Estudo da síntese e sinterização de pós compósitos do sistema Ta-Cu

Ta-Cu bulk composites combine high mechanical resistance of the Ta with high electrical and thermal conductivity of the Cu. These are important characteristics to electrical contacts, microwave absorber and heat skinks. However, the low wettability of Ta under Cu liquid and insolubility mutual these elements come hard sintering this composite. High-energy milling (HEM) produces composite powders with high homogeneity and refines the grain size. This work focus to study Ta-20wt%Cu composite powders prepared by mechanical mixture and HEM with two different conditions of milling in a planetary ball mill and then their sintering using hydrogen plasma furnace and a resistive vacuum furnace. After milling, the powders were pressed in a steel dye at a pressure of 200 MPa. The cylindrical samples pressed were sintered by resistive vacuum furnace at 10-4torr with a sintering temperature at 1100ºC / 60 minutes and with heat rate at 10ºC/min and were sintered by plasma furnace with sintering temperatures at 550, 660 and 800ºC without isotherm under hydrogen atmosphere with heat rate at 80ºC/min. The characterizations of the powders produced were analyzed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and laser granulometry. After the sintering the samples were analyzed by SEM, XRD and density and mass loss tests. The results had shown that to high intense milling condition produced composite particles with shorter milling time and amorphization of both phases after 50 hours of milling. The composite particles can produce denser structure than mixed powders, if heated above the Cu melting point. After the Cu to arrive in the melting point, liquid copper leaves the composite particles and fills the pores

Estudo da moagem de alta energia e sinterização de pós compósitos W-Cu

The Tungsten/copper composites are commonly used for electrical and thermal objectives like heat sinks and lectrical conductors, propitiating an excellent thermal and electrical conductivity. These properties are dependents of the composition, crystallite size and production process. The high energy milling of the powder of W-Cu produces an dispersion high and homogenization levels with crystallite size of W very small in the ductile Cu phase. This work discusses the effect of the HEM in preparation of the W-25Cu composite powders. Three techniques of powder preparation were utilized: milling the dry with powder of thick Cu, milling the dry with powder of fine Cu and milling the wet with powder of thick Cu. The form, size and composition of the particles of the powders milled were observed by scanning electron microscopy (SEM). The X-ray diffraction (XRD) was used to analyse the phases, lattice parameters, size and microstrain of the crystallite. The analyse of the crystalline structure of the W-25Cu powders milled made by Rietveld Method suggests the partial solid solubility of the constituent elements of the Cu in lattice of the W. This analyse shows too that the HEM produces the reduction high on the crystallite size and the increase in the lattice strain of both phases, this is more intense in the phase W

Influência das espécies ativas na absorção de intersticiais durante a carbonitretação a plasma do TI

Physical-chemical properties of Ti are sensible to the presence of interstitial elements. In the case of thermochemical treatments plasma assisted, the influence of different active species is not still understood. In order to contribute for such knowledge, this work purposes a study of the role played by the active species atmosphere into the Ar N2 CH4 carbonitriding plasma. It was carried out a plasma diagnostic by OES (Optical Emission Spectroscopy) in the z Ar y N2 x CH4 plasma mixture, in which z, y and x indexes represent gas flow variable from 0 to 4 sccm (cm3/min). The diagnostic presents abrupt variations of emission intensities associated to the species in determined conditions. Therefore, they were selected in order to carry out the chemical treatment and then to investigate their influences. Commercial pure Ti disks were submitted to plasma carbonitriding process using pre-established conditions from the OES measurements while some parameters such as pressure and temperature were maintained constant. The concentration profiles of interstitial elements (C and N atoms) were determined by Resonant Nuclear Reaction Analysis (NRA) resulting in a depth profile plots. The reactions used were 15N(ρ,αγ)12C and 12C(α,α)12C. GIXRD (Grazing Incidence X-Ray Diffraction) analysis was used in order to identify the presence of phases on the surface. Micro-Raman spectroscopy was used in order to qualitatively study the carbon into the TiCxN1 structure. It has been verified which the density species effectively influences more the diffusion of particles into the Ti lattice and characteristics of the layer formed than the gas concentration. High intensity of N2 + (391,4 nm) and CH (387,1 nm) species promotes more diffusion of C and N. It was observed that Hα (656,3 nm) species acts like a catalyzer allowing a deeper diffusion of nitrogen and carbon into the titanium lattice.

