Refractive materials for interlayer optical contacts with TiO2‐based organic/inorganic hybrids

Organic/inorganic hybrid materials were prepared by synthesizing from titanium tetraisopropoxide (TTIP), diethanolamine (DEOA), and water. Formulating the materials with thermosetting polymers, the composites were designed for refractive optical contacts with heat lamination of a film having >50 μm thickness. Inherent difficulties of TiO₂ and sol‐gel reaction of TTIP, i.e. photocatalytic properties and prompt sol‐gel reaction to form large TiO₂ particle, were avoided by stabilizing Ti with use of DEOA. The reactivity of the sol‐gel reaction and formation of TiO₂ crystal structure were suppressed by DEOA. However, suppression of the photocatalytic properties was not enough and needed a use of anti‐oxidant agent, 2,6‐di‐t‐butyl‐p‐cresol (BHT). The titanium‐based organic/inorganic hybrid materials and its epoxy composites were transparent in visible wavelength region and gave in the range of 1.66 to 1.73 of refractive indices depending on stoichometric parameters of TTIP, water, and DEOA for the hybrid materials. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Fabrication of superhydrophobic titanium surfaces by anodization and surface mechanical attrition treatment

A superhydrophobic surface of titanium was fabricated by anodization in sodium chloride solution followed by immersion in perfluorodecyltriethoxysilane. The surface characteristics of the anodic film (morphology, composition, microstructure, and adhesion) were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and scratch testing. The anodic film was comprised of TiO₂ and TiCl₃ with a thickness of 50 nm. The anodized titanium surface exhibited a hierarchical structure, which consisted of a microscale horn structure with a nanoscale strip-overlay. This structure provided superhydrophobicity (water contact angle: 151.9° and sliding angle: 3°) following the immersion process. Furthermore, coverage of the hierarchical structure on the anodized titanium surface was improved by performing surface mechanical attrition treatment (SMAT) to grain-refine titanium surface which was then anodized and it enhanced a slightly increased water contact angle. The thickness (200 nm) of the anodic film on the SMAT-pretreated titanium surface was much higher than that on the titanium surface (50 nm). This resulted from a large number of grain boundaries on the surface serving as a fast diffusion path during anodization. However, the adhesion of the SMAT-and-anodized film was worse than that formed by anodization only. This is due to a large number of pores within the SMAT-and-anodized film.     

Dye sensitized solar cells based on hydrothermally grown TiO2 nanostars over nanorods

A rutile titanium dioxide nanostar over nanorods is synthesized by a simple and cost-effective hydrothermal deposition method onto conducting glass substrates. In order to study the effect of precursor concentrations on the growth of TiO₂, the amount of Ti precursor is varied from 0.1 mL to 0.5 mL at the interval of 0.1 mL. These TiO₂ thin films are characterized for their morphological, structural, optical and J–V properties using various characterization techniques. SEM images showed the formation of densely packed nanostars over nanorods for 0.3 mL titanium tetraisopropoxide (TTIP). XRD patterns show the formation of polycrystalline TiO₂ with tetragonal crystal structure possessing rutile phase. Further, the TiO₂ thin films are used for dye sensitized solar cells using N3-dye.The films were photoelectrochemically active and can be viewed as a promising application in DSSC with maximum current density of 1.459 mA/cm² with enhanced photovoltage of 696 mV for the sample prepared at 0.3 mL TTIP.     

Preparation of submicron-sized porous titanium oxide particles by the swelling process

A method to prepare submicron-sized porous titanium oxide (TiO₂) particles is studied in this work. Polystyrene (PS) template particles were prepared by emulsifier-free emulsion polymerization. The polymer templates dispersed in the aqueous solution have been used for entrapping titanium(IV) isopropoxide (TTIP), by the swelling process in a suitable solvent mixture containing a swelling solvent (good solvent or poor solvent), a TiO₂ precursor (TTIP), and a chelating agent (AcAc), within the polymer templates, followed by hydrolysis/condensation reaction of TTIP confined in PS template particles by the addition of the chelating agent. The influence of various reaction parameters, such as mixtures of different weight ratios between the PS particles and desiccative TTIP, AcAc amounts, and the swelling solvent amounts and type, on the size, bulk, and composition of the particles was investigated. Porous TiO₂ particles have been prepared by thermal decomposition of the PS templates at 500 °C.     

