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1.
TiO2 powders with the range of 10-60 nm were prepared successfully by plasma spray in the self-developed plasma spray equipment.
The prepared nanopowders were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron
spectroscopy. The results showed that the prepared TiO2 nanopowders were the mixture of anatase phase and rutile phase, the main phase was anatase. There were O, Ti, and C elements
in powders; Ti element still existed in tetravalent. The photocatalytic degradation of methyl orange indicated that all methyl
orange (20 mg/L) can be degraded fully when the addition of prepared TiO2 nanopowders and illumination time were 1 g/L and 150 min, respectively. 相似文献
2.
In the present study, the effect of titania (TiO2) substrate grain size and orientation on the epitaxial growth of TiO2 splat was investigated. Interestingly, the splat presented comparable grain size with that of substrate, indicating the hereditary feature of grain size. In addition, hetero- and homo-orientation epitaxial growth was observed at deposition temperatures below 400 °C and above 500 °C, respectively. The preferential growth of high-energy (001) face was also observed at low deposition temperatures (≤?400 °C), which was found to result from dynamic nonequilibrium effect during the thermal spray deposition. Moreover, thermal spray deposition paves the way for a new approach to prepare high-energy (001) facets of TiO2 crystals. 相似文献
3.
CaTiO3 was decomposed by alkaline roasting method for the production of TiO2.The process included alkaline roasting, water leaching and acid leaching steps.In the alkaline roasting step, the factors such as roasting temperature and NaOH/CaTiO3 molar ratio were investigated and 99.5% TiO2 could be extracted from CaTiO3.In addition, it is believed that only ion-exchange between Ca2+ and Na+ takes place, while the structure of TiO 32-in CaTiO3 was not destroyed during the roasting process.In the acid leaching ... 相似文献
4.
The photoelectrochemical characteristics of plasma-sprayed porous TiO2, TiO2-5%ZnO, and TiO2-10%ZnO electrodes in 0.1 N NaOH solution were studied through a three-electrode cell system. The microstructure, morphology,
and composition of the electrodes were analyzed using an electron probe surface roughness analyzer (ERA-8800FE), scanning
electron microscopy, and x-ray diffraction. The results indicate that the sprayed electrodes have a porous microstructure,
which is affected by the plasma spray parameters and composition of the powders. The TiO2-ZnO electrodes consist of anatase TiO2, rutile TiO2, and Zn2Ti3O8 phase. The photoresponse characteristics of the plasma-sprayed electrodes are comparable to those of single-crystal TiO2, but the breakdown voltage is close to 0.5 V (versus that of a saturated calomel electrode). The short-circuit photocurrent
density (J
SC) increases with a decrease of donor concentration, which was calculated according to the Gartner-Butler model. For the lowest
donor concentration of a TiO2-5%ZnO electrode sprayed under an arc current of 600 A, the short-circuit J
SC is approximately 0.4 mA/cm2 higher than that of the TiO2 electrodes under 30 mW/cm2 xenon light irradiation. The J
SC increases linearly with light intensity.
The original version of this paper was published as part of the DVS Proceedings: “Thermal Spray Solutions: Advances in Technology
and Application,” International Thermal Spray Conference, Osaka, Japan, 10–12 May 2004, CD-Rom, DVS-Verlag GmbH, Düsseldorf,
Germany. 相似文献
5.
Air plasma-sprayed conventional alumina-titania (Al2O3-13wt.%TiO2) coatings have been used for many years in the thermal spray industry for antiwear applications, mainly in the paper, printing,
and textile industries. This work proposes an alternative to the traditional air plasma spraying of conventional aluminatitania
by high-velocity oxyfuel (HVOF) spraying of nanostructured titania (TiO2). The microstructure, porosity, hardness (HV 300 g), crack propagation resistance, abrasion behavior (ASTM G65), and wear
scar characteristics of these two types of coatings were analyzed and compared. The HVOF-sprayed nanostructured titania coating
is nearly pore-free and exhibits higher wear resistance when compared with the air plasma-sprayed conventional alumina-titania
coating. The nanozones in the nanostructured coating act as crack arresters, enhancing its toughness. By comparing the wear
scar of both coatings (via SEM, stereoscope microscopy, and roughness measurements), it is observed that the wear scar of
the HVOF-sprayed nanostructured titania is very smooth, indicating plastic deformation characteristics, whereas the wear scar
of the air plasma-sprayed alumina-titania coating is very rough and fractured. This is considered to be an indication of a
superior machinability of the nanostructured coating. 相似文献
6.
