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Si3N4/TiN ceramic composites have been prepared by hot pressing in a nitrogen atmosphere using fine Si3N4 and Ti powders and CaO–Al2O3 sintering aids and investigated. The results demonstrate that hot pressing was accompanied by titanium nitridation, yielding titanium nitride with the composition TiN0.9. Reaction between silicon nitride and the sintering aid led to the formation of a Ca-α-SiAlON with the composition Ca0.67(Si10Al2)(N15.3O0.7). In addition to the major phases, calcium aluminosilicate with the composition Ca3Al2Si3O12 was identified. Increasing the percentage of titanium nitride in the composites prepared at a temperature of 1650°C led to an increase in their density and Vickers microhardness: from 3.18 ± 0.03 to 4.33 ± 0.03 g/cm3 and from 17 ± 1.1 to 29.4 ± 0.9 GPa, respectively. [ABSTRACT FROM AUTHOR]

We have studied the effect of sodium fluoride as a sintering aid for β-sialons on the phase composition and physicomechanical properties of Si5AlON7 and Si4Al2O2N6. Two-step high-temperature firing of the β-sialons in the presence of NaF under a nitrogen atmosphere has been shown to cause no significant changes in the phase composition of the materials. The density and microhardness of the materials prepared using 0.5 and 5.0 wt % NaF are lower than those of the materials prepared without sintering aids, but the bending strength is higher by up to 14.3% in the case of Si5AlON7 prepared using 0.5 wt % NaF and by 4.9% in the case of Si4Al2O2N6 prepared using 5.0 wt % NaF. [ABSTRACT FROM AUTHOR]

Si3N4-based ceramics have been produced by hot pressing in the temperature range 1550–1650°C using α-Si3N4 starting powder and CaO–Al2O3 (48 : 52 wt %) sintering aids. The powders and the ceramics have been characterized by dilatometry, scanning electron microscopy, and X-ray diffraction, and we have measured the microhardness and density of the ceramic samples. The results demonstrate that the sintering aid reacted with Si3N4 to form Ca-α-SiAlON. At 40 wt % sintering aids, all of the silicon nitride was converted into Ca-α-SiAlON. We have clarified general trends in the effect of the amount of sintering aids on the properties of the ceramic samples. [ABSTRACT FROM AUTHOR]

Polycrystalline Al5O6N samples have been prepared by sol-gel synthesis followed by carbothermal reduction and nitridation. X-ray luminescence (XRL) spectra and thermoluminescence (TL) curves of Ce3+- and Eu2+-doped aluminum oxynitride have been measured in the temperature range 5-380 K and analyzed. Working TL peaks have been detected in the range 150-250 K for the Al5O6N:Ce3+ sample and in the range 140-200 K for the Al5O6N:Eu2+ samples. There are also lower temperature peaks: in the ranges 10-60 and 20-100 K. The XRL spectra of the samples have been measured at temperatures of 8 (for the first time) and 300 K. [ABSTRACT FROM AUTHOR]

Silicon nitride nanofilaments were synthesized at 1600°C in nitrogen on the surface of a ceramic substrate made of amorphous silicon oxynitride obtained by hexamethyl disilasane pyrolysis. The diameter of filaments represented by different morphological types (filaments, ribbons, needles) was 100–500 nm, and the length was several millimeters. [ABSTRACT FROM AUTHOR]

Silicon nitride nanofilaments were synthesized at 1600°C in nitrogen on the surface of a ceramic substrate made of amorphous silicon oxynitride obtained by hexamethyl disilasane pyrolysis. The diameter of filaments represented by different morphological types (filaments, ribbons, needles) was 100–500 nm, and the length was several millimeters. [ABSTRACT FROM AUTHOR]