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Synthesis and characterization of SDS assistant α-alumina structures and investigation of the effect of the calcination time on the morphology
摘要： In this paper, α-alumina structures were successfully prepared via hydrothermal synthesis supported with sodium dodecyl sulfonate anionic surfactant. The effect of the surfactant and the calcination time were investigated. The characterization of the samples calcinated at 1200 °C was performed using Raman spectroscopy, X-Ray Difraction analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy techniques. Experimental results showed that pure α-Al2O3 structures were obtained with different morphologies.
关键词： Hydrothermal synthesis,Calcination,Morphology,Sodium dodecyl sulfonate,Alumina
更新于2025-09-10 09:29:36
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On-substrate porous-anodic-alumina-assisted gold nanostructure arrays: Meeting the challenges of various sizes and interfaces
摘要： Arrays of 0- and 1-dimentional noble-metal nanostructures aligned on solid substrates are in demand for nanocatalysis, bio- and optical sensing, or biomolecular analysis. Here we introduce a range of advances based on a systematic research towards the porous-anodic-alumina (PAA)-assisted on- substrate arrays of gold nanostructures, such as rods and spheres, spatially-separated and highly aligned on a metal or semiconductor supporting layer via a blend of the anodizing, re-anodizing, and post- anodizing treatments applied to a thin layer of Al superimposed on selected valve metals (W, Ti, Hf), metal bilayers (W/Ti), or binary metal alloy layers (W-Ti). The achievements are due to (1) the improved self-organization in the PAA thin films during the self-localizing high-current anodization of the upper Al layer at challenging potentials ranging 100 to 250 V and 20 to 5 V, and (2) the enhanced penetration of the alumina barrier layer by the undergrowing metal oxide due to the increasing polarization (re- anodizing). The protrusions of the undergrown metal oxide can be either selectively dissolved away providing perfect nanoholes in the alumina barrier layer or left as formed in the barrier layer and annealed in vacuum to increase their electron conductance and serve as the supports for subsequent metal electrodeposition. Additionally, the in-situ amplitude-modulated constant-current pulse deposition mode combined with the original surface-wiping technique to remove the overdeposited gold allow for smooth nucleation and uniform finishing of perfect arrays of on-substrate gold nanospheres and nanorods, having diameters from 10 to over 250 nm and length up to 2.5 ?m.
关键词： gold nanorods,electrodeposition,barrier layer dissolution,nanodots,porous anodic alumina
更新于2025-09-10 09:29:36
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3D-FDTD modelling of optical biosensing based on gold-coated nanoporous anodic alumina
摘要： The suitability of using gold-coated nanoporous anodic alumina structures as a platform for reflectometry-based plasmonic biosensors is investigated by numerical simulation. Reflectance spectra of such structures has been obtained using 3D-FDTD while the sensing capabilities have been evaluated as the change in spectra upon the adsorption of a layer of a biological-related molecule (biolayer) on the gold coating and inner pore surface. Results show that the gold-coated nanoporous structure enables the coupling of normally incident light to a localized surface plasmon resonance, and that such resonance shifts upon the adsorption of the biolayer. A sensitivity can be defined as the resonance wavelength shift with the biolayer refractive index. It is demonstrated that smaller gold coating thicknesses result in an increase in sensitivity, but at the cost of a decrease in the resonance sharpness, what suggests the existence of an optimal gold coating thickness.
关键词： Gold-coated nanoporous anodic alumina,Biolayer,FDTD simulation,Reflectometry-based plasmonic biosensor
更新于2025-09-10 09:29:36
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Flow through polydisperse pores in an anodic alumina membrane: A new method to measure the mean pore diameter
摘要： We describe a novel technique for the characterization of the mean pore radius of self-ordered porous anodic alumina membranes. We have studied the flow of liquids through cylindrical membrane pores under conditions of very low Reynolds number (Re ? 1). We find that the flow data are well-described by Poiseuille’s law. Characterization is achieved through the application of the H?gen-Poiseuille equation on flow measurements conducted in a simple and compact experimental setup. This setup allows for the monitoring of flow as a result of the pressure difference between the two sides of the membrane without the use of sophisticated and costly laboratory equipment. The proposed method has been tested by flow experiments using liquids of various viscosities. Good agreement is found between the results obtained from the flow data and the pore radii measured by scanning electron microscopy. Consistent results for the mean pore radius for the same membrane have been obtained in all cases.
