Structural and mechanical properties of graded composite Al2O3/Ni obtained from slurry of different solid content

AbstractIn this work, an alumina-nickel graded hollow cylinders were prepared by the centrifugal slip casting. In the paper, the results for samples formed from slurries with different solid content: 45 vol.%, 40 vol.% and 35 vol.% are presented. The structure of the samples after sintering was examined by X-ray diffraction (XRD). The microstructure of the composite, especially the nickel particle size distributions were investigated by using scanning electron microscopy (SEM). An image analyzer has been used for the measurement of volume fraction of the nickel particles in the composites. The hardness was measured by using a Vickers hardness-testing. Based on hardness measurements KIC value were determined. The XRD results confirmed only two phases: Ni and α-Al2O3 in all samples. The preliminary macroscopic observation as well as SEM showed, that the microstructure of the sample cross-section is not homogeneous. Microstructural characterization revealed the gradation of nickel content along the radial direction of hollow cylinder. Three zones were distinguished, from outer surface towards the inner side of the tube. The maximum of volume fraction of nickel particles was obtained at the middle zone of the composites. The results of hardness-testing revealed that the maximum hardness values were observed in region at the inner edge of the casting due to an absence of nickel particles

Effet du chlore sur la colonisation bactérienne d'un réseau expérimental de distribution d'eau

La contamination bactérienne de la phase eau d'un réseau de distribution résulte d'une multiplication des bactéries sur les parois des canalisations d'eau (biofilms) suivie de leur arrachage et de leur transport dans le flux circulant. Ce travail met en évidence l'effet du chlore, d'une part, sur la formation des biofilms et, d'autre part, sur des biofilms déjà constitués. Des éprouvettes de matériaux neufs introduites dans des eaux présentant des concentrations en chlore total variant de 2,4 à 0,02 mg/l et véhiculant entre 0,5 x 106 et 5 x 105 cellules bactériennes/mi (dont 1 à 10 % de bactéries cultivables) sont rapidement colonisées (106 à 108 cellules/cm2). L'effet du chlore est sensible sur les cellules totales pour des concentrations de l'ordre de 1 à 2,4 mg/l. Sur les bactéries cultivables, un ralentissement de la croissance du biofilm est observé dès 0,3 mg/1 de chlore total. Par contre, des résiduels de 0,02 ou 0,05 mg/l sont sans effet sur la cinétique de formation des biofilms. Des résiduels moyens de chlore total compris entre 2,3 et 3,4 mg/l appliqués en continu pendant 14 jours sur un biofilm constitué d'environ 8,7 x 106 cellules par cm2 (1,7 % de bactéries cultivables), entraînent l'élimination d'environ 90 % des bactéries fixées (abattement d'1 logarithme) durant les premiers jours d'exposition. L'altération du biofilm exposé à un résiduel de chlore total de l'ordre de 1,3 mg/l est identique, mais toutefois plus étalée dans le temps. Ces essais réalisés sur des éprouvettes de PVC, PE et mortier de ciment n'ont pas permis la mise en évidence de comportements différents de ces 3 supports..Bacterial accumulation in drinking water systems results both of cell deposition on the pipe walls and attached bacteria growth. The presence of a complex biofilm (cells embedded in a matrix of exopolymers) leads to a continuous contamination of the water phase resulting from the erosion of the attached growing biomass. Then, many tentatives to lmit the formation of such a biofilm have been suggested as the removal of biodegradable organic matter fram water or as the application of disinfectant. However, the efficiency of chlorination of the distribution system is debatable. Indeed, adhesion is often described as a factor of protection of attached bacteria which counterbalances the expected effect of disinfectant. Then, the aim of this experimental work is using a model distribution system to evaluate (i) the kinetics of biofilm accumulation on coupons of new materials (Polyvinyl chlorure : PVC, polyethylene : PE, cement) disposed in a constantly chlorinated system (residual total chlorine from 0.021o 2.4 mg. l-1), (ii) the effect of chlorination on previously accumulated biofilms.The industrial pilot plant used in this study is comprised of five loops serially disposed (fig. 1). From previous study of simulation, one may assume that each loop works like a perfectly mixed reactor when the whole pilot plant is equivalent to an infinite tubular reactor with high axial dispersion coefficient. During the experiment, the pilot was continuously fed with finished drinking water front the surface water treatment plant of city of Nancy (i.e. natural finished water with its own chlorine demand, organic nutrients and heterotrophic bacteria).Total number of cells (epifluorescence counts) and heterotrophic plate count bacteria (15 days of incubation at 20 °C) were enumerated both in the water and, after sonication, on the surface of the coupons of tested materials.The first experimentations show that chlorine slows clown the kinetic of deposition of bacteria onto the pipe wall but never prohibits biofilm formation. When the drinking waters carried from 2.4 to 0.02 mg.1-1 of chlorine and from 0.5 to 5 x 105 ml-1 bacterial cells, biofilm is observed after 24 hours of immersion of the coupons with at least 101 to 106 bacteria/cm2. Respectively, the deposition or/and growth rates of total cells are drastically affected only for chlorine residual as high as 1 to 2.4 mg. 1-1. The number of heterotrophic plate count of the biofilm is affected with lower chlorine residual (around 0.3 mg.1-1) but residual concentration as low as 0.05 mg.1-1 are ineffective.The tentatives carried out in the second experience on preformed biofilms (2 months old biofilms, 8.7 x 106 cells/cm2) show that the continuous application of 2.3 to 3.4 mg. 1-1 of residual chlorine for 14 days, leads to the removal of only 90 % of attached total cells without modifications of the proportion of attached alive bacteria (around 1.7 %) into the biofitm. In other wards, a highly chlorinated networks shows at minima 106 attached cells/cm2. Its generally takes several days to reply to the chlorine demand of the system and to have a quasi steady state reactor in terms of residual chlorine.These assays carried out with three types of coupons (PVC, PE, cement lined cast iron) did not show any difference between the tested materials.The limited efficiency of chlorine against the biofilm can be explained by transfert limitations within the visquous layer, high consumption of chlorine by the biopolymers of the attached matrix (proteins...) or low sensitivity to the disinfectant of the slow growing attached bacteria. Then chlorination is really not a panacea in biofilm war but has to be applied in combination with other methods as biodegradable organic matter removal, hydraulic regime improvement..

