Hollow Glass Microspheres Research Articles

Recyclable solar evaporator based on hollow glass microspheres for water purification and desalination

Solar-driven interfacial steam generation (SISG) has attracted much more attention for its significant potential in water purification and desalination. Herein, we report the fabrication of a novel photothermal material (MHGM/Fe3O4/TiO2–Ag/PPy) by coating Fe3O4, TiO2 & Ag, and fluorosilane doped polypyrrole (PPy) on (3-Aminopropyl)triethoxysilane modified hollow glass microspheres (MHGM), respectively, and a certain amount of such hollow microspheres self-float on the water surface as a solar evaporator for efficient SISG. Benefiting from low thermal conductivity (0.0455 W m–1 k–1), strong light absorption (about 95%) and the gap between the microspheres provides the channels for water transportation, the as-prepared solar evaporator of MHGM/Fe3O4/TiO2–Ag/PPy shows a high water evaporation rate of 1.5516 kg m–2 h−1 under 1 kW m–2 solar irradiation. Moreover, the evaporator with unique spherical hollow structure exhibits excellent salt resistance, as well as efficient water purification and antibacterial performance. More importantly, the evaporator possesses magnetic property and can be magnetically recovered. Thus, the as-prepared solar evaporator shows great potential for practical applications, including seawater desalination, sterilization and synergistic water purification during freshwater production.

Ablative properties, thermal stability, and compressive behaviour of hybrid silica phenolic ablative composites.

Silica phenolic composites are used as thermal protection systems for high temperatures applications like atmospheric re-entry modules, rocket nozzles etc. Lightweight silica phenolic composites (SPGB) were developed using chopped silica fibre, phenolic matrix, and hollow glass microspheres through a compression moulding technique to achieve a cost advantage in thermal protection systems. Ablative properties were evaluated using an Argon plasma jet at a stagnation heat flux of 500 W/cm2. The mass-loss and erosion rates under plasma exposure reduced up to 48% and 32%, respectively, with the addition of hollow glass microspheres. The heat of ablation of composites increased up to 33%. The thermal degradation behaviour of raw materials and SPGB composites was investigated through thermogravimetric analysis, and the scientific know-how was established. Compressive behaviour under uniaxial loading was evaluated, and the theoretical model for the developed three-component composite was established.

Epoxy resin/hollow glass microspheres composite materials with low dielectric constant and excellent mechanical performance

AbstractThe materials with low dielectric constant and low dielectric loss are vital for high integration degree of the circuit board. Although many polymers like epoxy resin exhibit excellent comprehensive performance, their dielectric constant is unable to satisfy high electronic packaging application. In this work, we present a simple grafting strategy via reaction between the hollow glass microsphere and polyhedral oligomeric silsesquioxane followed by blending epoxy resin to fabricate epoxy resin hollow glass microspheres composite materials. The superior heat resistance of hollow glass microspheres (HGM) can improve the thermal performance of composites. Due to the addition of Ge‐POSS, P‐HGM exhibited a good interfacial compatibility with epoxy resin matrix and forms an interfacial adhesion region. With the P‐HGM loading of 20 wt%, the fabricated composite materials exhibited the low dielectric constant of 2.59 and low dielectric loss of 0.0145. At the same time, the tensile strength, impact strength and flexural strength were 42.15 MPa, 24.33 kJ/m2 and 90.82 MPa, respectively, which demonstrated that the epoxy resin hollow glass microspheres composite materials processed superb mechanical behavior. It suggests that this method is a promising potential for fabricating low dielectric composite materials.

Prefab Hollow Glass Microsphere-Based Immunosensor with Liquid Crystal Sensitization for Acute Myocardial Infarction Biomarker Detection.