Caracterização de compósitos Nb-20%cu obtidos por moagem de alta energia e sinterizados por fase líquida

In this work, was studied the formation of a composite of the refractory metal niobium with copper, through the process of high-energy milling and liquid phase sintering. The HEM can be used to synthesize composite powders with high homogeneity and fine size particle distribution. It may also produce the solid solubility in immiscible systems such as Nb-Cu, or extend the solubility of systems with limited solubility. Therefore, in the immiscible system Cu-Nb, the high-energy milling was successfully used to obtain the composite powder particles. Initially, the formation of composite particles during the HEM and the effect of preparation technique on the microstructure of the material was evaluated. Four loads of Nb and Cu powders containing 20%wt Cu were synthesized by MAE in a planetary type ball mill under different periods of grinding. The influence of grinding time on the metal particles is evaluated during the process by the withdrawal of samples at intermediate times of milling. After compaction under different forces, the samples were sintered in a vacuum furnace. The liquid phase sintering of these samples prepared by HEM produced a homogeneous and fine grained. The composite particles forming the sintered samples are the addition of a hard phase (Nb) with a high melting point, and a ductile phase (Cu) with low melting point and high thermal and electrical conductivities. Based on these properties, the Nb-Cu system is a potential material for many applications, such as electrical contacts, welding electrodes, coils for generating high magnetic fields, heat sinks and microwave absorbers, which are coupled to electronic devices. The characterization techniques used in this study, were laser granulometry, used to evaluate the homogeneity and particle size, and the X-ray diffraction, in the phase identification and to analyze the crystalline structure of the powders during milling. The morphology and dispersion of the phases in the composite powder particles, as well the microstructures of the sintered samples, were observed by scanning electron microscopy (SEM). Subsequently, the sintered samples are evaluated for density and densification. And finally, they were characterized by techniques of measuring the electrical conductivity and microhardness, whose properties are analyzed as a function of the parameters for obtaining the composite

Estudo sobre o efeito dos parâmetros de processamento dos pós e sinterização do aço inox 316l reforçado com NbC

This masther dissertation presents a contribution to the study of 316L stainless steel sintering aiming to study their behavior in the milling process and the effect of isotherm temperature on the microstructure and mechanical properties. The 316L stainless steel is a widely used alloy for their high corrosion resistance property. However its application is limited by the low wear resistance consequence of its low hardness. In previous work we analyzed the effect of sintering additives as NbC and TaC. This study aims at deepening the understanding of sintering, analyzing the effect of grinding on particle size and microstructure and the effect of heating rate and soaking time on the sintered microstructure and on their microhardness. Were milled 316L powders with NbC at 1, 5 and 24 hours respectively. Particulates were characterized by SEM and . Cylindrical samples height and diameter of 5.0 mm were compacted at 700 MPa. The sintering conditions were: heating rate 5, 10 and 15◦C/min, temperature 1000, 1100, 1200, 1290 and 1300◦C, and soaking times of 30 and 60min. The cooling rate was maintained at 25◦C/min. All samples were sintered in a vacuum furnace. The sintered microstructure were characterized by optical and electron microscopy as well as density and microhardness. It was observed that the milling process has an influence on sintering, as well as temperature. The major effect was caused by firing temperature, followed by the grinding and heating rate. In this case, the highest rates correspond to higher sintering.

Adição do resíduo de biomassa da cana-de-açúcar em pastas para cimentação de poços petrolíferos produtores de óleos pesados

