Cerâmica 

About: Cerâmica is an academic journal published by Associação Brasileira de Cerâmica. The journal publishes majorly in the area(s): Ceramic & Sintering. It has an ISSN identifier of 0366-6913. It is also open access. Over the lifetime, 1416 publications have been published receiving 9514 citations.

Synthesis and characterization of magnetic nanoparticles coated with silica through a sol-gel approach

Abstract: This paper investigates the influence of reaction medium pH on silica-coating of magnetite nanoparticles. Magnetite nanoparticles were prepared by means of a reduction-precipitation method using ferric chloride as a starting material, which was partially reduced to ferrous salts by Na2SO3 before alkalinizing with ammonia. The particles were coated by sol-gel method with either ammonia or HCl aqueous solutions for either base- or acid-catalyzed hydrolysis, respectively. Powder X-ray diffraction, Fourier-transform infrared, and Zeta Potential were used for the characterization of oxides and of the coated magnetic nanoparticles. The observed difference of pHIEP in KCl solution for pure silica (2.0), magnetite (5.0), and silica-coated magnetite (2.3) samples confirms that the coating process was effective since the charge surface properties of coated magnetic nanoparticles are close to that of pure silica, even though the Fourier-transform infrared spectra did not evidence the formation of Fe-O-Si bonds.

Review Article: recent advances in metal-ceramic brazing

Abstract: Metal-ceramic joining has slowly but steadily become an important manufacturing step. The evolution of joining processes has allowed ceramics to be used in combination with metals in a number of hybrid devices from traditional light bulbs and seals to improved cutting tools and modern monitoring and measuring electronic devices. New joining methods and newer approaches to conventional methods have been developed aiming at joints characterized by improved reliability, and interfaces capable of withstanding high-temperature resistance with minimum residual stresses. A summary of recent improvements on alternative approaches to ceramic-metal joining as well as new developments on brazing are presented herein. The present review also focuses on recent advances towards brazing metallized ceramics and the selection of filler alloys, since in a scenario that includes joining by laser and direct bonding with liquid transient phases, brazing continues to be by far the most widely used approach to joining as a result of its low-cost and possibility to join intricate geometries for large-scale production. Finally, methods to evaluate the mechanical strength and residual thermal stresses are presented in addition to alternative approaches to minimize residual stresses and, consequently, improve joint reliability.

A brief review on hydroxyapatite production and use in biomedicine

Abstract: Hydroxyapatite (HAp) is a bioceramic widely studied due to its chemical similarity with the mineral component of bones. Besides, it is biocompatible, bioactive and thermodynamically stable in the body fluid what poses it as an attractive material for a wide range of applications in the biomedical field. Several efforts have been focused on the synthesis of particles of this material aiming to the precise control of size and morphology, porosity and surface area. HAp is widely used as an implant for bone tissue regeneration, as a coating for metallic implants and in a drug-controlled release. In this sense, the objective of this review is to gather information related to HAp, providing readers with information about synthesis methods, material characteristics and their applications.

Argilas organofílicas: características, metodologias de preparação, compostos de intercalação e técnicas de caracterização

Abstract: As argilas sao materiais muito usados e que atualmente apresentam inumeras aplicacoes devido as interessantes propriedades que apresentam. A modificacao superficial de argilas e uma area que tem recebido bastante atencao dos pesquisadores porque por meio dos diversos tipos de modificacao e possivel a preparacao de novos materiais e novas aplicacoes. Este trabalho tem como objetivo apresentar uma revisao bibliografica sobre argilas organofilicas, especialmente as obtidas a partir de bentonitas e de sais quaternarios de amonio. Diversos estudos vem sendo realizados baseados em diferentes tecnicas e parâmetros de sintese desses materiais, incluindo argilas de diferentes regioes e diferentes agentes de modificacao, bem como as diferentes aplicacoes que sao propostas.

Sintering and mechanical properties of porcelains prepared from algerian raw materials

Abstract: A porcelana e um tipo de cerâmica altamente valorizada pela sua beleza e resistencia mecânica. O objetivo geral deste trabalho e utilizar materias-primas locais nas seguintes fracoes: 37% em peso de caulim, feldspato 35% em peso e 28% em peso de quartzo. Esta composicao foi escolhida com base em diagramas de fase ternarios (caulim, feldspato-quartzo). O comportamento de densificacao indicou que amostras sinterizadas a 1200 °C por 2 h com taxa de aquecimento de 5 °C/min, tem uma densidade de cerca de 2,50 g/cm3. Este valor e ligeiramente superior ao relatado para os produtos de porcelana convencional (2,45 g/cm3). Especimes de porcelana, com e sem calcinacao sinterizadas a 1200 °C por 2 h tem valores de resistencia a tracao de cerca de 45 e 73 MPa, respectivamente (valores equivalentes de resistencia a flexao de aproximadamente 122 e 197 MPa, respectivamente). Os valores de resistencia a flexao de ambos os especimes sao muito superiores aos relatados para porcelanas convencionais (variou entre 60 e 80 MPa). Mais ainda, o valor da micro-dureza das amostras sem calcinacao a 1200 °C e de 9,3 ± 0,2 GPa que e maior do que os produtos comerciais de porcelana (5,5 GPa).