B.V.M. Engineering College MSM Level of structure & Structure Property correlationship : Adodariya Shyam : Amit Chaudhary : Andhariya Jeet : Anuj Suthar

Technological Relevance Materials scientists and engineers have developed a set of instruments in order to characterize the structure of materials at various length scales. The features of the structure at each of these levels may have distinct and profound influences on a material’s properties and behaviour.

The goal to examine atomic structure (the nucleus consisting of protons and neutrons and the electrons surrounding the nucleus) in order to lay a foundation for understanding how atomic structure affects the properties, behaviour, and resulting applications of engineering materials. The structure of atoms affects the types of bonds that hold materials together.

Similarly, resolution refers to the fineness of details that is disclosed or revealed. Thus, details that are disclosed at certain level of observation will be different from those disclosed at some other level depending upon the measures. Engineers and scientists concerned with the development and practical applications of materials must understand the various types of structure. The knowledge about structures is useful for predicting or modifying properties of materials.

Level of Structure We can examine and describe the structure of materials at five different levels: 1.Macrostructure 2.Microstructure 3.Substructure 4.Crystal Structure 5.Electronic Structure and Nuclear Structure

Macrostructure The macrostructure of continuously cast copper (99.95% pure), etched, ∅ ≈ 83 mm.

Macrostructure of material can be examined with naked eye or by using a low magnification physical aid. The external appearance of material is due to the internal symmetry of crystals forming it. Length of scale for this level is approximately greater than 1000 nm at which features like porosity, surface coatings, internal or external cracks, fractured surfaces slag inclusions, materials' flow lines, segregation, heat affected zone, etc. can be observed.

Microstructure Micrograph of stainless steel showing grains and grain boundaries.

Substructure

Crystal structure

Crystal structure provides details of the atomic arrangement within a crystal. If arrangement of a few atoms which is called as unit cell, is studied then this information is sufficient to predict the atomic arrangement within the whole crystal, because a crystal consists of very large number of unit cells arranged in regularly repeating pattern in all the three dimensions.

The technique used for determining crystal structure is the x-ray diffraction technique. Thus, crystal structure means arrangement of atoms in three dimensional patterns; for example simple cubic structure, body centered cubic structure or hexagonal close packed structure etc.

Electronic structure This usually refers to the electrons in the outer most orbital of individual atoms making the solids. Spectroscopic techniques are used to determine the electronic structure. This study provides information about properties decided by the outer most valance electrons, such as electrical properties, magnetic properties, optical properties or even chemical bonding.

Nuclear structure: This structure is studied by spectroscopic techniques, such as nuclear magnetic resonance (NMR) and Mossbauer studies. In this, information regarding nucleus of atom can be studied in terms of the number of protons and neutrons and be utilized a nuclear science and nuclear physics.

Structure-Property Correlationship Properties of materials originate due to the internal structure which is related to the specific arrangement of atoms and their neighbors. Apart from this atomic level, materials also have sub atomic particles like electrons, protons, and neutrons; these particles, particularly electrons, also affect the properties of materials. Here, property means a specific response evoked/ offered by material against any imposed external stimuli. (Properties of materials are defined independent of size and shape of materials.)

In addition to the structures and properties, to other important components are involved in the material science and engineering of materials- namely. processing and performance. The structure of a material (product) depends, upon how it is processed. And material's performance will be a function of its properties. Thus, the inter relationship among processing, structure, properties and performance is linear. This relationship helps design, production and utilization of materials.

Properties off Metals based on structure

A metal is a lattice of positive metal 'ions' in a 'sea' of delocalised electrons. Metallic bonding refers to the interaction between the delocalised electrons and the metal nuclei. The physical properties of metals are the result of the delocalisation of the electrons involved in metallic bonding.

The physical properties of solid metals are: conduct heat conduct electricity generally high melting and boiling points strong malleable (can be hammered or pressed out of shape without breaking) ductile (able to be drawn into a wire) metallic lustre opaque (reflect light)

Properties of Polymers They consist of carbon, hydrogen, oxygen, nitrogen, or other nonmetallic elements bonded by strong covalent bonds. Three dimensional model of polyethylene

Properties of polymers are: 1.Light weight 2.Soft 3.Flammable 4.Good mouldability 5.Flexible 6.Poor conductor of electricity and heat Properties of polymers differs from metals and ceramics because of the unique, strong covalent bond they have.

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