1. Chapter 18 Micromeritics

2. Homework Chapter 22 (경구용 고형제) (pp. 563-577) 내용의 정리/요약 Hand writing할 것
Due date: Dec 7 (강의 시작 전)

3. Contents Particle Size and Size Distribution
Methods for Determining Particle Size
Particle Shape and Surface Area
Methods for Determining Surface Area
Derived Properties of Powder

4. Micromeritics
Science and technology of small particles

5. PARTICLE SIZE AND SIZE DISTRIBUTION

6. Particle Size Surface diameter(ds)
The diameter of a sphere having the same surface area as the particle
Volume diameter(dv)
The diameter of a sphere having the same volume as the particle

7. Particle Size Projected diameter(dp)
The diameter of a sphere having the same observed area as the particle
Stokes’ diameter(dst)
An equivalent sphere undergoing sedimentation at the same rate as the asymmetric particle

8. Average Particle Size
Fig. 18-1

9. Particle Size Distribution
Frequency distribution curve
Fig. 18-2

10. Particle Size Distribution
Cumulative percent curve
Fig. 18-3

11. Particle Size Distribution
Log-normal distribution curve
Fig. 18-4

12. Particle Size Distribution
Log-probability curve
Fig. 18-5

13. Particle Number (N) Number of particles per unit weight
e.g. if particle = sphere
Example 18-2

14. METHODS FOR DETERMINING PARTICLE SIZE

15. Microscopic Method
Based on number distribution of different particle size
Range : m
>200 counts ( counts)

16. Microscopic Method 장점 particle의 shape을 알 수 있다 단점 번거롭다
operater간 오차가 심하다
only two dimensions (길이, 폭)

17. Optical Microscopy 2 : Feret’s diameter 3 : Projected diameter
Fig. 18-7
1 : Martin diameter
2 : Feret’s diameter
3 : Projected diameter

18. Sieve Method This method uses a series of standard sieves
Range : m
20 mesh
100 mesh
No opening

19. Sieve Mesh number number of openings per inch Sieve opening
actual size of openings between wires
Sieve opening

20. Sedimentation The diameter is obtained by gravity sedimentation
Andreasen apparatus

21. Sedimentation Stoke’s law v : rate of settling h : distance of fall in
time t
s : density of particle
0 : density of
dispersion medium
g : acceleration due to
gravity
0 : viscosity of medium

22. Sedimentation Reynolds number Re Re > 0.2
 Stoke’s law cannot be used

23. PARTICLE SHAPE AND SURFACE AREA

24. Specific Surface
The surface area per unit volume (Sv) or per unit weight (Sw)
단위용량당의 표면적
단위중량당의 표면적

25. METHODS FOR DETERMINING SURFACE AREA

26. Adsorption Method
The volume in cubic centimeters of gas adsorbed per gram of adsorbent may be plotted against the pressure of the gas at constant temperature
𝑝 𝑉( 𝑝 0 −𝑝) = 1 𝑉 𝑚 𝑏 + 𝑏−1 𝑝 𝑉 𝑚 𝑏 𝑝 0
(18-18)
BET EQ.
𝑆 𝑤 = 𝐴 𝑚 𝑁 𝑀 𝜌 × 𝑉 𝑚 𝑐𝑚 2 /𝑔
(18-19)

27. Adsorption Method
Fig
Fig

28. Air Permeability Method
The principle resistance to the flow of a fluid, such as air, through a plug of compressed powder is the surface area of the powder
The flow rate through the plug, or bed, is affected by
the degree of compression of the particles
the irregularity of the capillaries

29. Air Permeability Method
Fig The Fisher subsieve sizer

30. DERIVED PROPERTIES OF POWDERS

31. Derived Properties of Powders
Porosity (공극률)
Packing arrangement (충전배열)
Densities of particles (입자밀도)
Bulkiness (분말용적)
Flow properties (유동성)
Compaction (압축성)

32. Porosity (e) Void volume (v) : the volume of space
Bulk volume (Vb) : occupied volume
True volume (Vp)

33. Packing Arrangements
Fig
e = 26%
e = 48%

34. Densities of Particles
True density ()
Density of the actual solid material
Granule density (g) (Particle density)
The mass of particles devided by the volume as
determined by the liquid(mercury) displace method
Bulk density (b) (Apparent density)
The mass of a powder divided by the bulk volume

35. Densities of Particles
Bulk density
Tap density
Granule density
True density

36. Bulkiness
Bulkiness(bulk) is specific bulk volume, the reciprocal of bulk density

37. Light vs. Heavy Powders Light(경질) : low bulk density or
large bulk volume
Heavy(중질) : high bulk density or
small bulk volume
Light powders
Heavy powders

38. Flow Properties
A bulk powder is some what analogous to a non-Newtonian liquid(plastic flow, dilatancy)
Flow property is affected by
particle size, shape, porosity, density, surface texture
Measurement : angle of repose() (= f(roughness))
tan  = 
 : coefficient of friction 