Beam collimators, which are usually made of tungsten alloy shielding, including linear accelerators and tungsten multi-leaf collimators and so on. Beam collimators are 'beam direction' devices used in the X-ray tube housing, along with an arrangement of mirrors and lights, in such a way that the light and X-ray fields match each other. They are made of lead shutters which completely absorb the photons, and thus reduce patient dose as well as focus the radiation accordingly to the area of interest. They allow different projections of X-ray fields.
 
In linear accelerators (linac), the primary collimator may be constructed of depleted uranium (DU) as this material is approximately 1.6 times more dense than lead. The secondary motorised collimators which greater define the beam shape are constructed of tungsten. Multi-leaf collimators (MLCs) which are now in widespread use in medical linacs consist of two collimator banks of thin tungsten 'leaves' with each bank consisting of 40 to 80 leaves (so a total of 80 to 160 leaves). This allows each tungsten leaf to move independently under computer control. MLCs allow even more diverse field shapes to be created which can shield organs at risk whilst allowing the complex shape of the tumour bed to be irradiated to allow maximum cell kill.

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Tungsten polymer Shielding’s density approaching twice that of high density Lead Blankets of similar thickness. Highly flexible and can be molded/formed into any shape. Often competitively priced to lead alternatives.

The advantages of tungsten polymer shielding system:

• Provides approx. 75% Attenuation as compared to solid lead
• Attenuation of 175% compared to a high density lead blanket
• Priced competitively to lead for many applications
• Available as a blanket, ribbon wrap or molded shapes; flexible or rigid
• Cut materials to fit without needing to seal edges - no residue
• Included fasteners, grommets, locking devices, etc., as required
• Improved fit-up --- molded applications typically will yield much higher reduction factors - less weight with same impact
• Tested to 550°F/288°C

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There are three ways for producing tungsten disulfide which are the following:
The first method: tungsten disulfide produces by firing decomposition method. Firstly, stirring tungsten acid and ammonia water with at 57 ~ 60 ℃ to react for three hours, heat prevention  more than 16 hours of natural sedimentation. After reaction get the sodium tungstate then to react with hydrogen sulfide gas, to generate tetrathiotungstate acid. Finally after calcination, the tetrathiotungstate acid will decompose to tungsten disulfide. During the reaction, heating should at 100 ~ 200 ℃ / hr temperature gradient from room temperature to of 700 ~ 1200 ℃. Then after  heat preservation for 24 to 48 hours, then at 30 ~ 110 ℃ / hour temperature gradient descending to room temperature, and finally crushing the material. Related chemical reaction of the reaction equation is as follows:
H2WO4 + 2NH3 • H2O → (NH4) 2WO4 + 2H2O
(NH4) 2WO4 + 4H2S → (NH4) 2WS4 + 4H2O
2 (NH4) 2WS4 + 3O2 → 2WS2 + 4NH3 + 2S + 2SO2 + H2O
The second method: putting sulfur vapor through the red-hot tungsten can form tungsten disulfide
The third method: mixing tungsten with stoichiometric sulfur  at 800 ℃ for 24 hours in a nitrogen atmosphere can be formed WS2. If changing the reaction conditions, namely in 6MPa reacted with 1800 ℃, can be formed orthorhombic WS2.

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Sulphur is a nonmetallic chemical element, and elemental sulfur is usually kind of yellow crystals, also known as sulfur. There are many elemental sulfur allotropes, such as rhombic sulfur, monoclinic sulfur and sulfur elasticity. Sulfur is an important element in the human body protein for human life is important. Sulfur is mainly used in fertilizers, gunpowder, lubricants, pesticides and anti-fungal agent production.
Tungsten trisulfide is a reddish brown powder and its chemical formula is WS3, molecular weight 280.11, CAS registry number 1215-19-8. Tungsten trisulfide slightly soluble in water, soluble in hot water, alkali metal carbonates and alkali metal hydroxides, in addition it can generate colloidal solution in hot water.
Producing tungsten trisulfide can use thermal decomposition method of ammonium tungstate (a kind of hydrogen sulphide saturated ammonium tungstate). Or making hydrogen chloride to react with ammonium tetrathiotungstate obtains tungsten trisulfide.

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Tungsten disulfide has similar lubricating properties with graphite, is widely used as a lubricant. And tungsten disulfide as a lubricant performance is better than molybdenum disulfide, mainly due to it properties which is low friction coefficient(0.03), high resistance to extreme pressure and oxidation resistance, namely, tungsten disulfide at 450 ℃ in the air begins to decompose, until 650 ℃ completely decomposed. On the other hand, at1100 ℃ in the vacuum it begins to decompose, until 2000 ℃ completely decomposed. This performance is conducive tungsten disulfide apply in high-temperature, high pressure, high speed, high load, as well as in chemical active media device operation.
Meanwhile tungsten disulfide on the metal surface has a good adsorption capacity can be added to make the original lubrication in engineering plastics or it can mix with volatile solvent sprayed on the metal surface, to improve the life of mold in press forging and workpiece surface finish.
Tungsten disulfide also can mix with the oil, fat oil to form tungsten disulfide, tungsten disulfide grease, wax and other tungsten disulfide solid lubricating block and lubricating film.

