Дисертації: "METAL ASSISTED TITANIUM DIOXIDE"

1

SINGH, MRITYUNJAY. "IVESTIGATIONS OF METAL ASSISTED TITANIUM DIOXIDE (TiO2) NANOCRYSTALS." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18623.

Повний текст джерела

Анотація:

7.1 Summary The research topic of the thesis entitled “Investigations of Metal Assisted Titanium Dioxide (TiO2) Nanocrystals” disclosed the structural, morphological, compositional and optical properties of TiO2 nanoparticles (NPs) and discussed their utility for photocatalytic applications. In the current thesis, TiO2 NPs were prepared using the sol-gel method and comprehensively explored their properties. The crystalline structural and optical characteristics of TiO2 NPs (like X-ray diffraction, absorption, photoluminescence, and time-resolved photoluminescence) along with photocatalytic applications have also been discussed in detail in the previous chapter. 7.2 Important Findings of Research Work Nanocrystals of anatase, mixed and rutile phases of TiO2 and metal-doped TiO2 have been synthesized via the sol-gel method. The prepared samples were characterized by various analytical tools. For the structural and surface morphology analysis, essential tools such as XRD, SEM and TEM were used. EDX analysis has been carried out for elemental identification present in prepared nanomaterials. TGA, FTIR spectroscopy, Raman spectroscopy, UV-visible & PL spectroscopy, time-resolved photoluminescence (TRPL) spectroscopy at varying temperatures were used to understand the structural and transitions following photoexcitation. TiO2 NPs were prepared by the sol-gel method with titanium isopropoxide as a precursor at different annealing temperatures. The analyzed XRD patterns, Raman and Fourier transform infrared spectra demonstrated the structural transformation from 160 amorphous to anatase and further to rutile phase while increasing annealing temperature. In addition, a mixed-phase of TiO2 NPs is formed, which consists of both phases. The absorption and photoluminescence (PL) spectra of mixed and rutile phases are shifted towards a longer wavelength region. The indirect band gap structure changed into the direct band gap during the structural transformation. Both absorption and PL spectra shifted towards lower energy regions, which might be due to the increase in size or the induced oxygen vacancies produced at a higher temperature. Furthermore, the photocatalytic activity of all the three different structural TiO2 NPs was examined. Furthermore, the photocatalytic performance of the different types of TiO2 NPs was examined through the degradation of a dye, rhodamine B (RhB), under UV radiation and measuring changes in absorption and PL spectra. The anatase phase structure shows higher photocatalytic activity than the rutile phase. However, the mix phase has the highest photocatalytic activity among all the structures, which degraded RhB entirely at a faster rate. On the other hand, the rutile phase is unable to take part in this process. Thus, the mix phase of TiO2 NPs is beneficial for industrial and environmental applications. The transition metal ions (Ag+, Cu2+, and Ni2+) doped and undoped TiO2 NPs have been synthesized using a cost-effective sol-gel method with a 1.0 wt% dopant concentration. The microstructure and chemical compositions of these NPs were examined using various techniques such as x-ray diffractometric, field emission scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared and absorption and photoluminescence (PL) spectroscopy. The absorption and photoluminescence (PL)-excitation spectra of metal-doped TiO2 NPs are shifted to the longer wavelength region, which indicates a reduced bandgap than the bare TiO2 NPs. The absorption and PL spectra of methylene blue (MB) in the presence of undoped and metal ions doped TiO2 NPs show dramatic changes upon UV-irradiation. The absolute absorption 161 intensity reduced entirely and the solution of MB became colorless in the presence of UV irradiation. The PL of the degraded dye exhibits a new band in the shorter wavelength region, which has a multi-exponential decay function and an increased average PL lifetime. The dye degradation rate is higher for metal ions doped catalyst and highest for Cu2+ doped TiO2 NPs. Thus, Cu ions-doped TiO2 shows the highest photocatalytic activity. The order of catalytic degradation rate under UV irradiation was found to be Cu– TiO2 > Ni– TiO2 >Ag– TiO2 >anatase TiO2. The analysis of the PL spectra and PL-decays reveals the formation of smaller species that emits at a shorter wavelength region, thus helps in understanding the degradation of dye molecules. TiO2 NPs synthesized by employing the sol-gel routes and annealed at a different temperature from 400 to 900 °C. Three different nanostructures were formed, namely anatase, mixed (anatase/rutile) and rutile phases. The structure and morphology of as-synthesized NPs were confirmed using XRD and FESEM analysis. The XRD analysis of TiO2 NPs was carried out in the 290 K to 77 K temperature range and found no significant change in XRD patterns that means thermally stable TiO2 NPs. The PL spectra and contour maps of TiO2 NPs show that the anatase phase falls in the visible region. However, mixed and rutile phases fall in both visible and NIR regions as the temperature decreases from 290 K to 77 K. The visible PL band is ascribed to donor-acceptor recombination. In contrast, oxygen vacancies serve as donors and hydroxyl groups function as accepter sites. NIR PL band attributed to the trapped electrons in rutile TiO2, which recombine with free holes and intrinsic defects. The fast component of the decay processes was aided by the immediate formation of trapped electrons in luminescence sites. The indirect trap processes were responsible for the power-law component in the rutile phase, which was the recombination of trapped electrons formed via a deep trap state. It was observed that the electron-hole pairs thermally separated, preventing the formation of STEs directly. The PL 162 and PL decay studies under weak excitation conditions prove to be a more valuable and appropriate method to evaluate the trap states distribution and their carrier dynamic effects, which were vibrant to understand the photocatalytic processes better. Two-dimensional (2D) layered MoS2 nanosheets (NSs), which possess a vast range of unique properties and hold great potential for various applications. MoS2 NSs were synthesized by a hydrothermal method and the obtained NSs bear crystalline and layered structure. Absorption and electroabsorption (E-A) spectra of MoS2 doped in a PMMA thin film were measured at different temperatures (290-40 K). The E-A spectra observed at the second harmonic of the modulation frequency of the applied electric field (1.0 kHz) were analyzed with an integral method by assuming the Stark effect as a dominant feature. The absorption spectra consist of multiple transitions, among which five transitions are contributed to the E-A spectra. The changes in electric dipole moment (Δμ) and polarizability (Δα) of each transition were determined at different temperatures. Two electronic resonance states were identified for two excitonic bands of MoS2 NSs, which showed a strong E-A signal.

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Liu, Dong. "Effects of metal modification on titanium dioxide for photocatalytic reduction of carbon dioxide." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/28624/.

Повний текст джерела

Анотація:

To study the effects of metal modification on titanium dioxide (TiO2) for photocatalytic reduction of carbon dioxide (CO2), a series of pure and metal modified TiO2 catalysts (referred as SG TiO2 and M/TiO2, respectively) were synthesized via a refined sol-gel process. The metals chosen to modify TiO2 included Cu, Zn, and Rh. These catalysts were then characterized by using various analytical techniques, including ICP-MS, powder XRD, XPS, TEM, N2 adsorption isotherms, Cu surface area and dispersion measurement, and DR UV-Vis. It was found that all the sol-gel derived TiO2 catalysts had the same crystalline phase of anatase, and similar particle sizes (11-16 nm) and surface areas (50.24-63.37 m2/g). It is worthy to note that, even though synthesized via the same sol-gel process, the three added metals modified their TiO2 supports differently. The added Cu and Zn were loaded on the surface ofTiO2 with their chemical states to be CU2O and ZnO, respectively. Whereas, the added Rh was substitutionally doped into the lattice of its TiO2 supports. The specific surface area and dispersion of the added Cu on the surface of CulTiO2 were further measured by using N2O as adsorbate. It was found that the aggregation of the added Cu occurred when the Cu ratio of Cu/TiO2 over-increased (over 0.03 wt%). The following CO2 photoreduction experiments confirmed that the added Cu and Rh were able to significantly improve the activity of TiO2 for CO2 photoreduction to methane, wherein the activities of the best performing 0.03 wt% Cu/TiO2 and 0.01 wt% Rh/TiO2 were around 10-times higher than that of SG/TiO2. The added Cu and Rh were expected to affect the activity of TiO2 via different ways. The combination of the loaded Cu and TiO2 was considered to be a composite semiconductor catalyst, and the Cu dispersion dominated the activity of Cu/TiO2. In comparison, the doped Rh was able to affect the activity of TiO2 by introducing an additional energy level to the band-gap of TiO2. Finally, TiO2 catalysts simultaneously loaded by Cu and doped by Rh (Rh/Cu/TiO2, synthesized via the identical sol-gel process) were also tested for CO2 photoreduction. The results indicate that the loaded Cu and doped Rh were able to synergistically enhance the activity of TiO2 for CO2 photoreduction, allowing the optimal Rh/Cu/TiO2 (0.06 wt% Rh/O.03 wt% Cu/TiO2) to present even better (at least 25 % higher) activity than any of the Cu/TiO2 or Rh/TiO2 in this work.

Стилі APA, Harvard, Vancouver, ISO та ін.

3

Ahonen, P. P. "Aerosol production and crystallization of titanium dioxide from metal alkoxide droplets /." Espoo [Finland] : Technical Research Centre of Finland, 2001. http://www.vtt.fi/inf/pdf/publications/2001/P439.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Hansen, Niklas D. J. "MICROWAVE ASSISTED SYNTHESIS OF TITANIUM DIOXIDE ELECTRODES FOR USE IN POLYMER DSSC." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176935.

Повний текст джерела

Анотація:

It’s widely known that microwaves can be a useful tool when it comes to heating many different kinds of materials. It’s much less known however that compared to regular convective heating it can exhibit catalytic properties. This project focuses on the difference between microwave heating and normal heating and its future in the field of solar cell manufacturing. The main purpose was to determine whether efficient DSSC could be manufactured by the use of microwaves. Focus was also put on the application for flexible polymers. Polymer sintering requires lower temperatures compared with the normally used substrates and they tend to have lower efficiencies. If the efficiencies can be raised these types of cells can become a cheap viable option by means of the so called roll-to-roll manufacturing. A clear improvement was seen in both efficiency and deviation when sintering by microwave heating compared to that of normal convective heating. Electrodes sintered by microwaves tend to show about double the performance in these cases. Another effect that was examined was the combined heating effect of TiO2 on conductive substrates. The combined heating of FTO and TiO2 can be about 30% higher than the additive heating. This is of course important from the perspective of manufacturing performance. Sintering a pure TiO2 paste by microwaves on a ITO:PEN substrate a DSSC efficiency of 5.5% was achieved which is a reasonably good result when compared with that of other polymer cells. Especially considering that this was a basic test. The electrode was only sintered for 2min and the paste was simple. This demonstrates that roll-to-roll printed DSSC is not a farfetched concept. Following that further work on similar cells are strongly encouraged. Some work was also put into creating solvothermally grown nanosheets combined with nanoparticles to create a hybrid cell in hopes of lowering electric resistivity and subsequently increasing overall solar cell performance. No real conclusions can be drawn in terms of increased performance. However there might be some indications of decreased losses but more time is needed on experimental work. The current results might however still prove valuable information for some readers.

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Ahonen, Petri. "Aerosol production and crystallization of titanium dioxide from metal alkoxide droplets /." Espoo : Technical Research Centre of Finland, 2001. http://www.vtt.fi/inf/pdf/publications/2001/P439.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Edusi, C. "Aerosol assisted chemical vapour deposition of titanium dioxide and tungsten oxide thin films." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1434745/.

