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1.
Ceria powders were prepared by gel combustion process using cerium nitrate and hitherto unexplored amino acids such as aspartic
acid, arginine and valine as fuels. The powders have been characterized by X-ray and laser diffraction. Cold pressed compacts
of these powders have been sintered at 1250°C for 2 h. Internal pore microstructure of the sintered compacts has been investigated
by small angle neutron scattering (SANS) over a scattering wave vector q range of 0.003–0.17 nm −1. The SANS profiles indicate surface fractal morphology of the pore space with fractal dimensionality lying between 2.70 and
2.76.
相似文献
2.
Self-cleaning of a surface of nanotube arrays of anodic titanium oxide (ATO) is demonstrated. The ATO was prepared in fluoride
ion containing sulfate electrolytes with a structure of 0.4 μm length, 100 nm pores diameter, 120 nm interpore distance, 25 nm
pore wall thickness, a 8×10 9 pores cm −2 pore density, and 68.2% porosity. Prepared as thin films either directly from a Ti foil or on a glass substrate, these arrays
have the property that water drops spread quickly over the surface of the films without irradiation. In contrast, a flat anatase
TiO 2 film requires irradiation with UV light for several minutes before the contact angle decreases to zero. The observed self-cleaning
behavior of the ATO thin films is due to the capillary effect of the nanochannel structure and the superhydrophilic property
of the anatase TiO 2 surface inside the tube. 相似文献
3.
Solid electrolyte Li 1.3Al 0.3Ti 1.7(PO 4) 3 was prepared by sol-gel method under different sintering conditions. The structural identification, surface morphology, electrochemical
window, ionic conductivity, and activation energy of the Li 1.3Al 0.3Ti 1.7(PO 4) 3 sintered pellets were investigated by X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and electrochemical
impedance spectroscopy. It is found that the sintering temperature and time have considerable effect on the properties of
the Li 1.3Al 0.3Ti 1.7(PO 4) 3 sintered pellets. The Li 1.3Al 0.3Ti 1.7(PO 4) 3 pellet sintered at 900 °C for 2 h is denser than the pellets sintered at other conditions. Different sintering conditions
result in the sintered pellet with different porosity. However, the sintering conditions have little effect on the electrochemical
window of Li 1.3Al 0.3Ti 1.7(PO 4) 3. Among the Li 1.3Al 0.3Ti 1.7(PO 4) 3 pellets sintered at various conditions, the pellet sintered at 900 °C for 2 h shows the highest ionic conductivity of 3.46 × 10 −4 S cm −1 and the lowest activation energy of 0.2821 eV. 相似文献
4.
Effect of porosity and pore size distribution on the low-frequency dielectric response, in the range 0.01–100 kHz, in sintered
ZrO 2—8 mol% Y 2O 3 ceramic compacts have been investigated. Small-angle neutron scattering (SANS) technique has been employed to obtain the
pore characteristics like pore size distribution, specific surface area etc. It has been observed that the real and the imaginary
parts of the complex dielectric permittivity, for the specimens, depend not only on the porosity but also on the pore size
distribution and pore morphology significantly. Unlike normal Debye relaxation process, where the loss tangent vis-à-vis the
imaginary part of the dielectric constant shows a pronounced peak, in the present case the same increases at lower frequency
region and an anomalous non-Debye type relaxation process manifests. 相似文献
5.
To date, the fastest lithium ion-conducting solid electrolytes known are the perovskite-type ABO3 oxide, with A = Li, La and B = Ti, lithium lanthanum titanate (LLTO)
Li3x La( 2 \mathord | / |
\vphantom 2 3 3 ) - x [¯]( 1 \mathord | / |
\vphantom 1 3 3 ) - x TiO3 {\rm Li}_{3x} {\rm La}_{\left( {{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-\nulldelimiterspace} 3}} \right) - x} \Box_{\left( {{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}} \right) - x} {\rm TiO}_3 and its structurally related materials. In this formula, [¯]\Box represents the vacancy. These materials have attracted much attention due to their application in lithium ion batteries used
as energy sources in microelectronic and information technologies. In addition to the well-established simple cubic, tetragonal
and orthorhombic perovskite type distorted cell structures, the hexagonal unit cell was reported in a recent study for Li0.5 La0.5 TiO3 − δ
, ( 0 £ d £ 0.06 )\left( {0 \le \delta \le 0.06} \right). We investigated the ionic conductivity in hexagonal La0.5 Li0.5 TiO3{\rm La}_{0.5} {\rm Li}_{0.5}\- {\rm TiO}_3 by molecular dynamics. We confirmed that ionic conductivity in this compound is due to the motion of lithium ions. We show
that both Arrhenius and Vogel–Tamman–Fulcher-type relationships could be used to express the high-temperature conductivity
of this compound. From our results, hexagonal LLTO exhibits almost 1.7–1.9 ×10 − 3 S cm − 1 at room temperature. Thus, due to its high ionic conductivity, this compound is expected to show some advantages in comparison
with the best conductors of this family, for usual applications of ionic conductors. 相似文献
6.
