Nanocrystalline
Encyclopedia
A nanocrystalline material is a polycrystalline
material with a crystallite
size of only a few nanometers. These materials fill the gap between amorphous materials without any longe range order and crystalline materials with a clear three dimensional long range order.
X-ray diffraction is commonly used to determine the crystallinity
of a material. When the crystallites of a polycrystalline
material become very small, the diffraction signals become very wide. A material can be called nanocrystalline when the diffraction signals are too sharp to originate from an amorphous material but too wide to determine the crystal structure
. The upper limit for the crystallite size of nanocrystalline materials is about 5 nm, the lower limit will be close to 0.5 nm.
Polycrystalline
Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation. The variation in direction can be random or directed, possibly due to growth and processing conditions. Fiber texture is an example of the latter.Almost all common metals, and many ceramics...
material with a crystallite
Crystallite
Crystallites are small, often microscopic crystals that, held together through highly defective boundaries, constitute a polycrystalline solid. Metallurgists often refer to crystallites as grains.- Details :...
size of only a few nanometers. These materials fill the gap between amorphous materials without any longe range order and crystalline materials with a clear three dimensional long range order.
X-ray diffraction is commonly used to determine the crystallinity
Crystallinity
Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion. In a gas, the relative positions of the atoms or...
of a material. When the crystallites of a polycrystalline
Polycrystalline
Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation. The variation in direction can be random or directed, possibly due to growth and processing conditions. Fiber texture is an example of the latter.Almost all common metals, and many ceramics...
material become very small, the diffraction signals become very wide. A material can be called nanocrystalline when the diffraction signals are too sharp to originate from an amorphous material but too wide to determine the crystal structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
. The upper limit for the crystallite size of nanocrystalline materials is about 5 nm, the lower limit will be close to 0.5 nm.