共查询到20条相似文献,搜索用时 15 毫秒
1.
Studies on the extraction of thorium, protactinium, uranium and neptunium from H2SO4 solutions by TLA indicated that these elements have low distribution coefficients (<0.1) at high acid concentrations. Additions of HCl or HBr to H2SO4 solutions enhances appreciably the extraction of the mentioned elements. A systematic investigation on the effect of halide concentration and solvetn concentration helped in explaining the observed enhancement as well as identifying the extracted complexes. 相似文献
2.
Vinod P. Raphael K. Joby Thomas K. S. Shaju Aby Paul 《Research on Chemical Intermediates》2014,40(8):2689-2701
The corrosion inhibition efficiency of 3-acetylpyridine-semicarbazide (3APSC) on carbon steel (CS) in 1.0 M HCl solution has been investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies. The results show that inhibition efficiency on metal increases with the inhibitor concentration. 3APSC exhibited marked inhibition towards carbon steel in HCl medium even at low concentrations. The adsorption of inhibitor on the surfaces of the corroding metal obeys the Langmiur isotherm and thermodynamic parameters (K ads, ?G ads 0 ) were calculated. Activation parameters of the corrosion process (E a, ?H* and ?S*) were also calculated from the corrosion rates. Polarization studies revealed that 3APSC act as a mixed-type inhibitor. Surface analysis of the metal specimens was performed by scanning electron microscopy. 相似文献
3.
This paper presents a new method for a rapid determination of the Avrami exponentn by nonisothermal thermoanalytic analysis (DSC and DTA, resp.). Contrary to conventional techniques this method can be used in the entire temperature range and therefore it is applicable to polymers crystallizing from the melt. The proposed technique is applied to injection moulded low density polyethylene (LDPE), injection moulded high density polyethylene (HDPE), unpigmented extruded polypropylene (PPunpigm.) and pigmented extruded polypropylene (PPpigm.). The resulting values for the Avrami exponentsn LDPE~2.9,n HDPE~1.3, \(n_{PP_{unpigm} }\) ~2.2 and \(n_{PP_{pigm} }\) ~ 2.1 derived by crystallization from the melt were compared with isothermal measurements and with results given by other authors. 相似文献
4.
R. J. Rosenberg A. -M. Forsbacka N. Gras 《Journal of Radioanalytical and Nuclear Chemistry》1991,152(1):117-126
The separation of metallic impurities from uranium by anion exchange with a Dowex 1×8 resin has been investigated. The following elements can be quantitatively separated from 400 mg uranium using a 1 cm diameter 15 or 30 cm long column. The elements Ag, Al, Ba, Ca, Cr, Cs, K, Mg, Mn, Na, Ni, Rb, REE, Sc, Th, Ti and Y can be separated by eluting the elements with conc. HCl. Uranium is retained by the resin. Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, REE and V can be separated by eluting with 0.01 N H2SO4. Uranium is retained by the resin. Cd and Zn can be separated by first eluting uranium with 0.5 N HCl and then eluting Cd and Zn with 1 N NH3. Hf, Zr and V can be separated by eluting with 5 N HCl but some uranium contamination is unavoidable. 相似文献
5.
Shu -Sing Chang 《Journal of Thermal Analysis and Calorimetry》1988,34(1):135-154
The heat of reaction and kinetics of curing of diglycidyl ether of bisphenol-A (DGEBA) type of epoxy resin with catalytic amounts of ethylmethylimidazole (EMI) have been studied by differential power-compensated calorimetry as a part of the program for the study of process monitoring for composite materials. The results were compared with those from 1∶1 and 1∶2 molar mixtures of DGEBA and EMI. A method of determination of heat of reaction from dynamic thermoanalytical instruments was given according to basic thermodynamic principles. The complicated mechanism, possibly involving initial ionic formation, has also been observed in other measurements, such as by time-domain dielectric spectroscopy. The behavior of commercially available DGEBA resin versus purified monomeric DGEBA were compared. The melting point of purified monomeric DGEBA crystals is 41.4 °C with a heat of fusion of 81 J/g. The melt of DGEBA is difficult to crystallize upon cooling. The glass transition of purified DGEBA monomer occurs around ?22 °C with aΔC p of 0.60 J/K/g. 相似文献
6.
