Surface morphologies of Mg-Gd alloy particle during its reactions with O_(2) and Teflon

Mg-Gd alloy particle has exhibited its unique combustion properties as the fuel of Mg/Teflon/Viton(MTV).Mg-Gd alloy/Teflon/Viton(MGTV)could burn at lower ambient pressure than MTV.To further investigate the reaction of MGTV in air,it was investigated via thermo gravity-differential scanning calorimetry(TG-DSC).Meanwhile,the morphologies and element distributions on the alloy surface during the reaction of MGTV in air were investigated via scanning electronic microscope-mapping-electronic differential spectrometer.Meanwhile,a similar experimental protocol on the Mg-Gd alloy particle during oxidation was also applied.The results showed that owning to a protective oxide shell,the onset oxidation temperature of Mg-Gd alloy is higher than Mg.However,the onset oxidation temperature of the exceeded Mg-Gd alloy in MGTV is significantly lower than that of the exceeded Mg in MTV.It was due to the existence of GdOF,which could significantly lower the oxidation temperature of the exceeded fuel.Furthermore,a possible reaction mechanism was proposed.The fascinating oxidation properties of Mg-Gd alloy suggested its promising applications in energetic materials.

Efficient flexible dye-sensitized solar cells from rear illumination based on different morphologies of titanium dioxide photoanode

The TiO_(2) with nanoparticles(NPs),nanowires(NWs),nanorods(NRs)and nanotubes(NTs)structures were prepared by using a in-situ hydrothermal technique,and then proposed as a photoanode for flexible dye-sensitized solar cell(FDSSC).The influences of the morphology of TiO_(2) on the photovoltaic performances of FDSSCs were investigated.Under rear illumination of 100 mW·cm^(−2),the power conversion efficiencies of FDSSCs achieved 6.96%,7.36%,7.65%,and 7.83%with the TiO_(2) photoanodes of NPs,NWs,NRs,and NTs and PEDOT counter electrode.The FDSSCs based on TiO_(2) NRs and NTs photoanodes have higher short circuit current densities and power conversion efficiencies than that of the others.The enhanced power conversion efficiency is responsible for their nanotubes and rod-shaped ordered structures,which are more beneficial to transmission of electron and hole in semiconductor compared to the TiO_(2) nanoparticles and nanowires disordered structure.

Simultaneous Morphologies and Luminescence Control of NaYF_(4)∶Yb/Er Nanophosphors by Surfactants for Cancer Cell Imaging

Hydrophilic rare-earth up-conversion nanophosphors(UCNPs)with small sizes and a strong up-conversion luminescence have attracted much interest.Herein the simultaneous control of morphologies and the up-conversion luminescence intensities was reported for NaYF_(4)∶Yb/Er nanophosphors by a facile hydrothermal procedure with different surfactants.With the change of the surfactants from polyvinylpyrrolidone(PVP)to sodium citrate(CIT),edetate disodium(EDTA)or sodium dodecyl benzenesulfonate(SDBS),the morphology of NaYF_(4)∶Yb/Er nanophosphors transformed from nanoparticles with a diameter of about 70.0 nm to hexagonal nanoblocks with a thickness of about 125.0 nm and a length of about 240.0 nm,nanorods with a diameter of about 700.0 nm and a length of about 2.6μm,or nanowires with a diameter of 250.0 nm and a length of about 3.2μm.Simultaneously,their up-conversion luminescence intensity went down gradually under laser irradiation at a wavelength of 980 nm due to the increase of photobleaching.PVP-capped NaYF_(4)∶Yb/Er nanoparticles exhibited the smallest size and the strongest up-conversion luminescence intensity.Biological experiment results revealed that NaYF_(4)∶Yb/Er nanophosphors exhibited a high biocompatibility and could be used as biological labels with a perfect signal-to-noise ratio for cancer cell imaging.

