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  • 1
    Online Resource
    Online Resource
    Ceramics Composites Derived From Polysiloxane / Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 / Ti
    Trans Tech Publications, Ltd. ; 2010
    In:  Materials Science Forum Vol. 660-661 ( 2010-10), p. 667-672
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 660-661 ( 2010-10), p. 667-672
    Abstract: In this work alumina based composites ceramics with a polymeric precursor (polysiloxane) and metallic Ti with two different size particle distribution, Ti without milling (ATM) and 5h milling (ATM5), were characterized. PMS thermogravimetric curve indicates that the weight loss percentage was about 20%. The densities achieved were 3,50g/cm3 and 3,70g/cm3 for samples prepared with Ti as received and 5h milling, respectively. During decomposition of the polymer during pyrolysis and sintering, the particles of the matrix may react with carbon and Si from the polymer precursor, metallic Ti and gas atmosphere, nitrogen, to form different phases. The ATM samples presented Al2O3 and TiCN. The specimens prepared with 5h milling Ti (ATM5) is constituted by mullite besides Al2O3 and TiCN. The ATM5 samples have smaller densities than ATM but there is no significant difference in the hardness values.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.660-661
    DOI: 10.4028/www.scientific.net/MSF.660-661.667
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2010
    detail.hit.zdb_id: 2047372-2
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  • 2
    Online Resource
    Online Resource
    Influence of Addition of Polysiloxane on Sintering of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉
    Trans Tech Publications, Ltd. ; 2014
    In:  Materials Science Forum Vol. 798-799 ( 2014-6), p. 696-702
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 798-799 ( 2014-6), p. 696-702
    Abstract: The effects of adding polysiloxane (polymethylsilsesquioxane) on the sintering behavior, microstructure and hardness of alumina ceramics have been studied. The sintering kinetics of cold-pressed specimens was studied by dilatometry. Polymer sintering aid was used for alumina based ceramics sintered at 1650o C. The sintered materials were characterized using helium picnometry, x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectrometry and Vickers indentation. The addition of polymethylsilsesquioxane yielded alumina/Si 2 Al 4 O 4 N 4 composites. The sintering studies in nitrogen atmosphere (1650 °C/1h) revealed that the highest densities were obtained for specimens with 1wt% PMS. The materials prepared with ceramic polymer precursors had higher hardness than the standard specimen. The preparation of ceramic composites using small amounts of polymer precursors is suited for alumina based ceramics. The processing route being simple, it has the potential to enable the manufacture of complex shaped pieces.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.798-799
    DOI: 10.4028/www.scientific.net/MSF.798-799.696
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2014
    detail.hit.zdb_id: 2047372-2
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  • 3
    Online Resource
    Online Resource
    Influence of Addition of Polymeric Precursors of Ceramics on Sintering of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉
    Trans Tech Publications, Ltd. ; 2012
    In:  Materials Science Forum Vol. 727-728 ( 2012-8), p. 1092-1097
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 727-728 ( 2012-8), p. 1092-1097
    Abstract: The effects of adding polymer precursor on the sintering behavior, microstructure and hardness of alumina ceramics have been studied. Polymer sintering aid polymethylhidrogensiloxane were used for alumina based ceramics sintered at 1650º C. The sintered materials were characterized using: (a) helium picnometry to determine apparent density; (b) x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray spectrometry to determine the microstructure and composition; (c) Vickers indentation analysis to determine the hardness and fracture toughness. The addition of polymethylhidrogensiloxane yielded alumina/mullite composites. The preparation of ceramic composites using small amounts of polymer precursors is suited for alumina based ceramics. The processing route being simple, it has the potential to enable the manufacture of complex shaped pieces.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.727-728
    DOI: 10.4028/www.scientific.net/MSF.727-728.1092
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2012
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  • 4
    Online Resource