Hsin Wang Ralph B. Dinwiddie Wallace D. Porter 《Journal of Thermal Spray Technology》2010,19(5):879-883
Thermal diffusivities of air plasma sprayed (APS) thermal barrier coatings (TBCs) were measured by the laser flash method.
The data were used to calculate thermal conductivity of TBCs when provided with density and specific heat data. Due to the
complicated microstructure and other processing-related parameters, thermal diffusivity of TBCs can vary as much as three-
to four-fold. Data collected from over 200 free-standing ZrO2-7-8wt.%Y2O3 TBCs are presented. The large database gives a clear picture of the expected “band” of thermal diffusivity values. When this
band is used as a reference for thermal diffusivity of a specific TBC, the thermal transport property of the TBC can be more
precisely described. This database is intended to serve researchers and manufacturers of TBCs as a valuable resource for the
evaluation of TBCs. 相似文献
7.
Xuezhang Liu Kui Wen Chunming Deng Kun Yang Changguang Deng Min Liu Kesong Zhou 《Journal of Thermal Spray Technology》2018,27(3):245-254
High plasma power is beneficial for the deposition efficiency and adhesive strength of suspension-sprayed photocatalytic TiO2 coatings, but it confronts two challenges: one is the reduced activity due to the critical phase transformation of anatase into rutile, and the other is fragmented droplets which cannot be easily injected into the plasma core. Here, TiO2 coatings were deposited at high plasma power and the position of suspension injection was varied with the guidance of numerical simulation. The simulation was based on a realistic three-dimensional time-dependent numerical model that included the inside and outside of torch regions. Scanning electron microscopy was performed to study the microstructure of the TiO2 coatings, whereas x-ray diffraction was adopted to analyze phase composition. Meanwhile, photocatalytic activities of the manufactured TiO2 coatings were evaluated by the degradation of an aqueous solution of methylene blue dye. Fragmented droplets were uniformly injected into the plasma jet, and the solidification pathway of melting particles was modified by varying the position of suspension injection. A nanostructured TiO2 coating with 93.9% anatase content was obtained at high plasma power (48.1 kW), and the adhesive coating bonding to stainless steel exhibited the desired photocatalytic activity. 相似文献
8.
Cold Spraying of TiO<Subscript>2</Subscript> Photocatalyst Coating With Nitrogen Process Gas 总被引:1,自引:0,他引:1
Motohiro Yamada Hiroaki Isago Hiromi Nakano Masahiro Fukumoto 《Journal of Thermal Spray Technology》2010,19(6):1218-1223
Titanium dioxide (TiO2) is a promising material for photocatalyst coatings. However, it is difficult to fabricate a TiO2 coating with anatase phase by conventional thermal spray processes due to a thermal transformation to rutile phase. In this
paper, anatase TiO2 coatings were fabricated by the cold spray process. To understand the influence of process gas conditions on the fabrication
of the coatings, the gas nature (helium or nitrogen) and the gas temperature are investigated. It was possible to fabricate
TiO2 coatings with an anatase phase in all spraying conditions. The process gas used is not an important factor to fabricate TiO2 coatings. The thickness of the coatings increased with the process gas temperature increasing. It indicates that the deposition
efficiency of the sprayed particles can be enhanced by controlling the spray conditions. The photocatalytic activity of the
coatings is similar or better than the feedstock powder due to the formation of a large reaction area. Concludingly, cold
spraying is an ideal process for the fabrication of a TiO2 photocatalyst coating. 相似文献
9.
