Preparation of reticulated MAX-phase support with morphology-controllable nanostructured ceria coating for gas exhaust catalyst devices

Reticulated porous Ti3AlC2 ceramic, a member of the MAX-phase family (Mn+1AXn phases, where M is an early transition metal, A is an A-group element, and X is carbon and/or nitrogen), was prepared from the highly dispersed aqueous suspension by a replica template method. Through a cathodic electrogeneration method, nanocrystalline catalytic CeO2 coatings were deposited on the conductive porous Ti 3AlC2 supports. By adjusting the pH value and cathodic deposition current, coatings exhibiting nanocellar, nanosheets-like, or bubble-free morphologies can be obtained. This work expects to introduce a novel practically feasible material system and a catalytic coating preparation technique for gas exhaust catalyst devices.

A Mechanistic Model for the Water-Gas Shift Reaction over Noble Metal Substituted Ceria

The water-gas shift (WGS) reaction was carried out in the presence of Pd and Pt substituted nanocrystalline ceria catalysts synthesized by solution combustion technique. The catalysts were characterized by powder XRD and XPS. The noble metals were found to be present in ionic form substituted for the cerium atoms. The catalysts showed highactivity for the WGS reaction with high conversions below 250 degrees C. The products of reaction were only carbon dioxide and hydrogen, and no hydrocarbons were observed even in trace quantities. The reactions were carried out with different amounts of noble metal ion substitution and 2% Pt substituted ceria was found to be the best catalyst. The various possible mechanisms for the reaction were proposed and tested for their consistency with experimental data. The dual site mechanism best described the kinetics of the reaction and the corresponding rate parameters were obtained.

Pd and Pt ions as highly active sites for the water-gas shift reaction over combustion synthesized zirconia and zirconia-modified ceria

Noble metal substituted ionic catalysts were synthesized by solution combustion technique. The compounds were characterized by X-ray diffraction, FT-Raman spectroscopy, and X-ray photoelectron spectroscopy. Zirconia supported compounds crystallized in tetragonal phase. The solid solutions of ceria with zirconia crystallized in fluorite structure. The noble metals were substituted in ionic form.The water-gas shift reaction was carried out over the catalysts.Negligible conversions were observed with unsubstituted compounds. The substitution of a noble metal ion was found to enhance the reaction rate. Equilibrium conversion was obtained below 250 degrees C in the presence of Pt ion substituted compounds. The formation of Bronsted acid-Bronsted base pairs was proposed to explain the activity of zirconia catalysts. The effect of oxide ion vacancies on the reactions over substituted ceria-zirconia solid solutions was established. (c)2010 Elsevier B.V. All rights reserved.

��Feminismo ind��gena? : Un an��lisis cr��tico del discurso sobre los textos de la mujer en el movimiento zapatista 1994-2009

This work analyses texts on indigenous women��s participation in the Mexican Zapatista Army, Ej��rcito Zapatista de Liberaci��n Nacional. The EZLN came to public attention after ten years of clandestine organization in 1994 in Chiapas, a southern state of Mexico neighboring Guatemala. Along the invasion of various municipalities in Chiapas, the Zapatista Army published their own Revolutionary Laws, directed to the Mexican government that included a section on women��s own laws. The indigenous women��s participation in a guerrilla movement in the economically poorest area of Mexico raised many questions among Mexican feminists and some of them fiercely criticized the laws for not being liberating or feminist at all. The question is, did the indigenous women want the laws to be feminist? To answer the main research question How is the position of women constructed in the Zapatista discourse? I analyze texts by various actors in the discourse within the theoretical framework of critical discourse analysis and the feminist theories of intersectionality. The connecting point in this interdisciplinary framework is the question of power and hegemony. The actors in the discourse are the women commanders themselves, the men commanders, the Zapatista spokesperson, subcomandante Marcos and the Mexican feminists. The texts analyzed are the letters of the EZLN to the media and discourses in public reunions, first published in Mexican newspapers and international discussion lists on the Internet and after 2005, on the Zapatista��s own webpage. The results show that instead of discussing whether the Zapatista women��s participation is feminist or not, the action itself provoked such wide discussion of the diversity within the feminist movement that it is a contribution itself. The work also shows that the use of language can be one tool in the quite recent paradigm of intersectionality in feminist theories.

