Tungsten (pronounced /'t??st?n/), also known as wolfram (/'w?lfr?m/, WOOL-fr?m), is a chemical element with the chemical symbol W and atomic number 74.

Tungsten Bar is found in several ores, including wolframite and scheelite. It is remarkable for its robust physical properties, especially the fact that it has the highest melting point of all the non-alloyed and the second highest of all the elements after carbon. Also remarkable is its very high density of 19.3 times heavier than water, and 71% heavier than lead. Tungsten is often brittle and hard to work in its raw state; if pure, it can be cut with a hacksaw.

The pure form is used mainly in electrical applications, but its many compounds and alloys have many applications, most notably in incandescent light bulb filaments, X-ray tubes (as both the filament and target), and superalloys.
Tungsten is the only from the third transition series that is known to occur in biomolecules, and is the heaviest element known to be used by living organisms.

In 1781, Carl Wilhelm Scheele discovered that a new acid, tungstic acid, could be made from scheelite (at the time named tungstenite). Scheele and Torbern Bergman suggested that it might be possible to obtain a new by reducing this acid. In 1783, José and Fausto Elhuyar found an acid made from wolframite that was identical to tungstic acid. Later that year, in Spain, the brothers succeeded in isolating Tungsten Rod by reduction of this acid with charcoal, and they are credited with the discovery of the element.

In World War II, tungsten played a significant role in background political dealings. Portugal, as the main European source of the element, was put under pressure from both sides, because of its deposits of wolframite ore. Tungsten's resistance to high temperatures and its strength in alloys made it an important raw material for the weaponry industry.The name "tungsten" (from the Nordic tung sten, meaning "heavy stone") is used in English, French, and many other languages as the name of the element. Tungsten was the old Swedish name for the mineral scheelite. The other name "wolfram" (or "volfram"), used for example in most European (especially Germanic and Slavic) languages, is derived from the mineral wolframite, and this is also the origin of its chemical symbol, W. The name "wolframite" is derived from German "wolf rahm" ("wolf soot" or "wolf cream"), the name given to tungsten by Johan Gottschalk Wallerius in 1747. This, in turn, derives from "Lupi spuma", the name Georg Agricola used for the element in 1546, which translates into English as "wolf's froth" or "cream" (the etymology is not entirely certain), and is a reference to the large amounts of tin consumed by the mineral during its extraction.

In its raw form, Tungsten Powder is a steel-gray that is often brittle and hard to work, but, if pure, it can be worked easily. It is worked by forging, drawing, extruding or sintering. Of all in pure form, tungsten has the highest melting point (3,422 °C, 6,192 °F), lowest vapor pressure and (at temperatures above 1,650 °C, 3,000 °F) the highest tensile strength. Tungsten has the lowest coefficient of thermal expansion of any pure. The low thermal expansion and high melting point and strength of tungsten are due to strong covalent bonds formed between tungsten atoms by the 5d electrons. Alloying small quantities of tungsten with steel greatly increases its toughness.

Naturally occurring tungsten consists of five isotopes whose half-lives are so long that they can be considered stable. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only 180W has been observed to do so with a half-life of (1.8 ± 0.2)×1018 yr; on average, this yields about two alpha decays of 180W in one gram of natural Tungsten Rod per year. The other naturally occurring isotopes have not been observed to decay, constraining their half-lives to be

    182W, T1/2 > 8.3×1018 years

    183W, T1/2 > 29×1018 years

    184W, T1/2 > 13×1018 years

    186W, T1/2 > 27×1018 years

Another 30 artificial radioisotopes of tungsten have been characterized, the most stable of which are 181W with a half-life of 121.2 days, 185W with a half-life of 75.1 days, 188W with a half-life of 69.4 days, 178W with a half-life of 21.6 days, and 187W with a half-life of 23.72 h. All of the remaining radioactive isotopes have half-lives of less than 3 hours, and most of these have half-lives below 8 minutes. Tungsten also has 4 states, the most stable being 179mW (T½ 6.4 minutes).

Elemental tungsten resists attack by oxygen, acids, and alkalis.
The most common formal oxidation state of tungsten is +6, but it exhibits all oxidation states from −2 to +6. Tungsten typically combines with oxygen to form the yellow tungstic oxide, WO3, which dissolves in aqueous alkaline solutions to form tungstate ions, WO2−4.

Tungsten Carbide Powder (W2C and WC) are produced by heating powdered tungsten with carbon and are some of the hardest carbides, with a melting point of 2770 °C for WC and 2780 °C for W2C. WC is an efficient electrical conductor, but W2C is less so. Tungsten carbide behaves similarly to unalloyed tungsten and is resistant to chemical attack, although it reacts strongly with chlorine to form tungsten hexachloride (WCl6).

Aqueous tungstate solutions are noted for the formation of heteropoly acids and anions under neutral and acidic conditions. As tungstate is progressively treated with acid, it first yields the soluble,"paratungstate A" anion, W7O6–24, which over time converts to the less soluble "paratungstate B" anion, H2W12O10–42. Further acidification produces the very soluble , H2W12O6–40, after which equilibrium is reached. The ion exists as a symmetric cluster of twelve tungsten-oxygen octahedra known as the Keggin anion. Many other anions exist as species. The inclusion of a different atom such as phosphorus in place of the two central hydrogens in produces a wide variety of heteropoly acids, such as phosphotungstic acid H3PW12O40.

 

 

source:answers|tungsten

A tungsten powder comprised of macro-spherical particles of tungsten disulfide having an average particle diameter of from about 5 to about 50 micrometers is prepared by successively treating spray-dried powders of ammonium metatungstate with heat in air and sulfidizing the resultant tungsten trioxide in a carbon disulfide-containing atmosphere at about 750° C. The tungsten disulfide powder may also be formed to have a bimodal particle size distribution of the macro-spherical particles and smaller, dispersed micro- to submicron-sized fine particles.

Tungsten is a heavy, gray metal with bluish overtones. When mixed with black carbon, tungsten carbide is created.
The compound is made by heating pulverized tungsten with black carbon, when hydrogen is present. Temperatures range from 2,550 to 2,900 degrees F or 1,400 to 1,600 degrees C. A common method for making the compound was developed in the 1920s in Germany and involves mixing powered tungsten carbide with cobalt. This mixture is then made into the required shape and heated to 2,550 to 2,900 degrees F or 1,400 to 1,600 degrees C. This heat melts the tungsten carbide partially, working as a cement. These Tungsten Carbide Powders are known by the names Carboloy and hardmetal.

Tungsten disulfide is a solid inorganic lubricate typically applied as a dry film to provide lubrication under conditions that are generally unsuitable for most organic-based lubricants, e.g. high loads, high temperatures (to 500° C. in air) and vacuum environments. Tungsten disulfide powders may be used as an lubrication-enhancing additive in various greases, oils, or self-lubricating polymers. Examples of these applications are described in U.S. Pat. Nos. 4,075,111, 4,715,972, and 5,013,466.

