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1.
Two-dimensional monolayer titania quantum dots (MTQDs) with ∼0.4 nm thickness and ∼2 nm lateral size are synthesized by supercritical water (SCW) treatment of titania nanotubes (TNTs). The morphology, chemical characteristics and the structure of MTQDs are studied. The formation mechanism of the MTQDs and the differences between SCW and low-temperature hydrothermal treatment are discussed. During the reaction, the high temperature, high pressure and high H+/OH− concentration of SCW dissolved TNTs into MTQDs, and the intercalation property of the “active” water clusters formed from the broken hydrogen bonding network facilitated the detachment of the MTQDs from the TNTs. The above two reasons lead to the capture of the dissolved tiny particles, which could hardly preserved in low-temperature hydrothermal treatment. The MTQDs may be the minimum constituent unit existing in the reality of the anatase TiO2. As a new member of the monolayer family, this new kind of 2D material may shed new light on the study of the monolayer materials. 相似文献
2.
The present study was aimed to investigate the morphological and phase transformations of hydrothermally prepared titanate nanotubes (TNTs) in supercritical water (SCW). We found that single-crystalline anatase nanocrystals including rhombic nanoparticles with the ends faceted with (1 0 1) facets and spindle-shaped nanorods mainly exposing (0 1 0) facets were rapidly generated in 10 min, of which the thicknesses were less than 5 nm. The morphologies and crystal forms of products treated for 6 and 8 min were investigated, showing that the outside nanotube walls were gradually decomposed meanwhile the inside tubular structures underwent a local shrinkage, followed by spontaneous phase transformations. We proposed that TNTs were transformed into anatase nanocrystals by two simultaneous processes. One is a dissolution-nucleation and crystal growth while the other is an in situ nucleation and crystal growth, resulting in the formation of rhombic and spindle-shaped morphologies, respectively. 相似文献
3.
Nawin Viriya-Empikul Noriaki Sano Takeyuki Kikuchi Sareeya Bureekaew Wiwut Tanthapanichakoon Tawatchai Charinpanitkul 《Journal of Industrial and Engineering Chemistry》2010,16(1):63-67
The titanate nanostructures with high UV absorption characteristics could be fabricated by hydrothermal method within a temperature range of 90–150 °C. TEM, XRD, BET analyses, and UV–vis spectroscopy were employed to elucidate the synthesized titanate nanostructure characteristics which were microstructure, phase transformation, specific surface area, and band gap energy, respectively. With an increase in the hydrothermal treating temperature from 90 to 120 °C, the specific surface area of titanate nanostructures was increased from 83 to 258 m2/g, while the band gap energy of titanate nanostructures was increased from 3.44 to 3.84 eV and then slightly decreased to 3.81 eV at 150 °C. The fabricated titanate nanostructures could exhibit higher UV adsorption capability but lower photocatalytic activity when compared with that of commercial TiO2 powders. 相似文献
4.
《Ceramics International》2016,42(5):5985-5994
Various morphologies of TiO2 nanostructures were synthesized by HNO3 assisted hydrothermal treatment with respect to the acid molarity (1 M, 3 M, and 8 M), temperature (110, 140, and 180 °C), and time (1, 3, and 6 h). An additional sample was synthesized inside the protonated titanate nanoribbon coated vessel with the acid molarity of 8M at 140 °C for 3 h. The crystal structure and morphology of the nanostructures synthesized were investigated using X-Ray diffractometer, scanning electron microscope, and transmission electron microscope. The results revealed that lower acid concentrations, longer synthesis durations and higher temperatures favored anatase phase formation. Meanwhile, a phase pure 3D lotus structure rutile TiO2 could be obtained by hydrothermal synthesis at 8M HNO3 concentration at 140 °C for 3 h using protonated H-titanate nanoribbons. A probable mechanism for the evolution of 3D rutile lotus structure was highlighted. 相似文献
5.
《Journal of the European Ceramic Society》2014,34(4):985-990
Reactive hot-pressing was scarcely applied to fabricate titanate ceramic waste forms designed for immobilizing high-level radioactive waste (HLW). However, compared with non-reactive processes, there is an advantage of producing high-density ceramics at reduced temperatures by reactive hot-pressing. CeIV-doped titanate composite ceramics with relative densities in excess of 99% were prepared by reactive hot-pressing at temperature as low as 1150 °C and pressure of 30 MPa for 1–4 h. The results show that low-temperature densification of the composite ceramics might be attributed to the plastic deformation under hot-pressing condition. In addition, aqueous stability testing was carried out using the standard MCC-1 static leach test method. The results demonstrate that the normalized elemental leach rate of Ca, Ce and Zr were fairly constant in a low value below 5 × 10−2 g m−2 d−1, 7 × 10−6 g m−2 d−1 and 6 × 10−6 g m−2 d−1 after 21 d. 相似文献
6.
