Graphene Titanium Research Articles

Fabricating graphene-titanium composites by laser sintering PVA bonding graphene titanium coating: Microstructure and mechanical properties

Abstract Graphene reinforced titanium (Ti-Gr) nanocomposite was prepared by laser sintering of the mixture of PVA bonding graphene sheets and titanium powders. During laser sintering process, the survival and uniform dispersion of graphene have been demonstrated, which embedded in Ti matrix, and formed Ti-Gr nanocomposites. Microstructures and components of the nanocomposites were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and Raman spectroscopy. The survival of graphene sheets in nanocomposite is due to rapid heating/cooling in laser sintering process. Hardness measurements showed that the laser sintered Ti-Gr nanocomposites achieved more than 2-fold Vickers Hardness value of barely sintered Ti.

Graphene-Titanium Interfaces from Molecular Dynamics Simulations.

Unraveling the physical and chemical properties of graphene-metal contacts is a key step toward the development of graphitic electronic nanodevices. Although many studies have revealed the way that various metals interact with graphene, few have described the structure and behavior of large pieces of graphene-metal nanostructures under different conditions. Here, we present the first classical molecular dynamics study of graphene-titanium (G-Ti) structures, with and without substrates. Physical and chemical properties of equilibrium structures of G-Ti interfaces with different amounts of titanium coverage are investigated. Adhesion of Ti films on graphene is shown to be enhanced by the vacancies in graphene or the electrostatic influence of substrates. The dynamics of pristine G-Ti structures at different temperatures on planar and nonplanar substrates are investigated, and the results show that G-Ti interfaces are thermally stable, that is, not prone to any reaction toward the formation of titanium carbide.

Novel titanium dioxide–graphene–activated carbon ternary nanocomposites with enhanced photocatalytic performance in rhodamine B and tetracycline hydrochloride degradation

A novel ternary nanocomposite consisting of activated carbon (AC) and titanium dioxide (TiO2) decoration in the presence of reduced graphene oxide (TiO2–rGO–AC) was fabricated by a facile hydrothermal synthesis method for use as a high-performance photocatalyst. The as-prepared TiO2–rGO–AC nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and UV–Vis diffuse reflectance spectroscopy. The results demonstrated that the TiO2 and activated carbon were well dispersed on the rGO surface. The photocatalytic performance of the TiO2–rGO–AC nanocomposite was evaluated as a catalyst for the photodegradation of rhodamine B. The degradation rate was 3.4 times higher than that of pure TiO2 under simulated solar light irradiation. The enhancement of photocatalytic performance is attributed to the adsorption of AC which significantly increased the organic molecule concentration near the catalytic surface, allowing the effective transfer and separation of photogenerated electrons. TiO2–rGO–AC photocatalyst is also effective for the degradation of tetracycline in aqueous solution, suggesting wide application of these nanocomposite materials in various fields including air purification and wastewater treatment.

Photocatalytic Degradation of Toluene, Butyl Acetate and Limonene under UV and Visible Light with Titanium Dioxide-Graphene Oxide as Photocatalyst

Photocatalysis is a promising technique to reduce volatile organic compounds indoors. Titanium dioxide (TiO2) is a frequently-used UV active photocatalyst. Because of the lack of UV light indoors, TiO2 has to be modified to get its working range shifted into the visible light spectrum. In this study, the photocatalytic degradation of toluene, butyl acetate and limonene was investigated under UV LED light and blue LED light in emission test chambers with catalysts either made of pure TiO2 or TiO2 modified with graphene oxide (GO). TiO2 coated with different GO amounts (0.75%–14%) were investigated to find an optimum ratio for the photocatalytic degradation of VOC in real indoor air concentrations. Most experiments were performed at a relative humidity of 0% in 20 L emission test chambers. Experiments at 40% relative humidity were done in a 1 m³ emission test chamber to determine potential byproducts. Degradation under UV LED light could be achieved for all three compounds with almost all tested catalyst samples up to more than 95%. Limonene had the highest degradation of the three selected volatile organic compounds under blue LED light with all investigated catalyst samples.

