Most of ammonium paratungstate (APT), about 80% is produced by ion exchange from the raw material of tungsten ore in tungsten metallurgy in China. There are three main steps in ion exchange: decompose tungsten ore, ion exchange, evaporate and crystallize. Today we provide a method that not only can remove Mo, Sb, As, Sn at one-time, but also recycle NH₄Cl, improve the recovery rate of WO₃, and eliminate waste water.

0-95% of the mother liquor is returned for preparing desorption agent, the remaining returned to prepare pre-ion-exchange solution, and take the following two ways according to the contents of impurities in the crystallization mother liquor:
1. If the mass ratio of WO₃/Mo in ammonium tungstate produced by ion exchange is below 5000, adding (NH4)₂S for vulcanization. Conditions for the vulcanization are: vulcanize at 10-75℃, use amount of 0.5-3g/l more than theoretical, then add copper sulfate or chloride or Cu(Ac)₂ at temperature of 10-80℃, the amount of Cu₂⁺ is 3-6 times of the theoretical. Filter after kept 1-3 hours, and the filtrate is evaporated and crystallized to prepare APT, crystallization mother liquor returned back directly.

2. if the mass ratio of WO₃/Mo is upper than 5000, evaporate and crystallize to generate  APT directly. Add (NH4)₂S into the crystallization mother liquor in advance for vulcanization. Conditions for the vulcanization are: vulcanize at 10-75℃, use amount of 1-3g/l more than the theoretical, then add copper sulfate or chloride or Cu(Ac)₂ at temperature of 10-80℃, the amount ofCu₂⁺ is 3-6 times of the theoretical and filter after heat preservation for 1-3 hours, filtrate return to reuse.

The main process for preparing coarse grain carbide crystal in China is adding alkali metals such as sodium in tungsten trioxide to generate coarse grain tungsten powder after hydrogen reduction, and carbonization at high temperature to get coarse tungsten carbide powder, and then grinding, forming, sintering process to prepare coarse grain carbide. Conventional methods of preparation sodium doped WO₃ are spray, artificial doping method, the defects of the two methods is sodium distributing not uniform in WO₃ thus affects the subsequent production, and leading particle growing not uniform, products of great difference in properties. Besides, the manufactures may have to buy equipments by using the spray method, thus resulting cost increased. So, is there any way to make the sodium mixed uniform, and do no need to purchase any other equipment? This paper we will provide a method for preparation of WO₃ uniform doped sodium.

Steps are as bellows:
1. Take the ammonium tungstate of WO3 concentrate 200~300 g/L as raw material, and Na+ mass concentration of PPM 10~40;
2. Add solid sodium salt according to the requirements of subsequent products, Na/WO₃ about 0.05%~0.25%, mix the solution;
3. Evaporate and crystallize, temperature controlled in 80~100℃ with the stirring speed of 50~200 r/min;
4. The end of crystallization when pH reaches 6.4~7.0, then stop heating and cooling down to 20~50℃;
5. Filter the liquid by vacuum filtration, dry to generate APT powder with uniform sodium;
6. Calcine APT in the claining furnace at 680~740℃to obtain tungsten trioxide powder with uniform sodium.

Ammonium metatungstate (AMT) is an appearance of white or slightly yellow crystalline powder, its water-soluble is 300g / 100ml, it slightly soluble in water; when the temperature reaches at 20 ℃, its solubility is less than 2%. Ammonium metatungstate is used in making metal tungsten, steel, fireproof fabric and for the ceramic industry. Usually, we take ammonium tungstate solution as raw material to obtain ammonium metatungstate solution by solvent extraction or ion exchange method, and then evaporate it to prepare crystals of ammonium metatungstate. Ammonium metatungstate is also used in the manufacture of various petrochemical catalysts and other tungsten compounds, and it is the main raw material refinery tungsten-based catalyst. According to the features of ammonium metatungstate slightly soluble in water, we prepare tungsten trioxide in this case.

Ammonium metatungstate preparing tungsten trioxide is based on taking ammonium metatungstate as raw materials, heating ammonium metatungstate to 220-280 ℃; it can be converted to ammonium metatungstate when it loses some ammonia and crystal water, and then continue to heat ammonium metatungstate to more than 600 ℃, when ammonium metatungstate loses all crystal water and ammonia, cooling and crystallization, the finished product is dried thoroughly into yellow tungsten trioxide.

There many methods of preparation of ammonium metatungstate, such as acid method, thermal decomposition method, ion exchange, solvent extraction method. The method of ammonium metatungstate preparing tungsten trioxide is simple and easy, and it meets the needs of industrial production.

Transmittance is physical vocabulary; it is the efficiency of light showing, the percentage of flux through its incident light flux transparent or translucent display devices. It denotes display device or through the efficiency of light; it directly affects the visual effect of the touch screen. Many touch screens are multilayer composite thin film, touch screen should include at least four characteristics: transparency, color distortion, sharpness and reflective.

Analyzing tungsten trioxide thin film by using XRD-600 diffractometer structure and morphology, which shows the transmittance of tungsten trioxide thin films are not different by comparing the sol - gel method and obtained by magnetron sputtering before annealing, and the transmittance of thin film decreases after annealing above 300 ℃, and the higher the annealing temperature, the transmittance is lower. Tungsten trioxide thin film samples are annealed below 350 ℃, the annealed thin film sample is gradually completed amorphous to crystalline transition state within the range of 350 ~ 400 ℃, after annealing at 400 ℃, the substrate also has a diffraction peak.

