水分子凝胶聚集态的DSC和AFM研究

合成了一种新型凝胶因子，能在很低的浓度下使水发生凝胶化，形成水分子凝 胶。通过原子力显微镜(AFM)以及透射电子显微镜(TEM)对水分子凝胶的微观形态进 行了表征，表明凝胶因子可以在水中聚集、自组装成延伸的螺旋缠绕细纤维结构， 并且得出了纤维束的平均直径在100nm左右，平均孔径在100nm左右。利用示差扫描 量热(DSC)的数据，计算了水分子凝胶体系的平均孔径大小在50～100nm左右，与 AFM和TEM观测的结果较吻合，从而验证了DSC理论推导计算的正确性。同时还得到 了不同浓度的水分子凝胶的凝胶—溶胶相转变温度Tcs在55—72℃之间，而且随着 凝胶因子浓度的增加，水分子凝胶体系的平均孔径呈减小的趋势，凝胶—溶胶相转 变温度呈上升的趋势。     

The Cross‐Sectional Structure of Vanadium Oxide Nanotubes Studied by Transmission Electron Microscopy and Electron Spectroscopic Imaging

Vanadium oxide nanotubes (VO_x‐NTs) are easily accessible in pure form from vanadium(V) alkoxides and amines by a sol‐gel reaction and a subsequent hydrothermal treatment. The wall structure of VO_x‐NTs containing hexadecylamine or dodecylamine as the structure‐directing template has been characterised by transmission electron microscopy (TEM). A standard method for preparing TEM specimens was modified in order to investigate the cross‐sectional structure of the tubes. The elemental distribution in the layered structure inside the tube walls has been visualised by electron spectroscopic imaging: vanadium oxide builds up the layers that appear with dark contrast in the TEM images while carbon, i. e., the organic template, is present in between. The bent VO_x layers inside the tube walls are preferentially scrolls rather than concentric cylinders. Moreover, some tubes are formed by a combination of both types. The layer structure inside the tube walls is frequently disordered, and several types of defects appear.     

The Synthesis of Levyne-Type Zeolite Studied by Thermal Analysis of Methylquinuclidine Aluminosilicate Gels

DSC, TG and quadrupole mass spectrometer data concerning methylquinuclidinium iodide (MeQ1), dried precursor gel, and crystalline levyne-type zeolite are discussed together with the thermal degradation of MeQ1 mixed with single inorganic components of the gel. It is shown that MeQ⁺ions play a role in the organization of the gel structure. This revised version was published online in July 2006 with corrections to the Cover Date.     

Microdeformation in Heterogeneous Polymers,Revealed by Electron Microscopy

Recent investigations of the tensile fracture behaviour of representative glassy and semicrystalline impact-resistant polymers are reviewed, with emphasis on the microdeformation behaviour as revealed by electron microscopy of sections from bulk specimens, where the crack-tip damage zone has been embedded and/or stained under load, and on thin films deformed in situ. The insight that such techniques have provided into the toughening mechanisms is discussed.     

乙二醇和丙三醇水溶液冻结特性的研究

利用差示扫描量热仪（Pyris-Diamond DSC），研究了乙二醇（甘醇）和丙三醇（甘油）水溶液的过冷行为、水合性质和它们的玻璃化转变温度及反玻璃化温度，分析了它们与分子中羟基个数的关系.进行了12组共24种不同浓度(质量分数）的溶液的差示扫描量热实验.过冷度的实验结果表明，在浓度相等的情况下，两种低温保护剂水溶液冻结的过冷度有相同的变化规律.水合实验的结果表明，浓度相同时，二者结合水的能力大体相当.玻璃化转变的实验表明，二者玻璃化转变温度与反玻璃化温度存在明显差异.     

