Reaction Mechanism of an Al-TiO2 System

2010 ◽  
Vol 97-101 ◽  
pp. 1624-1627 ◽  
Author(s):  
He Guo Zhu ◽  
Jing Min ◽  
Ying Lu Ai ◽  
Qiang Wu
Keyword(s):  
Free Energy ◽  
Reaction Mechanism ◽  
Heating Rate ◽  
Gibbs Free Energy ◽  
Thermodynamic Analysis ◽  
Volume Fraction ◽  
Reaction System ◽  
Exothermic Peak ◽  
Higher Temperature ◽  
Α Al2o3

The reaction mechanism of an Al-TiO2 system is discussed. Thermodynamic analysis indicates that the reaction between Al and TiO2 can occur spontaneously due to the negative Gibbs free energy of the Al-TiO2 reaction system. When the reinforcement volume fraction is 30%, there is an endothermic peak and an exothermic peak in the DSC curve. But when the reinforcement volume fraction increases to 100%, there are two independent exothermic peaks and the height of them increases obviously. With increasing the heating rate, the ignite temperature becomes higher and all the peaks move to the higher temperature direction. The reactions between Al and TiO2 consist of two steps: first, Al reacts with TiO2 to form the stable α-Al2O3 particles and the active Ti atoms; second, the active Ti atoms react with Al to form Al3Ti.

Study on the Reaction Mechanism of (α-Al2O3+TiB2+TiC)/Al Composites Fabricated by Al-TiO2-B4C System

2010 ◽  
Vol 150-151 ◽  
pp. 84-87
Author(s):  
He Guo Zhu ◽  
Jin Min ◽  
Da Chu ◽  
Huan Wang
Keyword(s):  
Free Energy ◽  
Reaction Mechanism ◽  
Gibbs Free Energy ◽  
Thermodynamic Analysis ◽  
Reaction System ◽  
Higher Temperature

The composites (-Al2O3+TiB2+TiC)/Al has been fabricated by using exothermic dispersion synthesis. Thermodynamic analysis indicated that the reaction between the Al and TiO2 can spontaneously occur due to the negative Gibbs free energy of the Al-TiO2 reaction system. With the increase of B4C/TiO2 mole ratios, the exothermic peaks increase move to the higher temperature and the corresponding ignite temperatures also increase. The reaction results indicate that when the B4C/TiO2＝0, the reinforcements are composed of -Al2O3, Al3Ti, with the increase of B4C/TiO2, the amount of Al3Ti decreases and the TiC and TiB2 form simultaneously. When the B4C/TiO2 increases to 1/3, the Al3Ti almost disappear and the reinforcements of the composites are consisted of -Al2O3, TiC and TiB2.

scholarly journals Thermodynamic Analysis of the Formation of FCC and BCC Solid Solutions of Ti-Based Ternary Alloys by Mechanical Alloying

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 510 ◽  
Author(s):  
Claudio Aguilar ◽  
Carola Martinez ◽  
Karem Tello ◽  
Sergio Palma ◽  
Adeline Delonca ◽  
...  
Keyword(s):  
Free Energy ◽  
Mechanical Alloying ◽  
Gibbs Free Energy ◽  
Thermodynamic Analysis ◽  
Solid Solutions ◽  
Ternary Systems ◽  
Solubility Limit ◽  
Ternary Alloys ◽  
Energy Of Mixing ◽  
Free Energy Of Mixing

A thermodynamic analysis of the synthesis of face-centred cubic (fcc) and body-centred cubic (bcc) solid solutions of Ti-based alloys produced by mechanical alloying was performed. Four Ti-based alloys were analysed: (i) Ti-13Ta-3Sn (at.%), (ii) Ti-30Nb-13Ta (at.%), (iii) Ti-20Nb-30Ta (wt. %) and (iv) Ti-33Nb-4Mn (at.%). The milled powders were characterized by X-ray diffraction, and the crystallite size and microstrain were determined using the Rietveld and Williamson–Hall methods. The Gibbs free energy of mixing for the formation of a solid solution of the three ternary systems (Ti-Ta-Sn, Ti-Nb-Ta and Ti-Nb-Mn) was calculated using an extended Miedema’s model, applying the Materials Analysis Applying Thermodynamics (MAAT) software. The values of the activity of each component were determined by MAAT. It was found that increasing the density of crystalline defects, such as dislocations and crystallite boundaries, changed the solubility limit in these ternary systems. Therefore, at longer milling times, the Gibbs free energy increases, so there is a driving force to form solid solutions from elemental powders. Finally, there is agreement between experimental and thermodynamic data confirming the formation of solid solutions.

