A novel method for the synthesis of polyamide 6 magnetic microspheres

Polyamide 6 (PA6) magnetic microspheres were firstly prepared via successively in situ polymerization using phase inversion technology of polymer pairs polyamide 6/polystyrene (PA6/PS) at extremely low PS content. The properties of PA6 magnetic microspheres, such as morphologies, diameter size distribution, magnetic properties, thermal stability, and the functional groups of the magnetic microspheres, were investigated by different techniques (i.e. SEM, TEM, DLS, VSM, FTIR, and DSC). The results indicated that the diameter distribution of PA6 magnetic microspheres was narrow, and the mean diameter size was about 7.7 μm. The saturation magnetization of magnetic microspheres reached 12.50 emu/g. Furthermore, the magnetic microspheres had abundant functional groups and better thermal stability.     

Non-isothermal crystallization of polyamide 6 matrix in all-polyamide composites: crystallization kinetic, melting behavior, and crystal morphology

The difference in the melting points of polyamide 66 (PA66) fiber and polyamide 6 (PA6) film permits the preparation of all-polyamide (all-PA) composites by film-packing. Good interface performance and integrated consolidation structure in this all-PA composite are contributed to the similar chemical composition between PA66 fiber and PA6 matrix. In this paper, the non-isothermal crystallization kinetics and melting behaviors of PA6 matrix in all-PA composite are studied by differential scanning calorimetry (DSC), in which the modified Avrami equation, Ozawa model, and Mo equation combining Avrami and Ozawa equation are employed. It is found that the Mo equation exhibits great advantages in treating the non-isothermal crystallization kinetics for both neat PA6 and PA6 matrix in all-PA composite. The crystal morphologies of single PA66 fiber–PA6 composite by polarizing microscope (POM) clearly show a transcrystallinity layer of PA6 around PA66 fiber that proves a remarkable nucleation effect of PA66 fiber surface on the crystallization of PA6 matrix.     

纳米量子点能级以及能隙计算和修正

用一个简单模型分析了量子点产生能级的原因,推导出能级与量子点尺寸的表达式。根据量子点表面势垒为有限值的特点以及表面存在衰减波,提出量子点内电子波函数不完全满足驻波条件的观点,在量子点的能级表达式中引入一个修正系数。结合量子点表面衰减波的特征,给出量子点修正系数的计算方法。通过理论计算表明：量子点的能级以及能级之间的能量差（间隙）不但与量子点的尺寸有关,而且与其边界条件有关。特别是对于非光滑的表面,其表面势垒对量子点的能级与能隙影响非常大。     

DDS体系在飞行器地面测试系统中的应用

针对飞行器地面测试系统需要满足多种不同类型的数据传输、较高的数据传输速率、较高的数据传输实时性的目的,采用广播式网络通信体系DDS数据通信体系进行飞行器地面测试系统构建的方法。通过某型号飞行器地面测试以及各项大型试验。得出DDS数据通信体系具有高实时性、系统网络架构易于扩展、能够适应不同类型数据传输、数据通信模式灵活可配置等诸多结论,DDS数据通信体系完全能够满足飞行器地面测试的应用需求。     

星载软件的语句级高效更新方法

为减少星载软件在轨更新过程对测控资源的需求量,缩短更新上注时间,提出了一种无需操作系统支持、上注数据量低、版本可灵活控制的语句级软件更新方法。该方法首先利用预编译命令进行程序空间优化,使得不同模块的代码在编译后存储于不同的段中,减少代码修改对加载文件的影响;其次通过逐段求解参考段与更新段之间匹配路径,并基于此进行各段的差异内容提取,大大降低差异补丁规模;然后通过版本引导程序设计,实现对卫星软件版本的灵活控制;最后通过对文件和程序进行可靠性设计,保证整个更新过程的安全性。结果表明:该方法在ZDPS-3A卫星平台进行了充分的测试,所提出的更新方法可应用于无操作系统的星载计算机,支持软件状态可回滚且更新过程可靠,同时相比传统的差异内容提取方法,补丁文件的规模降低量均值超过50.00%,可显著缩短更新上注时间。本方法能够充分满足星载软件低数据量更新的需求,可推广应用至包括微小卫星在内的多种航天器。     