A composite photocatalyst (La/TiO<,2>/Fe<,3>O<,4>) with a lanthanum doped TiO<,2> (La/TiO<,2>) shell and a magnetite core was prepared by coating photoactive LafTiO<,2> onto a magnetic Fe<,3>O<,4> core. The morphological, structural, and optical properties of as-prepared samples were charac- terized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of lanthanum content on the photocatalytie properties was studied, and the result revealed that 0.15 mol% La/TiO<,2>/Fe<,3>O<,4>exhibited the highest photoactiv- ity. The photocatalytic properties of the prepared photocatalyst under UV and visible light were investigated in aqueous solution using methyl orange (MO) as a target pollutant. The results showed that the prepared photocatalyst was activated by visible light and used as an ef- fective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, La/TiO<,2> was tightly bound to Fe<,3>O<,4> and could be easily recovered from the medium by a simple magnetic process. 相似文献
10.
Jae Young Park Sun-Woo Choi Kandasami Asokan Sang Sub Kim 《Metals and Materials International》2010,16(5):785-788
The feasibility of controlling the size of nanograins in TiO2 nanofibers by varying the duration of calcination is demonstrated in this study. This result opens up a new dimension in
understanding the physical properties of nanomaterials and their applications. Similar to the sintering behavior commonly
observed in bulk ceramics, the nanograins in nanofibers grow in size under a longer calcination time. 相似文献
11.
Sanghee Won Seunghee Go Wonhee Lee Kyunghoon Jeong Hyunsuk Jung Chongmu Lee Eungu Lee Jaegab Lee 《Metals and Materials International》2008,14(6):759-765
Thin TiO2 layers grown at 130°C on SiO2-coated Si substrates by atomic layer deposition (ALD) using TTIP and H2O as precursors were annealed, and the effects of the annealing temperature on the resulting electrical properties of TiO2 and the interface properties between a Pt electrode and TiO2 were examined using transmission line model (TLM) structures. The as-deposited TiO2 thin film had an amorphous structure with OH groups and a high resistivity of 6×103Ω-cm. Vacuum annealing at 700 °C transformed the amorphous film into an anatase structure and reduced its resistivity to 0.04Ω-cm.
In addition, the vacuum-annealing of the TiO2/SiO2 structure at 700°C produced free silicon at the TiO2-SiO2 interface as a result of the reaction between the Ti interstitials and SiO2. The SiO2 formed on the TiO2 surface caused a Schottky contact, which was characterized by the TLM method. The use of the TLM method enabled the accurate
measurement of the resistivity of the vacuum-annealed TiO2 films and the characterization of the Schottky contacts of the metal electrode to the TiO2. 相似文献
12.
E. A. Vasil’eva A. V. Tsurkan V. S. Protsenko F. I. Danilov 《Protection of Metals and Physical Chemistry of Surfaces》2016,52(3):532-537
The process of electrodeposition of an iron–titania composite electrochemical coating from methanesulfonate electrolyte is studied. TiO2 Degussa P 25 nanopowder (a mixture of crystalline modifications of rutile and anatase, with the latter prevailing) is used for preparation of suspension electrolyte. The dispersed phase content in the composition coating increases at a decrease in current density and increase in TiO2 in the suspension. It is shown that kinetics of codeposition is adequately described by the improved Guglielmi model. It is shown that inclusion of TiO2 particles into an iron matrix results in an increase in microhardness of the coating due to dispersion strengthening. Fe–TiO2 (anatase+rutile) coatings manifest photocatalytic activity with respect to the reaction of destruction of the methyl orange dye in aqueous solutions under exposure to UV radiation, and this activity is higher than in the case of similar coatings containing TiO2–rutile particles. 相似文献
13.
Titanium dioxide (TiO2) films with rod-like and sphere-like TiO2 particles were prepared on glass slides employing the sol-gel method. The shape and size of TiO2 particles were controlled using different concentrations of sodium dodecylbenzensulfonate (SDBS). By increasing the mole
ratio of SDBS, the shape of TiO2 particles transformed from rod-like to sphere-like. Also, the size of TiO2 particles became gradually smaller. Then, the size became bigger when an excess amount of SDBS was added. The films were
mainly composed of anatase titania and the relative content of anatase increased with the increasing amount of SDBS. The photocatalytic
activity of the TiO2 films that were added with SDBS was higher than that without SDBS. When the concentration of SDBS was 8.0 at%, the sample
exhibited the best photocatalytic activity. 相似文献
14.
