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Aluminum (Al) toxicity in acid soils is a significant limitation to crop production worldwide, as 13% of the world's rice is produced in acid soil with high Al content. Rice is likely the most Al-resistant cereal and also the cereal, where Al resistance is the most genetically complex with external detoxification and internal tolerance. Many Al-resistance genes in rice have been cloned, including Al resistance transcription factor 1 (ART1) and other transcription factors, organic acid transporter genes, and metal ion transporter gene. This review summarized the recent characterized genes affecting Al tolerance in rice and the interrelationships between Al and other plant nutrients.

We developed a simple and efficient strategy to prepare monodisperse amino-functionalized silica nanoparticles (SiNPs). Guanidine hydrochloride was selected as an amination reagent because it can be easily absorbed by SiNPs through charge interaction. The reverse microemulsion method was employed to synthesize guanidine-modified silica nanoparticles (SiNPs) in a one-pot procedure. The obtained SiNPs were then characterized through FTIR, SEM, and TEM. The nitrogen content on SiNP surfaces was directly measured by using an elemental analyzer. Results revealed that the amino group concentration on the SiNP surfaces was 1.5 × 10−6 mol mg−1. The monodispersity of the amino-functionalized SiNPs prepared through this method and the concentration of their amino groups were higher than those obtained via traditional methods. As such, these SiNPs were utilized to fix quantum dots on the SiNP surfaces. The guanidine-modified SiNPs coated with QDs were further characterized through SEM, TEM, and fluorescence spectroscopy. Furthermore, the modified SiNPs as basic nanocatalysts were used to catalyze the Henry reaction. Conversion was high under optimal conditions, and reaction time was remarkably shortened. The nanocatalysts could also be recycled for at least four additional cycles after they were centrifuged, washed with ethanol, air-dried, and immediately reused. Therefore, guanidine hydrochloride is a feasible amination reagent, and guanidine-functionalized SiNPs are promising materials in many fields because of their advantages.

nterdiffusion coefficients in α2-Ti3Al and γ-TiAl of conventional TiAl and TiAl-8Nb alloy were measured at the temperature ranging from 1273K to 1523K. Single-phase diffusion couples were employed, and the concentration profiles of Al after annealing were measured by an electron probe microanalyzer (EPMA), and the interdiffusion coefficients were calculated according to the Boltzmann-Matano method. The results showed that there was no significant concentration dependence of interdiffusion coefficients for all the alloys with various phases, and the values of interdiffusion coefficients covered three orders of magnitude (E-17-E-14) with the increase of temperature according to Arrhenius law. In α2-Ti3Al and γ-TiAl phase of conventional TiAl alloys, the pre-exponential factor and activation enthalpy were D0=3.95×10-5m2s-1,Q=276KJmol-1 ;D0=7.26×10-5m2s-1,Q=275KJmol-1 respectively. The pre-exponential factor and activation enthalpy were D0=4.54×10-6m2s-1, Q=244KJmol-1 in γ-TiAl phase of TiAl-8Nb alloys. However, the temperature dependence of interdiffusion coefficients in α2-Ti3Al of TiAl-8Nb alloys did not follow Arrhenius laws very well. With the addition of Nb, the interdiffusion coefficients increased significantly in α2-Ti3Al, but changed slightly in γ-TiAl at high temperature.

Low pressure turbine blades (LPT) made by investment casting from intermetallic titanium aluminide alloys for aero-engine applications have about 50% weight saving compared with that from nickel-based counterparts. Investment casting process of the low pressure turbine blades for high Nb containing TiAl alloy was simulated by Procast. The height of the blade is about 125mm and the thinnest part of it is about 6mm. Compositions of the cast and mould are Ti-45.5Al-8Nb (at %) and Zircon sand, respectively. The simulation result showed that there were porosities appearing in the centre of blades, which may be due to the formation of isolated liquid. In this work, the simulation, analysis and comparison of different casting ways were carried out. The result showed that compared with top and bottom casting, blades made by side casting have less porosity defects. And then the casting temperature, casting velocity, mould preheating temperature and interface heat transfer coefficient were optimized based on orthogonal design. The result also indicated that the influence of process parameters to porosity defects of blades can be ranked from strong to weak as follow: casting temperature>shell mould preheating temperature>casting velocity>interface heat transfer coefficient. When the casting temperature was 1700, the mould preheating temperature was 500, the casting velocity was 0.5 m·s-1, and the interface heat transfer coefficient was 500 W·m-2·K-1, the volume of porosity defects was the smallest.

