from the grain size or, rather, crystallite size found by X ray crystallography X ray diffraction ... identical except in orientation. The term crystallite boundary is sometimes, though rarely, used ... plane. This crystallite size strength relationship is given by the Grain boundary strengthening Hall ... more details
Unreferenced date December 2009 In materials science , dispersion is the fraction of atoms of a material exposed to the surface. In general D N sub S sub N sub T sub where D is the dispersion, N sub S sub is the number of surface atoms and N sub T sub is the total number of atoms of the material. Dispersion is an important concept in heterogeneous catalysis , since only atoms that are exposed to the surface are able to play a role in catalytic surface reactions. Dispersion increases with decreasing crystallite size and approaches unity at a crystallite diameter of about 1 nm. Related article Emulsion dispersion DEFAULTSORT Dispersion Materials Science Category Materials science Material stub de Dispersion Oberfl chenchemie no Dispersjon fi Dispersio kemia ... more details
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. Uncategorized date March 2011 ... more details
Multiple issues orphan August 2008 refimprove September 2008 In metallurgy , exfoliation corrosion is a form of intergranular corrosion that manifests itself by lifting up the surface grains of a metal by the force of expanding corrosion corrosion products occurring at the Crystallite grain boundaries just below the surface. It is visible evidence of intergranular corrosion. It is most often seen on extrusion extruded sections where grain thickness is less than in rolled forms. References Reflist DEFAULTSORT Exfoliation Corrosion Category Corrosion tech stub ... more details
seealso Shape factor A shape factor is used in Diffraction Bragg diffraction x ray diffraction and X ray crystallography crystallography to correlate the size of sub micrometre wiktionary Particle particle s, or crystallite s, in a solid to the broadening of a peak in a diffraction pattern. In the Paul Scherrer Scherrer equation, math tau frac K lambda beta cos theta math where K is the shape factor, is the x ray wavelength , is the line broadening at half the maximum Intensity physics intensity Full width at half maximum FWHM in radian s, and is the Bragg diffraction Bragg angle ref P. Scherrer, G ttinger Nachrichten Gesell. , Vol. 2, 1918, p 98. ref ref cite journal title The Scherrer Formula for X Ray Particle Size Determination authorlink Patterson, A. L. journal Phys. Rev. volume 56 issue 10 pages 978 982 year 1939 doi 10.1103 PhysRev.56.978 last1 Patterson first1 A. ref is the mean size of the ordered crystalline domains, which may be smaller or equal to the grain size. The dimensionless shape factor has a typical value of about 0.9, but varies with the actual shape of the crystallite. The Scherrer equation is limited to Nanotechnology nano scale particles. It is not applicable to grains larger than about 0.1 m, which precludes those observed in most Metallography metallographic and Ceramography ceramographic microstructures. It is important to realize that the Scherrer formula provides a lower bound on the particle size. The reason for this is that a variety of factors can contribute to the width of a diffraction peak besides crystallite size, the most important of these are usually inhomogeneous strain and instrumental effects. If all of these other contributions to the peak width were zero, then the peak width would be determined solely by the crystallite size and the Scherrer formula would apply. If the other contributions to the width are non zero, then the crystallite size can be larger than that predicted by the Scherrer formula, with the extra ... more details
Image Grain oriented electrical steel grains .jpg thumb right A photo of electrical steel coating removed showing polycrystalline structure Polycrystalline materials are solids that are composed of many crystallite s of varying size and orientation. The variation in direction can be random called random texture or directed, possibly due to growth and processing conditions. Fiber texture is an example of the latter. Almost all common metal s, and many ceramic s are polycrystalline. Some elements such as Sulfur, while usually occurring in polycrystalline form, may also occur as single crystals. ref C.Michael Hogan. 2011. http www.eoearth.org article Sulfur?topic 49557 Sulfur . Encyclopedia of Earth, eds. A.Jorgensen and C.J.Cleveland, National Council for Science and the environment, Washington DC ref The crystallites are often referred to as grains, however, powder grains are a different context. Powder grains can themselves be composed of smaller polycrystalline grains. ref http old.iupac.org goldbook P04723.pdf polycrystalline graphite Bot generated title ref Polycrystalline is the structure of a solid material that, when cooled, forms crystallite grains at different points within it. The areas where these crystallite grains meet are known as grain boundaries. See also Crystallography Grain boundary Monocrystal Polycrystalline silicon References reflist Category Crystals engineering stub ar de Polykristall es Policristalino fa fr Polycristal it Policristallo he ja no Polykrystallinsk pl Polikryszta pt Policristal ru ... more details