应用分析电子显微镜考察铂锡催化剂上的积炭

在高分散铂锡催化剂上分别以正丁烷,正己烷及长链烷烃为反应物经催化剂脱氢表面积炭。从电子显微镜图像观察到积炭有多种结构,最小的炭粒呈条纹排列,炭粒集聚形成球状炭黑及不同形状的石墨结晶。选区电子衍射分析炭(002)晶面间距有3.35～4.13A变化表明石墨化程度不同。三种积炭样品的电子能量损失谱相应地亦展示明显的差别。     

The Influence of Drawing in Hot Water on The Morphological Properties of Pet Films as Measured by DSC and Modulated DSC

PET films uniaxially drawn in hot water are studied by means of conventional DSC and modulated DSC (MDSC).Glass transition is studied by MDSC which allows to access the glass transition temperature T _g and the variations of ΔC _p=C _p1−C _pg (difference between thermal capacity in the liquid-like and glassy states at T=T _g). Variations of T _g with the water content (which act as plasticizer) and with the drawing (which rigidifies the amorphous phase) are discussed with regard to the structure engaged in these materials. The increments of ΔC _p at T _g are also interpreted using a three phases model and the 'strong-fragile’ glass former liquid concept. We show that the ‘fragility’ of the medium increases due to the conjugated effects of deformation and water sorption as soon as a strain induced crystalline phase is obtained. Then, ‘fragility’ decreases drastically with the occurring rigid amorphous phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

透射电镜三维重构确定金纳米粒子的立体结构

贵金属纳米颗粒具有局域表面等离激元这一特性使其具有丰富的光学性质,而这一特性受制于纳米颗粒所形成的立体几何形状,而透射电镜和扫描电镜的二维图像不能真切地观测和确定纳米颗粒所形成的立体几何结构。透射电镜三维重构技术可作为一种确定纳米颗粒立体结构的直观有效的方法。本文利用透射电镜的三维重构技术,选择合适的参数进行二维图像的采集、图像匹配对中及重构、立体模型的构建,从而通过构建的模型对两种金纳米颗粒样品的不同几何形状所产生的边界形态进行了确认和分析。     

Weathering Phenomena on Naturally Weathered Potash-Lime-Silica-Glass with Medieval Composition Studied by Secondary Electron Microscopy and Energy Dispersive Microanalysis

 Samples of two model glasses with chemical compositions similar to medieval stained glass were exposed to the natural environment at 23 test sites for a period of 6 months, 1 and 2 years within an exposure programme of the “Working Group of Effects on Materials, Including Historic and Cultural Monuments” of the Economic Commission for Europe of the United Nations. During the exposure the environmental data were measured and collected at each test site in order to enable a correlation between the pollutant load in the ambient atmosphere and the weathering phenomena of the glass samples. After the exposure, which was performed in a sheltered as well as in an unsheltered mode for gaining information about the influence of dry and wet deposition of air pollutants, the glass samples were analysed in the scanning electron microscope with energy dispersive microanalysis (SEM/EDX). Model glass M1 – a potassium rich glass – was covered to a high amount with crystalline weathering products (above all syngenite), whereas glass M3 – a glass with a higher Ca and Si content – turned out to be more stable against weathering. This glass was covered with gypsum and arcanite crystals but in total to a less extent than glass M1. Received March 30, 1998. Revision February 8, 2000.     

珍珠形胆结石的红外光谱和扫描电镜分析

磁疗获得的珍珠形胆结石是罕见的病例,作者利用红外光谱、扫描电子显微镜及Ｘ射线能谱对该胆结石进行了观察和研究。结果表明该胆结石的主要成分为胆固醇,并混有少量的蛋白质和无机钙盐,说明珍珠形胆结石虽然和珍珠具有相似的形貌,但组成是完全不同的。根据扫描电子显微镜的照片,作者推测结石的珍珠外形可能是因为片状的胆固醇分子形成胆甾型晶体而形成的。     

Hydrolysis of Titanium Alkoxides: Thermochemical, Electron Microscopy, Saxs Studies

