Shaolei Xie

Investigations of BaxSr1−xTiO3 ceramics and powders prepared by direct current arc discharge technique

BaxSr1−xTiO3 ceramics with x ranging from 0 to 1 were prepared by direct current arc discharge technique and studied by means of x-ray diffraction (XRD) and Raman spectroscopy. The cubic-tetragonal ferroelectric phase transition in BaxSr1−xTiO3 ceramics was found to occur at x ≈ 0.75. XRD investigation of as-grown BaTiO3 ceramics revealed co-existence of tetragonal and hexagonal modifications with a small amount of impurity phase BaTi4O9. No evidences of hexagonal phase were observed in Raman spectra of as-grown BaTiO3 ceramics, while Raman peaks related to hexagonal phase were clearly observed in the spectrum of fine-grain powders prepared from the same ceramics. A core-shell model for BaTiO3 ceramics prepared by direct current arc discharge technique is proposed. Absence of the hexagonal phase in any BaxSr1−xTiO3 solid solution with x < 1 is discussed in the frame of specific atomic arrangement.

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 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.

The Solid‐liquid Transformation of Low‐grade Solid Potash Deposit in Dalangtan Basin and the Simplification of the Liquid Phase System

We studied the solid-liquid transformation of low-grade solid potash deposit in Dalangtan Basin and simplified the liquid phase system.We did experiments to optimize conditions of the solid-liquid transformation.The Suitable

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 PbTiO3 and CaTiO3 ceramics prepared by a direct current arc discharge technique

ABSTRACT PbTiO3 and CaTiO3 ceramics are prepared at temperatures above 2000°C by a direct current arc discharge technique under an argon atmosphere, and the microstructure, components and morphology of each material are investigated. Both samples show the formation of a perovskite structure. Moreover, a tetragonal phase is found in the PbTiO3 ceramic material, and a cubical phase is formed in the CaTiO3 ceramic material. In this work, PbTiO3 and CaTiO3 ceramics were rapidly prepared using a simple DC arc discharge technique; we found this technique of ceramic material synthesis was much faster and better than conventional methods. The whole reaction process only takes 30 seconds because of ultrafast kinetics of crystallization.

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.

Research on the Evaporating Crystalization Behavior of the Magnesium Sulfate Subtypes Brine at High Temperature

Research the evaporating crystalization process of the magnesium sulfate subtypes brine at high temperature from Dalangtan salt lake in Qinghai province.It was revealed that the salt lake is a typical subtype magnesium