Alcohol based sols of cerium chloride (CeCl 3·7H 2O) and titanium propoxide (Ti(OPr) 4) in ethanol mixed in different mole ratios have yielded mixed oxide films on densification at 500 °C. The reversibility of the intercalation/deintercalation reactions has shown electrochemical stability of the films. Addition of TiO 2 in an equivalent mole ratio manifests in producing highly transparent films with appreciable ion storage capacity. The electrochemical studies have revealed the significant role of TiO 2 in controlling the ion storage capacity of the films, as it tends to induce the disorder. In addition, the films prepared from an aged sol are observed to exhibit a much higher ion storage capacity than the films deposited using the as-prepared sol. The X-ray photoelectron spectroscopic studies have provided information on the variation of Ce 4+/Ce 3+ ratio as a function of increased TiO 2 content in the films. This study has led to a better understanding of the increased ion storage capacity with the increased TiO 2 proportion. The transmission electron microscopic study has demonstrated the presence of CeO 2 nanograins even in films, which are amorphous to X-rays. Elucidation of the structural, optical and electrochemical features of the films has yielded information on aspects relevant to their usage in transmissive electrochromic devices. The films have been found to exhibit properties that can find application as counter electrode in electrochromic smart windows in which they are able to retain their transparency under charge insertion, high enough for practical uses. Also, the fastest coloration-bleaching kinetics for the primary electrochromic electrode (WO 3) working in combination with Ce/Ti (1:1) electrode stimulates the use of latter in electrochromic windows (ECWs). 相似文献
7.
Mo-Ti oxide films with compositions ranging from MoO 3 to TiO 2 were prepared by reactive DC magnetron sputtering using a newly developed high-rate technique with interacting plasma zones.
Optical and electrochemical measurements showed that an increase of the Ti content yielded increased electrochemical stability,
decreased coloration efficiency, and increased potential for electrochromic coloration. The films have interesting properties
for color-neutral electrochromic devices.
Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995 相似文献
8.
The interfaces between metal electrodes and the oxide in TiO 2-based memristive switches play a key role in the switching as well as in the I– V characteristics of the devices in different resistance states. We demonstrate here that the work function of the metal electrode
has a surprisingly minor effect in determining the electronic barrier at the interface. In contrast, Ti oxides can be readily
reduced by most electrode metals. The amount of oxygen vacancies created by these chemical reactions essentially determines
the electronic barrier at the device interfaces. 相似文献
9.
An increasing energy demand and environmental pollution create a pressing need for clean and sustainable energy solutions.
TiO 2 semiconductor material is expected to play an important role in helping solve the energy crisis through effective utilization
of solar energy based on photovoltaic devices. Dye-sensitized solar cells (DSSCs) are potentially lower cost alternative to
inorganic silicon-based photovoltaic cells. In this study, we report on the fabrication of DSSCs from anodic TiO 2 nanotubes (NT) powder, produced by rapid breakdown potentiostatic anodization of Ti foil in 0.1 M HClO 4 electrolyte, as photoanode. TiO 2 NT powders with a typical NT outer diameter of approximately 40 nm, wall thickness of approximately 8–15 nm, and length of
about 20–25 μm, have been synthesized. The counter electrode was made by electrodeposition of Pt from an aqueous solution
of 5 mM H 2PtCl 6 onto fluorine-doped tin oxide (FTO) glass substrate. The above front-side illuminated DSSCs were compared with back-side
illuminated DSSCs fabricated from anodic TiO 2 NTs that were grown on the top of Ti foil as photoanode. The highest cell efficiency was 3.54% under 100 mW/cm 2 light intensity (1 sun AM 1.5G light, Jsc = 14.3 mA/cm 2, Voc = 0.544 V, FF = 0.455). To the best of our knowledge, this is the first report on the fabrication of DSSC from anodic
TiO 2 NTs powder. The TiO 2/FTO photoanodes were characterized by FE-SEM, XRD, and UV–Visible spectroscopy. The catalytic properties of Pt/FTO counter
electrodes have been examined by cyclic voltammetry. 相似文献
10.
We report the fabrication of atomic point contacts and lateral tunnel junctions by using anodic oxidation of thin metal films with an atomic force microscope. In situelectrical measurements were used as feedback to control the fabrication of metal nanowires that were subsequently anodized through their cross section to form point contacts and tunnel junctions. When the conductance of an Al device is reduced below 5×10 −4S it starts to decrease in discrete steps of 2 e2/ h. In some devices we are able to stabilize the conductance at a value near 2 e2/ hwhich corresponds to a single, atomic-sized conducting channel. Similar experiments on Ti devices result in a continuous decrease of the conductance and the formation of stable tunnel junctions. This continuous behavior is a result of the large series resistance and the small oxide barrier height of the Ti/TiO xsystem. 相似文献
11.
Titanium oxide (TiO 2) and zirconium oxide (ZrO 2) thin films have been deposited on modified Si(1 0 0) substrates selectively by metal-organic chemical vapor deposition (MOCVD) method using new single molecular precursor of [M(O iPr) 2(tbaoac) 2] (M=Ti, Zr; tbaoac=tertiarybutyl-acetoacetate). For changing the characteristic of the Si(1 0 0) surface, micro-contact printing (μCP) method was adapted to make self-assembled monolayers (SAMs) using an octadecyltrichlorosilane (OTS) organic molecule which has -CH 3 terminal group. The single molecular precursors were prepared using metal (Ti, Zr) isopropoxide and tert-butylacetoacetate (tbaoacH) by modifying standard synthetic procedures. Selective depositions of TiO 2 and ZrO 2 were achieved in a home-built horizontal MOCVD reactor in the temperature range of 300-500 °C and deposition pressure of 1×10 −3-3×10 −2 Torr. N 2 gas (5 sccm) was used as a carrier gas during film depositions. TiO 2 and ZrO 2 thin films were able to deposit on the hydrophilic area selectively. The difference in surface characteristics (hydrophobic/hydrophilic) between the OTS SAMs area and the SiO 2 or Si-OH layer on the Si(1 0 0) substrate led to the site-selectivity of oxide thin film growth. 相似文献
12.
Nuclear magnetic resonance (NMR) techniques have been successfully used to characterize the evolving pore structure of partially
soluble pharmaceutical pellets as they absorb water and release soluble components. The restricted diffusivity of water trapped
within pellets, which have been immersed in water for differing times, has been measured by pulsed field gradient NMR. These
measurements have been used to calculate the surface-to-volume ratio and tortuosity of the pore structure. A one-shot Carr–Purcell–Meiboom–Gill
sequence has been used to measure the spin–spin ( T
2) relaxation time of water trapped within the pellets. These data have been regularized and then analyzed by the Brownstein–Tarr
model to provide a pore size distribution for the pellets as a function of increasing immersion time. It has been found that
pore structure changes significantly as water enters the pellet matrix. Two pellet formulations (herein referred to as placebo
and drug-loaded) were studied and showed the same trends of a decreasing surface-to-volume ratio and tortuosity with increasing
immersion time. At an immersion time of 10 min, both of these parameters decreased to approximately 70% of their values compared
to an immersion time of 2 min. The placebo material tested consistently had both a higher tortuosity and surface-to-volume
ratio than the drug-loaded material. At an immersion time of 2 min, the tortuosity for the placebo and drug-loaded materials
were about 18 and about 10, respectively, and surface-to-volume ratios of about 6 μm −1 and about 5 μm −1, respectively. The materials tested also show changes in their pore size distribution with immersion time. In both formulations
the mean and modal pore sizes increase with immersion time. The placebo material maintains an approximately similar mean and
modal pore size, about 2 μm over the timescales studied, suggesting a more symmetric pore size distribution. In the drug-loaded
pellets the mean pore size is much higher than the modal pore size, their values being 6.5 and 2.1 μm after 10 min immersion
time, respectively.