Synthesis and properties of homogeneously dispersed polyamide 6/MWNTs nanocomposites via simultaneous in situ anionic ring‐opening polymerization and compatibilization

Toluene 2, 4‐diisocyanate (TDI) functionalized multiwalled carbon nanotubes (MWNTs‐NCO) were used to prepare monomer casting polyamide 6 (MCPA6)/MWNTs nanocomposites via in situ anionic ring‐opening polymerization (AROP). Isocyanate groups of MWNTs‐NCO could serve as AROP activators of ?‐caprolactam (CL) in the in situ polymerization. Fourier transform infrared (FTIR) showed that a graft copolymer of PA6 and MWNTs was formed in the in situ polymerization. MWNTs‐PA6 covalent bonds of the graft copolymer constituted a strong type of interfacial interaction in the nanocomposites and increased the compatibility of MWNTs and MCPA6 matrix. The nanocomposites were characterized for the morphology, mechanical, crystallization, and thermal properties through field emission transmission electron microscopy (FETEM), tensile testing, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). FETEM analysis showed that MWNTs were homogeneously dispersed in MCPA6 matrix. The initial tensile strengths and tensile modulus of the nanocomposite with 1.5 wt % loading of MWNTs were enhanced by about 16 and 13%, respectively, compared with the corresponding values for neat MCPA6. DSC analysis indicated that the crystallization temperature of the nanocomposites was increased by 8°C by adding 1.5 wt % MWNTs compared with pure MCPA6. Besides, it was found that the thermal stability of MCPA6 was improved by the addition of the MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cracking in poly(trimethylene terephthalate) spherulites

The crack behavior of poly(trimethylene terephthalate) spherulites was studied mainly by polarizing optical microscopy, along with scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition to the effects of temperature and constraining substrate, another important factor, film thickness, on the formation of crack was first put forward and investigated. The emergence of the first crack occurred at 120°C during cooling after crystallization at 190°C for the sample with a thickness of 31.0 μm. For the spherulites growing between glass sheets, it was interesting that the sample with a thickness of 26.0 μm exhibited the largest number of cracks measured per 200 μm of radius, whereas samples thicker than 100 μm or thinner than 1 μm did not induce the formation of crack. Also, spherulites growing between two polyimide and two Teflon sheets showed no crack. Glass sheets lubricated with silicon oil restrained the number of cracks but did not eliminate cracks. SEM revealed that the cracking was about 900 nm in width. In addition, the AFM results suggest that the cracks had a depth of at least 150 nm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

汽车用耐刮擦改性聚丙烯的研制

制备了汽车用耐刮擦改性聚丙烯(PP),分析了不同耐刮擦滑爽剂、矿物填料、PP结晶度及增容剂等对材料耐刮擦性能的影响。结果表明,采用高结晶PP、较小粒径的矿物填料和反应型高聚硅氧烷制备的改性PP具有优异的耐刮擦性能,完全适用于汽车零部件。     

导弹武器全寿命周期成本分析与控制策略

随着科学技术的进步,各种武器装备在变得越来越先进的同时,其用于包括研制、生产、使用和维护在内的全寿命周期成本也变得越来越高。针对以导弹为例的各类武器装备成本居高不下的问题,总结调研了国内外相关成本分析与控制方法,对导弹武器装备进行了全寿命周期的成本分析,提出了导弹武器的全寿命周期成本管控综合策略与效费权衡思路,并从总体方案设计、元器件选型优化、生产制造三个主要方面提出了降低导弹武器成本的具体方法与措施,可为类似武器装备成本分析与控制研究或研制项目提供参考。     

Intergranular glassy phase free SiC ceramics retains strength at 1500 °C

We report SiC ceramics sintered with AlN and Sc₂O₃ (or Lu₂O₃) that retain room temperature strength to 1500 °C. The intergranular glassy phase has not been observed in the ceramics due to a designed-sintering additive and, thus, the unsatisfactory effect of glassy phases on the high temperature strength is eliminated.