High-Performance Ceramics III

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Authors: X.G. Wang, Jie Mo Tian, Chuan Zeng Zhang, Zhi Ping Guo, Li Min Dong, Chang An Wang
Abstract: Animal implants experiments are obligatory when developing human artificial hard tissues, such as bio-ceramics. Optical microscope is often used to inspect implant slices but may destroy original status when slicing up. We tried 3D high resolution CT to nondestructively study biocompatibility and degradation of bio-ceramics implants. 3D CT provides 3D structure information. Typical pixel size of 3D high resolution CT is 50 microns. Generally, implants differs with tissues in density and structure, on basis of which we can identify details with CT slice. Experiments of bio-ceramic implanted into rabbit hip are also showed. Interaction could be identified at interface between implant and tissue.
Authors: Shuang Xi Wang, W.-Y. Gao, T.C. Ma, Kai Ming Liang, X.H. Zhang
Abstract: A monolithic glass-ceramic lined steel elbow with 900-bend angle was fabricated using a self-propagating high-temperature synthesis gravitational-thermite process (SHS G-T process). The manufacture principle and some technologies were introduced. Experiment results showed that the inner surface of the composite elbow was smooth and there were no visible cracks and pores in it. The coating layer was symmetry and was of ~ 2.5 mm thick. It consisted of two zones (glass-like zone, columnar zone) and that there existed three phases (Al2O3, glass and Fe particles) in both of the two zones. However, the Al2O3 grains were different evidently in the two zones. XRD results showed that there was no hercynite phase in the coating layer.
Authors: Hua Shao, Kai Ming Liang, Feng Zhou, Fei Peng
Abstract: Crystallization sequence of MgO-Al2O3-SiO2-TiO2 system glass was investigated by means of DTA, XRD, SEM and EDS. The relationship between crystalline phases, heat treatment methods and thermal expansion coefficient (α) were well discussed. The results have shown that: The glass first underwent extensive phase separation into titanium-rich droplets in a silica-rich matrix, then magnesium aluminotitanate (MAT) initially precipitated in the droplet phases. With the crystallization temperature increased, β-quartzss, sapphirine, α-quartzss and α-cordierite made their appearance successively. The thermal expansion coefficient as a function of the heat treatment condition was studied.
Authors: An Min Hu, Kai Ming Liang, Feng Zhou, Fei Peng, Guoliang Wang
Abstract: The mechanical properties of spodumene-diopside glasses ceramics with 4-12% TiO2 were investigated. The main crystalline phases precipitated were eucryptite, β-spodumene and diopside. As TiO2 content increasing, the morphology of glass ceramics transformed from coarse to fine microstructure, then to reverse. The flexural strength, elastic moduli, Vickers hardness and fracture toughness of the glass-ceramics were measured. The flexural strength of glass–ceramics containing 9%TiO2 was 198MPa, the Young’s modulus and fracture toughness were 91.3GPa and 2.3 MPa·m1/2 respectively. It was indicated that the mechanical properties were correlated with crystallization and morphology of glass ceramics
Authors: G.C. Yuan, Q.G. Wu, G.X. Zeng, X.H. Zhang
Abstract: The nano-powder of Al2O3-SiO2-CaF2 bio-glass was prepared by the homo-precipitation method with some inorganic salts containing Al3+, Ca2+, Na+, F-, SiO3 2+, Cl- as starting-reagents. The composition and characteristics of the powders were studied with XRD, EDAX, TEM and DTA. The results indicate that the prepared powder belongs to amorphous compounds containing Al, Ca, Si, O and F atoms and the size of particle is in the range of 30 ~ 70 nm. Adding citric acid and the well-controlled desiccation process can slightly improve the dispersing effect of the powders; the mixture ratio of the reagents rarely affects the characteristic of powder. The crystal phase CaF2 was precipitated firstly from the amorphous structure when the temperature is above 600°C, with the temperature rising, Al2SiO5 and Al4.4Si1.2O9.5 etc. crystal phases were precipitated sequentially.
Authors: Guoliang Wang, Kai Ming Liang, Wei Liu, An Min Hu, Feng Zhou, Hua Shao
Abstract: By means of SEM, the micro-morphology of silver particles separated from borosilicate glass by the heat-treatment with an electric field is investigated. The distribution of the silver particles appears clusters. This result is explained by an energy viewpoint. Based on hermodynamics theory of phase separation, the calculation of the free energy change during the heat-treatment in an electric field is performed by means of the Ansoft Maxwell software. The results of this calculation analysis are found to be very close to the experimental data.
Authors: Fei Peng, Kai Ming Liang, Hua Shao, An Min Hu, Feng Zhou
Abstract: The nucleation and crystallization kinetics of glass obtained by melting coal fly ash with additives at 1550°C have been investigated. The optimum heat treatment schedule for the glass was nucleation at 825°C for 60min before crystallization at 962°C for 4h. The activation energy for crystallization of the glass-ceramics, obtained by the DDTA result, was 280.03 kJ/mol, lower than that of glass-ceramics obtained from pure reagents. The low activation energy is caused by impurities in fly ash, serving as nucleation agent. The results of XRD and SEM show that glass-ceramics developed nano-sized spherical wollastonite.
Authors: Xiao Dong Li, Jie Mo Tian, Chen Wang, Li Min Dong
Abstract: ZnO-Al2O3-SiO2 glasses with different surface conditions were surface crystallized by different heat treatment process. Differential thermal analysis (DTA), X-ray diffraction analysis (XRD) and scanning electronic microscope (SEM) were used to investigate the crystallization behavior of glasses, the crystalline components and microstructure of the as-got glass-ceramics. According to the DTA results, different heat treatment processes of surface crystallization on the glass were adopted. The SEM results show that surface conditions of glasses are important for the surface crystallization, and the thickness of surface crystalline layer increases with heat treatment time.
Authors: Zong Huai Li, Jiang Hong Gong, Zhi Jian Peng, He Zhuo Miao
Abstract: The nanoindentation load-displacement curves of soda-lime glass were analyzed with the widely adopted Oliver-Pharr method. The resultant nanohardness exhibits a significant indentation size effect (ISE). An empirical relationship between the peak load and the contact depth, which was established to analyze the ISE in microhardness tests, was suggested to be suitable for describing the load-dependence of the nanohardness. By comparing the best-fit values of the parameters included in this empirical relationship, the origin of the load-dependence of nanohardness was analyzed briefly.
Authors: Hong Li, Jin Shu Cheng, Xin Jiang Long
Abstract: CaO-Al2O3-SiO2 (CAS) glass-ceramic is a novel material developed in recent years. It has a number of excellent properties, such as shining appearance, high strength, and good erosion resistance. So its practical prospect is wide. Many glass and ceramic scientists have studied this glass-ceramic, but there have been no publication made regarding corrosion mechanism. In order to choose the most suitable refractory materials for melting furnace for this glass-ceramic system, the corrosion and erosion mechanism must be investigated. The results can then be used to design the furnace and predict the life of the melting furnace. Also such investigation will reveal the extent of contamination of the final glass-ceramic product. According to the experiment that the glass liquid corrodes refractory materials in static condition, various effective material test method were used, especially Electron Probe Microanalysis (EPMA). Using EPMA, the chemical species, morphology, size and distribution of refractory materials corroded can be observed, so we know the microstructure of refractory materials prior to and after being corroded as well as the features of changing. In this paper, the authors present the features of refractory materials microstructure prior to and after being corroded by means of analyzing these pictures, which is very useful to provide the reliable theory to establish the mechanism that CAS glass-ceramic liquid corrodes the refractory materials.

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