Formation of TiO2 hollow microparticles by spraying water droplets into an organic solution of titanium tetraisopropoxide (TTIP) — Effects of TTIP concentration and TTIP-protecting additives

Hollow, spherical TiO₂ microparticles of several tens of micrometers in diameter can be prepared by spraying water into an organic phase containing titanium tetraisopropoxide (TTIP) as a titanium source. The concentration of TTIP did not affect the shell thickness. On the contrary, the shell thickness was increased with the concentration of the additives such as acetic acid and acetylacetone, having effects to protect TTIP from hydrolysis and condensation. The formation of a hollow particle was described by a simple model involving the hydrolysis of TTIP at the water–oil interface, the inward diffusion of hydrolyzed titanium hydroxide through the passage in the shell and its incorporation into the TiO₂ shell by condensation. The reduction of porosity of shell inhibits the diffusion, resulting in the formation of hollow structure. The simulation based on this model predicted that the shell thickness increased as the diffusion rate increased or the reaction rate decreased, and was independent of the outer TTIP concentration. These predictions were in qualitative agreement with the experimental results.     

Fabrication and deodorizing efficiency of nanostructured core-sheath TiO2 nanofibers

In this work, we report the fabrication and deodorizing efficiency of nanostructured core-sheath TiO₂ nanofibers prepared by a combined technique of electrospinning and metallization. The morphologies and crystal structures of the resultant nanofibers were investigated by emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and wide angle X-ray diffraction (WAXD), respectively. The influence of annealing conditions, such as annealing temperature and time, various titanium isopropoxide (TTIP) weight fractions, which are based on the weight of the poly(vinyl acetate) (PVAc), on morphologies and crystal structures was evaluated for the nanostructured core-sheath TiO₂ nanofibers. UV blocking properties and deodorizing efficiency were also measured by UV-visible spectrometer and formaldehyde detector tube at room temperature, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of super-hydrophilic amorphous titanium dioxide thin film via PECVD process and its application to dehumidifying heat exchangers

The super-hydrophilic amorphous titanium dioxide (TiO₂) thin film was prepared by plasma-enhanced chemical vapor deposition (PECVD) process for an application to dehumidifying finned-tube heat exchangers. The chemical components and surface structure were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM). The wettability and long-term durability were investigated by measuring the water contact angle and by performing wet/dry cycles. The samples were subjected to 1000 times of wet/dry cycles to establish long-term durability. The water contact angle of the amorphous TiO₂ thin film was about 8° at as-deposited film with O₂ plasma treatment and was about 15° after 1000 wet/dry cycles. The amorphous TiO₂ thin film had excellent wettability and long-term durability under full wetting conditions.     

Growth behavior of titanium dioxide thin films at different precursor temperatures

The hydrophilic TiO₂ films were successfully deposited on slide glass substrates using titanium tetraisopropoxide as a single precursor without carriers or bubbling gases by a metal-organic chemical vapor deposition method. The TiO₂ films were employed by scanning electron microscopy, Fourier transform infrared spectrometry, UV-Visible [UV-Vis] spectroscopy, X-ray diffraction, contact angle measurement, and atomic force microscopy. The temperature of the substrate was 500°C, and the temperatures of the precursor were kept at 75°C (sample A) and 60°C (sample B) during the TiO₂ film growth. The TiO₂ films were characterized by contact angle measurement and UV-Vis spectroscopy. Sample B has a very low contact angle of almost zero due to a superhydrophilic TiO₂ surface, and transmittance is 76.85% at the range of 400 to 700 nm, so this condition is very optimal for hydrophilic TiO₂ film deposition. However, when the temperature of the precursor is lower than 50°C or higher than 75°C, TiO₂ could not be deposited on the substrate and a cloudy TiO₂ film was formed due to the increase of surface roughness, respectively.     

A mechanical and modelling study of magnetron sputtered cerium-titanium oxide film coatings on Si (100)

Ce/Ti mixed metal oxide thin films have well known optoelectrical properties amongst several other physio-chemical properties. Changes in the structural and mechanical properties of magnetron sputtered Ce/Ti oxide thin films on Si (100) wafers with different Ce:Ti ratios are investigated experimentally and by modelling. X-ray Photoemission Spectroscopy (XPS) and X-ray diffraction (XRD) confirm the primary phases as trigonal Ce₂O₃ and rutile form of TiO₂ with SiO₂ present in all prepared materials. FESEM imaging delivers information based on the variation of grain size, the mixed Ce/Ti oxides providing much smaller grain sizes in the thin film/substrate composite. Nanoindentation analysis concludes that the pure cerium oxide film has the highest hardness value (20.1?GPa), while the addition of excess titanium oxide decreases the hardness of the film coatings. High temperature in-situ XRD (up to 1000?°C) results indicate high thermal phase stability for all materials studied. The film with Ce:Ti?=?68%:32% has a new additional minor oxide phase above 800?°C. Contact angle experiments suggest that the chemical composition of the surface is insignificant affecting the water contact angle. Results show a narrow band of 87.7–95.7° contact angle. The finite element modelling (FEM) modelling of Ce/Ti thin film coatings based on Si(100); Si(110); silica and steel substrates shows a variation in stress concentration.     

Preparation of titanium dioxide/activated carbon composites using supercritical carbon dioxide

The penetration of titanium tetraisopropoxide (TTIP) dissolved in supercritical CO₂ into the nano-spaces of an activated carbon was studied for the preparation of a TiO₂-coated activated carbon. The conversion of TTIP to TiO₂ through thermal decomposition was confirmed by evolved gas analysis during heat treatment under a N₂ flow. Acetone was detected in the evolved gas, which suggested that some isopropoxide groups in TTIP reacted with the carbonyl groups on the activated carbon surface. This chemical reaction with carbon is expected to be advantageous for favorable attachment to the carbon surface. The crystallite size of anatase in the TiO₂/carbon composites was 4.1 nm, as estimated from the X-ray diffraction pattern, which almost corresponded to the graphene crystallite size; L_a (3.3-3.4 nm), as estimated from both the Raman spectrum and X-ray diffraction pattern. As the size of the crystallite prepared by bulk condensation of TTIP was more than 15 nm, these results confirmed that the anatase crystals were present in the carbon pores. Also, it was suggested that the crystal growth of TiO₂ was influenced by the carbon nano-spaces.     

The effect of TiO2 morphology on the surface modification of poly (ethylene terephthalate) for electroless plating

In this study, a surface modification of the poly (ethylene terephthalate) (PET) film using TiO₂ photocatalytic treatment was investigated. In order to enhance the adhesion strength between the PET film and the electroless copper film, the effects of TiO₂ crystal forms, TiO₂ particle sizes, and TiO₂ content, as well as treatment condition, upon the surface contact angle, surface characterization, and adhesion strength were investigated. Anatase TiO₂ with a particle size of 5 nm had a high catalytic activity and dispersibility in aqueous solution. After the optimal photocatalytic treatment, the surface contact angle of the PET film decreased from 84.4° to 19.8°, and the surface roughness of the PET film increased from 36 to 117 nm. The adhesion strength between the PET film and the electroless copper film reached 0.89?KN?m^?1. X-ray photoelectron spectroscopy analyses indicated the carbonyl group was formed on the PET surface after photocatalytic treatment, and the surface hydrophilicity was improved. Consequently, TiO₂ photocatalytic treatment is an environmentally friendly and effective method for the surface modification of the PET film.     

Performance enhancement of dye-sensitized solar cells using nanostructural TiO2 films prepared by a graft polymerization and sol–gel process

Nanostructural TiO₂ films with large surface areas were prepared by the combined process of graft polymerization and sol–gel for use in dye-sensitized solar cells (DSSCs). The surface of the TiO₂ nanoparticles was first graft polymerized with photodegradable poly(methyl methacrylate) (PMMA) via atom transfer radical polymerization (ATRP), after which the particles were deposited onto a conducting glass. The PMMA chains were removed from the TiO₂ films by UV irradiation to generate secondary pores, into which titanium isopropoxide (TTIP) was infiltrated. The TTIP was then converted into small TiO₂ particles by calcination at 450 °C, as characterized by energy-filtering transmission electron microscopy (EF-TEM) and field emission scanning electron microscopy (FE-SEM). The nanostructural TiO₂ films were used as a photoelectrode in solid-state DSSCs; the energy conversion efficiency was 5.1% at 100 mW/cm², which was higher than the values achieved by the pristine TiO₂ (3.8%) and nongrafted TiO₂/TTIP photoelectrodes (3.3%). This performance enhancement is primarily due to the increased surface area and pore volume of TiO₂ films, as revealed by the N₂ adsorption–desorption isotherm.     

