Ammonia nitridation

The complex iron carbonitride is the hard component in steels that have been annealed with ammonia (nitrided steels). Complex carbonitrides with iron metals are also present in superaHoys in the form of precipitates. 

V. Ucakar, F. Chevire, F.Tessier, N. Krendelsberger, R. Marchand, W. Lengauer. Formation of molybdenum nitrides by ammonia nitridation of Mo powder and sheet // Defect Diffusion Forum.- 2001.- V.194-199.- P.1607-1612. 

T24.3 Recall from Section 24.9(a) that heating complex oxides under stream of ammonia can lead to the partial reduction of metal oxide. It can also lead to the nitridation of the oxide forming oxide-nitrides and eventually, with high excesses of ammonia, nitrides. In this case, partial nitridation occurs ... 

Stainless steels and many higher alloys snch as Alloy 800 slowly develop a brittle nitride layer if exposed to a nitriding atmosphere at temperatnres exceeding about 750°F (400°C). By far the most common nitriding atmosphere is ammonia or a mixtnre rich in ammonia. Nitriding of stainless... 

Inorganic amides contain the ion NH2". They are formed by the action of ammonia on metals or by the ammonolysis of nitrides. The heavy metal amides are prepared by meta-thetical reactions in liquid ammonia, e.g. 

Boron nitride can be prepared by allowing ammonia to react with boron trichloride. The first product is boron amide which decomposes on heating to give the nitride ... 

Ammonia is also produced when an ionic nitride is hydrolysed, for example magnesium nitride, produced when magnesium burns in nitrogen ... 

As a starting material for other deuterocompounds. For example deuterium oxide, on magnesium nitride, gives deutero-ammonia, NDj with calcium dicarbide, deuteroethyne, C2D2, is obtained. 

Reactions of HCl and nitrides, borides, silicides, germanides, carbides, and sulfides take place at significant rates only at elevated (>650° C) temperatures. The products are the metal chlorides and the corresponding hydrides. The reactions most studied are those involving nitrides of aluminum, magnesium, calcium, and titanium, where ammonia (qv) is formed along with the corresponding metal chloride. 

Gate oxide dielectrics are a cmcial element in the down-scaling of n- and -channel metal-oxide semiconductor field-effect transistors (MOSEETs) in CMOS technology. Ultrathin dielectric films are required, and the 12.0-nm thick layers are expected to shrink to 6.0 nm by the year 2000 (2). Gate dielectrics have been made by growing thermal oxides, whereas development has turned to the use of oxide/nitride/oxide (ONO) sandwich stmctures, or to oxynitrides, SiO N. Oxynitrides are formed by growing thermal oxides in the presence of a nitrogen source such as ammonia or nitrous oxide, N2O. Oxidation and nitridation are also performed in rapid thermal processors (RTP), which reduce the temperature exposure of a substrate. 

There are two types of deposited films known as siUcon nitride. One is deposited via plasma-enhanced CVD at temperatures <350° C (18). In this process silane and ammonia react in an argon plasma to form siUcon imide [14515-04-9] SiNH. 

Lithium Amide. Lithium amide [7782-89-0], LiNH2, is produced from the reaction of anhydrous ammonia and lithium hydride. The compound can also be prepared by the removal of ammonia from solutions of lithium metal in the presence of catalysts (54). Lithium amide starts to decompose at 320°C and melts at 375°C. Decomposition of the amide above 400°C results first in lithium imide, Li2NH, and eventually in lithium nitride, Li N. Lithium amide is used in the production of antioxidants (qv) and antihistamines (see HiSTAMlNE AND HISTAMINE ANTAGONISTS). 

The magnesium nitride [12057-71 -5] produced does not form a stable film. If sufficient nitrogen is present this reaction can be self-sustaining. The nitride produced can react with water to form ammonia [7664-41 -7]. 

In a vacuum, uncoated molybdenum metal has an unlimited life at high temperatures. This is also tme under the vacuum-like conditions of outer space. Pure hydrogen, argon, and hehum atmospheres are completely inert to molybdenum at all temperatures, whereas water vapor, sulfur dioxide, and nitrous and nitric oxides have an oxidizing action at elevated temperatures. Molybdenum is relatively inert to carbon dioxide, ammonia, and nitrogen atmospheres up to about 1100°C a superficial nitride film may be formed at higher temperatures in the latter two gases. Hydrocarbons and carbon monoxide may carburize molybdenum at temperatures above 1100°C. 

Nitriding Metals or Metal Hydrides. Metals or metal hydrides may be nitrided using nitrogen or ammonia. Pure metal powders or pure metal hydride powders yield nitride products that are nearly as pure as the precursors. 

The nitrides of Groups 4(IVB) and 5(VB) elements form at ca 1200°C. The nitrides of magnesium and aluminum form at 800°C. Aluminum nitride, obtained by beating aluminum powder in the presence of ammonia or nitrogen at 800—1000°C, is formed as a white to grayish blue powder. A grade of... 

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