Titanium Dioxide Dispersions Research Articles

The effect of feed pretreatment on membrane microfiltration of titanium dioxide dispersions by ceramic tubular membranes

The influence of coagulant type and operating parameters on crossflow microfiltration of aqueous dispersions of titanium dioxide has been examined. The experiments were carried out with a tubular ceramic microfiltration membrane with a nominal pore size of 0.1μm at various operating parameters. Three chosen types of organic coagulants were used for a series of crossflow microfiltration experiments: polyacrylamide (PAM), poly(diallyldimethylammonium chloride) (PDADMAC), and poly(acrylamide-co-acrylic acid) partial sodium salt (PACA). The value of steady-state permeate flux has been experimentally evaluated for the crossflow microfiltration with and without pretreatment. The results of the experiments without coagulants showed that the flux initially declines rapidly and then stabilizes. The results also suggested that PDADMAC was a better coagulant for this system and its optimal concentration was 30 mg l−1. Finally, it was shown that pretreatment of the feed by PDADMAC resulted in a permeate flux that was more than three times higher than that obtained without any pretreatment. Moreover, there was a very positive effect of this coagulant on the particle size. Pretreatment by 30 mg l−1 PDADMAC led to an average particle size that was almost 18 times higher than that obtained without pretreatment. The other two coagulants did not produce such improvements: pretreatment of the feed by PAM increased the permeate flux by only 10%, while pretreatment by PACA gave even lower permeate flux than no pretreatment. This means that the results of various experiments have shown the need for careful selection of the coagulant due to their differing influences on the permeate flux. The relationship between the particle size of the dispersion and the permeate flux was found from the results of these experiments. A published mathematical model was used to estimate the permeate flux. The results of the experiments showed that the mathematical model was able to predict the steady-state permeate flux quite accurately in some cases.

Synthesis, Characterization and Aplication of TiO2 Alumina Pillared Montmorillonite Photocatalyst

Dispersion of TiO2 on montmorillonite pillared aluminium has been done successfully. The photocatalyst were prepared by intercalation of Al13 onto natural montmorillonite and then calcined at 500oC. Titania dispersion onto aluminium pillared montmorillonite was carried out by impregnation method at the theoritic concentration of 0.4, 0.8, 1 and 3% titania. The photocatalyst then characterized by XRD, porosimetry, SEM and Diffuse Reflectance Visible methods. Results of characterization showed that the basal spacing and specific surface area as well as total pore volume were decreased after dispersion of TiO2 on PILM, meanwhile SEM image exhibited that beside in the pores of PILM, the TiO2 was also dispersed on the surface of PILM. DR UV characterization result indicated that the band gap of TiO2 dispersed PILM for Ti/PILM 0,8%, Ti/PILM 1% and Ti/PILM 3% was 3.66, 3.19 and 3.19 eV respectively. Photodegradation optimum of methyl orange was found to be at Ti/PILM 1% Keywords : montmorillonite, pillarization, photocatalyst, methyl orange, TiO2

Sol–Gel Assisted Inkjet Hologram Patterning

Hereby, it is presented for the first time a method of producing holographic text and images using inkjet printing. For this purpose, colorless TiO2 ink with a high refractive index is used and deposited on top of exposed poly(ethylene terephthalate)‐based microembossed paper by an inkjet printer. Nanoscale coating the paper containing printed text or graphics with transparent polymers or lacquers provides an optical effect of selective preservation of the holographic pattern. The resulting image is preserved only at the site of the colorless ink with a high refractive index from an inkjet printer, allowing to quickly generate any image with a holographic effect. Achieving these results has succeeded through the use of a colloidal dispersion of nanocrystalline titania with a refractive index of 1.75 ± 0.08 in the entire visible range, which meets inkjet rheological requirements. It is shown that the diffraction effect and optical transparency in the visible region are fully preserved. For the first time, it is demonstrated the importance of chemically prepared nanomaterials and nanostructures for an application in the field of holography.

