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Science of Colloidal Processing
Published in M. N. Rahaman, Ceramic Processing and Sintering, 2017
Using the convention that repulsive potentials are positive and attractive potentials are negative, Fig. 4.15 shows an example of VA for the van der Waals attraction and VR for the double layer repulsion. The resultant curve for VT shows a deep minimum at M1 corresponding approximately to contact between the particles, a secondary minimum at M2, and a maximum between M1 and M2. For two particles initially far apart approaching one another to a separation M2, if the thermal energy (kT) of the particles is small compared to the depth of M2, the particles will not be able to escape from one another. Flocculation will result, leading to a sediment of loosely packed particles. Restabilization of the colloid can be achieved by heating (increasing kT), by changing the electrolyte concentration to increase the double layer repulsion, or a combination of the two. This process of restabilizing a flocculated suspension is referred to as peptization.
Science of Colloidal Processing
Published in Mohamed N. Rahaman, Ceramic Processing, 2017
Using the convention that repulsive potentials are positive and attractive potentials are negative, we have shown in Figure 4.15 an example of VA for the van der Waals attraction and VR for the double layer repulsion. The resultant curve for VT shows a deep minimum at M1 corresponding approximately to contact between the particles, a secondary minimum at M2, and a maximum between M1 and M2. For two particles initially far apart approaching one another to a separation M2, if the thermal energy (kT) of the particles is small compared to the depth of M2, the particles will not be able to escape from one another. Flocculation will result, leading to a sediment of loosely packed particles. Restabilization of the colloid can be achieved by heating (increasing kT), by changing the electrolyte concentration to increase the double layer repulsion, or a combination of the two. This process of restabilizing a flocculated suspension is referred to as peptization.
Science of Colloidal Processing
Published in Mohamed N. Rahaman, Ceramic Processing, 2017
Using the convention that repulsive potentials are positive and attractive potentials are negative, Figure 6.15 shows an example of VA for the van der Waals attraction and VR for the double layer repulsion. For this example, the resultant curve for VT shows a deep minimum at M1 corresponding approximately to contact between the particles, a secondary minimum at M2, and a maximum between M1 and M2. The stability of a suspension can be discussed in terms of the height of the maximum and the depth of the minima. For two particles initially far apart approaching one another to a separation M2, if their thermal energy (kT) is small compared with the depth of M2, the particles will not be able to escape from one another. Flocculation will result, leading to a sediment of loosely packed particles. Restabilization of the colloid can be achieved by heating (increasing kT), changing the electrolyte concentration to increase the double layer repulsion, or a combination of the two. This process of restabilizing a flocculated suspension is referred to as peptization.
Effect of ultra-sonication and peptization on the aqueous phase stability of iron oxide nanoparticles
Published in Inorganic and Nano-Metal Chemistry, 2020
Amarjeet Bisla, N. Srivastava, Rupali Rautela, Vinay Yadav, Praveen Singh, Abhishek Kumar, S. K. Ghosh, Srikant Ghosh, Rahul Katiyar
Peptization denotes the coating of various acids over the surface of IONPs. Several investigators have attempted covering the surface of IONPs with various acids to prevent their agglomeration and maintain uniform dispersal in the aqueous phase.[20–22] The long term colloidal stability of the IONPs is dependent on the electrostatic and steric repulsion mainly affected by pH.[23–25] The stability of a colloidal system is defined by particles remaining suspended in an equilibrium helped by prevention of agglomeration by Brownian movements. Peptization overcomes this agglomeration by disintegrating agglomerated particles by lowering the surface tension.[22] In the said process, the unbound acidic group of carboxylate dissociates and provides negative charge on the surface of peptized IONPs leading to electrostatic repulsion.[26,27] Moreover, exposition of carboxyl group over the peptized IONPs can be targeted for further functionalization and bio-conjugation for various biomedical applications involving cancer diagnosis, gamete imaging and sperm sorting.[22]