Ceramic Nanotubes Research Articles

Ceramic Nanotubes—Conducting Polymer Assemblies with Potential Application as Chemosensors for Breath Ammonia Detection in Chronic Kidney Disease

This paper describes the process of producing chemosensors based on hybrid nanostructures obtained from Al2O3, as well as ZnO ceramic nanotubes and the following conducting polymers: poly(3-hexylthiophene), polyaniline emeraldine-base (PANI-EB), and poly(3, 4-ethylenedioxythiophene)-polystyrene sulfonate. The process for creating ceramic nanotubes involves three steps: creating polymer fiber nets using poly(methyl methacrylate), depositing ceramic films onto the nanofiber nets using magnetron deposition, and heating the nanotubes to 600 °C to burn off the polymer support completely. The technology for obtaining hybrid nanostructures from ceramic nanotubes and conducting polymers is drop-casting. AFM analysis emphasized a higher roughness, mainly in the case of PANI-EB, for both nanotube types, with a much larger grain size dimension of over 5 μm. The values of the parameter Rku were close or slightly above 3, indicating, in all cases, the formation of layers predominantly characterized by peaks and not by depressions, with a Gaussian distribution. An ink-jet printer was used to generate chemiresistors from ceramic nanotubes and PANI-EB structures, and the metallization was made with commercial copper ink for printed electronics. Calibration curves were experimentally generated for both sensing structures across a wider range of NH3 concentrations in air, reaching up to 5 ppm. A 0.5 ppm detection limit was established. The curve for the ZnO:PANI-EB structure presented high linearity and lower resistance values. The sensor could be used in medical diagnosis for the analysis of breath ammonia and biomarkers for predicting CKD in stages higher than 1. The threshold value of 1 ppm represents a feasible value for the presented sensor, which can be defined as a simple, low-value and robust device for individual use, beneficial at the patient level.

Manufacturing of TiO2, Al2O3 and Y2O3 Ceramic Nanotubes for Application as Electrodes for Printable Electrochemical Sensors

This paper describes the process to obtain ceramic nanotubes from titanium dioxide, alumina and yttrium oxide by a feasible, replicable and reliable technology, including three stages, starting from an electrospinning process of poly(methyl methacrylate) solutions. A minimum diameter of 0.3 μm was considered optimal for PMMA nanofibers in order to maintain the structural stability of covered fibers, which, after ceramic film deposition, leads to a fiber diameter of 0.5–0.6 μm. After a chemical and physical analysis of the stages of obtaining ceramic nanotubes, in all cases, uniform deposition of a ceramic film on PMMA fibers and, finally, a uniform structure of ceramic nanotubes were noted. The technological purpose was to use such nanotubes as ingredients in screen-printing inks for electrochemical sensors, because no study directly targeted the subject of ceramic nanotube applications for printed electronics to date. The printing technology was analyzed in terms of the ink deposition process, printed electrode roughness vs. type of ceramic nanotubes, derived inks, thermal curing of the electrodes and the conductivity of electrodes on different support (rigid and flexible) at different curing temperatures. The experimental inks containing ceramic nanotubes can be considered feasible for printed electronics, because they offer fast curing at low temperatures, reasonable conductivity vs. electrode length, good printability on both ceramic or plastic (flexible) supports and good adhesion to surface after curing.

Preparing 3D Perovskite Li0.33La0.557TiO3 Nanotubes Framework Via Facile Coaxial Electro‐Spinning Towards Reinforced Solid Polymer Electrolyte

