UNCONVENTIONAL METHOD FOR THE CERAMIC SUSPENSIONS CHARACTERIZATION

Transcription

1 The First International Proficiency Testing Conference Sinaia, România 11 th 13 th October, 2007 UNCONVENTIONAL METHOD FOR THE CERAMIC SUSPENSIONS CHARACTERIZATION Maria Spataru 1, Marcela Muntean 2 1 National Institute for Research and Development in Electrical Engineering Advanced Research, INCDIE ICPE-CA, 313 Splaiul Unirii, Bucharest-3, Romania mspataru@icpe-ca.ro 2 University POLITEHNICA Bucharest, Department: Science and Engineering of Oxide Materials, 1-7 Gh. Polizu, , Bucharest, Romania P.O.Box 12-46, , Bucharest, Romania m_muntean@chim.upb.ro Abstract The paper proposes a new method, a spectrocolorimetric one, for the of the ceramic aqueous suspensions, containing Al 2 O 3 -ZrSiO 4. These suspensions are very useful for obtaining refractory products by slip casting. The traditional used ZrO 2 was changed with ZrSiO 4, which brings economical advantages. Were prepared a lot of samples with the same grinding times, of 5 h, and different quantities and qualities of additions such as sodium carboxymethylcellulose, Arabic gum and polyvinylalcohol for theirs defflocculating and stabilisation. It was found that is very difficult to select the best composition among them because of small differences. Spectrocolorimetric method settles the matter how will be shown. Key words Aqueous suspension, alumina-zircon, spectrocolorimetric method, ceramic suspensions 1. INTRODUCTION Aqueous systems from any type of materials (plastic or unplastic) are unstable ones, which require electrolytes, organic polymers, binders for stabilization. Able aqueous suspensions to shaping process through pouring in plaster mould, must to be: fluid, stable, to contain little water, a best percentage of adequately 409

2 additions, grain size dispersion according to mould of uniform products with good resistance in green state. Suspensions properties are determined by their flow behaviour and ceramic wall forming. or quality testing both of prepared suspensions and of casted products, in plaster moulds, were used a spectrocolorimetric method, unused with this end in view. The colorimetry as the science of colour measuring and its aspect can be used for quality appreciation of suspensions and oxide ceramic pastes. Suggested colorimetric method represents the ensemble of mathematical and physical models, which define the objective perception of colour and includes apparatus and measuring technique, as well, data administration [1]. A specific soft, Universe v.4.10, from HunterLab-Romegatest, is used. Spectral data of the suspensions are acquisitioned, stocked and processed through a procedure of specific measuring to opaque samples [2]. From spectral data, international standard parameters CIELAB 76: L*, a*, b* of colour are determined, were L* is the coordinate named luminance, white-black, %, a* is the chromaticity coordinate for colour zone red-green, %, b* is the chromaticity coordinate for colour zone yellow-blue, %. It must choice a decision procedure, type pass/fail, through the agency of colour partial differences: ΔL*, Δa*, Δb*, respectively, of total one: ΔE cmc. The differences are calculated depending on colorimetric standard, which can be the best sample or colorimetric mean of the samples. The aim of this paper is to show how the spectrocolorimetric method can be used for these kinds of ceramic materials. 2. EXPERIMENTAL PROCEDURE Aqueous suspensions were prepared from calcined alumina, Oradea, Romania, zirconium sand, Australia and rutil, Merck quality with Arabic gum (A.G.), sodium carboxymethylcellulose (Na-CMC) and polyvinyl alcohol (PVA) as deflocculant, dispersing agents and binders. The mixture of raw materials, additions and industrial water was grinded in ball mills for 5 hours. The suspensions composition is presented in Table 1. Sample Table 1 Composition of the suspensions Composition [%] Solid Water A.G. Na-CMC PVA B B B B B B Grinding time [h] 5 On prepared suspensions were determined: ph, viscosity, volume weight and grain size distribution. The values of ph were obtained with an electronic ph-meter, type Orion EA 940 from Thermo Electron Company. Suspensions viscosity was measured with a Rheomat RM 180 viscosity meter having measuring systems of type Brookfield. 410

3 The grain size distribution and mean grain size were determined with Fritsch particle size of type Analysette 22, laser method. Colour tests were realized with a portable spectrocolorimeter Mini Scan XE Plus, HunterLab: illuminant D 65, port of measure LAV, geometry 0 0 /45 0, angle of sight A specific soft, Universe v.4.10, from HunterLab-Romegatest, was used. 3. RESULTS AND DISCUSSIONS General characteristics of the suspensions such as: volume weight, ph, viscosity and mean grain size, are presented in Table 2. Table 2 Characteristics of the suspensions Suspension Volume weight η Φ ph med [g / l] [Pa. s] [μm] B B B B B B Remission spectra of B11-B16 suspensions are shown in Figure 1. Reflectance, [%] Wavelength, [nm] Figure 1 Remission spectra of B11-B16 suspensions A series of small specific absorptions (minimums of spectrum), probably, characteristics of base compounds of suspensions is ascertained from spectrum analysis. Spectrum is parallel, what confirms chemical species existence from which the suspensions are formed at varied concentrations. 411

4 International standard parameters CIELAB 76: L*, a*, b* of colour suspensions were determined from spectrum (Table 3) considering as standard, B14 sample. The B14 suspension was chosen as standard one from technological grounds [3]. Table 3 Physical and colorimetric properties of B11-B16 suspensions, depending on B14 standard, with theoretical tolerances Total differences of colour were calculated depending on a commercial factor (CF=0,40) and a ratio between luminance and chromaticity, l: c = 2 [4]. This commercial factor (of 0,40) is recommended for the samples, which have criterion of acceptability through the most severe. The partial differences were chosen between ± 0,30 limits. From the point of view of ΔE cmc, the B11 and B12 samples are rejected. B11 and B12 samples are qualitative thinner than B14 standard because of partial tolerance overfulfilment on yellow shade (Δb*). As well, B12 and B15 samples, which have the luminance bigger than standard, could suggest that only Arabic gum using as fluidity/stability addition is not enough for assurance of asked qualities from suspensions for pouring. Another criterion of decision could be white degree of samples. This can be used only for thin coloured samples. From Table 3 is observed that the greatest white degree is presented of B12 sample, which is inadequate from point of view of physical properties and of mechanical resistances in green state. Physical and colorimetric properties on sintered samples, came from B11-B16 suspensions through pouring in plaster moulds, are shown in Table 4. Total difference of colour, ΔE cmc, was calculated using the same commercial factor (CF=0,4), and ratio between luminance and chromaticity (l: c=2) as for the suspensions too, from which were poured the samples. The tolerances for partial differences of colour (ΔL*, Δa*, Δb*) are also identically. It s found no accepted sample except standard one. The sintered samples came from B11 and B16 are rejected of yellow-blue shade difference point of view, Δb*, and of total difference of colour, ΔE cmc. 412

5 Table 4 Physical and colorimetric properties on burnt sample from B11-B16, depending on B14 standard, with theoretical tolerances The samples came from B12 and B15 suspensions are rejected out of partial difference of luminance, ΔL*, and of partial difference of yellow-blue shade, Δb*, too. Comparatively with the sample came from B12, which is admitted on criterion of total difference of colour, ΔE cmc, the sample came from B15 is rejected on this one too. The sample from B13 is rejected out of all points of view. It results that the best sample is B14, obtained from B14 suspension through pouring in plaster mould. This sample has also a small sintering contraction. 4. CONCLUSIONS In conclusion, the next original aspects can be underlined: The paper propose a checking colorimetric method of ceramic suspensions quality; Two sets, of decision criterions of type pass/fail, were tested: total criterions based on colour differences between ΔE cmc and samples, partial criterions based on colour differences ΔL*, Δa*, Δb*; Proposed method is sensitive to highly small differences too; The best suspensions are B13 and B14 realised with 0,12% Na-CMC and 0,10% PVA additions (B13), respectively, with 0,12% Na-CMC + 0,08% A.G.+ 0,10% PVA (B14). B16 sample, with 0,12% Na-CMC, was also passed; The best sintered product is only that, which come from B14 suspensions, standard sample; Method can be used in various fazes of technological process for its corrections [5]; Quality testing, both suspensions and finite products, can be made with this method, as a global one. 413

6 REFERENCES [1] Popescu M.I Teză de doctorat/thesis- Metodă pentru controlul desfăşurării reacţiilor chimice şi biochimice /Method for control of chemical and biochemical reactions unfurl-în curs de susţinere/ in course of sustain, Universitatea POLITEHNICA din Bucureşti/ University POLITEHNICA of Bucharest Harold W. R. -olour and Appearance, Hunter Associatons Laboratory Inc., [2] Reston, pp , 1998 Spataru M., Muntean M., Mihail A.- Perete ceramic din barbotina alumina- [3] zircon / Ceramic wall from alumina- zircon slip casting, Romanian Journal [4] [5] of Materials, vol.33, no.4, pp , 2003 ISO International standard 105-J02, 1997; AATCC Test Method , ASTME Erginel N., Dogan B., Ay N. - The statistical analysis of colouring problems faced in ceramic floor tile industry, Euro Ceramics VIII, Engineering Materials Vol , pp , 2004, Trans Tech Publications, Switzerland Acknowledgements The paper was achieved with the support of S.C.ROMEGATEST from Bucharest, unique representative agent of HunterLab in Romania, whom we thank him on this occasion. 414