If I want to assess the structure of cement concrete, I will have to dehydrate the samples, which indicates that I am going to visualize the structure without the important hydration products such as CSH (calcium silicate hydrate) and CH (calcium hydroxide). Don't you think it does not portray a good message in the field of concrete or cement. (Nevertheless, if you search about SEM of cement- or concrete-based samples, you will come across a myriad of papers incorporating SEM testing of these products.)
It was an amazing explanation. Respected professor, how should be the sample preparation process if my sample needs to be maintained in an Ar-filled atmosphere?
I have the same issue with the explanation of the electron microscope tha I have with all explanations of electron tubes; the notion that thee is some sore of electron "beam" (consisting of electrons flowing through the device and at a fairly high percentage of the speed of light). People often ask how fast electrons flow through wires and the answer is said to be very slowly. A few hundredths of an inch per second per ampere. Although I don't think that's the actual flow of electrons but, there's a big discrepancy between hundredths of an inch per second and perhaps 150,000 miles per second as they leave a wire in a circuit and travel through a vacuum of a device and then back to plodding along again...when it's claimed (in all the electrical formulas) that the current (electron flow) is the same in all parts of a series circuit (as learned by anyone who has ever taken a class in basic electricity). How is that discrepancy explained away? I have yet to find anyone who has even tried. Yet we know, from direct observation of the circuit actions, that when a cathode is heated, that activity can be transferred to a fluorescent screen to light it up. What's the deal with that? The only answer that makes sense is that the fluorescent screen is receiving an image of the thermal activity of the cathode through some medium within the device (such as a TV CRT (Yeah, I know. Old school) or an electron microscope. A medium so mysterious and ethereal that the geniuses of science, in the 21st century still refer to it in the dictionary as a "hypothetical substance", ie" the ether. In a CRT the electrons stop at the cathode and are started up again at the anode and back through the circuit at electron-through-wires speeds. In an electron microscope the electrons stop at the cathode and pass through an accelerating electrode (called the "anode" in the schematic drawings of the electron microscope) and through other focusing and perhaps scanning electrodes but, not as electrons but, rather distortions of the ether field (which focuses the image of the cathode activity) onto the specimen. Since no electrons are striking the specimen, the image of the specimen seen also must come from the distortion of the ether field that activates the detectors (as the image of the cathode of a CRT activates the phosphors on the screen of a picture tube). In short, by thinking of the electron microscope as working by electrons striking the specimen, the engineers have fallen into the same trap that they learned (by rote and memorization) in electricity and electronics classes. Does getting the concept completely bass-ackwards prevent them from building practical devices? Obviously not but, it doesn't speak well of them when they don't care enough to try to actually undersand their chosen field of study and work. salaphyaics.com 1222922
intersting video . thanks for uploading. nice to see these . From India. YOur videos reach far away places and to people who have no other easy way of seeing all these. thanks again. One flatearther person told that there are no viruses. So, I started looking at how viruses are seen in sem. i wanted to know the principles. Hoping to find a virus sampling done !
Hi Duke University - SMIF, I have question about SEM, 1/ Could SEM see nano materials, clearly or blur ? (I mean it's a normal SEM, not FE-SEM or high resolution SEM). 2/ If my material reach nano scale, could I use SEM to prove this material reach nano size? 3/ Which is the best method, cheap and convenience for characterizing (shape and size) nano materials? I hope I would receive your answer soon. Thanks Duke University - SMIF so much.
Yes, you should be able to do this. We prepare this by sprinkling a fine layer of the powder onto carbon tape on an SEM stub and then sputter coat it with gold.
Thanks for the very nice lecture. I have 2 questions. 1. If I have two SEM images taken at different resolutions and scale, how co I compare the two on a uniform scale to be able to say one particle is smaller (or bigger) than the other? 2. In the legend of an SEM micrograph taken with a desktop scanning electron-microscopes phenom-pro, there is an measurement icon that looks like an eye. Is it representing some height or what?
I am not sure about your specific SEM. In general, a given SEM will have to be calibrated at each magnification. Typically, the SEM will produce a scale bar at the bottom of the image. Note: the scale bar is only as good as the calibration and can drift with time. So, recalibration may be necessary. For the best results, it is preferred to image a known standard simultaneously to ensure the most accurate dimensional measurements.
Wow!! The high mode really shows the square salt molecules we see in 3-D online generated images. Super clear image I’m impressed. Excepted blurrier images! I like the explanation of details. Easy to follow!
