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1.
This review includes research papers on different methods of preparation of Eu 2+ and Dy 3+-doped SrAl 2O 4 phosphors and papers reporting luminescence studies of the materials. The methods of preparation were compared and it was concluded that solid state reaction is the best method. Papers on characterization of these phosphors by X-ray diffraction and scanning electron microscopy are also discussed. The review ends with a few important conclusions. 相似文献
2.
Abstract A systematic study of the chromatography of metal ions on collidinium tungstoarsenate papers has been performed using seven different mixed solvent systems. R f values of 30 metal ions have been determined by ascending technique and are discussed. The study demonstrates that specific extraction of both Sn(ii) and Sn(iv) is possible in 0.1 mol dm ?3 HNO 3 in 80% (v/v) 1-propanol and their mutual separation can be carried out in solvent system 1 mol dm ?3 HCl in 33% (v/v) 1-propanol. In addition some binary and ternary separation of metal ions have also been achieved on these papers. For a comparison R f values on plain papers have also been determined in all the solvent systems. 相似文献
3.
Summary The chromatographic behaviour of 49 metal ions has been studied on papers impregnated with Sn(IV) and Ti(IV) antimonates in aqueous HNO 3 and mixed solvent systems containing dimethyl sulphoxide. Numerous separations have been achieved and the Alberti equation, for Sn(IV) and Ti(IV) antimonate papers, in the modified form: –nloga K +=R M + constant (a K +=activity of K +), has been verified. The effect of the concentration of impregnating reagents on these papers has been determined and compared with other papers. The effect of pH on R f, R i, log R f and R M values of metal ions has also been examined in aqueous systems. 相似文献
4.
Organic dyes are used in many industries, e.g., textile, cosmetics and food. Hence, contamination of organic dyes to water sources is a critical issue. To reduce water pollution by organic dyes, we propose a paper-like adsorbent with a practical and economical production procedure. Subsequently, a flexible adsorbent was produced using a one-step approach by vacuum filtration of graphene oxide (GO) and iron oxide nanoparticles (Fe3O4-NPs) containing dispersion through a membrane and quoted as GO/Fe3O4 paper. For comparison, GO paper was also prepared using the same procedure. Both papers were characterized using UV–VIS absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, electron diffraction X-ray analysis, X-ray photoelectron spectroscopy, and powder X-ray diffraction techniques. At the steady-state conditions, GO/Fe3O4 and GO papers were performed as adsorbent for cationic dyes of methylene blue, neutral red, and anionic dyes of methyl orange and fluorescein. In general, the removal efficiency of GO/Fe3O4 paper was higher than that of GO paper for adsorption of all dyes and this adsorbent revealed satisfactory adsorption properties for cationic dyes when compared to anionic dyes. 相似文献
5.
A comprehensive review on phase diagrams, crystal
structures and thermodynamic properties of ternary chlorides formed in the
systems ACl/LnCl 3 ( A=Na,
K, Rb, Cs) is presented. It continues an earlier review with the same contents
on the lanthanides from La to Gd [1]. In both papers the author's own
studies, published since 1985, together with original papers from other scientists
are treated. With the three larger cations compounds of the composition A 3LnCl 6,
A 2LnCl 5, ALn 2Cl 7
and beginning with holmium Cs 3Ln 2Cl 9
are formed. With sodium the compounds Na 3Ln 5Cl 18
( Ln=La to Sm) and NaLnCl 4
( Ln=Eu to Lu) also exist. The stability
of a ternary chloride in a system ACl/LnCl 3 is given
by the 'free enthalpy of synreaction', the formation of a compound
from its neighbour compounds in its system. This must be negative. A surprising result is that the highest
– melting compounds in the systems, A 3LnCl 6,
are formed from ACl and A 2LnCl 5
with a loss of lattice energy, U. They
exist as high-temperature compounds due to a sufficiently high gain in entropy
at temperatures where the entropy term TΔ S compensates the endothermic ΔH. 相似文献
6.
In order to go further in demonstrating that methanol can be used as a universal cellulose degradation indicator in power
transformers, the ageing study of standard wood kraft specimens in oil in the range of 60–130 °C (Gilbert et al. in Cellulose
16:327–338, 2009) has been extended to thermally-upgraded (TU) papers. The kinetic model that best tracks the ageing patterns was shown to
be a function that can accelerate or decelerate the pseudo-zero kinetics by the adjustment of a free parameter. The results
showed a non-negligible contribution of 1,4-β-glycosidic bond breaking in the crystalline regions suggesting that the degradation
at this level is not necessary occurring through a quantum mode mechanism. The results also showed a significant error in
the determination of the rate constants when obtained from isotherms of varying degree of depolymerization. In the case of
TU papers, provided that there is a sufficient amount of stabilizers in the fibrous structure, not only could the self-catalyzing
nature of the cellulose ageing process as well as the effect of an external supply of catalysts be lost but the chain-breaking
could decrease to nearly zero for an undetermined period well before reaching the levelling-off degree of polymerization.
