Tungsten can react with many halogens such as fluorine, chlorine, bromine and iodine.
Iodine is one of the halogen elements, is a shiny purple flake crystals, toxic and corrosive, and easy sublimation, after sublimation easily to desublimation. Due to its high vapor pressure, so under the low-grade fever it wills sublimation. Beside it is soluble in many organic solvents such as chloroform, carbon tetrachloride. Iodine is mainly used for making drugs, dyes, iodine, text paper and iodine compounds.
Tungsten diiodide is kind of brown powder and its CAS registry number is 13470-17-2. Its physical properties are as follows: chemical formula: WI2, molecular weight: 437.7, the relative density of 6.8025, insoluble in cool water, ethanol and CS2, but soluble in alkali, and can be decomposed in hot water. It will change into tungsten trioxide when heated in air and precipitation I2.
Currently there has two common ways for producing tungsten diiodide: The first one is making tungsten react with iodine at 950 ℃ to generate (W6I8) I4 that is tungsten diiodide ; the second one is at CO2 atmosphere with red heat to make tungsten react with iodine vapor to obtain tungsten diiodide.

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Tungsten tetraiodide is a black powder (no fixed melting point and boiling point), and it CAS system number is 14055-84-6.
Its physical properties are as follows: chemical formula: WI4, molecular weight: 691.458, relative density: 5.218, which decompose at the melting temperature, insoluble in water but can decompose in hot water, soluble in ether, chloroform and turpentine.
Its chemical properties are as follows: tungsten tetraiodide heat in the air will decompose into tungsten diiodide and iodine, and easy to hydrolysis and oxidation. Besides it easily restore by pyridine, acetonitrile and other nitrogen-containing ligand compounds in air to form the corresponding complexes.
Currently, there are two common ways for synthesis tungsten tetraiodide which as following: the first one can restore tungsten hexachloride by hydrogen iodide; the second is reacting bweet triiodide aluminum and tungsten dioxide.

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Tungsten shielding is used as a main manufacturing component in CT machines. It is mainly used in making detector arrays of scanners whereas its collimators are used in making circular radiation components. However, some manufacturers also use lead in making these products.

Tungsten alloy collimator is the device mainly used for making the beam of particles and waves narrow. Along with this property, it is also used as linear accelerator or cyclotron in various medical treatments. This collimator consists of simple structure with easy working phenomena e.g. fibre radiate light is converted into parallel light (Gaussian beam). The summary of its all features is that it efficiently maximises the light which is coupling into the device.

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Tungsten tetrafluoride is a reddish-brown or reddish black inorganic compound. Its physical properties are as follows: chemical formula: F4W, molecular weight: 259.83, molar mass: 295.8336128g / mol, which is easily hydrolyzed and oxidized. Tungsten tetrafluoride CAS registry number is 13766-47-7, ChemSpider registry number is 123101, and EC registry number is 139,582. When using tungsten hexafluoride for produce tungsten film, by chemical deposition method tungsten tetrafluoride and tungsten pentafluoride can play an intermediary role in this reaction. At  800℃ vacuum conditions it will occur disproportionation reaction to produce tungsten pentafluoride and tungsten difluoride. What’s more F4W is mainly used in organic synthesis.
There are some producing methods of tetrafluoride tungsten. The first one is by treatment of the coordination complex WCl4 (MeCN) with AsF3 to produce tungsten tetrafluoride. The second is produced by form the reaction of the tungsten hexafluoride (WF6) and wfilament at 600-800℃. The third is reacting between benzene and WF6 at 110 ℃. Fourth, it can be made of by reacting tungsten hexafluoride and phosphorus trifluoride reaction at room temperature which involve in liquid hydrogen fluoride.

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The sensitivity of probe depends on the used tungsten collimator. The basic sensitivity is determined by the standard collimator (40°). The sensitivity is shown in the figure - it's depending on the distance between lymph-node and probe tip. Tungsten articulatable hand-held probe’s sensitivity > 20,000 counts/s/MBq.

By increasing the dihedral angle the tungsten articulatable hand-held probe’s sensitivity increases significantly, while the spatial resolution gets worse.

