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Large-scale hydrogen storage is crucial for advancing liquid hydrogen technology. Due to liquid hydrogen's ultra-low boiling point and low heat of vaporization, effective insulation is necessary to minimize boil-off loss. Larger storage vessels use bulk-fill insulation like perlite and hollow glass microspheres (glass bubbles) operating at moderate vacuum (MV) levels. The choice of insulation material affects the construction schedule, capital cost, and operating costs of storage tanks. Therefore, studying evacuation properties of bulk-fill insulation materials is essential to advance hydrogen-based energy infrastructure. This study aimed to quantify and compare the pump-down times for 3M™ Glass Bubbles K1 and cryo-insulation grade perlite and to identify physical properties influencing pump-down times. Perlite, with its porous structure and low bulk density, was expected to enable faster gas evacuation, while glass bubbles were thought to hinder it. However, our research shows that dry 3M™ Glass Bubbles K1 have faster nitrogen evacuation rates. [Display omitted] • We highlight the impact of insulation material selection in minimizing LH2 boil-off. • We studied the evacuation properties of bulk-fill cryo-insulation materials. • We focused on hollow glass microspheres (glass bubbles) and perlite. • Our research shows dry 3 M™ Glass Bubbles K1 have faster nitrogen evacuation rates. [ABSTRACT FROM AUTHOR]

Copyright of Paint & Coatings Industry (0253-4312) is the property of Paint & Coatings Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Paint & Coatings Industry (0253-4312) is the property of Paint & Coatings Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The development of electronic fuze has placed higher demands on encapsulation resins, which are required to provide not only insulation and protection, but also higher impact resistance and good electromagnetic shielding performance. A new composite material consisting of hollow glass microspheres (HGM) and modified epoxy resin was developed. This material exhibits significant electromagnetic shielding capabilities for terahertz (THz) waves, as well as superior impact energy absorption properties. Bisphenol A‐type epoxy resin (E‐44) was modified using Al(OH)3, red phosphorus, carbon black, and SiO2, and the material properties were optimized by adjusting the HGM content. The electromagnetic shielding effectiveness and impact energy absorption of the composite material in the THz band were comprehensively tested using THz time‐domain spectroscopy and split Hopkinson pressure bar testing systems. Additionally, a comprehensive evaluation of the mechanical and dielectric properties, thermal conductivity, and thermal stability of the material was conducted. The results showed that the electromagnetic shielding effect of 60 vol.% HGM hybrid‐modified resins was the best, reaching 43.78 dB. The 20 vol.% HGM hybrid‐modified resins not only has a specific absorption energy of 18.51 J/cm3, but also has the best overall performance. This work has advanced the design and development of multifunctional and impact‐resistant potting epoxy resins. [ABSTRACT FROM AUTHOR]

The composites based on hollow glass microspheres (HGMs) decorated with nanoparticles of nickel and iron oxides were prepared from the nitrate solutions with ultrasound treatment. Further exposition of these composites in a hydrogen-helium flow leads to the formation of nanosized bimetallic particles of Ni(80)Fe(20) (number in the brackets is estimated as wt%) that are effective in the catalytic reaction of CO2 hydrogenation to methane. Investigation of CO2 conversion was carried out under gas chromatographic control, and methane yield was evaluated for composites with 20 and 60 wt% of grafted bimetallic mass. The TPD MS method was used to study the processes of desorption of particles involved in the mechanism of methane formation. Textural and structural characteristics of as-prepared and post-reacted composites were examined using low-temperature nitrogen adsorption and X-ray diffraction methods. [ABSTRACT FROM AUTHOR]

The composites based on hollow glass microspheres (HGMs) decorated with nanoparticles of nickel and iron oxides were prepared from the nitrate solutions with ultrasound treatment. Further exposition of these composites in a hydrogen-helium flow leads to the formation of nanosized bimetallic particles of Ni(80)Fe(20) (number in the brackets is estimated as wt%) that are effective in the catalytic reaction of CO2 hydrogenation to methane. Investigation of CO2 conversion was carried out under gas chromatographic control, and methane yield was evaluated for composites with 20 and 60 wt% of grafted bimetallic mass. The TPD MS method was used to study the processes of desorption of particles involved in the mechanism of methane formation. Textural and structural characteristics of as-prepared and post-reacted composites were examined using low-temperature nitrogen adsorption and X-ray diffraction methods. [ABSTRACT FROM AUTHOR]

