Question

The processes are commonly used for producing powder
1. Atomization
2. Reduction Process
3. Electrolytic process
4. All of the above

Answer 1

Correct Answer - Option 1 : Atomization

Explanation:

Methods of powder production:

There are several ways of producing metal powders, and most of them can be produced by more than one method. The choice depends on the requirement of the end product.

Some of the methods are described below:

1. Atomisation:

• Atomisation involves a liquid metal stream produced by injecting molten metal through a small orifice.
• The stream is broken up by jets of inert gas or air or water.
• The size and shape of the particle formed depend on the temperature of the molten metal, rate of flow, nozzle size and jet characteristics.
• The use of water results in a slurry of metal powder and liquid at the bottom of the atomisation chamber.
• This is the commonly used method of power production.

2. Reduction:

• The reduction of metal oxides (i.e. removal of oxygen) uses gases such as hydrogen and carbon monoxide, as reducing agents.
• By this mean, very fine metallic oxides are reduced to the metallic state.
• The powders produced are spongy and porous and have uniformly sized angular shapes.

3. Electrolytic process:

• Electrolytic deposition utilizes either aqueous solutions or fused salts.
• The powders produced are among the purest available.

4. Oxidation:

• Oxidation simply means adding of oxygen by use of oxidising agents.
• Chips of heavy metals, obtained during the shaping operation can be transformed into re-usable powder by means of oxidation and heavy reduction.
• The oxidation step leads to a total disintegration of chips into oxide powder.

Particles shape in metal powders and the methods by which they are produced are mentioned in the table below.

Shape	Processes by which it is produced
Spherical	Atomisation, carbonyl (Fe), precipitation from a liquid
Irregular	Chemical decomposition
Rounded	Chemical decomposition
Porous	Reduction of oxides
Angular	Mechanical disintegration, carbonyl (Ni)
Acicular	Chemical decomposition
Irregular rod like	Chemical decomposition, mechanical comminution
Flake	Mechanical comminution
Dendrite	Electrolytic