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Polyamorphism is also an important area in pharmaceutical science. The amorphous form of a drug typically has much better aqueous solubility (compared to the analogous crystalline form) but the actual local structure in an amorphous pharmaceutical can be different, depending on the method used to form the amorphous phase.
Amorphous solids are the opposite of crystalline. The atoms or molecules in amorphous substances are arranged randomly without any long-range order. As a result, they do not have a sharp melting point. The phase transition from solid to liquid occurs over a range of temperatures. [citation needed] Some examples include glass, rubber and some ...
Amorphous materials have an internal structure of molecular-scale structural blocks that can be similar to the basic structural units in the crystalline phase of the same compound. [4] Unlike in crystalline materials, however, no long-range regularity exists: amorphous materials cannot be described by the repetition of a finite unit cell.
Spin glass models can present these amorphous types of magnetism. [2] Due to random frustration, amorphous magnets possess many nearly degenerate ground states. [1] The terms for the amorphous magnetic phases were coined by Michael Coey in 1970s. [2] [3] [4] The Greek root spero/speri (Greek: διασπειρω, romanized: diaspeiro) means 'to ...
Tie molecules prevent the amorphous and crystalline phases from separating under an applied load. When a tensile stress is applied the semi-crystalline polymer first deforms elastically. While the crystalline regions remain unaffected by the applied stress, the molecular chains of the amorphous phase stretch.
Glass-ceramics have an amorphous phase and one or more crystalline phases and are produced by a so-called "controlled crystallization", which is typically avoided in glass manufacturing. Glass-ceramics often contain a crystalline phase which constitutes anywhere from 30% [m/m] to 90% [m/m] of its composition by volume, yielding an array of ...
The polymorphs of SiC include various amorphous phases observed in thin films and fibers, [3] as well as a large family of similar crystalline structures called polytypes. They are variations of the same chemical compound that are identical in two dimensions and differ in the third. Thus, they can be viewed as layers stacked in a certain sequence.
[3] [2] [4] [5] Whereas the β-rhombohedral phase is the most stable and the others are metastable, the transformation rate is negligible at room temperature, and thus all five phases can exist at ambient conditions. Amorphous powder boron and polycrystalline β-rhombohedral boron are the most common forms