Microstructural Development, Microstructural Characterization and Relation to Mechanical Properties of Dense Silicon Nitride

Abstract

Microstructural development during liquid-phase assisted densification of Si3N4 powder compacts is a function of powder properties, type and amount of additives as well as of processing conditions (time, temperature, pressure

The effect of Si content, firing temperature, and urea additive on the properties of nitride-bonded SiC refractories

“…The slight decrease in density at higher firing temperatures could be attributed to nitride phase decomposition. By increasing both the amount of b-Si 3 N 4 and the aspect ratio of this phase at higher firing temperatures, we conclude that the aspect ratio and grain diameter have a strong effect on improvement of the mechanical properties, as was reported by Woetting [11].…”

“…It is obvious, by increasing the amounts of Si in the primary batch, that the density of samples increases significantly to about 2.64 g/cm 3 . This could be attributed to nitride phase formation accompanied by a pore-filling effect [11]. The XRD patterns in (Fig.…”

“…3), and the a-to b-Si 3 N 4 phase transformation by the solution-diffusion-precipitation mechanism is improved [3]. By increasing the amount of Si (with iron impurity), the liquid phase is increased and then more b-Si 3 N 4 phase is formed in the matrix, which brings almost an improvement of mechanical properties [3,11].…”

Microstructure control and toughening of ZrB₂–SiC/Zr–Al–C composite ceramics by selecting additional powders mixed with ZrB₂ in ball milling for spark plasma sintering

“…The quantitative metallographic technique was adopted to determine the aspect ratio of ZrAlC grains, 33) and the maximum average aspect ratio of ZrAlC grains was estimated to be 7 for the ZSAZA sample, as shown in Table 2. It is generally believed that elongated grains with a high aspect ratio enhance the fracture toughness of a ceramic matrix, 34) and the incorporation of high aspect ratio reinforcements has been used to reduce the brittleness of ZrB 2 -based composites.…”

Influence of additives on microstructural changes in nitride bonded SiC refractories

“…8,9 In order to optimize the mechanical properties of Si 3 N 4 materials, it is necessary to know, the factors that MgO 0.5 1 2 3 ------Al 2 O 3 ----0.5 1 2 3 4 5 Binder 3 3 3 3 3 3 3 3 3 3 25 wt% Si as explained in our previous work. 13 The chemical compositions of samples are shown in Table 1.…”