Glass Cenospheres Research Articles

Damping properties and mechanism of aluminum matrix composites reinforced with glass cenospheres

The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method. Transmission electron microscopy and scanning electron microscopy were employed to characterize the microstructure of the composites. The low-frequency damping properties were examined by using a dynamic mechanical thermal analyzer, aiming at exploring the changing trend of damping capacity with strain, temperature, and frequency. The findings demonstrated that the damping value rose as temperature and strain increased, with a maximum value of 0.15. Additionally, the damping value decreased when the frequency increased. Dislocation damping under strain and interfacial damping under temperature served as the two primary damping mechanisms. The increase in the density of dislocation strong pinning points following heat treatment reduced the damping value, which was attributed to the heat treatment enhancement of the interfacial bonding force of the composites.

Quasi-static compressive properties and damage behavior of aluminum matrix syntactic composites with different diameters of glass cenospheres

Aluminum matrix syntactic composites have broad applications, including aerospace, transportation, military industries, and our daily life owing to lightweight and high energy absorption properties. However, its strength and energy absorption capacity still need improvement. In this study, we prepared an aluminum matrix syntactic composite with smaller diameters glass cenospheres. Due to the higher porosity of the glass cenospheres, the density of the syntactic composites ranged from 1.20–1.27 g cm−3, and the strength and energy absorption could reach up to 172.8 MPa and 75.3 MJ m−3, respectively. Combining finite element and in-situ digital image correlation results, the aluminum matrix syntactic composites with large diameter tend to form 45–90° cracks, resulting in a decrease in material strength with increasing glass cenospheres diameter.

Boosting energy absorption performance of aluminum matrix syntactic foam with carbon coated glass cenospheres

In this study, glass cenospheres are coated with resorcinol/formaldehyde resin in an alkaline solution, and the polymer layer is subsequently transformed into carbon shell by pyrolysis. Because carbon is a strong and light-weight material, the resulting aluminum matrix syntactic foam reinforced with carbon coated glass cenospheres shows low density of 1.35 g cm−3, and high energy absorption capacity of 80.3 MJ m−3. The excellent energy absorption properties are ascribed to the conformal carbon shell that can disperse stress, leading to high compressive strength of the foam. The improved wettability of filler surfaces by liquid metals during pressure infiltration casting is verified using both optical and electron microscopy. In addition, XRD results suggest that no obvious interfacial reactions happen during the preparation of foam.

Preparation and quasi-static compression properties of hybrid aluminum matrix syntactic foam reinforced with glass cenospheres and silicon carbide nanowires

Conventional hybrid aluminum matrix syntactic foam with various hollow fillers shows low density and high densification strain. However, its peak stress can hardly be increased, resulting in a limited improvement in the energy absorption capacity. Although composites can be reinforced by adding ceramic nanoparticles, it is difficult to achieve dispersion of both hollow and dense fillers in the metal matrix due to their distinct density difference. In this study, we use silicon carbide nanowires reinforced aluminum swarf as the source of ceramic fillers, and prepare hybrid aluminum syntactic foam reinforced by both glass cenospheres and silicon carbide nanowires. The resulting syntactic foam shows low density of 1.3 g cm −3 , high peak stress of 128.6 MPa, and high energy absorption capacity of 60.70 MJ m −3 . Moreover, we demonstrate a novel way to recycle silicon carbide reinforced aluminum composites for reprocessing. • HASF reinforced with a hollow and a dense nanowire filler. • Glass cenospheres and SiCnw forming high dispersion of microscale domains in HASF. • Reprocessing both metal matrix and SiCnw fillers at the same time. • HASF showing strength of 128.6 MPa and energy absorption capacity of 60.70 MJ m −3 .