The initial rate constants ( k
1o) for the depolymerization and methanol formation of these papers were found to be very near those of standard cellulose (giving
about the same activation energy), which indicates that they are obtained from the ageing patterns well before the retardant
action has fully taken place. The life extension of TU papers is achieved by a reduction with time of the frequency at which
the bonds are ruptured. Moreover, the production of methanol and chain-end groups showed about the same value for the frequency
factor, which introduces the possibility that the rate of production of CH 3OH from chopped chains is much higher than the rate of depolymerization, so that the latter becomes the rate determining step
of the overall reaction. On the other hand, the apparent yield of CH 3OH molecules per scission is seen to increase substantially with the amount of stabilizers (from ~0.4 to 0.8 and to 1.4 for
a paper containing 0 to 1.15 and to 3.9% (w/w) N 2) and to a lesser extent, with the moisture in the specimens. However, these variations could either be attributed to a modification
of the CH 3OH paper/oil partitioning by the stabilizers and moisture in fibrous structure. Finally, pre-aged systems (130 °C for 168 h)
conditioned at 20 °C for variable lengths of time provided further evidence that O 2 is not necessarily involved in CH 3OH production. 相似文献
7.
The thermal properties of cyanatocopper complexes with pyridine, bipyridine and phenanthroline are described in this paper. It was found that the thermal stabilities of the complexes were found to increase in the order pybipy 2(NCS)2 (L=pyridine and its methyl derivates) which are composed of the liberation of ligandsL and redox reactions of thiocyanate ligands with the central Cu(II) atom [1, 2]. The decomposition temperature of thiocyanate ligands depends on the properties of the ligandsL present in the coordination sphere. An analogous course of thermal decomposition was also observed for [Cu(bipy)2(NCX)](NCX) (X=S or Se) [3]. For the phenanthroline complexes [Cu(phen)2(NCX)2] (X=S or Se) the thermal stability was found to increase significantly (by about 140C) and the decomposition stoichiometry was also changed [3].The present paper contains the results of thermoanalytical studies on bipyridine and phenanthroline cyanatocopper complexes, and a comparison of the thermal properties of pyridine cyanato and isothiocyanatocopper complexes. 相似文献
8.
AbstractThioureas are important building blocks in medicinal chemistry; ferrocenes as highly hydrophobic moieties induce very interesting qualities in medicinal compounds. In this article, we have synthesized four ferrocene incorporated N,N′-disubstituted benzoyl thioureas ( 3a–3d) with general formula C 5H 5-Fe-C 5H 4C 6H 4Cl-NH-CS-NH-CO-C 6H 4(H/CH 3). Molecular structures of these compounds were characterized in solid and solution phases. In solution molecular structures were established by 1H and 13C NMR and cyclic voltammetry. In the solid state their structures were characterized by elemental analyses and FTIR spectroscopy. Two of the compounds ( 3a and 3d) had also been structurally determined by single crystal X-ray diffraction analysis. The electrochemical characterization showed a reversible process with one electron transfer from Fe(II) to Fe(III). The single crystal analysis showed strong intermolecular non-covalent interactions in these compounds. Molecular structures of these compounds were also studied by density functional theory (DFT) calculation . DFT studies showed good correlation between calculated parameters and experimental results of solution phase and solid state characterizations. Compounds 3a–3d were evaluated for DNA interaction and antioxidant activity. These compounds interact with DNA via electrostatic forces and liberate significant binding constants and energies. Antioxidant potential –CSN H and –CON H groups induce same level of free radical scavenging ability in these compounds. 相似文献
9.
Summary A systematic study of the chromatography of metal ions on stannic tungstate papers has been performed using acetone-HNO 3–H 2O systems. The effect of mole fractions of acetone, HNO 3 and H 2O on the R f values of the metal ions has been discussed in detail and a relationship between R f and mole fraction (X) of the solvent has been obtained as R f=mX+C. The usefulness of the study has been demonstrated by the specific extraction of titanium and thorium in HNO 3H 2O (12) and HNO 3:acetone:H 2O (161) systems. In addition, some binary and ternary separations of metal ions have also been achieved on these papers. 相似文献
10.
