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Synthesis of Superabsorbents Based on Agar and Modified Agar and Investigation of their Applications in Controlled Release of Potassium Nitrate as a Sample of Ionic Fertilizers
, M.Sc. Thesis Sharif University of Technology ; Pourjavadi, Ali (Supervisor)
Abstract
This thesis focouses on the preparation and super-swelling behavior of two superabsorbent hydrogel. In the first section, a new superabsorbent hydrogel based on agar was prepared and the effect of the ratio of some components(AA, AAM, MBA, APS and agar) on the swelling capasity of the hydrogel was studied. Maximum water absorbency of the optimized final product was found to be 614.5 g/g in distilled water. The structure of the hydrogel was characterized by FT-IR method and morphology of the samples was examined by scanning electron microscopy(SEM). Swelling behavior properties of optimized hydrogel sample in different swelling medium were investigated. In the second section, we report the...
Preparation of acrylated agarose-based hydrogels and investigation of their application as fertilizing systems
, Article Journal of Applied Polymer Science ; Volume 122, Issue 4 , November , 2011 , Pages 2424-2432 ; 00218995 (ISSN) ; Sadat Afjeh, S ; Seidi, F ; Salimi, H ; Sharif University of Technology
2011
Abstract
In this study, we attempt to synthesize novel acrylated agarose (ACAG)-based hydrogels with three different crosslinking densities. Acrylate groups were inserted onto agarose (AG) backbone through homogeneous reaction of acrylic monomers with AG backbone. Hydrogels were synthesized through radical copolymerization of a mixture of acrylic acid and 2-hydroxyethyl acrylate with ACAG in aqueous solution using ammonium persulfate as an initiator. Infrared spectroscopy (FTIR) was carried out to confirm the chemical structure of the hydrogel. Moreover, morphology of the samples was assessed by scanning electron microscopy. The equilibrium swelling capacities of synthesized hydrogels were evaluated...
Synthesis of soluble N-functionalized polysaccharide derivatives using phenyl carbonate precursor and their application as catalysts
, Article Starch/Staerke ; Volume 63, Issue 12 , 2011 , Pages 780-791 ; 00389056 (ISSN) ; Seidi, F ; Afjeh, S. S ; Nikoseresht, N ; Salimi, H ; Nemati, N ; Sharif University of Technology
2011
Abstract
Soluble N-functionalized basic and cationic polysaccharides have been synthesized using polysaccharide phenyl carbonate as a precursor. The products and intermediates were thoroughly characterized by conventional methods. The quaternization of amino intermediates in various conditions was studied. Moreover, the potential of basic polymers as green and selective catalysts in Knoevenagel reaction was investigated. In all cases, only one isomer was obtained
Study and Controlling Microstructure of Rapidly Solidified Multiprinciple Fe, Co and Ni Alloy
, M.Sc. Thesis Sharif University of Technology ; Tavakoli, Rouhollah (Supervisor) ; Aashuri, Hossein (Supervisor)
Abstract
Multi-principle alloys exhibit microstructure and different properties from most conventional alloys due to their high entropy, very slow diffusion and distorted crystal structure properties. Heat treatment, thermomechanical treatment, addition of alloying elements and control of solidification process are common methods of microstructure modification and property improvement. Among the solidification parameters, undercooling and cooling rate is one of the most suitable methods to obtain semi-stable and fine-grained phases. These parameters have been less studied in multi-principle alloys, while in the case of ferrous and cobalt alloys has been much studied. The main purpose of this type of...
Effect of two steps annealing on the microstructure and dynamic strain aging behavior of Al-6Mg alloy
, Article Materials Science and Engineering A ; Volume 798 , 2020 ; Khani Moghanaki, S ; Kazeminezhad, M ; Goodarzi, M ; Ghiasi Afjeh, S. M. B ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The microstructure of cold rolled Al–6Mg alloy is investigated after two steps annealing at different coupled temperatures of 250–320 °C and 320–400 °C for various times. Dynamic strain aging behavior in terms of serrated flow and strain rate sensitivity is investigated. The effect of three microstructural features, cell structure, recovered and recrystallized microstructures, on the strain rate sensitivity is elucidated. Two steps annealing process is utilized to capture the effect of recovery and precipitation phenomena on recrystallization and dynamic strain aging behaviors. The results show that the negative strain rate sensitivity of cold rolled specimen increases to positive values in...