What Is the Best Material for X-ray Collimation – Tungsten Metal or Tungsten Alloy?

A collimator is a device used to transform the divergent light or other radiation from a point light source into a parallel beam, and also is an absorber device used to limit X-rays, gamma rays, or nuclear particle beams to the size and angular spread required for a specific application. Normally, special measurements in spectroscopy and geometric and physical optics require this kind of light collimation.

For reasons of patient dose and image quality, X-ray collimation for radiography and fluoroscopy projection imaging is important. Actively collimating the volume of interest will reduce the overall integrated dose to the patient, thereby minimizing the risk of radiation. Less radiation will result in less X-ray scattering incident on the detector. This leads to improved object contrast and image quality.

In a linear accelerator (linac), the main collimator may be made of depleted uranium because the density of this material is approximately 1.6 times that of lead. The secondary electric collimator can better define the beam shape and is made of lead or tungsten. The multi-leaf collimator (MLC), which is now widely used in medical linear accelerators, consists of two thin tungsten "leaf" collimator groups, each group consisting of 40 to 80 leaves composition. 

As depleted uranium and lead materials are not easy to completely eliminated by the body after entering the human body, and will damage the internal organs, tungsten metal is the most popular materials for this device now. Generally spreading, the higher density of the material, the better radiation protection. Why tungsten alloy collimator is more popular compared with pure tungsten collimator? 

The density of tungsten metal is high, however, it is also easy to fragile during machining if you use powder metallurgy to produce, especially for complex collimator. Therefore, tungsten alloy, added with the element of nickel, copper or iron, help improve the problem. The alloy has high density, better processability and good anti-radiation, and thus most collimators are made of this material. 

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3D Printing Pure Tungsten Parts in the Medical Industry

Tungsten, also known as Wolfram, is a rare metal known for its highest melting point of all elements. In addition to excellent temperature resistance, the material also has strong abrasion resistance and chemical resistance. These good properties make it an ideal material for components that operate at extreme temperatures.

Pure tungsten does not have the hardness of composite materials, but its excellent heat resistance and radiation shielding properties are very useful in the nuclear and medical industries. The medical industry generally uses pure tungsten for MRI scans, collimators, and radiation shielding. But there is a problem: it is very brittle at room temperature, which means it is difficult to process using traditional techniques.

For simple collimators, radiation shielding and other products, powder metallurgy technology can be used to process, but for high precision and complex parts, using traditional technology is suffering. Therefore, the emergence of 3D printing has solved this thorny problem.

The principle of 3D printing is to use electrons accelerated in a vacuum to melt metal powder. By moving the electron beam, 3D components can be produced from metal by means of addition. This technology was originally developed for titanium alloys and materials that require high processing temperatures.

The tungsten metal powder is preheated before it is melted. This preheating procedure reduces the deformation and internal stress of the metal, making it possible to process materials that are easily broken at room temperature but deform when heated. The printed product basically does not need to be processed again, unless there are special requirements for precision or other requirements.

Tungsten provides characteristics rarely seen in 3D printing materials. It is non-magnetic, good at absorbing and shielding radiation, so that 3D printing pure tungsten parts can be widely used in the nuclear energy industry and medical industry. 3D printed tungsten collimator is one of them. Chinatungsten Online is a professional manufacturer of tungsten and molybdenum, which can provide 3D tungsten products.

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Why Use Thorium Tungsten Wires as Ion Source?

Many analytical and medical devices are using thorium tungsten wires as ion source. Why use thorium tungsten materials? What about tungsten or neodymium tungsten materials? 

Electrons are made available from a cathode in the source, which in most cases will use thermionic emission, i.e., heating the material so that electrons gain some energy and are able to escape the work function of the cathode material (the energy required per electron to leave the material). To lower work function, manufacturers would like to use thorium tungsten filaments. 