    Online Resource
    Titanium and Ti-13Nb-13Zr Alloy Porous Implants Obtained by Space-Holder Technique with Addition of Albumin
    Trans Tech Publications, Ltd. ; 2012
    In:  Key Engineering Materials Vol. 529-530 ( 2012-11), p. 574-579
    Details
    In: Key Engineering Materials, Trans Tech Publications, Ltd., Vol. 529-530 ( 2012-11), p. 574-579
    Abstract: Titanium and its alloys are the main metals studied as porous metallic implants by their excellent mechanical properties and biological interactions. Production methods of porous metallic materials are based on powder metallurgy (PM), because it allows the manufacturing of parts with complex shapes and dimensions close to the finals (near-net shape), and the addition of alloying elements reaching a satisfactory structural homogeneity, and porosity. The pore production by space-holder technique constitutes of mixing organic compounds with metal powder, which when removed by thermal treatment prior structures are kept in place. The objective of this study is to obtain porous implants of commercially pure titanium (cpTi) and Ti-13Nb-13Zr alloy by PM with space-holder technique and albumin as an additive. For the processing of the samples were used hydride titanium powder (TiH 2 ) to obtain cpTi samples, and metal powders of Ti, Nb and Zr in the stoichiometric proportions for obtaining the alloy samples. The samples were prepared by mixing the metallic powder to the albumin (30wt%) and filling a silicone model that was pressed isostatically (140 MPa). The thermal treatment was performed in an oxidizing atmosphere (350°C/1h) for the decomposition of organic material. The sintering was performed at a temperature of 1300°C (1h/cpTi, 3h/Alloy) in high vacuum furnace (10 -5 mBar) to all samples. The calculated porosity showed a significant difference between the samples cpTi (40%) and alloy (60%). The samples surface characterization showed very rough with high specific surface area. Samples of cpTi presented formation of necks arising from sintering. In the alloy samples were observed homogenous microstructure with the presence of α and β phases composing the Widmanstätten structure. It is possible to conclude that the same amount albumin allowed the formation of pores in the microstructure of cpTi and alloy although in different proportions, without harming the sintering of both and allowing diffusion of the alloy elements.
    Type of Medium: Online Resource
    ISSN: 1662-9795
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/KEM.529-530
    DOI: 10.4028/www.scientific.net/KEM.529-530.574
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2012
    detail.hit.zdb_id: 2073306-9
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  • 5
    Online Resource
    Online Resource
    Use of Fine Wastes from Dimension Stone Industry in the Manufacture of Ceramic Tile
    Trans Tech Publications, Ltd. ; 2012
    In:  Materials Science Forum Vol. 727-728 ( 2012-8), p. 703-709
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 727-728 ( 2012-8), p. 703-709
    Abstract: Large quantities of rock dust are daily discarded by dimension stone industries. These wastes can be reduced if they are selected according to their composition and used as base in other products. Two kinds of wastes (BS and OI) were mixed at different proportions with kaolinitic clay traditionally used as raw material in ceramic industry. BS has high contents of plagioclase, quartz, microcline and low biotitic; and OI has high quantities of microcline and plagioclase, besides quartz, biotitic, enstatite and edenite. At the same firing temperature, water absorption of samples with 50% BS, or less, didnt show significant differences in relation to samples with pure clay, but firing shrinkage and flexural strength decreased. On the other hand, mixtures with OI content up to 50% showed reduction of water absorption and firing shrinkage, while flexural strength was increased.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.727-728
    DOI: 10.4028/www.scientific.net/MSF.727-728.703
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2012
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  • 6
    Online Resource
    Online Resource
    Effect of the Acid Environment on the Electrochemical Behaviour of 1045 Steel Reinforced Cement
    Trans Tech Publications, Ltd. ; 2012
    In:  Materials Science Forum Vol. 730-732 ( 2012-11), p. 763-768
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 730-732 ( 2012-11), p. 763-768
