Resistance to Oxidation

Phase Temperature, °C Oxida- tion time, hr Change in weight Ref. Year Remarks 

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Two criteria are used to characterize the behavior of diesel fuel in this area these are color and resistance to oxidation. 

Volume reduction in service Thermal stability Resistance to oxidation, deaeration... 

For air compressors Operating safety Thermal stability, Volatility Resistance to oxidation Extreme pressure and anti-wear (compressors) properties Low coking tendency (hot reciprocating compressors)... 

For gear trains Protection from seizing and rapid wear Extreme-pressure and anti-wear properties Resistance to oxidation Thermal stability High viscosity Low pour point Anti-foaming properties Anti-corrosion properties... 

Thiazole is relatively resistant to oxidation, and very few reactions of this type have been recorded. Under photosensitized oxygenation, triphenylthiazole affords various products of ring cleavage depending on... 

Amberlite IRA-93 1.3 1.04 Styrene-DVB pH range is 0 to 9. Excellent resistance to oxidation and organic foul-... 

The Type K thermocouple (Table 11.59) is more resistant to oxidation at elevated temperatures than the Type E, J, or T thermocouple, and consequently finds wide application at temperatures above 500°C. It is recommended for continuous use at temperatures within the range — 250 to 1260°C in inert or oxidizing atmospheres. It should not be used in sulfurous or reducing atmospheres, or in vacuum at high temperatures for extended times. 

Flexural stress SiC mpture curves are shown in Figure 3 (27). AU. the forms tend to be fairly resistant to time-dependent failure by elevated temperature creep. In addition, SiC shows outstanding resistance to oxidation even at 1200°C as a result of formation of a protective high purity siUca surface layer (28). 

Surface Fluorination of Polymers. Fluorocarbon-coated objects have many practical appHcations because the chemically adherent surface provides increased thermal stabiHty, resistance to oxidation and corrosive chemicals and solvents, decreased coefficient of friction and thus decreased wear, and decreased permeabiHty to gas flow. Unusual surface effects can be obtained by fluorinating the polymer surfaces only partially (74). 

Lubricants. Glycerol can be used as a lubricant in places where an oil would fad. It is recommended for oxygen compressors because it is more resistant to oxidation than mineral ods. It is also used to lubricate pumps and bearings exposed to fluids such as gasoline and benzene, which would... 

The XeF+ cation forms Lewis acid—base adduct cations containing N—Xe—F linkages with nitrogen bases that are resistant to oxidation by the strongly oxidizing XeF+ cation having an estimated electron affinity of the XeF+ cation of 10.9 eV (12). The thermally unstable colorless salt,... 

Eigure 2 shows that even materials which are rather resistant to oxidation ( 2/ 1 0.1) are consumed to a noticeable degree at high conversions. Also the use of plug-flow or batch reactors can offer a measurable improvement in efficiencies in comparison with back-mixed reactors. Intermediates that cooxidize about as readily as the feed hydrocarbon (eg, ketones with similar stmcture) can be produced in perhaps reasonable efficiencies but, except at very low conversions, are subject to considerable loss through oxidation. They may be suitable coproducts if they are also precursors to more oxidation-resistant desirable materials. Intermediates which oxidize relatively rapidly (/ 2 / i — 3-50 eg, alcohols and aldehydes) are difficult to produce in appreciable amounts, even in batch or plug-flow reactors. Indeed, for = 50, to isolate 90% or more of the intermediate made, the conversion must... 

Between 6 and 30% of the radical attack on butane may occur at the primary hydrogen atoms (213). Since ca 6% of the butane goes to or through butyric acid (22), the middle of this range does not seem unreasonable. Because it is much more resistant to oxidation than its precursors or coproducts, acetic acid (qv) is the main product of butane LPO. 

Oxidation. Nitroparaffins are resistant to oxidation. At ordinary temperatures, they are attacked only very slowly by strong oxidi2ing agents such as potassium permanganate, manganese dioxide, or lead peroxide. Nitronate salts, however, are oxidi2ed more easily. The salt of 2-nitropropane is converted to 2,3-dimethyl-2,3-dinitrobutane [3964-18-9], acetone, and nitrite ion by persulfates or electrolytic oxidation. With potassium permanganate, only acetone is recovered. 

