Emad Ewais | Google - Academia.edu (original) (raw)
Papers by Emad Ewais
Journal of Materials Science and Engineering A, 2015
The bioactivity and physico-mechanical properties of calcia magnesia based composites developed i... more The bioactivity and physico-mechanical properties of calcia magnesia based composites developed in this study were investigated. Different composite mixtures containing calcia-magnesia have been processed with the addition of alumina, silica or zircon. These system powders were formed and fired at two different temperatures. The produced composites were characterized by means of X-ray diffraction, SEM (scanning electron microscope) equipped with EDS (energy dispersive X-ray spectrometry), density and apparent porosity measurements, mechanical testing and in-vitro evaluation in a SBF (simulated body fluid) solution. The compositions termed "I", "II" and "III" gave clear tendency towards the formation-ability of HA (hydroxyapatite). Composite "1" gave cubic and spindle HA crystallite, while composites "II" and "III" fired at 1,300 and 1,400 °C formed typically "cauliflower" morphology and their evaluated physico-mechanical properties are similar to the properties of human cortical bone. Thus, composites "II" and "III" might be a promising bone implant materials. Beside the bioactivitiy of composite "I", it also contains highly CA (cementing phase) and MA (bioinert) phases, therefore, it might be nominated as a promising bioceramic material especially for different purposes such as scaffold, bone replacement, bone repair and coating.
Journal of Asian Ceramic Societies, 2021
Sialons are the spotlight of current investigation as low-cost and outstanding alternatives to th... more Sialons are the spotlight of current investigation as low-cost and outstanding alternatives to the currently used metal alloys in various applications. The excellent hightemperature properties, high mechanical properties, structural reliability, good sinterability, easy densification with its low-cost processing make them superior candidates in many applications such as automotive engines, high-performance bearings, wear components, and gas turbine blades. In addition, the existence of two interstitial crystallographic sites in their crystal structure gives the opportunity to accommodate some rare earth element activators such as Eu 2+ , Yb 2+ , Ce 3+ , and Pr 3+. These types of sialonbased materials have recently found a new promising application as a luminescent material for white light-emitting diodes. The aim of this review is to survey and provide a comprehensive look at the most relevant and significant publications regarding the development of sialons and their processing into both structural and luminescent materials. Such information forms a database that could enable scholars and engineers to tailor a final product derived from sialons with specific characteristics for a certain application. This review article should be of concern to engineers and scientists interested in the development and utilization of sialons for structural and wLEDs applications.
International Journal of Materials Technology and Innovation, 2021
Journal of the Korean Ceramic Society
This research presents the possibility of producing durable foam glasses from glass cullet using ... more This research presents the possibility of producing durable foam glasses from glass cullet using SiC/AlN foaming agent. The foaming agent generated by the SiC and AlN couple results in a more homogeneous microstructure and thus the emergence of foam glasses with better properties compared to the nitride foaming agent used alone in our previous work. The fabricated foam had a crack-free, 3-D cellular structure with macropores whose geometries varied between elliptical-, pentagonal-, and hexagonal-shaped constructions. It also had a lightweight (≥ 0.18 g/cm3), high cold crushing strength (≤ 4.5 MPa), low thermal conductivity (0.09–0.16 W/m K), and contained more than ~ 89 vol.% gas bubbles enclosed between 11 vol.% impervious glass walls. The properties accomplished by the foam prepared in this work conform with the requirements of international standard for commercial glass foams, demonstrating its strong capability to be utilized in potential applications in sustainable buildings an...
