Estudo e desenvolvimento de um capacitor eletrolítico de nióbio

It seeks to find an alternative to the current tantalum electrolytic capacitors in the market due to its high cost. Niobium is a potential substitute, since both belong to the same group of the periodic table and because of this have many similar physical and chemical properties. Niobium has several technologically important applications, and Brazil has the largest reserves, around 96%. There are including niobium in reserves of tantalite and columbite in Rio Grande do Norte. These electrolytic capacitors have high capacitance specifies, ie they can store high energy in small volumes compared to other types of capacitors. This is the main attraction of this type of capacitor because is growing demand in the production of capacitors with capacitance specifies increasingly high, this because of the miniaturization of various devices such as GPS devices, televisions, computers, phones and many others. The production route of the capacitor was made by powder metallurgy. The initial niobium powder supplied by EEL-USP was first characterized by XRD, SEM, XRF and laser particle size, to then be sieved into three particle size, 200, 400 e 635mesh. The powders were then compacted and sintered at 1350, 1450 and 1550°C using two sintering time 30 and 60min. Sintering is one of the most important parts of the process as it affects properties as porosity and surface cleaning of the samples, which greatly affected the quality of the capacitor. The sintered samples then underwent a process of anodic oxidation, which created a thin film of niobium pentóxido over the whole porous surface of the sample, this film is the dielectric capacitor. The oxidation process variables influence the performance of the film and therefore the capacitor. The samples were characterized by electrical measurements of capacitance, loss factor, ESR, relative density, porosity and surface area. After the characterizations was made an annealing in air ate 260ºC for 60min. After this treatment were made again the electrical measurements. The particle size of powders and sintering affected the porosity and in turn the specific area of the samples. The larger de area of the capacitor, greater is the capacitance. The powder showed the highest capacitance was with the smallest particle size. Higher temperatures and times of sintering caused samples with smaller surface area, but on the other hand the cleaning surface impurities was higher for this cases. So a balance must be made between the gain that is achieved with the cleaning of impurities and the loss with the decreased in specific area. The best results were obtained for the temperature of 1450ºC/60min. The influence of annealing on the loss factor and ESR did not follow a well-defined pattern, because their values increased in some cases and decreased in others. The most interesting results due to heat treatment were with respect to capacitance, which showed an increase for all samples after treatment

Síntese, estudo cinético e análise microestrutural do sistema cério-níquel obtido pelo método pechini

The cerium oxide has a high potential for use in removing pollutants after combustion, removal of organic matter in waste water and the fuel-cell technology. The nickel oxide is an attractive material due to its excellent chemical stability and their optical properties, electrical and magnetic. In this work, CeO2-NiO- systems on molars reasons 1:1(I), 1:2(II) e 1:3(III) metal-citric acid were synthesized using the Pechini method. We used techniques of TG / DTG and ATD to monitor the degradation process of organic matter to the formation of the oxide. By thermogravimetric analysis and applying the dynamic method proposed by Coats-Redfern, it was possible to study the reactions of thermal decomposition in order to propose the possible mechanism by which the reaction takes place, as well as the determination of kinetic parameters as activation energy, Ea, pre-exponential factor and parameters of activation. It was observed that both variables exert a significant influence on the formation of complex polymeric precursor. The model that best fitted the experimental data in the dynamic mode was R3, which consists of nuclear growth, which formed the nuclei grow to a continuous reaction interface, it proposes a spherical symmetry (order 2 / 3). The values of enthalpy of activation of the system showed that the reaction in the state of transition is exothermic. The variables of composition, together with the variable temperature of calcination were studied by different techniques such as XRD, IV and SEM. Also a study was conducted microstructure by the Rietveld method, the calculation routine was developed to run the package program FullProf Suite, and analyzed by pseudo-Voigt function. It was found that the molar ratio of variable metal-citric acid in the system CeO2-NiO (I), (II), (III) has strong influence on the microstructural properties, size of crystallites and microstrain network, and can be used to control these properties

