Nitrided ferrosilicon

Dilution of Initial Ferrosilicon by Previously NItrided Ferrosilicon... 

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 7.8 Burned sample with additive of 50% of previously nitrided ferrosilicon.

The Badische AniKn- und Soda-Fabrik prepared a nitride of undetermined composition by heating a mixture of silica and carbon in an atm. of nitrogen. The reaction proceeds at a relatively low temp, if a hydroxide or salt of a metal be added. The product contains silicon nitride mixed with the nitride of the metal. The Badische Anilin- und Soda-Fabrik also removed many of the impurities—iron, carbon, silicates, carbides, silicides, and phosphides—by treatment with acids or mild oxidizing agents which do not affect the silicon nitride. A. S. Larsen and O. J. Storm prepared the nitride by the action of nitrogen on molten silicides—e.g. ferrosilicon. 

Aluminium carbide, 1027 Aluminium phosphide, 0083 Bismuth nitride, 0230 Caesium graphite, 2877 Calcium disilicide, 3938 Calcium phosphide, 3941 Calcium silicide, 3937 Copper diphosphide, 4278 Copper monophosphide, 4277 Copper(II) phosphide, 4284 Dialuminium octavanadium tridecasilicide, 0088 Dicobalt boride, 0128 Ditungsten carbide, 0561 Ferrosilicon, 4384 Hexalithium disilicide, 4684 Iron carbide, 0364... 

As a scavenger its efficiency depends upon its ability to unite with nitrides and oxides and carry them into the slag. It is more efficient for this purpose than ferrosilicon and ferromanganese. Consequently it is added after these alloys have pro duced the best results of which they are capable. Vanadium has accomplished surprising results in improving the quality... 

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

Dependence of nitriding degree on sample diameter has an extremum (Figure 7.3). For the ferrosilicon used for the study (containing 80.1% of silicon), the maximum of nitriding degree is achieved with a sample diameter of 50 mm. 

Figure 1.1 Dependence of nitriding degree (m 1) and burning rate (U 2) of ferrosilicon on nitrogen pressure.

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)... 

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 7.12 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).

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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