Refractories and Industrial Ceramics, 2021
Addition of various reinforcements was studied in an attempt to produce a TiC-Al 2 O 3 composite ... more Addition of various reinforcements was studied in an attempt to produce a TiC-Al 2 O 3 composite with high density, homogeneous microstructure, and outstanding mechanical properties for use in aggressive media using self-propagating high-temperature synthesis (SHS). Ductile Ni-metal powder (5-20 wt.%) and Al 2 O 3 and ZrO 2 (1 mole fraction) dilutions with and without Ni addition were introduced into TiC-Al 2 O 3 composite synthesized by combined SHS and direct consolidation (DC). The influence of the Ni content and dilution with Al 2 O 3 and ZrO 2 on the phase composition, densification behavior, microstructure, and mechanical properties of the synthesized TiC-Al 2 O 3 composite was investigated. The best results were obtained by adding Ni (5 wt.%) to the TiC-Al 2 O 3 composite. However, the chemical reactions between the starting precursors were disturbed and the composite characteristics worsened if the Ni content was increased to >5 wt.%. Accordingly, addition of 5 wt.% Ni was suggested to produce a highly dense TiC-Al 2 O 3 composite with a homogenized morphology and unparalleled mechanical properties. Moreover, the produced composites could be used successfully in aggressive media and tribological applications.
International Journal of Materials Technology and Innovation
This research presents the possibility of producing durable foam glasses from soda-lime glass was... more This research presents the possibility of producing durable foam glasses from soda-lime glass waste using SiC foaming agent via viscous flow sintering at 900 ℃. The use of SiC instead of the nitride foaming agent applied in a previous work results in a more homogeneous microstructure and thus the emergence of foamed glass with better mechanical properties. The fabricated foam had a crack-free, 3-D cellular structure with closed pores of various geometries. It also had a lightweight (~ 0.233 g/cm 3), high cold crushing strength (CCS) (3.37 MPa), low thermal conductivity (0.105 W/m-K), and contained more than ~ 92.7 vol.% gas bubbles enclosed between 7.3 vol.% impervious glass walls. The properties accomplished by the glass foam prepared in this work conform with the requirements of the international standard for commercial glass foams, demonstrating its strong capability to be utilized in potential applications in sustainable buildings and energy efficiency in the industry.
Journal of the Korean Ceramic Society, 2021
c-zirconia ceramic composites have been synthesized by spark plasma sintering (SPS) technique fro... more c-zirconia ceramic composites have been synthesized by spark plasma sintering (SPS) technique from commercial m-ZrO2, Y2O3 and waste-derived magnesium aluminate spinel (MA) powders. In this study, effect of MA addition on stabilization and reinforcement of 5 mol% yttria-stabilized zirconia (YSZ) was carefully investigated. Spark plasma sintering of designed powder mixtures at 1400 °C for 30 min and 40 MPa produce fully dense compacts with an average grain size of 0.5–10 μm. The pressure was gradually increased up to 40 MPa using argon gas and was kept until the end of the sintering process. The refined microstructure (0.5–10 μm) obtained in this study has achieved superior compaction resistance values that are ten times more than strength values of conventionally sintered specimens. Such improvement in compaction resistance of the sintered specimens was attributed to particle size refinement and grain boundary enhancement. What’s more, spark-plasma sintered composites containing 10–50 wt% MA revealed higher resistance to low temperature degradation (LTD) than the reference composite that doesn’t contain MA spinel; where about ~ 2.8% of t-ZrO2 was converted into m-ZrO2 in case of the latter composite while aging test didn’t influence at all on the structure of the former composites. The outcomes indicated that MA has a significant effect on m-ZrO2 stabilization into a cubic phase structure that concurrently owned an enhanced and comparable compression resistance to Yttrium-doped t-ZrO2 (Y-TZP). In this respect, the ternary oxide ceramic composite systems prepared in this study present huge potential for development c-ZrO2-based industrial ceramics with a wide spectrum of mechanical characteristics for high-tech engineering applications of harsh-stress and humid environments.