The Potiguar basin has large fields of viscous oil where the used method for recovering is based on vapor injection; this operation is carried out by injecting vapor in the oilwell directly, without the protection of a revetment through thermal insulation, what causes its dilation and, consequently, cracks in the cement placed on the annular, and lost of hydraulic insulation; this crack is occasioned by the phenomenon of retrogression of the compressive resistance due to the conversion of the hydrated calcium silicate in phases calcium-rich, caused by the high temperatures in the wells, subjected to thermal recuperation. This work has evaluated the application of composite pastes with addition of residue of biomass of ground sugar-cane bagasse as anti-retrogression mineral admixture for cementation of oil-wells subjected to thermal recuperation. The addition of the mineral residue was carried out considering a relative amount of 10, 20, 30, 40 and 59% in relation to cement mass, trying to improve the microstructure of the paste, still being developed a reference paste only with cement and a paste with addition of 40% of silica flour - renowned material in the oil industry as anti-retrogression additive. Pozzolanic activity of the ash was evaluated through XRD, TG/DTG, as the resistance to compression, and it was also determined the physical and mechanical behavior of the pastes when submitted to cure at low temperatures (22 and 38º C); besides it was evaluated the behavior of the pastes when submitted to two cycles of cure at high temperature (280ºC) and pressure (7 MPa). It was verified that the ash of the sugar-cane biomass presents pozzolanic reaction and has great efficiency in decrease the permeability of the paste by filler effect, as well as that addition of ash in a relative amount of 10, 20 e 30% increases cured compressive resistance at low temperatures. It was also showed that the ash in a relative amount of 40% and 59% has very significant efficiency as anti-retrogression additive, since it prevents the decrease of compressive resistance and forms hydrated calcium silicate type xenotlita and tobermorita which have more resistance and stability in high temperatures

Obtenção de uma porcelana dielétrica a partir de matérias-primas do Rio Grande do Norte

The dielectric porcelain is usually obtained by mixing various raw materials proportions and is used in the production of electronic equipment for various applications, from capacitors of high and low Power to insulators for low, medium, high and extra high voltage, which are used in distribution lines and transmission of electricity.This work was directed to the s tudy of technological properties of technic porcelain, made from raw materials extracted from pegmatites found in the regions of Seridó and the Alto Oeste of Rio Grande do Norte, which are made of kaolin, quartz and feldspar, abundant and high quality in these regions. The technic ceramics were obtained by mixing in appropriate levels, kaolin, feldspar, quartz and clay, the last item from a pottery in the city of Sao Gonçalo do Amarante, Rio Grande do Norte. During the development the following characterizations correlated to raw materials were made: laser particle sizing, x-ray diffraction, DTA and TG. The compositions studied were formed by uniaxial pressing at a pressure of 50 MPa and sintered at temperatures ranging from 1150 to 1350ºC and levels (times) of sintering between 30, 60, 90 and 120 minutes. The characterization of the samples were taken from the analysis of weight loss, linear shrinkage, porosity, stoneware curve, bulk density, flexural strength of three points, SEM and X-ray diffraction, TMA, Dielectric and cross Resistivity. The studied materials can be employed in producing the objects used in electrical engineering such as: insulators for low, medium and high-voltage electrical systems, command devices, bushing insulation for transformers, power capacitors, spark plugs, receptacles for fluorescent and incandescent light bulbs and others

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

Comportamento da adição do carbeto de nióbio (nBC) na matriz metálica do aço ferrítico 15kH2mfa

The 15Kh2MFA steel is a kind of Cr-Mo-V family steels and can be used in turbines for energy generation, pressure vessels, nuclear reactors or applications where the range of temperature that the material works is between 250 to 450°C. To improve the properties of these steels increasing the service temperature and the thermal stability is add a second particle phase. These particles can be oxides, carbides, nitrites or even solid solution of some chemical elements. On this way, this work aim to study the effect of addition of 3wt% of niobium carbide in the metallic matrix of 15Kh2MFA steel. Powder metallurgy was the route employed to produce this metallic matrix composite. Two different milling conditions were performed. Condition 1: milling of pure 15Kh2MFA steel and condition 2: milling of 15Kh2MFA steel with addition of niobium carbide. A high energy milling was carried out during 5 hours. Then, these two powders were sintered in a vacuum furnace (10-4torr) at 1150 and 1250°C during 60 minutes. After sintering the samples were normalized at 950°C per 3 minutes followed by air cooling to obtain a desired microstructure. Results show that the addition of niobium carbide helps to mill faster the particles during the milling when compared with that steel without carbide. At the sintering, the niobium carbide helps to sinter increasing the density of the samples reaching a maximum density of 7.86g/cm³, better than the melted steel as received that was 7,81g/cm³. In spite this good densification, after normalizing, the niobium carbide don t contributed to increase the microhardness. The best microhardness obtained to the steel with niobium carbide was 156HV and to pure 15Kh2MFA steel was 212HV. It happened due when the niobium carbide is added to the steel a pearlitic structure was formed, and the steel without niobium carbide submitted to the same conditions reached a bainitic structure

Monitoramento da morfologia costeira em setores da bacia potiguar sob influência da indústria petrolífera utilizando geodésia de alta precisão e laser escâner terrestre