It is of significance to construct continuous multiphase percolation channels with fast lithium‐ion pathway in hybrid solid electrolytes. 3D ceramic nanostructure frameworks have attracted great attention in this field. Herein, the three‐dimensional perovskite Li0.33La0.557TiO3 nanotubes framework (3D‐LLTO‐NT) is fabricated via a facile coaxial electro‐spinning process followed by a calcination process at 800 °C. The hybrid polymer electrolyte of 3D‐LLTO‐NT framework and poly (ethylene carbonate) (3D‐LLTO‐NT@PEC) shows improved ionic conductivity of 1.73 × 10−4 S cm−1 at ambient temperature, higher lithium‐ion transference number (tLi+) of 0.78 and electrochemical stability window up to 5.0 V vs Li/Li+. The all‐solid‐state cell of LiFePO4/3D‐LLTO‐NT@PEC/Li delivers a high specific capacity of 140.2 mAh g−1 at 0.1 C at ambient temperature. This outstanding performance is attributed to the 3D ceramic nanotubes frameworks which provide fast lithium ion transfer pathway and stable interfaces.

Tubular Clay Nano-Straws in Ordered Mesoporous Particles Create Hierarchical Porosities Leading to Improved CO2 Uptake

The use of solid adsorbents for CO2 capture is of importance in the development of technologies to remove this greenhouse gas. High surface area mesoporous materials are used to encapsulate or functionalize amines that selectively capture CO2. The MCM-41 class of hexagonally ordered mesoporous silicas have surface areas between 1000 and 1500 m2/g, which in principle allows a significant degree of capture when amines such as polyethyleneimine (PEI) are encapsulated within the pores and occupy the entire surface area of the materials. However, the tight 3 nm pore channels of MCM-41 create a challenge to the infiltration of PEI throughout the pore volume, resulting in much lower CO2 uptake at high PEI concentrations. This work describes the introduction of clay nanotubes (halloysite) with an inner diameter of 15–30 nm into MCM-41 pellets to mitigate such diffusional restrictions. The introduction of the nanotubes is through a one-step ship-in-a-bottle approach to synthesis in an aerosol-assisted system where MCM-41 is synthesized in droplets containing the halloysite. The morphology of the composite material is such that several nanotubes extend from the interior and protrude through the surface of the pellet like straws. These ceramic nanotubes are 0.5–2 μm in length, and their lumen diameter ranges from 15 to 30 nm, thus providing an improved entry pathway for molecules to access the interior of the MCM-41 pellets. The concept is used to enhance PEI loading in MCM-41, which leads to a significant increase in CO2 uptake levels. MCM-41 composites with halloysite nano-straws (MCM-41/HNT) show a doubling of CO2 uptake levels (7.1 wt %) and uptake kinetics (k = 0.11 s–1) in comparison to MCM-41 sorbents (3.9 wt % and k = 0.05 s–1) at 50 wt % PEI loading. This indicates the potential validity of the nano-straws to improve access to the interior of MCM-41, thus coupling enhanced molecular transport with a high surface area material. The generality of the concept indicates further applications to adsorption and catalysis.

A Highly Selective Novel Green Cation Exchange Membrane Doped with Ceramic Nanotubes Material for Direct Methanol Fuel Cells

Herein, a pair of inexpensive and eco-friendly polymers were blended and formulated based on poly (ethylene oxide) (PEO) and poly (vinyl alcohol) (PVA). FTIR, XRD, EDX and TEM techniques were used to describe a Phosphated titanium oxide (PO4TiO2) nanotube synthesised using a straightforward impregnation-calcination procedure. For the first time, the produced nanoparticles were inserted as a doping agent into this polymeric matrix at a concentration of (1–3) wt.%. FTIR, TGA, DSC and XRD were used to identify the formed composite membranes. Furthermore, because there are more hydrogen bonds generated between the polymer’s functional groups and oxygen functional groups PO4TiO2, oxidative stability and tensile strength are improved with increasing doping addition and obtain better results than Nafion117. The permeability of methanol reduced as the weight % of PO4TiO2 increased. In addition, the ionic conductivity of the membrane with 3 wt.% PO4-TiO2 is raised to (28 mS cm−1). The optimised membrane (PVA/PEO/PO4TiO2-3) had a higher selectivity (6.66 × 105 S cm−3 s) than Nafion117 (0.24 × 105 S cm−3 s) and can be used as a proton exchange membrane in the development of green and low-cost DMFCs.

