Shu Yin

Smart window coating based on F-TiO2-KxWO3 nanocomposites with heat shielding, ultraviolet isolating, hydrophilic and photocatalytic performance

A series of smart window coated multifunctional NIR shielding-photocatalytic films were fabricated successfully through KxWO3 and F-TiO2 in a low-cost and environmentally friendly process. Based on the synergistic effect of KxWO3 and F-TiO2, the optimal proportion of KxWO3 to F-TiO2 was investigated and the FT/2KWO nanocomposite film exhibited strong near-infrared, ultraviolet light shielding ability, good visible light transmittance, high photocatalytic activity and excellent hydrophilic capacity. This film exhibited better thermal insulation capacity than ITO and higher photocatalytic activity than P25. Meanwhile, the excellent stability of this film was examined by the cycle photocatalytic degradation and thermal insulation experiments. Overall, this work is expected to provide a possibility in integrating KxWO3 with F-TiO2, so as to obtain a multifunctional NIR shielding-photocatalytic nanocomposite film in helping solve the energy crisis and deteriorating environmental issues.

Solvothermal synthesis of different phase N-TiO2 and their kinetics, isotherm and thermodynamic studies on the adsorption of methyl orange.

The different crystal forms of nitrogen doped-titanium oxide (N-TiO2) with different particle sizes were produced by precipitation-solvothermal method and their adsorption mechanism were also investigated. The adsorption kinetics showed that rutile N-TiO2 displayed higher adsorption capacity than anatase for methyl orange (MO) and its adsorption behavior followed the pseudo-second-order kinetics. The equilibrium adsorption rate of N-TiO2 for MO was well fitted by the Langmuir isotherm model and the adsorption process was monolayer adsorption. The adsorption capacity decreased with increasing temperature. The average correlation coefficient was beyond 97%. The thermodynamic parameters (ΔaGm(ө), ΔaHm(ө), and ΔaSm(ө)) were calculated. It was found that anatase and rutile N-TiO2 had different adsorption enthalpy and entropy. The smaller the particle size, the greater the surface area and surface energy was, then ΔaGm(ө) decreased and the standard equilibrium constant increased at the same time. The adsorption process onto different crystalline phase N-TiO2 was exothermic and non-spontaneous.

Preparation of Stable Silver Nanoparticles Having Wide Red-To-Near-Infrared Extinction

Abstract The synthesis of silver nanoparticles (AgNPs) within the interlayer space of transparent layered titania nanosheet (TNS) films is investigated. A considerable number of silver ions (≈70% against the cation exchange capacity of the TNS) are intercalated in the TNS films using methyl‐viologen‐containing TNSs as a precursor. The silver ion (Ag+)‐containing TNS films are treated with aqueous sodium tetrahydroborate (NaBH4), resulting in a gradual color change to bright blue. Various structural analyses clearly show that crystalline AgNPs are generated within the interlayer space of the TNSs. The NaBH4‐treated films show intense and characteristic near‐infrared (NIR) extinction spectra up to 1800 nm. The stability of the AgNPs within the TNS against oxygen and moisture is also investigated, and 96% and 82% of the AgNPs remain after standing in air for 1 month and 1 year, respectively. The NIR extinctions of the AgNP‐containing TNS films are further extended by employing different preparation procedures, for example, using sintered TNS films as starting materials and irradiating the Ag+‐containing TNSs with ultraviolet (UV) light. The obtained AgNP‐containing TNS films exhibit photochemical activities in the production of hydrogen from ammonia borane under visible‐light irradiation and the decomposition of nitrogen monoxide under UV‐light irradiation.

Recent Advances in Visible-Light Driven Photocatalysis

Semiconductor photocatalysis has been considered a potentially promising approach for renewable energy and environmental remediation with abundant solar light. However, the currently available semiconductor materials are generally limited by either the har‐ vesting of solar energy or insufficient charge separation ability. To overcome the serious drawbacks of narrow light-response range and low efficiency in most photocatalysts, many strategies have been developed in the past decades. This article reviews the recent advancements of visible-light-driven photocatalysts and attempts to provide a compre‐ hensive update of some strategies to improve the efficiency, such as doping, coupling with graphene, precipitating with metal particles, crystal growth design, and heterostruc‐ turing. A brief introduction to photocatalysts is given first, followed by an explanation of the basic rules and mechanisms of photocatalysts. This chapter focuses on recent progress in exploring new strategies to design TiO2-based photocatalysts that aim to extend the light absorption of TiO2 from UV wavelengths into the visible region. Subsequently, some strategies are also used to endow visible-light-driven Ag3PO4 with high activity in photo‐ catalytic reactions. Next, a novel approach, using long afterglow phosphor, has been used to associate a fluorescence-emitting support to continue the photocatalytic reaction after turning off the light. The last section proposes some challenges to design high efficiency of photocatalytic systems.

Oxidation of Pentatitanium Trisilicide (Ti5Si3) Powder at High Temperature

The oxidation of pentatitanium trisilicide (Ti5Si3) powder at high temperature was investigated in order to determine the suitability of this ceramic material for advanced application in an oxidation atmosphere at high temperature. Titanium silicide has been attracted for years as an engineering ceramics due to its high hardness, high melting point, and good chemical stability. The samples were oxidized from 300 to 1000 °C for 1 to 5 h in air. The mass changes were measured to estimate the oxidation resistance of the sample. The mass gain of the sample oxidized at 1000 °C for 5 h was about 26 % of the theoretical oxidation mass change. The commercial powder, Ti5Si3 showed an excellent oxidation resistance at 1000 °C, because the surface film of both titanium dioxide and silicon dioxide formed by oxidation acted as an oxidation resistant layer.

