The Fe-silicon nitride synthesized by flashing combustion process was studied to determine the reaction temperature between Fe and silicon nitride, the account of N_2 given out in the course of the reaction, and the change of the microstructure during calcination. The results showed that at 1127.2℃ the Fe-silicon nitride self-reacts and releases N_2 and under 101.3 kPa the volume of N_2 given out in the course of the reaction is 20 times more than that of the starting material. N_2 is produced quickly, and completes in several decade seconds. With the producing of N_2, the structure of Silicon Nitride around Fe becomes loose and porous, or cracks are formed by the reaction between Fe and silicon nitride. So if it is made use of that Fe-silicon nitride self-producing N_2 at the high temperature, the performance of the material on a base of Fe-silicon nitride could be greatly improved.
Junhong ChenXueda WangJialin SunHuasheng ZhanWen Song
Saturated Ca(OH)_2 and AlCl_3 solutions were used to synthesize calcium aluminate hydrate precipitates at room temperature; high purity calcium aluminate powders with stable phases were made by calcination of the precursors at a temperature as low as 1100℃. PSD and BET analysis revealed the particles with sizes ranging from submicrometer to several micrometers and with a specific area of 13 nr/g. The measurement of hydraulic exotherm revealed that the exothermal rate is in peak for about 2 h. The exothermal quantities are 449.24 J/g at 12 h and 488.38 J/g at 24 h. Its strength development is quick and the 1 day curing strength is almost equal to 100％ of the 3 days curing strength in the mortar test.