Quantitative detection of cardiac troponin biomarkers in blood is an important method for clinical diagnosis of acute myocardial infarction (AMI). In this work, a whispering gallery mode (WGM) microcavity immunosensor based on a prefab hollow glass microsphere (HGMS) with liquid crystal (LC) sensitization was proposed and experimentally demonstrated for label-free cardiac troponin I-C (cTnI-C) complex detection. The proposed fiber-optic immunosensor has a simple structure; the tiny modified HGMS serves as the key sensing element and the microsample reservoir simultaneously. A sensitive LC layer with cTnI-C recognition ability was deposited on the inner wall of the HGMS microcavity. The arrangement of LC molecules is affected by the cTnI-C antigen—antibody binding in the HGMS, and the small change of the surface refractive index caused by the binding can be amplified owing to the birefringence property of LC. Using the annular waveguide of the HGMS, the WGMs were easily excited by the coupling scanning laser with a microfiber, and an all-fiber cTnI-C immunosensor can be achieved by measuring the resonant wavelength shift of the WGM spectrum. Moreover, the dynamic processes of the cTnI-C antigen—antibody binding and unbinding was revealed by monitoring the wavelength shift continuously. The proposed immunosensor with a spherical microcavity can be a cost-effective tool for AMI diagnosis.

Effects of the absorber, thickness and surface roughness on the electromagnetic wave absorption characteristics of magnesium phosphate cement

Magnesium phosphate cement (MPC) functionalized with excellent electromagnetic wave absorption performance, bonding capacity, fast hardening and early strength can meet the requirements for rapid electromagnetic radiation protection of military and civil building structures. Hollow glass microsphere (HGM) is added uniformly to improve the impedance matching of MPC to free space, so that the electromagnetic wave is able to be maximally introduced into MPC and effectively absorbed by carbon nanotubes (CNT) through high dielectric loss effect. Influences of HGM contents, thickness and surface roughness of specimens on the electromagnetic wave absorption performance of MPC are systematically investigated. Test results demonstrate that the electromagnetic absorption performance of MPC is significantly enhanced by the additions of HGM and CNT. The peak reflection loss and the bandwidth below −10 dB first increase and then decrease with increasing HGM content. Increasing the thickness of the MPC improves the electromagnetic reflection loss. The electromagnetic absorption properties of MPC are improved further by cutting notches. MPC blended with 50 vol% HGM and 1 wt% CNT (by MgO) with 5 mm deep notches spaced 18 mm apart has excellent electromagnetic absorption capacity as featured by a peak reflection loss of –33.5 dB and a bandwidth of 7.03 GHz below −10 dB. In the perspective of structural strengths, the modified MPC is able to repair damaged concrete of pre-fractured concrete. It achieves the dual features of absorbing electromagnetic waves and repairing existing concrete structures.

Facile surface coating of Ni–Co–P alloy particles on hollow glass microspheres for enhanced wave absorbing

Facile surface coating of Ni–Co–P alloy particles on hollow glass microspheres for enhanced wave absorbing

Synergistic effect of silica aerogels and hollow glass microspheres on microstructure and thermal properties of rigid polyurethane foam

Insulation materials with excellent thermal properties are pivotal components for the next-generation green building materials. In this study, several novel rigid polyurethane foam (RPUF) composites modified by silica aerogels and hollow glass microspheres (HGMs) were prepared. The microstructure, mechanical, physical and thermal properties of the specimens were characterized. The results showed that the addition of fillers changed the microstructure of RPUF. Furthermore, the thermal conductivity of rigid polyurethane foam filled with silica aerogels and HGMs (PUAH) decreased from 24.4 to 22.7 mW/mK, and the compressive strength of PUAH was 51.1% higher than that of pure RPUF. Thermogravimetric analysis (TGA) exhibited that the thermal stability of PUAH was improved, which was evidenced by the delayed thermal decomposition temperature. Notably, the results of cone calorimeter test (CCT) demonstrated that, compared with pure RPUF, the total heat release (THR) and total smoke production (TSP) of PUAH decreased by 23.2% and 21.6%, respectively. The above results proved that there was a synergistic effect of silica aerogels and HGMs in enhancing the various performance of RPUF composites.

Thermophysical properties of hybrid silica phenolic ablative composite: Theoretical and experimental analysis

AbstractSilica phenolic ablative composites are used in many high‐temperature applications like rocket/missile solid motor nozzles, space re‐entry vehicles, and so forth. As ablative composite with lower thermal conductivity and density can save considerable cost, a hybrid silica phenolic ablative composite was developed by establishing a novel processing methodology using chopped silica fiber, phenolic resin, and hollow glass microsphere. The thermophysical properties of the developed hybrid composite are analyzed and established the scientific know‐how. The developed composites, with 36% lower density, displayed 50% lower thermal conductivity and 50% lower thermal diffusivity than standard silica phenolic composite. Since a proper thermal conductivity model for a three‐component composite with matrix, fiber, and hollow glass microsphere is not available, the most suitable model for the developed composite is established.

