纳米SiC-Al_2O_3/TiC多相陶瓷复合材料显微结构的研究

考察了纳米SiC -Al2 O3/TiC多相陶瓷复合材料的断裂方式 .由于纳米SiC的加入 ,材料以穿晶断裂为主 .通过透射电镜观察 ,研究了纳米陶瓷复合材料中纳米SiC的分布 ,证明所制备的材料主要为晶内型纳米复合陶瓷 .在纳米SiC -Al2 O3/TiC多相陶瓷复合材料中 ,少量纳米SiC位于基体晶粒间 ,大多数纳米SiC位于基体晶粒内 ,而且纳米SiC的加入细化了基体的晶粒 .通过高分辨透射电镜观察 ,研究了纳米SiC -Al2 O3/TiC多相陶瓷复合材料中 ,纳米SiC与基体间界面结合状态 ,发现在两颗粒间的晶界几乎没有玻璃相 ,证明纳米陶瓷复合材料中晶界得到了加强 ,有利于材料力学性能的提高 .另外研究了裂纹在材料中的扩展行为 ,结果表明 ,纳米粒子对裂纹的扩展起到偏折和钉扎作用     

纳米SiC对Al2O3/TiC基多相陶瓷材料显微结构的影响

从烧结温度、基体晶粒大小、断裂方式、SiC在基体中的分布等几方面研究了纳米SiC颗粒的加入对Al2O3/TiC复相基体显微结构的影响.实验表明,纳米SiC颗粒的加入提高了烧结温度,抑制了基体晶粒的异常长大,明显细化了晶粒.试样的断裂方式从以沿晶断裂为主转变为以穿晶断裂为主.纳米SiC在基体中分布均匀,部分位于晶粒内,另一部分位于晶界上.这种显微结构有利于材料力学性能的提高.     

SiC晶须增强Al2O3—TiC复相陶瓷的研究

运用品须补强和粒子弥散双重手段,对氧化铝材料的性能进行改进。比较了Al_2O_3-TiC(AT),Al_2O_3/SiC_w(As),Al_2O_3-TiC/SiC_w(ATS)材料的力学性能,证实ATS材料有明显的迭加增强增韧效果,并具有良好的高温力学性能。抗氧化实验证实,将SiC晶须加入AT中以后,材料的抗氧化性能有明显改进。从热膨胀失配角度分析和SEM显微结构观察证实,ATS材料的主要增韧机理是界面解离和裂纹偏转。     

添加ZrO2对Al2O—SiC系复相陶瓷力学性能的影响

通过ZrO2强化增韧Al2O3-SiC系陶瓷，其复合材料的力学性能在一定程度上获得改善。ZrO2外加含量在0－40wt%范围内，复相陶瓷的断裂韧性保持上升，而其硬度则呈下降的趋势。少量添加ZrO2(≤10wt%)时，其强度得到提高，当ZrO2含量为10wt%左右，强度达到最大值；超过该含量后强度迅速下降。研究结果表明，复相陶瓷力学性能与瓷体中的二相粒子的相变增韧和热应力共配有关。X射线衍射分析研究表明，随着ZrO2含量增加，材料断口相变量增大，断裂韧性也相应提高，确是ZAS（ZrO2增韧Al2O3-SiC)复相材料中ZrO2(t)→ZrO(m)相变增韧起主要作用。当ZrO2添加含量增加时，二相粒子与基体热膨胀系数不匹配，而在复合材料中产生内应力导致瓷体强度降低，研究还表明10wt%ZrO2增韧Al2O3-SiC陶瓷是一种较佳的高温耐磨材料。     

α—Al2O3／SiC,莫来石／SiC和ZrO2／SiC二元复合材料的显微结构

用热压法制备了氧化物（刚玉、莫来石、氧化锆）与非氧化物（碳化硅）的二元复合陶瓷材料。采用ＴＥＭ和ＨＲＥＭ等手段对上述材料的显微结构和晶界附近的微区成分进行了研究，确定氧化物与碳化硅相可以直接结合并形成一定厚度的互扩散层。     

微波烧结Al2O3-TiC复合材料

用微波烧结制备Al2O3-TiC复合材料，并与常规烧结Al2O3-TiC复合材料对比，分析两种烧结方法对试样力学性能的影响，同时探讨添加剂对Al2O3-TiC复合材料烧结性能的影响。     