Повний текст джерела

Анотація:

This thesis focuses on the Aerosol Assisted Chemical Vapour deposition (AACVD) of titanium dioxide (TiO2) thin films using titanum (IV) isopropoxide (TTIP) and also reports the deposition of tungsten oxide via AACVD using tungsten hexacarbonyl [W(CO)6] in different solvents including methanol and ethanol. Chapter 1 of this thesis gives an overview of TiO2, including its properties and functions and the motivation for this project. In chapter 2 brief descriptions are provided of the main characterisation techniques used throughout this thesis. The substrate and solvent effect on the phase of TiO2 obtained by AACVD is outlined in chapter 3 and 4. TiO2 was deposited via the AACVD of TTIP in different solvents including methanol, ethanol and other solvents. The films deposited showed some substrate dependent morphology and properties. In particular at 550°C the films on steel show needle and rod like particles. XRD and Raman spectra of the TiO2 films showed that on steel or titanium substrates only the rutile form could be obtained, whereas on glass either anatase, anatase-rutile mixtures or rutile could be obtained depending on substrate temperature. Using methanol as the carrier solvent produced exclusively the rutile films on steel and predominantly rutile on glass substrates while the use of the other solvents produced exclusively the anatase phase on the steel under the same conditions. TiO2 was also deposited by AACVD from a mixture of ethanol and methanol solvents. As little as 15% of methanol in ethanol produces rutile as the predominant phase. The photocatalytic properties and the hydrophilicity of the films deposited are also reported. X-ray absorption spectroscopy (XAS) was used to map across the surface of the TiO2 films deposited as described in chapter 5. The X-ray absorption near edge structure (XANES) was used to determine the phase of TiO2 present at each point on the substrate. The AACVD deposition tungsten oxide using tungsten hexacarbonyl (W(CO)6) in methanol and ethanol is reported in chapter 6. Preferred orientation was observed when using either ethanol or methanol as the carrier solvent. In chapter 7 insitu work was attempted to investigate the mechanism of the deposited titania and tungsten oxide films. A new reactor vessel was designed, constructed and tested to allow synchrotron radiation in and out using a kapton window. The XANES pattern recorded during in-situ deposition were not of high enough to resolve the mechanism. The in-situ work carried out has great potential in the growth study of thin film deposition and can in the future help control the phase and composition of deposited films to produce more desirable properties.

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Bowering, Neil. "Transition metal modified titanium dioxide photocatalysts for the removal of nitric oxide." Thesis, University of Nottingham, 2004. http://eprints.nottingham.ac.uk/12513/.

Повний текст джерела

Анотація:

Photocatalytic NO decomposition and reduction reactions, using CO as a reducing gas, have been investigated over Ti02, Ag-Ti02 and Rh-Ti02 photocatalysts, using a purpose built continuous flow photoreactor. The transition metal modified Ti02 photocatalysts were prepared using wet impregnation techniques, and the effect of thermal processing parameters on their photocatalytic behaviour was studied. Prepared photocatalysts were characterised using a number of complementary techniques, including XRD, TEM, DSC, and XPS. The findings from these techniques were used to explain the observed photocatalytic properties. The activity and selectivity of the photocatalysts were found to be dependant on a number of factors; thermal pretreatment temperature, type and amount of the modifying element, chemical nature of the modifying element and the reaction conditions used. It was found, for Ti02 photocatalysts, that increasing the pretreatment calcination temperature resulted in lower NO conversion rates, due to removal of surface bound hydroxyl groups. A similar trend was observed for Ag-P25 photocatalysts, but the reduction in activity was greater due to the presence of larger silver clusters, which acted as recombination centres for photogenerated electron-hole pairs. The activity of the Ag-P25 photocatalysts decreased as the silver loadings increased, whilst the activity of the Rh-P25 photocatalysts remained largely unaffected by the metal concentration. Over Ti02 and Ag-Ti02 systems, the NO conversion rate was lower for the reduction reactions compared to decomposition reactions. This was attributed to the preferential adsorption of the CO molecules, blocking NO adsorption sites. Contrasting behaviour was observed over Rh-P25 systems and NO conversions as high as 87 % were recorded in the presence of CO. Silver modified catalysts were highly selective for N2 formation (90 %) whilst rhodium modified catalysts were more selective for N20 formation. These results are discussed with respect to the possible surface reactions and the chemical intermediates that may be formed.

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Romero, Luz. "Electric field assisted chemical vapour deposition processes on titanium dioxide thin films for photocatalysis." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/9004.

Повний текст джерела

Анотація:

This work investigates the use of the novel electric field assisted chemical vapour deposition (EACVD) process in the production of titanium dioxide thin films for photocatalytic applications on glass substrate. This work looks into the interaction of applied electric fields with the precursor species during the aerosol assisted chemical vapour deposition (AACVD) and atmospheric pressure chemical vapour deposition (APCVD) reaction of Titanium isopropoxide (TTIP) and Titanium (IV) Chloride (TiCl4) with different solvents. The electric field was generated by applying a potential difference between two fluorine-doped tin oxide glass sheets. The electric field was varied between 0 – 3000 Vm-1. The deposited films were analysed and characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy, UV-vis spectroscopy, water-contact angles and resazurin photcatalytic testing. It was observed that the application of electric fields produced changes in the morphology, particle size, growth rate, crystal orientation and crystal phases. Generally, films produced under the influence of the electric fields showed higher photo-activity than films produced in absence of electric fields. The deposited films produced from the electric field assisted aerosol chemical vapour deposition (EAACVD) showed higher photo-activity with applied AC electric fields than with applied DC electric fields. Likewise, they showed higher photo-activity than the deposited films produced from the electric field assisted atmospheric pressure chemical vapour deposition (EAAPCVD) with applied AC electric fields. The results obtained were explained by the interaction mechanisms between the electric fields and the precursor species, which differ depending on the CVD technique used. Although titanium dioxide photo-activity is comprised by a combination of factors, it was observed that an optimum can be obtained by varying both experimental conditions and field strength. In particular, optimum results were obtained for deposited films which showed long-shaped particles, reduced particle size and high preferential orientation in the anatase (004) plane. Electric field assisted chemical vapour deposition (EACVD) shows a great potential for the improvement of commercial products available in the market such as self-cleaning and antibacterial surfaces.

Стилі APA, Harvard, Vancouver, ISO та ін.

9

Omadoko, Ovuokenye. "Simple Photochemical Reduction of Carbon Dioxide to Formate." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/171.

Повний текст джерела

Анотація:

Simple Photochemical Reduction of Carbon Dioxide to Formate Ovuokenye Omadoko, Department of Chemistry, East Tennessee State University, Johnson City, Tennessee. There is a need to develop techniques for conversion of carbon dioxide to other useful products such as methanol, formaldehyde, formic acid, formate, methane, and hydrocarbons. Carbon dioxide can be converted into these products using different methods such as photochemical, electrochemical, thermochemical and hydrogenation by bacteria. Formate is of interest due to having wide industrial applications which include use in direct liquid fuel cells (DLFC’s), an additive in pyrolysis vapors, precursor for biological fuels, and is a key intermediate in methanogenesis breaking down complex organic compounds. In this work, conversion of carbon dioxide to formate was accomplished photochemically. The concentration of formate obtained was quantified using ion chromatography. The yield of formate, based on the amount of carbon dioxide in solution, was 1.54%, while the quantum yield near 1.0%. Detailed studies of the photoreduction process showed that amount of sensitizer, light intensity and pH affect the amount of formate generated.

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Mayo, Elizabeth Idonia Barton Jacqueline K. "Kinetics and thermodynamics of dye (group VIII metal)-sensitized nanocrystalline titanium dioxide photoelectrodes /." Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-06042004-153530.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Wang, Junwei. "Chemical doping of metal oxide nanomaterials and characterization of their physical-chemical properties." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1333829935.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Coleman, Nathaniel Jr. "Synthesis and characterization of metal doped titanium dioxide, transition metal phosphides, sulfides and thiophosphates for photocatalysis and energy applications." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/2060.

Повний текст джерела

Анотація:

This thesis covers synthetic investigations, characterization, and applications of transition metal doped titanium dioxide materials and transition metal phosphide/sulfide structures. Both areas are useful in heterogeneous catalysis, battery energy storage, and in semiconductor light to energy conversion. Two main synthesis routes have been investigated: 1) rapid solid state metathesis (SSM) of transition metal oxides, phosphides, sulfides, and thiophosphates, and 2) sealed ampoule routes of transition metal phosphides and thiophosphates. SSM reactions tend to yield kinetically controlled multiphase products while sealed ampoule routes gave more thermodynamically favorable single phase materials. Approximately 10 mol% of many first row transition metals (M = Cr, Mn, Fe, Co, Ni, Cu) were targeted for doping into TiO₂, using MClx, and sodium peroxide in SSM reactions, targeting an ideal mixed phase of M₀.₁Ti₀.₉O₂. X-ray diffraction showed rutile TiO₂ forms and no separate dopant metal phases were seen until subsequent 1000 °C annealing in air. EDS, ICP, and XPS analysis showed slightly lower than the targeted M:Ti ratios however, the manganese sample had more than the ideal 10 mol % of dopant. DRS data showed estimated bandgap energies of the doped samples within 1.33-2.55 eV. Magnetic susceptibility showed small paramagnetic responses from all samples that increase upon annealing. SEM showed that the doped SSM-TiO₂ samples were mixtures of aggregates and blocky particles. The synthesized doped titanias were tested for methylene blue and methyl orange photodegradation under UV and visible light and for H₂ generation from water reduction under UV light. The doped titania samples absorb significant amounts of methylene blue dye in the dark with the manganese doped TiO₂ sample being the most absorbent. Degradation of methylene blue under UV illumination was observed, however, only modest degradation under visible light was observed. The samples all performed better than Degussa P25 TiO₂ standard under visible light. The doped titanias did not degrade methyl orange well under UV light and they did not show detectable H₂ generation from water in UV light even with surface platinum additions. Transition metal phosphide, sulfide and thiophosphate materials were synthesized in two different ways. The metal halides FeCl₃, CoCl₂, NiCl₂, and CuCl₂, red phosphorus and elemental sulfur (or P₂S₅) were common to both SSM and ampoule reactions. Both SSM reactions and sealed glass ampoules are solvent-less direct solid state reactions to target FeP₂, CoP₃, NiP₂, CuP₂, FeS₂, CoS₂, NiS₂, CuS, FePS₃, CoPS₃, NiPS₃ and Cu₃PS₄ phases. SSM reactions utilized MClx/Li₃N mixtures to produce elemental metals to then react with P/S reagents leading to metal-rich phosphides, sulfur-rich phases or mixes of M-P-S and sulfur rich phases. Phosphorus-rich phases were seldom seen. Ampoule reactions in contrast, produced single phase phosphorus-rich phases and M-P-S products. Sulfide phases were not produced in ampoule systems. To encourage unique product morphologies, the metal phosphide and thiophosphates were directly synthesized on P25 TiO₂ powders, and pre-made molten fluxes (KCl/LiCl eutectic, tin, or bismuth) to encourage crystal growth of unique structures. M-P products were successfully synthesized in the eutectic and tin fluxes, except for FeP₂ in the halide eutectic flux. FeP₂ was grown in the tin flux at lower than normal reaction temperatures (500 °C vs 700 °C). M-P-S products were seen in the eutectic flux only, while SnS, M-P, or M –Sn-P products were observed in tin fluxes. All reactions were unsuccessful in bismuth flux. The deposition reactions yielded M-P and M-P-S products on P25 TiO₂ powder. The NiP₂ and CuP₂ products were seen while FeP₂ and CoP₃ were not observed. From these samples, only FeP and CoP was detected on P25 TiO₂. The M-P-S reactions formed the targeted phases on P25 TiO₂ successfully. These deposited materials were tested for their photo-reactivity towards water reduction. Preliminary tests for UV light induced and electrolytic hydrogen evolution were done using some ampoule synthesized M-P and M-P-S materials. None of the samples showed H₂ generation using UV light, however H₂ was detected from several MPx and MPxSy materials in this thesis under acidic electrochemical conditions at fairly low applied overpotentials of -40 mV to -240 mV.