International Journal of Applied Ceramic Technology, 2020
Refractories and Industrial Ceramics, 2020
In an attempt to optimize a qualified ceramic material with enhanced and outstanding characterist... more In an attempt to optimize a qualified ceramic material with enhanced and outstanding characteristics, the current work aims to study the processing of dense Si3N4 based ceramic composites by the hot pressing (HP) method. The proposed material consists of an equimolecular mixture of α- and β-Si3N4 with the addition of various amounts of MgO–Al2O3 spinel as sintering additive. Investigation of the different characteristics of the obtained ceramics with respect to densification parameters, hardness, fracture toughness, and bending strength and cold crushing strength was performed and correlated with their microstructure behavior. Results indicated that a dense, well distributed structure of silicon nitride ceramics was attained by the addition of various amounts of magnesium aluminate spinel. Moreover, insertion of MgO–Al2O3 mixtures into Si3N4 ceramics was established to enhance their grain growth demeanor and increase the elongated β-Si3N4 grains and their aspect ratio. Furthermore, it was revealed that increasing the MgO ratio relative to that of Al2O3 in the spinel structure was responsible for enhancing the different properties of the produced nitride ceramics. Results suggested that the obtained hot pressed Si3N4 ceramics seeded with β- Si3N4 particles can be a successful candidate in the automotive industry as alternative parts for vehicle engines.
Journal of the Korean Ceramic Society, 2020
Fully cubic-stabilized zirconia ceramic composites have been successfully fabricated by conventio... more Fully cubic-stabilized zirconia ceramic composites have been successfully fabricated by conventional sintering technique using commercial monoclinic zirconia, Yttrium oxide and waste-derived magnesia-rich spinel (MMA) powder mixtures. In this study, effect of MMA content and sintering temperature on stabilization and densification properties of zirconia has been duly considered. The obtained results showed that m-ZrO 2 in MMA-free Z0 reference specimen is partially stabilized upon temperature rising into tetragonal phase by Y 3+ ions diffusion inside zirconia structure. MMA-free Z0 reference specimen sintered at 1600 ºC showed m-and t-ZrO 2 dual-phase structure with a relative density of 80.2%. Unlike, upon rising the sintering temperature, Z10-Z50 composites containing 10-50 wt% MMA demonstrated higher relative density of more than 99% and showed variant behavior, where their m-ZrO 2 is transformed and stabilized into cubic form by diffusion of Y 3+ , Mg 2+ and Al 3+ ions inside zirconia lattice structure. The outcomes indicate that MMA has significantly improved both the densification and stabilization behavior of m-ZrO 2 through facilitating Y 3+ diffusion inside zirconia lattice structure.
International Journal of Applied Ceramic Technology, 2020
Journal of Alloys and Compounds, 2018
In the present work, based on the environmental issues and on the properties of glass foams, the ... more In the present work, based on the environmental issues and on the properties of glass foams, the foaming behavior of the float glass waste (soda-lime glass waste) generated from a lapping machine was systematically investigated at temperatures between 850 and 950 C using different percentages of nano aluminum nitride (2.5e7.5 wt%) as a foaming agent. Physical properties, compressive strength, the hot wire method, SEM and X-ray diffractometry were used to characterize foams and evaluate the foaming ability and the sintering process. The foaming process was found to depend on the initial batch composition and the sintering temperature. Bulk density of the obtained products is less than 0.5 g cm À3. The cold compressive strength of the foams ranged between 0.65 and 2.48 MPa and the thermal conductivity between 0.09 and 0.106 Wm À1 K À1. Both cold crushing strength and thermal conductivity increased with increasing foam density. The obtained results are promising and the present technology is cost-effective and suitable for the large scale production of a wide range of porous glass-ceramics that have appropriate properties to be used for various structural applications.
2016 International Renewable and Sustainable Energy Conference (IRSEC), Nov 1, 2016
Ceramic foams are promlsmg materials for volumetrie solar receivers in concentrated solar power (... more Ceramic foams are promlsmg materials for volumetrie solar receivers in concentrated solar power (CSP) plants. Understanding the solar heat flux distribution on the receiver is of great importance for optimizing the receiver volumetrie efficiency and thermal performance. This work presents a 3D optical analysis of ceramic based volumetrie solar receivers. The optical analysis is conducted using a Monte Carlo based solar ray tracing software. Ceramic foams are represented by idealized packed tetrakaidecahedron structures. The absorbed heat flux distribution and the effect of cell size, porosity and absorptivity on the penetration depth of the absorbed heat flux are investigated. Comparisons have been made with extruded honeycomb receivers. The results clearly demonstrate the dependence of flux distribution and penetration depth of solar rays on the material absorptivity and structure. The simulation results show a uniform heat flux distribution on the frontal faces with an intensity that increases with increasing the material absorptivity. Both the porosity and the cell size have a great effect on the penetration depth of the absorbed heat flux. In general, foam structure shows larger penetration depths than extruded honeycombs.
