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Effect of the acid environment on the electrochemical behaviour of 1045 steel r...
Nóbrega, Ana Cecilia Vieira da; Rocha, L. A.; Avila, E. A.; Martinelli, A. E.; Melo, D. M. A.; Sá, Maria das Vitórias Vieira Almeida deExternal corrosion is one of the most common causes of oilwell casing failure. Hostile environments can be due to acidizing treatments. Although it is common to add corrosion inhibitors and oxygen scavengers in acidic solutions to control external casing corrosion, their real efficiency is unknown yet. Therefore, it is important to establish how aggressive to steel are the different hostile environments to help...
Comportamento tribocorrosivo de sistemas metalocerâmicos odontológicos de Ni-Cr...
Araújo, A. M. A.; Martinelli, A. E.; Nascimento, R. M.; Melo, D. M. A.; Medeiros, A. L.; Rocha, L. A.; Avila, E. A.Partial fixed prosthodontic restoration is used to rehabilitate both the form and function of partial or total compromised teeth and must remain permanently joined to the remaining teeth. The most useful material in prosthodontics is feldspar porcelain, commercialized as aluminosilicate powders. Dental porcelains depict limited mechanical strength to rehabilitate extensive spaces. The association of porcelain w...
A correlation between Bogue's equations and Taylor's procedure for the evaluati...
Bezerra,U. T.; Martinelli,A. E.; Melo,D. M. A.; Melo,M. A. F.; Lima,F. M.The crystalline composition of Portland cement clinker is commonly established by Bogue's equations, which are based on a series of assumptions that seldom apply to oilwell cements. This is probably due to the presence of additional oxides and phase reconversion upon cooling of the clinker from the calcination temperature. Important differences are therefore observed between the numerical values yielded by the ...
Total catalytic wet oxidation of phenol and its chlorinated derivates with MnO2...
Luna,A. J.; Rojas,L. O. A.; Melo,D. M. A.; Benachour,M.; Sousa,J. F. deIn the present work, a synthetic effluent of phenol was treated by means of a total oxidation process-Catalyzed Wet Oxidation (CWO). A mixed oxide of Mn-Ce (7:3), the catalyst, was synthesized by co-precipitation from an aqueous solution of MnCl2 and CeCl3 in a basic medium. The mixed oxide, MnO2/CeO2, was characterized and used in the oxidation of phenol in a slurry reactor in the temperature range of 80-130ºC...
Synthesis and characterization of lanthanum- and yttrium-doped Fe2O3 pigments
Melo,D. M. A.; Melo,M. A .F.; Martinelli,A. E.; Silva,Z. R.; Cunha,J. D.; Lima,A. C.Iron oxide has been doped with rare earth ions (yttrium or lanthanum) aiming at producing ceramic pigments with hues that vary from orange to brown. The powders were synthesized from polymeric precursors using the Pechini method and subsequently calcined between 900 and 1100 ºC. The resulting pigments were characterized by BET, X ray diffraction, colorimetric analysis, UV-visible, infrared (FTIR), particle size...
Influência da temperatura de infiltração de alumínio gasoso em ligninocelulósic...
Andrade Jr.,T. E.; Rambo,C. R.; Sieber,H.; Martinelli,A. E.; Melo,D. M. A.A conversão de materiais ligninocelulósicos em cerâmicas biomórficas tem despertado particular interesse, por tratar-se de uma nova classe de materiais cerâmicos de alto valor agregado, produzidos a partir de matérias-primas de baixo custo e relevante papel econômico. Cerâmicas biomórficas são obtidas por meio do processo de biomodelagem, que consiste na reprodução ao nível micrométrico da estrutura natural do ...
Photoluminescence in ZrO2 doped with Y and La
Sousa,W. S. C. de; Melo,D. M. A.; Silva,J. E. C. da; Nasar,R. S.; Nasar,M. C.; Varela,J. A.This study aims to describe the synthesis and optical characterization of a nanometric zirconium oxide solid solution containing yttrium and lanthanum. Zirconium citrate, yttrium nitrate and lanthanum nitrate were mixed in the ratios: 94 mol% of ZrO2 - 6 mol% of Y2O3 and 92 mol% of ZrO2 - 6 mol % of Y2O3 - 2 mol % of La2O3. FTIR analysis shows organic material in decomposition and thermal analysis shows the tra...
Structural and morphological characterization of rare earth modified lead titanate
Lemos,F. C. D.; Melo,D. M. A.; Lima,P. S. de; Paskocimas,C. A.; Longo,E.; Silva,J. E.C. daRare earth modified lead titanate powders Pb1-xRExTiO3 (REPT), x = 0.01, 0.05, 0.07 and RE = Yb, Y, were prepared by the Pechini method. The materials were calcined under flowing oxygen at different temperatures from 300 to 700 ºC. Nanostructured REPT were investigated using X-ray diffraction, scanning electron microscopy and surface area analysis (BET). The results suggest that the modifier cation incorporated...
Room temperature photoluminescence of (RE)NiO3 (RE=La, Y, Er, Ho, Nd and La1-xYx)
Silva,Z. R.; Melo,D. M. A.; Lima,A. C.; Longo,E.; Melo,M. A. F.; Martinelli,A. E.The nature of visible photoluminescence (PL) at room temperature in amorphous (RE)NiO3 (RE=La, Y, Er, Ho, Nd and La1-xYx) is discussed. Powders of this system were prepared by the polymeric precursor technique. The presence of broad PL band emission spectra at room temperature indicated increasing structural order with addition of rare earth elements.
Caracterização e uso de xisto para adsorção de chumbo (II) em solução
Pimentel,P. M.; Silva Jr.,C. N.; Melo,D. M. A.; Melo,M. A. F.; Maldonado,G.; Henrique,D. M.Existe um grande interesse no uso de materiais de baixo custo para remoção de metais pesados em águas residuais. Novas técnicas de processamento e adsorventes incluindo argilas, resinas sintéticas, turfa e quitosana tem sido estudados objetivando substituir o carvão ativado. No presente trabalho, xisto retortado (XR), um rejeito sólido da transformação térmica do xisto oleígeno, foi caracterizado com o objetivo...
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