Yes / In this study, anti-corrosion concrete for sewage system was developed with nano TiO2 (NT) and reactive powder concrete (RPC). The corrosion resistances of NT modified RPC (NTMRPC) in high concentration enhanced sewage were investigated from the perspectives of biological, physical and chemical corrosion resistances, respectively. In addition, mechanical properties of NTMRPC after sewage corrosion were also studied. Research results indicated that NT can endow RPC with antimicrobial property through their microorganism biodegradation properties. The inhibition and elimination rates of NTMRPC to its surface microorganisms were 37.35% and 80.93%, respectively. After sewage corrosion, the surface roughness, mass loss and deterioration depth of RPC were decreased by 62.57%, 15.48% and 18.44% due to the NT inclusion, respectively. In addition, the pH values of RPC in the deterioration depth ranges of 0-3 mm and 3-6 mm were increased by 11.45% and 23.62%, respectively. NT can restrain the strength deterioration of RPC in high concentration enhanced sewage. This may be due to the improved sewage biological anti-corrosion performances of RPC by inhibiting/eliminating the microorganisms on the surface of RPC as well as the enhanced sewage physical/chemical anti-corrosion performances of RPC by improving the compactness of RPC. / The authors thank the funding provided by the National Science Foundation of China 513 (51978127 and 51908103), and National Key Research and Development Program of China 514 (2018YFC070560 and 2017YFC0703410).

The scaling down of Complementary Metal Oxide Semiconductor (CMOS) transistors requires replacement of conventional silicon dioxide layer with higher dielectric constant (K) material for gate dielectric. In order to reduce the gate leakage current, and also to maximize gate capacitance, ‘high K’ gate oxide materials such as Al2O3, ZrO2, HfO2, Ta2O5, TiO2, Er2O3, La2O3, Pr2O3, Gd2O3, Y2O3, CeO2 etc. and some of their silicates such as ZrxSi1–xOy, HfxSi1–xOy, AlxZr1–xO2 etc. are under investigation. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternate gate dielectric are (a) permittivity, band gap and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the materials/process used in CMOS devices and (f) reliability. In this study titanium dioxide (TiO2) is chosen as an alternate to silicon dioxide (SiO2). This thesis work is aimed at the study of the influence of process parameters like deposition rate, substrate temperature and annealing temperature on the electrical properties like maximum capacitance, dielectric constant, fixed charge, interface trapped charge and leakage current. For making this analysis we have used p–type single crystal silicon (<100>) as substrates and employed direct current (DC) reactive magnetron sputtering method with Titanium metal as target and Oxygen as reactive gas. TiO2 thin films have been deposited with an expected thickness of 50 nm with different deposition rates starting from 0.8 nm/minute to 2 nm/minute with different substrate temperatures (ambient temperature to 500ºC). Some of the samples are annealed at 750ºC in oxygen atmosphere for 30 minutes. SENTECH make Spectroscopic Ellipsometer is used for analyzing the optical properties such as thickness, refractive index etc. The thicknesses of all the samples that are extracted from the Ellipsometry are varying from 35 ± 2 nm to 50 ± 5 nm. Agilent make 4284A model L−C−R meter along with KarlSUSS wafer probe station is used for the C − V measurements and Keithley make 6487 model Pico ammeter/Voltage source is used for the I−V measurements. MOS capacitors have been fabricated with Aluminium as top electrode to perform the bi directional Capacitance−Voltage and also Current−Voltage analysis. The X–ray diffraction studies on the samples deposited at 500ºC showed that the films are amorphous. Dielectric constant (K) and effective substrate doping concentration (Na), flat band voltage (VFB), hysteresis, magnitude of fixed charges (Qf) as well as interface states density (Dit') and Equivalent Oxide Thickness (EOT) are obtained from the bi directional C−V analysis. A maximum dielectric constant of 18 is achieved with annealed samples. The best value of fixed charge density we have achieved is 1.2 x1011 per cm2 corresponding to the deposition rate of 2.0 nm/minute and with 500ºC substrate temperature. The ranges of Qf values that we have obtained are varying from 1.2x 1011 − 1.0 x1012 per cm2. It