Preparation of hydrophobic SiO<Subscript>2</Subscript>@(TiO<Subscript>2</Subscript>/MoS<Subscript>2</Subscript>) composite film and its self-cleaning properties

TiO₂/MoS₂ composite was encapsulated by hydrophobic SiO₂ nanoparticles using a sol–gel hydrothermal method with methyltriethoxysilane (MTES), titanium tetrachloride (TiCl₄), and molybdenum disulfide (MoS₂) as raw materials. Then, a novel dual functional composite film with hydrophobicity and photocatalytic activity was fabricated on a glass substrates via the combination of polydimethylsiloxane adhesives and hydrophobic SiO₂@(TiO₂/MoS₂) composite particles. The influence of the mole ratios of MTES to TiO₂/MoS₂ (M:T) on the wettability and photocatalytic activity of the composite film was discussed. The surface morphology, chemical compositions, and hydrophobicity of the composite film on the glass substrate were investigated by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and water contact angle (water CA) measurements. The results indicated that the composite film exhibited stable superhydrophobicity and excellent photocatalytic activity for degradation of methyl orange (MO) even after five continuous cycles of photocatalytic reaction when M/T was 7:1. The water CA and degradation efficiency for MO remained at 154° and 94%, respectively. Further, the composite film showed a good non-sticking characteristic with the water sliding angle (SA) at about 4°. The SiO₂@(TiO₂/MoS₂) composite consisting of hydrophobic SiO₂ nanoparticles and TiO₂/MoS₂ heterostructure could provide synergistic effects for maintaining long-term self-cleaning performance.     

Simultaneous Laser‐Induced Reduction and Nitrogen Doping of Graphene Oxide in Titanium Oxide/Graphene Oxide Composites

Titanium oxide/graphene oxide nanocomposite thin films were grown by ultraviolet (UV) matrix‐assisted pulsed laser evaporation (MAPLE) technique in controlled oxygen or nitrogen atmospheres. The effect of graphene oxide addition and laser‐induced reduction as well as nitrogen doping on the wetting behavior and photoactive properties of titanium oxide thin films was investigated. Hydrophobic to hydrophilic conversion of titanium oxide films takes place progressively as the relative amount of graphene oxide in the MAPLE composite target increases. Nitrogen doping leads to further decrease of the static contact angle of the composite films. The photoactive properties of the synthesized materials were investigated through the evolution of contact angle under UV light irradiation. Wetting properties of both TiO₂ and TiO₂/GO nanocomposite thin films improved upon exposure to UV light.     

Characterization and photocatalytic performance of nanosize TiO2 powders prepared by the solvothermal method

The solvothermal reaction of titanium tetra-isopropoxide (TTIP) in different alcohol solvents was investigated in the pressure range 40±2 bar to prepare Titanium (IV) oxide. The results show that the physical properties of the products, such as crystal size, shape, and structure, are strongly in fluenced by the types of solvents and temperature during the reaction. The effects of reaction conditions on the physical properties and the crystal structure of powder were investigated by using XRD, SEM, DLS, DSC and BET. The obtained TiO₂ powder prepared at an organic solvent condition exhibited submicron size and huge surface area with a narrow size distribution but some agglomeration. TiO₂ powder prepared at 1,4-butanediol and 623 K shows the highest photoactivity on the photodegradation rate of methyl orange.     

Continuous Generation of TiO 2 Nanoparticles by an Atmospheric Pressure Plasma-Enhanced Process

A novel method for the continuous generation of titanium dioxide (TiO₂) nanoparticles by dielectric barrier discharge process is presented using titanium tetraisopropoxide (TTIP) and water as precursors. The aerosol generator employs an atmospheric pressure plasma enhanced nanoparticle synthesis (APPENS) process of alternative current (AC). The influences of applied voltage, frequency and precursor molar ratio on the generated particles were described by the SEM, XRD, and SMPS analyses. The results showed that TiO₂ particles appear to be in a broad size range of bi-modal distribution when no voltage is applied. While after applying the AC plasma they become uni-modal distributed with average sizes range from around 30 to 60 nm. The applied electric frequency can be adjusted to either generate nanoparticles after the plasma reactor or develop a thin film in the reactor. An increase in the precursor molar ratio leads larger particles with a broader size distribution.     