The tungsten and carbon is made into a powder using a pulverizer. The materials are then placed into a crucible and heated using an arc of electricity. The two materials then combine creating the tungsten carbide.
Commercially available tungsten disulfide powders are composed generally of irregularly shaped flat platelets as shown in FIG. 1 . It has been postulated that these irregular platelets have chemically reactive edges which cause them to stick to machinery parts and undergo undesirable chemical reactions. Spherical fullerene-like tungsten disulfide nanoparticles have been shown to improve the tribological properties of Tungsten Bar disulfide. Such particles are described in International Application No. WO 01/66462 A2. The fullerene-like nanoparticles were made by sulfidizing WO  3  in a solid-gas reaction with H  2  S. The temperature in the reaction path ranged from 750° C. to 850° C. The size and geometry of the WS  2  particles was found to be determined by the size and geometry of the WO  3  particles being reduced. Larger oxide precursor particles (about 0.5 μm) were slower to convert necessitating the addition of an extra annealing step at 950° C. to complete the conversion. Although larger particles were thought to be a better lubricant in cases where the mating surfaces had higher surface roughness, the process described therein was limited to producing spherical particles up to 0.5 μm.

A gray, inorganic material, Tungsten Carbide Powder functions as a hardener in armor-piercing projectiles, the sharp edges of drills and saws, and cast iron. Besides industrial uses, it is also used to create jewelry due to its hardness and deduced risk of allergic reactions among those with sensitive skin, among other desirable properties.
A gray, inorganic material, tungsten carbide functions as a hardener in armor-piercing projectiles, the sharp edges of drills and saws, and cast iron. Besides industrial uses, it is also used to create jewelry due to its hardness and deduced risk of allergic reactions among those with sensitive skin, among other desirable properties.

In another embodiment, a bimodal distribution of macro-spherical and smaller, dispersed micron- to submicron-sized fine particles of tungsten disulfide are prepared by heating spray-dried powders of ammonium metatungstate in air, mixing the resultant tungsten trioxide with a tungsten metal powder , and sulfidizing the mixture in carbon disulfide at about 750° C. The resultant tungsten disulfide powder contains a bimodal distribution of the macro-spherical tungsten disulfide particles and fine tungsten disulfide particles having an average particle diameter of from about 0.5 to about 5 micrometers. Preferably, the fine particles have an average particle diameter of from about 1 to about 3 micrometers.

 

 

source:blog|tungsten carbide powder

Because it retains its strength at high temperatures and has a high melting point, elemental tungsten is used in many high-temperature applications, such as light bulb, cathode-ray tube, and vacuum tube filaments, heating elements, and rocket engine nozzles. Its high melting point also makes Tungsten Bar suitable for aerospace and high-temperature uses such as electrical, heating, and welding applications, notably in the gas tungsten arc welding process [also called tungsten inert gas (TIG) welding].

Because of its conductive properties and relative chemical inertia, tungsten is also used in electrodes, and in the emitter tips in electron-beam instruments that use field emission guns, such as electron microscopes. In electronics, tungsten is used as an interconnect material in integrated circuits, between the silicon dioxide dielectric material and the transistors. It is used in metallic films, which replace the wiring used in conventional electronics with a coat of tungsten (or Molybdenum Powder ) on silicon.

The electronic structure of tungsten makes it one of the main sources for X-ray targets, and also for shielding from high-energy radiations (such as in the radiopharmaceutical industry for shielding radioactive samples of FDG). Tungsten powder is used as a filler material in plastic composites, which are used as a nontoxic substitute for lead in bullets, shot, and radiation shields. Since this element's thermal expansion is similar to borosilicate glass, it is used for making glass-to-metal seals.

The hardness and density of tungsten are applied in obtaining heavy metal alloys. A good example is high speed steel, which may contain as much as 18% tungsten. Superalloys containing tungsten, such as Hastelloy and Stellite, are used in turbine blades and wear-resistant parts and coatings. Applications requiring its high density include heat sinks, weights, counterweights, ballast keels for yachts, tail ballast for commercial aircraft, and as ballast in race cars for NASCAR and Formula One. It is an ideal material to use as a dolly for riveting, where the mass necessary for good results can be achieved in a compact bar. In armaments, tungsten manufacturer , usually alloyed with nickel and iron or cobalt to form heavy alloys, is used in kinetic energy penetrators as an alternative to depleted uranium but may also be used in cannon shells, grenades and missiles to create supersonic shrapnel. High-density alloys of tungsten with nickel, copper or iron are used in high-quality darts (to allow for a smaller diameter and thus tighter groupings) or for fishing lures (tungsten beads allow the fly to sink rapidly). Some types of strings for musical instruments are wound with tungsten wires. Its density, similar to that of gold, allows tungsten to be used in jewelry as an alternative to gold or platinum. Its hardness makes it ideal for rings that will resist scratching, are hypoallergenic, and will not need polishing, which is especially useful in designs with a brushed finish.

 

 

 

                                     

 

Tungsten compounds are used in catalysts, inorganic pigments (e.g. tungsten oxides), and as high-temperature lubricants (tungsten disulfide). Tungsten Carbide Powder (WC) is used to make wear-resistant abrasives and cutters and knives for drills, circular saws, milling and turning tools used by the metalworking, woodworking, mining, petroleum and construction industries and accounts for about 60% of current tungsten consumption. Tungsten oxides are used in ceramic glazes and calcium/magnesium tungstates are used widely in fluorescent lighting, while tungsten halogen bulbs are frequently used to light indoor photo shoots, and special negative films exist to take advantage of tungsten's unique disentangling properties. Crystal tungstates are used as scintillation detectors in nuclear physics and nuclear medicine. Other salts that contain tungsten are used in the chemical and tanning industries.
Precautions

The data concerning the toxicity of tungsten is limited, but cases of intoxication by tungsten compounds are known, the lethal dose is estimated to be between 500 mg/kg and 5 g/kg for humans.  Tungsten is known to generate seizure and renal failure with acute tubular necrosis.
The effects of Tungsten Powder within the environment are essentially unknown, a concern that has arisen in response to increasingly widespread use of the material as a fishing sinker, some of which are inevitably lost into water bodies. The same unknown variable applies whenever tungsten may be deposited into the environment, either knowingly or inadvertently.

 

 

 

source:answers

A thermal spray powder is formed as a mixture of tungsten carbide granules and chromium carbide granules. The tungsten carbide granules each consists essentially of tungsten carbide bonded with cobalt, and the chromium carbide granules each consists essentially of chromium carbide bonded with nickel-chromium alloy. The powder may be asmixed with self-fluxing alloy powder. The powder preferably is sprayed with a high velocity oxygen-fuel thermal spray gun.

Tungsten is a heavy, gray metal with bluish overtones. When mixed with black carbon, tungsten carbide is created.
The compound is made by heating pulverized tungsten with black carbon, when hydrogen is present. Temperatures range from 2,550 to 2,900 degrees F or 1,400 to 1,600 degrees C. A common method for making the compound was developed in the 1920s in Germany and involves mixing powered tungsten carbide with cobalt. This mixture is then made into the required shape and heated to 2,550 to 2,900 degrees F or 1,400 to 1,600 degrees C. This heat melts the tungsten carbide partially, working as a cement. These tungsten carbide-cobalt creations are known by the names Carboloy and hardmetal.