Materials Research Express, 2018
Materials Research Express, 2019
Journal of Materials Engineering and Performance, 2017
Boron carbide powder was synthesized from boric acid and lactose mixtures via easy procedure. Bor... more Boron carbide powder was synthesized from boric acid and lactose mixtures via easy procedure. Boric acid and lactose solution mixtures were roasted in stainless steel pot at 280°C for 24 h. Boron carbide was obtained by heating the roasted samples under flowing of industrial argon gas at 1500°C for 3 h. The amount of borate ester compound in the roasted samples was highly influenced by the boron/carbon ratio in the starting mixtures and plays a versatile role in the produced boron carbide. The high-purity boron carbide powder was produced with a sample composed of lowest boron/carbon ratio of 1:1 without calcination step. Particle morphology was changed from nano-needles like structure of 8-10 nm size with highest carbon ratio mixture to spherical shape of >150 nm size with lowest one. The oxidation resistance performance of boron carbide is highly dependent on the morphology and grain size of the synthesized powder.
International Journal of Materials Engineering and Technology, 2016
Journal of Materials Science, 2016
The effect of the yttria powder additions on the synthesized nano-alumina particles from Al scrap... more The effect of the yttria powder additions on the synthesized nano-alumina particles from Al scrap was investigated. The Al scrap was dissolved in an aqua regia solution at the room temperature and then was precipitated at a pH of 9-10. After calcination of the formed gel, 0-20 wt% yttria particles were added and mixed. The dried slurries were compacted and sintered at a temperature range of 1550-1650°C. The phase composition, microstructure, densification, and mechanical properties of the sintered specimens were evaluated. Near fully dense alumina specimens at a temperature of 1550°C as well as the sintered insitu YAG-alumina composites at 1650°C were successfully produced. The high hardness for all specimens was recorded at a sintering temperature of 1650°C and attributed to the formation of YAG and grain growth of alumina. Furthermore, the addition of yttria and sintering temperature showed a significant effect on the sintered specimens microstructure, densification process, and phase composition.
Refractories and Industrial Ceramics, 2017
Insulating refractory bricks with different densities have been successfully produced from firing... more Insulating refractory bricks with different densities have been successfully produced from firing of sludge of water treatment produced from the water treatment plant at El-Kureimat power station (Giza, Egypt) and rice husk ash mixtures. Different batches from the sludge of water treatment (SWT) with varying amounts of rice husk ash (RHA) were well mixed, formed, dried, and finally fired at different temperatures ranging (800-1200°C). The filter pressed sludge was dried and fired at the same temperature range. The physico-mechanical properties of the fired specimens of sludge-rice husk ash batches and the filtered press sludge were investigated and evaluated. The results showed that the sludge of water treatment plant can be used successfully to produce high quality insulating refractory bricks for various thermal insulating applications.
A successful utilization of two waste metal oxides (Al-slag and silica fumes) in preparing valuab... more A successful utilization of two waste metal oxides (Al-slag and silica fumes) in preparing valuable cordierite ceramic material and the fabrication of the produced cordierite in a 3D porous structure have been achieved through this investigation. The optimum sintering conditions (in terms of sintering temperature and time) for producing dense mixture compact containing lower amount of undesirable phases beside the main desired cordierite phase were determined. The results revealed that a sintering temperature of 1325C and a sintering time of 2 h were the most appropriate conditions during cordierite synthesis. However, the key role for the successful fabrication of a porous ceramic body via replica method is to prepare a well-dispersed suspension from the mixture of raw materials. Herein the optimum conditions for preparing a well-dispersed suspension in terms of type and concentration of additives as well as suspension pH were evaluated. The using of 0.2% sodium silicate and a susp...
