巨磁电阻在数据存储领域的应用

用巨磁电阻 (GMR)材料构成的磁电子学新器件,已成功地应用于计算机存储领域。介绍了用于计算机硬磁盘驱动器的巨磁电阻磁头和巨磁电阻随机存取存储器,描述了它们的工作原理、性能特点及研究现状和发展趋势。     

银盐照相乳剂制备最新动向

通过分析《美国化学文摘》中关于银盐照相材料的乳剂制备专利,了解到近几年柯达、富士等公司申请的专利主要涉及富氯卤化银 T－颗粒乳剂的制备、在 T－颗粒上引入线性位错和碘化银补加方法。     

钴基金属微粉的制备及其磁性能

采用水合肼作还原剂,从铁、钴、镍、铜盐的醇—水溶液中还原制备 Co1－ xFex、 Co1－ xNix合金微粉和 Cu/Co铜包钴微粉。采用 X射线粉末衍射 (XRD)、透射电镜 (TEM)、穆斯堡尔谱 (MS)和振动样品磁强计 (VSM),对合成样品进行表征。 Co1－ xFex合金微粉为体心立方 (bcc)结构的固溶体,其颗粒形貌为由约 50 nm的四角片状微晶堆砌而成的约 300 nm的类球形团聚体。组成为 Co0.4Fe0.6的合金微粉,其比饱和磁化强度σ s=179.41 A· m2· kg－ 1,矫顽力 Hc=34.32 kA· m－ 1,而 Co0.6Ni0.4的合金微粉,其矫顽力较高, Hc=43.40 kA· m－ 1。     

玻璃纤维增强聚酰胺66耐冷却液性能研究

从冷却液对材料力学性能影响的角度出发,研究了玻璃纤维增强聚酰胺材料在冷却液中的老化作用。选用质量分数为30 %的玻璃纤维增强聚酰胺66（PA66/30 %GF）开展冷却液热老化试验（1008 h,125 ℃）,研究在冷却液加速热老化过程各阶段材料的弯曲强度和冲击性能,并从微观结构的变化来分析其机理。结果表明,杜邦和索尔维的PA66/30 %GF经历1008 h老化后,弯曲强度大于70 MPa,性能保持率超过25 %,适宜在冷却液环境中长期使用。     

碳纤维增强尼龙66复合材料的制备及性能

采用双螺杆挤出机熔融共混法制备了碳纤维(CF)增强尼龙66复合材料(PA66/CF),对其结构进行了表征,并研究了其力学性能。扫描电镜照片显示,在PA66/CF复合材料中,CF与PA66基体充分粘结在一起,其微观形貌表明,体系中碳纤长度为0.5~0.7 mm。力学性能测试发现,与尼龙66相比,PA66/CF复合材料各项力学性能指标均有大幅度提高。当加入4束碳纤维时,PA66/CF复合材料力学性能最佳,该复合材料的拉伸强度为200.2 MPa,与PA66相比提高了113.2 MPa;弯曲强度为280.2 MPa,比PA66提高了190.3 MPa;弯曲模量为13560.8 MPa,比PA66提高了10628.7 MPa;冲击强度为14.8 kJ/m^2,比与PA66提高了6.3 kJ/m^2。该PA66/CF复合材料密度较小、力学性能优良,可以广泛应用于风电叶片、发动机罩盖、仪表盘、车尾门等产品当中。     

