Decomposição catalítica da hidrazina sobre irídio suportado em compósitos à base de nanofibras de carbono para propulsão espacial: testes em condições reais

The aim of this work is to present the catalytic performance of iridium supported on carbon nanofibers with macroscopic shaping in a 2 N hydrazine microthruster placed inside a vacuum chamber in order to reproduce real-life conditions. The performances obtained are compared to those of the commercial catalyst Shell 405. The carbon-nanofiber based catalyst showed better performance than the commercial catalyst from the standpoint of activity due to its texture and its thermal conductivity.

Decomposição de argilas em forno de microondas e determinação simultânea dos seus constituintes principais por espectrometria de emissão óptica em plasma indutivamente acoplado

In this work a closed-vessel microwave-assisted acid decomposition procedure for clays was developed. Aluminum, Ca, Fe, K, Mg, Na, Si, and Ti were determined in clay digestates by inductively coupled plasma optical emission spectrometry. The most critical parameter for total decomposition of clays was the composition of the reagent mixture. The applied power and the heating time exerted a less critical influence. Best decomposition conditions were attained using a reagent mixture containing 4 mL aqua regia plus 3 mL HF and the heating program was implemented in 12 min. The accuracy of the results was demonstrated using two standard reference materials and a paired t-test showed a good agreement between determined and certified values at a 95% confidence level.

Avaliação da reação foto-fenton na decomposição de resíduos de carrapaticida

Experimental procedures based on factorial design and surface response methodology were applied to establishe experimental conditions for the decomposition of a 1:400 (v/v) Supocade® (chlorfenvinphos 13.8% and cypermethrin 2.6%) solution, used to control cattle ticks. Experiments exploring photo-oxidative reactions were performed with and without UV radiation, fixing exposition time and pesticide volume, and varying the oxidant mixture. The use of 3.6 mmol L-1 Fe2+ plus 1.9 mol L-1 H2O2 plus UV radiation provided destruction of 94% of the original carbon content and reduction of aromatic, aliphatic and carbinolic compounds, evaluated by determination of residual carbon content by ICP OES and NMR analysis.

Análise térmica aplicada ao estudo de materiais energéticos

This paper shows different aspects related to the application of different thermal analysis techniques in the study of energetic materials. The criteria used to choose the best technique and an exact approach to adjust the experimental data with a proper model are here discussed. The paper shows how to use the different thermal analysis results to help develop new compounds, to study the stability of some energetic materials and their compatibility, and the conditions necessary for a secure storing environment.

Biomateriais: deposição de hidroxiapatita sobre superfície de Ti-cp modificada por aspersão térmica

The osseointegrated titanium implants are reliable and safe alternatives to treatments for long periods of time. For surface modification, thermal aspersion of TiO2 was used. The samples with and without TiO2 were treated with NaOH and SBF in order to obtain a layer of HA. Characterization was done by SEM and FTIR. The images of HA obtained by SEM show a uniform morphology and a porous structure with spherical particles. The IR spectra show that the surface of Ticp/ TiO2 is more favorable for the HA deposit, as can be seen by the increase of the crystalline structure and the very intense and defined bands of the OH group of HA that is verified about 3571 and 630 cm-1. Thus the Ticp/ TiO2 surface presents a satisfactory nucleation of HA when compared to Ticp.

Proyecto de ejecución para las obras de concesión de dominio público para la reforma y adecuación de la central térmica y de la red de saneamiento en un hospital de 350 camas

El Hospital Punta de Europa en Algeciras (Cádiz), centro sanitario del Servicio Andaluz de Salud, desea optimizar la gestión de sus instalaciones de generación de energía térmica (vapor, agua caliente sanitaria y agua caliente de calefacción) y adecuarlas a la normativa vigente así como la sustitución de bajantes del edificio, para lo cual sacará a concurso público la licitación para la concesión de dominio público de dichas instalaciones. Para definir el alcance y condiciones de la citada concesión, el Hospital Punta de Europa (Algeciras) del Servicio Andaluz de Salud ha solicitado a Pedro Alonso Martín el estudio para la reforma y adecuación de las instalaciones productoras de energía térmica del citado Hospital. El objetivo principal de este trabajo es hacer un estudio, propuesta y valoración de las actuaciones necesarias para la reforma y mejora de la explotación de las instalaciones generadoras de energía térmica y de la red saneamiento interior del Hospital Punta de Europa de Algeciras (Cádiz). Las actuales instalaciones de generación térmica consumidoras de energía del hospital dentro del alcance de este Proyecto son: Generación de vapor (lavandería y esterilización). Producción de agua caliente sanitaria (ACS). Producción de agua caliente de calefacción. La mayoría de los equipos productores de energía datan del año 1975, por lo que en la mayoría de los casos se ha cumplido su plazo de amortización y periodo de vida útil. Se hace necesaria la instalación de gas natural, debido a que se tendrá que abastecer a todas las calderas de la central térmica. El diseño del sistema de producción de agua caliente sanitaria garantiza el máximo confort y economía del usuario, compatible con el máximo ahorro energético y la protección del medio ambiente, cubriendo las necesidades de agua caliente sanitaria mediante la combinación de un sistema de calderas a gas con los colectores solares.

Síntese, caracterização e avaliação catalítica de Vo x/Mg yAlo x na reação de decomposição do isopropanol

Vanadium oxide supported on hydrotalcite-type precursors was studied in the decomposition of isopropanol. Hydrotalcite-type compounds with different y = Mg+2/Al+3 ratios were synthesized by the method of coprecipitating nitrates of Mg+2 and Al+3 cations with K2CO3 as precipitant. The X-ray diffraction patterns of Al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. It was shown that chemical composition, texture, acid-base properties of the active sites and also Mg/Al ratio strongly affect the formation of the products in the oxidation of isopropanol. The Al-rich catalysts were much more active than the Mg-rich ones, converting isopropanol mainly to propylene.

