Synthesis and growth behavior of CeO2/ZrO2/LaAlO3 nanorods on hierarchical macroporous γ-alumina monoliths

Different kinds of metal oxide nanorods (CeO₂, ZrO₂ and LaAlO₃) grown on hierarchical macroporous γ-alumina monolith with excellent thermostability and mechanical strength are successfully synthesized by combining sol-gel method with boiled water-bath crystallization. Different kinds of metal oxide nanorods have different growth behavior. Monolayer stripe CeO₂ nanorods with approximately equal length accumulated by nanoparticles covered mainly on the surface of the skeleton. Minor ZrO₂ nanoparticles not only accumulated on the surface but also grew on hollow and conjunct part of the skeleton as well as the internal surface of the pore channels in a stagger and grid way. While the LaAlO₃ crystal particles were grown mainly on the skeleton surface of alumina monolith but hardly any on the internal surface. In addition, the dipping time and temperature of metal ions have important effects on the nanoparticles morphology. The unique combination of excellent support and auxiliaries candidates can be used as promising functional materials in the field of heat/mass transfer, microchannel and separation especially in heterogeneous catalysis.     

Synthesis and Characterization of ZnO Nanorods and Nanodisks from Zinc Chloride Aqueous Solution

ZnO nanorods and nanodisks were synthesized by solution process using zinc chloride as starting material. The morphology of ZnO crystal changed greatly depending on the concentrations of Zn²⁺ ion and ethylene glycohol (EG) additive in the solution. The effect of thermal treatment on the morphology was investigated. Photocatalytic activities of plate-like Zn₅(OH)₈Cl₂ · H₂O and rod-like ZnO were characterized. About 18% of 1 ppm NO could be continuously removed by ZnO particles under UV light irradiation.     

Synthesis of Nickel Phosphide Nanorods as Catalyst for the Hydrotreating of Methyl Oleate

Arrays of nickel phosphide nanorods were successfully synthesized by nanocasting using mesostructured silica SBA-15 as a hard template (HT-Ni₂P). After temperature-programmed reduction of the phosphate precursor infiltrated within the pore walls of SBA-15, the unsupported material was obtained by removing the silica matrix with diluted HF. The pore channel of the SBA-15 template stabilizes the Ni₂P particles, preventing sintering after the high reduction temperature and shaping their elongated morphology. Moreover, HT-Ni₂P catalyst shows an improvement in the textural properties with a significantly higher surface area than the reference sample synthesized in the absence of template. X-ray diffraction revealed that the only crystalline phase present in this material was Ni₂P. On the other hand, transmission electron microscopy shows that the catalyst is mainly constituted by agglomerates of nanorods. Through EDX microanalysis the efficient removal of silicon was confirmed. Under hydrotreating conditions, nanorods of Ni₂P show a fourfold enhancement in the conversion of methyl oleate with respect to conventional Ni₂P synthesized in absence of hard template. Nevertheless, when these data are normalized to surface area, the specific activity of HT-Ni₂P nanorods is significantly lower than that of the conventionally prepared sample. Differences in selectivity were also observed as Ni₂P nanorods favored the decarboxylation reaction leading to a higher yield of n-heptadecane.     

Morphology studies of doped polyaniline micro/nanocomposites containing TiO2 nanoparticles and Fe3O4 microparticles

To produce polyaniline (PAni) nanodevices that display excellent microwave absorbing behaviors, novel hexanoic acid-doped PAni micro/nanocomposites containing TiO₂ nanoparticles and Fe₃O₄ microparticles (PAni/HA/TiO₂/Fe₃O₄) were prepared by template-free method, particularly to improve the dielectric and magnetic property of PAni. PAni/HA/TiO₂/Fe₃O₄ synthesized at different polymerization temperatures and polymerization time by various TiO₂ and Fe₃O₄ contents, and particles size of TiO₂ were prepared. The aim of this research is to investigate the effect of synthesis condition on the morphology behaviors of nanorods/tubes. The resulted nanorods/tubes indicated that PAni micro/nanocomposites exhibited polymerization through elongation. PAni micro/nanocomposites synthesized at 0°C resulted in large amounts of nanorods/tubes compared with those synthesized at subzero temperature and above 0°C. PAni/HA/TiO₂ and PAni/HA/TiO₂/Fe₃O₄ synthesized using TiO₂ with diameter (particles size) 180 nm resulted in large amounts of nanorods/tubes (diameter nanorods/tubes = 80–140 nm) compared with those synthesized using TiO₂ with diameter of 30 and 6 nm. Increasing TiO₂ and Fe₃O₄ content above 10% will significantly reduce the amount of nanorods/tubes. In conclusion, synthesis parameters mentioned above are the significant factors that might affect the morphology behaviors of PAni nanostructures. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

