Zhaodong Nan

Structure transition from aragonite to vaterite and calcite by the assistance of SDBS.

Structure transition from aragonite to vaterite and calcite with the help of anionic surfactant sodium dodecyl benzene sulfonate (SDBS) was investigated, respectively, by a hydrothermal method. When the experimental temperature was controlled at 90 degrees C, aragonite of crystal calcium carbonate was transformed into vaterite with the assistance of SDBS. Pure vaterite was obtained as the concentration of SDBS reaches to 2.5 mM. When the experimental temperature was controlled at 120 and 150 degrees C, respectively, aragonite was transformed into calcite, and pure calcite was obtained as the concentrations of SDBS were equal to 1.0 and 2.5 mM, respectively. Possible formation mechanism of different CaCO(3) polymorphs was proposed based on the obtained experimental results.

Controlling the polymorph and morphology of CaCO3 crystals using surfactant mixtures.

Inspired by mineralization in biological organisms, fabrication of higher ordered CaCO(3) crystals modified by surfactants has received much attention. In our present work, mixed surfactants of hexadecyl(trimethyl)azanium bromide and sodium dodecyl sulfate were used to mediate the nucleation and growth of CaCO(3) crystals. When the concentration of sodium dodecyl sulfate in the solution is constant (0.1 mM), the polymorph of CaCO(3) crystals changed from pure vaterite to pure aragonite with increase of the ratio of hexadecyl(trimethyl)azanium bromide to sodium dodecyl sulfate. Various morphologies of vaterite and aragonite were obtained. Based on the time-resolved experiments, we suggest that the flower-like CaCO(3) formed via aggregation of hexagon-like vaterite induced by the surfactants. More importantly, we realized that a cluster-shaped morphology of aragonite was produced through the nucleation of aragonite at the surfaces of the hexagon-like vaterite.

Magnetic and Thermodynamic Properties of Nanosized Zn Ferrite with Normal Spinal Structure Synthesized Using a Facile Method

Normal spinel zinc ferrite (ZnFe2O4) nanoparticles (NPs) with zero net magnetization were synthesized by a facile coprecipitation method in which two kinds of organic alkali, namely, 1-amino-2-propanol (MIPA) and bis(2-hydroxypropyl)-amine (DIPA), were used. The diameters of the ZnFe2O4 NPs were determined to be about 7 and 9 nm for samples prepared with MIPA and DIPA, respectively, and the normal spinel structure was confirmed by the magnetic property measurement at room temperature and the temperature dependence of the direct current magnetization. These results are different from those reported in the literature, where ZnFe2O4 NPs show a nonzero net magnetization. The heat capacity of the ZnFe2O4 NPs synthesized using DIPA was measured using a physical property measurement system in the temperature range from 2 to 300 K, and the thermodynamic functions were calculated based on the curve fitting of the experimental heat capacity data. The heat capacity of the ZnFe2O4 NPs was compared with that of a nanosized (Zn(0.795)Fe(0.205))[Zn(0.205)Fe(1.795)]O4 material studied in the literature, indicating that the Debye temperature of the present sample is more comparable with that of the bulk ZnFe2O4 reported by Westrum et al.

Synthesis of Ce3+ doped ZnFe2O4 self- assembled clusters and adsorption of chromium(VI)

A solvothermal synthetic route was used to prepare Ce(3+) doped Zn ferrites, where sphere-like clusters aggregated by nanosized particles were fabricated. The size of the cluster and the saturation magnetization of the sample are decreasing with the increase of Ce(3+). These samples can be easily separated from aqueous solutions by applying a magnetic field and have a high loading capacity of Cr(VI). The Cr(VI) adsorption experiments indicated that the adsorption was divided into two processes, in which the first one took place about 6h, the second one took place between 6 and 96 h. The maximum adsorption capacity for Cr(VI) was determined to be 57.24 mg/g. Langmuir model was employed to fit the adsorption isotherm, which implied the single layer adsorption. The data of SBET, external area and porous area of the samples can be used to explain these adsorption processes. And the Ce(3+) ions doped in the sample induced the increasing adsorption capacity of Cr(VI). The adsorption process can be described by the pseudo-second-order kinetic model.