Easy formation process of anatase-TiO2 coating layer strongly bonded to titanium metal surface

Because of the formation of a surface passive film (rutile TiO₂) on its surface layer, titanium metal shows adequate corrosion resistance. As the surface layer (passive film) of titanium metal is very stable, any functionalization of the titanium metal has been generally performed using relatively complicated methods. This is because any direct oxidation of titanium metal only leads to the formation of rutile TiO₂ over the entire temperature range. Chemical reactions using titanium chemicals can easily produce anatase TiO₂ at temperatures of ≤600°C. Using precursors is one of the ways of producing an anatase TiO₂ coating on titanium metal. However, in previous studies, anatase TiO₂ layers easily peeled off when they were used in flowing water. Herein, we describe a simple process for obtaining an anatase TiO₂ coating layer strongly bonded to the titanium metal surface. In our process, titanium metal was pretreated with a reducing agent to create a surface TiH₂ layer, whose condensation reaction easily proceeds with a precursor (composed of oxalic acid and tetra-butoxy titanium). Subsequently, the treated titanium metal was calcinated at 550°C in air to achieve strong bonding between the anatase TiO₂ coating layer and titanium metal surface. The treated titanium metal exhibited excellent photocatalytic activity.     

Fabrication of ambient-curable superhydrophobic fluoropolysiloxane/TiO2 nanocomposite coatings with good mechanical properties and durability

Ambient-curable superhydrophobic fluoropolysiloxane/TiO₂ nanocomposite coatings were prepared simply by blending a hydrophobic binder with TiO₂ nanoparticles. The binder consisted of triethoxysilyl-terminated fluoropolysiloxane (FPU), polymethylphenyl-siloxane (PMPS), and 3-aminopropyltriethoxysilane. The surface wettability, morphology, mechanical properties, and artificial weatherability were thoroughly investigated, using contact angle analysis, SEM, AFM, pendulum hardness rocker measurements, and nanoindentation measurements, respectively. Superhydrophobic coatings could be fabricated with FPU/PMPS weight ratios of higher than 1:9, and TiO₂ loads of over 35 wt%. The superhydrophobic coatings had good mechanical strength, excellent artificial weathering durability, and resistance to organic contaminants. It was demonstrated that the TiO₂ nanoparticles acted both as building blocks for the construction of the micro-/nano-structured surface, and as a photocatalyst for the decomposition of organic contaminants.     

Laccase‐catalyzed polymerization drying of Chinese lacquer sap with TiO2 nanoparticles

Nano‐TiO₂/lacquer hybrid coatings are prepared by the blend of nano‐TiO₂ and lacquer sap. Nano‐TiO₂ particles are involved in the laccase‐catalyzed polymerization process of urushiol, which improves the properties of lacquer film. With increasing nano‐TiO₂ from 0 to 5 wt %, the drying time of lacquer film to reach hardened dryness decreases from >12 h to 8 h 30 min under 30 °C and 80% relative humidity. Gel permeation chromatography analysis shows that the addition of nano‐TiO₂ accelerates the polymerization of urushiol. It is also related to the formation of Ti? O? C bonds due to the reaction between nano‐TiO₂ and the radicals produced by laccase‐catalyzed oxidation. The pencil hardness, flexibility, and adhesion of hybrid lacquer film can be improved and reach 4H, 1 mm, and grade 2, respectively. Its inhibition rate against Escherichia coli and Staphylococcus aureus increases from 22.6% and ?21.4% to 49.2% and 67.8%, respectively. Furthermore, nano‐TiO₂ hybrid lacquer films also possess higher thermo‐stability than the raw lacquer film. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45865.     

超临界CO2快速膨胀法制备SiO2/聚氨酯超疏水涂层

用超临界CO₂快速膨胀法制备了SiO₂/聚氨酯超疏水涂层。首先用十三氟辛基三乙氧基硅烷（F-硅烷）和γ-(甲基丙烯酰氧基)丙基三甲氧基硅烷（KH-570）改性纳米二氧化硅,制备出含双键的纳米二氧化硅粒子,将其分散在超临界CO₂中,再利用超临界CO₂快速膨胀法将其喷射到双键封端的且已添加了引发剂的聚氨酯涂层表面,通过加热,使纳米二氧化硅粒子接枝在聚氨酯涂层表面,形成稳固粗糙结构,获得了超疏水性质。研究了喷嘴温度、反应釜温度和压力、偶联剂配比、表面粗糙度对涂层疏水性的影响。结果表明：涂层的静态水接触角可达到169.1°±0.6°;在喷嘴和釜内温度都为90℃,釜内压力为16 MPa,F-硅烷和KH-570配比为1∶1,表面粗糙度为7.3 μm时,所制得涂层具有较好的超疏水性,且具有优良的耐刮伤性。该法高效环保,涂层性能优良,适于大面积制备。