Papers by Keyword: Porous Ceramics

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Authors: Christiane Ribeiro, W.I. Rojas-Cabrera, M. Marques, José Carlos Bressiani, Ana Helena A. Bressiani
Abstract: In recent years, the processing of porous ceramic materials for implant applications has motivated the development and optimization of new technologies. To this purpose, a globular protein based (i.e. ovalbumin) consolidation approach has been proposed. In the present study, a porous hydroxyapatite:b-tricalcium phosphate - biphasic ceramics (BCP), was processed by consolidation using the protein-action technique. The processed ceramic materials exhibited appropriate pore configuration in terms of size, morphology and distribution. The in vitro reactivity and dissolution behavior of the ceramics was evaluated in SBF and biocompatibility in an osteoblasts culture, respectively. Overall, the materials tested showed biocompatibility and suitable properties for osteoconduction. A rough surface pattern displayed by the ceramics seemed to have improved both; cell adhesion and proliferation processes. In conclusion, this study revealed that the porous matrices obtained, promoted suitable development of cell metabolism without cellular death.
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Authors: Hai Xu, Jia Chen Liu, Ying Na Zhao, Zhen Guang Hou
Abstract: Highly porous silica ceramics were produced by gel casting with egg white protein (EWP) as a foaming agent and evaluated by measuring the porosity, mechanical strength and microstructure. After drying, the green bodies were debindered and sintered at 1300°C for 4 h. The influences of the EWP content on the open porosity as well as the strength were investigated. The porosity of the obtained porous silica ceramics was within 70.2%-86.1%, the bending strength decreased from 6.81 MPa to 5.48 MPa. It was found that the strength dependence of the porosity was well described by a modified exponential relation of the form σ=σ0exp(-BP), where P is the porosity and B is a constant (B = 1.37 was obtained by fitting the experimental data). This finding is in agreement with other literature data and seems to indicate a common feature of all porous ceramics.
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Authors: Yasushi Ikeda, Yasuo Nagano, Hiroshi Kawamoto, Naoki Takano
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Authors: Rodrigo de Matos Oliveira, Maria do Carmo de Andrade Nono, Gustavo de Souza Oliveira
Abstract: The growing interest for the environmental monitoring in order to minimize the potential risk of landslide in hillsides and to prevent new disasters, has led the improvement in the development of new materials for manufacturing of capacitive sensor devices more reliable, more versatile and at lower cost. In this sense, ceramics have shown advantages from the point of view of mechanical resistance, resistance to chemical attacks and physical and chemical stability in aggressive environments. In addition, these materials have a unique structure, consisting of grains, grain boundaries, surfaces and pores, the control of which permit the attainment of suitable microstructures to be used as moisture sensors. The goal of this work is to investigate the capability of porous ceramics sensor devices, developed in National Institute of Space Research (INPE), to monitor the soil water dynamics. For that, ceramics sensors microstructures were characterized through scanning electron microscopy (SEM), X-ray diffractometry (XRD) and Hg porosimetry techniques. Electrical measurements were performed in function of water addition in soil samples, up to the saturation limit, for different time intervals, in the same way it happens in area with landslide risk in periods of rain. The analyses of the results evidenced that the ceramics devices are promising ones concerning to their potential in the monitoring of environmental parameters.
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Authors: Rong Zhen Liu, Bo Wang, Ji Kuan Cheng, Jian Feng Yang, Ji Qiang Gao
Abstract: A novel method for preparing porous silicon carbide ceramics with high porosity had been developed by recrystallization of green bodies composed of α-SiC, β-SiC, remnant silicon and incompletely-reacted carbon. Fine microstructure and uniform pore structure of the resultant porous silicon carbide ceramics was obtained. The green bodies of porous ceramics were prepared by the precursor powder which contained α-SiC, carbon black and silicon powder. The precursor powder was sintered at 1600°C under Vacuum circumstance to obtain the green bodies; the sintering process is same with the reaction sintering silicon carbide. Then the green bodies were sintered to 2300°C for half an hour to recrystallization. The incompletely-reacted carbon was fully reacted with silicon. And the remnant silicon was excluded during the recrystallization process to create porous structures. The influence of composition of the precursor powder and the fabrication process (the moulding pressure) on the microstructure of sintering bodies was analyzed. X-ray diffractometry demonstrated the transformation of β-SiC to α-SiC during the recrystallization process. The density and the porosity of this material was 1.027g/cm3 and 67% respectively.
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Authors: Ping Fu, Zhi Liang Huang, Fang Zhang
Abstract: The cordierite porous ceramics were made from kaolinite, talc and α-alumina, formed by pressing and fired at 1200 °C for one hour. Starch was used as pore-forming agent. Physical/chemical properties and microstructure of products were characterized. The results show that samples exhibit relatively high strength, low coefficient of thermal expansion and well-distributed gradient pores. The pores of samples are homogeneous.
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Authors: Jie Zhou, Wan Yi Zhao, Guo Zheng Quan
Abstract: Research on microstructure and behavior of natural biomaterials contributes to understanding the biomimetic design. Yakbone bioceramic’s cross section with innumerable voids was observed via SEM approach, then a digital image processing technique was adopted to analyze the images. It is supposed that the pores can be classified into n series by different size level. A non-linear function between the pore size and series number got fitted which indicates a regression trend to zero as n rising to a large number. A non-linear convergent analysis of the function results in the porosity of porous microstructure of yakbone bioceramic. Furthermore, a plane helices characterization model was assumed to descript the multilevel voids distribution, then a series of helices parameters were designed for bionic yakbone porous microstructure with porosity tolerance of 2.5%. This parameter description of yakbone, a porous bioceramic with high strength and light weight, contributes to further research on the relationships between mechanical property and microstructure.
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Authors: Hao Huang, Da Ming Cheng, Jian Feng Tong, Bao Wei Li, Ling Wang
Abstract: A technique for the preparation of porous ceramic materials by gelcasting mothod is studied using a water-soluble epoxy resin combined with a amine hardener. The increase in the volume and rheological behavior of slurry , TGA and DSC of the green bodies are investigated. The influence of solid content on the relative density, the cell size distribution and the compressive strenghth is studied. The experimental results show that in the measurable shear rate range the rheology of slurry exhibt a shear thinning behavior, the relative density increase with the solid content, with the decrease of the relative densities the cell size increase. The compressive strength increased exponentially with the increase relative density, and the exponent, m, is 1.094.
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Authors: R.A. Terpstra, J.P.G.M. van Eijk, J.C.T. van der Heijde
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Authors: Rodrigo Sampaio Fernandes, Élson de Campos, José Luiz Minatti, Jerusa Góes Aragão Santana, Rogério Pinto Mota
Abstract: Several researches have been developed in order to verify the porosity effect over the ceramic material properties. The starch consolidation casting (SCC) allows to obtain porous ceramics by using starch as a binder and pore forming element. This work is intended to describe the porous mathematical behavior and the mechanical resistance at different commercial starch concentration. Ceramic samples were made with alumina and potato and corn starches. The slips were prepared with 10 to 50 wt% of starch. The specimens were characterized by apparent density measurements and three-point flexural test associated to Weibull statistics. Results indicated that the porosity showed a first-order exponential equation e-x/c increasing in both kinds of starches, so it was confirmed that the alumina ceramic porosity is related to the kind of starch used.
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