Introduction to Particle Size Analysis

Transcription

1 Introduction to Particle Size Analysis Ian Treviranus HORIBA, Ltd. All rights reserved.

2 What we ll talk about Featured technologies Defining particle size Understanding size metrics Differences between techniques Q&A

3 Featured technologies LA-950 Laser Diffraction SZ-100 Dynamic Light Scattering & Zeta Potential CAMSIZER & CAMSIZER XT Dynamic Image Analysis PSA300 Static Image Analysis SA-9600 Flowing Gas BET Surface Area

4 LA-950: Laser Diffraction Particle size performance leader Ninth generation Ultra durable Lowest total cost of ownership Suspension, emulsion, powder, paste, gel 10 nanometer 3 mm

5 SZ-100: Dynamic Light Scattering Particle size: 0.3 nm 8 µm Zeta potential: mv Molecular weight: 1x10 3 2x10 7 Da Patented ultra long-life graphite electrodes Lowest total cost of ownership Optional autotitrator

6 Image Analysis Dynamic: particles flow past camera Static: particles fixed on slide, stage moves slide

7 CAMSIZER Series High resolution size & shape Intelligent sieve correlation Patented dual capture CAMSIZER 30 µm 30 mm Free-flowing powders CAMSIZER XT 1 µm 3 mm Cohesive or free flowing

8 PSA300 High resolution size & shape Referee technique for micronized powders Turnkey, automated image analysis 1 µm 1,000 µm Cohesive or free flowing powders Optional Powder Disperser accessory

9 More Information Best Practices/Training Understanding Laser Diffraction PSA Results TR008 Troubleshooting Laser Diffraction Data TR010 Understanding Dynamic Light Scattering Results TR012 Help! How Can I Trust My Size Results? TR015 Refractive index selection, sampling, dispersion, system verification, method development and more Technology Intro to CAMSIZER TE002 Find the Best Analyzer for Your Application TE006 Intro to Static Image Analysis TE008 Intro to Dynamic Image Analysis TE009 Intro to Laser Diffraction TE010 Intro to Dynamic Light Scattering TE012 Intro to CAMSIZER XT TE015

10 Who Cares About Particle Size? Minerals Grinding 10 Portland Cement Glass Beads Abrasives Foods Cosmetics Pharmaceuticals Paint and Coatings Pharmaceutical Chemical Ceramics Cement Food Abrasives Cosmetics Mining Powder Metals University Other Metals and Ceramics Explosives and Fireworks

11 What we ll talk about Featured technologies Defining particle size Understanding size metrics Differences between techniques Q&A

12 Size Terminology 0.1µm 1.0µm 10µm 100µm nm nanometer nm Angstrom (Å) micrometer Micron or µm millimeter mm The most common designation is micrometers or microns. When very small, in colloid region, measured in nanometers, with electron microscopes or by dynamic light scattering. meter m

13 Poll! Which size ranges do you measure? 2013HORIBA, Ltd. All rights reserved.

14 Particle Diameter ( m) Size Ranges Ultrafine Inhalable Fine Coarse Relative Size of Common Material Tobacco Smoke Viruses Bacteria Carbon Black Paint Pigment Spores Beach Sand Human Hair Common Methods for Particle Size Analysis Electron Microscope Optical Microscope Static Angular Light Scattering Dynamic Light Scattering Electrozone Sensing Sedimentation Methods Field Flow Fractionation Light Obscuration Ultrasonic Spectroscopy

15 The Basics Which is the most meaningful size? different size definitions different results

16 The Basics What sizes can be measured?

17 Size Definitions Martins s Diameter: The distance between opposite sides of a particle measured on a line bisecting the projected area. To ensure statistical significance all measurements are made in the same direction regardless of particle orientation. Feret s Diameter: The distance between parallel tangents on opposite sides of the particle profile. Again to insure statistical significance, all measurements are made in the same direction regardless of particle orientation. Note: Both Martin s and Feret s diameters are generally used for particle size analysis by optical and electron microscopy. Equivalent Circle Diameter: The diameter of a circle having an area equal to the projected area of the particle in random orientation. This diameter is usually determined subjectively and measured by oracular micrometers called graticules. Equivalent Spherical Diameter: The diameter of a sphere that has the same volume as the irregular particle being examined. Equivalent Spherical Diameter Martin s Diameter Feret s Diameter

18 Particle Orientation Equivalent Spherical Diameter Martin s Diameter Feret s Diameter Martin s and Feret s Diameter s will vary as particles are viewed in different orientations. The result will be a DISTRIBUTION from smallest to largest. Equivalent Spherical Diameter Martin s Diameter Feret s Diameter

19 The Basics Particle Particle Distribution

20 The Basics Particle Size Particle Size Distribution 4 µm

21 Monodisperse vs. Polydisperse Monodisperse Polydisperse VOLUME VOLUME Particle Size Monodisperse Distribution: All particles are the same size Latex standards Particle Size Wide Distribution: Particles of Many Sizes Everything else

22 Logarithmic vs. Linear Scale Logarithmic X-Axis Distribution Linear X-Axis Distribution VOLUME VOLUME Particle Size Particle Size

23 Distribution Display VOLUME Histogram Cumulative Distribution Differential Distribution Particle Size Represented by series of segments or channels known as histogram. Number of channels based on design, practicality and aesthetics

24 Your Analyzer s Displays Frequency Frequency + cumulative (undersize) Histogram Multiple frequency + cumulative (undersize)

25 What we ll talk about Featured technologies Defining particle size Understanding size metrics Differences between techniques Q&A

26 Central Values Mean Weighted Average Center of Gravity Median 50% Point Mean Median and Mode Mode Peak of the distribution Most common value Size

27 What does Mean mean? Three spheres of diameters 1,2,3 units What is the average size of these spheres? Average size = (1+2+3) 3 =2.00 This is called the D[1,0] - the number mean

28 Many possible Mean values 1 Xnl D 2 [,] X ns D [ 20, ] X nv D [ 30, ] None of the answers are wrong they have just been calculated using different techniques 1 Xsv D 8 27 [,] X vm D [ 43, ]

29 Volume-based Mean diameter D[4,3] which is often referred to as the Volume Mean Diameter [ VMD ] D [4,3] = 4 Dn i i 3 D n i i Monitoring the D[4,3] value in your specification will emphasize the detection of large particles

30 Central Values revisited Mode Median Mean D[4,3] Mean Weighted Average Center of Gravity Median 50% Point Mode Peak of the distribution Most common value Size Remember: D[4,3] is sensitive to large particles

31 Most Common Statistics half are smaller than this diameter half are larger than this diameter D(v,0.5) median 10% of the particles lie below this diameter D(v,0.1) D(3,2) Size µm 90% of the particles lie below this diameter D(v,0.9) D(v,1.0) Never use the D100! D(4,3) sensitive to large particles sensitive to small particles

32 Standard Deviation -1 STD DEV 68.27% +1 STD DEV Normal (Gaussian) Distribution Curve = distribution mean = standard deviation Exp = base of natural logarithms -2 STD DEV +2 STD DEV 95.45% Mean Y = 1 2 Exp [ -(x - ) ]

33 Distribution Width Polydispersity Index (PI, PDI) Span Geometric Std. Dev. Variance Etc

34 For Your Reference Note: Span typically = (d90 d10)/ d50

35 For Your Reference

36 For Your Reference Error Calculations in LA-950 only

37 Skewness

38 Kurtosis (Peakedness) From highest to lowest peak: red, kurtosis 3 orange, kurtosis 2 green, kurtosis 1.2 black, kurtosis 0, cyan, kurtosis blue, kurtosis 1 magenta, kurtosis 1.2

39 Number vs. Volume Distributions r = 1 µm r =2 µm r = 3 µm v = 4 = 32 = 108 V = 4 r 3 3 V*3 = Total = = /432=2.8% 96/432=22.2% 324/432=75%

40 Beans!

41 Equivalent Volume Distributions

42 Equivalent Volume Distributions

43 Equivalent Volume Distributions

44 Equivalent Volume Distributions

45 Comparing Distribution Bases Same material shown as volume, number and area distribution Percent in Channel Number Area Volume Volume Distribution Mean = 12.65µm Median=11.58 µm SA=13467 cm 2 /cm 3 Std Dev.=8.29 Number Distribution Mean = 0.38µm Median=0.30 µm SA=13467 cm 2 /cm 3 Std Dev.= Particle Size

46 Statistical Issues with Distributions L Neumann, E T White, T Howes (Univ. Queensland) What does a mean size mean? 2003 AIChE presentation at Session 39 Characterization of Engineered particles November San Francisco Other references: L Neumann, T Howes, E T White (2003) Breakage can cause mean size to increase Dev. Chem. Eng. Mineral Proc. J. White E T, Lawrence J. (1970), Variation of volume surface mean for growing particles, Powder Technology,4,

47 Does the Mean Match the Process? Particle size measurements often made to monitor a process Size reduction (milling) Size growth (agglomeration) Does the measured/calculated mean diameter describe the change due to the process? It depends on which mean used

48 Size Reduction Scenario 10 x1 m 10 x 1 m 79.4 m 100 m breaks into two smaller particles 79.4 m

49 Size Reduction: Number Mean Ten particles of size 1; one of size 100 units Number mean = D[1, 0] = (10*1 + 1*100)/11 = 10 units.. Largest particle (100) breaks into two of (conserves volume/mass: = ) Have broken one What happens to the number mean? Mean = (10*1+2*79.37)/12 = units Surprise, surprise a 40.6% increase!

50 Size Reduction: Volume Mean Ten particles of size 1; one of size 100 units Volume Moment Mean D[4, 3] = (10* *100 4 )/(10* *100 3 ) ~ 100 units.. Largest particle (100) breaks into two of (conserves volume/mass: = ) Have broken one What happens to the D[4, 3]? New D[4, 3] = (10*1 4 +2* )/(10*1 3 +2* ) ~ units This shows the expected behavior

51 Can You See the Problem? Number mean = 10 Number mean = 14 Volume mean = 100 Volume mean = 79

52 Size Growth Scenario 10 1 m 10 1 m m m Ten 46.4 m particles agglomerate into one 100 m particle

53 Growth: Number Mean Ten particles of size 1; ten of size D[1, 0] = (10*1 + 10*46.42)/20 = units. Ten of agglomerate into one of 100 (conserves volume/mass: = ) Have agglomerated half; does mean increase? Mean = (10*1+1*100)/11 = 10 units Over a 50% decrease!

54 Growth: Volume Mean Ten particles of size 1; ten of size D[4, 3] = (10* * )/(10* * ) ~ 46.4 units (Note again the volume moment mean is dominated by the large particles). Ten of agglomerate into one of 100 (conserves volume/mass: = ) Have agglomerated half; does mean increase? D[4, 3] = (10*1 4 +1*100 4 )/10* *100 3 ~ 100 units This shows the expected behavior

55 Can You See the Problem? Number mean = 24 Number mean = 10 Volume mean = 46 Volume mean = 100

56 Practical Implications Not just a party trick topic! Do you know you can break particles and the mean will increase? Serious. Did an experiment. I thought I broke particles but the mean has increased (REAL experience) Should be aware it can happen! Analyse whole size distribution, not mean alone.

57 What we ll talk about Featured technologies Defining particle size Understanding size metrics Differences between techniques Q&A

58 PSA Method is Important Why should one consider various methods of particle size analysis? Material suppliers and users employ many different types of instruments Use a different technique = get a different answer It is important to understand how analysis methods differ in order to know how to compare data

59 Size Range by Technique ELECTROFORMED MESH SIEVES CENTRIFUGAL SEDIMENTATION ACOUSTIC SPECTROSCOPY OPTICAL MICROSCOPY / IMAGE ANALYSIS ELECTRICAL CONDUCTIVITY LIGHT OBSCURATION / ELECTRICAL SENSING ZONE DYNAMIC LIGHT SCATTERING LASER DIFFRACTION 10 nm 100 nm 1 µm 10 µm 100 µm 1 mm

60 What Size is Measured? Laser Diffraction Equivalent Spherical Diameter Dynamic Light Scattering Hydrodynamic Radius Image Analysis Lengths, Widths, Equivalent Spherical Acoustic Spectroscopy Equivalent Spherical Diameter

61 Particle Shape Definitions Acicular: Angular: Fibrous: Granular/Blocky: Spherical: Needle-shaped, rigid Edgy, hard angles Thread-like, non-rigid Irregular-shaped, low aspect-ratio Regular-shaped, unity aspect ratio Aspect ratio: Sphericity: Roundness: Breadth / length OR Length / breadth How spherical is the particle? How round is the particle?

62 Poll! What are the shapes of your particles? 2013HORIBA, Ltd. All rights reserved.

63 Poll! Do you use multiple sizing techniques? 2013HORIBA, Ltd. All rights reserved.

64 Hegman Gauge Used in paint and coatings industry Device has tapered center channel Slurry is placed in channel, then straight edge is drawn across it Hegman Number is where particles disturb smooth surface of slurry Information from largest particles only no distribution

65 Sieves Weigh % sample caught on known screen sizes Solid particles 30 m 30 mm (and larger) Advantages: Low equipment cost Direct measurement method No practical upper limit Available through Disadvantages: Limited lower range Time Consuming High Labor Cost Need Large Sample

66 Electrical Sensing Zone Coulter Principle Based on change in conductivity of aperture as particle traverses. Requires conducting liquid. Directly measures particle volume and counts. High resolution Used for blood cell counting more than industrial applications

67 Light Obscuration Light Obscuration: Liquid Flow Sensing Zone Light Source Light is blocked by single particles as they traverse the light beam Detector Advantages: Particle count available USP<788> testing High resolution histogram Disadvantages: Dilution required for particle size analysis Prone to cell clogging

68 Sedimentation Stokes Law Sedimentation of same density material in a viscous medium D = 18 µ V p (A - B) G Vp = Settling velocity of discrete particle G = Gravity constant A = Density of Particle B = Density of Carrier Fluid D = Diameter of discrete particle µ = Viscosity of Carrier Fluid Time Note: assumes settling of spherical particle Under-sizes compared to other techniques if non-spherical

69 Sedimentation Issues Comparison of Brownian Motion and Gravitational Settling Particle Diameter (In micrometers) (Movement in 1 second; Particle density of 2.0 grams/cc) Movement due to Brownian Motion >> > > ~ < << 55.4 Movement due to Gravitational Settling Below 1 micrometer, Brownian motion becomes an appreciable factor in particle dynamics. Gravity sedimentation may not be an appropriate measurement technique for very small particles.

70 Dynamic Light Scattering Most common technique for sub-micron sizing Range: 1 nm 1 m* Frequency Shifted Signal Frequency-Intensity Distribution Particles in suspension undergo Brownian motion due to bombardment by solvent molecules in random thermal motion. Stokes-Einstein R H kt 6 D * Density dependent, when does settling become prominent motion?

71 Manual Microscopy Count particles in a given field of view Use graticule to obtain size Repeat this process for a number of fields At least hundreds of particles must be sized Advantages: Simple Inexpensive Can see shape Disadvantages: Slow Measures very few particles Very tedious

72 Automated Microscopy Static: Particles fixed on slide, stage moves slide Dynamic: Particles flow past camera(s)

73 Automated Microscopy Objective & camera Subjective or automatic Decisions or black box Image Acquisition and enhancement Thresholding Image Processing Measurements Advantages: Quick size + shape info Statistically valid High resolution Particle images Disadvantages: Expense Knowing which numbers are important

74 Acoustic Spectroscopy Acoustic signal sent into concentrated sample Detector measure attenuation f (frequency, distance from source) Detector Signal source Signal output Advantages: Can accommodate high sample concentrations (no dilution) Rheological properties Also measure zeta potential Disadvantages: Need at least 1 wt% particles Need to know wt% Minimum sample = 15 ml

75 Laser Diffraction Converts scattered light to particle size distribution Quick, repeatable Powders, suspensions Most common technique

76 Poll! Which techniques do you use? 2013HORIBA, Ltd. All rights reserved.

77 What we ll talk about Featured technologies Defining particle size Understanding size metrics Differences between techniques Q&A

78 ありがとうございました اش ك ر Tacka dig ขอบค ณคร บ Gracias Σας ευχαριστούμε धन यव द 감사합니다 Danke Большое спасибо 谢谢 Grazie நன ற Obrigado

79 Ian Treviranus Product Line Manager Talk to us, ask questions Receive news of updates View application & technical notes (170+), webinars (60+), white papers.