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Electronic Origin of α″ to β Phase Transformation in Ti-Nb-Based Thin Films upon Hf Microalloying.

ABSTRACT: We present results on thin Ti-Nb-based films containing Hf at various concentrations grown by magnetron sputtering. The films exhibit α" patterns at Hf concentrations up to 11 at.%, while at 16 at.% Hf, the β-phase emerges as a stable structure. These findings were consolidated by ab initio calculations, according to which the α"-β transformation is manifested in the calculation of the electronic band energies for Hf contents between 11 and 18 at.%. It turns out that the β-phase transition originates from the Hf 5d contributions at the Fermi level and the Hf 6s hybridizations at low energies in the electronic density of states. Bonding-anti-bonding first neighbor features existing in the shifted plane destabilize the α″-phase, especially at high Hf concentrations, while the covalent-like features in the first neighborhood stabilize the corresponding plane of the β-phase. Thin films measurements and bulk total energy calculations agree that the lattice constants of both α″ and β phases increase upon Hf substitution. These results are important for the understanding of β-Ti-based alloys formation mechanisms and can be used for the design of suitable biocompatible materials.

SUBMITTER: Gutierrez Moreno JJ

PROVIDER: S-EPMC7142957 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Electronic Origin of α″ to β Phase Transformation in Ti-Nb-Based Thin Films upon Hf Microalloying.

Gutiérrez Moreno José Julio JJ Panagiotopoulos Nikolaos T NT Evangelakis Georgios A GA Lekka Christina E CE

Materials (Basel, Switzerland) 20200312 6

We present results on thin Ti-Nb-based films containing Hf at various concentrations grown by magnetron sputtering. The films exhibit α" patterns at Hf concentrations up to 11 at.%, while at 16 at.% Hf, the β-phase emerges as a stable structure. These findings were consolidated by ab initio calculations, according to which the α"-β transformation is manifested in the calculation of the electronic band energies for Hf contents between 11 and 18 at.%. It turns out that the β-phase transition origi ...[more]

PMID: 32178419

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Project description:Due to the resistance of some bacteria to antibiotics, research in the field of dealing with bacterial infections is necessary. A practical approach utilized in this study involves the preparation of an antibacterial thin film on the surfaces, which can effectively inhibit and reduce biofilm formation and bacterial adherence. In this study, we report the fabrication of bactericidal titanium (Ti) and copper (Cu) surfaces which involves a powerful co-sputtering method. This method provides a situation in which constituent elements are deposited simultaneously to control the composition of the thin film. Prepared samples were examined by energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and contact angle measurements. To evaluate antibacterial behavior, we used two bacterial strains Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Antibacterial activity of the prepared sample was assessed by determining the number of colony-forming units per milliliter (CFU/ml) using a standard viable cell count assay. Results indicated that as the Cu concentration increased, the nanoscale surfaces became rougher, with roughness values rising from 11.85 to 49.65 nm, and the contact angle increased from 40 to 80 degrees, indicating a hydrophilic character. These factors play a significant role in the antibacterial properties of the surface. The Ti-Cu films displayed superior antibacterial ability, with a 99.9% reduction (equivalent to a 5-log reduction) in bacterial viability after 2 h compared to Ti alone against both bacterial strains. Field emission scanning electron microscopy (FE-SEM) images verified that both E. coli and S. aureus cells were physically deformed and damaged the bacterial cell ultrastructure was observed. These findings highlight that adding Cu to Ti can improve the antibacterial ability of the surface while inhibiting bacterial adherence. Therefore, the Ti14-Cu86 sample with the highest percentage of Cu had the best bactericidal rate. Investigation of toxicity of Cu-Ti thin films was conducted the using the MTT assay, which revealed their biocompatibility and absence of cytotoxicity, further confirming their potential as promising biomaterials for various applications.

Dataset Information

Electronic Origin of α″ to β Phase Transformation in Ti-Nb-Based Thin Films upon Hf Microalloying.

Publications

Electronic Origin of α″ to β Phase Transformation in Ti-Nb-Based Thin Films upon Hf Microalloying.

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