Powders and high optical quality single crystal minirods of stoichiometric scheelite CaWO4 have been prepared by solid state reaction and floating zone methods, respectively, and their single phase formation, optical and scintillating properties have been evaluated by X-ray diffraction, optical absorption and radioluminescence measurements. All obtained results indicate that every sample is stoichiometric, while scintillation measurements reveal radioluminescence peaks at about 420 nm, 440 nm and 490 nm depending on the source of irradiation used. The single crystal samples exhibit higher radioluminescence light yield.

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

The rate of decay of a very phosphorescent sample of calcium tungstate was determined photographically and found to fit the empirical equation of Becquerel, <i>I</i>^-x = <i>a</i>+<i>bt</i>, within the experimental error, from thirty seconds to five minutes after the exposure to x-rays. The phosphorescence of this sample could not be detected photographically more than 50 hours after the exposure of 300 milliampere-seconds at a distance of 30 cm from the target. Under the same conditions the phosphorescence of normal calcium tungstate disappeared in one minute. The intensity of the phosphorescence was found to be closely proportional to the product of the intensity of the x-rays and the time of exposure up to a limiting value, beyond which increased exposure caused a negligible increase in the phosphorescence. In general, these properties are quite similar to those of the “phosphors” of Lenard and others.

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

The configuration coordinate model has been used to calculate the luminescence band of CaWO₄ at various temperatures. The force constant k_g of the harmonic vibration in the ground state has been computed from the vibrational Raman spectrum of WO₄/²~; the result is k_g = 5.8 × 10⁵dyne/cm. The force constant k_e for the excited state, deduced from the temperature dependence of the width at half the maximum intensity of the emission band, isk_e = 1.5 × 10⁵ dyne/cm. In order to obtain satisfactory agreement between theory and experiment we have to assume the variation in interatomic distance on excitation to be 0.20 Å which is in accordance with the analogous quantity of OsO⁴ where a calculation from spectroscopical data yields an expansion of 0.15 Å.

 

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Coarse and spherical tungsten powders are prepared by wet hydrogen reduction. Ammonium tungstate solutions with the additives of Li, Na and K alkali metal salts are used as raw materials. The effects of the type and content of the alkali metal salts as well as reduction time on the microstructure, chemical composition, phase composition and particle size of ammonium paratungstate and coarse tungsten powders are investigated by scanning electronic microscopy, energy dispersive spectroscopy, X-ray diffraction, and test sieves.

It is shown that ideal tungsten powders with good fluidity, sphericity, integrity and even distribution can be obtained by using the ammonium tungstate solution with 3g.L^-1 NaCl, KCl and Li₂CO₃ and reducing at 1000℃ for 180 min in wet hydrogen atmosphere. The average particle size of the obtained tungsten powders is 67um, the maximum particle size is 150 um, the biggest loose density is 13.41g.cm^-3, and the best powder flowability is 9s for 50g tungsten powders.




Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn
 

Tungsten is being widely applied in the modern science and industry, especially tungsten alloy, tungsten carbide and other tungsten heavy alloy which is of high wear resistance and high corrosion resistance. Among which coarse spherical tungsten powder is an important material for preparing coarse tungsten carbide powder. Coarse spherical tungsten powder is of higher density and hardness which is widely applied in mining tools, oil drills, cutting tools, etc.

Nowadays the main tungsten powder preparing method is calcinating ammonium paratungstate into blue tungsten oxide or yellow tungsten oxide and then process through hydrogen reduction. Tungsten powder prepared by this method is of regular multi crystal and grain size is between 2-5um. In 1980s, adding alkali metal salts in tungsten oxide and process mid-temperature reduction method will enlarge the grain size of tungsten powder. Adding Na and Li together will maximize the property of tungsten powder.


Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

 

Ammonium paratungstate preparing coarse spherical tungsten powder affecting factors are listed as below.

