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In this work, heterostructured catalyst Al2TiO5/TiO2 (ATO/Ti) was synthesized by a two-step method: low-temperature sol-gel process along with hydrothermal treatment in a neutral medium. Characteristics of the fabricated catalyst were analyzed by various techniques including X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller adsorption, UV-Vis diffuse reflectance spectroscopy, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and the point of zero charges. The content of ATO strongly affected the activity of ATO/Ti catalysts for photocatalytic degradation of cinnamic acid (CA). The catalyst, in which 33% TiO2 was replaced by ATO (33ATO/Ti), exhibited the highest activity for the removal of CA. Compared with the bare titanium oxide synthesized in water (TiO2(w)) as well as Al2TiO5 (ATO), the hybrid 33ATO/Ti catalyst exhibited the enhanced photocatalytic activity in the CA degradation under ultraviolet light. The enhancement in the catalytic activity of ATO/Ti could be related to the increase of the specific surface area and the reduction of bandgap energy obtained from the hybridization of TiO2(w) and ATO. The factors as the catalyst dosage ( C cat ), the airflow rate ( Q air ), and the solution initial pH (pH) affected the CA removal efficiency were studied on 33ATO/Ti catalyst. The optimum condition for photodegradation efficiency of CA was found to be at C cat = 0.75 g L − 1 , Q air = 0.3 Lmi n − 1 , and pH = 3.8 . The highest 60-minute removal efficiency of CA reached 77.1% on 33ATO/Ti compared with 67.1% and 30.4% on TiO2(w) and on ATO, respectively. The recyclability of the 33ATO/Ti was also measured at the optimal parameters. The results showed that, compared with TiO2, the hybrid catalyst was easier to recover and reuse, and its activity decreased by 35% after 6 continuous cycles.

In this work, 31.4 wt.% Ni/SBA-15 (Ni/SBA-15) nonpromoted and alkalized with ammonia solution and by MgO promoter catalysts were prepared and used for combined steam and CO2 reforming of CH4 (bireforming). Effect of concentration of ammonia solution (NH3(aq)) (10–25 vol.%) and Mg content (3–12 wt.%) on the properties of the Ni/SBA-15 catalysts was investigated by low-angle and powder X-ray diffraction (XRD), N2-BET isothermal adsorption, SEM, TEM, EDS mapping, H2-TPR, and CO2-TPD methods. The performance of the catalysts in bireforming was assessed in the temperature range of 550–800°C. The enhancement of dispersion of NiO particles, reducibility, and basicity of alkalized Ni/SBA-15 catalysts were responsible for improving the catalytic performance of this catalyst. The results revealed that the Ni/SBA-15 treated with 15-25% NH3(aq) solution and promoted with 3-9% Mg exhibited high activity for CH4 conversion. Meanwhile, Ni6Mg/SBA-15 showed the highest CO2 conversion. Among tested catalysts, Ni/SBA-15-20NH3 and Ni9Mg/SBA-15 samples had an almost equal activity with a CH4 conversion of nearly 97% and a CO2 conversion of about 84% at 700°C thanks to its moderate affinity with both CO2 and CH4. However, the H2/CO ratio of the product mixture remained at 2.02 on the Ni/SBA-15-20NH3 catalyst and almost 1 on the Ni9Mg/SBA-15 sample. These results might be related to the fact that the alkalization of the Ni/SBA-15 catalyst by NH3(aq) solution had an advantage over using MgO because side reactions were unlikely to occur.

In this work, a series of 10 wt% NiO/CeO2 catalysts (Ni/Ce) promoted by V2O5 with content varying in the range of 0–0.5 wt% was prepared by the co-impregnation method. The characteristics of the catalysts were investigated by several techniques including N2 physisorption (BET), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), EDS mapping, carbon dioxide temperature-programmed desorption (CO2-TPD), and hydrogen temperature-programmed reduction (H2-TPR). The activity of the catalyst was studied in the micro-flow system in a temperature range of 550 °C–800 °C, the feedstock composition CH4/CO2/H2O of 3.0/1.2/2.4 and the weight hourly space velocity (WHSV) of 30,000 ml.h−1.g−1. Adding V2O5 additive, on the one hand increases the reducibility and basicity of Ni/Ce catalyst, on the other hand reduces oxygen vacancies and increases the crystal size of CeO2, leading to various effects on catalyst activity depending on its content. Ni/Ce catalyst promoted with 0.3 wt% of V2O5 was the best among tested ones, on which at reaction temperature of 700 °C, the conversion of CH4 and CO2 reached 97% and 77% respectively, and the molar ratio of H2/CO was 2.1. Meanwhile, on non-promoted Ni/Ce catalyst, the corresponding quantities were 83%, 62% and 1.9, respectively. It is important to note that performance of both was stable for more than 30 h thanks to the better resistance to coke deposition and structural stability.