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Maake, Popoti Jacqueline. "Photovoltaic and gas sensing applications of transitional metal nanocomposites of poly(3-hexylthiophene)-titanium dioxide." University of Western Cape, 2021. http://hdl.handle.net/11394/8240.

Повний текст джерела

Анотація:

>Magister Scientiae - MSc
This thesis starts with the reviewing of studies on the loading of noble metals and nanostructured metal oxides into bulk heterojunction organic solar cell device architectures. The reviews focused on the innovative developments in the use of various fullerene derivatives as electron acceptors in organic solar cells. It additionally reflected on the effect of metallic nanoparticles (NPs), such as gold (Au) and silver (Ag), on the performance of organic solar cells. Besides the metallic NPs, the effect of metal oxide nanoparticle loading, e.g. CuO, ZnO and TiO2, on the organic solar cell performance, and the use of noble metals doped TiO2 on the gas sensing application were reviewed.
2024

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Gemmellaro, Pietro. "Titanium Dioxide Nanoparticles in the Field of Conservation of Cultural Heritage." Doctoral thesis, Università di Catania, 2012. http://hdl.handle.net/10761/964.

Повний текст джерела

Анотація:

This study deals with the preparation, characterization and photocatalytic activity in gas and aqueous media of undoped and doped TiO2 nanopowders and thin films. Nanocrystalline anatase TiO2 of 25 nm size with a 1 at. % dopants were successfully prepared by the cost effective sol gel method as powders, and applied on glass substrates with spin coating method. Techniques such thermal analyses, XRD, SEM, DLS, XPS, UV-Vis and Raman spectroscopy were used in order to characterize the obtained materials from a morphological, optical and structural point of view. Degussa TiO2 P25 nanopowder was used as a reference. Photodegradation experiments indicated that NO2 and MO solution can be degraded in gas phase and in the aqueous TiO2 suspensions respectively. A comparison of the photocatalytic efficiency of undoped and doped TiO2 immobilized onto substrates versus catalysts in suspended form is reported. Photocatalysis is a very promising method to face most of the problems connected with the increasing environmental pollution, and titanium dioxide, in its anatase crystallographic phase, which is one of the most investigated photocatalytic material and to be perfectly compatible with every day human activities.

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Wu, L. "The preparation of metal ions modified titanium dioxide and its application in water purification and disinfection." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19578/.

Повний текст джерела

Анотація:

Conventional water purification and disinfection generally involve potential hazardous substances, some of which known to be carcinogenic in nature. Titanium dioxide photocatalytic processes provide an effective route to destroy hazardous organic contaminants and bacteria, being operational in the UV domain with a potential application in the use of solar radiation. This work explores the possibility of the removal of organic pollutants and microbial contaminant by the application of TiO2 based photocatalysts. The production of series of metal ions doped or undoped TiO2 were carried out by sol gel method and wet impregnation method. Photoreactivity tests were carried out in a solar box with two UVA lamps. The photodegration of phenol and photodisinfection of E. coli in aquatic solution were selected as probe as a measure of photoreactivity. It is found that none of the doped TiO2 show any improvement compared with undoped TiO2 towards phenol degradation. In contrast, Cu doped TiO2 exhibits enhanced results from E. coli photodisinfection. The material properties of prepared photocatalysts were characterized in an attempt to understand the relation among preparation parameters (calcination temperature, the variations of dopant and the level of doping, etc.), material properties and the final photoactvity. The structural characterization includes Brunauer, Emmett and Teller (BET) method, X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS). Some field simulation experiments are also included in this research. The results of which proved TiO2 based photocatalytic process to be a promising alternative in the future application in water disinfection and degradation, especially in those tropical developing countries with abundant of solar irradiation and insufficient water sanitation. In the last part of this PhD work, a continuous flow photoreactor was designed. The effectiveness of the system was tested and fitted to mathematical models to describe the bacterial disinfection rate.

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Nyamukamba, Pardon. "Preparation and application of plasmon metal enhanced titanium dioxide photocatalyst for the removal of organics in water." Thesis, University of Fort Hare, 2016. http://hdl.handle.net/10353/2765.

Повний текст джерела

Анотація:

Advanced oxidation processes are capable of removing organic compounds that cannot be removed by conventional water treatment methods. Among the oxidation processes, photo-catalysis using titanium dioxide (TiO2) is a promising method but suffers from rapid electron-hole recombination rates and only absorbs UV light which is a small percentage (5 percent) of the total solar radiation. Therefore there is a need to reduce the recombination rates and also extend the absorption of the photo-catalyst into the visible region which constitutes 55 percent of the total solar radiation. The major aims of this study were to prepare plasmon metal decorated and doped TiO2 photo-catalysts immobilized on quartz substrates and test their photo-catalytic and antimicrobial activities. The effect of film thickness (loading) and use of different shapes of plasmon metal nanostructures was investigated. TiO2 thin films were prepared by a sputter coating technique while plasmon metal (Au & Ag)/carbon co-doped TiO2 by a simple sol gel process and plasmon metal films were prepared by the thermal evaporation technique. Different plasmon metal nanostructures (nanorods, dendrites, nanowires and spherical nanoparticles) were prepared using a wet chemical technique using sodium borohydride as the reducing agent. Nanocomposites of co-doped TiO2 photo-catalyst and plasmon elements of different proportions were also prepared. The prepared photo-catalysts were coated onto etched and MPTMS (3-Mercaptopropyl trimethoxysliane) treated quartz glass substrate which is a stable support favouring easy recovery. The prepared materials were characterized by XRD, HRTEM, TEM, HRSEM, FT-IR, SEM, PIXE and TGA while the doped TiO2 was characterized by XPS, BET, CHNS and Raman Spectroscopy. The effect of pH of solution, presence of other contaminants and salts in solution, initial concentration of the model pollutant and type of the plasmonic elements on the photocatalytic activity of TiO2 towards 4-(4-sulfophenylazo)-N,N-dimethyl aniline (methyl orange) were also investigated. The selected TiO2 photo-catalyst films were tested for antimicrobial properties. The effect of different types of plasmon elements on the antimicrobial activity of TiO2 against E. coli ATCC 3695 was evaluated under both sunlight and weak UV light. Under UV light, Ag showed the highest enhancement in photo-catalytic activity of TiO2 than Au and Cu. The photo-catalytic activity of TiO2 increased with an increase in Ag content to an optimum loading and then started to decrease with a further increase in loading. For Cu and Au, photo-activity activity increased with an increase in plasmon metal content. Under sunlight, Cu showed the highest enhancement of TiO2 photocatalytic compared to Ag and Au. The change in order of deposition showed that Au films enhanced the photo-activity better when they were deposited underneath rather than on top of TiO2 on quartz supports but Ag films performed better in enhancing photo-activity when they were deposited on top of TiO2. The use of bimetallic layers and three layer systems of different plasmon elements enhanced photo-catalytic activity better than the use of a monometallic layer. The presence of other organic contaminants and salts in solutions was found to reduce the photo-degradation of methyl orange due to preferential adsorption of other contaminants. When the pH was increased, the photocatalytic activity of TiO2 towards methyl orange was reduced. In antimicrobial studies, it was found that the plasmon elements greatly improved the antibacterial action of TiO2 against Escherichia coli ATCC 3695 in water and the best antibacterial action was observed with silver/carbon co-doped TiO2 photo-catalyst under sunlight The doped samples consisted of polydisperse nanoparticles which were found to be beneficial for photo-catalytic activity enhancement under sunlight.

Стилі APA, Harvard, Vancouver, ISO та ін.

17

Bayat, Narges. "Toxicity and biological impact of metal and metal oxide nanoparticles : Focus on the vascular toxicity of ultra-small titanium dioxide nanoparticles." Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-116708.

Повний текст джерела

Анотація:

The application of nanoparticles (NPs) in different technologies has led to tremendous advancement in those fields. Moreover, there is growing interest in application of ultra-small NPs (USNPs) at 1-3 nm due to their distinct molecule like features. Parallel to these promises, there is a growing concern regarding their safety. The main goal of this thesis was to investigate the toxicity and underlying mechanisms following exposure to different metal and metal oxide NPs as well as USNPs. Their effects were studied on Saccharomyces cerevisiae, on hepatocytes and endothelial cells and finally in vivo on zebrafish embryos (Danio rerio). By selecting the rutile form of titanium dioxide (TiO2-USNPs) without intrinsic or intracellular reactive oxygen species (ROS) production, we could study biological impacts solely due to size and direct interaction with the cells. We showed that TiO2-USNPs were not cytotoxic but induced DNA damage. They had anti-angiogenic effects both in vitro and in vivo. Also, at high concentrations they caused complete mortality in zebrafish embryos exposed in water, while at lower concentrations induced delay in hatching. When injected they caused malformations. They specifically induced the differential overexpression of transcripts involved in lipid and cholesterol metabolism in endothelial cells. In hepatocytes they induced the overexpression of proteins in the electron transport chain and decreased lipids in lipid rafts. At 30 nm, TiO2-NPs, were also not cytotoxic but were genotoxic. They had no effects in vivo or on angiogenesis. However, they induced differential expression of transcripts involved in endoplasmic reticulum (ER) stress and heat shock response as well as cholesterol metabolism. This suggests a more toxic response in the cells compared to TiO2-USNPs. Single walled carbon nanotubes (SWCNTs) despite having the highest oxidative activity among the NPs studied, were not severely cyto- or genotoxic but induced expression of transcripts involved in early ER stress response. Copper oxide (CuO-NPs) was the most toxic NPs studied due to both ion release and ROS production, affecting lipid metabolism of the cells. Silver (Ag-NPs) were also cytotoxic and caused the disruption of cellular components and lipids. ZnO-NPs were not cytotoxic, did not affect cellular lipids but they increased the size of vacuoles in yeast cells. Finally by using superparamagnetic iron oxide NPs (SPIONs) with different coatings, and using a mathematical model, a nano impact index (INI) was developed as a tool to enable the comparison of nanotoxicology data.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Altomare, M. "TOWARDS THE PHOTOCATALYTIC PRODUCTION OF SOLAR FUELS - NANOSTRUCTURED TITANIUM DIOXIDE FOR PHOTOCATALYSIS & PHOTO-ELECTROCHEMISTRY." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/229553.

