An insight into the changes in the thermal analysis curves of boehmite with mechanical activation

2014 ◽  
Vol 117 (1) ◽  
pp. 163-171 ◽  
Author(s):  
T. C. Alex
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.


2017 ◽  
Vol 68 (9) ◽  
pp. 2043-2047
Author(s):  
Georgeta Velciu ◽  
Adelina Carmen Ianculescu ◽  
Alina Melinescu ◽  
Virgil Marinescu ◽  
Maria Preda

In this work it was studying evolution of the reactions that occur at the formation of La1-xSrxCoO3-� from mixtures of La2O3, Co3O4 and SrCoO3, prepared by mechanical activation. It was found that distributions of the particles sizes after mechanical activation are unimodal and narrow. Thermal analysis shows that the reactions that occur under the temperature of 1000oC are dissociation reactions of the raw materials or of intermediate compounds formed in the process of mechanical activation. The first compound found, starting from 1000oC was LaCoO3, whereas Co3O4 and CoO were observed as secondary phases. By measuring the apparent density of the thermally treated samples, a good tendency to sintering was noticed. SEM images and EDX analyses allowed to highlight the high sinterability of the samples.


Author(s):  
Allen C. Smith ◽  
Narendra K. Gupta ◽  
Bruce J. Hardy ◽  
Kurt R. Eberl

In the thermal analysis of the 9977 package, it was found that calculated temperatures, determined using a typical thermal analysis code, did not match those measured in the experimental apparatus. The analysis indicated that the thermal resistance of the overpack in the experimental apparatus was less than that expected, based on manufacturer’s reported value of thermal conductivity. To resolve this question, the thermal conductivity of the installed foam was evaluated from the experimental results, using a simplified analysis. This study confirmed that the thermal resistance of the experimental apparatus was lower than that which would result from the manufacturer’s published values for thermal conductivity of the foam insulation. The test package was sectioned to obtain samples for measurement of material properties. In the course of the destructive examination a large uninsulated region was found at the bottom of the package, which accounted for the anomalous results. Subsequent measurement of thermal conductivity confirmed the manufacturer’s published values. The study provides useful insight into the use of simplified, scoping calculations for evaluation of thermal performance of packages.


2017 ◽  
Vol 5 (1) ◽  
pp. 49 ◽  
Author(s):  
Farit Kh. Urakaev ◽  
Vyacheslav S. Shevchenko ◽  
Vladimir V. Boldyrev

<p>The possibility of mechanochemical synthesis and influence of mechanical activation on thermal synthesis of borides and boron carbides of mass-low metals is investigated. The opportunity of mechanochemical synthesis in the mill AGO-2 of such compounds as AlB<sub>2</sub> and CaC<sub>2</sub>B<sub>2</sub> is established. Influence of mechanical activation in the mill SPEX 8000 on synthesis of such compound as Mg<sub>0.5</sub>Al<sub>0.5</sub>B2 is shown. Mechanical activation also influences on the process of thermal synthesis: compound Mg<sub>0.5</sub>Al<sub>0.5</sub>B<sub>2</sub> is obtained in the conditions inaccessible to traditional thermal synthesis; formation of compound Mg<sub>1-x</sub>Al<sub>x</sub>B<sub>2</sub> in literature up to x = 0.4 was established on shifts of reflexes (002) and (110) pure MgB<sub>2</sub> aside the large corners; in our case x = 0.5 and as it was necessary to expect shifts of these reflexes exceeds shifts measured in literature only for x ≤ 0.4. Features of synthesis in systems containing metal magnesium are considered. The opportunity of application of crystalline boron for mechanochemical synthesis of borides and boron carbides of mass-low metals is established, that it was not represented probable to make in its ceramic synthesis. We revealed also that thermal analysis in conditions of helium results in crystallization almost all activated samples, and the analysis of received X-ray reflexes unambiguously allows to assert that mechanical activation accelerates synthesis of reaction products in the investigated systems in comparison with the traditional methods of its synthesis.</p>


2016 ◽  
Vol 99 (10) ◽  
pp. 3443-3448
Author(s):  
Harishchandra Singh ◽  
Anil K. Sinha ◽  
Surya M. Gupta ◽  
Manvendra N. Singh ◽  
Haranath Ghosh

1966 ◽  
Vol 24 ◽  
pp. 322-330
Author(s):  
A. Beer

The investigations which I should like to summarize in this paper concern recent photo-electric luminosity determinations of O and B stars. Their final aim has been the derivation of new stellar distances, and some insight into certain patterns of galactic structure.


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