Preparation and Characterization of Polyborosiloxanesand Their Blends with Phenolic Resin as ShapeableCeramic Precursors简

Two polyborosiloxanes(PBSis) with char yield up to 74.13% at 800 °C were synthesized by the direct polycondensation of boric acid with phenyltrimethoxysilane in diglyme. The PBSis were characterized by gel permeation chromatography, IR spectroscopy as well as1H-,29Si- and11B-NMR. PBSi modified phenol-formaldehyde resins(PBSi/PFs) were prepared at different PBSi/PF mass ratios and were cured at 150 °C. The PBSi/PFs were characterized by IR spectroscopy, scanning electron microscopy, thermogravimetric analysis and tensile test. The results revealed that the cured PBSi/PFs had sea-island morphology and higher char yield than the common PF. PBSi/PF blend with PBSi/PF mass ratio of 0.4:1 had char yield up to 70.83% at 800 °C. The PBSi/PFs had tensile strength similar to PF. The ceramization of PBSi/PFs was also studied. The silicon boron oxycarbide(SiBOC) ceramics formed were characterized by IR spectroscopy and elemental analysis. This method provided a valuable way to prepare easily shapeable polymer blends as ceramic precursors.     

Electrospinning of nylon-6,6 solutions into nanofibers: Rheology and morphology relationships

The relationship between the rheological properties of nylon-6,6 solutions and the morphology of their electrospun nanofibers was established. The viscosity of nylon-6,6 in formic acid(90%) was measured in the concentration range of 5 wt%-25 wt% using a programmable viscometer. Electrospinning of nylon-6,6 solutions was carried out under controlled parameters. The chemical structure, morphology and thermal properties of the obtained nanofibers were investigated using Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM) and differential scanning calorimetry(DSC), respectively. Entanglement concentration(ce) was found to be 15 wt% and a power law relationship between specific viscosity and solution concentration was observed with exponents of 2.0 and 3.3 for semi-dilute unentangled(c ce) and semi-dilute entangled(c ce) regimes, respectively. The diameter and uniformity of the nanofibers were found to be dependent on the viscosity. Moreover, the average diameter of electrospun nanofibers was found to be dependent on zero shear rate viscosity and normalized concentration(c/ce) in a power law relationship with exponents of 0.298 and 0.816, respectively. For nylon-6,6 solutions, the entanglement concentration(ce = 15 wt%) provides the threshold viscosity required for the formation of a stable polymeric jet during electrospinning and producing uniform beadless fibers. For concentrations less than ce, beaded fibers with some irregularities are formed. DSC analysis showed an increase in crystallinity of all electrospun samples compared to original polymer. Furthermore, Based on FTIR spectroscopy, α phase is dominant in electrospun nanofibers and minor amount of β and γ phases is also available.     

不同变质程度煤的高分辨率透射电镜分析

利用高分辨率透射电子显微镜(HRTEM)分析了三种不同变质程度煤样的结构特征。基于傅里叶-反傅里叶变换方法,并结合Matlab、Arcgis和Auto CAD软件,通过图像分析技术,获得了HRTEM照片的晶格条纹参数。结果表明,三种煤样的晶格条纹呈现不同特征,按条纹长度分别归属于1×1-8×8共计八个类型。以3×3为临界点,在1×1和2×2中,ML-8中芳香层片的比例高于DP-4和XM-3;在3×3-8×8中,ML-8中芳香层片的比例低于DP-4和XM-3。对比HRTEM和XRD参数d002发现,随着镜质组反射率的增加d002都呈现递减趋势。     

Investigation on LaF3/porous silicon system for photonic application

<正>We present the investigation on LaF_3/porous silicon(PS) system that has properties of both the materials to be applied in photonics.Epilayers of LaF_3 are grown on PS under different anodization conditions using electron-beam evaporation(EBE).The characteristics of the LaF_3/PS system are analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDX),and photoluminescence(PL).XRD confirms the polycrystalline nature of the LaF_3 film.Nearly stoichiometric growth of LaF_3 on PS is established by EDX.Such a thin LaF_3 layer grown on PS leads to a good enhancement of PL yield of PS.But with the increasing thickness of LaF_3 layer,PL intensity of PS is found to decrease along with a small blue-shift.     