Efeito da incorporação de diatomita na estabilidade e permeabilidade de compósitos cimentíceos espumados aplicados a poços de petróleo

Lightweight oilwell cement slurries have been recently studied as a mean to improve zonal isolation and sheath-porous formation adherence. Foamed slurries consisting of Portland cement and air-entraining admixtures have become an interesting option for this application. The loss in hydrostatic pressure as a consequence of cement hydration results in the expansion of the air bubbles entrapped in the cement matrix, thus improving the sheath-porous formation contact. Consequently, slurries are able to better retain their water to complete the hydration process. The main objective of the present study was to evaluate the effect of the addition of an air-entraining admixture on the density, stability and permeability of composite slurries containing Portland cement and diatomite as light mineral load. Successful formulations are potential cementing materials for low fracture gradient oilwells. The experimental procedures used for slurry preparation and characterization were based on the American Petroleum Institute and ABNT guidelines Slurries containing a pre-established concentration of the air-entraining admixture and different contents of diatomite were prepared aiming at final densities of 13 to 15 lb/gal. The results revealed that the reduction of 15 to 25% of the density of the slurries did not significantly affect their strength. The addition of both diatomite and the air-entraining admixture increased the viscosity of the slurry providing better air-bubble retention in the volume of the slurry. Stable slurries depicted bottom to top density variation of less than 1.0 lb/gal and length reduction of the stability sample of 5.86 mm. Finally, permeability coefficient values between 0.617 and 0.406 mD were obtained. Therefore, lightweight oilwell cement slurries depicting a satisfactory set of physicochemical and mechanical properties can be formulated using a combination of diatomite and air-entraining admixtures for low fracture gradient oilwells

Comportamento reológico de materiais cimentícios para poços de petróleo contendo naftaleno condensado ou policarboxilato

Pastas a base de cimento Portland são utilizadas na cimentação de poços de petróleo. Elas consistem de uma mistura de partículas sólidas de cimento dispersas em água e aditivos. Atualmente, diversos materiais alternativos são utilizados como aditivos, objetivando a modificação e a melhoria das propriedades das pastas de cimento, especialmente no aumento da fluidez. Novos aditivos plastificantes são capazes de suportar as diversas condições de poços, promovendo propriedades no estado fluido compatíveis às condições exigidas para cimentação.Dispersantes são os componentes da pasta que garantem fluidez, além de proporcionar controle na água perdida por filtração na formação porosa, garantindo o sucesso da operação de bombeio. Em deter minados campos, além do efeito da profundidade, as condições geológicas das formações promovemvariações do gradiente de pressão e temperatura ao longo da profundidade vertical do poço. Recentemente, diversos aditivos químicos da indústria da construção civil tem sido estudados em condições de cimentação de poços de petróleo. Vários produtos testados tem apresentado desempenho superior aos produtos normalmente empregados pela indústria de petróleo com boa relação custo/benefício em função do volume de mercado da construção civil. Resultados promissores na seleção de aditivos com função dispersante da construção civil para operações de cimentação de poços de petróleo onshore foram obtidos para temperaturas até 80°C. O potencial de uso desses aditivos permite estabelecer novas soluções para problemas encontrados na cimentação de poços de petróleo HPHT, poços sujeitos à injeção de vapor, poços depletados e poços produtores de gás. Na construção civil, os superplastificantes permitem reduzir o fator água/cimento das argamassas proporcionando melhoria de propriedades como resistência mecânica e fluidez. Assim, o objetivo deste trabalho foi o estudo e a caracterização reológica de pastas constituídas de cimento Portland, água e aditivos do tipo plastificante, com função dispersante a base de naftaleno condensado e policarboxilato, na faixa de temperaturas de 58°C e 70ºC. As condições utilizadas para a avaliação dos aditivos alternativos foram baseadas em uma cimentação primária para um poço hipotético de 2200 m de profundidade e gradientes geotérmicos de 1,7°F/100 pés e 2,1°F/100 pés. Os resultados demonstraram a grande eficiência e o poder dispersivo do policarboxilato para as temperaturas estudadas. O aditivo promoveu alta fluidez, sem efeitos de sedimentação da pasta. O dispersante à base de naftaleno reduziutant o a viscosidade plástica como o limite de escoamento acimada concentração a partir de 0,13%. O modelo de Bingham descreveu bem o comportamento reológico das pastas com policarboxilato para todas as concentrações

