Transformers couple two sections of a circuit by electromagnetic induction. They are widely used to either transform alternating voltage levels or to transmit power or signals across galvanic isolation. Both of these functions are essential for the operation of sensors and controllers. Covering all aspects from idea to circuit performance and from design to manufacture, this paper presents the first comprehensive description of the making of miniaturized, rugged, up-to-100W transformers for embedding into multilayer circuit boards. For circular coils, the well-manageable Ampere-Laplace law is shown to yield reliable designs, predicting correctly the performance of manufactured hardware. This enables fast design without lengthy finite element modelling. In the low-power linear regime, basic relations describe how the device’s characteristics evolve from the material properties and device structure. While scattering Parameters are useful for the analysis of isolated transformers with their intrinsic parasitics, the interaction with the components of the final circuit and the aspects of power and efficiency are addressed by chain matrixes. While these design rules are similar for multilayer boards of different material (like epoxy, Teflon, ceramics), the manufacturing of ceramic board transformers is considered here in detail. Low-temperature-cofired ceramic (LTCC) boards being sintered at 900 °C are particularly suited for harsh environments with chemical or thermal stress as frequently found at sensor positions. The transformer performance usually benefits from or even requires an integrated ceramic core of higher permeability, a ferrite, to shape the magnetic flux. Methods to sinter ferrites inside a dielectric ceramic multilayerandto measure their performance are therefore described in detail.Asthe sintering behaviour of dielectricandmagnetic ceramics differs considerably, their simultaneous sintering is challenging.However, the sintering temperatures of the usefulMnZnand NiZnCu ferrites can be lowered to that of the dielectric material with only moderate loss of permeability by glass additives. Furthermore, thermal mismatch between materials causes catastrophic failure or at least stress and loss of magnetic performance during cooling to room temperature after sintering. This is avoidable by either adjusting the thermal expansion coefficient of the ferrite or by enclosing the ferrite between stressreleasing separation layers.We present the state of the art in materials development according to the first approach as well as fully functional devices made with the second technique. Other applications not directly addressed but well related to this work are characterized by low load resistance in relation to the coil resistance of the transformer. Efficient power transmission then requires that technological solutions are applied to achieve the lowest possible resistive loss inside the coils by an enlarged conductor cross-section. As this is par
{"title":"Circuit-Board-Integrated Transformers Design and Manufacture","authors":"R. Matz, T. Rabe, J. Töpfer, S. Ziesche","doi":"10.4416/JCST2019-00071","DOIUrl":"https://doi.org/10.4416/JCST2019-00071","url":null,"abstract":"Transformers couple two sections of a circuit by electromagnetic induction. They are widely used to either transform alternating voltage levels or to transmit power or signals across galvanic isolation. Both of these functions are essential for the operation of sensors and controllers. Covering all aspects from idea to circuit performance and from design to manufacture, this paper presents the first comprehensive description of the making of miniaturized, rugged, up-to-100W transformers for embedding into multilayer circuit boards. For circular coils, the well-manageable Ampere-Laplace law is shown to yield reliable designs, predicting correctly the performance of manufactured hardware. This enables fast design without lengthy finite element modelling. In the low-power linear regime, basic relations describe how the device’s characteristics evolve from the material properties and device structure. While scattering Parameters are useful for the analysis of isolated transformers with their intrinsic parasitics, the interaction with the components of the final circuit and the aspects of power and efficiency are addressed by chain matrixes. While these design rules are similar for multilayer boards of different material (like