was also found that, the samples deposited at higher substrate temperatures show lower Qf values than the samples deposited at lower temperatures. The same trend is observed in case of interface states density also. The range of Dit' values we have obtained are in the range of 1.0 x 1012 cm–2eV–1 to 9x1012 cm–2eV–1. The best value of Dit' we have obtained is 1.0x1012 cm–2 eV–1 for the sample deposited at 0.8 nm/minute deposition rate and with substrate temperature of 400ºC. From the flat band voltage values of different set of samples, it was found that the flat band voltage is decreasing and in turn trying to approach the analytical value for the films deposited at higher deposition rates. The minimum EOT that we have achieved is 11 nm that corresponds to the film, which is annealed at 750ºC in oxygen atmosphere. From the I−V analysis it was found that the leakage current density is increasing with increase in substrate temperature and the same trend is observed with annealed films also. The minimum leakage current density achieved is 1.72x10–6 A/cm2 at a gate bias of 1V (corresponding field of 0.3 MV/cm). From the time dependent dielectric breakdown analysis it was found that the leakage current is exhibiting a constant value during the entire voltage stress time of 23 minutes. From the I–V characteristics it was found that the leakage current is following the Schottky emission characteristics at lower electric fields (< 1MV/cm) and is following the Fowler–Nordheim tunneling mechanism at higher electric fields. Since our aim is to study the electrical properties of titanium dioxide thin films for the application as high K gate dielectric in microelectronic applications more emphasis is given on the electrical properties. The maximum dielectric constant we have achieved is in the comparable range of the values for this parameter. The leakage current density values obtained are higher than the required for the microelectronic devices, where as the interface state density values and fixed charge density values are in the same range of values that are reported with this particular oxide and more care has to be taken to minimize these parameters. The EOT values we have achieved are also falling into the range of values that it actually takes as it was reported in the literature.

Submitted in fulfillment of the requirements of the degree of Master of Engineering: Chemical Engineering, Durban University of Technology, Durban, South Africa, 2016. / River water is a life supporting watercourse to most communities in rural areas. It is used for both human and animal consumption, and is well becoming a collection channel for defecation and urination due to shortage or lack of access to running water and sanitation facilities. This has resulted to the contamination of water sources, which poses a great risk to human health. This has motivated researchers to study simple but yet robust systems to produce safe drinking water. Photocatalysis is one of such emerging disinfection technologies. Titanium dioxide (TiO2) which is one of the basic materials used for paint manufacturing has emerged as an excellent photocatalyst material for water purification. TiO2 was selected in this study because it is locally available with a potential to open a new market in water purification for the manufacturers. The setback in previous studies is the recovery of nano-scaled TiO2 (nTiO2) after purification when used as a suspension in treated water. Thus this study evaluates the performance of four grades of micro-scaled TiO2 (mTiO2) on the degradation of organic matters, Escherichia coli (E. coli) and total coliform in river water and to investigate the percentage recovery of the mTiO2 using a locally manufactured Polyester Woven Fabric Microfiltration (PWFMF) membrane. The PWFMF though uncharacterized has been used in a number of studies for treating domestic and industrial waste waters. The best-performing grade was used to optimize the degradation efficiency of E. coli in river water using the Design of Experiments (DOE) methodology. Grade 2 of the mTiO2, which is hydrated titanium dioxide with additions (ahTiO2) of particle size range of 0.2 – 53 µm at a concentration of 2.5 g/l displayed an advantageous photocatalytic activity. The results show that 80 % of the organics were removed in 3 hours and increased to 93% after 6 hours. Two particle size ranges of 0.2 – 53 µm and 54 – 75 µm at a concentration of 5 g/l degraded organic