Synthesis of Hierarchically Porous FAU/γ-Al2O3 Composites with Different Morphologies via Directing Agent Induced Method

Zeolite FAU composites with a macro/meso-microporous hierarchical structure were hydrothermally synthesized using macro-mesoporous γ-Al_2O_3 monolith as the substrate by means of the liquid crystallization directing agent(LCDA) induced method. No template was needed throughout the synthesis processes. The structure and porosity of zeolite composites were analyzed by means of X-ray powder diffraction(XRD), scanning electron microscopy(SEM) and N_2adsorption-desorption isotherms. The results showed that the supported zeolite composites with varied zeolitic crystalline phases and different morphologies can be obtained by adjusting the crystallization parameters, such as the crystallization temperature, the composition and the alkalinity of the precursor solution. The presence of LCDA was defined as a determinant for synthesizing the zeolite composites. The mechanisms for formation of the hierarchically porous FAU zeolite composites in the LCDA induced synthesis process were discussed. The resulting monolithic zeolite with a trimodal-porous hierarchical structure shows potential applicability where facile diffusion is required.

Mineral structure and crystal morphologies of high-iron hydrargillite

Various characterization methods, including scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller surface-area measurements, thermogravimetry–differential scanning calorimetry, X-ray diffraction, and infrared spectroscopy, were used to study the mineral structure and surface characteristics of high-iron hydrargillite. Gibbsite, goethite, and hematite were found to be the main mineral components of hydrargillite, whereas the goethite and hematite were closely clad to the surface of the multilayer gibbsite crystals. Compared with the synthetic gibbsite, the hydrargillite contained more structural micropores generated by the mineral evolution during the mineralization process. The gibbsite in hydrargillite contained less crystal water compared with the synthetic gibbsite, and it was a typical polymorphic structure. The isomorphous substitution of Al and Fe was observed in goethite. The dissolution-controlling step of hydrargillite was the ionic diffusion speed because of the goethite and hematite that closely covered and encapsulated the gibbsite crystals.

Microstructure Morphologies of Asphalt Binders using Atomic Force Microscopy

We investigated microstructure morphologies of three asphalts（SK, Karamay, and Esso） used in China using atomic force microscopy（AFM）. The topography and phase contrast images were obtained. Topographic profile and three dimensional images were described. Roughnesses of microstructure were calculated. And the chemical compositions of asphalt were tested to explain the microstructural mechanism of the asphalt. The results show that the topography and phase image in atomic force microscopy are appropriate to evaluate the microstructure of the asphalt binder. There are significant differences in microstructural morphologies including bee-like structure, topographic profile, 3D image, and roughness for three asphalts in this study. There are three different phases in microstructure of asphalt binder. The oil source and chemical composition of asphalt, especially asphaltenes content have a great influence on the microstructure.

Effect of Annealing Temperature on the Formation of Silicides and the Surface Morphologies of PtSi Films

The effect of annealing temperature on the formation of the PtSi phase. distribution of silicides and the surface morphologies of silicides films is investigated by XPS. AFM. It is shown that the phase sequences of the films change from Pt-Pt2Si-PtSi-Si to Pt+Pt2Si+PtSi-PtSi-Si or Pt+Pt2Si+PtSi-PtSi-st with an increase of annealing temperature and the reason for the formation of mixed layers is discussed.

Effect of Curing Poly(<i>p</i>-Phenylene Sulfide) on Thermal Properties and Crystalline Morphologies

Commercial poly(p-phenylene sulfide) (PPS) was thermally cured, which resulted in an increase of molecular weight due to cross-linking. Non-isothermal crystallization studies of samples cured for up to 7 days at 250?C showed a monotonous increase of crystallization temperature compared to pure PPS. However, a further increase of curing time decreased the crystallization temperature. The change in the half-crystallization time (t1/2) was similar to the crystallization temperature. Thus, the cross-linking of PPS affected crystallization behaviors significantly. To a certain extent, crosslinks acted as nucleation agents, but excessive cross-linking hindered the crystallization. Morphologies observed by polarized optical microscopy suggested that thermal curing for as little as 1 day contributed to the spherulitic structure having a smaller size, that was not observed with pure PPS.

