Titanate Nanofibers Research Articles

Kinetics of Alkali Metal Ion Exchange into Nanotubular and Nanofibrous Titanates

The kinetics of intercalation of Li+, Na+, K+, and Cs+ cations between the layers of titanate nanotubes and nanofibers have been studied in an aqueous suspension of nanotubes at 25 °C. The rate of intercalation was found to be similar for different cations and depended on the length of the nanotubes. The decrease in nanotube length resulted in a higher rate of ion exchange, indicating that the transport of cations in titanate nanotubes occurred probably along their length. In contrast, the transport of cations in titanate nanofibers probably dominated in the direction perpendicular to length. Correlations between the rate of intercalation and the crystal structure modification following intercalation have been established for nanotubular and nanofibrous titanates.

Zinc Titanate Nanofibers for the Detoxification of Chemical Warfare Simulants

Fabrication of a novel ceramic nanofiber system viz. zinc titanate using the well‐known electrospinning technology with polyvinylpyrrolidone as a binder is reported. Use of zinc titanates as reactive sorbents to detoxify chemical warfare agents is hypothesized and proved. The zinc titanate nanofibers are tested against simulants of nerve and mustard agents and show satisfactory destructive activity. The extent of detoxification is measured using GC‐MS analysis. The products of reaction of zinc titanate against the simulants are identified and are found to be relatively harmless. The possibility of replacement of conventional‐activated carbon by electrospun ceramic nanofibers for face masks and protective clothing is proposed.

Nd-substituted bismuth titanate ferroelectric nanofibers by electrospinning

Nd-substituted bismuth titanate (Bi 3.15Nd 0.85Ti 3O 12, BNT) nanofibers were synthesized by electrospinning method utilizing a solution that contained poly(vinylpyrrolidone) (PVP) and sol–gel precursor solution of BNT. The BNT/PVP composite fibers were calcined in air for 1 h at 500, 600, 700, 750, and 800 ∘ C , respectively. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used to characterize the as-synthesized and calcined BNT/PVP composite nanofibers. The experimental results showed that the diameter, morphology, and crystallization of the nanofibers are influenced by the calcination temperature. After calcination at 700 ∘ C , BNT fibers are fully crystallized and exhibit a polycrystalline bismuth-layered perovskite structure, with a diameter of 70–160 nm and a length of over 6 μ m .

Energy Harvesting From PZT Nanofibers

AbstractIn this paper, we demonstrated that Lead Zirconate Titanate (PZT) nanofibers can be used to harvest energy from dynamic loading and mechanical vibration. PZT nanofibers were fabricated by electrospinning process. SEM image of PZT nanofibers has shown that the average diameter of these fibers is about 150nm, which can be tuned from 50nm to 200 nm by varying the composition and viscosity of the precursor for electrospining. Titanium substrate with ZrO2 layer was used to collect the PZT nanofibers for the demonstration of energy harvesting from dynamic loading. The largest output voltage is 170mV under 0.5% strain; the frequency of the output voltage is the same as that of the input loading. Silicon substrate with trenches was used to collect the nanofibers for energy harvesting from vibration. The output voltage generated from 150Hz sinusoid vibration source has peak voltages of 64.9mV and -95.9mV. These experimental results suggest that PZT nanofibers have great potentials for energy harvesting from environments and being used as nanogenerators. Further study is under the way to optimize the design and improve the efficiency.

Biocompatible nanofiber scaffolds on metal for controlled release and cell colonization

This paper reports for the first time a preparation of biocompatible titanate nanofiber scaffolds on the surface of titanium foil/mesh via a one-step hydrothermal reaction. The length and diameter of the nanofibers can be controlled by varying the fabrication parameters, such as reaction temperature, precursor concentration, and reaction time. The nanofibers can self-organize into macroporous (mostly 0.5−10 μm in diameter) scaffolds potentially useful for developing new bioscaffolds, photocatalysts, sensors, and drug delivery vehicles.