matters to 90 % and 77 % in 3 hours respectively. The particle size range of 0.2 – 53 µm at a concentration of 5 g/l was then filtered using a PWFMF and turbidities went below 1 NTU after 20 minutes from feed turbidity of 470 NTU for all three trials. The average percentage recovery in 2 hours was 98.91 %. The four grades of mTiO2 were analyzed for E. coli and total coliform for 4 hours at concentrations of 2, 5 and 7 g/l. Grade 2 achieved the E. coli specification of 0 count/ 100 mL at 5 g/l in 2 hours and at 7 g/l in 0.5 hours. Grade 4 E. coli specification was achieved with 7g/l in 4 hours. Grades 2 and 4 performed better since they both achieved the E. coli and total coliform specifications. Grade 2 was the best performing grade and was considered for statistical studies. Grade 2 was then used on a comparative study between the Central Composite Design (CCD) and Box-Behnken Design (BBD), which are two of the major Response Surface Methodologies (RSM). The CCD compared to BBD provides high quality predictions over the entire design space. The CCD obtained optimum results for concentration of mTiO2 (X1), temperature (X2), initial pH (X3) and aeration (X4) which were 6.94 g/l, 28.75 OC, pH = 6.04, and 13.35 L/min for the maximum degradation efficiency of 99.85 % which showed comparable optimum results to the BBD that were 6.45 g/l, 28.28 OC, pH = 6.02 and 12.21 L/min for the maximum degradation efficiency of 99.80%. These theoretical model results were validated by practical experiments that produced the maximum degradation efficiency for CCD and BBD of 99.67 and 99.26 % respectively. Grade 2 of the mTiO2 can be used as a photocatalyst for river water purification due to its strong ability for the removal of E. coli. The additions used in grades 2 and 4 during production improved the photocatalytic activity. The PWFMF membrane showed a great performance of above 98 % particle recovery of mTiO2 from treated water, although there was an indication that the smallest particles were passing through the membrane. The RSM results gave approximately the same optimum results that were well within the limits, which were experimentally validated and showed that the models were sustainable. It is recommended that the effect of additions be studied on the structures or the charge stability of the two grades. / M

Heterogeneous photocatalysis is an advanced oxidation technology widely applied in environmental remediation processes. It is a relatively safe and affordable technology with a low impact on the environment and has found applications in a number of fields from chemical engineering, construction and microbiology to medicine. It is not catalysis in the real sense of the word as the photons which initiate the desired photocatalytic reaction are consumed in the process. The cost of these photons is by far the limiting economic factor in its application. From a technical standpoint, the inefficient use of the aforementioned photons during the photocatalytic reaction is responsible for the limited adoption of its application in industry. This inefficiency is characterised by low quantum yields or photonic efficiencies during its application. The mechanism of the technique of controlled periodic illumination which was previously proposed as a way of enhancing the low photonic efficiency of TiO2 photocatalysis has been investigated using a novel controlled experimental approach; the results showed no advantage of periodic illumination over continuous illumination at equivalent photon flux. When the technique of controlled periodic illumination is applied in a photocatalytic reaction where attraction between substrate molecules and catalyst surface is maximum and photo-oxidation by surface-trapped holes, {TiIVOH•}+ ads is predominant, photonic efficiency is significantly improved. For immobilized reactors which usually have a lower illuminated surface area per unit volume compared to suspended catalyst and mass transfer limitations, the photonic efficiency is even lower. A novel photocatalytic impeller reactor was designed to investigate photonic efficiency in gas–solid photocatalysis of aromatic volatile organic compounds. The results indicate photonic efficiency is a function of mass transfer and catalyst deactivation rate. The development of future reactors which can optimise the use of photons and maximize photonic efficiency is important for the widespread adoption of heterogeneous photocatalysis by industry.

