wdxrf

26

7

Research ArticleReceived: 5 October 2009 Revised: 4 March 2010 Accepted: 22 March 2010 Published online in Wiley Interscience: 7 May 2010

(www.interscience.com) DOI 10.1002/xrs.1258

Chemical characterisation by WD-XRFand XRD of silicon carbide-based grinding toolsM. F. Gazulla,∗ M. P. Gomez, M. Orduna and M. Rodrigo

This paper addresses the chemical characterisation of silicon carbide-based grinding tools. These are among the most widelyused grinding tools in the ceramic sector, and instruments are required that enable the grinding tool quality to be controlled,despite the considerable complexity involved in determining grinding tool chemical composition. They contain componentsof quite different nature, ranging from the silicon carbide abrasive to the resin binder. To develop the analysis method,grinding tools containing silicon carbide with different grain sizes were selected from different tile polishing stages. To developthe grinding tool characterisation method, the different measurement process steps were studied, from sample preparation,in which different milling methods (each appropriate for the relevant type of test) were used, to the optimisation of thedetermination of grinding tool components by spectroscopic and elemental analyses. For each technique, different particlesizes were used according to their needs. For elemental analysis, a sample below 150 µm was used, while for the rest of thedeterminations a sample below 60 µm was used. After milling, the crystalline phases were characterised by X-ray powderdiffraction and quantified using the Rietvel method. The different forms of carbon (organic carbon from the resin, inorganiccarbon from the carbonates and carbon from the silicon carbide) were analysed using a series of elemental analyses. The otherelements (Si, Al, Fe, Ca, Mg, Na, K, Ti, Mn, P and Cl) were determined by wavelength-dispersive X-ray fluorescence spectrometry,preparing the sample in the form of pressed pellets and fused beads. The chemical characterisation method developed wasvalidated with mixtures of reference materials, as there are no reference materials of grinding tools available. This method canbe used for quality control of silicon carbide-based grinding tools. Copyright c© 2010 John Wiley & Sons, Ltd.

Introduction

Polishing is a very important process stage in porcelain tilemanufacture, owing to the cost involved and the aesthetic andtechnical qualities it provides.[1] Porcelain tile polishing is per-formed with grinding tools that contain abrasives. The abrasivesused in the tile industry may be divided into two groups: naturalabrasives, notably corundum, quartz, diamond, emery (consistingof alumina, silicon and iron oxide) and garnet (a mixture of alkaline-earth silicates); and artificial abrasives, the most widely used beingsilicon carbide, corundum, boron carbide and artificial diamond.[2]

One of the most common ways of using abrasives in the tile in-dustry is as conglomerates of abrasives or grinding tools, i.e. form-ing a compact body of abrasive grains held together by a binder.[2]

The type of abrasive used depends basically on the type of materialto be machined. Thus, silicon carbide (SiC) is used when workingwith materials such as brass, aluminium, hard metal, glass, marbleor ceramics.[3] In general, SiC is used as abrasive in applications in-volving materials of high hardness for fine grinding and honing.[2]

In the ceramic tile sector, grinding tools are used in the tile pol-ishing stage, a stage that developed from the pursuit of aestheticqualities, seeking to imitate natural products like marble or granite,in addition to enhancing certain properties such as mechanicalstrength, resistance to chemical attack or stain resistance.[4]

Grinding tool properties and shape depend on the abrasivecomposition and grain size, binder and porosity. Conventionalgrinding tools usually contain aluminium oxide or SiC as abrasive,and a vitreous binder or resin.[5] Magnesium oxychloride is themost widely used binder owing to its low cost and simplemanufacturing process.[4]

The present paper focuses on the chemical characterisationof SiC-based grinding tools because these are among the mostwidely used grinding tools in the ceramic sector and a quality

control method is required that ensures constant quality, despitethe complexity involved in determining grinding tool chemicalcomposition.

These materials pose considerable problems for analysisbecause they contain components of very different nature, fromthe SiC abrasive itself to the resin (organic constituent).

The methods described in the literature on SiC analysis dealwith the analysis of refractory materials[6,7] or the determinationof the different forms of carbon present in SiC.[8 – 10] Other studieson powdered SiC highlight the problem of not having standardmaterials and the method of verifying the accuracy of the resultsby comparing the methods,[11] as well as impurity analysis withelectrothermal atomic absorption spectrophotometry and induc-tively coupled plasma optical emission spectrometry, particularlystressing how the sample is prepared.[12,13] There are also a seriesof standard methods of SiC analysis in various materials, such aswhen SiC is bonded with nitride, by total-carbon and free-carbonanalysis.[14] There are methods specified in Deutscher Institutfur Normung (DIN) standards for SiC phase calculation from thedetermination of total carbon and free carbon.[15] Various meth-ods, involving coulometry, gravimetry and conductimetry, aredescribed for determining free carbon[16] and total carbon.[17]

There are also different International Organization for Standardis-ation (ISO) test methods for the determination of total carbon andfree carbon by coulometry, gravimetry, conductimetry, infrared (IR)absorption, and thermoconductivity, and for the determination of

∗ Correspondence to: M. F. Gazulla, Instituto de Tecnología Ceramica,Asociacion de Investigacion de las Industrias Ceramicas, Universitat Jaume I,Castellon 12006, Spain. E-mail: [email protected]

Instituto de Tecnología Ceramica, Asociacion de Investigacion de las IndustriasCeramicas, Universitat Jaume I, Castellon 12006, Spain

X-Ray Spectrom. 2010, 39, 267–278 Copyright c© 2010 John Wiley & Sons, Ltd.

26

8

M. F. Gazulla et al.

Table 1. Selected grinding tools and abrasive grain size

Grinding tool Average grain size (µm)[16]

Grinding tool 36 525

Grinding tool 150 82

Grinding tool 280 36.5



SiC by direct methods or indirect (calculation) methods in SiCs andSiC-based refractories.[18,19]

However, no studies are reported in which all SiC-basedgrinding tool components are analysed, not even the SiC content.This study was therefore undertaken, primarily, to establish asystematic procedure for the characterisation of grinding toolsthat contain SiC, using elemental analysis, wavelength-dispersiveX-ray fluorescence spectrometry (WD-XRF), and X-ray diffraction(XRD) in order to have a rapid, simple and reliable method ofdetermining grinding tool composition and quality.

Experimental

Selection of the grinding tools

SiC-based grinding tools were selected from the differenttile polishing phases, thus involving grinding tools containingdifferent silicon carbide grain sizes. The selected grinding tools,as well as the average silicon carbide grain sizes, are detailed inTable 1.

