C. Nguyen

Bio: C. Nguyen is an academic researcher from University of Washington. The author has contributed to research in topics: Dielectric & Corrosion. The author has an hindex of 7, co-authored 7 publications receiving 921 citations.

Template-Based Growth of Various Oxide Nanorods by Sol–Gel Electrophoresis

Abstract: The ability to form oxide nanorods is of great interest in a number of areas. In this paper, we report the template-based growth of nanorods of several oxide ceramics, formed by means of a combination of sol–gel processing and electrophoretic deposition. Both single metal oxides (TiO2, SiO2) and complex oxides (BaTiO3, Sr2Nb2O7, and Pb(Zr0.52Ti0.48)O3) have been grown by this method. Uniformly sized nanorods of about 125–200 nm in diameter and 10 μm in length were grown over large areas with near unidirectional alignment. Desired stoichiometric chemical composition and crystal structure of the oxide nanorods was readily achieved by an appropriate procedure of sol preparation, with a heat treatment (700 °C for 15 min) for crystallization and densification.

Organic–inorganic hybrid coatings for corrosion protection

Abstract: The corrosion resistance of sol–gel derived, organic–inorganic, silica-based hybrid coatings with various amounts of organic content was studied. Hybrid sols were prepared by copolymerizing tetraethylorthosilicate (TEOS) and 3-methacryloxypropyltrimethoxysilane (MPS) with a two-step acid-catalyst process. Hybrid coatings were dip-coated on 304 stainless steel substrates and annealed at 300 °C for 30 min. Such prepared hybrid coatings were found to be relatively dense, uniform and defect free. The adhesion and flexibility of the coatings were characterized. The influences of the amount of organic component incorporated into the coatings and the aging of sols on corrosion protection were studied. Electrochemical analyses showed that the relatively dense hybrid coatings provided excellent corrosion protection by forming a physical barrier, which effectively separated the anode from the cathode. Some preliminary biocompatibility tests were also conducted on the hybrid coatings.

Electrophoretic Growth of Lead Zirconate Titanate Nanorods

Abstract: rise to mesoporous nanoparticles with radial channels. The uniform fragment length within the interior of the nanoparticles can be explained by the radial nature of the deformation field around each defect, or site-specific breakage of the 300 nm long native TMV rods. Indeed, chemical degradation of TMV does produce a stable fragment about 50 nm in length, which is similar in size to those encapsulated in the silica shell of the nanoparticles. However, we observed only a random distribution of particle lengths in control samples containing broken TMV tubes. Further work is in progress to confirm the model. In conclusion, nematic liquid crystals of TMV can be used to prepare silica mesostructures and nanoparticles with parallel or radial arrays of linear channels, respectively. The mesostructures are produced as micrometer-size inverse replicas of the nematic phase, and have a periodicity of approximately 20 nm, which is larger than that generally attainable by current methods. In contrast, the nanoparticles are less than 150 nm in size and consist of a dense silica core surrounded by an unusual radial array of mineralized TMV fragments, 50 nm in length. The channeled nanoparticles are produced at lower reactant concentrations and appear to originate from topological defects associated with the deformation and fracturing of silica±TMV clusters as the liquid crystalline state is re-established in the reaction mixture. The general stability of TMV liquid crystals suggests that it should be possible to use a similar approach to prepare a wide range of inorganic oxides, semiconductors and metal-based mesophases and nanoparticles with mesostructured interiors.

Doping effect in layer structured SrBi2Nb2O9 ferroelectrics

Abstract: This article reports a systematic study of doping effects on the crystal structure, microstructure, dielectric, and electrical properties of layer-structured strontium bismuth niobate, SrBi2Nb2O9 (SBN), ferroelectrics. Substitution in both the A site (Sr2+ by Ca2+ and Ba2+) and B site (Nb5+ by V5+) up to 30 at % were studied. It was found that crystal lattice constant, dielectric, and electrical properties of SBN ferroelectrics varied appreciably with the type and amount of dopants. The relationships among the ionic radii, structural constraint imposed by [Bi2O2]2+ interlayers, and properties were discussed.

Dielectric properties of layered perovskite Sr1−xAxBi2Nb2O9 ferroelectrics (A=La, Ca and x=0,0.1)

Abstract: In this letter, we report an experimental study on the influences of 10 at. % Ca2+ and La3+ doping on dielectric properties and dc conductivity of SrBi2Nb2O9 ferroelectric ceramics. All the samples were made by two-step solid-state reaction sintering at temperatures up to 1150 °C for 0.5–1 h in air. X-ray diffraction analysis indicated that single-phase layered perovskite ferroelectrics were obtained and no appreciable secondary phase was found. The Curie point was found to increase from 418 °C without doping to 475 °C with Ca2+ doping and to 480 °C with La3+ doping. Dielectric constants, loss tangent, and dc conductivity of SrBi2Nb2O9 ferroelectrics doped with Ca2+ and La3+ were studied and the relationships among doping, crystal structure, and dielectric properties were discussed.

Fabrication of Titania Nanofibers by Electrospinning

Abstract: This paper describes a procedure based on electrospinning for generating nanofibers of anatase with controllable diameters and porous structures. When an ethanol solution containing both poly(vinyl pyrrolidone) (PVP, Mw ≈ 1 300 000) and titanium tetraisopropoxide was injected through a needle under a strong electrical field, composite nanofibers made of PVP and amorphous TiO2 were formed (with lengths up to several centimeters) as a result of electrostatic jetting. These nanofibers could be subsequently converted into anatase without changing their morphology via calcination in air at 500 °C. The average diameter of these ceramic nanofibers could be controlled in the range from 20 to 200 nm by varying a number of parameters such as the ratio between PVP and titanium tetraisopropoxide, their concentrations in the alcohol solution, the strength of the electric field, and the feeding rate of the precursor solution. Both supported and free-standing mats consisting of anatase nanofibers have been successfully ...

One-dimensional titanium dioxide nanomaterials: nanotubes.

Abstract: In the present review we try to give a comprehensive and most up to date view to the field, with an emphasis on the currently most investigated anodic TiO2 nanotube arrays. We will first give an overview of different synthesis approaches to produce TiO2 nanotubes and TiO2 nanotube arrays, and then deal with physical and chemical properties of TiO2 nanotubes and techniques to modify them. Finally, we will provide an overview of the most explored and prospective applications of nanotubular TiO2.

Low-Temperature Synthesis of Soluble and Processable Organic-Capped Anatase TiO2 Nanorods

Abstract: We demonstrate the controlled growth of high aspect ratio anatase TiO2 nanorods by hydrolysis of titanium tetraisopropoxide (TTIP) in oleic acid (OLEA) as surfactant at a temperature as low as 80 °C. Chemical modification of TTIP by OLEA is proven to be a rational strategy to tune the reactivity of the precursor toward water. The most influential factors in shape control of the nanoparticles are investigated by simply manipulating their growth kinetics. The presence of tertiary amines or quaternary ammonium hydroxides as catalysts is essential to promote fast crystallization under mild conditions. The novelty of the present approach relies on the large-scale production of organic-capped TiO2 nanocrystals to which standard processing of colloidal nanocrystals, such as surface ligand exchange, can be applied for the first time. Concentrated colloidal titania dispersions can be prepared for a number of fundamental studies in homogeneous solutions and represent a new source of easily processable oxide materia...