Microstructural Evolution, Thermodynamics, and Kinetics of Mo-Tm2O3 Powder Mixtures during Ball Milling
نویسندگان
چکیده
The microstructural evolution, thermodynamics, and kinetics of Mo (21 wt %) Tm₂O₃ powder mixtures during ball milling were investigated using X-ray diffraction and transmission electron microscopy. Ball milling induced Tm₂O₃ to be decomposed and then dissolved into Mo crystal. After 96 h of ball milling, Tm₂O₃ was dissolved completely and the supersaturated nanocrystalline solid solution of Mo (Tm, O) was obtained. The Mo lattice parameter increased with increasing ball-milling time, opposite for the Mo grain size. The size and lattice parameter of Mo grains was about 8 nm and 0.31564 nm after 96 h of ball milling, respectively. Ball milling induced the elements of Mo, Tm, and O to be distributed uniformly in the ball-milled particles. Based on the semi-experimental theory of Miedema, a thermodynamic model was developed to calculate the driving force of phase evolution. There was no chemical driving force to form a crystal solid solution of Tm atoms in Mo crystal or an amorphous phase because the Gibbs free energy for both processes was higher than zero. For Mo (21 wt %) Tm₂O₃, it was mechanical work, not the negative heat of mixing, which provided the driving force to form a supersaturated nanocrystalline Mo (Tm, O) solid solution.
منابع مشابه
Microstructural Evolution of Dy2O3-TiO2 Powder Mixtures during Ball Milling and Post-Milled Annealing
The microstructural evolution of Dy₂O₃-TiO₂ powder mixtures during ball milling and post-milled annealing was investigated using XRD, SEM, TEM, and DSC. At high ball-milling rotation speeds, the mixtures were fined, homogenized, nanocrystallized, and later completely amorphized, and the transformation of Dy₂O₃ from the cubic to the monoclinic crystal structure was observed. The amorphous transf...
متن کاملHydrogen evolution activity of NiMo-MoO2 produced by mechanical milling
In this study, mechanical alloying was done by a high-energy planetary ball milling technique. A mixture of NiO and MoO3 and graphite powders were used as initial materials. After milling of powder mixture with 40 wt.% additional graphite, a temperature of 400, 550 and 1000 °C for 1 h was considered for the heat treatment of powder mixture. Also, powder mixtures containing 60, 80 and 100 wt.% a...
متن کاملStructural Evolution of Al-20% (wt) Al2O3 System during Ball Milling Stages
Production of nanostructured aluminum matrix composite powder by high energy ball milling is investigated. Scanning electron microscopy analysis as well as the tap and green density measurements were used to optimize the milling time needed for the completion of the mechanical milling process. Also, we studied the particles morphology and size distribution change with milling time and its corre...
متن کاملBehavior of Cu-Cr Powder Mixtures During Mechanical Alloying (TECHNICAL NOTE)
In the present work, the behavior of Cu-Cr powder mixtures during mechanical alloying has been studied. The powder mixtures with 1, 3 and 6 weight percents of Cr in Cu were treated. They were milled in a ball mill with two different speeds of 250 and 500 rpm using equal numbers of 1 and 2 centimeters balls. The weight ratio of balls to powders was 10 to 1 under argon atmosphere. Ethanol was use...
متن کاملEFFECT OF COMPOSITION AND MILLING TIME ON THE SYNTHESIS OF NANOSTRUCTURED Ni-Cu ALLOYS BY MECHANICAL ALLOYING METHOD
Ni and Cu elemental powder mixtures containing 25, 50, and 75% at Cu were subjected to mechanical alloying in a planetary ball mill under various milling times. Structural evolution was analyzed by means of X-ray diffraction and scanning electron microscopy. Experimental results indicated that nanostructured solid solution alloy powders having homogeneous distribution of Ni and Cu were formed b...
متن کامل