Advanced Materials Research Vols. 347-353

Abstract: The synthesis of α-nickel hydroxide has been achieved via a facile liquid-phase precipitation approach, using the mixed solvents of ethylene glycol and water as reaction medium at low temperature. The XRD characterization indicates that pure phase α-Ni(OH)₂ can be obtained under variable temperature and pH value. The products present a flower-like micro-/nano-structure assembled with curved nanosheets. The nanosheets have the width of 100~500 nm and the thickness of 20~70 nm. The cavities are formed in the structure due to the interconnection of curved nanosheets. The solvents play a key role in the formation of Ni(OH)₂ with different forms. Pure phase α-Ni(OH)₂ can only be synthesized in the mixed solvents of ethylene glycol and water. Cyclic voltammetry was applied to test the electrochemical activity of the as-synthesized α-Ni(OH)₂. The findings suggest that the α-Ni(OH)₂ with a micro-/nano-structure exhibits excellent electrochemical activity, which may be considered as a promising candidate of electrode material.

Abstract: Methane hydrate is ice-like clathrate compound that attracts global attention due to its huge potential as a future energy source. The constitutive law of methane hydrate-bearing sediments remains unknown and becomes a barrier in sustainable exploitation of methane hydrate from marine sediments. The Duncan-Change model is a nonlinear elastic model which was widely accepted by the geotechnical community in approximating the constitutive response of geo-materials. This model and its evolved versions were employed in this study to model the stress-strain response observed in triaxial tests on methane hydrate-bearing sands. Duncan-Chang type models capture well the strain hardening behaviors. However, they fall short of incorporating the dependency of temperature and saturation degree of methane hydrate, which have to be taken into account in future constitutive models of methane hydrate-bearing deposits.

Abstract: In the present work, ZnO nanostructures with tunable size were successfully synthesized on non-seeded Cu substrates by a simple electrodeposition method. The effects of growth conditions on the morphology of the products were studied in detail by scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-prepared products exhibited flake-like morphology when the concentration of ZnCl2 was higher enough, while the products showed flower-like morphology when the concentration was lower enough. Field emission investigation indicated that the nanoflowers exhibited good emission properties. The ZnO nanoflowers show potential application as field emitters.

Abstract: Novel diphoshinoamine(PNRNP) ligands have been used in ethylene oligomerization with Cr(III) compounds and cocatalyst. The results indicate that the catalyst system can yield 1-octene in selectivities up to 80%. Another novel diphoshinoamine ligands (((Ar₂P)₂N)₂R)(R=cyclopropylamine) also were synthesized and characterized. Factors which affect the result of ethylene tetramerisation, such as cocatalyst, temperature, pressure and the molar ratio of Al/Cr were examined. Steric effects and electric effects were also considered in this report.

Abstract: At present, for the most part of new construction Coal-fired units desulfurization system has canceled the GGH system in our country, using the wet chimney emissions, but when the Power plant operationed it always apper the phenomenon of “gypsum rain”. In this paper, using the method of extraction part of hot secondary air to heating clean flue gas, and use fluent for three-dimensional numerical simulation with pipeline has been transformed and before it hasn’t transformed, using the κ-ε model and SIMPLE algorithm for calculating. Through the comparison of simulation results and test results, the results indicated that using the methods of hot secondary air to heating clean flue gas to reduce gesso rain is feasible and reasonable.

Abstract: In this paper, we demonstrated the synthesis and electrochemical properties of carbon foams for use as supercapacitor electrode materials. Carbon foams were prepared by double templating method in which emulsion and nanosilica were used as soft template and hard template, respectively. By using Span 80 and Tween 80 as emulsifiers, resorcinol/formaldehyde aqueous solution which contained nanosilica as aqueous phase and 1iquid paraffin as oil phase, an O/W emulsion was obtained. Carbon foams were obtained by emulsion polymerization, carbonization and the subsequent removal of the hard template. The as-prepared carbon foams were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analyzer, and electrochemical workstation. The results indicate that the resultant carbon foams have specific surface area of 160 m2/g, total pore volume of 0.15 cm3/g and possess dual pore size distributions with macropore sizes of 0.5-2.0 μm and the most probable pore size of 4.1 nm. The electrochemical properties of the carbon foams have been investigated by cyclic voltammetry (CV) and galvanostatic charge- discharge with a three-electrode system in electrolyte of 6 mol/L KOH solution. The CV curves of the carbon foams show rectangular-like shape without obvious oxidation-reduction evolution peak, which suggests a typical nonfaradic adsorption/desorption reaction. The carbon foams present linear galvanostatic charge-discharge curve under the current densities of 1.0-5.0 A/g and their specific capacitance values are 60-90 F/g. The good electrochemical performances of carbon foams would provide candidate as electrode materials for supercapacitors.