Doping a tungsten wire with thorium can effectively improve the thermionic emission. Doping lowers the work function of the system, resulting in a thermionic current greater than the one produced from a pure W filament. Why it happens? What are the mechanisms that lower the work function?

An idea is that thorium is an α-emitter. The 4He nuclei then produce scattering sources for the electrons, enhancing the emission probability. And according to Electronics Engineer's Reference Book, the mechanism is that thorium is added to the tungsten filament, and then the whole thing is heated significantly hotter than its normal working temperature. This causes the thorium to migrate to the surface of the filament, resulting in essentially a thorium-plated tungsten filament. Thorium has a lower work-function than tungsten so the effective work-function of the filament is that of thorium.

Some manufacturers have tried alternative materials, like neodymium tungsten rods for lamp electrodes, it works good for certain lamps but it does not for other lamps. Just like mercury for many types of lamps, thorium tungsten seems to be very mighty. Only the problem is quantities for these lamp manufacturers and device manufacturers are not large as thorium belongs to radioactive material. 

Due to regulation in Europe, transfer of thorium powder is very limited if not banned, there are a lot of papers to talk about this thorium powder ban, because it can be considered as Radioactive if it is concentrated very high, such as thorium powder. however, for thorium wires or rods, they are usually low in concentration, which is harmless to the health. 

Chinatungsten Online is a professional manufacturer of tungsten for more than two decades, if you have got the purchasing plan for thorium tungsten wires or rods, do feel free to contact us.

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Differences of Tungsten Crucible Made by Sintering and 3D Printing

To be used for rare earth metal smelting, induction furnace heating element, quartz glass smelting, sapphire crystal growing furnace, ect., the material should be extremely refractory, such as clay, graphite, tungsten, molybdenum, china clay, or quartz or hard-to-melt metallic iron because the usual working temperature is above 2000℃.

Tungsten metal is the most popular one among them given that its smelting point is high to 3610℃. Especially for sapphire crystal growing furnace, the crucibles made from tungsten metal plays a key role in success rate of seed crystals and the quality of pulling crystals during the growth of sapphire crystals.

How is a tungsten crucible produced? Generally speaking, it can be divided into spinning, stamping, forging and sintering according to different manufacturing processes. For most types of crucibles, they are formed by sintering. 

For sintering crucibles, they have very high purity, high density, precise size and smooth surface, which are deeply loved by many users. They are usually manufactured by the isostatic pressure. The isostatic pressure-sintering mainly includes a batch of raw materials, powder loading, isostatic pressure pressing, high-temperature sintering, machining, finished product inspection, and other procedures. 

However, there is a new producing method for this product and the method is getting more and more popular among the world – 3D printing. 3D printing in tungsten or molybdenum can deals with many problems that sintering can not resolve now, for example, if you need a part very urgently, how can you get it within a few days? with a 3D metal print machine, you can get it in three to seven days. 

Meanwhile, it can also offer the ability to manufacture complex parts without the need for tooling. Tungsten crucible can be produced more cost effectively and faster by using it. Parts made by this method can be highly detailed and thin. Details as small as 100 μm with a positional accuracy down to 25 μm can be achieved.

It also has its drawback – cost highly. With the development of technology, the cost is reduced greatly compared to before. For small and complex parts, it is worth trying. Kindly contact Chinatungsten Online if you have any inquiry. 

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Why Tungsten Flux Can Be Used in the Carbon and Sulfur Analyzer as Additive

Tungsten flux is a kind of coarse particle made by breaking tungsten bars instead of sintered tungsten powder with purity of over 99.9%. There are others name for it, such as tungsten accelerator, tungsten chip accelerator, tungsten particles and tungsten granule. 

Owing to its unique physical and chemical properties, it is widely used in many fields, for example, it is very suitable as a catalyst in a carbon and sulfur analyzer, used as a filler for shielding materials or used in radiation protection doors and baffles. Meanwhile, it is also suitable as a counterweight filler. 

