Content: Tannery effluent with high salinity and chromium have a serious environmental impact. The traditional chrome tannage that involved the use of sodium chloride, acid and chromium is one of the main origins of salt and chromium pollution. In this study, a non-pickling, low-chrome tanning technology was developed. The novel Chrome-free agent SL can be directly employed to tan bated cattle pelts and the wet white was obtained. Then the shaved wet white was pre-treated by Poly-carboxylate auxiliary agent and tanned by chrome powder. It was tested that the shrinkage temperature of the wet white, the initial pH of chrome tanning, the consumption of chrome powder, the shrinkage temperature of the chrome-tanned leather, the content of Cr2O3 in effluent, the absorption of chromium and the other properties of the chrome-tanned leather. It was found that the shrinkage temperature of the wet white tanned by SL reached over 80oC, the optimal consumption of Poly-carboxylate auxiliary agent was 2wt% based on the weight of the shaved wet white, the better low-chrome tanning conditions were that the wet white was tanned by 4wt% chromium powder for 150～180min at room temperature when the initial pH value was 3.5. The next processes were same as traditional chrome tannage. Meanwhile, the shrinkage temperature of the leather tanned by the low-chrome tannage reached more than 95oC, the absorption of chromium was 96%, the content of Cr2O3 in the effluent was under 200mg/L. For the low-chrome tanned leather, the absorption of dyestuff, fat-liquor reached 99.5%, 82.5% respectively. Compared with the traditional chrome tanned process, not only the conventional pickling process was eliminated, the process was been shorten and reduce the pollution of sodium chloride, but it can reduce 50% of the consumption of Chrome powder, improve the absorption of chromium and can reduce content of Cr2O3 in effluent. Take-Away: 1. LUO JIAN-XUN, LI JING, LIAO XUE-PIN,etc.Cleaner Chrome Tanning – A Non-Pickling Process Using an Aliphatic Aldehyde as Pre-tanning Agent. J. Soc. Leather. Technol.Chem. 2012,96 (1):21-26. 2.LUO JIAN-XUN,FENG YANJUAN.Cleaner Processing of Bovine Wet-white: Synthesis and Application of a Novel Chrome-free Tanning Agent Based on an Amphoteric Organic Compound. J. Soc. Leather. Technol.Chem. 2015,99 (4):190-195. 3.XU JIA-LI, LUO JIAN-XUN.Synthesis and application of a polycarboxylate auxiliary agent. China Leather.2017,46(3):35-41.

L'acier inoxydable est utilisé dans de nombreuses applications biomédicales. Au contact d'un environnement biologique, des protéines s'adsorbent à la surface des aciers inoxydables. La maîtrise de la biocompatibilité nécessite la connaissance à l'échelle moléculaire de l'interaction biomolécule- surface. Nous développons une approche " bottom up " de cette interaction déclinée selon 3 axes : Complexification de la surface : Les films passifs en surface des aciers inoxydables sont composés à la fois d'oxydes de chrome et de fer et la surface α-Cr2O3 (0001) représente un modèle pertinent de ce film passif. Nous avons tout d'abord étudié l'adsorption des acides aminés (AA) sur une surface de Cr2O3 anhydre. Les acides aminés acides et basiques interagissent le plus fortement avec Cr2O3. Nous avons mis en évidence une différence de réactivité entre Cr2O3, Fe2O3 et un film de Cr2O3 enrichi en Fer en extrême surface, imputable à la structure électronique des cations Cr3+ et Fe3+. Activité de l'eau : Elle a été prise en compte en modélisant une surface hydroxylée et en extrapolant à l'interface solide liquide. L'étude de l'adsorption des AA sur une surface hydroxylée (en sphère externe) et en substitution de groupements -OH de surface a montré que seuls les acides aminés acides (Glu, Asp) peuvent s'adsorber en sphère interne. La formation de couches auto-assemblées de sphère externe est favorisée pour les acides aminés hydrophobes. Taille de la biomolécule : Dans cet optique nous avons développé une nouvelle méthodologie pour l'étude de l'adsorption de peptides sur des surfaces bien définies. Cette méthodologie est appliquée à l'exemple de l'adsorption du dipeptide de l'acide glutamique Glu2 sur Cr2O3. Une adsorption par multi-ancrage des résidus, de type sphère interne, est calculée.