In order to reuse the multiple solid waste and improve the porosity of geopolymer composites, a unique foaming process was developed to fabricate novel green foamed fly‐ash/slag‐based hollow glass microspheres/geopolymer (HGMs/FSGP) composites. A thorough investigation was carried out on the synergic effects of cetyltrimethylammonium bromide (CTAB), hydrogen peroxide (H2O2) and HGMs on the microstructure, strength and thermal conductivity. Results showed that the foamed HGMs/FSGP composites with the amorphous structure could be fabricated by foaming combined with HGMs at room temperature. The density of the samples changed from 1.16 to 0.47 g/cm3 with 1–5 wt.% H2O2. The acceptable compressive strength (0.71–15.05 MPa) of the HGMs/FSGP composites was attributed to the fractured HGMs, the good bond between HGMs and geopolymer matrix, and crack deflection across the HGMs. With proper H2O2 and HGMs, the composites obtained their lowest thermal conductivity of 0.116 W/(m⋅K), which could find use in insulation fields. [ABSTRACT FROM AUTHOR]

Syntactic foams are lightweight porous composites obtained by the addition of hollow glass microspheres (HGMs) to a polymer matrix. This work experimentally and numerically investigates the thermal behavior of epoxy‐based syntactic foams with enhanced multifunctionality produced by incorporating microencapsulated phase change materials (PCMs) as functional fillers, providing thermal energy storage and temperature stabilization due to its large latent heat of melting. Foams are fabricated using varying ratios of HGMs (0–40 vol%) and PCM (0–40 vol%) to achieve tuned densities and thermal properties with a total filler content of up to 40 vol%. A one‐dimensional numerical heat transfer model based on the enthalpy method is presented to simulate the thermal behavior of these materials. The model accurately incorporates the specific heat and thermal conductivity of the foam components, as well as the latent heat absorption during PCM melting (up to 68 J/g). The model is experimentally validated by demonstrating good agreement with the measurements of transient temperature profiles during heating tests on the foam samples. The validated tool is then leveraged to model the thermal response of the foams under a sinusoidally varying heat source, similar to the possible real applicative scenarios. These results can help optimize foam compositions balancing energy storage density, heat transfer properties, and structural support for lightweight energy storage systems. Potential applications include high‐efficiency thermal management in battery packs, electronic cooling, solar energy storage, and sustainable temperature‐controlled buildings. Highlights: Foams with 0–40 vol% PCM and 0–40 vol% HGM show up to 68 J/g latent heat.1D numerical model accurately captures thermal conductivity and PCM phase change.Validated model simulates thermal response under sinusoidal heat, optimizing foam composition.Foams act as thermal reservoirs, maintaining up to 5°C lower surface temperatures than epoxy. [ABSTRACT FROM AUTHOR]

