BS-6043-1.12-1994.pdf
I B S I BSxbOq3: SECr1.12 94 rn 1b24bb9 0418736 365 BRITISH STANDARD Method of sampling and test for Carbonaceous materials used in aluminium manufacture Part 1. Electrode pitch Section 1.12 Determination of mesophase content UI)C ciü9.ïl3.ï : í i G . ï ï 5 : 543.062 BS 6043 : Section 1.12 : 1994 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/06/2006 19:06:56 MSTNo reproduction or networking permitted without license from IHS -,-,- B S I BS16043: SECIL-LZ 94 m Lb24669 0438737 2 T l m was published under the Board and comes into effect on 15 June 1994 O RSI 1994 authority of the Standards Amd. No. Date The following BSI references relate to the work on this standard: Committee reference CICi24 Draft for comment 93ifio5981 DC ISBN O 580 22855 X BS 6043 : Section 1.12 : 1994 Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Chemicals Standards Policy Committee (CIC/-) to Echnical Committee CIC/24, upon which the following bodies were represented: Aluminium Federation British Ceramic Research Ltd. Chemical Industries Association Institute of Petroleum Refractories Association of Great Britain Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/06/2006 19:06:56 MSTNo reproduction or networking permitted without license from IHS -,-,- BSI BSab043: SECtL-LE! 94 W Lb24bbî 0418738 138 BS 6043 : Section 1.12 : 1994 Contents pw3e Committees responsible Inside front cover Fore word 2 Method 1 Scope 3 2 References 3 Definitions 4 Principle 5 Apparatus 6 7 Procedure 8 9 Test report Sampling and preparation of test sample Calibration and expression of results Annexes A (informative) Guidance on the polishing of pitch samples 8 B (informative) Guidance on scoring hits and half-hits 11 C (normative) Point counting 12 Figures 1 .A. 1 Satisfactory polished surface Typical microscopic appearance of mesophase particles under polarized light 3 10 A. 2 Marginally unacceptable polished surface 10 B. 1 Scoring of point-counting hits 11 List of references Inside back cover 1 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/06/2006 19:06:56 MSTNo reproduction or networking permitted without license from IHS -,-,- B S I BS*bO43: SEC*L.12 94 1624669 OY18739 07Y W BS 6043 : Section 1.12 : 1994 Foreword 2 This Section of BS 6043 has been prepared under the direction of the Chemicals Standards Policy Committee. BS 6043 provides methods of sampling and test for carbonaceous materials used in aluminium manufacture. The standard is published in four Farts, each Part being divided into Sections. Part 1 comprises a series of methods of test for electrode pitch as follows. Section 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13 Subject Sampling Wat,er content (Dean and Stark method) Softening point (ring and ball method) Content of toluene-insoluble material Content of quinoline-insoluble material Coking value Density Ash Sulfur content Volatile matter content (gas chromatographic method) C/H ratio of quinoline-insoluble material Mesophase content Sulfur content (routine method) Identical with IS0 6257 IS0 5939 IS0 5940 IS0 6376 IS0 6791 IS0 6998 IS0 8006 IS0 9055 - - Other international methods of test for electrode pitch are under consideration and, subject to approval by the United Kingdom, will be published as British Standards as they become available. It is essential to use BS 6043 : Section 1.1 in conjunction with this Section of BS 6043. This British Standard calls for the use of substances and/or procedures that may be injurious to health if adequate precautions are not taken. It refers only to technical suitability and does not absolve the user from legal obligations relating to health and safety at any stage. This standard describes a method of test only, and should not be used or quoted as a specification defining the characteristics of a product. Reference to this Section should state that the method of test used is in accordance with BS 6043 : Part 1 : Section 1.12 : 1994. Compliance with a British Standard does not of itself confer immunity from legal obligations. Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/06/2006 19:06:56 MSTNo reproduction or networking permitted without license from IHS -,-,- BSI BS*bO43: SEC*L.L2 94 m Lb24bbî 0438740 876 BS 6043 : Section 1.12 : 1994 Method 1 Scope This Section of BS 6043 describes a method for the determination of the mesophase content of electrode binder pitch by a microscopic point-counting procedure. 