《Ceramics International》2015,41(8):9426-9432
We demonstrate low-temperature formation of copper oxide (CuO) nanostructures as well as temperature-controlled variation of morphology by applying hydrothermal methods with copper(II) acetate Cu(CH3COO)2·H2O and 2-piperidinemethanol (2PPM) as starting materials. Monoclinic CuO nanostructures produced at 25 °C were of dendritic morphology with short nanorod-like substructures and exhibited a consequently large surface area (179 m2 g−1). Cyclic voltammetry measurements confirmed pseudocapacitive behavior of these dendritic CuO nanostructures giving specific capacitance ca. 28.2 F g−1 at a scan rate of 5 mV s−1. Oxide nanomaterials prepared in this investigation were characterized using powder X-ray diffraction, scanning and transmission electron microscopies, and nitrogen adsorption/desorption techniques. It is expected that these materials exhibit improved sensing and catalytic properties due to the increased availability of surface adsorption sites. 相似文献
7.
《Ceramics International》2017,43(11):8391-8395
Titanium dioxide (TiO2) films doped with different indium (In) concentrations have been prepared on SrTiO3 (STO) substrates by high vacuum metalorganic chemical vapor deposition (MOCVD). X-ray diffraction (XRD) analyses revealed the TiO2 films doped with low In concentrations to be [001] oriented anatase phase and the films with high In concentrations to present polycrystalline structures. The 1.8% In-doped TiO2 film exhibited the best electrical conductivity properties with the lowest resistivity of 8.68×10−2 Ω cm, a Hall mobility of 10.9 cm2 V−1 s−1 and a carrier concentration of 6.5×1018 cm−3. The films showed excellent transparency with average transmittances of over 85% in the visible range. 相似文献
8.
《Ceramics International》2016,42(15):16872-16881
Lithium zinc titanate (Li2ZnTi3O8) anode materials have been successfully synthesized using rutile-TiO2 with different particle sizes as titanium sources via a molten-salt method. Various physical and electrochemical methods are applied to characterize the effects of TiO2 particle sizes on the structures and physicochemical properties of the Li2ZnTi3O8 materials. When the particle size of TiO2 is too small (10 nm), it is difficult to homogeneously mix TiO2 with the other raw materials. Thus, the final product Li2ZnTi3O8 has poor crystallinity, large particle size, small specific surface area, pore volume and average pore diameter, which are disadvantageous to its electrochemical performance. Using TiO2 with the proper particle size of 100 nm as the titanium source, the Li2ZnTi3O8 (R-100-LZTO) with excellent electrochemical performance can be obtained. At 1 A g−1, 175.8 and 163.6 mA h g−1 are delivered at the 1st and the 200th cycles, respectively. The largest capacities of 163, 133.3 and 122.5 mA h g−1 are delivered at 2.5, 5 and 6 A g−1, respectively. The good high-rate performance of the R-100-LZTO originates from the good crystallinity, small particle size, large specific surface area and average pore diameter, low charge-transfer resistance and high Li+ diffusion coefficient. 相似文献
9.
《Ceramics International》2017,43(2):1968-1974
3D network-like porous MnCo2O4 nanostructures have been successfully fabricated through a facile and scalable sucrose-assisted combustion route followed by calcination treatment. Benefiting from its advantages of the unique 3D network-like architectures with large specific surface area (216.15 m2 g−1), abundant mesoporosity (2–50 nm) and high electronic conductivity, the as-prepared MnCo2O4 electrode displays a high specific capacitance of 647.42 F g−1 at a current density of 1 A g−1, remarkable capacitance retention rate of 70.67% at current density of 10 A g−1 compared with 1 A g−1, and excellent cycle stability (only 6.32% loss after 3000 cycles). The excellent electrochemical performances coupled with facile and cost effective method will render the as-fabricated 3D network-like porous MnCo2O4 as a promising electrode material for supercapacitors. 相似文献
10.