GROWTH MORPHOLOGIES OF A BINARY ALLOY WITH LOW ANISOTROPY IN DIRECTIONAL SOLIDIFICATION

Two new classes of growth morphologies, called doublons and seaweed, were simulated using a phase-field method. The evolution of doublon and seaweed morphologies was obtained in directional solidification. The influence of orientation and velocity on the growth morphology was investigated. It was indicated that doublons preferred growing with its crystallographic axis aligned with the heat flow direction. Seaweed, on the other hand, could be obtained by tilting the crystalline axis to 45°. Stable doublons could only exist in a range of velocity regime. Beyond this regime the patterns formed would be unstable. The simulation results agreed with the reported experimental results qualitatively.

Morphologies of a spherical bimodal polyelectrolyte brush induced by polydispersity and solvent selectivity

It is commonly realized that polydispersity may significantly affect the surface modification properties of polymer brush systems. In light of this, we systematically study morphologies of bidisperse polyelectrolyte brush grafted onto a spherical nanocolloid in the presence of trivalent counterions using molecular dynamics simulations. Via varying polydispersity, grafting density, and solvent selectivity, the effects of electrostatic correlation and excluded volume are focused, and rich phase behaviors of binary mixed polyelectrolyte brush are predicted, including a variety of pinned-patch morphologies at low grafting density and micelle-like structures at high grafting density. To pinpoint the mechanism of surface structure formation, the shape factor of two species of polyelectrolyte chains and the pair correlation function between monomers from different polyelectrolyte ligands are analyzed carefully. Also, electrostatic correlations, manifested as the bridging through trivalent counterions, are examined by identifying four states of trivalent counterions. Our simulation results may be useful for designing smart stimuli-responsive materials based on mixed polyelectrolyte coated surfaces.

Krylov Iterative Methods for Support Vector Machines to Classify Galaxy Morphologies

Large catalogues of classified galaxy images have been useful in many studies of the universe in astronomy. There are too many objects to classify manually in the Sloan Digital Sky Survey, one of the premier data sources in astronomy. Therefore, efficient machine learning and classification algorithms are required to automate the classifying process. We propose to apply the Support Vector Machine (SVM) algorithm to classify galaxy morphologies and Krylov iterative methods to improve runtime of the classification. The accuracy of the classification is measured on various categories of galaxies from the survey. A three-class algorithm is presented that makes use of multiple SVMs. This algorithm is used to assign the categories of spiral, elliptical, and irregular galaxies. A selection of Krylov iterative solvers are compared based on their efficiency and accuracy of the resulting classification. The experimental results demonstrate that runtime can be significantly improved by utilizing Krylov iterative methods without impacting classification accuracy. The generalized minimal residual method (GMRES) is shown to be the most efficient solver to classify galaxy morphologies.

A method for observing the three-dimensional morphologies of inclusions in steel

A method for observing the three-dimensional morphologies of inclusions by deeply eroding a steel sample with a kind of organic solution composed of bromine water, acetone, and HCl （volume ratio, 45：45：10） was introduced. Four different kinds of inclusions in ultra low carbon steel were compared by metallographic observation and erosion observation. The results show that the three-dimensional morphologies of different kinds of inclusions could be observed clearly and simply after erosion. The method is useful for the observation and analysis of inclusions made by deep erosion. It also provides a new way to control and remove inclusions based on the true morphologies of inclusions.

