Chapter 1. Properties of Materials.pdf

Properties of Materials PNOD 243 Dr. Sofiene MANSOURI [email protected] (Whatsapp:0533791123) Properties of Materials The properties of materials can be broadly classified into several categories. Here are some key properties: 1. Electrical Properties 2. Ma...

Properties of Materials PNOD 243 Dr. Sofiene MANSOURI [email protected] (Whatsapp:0533791123) Properties of Materials The properties of materials can be broadly classified into several categories. Here are some key properties: 1. Electrical Properties 2. Magnetic Properties 3. Optical Properties 4. Acoustic Properties 5. Thermal Properties 6. Chemical Properties 7. Other & Ecological properties 8. Mechanical Properties These properties determine how materials can be used in various applications, from construction to electronics and beyond. Understanding these properties is crucial for material selection in engineering and manufacturing processes. 2 1. Electrical Properties of Materials The electrical properties of materials describe how they interact with electric fields and currents. Here are the key electrical properties: 1. Electrical Conductivity Definition: The measure of a material's ability to conduct electric current. Units: Typically expressed in siemens per meter (S/m). Importance: High conductivity materials (e.g., copper, aluminum) are used in electrical wiring and components, while low conductivity materials (e.g., rubber, glass) are used as insulators. 2. Electrical Resistivity Definition: The measure of a material's opposition to the flow of electric current. Units: Expressed in ohm-meters (Ω·m). Relationship: Resistivity is the inverse of conductivity; materials with high resistivity are poor conductors. 3 1. Electrical Properties Resistance All substances have resistance to current flow. In the body resistance varies according to the nature of the tissue, lean tissues containing large amounts of water represent a path of low electrical resistance. On the other hand, fat and bones are poor conductors (high electrical resistance) with small amounts of fluids. 4  1. Electrical Properties Veins and arteries are the simplest path for the current because resistivity is much less than that of tissue and bone. Resistivity of blood: 150Ωcm Resistivity of tissues and bones ≈ 3000Ωcm L R= S 5 The volume increases during the systole and decreases during the diastole. ∆V = VSys-VDia 6  V = SL L L2 & V=  S L R R= S ❖The larger the volume of the fluid, the lower the resistance. R V = L 2 2 R0 7  1. Electrical Properties of Materials 3. Dielectric Properties Dielectric Constant (Permittivity): The ability of a material to store electrical energy in an electric field. Higher values indicate better storage capabilities. Importance: Dielectrics are essential in capacitors and insulation materials. 4. Superconductivity Definition: A property of certain materials that exhibit zero electrical resistance below a critical temperature. Importance: Superconductors are used in applications like MRI machines, particle accelerators, and power transmission. 8  1. Electrical Properties of Materials 5. Factors Influencing Electrical Properties Temperature: Generally, conductivity increases with temperature in metals, while it decreases in semiconductors. Frequency: In AC applications, the frequency of the electric field can influence the dielectric properties of materials. (ex. Bioimpedance) Ability to penetrate the high frequency current into the intracellular medium Low frequency High frequency 9 6. Applications Conductors: Used in electrical wiring, circuit boards, and connectors. Insulators: Essential for safety and efficiency in electrical systems, preventing unintended current flow. Capacitors and Resistors: Dielectric materials and resistive components are key in electronic circuits. Understanding the electrical properties of materials is crucial for designing and selecting materials used in electrical and electronic applications, ensuring performance and safety. 10 1. Electrical Properties of Materials  We can distinguish between: ⚫ Electrical conductivity: metals. ⚫ Electrical insulation: plastic, wood, stone, ceramics 11 2. Magnetic Properties of Materials The magnetic properties of materials describe how they respond to magnetic fields. Here are the key magnetic properties: 1. Magnetic Susceptibility Definition: A measure of how much a material will become magnetized in an external magnetic field. 2. Magnetic Permeability Definition: The ability of a material to support the formation of a magnetic field within itself. Importance: Determines how well a material can conduct magnetic lines of force. 