Preparation and Quasi-Static Compression Properties of Hybrid Aluminum Matrix Syntactic Foam Reinforced with Glass Cenospheres and Silicon Carbide Nanowires

Preparation and Quasi-Static Compression Properties of Hybrid Aluminum Matrix Syntactic Foam Reinforced with Glass Cenospheres and Silicon Carbide Nanowires

Fiber-reinforced cementitious composites incorporating glass cenospheres – Mechanical properties and microstructure

The effects of glass cenosphere particles on the properties of fiber-reinforced cement-based composites are explored in this study. Lightweight glass cenospheres were used as fillers in the cementitious composites and incorporated in various proportions. The developed composites were evaluated for mechanical strength parameters including compressive strength, flexural strength, tensile strengths, and elastic modulus. Microstructural investigations were also carried out. The results showed that utilizing glass cenospheres up to 30% (by cement weight) leads to adequate mechanical strength where the corresponding specific strength of 28kPa/kgm−3 could be achieved. Microstructural analyses further revealed that increased porosity due to glass cenospheres incorporation is primarily responsible for strength loss with increasing weight fraction.

Quasi-static and dynamic compression behavior of glass cenospheres/5A03 syntactic foam and its sandwich structure

5A03 aluminum matrix syntactic foam filled with glass cenospheres was synthesized using pressure infiltration technique. This paper focused on the compression behavior of syntactic foam at quasi-static (10−3s−1) and dynamic (strain rate 1×103s−1–3×103s−1) condition, and the dynamic response of syntactic foam core sandwich structure with two different wave impedance front-panels (A3 steel and AZ31) subjected to split-Hopkinson pressure bar. The syntactic foam at dynamic loading exhibited a maximum 43% increase in peak strength, 38% in plateau strength, and 23% in energy absorption capacity compared to quasi-static results, with 0.03 strain rate sensitivity similar to that of aluminum matrix. The dynamic compression behavior can be concluded as thin near-45° shear bands forming, deformed area propagating to the central and lateral parts, and finally densifying with significant lateral expansion. The sandwich structure exhibited great energy absorption capability due to the syntactic foam core. The higher wave impedance front-panel would be conducive to the energy absorption capability of syntactic foam core into full play.

Mechanical behavior of pure Al and Al–Mg syntactic foam composites containing glass cenospheres

Glass cenospheres were used as space holders for making aluminum matrix syntactic foams by pressure infiltration technique. The mechanical properties and failure behavior of cenospheres/Al syntactic foams with pure Al and Al–Mg alloys were investigated in the present work. The failure behavior of cenospheres in two syntactic foams was similar. However, the mechanical behavior of these two syntactic foams was different. Under compression process, the cenospheres/pure Al showed discontinuous shear band and drum shape, while cenospheres/Al–Mg exhibited continuous shear band and was divided by main shear zone. At the tensile state, the cenospheres in pure Al matrix syntactic foam debonded from the matrix, while the cenospheres in Al–Mg matrix syntactic foam was well-bonded and appeared to lamellar tearing. It is suggested that the difference of mechanical deformation behavior could be attributed to the matrix ductility and the forming of interfacial reaction product MgAl2O4 coatings.

Interfacial microstructure and compressive properties of Al–Mg syntactic foam reinforced with glass cenospheres

Glass cenospheres/Al syntactic foams are successfully produced with about 50% volume fraction using pressure infiltration process. The interfacial reactions between glass cenospheres and Al–Mg alloys (5A03 with 3wt% Mg and 5A06 with 6wt% Mg) have been deeply studied. The MgAl2O4 crystals produced by the reaction of 2Al(l)+Mg(l)+2SiO2(s) → 2MgAl2O4(S) + 2Si(S) are the main reaction products in the size of ∼100 nm and the reaction layer is about 800 nm thick. The interfacial reaction region is composed of a large amount of MgAl2O4 uniformly coating on the glass cenospheres due to the spherical structure of cenosphere. Si is believed to diffuse through the grain boundaries between the MgAl2O4 crystals and aggregate on the surface of the reaction zone. With the increase of Mg content in matrix such as 5A06 alloy, Si formed above transforms into Mg2Si by the reaction of 2 Mg(l) + Si(s) → Mg2Si(s). The compressive strength of composites increases with the increase of Mg content which is not only contributed to the improved strength of matrix but the suitable interfacial reaction coating and the forming of Mg2Si in matrix.

