Materials Literature
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Reoxidation of Cu0 (3.1 wt%) in ZSM-5 (nSi/nAl=20) produced by over-exchange (nCu/nAl=0.75) and a subsequent reduction with H2 (773 K, 30 min) was studied in an Ar stream using FTIR spectroscopy. Above 573 K, the decrease in the intensity of the OH stretching band at 3611 cm-1 raised the consideration that some Cu0 at…
We present a simplified model of shear thickening in concentrated colloids. The key idea of the model is that the trajectories of close approaching particles be simultaneously consistent with both the stress and the shear rate of the suspension. The weak shear thickening of Brownian hard spheres is reproduced. For coa…
The drying of wet Tetraethoxysilane-derived gels was studied by means of thermogravimetric analysis as a function of the time, from the instant when the samples were placed into a pre-heated oven, kept at 70, 83 and 100 °C. The precursor sol of the gel was obtained by sono-hydrolysis of the Tetraethoxysilane under aci…
Cubic Y zeolite were successfully synthesized using microwave heating for 18 - 25 min, whereas 10 - 50 h are required by hydrothermal heating technique depending upon the lattice Si/Al ratio. To this end, we used a commercial microwave oven modified in order to provide pulsed microwave pumping on the synthesis mixture…
Eu3+ doped bulk monoliths and thin films were obtained by sol-gel methods in the ZrO2, SiO2 and SiO2-TiO2 systems. Eu3+ 5D0 ® 7FJ emission and decay time characteristics were measured during the entire experimental preparation route from the initial sol to the final xerogels. The crystalline phases identified were tet…
This paper describes the determination of the thermal diffusivity of LiKSO4 crystals using the photoacoustic phase lag method, in the 77 K to 300 K temperature interval. This method is quite simple and fast and when it is coupled to a specially designed apparatus, that includes a resonant photoacoustic cell, allows fo…
Off-stoichiometric NiZn ferrite was obtained by hydrothermal process and compacted in torus form under different pressures. Two samples A1 and A2 - cobalt doped (0.5 %) were sintered at 1573 K in air atmosphere during 3 h. The magnetic properties were studied by vibrating sample magnetometry, Mössbauer spectroscopy an…
Commercialization of large-area electrochromic glazing is reviewed with respect to device configuration and materials employed. Device configurations including electrochromic solutions and solid state electrochromic layers are discussed as well as novel user-controlled photochromic and gasochromic devices.
Bottle grade virgin PET (polyethylene terephthalate) resin was investigated through five consecutive injection molding steps to simulate recycling cycles. Tests were carried out after each recycling to evaluate degradation, crystallinity (by density and Differential Scanning Calorimetry-DSC measurements), hardness, an…
Yttria stabilized zirconia sintered by silicate glass phase with addition of ytterbium or gadolinium was investigated. The grain growth rate was found to be higher in the gadolinium doped samples. The glass phase of the ytterbium doped sample showed partial crystallization on cooling. Grain conductivity was found to b…
This work describes an alternative method for the preparation of ferroelectric thin films based on pre-calcination of oxides, to be used as precursor material for a solution preparation. In order to show the viability of the proposed method, PbZr0.53Ti0.47O3 and Bi4Ti3O12 thin films were prepared on fused quartz and S…
The bandgap energy as a function of temperature has been determined for lead iodide. The monocrystal was obtained in a vacuum sealed quartz ampoule inside a vertical furnace by Bridgman's method. The optical transmittance measurement enables to evaluate the values of Eg. By a fitting procedure of Eg as a function of t…
Basic regularities of silicon nitride based materials microstructure formation and development in interrelation with processing conditions, type of sintering additives, and starting powders properties are discussed. Models of abnormal or exaggerated grain growth are critically reassessed. Results of several model expe…
The Al2O3-ZrO2 composite was studied by impedance spectroscopy, a non destructive technique that was found to be sensitive to the composite's microstructure. The observed decrease in the zirconia grain and grain boundary conductivities points to compression on zirconia grain by alumina matrix. This effect increased wi…
Granular systems composed by nanostructured magnetic materials embedded in a non-magnetic matrix present unique physical properties that depend crucially on their nanostructure. In this work, we have studied the structural and magnetic properties of NiZn-ferrite nanoparticles embedded in SiO2, a granular system synthe…
O. Haas and E. J. Cairns, Annu. Rep. Prog. Chem., Sect. C: Phys. Chem., 1999, 95, 163 DOI: 10.1039/PC095163
Abstract Epilithon, epiphyton, epipelon, epipsammon and plocon diatom samples and water chemistry samples were collected bimonthly from 11 stations along the Mesta River, Bulgaria between December 1989 and April 1991. Principal component analysis (PCA), correlation, and dominance analysis were employed for describing…
By electrochemical adsorption of glucose oxidase (GO) on a polypyrrole (PPy) nanotubular layer, a glucose biosensor has been fabricated. PPy microtubules can be synthesized by oxidative polymerization of the pyrrole monomer within the pores of a polycarbonate template. The activities of immobilized GO are investigated…
The filter feeding oligotrich ciliate Strobilidium lacustris, the raptorial prostome ciliate Balanion planctonicu~n and the diffusion feeding scuticociliate Histiobalantium bodamicurn could be cultivated for months/years on a sole &et of Cryptomonas sp., whereas the diatom Stephanodiscus hantzschii did not support the…