Phase constitutions of ZnNb2O6−TiO2 mixture ceramics were significantly changed according to the sintering temperature. Phase transition procedures and their
effect on the microwave dielectric properties of 0.42ZnNb2O6−0.58TiO2 were investigated using X-ray powder diffraction and a network analyzer. The fractions of the phases composing the mixture
were calculated by measuring integral intensities of each reflection. The structural transitions in 0.42ZnNb2O6−0.58TiO2 were interpreted as the association of two distinct steps: the columbite and rutile to ixiolite transition present at lower
temperatures (900–950°C) and the ixiolite to rutile transition at higher temperatures (1150–1300°C). These transitions caused
considerable variation of microwave dielectric properties. Importantly, τf was modified to around 0 ppm/°C in two sintering conditions (at 925°C for 2 hr and at 1300°C for 2 hr), by the control of
phase constitution. 相似文献
15.
Nano TiO2/Fe3O4 composite particles with different molar ratios of TiO2 to Fe3O4 were prepared via sol-gel method. X-ray diffraction, transmission electron microscopy, and vibration sample magnetometry
were used to characterize the TiO2/Fe3O4 particles. The photocatalytic activity of the particles was tested by degrading methyl blue solution under UV illumination
(254 nm). The results indicate that with the content of TiO2 increasing, the photocatalytic activity of the composite particles enhances, while the magnetism of the particles decreases.
When the molar ratio of TiO2 to Fe3O4 is about 8, both the photocatalytic activity and magnetism of the TiO2/Fe3O4 particles are relatively high, and their photocatalytic activity remains well after repeated use. 相似文献
16.
In Sung Kim Soon Jong Jeong Jae Sung Song Pan Seok Shin 《Metals and Materials International》2002,8(6):577-582
The present study describes the dielectric properties of RF sputtered Ta2O5 thin films as a function of the buffer layer and annealing condition. The buffer layers were Ti or TiO2. And the thin film was annealed in various conditions. The X-ray pattern results showed that the phase of the RF sputtered
Ta2O5 thin films was amorphous and this state was kept stable to RTA (rapid thermal annealing) even at 700°C. Measurements of the
electrical and dielectric properties of the reactive sputtered Ta2O5 fabricated in two simple metal insulator semiconductor (MIS) structures, (Cu/Ta2O5/Ti/Si/Cu and Cu/Ta2O5/TiO2/Si/Cu) indicated that the amorphous Ta2O5 grown on Ti possesses a high dielectric constant (30–70) and high leakage current (10−1–10−4 A/cm2), whereas a relatively low dielectric constant (−10) and low leakage current (−10−10 A/cm2) were observed in the amorphous Ta2O5 deposited on the TiO2 buffer layer. In addition, the leakage current mechanisms of the two amorphous Ta2O5 thin films were investigated by plotting the relation of current density (J) vs. applied electric field (E). The Ta2O5/Ti film exhibited three dominant conduction mechanism regimes contributed by the Ohmic emission at low electrical field,
by the Schottky emission at intermediate field and by the Poole-Frenkel emission at high field. In the case of Ta2O5/TiO2 film, the two conduction mechanisms, the Ohmic and Schottky emissions, governed the leakage current density behavior. The
conduction mechanisms at various electric fields applied were related to the diffusion of Ta, Ti and O, followed by the creation
of vacancies, in the rapid thermal treated capacitors. 相似文献
17.