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Tungsten disulfide is widely used in lubricant field, at the same time because its good performance in cracking, long service life and catalytic activity is stable and reliable, so it also be used in petroleum catalysts. Where it can serve as a hydrogen desulfurization catalyst, on the other hand it can be used in the polymerization, heavy Catalyst whole, hydration, dehydration and other processes of hydroxylation, so it has been widely applied to the oil refinery.
Tungsten disulfide can also apply in inorganic materials preparation technology which is the nano-tungsten disulfide can be used as an efficient catalyst. Since it can form the novel compounds capable with sandwich structure, nano tungsten disulfide monomolecular layer may be formed two-dimensional material, and be able to re-stack "structure room floor"with very large space the new particulate material, and in the process of re-stacking inserted substances can be added to make it a catalyst or sensitive display and superconducting materials, its huge internal surface area easily mixed with accelerator, a new type of highly efficient catalysts.
Tungsten disulfide also can as fuel cells, organic electrolyte rechargeable battery, as well as sensors’ anode and used to make nano-ceramic composite materials.

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Tungsten disulfide is used as solid lubricants, dry film lubricants, self-lubricating composite material, and wherein the nano tungsten disulfide solid lubricant is the best. Mainly because tungsten disulfide nano particles has low friction coefficient, high compressive strength, and with acid erosion resistance, good load performance, non-toxic, wide temperature range, long life and other advantages of lubrication and so it is widely used.
Meanwhile tungsten disulfide nano particles can also be used as an additive to produce high-performance lubricants. After the studies found adding the right amount of tungsten disulfide nano particles in the lubricant can greatly improve the lubricating properties of the lubricant. Under the same conditions, there will improve lubricating properties of adding nanometer WS2 base oil than conventional particles added base oil and has good dispersion stability, friction factor can be reduced by 20% to 50%, the film strength can be increased by 30% ~ 40%, which is far superior lubricating properties than molybdenum disulfide nano particles. With the addition of a lubricant nano particles combines the advantages of solid lubrication and lubrication, which is expected to realize from room temperature to high temperature (over 800 ℃) full lubrication. Therefore, tungsten disulfide nano particles can be used as additives synthesis new lubrication system which has broad application prospects.

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Nano tungsten disulfide due to its good performance and broad application prospects is widespread concern, there are many experts and scholars prepared a lot of research on it. However, tungsten disulfide natural mineral is relatively rare, general produce by chemical method to extraction, chemical synthesis method can produce high purity, low impurities and fine granular sulfide oxide. On the other hand it can produce different functional requirements sulfide oxide, therefore chemical synthesis method for produce nano tungsten disulfide has been widespread concern. But it also makes production costs high tungsten disulfide nano particles.
Currently, There are many methods for produce tungsten disulfide, such as ammonium tetrathiotungstate thermal decomposition method, hydrogen sulfide reduction method, high-energy ball milling method, carbon nanotubes space limitations method, hydrothermal synthesis method, hydrogen sulfide or sulfur vapor reduction method, high energy physics and chemistry combine method and so on. So that producing methods of nano tungsten disulfide general can be divided into two types, namely, direct reaction of tungsten and sulfide to form tungsten disulfide or making them react to form reaction precursor and then by ecomposition or reduction with appropriate to generate tungsten disulfide nanoparticles.

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Ammonium tetrathiotungstate, also known as ammonium thiotungstate and ammonium tetrathiot, it is a bright orange crystals with a metallic luster. The physical properties of ammonium tetrathiotungstate as follows: chemical formula: H8N2S4W, molecular weight: 348.18, density 2.71. Related System Number as follows: CAS registry number: 13862-78-7, MDL registry number: MFCD00061410, PubChem registry number: 24860418. Ammonium tetrathiotungstate has some harm to the environment, so during the operation can not be discharged it directly into lakes and rivers or sewer.
Making ammonium tungstate and tungstate to react to generate ammonium tetrathiotungstate and the producing process are as follows:
1. The ammonium tungstate by ammonia dissolved.
2.And then reaction with ammonium sulfide solution, the molar ratio S / W = 4-6：1, the reaction temperature: room temperature to 90 ℃, reaction time: 0.5 to 3 hours, static crystallization time: 8to24 hours.
3. Finally, the crystals were filtered, washed with water and washed with percutaneous ethanol, and finally dried to obtain ammonium tetrathiotungstate.

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301
Number of Players: Any number of players may play, but normally two individuals or two teams play.
Numbers in Play: All the numbers are in play, but some receive greater use than others. The 19 and 20, for instance are used extensively for scoring points since they are the highest numbers on the tungsten dartboard. All the numbers may be used to throw the necessary doubles in the game.
This game is generally played by two people but can be played by teams. Each player starts with 301 points. The goal for each player is to reach zero, exactly, by subtracting the amount they score in a turn from the amount they had left from the previous turn. The player cannot start subtracting until they double in (hits one of the 21 doubles on the tungsten dartboard including the double bull). Once the double is hit, then all scores will count. To end the game, the player must also double out (ie. If they have 32 left, then they will need use tungsten dart to hit a double 16 to win. If they then hit a single sixteen, leaving 16, their next target would be a double 8. If they should hit more points than they have left, then they have busted. Their turn is over and they will resume with the same score they started with on that throw the next time it is their turn to throw.). If they hit the double leaving them zero points, then they have won the game.

501
Number of Players: Any number of players may play, but normally two individuals or two teams play.
Numbers in Play: All the numbers are in play, but some receive greater use than others. The 19 and 20, for instance are used extensively for scoring points since they are the highest number on the tungsten dartboard. All the numbers may be used to throw the necessary doubles in the game.
This game is generally played as a team event, though we also play it in our single events. All players/teams start with 501 points. Unlike 301, you do not have to double-in, but can start on any number. Each player/team subtracts the amount they score from the amount they have left. To win, like 301 above, the player/team will need to double-out to reach zero.

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