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Classical nucleation theory (CNT) is the most common theoretical model used to quantitatively study the kinetics of nucleation. [1] [2] [3] [4]Nucleation is the first step in the spontaneous formation of a new thermodynamic phase or a new structure, starting from a state of metastability.
Nucleation is a common mechanism which generates first-order phase transitions, and it is the start of the process of forming a new thermodynamic phase. In contrast, new phases at continuous phase transitions start to form immediately. Nucleation is often very sensitive to impurities in the system. These impurities may be too small to be seen ...
Heterogeneous nucleation occurs in cases where there are pre-existing nuclei present, such as tiny dust particles suspended in a liquid or gas or reacting with a glass surface containing SiO 2. For the process of Hoffman nucleation and its progression to Lauritzen–Hoffman growth theory, homogeneous nucleation is the main focus.
Initially, nucleation may be random, and growth unhindered, leading to high values for n (3 or 4). Once the nucleation sites are consumed, the formation of new particles will cease. Furthermore, if the distribution of nucleation sites is non-random, then the growth may be restricted to 1 or 2 dimensions.
Recrystallization kinetics are commonly observed to follow the profile shown. There is an initial 'nucleation period' t 0 where the nuclei form, and then begin to grow at a constant rate consuming the deformed matrix. Although the process does not strictly follow classical nucleation theory it is often found that such mathematical descriptions ...
The methods used to determine the degree of crystallinity can be incorporated over time to measure the kinetics of crystallization. The most basic model for polymer crystallization kinetics comes from Hoffman nucleation theory. The crystallization process of polymers does not always obey simple chemical rate equations. Polymers can crystallize ...
For a more diffuse surface, a continuous growth mechanism may require changes over several successive layers simultaneously. Non-uniform lateral growth is a geometrical motion of steps—as opposed to motion of the entire surface normal to itself. Alternatively, uniform normal growth is based on the time sequence of an element of surface.
Under an aggregation-based model, nucleation sites are continually being generated and absorbed where the merging leads to particle growth. [31] The generation of the nucleation sites and the interaction energy between merging particles dictates the overall kinetics of the reaction. [32]