Planar deformation features , or PDFs , are optically recognizable microscopic features in crystallite grain s of silicate minerals usually quartz or feldspar , consisting of very narrow planes of glassy material arranged in parallel sets that have distinct orientations with respect to the grain s crystal structure . PDFs are only produced by extreme shock compressions on the scale of meteor impacts. They are not found in volcanic environments. Their presence therefore is a primary criterion for recognizing that an impact event has occurred. See also Shocked quartz Shock metamorphism References http www.lpi.usra.edu publications slidesets craters glossary.shtml http www.unb.ca passc ImpactDatabase essay.html http adsabs.harvard.edu abs 1993LPI....24..849L Impact cratering on Earth geol stub Category Impact geology es Rasgos de Deformaci n Planar ... more details
crystallization In chemistry, fractional crystallization is a method of refining substances based on differences in soluble solubility . If a mixture of two or more substances in solution is allowed to crystallize , for example by allowing the temperature of the solution to decrease, the precipitate will contain more of the least soluble substance. The proportion of components in the precipitate will depend on their solubility product s. If the solubility products are very similar a Cascade chemical engineering cascade process will be needeed to effectuate a complete separation. This technique is often used in chemical engineering to obtain very pure substances, or to recover saleable products from waste solutions. See also alphabetic order Crystal Crystal structure Crystallite Crystallization and Crystallization engineering aspects engineering aspects Fractional freezing Laser Heated Pedestal Growth Recrystallization chemistry Seed crystal Single crystal Pumpable ice technology References http acaschool.iit.edu lectures04 JLiangXtal.pdf Small Molecule Crystalization PDF at Illinois Institute of Technology website Category Chemical engineering Category Phase changes physical chemistry stub de Fraktionierte Kristallisation Chemie fr Cristallisation fractionn e chimie it Cristallizzazione frazionata this is only fractional crystallization in geology nl Kristalfractionatie pt Cristaliza o fracionada qu mica ... more details
wiktionary grain Grain refers to coarse particles e.g. grain of sand , grain of salt Food grain s, the small, hard, fruits or seeds of arable crops or the crops bearing these fruits or seeds. Includes the cereal grains caryopsis of grass plants pseudocereal s starchy grains produced by broadleaf plants used like true cereals Pulse legume pulses or grain legumes Whole grain s, the cereal grains that contain bran and germ as well as the endosperm oilseeds Film grain , the gritty texture sometimes apparent on images produced using photographic film or paper grainy Fine grained , designating a more finely differentiated form of a technical or abstract system, in contrast to coarse grained , a less differentiated one Grain unit , a unit of mass equal to 64.79891 milligrams, 1 7,000th of an avoirdupois pound Grain, or particle size , for particles of rock in geology Crystallite or grain in metallurgy, a single crystal inside solid state matter Solid fuel rocket Grain geometry Grain , a solid propellant charge, roughly a hollow cylinder, sometimes textured, and possibly very large Granular synthesis , a method for digital musical instruments operating on the microsound time scale Grain surfboard company , a company that manufactures hollow wooden surfboards Wood grain , the alignment and texture of the fibres in wood Or, more generally Grain cipher , a stream cipher designed for restricted hardware environments and submitted to eSTREAM in 2004 by Martin Hellman et al. Isle of Grain in Kent, England, on which lies the village of Grain GRAIN is an international non governmental organization for sustainable agriculture disambig ar cs Zrno rozcestn k de Grain es Grano eo Grajno fr Grain it Grano pt Gr o simple Grain disambiguation sk Zrno uk ... more details