The thesis was carried out within the ANR project « Stick’It » that aimed at developing new, low-cost and innovative technologies devoted to the design of 2D, 2,5D and 3D radiofrequency (RF) components including antennas printed on conformable materials. The targeted applications are primarily home-networking devices such as set-top boxes where their forms and dimensions are widely varied. Therefore, it is necessary to design antennas on flexible substrates.According to our needs for a substrate material that is flexible, low cost, with good RF properties, recycling ability, and especially ability to make 3D structures, after considering various dielectric materials for flexible electronics, paper substrate appeared to be the most suitable for our purpose.The work of this thesis conducted in three phases.In the first phase, it was the study of methods for characterization of materials to obtain their electromagnetic properties. After analysis, the method of perturbation using a cylindrical cavity was chosen for characterization of paper. The first results of this process were verified by realization and testing of simple antennas such as CPW-fed monopoles on paper and PET. Then, the measurement of E4D paper substrate was performed with 50 samples cut from various E4D paper sheets of three different thicknesses, 104 m, 210 m and 387 m. The results were analyzed statistically and gave r = 3.184, tan = 0.092.The dispersions of the results measured at 2.5 GHz are 0.25% for r and 0.26% for tan. These results were used for the next phase.In the second phase, different antennas were designed on 0.104-mm and 0.21-mm thick E4D paper including IFAs, SIW cavity-back antenna and microstrip-fed wideband monopole antennas. The prototypes were realized using screen printing technique and tested for matching property and radiation patterns.In the third phase the proposed antennas were studied in realistic package conditions, where a set-top box was made of ABS plastic with different dimensions. The first case was with two MIMO antennas orthogonally located in different ABS boxes with sufficient space, so that both of them can remain flat. The second case was a box with a restricted height, so that at least one of the antennas needs to be bent.Thus, a study of bending effect was carried out, first of all, with a simple straight dipole and a straight monopole on E4D paper, then with a wideband antenna proposed in the second phase. The study showed, that bending does not much affect the matching of the antenna over a wide frequency band. However, its radiation patterns rotate in the E-plane with a rotation angle depending on the bending location and bending angle.Then, the MIMO system of two antennas placed orthogonally in an ABS box with restricted height so that one antenna needed to be bent and another remained flat. In all cases of MIMO antenna system, we obtained good isolation (>20 dB) and Envelope Correlation Coefficient (ECC) less than 0.05.; Le travail de thèse a été réalisée dans le cadre du projet ANR «Stick’It» visant à développer de nouvelles technologies peu coûteuses et innovantes dédiées à la conception de composants