Part 1 : A Comparison of Three "Quarter Micron Polycrystaline Diamond" Slurries

"When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science, whatever the matter may be."
Baron William Thomson Kelvin 1883


"Quality is remembered long after the price is forgotten."

Among a series of products I have come out with for sharpening knives and honing razors, one of my products is a Polycrystaline Diamond product that is a quarter micron in size  I will announce my other products in a separate announcement. Among my diamond products I carry finer particle sizes in both monocrystaline and polycrystaline. I do not carry the monocrystaline product in the quarter micron size.Why not? Because there is an existing product of excellent quality already on the market that fills that role superbly. I could not improve upon that product and I endorse it's use. It is made by Hand American by my friend Keith. This product, along with all of his other products including half and one micron monocrystaline diamond, are of the highest quality - I use them in my knife sharpening service and they are an essential part of the products I personally use.

So for my coarsest diamond product, quarter micron, I chose to carry a quarter micron polycrystaline products. Why? Because the available products did not meet my standards of quality. For the finer sized grits, I carry both monocrystaline and polycrystaline.compounds. I believe that both have advantages and disadvantages and feel that my customers can make choices as to what best fits their technical and cost requirements.

In the first part of this study, I have had three products evaluated - mine and two of my competitors' polycrystaline diamond products. Both of these vendors describe their product as containing 'Dupont' Polycrystaline diamond in their product. They both offer a quarter micron product. Neither vendor specifies the concentration of diamonds in their product precisely referring to it as either 'heavy' or 'medium'. Both vendors advertise their product as having their particles in suspension and not requiring shaking.

My product contains 10.5 carats per 2 ounces. I know it does because I pay by the carat for my product and I specify this custom formulation. I had to have my products tested in this particle size - and smaller - to see if in fact I could make it more concentrated and still have it perform to my specifications. One of the issues of concern is particle agglutination or particles sticking together. It's why the vehicle is deionized water - no particle agglutination. My product DOES  require shaking, but as you will see all three products require shaking before use.

In addition to concentration, two other important characteristics are:

The actual particle size. What is the average particle size and how much does the particle size vary?


What the particles are actually made of - are they in fact polycrystaline diamond? Or even diamond at all.

OK so let's start at the basics. What is a carat? One carat is a fifth of a gram. It is a measure of weight. 21 carats is therefore 4.2 grams.

One ounce is 28.35 grams. Four ounces is 113.4 grams. So if you have 21 carats in four ounces, you have 4.2 grams of diamonds in 113.4 grams of water.. This is a concentration used in both Hand American diamond products and all of my products.

Here is a photograph of the Hand American product being compared to another product in this review, The photograph was taken by one of the vendors to compare products, showing an 'ours vs theirs' comparison. There was the clear implication that 'ours' was better than 'theirs' because 'ours' had a 'heavy concentration'. The third vendor's product in this review also has a creamy white consistency quite similar to this vendor's product.

This picture deserves a second look.

 What you see at the bottom of the vial on the right is 21 carats of diamonds taken after the slurry has settled for days vs an unsettled sample on the left. The 4 ounce bottle on the right is compared to the 2 ounce bottle on the left. So how many carats does the bottle on the left have? If it were the same concentration it would have half as many carats or 10.5 carats. I was curious to find out. I was curious to find this out of the other vendor in this study, but the results of the particle size determinations were so disappointing that I lost interest and didn't bother testing it. More about particle sizes in a moment.

Carat concentration can be determined by weighing a known weight of solution, drying it and weighing what remains to compute the percentage by weight. This test was done on my product and this vendor's product.

The results. My product showed 3.82% versus 1.21 % . Results were weighted to within one ten-thousandth of a gram. Put another way, the competitor's product contains almost a third (32%) as much carats as my product!

So my competitor contains 3.33 carats vs 10.5 carats of 'product' in my solution.

So to put this in perspective, going back to the above picture, the bottle on the left contains a sixth as much as the bottle on the right! Pretty amazing stuff!