Unreferenced date May 2009 Wide angle X ray scattering WAXS or Wide angle X ray diffraction WAXD is an X ray diffraction technique that is often used to determine the crystalline structure of polymer s. This technique specifically refers to the analysis of Bragg Peak s scattered to wide angles, which by Bragg s law implies that they are caused by sub nanometer sized structures. Wide angle x ray scattering is the same technique as Small Angle X ray Scattering SAXS only the distance from sample to the detector is shorter and thus diffraction maxima at larger angles are observed. The technique is a time honored but a somewhat out of favor technique for the determination of degree of crystallinity of polymer samples. A diffraction technique for polycrystalline films where only crystallites diffract which are parallel to the substrate surface. The diffraction pattern generated allows to determine the chemical composition or phase composition of the film, the texture of the film preferred alignment of crystallites , the crystallite size and presence of film stress. According to this method the sample is scanned in a wide angle X ray goniometer , and the scattering intensity is plotted as a function of the 2 angle. X ray diffraction is a non destructive method of characterization of solid materials. When X rays are directed in solids they will scatter in predictable patterns based upon the internal structure of the solid. A crystalline solid consists of regularly spaced atoms electrons that can be described by imaginary planes. The distance between these planes is called the d spacing . The intensity of the d space pattern is directly proportional to the number of electrons atoms that are found in the imaginary planes. Every crystalline solid will have a unique pattern of d spacings known as the powder pattern , which is a finger print for that solid. In fact solids with the same chemical composition but different phases can be identified by their pattern of d spacings. S ... more details
Unreferenced stub auto yes date December 2009 Orphan date December 2009 Geometric Dynamic Recrystallization GDR is a recrystallization metallurgy recrystallization mechanism that has been proposed to occur in several alloys, particularly aluminium , at high temperatures and low strain rates. It is a variant of dynamic recrystallization . The basic mechanism is that during deformation the Crystallite grains will be increasingly flattened until the boundaries on each side are separated by only a small distance. The deformation is accompanied by the serration of the grain boundaries due to surface tension effects where they are in contact with low angle grain boundaries belonging to sub grains. Eventually the points of the serrations will come into contact. Since the contacting boundaries are defects of opposite sign they are able to annihilate and so reduce the total energy in the system. In effect the grain will pinch in two new grains. The grain size is known to decrease as the applied stress is increased. However, high stresses require a high strain rate and at some point statically recrystallized grains will begin to nucleate and consume the GDRX microstructure. There are features that are unique to GDRX The recrystallisation spreads throughout the specimen over a strain range 0.5 1 in Al Mg Mn alloys without any change in flow stress. This is in contrast to discontinuous mechanisms where the flow stress normally decreases by 25 as the recrystallized grains form. GDRX results in grains that are around 3 times the sub grain size. Statically recrystallized grains are normally 20 30 times the sub grain size. DEFAULTSORT Geometric Dynamic Recrystallization Category Metallurgy Chem stub ... more details
Refimprove date October 2009 Acicular ferrite is a microstructure of ferrite that is characterised by needle shaped crystallite s or grains when viewed in two dimensions. The grains, actually three dimensional in shape, have a thin lenticular shape. This microstructure is advantageous over other microstructures because of its chaotic ordering, which increases toughness . ref Citation last Bhadeshia first Harshad Kumar Dharamshi Hansraj last2 Honeycombe first2 Robert William Kerr title Steels microstructure and properties page 155 publisher Butterworth Heinemann year 2006 edition 3rd url http books.google.com books?id 8okWjoJhP5AC&pg PA155 isbn 978 0 7506 8084 4 . ref It consists of a fine structure of interlocking ferrite plates sometimes called dark etching . Acicular ferrite is formed in the interior of the original Austenite austenitic grains by direct nucleation from the inclusions, resulting in randomly oriented short ferrite needles with a basket weave appearance. This interlocking nature, together with its fine grain size 0.5 to 5 um with aspect ratio from 3 1 to 10 1 , provides maximum resistance to crack propagation by Cleavage crystal cleavage . Acicular ferrite is also characterised by high angle boundaries between the ferrite grains. This further reduces the chance of cleavage, because these boundaries impede crack propagation. It is reported that nucleation of various ferrite morphologies is aided by nonmetallic inclusion in particular oxygen rich inclusions of a certain type and size are associated with the intragranular formation of acicular ferrite. Acicular ferrite is a fine Widmanst tten pattern Widmanst tten constituent, which is nucleated by an optimum intragranular dispersion of oxide sulfide silicate particles. Composition control of weld metal is often performed to maximise the volume fraction of acicular ferrite due to the toughness it imparts. Higher alloy contents generally delay transformation, during continuous cooling transformation ... more details
