SESMR (Sorption Enhanced Steam Methane Reforming), SMR (Steam Methane Reforming) avec capture de CO2 in situ par un adsorbant solide, peut amener à une exploitation durable du gaz naturel pour la production de H2. La thèse, partie du projet de recherche ASCENT (Advanced Solid Cycles with Efficient Novel Technologies), concerne le développement de matériaux combinés adsorbants catalyseurs Ni-CaO-mayenite pour le SESMR, aux fins d’étudier les influences dues à la fraction de Ni, aux sels précurseurs du Ni (Ni acétate ou Ni nitrate), et à la fraction de CaO disponible. Les techniques ICP AES, XRD, BET/BJH, SEM/EDS, TEM/EDS, TPR et TGA ont été utilisés pour caractériser les matériaux synthétisés. La réactivité a été évaluée par des tests en lit fixe à l’échelle du microréacteur, qui ont aussi permis une sélection des matériaux les plus prometteurs pour une étude de l’applicabilité industrielle par tests multi cycliques SESMR/régénération de solides par un réacteur automatisé à lit fixe. / Sorption enhanced steam methane reforming (SESMR), steam methane reforming (SMR) with in situ CO2 sorption by a solid sorbent, can lead to a sustainable exploitation of natural gas to produce H2. (CSCM). This thesis, as a part of ASCENT (Advanced Solid Cycles with Efficient Novel Technologies) project, deals with Ni-CaO-mayenite combined sorbent-catalyst material for SESMR, to study the effect of Ni fraction, its precursor salt (Ni nitrate or Ni acetate), and free CaO fraction. ICP AES, XRD, BET and BJH methods, SEM EDS, TEM EDS, TPR and TGA were used to characterize synthesized materials. Their reactivity was evaluated by tests in a packed bed microreactor, which served also as a screening tool to choose the most promising materials. Their industrial applicability was assessed by multicycle SESMR/regeneration tests in an automated packed bed bench scale rig.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Vasomotor tone is largely maintained by sympathetic nerves, myogenic reactivity and key local and circulating hormones. Acting together, these factors ensure moment-to-moment adjustments of net vascular tone required to maintain hemodynamic stability. In rat mesenteric small veins (MSV) and arteries (MSA), we investigated the contribution of the endothelium, L-type voltage operated calcium channels (L-VOCCs), PKC and Rho kinase to myogenic reactivity. The interaction of myogenic reactivity with norepinephrine (NE), endothelin-1 (ET-1), and sympathetic nerve activation was also investigated under conditions of changing transmural distending pressure. We also evaluated the relative contribution of alpha adrenergic (α-A) and endothelinergic receptors to NE and ET-1 contractile responses, respectively. Additionally, the effects of changing transmural pressure on endothelial dilator function of MSV were examined. Myogenic reactivity was not altered by nitric oxide synthase (NOS) inhibition or endothelium removal in both vessels. L-VOCCs blockade completely abolished arterial tone, while only partially reducing venous tone. PKC and Rho kinase inhibitors largely abolished venous and arterial myogenic reactivity. Increasing transmural pressure did not alter NE, ET-1, and bradykinin responses, but it significantly reduced neurogenic contractions. MSV were more sensitive to NE, ET-1 and sympathetic nerve activation compared with corresponding arteries. α-A and ET-1 receptor agonist and antagonist application revealed the participation of α1-A and ETA receptors in NE and ET-1 contractile responses, respectively. α2-A and ETB receptors appeared to mediate NE and ET-1 responses in MSV, respectively. Bradykinin induced-vasodilation was mainly reduced by NOS inhibition, and BKCa and SkCa blockade. These results suggest that myogenic factors are important contributors to net venous tone in MSV; PKC and Rho kinase activation are important to myogenic reactivity in both vessels, while L-VOCCs play a limited role in the veins versus the arteries; mesenteric veins maintain an enhanced sensitivity to NE, ET-1 and sympathetic nerve activation compared to the arteries with neurogenic contractions being affected by transmural pressure elevations; α1-ARs and ETA are the predominant receptors mediating contractile responses to NE and ET-1, respectively, with functional evidence indicating the presence of α2-ARs and ETB receptors in MSV; and venous endothelial dilator function is not affected by an elevation of transmural pressure. / Natural Sciences and Engineering Research Council of Canada (NSERC). Libyan Ministry of Education and Scientific Research.