Visst g��r kunden en stor del av jobbet. Referensramar f��r kunders medverkan vid tillkomsten av konsumenttj��nster

I detta arbete accentueras kunden som medverkande akt��r vid tillkomsten av tj��nster och specifikt d�� inom den konsumentorienterade sektorn, vilken ��r en naturlig del av v��rt vardagsliv. S��v��l kommersiella som icke-kommersiella tj��nster beaktas och p�� denna grund st��r kundrollen i centrum. Detta ��r prim��rt parallellt med valet av perspektiv, vilket genomg��ende f��r en fundamental betydelse. Kunders aktiva medverkan framst��r som en naturlig och v��sentlig ingrediens inom tj��nstesektorn, vilket understryks och po��ngteras i detta arbete inom ramen f��r en samlad bild av kunden i rollen som medverkande akt��r. D��rmed markeras betydelsen av att s��ka f��rst�� fenomenet ���kundmedverkan��� utifr��n en helhetssyn och med denna utg��ngspunkt tydligg��ra en helhet, en samlad bild, och de delar som bygger och formar denna. Tre ingredienser aktualiseras h��rvid som tongivande och dessa pr��glar den bild som i detta arbete framtr��der av kunden som medverkande part. I ett f��rsta steg klarl��ggs s��dana aktiviteter som bygger och formar kundens medverkan. Denne engagerar sig och presterar olika aktiviteter, insatser, vilka framst��r som ett fundament i fenomenet. P�� denna grund skapas och formas kundens input i tj��nsteprocessen, dennes processbidrag. D��rmed fokuseras kundens processn��ra funktion, samtidigt som vikten av att parallellt uppm��rksamma insatser respektive processbidrag betonas. Vidare klarl��ggs de effekter som kan uppkomma f��r s��v��l kunden sj��lv som tj��nsteorganisationen och andra inblandade kunder. Olika typer av effekter lyfts fram och tydligg��rs med koppling till bland annat tidsrelaterade inslag. Kunders inflytande p�� s��v��l kvalitetsupplevelser som produktivitet ��r h��rvid av naturligt intresse. Teoretisk analys och begreppsutveckling har varit tongivande inslag i forskningsstrategin, samtidigt som perspektivfr��gan har intagit en avg��rande position. Vidare har erfarenhetsbaserade bilder av ���kundens vardag��� byggt en v��sentlig grund, parallellt med teoretiska erfarenheter. I arbetet utvecklas och presenteras referensramar f��r kunders medverkan i tj��nsteprocessen. Inom ramen f��r en samlad bild erbjuds h��rigenom m��jligheter till analys av konsumentrelaterade verksamheter av skiftande karakt��r. Detta framst��r som v��sentligt med h��nsyn till de variationer som kan framtr��da inom tj��nstesektorn.

La m��sica en la fiesta del dios Xipe Totec

In Aztec mythology and religion, Xipe Totec ("our lord the flayed one") was a life-death-rebirth deity, god of agriculture, vegetation, the east, disease, spring, goldsmiths, silversmiths and the seasons. The music used for his worship has been described by a diversity of documents (carved stones, depicted codices, and chronicles made by the first European friars arrived to Mexico). This article explores the symbolic content of these descriptions, especially in association with Xochipilli Macuilxochitl, master of music and poetry.