The grinding tool number refers to the average abrasivegrain size according to the Federation of European Producersof Abrasives Products (FEPA) classification.[20] The FEPA standardsrate grinding tools in terms of average grain size as macrogrits andmicrogrits. Thus, grinding tool 36 and grinding tool 150, with alarger average grain size, belong to the macrogrit group, while the280, 600 and 1500 grinding tools belong to the microgrit group.Grain size is determined by dry sieving in the case of grinding tools

in the macrogrit group, while it is determined by sedimentation inthe microgrit group.[21]

Experimental

Different steps may be distinguished in the chemical characterisa-tion of SiC-based grinding tools, ranging from sample preparationto the determination of each grinding tool component by varioustechniques. Phase composition was analysed by XRD, while thechemical composition was determined by WD-XRF. The differ-ent forms of carbon as well as total carbon was determined byelemental analysis with a combustion furnace and IR detection.

A method of characterising SiC-based refractory bricks wasreported in a previous paper.[6] The same scheme was used in thisstudy to design a new method for analysing grinding tools thatcontain SiC as the principal abrasive. The initial approach to thisgrinding tool analysis method is schematically illustrated in Fig. 1.The different steps used in SiC-based grinding tool analysis aredescribed below.

Sample preparation

Sample preparation is critical for the determination of chemicalcomposition by WD-XRF for various reasons: on one hand, thereduction of the particle size allows the homogenisation of thesample to be analysed; on the other, a small particle size isnecessary to favour mixing with the flux and avoid the presenceof unmelted materials during bead preparation, and it is alsonecessary for pellet preparation to minimise the particle size effectin the measurement by WD-FRX. Therefore, a milling prior to theanalysis to obtain the appropriate particle size is necessary.

Grinding tools are very difficult materials to mill because of theirlow brittleness and high hardness, making sample preparationa key analysis step. The sample preparation was as follows: first,portions of the grinding tools were cut with a diamond disc; eachportion was then crushed in a jaw crusher, and subsequentlymilled. The crushing step is needed to entail the minimumcomminution required to enable the crushed fraction to be appro-priately used in the milling process, since in crushing the samplemay be contaminated by the jaw material, principally iron.[19]

Figure 1. Schematic illustration of the initial grinding tool analysis approach.

www.interscience.com/journal/xrs Copyright c© 2010 John Wiley & Sons, Ltd. X-Ray Spectrom. 2010, 39, 267–278

26

9

Chemical characterisation of grinding tools by WD-XRF and XRD

The sample was milled in a tungsten carbide ring mill for theminimum time required to obtain an optimum sample particlesize for the various determinations, since excessive milling couldoxidise SiC to SiO2. It is recommended that milling be performedfor the shortest time needed to obtain a particle size below150 µm.[15] As bead preparation needs small particle size, twomillings of the sample were necessary: first, the sample was milledto obtain a particle size below 150 µm and, subsequently, a secondmilling was carried out to obtain a particle size below 60 µm. Forthe determination of both particle sizes, the residues below 2% at150 and 60 µm were calculated by sieving the samples through150 and 60 meshes, respectively. The sample milled below 150 µmwas used for the determination of organic, inorganic and totalcarbon as well as sulfur, while the sample milled below 60 µmwas used for the determination of the crystalline phases and thechemical analysis. There was a specific milling of a fraction of thesample below 150 µm in an agate ring mill to obtain a fractionbelow 60 µm, at which the analysis of tungsten was carried out.

In addition to the oxidation problem that might occur in SiCmilling, milling in a tungsten carbide mill poses a possible samplecontamination problem: if the typical hardness values of thematerial to be analysed are compared with those of the tungstencarbide mill, SiC has a Knoop hardness of 2400 HK, while thatof tungsten carbide is 1900 HK.[3] As a result, ring wear occursand the sample is contaminated with tungsten carbide, therebymaking it necessary to correct the total carbon determination forthe amount of contamination.[19,22] This is done by analysing thetungsten concentration, there being no tungsten in the grindingtools. The resulting value is then used to determine the carbonresulting from the milling contamination, which will subsequentlyneed to be subtracted from the total carbon value.

Phase analysis

The crystalline phases in each studied grinding tool were identified,prior to WD-XRF analysis, by XRD in order to establish whetherand how much SiC was present and which admixtures might havebeen added to the grinding tools,[23] a particularly important issuefor chemical analysis.

The XRD data were obtained using a BRUKER Theta–Thetamodel D8 Advance diffractometer with Cu Kα radiation (λ =1.54183 Å). The generator settings were 45 kV and 30 mA. TheXRD data were collected in a 2θ of 5–90◦ with a step width of0.015◦ and a counting time of 1.2 s per step. A VÅNTEC-1 detectorwas used.

All the samples were measured in powder form. For this purpose,a sample milled below 60 µm was used.[24] The milled sample wasback-filled into an appropriate specimen holder for the instrumentused. The amount of specimen was just enough to underfill theholder when slightly pressed.

A quantitative phase analysis was also performed.[25,26] Datawere processed in a Rietveld refinement.[27,28] The Rietveld analysisprogram DIFFRACplus TOPAS version 4.2 was used in this study,assuming a pseudo-Voigt function to describe the peak shapes.The refinement protocol included the background, the scalefactors as well as the global-instrument, lattice, profile and textureparameters. The basic approach was to get the best diffractiondata, using, in this case, fluorite as an internal standard, identifyall the crystalline phases present in the sample and input basicstructural data for all phases. Then, the computer modelled thedata until the best fit to the experimental pattern was obtained.

WD-XRF analysis

First, pressed pellets were prepared for semi-quantitative WD-XRFanalysis of the elements present in the grinding tools, using a semi-quantitative analysis program based on fundamental parameters.On the basis of the semi-quantitative and XRD analysis, sampleswere then prepared as pellets and beads, depending on theelement to be analysed. By bead preparation, elements notsusceptible of volatilising during the process were analysed: Si, Al,Fe, Ca, Mg, K, Ti, Mn, P and W. Na and Cl are elements that, inthese materials, form phases that volatilise during the calcinationprocess because of the high temperatures involved, and thereforesample preparation was in the form of pellets.

Instrumental. Beads were prepared in a PANalytical modelPERL X’3 fusion bead preparation machine. The measurementswere made with a PANalytical model AXIOS X-ray fluorescencewavelength-dispersive spectrometer with a Rh tube, 4 kW powerand three detectors: flow gas proportional, scintillation and sealedgas. The WD-XRF measurement conditions used are given inTable 2.

Fused bead preparation. Whenever possible, sample preparationwas in the bead form as sample dilution with flux minimises thematrix effect, while the formation of a uniform glass suppressesthe influence of the mineralogical structure and the particle size.