Stereolithographic Additive Manufacturing of Diamond Photonic Crystal Composed of Titania and Alumina Micro Lattices

Three dimensional micro photonic crystals with a diamond structure made of a dense titania and alumina were fabricated successfully by using stereolithographic additive manufacturing. Photonic band gap properties were investigated in gigahertz and terahertz wave frequency ranges. Acrylic diamond lattice structures with nanometer sized particles of titania and alumina dispersion at 40 vol. % were fabricated by the stereolithography. The forming accuracy was 10 μm. After dewaxing and sintering process, the titania and alumina diamond lattice structures were obtained. The relative density reached above 98 %. Electromagnetic wave transmittances were measured by using a W-band millimeter waveguide connected with a network analyzer and a terahertz wave time domain spectroscopy. In the transmission spectra for the Γ-X <100> direction, a forbidden band was observed at 90 – 110 GHz and 0.4 – 0.6 THz. The band gap frequencies well agreed with calculated results by plane wave expansion (PWE) method. Additionally, simulated results by transmission line modeling (TLM) method indicated that a localized mode can be obtained by introducing a plane defect between twinned diamond lattice structures.

In situ characterisation of a concentrated colloidal titanium dioxide settling suspension and associated bed development: Application of an acoustic backscatter system

The ability to accurately characterise the settling of particulate suspensions is imperative in numerous industries for improved processing, optimisation and control. Characterisation is typically a non-trivial process, and in situ measurements that remove the restriction of requiring particular sample sizes are preferred. Here, for the first time, we explore the use of an acoustic backscatter system (ABS) to characterise key settling dynamics within a common colloidal mineral suspension, where backscatter attenuation is heightened due to the associated low scattering cross sections of the particles. Settling titanium dioxide dispersions with concentrations ranging from 0.05 to 3.00vol% were successfully profiled using ABS transducers of 1, 2 and 4MHz frequencies. This approach enabled the simultaneous visualisation of both the settling interface and sediment bed formation, generating sedimentation curves and elucidating settling velocities. Furthermore, backscatter attenuation was empirically correlated with the attenuation–concentration relationship established for homogenous dispersions, to obtain concentration profiles of the settling suspensions. The data depicted concentration changes as a function of time in a hindered settling suspension, and allowed observation of the segregation of a size polydisperse suspension. Data were compared with sedimentation data obtained via two common ex situ bench scale techniques. Critically, the acoustic backscatter method was validated as a powerful in situ characterisation tool for opaque concentrated heterogeneous dispersions, with the ability to provide concentration density information in conjunction with settling kinetics that are not easily attainable via other methods.

Adsorption and photocatalytic degradation of dyes on polyacrylamide/calcium alginate/TiO2 composite film

A casting solution was prepared by dispersing titanium dioxide ( TiO 2) nanoparticles in the sodium alginate and acrylamide aqueous solution. The casting solution was spread on a glass plate by a glass rod enlaced with brass wires to control the thickness of the sticky solution. Then polyacrylamide/calcium alginate/ TiO 2 (PAM/CA/T) composite film was obtained after UV irradiation and cross-linking by CaCl 2. The PAM/CA/T film was characterized by scanning electron microscope and transmission electron microscope. The PAM/CA/T film had good strength and toughness. And they did not rupture after swelling in 5 wt.% NaCl solution and still had good mechanical properties. The adsorption properties of the PAM/CA/T film were investigated by using different dyes as the adsorbates. The photocatalytic degradation properties of these dyes on the PAM/CA/T films were also researched. The results indicated that there was no difference in the adsorption efficiency of PAM/CA film and PAM/CA/T-30 film. The adsorption rates of all the dyes were fast. The pre-adsorption of dyes had little effect on the catalytic degradation of dyes on PAM/CA/T film. The PAM/CA/T hydrogel film provided a suitable carrier for TiO 2 in the photocatalytic degradation of dyes and the degradation efficiency of PAM/CA/T-30 film for methyl orange reached 80.76%. The PAM/CA/T film had good reusability and could degrade dyes in NaCl solution.

Metal oxide one dimensional photonic crystals made by RF sputtering and spin coating

We report here the analysis of the light transmission properties of one dimensional photonic crystals made by multilayers of silicon dioxide and titanium dioxide. A precise fabrication by radiofrequency sputtering of a photonic crystal allows us to accurately model the transmission spectrum of the crystal, by taking into account the wavelength dependent refractive indexes of the materials. We found that, while the dispersion of silicon dioxide is in good agreement with data reported in literature, the dispersion of titanium dioxide is more critical. Using such dispersions we could fit the transmission spectra of silicon dioxide/titanium dioxide one dimensional photonic crystals made by spin coating layer deposition starting from nanoparticle colloidal dispersions. The fit takes into account the porosity of the layers and the losses due to Rayleigh scattering.

Nano-TiO2 reinforced PEEK/PEI blends as biomaterials for load-bearing implant applications.

