With the different reaction conditions, tungsten react with bromine can produce different product. Such as bromine and tungsten react at 600 ℃ can generate WBr6. In other conditions, it is possible to generate tungsten pentabromide and [W5Br6] Br4.
Tungsten hexabromide is a blue-black glossy needles, chemical formula: WBr6, it is commonly used in the synthesis of organic compounds of tungsten. During at work works should to wear chemical goggles, gloves and respirators, etc., and pay attention away from fire to avoid explosion or fire to produce toxic fumes.
Synthesis methods of tungsten hexabromide are:
(1) Using boron tribromide reacts with and tungsten hexachloride to obtain tungsten hexabromide. Or using boron tribromide reacts with tungsten metal to obtain it.
(2) tungsten powder with stoichiometric bromine reacts in a vacuum at 500-800 ℃ sealed tube, to obtain tungsten pentabromide and tungsten hexabromide.

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Tungsten hexabromide is a blue-black needles crystal, its physical properties are as follows: chemical formula: WBr6, molecular weight: 663.264, relative density: 6.9, melting point: 309 ℃, boiling point: 327 ℃, soluble in carbon disulfide, diethyl ether , insoluble in cold water, hot water decomposition. Tungsten hexabromide easily hydrolyze into tungstic acid in humid air, and decomposes into pentabromide tungsten and bromine. CAS registry number: 13701-86-5. WBr6 can produce tungsten tetrabromide and tungsten pentabromide by disproportionation reaction. It is commonly used in the synthesis tungsten organic compounds.
Tungsten hexabromide should be sealed in storage container, placed in a cool, ventilated, and dry area which has safeguard procedures and away from fire and heat. Besides tungsten hexabromide should be stored separately with oxidant, avoid mixing storage. Keep away from food, drink and animal feed. At the same time the storage room should be equipped with the appropriate variety and quantity of fire equipment and other suitable material for leakage collect.
If tungsten hexabromide leaked first to remove the source of fire to prevent fire or explosion, and use any method to collect leakage with dry media to collect, prevented entering drains. Using water and detergent clean the floor and all the things which contaminated by tungsten hexabromide.

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Tungsten（V） bromide is the inorganic compound with the formula WBr5 and it also be known as tungsten pentabromide. The compound consists of bioctahedral structure with two bridging bromide ligands.
Tungsten pentabromide is the precursor to another tungsten compounds by reduction reactions. For example, tungsten pentabromide can be prepared by reduction with aluminum or tungsten. The WBr4 can be purified by chemical vapor transport. The reaction quotation is: 3 WBr5 + Al → 3 WBr4 + AlBr3. Excess tungsten pentabromide and aluminum tribromide are then by sublimation at 240℃.Tungsten dibromide can then be obtained heating the tetrabromide. At 450-500℃, gaseous tungsten pentabromide is evolved leaving yellow-green residue of WBr2. An analogous method can also be applied to the synthesis of tungsten chloride.
Because it is relatively easy to reduce tungsten pentahalides, they can be used as alternative synthetic routes to tungsten halide adducts. For example reaction of WBr5 with pyridine gives WBr4(py)2. The reaction equation of it is: 2 WBr5 + 7 C5H5N → 2 WBr4(C5H5N)2 + bipyridine + C5H5NHBr.

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Tungsten（V）bromide is a kind of brown-black crystals, easy hygroscopic and it also has another name which is tungsten pentabromide. And it is physical properties is: chemical formula: WBr5, molar mass: 583.39 g/mol, melting point: 286℃, boiling point: 333℃. Besides the CAS registry number is 13470-11-6 and PubChem number is 139467. According to X-ray diffraction, the structure for tungsten pentabromide consists of an edge-shared bioctahedron. What’s more the tungsten bromide consists of bioctahedral structure with two bridging bromide ligands.
Tungsten pentabromide is prepare by treating tungsten powder with bromine in the temperature range 650-1000℃. But the product is often contaminated with tungsten hexabromide.