Повний текст джерела

Анотація:

In spite of many efforts given during the last decades to find new alternative photocatalytic materials, titanium dioxide (TiO2) still represents the most widely employed semiconductor for photocatalytic applications, being photoactive, cheap, easily available, non-toxic, inert and, most of all, chemically stable. However, although exhibiting a powerful combination of extraordinary and attractive physico-chemical properties, it suffers from some issues, common to all semiconductors, related to the dynamic of the charge carriers. Precisely, trapping and recombination of valence band holes and conduction band electrons occur at a certain extent, anyway resulting in a drop of the process efficiency. Therefore, in view of limiting these detrimental phenomena, the charge transfer and the electric conductivity of a semiconductor can be enhanced, thus leading to an overall improvement of the photocatalyst performance. In the first part of the work, homemade and commercial TiO2 powders were studied as photocatalysts for different applications, including the liquid-phase photocatalytic oxidation of ammonia and formic acid, and the H2 production through photocatalytic reforming of water-methanol vapors. In this context, a dopant (NH4F) was used during the sol-gel synthesis of the semiconductor to stabilize the formation of the TiO2 anatase phase (typically more active than rutile TiO2 because of its higher electron mobility), especially when crystallization of the amorphous oxides was performed at high temperature (700 ˚C). Furthermore, the effects induced by noble metal nanoparticles deposition on TiO2 anatase powders were also investigated. In situ electron spin resonance spectroscopy was employed to determine the amount of electrons and holes trapping centers formed under irradiation, in the absence and in the presence of noble metal co-catalysts at the surface of TiO2, hence assessing also the ability of Au and Pt nanoparticles in trapping conduction band electrons. The results were of great usefulness not only to interpret the different H2 production rates but also to understand some mechanistic aspects concerning the selectivity towards the different oxidation products in the methanol photo-steam reforming reaction. In the second part of the work, the nanostructuring of the semiconductor was explored by fabricating TiO2 nanotube arrays through electrochemical anodization. The anodic oxides were employed for both photocatalytic and photo-electrochemical H2 production. In view of large-scale application, the anodization approach was studied on wide Ti substrate surfaces, in order to assess the feasibility of the scale up. Moreover, TiO2 nanotubes were also grown on Ti-based alloys. When fabricating the nanotubes under optimized conditions on Ti-Ta alloys, highly photoactive Ta-doped TiO2 nanotubes were obtained, exhibiting superior water splitting ability. When anodizing Ti-Au alloys, the TiO2 nanotubes resulted decorated with Au nanoclusters. These Au-decorated TiO2 nanotube arrays were used as efficient photocatalyst for H2 production from ethanol-water solutions. Finally, the fabrication of short TiO2 nanotube layers exhibiting an unprecedented level of self-ordering was achieved through an innovative anodization approach. The highly ordered topography allowed the subsequent self-ordering dewetting of Au, leading to Au nanoparticles of controllable size and distribution. These short, Au nanoparticles-filled TiO2 nanotubes exhibited advanced photoactivity ascribed to their reaction vessel-like geometry, fulfilling the requirements in terms of solid state charge carriers diffusion and liquid phase diffusion of oxidizing radicals.

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Boughaled, el Lakhmissi Redouan [Verfasser]. "Photocatalytically active and optically transparent titanium dioxide thin films prepared by ion assisted physical vapor deposition / Redouan Boughaled El Lakhmissi." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2013. http://d-nb.info/1042042500/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Greenstein, Katherine E. "Development of chemically active metal oxide composite nanofiber filters for water treatment." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2214.

Повний текст джерела

Анотація:

Small drinking water systems, often financially and resource-limited, face unprecedented challenges due to the current diversity and ubiquity of water pollutants. Well-characterized inorganic legacy pollutants, including arsenic, copper, hexavalent chromium, and lead, remain persistent in drinking water systems. In addition, emerging organic contaminants, like endocrine disrupting compounds and pharmaceuticals, are largely uncharacterized but prevalent in the environment and water supplies, calling into question what levels of these relatively new contaminants are truly safe in drinking water. Point-of-use (POU) and point-of-entry (POE) water treatment devices, installed at a specific tap or at the water entry point to a single facility, respectively, are necessary to ensure safe drinking water in contexts where centralized water treatment is not available or cannot adapt to meet new regulatory standards. While existing POU and POE technologies, including reverse osmosis and packed bed media filters, are effective for removing contaminants, installation costs, energy demands, and spatial footprints of these systems can inhibit their implementation. There is a need for new POU and POE technologies that remove a diversity of water contaminants while maintaining a small application footprint. Nanotechnology, referring to technology using material with at least one dimension or feature less than 100 nm in length, is ideal for meeting this need in drinking water treatment. With high surface area-to-volume ratios, nano-enabled treatment technologies exhibit enhanced reactivity with less material, keeping overall footprint relatively small. Specifically, electrospinning, a process in which a polymer precursor solution is electrified to produce a cohesive sheet of nanofibers, can be used to easily synthesize chemically active nanofiber filters for water treatment applications. In this study, we develop electrospun nanofiber filters that harness nano-scaled hematite (Fe2O3) for sorption of inorganic contaminants (e.g., As, Pb) and nano-scaled titanium dioxide (TiO2) for use with ultraviolet (UV) and visible light as an advanced oxidation process (AOP) for removal of emerging organic contaminants (e.g., benzotriazole, carbamazepine, DEET). Most importantly, we strive to optimize both reactivity and material strength to develop cohesive, durable filtration platforms that overcome barriers to use of nanomaterials in water treatment (e.g., concerns over leaching of nanoparticles deployed as suspensions). Herein, we first demonstrate reactivity optimization of pure (though brittle) TiO2 nanofiber photocatalysts by noble metal catalyst (Au) surface loading. Additionally, we optimize polymer-Fe2O3 composite nanofibers for reactivity while maintaining material flexibility by coating the doped polymer with additional Fe2O3 surfaces available for metal/metalloid uptake. Finally, we apply reactivity optimization and strategies to maintain material strength in the development of carbon/TiO2 nanofiber composites used for (photo)chemical filtration of water containing emerging organic contaminants. Ultimately, we find that nanofiber composites exhibit substantial reactivity and structural integrity in water treatment platforms. Outcomes of this work contribute to making nanomaterials, which have been studied for decades but have yet to be commercially employed for water treatment, practical for chemically active water filtration.

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Cacciato, Giuseppe. "Metal-TiO2 nanocomposites towards efficient solar-driven photocatalysis." Doctoral thesis, Università di Catania, 2019. http://hdl.handle.net/10761/4182.

Повний текст джерела

Анотація:

Water, together with energy and food, has been addressed as one of the main urgent problem of humanity. The reduction of fresh clean water sources will definitely lead to huge issues in the next future, especially in developing countries. The conventional wastewater treatments suffer some limitations related to the effectiveness in decontamination (mechanical filtration), in the heavy use of chemicals (chlorination), or in elevate operational costs and energy requirements (desalination and reverse osmosis). In this sense, new materials such as nanocomposites may overcome these issues taking advantage of the peculiar properties of materials at nanoscale. Research on novel nanotechnologies must bring advances in order to contrast and prevent water scarcity and pollution. In order to be effective, these nanotechnologies should run at low operational cost, even in places unequipped by strong infrastructures and in concert with conventional cheap methodologies. Among the alternative water purification methods, TiO2-based photocatalysis has attracted great attention due to material stability, abundance, non-toxicity and high decontamination efficiency. In this material, electron-hole pairs, generated by light absorption, separate from each other and migrate to catalytically active sites at the surface of the photocatalyst. Photogenerated carriers are able to induce the water splitting reaction and, consequently, to decompose organic pollutants. The main deficiency of this material, related to its large band gap, is that only the UV fraction of the solar spectrum is effective to this purpose. Several approaches have been proposed to overpass this issue and, among them, the use of metal-TiO2 nanocomposites with proper nanostructurarion seems very promising for water purification strategies. Aim of this work is to investigate the possibility to develop efficient solar-driven TiO2 photocatalyst taking advantage of metallic nanostructures to efficiently couple the incident light to the photoactive semiconductor. Two approaches have been followed: TiO2 nanoparticles obtained via pulsed laser ablation in liquid and optical engineering of multilayered metal-TiO2 thin films. The first approach maximizes the exposed surface, thus enhancing the photocatalytic efficiency. However, in this case nanomaterials is dispersed in the surrounding environment, and in order to avoid this drawback we have investigated, as second approach, the use of metal-TiO2 thin films.

Стилі APA, Harvard, Vancouver, ISO та ін.

22

MANCINI, Marilena. "Improved anodic materials for lithium-ion batteries: surface modification by metal deposition and electrochemical characterization of oxidized graphite and titanium dioxide electrodes." Doctoral thesis, Università degli Studi di Camerino, 2009. http://hdl.handle.net/11581/401752.

Повний текст джерела

Анотація:

The research work presented in this thesis has been carried out during my Ph.D. study at the Chemistry Department of Camerino University (Italy) and at the ''Centre for Solar Energy and Hydrogen Research Baden-Wa'¼rttemberg'' (ZSW) in Ulm, (Germany). [...] The thesis deals with the evaluation of the electrochemical performances of metal-modified anodes for lithium-ion batteries. The results obtained by using either partially oxidized graphite or TiO2 anatase as active materials for anode fabrication are presented. The obtained results have been the subject of the following scientific publications and proceedings of congress: F. Nobili, S. Dsoke, M. Mancini, R. Tossici, R. Marassi, ''Electrochemical investigation of polarization phenomena and intercalation kinetics of oxidized graphite electrodes coated with evaporated metal layers'', Journal of Power Sources, 180 (2008) 845-851. M. Mancini, F. Nobili, S. Dsoke, F. D'Amico, R. Tossici, F. Croce, R. Marassi, ''Lithium intercalation, interfacial kinetics of composite anodes formed by oxidized graphite and copper'', Journal of Power Sources (2008), in Press, doi:10.1016/j.jpowsour.2008.10.084. M. Mancini, P. Kubiak, J. Geserick, R. Marassi, N. Ha'¼sing, M. Wohlfahrt-Mehrens, ''Mesoporous anatase TiO2 composite electrodes: electrochemical characterization and high rate performances'', Journal of Power Sources (2008), in Press, doi:10.1016/j.jpowsour.2008.10.050. F. Nobili, S. Dsoke, M. Mancini, R. Marassi, ''Interfacial properties of copper coated graphite electrodes: coating thickness dependence'', Fuel Cells, Accepted, DOI: 10.1002/fuce.200800087. M. Mancini, P. Kubiak, J. Geserick, R. Marassi, N. Ha'¼sing, M. Wohlfahrt-Mehrens, ''Electrochemical performances of mesoporous anatase TiO2 electrodes modified by vacuum metal deposition'', 214th Meeting of the Electrochemical Society (ECS). Honolulu, Hawaii, USA, 12-17 October, 2008. Abs. 1261. P. Kubiak, M. Mancini, J. Geserick, R. Marassi, N. Ha'¼sing and M. Wohlfahrt-Mehrens, ''Mesoporous anatase TiO2 composite electrodes: electrochemical characterization and high rate performances'', IMLB-14, The 14th International Meeting on Lithium Batteries. TEDA, Tianjin, China, 22-28 June, 2008. Abs. 142. M. Mancini, F. Nobili, S. Dsoke, R. Tossici, R. Marassi, ''Metal coated oxidized graphite electrodes: electrochemical investigation of polarization phenomena and intercalation kinetics'', 11th UECT Ulm Electrochemical Talks 2008. Neu-Ulm, Germany, 10-12 June, 2008. Abs. p. 48. F. Nobili, S. Dsoke, M. Mancini, R. Tossici, R. Marassi, ''Electrochemical investigation of polarization phenomena and intercalation kinetics of oxidized graphite electrodes coated with evaporated metal layers'', 3rd German-Italian-Japanese Meeting of Electrochemists. Taormina-Messina, Italy, May 25-28, 2008. Abs p.s 41-42. M. Mancini, S. Dsoke, F. Nobili, R. Tossici, R. Marassi, ''Metal-oxidized graphite composite electrodes as anodes for lithium-ion batteries'', School of the Physical Chemistry Section: ''Composite Materials: from Molecular Sciences to nanotechnology''. Turin, Italy, 3-8 September, 2006. Abs. p. 94.