Different forms of tungsten trioxide thin film samples obtained at different annealing temperatures. In addition, the morphology and optical properties of tungsten trioxide thin films have a great impact on its gas-sensitive properties, such as relatively porous amorphous, which will help the adsorbed gas.

Doped tungsten low temperature ductility is the main influence factor of tungsten wire spooling property, and spooling property will largely affect use efficiency of the bulbs, so understanding the influence factors of low temperature ductility of doped tungsten wire, thereby to expand the applications of tungsten wire.                              

Theoretically, since the doped tungsten wire grains are longitudinally fibrous structure, and the fracture behavior is intragranular fracture, so it has good ductility. Beside, its plastic-brittle transition temperatures well below than room temperature can well meet the filament winding shaping requirement. However, due to the doped tungsten wire has complex production technology, and in the production process is prone to error, resulting in deterioration of low temperature ductility, affecting spooling property of tungsten wire. Here's a brief analysis of influence factors of the low temperature ductility of doped tungsten wire:

1. The purity of the raw materials
Experimental results show that high-purity tungsten powder having excellent ductility at room temperature, namely, tungsten itself is not brittle. Therefore, low temperature ductility of tungsten will mainly influenced by impurities. Nickel and iron impurity elemental content is too high will increase tungsten wire’s low temperature ductility, resulting in a certain degree difficulty of post-processing.

2. Additives
In order to make tungsten wire has good high temperature sag resistance, tungsten wire will dop some additional agents including Al, Si, and K and so on. But these elements will have no beneficial impact on low temperature ductility performance of the tungsten wire, so during the doping process should better control the amount of additional agents.

3. The surface condition of doped tungsten wire
During the processes, tungsten wire may appear more surface defects, which can mainly be attributed to surface mechanical damage and surface contamination. These defects will increase tungsten wire’s low temperature ductility. In order to eliminate surface defects caused by the machining usually uses electrolytic cleaning method to clean tungsten wire, so that it can improve the surface condition of tungsten wire, increase smoothness. Thereby reducing the tungsten wire’s stress concentration in the process of winding reduces low temperature ductility of tungsten wire.

Tungsten wire in the field of lighting systems are the most widely used, but to be applied to aircraft, ships and cars lights and other special lighting systems and as high precision gas chromatograph thermal conductivity wire, kinescope wire, UHF tube filament and thermocouple wire need to produce tungsten wire with more favorable properties. The experiment found that tungsten powder further doping rhenium on the basis of doped K, Si, and Al to produce tungsten-rhenium wire has good performance. Tungsten-rhenium wire not only maintain a high temperature sag resistance and improved tungsten room temperature shaping process, thereby improving the seismic performance of the tungsten wire.

Rhenium is a rare metal. At room temperature, it is grayed and crystal structure is sixty thousand close-packed. Its physical properties are as follows: Density: 21.04g / cm3; Melting point: 3180 ℃, the melting point of rhenium only lower than tungsten; boiling point: 5627 ℃; insoluble in hydrochloric acid and hydrofluoric acid. Rhenium is kind of ductility metal at room temperature which is easily formed into a sheet or wire, and the more purity of rhenium the easier molding process. But as the temperature rises rhenium will occurs work hardening in varying degrees, making it difficult to process deformation at high temperature. Therefore, as the additive element adding in tungsten wire can improve the high temperature sag resistance and shaping process at room temperature.

Tungsten-rhenium wire production processes:
1. Adding Si, Al, K and ammonium perrhenate (NH4Re4O) solution into tungsten trioxide (WO3), then after evaporation, drying, sieving, hydrogen reduction and other processes produce rhenium tungsten mixed powder. The doping mode will chose wet doping, because the wet doping can make more uniform distribution of rhenium in the tungsten-based. At the same time compared the effects of different content of rhenium doped on tungsten found rhenium added in an amount of 3% can produce more favorable performance tungsten-rhenium wire.
2. The mixed powder is pressed into a tungsten-rhenium strip, obtained billet after through sintered.
3. Finally, after swaging, drawing and other processes produce tungsten-rhenium wire.

In some deep oil well with high content of water and sand, high abrasion, the advantages of high density, excellent wear resistance and corrosion resistance of tungsten carbide valve ball becomes more obvious. Theoretically, the main failure modes include wearing, abrasion, fatigue cracks, collapse and so on, which makes the ball valve material fail earlier in oil drilling (such as bearing steel, ceramics) and shorten the service life (bearing steel is easily corroded by the liquid and has lower wear resistance; ceramics belongs to brittle materials and has lower impact ductility, which is easily to break).

Therefore, tungsten carbide valve ball makes up for the deficiency perfectly, which not only has high hardness, high density, high strength, excellent chemical stability of tungsten (W), but also remarkably improves the bending strength and impact ductility of oil drilling pump valve ball by adding cobalt (Co). Excellent resistance to wear and corrosion resistance greatly improved drilling efficiency, extend tool life, but also reduces operating costs. Recent years, the related researchers and scholars will further shift the focus to the cemented carbide valve ball, especially in the United States and some European industrial countries, tungsten carbide valve ball has been increasingly widely used, the type and quantity are continuing to increase, and toward the high temperature and pressure, high tightness, large-caliber, long service life and multifunction developing. The reliability and overall performance have reached a higher level, has been replaced with a valve part, control valve and end valve. In addition, with the innovation of tungsten carbide valve ball technology, it has a broader applying prospect in oil and gas pipelines, refinery cracker and nuclear industry, especially in medium and large caliber, medium and high pressure fields.