# Powder Metallurgy Mcqs

Q:

Which of the following characteristics does irregular shaped particles do not possess?

 A) Reduced apparent density B) Good pressing properties C) Good sintering properties D) Maximum flow rate

Explanation: Irregularly shaped particles possess reduced apparent density and flow rate but good pressing and sintering properties. Spherical shaped particles possess maximum apparent density and flow rate but reduced pressing and sintering properties.

131
Q:

The shape factor is given by the ratio of surface area to particle size.

 A) True B) False

Explanation: The shape factor is given by the ratio of surface area to particle size or as the ratio of the length of the particle to its breadth. The presence of cracks, fissures, or grain boundaries in the individual particles increases considerably the shape factor.

62
Q:

The adsorption method used for determining the specific surface makes use of which instrument?

 A) Fisher Sub-siever B) BET apparatus C) Hall Flowmeter D) Scott Volumeter

Explanation: The adsorption method used for determining the specific surface makes use of the BET apparatus, named after Brunauer, Emmett, and Teller, who developed this method. The permeability method used for determining the specific surface makes use of the Fisher Sub-siever apparatus and for measuring apparent density we may use either Hall Flowmeter or Scott Volumeter.

50
Q:

The unit for measuring the specific surface of the powder is _____

 A) cm²/gm B) cm/sec C) cm³/gm D) cm/gm²

Explanation: The specific surface of the powder is defined as the total surface area per unit weight (cm²/gm). It depends on the size, shape, density and surface conditions of the particle.

38
Q:

_____ measures the resistance to fluid flow through a compacted powder bed to calculate the specific surface of the powder.

 A) Permeametry B) Gas adsorption method C) Elutriation Method D) Sedimentation method

Explanation: Permeametry or permeability method measures the resistance to fluid flow through a compacted powder bed to calculate the specific surface of the powder. The principle involves measuring the pressure drop across the bed of packed powder particles contained in a chamber in relation to the fluid flow. This information is used to determine related properties of the powder such as specific surface area and average particle size.

48
Q:

______ determines the surface area of powder by measuring the amount of gas adsorbed by a monomolecular layer of the powder.

 A) Centrifugal method B) Gas absorption method C) Gas adsorption method D) Permeability method

Explanation: The gas adsorption method determines the surface area of powder by measuring the amount of gas adsorbed by a monomolecular layer of the powder. Nitrogen is the most commonly used gas. This method can also be used to determine the pore volume and size distribution, for pore diameters ranging from 600Ȧ down to 14Ȧ.

46
Q:

Which of the following particle shape is not produced by the chemical decomposition process of powder manufacture?

 A) Acicular B) Flaky (large and thin plate-like) C) Rod-like (irregular) D) Rounded

Explanation: Acicular (needle-like: 1D), rod-like (irregular: 1D), rounded (3D) particle shapes are produced on chemical decomposition process to manufacture powder. Flaky (large and thin plate-like) is possessed by ball-milled aluminum.

39
Q:

Which method cannot be used to determine the particle shape?

 A) Sieve analysis B) Optical microscopy C) SEM D) TEM