Sol-Gel Process for Advanced Materials

13/02/2026

The sol-gel process is a key enabling technology for developing advanced materials with precisely engineered properties, especially highly pure metal oxide by soft chemistry.

Generally, oxide can be obtained by thermal transition at high temperature to obtain glass or ceramic but also through thin layer application process such like PVD, CVD, plasma or sputtering. Sol-Gel, also called soft chemistry, implies the formation of oxide at moderate temperature mimicking the formation of silicate by diatomaceous algae.

By controlling hydrolysis and condensation reactions of liquid precursors at the molecular level, this method allows the creation of highly uniform inorganic networks through chemical routes. Coupled with the right application and drying process, sol-gel process enables to obtain highly pure composition of glass and ceramics, coatings, organic-inorganic hybrids or highly porous materials, also called aerogel.

Molecular design can be customised to achieve desired performance characteristics. This adaptability enables its use across diverse industries such as aeronautic, aerospace, railway, energy, automotive, medical device or consumer goods; and use including surface protection, improved adhesion, optical enhancement, high-temperature applications, catalysis, and additive manufacturing.

What is the Sol-Gel process?

The sol-gel process is both a versatile chemical method and a processing method used to synthesize inorganic oxide for advanced materials, particularly functionalized surface, coatings, thin films or highly porous materials, at moderate temperatures. It involves the transition of a system from a liquid solution called "sol" (a colloidal suspension of particles) into a solid "gel" phase. Starting from organometallic liquid monomers, these molecules hydrolyse in presence of water and polymerize through condensation process to form a solid matter. This transformation enables the formation of highly uniform network in a liquid binary media composed of water and alcohol.

Combined to the adequate drying process, the glass or ceramic materials can be obtained:

Colloids and particles with desire dimension (from nano- to micrometer) and shape (spherical, fibers, …) that can be used as filler or additives
Coating or thin layer for surface functionalization
Resin for 3D printing
Bulk material that could be used for ceramic preforms or optical fiber
Highly porous Aerogel for thermal insulation, drug delivery system or catalysis

One of the main advantages of sol-gel process is that, by combining soft chemistry to moderate temperature processing, inorganic oxide can be coupled to organic moieties without degrading them. This involves the creation of new kind of organic-inorganic hybrids materials combining advantages of both parts such as thermal stability, flexibility, hardness or optical properties.

Sol-Gel process offers application for functionalized surfaces on a wide range of substrates including metals, ceramics, polymers, and composites.

At Applus+ Laboratories, the sol-gel method is applied to develop high-performance coatings with tailored properties such as anti-scratch, hydrophobicity, thermal resistance, and fire protection; resin for 3d printing or porous Aerogel materials.

What are the characteristics of the sol-gel process?

Design by chemistry: influence of precursors type, inorganic atom (Silicium, Zirconium, Titanium, Vanadium, …), catalysis through pH modification (basic for particles design and acidic for resin design), additives (pore-forming agent, temperature reactivity, UV-curing, …)
Low-temperature synthesis: Ideal for temperature-sensitive substrates (from room temperature to 200°C)
High purity and homogeneity inorganic oxide: Molecular-level control over composition (i.e obtention of pure anatase TiO2, Silicon carbide, V2O5, …).
Versatile processing techniques: Dip-coating, spin-coating, spray-coating, and inkjet printing, 3D printing.
Drying specification: from room temperature to 800°C depending of required materials, supercritical drying for Aerogel.
Functionalization potential: Enables integration of optical, mechanical, catalysis and barrier properties.
Scalability: From lab-scale prototyping to industrial production up to 500 kg batches.

What are the steps in the sol-gel process?

1. Sol preparation: Mixing monomers/precursors (typically metal alkoxides or salts) with water, solvents and catalysts to ensure synthesis of material.

2. Hydrolysis and condensation: Chemical reactions form a 3D network of particles.

Through the addition of water, precursors hydrolyse and inorganic polymerization starts.
Polymerization and propagation occur through condensation.

3. Gelation: The sol transforms into a gel with increased viscosity. Poly-condensation enables the formation of large size oligomer that leads to the formation of solid resin in a liquid media.

4. Processing : The resin is processed by:

Wet deposition techniques such as spraying, spin- & dip-coating, coil-coating or inkjet. All these techniques are available at Apllus+ Laboratories.
3D printing or lithography for UV-reactive resin.

5. Aging and drying: Removal of solvents and stabilization of the gel structure. Drying can de bone at:

Standard pressure and temperature to obtain dense materials.
Supercritical temperature and pressure to obtain highly porous Aerogel (Porosity > 98%).

6. Thermal treatment: Final curing to enhance mechanical and chemical properties.

These steps can be adapted to produce coatings, powders, or monoliths depending on the application.

Sol-Gel process applications

The sol-gel process is used across multiple industries for:

Protective coatings: Anti-corrosion, anti-abrasion, and fire-resistant layers
Biomedical devices: Biocompatible and antibacterial surfaces
Optical components: Transparent and anti-reflective coatings
Hydrophilic, hydrophobic or easy-to-clean surface
Energy systems: Thermal and electrical conductive films and materials
Aerospace and automotive: Lightweight, durable surface treatments
Adhesion primer for bonding or paint adhesion enhencement

Applus+ Laboratories supports clients from formulation to industrialization, offering sol-gel synthesis, robotic deposition platforms, and small-series prototyping.