Materials Literature
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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…
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…
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…
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…
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…
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…
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…
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-…
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…
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…
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…
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…
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…
An investigation was carried out on the room temperature ageing of off-stoichiometric DGEBA/TETA epoxy formulations. The results obtained show that the epoxy rich mixtures have their inherent brittleness increased by the ageing treatment due to recrystalization of the unreacted epoxy monomers, although homopolymerizat…
The crystal structure and magnetic and electric transport properties of polycrystalline La 0.50 D 0.50 MnO 3−γ manganites (D=Ca, Sr) were studied experimentally depending on the concentration of oxygen vacancies. The La 0.50 Sr 0.50 MnO 3−γ system of anion-deficient compositions was found to be stable and possess a pe…
Abstract FTIR spectroscopy has been applied to NH 4 + -exchanged dioctahedral clay minerals to determine the molecular environment of NH 4 + and to quantify N concentration. FTIR under vapourpressure control, coupled with heating and freezing treatments has shown that NH 4 + ion symmetry varies with the nature of clay…
Thermally reversible adhesives are prepared through the reaction of aliphatic diamines and a diepoxy compound containing two Diels-Alder adducts. The diepoxy compound is formed via the Diels-Alder reaction between two epoxy-containing furans and a bismaleimide. The adhesive displays a T g of m 40°C and a constant shea…