Estudo paramétrico da segregação gravitacional na injeção contínua de vapor

Steam injection is the most used method of additional recovery for the extraction of heavy oil. In this type procedure is common to happen gravitational segregation and this phenomenon can affect the production of oil and therefore, it shoulds be considered in the projects of continuous steam injection. For many years, the gravitational segregation was not adequately considered in the calculation procedures in Reservoir Engineering. The effect of the gravity causes the segregation of fluids inside the porous media according to their densities. The results of simulation arising from reservoirs could provide the ability to deal with the gravity, and it became apparent that the effects of the gravity could significantly affect the performance of the reservoir. It know that the gravitational segregation can happen in almost every case where there is injection of light fluid, specially the steam, and occurs with greater intensity for viscous oil reservoirs. This work discusses the influence of some parameters of the rock-reservoir in segregation as viscosity, permeability, thickness, cover gas, porosity. From a model that shows the phenomenon with greater intensity, optimized some operational parameters as the rate flow rate steam, distance between the wells injector-producer, and interval of completion which contributed to the reduction in gravity override, thus increasing the oil recovery. It was shown a greater technical-economic viability for the model of distance between the wells 100 m. The analysis was performed using the simulator of CMG (Computer Modeling Group-Stars 2007.11, in which was observed by iterating between studied variables in heavy oil reservoirs with similar characteristics to Brazilian Northeast

Injeção de vapor e solvente como um método de recuperação avançada em reservatório avançada em reservatórios de óleo pesado

Currently a resource more and more used by the petroleum industry to increase the efficiency of steam flood mechanism is the addition of solvents. The process can be understood as a combination of a thermal method (steam injection) with a miscible method (solvent injection), promoting, thus, the reduction of interfacial tensions and oil viscosity. The use of solvent alone tends to be limited because of its high cost. When co-injected with steam, the vaporized solvent condenses in the cooler regions of the reservoir and mixes with the oil, creating a zone of low viscosity between the steam and the heavy oil. The mobility of the displaced fluid is then improved, resulting in an increase of oil recovery. To better understand this improved oil recovery method, a numerical study of the process was done contemplating the effects of some operational parameters (distance between wells, injection steam rate, kind of solvent and injected solvent volume)on the accumulated production of oil, recovery factor and oil-steam rate. Semisynthetic models were used in this study but reservoir data can be extrapolated for practical applications situations on Potiguar Basin. Simulations were performed in STARS (CMG, 2007.11). It was found that injected solvent volumes increased oil recovery and oil rates. Further the majority of the injected solvent was produced and can be recycled

Estudo da segregação gravitacional do processo de injeção de vapor em reservátórios heterogêneos

Due to reservoirs complexity and significantly large reserves, heavy oil recovery has become one of the major oil industry challenges. Thus, thermal methods have been widely used as a strategic method to improve heavy oil recovery. These methods improve oil displacement through viscosity reduction, enabling oil production in fields which are not considered commercial by conventional recovery methods. Among the thermal processes, steam flooding is the most used today. One consequence in this process is gravity segregation, given by difference between reservoir and injected fluids density. This phenomenon may be influenced by the presence of reservoir heterogeneities. Since most of the studies are carried out in homogeneous reservoirs, more detailed studies of heterogeneities effects in the reservoirs during steam flooding are necessary, since most oil reservoirs are heterogeneous. This paper presents a study of reservoir heterogeneities and their influence in gravity segregation during steam flooding process. In this study some heterogeneous reservoirs with physical characteristics similar those found in the Brazilian Northeast Basin were analyzed. To carry out the simulations, it was used the commercial simulator STARS by CMG (Computer Modeling Group) - version 2007.11. Heterogeneities were modeled with lower permeability layers. Results showed that the presence of low permeability barriers can improve the oil recovery, and reduce the effects of gravity segregation, depending on the location of heterogeneities. The presence of these barriers have also increased the recovered fraction even with the reduction of injected steam rate