Polyvinyl butyral composites containing halloysite nanotubes/reduced graphene oxide with high dielectric constant and low loss

Polymer-based composites with high dielectric constant and low loss are highly desirable due to their inherent advantages of easy processability, flexibility, and lightweight. Herein, a functional nanofillers, halloysite nanotubes (HNTs) decorated reduced graphene oxide (rGO) hybrid microstructures (HNTs@rGO) was successfully prepared via controllable electrostatic self-assembly and in-situ heat reduction method. These hybrid microstructures combine characteristics of natural 1D ceramic nanotubes with large aspect ratio and high electric conductivity of rGO micro-sheets, which provided ideal material collocation in the construction of microcapacitors. The HNTs not only effectively prevented direct contact between the rGO micro-sheets in the composites but also played an important role in forming dielectric interface within microcapacitors. Consequently, an HNTs@rGO/polyvinyl butyral (PVB) composites containing a very low content of 5 wt% rGO exhibited an ultra-high dielectric constant of 150 and an extremely low loss of 0.12 at 103 Hz. It is believed that the unique characteristics and facile fabrication process of HNTs@rGO/PVB composite make it a potentially excellent candidate for flexible polymer-based dielectric materials applied in the capacitor fields.

Low-temperature ozone treatment for carbon nanotube template removal: improving the template-based ALD method

This work addresses the production of stand-alone ceramic nanotubes by the template-based ALD method at low temperature. Nitrogen-doped multiwalled carbon nanotubes (CNTs) were coated with ZnO. Afterward, the template removal was evaluated by two different approaches: using oxidation in dry air or in an ozone-rich atmosphere. The samples treated by the two different methods were analyzed by XRD, TEM, SAED, and Raman spectroscopy. The dry air atmosphere requires high temperatures (~ 700 °C) for a complete CNT removal; at that temperature, the ZnO tubular shape is completely collapsed due to recrystallization. Under ozone atmosphere, the template can be removed at temperatures as low as 85 °C; this temperature is lower than the ALD preparation temperature (120 °C). The ozone treatment maintains the tubular shape of the ZnO nanostructures. Photocatalytic activity of the ZnO samples was evaluated using the photo-oxidation of Amaranth as probe reaction, showing a higher activity the ZnO nanotubes obtained from the low-temperature ozone treatment than the high-temperature processed materials. The use of ozone for the template removal reinforces the template-based ALD method to produce inorganic nanotubes.

Laser-etch patterning of metal oxide coated carbon nanotube 3D architectures

This paper describes a way to fabricate novel hybrid low density nanostructures containing both carbon nanotubes (CNTs) and ceramic nanotubes. Using atomic layer deposition, a thin film of aluminum oxide was conformally deposited on aligned multiwall CNT foams in which the CNTs make porous, three-dimensional interconnected networks. A CO2 laser was used to etch pure alumina nanotube structures by burning out the underlying CNT substrate in discrete locations via the printed laser pattern. Structural and morphological transitions during the calcination process of aluminum oxide coated CNTs were investigated through in situ transmission electron microscopy and high-resolution scanning electron microscopy. Laser parameters were optimized to etch the CNT away (i.e. etching speed, power and focal length) while minimizing damage to the alumina nanotubes due to overheating. This study opens a new route for fabricating very low density three dimensionally patterned materials with areas of dissimilar materials and properties. To demonstrate the attributes of these structures, the etched areas were used toward anisotropic microfluidic liquid flow. The demonstration used the full thickness of the material to make complex pathways for the liquid flow in the structure. Through tuning of processing conditions, the alumina nanotube (etched) regions became hydrophilic while the bulk material remained hydrophobic and electrically conductive.

Exceptional room-temperature plasticity in amorphous alumina nanotubes fabricated by magnetic hard anodisation.