Una gram��tica descriptiva del chabacano de Ternate

This dissertation is a descriptive grammar of Ternate Chabacano, a Spanish-lexifier Creole spoken by 3.000 people in the town of Ternate, Philippines. The dissertation offers an analysis of the phonological, morphological, and syntactic system of the language. It includes an overview of the historical background, the current situation of the speech community and a collection of annotated texts. Ternate Chabacano shares many characteristics with its main adstrate language Tagalog as well as the dialectal varieties of Spanish. At present, English also exerts an influence, nevertheless mainly affecting its lexicon. The description offered is based on fieldwork conducted in Ternate. Spoken language collected through thematic interviews forms the main type of the material analysed. Information regarding the informants and text types is included in the examples. Ternate Chabacano has a five-vowel system and 17 consonant phonemes. The morphology of the language is largely isolating. Clitics are used extensively for expressing adverbial relations. The verbal system is based on the preverbal markers that express the category of tense, modality and aspect, among which aspect is the main dimension. Complex predicates and verbal chains are used in order to further distinguish aspect and modality, as well as changes of voice and valency. Intransitive verbs express motion, states, and reflexive actions, even though the majority of verbs can occur in both intransitive and transitive clauses. Ternate Chabacano is a nominative-accusative type language but the typological configuration of the Philippine languages influences the marking of its constituents. A case in point is constituted by the nominal determination system. The basic constituent order in a clause is VSO. Equative and attibutive clauses are formed by juxtaposition while the locative clauses feature a copula. Indefinite terms are expressed through existential constructions. The negation of existential clauses differs from standard negation but both are intensified in the same way. In spoken discourse, tag-questions are common. Pragmatic elements and social formulas reflect largely the corresponding Tagalog expressions. Coordination and subordination occur typically without overt markers but a variety of markers exists for expressing different relations, especially those made explicit by adverbial clauses. Verbal chains form a continuum from serial verbs to complementation and ultimately to coordination.

Kinetics and mechanism for dye degradation with ionic Pd-substituted ceria

The degradation of the dye, Orange G, was carried out in the presence of H2O2 and Pd-substituted/impregnated CeO2. The effects of pH, initial dye concentration, initial H2O2 concentration, temperature, catalyst loading, and Pd content in the catalyst on the degradation of the dye were investigated. Eight to twelve percent degradation of the dye was obtained in 1 h when the reaction was carried out in the presence of CeO2 or H2O2 or Pd-substituted/impregnated CeO2 while 17% and 97% degradation was obtained when H2O2 was used with Pd-impregnated CeO2 and Pd-substituted CeO2, respectively. This difference clearly indicated that the ionic substitution of Pd played a key role in the degradation of the dye. A mechanism for the reaction was proposed based upon the catalyst structure and the electron transfer processes that take place in the metal ion substituted system in a reducible oxide. The reaction was found to follow first order kinetics and the influence of all the parameters on the degradation kinetics was compared using the rate constants. (c) 2011 Elsevier B.V. All rights reserved.

Combustion synthesis and properties of nanostructured ceria-zirconia solid solutions

Nanostructured ceria-zirconia solid solutions (Ce1 ��� xZrxO2, X = 0 to 0.9) have been synthesized by a single step solution combustion process using cerous nitrate, zirconyl nitrate and oxalyl dihydrazide (ODH) / carbohydrazide (CH). The as-synthesized powders show extensive XRD line broadening and the crystallite sizes calculated from the XRD line broadening are in the nanometer range (6���11 nm). The combustion derived ceria zirconia solid solutions have high surface area in the range of 36���120 m2/g. Calcination of Ce1 ���xZrxO2 at 1350 ��C showed three distinct solid solution regions: single phase cubic (x ��� 0.2), biphasic cubic-tetragonal (0.2 < x Image .8) and tetragonal (x > 0.8). When x ��� 0.9, the metastable tetragonal phase formed transforms to monoclinic phase on cooling after calcination above 1100 ��C. The homogeneity of Ce1 ��� xZrxO2 has been confirmed by EDAX analysis. The Temperature Programmed Reduction (TPR) measurement of Ce0.5Zr0.5O2 was carried out with H2 and the TPR profile showed two water formation peaks corresponding to the utilization of surface and bulk oxygen.

Water gas shift reaction over multi-component ceria catalysts

This study reports the activity of ionic substituted bimetallic Cu-Ni-modified ceria and Cu-Fe-modified ceria catalysts for low-temperature water gas shift (WGS) reaction. The catalysts were synthesized in nano-crystalline size by a sonochemical method and characterized by XRD, TEM, XPS, TPR and BET surface analyzer techniques. Due to the ionic substitution of these aliovalent base metals, lattice oxygen in CeO2 is activated and these catalysts show high activity for WGS at low temperature. An increase in the reducibility and oxygen storage capacity of bimetallic substituted CeO2, as evidenced by H-2-TPR experiments, is the primary reason for the higher activity towards WGS reaction. In the absence of feed CO2 and H-2, 100% conversion of CO with 100% H-2 selectivity was observed at 320 degrees C and 380 degrees C, for Cu-Ni-modified ceria and Cu-Fe-modified ceria catalysts. Notably, in the presence of feed H2O. a reverse WGS reaction does not occur over these ceria modified catalysts. A redox reaction mechanism, involving oxidation of CO adsorbed on the metal was developed to correlate the experimental data and determine kinetic parameters. (C) 2012 Elsevier B.V. All rights reserved.

