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Barium-Strontium Titanate/Porous Glass Structures for Microwave Applications. MATERIALS 2020; 13:ma13245639. [PMID: 33321860 PMCID: PMC7763980 DOI: 10.3390/ma13245639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 12/01/2020] [Accepted: 12/08/2020] [Indexed: 11/17/2022]
Abstract
Based on porous silicate glasses obtained by ion exchange, glass-ceramic materials containing a solid solution of barium-strontium titanate with a dielectric constant of more than 100 at microwaves, were synthesized for the first time. Glass-ceramic structures were studied using X-ray diffraction, secondary electron microscopy, Mössbauer spectroscopy and porometry methods. Electrical characteristics such as permittivity and losses of as-prepared and annealed in oxygen medium samples were also investigated at microwaves. It was shown that the method of obtaining porous glasses, due to ion exchange between KFeSi glass and LiNO3 and NaNO3 melts, allows for controlling a wide range of pore sizes and makes it possible to form glass porous structures with pores of the required size. The efficiency of the process of filling a porous matrix with a ferroelectric filler was investigated and the average depth of its penetration was estimated. It was shown that annealing glass-ceramic structures in an oxygen environment had a positive effect on their structural and electrical characteristics. Glass-ceramic structures demonstrate a significant increase in permittivity and a decrease in losses after high-temperature treatment in oxygen.
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Simba BG, Ribeiro MV, Suzuki PA, Alves MFRP, Strecker K, Santos CD. Mechanical properties of lithium metasilicate after short-term thermal treatments. J Mech Behav Biomed Mater 2019; 98:179-186. [PMID: 31247537 DOI: 10.1016/j.jmbbm.2019.06.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 06/06/2019] [Accepted: 06/10/2019] [Indexed: 11/19/2022]
Abstract
OBJECTIVES The properties of lithium-silicate dental glass-ceramics are very sensitive to heat treatments which are conducted after CAD/CAM (Computer Aided Design/Computer Aided Machining) processing. In particular, temperature variations inside the furnace chamber which may occur between different models of furnaces may result in altered mechanical properties of these materials. In this work, the effect of thermal treatment parameters on the transformation of lithium metasilicate (Li2SiO3) into lithium disilicate (Li2Si2O5) and on the resulting mechanical properties has been investigated. METHODS Lithium metasilicate samples. containing 59 vol% of amorphous phase, were thermal treated under vacuum at 820 °C for up to 9 min or at 840 °C for 7min (as control group). The samples were characterized by X-ray diffraction analysis using the Rietveld refinement and scanning electron microscopy. Hardness and fracture toughness (n = 30 indentations/group) were evaluated by the Vickers indentation technique. The elastic properties were measured by the Impulse Excitation Technique and the flexural strength (n = 15/group) was measured using the piston-on-three-ball (P-3B) testing assembly. Complementary Weibull statistic were conducted as statistical analysis. RESULTS The results indicate a progressive reduction of the Li2SiO3 phase with increasing isothermal holding time at 820 °C until the conversion into Li2Si2O5, is completed for treatments longer than 7 min. A complete transformation of Li2SiO3 into Li2Si2O5 has also been observed for the control group of samples treated at 840 °C for 7min. Samples of the control group exhibited hardness, fracture toughness, Young's modulus and Poisson ratio 5.76 ± 0.17 GPa, 1.60 ± 0.03 MPa m1/2, 100.3 GPa e 0.21, respectively. The reduction of the thermal treatment temperature to 820 °C reduced the fracture toughness and the Young's modulus between 5-10%. Furthermore, the fracture strength was significantly reduced by approximately 71%, because of the lower amount of elongated Li2Si2O5 grains and higher amount of residual amorphous phase. CONCLUSION In general, the glass-ceramic material containing residual amorphous phase associated with various crystalline phases, presented a reduction of its mechanical properties in relation to the lithium disilicate glass-ceramic. The reasons for these differences in the mechanical behavior are discussed by analyzing the influences of different phenomena such as thermal expansion anisotropy, residual stresses, amorphous phase content and microstructure on the properties.
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Affiliation(s)
- Bruno Galvão Simba
- UNESP/FEG, Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas, 12516-410, Guaratinguetá, SP, Brazil
| | - Marcos Valério Ribeiro
- UNESP/FEG, Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas, 12516-410, Guaratinguetá, SP, Brazil
| | - Paulo A Suzuki
- USP/EEL, Universidade de São Paulo, Escola de Engenharia de Lorena, Campus II, Polo Urbo Industrial Gleba AI6, s/n, 12600-000, Lorena, SP, Brazil
| | - Manuel Fellipe R P Alves
- USP/EEL, Universidade de São Paulo, Escola de Engenharia de Lorena, Campus II, Polo Urbo Industrial Gleba AI6, s/n, 12600-000, Lorena, SP, Brazil; UERJ/FAT, Universidade do Estado do Rio de Janeiro, Faculdade de Tecnologia, Rod. Presidente Dutra, km 298, 27537-000, Resende, RJ, Brazil
| | - Kurt Strecker
- UFSJ, Universidade Federal de São João Del´Rei, P(ça) Frei Orlando 170, 36307-352, S. João del Rei, MG, Brazil
| | - Claudinei Dos Santos
- UERJ/FAT, Universidade do Estado do Rio de Janeiro, Faculdade de Tecnologia, Rod. Presidente Dutra, km 298, 27537-000, Resende, RJ, Brazil.
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Abstract
In numerous research fields, especially the applications of electron and X-ray diffraction, stereographic projection represents a powerful tool for researchers. SPICA is a new computer program for stereographic projection in interactive crystallographic analysis, which inherits features from the previous JECP/SP and includes more functions for extensive crystallographic analysis. SPICA provides fully interactive options for users to plot stereograms of crystal directions and crystal planes, traces, and Kikuchi maps for an arbitrary crystal structure; it can be used to explore the orientation relationships between two crystalline phases with a composite stereogram; it is also used to predict the tilt angles of transmission electron microscopy double-tilt and rotation holders in electron diffraction experiments. In addition, various modules are provided for essential crystallographic calculations.
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Antipas G, Temleitner L, Karalis K, Kohara S, Pusztai L, Xenidis A. A containerless study of short-range order in high-temperature Fe–Si–Al–Ca–Mg–Cr–Cu–Ni oxide systems. J Mol Struct 2012. [DOI: 10.1016/j.molstruc.2012.03.056] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Liu H, Liu J. SP2: a computer program for plotting stereographic projection and exploring crystallographic orientation relationships. J Appl Crystallogr 2011. [DOI: 10.1107/s0021889811049582] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Stereographic projection is one of the most powerful research tools for crystallography in materials science. A new program for full operation of stereographic projections and in-depth exploration of crystallographic orientation relationships is described. It is specifically designed for materials researchers who are in need of tools for extensive crystallographic analysis. The difference from other popular commercial software for crystallography is that this program provides new options for users to plot and fully control stereographic projections of an arbitrary pole centre for an arbitrary crystal structure and to illustrate composite stereographic projections, which are necessary to explore the orientation relationships between two phases. The program is able to perform a range of essential crystallographic calculations.
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