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Chapter 18 Micromeritics. Homework  Chapter 22 ( 경구용 고형제 ) (pp. 563-577)  내용의 정리 / 요약  Hand writing 할 것  Due date: Nov 11 (pm 5 시 )

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Presentation on theme: "Chapter 18 Micromeritics. Homework  Chapter 22 ( 경구용 고형제 ) (pp. 563-577)  내용의 정리 / 요약  Hand writing 할 것  Due date: Nov 11 (pm 5 시 )"— Presentation transcript:

1 Chapter 18 Micromeritics

2 Homework  Chapter 22 ( 경구용 고형제 ) (pp )  내용의 정리 / 요약  Hand writing 할 것  Due date: Nov 11 (pm 5 시 )

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(d s ) The diameter of a sphere having the same surface area as the particle  Volume diameter(d v ) The diameter of a sphere having the same volume as the particle

7 Particle Size  Projected diameter(d p ) The diameter of a sphere having the same observed area as the particle  Stokes’ diameter(d st ) 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 particle 의 shape 을 알 수 있다  단점 번거롭다 operater 간 오차가 심하다 only two dimensions ( 길이, 폭 )

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

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

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 R e  R e > 0.2  Stoke’s law cannot be used

23 PARTICLE SHAPE AND SURFACE AREA

24 Specific Surface  The surface area per unit volume (S v ) or per unit weight (S w ) 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

27 Adsorption Method 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 DERIVED PROPERTIES OF POWDERS

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

31 Porosity (   Void volume (v) : the volume of space  Bulk volume (V b ) : occupied volume  True volume (V p )

32 Packing Arrangements Fig  

33 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

34 Densities of Particles Bulk densityTap density Granule densityTrue density

35 Bulkiness  Bulkiness(bulk) is specific bulk volume, the reciprocal of bulk density

36 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

37 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 


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