Liquid crystal states
Main article: Liquid crystal
Liquid crystal states have properties intermediate between mobile liquids and ordered solids. For example, the nematic phase consists of long rod-like molecules such as para-azoxyanisole, which is nematic in the temperature range 118-136 °C. In this state the molecules flow as in a liquid, but they all point in the same direction (within each domain) and cannot rotate freely.
Other types of liquid crystals are described in the main article on these states. Several types have technological importance, for example, in liquid crystal displays.
Amorphous solid
Main article: Amorphous solid
An amorphous or non-crystalline solid has a disordered structure like a liquid. However its molecules are relatively immobile so that it is usually classed as a solid. Common examples are glass, synthetic rubber and polystyrene and other polymers. Many amorphous solids soften into liquids when heated above their glass transition temperatures, at which the molecules become mobile.
Some liquids are non-Newtonian fluids whose viscosity depends on the applied force or shear, so that they become amorphous solids under certain flow conditions. An example used for simple demonstrations is a suspension of corn starch in water (at room temperature), which is liquid when still, but acts a solid when a sudden force is applied. This property is called shear thickening. Other suspensions such as wet paint exhibit the opposite effect, known as shear thinning.
Magnetically-ordered states
Transition metal atoms often have magnetic moments due to the net spin of electrons which remain unpaired and do not form chemical bonds. In some solids the magnetic moments on different atoms are ordered and can form a ferromagnet, an antiferromagnet or a ferrimagnet.
In a ferromagnet—for instance, solid iron—the magnetic moment on each atom is aligned in the same direction (within a magnetic domain). If the domains are also aligned, the solid is a permanent magnet, which is magnetic even in the absence of an external magnetic field. The magnetization disappears when the magnet is heated to the Curie point, which for iron is 768°C.
An antiferromagnet has two networks of equal and opposite magnetic moments which cancel each other out, so that the net magnetization is zero. For example, in nickel(II) oxide (NiO), half the nickel atoms have moments aligned in one direction and half in the opposite direction.
In a ferrimagnet, the two networks of magnetic moments are opposite but unequal, so that cancellation is incomplete and there is a non-zero net magnetization. An example is magnetite (Fe3O4), which contains Fe2+ and Fe3+ ions with different magnetic moments.
Main article: Liquid crystal
Liquid crystal states have properties intermediate between mobile liquids and ordered solids. For example, the nematic phase consists of long rod-like molecules such as para-azoxyanisole, which is nematic in the temperature range 118-136 °C. In this state the molecules flow as in a liquid, but they all point in the same direction (within each domain) and cannot rotate freely.
Other types of liquid crystals are described in the main article on these states. Several types have technological importance, for example, in liquid crystal displays.
Amorphous solid
Main article: Amorphous solid
An amorphous or non-crystalline solid has a disordered structure like a liquid. However its molecules are relatively immobile so that it is usually classed as a solid. Common examples are glass, synthetic rubber and polystyrene and other polymers. Many amorphous solids soften into liquids when heated above their glass transition temperatures, at which the molecules become mobile.
Some liquids are non-Newtonian fluids whose viscosity depends on the applied force or shear, so that they become amorphous solids under certain flow conditions. An example used for simple demonstrations is a suspension of corn starch in water (at room temperature), which is liquid when still, but acts a solid when a sudden force is applied. This property is called shear thickening. Other suspensions such as wet paint exhibit the opposite effect, known as shear thinning.
Magnetically-ordered states
Transition metal atoms often have magnetic moments due to the net spin of electrons which remain unpaired and do not form chemical bonds. In some solids the magnetic moments on different atoms are ordered and can form a ferromagnet, an antiferromagnet or a ferrimagnet.
In a ferromagnet—for instance, solid iron—the magnetic moment on each atom is aligned in the same direction (within a magnetic domain). If the domains are also aligned, the solid is a permanent magnet, which is magnetic even in the absence of an external magnetic field. The magnetization disappears when the magnet is heated to the Curie point, which for iron is 768°C.
An antiferromagnet has two networks of equal and opposite magnetic moments which cancel each other out, so that the net magnetization is zero. For example, in nickel(II) oxide (NiO), half the nickel atoms have moments aligned in one direction and half in the opposite direction.
In a ferrimagnet, the two networks of magnetic moments are opposite but unequal, so that cancellation is incomplete and there is a non-zero net magnetization. An example is magnetite (Fe3O4), which contains Fe2+ and Fe3+ ions with different magnetic moments.
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