关键词： Poiseuille’s law,scanning electron microscopy,anodic alumina membrane,mean pore diameter,flow measurement
更新于2025-09-10 09:29:36
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In-situ laser Pelletization of advanced ternary thermal barrier coating system
摘要： thermal transformation of cubic (c) phase to tetragonal (t) and monoclinic (m) phases. Powder technology is considered as a product cost effective technology to produce advanced ceramics. A 1 kW CO2 pulsed laser, working at 0.4 and 1.0 kW, 2-200 ms pulsed lengths and 1 mm laser beam diameter, was used to produce pellets from the loose powder of 8 wt% yttria partially stabilized zirconia (YPSZ) containing 8 wt% alumina. SEM equipped with EDS and WDS, X-ray diffraction, X-ray step scanned and Vickers microhardness were employed to evaluate and analyze the dimensions, quality, microstructure, chemical composition, phases, hardness and fracture toughness of the pellets. Homogeneous distribution of a fine scale duplex structure of nontransformable tetragonal (t') + α-alumina was obtained. The rapid solidification which followed the pelletization process after laser melting of the powder mixture prevented phase. Hardness higher than 19 GPa with a fracture toughness higher than 10 MPa.m1/2 was achieved. The results show the possibility of using a pulsed laser to produce completely re-melted and re-solidified spherical pellets with smooth surfaces under wide ranges of processing parameters. Also, it was found that there is a specific interaction time (pulsed length) required for melting and producing pellets at any level of power density. The pulsed lengths needed are in the range of 10-200 ms at power densities and specific energies values of 510 to 1275 W/mm2 and 5-255 J/mm2 respectively. Pellets diameters of 1000-4000 μm were effectively produced. The results clearly demonstrate a high efficiency of laser coupling with ceramic powders. Complete t' phase is formed by athermal transformation with a small amount of rhombohedral (r) phase.
关键词： Pellets,t’-phase,α-alumina,Zirconia-yttria-alumina,Laser pelletization
更新于2025-09-09 09:28:46
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Preparation and application of polystyrene-grafted alumina core-shell nanoparticles for dielectric surface passivation in solution-processed polymer thin film transistors
摘要： Polystyrene-grafted alumina nanoparticles were synthesized by silane coupling between dimethylchlorosilane-terminated polystyrene (PS) and gamma-type alumina nanoparticles and characterized. The surface grafting density of the polystyrene chains on the nanoparticles was estimated to be 0.13 molecules per square nanometer. The Al2O3-PS nanoparticles are solution processable in organic solvents, including ethyl acetate, butyl acetate, and toluene, which enabled preparation of blends with polystyrene or poly(methyl methacrylate). The dielectric constant of the Al2O3-PS nanoparticle/polymer blend films is composition tunable from 2.59 to 7.79. The alumina-PS nanoparticles and their blends with polymers were found to form efficient surface passivation films on the oxide dielectric layer in organic field-effect transistors (OFETs).
关键词： core-shell nanoparticle,alumina-polymer gate insulator,organic field-effect transistor,surface modification
更新于2025-09-09 09:28:46
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Rapid Fabrication of Porous Anodic Alumina Films with Large Interpore Distances in an Ethylene Glycol and Ammonium Dihydrogen Phosphate-Based Electrolyte
摘要： Porous anodic alumina (PAA) ?lms have become popular nanotemplates due to the ordered hexagonal pore array structure. The fabrication of well-ordered PAA ?lms with larger interpore distances is still a challenge to date. Here, we develop a unique electrolyte system based on the reaction products of ethylene glycol (EG) with ammonium dihydrogen phosphate (ADP). In the novel electrolytes, stable high-voltage anodization with extremely high current densities (the peak value is close to 300 mA cm?2) can be realized at 400 V or even higher without breakdown. In 5 wt% EG-ADP-based electrolyte containing phosphoric acid, a well-ordered PAA ?lm with an interpore distance of ～610 nm can be fabricated at 250 V at a high growth rate of 1.3 μm · min?1.