epoxy, Teflon, ceramics), the manufacturing of ceramic board transformers is considered here in detail. Low-temperature-cofired ceramic (LTCC) boards being sintered at 900 °C are particularly suited for harsh environments with chemical or thermal stress as frequently found at sensor positions. The transformer performance usually benefits from or even requires an integrated ceramic core of higher permeability, a ferrite, to shape the magnetic flux. Methods to sinter ferrites inside a dielectric ceramic multilayerandto measure their performance are therefore described in detail.Asthe sintering behaviour of dielectricandmagnetic ceramics differs considerably, their simultaneous sintering is challenging.However, the sintering temperatures of the usefulMnZnand NiZnCu ferrites can be lowered to that of the dielectric material with only moderate loss of permeability by glass additives. Furthermore, thermal mismatch between materials causes catastrophic failure or at least stress and loss of magnetic performance during cooling to room temperature after sintering. This is avoidable by either adjusting the thermal expansion coefficient of the ferrite or by enclosing the ferrite between stressreleasing separation layers.We present the state of the art in materials development according to the first approach as well as fully functional devices made with the second technique. Other applications not directly addressed but well related to this work are characterized by low load resistance in relation to the coil resistance of the transformer. Efficient power transmission then requires that technological solutions are applied to achieve the lowest possible resistive loss inside the coils by an enlarged conductor cross-section. As this is par","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"11 1","pages":"44-61"},"PeriodicalIF":0.5,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70791506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Spatafora, J. Isele, H. Ritzhaupt‐Kleissl, V. Hagenmeyer, J. Aktaa
The advanced design of the video inspection system GeoKam for optical inspection of deep boreholes requires the joining of a transparent ceramic window to the Inconel® 718 housing. Active brazing using Incusil ™ ABA as active brazing material gave the best results. Detailed design calculations were performed using the codes ABAQUS® and STAU. Design optimizations resulted in the construction of a sleeve as an adapter part between the ceramic and the Inconel® 718 housing. An important result of the calculations was to avoid sharp edges of the sleeve by realization of a chamfer in order to reduce the fracture probability. The results of the design calculations could be verified with model experiments.
{"title":"Avoiding Thermal-Stress-Induced Failures by Design Optimization when Brazing Perlucor® to Inconel® 718 Components","authors":"L. Spatafora, J. Isele, H. Ritzhaupt‐Kleissl, V. Hagenmeyer, J. Aktaa","doi":"10.4416/JCST2019-00011","DOIUrl":"https://doi.org/10.4416/JCST2019-00011","url":null,"abstract":"The advanced design of the video inspection system GeoKam for optical inspection of deep boreholes requires the joining of a transparent ceramic window to the Inconel® 718 housing. Active brazing using Incusil ™ ABA as active brazing material gave the best results. Detailed design calculations were performed using the codes ABAQUS® and STAU. Design optimizations resulted in the construction of a sleeve as an adapter part between the ceramic and the Inconel® 718 housing. An important result of the calculations was to avoid sharp edges of the sleeve by realization of a chamfer in order to reduce the fracture probability. The results of the design calculations could be verified with model experiments.","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"10 1","pages":"1"},"PeriodicalIF":0.5,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70791448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work has been supported by the Competitiveness Program National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Russian Ministry of Education and Science No. 02. A 03.21.0005; the Russian Science Foundation No16 - 19 - 10213; the Spanish Ministry of Economy and Competitiveness project MAT2015 - 67586-C3-R. E. Klyatskina acknowledges the Valencian Government for her Post-Doc. Contract APOSTD/2014/046 and A. Borrell acknowledges the Spanish Ministry of Economy and Competitiveness for her contract RYC2016 - 20915.