The research of anti-counterfeiting and encryption has always been a subject of universal concern all over the world. Herein, lanthanide metal–organic framework (Eu-MOF) and CH3NH3PbBr3 (MAPbBr3) perovskite were introduced onto pulp fibers (PFs) to prepare fluorescent anti-counterfeiting and encryption papers. Eu-MOF@PFs paper emitted red fluorescence at 254 nm UV excitation. The optimum preparation conditions of Eu-MOF@PFs were 2.5 mmol of Eu(NO3)3, 4 h of reaction time and room temperature. When MABr ink was written on Pb/Eu-MOF@PFs paper, the green fluorescent handwriting and red fluorescent paper were observed under 365 nm and 254 nm UV excitation, respectively. The appropriate addition amount of lead nitrate was 0.6 mmol. Pb/Eu-MOF@PFs paper was immersed in MABr solution to prepare MAPbBr3@Pb/Eu-MOF@PFs paper. Under 254 nm and 365 nm UV irradiations, MAPbBr3@Pb/Eu-MOF@PFs paper emitted red-green double fluorescence and the quantum yields of which were 3.11% and 2.48%, respectively. The crystal structure of MAPbBr3 was easily destroyed by polar solution, which realized on/off switching of the luminescence signal for multistage information encryption. The above paper-based fluorescence materials were potential for advanced anti-counterfeiting and encryption applications. 相似文献
11.
Among the perovskites, the rare earth manganites find application in several electrochemical devices because of their enhanced thermodynamic stability. In this paper, we present the results obtained on the preparation and characterization of La 0.95MnO 3+δ and Sm 0.95MnO 3+δ which were prepared by the solid state and sol–gel methods. XRD characterization of the manganites indicated that the crystal structure depends on the method of preparation and heat treatments. The ratio of Mn 3+ to Mn 4+ in these samples also depended on the method of preparation and heat treatments, as indicated by thermogravimetric (TG) and temperature programmed reduction (TPR) studies in Ar + 5% H 2 atmosphere. The standard molar enthalpy of formation, which is a measure of the thermodynamic stability of these compounds were determined using an isoperibol calorimeter. 相似文献
12.
Summary The formation of V 2O 5 fibrous microcrystals in the V 2O 5-NH 3-H 2O system has been investigated by electron microscopy. The morphology of these microcrystals is dependent on the concentration of the particular components in the colloidal system and on the time of aging. In some colloid systems the orientation of V 2O 5 fibrous crystals with their long axes parallel to one another is also possible. The microcrystal growth in these systems can be attributed to very effective conditions for the recrystallization of vanadium pentoxide crystals in equilibrium with ammonium vanadate in solution.With 3 figures 相似文献
13.
The concept of using paper chromatography on papers impregnated with liquid anion or cation exchangers is extended to the
separation of trace elements through filtration on filter papers loaded with suitable extractant. The uptake of uranium, thorium
and lanthanum from HCl and HNO 3 media of different molarities by a filter paper treated with tri-octyl amine (TOA) is investigated. The effect of the different
parameters on the uptake of the studied elements is experimented. A simple and fast radiochemical procedure is developed for
the separation of La, Th and U from each other. 相似文献
14.
In this work three different supports (γ-Al 2O 3, ZSM-5, and SAPO-34) of varying degree of acid sites and textural properties were used to evaluate the influence of support specifics in the Cu/supported nanocatalysts on NO conversion. The nanocatalysts were prepared by homogeneous deposition precipitation (HDP) method and characterized by N 2 pore size distribution, TEM, H 2-TPR for investigation the reducibility of the copper species and acidity measurement by NH 3 adsorption. The Cu/ZSM-5 and Cu/SAPO-34 catalysts were more active for NO conversion than Cu/γ-Al 2O 3 catalyst. The characterization and conversion differences in the copper supported on different types of support indicated that these differences arise from the differences in surface area, pore size distribution, and acidity of the supports. The higher SCR-DeNO activity of Cu/ZSM-5 and Cu/SAPO-34 nano-catalysts can be explained by higher surface area and acidity of ZSM-5 and SAPO-34 supports. These catalysts also have larger amount of reducible Cu species compared to Cu/γ-Al 2O 3 which correlates with the structure of the support used. Considering these findings, the NO conversion ability of Cu/supported catalysts has been correlated with support structure and acidity. 相似文献
15.
A comprehensive review on phase diagrams, crystal structures and thermodynamics of ternary chlorides formed in systems ACl/LnCl 3 ( A=Cs, Rb, K, Na; Ln=La−Gd) is presented. The review summarizes the author’s own studies, published since 1985, and original papers of other scientists.