Dans cette thèse, nous montrons dans des amas d’oxyde de chrome épitaxiés, la contrainte conduit à l'apparition d'une phase multiferroïques, ainsi qu'un effet magnéto-électrique géant tel que le coefficient ME est de plusieurs ordres de grandeur supérieur que le terme linéaire dans Cr2O3 massif. Cela illustre que des contraintes épitaxiales dans des amas manométriques de taille réduite, crée un nouveau matériau magnéto-électrique ouvrant la possibilité d'utiliser un champ électrique pour orienter l'aimantation du matériau. Le coefficient magnéto-électrique linéaire calculé (6.7ns.m-1) est de trois ordres de grandeur plus élevé que dans l’oxyde de chrome massif (4.17ps.m-1) . Nous avons alors exalter ce coefficient sur des amas d’oxyde de chrome fortement contraintes. Nous avons aussi déclarés une assemblée d’amas n’ont pas seulement super-paramagnétique mais aussi super-paraélectrique.Dans la deuxième partie de notre travail nous avons donc utilisé une méthode d’optique non-linéaire afin d’observer cette polarisation spontanée à la température ambiante.Les mesures du magnéto-transport à température ambiante ne permettent pas d’étudier la polarisation électrique dans le Cr2O3, puisque la magnétorésistance tunnel mesurée à RT est nulle. Nous avons donc cherché une autre méthode la génération de la seconde harmonique qui est une méthode d’optique non linéaire, qui peut donner des informations sur l’état de la polarisation électrique dans un matériau non centrosymétriques. Elle a été utilisée dans notre cas pour déterminer la polarisation d’amas d’oxyde de chrome Cr2O3 super-paraélectriques à température ambiante> / In this thesis, it was shown the strained nanometre size chromium oxide particles embedded in a single crystallise dielectric matrix exhibit magneto-electric coefficients several orders of magnitude larger than the linear terms in bulk Cr2O3 . These clusters are studied in a double tunnel junction Fe/MgO-Cr-MgO/Fe and their magnetization varies under bias voltage, opening the possibility of efficient use of electric field for controlling the magnetization of the material. It also provides evidence for the occurrence of a significant spontaneous electric polarization on the chromium oxide particles which not only behave as super-paramagnetic but also as super-paraelectric material. The electric polarization is of order of 0,22 μC cm-2 at low temperature. In order to study the electric and magnetic proprieties of these clusters with different transport conditions compared to the double tunnel junction in reference, we reproduced smaller clusters in dielectric matrix MgO as the upper magnetic layer of iron is replaced by a non magnetic layer Pd.In the second part of our work, we used a non- linear optical method to observe the spontaneous polarization at room temperature.The magneto-transport measurements at room temperature do not allow to study the electrical polarization in the Cr2O3, since the tunnel magnetoresistance measured RT is zero. We therefore sought an alternative method of generating the second harmonic which is a nonlinear optical method, which can provide information on the state of the electric polarization in a non- centrosymmetric material. It has been used in our case to determine the super- cluster Cr2O3 paraelectric at room temperature of chromium oxide polarization .Under application of a positive voltage , the variation of the SHG intensity gradually changing to 7 V with 40 % of the reports . We eliminated two major phenomena may induce this change as the influence of capacitive loads or a plasmonic effect , to suggest that this variation is due to the spontaneous polarization is aligned along the applied electric field. The variation of the SHG is observed for an electric field applied in the plane , but it shows instability . We attribute this change in this case an electro- migration in the MgO . we show the SHG variation in function of the voltage for several junctions studied an electric field perpendicular . It can be adjusted by a Langevin function of applied electric field.

