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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Tunable dye laser spectroscopy has been used to study energy transfer processes in CaWO₃:Sm³⁺ crystals. Fluorescence and excitation transitions for samarium ions in different crystal-field sites have been identified and their changes in width and position with temperature studied. This information is used to characterize energy migration among samarium ions as a function of temperature, samarium concentration, time after the laser pulse, and pressure. The interaction mechanism causing energy migration is identified as electric quadrupole-quadrupole. At low temperatures it was found that only single-step transfer between nearby ions takes place, while at high temperatures multi-step diffusion of energy occurs. These results are interpreted in terms of the Anderson (1958) localization concepts for systems with inhomogeneously broadened transitions, and quantitative estimates of the transfer rates and diffusion parameters are obtained.

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If the gap of tungsten contacts of distributor is reduced, then: the closing time of tungsten contacts will be prolonged; ignition coil ignition energy will store more; before the tungsten contacts opening, current formed in the primary coil will be relatively large; when the tungsten contacts are opened, the maximum secondary voltage is relatively high.

If the gap of tungsten contacts of distributor is increased, then: the closing time of tungsten contacts will be shortened, which resulting in ignition energy reduction and the maximum secondary voltage drop. And because the opening time of tungsten contacts open ahead, it will cause that ignition advance angle increases.

However, the gap of tungsten contacts of distributor is not too small. If the gap is too small, when tungsten contacts are closed, it will form a strong contact spark and lost the primary ignition energy, resulting in tungsten contact ablation. And because the cutoff of primary current circuit is not complete, so the maximum secondary voltage will be reduced.




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The normal value of tungsten contacts gap of the distributor is generally around 0.35mm-0.45mm. If the gap is large than normal value of 0.1mm, the engine will use more petrol than 3% of fuel; if small  than 0.1mm, then 5％of fuel.

Ignition energy, ignition advance angle and the maximum secondary voltage will affect the automotive ignition system performance. If the ignition energy is insufficient, it will cause the mixture gases do not ignite properly. If the ignition advance angle is too small or too large, so the mixture gases will not normally burn after ignition. If the maximum secondary voltage is low, then the spark plugs do not flash over normally. These factors will make the power of engine decline, fuel consumption rise and dysfunction and so on. So, appropriate tungsten contacts gap of the distributor can mitigate the impact of car ignition energy, ignition advance angle and the maximum secondary voltage to car ignition system.




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