2 References 2.1 Normative references This Section of BS 6043 incorporates, by dated or undated reference, provisions from other publications. These normative references are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this Section of BS 6043 only when incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments. 2.2 Informative references This Section of BS 6043 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Definitions 3.1 mesophase Optically anisotropic component identifiable as essentially spherical particles of diameter approximately 1 pm or larger, in pitches which have been subjected to prolonged thermal. treatment at temperatures above approximately 350 O C . NOTE. A guide to the typical microscopic appearance of mesophase particles under polarized light is given by the photomicrograph in figure 1. Guidance is also given in annex A on the differentiation of' mesophase from other anisotropic features which may be present in pitch. 3.2 counting points Points of intersection of the lines forming the crosses in the microscope eyepiece graticule. 3.3 hit Point-counting score allocated when the microscopic image of a counting point lies wholly within the boundary of the image of a mesophase particle. 3.4 half-hit Point-counting score allocated when the microscopic image of a counting point lies exactly over the image of the boundary between a mesophase particle and the isotropic background. NCYTE. Guidance on scoring hits and half-hits during point counting is given in annex B. NOTE. Linear magnification factor 500. The feature at A is a bubble void; the feature at B is a particle of carryover coke. The numerous small dark particles standing in slight, relief are primary quinoline-insoluble matter. Figure 1. Typical microscopic appearance of mesophase particles under polarized light 3 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/06/2006 19:06:56 MSTNo reproduction or networking permitted without license from IHS -,-,- BSI BS*6043: SEC*:ii.:iiz 94 = 1624669 0438743 722 m BS 6043 : Section 1.12 : 1994 4 Principle A representative sample of the pitch is melted and cast into a block, then a vertical cross section of the block is ground and polished to produce an essentially scratch-free surface for microscopic examination. The polished surface is examined in reflected polarized light, using a microscope having a nominal magnification of approximately x 500 and equipped with a first-order red compensator and crossed or partially crossed polars. The percentage of mesophase present in the sample is determined by a point counting procedure using a 100-point graticule successively positioned at a sufficient number of randomly selected fields over the whole of the polished surface. 5 Apparatus 5,l Ordinary laboratory apparatus. 5.2 Electric oven, capable of maintaining a temperature at least 60 K above the ring and ball softening temperature of the pitch samples (see BS 6043 : Section 1.3). 5.3 Casting moulds, typically of brass and capable of producing either a cubical block of side length approximately 25 mm, or a cylindrical block of approximately 25 mm diameter and approximately 25 mm height. 5.4 Silicone grease, normal laboratory grade, for use as a lubricant to prevent adhesion of the cast pitch block to the mould (5.3). 5.5 Waterproof abrasive grinding papers, typically having a silicon carbide abrasive on a paper backing with a pressure sensitive adhesive coating on the reverse side, by means of which the papers are mounted on flat glass or metal plates. NOTE. Normally three grades of abrasive will be necessary; coarse, medium and fine, e.g. 240, 600 and 1200 grit grades. The selection of the actual grades used is at the option of the operator. 5.6 Polishing pads, typically in the form of cloth discs of approximately 150 mm diameter, having pressure-sensitive adhesive backs and a velvet-like surface designed for use with alumina or diamond polishing compounds (5.7). The pads should be mounted on flat glass or metal plates. 5.7 Polishing compounds, typically alumina powders in a non-aggregating form, e.g. as dry powders or as aqueous pastes or suspensions. NOTE. The grades of polishing compounds used will depend on the preference of the operator, but typically two grades will be required, one a fast-cutting compound of about 3 p m to 5 pm average particle size for lapping and preliminary polishing, and a second of about 0.05 pm average particle size for finai polishing. 5.8 Plane lap, typically of metal or glass, for producing a flat, smooth surface on the ground pitch specimen prior to polishing. 