The influence of density and shape of hollow silicas (silica hollow tubes (SHT) or hollow glass microspheres (HGM)) on dielectric and heat‐resisting characteristics of poly(ether ketone ketone) (PEKK)/SHT and PEKK/HGM films was systematically investigated. The dielectric characteristics of PEKK/SHT or PEKK/HGM films decrease to a minimum, as their SHT or HGM contents approach 8 or 20 wt%, respectively, and the minimum dielectric constant (εr) and dielectric loss (tan δ) of PEKK/SHT or PEKK/HGM films decrease visibly with decreasing SHT densities. By filling with 0.46 g cm−3 mean density of SHT or HGM fillers, the minimum εr and tan δ of PEKK/SHT films are somewhat smaller than those of PEKK/HGM films. The linear coefficient of thermal expansion (LCTE) values of PEKK/SHT or PEKK/HGM films reduce and their onset degradation temperature values increase gradually with increasing SHT and HGM contents. Low εr/tan δ (2.11/0.0022 and 2.2/0.0027 at 1 MHz), LCTE (35.5 × 10−6 and 31.2 × 10−6 °C−1) and excellent heat‐resisting properties favorable for sixth generation (6G) ultrarapid communication are realized for appropriately prepared PEKK/SHT and PEKK/HGM substrate films. The free‐volume‐hole characteristics of PEKK/HGM or PEKK/SHT films approach a maximum as SHT or HGM contents reach an optimum value of 8 or 20 wt%, respectively. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Hollow glass microsphere (HGM) reinforced composites are a suitable alternative to energy absorption materials in the automotive and aerospace industries, because of their high crush efficiency and energy absorption characteristics. In this study, a polyurethane elastomeric matrix was reinforced with HGMs for HGM loadings ranging from 0 to 70 vol% (volume fraction). Quasi-static uniaxial compression tests were performed, subjecting the composite to compressive strains of up to 65%, to assess stress vs. strain and energy absorption characteristics. The results reveal that samples with a higher concentration of spheres generally exhibit better crush efficiency. Specifically, the highest crush efficiency was observed in samples with a 70 vol% HGM loading. A similar relationship was reflected in the energy absorption efficiency results, with the highest energy absorption observed in the 65 vol% sample. A correlation exists between the concentration of HGMs and important metrics such as mean crush stress and energy absorption efficiency. However, it is crucial to note that the optimal choice of sphere concentration varies depending on the desired performance characteristics of the material. [ABSTRACT FROM AUTHOR]

This study aims to precisely control the resonant frequency of synthetic composite foam materials with fixed dimensions. By incorporating rigid hollow glass microspheres XLD3000(XLD) and flexible hollow polymer microspheres MFL-81GCA(MFL) into the base resin (EP), we prepared synthetic composite foams containing different volume fractions of hollow microspheres (EP-XLD and EP-MFL). We conducted tests and analyses on the density, mechanical properties, resonant frequency, and microstructure of the EP-XLD and EP-MFL systems. Results indicate that as the volume fraction of hollow microspheres increases, the flexural specific modulus of the EP-XLD and EP-MFL systems, respectively, exhibits a linear increase and decrease, and the resonant frequency shifts linearly towards higher and lower frequencies. This trend aligns with theoretical predictions, affirming that the material's resonant frequency is closely related to its flexural modulus. This research not only deepens the understanding of the control mechanisms for the resonant frequency of synthetic composite foams but also proposes an innovative material design strategy with broad application potential, particularly in the fields of acoustics, damping, and structural materials, where it promises to significantly enhance material performance and meet specific engineering needs. [ABSTRACT FROM AUTHOR]

The effects of density and shape of hollow silica (functionalized silica hollow tubes (FSHT) or hollow glass microspheres (FHGM)) on dielectric constant (εr) and dielectric loss (tan δ) of hindered phenol (HP) grafted functional polypropylene (FPP)/FSHT, heat-treated FPP (HTFPP)/FSHT, FPP/FHGM or HTFPP/FHGM substrate films were systematically investigated. The dielectric or free-volume-hole characteristics of FPP/FSHT, FPP/FHGM, HTFPP/FSHT, or HTFPP/FHGM films decrease to a minimum, as FSHT or FHGM contents approach an optimal value of 4wt% or 8wt%, respectively, and their dielectric or free-volume-hole characteristics decrease or increase gradually with increasing HP molar%. The minimum εr and tan δ of FPP/FSHT or HTFPP/FSHT films decrease significantly with decreasing FSHT's densities. By filling with 0.46 g/cm3 identical density of hollow silica fillers, the minimum εr or tan δ procured for FPP/FSHT or HTFPP/FSHT films are somewhat smaller than those of corresponding FPP/FHGM or HTFPP/FHGM films. The linear coefficient of thermal expansion (LCTE) or onset degradation temperature (DTonset) of FPP/FSHT, HTFPP/FSHT, FPP/FHGM or HTFPP/FHGM films reduce or increase visibly with increasing FSHT or FHGM contents, respectively. All DTonset values of HTFPP/hollow silica films are ~ 150℃ higher than those of conventional PP polymers. Satisfactorily low εr/tan δ (1.74/0.0019, 1.83/0.0020, 1.83/0.0024 and 1.92/0.0028 at 1 MHz), LCTE (95 × 10–6/℃, 89 × 10–6/℃, 80 × 10–6/℃ and 74 × 10–6/℃) and pleasing heat-resisting properties for 6G ultrarapid communication are acquired for properly prepared FPP/FSHT, HTFPP/FSHT FPP/FHGM or HTFPP/FHGM substrate films having 1.2 HP molar% and 0.46 g/cm3 density of FSHT and FHGM fillers. Probable reasons accounting for these reduced dielectric, LCTE and improved heat-resisting characteristics are proposed. [ABSTRACT FROM AUTHOR]