The objective of this Doctoral Thesis was monitoring, in trimestral scale, the coastal morphology of the Northeastern coast sections of Rio Grande do Norte State, in Brazil, which is an area of Potiguar Basin influenced by the oil industry activities. The studied sections compose coastal areas with intense sedimentary erosion and high environmental sensitivity to the oil spill. In order to achieve the general objective of this study, the work has been systematized in four steps. The first one refers to the evaluation of the geomorphological data acquisition methodologies used on Digital Elevation Model (DEM) of sandy beaches. The data has been obtained from Soledade beach, located on the Northeastern coast of Rio Grande Norte. The second step has been centered on the increasing of the reference geodetic infrastructure to accomplish the geodetic survey of the studied area by implanting a station in Corta Cachorro Barrier Island and by conducting monitoring geodetic surveys to understand the beach system based on the Coastline (CL) and on DEM multitemporal analysis. The third phase has been related to the usage of the methodology developed by Santos; Amaro (2011) and Santos et al. (2012) for the surveying, processing, representation, integration and analysis of Coastlines from sandy coast, which have been obtained through geodetic techniques of positioning, morphological change analysis and sediment transport. The fourth stage represents the innovation of surveys in coastal environment by using the Terrestrial Laser Scanning (TLS), based on Light Detection and Ranging (LiDAR), to evaluate a highly eroded section on Soledade beach where the oil industry structures are located. The evaluation has been achieved through high-precision DEM and accuracy during the modeling of the coast morphology changes. The result analysis of the integrated study about the spatial and temporal interrelations of the intense coastal processes in areas of building cycles and destruction of beaches has allowed identifying the causes and consequences of the intense coastal erosion in exposed beach sections and in barrier islands

Significados e percepções de puérperas sobre as síndromes hipertensivas da gravidez e parto prematuro

Hypertensive syndromes in pregnancy (HSP) are configured as one of the major complications in the pregnancy and postpartum period and can lead premature newborn and subsequent hospitalization of the newborn to the Neonatal Intensive Care Unit (NICU). This study aimed to analyze the perceptions, meanings and feelings of mothers on the hypertensive syndromes in pregnancy and premature obstetric labor. The research was qualitative and has a theoretical methodological the Social Representations Theory(SRT) in the approach to the Central Nucleus Theory. The study included 70 women, mean age 29 years, predominantly school to high school, most of them married or in consensual union, primiparous and prevalence of cesarean delivery occurred between 32 and 37 weeks of pregnancy.The data were collected from may to december 2008 in the Maternity School Januário Cicco in Natal , and obtained through the following instruments for data collection: questionnaire including questions about socio-demographic status; the Free Words Association Test (FWAT) and and verbalized mental image construction used three stimuli: such as pregnancy with high blood pressure, preterm birth and NICU, and interview with the following guiding question: what it meant for you to have a pregnancy with high blood pressure and consequently the birth of a premature baby? Data analysis was performed using multi-method obtained from the data processing by EVOC (Ensemble Programmes Permettant L 'Analyze des Évocations) and ALCESTE (Analyse Lexicale par Contexte d'un Ensemble de Segment de Texte) and thematic analysis in categories. The results will be presented in four thematic units under the following representative universes: HSP, prematurity as a result of HSP, NICU and the social representations of mothers on the hypertensive disorder of pregnancy sequenced premature birth and hospitalization of the child in the NICU. The results obtained by multimethod analyses showed similar constructions and point to death as the central nucleus and negative aspects, coping strategies, need of care, knowledge about the disease, fragility and meanings of the NICU as peripheral elements. It is considered that the perceptions, meanings and feelings of puerperal women in relation to HSPs and to premature delivery are a negative social representation, with representational elements that may have influenced the adverse effects on the disease and its consequences. We suggest action on the peripheral elements of this representation, with adequate orientation, early diagnosis, effective conduct, receptive attitude on the part of the team, health promotion measures and effective public policies, in order to improve the care provided to puerperal women, making them feel welcome and minimizing their suffering

Estilo de vida individual de universitários jovens com excesso de peso da Universidade Católica de Murcia-Espanha

