scholarly journals Up-Cycling of Iron-Rich Inorganic Waste in Functional Glass-Ceramics

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 959
Author(s):  
Acacio Rincón Romero ◽  
Daniele Desideri ◽  
Aldo Boccaccini ◽  
Enrico Bernardo
Keyword(s):  
Glass Ceramics ◽  
Weakly Alkaline ◽  
Ceramic Foams ◽  
Mechanical Stirring ◽  
Recycled Glass ◽  
Magnetite Fe3o4 ◽  
High Dielectric Permittivity ◽  
Inorganic Waste ◽  
High Dielectric ◽  
Highly Porous

The intensive mechanical stirring of suspensions of recycled glass and inorganic waste powders in ‘weakly alkaline’ aqueous solutions (e.g., 2.5–3 NaOH), followed by viscous flow sintering at 800–1000 °C, easily yields highly porous glass-ceramic foams. The firing determines just the consolidation of powders with concurrent incorporation of pollutants from iron-rich waste, such as fly ash from coal combustion (FA). Engineered mixtures allow for the obtainment of chemically stable foams from treatments in air. Treatments in nitrogen are even more significant since they extend the conditions for stabilization and promote novel functionalities. In addition, the change in the atmosphere favors the formation of magnetite (Fe3O4), in turn enabling ultra-high dielectric permittivity and semiconductivity. Such a condition was further evidenced by preliminary tests on recycled glass combined with residues from the Bayer processing of aluminum ores or red mud (RM).

scholarly journals Glass-Ceramic Foams from Alkali-Activated Vitrified Bottom Ash and Waste Glasses

2020 ◽  
Vol 10 (16) ◽  
pp. 5714
Author(s):  
Miroslava Hujova ◽  
Patricia Rabelo Monich ◽  
Jaroslav Sedlacek ◽  
Miroslav Hnatko ◽  
Jozef Kraxner ◽  
...  
Keyword(s):  
Glass Ceramic ◽  
Bottom Ash ◽  
Soda Lime ◽  
Soda Lime Glass ◽  
Phase Assemblage ◽  
Weakly Alkaline ◽  
Glass Addition ◽  
Ceramic Foams ◽  
Weakly Alkaline Solution ◽  
Inorganic Waste

Both vitrified bottom ashes (VBAs) and waste glasses are forms of inorganic waste material that are widely landfilled, despite having some economic potential. Building on previous studies, we prepared glass-ceramic foams by the combination of VBA with either soda-lime glass (SLG) or borosilicate glass (BSG). Suspensions of fine powders in weakly alkaline solution underwent gelation, followed by frothing at nearly room temperature. Hardened “green” foams were sintered, with concurrent crystallization, at 850–1000 °C. All foams were highly porous (>70%), with mostly open porosity. The glass addition was fundamental in both gelation (promoting the formation of carbonate and silicate hydrated phases) and firing steps. While SLG addition enhanced the viscous flow sintering, without a significant impact on the crystallization of gehlenite, the main crystalline phase from the devitrification of VBA, BSG addition caused a reactive sintering, with remarkable changes in the phase assemblage. The glass addition generally also allowed lower sintering temperatures and yielded products with excellent crushing strength. However, only specific conditions resulted in the complete immobilization of pollutants (e.g., Cr3+ ions).

scholarly journals Biosilicate® Glass-Ceramic Foams From Refined Alkali Activation and Gel Casting

2021 ◽  
Vol 7 ◽  
Author(s):  
Enrico Bernardo ◽  
Hamada Elsayed ◽  
Acacio Rincon Romero ◽  
Murilo C. Crovace ◽  
Edgar D. Zanotto ◽  
...  
Keyword(s):  
Glass Ceramics ◽  
Casting Process ◽  
Alkali Activation ◽  
Weakly Alkaline ◽  
Ceramic Foams ◽  
Porous Bodies ◽  
Gel Casting ◽  
Fine Glass ◽  
Micro Tomography ◽  
45S5 Bioglass

Biosilicate® glass-ceramics are among the most valid alternatives to 45S5 Bioglass. They combine a similar bioactivity and bioresorbability as the 45S5 with superior mechanical strength, owing to the crystallization of a Na–Ca silicate phase. This crystallization may be experienced upon viscous flow sintering of fine glass powders, thus configuring a sinter-crystallization process. As crystallization is seldom complete, sintering can also be applied to semicrystalline powders. The sintering/crystallization combination may be exploited for shaping highly porous bodies, to be used as scaffolds for bone tissue engineering, in the form of foams. The present study aims at exploring a gel-casting process, based on the room temperature foaming of powders suspended in a “weakly alkaline” (1 M NaOH) aqueous solution, followed by sintering at 1,000°C. The gelation of suspensions is attributed to the formation of hydrated compounds, later decomposed upon firing. Amorphous powders provided more intense gelation than semicrystalline ones, promoted a more homogeneous foaming, and stimulated a substantial crystallization upon firing. The homogeneity of foamed samples was assessed using micro-tomography and was further improved by casting foamed suspensions (“foam casting”) before setting.

Polyimide/nanosized CaCu3Ti4O12 functional hybrid films with high dielectric permittivity

2013 ◽  
Vol 102 (4) ◽  
pp. 042904 ◽  
Author(s):  
Yang Yang ◽  
Ben-Peng Zhu ◽  
Zhi-Hong Lu ◽  
Zi-Yu Wang ◽  
Chun-Long Fei ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Hybrid Films ◽  
High Dielectric Permittivity ◽  
High Dielectric

scholarly journals Dielectric and varistor properties of rare-earth-doped ZnO and CaCu3Ti4O12 composite ceramics

2013 ◽  
Vol 03 (01) ◽  
pp. 1350001 ◽  
Author(s):  
Huafei Lu ◽  
Yuanhua Lin ◽  
Jiancong Yuan ◽  
Cewen Nan ◽  
Kexin Chen
Keyword(s):  
Rare Earth ◽  
Sol Gel ◽  
Nonlinear Coefficient ◽  
Composite Ceramic ◽  
Dielectric Behavior ◽  
Composite Ceramics ◽  
High Dielectric Permittivity ◽  
Doped Zno ◽  
Co Precipitation ◽  
High Dielectric

To investigate the multi-functional ceramics with both high permittivity and large nonlinear coefficient, we have prepared rare-earth Tb -and- Co doped ZnO and TiO 2-rich CaCu3Ti4O12 (TCCTO) powders by chemical co-precipitation and sol–gel methods respectively, and then obtained the TCCTO/ ZnO composite ceramics, sintered at 1100°C for 3 h in air. Analyzing the composite ceramics of the microstructure and phase composition indicated that the composite ceramics were composed of the main phases of ZnO and CaCu3Ti4O12 (CCTO). Our results revealed that the TCCTO/ ZnO composite ceramics showed both high dielectric and good nonlinear electrical behaviors. The composite ceramic of TCCTO: ZnO = 0.3 exhibited a high dielectric constant of ~210(1 kHz) with a nonlinear coefficient of ~11. The dielectric behavior of TCCTO/ ZnO composite could be explained by the mixture rule. With the high dielectric permittivity and tunable varistor behaviors, the composite ceramics has a potential application for the higher voltage transportation devices.

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