The hindering function of phosphate on the grain growth behavior of nanosized zirconia powders calcined at high temperatures

Nanosized zirconia was prepared by a hydrothermal method using ZrOCl₂·8H₂O and NaOH as raw materials. The obtained ZrO₂ powders were soaked in the phosphate solution with different concentrations. The as-prepared ZrO₂ powders and the powders treated with phosphate solution were calcined at different temperatures from 600 to 1000 °C. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray photoelectronic spectroscopy (XPS). The experimental results show that the untreated nanosized ZrO₂ grow and agglomerate to bulk when the ZrO₂ powders were calcined at high temperatures, while the ZrO₂ powders treated with phosphate solution grow slowly and remain nanosized crystal at the same calcination temperature. This phenomenon implied that phosphate treatment played an important role in inhibiting the crystal grain growth of ZrO₂. The possible inhibition mechanism could be explained to that P species on the surface of ZrO₂ can reduce the grain boundary mobility and prevent direct contact of ZrO₂ particles.     

Study on Mechanical and Tribological Property of Nanometer ZrO2-filled Polyoxymethylene Composites

The polyoxymethylene (POM) matrix composites with different contents of nano-ZrO₂ particles were prepared. The effect of ZrO₂ on the crystallization and thermal property of POM were investigated through polarizing microscopy (PLM) and differential scanning calorimetry (DSC). The surface hardness and the tribological performance were measured by Rockwell sclerometer and ring-on-block tribometer, respectively. The surface morphology of the wear scar were observed by scanning electron microscope (SEM). The results show that the nano-ZrO₂ acted as the nucleation agent in POM and decreased the crystallite size of POM, increased the crystal growth rate. The wear resistance was enhanced and the friction coefficient was changed a little.     

Improved tribological and thermo-mechanical properties of epoxy resin with micro-nano structured ZrO2/Ti3C2 particles

Inherent brittleness and poor wear resistance of epoxy resin severely restricts its practical application in many applications. In this present, a micro-nano structured ZrO₂/Ti₃C₂ particle was employed to improve the tribological and thermo-mechanical properties of epoxy resin. The micro-nano structured ZrO₂/Ti₃C₂ particles are synthesized by hydrothermal growth of nano-ZrO₂ onto the surface of accordion-like Ti₃C₂, and the ZrO₂/Ti₃C₂/epoxy composites are fabricated by solution blending and curing reaction. The surface morphology of ZrO₂/Ti₃C₂ particles and the fracture surface of ZrO₂/Ti₃C₂/epoxy composites were investigated. Test results indicated that the wear rate, storage modulus and glass transition temperature of epoxy resin is effectively improved by incorporation of ZrO₂/Ti₃C₂ particles, maybe ascribing to the strong interfacial interaction between micro-nano structured ZrO₂/Ti₃C₂ and epoxy matrix. In addition, the wear mechanism of ZrO₂/Ti₃C₂/epoxy composites were further revealed by analyzing their worn surfaces and wear debris. This work provides a promising strategy for improving the tribological and thermo-mechanical properties of epoxy.     

Dispersity and phase composition of some ultradisperse ZrO2-bearing powders

Results of an electron-microscopic study (including microdiflraction) and a x-ray laser microanalyzer study of the dispersity of powders in the ZrO₂-A1₂O₃ system containing from 94.9 to 29.6% ZrO₂ and obtained by plasmachemical synthesis are presented. The features of the crystalline and morphological structure of the powder particles are considered. It is inferred that the crystal structure and the morphology of the powder particles affect the properties of the powders in the manufacturing process.     

