不同冲击速度下泡沫铝变形和应力的不均匀性

利用常规Hopkinson杆实验装置和改进的Hopkinson杆实验装置对泡沫铝试件进行冲击压缩实验,同时用高速摄影装置对实验过程进行全程跟踪拍摄。通过改变冲击速度,观测到了3种不同的变形模式。将得到的高速摄影图像用数字图像相关方法进行分析,讨论了3种模式下全场应变不同的发展过程,并依此讨论应力的不均匀性,为研究不同冲击速度下变形不均匀对泡沫铝动态力学行为的影响提供了新的方法。     

环氧树脂/泡沫铝一体型复合夹层板压缩及弯曲试验研究

提出了一种环氧树脂/泡沫铝一体型复合夹层板,通过准静态试验以及与纯泡沫铝、传统蒙皮夹层板的对比研究了其破坏过程、破坏形貌、破坏机理及压缩和弯曲力学性能。分别通过压缩应力-应变曲线和弯曲荷载-挠度曲线分析了复合层厚度对压缩及弯曲力学性能的影响,并与传统夹层板的力学性能进行了比较。结果表明,随着夹层板中环氧树脂/泡沫铝复合层厚度增加,其压缩弹性模量和抗压强度增加,弯曲承载力提高。相比传统蒙皮夹层板,由于表层和芯层之间没有明显界面,大大提高了夹芯板的整体性,在受力过程中不会出现表层剥离等现象。     

超轻材料

超轻材料是一类密度小于10 mg/cm³的新型材料,具有良好的比强度和比刚度,是优异的物理化学性质和结构性能的统一体。随着人们对超轻材料强大性能的认识,国内外许多课题组都相继开展了对超轻材料的研究,并取得了一系列的成果。现有的超轻材料已经涵盖了硅系、金属及其氧化物、陶瓷、高分子聚合物、新型碳材料及其复合物等各类成分。超轻材料具有声吸收、能量吸收、减震缓冲、热绝缘等性能,在航空航天领域具有重要作用。超轻材料的性能主要取决于它的结构和组成材料的固体成分的性能,比如材料中孔隙的分布以及固体本身的硬度及强度都对性能有着重要的影响。本文根据材料结构的不同,将超轻材料分为气凝胶、泡沫材料、微点阵材料三类。本文对近年来超轻材料的材质及制备方法进行了简要的综述,并通过对各种材料的比较就该领域未来的发展进行了展望。     

Preparation of Boron-coated Expandable Graphite and Its Application in Flame Retardant Rigid Polyurethane Foam

A novel boron-coated expandable graphite(BEG) material was prepared by first wrapping polyvinyl alcohol(PVA) onto expandable graphite(EG) and then condensing with boric acid. The obtained BEG was characterized by scanning electron microscopy(SEM), Fourier transform infrared(FTIR) spectroscopy, X-ray photoelectron spectroscopy(XPS), and thermogravimetric analysis(TGA). The fire performance and mechanical properties of the rigid polyurethane foam(RPUF) filled with BEG were investigated by limiting oxygen index(LOI), horizontal and vertical burning, cone calorimetry(CONE), and electronic tensile tests. BEG shows an improved compactness of the char layers upon thermal expansion, which is effective for the flame retardancy of RPUF. With a loading of 10%, RPUF/BEG exhibited a higher LOI, >10% reduction in heat release rate and carbon monoxide release, as well as a decrease in smoke release during the beginning of combustion compared to RPUF/EG. Moreover, the compressive strength and modulus of RPUF/BEG were increased. The improved flame retardancy of BEG on RPUF can be attributed to the suppression of the "popcorn effect" of EG by PVA-boric acid, and the improved mechanical property can be attributed to the presence of PVA.     

