الهه صفایی

Research subject:

 Global warming is the most important worldwide problem. CO2 is one of the greenhouse gasses and its emission to the atmosphere causes global warming to increase. Porous adsorbents are great candidates for CO2 adsorption and graphene aerogels are porous nanostructures with very low density and hierarchical porosity which is suitable for CO2 adsorption. The source of pristine graphite for graphene oxide synthesis as a precursor plays a vital role in graphene aerogel nanostructure.  

Research approach:

 In the current study, graphene oxide by modified Hummers method was synthesized with three different graphite sources. Graphene aerogels were prepared with synthesized graphene oxides via hydrothermal and freeze-drying methods to investigate their effect on graphene aerogel nanostructure. Finally, the CO2 adsorption of graphene aerogels was evaluated. The samples were characterized by FTIR, XRD, SEM, and BET analysis.

 The results indicated that the source of graphite has a significant role in the process of oxidation of graphene oxide by the modified Hummers method. XRD results of graphene oxides showed successful oxidation of graphite. The normalizing FTIR peaks of graphene oxides showed different intensities of oxygenated functional group peaks. FE-SEM results of graphene aerogels showed that less oxidation of graphite powder caused agglomeration of graphite plates and thick walls were formed. The macropore size in the structure of obtained aerogels (GAB and GAE) was 2.28 and 3.84 µm respectively which affected the CO2 adsorption. Larger pores led to easier mass transfer of CO2 molecules and higher CO2 adsorption was achieved. Moreover, the high meso and micro surface area (111 and 115 m2/g respectively) in GAE increased CO2 adsorption up to 1.04 mmol/g compared to GAB (0.724 mmol/g).

This investigation, examine the association among accounting components based-on accrual approach & accounting components based-on operating cash flows approach with components of behavior of common shares return for the listed firms in Tehran Stock Exchanges. However since that the goals of present investigation is determining the relation between two or more phenomena, so it to be defines as correlation researches. . Sampling method is filtering or systematic removing. Volume of sample is equal to (100) firms during the six years, and so analyzed data of (600) firms-fiscal years in form of cross-section method. Statistical feedback from testing of hypotheses are done by correspondent canonical correlation analysis. . Statistical feedback of testing principle hypotheses, confirms that in ninety five percentage intervals confidence, there are significant & positive-imperfect association between synthetic linearity combinations of behavior of stock return with informative content of components based-on accrual approach, synthetic linear combinations of accounting components based-on operating cash-flows approach & synthetic linear combination of accounting consolidated components based-on accrual-operating cash flows approach. In addition to, informative content of synthetic linear combination of components based-on operating cash-flows approach, are higher than synthetic linear combination of accounting components based-on accrual approaches.