High Nb containing TiAl based alloys exhibit excellent corrosion resistance to molten zinc. They are expected to serve as the potential coating materials of corrosion resistance to molten zinc. Four TiAl-Nb alloys of good oxidation resistance and their powders were prepared by arc-melting and ball milling, respectively. The Microstructure, Hardness, Coefficient of thermal expansion, and grain size distribution of four as-cast TiAl-Nb alloys and their powders were investigated. In addition, EPMA analysis was employed to further examine the existential state of element Y in as-cast TiAl-Nb alloys. It was found that element Y existed in the form of YAl2 phase in the grain boundaries and triple junctions. Higher content of Al in TiAl-Nb alloy results in bigger Coefficient of thermal expansion. Lamellar microstructures and fine grains exert a positive influence on hardness. Powders prepared by ball milling displayed angular and irregular morphology. © (2012) Trans Tech Publications.

Hot dip galvanizing has been extensively employed for corrosion protection of steel structures. However, during the process of galvanization, the corrosion in molten zinc brings many problems to galvanization industry. In this study, as a material of corrosion resistance to molten zinc intended for application in Hot-dip galvanization, HVOF Ti28.15Al63.4Nb8.25Y (at.%) coatings with different bond coats (NiCr5Al, NiCoCrAlY, CoCrAlYTaSi, and NiCr80/20) were deposited onto 316L stainless steel substrate, respectively. The influences of different bond coats on HVOF Ti28.15Al63.4Nb8.25Y coatings were investigated. The results showed that bond coat had an obvious influence on improving the mechanical properties of HVOF Ti28.15Al63.4Nb8.25Y coatings. HVOF Ti28.15Al63.4Nb8.25Y coatings with NiCoCrAlY bond coat displayed the best mechanical properties. However, bond coats had no obvious effects on the microstructure, porosity, and hardness of HVOF Ti28.15Al63.4Nb8.25Y top coatings. The effects of as-received powder morphology and grain size on the characteristics of coatings were also discussed.

Natural gas (methane is the primary constituent) adsorbed on nanoporous materials is a promising alternative to compressed natural gas as a cleaning fuel. To understand the transport of methane confined in a nanoscale pore is useful for developing and optimizing some related industry processes. Equilibrium molecular simulation were carried out to study the transport behaviors of methane confined in two types silica pores, a cristobalite silica pore and an amorphous silica pore. Many factors, such as temperatures, densities of methane and surface structures of pore, which could affect the transport of methane, were examined in simulations. Simulations calculated the diffusion coefficients of methane at different densities and temperatures. The detailed microscopic structures of pores have a great correlation with the diffusion behaviors of methane. The diffusion coefficients of methane increased with increasing temperature, but decreased with the increase of density.

A three-phase epoxy-based composite with randomly distributed silver nanoparticles and BaTiO3 particles was synthesized. By the incorporation of silver nanoparticles into the epoxy resin, the dielectric properties of the resin were significantly enhanced, and this provided an ideal host for further mixing with BaTiO3 to prepare high-dielectric-constant, polymer-based dielectrics with high dielectric strength. The devices that adopted these composites demonstrated high relative dielectric constants of approximately 450, 110 times higher than that of the epoxy matrix, with a dielectric strength of 5 kV/mm at room temperature. These nanocomposites were found to be potentially useful for embedded capacitor applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 967–971, 2006

Effects of solvents on the cubic to tetragonal phase transition of barium titanate (BT) nanocrystals were investigated by solvothermal treatment. Different processing variables, such as temperature and time were taken into consideration for different solvents. There were no effects on the phase transition of BT below the boiling temperature of all the solvents. Above the boiling temperature, a nanocrystals of tetragonal barium titanate could be obtained from the commercial cubic phase BT powder (Cabot, BT-08). There were no significant changes of the particle size and morphology of the BT powders before and after the chemical treatment. There was small reduction of surface area and particle size observed in the chemically treated BT powders. The crystal structure, phase transition and morphology of the powders were analyzed by XRD, DLS, DSC, TGA and SEM.