Faggoting or faggoting and folding is a metalworking technique used in the smelting and forge forging of wrought iron , damascus steel , and other steel . Faggoting is a process in which rods or bars of iron and or steel are gathered like a bundle of sticks or faggot wood faggot and forge welding forge welded together. The faggot would then be Blacksmith Drawing drawn out lengthwise. The bar might then be broken and the pieces made into a faggot again or folded over, and forge welded again. Wrought iron which had been faggoted twice was referred to as Best if faggoted again it would become Best Best , then Treble best , etc. Faggoting stretches chemical impurities within the metal into long thin inclusions, creating a Crystallite grain within the metal. Best bars would have a tensile strength along the grain of about 23 short ton s per square inch 317 M Pascal unit Pa . Treble best could reach 28 short tons per square inch 386 MPa . The strengths across the grain would be about 15 lower. This grain makes wrought iron especially tricky to smith, as it behaves much like wood grain prone to spontaneous splitting along the grain. In old, very rusted pieces of wrought iron, the grain is revealed, making the iron bear a striking resemblance to reddish brown wood. Cementation process Blister steel that has been faggoted was known as shear steel if faggoted twice, as double shear steel. Steel that was intended to be treated this way was usually Case hardening carburised , presumably because it was slightly decarburised in the course of faggoting. References cite book last Bealer first Alex W. authorlink Alex W. Bealer title The Art of Blacksmithing publisher Castle Books year 1995 location Edison, NJ pages 28 35, 355 isbn 0785803955 Category Metalworking Category Steelmaking ... more details
Unreferenced date December 2009 Image ObsidianOregon.jpg right thumb 250px Obsidian gives conchoidal fractures Conchoidal fracture describes the way that brittle materials break when they do not follow any natural cleavage crystal planes of separation . Materials that break in this way include flint and other fine crystallite grain ed mineral s, as well as most amorphous solid s, such as obsidian and other types of glass . Conchoidal fractures can also occur in other materials under favorable circumstances. This material property was widely used in the Stone Age to make sharp tools, and minerals that fractured in this fashion were widely traded as a desirable raw material. Conchoidal fractures often result in a curved breakage surface that resembles the rippling, gradual curves of a mussel shell the word conchoid is derived from the word for this animal Greek konche ref cite web url http www.merriam webster.com netdict conchoidal title conchoidal accessdate 2010 10 30 work Merriam Webster Online ref . A swelling appears at the point of impact called the bulb of percussion . Shock waves emanating outwards from this point leave their mark on the stone as ripples. Other conchoidal features include small fissure s emanating from the bulb of percussion. They are defined in contrast to the facet ed fractures often seen in single crystal s such as semiconductor wafer electronics wafer s and gemstone s, and the high energy ductile fracture surfaces desirable in most structural applications. See the main article on Fracture . Lithics In Lithic flake lithic stone tool s, conchoidal fractures form the basis of flintknapper flint knapping , since the shape of the broken surface is controlled only by the stress physics stresses applied, and not by some preferred orientation of the material. This property also makes such fractures useful in engineering, since they provide a permanent record of the stress state at the time of failure . As conchoidal fractures can be produced only ... more details
File Flux pinning.ogg thumb Flux pinning giving stiffness to Meissner effect levitation Flux pinning is the phenomenon that magnetic flux magnetic flux lines do not move become trapped, or pinned in spite of the Lorentz force acting on them inside a electric current current carrying Type II superconductor . The phenomenon cannot occur in Type I superconductor s, since these cannot be penetrated by magnetic fields Meissner Ochsenfeld effect . Flux pinning is only possible when there are crystallographic defect defects in the crystalline structure of the superconductor usually resulting from crystallite grain boundaries or impurities . Importance of flux pinning Flux pinning is desirable in high temperature superconductor high temperature ceramic superconductors to prevent flux creep , which