Der Cr2O3 ist einer der wichtigsten Katalysatoren im Chlor/Fluor (Cl/F) Austauschreaktionen für die Produktion von chlorofluorocarbon (CFC) Alternativen. Es wird als ein ausgezeichneter heterogener Katalysator für Fluorierung Reaktionen gegründet. Die Dismutierung von CCl2F2 wurde verwendet, um die Wirkung von Halogenierung von Chrom(III) Oxyd auf Cl/F-Austauschreaktionen zu untersuchen und um den Unterschied zwischen den inaktiven und aktiven Katalysatoren herauszufinden. Die heterogenen Reaktionen wurden in einem tubular-flow Ni Reaktor und auch unter simulierten Reaktionsbedingungen in einem Reaktor durchgeführt, wo nach der Reaktion die Photoelektronspektroskopie (XPS) und die Auger-Elektronspektroskopie (XAES) Analysen konnte direkt ohne Luftkontakt, unter so genannt "in - situ" Bedingungen gefolgt werden. Es wurde gezeigt, dass die Probleme der Behandlung von Cr (III) 2p Photoelektronenspektren so gelöst werden können, dass ihnen relevante Daten für die chemische Charakterisierung von Oberflächen entnommen werden können. Hochaufgelöste Photoelektronspektroskopie von Cr2O3 Pulverproben zeigte deutlich die Existenz von spektralen Strukturen, die mit Multiplet-Aufspaltungen im jeweiligen Cr 2p Spektrum verbunden sind. Das Spektrum kann durch eine Peakfit-Analyse vertieft interpretiert werden in dem die Anfangswerte für die Peakparameter der Multiplet-Strukturen den jeweiligen Cr L2,3 XANES Spektren entnommen werden. Vom theoretischen Gesichtspunkt sollte dasselbe Verfahren auch eine Analyse der Cr 2p Photoelektronenspektren von alpha-CrF3, CrCl3 und anderen Chrom (III) Verbindungen ermöglichen. Die Unterschiede, die im Experiment für die Cr2O3, alpha-CrF3 und CrCl Photoelektronenspektren beobachtet werden, deuten auf die Tatsache, dass, obwohl in all diesen Fällen dieselben Multiplet-Aufspaltungen für Cr3+ erwartet werden, individuelle Einflüsse der Symmetrie und Ligandenfelder die Endgestalt des jeweiligen Cr 2p Photoelektronenspektrums definieren. Eine Analyse von Cr 3s Spektren kann zusätzlich wertvolle Finger-print Informationen zu chemischen Zuständen von Chrom in Cr (III) Verbindungen erbringen. Sowohl ex-situ als auch ´´in-situ´´ ESCA zeigen, dass sobald CCl2F2 zu Cr2O3 an 390 °C geführt wird, Fluorierung sowie Chlorierung an der Katalysator-Oberfläche findet statt. Wenn die XPS Oberflächenzusammensetzung etwa 4 Atom - % Fluorierung und 6 Atom - %-Chlorierung erreicht, wird die maximale katalytische Aktivität erhalten. Die längeren Reaktionszeiten ändern bedeutsam die erhaltene Oberflächenzusammensetzung von aktiviertem Chrom(III) Oxyd nicht. Der Fluorierung und Chlorierung von Chrom(III) Oxyd wurden weiter durch verschiedenen HF und HCl Behandlungen ebenso untersucht. Die aktivierten Chrom(III) Oxyd Proben und Referenzproben mit der weithin bekannten chemischen Struktur wurden auch durch Kantennahe Röntegenabsorptionsuntersuchungen (XANES), Flugzeit-statischesekundärionenmassenspektroskopie (TOF-SSIMS), Rasterelektronenmikroskopie (SEM), Fluor-Festkörper-NMR, Pyridin-FTIR, Nasschemie (F und Cl) Analyse, Pulver Röntgensbeugung (XRD) und Oberflächen (BET) Analyse untersucht. Die Ergebnisse der Referenzproben Cr2O3, Cr (OH) 3, CrF2 (OH), CrF3.3H2O, Alpha-CrF3, Beta-CrF3 und CrCl3 und aktivierte Cr2O3 Proben wurden verglichen. Die angewandten Charakterisierungsmethoden schlagen vor, dass die Bildung der Chrom-Oxydchlorid-Fluorid-Arten, bzw. Chrom-Oxyd Halogenide, an der Oberfläche ist genügend die katalytische Aktivität zu versorgen. Die Anwesenheit jedes CrF3 und/oder CrCl3 Phasen auf den aktivierten Chrom(III) Oxyd Proben wurde nicht entdeckt. / The Cr2O3 is one of the most important catalysts in the chlorine/fluorine (Cl/F) exchange reactions for the production of chlorofluorocarbon (CFC) alternatives. It is established as an excellent heterogeneous catalyst for fluorination reactions. The dismutation of CCl2F2 was used to probe the effect of halogenation of chromia on Cl/F exchange reactions in order to find out the difference between the inactive and active catalysts. The heterogeneous reactions were performed in a continuous flow Ni reactor and also under simulated reaction conditions in a reactor where after the reaction the X-ray photoelectron spectroscopy (XPS) and the X-ray excited Auger electron spectroscopy (XAES) analyses could be followed directly without air contact, under so called ´´in-situ´´ conditions. In order to be able to apply the Cr(III) 2p XPS analysis in the proper manner the spectroscopic features of the chromium(III) compounds of O, F and Cl were re-investigated. Latest generation of XPS spectrometers, which are able to analyze non-conductive powders with ultimate energy resolution, were used to reveal multiplet splitting features and satellite emission in the Cr 2p spectra. The energy positions of the multiplets were determined by total electron yield (TEY)- X-ray absorption near edge structure (XANES) spectroscopy. Using both high resolution