Preparation of sections of plastics and polymers for the electron microscope

Experimental details of a method for sectioning rubbers and plastics at room temperature are presented. Usually specimens are embedded in a butyl-isobutyl methacrylate mixture (provided that they do not dissolve in the monomer) which can be polymerised by ultra-violet light to varying hardness. This enables sections through fibres and surfaces to be obtained. Because of distortion of the surface layers the angle between the knife and specimen is critical. The thickness of these distorted surface layers rather than the total thickness of the specimen provides a limit to the resolution obtained. Choice of the sectioning angle was made primarily by means of sense of touch, so that a microtome design incorporating a direct transmission of pressure from specimen to hand is needed.     

双组分高固含量水性聚氨酯鞋胶的制备

报道了一种用于鞋胶的双组分水性聚氨酯胶粘剂,包括50％以上的高固含量水性聚氨酯分散体及水可分散多异氰酸酯固化剂的制备。测试结果表明,本实验所制得的样品具有较低的活化温度,范围在50- 75℃之间,且具有很好的耐热温度,耐温高达110℃。所制备的高固含量水性聚氨酯表现出优越的粘接性能,未加固化剂的单组分水性聚氨酯剥离强度(PVC／PVC)高达8．8N／mm。     

不同方法制备的铈锰固溶体及其催化醇胺偶联反应

为了研究不同制备方法对铈锰固溶体形貌、结构及其表面物种等的影响,阐明铈锰固溶体结构与其催化性能之间的关系,通过纳米铸型法、水热法、共沉淀法、热分解法制备出4种理论掺锰量为15%的铈锰固溶体〔Ce_(0.85)Mn_(0.15)O_x,n(Ce)∶n(Mn)=0.85∶0.15〕。采用XRD、FESEM、TEM、N_2-吸附脱附、ICP-OES、XPS对催化剂进行物化性质表征,并以苯甲醇和苯胺偶联反应作为探针反应来评估其催化性能。结果表明,以纳米铸型法制备的铈锰固溶体催化剂具有最佳的催化活性,其苯胺转化率达到了67.9%,N-苄叉苯胺的选择性为99.4%,时空产率为0.56 mmol/(g_(cat)·h)。与用其他3种方法制备的铈锰固溶体相比,纳米铸型法制备的铈锰固溶体具有较大的表面积、特定的介孔结构,催化剂表面拥有较高相对含量的Ce~(3+)、Mn~(3+),有利于吸附和活化氧分子,这些因素均有利于催化醇胺偶联反应。     

Effects of crystallinity and supermolecular formations on the interfacial shear strength and adhesion in GF/PP composites

Aim of this study was to screen the morphological effects on the interfacial shear strength (i) in glass fibre (GF) reinforced isotactic polypropylene (iPP) model composites. i was determined by a modified single fibre pull-out technique. It was established that the relation between i (5–6 MPa) and the yield stress of the iPP (y30 MPa) is at about 1:6 and that the i values were not influenced by the mophological superstructure set under isothermal crystallization conditions. Increased i was only observed when specimens were produced non-isothermally, by quenching (i9 MPa). This improvement could not be related to thermal shrinkage stresses. The enhancement in i was attributed to better wetting and improved adhesion due to the enlarged amorphous PP (aPP)-phase. A schematic adhesion model considering the wetting behaviour of aPP and iPP was proposed.     

On the lattice dynamics of solid solutions with a quantum paraelectric and a ferroelectric component

The lattice dynamics of displacive type phase transitions in solid solutions with a quantum paraelectric and a ferroelectric component is considered. Using the self-consistent phonon approximation and the coherent potential approximation the phonon spectrum of the disordered lattice is obtained and the concentration dependence of the phase transition temperature is calculated. Good agreement with experimental results for (Ba, Sr) TiO₃ is obtained.     

过渡金属掺杂铈-锆固溶体催化剂制备及其评价

选取过渡金属Cu、Co、Ni和Fe对Ce-Zr固溶体(CZO)进行掺杂改性,采用CO催化氧化为探针反应对其进行活性评价,考察过渡金属种类、掺杂量和掺杂方式对催化剂活性的影响.结果表明,对于过渡金属掺杂Ce-Zr固溶体,低温还原峰温度值越低,表面氧反应活性越高,催化剂活性越大,Cu掺杂的催化剂活性最高.共沉淀法与浸溃法制...     

Preparation and use of monoclinic solid solutions of zirconium and hafnium oxides

Conclusions The production technology for the manufacture of ceramic from zirconia-hafnia solid solutions has been developed. The ceramic can be used as tiles for supporting high-melting alloys heated to 2000–2300°C.The ceramic made from a zirconia-hafnia solid solution containing 40 mole% HfO₂ and 60 mole% ZrO₂ has excellent strength and thermal shock resistance and low vapor pressure.Translated from Ogneupory, No. 4, pp. 43–47, April, 1979.     

