Showing papers by "Wuhan University of Technology published in 2002"
TL;DR: In this article, a novel and simple method for preparing highly photoactive nanocrystalline F-doped TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in a mixed NH4F−H2O solution.
Abstract: A novel and simple method for preparing highly photoactive nanocrystalline F--doped TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in a mixed NH4F−H2O solution. The prepared F--doped TiO2 powders were characterized by differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV−vis absorption spectroscopy, photoluminescence spectra (PL), transmission electron microscopy (TEM), and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the crystallinity of anatase was improved upon F- doping. Moreover, fluoride ions not only suppressed the formation of brookite phase but also prevented phase transition of anatase to rutile. The F--doped TiO2 samples exhibited stronger absorption in the UV−visible range with a red shift in the band gap transition. The photocatalytic activity of F--doped TiO2 powders prep...
2,074 citations
TL;DR: Transparent anatase mesoporous (MTiO2) and TiO2 nanometer thin films were prepared on soda-lime glass and fused quartz via the reverse micellar method and sol-gel method, respectively as mentioned in this paper.
Abstract: Transparent anatase mesoporous TiO2 (MTiO2) and TiO2 nanometer thin films were prepared on soda-lime glass and fused quartz via the reverse micellar method and sol–gel method, respectively. The as-prepared MTiO2 and TiO2 films were then treated by dipping them in a H2SO4 solution. The MTiO2 and TiO2 films before and after surface acid treatment were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), BET surface area and UV–VIS spectrophotometry. The photocatalytic activity of the samples was evaluated by photocatalytic oxidation of acetone in air. It was found that MTiO2 thin films showed higher photocatalytic activity than that of the TiO2 thin films. This was attributed to the fact that MTiO2 thin films were composed of smaller monodisperse spherical particles about 15 nm and had higher specific surface areas. Furthermore, the monodispersity of TiO2 particles was beneficial to transfer and separation of photo-generated electrons and holes in the inner of and on the surface of TiO2 particle and reduced the recombination of photo-generated electrons and holes. The films deposited on quartz showed the highest photocatalytic activity because films deposited on quartz exhibited a better crystallization and had no sodium contaminant. The photocatalytic activity of MTiO2 and TiO2 thin films deposited on different substrates after treated with H2SO4 solution was significantly enhanced. Acid treatment was particularly effective for MTiO2/glass and TiO2/glass, which showed activity enhancement of four and over two times, respectively. This increase in activity has been correlated with the reduction of sodium ions and the increase in the adsorbed hydroxyl content on the surface of TiO2 films.
471 citations
TL;DR: Wang et al. as discussed by the authors developed an empirical model for the prediction of surface roughness in finish turning, which considers the following working parameters: workpiece hardness (material); feed; cutting tool point angle; depth of cut; spindle speed; and cutting time.
Abstract: Surface roughness plays an important role in product quality. This paper focuses on developing an empirical model for the prediction of surface roughness in finish turning. The model considers the following working parameters: workpiece hardness (material); feed; cutting tool point angle; depth of cut; spindle speed; and cutting time. One of the most important data mining techniques, nonlinear regression analysis with logarithmic data transformation, is applied in developing the empirical model. The values of surface roughness predicted by this model are then verified with extra experiments and compared with those from some of the representative models in the literature. Metal cutting experiments and statistical tests demonstrate that the model developed in this work produces smaller errors than those from some of the existing models and have a satisfactory goodness in both model construction and verification. Finally, further research directions are presented.
319 citations
TL;DR: In this paper, mesoporous TiO2 nanometer thin films were prepared on fused quartz by the dip-coating sol-gel method from a system containing a triblock copolymer as a template (or pore-forming agent), and then calcined at different temperatures.
Abstract: Mesoporous TiO2 nanometer thin films were prepared on fused quartz by the dip-coating sol–gel method from a system containing a triblock copolymer as a template (or pore-forming agent), and then calcined at different temperatures. These films were characterized by X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, BET surface area and UV-visible spectrophotometry. The photocatalytic activity and photo-induced super-hydrophilicity of the films were evaluated by the photocatalytic degradation of acetone and water contact angle measurement in air, respectively. It was found that the thin films calcined at 700 °C not only show the highest photocatalytic activity, but also possess the greatest light-induced hydrophilicity and the slowest conversion rate from the hydrophilic to a hydrophobic state. The former is attributed to the fact that the films calcined at 700 °C are composed of anatase and rutile, which
is beneficial in enhancing the transfer of photo-generated electrons from the anatase to the rutile phase, reducing the electron–hole combination rate in anatase and enhancing its activity. The high light-induced hydrophilicity and slow hydrophilic to hydrophobic conversion rate are due to the synergetic effect of good photocatalytic activity, sufficient surface hydroxyl content and a degree of surface roughness. Because of their high specific surface areas and mesoporous structures, the photocatalytic activity of mesoporous TiO2 thin films is higher than that of conventional TiO2 thin films.
