The Wonderful World of Scanning Electrochemical Microscopy (SECM)
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This document summarizes a presentation given by Dr. Janine Mauzeroll on scanning electrochemical microscopy (SECM). SECM is introduced, including operating modes and principles. Applications of SECM in studying multdrug resistance in cancer cells, electrochemical properties of battery materials, and corrosion of alloys are discussed. SECM allows visualization of heterogeneous electron transfer kinetics and mass transport at micro and nanoscale.
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The Wonderful World of Scanning Electrochemical Microscopy (SECM)
- 1. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll, PhD Professor of Chemistry Department of Chemistry McGill University The Wonderful World of Scanning Electrochemical Microscopy (SECM)
- 2. Laboratory for Electrochemical Reactive Imaging of Biological Systems The Wonderful World of Scanning Electrochemical Microscopy (SECM) Dr. Janine Mauzeroll discusses the fundamentals, critical experimental parameters and recent applications for Scanning Electrochemical Microscopy (SECM).
- 3. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll, PhD Professor of Chemistry Department of Chemistry McGill University The Wonderful World of Scanning Electrochemical Microscopy (SECM) Copyright 2021 J. Mauzeroll and InsideScientific. All Rights Reserved.
- 4. Laboratory for Electrochemical Reactive Imaging of Biological Systems Piled Higher and Deeper by Jorge Cham www.phdcomics.com title: "Thesis writing" - originally published 11/5/1999 4 Strange what also applies to talks…..
- 5. Laboratory for Electrochemical Reactive Imaging of Biological Systems
- 6. Laboratory for Electrochemical Reactive Imaging of Biological Systems 6 Janine Mauzeroll Today is all About…
- 7. Laboratory for Electrochemical Reactive Imaging of Biological Systems Bulk Diffusion Feedback mode (Insulating surface) Feedback mode (Conductive surface) Substrate generation – tip collection Tip generation – substrate collection Redox competition Direct mode Potentiometric mode 7 Janine Mauzeroll Modes of SECM
- 8. Laboratory for Electrochemical Reactive Imaging of Biological Systems x z y 8 Janine Mauzeroll Scanning Electrochemical Microscope
- 9. Laboratory for Electrochemical Reactive Imaging of Biological Systems • The rate of electrochemical reactions (v) is monitored through currents measured at the microelectrode (i). • We can study the substrate’s electrochemical reactivity in this way. 9 Janine Mauzeroll SECM Principle
- 10. Laboratory for Electrochemical Reactive Imaging of Biological Systems • In electrochemistry, we control ΔGRXN using Eapplied Product Reactant Oxidation A A+ + e Transition State 10 Janine Mauzeroll Controlling Charge Transfer
- 11. Laboratory for Electrochemical Reactive Imaging of Biological Systems v = Rate of electrochemical reactions i = Microelectrode currents n = # of electrons F = Faraday’s constant A = electrode area 1) Rate of electron transfer 2) Rate of mass transport 11 Janine Mauzeroll What Do I Need to Know to Quantify the Current?
- 12. Laboratory for Electrochemical Reactive Imaging of Biological Systems F = Faraday’s constant A = Electrode area k0 = Standard rate constant CO(0,t) ; CR(0,t) = Surface concentrations of species O,R α = Transfer coefficient E – E0’ = Overpotential (driving force applied) 12 Janine Mauzeroll • Reaction kinetics at an electrode surface follow the Butler-Volmer relationship Heterogeneous Electron Transfer Rate
- 13. Laboratory for Electrochemical Reactive Imaging of Biological Systems 13 Janine Mauzeroll Mass Transport in the Electrolyte
- 14. Laboratory for Electrochemical Reactive Imaging of Biological Systems Mass transport in electrolyte Electrode kinetics Butler-Volmer: First order kinetics: Concentration boundaries 14 Janine Mauzeroll Finite Element Modeling is Required in SECM