 

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Results of an extensive investigation of the optical properties of CaWO₄:Sm³⁺are reported. Absorption, fluorescence, and excitation spectra and pulsed fluorescence measurements were obtained at temperatures from below 8 K to room temperature on an undoped single crystal and crystals containing samarium concentrations ranging between 0.01% and 1.0%. An empirical energy-level diagram is determined for trivalent samarium in this host and the existance of several different nonequivalent crystal-field states is established. It is found that host-sensitized energy transfer to the samarium occurs in varying degrees from all four of the lowest excited states of calcium tungstate and the efficiency of transfer is different for different crystal-field sites. The ratios of the integrated fluorescence intensities and decay times were measured and from these the temperature and doping concentration dependences of the energy transfer rate were found for excitation in the different host excited states. A model is proposed to explain the results which is based on energy transfer from self-trapped excitons at low temperatures and thermally activated exciton hopping migration to activator-induced host traps at high temperatures. This model predicts the correct dependences for all of the observed data. Quantitative estimates indicate that exchange is somewhat stronger than dipole-dipole interaction for both migration and transfer and the exciton diffusion coefficient is found to be on the order of 10^-7cm²sec^-1.

 

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Cryogenic processing is referred to a range of below zero heat treatment, which are currently employed by the dozens of materials and components treatment process. Generally, it contains steps to cool the tungsten carbide inserts to the temperatures below -130℃ in order to permanently or semi-permanently alter their microstructures. As in such ways, it could offer tool’s improvement regarded to machining performance, wear resistance and ultimately increased service life.

Cryogenic processing of tungsten carbide inserts commonly involves a use of liquid nitrogen into a thermally insulate tank containing the parts to be treated. The three ways of application of cryogenic fluid include, to perform as a cryo-quench by direct immersion of parts, to cool air within the tank as a working fluid, and to create a dry atmosphere by acting as a gas which circulated by fans.


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Comparing with the results of normally vacuum sintered, the strengthening phenomena of hot isostatic tungsten carbide inserts by direct observation obtain following results,

Firstly, when closely examining the hot isostatic tungsten carbide inset, there is a slight change of WC in terms of grain size, the composition as well as distribution of the binder phase and etc., although these changes were considered to have no relation to the strength increasing. Secondly, the strengthening mechanism of hot isostatic tungsten carbide insert is directly related to a small number of large pores disappearance while the large pores usually exit in normally vacuum sintered ones. It should be noticed that since there are some large WC grains are contained in the structure, a sharp increase in strength is not always visualized as a result of hot isostatic pressing.

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Due to its high density, excellent absorption behaviour against radiation and environmental friendly characteristics, tungsten alloy can be widely used to produce tungsten Sr-90 radiation detector.Sr-90 undergoing beta decay is exposed to the aluminum sheets. On the other side of the sheet there is a tungsten Sr-90 radiation detector called Geiger counter which detects how much radiation has penetrated the sheet.

Sr-90 undergoes beta decay. Of the three types of radiation, beta radiation is the most appropriate due to its penetration powers as a thickness gauge for aluminum. This is due to the fact that alpha particles such a low penetrating power that it cannot pass through a sheet of paper, certainly not sheet metal, and gamma rays have such a high penetrating power that all gamma particles would easily pass through the aluminum. Beta particles have a moderate penetrating power that can be blocked by a thick sheet of aluminum, but it can pass through a thinner piece. This property makes it suitable for use as a thickness gauge of aluminum sheets.

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Geiger-Muller or GM detector used to measure very small amounts of radiation.Due to the excellent shielding against electromagnetic radiation, tungsten alloy materials are typically used for Geiger-Muller detector components.

Geiger-Muller detector is one kind of gas filled radiation detector. When radiation enters this device, it ionizes gas molecules. The electron lost propels toward a central electrode and as its velocity increases it ionizes other gas molecules. This creates an electric pulse which is measured and allows for the detection of radiation.

The magnitude of the electric field that made of tungsten alloy determines the detector's mode of operation. As it is high density, tungsten alloy exhibits excellent absorption behaviour against electromagnetic radiation such as X-rays and gamma-radiation. The field made of tungsten alloy is high enough to prevent the electron-ion pairs produced by the radiation.

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The materials and specification of three-layer composite tungsten points
The surface material of tungsten points: silver, copper, silver nickel, pure tungsten, silver oxide cadmium , silver tin oxide and so on;
The substrate of tungsten points: silver, silver alloy, copper, iron, nickel, stainless steel and so on;
The thickness of surface material: 0.03mm - 1.0mm;
The thickness of the substrate: 0.08mm - 3.5mm;
Three-layer composite tungsten points are mainly applied in relays, thermostats, circuit breakers, micro-switches and so on.

Advantage
In order to increase its welding ability, a pad is on the top of three-layer composite tungsten points, whose welding surface materials are copper, iron, nickel and other materials. To combine the welding parts, you can use melt metal---Cu, which has low contact resistance and stable electrical performance, therefore, it is easier to positioning, its required heating time is shorter, and their welded portions are more beautiful.


 

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