OSIST prEN 12698:2005

SLOVENSKI OSIST prEN 12698:2005

PREDSTANDARD
maj 2005
Chemical analysis of nitride bonded silicon carbide refractories
ICS 71.040.40; 81.060.10 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD
DRAFT
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2005
ICS
English version
Chemical analysis of nitride bonded silicon carbide refractories
Chemische Analyse von feuerfesten Erzeugnissen aus
nitridgebundenem Silicumcarbid
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 187.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations which
stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other language
made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12698:2005: E
worldwide for CEN national Members.

Contents Page
Foreword .3
1 Scope .4
2 Normative references.4
3 Choice of method of determination.4
4 Determination of free aluminium .5
5 Determination of total nitrogen.6
6 Determination of silicon nitride, silicon oxynitride and other phases.16
7 Determination of free silicon .19
8 Determination of free silica .19
9 Determination of carbon .21
10 Direct determination of free carbon content .24
11 Determination of silicon carbide.24
12 Determination of free alumina.25
13 Determination of β’-Sialon.26
Annex A (informative) Determination of free carbon — Hot chromic sulfuric iodic acid
method (9,2,1): Explanation for the evaluation of the different possible detection
methods.29
A.1 Coulometric detection system (Figure A,1) .29
A.2 Infrared absorption detection system .30
A.3 Conductometric detection system.31
Annex B (normative) x-ray diffraction data for the determination of β’-Sialon content.32
B.1 General .32
B.2 Theoretical peak positions and Miller indices (h, k, l) of β’-sialon for z=3. .32
B.3 Example of calculation of Z-Number for β’-sialon .33
Bibliography.37