- 15. Laboratory for Electrochemical Reactive Imaging of Biological Systems Normalized Electrode current is a function of L, Rg, κ κ C. Lefrou and R. Cornut, ChemPhysChem, 11, 547 (2010) Probe Approach Curve Analytical Approximations
- 16. Laboratory for Electrochemical Reactive Imaging of Biological Systems Positive FB Negative FB 16 Janine Mauzeroll Tracking Substrate Reactivity using SECM
- 17. Laboratory for Electrochemical Reactive Imaging of Biological Systems Red Ox L (tip-substrate distance) NiT (tip current) e- e- 17 Janine Mauzeroll Substrates with Finite Kinetics
- 18. Laboratory for Electrochemical Reactive Imaging of Biological Systems Classical Probes Multifunctional Probes Danis, L.; Mauzeroll, J. et. al. Anal. Chem. 2015. p 2565 Danis, L.; Mauzeroll, J. et. al. Anal. Chem. 2015. p 2565 Katemann, B. B.; Schuhmann W. ElectroAnalysis 2002. p 22 Walsh, D. A.; Bard, A. J.; et. al. Anal. Chem. 2005. p 5182
- 19. Laboratory for Electrochemical Reactive Imaging of Biological Systems Polcari, D.; Dauphin-Ducharme, P.; Mauzeroll J., Chem. Rev., 116, 13234 (2016) Application Fields of SECM
- 20. Laboratory for Electrochemical Reactive Imaging of Biological Systems Cancer Cells Batteries Corrosion 20 Janine Mauzeroll Three Short Stories
- 21. Laboratory for Electrochemical Reactive Imaging of Biological Systems Expression and Functional Activity of Multidrug Resistance-Associated Protein 1 using SECM Polcari, D.; Mauzeroll, J. et al., Anal. Chem., 89, 8988 (2017). Kuss, S.; Mauzeroll, J. et al., Anal. Chem., 87, 8096 (2015). Kuss, S.; Mauzeroll, J. et al., Anal. Chem., 87, 8102 (2015). Kuss1, Polcari1 et al., PNAS 110, 9249 (2013)
- 22. Laboratory for Electrochemical Reactive Imaging of Biological Systems Drug-Sensitive Cancer Cell (Ex: HeLa Cells) Multidrug Resistant Cancer Cell (Ex: HeLa-R Cells) 22 Janine Mauzeroll Multidrug Resistance (MDR)
- 23. Laboratory for Electrochemical Reactive Imaging of Biological Systems Drug-Sensitive Cancer Cell (Ex: HeLa Cells) MDR Cancer Cell (Ex: HeLa-R Cells) 0.05 µM 0.10 µM Untreated 0.05 µM 0.10 µM Untreated Drug Challenge Janine Mauzeroll 25
- 24. Laboratory for Electrochemical Reactive Imaging of Biological Systems Cell Patterning for SECM Janine Mauzeroll 24
- 25. Laboratory for Electrochemical Reactive Imaging of Biological Systems No Interaction Negative Feedback Diffusion into Cell Positive Feedback Measuring MRP1 Activity Janine Mauzeroll 25
- 26. Laboratory for Electrochemical Reactive Imaging of Biological Systems • Extract tip to substrate distance, L, at each image pixel • Then extract heterogeneous kinetics , κ, at each image pixel Two Step Process Convolution Janine Mauzeroll 26
- 27. Laboratory for Electrochemical Reactive Imaging of Biological Systems (cm s -1 ) Effect of Pattern Size Polcari, D.; Mauzeroll, J. et al., Anal. Chem., 89, 8988 (2017)
- 28. Laboratory for Electrochemical Reactive Imaging of Biological Systems (cm s -1 ) Time-Lapse Imaging Polcari, D.; Mauzeroll, J. et al., Anal. Chem., 89, 8988 (2017)
- 29. Laboratory for Electrochemical Reactive Imaging of Biological Systems Polcari, D.; Mauzeroll, J. et al., Anal. Chem., 89, 8988 (2017) Activity of Six Different Cell Populations
- 30. Laboratory for Electrochemical Reactive Imaging of Biological Systems Cancer Cells Batteries Corrosion 30 Janine Mauzeroll Three Short Stories
- 31. Laboratory for Electrochemical Reactive Imaging of Biological Systems Localized Investigations of the Electrochemical Properties of Lithium Battery Materials Using Micropipette Dayeh, M.; Snowden, M. E.; Ghavidel, M.; Payne, N.; Gervais, S.; Mauzeroll, J.; Schougaard, S. B. Journal of Power Sources 2016, 325, 682-689. ChemElectroChem, 2019, 6, 195–201 Analytical Chemistry 2019, 91(24), 15718-15725 Analytical Chemistry 2020, 92, 10908-10912.