Journal of Materials Science and Engineering A, 2015
The bioactivity and physico-mechanical properties of calcia magnesia based composites developed i... more The bioactivity and physico-mechanical properties of calcia magnesia based composites developed in this study were investigated. Different composite mixtures containing calcia-magnesia have been processed with the addition of alumina, silica or zircon. These system powders were formed and fired at two different temperatures. The produced composites were characterized by means of X-ray diffraction, SEM (scanning electron microscope) equipped with EDS (energy dispersive X-ray spectrometry), density and apparent porosity measurements, mechanical testing and in-vitro evaluation in a SBF (simulated body fluid) solution. The compositions termed "I", "II" and "III" gave clear tendency towards the formation-ability of HA (hydroxyapatite). Composite "1" gave cubic and spindle HA crystallite, while composites "II" and "III" fired at 1,300 and 1,400 °C formed typically "cauliflower" morphology and their evaluated physico-mechanical properties are similar to the properties of human cortical bone. Thus, composites "II" and "III" might be a promising bone implant materials. Beside the bioactivitiy of composite "I", it also contains highly CA (cementing phase) and MA (bioinert) phases, therefore, it might be nominated as a promising bioceramic material especially for different purposes such as scaffold, bone replacement, bone repair and coating.
Journal of Asian Ceramic Societies, 2021
Sialons are the spotlight of current investigation as low-cost and outstanding alternatives to th... more Sialons are the spotlight of current investigation as low-cost and outstanding alternatives to the currently used metal alloys in various applications. The excellent hightemperature properties, high mechanical properties, structural reliability, good sinterability, easy densification with its low-cost processing make them superior candidates in many applications such as automotive engines, high-performance bearings, wear components, and gas turbine blades. In addition, the existence of two interstitial crystallographic sites in their crystal structure gives the opportunity to accommodate some rare earth element activators such as Eu 2+ , Yb 2+ , Ce 3+ , and Pr 3+. These types of sialonbased materials have recently found a new promising application as a luminescent material for white light-emitting diodes. The aim of this review is to survey and provide a comprehensive look at the most relevant and significant publications regarding the development of sialons and their processing into both structural and luminescent materials. Such information forms a database that could enable scholars and engineers to tailor a final product derived from sialons with specific characteristics for a certain application. This review article should be of concern to engineers and scientists interested in the development and utilization of sialons for structural and wLEDs applications.
International Journal of Materials Technology and Innovation, 2021
Journal of the Korean Ceramic Society
This research presents the possibility of producing durable foam glasses from glass cullet using ... more This research presents the possibility of producing durable foam glasses from glass cullet using SiC/AlN foaming agent. The foaming agent generated by the SiC and AlN couple results in a more homogeneous microstructure and thus the emergence of foam glasses with better properties compared to the nitride foaming agent used alone in our previous work. The fabricated foam had a crack-free, 3-D cellular structure with macropores whose geometries varied between elliptical-, pentagonal-, and hexagonal-shaped constructions. It also had a lightweight (≥ 0.18 g/cm3), high cold crushing strength (≤ 4.5 MPa), low thermal conductivity (0.09–0.16 W/m K), and contained more than ~ 89 vol.% gas bubbles enclosed between 11 vol.% impervious glass walls. The properties accomplished by the foam prepared in this work conform with the requirements of international standard for commercial glass foams, demonstrating its strong capability to be utilized in potential applications in sustainable buildings an...