Wear resistance is a common requirement for thermal sprayed coatings, and carbide powders are frequently used, for example tungsten carbide. British patent specification No. 867,455 typifies cobalt bonded tungsten carbide powder admixed with a sprayweld self-fluxing powder for producing coatings. Often such coatings are subsequently fused. Self-fluxing alloys are nickel, cobalt or iron based alloys with chromium and with small amounts of boron, silicon and carbon which serve as fluxing agents and hardeners. Examples of self-fluxing alloys are disclosed in the aforementioned British patent specification and U.S. Pat. Nos. 3,743,533 and 4,064,608. Iron base alloys with molybdenum, boron and silicon are disclosed in U.S. Pat. No. 4,822,415.

The cobalt- tungsten carbide itself is also sprayed neat, i.e. without the self-fluxing ingredient, best results being with high velocity, particularly plasma spray or a high velocity oxygen-fuel (HVOF) gun or a detonation gun. The granules of a powder typically are formed of subparticles of tungsten carbide and cobalt, spray dried, sintered or fused, the result being crushed and classified into a powder of proper size for thermal spraying.

Another carbide is chromium carbide that is utilized for higher temperature applications. This carbide may be sprayed without any metal binder, but it usually is clad or bonded with nickel or nickel alloy, such as nickel-chromium alloy, such as described in U.S. Pat. Nos. 3,150,938 and 4,606,948.

Tungsten carbide manufacturer and chromium carbide have been combined together with nickel for the detonation process as taught in U.S. Pat. Nos. 3,071,489. In one aspect of this patent, the elemental ingredients are all mixed together, and then sintered and crushed into a powder. In another aspect, separate powders of tungsten carbide, chromium carbide and nickel are blended to form a powder mixture of the three ingredients. In this form there is a tendency for the carbide to lose carbon in the flame. The two carbides also have been combined together with cobalt (without nickel) in a powder formed by casting and crushing, or by sintering, as taught in U.S. Pat. No. 4,925,626. Cobalt does not have as high corrosion resistance as nickel.

The latter patent teaches a method for producing a coating material of WC-Co-Cr alloy for high velocity oxygen-fuel thermal spraying. A mixture is prepared of tungsten carbide, cobalt and chromium, the latter being in the form of chromium carbide. The mixture is alloyed by by spray drying followed by sintering and plasma densification.

U.S. Pat. No. 4,588,608 teaches a powder for the detonation process, in which the powder is a cast and crushed composition of tungsten carbides , chrominum and cobalt. Two proprietary coatings of this nature are LW-45 and LW-15 produced by Praxair, Inc., Danbury, Conn., by the detonation process. LW-45 nominally contains 8% cobalt 4% chromium and balance tungsten carbide. LW-15 nominally contains 84% tungsten, 8% cobalt, 3% chromium and 5% carbon. These coatings have been utilized in specified applications such as petrochemical gate valves.

The tungsten and carbon is made into a powder using a pulverizer. The materials are then placed into a crucible and heated using an arc of electricity. The two materials then combine creating the tungsten carbide.
A gray, inorganic material, tungsten carbide functions as a hardener in armor-piercing projectiles, the sharp edges of drills and saws, and cast iron. Besides industrial uses, it is also used to create jewelry due to its hardness and deduced risk of allergic reactions among those with sensitive skin, among other desirable properties.

An object of the present invention is to provide an improved powder of Tungsten Bar and chromium carbide for the thermal spray process. Another object is to provide improved corrosion resistance in wear resistant carbide coatings. Further objects are to provide improved impact and toughness in such coatings.

The foregoing and other objects are achieved by a thermal spray powder formed as a mixture of tungsten carbide granules and chromium carbide granules. The tungsten carbide granules each consist essentially of Tungsten Carbide Powder bonded with cobalt, and the chromium carbide granules each consist essentially of chromium carbide bonded with nickel-chromium alloy. The powder may be admixed with a self-fluxing alloy powder, advantageously iron based.

Objects are also achieved by a method of producing a carbide coating utilizing a thermal spray gun having a combustion chamber with an open channel for propelling combustion products into the ambient atmosphere at supersonic velocity. The method comprises preparing a substrate for receiving a thermal sprayed coating, feeding through the open channel a carbide powder, injecting into the chamber and combusting therein a combustible mixture of combustion gas and oxygen at a pressure in the chamber sufficient to produce a supersonic spray stream containing the powder issuing through the open channel, and directing the spray stream toward the substrate so as to produce a coating thereon. The carbide powder is formed as a mixture as set forth above.

 

 

source:blog|tungsten

The invention is directed to the production of tungsten and tungsten carbide in powder form. More particularly, this invention is directed to the production of tungsten and tungsten carbide powder of coarse particle size.

There are generally two forms of tungsten carbide. Monotungsten carbide has the formula WC, and ditungsten carbide has the formula W 2 C. Of the two, WC is more applicable for use in the manufacture of many objects such as, without limitation, dies and cutting and drilling tools. In producing such dies and tools, the WC form of tungsten carbide powder may be combined with a bonding agent such as cobalt and sintered together to form what is known in the art as a cemented carbide structure.

In certain applications it would be desirable to produce tools from WC powder particles which comprise a polycrystalline structure of coarse grains or crystals. This is particularly true regarding many mining and drilling tools.

U.S. Pat. No. 2,113,171 to Cooper describes one process for producing the WC form of tungsten carbide powders . In this process, very fine powdered tungsten is mixed with very fine powdered carbon such as lamp-black. The mixture is thoroughly blended and the powder is heated in a hydrogen atmosphere for thirty to forty-five minutes at about 1200° C. to 1600° C. The preferred temperature is 1400° C.

A similar patent of interest is U.S. Pat. No. 3,850,614 to Bleecker which describes the production of WC by carburizing pure tungsten powder and pure carbon black at 2750° F. or about 1340° C.

It is believed that the process generally used in producing WC for use in cutting and mining tools is of the type described in Cooper involving temperatures of about 1200° C. to about 1600° C. For example, the process of Bleecker falls within this range and produces WC for use in the production of extremely fine powder in 1.1 to 1.3 micron range. In addition, particles having finer grain sizes are not particularly mechanically stable and are therefore subjected to a greater degree of attrition during milling than desired.

The compound is made by heating pulverized Tungsten Bar with black carbon, when hydrogen is present. Temperatures range from 2,550 to 2,900 degrees F or 1,400 to 1,600 degrees C. A common method for making the compound was developed in the 1920s in Germany and involves mixing powered tungsten carbide with cobalt. This mixture is then made into the required shape and heated to 2,550 to 2,900 degrees F or 1,400 to 1,600 degrees C. This heat melts the tungsten carbide partially, working as a cement. These tungsten carbide-cobalt creations are known by the names Carboloy and hardmetal.

There has been a continuing need for a cemented carbide composed of large, uniform grains for use in mining bits. Typically, coarse grained cemented carbide is made from coarse grained tungsten carbide which, in turn, is made from tungsten metal powder having a large particle size.

A uniform, large size tungsten powder having metallurgical properties which make it suitable for the production of large size tungsten carbide powder is produced by doping a tungsten oxide starting powder with a lithium compound prior to reduction. The lithium compound is a high melting lithium compound which decomposes during the hydrogen gas reduction step to yield a large size tungsten powder having a very low level of lithium.

 

 

 

 

 

 

 

To produce coarse grain tungsten carbide, the large grain size tungsten powder is intimately mixed with carbon powder in amounts allowing for at least one atom of carbon for each atom of tungsten. Such mixture is heated to a temperature falling within the range of about 1300° C. to any temperature less than that which will melt tungsten carbide and such heating is continued for a time sufficient to carburize the tungsten powder to tungsten carbide. Such monotungsten carbide is then cooled for further processing.

