a. "The compaction of MgO powder". 

b. "The compaction of a mixture of different concentrations of mullite and MgO powders".

(c) Sintering of compacted MgO and mixture of mullite and MgO powders.                

(a) 2.1 Objective:

The objective of this experiment is to get the green density of powders and their effect on the processing characteristics.

(a) 2.2 Introduction:

Magnesium oxide is hygroscopic, resulting in the uptake and retention of moisture under certain humidity and temperature conditions. Magnesia or magnesium oxide is an alkaline earth metal oxide. The majority of magnesium oxide produced today is obtained from the calcinations of naturally occurring minerals. Magnetite, MgCO₃, is being the most common.

(a) 2.3 Applications of MgO:

1)      MgO more suited to refractory applications.

2)      Fused MgO is used for a variety of refractory and electrical applications.

3)      MgO powder is widely used as a filling for electrical heating elements for applications in contact with air or liquid

(a) 2.4 Characteristics of MgO: 

1)      Moisture Penetration.
2)      Dielectric Strength (Although the dielectric strength of magnesium oxide insulation decreases with temperature),
3)      Insulation Resistance  (The insulation resistance of magnesium oxide decreases with increasing temperatures)
4)      Unlike most electrical insulations, magnesium oxide has a relatively high thermal conductivity. 

5)      The power factor of magnesium oxide insulation is very low compared to that of most electrical cable insulations.

(a) 2.5 Apparatus Used:

 1.      MgO powder                                         

2.      Core die

3.      Gloves

4.      Mask

5.      Vernier calipers

6.      Weight balance

7.      Hydraulic press

                                                                                                Figure 2.1: Core dies (1.3cm dia)

(a) 2.6 Procedure:                                    

    First we took total weight 1.2g powder and weighted it. Now put this powder in the core die along with spacer.  Then in Hydraulic Press, we have to place the core die on the middle of the bench and push the powder into the core die to compact it. Now by handle move the bottom bench towards upper bench.10, 000-15,000 Psi pressure applied on the plunger to move downwards into the die and compact the powder. After sometimes we come out the core die from hydraulic press and then opened the core die thus we can easily saw compact powder. Now we are using the handle slowly and carefully because compact can be damage if it strikes with the supporting plate. We weighted it again. And find the diameter and height of the pellet by using vernier calipers. And calculate its volume change and then calculate the compact density.

(a) 2.7 Observation and Calculation: ( MgO  Powder )              

                                                                                       Figure 2.2:  Hydraulic press (carver)                                                                                                                        

(b)  The compaction of a mixture of different concentration of mullite and MgO powders.

(b) 2.1Introduction of Mono Mill:

The mono mill performs mixing by continually revolving the large plate and rotating the container. To further improve the mixing efficiency, grinding media can be added into the containers.

Speed of rotation of the container can be adjusted along with the proper control of time for the rotation periods. Which can be referred as rotation speed which is in the rotation per min.rpm?                                                             

(b) 2.2 Apparatus used:                                        

1. Mullite and MgO powder

 2. Mono mill machine and Balls                              

 3. Weight balance and vernier calipers                                                  

 4.  Hydraulic press (carver)                                                      

                                                                                 (b)   Figure 2.1: Mono Mill  

  (b) 2.2 Procedure

First we took powders of MgO and mullite of three different compositions and   weighted it. We took them and mixed in the mono mill one by one and to make three sample of MgO and mullite mixture. For two samples, we used 28 balls and rpm 250 are applied for 2 to 3min and for third sample, we used 4 balls and rpm 150 are applied for 3 min. We successfully mixed the powders and three samples mixture container different composition of MgO and mullite powders contain. Now put these three samples one by one in the steel sleeve having pellet injector and the core die along with spacer. Then in Hydraulic Press, we have to place the core die on the middle of the bench and push the powder into the core die to compact it. Now by handle move the bottom bench towards upper bench.10,000-15000 Psi pressure applied on the plunger to move downwards into the die and compact the powder. After sometimes we come out the core die from hydraulic press and then opened the core die thus we can easily saw compact powder. Now we are using the handle slowly and carefully because compact can be damage if it strikes with the supporting plate. We weighted it again. And find the diameter and height of the pellet by using vernier calipers. And calculate its volume change and then calculate the compact density. Volume (V) = πr²h. And then calculate the compact density

                                      Green Density = Mass/Volume

2.4 Result:

The green density of Mgo is 1.229g/cm³ and the green density of a mixture of different concentration of MgO and Mullite powders are 1,2, and 3 samples 2.26g/cm³,2.26g/cm³ and 1.97g/cm³ respectively.

 

(c) Sintering of compacted MgO and mixture of mullite and MgO powders.                

(c) 2.1 Objective:

The objective of sintering to find out the sintered density of MgO and mixture of  mullite and MgO powders.

(c) 2.2 Introduction:

Sintering is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction. Sintering happens naturally in mineral deposits or as a manufacturing process use with metals ceramics plastics, and other materials. The atoms in the materials diffuse across the boundaries of the particles, fusing the particles together and creating one solid piece. Because the sintering temperature does not have to reach the melting point of the material, sintering is often chosen as the shaping process for materials with extremely high melting points

(c) 2.3 Properties:

Sintering is effective when the process reduces the porosity and enhances properties such as strength, electrical conductivity, translucency and thermal conductivity.  It may be useful to increase its strength but keep its gas absorbency constant as in filters or catalyst.

(c) 2.4 Application:

Sintering is one of the final stage of ceramics and it is used to increase the strength of the compacted materials.

( c) 2.5 Apparatus Used:

1.      Compacted MgO powder                                                     
            

2.      Compacted mixture powders

3.      Gloves and mask

4.      Tongs

5.      Vernier calipers

6.      Weight balnce                                

7.     Muffle furnace (Nabertherm)                        

            (c) Figure 2.1: muffle furnace (Nebertherm)

                                                                                

(c) 2.6 Procedure:

Green compacted samples or pellets are placed in muffle furnace for sintering. We give different sintering time to each samples which are to be sintered The MgO pellets are heated at 1250^oc for 30mint as sintering time and given a soaking time 30 mints and 1g mixture of MgO+Mullite Powder is heated at 1250^oc for 1 hour as sintering time.1.2g mixture of MgO+Mullite powder are heated at 1250^oc for 2 hours as sintering time and then calculate its density.1.4g mixture of MgO+Mulllite Powder is heated at 1250^oc for 3 hours as sintering time. We weighted it again after sintering and find out the diameter and height of pellets by vernier caliper. Finally, calculate the volume and compact density of sintered pellets

(c ) 2.7 Observation and Calculation:

Serial number	Compact density	Sintered   Density
G1	1.74g/cm3	1.76g/cm3
G2	1.8g/cm3	1.75g/cm3
G3	1.8g/cm3	1.94g/cm3
G4	1.84g/cm3	0.796g/cm3
G5	1.884g/cm3
G5-1	2.26g/cm3
G5-2	2.26g/cm3
G5-3	1.97g/cm3

2.6  Result:

 Green density of MgO powder is 1.884g/cm³ and green density of a mixture of different concentration of three samples are 2.26g/cm³, 2.26g/cm³and 1.97g/cm³ and sintered density cannot be find out because all samples are firmly stick with the steel plate and broken so  therefore sintered density