ACMAL spring break schedule

I will be out next week but I’ll mostly be in town. I could come in if needed. Aleister will be here working working 2 hours each day for coating samples and helping users. He plans to be here at midday.

The labs will be open all week between 8 – 5 and restricted users will work then. Unrestricted users have 24 hour access. Newly trained users, please work while Aleister is at work in case you have trouble.

Call Aleister or me if you have trouble. Aleister 520-576-3557. Owen 906-369-1875.

Thanks, Owen


IMPORTANT Saturating ESEM filament

We have made changes to the process of saturating the ESEM filament.  Now we use Scan>Horizontal Line and monitor that line as the Filament slider is changed.  Saturation occurs when the horizontal line stops increasing when the slide is increased.  The point when it stops increasing is saturation, so you may overshoot and have to slide it back slightly.  When you complete saturation return to Scan>Full Screen to stop the line.  Click Filament Limit as you usually would.  Any of you who learned to saturate the filament on the 6400 SEM will recognize this technique.

I want to show you how to do this so let me know when you’d want to see it done.  It is really easy and there is no ambiguity when setting saturation like using the “football”.  We will be making changes to the standard operating procedure.

This a a precise technique and the filament will last longer.


ESEM back online now

The ESEM is back online and ready to use.

I’m not certain what went wrong but I’m suspicious of the AZtec scan grabber. The AZtec software acquires an ESEM image by taking control of the ESEM scan hardware. When the scan is complete it should release the ESEM hardware. I have seen a few times that it doesn’t release. If you have trouble seeing a scanning ESEM image after acquiring with AZtec try to shut down the AZtec software and see if the scan returns. If it still down’t return contact me and I’ll take a look at it.


Spontaneous Selective Deposition of Iron Oxide Nanoparticles on Graphite as Model Catalysts

Chathura de Alwis (Chemistry), Timothy R. Leftwich (MSE), Pinaki Mukherjee (MSE), Alex Denofrea (Chemistry) and Kathryn A. Perrine (Chemistry) published a paper titled “Spontaneous selective deposition of iron oxide nanoparticles on graphite as model catalysts” in Nanoscale Advances in 2019.

DOI: 10.1039/c9na00472f

Extract

Iron oxide nanomaterials participate in redox processes that give them ideal properties for their use as earth-abundant catalysts. Fabricating nanocatalysts for such applications requires detailed knowledge of the deposition and growth. We report the spontaneous deposition of iron oxide nanoparticles on HOPG in defect areas and on step edges from a metal precursor solution.

Various defects were created on the highly oriented pyrolytic graphite (HOPG) surface using either argon (Ar+) sputtering or a focused ion beam (FIB) to provide defects for nucleation sites. A Hitachi 2000 A FIB instrument was used to create tailored arrays of defects on HOPG using a Ga+ beam.

The sputter rate was calculated using the amount of materials removed, by recording a height profile of 1 nm using atomic force microscopy (AFM) and the time to sputter the pattern.

All the samples were imaged using a Hitachi S-4700 cold field emission high resolution field emission scanning electron microscopy (FE-SEM) instrument.

X-ray photoelectron spectroscopy (XPS) was performed using a PHI 5800 to analyze the elemental composition and oxidation state of surface species of the iron oxide nanoparticles grown on the HOPG surface.

Scanning transmission electron microscopy (STEM) imaging and energy dispersive X-ray spectroscopy (EDS) mapping were used to measure the phase and composition of iron oxide nanoparticles after annealing and to confirm if the deposition was preferential at the defect sites of graphite. A FEI Titan Themis aberration corrected scanning transmission electron microscope was used to obtain atomically resolved electron images and EDS maps of the iron oxide nanoparticles on the graphene coated TEM grid. The microscope was operated at 200 kV using a point resolution of the aberration corrected STEM mode of 0.08 nm. The microscope was equipped with a SuperX™ X-ray detector, which is composed of 4 detectors for fast X-ray mapping in STEM mode. The EDS mapping of the sample was performed on specific particles with an average beam current of 100 pA.

Acknowledgements

Equipment for obtaining the AFM images in this project was provided by NSF CHE #1725818. The electron microscopy research was performed at the Applied Chemical and Morphological Analysis Laboratory, at Michigan Technological University. The electron microscopy facility is supported by NSF MRI 1429232. We acknowledge the Michigan Tech REF-RS fund for support of this work and the David J. and Valeria Pruett Graduate Research Fellowship. We acknowledge the Applied Chemical and Morphological Analysis Laboratory (ACMAL) for staff assistance and use of facilities.

Recommended Citation

de Alwis, C., Leftwich, T., Mukherjee, P., Denofre, A., & Perrine, K. (2019). Spontaneous selective deposition of iron oxide nanoparticles on graphite as model catalysts. Nanoscale Advances, 1(12), 4729-4744.

http://doi.org/10.1039/C9NA00472F

Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/1246


Liz Miller’s schedule

Liz Miller will be out of town for 6 weeks beginning next week. Aleister and I will try to pick up the work she was doing during her absence. One area that he and I cannot assume is EBSD. We have asked someone to help us with that but the response will be slowed. So, plan your EBSD work ahead of time – don’t wait until the last minute or your work will be delayed.

Liz will return to work on April 6th.


ESEM EDS detector alarm

EDS detectors works like a thermos bottle that slow liquid nitrogen evaporation. When the vacuum in the detector deteriorates the liquid nitrogen that cools the detector evaporates quicker. That is happening in the ESEM detector. We refill the detector twice each week but depending on the timing you might hear an alarm signaling that the liquid nitrogen is low. The alarm is a beep signal every few seconds. Here is the important part of this message – if you hear the alarm let me, Aleister or Liz know so we can refill it.

I will have the vacuum replenished in the summer when ESEM use drops.

Thanks, Owen


Analytical Electron Microscopy at Nanoscale Feb. 13

Pinaki Mukherjee
Pinaki Mukherjee

ME-EM Graduate Seminar Speaker Series

proudly presents:

Pinaki Mukherjee, PhD

Michigan Technological University

Abstract: This talk presents an overview of state-of-the-art capabilities of the aberration-corrected scanning transmission electron microscope (ac-STEM) at ACMAL, Michigan Tech. The FEI Titan Themis microscope we have here is one of a kind in the whole nation in terms of capabilities. These capabilities have been developed in last two years and most of them are already available for users. We have a wide range of imaging and spectroscopic techniques that enables a user to identify elements at atomic scale (~ 0.1 nm). READ MORE

Thursday, February 13 at 4:00 p.m.

Electrical Energy Resources Center (EERC), 103
1400 Townsend Drive, Houghton, MI 49931