can create a pseudo electrical resistance resistance and depress both critical current density and critical field. Degradation of a high temperature superconductor s properties due to flux creep is a limiting factor in the use of these superconductors. SQUID magnetometers suffer reduced precision in a certain range of applied field due to flux creep in the superconducting magnet used to bias the sample, and the maximum field strength of high temperature superconducting magnets is drastically reduced by the depression in critical field. See also Flux pumping Meissner effect Superconductivity Type II superconductor Abrikosov vortex Pinning force References http www.futurescience.com scintro.html Future Science introduction to high temperature superconductors. http www.americanmagnetics.com tutorial supercon.html American Magnetics tutorial on magnetic field exclusion and flux pinning in superconductors. http quench analysis.web.cern.ch quench analysis phd fs html node41.html Cern Lhc documentation Stability of superconductors. Other sources Flux Pinning of Bi sub 2 sub Sr sub 2 sub CaCu sub 2 sub O sub 8 Delta sub High T sub c sub Superconducting Tapes Utilizing Sr,Ca sub 14 sub Cu ... more details
. This boundary can be conceived as forming from a single, contiguous crystallite or grain which is gradually ... during Annealing metallurgy heat treatment . See also commonscat Crystal Crystallite Crystallography ... more details
Refimprove date February 2008 Main Silicon thin film cell Image Nano Si 640x480.jpg thumb 300px right Silicon nanopowder Nanocrystalline silicon nc Si , sometimes also known as microcrystalline silicon c Si , is a form of porous silicon . ref http www.semiconductor.net index.asp?layout siTechNews&industryid 47307&starting 341 Technical articles ref It is an allotropy allotropic form of silicon with paracrystalline structure is similar to amorphous silicon a Si , in that it has an amorphous solid amorphous phase. Where they differ, however, is that nc Si has small grains of crystalline silicon within the amorphous phase. This is in contrast to polycrystalline silicon poly Si which consists solely of crystalline silicon grains, separated by grain boundaries. . The difference comes solely from the grain size of the crystalline grains. Most materials with grains in the micrometre range are actually fine grained polysilicon, so nanocrystalline silicon is a better term. The term Nanocrystalline silicon refers to a range of materials around the transition region from amorphous to microcrystalline phase in the silicon thin film. The crystalline volume fraction as measured from Raman spectroscopy is another criteri n to describe the materials in this transition zone. nc Si has many useful advantages over a Si, one being that if grown properly it can have a higher electron mobility , due to the presence of the silicon crystallite s. It also shows increased absorption in the red and infrared wavelength s, which make it an important material for use in a Si solar cell s. One of the most important advantages of nanocrystalline silicon, however, is that it has increased stability over a Si, one of the reasons being because of its lower hydrogen concentration. citation needed date November 2008 Although it currently cannot attain the mobility that poly Si can, it has the advantage over poly Si that it is easier to fabricate, as it can be deposited using conventional low temperatu ... more details
Chembox Watchedfields changed verifiedrevid 386912551 ImageFile Silver behenate.svg ImageSize 250px IUPACName Silver I docosanoate OtherNames Silver docosanoate Behenic acid silver salt Section1 Chembox Identifiers CASNo 2489 05 6 CASNo Ref cascite correct CAS PubChem 164971 ChemSpiderID 144632 SMILES Ag . O C O CCCCCCCCCCCCCCCCCCCCC StdInChI 1S C22H44O2.Ag c1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 h2 21H2,1H3, H,23,24 q 1 p 1 StdInChIKey AQRYNYUOKMNDDV UHFFFAOYSA M Section2 Chembox Properties Formula AgC sub 22 sub H sub 43 sub O sub 2 sub MolarMass 447.2287 g mol Appearance Density MeltingPt BoilingPt Solubility Section3 Chembox Hazards MainHazards FlashPt Autoignition Silver behenate is a silver salt chemistry salt of the long chain fatty acid behenic acid . It is a possible low angle diffraction standard that was characterized using the powder diffraction technique. Diffraction patterns obtained with 1.54 synchrotron and Cu Ka radiations showed thirteen regularly spaced 001 peaks in the range 1.5 20.0 q. Description With the National Institute of Standards and Technology s standard reference material silicon as an internal standard, the long spacing of silver behenate was accurately determined from the profile fitted synchrotron diffraction peaks, with d001 58.380 3 5.8380 3 nm . This result was in agreement with that obtained from the Cu Ka pattern. The profile widths of the silver behenate peaks were found to be consistently larger than those of the silicon peaks, indicating significant line broadening for silver behenate. The average crystallite size along the long spacing direction of silver behenate was estimated using the Scherrer equation, giving D avg 900 50 85 95 nm . Because silver behenate has a large number of well defined diffraction peaks distributed evenly in the 1.5 20.0 2q range, it is suitable for use as an angle calibration standard for low angle diffraction. However, care must be taken if silver behenate is to ... more details
