Fly Ash Cenospheres Research Articles

Preparation of HPW-CS/TiO2/FACS photocatalysts for degradation of tetracycline hydrochloride

Molecular imprinting technology in combination with photodegradation technology was applied to synthetize HPW-CS/TiO2/FACS photocatalysts. The novel photocatalyst could not only exhibit high photocatalytic activity but be easy to reuse because the fly-ash cenospheres (FACS) were adopted for carrier. The compound photocatalyst was characterised by X-ray diffraction, UV–vis diffuse reflectance spectra (UV–vis DRS), Fourier Transform Infra Red spectroscopy and Scanning electron microscopy. Meanwhile, the effects of amount of heteropolyacid, dosage of chitosan and calcination temperature on the photocatalytic activity of the photocatalyst were investigated.

Effect of Fly-Ash Cenospheres on Properties of Clay-Ceramic Syntactic Foams.

A low-density clay ceramic syntactic foam (CSF) composite material was successfully synthesized from illitic clay added by fly ash cenospheres (CS) using the semi-dry formation method. The content of CS varied in the range of 10, 30, 50 and 60 vol %. Furthermore, reference samples without cenospheres were produced for property comparison. The materials comprising different amount of the additives were fired at temperatures of 600, 950, 1000, 1050, 1100, 1150 and 1200 °C. Firing times were kept constant at 30 min. Processing characteristics of the materials were evaluated in terms of density achieved and shrinkage observed as functions of both the CS content and the sintering temperature. The compressive strength and water uptake were determined as application-oriented properties. Except for the reference and the low CS level samples, the materials show an increase in strength with the increase in firing temperature, and a decrease of mechanical reliability with a decrease in density, which is typical for porous materials. Exceptions are the samples with no or low (10 vol %) content of cenospheres. In this case, the maximum strength is obtained at an intermediate sintering temperature of 1100 °C. At a low density (1.10 and 1.25 g/cm3), the highest levels of strength are obtained after sintering at 1200 °C. For nominal porosity levels of 50 and 60 vol %, 41 and 26 MPa peak stresses, respectively, are recorded under compressive load.

Fabrication and photocatalytic activity of floating type Ag3PO4/ZnFe2O4/FACs photocatalyst

We used floating solid fly ash cenospheres (FACs) as the carrier to prepare Ag3PO4/ZnFe2O4/FACs composite materials using sol-gel and liquid phase deposition methods We studied the material photocatalytic activity in visible light and used methylene blue as the goal pollutant. Compared with single powder catalysts, Ag3PO4/ZnFe2O4/FACs composites have the highest photocatalytic efficiency and could float in water because FACs are lightweight and hollow. Moreover, the composite materials can absorb high amounts of light energy and are conducive for catalyst recycling and reuse. Recycling experiments showed that the Ag3PO4/ZnFe2O4/FACs catalyst retained high photocatalytic activity after five times of recovery.

Analysis of interface between components in AZ91 magnesium alloy foam composite with Ni-P coated fly ash cenospheres

The interface between the components in magnesium matrix foam composites with fly ash cenospheres has been analysed. The composite based on AZ91 commercial magnesium alloy with hollow aluminosilicate cenospheres was fabricated by the negative pressure infiltration technique. Ni-P coated cenospheres heated to 773 K were used in this study. Analyses of the composite microstructure were carried out by light microscopy, XRD, scanning and transmission electron microscopy. The fabricated composite was characterized by uniform distribution of cenospheres free from damage and unfilled by the AZ91 alloy within the matrix. Analyses of the composite matrix microstructure revealed that it was composed of α-Mg, α+γ divorced eutectic, γ discontinuous precipitates and an Al8Mn5 intermetallic phase. Examinations of the composite interfaces disclosed that Ni3P and Ni phases were formed inside the Ni-P coatings during heating of the cenospheres. Additionally, NiO was created in the external layer of the Ni-P coatings due to the oxidation reaction. The presented results unequivocally revealed that the used Ni-P coating, especially the NiO layer, on the cenospheres prevent reactions between the molten AZ91 alloy and fly ashes.

Effect of fly ash cenosphere pore formers on the microstructure and mechanical properties of vitrified diamond grinding wheels

This paper focuses on the influence of fly ash cenosphere (as a pore former) content and particle size on the porosity, microstructure and mechanical properties of vitrified bond diamond tools. The sintered specimens were examined using comprehensive thermal analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, three point bending tests and porosity measurements. The porous morphological parameters (volume, size and distribution of pores) of the sample correlated with the content and size of the fly ash cenosphere, and diffusion layers were formed between the pore former and the vitrified matrix. The bending strength of the porous vitrified matrix varied between 27.28 and 35.92MPa as the porosity changed from 40.66–43.97%. Based on response surface methodology (RSM) studies, two second-order response models for the open porosity and bending strength were established, and the utilization of the response surface model was evaluated with regards to the content and size of fly ash cenosphere present.

