SiC－AlN－Y_2O_3复相陶瓷的制备与性能

通过热压烧结技术，ＳｉＣ、ＡｌＮ和Ｙ２Ｏ３粉末混合作在１９２０～２０５０℃、Ａｒ气氛下形成了致密的复相陶瓷．在室温下ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相材料的抗弯强度和断裂韧性分别达到６００ＭＰａ和７ＭＰａ·ｍ１／２以上运用ＸＲＤ、ＳＥＭ和ＴＥＭ分析致密样品的断裂裂纹、形貌和组成．ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相陶瓷在１３７０℃氧化试验３０ｈ，其氧化产物为莫来石．     

SiC Particles Coated by Chromium Silicides

The interaction of chromium vapors with powderlike silicon carbide (SiC) was investigated by X-ray phase analysis, X-ray microanalysis, the EPR method, electron microscopy, and the BET method. It has been established that in the temperature range of 147 K to 2023 K under a pressure of 1.3 Pa, the main interaction product is chromium silicide (Cr₅Si₃), which forms a surface layer on SiC particles in zones with a mean temperature (T _mean) of 1773 K to 1473 K. Moreover, Cr₅Si₃ vapors passing through the disperse SiC system condense in cold-temperature zones on SiC particles and aggregates.     

SiC-Whisker-Reinforced Glass-Ceramic Composites: Interfaces and Properties

Different types of SiC whiskers were incorporated into lithium aluminosilicate (LAS) and calcium aluminosilicate (CAS) glass-ceramic matrices. Interfaces in these composites were characterized using Auger spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the observations were correlated with measurements of fracture toughness and strength. The chemistry and morphology of the resulting interfaces affected the composite strength and toughness and controlled the mode of crack propagation. Certain types of SiC whiskers were characterized by a carbon-rich near-surface chemistry that became more carbon rich after composite fabrication. In these materials, the flexural strength at 20°C increased by up to 400% and the fracture toughness increased by up to 500%. Crack propagation modes were characterized by crack deflection, whisker–matrix debonding, and crack bridging. In contrast, SiC whiskers with stoichiometric near-surface chemistry generally did not form carbon-rich interfaces during composite fabrication, resulting in composites with low strength and fracture toughness.     

碳化铁——新型的直接还原铁产品

由于短流程工艺的兴起，优质废钢短缺，人们对碳化铁的兴趣日益增加，本文介绍了碳化铁的特点及生产背景，并与海绵铁、热压块铁产品作了比较，最后分析了碳化铁在我国的发展前景。     

电石包装桶密封结构的发展与研究

介绍了特殊的化工材料－电石包装结构及容器的设计改进。首先分析了密封性、非密封性包装桶的利弊；也介绍了减压阀包装桶和充氮卷封型电力包装桶的结构及使用性能；最后提出了新型充氮密封结构的包装桶，较好解决了电石的包装。     

EDTA直接滴定法联测硬质合金中钴镍

以紫脲酸铵为指示剂，用ＥＤＴＡ为滴定剂，在氨性介质中联测Ｃｏ，Ｎｉ。首先取一份试液，用ＥＤＴＡ直接滴定剂Ｃｏ－Ｎｉ的合量。然后，另取一份试液，用（ＮＨ４）２Ｓ２Ｏ８掩蔽Ｃｏ，再用ＥＤＴＡ滴定测得Ｎｉ分量。该方法用于硬质合金中Ｃｏ，Ｎｉ的测定，结果满足。     

低活性Fe-Cr-Mn(W,V)奥氏体合金长期时效高温力学性能和相稳定性研究

研究了用于核反应堆中的低活性Fe -Cr-Mn(W ,V)奥氏体合金不同温度长期时效 (10 0 0h)后的高温拉伸性能 (40 0℃ )及相稳定性。结果表明 :Fe -Cr -Mn(W ,V)奥氏体合金经长期时效后 4 0 0℃时的屈服强度 (或σ0 2 ,40 0℃)随时效温度从 35 0℃至 4 5 0℃上升变化不大 ,4 5 0℃至 5 5 0℃从 2 95MPa上升到 4 4 4MPa,5 5 0℃至 6 5 0℃保持在 4 90MPa左右 ;抗拉强度 (σb)在 35 0℃至 4 5 0℃比较平稳 ,4 5 0℃至 5 5 0℃从 6 38MPa上升到 75 9MPa ,5 5 0℃至6 5 0℃保持在 75 0MPa左右 ;合金延伸率 (δ/ % ) 35 0℃至 4 5 0℃比较稳定 ,4 5 0℃至 5 5 0℃下降较快 ,在 5 5 0℃至 6 5 0℃下降比较平缓 ,6 5 0℃时δ值为 19%左右。合金经不同温度 (35 0℃～ 6 5 0℃ )长期时效组织为稳定的奥氏体相及少量碳化物 ,在 4 5 0℃以下长期时效 ,合金中无大量碳化物析出 ,4 5 0℃以上时效时 ,碳化物析出量明显增加 ,6 5 0℃时在晶界集聚 ,导致合金拉伸强度上升而塑性下降     

Diffusion-Accommodated Grain Boundary Sliding and Dislocation Glide in the Creep of Sintered Alpha Silicon Carbide

Constant compressive stress creep experiments in the temperature and stress ranges of 1770 to 2020 K and 35 to 373 MPa have been performed on polycrystalline alpha SiC. Specimens having average grain sizes of 3.5, 4.9, and 7.5 μm have been studied in order to determine the grain size dependence of steady-state creep in this material and to distinguish the relative contributions of diffusion-accommodated grain boundary sliding and dislocation glide. Analysis of steady-state creep rate data revealed different kinetics of creep below and above 1920 K as follows: activation energies of 387–541 and 838–877 kJ/mol, stress exponents of 1.0–1.4 and 1.4–2.5, and inverse grain size exponents of 2.5 and 4. The m value of 2.5 indicated Coble-controlled creep with a contribution of Nabarro–Herring creep in the low-temperature range. The m value was less reliable for the high-temperature range because of the large differences in the microstructures of the three materials. The large number of high aspect ratio grains with increasing average grain size resulted in different contributions of diffusion-accommodated grain boundary sliding and dislocation glide between thsee materials.     

Deformation of Alumina/Titanium Carbide Composite at Elevated Temperatures

The deformation behavior of an Al₂O₃/30 wt% TIC composite in uniaxial tension was evaluated under vacuum over the temperature range of 1300° to 1550°C. The Al₂0₃/TiC composite exhibited the maximum elongation of 66% at an initial strain rate of 1.19 X l0^-4 s^-1 at 1550°C. The stress exponent calculated from peak stresses of true stress-true strain curves at 1500^OC was 3.8, which was in good agreement with that obtained by changing the crosshead speed during the tension test. The apparent activation energy at 20 MPa was 853 kJ/mol. In addition the deformation of the Al₂O³/TiC composite in uniaxial tension at elevated temperature was accompanied by cavitation.     

无低温过渡高温还原钼粉试验研究

无低温过渡 ,高温还原下得到 0 <50 0mg/kg ,F .s .s.s 5 .6～ 6 .5μm低氧、粗颗粒钼粉。还原时间短 ,装舟厚度最大 65mm ,可大幅度提高单台钼粉还原炉生产率