbacks of aspartame is its instability to heat and acid. Under acidic conditions aspartame slowly hydrolyzes leading to a loss of sweetness, chemical interaction, and microbial degradation. The shelf life of the aspartame-sweetened products with high water content is limited to about 6 months, after which it breaks down into its constituent components and loses its sweetening abilities. At elevated temperatures, solid aspartame slowly releases methanol to form aspartyl phenylalamine and the dioxopiperazine. This reaction is especially favored at neutral and alkaline pH values. Because of this reason, aspartame cannot be used in hot baking foods. 

A second example which illustrates the utility of IS to solid state chemists is the application of impedance analysis to zirconia-yttria solid electrolytes (Bauerle [1969]). At elevated temperatures solid solution zirconia-yttria compounds are known to be oxygen-ion conductors which function by transport of oxygen ions through vacancies introduced by the dopant yttria. By examining cells of the form... 

Shimura, T., Fujimoto, S., Iwahara, H. (2001). Proton conduction in non-perovskite-t)fpe oxides at elevated temperatures. Solid State Ionics, 143, 117—123. 

Dithiocarbaimte Pesticides, liquid. 3005 28 Elevated Temperature Solid, n.o.s.. 3258 31... 

T. Shimura, K. Suzuki, H. Iwahara, Conduction properties of Mg-, Fe- or Co-substituted Sr2Ti04 at elevated temperatures. Solid State Ionics 125, 313-318 (1999)... 

At elevated temperatures, solid sodium chlorate (NaClOs) decomposes to produce sodium chloride, NaCl, and O2 gas. A 0.8765 g sample of impure sodium chlorate was heated until the production of oxygen ceased. The oxygen gas was collected over water and occupied a volume of 57.2 mL at 23.0 "C and 734 Torn Calculate the mass percentage of NaClOs in the original sample. Assume that none of the impurities produce oxygen on heating. The vapor pressure of water is 21.07 Torr at 23.0 °C. 

Crystalline solid m.p. 35-36 "C, b.p. 154--156 C, prepared by oxidizing A,A -dicycIo-hexylthiourea with HgO in carbon disulphide solution, also obtained from cyclohexylamine and phosgene at elevated temperatures. Used as a mild dehydrating agent, especially in the synthesis of p>eptides from amino-acids. Potent skin irritant. 

Non-soap greases using finely divided solids as thickeners are useful as lubricants at elevated temperatures. Materials used include organO Clays such as dimethyldioctyl-decyl-ammonium bentonite (Bentone greases) or selected dyestuffs which produce brightly coloured greases. 

Sodium terbium borate is used in solid-state devices. The oxide has potential application as an activator for green phosphors used in color TV tubes. It can be used with Zr02 as a crystal stabilizer of fuel cells which operate at elevated temperature. Few other uses have been found. 

The procedures used for estimating the service life of solid rocket and gun propulsion systems include physical and chemical tests after storage at elevated temperatures under simulated field conditions, modeling and simulation of propellant strains and bond tine characteristics, measurements of stabilizer content, periodic surveillance tests of systems received after storage in the field, and extrapolation of the service life from the detailed data obtained (21—33). 

Storage. Phenol is shipped in dmms, tank tmcks, and tank cars. It is loaded and shipped at elevated temperatures as a bulk Hquid. In storage, phenol may acquire a yeUow, pink, or brown discoloration which makes it unusable for some purposes. The discoloration is promoted by the action of water, light, air, and catalysts, eg, traces of iron or copper. When stored as a solid in the original dmm or in nickel, glass-lined, or tanks lined with baked phenolic resin, phenol remains colorless for a number of weeks. 

Wax usually refers to a substance that is a plastic solid at ambient temperature and that, on being subjected to moderately elevated temperatures, becomes a low viscosity hquid. Because it is plastic, wax usually deforms under pressure without the appHcation of heat. The chemical composition of waxes is complex all of the products have relatively wide molecular weight profiles, with the functionaUty ranging from products that contain mainly normal alkanes to those that are mixtures of hydrocarbons and reactive functional species. 

Table 1 fists many metal borides and their observed melting points. Most metals form mote than one boride phase and borides often form a continuous series of solid solutions with one another at elevated temperatures thus close composition control is necessary to achieve particular properties. The relatively small size of boron atoms facilitates diffusion. 

In selec ting the machines of choice, the use of specific speed and diameter best describe the flow. Figure 10-67 shows the characteristics of the three types of compressors. Other considerations in chemical plant service such as problems with gases which may be corrosive or have abrasive solids in suspension must be dealt with. Gases at elevated temperatures may create a potential explosion hazard, while air at the same temperatures may be handled qmte normally minute amounts of lubricating oil or water may contaminate the process gas and so may not be permissible, and for continuous-process use, a high degree of equipment rehability is required, since frequent shutdowns for inspec tion or maintenance cannot be tolerated. 

Many reactions of solids are industrially feasible only at elevated temperatures which are often obtained by contact with combustion gases, particularly when the reaction is done on a large scale. A product of reaction also is often a gas that must diffuse away from a remaining solid, sometimes through a solid product. Thus, thermal and mass-transfer resistances are major factors in the performance of solid reactions. 

Diffusion of ions or molecules in solids is preliminary to reaction. It takes place through the normal crystal lattices of reactants and products as well as in channels and fissures of imperfect crystals. It is slow in comparison with that in fluids even at the elevated temperatures at which such reactions have to be conducted. In cement manufacture, for instance, reaction times are 2 to 3 h at 1,200 to 1,500°C (2,192 to 2,732°F) even with 200-mesh particles. 

In nonreactive materials, regions of elevated temperature, or hot spots, have an influence on material strength. In solid explosives this is also true, but the additional effeet is to start exothermal ehemieal reaetions which then lead to detonation. The hot-spot temperatures generated in typical secondary explo-... 

Thermal energy, power generation, and incineration have several factors in common. All rely on combustion, which causes the release of air pollutants all exhaust their emissions at elevated temperatures and all produce large quantities of ash when they consume solid or residual fuels. The ratio of the energy used to control pollution to the gross energy produced can be a deciding factor in the selection of the control system. These processes have important differences which influence the selection of specific systems and devices for individual facilities. 

In inorganic solids, luminescence spectra can be categorized as intrinsic or extrinsic. Intrinsic luminescence, which appears at elevated temperatures as a near Gauss-ian-shaped band of energies with its peak at a photon energy is due to... 

Incorporation of powdered solid carbon dioxide which volatilises at elevated temperatures. This process has been used in conjunction with PVC pastes. 

Maleic anhydride is commonly prepared by passing a mixture of benzene vapour and air over a catalyst (e.g. a vanadium derivative) at elevated temperatures (e.g. 450°C). It is a crystalline solid melting at 52.6°C (the acid melts at 130 C). 

Hot melts are 100% solid thermoplastic compounds. They are compounded and applied in the molten state at elevated temperatures. The resultant properties are obtained by cooling. Due to the quick cooling, bonds can be established in a very short time. 

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