Ce–Ti–Ge system at 1170 K

Phase equilibria in the Ce–Ti–Ge system were investigated by X-ray powder diffraction, electron probe X-ray analysis and the isothermal section at 1170 K was obtained. We confirmed the CeFeSi-type CeTiGe compound (a=0.4135 (1) nm, c=0.7921 (1) nm, space group P4/nmm, No. 129). A new compound, Ce₂₀Ti₂₀Ge₆₀, was found (a=0.3967(6) nm, c=6.054 (2) nm, space group P4). It is obvious that the ThSi₂-type Ce₃₃Ti₇Ge₅₄ compound (a=0.4217 (1) nm, c=1.4184 (3) nm, space group I4₁/amd, No. 141) belongs to the extended solid solution region of the ThSi₂-type CeGe₂ compound.     

Complete, reversible H/Li ion exchange reaction between rhombohedral LiMO3 and perovskite-type HMO3 (M=Nb, Ta)

We demonstrate for the first time the complete, reversible H⁺/Li⁺ ion exchange reaction between HMO₃ and LiMO₃ (M=Nb, Ta) using molten LiNO₃ at 320°C for 5 days. HMO₃ were prepared from LiMO₃ by ion exchange reactions using dilute HNO₃. The results reveal that both LiMO₃ prepared by normal solid state reaction between Li₂CO₃ and M₂O₅, and by ion exchanged from HMO₃ using molten LiNO₃ are isostructural. LiMO₃ prepared using HMO₃ yields nearly uniformly sized crystallites in contrast to those prepared by conventional solid state synthesis. The present method is simple and inexpensive compared to other methods of preparation of high purity LiMO₃ powders.     

On the design of the RTO unit using CFD

The objective of this work is to study alternative designs for a flow mixing tank to be installed ahead of a regenerative thermal oxidation (RTO) unit in an asphalt plant. A study of the steady-state flow field in the unit was conducted applying computational fluid dynamics (CFD). The governing equations (mass, momentum, energy and turbulence) were solved using the commercial code Fluent. The simulation results provided insight into the effectiveness of the numerical predictions of conditions in the mixer and led to practical responses in terms of a better design of the industrial RTO unit.     

Chemistry of thermal ageing in aerospace epoxy composites

The detailed chemical reactions involved in the thermal ageing (at 120°C) of a typical aerospace epoxy composite have been studied by the mid‐Fourier transform infrared spectroscopy (FTIR) spectral characterization of selected model compounds. The FTIR spectra indicate that at this particular temperature, the major reaction in the resin structure is probably an oxidation of a CH₂ group adjacent to the nitrogen atom of the tetraglycidyldiaminodiphenyl methane unit of the molecular structure, particularly where it is attached to one isomer of the diaminodiphenylsulfone hardener unit. The FTIR changes indicate that the major product is an amide group but other minor changes are also detailed and differences in the chemical changes seen at other ageing temperatures highlighted. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2210–2219, 2006     

Production and characterization of laccase and manganese peroxidase from the ligninolytic fungus Fomes sclerodermeus

Fomes sclerodermeus was grown on semi‐defined media based on yeast extract, peptone and glucose (YPG). The fungus produced a minimum basal level of laccase activity irrespective of culture medium. The highest laccase production (20 U cm^?3) was obtained in cultures supplemented with CuSO₄. Manganese peroxidase (MnP) could only be detected when MnSO₄ was added to the medium. None of the aromatic compounds tested stimulated further laccase or MnP production. Laccase and MnP stimulated by Cu²⁺ or Mn²⁺ respectively were purified. Two different laccase isoenzymes with the same molecular mass (67 kDa) and N‐linked carbohydrate content (3%) and a slight difference in their pI values (3.41 and 3.48) were characterized. In addition, two different MnP isoenzymes with the same molecular mass (47 kDa) and N‐linked carbohydrate content (4%) and different pI values (3.35 and 3.45) were characterized. Both enzymes showed good stability at 25 °C and over a wide range of pH. Both laccases oxidize ABTS (2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) more efficiently than 2,6‐dimethoxyphenol (DMP) with similar efficiency values (K_cat/K_m) while the MnP I, the major peroxidase isoenzyme in the studied conditions, oxidizes the Mn²⁺ and Mn‐mediated activity on DMP more efficiently than MnP II. Copyright © 2006 Society of Chemical Industry     

Thermoreversible gelation of poly[hexyl isocyanate]: Effect of solvent type

The thermoreversible gelation of poly[hexyl isocyanate] (PHIC), a rather stiff polymer, has been studied in two closely-related solvents of the alcane series, namely heptane and octane. Temperature-concentrations phase diagrams have been established for both systems. The occurrence of polymer-solvent compound is suggested in heptane but not in octane. This conclusion receives further support from neutron diffraction investigations through the use of the isotopic labelling technique. Finally, it is observed that the morphology is also affected by the solvent type although still displaying a fibrillar network structure.     

Synthesis and structure of the tetradeca-iron(III) oxide–alkoxide cluster [Bu4N]2[Fe14O8(OCH2CH3)20Cl8]

The iron(III) oxide–alkoxide cluster, di-tetra-n-butylammonium octachloro-tetra(μ₃-oxo)-tetra(μ₄-oxo)- icosa(μ₂-ethoxo)-tetradeca-iron(III), has been isolated and its X-ray crystal structure determined.     

含手性膦配体MBPA和邻巯基吡啶配体PyS的过渡金属钯(Ⅱ)化合物的2D NMR研究

利用一维和二维NMR技术,对含手性膦配体MBPA和邻巯基吡啶配体PyS的过渡金属Pd(Ⅱ)化合物Pd(3-MBPA)(PyS)Cl)(1),Pd(2-MBPA)(PyS)Cl)(2)。进行~1H和~(13)C NMR谱分析,归属了所有的~1H和~(13)CNMR谱线,并对配体在配位前后的化学位移的变化作了简单讨论。     

New Hydrolytic Process for Producing Zirconium Dioxide, Tin Dioxide, and Titanium Dioxide Nanoparticles

Nanocrystalline ZrO₂, SnO₂, and TiO₂ were synthesized through a simple hydrolytic process based on the etherification of alcohols. The obtained products had good uniformity and were less aggregated than in other synthesis techniques. The synthesis of ZrO₂ and SnO₂ in this process was dependent mainly on the reaction temperature, whereas the morphologies of TiO₂ exhibited a dependence on the alcohols used.