So the 'white stuff' isn't diamond at all - it is the liquid suspending the 'diamonds'. The 'Heavy concentration' product actually contains a third the amount of my 2 oz bottle and a sixth the amount of the 4 oz bottle in the picture. I should be charging three times the price for my spray based on carat weight determinations alone!

So let's talk about Dupont's polycrystaline diamonds. Naturally occurring polycrystaline diamonds are exceedingly rare and expensive. Dupont in the 1970's developed a process for creating polycrystaline diamond from carbon synthetically (not a natural product). This technology was sold to another company so technically Dupont doesn't make the product any longer. The process has been refined and the resulting polycrystaline product is NOT white, but black. I have samples of this product in a liquid preparation. It is light grey in color - not white. The process involves an explosion at very high pressures for a very short duration converting the graphite to 'Dupont' polycrystaline diamond. Again this name is obsolete. Both of these vendors refer to their product as containing 'Dupont' polycrystaline diamond.

Particles - how big are they and what are they? Well it turns out that particle sizes can be measured quite accurately. Using an extremely accurate lab instrument, a laser scattering Particle Size Distribution analyzer or PSD for short, you can measure the particles in a slurry and tally them up, computing the average particle size and how many particles of each size are in the slurry. You can graph this out as a bar graph or as a curve, with the bar graph showing the amount of particles in each size category and the line showing - starting from the smallest detectable particles a cumulative total of the amount of particles. From this curve, you can show where half the particles are size wise for instance by locatiing when the line crosses 50% - or any other percentage along the curve.

Here is a PSD of my quarter micron Polycrystaline diamond product. I have this analysis of my products, including my CBN products.




Here's the details:
Mean particle size 0.22 microns (0.09 - 0.59) microns.

What does this mean? If 16000 grit is a 1 micron particle  0.22 microns is an average particle size of 73,000 grit. Quarter microns would be  64000 grit so it is within specification - actually finer.


Here is another competitor's product PSD report




This one actually has TWO humps. In all likelihood it is an impure mix of compounds.


Here's the details:
Mean particle size 20.09 microns (0.51-229) microns. Very low carat weight Polycrystaline diamond mixed with Alumina and other 'findings'. So the average particle size is 800 grit! The largest particles in the slurry are an astounding  70 grit particles !!

After seeing this, the concentration determination was pretty meaningless to bother with.


On to the last product. I had the test repeated twice to test the accuracy of the testing procedure and to be sure the sample was properly and consistently tested

Here's the details:
Mean particle size 0.37 microns (BOTH RUNS) 
Range (0.12-1.32 microns) first run, .(0.10-1.73 microns)second run.
 No more than 0.05% POLYCRYSTALINE diamond is in this product with the remainder either monocrystaline diamond or alumina!


Converting this to grits, this mean particle size is 43,000 grit.or right inbetween a quarter  (64000 grit) and half (32000 grit) micron particle.

Or to compare it to my product which is 73000 grit, 48000 grit is 1.5 times coarser ! The largest particles in this product are 2-3 times the size of the largest particles in mine.

My product is 100% polycrystaline diamond.

SUMMARY

So I presented a lot of data here comparing three products claiming to be polycrystaline diamond. I gave detailed analyses of all three products - mine, and vendors one and two. One vendor had truly horrible specifications when subjected to particle sizing distribution analysis (PSD), so much so that no further testing was performed. The second vendor's product contained less than half of one percent polycrystaline diamond with the remainder either containing either monocrystaline diamond or alumina. Given the color of the product and that neither mono or polycrystaline diamonds are white, I suspect the later although further testing is in progress to provide more detail on this point.(Stay tuned for part two). The concentration of this mix of particles in total was a third of mine and had an average particle size one and a half times larger.with the largest particles noted as large as 1.7 microns or  over 9000 grit.

So given these analyses, it is probably worth asking if any of you reading this have actually tried REAL quarter micron Polycrystaline diamond yet?

Here's a picture of my product. Each batch is given a lot number for quality assurance purposes and I put my name on my product.

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Ken