Crystalline aluminum oxide is a brittle ceramic material. Here we show that individual alumina nanotubes with internal and external radii of ∼15 nm and ∼50 nm, respectively and lengths of the order of 100 μm can be readily separated from amorphous alumina membranes fabricated by a hard anodisation process under a magnetic field of up to 1.5 T. The ceramic nanotubes are extremely flexible and exhibit an exceptional plasticity of ±70% at room temperature without breaking. Elastic properties investigated by the double clamped beam method include a tensile strength of 4.1 GPa, corresponding to a breaking strain of 5%. These values are respectively 17 and 70 times greater than those of polycrystalline alumina fibres. The plasticity of anodic amorphous alumina helps explain the formation of ordered arrays of nanopores in the alumina membranes.

Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix

Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the ‘drop-cast’ method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young’s modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young’s modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.

Rapid and sensitive ethanol sensor based on hollow Au/V2O5 nanotubes via emulsion-electrospinning route

Hollow electrospun V2O5 and Au/V2O5 nanotubes have been successfully synthesized by combining emulsion electrospinning (EE) and post calcination treatment. Immiscible polyvinyl pyrrolidone (PVP)/metal salts/dimethylformamide (DMF) solution and polystyrene (PS)/DMF solution are chosen for the EE to form PS@(PVP/metal salts) core-sheath nanofibers, in which PS nanorods were formed and encapsulated within in the PVP/metal salts nanofibers owing to the stretching forces and de-emulsified force during the electrospinning. Excellent sensitivity and rapid response–recovery behaviors against ethanol have been successfully achieved based on our hollow ceramic (V2O5 and Au/V2O5) nanotubes.

Ceramic nanotubes for polymer composites with stable anticorrosion properties

The use of natural halloysite clay tubes 50 nm in diameter as nanocontainers for loading, storing, and slowly releasing organic corrosion inhibitors is described. Loaded nanotubes can be mixed well with many polymers and dyes in amounts of 5–10 wt % to form a ceramic framework (which increases the strength of halloysite composites by 30–50%), increase the adhesion of these coatings to metals, and allow for the slow release of corrosion inhibitors in defects of coatings. A significant improvement of protective anticorrosion properties of polyacryl and polyurethane coatings containing ceramic nanotubes loaded with benzotriazole and hydroxyquinoline is demonstrated.

Core-shell composite metal catalysts incased into natural ceramic nanotubes

The bimetallic halloysite nanotubes were prepared by the injection of halloysite- containing aerosols into the microwave plasma reactor. Nanotubes contain metal nanoparticles formed from the metal salt solution in the lumen of nanotubes and the iron oxide nanoparticles at the outer surface of nanotubes. Such halloysite composites may be sputtered onto the surface of the porous carrier forming the nanostructured catalyst, as was shown by the pure halloysite sputtering onto the model porous ceramic surface.

Synthesis of ceramic nanotubes using AAO templates

In this paper, the metal aluminum oxide ceramic nanotubes (M–Al–O, M = Zn, Mg and Ba) were synthesized by the use of porous anodic aluminum oxide (AAO) template. Metal oxide nanotubes were firstly formed from the thermal decomposition of respective nitrates within the pores of AAO templates. Then M–Al–O nanotubes were synthesized through the solid-state chemical reaction between the metal oxide nanotubes and AAO. TEM observation shows that the as-prepared samples are nanotubes and XRD measurement reveals that M–Al–O nanotubes (M = Zn, Mg and Ba) are crystalline in nature with spinel structure.

SiOC ceramic nanotubes of ultrahigh surface area

Silicon oxycarbide ceramic nanotubes have been successfully synthesized by inert atmosphere pyrolysis of polysilicone nanotubes using a sacrificial alumina membrane as a template at different pyrolysis temperatures. Scanning electron microscopy images show that the silicon oxycarbide ceramic nanotubes have well-aligned tubular structures. X-ray diffraction patterns and Raman spectra reveal that the obtained silicon oxycarbide ceramic nanotubes are amorphous below 1200 °C and are mainly composed of SiO 2 crystallites and free carbon when the temperature exceeds 1300 °C. Nitrogen-sorption isotherms indicate that the silicon oxycarbide ceramic nanotubes have high Brunauer–Emmett–Teller (BET) specific surface areas (up to 1387 m 2/g), large pore volumes (up to 1.82 cm 3/g).

