Importance of Engineering Materials in Present World (PDF)

International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Index Copernicus Value (2015): 78.96 | Impact Factor (2015): 6.391 termed as the thermal conductivity. The higher the to their exce...

International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Index Copernicus Value (2015): 78.96 | Impact Factor (2015): 6.391 termed as the thermal conductivity. The higher the to their excellent magnetic properties alongwith their high value of thermal conductivity, the greater is the rate at electrical resistivity these materials today, find use in a which heat will be transferred through a piece of variety of applications like magnetic recording tapes, given size. Copper and aluminum are good inductors and transformers, memory elements, microwave conductors of heat and therefore, extensively used devices, bubble domain devices, recording hard cores, etc. whenever transfer of heat is desired. Bakelite is a Hysteresis, permeability and coercive forces are some of the magnetic properties of magnetic substances which are to be poor conductor of heat and hence used as heat considered for the manufacture of transformers and other insulator. The heat flow through an area A which is electronic components. perpendicular to the direction of flow is directly proportional to the area (A) and thermal gradient 4) Electrical Properties- Electrical conductivity, (dt/dx). resistivity, dielectric strength, the stimulus is an electric c) Thermal Expansion: All solids expand on heating field are few important electrical properties of a material. and contract on cooling. Thermal expansion may take A material which offers little resistance to the passage of place as linear, circumferential or cubical. A solid an electric current is said to be a good conductor of which expands equally in three mutually orthogonal electricity. The electrical resistance of a material depends directions is termed as thermally isotropic. The on its dimensions and is given by: Usually resistivity of a increase in any linear dimension of a solid, e.g. material is quoted in the literature. Unit of resistivity is length, width, height on heating is termed as linear Ohm-metre. On the basis of electrical resistivity expansion. The coefficient of linear expansion is the materials are divided as: a) Conductors increase in length per unit length per degree rise in b) Semiconductors temperature. The increase in volume of a solid on c) Insulators. heating is called cubical expansion. The thermal In general metals are good conductors. Insulators have very expansion of solids has its origin in the lattice high resistivity. Ceramic insulators are most common vibration and lattice vibrations increases with the rise examples and are used on automobile spark plugs, Bakelite in temperature. Obviously, the thermal conductivity handles for electric iron, plastic coverings on cables in (K) and electrical conductivity (σ) vary in the same domestic wiring. fashion from one material to another. d) Thermal Resistance (RT): It is the resistance offered 5) Optical properties - The optical properties of materials, by the conductor when heat flow due to temperature e.g. refractive index, reflectivity and absorption difference between two points of a conductor. It is coefficient etc. affect the light reflection and transmission given by: where H _ rate of heat flow and ᶿ1 and ᶿ2 the stimulus is electromagnetic or light radiation. are temperatures at two points (°C). e) Thermal Diffusivity (h): It is given by: A material 6) Chemical Properties -These properties includes atomic having high heat requirement per unit volume weight, molecular weight, atomic number, valency, chemical composition, acidity, alkalinity, etc. These possesses a low thermal diffusivity because, more properties govern the selection of materials particularly heat must be added to or removed from the material in Chemical plant. Deteriorative characteristics relate to for effecting a temperature change. the chemical reactivity of materials. In addition to f) Thermal Fatigue: This is the mechanical effect of structure and properties, two other important components repeated thermal stresses caused by repeated heating are involved in the science and engineering of and cooling. The thermal stresses can be very large, materials— namely, ―processing‖ ―performance.With involving considerable plastic flow. We can see that regard to the relationships of these four components, the fatigue failures can occur after relatively few cycles. structure of a material will depend on how it is The effect of the high part of the temperature cycle on processed. Furthermore, a material‗s performance will be the strength of material plays an important factor in a function of its properties. reducing its life under thermal fatigue. 3. Classification of Materials in Engineering 3) Magnetic properties demonstrate the response of a material to the application of a magnetic field. Materials The traditional method is to classify them according to their in which a state of magnetism can be induced are termed nature into metals, ceramics, polymers and composites. The magnetic materials. There are five classes into which factors which form the basis of various systems of magnetic materials may be grouped: classifications of materials in material science and (i) diamagnetic engineering are: (ii) paramagnetic 1. The chemical composition of the material, (iii) ferromagnetic 2. The mode of the occurrence of the material in the nature, (iv) antiferromagnetic 3. The refining and the manufacturing process to which the material is subjected to prior to acquiring the required (v) ferrimagnetic. properties, Iron, Cobalt, Nickel and some of their alloys and compounds 4. The atomic and crystalline structure of material and possess spontaneous magnetisation. Magnetic oxides like 5. The industrial and technical use of the material. ferrites and garnets could be used at high frequencies. Due Volume 6 Issue 3, March 2017 