The Experts below are selected from a list of 507 Experts worldwide ranked by ideXlab platform
Cristina Leonelli - One of the best experts on this subject based on the ideXlab platform.
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Porcelain stoneware with pegmatite and nepheline syenite solid solutions: Pore size distribution and descriptive microstructure
Journal of The European Ceramic Society, 2013Co-Authors: T. Bakop, C. Djangang, U.c. Melo, Miriam Hanuskova, Cristina LeonelliAbstract:Abstract Investigations correlating the pore size distribution-cumulative pore volume to the microstructure are used to compare the efficiency of two solid solutions of pegmatite and nepheline syenite as fluxing agents for the design of porcelainized stoneware. Particularly the Fusibility of the two solid solutions was modified by adjusting the CaO content of the bodies. As results, the pegmatite based flux produced an extended viscous phase capable on embedding the crystalline phases and close open porosity as from 1175 °C. Conversely, the bodies with nepheline syenite remained relatively porous up to 1225 °C although the similar results of the mechanical strength at this temperature. The investigations on microstructure, pores size distribution and cumulative pore volume indicated almost complete reduction of the open pores in the pegmatite based bodies and the development of a band of closed pores ranged between 0.080 and 0.9 μm showing P series as a more compact structure. For the nepheline syenite based bodies, the incomplete reduction of the open pores and the relative absence of the band of pores between 0.080 and 0.9 μm were ascribed to the difference in Fusibility and the viscosity of the glassy phases. These differences were interpreted in term of the differential action of CaO in Na 2 O–Al 2 O 3 –SiO 2 and K 2 O–Al 2 O 3 –SiO 2 on the amount and viscosity of the liquid phase formed already described in the literature.
Zongqing Bai - One of the best experts on this subject based on the ideXlab platform.
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comparison study of Fusibility between coal ash and synthetic ash
Fuel Processing Technology, 2021Co-Authors: Zongshuai Yuan, Lingxue Kong, Jin Bai, Ji Wang, Zongqing BaiAbstract:Abstract Coal ash Fusibility plays an essential role in selecting coal and determining operation condition for different gasifiers. To understand main factors on ash Fusibility for adjustment, the synthetic ash which composed of pure oxides is widely used in previous study instead of the real coal ash. However, the comparison on Fusibility between coal ash (CA) and synthetic ash (SA) is still unknown. In this study, four typical coals were selected to compare Fusibility between CA and SA. The results indicated that the SA is not suitable to simulate all CA for Fusibility study. For the ash with high-calcium-low-iron, SA can be used because of the same mineral transformation at high temperatures. The AFTs of the ash with high-calcium-high(medium)-iron is higher than that of SA, resulting from difference between gehlenite and akermanite. Mullite is detected in CA with low-calcium-low-iron, so the SA cannot replace CA to investigate Fusibility for absence of mullite. Besides, Fusibility of samples with low liquid content and high viscosity of liquid cannot be simulated by synthetic ash due to different mass transfer rate. The ashes with chemical compositions located in high-melting-temperature region shows an obvious different Fusibility between CA and SA because of the low liquid content.
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flow properties of ash and slag under co gasification of coal and extract residue of direct coal liquefaction residue
Fuel, 2020Co-Authors: Xi Cao, Lingxue Kong, Jin Bai, Zongqing Bai, Baozi Peng, Zhen Liu, Ziyang Feng, Andrzej SzlekAbstract:Abstract Efficient utilization of the extraction residue (ER) of direct coal liquefaction residue is a bottle neck for the efficiency of direct coal liquefaction process. The co-gasification of the ER and coal is a promising way for large-scale utilization of ER. Flow properties of the feedstock including ash Fusibility and slag viscosity are important parameters for the gasification process. To optimize co-gasification of the ER and coal, the ash Fusibility and slag viscosity behavior of ER and coal under gasification conditions were studied. The results show that the ash fusion temperatures (AFTs) of the blending were lowered with the increasing blending ratio of ER due to the high content of calcium and iron in ER. The content of quartz and anorthite in the blended ashes decreased with the increasing ER blending ratio. The slag viscosities at high temperatures also decreased as the blending ratio of ER increased. The high content of calcium and iron in ER resulted in the decrease in the slag polymerization degree because of the break of Si-O structure and transformation from [AlO4]5− to [AlO6]9−. Besides, the slag presented the behavior of a crystalline slag when the ER blending ratio was increased up to 25% for the formation of anorthite during cooling. For the entrained flow gasification, the ER addition can effectively lower the operation temperature of the gasifiers, improve the gasification efficiency and avoid the slag tapping problems. The optimal ER addition should be in the range of 10–20%, and the corresponding tapping temperature was 1258–1575 °C.