Síntese, caracterização e análise térmica dos sais de lítio, sódio e potássio do ácido palmítico e do seu éster etílico

Alkaline salts of the palmitic acid were synthesized and characterized from aqueous and ethanolic medium. The salts were characterized by elemental analysis (EA) and infrared spectroscopy (IR). EA and IR, being its synthesis comproved, also characterized the ethyl palmitate. All the salts and the ester were submitted to thermal analysis using thermogravimetry (TG), and differential thermal analysis (DTA) in the temperature ranging from room to 700 ºC under air dynamic atmosphere. Differential scanning calorimetry (DSC) measurements were taken from -90 ºC up to temperatures close to the starting of the decomposition temperature, determined by thermogravimetry, using heating and cooling cycles.

Uso da cinza da casca do arroz (CCA) obtida da geração de energia térmica como adsorvente de Zn(II) em soluções aquosas

The removal study was conducted using 1.00 g of the rice husk ash (RHA) and 20.0 mL solution with concentrations in the range of 10-1000 mg/L of Zn(II). The influence of contact time, initial metal concentration, agitation and pH of the removal process was investigated. Superior removals to 95% were obtained at the end of 24 h of contact. The agitation increased in 20% the removal of Zn(II), being needed only 5 min to reach the equilibrium. The adsorption process was studied by the models of isotherms of Langmuir, Freundlich and BET, obtaining results of R L and 1/n for a process favorable of adsorption. BET isotherm best represents the equilibrium adsorption. The results showed that the RHA has the largest capacity and affinity for the removal of Zn(II).

Argilas como catalisadores verdes na esterificação do colesterol: caracterização espectroscópica e identificação de polimorfos por métodos de análise térmica. Uma proposta laboratorial interdisciplinar para o 1º ciclo universitário

A laboratory experiment that enables the professor to introduce the problematic of sustainable development in pharmaceutical chemistry to undergraduate students is proposed, using a simple synthetic procedure. Cholesteryl acetate is prepared by the esterification of cholesterol using Montmorillonite K10 as heterogeneous catalyst. Cholesterol and cholesteryl acetate are characterized by spectroscopic (¹H RMN, 13C RMN, FTIR) and thermal analysis techniques. The thermal methods are used to introduce the concepts of polymorphism and the nature of mesophases.

Análise térmica aplicada à caracterização da sinvastatina em formulações farmacêuticas

Thermogravimetry (TG) and differential scanning calorimetry (DSC) are used in pharmaceutical studies for drugs characterization, purity, formulations compatibility, polymorphism identification, stability evaluation, and thermal decomposition of drugs and pharmaceutical formulations. Simvastatin showed fusion at 138.5 ºC and thermal stability up to 248 ºC. Simvastatin was incompatible with preservative excipient butylhydroxyanisole (BHA) performing a process of crystal amorphization. The drug showed morphological polymorphism, where it has the same unit cell but with different crystal habits according to the recrystallization solvent.

Estudo das condições de estocagem do bagaço de cana-de-açúcar por análise térmica

An evaluation was made of the properties of sugarcane bagasse during the storage process for subsequent burning in a boiler. Samples of bagasse were collected over a period of 150 days from the Caeté sugar mill (MG) at various points of the stockpile soon after the sugarcane was pressed to extract its juice, as well as from natural bagasse, dry and damp. Thermal analyses of the samples were carried out and the results indicated that, during the storage of bagasse, dry or damp, the biomass loses up to 32% of its calorific power, due to decomposition of the hemicellulose.

Análise térmica aplicada a fármacos e formulações farmacêuticas na indústria farmacêutica

Several matters of the pharmaceutical demonstrate the great importance of thermal analysis application, especially TG and DSC for the pharmaceutical industry future, namely: characterization of the drugs with the thermal events definition, in studies of drug purity, in the polymorphs identification, in compatibility studies of solid dosage pharmaceutical formulations, in drugs and pharmaceutical formulations thermal stability, and in determination of shelf life for isothermal degradation kinetics by extrapolation using the Arrhenius equation. Thus, the test results obtained from thermal analysis are directly related to the quality of a pharmaceutical product, whether the stability or bioavailability of the pharmaceutical product.

Efeitos da história térmica nas propriedades do polímero pet: um experimento para ensino de análise térmica

Polyethilenetherephtalate (PET) is commonly used in manufacturing of beverage bottles representing a didactic appeal in thermal analysis education due to its presence in the student's day life. Additionally such polymer presents well defined thermal analytical curves and a well known thermal behavior. TGA curve is used to present the thermal stability. The thermal history effects in the thermal properties of a PET sample from a soft drink bottle are used to demonstrate the effect of different heating/cooling conditions on glass transition, melting, crystallization and crystalline degree using DSC curves.

O efeito da desativação térmica nas propriedades oxirredutoras e na atividade catalítica de catalisadores CZ e Pd-CZ

Automotive catalyst, using in Brazil since 1992, is a essential technology for vehicular emissions control. Noble metals are the active phase of these catalysts, and cerium zirconium mixed oxides (CZ), responsibles for the oxygen storage capacity (OSC), one of the most important aspect for the operational performance of the catalyst. In this context, the oxireduction properties analysis of CZ and Pd/CZ (palladium supported in CZ) system are the objective of this study, as well as, the impact of the thermal aging in the OSC. Aging consisted of treatments at 900 or 1200 °C, for 12 or 36 h, in oxidizing condition.