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Topic: Dendrite (metal)

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	Whisker (metallurgy) - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-09-08)
		Metal whiskers are a crystalline metallurgical phenomenon whereby metal grows tiny, filiform hairs.
		Metal whiskers differ from metallic dendrites in several respects; dendrites are fern-shaped, and grow across the surface of the metal, while metal whiskers are hair like and project at a right-angle to the surface.
		Dendrite growth requires moisture capable of dissolving the metal into a solution of metal ions which are then redistributed by electromigration in the presence of an electromagnetic field.
	en.wikipedia.org /wiki/Whisker_(metallurgy) (450 words)

	Flux (metallurgy) - Wikipedia, the free encyclopedia
		In metallurgy, flux is a substance which facilitates soldering, brazing, and welding by chemically cleaning the metals to be joined.
		Common fluxes are: ammonium chloride or rosin for soldering tin; hydrochloric acid and zinc chloride for soldering galvanized iron (and other zinc surfaces); and borax for brazing, and welding ferrous metals.
		In soldering of metals, flux serves a threefold purpose: it removes oxidation from the surfaces to be soldered, it seals out air thus preventing further oxidation, and by facilitating amalgamation improves wetting characteristics of the liquid solder.
	en.wikipedia.org /wiki/Flux_(metallurgy) (433 words)

	Metallurgical and Microstructural Analysis Using Atomic Force Microscopy — Supplier Data By Pacific
		The most commonly used tools for studying metals in both industry and research are the optical microscope, the scanning electron microscope and the transmission electron microscope.
		Dendrite (from Greek dendron - a tree) - a crystal that has a treelike branching pattern most evident in cast metals slowly cooled through the solidification range.
		Dendrite structure is not apparent for this sample in SEM.
	www.azom.com /Details.asp?ArticleID=3251 (1051 words)

	What Are Dendrites? (Site not responding. Last check: 2007-09-08)
		What's most important is that the shape, size, and speed of growth of these dendrites are all factors that profoundly influence the final properties of cast and welded metals.
		For example, the dendrites affect how hard or soft a material is, how stretchable or springy it behaves, and how much you can bend or stretch it before it breaks.
		The dendrites affect whether the material is a good or a poor conductor of electricity.
	www.rpi.edu /locker/56/000756/dendrite.html (364 words)

	NASA: Why study Materials Science in Space? (Site not responding. Last check: 2007-09-08)
		Furthermore, the manner in which dendrites form in the near-absence of gravity is different than the conventional mathematical theory of dendrite growth would predict, in both the speed of dendrite growth, as well as in the spatial dimensions of the tip of the dendrite.
		A significant fraction of the metallic or alloy components of automobiles, buildings, bridges, railroad cars, and a host of other things are made by first melting the metal or alloy, then solidifying it into the part or component that is desired.
		However, as the metal solidifies, the boundary between the liquid portion of the metal and the solidified portion, can often move particles around, adversely effecting their distribution.
	spacescience.spaceref.com:16080 /usmp4/manda_why.htm (1865 words)

	Kaiser Aluminum (Site not responding. Last check: 2007-09-08)
		The base of the mold is a platform that is gradually lowered while the metal solidifies, the frozen shell of metal acting as a retainer for the liquid metal below the wall of the mold.
		The ingot is usually cooled by the impingement of water directly on the mold or on the walls of the solid metal as it is lowered.
		Deep Drawing -- The process of cold working or drawing sheet or strip metal blanks by means of dies on a press into shapes which are usually more or less cup-like in character involving considerable plastic deformation of the metal.
	www.kaiseral.com /glossary_d.htm (795 words)

	Welding: Solidification and Microstructure
		Dendritic growth of the solid, with its multiple branches, is shown in Figure 3.
		As mentioned earlier, since solidification of the weld metal proceeds spontaneously by epitaxial growth of the partially melted grains in the base metal, the FZ grain structure is mainly determined by the base metal grain structure and the welding conditions.
		The regions of differently oriented dendrites develop because growth occurs along the preferred <100> growth directions, and the choice of which growth direction will prevail among the six possible variants is based on the relation between weld pool shape and dendrite orientation.
	www.tms.org /pubs/journals/JOM/0306/David-0306.html (4077 words)