radiofréquences (RF) 2D, 2,5D et 3D, notamment des antennes imprimées sur des matériaux conformes. Les applications ciblées sont principalement des appareils de réseaux domestique, tels que les décodeurs, dont les formes et les dimensions sont très variées. Par conséquent, il est nécessaire de concevoir des antennes sur des substrats souples.Selon nos besoins pour un matériau de substrat flexible, peu coûteux, avec de bonnes propriétés RF, la capacité de recyclage et en particulier la capacité à fabriquer des structures 3D, après avoir étudié différents matériaux diélectriques pour l’électronique flexible, le papier s'est trouvé le plus adapté.Les travaux de cette thèse se sont déroulés en trois phases.Dans la première phase, c'était l'étude des méthodes de caractérisation des matériaux pour obtenir leurs propriétés électromagnétiques. Après l'analyse, la méthode de perturbation utilisant une cavité cylindrique a été choisie pour la caractérisation du papier. Les premiers résultats de ce processus ont été vérifiés en réalisant et en testant des antennes simples telles que des monopoles alimentés par CPW sur du papier et du PET. Ensuite, la mesure du papier E4D a été effectuée avec 50 échantillons découpés dans différentes feuilles de papier E4D de trois épaisseurs différentes, 104 m, 210 m et 387 m. Les résultats ont été analysés statistiquement et ont donné r = 3.184, tan = 0.092. Les dispersions des résultats mesurés à 2,5 GHz sont 0.25% pour r et 0.26% pour tan. Ces résultats ont été utilisés pour la phase suivante.Au cours de la deuxième phase, les antennes différentes ont été conçues sur le papier E4D d'épaisseur 0,104 mm et 0,21 mm, notamment des IFA, des antennes SIW et des antennes monopoles alimentées par une ligne microruban. Les prototypes ont été réalisés à l'aide d'une technique de sérigraphie et testés pour déterminer les propriétés de l'adaptation et les diagrammes de rayonnement.Dans la troisième phase, les antennes proposées ont été étudiées dans des conditions d'emballage réalistes, où un boîtier décodeur était en plastique ABS avec différentes dimensions. Le premier cas concernait deux antennes MIMO placées orthogonalement dans des boîtiers ABS différents, avec un espace suffisant pour que les deux puissent rester plats. Le second cas était une boîte à hauteur limitée, de sorte qu’au moins une des antennes doit être pliée.Ainsi, une étude de l'effet de flexion a été réalisée, tout d'abord avec un simple dipôle droit et un monopole droit sur le papier E4D, puis avec une antenne à large bande proposée dans la seconde phase. L’étude a montré que la flexion n’affecte pas beaucoup l’adaptation de l’antenne sur une large bande de fréquences. Cependant, ses diagrammes de rayonnement tournent dans le plan E avec un angle de rotation dépendant de la position de pliage et de l'angle de flexion.Ensuite, le système MIMO de deux antennes placé orthogonalement dans un boîtier ABS de hauteur limitée, de sorte qu’une antenne doit être pliée et une autre reste plate. Dans tous les cas de système d'antenne MIMO, nous avons obtenu une bonne isolation (> 20 dB) et un coefficient de corrélation (ECC) inférieur à 0,05.