Size sorting of floating spheres based on Marangoni forces in evaporating droplets

The high throughput size sorting of particles in liquid suspensions is of interest for a variety of microanalytical and micromanufacturing applications. Hollow glass cenospheres of various diameters ranging from 5 to 200 µm are sorted according to size by evaporation of isopropyl alcohol droplets on an unpatterned glass substrate. By raising the temperature of the glass substrate, a stable Marangoni convection is developed inside the droplet. At a substrate temperature of 55 °C, more of the larger spheres (150–200 µm) are deposited near the droplet center, but smaller spheres <50 µm are found everywhere throughout the dried region. Better sorting is observed when the temperature of the substrate is above the boiling point of the liquid. When the substrate temperature is 85 °C, higher than the boiling point of IPA, most of the spheres <50 µm are transported close to the droplet edge. In the center of the dried pattern obtained from a 0.5 µl droplet, the spheres with >150 µm diameter outnumber those with <50 µm diameter by 6×. The deposited spheres remain attached to the substrate surface when dry. The self-assembled nature of this drying pattern results in size sorting.

A new microfiltration photocatalytic reactor for DDT removal

In this paper, a process combining stainless steel membrane and UV/TiO2 is developed to degrade DDT in water. The photocatalyst TiO2 was deposited on a kind of glass cenospheres whose diameters ranged from 20 to 200 μm, so they could be kept in the reactor by microfiltration membrane. The influence of different variables (TiO2 concentration, radiation) on the reaction rate was tested. According to the experiment, the removal was mainly caused by adsorption during the early stages of the reaction and mainly by UV/TiO2 degradation in the later stages. Three sample solutions with DDT concentrations: C0 = 30, 40 and 50 μg/L, were treated in the reactor and the removal rate of DDT was found to be 98.3%, 97.8% and 97.6%, respectively. Adequate dosage of the catalyst increased the generation rate of electron/hole pairs which promoted the formation of OH radicals for enhancing photodegradation.

Porous Crystalline Silica (Gubka) as a Inorganic Support Matrix for Novel Sorbents

ABSTRACTInorganic ion exchange media typically exist as fine powders, making large-scale use impractical, unless the media can be affixed to an appropriate matrix. Likewise, organic chelating agents are typically dissolved in a solvent and absorbed into porous matrices for use in extraction chromatography. The most common matrices utilized in both cases are organic materials, that are not compatible with high radiation fields or acceptable as final waste forms. Recent investigations have shown that ion exchange sorbents can be effectively loaded within a porous crystalline silica (Gubka) matrix. This approach allows for target radionuclides to be adsorbed into a porous micro-crystalline glass matrix which encapsulates the contaminant and becomes the final waste form. Subsequent to adsorption of the radionuclides, the Gubka matrix can be compressed in a hot uniaxial press, resulting in an even greater volume reduction. The porous glass matrix is produced in Russia using fly ash residue from coal combustion power generating plants. It consists of consolidated arrays of hollow glass cenospheres and is termed Gubka which is the Russian word for sponge. This paper describes results of a collaborative research program between the Khlopin Radium Institute, St.Petersburg, Russia, the Institute of Chemistry and Chemical Technologies, Krasnoyarsk, Russia, the Mining and Chemical Combine, Zheleznogorsk, Russia, and the Idaho National Engineering and Environmental Laboratory. Ammonium molybdophosphate (AMP) for the removal of cesium from acidic liquid waste has been successfully incorporated into Gubka matrices. Test results for cesium removal, using AMP-Gubka, are discussed.