Kaushik Sanyal Sangita Dhara S. Sanjay Kumar N. L. Misra P. K. Mollick P. T. Rao R. Venugopalan Rajesh V. Pai N. Kumar S. K. Mukerjee J. K. Chakravartty S. K. Aggarwal 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(3):1357-1361
A Total Reflection X-Ray Fluorescence (TXRF) methodology, employing burn-leach test, was developed to assess the quality of SiC layer in tristructural isotropic (TRISO) coated UO2 particles prepared in BARC. The coated particles were heated at 1,123 K for about 96 h to constant weight. The calcined particles, thus obtained, were then heated in suprapure concentrated nitric acid. The supernatant was analysed for trace elements by TXRF. No uranium was detected in this supernatant solution. The study demonstrates the good quality of SiC layer and applicability of TXRF for burn leach test of TRISO coated UO2 particles prepared. 相似文献
7.
Paramananda Jena N. Nallamuthu K. Hari Prasad M. Venkateswarlu N. Satyanarayana 《Journal of Sol-Gel Science and Technology》2014,72(3):480-489
Scheelite type BaMoO4 nanofibers were prepared by using acrylamide assisted sol–gel process and electrospinning technique. The prepared Scheelite BaMoO4 nanofibers were characterized by using TG/DTA, XRD, FTIR, FT-Raman and SEM–EDX techniques. Thermal behavior, crystalline phase and structure of the prepared BaMoO4 nanofibers samples were confirmed from the analysis of the obtained results of TG/DTA, XRD, FTIR and FT-Raman respectively. SEM micrographs along with EDX showed the formation of one dimensional (1D) nanofibers 100–350 nm diameters and existence of Ba, Mo and O elements in the BaMoO4 nanofibers sample. The electrical conductivity of BaMoO4 nanofibers as a function of temperature 200–400 °C under air was evaluated by analyzing the measured impedance data using the winfit software. The newly prepared Scheelite type BaMoO4 nanofibers showed electrical conductivity of 0.92 × 10?3 S/cm at 400 °C. 相似文献
8.
Tracer concentrations of Hf(IV) were extracted by 60% TBP solution in benzene from 5M HClO4, 5M HCl, 6M HNO3 and 8M H2SO4 solutions, and by 1·10?4 M TOPO solution in benzene from 2M HClO4 and 2M HCl solutions in the presence of a variety of organic solvents miscible with the aqueous phase. Whereas for TBP these solvents caused an increase of HF(IV) extraction, an opposite effect was observed for TOPO. The results were discussed from the point of view of various solute-solvent and solvent-solvent interactions. 相似文献
9.
R. I. Drašković R. Radosavljevič T. Tasovac 《Journal of Radioanalytical and Nuclear Chemistry》1975,28(1-2):231-248
Trace elements in some continental water systems in Yugoslavia have been investigated by IAA. The results of the determination of trace elements are presented in this paper on the basis of the theory of concentration parameters (Cx) for the components of the rivers (dissolved materials in water, suspended and bed materials, plankton, benthos, algae, crustacea and fishes) lakes, swamps and in the soils. The investigated water system were rivers Danube, Sava, Tisa and V. Morava, lakes of Skadar, Ohrid, Dorjan, Bor, the Melenci Swamp and the soils from different regions of the Danube basin. This paper presents a short survey of our investigation of some continental water system in Yugoslavia by IAA. 相似文献
10.
