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1.
Juliu Voicu 《Colloid and polymer science》1934,67(2):148-154
Zusammenfassung Die an den in einer vorangehenden Abhandlung aufgestellten Gleichungen der wiederholten Auszüge xp=(x0
p- K) (1−r)pq+K (A) oder xp=Ax(1−r)pq+K (a)θ
p=θ
0
p
−K
θ
)(1−r)pq+K
θ
(B) oderθ
p=A
θ
(1−r)pq+K
θ
(b) angestellten überlegungen betrafen unter anderem die Bestimmung der Parameter Ax, A
θ
, K und K
θ
durch graphische Darstellung. Es wurde auch der auf die Werte von K und K
θ
ausgeübte Einflu?, der durch ?nderung von m, der Menge des Adsorbenten, und von V, des Volumens der L?sung, infolge einer
?nderung in der quantitativen Zusammensetzung des Systems entstand, er?rtert.
Es wurde auf die Verkleinerung von K und K
θ
, die nach einer gewissen Zahl von Auszügen infolge einer zu starken Verdünnung der L?sung des Systems eintreten mu?, aufmerksam
gemacht. Diese Verkleinerung erkl?rt sich aus der Anwesenheit des Koeffizienten a und des Exponenten n der Adsorptionsisotherme
in den Gleichungen
; denn die beiden Werte von α und n sind nur für einen beschr?nkten Konzentrationsbereich praktisch konstant.
Es wurde auch gefunden, da? die Werte vonθ, der Substanzmenge in L?sung, oder von x, der Konzentration in 1 ccm, die nach einem Auszug einer beliebigen Ordnung bestimmt
wurden, den Gleichungen (b) und (a) für die Werte p′ von p, die andere sind als der zum untersuchten System geh?rende Wert,
genügen unter der Bedingung, für K, K
θ
, Ax und A
θ
angemessene Werte zu finden. Die oben erw?hnte Schlu?folgerung gilt auch für p=1. Man erh?lt die beiden Gleichungen x=A′(1−r)q+ K′ (E)θ=A (1−r)q+K′θ, (F) die x undθ, die einer Auszugsordnung q entsprechen, direkt ergeben. Die Parameter A′, A, K′ und K′θ k?nnen graphisch ermittelt werden.
Multipliziert man die Gleichung (F) mit r, dem bei dem Auszug entnommenen Volumteil, so erh?lt man die dem System durch einen
Auszug entzogene Substanzmenge aq: aq=rA(1−r)q−1+ c, (G) wo c=rK′θ.
Am Schlu? der Abhandlung wird auf bestimmte Vorteile der Gleichungen (F) und (G) aufmerksam gemacht.
I. Teil: Kolloid-Z.66, 322 (1934).
übersetzt von E. Lottermoser (Leipzig). 相似文献
2.
D. Berger C. Matei F. Papa G. Voicu V. Fruth 《Progress in Solid State Chemistry》2007,35(2-4):183-191
We report the synthesis of La1−xSrxCoO3 nanopowders by solution combustion method using metal nitrates and -alanine (alanine method) or urea (urea method) as fuel. The influence of metal nitrates/organic substance molar ratio and the type of fuel was investigated. The isolated complex precursors were characterized by atomic absorption spectroscopy (AAS), FT-IR spectra and DTA–TG analysis. The La1−xSrxCoO3 (x = 0–0.3) powders were characterized by X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray analysis (SEM–EDX), as well as by specific surface area measurements. XRD patterns indicate the formation of single-phase LaCoO3 (rhombohedral) when as-synthesized powders were calcined at 873 K, 3 h in the case of the alanine method and at 1073 K, 3 h for urea-based system. Also, strontium doped lanthanum cobaltites obtained by both methods at 1273 K are single phase with rhombohedral perovskite-like structure as XRD data have proved. SEM investigation of pure and doped lanthanum cobaltites reveal that the samples prepared by both methods have fine particles with tendency of agglomerates formation with different shapes, spongy aspect and high porosity. La1−xSrxCoO3 nanopowders obtained by alanine method have larger specific surface area values than those prepared by urea method. 相似文献
3.
L. C. Nistor S. V. Nistor V. Teodorescu I. Voicu 《Crystal Research and Technology》1979,14(12):1525-1528
Single crystals of CaF2 doped with ThO2 were grown by the Czochralski-Kyropoulos technique in graphite crucibles. The distribution of thorium in the as grown crystals has been investigated by optical and transmission electron microscopy, selected area diffraction and optical spectroscopy. 相似文献
4.
L. Gavrila FlorescuE. Vasile I. SanduI. Soare C. FleacaR. Ianchis C. LuculescuE. Dutu R. BirjegaI. Morjan I. Voicu 《Applied Surface Science》2011,257(12):5270-5273
The work presents preliminary studies with the goal to extend the share of long graphene ribbons in laser-synthesized carbon black. Investigations revealed the existence, as a major constituent, of graphene ribbons composed of up to 10-15 graphene layers, spaced at ∼0.35-0.37 nm and of tens of nanometres in length. The samples used to study the development of this specific structure were obtained from sensitized acetylene-based mixtures and the experiments were performed following the variation of both the experimental parameters and gas composition. 相似文献
5.
