I have been trying to disperse Fe304 nanoparticles in PVA solution by using a bath sonicator for 12-15 hours. After sonication, upon doing TGA analysis (in Nitrogen) to check for the percent of Fe304 nanoparticles present the result is very odd.
I have attached a picture of the TGA analysis, as can be seen the percentage weight goes below 0%, metals need much higher temperatures to degrade so I don’t understand how it is possible for the weight % to become 0 at 800C.
I have repeated the process a number of times, and have also used a probe sonicator for more efficient dispersion but the result is always the same. Any suggestions on what could be the cause would be really helpful.
Thank you.
This is a typical TGA curve of polymer degradation through carbonization. Did you confirm the presence of nanoparticles in the sample taken for TGA analysis? Even the color of the sample become black. I mainly suspect instrumental error. Because, the % wt. reaches 0 at 750 C itself. But, carbon residues are stable or shows slow degradation in inert atmosphere @ this temperature.
If you use high conc. PVA solution, simple ultrasonication will not help you to get better dispersion. Try to combine ultra sonication and string. It is better to avoid magnetic stirring. Use a probe stirrer and bath sonicator.
Appreciate your feedback Dr. Tamilarasan,,
Actually i was doing TGA to confirm the presenc e of NP by studying the weight % after decomposition of PVA. Yes, there was a complete change in color of the PVA solution, it went from clear to dirty brown.
Initially I suspected instrumental error so I did it again but the result was the same, I even tried it using another TGA machine but got similar result,.
I have used diff conc of PVA solution (8-13%), also I have used probe sonicator as well but to no avail...
Dear Dr. Tanvir:
Really, will be impossible that a serie TG analysers can exhibit a same problem with same thermogram. This find suggests that nanoparticles oxide are the key of phenomena.
The Fe3O4 oxide of metal transition cation, in which there are two valences at Fe cations, Fe2O3.FeO. For this material, can be expected a complex distribution of cation in the crystalline structure, surface activity and a possible development of several magnetic behaviour (ferro, para, super...) depending on the particle size and synthesis method.
During the thermal decomposition it is possible that nanoparticles be segregate from PVA mixture, at low temperature domain.
As a function of the temperature increasing, the pyrolisis of polymer start up. A priori, if a classical thermal decomposition is highlighted, H2O, CO and CO2 will be synthesized.
See, now the delopment of a local atmosphere should be further considered. This atmosphere is not correlationed with atmosphere of the furnace of the analyser. Now, as a whole, three parameters are relevant as follow: the presence of H2O, a specific partial pressure of oxygen PO2 and temperature. A wide set of combinations of these parameters, in the presence of monoxide of carbon and dioxide of carbon provide an atmosphere of reductor character. Sometimes, the oxide of metal transition participates of synthesis of one or more gas. While the process occour, metal is gradually produced. In this sense, is possible that residue exhibits a weight lower than original weight of nanoparticles added. The material residuary can be analysed via infrared, if significant portion of metal be present a magnet type NdFeB can also used to fast qualitative detection.
Please consider another techniques of characterization of the composite as mid- infrared spectroscopy, perhaps UV-vis spectroscopy but Mossbauer spectroscopy will be effective.
Kind regards
Marcos Nobre (M. A. L. Nobre)
Magnetite-PVA nanocomposite can be prepared by introducing mixture of 10 ml of 2
M FeSO4 and 40 ml of 1 M Fe2(SO4)3 into 400 ml of 5% PVA and 0.6 M NH4OH
solution with stirring. The reacting solution is kept at a constant pH of 12
throughout the course of precipitation with the addition of 3 M NH4OH. The solution
was poured into Petri dishes, and allowed to dry to form the films by
casting under ambient temperature for one day in a dark room
Magnetite-PVA nanocomposite can be prepared by introducing mixture of 10 ml of 2 M FeSO4 and 40 ml of 1 M Fe2(SO4)3 into 400 ml of 5% PVA and 0.6 M NH4OH solution with stirring. The reacting solution is kept at a constant pH of 12 throughout the course of precipitation with the addition of 3 M NH4OH. The solution is poured into Petri dishes, 15 ml/dish, and allowed to dry to form the films by casting under ambient temperature for one day in a dark room
Appreciate the suggestion Sayed, but I need to electrospin the magnetized PVA solution so I need it to be liquid. Could you suggest a preparation method for fe304 nanoparticles?
After preparation of fe304 nanoparticle by precipitation method you can disperse it in PVA solution by very rapid stirring for enough time.
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