Applied Mechanics and Materials Vol. 319

Abstract: Eu²⁺, Dy³⁺ co-doped strontium aluminate (SrAl₂O₄) phosphor with high brightness and long afterglow were prepared by nano pseudo-boehmite particulate sol method. The precursor was prepared by peptizing AlOOH powders with HNO3 as peptize agent. The influence of preparation parameters on crystal structure and luminescent properties of the phosphor have been studied systematically. Monoclinic SrAl₂O₄ host with single-phase can be obtained by controlling sintering temperature at 1200°C, 4Wt%B2O3 and RSr/Al=0.34. The sample exhibits an intensive emission peak at 515 nm and the luminescent intensity decay with I=277.78t-1.079 .

Abstract: Aurivillius phase ferroelectrics Ba(Bi_1−xLa_x)₄Ti₄O₁₅(x=0-0.05) (BBiL_xT) was synthesized by a modified high-temperature solid-phase route.The structure, the dielectric, the ferroelectric and the aging properties were investigated systematically. With the La³⁺ doping, the room temperature relative permittivity of the samples is increased, and dielectric loss is decreased. For the BBiL_xT phase, only a weak variation with respect to the F2mm space group can be suggested from single crystal X-ray diffraction. The microstructure confirms the samples have a well-proportioned grain size and a higher density. The substitution also results in a marked improvement in the remnant polarization. The doping of La³⁺ in BBiLxT ceramics increased the room temperature relative permittivity aging properties.

Abstract: A limonitic nickel laterite was leached by sulfuric acid at atmospheric pressure. Kinetics of leaching within the temperature range of 75-100°C was studied. The leaching kinetics followed the shrinking core model. The diffusion through the liquid film could be negligible under the agitation speed of 600rpm or above. Surface chemical reaction was the rate-controlling step. The semi-empirical kinetic equation was determined and the activation energy was 52.843kJ/mol.

Abstract: The melting temperature-pressure phase diagram [Tm(P)-P] for magnesium oxide (MgO) is predicted through the Clapeyron equation where the pressure-dependent volume difference is modeled by introducing the effect of surface stress induced pressure. MgO is a material of key importance to earth sciences and solid-state physics: it is one of the most abundant minerals in the Earth and a prototype material for a large group of ionic oxides.

Abstract: Formation of depletion region and the charge distribution are analyzed using multi-charges’ migration under a polling field in fused silica. The internal fields induced are calculated based on a junction model. The field distributions and their intensities within the whole depletion inside the silica are calculated. The maximum field is on the order of 109 V/m in a abrupt junction, and the optical nonlinearities generated by this internal field are consistent with the experimental results published, which proves the junction model is reasonable and feasible to calculate optical nonlinearity in air by thermal polling.

Abstract: Alkenyl succinic anhydride (ASA) is widely used to hydrophobize paper and paper board in papermaking industry. Montmorillonite (MMT) particles modified by trifunctional silylating agent were used as particulate emulsifier to prepare binary mixed sizing agent. It was found that stable ASA\liquid paraffin Pickering emulsions can be prepared by using grafted-MMT particles and the optimal dosage of LP oil was 50 vol.%. The ASALP Pickering emulsions exhibited some kinds of a solidlike viscoelastic behavior, which can be explained by the particulate network formed by grafted-MMT particles in the emulsion. Addition of LP oil not only improved the stability of ASA emulsions stabilized by particulate emulsifier, but also significantly promoted the internal paper sizing performance of ASA.

Abstract: The boron-containing phenol-formaldehyde resin-based ceramifying composites that used muscovite mica and glass frits loaded boron-containing phenol-formaldehyde resin (BPF) as matrix, high silica fiberglass fabric as reinforcements, were pyrolyzed into ceramic gradually in the air. Glass frits were fused into liquid phase and spread to the surface to make muscovite mica form compact mullite ceramic shell. The shell restrained oxygen into the internal effectively in order to reduce the thermo-oxidative degradation of BPF resin. X-ray diffraction analysis (XRD) showed that aluminium borate (Al₈B₄O₃₃) and mullite (Al₆Si₂O₁₃) crystalline phases after pyrolysis. SEM demonstrated the ceramifying progress of the microstructure of the composites, and EDS analyzed the micro-chemical composition.

Abstract: In the media of pH 2.72 HCl-N_aA_c, Fe3O4 nanoparticles in size of 10 nm exhibited strong catalytic effect on the slow reaction of H₂O₂ and the substrate dopamine (DA) to form dark red small molecule polymer particles, which exhibited two absorption peaks at 305nm and 435nm. In the optimum conditions, as the concentration of H₂O₂ increased, the absorption value at 300 nm increased linearly. The increased absorption intensity (ΔA305nm) was linear to the H₂O₂ in the range of 0.5-35 μmol/L, with a linear regression equation of ΔA305nm=0.014C +0.043, a relative coefficient of 0.9997 and detection limit of 0.13 μmol/L H₂O₂, respectively. The proposed method was applied to detect H₂O₂ samples, with satisfactory results.

Abstract: Nanocrystalline and porous barium titanate (BaTiO3) nanofibers with diameter 200-400 nm were synthesized via electrospinning and followed calcinations. The morphology and microstructure of the nanofibers were characterized using field emission scanning electron microscope, X-ray diffractometer and transmission electron microscope, respectively. And the electrical and humidity sensing properties of the nanofibers were also measured. The results reveal that the BaTiO3 nanofibers have a conductivity of about 0.3 S/cm, and show an ultrafast response time (~0.7 s) and a recovery time (~0.4 s) to humidity at room temperature. In addition, the sensing mechanism was also discussed briefly based on its nanocrystalline and porous microstructure of the electrospun material.