Ignition mechanism of mechanically activated Me–Si(Me = Ti, Nb, Mo) mixtures

2004 ◽  
Vol 19 (5) ◽  
pp. 1558-1566 ◽  
Author(s):  
U. Anselmi-Tamburini ◽  
F. Maglia ◽  
S. Doppiu ◽  
M. Monagheddu ◽  
G. Cocco ◽  
...  
Keyword(s):  
High Temperature ◽  
Reaction Mechanism ◽  
Mechanical Activation ◽  
Ignition Temperature ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Ignition Mechanism ◽  
Ignition Characteristics ◽  
Different Response

The influence of mechanical activation on the characteristics and mechanism of ignition of self-propagating high-temperature synthesis processes of different silicides in the systems Me–Si (Me =Ti, Nb, Mo) was investigated. The results show that mechanical activation does not alter the mechanism involved but influences significantly the ignition characteristics. The influence, however, strongly depends on the stoichiometry of the mixtures. The composition Ti:Si = 1:2 shows the largest influence, with the ignition temperatures decreasing from 1400 °C for unmilled powders to about 600 °C for powders milled for several hours. The compositionsTi:Si = 5:3, Nb:Si = 1:2 show less pronounced decreases, while the compositionMo:Si = 1:2 shows no decrease. These differences are discussed in terms of the role of microstructure in the reaction mechanism and the different response of the systems to contamination, particularly from oxygen. The results suggest that for these systems self-ignition processes during milling cannot be explained only on the basis of the decrease in the ignition temperature.

scholarly journals Mechanical activation assisted self-propagating high- temperature synthesis of Si/Al2O3composites

2009 ◽  
Vol 144 ◽  
pp. 012080 ◽  
Author(s):  
T F Grigoryeva ◽  
Yu D Kaminsky ◽  
M R Sharafutdinov ◽  
T L Talako ◽  
I A Vorsina ◽  
...  
Keyword(s):  
High Temperature ◽  
Mechanical Activation ◽  
Temperature Synthesis ◽  
High Temperature Synthesis

Reaction mechanism of self-propagating high-temperature synthesis reaction in the Ni–Ti–B4C system

2008 ◽  
Vol 23 (9) ◽  
pp. 2519-2527 ◽  
Author(s):  
Y.F. Yang ◽  
H.Y. Wang ◽  
R.Y. Zhao ◽  
Y.H. Liang ◽  
Q.C. Jiang
Keyword(s):  
High Temperature ◽  
Reaction Mechanism ◽  
Intermetallic Compounds ◽  
Eutectic Point ◽  
The Self ◽  
Mutual Diffusion ◽  
Synthesis Reaction ◽  
Temperature Synthesis ◽  
Early Appearance ◽  
High Temperature Synthesis

The SHS reaction in the Ni–Ti–B4C system starts with the formation of Ni–Ti and Ni–B intermetallic compounds from the solid interacted reaction among the reactants and, subsequently, the formation of Ni–Ti and Ni–B liquid at the eutectic point. Meanwhile, some C atoms from the reaction between Ni and B4C can dissolve into Ni–Ti liquid to form TiC. The heat generated from these reactions can promote the mutual diffusion of Ni–Ti–C and Ni–B liquid and simultaneously accelerate the formation of Ni–Ti–C–B liquid. Finally the precipitation of TiC and TiB2 occur when the C and B atoms in the liquid become supersaturated. The addition of Ni not only promotes the occurrence of the self-propagating high temperature synthesis (SHS) reaction by forming Ni–Ti liquid, but also accelerates the SHS reaction by forming Ni–B liquid and dissociative C. The early appearance of dissociative C from the reaction between Ni and B4C causes the formation of TiC prior to that of TiB2.

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