{"title":"Structure Features and Properties of Graphene/Al 2 O 3 Composite","authors":"Valencia Spain n","doi":"10.4416/JCST2018-00006","DOIUrl":"https://doi.org/10.4416/JCST2018-00006","url":null,"abstract":"This work has been supported by the Competitiveness Program National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Russian Ministry of Education and Science No. 02. A 03.21.0005; the Russian Science Foundation No16 - 19 - 10213; the Spanish Ministry of Economy and Competitiveness project MAT2015 - 67586-C3-R. E. Klyatskina acknowledges the Valencian Government for her Post-Doc. Contract APOSTD/2014/046 and A. Borrell acknowledges the Spanish Ministry of Economy and Competitiveness for her contract RYC2016 - 20915.","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"9 1","pages":"215-224"},"PeriodicalIF":0.5,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44980344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Boilet, P. Aubry, L. Henrard, O. Deparis, P. Palmero, V. Lardot, F. Cambier, R. Pérez
Three YAG powders were densified by means of spark plasma sintering (SPS), with the aim of developing optically transparent ceramics. The influence of the physico-chemical characteristics of the powders (purity, agglomeration state and stoichiometry) on the sintering and the optical transmission was investigated. Depending on the powder type, different pre-treatments and/or post-treatments were necessary to increase both homogeneity and optical transmission of the densified parts. In the case of agglomerated powders, dispersion by ultrasonication was efficient and led to better homogeneity and higher optical transmission. Post-treatments such as annealing and post-hipping in air were helpful to reduce oxygen vacancies and residual porosities and improved the optical transmission of the ceramics. The highest values of real in-line transmission (RIT) were obtained under SPS conditions of 50 MPa at 1500 °C and after annealing in air at 1150 °C for 12 h. The achieved RIT value was equal to 66 % at the wavelength of 600 nm.
{"title":"Improving optical transmission of spark-plasma-sintered yag ceramics: Effect of powder conditioning and post-treatments","authors":"L. Boilet, P. Aubry, L. Henrard, O. Deparis, P. Palmero, V. Lardot, F. Cambier, R. Pérez","doi":"10.4416/JCST2017-00052","DOIUrl":"https://doi.org/10.4416/JCST2017-00052","url":null,"abstract":"Three YAG powders were densified by means of spark plasma sintering (SPS), with the aim of developing optically transparent ceramics. The influence of the physico-chemical characteristics of the powders (purity, agglomeration state and stoichiometry) on the sintering and the optical transmission was investigated. Depending on the powder type, different pre-treatments and/or post-treatments were necessary to increase both homogeneity and optical transmission of the densified parts. In the case of agglomerated powders, dispersion by ultrasonication was efficient and led to better homogeneity and higher optical transmission. Post-treatments such as annealing and post-hipping in air were helpful to reduce oxygen vacancies and residual porosities and improved the optical transmission of the ceramics. The highest values of real in-line transmission (RIT) were obtained under SPS conditions of 50 MPa at 1500 °C and after annealing in air at 1150 °C for 12 h. The achieved RIT value was equal to 66 % at the wavelength of 600 nm.","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"9 1","pages":"19-28"},"PeriodicalIF":0.5,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42939045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. G. Schmidt, K. Andersen, E. Stamate, A. Kaiser, K. Hansen
Ce0.9Gd0.1O1.95 (CGO) electrolytes for electrochemical flue gas purification were fabricated by means of tape casting with different types, shapes and sizes of pore-formers. The sintered bodies were characterized with electrochemical impedance spectroscopy, to investigate the role of the different pore-formers on the electrochemical properties of the cast tapes. A strong effect of the different pore-formers on the conductivity (both grain interior and grain boundary conductivities) was observed. In addition, the conductivity data were also correlated with previously obtained gas permeability data. The conductivity data correlated with the permeability data in the sense that a higher permeability lead to a lower conductivity. The porosity of the samples also influenced the conductivities. The higher the porosity of the sintered bodies, the lower the conductivity was, as expected.