Quantitative Description of the Spinel Phase (NiAl2O4) Located into Al2O3 Matrix

The presented work focuses on the quantitative description of the spinel phase (NiAl2O4) located into Al2O3 matrix. Three series of samples were prepared. Series I, II and III containing following amount of nickel powder: 0.21% vol, 0.43% vol and 1.3% vol respectively. In order to obtain nickel aluminate spinel sintering was carried out in an oxidizing atmosphere (air). Based on the SEM observation and XRD analysis the presence of spinel phase was confirmed in all samples. Difference in volume fraction of the Ni in the compacts before sintering, resulted in the different content of the spinel phase in the final material. All tested composites were characterized by homogeneous distribution of NiAl2O4 in the whole volume of the material. The purpose of the study was also the use the stereological analysis to determine the shape parameters of new phase

Identification of 1BL/1RS translocation and 1B/1R substitution using STS-PCR markers and C-banding in wheat

W pracy identyfikowano translokację 1BL/1RS w polskich odmianach pszenicy oraz substytucję 1B/1R w linii 'Grana'/'Dańkowskie Złote', stosując markery cytologiczne i molekularne. Analizując rozmieszczenie prążków heterochromatynowych w chromosomach, zidentyfikowano substytucję 1B/1R w linii 'Grana'/'Dańkowskie Złote' oraz translokację 1BL/1RS w odmianach 'Aleta', 'Jubilatka', 'Lama', 'Lanca', 'Olma', 'Weneda' i "Wilga'. Wyniki te potwierdzono przy pomocy metody STS-PCR. Zastosowano dwa startery J07IF1 (5'-TAAGCC- GTAAAGCATGGTGCAC-3') i J07IR1 (5 '-CTTCAACGAATGTTTTCCTC- TTC-3') specyficzne dla krótkiego ramienia chromosomu 1R. Po zakończeniu reakcji i rozdzieleniu za pomocą elektroforezy stwierdzono obecność prążka o wielkości 1200 par zasad (pz) tylko w odmianach: 'Aleta', 'Jubilatka', 'Lama', 'Lanca', 'Olma', 'Weneda' i 'Wilga' oraz w linii substytucyjnej 'Grana'/'Dańkowskie Złote' a także w życie odmiany 'Dańkowskie Złote'.In the paper the translocation 1BL/1RS in Polish wheat cultivars and substitution 1B/1R in 'Grana'/'Dańkowskie Złote' line were identificated using cytological and molecular markers. On the basis C-banding method the substitution 1B/1R in 'Grana'/'Dańkowskie Złote' line and the translocation 1BL/1RS in 'Aleta', 'Jubilatka', 'Lama', 'Lanca', 'Olma', 'Weneda' and 'Wilga' cultivars were identificated. These results were confirmed using the STS-PCR method. Two primers J07IF1 (5'-TAAGCCGTAAAGCATGGTGCAC-3') and J07IR1 (5'- CTTCAACGAATGTTTTCCTCTTC-3'), specific to short arm of 1R chromosome were used. After the reaction and the electrophoretic separation, the presence of a fragment of the size 1200 bp was found only in the cultivars 'Aleta', 'Jubilatka', 'Lama', 'Lanca', 'Olma', "Weneda' and 'Wilga' as well as in 'Grana'/'Dańkowskie Złote' substitution line and in 'Dańkowskie Złote' rye