A robust superhydrophobic surface and origins of its self-cleaning properties

A hierarchical surface was fabricated by electrodeposition of copper coating and chemical oxidation to form copper oxide, and the surface energy was lowered by chemical modification. The optimum parameters including seven days of chemical modification, 0.12mol/L of (NH4)2S2O8, 2.5mol/L of KOH and 60°C of oxidation temperature were used to fabricate the superhydrophobic surface with a water contact angle up to around 160° and a sliding angle about 3° on a steel substrate. Silver mirror effect and simple calculation showed that the wetting state between a water droplet and the hierarchical superhydrophobic surface was the Cassie state. This superhydrophobic surface had excellent self-cleaning properties for two different sizes (∼50μm and 150μm) of fly-ash cenospheres, and we gave the reason for its self-cleaning properties by the force involved at the interface. We also investigated the dynamics of water droplets impinging onto the superhydrophobic surface with different impact velocities, ranging from 0.31m/s to 1.71m/s, and found that all the water droplets could rebound from the superhydrophobic surface, with no trace of adhesion. In addition, a variety of tests were performed to assess the robustness of the superhydrophobic surfaces.

Green lightweight ferrocement incorporating fly ash cenosphere based fibrous mortar matrix

This paper presents an experimental assessment on the suitability of fly ash cenosphere (FAC), a waste residue from coal fired power plants, for use in lightweight ferrocement construction. Ferrocement is a special type of thin walled reinforced concrete constructed of hydraulic cement mortar and closely spaced layers of steel wire mesh. In this study, the mortar mix was prepared by replacing the sand (a typical ingredient of ferrocement matrix) with FAC at 40 %, 50 % and 60 % FAC weight fractions in mortar. Single and double layers of galvanized iron welded wire mesh were used as the main reinforcement while small volume fraction (0.50 %) of PVA fibers was also added as a discontinuous reinforcement resulting in a hybrid composite. The mortar mixes were tested for mechanical strength including compressive strength, elastic modulus and Poisson’s ratio whereas the ferrocement composites were evaluated for flexural performance. The ferrocement composite properties were compared with high strength quartz sand mortar matrix as well. FAC was found to be excellent in producing structural lightweight ferrocement composites (density 1332.09–1457.89 kg/m3) with excellent mechanical properties. The PVA fibers helped improve the inherent brittleness of FAC composites. Thus, lightweight ferrocement elements with higher specific strength (18.39–26.65 kPa/kgm−3), flexural strength (14.47–28.13 MPa), and tensile strength (5.69–11.06 MPa) can be produced, with utilizing FAC waste residue. The use of such composites in construction can promote sustainable development by minimizing waste.

“Cenosphere–Molybdenum Disulfide”–New Filler–Lubricant Combination for Performance Synergism in Composite Friction Materials

Short-fiber (e.g., steel wool, rock fibers, and kevlar) reinforced flyash cenosphere–molybdenum disulfide combination-filled phenolic composite materials for friction braking applications were developed and evaluated for their physical (density, void fraction, acetone extraction, and ash content), mechanical (hardness, compressibility, shear strength), and thermal characteristics (thermogravimetric analysis (thermo gravimetric analysis (TGA)/differential thermo gravimetry). Performance correlations between thermomechanical characteristics and friction braking data obtained from Krauss friction testing machine is attempted. The frictional fade (μF) and recovery (μR) behavior vis-a-vis amplitude of friction fluctuations (μmax–μmin) performance were observed to be enhanced due to the incorporation of “cenosphere–molybdenum disulfide” combination. The enhanced wear resistance was attributed to the lower temperature sensitivity of posttemperature degradation kinetics. Analysis of friction and wear data indicated μF and intrinsic material coefficients to be major determinants for μP and wear, respectively. Our study demonstrates the performance synergism due to the incorporation of cenosphere–molybdenum disulfide as the hybrid “filler–lubricant” combination in composite materials for friction braking application.

