β′-α′-Sialon 二相陶瓷

采用一种新方法制备β′-Sialon 活性粉料,以 Y_2O_3和 Al_2O_3等为添加剂,经高温无压烧结,制得了β′-α′-Sialon 二相陶瓷。它的抗折强度室温时为564MN/m~2,1200℃时为450MN/m~2,硬度 HR_A 为92～93,断裂韧性K_(1c)为4.74MN/m~(3/2)。     

Densification process of α′-sialon ceramics

The liquid-phase sintering process of -sialon ceramics has been investigated by high-temperature dilatometry and microstructural observation. In addition, isothermal shrinkage measurements have been performed to examine the densification kinetic parameter. It has been confirmed that densification kinetic parameters in the solution-reprecipitation stage are much larger than the rate exponent predicted for the classic liquid-phase sintering model, and are slightly smaller than that for the viscous flow process. Rapid shrinkage was observed in the solution-reprecipitation stage from the results of shrinkage rate, and corresponds to pore elimination by particle rearrangement and cooperative flow of particle/liquid mixture. These processes provide the major contribution to shrinkage. In addition, the liquid flow process occurs when the silica content in the raw powder increases, but it is retarded due to the formation of -sialon. It is anticipated that particle rearrangement and cooperative flow, as well as liquid-flow processes, take place in the solution-reprecipitation stage of sintering of Si₃N₄-based materials, and cause a large amount of shrinkage.     

α′-β′-Sialons-YAG陶瓷无压烧结性能的多元分析和设计

本工作应用多元分析方法研究了α′-β′-Sialons-YAG 陶资的无压烧结性能.结果表明,具有不同烧结致密化类型的陶瓷试样训练点位于主成份平面的不同区域.部分最小二乘方模型建立了陶瓷组份与烧结密度的定量关系,并预报了可具有较高的致密化程度的陶瓷组份.     

Diffraction studies of β″-magnesium sialon

The compositions of high magnesium content -magnesium sialon crystals within the 3M/4X plane of the Mg-Si-Al-O-N system indicate some form of metal atom ordering wihtin the structure. Although it is not possible using X-ray diffraction to detect weak additional reflections arising from the ordering between magnesium, aluminium, and silicon atoms, such weak reflections are revealed on electron diffraction photographs for a phase, resulting in a tripling of the hexagonal latticec-dimension. These show to have a structure very similar to rhombohedral willemite (Zn₂SiO₄), with the (Mg, Al) metal atoms ordered with respect to the silicon atoms in a 21 ratio. However, there are some additional weak diffraction spots with indices not obeying the rhombohedral condition of –h+k+l=3n. It is proposed that the structure of this is identical to that of willemite and the extra spots are a result of some form of twinning, which implies the existence of ordered microdomains.     

Mechanical properties of β-Si3N4 whisker reinforced α′-SiAlON ceramics

The effects of -Si₃N₄ whisker additions on the mechanical properties of -SiAlON ceramics were studied. The room temperature fracture toughness and fracture strength of the composites increased with increasing whisker content, and were 6.5 MPa m^1/2 and 900 MPa, respectively, for the addition of 30 vol% whiskers. Although creep resistance of the composites was not enhanced at 1200°C, the whisker additions were observed to be beneficial in reducing the oxidation induced slow crack growth of -SiAlON that occurred at 1300 °C, and thereby, improved the creep resistance of the composites at 1300°C.ORNL Postdoctoral Fellow, Oak Ridge Institute of Science and Technology, Oak Ridge Associated University.     

5,5′-二硝胺基-3,3′-联-1,2,4-三唑的晶体结构与热性能

制备和培养了5,5′-二硝胺基-3,3′-联-1,2,4-三唑(DNABT)单晶,采用X射线单晶探射仪测定了晶体结构,该晶体属单斜晶系,空间群为P21/n(14),晶体学参数为a=0.5236(6)nm,b=1.7832(7)nm,c=0.6308(7)nm,β=112.48(2)°,V=5.428(106)nm3,z=2,D=1.788g/cm3。采用TG-MS技术研究了DNABT的热性能,在热分解峰温为201℃时检测到m/z=30(NO+)、m/z=28(N2+)、m/z=44(N2O+)、m/z=27(HCN+)等离子峰,在吸热峰温为96.49℃时检测到m/z=47(HNO2+),表明DNABT在失去结晶水的过程中伴随分解过程。     

Manufacturing of cellular β-SiAlON/β-SiC composite ceramics from cardboard

Light-weight, cellular β-SiAlON/SiC ceramics were produced via dip-coating of an Al/Si-powder containing preceramic polymer slurry into corrugated cardboard. The coated cardboard preforms were pyrolyzed in Ar-atmosphere at 1200°C, where the cellulose fibres decomposed into carbon. Simultaneously the Al/Si melt infiltrated into the porous carbon and formed β-SiC. Subsequent nitridation at temperatures between 1200–1530°C resulted in the formation of a β-SiC-containing composite. Different pre-oxidation treatment resulted in a variation of the oxygen content in the solid solution phase (z = 0.6–1.2).     