<p>För att undersöka skillnad i prestationsförmåga mellan celler sensiterade med växtextraktsbaserad färg, och celler sensiterademed ruteniumkomplex-baserad färg, samt huruvida presskraften påverkar en cells prestationsförmåga, tillverkades icke-slutna fotoelektrokemiska färg-sensiterade solceller med tunnfilmsfotoelektroder av pressad, nanoporös titandioxid.</p><p>Cellerna pressades med tre olika presskrafter och sensiterades med växtextraktsfärg från rödkål, rödbeta, viol och henna, samt en ruteniumkomplex-baserad färg som fick utgöra kontrollbetingelse. För varje cell uppmättes IPCE- och iV-värde och motsvarande fyllnadsgrad (fill factor) och dessa jämfördes.</p><p>Ingen signifikant skillnad kunde fastställas mellan celler pressade med olika presstryck. Bland cellerna sensiterade med växtextraktbaserad färg presterade rödbeta bäst. Cellen med högst effektivitet hade fyllnadsgraden 70%. Emellertid uppvisade de växtfärgade cellerna genomgående sämre effektivitet än de rutenium-sensiterade och fotoströmmarna var mycket låga. IPCE-värdena var allmännt låga: den bäst presterande cellen hade ett IPCE-värde på något över 0,06 i våglängdsintervallet 440-470 nm. En förklaring till detta är de övriga ämnen som förutom pigment återfinns i de växtbaserade färgerna. Dessa hindrar pigmentmättnad och förhindrar att växtfärgen når ruteniumfärgens intensitet. En annan anledning består i svårigheten att passa ihop energinivåerna i cellens elektrolyt-halvledarsystem med energinivåerna hos pigmentet i växtfärgen.</p> / <p>Non-sealed photoelectrochemical dye sensitised solar cells (DSSC) with pressed nanoporous TiO2 thin film photoelectrodes were manufactured for the purposes of finding out whether plant extractbased dye sensitised cells can perform as well as ruthenium complex-based dye sensitised cells and whether the pressing force affects the cell performance.</p><p>The cells were pressed with three different pressing forces and sensitised with plant extracts from red cabbage, beetroot, violet and henna, as well as with a ruthenium complex-based dye for comparison. The IPCE and iV values and the corresponding fill factors of the cells were evaluated and compared.</p><p>No significant difference between the cells pressed with different pressing forces could be established. Among the plant extract-based dye sensitised cells the ones sensitised with beetroot extract performed best. The cell that achieved the highest efficiency had a fill factor of 70%. Compared to the ruthenium-sensitised cells the overall performance of the plant dye sensitised cells were very poor and the produced photocurrents very low. The IPCE values were generally low: one of the best-performing cells had an IPCE value of slightly over 0.06 in the 440-470 nm wavelength ranges. One reason for this is that it is difficult to obtain a plant extract dye as intense and deep in colour as ruthenium complex-based dyes, since pigment saturation is obstructed by the presence of other chemical compounds in the plant extracts. Another is that it is a delicate and difficult matter to match the energy levels in the electrolyte-semiconductor system with the energy levels of the pigments in the plant extract dye.</p>

Une exposition aux nanoparticules (NP) de dioxyde de titane (TiO2) peut entraîner un remodelage matriciel, dans lequel la Matrix Metalloprotéase-1 (MMP-1) notamment pourrait jouer un rôle important. Pour vérifier cette hypothèse, nous avons 1/ mesuré l' expression de la MMP-1 sur des fibroblastes pulmonaires humains après exposition à des particules de TiO2 de différentes tailles, formes et variétés cristallines, ainsi qu' une NP de noir de carbone (NC), et 2/ administré des NP de TiO2 et de NC sur un modèle d‟emphysème pulmonaire induit par l' élastase chez le rat. Sur les fibroblastes pulmonaires humains, certaines NP de TiO2 induisent l' expression de la MMP-1 via l' interleukine-1β (IL-1β) et augmentent son activité. Les particules de TiO2 micrométriques induisent l' expression de la MMP-1 sans lien avec l' IL-1β et les NP de NC ne modulent pas l' expression de la MMP-1. L' exposition des rats aux NP de TiO2 n' entraîne pas d' effet ; l' exposition aux NP de NC entraîne une inflammation et une induction de l' expression de la MMP-12. Cette exposition aggrave, de plus, l' inflammation provoquée par