Jiang Zhonghong

Low temperature synthesis of ZrO2TiO2SiO2 glasses from Zr(NO3)4 · 5H2O, Si(OC2H5)4 and Ti(OC4H9)4 by the sol-gel method

Abstract ZrO 2 - and/or TiO 2 -containing silicate glasses have been attracting more and more scientists and technologists due to their low thermal expansion and excellent resistance to alkali corrosion. But it is difficult to make these glasses by the conventional melting method because of their extraordinarily high melting temperatures. In the present work, however, glasses in the ZrO 2 TiO 2 SiO 2 systems have been successfully synthesized by the sol-gel route using Zr(NO 3 ) 4 · 5H 2 O, Si(OC 2 H 5 ) 4 and Ti(C 4 H 9 ) 4 as starting materials. Transparent glass pieces were obtained containing 20 mol.% TiO 2 and up to 30 mol.% ZrO 2 . Detailed studies were carried out on the whole synthesis process including hydrolysis, polymerization, gelling and conversion from gel to glass. Research results on the viscosity evolution of the reaction systems showed that environmental humidity and catalyst had important effects on the gelling process. During heat treatment, the colour of the dry gels gradually changed and DTA data indicated that at about 650°C the conversion from gel to glass would be completed. The information about the structural variation of the gels during heat treatment has been obtained by means of X-ray diffraction, infrared spectroscopy and the results suggest the different function of Zr 4+ ions from Ti 4+ ions in this kind of glass, i.e. Ti 4+ ions act as network formers, while Zr 4+ ions act as network modifiers.

NMR, IR and Raman spectra study of the structure of borate and borosilicate glasses

Abstract Comparative studies on the IR and NMR of some binary borate systems and ternary borosilicate systems were made. The results of NMR in R 2 OB 2 O 3 , La 2 O 3 B 2 O 3 and Na 2 OB 2 O 3 SiO 2 glass systems were measured and calculated using the phase diagram model. The authors believe that the structure of a simple glass resembles the related congruent melting compound, a multicomponent glass can be regarded as the melting mixture of some adjacent congruent melting compounds in the phase diagram. The structure and properties of glass can be calculated by level rule.

Glass formation regions and chemical durability of some ZnCl2-based halide systems

Abstract This paper describes the glass formation behavior and chemical durability of some ZnCl 2 -based halide glasses. Different corrosion mechanisms are discussed with respect to oxide glass and halide glass.

High Efficiency Infrared to Visible Upconversion in Er3+/Yb3+-Doped Lead Halide Tellurite Glass

Strong upconversion luminescence of Er3+/Yb3+-doped lead halide tellurite glass under 976 nm excitation is demonstrated. Three emission bands centred at 525 nm, 545 nm, and 655 nm resulting from the transitions from the excited states 2H11/2, 4S3/2, and 4F9/2 to the ground state 4I15/2, respectively, are observed even at 60 mW pumping power. The power dependent intensity and the upconversion mechanisms responsible for the luminescence are evaluated and discussed. The obtained results might provide useful information for the developments of upconversion lasers.

Some aspects of phase separation in glasses

Abstract The advances of research into phase separation and its mechanism (including thermodynamics and kinetics) are reviewed in this paper. Some research on phase separation in China has been reported. We pay particular attention to the different methods of predicting the phase separation regions, and the three proposed methods by the author are: (1) mathematical curve fitting, (2) thermodynamic method, and (3) a method by means of the modern continuous phase transition theory. A great number of immiscibility boundary curves of silicate and borate binary systems have been calculated.

Research on some IR transmission halide glass systems

Abstract In order to find new IR transmission halide glass systems, we have prepared several hundred compositions of halide glass. The glass formation regions have been studied in a large number of ternary systems. Based on the behavior of the glass-formation regions some principles about halide glass formation were discussed. The crystallisation characteristics of halide glasses were studied by DTA, X-ray diffraction and SEM. Some comparatively stable glasses have been prepared.

Variations of structure and homogeneity in the transformation process from gel to glass in some silicate systems

Abstract In the present work the variations of structure and homogeneity in the transformation process from gel to glass in some silicate systems are investigated. Emphasis is placed on the different roles of titanium ions Ti 4+ in the glasses.

Quantitative prediction of immiscibility boundaries in binary systems by means of the universality of phase separation

Abstract A method used for predicting immiscibility boundaries by means of the universal character of phase separation and the quantitative equations is advanced in this paper. It is assumed that the immiscibility boundary near the critical point can be quantitatively predicted if the critical point or two or more experimental points are known. The measured regions of demixing in ROB2O3 (R = Mg, Ca, Sr, Ba) systems are shown to agree with the predicted regions.

Quantitative calculation of immiscibility ranges of multi-component borate, silicate and borosilicate glass systems

Abstract Using the phase diagram data of binary systems, in this paper a great number of binary immiscibility equations have been calculated by computer. Based on those equations, the formulae for the calculation of ternary and multi-component systems have been derived. Generally, the results of the calculation agree with the experimental data.

STUDY OF CRYSTALLIZATION KINETICS IN NEW OPTICAL GLASSES

With thermal analysis method and nonisothermal Johnson-Mehl-Avrami equation lnT p 2 /α=lnE/R+E/RT p -lnk 0 , kinetic parameters of crystallization are resolved in La 2 O 3 -Nb 2 O 5 -B 2 O 3 , La 2 O 3 -BaO-B 2 O 3 , fluoride and fluorophosphate glasses. Characteristics of crystallization in these optical glasses are described and compared with k(T p )=k 0 exp(-E/RT p ) values. It is concluded that most stable glasses could be obtained after proper composition adjustment in each glass systems. As a new stability criterion k(T p ) has provided a convenient approach to determine the stability of optical glasses.