Investigation on the Sr-doped ceria Ce1-xSrO2-delta (x=0.05-0.2) as an electrolyte for intermediate temperature SOFC

The effect of Sr doping in CeO2 for its use as solid electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been explored here. Ce1-xSrxO2-delta (x = 0.05-0.2) are successfully synthesized by citrate-complexation method. XRD, Raman, FT-IR, FE-SEM/EDX and electrochemical impedance spectra are used for structural and electrical characterizations. The formation of well crystalline cubic fluorite structured solid solution is observed for x = 0.05 based on XRD and Raman spectra. For compositions i.e., x > 0.05, however, a secondary phase of SrCeO3 is confirmed by the peak at 342 cm(-1) in Raman spectra. Although the oxygen ion conductivity was found to decrease with increase in x, based on ac-impedance studies, conductivity of Ce0.95Sr0.05O2-delta was found to be higher than of Ce0.95Gd0.1O2-delta and Ce0.8Gd0.2O2-delta. The decrease in conductivity of Ce1-xSrxO2-delta with increasing dopant concentration is ascribed to formation of impurity phase SrCeO3 as well as the formation of neutral associated pairs, Se `' Ce V-o. The activation energies are found to be 0.77, 0.83, 0.85 and 0.90 eV for x = 0.05, 0.1, 0.15 and 0.20, respectively. (C) 2014 Elsevier B.V. All rights reserved.

Novel AgBr/Ag3PO4 Decorated Ceria Nanoflake Composites for Enhanced Photocatalytic Activity toward Dyes and Bacteria under Visible Light

The aim of this study was to develop heterogeneous visible light active photocatalysts using AgBr and Ag3PO4 using CeO2 nanoflakes as an efficient substrate. Ascorbic acid was employed as a fuel to synthesize fine ceria nanoflakes by a facile solution combustion process. AgBr and Ag3PO4 were decorated on ceria to prepare AgBr/Ag3PO4/ceria nanocomposites. The structure of the composite was determined by X-ray diffraction analysis. Novel flakelike morphology was revealed using electron microscopy techniques. The nanocomposites exhibit excellent photocatalytic activity under visible light compared to pristine ceria nanoparticles. The nanocomposite catalyst particles degraded both anionic and cationic dyes. It also exhibited efficient antimicrobial activity under visible light. The AgBr/Ag3PO4/ceria nanocomposite was characterized using X-ray diffraction analysis, diffuse reflectance spectroscopy, electron microscopy, BET surface area analysis, and X-ray photoelectron spectroscopy, and the reasons for enhanced photocatalytic activity were elucidated. The presence of silver based semiconductors on ceria has shown to decrease charge recombination through photoluminescence analysis that attributed for enhanced photocatalytic activity. The AgBr/Ag3PO4/ceria nanocomposite has shown a stable performance after many repeated cycles.

Microkinetic Modeling of CO Oxidation on Ionic Palladium-Substituted Ceria

This study presents a plausible dual-site mechanism and microkinetic model for CO oxidation over palladium-substituted ceria incorporating the theoretical oxygen storage capacity of different-catalysts into the kinetic model. A rate expression without prior assumption of rate-determining steps has been developed for the proposed microkinetic model using reaction route analysis. Experiments were conducted using various percentages of palladium in ceria that were synthesized by solution combustion. Obtained catalysts were characterized by X-ray diffraction, X-ray photoelectron spectra, and Brunauer-Emmett-Teller surface area measurements. A detailed mechanism was, developed, and the kinetic parameters and rate expression were validated with the conversion data obtained in the presence of the catalysts. Furthermore, a reduced rate expression based on rate-determining step and most abundant reactive intermediate approximation was obtained and tested against the original rate expression for different experimental conditions. From the results obtained it was concluded that the simulated rate predictions matched the experimental trend with reasonable accuracy, validating the kinetic parameters proposed it this study.