3. Types of Magnetic Materials Ferromagnetic Materials: Exhibit strong magnetization and retain magnetic properties after the external field is removed (e.g., iron, cobalt). Paramagnetic Materials: Weakly attracted by a magnetic field and do not retain magnetization (e.g., aluminum, platinum). 12  2. Magnetic Properties of Materials 4. Coercivity Definition: The resistance of a ferromagnetic material to becoming demagnetized. Importance: High coercivity materials are used in permanent magnets. 5. Remanence Definition: The magnetization remaining in a material after an external magnetic field is removed. Importance: Important for applications requiring permanent magnets. 6. Magnetic Domains Definition: Small regions within ferromagnetic materials where the magnetic moments are aligned. Importance: The alignment of these domains determines the overall magnetic properties of the material. 13 2. Magnetic Properties of Materials Applications Electronics: Used in transformers, inductors, and magnetic storage devices (e.g., hard drives). Motors and Generators: Magnetic materials are essential for converting electrical energy to mechanical energy and vice versa. Medical Imaging: Magnetic resonance imaging (MRI) relies on specific magnetic properties of materials. Understanding the magnetic properties of materials is essential for designing and selecting materials for various applications in electronics, power generation, and medical technologies. 14  3. Optical Properties The optical properties of materials describe how they interact with light and other electromagnetic radiation. Here are the key optical properties: 1. Refractive Index Definition: A measure of how much light is bent, or refracted, when entering a material. Formula: n = c / v​ where n is the refractive index, c is the speed of light in vacuum, and v is the speed of light in the material. Importance: Determines how materials are used in lenses, optical fibers, and coatings. 15 3. Optical Properties: Light refraction Diopter A diopter is a transparent surface separating two medium with different index of refraction. n1 Diopter n2 Refraction index ni of a medium ni is the ratio of the speed of light C in a vacuum to the speed of light V in the medium ni = C/V 16 Speed of light in different media 17 3. Optical Properties: Light refraction P Q OP: incidence ray OQ: reflected ray θ1 OR: refracted ray Diopter θ2 R Θ2: angle of refraction n1.sin θ1 = n2.sin θ2 18 Light refraction - Critical angle θc n1.sin θ1 = n2.sin θ2 Sin θ2 = (n1/n2) sin θ1 Critical angle θc Θ2 = 90° then θ1 = θc If θ1 > θc : no refracted ray : total reflection 19 Exercise Determine θc for the diopter glass / air n1 (glass) = 1.5 ; n2 (air) = 1 n1.sin θ1 = n2.sin θ2 ➔sin θ1 = (n2/n1) sin θ2 = (1/1.5) * sin θ2 = 0.67 sin θ2 ➔Critical angle if Θ2 = 90° then θ1 = θc ➔sin θ2 = 1 ➔ sin θ1 = 0.67 ➔ θ1 = θc = 42.07o 20 3. Optical Properties 2. Absorbance Definition: The capacity of a material to absorb light, preventing it from passing through. Importance: High absorbance materials are used in applications like solar panels and coatings to minimize glare. 3. Transmittance Definition: The fraction of incident light that passes through a material. Importance: Materials with high transmittance are essential in applications like windows, screens, and optical devices. 4. Scattering Definition: The process by which light is redirected in different directions when it encounters small particles or irregularities in a material. Importance: Scattering affects the clarity and color of materials, influencing applications like fog lights and display screens. 21 3. Optical Properties 5. Reflectance Definition: The fraction of light that is reflected off the surface of a material. Importance: High reflectance materials are used in mirrors and reflective coatings. 6. Luminescence Definition: The emission of light from a material that has absorbed photons, which can occur through various mechanisms (e.g., fluorescence, phosphorescence). Applications: Used in lighting, displays, and glow-in-the-dark materials. 22 3. Optical Properties Applications Optical Devices: Lenses, prisms, and optical fibers rely on specific optical properties to function effectively. Display Technologies: Understanding these properties is crucial for screens, projectors, and lighting systems. Coatings: Anti-reflective and reflective coatings are designed based on optical properties to enhance performance. Understanding the optical properties of materials is essential for the development of various technologies, including telecommunications, imaging systems, and consumer electronics. 23  3. Optical Properties  Can you see light through a material? ⚫ Opaque: Light don’t pass. Wood & Metals. ⚫ Translucent: Light passes, but we cannot see objects behind them clearly. Some types of glass and plastic. ⚫ Transparent: We can see perfectly through them: Glass and some plastics. Transparent Translucent Opaque 24