Quantitative Description of the Spinel Phase (NiAl2O4) Located into Al2O3 Matrix

The presented work focuses on the quantitative description of the spinel phase (NiAl2O4) located into Al2O3 matrix. Three series of samples were prepared. Series I, II and III containing following amount of nickel powder: 0.21% vol, 0.43% vol and 1.3% vol respectively. In order to obtain nickel aluminate spinel sintering was carried out in an oxidizing atmosphere (air). Based on the SEM observation and XRD analysis the presence of spinel phase was confirmed in all samples. Difference in volume fraction of the Ni in the compacts before sintering, resulted in the different content of the spinel phase in the final material. All tested composites were characterized by homogeneous distribution of NiAl2O4 in the whole volume of the material. The purpose of the study was also the use the stereological analysis to determine the shape parameters of new phase

Microstructure Characterization of Composite from ZrO2 – Ti System

In this work the microstructure analysis of composite from ZrO2 – Ti system were presented. For the preparation of the composite samples nanometric ZrO2 powder stabilized by 3 mol% of Y2O3 and micrometric titanium powder were used. The composites with 10 vol.% addition of titanium particles were prepared by slip casting method. The sintering process was conducted at 1450°C with 2 hours’ dwell time, in the inert atmosphere of argon. The microstructure observations were carried out with the use of SEM and STEM microscopes. The quantitative analysis and stereological characterization were performed. The SEM and STEM observations allowed characterizing the microstructure of composite samples. Especially, the interface between titanium particles and zirconia matrix was described. The growth of the zirconia grains around the Ti rich areas was observed. The increase of the zirconia grains size results from the reaction on the interface between titanium particle and zirconia matrix during the sintering process

Formation the gradient composite from the ceramic-metal system by centrifugal slip casting

Zapotrzebowanie na nowe materiały kompozytowe nieustanie się zwiększa. Rosną również oczekiwania odnośnie jakości nowych kompozytów oraz metod ich wytwarzania. Aktualnie kierunki rozwoju w zakresie wytwarzania materiałów kompozytowych koncentrują się na poprawie właściwości oraz opracowaniu nowych metod pozwalających wytwarzać kompozyty gradientowe. Głównym problemem stawianym przed inżynierami podczas projektowania kompozytów gradientowych jest kontrolowanie rozmieszczenia cząstek wzdłuż wybranego kierunku. Jedną z metod pozwalających uzyskać kompozyt gradientowy z układu ceramika-metal jest odlewanie odśrodkowe mas lejnych (ang. centrifugal slip casting). Metoda ta łączy w sobie klasyczne odlewanie z gęstwy z działaniem siły odśrodkowej. Pozwala na wytworzenie gotowego wyrobu w kształcie tulei. Wytworzone kompozyty charakteryzują się gradientową budową. Prace prowadzone były dla układu Al2O3-Ni. Na ich przekroju można dostrzec trzy strefy różniące się rozmieszczeniem cząstek niklu.Demands for new composite materials are continuously increasing, as well as quality requirements for the new composites and methods of their preparation. Currently, directions of development in the production of composite materials focus on improving the properties and inventing of new methods to produce graded composites. The main problem for the engineers designing functionally gradient composites, is to control distribution of the particles along the gradient direction. One of the method to obtain FGM ceramicmetal composite is the centrifugal slip casting. This method combines the classical slip casting with the centrifugal force. It allows the production of finished products in the shape of a hollow cylinder. This investigation was carried out for the Al2O3-Ni system. The resulting composites are characterized by microstructure with the gradient concentration of nickel particles, which has a three-zone microstructure

Microstructure Characterization of Composite from ZrO2 – Ti System

In this work the microstructure analysis of composite from ZrO2 – Ti system were presented. For the preparation of the composite samples nanometric ZrO2 powder stabilized by 3 mol% of Y2O3 and micrometric titanium powder were used. The composites with 10 vol.% addition of titanium particles were prepared by slip casting method. The sintering process was conducted at 1450°C with 2 hours’ dwell time, in the inert atmosphere of argon. The microstructure observations were carried out with the use of SEM and STEM microscopes. The quantitative analysis and stereological characterization were performed. The SEM and STEM observations allowed characterizing the microstructure of composite samples. Especially, the interface between titanium particles and zirconia matrix was described. The growth of the zirconia grains around the Ti rich areas was observed. The increase of the zirconia grains size results from the reaction on the interface between titanium particle and zirconia matrix during the sintering process