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Mileyeva-Biebesheimer, Olga. "An Investigation into Metal Oxide Nanoparticle Toxicity to Bacteria in Environmental Systems Using Fluorescence Based Assays." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302125170.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Grant, Ann W. "Surface studies of model catalysts using metal atoms and particles on ZnO(0001)-Zn and -O and TiO₂(110) /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/8499.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Siriwongrungson, Vilailuck. "Characterisation of Step Coverage by Pulsed-Pressure Metalorganic Chemical Vapour Deposition: Titanium Dioxide Thin Films on 3-D Micro- and Nano-Scale Structures." Thesis, University of Canterbury. Mechanical Engineering, 2010. http://hdl.handle.net/10092/3615.

Повний текст джерела

Анотація:

An examination of the possibility of applying pulse pressure metalorganic chemical vapour deposition (PP-MOCVD) to conformal coating and an investigation of PP-MOCVD processing parameters were undertaken using the deposition of thin, conformal titanium dioxide (TiO₂) on 3-D featured and non-featured substrates. The characterisation of the conformality and wettability analysis of thin TiO₂ was carried out using titanium tetraisopropoxide (TTIP) dissolved in toluene as a precursor and featured silicon (Si) and silicon nitride (Si₃N₄) as substrates. The features on the substrates were in micro- and nano-scale with the aspect ratio up to 2:1. The processing parameters investigated were temperatures between 400 and 600°C, reactor base pressures from 50 to 200 Pa, injection volumes between 50 and 250 µl, precursor concentrations in the range of 0.15 to 0.50 mol% and pulsing times from 10 to 20 sec. The surface morphology and thickness were examined using a scanning electron microscope (SEM). The composition of the films was qualitatively identified by energy dispersive X-ray spectroscopy (EDS). X-ray diffraction (XRD) and Raman spectroscopy were used to analyse the phase and grain size. The surface roughness and grain size were evaluated using atomic force microscopy (AFM). The optical properties were characterised using UV-VIS light spectroscopy. The anti-sticking characteristic was examined by wettability analysis, measuring the contact angle of the film with water. The research examined the relationships between processing parameters and growth rate, conformality, surface roughness, grain size, phase and water contact angle. A new measurement for thin film conformality was derived based on a statistical analysis of a large number of film thickness measurements on a fracture surface over the lithographed features. The best conformality of 0.95 was obtained for micro-scale features at the lowest temperature in the range of investigation, 400℃, with pulse exposure characterised by a base pressure of 100 Pa, TTIP concentration of 0.50 mol%, injection volume of 50 µl and pulsing time of 10 sec. Conformality for micro-scale features was in the range of 0.82 to 0.97 over a wide range of deposition temperatures. Conformality was as low as 0.45 over nano-scale structures at the higher exposure rate. The conformality decreased as the temperature and precursor concentration increased. The precursor injection volume was found to have minor influences on conformality. The growth rate increased as the temperature increased and reached the maximum at the deposition temperature of 450℃ with the precursor concentration of 0.50 mol% and injection volume of 100 µl. The base pressure and relaxation time had slight influences on the growth rate over the deposition temperature range of 400 to 500℃. The growth rate was increased as the precursor concentration and precursor injection volume increased. The deposited TiO₂ films exhibited columnar growth and anatase phase. The base pressure and pulsing time had no obvious effects on grain size and surface roughness. The grain size decreased as the deposition temperature increased. The surface roughness increased as the deposition temperature increased. Contact angles of over 100° were found with conformality of over 0.80. The variation in contact angle was related to the surface morphology of the deposited films. The contact angle increased as the grain size decreased. High wettability was found for films in the mid-range of pulse exposure, in this study at pulse exposure of 53, or at high deposition temperature, in this case at 600°C. The as-deposited TiO₂ thin films were hydrophobic depending on the surface morphology, surface roughness and grain size.

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Bender, Edward Thomas. "Spectroscopic Characterization of Metal Oxide Nanofibers." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1145294467.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Nguyen, Phuong Thi Minh. "Synthesis and physicochemical evaluation of metal oxide powders which reveal antibacterial activity under dark conditions." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13142993/?lang=0, 2020. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13142993/?lang=0.

Повний текст джерела

Анотація:

濃度3Mの硝酸亜鉛水溶液中170°Cで7 h水熱処理し，ついで大気中600℃で再酸化処理して合成した酸化亜鉛ZnOは持続的な暗所抗菌性を示す．このZnOについて物理化学な物性を詳細に検討した．また，カリウムKとりんPを1:3の原子比率で添加固溶させたアナターゼ型酸化チタンTiO2は暗所でも抗菌性を示すことを新たに見出した．その抗菌性発現のメカニズムについて検討した結果を報告する．
Both ZnO and TiO2 have high potential as antibacterial agents which are able to apply in various fields. Although there are already many studies about these materials focusing on their antibacterial activity, they are still getting more attention from researchers due to their unclear mechanism under dark. There have been very few reports mentioning clearly about this. Besides, the effects of the preparation methods and their physicochemical properties to the antibacterial property of ZnO, TiO2 and doped TiO2 under dark also have not been well-characterized. In the present study, synthesis and physicochemical evaluation of metal oxides which reveal antibacterial activity even in the dark conditions have been performed.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Yang, Xiaojiao. "Synthesis and Characterization of Hybrid Metal-Metallic Oxide Composite Nanofibers by Electrospinning and Their Applications." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1022/document.

Повний текст джерела

Анотація:

Nous présentons dans ce manuscrit l'élaboration par électrofilage (ES) de nanofibres hybrides métal/oxyde métallique (HMMOC) et leurs caractérisations physico-chimiques. Leurs utilisations dans le cadre d’applications de type « énergie » et « environnement » ont été évaluées. En particulier, la photocatalyse de nanofibres TiO2-Au pour la dégradation en solution aqueuse du bleu de méthylène et l’utilisation de nanofibres WO3-Au comme capteurs de gaz (VOCs) ont été examinées. En lien étroit avec les résultats obtenus sur l'évaluation des performances comme photocatalyseurs ou capteurs à gaz de ces nouvelles structures HMMOC, l'influence de nombreux paramètres a été étudiée : la concentration en ions aurique, la méthode utilisée pour introduire ces derniers à l’intérieur ou les déposer à la surface des nanofibres d’oxydes et finalement le traitement thermique. En effet, on peut soit mélanger directement, avant la procédure d’électrofilage, la solution contenant les ions aurique à la solution polymérique (composée de PVP, PAN, ou PVA contenant le précurseur d'oxyde métallique), soit déposer sous forme de goutte cette solution d’ions Au à la surface des nanofibres d’oxyde métallique une fois la procédure d’électrofilage effectuée. Quant au traitement thermique, il joue un rôle multiple puisqu’il permet à la fois, d’éliminer les composés organiques des solutions polymériques, participant ainsi à la structuration de la partie oxyde du HMMOC, mais aussi de réduire les ions Au sous forme de nanoparticules.Des résultats prometteurs en photocatalyse ont été obtenus sur des fibres optimisées de TiO2 contenant des nanoparticules d’Au de 10 nm (concentration en Au : 4 wt%). En effet, pour cet échantillon, on montre une dégradation 3 fois plus rapide du bleu de méthylène en solution aqueuse que celle obtenue sur les nanofibres de TiO2 de références et sur le catalyseur commercial P25. De la même manière, des nanofibres de WO3 décorées de nanoparticules d’Au de 10 nm, utilisées comme capteurs de gaz, permettent d’obtenir une réponse 60 fois plus importante que dans le cas de nanofibres de WO3 pure et en améliorant grandement la sélectivité par rapport au n-butanol
We present in this manuscript the elaboration by Electrospinning (ES) process of hybrid metal-metallic oxide composite (HMMOC) nanofibers (NFs), and their physical-chemical characterizations. Their applications, especially the photocatalysis of TiO2-Au composite NFs for photocatalytic degradation for methylene blue (MB) in an aqueous solution and WO3-Au composite NFs for gas sensing of the volatile organic compounds (VOCs) have been investigated. According to the performance evaluation results as photocatalyst or gas sensors, the influence of many parameters have been studied: gold ions concentration, the way to introduce them into or at the NFs surface, typically by mixing them into the polymeric solution (composed of PVP, PAN, or PVA with the metallic oxide precursor) before the ES process or by simple droplet deposition onto the NFs after ES process, and finally the annealing treatment. This latter plays an important role since it both removes the organic components of the polymeric solution, thus forming the metal oxide and in-situ participates to the Au reduction.Concerning the photocatalytic properties, an optimized HMMOC material based on TiO2 NFs including 10 nm Au nanoparticles (NPs) has been obtained and shows 3 times significantly improvement of MB degradation compared to pure TiO2 NFs and the commercial catalyst P25. For gas sensing elaboration, we have shown that a HMMOC material based on WO3 NFs decorated at their surface with 10 nm Au NPs can exhibit 60 times higher response and significantly improved selectivity toward n-butanol compared with pure WO3 NFs

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Nebatti, Ech-Chergui Abdelkader [Verfasser], Burak [Akademischer Betreuer] Atakan, and Volker [Akademischer Betreuer] Buck. "Functional doped metal oxide films : [[Elektronische Ressource]] : Zinc oxide (ZnO) as transparent conducting oxide (TCO) Titanium dioxide (TiO2) as thermographic phosphor and protective coating / Abdelkader Nebatti Ech-Chergui. Gutachter: Volker Buck. Betreuer: Burak Atakan." Duisburg, 2011. http://d-nb.info/1015428088/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Santos, Jose Carlos Sousa dos. "Caracterização de revestimentos de TiO2 depositados por aspersão termica a plasma sobre a liga Ti-13Nb-13Zr." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263110.

Повний текст джерела

Анотація:

Orientador: Cecilia Amelia de Carvalho Zavaglia
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-12T14:04:29Z (GMT). No. of bitstreams: 1 Santos_JoseCarlosSousados_M.pdf: 6317167 bytes, checksum: 3007b440a82fcaab621d5cef423c3334 (MD5) Previous issue date: 2008
Resumo: A liga Ti-13Nb-13Zr tem sido proposta em estudos de pesquisa como uma nova alternativa dentre as ligas biomédicas por apresentar em sua formulação alguns dos elementos metálicos de maior compatibilidade como: titânio, nióbio e zircônio; considerados como metais válvulas, onde apresentam excelente resistência à corrosão, excelente propriedades mecânicas e baixa densidade. O substrato da liga Ti-13Nb-13Zr foi revestido com titânia (TiO2) por aspersão térmica a plasma visando viabilizar a sua utilização como implantes biomédicos. Foram utilizadas técnicas de caracterização desses substratos revestidos para avaliar os efeitos da titânia sobre as propriedades mecânicas e físico-químicas da liga Ti-13Nb-13Zr. Foram obtidos revestimentos de boa qualidade com baixa porosidade, baixo nível de partículas não fundidas e com boa adesão. O ensaio de riscamento com e sem tratamento térmico não apresentou alterações significativas nos valores da carga crítica. Os resultados experimentais obtidos do substrato da liga Ti-13Nb-13Zr revestido com titânia após o ensaio de riscamento apresentou uma boa adesão do depósito ao substrato o que viabilizará em futuro o seu uso em implantes ortopédicos.
Abstract: The Ti-13Nb-13Zr alloy has been proposed by researchers as new alternative amongst the biomedical alloys for presenting on its composition some of the metallic elements of better compatibility; as titanium, niobium and zirconium; considered as metals valves, by presenting excellent corrosion resistance, excellent mechanical properties and low density. The Ti-13Nb-13Zr alloy substratum was coated with titanium dioxide (TiO2) by plasma thermal aspersion aiming its biomedical application. Titanium influence on the mechanical and physico-chemical properties was determined and coatings were found to be of good quality exhibiting low content of an melted particles and good adhesion. The scratch test with and without thermal treatment did not have significant alterations on the values of the critical load. The results obtained on these experiments showed that TiO2 coating on Ti-13Nb-13Zr alloys has good potencial for orthopedics implantations since it exhibits good adhesion and good mechanical properties.
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Soliveri, G. "PATTERNING AND MODULATION OF OXIDE SURFACE PROPERTIES." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/329471.

