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Lecture

Surfaces and Interfaces: Thermodynamics and Kinetics

In course

MSE-464: Assembly techniques

Introduction to the assembly of materials by homogeneous or heterogeneous joints (welding, bonding, mechanical assembly). Mechanical and environmental resistance of joints. ...

Description

This lecture covers the concepts of surface and interface energy, thermodynamics of wetting, contact angle, and kinetics of wetting for both non-reactive and reactive systems. It explains the relationship between surface tension, surface energy, and interface energy, as well as the impact of geometric and chemical inhomogeneities on wetting behavior. The lecture also discusses the work of adhesion, cohesion, and the dynamic contact angle, providing insights into the factors influencing bond strength. Additionally, it explores the effects of surface roughness, surface tension of alloys, and superhydrophobic surfaces. Kinetic aspects of spreading in reactive systems are analyzed, focusing on dissolution kinetics and the behavior of systems forming a reaction phase.

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Ontological neighbourhood

Chemistry

Physical chemistry: Surface science

Related concepts (18)

Surface energy

In surface science, surface free energy (also interfacial free energy or surface energy) quantifies the disruption of intermolecular bonds that occurs when a surface is created. In solid-state physics, surfaces must be intrinsically less energetically favorable than the bulk of the material (the atoms on the surface have more energy compared with the atoms in the bulk), otherwise there would be a driving force for surfaces to be created, removing the bulk of the material (see sublimation).

Surface tension

Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to float on a water surface without becoming even partly submerged. At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion). There are two primary mechanisms in play.

Wetting

Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. This happens in presence of a gaseous phase or another liquid phase not miscible with the first one. The degree of wetting (wettability) is determined by a force balance between adhesive and cohesive forces. Wetting is important in the bonding or adherence of two materials. Wetting and the surface forces that control wetting are also responsible for other related effects, including capillary effects.

Hydrophobe

In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle.

Adhesion

Adhesion is the tendency of dissimilar particles or surfaces to cling to one another (cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can be divided into several types. The intermolecular forces responsible for the function of various kinds of stickers and sticky tape fall into the categories of chemical adhesion, dispersive adhesion, and diffusive adhesion.

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