Optimization of electrical discharge machining process parameters for Al6061/cenosphere composite using grey-based hybrid approach

Fly ash has congregated considerable attention as a potential reinforcement for aluminum matrix composites (AMCs) to enhance selective properties and reduce the cost of fabrication. However, poor machinability of such AMCs limits their application. The present study focuses on the preparation of cenosphere fly ash reinforced Al6061 alloys by compo casting method. X-ray diffraction analysis of the prepared AMCs exposes the presence of cenosphere particles without any formation of other intermetallic compounds. In this study, electrical discharge machining (EDM) was engaged to examine the machinability of the prepared metal matrix composite (MMCs). The measured performance characteristics for the various combinations of input process parameters were considered to be MRR, EWR and SR. Face centered central composite design (CCD) of response surface method (RSM) was employed to design the number of experimental trials required and a hybrid approach of grey-based response surface methodology (GRSM) was imposed for predicting the optimal combination of processing parameter in EDM process. Generous improvement was observed in the performance characteristics obtained by employing both the optimal setting of machining parameters. The optical 3D surface profile graphs of the ED machined surface also revealed the improvement in surface quality and texture employing the optimal processing conditions proposed by hybrid GRSM approach.

Properties improvement of fly ash cenosphere modified cement pastes using nano silica

In this study, the effect of nano silica (NS) on the properties of cement pastes incorporated with of fly ash cenospheres (FACs) has been investigated. A fixed amount of 1 % NS was added to cement pastes containing various proportions of FAC. It was found that NS was beneficial in improving the mechanical strength of the FAC modified cement pastes. At the 7 – day age, the strength increase for NS modified pastes was about 17 % as compared to pastes without NS. However, the strength enhancement effect decreased with increasing age and FAC content. The dense microstructure of the NS modified pastes compensated for the higher porosity associated with FAC incorporation, leading to the reduced total porosity. With NS, there was better bonding of the FAC particles in the matrix, due to the enhanced interface. The reduced Ca(OH)2 content and partially consumed FAC spherical shells at the early age showed that NS increased the pozzolanic activity of FAC in the cement pastes.

AZ91 magnesium matrix foam composites with fly ash cenospheres fabricated by negative pressure infiltration technique

The feasibility of fabricating magnesium matrix foam composites with fly ash cenospheres by the negative pressure infiltration technique has been demonstrated. An AZ91 commercial magnesium alloy was chosen as the matrix. Two kinds of hollow aluminosilicate cenospheres, as-received and NiP coated, were used in this study in order to determine the influence of the NiP coating on the composite microstructure. Analyses of the fabricated composite microstructures were carried out by light microscopy, the X-ray diffraction technique, scanning electron microscopy and the Raman spectroscopy method. Additionally, the theoretical and measured density of the fabricated composites was analysed. Composites fabricated by the negative pressure infiltration technique were characterised by uniform distribution of 60vol% cenospheres. Both cenospheres filled and unfilled by the matrix alloy were observed in the composite with as-received fly ashes. Mg2Si and MgO compounds were revealed as products of reactions between the components in this material. In contrast, intact hollow cenospheres were present in the microstructure of the composite with NiP coated cenospheres. This composite had a minimum value of measured density equal to 1.1893g/cm3, which was in agreement with the theoretical value calculated using the rule of mixtures.

Machinability of cenosphere particulate–reinforced AA6061 aluminium alloy prepared by compocasting

Cenosphere fly ash particles as waste by-product of gas thermal power plant are successfully incorporated into AA6061 aluminium alloy by improved wettability casting process called compocasting technique to enlarge the application barrier of existing advanced metal matrix composites due to their high fabrication cost. Thereafter, microstructure, interface and composition of the prepared composites were analysed from the X-ray diffraction analysis patterns and scanning electron microscopy equipped with energy-dispersive X-ray techniques. Furthermore, machinability characteristics were identified by wire electrical discharge machining to explore the co-relations among the machining variables and the performance measures such as cutting rate, kerf width and surface roughness for the prepared composites by varying one parameter at a time and keeping the other parameters as constant. The morphological study reveals that there is a uniform distribution of fly ash particles in aluminium matrix phase without formation of any intermetallic compound caused by interfacial reaction. The machinability study indicates that pulse-on-time and pulse-off-time are the most significant process variables that affect the machining performance of the prepared composites. However, wire feed is found to impose the least significant effect among the three process parameters. Also, the neat AA6061 aluminium alloy (0% AA6061/cenosphere composites) exhibited superior machining performance compared to both the reinforced composites (4% and 8%) at similar machining conditions.