PMI泡沫复合材料的太赫兹谱特性实验研究

聚甲基丙烯酰亚胺(polymethacrylimide, PMI)泡沫复合材料具有众多优良特性,被广泛应用于航天航空、军工、船舶、汽车及高速列车等各个领域。而作为新型的夹层结构材料,其太赫兹(Terahertz, THz)波段的性能检测尚未见报道。基于THz时域光谱分析方法,对国内外两种型号的PMI泡沫复合材料在太赫兹波段透射及反射的实验获得的时域波形、功率密度谱进行了分析比较,基于MATALB编程、Origin8.0数据处理,应用时域、频域方法计算分析了不同厚度的德固赛(型号：Rohacell WF71)、美沃科技发展有限公司生产的(型号：SP1D80-P-30) PMI泡沫复合材料的透射率(传输函数)、吸收率、反射率以及折射率等光学参数。研究结果表明：通过对比空气、氮气中的不同测量结果,解释了湿度对测量结果的影响。PMI泡沫复合材料的折射率为1.05左右,功率谱的衰减是由于测试平台本身信号较弱、样品较厚且PMI泡沫的内部微结构的散射,造成THz波在>0.6 THz波段表现出明显的衰减。该结论为THz波段在PMI泡沫复合材料方面的应用提供了理论依据,同时也为太赫兹无损探伤(non-destructive testing, NDT)技术在PMI泡沫复合材料方面的应用做了一个良好的铺垫。     

泡沫混排解堵数学模型及数值模拟

建立泡沫井筒流动模型与泡沫地层渗流模型,得到完整的泡沫混排解堵数学模型;利用数值方法对模型进行耦合求解,得到泡沫压力,质量,密度在井筒中的分布及井口井底压力的变化规律.在固定井口回压情况下,得到井底压差的变化规律.结果表明:随着井深的增加,泡沫压力增加,质量减小,密度增加;固定井口回压,井底压差则逐渐变小.     

二氧化钒/泡沫镍—体化电极材料的制备及其电化学特性研究

采用五氧化二钒,草酸和泡沫镍作为原料,经一步水热反应法,成功制备出二氧化钒/泡沫镍一体化电极.X-射线衍射仪(XRD)和扫描电子显微镜(SEM)用来表征二氧化钒/泡沫镍电极材料的物相和形貌.结果显示,当草酸浓度为0.1 mol·L-1时,制备的二氧化钒具有纳米片状结构,其厚度为80 ～ 140 nm.电化学结果显示,二氧化钒/泡沫镍一体化电极材料,其比电容高达3.99 F·cm-2(在电流密度为1 mA·cm-2),这是由于生长在泡沫镍上片状二氧化钒具有高的比表面积.经过2000次的循环后,二氧化钒/泡沫镍电极的比电容仅损失9.95;,显示很好的循环稳定性.     

Thermodynamic studies on thin liquid films. III: Miscibility in adsorbed films at film interfaces

Thermodynamic treatment of surfactant mixture was developed for the adsorption at interfaces of thin liquid films and applied to the study of the foam film stabilized by decyl methyl sulfoxide (DeMS) in the presence of NaCl. The total surface density of NaCl and DeMS and the mole fraction of DeMS in the adsorbed film at the film surface were numerically evaluated by applying thermodynamic equations to the film tension as a function of the total molality of NaCl and DeMS and the mole fraction of DeMS in the mixture. Miscibility of NaCl and DeMS at the film surface was clarified by a phase diagram of adsorption and compared with that at the meniscus adjacent to the foam film. Judging from a phase diagram of phase transition, the transition in the DeMS foam film between common black and Newton black films, observed in part II, is a negative azeotropic transformation caused by the attractive interaction between the head group of DeMS molecule and Na⁺ or Cl^– in the adsorbed film.     

超轻多孔金属的进展与物理学

简述了超轻多孔金属的结构、性能，研究从材料范畴发展为物理学范畴。发展的新趋势为，将国家高技术目标需求与科学前沿相结合，将认识与实践相结合。     

X-ray fluorescence spectrometric determination of germanium after extraction with polyurethane foam

Germanium is extracted onto polyurethane foam as molybdogermanate, and determined by X-ray fluorescence spectrometry in the dried foam. The extraction is effective between pH 0.5 and 3.7 and as little as 7 μg of germanium can be detected in 100 ml of aqueous solution.