Effects of α-Si3N4 and AlN addition on formation of α-SiAlON by combustion synthesis

Fabrication of mixed α/β-SiAlON powders via salt-assisted combustion synthesis

“…However, the CS of SiAlONs with Si, Al, SiO 2 , or other metal oxides under N 2 at a specific applied pressure usually gives a low product yield owing to the existence of unreacted Si, caused by the melting and coalescence of silicon particles at the combustion front. To decrease the combustion temperature as well as to reduce the overall heat released from nitridation of Al and Si, it is necessary to add a large amount of Si 3 N 4 and AlN instead of Si and Al [15,16]. In addition, NH 4 Cl or NH 4 F additives are also required to be added to the starting materials in order to achieve complete nitridation [13,17].…”

Effects of α- and β-Si3N4 as precursors on combustion synthesis of (α+β)-SiAlON composites

“…1(a) and (b), the SHS process is characterized by one localized reaction zone spreading spirally along the sample. Instead of developing a planar combustion front propagating longitudinally, the presence of a spinning combustion wave implies that the synthesis reaction is not sufficiently exothermic [25]. According to Ivleva and Merzhanov [31], once the heat flux liberated from selfsustaining combustion is no longer adequate to maintain the steady propagation of a planar front, the combustion front forms one or several localized reaction zones.…”

“…Fabrication of ␣-and ␤-SiAlON has been conducted by a variety of processing routes, such as hot isostatic pressing (HIP) [2,4], hot pressing (HP) [10][11][12], gas pressure sintering [7][8][9]13], pressureless sintering [14], liquid-phase sintering [15], carbothermal reduction and nitridation (CRN) [16,17], and combustion synthesis [18][19][20][21][22][23][24][25]. For example, Mandal [4] prepared different ␣-SiAlONs using Si 3 N 4 , AlN, Al 2 O 3 , and Me x O y (where Me = Sr, Ca, La, Ce, Nd, and Yb) by HIP at 1800 • C for 2 h, and observed an elongated morphology in the (Nd + Ca)-and (Ce+Ca)-doped products.…”

“…The ␤ phase of SiAlON with z = 3 and 4 was also produced by combustion synthesis using mechanically activated Si, Al, and Al 2 O 3 powders in nitrogen of 1 MPa [24]. Recently, Yeh and Sheng [25] produced elongated Yb ␣-SiAlON by SHS from the powder compacts with ␣-Si 3 N 4 /Si = 0.4-0.5 in nitrogen of 2.17 MPa, while the ␣-SiAlON in the form of equiaxed gains was synthesized from the samples with AlN/Al = 0.85-1.0.…”

“…The objective of this study aims to investigate the influence of ␣-and ␤-Si 3 N 4 as the precursors on the phase and morphology of SiAlON produced through combustion synthesis in the SHS mode under gaseous nitrogen. Unlike the previous study preparing ␣-SiAlON [25], this study is focused on formation of the (␣ + ␤)-SiAlON composite. The powder compacts were formulated with different molar ratios of Si/Si 3 N 4 and various proportions of ␣/␤-Si 3 N 4 .…”