Synthesization and crystallization mechanism of nano-scale γ-AlOOH with various morphologies

Nano-scale γ-AIOOH with various morphologies, such as whisker, bar, ball, and sheet, was synthesized successfully and control- lably through a facile hydrothermal method just by adjusting the pH value of the solvent. Based on the analysis of the experimental data, the growth mechanism of nano-scale γ-AlOOH in the hydrothermal process was established. It is proposed that the growth unit and the growth direction are determined by the pH value of the solution and the growth unit, respectively. One-dimensional γ-AlOOH, such as whisker and bar, is formed in lower pH ranges, while two-dimensional γ-AlOOH sueli as sheet is formed only in high pH environment following the plane expansion crystallization mechanism.

Quasi-static simulation of droplet morphologies using a smoothed particle hydrodynamics multiphase model

Numerical simulation of the morphology of a droplet deposited on a solid surface requires an efficient description of the three-phase contact line. In this study, a simple method of implementing the contact angle is proposed, combined with a robust smoothed particle hydrodynamics multiphase algorithm (Zhang 2015). The first step of the method is the creation of the virtual liquid-gas interface across the solid surface by means of dummy particles, thus the calculated surface tension near the triple point serves to automatically modulate the dynarnic contact line towards the equilibrium state. We simulate the evolution process of initially square liquid lumps on fiat and curved surfaces. The predictions of droplet profiles are in good agreement with the analytical solutions provided that the macroscopic contact angle is accurately implemented. Compared to the normal correction method, the present method is straightforward without the need to manually alter the normal vectors. This study presents a robust algorithm capable of capturing the physics of the static welling. It may hold great potentials in bio-inspired superhydrophobic surfaces, oil displacement, microfluidics, ore floatation, etc.

Effects of laser heat treatment on the fracture morphologies of X80 pipeline steel welded joints by stress corrosion

The surfaces of X80 pipeline steel welded joints were processed with a CO2 laser, and the effects of laser heat treatment （LHT） on H2S stress corrosion in the National Association of Corrosion Engineers （NACE） solution were analyzed by a slow strain rate test. The fracture morphologies and chemical components of corrosive products before and after LHT were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively, and the mechanism of LHT on stress corrosion cracking was discussed. Results showed that the fracture for welded joints was brittle in its original state, while it was transformed to a ductile fracture after LHT. The tendencies of hydrogen-induced corrosion were reduced, and the stress corrosion sensitivity index decreased from 35.2% to 25.3%, indicating that the stress corrosion resistance of X80 pipeline steel welded joints has been improved by LHT.

INTERFACE MORPHOLOGIES AND MICROSTRUCTURES DURING DENDRITE-TO-CELL TRANSITION AT HIGH GROWTH RATE

The interface morphologies and microstruetures of the directionally solidified Ni-5wt-% Cu alloy during dendrite-to-cell transition at high growth rates have been investigated with a newly developed apparatus for unidirectional solidification with the temperature gradient at the solid/liquid interface higher than 1000 K/cm.The results show that in the vicinity of dendrite-to-cell transition point,the well developed sidebranches become shrivelled with the increase of growth rate and disappear at the dendrite-to-cell transition,and the primary spacing decreases simultaneously.Moreover,the length of mushy zone decreases greatly dur- ing the dendrite-to-cell transition.Cells obtained at high growth rates have very similar morphologies to those at low growth rates,but with much smaller cell spacings and unsmoothed cell walls which may be attributed to the different stability conditions of the cell walls at low and high growth rates respectively.

The Surface Morphologies and Spectroscopy Analysis of VC Coatings on the Substrate of Cr12MoV Prepared by TD Process after Salt Spray

The normal temperature corrosion of VC coating on the substrate of Cr12MoV prepared by TD process was tested in 5% NaCl aqueous solution, its surface morphologies and corrosion components after salt spray were observed with SEM and EDS, respectively, and the effects of salt spray on micro-structures of VC coating were analyzed. Moreover, the invalidation mechanism of VC coating after salt spray and its effect on substrate material were discussed. The experimental results shown that the uniformity and integrity of VC coating surface are destroyed by salt spray for 120 h, a large number of the pits are produced on the coating surface, and the coating falls off, which speeds corrosion breakage of its substrate; the oxidated film on its surface becomes rougher, broken and discontinuous, and falls off easily, which reduce the ability of resistance salt spray; the failure modes of VC coating after salt spray are expressed with falling off of oxidated film, stress concentration and pore effect and so on, the corrosion breakage of oxidated film is the corrosion result of deoxidization corrosion from oxygen and HCl produced by NaCl and vapor.