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effect of cao fe2o3 ratio on Fusibility of coal ashes with high silica and alumina levels and prediction
Fuel, 2020Co-Authors: Wenju Shi, Lingxue Kong, Jin Bai, Zongqing Bai, Stefan Guhl, Huiling Zhao, Bernd MeyerAbstract:Abstract Ash Fusibility which is usually investigated and evaluated by the ash chemical compositions is widely used to guide the coal selection in boiler and gasifier. Calcium and iron are the main basic oxides in coal ash, which tend to decrease ash fusion temperatures (AFTs). However, the change of AFTs varied with CaO/Fe2O3 mass ratio is not yet revealed. In this work, effect of CaO/Fe2O3 ratio on the Fusibility of ash with high silica and alumina levels was explored under weak reducing atmosphere (CO: CO2 = 3/2, volume ratio). Thermodynamic calculations were applied to investigate the fusion behavior. A general rise of AFTs with the increasing CaO/Fe2O3 ratio was verified, especially for the coal ash with low SiO2 + Al2O3 level and SiO2/Al2O3 mass ratio. Mullite and anorthite are main refractory minerals phase of the ash samples with high SiO2 and Al2O3 levels. The fusion of the ash in anorthite primary phase is the “soft-melting” mechanism, and liquidus temperature was well used to predict flow temperature (FT). However, the liquidus temperature should not be used to predict FT of the ash in mullite primary phase due to the “melting-dissolve” mechanism. A Tmullite model was proposed to predict FT for the ashes in mullite primary phase. The deviation of predicted and measured FT was within the measuring error range (±40 °C), which was supported by 25 real coal ashes.
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the role of residual char on ash flow behavior part 3 effect of fe2o3 content on ash Fusibility and carbothermal reaction
Fuel, 2019Co-Authors: Ji Wang, Lingxue Kong, Jin Bai, Zongqing Bai, Stefan Guhl, Huiling Zhao, Kang Xue, Xiaolong Zhu, Markus Reinmoller, Bernd T MeyerAbstract:Abstract Residual char shows an obvious influence on ash Fusibility through carbothermal reaction. Besides of SiO2, Fe2O3 can also react with residual char to produce metallic iron (Fe) and Fe3Si by Fe-char reaction at high temperatures. Effects of Fe2O3 content on Fusibility and carbothermal reaction of ash with residual char were investigated in this work. The results showed that refractory mineral, metallic iron (Fe), Fe3Si and SiC, are formed by Fe-char reaction and carbothermal reaction between mineral and residual char. When Fe2O3 content of ash is lower than 12%, ash fusion temperatures (AFTs) of ash ascend with the increasing residual char content. However, when Fe2O3 content in ashes is more than 12%, flow temperature (FT) of ashes shows a decrease when residual char content increases from 10% to 15%. In the former case, residual char mainly engages in carbothermal reaction, and ash Fusibility is largely dependent on SiC content which increases with the increasing residual char content. In the latter case, most of residual char is involved in Fe-char reaction. The AFTs of ashes largely depends on Fe3Si at high temperatures. An increase in Fe2O3 content is favorable to formation of Fe3Si. Besides, Fe2O3 in ash lowers temperature of carbothermal reaction from 1500 °C to 1300–1400 °C, while the increase of Fe2O3 content is detrimental to formation of SiC.