247 citations
TL;DR: In this article, the authors reported synthesis and electrical and thermal transport properties for several filled skutterudite compounds doped with Ni: Ba0.3NixCo4−xSb12 with 0
Abstract: Synthesis and electrical and thermal transport properties are reported for several filled skutterudite compounds doped with Ni: Ba0.3NixCo4−xSb12 with 0
223 citations
TL;DR: In this article, the effects of hot pressing parameters on the TiB 2 ceramic microstructure and mechanical properties were studied by measuring three point bending testing and single edge notched bending tests, respectively.
Abstract: In this paper, a titanium diboride ceramic was produced by the hot pressing sintering method. The effects of hot pressing parameters on the TiB 2 ceramic microstructure and mechanical properties were studied. The bending strength and fracture toughness were measured by three point bending testing and single edge notched bending tests (SENB), respectively. The microstructure features of the TiB 2 sintered material were revealed by means of SEM and TEM. The results show that the TiB 2 grain size increases quickly with the increasing temperature and time during hot pressing sintering. The density and the TiB 2 grain size have a great influence on the mechanical properties. The bending strength decreases with increasing TiB 2 grain size, whilst the fracture toughness increases.
204 citations
TL;DR: In this paper, a simple method for preparing highly photoactive nano-sized TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in pure water or the EtOH/H2O mixed solution under ultrasonic irradiation.
Abstract: A simple method for preparing highly photoactive nano-sized TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in pure water or the EtOH/H2O mixed solution under ultrasonic irradiation. The prepared TiO2 powders were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the photocatalytic activity of TiO 2 powders prepared by this method from pure water or the EtOH/H2O mixed solutions with the molar ratio of EtOH/H2O = 1 exceeded that of Degussa P-25. The molar ratios of EtOH/H2O obviously influenced the crystallization, crystallite size, BET surface areas and photocatalytic activity of the prepared TiO 2 powders. Ultrasonic irradiation obviously enhanced the photocatalytic activity of TiO 2 powders whether the solvent is pure water or the EtOH/H2O mixed solutions. This may be ascribed to the fact that ultrasonic irradiation enhances hydrolysis of titanium alkoxide and crystallization of TiO2 gel. © 2002 Elsevier Science B.V. All rights reserved.
171 citations
TL;DR: In this article, the photoinduced super-hydrophilicity and photocatalytic activity of transparent mesoporous TiO2 (MTiO2) and nanometer thin films were evaluated via the modified reverse micellar and sol-gel methods.
Abstract: Transparent mesoporous TiO2 (MTiO2) and TiO2 nanometer thin films were prepared on fused quartz via the modified reverse micellar and sol–gel methods. The MTiO2 and TiO2 films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray diffraction (XRD), BET surface area and UV–Vis spectrophotometry. The photoinduced super-hydrophilicity and photocatalytic activity of the films were evaluated by the water contact angle measurement and photocatalytic oxidation of acetone in air, respectively. It was found that MTiO2 thin films at 500 °C showed higher photocatalytic activity and better light-induced hydrophilicity than the TiO2 thin films. This is attributed to the following reasons: (1) MTiO2 thin films are composed of smaller monodisperse spherical particles about 15 nm diameter, and possess more mesopores between spherical particles and higher surface areas and surface roughness, (2) the monodispersity of MTiO2 particles was beneficial to the transfer and separation of photo-generated electrons and holes inside of and on the surface of TiO2 particles, and reduced the recombination of photo-generated electrons and holes. At 900 °C, the MTiO2 and TiO2 films appeared to be in the rutile phase, but showed photoinduced hydrophilicity and no photocatalytic activity. This confirmed that the mechanism of photoinduced super-hydrophilicity of the films is different from that of photocatalytic oxidation.
159 citations
TL;DR: In this paper, the authors present a brief derivation of the temperature distribution in the sample and the die in spark plasma sintering, and point out that temperature difference is inevitable in the samples of SPS system.
