The fate of Fe3+ ions in the system {AlO(OH)-xerogel/Fe-compounds} after mechanical activation and different thermal treatments studied by Mössbauer, ESR spectroscopy and thermal analysis

ISIAME 2008 ◽  
2009 ◽  
pp. 225-231
Author(s):  
R. Stößer ◽  
M. Menzel ◽  
M. Feist
Clay Minerals ◽  
1980 ◽  
Vol 15 (4) ◽  
pp. 421-428 ◽  
Author(s):  
T. Mozas ◽  
S. Bruque ◽  
A. Rodriguez

AbstractHydration/dehydration behaviour and the effect of various thermal treatments on montmorillonites saturated with lanthanide ions have been investigated by X-ray diffraction, thermal analysis (DTA, TG, DTG), IR spectroscopy and sorption-desorption of water vapour techniques. Heating at 150°C under 10−5 torr did not eliminate all the interlayer water of the montmorillonite, neither did it affect the CEC. Heating above 160°C caused a reduction in CEC. At 25°C La-montmorillonite takes up a maximum of three water layers in the interlayer space, the water molecules adopting a nonacoordinated distribution around the La3+ cation.


Author(s):  
Xiangli Long ◽  
Qingyan Liang ◽  
A Politov ◽  
Hong Gao ◽  
Yansheng Li ◽  
...  

2014 ◽  
Vol 802 ◽  
pp. 41-45
Author(s):  
Mauricio de Castro ◽  
Osvaldo Mitsuyuki Cintho ◽  
José Deodoro Trani Capocchi

The processes of high-energy milling and gained importance among the unconventional methods. In this work, we seek to compare the power supply two types of high energy mills (vibratory mill (SPEX) and planetary mill) with the variation of the milling power. The millings were carried out with a mixture of chromium oxide and aluminum metalic. The reduction of chromium oxide does not occur instantaneously, but gradually as the progress of milling with mechanical activation of powders, this mechanical activation occurs leading to the solid state reaction occurs. The results were obtained for thermal analysis of the samples. The energy released varies, exhibiting a maximum mechanical activation for the range of powers milling studied. The correlation between the energy mills can be made by identifying the milling power is reached at which the maximum in each mechanical activation mill and quantifying this activation.


2018 ◽  
Vol 53 ◽  
pp. 54-63
Author(s):  
Mohsen Saboktakin Rizi ◽  
Hamid Reza Javadinejad ◽  
Sayed Ahmad Hosseini ◽  
Ebrahim Aghababaie

In this work, Nono-crystalline aluminum carbide particles were synthesized using both mechanical and thermal treatments. Frist, Al and graphite powders had been milled in a planetary ball mill. Then, milled mixtures have been annealed isothermally after the mechanical activation. The effects of two processes on the synthesized products were separately studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and simultaneous thermal analysis (STA) methods. Further, the grain size, lattice strain and dislocation density values were calculated according to XRD data. The results showed that mechanical alloying process can create an ultra-fine microstructure. The grain size was mostly reduced after 40 h milling as well as the heat treatment at 550 °c and 2 h. in fact, the high rate of plastic deformation of aluminum particle during milling process lead to rising the internal energy of particles, and finally, nanocrystals of Al4C3formed with the size of 14 nm. However, thermal analysis indicated that the mechanical activation of aluminum and the presence of carbon can play key roles in synthesis of aluminum carbide. Key words: Mechanical alloying, annealing, Al and graphite powders, Solid state reaction, Nono-crystalline aluminum carbide.


Cerâmica ◽  
2018 ◽  
Vol 64 (369) ◽  
pp. 64-68
Author(s):  
H. S. Santos ◽  
A. M. Cesio ◽  
M. Gauna ◽  
V. F. Justo ◽  
C. Volzone

Abstract Beidellite clay mineral after intercalation of OH-Cr(III) species were thermally analyzed up to 1350 °C in oxygen and nitrogen atmospheres. OH-Cr-beidellite can be used as a pillared clay precursor for catalysis or as adsorbent applications. However, in this paper beidellite enriched in chromium were analyzed at different thermal treatments up to high temperature for evaluating structural changes for possible future ceramic applications. The structural changes were followed by thermal analysis and X-ray diffraction. The thermal treatment of OH-Cr-beidellite in oxygen and nitrogen atmospheres developed different mineralogical phases up to 1050 °C, but at higher temperatures, the same phases were developed in both atmosphere treatments. Eskolaite phase (Cr2O3) appeared in the sample after heating at 400 °C in oxygen atmosphere, whereas grimaldite (CrO-OH) in nitrogen atmosphere, maintaining the starting phases. At 1000 °C the raw clay minerals disappeared, as it is knew. At 1050 °C in nitrogen atmosphere, grimaldite was absent and eskolaite appeared. At 1350 °C in the samples calcined in both atmospheres, quartz, cristobalite and mullite as the main phases and in lower contents aluminum oxide and aluminum-chromium oxide [(Al,Cr)2O3] were present.


2011 ◽  
Vol 681 ◽  
pp. 358-363
Author(s):  
S. Mohsen Sadrossadat ◽  
Ru Lin Peng ◽  
Sten Johansson

Residuals stresses can be present in almost every industrial component. Manufacturing processes such as casting, welding, and heat treatment are the most common causes of residual stresses. Thermal residual stresses could be developed in a component during heat treatment process as a result of non-uniform heating or cooling operations. In this study, experiments were carried out to develop insights into and understanding of the residual stresses that can arise during thermal treatments of Al-Si components. Due to the complexity of residual stresses analysis in real components, a common mixed-section casting was employed. In order to fulfill the requirements of performing different thermal treatments, a special cooling apparatus was designed and built. A number of the casting components of an Al-Si alloy were annealed for stress relief, and then removed from the furnace and cooled with different water flow rates. Then, the amount of accumulated residual stresses in the components was measured relaxation of stress using cutting. Thermal analysis and residual stress measurement for different thermal treatment regimes showed that by choosing a specific holding temperature before direct cooling, the value of residual stress increases linearly with flow rate of cooling. On the other hand, for a constant value of cooling water flow, ∆Tmaxand residual stress level decreases when the value of base temperature of furnace decreases. Moreover, the cutting method can be a suitable method for measuring thermal residual stresses in Al-Si components and thermal analysis is a powerful technique to predict residual stresses.


Author(s):  
Paresh S. More ◽  
Bipin H. Mehta

Transition metal complexes of the type ML.nH2O [Where M= Co(II),Ni(II),Cu(II) and Zn(II), L= Schiff base of 5 nitro salicylaldehyde and anthranalic acid, n= 0,1 …..] were characterized by using 1H NMR,TGA, Diffused refluctance and ESR spectroscopy. On the basis of above studies Co(II), Ni(II) shows tetrahedral structure, Cu(II) shows binuclear structure and Zn(II) shows square planar structure.


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