The invention also relates to a monotungsten carbide object and method of producing same. To produce such an object tungsten carbide powder is produced in the manner described in the immediately preceeding paragraph. The cooled tungsten carbide powder is mixed with a binding agent such as, for example, cobalt. The binding agent may include a hydrocarbon solvent such as heptane and a lubricant such as paraffin wax. Subsequently, the binding agent/monotungsten carbide mixture is pressed into a predetermined formed object which is sintered.

The tungsten and carbon is made into a powder using a pulverizer. The materials are then placed into a crucible and heated using an arc of electricity. The two materials then combine creating the tungsten carbide.
A gray, inorganic material, tungsten carbide functions as a hardener in armor-piercing projectiles, the sharp edges of drills and saws, and cast iron. Besides industrial uses, it is also used to create jewelry due to its hardness and deduced risk of allergic reactions among those with sensitive skin, among other desirable properties.

The present invention relates to the production of Ferro Molybdenum from molybdenite concentrate, particularly from copper-bearing molybdenum concentrates.

In the production of molybdenite concentrate from molybdenum ores derived from deposits containing copper and molybdenum minerals, a complete separation of the copper and molybdenum mineral cannot always be obtained. In the present manufacturing process for ferro- molybdenum, the molybdenite concentrate is roasted with air or oxygen, whereafter the commercial molybdenum oxide obtained is used in steel production directly or after metallo-thermic reduction (e.g. with ferro-silicon) to ferro- molybdenum. In both cases the copper content of the concentrate remains unaffected, i.e. the copper accompanies the molybdenum oxide or ferro- molybdenum, which is a drawback in their use for the production of steel. It is normally required that the ferro- molybdenum shall contain a maximum copper content, often 0.5% copper.

Sulfur dioxide is generated during roasting of the molybdenite concentrate, which creates difficult environmental problems.

The present invention is directed towards removing or reducing these difficulties by providing a process in which roasting is completely or partly eliminated, and the majority of the sulfur as well as copper which is possibly present is transferred to a sulfide-bearing slag.

This is achieved according to the invention in that molybdenum sulfide in the molybdenite concentrate is reduced directly with the help of a melt of ferro-manganese or a mixture of ferro-manganese and iron in such a way that partly there is formed a metal phase mainly consisting of ferro- molybdenum purified from copper and sulfur, and partly a slag phase mainly consisting of manganese sulfide, the latter containing the majority of the copper which is possibly present. The manganese sulfide obtained has commercial utilisation possibilities as an additive in the Ferro Molybdenum manufacturer of certain kinds of steel.

The process according to the invention is suitably carried out by melting ferro-manganese or a mixture of ferro-manganese and iron in an electric arc furnace, induction furnace, or converter having a refractory lining, whereafter the molybdenite concentrate is introduced. The iron content should be kept at a level such that the slag phase as well as the metal phase can be tapped without difficulty from the furnace after completed reaction. The furnace or the converter is suitably so formed that the concentrate can be introduced in the form of a suspension in a gas. The refractory liner of the furnace suitably consists of alumina.

Baths of iron, manganese and molybdenum contain a certain amount of carbon, which varies according to the choice of raw material, and especially the choice of ferro-manganese quality. An oxidising agent can be added simultaneously with or after adding the molybdenite concentrate, to reduce the carbon content in the bath. The oxidising agent can consist of molybdenum oxide (roasted molybdenite concentrate) or iron ore concentrate. Alternatively, decarburization can be carried out using air or oxygen.

Ferro alloy is a product of molybdenum oxide reduction. It is derived from a batch-type of operations done by means of a thermit process or by using an electric furnace reduction activity. While this production process is easy, it however carries the potential of being harmful to the environment due to its air and noise consideration.

Being able to accomplish a molybdenum oxidation reduction process is highly significant as the element is an extremely hard and useful metal, and it can be used on various steelmaking operations and other industrial applications. Steel materials containing ferro alloy are known to withstand wear and tear, thus ensuring its durability.

A molybdenum oxide reduction process is conducted under extremely high temperatures, as molybdenum is a hard element and has the sixth highest melting point. Molybdenite, molybdenum compound, is roasted at a high temperature in order to extract all the oxygen present. The process usually takes a number of steps depending on the purpose of the element. Afterward, pure reduced high-grade molybdenum oxide is produced and applied on various catalysts.

A contact structure provides electrical contact between two polycrystalline silicon interconnect layers. The lower layer has a silicide layer on its upper surface. The upper polycrystalline silicon layer can be doped with a different conductivity type, and makes an ohmic contact with the silicided region of the lower polycrystalline silicon layer.

Chemical vapor deposition (CVD) is a chemical process that uses a chamber of reactive gas to synthesize high-purity, high-performance solid materials, such as electronics components. Certain components of integrated circuits require electronics made from the materials polysilicon, silicon dioxide, and silicon nitride. An example of a chemical vapor deposition process is the synthesis of polycrystalline silicon from silane (SiH4), using this reaction:

In semiconductor circuits, it is known that ohmic contacts are desirable between interconnect layers. An ohmic contact is one in which no P-N junction is formed.

When polycrystalline silicon interconnect lines having different conductivity types make contact, a P-N junction is formed. A similar junction can be formed when polycrystalline silicon having the same conductivity type, but very different doping levels (such as N - - to N + ) make contact. For various reasons, it is often desirable to have interconnect having different conductivity types make contact, and it would be desirable to provide an ohmic contact for such structures.
It is therefore an object of the present invention to provide an ohmic contact between polycrystalline silicon interconnect layers having different conductivity types.

It is another object of the present invention to provide such a contact which is easily formed with a process compatible with existing process technologies.

It is a further object of the present invention to provide such a contact which is suitable for use in an SRAM structure to provide a load.

Therefore, according to the present invention, a contact structure provides electrical contact between two polycrystalline silicons interconnect layers. The lower layer has a silicide layer on its upper surface. The upper polycrystalline silicon layer can be doped with a different conductivity type, and makes an ohmic contact with the silicided region of the lower polycrystalline silicon layer.

In the silane reaction, the medium would either be pure silane gas, or silane with 70-80% nitrogen. Using a temperature between 600 and 650 °C (1100 - 1200 °F), and pressure between 25 and 150 Pa — less than a thousandth of an atmosphere — pure silicon can be deposited at a rate of between 10 and 20 nm per minute, perfect for many circuit board components, whose thickness is measured in microns. In general, temperatures inside a chemical vapor temperature deposition machine are high, while pressures are very low. The lowest pressures, under 10−6 pascals, are called ultrahigh vacuum. This is different than the use of the term "ultrahigh vacuum" in other fields, where it usually refers to a pressure below 10−7 pascals instead.

Some products of chemical vapor deposition include polycrystalline silicon manufacturer , carbon fiber, carbon nanofibers, filaments, carbon nanotubes, silicon dioxide, silicon-germanium, tungsten, silicon carbide, silicon nitride, silicon oxynitride, titanium nitride, and diamond. Mass-producing materials using chemical vapor deposition can get very expensive due to the power requirements of the process, which partially accounts for the extremely high cost (hundreds of millions of dollars) of semiconductor factories. Chemical vapor deposition reactions often leave byproducts, which must be removed by a continuous gas flow.