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the role of residual char on ash flow behavior part 1 the effect of graphitization degree of residual char on ash Fusibility
Fuel, 2018Co-Authors: Ji Wang, Lingxue Kong, Jin Bai, Zongqing BaiAbstract:Abstract Residual char is widely found in the slag from gasifier, which significantly influences the ash Fusibility due to carbothermal reaction. Residual char has different graphitization degree owing to the residence time and operating temperature of the gasifier, while the effect of graphitization degree of residual char on ash Fusibility and carbothermal reaction is still unknown. In this work, graphite, activated carbon and high temperature demineralized coal char were selected to investigate the effect of graphitization degree of residual char on ash Fusibility under an Ar atmosphere. X-ray diffraction (XRD) and Siroquant software were used to investigate the mineral transformation of the ashes with residual char at high temperatures. Thermogravimetric combined with mass spectrum and differential thermal analysis (TG-MS-DSC) were used to study the effect of graphitization degree of residual char on mineral and carbothermal reaction during heating. When the ash contains same content of residual char, the ash fusion temperatures (AFTs) increase as the graphitization degree of residual char increases. The influence by residual char is more obvious when the mass fraction exceeds 5%. The increase of graphitization degree of residual char impedes the mineral reaction and the carbothermal reaction. The initial temperature of the mineral reaction increases from 1229.3 °C to 1247.2 °C and 1260.4 °C for the ashes with activated carbon, coal char, and graphite, respectively. The peak temperatures of the carbothermal reaction are 1306, 1319 and 1339 °C. At the temperature below 1300 °C, the increase of AFTs is attributed to the increase in the content of cristobalite, and the decrease in the content of anorthite. Above 1300 °C, the increase of AFTs is caused by the increase of the amount of unreacted residual char. Besides, the residual char benefits the formation of FeSi, which also leads to increases of the AFTs.
Yitian Fang - One of the best experts on this subject based on the ideXlab platform.
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Effect of Na2O in Ash Composition on Petroleum Coke Ash Fusibility
Energy & Fuels, 2019Co-Authors: Jiazhou Li, Jiansheng Zhang, Jiantao Zhao, Yitian FangAbstract:Petroleum coke (petcoke) ash Fusibility is closely related to the ash-related fouling and slagging, which have significant effects on its clean and efficient utilization. Sodium (Na) element in petcoke ash is considered to induce ash fouling and slagging. In this paper, we investigate the effect of Na2O on the petcoke ash Fusibility from the perspectives of atmosphere, Na2O content, and temperature. The crystalline minerals and surface morphologies of high-temperature ashes were determined by X-ray diffraction and scanning electronic microscopy, respectively. Thermodynamic software FactSage was applied to calculate the ash melting process. The results show that the ash fusion temperature (AFT) of petcoke ash exhibits a continuous decline with the addition of Na2O at both oxidizing and reducing atmospheres, which is ascribed to the mineral transformation behaviors of high-temperature ashes. Under oxidizing atmosphere, the low-melting Na-bearing albite (NaAlSi3O8) formed at high-temperature ash with the add...
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effect of na2o in ash composition on petroleum coke ash Fusibility
Energy & Fuels, 2019Co-Authors: Jiansheng Zhang, Jiantao Zhao, Yitian FangAbstract:Petroleum coke (petcoke) ash Fusibility is closely related to the ash-related fouling and slagging, which have significant effects on its clean and efficient utilization. Sodium (Na) element in pet...
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investigating a high vanadium petroleum coke ash Fusibility and its modification
Fuel, 2018Co-Authors: Qing'an Xiong, Jiantao Zhao, Jie Shan, Yitian FangAbstract:Abstract Petroleum coke (petcoke), especially high vanadium (V) petcoke, has been produced increasingly because of the growing consumption of petroleum oil. Petcoke ash Fusibility is closely related to ash slagging, which has an important impact on the clean and efficient utilization of petcoke. This study investigates a high V petcoke ash Fusibility and its modification by coal blending and flux addition at reducing atmosphere. X-ray diffraction (XRD) and scanning electronic microscopy (SEM) were used to determine the crystalline minerals and surface morphology of high-temperature ash slag, respectively. The ash fusion process was predicted by thermodynamic equilibrium calculations. The results show that Shengli Oilfield petcoke (SL) has a high ash fusion temperature (AFT), whereas coal blending and flux addition can effectively decrease the AFT of SL, which may be ascribed to the mineral transformations during ash fusion process. The synergistic effects of high-melting vanadium trioxide (V 2 O 3 ) and coulsonite (FeV 2 O 4 ) result in the high AFT of SL. When SL blends with Shenmu (SM) coal and Qi coal (QC), the formation of low-melting andradite (Ca 3 Fe 2 Si 3 O 12 ) and the decrease of V 2 O 3 contribute to the progressive decline of AFT. When the addition of flux calcium oxide (CaO) reaches 10%, the low-melting calcium orthovanadate (Ca 3 V 2 O 8 ) formed under reducing atmosphere decreases the AFT. With increasing CaO content, the content of V 2 O 3 and FeV 2 O 4 decreases while that of Ca 3 V 2 O 8 and Ca 3 Fe 2 Si 3 O 12 increases gradually, which further leads to a decrease in the AFT.
