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Warm Compaction Process of Alumina Nano-Powders Using Molecular Dynamics Method

Vafaei Safti, Mohammad Reza | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57316 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khoei, Amir Reza
  7. Abstract:
  8. Alumina is a primary material in ceramics used in various fields including construction materials, electronics industries, optical fibers, artificial joints, chemical sensors, automotive industries, aerospace industries, various coatings, and so forth, with numerous applications. Therefore, manufacturing ceramic components based on alumina is a significant issue in the industry. Among the primary methods for manufacturing ceramic components is the use of powder compaction processes, which are divided into two categories: cold compaction and warm compaction. In cold compaction, the shaping of components from powder is carried out by applying high pressures, while in warm compaction, mechanical loading accompanied by heating is used simultaneously. In addition to the ability to produce components with cohesive and compact mechanical properties, warm compaction is also economically viable. By appropriately selecting the dimensions of the mold and the possibility of size variation in the desired sample, the shape and angles of the final piece are minimized. This process allows for the use of most raw materials with minimal waste. Other advantages of this method include the suitable and quality surface of the manufactured parts, controllable porosity, and good long-term performance of the parts. In industries, after the operations of heat treatment, compaction, and consolidation of metal powders, thermal treatment operations are carried out at high temperatures and under controlled pressure, where the compacted metal is welded and forms a strong homogenous structure. In this research, the simulation of the warm compaction process of alumina nanoparticles is performed using the molecular dynamics method. By using the molecular dynamics method, which is a powerful tool for analyzing and investigating nano-scale phenomena, mechanical and thermal properties of nanoparticles can be accurately predicted during compaction. In the molecular dynamics method, the equations of motion governing the particles forming the body are written, and using the potential function between atoms, the force applied to each other is obtained. Then, by employing one of the numerical integration methods, the position and velocity of particles are updated at different time steps. In the simulation of the warm compaction process, after creating the initial structure and selecting the appropriate atomic potential, loading and heating processes are carried out simultaneously, and the behavior of nanoparticles during the process is examined. The molecular dynamics simulation process has been conducted using LAMMPS and for the purpose of visualizing, OVITO has been used. In this research, after modeling the warm compaction process of alumina nanoparticles using the molecular dynamics method, various mechanical and thermal properties of the sample are independently examined at the end of the process and during the process concerning the time under investigation. Additionally, for validation purposes, the results obtained from the study are compared with valid laboratory data, and the accuracy of the simulation is evaluated
  9. Keywords:
  10. Warm Compaction ; Molecular Dynamics ; Alumina Nanoparticles ; Powder Compaction ; Alumina Powder ; Reax FF Potential Function ; LAMMPS Software

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