Avaliação de produtos naturais no controle de biofilmes formados em sistema dinâmico

The biofilms microbial forms of association are responsible for generating, accelerating and / or induce the process of corrosion. The damage generated in the petroleum industry for this type of corrosion is significatives, representing major investment for your control. The aim of this study was to evaluate such tests antibiograms the effects of extracts of Jatropha curcas and essential oil of Lippia gracilis Schauer on microrganisms isolated from water samples and, thereafter, select the most effective natural product for further evaluation of biofilms formed in dynamic system. Extracts of J. curcas were not efficient on the complete inhibition of microbial growth in tests type antibiogram, and essential oil of L. gracilis Schauer most effective and determined for the other tests. A standard concentration of essential oil of 20 μL was chosen and established for the evaluation of the biofilms and the rate of corrosion. The biocide effect was determined by microbial counts of five types of microorganisms: aerobic bacteria, precipitating iron, total anaerobic, sulphate reducers (BRS) and fungi. The rate of corrosion was measured by loss of mass. Molecular identification and scanning electron microscopy (SEM) were performed. The data showed reduction to zero of the most probable number (MPN) of bacteria precipitating iron and BRS from 115 and 113 minutes of contact, respectively. There was also inhibited in fungi, reducing to zero the rate of colony-forming units (CFU) from 74 minutes of exposure. However, for aerobic and anaerobic bacteria there was no significant difference in the time of exposure to the essential oil, remaining constant. The rate of corrosion was also influenced by the presence of oil. The essential oil of L. gracilis was shown to be potentially effective

Estudo do processo de combustão in-situ em reservatórios maduros de óleos médios e leves (high pressure air injection)

Nearly 3 x 1011 m3 of medium and light oils will remain in reservoirs worldwide after conventional recovery methods have been exhausted and much of this volume would be recovered by Enhanced Oil Recovery (EOR) methods. The in-situ combustion (ISC) is an EOR method in which an oxygen-containing gas is injected into a reservoir where it reacts with the crude oil to create a high-temperature combustion front that is propagated through the reservoir. The High Pressure Air Injection (HPAI) method is a particular denomination of the air injection process applied in light oil reservoirs, for which the combustion reactions are dominant between 150 and 300°C and the generation of flue gas is the main factor to the oil displacement. A simulation model of a homogeneous reservoir was built to study, which was initially undergone to primary production, for 3 years, next by a waterflooding process for 21 more years. At this point, with the mature condition established into the reservoir, three variations of this model were selected, according to the recovery factors (RF) reached, for study the in-situ combustion (HPAI) technique. Next to this, a sensitivity analysis on the RF of characteristic operational parameters of the method was carried out: air injection rate per well, oxygen concentration into the injected gas, patterns of air injection and wells perforations configuration. This analysis, for 10 more years of production time, was performed with assistance of the central composite design. The reservoir behavior and the impacts of chemical reactions parameters and of reservoir particularities on the RF were also evaluated. An economic analysis and a study to maximize the RF of the process were also carried out. The simulation runs were performed in the simulator of thermal processes in reservoirs STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator) from CMG (Computer Modelling Group). The results showed the incremental RF were small and the net present value (NPV) is affected by high initial investments to compress the air. It was noticed that the adoption of high oxygen concentration into the injected gas and of the five spot pattern tends to improve the RF, and the wells perforations configuration has more influence with the increase of the oil thickness. Simulated cases relating to the reservoir particularities showed that smaller residual oil saturations to gas lead to greater RF and the presence of heterogeneities results in important variations on the RF and on the production curves