In-situ microwave synthesis of graphene–TiO2 nanocomposites with enhanced photocatalytic properties for the degradation of organic pollutants

Graphene–titanium oxide (G–TiO2) nanocomposites were synthesized by a novel surfactant free, environmentally friendly one-port in-situ microwave method. The structure of the nanocomposite was characterized by the X-ray diffraction analysis and the morphology by using scanning electron microscopic and transmission electron microscopic images. The functional groups and carbon band structures were identified using FTIR and Raman spectral analysis. TiO2 nanoparticles in the size range of 5–10nm were distributed on the graphene sheets. The surface area of pure TiO2 and G–TiO2 nanocomposite was measured to be 20.11 and 173.76m2/g respectively. The pore volume and pore size of TiO2 were 0.018cm3/g and 1.5266nm respectively. G–TiO2 composite possesses higher pore volume (0.259cm3/g) and pore size 3.2075nm. The binding states of C, O and Ti of nanocomposite were analyzed by X-ray photoelectron spectroscopy, which confirmed the chemical bonding between graphene–TiO2. The photocatalytic activity of pure TiO2 and G–TiO2 nanocomposite was studied under UV and visible light irradiation sources with methylene blue dye. It has been observed that the degradation was faster in G–TiO2 nanocomposite than pure TiO2 nanoparticles. The rate constant and half life time were calculated from the kinetic studies of the degradation. The highest degradation efficiency of 97% was achieved in UV light and 96% for visible light irradiation with G–TiO2 as a catalyst. The studies reveal that G–TiO2 nanocomposite can be an effective catalyst for industrial waste water treatment.

Generation of Graphene-titanium Dioxide Nanotubes Catalytic Board and Its Photocatalysis Capability to Degrade Pentachlorophenol

Considering that the photocatalysts used in research are generally in powder form, which increase the difficulty of efficient recycle in practice, this research focused on the generation of graphene-titanium dioxide nanotubes catalytic board. Graphene oxide and TiO2 powder were used as precursors; the sol-gel like coating method along with hydrothermal method was adopted to synthesize the catalytic board. The generated board presented a uniform surface morphology and in its most regions, the catalyst was loaded in the form of a single layer or few layers. During the photodegradation process in the eluent system, under solar irradiation, the removal ratio of the pentachlorophenol (PCP) could reach almost 100% within 30 min, the degradation rate was increased by more than 5 times compared with the eluent without addition of photocatalyst; while under xenon lamp, the degradation rate was increased by 10 times. After long-time soaking and repeated use, the photocatalytic activity of the board did not decrease obviously, which is suitable for long-term use. The application of the board could solve the problem of immobilized catalyst and enable catalyst recycling in subsequence processing.

Thermal and Mechanical Properties of Graphene–Titanium Composites Synthesized by Microwave Sintering

The x wt% graphene–Ti composites (x = 0, 0.2, 0.3 and 0.4) were obtained using the powder metallurgy method. The X-ray diffraction results demonstrated that the peak intensity of graphene increased monotonically with increasing graphene content. Furthermore, the number of grain boundary and interface between graphene and matrix increased as graphene increased, which led to a sharp rise of thermal resistances. The thermal conductivity and specific heat capacity of composites initially decreased drastically with addition of graphene, but then increased with increasing graphene content from 0.2 to 0.4 wt%. This phenomenon was connected with the graphene content and the characteristics of Ti matrix (pores, grain boundary and interface between graphene and matrix). The variation of the compressive strength of composites was attributed to the interaction effects of the average grain size of the Ti matrix (d m) and the volume fraction (V f) and aspect ratio (λ) of graphene.

Graphene-titanium dioxide nanocomposite based hypoxanthine sensor for assessment of meat freshness

We report on the fabrication of a graphene/titanium dioxide nanocomposite (TiO2-G) and its use as an effective electrode material in an amperometric hypoxanthine (Hx) sensor for meat freshness evaluation. The nanocomposite was characterized by TEM, XRD, FTIR, XPS, TGA, BET, and CV using the redox couples [Fe(CN)6]−3/−4 and [Ru(NH3)6]+3/+2 respectively. The TiO2/G nanocomposite offered a favorable microenvironment for direct electrochemistry of xanthine oxidase (XOD). The fabricated Nafion/XOD/TiO2-G/GCE sensor exhibited excellent electro catalytic activity towards Hx with linear range of 20μM to 512μM, limit of detection of 9.5μM, and sensitivity of 4.1nA/μM. In addition, the biosensor also demonstrated strong anti-interference properties in the presence of uric acid (UA), ascorbic acid (AA) and glucose. Minimal interference of xanthine (Xn) was observed at ~7%. Moreover, the biosensor showed good repeatability (4.3% RSD) and reproducibility (3.8% RSD). The reported biosensor was tested towards the detection of Hx in pork tenderloins stored at room temperature for seven days. There was a good correlation (r=0.9795) between biosensor response and measurements obtained by a standard enzymatic colorimetric method. The TiO2-G nanocomposite is therefore an effective electrode material to be used in electrochemical biosensors to assess the freshness of meat.

