AFM, SEM and GIXRD studies of thin films of red polycarbazolyldiacetylenes

In this paper we report the results of a morphological and structural investigation on film properties of a soluble polydiacetylene, the poly[1,6-bis(3,6-dihexadecyl-N-carbazolyl)-2,4-hexadiyne] (polyDCHD-HS). The red films of this polymer, prepared by standard spin-coating techniques, revealed absence of linear dichroism and birefringence in contrast with the ordered mesophases detected by powder X-ray studies. In order to interpret the optical behavior of this polymer, we performed AFM and SEM studies of polyDCHD-HS films spun on hydrophylic and hydrophobic glass substrates. We found the presence of surfaces organized in rod-like particles, more regularly oriented on the hydrophylic substrate. GIXRD studies, carried out on films sufficiently thick to allow the observation of the diffraction pattern, reveled the presence of a lamellar structure with a spacing of 3.22 nm. The low intensity of the diffraction peaks and the isotropic linear optical properties of the films show that the lamellar mesophases are not extended over large areas. These findings were compared with the data obtained from AFM and SEM studies on films of two other polydiacetylenes, the poly[1-(3,6-dihexadexyl-N-carbazolyl)-6-(N-carbazolyl)-2,4-hexadyine] (polya-DCHD) and the poly[1,6-bis(3,6-dipalmitoyl-N-carbazolyl)-2,4-hexadyine] (polyDPCHD), spun on hydrophylic glass substrate. The results confirmed the presence of nodular morphologies which seem to be a general characteristic of this class of materials. The particles organization appears instead related to the chemical nature of the substituents on the carbazolyl rings.     

基于爆轰波原理声源定位方法初探

基于弹丸发射时所发出的爆轰波,利用传感器接收时差信息,从而确定声源位置。本文建立了该声源定位反问题的物理和数学模型,并依据该模型寻求适当的数值解法,最后针对延拓-广义逆法声源定位问题进行了演算和简要分析。     

Scientific legacy of Stanley Ruby

Stanley L. Ruby (1924–2004) made major contributions to Mössbauer spectroscopy and was the first to suggest the feasibility of observing the Mössbauer effect using synchrotron radiation. In this article we recall his scientific legacy that have inspired his scientific colleagues.     

Scattering from infinite rough tubular surfaces

We study the Helmholtz equation in the exterior of an infinite perturbed cylinder with a Dirichlet boundary condition. Existence and uniqueness of solutions are established using the variational technique introduced (SIAM J. Math. Anal. 2005; 37 (2):598–618). We also provide stability estimates with explicit dependence of the constants in terms of the frequency and the perturbed cylinder thickness. Copyright © 2006 John Wiley & Sons, Ltd.     

THE FIRST EXPERIMENT OF A THz GYROTRON WITH A PULSE MAGNET

A THz gyrotron with a pulse magnet has been designed, constructed and operated in FIR FU. It is developed as one of high frequency gyrotrons included in Gyrotron FU Series. The gyrotron has already achieved the first experimental result for high frequency operations whose radiation frequency exceeds 1 THz. In this paper, the design detail and the operation test results for sub-terahertz to terahertz range are described. The second harmonic operation is confirmed experimentally at the expected frequency of 1.005 THz due to TE_6,11 cavity mode at the magnetic field intensity of 19.0 T.     

Adhesion studies of latex film surfaces on the meso- and nanoscale

In this paper the effects of surface roughness and annealing temperature (T) of latex coating films on adhesion are discussed for the different stages of the film formation process. The surface free energy of latex films was assessed in terms of practical work of adhesion (W) (or adherence) using a custom-built adhesion-testing device (ATD), atomic force microscopy (AFM), and contact angle measurements. For preannealed latex films surface roughness averages (R_a) were determined from AFM height images and were related to the values of W obtained from ATD measurements at room temperature. The results obtained using these tests exhibiting surface behavior on different length scales indicate a dependence of the measured adhesion on surface roughness and temperature, as well as on the length scale of the measurements.First preannealed samples were studied, which were obtained by heat treatment above the respective glass transition temperatures (T_g). Increasing the temperature of preannealing resulted in a decrease of the adherence observed in ATD experiments at room temperature. However, on the nanoscale, using AFM, no significant variation of the adherence was observed. This observation can be explained by roughness arguments. Preannealing decreases roughness which results in lower adherence values measured by ATD while for essentially single asperity AFM experiments roughness has an insignificant effect. Specimens were also annealed over a constant period of time (90 min) at different temperatures. At the end of the heat treatment, adhesion was measured at the treatment temperature by ATD. The amplified effect of temperature observed in this case on adherence is attributed to the combination of roughness decrease and increasing test temperature. In a third set of experiments completely annealed samples were studied by ATD as well as by AFM as a function of temperature. With increasing T values ATD showed a decrease in adherence, which is attributed to a decreasing surface free energy of the annealed films at elevated T values. AFM, on the other hand, showed an opposite trend which is assigned to increasing penetration of the tip into the tip/wetting polymer samples versus increasing temperature. Finally, annealing isotherms as a function of time were investigated by ATD in situ at different temperatures. This last set of experiments allowed us to optimize annealing time and temperature to achieve complete curing.     

塑料闪烁体的辐照特性

利用⁶⁰Co放射源分别对3种塑料闪烁体(BC-408, EJ-200, BC-404)进行辐照损伤研究, 比较辐照前后的透射谱、发射谱及光产额的变化, 发现3种闪烁体在低剂量具有较好的抗辐照性能; 当照射剂量超过1.44×10⁴Gy时,透射谱明显变坏, 光输出减少很严重, 但发射谱却保持不变.     

同步辐射x射线光刻制作深亚微米T形栅

x射线光刻非常适合用于深亚微米T形栅的制作,这是因为它的高分辨率、大的曝光视场和高的生产效率足以满足MMIC制造工艺的要求。本文中我们首先对我们的x射线掩模制造工艺进行介绍,然后论述了一种用于制造深亚微米T形栅的两层胶工艺,介绍了所取得的一些研究结果,最后对国内的深亚微米光刻现状进行了简要分析。     

红外小目标与背景辐射对比度的研究

红外目标与背景的对比度特征是红外探测系统检测的重要特征。研究了目标和背景在探测器上的辐射照度,提出了一种红外小目标与背景的辐射对比度,分析了该目标与背景对比度的相关因素。     

The epitaxial sexiphenyl (0 0 1) monolayer on TiO2(1 1 0): A grazing incidence X-ray diffraction study

A para-sexiphenyl monolayer of near up-right standing molecules (nominal thickness of 30 Å) is investigated in-situ by X-ray diffraction using synchrotron radiation and ex-situ by atomic force microscopy. A terrace like morphology is observed, the step height between the terraces is approximately one molecular length. The monolayer terraces, larger than 20 μm in size, are extended along the [0 0 1] direction of the TiO₂(1 1 0) substrate i.e. along the Ti-O rows of the reconstructed substrate surface. The structure of the monolayer and its epitaxial relationship to the substrate is determined by grazing incidence X-ray diffraction. Extremely sharp diffraction peaks reveal high crystalline order within the monolayer, which was found to have the bulk structure of sexiphenyl. The monolayer terraces are epitaxially oriented with the (0 0 1) plane parallel to the substrate surface (out-of-plane order). Four epitaxial relationships are observed. This in-plane alignment is determined by the arrangement of the terminal phenyl rings of the sexiphenyl molecules parallel to the oxygen rows of the substrate.