The micro-structure of graphite in SEM is like onion pulp or corn. The main point is how long or how to decide the grain boundaries. The measurement is also very easy. To decide the grain boundaries is difficult task. Any suggestion, I will be very much grateful.
It might happen for highly amorphous and too small particle size sample while for crystalline particles, grain size can be easily identified. In this case, it recommended to perform high resolution SEM or TEM. Good luck!
The following paper can be useful:Article Grain growth from amorphous phase
@ M.A.I. Mraci: I am not sure whether you are talking about the same. First: What is a grain? Usually it is defined as crystalline, cf. Wikipedia for grain growth: Grain growth is the increase in size of grains (crystallites) in a material at high temperature. This occurs when recovery and recrystallisation are complete and further reduction in the internal energy can only be achieved by reducing the total area of grain boundary. The term is commonly used in metallurgy but is also used in reference to ceramics and minerals.
In so far, I am not sure whether the term grain sie in the mentioned paper would better be substituted by particle size. I've never heard about amorphous "grains", also I know that people use it like "slang". I would prefer to define terms in the beginning and don't mix them. My recommendation is to keep the term grain as crystalline volume with defined orientation.
This is the next problem: If you say, grain, you need to define the minimum misorientation which still is accepted to belong to a grain. Another question discuss this and a common definition say, 15°. Well, I am not that strict although I know the reason. Sometimes it makes only sense to define something as new if the properties considerably change. In TEM or SEM you already can see much smaller misorientations.
Regarding the initial question I have to admit that this is exactly my major "problem". The segmentation of your pulps or onion like graphite depends on the size of misorientation angle you want differentiate. Not everything what is visible guides you to the correct solution.
If you could share some pic of this pulp like structure, then perhaps it is easier to answer. I feel that the tilt angle you are using is not correct. also the resolution of your "pulpy samples" needs to be improved. HR-SEM would give better results I suppose, if you can afford it.
Dear Awani,
I agree with Waqas. Please send a picture of your sample for better explanation. Otherwise, please carry TEM experiment.
Thanks.
Thank you sir, (Gert Nolze ) for a depth understanding about grains. Actually I saw the term 'grain size of graphite' in (Nemeth sir paper 2010, in Nuclear Engineering and Design). I am sending the paper. The grain size of graphite is highlighted in the text. Sir (Gert Nolze ) , please clarify my doubt. For this I will be very grateful to you.
with respect and regard
Awani Bhushan
Well, I do not have the time to read the entire paper, but only from the images it looks to me that they simply defined "closed volumes of homogeneous chemistry" as "grains". If so, this is certainly a misleading definition but not very rare. First you always have to check what people denominate with certain terms.
Respected sir
I am adding some images from SEM of graphite in solid form. Your suggestion is very valuable for me.
DEb = Eeff - Ebulk =( h^2/8 effective mass R^2) -(1.8e^2/R permitivity)
Where R is the particle radius.
The optical band gap of the nanocrystalline particles depends on the particle radius due to quantum confinement. The approach to quantitative determination of the size dependence of the band gap energy (Eb) is based on the effective mass approximation (EMA). The increase in optical band gap (DEb) of a nanocrystalline semiconductor may be represented by the above formula
Where Eeff is the band gap of the nanocrystalline material, Ebulk is the band gap of the material in bulk form, m is the electron – hole effective mass and e is the dielectric constant and is equal to depends on the oxide material. The first term in the equation represents the particle –in-box quantum localization energy and had simple 1/ R^2 dependence, where R is the particle radius .
The second term represents the Coulomb energy with 1/R dependence. The radii of the nanocrystals of materials calculated from equation match reasonably well with the previously calculated values .
Many researcher reported that R is the particle radius of the material well matched with the results of SEM observation.
Thank you Ayesha Mariam mam, for great answer
I want more knowledge, can you suggest me some text book on the same topic.
to evaluate you image, using SEM it is possible to see the same grain of graphite in SEM with more lower tention
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