Properties investigation of fiber reinforced cement-based composites incorporating cenosphere fillers

The objective of this research study is the in-depth evaluation of the characteristics of fiber reinforced cement-based composites containing fly ash cenospheres (FACs) as lightweight filler material. The resulting composites showed excellent mechanical properties with higher specific strength as 34.69–24.11kPa/kgm−3. The 28 – day compressive, flexural and tensile strengths were determined in the range of 55.92–30.38MPa, 9.29–5.38MPa, and 3.51–1.66MPa, respectively. The higher pozzolanic activity of FACs contributed towards the better mechanical properties even at lower density. Microstructural analyses of the composites were carried out by SEM, nitrogen adsorption, and mercury intrusion porosimetry (MIP) while TGA was used for phase identification and phase transformation studies, respectively. The results indicated that FAC is a promising material for producing strong and lightweight structural members for use in building construction which can promote sustainable development. However, excessive FACs content in the composite may lead to higher porosity due to hollow spherical shape and chemical composition of FAC particles which affects the mechanical behavior and durability of cement-based composite.

Effects of Different Lightweight Functional Fillers for Use in Cementitious Composites

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 m3) 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.

Mechanical, Dynamic Mechanical and Thermal Properties of Banana Fiber/Recycled High Density Polyethylene Biocomposites Filled with Flyash Cenospheres

This study presents the preparation of Natural fiber-reinforced biocomposites based on Recycled High Density Polyethylene (RHDPE)/Banana Fiber (BF)/Fly ash Cenospheres (FACS) and aims to increase the economic value of these waste materials. Maleic anhydride grafted HDPE (MA-g-HDPE) was used as a compatibilizer to increase the dispersion of fibers into the polymer matrix as well as to increase the compatibility between the matrix and fillers. Variation in mechanical, thermal and dynamic mechanical properties with the addition of FACS in RHDPE/BF composites was investigated. It was observed that 7.5 wt% FACS, 30 wt% BF and 3 wt% MA-g-HDPE within RHDPE matrix resulted in an increase in tensile strength to 17%, tensile modulus to 188%, flexural strength to 38%, flexural modulus to 159% and hardness to 37% as compared with the RHDPE matrix. Significant enhancement in the thermal stability of the RHDPE/BF biocomposites was also observed in presence of FACS under thermogravimetric analysis. The morphology of the prepared biocomposites has been examined by using scanning electron microscopy. Dynamic mechanical analysis tests revealed an increase in storage and loss modulus of the biocomposite system. The use of such recycled material, agricultural and industrial wastes increased the properties of the final product suggesting their use to be a good alternative in the production of polymeric composites.

Influence of Curing Conditions on the Compressive Strength of Foamed Concrete

The foamed concrete (500 kg/m3 and 800 kg/m3 ) was produced by physical foaming using ordinary Portland cement (P.O 42.5R), vegetable protein foaming agent, fly ash from power plant and fly ash cenospheres (FACs) as raw materials. The air-void structure and the hydration products of the samples were characterized by SEM, XRD and other testing methods. The influence of standard curing, immersed curing with saturated Ca(OH)2 water solution, water spray curing and air curing on the strength and pore wall density of hardened foamed concrete were explored. The results showed that the lower the relative humidity in the curing process was, the more porous existed in the pore wall of the foamed concrete. The relative humidity imposed large influence on the compressive strength of the low-density foamed concrete, which was contrary in case of high-density foamed concrete. The compressive strength of the foamed concrete mixed with FACs was largely enhanced and the FACs played a more important role in the improvement of the strength of the low-density foamed concrete than that of the high-density foamed concrete.

High-temperature damping capacity of fly ash cenosphere/AZ91D Mg alloy composites

Abstract In this study, fly ash cenospheres were added to semisolid AZ91D Mg alloy to prepare fly ash cenosphere/AZ91D (FAC/AZ91D) composites by means of compo-casting. The high-temperature damping capacity of FAC/AZ91D composites was investigated as compared with AZ91D Mg alloy. The results show that the damping capacities of FAC/AZ91D composites and AZ91D Mg alloy strongly depend on the measuring temperature. The FAC/AZ91D composites show better damping capacity than AZ91D Mg alloy. The 10 wt.% FAC/AZ91D composites exhibit the best damping capacity from room temperature to 125°C, whereas the 2 wt.% FAC/AZ91D composites show the highest damping capacity at 125°C–320°C. The damping mechanism was analyzed by microstructure observation at elevated temperatures. The damping-temperature curves exhibit a damping peak at approximately 150°C, and the activation energy of the damping peak was calculated according to the Arrhenius equation. Furthermore, the peak temperature increases with increasing frequencies. The damping peak is related to the thermal activation relaxation process, and its mechanism is the dislocation-induced damping.