- 32. Laboratory for Electrochemical Reactive Imaging of Biological Systems Malak Dayeh 1 μm 1 μm 1 μm Are all battery particles created equal? 32
- 33. Laboratory for Electrochemical Reactive Imaging of Biological Systems 20 µm Single particle battery Measuring Isolated Active Particles 33
- 34. Laboratory for Electrochemical Reactive Imaging of Biological Systems 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 -400 -200 0 200 400 600 i (pA) E (V) vs. Li/Li+ distance (μm) i (μA) distance (μm) i (μA) Approach Land Retract Measure Scanning Micropipette Contact Method 34
- 35. Laboratory for Electrochemical Reactive Imaging of Biological Systems 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 -400 -200 0 200 400 600 i (pA) E (V) vs. Li/Li+ distance (μm) i (μA) distance (μm) i (μA) Approach Land Retract Measure Scanning Micropipette Contact Method 35
- 36. Laboratory for Electrochemical Reactive Imaging of Biological Systems Malak Dayeh - Very low water and oxygen content (~ 1 ppm) - The only gas present is Argon Electrode Pipette Substrate Development of SMCM in Anaerobic Conditions 36
- 37. Laboratory for Electrochemical Reactive Imaging of Biological Systems Malak Dayeh 2μm Journal of Power Sources 2016, 325, 682–689. LiFePO4 Li+ + e- + FePO4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 -20 -10 0 10 20 1 mV/s 5 mV/s 10 mV/s 20 mV/s 50 mV/s Potential / V (vs. Li/Li+ ) Current / p A Epf ipf 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 -600 -400 -200 0 200 400 600 Current / p A Potential / V (vs. Li/Li+ ) SMCM on Isolated LiFePO4 Active Particles
- 38. Laboratory for Electrochemical Reactive Imaging of Biological Systems Electrochemistry and Electron Microscopy Malak Dayeh 0 1 2 3 4 5 6 7 0 10 20 30 40 Particle Area (µm2 ) i pf (pA) 0.0 0.4 0.8 1.2 1.6 2.0 Q f (nC) - Particle cross section areas obtained from SEM are compared to the forward (oxidation) peak current and the integrated charge. - A larger cross section area correlates to both a higher peak current and increased charge. LiFePO4 Li+ + e- + FePO4 Journal of Power Sources 2016, 325, 682–689. 38
- 39. Laboratory for Electrochemical Reactive Imaging of Biological Systems 2 µm i 2 µm iii 2 µm ii Malak Dayeh 6% 27% 67% 0 100 Shifted peak Double peak Single peak Differences in electrochemical performances Journal of Power Sources 2016, 325, 682–689. Particles’ Heterogeneities
- 40. Laboratory for Electrochemical Reactive Imaging of Biological Systems 40 Malak Dayeh Summary SMCM technique is: Valuable tool for probing the localized electroactivity of battery active material Capable of detecting heterogeneity in material properties distribution ❌Considered as a quality control tool for active material fabrication, and monitoring batch-to-batch variations in particle properties � Particle volume still evaluated by external means
- 41. Laboratory for Electrochemical Reactive Imaging of Biological Systems Malak Dayeh Future Direction: Two Diffusion Regimes Journal of Power Sources 2010, 195(24), 7904-7929. Li+ LFP 1 2 LiFePO4 Li+ + e- + FePO4 1: Transport of Li+ ions in electrolyte 2: Diffusion of Li+ ions within LFP particle
- 42. Laboratory for Electrochemical Reactive Imaging of Biological Systems Use SICM to measure porous film conductivity Analytical Chemistry 2019, 91(24), 15718-15725
- 43. Laboratory for Electrochemical Reactive Imaging of Biological Systems A composite cathode is a porous film Analytical Chemistry 2019, 91(24), 15718-15725
- 44. Laboratory for Electrochemical Reactive Imaging of Biological Systems SICM approach curve= film conductivity Analytical Chemistry 2019, 91(24), 15718-15725
- 45. Laboratory for Electrochemical Reactive Imaging of Biological Systems From Macro to Micro: Using Electrochemical Methods to Investigate the Effect of Alloy Chemistry on Corrosion Gateman, S.M.; Stephens, L.I.; Perry, S.C.; Lacasse, R.; Schulz, R.; Mauzeroll, J. Nature Materials Degradation 2018, 2, 1-8. Nature Materials Degradation 2019, 3, 25.
- 46. Laboratory for Electrochemical Reactive Imaging of Biological Systems 1. Stainless Steels have inclusions promoting corrosion Janine Mauzeroll Elemental Composition of SS 444 Fe Cr Mo Si Ni Nb Mn V Cu Ti Supplier’s Claim 79.9 17.07 1.89 0.17 0.24 0.307 0.28 0.1 1 0.063 0.15 Experimental ICP-OES 79.54 17.3 1.93 -- 0.25 -- 0.3 0.1 1 0.08 -- Gateman, S. M., et al., npj Mater. Degrad, 2018, 2, 5.
