رسائل دكتوراة
English
2015
DEVELOPMENT OF NANOSTRUCTURED Ti AND Nb-BASEDALLOYS FOR BIOMEDICAL APPLICATIONS
Nasser Al Aqeel, Mohamed Abdrabou Hussein
كلية الهندسة-جامعة الملك فهد للبترول والمعادن · السعودية
Titanium and Titanium-based alloys are generally preferred in the medical and dentistry fields compared to conventional alloys due to their enhanced mechanical properties and biocompatibility. Ti-based alloys were utilized with the addition of elements like Al, V, Cr, and Ni. However, it was reported that these elements have adverse effects on the utilization of these particular alloys, such as toxicity and genotoxicity which ultimately lead to lower biocompatibility. In addition, the osseointegration of such newly developed implant materials is one of the main goals of biomaterials research for dental and orthopedic applications to obtain enhanced interaction with cells.This dissertation focuses on developing nanostructured Ti and Nb-based alloys with non-toxic elements and enhanced mechanical properties for biomedical applications by mechanical alloying and spark plasma sintering. Different compositions were synthesized by ball milling and then characterized using XRD, TEM, and SEM. Afterwards, selected milled powders were sintered using spark plasma sintering. Microstructural evaluation and mechanical characterization were carried out for the sintered samples to investigate the effect of spark plasma sintering parameters on the microstructure and mechanical properties of the sintered alloys using XRD, FE-SEM, TEM, micro hardness, and nanoindentation measurements. The results for the binary Nb-Zr system showed that a nanostructured Nb-Zr alloy with an average grain size of between 100-300 nm was successfully synthesized for the first time using the MA-SPS techniques. A maximum hardness and relative density of 584 HV and 97.9% were achieved respectively. The results also showed that the increased energy of the system due to MA led to the formation of solid-solutions at earlier time, then amorphous phase with further milling, which mechanically crystallized to an FCC phase on continued milling. In addition, an amorphous phase at Zr contents lower than 40% was achieved for the first time. The results of ternary Ti-Nb-Zr system showed that nanostructured Ti20Nb13Zr at% near-β alloy with non-toxic elements and enhanced mechanical properties were successfully fabricated for the first time using the MA-SPS techniques. The results showed that at SPS temperature of 1200 °C, a nearly full density structure was obtained. The microstructure of the obtained alloy consist of a β-Ti (bcc) matrix which surround a α-Ti (hcp) region. The obtained alloy was chemically homogenized with a micro hardness value, HV of 657. The obtained nanostructured alloy having an average grain size of the dispersed α phase of 70 -140 nm. The nanostructured alloy increases the adhesion of osteoblast which will lead to enhanced interaction with cells compared to their coarse-grained counterparts. The developed nanostructured Ti–20Nb–13Zr at% alloy is a potential candidate for biomedical applications such as implant material for dental and orthopedic applications.