Laser diffraction particle size distribution (PSD) of alumina and quartz powders in aqueous dispersion; reference method for non-plastic ceramic powders in the 0.05–500 µm range.
ASTM C1070
Revision: 2020
Sample preparation
Standard test method for determining particle size distribution of alumina or quartz by laser light scattering
Scope: Laser diffraction particle size distribution (PSD) of alumina and quartz powders in aqueous dispersion; reference method for non-plastic ceramic powders in the 0.05–500 µm range.
Test method
Deagglomerated particles circulate through a laser beam; scatter signals are converted to volume-based equivalent spherical diameter using Fraunhofer and/or Mie theory; d10, d50, and d90 are reported.
Specimen requirements
Powder must be fully deagglomerated in aqueous suspension via wetting, mechanical shear, and dispersant stabilization; respirable crystalline silica exposure must be controlled when handling quartz.
ASTM C1070 — Particle size distribution by laser light scattering
Alumina and quartz powder characterisation
Original publication: 2001; last reapproval: 2020.
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The information on this page is a summary prepared by Vector Scientific Testing Devices based on a review of the applicable standard; it does not replace the official standard text. For the complete and binding document, obtain the standard from the relevant standards body (e.g. TSE, ASTM International, CEN) through official channels. Vector accepts no liability for direct or indirect loss arising from reliance on this summary.
1. Purpose and scope
Objective: To determine the particle size distribution (PSD) of alumina (Al₂O₃) and quartz (crystalline silica) powders by laser light scattering — materials used in industrial ceramics, refractories, abrasives, and electronic substrate feedstocks.
Measurement range: Approximately 0.05 µm to 500 µm; the method focuses on aqueous dispersion of non-plastic ceramic powders.
Note: Micronized size distribution directly affects sintering behaviour, rheology, and final mechanical strength; this standard enables consistent, repeatable PSD reporting between producers and customers.
2. Test method
Particles are held in suspension after deagglomeration and passed continuously through a circulating cell in front of a laser beam. Scattered light is collected by angle-sensitive detectors and processed digitally.
| Analytical parameter | Technical detail |
|---|---|
| Measurement principle | Laser diffraction / light scatter intensity |
| Measurement range | 0.05 µm – 500 µm |
| Analysis theory | Fraunhofer diffraction, Mie scattering, or hybrid optical models |
| Dispersion | Aqueous suspension |
| Reported statistics | Volume distribution curves, d10, d50 (median), d90 |
Signals are converted to a volume-based equivalent spherical diameter distribution assuming spherical particles. Laser diffraction is an indirect method — results should be used as a relative QC indicator, not compared one-to-one with microscopy.
3. Specimen requirements
Accuracy depends on the powder being fully deagglomerated and stabilized as single particles in aqueous suspension. High surface energy of alumina and quartz promotes flocculation in water, which can artificially inflate measured sizes.
The dispersion workflow has three stages:
- Wetting — surfactants to lower surface tension
- Deagglomeration — mechanical shear / cutting forces
- Stabilization — dispersants providing electrostatic or steric repulsion
3.1 Typical wetting agents and dispersants
| Agent | Foaming tendency | Typical addition | Role |
|---|---|---|---|
| Alcohol ethoxylate | Medium | 0.1 – 0.5 % | Balanced wetting |
| Sulfosuccinate | High | 0.1 – 0.5 % | Fast interfacial penetration |
| Fluorosurfactant | Low | 0.01 – 0.1 % | Effective at ultra-low dose |
| Polyether siloxane | Medium | 0.1 – 0.5 % | Controlled-foam dispersion |
| Acetylenic diol | Low | 0.05 – 0.2 % | Low-foam wetting |
| Polycarboxylate polymer | Very low | 0.2 – 1.0 % | Steric / electrostatic stability |
Quartz / silica warning: Crushing, milling, and handling can release respirable crystalline silica (RCS). Use wet methods, dust extraction, and enclosed work areas (Section 7).
4. Compatible Vector equipment
An ASTM C1070 workflow spans integrated laboratory steps from raw mineral to sub-micron dispersion. The Vector systems below support sample preparation, cross-check measurements, and safe handling.
| Code | Equipment | Role in ASTM C1070 workflow |
|---|---|---|
| VTR-1011 | Nysos jaw crusher | Contamination-free primary crushing (tungsten carbide jaws) |
| VTR-1011-XL | Thor jaw crusher | High-throughput continuous crushing |
| VTR-1012 | Hercules vibratory disc mill | Analytical fine grinding (60–90 µm) |
| VTR-1012XL | Hercules XL disc mill | Large-volume automated grinding sets |
| VTR-1012C | Gaia vibratory disc mill | Continuous-line recirculation |
| VTR-13-018 | Ultrasonic water bath | Cavitation deagglomeration |
| VTR-13-017 | Water distiller | High-purity carrier water |
| VTR-1016 | Automatic Blaine tester | Specific surface area cross-check |
| VTR-1014 | Alpine air-jet sieve | Coarse agglomerate / oversize control |
| VTR-1041 | Analytical sieve shaker | Coarse fraction sieving |
| VTR-1027 | XRF pellet press | Spectroscopic pellet preparation |
| VTR-13-015 | Laboratory fume hood | Dusty / wet-chemistry prep steps |
See also ASTM C204 and EN 196-6 for Blaine fineness cross-checks.
5. Optical theory: Fraunhofer and Mie
Fraunhofer model: Simplified approach assuming particles are much larger than the wavelength (practically several µm and above) and opaque; no refractive index input required. Sensitivity drops for sub-micron alumina/quartz where refraction and absorption dominate.
Mie theory: Models refraction, reflection, and absorption at particle boundaries; requires the complex refractive index of alumina or quartz in water (real and imaginary components).
Large particles scatter at narrow angles with high intensity; fine particles scatter broadly at low intensity — the inverse relationship that underpins laser PSD.
6. Vector sample-preparation workflow
- Primary crushing — Nysos or Thor for feed up to 90 mm; tungsten carbide jaws minimise iron contamination.
- Analytical milling — Hercules or Hercules XL to 60–90 µm; Gaia for continuous lines.
- Ultrasonic dispersion — VTR-13-018 breaks sub-micron agglomerates; carrier water from VTR-13-017.
- Cross-checks — Automatic Blaine for specific surface area; Alpine air-jet sieve and analytical sieve shaker for coarse fractions.
- Chemical characterisation — XRF pellet press for composition verification.
7. Occupational health and safety
Quartz contains high levels of crystalline silica. Respirable crystalline silica (typically ≤ 10 µm) released during crushing and milling can cause silicosis and other lung disease.
| Regulatory reference | Parameter | Limit (8 h TWA) |
|---|---|---|
| OSHA 29 CFR 1910.1053 | PEL | 50 µg/m³ |
| OSHA 29 CFR 1910.1053 | Action level | 25 µg/m³ |
Operational requirements:
- Avoid dry sweeping and compressed-air blow-down; prefer wet handling and local exhaust.
- Connect integrated dust ports on Nysos and Thor crushers to Class H industrial vacuums (HEPA H13/H14).
- Perform dusty weighing and wet-chemistry prep under VTR-13-015 fume hood.
- Personnel should wear P3 particulate respirators (EN 149) or powered air-purifying masks where exertion is high.