Crystal defects and coherent intergrowth of α- and β-crystals in Y-Ce doped sialon materials

Sialon material doped with a mixture of yttrium and cerium in a molar ratio of 1 to 3, up to a total amount of 6 wt% has been investigated with high resolution transmission electron microscopy (HREM). The-sialon crystals were shown to contain defects of types not previously reported. These include stacking faults, shear and coherent intergrowth of- and-sialon crystals. For some of the defects structural models are proposed and verified by image simulations.     

用硅灰和氧化铝合成β′-Sialon

硅灰是生产硅铁及半导体硅时产生的一种工业废料。1981年世界硅灰产量为130万t,我国约3万t,目前大量弃置。它粒径小,活性高,且成份稳定,是一种理想的SiO_2原料。华东化工学院无机材料系采用硅灰和氧化铝作原料,加入炭黑及少量反应促进剂,造粒后,在垂直式反应炉中1450℃通氮气流进行碳热还原反应,制得Sialon粉末,经X-射线物相鉴定为β'-Sialon。该合成粉末可用于耐火材料SiO_2、Al_2O_3的结合剂,及烧结块状的α'或β'-Sialon材料。还可用作金属成型的模具材料,切削材料等。     

The effect of crystallization of the grain-boundary phase on ambient temperature fatigue short-crack growth behaviour in Y-α′-β′-Sialon

The cyclic fatigue short-crack growth behaviour of Y---Sialons with both crystallized and amorphous grain-boundary phases, were investigated to determine whether crystallization of grain boundaries affected crack-growth behaviour under cyclic and monotonic loads. Micromechanisms for fatigue-crack growth in Y---Sialon were examined by scanning electron microscopy and high-resolution electron microscopy. These results show that the wear debris on the fatigue fracture surfaces gave evidence of a frictional wear crack-growth mechanism. Comparison of fatigue short-crack growth rates for Sialon of crystallized grain-boundary phases with that for the amorphous grain-boundary phases indicated that crystallization of grain-boundary phases does not appear to affect cyclic fatigue growth behaviour, similar to long-crack growth behaviour. The similarity of fatigue short-crack growth behaviour in both the crystallized and amorphous grain boundaries sialons is rationalized in terms of the thin residual amorphous grain-boundary regions.     

从β-聚丙烯到β-聚丙烯共混物

相对于聚丙烯(PP)共混物,β-PP共混物研究很少。文中对本实验室近几年开展的β-成核PP与聚苯乙烯(PS)、丙烯腈-苯乙烯共聚物(AS)、丙烯腈-丁二烯-苯乙烯共聚物(ABS)、尼龙(PA)、对苯二甲酸乙二醇酯(PET)共混物的制备、结构与性能进行了总结。重点讨论了不同第二组分及其用量、结晶度与极性,增容和制备方法等对PP共混物的β-成核作用的影响。观察到PS、AS和ABS对β-成核作用影响很小,可获得高β-晶含量的PP共混物。β-成核PP与PA、PET共混物的β-成核作用取决于制备方法,降低PET结晶度的方法和加入相容剂有利于共混物β-晶的形成。第二组分极性并不是影响共混物β-成核作用的主要因素。     

N,N′-二苯基丁二酰胺诱导生成β晶型等规聚丙烯

研究了酰胺化合物——N,N′-二苯基丁二酰胺(DPS)的用量和结晶温度对聚丙烯中β晶型含量和结晶度的影响。发现DPS是聚丙烯的高效β成核剂,随着DPS含量的增加,聚丙烯中β晶型含量不断增多。等温结晶试验表明,添加0.2%DPS的聚丙烯样品在结晶温度为120℃时生成最大含量β晶型,此时β晶型的相对含量达到89.06%。     

4-氰基-3,5,2′-三氟-4′-(反-4″-正丙基环己基)联苯的合成

以4-正丙基环己酮,3-氟溴苯和液晶中间体4-溴-2,6-二氟苯基氰为原料经5步反应合成4-氰基-3,5,2′-三氟-4′-(反-4″-正丙基环己基)联苯,经IR、MS、1HNMR数据分析确定了目标化合物结构.     

