Advanced Materials Research Vols. 239-242

Abstract: Graphene normally has weak interface compatibility to organics. In this paper, the surface of graphene is modified in order to improve its compatibility with polymer matrixes. Therefore, a Silane Coupling Agent(SCA) γ-Glycidoxypropyltrimethoxysilane is used to modify graphene. The results of the TEM, FTIR and sedimentation test show that SCA grafting can improve the graphene’s dispersion stability in polar organic solvent. Then modified graphene is added to epoxy resin to obtain an epoxy resin composite. The conductivity of the epoxy resin compostie can reach 8.00E-009 s/m. When additional percentage of SCA is over 0.5%, the dielectric constant (ε) has a remarkable increase.

Abstract: The fly ash with a loose and porous structure has definite absorbent ability, which has a good effect on soil improvement. Illite belongs to clay minerals, it has absorbent ability and higher potassium, which can improve the soil fertility. In this study, poly(acrylic acid sodium-co-acrylamide)(PAANa-AM)/fly ash-illite superabsorbent composite was firstly prepared by solution polymerization. The structures were characterized using scanning electron microscope, X-ray diffraction, and infrared spectrum. The results showed that the fly ash and illite dispersed well in the composite. The K⁺ in illite was replaced by Na⁺ in acrylic acid sodium and thus the illite structure turned into paragonite during the process of preparing composite, however, the structure of fly ash was maintained in the composite. Moreover, the hydroxide radical in illite reacted with the carbonyl group in acrylic acid during polymerization. The best absorbent capacities of the composite in distilled water, tap water and normal saline were 1695, 445 and 106 g/g, respectively, which exceeded the requirements of The National 863 Program and Ministry of Agriculture of People’s Republic of China. The potassium release was measured using atomic absorption spectrometry and the results indicated that the composite can release 12.80% of the potassium ion in fly ash and illite. The superabsorbent material has low cost and favors improvement of soil and potassium-deficiency.

Abstract: The ATRP of N-isopropylacrylamide (NIPAM) was carried out in DMF/water at 60 °C to afford a novel linear end-functionalized poly(N-isopropylacrylamide) with acetylated β-CD (AcCD-PNIPAM) and the structures of the products were characterized. The number-average molecular weight (M_n) and the polydispersity index (PDI) of the polymer were obtained from gel permeation chromatography (GPC) analysis. The end-functionalized PNIPAM with β-CD (CD-PNIPAM) was obtained by deacetylation from AcCD-PNIPAM. The lower critical solution temperature (LCST) for the aqueous solutions of CD-PNIPAM, measured by means of ultraviolet-visible spectroscopy (UV-vis), was 4~5 °C higher than that of AcCD-PNIPAM. Ferrocene was included into CD-PNIPAM with mole ratio of 1:1 and the inclusion complex was characterized by cyclic voltammetry (CV) technology.

Abstract: Magnesium-based hydrogen storage powders were prepared by reactive milling under hydrogen atmosphere. The crystallitic carbon, prepared from anthracite coal by demineralization and carbonization, was used as milling aid and synergic hydrogen storage additive of magnesium. Dispersive powders of particle size about 20 to 60 nm and hydrogen capacity of 4.78 wt.% were prepared from magnesium with 40 wt.% of crystallitic carbon by 3 h of milling under 1 MPa of hydrogen atmosphere. The hydrogen stored in carbon increased with the addition of Al, Mo, Co and Fe. FT-IR showed that the carbon atoms at the edges of crystallitic carbon particles were hydrogenated into C-H during reactive milling with hydrogen. The initial dehydrogenation temperature of hydrogen-storage material 60Mg40C is 275.8 °C, and its dehydrogenation plateau pressure at 300 °C is 0.2 MPa and the length of the plateau is 5.0 wt.% of hydrogen capacity.

Abstract: At present work, the microstructure and corresponding hardness of 17-4PH stainless steel were investigated by the process of CO₂ laser surface quenching and aging treatment. The hardness of the phase transformation zone in the hardened layer was 433.2HV, higher than 378.1HV of the matrix, which was attributed to the fine-grain and solution strengthening after laser quenching. The hardness of the phase transformation zone increased further to 464.5HV after an aging treatment at 520°C due to the precipitation strengthening of fine secondary phase particles.

Abstract: Low-temperature sintered Ca[(Li_1/3Nb_2/3)_0.8Ti_0.2]O_3-δ (CLNT) microwave dielectric ceramics with V₂O₅ and ZnO additives were prepared by the conventional solid state reaction method. The sintering behavior and microwave dielectric properties of CLNT ceramics were investigated. The main diffraction peaks of all the specimens sintered at the temperature under 1150^◦C split due to the coexistence of the non-stoichiometric phase and stoichiometric phase, which all possess CaTiO3-type perovskite structures. ZnO and V₂O₅ combined additives lowered the sintering temperature of CLNT ceramics from 1150^◦C to 1090^◦C. and the Qf values were improved from 18,210 GHz to 20,740 GHz. The CLNT ceramics with 4 wt% ZnO addition sintered at 1090^◦C showed good microwave dielectric properties with ε_r ~39.7, Qf ~20,740 GHz, τf ~8.6 ppm/^◦C. The relationship between dielectric properties and the sintering behavior was also discussed.

Abstract: Y₂O₃ coatings were prepared on aluminum substrates using plasma spraying with argon as primary gas. Structure and morphology were characterized by using X-ray diffraction, scanning electron microscopy and metallographic analysis. Results show that Y₂O₃ coating’s porosity is 5.6%. Coatings prepared with helium as secondary gas are purely white. However, there are black spots when hydrogen is used as secondary gas. A phase transformation from cubic to monoclinic tends to take place during the spraying operation under argon and hydrogen atmosphere. However this prejudicial transformation can be suppressed by using helium instead of hydrogen.

Abstract: In this paper, Bi₂O₃ doped with different amount of La³⁺ was prepared. The prepared photocatalysts were characterized by BET, XRD, UV-VIS diffuse reflectance and XPS. The results show that 3%La³⁺-Bi₂O₃ prepared has the highest BET surface area, pore volume, the smallest pore size. 3%La³⁺-Bi₂O₃ exhibits the best photocatalytic activity. The results of further experiments show that the specific surface area, UV-Vis diffuse reflectance and the binding energy all play an important role in promotion of photocatalytic activity of Bi₂O₃ nanostructure.

Abstract: Molecular pump with magnetic suspension is an important vacuum extractor. The machining accuracy of turbine-rotor has crucial influence on the key parameters of molecular pump, such as pumping speed, compression ratio. A clamping accuracy detection and display system of semi-fished turbine-rotor was established. The maximum coaxiality error and its position could be detected, displayed and recorded easily. With a precision fine tuning device, coaxiality error could be reduced from 30µm to 10µm. This system effectively reduces the turbine-rotor’s centrifugal force, and increases the stability of molecular pump with magnetic suspension.

Abstract: Carbon micro-spheres were obtained using β-cyclodextrin as the raw materials via hydrothermal synthesis and carbonization. The product had a perfect shape, smooth surface and narrow pore diameter distribution. The diameters were in the range of 400-700 nm. Then product was activated by ethanol and ammonium bicarbonate at low temperature in the closed system, respectively. The results showed that ammonium bicarbonate had better activation effect than ethanol. Moreover, specific surface area and pore volume of activated carbon micro-spheres reached to 1125 m² g⁻¹ and 0.485 mL g⁻¹, respectively. As electrode materials of supercapacitors, the specific capacitance were improved from 154 F g⁻¹ to 226 F g⁻¹, increased by 46%.