Poly(vinyl butyral) -polyaniline-magnetically functionalized fly ash cenosphere composite film for electromagnetic interference shielding

The present study is about the electromagnetic interference (EMI) shielding effectiveness of polymer magnetically functionalized industrial waste fly ash cenosphere (FAC, hollow microspheres) composite film. The size range of the used FAC was 5-70 mu m (average size similar to 45 mu m) and these were Co/Ni coated chemically and efficiently functionalized by in situ synthesis of polyaniline under nitrogen at -30 +/- 2 degrees C. Poly(vinyl butyral) polyaniline-Co/Ni-FAC composite films (PVB-PANI-Ni/Co-FAC) were prepared by solution processing and electromagnetic interference (EMI) shielding property was investigated in the J-band (5.8-8.2 GHz) and X-band (8.2-12.4 GHz) frequency range. The most effective EMI shielding effectiveness (SE) of similar to 20 +/- 1 dB and similar to 23 +/- 1 dB was obtained for PVB-PANI-Ni-FAC (PVBPNC) film (thickness 259 +/- 2 mu m) in the frequency range 5.8-8.2 GHz and 8.2-12.4 GHz respectively, whereas EMI SE of PVB-PANI film (268 +/- 2 mu m) was found to be similar to 11 +/- 0.52 dB and similar to 13 +/- 1 dB. For all the composite films, majority of EMI shielding occurs due to the absorption. The obtained EMI shielding due to absorption (SEA) of PVBPNC film was found to be similar to 17 +/- 1 dB and similar to 20 +/- 0.53 dB for J-band and X-band, respectively. In contrast to PVB-PANI (PVBP) film the SEA of PVB-PANI-Co/Ni-FAC composite film was found to increase with frequency. This behaviour of these composite films is exchanged as due to the increase of frequency dependent conductivity and EM attenuation constant. The dielectric studies, also carried out in this investigation, calculated complex permittivity (epsilon* = epsilon' - i epsilon `'), and complex permeability (mu* = mu' - i mu `') values show the excellent electrical (epsilon `') and magnetic loss (mu `') for enhancing the EMI shielding due to absorption. (C) 2016 Elsevier Ltd. All rights reserved.

Preparation, characterization, and photocatalytic activity evaluation of Fe–N-codoped TiO2/fly ash cenospheres floating photocatalyst

Nitrogen-doped titanium dioxide (TiO2) and Fe-N-codoped TiO2 layers on fly ash cenospheres (FAC) as floating photocatalyst were successfully prepared through sol-gel method. Photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)-Vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption analyses for Brunauer-Emmett-Teller (BET) specific surface area. Photocatalytic efficiency of the prepared catalyst was evaluated through using the decomposition of Rhodamine B (RhB) as a model compound under visible light irradiation. Photocatalytic activity and kinetics of catalyst under visible light were detected in details from different Fe/Ti mole ratios by detecting photodegradation of RhB. Experimental results show that when the calcination temperature was 550°C, the dosage of FAC was 3.0g, and the mole ratio of Fe/Ti was 0.71%; the synthesized Fe-N-TiO2/FAC photocatalyst presented as anatase phase and that N and Fe ions were doped into TiO2 lattice. The material's specific surface area was 34.027m2/g, and UV-Vis diffuse reflectance spectroscopy shows that the edge of the photon absorption has been red shifted up to 400-500nm. Fe-N-codoped titanium dioxide on FAC had excellent photocatalytic activity during the process of photodegradation of RhB under visible light irradiation.

Lightweight polyaniline-cobalt coated fly ash cenosphere composite film for electromagnetic interference shielding

Thermal power plant's solid environmental waste fly ash cenosphere (FAC) is cobalt coated chemically and functionalized by in situ synthesis of polyaniline (PANI) under nitrogen atmosphere at -30 +/- 2 degrees C and characterized by various techniques. The electromagnetic interference shielding effectiveness (EMI SE) of free standing PANI/Co-FAC (PCC) films prepared by solution casting indicates an appreciable shielding. The most effective average EMI SE of similar to 30 dB was obtained for 89 +/- 3 mu m thicker flexible film over the frequency range of 12.4-18 GHz (Ku-band). Mechanistically, EMI shielding due to absorption was found to be dominant. The obtained shielding effectiveness due to absorbance (SEA) of PCC film is nearly two times higher than PC film. The microwave conductivity (sigma) of PCC film (157-184 Sm-1) is much higher than PC film (118-142 Sm-1). Moreover, the high EM attenuation constant (alpha) value of PCC film indicates excellent suitability of EMI shielding due to absorption.