Key Engineering Materials Vol. 591

Abstract: In this paper, La_0.75Sr_0.25MnO_3-δ (LSM) and La_0.6Sr_0.4CoO_3–δ (LSCO)coatings were prepared by the atmospheric plasma spraying method andflame spraying method. Both coatings were annealedat 800 °C, 900 °C, 1000 °C for 5 h, 10h, 15 h and 20 h. Oxygen content of LSM and LSCO coatings weredetermined by redox titration. It is interesting to noted that, oxygen content of LSM and LSCO coatings strongly varied with the annealing temperature andannealing time. The experimental results show that, at same annealingtemperature, oxygen vacancy decreases with the increase of annealing time. For LSM coatings, at 800 °C,the oxygen vacancy, δ, were decreased from 0.419 to 0.353, 0.310 and to 0.258 with theannealing time increased from 5 hto 10 h, 15 h and to 20 h. Under the same annealing time, oxygen vacancydecreased with increase of annealingtemperature. For LSCO coatings, the oxygen vacancy, δ, were decreased from0.698 to 0.573 and to 0.535 after annealed at 800 °C, 900°C and 1000 °C for 5 h.

Abstract: Phase characterization is critical in material properties probing. In this study, Raman scattering was employed to identify the phase of YSZ co-doped with CeO₂/Gd₂O₃. As a comparing, XRD for co-doped YSZ was also measured. The results show that introducing a small amount of CeO₂/Gd₂O₃ into YSZ can lead to a change on Raman spectroscopy. Raman peaks appear with co-doping is attributed to the local structure change which caused by the re-distribution of vacancy. Comparing to XRD, Raman spectroscopy shows a more sensitive on the phase identify for the YSZ with a small amount dopant.

Abstract: Synthesis of zeolite A by the use of natural materials (naturally stellerite) has been achieved without template agent. The final product was tested with X-ray diffraction, which was identified as the zeolite A. Then, the raw material and each step product were tested with Fourier Transformation Infrared (FT-IR). Comparing their FT-IR, we analyzed their spectrum characteristics, differences and reasons.

Abstract: Boron nitride(BN) fibres were synthesized by modified technique of Economy’s method. The products were characterized by X-ray diffraction (XRD), fourier transform infrared (FT-IR) absorption spectroscopy, field-emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectrum (EDS) and X-ray photoelectron spectroscopy (XPS). The results showed that BN fibers were mainly hexagonal boron nitride (h-BN) with diameters of 5-8 μm and the major compositions of BN fibers are B and N with a very small amount of O and C. At last, the chemical composition of samples were determined by the chemical analysis test method like GB/T 16555-2008 and GJB 507-1998.

Abstract: The pyrolysis ceramic dynamic process of ZrC ceramic precursor was characterized by means of on-line TG-DSC-FTIR-MS coupling technique, and the conversion mechanism of ZrC ceramic was investigated based on XRD, SEM, TEM and XRF. ZrC ceramic could be obtained at 1400°C lower than theoretic temperature when Zirconium element is reduced by carbon from ZrO₂. The results showed that ZrC ceramic precursor presented storage stability and excellent solubility in toluene. Ethanol, carbon dioxide, acetone and tetrahydrofuran (THF) were given off before heat treatment at 1100°C, and the pyrolysis product held in the form of ZrO₂ and amorphous carbon. ZrC crystals were gradually formed when heated up to 1200°C and obtained completely at 1400°C. This ZrC ceramic precursor provides promising candidate for oxidation resistance and ablation resistance ZrC-SiC ceramic matrix composites.

Abstract: In this paper, the clay was intercalated with polyacrylic acid, and then studied the influences of intercalation on rheological property of ceramic billet. The study indicated that the intercalation changed the properties of clay interlayer domains, such as the interlayer bonding water, the content of free water and the bonding force between the layers, etc. The plasticity index of ceramic billet increased significantly when the amount of intercalation is more than 3.0 wt. The plasticity index increased from 1.09m·N to 4.19m·N when the additive is 5.0wt, increased by 383%. And also its yield strength has improved significantly, the fracture pressure increased from 100N to 600N. These phenomena indicate that the machinability of billet improved significantly.

Abstract: SiO₂ nano/submicron-structures have attracted tremendous interest due to their importance in extensive applications. In this work, SiO₂ nano/submicron-rods were successfully synthesized by a simple method through pyrolyzing an amorphous polysilazane preceramic powder with catalyst FeCl₂. The synthesized nano/submicron-rods possess well-defined shape with diameter of 700-900 nm and high purity.

Abstract: Bioglass is a good bioactive material and has been used in many medical fields, include drug delivery systems, non-load-bearing implants and bone cements. Sol-gel is a good method in the preparation of coating materials. It also can be used in the preparation of bioactive glass. In this paper, the principles and technical processes are introduced. The effects on characteristics of bioactive glasses of the factors such as H₂O dosage, ethanol dosage, gel temperature and activator are analyzed in detail. The research progress in preparation of sol-gel bioactive glasses is summarized. Finally the development foreground of sol-gel bioglass is also expected.

Abstract: This paper studied the Na₂O-B₂O₃-SiO₂-CaO-P₂O₅-F glass-ceramics and obtained the complex biological glass-ceramics with low sintering temperature, high mechanical properties and good biological activity. In this paper, the better basic point was selected in phase region of Na₂O-B₂O₃-SiO₂ glass system. It was studied that the effect of different percent of CaO, P₂O₅ and F addition on the mechanical properties and biological activity of the glass-ceramics. The glass powder was prepared by melting and quenching in water, and then by molding and sintering, composite glass-ceramics materials was obtained. With the help of DSC, XRD and SEM analysis methods and testing means, the phases and heat treatment systems of the material were determined, and the microstructure of materials in the different heat treatment conditions was observed. The biological activity was tested in SBF simulated body fluid . Research shows that: the introduction of F can effectively reduce the melting temperature of the material and is helpful to crystallization. The introduction amount of CaO, P₂O₅ and F can affect the biological activity of glass-ceramics. In the range of introducing CaO, P₂O₅ and F in this paper, the mechanical properties and biological activity of glass-ceramics increase with the amount of the introduction of CaO, P₂O₅ and F.