Papers by Keyword: SnO₂

Abstract: It is shown that successive ionic layer deposition (SILD) method can be used for a surface functionalizing of the SnO₂ films and improving their gas sensing properties. It was found that gold clusters deposited on the SnO₂ surface were active to both reducing and oxidizing gases. However, the most significant increase in the conductivity response was observed during detection of ozone. It was established that the effect of the SnO₂ surface decoration by AuNPs on gas sensing characteristics depends on the number of deposition cycles, i.e. the size of gold clusters. Moreover, there is an optimal level of surface doping, and it corresponds to a very small degree of the surface coverage by gold. Models showing the promotional role of Au additives were then discussed, and the mechanism of sensitization in the SnO₂:Au-based gas sensor are proposed.

Abstract: SnO₂ nanowires have been fabricated using thermal evaporation of the mixed powders of SnO₂ and active carbon with Au catalysts. The morphology and structure of the prepared nanowires are determined on the basis of field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometer (EDS), x-ray diffraction (XRD) and transmission electron microscopy (TEM). The comb-shape interdigitating electrode made by MEMS technology is used to auxiliary investigating the gas sensing performance of the synthesized SnO₂ nanowires. The SnO₂ nanowires have sensing response to acetylene concentration of 1000 ppm under operated temperature of 300°C. The gas sensing mechanism is attributed to the gas adsorption and desorption processes occurring on the surface of the gas sensing material.

Abstract: SnO₂ nanocrystalline thin films (NCTFs) with high quality and low infrared emissivity were synthesized through a simple hydrothermal process designed by orthogonal design theory. The microstructure, morphology, photoluminescence (PL) property and the infrared emissivity (IRE) property of as-prepared products were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fluorescence spectrophotometer, and infrared spectroradio meter (ISM) respectively. The results show that two emission peaks are observed in PL spectra, which can be deconvoluted by Gaussian profile fitting into four emission peaks centered at about 380, 420, 460 and 520 nm respectively. The influences of crystallinity, concentration of particles and resistivity on IRE were systematically investigated, revealing that the better crystallinity, higher particle density and better conductivity are favorable for lowering IRE.

Abstract: Fabrication of high sphericity, monodispersed microspheres (100~600 nm) of various oxides (SiO₂, TiO₂, ZnO, In₂O₃, SnO₂) via sol-gel process and polystyrene (PS) microspheres (200~400 nm) via emulsion polymerization is presented. A high colloidal stability suspension was obtained by adjusting the zeta potential of such spheres and pH of the colloid. The 3-D photonic crystal (PhC) templates of opaline structure on ITO-coated glasses and silicon wafers were easily formed under electrophoretic self-assembly (EPSA) of microspheres under the influence of exerting electrical forces. Different setups of counter-electrode were attempted to establish an electrical field. The lattice constant of an ordered opal structure by EPSA can also be tuned by the electrical field gradient. Interestingly various self-assembled 3-D structures of silica microspheres in either symmetrical curvilinear profile or triangular ridges can be produced through EPSA route using specific counter-electrode setups. The measured optic properties of such 3-D PhC templates manifest photonic bandgap (PBG) based on planar-wave expansion (PWE) simulation to verify the existence of real PBG in PhC samples with tunable nanostructures. The PS PhC templates are currently used to easily transform into inverse opal structure (IOS) by infiltrating sol of other oxides with high dielectric constant (e.g. ZnO or TiO₂) and filled with metallic nanoparticles (Ni or Cu) by electrochemical deposition or chemical bath deposition (CBD).

Abstract: A promising anode material for lithium ion batteries is reported in this paper. It is one-dimensional SnO₂−graphene composite nanofibers (SnO₂−G nanofibers) fabricated by using electrospinning technique. In the study, X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to characterize its structural and morphological properties. Samples with different ratio of SnO₂ to graphene (wt%) are prepared to investigate its electrochemical performance. Galvanostatic charge/discharge tests reveals that Li-insertion/extraction is carried out through a two-phase reaction mechanism that is supported by galvanostatic charge−discharge profiles. It is found that the optimal proportion of SnO₂ to graphene is 8:1 (wt%) for the electrospun composite materials. Furthermore, micro thin film batteries have been fabricated and tested. The results show that initial discharge capacity is 301.86 mA h g⁻¹ at current density of 50 μA g⁻¹, and battery can retain 63.3% of reversible capacity after 300 cycles, which is 5 times higher than bare SnO₂.