1.Adding NaCl and Li₂CO₃ will affect the grain size of ammonium paratungstate. Adding NaCl and LiCO₃ will enlarge the grain size of ammonium paratungstate. But the effect of Li2CO3 is more apparent. The grain size can reach 60um.

2.As the reduction time prolonged, grain size of tungsten powder increases. This is because the fine tungsten oxide particles volatilize and deposit on the tungsten macro tungsten powder which increase grain size of tungsten powder gradually.

3.Adding additives. Adding alkali metal salt will enlarge the grain size of tungsten powder. When the grain size is between 45-61um, tungsten powder grain size grows rapidly. It turns out that Li will maximize the growing of tungsten powder. When the particle size reaches 100um, the growing speed slows down, the average size of tungsten powder reaches 67um which can meet the requirement in industry.




Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Tungsten powder is not only the raw material of tungsten carbide, but also for tungsten alloy. It can be applied in machining, mining explore, geological drilling, construction tools, military area, etc. In order to promote the property of materials, prepare submicron spherical tungsten powder is a tendency.

Submicron spherical tungsten powder after sintering can promote the hardness and density of metal materials which improve its property. If the distribution of submicron tungsten powder is closed, materials after sintering will still be fine particles, it will affect mechanical property of materials. Methods for preparing submicron tungsten powder include ball milling, reduction under dry atmosphere, hydrogen reduction, tungsten acid reduction, etc. These methods have a lot of disadvantages such as it is of high cost and low producing efficiency which is not fit for industrial production.

Ammonium paratungstate preparing submicron spherical tungsten powder is more environmental friendly, easy to operate, the parameter is under easy control, the equipment is accessible and it is more suitable for massive production.




Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Coherent emission at 1.047 μ from trivalent praseodymium in calcium tungstate was observed. This emission coincides with strong infrared fluorescence at the same wavelength and was found to be stimulated mostly by absorption of blue light by the ³P₀, ³P₁, and ³P₂ bands. The emission corresponds to a ¹G₄↠³H₄ transition with the terminal level 377 cm−1 from the ground state. The oscillation threshold was the same at 4.2°, 20°, and 78°K. No stimulated emission was observed at room temperature. The lifetime of the metastable state ¹G₄ is 50×10−3 sec. A new technique used to measure the lifetime is described. 

 

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Average grain size and distribution of particle of ammonium paratungstate is affected by the PH value of solution. Nucleary speed and crystalline speed is affected by PH value apparently. After crystallization, the PH value is controlled between 8.0-7.8, it will reduce the nucleary amount and forming speed, the small amount of crystal nucleus can turn into large grain size steadily, also the limited PH value will make the coarse ammonium paratungstate which is distributed evenly.

Adding 10%-20% dilute hydrochloride acid into solution to the PH value 6.5-7.5, the apparent density of crystal decreases, the crystal shape is regular which makes it more convenient to prepare fine ammonium paratungstate particle. By adjusting crystallization mother liquor to the ideal PH value 6.0-8.0 and heat to above 50 degree Celsius will obtain high purity ammonium paratungstate crystal.




Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn
 

Tungsten diselenide (WSe2) conductivity is ten parts per million than the best conductivity which is diamond, it is the world's lowest conductivity material. In general, poor conductivity material (or insulator) is a porous material, but also one of the most insulation materials. Tungsten diselenide has low thermal conductivity, which is the system heat loss is not easy, so the system's energy conversion efficiency will be higher. If can full to use its insulation properties, will likely significantly increase the efficiency of energy use.
And because the main structure is composed of the upper and lower layer which is the selenium atom and the intermediate layer are tungsten atoms. This structure of WSe2 material like graphene can absorb light and the light absorption can be used to produce electricity. With further study, the researchers according to this feature of tungsten diselenide developed diodes which produce by tungsten diselenide, and this material can be applied to thin flexible solar cells.

Tungsten Manufacturer & Supplier: Chinatungsten Online -http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn