Pub Date : 2012-04-25DOI: 10.1002/9781118408049.CH18
N. Manjooran, G. Pickrell
Porous materials are used for a variety of applications including filtration, aeration, materials handling, sorbents, structural materials and sensors. In this paper, we discuss the processing and characterization of nano-structured porous ceramics. In this work, single celled fungi have been used to make pores that are in the micron size range in the material. Porosity of structures formed with nano sized silicon carbide; silicon nitride and silicon dioxide have been studied and characterized using the scanning electron microscope. This procedure of making porous materials can reduce costs during industrial production by reducing the storage space and eliminating the energy needed to remove the fugitive materials normally used.
{"title":"Complementary Fungus‐Derived Micro‐Porosity in Nano Materials","authors":"N. Manjooran, G. Pickrell","doi":"10.1002/9781118408049.CH18","DOIUrl":"https://doi.org/10.1002/9781118408049.CH18","url":null,"abstract":"Porous materials are used for a variety of applications including filtration, aeration, materials handling, sorbents, structural materials and sensors. In this paper, we discuss the processing and characterization of nano-structured porous ceramics. In this work, single celled fungi have been used to make pores that are in the micron size range in the material. Porosity of structures formed with nano sized silicon carbide; silicon nitride and silicon dioxide have been studied and characterized using the scanning electron microscope. This procedure of making porous materials can reduce costs during industrial production by reducing the storage space and eliminating the energy needed to remove the fugitive materials normally used.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"406 1","pages":"193-198"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79766604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118406069.CH10
O. Wilson, Latosha Marshall
The synthesis of novel hydroxyapatite (HAP)/polymer composites with enhanced load bearing capabilities is a very important goal in the field of orthopedic biomaterials. Three of the main factors that can contribute to improving the mechanical properties of composites are decreased particle size (nanoscale), molecular level dispersion, and improved interfacial bond strength between the polymer matrix and the hydroxyapatite particles. However, these issues have been difficult to address in the synthesis and processing of HAP/polymer composites because the incorporation of nanoscale HAP in polymers at high solids loadings is extremely difficult. In addition, the surface chemistry of HAP makes the selection of suitable interfacial bond strength enhancement agents difficult. In this study, nanophase HAP particles were modified by surface grafting dodecyl alcohol molecules in an attempt to improve the degree of dispersion during mixing with poly(propylene carbonate) (PPC). The surface modified HAP and HAP/PPC composites were characterized via BET N 2 adsorption, transmission electron microscopy (TEM), Fourier transform spectroscopy (FTIR), and thermal gravimetric analysis (TGA). The HAP surface treatment slightly increased the degree of mixing that could be achieved between the HAP and PPC matrix. However, the presence of inhomogeneous regions indicates that the level of mixing must be improved to obtain true molecular dispersion.
{"title":"Molecularly Dispersed Hydroxyapatite Polymer Nanocomposites","authors":"O. Wilson, Latosha Marshall","doi":"10.1002/9781118406069.CH10","DOIUrl":"https://doi.org/10.1002/9781118406069.CH10","url":null,"abstract":"The synthesis of novel hydroxyapatite (HAP)/polymer composites with enhanced load bearing capabilities is a very important goal in the field of orthopedic biomaterials. Three of the main factors that can contribute to improving the mechanical properties of composites are decreased particle size (nanoscale), molecular level dispersion, and improved interfacial bond strength between the polymer matrix and the hydroxyapatite particles. However, these issues have been difficult to address in the synthesis and processing of HAP/polymer composites because the incorporation of nanoscale HAP in polymers at high solids loadings is extremely difficult. In addition, the surface chemistry of HAP makes the selection of suitable interfacial bond strength enhancement agents difficult. In this study, nanophase HAP particles were modified by surface grafting dodecyl alcohol molecules in an attempt to improve the degree of dispersion during mixing with poly(propylene carbonate) (PPC). The surface modified HAP and HAP/PPC composites were characterized via BET N 2 adsorption, transmission electron microscopy (TEM), Fourier transform spectroscopy (FTIR), and thermal gravimetric analysis (TGA). The HAP surface treatment slightly increased the degree of mixing that could be achieved between the HAP and PPC matrix. However, the presence of inhomogeneous regions indicates that the level of mixing must be improved to obtain true molecular dispersion.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"3 1","pages":"91-100"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82515613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118408162.CH31
M. Cole, W. Nothwang, S. Hirsch, É. Ngo, C. Hubbard, R. Geyer
Ba (1-x) Sr x TiO 3 (BST) thin films appear to be excellent candidates for microwave phase shifters. However, the major issue impeding the utilization of BST films in beam steering devices is the simultaneous achievement of the required performance properties. These properties, at frequencies > 10 GHz, include a dielectric permittivity ≤500, low dielectric loss (<2%), high tunability (-2:1), low leakage current characteristics, and low operating control voltages (<10V). Additionally, these properties must be obtained via an industry standard growth and processing methods. Our approach to satisfy the above mentioned dielectric properties of BST based films is focused on material compositional design and optimized film processing parameters. A systematic study was employed to examine the influence of low concentration Mg acceptor doping and optimized post-deposition annealing conditions on the structure and microwave dielectric properties of BST based thin films fabricated via the metalorganic solution deposition technique. The Mg doping was found to have a strong influence on the material properties of the BST films whereby the films permittivity, dissipation factor, and leakage characteristics were significantly reduced with respect to that of undoped BST. Optimum material properties were achieved for the 5 - 7 mol% Mg doped BST films. At these doping concentrations the dissipation factor (10 GHz) for both films was less than 1.7%. The leakage characteristics were 5.78x10 -8 and 7.97x10 -9 , respectively, and the tunability was ∼40%. Our results suggest that Mg doping and optimized post-deposition annealing served to mitigate the oxygen vacancies thereby lowering the films dielectric loss. Furthermore, the acceptor doping maintained the dielectric permittivity well below 500. Our results suggest the 5-7 mol% Mg doped BST thin films to be commercially viable for microwave phase shifter devices.
Ba (1-x) Sr x tio3 (BST)薄膜是微波移相器的理想候选材料。然而，阻碍BST薄膜在光束转向装置中应用的主要问题是同时实现所需的性能特性。这些特性，在频率> 10 GHz时，包括介电常数≤500，低介电损耗(<2%)，高可调性(-2:1)，低漏电流特性和低工作控制电压(<10V)。此外，这些特性必须通过行业标准的生长和加工方法获得。为了满足BST基薄膜的上述介电性能，我们的方法主要集中在材料成分设计和薄膜加工参数的优化上。系统研究了低浓度Mg受体掺杂和优化的沉积后退火条件对金属有机溶液沉积技术制备的BST基薄膜结构和微波介电性能的影响。Mg掺杂对BST薄膜的材料性能有很大的影响，相对于未掺杂的BST，薄膜的介电常数、耗散系数和泄漏特性显著降低。在5 ~ 7mol % Mg掺杂的BST薄膜中获得了最佳的材料性能。在这些掺杂浓度下，两种薄膜的耗散系数(10 GHz)均小于1.7%。泄漏特性分别为5.78x10 -8和7.97x10 -9，可调性为~ 40%。我们的研究结果表明，Mg掺杂和优化的沉积后退火有助于减少氧空位，从而降低薄膜的介电损耗。此外，受体掺杂使介电常数保持在500以下。我们的研究结果表明，5- 7mol % Mg掺杂的BST薄膜用于微波移相器器件具有商业可行性。
{"title":"High Performance Thin Films for Microwave Phase Shifter Applications: Device Requirements, Material Design, and Process Science Considerations","authors":"M. Cole, W. Nothwang, S. Hirsch, É. Ngo, C. Hubbard, R. Geyer","doi":"10.1002/9781118408162.CH31","DOIUrl":"https://doi.org/10.1002/9781118408162.CH31","url":null,"abstract":"Ba (1-x) Sr x TiO 3 (BST) thin films appear to be excellent candidates for microwave phase shifters. However, the major issue impeding the utilization of BST films in beam steering devices is the simultaneous achievement of the required performance properties. These properties, at frequencies > 10 GHz, include a dielectric permittivity ≤500, low dielectric loss (<2%), high tunability (-2:1), low leakage current characteristics, and low operating control voltages (<10V). Additionally, these properties must be obtained via an industry standard growth and processing methods. Our approach to satisfy the above mentioned dielectric properties of BST based films is focused on material compositional design and optimized film processing parameters. A systematic study was employed to examine the influence of low concentration Mg acceptor doping and optimized post-deposition annealing conditions on the structure and microwave dielectric properties of BST based thin films fabricated via the metalorganic solution deposition technique. The Mg doping was found to have a strong influence on the material properties of the BST films whereby the films permittivity, dissipation factor, and leakage characteristics were significantly reduced with respect to that of undoped BST. Optimum material properties were achieved for the 5 - 7 mol% Mg doped BST films. At these doping concentrations the dissipation factor (10 GHz) for both films was less than 1.7%. The leakage characteristics were 5.78x10 -8 and 7.97x10 -9 , respectively, and the tunability was ∼40%. Our results suggest that Mg doping and optimized post-deposition annealing served to mitigate the oxygen vacancies thereby lowering the films dielectric loss. Furthermore, the acceptor doping maintained the dielectric permittivity well below 500. Our results suggest the 5-7 mol% Mg doped BST thin films to be commercially viable for microwave phase shifter devices.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"27 1","pages":"287-296"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84086032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118408049.CH1
M. Berrada, F. Gray, T. Kuntzsch, M. Coumil
Zinc sulfide multiscale aggregates can be obtained by homogeneous precipitation in a stirred reactor. Particle size distributions and morphologies are studied as a function of several operating parameters: pH, concentration in reactants (thioacetamide and zinc sulfate), temperature and stirring rate. Four size scales are observed. Stirring rate and pH have an influence respectively on the largest and the smallest size scale. Concentration in thioacetamide has an effect on the largest scales. All size scales depend on temperature.
{"title":"Multi‐Scale Agglomerate Synthesis by Homogeneous Precipitation","authors":"M. Berrada, F. Gray, T. Kuntzsch, M. Coumil","doi":"10.1002/9781118408049.CH1","DOIUrl":"https://doi.org/10.1002/9781118408049.CH1","url":null,"abstract":"Zinc sulfide multiscale aggregates can be obtained by homogeneous precipitation in a stirred reactor. Particle size distributions and morphologies are studied as a function of several operating parameters: pH, concentration in reactants (thioacetamide and zinc sulfate), temperature and stirring rate. Four size scales are observed. Stirring rate and pH have an influence respectively on the largest and the smallest size scale. Concentration in thioacetamide has an effect on the largest scales. All size scales depend on temperature.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"39 1","pages":"1-9"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80519009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118407974.CH9
N. Shimodaira, Kazuya Saito, E. Sekiya, A. Ikushima
Structural changes including relaxation process of 5 mol% fluorine doped silica glass with low initial fictive temperature (T f ) of 700°C has been studied by in-situ Raman spectroscopy at temperatures 27 - 1300°C. With increasing temperature, ω 1 , ω 3 and ω 4 bands, attributed to fundamental skeletal vibrations, monotonously shift in their respective ways, suggesting that both the decreases of average Si-O-Si bond angle and Si-O bond stretching force constant simultaneously occur. On reaching T f , intensity of the D 2 line, thought to be attributed to three-membered ring structure, showed a steady increase with increasing temperature, while all the fundamental vibrations were insensitive to the progress of structural relaxation. From the plot of the D 2 area vs. the inverse "actual" temperature, activation energy of the D 2 formation was estimated to be 0.43 eV, which is very close to the previously reported values estimated from the inverse "fictive" temperature. Furthermore, based on the central-force network model and the Badger's law, the change rate of average Si-O-Si bond angle was estimated from shift of ω 4 frequency to be about -0.02°/°C, which is several times higher than that in T f dependence.
{"title":"In-situ observation of relaxation process in f-doped silica glass by raman spectroscopy","authors":"N. Shimodaira, Kazuya Saito, E. Sekiya, A. Ikushima","doi":"10.1002/9781118407974.CH9","DOIUrl":"https://doi.org/10.1002/9781118407974.CH9","url":null,"abstract":"Structural changes including relaxation process of 5 mol% fluorine doped silica glass with low initial fictive temperature (T f ) of 700°C has been studied by in-situ Raman spectroscopy at temperatures 27 - 1300°C. With increasing temperature, ω 1 , ω 3 and ω 4 bands, attributed to fundamental skeletal vibrations, monotonously shift in their respective ways, suggesting that both the decreases of average Si-O-Si bond angle and Si-O bond stretching force constant simultaneously occur. On reaching T f , intensity of the D 2 line, thought to be attributed to three-membered ring structure, showed a steady increase with increasing temperature, while all the fundamental vibrations were insensitive to the progress of structural relaxation. From the plot of the D 2 area vs. the inverse \"actual\" temperature, activation energy of the D 2 formation was estimated to be 0.43 eV, which is very close to the previously reported values estimated from the inverse \"fictive\" temperature. Furthermore, based on the central-force network model and the Badger's law, the change rate of average Si-O-Si bond angle was estimated from shift of ω 4 frequency to be about -0.02°/°C, which is several times higher than that in T f dependence.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"51 1","pages":"79-86"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82624928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118408100.CH12
E. Zaretsky, V. Paris, G. Kanel, A. Rajendran
Planar impact experiments widely used for determining dynamic strength of hard materials do not provide a possibility to obtain information about the mode, ductile or brittle, of their inelastic response or about thresholds conditions of their compressive failure. Using the controlled sample pre-stressing in the experiments (E. Zaretsky and G. Kanel, APL, 2002, 81, 119) allows one only to conclude whether the response of the studied material at the stress level of elastic limit is brittle or ductile leaving the problem of the material compressive failure threshold still unsolved. The experimental/numerical technique for determination of compression failure threshold of brittle solids is presently suggested. The technique is based on measuring the velocity of the sample/window interface while the sample front surface is struck by curved copper impactor. The divergent stress flow produced by such loading results in the incipient compressive failure of the sample and, respectively, in the appearance of the failure signatures at the measured velocity profile. Reproducing these signatures with aid of AUTODYN 2D commercial computer code including the constitutive and failure description of the studied material yields the values of the principal stress tensor components corresponding to the brittle failure initiation. The locus of these values in the principal stress space is the material compressive failure surface.
{"title":"Compressive Failure Threshold of Brittle Materials","authors":"E. Zaretsky, V. Paris, G. Kanel, A. Rajendran","doi":"10.1002/9781118408100.CH12","DOIUrl":"https://doi.org/10.1002/9781118408100.CH12","url":null,"abstract":"Planar impact experiments widely used for determining dynamic strength of hard materials do not provide a possibility to obtain information about the mode, ductile or brittle, of their inelastic response or about thresholds conditions of their compressive failure. Using the controlled sample pre-stressing in the experiments (E. Zaretsky and G. Kanel, APL, 2002, 81, 119) allows one only to conclude whether the response of the studied material at the stress level of elastic limit is brittle or ductile leaving the problem of the material compressive failure threshold still unsolved. The experimental/numerical technique for determination of compression failure threshold of brittle solids is presently suggested. The technique is based on measuring the velocity of the sample/window interface while the sample front surface is struck by curved copper impactor. The divergent stress flow produced by such loading results in the incipient compressive failure of the sample and, respectively, in the appearance of the failure signatures at the measured velocity profile. Reproducing these signatures with aid of AUTODYN 2D commercial computer code including the constitutive and failure description of the studied material yields the values of the principal stress tensor components corresponding to the brittle failure initiation. The locus of these values in the principal stress space is the material compressive failure surface.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"18 1","pages":"131-145"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82780021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118407844.CH17
P. Sun, H. Wu
In this study, the effects of metakaolin content on workability and mechanical properties of fly ash based inorganic polymeric materials are investigated. Raw materials used include fly ash (FA), metakaolin (Meta), sodium hydroxide (NaOH), silica fume (SF), water and sand. FAM is defined as the total weight of FA and Meta. The ratios of Meta/FA investigated are 0%, 10%, 20% and 30%; NaOH/FAM are 0%, 5%, 7.5%, and 10%; and SF/FAM are 0%, 5%, 7.5%, and 10%. The slump and demold age of each batch are measured, also the compressive strength of prism specimens at ages of 1 day, 7 days and 28 days. Possible effects of various compositions on workability and compressive strength will be discussed in this paper, and attention will be given to the mechanism of the added Al-rich constituent in the polymerization reaction of fly ash based inorganic polymeric materials.
{"title":"On Mix Compositions of Fly Ash Based Inorganic Polymeric Materials","authors":"P. Sun, H. Wu","doi":"10.1002/9781118407844.CH17","DOIUrl":"https://doi.org/10.1002/9781118407844.CH17","url":null,"abstract":"In this study, the effects of metakaolin content on workability and mechanical properties of fly ash based inorganic polymeric materials are investigated. Raw materials used include fly ash (FA), metakaolin (Meta), sodium hydroxide (NaOH), silica fume (SF), water and sand. FAM is defined as the total weight of FA and Meta. The ratios of Meta/FA investigated are 0%, 10%, 20% and 30%; NaOH/FAM are 0%, 5%, 7.5%, and 10%; and SF/FAM are 0%, 5%, 7.5%, and 10%. The slump and demold age of each batch are measured, also the compressive strength of prism specimens at ages of 1 day, 7 days and 28 days. Possible effects of various compositions on workability and compressive strength will be discussed in this paper, and attention will be given to the mechanism of the added Al-rich constituent in the polymerization reaction of fly ash based inorganic polymeric materials.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"42 1","pages":"189-201"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90883507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118408391.CH4
R. Gadow, K. Niessen, A. Candel
A pilot plant equipment for continuous coating of technical textiles is implemented to establish thermal spraying as a new and promising coating technique in the textile industry. In order to apply thermal spraying to temperature sensitive and flexible fiber structures two main difficulties have to be taken into account. First, the flexible structure of a textile fabric has to be fixed and stretched to achieve a sufficient mechanical support. Second, the kinetic and thermal energy of the molten particles and the hot gas jet may damage the fibers and their woven structure both mechanically and chemically. Special winding equipment is designed to allow various fabrics to be fixed and stretched in a way that enables the coating of wound fabrics from "coil to coil". With this equipment even temperature sensitive fabrics, like cotton or polyester, but also aramide, carbon and oxide ceramic fabrics are coated by atmospheric plasma spraying or electric arc wire spraying in the case that higher deposition rates are required. Fabric coils up to a web width of 1500 mm can be coated continuously with a well-defined pre-stress in one single procedure.
{"title":"Advanced Robot Assisted Process for the Series Production of Optimized Oxide Ceramic Coatings on Textile Surfaces","authors":"R. Gadow, K. Niessen, A. Candel","doi":"10.1002/9781118408391.CH4","DOIUrl":"https://doi.org/10.1002/9781118408391.CH4","url":null,"abstract":"A pilot plant equipment for continuous coating of technical textiles is implemented to establish thermal spraying as a new and promising coating technique in the textile industry. In order to apply thermal spraying to temperature sensitive and flexible fiber structures two main difficulties have to be taken into account. First, the flexible structure of a textile fabric has to be fixed and stretched to achieve a sufficient mechanical support. Second, the kinetic and thermal energy of the molten particles and the hot gas jet may damage the fibers and their woven structure both mechanically and chemically. Special winding equipment is designed to allow various fabrics to be fixed and stretched in a way that enables the coating of wound fabrics from \"coil to coil\". With this equipment even temperature sensitive fabrics, like cotton or polyester, but also aramide, carbon and oxide ceramic fabrics are coated by atmospheric plasma spraying or electric arc wire spraying in the case that higher deposition rates are required. Fabric coils up to a web width of 1500 mm can be coated continuously with a well-defined pre-stress in one single procedure.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"10 1","pages":"33-42"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86309522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118408162.CH6
J. Zaykoski, Curtis A. Martin, I. Talmy, G. Zoski
Two-phase dielectrics composed of a high dielectric constant phase (BaTiO 3 ) in combination with a high dielectric strength and low-loss phases have been investigated as candidates for high-voltage capacitors on Navy electrically powered systems. Second phase materials included BaO.Al 2 O 3 .2SiO 2 , MgAl 2 O 4 , and MgO, which showed good chemical compatibility with BaTiO 3 . Solid solubility was observed in the BaTiO 3 - LaAlO 3 system. The optimum sintering conditions were determined for each system, and the phase composition, microstructure, and dielectric properties of the composite materials were characterized. A significant decrease in changes of dielectric constant and volume changes at transformation temperature, as well as the shift of T c were observed for all the systems and related to stresses between the phases as a result of differences in the properties of the components. A decrease in the tetragonality of BaTiO 3 was also observed. The experimental dielectric data show that no single theoretical model can describe the behavior of two-phase materials in all the systems studied. However, they are all in the desirable range showing promise for development of capacitors utilizing the advantageous properties of the components.
{"title":"Two‐Phase Ceramic Dielectrics","authors":"J. Zaykoski, Curtis A. Martin, I. Talmy, G. Zoski","doi":"10.1002/9781118408162.CH6","DOIUrl":"https://doi.org/10.1002/9781118408162.CH6","url":null,"abstract":"Two-phase dielectrics composed of a high dielectric constant phase (BaTiO 3 ) in combination with a high dielectric strength and low-loss phases have been investigated as candidates for high-voltage capacitors on Navy electrically powered systems. Second phase materials included BaO.Al 2 O 3 .2SiO 2 , MgAl 2 O 4 , and MgO, which showed good chemical compatibility with BaTiO 3 . Solid solubility was observed in the BaTiO 3 - LaAlO 3 system. The optimum sintering conditions were determined for each system, and the phase composition, microstructure, and dielectric properties of the composite materials were characterized. A significant decrease in changes of dielectric constant and volume changes at transformation temperature, as well as the shift of T c were observed for all the systems and related to stresses between the phases as a result of differences in the properties of the components. A decrease in the tetragonality of BaTiO 3 was also observed. The experimental dielectric data show that no single theoretical model can describe the behavior of two-phase materials in all the systems studied. However, they are all in the desirable range showing promise for development of capacitors utilizing the advantageous properties of the components.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"20 1","pages":"55-67"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77684711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-04-25DOI: 10.1002/9781118408391.CH8
Chiraporn Auechalitanukul, W. Cannon
To study hot-pressing densification rates of single-grain and multi-grain zirconia powders, spray-dried granules of ZrO 2 -3%Y 2 0 3 (D(10-90) = 35-90 μm) were densified at 1400 °C. Ball milling was utilized to break up the inter-agglomerate bridges. The resulting powder represented the multi-grain particle (MGP). Single-grain particle (SGP) of comparable grain size was obtained by intensive ball milling of the dense granules to the grain size (-0.35 μm diameter). To compare the densification behavior of these powders, specimens of each powder were hot-pressed in a SiC die at 1350 °C for 1 hour. The highest density was achieved by hot pressing MGP screened to +75 pm. The MGP densities by particle creep of the polycrystalline powder controlled by the diffusion distance on the order of the grain size while the SGP is thought to densify primarily by pressure-assisted sintering, i.e., diffusion along the neck between particles. The difference in final density reflects the initially higher packing density of the MGP powder.
{"title":"Densification of single-grain vs. multi-grain zirconia powders","authors":"Chiraporn Auechalitanukul, W. Cannon","doi":"10.1002/9781118408391.CH8","DOIUrl":"https://doi.org/10.1002/9781118408391.CH8","url":null,"abstract":"To study hot-pressing densification rates of single-grain and multi-grain zirconia powders, spray-dried granules of ZrO 2 -3%Y 2 0 3 (D(10-90) = 35-90 μm) were densified at 1400 °C. Ball milling was utilized to break up the inter-agglomerate bridges. The resulting powder represented the multi-grain particle (MGP). Single-grain particle (SGP) of comparable grain size was obtained by intensive ball milling of the dense granules to the grain size (-0.35 μm diameter). To compare the densification behavior of these powders, specimens of each powder were hot-pressed in a SiC die at 1350 °C for 1 hour. The highest density was achieved by hot pressing MGP screened to +75 pm. The MGP densities by particle creep of the polycrystalline powder controlled by the diffusion distance on the order of the grain size while the SGP is thought to densify primarily by pressure-assisted sintering, i.e., diffusion along the neck between particles. The difference in final density reflects the initially higher packing density of the MGP powder.","PeriodicalId":83360,"journal":{"name":"Transactions (English Ceramic Circle)","volume":"8 1","pages":"73-80"},"PeriodicalIF":0.0,"publicationDate":"2012-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82700518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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