Abstract: The paper presents a brief derivation of the temperature distribution in the sample and the die in spark plasma sintering. It aims to point out that temperature difference is inevitable in the samples of SPS system. Under certain conditions, the difference may reach a few hundreds of degrees of centigrade. Experiments also proved the existence of such a difference, which is larger than the one under steady-state temperature distribution.
157 citations
TL;DR: The relationship between photoinduced hydrophilicity and surface microstructure of porous TiO2 thin films has been investigated in this article, which proves that suitable surface microstructures can enhance the photo-induced super-hydrophilic properties of porous thin films and hinder the conversion from a hydrophilic to hydrophobic state.
Abstract: The relationship between photoinduced hydrophilicity and surface microstructure of porous TiO2 thin films has been investigated. Porous TiO2 thin films on soda-lime glass were prepared by the sol–gel method from alkoxide solutions containing polyethylene glycol (PEG). These materials were characterised by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and UV-Vis transmittance measurements. The larger the amount of PEG used in preparing the thin films, the larger was the pore size produced from the thermal decomposition of PEG. This generated also a relatively rough thin film surface with a strong affinity for hydroxyl groups. This study proves that suitable surface microstructures can enhance the photoinduced super-hydrophilic properties of porous TiO2 thin films and hinder the conversion from a hydrophilic to a hydrophobic state. Among the porous TiO2 thin films tested, the
one with a PEG to TiO2 mass ratio of 12.5% exhibited the best photoinduced super-hydrophilic property and the slowest conversion rate from the hydrophilic to a hydrophobic state.
114 citations
TL;DR: In this article, the results show that when the V2O5 xerogel is modified by the intercalation of polyethylene oxide (PEO), the H atoms in PEO are hydrogen-bonded with the O atoms of the VO bonds of the V 2O5xerogels, which effectively shielded against electrostatic interactions between the VO5 interlayer and Li+ ions.
Abstract: V2O5 xerogel films modified by poly(ethylene oxide)
(PEO) were obtained via the sol–gel method. Investigations were conducted by X-ray diffractometry (XRD), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. The results show that when the V2O5 xerogel is modified by the intercalation of PEO, the H atoms in PEO are hydrogen-bonded with the O atoms of the VO bonds of the V2O5 xerogel, which effectively shielded against electrostatic interactions between the V2O5 interlayer and Li+ ions. The reversibility of insertion/extraction of Li+ ions is greatly improved by modification of the V2O5 xerogel with PEO.
TL;DR: In this article, the uniform transparent TiO2/SiO2 nanometer composite thin films were prepared via sol-gel method on the soda lime glass substrates, and were characterized by X-ray photoelectron spectroscopy (XPS), FTIR spectrography, UV-VIS spectrographic, transmission electron microscopy (TEM), XRD, and BET surface areas.
Abstract: The uniform transparent TiO2/SiO2 nanometer composite thin films were prepared via sol-gel method on the soda lime glass substrates, and were characterized by X-ray photoelectron spectroscopy (XPS), FTIR spectroscopy, UV-VIS spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface areas. It was found that the addition of SiO2 to TiO2 thin films could suppress the grain growth of TiO2 crystal and increase the hydroxyl content of the surface of TiO2 films. The photocatalytic activity of the as-prepared TiO2/SiO2 composite thin films increases for SiO2 content of less than 5 mol%.
TL;DR: In this article, a photocatalytically active Pb-doped TiO2 thin films were prepared on a soda-lime glass substrate by sol-gel dip-coating technique using TiO 2 sols containing lead(II) nitrate.
Abstract: Photocatalytically active Pb-doped TiO2 thin films were prepared on a soda-lime glass substrate by sol-gel dip-coating technique using TiO2 sols containing lead(II) nitrate The thin films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), UV-VIS spectroscopy and X-ray diffraction (XRD) A shift of the UV-VIS absorption towards longer wavelengths was observed, which indicated a decrease in the band-gap of TiO2 upon Pb doping XRD results showed both pure and Pb-doped TiO2 thin films were polycrystalline, anatase type, and oriented predominantly to the (101) plane A slight shift in the d-spacing for the Pb-doped film indicated the incorporation of Pb into the TiO2 lattice to form Pb
x
Ti1−x
O2 solid solution AFM results showed Pb-doped TiO2 thin films were composed of larger TiO2 particles and had rougher surface, compared with un-doped TiO2 thin films XPS results showed that except for the enrichment of Pb near the surface, Pb exists in the forms of Pb
x
Ti1−x
O2 and PbO Dimethyl-2,2-dichlorovinyl phosphate (DDVP) was efficiently degraded in the presence of the Pb-doped TiO2 thin films by exposing the insecticide solution to sunlight The mechanism of photocatalytic activity enhancement of the Pb-doped TiO2 thin films was discussed
TL;DR: In this article, the effects of lime and fly ash on the geotechnical characteristics of expansive soil were investigated and an experimental program was undertaken to study the individual and admixed effects.
