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The Impact of Temperature on Surface Activity and Stability of Surface Modified Nano Particles

Masoudi, Ghasem | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50904 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Mohammadi, Ali Asghar
  7. Abstract:
  8. Surface modification is an important property of nano particles. In this project surface of silica nano particles modified with hydrophobic and hydrophilic groups to imrprove surface activity of nano particles. Purpose of this project is to study surface activity of surface modified silica nano particles in different temperatures from 20 to 70 degree centigrade. Also effect of salt and time on the surface activity is studied. At first nano particles modified just with haydrophobic groups and then just with hydrophilic groups (hydrophobic and hydrophilic nano particles) and after that, the surface modification done with both hyadrophilic and hydrophobic groups (amphiphilic nanoparticles). After surface modification surface tension and interfacial tension measured in different conditions to study surface activity. Hydrophobic groups are propyl tri methoxy silane, hexyl tri chloro silane and octyl tri methoxy silane. Hydrophilic group is poly ethylene glycol methyl ether and connected to the surface of silica with a silane agent. Hydrophilic and hydrophobic nano particles have less effect on the surface activity in compare with amphiphilic nano particles. By increasing temperature because of weakening the inter molecular forces, surface and interfacial tension decreases. In pure liquids usually this decreasing in surface and interfacial tension is linear with increasing temperature but in presence of surface modified nano particles by increasing temperature at first because of hydrogen bonding breakage surface and interfacial tension decreases with high slope but gradually with breakage of all hydrogen bonds the slope decreases but in temperature above 50 degree centigrade Si-O-Si bond start to break and produce the OH hydrophilic group that cuases increasing in surface and interfacial tension. Presence of salt besides of surface modified nano particles cuase in decreasing of surface and interfacial tension
  9. Keywords:
  10. Amphiphilic Nanoparticle ; Hydrophobicity ; Temperature Effect ; Hydrofilicity ; Surface Modification ; Surface Functionality

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