航空航天用永磁材料磁性温度稳定性研究

通过-70～300℃高低温试验对航空航天用永磁材料进行了老化处理以稳定其磁性能;此外还运用AMT-4高温硬磁测试系统对其在20～180℃范围内磁性能变化进行了研究。结果表明,老化试验可提高AlNiCo8永磁合金的磁性能的稳定性,且随着高低温处理温差的增加,磁性能越来越稳定。在20～180℃范围内,随着温度的升高,AlNiCo8永磁合金的磁能积、剩磁和矫顽力都有所变小。     

蔗糖酯合成的动力学研究

由蔗糖和棕榈酸乙酯在催化剂等助剂的作用下 ,采用无溶剂酯交换法合成棕榈酸蔗糖酯 .在实验的基础上 ,以蔗糖为关键组分研究了蔗糖酯合成的宏观动力学模型 .实验结果表明 :该反应为表观一级可逆反应 ,得出该表观一级可逆反应的动力学模型XA-XAe=(XA0 -XAe)e-kt,并求取了模型参数     

Synthesis and Properties of Micron-size Magneic Polymer Spheres with Epoxy Groups

Micron-size superparamagnetic poly(styrene-divinylbenzene-glycidyl methacrylate) (PSt-DVB-GMA)spheres were prepared via a modified suspension copolymerization method. Oleic acid coated magnetite (Fe_3O_4)nanoparticles made by co-precipitation were first mixed with monomers of St, DVB, GMA, and benzoyl peroxide(BPO) to form oil in water suspension with the presence of poly(vinyl pyrrolidone) (PVP-K30) as a stabilizer.Then the temperature of mixture was increased at a controlled rate to obtain small and relatively uniform droplets.Finally, the copolymerization reaction was initiated by the decomposition of BPO. The morphology and propertiesof magnetic PSt-DVB-GMA microspheres were examined by SEM, TEM, VSM, XRD and FT-IR. The magneticmicrospheres obtained have very small size (about 4-7μm) in diameter with narrow size distribution and super-paramagnetic characteristics. Powder X-ray diffraction measurements show the inverse cubic spinel structure forthe magnetite dispersed in polymer microspheres. FT-IR     

分散聚合法合成含有环氧基的无孔超顺磁性微球及其表征

Non-porous superparamagnetic polymer microspheres with epoxy groups were prepared by dispersion polymerization of glycidyl methacrylate (GMA) in the presence of magnetic iron oxide (Fe3O4) nanoparticles coated with oleic acid. The polymerization was carried out in the ethanol/water medium using polyvinylpyrrolidone (PVP) and 2,2'-azobisisobutyronitrile (AIBN) as stabilizer and initiator, respectively. The magnetic microspheres obtained were characterized with scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) and Fourier transform infrared spectroscopy (FTIR). The results showed that the magnetic microspheres had an average size of 1μm with superparamagnetic characteristics. The saturation magnetization was found to be 4.5emu·g-1. There was abundance of epoxy groups with density of 0.028 mmol·g-1 in microspheres. The magnetic PGMA microspheres have extensive potential uses in magnetic bioseparation and biotechnology.     

磁性聚醋酸乙烯酯微球的制备及表面功能化修饰

在油酸包覆的Fe3O4磁流体存在条件下,以醋酸乙烯酯为聚合单体,二乙烯苯为交联剂,过氧化苯甲酰为引发剂,聚乙烯醇为稳定剂,采用改良悬浮聚合法制备了粒径在数微米之间的磁性聚醋酸乙烯酯微球,对制备的磁性微球进行了表面功能化修饰。利用扫描电镜、振动样品磁强计和Fourier变换红外光谱分别检测了磁性微球的形貌、磁性能以及微球表面修饰的活性功能基团。结果表明:微球大小在1～7μm,平均粒径为3.8μm,粒径分布相对较窄;比饱和磁化强度为15.0emu/g,具有超顺磁性。     

新型表面活性剂烷基多苷制备方法研究进展

烷基多苷是新一代非离子表面活性剂,它与其他表面活性剂配伍性好,对皮肤刺激性低,生物降解性好,毒性低．自８０年代以来,烷基多苷的生产工艺研究一直倍受关注．介绍了烷基多苷的主要合成方法,分析其后处理工艺,展望其发展趋势,并重点阐述以淀粉为主要原料在酸性催化剂存在下合成烷基多苷方法的研究进展．     

振动因素对航天永磁材料的影响研究

采用三因数三水平正交试验模拟了AlNiCo永磁合金在航空航天振动环境,并结合方差分析法,分析了各因素对材料磁性能的影响.结果表明,经过振动后材料未发生明显缺陷,磁性能仍在要求的范围内;各参数对磁性能的影响不显著,时间、频率、加速度对矫顽力都有一定影响,影响大小顺序为时间、加速度、频率,对其它磁性能影响很小.     

带环氧基的超顺磁性高分子微球的制备及其性能表征

Micron-size superparamagnetic poly(styrene-divinylbenzene-glycidyl methacrylate) (PSt-DVB-GMA)spheres were prepared via a modified suspension copolymerization method. Oleic acid coated magnetite (Fe3O4) nanoparticles made by co-precipitation were first mixed with monomers of St, DVB, GMA, and benzoyl peroxide (BPO) to form oil in water suspension with the presence of poly(vinyl pyrrolidone) (PVP-K30) as a stabilizer.Then the temperature of mixture was increased at a controlled rate to obtain small and relatively uniform droplets.Finally, the copolymerization reaction was initiated by the decomposition of BPO. The morphology and properties of magnetic PSt-DVB-GMA microspheres were examined by SEM, TEM, VSM, XRD and FT-IR. The magnetic microspheres obtained have very small size (about 4-7 μm) in diameter with narrow size distribution and superparamagnetic characteristics. Powder X-ray diffraction measurements show the inverse cubic spinel structure for the magnetite dispersed in polymer microspheres. FT-IR spectroscopy indicates extensive oxirane groups existed on the surface of magnetic PSt-DVB-GMA microspheres.     

IEEE802.15.3a两种物理层建议的比较

无线个域网是当前无线通信研究的热点之一,IEEE802.15.3a对发射信号的功率、短距离的高速率信息传输等方面提出了更高的要求。由于FCC对超宽带信号进行了重新定义,使得产生超宽带信号的方式并不局限在冲激无线电范畴,利用OFDM技术与DS CDMA技术也能实现超宽带通信。当前IEEE802.15.3a的2种主流技术(MB OFDM和DSCDMA)之间争执不下,将对2种技术进行详细的比较,比较结果显示,在当前的技术水平下,MB OFDM技术具有一定的优势。