Can I say particles and grains are same thing? If yes, would it be correct to say during sintering that two grains are going to be bonded?
Basically, particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. A grain is a domain of a solid state matter that has the same structure as a single crystal, so a grain can also be termed as crystallite. Most of the materials are polycrystalline in nature and they are thus made of many crystallites. Thence we can conclude that particles are composed of a lot of crystallites or grains.
Sintering forms solid bonds between particles when they are heated. In the case of crystalline materials, densification promotes bonding of crystallites. Consequently, in this case, the resulting material consists of grains, grain boundaries and residual porosity. In the case of amorphous materials, no such grain boundaries are present at the sintering bonds.
Fernando Costa Oliveira
Lisboa, 30th November 2015
Particles may be multicrystalline or a single crystal but a grain is a single crystal like we observe within a multicrystalline metal.
It hasn't been explicitely mentioned that particles can be also amorphous (like glass particles). Minerals can be glassy as well so that we are talking therey about particles as well when they are isolates. Otherwise it would be a glassy matrix.
In materials science or engineering, the term particle usually means a (small) self-contained object that stands alone. The word grain usually means a (small) self-contained object that stands inside a bulk substance. You can compress particles and sinter them to make a bulk substance. This removes the "air" spaces between the particles. The resulting bulk substance can then be considered to have grains, which were for the most part the same as the starting particles. How far you carry this analogy depends on whether you are talking with a layman on the street or a well-seasoned materials scientist / engineer.
"Particle" is a very generic term as opposed to a grain or Crystallite. Regardless, it is correct to say that sintering bonds grains.
You cannot take particle as grains for various reasons explained by many people as given above. During sintering bond between neighbour particle takes place, it dosent means it would leads to separate grains atlast. Finally, it would results in formation of grains which would develop from more number of particles.
A particle usually is an aggregate composed of grains or a single grain, while grain usually is used as a single crystal.
Mostly, it is: particle - for powdered substances, grain - for polycrystalline solids (mean grain size is one of the most important characteristics for them). Easy to remember!
As mentioned before, crystallinity is the main difference. In order to talk about grains, the material has to be crystalline, but the term particle can be used in a broader term. Once particles come together and contact points (or rather areas) between them develop, we then frequently characterize these contact areas as grain boundaries. Strictly speaking the existences of the grain boundaries require the "particles' to be crystalline.
No, in materials science, "particles" and "grains" are two different terms that describe different microstructural features, regardless the technique employed (sintering, casting, etc). Some of their differences have been well described above.
It is also wrong to say/write that "...during sintering two grains are going to be bonded...". Although this could, also, potentially occur (i.e. a powder particle could become a single grain in a sintered material), the proper phrase is to say "...during sintering two particles are going to be bonded...".
These are the direct, clear answers to your specific question. After that, yes, we can have a long discussion about how a "particle" or "grain" is defined, with various answers and opinions.
I hope I helped.
Thanks to all. lot of perception about particle and grain is now cleared. Especially Theodoros Koutsoukis thank you sir.
The discussion and explanations are interesting besides some of them are not exactly correct. As a specialist in the material science engineering and professor whose subject is in material science, specially related to nano-powders and sintered materials (ceramics) i would like to mention that PARTICLES are mainly addressed to POWDERS and GRAINS to sintered materials-ceramics
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