    Abstract: External 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 decide which acidic systems can be used. A comparative evaluation of the corrosion of steel immersed in hardened cement slurries submitted to commonly acidizing agents is suggested. The performance of Special Class Portland Cement Slurries reinforced with polished SAE 1045 steel was evaluated by electrochemical measurements as a function of time. Open circuit potential, polarization curves and electrochemical impedance spectroscopy were studied. 15.0 wt% HCl, 12.0 wt% HCl + 3.0 wt% HF (regular mud acid), 10.0 wt% HAc + 1.5 wt% HF and a simulated hardened cement slurry pore solution were used as electrolytes. The most aggressive acid solution to plain Portland hardened cement slurries was the regular mud acid. 10.0 wt% HAc + 1.5 wt% HF electrolytes were the least aggressive ones, showing open circuit potentials around +250 mV compared to -130 mV of the simulated hardened cement slurry pore solution after the first 24 hours of immersion. This behavior was observed during two months at least. Similar corrosion rates were shown between both electrolytes, around 0.01 μA.cm -2 . Total impedance values, insipient arcs and large polarization resistance capacitive arcs on the Nyquist plots, indicating passivity process, confirmed the behaviour of the system in the 10.0 wt% HAc + 1.5 wt% HF electrolyte.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.730-732
    DOI: 10.4028/www.scientific.net/MSF.730-732.763
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2012
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  • 7
    Online Resource
    Online Resource
    Zn-TiO〈sub〉2〈/sub〉 and ZnNi-TiO〈sub〉2〈/sub〉 Nanocomposite Coatings: Corrosion Behaviour
    Trans Tech Publications, Ltd. ; 2010
    In:  Materials Science Forum Vol. 636-637 ( 2010-1), p. 1079-1083
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 636-637 ( 2010-1), p. 1079-1083
    Abstract: This work presents the corrosion behaviour of the as-prepared of Zn-TiO2 and ZnNi-TiO2 films in neutral Na2SO4 solution and a first attempt to correlate with their composition, morphology and structure. The films were prepared by galvanostatic pulse method onto steel electrodes, at room temperature. The X-ray diffraction study revealed that the ZnNi alloy consists of a homogenous Ni5Zn21 phase and that the preferred crystallographic orientation of Zn deposits changes in the presence of TiO2. The SEM results show that the morphology of the metallic coating is function of the metal phase composition and become more porous in the presence of 1.5 wt% TiO2.The corrosion parameters for the nanocomposite coatings were compared with those of pure Zn and ZnNi electrodeposits, and the ZnNi-TiO2 nanocomposite coating shows the less cathodic corrosion potential.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.636-637
    DOI: 10.4028/www.scientific.net/MSF.636-637.1079
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2010
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  • 8
    Online Resource
    Online Resource
    pH Effect on the Dissolution Behavior of the Microspheres Containing Strontium Ranelate
    Trans Tech Publications, Ltd. ; 2014
    In:  Key Engineering Materials Vol. 631 ( 2014-11), p. 315-320
    Details
    In: Key Engineering Materials, Trans Tech Publications, Ltd., Vol. 631 ( 2014-11), p. 315-320
    Abstract: Strontium is known for efficient actions on bone formation and resorption. Strontium ranelate (SrR) is a commercial drug which maintains this balance during bone turnover, reducing the risks of vertebral fractures in the patients. Calcium phosphate bioceramics associated with alginate matrices containing strontium (Sr) could improve bone regeneration due to gradual Sr release. In this report, the strontium ranelate was incorporated on microspheres of alginate (ALG)/β-tricalcium phosphate in a single route of the production. Energy dispersive spectroscopy showed that strontium was incorporated on the surface of the microspheres produced. The dissolution behaviour into a buffer solution at pH 4.0 and at 7.4 was evaluated, measuring Sr content on the microspheres after in vitro assays by atomic absorption spectrometry. Dissolution tests showed a rapid strontium release in both assays, however, it was more pronounced at pH 4.0. Fourier transform infrared spectra indicated the presence of a new precipitated phase at pH 7.4 up after 14 days. Scanning electron microscopy of the microspheres submitted to in vitro revealed that the microspheres at pH 4.0 buffer underwent erosion up to 7 days, while the ones in pH 7.4 buffer, eroded in 48h. This behaviour is due to the high swelling rate of the microspheres in neutral pH. The solubility of the microspheres favors its use as a great material for a local strontium release and remodeling bone.
