Preparation of Titanium Nitride/Alumina Laminate Composites

A preparation route for TiN/Al₂O₃ laminate composites has been described. A water-based process using Al₂O₃ and TiN slurries with solids contents of 40 and 35 vol%, respectively, was used to make TiN and Al₂O₃ tapes. The removal of the binder was monitored by weight-loss measurements in a thermogravimetry unit. Bodies composed of Al₂O₃ and TiN tapes were densified at temperatures of 1400° and 1500°C using the Spark Plasma Sintering^® (SPS) technique. Densities of >98% of the theoretical densities were approached. Crack-free and almost fully densified TiN/Al₂O₃ compacts were prepared by heating the burned-out green bodies to the final sintering temperature (1500°C) at a rate of 100°C/min, and with a holding time of 5–10 min, under a pressure of 75 MPa. The microstructures of the obtained compacts were studied using scanning electron microscopy. Grain sizes in the sintered Al₂O₃ and TiN compacts were similar to those of the precursor powders. Hardness and indentation fracture toughness were measured at room temperature, and the monolithic compacts as well as the laminate composites exhibited anisotropic mechanical behavior; i.e., the cracks propagated much more easily in a direction parallel to the laminas than perpendicular to them.     

Vibrational spectroscopic characterization of rigid rod polymers: 3. Microstructural changes in stressed polymers

Highly oriented poly(p-phenylene benzobisthiazole) films were stressed in a miniature hydraulic tensile tester interfaced to a fast scanning Fourier transform infra-red spectrometer. The changes in relative intensity, polarization, frequency and shape of infrared bands have been useful in the elucidation of microstructures. With the short time resolution achievable, vibrational bandshape and frequency have been shown to change at different rates when an external stress was applied.     

吊车断裂弹簧钢板的焊接修复

吊车上的板弹簧是一个很重要的零件,它在反复应力下工作,承受较大的冲击负荷和振动,要求其应具有较高的疲劳强度、抗拉强度等性能。由于板弹簧为碳含量较高的合金钢,焊接性差,修复断裂的板弹簧较困难。某公司的一台日本进口TL-252型25t吊车,在使用二年内先后发现五块弹簧钢板断裂,给现场施工带来了不便和一定的经济损失。经制定严格的工艺,对断裂板弹簧成功地进行了焊接修复,修复后使用效果很好。1板簧材料及可焊性分析断裂的弹簧钢板为日本钢号SUP6,相当于我国的60Si2Mn弹簧钢,其化学成份见表1。表1SUP6钢的化学成份(%)C Si Mn S P …     

Studies of microhardness and mar resistance using a scanning probe microscope

Scanning probe microscopy (SPM) is in a period of rapid development. It shows great promise for characterizing coating surfaces. This paper describes modification of an SPM so that it can be used to mar the surfaces of coatings under controlled conditions and to characterize the mars. Mar resistance of coatings is analyzed in terms of a ‘three response, two mechanism model.' The three responses (fracture, elastic, and plastic) can be measured quantitatively using the SPM. Of the three responses, only two (fracture and plastic deformation) are marring mechanisms – elastic deformations recover instantaneously. In some cases mars resulting from plastic deformation may recover slowly with time or with immersion in water; this phenomenon is attributed to viscoelastic creep. Microhardness is also measured with the modified SPM. Some thermoset coatings appear to be substantially harder near their surfaces than in the mass of material, and such materials may respond quite differently to stress applied at different levels near the surface. This finding has important implications for all coating properties that are strongly influenced by the surface. A quantity called ‘micro mar resistance' is defined. It may be useful for comparing different coatings under specified conditions of marring. However, there can be no single quantity that expresses ‘mar resistance' of a coating under all conditions.     

加压下二氧化碳在二甲基甲酰胺中的溶解度研究

本文报道了二氧化碳在二甲基甲酰胺中的溶解度,实验温度分别为15、20、25、30、35、40、45℃,实验压力为207.21—1684.02kPa.并且提出一个考虑了过量熵的、用溶度参数表示的活度系数方程.     

淤浆鼓泡床中固体粒子的悬浮特性

研究了三相鼓泡床中的临界固含率,以空气作气相,水、乙醇-水、丙酮-水、萜松醇-二甲苯作液相,石英砂、煤、雷奈镍作为固相。分析了鼓泡柱的高径比、气体速度、固体粒子的大小和比重、液体的粘度对临界固含率的影响,提出了含有这些参数的无因次数群的关联式,讨论了本文提出的关联式和文献报导的差别。     

游戏产品有效粘合用户时间的策略研究

通过对游戏的分类、发展历程梳理以及用户的需求分析,结合游戏产生过程给出了游戏产品有效粘合用户时间的策略,最后预测了游戏的发展趋势。     

关于控制氯代烃的政策选择

本文分析了氯代烃的生产所引起的环境问题,并提出了减少氯代烃环境影响的政策选择的基本原则。     

A recognition method of vibration parameter image based on improved immune negative selection algorithm for rotating machinery

To overcome the limitations of traditional monitoring methods, based on vibration parameter image of rotating machinery, this paper presents an abnormality online monitoring method suitable for rotating machinery using the negative selection mechanism of biology immune system. This method uses techniques of biology clone and learning mechanism to improve the negative selection algorithm to generate detectors possessing different monitoring radius, covers the abnormality space effectively, and avoids such problems as the low efficiency of generating detectors, etc. The result of an example applying the presented monitoring method shows that this method can solve the difficulty of obtaining fault samples preferably and extract the turbine state character effectively, it also can detect abnormality by causing various fault of the turbine and obtain the degree of abnormality accurately. The exact monitoring precision of abnormality indicates that this method is feasible and has better on-line quality, accuracy and robustness.     

Research on the friction and wear mechanism of Poly(vinyl alcohol)/hydroxylapatite composite hydrogel

Poly(vinyl alcohol)/Hydroxylapatite (PVA/HA) composite hydrogel was prepared with poly(vinyl alcohol) and hydroxylapatite as raw materials, using the method of repeated freezing and thawing. The morphologies of PVA/HA composite hydrogel were observed by means of high-accuracy 3D profiler and scanning electron microscope (SEM). The compressive elastic modulus and the stress relaxation characteristics of PVA/HA composite hydrogel were measured using the flat-head cylinder indenter. The friction and wear tests between PVA/HA composite hydrogel and bovine knee articular cartilage were performed on the micro-tribometer. The worn morphologies of PVA/HA composite hydrogel were observed with environmental scanning electron microscope (ESEM). The results showed that PVA/HA composite hydrogel has the cross-link network microstructure which is similar to that of the natural bovine knee articular cartilages. With the increase of freezing-thawing cycles and the HA content, the degree of cross-link and the crystallization of PVA/HA composite hydrogel both increase, the elastic modulus increases evidently, the rate of stress relaxation is improved and the value of balance stress decreases. The friction coefficient decreases with the increase of the freezing-thawing cycles and the HA content. The more the freezing-thawing cycles are, the earlier the friction coefficient reaches the stable balance value. The friction deformation depth between PVA/HA composite hydrogel and bovine knee articular cartilage is inversely proportional to freezing-thawing cycles and the HA content. The main wear mechanisms of PVA/HA composite hydrogel are plastic flowing and adhesive flaking. The wear severity degree decreases with the increase of freezing-thawing cycles and the HA content. Supported by Key Program of the National Natural Science Foundation of China (Grant No. 50535050), Program for New Century Excellent Talents in University (Grant No. NCET-06-0479) and Natural Science Foundation of Jiangsu Province (Grant No. BK2005403)