Hydrolysis of Ti(OR)₄ (R = Et, ⁱ Pr, ⁿ Bu) at various concentrations of titanium alkoxides and ratios h = [H₂O] /[Ti(OR)₄] is studied in alcoholic medium by means of calorimetry, electron microscopy, SAXS, and chemical analysis. The measured values for heat of hydrolysis of Ti(OR)₄ by excess water (– H _h ) at 298.15 K comprise 14.2, 64.9, 19.3 kJ/mol for R = Et, R = Et, ⁱ Pr, ⁿ Bu respectively. – H _h increases drastically in the region of 0h ratio. In the solid hydrolysis product with the composition TiO _x (OR)_4–2x ·y ROH, both x and y increase with increase of Ti(OR)₄ concentration in solution. Bushy network first formed in solution as a result of hydrolysis gradually structures with formation of well-shaped spherical particles with diameters 0.2m. SAXS curves analysis in the range of scattering vector values s = 0.07–4.26 nm^–1 for Ti(OBu)₄ hydrolysis products allows us to suggest their multilevel nature. Speculations on the structure of titanium oxobutoxide were made on the basis of the well-known structural data for crystalline first hydrolysis products of Ti(OEt)₄ and Ti(O ⁱ Pr)₄. It is suggested to perform hydrolysis of Ti(OBu)₄ with addition of water in two steps which allows us to decrease the rate of the solid precipitate formation, to regulate particles morphology in a wide range and to obtain well-shaped spherical species more than one micron in size. The influence of the powder size distribution on the grain growth during ceramic sintering is discussed.     

The behaviour of water molecules associated with structural changes in negatively charged phosphatidyl-glycerol assemblies as studied by DSC

Variation of the thermotropic behaviour of both lipid assemblies and associated water molecules with an increase in water content was investigated for negatively charged phosphatidyl-glycerol (PG)-water system up to 90 wt.% water by DSC. The number of water molecules existing in interbilayer regions of the present gel phase was estimated from a deconvolution analysis of ice-melting DSC curves. On the basis of a result of the calorimetric analysis, a water-distribution diagram was constructed over the water content range from 0 to 90 wt.%. The diagram presented a continuous incorporation of interlamellar water up to 90 wt.% water, related to unilamellar-vesicle forming properties of charged lipids. Furthermore, similarly to a result for neutral lipid systems previously reported by us, the present diagram also showed the existence of a specific water content region (i.e., pre-region) where a structural change of planar to curved bilayers for multilamellar structures proceeds with the aid of bulk-like water before finally reaching unilamellar vesicles.     

电子显微技术应用于生物纳米材料表征与测试的研究进展

该文简述了电子显微技术的发展历程,并介绍了现代电子显微镜的新功能。针对生物纳米材料理化性能与功能应用的特殊性,结合研究实例,重点阐述运用电子显微结构表征与原位分析测试技术指导构建新颖纳米结构、揭示材料与细胞/组织相互作用并发挥功能的机制。并在此基础上,展望了电子显微技术在生物纳米材料研究领域的发展方向(大尺寸图像拼接、三维重构、动态原位实时成像)。     

TMDSC and Dynamic Rheometry,Gelation, Vitrification and Autoacceleration in the Cure of an Unsaturated Polyester Resin

The free radical cross-linking copolymerization of an unsaturated polyester resin with styrene is studied in isothermal conditions using temperature modulated differential scanning calorimetry (TMDSC) and dynamic rheometry. The dynamic rheometry measurements show that gelation occurs at a conversion below 5%, while TMDSC measurements show that an important autoacceleration starts near 60% conversion, giving rise to a maximum cure rate closely before the (partial) vitrification of the system near 80%. This indicates that the autoacceleration is not due to the sharp increase in bulk viscosity at gelation, but rather to a change in molecular mobilities at higher conversion.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal,Mechanical and Morphological Behavior of Poly(propylene)/Wood Flour Composites

The comparative studies on the thermal, mechanical and morphological behavior of compression molded poly(propylene) (PP)/wood flour (WF) composites were performed using wood flours (WFs) of different origins. The comparison has been made on the basis of results obtained from thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile testing. It has been demonstrated that an addition of 5 wt.-% of maleic anhydride grafted polypropylene (PP-g-MA) has a significant effect on the morphological and thermomechanical behavior of the composites. Although, microscopic examinations revealed no significant differences in the morphology of the compatibilized composites, a remarkable improvement of thermal degradation behavior was observed. From the view point of mechanical properties, the composites with high amount of filler (60 wt.-%) showed similar behavior irrespective of the origin of wood flour.     

