Positron emission tomography (PET) is one of the nuclear medicine techniques availablefor diagnosis.Whilst X-rays provide information on the structure of the body, PET shows the chemical function of a particular organism.  PET involves the injection of FDG (aglucose-based radio nuclide) from a shielded syringe into the patient. As the FDG travels through the patient's body it emits gamma radiation, which is detected by a gamma camera, from which the chemical activity within cells and organs can be seen. Any abnormal chemical activity may be a sign that tumours are present.

Tungsten alloy is ideal for shielding against both X- 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 the effectiveness of the shielding characteristics.

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There are two forms of WC, a hexagonal form, α-WC (hP2, space group P6m2, No. 187), and a cubic high-temperature form, β-WC, which has the rock salt structure. The hexagonal form can be visualized as made up of hexagonally close packed layers of metal atoms with layers lying directly over one another, with carbon atoms filling half the interstices giving both tungsten and carbon a regular trigonal prismatic, 6 coordination. From the unit cell dimensions the following bond lengths can be determined; the distance between the tungsten atoms in a hexagonally packed layer is 291 pm, the shortest distance between tungsten atoms in adjoining layers is 284 pm, and the tungsten carbon bond length is 220 pm. The tungsten-carbon bond length is therefore comparable to the single bond in W(CH3)6 (218 pm) in which there is strongly distorted trigonal prismatic coordination of tungsten.

Molecular WC has been investigated and this gas phase species has a bond length of 171 pm for 184W12C.


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Making spectrographic chemical analysis of tungsten carbide ball can be difficult and uncertain,  so the accepted procedure is to use a magnetic permascopic evaluation.

The same exactness of chemistry and physical properties in tungsten carbide ball that are experienced with alloy metals cannot be expected, as T.C. is made from a physical mixture of a pure metal powder and a powdered ceramic. There will naturally be more variability in performance.


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The tungsten carbide powder and powdered cobalt metal are mechanically mixed to form a uniform combination. To this combination is added a polymer or wax that acts as a mechanical binder in the pre-sintered stage. A carefully measured volume of this combined powder is compressed by a double acting press to form the tungsten carbide ball blank, or pre-form. The binder is removed by placing the preformed parts in a vacuum chamber and raising the temperature. The binder out gasses and is trapped down stream as a liquid.

Next, the combined tungsten carbide and cobalt pre-forms are sintered or fused into a solid mass by heating them to a high temperature in a vacuum or hydrogen atmosphere furnace.

Some tungsten carbide ball sizes are Hot Isocratic Pressed or hipped. The newest procedure is to Sinter-HIP the parts in a single operation. Using micro size diamond dust, they are then finished lapped and polished to final size and microinch roundness with a sub-microinch surface finish.


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Tungsten Carbide is neither a metal nor is it a ceramic. It is a cermetal although this isn't a widely used term. This is a combination of a large percentage of Tungsten Carbide ceramic particles bonded together by a small percentage of a metallic binder, to form a solid mass.

Tungsten Carbide is extremely stiff, with a Young's modulus of elasticity of 98,000,000 pounds per square inch, compared with steel at 30,000,000 PSI. This high stiffness makes cemented tungsten carbide balls a good choice for ball-sizing and they provide premier results as components of kinematic couplings.


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Tungsten carbide ball material is an incredible material. It was originally developed for use as a cutting tool, in machine tools applications, where it still finds wide use today.

It is extremely hard at 91 HRA which is equivalent to 1500 Vickers 30. This material is very wear resistant, with some abrasion tests showing it at 30 times hard steel. It has good long-term dimensional stability, which makes a good material for gage applications.


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Tungsten alloys are generally used by aerospace designers for balancing components or reducing vibration. The high density of tunsten alloys materials allows maximum sensitivity from optimum mass and is particularly valuable in situations where a large mass has to be contained in a confined space.

Examples of applications where tungsten alloys have been used include:

Components such as ailerons, flaps, rudders and elevators are fitted with counterweights to optimize their performance.

Trim weights are used to achieve final balance in an individual component, assembly or complete aircraft.


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The density and strength of tungsten alloys make them the first choice for radiation shielding applications.Their energy-absorbing qualities are excellent choices to protect sensitive electronic equipment, as well as delicate human tissue.

Tungsten alloys are used for radioactive source containers, gamma radiography, syringe shields, oncology treatment systems and oncology instruments. Tungsten alloys provide unsurpassed strength, control and protection.

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Precision-made tungsten parts and high-density tungsten alloys are used in a variety of applications, from multi leaf collimators and medical isotope production, transport and containment to radiation shielding materials, syringe shields, lead shielding replacement parts, and oncology treatment systems and instruments.

Tungsten alloys are used in a variety of diagnostic and therapeutic medical technologies. High-density alloys for multileaf collimators are used to comprise the individual leaves, which can move independently in and out of the path of a particle beam. This crucial device directs a beam and focuses radiotherapy treatment to precisely conformed shapes, delivering correct therapy doses to patients. Multileaf collimators are widely used in radiology departments and are an integral part of radiotherapy.


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Heated tungsten
A heated filament made from the metal tungsten. Much in the way that an incandescent lightbulb works, the high voltage that is fed through the filament causes electrons to be kicked off the filament. The amount of energy required is known as the work function.

Lanthanum hexaboride (LaB₆)
The LaB₆ filament is also a thermal filament. However, its work function is lower than for a tungsten filament, so it is more efficient.

Tungsten field emission gun (FEG)
The FEG gun is not a thermal filament. Instead, electrons are expelled by applying a very powerful electric field very close to the filament tip. The size and proximity of the electric field to the electron reservoir in the filament causes the electrons to tunnel out of the reservoir.

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