NetNotes
I’m in an unusual environment: a makerspace or hackerspace in Chicago, which to my knowledge has the most public access policy of any SEM. Any adult can join for $40/month, which gets them 24/7 access to the SEM, as well as access to the rest of the tools in the space. I can’t assume any science background with people who want to use it. I’ve put together a 3-hour PowerPoint course, which is a prerequisite. Then I schedule about 1 1/2 hours of hands on training. Then they are free to use the scope without supervision. Generally, there is some level of self-selection because there is a time commitment to go through this. Still, I find that many people don’t come back and use it. This is true of many of the tools at the space. People see a scarcity of training classes on, say, the milling machine or our large CNC router, and they sign up just in case, even if they don’t have a project that could use it. We haven’t found a good way around this problem, and with nearly 400 members, and all tool authorizations done by volunteers, it is a source of stress for the organization. I have put in place a tiered access structure for the SEM, and right now have only implemented the bottom tier. This training doesn’t permit users to change samples, use the sputter coater, critical point dryer, backscatter detector, or EDX. Users need to work with me to prep samples, so I can make sure nobody is going to put something wet or that will outgas in the chamber. Many of the users just want to see how a SEM works, so I keep interesting samples in the chamber at all times. So far, the only user breakage problem I’ve had was someone who couldn’t differentiate between first and second peak, and kept raising filament current until it blew. Not that big a deal. That’s also why I’ve been nervous about letting anyone do sample prep, risk running the sample into the BSD, or have a liquid nitrogen accident with the EDX. Also, our sputter coater is very finicky, and the Ar pressure difference between the plasma extinguishing and the power supply overloading is quite difficult to maintain with the needle valve. Additionally I may have been too hasty buying a CPD; we don’t have a fume hood, so I’m not comfortable fixing wet samples in glutaraldehyde, and we’ve done absolutely nothing with wet samples. (I also don’t have formal training myself, and I’ve been hoping to find a mentor in the Chicago area to help out.) Cheers, Ryan I’m in an unusual environment: a makerspace or hackerspace in Chicago, which to my knowledge has the most public access policy of any SEM. Any adult can join for $40/month which gets them 24×7 access to the SEM, as well as access to the rest of the tools in the space. I can’t assume any science background with people who want to use it. I’ve put together a 3-hour PowerPoint course, which is a prerequisite. Then I schedule about 1 1/2 hours of hands on training. Then they are free to use the scope without supervision. Generally, there is some level of self-selection because there is a time commitment to go through this. Still, I find that many people don’t come back and use it. This is true of many of the tools at the space. People see a scarcity of training classes on, say, the milling machine or our large CNC router, and they sign up just in case, even if they don’t have a project that could use it. We haven’t found a good way around this problem, and with nearly 400 members, and all tool authorizations done by volunteers, it is a source of stress for the organization. I have put in place a tiered access structure for the SEM, and right now have only implemented the bottom tier. This training doesn’t permit users to change samples, use the sputter coater, critical point dryer, backscatter detector, or EDX. Users need to work with me to prep samples, so I can make sure nobody is going to put something wet or that will outgas in the chamber. Many of the users just want to see how a SEM works, so I keep interesting samples in the chamber at all
2015 July •
www.microscopy-today.com
times. So far, the only user breakage problem I’ve had was someone who couldn’t differentiate between first and second peak, and kept raising filament current until it blew. Not that big a deal. That’s also why I’ve been nervous about letting anyone do sample prep, risk running the sample into the BSD, or have a liquid nitrogen accident with the EDX. Also, our sputter coater is very finicky, and the Ar pressure difference between the plasma extinguishing and the power supply overloading is quite difficult to maintain with the needle valve. Additionally I may have been too hasty buying a CPD; we don’t have a fume hood, so I’m not comfortable fixing wet samples in glutaraldehyde, and we’ve done absolutely nothing with wet samples. I also don’t have formal training myself, and I’ve been hoping to find a mentor in the Chicago area to help out. Ryan Pierce
rdpierce@pobox.com Sun Apr 12
SEM: observing ice
We are trying to observe ice in the SEM. T e purpose is visualizing the transition of high-density ice (ice II or III) to low-density ice, either ice Ic or Ih using EBSD. T e cryo stage in the present setup does not get lower than − 140 ° C and this is only just below the recrystallization temperature. To prevent charging, gas is admitted into the microscope. T is, however, has a tremendous eff ect on the stage temperature which can easily goes up to − 110°C, way above the recrystallization temper- ature. As a result we have so far of course not been able to identify the high-pressure ice polymorphs. T e best remedy would very probably be to improve the cold stage so we can reach lower temperatures, and for the future this may well be what will be done. For the time being I am looking for alternatives to admitting gas to prevent charging. Two ideas popped up: freezing salt water or freezing a conductive nanoparticle solution, e.g. gold or silver or as was suggested by Guenter Resch carbon rods. T e rationale being that in the eutectica between the pure ice crystals a high concentration of ions or nanoparticles forms a network of conductive material that might or might not assist in reducing charge build up. Does anyone of you have experience in this area or have alternative ideas? Jan Leunissen
leunissen@aurion.nl Mon Mar 16 In my past life I ran a FE-SEM with cryostage, and charging of ice was of little issue at 1-2 kV. Most frequently, 1 or 1.5 kV. What sort of instrument are you using? Can you get a low enough kV to reach charge balance? And adding nanoparticles, salt water, etc. I’d wonder about that. Yes, the crystallization process does exclude ions and such to produce the ice crystals (sea ice is really interesting because of this), but I doubt that process is 100% complete. I suspect it would be less complete with nanoparticles than it is with ions. Which means adding salts or nanoparticles will affect the properties you’re trying to study. Plus, the added salts/nanoparticles are going to add electrical effects to your samples, even if they are excluded from the crystals. What do these do? Phil Oshel oshel1pe@cmich. edu Tue Mar 17
I have no experience in SEM of ice, but from other posts to this list, I would try low-voltage SEM to balance electrons staying in the specimen with secondary electrons leaving the specimen. An additional comment is that trying to freeze salt water is likely to result in crystals of ice surrounded by molecules of salt, since most salts do not dissolve in ice. One exception, which I have also considered in order to increase the conductivity of ice, is NH 4 F, since both NH 3 and HF can incorporate into the ice structure--the reference for this is a book called Physics of Ice, the name of the author of which I do not remember. Bill Tivol wtivol@sbcglobal. net Tue Mar 17
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