Tungsten Copper Contact —Ultrasonic NDT

Tungsten copper contact is also known as tungsten copper electrical contact or tungsten copper contact tip, which is a kind of psudoalloy that consist of W and Cu two kinds metals of immiscible and without the formation of intermetallic compounds. Consequently, it not only has high hardness, high melting point, high strength, low coefficient of thermal expansion and excellent wear resistance and corrosion resistance of W, but also has perfect electrical and thermal conductivity and plasticity of Cu. And it has been played an important role in some high-voltage switch, breaker, and instrument components.

Currently, preparation of tungsten copper contacts is mainly used in PM (powder metallurgy) technology, the corresponding method used for the performance testing, such as the density, the hardness, the compressive strength, the tensile strength and micro-structure, etc., will have some damages on the integrity of tungsten copper products and lead to failure. And these tools to test for products in large quantities can only do a certain proportion of sample, which is difficult to have some representation. If the unqualified tungsten copper contacts undetected used in actual production is likely buried security risk, both for production or personal safety is extremely unfavorable. So the relevant researchers use Non-destructive testing techniques to measure and evaluate the mechanical properties of tungsten copper related products.

Ultrasonic NDT (Non-destructive Testing) is a kind of process that ultrasound can penetrate deep into the use of a metallic material, by entering a cross-sectional another cross-sectional; edge reflection occurs at the interface characteristics of the parts to check for defects. When the ultrasonic beam from the surface of the part by the probe pass to the metal inside encounter defects and Part underside of the reflected wave occurs, respectively, form a pulse waveform on the screen, based on these pulse waveforms to determine the location and size of the defect. Compared with other detecting methods, Ultrasonic NDT has many advantages, such as:

1. Ultrasound has perfect penetration ability, low transmission loss and the probing depth of up to several meters;
2. High sensitivity, it can be found with the diameter of the air-based reflectance 0.1-1mm equivalent reflector;
3. Accurate positioning, to assume the shape and the size are also more accurate;
4. Convenient in operation and it is suitable for the most materials;
5. The entire testing process will not cause environmental pollution, no harm to the human body completely.

tungsten copper contact

 

Automobile Exhaust Denitration Catalyst Uses Tungsten Trioxide

honeycomb denitration catalystOne of the most challenging tasks in the environmental protection field is to reduce nitrogen oxide in the exhaust emissions. With the daily increasing of the usage amount of global automobile, the automobile exhaust has become one of the main sources of nitrogen oxides, which the governance has become particularly important. There are usually two methods to improve the denitration process of automobile exhaust, which are the methods of improving combustion process and flue gas denitrification. In the methods of improving combustion process, with the process changing, the NOx eliminate efficiency also will show a difference; however, it is denitration efficiency almost controlled among 50~60%. In the flue gas denitrification process, especially the using of catalytic method, its denitration efficiency can reach a relatively high level, and thus to have a widely application.
 
Denitration catalyst is the core part of the whole SCR system. Denitration catalyst is commonly using titanium dioxide as a carrier, and vanadium pentoxide as the active material which plays the role of oxidizing, otherwise, tungsten trioxide and other substances are added as the additives for enhancing its denitration performance. By controlling the amount of each component, we can get the high efficient of catalyst. Research has indicated that the SCR catalyst which is composed of a homogeneous mixture of titanium dioxide (80~90wt%), tungsten trioxide (6~10wt%) and vanadium pentoxide (highest of 3wt%), wherein the making up prescription may contain silica (0~ 10wt%), is a automobile exhaust denitration catalyst with a high activity.
 
In the tungsten trioxide denitration catalyst, titanium dioxide is used as an active carrier of high surface area to carry the active component of vanadium pentoxide, in which vanadium pentoxide decides the NOx reduction activity of the catalyst at a low or middle operating temperature. However, an excess of vanadium pentoxide will result in the sulfur dioxide gas being oxidized to sulfur trioxide. Therefore, for the purposes of the high sulfur content in the exhaust gas, the amount of vanadium pentoxide in the catalyst is supposed to be maintained at a low level (1wt% or even less), thus the catalyst can play a relatively high activity. Tungsten trioxide (or molybdenum trioxide) as the chemical additive or structural aid, can be used for extending the operating temperature range, and enhancing the anti-vulcanization property of the catalyst, thus effectively preventing the conversion of sulfur dioxide to sulfur trioxide. Silica is often used to improve the strength and stability of the catalyst.
 
With the expansion of SCR denitration projects, tungsten trioxide will have a very broad application prospect in the developing of catalyst and non-precious metal of the automobile exhaust denitration catalyst which is used under the lean-burn conditions.

 

Tungsten Powder made by Waste Tungsten Bar- Chemical Vapor Migration

With the rapid development of industry, although it has high economic benefits, but the damage of the environment is on the increase every year. Due to ecological environment worsening and water resource shortage, the human living environment will face the serious challenge. The ecological environment is fragile, and the task of ecological construction and environmental protection is still heavy. And therefore countries pay more and more attention to the recovery of metals. Japan set up a special committee for tungsten recovery in 1975, which is called WR for short. The commission estimates that 31.3 tons of tungsten can be recycled while producing 100 tons of carbide. Or we can say that is the 31.3 percent recovery, the actual recovery rate in Japan is 10% and the United States is 20%. The equipment for chlorination pulping process is relatively simple, and it has a wide adaptability of raw materials, at present, this method is considered as one of the most promising methods. In recent years, ultrafine tungsten powder extracted from the waste tungsten bar through the chemical vapor migration has aroused general concern. Chemical vapor migration is a chemical process used to produce high quality, high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. Microfabrication processes widely use this way to deposit materials in various forms, including monocrystalline, polycrystalline, amorphous, and epitaxial.