Authors' address: Michael D. Mantle, Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge
CB2 3RA, UK 相似文献
13.
Oxygen-vacant titanium dioxide (TiO 2−x
) nanoparticles were synthesized using thermal plasma as a heating source at various applied plasma currents and He/Ar ratios.
Samples with diverse characteristics were developed and the mercury removal effectiveness was subsequently evaluated. TiO 2 nanoparticles possessing high purity and uniform particle sizes were successfully synthesized using metal titanium and O 2 as precursors and Ar as plasma gas. TiO 2−x
in anatase phase with a particle size at 5–10 nm was formed at the He/Ar volume ratio of 25/75. Further increasing the He/Ar
ratio elevated the plasma temperature, causing the tungsten to melt, vaporize from the cathode, and then dope into the formed
TiO 2 nanoparticles. The doped W appeared to inhibit the growth of nanoparticles and decrease the crystallinity of formed anatase.
The effectiveness of oxygen-vacant sites on Hg 0 removal under the visible light circumstance was confirmed. Hg 0 removal by the TiO 2−x
nanoparticles was enhanced by increasing the O 2 concentration. However, moisture reduced Hg 0 capture, especially when light irradiation was applied. The reduction in Hg 0 capture may be resulted from the competitive adsorption of H 2O on the active sites of TiO 2−x
with Hg 0 and transformed Hg 2+. 相似文献
14.
Performance of dye-sensitized solar cells (DSSCs) based on TiO 2 nanotubes (NTs) filled with TiO 2 nanoparticles (NPs) was studied as a function of NT height ( h). The NT height was varied in the range of 1.5–7.0 μm, while the NT diameter was kept constant at ~80 nm. The studies showed
that DSSC efficiency, current density, and fill factor linearly increased with h and ranged in 1.76–6.5%, 3.62–13.2 mA/cm 2, and 0.66–0.76, respectively, within the h range studied. The electrochemical impedance spectroscopy was also performed to study DSSC electron transport properties.
Based on both photovoltaic and electrochemical impedance spectroscopy data, the results were explained as being due to the
increased dye loading that led to higher light-harvesting efficiency. 相似文献
15.
Nanoporous TiO 2 having enhanced surface area was synthesized by sol–gel method. An “environmental friendly” method for production of furfuryl
alcohol was presented by electrocatalytic reduction of furfural to furfuryl alcohol in ionic liquid medium at the surface
of nanoporous TiO 2 film electrode. The heterogeneous catalytic redox behaviour of a nanoporous TiO 2 film electrode surface was investigated by cyclic voltammetry (CV). It was found that the catalytic reduction of furfural
by Ti(IV)/Ti(III) redox system on the nanoporous TiO 2 film surface. The electrode reaction mechanism is called catalytic (EC′) mechanism, current density can reach 38 mA/cm 2 and yielding an overall conversion efficiency of 61.7%. 相似文献
16.
Nanostructured titanium dioxide (TiO 2) thin films have been prepared on metal substrates using a facile layer-by-layer dip-coating method. The phase structure and morphologies of preparing samples were characterized by means of X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results confirm that films are highly crystalline anatase TiO 2 and free from other phases of titanium dioxide. Scanning electron microscopy (SEM) shows that the nanoparticles are sintered together to form a compact structure. The electrical properties of samples were investigated by cutternt-voltage analysis, the result indicates that a rectifying junction between the nanocrystalline TiO 2 film and metal substrate was formed. The photoelectrochemical characteristics recorded under 1.5 AM illumination indicates that the as-fabricated thin film electrode possesses the highest photocurrent density at 450 °C, which is 1.75 mA/cm 2 at 0 V vs. Ag/AgCl. 相似文献
17.