关键词： Porous anodic alumina,high-voltage anodization,ethylene glycol,ammonium dihydrogen phosphate,interpore distance
更新于2025-09-09 09:28:46
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Innovative low temperature plasma approach for deposition of alumina films
摘要： Alumina films were deposited from a new plasma method using aluminum acetylacetonate (AAA) powder as precursor. The AAA was sputtered in argon and oxygen plasma mixtures. It was investigated the effect of the oxygen proportion (O2%) on the properties of the coatings. Deposition rate was derived from the layer height measured by profilometry. The elemental composition and molecular structure of the films were determined by Rutherford backscattering and infrared spectroscopies, respectively. Grazing incidence X-ray diffraction was used to investigate the microstructure of the films while hardness was determined by nanoindentation technique. Inspections on the surface morphology and on the film composition were conducted associating scanning electron microscopy and energy dispersive spectroscopy. Incorporation of oxygen affects the plasma kinetics and consequently the properties of the coatings. As moderated concentrations of oxygen (< 25%) are added, the structure is predominantly organic containing stoichiometric amorphous alumina. On the other hand, as high O2% (> 25%) are incorporated, the structure become rich in metallic aluminum with carbon rising at low proportions. The deposited layer is not homogeneous in thickness once the chemical composition of the precursor is changed by the action of the reactive oxygen plasma. Oxygen ablation on the film surface also contributes to the lack of homogeneity of the structure, especially as high oxygen proportions are imposed. Hardness data (0.5-2.0 GPa) corroborated the idea of an amorphous structure. Based on the results presented here it was possible to identify the oxygen concentration in the plasma atmosphere which mostly removed organics while preserving the stoichiometric alumina precipitation, subject of great relevance as one considers the reduction in the energy necessary for the creation of fully oxide coatings.
关键词： composition,reactive plasma sputtering,aluminum acetylacetonate,morphology,alumina,structure
更新于2025-09-04 15:30:14
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Characteristic of silica xerogel from rice husk ash wastes sintered by microwave and conventional
摘要： An attempt was made to produce silica from an agricultural waste, rice husks ash (RHA), as well as studied them. The high percentage silica content from ash of rice husks was used as silica source for sodium silica solution. Different heating temperature, time and acid treatments was studied for silica extraction. The composite is characterized and its microwave properties is investigated after sintering from 400 to 1200 oC. The results show the existing phases crystoballite at 1100 oC in microwave sintering. Preliminary experiment for reflection losses of silica alumina composite show that there are relation between degree of crystallinity and their reflection loss.
关键词： rice husk ash,microwave,alumina,Silica xerogel,sintering
更新于2025-09-04 15:30:14
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Fluorescent nanodiamond array deposition on porous anodized aluminum oxide using asperity assisted capillary force assembly
摘要： Array ordering of nanodiamonds with nitrogen-vacancy centers using porous anodized aluminum oxide (PAAO) templates is studied. Particle sorting and array formation are demonstrated with a polydisperse suspension of irregularly shaped diamonds with 28 nm number mean value diameter. The assembly is governed by a balance of withdrawal speed and evaporation driven particle flux, which is influenced by the asperities of the PAAO surface during the capillary and convective assembly dip-coating process. The resulting structures are dense (50 nm average center separation) isolated (non-touching) nanoparticle arrays with a size distribution that matches the topology of the template surface. The fluorescence signal is detected from arrays with an approximately 1:1 particle/pore filling ratio.
关键词： fluorescent nanodiamond,colloid assembly,porous anodic alumina,templated deposition
更新于2025-09-04 15:30:14