{"title":"The Role of Pore-Formers on Grain Interior and Grain Boundary Conductivity in Tape-Cast Porous Sheets for Electrochemical Flue Gas Purification","authors":"C. G. Schmidt, K. Andersen, E. Stamate, A. Kaiser, K. Hansen","doi":"10.4416/JCST2017-00024","DOIUrl":"https://doi.org/10.4416/JCST2017-00024","url":null,"abstract":"Ce0.9Gd0.1O1.95 (CGO) electrolytes for electrochemical flue gas purification were fabricated by means of tape casting with different types, shapes and sizes of pore-formers. The sintered bodies were characterized with electrochemical impedance spectroscopy, to investigate the role of the different pore-formers on the electrochemical properties of the cast tapes. A strong effect of the different pore-formers on the conductivity (both grain interior and grain boundary conductivities) was observed. In addition, the conductivity data were also correlated with previously obtained gas permeability data. The conductivity data correlated with the permeability data in the sense that a higher permeability lead to a lower conductivity. The porosity of the samples also influenced the conductivities. The higher the porosity of the sintered bodies, the lower the conductivity was, as expected.","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"8 1","pages":"485-492"},"PeriodicalIF":0.5,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70791547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-01DOI: 10.15496/PUBLIKATION-31007
Stefan Käßner, Nadja Wichtner, C. Berthold, K. Nickel
{"title":"Novel Cement-Ceramic Encapsulation Material for Electronic Packaging","authors":"Stefan Käßner, Nadja Wichtner, C. Berthold, K. Nickel","doi":"10.15496/PUBLIKATION-31007","DOIUrl":"https://doi.org/10.15496/PUBLIKATION-31007","url":null,"abstract":"","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"9 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67155557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents the design and processing of interlocked interfaces of graded bioactive calcium phosphate coatings on a load-bearing zirconia substrate. Such interfacial structures can effectively enhance bonding between the coating and substrate, and suppress the residual stress across the interfacial region. Multiple coating layers with graded interconnected micropore structures, and common phases across the layer boundary have been considered to minimize the likelihood of interfacial cracking/delamination. The Focused Ion Beam (FIB) technique was used to reveal microscopic details of the interlocked interface formed by the common calcium phosphate and zirconia phases in both the microporous coating and the dense substrate. The interface microstructure and phase characteristics in the substrate and coatings were confirmed by means of FIB-SEM and X-ray diffraction (XRD) analysis respectively. A preliminary Finite Element Modelling (FEM) study shows that graded and interconnected micropore structures in multiple coating layers and tailored material composition can further reduce the interfacial residual stresses. The flexural and bonding strength of the composite and coating/substrate interface respectively have been characterized. A preliminary and limited in vitro cell test shows that the composite has no cytotoxicity to the fibroblasts. A successful interface design is crucial for bioceramic composite design that combines strength and bioactivity to deliver a potential candidate for load-bearing application.
{"title":"Interface design and processing of bioactive microporous calcium phosphate coatings on load-bearing zirconia substrate","authors":"R. Sultana, J. Yang, Z. Sun, Xiaozhi Hu","doi":"10.4416/JCST2017-00005","DOIUrl":"https://doi.org/10.4416/JCST2017-00005","url":null,"abstract":"This study presents the design and processing of interlocked interfaces of graded bioactive calcium phosphate coatings on a load-bearing zirconia substrate. Such interfacial structures can effectively enhance bonding between the coating and substrate, and suppress the residual stress across the interfacial region. Multiple coating layers with graded interconnected micropore structures, and common phases across the layer boundary have been considered to minimize the likelihood of interfacial cracking/delamination. The Focused Ion Beam (FIB) technique was used to reveal microscopic details of the interlocked interface formed by the common calcium phosphate and zirconia phases in both the microporous coating and the dense substrate. The interface microstructure and phase characteristics in the substrate and coatings were confirmed by means of FIB-SEM and X-ray diffraction (XRD) analysis respectively. A preliminary Finite Element Modelling (FEM) study shows that graded and interconnected micropore structures in multiple coating layers and tailored material composition can further reduce the interfacial residual stresses. The flexural and bonding strength of the composite and coating/substrate interface respectively have been characterized. A preliminary and limited in vitro cell test shows that the composite has no cytotoxicity to the fibroblasts. A successful interface design is crucial for bioceramic composite design that combines strength and bioactivity to deliver a potential candidate for load-bearing application.","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"8 1","pages":"265-276"},"PeriodicalIF":0.5,"publicationDate":"2017-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45723858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work presents a low-cost and large-scale synthesis technique for silicon nitride nanofibers and nanobelts based on the use of mesoporous silica-carbon nanocomposites as precursors via a carbothermal reduction and nitridation reaction. The growth mechanisms have been investigated by carrying out heat-treatment of precursors with different C/SiO2 ratios in a flowing nitrogen gas with different flow rates. Highly crystalline silicon nitride nanofibers and nanobelts were obtained after easy separation from the unreacted powder underneath. A higher C/SiO2 ratio gives a better yield of nitride products. The thickness of the ribbons can be maintained as constant while the width of the ribbons can be controlled by tailoring the flow rate of nitrogen gas. The growth direction of Si3N4 nanobelts is parallel to the [100] crystallographic orientation of a-Si3N4.