Table 2. Measurement conditions for chemical analysis by WD-XRF

Element Line CrystalCollimator

(µm) DetectorVoltage

(kV)Intensity

(mA)Angle(2θ )

Time(s)

Si Kα InSb 111-C 550 Flow 30 100 144 799 40

Al Kα PE 002 550 Flow 30 100 144 943 40

Fe Kα LiF 200 150 Flow + sealed 60 50 57 515 20

Ca Kα LiF 200 550 Flow 30 100 113 152 16

Mg Kα PX 1 550 Flow 30 100 22 703 30

K Kα LiF 200 550 Flow 30 100 136 739 12

Ti Kα LiF 200 150 Flow + sealed 40 75 86 167 18

Mn Kα LiF 200 150 Flow + sealed 60 50 62 971 16

P Kα Ge 111 550 Flow 30 100 141 042 16

Na Kα PX 1 550 Flow 30 100 27 435 40

Cl Kα Ge 111 550 Flow 30 100 92 767 60

X-Ray Spectrom. 2010, 39, 267–278 Copyright c© 2010 John Wiley & Sons, Ltd. www.interscience.com/journal/xrs

27

0


Table 3. Chemical composition and uncertainty of the kaolin usedfor the dilutions of the samples for the analysis of Na and Cl in pellets

Kaolin used for dilution

Element Composition (wt%)

SiO2 49.8 ± 0.2

Al2O3 36.10 ± 0.15

Fe2O3 0.46 ± 0.02

CaO 0.10 ± 0.02

MgO 0.08 ± 0.01

Na2O <0.01 ± 0.01

K2O 0.45 ± 0.02

TiO2 0.14 ± 0.02

MnO <0.01 ± 0.01

P2O5 0.06 ± 0.01

Cl <0.01 ± 0.01

Loss on ignition (1025 ◦C) 12.7 ± 0.1

In a previous study,[6] it had been verified that samples witha high SiC content could not be prepared as beads. In thepresent study, it was verified that beads could be prepared whenthe SiC concentration was smaller than 10% and the particlesize was below 60 µm. Therefore, for bead preparation, the SiCconcentration and particle size needed to be below 10% and60 µm, respectively.

As a result, the sample obtained in the first milling step wasmilled again to obtain a residue below 2% at 60 µm by sieving itthrough a 60-µm mesh, as was explained in sample preparationsection. This sample with a particle size below 60 µm was used notonly for bead preparation but also for pellet preparation. For beadpreparation, the samples were weighed into a platinum crucibleand the flux (a 50 : 50 mixture of lithium metaborate and lithiumtetraborate) was added in a 1 : 10 sample/flux ratio. A 250 g l−1 so-lution of LiI from Merck was used as a bead-releasing agent, addedat a concentration of 2% of the total weight of the sample and flux.

The samples were calcined at a temperature of 1025 ◦C toeliminate volatile components, and partially oxidise the carbide,before being prepared as beads. The resulting beads then allowedSi, Al, Fe, Ca, Mg, K, Ti, Mn, P and W to be analysed. Loss on ignitionwas determined at a temperature of 1025 ◦C using a LECO modelTGA-701 thermogravimetric analyser.

Pellet preparation. Na and Cl were characterised using anuncalcined sample milled at a particle size below 60 µm, preparedas pressed pellets, weighing out 9.0000 g sample, adding 2.5 mlof a 13.7% solution of n-butyl methacrylate in acetone as a binder,mixing them in an agate mortar and forming at a pressure of100 kN in a hydraulic press.[29] Different dilutions of the sampleswere made by mixing the sample in a tungsten carbide ring millwith high-purity kaolin with controlled composition, free of theelements to be analysed, in order to obtain a matrix similar tothat of the calibration and validation standards used in the WD-XRF measurement and to minimise any possible errors due tomatrix effects. The chemical composition of the kaolin used for thedilutions, along with the uncertainty, is presented in Table 3.

WD-XRF measurement calibration and validation. QuantitativeWD-XRF chemical analysis requires the availability of referencematerials. However, since reference materials corresponding to

Table 4. Composition of the CSs for WD-FRX measurement, samplesbeing prepared as beads

Composition (wt%)

Reference material CS 1 CS 2 CS 3 CS 4 CS 5

SRM 1886a Portland Cement 4.9 1.0 15.0 10.0 3.0

BCS-CRM No 267 silica Brick 10.5 19.0 10.0 13.0 30.0

BCS-CRM No 319 Magnesite 40.0 49.0 58.0 44.7 43.8

BCS-CRM No 348 Ball Clay 43.5 30.0 – – –

SRM 70a potassium Feldspar 0.5 – – – –

CERAM AN41 China Clay – – 15.0 32.0 22.0

WO3 Merck 0.6 1.0 2.0 0.30 1.2

Table 5. Composition of the CSs for WD-FRX measurement, samplesbeing prepared as pellets

Composition (wt%)

Certified reference material CS 6 CS 7 CS 8 CS 9 CS 10

GBW03102 Kaolin 99.0 97.0 94.0 90.0 85.0

NaCl from Fluka 1.0 3.0 6.0 10.0 15.0

the types of samples being studied are commercially unavailable,reference materials were appropriately mixed in order to obtaincompositions similar to those of the samples to be analysed.

The WD-XRF measurements were calibrated and validated withthe following reference materials and chemical standards:

1. Reference materials for calibration using WD-XRF: SRM 98bPlastic Clay, BCS-CRM No 348 Ball Clay, SRM 70a PotassiumFeldspar, CAS 5 Ball Clay, CERAM AN41 China Clay, CERAM2CAS1 Ball Clay, BCS-CRM No 267 Silica Brick, GBW03102 Kaolin,BCS-CRM No 319 Magnesite, SRM 1886a Portland Cement, NaClfrom Fluka and WO3 from Fluka.

2. Reference materials for validation using WD-XRF: BCS-CRMNo. 389 High-purity Magnesite, BCS No. 394 Calcined Bauxite,EURONORM-ZRM No. 777-1 Silikastein, EURONORM-CRM No.782/1 Dolomite, GBW03123 Wollastonite, GBW03122 Kaolin,IPT-72 Sodium Feldspar, NaCl from Merck, MgCl2 from Merckand WO3 from Merck.

Table 4 shows the composition of each calibration standard (CS)for the analysis of Si, Al, Fe, Ca, Mg, K, Ti, Mn, P and W, the samplesbeing prepared as beads.

Table 5 shows the composition of each CS for the analysis of Naand Cl, the samples being prepared as pellets. The mixing of bothmaterials was done in a tungsten carbide ring mill.

