Refractory materials, Mechanical Engineering

Refractory Materials

These materials are made up of engineering ceramics that are quite expensive in their pure forms. Such materials are also complicated to form. Most industrial refractory materials are made of ceramic of mixture compounds. These compounds are heat resistant caused by their high melting point. Table no.1 illustrates melting point temperatures of various ceramic compounds.

                                                          Table no.1: Melting Points of Some Ceramic Compounds

Compound

Melting Point

(oC)

Titanium Carbide, TiC

3120

Tungsten Carbide, WC

2850

Magnesium Oxide, MgO

2798

Zirconium Dioxide, ZrO2

2700

Silicon Carbide, SiC

2500

Boron Carbide, B4C

2450

Aluminium Oxide, Al2O3

2050

Silicon Nitride, Si3N4

1900

Silicon Dioxide, SiO2

1715

Titanium Dioxide, TiO2

1605

The compounds are most widely utilized in industrial refractory materials are Al2O3, Si3N4, SiC and ZrO2. Various types of refractory oxides are mixed along with these compounds. Various of the thermal properties of these ceramics were demonstrated earlier. This has already been stated as: these are brittle materials and illustrates low tensile strength. They are more determined by their flexural strength and compressive strength. Their fracture toughness is also low. Table no.2 describes mechanical properties of widely utilized ceramic materials. This is seen from these data such compressive strength is more than 10 times higher than tensile strength. Though, one should remain in mind that brittle material, like ceramics are, can't yield consistent values of strength mostly tensile strength due to presence of various micro defects. Statistical approach should be adopted if load carrying member in ceramic has to be implicated. At the similar time this can also be understood that larger components along with larger surface area have higher possibility of carrying crack like defects and thus large sizes must be refused. The experimental process for tensile strength determination do not prove capable and for this reason 3 point bend tests give better strength indicator that is flexural strength. The modulus of elasticity of such materials is quite high-often as elevated as 1000 to 2000 times tensile strength. The elasticity modulus is largely dependent on the level of porosity and proportion of impurities. A significant high temperature behaviour related with ceramics is that whereas this may not sustain specific load at low temperature, the similar load may be sustained beyond specific high temperature. This phenomenon happens because of crack's tip rounding like flaw at high temperature. This flaw rounding brings down the stress concentration factor to a finite rate from infinity. The temperatures beyond that ceramics can be assists to carry stresses are calculated in respect of several ceramics. For illustration, for alumina such temperature is 1400oC while for silicon nitride it is 1600oC.

                                                 Table no.2: Mechanical Properties of some Ceramics Materials

Material

Density kg/m3

Compressive Strength (MPa)

Tensile Strength (MPa)

Flexural Strength (MPa)

Fracture

Toughness

MPa     m

Al2O3 (99%)

3850

2585

207

345

4.0

Si3N4 (Hot Pressed)

3190

3450

-

690

6.6

Si3N4 (Reaction

Bonded)

2800

770

-

255

3.6

SiC (Sintered)

3100

3860

170

550

4.0

ZrO3, 9% MgO (Partially Stablised)

5500

1860

-

690

8.0

In the given sections we illustrate a few refractory materials that are widely utilized along with signification of manufacturing utilized to bring them in usable forms.

Posted Date: 2/27/2013 1:47:38 AM | Location : United States







Related Discussions:- Refractory materials, Assignment Help, Ask Question on Refractory materials, Get Answer, Expert's Help, Refractory materials Discussions

Write discussion on Refractory materials
Your posts are moderated
Related Questions
V elocit y Ratio for Open Belt Drive: Figure Consider a simple belt drive (that is one driver and one follower) as shown in the figure given below Let D 1

Q. Show the Welding Processes and Restrictions? Welding may be performed manually, semi-automatically and or automatically using any process or combination of processes accepte

Compute the angular velocity of the wheel: A wheel of 0.5 m radius rolls over a horizontal surface without slipping as illustrated in Figure (a). The velocity of its centre is

(Buoyancy of a submerged body; compressibility of air) A grade 4 science student inverts a cup full of air into a water tank. If it takes 1 lb of force to hold the cup down 3

Explain Zeroth law and 1 st law of thermodynamics. Describe Internal energy and Enthalpy. What is a PMMFK. Give the expression for reversible workdone in a thermodynamic system

Determine Maximum fibre stress: A beam of rectangular section of 80 mm to 120 mm carries a uniformly distributed load of 40 kN/m over a span of 2 m an axial compressive force

Computer systems to plan manage, and control the operations of a manufacturing plant through either direct or indirect computer interface with the plants production resource

Determine maximum shearing stress in shaft:   A propeller shaft 100 mm in the diameter, is 45 m long, transmits 10 MW at 80 rotation per minute. Determine maximum shearing str

A beam, 6 m long is simply supported at the ends, and carries a uniformly distributed load of 15 KN/m and three loads of 10 KN, 20 KN and 30 KN acting respectively at the centre po

Welding is a material joining process used in making welds and a weld is a localised coalescence of metals or non metals produced either by heating the materials to suitable temper