ساخت و مشخصه يابي نانو كامپوزيت متخلخل NiTi-TiN به روش سنتز احتراقي

چكيده انگليسي :

tW Fabrication and Characterization of Porous NiTi TiN Nanocomposite via SHS Method Mohamadreza Valaei m valaei@ma iut ac ir Date of Submission January 30 2012 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree MSc Language FarsiSupervisor prof Ali Saidi a saidi@cc iut ac irAbstract Porous NiTi PNT shape memory alloys has been attracted extremely attention in recent years as suitablebiomaterial for use as dental or orthopedic implants due to their unique mechanical properties and goodbiocompatibility Their porous structure permits the formation and ingrowth of new bone tissue However pores can act as the weakener factor of mechanical properties and obstacle its use as hard tissue implants forheavy load bearing applications The erosion possibility at load bearing surfaces of this materials is anotherimportant challenge for such applications It has been demonstrated that embedding a small amount of hardnanoparticles in the matrix can effectively strengthen and enhance the wear resistance of the intermetallics However addition of ceramic nanoparticles to the PNT matrix has not been reported so far The first purposeof present research was the fabrication of PNT using Mechanically Activated Self Propagating High Temperature Synthesis MASHS method The second objective was production of porous NiTi TiNnanocomposites employing optimized processing conditions of MASHS In the first set of experiments several reactant mixtures of activated Ni and Ti elemental powders with varying chemical compositions with0 5 and 10 wt TiN nanoparticles were prepared for combustion synthesis in argon or nitrogen atmosphere In the next stage the effect of various parameters such as milling time process control agent PCA and preheating temperature on the behaviuor of combustion wave and properties of products wereinvestigated The results showed that mechanical activation led to formation of stable combustion front waveand porous products with fine and homogeneous microstructure However excessive milling led to shiftingthe mechanism of reaction to purely solid state combustion and insufficient strength in final products UsingX ray diffraction XRD and energy dispersive X ray spectroscopy EDS it was shown that B2 NiTi andB19 NiTi were present as the dominant phase in all samples with some amount of Ni3Ti and NiTi2intermetallic compounds The porosity measurement revealed that the general porosity of samples werebetween 42 to 59 vol and the open porosity ratio was in the range of 61 to 91 The pore structures of theproducts were also studied by scanning electron microscopy SEM and the size of most pores weredetermined between 100 to 600 4 5# $ # 5 6 5 $ 57 was found to have a significanteffect on the pore morphology and amount of secondary phases Mechanical properties of selected MASHS synthesized porous products was evaluated by utilizing the uniaxial compression test and results indicatedthat the ultimate compressive strength of NiTi 5 TiN nanocomposite was 55 higher than NiTi samplewithout reinforcing phase However adding 10wt TiN nanoparticles caused to increasing the Young smodulus lowering the strength and intensive brittleness of product It is worthy to mention that althoughPNT synthesized in this study possess the qualification demands for use as biomedical implants howevermerely porous NiTi 5 TiN nanocomposite is advisable as a novel candidate for heavy load bearingorthopedic implants from the mechanical properties viewpoint Keywords Porous Nitinol TiN Nanocomposite Mechanical Activation Combustion Synthesis

والايي، محمدرضا

ساخت و مشخصه يابي نانو كامپوزيت متخلخل NiTi-TiN به روش سنتز احتراقي

نايتينول متخلخل , فعال سازي مكانيكي