Robust composite aerogels with excellent flame retardant and thermal insulation properties based on modified hollow glass microspheres

The development of high-performance flame-retardant materials with better thermal insulation properties is of great significance to modern building energy conservation. In this study, we report the facile and scalable fabrication of novel aerogels (SA-HGM-APP) based on the building blocks of ammonium polyphosphate (APP) coated hollow glass microspheres (HGM) and matrix material sodium alginate (SA) by freeze drying method. The as-prepared composite aerogel exhibits better thermal stability (decomposition temperature over 210°C). In addition, SA-HGM-APP composite aerogels have good thermal insulation properties and low thermal conductivity, which is 0.035 W m−1 K−1. More importantly, the peak heat release rate (pHRR) is 14.14 kW m−2, the limiting oxygen index (LOI) value is as high as 100%, and the aerogel composite material can reach UL-94 V-0 grade, so it shows excellent flame retardancy. These results attributed to a synergistic effect, which combines the rich porous structure derived from HGM, so that SA and APP have better thermal insulation and excellent non flammability, thus providing excellent flame retardancy. SA-HGM-APP aerogel composite has many advantages, such as simple preparation method and high mechanical strength. It has great potential in future thermal insulation and flame retardancy applications.

Rheological and hardened properties of self-compacting concrete using hollow glass microspheres as a partial replacement of cement

The main purpose of this research was focused mainly on the rheological influence of the “ball bearings” behavior of hollow glass microspheres (HGM), which affect the workability and stability of cementitious materials. They were used as partial replacement of cement on self-compacting concrete (SCC), in rates of 0% and 5%, promoting a possible reduction in the chemical admixtures consumption. The rheological properties were determined experimentally by direct tests using a rotational concrete rheometer and indirectly by empirical tests such as the slump flow, J-ring and L-box. From the data collected experimentally in direct tests, the behavior of mixtures was deeply analyzed by comparing the Bingham and the modified Bingham model, considering the influence of the plug flow. For this analysis, algorithms based mainly on the Reiner-Riwlin equations were developed with the purpose of showing in a simpler and more schematic way the iterative models applied in each case, contributing to the advancement of rheology of cement-based materials. In addition to rheological tests carried out, concrete properties in the hardened state were also measured at 28 days of curing. Young's modulus, Poisson's ratio, compressive strength, tensile strength, bending strength and chloride migration coefficient in a non-steady state were measured. The experimental results indicate that HGM incorporation improved the properties in the fresh state and slightly reduced the hardened properties of the SCC mixtures.

Hollow glass microspheres modified polyurethane sponge with enhanced flame retardancy

AbstractNowadays, with the continuous improvement of domestic fire safety requirements, the development of materials with better thermal insulation and flame retardant performance is of great significance to modern building energy conservation. Herein, hollow glass microspheres (HGM) modified polyurethane sponge (PU‐HGM) with enhanced flame retardancy is prepared by dipping HGM onto PU sponge through polydimethylsiloxane. The PU‐HGM sponge exhibits porous network structure with rich micron sized pores, as well as the HGM with closed hollow spherical structure endow the prepared PU‐HGM better thermal insulation performance, and the thermal conductivity is 0.050 W m−1 K−1. Besides, the PU‐HGM maintains excellent elasticity of PU sponge, and shows strong mechanical strength, the stress of PU‐HGM sponge was as high as 882 kPa at 70% strain after 3 cycles. More importantly, compared with pure PU sponge, the PU‐HGM shows excellent flame retardancy. It keeps its original shape after combustion, and no obvious flame was observed on the surface of PU‐HGM sponge. Thus, combined with its high mechanical strength, low material cost, simple and scalable preparation method, the as‐prepared PU‐HGM sponge shows great potential for application in the field of heat insulation and flame retardant.

