(a) 6.1 Objective:

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

(a) 6.2 Introduction:

Silicon dioxide also known as silica and with the chemical formula of SiO₂ and most commonly found in nature as quartz and in many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as synthetic product. Notable examples include fused quartz fumed silica, silica gel and aero gels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries. Iron oxides are widespread in nature, play an important role in many geological and biological processes, and are widely used by humans, e.g., as iron ores pigments catalysts in termite and hemoglobin. Common rust is a form of iron (III) oxides. Iron oxides are widely used as inexpensive, durable pigments in paints, coatings and colored concretes. Colors commonly available are in the "earthy" end of the yellow/orange/red/brown/black range. When used as a food coloring

(a) 6.3 Apparatus used: 

1)      Silica and Fe powders                        

(a) Figure 6.2: Hydraulic press (Carver)

2)      Core die            

3)      Carver Hydraulic press

4)      Spacer                     

5)      plunger                                                               

6)      Vernier calipers                       

7)      Gloves

 

(a) Figure 6.1: Core Die (1.3cm dia)

 

 

 

 

                  

(a) 6.7 Procedure:                                                               

First we took total weight 1.5g powder in which 1g silica (SiO₂) and  0.5g FeO and weighted it. We successfully mixed the powders by hand for 5 mints. Now put this mixture of 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 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) 6.8 Observation and Calculation:

Weight of sample	1.5g       (1g silica+ 0.5g FeO)
Diameter of sample (d)	1.3cm
Height of sample  (h)	0.401cm
Radius of sample   (r)	0.65cm

Volume (V) = πr2h                                             r=d/2                            =  3.1415*(0.65cm)2 *0.401cm                            =0.5322 cm3 Green density=mass/volume                           =1.5g/0.5322cm3  Green density     =2.8g/cm3

 

(a) 6.9 Result:         

      Green density of 2.8g/ cm³ of silica and FeO are obtained. 

 (b) Sintering of compacted mixture SiO₂ and FeO powders

(b) 6.1 Objective:

The objective of sintering to find out the density of a mixture of TiO₂ and FeO powders.

(b) 6.2 Introduction:

Sintering is the process of compacting solid mass of material by heat without melting it to the point of liquefaction. Sintering happens naturally in mineral deposits or as a manufacturing process used 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.

(b) 6.3 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.

(b) 6.4 Application:

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

(b)    Figure 6.1: Muffle furnace (Nebertherm)

(b) 6.5 Apparatus required:

1.      Compacted mixture powders(TiO₂+Fe)

2.      Gloves

3.      Tongs

4.      Vernier calipers

5.      Weight balance

6.      Muffle furnace( Nabertherm)                                                         

7.      Mask                                                                                                                                                                                                                  

(b) 6.6 Procedure:

Green compacted samples or pellets are placed in muffle furnace for sintering. The pellets are heated at 950◦c for 120 mints to each sample which is to be sintered and given a same soaking time 120 mints. 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.

(b) 6.7 Observation and Calculation:

Weight of sample	1.72g
Diameter of sample (d)	1.381cm
Height of sample  (h)	0.43cm
Radius of sample   (r)	0.6905cm

Volume (V) = πr2h                                             r=d/2                            =  3.1415*(0.6905cm)2 *0.43cm                                 = 0.6440cm3 sintered density=mass/volume                           =1.72g/0.6440cm3  sintered density      =2.6g/cm3

 

 

(b) 6.8 Result:

Sintered density of silica and FeO 2.6g/cm³ are obtained at temperature 950◦c.