The thesis is submitted as a partial fulfillment of the requirements for the Master of Mechanical Engineering degree. Cover: 𝐶𝑢51𝑍𝑟30𝐻𝑓14𝐴𝑔5 sample of metallic glass synthesized by melt spinning technique (Photo: Tamim Ahmad Mohammad Ahmad). The thesis deals with the electrochemical investigation of metallic glass based on copper and zirconium 𝐶𝑢51𝑍𝑟30𝐻𝑓14𝐴𝑔5.
Studying the corrosion behavior of the new melt-spun metallic glass ribbons contributes to further research into the possibility of building future biological implants. The results of the experiments carried out in this work show that the addition of Ag and Hf in the new metallic glass 𝐶𝑢51𝑍𝑟30𝐻𝑓14𝐴𝑔5 generally results in better corrosion resistance than previously investigated. The results will contribute to further studies on the possible uses of the new metallic glass, in addition to its potential use in biological implants.
وتقع موينوكرزلاو في قاعدة هذه العائلة والتي تسمى (𝐶𝑢51𝑍𝑟30𝐻𝑓14𝐴𝑔5) ويدعمها عدد كبير من كاتالا كولسارد ماهاسيت.
Introduction
Overview
Metallic glasses come in two main types: the metal-metallic type and the metal-metalloid type. As the name suggests, metallic-metallic glass is composed of metals only, while metallic-metalloid type can have up to 20% metalloid atoms such as carbon, phosphorus, boron and silicon (Suryanarayana & Inoue, 2011). There are several methods for producing metallic glasses such as plane casting, melt extraction, double roll and melt spinning.
In this thesis, the metallic glass to be studied is produced using the melt-spinning technique where the molten alloy hits a rotating disc which throws the resulting thin metallic glass ribbon away and falls off due to centrifugal force (Suryanarayana, 1984). In the production of the metallic glasses, the amorphous nature should be investigated using X-ray diffraction research.
Statement of the Problem
3 support the revolution of introducing other new biocompatible metal glasses that solve the disadvantages of current alloys. Medical implants carry some potential risks because of their composition and the way they interact with the body, or sometimes how the body reacts to their presence.
Research Objectives
Relevant Literature
- Advanced Materials
- Rapid Solidification Processing
- Melt Spinning Technique
- Metallic Glasses
- Main Types of Metallic Glasses
- Bulk Metallic Glasses
- Melt Spun Ribbons
- Physical Properties of Metallic Glasses
- Mechanical Behavior
- Copper-Zirconium Based Metallic Glasses
- Evaluation of the Corrosion Behavior of the Metallic Glass
- X-Ray Diffraction
- Potentiodynamic Polarization PDP
- Electrochemical Impedance Spectroscopy EIS
- Data Representation: Nyquist Plot
- Data Representation: Bode Plot
- Equivalent Circuit models
- Scanning Electron Microscopy with
- Research Gap
- Potential Contributions and Limitations of the Study
Some of the advantages of using the melt spinning technique are that the scientists have optimized the process and the melt spinners can be found on the market. In addition, the technique yields ribbons with uniform structures and cross-sections, which helps to study the properties of the resulting metallic glass (Suryanarayana & Inoue, 2011). Since the melt-spun ribbons are easier to process and analyze in the TEM, the scientists use them to study the crystallization behavior of the bulk metal glasses of the same composition.
Additionally, the XRD pattern of bulk metallic glasses is more complex to identify (Suryanarayana & Inoue, 2011). In the graphs of metallic glass 𝐶𝑢51𝑍𝑟30𝐻𝑓14𝐴𝑔5, there should be no sharp peaks indicating crystalline nature. In the PDP results, it is expected from previous literature that the corrosion resistance of metallic glass decreases with increasing 𝐶𝑙−.