In this article, the surface modification methods of hollow glass microspheres and their applications in coatings were briefly introduced. The latest research progress in thermal insulation coatings, fireproof coatings, wave-absorbing coatings and anticorrosive coatings was summarized, and the future direction of the application of hollow glass microspheres in coatings was prospected. [ABSTRACT FROM AUTHOR]

A lightweight water-soluble core mold material for hollow shell composites was prepared by hot drying process with polyvinylpyrrolidone (PVP) aqueous solution as the adhesive and hollow glass microspheres as the matrix material. The effects of the content of adhesive and different treatment methods on the flexural strength, compressive strength and dissolution rate of the core mold were studied, and the microstructure of the core mold material was observed by scanning electron microscope. The results show that adhesive dosage of 40%, the flexural strength and compressive strength could reach up to 3.346 MPa and 3.499 MPa, with a water solubilization rate of 0.238 g/s. After the coupling agent treatment and high temperature treatment, the core mold strength and dissolution rate are improved, and the modification effect is good; small filler sizes can effectively fill the gap formed by matrix materials accumulation, improve the mechanical strength and affect the water solubility rate. The properties of water-soluble core can meet the requirements of resin transfer molding (RTM) and vacuum bag molding, which provides a solution for the integrated molding of profiled hollow profiles. [ABSTRACT FROM AUTHOR]

Cement-based sensors have attracted considerable attention due to their potential for self-sensing applications, particularly in the realms of structural health monitoring and traffic management, as they eliminate the need for external sensors. However, the performance of these sensors can be adversely affected by various environmental factors, with water ingress being a particularly critical concern that can destabilize their piezoresistive sensing capabilities. In this study, hollow glass microspheres (HGM), recognized for their superhydrophobic properties, were incorporated into cement-based sensors to improve their piezoresistive sensing stability under conditions of water ingress. Carbon nanotubes (CNT) were employed as the conductive filler, and the hybrid effects of CNT and HGM were systematically investigated using a range of characterization techniques. The study experimentally assessed the impact of HGM on the compressive strength, electrical resistivity, and water absorption characteristics of the cementitious composites. Furthermore, the enhancement in sensing performance due to HGM was evaluated with respect to sensitivity, linearity, and stability under both monotonic and cyclic loading scenarios. The experimental findings revealed that while HGM initially reduces water absorption, this effect diminishes over prolonged periods of water exposure. Additionally, HGM prevents CNT-based conductive networks from water ingress, thereby improving sensing stability after water exposure. Consequently, the utilization of HGM is anticipated to enhance the sensing stability of cement-based sensors under water ingress conditions.

Polymer matrix syntactic foams made of hollow glass microspheres (HGMs) and epoxy resin are widely used in underwater vehicles providing buoyancy due to their advantages of low density and high mechanical strength. When HGMs is strong enough, surface modification of HGMs is an effective method to improve the compressive strength of syntactic foams. However, the effects of different surface modifiers on the physical properties of HGMs and the compressive strength of syntactic foams have rarely been systematically studied. It is of great significance to enhance the interfacial strength of syntactic foams. Herein, the T40 HGMs was treated by different modifiers (HCl, NaOH, Li2SiO3, Me3SiONa, KH550, KH560, KH570, and Volan), physical properties of modified HGMs were studied, including true density, angle of repose, isostatic compressive strength, specific surface area, and contact angle. Furthermore, the effects of modified HGMs on the compressive strength of syntactic foams were also studied. The results showed that the compressive strength depend largely on the interface bonding between HGMs and resin matrix. This work can provide some references for mechanical property reinforcement of syntactic foams with high filling ratio and plenty of interface zones.