Polymorph Identification and Crystal Structure Determination by a Combined Crystal Structure Prediction and Transmission Electron Microscopy Approach

Electron diffraction offers advantages over X‐ray based methods for crystal structure determination because it can be applied to sub‐micron sized crystallites, and picogram quantities of material. For molecular organic species, however, crystal structure determination with electron diffraction is hindered by rapid crystal deterioration in the electron beam, limiting the amount of diffraction data that can be collected, and by the effect of dynamical scattering on reflection intensities. Automated electron diffraction tomography provides one possible solution. We demonstrate here, however, an alternative approach in which a set of putative crystal structures of the compound of interest is generated by crystal structure prediction methods and electron diffraction is used to determine which of these putative structures is experimentally observed. This approach enables the advantages of electron diffraction to be exploited, while avoiding the need to obtain large amounts of diffraction data or accurate reflection intensities. We demonstrate the application of the methodology to the pharmaceutical compounds paracetamol, scyllo‐inositol and theophylline.     

Sulfur Compounds. 164 Thermal Polymerization of the Cyclic Seleniumsulfide 1,2-Se2S5 Studied by DSC,HPLC, Raman Spectroscopy,and X-Ray Diffraction

Solid 1,2-Se₂S₅ polymerizes endothermically at 47°C to give a linear polymer which after stretching and extraction consists of helical molecules similar to those of polymeric sulfur. Heating of the polymer results in slow exothermic depolymerization at 84°C to give a mixture of seven cyclic Se_nS_8–n molecules which melts at 111°C. When the polymeric Se₂S₅ is refluxed with CS₂ the initial depolymerization Products are 1,2-Se₂S₅, SeS₅ and 1,2,3-Se₃S₅ but in addition SeS₇ and 1,2-Se₂S₆ are formed. These results indicate the atomic sequence –Se? S₅? Se– in the polymer. The powder x-ray diffraction pattern and Raman spectrum of the polymer as well as its lattice parameters are reported and the Probable mechanism of its depolymerization is discussed.     

Atomic Force Microscopy,Transmission Electron Microscopy,and Photon Correlation Spectroscopy: Three Techniques for Rapid Characterization of Optimized Self-Nanoemulsiying Drug Delivery System of Glibenclamide,Carvedilol, and Lovastatin

This article looks at atomic force microscopy as an important aid to characterize the self-nanoemulsifying formulation of glibenclamide, lovastatin, and carvedilol in conjunction with other sophisticated technique, viz., transmission electron microscopy and photon correlation spectroscopy. Sizes obtained by processing the atomic force microscopy (AFM) image are comparable with those obtained from transmission electron microscope. Although in the present study, the mean particle size obtained from photon correlation spectroscopy does not correlate to the findings of atomic force microscopy and transmission electron microscopy, but the poly-disperse index values correlate well with the findings of AFM and transmission electron microscopy where uniform particle size was observed in aqueous dispersion of self-nanoemulsifying formulation of glibenclamide, lovastatin, and carvedilol.     

Thermal characterization of HCN polymers by TG-MS, TG, DTA and DSC methods

This paper presents a thermogravimetry (TG) study of hydrogen cyanide polymers, synthesized from the reaction of equimolar aqueous solutions of sodium cyanide and ammonium chloride. Differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were also used to evaluate the thermal behaviour of these black polymers, which play an important role in prebiotic chemistry. A coupled TG-mass spectrometer (MS) system allowed us to analyze the principal volatile thermal decomposition and fragmentation products of the isolated HCN polymers under dynamic conditions and an inert atmosphere. After dehydration, a multi-step decomposition occurred in this particular polymeric system, due to the release of ammonia, hydrogen cyanide (depolymerization reaction), isocyanic acid (or cyanic acid) and formamide; these two latter species allow us identify bond connectivities. Finally, data collected from TG experiments in an oxidative atmosphere showed significant differences at higher temperatures, above 400 °C. According to these results, the different techniques of thermal analysis here applied have demonstrated to be an adequate methodology for the study and characterization of this complex macromolecular system, whose structure remains controversial even today.