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effect of silica and alumina on petroleum coke ash Fusibility
Energy & Fuels, 2017Co-Authors: Xiaoyu Wang, Jiantao Zhao, Bing Wang, Yitian FangAbstract:Silica (Si) and alumina (Al) elements are always considered to be the important inducements for ash sintering and slagging in the boilers. The effects of SiO2/Al2O3 (S/A) and (SiO2 + Al2O3) ratios on the synthetic petroleum coke (petcoke) ash Fusibility are investigated in this work. Experimental methods including ash fusion temperatures (AFTs) tests, X-ray diffraction, and scanning electronic microscopy are applied to investigate the AFTs, the mineral composition, and surface morphologies of high-temperature ashes. Moreover, thermodynamic equilibrium calculations are also used to predict the ash fusion process. The results show that the AFTs of petcoke ash samples are closely related to the addition of S/A and (SiO2 + Al2O3). The dominant crystalline phases formed in high-temperature ashes with different S/A and (SiO2 + Al2O3) are gehlenite (Ca2Al2SiO7), quartz (SiO2), nickel orthosilicate (Ni2SiO4), and mullite (Al6Si2O13). The AFTs drop sharply with increasing S/A until it reaches 1.5, which may be asc...
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Effect of Ash Composition (Ca, Fe, and Ni) on Petroleum Coke Ash Fusibility
Energy & Fuels, 2017Co-Authors: Jiazhou Li, Xiaodong Chen, Jiantao Zhao, Qing'an Xiong, Yitian FangAbstract:Ash fusion behavior is closely associated with ash-related problems including fouling, sintering, and slagging, which results in a negative effect on the utilization of petroleum coke (petcoke). Petcoke ash contains high levels of vanadium (V), nickel (Ni), iron (Fe), and calcium (Ca). The chemical composition of ash plays an intrinsic role in determining ash Fusibility. To better understand the modification mechanism of the ash fusion temperatures (AFTs), this study investigates the influences of ash composition (CaO, Fe2O3, and NiO) on the synthetic petcoke ash Fusibility from the perspectives of ash composition change and temperature rising. The AFTs of synthetic ash samples were identified by the ash Fusibility tester. X-ray diffraction (XRD) and scanning electronic microscopy (SEM) were applied to explore the relationships between the experimental AFTs and the variation of mineral composition and microstructure of high-temperature ash slag. Moreover, the ash melting process was predicted by the SiO2–...
Lingxue Kong - One of the best experts on this subject based on the ideXlab platform.
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comparison study of Fusibility between coal ash and synthetic ash
Fuel Processing Technology, 2021Co-Authors: Zongshuai Yuan, Lingxue Kong, Jin Bai, Ji Wang, Zongqing BaiAbstract:Abstract Coal ash Fusibility plays an essential role in selecting coal and determining operation condition for different gasifiers. To understand main factors on ash Fusibility for adjustment, the synthetic ash which composed of pure oxides is widely used in previous study instead of the real coal ash. However, the comparison on Fusibility between coal ash (CA) and synthetic ash (SA) is still unknown. In this study, four typical coals were selected to compare Fusibility between CA and SA. The results indicated that the SA is not suitable to simulate all CA for Fusibility study. For the ash with high-calcium-low-iron, SA can be used because of the same mineral transformation at high temperatures. The AFTs of the ash with high-calcium-high(medium)-iron is higher than that of SA, resulting from difference between gehlenite and akermanite. Mullite is detected in CA with low-calcium-low-iron, so the SA cannot replace CA to investigate Fusibility for absence of mullite. Besides, Fusibility of samples with low liquid content and high viscosity of liquid cannot be simulated by synthetic ash due to different mass transfer rate. The ashes with chemical compositions located in high-melting-temperature region shows an obvious different Fusibility between CA and SA because of the low liquid content.
