Preparation of porous cordierite ceramic using a silica secondary resource (silica fumes) for dust filtration purposes

E.M.M. Ewais,A.M.M. Ameen,Y.M.Z. Ahmed 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.6

Cordierite-based porous ceramic samples were successfully prepared using a mixture composed of waste silica fumes, bauxite and talc via a polymeric sponge replica technique. Firstly, the optimum sintering conditions (in terms of sintering temperature and time) for acquiring as much of the cordierite phase with the absence of undesirable ones were determined for a dense mixture compact. The results revealed that a sintering temperature of 1350℃ and a sintering time of 2 h were the most appropriate conditions during cordierite synthesis. Secondly, 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. Here 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 suspension pH of 8 were found to be the most favorable conditions for obtaining a well-dispersed suspension. Thirdly, in order to prepare porous cordierite, polyurethane foam was impregnated with a well-dispersed suspension and sintered at the optimum conditions conducted for a dense cordierite sample. The porous cordierite produced was found to possess 46.4% total porosity. The porosity was comprised of large and small interconnected pore surrounded by a web of ceramic. This structure is suitable for applications in filtering purposes. Cordierite-based porous ceramic samples were successfully prepared using a mixture composed of waste silica fumes, bauxite and talc via a polymeric sponge replica technique. Firstly, the optimum sintering conditions (in terms of sintering temperature and time) for acquiring as much of the cordierite phase with the absence of undesirable ones were determined for a dense mixture compact. The results revealed that a sintering temperature of 1350℃ and a sintering time of 2 h were the most appropriate conditions during cordierite synthesis. Secondly, 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. Here 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 suspension pH of 8 were found to be the most favorable conditions for obtaining a well-dispersed suspension. Thirdly, in order to prepare porous cordierite, polyurethane foam was impregnated with a well-dispersed suspension and sintered at the optimum conditions conducted for a dense cordierite sample. The porous cordierite produced was found to possess 46.4% total porosity. The porosity was comprised of large and small interconnected pore surrounded by a web of ceramic. This structure is suitable for applications in filtering purposes.

Effect of magnesia rich spinel on densification and stabilization behavior of monoclinic zirconia

Abdelgawad Mahmoud,El-Gamal S. M. A.,Ewais Emad M. M.,Li Shufeng 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.3

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, eff ect of MMA content and sintering temperature on stabilization and densifi cation 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 diff usion 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 diff usion 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+ diff usion inside zirconia lattice structure.

Utilization of Trichogramma in Rice Stem Borer Control in Egypt

M. R. Sherif,A. S. Hendawy,M. A. Ewais,E. A. Agamy,M. M. EI-Habashy 한국응용곤충학회 2005 한국응용곤충학회 학술대회논문집 Vol.2005 No.05

Low temperature synthesis of nano-crystalline h-boron nitride from boric acid/ urea precursors

Dina H.A. Besisa,Mahmoud A. A. Hagras,Emad M.M. Ewais,Yasser M. Z. Ahmed,Zaki I. Zaki,Adel Ahmed 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.12

Nano-crystalline hexagonal-boron nitride (h-BN) have promised a broad range of interesting applications due to its uniquecharacteristics. In this work, nano-structured h-BN has synthesized by a low temperature-one step reaction of completelydissolved solution of commercial and low cost boric acid and urea fertilizer. Effect of different concentrations of urea, reactionatmosphere (air-N2) and firing temperature (600, 800 oC) on the production of h-BN and type of yield were investigated. Theformation of hexagonal boron nitride was proved from the binding energy for boron and nitrogen obtained from the X- rayphotoelectron spectrum (XPS). The structural phase of the product was confirmed by X-ray diffraction (XRD), Fourier transforminfrared (FT-IR) and differential thermal analysis (DTA). Transmission electron microscopy (HRTEM) has revealed the nanostructure nature of the synthesized boron nitride. The results indicated that, nano-crystalline h-BN with a crystallite size of ≈ 4.5nm has formed at low temperature of 800 oC. Moreover, a good thermal stability and oxidation resistance of h-BN can besynthesized with low cost and at low temperature in the nanoscale and has high potential to be used in advanced applications.

Biotechnological application of plant growth-promoting endophytic bacteria isolated from halophytic plants to ameliorate salinity tolerance of Vicia faba L.

