I have conducted XRD and TGA of powdered slag sample. XRF data shows about 4.5% of MgO. Derivative curve of the TG data (pic attached) show a mass loss between 290 and 480 °C, with the endothermic peak maxima centred around 390 °C. Based on the past literature, the mass loss appears to be that of Mg(OH)2. I couldn't find any strong peak of Mg(OH)2 in the XRD data. Just wondering if Mg(OH)2 can have amorphous characteristics. I have attached the derivative curve of the TG data (image file) and the .raw xrd file compressed as .rar file.
You have a small amount (4.5%) of Mg(OH)2 in the material so a strong peak isn't expected unless your x-ray irradiation is prolonged. I believe that brucite (https://en.wikipedia.org/wiki/Brucite) is usually crystalline but in a slag based material I'm not so sure, so someone with a better skill set should reply. Perhaps you can form a Mg-based glass or glass-like material?
The analysed slag may indeed contain either amorphous or poorly crystallized Mg(OH)2. You may possibly want to refer to: R.C. Turner, I. Hoffman, D. Chen, "Thermogravimetry of the dehydration of Mg(OH)2", Can. J. of Chem., 41(2) 1963, 243-251:
http://dx.doi.org/10.1139/v63-039#.VcAlljhRHZ4
Dear Rajeev,
Please note that:
1. Brucite [Mg(OH)2] is a crystalline phase (Trigonal - Hexagonal) and hasn's amorphous characteristics.
2. If 4.5% MgO in the composition is completely related to brucite, so the brucite content is about 6.5Wt% that is insufficient content for obvious peaks in XRD pattern.
3. Brucite and other minerals such as olivine and serpentine may show some overlapped peaks in XRD pattern.
4. The endothermic peak in TGA, can be related to other minerals so this should be considered in your work.
Thanks Abbas,
XRF shows 4.5% MgO in Slag, i'm trying to figure out what phase has possibly formed from that. I see three mass losses in TGA. The first sharp endothermic peak relates to gypsum, which is evident in XRD as well. The last peak possibly relates to calcite and Argonite. I found their relavent XRD peaks, though small ones. I'm trying to identify the middle broad peak in TGA and also trying to figure out if possibly the MgO might have got hydrated to form Mg(OH)2
Dear Rajeev,
If the XRD pattern (or other phase analyse methods) at 500oC has 4.5wt% MgO as periclase phase, so the MgO content in the raw material is completely related to brucite
As has been said by Carlos Araújo Queiroz , most probably the Mg(OH)2 presrent is in the amorphous form. The mass loss can be due to the dehydration of Mg(OH)2 to MgO,
Mg(OH)2 transforms readily to Hydromagnesite; so possibly your rather small amount of Mg-Ox. is a mixture of both materials, by this falling under the detection limit of XRD recording. In addition, the XRD pattern of hydromagnesite is extremely complex which supports its disappearing in the background. In similar cases (here: some undefined Sn-Oxides) I tempered the material to get finally well defined oxide peaks as a proof of the presence of some Sn material in a mixture of metal oxides. Possibly (depending on your approach) you also could temper your material; Periclase shows a very simple and well defined pattern the peaks of which can easily be detected..
Good luck
D. Zachmann
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