Persistent Methyl Orange Degradation Ability of MgAl2O4:(Pr3+,Dy3+)/M-TiO2 Luminescent Photocatalyst

Metal ions (Cr, Ni, Co) doped titania (M-TiO2) coupled with the long after glow phosphor MgAl2O4:(Pr3+, Dy3+) particles were synthesized by the sol-gel method, with the best mass ratio of MgAl2O4:(Pr3+, Dy3+) to M-TiO2 as 4:6. MgAl2O4:(Pr3+, Dy3+)/M-TiO2 had the persistent methyl orange (MO) photocatalytic degradation ability and the photocatalytic degradation went on reacting more than 90 min in dark after turning off the light. MgAl2O4:(Pr3+, Dy3+) emitted the light as a light source in dark which was absorbed by M-TiO2. The differences of MgAl2O4:(Pr3+, Dy3+)/Cr-TiO2, MgAl2O4:(Pr3+, Dy3+)/Ni-TiO2 and MgAl2O4:(Pr3+, Dy3+)/Co-TiO2 might be attributed to the difference in the metal ions doping. The composite MgAl2O4:(Pr3+, Dy3+)/Cr-TiO2 revealed the highest ability of persistent photocatalytic degradation methyl orange. Different metal ions doping made the TiO2 with different band gap.

Synthesis of TiO2/Fly Ash Cenospheres by Sol–Gel Method and Their Photacatalytic Activities Under Visible Light

Fly ash is a solid waste discharged from thermal power plant. Specific surface area of floating fly ash cenospheres (FACs) would increase after it was modified. The photocatalytic composite of TiO2/FACs was successfully synthesized by sol-gel method using the carrier of modified FACs and tetrabutyl titanate as starting materials. The different influence factors on the photocatalytic performance of TiO2/FACs composites were characterized through SEM, EDS, XRD, UV-vis DRS and BET surface measurements. The UV-vis DRS spectra revealed that the absorption edge of TiO2 is 387 nm while that of TiO2/FACs photocatalysts red-shifts to 500 nm. Photocatalytic activity of TiO2/FACs was evaluated by the photocatalytic depigmentation of methyl orange solution (MO, 20 mg L-1, pH = 6.3) under visible light irradiation. It was found that the specific surface area, surface roughness and activity of FACs were increased by NaOH solution activation. The degradation rate of MO reaches 52% in 180 min under the visible light illumination. But too much FACs could decrease its photocatalytic activity and degradation rate. And the recovery test indicated that TiO2/FACs photocatalyst was rather stable, easy to recover from the treated wastewater.

Synthesis of morphology controllable aluminum nitride by direct nitridation of γ-AlOOH in the presence of N2H4 and their sintering behavior

ABSTRACT Direct nitridation process has been performed to synthesize morphology controllable aluminum nitrides (AlN). Three different morphologies of γ-AlOOH were treated under NH3 flow at 1400°C for 4 h. Hydrazine (N2H4) was employed in this study as a nitriding agent to promote nitridation reaction. In the presence of hydrazine, a high purity of aluminum nitride (AlN) could be achieved with less than 5 wt.% of oxygen impurities. Interestingly, after being exposed to elevated temperatures, the initial morphology was still retained. Whereas the TEM measurement indicated surface roughening due to the release of H2O. The investigation of sintering behavior of the prepared AlN powders revealed that plate-like morphology had the lowest shrinkage completing temperature (1574°C). GRAPHICAL ABSTRACT

Synthesis and characterization of glycolate precursors to MTiO3 (M = Ni2+, Co2+, Zn2+)

Abstract Novel glycolate precursors to metal titanates MTiO3 (M = Ni2+, Co2+, Zn2+) were synthesized by heating metal acetate and titanium isopropoxide in ethylene glycol up to 190 °C during distilling the water to avoid hydrolysis of precursors. These glycolate precursors were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), thermal analysis (TG-DTA), and scanning electron microscopy (SEM). The obtained three isostructural glycolate precursors were containing metal (Ni, Co, Zn), titanium, and ethylene glycol with a ratio of 1:1:4. The crystal growth processes of three precursors were different from each other. These precursors revealed homogeneous and well-defined rod-like structure with 0.5–3.0 μm in thickness and 4–20 μm in length. The obtained metal titanates were consisted of microrods with 0.4–1.5 μm in thickness and 2–15 μm in length.

Anatase Type Titanium Dioxide Prepared by Oxidation of Titanium Carbide

Titanium carbide has been attractive for years an engineering ceramics due to its high hardness, high melting point, and good chemical stability. Similarly, titanium dioxide has excellent anti-microbial ceramic material by photon energy. In this study, the anatase type titanium dioxide layer prepared by oxidation of the titanium carbide powder by high temperature oxidation in air atmosphere was investigated in order to determine the possibility of its photocatalyst materials by radiant energy. TiC powder samples of different grain size were gained by ball mill. These samples were oxidized at room temperature to high temperature. The samples exhibited a steady mass gain with increasing oxidation temperature. Based on the results of the X-ray diffraction analysis, anatase type TiO2 was detected on the titanium carbide samples. It is considered, the titanium carbide showed convension anatase type titanium dioxide layer produced by oxidation.