Equilibrium colloid stability measurements with nonionic surfactant (C12E8) stabilised polybutyl methacrylate (PBMA) latex dispersions indicate a sudden temperature induced destabilisation coinciding with the glass transition temperature,Tg, of the polymer. In control experiments with polystyrene latex particles of similar size, for whichTg was not approached, the flocculation temperature was significantly higher. The effect is interpreted in terms of a reduced adsorbed layer thickness aboveTg caused by mixing of part of the surfactant molecule with the polymer. This interpretation is supported by DSC, elastic modulus and mechanical damping measurements on films made from dispersions of the same latex containing commercial nonionic surfactants. These measurements indicate a shift inTg in the presence of surfactant consistent with partial penetration of the polymer surface by the surfactant. In addition, C12E8 adsorption measurements show increased adsorption (or absorption) onto PBMA aboveTg which is irreversible on both dilution and temperature reduction. 相似文献
11.
M. Lindinger St. Becker G. Bollen K. Dasgupta R. Jertz H. -J. Kluge L. Schweikhard M. Vogel K. Lützenkischen 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):441-443
Doublet mass measurements of the isobars28Si3 and12C7 are performed by use of a Penning trap mass spectrometer and the Fourier transform ion cyclotron resonance (FT-ICR). The carbon and silicon cluster ions are produced by laser ablation. Results of these preliminary measurements are presented. 相似文献
12.
Gomaa A. M. Ali Osama A. Fouad Salah A. Makhlouf Mashitah M. Yusoff Kwok Feng Chong 《Journal of Solid State Electrochemistry》2014,18(9):2505-2512
In this study, Co3O4/SiO2 nanocomposites have been successfully synthesized by citrate–gel method by utilizing SiO2 matrix for Co3O4 embedment. Spectroscopy analyses confirm the formation of high crystalline Co3O4 nanoparticles; meanwhile, microscopy findings reveal that the Co3O4 nanoparticles are embedded in SiO2 matrix. Electrochemical properties of the Co3O4/SiO2 nanocomposites were carried out using cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) in 5 M KOH electrolyte. The findings show that the charge storage of Co3O4/SiO2 nanocomposites is mainly due to the reversible redox reaction (pseudocapacitance). The highest specific capacitance of 1,143 F g ?1 could be achieved at a scan rate of 2.5 mV s?1 in the potential region between 0 and 0.6 V. Furthermore, high-capacitance retention (>92 %) after 900 continuous charge–discharge tests reveals the excellent stability of the nanocomposites. It is worth noting from the EIS measurements that the nanocomposites have low ESR value of 0.33 Ω. The results manifest that Co3O4/SiO2 nanocomposites are the promising electrode material for supercapacitor application. 相似文献
13.
The evaluation of a fully automated quantitative proton nuclear magnetic resonance spectroscopy (qNMR) processing program, including the determination of its processing uncertainty, and the calculations of the combined uncertainty of the qNMR result, is presented with details on the use of a trimmed purity average. Quantitative NMR spectra (1359) were collected over a 4-month period on various concentrations of pseudoephedrine HCl dissolved in D2O (0.0610 to 93.60 mg/mL) containing maleic acid (the internal standard) to yield signal-to-noise ratios ranging from 3 to 72,000 for analyte integral regions. The resulting 5436 purities exhibited a normal distribution about the best estimate of the true value. The median absolute deviation (MAD) statistical method was used to obtain a model of uncertainty relative to the signal-to-noise of the analyte’s integral peaks. The model was then tested using different concentrations of known purity chloroquine diphosphate. qNMR results of numerous illicit heroin HCl samples were compared to those obtained by capillary electrophoresis. Graphical Abstract
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14.
A. S. Platchinda M. Ranogajec-Komor A. Vértes 《Journal of Radioanalytical and Nuclear Chemistry》1972,10(1):89-94
The Mössbauer spectra of quenched aqueous iron(III) salt solutions containing HClO4, H2SO4, HCl, respectively, were measured. The magnetic hyperfine structure of the spectra was studied as a function of the change of acid and iron concentrations. In the solutions of FeCl3 containing 8.5N HCl we suppose the presence of octahedral [FeCl4(H2O)2]? complex. 相似文献
15.