5,5′-二硝胺基-3,3′-亚甲基-联-1,2,4-三唑的合成、分子构型及热性能

以氨基胍碳酸氢盐(AG·HCO3)与丙二酸为原料,经合环反应得到5,5′-二胺基-3,3′-亚甲基-联-1,2,4-三唑(DAMT),再通过HNO3-NH4NO3体系硝化得到目标产物5,5′-二硝胺基-3,3′-亚甲基-联-1,2,4-三唑(DNAMT),总产率为92.1%。采用量子化学方法计算确定具有硝基亚胺结构的DNAMT分子构型更加稳定。通过热重和差示扫描量热法等方法研究DNAMT的热行为,升温速率10K/min时,DNAMT的初始热分解温度为248.7℃,峰温为260.9℃,放热量为1849.4J/g。计算得到DNAMT的热分解反应活化能E为225.3kJ/mol,指前因子A为1.585×1022s-1。热力学方程计算得到DNAMT的初始分解温度Te0以及自加速分解温度TSADT均为225.8℃,热爆炸临界温度Tb为235.4℃;DNAMT热分解反应的热力学参数ΔH≠、ΔS≠、ΔG≠分别为222.3kJ/mol、174.3J/(K·mol)和132.7kJ/mol。     

Analysis of Si3N4+β-Si3N4 whisker ceramics

Dense Si₃N₄+-Si₃N₄ whisker composite ceramics were fabricated by hot pressing powder-whisker mixtures. Addition of -Si₃N₄ whiskers had no significant influence on the densification behaviour for up to 20 wt% addition. Light microscopy and scanning and transmission electron microscopy were used to study their microstructure and fracture behaviour. An increase in fracture toughness was observed for -Si₃N₄ whisker additions of up to 10 %. The main toughening mechanisms observed were crack deflection, crack branching, whisker-matrix debonding and whisker pull-out.     

N,N′-4,4′-二苯甲烷双马来酰亚胺的合成工艺与应用

综述了合成N,N′-4,4′-二苯甲烷双马来酰亚胺(BDM)的醋酐脱水法、共沸蒸馏法、及其他改进工艺存在的问题。指出未来产品合成工艺采用一步法,就能够满足国内研发多功能的产品对收率、性能、合成成本、污染控制等方面的需求。     

新型空穴传输材料N,N′-二(α-萘基)-N,N′-二苯基-4,4′-联萘胺的合成与光电性质

以4,4′-联萘胺为母体,以最常用的空穴传输材料N,N′-二(α-萘基)-N,N′-二苯基-4,4′-联苯胺(α-NPD)为样板,合成了新型空穴传输材料N,N′-二(α-萘基)-N,N′-二苯基-4,4′-联萘胺(α-NPN)。通过核磁共振氢谱和元素分析进行了结构表征。差热分析测定其玻璃化温度(Tg)达到128℃。相对于α-NPD,α-NPN的吸收光谱和光致发光光谱都发生了红移。循环伏安法测定其氧化电势为1.20V,比α-NPD的1.02V稍高。该化合物可发明亮的蓝色荧光(461 nm),积分球测定其薄膜荧光量子效率为8.5%,比α-NPD的5.5%高。初步确定α-NPN可作为有机电致发光空穴传输材料。     

Phase relationship between β′- and O′-sialon at 1623 K

-sialon whiskers and co-products of synthesis, such as -sialon powders and O-sialon powders, were annealed at 1623 K for 8 h in a closed graphite reaction tube under 1 atm nitrogen. Phase stabilities, Si/Al ratios, and crystallographic features were investigated. The O-sialon phase, which formed in the early stage of synthesis when oxygen partial pressure was relatively high, became less stable in the present annealing condition and decomposed. The majority of released aluminium and possibly oxygen from the decomposed O-powder was incorporated into -sialon whiskers with little change in its lattice parameters, when the -sialon whiskers were included in annealing. The aluminium contents were always lower in the -whiskers than in the powders even after increasing its aluminium content during 8 h annealing. The lattice parameters of both -whiskers and powders increased with increasing aluminium content and became closer after annealing. The lattice parameters of -whiskers remained the same before and after annealing despite the increased aluminium content, while the lattice parameters of -powders decreased despite its aluminium content remaining unchanged. The lattice parameters of O-sialon increased with increasing aluminium content, and the increase in thea direction is the largest when compared with other parameters.     

4-羟基苯甲酸-2′-辛酯的合成

以对羟基苯甲酸为起始原料 ,经羟基保护、酯化和脱羟基保护三步反应 ,合成了难以用传统酯化法制备的 4 羟基苯甲酸 2′ 辛酯 ,总收率 6 5 % ,产物结构经IR及MS鉴定。