Nanomaterial introduction

  A nanometer is a scale, and nanotechnology is a complete system integrating advanced science and technology. Its basic meaning is to understand and transform nature within the scope of nanoscale and innovate materials through direct operation and arrangement of atoms and molecules. Nanoscience and technology mainly include nanosystem physics, nanochemistry, nanomaterials science, nanobiology, Nano Electronics, nano processing, Nano Mechanics.

Nanomaterials are the most dynamic and abundant branch of Science in the field of nanotechnology. In the 1980s, nanomaterials refer to the solid materials composed of nanoparticles, in which the size of nanoparticles is no more than 100 nm. The preparation and synthesis technology of nanomaterials is the main research direction at present. Although some progress has been made in the synthesis of samples, a large number of bulk samples can not be prepared so far. Therefore, the preparation of nanomaterials plays an important role in its application.

1. Properties of nanomaterials

Physicochemical properties The melting point and crystallization temperature of nanoparticles are much lower than those of conventional powders. This is due to the high surface energy and high activity of nanoparticles, which consumes less energy during melting. For example, the melting point of general lead is 600k, while the melting point of 20nm lead particles is lower than 288k; nano metal particles show electrical insulation at low temperature; nanoparticles have strong light absorption, so almost all kinds of nanoparticle powders are in the form of Nanomaterials have strange magnetism, which is mainly manifested in the different magnetic properties of nanoparticles with different particle sizes. When the particle size is higher than a certain critical size, it shows high coercivity, while when the particle size is lower than a certain size, the coercivity is very small. For example, the coercivity of nickel particles with the particle size of 85 nm is very high, while that of nickel particles with particle size less than 15 nm is close to zero Because of its large specific surface area, the surface chemical activity of the particles is much higher than that of the normal powder. The diffusion and sintering properties of nanostructured materials are 1014 ~ 1020 times of lattice diffusivity in normal state and 102 ~ 104 times of grain boundary diffusivity. Therefore, nanostructured materials can be effectively doped at a lower temperature, and immiscible gold can be formed into a new alloy phase at a lower temperature. Another result of the increase of diffusion ability is that the sintering temperature of nanostructured materials can be greatly reduced, so densification can be achieved at a lower temperature.

Mechanical properties compared with ordinary materials, the mechanical properties of nano materials have significant changes, the strength and hardness of some materials are increased by times; nanomaterials also show Superplastic State, that is, a large amount of elongation before fracture.

2. Application of nanomaterials

Nano metal: for example, nano iron material is made by pressing 6-nanometer iron crystal. Compared with ordinary iron, the strength is increased by 12 times and the hardness is increased by 2-3 orders of magnitude. Special steel with high strength and high toughness can be produced by using nano iron material. As for the metal with high melting point and difficult to form, as long as it is processed into nanopowder, it can be melted at a lower temperature and made into high-temperature resistant components, which can be used to develop ultra-high temperature materials in the new generation of high-speed engines. "Nanosphere" lubricant: the full name of "atomic self-assembly nanosphere solid lubricant", which is made of aluminum-based alloy with icosahedral cluster structure and processed by unique nano preparation technology. The new surface can be formed on the friction surface by using high-speed airflow comminution technology and accurately controlling the particle size of additives, which can repair the locomotive engine. Its composition design and preparation process are innovative and fill the blank technology of lubricating oil alloy based additives. Adding nanospheres to a locomotive engine can save fuel, repair worn surfaces, enhance locomotive power, reduce noise, reduce pollutant emission, and protect the environment. Nanoceramics: first of all, the sintering temperature of ceramics can be reduced by using nanopowder, which simplifies the production process. At the same time, nanoceramics have good plasticity and even superplasticity, which solves the weakness of the toughness of ordinary ceramics and greatly expands the application field of ceramics. The diameter of the carbon nanotube is only 1.4nm, which is only 1% of the thinnest circuit width on the computer microprocessor chip. Its mass is 1 / 6 of that of the same volume steel, but its strength is 100 times that of steel. Carbon nanotube will become the preferred material of high-energy fiber in the future, and will be widely used to manufacture ultra-fine wires, switches, and nanoelectronic circuits. Nanocatalyst Because the surface area of nanomaterials is greatly increased, and the surface structure has changed greatly, so the surface activity is enhanced. Therefore, nanomaterials can be used as catalysts, such as ultrafine boron powder and ammonium perchromate powder, which can be used as effective catalysts for explosives; ultrafine platinum powder and tungsten carbide powder are efficient hydrogenation catalysts; ultrafine silver powder can be used as a catalyst for ethylene oxidation; ultra-fine silver powder can be used as a catalyst for ethylene oxidation Fine Fe3O4 particles as the catalyst can decompose CO2 into carbon and water at low temperature; adding a small amount of nickel powder into rocket fuel can increase the combustion efficiency by many times.

To manufacture quantum components, quantum boxes must be developed first. A quantum box is a tiny structure with a diameter of about 10 nanometers. When an electron is closed in such a box, the electron will have an unusual performance due to the quantum effect. Using this phenomenon, we can make quantum devices. Quantum devices work mainly by controlling the phase of the electron wave so that it can achieve higher response speed and lower power consumption. Quantum devices can also greatly reduce the volume of components and simplify the circuit. Therefore, the rise of quantum devices will lead to an electronic technology revolution. People are looking forward to using quantum devices to produce 16 GB DRAM in the 21st century. Such a memory chip can store the information of 1 billion Chinese characters.

China has developed an emulsifier made by nanotechnology. After adding gasoline in a certain proportion, the fuel consumption of cars like Santana can be reduced by about 10%. Nanomaterials have excellent hydrogen storage capacity at room temperature, and about 2 / 3 of hydrogen energy can be released from these nanomaterials at room temperature and pressure, so it is unnecessary to use expensive cryogenic liquid hydrogen storage devices

3. PVD and CVD Manufacturing

As the best tool for micro-scale manufacturing, VD (physical/chemical vapor deposition) technology is frequently used to create certain types of nanomaterials. This technology allow us to deposit atoms layer by layer. This is very important to create 2-dimensional materials, such as graphene and *2D boron nitride. Also, as the material is growing by atoms, it could form some special microstructures. 

*In most of cases, boron nitride is not a 2D nanomaterial, but a structural ceramic. Check here for more about boron nitride ceramics

Vaport deposition process is a great tool for human not only in micro-scale material building but also in normal size products such as decorations coatings. As an example, it could be used to make gold coatings for jewelry. As the material (e.g. sputter targets) consumed could be both pure metal and alloy or oxides, the color of coating can be quite abundant.