The process steps and structures described below do not form a complete process flow for manufacturing integrated circuits. The present invention can be practiced in conjunction with integrated circuit fabrication techniques currently used in the art, and only so much of the commonly practiced process steps are included as are necessary for an understanding of the present invention. The figures representing cross-sections of portions of an integrated circuit during fabrication are not drawn to scale, but instead are drawn so as to illustrate the important features of the invention.

Referring to FIG. 1, a semiconductor substrate 10 is partially covered with an oxide layer 12. The oxide layer 12 is not complete over the entire surface of the substrate 10, but that portion of interest to the present description has no openings to the substrate 10.

A polycrystalline silicon layer 14 lies on the oxide layer 12. In the illustrative embodiment, layer 14 is doped N-type. The polycrystalline silicon layer 14 has been silicided to form a silicide layer 16 thereon. The polycrystalline silicon 14 and silicide layer 16 have been patterned in a previous processing step as known in the art to form a signal line. The polycrystalline silicon layer 14 may be a first polycrystalline silicon layer, such as commonly used to form gate electrodes of field effect devices. Alternatively, polycrystalline silicon layer 14 may be a second or later level used for interconnect between different portions of an integrated circuit device. At the processing stage shown in FIG. 1, the transistors of the device have already been formed.

Once the polycrystalline silicon and silicide layers 14, 16 have been formed and patterned, an oxide layer 18 is formed over the surface of the device. Oxide layer 18 is typically a thin oxide layer, having a thickness of between 500 and 1000 angstroms. The thickness of oxide layer 18 may be any thickness which is compatible with the fabrication process with which the invention described herein is being used.

Referring to FIG. 2, oxide layer 18 is patterned and etched to define a contact opening 20 to the upper surface of the silicide layer 16. A layer of polycrystalline silicon 22 is then deposited over the surface of the device.

A light dosage of boron is implanted into the polycrystalline silicon layer 22 in order to convert it to a P-type conductor. A typical dosage would be approximately 10 13 atoms/cm 2 .

Referring to FIG. 3, the polycrystalline silicon layer 22 is then masked, and a heavy arsenic implant made to define an N + region 24. A typical dosage for such implant is 5×10 15 atoms/cm 2 . Such doping level is used to allow the N + region 24 to be used as a power supply line.

A P-N junction 26 is formed at the interface between the N + region 24 and the lightly P-doped polycrystalline silicon layer 22. The doping of polycrystalline silicon layer 22 is low enough to define a resistor, but is sufficiently high to cause degeneration in the contact opening 20, providing an ohmic contact between the polycrystalline silicon layer 22 and the silicide layer 16. Thus, although the polycrystalline silicon layer 14 is N-type, no P-N junction is formed at the contact between the two layers 14, 22.

After formation of the highly doped N + regions 24, the polycrystalline silicon layer 22 is etched to define interconnect, leaving the structure shown in FIG. 3. The device is then ready for formation of further oxide and interconnect levels as desired.

Referring to FIG. 4, a 4-transistor SRAM cell is shown. The contact structure formed in FIG. 1-3 is suitable for use as a load element in the cell of FIG. 4.

Cross-coupled field effect devices 30, 32 form the basis of the SRAM cell. Access transistors 34, 36 connect the bit line BL and complemented bit line BL' to common nodes 38, 40, respectively. Access transistors 34, 36 are driven by the word line 42 as known in the art. Node 38 is connected to the power supply line V cc through resistor 44 and diode 46. Node 40 is connected to V cc through resistor 48 and diode 50.

Node 38 corresponds to contact opening 20 in FIG. 3. Resistor 44 corresponds to polycrystalline silicon region 22 of FIG. 3, with diode 46 being formed at the junction 26. Node 40, resistor 48, and diode 50 correspond to FIG. 3 in a similar manner.

Since the contact at contact opening 20, corresponding to nodes 38 and 40, is an ohmic contact, the load for the SRAM cell is formed by a resistor and a diode rather than back-to-back polycrystalline silicon diodes. In some SRAM cell designs, this can provide improved performance over the use of a resistor alone, or back-to-back polycrystalline silicon diodes.

A similar ohmic contact can be formed between a lower polycrystalline silicon layer which is doped P-type and an upper N-type layer. The silicide layer prevents formation of a P-N junction in the contact opening.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

This invention concerns armor penetrators. Such penetrators are disclosed in U.S. Pat. Nos. 4,885,031, 4,836,108, 4,784,690, 4,749,410 and 4,458,599.

U.S. Pat. No. 4,885,031 discloses penetrators having a composition of 88 to 98% Tungsten Bar , 0.25 to 1.5% ruthenium or rhenium, balance of nickel and iron.

U.S. Pat. No. 4,836,108 discloses compositions of tungsten-nickel, tungsten-molybdenum, tungsten-nickel-iron and tungsten-nickel plus copper, molybdenum, titanium.

U.S. Pat. No. 4,784,690 discloses compositions of at least 90% tungsten, the balance being nickel, iron, copper, cobalt, rhenium, ruthenium.

U.S. Pat. No. 4,749,410 discloses compositions of tungsten-nickel plus iron, copper or cobalt.
Tungsten Rod is a metallic chemical element classified among the transition metals of the periodic table of elements. It is well known for its strength and durability, which make it extremely useful in a wide range of industrial applications. Some consumers also own products which contain tungsten or were produced with tungsten. The world's major sources of this element are Russia, Austria, China, and Portugal, where it is extracted from minerals such as scheelite and wolframite.

A penetrator in accordance with this invention has a composition of 90 to 98 weight percent tungsten, the balance being nickel and cobalt, the weight ratio of nickel to cobalt being between 1:1 to 9:1. The advantage of a penetrator having this composition is that it resists bending moments, thereby desirably reducing limit velocity. Limit velocity refers to the velocity needed to penetrate a target.
This element is not found in a pure form in nature. When it is isolated, tungsten in a very hard, brittle, gray to white metal which is extremely corrosion resistant. It has the highest melting point and tensile strength of any metal, and it also has the lowest vapor pressure point. The metal is identified with the symbol W on the periodic table of elements, a reference to its alternate name, wolfram. Tungsten Powder 's atomic number is 74.

People have known about the existence of tungsten since at least the early 1700s, when observers noted that the metal interacted with tin. In 1784, the de Elhuyar brothers managed to isolate tungsten in Spain, using tungstic acid extracted from wolframite. Tungsten has classically been a very valuable metal, since its durability and strength make it extremely useful for military and industrial uses. The name of the element comes from the Swedish tung, or “heavy,” and sten, for “stone.”

One of the most famous uses of tungsten is as a filament in light bulbs. The metal is also used in an assortment of alloys to increase their hardness and tensile strength. Many structural metal alloys incorporate Tungsten Carbide Powder since the metal has an extremely high melting point, and the element is also used to make wear-resistant tools. While tungsten tools can be expensive, many workers like them because of their durability and long lifetimes.

We believe that this composition has improved resistance to bending for the following reasons.