In addition, the stability of the samples is expected to decrease, which is usually indicated by a decrease in 𝐸𝑐𝑜𝑟𝑟. In the semicircle of the Nyquist plot, the diameter represents the polarization resistance of the samples. Polarization resistance is a good indicator because it is directly related to the corrosion resistance of the sample.
That is, the higher the polarization resistance, the higher the corrosion resistance of the alloy or metallic glass (“Electrochemical Impedance Spectroscopy”, 2016). In the Bode graph, the phase shift (𝞍) and the absolute value of the impedance |𝑍| are plotted against the log frequency as shown in Figure 6 below. The copper-zirconium-based metallic-glass equivalent circuit in hand is found to have two resistances (R), one capacitance element (C), and a constant phase element (CPE).
In addition to the circuit components listed below, there are several components that are beyond the scope of the tests in this thesis ("The Circuit Description Code explained", 2016). The electrochemical study of 𝐶𝑢51𝑍𝑟30𝐻𝑓14𝐴𝑔5 metallic glass behavior will introduce the new metallic glass to the industry. However, the applications of metallic glasses are still limited due to the difficulty in synthesizing bulk metallic glasses thereof.
Other possible applications are expected to be suggested once the corrosion behavior of metallic glass is understood.
Methods
Introduction to the Research Methods
Data Collection
- Synthesizing the 𝐶𝑢 51 𝑍𝑟 30 𝐻𝑓 14 𝐴𝑔 5 Metallic Glass Samples
- Verifying the Amorphous Nature of the 𝐶𝑢51𝑍𝑟30𝐻𝑓14𝐴𝑔5
- Preparation of Various Solutions
- Corrosion Behavior Evaluation
- Corrosion Behavior Evaluation Using the
- Surface Morphology Analysis Using SEM Coupled with EDS
Different solutions were prepared in the laboratory to perform potentiodynamic polarization tests. (8) Where 𝑀1 is the required molarity of the solution, 𝑉1 is the volume of the required solution, 𝑀2 is the molarity of HCl and 𝑉2 is the volume of HCl. Similarly, 8.3 mL and 83 mL of concentrated solution in 1000 mL of distilled water were required to prepare 0.1 M and 1 M concentration of HCl solution, respectively.
After drying the samples with air and during the preparation of the solutions, the tests were performed at room temperature. To test the samples in an acidic environment, we prepared a solution of HCl in three concentrations of 0.01 M, 0.1 M and 1 M. As we have already mentioned, the procedure is repeated for three concentrations of a neutral NaCl solution and a basic pH NaOH solution. 8, pH 10 and pH 12 levels (Nair et al., 2019).
Potentiodynamic polarization tests were performed at a scan rate of 0.000167 (𝑉 . 𝑠) in 100 ml of prepared solutions. Before starting the tests, the samples are immersed in the electrolyte solution for 20 minutes to obtain a stable potential. Impedance analysis is performed using EC-Lab software, which converts the impedance data into an equivalent circuit using the following steps.
The software has several built-in common circuits that are commonly used in the electrochemical analysis of materials. The Nyquist and Bode plots are used to represent the data, where in the Nyquist plot the negative of the imaginary part of the impedance is plotted versus the real part of the impedance as discussed in the literature chapter earlier. On the other hand, the bode plots have once the phase shift plotted against the log frequency, and once with the absolute value of the impedance versus the log frequency.
Further description is discussed in the literature review in the first chapter of this thesis. Thermo Scientific Prisma E scanning electron microscopy coupled with energy dispersive X-ray spectroscopy is used to examine the surface of the 𝐶𝑢51𝑍𝑟30𝐻𝑓14𝐴𝑔5 metallic glass samples, as shown in Figure 9.