- 47. Laboratory for Electrochemical Reactive Imaging of Biological Systems Extracting Kinetic Rate Constants Using FEM Janine Mauzeroll 2.85 x 10-2 cm/s 0.2 x 10-2 cm/s Gateman, S. M., et al., npj Mater. Degrad, 2018, 2, 5.
- 48. Laboratory for Electrochemical Reactive Imaging of Biological Systems SS 444 is extremely corrosion resistant according to ASTM standard PDP measurements, but is vulnerable to localized corrosion. Gathered experimental and theoretical evidence of a microgalvanic coupling effect between the Ti/Nb rich inclusions/precipitates and the surrounding metal matrix. 1. Conclusions Janine Mauzeroll 1 cm Gateman, S. M., et al., npj Mater. Degrad, 2018, 2, 5.
- 49. Laboratory for Electrochemical Reactive Imaging of Biological Systems 2. HVOF Thermal Spray Coatings Corrosion? Janine Mauzeroll T= ~2000 K 100 µm 100 µm Struers, 2005, Metallographic preparation of thermal spray coatings
- 50. Laboratory for Electrochemical Reactive Imaging of Biological Systems Tafel Analysis of Coatings: Active Corrosion All tests were performed in 3.5 wt% NaCl at a scan rate of 0.167 mV/s. All coatings are tested as received without the use of grinding/ polishing. Janine Mauzeroll Scan direction Ecorr Anodic Cathodic Anodic Cathodic Gateman, S. M., et al., npj Mater. Degrad, 2018, 2, 5.
- 51. Laboratory for Electrochemical Reactive Imaging of Biological Systems Scanning Electrochemical Microscopy: Feedback Mode Insulating substrate = Topography Conductive Substrate = Topography + Reactivity Insulator Conductor Janine Mauzeroll 61 X
- 52. Laboratory for Electrochemical Reactive Imaging of Biological Systems Minimal Passivation Detected using SECM Janine Mauzeroll Gateman, S. M., et al., npj Mater. Degrad, 2018, 2, 5.
- 53. Laboratory for Electrochemical Reactive Imaging of Biological Systems Micro Polarization of a Single Powder Particle Janine Mauzeroll Gateman, S. M., et al., npj Mater. Degrad, 2018, 2, 5.
- 54. Laboratory for Electrochemical Reactive Imaging of Biological Systems Linked the stainless steel thermal spray coating’s weak corrosion resistance to the precursor powder Identified regions of vulnerability across a single powder particle using scanning electrochemical probe methods Highlighted the power of using macro and micro electrochemical methods to characterize load bearing materials Showcased the importance of powder metallurgy in coating technologies 2. Conclusions Janine Mauzeroll 54
- 55. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll 55 Mineral oil: Insulating Hydrophobic Colorless OI-SMCM 3. Oil-Immersed Scanning Micropipette Contact Method
- 56. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll Mineral Oil Reduces Background Noise 2.2 pA in air 5.2 pA in humidified cell 1.35 pA in mineral oil Background noise (pA) Time Current Threshold Time A low background noise will reduce the risk of breaking micropipette when landing.
- 57. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll 57 OI-SMCM Ecorr Map Reveals Microscale Heterogeneities 20 μm Al 20 μm Fe 20 μm
- 58. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll 58 Predict Galvanic Couples 610 608 5 μm Fe-rich inclusion exhibits cathodic behavior relative to the Al matrix area, which implies the surrounding Al will be consumed as the anode in the galvanic couple with the inclusion.
- 59. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll 59 OI-SMCM Icorr Map Exhibits Microscale Corrosion Kinetics 20 μm
- 60. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll 60 Microgalvanic Corrosion 13 12 30 29 Galvanic couples Oxygen reduction on inclusion surface: cathodic branch (13 and 30). Surrounding Al dissolution: the anodic branch (12 and 29). Ecorr at the meeting points are more anodic relative to that of Al matrix. Therefore, the Al surrounding the Fe-rich inclusions is more susceptible to corrosion.