Estudo da injeção de CO2 em reservatórios carbonáticos de dupla-porosidade

As rochas carbonáticas ocupam, numa visão global, um expressivo volume da crosta terrestre. De maneira geral, pode-se dizer que essas rochas estão presentes nas diversas unidades litoestatigráficas da Terra. Os reservatórios carbonáticos são reservas naturalmente fraturadas que exigem uma abordagem diferenciada na modelagem em programas de simulação numérica. Os modelos de dupla porosidade são descritos por funções de tranferências que modelam o fluxo de óleo entre matriz e fraturas. Em um reservatório carbonático naturalmente fraturado o sistema de fraturas é determinante no escoamento de fluidos dentro da reserva. Os maiores reservatórios carbonáticos do mundo estão situados no Oriente Médio e na América do Norte. As maiores reservas de óleo brasileiras encontradas neste tipo de reservatório estão localizadas nos campos do Pré-Sal. No Pré-Sal, um volume significativo de dióxido de carbono é produzido juntamente com o óleo. A disponibilidade de um volume consideravél de dióxido de carbono derivado da produção de óleo no Pré-Sal favorece a utilização dos processos de EOR (Enhanced Oil Recovery) por injeção de gás. O processo de injeção de dióxido de carbono vem sendo utilizado em uma grande quantidade de projetos pelo mundo. A afinidade existente entre o óleo e o dióxido de carbono causa uma frente miscível entre as duas fases causando inchamento e vaporização do óleo dentro do reservatório. Para o estudo, foi utilizado um modelo base de reservatório de dupla-porosidade, desenvolvido pela CMG para o 6° Projeto de Soluções Comparativas da SPE, que modela sistemas de fraturas e de matriz e a tranferência de massa fluida entre elas, características de reservatórios naturalmente fraturados. Foi feita uma análise da injeção de diferentes vazões de dióxido de carbono no modelo base e em modelos semelhantes, com aumento e redução de 5 e 0.5 pontos nas propriedades de porosidade e permeabilidade da matriz, respectivamente, tendo a produção de óleo como resultado. A injeção de 25 milhões de pés cúbicos por dia de CO2 foi a vazão que obteve a melhor fator de recuperação

Estudo dos parâmetros operacionais do processo de combustão in situ em reservatório de petróleo pesado

The occurrence of heavy oil reservoirs have increased substantially and, due to the high viscosity characteristic of this type of oil, conventional recovery methods can not be applied. Thermal methods have been studied for the recovery of this type of oil, with a main objective to reduce its viscosity, by increasing the reservoir temperature, favoring the mobility of the oil and allowing an increasing in the productivity rate of the fields. In situ combustion (ISC) is a thermal recovery method in which heat is produced inside the reservoir by the combustion of part of the oil with injected oxygen, contrasting with the injection of fluid that is heated in the surface for subsequent injection, which leads to loss heat during the trajectory to the reservoir. The ISC is a favorable method for recovery of heavy oil, but it is still difficult to be field implemented. This work had as an objective the parametric analysis of ISC process applied to a semi-synthetic reservoir with characteristics of the Brazilian Northeast reservoirs using vertical production and vertical injection wells, as the air flow injection and the wells completions. For the analysis, was used a commercial program for simulation of oil reservoirs using thermal processes, called Steam, Thermal and Advanced Processes Reservoir Simulator (STARS) from Computer Modelling Group (CMG). From the results it was possible to analyze the efficiency of the ISC process in heavy oil reservoirs by increasing the reservoir temperature, providing a large decrease in oil viscosity, increasing its mobility inside the reservoir, as well as the improvement in the quality of this oil and therefore increasing significantly its recovered fraction. Among the analyzed parameters, the flow rate of air injection was the one which had greater influence in ISC, obtaining higher recovery factor the higher is the flow rate of injection, due to the greater amount of oxygen while ensuring the maintenance of the combustion front

Avaliação do petróleo por termogravimetria para simulação de curva PEV, fator de caracterização e resíduo de carbono