Preparation of stable magnetic nanofluids containing Fe3O4@PPy nanoparticles by a novel one-pot route

Stable magnetic nanofluids containing Fe3O4@Polypyrrole (PPy) nanoparticles (NPs) were prepared by using a facile and novel method, in which one-pot route was used. FeCl3·6H2O was applied as the iron source, and the oxidizing agent to produce PPy. Trisodium citrate (Na3cit) was used as the reducing reagent to form Fe3O4 NPs. The as-prepared nanofluid can keep long-term stability. The Fe3O4@PPy NPs can still keep dispersing well after the nanofluid has been standing for 1 month and no sedimentation is found. The polymerization reaction of the pyrrole monomers took place with Fe3+ ions as the initiator, in which these Fe3+ ions remained in the solution adsorbed on the surface of the Fe3O4 NPs. Thus, the core-shell NPs of Fe3O4@PPy were obtained. The particle size of the as-prepared Fe3O4@PPy can be easily controlled from 7 to 30 nm by the polymerization reaction of the pyrrole monomers. The steric stabilization and weight of the NPs affect the stability of the nanofluids. The as-prepared Fe3O4@PPy NPs exhibit superparamagnetic behavior.

Size-controlled synthesis of rod-like α-FeOOH nanostructure.

One-dimensional goethite (α-FeOOH) nanorods were successfully fabricated by a hydrothermal route without any template. Experimental results reveal that concentrations of Fe(3+) and ethylenediaminetetraacetic disodium salt (Na2EDTA) affect the phase composition and size of the as-synthesized products. The size of the rod-like α-FeOOH increased when the concentration of Na2EDTA was increased, where Na2EDTA acts as a nucleation inhibitor. α-Fe2O3 nanoparticles were produced when the concentration of Fe(3+) was increased from 0.02 to 0.08 and 0.40 M. A possible formation mechanism was proposed based on the results of the time dependent experiments. Different electrolytes and surfactants can affect the size and the aspect ratio of the as-prepared nanorod-like α-FeOOH. Na2SO4 induced the decreasing of the size of the as-prepared sample. KCl and PVP affected the aspect ratio of the nanorods.

The effects of environmental conditions on the growth of petroleum microbes by microcalorimetry

Abstract The growth and metabolism ability of two strains of petroleum microbe isolated from oil reservoirs was studied by calorimetry. Thermal power–time curves under various environmental conditions (including temperature, acidity, salinity and carbon source) were determined. Typical microbial growth thermal power–time curves were obtained. By fitting the curves mathematically with the ‘three-point method’ under an inhibitory condition, the growth rate constants and the optimum growth conditions (including temperature, acidity and salinity) of the microbes studied were obtained. Irregular thermal power–time curves were obtained when the petroleum microbe E grew in the media containing different carbon sources.

Calorimetric Curves of B–Z Oscillation Reaction Systems At Different Temperatures

In this paper studies on the oscillation regularity of the classical B–Z reaction system, and the calorimetric curves of the reaction system measured at three temperatures, 25, 27 and 29°C are described. A new way is presented for studying the regularity properties of chemical oscillation phenomena from the viewpoint of reaction heat effects.

Determination of power—time curves of bacterial growth and study of optimum allowable concentration of a synthetic medicine

The power-time curves ofS. flexneri 6,S. flexneri 3b,S. dysenteae andE. coli were determined by using the 2277 Thermal Activity Monitor (Sweden). From these curves, by using a microorganism growth experimental model with inhibitory conditions, the growth rate constant (μ) was determined at different medicinal concentrations, with the optimum allowable concentration of the synthetic medicine.ZusammenfassungMittels eines Thermal Activity Monitor 2277 (Schweden) wurden die Potenz-Zeit-Kurven vonS. flexneri 6, S. flexneri 3b, S. dysenteae undE. coli ermittelt. Anhand dieser Kurven wurde unter Anwendung eines experimentellen Modells für das Wachstum von Mikroorganismen unter Inhibitorbedingungen die Wachstumsgeschwindigkeitskonstante (μ) bei verschiedenen Arzneimittelkonzentrationen und in Ableitung davon die optimal erreichbare Konzentration des synthetischen Arzneimittels bestimmt.

Thermokinetic investigation of effects of carbon source on petroleum bacterial growth

Abstract The growth power–time curves of a strain of petroleum bacteria, B-2, in various kinds of cultures containing different kinds of carbon sources, glucose, n -tetradecane, n -hexadecane and n -octadecane, and different kinds of microemulsions have been determined by using a 2277 Thermal Activity Monitor. The curves showed a single peak for cultures containing a single carbon source, glucose, and two peaks for cultures containing two kinds of carbon sources, glucose and one of the n -alkanes. The first peak indicated that bacteria grew by consuming glucose and the second peak indicated that bacteria grew by consuming n -alkane. The curves were complex when the bacterium grows in a microemulsion culture. According to a kinetic equation of bacterial growth under limited conditions, the rate constants of bacterial growth were obtained. The results showed that the microemulsion culture was more appropriate to bacteria to grow on n -alkanes.