    Type of Medium: Online Resource
    ISSN: 1662-9795
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/KEM.631
    DOI: 10.4028/www.scientific.net/KEM.631.315
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2014
    detail.hit.zdb_id: 2073306-9
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  • 9
    Online Resource
    Online Resource
    Bone Tissue Response in a Metallic Bone Architecture Microstructure
    Trans Tech Publications, Ltd. ; 2014
    In:  Journal of Biomimetics, Biomaterials and Biomedical Engineering Vol. 20 ( 2014-6), p. 73-85
    Details
    In: Journal of Biomimetics, Biomaterials and Biomedical Engineering, Trans Tech Publications, Ltd., Vol. 20 ( 2014-6), p. 73-85
    Abstract: Porous metallic structures have been developed to mimic the natural bone architecture, having interconnected porosity, disposing enough room to cell migration, anchoring, vascularization, nourishing and proliferation of new bone tissue. Research involving porous titanium has been done with purpose to achieve desirable porosity and increasing of bone-implant bond strength interface. Samples of titanium were prepared by powder metallurgy (PM) with addition of different natural polymers (cornstarch, rice starch, potato starch and gelatin) at proportion of 16wt%. In aqueous solution the hydrogenated metallic powder (TiH 2 ) and the polymer were mixed, homogenized and frozen in molds near net shape. The water was removed in kiln and the polymer by thermal treatment in air- (350°C/1h) before sintering in high-vacuum (1300°C/1h). The biological evaluation was performed by in vivo test in rabbits. Histological analysis was performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (SEM-EDS) and fluorescence microscopy (FM). The processing methodologies using natural low cost additives propitiate the production of porous metallic implants in a simplified manner, with different porosities, proper porosity degree (40%), distribution, and maximum pore size of 80 μm to 220 μm depending of natural polymer used. The samples added with rice starch, presented the most similar structure organization when compared to the bone tissue microstructure organization of the trabecular bone. All implants osseointegrated, the pore microarchitecture and its interconnected network allowed bone ingrowth in all pore sizes, but the continuous bone maturation occurred in pores bigger than 80 μm.
    Type of Medium: Online Resource
    ISSN: 2296-9845
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/JBBBE.20
    DOI: 10.4028/www.scientific.net/JBBBE.20.73
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2014
    detail.hit.zdb_id: 2786067-X
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  • 10
    Online Resource
    Online Resource
    Influence of Rhombohedral Graphite Phase on the Diamond Nucleation
    Trans Tech Publications, Ltd. ; 2012
    In:  Materials Science Forum Vol. 727-728 ( 2012-8), p. 1364-1368
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 727-728 ( 2012-8), p. 1364-1368
    Abstract: The high pressure and temperature, synthesis of diamond from carbonaceous materials, is a complex process highly dependent on variables such as the catalyst/solvent, the crystalline structure of the precursor material, the processing conditions and the type of compressive chamber. The optimum susceptible precursors to be transformed into diamond are those possessing the perfect hexagonal graphite structure, which is the thermodynamically most stable form of carbon at atmospheric pressure and ambient temperature. However, the majority of both industrial and natural graphites, presents a mixture of different atomic structural arrangements that greatly influence the process of diamond synthesis. In this works the influence of rhombohedral and hexagonal phases existing in the graphite was performed by means of a software refinement of the crystal structures using the Rietveld method. The thermobaric treatment, which determine the structural parameters, was conducted in a high pressure anvil type device with a central concavity. All experiments were carried out at 1200°C and pressures varying from 4.3 to 5.0 GPa. It was determined that the degree of graphite to diamond transformation is directly associated with the content of rhombohedral phase.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.727-728
    DOI: 10.4028/www.scientific.net/MSF.727-728.1364
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2012
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