Table 6 details the element concentration ranges, together withthe root mean square (RMS) values for the corresponding calibra-tion curves. The RMS value is obtained from the following equation:

RMS =

√√√√∑

(C∗ − C)2

n − p(1)

where C∗ is the theoretical concentration, C is the calculatedconcentration, n is the number of CS and p is the number ofparameters calculated from the regression (slope, ordinate at theorigin and inter-element coefficients)


27

1


Table 6. Element concentration ranges and RMS values for thecalibration curves

Element(wt%) RMS

Concentrationrange

SiO2 0.3 21.0–40.7

Al2O3 0.3 6.7–14.5

Fe2O3 0.04 2.40–2.88

CaO 0.10 2.18–11.70

MgO 0.4 36.5–52.9

K2O 0.04 0.28–1.06

TiO2 0.017 0.054–0.504

MnO 0.006 0.072–0.107

P2O5 0.008 0.001–0.032

W 0.02 0.24–1.59

Na2O 0.10 0.93–8.28

Cl 0.13 0.6–9.1

Table 7. LOQ of the elements analysed in the grinding tools

Element LOQ (wt%)

SiO2 0.1

Al2O3 0.05

Fe2O3 0.01

CaO 0.01

MgO 0.1

K2O 0.01

TiO2 0.01

MnO 0.01

P2O5 0.01

W 0.01

Na2O 0.02

Cl 0.01

The limit of quantification (LOQ) was determined from themeasurement of a sample which has 0.5 times the concentrationof the lowest calibration sample for each analyte. That samplewas measured seven times under reproducibility conditions. Incompliance with the International Union of Pure and AppliedChemistry rules, the LOQ, which expresses the ability to quantifyan analyte, is calculated from the expression:[30]

LC = 10 × s (2)

Table 7 shows the LOQ for each element calculated fromEqn (2).

Elemental analysis of organic carbon, carbon at 950 ◦C, total carbonand sulfur

Total carbon and total sulfur were determined with a LECO modelCS-200 carbon and sulfur elemental analyser, consisting of aninduction furnace that reaches temperatures of 2000 ◦C operatingin oxygen atmosphere, and CO2 and SO2 detection system withrespective IR cells.

This test simultaneously analysed all forms of carbon presentin the samples: carbon from the resin, from the SiC and from thecarbonates.

In order to determine the quantities of the different componentsin the sample, it is necessary to identify the different forms ofcarbon. Thus, at temperatures around 500 ◦C, it may be assumedthat all the carbon from the organic matter has decomposed, whichin the present case would correspond to carbon from the resin.Carbonates decompose at higher temperatures: CaCO3 between850 and 930 ◦C, MgCO3 between 650 and 730 ◦C and dolomitebetween 650 and 930 ◦C. As a result, at 950 ◦C all the carbonpresent in the sample has been analysed, except the carbon fromthe SiC since, with the technique used, without the addition of acatalyst, SiC does not decompose at temperatures below 1100 ◦C,which was determined by differential thermal analysis.

In order to determine the different forms of carbon, aninstrument is therefore required that allows the test temperatureto be modulated. Organic carbon (Corg) and carbon at 950 ◦C(Corg + Cinorg) were determined with a LECO model RC-412 carbonelemental analyser, subjecting the sample to a heating process at500 and 950 ◦C, respectively, in a tube furnace with a circulatingoxygen stream in which combustion took place. CO2 was releasedin the reaction, which was led to an IR cell.

The reference materials used to validate the determination oftotal carbon, carbon at 950 ◦C, organic carbon and sulfur aredetailed below.

1. Reference material with certified free carbon concentrations:SRM 112b Silicon Carbide.

2. Reference materials with certified total carbon concentrations:BCS-CRM 359 Nitrogen Bearing Silicon Carbide, 112b SiliconCarbide, GBW07402 Soil, and GBW07404 Soil.

3. Reference materials with certified organic carbon concentra-tions: GBW07402 Soil, GBW07403 Soil, and GBW07404 Soil.

4. Reference materials with certified sulfur concentrations:GBW07402 Soil, GBW07404 Soil, and SRM 1886a PortlandCement.

Table 8 shows the LOQ of total carbon and sulfur for CS-200analyser and the LOQ of carbon at 950 ◦C and organic carbon forRC-412 analyser, calculated from Eqn (2).

Determination of silicon carbide

The traditional gravimetric method of determining silicon carbideis a very long and tedious procedure, involving extensive handlingof the sample.[31] In this method, each sample component is madeto react with different acids until SiC is obtained just by itself.Such sample treatment can lead to errors by default or excess,depending on particle size and the other phases in the sample.[6]

SiC content in the studied grinding tools was thereforedetermined by analysis of total carbon and carbon at 950 ◦C,as set out in the consulted test standards,[14,15,18,19] in which siliconcarbide content is indirectly calculated from the result obtainedon subtracting the carbon analysed at 950 ◦C from total carbon.

Table 8. LOQ of S, Ctotal, Corg and C950 ◦C

ElementLOQ

(mg·kg−1)

S 50

Ctotal 100

Corg 100

C950 ◦C 100


27

2


Table 9. Crystalline phases identified in the studied grinding tools

Crystalline phases

Name Formula

Silicon carbide SiC

Halite NaCl

Magnesium hydroxychloride hydrate (Mg3(OH)5Cl)· 4H2O

Bassanite CaSO4(0.5·H2O)

Dolomite CaMg(CO3)2

Calcite CaCO3

Magnesite MgCO3

Periclase MgO

Talc Mg3(OH)2Si4O10

Brucite Mg(OH)2

Quartz SiO2

Corundum α-Al2O3

Sodalite Na4Cl(Al3Si3O12)

Table 10. Composition of the validation standards for WD-XRFmeasurement, samples being prepared as beads

Composition (wt%)

Reference material A B C D G H

BCS No. 389 49.9 49.9 53.7 53.2 52.0 50.1

BCS No. 394 18.7 13.5 15.5 12.1 15.6 14.2

EURONORM-ZRM Nr. 777-1 21.5 11.8 11.3 16.8 11.1 12.3

GBW03123 2.5 19.8 7.9 5.9 7.9 8.9

IPT-72 7.4 5.0 11.6 12.0 11.6 12.0

WO3 MERCK – – – – 1.8 2.5

Results

Crystalline phase analysis

The qualitative crystalline phase determination of the studiedgrinding tools is presented in Table 9.

The mineralogical analysis shows that, among other phases,these grinding tools contain magnesium oxychloride, which, asreported in the literature, is one of the most extensively usedbinders in grinding tool manufacture,[4] and silicon carbide (themost widely used abrasive in the polishing process in the ceramicsector). Other phases also appear, such as corundum, whichare added as an admixture to optimise the polishing process(enhancing grinding tool hardness and contact with the surface tobe polished), and sulfates, which increase grinding tool resistanceto water when the tools work in an aqueous medium,[23] as well assmaller quantities of calcium and magnesium carbonates, halite,talc, quartz and sodalite.

Chemical analysis

Results of the validation standards

In order to validate the WD-XRF measurements, compositionswere prepared by mixing certified reference materials. Thecomposition of each validation standard is presented in Table 10,the samples being prepared as beads.