Tuning the morphologies of SiC nanowires via the change of the Co_xSi_y melts

SiC nanowires and SiC/SiO2 core-shell structural nanowires were synthesized via a simple thermal evaporation of CoxSiy melts at the temperature of 1500?C. The morphologies and yields of those SiC nanowires can be tuned by altering the composition of CoxSiy. Nanowires obtained by thermal evaporation of Co Si are composed of SiC/SiO2 core-shell nanostructures with lengths up to several hundreds of micrometers, diameters of 4050 nm, and the thickness of amorphous SiO2 wrapping shell about 20 nm. SiC nanowires prepared by thermal evaporation of Co Si2 and Co2 Si melt are found to be hexagonal-prism-shaped nanorods, and the diameter of those nanorods is about 150 nm and the length is about 10 microns. All the SiC nanowires obtained possess [111] preferred growth direction with a high density stacking faults and twin defects. Taking into consideration the binary alloy diagram of Co Si and the participation of oxygen, we propose the vapor-solid growth mechanism of SiC nanowires and discuss the effect of the supersaturation of Si O on the morphology and yields of SiC nanowires.

Effects of HNO_3 concentration on the pit morphologies of aluminum foil etched in HNO_3–HCl and HNO_3–H_2SO_4–HCl solutions

In this work, the effects of HNO3 concentration on the pit morphologies of high-cubic-texture aluminum foil etched in HNO3-HCl and HNO3-H2SO4-HCl solutions were investigated. When the aluminum foil was etched in HNO3-HCl solutions, the morphologies of pits transformed from irregular tunnels to typical tunnels （as inverted pyramids） and shallow cuboids as the HNO3 concentration in the etchant solution was increased. However, as the HCl concentration in the etchant solution was increased, the morphologies of pits transformed from shallow cuboids to typical tunnels （as inverted pyramids） and irregular tunnels. When the aluminum foil was etched in n N HNO3-（7.2-n） N H2SO4-0.8 N HCl solutions, the morphologies of the pits transformed from typical tunnels （i.e., the number of sub-tunnels formed on the main tunnels increased） to irregular tunnels （corrugated tnnnels and polyline tunnels） as the HNO3 concentration in the etchant solution was increased. These effects are attributed primarily to corrosion on the （100） and （010） faces of pits being accelerated and to the （001） faces be- ing prone to passivation to different degrees when various concentrations of HNO3 are added to the etchant solutions.

Syntheses and Evaluations of CdS with Various Morphologies for Photocatalytically Reducing CO_2

A series of CdS with various shapes of microsphere, flower-like and leaf-like were templatefreely synthesized by a hydrothermal method. Powder X-ray diffraction（XRD）, Brunauer-Emmett-Teller（BET）, scanning electron microscopy（SEM） and UV-vis absorption spectroscopy（UV-vis） were applied to characterize the morphology, optical and other physical properties of the as-prepared CdS. An optical spectrum analyzer was used to measure the wavelength of the illuminant on the slurry in the activity evaluations of photocatalytic reduction of CO2 over CdS. Both sources of cadmium and sulfur had great impact on the CdS morphology as can be seen in the SEM images. By means of a series of activity evaluations, the microspheric CdS made from cadmium nitrate and thioacetamide showed better photocatalytic activity for the reduction of CO2 to methyl formate（MF） in methanol than the flower-like and leaf-like CdS catalysts.