Design of SiO2/ZrO2 core–shell particles using the sol–gel process

Core–shell particles of SiO₂/ZrO₂ were developed using a sol–gel process. Spherical core particles of SiO₂, 320 nm in diameter, were initially prepared using tetraethylorthosilicate (TEOS), and then uniformly shelled with ZrO₂ nano-particles synthesized with zirconium(IV) butoxide (TBOZ). The deposition of ZrO₂ nano-particles on the SiO₂ core particles was generally promoted when increasing the H₂O and TBOZ concentrations and temperature of the sol–gel process. However, micron-sized homo-aggregates of ZrO₂ were formed above certain concentrations of H₂O and TBOZ due to self-aggregation of the nano-ZrO₂ particles. It was very interesting to discover that a chemical bonding between zirconium and silicon bridged by oxygen (Si–O–Zr bond) was developed during the formation of the ZrO₂ shell around the core particles, as the silane groups on the core particles were condensed with zirconium hydroxyl groups during the deposition of ZrO₂. XPS and FT-IR confirmed the chemical bonding of Si–O–Zr in the core–shell particles.     

Transparent dispensible high‐refractive index ZrO2/epoxy nanocomposites for LED encapsulation

In this study, we report a facile ex situ approach to preparing transparent dispensible high‐refractive index ZrO₂/epoxy nanocomposites for LED encapsulation. Highly crystalline, near monodisperse ZrO₂ nanoparticles (NPs) were synthesized by a nonaqueous approach using benzyl alcohol as the coordinating solvent. The synthesized particles were then modified by (3‐glycidyloxypropyl)trimethoxysilane (GMS) ligand. It was found that, with tiny amount of surface‐treating ligand, the modified ZrO₂ NPs were able to be easily dispersed in a commercial epoxy matrix because of the epoxy compatible surface chemistry design as well as the small matrix molecular weight favoring mixing. Transparent thick (1 mm) ZrO₂/epoxy nanocomposites with a particle core content as high as 50 wt % and an optical transparency of 90% in the visible light range were successfully prepared. The refractive index of the prepared composites increased from 1.51 for neat epoxy to 1.65 for 50 wt % (20 vol %) ZrO₂ loading and maintained the same high‐Abbe number as the neat epoxy matrix. Compared with the neat epoxy encapsulant, an increase of 13.2% in light output power of red LEDs was achieved with the 50 wt % ZrO₂/epoxy nanocomposite as the novel encapsulant material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3785–3793, 2013     

Nitrogen-doped anatase titania nanorods with reactive {101} + {010} facets exposure produced from ultrathin titania nanosheets for high photocatalytic performance

To obtain high performance catalysts for the photooxidation of organic pollutants in water, nitrogen-doped TiO₂ nanorods with {101} + {010} facets exposure were successfully synthesized by using ultrathin two-dimensional titania nanosheets as precursor. The nitrogen-doped one-dimensional nanorods had a uniform size within 100 nm. The crystal structure of nitrogen-doped TiO₂ nanorods (anatase) didn't alter even though subjected from morphology transformation, however, their crystallinity improved tremendously, and the exposure and proportion of active facets changed, which synergistically boosted the catalytic efficiency. This integrated technology including modification, morphology and phase control might be indicative for fabrication of advanced photocatalysts to remedy environmental pollutant and produce clean energy in the future.     

Glycine-nitrate solution combustion synthesis of lithium zirconate: Effect of fuel-to oxidant ratio on phase,microstructure and sintering

Pure monoclinic lithium zirconate (Li₂ZrO₃) powder was synthesized by solution combustion route using glycine as fuel and nitrates as oxidants. Effect of fuel-to-oxidizer ratio (φ = 0.5–1.25) on synthesis condition, phase, powder morphology, sintering and thermodynamic aspects was systematically investigated. Thermodynamic analysis reveals; mode of combustion, adiabatic flame temperature, amount of gases and powder characteristics can be controlled by adjusting φ. The crystallite size of Li₂ZrO₃ powder was in the range of 18–40 nm. The powders consist of micrometric soft-agglomerates of irregular flake shape particles. The residual Li₂O in Li₂ZrO₃ powder was found to be in the range 155–469 μg/g. The Li₂ZrO₃ powder synthesized by present method shows significantly enhanced sinter-ability as compared to conventional solid-state method. The Li₂ZrO₃ pellets were sintered close to 98% of T.D. at 1000 °C with grain size 1–2 μm. Increase of sintering temperature to 1050 °C results abnormal grain growth with large number of closed pores.     