Abstract: An experimental program was undertaken to study the individual and admixed effects of lime and fly ash on the geotechnical characteristics of expansive soil. Lime and fly ash were added to the expansive soil at 4%–6% and 40%–50% by dry weight of soil, respectively. Testing specimens were determined and examined in chemical composition, grain size distribution, consistency limits, compaction, CBR, free swell and swell capacity. The effect of lime and fly ash addition on reducing the swelling potential of an expansive soil is presented. It is revealed that a change of expansive soil texture takes place when lime and fly ash are mixed with expansive soil. Plastic limit increases by mixing lime and liquid limit decreases by mixing fly ash, which decreases plasticity index. As the amount of lime and fly ash is increased, there are an apparent reduction in maximum dry density, free swell and swelling capacity under 50 kPa pressure, and a corresponding increase in the percentage of coarse particles, optimum moisture content and CBR value. Based on the results, it can be concluded that the expansive soil can be successfully stabilized by lime and fly ash.
TL;DR: In this article, an explicit method is introduced to solve inverse problems for composites with imperfect interfaces, and the method is applied to determine the thermal conductivity of constituents and the interfacial thermal resistance in SiC-particulate-reinforced aluminum-matrix composites.
Abstract: An explicit method is introduced to solve inverse problems for composites with imperfect interfaces. We apply the method to determine the thermal conductivity of constituents and the interfacial thermal resistance in SiC-particulate-reinforced aluminum-matrix composites and to estimate the whisker thermal conductivity, the interfacial thermal resistance, and the whisker alignment distribution in two types of SiC-whisker-reinforced lithium aluminosilicate glass-ceramic composites from their measured effective thermal conductivity reported in the literature. Certain bounds for these three properties of both SiC-whisker-reinforced glass-ceramic composites are obtained, and reasonable estimates for their exact values from room temperature to 500°C are made. The inverse problem is quite sensitive to noise in the measurements. We also comment on existing estimates.
TL;DR: In this paper, the fracture toughness and bending strength of the composites were tested, respectively, by X-ray diffraction (XRD) patterns showed that the sintered products mainly consisted of TiAl and Ti 2 AlC phases.
TL;DR: In this paper, the effect of four kinds of selenium compounds on Staphylococcus aureus growth was studied by microcalorimetry, and the extent and duration of the inhibitory effect on the metabolism as judged from the rate constant (k ), varied with the different drugs.
TL;DR: The classification results obtained experimentally demonstrate that the feature extraction from bispectra for concrete flaw detection has good detection rates in varying environments.
Abstract: The problem addressed in this paper is the detection and classification of flaws in concrete structure. It is known that higher-order spectra contain information not present in the power spectrum and can suppress Gaussian noise. Thus estimates of higher-order spectra have been shown to be useful in certain signal processing problems. This paper is concerned with the feature extraction from bispectra for concrete flaw detection. Impact-echo experiments are carried out for three different types of flaw in concrete structure. For each monitoring signal, after bispectral estimation, features are selected from the modules of bispectra in the primary region. For automatic interpretation, a multilayer back-propagation neural network is used as a classifier. Both clean data and data with additive white Gaussian noise are used for training and testing. The classification results obtained experimentally demonstrate that this method has good detection rates in varying environments.
TL;DR: The design and implementation of key technologies of JMAP, a Java-based mobile agents platform that provides a flexible and efficient agent coordination mechanism and a reliable agent migration mechanism, and supports persistence of agent state and agent security are described.
TL;DR: In this paper, a conductive asphalt concrete with a resistivity around 10−103Ω·m was obtained, which is a new type of multifunctional concrete, and the mix proportion by weight was shown as follows.
Abstract: Materials such as Koch AH—70, basalt aggregate, limestone powder and graphite particles were used to prepare conductive asphalt concrete, which is a new type of multifunctional concrete. The mix proportion by weight was shown as follows. Fine aggregates (2.36–4.75 mm): fine aggregates (<2.36mm): lime-stone powder: asphalt=120∶240∶14∶30. The content of added graphite particles ranged from 0% to 20% (by the weight of asphalt concrete). A conductive asphalt concrete with a resistivity around 10–103Ω·m was obtained. Special attention was paid to the effects of graphite content, graphite physical-chemical properties, asphalt content and temperature on the resistivity. Furthermore, an attempt was made to develop an electrically conductive model for asphalt concrete.