We report the synthesis of tetragonal sub-micron barium titanate particles through a low-temperature solvothermal treatment. Effort has been concentrated on the variation of particle characteristics including particle size and c / a ratio, as a function of treatment conditions. The tetragonality of the treated BaTiO 3 particles increased from 30% to 80%, confirmed by X-ray diffraction and differential scanning calorimetry. No appreciable change in particle morphology was observed after the treatments. Extraction of the lattice hydroxyls and consequential reduction of porosity were believed to be the cause of the tetragonality raise, as confirmed by infrared spectroscopy, solid-state nuclear magnetic resonance and specific surface area investigation. This work presents a practical and simple route for preparing freestanding tetragonal BaTiO 3 particles.

A modified autoclave was used to investigate the crystallization mechanism of BaTiO 3 during the hydrothermal reaction of Ba(OH) 2 and TiO 2 anatase. An uneven distribution of the crystallized BaTiO 3 particles was observed: more than 99 wt.% of total BaTiO 3 particles remained where the precursor TiO 2 was put; less than 1 wt.% was collected from the areas away from the TiO 2 . According to the experimental observations in this work and proofs reported in the literature, we propose that the crystallization mechanism is dissolution–precipitation in nature, but the soluble Ti 4+ species can only redisperse in a short distance away from TiO 2 particles before precipitation. In other words, the nucleation of hydrothermal BaTiO 3 starts at a low concentration of Ti 4+ . The mechanism of the Ba(OH) 2 –Ti(OH) 4 reaction is a fast dehydration process.

Europium-doped yttrium oxide phosphors were obtained by firing precursors prepared by urea precipitation in ethanol and ethylenediamine. The precipitation in non-aqueous solution was carried out in an autoclave at 150°C to allow the decomposition of urea. The photoluminescent intensities of the phosphors prepared in ethanol and ethylenediamine increased by about 30% compared to that of the phosphor prepared by the conventional urea homogeneous precipitation in aqueous solution. Amorphous carbonates and amorphous hydroxides/carbonates mixtures were identified as precursors from ethanol and ethylenediamine, respectively. The morphology and particle size were studied by SEM and dynamic laser scattering method.

A novel and simple synthesis route for the production of ZnS:Cu,Al sub-micron phosphor powder is reported. Both the host and activator cations were co-precipitated from an ethanol medium by mixing with a diluted ammonium sulfide solution. The co-precipitated ZnS:Cu,Al was in cubic zinc blende structure after an intermediate-temperature furnace annealing. Strong photoluminescent and cathodoluminescent (CL) emission were observed, which was attributed to the 3d 10 -3d 9 4s 1 radiative transition at those copper sites. At an accelerating voltage of 1 kV, the CL intensity of the co-precipitated ZnS:Cu,Al sample was recorded 94% of the commercial reference phosphor with the same composition made by high temperature solid-state-reaction method. The particle size of the co-precipitated phosphor powders was found to be controllable simply through adjusting the reactant concentrations. The particle size of the annealed samples was measured by dynamic light scattering, which showed a mean particle diameter between 200 and 700 nm depending on the co-precipitation conditions.

We studied the effect of dopant concentration in ZnS:Cu, Al phosphor. Photoluminescent (PL) intensity of the chemically etched phosphor particles increased up to 140%, which proved the existence of a dopant concentration gradient. Calculation revealed the quantitative relationship between the dopant concentration and the luminescent intensity by relating the concentration gradient to the PL intensity. The result showed that the most efficient concentration is 100 ppm copper and the concentration quenching starts at 152 ppm.