26 April 2023
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Story Leonie Bolleurs
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Photo Charl Devenish
The UFS has conferred a Doctor of Philosophy degree, majoring in Physics, upon Dr Songyou Lian from the Guangdong Province in China.
During the recent April 2023 graduation ceremonies, the University of the Free State (UFS) conferred a Doctor of Philosophy degree, majoring in
Physics, upon
Dr Songyou Lian from the Guangdong Province in China.
Dr Lian's PhD thesis, titled Grain Boundary Diffusion and Surface Segregation Under Stress: Theoretical, Experimental, and Molecular Dynamics Investigation, resulted in the publication of eleven articles in international journals with him as the first author. He also made valuable contributions to five additional articles as a non-first author. These articles included theoretical investigations, experiments, and molecular dynamics simulations.
His exceptional publication record is a testament to his hard work and unwavering drive to continuously improve and become a better version of himself in the future.
Practical applications
“In this research that can be applied to practical problems of water vapour diffusion in barrier films used to preserve food freshness, I focused on understanding how atoms move and behave on the surface and inside materials (grain boundary diffusion and surface segregation),” says Dr Lian, whose fascination with understanding the fundamental behaviour of materials at the atomic level sparked his interest in this specific study.
“I would like to contribute to developing new materials with specific properties or improving existing materials for various applications. The quantification of depth profiling, grain boundary diffusion, and surface segregation are all critical phenomena that influence the behaviour of materials. By studying these processes, we can gain a deeper understanding of how materials behave under different conditions, which is helpful for the design of new materials with specific properties,” he remarks.
“Surface segregation, or the preferential enrichment of some aspects at the surface of a material, can be used to modify the surface properties of a material. This can have significant implications for a wide range of applications, including corrosion resistance, wear resistance, and adhesion. Surface segregation and grain boundary diffusion can also play an important role in the behaviour of thin films, which have widespread uses in, for instance, electronic devices, coatings, and solar cells,” he says.
With his PhD study involving a range of techniques, including experiments and simulations, Dr Lian is very excited about the new high-resolution transmission electron microscope (HRTEM) purchased by the
UFS Centre for Microscopy, which can be used to study grain boundary diffusion and surface segregation at the atomic level. “This piece of equipment allows scientists like me to study materials in unprecedented detail,” says Dr Lian.
Other research aspects
Besides his focus on grain boundary diffusion and surface segregation, Dr Lian's research involved several other aspects, including the effect of the sputtering process on the depth concentration profile, which investigates the sputtering process on the distribution of atoms at varying depths. This was accomplished by employing the mixing-roughness-information depth (MRI) model to determine how fast the atoms were moving and how factors such as the roughness and mixing length affected the measured diffusion coefficient.
Later in his study, Dr Lian proposed a method to obtain the diffusion coefficient (measuring how quickly particles move from an area of high concentration to an area of low concentration due to random motion) from the concentration-depth profile of thin film with grain boundaries.
Another area of focus in the study was the movement of water vapour through thin films. He also investigated the effect of stress on the separation and movement of materials on the film's surface, using computer simulations to gain a better understanding of these processes.
Future steps
Dr Lian was introduced to the UFS during a collaboration between the UFS Department of Physics and the Department of Physics at the
Shantou University.
“I value the relationships I have built with the UFS Department of Physics, and specifically my supervisor,
Prof Koos Terblans (Head of the Department of Physics at the UFS), and hope to collaborate on future research projects and articles,” says Dr Lian, who aspires to make a positive impact on society through his research contributions.