Al2O3/SiC/(W, Ti)C多相复合陶瓷材料的研究

建立了多相复合陶瓷材料增强相极限体积含量的理论模型,并采用热压工艺制得AI2O3/SiC/(W,Ti)C多相复合陶瓷材料,该材料具有良好的综合力学性能。研究表明：只有在合适的热压工艺和组分条件下才能获得良好的微观结构与力学性能。该陶瓷材料的增韧机制主要是裂纹偏转。此外,大量孪晶和位错的存在对材料的增韧补强也有所贡献。     

ZrO2—3Al2O3—2SiO2—Al2O3／SiCn纳—微米复相陶瓷的反应烧结技术

概述复相陶瓷和纳米陶瓷的主要内容和机理,介绍反应烧结ZrO3-3Al2O3-2SiO2-Al2O3/SiCn纳米复相陶瓷技术的研究内容,技术路线,工艺原理和发展前景。     

纳米Al2O3／PTFE复合材料的制备及其力学性能

以纳米Al2O3为填料,制备了纳米Al2O3填充PTFE复合材料,研究了纳米Al2O3的含量对PTFE复合材料性能的影响。结果表明,纳米Al2O3的加入使PTFE的拉伸强度和断裂延伸率有所下降,硬度增加;当Al2O3的质量分数为10％时,PTFE复合材料的综合力学性能最佳,随着Al2O3含量的逐渐增加,会使PTFE复合材料从韧性材料向脆性材料转化。     

The effect of TiO2 additive on sinterability and properties of SiC-Al2O3-Y2O3 composite system

In the current research, the effects of TiO₂ additive on mechanical and physical properties of SiC bodies, sintered by liquid phase methods were investigated. Al₂O₃ and Y₂O₃ were used as sintering-aids (10?wt% in total) with an Al₂O₃/Y₂O₃ ratio of 43/57 to provide liquid phase during Sintering. TiO₂ was also used as the oxide additive with an amount ranging from 0 to 10?wt%. After scaling and mixing the starting materials by a planetary mill, the obtained slurry was dried at 100?℃ for four hours. The derived powders were finally pressed under a pressure of 90?MPa. The samples were then pyrolyzed and sintered at 600?℃ and 1900?℃, respectively under argon atmosphere for 1.5?h. Phase analysis showed no trace of TiO₂ after the sintering process, demonstrating the complete TiO₂ to TiC transformation. The results showed that an increase in TiO₂ content up to 5?wt%, led an improvement in all the measured properties including the relative density, hardness, Young's modulus, bending strength, indentation fracture resistance and the brittleness factor, reaching to 96.2%, 24.4?GPa, 395.8?GPa, 521?MPa, 5.8?MPa?m^1/2 and 286.5?×?10^?6 m^?1, respectively. However more than 5?wt% additive resulted in a decrease in all the above-mentioned properties. Microstructural studies demonstrated that crack deflection and crack bridging were the major mechanisms responsible for an increase in the indentation fracture resistance.     

La2O3—TiO2系陶瓷物相与介电性能研究

固相法合成La2O3-TiO3系陶瓷介质材料,XRD、SEM、EDS分析其结构、形貌和成分。高精度电容测量仪测试其介电性能。La2O3/TiO2比1:2、2：9组分可获得极低介质损耗,XRD分析主晶相为La2Ti2O7和La4Ti9O24,La2O3/TiO2比1：3组分可获得La2/3TiO3、La4Ti9O24复相,缺陷型钙钛矿相La2/3TiO3不利于介质损耗降低。EDS分析表明晶界富集Si杂质,有效促进了液相烧结。     

柠檬醛在La2O3/γ-Al2O3催化剂上的等温吸附

对柠檬醛-乙酸乙酯溶液中柠檬醛在La₂O₃/γ-Al₂O₃催化剂上等温吸附行为进行了研究。结果表明,30 ℃柠檬醛在La₂O₃/γ-Al₂O₃催化剂上的吸附动力学符合准二阶吸附动力学模型,吸附动力学方程为：1/q_t=2.350/t+0.063 3(R²=0.998 5)。（30~65） ℃柠檬醛在La₂O₃/γ-Al₂O₃催化剂上的等温吸附符合Langmuir方程,温度升高使柠檬醛的饱和吸附量增加,吸附热为32.19 kJ·mol^-1。     

Effect of Al2O3 on mechanical properties of Ti3SiC2/Al2O3 composite

The effect of Al₂O₃ on mechanical properties of Ti₃SiC₂/Al₂O₃ composite fabricated by SPS was studied systematically. The results show that the hardness of the Ti₃SiC₂/Al₂O₃ composite can reach 10.28 GPa, 50% higher than that of pure Ti₃SiC₂. However, slight decrease in the other mechanical properties was observed with Al₂O₃ addition higher than 5–10 vol.%, which is believed to be due to the agglomeration of Al₂O₃ in the composite.     