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flow properties of ash and slag under co gasification of coal and extract residue of direct coal liquefaction residue
Fuel, 2020Co-Authors: Xi Cao, Lingxue Kong, Jin Bai, Zongqing Bai, Baozi Peng, Zhen Liu, Ziyang Feng, Andrzej SzlekAbstract:Abstract Efficient utilization of the extraction residue (ER) of direct coal liquefaction residue is a bottle neck for the efficiency of direct coal liquefaction process. The co-gasification of the ER and coal is a promising way for large-scale utilization of ER. Flow properties of the feedstock including ash Fusibility and slag viscosity are important parameters for the gasification process. To optimize co-gasification of the ER and coal, the ash Fusibility and slag viscosity behavior of ER and coal under gasification conditions were studied. The results show that the ash fusion temperatures (AFTs) of the blending were lowered with the increasing blending ratio of ER due to the high content of calcium and iron in ER. The content of quartz and anorthite in the blended ashes decreased with the increasing ER blending ratio. The slag viscosities at high temperatures also decreased as the blending ratio of ER increased. The high content of calcium and iron in ER resulted in the decrease in the slag polymerization degree because of the break of Si-O structure and transformation from [AlO4]5− to [AlO6]9−. Besides, the slag presented the behavior of a crystalline slag when the ER blending ratio was increased up to 25% for the formation of anorthite during cooling. For the entrained flow gasification, the ER addition can effectively lower the operation temperature of the gasifiers, improve the gasification efficiency and avoid the slag tapping problems. The optimal ER addition should be in the range of 10–20%, and the corresponding tapping temperature was 1258–1575 °C.
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effect of cao fe2o3 ratio on Fusibility of coal ashes with high silica and alumina levels and prediction
Fuel, 2020Co-Authors: Wenju Shi, Lingxue Kong, Jin Bai, Zongqing Bai, Stefan Guhl, Huiling Zhao, Bernd MeyerAbstract:Abstract Ash Fusibility which is usually investigated and evaluated by the ash chemical compositions is widely used to guide the coal selection in boiler and gasifier. Calcium and iron are the main basic oxides in coal ash, which tend to decrease ash fusion temperatures (AFTs). However, the change of AFTs varied with CaO/Fe2O3 mass ratio is not yet revealed. In this work, effect of CaO/Fe2O3 ratio on the Fusibility of ash with high silica and alumina levels was explored under weak reducing atmosphere (CO: CO2 = 3/2, volume ratio). Thermodynamic calculations were applied to investigate the fusion behavior. A general rise of AFTs with the increasing CaO/Fe2O3 ratio was verified, especially for the coal ash with low SiO2 + Al2O3 level and SiO2/Al2O3 mass ratio. Mullite and anorthite are main refractory minerals phase of the ash samples with high SiO2 and Al2O3 levels. The fusion of the ash in anorthite primary phase is the “soft-melting” mechanism, and liquidus temperature was well used to predict flow temperature (FT). However, the liquidus temperature should not be used to predict FT of the ash in mullite primary phase due to the “melting-dissolve” mechanism. A Tmullite model was proposed to predict FT for the ashes in mullite primary phase. The deviation of predicted and measured FT was within the measuring error range (±40 °C), which was supported by 25 real coal ashes.
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the role of residual char on ash flow behavior part 3 effect of fe2o3 content on ash Fusibility and carbothermal reaction
Fuel, 2019Co-Authors: Ji Wang, Lingxue Kong, Jin Bai, Zongqing Bai, Stefan Guhl, Huiling Zhao, Kang Xue, Xiaolong Zhu, Markus Reinmoller, Bernd T MeyerAbstract:Abstract Residual char shows an obvious influence on ash Fusibility through carbothermal reaction. Besides of SiO2, Fe2O3 can also react with residual char to produce metallic iron (Fe) and Fe3Si by Fe-char reaction at high temperatures. Effects of Fe2O3 content on Fusibility and carbothermal reaction of ash with residual char were investigated in this work. The results showed that refractory mineral, metallic iron (Fe), Fe3Si and SiC, are formed by Fe-char reaction and carbothermal reaction between mineral and residual char. When Fe2O3 content of ash is lower than 12%, ash fusion temperatures (AFTs) of ash ascend with the increasing residual char content. However, when Fe2O3 content in ashes is more than 12%, flow temperature (FT) of ashes shows a decrease when residual char content increases from 10% to 15%. In the former case, residual char mainly engages in carbothermal reaction, and ash Fusibility is largely dependent on SiC content which increases with the increasing residual char content. In the latter case, most of residual char is involved in Fe-char reaction. The AFTs of ashes largely depends on Fe3Si at high temperatures. An increase in Fe2O3 content is favorable to formation of Fe3Si. Besides, Fe2O3 in ash lowers temperature of carbothermal reaction from 1500 °C to 1300–1400 °C, while the increase of Fe2O3 content is detrimental to formation of SiC.
