Ferrosilicon combustion

Figure 7.6 Temperature history of ferrosilicon combustion in nitrogen =4 MPa,...

Dependence of conversion degree on the amount of additive (previously nitrided ferrosilicon) is shown in Figure 7.7. A burned sample with additive of 50% previously nitrided ferrosilicon is shown in Figure 7.8, The peculiarity of ferrosilicon combustion in nitrogen with dilution of raw material by the final product is the... 

Figure 7.12 SEM image of products of ferrosilicon combustion in nitrogen, (a) Solidified drop of iron-silicon melt with crystals of silicon nitride and (b) upper half of the same drop with "flowing down" crystals of silicon nitride forming a large crystal (in the background).

Ferrosilicon containing 30-75% of silicon is hazardous, particularly when finely divided, and must be kept in a moisture-tight drum. In contact with water, the impurities present (arsenide, carbide, phosphide) evolve extremely poisonous arsine, combustible acetylene and spontaneously flammable phosphine [1 2],... 

FERROSILICON (8049-17-0) Combustible solid. Dust or powder forms explosive mixture in air. Reacts with water, producing toxic fumes and explosive hydrogen and acetylene gases. Strong oxidizers can cause ignition and explosions, especially with finely divided material. Reaction with acid, acid fumes, or oxidizers can cause the emission of toxic fumes. Incompatible with sodium hydroxide. 

Synthesis of Silicon Nitride by Combustion of Ferrosilicon in Nitrogen... 

The combustion of ferrosilicon in nitrogen is carried out in the self-oscillating mode but not in the stationary one. At the same time, harmonic oscillations are transformed into relaxation ones which consist of alternating flashes and depression. Propagation of a combustion wave is carried out as follows a bright flash is observed after the initiation of the reaction and then intensity of the flush gradually decreases and eventually ceases. Then, at some distance downward from... 

Figure 7.5 A photograph of a sample of a product of combustion of ferrosilicon in nitrogen in a self-oscillation mode (longitudinal chip). Each light layer is enriched with silicon nitride each dark layer is enriched with iron silicides.

Thus, the unstable (self-oscillating) combustion of ferrosilicon in nitrogen is accompanied by a low nitriding degree of combustion products and leads to their chemical and phase inhomogeneity. SHS process control is required to achieve the phase and chemical homogeneity of SHS products and the maximum (m = 1)... 

Figure 7.9 XRD pattern fragment of raw ferrosilicon FS 65 (a), combustion product (b), and combustion product in the presence of ammonium fluoride (c) 1-(i-Si3N4, 2-a-Si3N4, 3-a-Fe, 4-FeSi2, 5-FeSi, and 6-Si.

To understand the process of ferrosilicon nitriding in the combustion mode, the method of stopping the combustion wave by rapid nitrogen pressure release and filling the apparatus by argon was used. The microstructure analysis of quenched samples with the use of X-ray microanalysis and SEM analysis allowed us to... 

The process of nitride formation during combustion of ferrosilicon in nitrogen can generally be described by four mechanisms solid-gas, liquid-gas, vapor-gas, and vapor-liquid-crystal (VLC). Experimentally measured combustion temperatures (1900 - 2100°C) indicate that silicon will be either in the liquid state as an iron-silicon melt or in the gaseous state during SHS. Under the... 

Figure 7.13 SEM images of combustion products of ferrosilicon in nitrogen, (a, b) Whisker crystals of silicon nitride (arrows point to globules at tops of crystal growing by VLC...

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