Повний текст джерела

Анотація:

Most of the topics dealt with in this thesis belong to surface science. The starting point was the fundamental understanding of phenomena at the oxide-gas interface and the effect of its modification. Such knowhow was then used to solve (or, at least, to attempt to solve) issues of critical impact in everyday life: the increasing lifetime of building materials employed in low-impact smart houses; the fouling prevention in electroanalytical sensors for neurotransmitter detection; the unspecialized laboratories accessibility to microlithography, critical to device miniaturization. These challenges might seem not related, but they actually share deep scientific and technological foundations. The physicochemical modification of oxide surfaces, the creation of organic/inorganic hybrids and the exploiting / the enhancing of semiconductor peculiar properties allowed us, starting from the foundation, the realization of proof-of-concept protocols and devices, ready for the pre-commercial development. The Leitmotif of my research was the synthesis and the modification of titanium dioxide surfaces. TiO2 has been the main character in physico, physicochemical and material science researches of the last 50 years. Biocompatibility and low cost make it engaging for many applications. Its (near-UV active) semiconductor features, well known and abundantly investigated by the scientific community, are acquiring central interest also in many markets with the development of self cleaning coatings, windows and asphalts, anti-fogging mirrors and self-sterilizing surgery rooms and instrumentations. New generation batteries and solar cells are going to be developed as commercial prototypes. One of the biggest challenges in the titania fundamental research is the enhancement of activity in the solar spectrum. First, the most recent aspects in titania doping and promotion were touched. While, in the last twenty years, great effort has been made in the mono-atomic doping of titania and in the understanding of the influence of the dopant position in the titania lattice and its electronic behavior, the most recent literature describes the co-promotion of the material by two (or more) atoms doping. The metal/non-metal codoping seems especially promising; the synergetic effect of the two atoms in the TiO2 lattice was both theoretically and experimentally proved. In this contest, the N/Nb codoping was analyzed, investigating the effect of the atoms in the lattice from morphological (surface area, porosity and crystallographic structure) and electronic point of view (EXAFS, UV-Vis absorption and EPR analyses). N/Nb codoping was compared with N/Ta co-doped samples, synthesized by two different procedures. The photoactivity of the two sample families was tested by a model reaction (the degradation of ethanol, throughout acetaldehyde intermediate) both under UV and solar simulated irradiation. Then, a different approach in the modification of surfaces was tested. The assembly of organic/inorganic hybrids was tested; thanks to the formation of organic mono- or multi-layers at the surface,they can tune the chemistry, the polarity and the adhesion properties of the interface. Siloxanes were used as active agents, thanks to their compatibility with oxide materials and, especially, for the ability to self-assemble at the surface to form a monolayer. Siloxanes are able to react with the -OH groups at the surface, chemisorbing and polymerizing at the interface in such a way to form a monolayer with tunable functionalities. Many different silanes were tested and their dipole momenta were related to their wettability properties. Such siloxanes chemisorb strongly both from the gas phase and the liquid phase. Their reactivity, both on smooth and rough surfaces, was tested vs the temperature of functionalization in gas phase. Many characterization techniques were adopted to understand the behavior of such molecules from a molecular point of view: magnetic (solid state NMR), microscopic (SEM, TEM, AFM), optical and electrochemical (CV and EIS). The science of adhesion and wettability was also adopted for the development of superhydrophobic coatings. Titanium dioxide particles with engineered morphology were used as the best candidate to create superhydrophobic/superhydrophilic patch-wise surfaces, exploiting their photoactivity (photolithograpy). The core of the thesis was the synthesis, modification and application of transparent photoactive thin films. A procedure for the synthesis of smooth, transparent and photoactive TiO2 thin layers was developed, and used to produce highly applicative devices and protocols. Such synthetic strategy is highly tunable and reproducible; the obtained films are robust and active and, most of all, require simple instrumentation (sol-gel procedure), which is highly appealing for the market. The films were properly characterized both form the morphological/mechanical and photochemical point of view. Apart their transparency and their thickness, the films were highly crystalline (pure anatase phase). Such procedure was firstly designed as a proof-of-concept for self-cleaning windows, but, thanks to its versatility and the high activity of the films, it leads the path towards highly applicative procedures and devices. The smoothness and the photoactivity brought me to the field of photolithograpy, especially in the direction of microlithography. The high activity of the titania allowed the use of safe and low-energetic lamps. No collimation was required to obtain a resolution lower than 5 µm. First of all, I tested the lithography on siloxane monolayer films, as a proof-of-concept of resolution and efficiency. But siloxanes, as many other self-assembled monolayer molecules, can be the pillars for 3D fabrication. Such monolayers were used as polymerization initiators for polymer brushes. If the initiators of polymerization are patterned, patterned polymer brushes will be obtained. That was the first report of polymer-brushes lithography exploiting the photoactivity of TiO2. Remote photocatalytic lithography makes this procedure extremely versatile. Exploiting the remote photocatalysis, in principle, any material can be used as a support for patterned polymer brushes growth (provided that the initiator are able to graft the surface). The developed protocol for the synthesis of TiO2 thin films was also used to design and engineer complex electrodes for cyclovoltammetric analyses of biological samples. Electrochemistry seems to be the best candidate for the development of an analytical option with sensitivity comparable with present analytical procedures but reduced time-per-analysis and cost. Unfortunately, catecholamines chemisorb and polymerize on metal and oxide electrodes quickly, making the device useless. Covering the electrode by a homogeneous, nano-porous thin layer of titania makes the surface photoactive. That is the first example in literature of self-cleaning nano-engineered electrodes for cyclic voltammetry. After the detection, also in simulated human serum and liquor, a fast and simple irradiation of the device, under non-hazardous UV-A lamp, degrades all the fouling on the surface without altering its features. The sensor, after each UV treatment, recovers its pristine performances, with full recovery in terms of selectivity and sensitivity. Irradiation trials were also performed directly in the analytical mixture, as a proof of concept for on-site application. Modern era requires flexible and light materials for the building industry. Polymers are acquiring more and more interest thanks to their increasing performances and their smart properties. The drawbacks of such materials are connected to the low resistance to the UV light, the softness and the difficulties in cleaning procedure. The use of organic/inorganic hybrid, or better the coverage of plastic materials with an oxidic thin layer, can solve many of these problems, lengthening the lifetime of such materials. If the covering oxide is also photoactive, the material can be self-cleaned when exposed to solar light. That is a big chemical challenge, because of many synthetic problems. Two different approaches were tested to solve this relevant issue. On one side, the hydrophobicity of ionic liquid modified SPES (sulfonated polyether sulfone) was combined with designed morphological features to confer superhydrophobicity. On the other side, the polymeric surface was covered with a transparent titania layer active in the near UV-region, able to mineralize organic molecules chemisorbed at the surface. Eventually, a different approach to modify oxidic (and not only) surfaces is the creation of a homogeneous layer of Ag nanoparticles by an innovative microwave procedure. That simple and accessible strategy allowed us to produce plasmonic surfaces (thanks to the dimension and the homogeneity of the Ag particles) with countless applications. The layer was shown to be a very active substrate for surface enhancement Raman spectroscopy (SERS). Thanks to the versatility of the synthetic method, all shapes and dimensions can be covered. That makes it a perfect candidate for the production of new generation of SERS sensors. The sensitivity towards molecules of environmental and biomedical interest was proved.

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Rico, Santacruz Marisa. "Band gap control in hybrid titania photocatalysts." Doctoral thesis, Universidad de Alicante, 2014. http://hdl.handle.net/10045/42201.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

33

You, Sheng Mu. "Metal organic frameworks as efficient photosensitizer for TiO₂ nanoarray anode and application to water splitting in PEC cells Fe/Ni Bimetallic organic framework deposited on TiO₂ nanotube array for enhancing higher and stable activity of oxygen evolution reaction Novel nano-architectured water splitting photoanodes based on TiO₂-nanorod mats surface sensitized by ZIF-67 coatings Surface sensitization of TiO₂ nanorod mats by electrodeposition of ZIF-67 for water photo-oxidation Electrochemically capacitive deionization of copper (II) using 3D hierarchically reduced graphene oxide architectures." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASF015.

Повний текст джерела

Анотація:

Les réserves de combustibles fossiles diminuent et leur utilisation illimitée depuis la révolution industrielle a généré de profonds changements du climat, notamment des cycles de la température atmosphérique. Stocker l'énergie solaire sous forme d'hydrogène produit par dissociation de l'eau est un moyen idéal pour combattre le réchauffement climatique. Les matériaux de la famille des «metal organic framework» (MOF) commencent à être utilisés comme photo-électrocatalyseurs, notamment pour la photo-dissociation de l'eau. Leur porosité extrêmement élevée et leur grande polyvalence, tant chimique que structurelle, les désignent comme des candidats potentiels pour faciliter l'absorption du rayonnement solaire et catalyser la dissociation de l'eau dans les cellules photoélectrochimiques. En contrôlant la composition chimique et le dopage du linker utilisé dans le MOF, il est possible d'ajuster l'énergie de la bande interdite, de favoriser la fonctionnalisation sur des substrats très variés ou encore d'ajuster leur résistance à la corrosion dans divers environnements chimiques. Ce sont donc des matériaux d'un grand intérêt pour la catalyse, l'électrocatalyse ou la photo-électro-catalyse. D'autre part, le TiO₂ nano-structuré, par exemple sous forme de tapis d’épaisseur micrométrique de nanotubes ou de nanofils, parfois appelé TNA, est un matériau bien adapté à la construction de photoanodes pour le dégagement d'oxygène en milieu aqueux. Il a déjà été largement étudié et décrit dans la littérature. Au cours de notre thèse, nous avons fabriqué des matériaux composites constitués de MOF de métaux de transition (Ni, Co, Fe) déposés sur TNA (TDNR et TNTA). Pour cela, nous avons utilisé une méthode électrochimique d'électrodéposition. Cela nous a permis de déposer des nanoparticules métalliques sur du TNA à potentiel fixe - 1,0 V puis de les transformer par réaction chimique avec des ligands organiques (BTC, BDC, et 2MZ) par voie thermo-thermique. Les matériaux obtenus présentent une activité électrocatalytique significative et une excellente durabilité photoélectrochimique. Ces matériaux composites ont été utilisés avec succès comme phase active dans des photo-électrodes pour la réaction de dégagement d'oxygène moléculaire (OER)
The fossil fuel reserves are dwindling and their unrestricted use has generated profound changes in Earth's surface temperature and climate. Storing solar energy in the form of hydrogen produced by dissociation of water is an ideal way to mitigate global warming. Materials from the “metal organic framework” (MOF) family are starting to be used as photo-electrocatalysts, especially for photo-dissociation of water. Their extremely high porosity and their great versatility, both chemical and structural, designate them as potential candidates to facilitate the absorption of solar radiation and catalyze the dissociation of water in photoelectrochemical cells. By controlling the chemical composition and doping of the linker used in the MOF, it is possible to adjust the band gap energy, to favor the functionalization on very varied substrates or even to adjust their resistance to corrosion in various chemical environments. They are therefore materials of great interest for catalysis, electrocatalysis or photo-electro-catalysis. On the other hand, nano-structured TiO₂, for example in the form of nanotube or nanowire mats, sometimes called TiO₂ nanoarray (TNA), is a material very suitable for the construction of photoanodes for the evolution of oxygen in aqueous medium. It has already been extensively studied and described in the literature. During our thesis, we manufactured composite materials made up of MOFs of transition metals (Ni, Co, Fe) deposited on TNA (network of nanotubes or nanowires). For this we used an electrochemical method of electrodeposition (cyclic voltammetry). This allowed us to deposit metallic nanoparticles on TNA with fixed potential - 1.0 V and then transform them by chemical reaction with organic ligands (1,3,5-benzenetricarboxylic acid, BTC, 1,4-benzenedicarboxylic acid, BDC and imidazole, 2MZ) by thermal-thermal route. The materials obtained exhibit significant electrocatalytic activity and excellent photoelectrochemical durability. These composite materials have been successfully used as an active phase in photo-electrodes for the oxygen release reaction (OER)