Popescu C. Voicu I. Alexandrescu R. Morjan I. Dumitras D. Popescu M. Fatu D. 《Journal of Thermal Analysis and Calorimetry》1999,56(1):183-189
This paper reports on the synthesis of various iron oxides by the IR laser processing of different iron salts. X-ray diffraction
techniques were used to characterize the reaction products. Some differences in terms of crystallite size and isotropy between
these oxides and those obtained from the same salt by thermal means are described and explained.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Dolocan VO 《J Phys Condens Matter》2011,23(44):446005
The spin-wave modes of cylindrical nanowires of moderate diameter-to-length ratios are investigated in this paper. Based on three-dimensional simulations and analytical calculations we determine the spatial structures of the modes. We show that standing spin waves and localized edge modes form the discrete spectrum of the nanowires. Using a simple analytical model we infer an extended dispersion relation for spin waves in cylinders. Considering the variation of the demagnetizing (internal) field we show that the localized dipole-exchange modes at the edges are always present. 相似文献
7.
Thierry Mar Nicolas Galanis Ionut Voicu Jacques Miriel Ousmane Sow 《Experimental Thermal and Fluid Science》2008,32(5):1096-1104
Velocity vectors in a vertical coaxial double-duct heat exchanger for parallel ascending flow of water under conditions of laminar mixed convection have been determined experimentally using the particle image velocimetry technique. The measured velocity distributions for large annular flow rates, resulting in an essentially isothermal environment for the stream in the inner tube, are in very good agreement with corresponding numerical predictions. For flow rates of the same order of magnitude in the inner tube and the annulus, and corresponding temperature differences of about 20 °C, experimental observations show that flow reversal occurs simultaneously in both streams over large axial distances for both heating and cooling of the flow in the inner tube. 相似文献
8.
Mihai Cosmin Corobea Oana Muhulet Florin Miculescu Iulian Vaile Antoniac Zina Vuluga Dorel Florea Dumitru Mircea Vuluga Maria Butnaru Daniela Ivanov Stefan Ioan Voicu Vijay Kumar Thakur 《先进技术聚合物》2016,27(12):1586-1595
In this study, a new class of heterogeneous membranes based on cellulose acetate (CA) polymer and a complex filler clay‐silica nanowires (SiO2NWs) was investigated for potential biomedical applications. SiO2NWs were synthesized using natural clay through a facile sol–gel method and were dispersed in the polymer solution by sonication in the 1.25, 2.5, and 5% weight ratio to the CA acetate polymer. Membranes were subsequently prepared via phase inversion by precipitation of the CA polymer in water. The pristine CA membrane and SiO2NWs based nanocomposites membranes were characterized using different characterization techniques. The presence of the SiO2NWs in the CA membrane was found to significantly enhance the protein retention, water wettability and thermal as well as mechanical properties in comparison to the pristine CA membrane. Water flows studies at different temperatures and the retention of bovine serum albumin have been studied and the nanocomposite membranes were found to exhibit superior performances compared with the pristine CA membranes. SiO2NWs‐CA membranes showed a much higher stability to the water temperature change during separation than CA membranes. Morphological changes clearly revealed that the composite membrane were much more compact than the pristine CA membranes. The rabbit dermal fibroblasts cell viability in cultures after 72 hr of incubation was found to be greater than 80%. These newly synthesized composite membranes exhibit a high potential to be used for various medical applications because of their non‐cytotoxic characteristics. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
9.
I. Morjan I. Soare R. Alexandrescu R.-E. Morjan L. Gavrila-Florescu G. Prodan I. Sandu E. Popovici F. Dumitrache I. Voicu M. Scarisoreanu 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):26
We report about the synthesis of carbon nanotubes by catalytic LCVD (C-LCVD), using a CW CO2 laser and alternatively, C2H2/C2H4/NH3 and C2H2/C2H4-containing gas mixtures. Different core–shell Fe–C nanocomposites (as synthesized and toluene extracted) were used employed as catalysts. The nanotubes grown from Fe–C residue demonstrate the lowest mean diameters. Prevalent curled and coiled morphologies are obtained for the CNTs grown in the presence of ammonia. 相似文献
10.
Hydration and hardening processes of Portland cements obtained from clinkers mineralized with fluoride and oxides 总被引:1,自引:0,他引:1
Alina Bădănoiu Jenica Paceagiu Georgeta Voicu 《Journal of Thermal Analysis and Calorimetry》2011,103(3):879-888
The hydration and hardening processes of Portland cements prepared from clinkers mineralized with sodium fluoride and/or oxides
(SnO2 or CuO) was studied. Type I cements (CEM I) were prepared by grinding with gypsum (5%) of clinkers obtained by the burning
of an industrial raw mix with different mineralizers: sodium fluoride, oxides (CuO and SnO2) or mixtures of sodium fluoride and oxide (NaF + CuO or NaF + SnO2). The influence of foreign ions on the clinker morphology was assessed by scanning electronic microscopy (SEM) and energy
dispersive X-ray spectrometry (EDX). The hydration processes of modified cements were examined by X-ray diffraction analysis
(XRD) and thermal analysis techniques (TG and DTA). The main properties of the cements, i.e., flexural and compressive strengths,
setting time, and soundness were also determined. A good correlation between the chemically bound water or portlandite content
in pastes hydrated 2–28 days and compressive strength developed by mortars was observed. The influence of mineralizers on
the kinetic of hydration processes and main properties of cements is different—0.5% NaF and 0.5% SnO2 and their mixture increase the rate of cement hydration and hardening processes, opposite to 0.5% CuO that reduce the rate. 相似文献