Abstract: In this paper, a phase-change-material/lightweight aggregate (PCM-LWA) composite thermal energy storage material was prepared by absorbing the lauryl alcohol, which is one kind of phase change materials, into porous lightweight aggregates (LWAs) that have an excellent absorbability. In such a composite, the lauryl alcohol serves as a latent heat storage material and the porous lightweight aggregate acts as the supporting material. In order to prevent the melted lauryl alcohol leak from the porous LWAs, surface seal processing for the PCM-LWA was necessary. In this research, pure cement paste and polymer modified cement paste were used to seal the PCM-LWA surface. Through comparison between the differential scanning calorimetry (DSC) tests for lauryl alcohol and PCM-LWA, it can be known that the solid-liquid phase change temperature of the composite PCM-LWA was slightly higher than that of the lauryl alcohol, and latent heat of the PCM-LWA was smaller than that of the pure PCM.

Abstract: Nanocrystalline Co_xZn_1-xCr₂O₄ (x=0.7, 0.8, 0.9, 0.95, and 1) was synthesized by the low-temperature combustion synthesis method using citric acid as reductant and metal nitrates as oxidants. XRD, TEM, FT-IR and DSC were employed to characterize the structure, morphology, infrared curve and the catalytic performance for the ammonium perchlorate (AP) decomposition of the sample, respectively. Results show that cubic spinel-type solid solution of 30 nm Co_xZn_1-xCr₂O₄ particles can be obtained at 800 °C. The absorption bands in IR curve at 528 cm^-1 and 627 cm^-1 corresponding to the vibration of octahedron group [CrO₆], the peaks slightly shift to high wave number with the increase of the x value. Compared with the thermal decomposition of pure AP, adding Co_xZn_1-xCr₂O₄ nanoparticles in AP decreases its decomposition temperature by 58~68 °C and increases its apparent decomposition heat to 1049.62~740.13 J/g, exhibiting significant catalytic effect. Catalytic mechanism is due to the lattice of transition metal ions Co^{2 +} and Cr^{3 +} in the outer d orbital electron transfer, which provides a good space and produces complex with NH₃ ligands of ammonium perchlorate’s dissociation products.

Abstract: In this paper, we demonstrated the preparation and electrochemical performance of mesoporous carbon foams as electrode materials for ultracapacitors. By using n-octane as oil phase, cetyltrimethylammonium bromide (CTAB) and butanol as emulsifiers, resorcinol and formaldehyde dissolved in water as the aqueous phase, an O/W microemulsion system was obtained. Mesoporous carbon foams (MCFs) were prepared by the polymerization of the O/W microemulsion, followed by drying and carbonization and subsequently activation at 1273 K by KOH under nitrogen atmosphere. The mesoporous carbon foams were characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analyzer. The results show that MCFs have specific surface area of 666.7 m2/g, total pore volume of 0.36 cm3/g and the most probable pore size of 4 nm. The electrochemical properties of the resultant mesoporous carbon foams have been investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge with a three-electrode system in electrolyte of 6 mol/L KOH solution. The CV curves show quite rectangular shape under the scan rate of 5-20 mV/s, suggesting a typical nonfaradic adsorption/desorption reaction. The mesoporous carbon foams possess linear galvanostatic discharge curves under the current densities of 10-50 mA/cm2 and corresponding specific capacitance values are 132.6-172.1 F/g. Thus the MCFs have good electrochemical performance and they provide an important candidate for electrode materials used in ultracapacitors.

Abstract: The nanocrystalline and amorphous Mg2Ni-type Mg20Ni10-xMnx (x = 0, 1, 2, 3, 4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys were measured. The results show that the substitution of Mn for Ni, instead of changing the major phase Mg2Ni, leads to the formation of Mg and MnNi phases. No amorphous phase is detected in the as-spun Mn-free alloy, but the as-spun alloys substituted by Mn display the presence of an amorphous phase, suggesting that the substitution of Mn for Ni enhances the glass forming ability of the Mg2Ni-type alloy. The hydrogen absorption capacity of the as-cast alloys first increases and then decreases with the variation of the amount of Mn substitution. The hydrogen desorption capacity of the alloys markedly increases with growing Mn content.