Ultra-low thermal conductivity thermal barrier coatings from recycled fly-ash cenospheres

Chávez-Valdez, A.; Morquecho, Ana María Arizmendi; Vargas‐Gutiérrez, G.; Almanza-Robles, J.M.; Alvarez-Quintana, J.

doi:10.1016/j.actamat.2011.01.011

Cited by 78 publications

(24 citation statements)

References 28 publications

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“…9,10 Also, they are been studied for the production of ceramic composite foams with different properties. 11,12 In recent years, new functional materials have been developed based on a detailed characterization of narrow fractions of cenospheres with specific composition and structure. 13,14 Among these materials are high-selectivity microspherical membranes for diffusion separation of gases, 15−17 effective composite sorbents, 18,19 including those capable of operating in corrosive medium, 20,21 magnetically controlled encapsulated pH-sensitive spin probes for the examination of biological objects, 22 supported catalyst systems, 23−26 and emulsion explosive sensitizers capable of replacing expensive hollow synthetic microspheres.…”

Section: ■ Introductionmentioning

confidence: 99%

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

et al. 2015

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The relationship between the chemical composition and shell structure of cenospheres with a low bulk density of 0.40−0.45 g/cm 3 and a high Al 2 O 3 content of 33−38 wt % has been systematically studied. It was established that the composition of the narrow fractions of cenospheres can be described by the general regression equation SiO 2 /Al 2 O 3 = 4.34 − 0.08[Al 2 O 3 ] with the correlation coefficient of r = −0.99. The phase composition includes the glass phase (57−73 wt %), mullite (25−40 wt %), and quartz (1.2−2.5 wt %). An increase in the Al 2 O 3 content leads to an increase in the size of particles and the porosity of their shells. In the obtained fractions of cenospheres, there are two types of globules: spherical globules with a singlering structure and foamy globules with a network structure. It is established that the composition of individual particles with a network structure localized in the range of the Al 2 O 3 content from 43 wt % to 51 wt % and can be described by the regression equation SiO 2 /Al 2 O 3 = 2.71 − 0.04[Al 2 O 3 ] with the correlation coefficient of r = −0.97. The framework of these particles permeated by mullite microcrystallites and coated with a nanoscale surface film. The structure-forming mineral precursor of these particles is kaolinite. The gross composition of the shell of individual globules with a single-ring structure localized in the range of the Al 2 O 3 content from 26 wt % to 42 wt % and can be described by the general regression equation SiO 2 /Al 2 O 3 = 4.71− 0.09[Al 2 O 3 ] with the correlation coefficient of r = −0.98. The outer and inner surfaces of the shell are covered by large and small in-plane localized mullite crystals hidden by the nanoscale film. The spherical shape and their crystalline framework are formed from the illite melt with inclusions of products of the thermal conversion of other mineral forms. ■ INTRODUCTIONIn the process of generating power from coal, large quantities of coal combustion products (CCPs) are produced. According to the various estimates, combustion of coal in the Russia alone generates ∼25 million tons of CCPs per year but utilization rate does not exceed 15%. 1 The complex composition of CCPs, including the fly ash, has proven to be a barrier to its bulk utilization in many fields. Extraction of concentrates of microspherical components with specific characteristics from fly ashes of variable composition provides wider opportunities for the multicomponent use of fly ashes produced from coal combustion. 2,3 The unique properties of cenospheres, namely, their low density, sphericity of particles, and high strength and nontoxicity, make them useful for a variety of fields of applications. Thus, concentrates of cenospheres are used as fillers of lightweight composite materials, such as concretes, 4,5 polymers and resins, 6−8 and metal alloys. 9,10 Also, they are been studied for the production of ceramic composite foams with different properties. 11,12 In recent years, new functional materials have been developed based on a d...

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Section: ■ Introductionmentioning

confidence: 99%

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

et al. 2015

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“…In the recent years, researchers have also been trying to investigate some other materials like cenosphere (Chávez-Valdez et al 2011;Kwan and Chen 2013;Pichór 2009;Wang et al 2012Wang et al , 2013Wu et al 2015;Xu et al 2015) and aerogel particles (Gao et al 2014;Hanif et al 2016;Kim et al 2013;Ng et al 2015) for their use as LWF. Xu et al found that even though incorporating cenosphere in magnesium oxy-chloride cement composite reduces the compressive strength, still high levels of strength (60 MPa) are achieved (Xu et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Effects of Different Lightweight Functional Fillers for Use in Cementitious Composites

Hanif

Cheng

et al. 2017

Int J Concr Struct Mater

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Abstract:The effects of different lightweight functional fillers on the properties of cement-based composites are investigated in this study. The fillers include fly ash cenospheres (FACs) and glass micro-spheres (GMS15 and GMS38) in various proportions. The developed composites were tested for compressive, flexural and tensile strengths at 10 and 28-day ages. The results indicated that both FACs and GMS38 are excellent candidates for producing strong lightweight composites. However, incorporation of GMS15 resulted in much lower specific strength values (only up to 13.64 kPa/kg m 3 ) due to its thinner shell thickness and lower isostatic crushing strength value (2.07 MPa). Microstructural analyses further revealed that GMS38 and GMS15 were better suited for thermal insulating applications. However, higher weight fraction of the fillers in composites leads to increased porosity which might be detrimental to their strength development.

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“…34 Therefore, extracting from experimental data obtained from ref. 34 Therefore, extracting from experimental data obtained from ref.…”

Section: Thermogravimetric Analysis (Tga)mentioning

confidence: 99%

Thin film encapsulation of nano composites of polycarbonate (PC) for thermal management systems

2014

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The configuration of thin film polycarbonate (PC) is formulated, aiming for a financially efficient approach of the solvent casting method by grafting waste fly ash cenosphere (FAC) encapsulated with tetraethoxysilane (TEOS) as a grafting agent. The research study emphasized on the routine practice of controlled thermal dissipative electronic widgets by a systematic characterization analysis. FTIR exemplifies the surface adherence characteristics of the GFAC (Grafted Fly Ash Cenosphere) over PC, by confirming the efficient grafting between silane and FAC at 2950 cm À1 due to the flexible vibrations by the -OH group. The PC-FAC composite showed the characteristic triplet signature peaks of PC at 1152, 1188 and 1227 cm À1 .Following the hierarchy, the morphological study analyzes the surface molecular interaction between the PC/GFAC and their electronic properties by FESEM. AFM confers the topographical study of pristine PC, which measures the surface roughness of pristine PC as 4.5 nm which mitigates to 0.7 nm for the PC/GFAC and justifies the homogenous dispersion of GFAC in PC, thus directing the consequential study of TGA. It examines controlled surface thermal conduction and authenticates the noble thermal stability of the PC/GFAC with a char yield of 36% (approximately more than twice that of pristine PC) at 800 C by TGA. The PC/GFAC affirms a 70 C lag in the onset of thermal degradation, at 430 C, as compared with pristine PC, which starts to decompose at 360 C. Thus, the silane grafted nano composites of PC expands the operable temperature range for the electronic elemental properties usage. The present investigation procures attention on the thermal characteristics of the PC/GFAC, illustrated by the conduction modeling parameter across the spherical wall of the cenosphere and the interfacial heat transfer for the PC/GFAC composite, pertaining to a worthwhile and serviceable thermal management praxis.

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Ultra-low thermal conductivity thermal barrier coatings from recycled fly-ash cenospheres

Cited by 78 publications

References 28 publications

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

Effects of Different Lightweight Functional Fillers for Use in Cementitious Composites

Thin film encapsulation of nano composites of polycarbonate (PC) for thermal management systems

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