Introduction to Materials Science and Engineering PDF

Introduction  Material Science  Involves determining the relationship between the structures and properties of materials  A material scientist tries to determine the relationship of material properties to the response of the material  For example, what is the relationship between...

Introduction  Material Science  Involves determining the relationship between the structures and properties of materials  A material scientist tries to determine the relationship of material properties to the response of the material  For example, what is the relationship between the pressure and temperature of a material?  Materials Engineering  Study on the process of creating or designing a new material based on an existing material with similar properties  Materials Engineer  Tries to create a new material with the desired properties based on an existing material with similar properties  For example, car window glasses previously breaks into splinters causing severe injury. To make the glass safer, the glass is tempered by increasing its internal stress such that when broken, will crumble into granular chunks  Microscopic vs. Macroscopic  Microscopic structure is defined as the material structure that can be seen with microscopes such as  Optical microscope  Scanning electron microscope  Atomic force microscope  Macroscopic structure is defined as structures that can be seen by unaided eye  Structure of a Material  The structure of a material usually relates to the arrangement of its internal components.  For example, materials are composed of atoms that may have specific atomic configuration (e.g. crystalline or noncrystalline)  Properties of a Material  Defined as the characteristic of a material that differentiate it from other materials. It is independent on its size and shape  Material properties are grouped into six:  Mechanical  Electrical  Thermal  Optical  Magnetic  Deteriorative  Mechanical properties relate deformation to an applied load or force  Electrical properties, such as electrical conductivity and dielectric constant, the stimulus is an electric field  Thermal behavior of solids can be represented in terms of heat capacity and thermal conductivity  Magnetic properties demonstrate the response of a material to the application of a magnetic field.  Optical properties, the stimulus is electromagnetic or light radiation  Deteriorative characteristics relate to the chemical reactivity of materials. Four Components of Materials  The structure of a material depends on how it is made or processed while the performance of the material depends on its properties. The four components of a material are interrelated:  For example, even though graphite and diamond are made up of carbon atoms, they are processed differently to produce a different material Why Study Materials?  For the engineer and scientist, it is necessary to study materials to enable to select the necessary material for a specific purpose  Usually there is a tradeoff between one characteristic to another  For example, a ductile material have limited strength and vice versa. Therefore, as an engineer, it is necessary not only to know the right specifications but also the limitation induced by the increased performance of the material  Deterioration of material property is also important. For example, if you have a beach house, you need to determine if the roof of the house is highly resistant to corrosive attack. Note that salt is corrosive that can shorten the lifetime of your roof  You need to have basic knowledge about the economic consideration of creating or replacing traditional materials  For example, solar panels are very effective in replacing electrical sources but they are very expensive. Return of investment will usuall be around 15 years.  Buying expensive leather shoes might be cheaper in the long run compared with buying cheaper synthetic leather shoes  The more familiar you are with the various characteristics and structure–property relationships, as well as processing techniques of materials, the more proficient and confident you will be to make judicious materials choices based on these criteria. Classification of Materials  Basic Classification  Metals  Polymers  Ceramics  Advance Materials  Composites  Semiconductors  Biomaterials  Metals  Metals includes Cu, Fe, Al, Zn  Metallic alloys includes small amounts of nonmetalllic materials such as carbon, nitrogen and oxygen  In terms of density, metals are denser than ceramics and polymers. Bar-chart of room temperature density values for various metals, ceramics, polymers, and composite materials Bar-chart of room temperature stiffness Bar-chart of room temperature strength Bar-chart of room-temperature resistance to fracture Bar-chart of room temperature electrical conductivity ranges  Ceramics  Ceramics are compounds between metallic and nonmetallic elements  They are most frequently oxides, nitrides, and carbides  Examples includes:  Porcelain  Glass  Tiles  Alumina  Silica  Ceramics are relatively stiff , strong and hard  However, they are brittle and easy to fracture  Insulators and more resistant to heat and harsh environment compared with metals and polymers  Polymers  Polymers include the familiar plastic and rubber materials  Chemically based on carbon, hydrogen and other nonmetallic elements like oxygen, nitrogen and silicon  Examples are  Polyethylene  Nylon  Polyvinyl chloride (PVC)  Polystyrene (styrofoam)  Rubber  Polymers usually have low densities  Not stiff nor as strong as ceramics and metals  Ductile and pliable  Inert and unreactive to most harsh environment  One major drawback of polymers is its low melting temperature  Knowledge Application  What are the Pros and Cons in the container of most carbonated drinks?  There are 3 kinds of containers used in most carbonated drinks:  Glass bottles (Ceramics)  Plastic bottles (Polymer)  Aluminum cans (Metal)  Glass bottles have the following advantages:  Can able to store the carbon dioxide in the beverage for longer times  Cheaper than Aluminum cans  The disadvantage is it can easily breaks and heavier than the other containers  Aluminum cans are lighter and quickly cools. It can easily be recycled and can paint the surface. However, it is more expensive  Plastic containers are relatively cheaper than aluminum cans but can only store the carbon dioxide at shorter times  Composites  Composite is composed of two (or more) individual materials, which come from either metals, ceramics, and polymers  Examples are:  Fiberglass or Glass fiber reinforced polymer (GFRP)  Composed of glass fibers in epoxy or polyester  Carbon fiber reinforced polymer (CFRP)  Carbon fiber in epoxy or polyester. Better than fiberglass but more expensive