K. E. Polunin N. P. Sokolova A. M. Gorbunov R. A. Bulgakova I. A. Polunina 《Protection of Metals and Physical Chemistry of Surfaces》2009,45(6):685-692
Adsorption interactions of stilbene (1,2-diphenylethylene) and its hydroxy- and methoxyderivatives with nanodispersed TiO2 aerogel surface were studied by means of Fourier IR radiosity spectroscopy. Stilbene trans- and cis-isomers were shown to be weakly adsorbed on TiO2 surface forming hydrogen bonds. UV irradiation (wavelength 285–305 nm) of adsorbed compounds results in their partial destruction,
yielding aldehydes, ketones, and carboxylates. The products of stilbene photolysis are strongly bound to TiO2 surface. Modification of TiO2 surface with trans-hydroxystilbenes is characterized by the formation of various hydrogen bonds and surface colored quinoid compounds. The interaction
of TiO2 with trans-methoxystilbenes changes the state of surface hydroxyl groups and yields stable carboxylate compounds. UV irradiation results
in the partial destruction of adsorbed stilbenoids, yielding aldehyde, ketone, and carboxylate surface compounds. 相似文献
18.
Émilien Darthout Guillaume Laduye François Gitzhofer 《Journal of Thermal Spray Technology》2016,25(7):1264-1279
The solution precursor plasma spray process, in which a solution of metal salts is axially injected into an induction thermal plasma, is suitable for deposition of nanostructured environmental barrier coatings. The effects of main processing parameters, namely the solution precursor concentration, spraying distance, reactor pressure, and atomization gas flow rate, have been analyzed using D-optimal design of experiments regarding the deposition rate and coating porosity responses. Among these four parameters, the solution precursor concentration had the greatest influent on the coating structure, followed by the spraying distance and reactor pressure, and finally the atomization gas flow rate with a small contribution. It is pointed out that the species that impact on the substrate are agglomerates of nanoparticles. The equivalent thermal conductivity of selected coatings was computed from experimental temperature evolution curves obtained by laser flash thermal diffusivity analysis, using two methods: a multilayer finite-element model with optimization, and a multilayer thermal diffusion model. The results of the two models agree, with coatings exhibiting low thermal conductivity between 0.7 and 1 W/(m K) at 800 °C. 相似文献
19.
Despite of many attractive properties of TiO2, the drawback of TiO2 ceramic is low fracture toughness for widely industrial application. The method to improve the fracture toughness and hardness has been reported by addition of reinforcing phase to fabricate a nanostructured composite. In this regard, graphene has been evaluated as an ideal second phase in ceramics. Nearly full density of nanostructured TiO2-graphene composite was achieved within one min using pulsed current activated sintering. The effect of graphene on microstructure, fracture toughness and hardness of TiO2-graphene composite was evaluated using Vickers hardness tester and field emission scanning electron microscopy. The grain size of TiO2 in the TiO2-x vol% (x = 0, 1, 3, and 5) graphene composite was greatly reduced with increase in addition of graphene. Both hardness and fracture toughness of TiO2-graphene composites simultaneously increased in the addition of graphene. 相似文献
20.
M. Bargui M. Messaoud K. Elleuch 《Surface Engineering and Applied Electrochemistry》2017,53(5):467-474
This paper deals with the elaboration of a stable suspension of TiO2 nanoparticles and their incorporation by electrophoretic deposition into pores of an anodized 5754 aluminum alloy. The as-synthesized TiO2 nanopowder was characterized by the X-ray diffraction, scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy and IR spectroscopy. During this work, both the transmission electron microscopy and particle analysis showed that the resulting particles had a narrow size distribution with a crystallite size of about 15 nm. The zeta potential and stability of TiO2 nanoparticles dispersed with poly(acrylic acid) in an aqueous solution were also measured. A porous anodic film was synthesized in the phosphoric acid-base electrolyte and then filled by 15 nm TiO2 particles via electrophoresis. In addition, the effect of poly(acrylic acid) and pH on the suspension stability has been investigated. It was also demonstrated that by adding glycine in buffered suspension gelating phenomenon can be avoided that inhibits the insertion of nanoparticles inside the pores of an anodic film. It was also noted that an applied electric field greatly influences the electrophoretic deposition process. The field emission gun-scanning electron microscopy observations showed that larger (125 nm in diameter) and linear (6 μm in length) pores are successfully filled in 5 min. 相似文献