Effect of Carbothermal Reduction Nitriding of Si/SiO2 Composite Green on Properties of Fused Silica Ceramics

Si/SiO2 composite green body with solid content of 50% was prepared by low toxic gel system and sintered in nitrogen at high temperature. Nitrogen compounds were synthesized in situ on fused silica ceramic substrate. The influence of different temperatures on nitriding reaction was discussed: different temperatures were used for nitriding at 1350 °C, 1400 °C, 1450 °C, 1500 °C. The effect of different nitriding times on nitriding reaction was discussed: different holding times were used for nitriding +1 h, 1.5 h, 2 h and 2.5 h. The best nitriding process was obtained by analyzing the composition, microstructure and properties of the nitrided samples.

Preparation of ε-Fe(Si)3N Powder Using a Salt Bath Nitriding Reaction and a Study on the Soft Magnetic Properties of the Powder

In this paper, a single phase ε-Fe(Si)3N powder was successfully synthesized through the salt bath nitriding reaction method. The flaky FeSi alloy powder was used as the iron source, and non-toxic CO(NH2)2 was used as the nitrogen source. The nitridation mechanism, the preparation technology, the soft magnetic properties, and the magnetization temperature dependence of the powder were studied. The research result showed that ε-Fe(Si)3N alloy powders were synthesized in a high temperature nitrification system after the surface of flaky FeSi alloy powders were activated by a high-energy ball mill. The optimum nitriding process was nitridation for 1 h at 550 °C. The ε-Fe(Si)3N powder had good thermal stability at less than 478.8 °C. It was shown that ε-Fe(Si)3N powder has good soft magnetic properties, and the saturation magnetization of the powder was up to 139 emu/g. The saturation magnetization of ε-Fe(Si)3N powder remains basically constant in the temperature range of 300–400 K. In the temperature range of 400–600 K, the saturation magnetization decreases slightly with the increase of temperature, indicating that the magnetic ε-Fe(Si)3N powder has good magnetization temperature dependence.

Neutron diffraction and gravimetric study of the manganese nitriding reaction under ammonia decomposition conditions

In situ neutron diffraction of ammonia decomposition over manganese reveals the structures of different nitrides and kinetic information about their formation.

Neutron diffraction and gravimetric study of the iron nitriding reaction under ammonia decomposition conditions

In situ neutron diffraction of the ammonia decomposition reaction over iron shows the catalyst to be Fe or Fe4N depending on the conditions.

Control of iron nitride formation by a high magnetic field

The influence of high magnetic field on nitriding behavior was investigated in a mixture of NH3 and H2. It was found that high magnetic field could shift the equilibrium of nitriding reaction; this proved that the critical nitrogen potential to form γ′-Fe4N and ε-Fe3N phase was evidently enhanced compared with conventional nitriding. This research provides a new approach for a selective nitriding process.

Fabrication of Si Nitride Coating onto Metal Substrate by Reactive RF Plasma Spraying

Si3N4thick coating was fabricated by reactive RF plasma spraying, in which elemental Si reacted with surrounding nitrogen plasma. It was possible to fabricate the Si3N4coating by reactive spraying on a graphite substrate. As for the substrate, however, graphite is difficult to apply to the practical structural parts because of its low mechanical strength. Thus, it was necessary to realize Si3N4coating onto the metal substrate. In this research, Ti alloy, carbon steel and Ni alloy were used as the metal substrates. Ti alloy was difficult to apply to the formation of Si3N4coating because the preferential reaction of Ti-N prevented the nitriding reaction of Si-N. On the carbon steel substrate, pure Si coating was fabricated. However, nitriding reaction was difficult to occur on this substrate because the melting point of carbon steel was lower than the reaction temperature of Si-N. Ni alloy, one of the useful heat-resistant alloys, was also tried as the substrate. Finally, the feasibility of some kinds of interlayer between Si3N4and steel substrate was clarified to improve the bonding property between Si3N4and metal substrate.