With the larger alkali metal ions compounds such as A 3LnCl 6, A 2LnCl 5 and ALn 2Cl 7were obtained. With sodium additional compounds NaLnCl 4 and Na 3Ln 5Cl 18 were obtained. The crystal structures are discussed with the concept of ionic radii, which determine the coordination numbers
of Ln 3+ and A + cations against Cl − anions. The formation enthalpies of the compounds from ACl and LnCl 3 were determined by solution calorimetry. Gibbs’ free energies and entropies for these reactions were obtained by e.m.f. measurements
vs. temperature.
The stability of a ternary chloride in a systemACl−LnCl 3 is given by the ‘free enthalpy of synproportionation’, that is, the formation of a compound from its neighbour compounds
in the system. This Δ G
0
syn must be negative. A surprising result is, that the highest-melting compounds in the systems, A 3LnCl 6, are formed from ACl+A 2LnCl 5 by a loss in lattice energy. They exist as high-temperature compounds due to sufficiently high gain in entropy at temperatures
where TΔ S>Δ H.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
The kinetics of alkyl group migration in RMn(CO) 5 complexes ( R=CH 3, C 2H 5 and C 3H 7) were studied. Isomers of CH 3Mn(CO) 5 with an agostic structure, an η 1 structure, and an η 2 structure were found to be local minima on the system's potential energy surface. Transition states for the inter-conversion of these species were also located. The activation free energy for this migration reaction was compared with experimental data and provides insights into the important steps in the overall reaction mechanism. 相似文献
17.
This paper is continuation of the study concerning the solubility-temperature dependence data for some phenolic compounds (PhC), contained in olive mill wastewater (OMWW), in two nitrate salts (KNO 3 and NaNO 3) aqueous solutions. The solubilities of PhC were determined in the temperature ranging from (293.15 to 318.15) K. It has been observed that the solubility, in aqueous nitrate solutions, increases with increasing temperature. Results showed that alkali metal nitrate has a salting-out effect on the solubility of PhC. The effect of the anion of the electrolyte on the solubility of PhC is observed by comparing these results with values reported in the previous papers for the effect of LiCl, NaCl and KCl. For each cation, the solubilites of the phenolic compounds are higher with nitrate anion than with chloride anion. Results were interpreted in terms of the salt hydration shells and the ability of the solute to form hydrogen-bond with water. The solubility data were accurately correlated by a semi empirical equation. The standard molar Gibbs free energies of transfer of PhC (Δ trG°) from pure water to aqueous solutions of the nitrate salts have been calculated from the solubility data. The decrease in solubility is correlated to the positive Δ trG° value which is mainly of enthalpic origin. 相似文献
18.
Abstract A new adsorbent zinc silicate has been used for the paper chromatographic separations of different phenols. R F values have been determined and compared with those obtained on plain papers. A new term R i has been calculated for various phenols. The dependance of R i and R F on various factors have also been studied and discussed. 相似文献
19.
Mass attenuation coefficients of amino acids viz. glycine (C 2H 5NO 2), l-Serine (C 3H 7NO 3), l-Theronine (C 4H 9NO 3), l-Proline (C 5H 9NO 2), l-Valine (C 5H 11NO 2) and l-Phenylalanine (C 9H 11NO 2) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by the gamma-ray transmission method in a narrow beam good geometry setup. Precisely measured densities of these solutions were used for the determination of these coefficients which varied systematically with the corresponding changes in the concentrations (g/cm 3) of the solutions. Molar extinction coefficients of amino acids were then obtained at these energies and were found to be in good agreement with the theoretical results. In addition, total interaction cross sections of amino acids in aqueous solutions were also calculated. 相似文献
20.
Direct synthesis of nanosheet Fe-ZSM-5 catalysts and their use for selective catalytic reduction (SCR) of NO x by ammonia were studied. XRD, BET, SEM, EPR, and NH 3-TPD were used to understand the properties of catalysts with different iron loading. XRD confirmed the presence of the ZSM-5 crystal phase, and there was no Fe 2O 3 phase on the surface of the crystals. SEM showed the Fe-ZSM-5 catalysts comprised microspheres made up of nanosheets. EPR indicated that the iron was present as isolated Fe 3+and FeO x oligomers uniformly dispersed throughout the crystals. NH 3-TPD indicated that Fe-ZSM-5 (20,1:1) had maximum acid sites and density at approximately 250 and 450 °C, respectively. Fe-ZSM-5 (20,1:1) had the highest activity in the SCR reaction with NH 3. It was also confirmed that Fe-ZSM-5 (20,1:1) had excellent resistance to SO 2 and H 2O under the SCR reaction conditions. The effects of water vapor and SO 2, iron loading, and the Si/(Fe + Al) ratio were also investigated for these catalysts. 相似文献
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