SCIMED™ Brand Diamond Anvils

The very finest diamond anvils for use in a diamond anvil cell

Introduction:
Diamond anvil cells are used worldwide for the study and characterization of materials, which could be in solid, liquid or gaseous form, under high pressure (up to GPa range) and in excess of 1000°C. The typical diamond anvil cell has the provision for conducting a wide range of diffraction and spectroscopy as well as microscopy measurements. For example, one can expose samples while in the high pressure environment to electromagnetic radiation in the x-ray, IR, visible, or UV ranges. A wide range of electrical measurements are also possible while the sample is under high pressure.

While the cell itself is made of typically not "high pressure" materials, such as stainless steel, the high pressure is produced by magnifying applied forces through the "diamond anvils". And as one might expect, the quality of the end results depends to a large degree on the quality of the diamond itself, not just in terms of the diamond quality (e.g. clarity, freedom from occlusions, faceting) but also on the precision of the manufacturing of the anvils.

Who uses diamond anvil cells and diamond anvils:
The short answer: Just about anyone who has the need or interest in knowing how something behaves under high pressure. For example, there are numerous applications in the geological sciences where one wants to look at high pressure phase transformations, crystallography, melting points, equations of state, etc. Polymer researchers want to better understand the behavior of various polymers under pressure and the effects of high pressure when crystallized under high pressure. There is a growing number of researchers wanting to better understand the crystallization of materials under high pressure such as in the chemical, pharmaceutical and inorganic areas. With the use of synchrotron x-rays, one can impinge the beam through the diamond anvil cell for the characterization of the material under pressure. Researchers conducting Raman scattering studies need the kind of properties in an anvil that can be delivered only with high quality natural diamond.

Producers of the diamond anvil cells:
Many diamond anvil cells were actually built by researchers, perhaps in the past before there were commercial sources for the finished cells. Today, there are several firms, one being SCIMED, who manufacture diamond anvil cells. Because the "industry" of diamond cell users got started around "custom made" equipment, there was a proliferation of the types of diamond anvils used, and consequently, when a diamond anvil set has to be replaced, it becomes a relatively expensive one-off kind of production undertaking. In order to reduce the cost to the end user customer, we have attempted to offer a "short list" of standard "off-the-shelf" products and since they are being produced in quantity (relative to the one-off sizes and shapes), their prices are noticeably lower.

How diamond anvils fail:
The principal mode of failure is the result of misalignment of the anvils. When there is misalignment, such a failure results in the shattering of the diamond into a fine powder. Experienced users rarely experience such misalignment failures. We make the further point that most misalignment failures today involve newcomers to the field of diamond anvil cell research.

Another major cause of misalignment of the diamond anvils can be traced straight back to the quality of the diamond itself. For example, if the symmetry of the cut is not within specified tolerances, the changes of failure are greatly increased. A lower quality diamond with inclusions, which result in unacceptable stress gradients and stress lines can almost always result in an anvil failure.

Why is the presence of birefringence in the diamond not acceptable?
The presence of birefringence indicates optical anisotropies within the diamond lattice, and which is an indication of internal stresses within the diamond. Most but not all diamonds do exhibit birefringence, and therefore, most diamonds do exhibit some internal stresses. The point is that some diamonds have more internal stresses, as measured by their birefringence, than others. And consequently, SCIMED offers the diamond anvils in the "standard" level of birefringence, as well as in "low birefringence" (LB) and for the most critical of applications (e.g. involving the very highest of pressure), we offer "ultra low birefringence" (ULB) grade. As one might expect, since the diamond used in natural and the frequency of occurrence in nature is much higher for the standard birefringence, for those requiring either LB or ULB, the pricing is also higher.

Selection of the right birefringence:
This is a difficult question for us to answer. Some customers demand we supply only anvils in ULB. We also know that customers doing work at low pressures seem quite satisfied with the "standard" grade. Some customers end up with a diamond anvil that lasts literally years and years whereas other customers are purchasing 30 -40 anvils per year. Clearly, the upper limit of the pressure being used as well as the experiment itself has something to do with the lifetime of the anvil, and also the determination as to whether one requires a low or ultra low birefringence anvil or if they could do just fine with a "standard" grade anvil.

Fluorescence of the diamond:
Lattice mismatches, when combined with impurities, within the diamond give rise to fluorescence which for some researchers can be very undesirable (for their measurements). The standard diamond quality provided contain "standard fluorescence". In other words, they are indeed fluorescent and are at the level one comes to expect from most all natural diamonds. However, we are able to provide "low fluorescence" anvils as a special order, and of course, at a higher price. We don't believe most people need "low fluorescence" or even "ultra low fluorescence" but for those who do, they do have that option.

Type of diamonds available:
There are three types of diamonds used by SCIMED and SPI Supplies:

Natural Ia

Natural IIa

Synthetic Ib

The most commonly asked for diamond is Natural Ia. It is also lowest price of the three diamond grades. Natural Ia and IIa to the eye look the same, neither looks "yellow" but Ia contains more nitrogen than IIa. The only difference is that Natural Ia contains significantly more nitrogen than Natural IIa and this higher level of nitrogen results in absorption of the incoming electromagnetic radiation at specific wavelengths which, depending on the kind of experiment being done, may or may not be detrimental. We can of course supply anvils in Natural IIa but at a higher price relative to Natural Ia.

We can also supply the anvils in Synthetic Ib but quite frankly, the quality is perhaps not quite as good as Natural Ia but the price would be more or less comparable to that of Natural Ia.

Selection of the "Design":
The "standard" design was actually been optimized for use with high pressure, for example, the stress distribution has been optimized,. and the "conventional wisdom" says that it can be taken to higher pressures with out breaking. It is also more expensive which might explain, at least in part why roughly 70% of all customers order the "Brilliant" design and not the "standard" design. There are also some who believe that with the properly designed cell, one can take the Brilliant design to the same pressures as one could take the "standard" design. We don't have our own opinion about this point, and can only report the information as we see it and allow our customers to make their own decisions.

Custom manufacturing of diamond anvils:
We have listed as standard products the most popular sizes and geometries of diamond anvils requested by our worldwide customer base. We can of course custom manufacture just about anything you might require. Let us know what you need and we can respond with firm pricing.

Available products:

Brilliant Diamond Anvil Design

Material:	Natural Ia Diamond
Maximum diameter:	3.0 mm
Culet diameter:	0.4 mm
Height:	1.6 mm
Birefringence:	Standard
Fluorescence:	Standard
Bevel:	None
Compatible with:	D'Anvils, Diacell, SCIMED, others

SPI #	Each		In Stock
09907-AB	$ 425.00		No

Material:	Natural Ia Diamond
Maximum diameter:	4.0 mm
Culet diameter:	0.7 mm
Height:	2.2 mm
Birefringence:	Standard
Fluorescence:	Standard
Bevel:	None
Compatible with:	D'Anvils, Diacell, SCIMED, others

SPI #	Each		In Stock
09913-AB	$ 1254.00		No

Standard Diamond Anvil Design:

Material:	Natural Ia Diamond
Maximum diameter:	3.0 mm
Culet diameter:	0.3 mm
Height:	2.0 mm
Birefringence:	Standard
Fluorescence:	Standard
Bevel:	None
Compatible with:	D'Anvils, Diacell, SCIMED, others

SPI #	Each		In Stock
09920-AB	$ 1305.60		No

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