It is believed that a reduced grain size enhances the resistance to bending. In liquid phase sintering, the matrix liquifies and saturates with tungsten. When the solubility of tungsten in the Ni/Co matrix has reached its maximum, the small tungsten particles will dissolve and reprecipitate out on the larger tungsten particles. Growth of the tungsten grains will continue by particle coalescence. To reduce the grain size, the liquid-solid interfacial energy must be reduced. Cobalt is believed to decrease the liquid-solid interfacial energy by decreasing the solubility of tungsten manufacturer in the matrix. Therefore, a tungsten penetrator having a composition as per this invention will have enhanced resistance to bending.

In one example, the W--Ni--Co alloy consisted of, by weight percent, 93 tungsten, 5.6 nickel, 1.4 cobalt. Bars were isostatically pressed from this composition at about 35 KSI and were then solid state sintered at 1420° C. for three hours to achieve densification of over 90%. The bars were then liquid phase sintered at 1530° C. for 45 minutes to develop heavy alloy structure. The bars were then heat treated at 1200° C. in vacuum for three hours to remove hydrogen.

Tungsten product does have some safety precautions. Dust from the metal can be flammable or explosive, and it also irritates mucus membranes such as the inside of the nose and mouth. In some regions, tungsten has been linked with serious infections of the lungs in people who work with the element on a regular basis without adequate protections. Tungsten exposure has also been correlated with increased rates of cancer, although hard evidence to turn the correlation into causation has not been uncovered.

Metallic chemical element, one of the transition elements, chemical symbol Mo, atomic number 42. It is a silvery gray, relatively rare metal with a high melting point (4,730 °F [2,610 °C]) that does not occur uncombined in nature. Since molybdenum and its alloys have useful strength at temperatures that melt most other metals and alloys, they are used in high-temperature steels. Applications include reaction vessels; aircraft, missile, and automobile parts; and electrodes, heating elements, and filament supports. Some Molybdenum Powder (in which it has various valences) are used as pigments and catalysts. Molybdenum disulfide is a solid lubricant, used alone or added to greases and oils.

A chemical element, Mo, atomic number 42, and atomic weight 95.94, in the periodic table in the triad of transition elements that includes chromium (atomic number 24) and tungsten (atomic number 74). Research has revealed it to be one of the most versatile chemical elements, finding applications not only in metallurgy but also in paints, pigments, and dyes; ceramics; electroplating; industrial catalysts; industrial lubricants; and organometallic chemistry. Molybdenum is an essential trace element in soils and in agricultural fertilizers. Molybdenum atoms have been found to perform key functions in enzymes (oxidases and reductases), with particular interest being directed toward its role in nitrogenase, which is employed by bacteria in legumes to convert inert nitrogen (N2) of the air into biologically useful ammonia (NH3). See also Periodic table.

Molybdenum is widely distributed in the Earth's crust at a concentration of 1.5 parts per million by weight in the lithosphere and about 10 parts per billion in the sea. It is found in at least 13 minerals, mainly as a sulfide [molybdenite (MoS2)] or in the form of molybdates [for example, wulfenite (PbMoO4) and magnesium molybdate (MgMoO4)].

Although Ferro Molybdenum is closer to chromium in atomic weight and atomic number, its chemical behavior is usually very similar to that of tungsten, which has nearly the same atomic radius. (This is due to the so-called lanthanide contraction in which atomic radii decrease for elements 57 to 71 found in the period between molybdenum and tungsten.) See also Chromium; Lanthanide contraction; Tungsten.

Molybdenum atoms contain six valence electrons (4d55s1), which are employed with great versatility in forming compounds and complexes in which electronic configurations vary from d0 (no d electrons in oxidation state + 6) to d8 (8 d electrons in oxidation state −2). The +6 state is preferred, but all states from −2 to +6 are known. States usually exhibit a variety of coordination numbers (4 to 9), and include polynuclear complexes and metal-metal bonds in metallic clusters with two to six metal atoms in their metallic cores. Molybdenum forms a very large number of compounds with oxygen. Low-valent molybdenum [for example, Mo(CO)6 and Mo2, Mo3, and Mo6 clusters] has a very rich organometallic chemistry, including clusters that are being studied as models for Molybdenum Powder surfaces that catalyze organic reactions employed in industrial syntheses and oil refining. The ability of molybdenum atoms to vary oxidation state, coordination number, and coordination geometry and to form metal-metal bonds in clusters accounts in part for the large number of industrial catalysts and biological enzymes in which Mo atoms are found at the active site for catalysis. See also Chemical bonding; Coordination chemistry; Electron configuration.

Molybdenum is a high-melting silver-gray metal, strong even at high temperatures, hard, and resistant to corrosion (see table). It also exhibits high conductivity, a high modulus of elasticity, high thermal conductivity, and a low coefficient of expansion. Its major use is in alloy steels, for example, as tool steels (≤10% molybdenum), stainless steel, and armor plate. Up to 3% molybdenum is added to cast iron to increase strength. Up to 30% molybdenum may be added to iron-, cobalt-, and nickel-based alloys designed for severe heat- and corrosion-resistant applications. It may be used in filaments for light bulbs, and it has many applications in electronic circuitry. See also Alloy.

Molybdenum trioxide, molybdates, sulfo-molybdates, and metallic molybdenum are found in thousands of industrial catalysts used in oil refining, ammonia synthesis, and industrial syntheses of organic chemicals. Molybdenum Powder manufacturer (IV) in aqueous solution is a powerful catalyst for the reduction of inert oxo-anions such as perchlorate (ClO4−) or nitrate (NO3−) as well as other oxidized nonmetals such as azide ion (N3−) and dinitrogen (N2). The trinuclear cation MO3O44+ is inert, unreactive, and noncatalytic. See also Catalysis; Homogeneous catalysis.

The molybdenum enzymes comprise two major categories. The first category contains the single, highly important enzyme nitrogenase, which is responsible for biological nitrogen fixation. The second category contains all other known molybdenum enzymes, which are crucial for the metabolism of bacteria, plants, and animals, including humans.

 

 

from:answers

tungsten (tung'st?n) [Swed.,=heavy stone], metallic chemical element; symbol W; at. no. 74; at. wt. 183.85; m.p. about 3,410°C; b.p. 5,660°C; sp. gr. 19.3 at 20°C; valence +2, +3, +4, +5, or +6. Tungsten is a very hard, silver-white to steel-gray metal with a body-centered cubic crystalline structure. In its chemical properties it resembles molybdenum, the element above it in Group 6 of the periodic table. It is sometimes called wolfram, and the chemical symbol is taken from this name; in naming compounds of tungsten, use of the name wolfram as a root is preferred. Tungsten is one of the most dense metals and has a higher melting point than any other metal.

Pure tungsten is ductile, and wires made of it, even those of very small diameter, have a very high tensile strength. The element is resistant to ordinary acids and aqua regia but dissolves in a mixture of hydrofluoric and nitric acids. It forms compounds with carbon, chlorine, oxygen, sulfur, and some other elements. It is hexavalent in its most important compounds. It forms tungstic acid (H2WO4), or wolframic acid, which is the basis of a series of salts called tungstates, or wolframates. Tungsten metal is used extensively for filaments for light bulbs and electronic tubes. Carboloy, stellite, and Tungsten Rods are of importance in industry because they retain their hardness and strength at high temperatures.
Tungsten is usually added to steel in the form of ferrotungsten, obtained by the reduction of ferrous tungstate in an electric furnace. Tungsten carbide is used in place of diamond for dies and as an abrasive. Sodium wolframate is used in the fireproofing of fabrics, in the weighting of silk, and as a mordant in dyeing. Tungsten does not occur uncombined in nature; large deposits of its ores are found in various parts of the world. The trioxide occurs in nature as the mineral wolfram ochre; scheelite and wolframite are the chief wolframate minerals.Tungsten Powder is usually prepared from the trioxide by reduction with hydrogen or carbon. Tungsten was first isolated from tungstic acid in 1783 by the de Elhuyar brothers.

