ISO 20203:2005 download.Carbonaceous materials used in the production of aluminium Calcined coke Determination of crystallite size of calcined petroleum coke by X-ray diffraction.
ISO 20203 is based on ASTM D5187-91(2002)161 published by ASTM International, 100 Barr Harbor Drive, P0 Box C700, West Conshohocken, PA 19428-2959. United States.
ASTM D5187-91(2002) was developed under the jurisdiction of ASTM Committee D02 on Petroleum Products and Lubricants as the direct responsibility of Subcommittee D02,05.OD on Petroleum Coke Sampling and Procedures, and was published in December 1991.
The crystallinity of petroleum coke, as reflected by the L( value, is a general measure of quality affecting suitability for end use and is a function of the heat treatment used.
The crystallite height is used to determine the extent of such heat treatment, for example, during calcination. The value of the L determined is not affected by coke microporosity or the presence of foreign, non- crystalline mateflals such as dedust oil.
ISO 20203 describes a test method for the determination of the mean crystallite height of a representative, pulverized sample of calcined petroleum coke by interpretation of an X-ray diffraction pattern produced through conventional X-ray scanning techniques.
It applies to carbonaceous materials used in the production of aluminium.
Calcined petroleum coke contains crystallites of different heights. This test method covers the determination of the average height of all crystallites in the sample by empirical interpretation of the X-ray diffraction pattern. The crystallite diameter (La) is not determined by this test method.
2 Terms and definitions
For the purposes of this document, the following terms, abbreviated terms and definitions apply.
crystallites
stacks of graphitic carbon platelets located parallel to one another
2.2
mean or average height of crystallites in a sample
NOTE It is expressed as a hnear dimension, in nanornetres.
2.3
h#l(002)
Miller indices of the crystalline planes of graphite corresponding to a lattice spacing (1) of O335 nm
2.4
glancing angle produced when a parallel beam of uniform X-rays impinges upon a crystalline lattice and measured by the X-ray goniometer
NOTE It is usually expressed in 2E.
3 Principle
A padted sample pulverized to less than 75 isn is subecIed to a monochromatic X-ray beam and rotated to
produce a dtffracon pattern under specifIc conditions, The ktcatlon and shape of the peak wIth kM (002) at
d = 0335 ran is used to calculate L by manual interpretation of the peak or by computer simulation.
4 Apparatus
4,1 X-ray powder dlffracton’ieler, equipped with an X-ray source set for Cu-Kci radiation. a monochromator or tiller for restricting the wavelength range, a sample holder, a radiation detector. a signal prcesaor. and readout (chart or computer memory). The diffraciometer shall be capable of rate scarwilng at lImln or incrementally step scaraling at 0,Tlslep.
4,2 Sample holders, as speofied by the manufacturer of the diffrac)omeler, that enable packing of a pulverized sample of sufficient heiit to expose a level, smooth surface to the X-ray beam
4.3 Bnquetling press, capable of generating pressures L4 to 70 MPa.
4.4 Compressible aluminum caps, used as a support for producing a bflquetted sample
4.5 Silicon or quartz sample, of reference material quality suitable for cakbralmg the diffradomeler
NOTE These materials are auaily evatiable from naborial relerence organlzabons e.g. the NalIonaI Iiwfltute of
Standards and Technology m USA.
5 Reagents and materials
Use only reagents of recognized analytical grade and only distilled waler or waler of equivalent puflty (see (1. (2j and 131 in the Btliogrephy).
5.1 Acetone.
5.2 Polyethylene glycol, approximate moleaular weight of 200.
5.3 BInding agent, prepare a solution of polyethylene glycol and acetone, so that the proportion of
polyethylene glycol In the solution, expressed as a mass fraction (w) by percentage of the total composition. le
15%, by adding 159 of polyethylene glycol 10859 of acetone
6 Sample preparation
6.1 General
For recommended practices for obtaining, handimg and preparing coke samples, refer to ISO 6375151,
Reduce and divide the gross sample to obtains laboratory analysis sample.
Divide. by rifflrng, a minimum of 1009 from Ihe laboratory analysis sample
Crush lOOg of the test sample such that 98% will pass through a 75 pm (No. 200) sieve
6.1.1 Any of the packing techniques listed In 6.2 may be used for pecking the sample Into the X-ray diffractometer specimen holder.
6.2 Packing techniques for X-ray diffraction specimen holder
6.2.1 Back-fill technique
Put the window on a glass slide (Slide 1) and transfer sufficient quantities or sample into the window, Work the sample towards the corners of the holder using a glass slide or spatula. Press down using a flat glass slide and scrape off any excess matenal. Place a glass slide (Slide 2) on top of the sample and secure with tape. Remove Slide I to expose a flat, smooth surface before inserting into the diffractometer for analysis.
6.2.2 Front-fIll technique
Place a confining ring over the round sample holder and fill the holder cavity and ring with sample. The ring will initially overfill the sample holder Work the sample into the entire cavity and ring. Scrape the excess off with a glass plate or spatula. Press down using a flat glass slide. Remove any excess material on the front face of the holder. Repress the sample with the glass slide while turning clockwise and anticlockwise. Continue until the sample Is level with the holder face. Place the sample in the diffractometer holder.
6.2.3 SIde-loading technique
Pack the sample. Clamp a glass slide over the top face to form a temporary cavity wall. With the holder in a vertical position, drift the powdered sample into the end opening. If necessary, use a cardboard pusher cut to fit the cavity, to lightly compress the sample so it will remain in the cavity. Return the holder to a horizontal position and carefully remove the glass slide. Place the sample in the diffractometer holder.
6.2.4 Briquettlng technique
Weigh out 4.0 g of the sample onto a watch glass and pipette exactly 3 ml of the binding agent onto the sample and mix thoroughly with a spatula. Place the sample under an infrared-heat lamp and allow the acetone to evaporate. Typically, about I or 2 mm will be required to eliminate the acetone odour from the sample. Break up the caked sample with a spatula and transfer to an aluminum cap whose diameter is compatible with the sample holder of the diftractometer. Place the cap In a briquetting press and press at 48 MPa, Transfer the pelletized sample to the sample holder and insert into the diffractometer for analysis.
11.2 Repeatability
The difference between successive results, by the same operator using the same apparatus under constant operating conditions on identical test materials, will, in the long run, in normal and correct operation of the test method, exceed the following value only in one case in twenty:
repeatability = O,021X where
X the average of two results. in nanometres.
11.3 Reproducibility
The difference between two single and independent results obtained by different operators working in different laboratories on Identical test materials will, in the long run, in normal and correct operation of the test method, exceed the following values only In one case in twenty:
reproducibility = o,11x where
X = the average of two results, in nanometres.
11.4 Bias
The bias of this test method has not been determined since there is no accepted reference material suitable for determining the bias for the procedure in this test method for measuring crystallinity of petroleum coke.