{"title":"Large-scale synthesis of α-Si3N4 nanofibers and nanobelts from mesoporous silica-carbon nanocomposites","authors":"Kun Wang, H. Wang, Y-B. Cheng","doi":"10.4416/JCST2016-00118","DOIUrl":"https://doi.org/10.4416/JCST2016-00118","url":null,"abstract":"This work presents a low-cost and large-scale synthesis technique for silicon nitride nanofibers and nanobelts based on the use of mesoporous silica-carbon nanocomposites as precursors via a carbothermal reduction and nitridation reaction. The growth mechanisms have been investigated by carrying out heat-treatment of precursors with different C/SiO2 ratios in a flowing nitrogen gas with different flow rates. Highly crystalline silicon nitride nanofibers and nanobelts were obtained after easy separation from the unreacted powder underneath. A higher C/SiO2 ratio gives a better yield of nitride products. The thickness of the ribbons can be maintained as constant while the width of the ribbons can be controlled by tailoring the flow rate of nitrogen gas. The growth direction of Si3N4 nanobelts is parallel to the [100] crystallographic orientation of a-Si3N4.","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"8 1","pages":"259-264"},"PeriodicalIF":0.5,"publicationDate":"2017-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45040235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marjaana Karhu, J. Lagerbom, Päivi Kivikytö-Reponen, A. Ismailov, E. Levänen
Self-propagating high-temperature synthesis (SHS) is a widely known and extensively studied highly exothermicreaction-utilizing technique for making certain advanced composites and intermetallic compounds. However, only few studies have been published about the SHS of pure aluminosilicate ceramics. In the current work, possibilities for aluminosilicate ceramic synthesis and sintering requiring less energy based on the utilization of SHS in air was studied. Kaolinite powder and exothermically reactive metallic aluminium powder were used as raw materials. Thermodynamic calculations for the possible reactions and reaction paths were performed to show the theoretical possibilities for SHS utilization. The chemical reactions, thermal expansion behaviour and formed phaseand microstructures after SHS were compared to the conventional reaction sintering of mullite. Results conclude that highly exothermic reactions above 900 °C relating mainly to aluminium oxidation can ignite the SHS reaction in air atmosphere. After initialization, the reaction proceeded in a self-sustaining manner through entire test pieces, resulting in the formation of an Al2O3 Si phase structure. Thermodynamic calculations showed the total energy balance for mullite formation from aluminium and kaolinite mixtures as highly exothermic in nature only if sufficient oxygen is available to complete the reactions. However, future research is needed to fully utilize SHS in aluminosilicate ceramics processing.