When a permanent magnet is considered for an application, the quantity that quantifies the usability of that material is the magnetic energy product (BH)max. In today’s world, rare earth transition metal permanent magnets like Nd-Fe-B, Sm-Co possesses the maximum magnetic energy product. But still for the industrial application, the ferrite permanent magnets are the primary choice over these rare transition metal magnets. Thus, in the present context, the magnetic energy product of the low cost ferrite system makes it unsuitable for the high magnetic energy application. In this regard, exchange spring magnets which combine the magnetization of the soft phase and coercivity of the hard magnetic phases become important in enhancing the magnetic energy product of the system. In this thesis, the exchange spring behaviour is reported for the first time in hard/soft oxide nanocomposites by microstructural tailoring of hard Barium Ferrite and soft Nickel Zinc Ferrite particles. We have analyzed the magnetization reversal and its correlation with the coercivity mechanism in the Ni0.8Zn0.2Fe2O4/BaFe12O19 exchange spring systems. Using this exchange spring concept, we could enhance the magnetic energy product in Iron Oxide/ Barium Calcium Ferrite nanocomposites compared to the bare hard ferrite by ~13%. The presence of the exchange interaction in this nanocomposite is confirmed by the Henkel plot. Moreover, a detailed Reitveld study, magnetization loop and corresponding variation of the magnetic energy product, Henkel plot analysis and First Order Reversal Curve analysis are performed on nanocomposites of hard Strontium Ferrite and soft Cobalt Ferrite. We have proved the exchange spring behaviour in this composite. In addition, we could successfully tailor the magnetization behaviour of the soft Cobalt Ferrite- hard Strontium Ferrite nanocomposite from non exchange spring behaviour to exchange spring behaviour, by tuning the size of the soft Cobalt Ferrite in the Cobalt Ferrite/Strontium Ferrite nanocomposite. The relative strength of the interaction governing the magnetization process in the composites has been studied using Henkel plot and First Order Reversal Curve method. The FORC method has been utilized to understand the magnetization reversal behaviour as well as the extent of the irreversible magnetization present in both the nanocomposites, having smaller and larger particle size of the Cobalt Ferrite. It has been found that for the all the studied composites, the pinning is the dominant process for magnetization reversal. The detailed structural analysis using thin film XRD, angle dependent magnetic hysteresis and remanent coercivity measurement, coercivity mechanism by micromagnetic analysis and First Order Reversal Curve analysis are performed for thin films of Strontium Ferrite which are grown on c-plane alumina using Pulsed Laser Deposition (PLD) at two different oxygen partial pressures. The magnetic easy directions of both the films lie in the out of plane direction where as the in plane direction corresponds to the magnetic hard direction. Depending on the oxygen partial pressure during deposition, the magnetization reversal changes from S-W type reversal to Kondorsky kind of reversal. Thus, the growth parameter for the Strontium Ferrite single layer which will be used further as a hard layer for realizing oxide exchange spring in oxide multilayer, is optimized. The details of the magnetic and structural properties are analyzed for Nickel Zinc Ferrite thin film grown on (100) MgAl2O4. We have obtained an epitaxial growth of Nickel Zinc Ferrite by tuning the growth parameters of PLD deposition. The ferromagnetic resonance and the angle dependent hysteresis loop suggest that, the magnetic easy direction for the soft Nickel Zinc Ferrite lie in the film plane whereas the out of plane direction is the magnetic hard direction. Using the growth condition of respective Nickel Zinc Ferrite and Strontium Ferrite, we have realized the exchange spring behaviour for the first time in the trilayer structure of SrFe12O19 (20 nm)/Ni0.8Zn0.2Fe2O4(20 nm)/ SrFe12O19 (20 nm) grown on c-plane alumina (Al2O3) using PLD. The FORC distribution for this trilayer structure shows the single switching behaviour, corresponding to the exchange spring behaviour. The reversible ridge measurement shows that the reversible and the irreversible part of the magnetizations are not coupled with each other.