聚醚型聚氨酯预聚体合成工艺研究

以聚醚多元醇和异氰酸酯为原料合成聚氨酯预聚体。通过测定—NCO的含量,研究了预聚反应时间和反应温度对预聚反应的影响;研究了R值[n(—NCO)/n(—OH)],反应时间和温度对预聚物黏度的影响,并探讨了预聚反应过程中含水量、预聚体贮存时间对弹性体性能的影响。     

铝合金环保型钝化及其与漆膜的配套性能

为了进一步提高三价铬钝化膜的耐蚀性及其与漆膜的配套性能,以2024铝合金为基材,筛选出钝化液中的配位剂和缓蚀剂,并确定其工艺条件,开发了一种性能优良的环保型三价铬钝化液。结果表明：经硅溶胶封闭处理后的三价铬钝化膜结构致密,电化学性能优良,耐中性盐雾试验可达168h,其耐蚀性与Alodine1200六价铬钝化工艺相当;与环氧底漆和聚氨酯面漆的配套性好。     

电偶对中6A01铝合金的电化学腐蚀行为研究

为了解决高速列车环境下6A01铝合金的电偶腐蚀问题,利用电化学阻抗谱和极化曲线等电化学方法研究了6A01铝合金在不同溶液中的电偶腐蚀行为.结果表明:6A01铝合金在NaCl溶液和模拟污水溶液中以点蚀为主,模拟污水溶液中铝合金的腐蚀速率较小,腐蚀速率随时间先增大后减小,再增大再减小,最后趋于稳定,铝合金的耐蚀性能减弱.铝...     

条形微裂纹对16MnR钢解理断裂韧性的影响

在常温下对热轧16MnR低合金钢缺口试样进行了不同预加载荷的正反弯曲试验,以在缺口前引入不同尺寸的条形微裂纹,然后通过高温回火消除残余应力和加工硬化,随后在—196℃下进行4点弯曲断裂试验,研究了条形微裂纹尺寸对缺口试样解理断裂韧性的影响。结果表明:当预载荷比(P₀/P_gy)小于0.861时,预载荷对解理断裂韧性影响较小;当预载荷比大于0.861后,条形缺陷在外加载荷作用下撕裂而形成的条形微裂纹,并且随预载荷比的增大条形微裂纹数量增多、尺寸增大、分布区域扩大,断裂载荷、断裂吸收功随预载荷比的增加而迅速下降;条形微裂纹所引起的局部高应力应变范围增大,使解理起裂源分布范围增大,也造成了缺口韧性参数P₁和W数值的分散。     

The reinforcement role of different amino-functionalized multi-walled carbon nanotubes in epoxy nanocomposites

Functionalization with different amino groups of multi-walled carbon nanotubes was achieved and nanotube-reinforced epoxy nanocomposites were prepared by mixing amino-functionalized multi-walled carbon nanotubes with epoxy resin. Differential scanning calorimetry, thermogravimetric analysis and bending tests were used to investigate the thermal and mechanical properties of the nanocomposites. The results showed that different kinds of amino-functionalized multi-walled carbon nanotubes would have different effects on the thermal and mechanical properties of the nanocomposites. The reinforcement mechanism of amino-functionalized multi-walled carbon nanotubes in epoxy resin was discussed.     

Wet and dry tribological behaviors of circular islandic protrusion patterns on M2 steel discs under spinning condition

Under spinning conditions, lubricant on islandic spot patterned M2 steel disc experiences centrifugal and tangential force components. Depending upon the relative position of the spots and the flow of lubricant, accumulation of lubricant in front of patterned islandic spots creates thrusting to mating part and subsequently reduces contact between the mating couple. Whilst wear debris is likely to be spun off the plateau of the spots to their neighbouring valleys so as to reduce wear. Hence, it gives favorable tribological characteristics. Aiming at verifying such mechanisms, studies were performed on M2 steel disc specimens slid with ASSAB 17 tool steel pin. The M2 steel disc specimens were respectively （i） machined with non-patterned （NP）, （ii） etched to produce in-lined （INE） islandic patterns, and （iii） etched to produce staggered （STE） islandic spot patterns. Results indicated that the INE patterned discs gave most favorable wear characteristics, the NP of the worse characteristics whilst the STE ranged in the middle. However, the actual contact mechanism leads to the descending sequence of favorable friction behaviors nominally as： NP, INE and STE.     

Tribological behaviors of spot-textured TiN coatings on M2 high-speed steel under boundary lubricated conditions

The effect of sliding duration on the tribological behaviors of spot patterned coatings was investigated. Two patterns based on physical vapor deposition （PVD） TiN coatings were used, such as, in-lined （IN） and staggered （ST） spots. The tribological behaviors were evaluated by using a Cameron-Plint wear test rig. The M2 steel discs deposited TiN coatings with IN and ST patterns slid against the ASSAB 17 tool steel pins at a speed of 0.23 m/s, in Shell Tellus T32 lubricant and were loaded with 900 N. The testing results on disc specimens with two types of PVD TiN spot patterns, all coated with a bias voltage of-180 V and slid for 4, 8 and 11 h respectively, were presented. The results revealed that the in-lined coatings possessed relatively better wear behaviors than the staggered pattern coatings. Mechanisms for such superiority and for the cause of peeling were discussed. A relevant design approach was suggested for the application of such patterned coatings.     

低碳模式下的电泳涂装前处理技术

从低碳的模式出发,总结了传统电泳涂装前处理过程中,实现低能耗、低排放、低污染的技术原则和方法。介绍了新型转化膜技术的发展和应用情况,以及新型转化膜实际应用过程中亟待解决的问题。展望了涂装前处理技术的发展方向。     

掺杂钙钛矿钴氧化物La0.75Sr0.25Co1-xFexO3(x=0,0.1)的电磁特性

采用溶胶-凝胶方法制备了La0.75Sr0.25Co1-xFexO3(x=0,0.1)多晶样品,通过室温X射线衍射、标准四探针法以及直流磁化强度测量对材料结构及电磁特性进行研究。结果表明,铁的掺入晶格结构基本没有发生变化,但掺铁后体系的电阻率增大,出现半导体-金属的转变,材料磁性明显下降,转变温度向低温方向移动,系统在低温下由自旋团簇玻璃态转变为自旋玻璃态。     

38CrMoAlA钢大模数齿轮深层离子渗氮工艺探讨

对38CrMoAlA钢大模数齿轮进行了深层离子渗氮工艺试验,检测了离子渗氮层的组织和显微硬度分布.结果表明,38CrMoAlA钢大模数齿轮经深层离子渗氮后,其耐磨性显著提高.中碳合金钢大模数齿轮深层离子渗氮工艺或许将部分代替低碳合金钢气体大模数齿轮的渗碳、淬火工艺.