《Carbon》2013
Nano graphene oxide (NGO) was produced by further refluxing graphene oxide (GO) sheets in HNO3, and carboxylic acid functionalized graphene oxide (GO–COOH) was obtained by a simple etherification reaction between GO and chloroacetic acid. The GO, GO–COOH and NGO sheets are combined with TiO2 nanorods by a two-phase assembling method, and confirmed by transmission electronic microscopy. The GO–TiO2, GO–COOH–TiO2 and NGO–TiO2 composites are used in a comparative study of photocatalytic H2 generation activity under UV light irradiation. The H2 generation rate of TiO2 nanorods was slightly increased from 15 to 30 mL h−1 g−1 by replacing oleic acid ligands with hydrophilic dopamine, and significantly increased to 105 mL h−1 g−1 after combining with GO sheets. The further comparative study shows that GO–COOH–TiO2 composite has higher H2 generation rate of 180 mL h−1 g−1 than that of GO–TiO2 and NGO–TiO2 composites. 相似文献
11.
《Ceramics International》2016,42(13):14667-14674
Nanocomposites combining high breakdown strength (BDS) polymer and high dielectric permittivity ceramic fillers have shown great potential for pulsed power application. Here a new composite material based on surface-functionalized Ba0.6Sr0.4TiO3 nanofibers/poly(vinylidene fluoride) (BST NF/PVDF) has been prepared by solution casting. The nanocomposites containing 2.5 vol% isopropyl dioleic(dioctylphosphate) titanate (NDZ 101)-functionalized BST NF (N-h-BST NF) have large energy density of 6.95 J cm−3 at 380 MV m−1, which is 1.85 times larger than that of the pure PVDF at the same electric field. Also, the discharge speed of the nanocomposites containing 7.5 vol% N-h-BST NF is approximately 0.11 μs. The good properties, together with the large energy density and fast discharge speed, make this material a promising candidate for pulsed power capacitor. 相似文献
12.
《Catalysis communications》2010,11(15):2051-2055
Mesoporous TiO2 was prepared by simply controlling the hydrolysis of Ti(OBu)4 with the help of acetic acid. The mesoporous TiO2 had a well-crystallized anatase phase and a high surface area of 290 m2 g−1 with a pore size of about 4 nm. The anatase phase and the mesoporous structure were maintained in the VOx/TiO2 catalyst with a monolayer dispersion of V2O5, however, the surface area decreased to 126 m2 g−1. The catalyst was highly active and selective for methanol oxidation, giving about 55% conversion of methanol and 85% selectivity to dimethoxymethane at 423 K. 相似文献
13.
《Ceramics International》2017,43(5):4411-4418
A new efficient photocatalyst consisting of TiO2-activated carbon composite (TiO2/AC) was synthesized by sol-gel process and applied to decomposition of tetracycline (TC). Its properties and catalytic activity were evaluated in comparison with bare TiO2 and P25, based on several characterization techniques and TC photodegradation kinetic studies. The results showed TiO2/AC has better structural and electronic features for photocatalysis; SBET of 129 m2 g–1, exclusively anatase phase, crystal size of 8.53 nm and band gap energy of 3.04 eV. The catalytic activity of the material was evaluated based on photodegradation kinetic studies of TC from aqueous solution (with initial concentration=50 mg L−1 and catalyst dosage=1.0 g L−1). Non-linear kinetic model of pseudo-first order were fitted to the resulting experimental data. The apparent first-order rate constant (kapp=42.9×10–3 min–1) and half-life time (t1/2=16.1 min) determined for TiO2/AC were better than those for P25 and bare TiO2. TC degradation by-products were investigated by HPLC-MS, showing TC was completely degraded after 75 min, producing fragments with m/z smaller than 150. 相似文献
14.
《Carbon》2013
We present a simple and fast approach for the synthesis of a graphene–TiO2 hybrid nanostructure using a microwave-assisted technique. The microstructure, composition, and morphology were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, Raman microscopy, X-ray photoelectron spectroscopy, and field-emission scanning electron microscopy. The electrochemical properties were evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests. Structural analysis revealed a homogeneous distribution of nanosized TiO2 particles on graphene nanosheets. The material exhibited a high specific capacitance of 165 F g−1 at a scan rate of 5 mV s−1 in 1 M Na2SO4 electrolyte solution. Theenhanced supercapacitance property of these materials could be ascribed to the increased conductivity of TiO2 and better utilization of graphene. Moreover, the material exhibited long-term cycle stability, retaining ∼90% specific capacitance after 5000 cycles, which suggests that it has potential as an electrode material for high-performance electrochemical supercapacitors. 相似文献
15.
