Colloidal Silica
Colloidal silica, also known as silica sol, is a stable suspension of amorphous silica nanoparticles in liquid. It is used as a binder in investment casting shell building, a polishing agent in semiconductor manufacturing, a coating additive, and a catalyst support. Buyers need clarity on particle size, SiO₂ concentration, pH grade, and shelf stability before selecting a supplier.
## Why buyers start here
Colloidal silica is the primary binder for investment casting shell molds and a critical polishing compound in semiconductor wafer manufacturing. Its performance depends on precise control of particle size, concentration, and pH — making grade selection and supplier consistency essential.
## Key specifications to verify
| Property | Typical Range | Why It Matters |
|----------|--------------|----------------|
| SiO₂ concentration | 20%–50% | Higher concentration reduces shipping cost per unit of active material |
| Particle size | 5–100 nm | Determines binding strength, polish rate, and film formation |
| pH | 2–11 (grade-dependent) | Affects stability and compatibility with other slurry components |
| Specific surface area | 50–500 m²/g | Influences reactivity and viscosity |
| Viscosity | 3–50 cP | Affects application behavior in coating and casting |
| Shelf life | 6–24 months | Storage stability impacts logistics planning |
## pH grades and their uses
**Acidic silica sol (pH 2–4)**: Used in catalyst supports, textile treatment, and as an anti-slip coating agent. Stable at low pH, coagulates when pH rises above 5.
**Alkaline silica sol (pH 8–11)**: Most common for investment casting binders and polishing slurries. Stable at high pH, offers the widest particle size range.
**Neutral silica sol (pH 6–8)**: Used in coatings, paper treatment, and water purification. Requires careful formulation to maintain stability.
## Common applications
- **Investment casting**: Primary binder for ceramic shell molds (most common use)
- **Semiconductor polishing**: CMP (chemical mechanical planarization) slurries
- **Coatings and paints**: Wear-resistant and anti-corrosion additives
- **Catalyst production**: High-surface-area support material
- **Textile treatment**: Antistatic and stiffening finishes
- **Refractory binders**: High-temperature bonding agent
## What to clarify before inquiry
Share the target application, required particle size range, preferred SiO₂ concentration, pH grade, expected monthly volume, and any specific viscosity or shelf-life requirements.
Buyer concerns
- Particle size distribution
- SiO₂ concentration
- Shelf stability
- Viscosity control
Sourcing considerations
- Specify particle size range (5–100nm)
- Confirm pH requirement for application
- Verify storage and transport conditions