| Opal glass has been widely used in construction, decoration, utensils, lighting, dental materials and other daily life materials because of its soft color and elegance. However, due to the volatilization of fluoride of conventional fluoride glass, which is harm to the environment and is threat to health. Even worse, the erosion of fluoride to the furnace has also caused great economic losses in the production, so the study of non-fluorine-opaque glass has been widely concerned. Phosphate opaque glass is one of the most important development direction of opal glass, which uses phosphate as opacifying agent, can avoid the volatilization of fluoride, save the cost and reduce the pollution.In this paper, Na2O-CaO-SiO2-P2O5 system(abbr. NCSP) opal glass was prepared by the melting method, alone changing the amount of ZnO, CaO, B2O3, and through the same mass of K2 O gradually replaced Na2 O in the formula components. The physical performances of glass were measured through bulk density and bending strength; the acid-resistance and alkaliresistance were used to test chemical stability; the change of molecular structures was analyzed by FT-IR; the linear expansion was analyzed by thermal expansion instrument; opal glass crystallization properties were analyzed by X-ray diffraction(XRD); the microstructure of the material was observed by scanning electron microscopy(SEM). And to explore the effect of different oxides on structure and properties of the system opal glass, this process is expected to obtain high whiteness, low expansion coefficient, good phase opal glass. In the end, using respectively acid and alkali erode the prepared opal glass, through the mass loss of the samples, ion precipitation of sample in erosion liquid, scanning electron microscope(SEM) observes the surface changes of the glass after the erosion, the effect of acid and alkali with different temperatures, different time and different concentration on chemical stability of the opal glass could be worked out.Research results show: the addition of a certain amount of ZnO increased the opacity of the glass, and then increased the whiteness of glass. Adding a small amount of zinc oxide can promote the generation of Na3Ca6(PO4)5 crystal. Also, too many zinc oxide would lead to generate Zn2P2O7 crystal, to a certain extent, the thermodynamic properties of the glass were also affected, the bending strength and density of the glass had been improved. When the amount of ZnO was 5%, the coefficient of thermal expansion was lowest to 8.018×10-6/℃, and the addition of ZnO reduced the crystallization temperature of the sample. On the basis of the research on the amount of ZnO, changing the amount of CaO, CaO had a larger impact on the phosphorus phase size of this system opal glass, with the increase of mass fraction of CaO, the opaque glass was changed into semi opaque, causing the sample whiteness decreased, when the CaO amount was 14%, the whiteness was 78.01%, which was related to the field strength and ionic polarization of Ca2+. The increase of the amount of CaO promoted the increasing of Na3Ca6(PO4)5 crystal and improved Zn2P2O7 crystal intensity, the bending strength and density of the samples showed increasing trend due to the increase of the crystalline phase.On the basis of the research on the amount of CaO, changing the addition of B2O3 had an influence on the internal structure, the number of O-Si-O bonds inside the glass was reduced, the number of [BO3] triangle increased; the size of the phosphorus phase gradually increased, and the edge of the phase became more round. Adding amount of B2O3 can promote the generation of crystal of Na3Ca6(PO4)5; because the [BO3] triangle made the internal structure became loose, the density was gradually reduced, and then the acid and alkali resistance was gradually weakened; when the B2O3 amount was 10%, the coefficient of thermal expansion was 7.9221×10-6/℃. On the basis of the research on the amount of B2O3, with the same mass of K2 O replaced Na2 O, the size of became more small, separation phase edge became more round, the whiteness gradually increased, when K2 O content was 6%, the highest whiteness was 86.35%; this was because K+ polarization was larger, it was advantageous to reduce the phase surface tension. Due to the decrease of the amount of Na+, the intensity of Na3Ca6(PO4)5 crystal peak gradually decreased; with K2 O instead of Na2 O, because K+ ion radius was larger than Na+ radius, causing the gap between the glass structure became larger, and reduced the bending strength as well as the density of the sample, it also resulted in the acid and alkali resistance was gradually weakened.The chemical stability of the glass with better performance was studied. In hydrochloric acid solution and NaOH solution, with the increasing of erosion time, the weight loss rate of the glass firstly increased and then decreased, on the 30 th day, the weight loss of glass samples in NaOH solution was 45 times that of the sample in hydrochloric acid solution, and the acid resistance was stronger than alkali resistance. The increasing of temperature was helpful to increase the reaction rate of the hydrochloric acid and the glass sample. The erosion mechanism of the sample in hydrochloric acid was mainly based on the exchange of Na+ in sample and H+ in acid. However in the NaOH solution Si and P presented higher precipitation amout than other ions, hydroxyl attacked seriously the internal network structure of the glass, which resulted in a large number of powder dropped. |
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