What Problems Can Nanotechnology Solve For Ceramic Materials

The nano-ceramic generally refers to the advanced ceramic material whose grain size, grain boundary width, second phase distribution, defect size, etc. of the ceramic crystal phase are all within 100nm. Nanoization is a revolution in the ceramic industry, which is generally valued by all the countries producing ceramics in the world. Then, what "problems" of ceramic materials have been solved by the emergence of nanotechnology?

"Nanoceramic is a strategic way to solve the brittleness of ceramics"

Since the ceramic material has ionic bonds and covalent bonds as the main bonding bonds, the ceramic material has relatively high compressive strength and hardness. However, the brittleness of ceramics is extremely high, and the fracture toughness and bending strength are low, which limits the application of ceramic materials.

Because nano-ceramic has a large grain boundary interface, the arrangement of atoms on the interface is disordered, and it is easy to migrate under the action of external stress, so it shows ductility and toughness better than ordinary ceramics.

Improve hardness and plasticity

In terms of hardness, nano ceramics are 5 times or even higher than ordinary ceramics. At 100°C, the hardness of nano-TiO2 ceramics is 1.3GPa, while that of ordinary ceramics is about 0.1GPa. SunZ et al prepared Al2O3 nano-ceramics, which has a theoretical density of 97.6% and an average particle size of 1.1 μm, and its hardness is as high as 23GPa, which is much higher than that of ordinary Al2O3 ceramics.

In terms of superplasticity, superplasticity means that in a tensile test, at a certain strain rate, the material will produce a large tensile deformation. Ordinary ceramics are brittle materials that do not have superplasticity at room temperature and are difficult to deform. The reason is that its internal slip system is less, the dislocation movement is difficult, and the dislocation density is small. Only when the temperature is above 1000°C can ceramics have a certain shape. It is generally believed that if you want to have superplasticity, you need to have a small particle size and a fast diffusion path. Nano-ceramic not only has a smaller particle size, but also has a complex and chaotic atomic arrangement at the interface, and contains many unsaturated bonds. Atoms are easy to move under deformation, so they show good ductility.

affect ferroelectricity

In terms of ferroelectricity, the crystal size of ceramics directly affects its ferroelectric properties. As the grain size decreases, its ferroelectric properties will gradually decrease. When its size is small enough, the entire ferroelectric properties of the material disappear. Therefore, researchers have done a lot of research on this critical value. Some researchers sintered BaTiO3 ceramics at 6GPa and 1000°C, and characterized their ferroelectricity with dielectric transition peaks. When the frequency is 1kHz, there is a broad nodal transition peak near 120℃, and the dielectric constant is 1920. The ferroelectricity disappearance critical size of the barium titanate nano-ceramics obtained under high pressure is less than 30nm.

In addition, the advantages of nanonization are: as the particle size of the powder decreases, it is more conducive to achieving the compactness of ceramics at low temperatures.

Application of nano ceramics

protective material

In terms of protective materials, nano-ceramics show surprising advantages. Due to the extremely poor toughness of ordinary ceramics, processes such as interface damage and crack propagation will occur after being impacted, which greatly restricts the development of ceramics in terms of ballistic resistance. The nano-ceramic has excellent toughness and can resist impact extremely well. Introducing nano-ceramics into tank armor materials can effectively improve the tank's bullet resistance; introducing it into the surface of gun barrels and gun barrels can improve its impact resistance and ablation resistance. Body armor made of nano-ceramics and carbon nanotubes has excellent anti-ballistic effect.

Bioceramics

With the in-depth study of nanomaterials, the advantages of nano-bioceramic materials will gradually appear, and their strength, toughness, hardness and biocompatibility will be significantly improved. The performance of hydroxyapatite composite ceramics doped with nano-scale silicon carbide is much higher than that of hydroxyapatite ceramics alone, and its flexural strength, fracture toughness, and compressive strength are all significantly improved, reaching the level of biological hard tissue. Level. Nanoparticles are easy to transport in the body, and this feature is applied by scientists to radiation therapy. Doping nano-ceramic particles with chemical elements that can emit β-rays, making them into β-ray source materials, and implanting them near the target can precisely treat cancerous tissues.

high temperature material

Nano-ceramic materials have high heat resistance, good high temperature oxidation resistance, low density, high fracture toughness, corrosion resistance and wear resistance, which can improve the temperature before the turbine of the aero-engine, thereby increasing the thrust-to-weight ratio of the engine and reducing fuel consumption Both play an important role and are expected to become ideal materials for high-temperature components of naval and military turbine engines, which can improve engine efficiency, reliability and working life.

In addition, nano-ceramics can also be applied to the substrate in the form of a coating. Compared with conventional coatings, it is found that the number of thermal shocks of nano-ceramic coatings is much higher than that of ordinary ceramic coatings.

Absorbing material

In addition to excellent mechanical properties and thermophysical properties, nano-ceramic materials have high mechanical strength and good chemical stability. At the same time, they have the function of absorbing waves and can meet the requirements of stealth. They have been widely used as absorbents.

Tool material

Ceramic cutting tools are an important application field of modern structural ceramics. Ceramic cutting tools not only have high hardness and high wear resistance, but also maintain excellent mechanical properties at high temperatures, making them ideal materials for manufacturing cutting tools. The existing ceramic tool materials are difficult to be widely used in higher cutting speeds, and nano-ceramic tools have excellent performance compared with traditional ceramic tools. Cutting speed, mechanical properties, cutting reliability and tool life, thus greatly improving productivity.