The thesis was carried out within the ANR project « Stick’It » that aimed at developing new, low-cost and innovative technologies devoted to the design of 2D, 2,5D and 3D radiofrequency (RF) components including antennas printed on conformable materials. The targeted applications are primarily home-networking devices such as set-top boxes where their forms and dimensions are widely varied. Therefore, it is necessary to design antennas on flexible substrates.According to our needs for a substrate material that is flexible, low cost, with good RF properties, recycling ability, and especially ability to make 3D structures, after considering various dielectric materials for flexible electronics, paper substrate appeared to be the most suitable for our purpose.The work of this thesis conducted in three phases.In the first phase, it was the study of methods for characterization of materials to obtain their electromagnetic properties. After analysis, the method of perturbation using a cylindrical cavity was chosen for characterization of paper. The first results of this process were verified by realization and testing of simple antennas such as CPW-fed monopoles on paper and PET. Then, the measurement of E4D paper substrate was performed with 50 samples cut from various E4D paper sheets of three different thicknesses, 104 m, 210 m and 387 m. The results were analyzed statistically and gave r = 3.184, tan = 0.092.The dispersions of the results measured at 2.5 GHz are 0.25% for r and 0.26% for tan. These results were used for the next phase.In the second phase, different antennas were designed on 0.104-mm and 0.21-mm thick E4D paper including IFAs, SIW cavity-back antenna and microstrip-fed wideband monopole antennas. The prototypes were realized using screen printing technique and tested for matching property and radiation patterns.In the third phase the proposed antennas were studied in realistic package conditions, where a set-top box was made of ABS plastic with different dimensions. The first case was with two MIMO antennas orthogonally located in different ABS boxes with sufficient space, so that both of them can remain flat. The second case was a box with a restricted height, so that at least one of the antennas needs to be bent.Thus, a study of bending effect was carried out, first of all, with a simple straight dipole and a straight monopole on E4D paper, then with a wideband antenna proposed in the second phase. The study showed, that bending does not much affect the matching of the antenna over a wide frequency band. However, its radiation patterns rotate in the E-plane with a rotation angle depending on the bending location and bending angle.Then, the MIMO system of two antennas placed orthogonally in an ABS box with restricted height so that one antenna needed to be bent and another remained flat. In all cases of MIMO antenna system, we obtained good isolation (>20 dB) and Envelope Correlation Coefficient (ECC) less than 0.05., Le travail de thèse a été réalisée dans le cadre du projet ANR «Stick’It» visant à développer de nouvelles technologies peu coûteuses et innovantes dédiées à la conception de composants radiofréquences (RF) 2D, 2,5D et 3D, notamment des antennes imprimées sur des matériaux conformes. Les applications ciblées sont principalement des appareils de réseaux domestique, tels que les décodeurs, dont les formes et les dimensions sont très variées. Par conséquent, il est nécessaire de concevoir des antennes sur des substrats souples.Selon nos besoins pour un matériau de substrat flexible, peu coûteux, avec de bonnes propriétés RF, la capacité de recyclage et en particulier la capacité à fabriquer des structures 3D, après avoir étudié différents matériaux diélectriques pour l’électronique flexible, le papier s'est trouvé le plus adapté.Les travaux de cette thèse se sont déroulés en trois phases.Dans la première phase, c'était l'étude des méthodes de caractérisation des matériaux pour obtenir leurs propriétés électromagnétiques. Après l'analyse, la méthode de perturbation utilisant une cavité cylindrique a été choisie pour la caractérisation du papier. Les premiers résultats de ce processus ont été vérifiés en réalisant et en testant des antennes simples telles que des monopoles alimentés par CPW sur du papier et du PET. Ensuite, la mesure du papier E4D a été effectuée avec 50 échantillons découpés dans différentes feuilles de papier E4D de trois épaisseurs différentes, 104 m, 210 m et 387 m. Les résultats ont été analysés statistiquement et ont donné r = 3.184, tan = 0.092. Les dispersions des résultats mesurés à 2,5 GHz sont 0.25% pour r et 0.26% pour tan. Ces résultats ont été utilisés pour la phase suivante.Au cours de la deuxième phase, les antennes différentes ont été conçues sur le papier E4D d'épaisseur 0,104 mm et 0,21 mm, notamment des IFA, des antennes SIW et des antennes monopoles alimentées par une ligne microruban. Les prototypes ont été réalisés à l'aide d'une technique de sérigraphie et testés pour déterminer les propriétés de l'adaptation et les diagrammes de rayonnement.Dans la troisième phase, les antennes proposées ont été étudiées dans des conditions d'emballage réalistes, où un boîtier décodeur était en plastique ABS avec différentes dimensions. Le premier cas concernait deux antennes MIMO placées orthogonalement dans des boîtiers ABS différents, avec un espace suffisant pour que les deux puissent rester plats. Le second cas était une boîte à hauteur limitée, de sorte qu’au moins une des antennes doit être pliée.Ainsi, une étude de l'effet de flexion a été réalisée, tout d'abord avec un simple dipôle droit et un monopole droit sur le papier E4D, puis avec une antenne à large bande proposée dans la seconde phase. L’étude a montré que la flexion n’affecte pas beaucoup l’adaptation de l’antenne sur une large bande de fréquences. Cependant, ses diagrammes de rayonnement tournent dans le plan E avec un angle de rotation dépendant de la position de pliage et de l'angle de flexion.Ensuite, le système MIMO de deux antennes placé orthogonalement dans un boîtier ABS de hauteur limitée, de sorte qu’une antenne doit être pliée et une autre reste plate. Dans tous les cas de système d'antenne MIMO, nous avons obtenu une bonne isolation (> 20 dB) et un coefficient de corrélation (ECC) inférieur à 0,05.