Synthesis of Graphene Titanium Dioxide Composites as Photocatalytic Materials for Degradation of Moderacid Black

Synthesis of Graphene Titanium Dioxide Composites as Photocatalytic Materials for Degradation of Moderacid Black

Graphene-enhanced waveguide-resonance gratings

We demonstrate that the integration of graphene strongly influences optical properties of the subwavelength gratings, opening a way toward nanophotonic devices. By using the Fourier-expansion modal method, we demonstrate that graphene–titanium dioxide nanostructures can be used for designing polarization-insensitive absorbers and biochemical sensors.

Facile synthesis of graphene-titanium dioxide nanocomposites as anode materials for Na-ion batteries

Graphene-titanium dioxide (TiO2) materials were prepared using titanium tetrachloride (TiCl4) and graphite oxides (GO) via a simple and continuous vapor reaction process. TiO2 nanoparticles obtained from the reaction assembled into clusters loading on graphene or attached onto graphene individually to form graphene-TiO2 nanocomposites. Graphene not only could enhance the nanocomposite electric conductivity but also is useful to improve the material porosity. The nanocomposites exhibited an enhanced performance for Na-ion battery anode with a specific capacity of 115 mAhg−1 at a current of 1 A/g and a stable specific capacity of 102 mAhg−1 at 0.1 A/g after 300 cycles.

Selective photodegradation and enhanced photo electrochemical properties of titanium dioxide–graphene composite with exposed (001) facets made by photochemical method

We report for the first time, titanium dioxide–graphene (HRTiO2–Gr) composite with exposed (001) facets by a photochemical reduction method and its selective photocatalytic properties. The drastic reduction in the photoluminescence intensity of the composite indicates effective charge separation. The composite with 10wt% Gr (HRTiO2–Gr10) exhibits higher photodegradation (PD) of methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) compared to that of the P25. The composite exhibits selectivity in its PD properties, with higher photocatalytic activity for the positive dyes, MB and RhB. This is attributed to the synergistic effect of the unique pore morphology and the surface properties of the composite due to the negative Gr. Higher selectivity in the PD of the positive dyes is observed in the mixture of the positive and negative dyes. In addition, HRTiO2–Gr10 exhibits lower charge transfer resistance than that of the HRTiO2 and P25. The improved charge transfer resistance is assigned to the thin Gr sheets which improves the charge transfer at the interfaces. Our results suggest that the PCR method of preparation facilitates higher loading of high quality thin Gr sheets with improved dispersion and interaction with TiO2 thus imparting the composite selective and enhanced photocatalytic properties.

Swift Heavy Ion Induced Optical and Electronic Modifications of Graphene–TiO2 Nanocomposites

The effect of swift heavy ions irradiation on optical and electronic properties of chemically synthesized graphene–TiO2 nanocomposites is presented. Modification of surface properties of these nanocomposites by irradiation with three different ions and with varying fluence was analyzed by Raman spectroscopy, transmission electron microscopy, and scanning Kelvin probe microscopy techniques. Raman spectra of irradiated samples exhibit systematic changes in the characteristic peaks of both graphene and TiO2. The nanocrystallite dimension calculated from Raman peak intensity decreases with fluence, indicating the occurrence of peripheral fragmentation. Furthermore, measurement of the surface contact potential difference using scanning Kelvin probe reveals that the work function of graphene–titanium dioxide nanocomposites can be effectively increased by more than 1 eV.

Efficient gaseous toluene photoconversion on graphene–titanium dioxide nanocomposites with dominate exposed {0 0 1} facets

A series of GnTiO2 {001} nanocomposites (GTN) with dominate exposed {001} facets has been synthesized by various dosage of graphite oxide (GO) and hydrofluoric acid (HF) during a facile solvothermal process successfully. The photocatalytic degradation efficiency (PDE) of the optimal sample reached up to 98.7% for liquids methyl orange and up to 78.6% for gaseous toluene under the UV-light irradiation for 30min, which is much higher than P25. The effects mechanism of HF and GO on the percentage of {001} facets exposed and the crystal morphology are investigated by XRD, SEM, TEM, UV–Vis, XPS and BET measurement, particularly. Cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) were used to explore the electron transfer mechanisms of GnTiO2 {001} nanocomposites. These results reveal the enhanced photocatalytic properties attribute to the excellent electron transport of Gn and highly reactive {001} facets can facilitate the separation of photo-generated charge carriers. Moreover, Gn can extend the absorption range of light and improve the adsorptivity of pollutant molecules.