	Tin whiskers @ xsorbit Free Message Boards
		Metal whiskers and metallic dendrites are as different as apples and oranges.
		Dendrites are fern shaped, and grow across the surface of the metal like corn on a Kansas plain, while metal whiskers resemble hair, and jut at nintey degrees from the metal face.
		In addition, the ferns need water: dendrite growth requires moisture to dissolve the metal in soup, a form of solution of metal ions stirred into electromigration by the invisible spoon of electromagnetism.
	www.xsorbit1.com /users/incandescent/index.cgi?board=K&action=display&num=1105409487 (1153 words)

	Successful Isothermal Dendritic Growth Experiment (IDGE) Proves Current Theories of Dendritic Solidification are Flawed (Site not responding. Last check: 2007-09-08)
		The size, shape, and orientation of the dendrites have a major effect on the strength, ductility (ability to be molded or shaped), and usefulness of an alloy.
		IDGE had been planned to produce 20 dendritic growths after supercoolings from 0.1 to 1.0 K. Instead, 58 dendrites were solidified at over 20 different supercoolings, ranging from about 0.05 to 1.93 K. Supercooling is the term used to describe the condition in which a dendrite solidifies at a temperature below its normal freezing point.
		Dendrite tip radii, tip solidification speed, and volumetric solidification rates were determined from the space and Earth data.
	www.grc.nasa.gov /WWW/RT1995/6000/6722m.htm (701 words)

	Introduction (Site not responding. Last check: 2007-09-08)
		The main reason for this is to compensate for the segregation of molybdenum during weld solidification and to decrease the risk of forming intermetallic phases even when the weld metal is diluted to a considerable level from the base material [Ref.2].
		For a weld metal with the same composition as the base metal, pitting corrosion initiates at the dendrite cores in oxidising chloride environments.
		The high nickel content in the weld metal helps in avoiding secondary phases to be formed in spite of the high molybdenum level.
	www.corrosionsource.com /technicallibrary/ssw/abstracts/welding/Sw99_056.htm (214 words)

	S to Z of an archaeometallurgical glossary of terms used in the study ancient and historic metal-working A
		Normally, when a metal or other multicomponent systems solidify the composition of the solid that first freezes will be different from that of the liquid; it will have a lower concentgration of the lower melting point component.
		Smelting is the process of extracting the metal from its ore. This involves a chemical reaction between the ore and the fuel, or between the heated ore and a reducing atmosphere.
		The broken metal was then melted in crucibles together with a basic flux to absorb the sulphur introduced by the use of coal.
	users.ox.ac.uk /~salter2/glossary/glos-s.html (4025 words)

	Metal crystals covered glass TRN 050102
		The researchers coaxed a flat layer of metal crystals, or dendrites, to grow on glass or plastic surfaces by immersing the insulators in a solution containing the metal, and applying the right amount of electrical current.
		The researchers' key discovery was realizing that metal dendrites, the frost-like patterns of metal coming out of the solution, could be coaxed to completely cover a flat surface.
		In studying metal dendrite growth "I discovered that the deposit would become more space-filling, and completely covering instead of dendritic, for the higher values of the current," said Fleury.
	www.trnmag.com /Stories/2002/050102/Metal_crystals_cover_glass_050102.html (691 words)

	Glossary and Terms of the Foundry Industry
		The useless metal projecting on a casting which corresponds to the position of a riser in the mold.
		It delays the flow of metal long enough to allow the basin to fill before it melts to permit only clean metal from the bottom of the basin to enter the downsprue.
		Removal of excess oxygen from molten metal, usually accomplished by adding materials with a high affinity for oxygen, the oxides of which are either gaseous or readily form slags.
	www.sfsa.org /sfsa/glossary/deftrmdd.html (2278 words)

	ERA Technology \| Contamination and moisture effects on printed circuit board reliability
		The process is electrochemical with metal dissolving at one “electrode” – the anode, and being electrodeposited at the opposite electrode – the cathode.
		Dendrites can be silver, copper, tin, lead or a combination of metals and cause failures in electrical equipment by short circuits.
		Dendrite growth can be very rapid; failures have been known to occur in less than 30 minutes but can take several months or more.
	www.era.co.uk /news/rfa_feature_05a.asp (806 words)

