AskDefine | Define amorphous

Dictionary Definition

amorphous adj
1 having no definite form or distinct shape; "amorphous clouds of insects"; "an aggregate of formless particles"; "a shapeless mass of protoplasm" [syn: formless, shapeless]
2 lacking the system or structure characteristic of living bodies [syn: unstructured]
3 without real or apparent crystalline form; "an amorphous mineral"; "amorphous structure" [syn: uncrystallized, uncrystallised]

User Contributed Dictionary

English

Pronunciation

/əˈmɔrfəs/

Adjective

  1. lacking a definite form or clear shape
    The enormous pile of spaghetti landed in an amorphous heap on the floor.
  2. being without definite character or nature
  3. lacking organization or unity
  4. A state of solid that is not in crystal and its regular structure is crystal.

Translations

lacking a definite form or clear shape
being without definite character or nature
  • Croatian: amorfan
  • Esperanto: amorfa
  • German: amorph
  • Italian: amorfo
lacking organization or unity
physics: state of solid that is not in crystal
  • Japanese: アモルファス
Translations to be checked

Extensive Definition

An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. (Solids in which there is long-range atomic order are called crystalline solids or morphous). Most classes of solid materials can be found or prepared in an amorphous form. For instance, common window glass is an amorphous ceramic, many polymers (such as polystyrene) are amorphous, and even foods such as cotton candy are amorphous solids.
In principle, given a sufficiently high cooling rate, any liquid can be made into an amorphous solid. Cooling reduces molecular mobility. If the cooling rate is faster than the rate at which molecules can organize into a more thermodynamically favorable crystalline state, then an amorphous solid will be formed. Because of entropy considerations, many polymers can be made amorphous solids by cooling even at slow rates. In contrast, if molecules have sufficient time to organize into a structure with two- or three-dimensional order, then a crystalline (or semi-crystalline) solid will be formed. Water is one example. Because of its small molecular size and ability to quickly rearrange, it cannot be made amorphous without resorting to specialized hyperquenching techniques.
Amorphous materials can also be produced by additives which interfere with the ability of the primary constituent to crystallize. For example, addition of soda to silicon dioxide results in window glass, and the addition of glycols to water results in a vitrified solid.
Some materials, such as metals, are difficult to prepare in an amorphous state. Unless a material has a high melting temperature (as ceramics do) or a low crystallization energy (as polymers tend to), cooling must be done extremely rapidly. As the cooling is performed, the material changes from a supercooled liquid, with properties one would expect from a liquid state material, to a solid. The temperature at which this transition occurs is called the glass transition temperature or Tg.

Toward a strict definition

It is difficult to make a distinction between truly amorphous solids and crystalline solids in which the size of the crystals is very small. Even amorphous materials have some short-range order at the atomic length scale due the nature of chemical bonding. Furthermore, in very small crystals a large fraction of the atoms are located at or near the surface of the crystal; relaxation of the surface and interfacial effects distort the atomic positions, decreasing the structural order. Even the most advanced structural characterization techniques, such as x-ray diffraction and transmission electron microscopy, have difficulty in distinguishing between amorphous and crystalline structures on these length scales.
The transition from the liquid state to the glass, at a temperature below the equilibrium melting point of the material, is called the glass transition. It was found that the topology of bonds changes at glass transition from 3D below to fractal (<3) above the glass transition. This change characterises the glass transition as a percolation transition in the system of broken bonds assotiated by a decrease of Hausdorff dimension. From a practical point of view, the glass transition temperature is approximately the temperature at which the viscosity of the liquid exceeds a certain value (about 1012 Pa·s). The transition temperature depends on cooling rate, with the glass transition occurring at higher temperatures for faster cooling rates. The precise nature of the glass transition is the subject of ongoing research. While it is clear that the glass transition is not a first-order thermodynamic transition (such as melting), there is debate as to whether it is a higher-order transition, or merely a kinetic effect.

References

amorphous in Czech: Amorfní látka
amorphous in Danish: Amorf
amorphous in German: Amorphes Material
amorphous in Estonian: Amorfne aine
amorphous in Modern Greek (1453-): Άμορφο σώμα
amorphous in Esperanto: Amorfa solido
amorphous in Persian: جامد آمورف
amorphous in French: Matière amorphe
amorphous in Korean: 비결정성 고체
amorphous in Croatian: Amorfna tvar
amorphous in Italian: Solido amorfo
amorphous in Lojban: nalvelganzu sligu
amorphous in Dutch: Amorf materiaal
amorphous in Japanese: アモルファス
amorphous in Norwegian: Amorf
amorphous in Polish: Ciało amorficzne
amorphous in Portuguese: Sólido amorfo
amorphous in Russian: Аморфные тела
amorphous in Simple English: Amorphous solid
amorphous in Finnish: Amorfinen aine
amorphous in Swedish: Amorf
amorphous in Tamil: சீருறாத் திண்மம்
amorphous in Vietnamese: Chất rắn vô định hình
amorphous in Turkish: Amorf katı
amorphous in Ukrainian: Аморфний стан
amorphous in Chinese: 无定形体

Synonyms, Antonyms and Related Words

aberrant, abnormal, adrift, afloat, aimless, aleatoric, aleatory, alternating, amorphic, anarchic, anomalistic, anomalous, baggy, blind, blobby, blurred, blurry, broad, capricious, casual, chance, chancy, changeable, changeful, chaotic, characterless, clear as mud, cloudy, confused, dark, desultory, deviable, deviative, different, dim, disarticulated, discontinuous, disjunct, disordered, disorderly, dispersed, disproportionate, divergent, dizzy, eccentric, erratic, fast and loose, featureless, fickle, fitful, flickering, flighty, flitting, fluctuating, foggy, formless, freakish, frivolous, fuzzy, general, giddy, gratuitous, haphazard, hazy, heteroclite, heteromorphic, hit-or-miss, ill-defined, immethodical, impetuous, imprecise, impulsive, inaccurate, inchoate, incoherent, inconsistent, inconstant, indecisive, indefinable, indefinite, indeterminable, indeterminate, indiscriminate, indistinct, inexact, infirm, inform, irregular, irresolute, irresponsible, kaleidoscopic, lax, loose, lumpen, mazy, meaningless, mercurial, misshapen, misty, moody, muddy, murky, nebulous, nondescript, nonspecific, nonsymmetrical, nonsystematic, nonuniform, obscure, opaque, orderless, planless, promiscuous, rambling, random, restless, roving, scatterbrained, senseless, shadowed forth, shadowy, shapeless, shifting, shifty, shuffling, spasmodic, spineless, sporadic, stochastic, straggling, straggly, stray, straying, subnormal, sweeping, systemless, transcendent, unaccountable, unarranged, uncertain, unclassified, unclear, uncontrolled, undefined, undependable, undestined, undetermined, undirected, undisciplined, unfixed, unformed, ungraded, unjoined, unmethodical, unnatural, unordered, unorganized, unplain, unpredictable, unreliable, unrestrained, unsettled, unshaped, unsorted, unspecified, unstable, unstable as water, unstaid, unsteadfast, unsteady, unsymmetrical, unsystematic, ununiform, vacillating, vagrant, vague, variable, veiled, vicissitudinary, vicissitudinous, volatile, wandering, wanton, wavering, wavery, wavy, wayward, whimsical, wishy-washy
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