Individual lifestyle includes health and risk behaviors that can altar health status. Excess weight is a public health problem of modern civilization and there is an estimated mean prevalence of 45% in European countries. In Spain, the Murcia Region is an area of high morbidity and mortality from cardiovascular disorders. In this study we assess the differences in health and risk behaviors in ove/weight and normal weight undergraduates at the Universidad Católica San Antonio de Murcia (UCAM). Methods: Transversal design of parallel groups (overweight - cases and normal weight - control) , formed using the anthropometric technique. A questionnaire applied to a sample of 471 undergraduates of either sex, between the ages of 18 and 29 years, enrolled in 4 bachelor degree courses (ADE, CA, PER, PUB) at UCAM. We performed a standardized measurement of body mass (weight in kg), height (in meters) using a Seca® scale with calibrated stadiometer, waist and hip circumferences (in cm) with an inelastic tape and skinfolds thickness (triceps and subscapular in mm) with a Holtain® caliper, to calculate body mass index (BMI), waist-to-hip ratio (WHR) and the sum of skinfolds (SSF). We applied a lifestyle questionnaire about alcohol and tobacco consumption, knowledge and behaviors related to health indicators (arterial pressure and cholesterol), diet and physical activity. The information was collected in April and May, 2001 at the UCAM laboratory of Applied Nutrition. Statistical analysis: analysis of independent groups, contingency tables that reveal which qualitativa variables show differences and associations between the groups, Pearson's chi-square,and a significance levei of p < 0.05 followed by a residual analysis (1.96). Descriptive statistics (mean and standard deviation) were used to establish the two groups: case and contrai with 65 men and 26 women each who had BMI < 25 kg/m2. Results: A total of 65 of the men assessed (14%) and 26 (6%) of the women were overweight. Mean body mass index of the case group was 27. 78 ±: 2.83 kg/m2 in the men and 26.26 ± 1.37 kg/m2 in the women, while contrai group men had mean BMI of 22.36 ± 1.72 kg/m2, while for the women it was 20.76 ±: 2.13 kg/m2. The self-declared values of weight and height were underestimated, but with high accuracy, sensitivity and specificity. Thus, these can be used to calculate the BMI of overweight Spanish undergraduates. Regular vigorous physical activity was observed only in normal weight men. The analysis showed the following significant differences for the qualitativa variables of the two groups. The contrai group was interested in arterial hypertension, believed that they were not overweight, that they had no abdominal fat, and had not considered controlling 'fatty food consumption. Those who thought of controlling it sometimes, did so without professional help. However, part of the overweight group believed that they were overweight and had abdominal fat between average and considerable, had often or always considered controlling fatty foods and had often or always tried to control consumption with the help of professionals. They had always thought of engaging in physical activities, unlike the normal weight individuals. Nearly all (95%) of the overweight undergraduates and most (75%) of the normal weight group reported that they sometimes or always controlled fatty food ingestion. Mean physical activity was nearly twice as high in the summer than in the winter. Conclusions: The overweight undergraduates in this sample displayed a lifestyle with a greater number of healthy behaviors when compared to normal weight individuals

Métodos para estudo das respostas metabólicas de cães e gatos a diferentes alimentos

Durante o processo de assimilação e uso dos alimentos, diferentes respostas metabólicas podem ser desenvolvidas pelo organismo dos animais. Estas respostas são fruto da integração de mecanismos complexos, que envolvem os sistemas neuro-endócrino e o funcionamento dos órgãos, sendo influenciadas pela dieta, espécie animal, idade, condição fisiológica e composição corporal. Este trabalho enfoca a importância fisiológica e os métodos de estudo das respostas pós-prandiais aos carboidratos, bem como as alterações fisiológicas conseqüentes ao balanço eletrolítico da dieta. A quantidade, estrutura química e processamento industrial do amido determinam boa parte da resposta pós-prandial de glicose e insulina de cães. em gatos, outros mecanismos parecem ser mais importantes, como a ingestão de aminoácidos. A fibra alimentar também altera a resposta pós-prandial ao alimento, devendo ser consideradas sua quantidade, solubilidade e fermentabilidade no desenvolvimento das dietas. Os métodos de estudo destas respostas incluem avaliação das respostas glicêmica e insulínca pós-prandiais, teste endovenoso de tolerância à glicose e à arginina. O clâmp euglicêmico apresenta-se também como ferramenta de estudo, no entanto revela informações mais relacionadas ao animal do que à dieta. A compreensão do conjunto de alterações metabólicas aos carboidratos é importante no estudo do controle da saciedade, composição corporal e inúmeras doenças degenerativas e endócrinas. A concentração e relação entre os macro-elementos da dieta (Na, Cl, K, P, Ca, Mg e S) e dos aminoácidos sulfurados (metionina, cistina e taurina) interferem em inúmeras funções orgânicas, como a cardiovascular, neuromuscular, metabolismo ósseo, renal e pulmonar, refletindo-se no equilíbrio hidro-eletrolítico e ácido-básico orgânicos. de importância prática para cães e gatos encontram-se a relação destes nutrientes com cardiopatias, nefropatias, osteodistrofias e urolitíases. A relação entre os macro-elementos é estabelecida em mmol/kg de matéria seca da dieta, calculando-se seu balanço cátion-ânion (excesso de bases ou ânions dietéticos não determinados). Suas repostas orgânicas são medidas, dentre outros métodos, pela hemogasimetria, balanço hídrico, mensuração do volume dos espaços extracelular e vascular, supersaturação e pH urinários.