The BLM layer uses a glue layer of chromium or titanium. These metals stick well to other metals and most dielectrics, but they are not solderable. Copper, nickel, and silver have been used as the solder-wetting layer for BLM in appHcations involving 95% lead—5% tin solders. Gold is commonly used as the oxidation layer on account of its resistance to oxidation and its excellent solderabiUty. 

Alloy selection depends on several factors, including electrical properties, alloy melting range, wetting characteristics, resistance to oxidation, mechanical and thermomechanical properties, formation of intermetaUics, and ionic migration characteristics (26). These properties determine whether a particular solder joint can meet the mechanical, thermal, chemical, and electrical demands placed on it. 

The platinum-group metals (PGMs), which consist of six elements in Groups 8— 10 (VIII) of the Periodic Table, are often found collectively in nature. They are mthenium, Ru rhodium, Rh and palladium, Pd, atomic numbers 44 to 46, and osmium. Os indium, Ir and platinum, Pt, atomic numbers 76 to 78. Corresponding members of each triad have similar properties, eg, palladium and platinum are both ductile metals and form active catalysts. Rhodium and iridium are both characterized by resistance to oxidation and chemical attack (see Platinum-GROUP metals, compounds). 

Ruthenium and osmium have hep crystal stmetures. These metals have properties similar to the refractory metals, ie, they are hard, britde, and have relatively poor oxidation resistance (see Refractories). Platinum and palladium have fee stmetures and properties akin to gold, ie, they are soft, ductile, and have excellent resistance to oxidation and high temperature corrosion. 

Under atmospheric conditions, 3-aminophenol is the most stable of the three isomers. Both 2- and 4-aminophenol are unstable they darken on exposure to air and light and should be stored in brown glass containers, preferably in an atmosphere of nitrogen. The use of activated iron oxide in a separate cellophane bag inside the storage container (116), or the addition of staimous chloride (117), or sodium bisulfite (118) inhibits the discoloration of aminophenols. The salts, especially the hydrochlorides, are more resistant to oxidation and should be used where possible. 

The pyrazole ring is resistant to oxidation and reduction. Only ozonolysis, electrolytic oxidations, or strong base can cause ring fission. On photolysis, pyrazoles undergo an unusual rearrangement to yield imidazoles via cleavage of the N —N2 bond, followed by cyclization of the radical iatermediate to azirine (27). 

Borides and Silicides. These materials do not show good resistance to oxidation. Some siUcides, however, form Si02 coatings upon heating which retards further oxidation. Molybdenum disiUcide [1317-33-5] MoSi2, is used widely, primarily as an electrical heating element. 

Oxidation. Disulfides are prepared commercially by two types of reactions. The first is an oxidation reaction uti1i2ing the thiol and a suitable oxidant as in equation 18 for 2,2,5,5-tetramethyl-3,4-dithiahexane. The most common oxidants are chlorine, oxygen (29), elemental sulfur, or hydrogen peroxide. Carbon tetrachloride (30) has also been used. This type of reaction is extremely exothermic. Some thiols, notably tertiary thiols and long-chain thiols, are resistant to oxidation, primarily because of steric hindrance or poor solubiUty of the oxidant in the thiol. This type of process is used in the preparation of symmetric disulfides, RSSR. The second type of reaction is the reaction of a sulfenyl haUde with a thiol (eq. 19). This process is used to prepare unsymmetric disulfides, RSSR such as 4,4-dimethyl-2,3-dithiahexane. Other methods may be found in the Hterature (28). 

Raw NBR containing 1.5% of the built-in antioxidant retained 92% of its original resistance to oxidation after exhaustive extraction with methanol. NBR containing a conventional aromatic amine antioxidant (octylated diphenyl amine) retained only 4% of its original oxidative stabiUty after similar extraction. 

At ambient temperatures beryUium is quite resistant to oxidation highly poHshed surfaces retain the brilliance for years. At 700°C oxidation becomes noticeable in the form of interference films, but is slow enough to permit the working of bare beryUium in air at 780°C. Above 850°C oxidation is rapid to a loosely adherent white oxide. The oxidation rate at 700°C is paraboHc but may become linear at this temperature after 24—48 hours of exposure. In the presence of moisture this breakaway oxidation occurs more rapidly and more extensively. BeryUium oxide [1304-56-9] BeO, forms rather than beryUium nitride [1304-54-7] Be2N2, but in the absence of oxygen, nitrogen attacks beryUium above 900°C. 

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