Titanium deuterides TiD 1.92, TiD 1.98, and TiD 2.0 have been studied by 2H and 47, 49Ti NMR in a magnetic field of 7.04 T and a temperature range of 120–500 K. At all temperatures and compositions, the 2H NMR line is a singlet described by the Gaussian function. The contribution of demagnetizing fields to the 2H NMR shift is ∼50 ppm. The titanium NMR spectra for all compositions comprise two signals due to the 47Ti and 49Ti isotopes. The shift between these signals depends on the deuterium content and temperature. The 47, 49Ti NMR line shape, width, and shifts have been considered in the framework of second-order quadrupole effects for a tetragonal
lattice distortion and random distribution of vacancies. The Knight shifts σ( 2H) and K( 47, 49Ti) are a function of temperature with a clearly pronounced singularity at ∼300 K. The contact, orbital, and polarization
contributions to the Knight shifts have been estimated from analysis of the temperature dependences of σ( 2H) and K( 47, 49Ti). 相似文献
18.
The Li 1−x
La
x
/3Zr 2(PO 4) 3 NASICON-type compounds (0 ≤ x ≤ 1) have been synthesized in powder form by a sol-gel method and sintered for ionic conductivity measurements. In order
to improve the compactness of the ceramic without decomposition of the compound, several sintering processes have been tested
for one member of the solid solution ( x = 0.6): the use of sintering aids (ZnO, B 2O 3, TiO 2 and LiNO 3), a ball-milling of the synthesized powder, a flash heating, high isostatic pressure, and spark plasma sintering. Finally,
a satisfactory compactness of 85% is obtained compared to the referenced value (63%) obtained by uniaxial and isostatic pressing.
The ionic conductivity study was performed by impedance spectroscopy. It shows that, despite the formation of vacancies, the
substitution Li +→ 1/3 La 3+ + 2/3 □ has unfortunately no influence on the conduction for 0 ≤ x ≤ 0.7 since the ionic conductivity remains identical to the LiZr 2(PO 4) 3 one. For higher x values, the ionic conductivity strongly decreases. 相似文献
19.
Ti6Al7Nb has been used as an implant material because of its good corrosion resistance and high mechanical properties. However, the presence of aluminium (Al), which may lead to ostemalacia, anaemia and nervous system disorders, limited its wide clinical use. In this study, a titanium oxide (TiO 2) nanoporous layer was fabricated on a Ti6Al7Nb alloy using an electrochemical anodic oxidation method. The structure of the TiO 2 nanoporous layer was examined by scanning electron microscopy. The chemical compositions of the samples were analysed by X-ray photoelectron spectroscopy (XPS). Biocompatibility was evaluated by culturing rat osteoblast cells. The result showed that TiO 2 nanoporous layers comprise a mixed oxide containing TiO 2 and a small amount of nobium oxides (Nb 2O 5) and almost no elemental aluminium. The outer layer of the TiO 2 nanoporous layer comprises highly ordered nanotubes and the inner layer forms disordered nanopores. The TiO 2 nanoporous layer could support the adhesion, proliferation, differentiation and gene expression of osteoblast cells. Therefore, a TiO 2 nanoporous layer could enhance the biocompatibility of Ti6Al7Nb alloy and is as a promising candidate for Ti6Al7Nb alloy implants. 相似文献
20.
A mixed oxide consisting of TiO 2 as the major phase and CeO 2−y (0< y<0.5) as the dopant phase was prepared via the sol-gel reaction of Ti( i-OC 3H 7) 3 in an aqueous solution of Ce(NO 3) 3. The resulting oxide powders with different CeO 2−y contents were all composed of nano-sized spheres. The CeO 2−y phase was identified to have retarding effect on the phase transition from anatase TiO 2 to rutile TiO 2 at calcinations temperature as high as 800 °C, which would otherwise be a thorough conversion. The CeO 2−y-TiO 2 powders could apparently shift the UV-absorption band of TiO 2 toward visible range, and there was an optimal CeO 2−y content in association with the maximum absorbance. This effect is interpreted as the existence of an n-type impurity band, due to the substitution of Ti 4+ for Ce 3+/4+ at the interface between the two oxides, in the gap of TiO 2. According to X-ray photoelectron spectroscopy (XPS) investigation, the Ti element mainly existed as the chemical state of Ti 4+ and the Ce oxide doping did not affect the peak position of Ti 2p. The Ce 3d spectrum of CeO 2−y-doped TiO 2 sample basically denotes a mixture of Ce 3+/4+ oxidation states giving rise to a myriad of peaks. 相似文献
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