Classification of Materials - Metals, Ceramics, Polymers, Composites, Semiconductors, Biomaterials

Classification of materials
Classification of Materials

Hi everyone, welcome to this topic on Introduction to material science and engineering. In today's topic we will see the classification of materials. What are the different categories under which a given material can be put to and what are the basic properties and differences amongst each other. Here initially let me jot down all the different categories of materials the first is metals. As you might know a majority of the elements in the periodic table fall under the category of metals and by metal I do not mean just metal as in iron or magnesium. This also refers to the alloys associated with the metal. So steel will also be put under the metal category, then we have something known as ceramics. Ceramics by the day-to-day you might be knowing that clay pottery is and those things are ceramics. But in fact the materials which fall under the ceramic category are much more diverse group. We'll see about that then, what we had know as polymers the most prominent one are the polythene sand plastics which is used to carry day-to-day items though that is environmentally not friendly. So it's not advised to do so then we have what is known as composite materials, something known as semiconductors and biomaterials. So the initial four of them the metal ceramic polymer and composite are the most broad categorization of the materials. Semiconductor kind of fits into this scope are the biomaterials so basically these things are a subgroup. Let's say but mainly we have what is known as metal ceramic polymer composite. 

Metals in Classification of Materials

Now let us pick each of them one by one and see to begin with metals in classification of materials the most prominent property of metal that the electrons in a metal are non-localized. When we will discuss about the atomic arrangement of electrons protons and neutrons we will see that the metals have what is known as non localized electrons. The outer valence electrons do not belong to individual atom rather it belongs to the whole bulk of the material and this non localized electron kind of gives the properties to the material. So influences the properties then we have what is known as good conductor. Since there is non localized electron those electrons are free to carry charge. Thereby conduct electricity that is a trademark property of metals. Metals normally have a lustrous appearance that is they are more on the signee side. These four are very basic properties.

Ceramics in Classification of Materials

There are many more properties of metals which we'll explore in details in further chapters. But to give you at least this are kind of the properties then ceramics. Ceramics in classification of materials are mainly oxides nitrides and carbides. So if you have some oxide zirconium dye boride varieties are also ceramics or carbide. Those things and fall under the ceramic category. Then we have insulating properties so ceramics are normally non conductors or they are very good insulators. Thereby a lot of application of ceramic is in the field where they need to be insulation from electricity or insulation from heat. But there is also extremely important conducting properties under different circumstances and those things we will see in details later. Ceramics are hard and brittle they have a very high hardness and they break easily. If you drop a ceramic material the chances are high that it will break immediately. 

Polymers in Classification of Materials

Let's discuss about polymers in classification of materials, polymers are mainly made of comfort of organic molecules. Some of the examples of polymer can be rubber and plastic. These are day-to-day examples which you encounter every day. But the extent to which polymers are being used is much more broader than just rubber and plastic. Polymers are normally very large change molecules. The molecules are not small molecules they are quite large and that makes the molecules bulky. They have a very high molecular weight and polymers are normally low-density materials. They are not very compact the molecules are not compactly packed. Thereby their density is low and polymers mostly are flexible materials. Need not be the case always but generally speaking they are on the flexible side compared to ceramics materials or metals. 

Composites in Classification of Materials

Let's see water composite in classification of materials till now what we have seen is at all the three metals. Ceramics and polymers are made out of one type of material. But composites are made of more than one material, they might have two metals. Let's say but they might have a metal and a ceramic. They might have a metal and a polymer or any combination. Thereof it may have more than two material. What is the reason of using more than one material? Suppose you have one material which has very high strength and you have another material which is quite flexible. But the first material is not flexible and second material does not have a high strength. So what you can do is you can combine the two materials and get a moderately good flexibility while retaining a moderately good strength. Depending on the application you can find combinations of materials which gives you the relevant properties. You need for the application that is the power that composite material provides us with. Basically composite materials provide best property of constituent material and one simple example is concrete that is used for house building that has Grable sand cement and water. There are different materials you see and those each material brings a inherent property with itself and they combined together to give our required application. The binding property of the whole concrete system. Now we have seen the four broad classifications of materials.

Semiconductor in Classification of Materials

Let us jump into the two kind of subcategories of material one is semiconductor in classification of materials as the name suggests and a semiconductor is a material which has intermediate conductivity. They are not as good conductor as metals but they are not a insulator and this semi conductivity of the material has interesting applications. Especially in the integrated chip system or the electronic area you need to control the amount of conduction that takes place and semiconductors give you precisely that control. How can you control a material which is a semiconductor. Let us say for example, silicon has a certain conductivity but by something what is known as doping? Adding different element to the silicon base in very controlled amount can help you fine tune the amount of conductivity you want to provide in the material. So semiconductors are basically very good at adjusting the amount of conductivity. Based on the amount of additional element you dope into that material, that gives you a fine tuned way to control conductivity and obviously this has brought about the integrated chip revolution. Which is kind of the modern revolution in the sense that all the electronic gadgets you see today is due to this semiconductor industry. 