Tungsten (pronounced /'t??st?n/), also known as wolfram (/'w?lfr?m/, WOOL-fr?m), is a chemical element with the chemical symbol W and atomic number 74.

A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite. It is remarkable for its robust physical properties, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. Also remarkable is its very high density of 19.3 times heavier than water, and 71% heavier than lead. Tungsten is often brittle and hard to work in its raw state; if pure, it can be cut with a hacksaw.

The pure form is used mainly in electrical applications, but its many compounds and alloys have many applications, most notably in incandescent light bulb filaments, X-ray tubes (as both the filament and target), and superalloys.

Tungsten Carbide Powder is the only metal from the third transition series that is known to occur in biomolecules, and is the heaviest element known to be used by living organisms.
In 1781, Carl Wilhelm Scheele discovered that a new acid, tungstic acid, could be made from scheelite (at the time named tungstenite). Scheele and Torbern Bergman suggested that it might be possible to obtain a new metal by reducing this acid.[8] In 1783, José and Fausto Elhuyar found an acid made from wolframite that was identical to tungstic acid. Later that year, in Spain, the brothers succeeded in isolating tungsten by reduction of this acid with charcoal, and they are credited with the discovery of the element.

In World War II, tungsten played a significant role in background political dealings. Portugal, as the main European source of the element, was put under pressure from both sides, because of its deposits of wolframite ore. Tungsten's resistance to high temperatures and its strength in alloys made it an important raw material for the weaponry industry.

 

 

from:answers

As a bit of a health nut, I've kept quiet about something I didn't start consuming regularly until moving to Portland, Ore., aka Beervana. Yes, that something is beer. That bastion of bad health. The oh-so-tasty temptress. The barren wasteland of big bellies.

Or maybe beer has gotten a worse reputation than it deserves. In recent years, researchers have extolled several healthy side effects of beer (in moderation, of course), from its role in limiting kidney stones and gallstones to lowering the risk of adult-onset diabetes and even, due to its folate content, helping prevent cancer.

And that's not all. Silicon, present to varying degrees in various beers, has been linked to higher bone-mineral density in animals--including, of course, in humans. So researchers at the University of California at Davis set out to analyze 100 commercial beers to determine silicon content. They report their findings this week in the Journal of the Science of Food and Agriculture.

The average beer contains 29.4 parts per million (ppm), with my personal favorite--India Pale Ales (this is very validating)--topping the list at a whopping 41.2 ppm. Ales in general average 32.8 ppm, and my least favorite, lagers, were down around 20. Hey, maybe my body actually knows what kind of beer to drink!

"The wine guys have stolen the moral high ground," said Charles Bamforth, a biochemist and professor of food science at UC Davis who also goes by the title Anheuser-Busch Endowed Professor. He adds:

    The reality is there's now growing consensus around the world that the active ingredient in alcoholic beverages that counters atherosclerosis is alcohol. It doesn't matter if it's wine or beer. I resent the stance that people take that wine is better. It's not.

Bamforth's team's findings suggest that raw ingredients and brewing techniques determine how much silicon is in the final pour. They found that malt, a sprouted grain, is the greatest source of Polycrystalline Silicon ; starches in sprouted barley or wheat break down into sugars that yeast converts into alcohol. (Barley contains even more silicon than wheat.)

The jury is still out on how much silicon is best. Katherine Tucker, a nutritional epidemiologist at Northeastern University in Boston, says people tend to consume an average of between 20 mg and 50 mg of silicon a day, and studies suggest that people should get at least 46. Depending on the kind of beer being consumed, you can get about that much in two or three beers. Besides beer, Polycrystalline Silicon sources include fruit, vegetables, and whole grains, news I took singing "la la la" with my hands over my ears.

Apparently the average guy--who nutritionists generally agree should stop at two drinks a day--gets most of his silicon through beer; the average lady--who they say should stop at one--through grains and veggies. Since I am a lover of grains, veggies, and beer alike, I shall henceforth be called Silicon Wonder Woman. After all, I can control my wireless mouse on my beer-happy (or is it hoppy?) abs.

 

from:news.cnet

The report is devoted to investigation of current standing of market of tungsten in CIS countries and forecast of the market development. The report consists of 7 Sections, contains 132 pages, including 31 Figures, 54 Tables and Appendix. This work is desk study. As information sources, we used data of Rosstat, Inter-state Committee on Statistics of CIS countries, Federal Customs Service of Russia, official domestic railage statistic of JSC RZhD (former Ministry of Railway Transport of Russia), sectoral (industrial) and regional press, annual and quarterly reports of companies, as well as data from web-sites of company-producers and consumers of tungsten.

The first Section of the report presents brief characteristics of standing of world market of Tungsten Bar (reserves, production, prices).
The second Section is devoted to description of mineral resources base of tungsten in the CIS.
The third Section is devoted to analysis of production, export, import and consumption of tungsten concentrate in CIS countries. The Section presents in details technology of production of tungsten concentrate, as well as description of the main company-producers of tungsten concentrate in CIS countries.
The fourth Section is devoted to description of production, export and import of tungsten-containing products in the CIS. The Section presents data on production of ferrotungsten, of tungsten anhydride and ammonia paratungstate, tungsten metal, tungsten carbide and hard alloys, as well as description of the main company-producers of the products.

The fifth Section presents analysis of consumption of Tungsten Rod , including supply-demand balance of the product, dynamics and pattern of the consumption of tungsten metal in Russia, as well as brief characteristics of end-uses.
The sixth Section is devoted to projects and investments in tungsten industry in CIS countries (projects on development and resuming mining of tungsten in CIS countries are presented here).
The seventh Section of the report presents current standing and forecast of production and consumption of tungsten in the CIS up to 2010
The Appendix includes addresses and contact information on the main company-producers of tungsten products in CIS countries

According to the analysis of authoritative industry experts,The global supply of tungsten mainly consists of two parts,Part of the new supply of tungsten are concentrate production,This part of the total supply of tungsten accounted for 76%,Another part of the final tungsten product from the waste material,accounted for 24%,According to nationwide survey of Tungsten Industry by China Tungsten Industry Association in 2004,our country’s utilization of waste tungsten is very low,Only 10% of tungsten supply,in the advanced countries, utilization of waste tungsten are generally above 30%,generally speaking,The cost of recycling waste tungsten are lower than the tungsten ore smelting processing costs,But requires greater investment and stronger environmental protection technical support.

In china the develop of economy is the first,Although many intellectuals have loudly called for protection of the environment,but in China,Every day a large number of industrial wastes, wastewater is discharged out of,Serious pollute our environment for survival,This is why China’s low rate of utilization of waste recycling tungsten,How can the economic development and environmental protection be better coordinated,Now it still seems a very difficult problem,Because up to now still not a very good program proposed.

