Advanced Materials Research Vols. 399-401

Abstract: In order to improve the acid resistance and reduce the apparent density of fracturing proppants, TiO₂ powder added in the system of BaO-MgO-Al₂O₃ fracturing proppants were prepared by the technique of pressureless sintering. The properties of the samples were investigated by the measurements of acid solubility, X-ray diffraction and scanning electron microscopy. The results show that the acid solubility of alumina matrix fracturing proppants contenting TiO₂ of the 4wt% and BaO/MgO with the ratio of 3:7 is 0.15%. It is an important development in acid resistance performance of fracturing proppants research on laboratory. TiO₂ is added to the raw materials and then calcine them to ceramics, which can reduces the sintering temperature, promote the densification and improve acid-resistant property of fracturing proppants.

Abstract: In this work, synthesis of the nanocrystalline Ce_0.8Nd_0.2O_1.9 Solid solution Powders by a nitrate-glycine gel-combustion process was investigated. The effects of glycine/metal ratio and calcination temperature on the powders phase structure, morphology and particle were investigated. TG-DSC curves and XRD peak of different glycine/metal ratio show that smaller particle size can be obtained with a slightly fuel-deficient ratio. XRD results indicate that the as-prepared powders are crystallinzed in a single fluorrite structure. The crystalline size ranges from 9 nm to 24 nm, which increases with the increase of calcination temperature. The SEM results imply some organic agent may be eliminated by high temperature calcination process.

Abstract: The glass-ceramics were made of arc-melting slag from incinerator fly ash mixed with glass cullet additive by sintering method. The effects of ball milling time and powder compaction pressure on the microstructure, physical and mechanical properties of the glass–ceramics were respectively investigated. Results showed that with milling time delaying, granularity of the parent glass evidently reduces, the major phases of glass–ceramics have no change but the diffraction peaks present intensive trend, the crystal sizes of glass–ceramics decrease, the properties such as volumetric densities, compressive strength, bending strength and toughness are improved, the appropriate milling time is 6h with fifty percent of the volume (d50 value) of 10.62μm. The physical and mechanical properties first increase and then decrease with compaction pressure increasing, and the optimal compaction pressure is 60MPa.

Abstract: Ag₂O-CaO-Fe₂O₃-SiO₂ glass-ceramic was prepared by the sol-gel method. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were used to investigate crystallization process of Ag₂O-CaO-Fe₂O₃-SiO₂ glass. The kinetic results show that the values of the activation energy and frequency factor of the glass are 441.991 KJ/ mol and 1.58×10²⁰, respectively. And the dimensionality of crystal growth, n, decreases as the heating rate increases. The crystalline phases of the glass-ceramic are magnetite, wollastonite and minor hematite. The saturation magnetization and coercive force of the heat-treated glass are 0.08 Wb/m² and 14 KA/m at room temperature. The glass-ceramic has some capacity of anti-microbial.

Abstract: Large area (13mm*13mm) PbS thin films with (200) preferred orientation were prepared by chemical deposition. The optical properties of PbS films with annealing treatment in various forming gases with different ratio of nitrogen-oxygen (100ml/min of N₂&O₂(3:1), 100ml/min of N₂&O₂(2:1), 100ml/min of N₂&O₂(1:1), 50ml/min of O₂) were deeply analyzed. X-ray diffraction (XRD), scanning electron microscope (SEM), high and low temperature test chamber and other test methods for photosensitivity were used to investigate the structure and photoelectric properties of PbS films. The results showed that with proper amount of oxidation (when nitrogen-oxygen ratio was 1:1), the impurity barrier tended to fully grow, impurity activation energy increased to 0.314eV, dark resistance reached up to 30.2MΩ, and the photoconductive sensitivity of PbS thin film under this process was about 4 times larger compared with air annealing. According to the analysis of XRD patterns and surface morphologies of films, it can be seen that nitrogen in this process was not only to prevent PbS thin films from excessive oxidation, but also inhibited the formation of surface defects and enhanced the stability of PbS device.

Abstract: In this paper the powders of Zn_1-xCo_xO (x=0, 0.01, 0.02, 0.025, 0.05, 0.1) were fabricated by the conventional solid state reaction. The crystal structure was characterized by x-ray diffraction (XRD). The electromagnetic parameters were measured using vector network analyzer (VNA), the infrared emissivity in the wavelength range of 3-5μm and 8-14μm was measured by Dual-band infrared emissivity measuring instrument. The absorption bandwidth of the double-layer microwave absorber is obviously more than that of the single-layer absorber. The bandwidth of the double-layer microwave absorber for reflection loss R<-8dB is 2.64GHz over the range of 8.2-18GHz. The thickness of the absorbers is only 4 mm. The infrared emissivity is only 0.39 in the range of 3-5μm and 0.81 in the range of 8-14μm.

Abstract: Two novel silica based terbium complexes (Tb(Bipy)3 and Tb(Tyr)₃) were encapsulated into poly(N-isopropylacrylamide) and two hydrogels with intense green emission were developed. The variation of intensity changes by Tb(III) 5D4 → 7F5 transition indicated the gradual reduction tendency upon the increasing temperature. The declined luminescence behaviors of the two gels undergo the linear decay process (5~30°C). During lower critical solution temperature (33°C) stage, the emission responses significantly improved unexpectedly. Moreover, the terbium emissive species-loaded hydrogels exhibited much enhanced mechanical properties than pure gel.

Abstract: The magnetization reversal mechanism of the magnetic films system with the different magnetic anisotropy, exchange coupling, interface coupling, etc. has been simulated by Monte-Carlo method. The results show that the decrease of magnetic anisotropy is in favor of motion of domain walls, but is not conducive to consistent rotation. The interface coupling of both the ferromagnetic film and the antiferromagnetic film are helpful to the motion of domain walls while the antiferromagnetic film coupling is the more effective. Meantime, the evolution of the microscopic magnetic domain structures has been inspected intuitively while the system is in the process of magnetization.

Abstract: Two new coordination polymers, [Zn(PyHBIm)₂(IPA)]•3H₂O (1), [Cd(PyHBIm)(IPA)(H₂O)₂]•2H₂O (2), were synthesized under hydrothermal conditions based on 2-(3-pyridyl)benzimidazole (3-PyHBIm) and isophthalic acid (IPA). The complexes were characterized by single crystal X-ray diffraction. They contain simple 1D chains and can be assembled into a 3D network through aromatic π–π stacking interactions and hydrogen bonding interactions. Their luminescent properties were studied in the solid state at room temperature.

Abstract: A novel photochromic diarylethene was synthesized and its photochromism, fluorescence properties have been investigated. It underwent reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light in hexane. The results showed that this compound exhibited reversible photochromism and good fluorescent switching in solution and in PMMA upon irradiation with UV light and visible light.