Hydrostatic strength of hollow glass microspheres composites: Influencing factors and modelling

This study deals with the hydrostatic strength of hollow glass microspheres composites, commonly known as syntactic foams, using model materials made of 0.15 g/cm3 microspheres with 3 types of matrix, two epoxies and one paraffin. More than 100 model material samples are characterized for that work. The hydrostatic strength of these composite materials is determined in a pressure vessel, which can go up to 100 MPa. Two major parameters are studied: stiffness of the matrix and microsphere volume content within the composite material. The results clearly show that the hydrostatic strength of the syntactic foam can be improved by an increase in matrix stiffness or a reduction in microspheres content. Based on experimental data an empirical model with two parameters is proposed to describe the hydrostatic strength of syntactic foam. The relevance of the model is discussed.

Lightweight epoxy foams prepared with arranged hollow-glass-microspheres/epoxy hollow spheres

The research on lightweight epoxy foams is of great significance to weight reduction for aerospace, aviation, shipbuilding, high-speed railway, and other fields. In this study, a novel lightweight epoxy foam with a macro-sized hollow structure was designed and prepared using arranged hollow glass microspheres/epoxy resin (HGMs/EP) hollow spheres as filler and EP as a matrix by template and molding method. The density and uniaxial compression properties of the prepared hollow spheres could be tuned between 0.14 and 0.27 g/cm3 and 0.30 ± 0.01 MPa to 2.39 ± 0.17 MPa through adjusting the shell thickness, respectively. The bending and compression performance of arranged hollow spheres reinforced epoxy foams were investigated, and the failure mechanism was analyzed as well. The highest specific flexural strength, the specific flexural modulus, the specific compression strength, and the specific compression modulus of obtained epoxy foams was 30.77 ± 3.04 MPa cm3/g, 2.66 ± 0.19 GPa cm3/g, 45.78 ± 1.58 MPa cm3/g, and 1.60 ± 0.26 GPa cm3/g, respectively. This work presents a novel syntactic epoxy foam with low density, good specific flexural strength, and specific compression strength with fewer hollow glass microspheres, which can provide a preparation method for lightweight structural materials.

Strategy for preventing explosive spalling and enhancing material efficiency of lightweight ultra high-performance concrete

The highly dense structure which causes the risk of explosive spalling is one of the major limitations of using ultra high-performance concrete (UHPC). This study developed a lightweight UHPC (L-UHPC) and proposed a strategy to improve its material efficiency and lower the risk of explosive spalling. High-strength hollow glass microspheres and fine lightweight aggregates were jointly used in the UHPC system to achieve light weight and ultra high strength. The L-UHPC was cured at different curing regimes to maximize its material efficiency and prevent its spalling after exposure to high temperature. The experimental results showed that the combination of lightweight materials and dry heat curing was effective in reducing the density (<1800 kg/m3) and enhancing the compressive strength (>150 MPa) of the L-UHPC. By means of minimizing the amount of internal free water, the heat curing approach contributed to avoiding the thermal spalling of the L-UHPC exposed to fire conditions. Microstructural results indicated that the elevated temperature curing promoted the pozzolanic reaction and increased the microhardness of the paste matrix by increasing silicate polymerization of the C-S-H structure. The created voids of the collapsed glass microspheres might accommodate some internal vapor pressure and mitigate the degradation caused by the high temperature exposure. The synergetic effect of the porous materials and the dry heat curing lowered the thermal conductivity and significantly improved the material efficiency of the L-UHPC.

Form-stable phase change composites with high thermal conductivity and electrical insulation

The commercialization of phase change materials (PCMs) based on paraffin is obstructed by the drawbacks of leakage and low thermal conductivity. Herein, we developed form-stable phase change composites via trapping paraffin into triblock copolymer. The hybrid filler, namely boron nitride and Ag-coated hollow glass microspheres (Ag@HGMs), was introduced to enhance the thermal conductivity of the composites. The latent heat values of composites could be easily tailored in a range of 157.6–192.4 J g−1 by changing the loading of filler. Interestingly, the addition of boron nitride and Ag@HGMs hybrid filler has little impact on electrical insulation property, and displays a synergistic effect on the heat transfer improvement within the composites. The sample BN/Ag@HGMs-4 exhibits excellent latent heat, electrical insulation performance, thermal recycling properties and stability, and the thermal conductivity reaches up to 1.54 W m−1 K−1, which has great potential application in thermal management and heat energy collection system.