Why tungsten flux is used as the flux during the combustion process of high frequency furnace in the analysis of infrared carbon and sulfur? 

With a melting point of 3380°C, tungsten is the most difficult metal to melt. However, the metal is easy to oxide. Tungsten begins to oxidize and emit a lot of heat when oxygen is passed through at 650°C. The infrared carbon-sulfur analyzer has the characteristics of high instantaneous heating value and fast reaction speed, so tungsten particles are needed as additive.

Some people may consider this product only as flux, actually, it can be used as additive. In the infrared carbon-sulfur analyzer, tungsten granule also generates heat, adjusts the acidity and alkalinity of the medium, stirs, catalyzes, stabilizes combustion, and anti-interference. Its roles are important and multiple.

With the help of the flux, the accuracy of the measurement value tested by carbon and sulfur analyzers can be effectively improved. The carbon and sulfur analyzer can quickly and accurately analyze the carbon and sulfur content in solid and fluid materials such as carbon steel, high, medium and low alloy steel, pig iron, gray cast iron, ductile iron, alloy cast iron, various iron alloys, ferrosilicon, ferromanganese, nickel iron, lithium iron, ferrochromium, rare earth metals, and coke, coal, slag, catalyst, ores and so one. 

As a professional manufacturer over two decades, Chinatungsten Online provides high-purity tungsten granule as well as many other parts. Please contact us if you have any inquiry. 

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China’s Zhangyuan Tungsten Raised Its Bid Price for APT

Analysis of latest tungsten market from Chinatungsten Online

China’s domestic tungsten price continued to rise in the week ended on Friday, August 06, 2021, benefiting from tightening availability of raw materials, new bid prices and average forecast prices for early August shoring up market confidence and increased demand. 

China’s Ganzhou Tungsten Association (GTA) released its average tungsten forecast prices for August: 55% black tungsten concentrate price was $17,698.4/t, up $1,904.8 month-on-month; APT price was $303.1/mtu, up $21.5/mtu; medium particle tungsten powder price was $41.7/kg, up $5.2/kg compared from July.

Jiangxi Tungsten’s bid price of high-grade black tungsten concentrate was $18,015.9/t for the first half of August, up $873/t compared with the second half of July. 

Zhangyuan Tungsten’s bid prices for the first half of this month: black tungsten concentrate (WO3≥55%) was quoted at $17,698.4/t, up $1,031.7/t; scheelite concentrate (WO3≥55%) was quoted at $17,460.3/t, up $1,031.7/t; APT was quoted at $303.1/mtu, up $17.9/mtu compared with the second half of July. 

Prices of tungsten products on August 9, 2021

Picture of tungsten ore 

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China Tungsten Price Was in the Upward Trend in Early July, 2021

Analysis of latest tungsten market from Chinatungsten Online

China tungsten price was in the upward trend in the week ended on Friday, July 09, 2021 with the impact of increased bid prices from listed enterprises for the first half of this month. 

At the beginning of July, China’s domestic and foreign cemented carbide enterprises successively increased their offers of alloy products. Raw material manufacturers had strong rised mentality and downstream buyers had to accept their high offers. But except for actual needs, consumers were still cautious of high-price transactions. 

The price in the tungsten concentrate market is exploring towards $16,666.7/ton. Low-price resources were hard to be purchased while high-price deals were reported rarely. Mainstream offers for ammonium paratungstate (APT) hovered around $278/mtu. Factories worried about the risk of price inversion and some of them stopped quoting. For the tungsten powder market, some suppliers made offers up to $38.1/kg, but actual deals concluded at about $37.5/kg. 

In the short term, as domestic epidemic has been affectively contained, the economic recovery and the release of domestic demand are relatively optimistic, plus with the increase in production and operation costs of raw materials, labor, logistics and freight, environmental protection and others, participants have good expect for the outlook.

Prices of tungsten products on July 12, 2021

Picture of tungsten acid 

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