- 61. Laboratory for Electrochemical Reactive Imaging of Biological Systems 3. Conclusions Janine Mauzeroll 61 Oil-Immersed SMCM: Allows for the use of highly evaporative electrolyte solutions Long-time stability for a large map Expands the application of SMCM
- 62. Laboratory for Electrochemical Reactive Imaging of Biological Systems Acknowledgements 62 Janine Mauzeroll
- 63. Laboratory for Electrochemical Reactive Imaging of Biological Systems Corrosion Cancer Cells Batteries Spectroelectrochemistry Catalysis Biofilms Enzyme Films Polymer Films Janine Mauzeroll Final Thoughts… 63
- 64. Laboratory for Electrochemical Reactive Imaging of Biological Systems THANK YOU TO MY 64 Janine Mauzeroll
- 65. Laboratory for Electrochemical Reactive Imaging of Biological Systems BSc (30) Meng, B; Potts, K.; Robert, A.; Lin M., Sifakis, J.; Gordon, J. Chen, Y. ; Gateman, S. Langlois-T., T; .Sangji, H. Boudreau, C.; Vassileva, I. Wei, X.; Mack, T. Salvatore, D.; Kwan, A. Yong, K.; St-Pierre, C. Poirier, S.; Wezel, N. Meyrignac, P.; Fabre, D. Joliton, A.; Gariepy, V. Bavencove, A.; Benlounes, K. Dansereau, D.; Tieu, J. Noel, J.; Pierre, J. MSc/PhD (18) Dawkins, J.; Li, Y; Pan, Y.; Moussa, S. Odette, W.; Dayeh, M. Danis, A.; Payne, N. Mazurkiewicz, S. Polcari, D; Dauphin D., P. Danis, L.; Kuss, S. Mezour, A.; Mayoral, M. Beaulieu, I; Correia, L Lukova, N. PDF (8) Ghavidel, R. Perry, S. Noyhouzer, T. Kuss, C Snowden, M. Mengesha , U. Thrin, D. Cornut, R. Collaborators (15) S. Canesi (UQAM) B Kraatz (UofT) I. Halalay (GM) E. Ruthazer, (McGill) H. Sleiman, (McGill) M. Geissler (NRC) D. Bélanger (UQÀM) M. Lafleur (UdeM) M. Morin (UQÀM), S. Schougaard (UQÀM) D. Shoesmith, (UWO) G. Botton, (McMaster) R. Lacasse, (HQ) R. Schulz, (HQ) C. Heineman (HEKA)
- 66. Laboratory for Electrochemical Reactive Imaging of Biological Systems To Companies, Funding Agencies & Universities $$ $$ Discovery, CRD Strategic, Create & UFA Nouveau Chercheur & Équipes $$
- 67. Laboratory for Electrochemical Reactive Imaging of Biological Systems Janine Mauzeroll
- 68. Thanks for participating! • Watch the webinar here: The Wonderful World of Scanning Electrochemical Microscopy • Want to learn more about the technology? Visit: www.elproscan.com
Notes de l'éditeur
- In the SECM experiment, the tip and sample (substrate) are immersed in a solution containing electrolyte, and an electroactive species (e.g. substance O at concentration CO* and with diffusion coefficient DO). The cell also contains auxiliary and reference electrodes.
- Steady state Conductor/insulator and implications for negative/positive feedback Fixed tip-substrate distance Local substrate reactivity Not ideal but blurred
- Multiple probes, one device. Reduced time and error. Tandem techniques: SECM-AFM, SECM-SICM. Broad variety of probe geometries.
- Do expression and activity correlate?
- Patterning facilitates microelectrode positioning and reduces experiment time Allows for reproducible measurements
- Fc induces an increase in GSH
- Blebbing and apoptosis
- Due to the inclusion’s square geometry, a 3D model was created and implemented to extract more precise values for local rate constants over the conductive inclusions and the passive film. Comparing to pure negative feedback, the values reported over the passive film show difficulty the passive film has to regenerate the redox medaitor. When approaching an inclusion however, the PAC is very similar to the current obtained over a pure conductive substrate. This experiment tells us that our passive film is discontinuous over the inclusions and is therefore not protecting this vulnerable sites. Important to extract local rate constants to compare values of that and the thermal spray coatings in later studies to come.
- thermal spraying is a process in which molten, semi-molten or solid particles are deposited on a substrate. Consequently, the spraying technique is a way of generating a ‘stream’ of such particles. Coatings can be generated if the particles can plastically deform at impact with the substrate, which may only happen if they are molten or solid and sufficiently rapid. Their heating and/or acceleration are practical if they occur in a stream of gas.1 Thus, an academic classification of spray techniques is based on the way of generation of such streams. Left SE-SEM image: shows gradient of porosity within the coatings right BSE-SEM image: shows the hetergeneity of the coatings with dark oxide strings and lighter metallic particles. Cooling is very fast in comparison to typical cooling rates In High Velocity Oxy-Fuel Combustion spraying (HVOF) fuel gas and oxygen are fed into a chamber in which combustion produces a supersonic flame, which is forced down a nozzle increasing its veloc- ity. Powder of coating material is fed into this stream and the extreme velocity of the particles when hitting the substrate creates a very dense, strong coating (Fig. 5). LEAD Question: The very high kinetic energy of the particles when striking the substrate ensures an adequate mechanical bond even without the particles being fully molten. Hardness vs. bulk substrate Hardness increases due to oxidization of the metal Good wear applications Low porosity Minimal alteration of mechanical properties of substrate
- **label cathodic and anodic branches** When comparing the Tafel plots of the bulk vs. a coating, however, the coatings are much more active with a more negative Ecorr (~-470 mV vs. SCE) and show very different kinetic limitations in their cathodic/anodic branches. The coatings seem to actively corrode, indicating the degradation mechanism of uniform corrosion. We can recall that mechanical failure of components due to localized corrosion is catastrophic because the failure is usually rapid and unexpected. Uniform corrosion, in which the surface gradually degrades, is preferred because it is simpler to detect, predict, and often, to control. We are interested as to why thermal spray coatings undergo a different degradation mechanism in comparison to the bulk material used to make the coatings. Undergo a significant change in thermal oxidization and forming Fe/Cr oxides along the surface, but also the material is in powder form. Is this due to the HVOF thermal spray process or from powder fabrication processes?
- 3 electrode setup: with working electrode’s position controlled using 3D piezoelectric motors. When approach the surface of the substrate, and in the presence of a redox mediator, information about local reactivity can be found. Insulator: cannot regenerate the mediator, only information about topography Conductor: regenerates the mediator, creates feedback loop. Topography and reactivity
- The potential was scanned from -2 V to 0 V or until droplet instability (loss of surface tension) was observed via a loss of electrical connection at a scan rate of 100 mV/s. The micropipette was then retracted from the substrate’s surface by 10 μm, leaving the droplet of electrolyte residue from the previous measurement behind. A fresh micro droplet at the end of the tip is then exposed and moved to the next designated area where it is approached towards the surface at a rate of 1 μm/s until a spike in the WE’s current was measured. The micro electrochemical behavior of the pure Mg and Al were first tested using SMCM. A minimum of five PDP measurements were collected at different points on each metal far away (>100 μm) from the intermetallic regions. Solvent is ethylene glycol
- The Mg-Al diffusion couple’s chemical composition was investigated using EPMA Back-Scattered Electron (BSE) image and WDS line scanning measurements (Figure 3). The interface between the two metals was imaged, where the darker part is lighter metal, Mg (right) and the brighter is heavier metal, Al (left). Rather than a smooth transition between Mg and Al, WDS line scans across the Mg-Al interface expose distinct intermetallic layers. The diffusion depth of Al in the bulk Mg is only about 50 μm. The concentration of Al increases linearly from 0 to about 10 wt.%, which is the solubility limit of Al in Mg at 673 K.39 Two intermetallic phases, Mg17Al12 and Mg2Al3, are observed in 87 and 286 m thickness, respectively. As expected from the phase diagram, Al concentration in Mg17Al12 layer is progressively increasing with distance, while Al concentration in Mg2Al3 layer is nearly constant. Mg is diffused to bulk Al up to about 100 m depth.
- Although all experiments were performed with caution to prevent noise, fluctuations in the pico range current were still present due to instrumental noise. All data was smoothed using a 100-point moving boxcar average (Figure 4A). All experiments were performed within the time limit of 40 min, i.e., the amount of time Ag/AgCl QRCEs have been reported to be stable for in 0.1 M LiCl electrolyte.42
- Add the picture of david to the acknowldgemens as well as sam perry
- In fact, this award is really a reflection of my team’s hard work. I want to thank them all.
- I am lucky to work with such creative, dynamic and politically incorrect people. We work hard, we have a lot of fun together and I could not ask for a better team. I also acknowledge my precious collaborators and their students. We learn so much from their expertise. So we thanks them for this continued scientific education.
- I want to acknowledge the companies, Funding Agencies and Universities that have provided the generous financial support to our team. Without their sustained support, none of the infrastructure, operation funds, student and postdoctoral fellowships would be possible. Without their sustained support none of our work would come to fuition.
- But before I delve into the science, I would like to start off with a few acknowledgments.