Gd1−xSrxFeO3−δ ferrites have been studied by means of X-ray powder diffraction in the whole composition range. Single-phase solid solution is found for x<0.09 and for x>0.63. At intermediate Sr content, phase segregation takes place. Compounds with x?0.05 crystallize in the orthorhombic structure, space group Pbnm. Oxygen-deficient Gd1−xSrxFeO3−δ with x?2/3 are cubic or nearly cubic. The oxygen vacancies stabilize the cubic phase for x=2/3 whereas highly oxidized samples show an orthorhombic distortion, which has not been observed earlier. Magnetic and electrical properties have been measured for the single-phase solid solutions. Gd1−xSrxFeO3−δ compounds with x?2/3 order antiferromagnetically below ∼100 K. In the paramagnetic region, their susceptibility follows the Curie-Weiss law in all but SrFeO2.96 compound. These ferrites show semiconducting behavior in the electrical transport likely related to atomic disorder. We find that the conductivity activation energy becomes larger by increasing either the Gd content or the oxygen vacancies. 相似文献
Syntheses and Structures of [Cu20Ga10Cl4Se23(PEt2Ph)12] and [Cu14In6Se7(iPrSe)18] CuCl and GaCl3 react with Se(SiMe3)2 in thf solution to yield in the presence of PEt2Ph [Cu20Ga10Cl4Se23(PEt2Ph)12] ( 1 ). Reaction of CuCl, InCl3 and TMEDA with iPrSeSiMe3 in DME results in the crystallisation of [Cu14In6Se7(iPrSe)18] ( 2 ). The structures of 1 and 2 were determined by X‐ray single crystal structure analysis and display two new types of molecular clusters formed by the elements of group 11, 13, and 16. However, both cluster structures show no analogy to the structures of the related bulk phases. 相似文献
A new amphiphilic cellulose derivative phenoxyhydroxypropylhydroxyethylcellulose of substitution degree up to 0.67 was synthesized
by reaction of water-soluble hydroxyethylcellulose with 2,3-epoxypropylphenylether in the presence of sodium hydroxide as
a catalyst. The chemical composition of the derivative was confirmed by means of UV, IR- and 13C-NMR-spectroscopy. The derivatives with substitution degree up to 0.12 are soluble in water and water–alcohol mixtures. With
increasing substitution degree, the polymers lose their water solubility, but still dissolve in water–alcohol mixtures. All
products are soluble in aprotic solvents. The effect of the reaction conditions, such as temperature and molar ratios of reaction
components, on both the reaction rate and degree of substitution was investigated. 相似文献
Phenoxyacetic acid distribution in two-phase systems n-aliphatic hydrocarbon (C5–C8) – water and its dimerization in organic phase were investigated. The values of distribution coefficient (DHR), distribution constant (KD), and dimerization constant (Kdim) of acid were obtained. The empirical correlations of these quantities with Hildebrand solubility parameter of organic solvents were established. The influence of pH of the aqueous phase as well as the polarity of the applied organic solvents on phenoxyacetic acid physical chemistry in
the two-phase systems was described. 相似文献
The alkoxyallene derived from 1,3-benzylidene-l-erythritol when treated with chlorosulfonyl isocyanate provided diastereomeric β-lactams with moderate stereoselectivity. After the intramolecular alkylation of the nitrogen atom, these afforded compounds having oxacepham skeletons. The exo-isopropylidene group enabled the introduction of a variety of substituents to the C-7 carbon atom of the cepham, whereas removal of the benzylidene protection followed by the oxidation of 3-OH to the ketone allowed carboxylation of the C-2 carbon atom. 相似文献
Poly(ethylene terephthalate) (PET) film was modified by reaction with hydrazine (HD), ethylenediamine (EDA), 1,2-diaminopropane (1,2-DAP) and 1,3-diaminopropane (1,3-DAP). The maximal amount of amine functionalities introduced in the chosen conditions on the surface was found as 0.07, 3.35, 0.76 and 1.99 nmol cm−2 for HD, EDA, 1,2-DAP and 1,3-DAP respectively. During the modification process etching of the sample and an increase of stiffness takes place. FTIR-ATR spectra prove that the surface chemistry after modification in amine solution is very complex. The lack of clear correlation between the surface tension and surface concentration of amine functionalities seems to confirm that. For immobilization purpose invertase, laccase and tyrosinase were used. The amount of covalently attached proteins at first increases with the increase of surface concentration of amine groups but after reaching a certain level of amine groups, decrease of the immobilization level was observed. All enzymes tested showed highest activity for a moderate level of aminolysis and this activity had the highest values for EDA-modified PET. 相似文献
A capacitive sensor based on S-{12-[1-(pyridin-4-ylmethyl)-1H-1,2,3-triazol-4-yl]dodecyl} ethanethioate (FT), a compound with a functional group exhibiting selective affinity towards Cr(VI) ions, was developed. FT was mixed with shorter-chain thiol-decanethiol (DT), to obtain an Au electrode surface well covered by a thiol monolayer. The composition and high quality of self-assembled monolayers (SAMs) were crucial factors influencing the performance of the capacitive sensor. In this work, SAMs formed from FT and DT mixtures with different compositions were studied. For physicochemical characterization of SAMs X-ray photoelectron spectroscopy (XPS), contact angle measurements as well as atomic force microscopy (AFM) were used. Cyclic voltammetry was employed to estimate an electrode surface coverage. Based on the obtained results, the composition of thiol layer providing the best parameters for capacitive sensing of chromium(VI) was chosen. Moreover, the analytical performance of sensor was verified.
The salinity of European soil is increasing every year, causing severe economic damage (estimated 1–3 million hectares in the enlarged EU). This study uses the biomass of halophytes—tall fescue (grass) and hemp of the Białobrzeskie variety from saline soils—for bioenergy, second generation biofuels and designing new materials—fillers for polymer composites. In the bioethanol obtaining process, in the first stage, the grass and hemp biomass were pretreated with 1.5% NaOH. Before and after the treatment, the chemical composition was determined and the FTIR spectra and SEM pictures were taken. Then, the process of simultaneous saccharification and fermentation (SSF) was carried out. The concentration of ethanol for both the grass and hemp biomass was approx. 7 g·L−1 (14 g·100 g−1 of raw material). In addition, trials of obtaining green composites with halophyte biomass using polymers (PP) and biopolymers (PLA) as a matrix were performed. The mechanical properties of the composites (tensile and flexural tests) were determined. It was found that the addition of a compatibilizer improved the adhesion at the interface of PP composites with a hemp filler. In conclusion, the grass and hemp biomass were found to be an interesting and promising source to be used for bioethanol and biocomposites production. The use of annually renewable plant biomass from saline soils for biorefinering processes opens up opportunities for the development of a new value chains and new approaches to sustainable agriculture. 相似文献