Effect of soda-lime-silica glass addition on the physical properties of ceramic obtained from white rice husk ash

Transcription

1 Paper Effect of soda-lime-silica glass addition on the physical properties of ceramic obtained from white rice husk ash Nasim Heidari BATENI, *,³ Mohd Nizar HAMIDON *, ** and Khamirul Amin MATORI ***, **** *Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia, **Functional Device Laboratory, Institute of Advanced Technology, University Putra Malaysia, ***Department of Physics, Faculty of Science, Universiti Putra Malaysia, ****Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, This study reports on the effect of soda-lime-silica (SLS) glass on the physical properties of the ceramic material obtained from white rice husk ash (WRHA). The crystallisation behaviour of samples was investigated by XRD analysis after different heat treatments. The bulk density and linear shrinkage (LS) of the samples were determined using Archimedes method and direct geometric measurement, respectively. The residual pore contents of the specimens were determined using SEM micrographs. The results show that the bulk density and LS of the samples increased and the porosity decreased as the sintering temperature increased. The XRD analysis results show the formation of cristobalite to be a major phase and some tridymite phase was detected in the specimens The Ceramic Society of Japan. All rights reserved. Key-words : Soda-lime-silica glass, White rice husk ash, Crystallisation, Physical properties [Received September 11, 2013; Accepted December 16, 2013] 1. Introduction The sources of silica and silicon in biomass resources such as rice husk (RH) are being studied intensively for use in chemical, electrical and cement industrial applications. 1) RH is an agricultural waste product that is available in rice-producing countries. More than two million tons of RH are produced annually in Malaysia. 2) The typical chemical composition of RH (on 20% basis ash) is 22% lignin, 38% cellulose, 18% pentosans and 2% other organic matter. 2) 5) Thus, RH is known to have a high silica ash content (20 25%). 6) 10) Thermal combustion of RH at moderate temperatures in air atmosphere yields an amorphous silica content >90%. 2),5),9),11) 13) The silica obtained from RH is useful in the manufacture of semiconductors, solar cells for photovoltaic power generation 14) 16) and other electronic applications. Furthermore, silica is most commonly found in nature as quartz or silica sand, which are increasingly being used as a piezoelectric material to harvest energy from the environment. 17) 20) Piezoelectric materials are able to generate an electric potential in response to an applied mechanical stress and energy in the environment. Hence, as a hypothesis, WRHA can be considered a piezoelectric-based ceramic material because of its high silica content and WRHA can exhibit piezoelectric properties after polarisation, although there is difference in the crystal structure of quartz and that of the ceramic obtained from WRHA. The temperature and the time of heat treating are important factors in determining the amorphous or crystalline structure of WRHA. 21) Deer et al. 22) observed that with heat treatment in the range of C, amorphous WRHA transforms into cristobalite and ³ Corresponding author: N. H. Bateni; nasim @ gmail.com 2014 The Ceramic Society of Japan DOI tridymite, depending on the impurities in the ash. Furthermore, sintering phenomenon affects the porosity, density and LS of WRHA. Researches have shown that the apparent porosity of the material decreases and the density and LS increases as the sintering temperature of WRHA increases. 23) SLS glass, also called soda-lime-glass, is the most common type of glass, 24) used for windowpanes, glass containers (jars and bottles for food, beverages, and some commodity items) and flat glass or container wares. Most commercially made glasses are composed primarily of silica ( wt %). 25) In addition to silica, glasses also contain other oxides such as CaO, Na 2 O, K 2 O and Al 2 O 3, which influence their properties. 26) In this work, commercial SLS glass was added to WRHA to take advantage of SLS glass s chemical stability 27) to improve the resistance of the pellets to cracking. Sintering phenomenon also affects the SLS glass structure. Prado et al. 26) found that as a result of sintering at temperature above 680 C, the glass will develop a crystalline structure. An investigation of the effect of sintering on the density of SLS glass showed that increasing the sintering temperature above 627 C, increases the density of SLS glass and decreases its apparent porosity. 28) The purposes of the present study were to characterise the ceramic obtained from SLS glass and WRHA mixtures and investigate the effect of SLS glass addition on the physical properties and microstructure of WRHA using Archimedes principle, XRF analysis, scanning electron microscopy and X-ray analysis techniques. 2. Material and experimental procedures RHs were washed thoroughly with tap water several times and then with distilled water three times to remove mud, soil, impurities and other contaminants present in the raw material. The 161