File Monokristalines Silizium f r die Waferherstellung.jpg left 135px Image Silicon unit cell 3D balls.png thumb Unit cell of silicon diamond cubic structure, lattice spacing 5.43071 ngstr m . right Monocrystalline silicon or single crystal Si , or mono Si is the base material of the electronic industry. It consists of silicon in which the crystal lattice of the entire solid is continuous, unbroken with no grain boundaries to its edges. It can be prepared Intrinsic semiconductor intrinsic , i.e. made of exceedingly pure silicon alone, or Doping semiconductor doped , containing very small quantities of other elements added to change in a controlled manner its Semiconductor semiconducting properties. Most silicon monocrystal s are grown by the Czochralski process , in the shape of cylinders up to 2 m long and 30 cm in diameter figure at left , which, cut in thin slices, give the Wafer electronics wafer s onto which the microcircuit s will be fabricated. Single crystal silicon is perhaps the most important technological material of the last decades the silicon era ref W.Heywang, K.H.Zaininger, http books.google.com books?id ATFo8Pr67uIC&pg PA25&dq 22silicon era 22&hl en&ei tGdFTMrmK8Oblgfi763tAw&sa X&oi Silicon the semiconductor material , in Silicon evolution and future of a technology , P.Siffert, E.F.Krimmel eds., Springer Verlag, 2004. ref , because its availability at an affordable cost has been essential for the development of the electronic devices on which the present day electronic and informatic revolution is based. File ICC 2008 Poland Silicon Wafer 1 edit.png VLSI devices Intel fabricated on a single crystal silicon wafer thumb right Monocrystalline is opposed to amorphous silicon amorphous silicon , in which the atomic order is limited to short range order only. In between the two extremes there is polycrystalline silicon , which is made up of small crystals, known as crystallite s . Mono Si in electronics The monocrystalline form is used in the se ... more details
and solvent have Similar atomic radius atomic radii 15 or less difference Crystallite Same crystal structure ..., perhaps Lamellar structure lamella or crystallite grains . Application In the phase diagram, the unalloyed ... more details
faces of a crystallite, which is a weakness of this model. The structure transition model Main ... a photovoltage parallel to the surface is developed in each crystallite. See also Semiconductors ... more details
wiktionary supersaturation Image KDP crystal.jpg thumb right 250px Enormous, highly pure, single crystal substances can be grown from a solution at the metastable boundary between an unsaturated and supersaturated solution. Here, a monopotassium phosphate crystal grown to create frequency doubling optics for the National Ignition Facility NIF laser. http crystals.llnl.gov KDP solution chem.html The term supersaturation refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances. It can also refer to a vapor of a compound that has a higher partial pressure than the vapor pressure of that compound. Condensation Small particles seed crystal seeds can trigger particle physics trigger the separation of the dissolved material from the solvent or condensation of the vapor. Seeds triggering the conversion of vapor are referred to as condensation nuclei , as in the case of water vapor . In the solid form these seeds can lead to the formation of crystallite s or even large single crystal s. Supersaturation is a measure of the deviation of a dissolved salt crystal from its equilibrium state. Preparation Supersaturated solutions are prepared or result when some condition of a saturated solution is changed, for example temperature , volume as by evaporation , or pressure . Examples Carbonated water is a supersaturated solution of carbon dioxide gas in water . At the elevated pressure in the bottle , more carbon dioxide can dissolve in water than at atmospheric pressure . At atmospheric pressure, the carbon dioxide gas escapes very slowly from the supersaturated liquid . This process may be accelerated by the presence of nucleation sites within the solution, such as small bubbles, caused by shaking the bottle, or another solute, such as sugar powder or a Widget beer widget . A Diet Coke and Mentos eruption is a rather extreme example. Some beverage products such as ales and stouts, e.g. Guinness , rely on thi ... more details
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