The results obtained in the WD-XRF measurement of thevalidation standards, along with their uncertainty, are listed in

Table 11[32]; cknown was calculated from the values of the standardsused, while cexp was obtained from the measurements.

The uncertainty was calculated from the expression:

u = t × s√n

(3)

where u is measurement uncertainty with a 95% level ofconfidence, t is statistical value of Student’s-t for 95% probabilityand (n − 1) degrees of freedom and n is the number ofmeasurements of the sample.

At least three measurements were made under reproducibilityconditions.

In order to compare the results obtained with the knownvalues of the validation standards, the difference between bothwas compared with the related uncertainty, i.e. the combineduncertainty of the known and measured values, as set out in theliterature.[33]

The absolute value of the difference between the averagemeasurement value and the known value is calculated as follows:

�m = |cexp − cknown| (4)

where �m is the absolute value of the difference between themeasurement and the known value, cexp is the measured valueand cknown is the known value.

The uncertainty of �m is calculated from the uncertainty ofthe known value and the uncertainty of the measurement resultaccording to the following formula:

u�m =√

u2exp + u2

known (5)

where u�m is the combined uncertainty of the result and of theknown value, uexp is the uncertainty of the measurement resultand uknown is the uncertainty of the known value.

The expanded uncertainty U�m is obtained by multiplying u�m

by a coverage factor (k), which is usually equal to 2 and correspondsapproximately to a 95% level of confidence. Therefore,

U�m = 2 × u�m (6)

The fitness of the method was verified by comparing �m

with U�m, so that if �m ≤ U�m, there is no significant differencebetween the measurement result and the known value. The resultsof this comparison are detailed in Table 12.

The results obtained show that �m ≤ U�m is obeyed, so thatthere are no significant differences, which validates the developedmeasurement method for both the major and the minor elements.

In order to validate the WD-XRF measurement of Cl andNa, in which the sample was prepared as pellets, validationstandards were prepared by mixing different quantities of NaClwith controlled kaolin that contained none of the elements tobe analysed. To ensure mixture homogenisation, the compositionwas mixed in a tungsten carbide ring mill, after which pelletswere prepared under the same conditions as those used for thesamples. The compositions of the prepared validation standardsare detailed in Table 13 and the results obtained in the WD-XRFmeasurement of Cl and Na are given in Table 14. The comparisonof the measurement results of the validation standards with theknown value in the Cl and Na measurement are given in Table 15.


27

3


Tab

le1

1.

Resu

lts

ob

tain

edin

the

WD

-XRF

mea

sure

men

toft

he

valid

atio

nst

and

ard

s

Val

idat

ion

AB

CD

GH

stan

dar

dco

mp

on

ents

(wt%

)c k

no

wn

c exp

c kn

ow

nc e

xpc k

no

wn

c exp

c kn

ow

nc e

xpc k

no

wn

c exp

c kn

ow

nc e

xp

SiO

228

.0±

0.2

27.9

±0.

225

.7±

0.2

25.9

±0.

223

.6±

0.2

23.7

±0.

227

.9±

0.2

28.0

±0.

223

.5±

0.2

23.4

±0.

225

.3±

0.2

25.1

±0.

2

Al 2

O3

18.4

0±

0.06

18.5

±0.

113

.30

±0.

0613

.2±

0.1

16.4

0±

0.06

16.4

±0.

113

.40

±0.

0613

.3±

0.1

16.4

4±

0.06

16.4

±0.

115

.29

±0.

0615

.4±

0.1

Fe2

O3

0.59

±0.

020.

57±

0.03

0.53

±0.

020.

54±

0.03

0.53

±0.

020.

53±

0.03

0.47

±0.

020.

49±

0.03

0.53

±0.

020.

51±

0.03

0.50

±0.

020.

49±

0.03

CaO

2.48

±0.

042.

51±

0.05

9.20

±0.

059.

24±

0.10

4.44

±0.

044.

42±

0.05

3.78

±0.

043.

79±

0.05

4.40

±0.

044.

43±

0.05

4.81

±0.

044.

84±

0.05

Mg

O48

.3±

0.2

48.5

±0.

248

.4±

0.2

48.2

±0.

252

.1±

0.2

52.2

±0.

251

.6±

0.2

51.7

±0.

250

.4±

0.2

50.5

±0.

248

.6±

0.2

48.8

±0.

2

K2

O0.

15±

0.01

0.17

±0.

010.

13±

0.01

0.13

±0.

010.

21±

0.01

0.21

±0.

010.

22±

0.01

0.23

±0.

010.

21±

0.01

0.22

±0.

010.

22±

0.01

0.23

±0.

01

TiO

20.

68±

0.01

0.66

±0.

040.

48±

0.01

0.47

±0.

040.

54±

0.01

0.55

±0.

040.

46±

0.01

0.48

±0.

040.

54±

0.01

0.52

±0.

040.

51±

0.01

0.50

±0.

04

Mn

O0.

01±

0.01

0.01

±0.

010.

02±

0.01

0.02

±0.

010.

01±

0.01

0.01

±0.

010.

01±

0.01

0.01

±0.

010.

01±

0.01

0.01

±0.

010.

01±

0.01

0.01

±0.

01

P 2O

50.

12±

0.01

0.12

±0.

010.

09±

0.01

0.09

±0.

010.

16±

0.01

0.16

±0.

010.

15±

0.01

0.14

±0.

010.

16±

0.01

0.15

±0.

010.

16±

0.01

0.15

±0.

01

W–

––

––

––

–1.

43±

0.01

1.45

±0.

021.

98±

0.01

1.97

±0.

02

Nu

mb

ero

frep

licat

es:a

tle

astn

=3

inre

pro

du

cib

ility

con

dit

ion

s.


27

4


Table 12. Comparison of the measurement result of the validation standards with the known value, where �m is the difference between themeasured and the known value, and U�m is the expanded uncertainty

Validation A B C D G Hstandardcomponents (wt%) �m U�m �m U�m �m U�m �m U�m �m U�m �m U�m

SiO2 0.1 0.57 0.2 0.57 0.1 0.57 0.1 0.57 0.1 0.57 0.2 0.40

Al2O3 0.1 0.23 0.1 0.23 0 0.23 0.1 0.23 0.04 0.23 0.11 0.23

Fe2O3 0.02 0.07 0.01 0.07 0 0.07 0.02 0.07 0.02 0.07 0.01 0.07

CaO 0.03 0.13 0.04 0.22 0.02 0.22 0.01 0.13 0.03 0.13 0.03 0.13

MgO 0.2 0.57 0.2 0.57 0.1 0.57 0.1 0.57 0.1 0.57 0.2 0.57

K2O 0.02 0.03 0 0.03 0 0.03 0.01 0.028 0.01 0.03 0.01 0.03

TiO2 0.02 0.08 0.01 0.08 0.01 0.08 0.02 0.08 0.02 0.08 0.01 0.08

MnO 0 0.03 0.01 0.03 0 0.03 0 0.03 0 0.03 0 0.03

P2O5 0 0.03 0.01 0.03 0 0.03 0.01 0.03 0.01 0.03 0.01 0.03

W – – – – – – – – 0.02 0.04 0.01 0.04

Table 13. Composition of the validation standards for the WD-XRFmeasurement of Cl and Na