Direct Hydrothermal Processing of Long Titanate Nanofibers from Natural Rutile

Via the direct hydrothermal processing using natural rutile as a starting material, long titanate nanofibers (typically 10-500 μm in length and 20-50 nm in diameter) have been successfully synthesized in high yield Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), electron diffraction, and UV-Vis spectroscopy demonstrated that the as-synthesized nanofibers presumably consisted of sodium hydrogen trititanate ((Na,H)2Ti3O7, e.g., Na0.4H1.6Ti3O7) including some hexatitanate-type defects ((Na,H)2Ti6O13). The direct hydrothermal treatment for natural rutile will be a promising low-cost processing for 1-D nanomaterials, which can act not only as the reaction step but also as the purification.

Direct Hydrothermal Processing of TiO2 Nanofibers from Natural Rutile Sand

Titanate nanofibers were synthesized by hydrothermal method (150 oC for 72 h) using natural rutile sand as the starting materials. TiO2 (B) and anatase TiO2 (high crystallinity) nanofibers with the diameters of 20-100 nm and the lengths of 10-100 μm were obtained by calcined titanate nanofibers for 4 h at 400 oC and 700 oC (in air), respectively. The samples characterized by XRD, SEM, TEM, SAED, HRTEM, and BET surface area. This synthesis method provides a simple route to fabricate one- dimensional nanostructured TiO2 from low cost material.

Electrospinning of polycrystalline barium titanate nanofibers with controllable morphology and alignment

We report the fabrication of BaTiO 3 nanofibers with controllable aspect ratio by electrospinning. Polycrystalline ribbon-like nanofibers ∼200 nm in width and ∼75 nm in thickness with grain sizes <30 nm were prepared by electrospinning a solution that contained barium-titanium alkoxide and poly(vinyl pyrrolidone). Varying the concentration of alkoxide precursor resulted in the formation of BaTiO 3 fibrils <50 nm in diameter and fibers with ribbon-like morphology. Analysis by XRD and Raman scattering showed that amorphous BaTiO 3 without residual polymer could be generated by calcination at 500 °C, while for fibers calcined at 700 °C, the polarized ferroelectric tetragonal phase was obtained.

Sequence of Events for the Formation of Titanate Nanotubes, Nanofibers, Nanowires, and Nanobelts

The formation of H2Ti3O7 nanotubes, nanofibers, nanowires, and nanobelts via alkali hydrothermal synthesis was studied in detail by TEM and HRTEM. The effects of preparation parameters, such as reaction temperature, duration, and cooling process, on the morphologies of the products are clarified. A universal formation mechanism is proposed based on the growth, split, wrapping, and thickening of Na2Ti3O7 nanointermediates, which links all kinds of morphologies observed for H2Ti3O7 nanoentities.

Nanofibers of barium strontium titanate (BST) by sol–gel processing and electrospinning

This paper describes the fabrication of barium strontium titanate (Ba 0.6Sr 0.4TiO 3 or BST) nanofibers by electrospinning method using a solution that contained poly(vinylpyrrolidone) and a sol–gel solution of BST. The as-spun and calcined BST/PVP composite nanofibers were characterized by TG-DTA, X-ray diffraction, FT-IR, SEM and TEM, respectively. After calcination of the as-spun BST/PVP composite nanofibers at above 700 °C in air for 2 h, BST nanofibers of 188 ± 25 nm in diameter having well-developed cubic-perovskite structure were successfully obtained. The crystal structure and morphology of the nanofibers were influenced by the calcination temperature. Calcination at below 700 °C resulted in amorphous phase whereas BST with second phase such as barium titanate were formed at above 700 °C. Diameters of the nanofibers decreased from 208 ± 35 to 161 ± 18 nm with increasing calcination temperature between 600 and 800 °C.