5.9 Lubricant, for use during the grinding and polishing operations to minimize scratching of the surface of the specimen due to aggregation of the pitch particles produced. The lubricant shall be compatible with the polishing compounds (5.7). NOTE. For dry powders a 1 '%, (mim) aqueous solution of a non-ionic synthetic surfactant, e.g. polyethoxylated alkylphenol, has been found suitable. 5.10 Soft paper tissues, for removing surplus water from the specimen after the polishing process. 5.11 Binocular microscope, equipped and set up for use with reflected polarized light and fitted with a first-order red compensator and a mechanical stage having at least 30 mm movement in each of the X and Y directions. The nominal magnification of the system should typically be approximately x 500. One eyepiece of the microscope should be capable of being fitted with the counting graticule (5.12). 5.12 Counting graticule, capable of being fitted in the eyepiece of the microscope (5.11) and having a 100 counting points in the form of a 10 x 10 array within a square frame. The size of the graticule should be such that at the microscopic magnification being used the image contained within the square frame represents a square of the specimen surface of side length approximately 100 pm to 200 pm. 5.13 Stage micrometei; typically having 100 pm and 10 pm divisions, for calibrating the image area covered by the counting graticule (5.12). 5.14 Microscope slides, fitting the stage of the microscope (5.11). 5.15 Mounting medium, soft, kneadable non-creeping material for mounting the polished specimen on to the microscope slide (5.14). 5.16 Mounting press, capable of positioning the polished specimen in the mounting medium (5.15) on the microscope slide (5.14) with the polished surface uppermost and aligned parallel to the lower surface of the microscope slide (5.14). 6 Sampling and preparation of test sample Prepare a representative test sample of approximately 50 g of the pitch by the method described in clause 8 of BS 6043 : Section 1.1 1981. 4 Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Licensee=University of Hong Kong/5910986001 Not for Resale, 12/06/2006 19:06:56 MSTNo reproduction or networking permitted without license from IHS -,-,- B S I BS*bO43: SEC*L.12 74 162i.lbb9 0418742 bb7 BS 6043 : Section 1.12 : 1994 7 Procedure 7.1 Preparation of cast block Place the test sample (see clause 6) in a loosely-lidded metal or glass container of approximately 100 ml capacity and heat it in the oven (5.2) at a temperature approximately 60 K higher than the ring and ball softening point of the pitch. During the melting process stir the sample occasionally to assist the escape of any bubbles. Lightly grease the internal surfaces of the casting mould (5.3) using the silicone grease (5.4); avoid excessive use of the grease as this may subsequently cause contamination of the specimen surface during polishing. When the pitch sample is fluid and free from bubbles stir it gently with a glass rod or spatula then pour it in a steady stream to fill the mould. Allow the mould and its contents to cool to room temperature; avoid the use of rapid cooling, e.g. with cold water, as this may induce stresses resulting in cracking during the subsequent processes. 7.2 Preparation of the polished surface 7.2.1 General For point-counting purposes the polished surface shall satisfy the following criteria. a) It shall form a representative cross section of the specimen under examination. b) It shall be flat. e) It shall be as free as possible of blemishes, e.g. pits, cracks, scratches, smearing or surface deposits. These criteria may be satisfied by a variety of combinations of manual and/or mechanical grinding and polishing techniques, and the selection of particular methods is at the option of the operator provided that the end result satisfies the above criteria. The processes involved in producing a polished pitch surface can be divided into five stages as follows: a) coarse grinding to expose the required cross section; b) additional grinding stages using successively finer grades of abrasive papers to reduce the severity of the scratching of the surface of the specimen; e) lapping on a flat plate using a slurry of a fast-cutting polishing compound to remove the scratches formed in the last grinding stage and leave a flat, matt surface; d) initial polishing on a cloth pad with a slurry of a fast-cutting polishing compound to produce a rough-polished surface above which any hard particles present in the specimen stand in sl