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Paper ID: ART20171428 435  International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Index Copernicus Value (2015): 78.96 | Impact Factor (2015): 6.391 Common engineering materials that fall within the scope of 3) Ferrous Metals: Iron is the principal constituent of these material science and engineering may be classified into one ferrous metals. Ferrous alloys contain significant amount of the following six groups: of non-ferrous metals. Ferrous alloys are extremely 1. Metals (ferrous and non-ferrous) and alloys important for engineering purposes. On the basis of the 2. Ceramics percentage of carbon and their alloying elements present, 3. Organic Polymers these can be classified into following groups: 4. Composites including Wood materials (a) Mild Steels: The percentage of carbon in these 5. Semi-conductors materials range from 0.15 % to 0.25 %. These are 6. Biomaterials 7. Advanced Materials moderately strong and have good weldability. The production cost of these materials is also low. 3.1 Metals and alloys are inorganic materials composed of (b) Medium Carbon Steels: These contains carbon one or more metallic elements. They may also contain a between 0.3 % to 0.6 %. The strength of these small number of non-metallic elements. All the elements are materials is high but their weldability is broadly divided into metals and non-metals according to comparatively less. their properties. Metals are element substances which readily (c) High Carbon Steels: These contains carbon varying give up electrons to form metallic bonds and conduct from 0.65 % to 1.5 %. These materials get hard and electricity. Some of the important basic properties of metals tough by heat treatment and their weldability is poor. are: The steel formed in which carbon content is up to 1.5 a) Metals are usually good electrical and thermal %, silica up to 0.5%, and manganese up to 1.5 % conductors, along with traces of other elements is called plain b) At ordinary temperature metals are usually solid, c) To some extent metals are malleable and ductile, carbon steel. d) The freshly cut surfaces of metals are lustrous, (d) Cast Irons: The carbon content in these substances e) When struck metal produce typical sound, and vary between 2 % to 4%. The cost of production of f) Most of the metals form alloys - When two or more pure these substances is quite low and these are used as metals are melted together to form a new metal whose ferrous casting alloys. properties are quite different from those of original 4) Non-Ferrous Metals: Out of several non-ferrous metals metals, it is called an alloy. only seven are available in sufficient quantity reasonably at low cost and used as common engineering metals. Metals usually have a crystalline structure and are good These are aluminum, tin, copper, nickel, zinc and thermal and electrical conductors. Many metals are strong magnesium. Some other non-ferrous metals, about and ductile at room temperature and maintain good strength fourteen in number, are produced in relatively small at high and low temperatures. Metallic materials possess quantities but these are of vital importance in modern specific properties like plasticity and strength. Few industry. These include chromium, mercury, cobalt, favourable characteristics of metallic materials are high lustre, hardness, resistance to corrosion, good thermal and tungsten, vanadium, molybdenum, antimony, cadmium, electrical conductivity, malleability, stiffness, the property zirconium, beryllium, niobium, titanium, tantalum and of magnetism, etc. Metals may be magnetic, non-magnetic manganese. in nature. 5) Sintered Metals: These materials possess very different properties and structures as compared to the metals from These properties of metallic materials are due to: which these substances have been cast. Powder 1) The atoms of which these metallic materials are metallurgy technique is used to produce sintered metals. composed The metals to be sintered are first obtained in powered 2) The way in which these atoms are arranged in the space form and then mixed in right calculated proportions. lattice. After mixing properly, they are put in the die of desired shape and then processed with certain pressure. Finally, Metallic materials are typically classified according to their one gets them sintered in the furnace. use in engineering as under: 6) Clad Metals: A sandwich ‗of two materials is prepared 1) Pure Metals: They are obtained by refining the ore. in order to avail the advantage of the properties of both Mostly, pure metals are not of any use to the engineers. the materials. This technique is termed as cladding. However, by specialised and very expensive techniques, Using this technique stainless steel is mostly embedded one can obtain pure metals (purity ~ 99.99 %), e.g. with a thick layer of mild steel, by rolling the two metals aluminum, copper, etc. together while they are red hot. This technique will not 2) Alloyed Metals: Alloys can be formed by blending two allow corrosion of one surface. Another example of the or more metals or at least one being metal. The properties use of this technique is cladding of duralumin with thin of an alloy can be totally different from its constituent sheets of pure aluminum. The surface layers, i.e. outside substances, e.g. 18-8 stainless steel, which contains 18 layers of aluminum resist corrosion, whereas inner layer %, chromium and 8 % nickel, in low carbon steel, carbon of duralumin imparts high strength. This technique is is less than 0.15 % and this is extremely tough, relatively cheap to manufacture. exceedingly ductile and highly resistant to corrosion. Volume 6 Issue 3, March 2017 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Paper ID: ART20171428 436  International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Index Copernicus Value (2015): 78.96 | Impact Factor (2015): 6.391 3.2 Ceramics are inorganic materials consisting of both 4. The Importance of Engineering Materials in