Refractories and Industrial Ceramics, 2021
Addition of various reinforcements was studied in an attempt to produce a TiC-Al 2 O 3 composite ... more Addition of various reinforcements was studied in an attempt to produce a TiC-Al 2 O 3 composite with high density, homogeneous microstructure, and outstanding mechanical properties for use in aggressive media using self-propagating high-temperature synthesis (SHS). Ductile Ni-metal powder (5-20 wt.%) and Al 2 O 3 and ZrO 2 (1 mole fraction) dilutions with and without Ni addition were introduced into TiC-Al 2 O 3 composite synthesized by combined SHS and direct consolidation (DC). The influence of the Ni content and dilution with Al 2 O 3 and ZrO 2 on the phase composition, densification behavior, microstructure, and mechanical properties of the synthesized TiC-Al 2 O 3 composite was investigated. The best results were obtained by adding Ni (5 wt.%) to the TiC-Al 2 O 3 composite. However, the chemical reactions between the starting precursors were disturbed and the composite characteristics worsened if the Ni content was increased to >5 wt.%. Accordingly, addition of 5 wt.% Ni was suggested to produce a highly dense TiC-Al 2 O 3 composite with a homogenized morphology and unparalleled mechanical properties. Moreover, the produced composites could be used successfully in aggressive media and tribological applications.
International Journal of Materials Technology and Innovation
This research presents the possibility of producing durable foam glasses from soda-lime glass was... more This research presents the possibility of producing durable foam glasses from soda-lime glass waste using SiC foaming agent via viscous flow sintering at 900 ℃. The use of SiC instead of the nitride foaming agent applied in a previous work results in a more homogeneous microstructure and thus the emergence of foamed glass with better mechanical properties. The fabricated foam had a crack-free, 3-D cellular structure with closed pores of various geometries. It also had a lightweight (~ 0.233 g/cm 3), high cold crushing strength (CCS) (3.37 MPa), low thermal conductivity (0.105 W/m-K), and contained more than ~ 92.7 vol.% gas bubbles enclosed between 7.3 vol.% impervious glass walls. The properties accomplished by the glass foam prepared in this work conform with the requirements of the international standard for commercial glass foams, demonstrating its strong capability to be utilized in potential applications in sustainable buildings and energy efficiency in the industry.
Journal of the Korean Ceramic Society, 2021
c-zirconia ceramic composites have been synthesized by spark plasma sintering (SPS) technique fro... more c-zirconia ceramic composites have been synthesized by spark plasma sintering (SPS) technique from commercial m-ZrO2, Y2O3 and waste-derived magnesium aluminate spinel (MA) powders. In this study, effect of MA addition on stabilization and reinforcement of 5 mol% yttria-stabilized zirconia (YSZ) was carefully investigated. Spark plasma sintering of designed powder mixtures at 1400 °C for 30 min and 40 MPa produce fully dense compacts with an average grain size of 0.5–10 μm. The pressure was gradually increased up to 40 MPa using argon gas and was kept until the end of the sintering process. The refined microstructure (0.5–10 μm) obtained in this study has achieved superior compaction resistance values that are ten times more than strength values of conventionally sintered specimens. Such improvement in compaction resistance of the sintered specimens was attributed to particle size refinement and grain boundary enhancement. What’s more, spark-plasma sintered composites containing 10–50 wt% MA revealed higher resistance to low temperature degradation (LTD) than the reference composite that doesn’t contain MA spinel; where about ~ 2.8% of t-ZrO2 was converted into m-ZrO2 in case of the latter composite while aging test didn’t influence at all on the structure of the former composites. The outcomes indicated that MA has a significant effect on m-ZrO2 stabilization into a cubic phase structure that concurrently owned an enhanced and comparable compression resistance to Yttrium-doped t-ZrO2 (Y-TZP). In this respect, the ternary oxide ceramic composite systems prepared in this study present huge potential for development c-ZrO2-based industrial ceramics with a wide spectrum of mechanical characteristics for high-tech engineering applications of harsh-stress and humid environments.