Yb2O3 and Y2O3 co-doped zirconia ceramics

A suspension stabilizer-coating technique was employed to prepare x mol% Yb₂O₃ (x = 1.0, 2.0, 3.0 and 4.0) and 1.0 mol% Y₂O₃ co-doped ZrO₂ powder. A systematic study was conducted on the sintering behaviour, phase assemblage, microstructural development and mechanical properties of Yb₂O₃ and Y₂O₃ co-doped zirconia ceramics. Fully dense ZrO₂ ceramics were obtained by means of pressureless sintering in air for 1 h at 1450 °C. The phase composition of the ceramics could be controlled by tuning the Yb₂O₃ content and the sintering parameters. Polycrystalline tetragonal ZrO₂ (TZP) and fully stabilised cubic ZrO₂ (FSZ) were achieved in the 1.0 mol% Y₂O₃ stabilised ceramic, co-doped with 1.0 mol% Yb₂O₃ and 4.0 mol% Yb₂O₃, respectively. The amount of stabilizer needed to form cubic ZrO₂ phase in the Yb₂O₃ and Y₂O₃ co-doped ZrO₂ ceramics was lower than that of single phase Y₂O₃-doped materials. The indentation fracture toughness could be tailored up to 8.5 MPa m^1/2 in combination with a hardness of 12 GPa by sintering a 1.0 mol% Yb₂O₃ and 1.0 mol% Y₂O₃ ceramic at 1450 °C for 1 h.     

Corrosion mechanisms of Al2O3/MgAl2O4 by V2O5, NiO, Fe2O3 and vanadium slag

The effects of V₂O₅, NiO, Fe₂O₃ and vanadium slag on the corrosion of Al₂O₃ and MgAl₂O₄ have been investigated. The specimens of Al₂O₃ and MgAl₂O₄ with the respective oxides above mentioned were heated at 10 °C/min from room temperature up to three different temperatures: 1400, 1450 and 1500 °C. The corrosion mechanisms of each system were followed by XRD and SEM analyses. The results obtained showed that Al₂O₃ was less affected by the studied oxides than MgAl₂O₄. Alumina was only attacked by NiO forming NiAl₂O₄ spinel, while the MgAl₂O₄ spinel was attacked by V₂O₅ forming MgV₂O₆. It was also observed that Fe₂O₃ and Mg, Ni, V and Fe present in the vanadium slag diffused into Al₂O₃. On the other hand, the Fe₂O₃ and Ca, S, Si, Na, Mg, V and Fe diffused into the MgAl₂O₄ structure. Finally, the results obtained were compared with those predicted by the FactSage software.     

Coarse-grained refractory composites based on Nb-Al2O3 and Ta-Al2O3 castables

Coarse-grained refractory composites, with grain sizes between 20 and 5000?µm, based on Nb-Al₂O₃ and Ta-Al₂O₃ castables were produced for the first time and characterised in terms of shrinkage after sintering, splitting tensile strength, compressive strength, porosity and the measurement of the elastic properties (E, G and $\nu$). After sintering at a temperature of 1600?°C, the shrinkage of the composites was 1.5% and 0.3%. Measured values of splitting tensile strength were between 5.5 and 15?MPa and the ones of compressive strength were between 23 and 89?MPa. Values of E and G were between 117 and 45?GPa and 48–17?GPa, respectively, for samples with 11–45?vol% refractory metal. Poisson's ratio was found to be very sensitive to the bonding between the fine matrix and coarse-grained particles of the composites. Its value increased from 0.25 for good bonding to $\nu =0.43$ in case of poor bonding between the coarse metal particles and the fine ceramic matrix. DTA/TG measurement under air atmosphere showed that the metal-ceramic composites start to oxidise at temperatures above 450?°C.