In the interweaving of technology and life, the names "silicon" and "silicone" are often used interchangeably, but they are actually two types of materials with very different properties. Silicon, as the "foundation" in the periodic table, supports strategic industries such as semiconductors and photovoltaics; while silicone, with its unique molecular structure, has become a "universal material" in the fields of medical care, food, electronics, etc. This article will reveal the essential differences between these two "same name but different surnames" materials from three dimensions: chemical nature, physical properties, and application scenarios.
Chemical nature: the leap from atoms to polymers
Silicon (Si) is a non-metallic element of the third period of the periodic table, group IVA, and its content in the earth's crust is second only to oxygen. Its single substance exists in two forms: crystalline and amorphous: crystalline silicon is steel gray, has a diamond-type cubic crystal structure, and is a typical semiconductor material; amorphous silicon is a black powder, which is often used in the light-absorbing layer of photovoltaic cells. Silicon has stable chemical properties. It only reacts with hydrogen fluoride at room temperature, and can react with non-metals such as oxygen and nitrogen at high temperatures to form compounds such as silicon dioxide and silicon nitride.
Silica Gel is a synthetic porous adsorption material with a chemical formula of mSiO₂·nH₂O. Its preparation process includes steps such as sodium silicate acidification, condensation, gelation, and aging, and finally forms a three-dimensional network structure composed of Si-O tetrahedrons. This structure gives silica gel two major characteristics: one is that the specific surface area is as high as 600-1000 m²/g, and the other is that the surface is covered with a large number of hydroxyl groups (-OH), making it a polar adsorbent.
Physical properties: the opposition between rigidity and elasticity
The physical properties of silicon alone show the contradiction of "hardness and flexibility":
Hardness: The Mohs hardness of crystalline silicon reaches 7, which is close to quartz (hardness 7), and can cut glass;
Brittleness: It is easy to cleave and break along the crystal plane under external force, and it needs to be doped with elements such as phosphorus and boron to improve toughness;
Conductivity: The conductivity of pure silicon is only 10⁻³ S/m, but after doping, the conductivity can be increased by 10⁶ times, becoming an n-type or p-type semiconductor.
Silicone rubber exhibits the adaptability of "both hard and soft":
Elasticity: The elastic modulus of vulcanized silicone rubber is only 0.01-1 MPa, and it can be stretched to 300% of its original length without breaking;
Porosity: By adjusting the pH value and aging temperature, the pore size can be controlled in the range of 0.7-300 nm, forming large pores, coarse pores, fine pores and other types;
Thermal stability: It can be used for a long time in an environment of -60℃ to 250℃, far exceeding the range of -50℃ to 120℃ of ordinary rubber.
Application scenario: Cross-border from chips to accessories
The application of silicon single substance is highly focused on high-tech fields:
Semiconductor industry: Monocrystalline silicon wafers are the basic materials of integrated circuits, and the global market size will reach US$50 billion in 2024;
Photovoltaic industry: The conversion efficiency of polycrystalline silicon cells has exceeded 24%, accounting for 85% of the global photovoltaic installed capacity;
Special alloys: Ferrosilicon alloys (containing 45%-90% silicon) are used for steelmaking deoxidation, and silicon-manganese alloys can improve the strength of steel.
The application of silicone is extensive and "silent":
Medical field: Medical grade silicone has passed ISO 10993 biocompatibility test and is used for implants such as artificial heart valves and catheters;
Food industry: Silicone molds that meet FDA standards can withstand temperature differences from -40℃ to 230℃ and are used in chocolate and cake making;
Fashion accessories: By adding pigments and additives, silicone can be made into colorful and soft bracelets and necklaces. Its wear resistance makes the life of accessories more than 3 times that of ordinary plastics;
Environmental adsorption: The adsorption amount of CO₂ by modified silica adsorbent can reach 3.2 mmol/g, which can be used for industrial waste gas treatment.
The difference between silicon and silicone is essentially a dialogue between "atomic economy" and "molecular engineering". Silicon achieves semiconductor properties by precisely controlling the crystal structure, while silicone achieves adsorption function by regulating pore structure and surface chemistry. This difference tells us that material innovation requires not only deep cultivation of the essential characteristics of basic elements, but also mastering the "art" of molecular design and microstructure regulation.