Papers by Keyword: Crystalline Phase

Abstract: It’s generally accepted that the transport of lithium ions in solid polymer electrolytes exists mainly in the amorphous regions, thus the research has focused on reducing the crystallinity to obtain high conductivity at room temperature. However, the point has been challenged: crystalline systems can provide a better ionic conductivity. In this paper, PEO/LiClO₄ polymer electrolytes with different lithium-oxygen ratios were prepared by melt-blending. The results show that [EO]/ [Li⁺] = 3 system has higher ionic conductivity, 4.26×10^-6 S/cm, more than twice as that of [EO]/ [Li⁺] = 4 system. DSC and XRD results show PEO₃:LiClO₄ crystalline phase present in both systems, the crystallinity of [EO]/ [Li⁺] = 3 system is higher. It illustrates the generally accepted mechanism is not suitable for these systems, suggesting the high conductivity of [EO]/ [Li⁺] = 3 system is due to the unique crystal structure of PEO₃:LiClO₄. Besides, as the crystallinity increases, the tensile strength of [EO]/ [Li⁺] = 3 system increases greatly, to 1.43 MPa. In addition, because of the high melt temperature of PEO₃:LiClO₄, the electrolytes will gain excellent heat resistance. In summary, this paper provides a new idea to prepare polymer electrolytes with high ionic conductivity, improved strength and excellent heat resistance in large scale.

Abstract: The crystallization activation energies and crystalline phases of lithium-iron-phosphate (LIP) glasses with alkali and alkali-earth metal oxides have been studied and compared. The results indicate that the alkali and alkali-earth metal oxides reduce the glass crystallization. Moreover, the alkali metal oxides result in the changes in the crystalline phase, while the alkali-earth metal oxides make the glass crystallization more sensitive to the thermal treatment conditions.

Abstract: Commercial poly (vinylidene fluoride) (PVDF) films are uniaxially stretched with varying rates at 110 °C in order to endow PVDF piezo-and pyroelectric by crystalline-phase transition from α to β during the stretching. The crystalline phases are determined by infrared spectroscopy. The β-phase content and its fraction in films increase as a result of stretching with high rates. In addition, higher stretching rates yield a slight increase of γ phase. The crystallite size is evaluated by means of X-ray diffraction. It is found that the β-phase crystallites become smaller with fast stretching, whereas the α-phase crystallites are cracked and disappear at high-speed stretching of 2.5 /min.

Abstract: The given study investigates the influence of pozzolanic admixtures both micro- and nanosize silica and biomass ashes on microstructure and properties of hydration process of cement paste. The investigations were carried out by - XRD, SEM and FTIR. Pozzolanic activity of the concrete admixtures strongly depends on their chemical composition, content of reactive silica as well as the specific surface area. The micro- and nanosilica pozzolanic additives demonstrated the higher values of pozzolanic activity. Those activate the process of mineralization and are acting both as the cementitious admixture as well as the fine filler.

Abstract: MgO-Al₂O₃-SiO₂ ceramics were recently explored as infrared radiance materials to provide an environmental friendly energy candidate for industrial heating and drying. Cu ferrite was selected to dope MgO-Al₂O₃-SiO₂ ceramics, forming a series of composite ceramics via solid-state reaction method to enhance the infrared radiation properties. The phase identification and morphologies of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The infrared emissivity was examined by Fourier transform infrared (FTIR) spectrometer. The results showed that an improvement of infrared radiation properties can be achieved by doping Cu ferrite in MgO-Al₂O₃-SiO₂ ceramics. With increasing the dopant content from 0 wt % to 10.0 wt %, the crystallization behavior changed accordingly. A positive correlation was found between the infrared emissivity and the lattice strain. The highest infrared emissivity (0.91±0.01) was obtained after sintering at 1150 °C for 2 h with Cu ferrite content was 7.5 wt %, in which the maximum lattice strain (0.282 %) occurred. MgO-Al₂O₃-SiO₂ ceramics doped with Cu ferrite have potential for the application of infrared heating and drying fields.

Abstract: Effects of TiO₂ on crystalline phase of mold fluxes were studied by the mineral phase microscope and the XRD. The results showed that on the experimental condition, the main crystalline phase of mold fluxes were cuspidine, wollastonite and melilite. When TiO₂ added into the mold fluxes, perovskite would be found. TiO₂ promoted Perovskite to crystallization and limited Cuspidine to growth. The morphologies and content of wollastonite and melilite were greatly affected by TiO₂ adding, especially, as 20% TiO₂ added into the mold fluxes.

Abstract: A series of gels with 3Al2O3•2SiO2 were prepared by Sol-gel method and heated at several temperatures for 2 h to synthesize Ti, Fe-doped mullite. The powers were characterized by differential thermal analysis (DSC-TG) and X-ray powder diffraction (XRD). Phase separation was promoted by doping both TiO2 and Fe2O3; with increasing the amount of dopant ions the formation temperature of Si-Al spinel decreased and the formation temperature of mullite increased by TiO2 doping but decreased by Fe2O3 doping. The formation temperature of pure mullite was about 1250-1350 °C.

Abstract: The crystalline phase and morphology of the products formed during the synthesis of yttrium oxide via the hydrothermal treatment yttrium nitrate were characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. Products with high OH/NO₃ ratios are formed with the increasing of hydrothermal treatment. The crystalline phases are evolved from Y₂(OH)_5.14(NO₃)_0.86•H₂O toY₄O(OH)₉(NO₃) and finally Y(OH)₃. The hydrothermal reaction conditions play an important role in the synthesis of the microstructures. Results show the particle size and final morphology of samples could be controlled by reaction temperature, reaction time, and OH^- concentration. Sheets, hexagonal and needle-like Y₂O₃ powders are obtained with the hydrothermal treatment of yittrium nitrate at 180 oC to 200oC for 2-8 hours at pH 9-13.

Abstract: Fe-based amorphous alloy coating with a composition of Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ was prepared by high velocity fuel(HVOF) technique. The influence of heat treatment on crystalline behavior, the phase structure and corroded morphology of the coating was investigated by Differential Thermal Analysis(DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy(SEM), respectively. The experimental results indicate that the amorphous alloy coating exhibited a two-step crystallization process with crystallization peak temperature at 698°C and 822°C, respectively. Amorphous coating exhibits excellent corrosion resistance than that of the corresponding nano-crystalline coating with heat treatment at 700°C for 2h, 8h and 12h. Furthermore, the nano-crystalline coating annealed 700°C for 12h suffers slight homogeneity corrosion, which did not exhibit obvious pitting on comparison with coating holding 2h and 8h.

Abstract: Glass-coated Cu-Mn-Ga microwires were fabricated by Taylor-Ulitovsky technique. By means of energy dispersive spectroscopy microanalysis, an average alloy composition of Cu56Ga28Mn16 was determined. The temperature dependence of magnetization measured at a low magnetic field showed the coexistence of two ferromagnetic phases. The Curie temperature of one phase is 125 K and above room temperature for the other one. X-ray diffraction at room temperature and at 100 K reflects the presence of the same three crystalline phases corresponding to the cubic B2 Cu-Mn-Ga structure as a main phase and the minor phases of fcc Cu rich solid solution with Mn and Ga and the monoclinic CuO.