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Jena, Anirudha. "Development of Metal Oxide/Composite Nanostructures via Microwave-Assisted Chemical Route and MOCVD : Study of their Electrochemical, Catalytic and Sensing Applications." Thesis, 2012. https://etd.iisc.ac.in/handle/2005/3233.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Jena, Anirudha. "Development of Metal Oxide/Composite Nanostructures via Microwave-Assisted Chemical Route and MOCVD : Study of their Electrochemical, Catalytic and Sensing Applications." Thesis, 2012. http://hdl.handle.net/2005/3233.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Chen, Jiun-Yu, and 陳俊佑. "Polymer-Assisted Electrospinning of Mesoporous Titanium Dioxide Nanofibers." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/98092938000120437630.

Повний текст джерела

Анотація:

碩士
國立成功大學
材料科學及工程學系碩博士班
94
Titanium dioxide nanofibers were fabricated via a polymer-assisted electrospinning technique. A mixture of titanium-tetraisopropoxide (TTIP) and poly(vinylpyrrolidone) (PVP) in an alcohol medium utilized as the sol-gel solution was ejected through a needle under a strong electrical field. In company with the solvent evaporation and the sol-gel solidification, highly charged polymer jet induces the formation of polymer/metal oxide nanofibers before reaching to the ground electrode. Calcination process was carried out afterward to encourage the crystallization and phase transformation of titania, as well as the removal of polymer domains. Electrospinning process and calcined titania nanofibers exhibited strong relationship with the presence of polymer media. Process parameters and the characterizations of nanoconstructed titania nanofibers were investigated and discussed. Micron-scaled thick films produced by the same PVP/TTIP sol-gel solutions were prepared to compare with one-dimensional titania nanofibers.

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Hsu, Wen-Fang, and 徐雯芳. "Thermal fabrication of titanium dioxide-coated titanium photoanodes for electrochemical-assisted photocatalytic degradation of orange G." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/th9865.

Повний текст джерела

Анотація:

碩士
國立交通大學
工學院永續環境科技學程
104
The rise of dye industry leads to large quantity of dye wastewater. Dye wastewater are rich in high organic content, which has chroma characteristics. The dye waste water will pollute water body and damage the aquatic ecological system if they are not treated properly prior being discharged. Advanced oxidation processes (AOP) are started to receive more attentions in treating dye wastewater decolorization.Recently, photo-catalysis process by using titanium dioxide (TiO2) was the most widely applied technique for this process . In this thesis, We focus on the fabrication of TiO2 films on Ti mesh substrate by direct calcinations process by applying different calcination temperatures. The photoelectron – chemical properties of the as prepared titanium dioxide-coated titanium photoanodes were also investigated. The surface morphology, crystal phase, and chemical composition were investigated using ICP-MS, XRD, SEM and XPS, respectively. In addition, optimum electrical parameters was determined by using electrochemical current balance. Furthermore, the fabricated titanium dioxide-coated titanium photoanodes were applied for degrading azo d acid orange G.The dye degradation efficiency of TiO2 photoanode films were applied in different combined-energy system, including： photolysis, photo-catalysis electro-catalysis, photoelectro- catalysis and photoelectro-Fenton catalysis were evaluated. The well-fabricated rutile titanium dioxide-coated titanium photoanodes in this study shows a high photocurrent density of 226.57μA cm-2 with great dispersion, big surface area and large crystalline size.The samples were prepared by applying HCl for surface cleaning, post treatment calcined at 700oC in air for 2 hours subsequently. The maximum utilization of electrode area were under the electrochemical current balance. The order of degradation modes with respect to decreasing the degradation efficiency of OG is： PEF > EPC > EC > PC oxidation. In the feasibility test for dye degradation, photoelectro-Fenton catalysis system using TiO2 photoanode achieved high decolorization rate 38.48% for 3 hours. Therefore, these results suggest that titanium dioxide-coated titanium photoanodes prepared in this study is suitable for the application of dye wastewater treatment to achieve high removal efficiency in order to accomplish effective water purification purpose.

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Kao, Jui-Yang, and 高瑞陽. "Study on Preparation of Titanium Dioxide Dispersion Solution Assisted by Supercritical Carbon Dioxide and Its Stability." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/53757060992785218787.

Повний текст джерела

Анотація:

碩士
國立中興大學
化學工程學系所
105
Titanium dioxide dispersion solution was widely applied for coating, cosmetic, photocatalytic, antibacterial agents, environmental and so on. However, between of particles and particles have the Van Der Waals’ forces, resulting in reduce the stability of titanium dioxide dispersion solution, and affecting their application. Therehore, how to reduce the secondary average particle size and enhance the stability of the dispersion solution is a very important issue. In this study, we preparation of titanium dioxide dispersion solution assisted by supercritical carbon dioxide.The base fluid was deionized water, and sodium hexametaphosphate was added as a dispersant, and then we changed the different dispersion conditions of supercritical carbon dioxide, such as temperature, pressure, saturation time, dispersion solution concentration, co-solvent of base fluid and the process methods to investigate the secondary average particle size and uniformity of the titanium dioxide dispersion in base fluid. Finally, we discussed the stability of titanium dioxide dispersion in solution. In the experiment, we characterized titanium dioxide dispersion solution by ultraviolet-visible absorption spectroscopy (UV-Vis), high-speed centrifugation, pH meter, transmission electron microscopy (TEM) and zeta potential instrument. As shown in the results, we surmise the following remarks: (1)When the concentration of titanium dioxide dispersion in solution with sodium hexametaphosphate was 0.1 wt%, the secondary average particle size was 366±295 nm and 148±68 nm, rescpectively, measured from the TEM before and after dispersing with supercritical carbon dioxide; and then reduced the concentration of titanium dioxide dispersion in solution to 0.005 wt%, the secondary average particle size was 127±68 nm after dispersing with supercritical carbon dioxide. It means that supercritical carbon dioxide penetrates the pores of aggregated particles, and then rapidly depressurize to separate aggregated particles in solution. (2)Under the conditions of 0.1 wt% titanium dioxide dispersion in solution, the temperature of 55℃, the pressure of 4000 psi, and the saturation time for 30 min, the dispersion of supercritical carbon dioxide was repeat by three times, which results in that the secondary average particle size was 126±63 nm measured from the TEM. This was that because the particle size of the second dispersion was smaller than that of the first dispersion, so that the supercritical carbon dioxide can penetrate the smaller pores in the aggregated particles and increase its dispersibility. It means that repeated the same conditions dispersion of supercritical carbon dioxide can decrease the secondary mean particle size of aggregates particle in solution. (3)As the concentration of titanium dioxide dispersion in solution was 0.005 wt%, and the addition of sodium hexametaphosphate was twice times of concentration of titanium dioxide, the maximum zeta potential of dispersion solution was -53.7 mV by zeta potential instrument. This suggests that the sodium hexametaphosphate as a dispersant will dissociate from the phosphate ions and adsorbed on the surface of the titanium dioxide particles, induceing that titanium dioxide dispersion in solution has a large negative charge of the electrostatic repulsive force and has good stability. And supercritical carbon dioxide dissolved in the dispersion will produce carbonic acid, which pH value was 6.25 in the dispersion solution. The secondary average particle size was 317 nm measured from the DLS. (4)By means of UV-Vis associated with high-speed centrifugation method, the addition of sodium hexametaphosphate was confirmed to enhance the dispersion of titanium dioxide in solution by supercritical carbon dioxide, which the optimal volume ratio of ethylene glycol and deionized water was 1：1 and its stability increased by 72.7%. It will help to enhance the stability of the solution. Because the viscosity of ethylene glycol was higher than deionized water, which can slow down the collision between particles and particles, so that enhance the stability of the solution. (5)The lifetime of as-prepared 0.1 wt% TiO2 dispersion solution achieve three weeks measured by sedimentation method in this study. The volume ratio of ethylene glycol and deionized water was 1：1. It will help to enhance the stability of the solution.

Стилі APA, Harvard, Vancouver, ISO та ін.

39

SYU, YONG-SHENG, and 許永勝. "Titanium dioxide optical thin film deposited by plasma-assisted DC sputtering deposition." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/54430441664798500475.

Повний текст джерела

Анотація:

碩士
輔仁大學
物理學系碩士班
102
In this study ,we coat titanium dioxide optical films by the DC sputtering system and adding plasma source fluxing way. In general, optical films must have a good stable refractive index and absorption of small features, titanium dioxide in multilayer applications on a high refractive index material. The coating can be expected in this experiment a higher refractive index and low optical absorption of the titanium dioxide film. Unlike in the past the experimental part is fluxing way , using homemade plasma source system to replace end-Hall ion source. The advantages of this plasma source is no overheating problems. Learned from the paper,because the temperature over 300 degrees will be crystallize. Will result in the problem of excessive absorption.This plasma source using high voltage way so that the gas dissociation , in addition to effectively reduce the temperature problem. It can also reduce filament pollution and filament broken and other issues. The samples will be use ellipsometry, spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy measurements thin film characteristics, analyze its refractive index, absorption, structural and surface binding energy. To identify suitable for coating parameters of optical thin film of titanium dioxide. The results showed that when the sputtering power of 200 W, the ion current 0.8 mA, the refractive index of the film has the best value and the lowest absorption. Plasma source confirmed to join fluxing can effectively help the film formation.

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Jhuang, Chun-Cing, and 莊淳青. "The environmentally friendly of the fabricated metal-doped titanium dioxide nanomaterials." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/10418381008085142966.