Facile green synthesis of graphene–titanium nitride hybrid nanostructure for the simultaneous determination of acetaminophen and 4-aminophenol

We demonstrate herein a newly developed electrochemical sensor base on the reduced graphene oxide–titanium nitride (RGO–TiN) nanohybrid. The nanohybrid was prepared by mixing the TiN nanoparticles and GO dispersion and then treating with glucose and Zn foils. The morphologies and microstructures of the as-prepared nanohybrid were characterized by UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy. The as-prepared RGO–TiN nanohybrid exhibited excellent electrocatalytic activity toward the simultaneous detection of acetaminophen (ACOP) and 4-aminophenol (4-AP). As a result, the linear detection ranges were 0.06–660μM for ACOP and 0.05–520μM for 4-AP, respectively, with the low detection limits of 0.02μM for ACOP and 0.013μM for 4-AP. Based on the excellent performance, it was demonstrated that the prepared RGO–TiN nanohybrid was a promising candidate for advanced electrode material in electrochemical sensing field and the as-prepared RGO–TiN nanohybrid may find more applications for the detection of various analytes.

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.

Polymer based graphene/titanium dioxide nanocomposite (GTNC): an emerging and efficient thermoelectric material.

PSS)-GTNC, polyvinyl acetate (PVAc)-GTNC, PEDOT:PSS-graphene, and PVAc-graphene by ultrasonication followed by hot compaction towards their thermoelectric application. The filler (graphene, GTNC) concentration and polymer matrix were judiciously varied and optimized for the sake of high electrical conductivity and Seebeck coefficient which leads to a higher power factor (PF). The PVAc based composite with a composition of PVAc (20%) and GTNC (80%) was found to be the most promising material with an electrical conductivity of 2.6 × 10(4) S m(-1) and a Seebeck coefficient of -42 μV K(-1) at room temperature (RT). As a result, the PF reaches 47 μW m(-1) K(-2) at RT which is approximately 37 times, 5 times and 3 times higher than that for the PVAc-graphene based composite, the PSS-GTNC based composite and the PSS-graphene based composite respectively. The origin of the thermoelectric performance of the GTNC composite seems to be from the synergistic effect of graphene nanosheets and TiO2 nanoparticles. The composite shows a large power factor value without using any conducting polymer.

Photoreduction of carbon dioxide by graphene–titania and zeolite–titania composites under low-intensity irradiation

As it is the most important of the greenhouse gases, the utilization and reduction of carbon dioxide have attracted a great attention. As compared to the technological demands for carbon capture and storage (CCS), carbon dioxide reduction is a safe and effective way to convert carbon dioxide to fuel. In this research, two different catalysts, graphene–titania and zeolite–titania, are used to achieve the carbon dioxide reduction. The characteristics of these materials are analyzed by Brunnauer–Emmett–Teller, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible, scanning electron microscope and transmission electron microscopy. Because of the different features of the catalysts, various products can be generated through different pathways. Formic acid and methanol are the final products when graphene is used as the catalyst, but only methanol can be generated when zeolite–titania is used as the catalyst. The reaction mechanisms and pathways are discussed.

Adsorption property of Cr(vi) on magnetic mesoporous titanium dioxide–graphene oxide core–shell microspheres

Novel Fe3O4@mTiO2@GO microspheres for the fast removal of Cr(VI) were synthesized by immobilizing a mesoporous TiO2 shell on the surface of magnetic Fe3O4 nanoparticles prior to binding with GO. The characterization results from FTIR, SEM, VSM and XRD showed that Fe3O4@mTiO2@GO was successfully prepared with a large surface area and good magnetic responsiveness. It was shown that the sorption of the microspheres for Cr(VI) was strongly dependent on pH value and contact time. As Cr-removal adsorbents, the maximum Cr-removal capability of microspheres was 117.94 mg g−1. The equilibrium adsorptions were well-described by the Freundlich isotherm mode and its kinetics followed pseudo-second-order rate equation. Moreover, the Fe3O4@mTiO2@GO microspheres could be regenerated and used repeatedly by simple treatment without obvious structure and performance degradation. These results demonstrated the potential applications of Fe3O4@mTiO2@GO microspheres in the efficient Cr-removal from wastewater and purification of polluted water.

Graphene–Titania Hybrid Photoanodes by Supersonic Kinetic Spraying for Solar Water Splitting

We report the synthesis of graphene–TiO2 (G–TiO2) composite films that exhibit significantly enhanced photoelectrochemical water‐splitting performance relative to pure TiO2. Supersonic kinetic spraying was used to produce strongly adhered, electrically and mechanically robust G–TiO2 composite films containing 0.1, 0.5, 1.0, and 5.0 wt.% graphene. Films with an intermediate graphene content of 1.0 wt.% demonstrated the best water‐splitting performance. G–TiO2 composite films with 1.0 wt.% graphene exhibited photocurrent density ten times that of pure TiO2 films. The electron transfer between TiO2 and graphene suppresses the recombination of photoinduced charge carriers and prolongs the electron excited‐state lifetime, which contributes to the enhanced photoelectrochemical water‐splitting performance.