Biocompatible ternary nanocomposites based on poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI) blends reinforced with bioactive titanium dioxide (TiO2) nanoparticles were fabricated via ultrasonication followed by melt-blending. The developed biomaterials were characterized using FT-IR, SEM, XRD, DSC, TGA, and DMA. Further, their water-absorption, tensile, tribological, dielectric, and antibacterial properties were evaluated. PEI acts as a coupling agent, since it can interact both with PEEK via π-π stacking and polar interactions as well as with the nanoparticles through hydrogen bonding, as corroborated by the FT-IR spectra, which resulted in a homogeneous titania dispersion within the biopolymer blend without applying any particle surface treatment or polymer functionalization. A change from promotion to retardation in the crystallization rate of the matrix was found with increasing TiO2 concentration, while its crystalline structure remained unaltered. The nanoparticles stiffened, strengthened, and toughened the matrix simultaneously, and the optimal properties were achieved at 4.0 wt % TiO2. More interesting, the tensile properties were retained after steam sterilization in an autoclave or exposure to a simulated body fluid (SBF). The nanocomposites also displayed reduced water absorption though higher thermal stability, storage modulus, glass transition temperature, dielectric constant, and dielectric loss compared to the control blend. Further, remarkable enhancements in the tribological properties under both SBF and dry environments were attained. The nanoparticles conferred antibacterial action versus Gram-positive and Gram-negative bacteria in the presence and the absence of UV light, and the highest inhibition was attained at 4.0 wt % nanoparticle concentration. These nanocomposites are expected to be used in long-term load-bearing implant applications.

A graphene titanium dioxide nanocomposite (GTNC): one pot green synthesis and its application in a solid rocket propellant

A green process was developed for a graphene–titanium dioxide nanocomposite (GTNC) synthesis by dispersing titanium dioxide (TiO2) nanoparticles and graphene nano-sheets (GNSs) in ethanolviaultrasonication followed by microwave irradiation.

Pd–Ti-MCM-48 cubic mesoporous materials for solar simulated hydrogen evolution

A facile synthetic method (in as little as four hours) for simultaneously loading high amounts of titania (Si/Ti = 3) and Pd0 co-catalyst (0.1 wt.% per gram of total catalyst) in cubic mesoporous MCM-48 material was developed at room temperature. The solar simulated photocatalytic hydrogen evolution from photocatalysts containing Pd0 and TiO2 nanoclusters in periodic cubic MCM-48 and aperiodic mesoporous silica was compared. The results indicate that the periodicity of the mesoporous silica support, the oxidation state of Pd, the location and dispersion of Pd0 have a significant impact on the photocatalytic activity. Periodic cubic MCM-48 mesoporous silica containing Pd0 in close contact with titania exhibit superior hydrogen evolution rates compared to Pd0-TiO2 containing aperiodic mesoporous silica. The highly ordered and open three-dimensional mesoporous cubic MCM-48 support has high surface area and facilitate good dispersion and close contact of titania and Pd0. At very low loadings of 0.1 wt.% of Pd, hydrogen yield was found to be 560 μ mol h−1, which is among the highest reported in the literature for Pd0 containing TiO2 based materials under solar simulated conditions. The results suggest that the pore architecture of the support is also an important parameter that governs the photocatalytic activity. In addition, the Pd0-mesoporous materials in general possess higher activity than Pd2+ containing mesoporous materials. The photocatalysts were extensively characterized by a variety of techniques such as powder X-ray diffraction (XRD), nitrogen sorption analysis, transmission and scanning electron microscopic studies, photoluminescence, diffuse reflectance spectroscopy (DRS), CO Chemisorption, and X-ray photoelectron spectroscopy (XPS).

Photocatalytic applications of paper-like poly(vinylidene fluoride)–titanium dioxide hybrids fabricated using a combination of electrospinning and electrospraying

A paper-like photocatalyst was fabricated by electrospraying an N,N′-dimethylformamide (DMF) dispersion of titanium dioxide (TiO2) nanoparticles (NPs) on a poly(vinylidene fluoride) nanofiber (PVDF NF) mat prepared by electrospinning. Morphological studies revealed that the TiO2 NPs uniformly deposited as clusters on the surface of the PVDF NF mat. The immobilized amount of TiO2 was found to be 2.08, 2.44, 3.80, and 4.73mg per 45cm2 of PVDF–TiO2 hybrids for the electrospraying of 10, 20, 40, and 60ml of TiO2–DMF, respectively. The hybrid photocatalysts were effective in degrading bisphenol A (BPA), 4-chlorophenol (4-CP), and cimetidine (CMT), which dissolved in both deionized water and secondary wastewater effluents, with activity being proportional to the quantity of TiO2 NPs immobilized. For the highest loading amount of TiO2, BPA, 4-CP, and CMT degraded completely within 100, 100, and 40min of UV irradiation, respectively. Stable photo-oxidation of CMT was maintained through 10 repeated cycles. During these cycles, it was confirmed that there was no loss of TiO2 NPs by inductively coupled plasma optical emission spectrometry. Our results suggest that effective and stable PVDF–TiO2 hybrid photocatalysts can be fabricated on a large scale by combining electrospinning and electrospraying techniques.

Effects of Humidity on Gessoes for Easel Paintings

ABSTRACTGessoes are widely used in easel painting as grounds or preparatory layers; in art conservation, gessoes are employed as infill materials to level a loss in the paint surface in preparation for inpainting. The goal of this investigation was to establish the relationship between the mechanical behavior of various gessoes when exposed to different relative humidities (25%, 50%, and 100%) and to compare modern commercial gesso products with a traditional gesso. The materials included two commercial artists’ acrylic gessoes (composed of largely titanium dioxide and aqueous dispersions of acrylic polymers), two commercial spackling compounds frequently used in the conservation of easel paintings, and a traditional gesso (calcium carbonate and rabbit skin glue). Uniaxial tensile testing was used to characterize the elastic modulus, strain at failure, and ultimate tensile strength (UTS) of the materials. By understanding the physical limits of these materials under different conditions, damage to artworks and the failure of conservation treatments containing these types of materials may be prevented or reduced.

Concentration factor and rheology of aqueous titanium dioxide dispersions

The rheological properties of aqueous titanium dioxide dispersions have been studied by rotational viscometry. It has been established that the studied disperse systems are highly structured, and their degree of structuring dramatically increases with the volume fraction φ of the solid phase. At solid phase contents φ ≥ 0.164, the breakage of the disperse structure is accompanied by the appearance of local discontinuities and an abnormal dependence of viscosity on shear stress. The results obtained have been analyzed in terms of the Uriev theory of aggregated systems. The radii of aggregates and maximum solid phase content φm that corresponds to the formation of a continuous disperse structure under the conditions of dynamic impact have been calculated.

Estimation of microstructure of titania particulate dispersion through viscosity measurement

Aggregate structure and its variation with shear rate are investigated using viscosity data of titania (TiO2) dispersion consisting of anatase titania particles of 200nm in diameter and ethylene glycol. The particle volume fraction ϕ ranges from 0.01 to 0.1 and the viscosity measurement is performed at shear rates 1–201s−1. The viscosity data exhibit that the dispersion is shear-thinning and titania particles exist in the form of aggregates in the dispersion. The Krieger–Dougherty equation is used to obtain the intrinsic viscosity which is related with the aggregate structure and size. It is found that the intrinsic viscosity for ϕ ≤0.04 is different from that for ϕ ≥0.05 where gel-like behavior is observed in sedimentation test. A scaling relation is applied to correlate the intrinsic viscosity at low ϕ with the aggregate structure characterized by fractal dimension df and exponent for shear dependence of aggregate size m. Logarithmic linearity between the intrinsic viscosity and shear rate indicates that the aggregates are rigid and thus m is close to 1/3. Therefore, df is 1.9813. Yield stress as a function of ϕ also provides information on m and df at the shear rate just above yield point. The fractal dimension df from the yield stress data is 1.9818 when m=1/3, which is nearly equal to 1.9813 from the intrinsic viscosity data.

Soft Lithographic Printing of Titanium Dioxide and the Resulting Silica Contamination Layer

ABSTRACTSoft lithographic printing techniques can be used to print nanoparticle dispersions with relative ease while allowing for a measureable degree of controllability of printed feature size. In this study, a Polydimethylsiloxane (PDMS) stamp was used to print multi-layered, porous, nanoparticle dispersions of titanium dioxide (TiO2), for use in a dye-sensitized solar cell application. The gelled patterns were then sintered and the surface of the printed sample was chemically analyzed.X-ray photoelectron spectroscopy (XPS) was used to determine the surface constituents of the printed sample. The presence of a secondary peak feature located approximately 2.8 eV above the high resolution O1s core level binding energy peak was attributed to a contamination layer. Fourier transform infrared spectra (FTIR) of the printed sample revealed the presence of vibrational modes characteristic of the asymmetric bond stretching of silica, located at approximate wavenumbers of 1260 and 1030 cm-1.Soft lithographic techniques are a viable manufacturing technique in a number of disciplines and sintered nano-oxide dispersions are readily used as reaction centers in a number of technologies. The presence of a residual, bonded silicate contamination layer may preclude the soft lithographic printing of chemically active oxide surfaces.