Mahgoub Hany A. M.,Fouda Amr,Eid Ahmed M.,Ewais Emad El-Din,Hassan Saad El-Din 한국식물생명공학회 2021 Plant biotechnology reports Vol.15 No.6

Salinity is a major problem affecting crop production all over the world. A wide range of adaptation strategies are required to overcome this problem. Endophytic bacteria can build a symbiotic association with their host to improve host plant salt tolerance. In this study, eighteen bacterial endophyte strains were isolated from two native halophytic plants Arthrocnemum macrostachyum and Spergularia marina, and identified as Bacillus, Brevibacillus, Agrobacterium, and Paenibacillus. These endophytic strains exhibit plant growth-promoting activities including phosphate solubilizing, ammonia production, bio- control of phytopathogen, extracellular enzymatic activities, and indole-3-acetic acid production under normal and salinity stress. A pot experiment was conducted under field conditions to alleviate the harmful effects of soil salinity on bean (Vicia faba L.) by inoculating their seeds with the most potent bacterial isolates Bacillus subtilis (AR5) and Bacillus thuringiensis (BR1). Salinity treatments induced a significant decrease in both growth parameters and metabolic activities, while the activ- ity of antioxidant enzymes and proline content was significantly increased. However, salinity stress induced higher contents of Na+ and decreased contents of N+, P3+, K+, Ca2+, Mg2+, and K+:Na+, it was found that treatment with B. subtilis (AR5) and B. thuringiensis (BR1) individually or in a combination mitigated the effect of salt stress and improved the plant height, shoot dry weights, proline contents, enzymes activities as well enhanced the accumulation of mineral nutrients in shoot plants. Our results concluded that treatment with co-inoculation of B. subtilis (AR5) and B. thuringiensis (BR1) exerted the greatest effect in alleviating the harmful effect of soil salinity stress and can be used as a suitable bio-approach to reclaim salinity-stressed soils.

MgAl2O4-reinforced c-ZrO2 ceramics prepared by spark plasma sintering

El-Amir Ahmed A. M.,Li Shufeng,Abdelgawad Mahmoud,Ewais Emad M. M. 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.5

c-zirconia ceramic composites have been synthesized by spark plasma sintering (SPS) technique from commercial m-ZrO 2 , Y 2 O 3 and waste-derived magnesium aluminate spinel (MA) powders. In this study, eff ect 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 refi ned 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 refi nement 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-ZrO 2 was converted into m-ZrO 2 in case of the latter composite while aging test didn’t infl uence at all on the structure of the former composites. The outcomes indicated that MA has a signifi cant eff ect on m-ZrO 2 stabilization into a cubic phase structure that concurrently owned an enhanced and comparable compression resistance to Yttrium-doped t-ZrO 2 (Y-TZP). In this respect, the ternary oxide ceramic composite systems prepared in this study present huge potential for development c-ZrO 2 -based industrial ceramics with a wide spectrum of mechanical characteristics for high-tech engineering applications of harsh-stress and humid environments.

Production of high-quality glass foam from soda lime glass waste using SiC-AlN foaming agent

El-Amir Ahmed A. M.,Attia Mohammed A. A.,Fend Thomas,Ewais Emad M. M. 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.4

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/cm 3 ), 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 and energy efficiency in industry.

Establishment of callogenesis and plant regeneration protocols for endemic Origanum syriacum ssp. sinaicum

Abd El-Motaleb M.,Abd El-Hameid Asmaa R.,Helmy Wafaa A.,Ewais E. A.,Abdel-Hady M. S. 한국작물학회 2023 Journal of crop science and biotechnology Vol.26 No.4

Origanum syriacum ssp. sinaicum is a medicinal perennial endemic herb grown in the mountain areas in Saint Katherine, Sinai, Egypt. Leaves of this species have a history of use in traditional herbal medicine. The efects of Murashige and Skoog’s medium (MS) containing auxins alone or in combination with cytokinin to produce calli were investigated. The obtained results showed that MS medium containing 2 mg L−1 2,4-dichlorophenoxyacetic acid (2,4-D) alone recorded the earliest callusing time and the best callus percentage formation. The combination of 0.25 mg L−1 6-benzylaminopurine (BA) with 2 mg L−1 2,4-D resulted in the highest callus percentage and fresh weight. The diferent levels of growth regulators in the media exhibited the morphological changes in calli. Nodal segments were more efective than leaf explants in terms of callus percentage, callus fresh and dry weight, and callus initiation time. After 45 days of callus culture, the combination of 1 mg L−1 BA with 0.25 mg L−1 α-naphthalene acetic acid (NAA) was successful in promoting organogenesis, resulting in a high frequency of shootlets. The maximum number of rooting shootlets was achieved by supplementing the MS medium with 0.5 mg L−1 indole-3 butyric acid (IBA). This study reports an efective plant regeneration protocol that can be used for the conservation of endemic species.