Influence Of High-voltage Electric Field On The Structure And Property Of Glass

The properties of material have a strong relation with material composition, preparation process, structure etc.; for example, the chemical stability of plat glass depends on the chemical composition of glass, as well as the molding process and the distribution state of ionic species. Piezoeletric property and nonlinear optical property of directional polar glass great related with the orientation degree of grain; different preparation process can obtain different glass with various oriention degree of grain and microstructure. The grain of glass-cramic obtained by traditional preparation show in a disordered state, while glass-ceramic prepared by special process have orientation structure. At present, traditional preparation process theory and application research of glass were relatively mature, but in special conditions such as the introduction of outfield affecting the preparation process of glass and its structure and properties were rare studied. Thus the introduction of special conditions' such as high-voltage electric field, ultrasound, magnetic field and others to improve and control the microstructure and properties of material during the preparation process of material gradually becomes an important research subject and preparation method in material science.In this paper, the float-glass and SrO-TiO2-SiO2 glass-ceramic were selected as the research objective. The first point of this paper includes researches and experiments on how to increase the chemical resistance of float-glass surface, applying a high-voltage electric field. The paper comprehensively introduced the existing methods of improving chemical stability of glass surface to prevent weathering and the high-voltage electric field applied in this method. On the basic of systemic analysis the production conditions of float-glass technology and simulation around the laboratory, float-glass was treated under high-voltage electric field. Uv-Vis Spectrophotometer analysis was used to research the optical properties of the upper surface of the float-glass. The variation of bonds in the upper surface was investigated by Infrared Reflection Spectroscopic (IRRS) analysis. While Glow Discharge-Optical Emission Spectrometry (GD-OES) analysis was employed as verifying method to study the variation contents of element on the quality of float-glass upper surface. Using scanning Electron Electronic Spectrum(EDAX) analysis to analyse concentration distributions of elements in glass 0～20μm from the surface. The impact of high-voltage electric field on the structure and properties of float-glass were discussed, and the mechanism of ion migration and diffusion of float-glass in high-voltage electric field was also studied.In another point of this paper, Sr2TiSi208 glass-ceramic with polar oriented structure were fabricated through a special isothermally orientating crystallization process. The phase composition, microstructure and properties, the influence of high-voltage electric field on microcosmic structure, morphology and piezoelectric properties of glass-ceramic were investigated using XRD, SEM, EDAX and absorbance spectrum. Meanwhile, the changes in crystallization activation energy and crystal orientation index of glass under the auxiliary high-voltage electric field were calculated. Finally, the paper discussed the mechanism of orientation crystallization mechanism of glass under the auxiliary high-voltage electric field.My main works and progress obtained includes as follows:(1) The existence of Na+ in float glass is the major cause of weathering. In the high-voltage electric field, glass transmittance and infrared reflectance rate decreased, Na+ on the surface will move inwards resulting in low alkali and silicon-rich layer on the surface; while the concentration of Na+ under the surface will increase in this electric field, and with the infiltration of Sn, the structure become more dense, making the glass transmittance reduced.(2) With the heating-treatment under high-voltage electric field increasing, peaks of infrared spectral reflectance of glass have not changed, but the position of peak decreased obviously. Infrared reflectivity on the glass surface decreased with the processing temperature increasing; in 3min, the infrared reflectance and transmittance reduces with increases processing time in the electric field; The higher the applied electric field intensity, the stronger the ion migration ability of the glass in the direction electric field; the energy spectrum results show that the higher the field intensity, the more Na+ on the surface of glass migrating towards internal, and the Na+ content on the lower surface increases slightly.(3) A migration diffusion model of ion in glass under high-voltage electric field was simulated, and the main factors of ion migration diffusion were discussed; including chemical composition and structure of glass, electric processing temperature and processing time, leak current strength, etc.(4) High-voltage electric field was imposed on glass in the simulated annealing temperature range of float-glass. In the synergy of temperature and electric field; when the leakage current density is not greater than 150μA/cm, the high-voltage electric field improves the chemical stability of the glass surface (air interface) near the cathode, while the chemical stability of the glass surface (tin in surface) near the negative changes little. The weathering of glass treated in electric field was improved compared with the untreated sample. High-voltage electric field can effectively improve surface (especially the air interface) chemical stability of float-glass.(5) This report select the 2.0SrO-1.0TiO2-2.9SiO2 (mol%) glass system, and polar oriented Sr2TiSi2O8(STS) glass-ceramics were fabricated through a special isothermally orientating crystallization process. The polarity glass-ceramic has good piezoelectric properties, its piezoelectric constant d33 is 10×12-12C/N; In the electric constant temperature field, crystal in general showed c-axis perpendicular to the glass surface of the crystal growth preferential orientation. The relative orientation crystallization index OIconstant temperature is 0.231, OIelectric field is 0.897, and compared with the crystallization prepared in constant temperature, the crystalline directional index of electric field-assisted Sr2TiSi2O8 glass-ceramics enlarged, the degree of grain orientation increased.(6) Based on DTA analysis method the factors of crystallization kinetics of Sr2TiSi208(STS) glass were studied to calculate the STS glass crystallization activation energy and control factors. The results show that:in the condition of auxiliary electric constant temperature, the applied electric field reduces the activation energy of micro-crystals of the polarity crystals, the activation energy is 324 kJ/mol, smaller than the unloaded 347 kJ/mol;(7) By applying EDX analysis method to measure Ti ion distribution in the Sr2TiSi2O8 glass with the direction of crystallization layer, Ti ion occurred segregation phenomenon in the crystallization. The depletion layer of Ti ion appears that Ti ion has a trend of migration to the glass surface in the nucleation process; In SrO-TiO2-SiO2 glass-ceramics, the impact of volume effect on the oriented crystallization of glass-ceramics in the glass-crystal transition was discussed, the distribution of the electrostatic field based on the dipole model and the undulation in the energy of the crystal growth was calculated. The results indicate that in auxiliary electric constant temperature field of grain orientation process in the polar glass-ceramics, the growth rate of grains have great difference in different directions.(8) The impacts of electric field on the whole process of crystal growth include nucleation process, crystal growth dynamics, the transmission of solute, the growth of solutes in front of the interface, the EDL effect of the external electric field led to Ti4+ ions diffusion strengthen near the cathode glass surface, due to the strong nucleation ability of Ti4+ ions accelerates the nucleation growth in crystallization front of STS glass. The influence of electric field on the nucleation and crystallization of glass related with glass phase and the dielectric constant of the crystal phase precipitated. Both the temperature field and additional high-voltage electric field provide the energy for further crystallization of Sr2TiSi2O8 microcrystalline near the cathodic glass surface area with the energy required for further crystallization, further enhancing the crystallization. Meanwhile in the electric constant temperature field, the applied electric field reduces the activation energy of polarity micro-crystals, changes the grain growth rate in different directions, significantly affects the grain orientation growth of glass-ceramics and benefits the preferred orientation growth of polarity micro-crystal.