(a) Briefly explain why porosity decreases the thermal...

Name: Problem 19, Chapter 19: Materials Science and Engineering: An Introduction
Uploaded: 2021-11-09T04:54:02-08:00
Duration: 1 min 42 s
Channel: Ameer Said
Description: (a) Briefly explain why porosity decreases the thermal conductivity of ceramic and polymeric materials, rendering them more thermally insulative. (b) Briefly explain how the degree of crystallinity affects the thermal conductivity of polymeric materials and why.

(a) Briefly explain why porosity decreases the thermal conductivity of ceramic and polymeric materials, rendering them more thermally insulative. (b) Briefly explain how the degree of crystallinity affects the thermal conductivity of polymeric materials and why.

Labs

Want to see this concept in action?

NEW

Explore this concept interactively to see how it behaves as you change inputs.

View Labs

Key Concepts

Porosity

Porosity refers to the percentage of void or empty spaces within a material's structure. This concept is crucial because in ceramics and polymers, these voids typically contain air, which is a poor conductor of heat. Thus, a higher porosity disrupts the continuous solid phase that would otherwise allow efficient heat flow, resulting in a lower overall thermal conductivity and enhanced insulative properties.

Thermal Conductivity

Thermal conductivity is the property of a material that indicates its ability to transfer heat. It depends on the material’s composition and structure, including factors such as porosity and the degree of crystallinity. In materials with structural discontinuities or high disorder, heat is not conducted as efficiently, thereby reducing thermal conductivity.

Crystallinity

Crystallinity measures the extent to which a polymer exhibits an ordered, regular structure as opposed to a disordered, amorphous state. Higher degrees of crystallinity provide more ordered molecular pathways that facilitate the efficient transport of thermal energy (phonons), leading to higher thermal conductivity. In contrast, increased amorphous content results in reduced heat transfer due to the lack of well-defined pathways.

Transcript

Please give Ace some feedback