MATSE 81
Materials in Today's World

Classification of Materials

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Matter is composed of solid, liquid, gas, and plasma. In this course, we are going to be looking at solids which we will break down into three classical sub-classifications: metals, ceramics, and polymers. 

In the reading for this lesson, representative characteristics of the three sub-classifications will be presented. In lesson three the chemical makeup and atomic structure will be further explored. The microstructure of the three classifications will be explored in their lessons. 

Composites is a special additional classical sub-classification. Composites are composed of two (or more) distinct materials (metals, ceramics, and polymers) to achieve a combination of properties. Composites are introduced in this lesson in the reading and we will have a later lesson devoted to them as well. (Note: composites should not be confused with alloys. We will learn later that alloys are a mixing of a metal with other elements. In an alloy the elements are blended, they are no longer distinct components.)

Advanced materials are materials that are utilized in high-tech applications. These materials are typically enhanced or designed to be high-performance materials - many times with very specific tasks in mind. 

Semiconductors are materials that can be made to switch from an insulator (off) to a conductor (on) by the application of voltage. The flow of electrons in semiconductors is somewhere between insulators, i.e., those that do not readily conduct electricity; and conductors, those materials which freely allow the flow of electrons. These materials have enabled our digital electronic age. The development of semiconductors for integrated circuits has allowed for the electronics and computer revolution that we have experienced in the last 50 years. 

Nanomaterial, whose sizes typically range from 1 to 100 nanometers, are materials in which size and/or geometry can play a significant role in the dominant materials properties. In this size range, quantum mechanical effects can dominate, as well as, chemistry due to a large number of the atoms being surface atoms instead of atoms in bulk. In addition to size effects, these materials sometimes exhibit unique functionality due to their geometry. For example, gold nanoparticles can be very chemically active, unlike bulk gold. This effect is due to a large number of unsatisfied bonds on the surface of the gold nanoparticle. 

Biomaterials are materials implanted into the body. In addition to performing their design function, they also have to have the ability to survive in the body (be biocompatible). The body can be a 'hostile' environment for materials. The body might attack the biomaterial as a foreign body (immune response) and the environment (wet and chemically active) in the body is typically one that leads to corrosion. 

Smart materials are materials that are designed to mimic biological behavior. They are materials that, like biological systems, ‘respond to stimuli.' When determining whether a material system is utilizing a smart material, it is usually useful to identify the stimuli and the response that the material will exhibit, as well as, what biological system it is mimicking.

The readings and videos in the last two lessons of this course will explore advanced materials in more detail. Now that I have set the stage it is time for you to begin the additional reading for this lesson.