Sunday, February 5, 2012
Before its discovery, most of its properties had been predicted and described in the classic articles about elements natural system and its application for describing yet no discovered elements by Dmitri Mendeleev, who called the hypothetical element eka-aluminium, on the basis of its position in his periodic table. His prediction was brilliantly when the new element was discovered spectroscopically by Paul-Emile Lecoq de Boisbaudran in 1875 by its characteristic spectrum in an examination of a zinc blend from the Pierrefitte Mountain in Pyrenees. He called the new-discovered element gallium (Latin Gallia meaning Gaul (essentially modern France); also gallus, meaning "rooster"), the French for which is "le coq", mentioning the Lecoq de Boisbaudran's surname.
Gallium's discovery had been the greatest Gallium triumph of Mendeleev's periodic system.
Gallium is a typical trace element, poor metal, sometimes considered as a rare element. Its crustal abundance is quite big, 1.5x10-3 mass %. However gallium does not exist in free form in nature, and concentration is less than 100 ppm or 0.01% of a rock's composition. Gallium minerals were unknown even 100 years ago before Ramdorf's report about new mineral species of gallium ores from Tsumeb, Namibia and Kipushi mine in Zaire. It was gallium and copper sulphides mixture CuS2 called gallite and described by Strunz, Geier and Seeliger in 1958. Primary zinc-rich ore body contains the minerals sphalerite, cobalt-bearing chalcopyrite, germanite and gallite. Sphalerite from floutite-sulphide deposits is especially rich by gallium. Gallium is found and extracted as a component in bauxite, germanite, and sphalerite. Apatite-nepheline ores deposited in Khibin range of the Kola region of Russia are also very rich by gallium (0.01 - 0.04%). Gallium's concentrations in other minerals are as follows: sphalerite (ZnS) - 0.001%, pyrite (S2) - 0,001%, germanite (Cu3S4) - 1.85%, zircon (zirconium silicate ZrSiO4) - 0.001 - 0.005%, spodumene (LiAlSi2O6) - 0.001 - 0.07%. Some flue dusts from burning coal esp. in England have been shown to contain small quantities of gallium, typically less than 1.5% by weight.
Gallium abundance in Universe is estimated to be 10-6% by mass or 2x10-7% (by atom.); 4x10-6% (mass.) or 6x10-7% (atom) on the Sun; in meteorites 7.8x10-4% by mass and in seawater 3x10-9% by mass.
Gallium'a role for life processed is not understood. According to some hypotheses gallium's presence in English coal is a result of some vital processes. Galium is needed for some fungi such as myco Aspergillus which is a close relative to mold and for Lemna minor, lesser duckweed, which is one the world's smallest flowering wetland plants.
Aluminum mixed with gallium will react with water to produce hydrogen and aluminum oxide so has been considered by (Purdue) and others as a fuel candidate as gasoline becomes either scarce or expensive.
[From the internet]
"Their (Purdue) hydrogen-releasing formula, which is patent-pending, is 90 percent bulk aluminum and 10 percent liquid metal alloy, consisting of gallium, indium and tin. The gallium dissolves the aluminum, allowing it to react with the oxygen in the seawater. The hydrogen atoms break free from the water molecule. The end product is aluminum hydroxide, which can be recycled back into aluminum.
Despite their seawater hydrogen recipe calling for indium, which has supply issues, the researchers contend it could be cost-competitive."
Hydrogen is often advocated as an energy medium. Here are some relevant facts.
Hydrogen is the lightest of the elements with an atomic weight of 1.0. Liquid hydrogen has a density of 0.07 grams per cubic centimeter, whereas water has a density of 1.0 g/cc and gasoline about 0.75 g/cc. These facts give hydrogen both advantages and disadvantages. The advantage is that it stores approximately 2.6 times the energy per unit mass as gasoline, and the disadvantage is that it needs about 4 times the volume for a given amount of energy. A 15 gallon automobile gasoline tank contains 90 pounds of gasoline. The corresponding hydrogen tank would be 60 gallons, but the hydrogen would weigh only 34 pounds.
New fuel for 21st century -- aluminum +(gallium, indium,tin) alloy pellets?
"Pellets made out of aluminum and gallium can produce pure hydrogen when water is poured on them, offering a possible alternative to gasoline-powered engines, U.S. scientists say.
Hydrogen is seen as the ultimate in clean fuels, especially for powering cars, because it emits only water when burned. U.S. President George W. Bush has proclaimed hydrogen to be the fuel of the future, but researchers have not yet found the most efficient way to produce and store hydrogen.
The metal compound pellets may offer a way, said Jerry Woodall, an engineering professor at Purdue University in Indiana who invented the system.
"The hydrogen is generated on demand, so you only produce as much as you need when you need it," Woodall said in a statement. He said the hydrogen would not have to be stored or transported, taking care of two stumbling blocks to generating hydrogen.
For now, the Purdue scientists think the system could be used for smaller engines like lawn mowers and chain saws. But they think it would work for cars and trucks as well, either as a replacement for gasoline or as a means of powering hydrogen fuel cells.
"It is one of the more feasible ideas out there," Jay Gore, an engineering professor and interim director of the Energy Center at Purdue's Discovery Park, said in a telephone interview on Thursday. "It's a very simple idea but had not been done before."
On its own, aluminum will not react with water because it forms a protective skin when exposed to oxygen. Adding gallium keeps the film from forming, allowing the aluminum to react with oxygen in the water.
This reaction splits the oxygen and hydrogen contained in water, releasing hydrogen in the process.
"I was cleaning a crucible containing liquid alloys of gallium and aluminum," Woodall said. "When I added water to this alloy -- talk about a discovery -- there was a violent poof."
What is left over is aluminum oxide and gallium. In the engine, the byproduct of burning hydrogen is water.
"No toxic fumes are produced," Woodall said.
"When and if fuel cells become economically viable, our method would compete with gasoline at $3 per gallon even if aluminum costs more than a dollar per pound."
Recycling the aluminum oxide byproduct and developing a lower grade of gallium could bring down costs, making the system more affordable, Woodall said.
The Purdue Research Foundation holds title to the primary patent, which has been filed with the U.S. Patent and Trademark Office. An Indiana startup company, AlGalCo LLC., has received a license for the exclusive right to commercialize the process."
Gallium oxide is precipitated in hydrated form upon neutralization of acidic or basic solution of gallium salt. Also, it is formed on heating gallium in air or by thermally decomposing gallium nitrate at 200-250˚C. It can occur in five different modifications, α,β,δ,γ and ε. Of these modifications β-Ga2O3 is the most stable form.
Preparation Methods for the Five Modifications
β-Ga2O3 is prepared by heating nitrate, acetate, oxalate or other organic derivatives above 1000˚C.
α-Ga2O3 can be obtained by heating β-Ga2O3 at 65kbars and 1100˚C for 1 hour giving a crystalline structure. The hydrated form can be prepared by decomposing precipitated and "aged" gallium hydroxide at 500˚C.
γ-Ga2O3 is prepared by rapidly heating the hydroxide gel at 400˚C-500˚C.
δ-Ga2O3 is obtained by heating Ga(NO3)3 at 250˚C.
ε-Ga2O3 is prepared by briefly heating δ-Ga2O3 at 550˚C for 30 minutes.[4