Microstructure and synthesis mechanism of dysprosia-stabilized zirconia nanocrystals via chemical coprecipitation

In this study, zirconia (ZrO₂) and dysprosia-stabilized zirconia (DySZ) nanocrystals were synthesized using a chemical coprecipitation method. The crystal structure and micromorphology of the as-synthesized powders, as well as the structural evolution from precursors to oxides were investigated, and the synthesis mechanism was also examined. Results show that pure ZrO₂ powders mainly comprise the monoclinic ZrO₂ phase with trace tetragonal ZrO₂, while the DySZ powders exhibit a tetragonal ZrO₂ structure. In addition, the crystal growth rate of DySZ is far slower than that of the pure ZrO₂ under elevated calcination temperature. The addition of Dy could significantly improve the phase stability of DySZ powder and effectively inhibit the crystal growth of DySZ. In the DySZ precursor, the binding energy of chemical bonds is significantly difference than in the ZrO₂ precursor. A composite hydroxide can be formed with -Zr-OH-Dy- and -Zr-OH-Zr- units in the tetramer structure because of the in-situ substitution of Zr by Dy atoms. Both the ZrO₂ and DySZ precursors exhibit analogous dehydration and crystallization behaviours in calcination process. Dy-doping plays a significant role in stabilizing both the intermediate product and the DySZ crystal.     

Synthesis and structural,optical, photocatalytic,and electrochemical properties of undoped and yttrium-doped tetragonal ZrO2 nanoparticles

Template-free undoped and yttrium-doped tetragonal ZrO₂ nanoparticles were successfully synthesized using a hydrothermal technique, and their structural, morphological, optical, and electrochemical properties were characterized. The photocatalytic activity for the dye degradation of the Rhodamine B (RhB) was also studied under UV light irradiation. The tetragonal crystal phase of the nanoparticles was confirmed by XRD analysis. The observed peak shift in XRD patterns confirmed the incorporation of dopant into host lattice. The Yttrium-doped ZrO₂ nanoparticles showed a higher specific surface area and smaller optical band gap (191.5?m²/g and 3.66?eV) than the pristine ZrO₂ nanoparticles (108.6?m²/g and 4.94?eV). The yttrium-doped ZrO₂ nanoparticles exhibited greater photocatalytic activity (~98%) than the pure ZrO₂ nanoparticles within 40?min, due to their high specific surface area and reduced photogenerated charge carrier recombination rate. The Nyquist plot of yttrium-doped sample exhibited lower charge transfer resistance than that of the undoped sample. The photocurrent of the doped sample (28.6?mA/cm²) was ~9 times higher than that of pristine ZrO₂ sample (3.2?mA/cm²). The doped sample showed stable and higher photocurrent density up to 520?s under light illumination.     

Morphology-Controllable Synthesis of CeO2 on a Pt Electrode

Nanoscale cerium dioxides with shape of nanoparticles, nanorods, and nanotubes were electrochemically synthesized. The morphology of CeO₂ was modulated by changing electrode potential and potential direction. CeO₂ nanorods and CeO₂ nanotubes were synthesized via the potentiostatic and cyclic voltammeteric methods, respectively. The morphology and structure of the obtained CeO₂ were characterized by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). A possible formation mechanism has been suggested to illuminate the relationship between the preparation condition and the morphology of CeO₂.     

Solvent effect on synthesis of zirconia support for tungstated zirconia catalysts

Solvothermal reaction of zirconium n-butoxide (ZNB) in different solvent media, such as 1,3-pentanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol resulted in the formation of zirconium dioxide (ZrO₂) nanostructure. Then, the 15%W/ZrO₂ (WZ) catalysts using different zirconia supports were prepared by impregnation method. The effects of solvent on preparation of zirconia on the catalytic performance of WZ catalysts in esterification of acetic acid and methanol at 60 °C were investigated. The experimental results showed that ZrO₂ particles prepared in 1,4-butanediol (ZrO₂-BG) have a spherical shape, while in other glycols the samples were irregularly-shaped particles. The reaction results of esterification illustrated that the W/ZrO₂-BG catalysts had high surface acidity and showed high acetic acid conversion. The W/ZrO₂-PeG catalysts (ZrO₂ particles prepared in 1,5-pentanediol, PeG) exhibited the lowest surface acidity among other samples due to strong interaction of proton species and the zirconia supports as proven by TGA. One of the possible reasons can be attributed to different amounts of carbon residue on the surface of catalysts.     

