TM-89 Determination of Aluminum Oxide in High Friction Surface Treatments (HFST)

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Scope. This method tests High Friction Surface Treatments (HFST) by analytical and instrumental analysis to determine Al2O3 by difference.

Summary of Method. Two samples of similar weight are fused in separate graphite crucibles containing lithium meta-borate and the fused pellets from each crucible are transferred to a 1:24 HNO3 solution. The solution is brought to volume and analyzed on an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) for major and minor oxides, except Al2O3. An aliquot is taken from solution and ammonium hydroxide (NH4OH) plus methyl red are added. Aluminum, silicon, iron, phosphorus and titanium are precipitated out of solution, boiled on a hot plate, filtered and ignited in a 1000° C muffle furnace. It is cooled, weighed and recorded. The final weight is divided by the initial aliquot weight and % recovery is determined. The major and minor oxides from the ICP analysis are subtracted from the % recovered and the difference is Al2O3.

Equipment and Reagents

1. Glass beaker, 250 ml

2. Nitric Acid (HNO3), trace metal grade

3. Deionized water, generated through reverse osmosis system

4. Ammonium Hydroxide (NH4OH), certified ACS Grade

5. Methyl red indicator (0.2 gram) dissolved in 100 ml 95% ethanol

6. Filter paper, rapid filtering, #41 or equivalent

7. Graphite crucibles, 8 ml capacity

8. Clear plastic beaker (polypropylene), 400 ml capacity

9. Magnetic stir bar, length of bar should be 1/2" shorter than the inside diameter of the beaker

10. Lithium Meta-borate (LiBO2), reagent grade, anhydrous

11. Yttrium Stock Solution, 1000 ppm

12. Platinum crucible, 15 ml capacity

13. Filter funnel

14. Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), capable of internal standard correction.

15. Muffle furnace, 1000° C capability

Procedure. Add 1/4 teaspoon of LiBO2 to 2 graphite crucibles and using a test tube, with approximately the same inner diameter of the crucible, press down to make a bed at the bottom of the crucible. Weigh 0.1000 g +/- .0005 g into each graphite crucible and cover the sample with a 1/4 teaspoon of LiBO2. Using tongs, place crucibles into a pre-heated 1000° C muffle furnace for 30 minutes. Add 150 milliliters of 1:24 HNO3 to a 400 ml capacity clear plastic Polypropylene beaker. After 30 minutes in muffle furnace, remove first graphite crucible and transfer the fused pellet into the 150 ml 1:24 HNO3. Remove second crucible and transfer the fused pellet into the same 150 ml 1:24 HNO3. Stir for at least 10 minutes and filter through a #41 filter paper into a 200 ml volumetric flask containing 1 ml yttrium. Dilute to volume.

Analyze on the ICP-OES for SiO2, Fe2O3, P2O5 and TiO2 using the aggregate test template set-up with applicable calibration standards. Other oxides such as Ca, Mg, Na, K, Zn, Mn, Ba, Sr and Cr will also be determined during the run.

Take a 50 ml aliquot (0.05 gram) from the 200 ml volumetric flask and transfer to a 250 ml beaker. Add 3 drops of methyl red indictor solution. Add NH4OH drop-wise to the beaker until the solution turns yellow. Place watch glass over beaker and boil on hot plate for 60 seconds and let precipitate settle for no more than 5 minutes. Si, Fe, Al, P and Ti will precipitate out of solution. Filter through a #40 filter and wash with hot 20 grams ammonium nitrate per 1 liter of deionized water. Wipe inside the beaker with a folded #40 filter paper and transfer to filter containing precipitates. Transfer to a pre-weighed platinum crucible and ignite to 1000° C for 2 hours. Remove the crucible, cool, weigh and record. Divide the final recovered weight against the initial weight (0.05 gram) and calculate % recovery. Subtract SiO2, Fe2O3, P2O5, TiO2 and any other detected oxides (ICP-OES analysis) from recovered weight and this will yield the % Al2O3 by difference.

Note: Make sure to run a QC standard concurrently with the sample to verify validity of results.