膜催化研究IV: 钯-氧化铝/陶瓷复合膜

本文在无机氧化铝膜的基础上掺入钯, 用sol-gel法制得钯-氧化铝/陶瓷复合膜, 将该膜用于乙醇脱氢制乙醛反应, 分别考察了反应温度、乙醇进样量以及内管惰性气体吹扫气流对乙醛产率的影响, 并在相同条件下比较了常规反应器及单纯氧化铝膜反应器的结果。实验数据表明, 氧化铝膜中掺入钯后可显著提高乙醛产率。本文测定了该复合膜的H2/Ar分离系数、孔径分布, 并利用电子显微镜、X射线衍射等手段对其进行了表征。     

裂解温度对CVD法制备多壁碳纳米管的影响

用SEM、TEM、HRTEM及拉曼光谱方法研究了催化裂解乙炔制备多壁碳纳米管过程中裂解温度的影响,结果表明,在650℃～700℃裂解乙炔,可获得产量高、直径分布均匀、石墨程度高的多壁碳纳米管,并对裂解温度影响机制进行了分析和探讨。     

“锥形嵌套"结构CNx纳米管的生长机理及拉曼光谱研究

在氮气、氢气以及氯化铵热解产生的氨气环境下,以钴作为催化剂,在780℃—940℃温度范围内使二甲苯与二茂铁受热分解,合成了CNx纳米管.在高分辨率透射电子显微镜下观察,合成的纳米管呈现“锥形嵌套”的形貌特征.从不同结构的分子面形成能的角度探讨了CNx纳米管的催化生长机理.不同温度下所制备样品的拉曼光谱研究表明,ID/IG值可以反映氮的掺杂所带来的纳米管结晶有序程度的降低,并通过G带向高波数移动证实了氮的掺杂.     

双离子(40Ar+, C2H+6)辐照合成金刚石纳米晶颗粒

用双离子(⁴⁰Ar⁺，C₂H⁺₆)辐照实验完成了从多壁碳纳米管向金刚石纳米晶颗粒的转变.对转变机理进行了初步探讨.这一探索有望能成为一种金刚石纳米晶合成的新途径.由此可知，多重荷能离子辐照用于其他材料纳米结构的制备也不是凭空设想. 关键词： 金刚石纳米晶 离子辐照 透射电子显微镜     

利用TEM对Si基片与MgO基片上生长的薄膜特性的研究

对生长在Si和MgO单晶基片上的不同厚度的单层NbN薄膜、双层薄膜AlN/NbN以及三层薄膜NbN/AlN/NbN应用透射电子显微镜(Transmission Electron Microscope,TEM)技术进行了分析研究,对这几种薄膜样品的微观结构、薄膜厚度以及各个边界的一些直观细节给出了较为清晰的图像。由透射电子显微镜的电子衍射图案计算了薄膜和单晶衬底的晶格常数,并与我们以前采用X射线衍射技术分析的结果进行了比较,结果有很好的吻合。     

微波等离子体化学气相沉积合成掺氮金刚石薄膜的缺陷和结构特征及其生长行为

Diamond film was deposited in CH₄ and H₂ gas mixture with a small amount of N₂ by microwave plasma assisted chemical vapor deposition (MPCVD). Scanning electron microscopy, Raman spectroscopy and transmission electron microscopy were applied to characterize the film. The results showed that the growth of grains are different the central region and the edge. In the central region, diamond grains nucleated with a density as high as 4.8×10⁸ cm^-2 and were preferential in 〈001〉 orientation. The inner grains formed an area without stacking faults,which was surrounded by a rim with a high density of stacking faults. A growth model was suggested to interpret the morphological feature and the behavior of preferential growth. At the edge, the grains were identified to be 6H polytypes of diamond and a new twin relationship of grains was found. Besides, the effect of the N dopant on the growth behavior of the diamond film deposited by MPCVD was discussed in connection with the growth rate of the film. 关键词： 金刚石 结构表征 透射电子显微镜 多型金刚石