Fatih GÜNDÜZ 030060144 9th week Answers Part 2

Atomisation (Atomization) : (Previous) (Better)

Atomization has been classified into categories, namely gas, water and centrifugal. Virtually, any material that can be melted can be made into powder by disintegration of the liquid. Aside from chemical reactivity, which may necessitate specific atmosphere or materials, the process is independent of the normal physical and mechanical properties associated with the solid material. The method is being widely adopted, especially because of the relative case of making high purity metals and prealloyed powders directly from the melt. The basic procedure employed is to force a liquid through an orifice, possibly at a bottom of a crucible and impinge a gas or liquid stream on the emerging melt. A great deal depends on the exact design of the orifice. It may induce turbulence in the melt which atomizes the material directly and allows the impinging gas or liquid to reduce the size of the particle still faster.

(Upadhyaya G. S., Powder metallurgy technology, p. 10)

 Atomisation (Atomization) : (New) (Mechanical Process)

 Atomisation is commonly used for metals which have low melting point-like Pb, Zn, Cd, Sn, etc. In this process, the molten metal is forced through a small orifice and is broken by a powerful jet of compressed air. As a result, the jet of liquid metal is changed into very small particles that are spherical in shape. The collision between the stream of metal and air produces very small particles which are called atoms and hence the process is called atomisation. This process requires careful control of temperature and pressure. Oxidation can be prevented by providing an inert atmosphere.

(Applied Chemistry:, 2. cilt, V.M. Balsaraf, p.47)

Compressibility : (Previous)

Compressibility is a measure to which a powder will compress or densify upon application of external pressure. Compressibility is reported as the density in g/cm3, rounded to the nearest 0.01 g/cm3, at a specified compaction pressure, or as the pressure needed to reach a specified density. Typically, a cylinder or rectangular test piece is made by pressing powder in a die, with pressure applied simultaneously from top and bottom.

Compressibility of the powder is influenced by factors like: inherent hardness of the concerned metal or alloy, particle shape, internal porosity, particle size distribution, presence of nonmetallics, addition of alloying elements or solid lubricants.

(Upadhyaya G. S., Powder metallurgy technology, p. 26)

Compressibility : (New)(Better)(Material Property)

A property of materials: the strength of a material is a measure of its ability to witstand deformation by forces. One of the ways to deform a material is by compressing it; compression is a squeezing force.(Other common ways to deform materials are by pulling forces - tension - and by twisting forces - tosions.) Tesiting materials' compressibility can be done in the primary classroom by a squeeze test, possibly as part of an investigation to discover which material would be suitable for Goldilocks' chair - is it too hard, too soft or just right?

(The Primary Science and Technology Encyclopedia, Christopher Collier,Dan Davies,Alan Howe,Kendra McMahon, p.24)