Biomaterials in Classification of Materials

Finally let us discuss briefly about biomaterials in classification of materials. Now water biomaterials exact definition is that these are materials which are compatible this body, mainly in our case with the human body. Let's say there is a need for knee surgery replacement of the knee or the hip bone. When you are inserting something into the body like the hip joint, that new material introduced to the body should be biocompatible or it should be compatible with your body. Else it will degrade inside the body and that will lead to a very tragic condition inside the body, which can eventually lead to even death. Such materials which is compatible with the body and which can be placed inside the body safely are known as biomaterials. This has a wide application as you can think. In the medical area mainly used in implants as I explained about it. It can be any of the above five on mainly the four categories that is metal, ceramic, polymer or composite not necessarily. A semiconductor itself falls under a combination of these categories. This gives you a broad picture about what are the different kinds of materials. In this topic we mainly focus on metals and metal alloys but we'll have discussions on ceramics composite and polymer too because, they are interesting topics. But they in themselves are much wider topics and can be offered on each of them individually with this classification. 

Let's see what the future demands in the area of material science and engineering. Till now, what we have seen, the history about material science and engineering. How did it come about into being water the present applications of it and then we saw different kinds of material. Now what is the future of it one very simple thing which you can on your own-self is that sophisticated materials while maintaining the environment. What do I mean by this we need to keep on coming with new materials fit ever-increasing demand of new applications. Ever-increasing demand in terms of strength our particular electrical application or magnetic application. We need to keep coming up with new and better materials so that what sophisticated material means and maintaining environment global climate change is a very important thing that needs to be taken into consideration and we need to work towards maintaining the environment while making our own life better. We need to create the materials in such a way that the materials in itself do not harm the environment or while manufacturing the material. The environment is harmed as less as possible. The nuclear revolution needs new materials. What is the nuclear revolution? Till date our source of energy is mainly from the coal industry. There are renewable sources of energy being generated and used of late with knowledge about how much harm hold us to the environment burning coal and stuff. But still one of the most important area which is not yet tapped into is the nuclear. The regime it's being used but not to its full extent. The nuclear revolution needs to take place that's the source of infinitely large amount of energy but it's a very risky deal. So new and sophisticated materials which can withstand very harsh conditions and which can protect us from nuclear radiations. Such things needs to be come up with so that is a challenging field which is one of the futures of material science and engineering. You need to bring about ingenious noble ideas to deal with this problem then the transportation sector. The whole transportation sector is a game where you are trying to reduce the weight thereby increasing the efficiency of the vehicles which is one of the most important research area. The for weight reduction is one of the most prominent ideas that we need to be working on and in fact a lot of research is going on in that field. This is actually a very well-known field which is already being explored into but, which has a lot of future prospect to solar technology. As I mentioned about the energy we keep coming back to energy why because that is direct relevance with the climate change. 

What is Solar Technology?

So coming to solar technology, solar technology is already being put to use. There are a lot of things that are running on day to day scale using the solar technology but do you know what is the main problem with solar technology. The main problem is that the efficiency of the materials which we have at present to capture the solar radiations is very low. It's in the range of around 20%. We are actually not utilizing the solar energy as much as we can. We need to find new materials and new ways to harness the efficiency much higher than 20% or even a little higher than 20% that is also going to give a lot of increase in the energy input. Through the solar technologies work needs to be done in that field. Then coming back to the metals point metal extraction methods. Metals normally except for the noble metals do not lie around in the Earth's crust. You need to dig out the poor and then put it through extraction processes and then the metal is obtained from it. But this is a highly energy intensive property, a lot of energy goes into extraction of metals or different materials. However needs to be done in finding methods which reduces the amount of energy required and finally new material development. What I mean is that there is need of materials which we even do not know what kind of materials future will demand. New things to be developed and accordingly new materials need to be developed. This is the zone of uncertainty that there in the material science and engineering domain but the exciting thing about it that you get to do things with you do not even know today.  So to sum up the future demands as you can see is mainly focused on the energy sector directly or indirectly. In addition to that new and sophisticated material development is also a broad field where the future of materials engineering. So hopefully today's topic gave you an understanding about the different categories of material and what the future demands us and where the future of material science and engineering lie. 

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