{"title":"Reaction Heat Utilization in Aluminosilicate-Based Ceramics Synthesis and Sintering","authors":"Marjaana Karhu, J. Lagerbom, Päivi Kivikytö-Reponen, A. Ismailov, E. Levänen","doi":"10.4416/JCST2016-00094","DOIUrl":"https://doi.org/10.4416/JCST2016-00094","url":null,"abstract":"Self-propagating high-temperature synthesis (SHS) is a widely known and extensively studied highly exothermicreaction-utilizing technique for making certain advanced composites and intermetallic compounds. However, only few studies have been published about the SHS of pure aluminosilicate ceramics. In the current work, possibilities for aluminosilicate ceramic synthesis and sintering requiring less energy based on the utilization of SHS in air was studied. Kaolinite powder and exothermically reactive metallic aluminium powder were used as raw materials. Thermodynamic calculations for the possible reactions and reaction paths were performed to show the theoretical possibilities for SHS utilization. The chemical reactions, thermal expansion behaviour and formed phaseand microstructures after SHS were compared to the conventional reaction sintering of mullite. Results conclude that highly exothermic reactions above 900 °C relating mainly to aluminium oxidation can ignite the SHS reaction in air atmosphere. After initialization, the reaction proceeded in a self-sustaining manner through entire test pieces, resulting in the formation of an Al2O3 Si phase structure. Thermodynamic calculations showed the total energy balance for mullite formation from aluminium and kaolinite mixtures as highly exothermic in nature only if sufficient oxygen is available to complete the reactions. However, future research is needed to fully utilize SHS in aluminosilicate ceramics processing.","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"8 1","pages":"101-112"},"PeriodicalIF":0.5,"publicationDate":"2017-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49425811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A TiB2-SiC-5 wt %Ni ceramic composite with high flexural strength and fracture toughness was fabricated in the reactive hot pressing (RHP) process. Different sintering times and sintering temperatures were employed. The strengthening and toughening mechanisms were investigated in detail. The composition and microstructure were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and energy-dispersive spectroscopy (EDS). The sintering time and sintering temperature had a significant influence on the mechanical properties and microstructure of the composite. The mechanical properties decreased as the sintering time was increased from 30 to 45 min, and subsequently increased with the further increase of the sintering time. The mechanical properties of the composite increased gradually as the sintering temperature increased. For the investigated range of parameters, the composite prepared at 1700 °C for 30 min had the optimum comprehensive mechanical properties with flexural strength of 1121 ± 31 MPa, fracture toughness of 7.9 ± 0.58 MPa⋅m1/2 and hardness of 21.3 ± 0.62 GPa. The improved flexural strength and fracture toughness of the composite were attributed to the strengthening and toughening effects of Ni and the elongated TiB2 grains, the intragranular nano-particle structure, and the dislocations and stacking fault. The clean interface is also conducive to the improved flexural strength.
{"title":"Mechanical Properties, Strengthening and Toughening Mechanisms of Reactive-Hot-Pressed TiB2-SiC-Ni Ceramic Composites","authors":"G. Zhao, C. Huang, N. He, H. Liu","doi":"10.4416/JCST2016-00110","DOIUrl":"https://doi.org/10.4416/JCST2016-00110","url":null,"abstract":"A TiB2-SiC-5 wt %Ni ceramic composite with high flexural strength and fracture toughness was fabricated in the reactive hot pressing (RHP) process. Different sintering times and sintering temperatures were employed. The strengthening and toughening mechanisms were investigated in detail. The composition and microstructure were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and energy-dispersive spectroscopy (EDS). The sintering time and sintering temperature had a significant influence on the mechanical properties and microstructure of the composite. The mechanical properties decreased as the sintering time was increased from 30 to 45 min, and subsequently increased with the further increase of the sintering time. The mechanical properties of the composite increased gradually as the sintering temperature increased. For the investigated range of parameters, the composite prepared at 1700 °C for 30 min had the optimum comprehensive mechanical properties with flexural strength of 1121 ± 31 MPa, fracture toughness of 7.9 ± 0.58 MPa⋅m1/2 and hardness of 21.3 ± 0.62 GPa. The improved flexural strength and fracture toughness of the composite were attributed to the strengthening and toughening effects of Ni and the elongated TiB2 grains, the intragranular nano-particle structure, and the dislocations and stacking fault. The clean interface is also conducive to the improved flexural strength.","PeriodicalId":48807,"journal":{"name":"Journal of Ceramic Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":0.5,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70791495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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