Jinshu Cheng

Effect of nucleating agents and heat treatments on the crystallization of magnesium aluminosilicate transparent glass-ceramics

The crystallization behavior and transparent property of MgO-Al2O3-SiO2 (MAS) glasses with TiO2 and TiO2+ZrO2 as nucleating agents were discussed by differential thermal analysis, X-ray diffraction, field emission-environment scanning electron microscope, energy dispersive spectrum and UV-VIS-NIR scanning spectrophotometer. It was found that the glass crystallized at 950 °C with ZrO2 less than 3% could obtain transparent glass ceramic, which presented purple to colorless. With the nucleating agent additives (5% TiO2+3% ZrO2), the colorless transparent glass-ceramics with spinel as the main crystal phase could be prepared, and the transmittance reached about 80%. As the crystallized temperature increase to 1 000 °C, besides spinel(MgAl2O4), sapphirine (Mg3.5Al9Si1.5O20) and ZrTiO4 precipitated from matrix glass, and the transmitance of glass-ceramic decreased.

Effect of TiO2 on crystallization of the glass ceramics prepared from granite tailings

The effect of TiO2 on the crystallization behaviors of the glass ceramics prepared from granite tailings was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). The results showed that the crystallization peak temperature decreased firstly, and then increased with the increase of TiO2 content. The optimum addition amount of TiO2 was 8 wt%. With a single-step heat treatment at 924 °C for 1 h, augite precipitated as the only crystalline phase both on the surface and in the interior. The avrami parameter of the sample was 3.25, suggesting a two-dimensional crystallization mechanism. The activation energies for phase separation and crystallization of augite were 321.75 and 698.83 kJ/mol, respectively.

Effect of SiO2/B2O3 Ratio on the Property of Borosilicate Glass Applied in Parabolic Trough Solar Power Plant

This work aimed to analyze the glass material used for sealing the end of a thermal collector in a parabolic trough solar power plant. Based on matched sealing requirements and application performance of glass and Kovar alloy 4J29, one borosilicate glass material (GD480S), whose expansion coefficient was similar to that of Kovar alloy 4J29, was studied. Moreover, the effect of the ratio of SiO2 to B2O3 on the glass properties was explored in detail by Fourier transform infrared spectroscopy. As the SiO2 to B2O3 ratio in the glass increased from 4.18 to 5.77, the expansion coefficient showed a decreasing trend from 4.95×10−6/°C to 4.55×10−6/°C. In addition, the water resistance performance improved, enabling the glass material to seal well with the alloy for application in a trough solar power plant. Thus, the increase in the SiO2 to B2O3 ratio made the glass structure more compact and improved the glass performance to meet the requirements of an industrial tubular receiver.

Surface and interface characterization of oxygen plasma activated anodic bonding of glass–ceramics to stainless steel

Abstract The anodic bonding of RAS glass–ceramics to stainless steel were carried out at 350–400xa0°C and 800–1000xa0V under atmosphere, the micro-topography and compositions of the bonding interfaces also were investigated. With the assistant of oxygen plasma activated, anodic bonding was achieved at 350xa0°C and 800xa0V for 23xa0min under atmosphere, and the anodic bonding strength was up to 1.23xa0MPa. Experiments results pointed out oxygen plasma could help forming the bonding with glass–ceramics to stainless steel, and the width of cation depletion layer about 50xa0μm, lithium iron oxide (LiFe 5 O 8 and Li 5 FeO 4 ) were observed on the surface of glass–ceramics after anodic bonding.

Al–Si Thin Films Assisted Anodic Bonding of R2O–Al2O3–SiO2 Glass–Ceramics to Stainless Steel

In this work the anodic bonding of R2O–Al2O3–SiO2 glass–ceramic to stainless steel (No. 430), together with Al–Si thin films, was investigated for the first time. Relatively smooth and dense non-crystalline Al–Si thin films with a thickness of about 60 nm, were deposited on stainless steel surfaces by DC magnetron sputtering. The anodic bonding process was performed at 350°C and between 500 V and 800 V for 23 min in air and the micro-topography and compositions of the bonding interfaces were investigated by XRD, SEM and EDS. Bonding reaction products of lithium iron oxide (LiFe5O8 and Li5FeO4) were observed on the surface of glass–ceramics after anodic bonding had taken place. By comparing the bonding process of glass–ceramic to stainless steel, with and without an Al–Si thin film, our experimental results show that the presence of the Al–Si thin film resulted in a decrease in the bonding voltage and also assisted in the bonding process.

Effects of rare earth oxides on viscosity, thermal expansion, and structure of alkali-free boro-aluminosilicate glass

Effects of rare earth oxides (Y2O3, La2O3, and Er2O3) on the viscosity, thermal expansion, and structure of alkali-free boro-aluminosilicate glasses were investigated by the rotating crucible viscometer, dilatometry and FT-IR absorption spectra. The results showed that the melting temperature of alkali-free boro-aluminosilicate glasses decreased from 1 697.55 to 1 662.59, 1 674.37 and 1 640.87 °C with the introduction of 1 mol% La2O3, Y2O3 and Er2O3, respectively. However, the glass transition temperature Tg, dilatometric softening temperature Td and coefficient of thermal expansion of alkali-free boro-aluminosilicate glasses increased when adding the rare-earth oxides. At high temperatures, incorporating rare earth oxides into glass resulted in the peak at about 1 085 cm-1 towards lower wavenumber and the absorption band in the region of 850-1 260 cm-1 broader, which indicated that rare earths acted as network modifiers and increased the numbers of non-bridging oxygen in the glass melts. However, the rare earths had an opposite effect and accumulated the glass structure at low temperatures near Tg.

Preparation and characterization of a stable nano-sized Zn x Co 1– x Al 2 O 4 ink for glass decoration by ink-jet printing

A stable inorganic glass ink was prepared by mechanically grinding a mixture of a blue pigment (ZnxCo1–xAl2O4) and low-melting-point glass powders in a specific organic solvent, which possesses a lower annealing temperature compared with ceramic ink. The ZnxCo1–xAl2O4 based pigment was synthesized by solid-state reaction and the best sintering temperature should be at 1300°C or above according to the observation of XRD. ZnxCo1–xAl2O4 shows blue color both in a powder form and coating. The average particle size of pigments and glass powders mixture decreases with the increase of glass powders and milling time. SEM cross-sectional images of annealed coating samples illustrate that the pigments are well dispersed in the ink layer and the glass adhesive binds well on the surface of glass plate, enhancing the mechanical strength of the ink layer. All the obtained results collectively revealed that the prepared nano-sized ZnxCo1–xAl2O4 ink can be applied in glass decoration.

Study on sintered glass ceramics from Nb-Ta tailings

In this paper, particle sintering technology was used to transform tantalum niobium tailings (Nb-Ta tailings) into glass ceramic products. CaO, ZnO and BaO were used to adjust the composition of the glass. β-wollastonite was found as the major crystalline phase in all treated samples. With the CaO increasing, the intensity of crystal diffractive peaks is also increasing. The formation of β-wollastonite crystal can be accelerated by the increasing of CaO. The sintering is processed under the participation of liquid phase, and the increase of sintering temperature does a great favor on descending the liquid phase viscosity of glass particles, which consequently is available for sintering. The density and sintering quality of the samples prepared by two-step sintering are higher than that of one-step sintering. As the sintering temperature increases, the surfaces of the samples become better and have beautiful luster.

Crystallization and luminescence properties of Eu2+ doped diopside glass ceramics

Eu2+ doped glass ceramics have been prepared and characterized. The crystallization and optical properties of the glass ceramics were studied by XRD, SEM, and fluorescence spectra. The precipitated crystalline phase in the glass ceramics was prismatic diopside (CaMgSi2O6) and plate-like cristobalite (β-SiO2). As the heat treatment time increases, the content of crystals increases gradually. Fluorescence measurements showed that Eu2+ ions entered into the diopside crystalline phase and induced a much stronger emission in the glass ceramics than that in the corresponding glass. With increase of Eu2+ content, concentration quenching was observed.

Mechanism of surface depression on foam glass

The mechanism of the surface depression of the foam glass was studied. A method of powder sintering with plate glass as the raw material and carbon black as the foaming agent was adopted to investigate the influences of foaming temperature, soaking time, moisture content in the release agent, and flame preheating temperature on the surface depression of a foam glass blank. The results indicated that insufficient cooling rate and rapid foaming process that could not react synergistically with the surface tension and viscosity of the glass melt aroused the mismatching between the glass melt and the expansion or contraction of gas, resulting in upper surface depression of foam glass. Besides, the batch carbon black at high temperature reacted with residual water in advance to generate large amounts of gas and form the air space which could expand inside, leading to lower surface depression of foam glass.