International Journal of Applied Ceramic Technology, 2020
Refractories and Industrial Ceramics, 2020
In an attempt to optimize a qualified ceramic material with enhanced and outstanding characterist... more In an attempt to optimize a qualified ceramic material with enhanced and outstanding characteristics, the current work aims to study the processing of dense Si3N4 based ceramic composites by the hot pressing (HP) method. The proposed material consists of an equimolecular mixture of α- and β-Si3N4 with the addition of various amounts of MgO–Al2O3 spinel as sintering additive. Investigation of the different characteristics of the obtained ceramics with respect to densification parameters, hardness, fracture toughness, and bending strength and cold crushing strength was performed and correlated with their microstructure behavior. Results indicated that a dense, well distributed structure of silicon nitride ceramics was attained by the addition of various amounts of magnesium aluminate spinel. Moreover, insertion of MgO–Al2O3 mixtures into Si3N4 ceramics was established to enhance their grain growth demeanor and increase the elongated β-Si3N4 grains and their aspect ratio. Furthermore, it was revealed that increasing the MgO ratio relative to that of Al2O3 in the spinel structure was responsible for enhancing the different properties of the produced nitride ceramics. Results suggested that the obtained hot pressed Si3N4 ceramics seeded with β- Si3N4 particles can be a successful candidate in the automotive industry as alternative parts for vehicle engines.
Journal of the Korean Ceramic Society, 2020
Fully cubic-stabilized zirconia ceramic composites have been successfully fabricated by conventio... more Fully cubic-stabilized zirconia ceramic composites have been successfully fabricated by conventional sintering technique using commercial monoclinic zirconia, Yttrium oxide and waste-derived magnesia-rich spinel (MMA) powder mixtures. In this study, effect of MMA content and sintering temperature on stabilization and densification properties of zirconia has been duly considered. The obtained results showed that m-ZrO 2 in MMA-free Z0 reference specimen is partially stabilized upon temperature rising into tetragonal phase by Y 3+ ions diffusion inside zirconia structure. MMA-free Z0 reference specimen sintered at 1600 ºC showed m-and t-ZrO 2 dual-phase structure with a relative density of 80.2%. Unlike, upon rising the sintering temperature, Z10-Z50 composites containing 10-50 wt% MMA demonstrated higher relative density of more than 99% and showed variant behavior, where their m-ZrO 2 is transformed and stabilized into cubic form by diffusion of Y 3+ , Mg 2+ and Al 3+ ions inside zirconia lattice structure. The outcomes indicate that MMA has significantly improved both the densification and stabilization behavior of m-ZrO 2 through facilitating Y 3+ diffusion inside zirconia lattice structure.
International Journal of Applied Ceramic Technology, 2020
Journal of Alloys and Compounds, 2018
In the present work, based on the environmental issues and on the properties of glass foams, the ... more In the present work, based on the environmental issues and on the properties of glass foams, the foaming behavior of the float glass waste (soda-lime glass waste) generated from a lapping machine was systematically investigated at temperatures between 850 and 950 C using different percentages of nano aluminum nitride (2.5e7.5 wt%) as a foaming agent. Physical properties, compressive strength, the hot wire method, SEM and X-ray diffractometry were used to characterize foams and evaluate the foaming ability and the sintering process. The foaming process was found to depend on the initial batch composition and the sintering temperature. Bulk density of the obtained products is less than 0.5 g cm À3. The cold compressive strength of the foams ranged between 0.65 and 2.48 MPa and the thermal conductivity between 0.09 and 0.106 Wm À1 K À1. Both cold crushing strength and thermal conductivity increased with increasing foam density. The obtained results are promising and the present technology is cost-effective and suitable for the large scale production of a wide range of porous glass-ceramics that have appropriate properties to be used for various structural applications.
2016 International Renewable and Sustainable Energy Conference (IRSEC), Nov 1, 2016
Ceramic foams are promlsmg materials for volumetrie solar receivers in concentrated solar power (... more Ceramic foams are promlsmg materials for volumetrie solar receivers in concentrated solar power (CSP) plants. Understanding the solar heat flux distribution on the receiver is of great importance for optimizing the receiver volumetrie efficiency and thermal performance. This work presents a 3D optical analysis of ceramic based volumetrie solar receivers. The optical analysis is conducted using a Monte Carlo based solar ray tracing software. Ceramic foams are represented by idealized packed tetrakaidecahedron structures. The absorbed heat flux distribution and the effect of cell size, porosity and absorptivity on the penetration depth of the absorbed heat flux are investigated. Comparisons have been made with extruded honeycomb receivers. The results clearly demonstrate the dependence of flux distribution and penetration depth of solar rays on the material absorptivity and structure. The simulation results show a uniform heat flux distribution on the frontal faces with an intensity that increases with increasing the material absorptivity. Both the porosity and the cell size have a great effect on the penetration depth of the absorbed heat flux. In general, foam structure shows larger penetration depths than extruded honeycombs.