Abstract: A reproducible organometallic approach was used in order to prepare zinc oxide gas sensitive layers. Various ZnO nanostructures with well-defined morphology were prepared by controlled hydrolysis of suitable organometallic precursor. These nanomaterials were deposited on miniaturized gas sensors substrates by an ink-jet method. The as prepared devices were tested towards different reducing gases, namely: CO, C₃H₈, and NH₃. We showed that the morphology of these nanostructures significantly influences the sensor response level and selectivity to the reducing gases.

Abstract: We report structural, optical and magnetic behavior of polyvinylpyrrolidone (PVP) capped iron containing tin dioxide (SnO₂) nanoparticles synthesized via facile cost effective, environmentally benign, low temperature hydrothermal process. X-ray diffraction pattern of pristine SnO₂ revealed the formation of tetragonal rutile phase with lattice parameter, a = 0.479 nm, c = 0.323 nm; crystallite size being about 3 nm. The incorporation of iron resulted in progressive increase of unit cell parameters and average crystallite size, despite the fact that Fe³⁺ ion has lower ionic radius than Sn⁴⁺. The high resolution electron micrographs revealed the [110] preferred crystal orientation.

Abstract: ZnO/SnO₂/montmorillonite that could flocculate and restrict the growth of Microcystis aeruginosa used as a probe of cyanobacterial was prepared and characterized by means of XRD and TEM. In ZnO/SnO₂/montmorillonite, ZnO and SnO₂ nanoparticles disperse on montmorillonite surface. The determinations of chlorophyll a levels and total soluble protein content demonstrate that ZnO/SnO₂/montmorillonite has stronger flocculation effect on Microcystis aeruginosa compared with natural montmorillonit under visible light, and has a good photocatalytic degradation effect on Microcystis aeruginosa under UV irradiation. Under UV, 96.79% removal efficiency is achieved for Microcystis aeruginosa in 1h using 50mg.L^-1 ZnO/SnO₂/montmorillonite. The synergy of absorption flocculation and photocatalysis of ZnO/SnO₂/montmorillonite promotes the removal of Microcystis aeruginosa.

Abstract: The effect of the formation of CuO flowers and SnO₂ on tin whiskers formation and growth in 30°C/60%RH environmental condition for tin surface finish had been studied. Immersion plating method was used to coat a layer of tin onto a copper, Cu substrates. The coated surface was subjected to external stress by micro hardness indenter with 2N load in order to simulate an external stress in coating layer and to promote the formation of tin whiskers. FESEM and EDX was used to study the type and chemical composition of whiskers and oxides formed. Image analyser was used to measure the whiskers length using JEDEC Standard No 22-A121A. After 1 week of the exposure under 30°C/60%RH environmental condition, kinked-type whiskers were formed and the whiskers growth were discontinued at week 4 due to the distruction at the end-tip of kinked-type tin whisker to grow further when it touched the coating surface. An obervation until 52 weeks of exposure time found that the formation and growth of CuO flowers and the oxidation of non-kinked-type of tin whiskers to form SnO₂ promoted by external stress also contributed to the discontinuity of whiskers growth.

Abstract: SnO₂ ceramics were synthesized by SPS. Phase compositions and microstructures are examined by XRD, SEM and EDS, respectively. Sb₂O₃ used in our research were beneficial to lower the sintering temperature and promote the densification of SnO₂ ceramics. The SEM results show a homogeneous microstructure is approached consistent with the density measurement at 850-1000 °C. The XRD show all antimony ions came into the lattice of SnO₂ to substitute for tin ions when the content of Sb₂O₃ are 0.1-2.5 mol%. The grain boundary are no SnO and Sb₂O₃, only SnO₂. The mechanism of SPS sintering process is the local high temperature to produce the abnormal growth of the grain, and evaporation-condensation; and solid solution of Sb³⁺ go into the SnO₂ lattice produce oxygen vacancy to promote densification