Plasma-Enhanced Graphene Coatings on Ti-6Al-4V: Insights from Non-Destructive Characterization.

Area of Science:

• Materials Science
• Surface Engineering
• Nanotechnology

Background:

• Titanium alloys, particularly ELI grade Ti-6Al-4V, are widely used in biomedical applications due to their biocompatibility and mechanical properties.
• Improving the surface characteristics of titanium alloys is crucial for enhancing their functionality and expanding their application scope.
• Graphene, a 2D material with exceptional electronic and thermal properties, offers potential for surface modification.

Purpose of the Study:

• To deposit graphene coatings on ELI grade Ti-6Al-4V alloy substrates using Plasma Enhanced Chemical Vapor Deposition (PECVD).
• To characterize the graphene-coated titanium alloy surfaces using non-destructive techniques.
• To evaluate the potential of these modified surfaces for thermoelectric sensing and biomedical applications.

Main Methods:

• Graphene coatings were deposited via Plasma Enhanced Chemical Vapor Deposition (PECVD) using a 1:1 H2:CH4 gas mixture at 850 °C, 150 W plasma power, and 15 min duration.
• Material characterization involved Raman Spectroscopy, Thermoelectric Potential measurements (Seebeck coefficient) with varied tip systems and temperature gradients, and surface roughness analysis.
• Eddy current analyses were performed to assess electrical properties and sensitivity to sample variations.

Main Results:

• Uniform, micrometric graphene coatings were successfully deposited on Ti-6Al-4V ELI substrates, confirmed by Raman spectroscopy.
• Graphene-coated substrates exhibited metallic-like behavior and suitability for thermoelectric sensing, with enhanced sensitivity observed using high-sensitivity probes.
• Eddy current analysis showed low-frequency sensitivity and identified relationships between substrate thickness, phase angle, and electrical conductivity, attributed to coating interactions.
• Surface roughness slightly increased but remained comparable to the base alloy, ensuring biomedical compatibility.

Conclusions:

• PECVD is an effective method for depositing uniform graphene coatings on Ti-6Al-4V ELI alloys.
• The graphene-modified titanium alloy surfaces demonstrate promising thermoelectric properties for sensing applications.
• The enhanced surface characteristics suggest potential for implantable/wearable temperature sensors, energy harvesting, and smart biomedical interfaces.