The first is to use chloridize the cutting of both ends of the clamping head of tungsten bar while vertical sintering at environment of 950 ℃. Chloride will be supplied to reduction tubes with argon, and then being deoxidized by hydrogen. Chlorine is loaded in industrial bottle, and mixed with argon after dehydrating by concentrated sulfuric acid. Deoxidizing hydrogen with palladium asbestos at the temperature of 350 ℃, then drying it by silica gel and molecular sieve. Finally, gathering the ultrafine tungsten powder obtained by the reaction in powder collecting pipe. After purifying and absorbing hydrogen chloride, exhaust gas which contains hydrogen would be emitted and combustion. The final wolfram powder would have 0.64% oxygen, 0.075% chlorine, and 0.033% chlorinated residue.

Adopting chemical vapor migration methods can also produce the same quality of wolfram powder. Although the aluminum content is higher, all other metal impurities are mostly below or equal to the ultrafine wolfram powder. On the one hand, it can greatly reduce industrial costs. On the other hand, it helps to promote the application of wolfram powder.

wolfram powder and tungsten bar

Tungsten Bronze Metaniobate Lead High Temperature Ceramics Preparation

Preparation of lead metaniobate high temperature ceramic with tungsten bronze structure relates to high temperature piezoelectric ceramics, PbNb2O6 piezoelectric ceramics have many outstanding features, such as poor quality factor (Qm <10), the single vibrational mode (Kt >> Kr) and high Curie temperature (Tc = 570 ℃), etc.. So it has a very broad application in the prospects of industrial inspection, medical diagnostics and high-temperature sensors.
 
There is the preparation process of metaniobate lead high temperature ceramics with tungsten bronze structure, the formula of the ceramic composition is Pb1-xMexNb2O6(Base material)+additive ywt%(the total weight of base material is 100), of which, Me=Ca、Ba; x=0.02~0.12; the additives are Sm2O3、Ce2O3、Nd2O3 and Te2, y=0.03~0.3%. The specific preparation process is as follows. 
 
Powder synthesis: Mix PbNb2O6 as the stoichiometric formula and the nanoscale (~ 100nm) CaO, BaO, TiO2 and Sm2O3, Ce2O3, Nd2O3 and Te2, put into the ball mill, the ratio of ball and materials is 1:5, mix for 6 to 8 hours, the powder was taken out briquetting (pressure 100MPa), in a sintering furnace at a heating rate of 2 ~ 5 ℃ / min, heated to 850 ℃, and after heat preservation for 2 hours to cool at the rate of > 250 ℃ / min to room temperature, and then take out and pulverized compacts and placed them into the ball mill finely grounding for 6 to 8 hours, the powder is moved to the sintering furnace, the temperature rose at heating rate of 2 ~ 5 ℃ / min to 1260 ~ 1270 ℃, and after heat preservation for 2 hours to cool at the rate of > 250 ℃ / min to room temperature, and transferred to the ball mill for fine grinding 32 to 48 hours, the powder for ceramic synthesis is obtained.
 
(2) Ceramic firing and polarization: Make the resulting powder into the piezoelectric ceramic green bodies by adding adhesive dry pressing method, after green bodies plasticized, put into an alumina crucible, in a sintering furnace with a heating rate of 2 ~ 5 ℃ / minute, sintered at 1290 ~ 1315 ℃, after heat preservation for 0 to 0.5 hours, to cool at 250 ℃ / min cooling rate, after cold working and the trimming, and then placed in the eight shelves at 5000V / mm / 180 ℃ / 10min, go through high power polarization, to obtain the piezoelectric ceramic products.

tungsten oxide ceramics

 

Tungsten Bar and Satellite

In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are sometimes called artificial satellites to distinguish them from natural secondary planets such as moon. The world's first artificial secondary planet, the Sputnik 1, was launched by the Soviet Union in 1957. In the whole solar system, except for Mercury and Venus, the other planets are all natural objects. Wolfram is a rare non-ferrous metal in the world, and its annual output is very low. In addition, it is very versatile and mainly applied in the casting material. Nowadays, the total number of natural objects is at least 160. For example, in the solar system, the sun is a fixed star, and the earth and other planets orbit around the sun, and the moon and other planets orbit around the earth, these planets are called natural secondary planet.

Not long ago, there has been a weapon called satellite powered gun, which is also known as "God's scepter." This is an extraterrestrial combat device which is still being researching and developing. Theoretically, this weapon can shoot to the ground with tungsten bar through its track, and it can cover any range of the entire planet. Tungsten metal is lustrous and silvery white in color, and does not occur naturally (it has an abundance of 1 ppm in the earth's crust). Attack that originates from space, not only has the capability to destroy large tracts of ground buildings, but also destroys hundreds of meters deep underground bunkers. Powered gun can hit the ground by gravity, and it can be accelerated to the speed of 3403 m / sec which is the same as the destruction of nuclear weapons, but it would not cause catastrophic nuclear radiation.

In the movie "GI Joe 2", it is mentioned that the "silos" can be considered as a geostationary secondary planet, tungsten bar will do elliptical motion around the earth with "silos" in the absence of thrust. However, according to the law of conservation of energy, kinetic energy of landing of this type of tungsten products does not exceed its own potential energy of the near-Earth orbit, and its potential energy in the near-Earth orbit cannot exceed kinetic energy of its rocket launching. So, in fact floor  kinetic energy of tungsten bar is probably less than a quarter of the rocket fuel energy, and therefore, such weapons are currently still in the theoretical condition.

wolfram bar and satellite

 

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