Lesson 5

Question 1

it is formed by joining bars of two different metals together so that there is intimate contact between the two faces

Answer 1

diffusion couple

Question 2

these are mixtures of two or more solid where atleast one is metal

Answer 2

alloys

Question 3

three types of diffusion in solids

Answer 3

1. diffusion that follows fick’s law
2. diffusion in porous solids
3. diffusion in porous solids and capillaries

Question 4

this type of diffusion in solids is used if there’s a uniform and homogeneous solid

Answer 4

diffusion that follows fick’s law

Question 5

this type of diffusion in solids is used if independent on the actual structure of the solid

Answer 5

diffusion that folows fick’s law

Question 6

this type of diffusion in solids is used when fluid or solute diffusing is dissole in the solid to form homogeneous solution

Answer 6

diffusion that follows fick’s law

Question 7

it is the capacity of the solute to dissove in a substance

Answer 7

solubility

Question 8

ability of the substance to pass through a membrane

Answer 8

permeability

Question 9

degree of diffusion through a membrane

Answer 9

permeability

Question 10

these are assumed constant

Answer 10

mass diffusivities

Question 11

these are independent upon the fluid’s pressure (outside of the solid)

Answer 11

mass diffusivities

Question 12

these are experimentall determined

Answer 12

mass diffusivities

Question 13

this type of diffusion in solids is used if there are pores and interconnected voids

Answer 13

diffusion in porous solids

Question 14

it is the correction for the path the solute takes

Answer 14

tortuosity

Question 15

it is the measure of void space in a material

Answer 15

porosity/void fraction

Question 16

relationship between porosity and tortuosity

Answer 16

they are indirectly proportional

Question 17

it is the average ditsnace a gas molecule travels before it collides with another molecule

Answer 17

mean free path

Question 18

types of diffusion of gases in small capillary tubes

Answer 18

1. knudsen diffusion
2. molecular diffusion
3. transition-region diffusion

Question 19

a type of diffusion of gases where the molecule collides with the wall and molecule-wall collisions are important

Answer 19

knudsen diffusion

Question 20

a type of diffusion of gases in small capillary tubes where molecule-molecule collisions predominate and molecule-wall collisions are few

Answer 20

molecular diffusion

Question 21

molecule-molecule collisions and molecule-wall collisions are important

Answer 21

transition-region diffusion