Composition (wt%)

Chemical standards E F

Kaolin 97 93

NaCl 3 7

Table 14. Results of the validation standards for the WD-XRFmeasurement of Cl and Na

E F

Element cknown cexp cknown cexp

Cl (wt%) 1.82 ± 0.05 1.84 ± 0.05 4.24 ± 0.05 4.31 ± 0.05

Na2O (wt%) 1.59 ± 0.05 1.64 ± 0.05 3.71 ± 0.05 3.75 ± 0.05

Number of replicates: at least n = 3 in reproducibility conditions.

Table 15. Comparison of the measurement results of the validationstandards with the known value in the Cl and Na measurement, where�m is the difference between the measured and the known value andU�m is the expanded uncertainty

E F

Element �m U� �m U�

Cl (wt%) 0.02 0.14 0.07 0.14

Na2O (wt%) 0.05 0.14 0.04 0.14

The outcomes show that �m ≤ U�m is always obeyed, so thatthere are no significant differences, which validates the developedmethod for the measurement of both Cl and Na.

The results obtained in the validation of the measurement oforganic carbon, carbon at 950 ◦C, total carbon and sulfur are givenin Table 16, where the uncertainty was calculated from Eqn (3).The outcomes of the comparison of both results, calculating theabsolute value of the difference between the measurement andthe known value (�m) and the expanded uncertainty (U�m), aredetailed in Table 17. The results show that �m ≤ U�m is obeyed,so that there are no significant differences, which validates the

developed measurement method for the determination of organiccarbon, carbon at 950 ◦C, total carbon and sulfur.

Results of the analysis of grinding tool samples

Analysis of W. In order to determine the carbon from the siliconcarbide phase, the WC concentration in the sample (resulting fromsample contamination caused by milling in the tungsten carbidering mill) needs to be determined. This was done by analysing theW concentration by WD-FRX, using this value to calculate the WCconcentration and, from this, calculating the C concentration. Theresults obtained for W, WC and C from the sample contaminationin milling are presented in Table 18.

Analysis of Si, Al, Fe, Ca, Mg, Na, K, Ti, Mn, P, S, Cl, Corg, Ctotal and C950 ◦C.Corg, Ctotal, C950 ◦C, Na, Cl and S were analysed in the uncalcinedsample, while Si, Al, Fe, Ca, Mg, K, Ti, Mn and P were analysed inthe calcined sample.

The results obtained for organic carbon, carbon at 950 ◦C, totalcarbon and carbon from the silicon carbide phase are listed inTable 19. Carbon from SiC was calculated by subtracting the valueof carbon at 950 ◦C and the value of carbon from the WC phase,caused by milling contamination, from total carbon.

The complete analysis of each sample, the value of SiO2, whichincludes all the silicon present in the sample (expressed as anoxide), comprising the silicon forming SiC and the silicon formingSiO2, is presented in Table 20.

Quantification of crystalline phases. The quantitative analysis ofcrystalline phases was performed using the Rietveld method.

However, it was not possible to obtain resolved structuresof magnesium oxychloride and sodalite phases for refinementusing the Rietveld approach. To solve this problem, all sampleswere mixed with a known concentration of fluorite, used asan internal standard. This allowed determining the percentagecorresponding to the sum of these crystalline phases. With thehelp of the chemical analysis, the concentration of these crystallinephases was determined separately.

The validation of the quantification of the other compoundswas carried out by preparing mixtures of known concentration ofsilicon carbide, halite, talc, quartz and corundum and processingthem as had been done for the samples.

Good adjustment factors were obtained in all cases.


27

5


Tab

le1

6.

Resu

lts

ob

tain

edin

the

det

erm

inat

ion

ofo

rgan

icca

rbo

n,c

arb

on

at95

0◦ C

,to

talc

arb

on

and

sulfu

ro

fth

ean

alys

edre

fere

nce

mat

eria

ls

SRM

112b

GB

W07

404

BC

S-C

RMN

o.3

59G

BW

0740

2SR

M18

86a

Co

nce

ntr

atio

n(w

t%)

Co

nce

ntr

atio

n(w

t%)

Co

nce

ntr

atio

n(w

t%)

Co

nce

ntr

atio

n(w

t%)

Co

nce

ntr

atio

n(w

t%)

Elem

ent

Cer

tifie

dEx

per

imen

tal

Cer

tifie

dEx

per

imen

tal

Cer

tifie

dEx

per

imen

tal

Cer

tifie

dEx

per

imen

tal

Cer

tifie

dEx

per

imen

tal

C95

0◦ C

0.26

±0.

030.

24±

0.03

0.65

±0.

100.

64±

0.04

––

0.75

±0.

100.

75±

0.04

––

Cto

tal

29.4

3±

0.08

29.4

8±

0.15

0.65

±0.

100.

66±

0.05

23.4

6±

0.13

23.5

0±

0.15

0.75

±0.

100.

77±

0.05

––

S–

–18

0±

36(p

pm

)19

0±

50(p

pm

)–

–21

0±

43(p

pm

)23

0±

50(p

pm

)0.

834

±0.

032

0.84

6±

0.05

Co

rg–

–0.

62±

0.08

0.63

±0.

04–

–0.

49±

0.08

0.50

±0.

03–

–

Nu

mb

ero

frep

licat

es:a

tle

astn

=3

inre

pro

du

cib

ility

con

dit

ion

s.


