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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In general, the normal gap value of tungsten points of the distributor is between 0.35mm and 0.45mm. If the gap is large than normal gap value of 0.1mm, the petrol consumption of car engine will more than 3% of normal petrol consumption; if smaller than 0.1mm of normal gap value, then the consumption will add 5％of fuel.

The influence factors of the automotive ignition system performance are ignition advance angle, ignition energy and the maximum secondary voltage. If the ignition advance angle is too large or small, the mixture gases would not burn normally after igniting. If the ignition energy is not sufficient, the mixture gases would not properly ignite. If the maximum secondary voltage is low, the spark plugs would not normally flash over. The factors described above will decline the power of engine, rise fuel consumption and dysfunction and other aspects. Therefore, if the gap of tungsten points of distributor is proper, the influence of car ignition advance angle, ignition energy and the maximum secondary voltage to car ignition system will be reduced.


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Silver tungsten points’ preparation can adopt infiltration or powder metallurgy method.

Silver material properties:
Low wear resistance;
Low melting point;
Low hardness;
Volatile;
Good thermal conductivity;

The silver point is easier to form arcs and weld when its load is large;
Under the influence of DC, silver film form electrical erosion spikes because of silver’s low hardness and volatile characteristics;
Silver will form silver sulfide film in the surface of sulfur or sulfur compounds at the condition of high temperature and humidity,.

The content of tungsten of silver tungsten points is usually around 20% -80%. Silver tungsten points’ merits: arc erosion resistance, excellent electrical wear resistance, good electrical and thermal conductivity, good oxidation resistance and good anti-welding capability. Silver tungsten points’ defects: unstable contact resistance. Tungsten will produce mixed oxide when the silver tungsten points operating frequently and the splash degree of contact resistance of the film surface will improved.

Silver tungsten points’ application: widely applied in micro-switches, circuit breakers, thermostats, etc., and can also be used as a part in high current heavy equipment and electrical points.


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Tungsten points, also known as tungsten electrical points or tungsten contacts, which are used in equipment, instruments and switching equipment as a contact part. They are playing a role in turning on and turning off the current. Thus, tungsten points will influence the properties of the switching devices directly when they are in running state. People began to use contact materials about a hundred years ago, which started with pure silver, pure gold and pure platinum and other contact materials. People began to use alloy materials until the 1940s, such as, gold silver, platinum indium and silver copper materials. People gradually found composite materials of precious metal after the 1960s. People gradually turn their attention to tungsten materials since tungsten was found in 1781.

Tungsten contact materials possess high purity, high melting point (up to 3422 ° C), high density, high hardness, nice wear resistance, good corrosion resistance, low conductivity and other properties.

Properties of silver material are: silver owns excellent processing performance, the best thermal conductivity and high antioxidant capacity and other properties in all metals.


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