Summary of Application Fields of Gel-Processed Silica

1. Basic Definition and Preparation

1.1 Core Definition

Gel-processed silica, also known as aerogel-processed silica or colloidal silica, is an amorphous silica material prepared by the sol-gel method. Using sodium silicate, tetraethyl orthosilicate, etc. as silicon sources, it is made through processes such as sol formation, aging, and drying (supercritical or freeze-drying to retain pores). Its core characteristics include a high specific surface area, well-developed pore structure, controllable particle size distribution, and excellent chemical stability.

It differs significantly from precipitated silica, with specific comparisons as follows:

1.2 Core Preparation Steps (Sol-Gel Method)

• Sol Preparation: Under the action of acid/alkaline catalysts such as hydrochloric acid and ammonia water, the silicon source undergoes hydrolysis and polycondensation reactions to form silica nanoparticles, which are dispersed in the solution to form a stable sol.
• Gelation: The polycondensation reaction continues, and the nanoparticles form a three-dimensional network structure through Si-O-Si bonds, encapsulating the liquid, and the system loses fluidity to become a wet gel.
• Aging: The wet gel is left to stand at a specific temperature, the network structure is further cross-linked and strengthened, and the liquid in the pores diffuses slowly to improve mechanical strength.
• Drying: Supercritical drying (to prevent pore collapse) or freeze-drying is used to remove the liquid medium, obtaining porous and lightweight xerogel or aerogel finished products.

2. Main Application Fields

Relying on the characteristics of "high specific surface area, high porosity, high purity, and low bulk density," gel-processed silica is widely used in multiple fields:

2.1 Rubber and Tire Industry: High-Performance Reinforcing Agent

1. Reinforcement Mechanism: The hydroxyl groups (-OH) of silica form chemical bonds with rubber molecules (isoprene rubber, styrene-butadiene rubber, etc.) through silane coupling agents (e.g., Si69), improving the tensile strength, tear strength, and wear resistance of rubber.
2. Core Advantages: Reduces tire rolling resistance (lowering fuel consumption), improves wet grip (enhancing safety), and does not affect anti-aging performance.
3. Application Scenarios: High-end passenger car tires, new energy vehicle tires, racing tires, etc.

2.2 Cosmetics and Personal Care: Multi-Functional Additive

Due to its non-toxicity, high adsorption, and good skin feel, it has become a key ingredient, with functions including:

1. Physical Sunscreen Agent: Nanoparticles reflect and scatter ultraviolet rays (UVA/UVB), without skin irritation caused by chemical sunscreens, used in sunscreens and isolation creams.
2. Adsorption Conditioner: Adsorbs excess oil on the skin, improving the "oily shine" of oily skin, used in oil-controlling loose powder, setting powder, and liquid foundation.
3. Skin Feel Modifier: Tiny particles fill skin texture, improving the smoothness of product application and reducing pilling, used in creams, emulsions, and lipsticks.

2.3 Food and Pharmaceutical Industry: Safe Additive and Carrier

It meets food-grade (e.g., FDA certification) and pharmaceutical-grade standards, with application directions as follows:

1. Food Anti-Caking Agent: Prevents agglomeration of powdered foods such as milk powder, coffee powder, protein powder, and condiments during storage, adsorbs moisture, isolates particles, and does not affect taste and nutrition.
2. Pharmaceutical Carrier: With high porosity and specific surface area, it carries antibiotics, probiotics, sustained-release drugs, etc., achieving controlled release rate, improving stability, and reducing irritation, used in capsules, tablets, and oral liquids.
3. Catalyst Carrier: In the synthesis of pharmaceutical intermediates, it carries noble metal catalysts, improving catalyst dispersibility and reaction efficiency, and is easy to separate from products, reducing purification costs.

2.4 Coating and Ink Industry: Performance Modifier

It can significantly improve the comprehensive performance of coatings and inks, with specific applications:

1. Matting Agent: The porous structure scatters light, making the coating surface show a matte effect without affecting coating adhesion and scratch resistance, used in furniture paint, automotive matte paint, and printing ink.
2. Rheology Modifier: Adjusts the viscosity and fluidity of coatings through particle interactions, prevents pigment sedimentation (e.g., color pastes), and improves construction "sagging" (avoiding uneven coating).
3. Wear and Corrosion Resistance Agent: Added to metal anti-corrosion coatings, it forms a dense silica protective layer, improving salt spray resistance and weather resistance (anti-ultraviolet aging), used in marine coatings, bridge coatings, and industrial equipment coatings.

2.5 Electronics and New Energy Fields: High-Performance Functional Materials

Applications are expanding rapidly with industrial development:

1. Electronic Packaging Material: High-purity products are used as fillers for semiconductor chip packaging adhesives, improving insulation, thermal conductivity (aiding heat dissipation), and moisture-heat resistance, protecting chips from environmental interference.
2. Lithium Battery Separator Coating: The ultra-thin coating improves the high-temperature resistance of the separator (preventing thermal runaway), ionic conductivity (reducing internal resistance), and inhibits lithium dendrite growth, used in new energy vehicle lithium batteries and energy storage batteries.
3. Optical Glass Polishing Agent: High-purity, uniform particle size micro-powder can be used for precision polishing of optical glass such as mobile phone lenses, camera lenses, and optical fibers, avoiding scratches and ensuring optical accuracy.

2.6 Other Special Fields

1. Environmental Governance: Used as an adsorbent to treat wastewater (adsorbing heavy metal ions and organic pollutants) and waste gas (adsorbing VOCs and sulfur dioxide), or as a soil amendment to adjust air permeability.
2. Thermal Insulation Material: Aerogel products (aerogel blankets, aerogel boards) have extremely low thermal conductivity (0.012-0.02 W/(m·K)) and are one of the best thermal insulation materials, used in aerospace (spacecraft thermal insulation), building insulation (ultra-low energy consumption buildings), and industrial pipeline insulation.

3. Development Prospects

Gel-processed silica has gradually penetrated from traditional industries such as rubber and coatings into high-end manufacturing fields such as new energy and electronics, as well as life and health fields such as pharmaceuticals and cosmetics, and has become a key material in the new material industry. With the advancement of preparation technology (reducing costs and expanding functional modification), its application scenarios will be further expanded. In the future, it is expected to play a greater role in carbon neutrality (green tires, thermal insulation materials) and high-end medical care (targeted drug carriers) and other fields.