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Rheologentagung 2003 Meeting of the German Society of Rheology

Surface modification of titanium by plasma nitriding

A systematic investigation was undertaken on commercially pure titanium submitted to plasma nitriding. Thirteen different sets of operational parameters (nitriding time, sample temperature and plasma atmosphere) were used. Surface analyses were performed using X-ray diffraction, nuclear reaction and scanning electron…

Aspectos microscópicos da influência dos processos de esterilização em pontas diamantadas

This paper shows a study about the influence of type and number of sterilizations in the cutting ability of diamond points used in dentistry. As a result, the sterilization using the oven was the process, which didn't result in a decreasing in the cutting ability of the diamond points and, until the second sterilizati…

Microhardness and chemical composition of human tooth

Hardness of human tooth, both in enamel and dentin, has been measured at different sites using a Vicker's diamond. In this work we show that these values are almost constant all along the enamel and dentin thicknesses. Indentations were done from outer enamel surface to inner dentin layer, going through the enamel-den…

Tailoring activated carbon by surface chemical modification with O, S, and N containing molecules

In this work the surface of activated carbon was chemically modified in order to introduce O, S and N containing groups. The activated carbon surface was selectively oxidized with concentrated HNO3 under controlled conditions. Characterization by thermogravimetric analyses, infrared spectroscopy and NaOH titration sug…

Editorial

Teste in vitro de citotoxicidade: estudo comparativo entre duas metodologias

A avaliação in vitro da biocompatibilidade de diferentes tipos de biomateriais foi realizada pelo teste de citotoxicidade em cultivo de células de tecido conectivo de camundongos, NCTC Clone 929 da American Type Culture Collection. O estudo comparativo do ensaio de citotoxicidade foi realizado com duas metodologias: 1…

Surface composition analysis of PP films treated by corona discharge

Polypropylene films (PP) surface treated by corona discharge in air was analyzed to verify the changes on surface composition. The presence of oxidized polar groups on the film surface, mainly, C=O, C-O and COH, was confirmed by infrared spectroscopy (FTIR/ATR) and atomic force microscopy (AFM) revealed a dramatic cha…

Congresos, Seminarios y Cursos

Weathering effects on materials from historical stained glass windows

A selection of materials (stained glasses, lead cames, support elements and putty) from historical stained glass windows of different periods (13th-19th centuries) have been studied. Optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray diffraction were used as characterizati…

Modifications in concrete superficial properties due to the use of different formworkrelease agents and plastic additives

The actual research study, carried out in the Laboratory of Construction Materials of the ETSAM., analyses the modifications in superficial properties (regarding colour and texture) of grey Portland cement mortars due to the use of different formworks release agents (car oil, mineral oil and paraffin) and to the addit…

Diffusion of the 65Zn radiotracer in ZnO polycrystalline ceramics

Zinc self-diffusion coefficients were measured in polycrystalline ZnO of high density (>99% of the theoretical density) and of high purity (> 99.999%). The diffusion experiments were performed from 1006 to 1377 °C, in oxygen atmosphere, for times between 16 and 574 h. The diffusion profiles were established by means o…

Evaluación de la dureza superficial en amalgamas en función de tipos de aleaciones, momentos y tipos de pulimentos

The aim of this study was to analyze in vitro surface hardness (micro-indentation tester Wolpert) of different types of amalgam alloys varying the technique and polishing time. Tested were the amalgam: Velvalloy, Permite e Dispersalloy. For each material, 2 polishing techniques were accomplished: T1 (bladed finishing…

Blendas biodegradáveis de poli(3-hidroxibutirato)/poli(e-caprolactona): obtenção e estudo da miscibilidade

Due to its biodegradability, poly(3-hydroxybutyrate) P(3-HB) has attracted much attention in the environmental sector. However, some characteristics of this polymer, such as high crystallinity, poor processability and high brittleness, have lead several research groups to study polymeric blends in order to modify P(3-…

Preparation of highly dispersed Ru-Sn bimetallic supported catalysts from the single source precursors Cp(PPh3)2Ru-SnX3 (X = Cl or Br)

In this work highly dispersed Ru-Sn bimetallic catalysts have been prepared from organobimetallic Cp(PPh3)2Ru-SnX3 (X = Cl or Br) complexes. These single source precursors can be easily impregnated in high surface area supports, such as activated carbon and sol-gel SiO2, and upon controlled thermal treatment the ligan…

Nonohmic behavior of SnO2.MnO2-based ceramics

The present paper describes the nonohmic behavior of the SnO2.MnO-based system and analyzes the influence of the sintering time and the Nb2O5 concentration on this system's electrical properties. A nonlinear coefficient of ~7 was obtained for a 0.2 mol%-doped Nb2O5 composition, which is comparable to other values repo…

Application of an artificial neural network to ready-mixed concretes mix design

This paper presents the practical application of cm artificial neural network (ANN) to the problem of concrete mix in a factory. After a brief introduction to the complex problem of concrete mixes design and a quick review of the fundamental basis of neurocomputation, an optimal neural network model has been developed…

Sintesis de ceramicos de ZnO dopados con praseodimio y cobalto

Zinc oxide, ZnO, is a very interesting compound in science and electronic ceramics technology. ZnO ceramics containing some additives were reported to show varistor action with excellent nonlinearity in current - voltage characteristics. However, investigations were restricted to the ZnO - Bi2O3 ceramic system. Other…

Erratum

Comparative study of high temperature oxidation behaviour in AISI 304 and AISI 439 stainless steels

This work deals with a comparison of high temperature oxidation behaviour in AISI 304 austenitic and AISI 439 ferritic stainless steels. The oxidation experiments were performed between 850 and 950 °C, in oxygen and Ar (100 vpm H2). In most cases, it was formed a Cr2O3 protective scale, whose growth kinetics follows a…