l' élastase, ce qui n' est pas observé avec les NP de TiO2. Au total, notre travail montre bien un rôle pour les NP de TiO2 dans le remodelage matriciel, via l' induction et l' activation de la MMP-1 in vitro. In vivo, les NP de NCpeuvent aggraver ceertaines réponses à l' élastse. La composition chimique et la taille des particules semblent être des déterminants importants de leurs effets. / Exposure to titanium dioxide (TiO2) nanoparticles (NP) can lead to matrix remodeling, a phenomenon in which Matrix metalloprotease-1 (MMP-1) notably could play an important role. To validate this hypothesis, we 1/ studied MMP-1 expression in human pulmonary fibroblasts after exposure to TiO2 particles of different sizes, shapes and crystal phases and one Carbon Black (CB) NP, and 2/ measured the effect of TiO2 CB NP on an elastase-induced emphysema model in rats.On human lung fibroblasts, some TiO2 NP induced MMP-1 through an interleukin-1β (IL-1β) dependent mechanism, and increased MMP-1 activity. TiO2 micrometric particles induced MMP-1 without IL-1β implication, and CB NP did not induce MMP-1. Rat exposure to TiO2 NP had no effect but exposure to NC NP induced inflammation and MMP-12 expression. TiO2 NP did not modulate elastase effects. NC NP aggravated elastase-induced inflammation.In total, our work shows a role for TiO2 NP in matrix remodeling, via MMP-1 induction and activation in vitro. In vivo, CB NP can aggravate some elastase-induced effects. Particles composition and size seem to be important determinants of their effect.

L'objectif de cette étude était de réaliser des revêtements de TiO2 présentant une large variété de morphologies et d'établir des corrélations entre la structure de ces couches et leurs propriétés fonctionnelles, notamment la photocatalyse. Deux voies de synthèse employant le même précurseur, le tétra-isopropropoxide (TTIP) de titane, ont été utilisées, le procédé sol-gel et le dépôt chimique en phase vapeur (MOCVD). L'emploi de ces deux techniques permet de produire TiO2 sous une large gamme de morphologies mais avec des variétés polymorphiques similaires. Les revêtements synthétisés ont été caractérises afin de déterminer leur composition polymorphique, la taille des cristallites, la surface spécifique, la rugosité et l'épaisseur. Puis leur activité photocalytique pour la dégradation du bleu de méthylène a été déterminée. Par voie sol-gel, des dispersions de nano-cristallites de TiO2 dans l'eau, stables sur une longue durée (plus d'un an) en termes de composition polymorphique, taille d'agglomérats et de cristallites ont été synthétisées. Les revêtements ont été réalisés par tape-casting et dip-coating. Pour la synthèse en MOCVD, un plan d'expérience (PeX) a été utilisé, à notre connaissance pour la première fois. Il a permis de déterminer, d'une manière efficace et économique (avec un nombre minimum de tests expérimentaux), les paramètres les plus importants du procédé contrôlant les diverses propriétés quantifiables du revêtement. Il a aussi permis de mettre en évidence les interactions entre les paramètres de synthèse et leur effet sur la structure du revêtement. Les conclusions tirées du PeX sont en accord avec les résultats obtenus lors des études précédentes. L'analyse en composantes principales (ACP) a été réalisée pour avoir une vue globale de la façon dont les diverses propriétés des revêtements sont reliées entre elles / The overall objectives of this study was to find an environmental-friendly and simple procedure to synthesize titanium-dioxide, as well as, to determine the relation between the structural and functional properties of titanium dioxide coatings. Both of these objective have been attained in this study. By the sol-gel technique, titanium dioxide sols were synthesized by the hydrolysis of titanium(IV)isopropoxide. Nanocrystalline dispersions of TiO2 in water were prepared that were suitable for coatings and having long-term stability (more than 1 year) in terms of polymorphic composition, crystallite and agglomerate size. A design of experiments (DoE) was utilised, to our knowledge, for the first time in MOCVD for the synthesis of TiO2 coatings. It was employed to determine, in a timely and economical manner, the most significant process parameters for any quantifiable property of the coating and to highlight the interaction