Hence to understand the properties of materials it is very important to study

Hence to understand the properties of materials it is

This preview shows page 29 - 32 out of 79 pages.

Hence, to understand the properties of materials, it is very important to study the atomic bonding of materials. Atomic bonds in materials are of following types: (i) Ionic bond formed by exchanging of valence electrons between atoms of metals and non- metals. (ii) Covalent bonds formed by sharing of electrons between atoms of non-metals. (iii) Metallic bonds found in metals. Corrosion Resistance Corrosion is a gradual chemical or electrochemical attack on a metal by its surrounding medium. Due to the corrosion, metal starts to be converted into an oxide, salt or some other compound. Corrosion of a metals is affected by many factors such as air, industrial atmosphere, acid, bases, salt solutions & soils, etc. Corrosion has a very adverse effect on material. Due to corrosion, the strength & life of material is reduced, which results. Corrosion resistance of a material is the ability of a material to resist oxidation in atmospheric condition. Generally pure metals such as iron, copper, aluminium, etc. get corroded slowly in atmosphere. To avoid the corrosion of these metals in pure form, we use these metals in form of alloys such as stainless steel, brass, bronze, German silver, Gunmetal, etc. Acidity or Alkalinity Acidity or Alkalinity is a very important chemical property of engineering materials. A material’s being acetic or alkane, is decided by the ph value of the material. Ph value of material varies from 0 to 14. Ph value of 7 is considered to be neutral. Ordinary water has ph value of 7. Materials which have ph value below 7 are called acetic, and materials which have ph value greater than 7 are called alkanes. Acidity or alkalinity of a material indicates how they will react with other materials.
Image of page 29
~ Page 30 of 79 ~ Electrical Properties of Engineering Materials To finalize the material for an engineering product / application, we should have the knowledge of Electrical properties of materials . The electrical properties of a material are those which determine the ability of material to be suitable for a particular electrical engineering application. Some of the typical electrical properties of engineering materials are listed below: o Resistivity o Conductivity o Temperature coefficient of Resistance o Permittivity o Thermoelectricity Resistivity This is the property of a material which resists the flow of electric current through it. It is the reciprocal of conductivity . It is d ented by ‘ρ’. Resistivity of a material of a conductor can be determined as below: where, ‘R’ is the resistance of conductor in Ω ‘A’ is the cross sectional area of conductor in m 2 ‘l’ is the length of the conductor in meter. SI unit of resistivity of is Ω¦ -meter. Resistivity of some materials is listed below. S/No. Element Resistivity at 20°C in Ω - m 1 Silver 1.59 X 10 -8 2 Copper 1.7 X 10 -8 3 Gold 2.44 X 10 -8 4 Aluminium 2.82 X 10 -8 5 Tungsten 5.6 X 10 -8 6 Iron 1.0 X 10 -7 7 Platinum 1.1 X 10 -7 8 Lead 2.2 X 10 -7 9 Manganin 4.82 X 10 -7 10 Constantan 4.9 X 10 -7 11 Mercury 9.8 X 10 -7 12 Carbon (Graphite) 3.5 X 10 -5 13 Germanium 4.6 X 10 -1 14 Silicon 6.4 X 10 2
Image of page 30
~ Page 31 of 79 ~ 15 Glass 10 10 to 10 14 16 Quartz (fused) 7.5 X 10 17 Conductivity It is the property of a material to allow the flow of electric current.
Image of page 31
Image of page 32

You've reached the end of your free preview.

Want to read all 79 pages?

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors