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Particle size distribution (Granulometry)

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Endpoint:
particle size distribution (granulometry)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Principles of method if other than guideline:
Granulometry (primary particle size and shape, aggregate/agglomerate size and primary particle size distribution (number-based)) was determined by Transmission Electron Microscopy (TEM).
The specimens were examined using a Tecnai Spirit microscope (FEI, Eindhoven, The Netherlands) and using ParticleSizer software.
GLP compliance:
no
Type of method:
microscopic examination
Type of particle tested:
primary particle
Type of distribution:
counted distribution
Percentile:
D25
Mean:
7 nm
Remarks on result:
other: Min. Feret diameter
Key result
Percentile:
D50
Mean:
8 nm
Remarks on result:
other: Min. Feret diameter
Percentile:
D75
Mean:
9 nm
Remarks on result:
other: Min. Feret diameter
Percentile:
other: Mean
Mean:
8.4 nm
St. dev.:
2.2
Remarks on result:
other: Min. Feret diameter

 

 

Column

Size

(number of observations)

Mean

(nm)

Std Dev

(nm)

Max

(nm)

Min

(nm)

Median

(nm)

25%

(nm)

75%

(nm)

Area

10220

66.5

65.6

4000.0

24.6

56.5

46.7

70.4

Area Conv. Hull

10220

67.5

66.0

4000.0

24.9

57.3

47.4

71.4

Peri.

10220

27.8

7.6

244.0

17.0

26.0

24.0

30.0

Peri. Conv. Hull

10220

28.0

7.5

229.0

17.0

27.0

24.0

30.0

Feret

10220

9.4

2.6

81.0

6.0

9.0

8.0

10.0

Min. Feret

10220

8.4

2.2

61.0

5.0

8.0

7.0

9.0

Maximum inscribed circle diameter

10220

8.4

2.1

57.0

5.0

8.0

7.0

9.0

Area equivalent circle diameter

10220

8.9

2.3

68.0

6.0

8.0

8.0

9.0

Long Side Length MBR

10220

9.0

2.5

79.0

5.0

9.0

8.0

10.0

Short Side Length MBR

10220

8.4

2.2

61.0

5.0

8.0

7.0

9.0

Aspect Ratio

10220

1.064

0.062

2.100

1.000

1.048

1.022

1.087

Circ.

10220

0.002

0.001

0.015

0.001

0.002

0.002

0.002

Elong.

10220

12.339

0.245

16.855

11.810

12.304

12.221

12.402

Convexity

10220

0.277

0.083

0.736

0.032

0.276

0.220

0.332

Solidity

10220

1.000

0.003

1.000

0.934

1.000

1.000

1.000

Conclusions:
TEM analysis showed that the sample consists mainly of single primary particles. A variation in the size of the primary particles of the nanomaterial is found on all the TEM images. The primary particles are relatively homogeneous in size and shape. The 2D morphology of the primary particles of the NM is more or less spherical. The median minimal Feret diameter of the primary particles was 8.0 nm.
Endpoint:
particle size distribution (granulometry)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Principles of method if other than guideline:
Granulometry (primary particle size and shape, aggregate/agglomerate size and primary particle size distribution (number-based)) was determined by Transmission Electron Microscopy (TEM).
The specimens were examined using a Tecnai Spirit microscope (FEI, Eindhoven, The Netherlands) and using ParticleSizer software.
GLP compliance:
no
Type of method:
microscopic examination
Type of particle tested:
primary particle
Type of distribution:
counted distribution
Percentile:
D25
Mean:
25 nm
Remarks on result:
other: Min. Feret diameter
Key result
Percentile:
D50
Mean:
34 nm
Remarks on result:
other: Min. Feret diameter
Percentile:
D75
Mean:
48 nm
Remarks on result:
other: Min. Feret diameter
Percentile:
other: Mean
Mean:
39.9 nm
St. dev.:
20.5
Remarks on result:
other: Min. Feret diameter

Column

 

Size

(number of observations)

Mean

 

Std Dev

Max

Min

Median

25%

75%

Area

(nm2)

1364

1978,6

2327,2

20000,0

119,0

1000,0

660,7

2000,0

Area Conv. Hull

(nm2)

1364

2047,6

2455,6

22000,0

152,2

1000,0

671,3

2000,0

Peri.

(nm)

1364

148,7

78,6

591,0

49,0

125,0

93,0

180,0

Peri. Conv. Hull

(nm)

1364

149,1

77,1

553,0

49,0

126,0

94,0

181,0

Feret

(nm)

1364

53,4

28,3

190,0

17,0

44,0

33,0

65,0

Min. Feret

(nm)

1364

39,9

20,5

161,0

11,0

34,0

25,0

48,0

Maximum inscribed circle diameter

(nm)

1364

38,2

18,0

122,0

8,0

33,0

25,0

46,0

Area equivalent circle diameter

(nm)

1364

45,2

22,4

161,0

12,0

39,0

29,0

55,0

Long Side Length MBR

(nm)

1364

50,5

26,7

182,0

16,0

42,0

31,0

62,0

Short Side Length MBR

(nm)

1364

40,4

20,9

168,0

11,0

34,0

26,0

48,0

Aspect Ratio

(N/A)

1364

1,258

0,250

3,278

1,000

1,187

1,067

1,370

Circ.

(N/A)

1364

13,564

1,475

24,341

7,525

13,108

12,521

14,189

Elong.

(N/A)

1364

0,441

0,144

0,837

0,093

0,447

0,332

0,546

Convexity

(N/A)

1364

0,998

0,010

1,000

0,839

1,000

1,000

1,000

Solidity

(N/A)

1364

0,974

0,019

1,000

0,837

0,981

0,970

0,986

Conclusions:
TEM analysis showed that the sample consists mainly of small single primary particles and agglomerates of larger primary particles. A fraction of nearly spherical single primary particles is present (~ 20nm). A variation in the size of the primary particles of the nanomaterial is found on all the TEM images.
The 2D morphology of the primary particles of the NM is more or less spherical. The median minimal Feret diameter of the primary particles was 34.0 nm.

Description of key information

Silver is produced in various forms: powders (non-nano and nano-size) and massives (ingots, wires...).

Powders are produced with variable specifications, including various particle size distributions. Member companies of the Precious Metals Consortium have provided two representative samples of commercial non-nano silver metal powders (Batches PMC 1 and PMC 2) and provided particle size data. In addition to these specifications provided by the producers, experimental investigations on the dustiness (rotating drum method) and on the particle size distribution of material that becomes airborne during such tests have been performed.

Further, particle size data have been generated for the nanosilver forms covered by the REACH registration dossier (Nano sample 1 and 2).

Additional information

The particle size parameters for the two representative samples of silver metal powders (non-nano PMC 1 +2) are presented in the following format:

Batch: D10, D50, D90; Mass Median Aerodynamic Diameter of airborne dust (geometric standard deviation):

Batch PMC 1: 12 µm, 30 µm, 50 µm; 30.1 µm (1.7)

Batch PMC 2: 0.8µm, 2 µm, 11 µm; 25.4µm (2.8)

Further, two members of the Precious Metals REACH Consortium registering nanosilver have provided nanosilver products for physico-chemical characterisation. Nanosilver is usually marketed in suspension/wet powder form. The table below gives an overview of registered nanosilver products. For confidentiality reasons, the information on coatings and solvents has been omitted from the summary table below. The morphology was determined by visual inspection of TEM images. Quantitative analysis was done by TEM combined with ParticleSizer software. The volume specific surface area was calculated from the particle size (mean diameter).

Code Type Size of primary particles by TEM (Min. Feret diameter) Morphology

Volume Specific Surface Area

1

suspension/wetted powder

Min = 5 nm, D25 = 7 nm, D50 = 8 nm, D75 = 9 nm, Max = 61 nm

spherical

714 m2/cm3

2

suspension/wetted powder

Min = 11 nm, D25 = 25 nm, D50 = 34 nm, D75 = 48 nm, Max = 161 nm

spherical

150 m2/cm3