Paul Nnamchi - Academia.edu (original) (raw)
Papers by Paul Nnamchi
Intermetallics, 2013
First principles calculations have been performed to study the structural, heats of formation, el... more First principles calculations have been performed to study the structural, heats of formation, elastic properties, and densities of states of eight MgeAE (AE ¼ Ca, Sr, Ba) intermetallic compounds. The obtained results indicate that with increasing atom weight and concentration of AE, the bulk moduli decrease monotonously, and the larger the electronegativity difference is, the smaller the elastic modulus would be. Based on the ratios of shear moduli to bulk moduli, it has been found that Mg 2 Ca, Mg 38 Sr 9 , Mg 2 Sr, Mg 17 Ba 2 and Mg 23 Ba 6 behave in a brittle manner, and Mg 17 Sr 2 , Mg 23 Sr 6 and Mg 2 Ba behave in a ductile manner. Our calculations of the densities of states, heats of formation, and elastic constants of all the eight Mg compounds indicate that they are all conductors, thermodynamically and mechanically stable.
Stress shielding phenomenon has become a major drawback to the use of metallic biomaterials for o... more Stress shielding phenomenon has become a major drawback to the use of metallic biomaterials for orthopaedic implants applications. In this study, a Ti \ \Mo\ \(Nb, Zr and Nb + Zr) alloy system was investigated to design and develop novel low elastic Young's modulus Ti based alloy for implant application. The development and application of predictive modelling and simulation are transforming the materials engineering discovery process. To this end, ab initio calculation was used to evaluate the effects of composition on structural, elastic and electronic properties of the materials. The data obtained from both theory and experiment were analysed and compared with each other. Notable findings include low elastic Young's modulus values of 70.2 GPa, 80.6 GPa, 76.5 GPa, 59.1 GPa and 32.3 GPa for the Ti\ \6Mo\ \6Zr, Ti\ \6Mo\ \6Nb, Ti\ \6Mo\ \6Nb\ \2Zr, Ti\ \6Mo\ \5Nb\ \3Zr and Ti \ \6Mo\ \4Nb\ \4Zr alloys, respectively ascribed to the unique elastic softening of their C′ and C 44 shear moduli. The consistency in both results is discussed in terms of the sensitivity of the physical and electronic properties to the alloying additions. Thus, the result indicates the approach can enhance the reduction of elastic Young's mod-ulus of metallic biomaterials for replacing some commonly used high modulus materials and prevent stress shielding in orthopaedic implants.
Electrochemical characterisation Biomedical application Non-toxic element low elastic modulus a b... more Electrochemical characterisation Biomedical application Non-toxic element low elastic modulus a b s t r a c t
Intermetallics, 2013
First principles calculations have been performed to study the structural, heats of formation, el... more First principles calculations have been performed to study the structural, heats of formation, elastic properties, and densities of states of eight MgeAE (AE ¼ Ca, Sr, Ba) intermetallic compounds. The obtained results indicate that with increasing atom weight and concentration of AE, the bulk moduli decrease monotonously, and the larger the electronegativity difference is, the smaller the elastic modulus would be. Based on the ratios of shear moduli to bulk moduli, it has been found that Mg 2 Ca, Mg 38 Sr 9 , Mg 2 Sr, Mg 17 Ba 2 and Mg 23 Ba 6 behave in a brittle manner, and Mg 17 Sr 2 , Mg 23 Sr 6 and Mg 2 Ba behave in a ductile manner. Our calculations of the densities of states, heats of formation, and elastic constants of all the eight Mg compounds indicate that they are all conductors, thermodynamically and mechanically stable.
Stress shielding phenomenon has become a major drawback to the use of metallic biomaterials for o... more Stress shielding phenomenon has become a major drawback to the use of metallic biomaterials for orthopaedic implants applications. In this study, a Ti \ \Mo\ \(Nb, Zr and Nb + Zr) alloy system was investigated to design and develop novel low elastic Young's modulus Ti based alloy for implant application. The development and application of predictive modelling and simulation are transforming the materials engineering discovery process. To this end, ab initio calculation was used to evaluate the effects of composition on structural, elastic and electronic properties of the materials. The data obtained from both theory and experiment were analysed and compared with each other. Notable findings include low elastic Young's modulus values of 70.2 GPa, 80.6 GPa, 76.5 GPa, 59.1 GPa and 32.3 GPa for the Ti\ \6Mo\ \6Zr, Ti\ \6Mo\ \6Nb, Ti\ \6Mo\ \6Nb\ \2Zr, Ti\ \6Mo\ \5Nb\ \3Zr and Ti \ \6Mo\ \4Nb\ \4Zr alloys, respectively ascribed to the unique elastic softening of their C′ and C 44 shear moduli. The consistency in both results is discussed in terms of the sensitivity of the physical and electronic properties to the alloying additions. Thus, the result indicates the approach can enhance the reduction of elastic Young's mod-ulus of metallic biomaterials for replacing some commonly used high modulus materials and prevent stress shielding in orthopaedic implants.
Electrochemical characterisation Biomedical application Non-toxic element low elastic modulus a b... more Electrochemical characterisation Biomedical application Non-toxic element low elastic modulus a b s t r a c t