Advanced Materials Research Vols. 284-286

Abstract: In order to further understand the relationship between technology and metallographic microstructure for the large-scale production of non-orientation silicon steel, hot assembles rolling mill samples at different shearing deformation strip were selected and analyzed. The results show that the surface microstructure in finishing section at the first meeting to the fourth-pass is band-shape deformed ferrite plus equiaxed recrystallization ferrite, while the center is deformed ferrite. With the increase of shearing deformation, number of rheological ferrite increase, and become more slender.

Abstract: According to actual circumstance of Tang Shan ferritic stainless Steel Company, making use of some scene technology parameter and referring a lot of document data, the three-dimensional mathematical model which coupled the molten steel flow with heat transfer is established by adopting the simulation software FLUENT. The result shows: The surface flow velocity and turbulent kinetic energy in liquid surface centerline is appear symmetrical around the two side in ideal condition without the nozzle clogging, but the nozzle clogging show asymmetric distribution, different place and size clogging appear different flow field and temperature. The nozzle clogging of surface temperature and mold lower temperature are higher than the sides without the nozzle clogging. Nozzle clogging is disadvantage of the removal inclusion.

Abstract: Microstructure and quality of sinter of Sijiaying iron ore were studied systematically by means of optical microscope. Results show that the content of sinter of different ratio of Sijiaying iron ore are simple, the content of metal phase are magnetite and hematite, binding phases mainly are calcium ferrite and dicalcium silicate, and the contents of calcium ferrite are higher. The whole microstructure of sinter is uniform, which is interweaving corroded structure. The magnetites are major tiny allotriomorphic crystal. The shape of calcium ferrite is needle-like. The quality of sinter can meet the production request when the proportions of Sijiaying iron ore are from 50% to 100%.

Abstract: Yttrium Aluminium Garnet (YAG) has a extensive applications in many fields because of its excellent properties. In this study the products synthesized by co-precipitation method is regular, and the reaction is complete, the YAG ceramic obtained is white, its density is 2.42g/cm³ and shrinkage is 7.78%. The YAG ceramic tablets were investigated by Field emission scanning electron microscopy (FE-SEM), Electron probe microanalysis (EPMA) and X-ray diffractometer (XRD). The results show that the structure of YAG ceramic is loose with spherical grain size of 0.2-0.3μm. The main mineral phase of YAG ceramic is composed of polycrystalline Al₅Y₃O₁₂ with good crystallinity, and containing very small amount of unreacted alumina and other impurities.

Abstract: Superfine Ag₂WO₄ antibacterial powders, which are prepared by supersonic assisted homogeneous precipitation method, is added 1.0-1.5wt.% to sanitary ceramics, having 90% antimicrobial action, and achieve good bactericidal effects. The antibacterial ceramics with Ag₂WO₄ were soaked into acid and alkali for 3 months, and antibacterial activities had little change, keeping good antimicrobial durability. Finally, the antibacterial mechanism of Ag₂WO₄ ceramics is advanced.

Abstract: According to the conceptual model of high-level radioactive waste (HLW) geological disposal, first, HLW is carried out solidification treatment. Radioactive nuclide was simulated by Cerium (Ce), and Ce was solidified in the zirconite ceramic, solidified bodies of zircon ceramic with Ce were prepared by sol-gel method. In this paper, the basic principle and technological process of ceramic solidification is introduced. The samples were characterized and analyzed by XRD, SEM and EPMA, etc.. The results show that, the surface properties of ceramic tablet is better, and with high shrinkage after sintering, the lower compression force, the higher shrinkage of the ceramic tablet. Most of the diameter of Ceramic grains are in the range of 0.5-5 μm, existing some amorphous phase among the grains. Washing by ammonia, crystallization degree of sample is higher than without treatment, and can form crystals of (Zr,Ce) O₂ and (Zr, Ce) SiO₄.

Abstract: Explosion suppression and isolation apparatus act as the last barrier to minimize casualties and property loss. Regrettably, the present techniques, such as water tubs and dust barriers, cannot effectively suppress multiple and continuous explosions. Being a porous medium, foam ceramics are characterized with large porosity and strong resistance against high temperature and shocks. Theoretical analysis and experimental study suggest that, due to numerous collisions with the walls in foam ceramics, the free radicals –generated in the chemical reactions of gas combustion and responsible for flame propagation, can be significantly destroyed, the reactive heat release be restrained, thus making the chemical reactions non-self-sustained. As a result, flame propagation is quenched. Furthermore, foam ceramics can markedly attenuate shock waves. Thus, if properly designed and arranged in the roadways, the material is expected to become a new-generation gas explosion suppression and isolation method in coal mines.

Abstract: The effect of Yb₂O₃ addition on sintering of MgO ceramics was studied in this work. Increasing of Yb₂O₃ addition is helpful to densification and grain growth. The effect of Yb₂O₃ amount on densification decreased when the sintering temperature was increased from 1400°C to 1550°C. Quick densification and rapid grain boundary mobility in Yb₂O₃ doped samples come from the point defect because the dopant mainly located at the grain boundary, and this is meaningful for grain growth and densification. The results also illustrate that sintering time and sintering temperature would noticeably affect grain growth and densification process, which is not related to the amount of Yb₂O₃ addition.

Abstract: High-porosity silicon nitride ceramics with excellent mechanical properties were fabricated by the carbothermal reduction of SiO₂. The influences of sintering conditions on microstructure and mechanical properties were studied. The results showed that microstructure and mechanical properties of porous silicon nitride ceramics were dependent mostly on the sintering conditions. The sintered porous silicon nitride ceramics exhibited the formation of fibrous microstructure with submicrometer-sized, high-aspect ratio b-Si₃N₄ grains, and uniform pore structure. Porous Si₃N₄ ceramics with a porosity of about 70%, and a flexural strength of about 70 MPa were obtained by sintering at 1750°C, with lower rate of temperature rise and no retaining time. The high strength was attributed to fine, high-aspect ratio b-Si₃N₄ grains and uniform pores between grains.

Abstract: Second phase and defect formation mechanism of (Bi_0.5(Na_1-xK_x)_0.5)TiO₃ (BNKT100x) ceramics were investigated using electron microscopy, x-ray photoelectron spectroscope (XPS) and electrical properties measurements. Experimental results indicated that second phase formation induces Bi-rich regions and compositional inhomogeneity within matrix due to thermodynamic stability of potassium titanate. Ti valence transition for BNKT ceramics sintered in air might be ascribed to formation of the secondary phase, rather than simply attributed to volatilization of bismuth. Li substitution at A-site in BNKT ceramics suppresses formation of the second phase and Ti valence transition. Appropriate Li doped BNKT ceramics suppress oxygen vacancies and titanium valence transition, and therefore decrease the leakage current.