A novel TiO2 − xNx/BN composite photocatalyst was prepared via a facile method using melamine–boron acid adducts (M·2B) and tetrabutyl titanate as reactants. The morphological results confirmed that nitrogen-doped TiO2 nanoparticles were uniformly coated on the surface of porous BN fibers. A red shift of absorption edge from 400 nm (pure TiO2) to 520 nm (TiO2 − xNx/BN composites) was observed in their UV–Vis light absorption spectra. The TiO2 − xNx/BN photocatalysts exhibited enhanced photocatalytic activity for the degradation of Rhodamine B (RhB) and the highest photocatalytic degradation efficiency reached 97.8% under visible light irradiation for 40 min. The mechanism of enhanced photocatalytic activity was finally proposed. 相似文献
16.
Jaturong Jitputti Thitima Rattanavoravipa Surawut Chuangchote Sorapong Pavasupree Yoshikazu Suzuki Susumu Yoshikawa 《Catalysis communications》2009,10(4):378-382
Monodispersed flower-like titanate superstructure was successfully prepared by simple hydrothermal process without any surfactant or template. N2-sorption analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) observation of as-synthesized product revealed the formation of flower-like titanate with diameter of about 250–450 nm and BET surface area (SBET) of 350.7 m2 g?1. Upon thermal treatment at 500 °C, the titanate nanosheets were converted into anatase TiO2 with moderate deformation of their structures. The as-prepared flower-like titanate showed high photocatalytic activity for H2 evolution from water splitting reaction. Moreover, the sample heat treated at 500 °C exhibited higher photocatalytic activity than that of commercial TiO2 anatase powder (ST-01). 相似文献
17.
《Carbon》2013
Flexible and binder-free graphene–TiO2 paper was prepared by a simple route. A unique 3-D nano-structure was achieved with nano-sized TiO2 intercalated between graphene layers as pillars, significantly increasing the Li-ion insertion/extraction rate. At a current rate of 2 Ag−1, the specific capacity can reach 122 mAhg−1 after 100 charge/discharge cycles. More remarkably, the flexible graphene/TiO2 hybrid paper shows an excellent stability when the rates decrease from 4 Ag−1 back to 200 mAg−1 with the retained capacity of 175 mAhg−1. 相似文献
18.
《Ceramics International》2015,41(4):5484-5491
Porous chitosan–SiO2 membranes were prepared by ultrasonic mixing solution-cast and porogen removal method at different SiO2 weight ratios. To remove SiO2 from chitosan membranes, NaOH solution was used to dissolve SiO2. Porous chitosan:SiO2 membrane with the weight ratio 1:2 produced optimum average pore size (8.5 μm) with an amorphous structure and the highest water uptake (257.1%). Further soaking of this membrane in NH4CH3COO electrolyte solution for two days produced the highest conductivity (3.6×10−3 S cm−1) and optimum breakdown voltage (1.8 V). Fabrication of coin cell proton battery displayed an open circuit potential of 1.5 V for 7 days, maximum power density (6.7 mW cm−2) and small current resistance (0.03 Ω). The specific discharge capacities obtained from discharge profile of 39.7 mA h g−1 (0.5 mA) and 43.8 mA h g−1 (1.0 mA) increased as the discharge currents were increased. These results showed that a porous chitosan–SiO2 membrane is suitable membrane for the proton batteries. 相似文献
19.
Cu was loaded on the S-doped TiO2 by electroless plating method. The prepared Cu/S–TiO2 exhibited high photocatalytic activity for hydrogen generation, and the yield is up to 7.5 mmol h− 1 g− 1cat in methanol solution. Their physical structure and chemical properties were characterized by UV–Vis, XRD, XPS and EXAFS. The copper species were CuO and Cu2O, and the sample showed excellent visible light absorption ability. Comparing with the sample prepared by chemical reducing method, the electroless plated copper on S–TiO2 was highly dispersed, which could facilitate photo-generated charges capture, transfer and separation. 相似文献
20.
《Journal of the European Ceramic Society》2017,37(11):3595-3602
Li2TiO3 is a candidate material for tritium breeding in the future nuclear fusion reactor. In this study, Li2TiO3 powder was synthesized by ultrasonic-assisted solution combustion synthesis (USCS) in a single step. The ultrasonic transducer with the power of 1000 W was introduced in the synthesis process. The crystallite size of Li2TiO3 powder prepared by utilization of ultrasonic power is significantly decreased to ∼5.0 nm, while the one obtained without ultrasonic power is 20.0 nm. Li2TiO3 ceramic sintered from USCS powder at 800 °C exhibits the small grain size of 330 nm and the open pores size of 140 nm. The crush load of the ceramic reaches 37.2 N although the structure is porous. Compared with the ceramic prepared by solid-state reaction and conventional solution combustion synthesis, USCS sample has a higher conductivity of 2.0 × 10−6 S m−1 at room temperature, indicating the lower tritium diffusion barrier in the ceramic. 相似文献