MnO2 with controlled phase for use in supercapacitors

Nanostructured MnO₂ has been synthesized using a simple and rapid microwave‐assisted hydrothermal (MHT) technique through the decomposition of KMnO₄ in a hydrochloric acid solution. The effects of hydrothermal temperature and ramp rate were examined and discussed. It was found that a lower temperature (140°C) favors the formation of cauliflower‐like δ‐MnO₂ particles while a higher temperature (160°C, 180°C, or 200°C) favors the formation of α‐MnO₂ nanorods. The dimensions of the obtained MnO₂ nanorods were affected by the ramp rate. The cauliflower‐like δ‐MnO₂ particles have higher specific surface areas than the α‐MnO₂ nanorods. Supercapacitors having the obtained MnO₂ as the electrodes were evaluated using cyclic voltammetry and electrochemical impedance spectroscopy in a 1 mol·L^?1 Na₂SO₄ solution within a potential window of ?0.1‐0.9 V. The cauliflower‐like δ‐MnO₂ electrodes give higher capacitance, up to 202 F/g, than the nanorods α‐MnO₂ electrodes, at most 61 F/g.     

Zirconium oxide supported on Pd(100): Characterization by scanning tunneling microscopy and tunneling spectroscopy

Scanning tunneling microscopy (STM) and tunneling spectroscopy (TS) were used to characterize the structure of a model metal-supported dispersed metal oxide, ZrO₂ on Pd(100). STM images illustrate changes in the surface morphology of the ZrO₂ resulting from various chemical treatments. When the sample was treated in O₂, the ZrO₂ appeared as a smooth, featureless overlayer of varying thickness wetting the Pd. After treatment in H₂, the ZrO₂ formed non-wetting particles on the Pd, with a sharp Pd-ZrO₂ interface. TS provided a fingerprint that verified the presence of a semiconducting overlayer on a metallic support. These results appear to be consistent with X-ray absorption spectra of ZrO₂ supported on Pd black, reported elsewhere.     

Synthesis and gas sensing properties of SnO<Subscript>2</Subscript> nanoparticles with different morphologies

The SnO₂ particles with different morphologies of nanorod, nanosheet, nanoparticle and nanodot were synthesized by liquid-phase methods. In addition, Pt was loaded on each prepared SnO₂ by dispersing SnO₂ particles into PtCl₄ ^2? aqueous solutions containing 0.67 vol% methanol, followed by UV light irradiation for 6 h. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurement. The gas sensing properties of the synthesized SnO₂ were tested by detecting the change in electric resistivity in flowing aceton and methanol gases with nitrogen base. The gas sensing properties greatly changed depending on not only the specific surface area, but also the exposed crystal plane, i.e., the SnO₂ nanorods exposing (111) planes showed the excellent sensitivity and quick response ability, indicating the excellent gas sensing ability of the (111) plane. Furthermore, the Pt loading exceedingly enhanced the gas sensing properties.     

Experimental investigation of mechanical,thermal, and ablation performance of ZrO2/SiC modified C-Ph composites

In this study, an effort has been made to improve the mechanical, thermal, and ablation performance of carbon-phenolic (C-Ph) composites. The ZrO₂, SiC, and ZrO₂/SiC hybrid fillers were synthesized using sol-gel method followed by individual incorporation into C-Ph composites. The thermal stability and flexural strength of these C-Ph composites were analyzed using thermogravimetry analysis and three-point bending test, respectively. A significant improvement in the flexural strength and modulus of the reinforced C-Ph composites was observed and also exhibited the higher thermal stability. The oxyacetylene flame test was conducted to measure the ablation behavior of these filler reinforced C-Ph composites under a heat flux of 4.0 MW/m² for 60 seconds. ZrO₂/SiC0.5 reinforcement in the C-Ph composite decreased the linear and mass ablation rates by 46% and 22%, respectively when compared with pure C-Ph composite. The surface morphology analysis revealed that the burnt composite covered with the ZrC ceramic phase and SiO₂ bubble-like structure, which could have improved the ablation resistance of composites. These results were found well within the acceptable range when using the surface energy dispersive spectroscopy and X-ray diffraction analysis.