Thermoanalytical procedures to identify the morphology of polycrystalline materials

Polypropylenes of differing morphologies were examined by differential thermal analysis. The problems of reordering during the programmed heating are discussed. Four potential procedures by which the reordering could be inhibited are considered, and three of these are experimentally assessed. Their advantages and deficiencies are identified. Two pretreatments, an etching and a crosslinking, are recognised as able to qualitatively characterise the initial morphology, with a preference for the former. A test to identify the occurrence of reordering is identified. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

An efficient lasing action from pyrromethene 556 dye-doped organically modified silicates

Organically modified solid-state silicates (ORMOSILS) doped with a new laser dye 1,3,5,7,8-pentamethylpyrromethene-2,6-disulfonate-BF₂ complex (pyrromethene 556) have been synthesized by a sol-gel method and the compositional effects on pore characteristics, fluorescence and lasing properties have been investigated. It is found that the use of dimethylsulfoxide and γ-glycidoxypropyltrimethoxysilane could greatly change the structure properties of sol-gel derived ORMOSILS cage, and thus the fluorescence and lasing properties of the materials could improve significantly. A successful laser oscillation from this dye-doped ORMOSILS sample has been achieved upon pumping with a Q-switched frequency-doubled Nd:YAG laser at 532 nm. A slope efficiency of 54% with a useful lifetime greater than 10,000 shots has been demonstrated at a pump repetition rate of 1 Hz and a pump intensity of 1 J/cm² by using the new ORMOSILS cage on our newly designed laser system. Our results have shown that it is possible to obtain a high-efficiency with a long-lifetime for a compact new laser device by low cost dye-doped solid-state ORMOSILS.     

High-T c superconducting magnetic bearings for rotation-based devices

Summary A Modified-Melt-Powder-Melt-Growth (MMPMG) technique has been developed for the preparation of melt-textured Y-Ba−Cu−O pellets. To test their performances, the samples were characterized with respect to their microstructure, pinning strength and interaction force with permanent magnets. A superconducting magnetic bearing was built and integrated in a levitating flywheel system for energy storage. Paper presented at the “VII Congresso SATT?, Torino, 4–7 October 1994. Under a Fondazione Confalonieri grant.     

Progress in the quality assurance of environmental trace organic analysis

An overview is given on the stepwise learning programmes undertaken to identify the main sources of error associated with the determination of the mandatory organic contaminants in the marine monitoring programmes. Details are given on the preparation and use of LRMs and CRMs to maintain analytical control and quantify the laboratory errors in relation to the measurement of changes in the environment.     

不锈钢丝网上薄膜TiO2光催化剂的Raman光谱研究

用Raman光谱方法来研究用Sol Gel法负载于金属丝网的薄膜TiO2 光催化剂的物相结构、厚度以及粒径大小。研究结果显示 ,薄膜达到一定厚度能够阻止基底Fe元素向薄膜表层的扩散 ;在 4 0 0℃下灼烧制得的薄膜TiO2 光催化剂具有锐钛矿晶型 ,而高于 4 0 0℃时 ,将出现金红石相TiO2 ;锐钛矿晶型TiO2 的Raman特征峰产生偏移 ,表明薄膜粒径的变化 ,通过计算表明 ,薄膜TiO2 的粒径为 10nm左右 ,TEM的分析结果也与之一致。     

FexNi100−x nanometric films deposited by laser ablation on SiO2/Si substrates

Fe_xNi_100−x nanometric films were deposited on SiO₂/Si substrates at room temperature using the pulsed laser deposition technique. The targets were Fe-Ni amorphous magnetic foils with composition Fe₅₀Ni₅₀, Fe₃₅Ni₆₅ and Fe₂₂Ni₇₈. Morphological and structural properties of the deposited films were investigated using scanning electron microscopy, Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, and X-ray reflectivity. Electrical and magnetic characteristics of the films were investigated by using the four-point probe and the magneto-optic Kerr effect techniques, respectively. The film properties are strictly dependent on the Fe-Ni compositional ratio.     

Indentation responses of piezoelectric films

Frictionless indentation responses of transversely isotropic piezoelectric film/rigid substrate systems under circular cylindrical indenter (i.e., punch), conical indenter (i.e., cone), and spherical indenter (i.e., sphere) are investigated. Both insulating and conducting indenters are considered. The technique of Hankel transformation is employed to derive the corresponding dual integral equations for the mixed boundary value indentation problems. For the two limiting cases of infinitely thick and infinitely thin piezoelectric films, closed-form solutions are obtained. For piezoelectric films of finite thickness, a numerical method is constructed to solve the dual integral equations and semi-empirical models having only two unknown parameters are proposed for the responses of indentation force, electric charge and electric potential, and contact radius. With the two parameters inferred from the numerical results, the semi-empirical formulae are found to provide good estimates of the indentation responses for the two limiting cases of infinitely thick and thin piezoelectric films, as well as those in between. The inferred parameters in the proposed semi-empirical formulae for normalized indentation force and electric charge are checked against four different piezoelectric materials and are found to be insensitive to the selection of piezoelectric materials. It is believed that the proposed semi-empirical indentation formulae are useful in developing experimental indentation techniques to extract the material properties of piezoelectric films.     

Axisymmetric frictionless contact of functionally graded materials

The main interest of this study is a new method to solve the axisymmetric frictionless contact problem of functionally graded materials (FGMs). Based on the fact that an arbitrary curve can be approached by a series of continuous but piecewise linear curves, the FGM is divided into a series of sub-layers with shear modulus varying linearly in each sub-layer and continuous at the sub-interfaces. With this model, the axisymmetric frictionless contact problem of a functionally graded coated half-space is investigated. By using the transfer matrix method and Hankel integral transform technique, the problem is reduced to a Cauchy singular integral equation. The contact pressure, contact region and indentation are calculated for various indenters by solving the equations numerically. An erratum to this article can be found at     

Modification of multiwalled carbon nanotubes by carboxy groups and determination of the degree of functionalization

Multiwalled carbon nanotubes were modified by carboxy groups. Four independent methods for the determination of the degree of functionalization of the surface were proposed: ¹³C NMR spectroscopy, thermogravimetry, titrimetry, and fluorimetry. The first two methods show the total content of carboxy groups in the sample, and the latter two methods give information about the content of the surface groups only. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 291–295, February, 2008.