XPS and XANES spectra a peak-fit analysis, which is also applicable for normally resolved Cr 2p XPS spectrum, was proposed. In order to overcome the known background problem by drawing the background in the broad Cr 2p window including the high binding energy satellite, a modified Shirley background, which is a combination of a linear and Shirley function, was used. Moreover, the spectroscopic features of the Cr(III) 3s XPS spectrum, which is relatively simpler than the Cr 2p one, were also surveyed. An alternative chemical analysis was proposed by using chemical state plots for Cr 3s. Both ex- and in-situ ESCA show that as soon as Cr2O3 is conducted to CCl2F2 at 390 °C fluorination as well as chlorination takes place at the catalyst surface. When the XPS surface composition reaches approximately 4 atom-% fluorination and 6 atom-% chlorination, maximum catalytic activity is obtained. Applying longer reaction times do not change significantly the obtained surface composition of the activated chromia. The fluorination and chlorination of chromia was further investigated by various HF and HCl treatments as well. The activated chromia samples and reference samples with well known chemical structure were also characterized by XANES, time of flight - static secondary ion mass spectroscopy (TOF-SSIMS), scanning electron microscopy (SEM), fluorine solid state NMR, pyridine-FTIR, wet chemical (F and Cl) analysis, X-ray powder diffraction (XRD) and surface area (BET) analysis. The results for the references Cr2O3, Cr(OH)3, CrF2(OH), CrF3.3H2O, alpha-CrF3, beta-CrF3 and CrCl3 and activated Cr2O3 samples were compared. The applied characterization methods suggest that the formation of chromium oxide chloride fluoride species, e.g. chromium oxide halides, at the surface is sufficient to provide catalytic activity. The presence of any CrF3 and/or CrCl3 phases on the activated chromia samples was not detected.

Metal Oxide (MO)semiconductors are one of the most widely used materials in commercial gas sensor devices. The basic principle of chemoresistive gas sensor operation stems on the high sensitivity of electrical resistance to ambient gaseous conditions. Depending on whether the oxide is "p type" or "n type", the resistance increases (or decrease), when placed in atmosphere containing reducing (or oxidizing) gases. The study of conductometric metal oxide semiconductor gas sensors has dual importance in view of their technological device applications and understanding fundamental MO-gas interactions. Metal oxides based sensors offer high thermal, mechanical and chemical stability. A large number of MOs show good sensitivities to various gases like CO, NOX, SOX, NH3, alcohols and other Volatile Organic Compounds (VOCs). VOCs are very common hazardous pollutants in the environment. Gas sensors are in great demand for their various applications such as food quality control, fermentation industries, road safety, defence, environmental monitoring and other chemical industries. The aim of the study is to explore the possibility of advancements in semiconducting MO based gas sensor devices through tuning microstructural parameters along with chemical dopants or additives. And further to investigate the underlying mechanism of conductometric MO gas sensors. The novel synthesis method employed is based on the solution combustion method coupled with ultrasonically nebulized spray pyrolysis technique. The well studied SnO2 and relatively unexplored Cr2O3 oxide systems are selected for the study. The non-equilibrium processing conditions result in unique microstructure and defect chemistry. In addition, using this technique MO - Reduced Graphene Oxide (RGO) nanocomposite films has also been fabricated and its application to room temperature gas sensor devices is demonstrated. The thesis comprises of seven chapters. the following section describe the summery of individual chapters. The Chapter 1 describes the introduction and background literature of this technology. A brief review of developments in gas sensor technology so far has been enlisted. This chapter also gives a glimpse of applications of MO semiconductors based sensors. The underlying mechanism involved in the sensing reaction and the primary factors influencing the response of a gas sensor device are enlisted. Further in the later part of the chapter focused the material selection criteria, effect of additives/dopants and future prospects of the technology. The end of this chapter highlights the objective and scope of the work in this dissertation. In the Chapter 2 the the materials selection, characterization techniques and particularly the experimental setups used are elaborated. This includes the deposition method used, which is developed in our group and the the in house built gas sensing system including its working principles and various issues have been addressed. The Ultrasonic Nebulized Spray Pyrolysis of Aqueous Combustion