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In order to study the solid-phase reduction process of CaWO₄ and Si at low temperature during steelmaking process by direct alloying,the thermo-analysis experiments on CaWO₄ and Si powder mixture have been carried out by using differential thermal analyzer with constant heating rate 10℃/min,the reaction products and reaction ratio of CaWO₄ and Si pellets at 1 400℃for 30 min are analyzed by high temperature furnace constant temperature test and combined with melting point measure test the behavior of physical change of pellets in heating process is analyzed.Experimental results show that the reduction reactions of CaWO₄ and Si occurred at less than 1 400℃are all solid-phase reaction,the products of reaction are W, WSi₂, W₅Si₃, Ca3(Si₃O₉) and SiO₂,the reduction ratio of CaWO₄ pellets at 1400℃for 30 min is up to 93.41%,and during solid-phase reaction process the CaO could not increase the reaction rate;with condition of constant heating rate at less than 1 400℃,the apparent reaction of CaWO₄ and Si conforms to Avarami-Erofeev equation,the mechanism of reaction is random nucleation and subsequent growth,and the apparent reaction dynamical equation is da/dt = 11.68e～(-51.75×10～3/RT)·4(1-α)[-ln(1-α)]～(3/4).

 

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There are many ways for synthesis tungsten oxytetrafluoride, generally including the following four: the first method is through tungsten hexafluoride (WF6) primary hydrolysis to obtain tungsten oxytetrafluoride(WOF4);the second is using tungsten oxytetrachloride(WOCl4) react with hydrogen fluoride; third is through tungsten hexafluoride (WF6) react with tungsten trioxide to produce tungsten oxytetrafluoride; the fourth is after frit reaction between  tungsten trioxide and lithium fluoride to obtain tungsten oxytetrafluoride. Here introduce two ways for produce tungsten oxytetrafluoride which is the most widely used and processes are relatively simple.
(1) Put the fluorine gas into reactor where has tungsten trioxide powder with 230-400℃, after the reaction the gaseous WOF4 will be expelled from the reaction vessel, and condense in trap where the trap is heated to 130 ℃.
(2) First, mixing fluorine and oxygen, wherein the molar ratio is F2: O2 = 3: 1. Then pass into the tungsten powder, after reaction there will generate WOF4 also produce a small amount of tungsten hexafluoride. But tungsten hexafluoride is a volatile substance, so it can be got rid of at room temperature by vacuum method. Finally, use vacuum sublimation to produce WOF4 which is more pure.

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Tungsten can react with fluorine gas, which is tungsten powder react with fluorine gas should at 200 ℃, but  fine powder at room temperature can be reacted with fluorine gas. Besides tungsten rod needs at 300 ℃ can it react with the fluorine .
Tungsten tetrafluoride is a white monoclinic crystalline, CAS registry number: 13520-79-1. Its physical properties are as follows: chemical formula: WOF4, molecular weight: 275.9, melting point: 110 ℃, boiling point: 185 ℃, vapor pressure (P unit is mmHg, 1mmHg = 133.322Pa, T to K): 105-186 ℃ lgP = 9.69-3125 / T, 50 -104 ℃ lgP = 10.96-3605 / T. Besides, it is easily hydrolysis and deliquescence, in moist air the color will turn yellow, and generate hydrofluoric acid, but insoluble in tungsten tetrachloride. Meanwhile tungsten oxytetrafluoride and tungsten hexafluoride having similar strong reactivity can react with organic compound and metal chlorides. But when compared to tungsten hexafluoride found tungsten oxytetrafluoride has more stable reactivity. 

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Tungsten articulatable hand-held probe is the smart answer to the question of whether a straight or an angled probe is more suitable for the localization of sentinel lymph nodes in breast cancer, melanoma, prostate cancer or other cancers. Tungsten articulatable hand-held probe was designed for the radiation energy of the most used nuclide 99mTc (140 keV) and has optimal parameters for it.

The side shield of tungsten articulatable hand-held probe is made by tungsten collimators, which are integrated in the stainless steel probe tube. The detectable energy range is from 70 keV (201Tl) up to 511keV (PET nuclide). Tungsten articulatable hand-held probe can not be used with the optional PET collimator sleeves. The collimators are built into stainless steel tubes that can be unscrewed and steam sterilized separately.

Material of tungsten side shield: Tungsten, lateral thickness 3.15 mm (at all collimator sleeves with D = 15 mm), rear thickness 5 mm, side shielding = 99.97 % @ 140 keV (99mTc).

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If the gap of tungsten points of distributor is becoming smaller, it will prolong the closing time of tungsten points; it will store more ignition coil ignition energy; current formed in the primary coil will be relatively larger before the tungsten points is opening; the maximum secondary voltage is relatively higher when the tungsten points be opened.

If the gap of tungsten points of distributor is becoming bigger, it will shorten the closing time of tungsten points, which will bring about the result that the ignition energy will reduced and the maximum secondary voltage will dropped. And it will have the consequences that ignition advance angle will increase because the opening time of tungsten points is ahead.

So, the gap of tungsten points of distributor should be not too small. If the gap is too small, it will strong contact spark will be formed and the primary ignition energy will be lost when tungsten points are closed, ultimately tungsten points will ablate. And the maximum secondary voltage will be reduced because primary current circuit setting off incompletely.


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