טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentKatz-Demyanetz Alexander
SubjectKinetics of Reactions and Reactive Synthesis of Metal-
Ceramic Composites in Ni-Ti-B System in the
Presence of Ti2Ni and NiB Transient
Liquid Phases
DepartmentDepartment of Materials Science and Engineering
Supervisors Professor Elazar Gutmanas
Dr. Irena Gotman


Abstract

Kinetics of reactions and reactive synthesis of metal-ceramic composites were studied in Ni-Ti-B system in presence of Ti2Ni and NiB transient liquid phases.  Experiments were performed on consolidated powder blends and consolidated blend of Ti-Ti2Ni eutectic powder and 100 µm diameter B-fibers at different exposures and temperatures. Reactions in solid state were also studied. The microstructure was studied employing SEM/EPMA, HRSEM/EPMA/EBSD, qualitative and quantitative XRD.  The relevant activation energies for different reactions were calculated, compared between them as well as with the existing data.

It was found that the reaction rate in the consolidated powder blends was much higher than in the consolidated powders - B fiber systems. This is a result of the initial reagents' morphology: at the vicinity of concave surfaces of B-rich phase particles, the nucleation of the reaction products is homogeneous and occurs in the liquid phase, while on convex surfaces of B-particles the nucleation of borides is heterogeneous and occurs at the interface. In the latter case the effect of the liquid phase on reaction kinetics is insignificant.   

The effect of the curvature of the reacting solid phase on reaction kinetics and products was confirmed on Ti/Ti2Ni eutectic - glassy carbon foam system.

Kinetics of reactions was also studied in Ti/NiB and (Ti-Ti2Ni)/BN consolidated powder blends in pressure-assisted thermal explosion mode of SHS. The activation energies of the processes were calculated using analysis of heating curves. The values obtained for activation energies correspond to interface-reaction control.