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the role of residual char on ash flow behavior part 1 the effect of graphitization degree of residual char on ash Fusibility
Fuel, 2018Co-Authors: Ji Wang, Lingxue Kong, Jin Bai, Zongqing BaiAbstract:Abstract Residual char is widely found in the slag from gasifier, which significantly influences the ash Fusibility due to carbothermal reaction. Residual char has different graphitization degree owing to the residence time and operating temperature of the gasifier, while the effect of graphitization degree of residual char on ash Fusibility and carbothermal reaction is still unknown. In this work, graphite, activated carbon and high temperature demineralized coal char were selected to investigate the effect of graphitization degree of residual char on ash Fusibility under an Ar atmosphere. X-ray diffraction (XRD) and Siroquant software were used to investigate the mineral transformation of the ashes with residual char at high temperatures. Thermogravimetric combined with mass spectrum and differential thermal analysis (TG-MS-DSC) were used to study the effect of graphitization degree of residual char on mineral and carbothermal reaction during heating. When the ash contains same content of residual char, the ash fusion temperatures (AFTs) increase as the graphitization degree of residual char increases. The influence by residual char is more obvious when the mass fraction exceeds 5%. The increase of graphitization degree of residual char impedes the mineral reaction and the carbothermal reaction. The initial temperature of the mineral reaction increases from 1229.3 °C to 1247.2 °C and 1260.4 °C for the ashes with activated carbon, coal char, and graphite, respectively. The peak temperatures of the carbothermal reaction are 1306, 1319 and 1339 °C. At the temperature below 1300 °C, the increase of AFTs is attributed to the increase in the content of cristobalite, and the decrease in the content of anorthite. Above 1300 °C, the increase of AFTs is caused by the increase of the amount of unreacted residual char. Besides, the residual char benefits the formation of FeSi, which also leads to increases of the AFTs.
T. Bakop - One of the best experts on this subject based on the ideXlab platform.
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Porcelain stoneware with pegmatite and nepheline syenite solid solutions: Pore size distribution and descriptive microstructure
Journal of The European Ceramic Society, 2013Co-Authors: T. Bakop, C. Djangang, U.c. Melo, Miriam Hanuskova, Cristina LeonelliAbstract:Abstract Investigations correlating the pore size distribution-cumulative pore volume to the microstructure are used to compare the efficiency of two solid solutions of pegmatite and nepheline syenite as fluxing agents for the design of porcelainized stoneware. Particularly the Fusibility of the two solid solutions was modified by adjusting the CaO content of the bodies. As results, the pegmatite based flux produced an extended viscous phase capable on embedding the crystalline phases and close open porosity as from 1175 °C. Conversely, the bodies with nepheline syenite remained relatively porous up to 1225 °C although the similar results of the mechanical strength at this temperature. The investigations on microstructure, pores size distribution and cumulative pore volume indicated almost complete reduction of the open pores in the pegmatite based bodies and the development of a band of closed pores ranged between 0.080 and 0.9 μm showing P series as a more compact structure. For the nepheline syenite based bodies, the incomplete reduction of the open pores and the relative absence of the band of pores between 0.080 and 0.9 μm were ascribed to the difference in Fusibility and the viscosity of the glassy phases. These differences were interpreted in term of the differential action of CaO in Na 2 O–Al 2 O 3 –SiO 2 and K 2 O–Al 2 O 3 –SiO 2 on the amount and viscosity of the liquid phase formed already described in the literature.
