网络修饰离子对乳浊玻璃的析晶及乳浊度的影响
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Glass Technology: European Journal of Glass Science and Technology Part A Volume 52 Number 3 June 201167
Glass Technol.: Eur. J. Glass Sci. Technol. A, June 2011, 52 (3), 67–721. IntroductionOpal glasses are typically phase separated glasses with opacity resulting from light diffraction and inter-nal light scattering between the separated phases.(1–3) These phases could be either crystals or immiscible phases. Usually, the production of opal glass requires the addition of a certain amount of fluorine into the batch which in silicate glasses leads to the formation of fluorides during cooling of the melt. In this case the glass exhibits a dense white opaque appearance due to the difference in the refractive index between the light scattering crystals and the glass matrix.(4–6) However, there is a serious environmental problem, due to fluorine volatilization which is harmful to both humans and plants. Moreover, the presence of fluorine in the glasses leads to a rapid corrosion of the kiln refractories. Therefore, it is important for glass technologists to find alternative chemical composi-tions in order to produce fluoride free opal glasses.Phase separation in glasses is an important topic of modern glass research due to its great influence on both crystallization and glass properties. Many glass properties may be changed by phase separa-tion since the microstructure of the phase separated glass is very different from that of its parent glass.(7) Most borosilicate glasses phase separate upon heat treatment.(8,9) Similarly, phase separation can occur in phosphosilicate glasses. It has been shown that the addition of RO oxides (R=Ca, Mg, Ba, Zn and similar) into the phosphosilicate glasses can enhance opac-ity as a result of the increased phase separation.(10) However, to the best of our knowledge, few studies have been carried out concerning the effects of oxide modifiers and heat treatment on the opalescence of phosphosilicate glasses, as well as on the morpho-logical changes of the opal glasses. In this study, we attempt to develop new types of opal glasses and to identify the main factors influencing the opalescence effect.
2. Experimental2.1 Sample preparationThe glasses studied in this work belong to the SiO2 –Al2O3–P2O5–Me2O–MO system (Me2O=Li2O, Na2O, MO=MgO and CaO), the detailed compositions of which are shown in Table 1. Sample OP1 contains 31 mol% network modifying oxides (16% Na2O and 15% CaO). Substitution of 7·5 mol% MgO for CaO results in sample OP2. Substitution of 8 mol% Li2O for Na2O results in sample OP3. Appropriate mixtures of reagent grade chemicals (SiO2, Al2O3, (NH4)2HPO4, Li2CO3, Na2CO3, MgO and CaCO3) were melted in a platinum crucible at temperatures ranging from 1450 to 1500°C in an electric furnace for 2 h. Then the melts were poured into stainless steel moulds and slowly
Effect of network modifiers on the opalescence and crystallization behaviour of opal glasses
Shujiang Liu,1 Guangrong Li,1 Yuanzheng Yue,1,2* Lina Hu3 & Wen He1
1 Key Laboratory for Glass & Ceramics, Shandong Polytechnic University, 250353 Jinan, China2 Section of Chemistry, Aalborg University, DK-9000 Aalborg, Denmark3 Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials, Shandong University, Jinan 250061, China
Manuscript received 21 February 2011Revised version received 19 April 2011Accepted 19 April 2011
In this paper we report on the phase separation, crystallization and opalescence of a series of the aluminophosphosilicate glasses by substitution of one type of network modifying oxide for another. Using x-ray diffraction, we have found that the NaCaPO4 crystals are present in all quenched glasses, which greatly enhances the opalescence effect. The glasses remain transparent when Na2O and CaO are present, whereas they become opalescent when Li2O and MgO are partially substituted for Na2O and CaO, respectively. A heat treatment at 600°C for 20 h leads to a dramatic increase in the opalescence of the glasses. This is attributed to rapid growth of hexagonal NaCaPO4 crystals. Besides NaCaPO4 crystals, AlPO4 crystals are identified when Li2O, Na2O, CaO and MgO co-exist.
Corresponding author. Email yy@bio.aau.dkTable 1. Chemical compositions and characteristic temperatures of glasses (mol%)Sample no. SiO2 Al2O3 P2O5 Li2O Na2O MgO CaO Tg (°C) Tc (°C) Tp (°C)OP1 63·5 3 2·5 16 15 587 700 752OP2 63·5 3 2·5 16 7·5 7·5 566 676 728OP3 63·5 3 2·5 8 8 7·5 7·5 490 600 642