Petroleum evaluation is analyze it using different methodologies, following international standards to know their chemical and physicochemical properties, contaminant levels, composition and especially their ability to generate derivatives. Many of these analyzes consuming a lot of time, large amount of samples , supplies and need an organized transportation logistics, schedule and professionals involved. Looking for alternatives that optimize the evaluation and enable the use of new technologies, seven samples of different centrifuged Brazilian oils previously characterized by Petrobras were analyzed by thermogravimetry in 25-900° C range using heating rates of 05, 10 and 20ºC per minute. With experimental data obtained, characterizations correlations were performed and provided: generation of true boiling point curves (TBP) simulated; comparing fractions generated with appropriate cut standard in temperature ranges; an approach to obtain Watson characterization factor; and compare micro carbon residue formed. The results showed a good chance of reproducing simulated TBP curve from thermogravimetry taking into account the composition, density and other oil properties. Proposed correlations for experimental characterization factor and carbon residue followed Petrobras characterizations, showing that thermogravimetry can be used as a tool on oil evaluation, because your quick analysis, accuracy, and requires a minimum number of samples and consumables

Análise de cDNAs identificados em bibliotecas substrativas de cDNA para floração de variedades de cana-de-açúcar cultivadas no Rio Grande do Norte(RN): fator de transição NAC, Calmodulina e Fosfatidiltransferase

The flowering is a physiological process that it is vital for plants. This physiological process has been well studied in the plant model Arabidopsis, but in sugarcane this process is not well known. The transition of the shoot apical meristem from vegetative to flowering is a critical factor for plant development. At Brazil northeastern region, the transition to flowering in sugarcane has an important effect as it may reduce up to 60% its production. This is a consequence of the sugar translocation from stalks to the shoot apical meristem which is necessary during the flowering process. Therefore, the aim of this work was to explore and analyze cDNAs previously identified using subtractive cDNA libraries. The results showed that these cDNAs showed differential expression profile in varieties of sugarcane (early x late flowering). The in silico analysis suggested that these cDNAs had homology to calmodulin, NAC transcription factor and phosphatidylinositol, a SEC14, which were described in the literature as having a role in the process of floral development. To better understand the role of the cDNA homologous to calmodulin, tobacco plants were transformed with overexpression cassettes in sense and antissense orientation. Plants overexpressing the cassette in sense orientation did not flowered, while plants overexpressing the cassette in the antissense orientation produced flowers. The data obtained in this study suggested the possible role from CAM sequence, SEC14 and NAC in the induction/floral development pathway in sugarcane, this is the first study in order to analyze these genes in the sugarcane flowering process.

Acesso aos serviços odontológicos e incidência de cárie em adolescentes e fatores de risco em município do Nordeste Brasileiro, 2006

The aims of this study were to analyze the access of dental services by child population, to determine the prevalence of dental caries, gingivitis and malocclusion in resident children from the municipal district of Sobral Ceará and to evaluate the incidence of the dental decay in adolescents associated with the factors related to socioeconomic condition, access to health services and self-perception. This study had as main factor the multidisciplinary represented by the participation of health professional (doctors, dentists, nurses) in the development of the survey's initial reference; student from Human Sciences area to apply the structured questionnaire in domiciliary visits; statistics professionals in the orientation of the analysis to be held and family health team (community health agents, dentists and dental clinic assistants) in the scheduling of domiciliary visits and the accomplishment of oral exam. The sample was determined from the domicile record that included children born between 1990 and 1994 to develop the research Children health conditions in the municipal district of Sobral Ceará . The first sample comprised 3425 parents of children from 5 to 9 years old, living in the urban area at the municipal district of Sobral Ceará, aiming at identifying the most important factors associated to the access to dental service. From this sample, 1021 children were selected in a systematic way, for the accomplishment to the epidemiological study of decay, gingivitis and malocclusion. In the study's third phase, in order to arrange the group to be followed, 688 adolescents were examined and interviewed, by means of the active search from the 1021 individuals that had been previously examined. It was observed that 50.9% of the children had access to dental service at least once in a lifetime. Of this total, 65.3% accomplished it during the last year, and 85.4% of these did in public services, what allows to identify the importance of this sector in the access to dental services. It was observed that the factors that most affected the access to dental 129 services were related to socioeconomic condition, such as the access to health plan, the possession of toothbrush, garbage collecting, mother s schooling, sewerage treatment and malnutrition. In relation to oral diseases, an increase in the DMF-T index according the age was observed, from 0.10 in five years old to 1.66 in the nine years old, while with the dmf-t index, the inverse happened, since the index decreased from 3.59 in five years old to 2.69 in nine years old. In relation to gingivitis, an average 32.7% of the children presented gum bleeding. In what concerns malocclusion, it was observed that 60.3% of the children didn't present any problem, 30.17% had light malocclusion and 9.5% severe malocclusion. The average incidence of dental caries was 1.86 teeth per youngster. Among the studied variables, tooth pain in the last six months, mother's income and school snack, adjusted by the perception about the need of treatment, the mother's schooling and the dentist's appointment at least once in a lifetime, were the variables that presented positive relationship with the high incidence of dental caries on this population by logistic regression. Variables of socioeconomic nature, related to the access to health services and behavior and biological variables presented a relationship with the high caries incidence. The study point out to the need of developing health actions in a humanized way, by an oral health team effectively bound to the population's interest, with the great objective to provide, with the public health services managers, adequate conditions to improve oral health