Повний текст джерела

Анотація:

碩士
臺北市立教育大學
環境教育與資源研究所
101
ABSTRACT In recent years, with the continuous development of modern industrial society and technological progress, although the quality of human life so constantly increasing, but it is accompanied by environmental pollution, destruction and lack of energy. So, people gradually began to focus on the green concept, and research and development can replace fossil fuels and to reduce environmental pollution and green products. The catalytic properties of titanium dioxide having a light for the current internationally highly regarded photocatalytic technology products can be widely used in deodorant, decomposition of organic pollutants, pollution, air purification, sterilization and antibacterial purposes. This study hopes to assess life cycle assessment framework of thinking different transition metal-doped titanium dioxide nanomaterials, their preparation stage and the use phase impact on the environment size to use as a green product design concept of the reference. This study will be divided into two parts, the first part is modified titanium dioxide, one began to use anodic oxidation method for preparing titania nanotubes and doped with different transition metal modified hoped that through different transition metal doping, can improve the efficiency of photocatalytic titanium dioxide, increase the absorption of visible light, in order to explore different transition metal-doped titanium dioxide photocatalytic decomposition of its ability and antibacterial capabilities. The second part is divided into different transition metal doped titanium dioxide nanomaterials life cycle assessment is divided into stages of preparation and use of evaluation stage, collecting input stage of preparation of the material, energy as a life-cycle assessment database, and methylene blue degradation experiments as the use phase assessment analysis to understand the different transition metal-doped environmentally friendly nature. The life cycle assessment of four different processes of titanium dioxide nanomaterials, their contribution to the overall environmental impact: Case III (Ag-1.5Mm/0.5hr)> Case IV (undoped nanotubes)>Case I (Ag-1.5Mm/0.5hr)> Case II (Pt-1.5Mm/0.5hr), environmental friendliness optimal platinum-doped titanium dioxide material. The main contribution of environmental impact factors are the use of electricity. Keywords: life cycle assessment, titanium dioxide, doped with transition metals, photocatalysis.

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Wu, Po Yeh, and 吳柏曄. "Synthesis and Photocatalytic Performance of Transition Metal Doped Titanium Dioxide Nanofibers." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/66584271774785077212.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Malibo, Petrus Molaoa. "Extending the understanding of metal loading sites on a novel titania nanocatalyst." Thesis, 2016. http://hdl.handle.net/10539/21001.

Повний текст джерела

Анотація:

The hydrothermal method of synthesis was successfully utilized to produce the rutile dandelion support onto which different noble metals were deposited using the deposition precipitation method to prepare the Au-TiO2, Pt-TiO2, Pd-TiO2 and Rh-TiO2 catalysts. The catalysts were prepared at different metals loadings. The deposition precipitation method was also employed to deposit the same metals (Au, Pt, Pd and Rh) onto the rutile (110) and (111) crystal surfaces to model the catalysts. Transmission electron microscopy, scanning electron microscopy and powder X-ray diffraction were used as the main characterization techniques to study the preferred deposition sites of the metals as well as the composition of the catalysts. TEM analysis showed the metals to deposit onto the sides and tips of the rutile nanorods making up the dandelion support structure. SEM analysis showed the metals to deposit onto the (110) and (111) crystal surfaces with the exception of Pd which deposited onto the (111) and (001) surfaces only. TEM analysis showed that the metals agglomerated following Temperature-Programmed Reduction (TPR) under H2 gas. TPR analysis showed strong-metal-support interaction for the Pt, Pd and Rh catalysts.

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Huang, Wei Kang, and 黃瑋康. "Preparation and Photocatalytic Performance of Metal Nanoparticles Decorated Hydrogenated Titanium Dioxide Nanofibers." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/zz497v.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Sharma, Sudesh. "Preparation and study of transition metal doped titanium dioxide for spintronic applications." Thesis, 2010. http://localhost:8080/iit/handle/2074/4363.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Ephraim, J. K., and Rajnikant Patel. "Solid-Solid Phase Transformation During the Reduction of Titanium Dioxide (Anatase) to Produce High-Grade Titanium Powder." 2015. http://hdl.handle.net/10454/9146.

Повний текст джерела

Анотація:

No
Production of titanium is challenging and expensive due to the energy energy-intensive and time-consuming processes used at present. Current commercial production method reduces titanium tetrachloride with magnesium or sodium to produce titanium metal. Several researchers have attempted electro-deposition of titanium from ionic solutions but have faced difficulties in eliminating multivalent titanium ions and highly reactive dendrite products. In this paper, we report, for the first time, the solid-solid phase transformation of titanium dioxide with calcium metal, under suitable conditions, to form solid titanium metal powder (>98% pure) without any oxygen impurity. On phase characterisation, it was found that homogeneous alpha-titanium was produced. The paper also includes the results and interpretations obtained using quantitative analysis, X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and phase diagram. The process is simple, green, rapid and cheap compared to the existing methods.

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Lin, Yin-Chieh. "FLAME ASSISTED CHEMICAL VAPOR DEPOSITION OF PHOTOCATALYTIC TITANIUM DIOXIDE COATING ON ALUMINUM FIN STOCK." Thesis, 2013. http://hdl.handle.net/1974/8150.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

47

HSUEH, CHENG-NAN, and 薛正男. "Metal-Organic Chemical Vapor Deposition of Titanium Dioxide and Aluminum Titanate Thin Films." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/92011522089339141362.

Повний текст джерела

Анотація:

碩士
國立東華大學
材料科學與工程學系
90
Abstract Thin film technology has been widely applied in semiconductor and electro-optic industries and on the fine machinery to have materials in a small size and/or in new functions with high pay-off. In this study, chemical vapor deposition (CVD) technique was used to deposit the dielectric Al2O3，TiO2，and Al2O3-TiO2 films on the silicon wafers and glass plates under the various coating conditions of low temperature and low pressure. This research was focused on the evaluations of films growth, crystalline structure, microstructure, scratch resistance, optical properties, and electrical properties by changing the experimental parameters including substrate temperature, the flow rate of CO2/H2, ATSB (aluminum tri sec-butoxide), and TiCl4 (titanium chloride). The results showed that growth rates of the Al2O3，TiO2，and Al2O3-TiO2 films decreased as the substrate temperature increased. The fastest growth rate was nearly 1.37mm/hr, and grain size decreased as the flow rate of VATSB decreased. The TiO2, and Al2O3 films were smoother and denser than the Al2O3-TiO2 films. TiO2 thin films showed the anatase phase at 350℃ and the rutile phase at 500℃. All Al2O3-TiO2 films were showed amorphous structure. Regarding to mechanical properties, there was a good adhesion to glass substrate, critical load was range 10~21 N. Residual stress was compressive for the TiO2 and Al2O3-TiO2 films. The residual stress was 1000-7000 MPa for TiO2 films and changed with temperature and VCO2/VH2, while 200-2000 MPa for Al2O3-TiO2 films and increased with temperarure. The residual stress of Al2O3 was tensile and ranged from 1000 to 7000 MPa. In respect of electrical properties, the dielectric constants of the Al2O3-TiO2 films reaching a highest value of 300 were related to the composition of the films. Under the processing condition of VTiCl4= VCO2= VH2= 50 sccm, VATSB= 75 sccm, and substrate temperature = 350℃, the electrical property was good, the value of dielectric constant was 232, and the loss tangent was 0.145. The resistivity of the Al2O3 films were higher than 1012 Ω-cm. After annealing, the resistivity of the TiO2 films increased from 108 to 1010 Ω-cm. The resistivity of the Al2O3- TiO2 films were in the range of 1010 ∼ 1011 Ω-cm, but decreased below 108 Ω-cm after annealing. For optical properties, transmittance of Al2O3 was superior to TiO2 which had higher refractive indices in the range of 2.2~2.7.

Стилі APA, Harvard, Vancouver, ISO та ін.

48

Mayo, Elizabeth Idonia. "Kinetics and Thermodynamics of Dye (Group VIII Metal)–Sensitized Nanocrystalline Titanium Dioxide Photoelectrodes." Thesis, 2004. https://thesis.library.caltech.edu/2442/1/Elizabeth_I_Mayo.pdf.

Повний текст джерела

Анотація:

This thesis reports a comprehensive series of experiments involving complementary kinetics and thermodynamic measurements directed at isolating the important individual reactions in dye-sensitized nanocrystalline titanium dioxide solar cells (DSSCs). These experiments were done in conjunction with steady-state photoelectrochemical measurements; a combination which allowed a greater understanding of the overall mechanisms and driving forces of these systems.

Alternative two-electron redox couples were studied and efficiency increases of >40% were achieved when compared to similar systems using iodide/triiodide. Surface treatment with carboxylic acids minimized direct reduction of the redox couple by electrons in the titanium dioxide, and interestingly, the photocurrent also increased resulting in overall efficiency increases as high as 20%. Bridging ligands were used in an attempt to minimize recombination of the injected electrons with the resulting oxidized dyes, but DSSCs with these sensitizers showed poor conversion efficiencies and no distance dependence for injection or recombination was observed. The lack of distance dependence was attributed to the flexible single carboxyl anchoring group. To further investigate the effect of binding mode, a series of carboxyl-modified ruthenium bipyridyl sensitizers were studied. A single carboxyl anchoring group resulted in unstable DSSCs due to enhanced desorption as well as poor photon-to-current conversion efficiencies. These dyes injected efficiently into TiO₂ on the nanosecond timescale, and regeneration of the oxidized sensitizers competed effectively with recombination. Consequently, individual kinetics measurements could not explain the decreased steady-state performance. The regeneration rates of these dyes in solution were found to rapid, approaching the diffusion controlled limit. The regeneration rate was dependent on the number and electron-withdrawing nature of the pendant groups, with the rate decreasing with increasing number of electron withdrawing substituents. Iridium dyes with cyclometalating ligands were shown to be efficient sensitizers in DSSCs, with quantum yields on the order of a ruthenium analogue having similar spectral overlap. Overall, the repeated inconsistencies between the steady-state behavior and the measured individual kinetics processes indicate that the current kinetic model is insufficient to accurately predict photoelectrochemical behavior.

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Huang, Kuo-An, and 黃國安. "Preparation and photocatalytic properties of nanometric-sized titanium dioxide powders doped with metal." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/07118633442920241453.

Повний текст джерела

Анотація:

碩士
國立高雄應用科技大學
化學工程與材料工程系
98
In this study, TiO2-xNy precursor was prepared by adding titanium tetrachloride solution into alkaline solution with stirring to produce a precipitation, then washing with water and drying in the oven. However, the TiO2-xNy were synthesized by doped three different metal ions (copper, nickel, platinum) with the precipitation and calcined at 300 ~ 700 ℃. The morphology and crystallinity of titanium dioxide was controlled by various calcination temperatures. The investigation was focused on the effect of TiO2-xNy properties with changing calcination temperatures and metal ions added. FTIR, XRD and SEM instruments were implemented to investigate the effect of different metal ions and various sintering temperatures. The photocatalytic performance of TiO2-xNy photocatalyst powder obtained at various preparatory conditions was also studied. The results show that high purity TiO2-xNy powders can be obtained with particle size 30 ~ 40 nm as calcined at 500 ℃ for 3 hours. Pt/TiO2-xNy powder obtained at 700 ℃ can achieve the best photocatalytic efficiency, with methylene blue removal rate of 100 % in 3 hours.

Стилі APA, Harvard, Vancouver, ISO та ін.

50

Liu, Po I., and 劉柏逸. "Microwave-assisted ionothermal synthesis of titanium dioxide/activated carbon composite electrode materials for capacitive deionization." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/j7999k.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Дисертації з теми "METAL ASSISTED TITANIUM DIOXIDE"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями