while foams of silicon carbide can be used very advantageously as a temperature-resistant and corrosionresistant insulating material and filter material or catalyst support. Pipes, crucibles, bricks or the like of these mixtures are suitable for use as high temperature materials because of their good chemical resistance.

Silicon carbide continuous filaments can be manufactured in accordance with a known process by exposing a carbon filament, manufactured according to conventional processes, to a silicon tetrachloride gas atmosphere at 800 1,200C (U.S. Pat. No. 3,433,725). According to a further known process, silicon carbide continuous filaments are obtained by coating a thin tungsten filament with silicon carbide, which is formed on the tungsten surface, kept at 1,200 to 1,300C, by pyrolysis of methyldichlorosilane (F. Galasso, et al., Appl. Phys. Lett. 9 (1966) 37). The disadvantage of these processes is that relatively thick silicon carbide fibers result which are difficult to handle, and their high manufacturing cost prevents a broad application.

Shaped articles such as, for example, pipes, crucibles or bricks can be manufactured according to known processes by sintering pulverulent silicon carbide, with addition of silicon powder, in appropriate molds, in most cases with the use of high pressures and temperatures, in the presence of nitrogen. In these cases, the silicon nitride formed acts as a sintering aid.

It is furthermore known to manufacture silicon carbide coatings on suitable shaped articles by pyrolysis of a mixture of slicon tetrachloride, toluene and hydrogen (K. Moers, Z. anorg. allg. Chem. 198 (1931) 243).

Foams of silicon carbide can be manufactured according to the process of U.S. Pat. No. 3,100,688, by reacting a mixture of finely divided silicon dust and carbon dust with dilute hydrofluoroic acid and heating the foam thereby formed, after drying, to a temperature of between l,400 and 2,200C under an inert gas.

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Black SiC is a man made mineral with a high thermal conductivity rating of 100 W/m-K. It is extremely hard, around a Mohs 9.1 or 2550 Knoop. It has high strength at elevated temperatures. For example, at 1000oC, SiC is 7.5 times stronger than Al203 (aluminum oxide). Black SiC will contain some free silicon and carbon and thus is not as pure as green SiC. Black will range in purity from 97-99% pure, depending on grit size. Green SiC is made from Silica sand and coke, and is extremely pure. Hexagonally shaped, it breaks into very sharp particles. Our green SiC is 99.5% pure, exceeding JIS, ISO, & FEPA standards.

Green SiC is harder than black, coming in at a 9.4 Mohs and 2600 on the Knoop scale. Green is often the media of choice when it comes wire sawing. The micronization process of manufacturing our green SiC is controlled by a computer. Then the material is water classified/separated - this produces a very tight particle size distribution, as well as a reduction in fines, as preferred for accurate wire sawing applications. Unless your application requires an extremely pure SiC, by default, black is preferred due to its more economic pricing.

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Compared to traditional radiation shielding materials, tungsten alloys provide excellent value. A high-density alloy can provide the same energy absorption as lead using 1/3 less material! Unlike lead, you’ll also reduce administration costs by eliminating the need to obtain special licensing—it’s not required.

Experts find that radiation exposure could be reduced by maxing shielding. The density of a material is related to its radiation stopping ability. Higher density means better stopping power and shielding. Due to a higher density, tungsten alloy has a much higher stopping power than lead. It is greater linear attenuation of gamma radiations means that less is required for equal shielding. Alternatively equal amounts of tungsten alloy shielding provide diminished exposure risks than equivalent lead shielding.

Tungsten alloy is a suitable raw material for radiation protection, as its combination of radiographic density (more than 60% denser than lead), machinability, good corrosion resistance, high radiation absorption (superior to lead), simplified life cycle and high strength. It can provide the same degree of protection as lead whilst significantly reducing the overall volume and thickness of shields and containers. Besides, compared with lead or depleted uranium in the past, tungsten alloy is more acceptable in this case, for they are non-toxic.

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Tungsten alloy is ideal for shielding against X-rays and gamma radiation. The very high density of tungsten shielding (more than 60% denser than lead) allows a reduction in the physical size of shielding components, without compromising their rigidity or the effectiveness of the shielding characteristics.

Whether you need to protect sensitive electronic equipment or delicate human tissue, the energy-absorbing properties of T&D’s tungsten alloys make them exceptional choices for radiation shielding applications, in both medical and industrial settings.

1) Shielding in medical

multi leaf collimator

shielding protection tank for medical radiation

shielding syringe for liquid medicine radiation

tungsten alloy containers, such as tank, box for storing radioactive materials

autocollimator and tungsten collimation bar for medical lineal accelerator, nuclear industry and container system inspection

shielding for Co60 and other radiation

gamma radiography shield

2) Shielding in industry

shielding block

flaw detector

large container inspection devices

radioactive source containers

Nuclear shielding wall etc.

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Tungsten alloy is used in many radiation-shielding applications including industrial, nuclear and medical.

Tungsten alloy is used in many radiation-shielding applications including industrial, nuclear and medical. Because of its high density and high atomic number, is an effective construction material for shielding against gamma rays and x-rays. Lead and boron carbide can shield radiation too, but cannot perform as well as tungsten alloy.

Tungsten alloy is a suitable raw material for tungsten alloy radiation container, because of tungsten alloy radiation container combination of radiographic density (more than 60% denser than lead), good machinability, good corrosion resistance, high radiation absorption (superior to lead), simplified life cycle and high strength. Tungsten alloy radiation shielding can provide the same degree of protection as lead whilst significantly reducing the overall volume and thickness of shields and containers. Moreover, compared with lead or depleted uranium, tungsten alloy is more acceptable in this case, for it is non-toxic and environmentally friendly material.

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Tungsten alloys is a best choices for radiation shielding applications, in both medical and industrial settings. Compared to traditional radiation shielding materials, tungsten alloys radiation shielding provide excellent value. A high-density alloy can provide the same energy absorption as lead using 1/3 less material. People are taking advantage of tungsten alloy's reliable radiation shielding properties.

Our tungsten alloys radiation shields are used for radioactive source containers, gamma radiography, shields, and industrial instrumentation. The radiation shielding is also serving as collimators and radiation shielding in cancer therapy, as well as syringe protection for radioactive injections.

The usage of tungsten alloy in radiation protection is not subject to NRC, EPA, or special OSHA regulations, so it has been widely used, such as:

Tungsten alloy radioactive source containers

gamma radiation shielding made by tungsten alloy
    
Shielding block of tungsten alloy
   
Source holders for oil well logging and industrial instrumentation
    
Tungsten alloy X-ray collimators
    
Tungsten alloy PET syringe shield
    
Shielding in cancer therapy machines
    
Syringe protection for radioactive injections
    
Tungsten alloy syringe shielding
    
Nuclear shielding wall
    
FDG container
    
Inspect welds
    
Nuclear testing equipment
    
Nuclear power plant shielding
    
Radiation shielding barrel
    
Isotope production, transport, and containment
    
Personal protection equipment for emergency responders
    
Large container inspection devices
    
Oncology Isotopic and accelerator based platforms
    
Pipe-line inspection Gamma
    
Defense for nuclear submarines

Tungsten Alloy Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-alloy.com
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Why we need tungsten alloy radiation shielding?

As medical science developing so repaid, there is more and more radiation in our life, which has become a new trouble, such as X-ray radiation, gamma radiation (energetic electromagnetic radiation), radiation of alpha particles (helium atoms) beta particles (electrons) and cosmic radiation, etc.

In order to protect patients and other people safe from harmful effects of ionizing radiation, such as breast cancer, skin cancer, etc. One type of excellent radiation-absorbing medium is badly needed.

Advantages of tungsten alloy radiation shielding

Experts find that radiation exposure could be reduced by maxing shielding. The density of a material is related to its radiation stopping ability. Higher density means better stopping power and shielding. Due to a higher density, tungsten alloy has a much higher stopping power than lead. Its greater linear attenuation of gamma radiations means that less is required for equal shielding. Alternatively equal amounts of tungsten alloy shielding provide diminished exposure risks than equivalent lead shielding.

Tungsten alloy is a suitable raw material for radiation protection, as its combination of radiographic density (more than 60% denser than lead), machinability, good corrosion resistance, high radiation absorption (superior to lead), simplified life cycle and high strength. It can provide the same degree of protection as lead whilst significantly reducing the overall volume and thickness of shields and containers. Besides, compared with lead or depleted uranium in the past, tungsten alloy is more acceptable in this case, for they are non-toxic.
 

Tungsten Alloy Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-alloy.com
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Whether you need to protect sensitive electronic equipment or delicate human tissue, the energy-absorbing properties of Mi-Tech Metals’ tungsten alloys make them exceptional choices for radiation shielding applications, in both medical and industrial settings.

Our tungsten alloys are used for radioactive source containers, gamma radiography, shields, and source holders for oil-well, logging, and industrial instrumentation. High-density alloys also serve as collimators and radiation shielding in cancer therapy, as well as syringe protection for radioactive injections. When you need to direct a specific amount of radiation to a targeted area, tungsten alloys provide the control you need. Mi-Tech Metals’ high-density alloys will continue to perform, even under extreme, high-heat conditions.

Compared to traditional radiation shielding materials, tungsten alloys provide excellent value. A high-density alloy can provide the same energy absorption as lead using 1/3 less material! Unlike lead, you’ll also reduce administration costs by eliminating the need to obtain special licensing—it’s not required.

Clients all across the globe are taking advantage of tungsten alloy’s reliable radiation shielding properties. If you need to protect yourself, your patients or your equipment from the harmful effects of excess radiation, call a Mi-Tech Metal professional to discuss the benefits of our high density metals today.
 

Explores the tungsten rhenium thermocouples thermoelectric air at high temperature stability, regularity conclusions drawn as follows:

(1) Tungsten rhenium thermocouple in the air, due to high temperature oxidation, causing mutations cause thermocouple thermoelectric power failure. Among them, at 1000 ℃, thermopower negative drift occurs; 800 ℃ and 900 ℃, thermopower positive drift occurs.

(2) Tungsten-rhenium thermocouples stability of each pole is different: 1000 ℃ positive instability occurs first thermopower negative drift; 800 ℃ and 900 ℃, the negative instability occurs first thermopower negative drift.

(3) Tungsten-rhenium thermocouples thermal emf sudden failure reasons, not due to selective oxidation of alloying elements, but because of a pole alloy wire is completely oxidized to oxides, the nature of the material has undergone a fundamental change. 1000 ℃, because of its positive completely oxidized tungsten rhenium thermocouples cause sudden failure; 800 ℃ and 900 ℃, it is negative.

(4) Tungsten-rhenium thermocouples sudden failure, thermoelectric power and volume resistivity of both mutations. Thus, the resistance measurement can predict its life.

(5) After failure of tungsten rhenium thermocouple thermoelectric power is still the illusion, which is its oxidation products with high conductivity rhenium oxide sake.


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A Tungsten Rhenium Thermocouples Positive and Negative Comparative Stability

Tungsten- rhenium thermocouple in the air oxidation will occur after a certain time thermopower mutation to constitute the positive and negative tungsten -3% -25 % rhenium and tungsten rhenium alloy oxidation rate is different. Which can be expected, the stability of the thermocouple will they produce different effects . It can be seen from Figure 1 : Tungsten rhenium thermocouples having different stability of positive and negative . 1000 ℃, tungsten rhenium 3 pole poor stability, thermopower mutation first occurred , and tungsten rhenium 25 very good stability , a later mutates. Stability of the positive and negative differences are two kinds of tungsten and rhenium alloy oxidation behavior consistent . 800,900 ℃ , with the decrease in the content of rhenium , tungsten rhenium alloy antioxidant capacity enhancement. -3% Tungsten rhenium relatively good adhesion due to the formation of a layered structure oxide film having less than 25% of rhenium, tungsten corrosion rate ; 1000 ℃ , the rhenium content is higher, the stronger the oxidation resistance of alloys . As a result of 25% tungsten, rhenium oxide layer formed by reaction sintering of the oxide film layer structure , the outer layer is less rich tungsten rhenium oxide thin , inner layer is a dense tungsten , rhenium oxide mixed layer , relative to the base ratio, rhenium has enriched . Reaction sintering the oxide film becomes more dense , increased to 25% of tungsten rhenium at 1000 ℃ antioxidant capacity , the corrosion rate is lower than -3% of tungsten rhenium . Therefore , tungsten rhenium 3 pole less stable at 1000 ℃ , the first occurrence of thermopower mutations. Therefore, positive and negative changes in the sequence of stability is a direct reflection of the level of oxidation rate .

2 . Tungsten rhenium thermocouple thermoelectric power thermoelectric mutation causes

Positive and negative relative stability during the experiment at the same time , using two 0.8 mm nickel chromium wire 2cm long were suspended tungsten -3 % -25 % tungsten, rhenium and rhenium alloy wire of a group, working with the thermocouple placed on the same side of the temperature zone 1000 ℃ , when mutations occur when the first thermoelectric take a set of samples , the second mutation then remove another set of samples , respectively, electron microprobe analysis . The results show that : the first time thermopower mutation , -3% tungsten rhenium alloy anode has been completely oxidized, and the negative -25 % tungsten rhenium alloy wire core part still alloy phase . The second thermoelectric mutated, it is also negative alloy phase has been fully oxidized [1] . Thus , tungsten rhenium thermocouple thermoelectric power is due to the positive and negative mutations caused by oxidation .

To further confirm this phenomenon, making the overall stability test thermocouple , remove mutations moment thermocouple, will end its work made ​​metallographic sample . Based on our 1000 ℃ tungsten rhenium thermocouple potential mutations just occurred working end time by metallographic analysis of morphology , thermocouple potential mutation causes the selective oxidation of alloying elements is not caused by changes in composition , but the pole due to oxidation of a thermocouple the original tungsten rhenium alloy turned into oxides. This is a qualitative component , that is, from alloy into oxides , this phenomenon is associated with tungsten- rhenium alloy high temperature oxidation behavior consistent . Under the experimental conditions , as rhenium and tungsten oxide evaporation , resulting in the oxidation of the tungsten rhenium alloy catastrophic oxidation follows a linear law of cracking . Cracks formed during the oxidation , loose oxide layer is difficult to form the oxygen diffusion resistance, so that the oxidation reaction occurs at the metal / oxide layer interface ; since rhenium is far less than the oxygen affinity of tungsten , and their oxides generated with a more the steam thus large tungsten rhenium alloy does not occur during the oxidation of rhenium selective oxidation , the oxide layer which are made from tungsten and rhenium oxide mixture. Thus , in an oxidizing atmosphere , there is no selective oxidation caused by the diffusion of metal cations as a result of gradual change in the alloy composition . Thus, as the oxidation process proceeds, shrinking alloy wire cross-section , but the composition changed, until eventually completely oxidized into oxide , the material properties of a fundamental change , closely related thermoelectric properties also changed completely , thus tungsten- rhenium thermocouple leads thermopower mutations. Through the above experiment , the first to reveal the potential of tungsten rhenium thermocouple nature of mutations . Further, since the tungsten- rhenium alloy is generated after oxidation of rhenium oxide has a high electrical conductivity , resulting in the tungsten- rhenium thermocouple has failed circuit illusion thermopower still occurs , which would address the long outstanding problem.

3 tungsten rhenium thermocouples oxidation technology and antioxidant tungsten rhenium thermocouples

Tungsten- rhenium thermocouple thermoelectric effect in the air is the main factor unstable oxidation, and in order to replace platinum-rhodium thermocouple they can only work in an oxidizing atmosphere , so can be used as oxidation technology : ① Coating Protection Act ; ② evacuated sealed protection Act ; ③ evacuated inflatable seal protection law ; ④ filling sealing protection laws.

Coating Protection Act technically there are still some problems, and taking the time to fill or seal protection law has passed the batch test, every year at least one thousand or more antioxidant tungsten rhenium thermocouple temperature measurement for industrial furnaces . Since the protective tube for the artificial creation of tungsten- rhenium thermocouple working non-oxidizing atmosphere , resistance to oxidation of the tungsten rhenium thermocouple term stability. Author entities using patented technology to produce tungsten rhenium thermocouple type antioxidant , after sintering plant in Anshan pellet furnace ( oxidizing atmosphere ) using seven months (5000h), after removal of the test results showed that it stable performance, precision up to 1% , and can continue to use.


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