阻燃型鳞片石墨/尼龙6导热复合材料

为了使树脂基导热复合材料兼具优异导热性能和阻燃性能,分别选用RPM/Mg(OH)2、BPS/Sb2O3、HS-PNPAZ/Mg(OH)2作为阻燃剂,鳞片状石墨作为导热填料,PA6作为基体树脂,采用双螺杆挤出机制备了阻燃型鳞片状石墨/PA6导热复合材料。对比了不同阻燃剂体系对复合材料导热和阻燃性能的影响。结果表明,不同阻燃剂对复合材料导热系数的影响较小,复合材料的导热系数主要受鳞片状石墨的影响。当鳞片状石墨含量为40份时,复合材料的导热系数均大于2.0 W/(m·K)。BPS/Sb2O3和HS-PNP-AZ/Mg(OH)2在鳞片状石墨/PA6复合材料中无阻燃效果,不适合用于鳞片状石墨/PA6复合材料体系的阻燃。RPM/Mg(OH)2在鳞片状石墨/PA6导热复合材料中具有优异的阻燃效果,可使复合材料的阻燃性能达到UL 94~1.6 mm V-0级别。     

高填充尼龙6基复合材料非等温结晶行为的研究

采用熔融共混法制备了高填充尼龙6(PA6)基复合材料,使用差示扫描量热仪研究了复合材料的非等温结晶动力学,并采用不同方法对测试结果进行了分析,结果表明:Avrami-Ozawa方程联用能够较为准确地描述体系的结晶行为。     

注塑工艺对钛酸钾晶须改性POM和PA66共混体系力学性能的影响

用注塑成型方法制备了聚甲醛(POM)、钛酸钾晶须改性POM复合材料(ZA343)、PA66及钛酸钾晶须改性PA66复合材料(ZN262B)样品,运用控制变量法考察了工艺参数对其力学性能的影响。结果表明:ZA343和ZN262B相对于POM和PA66的拉伸强度分别提高53.8%和87.1%。当注射温度为210℃、模具温度为90℃、注射压力为55 MPa时,ZA343的拉伸强度最大为89.1 MPa;当注射温度为315℃、模具温度为60℃、注射压力为60 MPa时,ZN262B的拉伸强度最大为127.6 MPa。     

Long‐Term Properties of Injection‐Molded Micro‐Parts: Influence of Part Dimensions and Cooling Conditions on Aging Behavior

A variety of polymer parts used in microsystems technology is produced by injection molding. For dimensioning and design of these products, both the material properties and changes during the life cycle have to be taken into account. The aging behavior of parts with decreasing dimensions or of parts processed under different cooling conditions is discussed in terms of their morphological and mechanical long‐term properties. The results indicate that a decreasing part size leads to higher post‐crystallization and higher thermo‐oxidative degradation. This leads to size‐dependent changes in mechanical properties. Adjusted process conditions by application of thermal low‐conductive mold materials can favor the process‐related properties and thus the long term properties can be improved.

     

Morphology and mechanical property changes in compatibilized high density polyethylene/polyamide 6 nanocomposites induced by carbon nanotubes

Addition of carbon nanotubes to immiscible polymer blends with co‐continuous morphology features to improve the electrical conductivity has attracted much attention in recent years; however, less attention has been paid to the effect of carbon nanotubes on the morphology and corresponding physical properties of immiscible polymer blends with typical sea‐island morphology. In this work, therefore, functionalized multiwalled carbon nanotubes (FMWCNTs) were introduced into an immiscible high density polyethylene/polyamide 6 (HDPE/PA6) blend which was compatibilized by maleic anhydride grafted HDPE (HDPE‐MA). The distribution of FMWCNTs and the phase morphologies of the nanocomposites were characterized using scanning electron microscopy and transmission electron microscopy. The crystallization and melting behaviors of the components were analyzed by differential scanning calorimetry, which is thought to be favorable for an understanding of the distribution of FMWCNTs. It is interesting to observe that the morphology of PA6 particles is very dependent on the method of preparation of the nanocomposites. Correspondingly, FMWCNTs exhibit an apparent reinforcement effect and/or an excellent toughening effect for the compatibilized HDPE/PA6 blend, depending upon their distribution state and the variation of PA6 morphology. This work proves that FMWCNTs have a potential application in further improving the mechanical properties of compatibilized immiscible polymer blends. Copyright © 2012 Society of Chemical Industry