Development and characterization of surface functionalized hierarchical carbon fiber reinforced hybrid polypropylene composites

Light-weight hybrid composites of relevant industrial applications were prepared using surface functionalized hierarchical carbon fibers ( f-CF), silane treated hollow glass microspheres (HGM), and a blend of polypropylene (PP) and maleic anhydride-grafted-styrene ethylene butylene styrene as the base polymer matrix. The f-CF were prepared by coating amine functionalized carbon nanotubes onto silane treated CF using an ultrasonic assisted electrophoretic deposition technique to improve fiber-matrix interfacial adhesion. For hybrid composition of 20 wt.% f-CF and 10 wt.% HGM, the tensile strength and modulus improved by ∼141 and ∼536% over neat PP while flexural strength and modulus increased by ∼118% and ∼583% respectively. Impact strength of 11.06 kJ/m2 was obtained and uniform dispersion and distribution of f-CF and HGMs was observed in Scanning electron microscope (SEM) images. Desirable reduction in density and melt viscosity along with improvement in composite stiffness were observed due to addition of HGM filler. Compared to PP, the crystallization temperature increased by ∼12°C while a maximum decrease of ∼5°C in melting temperature was obtained for the hybrid composites. Crystallinity of the hybrid composites decreased with an evident β crystal formation brought in by the nucleation.

Simultaneous Effects of Carboxyl Group-Containing Hyperbranched Polymers on Glass Fiber-Reinforced Polyamide 6/Hollow Glass Microsphere Syntactic Foams.

The hollow glass microsphere (HGM) containing polymer materials, which are named as syntactic foams, have been applied as lightweight materials in various fields. In this study, carboxyl group-containing hyperbranched polymer (HBP) was added to a glass fiber (GF)-reinforced syntactic foam (RSF) composite for the simultaneous enhancement of mechanical and rheological properties. HBP was mixed in various concentrations (0.5–2.0 phr) with RSF, which contains 23 wt% of HGM and 5 wt% of GF, and the rheological, thermal, and mechanical properties were characterized systematically. As a result of the lubricating effect of the HBP molecule, which comes from its dendritic architecture, the viscosity, storage modulus, loss modulus, and the shear stress of the composite decreased as the HBP content increased. At the same time, because of the hydrogen bonding among the polymer, filler, and HBP, the compatibility between filler and the polymer matrix was enhanced. As a result, by adding a small amount (0.5–2.0 phr) of HBP to the RSF composite, the tensile strength and flexural modulus were increased by 24.3 and 9.7%, respectively, and the specific gravity of the composite was decreased from 0.948 to 0.917. With these simultaneous effects on the polymer composite, HBP could be potentially utilized further in the field of lightweight materials.

Manufacture Hollow Glass Microsphere (HGS) in University Laboratory Scale (Phase 1)

Hollow Glass Microsphere (HGS) can be used as an additive of drilling fluid to decrease the density and hydrostatic pressure without changing the chemistry characteristic to make underbalanced drilling condition. HGS is relatively easier to be mixed with the fluid without complicated equipment, can prevent formation damage, and can improve oil and gas production. There are various HGS commercial products that have been developed in the industry for various purposes with a density range 0.125-1.1 gr/cm3, grain size range 2-120 μm, and compressive strength up to 200 MPa. HGS has been successfully used in underbalanced drilling operation in several oil and gas fields in Indonesia. HGS costs less than UBD and the application shows good results with the improvement of oil and gas production. However, the cost of commercial HGS products in the market is very expensive. Petroleum Engineering Study Program Institut Teknologi Bandung (ITB) performed the HGS research in three phases. The first phase reported in this paper was to manufacture HGS in the university laboratory scale. HGS was manufactured based on various chemical compositions and temperature and time variation of the burning process. Scanning Electron Microscope (SEM), Energy Dispersive Spectrometry (EDS), and X-Ray Diffraction (XRD) analysis were performed to identify and characterize the raw chemical material and manufactured HGS. HGS was successfully manufactured with the following characteristics: low density (<0.8 gr/cm3) and low grain size (20-40 μm). These characteristics show that HGS can compete with commercial industry HGS products that have been successfully used in the underbalanced drilling operation. The second phase is to scale-up manufacture HGS from university laboratory scale to industrial scale. The third phase is to test the manufactured HGS with drilling fluid according to the American Petroleum Institute (API) Spec. 13A and API Spec. 13B-1.