between these operating parameters, as well as, the correlation between the structure of the coating and the process. The conclusions drawn from the DoE were compared to results obtained by previous studies and were found to concur. Therefore, the DoE was successful in screening the most important process parameters, with a minimum number of experimental trials. For most of the properties that were under investigation, the DoE showed that, the deposition temperature and reactor pressure were, often-times, the most significant. Therefore, to change the microstructure and composition of MOCVD coatings, changing these process parameters will ensure the highest impact. It has to be stressed that the conclusions drawn from the DoE are restricted to the experimental range that was under investigation. Principal Component Analysis (PCA) was conducted to have an overall view of how the different properties of the coatings related with one another. The interpretations made from this analysis were that the photocatalytic (PC) activity of the coatings produced did not relate strongly to the polymorphic composition, which is contrary to literature review and is explained to be a result of the different morphologies that lead to different porosities and specific surface area. The PC activity did not depend on the mass over a critical mass. With this analysis it appeared to be clear that the porosity and specific surface area played a larger role than polymorphic composition. This hypothesis has to be verified because we did not succeed in determining the specific surface area of our coatings during this study. However, some preliminary tests have been conducted showing that cyclic voltametry could be used to evaluate the surface area of our films

Doctor of Philosophy / Department of Chemistry / Kenneth J. Klabunde / Solar energy driven catalytic systems have gained popularity in environmental remediation recently. Various photocatalytic systems have been reported in this regard and most of the photocatalysts are based on well-known semiconducting material, Titanium Dioxide, while some are based on other materials such as Silicon Dioxide and various Zeolites. However, in titania based photocatalysts, titania is actively involved in the catalytic mechanism by absorbing light and generating exitons. Because of this vast popularity of titania in the field of photocatalysis it is believed that photocatalysis mainly occurs via non-localized mechanisms and semiconductors are extremely important. Even though it is still rare, photocatalysis could be localized and possible without use of a semiconductor as well. Thus, to support localized photocatalytic systems, and to compare the activity to titania based systems, degradation of organic air pollutants by nanostructured silica, titania and mixed silica titania systems were studied. New materials were prepared using two different approaches, precipitation technique (xerogel) and aerogel preparation technique. The prepared xerogel samples were doped with both metal (silver) and non-metals (carbon and sulfur) and aerogel samples were loaded with Chromium, Cobalt and Vanadium separately, in order to achieve visible light photocatalytic activity. Characterization studies of the materials were carried out using Nova BET analysis, DR UV-vis spectrometry, powder X-ray diffraction, X-ray photoelectron Spectroscopy, FT-IR spectroscopy, Transmission Electron Microscopy, etc. Kinetics of the catalytic activities was studied using a Shimadzu GCMS-QP 5000 instrument using a closed glass reactor. All the experiments were carried out in gaseous phase using acetaldehyde as the model pollutant. Kinetic results suggest that chromium doped silica systems are good UV and visible light active photocatalysts. This is a good example for a localized photocatalytic activity. In contrast, our xerogel system shows comparatively high visible light photocatalytic activity for the titania based system, showing the importance of non-localized nature of photocatalysis. The Cobalt doped silica system shows interesting dark catalytic activity towards acetaldehyde and several other pollutants. Thus, in summary, based on the different activities we observed during our studies these materials could be successfully used to improve the quality of both indoor and outdoor air.

