氮化制度对Si-Al-Al2O3体系合成Sialon的影响

以SiC、α-Al2O3微粉、Si粉、Al粉为原料,在1450℃流动氮气中制备Sialon/SiC材料。研究了不同温度保温氮化对Sialon合成的影响。研究结果表明:有部分硅粉残余没有氮化;在1100℃保温氮化的氮化率高于在1150℃、1200℃保温氮化;1100℃保温氮化,残余Si量少、分布均匀,残余硅熔聚现象较轻,利于Sialon的合成。     

Al2O3-SiC-C质主铁沟浇注料的结合相研究

对高炉主出铁沟用Al2O3-SiC-C质浇注料的结合相变化进行了分析，其中涉及到溶胶结合、氮化硅铁为添加物形成的sialon结合、水泥形成的水硬性结合。溶胶结合强度主要来自于化学结合；而sialon结合、水泥结合的强度仍然来自少量水泥形成的水硬性凝固相的作用，因此对烘烤工艺、使用效果的影响不同。     

β-sialon结合SiC复相材料的分相抗氧化行为

对粘土类原料碳热还原及氮化反应法合成的β-sialon结合SiC复相耐火陶瓷材料进行了不同氧化条件下的抗氧化性实验。研究表明：1300℃时的氧化过程在12h内为化学反应控制阶段，12h后为扩散控制阶段。扩散控制阶段反应符合Ginsterlinger扩散动力学关系。首次分别得到复合状态下的β-sialon基质相、SiC颗粒相及β-sialon结合SiC复合相在1300℃下的分相扩散控制型抗氧化反应动力学方程，从各相的扩散控制型反应级数确认了β-sialon基质相对SiC颗粒相的高温氧化保护作用以及复相材料具有的优异抗高温氧化性能。     

On the origin of fine structure in the photoluminescence spectra of the β-sialon:Eu2+ green phosphor

Abstract

The photoluminescence (PL) and PL excitation (PLE) spectra of Si_6?zAl_zO_zN_8?z (β-sialon):Eu²⁺ phosphors with small z values (z=0.025–0.24) were studied at room temperature and 6 K. The PL and PLE spectra exhibit fine structure with the PL lines being as sharp as 45–55 nm even at room temperature; this fine structure was enhanced by decreasing the z value. These results can be used for expanding the color gamut of liquid crystal displays, particularly in the blue–green region. From low-temperature measurements, the fine PLE structure was ascribed to discrete energy levels of ⁷F_J states. The 4f⁶5d excited states of Eu²⁺ are considered to be localized near the 4f orbital. This is because the bonding of Eu²⁺ with surrounding atoms is ionic rather than covalent. Lattice phonon absorptions were also observed in the PLE spectrum, revealing that the optically active Eu²⁺ ions are located in the β-sialon crystal. The PL spectrum of the sample with the smallest z value (0.025) consists of a sharp zero-phonon line and lattice phonon replicas, which results in a sharp and asymmetric spectral shape.     

Physicochemical Investigation of the Reaction of Components of the Si — Al — O — N — Ti System in the Si3N4 — Al2O3 — AlN — SiO2 — TiN — TiO2 Region. Part 2. Subsystems Si3N4 — AlN,TiN — AlN,Al2O3 — AlN

The reaction of components of the Si — Al — O — N — Ti system in its elements Si ₃N₄ — AlN, TiN — AlN, and Al ₂O ₃ — AlN was investigated by differential thermal and x-ray diffraction analysis. It was established that upon hot pressing mixtures of Si₃N ₄ and AlN (up to 1950°C) free silicon is formed by the decomposition of Si ₃N₄, which reacts with oxygen present as an impurity to form SiO. When TiN reacts with AlN a phase with the spinel structure (Al₂₃O ₂₇N ₅), which can form only in the presence of excess oxygen, appears in addition to the initial components. Spinel is also produced by the reaction of Al ₂O₃ with AlN. In this case a eutectic between Al ₂₃O₂₇N₅ and Al₂O₃ is observed.     

Sintering Behavior of Hot-Pressed Ca–αSialon Ceramics

On the basis of phase relationships in the Ca–Si–Al–O–N system, a Ca––sialon ceramic was synthesized using the hot-pressing technique. The reaction sequences and densifications of the Ca––sialon vs. firing temperatures have been characterized in detail. The present experiments reveal a reaction sequence as follows: at 1250°C the reactant mixture started to soften, at 1300°C a gehlenite phase was produced, at 1500°C the gehlenite phase was resolved into a liquid phase and a Ca––sialon started to form, and at 1600°C the formation of Ca––sialon was complete. The product was stable and almost entirely single phase Ca––sialon. Accompanying to the above sequences, densification also proceeded via a liquid-phase sintering, particle rearrangement, solution–reprecipitation, and grain growth process. In the final microstructure elongated grains of Ca––sialon were obtained, improving the fracture toughness of this Ca––sialon ceramic.     

Sialon陶瓷的无压烧结

以Si_3N_4、Al_2O_3和AlN为原料,Y_2O_3为烧结助剂,采用无压烧结制备Sialon陶瓷．对试样的体积收缩率、抗弯强度、洛氏硬度等力学性能进行测试,扫描电镜(SEM)观察表明,在无压烧结条件下,采用埋粉烧结并充N_2保护,烧结温度为1700℃,保温90min可得到Sialon陶瓷,其中成分为54%α-Si_3N_4 32%Al_2O_3 8%AlN 6%Y_2O_3的Sialon陶瓷,其抗弯强度为390．08MPa,硬度为92．5HRA,显微结构为明显的柱状晶．     

In situ synthesis of PcBN composites from Sialon–TiN–TiB2 binder and cBN under high temperature and pressure

Polycrystalline cubic boron nitride (PcBN) composites were synthesized in situ with TiB₂, TiN, and Sialon as binders under ultrahigh temperature (1550°C) and high pressure (5.5 GPa). X-ray diffractometry, universal testing machine, field emission scanning electron microscopy, and transmission electron microscopy were used to study the effect of Sialon content (0%, 20%, 40%, 60%, and 80% by mass of binder) on the phase composition, microstructure, and mechanical properties of PcBN composites. The results show that the main phases in the system are lamellar TiN, needle-rodlike TiB₂, and irregular long-rodlike Sialon. Some TiB₂ grows along the (1 0 −1 0) face, and Sialon grows along the (0 0 0 1) face. The density and mechanical properties of the sintered product are significantly improved due to the formation of Sialon. When the content of Sialon is 60%, the binder is uniformly distributed, the cBN interface is well bonded, and the density is the highest. At this time, the strength reaches the maximum 34.57 GPa, the fracture toughness is 6.82 MPa m^1/2, and the flexural strength reaches the maximum 870.79 MPa. On the whole, cBN composites have excellent prospects for future applications in cutting inserts due to their excellent mechanical properties.