Foreword
This document (prEN 12698:2005) has been prepared by Technical Committee CEN/TC 187
“Refractories”, the secretariat of which is held by BSI.
This document is currently submitted to the CEN Enquiry.
1 Scope
This part of EN 12698 describes the methods for the analysis of all refractory products containing nitride
bonded silicon carbide, irrespective of the Silicon carbide level. It includes details of sample preparation,
general principles of chemical analysis and detailed methods for the determination of carbon, silicon
carbide, free aluminium, free silicon, total nitrogen and oxygen.
Silicon nitride, silicon oxynitride, silicon, free silica and silicon aluminium oxynitride (sialon) can be
determined by XRD.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN ISO 21068 Chemical analysis of silicon carbide refractories
ISO 3310-1 Test sieves -- Technical requirements and testing -- Part 1: Test sieves of metal wire cloth
ISO 5022 Sampling of shaped refractories
ISO 8656 Sampling of unshaped refractories
ISO 5725 Precision of test methods — Determination of repeatability and reproducibility for a standard
test method by inter-laboratory tests
3 Choice of method of determination
A list of methods and the relevant European Standards is given in Table 1.
Table 1 — Methods and relevant European Standards
Item tested European Standard
Carbon and silicon carbide EN ISO 21068
Free silicon EN ISO 21068
Oxygen EN ISO 21068
Free aluminium EN 12698
Total nitrogen EN 12698
Silicon nitride/oxynitride, free silica EN 12698
XRD EN ISO 21068
and EN 12698
Sialon EN 12698
Free carbon EN ISO 21068
or EN 12698
Total carbon EN ISO 21068
Silicon carbide EN ISO 21068
and EN 12698
Free alumina EN 12698
Carbon and silicon carbide can be determined by evolution of carbon dioxide on combustion in a stream
of oxygen at selected temperatures. The carbon dioxide evolved can be conveniently measured
coulometrically, gravimetrically or by infra-red detection by absorption onto soda lime.
Free aluminium can be determined by evolution of hydrogen on treatment with hydrochloric acid and
measurement of the gas volume in a nitrometer. Free silicon can be determined on the same sample by
treatment with sodium hydroxide after washing by decantation.
Total nitrogen can be determined by a variety of methods.
Distinction between silicon nitride and aluminium nitride can be made by the reaction with sodium
hydroxide solution, while aluminium nitride is quantitatively decomposed in this way yielding free
ammonia, silicon nitride is unaffected.
A convenient commercial apparatus for the determination of total oxygen consists of an induction furnace
in which the sample is heated with pure carbon. Carbon dioxide and carbon monoxide are measured by
infra red absorption and the integrated signals are combined to give the total oxygen content.
Specification of many of the constituents can often be made by use of XRD techniques, e.g. free silicon,
silicon nitride, silicon oxynitride, quartz and cristobalite peaks.
4 Determination of free aluminium
4.1 Principle
The volume of hydrogen generated by the action of dilute hydrochloric acid on any free aluminium in a
sample is measured.
It is not a very specific method.
If the sample is known to contain carbonate, then the volume of hydrogen evolved is corrected for the
known carbonate present.
NOTE The free aluminium content can also be determined by evolution of hydrogen using sodium hydroxide. In
this case, the volume of hydrogen evolved shall be corrected for the known silicon content. Free iron will also evolve
hydrogen; correction shall be made for the known for the known iron content.
4.2 Reagents
Use distilled water or water which has been fully demineralized by ion exchange (de-ionized water) and
reagents of analytical grade.
4.2.1 Dilute hydrochloric acid, 1+1 by volume
4.3 Apparatus
4.3.1 Nitrometer, as used for the determination of free silicon.
4.3.2 Balance capable of reading to the nearest 0.1 mg
4.4 Procedure
Weigh 0,5000 g ± 0,0100 g of sample into a clean, dry nitrometer tube. Place a dry ignition tube also
inside the tube, and holding the nitrometer tube upright, introduce about 5 ml of dilute hydrochloric acid
into the ignition tube, using a long dropping pipette, and without letting any touch the sample.
Carefully fit the bung of the apparatus making sure of a good seal. Equalise the pressure as in the free
silicon determination and leave the 3-way tap in a position that connects the sample and graduated tube.
Tip the acid out of the ignition tube onto the sample. Shake gently and allow to stand about 15 minutes.
Read off the volume after equalising the pressure. Shake gently and read again after another 5 min to
10 min. Record the final volume reading when consecutive readings are the same. Also note the
temperature and barometric pressure.
NOTE For frequent use of this method, it is recommended that a conical flask with airtight sample insert device,
e.g. a side-on positioned ground-in connection and ground-in stopper with weighing bottle (special version) is used.
The weighed sample is placed into the stopper-connected weighing bottle. The hydrochloric acid added to the flask.
After equalising of pressure, the sample powder is added to the acid by turning the stopper.
4.5 Calculation and expression of results
Correct the volume reading to the gas volume at Standard Temperature, V in ml, using the equation:
(STP)
(P − ρ) 273
V = V ⋅ ⋅ (1)
(STP) 1
760 (273 +T )
where
V is the measured volume, in ml;
P is the atmospheric pressure at time of measurement, in mPa;
ρ is the partial pressure of water vapour at the measured temperature, in mPa;
o
T is the measured temperature, in C.
Calculate the percentage of free aluminium, A, using the equation:
(2)
A = V ⋅0,000804⋅
(STP)
m
where
m is the mass of the sample, in g.
Report the result to the nearest 0,1 %.
5 Determination of total nitrogen
5.1 Determination of total nitrogen by carrier gas fusion (CGF)
5.1.1 Principle
A sample, prepared as described in clause 5.1.4, is decomposed in a graphite crucible in a stream of
carrier gas (helium) by heating to a temperature above 2 400 ºC in a resistance furnace (electrode
furnace).
The gases released are mainly nitrogen, carbon monoxide and hydrogen. The carbon monoxide and
hydrogen are oxidized, respectively, to carbon dioxide and water and then removed by absorption.
Alternatively, oxidation may be confined to the carbon monoxide and gases other than nitrogen are
removed, for example, using a molecular sieve. The change in thermal conductivity due to the nitrogen
component is then measured.
The details of the determination procedure may vary with the type of apparatus used and it is therefore
only possible to give general instructions which can be used with any type of apparatus, whose nitrogen
content has been determined by an absolute method (see 5.2 and 5.3). Using the gas calibration, the
validity of the results shall be confirmed by analysing a reference material having a similar extraction
behaviour.
5.1.2 Reagents
Use distilled water or water which has been fully demineralized by ion exchange (de-ionized water) and
reagents of analytical grade.
5.1.2.1 Helium, having a minimum purity of 99,99 %.
5.1.2.2 Nitrogen, having a minimum of 99,99 %.
5.1.2.3 Catalysts, such as copper oxide.
5.1.2.4 Sorption agents for removing water vapour and carbon dioxide, e.g. magnesium perchlorate,
sodium hydroxide on a support, or a molecular sieve.
5.1.3 Apparatus
5.1.3.1 Commercially available apparatus consisting of a resistance furnace and a measuring unit for the
determination of nitrogen in a stream of carrier gas using a thermal conductivity cell. An example of a
suitable apparatus is given in Figure 1.

Key
1. Resistance furnace
2. Apparatus for oxidizing carbon monoxide and hydrogen
3. Carbon dioxide and water vapour absorption tubes
4. Thermal conductivity cell
Figure 1 — Gas flow diagram for the determination of total nitrogen by carrier gas fusion

5.1.3.2 Analytical balance capable of measuring to the nearest 0,01 mg.
5.1.3.3 Graphite crucibles having approximately the same electrical resistance. The crucibles shall
contain only extremely small amounts of nitrogen which can be removed by degassing.
5.1.4 Sampling
Sample shaped and unshaped products using the procedures given in ISO 5022 and ISO 8656
respectively.
In samplin
...