The mixing of polymers and nanoparticles makes it possible to give advantageous macroscopic material performance by tailoring the microstructure of composites. In this thesis, five combinations of nano inclusion and polymer matrix have been investigated. The first type of composites is titanium dioxide/ polyaniline combination. The effects of 4 different doping-acids on the microstructure, morphology, thermal stability and thermoelectric properties were discussed, showing that the sample with HCl and sulfosalicylic dual acids gave a better thermoelectric property. The second combination is titanium dioxide/polystyrene composite. Avrami equation was used to investigate the crystallization process. The best fit of the mass derivative dependence on temperature has been obtained using the double Gaussian dependence. The third combination is titanium dioxide/polyaniline/ polystyrene. In the titanium dioxide/polyaniline/ polystyrene ternary system, polystyrene provides the mechanical strength supporting the whole structure; TiO2 nanoparticles are the thermoelectric component; Polyaniline (PANI) gives the additional boost to the electrical conductivity. We also did some investigations on Polyethylene odide-TiO2 composite. The cubic anatase TiO2 with an average size of 13nm was mixed with Polyethylene-oxide using Nano Debee equipment from BEE international; Single wall carbon nanotubes were introduced into the vinyl acetate-ethylene copolymer (VAE) to form a connecting network, using high pressure homogenizer (HPH). The processing time has been reduced to 1/60 of sonication for HPH to give better sample quality. Theoretical percolation was derived according to the excluded volume theory in the expression of the threshold as a function of aspect ratio.

L'objet de cette thèse traite du dépôt de couches minces photocatalytiques de dioxyde de titane par l'utilisation d'un dispositif plasma à la pression atmosphérique. Le dispositif industriel utilisé permet le traitement du substrat en post-décharge à basse température. L'objectif à terme est le développement d'un procédé de dépôt en vue de recouvrir des pièces 3D thermosensibles d'un revêtement autonettoyant à moindre coût. Après avoir mis en évidence les bonnes propriétés photocatalytiques des dépôts effectués dans le cadre de cette thèse, le présent travail s'est focalisé sur la compréhension des mécanismes responsables cette photocatalycité. Pour ce faire, trois séries de dépôts correspondant à trois températures de substrat différentes ont été étudiées selon leur composition chimique, leurs mécanismes de croissance et leur cristallinité. Il ressort de cette étude que la photoactivité des dépôts est essentiellement le fait de leur importante surface spécifique ; la cristallinité, bien que présente à haute température de substrat, semblant avoir une influence moindre. Cette surface spécifique est quant à elle due à la croissance d'agglomérats, dont l'adhésion au dépôt diminue avec leur taille. Formés en phase gaz dans des boucles de recirculation, ceux-ci semblent se développer du fait de multiples phénomènes : croissance CVD à leur surface, « agglomération de surface » et « redépôt ». Aussi, il apparait qu'à débit de précurseur donné, leur nombre et leur taille sont deux facteurs intimement liés. Ainsi, en vue de l'optimisation du procédé de dépôt, la maîtrise de leur formation est nécessaire. Celle-ci passe par la diminution du débit de précurseur, de la puissance incidente et de l'ensemble des débits de gaz, telles sont les perspectives principales de ce travail / This PhD work deals with the deposition of photocatalytic thin films of titanium dioxide at low temperature in the post-discharge of an atmospheric pressure plasma process. The main objective is the development of a low cost route for the deposition of self-cleaning coatings on 3D thermosensitive substrates. The deposited coatings present good photocatalytic properties which origin is firstly investigated. The elemental composition, the growth mechanisms and the crystallinity of three series of coatings corresponding to three different deposition temperatures are studied. The high specific surface of the coatings, due to the growth of agglomerates, appears to be the main parameter responsible for such photocatalytic properties. But these agglomerates are also responsible for the poor mechanical properties of the coatings as their adhesion decreases with their size. These agglomerates are formed in gas phase in recirculation loops and develop through multiple phenomena: CVD growth, agglomeration at the surface of the coating and redeposition due to the influence of the post-discharge on the surface of the coating. Moreover, at a given precursor flow rate, their number and their size are interlocked. Thus, with the aim of optimizing the deposition process, the control of the formation of such structures through the decrease of the precursor flow rate, the power input and the gas flows are mandatory and are a perspective of this PhD work