Examination of Size-Induced Ferroelectric Phase Transitions in Template Synthesized PbTiO3 Nanotubes and Nanofibers

Here we report on the application of sol-gel template synthesis to the investigation of size-induced ferroelectric phase transitions in lead titanate (PbTiO 3 ) nanotubes and nanofibers. A 0.8 M chelate sol-gel, made from titanium(IV) tertabutoxide and lead(II) trihydrate acetate, was applied to two different templates. Nanotubes were formed within 200-nm-pore Whatman anodisc aluminum oxide membranes, and nanofibers were prepared using 50-, 100-, and 200-nm Whatman track-etched polycarbonate membranes. Transmission electron microscopy images revealed that the tubes comprised grains of ≤20 nm and the fibers comprised individual grains ≤200 nm in width when a 200-nm pore size template is used. An examination of how the grain/crystallite size and aspect ratio of one-dimensional morphologies affect the ferroelectric phase transition was monitored through the comparison of bulk powders and the nanostructured materials using electron diffraction, X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry.

Synthesis of titanate, TiO 2 (B), and anatase TiO 2 nanofibers from natural rutile sand

Titanate nanofibers were synthesized by hydrothermal method (150 °C for 72 h) using natural rutile sand as the starting materials. TiO 2 (B) and anatase TiO 2 (high crystallinity) nanofibers with the diameters of 20–100 nm and the lengths of 10–100 μm were obtained by calcined titanate nanofibers for 4 h at 400 and 700 °C (in air), respectively. The samples characterized by XRD, SEM, TEM, SAED, HRTEM, and BET surface area. This synthesis method provides a simple route to fabricate one-dimensional nanostructured TiO 2 from low cost material.

Layered sodium titanate nanofiber and microsphere synthesized from peroxotitanic acid solution

In this paper, we report titania and titanate nanofiber synthesized by using peroxotitanic acid solution as a titanium source. The peroxotitanic acid solution was mixed with NaOH aqueous solution, followed by the hydrothermal treatment with or without vigorous agitation. In TEM and SEM images for solids obtained by the synthesis with vigorous agitation, nanofibers are observed. On the other hand, microspheres as well as nanofibers were observed in solids obtained by the synthesis without agitation. The microspheres are composed of nanofibers and nanosheets. EDX analysis for the obtained solids detected Ti and Na, indicating that the obtained solids are sodium titanate. As a reference, synthesis by using TiO 2 particles instead of the peroxotitanic acid solution was also performed. The Na to Ti mole ratio for the peroxotitanic acid based solid determined by EDX was 0.55 which is twice the value of 0.26 for the TiO 2 particle based solid. The obtained sodium titanate could be converted into anatase-type titania by the HCl treatment of the sodium titanate and the subsequent calcination.

Synthesis of barium titanate (BaTiO3) nanofibers via electrospinning

Barium titanate nanofibers were synthesized by electrospinning utilizing sol–gel precursors. The electrospun polymer–ceramic composite fibers were heat treated to yield perovskite barium titanate fibers after annealing at 750 °C for 1 h. The morphology, microstructure and crystal structure were investigated by SEM, XRD and TEM. Typical fiber diameter was between 80 and 190 nm with fiber lengths exceeding 0.1 mm. This is the first time stand-alone electrospun complex oxide ferroelectric nanofibers are reported. Due to the high electric field of electrospinning (1–2 kV/cm) the electrochemistry is expected to have an impact on the ferroelectric nanofiber properties.

Pb(Zr0.5, Ti0.5)O3 nanofibres by electrospinning

Lead zirconate titanate Pb(Zr0.5, Ti0.5)O3 nanofibres with diameters ranging from 200–300 nm have been synthesized by calcination of the electrospun lead zirconate titanate/polyvinyl acetate composite fibres. The morphology and crystalline phase features of these lead zirconate titanate (PZT) nanofibres have been studied by various physico-chemical methods such as SEM, AFM, XRD and FT–IR. The formation of perovskite PZT phase was observed at temperatures as low as 550 °C.