metallic and non-metallic elements bonded together Our Present World chemically. Ceramics can be crystalline, non-crystalline or a mixture of both. Generally, they have high melting points Development of new materials has followed a number of and high chemical stabilities. They also have high hardness different pathways, depending on both the nature of the and high temperature strength but tend to be brittle. problem being pursued and the means of investigation. Ceramics are usually poor electrical conductors. Breakthroughs in the discovery of new materials have ranged from pure serendipity, to trial-and-error approaches, 3.3Polymers are organic materials which consist of long to design by analogy to existing systems. These molecular chains or networks containing carbon. Most methodologies will remain important in the development of polymers are non-crystalline, but some consist of mixtures materials but as the challenges and requirements for new of both crystalline and non-crystalline regions. They materials become more complex, the need to design and typically have low densities and are mechanically flexible. develop new materials from the molecular scale through the Their mechanical properties may vary considerably. Most macroscopic final product will become increasingly polymers are poor electric conductors due to the nature of important. The use of molecular modeling and the the atomic bonding. engineering of new materials into useable forms or devices are of particular importance. 3.4 Composites are mixtures of two or more types of materials. The constituent elements in a composite retain 4.1 Current Trends and Advances in Materials their identities (they do not dissolve or merge completely into each other) while acting in concert to provide a host of Timber, steel and cement are the materials which are widely benefits such as light weight, high strength, corrosion used for engineering applications in huge quantities. The resistant, high strength-to-weight ratio, directional strength - consumption of steel in any country is considered as an tailor mechanical properties, high impact strength, high indicator of its economic well being. For high temperature electric strength (insulator), radar transparent, non-magnetic, applications. Newer materials for combined resistance to low maintenance, long-term durability, parts consolidation, high temperature and corrosion are increasing rapidly and dimensional stability, small to large part geometry – material scientists and engineers are busy in developing such styling/design – sculptural form, customized surface finish, materials. Different kinds of ceramics, though difficult to rapid installation. Usually, they consist of a matrix phase shape and machine, are finding demand for their use at high and a reinforcing phase. They are designed to ensure a temperatures. Recently prepared new metallic materials in combination of the best properties of each of the component conjunction with new processing techniques as isostatic materials. There is also an increasing trend to classify pressing and isothermal forging are capable of imparting engineering materials into two further categories: structural better fatigue properties to aircraft components. Powder materials and functional materials. Structural materials, as metallurgy technique while producing finished surfaces and the name indicates, are materials used to build structures, cutting down metal cutting cost is much capable of bodies and components. For instance, in a car the body, imparting improved mechanical properties under different frame, wheels, seats, inside lining, engine and various loading conditions. Surprisingly, rapid cooling technology mechanical transmission parts are all constructed from achieving cooling rates in the vicinity of one million degree structural materials. Celsius per second and this is being used to produce metal powders which can be used in such product producing 3.5 Semi-ConductorsThese are the materials which have techniques as powder metallurgy and hot isostatic pressing electrical properties that are intermediate between the to obtain temperature resistant parts. Nowadays, electrical conductors and insulators. The electrical metallurgists have produced several molybdenum and characteristics of semi-conductors are extremely sensitive to aluminium alloys as well as alloys of titanium and nickel to the presence of minute concentrations of impurity atoms; meet anticorrosion properties at elevated temperatures. these concentrations may be controlled over very small Polymeric materials are growing at annual rate of 9% and spatial regions. Semi-conductors form the backbone of have grown in volume more than any other material. In electronic industry. The semi-conductors have made several applications plastics have replaced metals, wood, possible the advent of integrated circuitrythat has totally glass and paper. A new trend in plastic technology is the revolutionized the electronics and computer industries. They production of synergistic plastic alloys which have better affect all walks of life whether it is communications, properties than individual members producing the alloy. computers, biomedical, power, aviation, defence, Recent discovery of plastic conductors may have wider entertainment, etc. The field of semi-conductors is rapidly impact in near future. The major drawback of ceramics is the changing and expected to continue in the next decade. brittleness and difficulty in cutting and shaping. When Organic semi-conductors are expected to play prominent mixed with metal powder like molybdenum, ceramic role during this decade. Diamond as semiconductor will also produce cements, which are expected to be useful cutting be important. Optoelectronic devices will provide three materials. Tool bits of cements are expected to find various dimensional integration of circuits, and optical computing. applications in attaining high cutting speeds and producing better surface finish. Alumina, a well-known ceramic is expected to be successfully reinforced with fibres of molybdenum. Due to micro cracking of molybdenum fibres, the attempts to achieve better strength in such composite ceramics have not been successful yet. However, such Volume 6 Issue 3, March 2017 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Paper ID: ART20171428 437  International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Index Copernicus Value (2015): 78.96 | Impact Factor (2015): 6.391 composites have been found to exhibit better impact and of our lives during this decade with revolution in aviation, thermal shock resistance. pollution control, and industrial processes. 