National audience; Dans le cadre du projet ANR « Stick'It », les travaux exposés ici concernent deux structures d'antenne monopôle à large bande sur papier "Sapin" et "Sapin modifié". Il s'agit d'antennes Ultra la Large Bande fonctionnant entre 2.2 GHz et 10 GHz. Cette bande de fréquence couvre deux bandes de fréquence de WLAN. Ces deux antennes ont une taille de 51 × 28 mm² et 45 × 28 mm² avec un gain réalisé de 1,3 dBi et 1,1 dBi à 2,45 GHz et de 1 dBi et 1,6 dBi à 5,5 GHz, respectivement. Elles sont conçues sur des papiers de 100 µm d'épaisseuret présentent une bonne adaptation. Les résultats de simulation et de mesure ont montré un bon accord, et ont confirmé une bonne performance des antennes proposées.

A series of Ni/α-Al2O3 (NiAl) catalysts promoted by CeO2 was prepared by co-impregnation methods with content of (NiO+CeO2) being in the range of 10-30 wt%. The NiO:CeO2 weight ratio was fluctuated at 1:1, 1:2 and 1:3. Several techniques, including X-ray powder diffraction (XRD), Hydrogen temperature-programmed reduction (H2-TPR), and transmission electron microscopy (TEM) were used to investigate catalysts’ physico-chemical properties. The activity of these catalysts in dry reforming of CH4 was investigated at temperature range of 550-800 °C. The results revealed that the most suitable CeO2 promoted Ni catalyst contained 20 wt% of (NiO+CeO2) and NiO:CeO2 weight ratio of 1:2. The best catalytic performance of catalyst [20(1Ni2Ce)Al] due to a better reducibility resulted in a higher amount of free small particle NiO. At 700 °C and CH4:CO2 molar ratio of 1:1, the conversion of CH4 and CO2 on the most suitable CeO2 promoted Ni catalyst reached 86% and 67%, respectively; H2 and CO selectivity of 90% and H2:CO molar ratio of 1.15 were obtained. Being similar to MgO [1], promoter CeO2 could improve catalytic activity of Ni/α-Al2O3 catalyst at a lower range of temperature. Besides, both MgO and CeO2 had a great impact on improving coke resistance of Ni catalysts. At higher temperature, the role of CeO2 as well as MgO in preventing coke formation on catalyst was clarified by temperature-programmed oxidation (TPO) technique. Coke amount formed after 30-h TOS on 20(1Ni2Ce) catalyst was found to be 22.18 mgC/gcat, being less than on non-promoted catalyst (36.75 mgC/gcat), but more than on 20(1Ni2Mg)Al one (5.25 mgC/gcat).

International audience

Nanorods (NR), nanoparticles (NP), and nanocubes (NC) of ceria were prepared by hydrothermal method and used as supports for NiO catalysts for bireforming of CH4 in this investigation. Effects of NiO contents (5-20 wt.%), quantities of reagents, and calcination duration (1-3 h) at 800°C were investigated. Several techniques, including N2 physisorption measurements, X-ray powder diffraction, hydrogen temperature-programmed reduction, scanning electron microscope (SEM), and transmission electron microscopy (TEM) were used to investigate the physico-chemical properties of catalysts. The catalytic performance of the Ni/CeO2 catalysts in combined steam and CO2 reforming of CH4 (bi-reforming) was assessed in the temperature range of 550-800°C. The results revealed that a better duration for calcination is 2 h. After reduction at 800°C for 2 h, catalyst 10 wt% NiO/CeO2-NR was more active and exhibited much higher activity at lower reaction temperature range than others. The high surface area and better reducibility were responsible for improving performance of this catalyst. Moreover, strong metal support interaction (SMSI) was attributed to the better anti-sintering ability leading to a higher stability with time on stream (TOS) of this catalyst. Besides, this improvement of anti-carbon deposition for 10 wt% NiO/CeO2-NR catalyst also owned to CeO2 nature of oxygen capacity. At reaction temperature of 700°C, its catalytic performance could remain over 30 h until deactivation initiated. Coke amount formed after 30 h of TOS was found to be as low as 1.84 mgC/gcat by using temperature programmed oxidation technique.

In this paper, we present a new approach to extract parasitic elements of high electron mobility transistors (HEMTpsilas). By using genetic algorithm (GA), the values of biased-independent parasitic elements will be determined by minimizing the error between calculated and measured S-parameters. Some optimization examples are given for an HEMT from 1 up to 25 GHz. The results show that the proposed method is suitable to determine exactly many parasitic parameters of HEMT model with the excellent fit between measured and calculated S- parameters.