Phase Transition between Nanostructures of Titanate and Titanium Dioxides via Simple Wet-Chemical Reactions

Titanate nanofibers of various sizes and layered structure were prepared from inorganic titanium compounds by hydrothermal reactions. These fibers are different from "refractory" mineral substances because of their dimension, morphology, and significant large ratio of surface to volume, and, surprisingly, they are highly reactive. We found, for the first time, that phase transitions from the titanate nanostructures to TiO(2) polymorphs take place readily in simple wet-chemical processes at temperatures close to ambient temperature. In acidic aqueous dispersions, the fibers transform to anatase and rutile nanoparticles, respectively, but via different mechanisms. The titanate fibers prepared at lower hydrothermal temperatures transform to TiO(2) polymorphs at correspondingly lower temperatures because they are thinner, possess a larger surface area and more defects, and possess a less rigid crystal structure, resulting in lower stability. The transformations are reversible: in this case, the obtained TiO(2) nanocrystals reacted with concentrate NaOH solution, yielding hollow titanate nanotubes. Consequently, there are reversible transformation pathways for transitions between the titanates and the titanium dioxide polymorphs, via wet-chemical reactions at moderate temperatures. The significance of these findings arises because such transitions can be engineered to produce numerous delicate nanostructures under moderate conditions. To demonstrate the commercial application potential of these processes, we also report titanate and TiO(2) nanostructures synthesized directly from rutile minerals and industrial-grade rutiles by a new scheme of hydrometallurgical reactions.

Natural rutile-derived titanate nanofibers prepared by direct hydrothermal processing

Long titanate nanofibers (typically 10–500 μm in length and 20–50 nm in diameter) were successfully prepared in high yield by the direct hydrothermal processing using natural rutile as a starting material. Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, electron diffraction, and x-ray diffraction demonstrated that the as-synthesized nanofibers presumably consisted of sodium hydrogen trititanate [(Na,H)2Ti3O7,e.g., Na0.4H1.6Ti3O7] including some hexatitanate-type defects [(Na,H)2Ti6O13]. A partial topotactic condensation model explained their nanostructure well. Although the as-synthesized fibers are defective, they can be cured by a post-heat-treatment in air. The direct hydrothermal treatment for natural rutile will be a promising low-cost process for one-dimensional nanomaterials, which can act not only as a reaction step but also as a purification step.

Synthesis of Titanate Nanofibers and Nanotubes

A simple, mild and low-cost refluxing method was successfully used to synthesize titanate nanofibers and nanotubes. Properties of the as-prepared samples were characterized by means of TEM and XRD techniques. Optimization of the experimental conditions allowed, respectively, the preparation of titanate nanofibers and nanotubes. The photocatalytic activities of the prepared products were also investigated. The results indicated that titanate nanofibers and nanotubes had no photocatalytic activities for the degradation of methyl orange. Calcined at different temperature, the photocatalytic activities of the products increased, accompanying the change of structures.

Nickel titanate nanofibers by electrospinning

Nickel titanate/poly(vinyl acetate) (PVAc) composite nanofibers were prepared by sol–gel processing and electrospinning technique. Rhombohedral nickel titanate fibers with 150–200nm diameter were obtained by high temperature calcination of the composite fibres. Structural, morphological and crystalline phase features of electrospun NiTiO3 fibers were studied by SEM, AFM, XRD and FT-IR. The fibrous nature of nickel tiatanate was stable even after calcination at 1273K.

Hydrogen titanate nanofibers covered with anatase nanocrystals: a delicate structure achieved by the wet chemistry reaction of the titanate nanofibers.

Hydrogen titanate nanofibers synthesized by a hydrothermal reaction, are chemically reactive, readily reacting with dilute acid. This reaction is a topochemical process in which in situ phase transition from H-titanate to anatase takes place and the product retains the fibril morphology. The extent of this reaction can be precisely controlled, allowing us to achieve a delicate composite structure at nanoscale: long titanate fibers of 40-100 nm thick and up to 30 mum long covered with anatase nanocrystals of 10-30 nm. The structure has desired photocatalytic properties and can be separated readily after use. This study demonstrates new opportunities to create delicate inorganic nanostructures with advanced functions by wet chemical reactions.