4.2 Further Advances in Materials Development from 4.5 Nano-Structured Materials and Nanotechnology View Point of New and Advanced Materials Nanotechnology is a field that deals with control of Recent development especially from the point of view of structures and devices at atomic, molecular and super- new and advanced materials could be classified into: molecular levels as well as the efficient use and manufacture of these devices. Key areas in Nanotechnology are: 4.3 Advanced Materials 1) Nano-medicine for disease detection and treatment 2) Nano-engineered materials for improved agriculture The materials that are utilised in high-technology (or high- 3) Nanotechnology for energy tech) applications are sometimes called advanced materials. 4) Nano porous materials for water filtration By high technology we mean a device or product that Nanostructured materials are those materials whose operates or functions using relatively intricate and structural elements clusters, crystallites or molecules have sophisticated principles; for example, electronic equipment dimensions in the range of 1-100 nm. These small groups of (VCRs, CD players, etc.), computers, fiber optic systems, atoms, in general, go by different names such as spacecraft, aircraft and military rocketry. These advanced nanoparticles, nanocrystals, quantum dots and quantum materials are typically either traditional materials whose boxes. One finds a remarkable variations in fundamental properties have been enhanced or newly developed high electrical, optical and magnetic properties that occur as one performance materials. Furthermore, advanced materials progresses from an infinitely extended solid to a particle of may be of all material types (e.g., metals, ceramics, and material consisting of a countable number of atoms. The polymers) and are normally relatively expensive. In various types of nanostructured materials which has been subsequent chapters are discussed the properties and considered for applications in opto-electronic devices and applications of a good number of advanced materials—for quantum- optic devices are nano-sized powders of silicon, example, materials that are used for lasers, ICs, magnetic silicon-nitride (SiN), silicon-carbide (SiC) and their thin information storage, liquid crystal displays (LCDs), fiber films. Some of these are also used as advanced ceramics optics, and the thermal projection system for the space with controlled micro structures because, their strength and shuttle orbiter. toughness increase when the grain size diminishes. Carbon- based nanomaterials and nanostructures including fullerenes 4.4 Smart Materials (Materials of the Future) and nanotube plays an increasingly significant role in nanoscale science and technology. Smart or intelligent materials form a group of new materials now being developed that will have a significant influence on many of our technologies. In addition, the concept of smart materials is being extended to rather sophisticated systems that consist of both smart and traditional materials. The field of smart materials attempts to combine the sensor, actuator and the control circuit on as one integrated unit. Actuators may be called upon to change shape, position, natural frequency, or mechanical characteristics in response to changes in temperature, electric fields, and magnetic fields. The combined system of sensor, actuator and control circuit on as one IC unit, emulates a biological system. These are known as smart sensors, microsystem technology Figure 1: nano materials structure (MST) or microelectromechanical systems (MEMS). Materials/devices employed as sensors include optical 4.6 Quantom Dots (QDS) fibers, piezoelectric materials, and MEMS. MEMS devices are small in size, light weight, low cost, reliable with large Rapid progress in the fabrication of semiconductor batch fabrication technology. They generally consist of structures has resulted into the reduction of 3D bulk systems sensors that gather environmental information such as to 2D & 1D, and ultimately to 0D systems. Quantum dots pressure, temperature, acceleration etc., integrated represent the ultimate reduction in the dimensionality of electronics to process the data collected and actuators to semiconductor devices. These are 3D semiconductor influence and control the environment in the desired manner. structures only nanometer in size confining electrons and The MEMS technology involves a large number of holes. QDs operate at the level of single electron which is materials. Silicon forms the backbone of these systems also certainly the ultimate limit for an electronic device and are due to its excellent mechanical properties as well as mature used as the gain material in lasers. QDs are used in quantum micro-fabrication technology including lithography, etching, dot lasers, QD memory devices, QD photo detectors and and bonding. Other materials having piezoelectric, even quantum cryptography. The emission wavelength of a piezoresistive, ferroelectric and other properties are widely quantum dot is a function of its size. So by making dots of used for sensing and actuating functions in conjunction with different sizes, one can create light of different colors. silicon. The field of MEMS is expected to touch all aspects Volume 6 Issue 3, March 2017 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Paper ID: ART20171428 438