A tri-layer floating photocatalyst/adsorbent for the removal of organic compounds from wastewater: Layer-by-layer deposition of silicalite-1 and titania on hollow glass microspheres

Removal of organic compounds from wastewater is necessary to ensure that aquatic organisms are not adversely affected. In the past, it had been shown that zeolite-based systems provide good opportunities for wastewater treatment; however, most of the zeolite systems reported thus far face the disadvantages of sinking in water and saturated adsorption site. Therefore, in the current study, we attempted to develop zeolite-based composite systems with good floatability, adsorption capacity, and photocatalytic activity. In addition, our aim was to ensure that these composites could be easily separated from the treated water. Thus, a tri-layer floating photocatalyst/adsorbent was prepared via the layer-by-layer deposition of silicalite-1, a pure silica MFI-type zeolite (PSZ), and TiO 2 on hollow glass microspheres (HGMs). A thin layer of silicalite-1 was crystallized on the dense walls of HGMs to fabricate floating adsorbents (PSZ-HGMs). Subsequently, a layer of TiO 2 was deposited on PSZ-HGM surfaces using the sol–gel method to develop photocatalytic composites (TiO 2 /PSZ-HGMs). A good PSZ coverage and attachment were achieved on HGM surfaces by adding HGMs to an alkali solution containing tetrapropylammonium hydroxide and tetraethyl orthosilicate, followed by hydrothermal synthesis at 180 °C for 40 h. Subsequent deposition of TiO 2 was effective in homogeneously covering the PSZ surface without clogging the zeolite pores. The wastewater treatment capacity of the synthesized materials was verified using methylene blue (MB). It was found that TiO 2 /PSZ-HGMs, which exhibited both photocatalytic and adsorption activities, acted synergistically with UV-C irradiation to drastically degrade MB concentration by ∼ 98% within 2 h. Therefore, these materials may be considered to have high potential in wastewater-treatment processes. • Newly designed tri-layer floating TiO 2 /pure silica MFI-type zeolite/hollow glass microsphere (TiO 2 /PSZ/HGMs) was developed. • The effects of HGM size distribution, precursor composition, and synthesis time on PSZ layer formation on HGM were examined. • Anatase/rutile-TiO 2 were homogeneously embedded onto PSZ/HGMs without clogging the zeolite pores by using the sol–gel method. • Optimized TiO 2 /PSZ/HGMs could remove 98% of methylene blue under UV-C irradiation for 2 h.

Influence of Heat Treatment on Microstructure and Performance of Degradable Mg Matrix Composites Reinforced with Hollow Glass Microsphere

Recently degradable Mg matrix composites as a promising candidate for degradable downhole tools application have aroused extensive interest. In the present work, the effects of heat treatment (solution treatment and artificial aging) on the microstructure, mechanical properties and degradation behaviors of the newly developed hollow glass microsphere reinforced Mg-Al15-Zn6-Cu1.5 composites were investigated. The results show that the solution treatment causes the β-Mg17Al12 phase and Mg32(Al,Zn)49 phase to dissolve into the α-Mg matrix and the coarse eutectic τ-Al2CuMg phase to translate into blocky morphology. Aging treatment causes the β phase to precipitate at the grain boundaries or the edge of the residual second phases in lamellar and blocky morphology. After solution treatment, the ductility of the composites was significantly increased, while the following aging treatment could significantly increase the ultimate compressive strength (UCS), hardness and degradation rate. The composites solution treated at 420 °C for 20 h and aged at 200 °C for 24 h shows the higher degradation rate of 6.5 mg·cm-2·h-1 in 3 wt.% KCl at ambient temperature, with UCS of 471 MPa, Brinell hardness of 115 HB and fracture strain of 8.7 %, this outstanding comprehensive performance is more suitable for degradable downhole tools application.