Sincerely wish that,in the near further,the develop of china economic keep on growing,meanwhile the environment will be better,we can see the blue sky and white cloud, we can hear the birdies singing in the sky.

from:reportlinker

Ferro molybdenum is an important iron molybdenum alloy, with a molybdenum content of 60-70%  It is the main source for molybdenum alloying of HSLA steel. The molybdenum is mined and is subsequently transformed into the molybdenum(VI) oxide MoO3. This oxide is mixed with iron oxide and aluminium and is reduced in the an aluminothermic reaction to molybdenum and iron. The ferromolybdenum can be purified by electron beam melting or used as it is. For alloying with steel the ferromolybdenum is added to molten steel before casting. Among the biggest suppliers of Ferro molybdenum in Europe is the German trading house Grondmet in Düsseldorf, Germany.

Molybdenum (pronounced /?m?l?b'di?n?m/ mol-ib-DEE-n?m, from Neo-Latin Molybdaenum, from Ancient Greek Μ?λυβδος molybdos, meaning lead), is a Group 6 chemical element with the symbol Mo and atomic number 42. The free element, which is a silvery metal, has the sixth-highest melting point of any element. It readily forms hard, stable carbides, and for this reason it is often used in high-strength steel alloys. Molybdenum does not occur as the free metal in nature, but rather in various oxidation states in minerals. Industrially, molybdenum compounds are used in high pressure and high temperature applications, as pigments and catalysts.

Molybdenum minerals have long been known, but the element was "discovered" (in the sense of differentiating it as a new entity from minerals salts of other metals) in 1778 by Carl Wilhelm Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm.

Most molybdenum compounds have low water solubility, but the molybdate ion MoO2−4 is soluble and will form if molybdenum-containing minerals are in contact with oxygen and water. Recent theories suggest that the release of oxygen by early life was important in removing molybdenum from minerals into a soluble form in the early oceans, where it was used as a catalyst by single-celled organisms. This sequence may have been important in the history of life, because molybdenum-containing enzymes then became the most important catalysts used by some bacteria to break into atoms the atmospheric molecular nitrogen, allowing biological nitrogen fixation. This, in turn allowed biologically driven nitrogen-fertilization of the oceans, and thus the development of more complex organisms.

At least 50 molybdenum-containing enzymes are now known in bacteria and animals, though only the bacterial and cyanobacterial enzymes are involved in nitrogen fixation. Due to the diverse functions of the remainder of the enzymes, molybdenum is a required element for life in higher organisms (eukaryotes), though not in all bacteria.

In its pure form, Molybdenum Powder is silvery white metal with a Mohs hardness of 5.5. It has a melting point of 2,623 °C (4,753 °F); of the naturally occurring elements, only tantalum, osmium, rhenium, tungsten and carbon have higher melting points. Molybdenum burns only at temperatures above 600 °C (1,112 °F).[4] It has one of the lowest coefficient of thermal expansion among commercially used metals. Tensile strength of molybdenum wires increases about 3 times from about 10 to 30 GPa when their diameter decreases from ~50–100 nm to 10 nm.

There are 35 known isotopes of molybdenum ranging in atomic mass from 83 to 117, as well as four metastable nuclear isomers. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98 and 100. Of these naturally occurring isotopes, only molybdenum-92 and molybdenum-100 are unstable. All unstable isotopes of molybdenum decay into isotopes of niobium, technetium and ruthenium.

Molybdenum-98 is the most abundant isotope, comprising 24.14% of all molybdenum. Molybdenum-100 has a half-life of about 1019 y and undergoes double beta decay into ruthenium-100. Molybdenum isotopes with mass numbers from 111 to 117 all have half-lives of approximately 150 ns.

As also noted below, the most common isotopic molybdenum application involves molybdenum-99, which is a fission product. It is a parent radioisotope to the short-lived gamma-emitting daughter radioisotope technetium-99m, a nuclear isomer which is used in various imaging applications in medicine.

 

from:wiki

A ballistic vest, bulletproof vest or bullet-resistant vest is an item of personal armor that helps absorb the impact from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso. Soft vests are made from many layers of woven or laminated fibers and can be capable of protecting the wearer from small caliber handgun and shotgun projectiles, and small fragments from explosives such as hand grenades.

Metal or ceramic plates can be used with a soft vest, providing additional protection from rifle rounds, and metallic components or tightly-woven fiber layers can give soft armor resistance to stab and slash attacks from a knife. Soft vests are commonly worn by police forces, private citizens and private security guards or bodyguards, whereas hard-plate reinforced vests are mainly worn by combat soldiers, police tactical units and hostage rescue teams.

Modern body armor may combine a ballistic vest with other items of protective clothing, such as a combat helmet . Vests intended for police and military use may also include ballistic shoulder and side protection armor components, and bomb disposal officers wear heavy armor and helmets with face visors and spine protection.
Ballistic vests use layers of very strong fiber to "catch" and deform a bullet, mushrooming it into a dish shape, and spreading its force over a larger portion of the vest fiber. The vest absorbs the energy from the deforming bullet, bringing it to a stop before it can completely penetrate the textile matrix. Some layers may be penetrated but as the bullet deforms, the energy is absorbed by a larger and larger fiber area.

While a vest can prevent bullet penetration, the vest and wearer still absorb the bullet's energy. Even without penetration, modern pistol bullets contain enough energy to cause blunt force trauma under the impact point. Vest specifications will typically include both penetration resistance requirements and limits on the amount of impact energy that is delivered to the body.

Vests designed for bullets offer little protection against blows from sharp implements, such as knives, arrows or ice picks, or from bullets manufactured of non-deformable materials, i.e. those containing a steel core instead of lead. This is because the impact force of these objects stays concentrated to a relatively small area, allowing them to puncture the fiber layers of most bullet-resistant fabrics.

Textile vests may be augmented with metal (steel or titanium), ceramic or polyethylene plates that provide extra protection to vital areas. These hard armor plates have proven effective against all handgun bullets and a range of rifles. These upgraded ballistic vests have become standard in military use, as soft body armor vests are ineffective against military rifle rounds. Corrections officers and other law enforcement officers often wear vests which are designed specifically against bladed weapons and sharp objects. These vests may incorporate coated and laminated para-aramid textiles or metallic components.

Due to the various different types of projectile, it is often inaccurate to refer to a particular product as "bulletproof" because this implies that it will protect against any and all threats. Instead, the term bullet resistant is generally preferred.

Body armor standards are regional. Around the world ammunition varies and as a result the armor testing must reflect the threats found locally. Law enforcement statistics show that many shootings where officers are injured or killed involve the officer's weapon. As a result each law enforcement agency or para-military organizations will have their own standard for armor performance if only to ensure that their armor protects them from their own weapon. While many standards exist a few standards are widely used as models. The US National Institute of Justice ballistic and stab documents are examples of broadly accepted standards. In addition to the NIJ, the UK Home Office Scientific Development Branch (HOSDB - formerly the Police Scientific Development Branch (PSDB)) standards are used by a number of other countries and organizations. These "model" standards are usually adapted by other counties by incorporation of the basic test methodologies with modification of the bullets that are required for test. NIJ Standard-0101.06 has specific performance standards for bullet resistant vests used by law enforcement.

 

from:wiki