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Synthesis and Characterization of Silsesquioxane-Based Polymer Hybrids with Controlled Structure

Ricardo O.R. Costa、Wander L. Vasconcelos、Richard M. Laine2002-09-01Materials Research

We have developed a method to obtain polymer hybrids with control of inorganic content and molecular configuration. Hybrid poly(methyl methacrylate) (PMMA) was obtained via atom transfer radical polymerization (ATRP) initiated by octafunctional cubic silsesquioxanes using CuCl as catalyst. Two different ATRP initiator…

Alkaline cement mortars. Chemical resistance to sulfate and seawater attack

F. Puertas、R. Gutiérrez、A. Fernández-Jiménez 等 5 位作者2002-09-01Materiales de Construccion

The durability and chemical resistance of alkali activated slag and fly ash/slag mortars in contact with sulfates and seawater media have been studied. Two methods were used in the evaluation of such durability: Kock-Steinegger and ASTM C1012. A mineralogical and a microstructural characterization of mortars were done…

Bioactive Hierarchical Structures for Genetic Control of Bone Morphogenesis

Pilar Sepulveda、Larry L. Hench2002-09-01Materials Research

For thirty years it has been known that certain compositions of Na2O-CaO-P2O5-SiO 2 glasses will form a mechanically strong, chemical bond to bone. These materials have become known as bioactive glasses and the process of bonding is called bioactive fixation. Bioactive glasses are widely used clinically in the repair…

Effects of High Temperature on the Residual Performance of Portland Cement Concretes

Evandro Tolentino、Fernando S. Lameiras、Abdias M. Gomes 等 5 位作者2002-09-01Materials Research

In this work we analyzed the "residual" performance of Portland cement concretes heat-treated at 600 °C after cooling down to room temperature. Concretes with characteristic compressive strength at 28 days of 45 MPa and of 60 MPa were studied. The heat-treatment was carried out without any imposed load. We measured th…

The use of a non-standard high calcium fly ash in concrete and its response to accelerated curing

C. D. Atis、C. Bilim、F. Ozcan 等 5 位作者2002-09-01Materiales de Construccion

An experimental work was carried out to investigate the use of a non-standard high calcium fly ash in concrete. The response of the same fly ash to the accelerated curing was also explored. With three different cementitious material contents, a total of 48 concretes were produced. The water/ cement ratios were varied…

In Vivo Evaluation of Hydroxyapatite Foams

P. Sepulveda、A.H. Bressiani、J.C. Bressiani 等 5 位作者2002-09-01Materials Research

Porous hydroxyapatite manufactured by foaming of aqueous ceramic suspensions and setting via gelcasting of organic monomers was tested for in vivo biocompatibility in rabbit tibia for a period of 8 weeks. The foams provide tortous frameworks and large interconnected pores that support cell attachment and organisation…

Microstructural Characterization of Reaction Products on Iron Based Alloys Exposed to H2/H2S Atmospheres at High Temperatures

Marina F. Pillis、Lalgudi V. Ramanathan2002-09-01Materials Research

Thermogravimetric measurements in H2/H2S environments for up to five hours were carried out to determine the sulphidizing behavior of Fe-20Cr and Fe-20Cr-0.7Y alloys. These measurements helped to determine the mechanism of sulphidization in the early stages. The reaction products were characterized using a scanning el…

Tests to characterize the behaviour of natural stone in contact with water

C. Vielba Cuerpo、F. Hernández Olivares2002-09-01Materiales de Construccion

This paper presents an experimental analysis of the stone behaviour in contact with water in the different construction uses. In any of these cases is analyse how the water penetrates into the material. As a result of the study the need of modification of the UNE test standards is concluded. It is proposed a procedure…

Numerical Characterization of Concrete Heterogeneity

Roque Luiz Pitangueira、Raul Rosas e Silva2002-09-01Materials Research

In this paper, a finite element model including both material heterogeneity and size effects is presented. The concrete is considered as a statistical combination of constituent phase with different properties (aggregate, mortar and interface material). The material point response is based on a combination of the rand…

Interaction Between Second-Phase Particle Dissolution and Abnormal Grain Growth in an Austenitic Stainless Steel

J.C. Dutra、F. Siciliano Jr.、A.F. Padilha2002-09-01Materials Research

The continuing development of stainless steels has resulted in complex steel compositions with substantial amounts of alloying elements. The benefits of such additions invariably come attached to unavoidable disadvantages. One of the most critical item is the potential microstructural instability of the material. Allo…