TL;DR: In this paper, the exact analysis of free flexural vibrations of non-uniform Euler-Bernoulli beams carrying an arbitrary number of single-degree of freedom and two-degree-of-freedom spring-mass systems is presented.
TL;DR: In this article, a high-speed image recorder was used to monitor and analyze the features of combustion processes, and the propagating combustion wave model was found to become unstable with increasing diluent additive amount in raw mixture.
TL;DR: In this paper, the effects of polyethylene glycol (PEG) addition to the precursor solution on the microstructure and roughness of the resultant thin films were investigated by atomic force microscopy (AFM).
Abstract: Porous titanium dioxide thin films were prepared from alkoxide solutions with and without polyethylene glycol (PEG) by the sol-gel method on soda-lime glass. The effects of PEG addition to the precursor solution on the microstructure and roughness of the resultant thin films were investigated by atomic force microscopy (AFM). It was found that TiO2 films prepared from the precursor solution without PEG had granular microstructure and flat texture, and was composed of about 100 nm spherical particles. With an increase in the times of coating cycles, the roughness of films decreased and the size of TiO2 particles increased. On the other hand, the larger the amount and molecular weight of the added PEG in precursor solutions, the larger the diameter and the depth of pores in the resultant films on the decomposition of PEG during heat-treatment. The surface of the films was also rougher, and fewer pores were produced during heat-treatment. The mechanism of porous structure formation in the TiO2 films was explained using the principle of spinodal phase separation.
TL;DR: This paper applies and compares the nonlinear regression analysis and neural network modeling methods in developing empirical models for estimating the digitizing uncertainty and can aid error prediction, accuracy improvement, and operation parameter selection in computer-aided reverse engineering and automatic inspection.
Abstract: The coordinate measuring machine is one of the two types of digitizers most popularly used in reverse engineering. A number of factors affect the digitizing uncertainty, such as travel speeds of the probe, pitch values (sampling points), probe angles (part orientations), probe sizes, and feature sizes. A proper selection of these parameters in a digitization or automatic inspection process can improve the digitizing accuracy for a given coordinate-measuring machine. To do so, some empirical models or decision rules are required. This paper applies and compares the nonlinear regression analysis and neural network modeling methods in developing empirical models for estimating the digitizing uncertainty. The models developed in this research can aid error prediction, accuracy improvement, and operation parameter selection in computer-aided reverse engineering and automatic inspection.
TL;DR: In this article, a new method of burning Portland cement clinker is studied, and the experimental results show that after the raw meal is heated at a low electric heating temperature (1000-1200 °C) and then further sintered with microwave for 1 to 2 min, Portland cement can be formed.
TL;DR: In this article, the influence of deposition temperature in the range 25 −400°C on the composition and bonding structure of carbon nitride films was systematically studied using atomic force microscopy (AFM), Fourier transform infrared (FTIR), Raman and X-ray photoelectron spectroscopy (XPS).
TL;DR: In this article, the expansion ratio of ASC mortars due to alkali aggregate reaction (AAR) was studied by using atomic absorption spectrometry, and the amount of free alkali was measured at 90d.
Abstract: By means of “Mortar Bar Method”, the ratio of cement to aggregate was kept as a constant 1∶2,25 the water-cement ratio of the mixture was 0.40, and six prism specimens were prepared for each batch of mixing proportions with dimensions of 10×10×60mm3 at 38±2°C and RH≧95%, the influences of content and particle size of active aggregate, sort and content of alkali component and type of slag on the expansion ratios of alkali-activated slag cement (ASC) mortars due to alkali aggregate reaction (AAR) were studied. According to atomic absorption spectrometry, the amount of free alkali was measured in ASC mortars at 90d. The results show above factors affect AAR remarkably, but no dangerous AAR will occur in ASC system when the amount of active aggregate is below 15% and the mass fraction of alkali is not more than 5% (Na2O). Alkali participated in reaction as an independent component, and some hydrates containing alkali cations were produced, free alkalis in ASC system can be reduced enormously. Moreover, slag is an effective inhibitor, the possibility of generating dangerous AAR in ASC system is much lower at same conditions than that in ordinary Portland cement system.
TL;DR: In this paper, the authors investigated the electrical emission in mortar under low compressive loading and cyclic loading and found that the electrical emissions in mortar can be explained by the opening of microcracks, the flow of liquid in mortar, and the charge leakage.