27

6


Table 17. Comparison of the measurement result of the validation standards with the known value for organic carbon, carbon at 950 ◦C, totalcarbon and sulfur, where �m is the difference between the measured and the known value and U�m is the expanded uncertainty

SRM 112b GBW07404 BCS-CRM No 359 GBW07402 SRM1886a

Element �m U�m �m U�m �m U�m �m U�m �m U�m

C950 ◦C (wt%) 0.02 0.08 0.01 0.21 – – 0 0.22 – –

Ctotal (wt%) 0.05 0.34 0.02 0.22 0.04 0.40 0.02 0.22 – –

S (wt%) – – 10 ppm 123 ppm – – 20 ppm 132 ppm 0.01 0.12

Corg (wt%) – – 0.01 0.18 – – 0.01 0.17 – –

Table 18. Results of the determination of carbon from the WC phase

Grinding tool 36 Grinding tool 150 Grinding tool 280 Grinding tool 600 Grinding tool 1500

W (wt%) 0.90 ± 0.01 0.82 ± 0.01 0.85 ± 0.01 0.90 ± 0.02 0.96 ± 0.01

WC (wt%) 0.96 ± 0.01 0.87 ± 0.01 0.90 ± 0.01 0.96 ± 0.02 1.02 ± 0.01

CWC (wt%) 0.06 ± 0.01 0.05 ± 0.01 0.06 ± 0.01 0.06 ± 0.01 0.06 ± 0.01


Table 19. Results of total carbon, carbon at 950 ◦C and carbon from the silicon carbide phase

C content (wt%) Grinding tool 36 Grinding tool 150 Grinding tool 280 Grinding tool 600 Grinding tool 1500

Ctotal 6.39 ± 0.06 4.58 ± 0.05 6.29 ± 0.06 4.83 ± 0.05 5.44 ± 0.06

Corg 3.19 ± 0.04 3.10 ± 0.04 3.21 ± 0.04 3.09 ± 0.04 3.12 ± 0.04

C950 ◦C 3.65 ± 0.04 3.63 ± 0.04 4.41 ± 0.04 3.57 ± 0.04 3.88 ± 0.04

CSiC 2.70 ± 0.10 0.90 ± 0.09 1.80 ± 0.10 1.20 ± 0.09 1.50 ± 0.10


Table 20. Complete chemical analysis of the studied grinding tools

Grinding toolcomponents (wt%) Grinding tool 36 Grinding tool 150 Grinding tool 280 Grinding tool 600 Grinding tool 1500

SiO2 total 24.0 ± 0.2 15.8 ± 0.1 14.1 ± 0.1 9.9 ± 0.1 13.4 ± 0.1

Al2O3 9.8 ± 0.1 13.6 ± 0.1 7.66 ± 0.05 10.1 ± 0.1 7.2 ± 0.1

Fe2O3 0.41 ± 0.01 0.13 ± 0.01 0.69 ± 0.02 0.61 ± 0.01 0.69 ± 0.01

CaO 1.41 ± 0.04 0.70 ± 0.02 4.62 ± 0.04 1.83 ± 0.03 1.47 ± 0.03

MgO 31.4 ± 0.3 31.2 ± 0.3 29.3 ± 0.3 28.4 ± 0.3 29.5 ± 0.3

Na2O 5.88 ± 0.04 8.08 ± 0.04 8.68 ± 0.04 12.6 ± 0.05 12.8 ± 0.06

K2O 0.04 ± 0.01 0.06 ± 0.01 0.02 ± 0.01 0.03 ± 0.01 0.04 ± 0.01

TiO2 0.27 ± 0.01 0.37 ± 0.01 0.27 ± 0.01 0.25 ± 0.01 <0.01 ± 0.01

MnO 0.03 ± 0.01 <0.01 ± 0.01 0.03 ± 0.01 0.03 ± 0.01 0.04 ± 0.01

P2O5 <0.01 ± 0.01 <0.01 ± 0.01 0.02 ± 0.01 0.02 ± 0.01 0.01 ± 0.01

SiC 9.0 ± 0.3 3.0 ± 0.3 6.0 ± 0.3 4.0 ± 0.3 5.0 ± 0.3

LOI (1025 ◦C) 36.1 38.5 44.9 49.4 47.6

S 0.65 ± 0.04 0.56 ± 0.04 0.35 ± 0.03 0.31 ± 0.03 0.38 ± 0.03

Cl 14.0 ± 0.1 15.8 ± 0.1 15.8 ± 0.1 18.2 ± 0.1 23.2 ± 0.1


Characterization of the grinding tools. The complete analysis ofthe SiC-based grinding tools, taking into account the phase analysisobtained, is presented in Table 21.

The chemical and mineralogical analysis data show that thestudied grinding tools are basically made up of SiC and corundumas abrasives and magnesium oxychloride as binder, in additionto other minor constituents such as halite, bassanite, dolomite,

calcite, periclase, talc, brucite and quartz, in variable quantities,depending on the grinding tool.

When the analysis results for the silicon carbide phase in thegrinding tools obtained by XRD and elemental analysis of thedifferent forms of carbon are compared, no significant differencesare observed. Either method can therefore be used, depending onthe available equipment.


27

7


Table 21. Composition, expressed as a percentage by weight, of the components present in the studied grinding tools

Crystalline phases (wt%) Grinding tool 36 Grinding tool 150 Grinding tool 280 Grinding tool 600 Grinding tool 1500

Silicon carbide (SiC) 9.0 ± 0.5 3.0 ± 0.3 6.0 ± 0.5 4.0 ± 0.5 5.0 ± 0.5

Halite (NaCl) 11.0 ± 0.5 13.0 ± 0.5 13.0 ± 0.5 16.0 ± 0.8 21 ± 1

Magnesium hydroxychloridehydrate ((Mg3(OH)5Cl)·4H2O) + other organicbinders)

53 ± 2 56 ± 2 58 ± 2 60 ± 3 53 ± 2

Bassanite (2CaSO4(H2O)) <1 1.0 ± 0.3 <1 1.0 ± 0.3 <1

Dolomite (CaMg(CO3)2) <1 <1 5.0 ± 0.5 2.0 ± 0.3 2.0 ± 0.3

Calcite (CaCO3) <1 <1 5.0 ± 0.5 2.0 ± 0.3 1.0 ± 0.3

Magnesite (MgCO3) <1 <1 <1 <1 <1

Periclase (MgO) 1.0 ± 0.3 1.0 ± 0.3 <1 <1 1 ± 0.3

Talc (Mg3(OH)2Si4O10) 9.0 ± 0.5 <1 5.0 ± 0.5 4.0 ± 0.5 4.0 ± 0.5

Brucite (Mg(OH)2) 3.0 ± 0.3 3.0 ± 0.3 <1 3.0 ± 0.3 3.0 ± 0.3

Quartz (SiO2) 5.0 ± 0.5 10.0 ± 0.5 1.0 ± 0.3 <1 4.0 ± 0.5

Alumina and corundum(α-Al2O3)

10.0 ± 0.5 13.0 ± 0.5 6.0 ± 0.5 9.0 ± 0.5 6.0 ± 0.5

Sodalite (Na4Cl(Al3Si3O12)) <1 <1 2.0 ± 0.3 <1 <1


Figure 2. Synoptic scheme of the steps used in the full characterisation of silicon carbide-based grinding tools.

The method proposed in this paper for the completecharacterisation of SiC-based grinding tools is schematically il-lustrated in Fig. 2.

Conclusions

1. A method is presented for the complete chemical charac-terisation of SiC-based grinding tools, using elemental andspectroscopic analysis techniques to determine all grindingtool components. The method can be used for grinding toolquality control.