Stochastic Effects in Microstructure

M.E. Glicksman、K.G. Wang、P. Crawford2002-09-01Materials Research

We are currently studying microstructural responses to diffusion-limited coarsening in two-phase materials. A mathematical solution to late-stage multiparticle diffusion in finite systems is formulated with account taken of particle-particle interactions and their microstructural correlations, or "locales". The transi…

Porous Structure Characterization in Titanium Coating for Surgical Implants

M.V. Oliveira、L.C. Pereira、C.A.A. Cairo2002-09-01Materials Research

Powder metallurgy techniques have been used to produce controlled porous structures, such as the porous coatings applied for dental and orthopedic surgical implants, which allow bony tissue ingrowth within the implant surface improving fixation. This work presents the processing and characterization of titanium porous…

Synthesis and Characterization of LaNiO3, LaNi(1-x)Fe xO3 andLaNi(1-x)Co xO3 Perovskite Oxides for Catalysis Application

Sania M. de Lima、José Mansur Assaf2002-09-01Materials Research

Mixed metal oxides with perovskite-type structure show a great potential to be used in catalysis, electrocatalysis and electronic ceramics. Perovskites oxides catalysts with the composition LaNiO3, LaNi(1-x)Fe xO3 and LaNi(1-x)Co xO3 (x = 0.4 and 0.7) have been synthesized by the precipitation method to be used in the…

Catalysts for Methane ReformingCatalytic Processes in Materials ScienceCatalysis and Oxidation Reactions

Development of a Computer Application to Simulate Porous Structures

S.C. Reis、V. Vasconcelos、M.C. Leite 等 4 位作者2002-09-01Materials Research

Geometric modeling is an important tool to evaluate structural parameters as well as to follow the application of stereological relationships. The obtention, visualization and analysis of volumetric images of the structure of materials, using computational geometric modeling, facilitates the determination of structura…

Editorial

Wander L. Vasconcelos、Edgar D. Zanotto2002-09-01Materials Research

Theoretical - Experimental Analysis of Cellular and Primary Dendritic Spacings during Unidirectional Solidification of Sn-Pb Alloys

Otávio L. Rocha、Claudio Siqueira、Amauri Garcia2002-09-01Materials Research

Structural parameters as grain size, dendritic and cellular spacings, segregated products, porosity and other phases are strongly influenced by the thermal behavior of the metal/mold system during solidification, imposing a close correlation between this and the resulting microstructure. Several unidirectional solidif…

Aluminum Alloy Microstructure PropertiesSolidification and crystal growth phenomenaMetallurgy and Material Forming

Cucurbituril as a New Macrocyclic Ligand for Complexation of Lanthanide Cations in Aqueous Solutions

Denis G. Samsonenko⧫、Janusz Lipkowski、O.A. Geras'ko 等 9 位作者2002-09-01European Journal of Inorganic Chemistry

(Aqua)lanthanide complexes with cucurbituril {[Gd(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (1), {[Gd(NO3)(C2H5OH)(H2O)3](C36H36N24O12)}(NO3)2·5.5H2O (2), {[Ho(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (3), {[Yb(NO3)(H2O)4](C36H36N24O12)}(NO3)2·6H2O (4), {[La(H2O)6(SO4)](C36H36N24O12)}(NO3)·12H2O (5), {[Gd(H2O)4]2(C36H36N24O1…

Supramolecular Chemistry and ComplexesLanthanide and Transition Metal ComplexesRadioactive element chemistry and processing

Optimization of the ΔE effect in thin films and multilayers by magnetic field annealing

Alfred Ludwig、Eckhard Quandt2002-09-01IEEE Transactions on Magnetics

The /spl Delta/E effect of amorphous (Fe/sub 90/Co/sub 10/)/sub 78/Si/sub 12/B/sub 10/ and Tb/sub 40/Fe/sub 60/ thin films as well as of Tb/sub 40/Fe/sub 60//Fe/sub 50/Co/sub 50/ multilayers deposited on Si substrates using magnetron sputtering has been investigated. Influences of sputtering parameters and especially…

Metallic Glasses and Amorphous AlloysMagnetic Properties and ApplicationsMagnetic properties of thin films