Materials Research Express, 2018
Materials Research Express, 2019
Journal of Materials Engineering and Performance, 2017
Boron carbide powder was synthesized from boric acid and lactose mixtures via easy procedure. Bor... more Boron carbide powder was synthesized from boric acid and lactose mixtures via easy procedure. Boric acid and lactose solution mixtures were roasted in stainless steel pot at 280°C for 24 h. Boron carbide was obtained by heating the roasted samples under flowing of industrial argon gas at 1500°C for 3 h. The amount of borate ester compound in the roasted samples was highly influenced by the boron/carbon ratio in the starting mixtures and plays a versatile role in the produced boron carbide. The high-purity boron carbide powder was produced with a sample composed of lowest boron/carbon ratio of 1:1 without calcination step. Particle morphology was changed from nano-needles like structure of 8-10 nm size with highest carbon ratio mixture to spherical shape of >150 nm size with lowest one. The oxidation resistance performance of boron carbide is highly dependent on the morphology and grain size of the synthesized powder.
International Journal of Materials Engineering and Technology, 2016
Journal of Materials Science, 2016
The effect of the yttria powder additions on the synthesized nano-alumina particles from Al scrap... more The effect of the yttria powder additions on the synthesized nano-alumina particles from Al scrap was investigated. The Al scrap was dissolved in an aqua regia solution at the room temperature and then was precipitated at a pH of 9-10. After calcination of the formed gel, 0-20 wt% yttria particles were added and mixed. The dried slurries were compacted and sintered at a temperature range of 1550-1650°C. The phase composition, microstructure, densification, and mechanical properties of the sintered specimens were evaluated. Near fully dense alumina specimens at a temperature of 1550°C as well as the sintered insitu YAG-alumina composites at 1650°C were successfully produced. The high hardness for all specimens was recorded at a sintering temperature of 1650°C and attributed to the formation of YAG and grain growth of alumina. Furthermore, the addition of yttria and sintering temperature showed a significant effect on the sintered specimens microstructure, densification process, and phase composition.
Refractories and Industrial Ceramics, 2017
Insulating refractory bricks with different densities have been successfully produced from firing... more Insulating refractory bricks with different densities have been successfully produced from firing of sludge of water treatment produced from the water treatment plant at El-Kureimat power station (Giza, Egypt) and rice husk ash mixtures. Different batches from the sludge of water treatment (SWT) with varying amounts of rice husk ash (RHA) were well mixed, formed, dried, and finally fired at different temperatures ranging (800-1200°C). The filter pressed sludge was dried and fired at the same temperature range. The physico-mechanical properties of the fired specimens of sludge-rice husk ash batches and the filtered press sludge were investigated and evaluated. The results showed that the sludge of water treatment plant can be used successfully to produce high quality insulating refractory bricks for various thermal insulating applications.
A successful utilization of two waste metal oxides (Al-slag and silica fumes) in preparing valuab... more A successful utilization of two waste metal oxides (Al-slag and silica fumes) in preparing valuable cordierite ceramic material and the fabrication of the produced cordierite in a 3D porous structure have been achieved through this investigation. The optimum sintering conditions (in terms of sintering temperature and time) for producing dense mixture compact containing lower amount of undesirable phases beside the main desired cordierite phase were determined. The results revealed that a sintering temperature of 1325C and a sintering time of 2 h were the most appropriate conditions during cordierite synthesis. However, the key role for the successful fabrication of a porous ceramic body via replica method is to prepare a well-dispersed suspension from the mixture of raw materials. Herein the optimum conditions for preparing a well-dispersed suspension in terms of type and concentration of additives as well as suspension pH were evaluated. The using of 0.2% sodium silicate and a susp...