2 JCS-Japan Bateni et al.: Effect of soda-lime-silica glass addition on the physical properties of ceramic obtained from white rice husk ash Table 1. The mixture samples consisting of starting powders with the different mixing ratio Samples Composition (wt %) WRHA SLS glass S S S RHs were allowed to dry initially at room temperature for 72 h and then were dried in an electric oven at 120 C for 16 h. The washed and dried RHs were transferred to a crucible and heated at 700 C for 6 h in air by an electric furnace to produce amorphous WRHA. The calcined powders were ground in a mortar and screened manually through a sieve to obtain the desired grain size (45- m). In addition, waste SLS glass bottles were washed and dried at room temperature and crushed with a plunger and hammer and sieved manually to obtain SLS glass powder with a 45- m grain size. Mixtures consisting of 97.5, 95 and 92.5 wt % of WRHA and 2.5, 5 and 7.5 wt % of SLS glass, respectively, were mixed in a rotary ball mill for 24 h. The powdered mixtures were directly pressed to form a pellet by blending with the organic binder polyvinyl alcohol (PVA). Pellets in 13 mm diameter and approximately 2.7 mm thickness were pressed using a die-pressing technique. The chemical compositions of the sintered pellets and the starting powders were measured by X-ray fluorescence (XRF) (Fluorescence X-ray spectrometer EDX720/ 800HS/900HS). The bulk density of the sintered samples was measured in acetone using Archimedes method, and the LS was measured by direct geometric measurement. The following LS equation was derived: LS ¼ 1 d a d o 100 where: LS = Linear shrinkage (%) d a = Average pellet diameter after sintering (mm) d o = Original pellet diameter (mm) The morphology of the specimens was verified by scanning electron microscopy using a Hitachi Model S-3400N scanning electron microscope. Meanwhile, pellets, according to Table 1, were sintered at 900, 1000 and 1200 C for 3 h and phase identification of the sintered specimens was evaluated by XRD (Philips PW 3040 MPD) with 2ª in the range of The crystal structure of the samples was determined using X Pert HighScore Plus software. 3. Result and discussions The results of the phase analyses of the WRHA and SLS glass powders are shown in Fig. 1. This figure shows the amorphous structure of SLS glass and a single diffuse band centred at 21, which indicates the amorphous structure of the silica present in the WRHA treated at 700 C for 6 h. This finding is consistent with the findings of Della et al. 21) Table 2 shows the chemical composition of the SLS glass and WRHA before sintering. The results illustrate that the main constituent of WRHA is silica at 94.3 wt %, which is consistent with the findings of Mishra et al., 13) who found that WRHA contains approximately wt % silica. Table 2 also shows that the SLS glass was found to be wt % silica, which is consistent with values reported by Zanotto, Strnad et al. and Arciniega et al. 27),29),30) It should also be noted that in addition to SiO 2, the SLS glass, the WRHA and ð1þ Fig. 1. The results of the XRD analyses of WRHA and SLS glass. Table 2. The chemical composition of SLS glass and calcined WRHA Element(s) SLS glass (wt %) WRHA (wt %) SiO CaO Fe 2 O SO K 2 O MnO Cr 2 O ZrO SrO ZnO NiO CuO Table 3. The silica content of the specimens at different sintering temperatures Samples 900 C 1000 C 1200 C (wt %) S S S the mixture samples were found to contain other oxides such as CaO, K 2 O and Fe 2 O 3, which were presumed to be impurities that tend to change the properties of material. 12),26),31) 34) Table 3 lists the percentages of silica in the specimens (S 1,S 2 and S 3 ), which are also consistent with the values reported by Mishra et al. 13) These results indicate that the addition of SLS glass to WRHA yielded silica elements in our samples with almost the same range of purity approximately wt %. Furthermore, the silica content decreased with the further addition of SLS glass, most likely because of the impurities that make up approximately 40 wt % which of the SLS glass, as determined by XRF and as listed in Table 2. The LS and bulk density of three sintered specimens were determined according to Eq. (1) and Archimedes method, and the results are shown in Fig. 2. According to Fig. 2(a), the average density of specimens S 1,S 2 and S 3 at 900 C was 1.7 g/cm 3, while the density of pure WRHA at this temperature is approximately 1.23 g/cm 3. The difference between the two is due to the 162