2. The phases making up the grinding tools were analysed andquantified by XRD. This provided the information needed toaddress the chemical analysis, since grinding tools, in additionto containing abrasives and binders, also contain different

quantities of other admixtures, such as sulfates, to provideindividual grinding tools with different properties.

3. Milling is an important step in grinding tool chemical analysis.Milling can be performed in a WC mill provided millingconditions are suitably controlled to obtain an appropriateparticle size distribution; the contamination that the materialundergoes during milling is also duly corrected by tungstenanalysis.

4. WD-XRF was used in analysing the elements in the grindingtools. Samples were prepared as beads and pellets, dependingon the element to be analysed. The absence of certifiedreference materials with a composition similar to that of theanalysed samples made it necessary to prepare compositionsby mixing the available reference materials in order to validatethe measurements.


27

8


5. Carbon elemental analysers with variable operating temper-ature were used to determine the different forms of carbon:organic carbon, carbon at 950 ◦C (corresponding to organiccarbon and carbon from the carbonates) and total carbon com-prising all forms of carbon: organic carbon, inorganic carbonand carbon from the silicon carbide phase. This informationenabled the SiC concentration to be calculated, since SiC can-not be separated by the gravimetric method without oxidisingin the course of the process or other sample componentsbeing retained together with the SiC.

6. The SiC in these SiC-based grinding tools can be determined bythe two developed methods, namely by XRD or by elementalanalysis, since both methods yield good results.

Acknowledgements

This study was funded by the Valencia Institute of Smalland Medium-sized Enterprise (IMPIVA) in frame of the Re-search, Development and Innovation programme, through theIMIDIC/2007/103 and IMIDIC/2008/15 projects, corresponding tothe Plan for company services centres and REDIT Technology In-stitutes, as well as by the European Union through the EuropeanRegional Development Fund.

References

[1] I. M. Hutchings, Y. Xu, E. Sanchez, M. J. Ibanez, M. F. Quereda, in IXWorld Congress on Ceramic Tile Quality. QUALICER 2006. Camarade oficial comercio, industria y navegacion: Castellon, 2006,pp P.BC405.

[2] M. F. Blanch, Abrasivos, Marcombo, Barcelona: 1979.[3] Ceramics and Glasses, ASM International: Materials Park, Ohio 1991.[4] M. F. Quereda, Porcelain Tile Polishing: A Study Process Variables

and Materials Characteristics, Universitat Jaume I, Castellon, 2008,[Doctoral dissertation].

[5] S. Malkin, C. Guo, Grinding Technology. Theory and Applications ofMachining with Abrasives (2nd edn), Industrial Press: New York,2008.

[6] M. F. Gazulla, M. P. Gomez, M. Orduna, A. Barba, J. Eur. Ceram. Soc.2006, 26, 3451.

[7] R. J. Julietti, B. C. E. Reeve, Br. Ceram. Trans. J. 1991, 90, 85.[8] K. A. Schwetz, J. Hassler, J. Less Common Met. 1986, 117, 7.[9] A. Kerber, R. Dietrich, R. Ibendahl, in Ceramic Powder Processing

Science(Eds: H Hausner, G. L. Messing, S. Hirano), DeutscheKeramische Gesellschaft: Cologne, 1989, pp 359.

[10] A. Roßerg, K. Otto, P. Matthe, CFI Ceram. Forum Int. 1992, 69, 251.[11] S. Rumei, C. Minghao, AI Xingtao, in 6th International Symposium

on Science and Technology of Sintering, International AcademicPublishers: [s.l.], 1995, 130.

[12] B Docekal, J. A. C. Broekaert, T. Graule, P. Tschopel, G. Tolg Fresenius,J. Anal. Chem. 1992, 342, 113.

[13] M. Franek, V. Krivan Fresenius J. Anal. Chem. 1992, 342, 118.[14] EN 12698-1 2007 Chemical analysis of nitride bonded silicon carbide

refractories. Part 1: chemical methods.[15] DIN 51075-01: 1982. Testing of ceramic materials; chemical analysis

of silicon carbide, sample preparation and calculation of siliconcarbide content.

[16] DIN 51075-02: 1984. Testing of ceramic materials; chemical analysisof silicon carbide, direct determination of the free carbon content.

[17] DIN 51075-03: 1982. Testing of ceramic materials; chemical analysisof silicon carbide, determination of the total carbon content.

[18] ISO 21068-2: 2008 Chemical analysis of silicon-carbide-containingraw materials and refractory products. Part 2: Determination of losson ignition, total carbon, free carbon and silicon carbide, total andfree silica and total and free silicon.

[19] ISO 21068-1: 2008 Chemical analysis of silicon-carbide-containingraw materials and refractory products. Part 1: General informationand sample preparation.

[20] FEPA http://www.fepa-abrasives.org [12 January 2008].[21] FEPA-Standard for bonded abrasive grains of fused aluminium

oxide and silicon carbide 42-GB-1984 Part 1: designation – Grainsize distribution.

[22] EN ISO 12677: 2003 Chemical analysis of refractory products byXRF – Fused cast bead method.

[23] C. Wang, X. Wei, H. Yuan, Mater. Manuf. Process. 2002, 17, 401.[24] V.E. Buhrke, R. Jenkins, D.K. Smith (Eds) A Practical Guide for the

Preparation of Specimens for X-Ray Fluorescence and X-Ray DiffractionAnalysis. Wiley-VCH: New York, 1998, 171.

[25] A. L. Ortiz, F. Sanchez-Bajo, F. L. Cumbrera, F. Guiverteau, Mater.Lett.2001, 49, 137.

[26] A. L. Ortiz, F. Sanchez-Bajo, N. P. Padture, F. L. Cumbrera,F. Guiverteau, Quantitative Polytype-Composition Analysis ofSiC Using X-ray Diffraction: A Critical Comparation Between thePolymorphic and the Rietveld Method, University Press: Oxford,1996.

[27] R. A. Young (Ed.) The Rietveld Method. University Press: Oxford, 1996.[28] H. M. Rietveld, J. Appl. Crystallogr. 1969, 2, 65.[29] EN 15309: 2007 Characterization of waste and soil. Determination

of elemental composition by X-ray fluorescence.[30] J. Tschmelak, G. Proll, G. Gauglitz, Anal. Bioanal. Chem. 2004, 378,

744.[31] Carborundum: Chemical analysis of silicon carbide for surface

impurities. 1964.[32] ISO/TAG 4-WG 3: 1995 Guide to the expression of uncertainty in

measurement.[33] T. Lisinger, Comparison of a Measurement Result with the Certi-

fied Value, 2005, http://www.erm-crm.org/html/ERM products/application notes/application note 1/application note 1 englishen.pdf [24 April 2009].


wdxrf

Documents