	Isothermal Dendritic Growth Experiment Is Controlled From University (Site not responding. Last check: 2007-09-08)
		In addition, data were acquired that revealed that the residual microgravity environment of space does not affect the direction and orientation of dendritic growth, as was previously theorized.
		More than 120 dendrites were grown over the 15 days of operation--more than double the data returned from the first flight.
		Dendrite tip radii, tip solidification speed, and volumetric solidification rates have been determined from data gathered in space and on Earth.
	www.grc.nasa.gov /WWW/RT1996/6000/6722m.htm (649 words)

	Glosssary of Corrosion Related Terms
		The potential of a metal surface necessary to decompose the electrolyte of a cell or a component/substance thereof.
		Conduction of electric current from an underground metallic structure by means of a metallic conductor.
		Forced drainage is that applied to underground metallic structures by means of an applied electromotive force or sacrificial anode.
	www.corrosionsource.com /handbook/glossary/d_glos.htm (1015 words)

	WPI Advanced Casting Research Center - Research Programs
		Solidification of these alloys is characterized by four events: (1) a short nucleation event, followed by (2) growth of the dendrites until they impinge on one another, (3) growth and coarsening of the dendrite arms, and finally (4) eutectic precipitation.
		During solidification, the primary aluminum phase forms as dendrites at the liquidus temperature of the alloy.
		-Al dendrites is halted resulting in large number of equiaxed eutectic Al grains nucleating before the nucleation of the eutectic silicon and hence silicon is forced to grow in between the Al grains as a fibrous coral morphology.
	www.wpi.edu /Academics/Research/ACRC/Research/eutectic1.html (1056 words)

	Principal Metals
		A method whereby the raw slit edge of metal is removed by rolling or filing.
		The process of cold working or drawing sheet or strip metal blanks by means of dies on a press into shapes which are usually more or less cup-like in character involving considerable plastic deformation of the metal.
		Removing gases from the molten metal by means of a vacuum process in combination with mechanical action.
	www.principalmetals.com /glossary/ddoc.htm (984 words)

	Empfasis - SIR Testing
		Metal conductors, like lead from a tin-lead HASL coating, grow from a positively charged conductor (cathode) to a negatively charged adjacent conductor (anode) creating a short circuit between the conductors.
		Metallic salts from copper based metals, which conduct electricity and create shorts across the leads or traces, can also be formed in the process.
		Dendrites and conductive salts both have the effect of lowering the insulation resistance and ultimately result in short circuits or current leakage.
	www.empf.org /empfasis/feb04/sirtesting.htm (1160 words)

	Development Focus: New Models for Microfluidics (Site not responding. Last check: 2007-09-08)
		Cast metal parts are sometimes unusable because they have internal gas pockets, or bubbles, which develop when the metal shrinks during solidification.
		This type of porosity is also caused by metal shrinkage during solidification, but its character is different from macro-porosity because it develops at a later stage in the solidification process.
		Most important are the metal densities at the liquidus and solidus temperatures and the critical solid fraction (solid fraction for rigidity).
	www.flow3d.com /newsletters/04/fall04nmmp.htm (608 words)

	Rechargeable aqueous metal-halogen cell - Patent 4049886
		A particular disadvantage of the zinc electrode is the formation of needle-like zinc dendrites during cell charging which often lead to electrical cell shorting.
		Unlined metals, such as tantalum, niobium and molybdenum can also be employed for the casing.
		My invention is not concerned with zinc dendrite suppression but with the complexing of bromide and iodine with an organic complexing additive of nitrobenzene to prevent excessive self discharge of the cell.
	www.freepatentsonline.com /4049886.html (2127 words)

	crystallization (Site not responding. Last check: 2007-09-08)
		Now consider a pure metal at its freezing point where both the liquid and solid states are at the same temperature.
		Finally, as the amount of liquid decreases, the gaps between the arms of the dendrite will be filled and the growth of the dendrite will be mutually obstructed by that of its neighbors.
		The crystals found in all commercial metals are commonly called grains because of this variation in external shape.
	www.tech.farmingdale.edu /depts/met/met205/crystallization.html (558 words)