Theimddynamically Stable Metal / III-V Compound-Semiconductor Interfaces

1985 ◽  
Vol 54 ◽  
Author(s):  
R. Stanley Williams ◽  
Jeffrey R. Lince ◽  
Thomas C. Tsai ◽  
John H. Pugh
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Compound Semiconductor ◽  
Enthalpy Change ◽  
Reaction Products ◽  
Bulk Materials ◽  
Semiconductor Interface ◽  
Group V ◽  
Semiconductor Interfaces ◽  
Higher Temperature

ABSTRACTChemical reactions that occur at a metal/III-V compound-semiconductor interface should be minimized if the change in Gibbs free energy of the bulk materials with respect to any possible reaction products is positive. However, the large positive change in entropy caused by vaporization of the highly volatile group V elements is a very important contribution to the Gibbs free energy of these systems, especially at higher temperatures. Thus, a particular metal/III-V compound-semiconductor interface may be thermody-namically stable at one temperature, but unstable with respect to sublimation of elemental group V species at a higher temperature if the enthalpy change for the reaction is positive. Examination of bulk phase diagrams makes it possible to rationalize the reaction products observed and to predict which will be the most stable interface for any particular metal/III-V system.

Investigation on the Austenitic Reverse Transformation of 0.2C-3Mn-1.7Si Steel with an Ultra-Slow Heating Rate

2014 ◽  
Vol 1004-1005 ◽  
pp. 214-220
Author(s):  
Bao Xiang Zhang ◽  
Xiao Lu Gui ◽  
Gu Hui Gao ◽  
Zhun Li Tan ◽  
Bing Zhe Bai
Keyword(s):  
Heat Treatment ◽  
Free Energy ◽  
Heating Rate ◽  
Experimental Results ◽  
Reverse Transformation ◽  
Slow Heating ◽  
Higher Temperature ◽  
Intercritical Region ◽  
Increasing Temperature ◽  
Martensite Matrix

In order to clarify the austenite reverse transformation of a 0.2C-3Mn-1.7Si steel during intercritical region with an ultra-slow heating rate of 0.05°C/s, DIL (dilatometer), SEM, XRD and EPMA were carried out. The experimental results indicated that the dilatometric cures exhibited the shape of two “valleys” and the growth of austenite from quenched martensite was composed of three consecutive sub-stages. This phenomenon is associated with Mn-rich and Mn-poor regions in martensite matrix. During the heat treatment,the austenite forms firstly in region enriched in Mn. However, with increasing temperature, the growth of γ is restrained owing to the concentration of Si. Upon the further process of heating, the free energy for the reverse transformation increases, and the residual Mn-depleted regions start to transform at a higher temperature.

Study on the Reaction Mechanism of Al-ZrO2-B4C System

2011 ◽  
Vol 675-677 ◽  
pp. 839-842 ◽  
Author(s):  
He Guo Zhu ◽  
Da Chu ◽  
Huan Wang ◽  
Jing Min ◽  
Ying Lu Ai
Keyword(s):  
Reaction Mechanism ◽  
Volume Fraction ◽  
Exothermic Peak ◽  
Molar Ratio ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Zro2 System

The composite (a-Al2O3+ZrC+ZrB2)/Al has been fabricated by using exothermic dispersion synthesis. When the reinforcement volume fraction is 100%, there are two exothermic peaks occurred in DSC curve of the Al-ZrO2 system. But when the reinforcement volume fraction is 30%, there is only one exothermic peak occurred in the DSC curve and the height of it decreases. When the molar ratio of B4C/ZrO2 is 0, the reaction products are consisted of a-Al2O3 grains and Al3Zr blocks. With an increase in the molar ratio of B4C/ZrO2, the amount of the Al3Zr decreases and the phases of ZrB2 and ZrC are formed. When the molar ratio of B4C/ZrO2 increases to 1/3, the Al3Zr almost disappear and the reinforcements of the composites are composed of a-Al2O3, ZrC and ZrB2. The corresponding XRD (X-ray diffraction) patterns also testify this.

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