Results and Discussions
Overview of the Main Findings
- XRD
- Potentiodynamic Polarization (PDP)
- HCl Solution PDP Results
- NaCl Solution PDP Results
- NaOH Solution PDP Results
- Potentiodynamic Polarization Results Summary
- Electrochemical Impedance Spectroscopy Results
- Scanning Electron Microscopy (SEM)
- Energy Dispersive Spectroscopy (EDS)
However, the samples tested in 0.01 M and 0.1 M, 𝐶𝑢51𝑍𝑟30𝐴𝑔5𝐻𝑓14 show passive regions in the anodic curve, indicating better corrosion resistance in lower concentrations than in higher concentrations of −. In addition, the 𝐸𝑐𝑜𝑟𝑟 value becomes more negative as the 𝐶𝑙− content increases, which means a decrease in the stability of the metallic glass ribbons (Nair et al., 2019). It is clear from the polarization curves below for the samples tested in the three molar concentrations of the neutral NaCl solution that the metallic glass shows clear passivity in the anodic curve.
The metallic glass 𝐶𝑢51𝑍𝑟30𝐴𝑔5𝐻𝑓14 shows a decrease in corrosion resistance as the 𝐶𝑙− content increases, which is evident in Figure 12, where the sample tested at the highest concentration of 𝐶𝑙 moves to 1 M−10. The behavior of the metallic glass in the alkaline NaOH solution was evaluated in pH 8, pH 10, pH 12 levels. The metallic glass shows a clear passive region in the three pH levels, indicating good corrosion resistance in alkaline solutions.
Larger curve radii in the Nyquist plots correspond to greater corrosion resistance. Furthermore, the radius of the Nyquist curves decreases as the 𝐶𝑙− content increases, as shown in the strip curves tested in 0.1 M and 1 M HCl solutions. Using the same method, metallic glass samples 𝐶𝑢51𝑍𝑟30𝐴𝑔5𝐻𝑓14 were tested in neutral NaCl solution at three different concentrations which are 0.01 M, 0.1 M and 1 M.
It means that 𝐶𝑢51𝑍𝑟30𝐴𝑔5𝐻𝑓14 has the lowest corrosion resistance at the highest pH value (pH 12 of NaOH) and is more susceptible to corrosion than at lower pH values (pH 8 and pH 10). Interestingly, the 𝐶𝑢51𝑍𝑟30𝐴𝑔5𝐻𝑓14 metal glass samples show a decrease in charge transfer resistance as the pH level increases. The metal glass 𝐶𝑢51𝑍𝑟30𝐴𝑔5𝐻𝑓14 shows a similar behavior in the neutral NaCl solution, with the pits increasing in diameter and quantity as the 𝐶𝑙− increased.
As can be seen in Figures 24-26 below, the corrosion in the samples tested in 0.01 M showed almost no pitting. In the alkaline solution NaOH, 𝐶𝑢51𝑍𝑟30𝐴𝑔5𝐻𝑓14 shows an interesting behavior where there are no significant corrosion pits in the samples tested in pH 8 and pH 10. In Figures 33-41 is the spectral mapping of the various samples obtained using the EDS solutions. .
Similarly, the content of elements in the passive film of the samples tested in 0.1 M and 1 M NaCl is more than that in 0.1 M and 1 M HCl solution, which indicates that the passive film is formed more lightly in the NaCl solution again.
Conclusion
Managerial Implications
Research Implications
The results of the investigation of the new material could suggest an expansion of the range of materials used in biological implants to replace the materials used today with new improved materials in terms of their biocompatibility and corrosion resistance. Retrieved June 18, 2023, from https://www.gamry.com/application-notes/EIS/basics-of-electrochemical-impedance-spectroscopy/. Preparation of Zr_65Al_75Ni_10Cu_175 metal glasses based on point-line-face-body theory.
19 June 2023, from https://www.thermofisher.com/sa/en/home/electron-microscopy/products/scanning-electron-microscopes/prisma-esem.html. Zr-based bulk metal glass with high glass-forming ability, corrosion resistance and thermal stability. Additively manufactured large Zr based bulk metal glass composites with the desired deformation ability and corrosion resistance.
Corrosion resistance of crystalline and amorphous CuZr alloys in NaCl aqueous medium and the effect of corrosion inhibitors.