The silica nanoparticles were prepared by the sol–gel process, and then twice modified and grafted by polyethylenimine (PEI) on their surface. After quaternary ammonium reaction and chelated copper reaction, the PEI/SiO2, QPEI/SiO2, PEI–QPEI/SiO2 and Cu (II)/PEI–QPEI/SiO2 nanopowders were obtained in turn. The morphology and structure of the products were characterized through SEM, EDX, HRTEM, FTIR and element analysis. At the same time, the antibacterial activity of the products to E. coli and Candida were evaluated through quantification and qualitative ways, e.g. microcalorimetric method and culture dish method. The results suggested that the Cu (II)/PEI–QPEI/SiO2, a novel three-component functional nanopowder, presented the best antibacterial activity to both E. coli and Candida duo to the synergistic sterilization capability of the ammonium salt and copper ions, compared with other products. It indicated that the Cu (II)/PEI–QPEI/SiO2 nanopowder could be a novel antibacterial nanomaterial to widely application in preventing and minimizing bacteria of the organism and environment in future. 相似文献
16.
S. Reusch H. Genz W. Löw A. Richter 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1986,3(4):379-389
We have developed a method to determineL-subshell ionization cross sections and report here on the first measurements of electron inducedL-subshell cross sections for target elements (29≦Z≦79) at electron bombarding energies between 50≦E 0≦200 keV. The method involves the detection of characteristic X rays by means of a high resolution flat crystal spectrometer of known reflectivity and is based on the correlation of measured X ray intensities, Auger- and Coster-Kronig yields and radiative transition probabilities with theL-subshell cross section. 相似文献
17.
The mechanism and kinetics of electrochemical formation of anodic oxide films on iron-triad metal monosilicides in the 0.5 M H2SO4 solution in the potential range of 0.5 to 1.5 V (NHE) were studied by the methods of polarization and impedance measurements. It was concluded that the oxide films on the surface of studied silicides consisted predominantly of SiO2 and exhibited high barrier properties. The oxide film thickness and specific resistance in relation to the electrode potential were calculated from the impedance data. The constants of oxide film growth were determined. 相似文献
18.
Moamen S. Refat Mohamed I. Kobeasy Manal A. EL-Shazly 《Russian Journal of General Chemistry》2014,84(7):1411-1416
Selenium(IV) complex of vitamin B6 has been prepared using Se(IV) tetrachloride and characterized using spectroscopy (IR, UV-Vis, H NMR), molar conductance measurements, thermal analysis (DTA and TGA) and SEM imaging. Micro-analytical and spectral data show that the formed selenium(IV) complex is 1 : 2 (Se : vitamin B6) molar ratio. Vitamin B6 and its selenium complex were screened for in vitro antioxidant activity. The complex exhibited stronger antioxidant activity in 2.2-diphenyl-1-picrylhydrazyl (DPPH) radical assay compared to the free vitamin B6 ligand. 相似文献
19.
S. Järnström J. Dahlbacka P. Pakarinen V. Näntö M. Grönroos 《Journal of Radioanalytical and Nuclear Chemistry》1983,79(2):207-213
The authors present an application of the PIXE (Particle Induced X-ray Emission) method: determination of trace element concentrations in uterine tissue after wet digestion by HNO3. A method for calibration of the system is described. Results of the analysis of a NBS reference material (National Bureau of Standards), SRM 1577 bovine liver, are given and possible sources of error are discussed. In the authors’ experience, the combination of wet digestion and PIXE provides a tool for reliable analysis of trace element concentrations in tissues. 相似文献
20.
Data on water activity in solutions of a series of 3 : 1 and 1 : 3 electrolytes [AlCl3, Al(NO3)3, LaCl3, La(NO3)3, H3PO4, NaH2PO4] have been generalized in the frame of solvation excesses concept. Solvation excess reflects the distribution of the selected structural elements (ions or solvent particles) in the solution. The computed values have demonstrated the opposite contributions of ion association and hydration of ions and ion associates. Solvation excess concept allows determination of water molecules fraction constituting the excess at ions and their associates. The comparison of results obtained with different choice of model structural units has shown the electrolyte concentration ranges of validity of the respective models. 相似文献