Material Properties: Electrical, Chemical & More
Material Properties
Electrical Properties
c1) Electrical Conduction: Allows high levels of energy to be transferred, such as in airlines and power distribution transformers and motors.
c2) Semiconductor: Allows the transmission of electricity, subject to potential difference variables such as temperature. Germanium and silicon are alloyed with nitrogen, phosphorus, and arsenic.
c3) Electrical Insulation: Aims at no power transmission in very high electric fields, e.g., ceramics and polymers.
Magnetic Properties
The interaction between magnetic induction intensity and magnetic field. The material intended to allow the passage of magnetic flux depends on the permeability of how electrical conductance relates its current status with the magnetic field induced.
Chemical Properties
This type of energy involves electrochemical reactions, including both direct electrodeposition, such as corrosion, and indirect processes. The generation of chemical energy is controlled by the materials’ resistance to corrosion and the electrolyte’s ability to transfer energy.
- Combustion: A self-sustaining exothermic reaction in the presence of a fuel (solid, liquid, or gaseous). It is associated with the oxidation of a fuel by atmospheric oxygen, emitting light and producing a visible flame.
- Ignition: A phenomenon that begins with self-sustaining combustion. It is produced by introducing an external agent such as an ignition flame, ember, or spark. Ignition caused without an external agent is called self-ignition and only needs to reach a temperature higher than the minimum ignition temperature.
- Oxidation: The process in which atoms transfer electrons to other atoms or molecules, causing the oxidation of some solid materials. It involves a movement, change, or release of energy.
- Corrosion: The chemical, mechanical, or electromechanical action (slow or fast) that degrades and destroys solid materials, such as metals. It results in the loss of balance of cohesive forces, which maintain the cohesion of the solid matter. This is the result of the balance of attraction forces between positive atomic nuclei and negatively charged atoms, and the repulsion forces of the electrons among themselves and their atomic nuclei, corroding the surface.
Types of Corrosion
- Surface Corrosion: It is more benign, less harmful, and dangerous. The material gradually wears away homogeneously, with equal mean penetration at all points of the metal. It is a gradual attack, and the useful life of materials can be accurately determined. When corrosion is intermediate (between uniform and localized), it is called plate corrosion.
- Pitting Corrosion: Occurs when the metal surface has been passivated and exposed to an aggressive medium. Corrosion is localized in isolated areas and propagates into the solid material, forming highly corroded microscopic tunnels.
- General Corrosion: The most common form of corrosion and the most important in economic terms. It is a uniform attack on the exposed metal surface, with minor variations in the depth of damage. It is neutralized using special coatings to minimize the attack.
- Galvanic Corrosion: Severe damage occurs by joining two or more dissimilar metals that are electrically coupled. The potential difference between the coupled metals causes a current flow between them, where the most active metal suffers from accelerated corrosion, and the other, less active metals, experience delayed or eliminated corrosion.
- Crevice Corrosion: Present in confined spaces or in crevices formed when components are in close contact. The notch must be very narrow, with a dimension less than one millimeter. Larger spaces do not exhibit this type of corrosion. It is not necessary that both surfaces be metal; they can be polymers, asphalt, neoprene, or glass. Care must be taken in the application and selection of materials for expansion joints.