High-temperature oxidation and

Metallurgy. The strong affinity for oxygen and sulfur makes the rare-earth metals useflil in metallurgy (qv). Mischmetal acts as a trap for these Group 16 (VIA) elements, which are usually detrimental to the properties of steel (qv) or cast iron (qv). Resistance to high temperature oxidation and thermomechanical properties of several metals and alloys are thus significantly improved by the addition of small amounts of mischmetal or its siUcide (16,17). 

Since the paper by Pilling and Bedworth in 1923 much has been written about the mechanism and laws of growth of oxides on metals. These studies have greatly assisted the understanding of high-temperature oxidation, and the mathematical rate laws deduced in some cases make possible useful quantitative predictions. With alloy steels the oxide scales have a complex structure chromium steels owe much of their oxidation resistance to the presence of chromium oxide in the inner scale layer. Other elements can act in the same way, but it is their chromium content which in the main establishes the oxidation resistance of most heat-resisting steels. 

In case of the use of polycrystalline adsorbent subject to high temperature oxidation and characterized by almost stoichiometric content of the surface its electric conductivity can be linked with penetration of the current carriers through high intercrystalline barriers. The effect of adsorption on electric conductivity of adsorbents of such type is mainly manifested through the change of heights in intercrystalline barriers controlled by the value of the surface charge. 

Yttrium alloys have many applications. The metal doped with rare earths such as europium is used as phosphor for color television receivers. When added to iron, chromium, vanadium, niobium, and other metals it enhances resistance of these metals and their alloys to high temperature oxidation and recrystallization. It is a deoxidizer for vanadium and other nonferrous metals. Yttrium-aluminum garnets are used in lasers and in jewelery gemstones. Yttrium-iron garnets are used as transmitters and as transducers of acoustic energy. 

Total nitrogen was determined in water using high-temperature oxidation and chemiluminescence,119 as well as microwave digestion-UV spectrophotometry.120 Total nitrogen in solid waste was determined by modified Kjeldahl-Nessler reagent colorimetrically and modified Kjeldahl titration with hydrochloric acid.121 No significant differences were found between the two methods in terms of accuracy and precision. 

Yang, C., R. Wu, P. Zhu, and X. Yang. 2007. Determination of total nitrogen in water using high temperature oxidation and chemiluminescence method. Fenxi Huaxue 35 529-531. 

N-Type Thermocouple (Nicrosil vs. Nisil). The type-N thermocouples (nickel-chromium-silicon vs. nickel-silicon) thermocouples are used at temperatures exceeding 1200°C, because they resist high-temperature oxidation and have a sensitivity of 39 pV/°C at 900°C. 

Introduction to high temperature oxidation and corrosion. ASM International, Materials Park [iv] Kroger FA (1964) The chemistry of imperfect crystals. North-Holland, Amsterdam... 

The widespread use of vegetable oils as lubricant basestocks will depend largely on how well they perform during high-temperature oxidation and low-temperature applications. 

The data in tables A1.2a and A1.2b are taken from Keene O) and Wolf ), respectively. The data for dy/dT from Keene s compilation tend to be higher than those of Wolf. In general, these measurements are less reproducible than those presented in table Al. 1 because, at the high temperature, oxidation and other surface reactions may occur. The absolute accuracy of these data diminishes accordingly. 

D. J. Young, Editor, High Temperature Oxidation and Corrosion of Metals, Elsevier, Amsterdam (2008). 

Fine wire thermocouples are of low cost and easy to use. They have relatively short response times and good spatial resolution. However, they are somewhat intrusive to the flame. Corrections are also required due to heat transfer effects at the junction bead. These include radiation from the bead to the environment and the heat conduction along the thermocouple wires. Often the junction must be coated to prevent catalytic reactions. There are material limitations, due to high temperature oxidizing and reducing conditions. They can only make so many point measurements over a span of time to get a temperature profile. 

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