Jinhe Sun

Equilibrium models and kinetic for the adsorption of methylene blue on Co-hectorites.

The adsorption of methylene blue (MB) onto the surface of cobalt doping hectorite (Co-hectorite) was systematically studied. The physical properties of Co-hectorites were investigated, where characterizations were carried out by X-ray diffraction (XRD) and Electron Diffraction Spectrum (EDS) techniques, and morphology was examined by nitrogen adsorption. The sample with a Co content 5% (m/m) had a higher specific surface area than other Co-hectorites. The pore diameters were distributed between 2.5 and 5.0 nm. The adsorption results revealed that Co-hectorite surfaces possessed effective interactions with MB and bases, and greatest adsorption capacity achieved with Co content 5%, where the best-fit isotherm model was the Langmuir adsorption model. Kinetic studies were fitted to the pseudo-second-order kinetic model. The intraparticle diffusion was not the rate-limiting step for the whole reaction.

Diverting the phase transition behaviour of adipic acid via mesoporous silica confinement

Manipulating the phase transition behaviour of phase change materials (PCMs) to a favorable range is an urgent issue which poses a considerable challenge to their widespread application, since PCMs with desirable operational temperatures and high efficiency are very few in practice. An attempt to address this puzzle is presented by confining adipic acid in silica scaffolds through an impregnation method. Three different nanoscale chambers – 2D-hexagonal silicas MCM-41 and SBA-15, and 3D-silica mesoporous foam (MCF) – were employed. In this way, novel form-stable PCMs were developed, which acquired size-dependent thermal behaviour. The evolution of thermal behaviour as a function of pore size was investigated. Phase transition temperature (Tm) deviations presented a strong linear relationship with inverse pore sizes, conforming to the modified Gibbs–Thomson equation. Enthalpy changes (ΔHm) shared the same trend with Tm, as pore sizes decreased, while the variation of phase transition temperatures (ΔTm) was in the opposite direction. Unlike the bulk state, the phase transition temperature of adipic acid in a confined space could be regulated over 90 °C. The maximum thermal storage efficiency was 72% with respect to the confined acid content. Thus, the solid–liquid phase transition behaviour of adipic acid in a confined space could be altered, and the manipulation of thermal behaviour was achieved.

Preparation and luminescence properties of lanthanide (Eu3+, Sm3+) complexes and their hectorite-based composites

The complexes of europium and samarium with phthalates ligands were synthesized and characterized. The luminescence behaviors of the lanthanide complexes as well as their hectorite-based composites were investigated by fluorescence spectra. The results indicated that the lanthanide complexes showed slightly lower intensities in hectorite matrix than that of corresponding pure complexes. The lanthanide ion relative fluorescence intensity (LRFI) was enhanced when the lanthanide complexes were doped into hectorite.

One-step template-free solution route for Cu(OH) 2 nanowires

Cu(OH)2 nanowires with a diameter of 8–10 nm and lengths of tens of micrometers were fabricated in the basic solution by dropping simply NaOH solution into CuCl2 solution at ambient temperature. The formation mechanism of nanowires was discussed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the samples.

Preparation and characterization of the shape-stabilized phase change material based on sebacic acid and mesoporous MCM-41

Shape-stabilized composite phase change materials composed of sebacic acid (SA) and MCM-41 were prepared by a facile blending and impregnating method. Various characterization techniques were carried out to characterize their structural and thermal properties, including thermogravimetry (TG) analyses and differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy. The XRD and FT-IR results indicated the interactions between SA and MCM-41, such as the capillary force and the hydrogen bonding, resulting in the confined crystallization process. As a result, the SA that was confined was amorphous. The TG analysis results showed that the presence of MCM-41 practically resulted in an overlapping of the two decomposition stages. The DSC analysis demonstrated that a decrease in the SA content was accompanied by a continuous decrease in the melting point and phase change enthalpy of the composites.

Preparation and thermal characterization of oxalic acid dihydrate/bentonite composite as shape-stabilized phase change materials for thermal energy storage

Oxalic acid dihydrate (OAD) which has very high initial phase transition enthalpy is a promising phase change material (PCM). In this paper, shape-stabilized composite PCMs composed of OAD and bentonite were prepared by a facile blending method to overcome the problem of leakage. FT-IR results indicated the interactions between OAD and bentonite, such as the capillary force and the hydrogen bonding, resulting in the confined crystallization process. As a result, the OAD was confined to be amorphous. The thermogravimetric analysis and scanning electron microscope results showed that sample had the best coating effect when the amount of bentonite was 17.7%. The differential scanning calorimetry analyses demonstrated that a decrease in the OAD content was accompanied by a continuous decrease in the melting point and phase change enthalpy of the composites.

Phase Formation and Microstructure of BaTiO3 Ceramics Prepared by Direct Current Arc Discharge Process

BaTiO3 (BT) ceramics are prepared above 2000°C by direct current arc discharge plasma process in argon atmosphere. The results show the formation of the perovskite structure. However, the coexisting of tetragonal phase and hexagonal phase is found in the structure. It is also found that a small amount of BaTi4O9 compound appears. With the sintering temperature increasing, the structure becomes more homogeneous because of interdiffusion of constituent ions and phase transition. The hexagonal phase gradually disappears and BaTi4O9 compound could also be traced.

Fabrication of multilayer pancakelike basic magnesium carbonate.

The properties of nanomaterials was strongly affected by their microstructures. Here Mg5(CO3)4(OH)2 x 4H2O multilayer pancakelike structures were fabricated successfully by reaction of MgCl2 and Na2CO3 in aqueous solution at 363 K. The growth process of nanostructures was observed by XRD and SEM. Several transition states of multilayer pancakelike basic magnesium carbonates were observed, which help to understand better the formation process of this hierarchical nanostructures. The formation mechanism of Mg5(CO3)4(OH)2 x 4H2O multilayer pancakelike structures was discussed and helical growth was proposed. The amorphous nanoparticles were formed firstly. Then nanopartilces aggregated and oriented assembly under the direction of chemical bonds with the help of water molecules. The multilayer pancakelike basic magnesium carbonates was formed by helical growth of wafers along (100) and (001) direction. The diameter and volume decreased with the increasing concentration of reactants.