Cholesteric order in aqueous solutions of the polysaccharide Xanthan

Summary Measurements of birefringence, optical rotation and laser light diffraction show that aqueous solutions of the polyelectrolytic polysaccharide Xanthan at a concentration of 7.5 % (vol/vol) have long range order very similar to cholesteric liquid crystals. The cholesteric screw is left handed implying a rod-like conformation and right handed helicity of individual molecules. The cholesteric phase separates from a less concentrated isotropic solution and spherolites are formed.     

Investigating the structure of non-graphitising carbons using electron energy loss spectroscopy in the transmission electron microscope

We have investigated the structure and bonding in phenolic resin-based carbons as a function of heat treatment using a combination of high resolution transmission electron microscopy, electron energy loss spectroscopy, X-ray diffraction, gas adsorption and density measurements. On heat treatment, the initially amorphous material transforms to a micro-porous material containing small graphitic packets enclosing elongated pores, with a relatively small change in density but an appreciable change in planar carbon sp²-content as well as the development of significant curvature in the graphitic layers. The results from the different characterisation techniques are discussed and wherever possible, cross-correlated. They are also compared with proposed models for the microstructural development in non-graphitising carbons and also with the corresponding data obtained from graphitisable carbons. Overall the data provides strong evidence for a fullerene-based model for the microstructural development in non-graphitising carbons and more generally, the interpretation of the current EELS data has important implications for the spatially localised analysis of poorly crystalline carbon materials.     

Development of new techniques for scanning electron microscope observation using ionic liquid

Based on our previous discovery that ionic liquid (IL) can be observed by a scanning electron microscope (SEM) without charging the liquid, we have developed several novel techniques for SEM observation. Coating of insulating sample with IL is useful for providing electronic conductivity to the samples like metal or carbon coating by vacuum vapor deposition. In this case, dilution of the IL with appropriate volatile solvent like alcohol is effective for coating thin layer of IL on the sample. As a biological sample, seaweed including IL was attempted to be observed by SEM. A seaweed leaf swollen by water was put in an IL bath and the bath was put in an outgassed desiccator to replace water in the seaweed leaf with IL. The resulting sample gave a SEM image of the swollen seaweed whose thickness was several times larger than dried one. Furthermore, the introduction of the IL in vacuum chamber allowed us to develop the in situ electrochemical SEM observation system. Using this system, we observed changes in polypyrrole film thickness caused by the redox reaction of the film and the electrochemical deposition of silver and its oxidative dissolution. It was also found that the energy dispersive X-ray fluorescence (EDX) analysis was available even for the electrode polarized in IL.     

An electron microscope study of the microstructure of some rubber-reinforced polystyrenes

Rubber-reinforced polystyrenes were prepared by graft copolymerization using various butadiene polymers and copolymers. Electron microscopy showed that variations in the pre-polymerization temperature, composition of the rubber, and molecular weight of the rubber influenced the size and structure of the dispersed rubber particles. Microstructures and impact strengths comparable to those of commercial materials were obtained from a limited range of conditions. Solution styrene-butadiene copolymers and a polybutadiene of low molecular weight gave unusual microstructures although polystyrenes of inferior impact strength were obtained. A particle size of 2 μm or greater was required to obtain reasonable improvements in impact strength. The particle size increased with an increase in the initial viscosity of the rubber in styrene solution provided that rubber type and concentration, and pre-polymerization temperature were constant. The effects of these three variables on particle size could not be related to viscosity changes.     

无机高分子复合絮凝剂的扫描电镜制样新方法

常规方法制备无机高分子复合絮凝剂扫描电镜样品时,试样的结构和整体性容易受到破坏,不能反映样品的真实形貌;而且因试样粘得过多和不匀,影响观测结果。本文通过将絮凝剂溶液滴在干净的玻片上,待干燥后,直接将玻片粘在样品座上,用扫描电镜观察,获得清晰的形貌,有效地解决了问题。     

Low-temperature scanning electron microscope analysis of the portland cement paste early hydration

The use of the frozen hydrated scanning electron microscopy (FHSEM) in the study of cement paste is described. This technique permits analysis of the fractured surface of cement paste in a fully hydrated state with water present as ice in a low temperature scanning electron microscope. At 110 K the paste has a substantial increase in mechanical strength, because water is converted from liquid to a solid state, and this permits the use of bulk specimens at very early hydration. Some preliminary results for 1 hour hydration are presented and future applications of this technique are discussed.