Electrospun Polyaniline/Poly(methyl methacrylate)‐Derived Turbostratic Carbon Micro‐/Nanotubes

Nanotubes have great potential for applications in a rapidly increasing range of fields: catalysis, medicine, pharmacy, pheromone-release systems for crop protection, sensorics, and photonics. This is due to their high anisotropy, huge specific surface area that enhances reactivity, high rate of adsorption, and efficiency of transport processes both within and across the nanotube walls. Electrospinning is a process that produces continuous polymer fibers through the action of an external electric field imposed on a polymer solution (for a review of this process see previous publications). To manufacture nanotubes, two fundamentally different approaches have been reported: self-assembly and template-based methods. In the TUFT (tubes by fiber templates) process, electrospun nanofibers themselves are used as templates to produce nanotubes. The template-based TUFT process for nanotube production consists of three stages: i) the electrospinning of template nanofibers, ii) shell deposition via chemical or physical vapor deposition (CVD or PVD, respectively), and iii) core removal by thermal or chemical means. Recently, a new technique was introduced that allows the co-electrospinning of polymer solutions from a spinneret containing two coaxial capillaries. Using this technique, coelectrospinning of immiscible and miscible pairs of polymer solutions produced nanofibers with core/shell structures. This technique was then used to co-electrospin conjugated polymer nanofibers and to make the PCL/gelatin (PCL: poly(e-caprolactone)) core/shell structure that holds great potential for controlled drug delivery and as a scaffold for tissue engineering. It was possible to co-electrospin almost non-spinnable polymers such as the conducting polymer polyaniline (PAni). Using this same co-electrospinning technique, ceramic sol–gel precursors were added to the shell solutions to create ceramic nanotubes. The core material—a heavy mineral oil—was later extracted with octane. The aim of the present work is to produce hollow carbon nanotubes by co-electrospinning two polymer solutions. The process was carried out in two stages. In the first stage, use was made of the non-solvent effect on one of the polymers to facilitate the creation of a solid interface between the nanofiber’s core and shell. In the second stage, the nanofibers were subjected to heat treatment to degrade the core polymer and carbonize the polymer shell. Figure 1 shows a typical pattern of the co-electrospinning process close to the core/shell spinneret. The core-polymer capillary protrudes 0.3 to 1 mm below the shell capillary. As

Synthesis and microstructure observation of carbide ceramic nanotubes from carbon nanotubes as a template material.

Synthesis and microstructure observation of carbide ceramic nanotubes from carbon nanotubes as a template material.

Hydrothermal Synthesis of Thin Films of Barium Titanate Ceramic Nano‐Tubes at 200°C

A novel, low‐temperature synthesis method for producing BaTiO3 thin films patterned in the form of nano‐tubes (“honeycomb”) on Ti substrates is reported. In this two‐step method, the Ti substrate is first anodized to produce a surface layer (∼200–300‐nm thickness) of amorphous titanium oxide nano‐tube (∼100‐nm diameter) arrays. In the second step, the anodized substrate is subjected to hydrothermal treatment in aqueous Ba(OH)2, where the nano‐tube arrays serve as templates for their hydrothermal conversion to polycrystalline BaTiO3 nano‐tubes. This opens the possibility of tailoring the nano‐tube arrays and of using various precursor solutions and their combinations in the hydrothermal bath, to produce ordered, patterned thin‐film structures of various Ti‐containing ceramics. These could find use not only in a variety of electronic device applications but also in biomedical applications, where patterned thin films are also desirable.

Preparation of Ceramic Nanotubes for Photovolatic Applications

Preparation of Ceramic Nanotubes for Photovolatic Applications