3 JCS-Japan Fig. 2. (a) Bulk density (g/cm 3 ) (b) LS (%) of specimens sintered at different temperatures, symbols S 1,S 2 and S 3 are WRHA-SLS glass mixture samples consisting of 2.5, 5 and 7.5 wt % of SLS glass, respectively. Fig. 3. SEM micrographs of S 1 after sintering at 900, 1000 and 1200 C. existence of SLS glass in the mixture pellets, which decreases their porosity because interstitial cations (Na +,Ca + ) enter into the vacant sites of the network and increase the density 25) of WRHA-SLS glass mixture specimens. Sample 3, which had the highest SLS glass content (7.5 wt %), had the highest bulk density and the lowest LS, for the reason explained above. Increased densification of specimens above 900 C occurs because of the viscous flow of amorphous material into the pores and matter transport in amorphous material during the sintering process, mainly by viscous flow, which is referred to as viscous sintering. The viscosity decreases as the content of impurities increases and decreases as the sintering temperatures increases, as reported by Nayak and Bara. 35) For this reason, the density of the samples increased with increasing sintering temperature. 25) Figure 3 reveals the surface morphology of S 1 as a polished pellet at 900, 1000 and 1200 C. These SEM micrographs show that many residual pores were distributed within the sample, meaning that the sample is a porous material. A comparison of the pore distributions corresponding to the three temperatures showed that the surface of S 1 at 1200 C had few pores, whereas at 900 C, the sample had a porous surface. As Fig. 2(a) shows, the relationship between the density and porosity is not linear. 163

4 JCS-Japan Bateni et al.: Effect of soda-lime-silica glass addition on the physical properties of ceramic obtained from white rice husk ash into tridymite and cristobalite phases. A weak peak of tridymite at 20.7 was accompanied by a strong peak of cristobalite at 22, and weak peaks at 27.5, 28.5, 31.5 and 2ª = 36.4 can be detected in Fig. 4(b). After sintering at 1200 C, a tridymite phase appeared at 23.7 and 39.4 and contained the most intense peak at These results demonstrate that the reaction sintering process can efficiently produce a phase transformation from cristobalite to tridymite. A weak tridymite peak at 2ª = 20.7 accompanied a strong cristobalite peak at 22, and additional weak tridymite peaks at 23.4, 27.6 and 37.9 can be observed in Fig. 4(a). The figure also shows that the peak intensity of tridymite at 20.7, 23.4, 27.6, 29.7 and 37.9 increased with further addition of SLS glass in specimens sintered at 1200 C. These increases are due to impurities (K + ) in the SLS glass. Indeed, these consequences are evidence that at higher temperatures, the proportion of tridymite in WRHA-SLS glass mixture specimens increases while the proportion of cristobalite decreases, which is consistent with the result reported for WRHA by Shinohara and Kohyama in ) They found that at higher temperatures (up to 1000 C) or after a long burning time, the proportion of tridymite in WRHA increases while the proportion of cristobalite decreases. The tridymite phase occurs due to the presence of alkali ions such as Ca +2 and K + as flux in the pellets. 1),34) Tridymite is the only SiO 2 phase (polymorphic structure) that is able to accommodate K + (interstitial cations) in its voids. 1),6),25) As Fig. 4(a) shows, the crystallisation of tridymite increased as the ratio of alkali increased with the increase of the SLS glass content (which increased the impurity content). Shinohara and Kohyama 1) reported that tridymite was the dominant crystalline phase in a WRHA sample with 3 wt % potassium at high sintering temperature and that a low K 2 O content leads to cristobalite being the dominant phase after sintering at high temperatures. The average potassium content of the samples in this work was 1.38 wt %; thus, the dominant crystallised phase at high temperatures (above 900 C) is cristobalite, according to Fig. 4. Fig. 4. The results of the XRD analyses of (a) the mixture samples (S 1,S 2 and S 3 ) sintered at 1200 C (b) S 2 consisting of 5 wt % SLS glass and 95 wt % WRHA at three different temperatures. Symbols C and T are peak position of cristobalite and tridymite respectively. The same nonlinearity was reported by Haslinawati et al. and by Nayak et al., 34),35) who noted that the density increases with decreasing pore content and increasing sintering temperature. Figure 4 shows the results of the XRD analyses of the three samples (S 1,S 2 and S 3 ) at 1200 C [Fig. 4(a)] and the results for S 2 at various sintering temperatures [Fig. 4(b)]. According to the results shown in Fig. 4(b), a crystalline structure was observed after sintering up to 900 C. This result is consistent with the findings of Nayak and Bera 35) who reported in 2009 that amorphous silica of WRHA transforms into crystalline form (depending on the impurities present in the ash) upon heat treatment in the temperature range of C. Figure 4(b) shows that the two forms of crystalline silica were cristobalite and tridymite and that the predominant phase was cristobalite. Matori et al.2) and Govindarao 3) reported that amorphous silica can change to quartz upon heat treatment at temperatures in the range of C, to -tridymite at temperatures in the range of C and to -cristobalite at temperatures in the range of C. In this study, the quartz phase in the samples disappeared upon sintering at temperatures up to 900 C and was transformed 4. Conclusions The pellets produced from WRHA with added SLS glass were investigated to determine the effects of SLS glass addition on the crystallisation, density, porosity and LS of the WRHA ceramic. The XRD results indicate that SLS glass does not change the crystalline structure of WRHA. In fact, the addition of SLS glass supports the formation of the crystal phase of WRHA. Moreover, both crystalline forms (cristobalite and tridymite) were observed in WRHA-SLS glass mixture samples sintered at temperatures 900, 1000 and 1200 C. The proportion of cristobalite decreases and the proportion of tridymite increases as the sintering temperature increases above 1000 C due to the presence of potassium. Increasing the sintering temperature increases the density and LS and decreases the porosity of WRHA-SLS glass mixtures, indicating that the addition of SLS glass accelerates the densification of WRHA during sintering. References 1) Y. Shinohara and N. Kohyama, Ind. Health, 42, (2004). 2) K. A. Matori, M. M. Haslinawati, Z. A. Wahab, H. A. A. Sidek, T. K. Ban and W. A. W. A. K. Ghani, MASAUM J. Basic Appl. Sci., 1, (2009). 3) V. M. H. Govindarao, J. Sci. Ind. Res., 39, (1980). 4) J. James and M. S. Rao, Thermochim. Acta, 97, (1986). 5) S. Chandrasekhar, K. G. Satyanarayana, P. N. Pramada, P. Raghavan and T. N. Gupta, J. Mater. Sci., 38,

5 JCS-Japan (2003). 6) C. Real, M. Alcala and J. M. Criado, J. Am. Ceram. Soc., 79, (1996). 7) R. K. Chouhan, B. Kujur, S. S. Amritphale and N. Chandra, Mortar. Sil. Ind., 65, (2000). 8) M. Patel, A. Karera and P. Prasanna, J. Mater. Sci., 22, (1987). 9) T. H. Liou, Mater. Sci. Eng., A, 364, (2004). 10) E. J. Siqueira, I. V. P. Yoshida, L. C. Pardini and M. A. Schiavon, Ceram. Int., 35, (2009). 11) L. Xiong, E. H. Sekiya, P. Sujaridworakun, Sh. Wada and K. Saito, J. Met., Mater. Miner., 19, (2009). 12) L. Xiong, K. Saito, S. Wada and E. H. Sekiya, J. Met., Mater. Miner., 19, (2009). 13) P. Mishra, A. Chakraverty and H. D. Banerjee, J. Mater. Sci., 20, (1985). 14) S. D. Genieva, S. Ch Turmanova, A. S. Dimitrova and L. T. Vlaev, J. Therm. Anal. Calorim., 93, (2008). 15) L. P. Hunt, J. P. Dismukes, J. A. Amick, A. Schei and K. Larsen, J. Electrochem. Soc., 131, (1984). 16) L. Sun and K. Gong, Ind. Eng. Chem. Res., 40, (2001). 17) Sh. Mehraeen, S. Jagannathan and K. Corzine, IEEE international conference on industrial Technology, 1 8 (2008). 18) A. Khaligh, P. Zeng and C. Zheng, IEEE Trans. Ind. Electron., 57, (2010). 19) S. P. Beeby, M. J. Tudor and N. M. White, Meas. Sci. Technol., 17, (2006). 20) O. Nizhnik, K. Higuchi and K. Maenaka, J. Low Power Electron. Appl., 1, (2011). 21) V. P. Della, I. Kühn and D. Hotza, Mater. Lett., 57, (2002). 22) W. A. Deer, R. A. Howie and J. Zussmaan, Rock Forming Minerals, Longmans, London, (1963). 23) J. P. Nayak and J. Bera, Appl. Surf. Sci., 257, (2010). 24) H. A. Schaeffer, Solid State Ionics, 105, (1998). 25) V. L. Houerou, J. C. Sangleboeuf, S. Deriano, T. Rouxel and G. Duisit, J. Non-Cryst. Solids, 316, (2003). 26) M. O. Prado, C. Fredericci and E. D. Zanotto, J. Non-Cryst. Solids, 331, (2003). 27) E. D. Zanotto, J. Non-Cryst. Solids, 129, (1991). 28) M. O. Prado, C. Fredericci and E. D. Zanotto, J. Non-Cryst. Solids, 331, (2003). 29) Z. Strnad and R. W. Douglas, Phys. Chem. Glasses, 14, (1973). 30) S. M. P. Arciniega, A. Alvarez-Mendez, L. C. Torres-Gonzalez and E. M. Sanchez, Revista Mexicana de fisica, 55, (2009). 31) H. Riveros and C. Garza, J. Cryst. Growth, 75, (1986). 32) S. Pukird, P. Chamninok, S. Samran, P. Kasian, K. Noipa and L. Chow, J. Met., Mater. Miner., 19, (2009). 33) A. Onojah, A. N. Amah and B. O. Ayomanor, Am. J. Sci. Ind. Res., 3, (2012). 34) M. M. Haslinawati, K. A. Matori, Z. A. Wahab, H. A. A. Sidek and A. T. Zainal, International Journal of Basic & Applied Sciences IJBAS, 9, (2009). 35) J. P. Nayak and J. Bera, Phase Transitions: A Multinational Journal, 82, (2009). 165