High dispersion of TiO2nanocrystals within porous carbon improves lithium storage capacity and can be applied batteries to LiNi0.5Mn1.5O4

A new and simple strategy was developed to effectively disperse titanium dioxide (TiO2) nanocrystals into porous carbon (PC), and a series of hierarchical PC–TiO2composites with different architectures were synthesized.

Environmental problems of finely dispersed titanium dioxide production

Finely dispersed titanium dioxide is widely used in modern technologies. Proved reserves of titanium ores in Russia are expected to meet industrial needs. However, the available facilities for the manufacture of titanium dioxide from ores are clearly insufficient, which naturally requires new plants to be put into operation. The technologies used for the production of titanium dioxide were developed as early as 1940s, when ecological aspects of the production process were almost not taken into account. The present survey analyzes environmental problems related to the titanium dioxide production according to the sulfate and chloride technologies in comparison with the fluoride process proposed for industrial implementation. The fluoride process has been examined as applied to ilmenite from the Turan deposit in Tomsk oblast, and some actions directed toward improvement of ecological parameters of this process have been proposed.

나노 TiO2와 나노 은의 광증착을 이용한 폴리우레탄 멤브레인의 항균성 부여 연구

Polyurethane membrane was chosen as an alternate for Gore-Tex used in outdoor sportswear. Antimicrobial property was induced by dispersing titanium dioxide () particles on the surface of the membrane via sonication. Furthermore, Ag particle was photodeposited on the particles via UV irradiation to enhance the photocatalytic activity. Measurements using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy showed that and Ag particles were evenly deposited on the membrane. In addition, the antimicrobial property against Klebsiella pneumoniae and Staphylococcus aureus was validated using the shake flask method and clear zone method.

Multi-functional Polyester Hollow Fiber Nonwoven Fabric with Using Nano Clay/Nano TiO2/Polysiloxane Composites

Surface modification and property improvement of hollow polyester fiber nonwoven fabric is very important due to the application of substrate in the various fields. Here, nano clay, nano TiO2 and polysiloxane softener as been applied on the hollow polyester fiber nonwoven fabric through conventional impregnation-dry-cure method in order to enhance the fabric properties. The alkaline hydrolysis of polyester was performed on the nonwoven surface to functionalize the fabric and increase the nanoparticles uptake. The nano clay was first dispersed by using nonionic dispersing agent, and then nano titanium dioxide dispersion was added dropwise to the prepared nano clay dispersion. Also, other dispersions were prepared with adding polysiloxane softener and polyurethane resin under sonication. The SEM images and EDX/XRD patterns indicated the presence of various applied particles on the surface of the fabric. Thermal gravimetric analysis was employed to investigate the thermal decomposition behavior of the treated samples. Self-cleaning properties of polyester nonwoven treated by TiO2/nano clay/polysiloxane composite was followed by degradation of methylene blue under daylight irradiation at ambient temperature. It was found that nano clay/TiO2/polysiloxane composite on the fabric surfaces improved self-cleaning property, thermal stability above 400 °C, and water absorption properties of the fabric.

Synthesis and Characterization of Anionic Polyurethane Dispersants for Waterborne Paints

Anionic polyurethane dispersants APUDs were used as dispersing agents in formulation of waterborne paints. The APUDs were synthesized by three steps. In the first step, macromonomer diisocyanate having carboxylic acid was prepared by isophorone diisocyanate IPDI, dimethylol propionic acid DMPA in presence of acetone as solvent and dibutyltin dilaurate DBTDL as catalyst. Then, carboxylic polyurethane was prepared by reaction macromonomer diisocyanate having carboxylic acid groups with alcohols. In this work, alcohols were 1,4-butanediol and 1,6-hexanediol as difunctional alcohols, trimethylol propane as trifunctional alcohol and pentaerythritol as tetrafunctional alcohol. The final step involved neutralization and dispersion in water, where acidic polyurethane was neutralized by the addition of triethylamine TEA. The polymers have been characterized with 1H-NMR and FT-IR. The dispersion of APUDs depends on their molecular weights and chemical structures. Dispersion of titanium dioxide in typical waterborne acrylic resin has been investigated.