Quick Search
CAS no: 112945-52-5
EC / List no: 601-216-3
Chemical formula: SiO2
Synonyms:amorphous fumed silica, amorphous silica, amorphous silica gel, amorphous silicon dioxide, fumed silica, pyrogenic silica, pyrogenic colloidal silica, colloidal amorphous silica, silica, silica gel, silica (nano), silica colloidal amorphous, silica amorphous fumed, silica fumed, silicon dioxide, silicon dioxide amorphous, silicon(IV) oxide, silicondioxide, synthetic amorphous silica, synthetic amorphous silica fumed, synthetic silica, aquafil, butosil, dioxosilane, sílice amorfa, kiseldioxid amorf
Amorphous silica, commonly known as silicon dioxide (SiO₂), is a non-crystalline inorganic material that plays a critical role in a wide range of industries, including food,
pharmaceuticals, cosmetics, electronics, and construction. Unlike crystalline silica (such as quartz), amorphous silica does not possess a long-range ordered structure,
which gives it unique physicochemical properties such as high surface area, adsorption capacity, and chemical stability.
Key Properties of Amorphous Silica
Molar Mass: 60.08 g/mol (SiO₂)
Appearance: White, fine powder (amorphous, non-crystalline)
Solubility: Insoluble in water; soluble in strong alkalis
Density: ~2.0–2.2 g/cm³ (varies by type)
Boiling Point: Not applicable (decomposes at very high temperatures)
Melting Point: ~1600–1700°C (softening point; no true melting due to amorphous structure)
pH Behavior: Slightly acidic to neutral (typically pH 5.5–7.5 in aqueous dispersion)
Odor: Odorless
Amorphous silica is defined by its random, non-crystalline atomic arrangement. While the basic unit consists of silicon atoms bonded tetrahedrally to oxygen atoms, the lack of long-range periodicity differentiates it from crystalline forms.
Industrial Applications
Food Industry
Amorphous silica is widely used as a food additive (E551) due to its inert and safe nature:
Anti-caking agent in powdered foods
Flow enhancer for spices, coffee creamers, and supplements
Carrier for flavors and active ingredients
Pharmaceuticals
In pharmaceutical formulations, amorphous silica functions as:
Excipient and tablet disintegrant
Flow agent to improve powder processing
Adsorbent for liquid active ingredients
Stabilizer for drug formulations
Cosmetics and Personal Care
Silica is a key ingredient in cosmetics due to its sensory and functional benefits:
Oil absorption and mattifying effect
Soft-focus and light-diffusing properties
Texture improvement in powders and creams
Mild abrasive in toothpaste
Rubber and Tire Industry
Amorphous silica is used as a reinforcing filler:
Enhances tensile strength and durability
Improves abrasion resistance
Plays a crucial role in energy-efficient “green tires”
Paints, Coatings, and Adhesives
Controls viscosity and prevents sagging
Improves dispersion of pigments
Enhances durability and corrosion resistance
Plastics and Polymers
Anti-blocking agent in plastic films
Rheology modifier in resins and coatings
Improves mechanical performance
Paper Industry
Enhances printability and ink absorption
Improves opacity and brightness
Electronics and Microelectronics
Amorphous silica is essential in high-tech applications:
Electrical insulation in semiconductor devices
Substrate material in microchips
Optical fibers for telecommunications
Nanotechnology and nanoelectronics
Biotechnology and Nanotechnology
The interaction between silica and biomolecules has enabled advanced innovations:
DNA sequencing technologies (nanopore sensors)
Drug delivery systems
Biosensors and diagnostic tools
Self-assembled nanostructures
Construction Materials
Silica fume used as a pozzolanic additive in concrete
Enhances strength, durability, and chemical resistance
Improves microstructure and reduces permeability
Agriculture and Animal Feed
Anti-caking agent in feed additives
Carrier for vitamins and nutrients
Used in agrochemical formulations
Environmental and Specialty Applications
Moisture control (desiccants)
Liquid clarification (beer, wine, juices)
Filtration and adsorption systems
Insect control via dehydration mechanism
Amorphous silica is defined by its random, non-crystalline atomic arrangement. While the basic unit consists of silicon atoms bonded tetrahedrally to oxygen atoms, the lack of long-range periodicity differentiates it from crystalline forms.
This structural difference leads to:
Higher reactivity and surface functionality
Greater solubility in biological environments
Lower toxicity compared to crystalline silica
Enhanced interaction with polymers, liquids, and biomolecules
Key Properties and Advantages
Amorphous silica exhibits a unique combination of physical and chemical properties:
High surface area and porosity
Excellent adsorption and carrier capabilities
Chemical inertness and thermal resistance
High dielectric strength
Thixotropic behavior (viscosity control)
Optical transparency (in high purity forms)
Non-toxic and biocompatible characteristics
These properties make it an essential functional additive in numerous formulations.