Redução da morbi-mortalidade na síndrome de hellp completa com o uso de altas doses de dexametasona

Objective: To determine the clinical maternal and neonatal outcomes in HELLP syndrome patients treated with dexamethasone who either developed renal injury or renal insufficiency and to identify predictive values of urea and creatinine for the identification of subjects with HELLP syndrome at risk of developing renal insufficiency. Methods: Non-radomized intervention study of dexamethasone use in HELLP syndrome. A total of 62 patients were enrolled at Maternidade Escola Januário Cicco (MEJC). Patients received a total of 30 mg of dexamethasone IV, in three doses of 10 mg every 12 hours. A clinical and laboratory follow up were performed at 24, 48 and 72 hours. Patients were followed up to 6 months after delivery. Patients were grouped in accordance to renal function, i.e, normal and some type of renal lesion. Renal lesion was considered when creatinine was equal or greater than 1.3 mg/dl and diuresis less than 100 ml in 4 hours period and renal insufficiency was defined when dialysis was needed. Results: A total of 1230 patients with preeclampsia were admitted at MEJC. Of those 62 (5%) developed HELLP syndrome. There was no statistical difference in the groups with renal involvement or normal renal function with respect to the demographics, type of anesthesia used and delivery, and weight of the newborn. An improvement in the AST, ALT, LDH, haptoglobine, antithrombine, fibrinogenen and platelets was observed within 72 hours after dexamethosone use. There was a significant increase in the diuresis within the interval of 6 hours before the delivery and 24 hours after it. Of the 62 patients, 46 (74. 2%) had normal renal function and 16 (25.8%) evolved with renal lesion, with 5 (8.1%) needing dialysis. These 5 patients who received dialysis recovered the xi renal function. The delay in administering dexamethasone increased in 4.6% the risk of development of renal insufficiency. Patients with renal insufficiency had received significantly more blood products than subjects without renal lesion (p=0.03). Diuresis, leukocytes, uric acid, urea, creatinine were significantly different between the groups with normal renal function, renal lesion and renal insufficiency. The levels of creatinine 1.2mg/dl and uric acid 51mg/dl, at admission are predictive of subjects who will evolve with renal lesion (p<0.001). Maternal mortality was 3.2%. None of the subjects with renal insufficiency evolved with chronic renal disease. Conclusions: Dexamethasone in patients with HELLP syndrome seems to reduce significantly the hepatic microthrombosis and normalize hemostasis as seen by improvement of liver function. Renal injury can be considered, in HELLP syndrome, when creatinine levels are greater than 1.3 mg/dl and diuresis less than 100 ml/h in interval of 4 hours. The level of creatinine greater than 1.2 mg/dl and urea greater than 51mg/dl are predictive of subjects with HELLP syndrome who will develop renal injury. Patients who receive more red cell packs develop renal insufficiency. Finally, the delay in administering dexamethasone increases the risk of developing renal insufficiency