Processamento mínimo em goiabas 'Paluma' e 'Pedro Sato': 2. Avaliação química, sensorial e microbiológica

Foram utilizados frutos de goiabeiras das cultivares Pedro Sato e Paluma, provenientes de pomar comercial, no estádio de maturação de vez, correspondente à coloração verde-mate e considerados ótimo para o consumo. Os frutos foram inicialmente imersos em solução de hipoclorito de sódio (150mg de cloro.L-1) por 5 minutos, para desinfecção superficial. Pessoas treinadas, utilizando proteção adequada e equipamentos desinfetados descascaram os frutos, cortaram-nos longitudinalmente ao meio e eliminaram a polpa com as sementes, em ambiente a 12°C. Após enxágüe com água clorada (20mg de cloro.L-1) foram embalados em contentores de tereftalato de polietileno (PET) com tampa. Estas unidades foram armazenadas a 3°C por 10 dias. Foram realizadas análises microbiológicas ao longo do período. Determinaram-se quimicamente os conteúdos de lignina, ácido ascórbico, acidez total titulável, sólidos solúveis totais e porcentagem de solubilização das pectinas, bem como as variáveis sensoriais de textura, sabor e preferência. A textura tornou-se mais frágil e os conteúdos de ácido ascórbico se reduziram, ao longo do período de armazenamento, nos produtos de ambas as cultivares. Durante este período houve aumento no conteúdo de lignina e manutenção dos conteúdos de sólidos solúveis totais (SST), acidez total titulável (ATT) e da relação SST/ATT. O produto da cultivar Pedro Sato apresentou menor perda de textura que o da 'Paluma', sendo considerado pelos provadores como o mais saboroso e, portanto, o mais preferido. Devido aos cuidados higiênicos tomados durante o processamento o produto apresentou baixa contagem microbiana (< 10³ UFC.g-1), em todas as avaliações efetuadas.

Processamento mínimo de mamão 'formosa'

Este trabalho foi conduzido para verificar o efeito do tamanho do corte, 2,5 x 2,5cm (corte 1) e 2,5 x 5,0cm (corte 2), e da temperatura de armazenamento (3, 6 e 9ºC), na velocidade da modificação da atmosfera ambiente e nas características químicas de mamões do grupo `Formosa' minimamente processados e embalados em copos plásticos (500ml). A concentração de CO2 no interior destes copos aumentou 2 a 3 vezes, durante as primeiras 6 horas após o corte, para depois diminuir e se estabilizar. Esta concentração aumentou com o aumento da temperatura de armazenamento. A umidade dos pedaços diminuiu consideravelmente nos dois primeiros dias, e a temperatura que melhor conservou a umidade foi a de 6ºC. A acidez total titulável foi menor no corte 2, com as maiores reduções a 6 e 9oC. Os teores de sólidos solúveis totais não variaram entre os tratamentos, e os cuidados higiênicos adotados durante o processamento permitiram a obtenção de produtos com baixa contagem microbiana, 10³UFC.g-1 nos pedaços armazenados a 9ºC após sete dias, e com boa manutenção da qualidade sensorial das mesmas. Estes resultados permitem indicar o mamão `Formosa' para a produção de produtos minimamente processados, na forma de pedaços, com conservação refrigerada (3 e 6ºC ) por um período de 7 dias.