The elastic (Young’s) modulus also varies pronouncedly with the thickness of film which is less than about 10 μm, but it approaches a constant when the thickness is more than about 10 μm. The relationship between elastic modulus and the thickness is shown in Figure 10. The main reason of this phenomenon seems to associate with the growth mechanism and its influence factors of the Pth films. When the thickness is less than 10 μm, the Pth mainly grows up in a stable manner on the base layer. But with increasing thickness, more and more agglomerated molecule groups are formed away from the base layer. Therefore, many micro-defects such as micro-cracks and micro-voids easily exist in the adjacent surface layer. At the same time, the binding energy of these agglomerated molecule groups becomes smaller and smaller because of the electrochemical influence or the influence of the metal substrate. Therefore, the microstructures of Pth films will change as the thickness increases. A thin film with the thickness of about 4 μm generally has a perfect microstructure with few defects
The concept refers to the change in the elastic modulus, a measure of a material's stiffness, as the size of the material is altered. This can occur due to various factors such as microstructure, defects, and stress.
The elastic modulus typically decreases as the size of the material decreases. This is because smaller materials have a larger surface area to volume ratio, leading to more surface effects that can affect the material's stiffness.
Studying this variation can provide insights into the mechanical behavior of materials at different scales and help improve the design of micro and nano-scale structures. It can also aid in understanding the effects of material defects and facilitate the development of new materials with desired properties.
Yes, in some cases, the elastic modulus may increase with size. This is known as the size effect and is observed in materials with a hierarchical microstructure or when the material is under high stress conditions.
The variation can be measured using experimental techniques such as nanoindentation or micro-compression tests to determine the stiffness at different scales. Computational methods such as molecular dynamics simulations can also be used to study the effect of size on the elastic modulus.