	Isothermal Dendritic Growth Experiment (IDGE) (Site not responding. Last check: 2007-09-08)
		The Isothermal Dendritic Growth Experiment (IDGE) is a fundamental microgravity materials science experiment to be flown as part of the second United States Microgravity Payload (USMP-2) aboard the Space Shuttle Columbia.
		Dendrites - from the ancient Greek word for tree - are tiny branching structres that form inside molten metal alloys when they soldiify during manufacturing.
		SCN was chosen because it mimics the behavior of metals but is a transparent, low-melting-point material, thus allowing photography of the dendrites and the design of a safer, less expensive space apparatus.
	zeta.lerc.nasa.gov /expr2/idge.htm (1446 words)

	USMP-4 Status Reports
		When such metals are processed on Earth, gravity causes the liquids to separate - much the same way as water and oil.
		Metal alloys form dendrites when they crystallize, ultimately creating the strong materials used in production of automobiles and jet engines.
		Three different sample cartridges containing the metal bismuth, with small additions of tin, will be processed in the furnace using directional solidification - a common method for growing semiconductors and metal alloys.
	liftoff.msfc.nasa.gov /Shuttle/USMP4/realtime/pao02.html (834 words)

	Electric Snow Crystal Growth
		We analyzed dendrite growth in the presence of an applied voltage [1], for the special case where the growing crystal has no facets.
		A normal dendrite first was grown on a metal wire, and allowed to reach a steady state, where it grew with a constant tip velocity of about 3 microns/sec.
		As the voltage increased the dendrite tip velocity increased until at 1300 volts it was growing at about 4 microns/sec.
	www.its.caltech.edu /~atomic/snowcrystals/electric/electric.htm (884 words)

	WPI Metal Processing Institute - CHTE project focuses on solution treatment of aluminum alloys
		Dendrite arm spacing and percent porosity are being used to characterize the as-cast microstructure.
		In the latter, Deff is the appropriate interdiffusion coefficient for the selected solution treatment temperature, tS is the solution treatment time, and d2 is the square of the dendrite arm spacing of the initial as-cast microstructure.
		The process-microstructure and process-property maps will be available to heat-treaters and process design engineers to guide in the selection of the most economical solution treatment parameters and to achieve the desired combination of microstructure and properties in key components.
	www.wpi.edu /Academics/Research/MPI/News/Releases/2000/amp200012.html (1211 words)

	CHESS News 2006 - Li, Brody, Kazimirov
		The dendritic structure evolves continuously during solidification, and size and entanglements of the dendrites play a critical role in the mechanical properties of materials during subsequent processing and in service.
		Once a dendritic front formed within the field of view, a modified, remotely controlled “point and shoot” 35-mm camera was loaded with high-resolution x-ray film and frame advanced to capture a growth sequence.
		With their x-ray microradiographs, they were able to characterize zone fronts moving at up to 26 microns per minute (no upper limit was determined) and measure values to agree well with analytic models describing the kinetics of TGZM.
	news.chess.cornell.edu /articles/2006/alloy.html (827 words)

	Advantages
		Metal migration, commonly called dendrite growth, is a classic cause of internal shorting in electronic devices when silver and/or lead are present.
		The mechanism for dendrite growth includes a voltage potential between metal electrodes and the presence of moisture.
		Failure occurs after moisture penetrates the body of a molded network during the thermal shock of soldering and the aqueous cleaning process.
	www.ctscorp.com /components/resistor_networks/advantages.htm (210 words)

	193 (Site not responding. Last check: 2007-09-08)
		In the rechargeable lithium batteries that are targeted for use with electric and hybrid electric vehicles, the use of lithium metal directly as the anode could provide higher voltage and higher capacity.
		However, the principal impediment using these lithium metal anodes is the occurrence of lithium dendrite growth during charging, which limits both the maximum current density that can be imposed and the number of cycles.
		In Phase I, the role of the anode/electrolyte charge transfer resistance on dendrite growth will be theoretically addressed by solving the requisite mixed boundary value problem for various values of the charge transfer resistance, which correspond to the situation with and without composite interlayers.
	www.er.doe.gov /sbir/awards_abstracts/sbirsttr/cycle22/phase1/193.htm (273 words)

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