Ⅰ. Characteristics of Nanodiamond
Diamond is the hardest material on Earth and one of the most valuable. Among all natural and synthetic materials, diamond possesses the highest hardness and thermal conductivity, the broadest range of optical transparency, and the highest refractive index. It also exhibits exceptional wear resistance, as well as superior acoustic properties, radiation resistance, and corrosion resistance. In short, diamond is the most perfect functional material in the material world to date. Due to its potential applications in military and various sectors of the economy, diamond powder has garnered increasing attention, leading to advancements in its production technology.
Nanodiamonds are synthesized through the detonation of TNT and RDX, creating a high-pressure (200,000 atmospheres) and high-temperature (3000K) environment that produces spherical nanoscale diamond particles. These nanodiamonds exhibit dual properties, combining the characteristics of both nanoparticles and superhard materials. Their thermodynamic stability makes them ideal for integration into various materials, enhancing their properties and forming new nanocomposite materials. Nanodiamonds are the finest form of diamond powder currently available, synthesized artificially as they do not occur naturally. They possess unparalleled hardness and corrosion resistance, and due to their extremely small grain size (down to 10 nanometers), they exhibit a high surface area, which gives them exceptional physical reactivity and micro-adsorption properties. After resolving issues related to nanoparticle aggregation and assembly, nanodiamonds can effectively eliminate interface tension problems, making them useful for a variety of applications, including anti-wear, friction reduction, and composite material reinforcement.
Ⅱ. Current Status of Nanodiamond Development Domestically and Internationally
Nanodiamond production is primarily achieved through the detonation of graphite, known as the graphite detonation method. Traditional grinding techniques can only reduce diamond particles to about 200 nanometers, which is still not within the nanometer scale required for true nanoscale structures. This method is relatively straightforward to implement, and Taiwan has been an early adopter in developing nanodiamond synthesis and applications. Many of the nanodiamond-based products developed domestically are considered to be at an internationally advanced level.
1. Defense Applications
(1) Stealth and Anti-Corrosion Coatings: Nanodiamonds exhibit high transparency and absorption of radar waves, infrared, and ultraviolet light. When applied as coatings to aircraft, tanks, missiles, and naval vessels, they can enhance stealth capabilities and prevent corrosion.
(2) Explosives: Adding nanodiamonds to explosives can significantly enhance the explosive power.
(3) Electroplating in Armor: Nanodiamonds can be electro-brushed onto protective armor of armored vehicles and tanks, as well as electroplated into gun and cannon barrels.
(4) Textiles: Incorporating nanodiamonds into fabric fibers results in highly durable, self-cleaning, UV-resistant, and stealth materials.
2. Lubricants
Nanodiamonds treated through nano-assembly technology can eliminate interfacial tension, allowing them to evenly and thermodynamically stably suspend in lubricants. This suspension acts like billions of bearing balls in the lubricant, reducing sliding friction to rolling friction. This creates a diamond ball-bearing structure between engine cylinder walls and pistons, which never wears out and fills in any wear or rough spots. This can significantly extend the life of engines.
3. Mechanical Applications
(1) Electroplating: Nanodiamond-based composite electroplating solutions, including nickel, chrome, copper, zinc, cobalt-phosphorus coatings, can be applied to cutting tools, extrusion molds, gears, shafts, cylinders, and nozzles. These coatings improve wear resistance by 2-4 times and increase microhardness by 1-4 times.
(2) Metal Composites: Nanodiamonds combined with other metal particles in a hydrogen environment can be used to create high-strength, wear-resistant metal composites, which are widely applied in manufacturing engine blocks, pistons, and oil drilling bits.
4. Electronics Applications
(1) Nanodiamond Semiconductor Materials: Using the detonation method, nanodiamond semiconductor materials can be created. These materials exhibit a wide bandgap (up to 5.5 eV, five times higher than traditional silicon semiconductors) and high electron and hole mobility (hole mobility is four times that of silicon). As a result, the circuit operating speed is significantly enhanced. Nanodiamond semiconductors are ideal for high-reliability, radiation-resistant devices since they do not accumulate carriers due to radiation, unlike other materials.
(2) Doped Nanodiamonds: By doping nanodiamonds with boron or aluminum, the resistivity drops from 7.7×10^7 ohm·cm to 0.1-2 ohm·cm, expanding the possibilities for producing nanodiamond semiconductor and electrode materials.
(3) Field Emission Displays: Nanodiamonds exhibit excellent cold cathode field emission effects, making them highly suitable for ultra-thin, high-definition, low-power consumption, wide-viewing angle displays, which could potentially replace LCD technology.
(4) Protective Films: Nanodiamonds can be used to form protective coatings for integrated circuits, hard drives, and magnetic heads, offering enhanced durability and performance.
5. Composite Materials Applications
Nanodiamonds have a high surface reactivity due to the presence of functional groups like carboxyl, hydroxyl, and carbonyl on their surface. This enables them to form strong bonds with metals, rubbers, polymers, and fabrics, enhancing their properties with only a small amount of nanodiamonds added.
(1) Coatings: By suspending nanodiamonds in paints, a durable and scratch-resistant coating can be applied to vehicles. This coating also provides UV protection, is hydrophobic (water-repellent), self-cleaning, and enhances the paint’s uniformity, durability, and weather resistance. When applied to ships, it offers excellent resistance to seawater corrosion.
(2) Rubber and Polymers: Adding nanodiamonds to rubber and polymers can significantly improve their performance. For example, tire burst strength can increase from 53 MPa to 154 MPa. Rubber products see a doubling of elasticity and a 2-2.5 times increase in wear resistance. Nanodiamonds also enhance the properties of rubber components used in engines and seals, improving elasticity in low temperatures and overall durability.
(3) Ceramics: Incorporating small amounts of nanodiamonds into ceramic products greatly enhances their toughness and reduces brittleness while increasing wear resistance, making them more durable and suitable for high-performance applications.
6. Biomedical Applications
Nanodiamond coatings are widely used in biomedical materials due to their excellent biocompatibility and wear resistance. These coatings can be applied to surfaces like teeth, jawbones, and leg joint prosthetics, improving their longevity and interaction with biological tissues.
7. Other Applications
(1) Polishing Materials: Nanodiamonds can be formulated into precision polishing liquids and pastes, used in the fine polishing of gemstones such as sapphires and rubies, as well as high-end optical lenses, achieving ultra-smooth surfaces.
(2) Hydrogen Storage: Due to their extremely large surface area, nanodiamonds have a strong capacity to absorb and store hydrogen. This makes them a promising material for use in fuel cells, which could play a significant role in the development of new, cleaner energy sources, potentially reducing pollution.
In conclusion, nanodiamonds represent the pinnacle of modern technological advancement with a wide range of applications. With their unique properties, they offer immense potential for future innovations and market growth.