Mixture (UNSPACM) is a novel deposition method devised, which is a combination of conventional spray pyrolysis and solution combustion technique. Spray pyrolysis is versatile, economic and simple technique, which can be used for large area deposition of porous films. The intention is to exploit the exothermicity of combustion reaction in order to have high crystallinity, smaller crystallite size with high surface area, which are extremely important in gas sensor design and its efficiency. Further the gas sensing system and its operation are discussed in detail including the advantages of vertical sensing chamber geometry, wider analyte concentration range (ppm to percentage) obtained through vapor pressure data and simultaneous multi sensor characterization allowing better comparison. Here in this work, Chromium oxide (Cr2O3) and Tin oxide (SnO2) are selected as gas sensing materials for this work as a p-type and n-type metal oxide semiconductors respectively. Nevertheless Cr2O3 is a less explored gas sensing material as compared to SnO2, which is also being used in many commercially available gas sensor devices. Thus, studying and comparing gas sensing properties of a relatively novel and a well established material would justify the potential of the novel deposition technique developed. In Chapter 3, the effect of exothermic reaction between oxidizer and fuel, on the morphology, surface stoichiometry and observed gas sensing properties of Cr2O3 thin films deposited by UNSPACM, is studied. An elaborative study on the structural, morphological and surface stoichiometry of chromium oxide films is undertaken. Various deposition parameters have been optimized. An extensive and systematic gas sensing study is carried out on Cr2O3 films deposited, to achieve unique microstructure. The crystallinity and microstructure are investigated by varying the deposition conditions. Further, the effect of annealing in oxygen gas atmospheres on the films was also investigated. The gas sensing properties are studied for various VOCs, in temperature range 200 - 375 oC. The possible sensing mechanism and surface chemical processes involved in ethanol sensing, based on empirical results, are discussed. In chapter 4, the effect of 1% Pt doping on gas sensing properties of Cr2O3 thin films prepared by UNSPACM, is investigated. The chemical analysis is done using x-ray photoelectron spectroscopy to find the chemical state of Pt and quantification is done. The gas sensing is done towards gases like NO2, Methane and Ethanol. The enhancement in sensitivity and remarkable reduction in response as well as recovery times have been modeled with kinetic response analysis to study the variation with temperature as well as concentration. Further the analysis of observations and model fittings is discussed. The Chapter 5 deals with the defects induced ferromagnetism and gas sensing studies SnO2 nanoparticles prepared by solution combustion method. The structural, chemical analysis of as-synthesized and annealed SnO2 nanoparticles reveal gradual reduction in defect concentration of as-prepared SnO2. The findings of various characterization techniques along with optical absorption and magnetic studies to investigate the defect structure of the material are presented. As defects play crucial role in gas sensing properties of the metal oxide material, the defect induced room temperature ferromagnetism in undoped SnO2 has been used as a potential tool to probe the evidence of the defects. Finally a correlation is established between observed room temperature ferromagnetism and gas sensing studies and primary role of defects in gas sensing mechanism over microstructure is realized . The Chapter 6 presents the deposition of SnO2 thin films by UNSPACM method on glass substrates for gas sensing application. The readiness of UNSPACM in making sensor materials with unform dopant distribution is demonstrated in order to improve the sensor performance in terms of response and selectivity. The chemical composition, film morphology and gas sensing studies are reported. The SnO2 is doped with Cr and Pt to enhance the sensing properties of the material. The doped Oxide films are found to show enhancement in sensitivity and improve the selectivity of the films towards specific gases like NO2 and CO. Further in Chapter 7 an effort has been made to overcome the problem of high operating temperature of metal oxide gas sensors through use of Reduced Graphene Oxide (RGO) and metal oxide nanocomposite films. Although RGO shows room temperature response towards many toxic and hazardous gases but it exhibits poor sensor signal recovery. This has been successfully solved by making nanohybrids of RGO and SnO2. It not only improves the sensor signal kinetics but it enhances the sensitivity also. Thus this chapter endeavors towards low power consumption gas sensing devices. The key findings and future aspects are summarized in the Chapter 8.