Effect of nucleating agents on microstructure and mechanical properties of SiO_2-Al_2O_3-ZrO_2 glass-ceramics

SiO2-Al2O3-ZrO2 glasses with different nucleating agents were crystallized under special processing schedule. The microstructure and mechanical properties of the glass-ceramics in SiO2-Al2O3-ZrO2 system were investigated by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction and three-point bending method. The results show that ZrO2 is not an effective nucleating agent in SiO2-Al2O3-ZrO2 system, while TiO2 is effective for the separation of spinel, and P2O5 facilitates solubility of ZrO2 in glass and crystallization. The main crystalline phases of the glass-ceramics are spinel, anorthite and tetragonal zirconia. With the increase of ZrO2 content in the glass, glass-ceramics show higher bending strength （120MPa） than others.

Microstructure and Mechanical Properties of Mica Glass-Ceramics Prepared by Pressureless Sintering a Phlogopite and Various Additives

Mica glass-ceramics were prepared by pressureless sintering with a phlogopite and various additives as raw materials. The effects of CaF2 content, Li2O content, ZrO2 content, and sintering temperature on the microstructure and mechanical properties of the mica glass-ceramics were investigated by X-ray diffraction, scanning electron microscopy, and mechanical testing, respectively. The results show that the additive of ZrO2 has the best reinforcing effect on the flexural strength of the mica glass-ceramics. The smaller powder particles and the larger forming pressure result in the larger bulk density of the mica glass-ceramics samples. The main crystallite phases of samples with ZrO2 as additive were phlogopite and quartz with sintering temperature lower than 1120 ℃. The crystal phase of glass ceramics appeared fiberform and cross arranges with good lap. The highest value of flexural strength, 63.7 MPa, was shown on sample with 10wt% ZrO2 as additive and sintering temperature of 1120 ℃.

Effects of ZrO_2 on the Microstructure of a Mica Glass-ceramic

The effects of ZrO2 on the crystallinity of mica and microstructure of a machina- ble glassceramic were studied. It was found that ZrO2 is an effective nucleation agent in mica glass- ceramics. Stabilized by Ca2+, a lot of t--ZrO2 particles precipitate from ZrO2-mica glass-ceramics. The ZrO2 particles can effectively limit the growth of mica crystal and benefit the mechanical properties of glass-ceramics.

Effect of crystallization of CaO-P_2O_5-SiO_2-MgO-F^- glass-ceramics on its mechanical properties

The microstructure of CaO-P_2O_5-SiO_2-MgO-F^- glass-ceramics duringcrystallization were investigated and the crystallized phases were identified with DTA (DifferentialThermal Analysis), SEM (Scanning Electron Microscope) and XRD (X- ray Diffraction) techniques. Themechanical properties such as bending strength and fracture toughness, as well as their changes withadvancing crystallization were determined. The results show that the changes of the mechanicalproperties are correlated with the microstructures. The sample heated up to 810 deg C and soaked for4 h has smaller crystalline size and less volum fraction of fluorophlogopite, so it has higherbending strength (about 190 MPa), and higher crack toughness (about 2.63 MPa centre dot m^1/2).

Mineral-phase evolution and sintering behavior of MO–SiO_2–Al_2O_3–B_2O_3 (M = Ca,Ba) glass-ceramics by low-temperature liquid-phase sintering

In this work, network former SiO_2 and network intermediate Al_2O_3 were introduced into typical low-melting binary compositions CaO·B_2O_3, CaO·2B_2O_3, and BaO·B_2O_3 via an aqueous solid-state suspension milling route. Accordingly, multiple-phase aluminosilicate glass-ceramics were directly obtained via liquid-phase sintering at temperatures below 950°C. On the basis of liquid-phase sintering theory, mineral-phase evolutions and glass-phase formations were systematically investigated in a wide MO–SiO_2–Al_2O_3–B_2O_3(M = Ca, Ba) composition range. The results indicate that major mineral phases of the aluminosilicate glass-ceramics are Al_(20)B_4O_(36), CaAl_2Si_2O_8, and BaAl_2Si_2O_8 and that the glass-ceramic materials are characterized by dense microstructures and excellent dielectric properties.

Influencing the Crystallization of Glass-Ceramics by Ultrashort Pulsed Laser Irradiation after Nucleation

An ultra-fast laser with central wavelength at 1064?nm and 10?ps pulse duration?was used to tightly focus laser radiation?with a microscope objective inside the volume of nucleated Lithium Aluminosilicate (LAS) glass-ceramic. The nonlinear absorption?of the LAS glass-ceramic was measured?for different laser parameters and a thermal simulation was performed to determine the temperature field inside the laser-modified area. After laser processing,?the samples were crystallized in a furnace and the effect of the laser-induced modifications on the microstructure was analyzed with SEM. The SEM analysis shows an increase in the length and size of whisker-shaped?β-spodumene crystals in the laser-modified area. By increasing the dimension of these whisker-shaped crystals, the flexural strength of LAS can be improved locally.?First?four-point bending flexural tests were performed to examine the influence on the mechanical properties.

球晶材料的TEM—EDAX剖析

观察了R2O－RO－Al2O3-SiO2系某一整体析出球晶的微晶玻璃中球晶的生长过程．获得随着晶化时间的增加或晶化温度升高，球晶直径增大；但球晶数目保持不变．发现了核化温度与球晶直径关系呈抛物线型．以TEM－EDAX剖析了球晶的雏型内部和近邻玻璃基体的显微结构及其演变．清楚地揭示了球晶生长过程中所发生的组成变化．

Joining dense Si3N4 to porous Si3N4 by using an anorthite based glass-ceramic

This study focuses on the design,characterization and testing of a novel anorthite based glass-ceramic solder for joining dense Si3N4 and porous Si3N4 ceramic.It was found that the glass solder possesses a favorable wetting ability on two ceramic surfaces.Additionally,the influence of crystallization treatment on the microstructure and shear strength of joints was investigated.The results showed that CaAl2 Si2O8 was the main product in the seam.After crystallization treatment,the crystallinitiy of the seam and shear strength of joints were improved obviously.The shear strength of joints after crystallization was 52 MPa at room temperature,and it increased to 59 MPa at 850℃.Finally,the joining mechanism of the dense Si3N4/glass-ceramic/porous Si3N4 bonded joints was proposed.Intergranular diffusion of elements was identified as the main mechanism of bonding in the interface of dense Si3N4/glass-ceramic.In the porous Si3N4 side,the bonding was achieved by infiltration that was controlled by capillarity and resistance of the viscous forces.

A review on the dielectric materials for high energy-storage application

With the fast development of the power electronics,dielectric materials with high energy-storage density,low loss,and good temperature stability are eagerly desired for the potential application in advanced pulsed capacitors.Based on the physical principals,the materials with higher saturated polarization,smaller remnant polarization,and higher electrical breakdown field are the most promising candidates.According to this rule,so far,four kinds of materials,namely antiferroelectrics,dielectric glass-ceramics,relaxor ferroelectric and polymer-based ferroelectrics are thought to be more likely used in next-generation pulsed capacitors,and have been widely studied.Thus,this review serves to give an overall summary on the state-of-the-art progress on electric energy-storage performance in these materials.Moreover,some general future prospects are also provided from the existed theoretical and experimental results in this work,in order to propel their application in practice.