Copyright of Silicone Material is the property of Silicone Material Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Epoxy sheet molding compound (ESMC) composites have good mechanical properties, insulation performance, and corrosion resistance, and are widely used in the automotive industry. However, the density of a typical ESMC composite is high, which limits its wider application. Lightweight fillers can reduce the density of ESMC composites, but the addition of lightweight fillers can lead to a decrease in the mechanical properties of the composite. In this paper, we describe our research in which hollow glass microspheres (HGM) were utilized to decrease the density of the ESMC composites. In addition, surface modification of the HGM was performed to enhance the compatibility between the HGM and the epoxy resin (EP), thus improving the mechanical properties. Further, montmorillonite (MMT) was introduced to further improve the mechanical properties of the ESMC composites. The results showed that the density of the prepared composite was about 1.5 g/cm3, which was significantly lower than the industry standard sheet molding compound (SMC) density of 1.9 g/cm3. The flexural strength and impact strength of the resulting ESMC composites containing the modified HGM and an appropriate amount of MMT (EP/SiHGM/MMT-1) reached the maximum value of 80.0 MPa and 28.6 kJ/m2, respectively, which were 39.9 and 51.3% higher than that of the ESMC composite containing only HGM (EP/HGM/MMT-0). On the one hand, the modified HGM was well dispersed in the EP for the chemical bonding effect. On the other hand, the fiber/matrix interface was further improved after introducing an appropriate amount of MMT. Thus, the resulting ESMC composite exhibited low density and excellent mechanical properties and showed great potential for applications that require lightweight and high strength. [ABSTRACT FROM AUTHOR]

This study addresses the global plastic waste crisis and the urban heat island effect by developing an innovative solution: recycled plastic roof tiles embedded with phase change material (PCM) and coated with hollow-glass-microsphere-based white paint. The samples were fabricated with cow pie fibers, OM37 and OM42 PCM materials with different wt./vol. values, i.e., 15/50, 20/50, 25/50, 30/50 ratios. The fabricated tiles were coated with hollow glass microspheres to provide a reflective layer. The tiles' effectiveness was evaluated through morphological examination and thermal analysis. The SEM analysis revealed an excellent bonding ability for the PCM blend, i.e., OM37 and OM42 at a 20/50 ratio (wt./vol.) with cow pie fibers. Adding cow pie fibers to the PCM shifted the melting points of OM37 and OM42, indicating an increased heat storage capacity in both blends. The thermal conductivity results revealed decreased thermal conductivity with an increased cow pie fiber percentage. The recycled plastic roof tile of the PCM composite at a 20/50 (wt./vol.) ratio showed good thermal properties. Upon testing in real-time conditions in a physical setup, the roof tiles showed a temperature reduction of 8 °C from outdoors to indoors during the peak of summer. In winter, cozy temperatures were maintained indoors due to the heat regulation from the roof. [ABSTRACT FROM AUTHOR]

In order to increase both the strength and toughness of monomer cast nylon 6 (MCPA6), hollow glass microspheres and hollow glass microspheres coated by polyurethane were added to the anionic polymerization reaction system of caprolactam monomer. The reinforced and toughened cast nylon 6 composites were fabricated. The structure of the samples were characterized by infrared spectroscopy, the results showed MCPA6 was synthesized. Compared with pure MCPA6, the addition of polyurethane coated hollow glass microspheres increased the tensile strength, elongation at break, and impact strength of the sample by 27.12%, 48.84%, and 89.71%, respectively. Observing the cross-section of the impact samples through scanning electron microscopy, there were cracks and gaps between the hollow glass microspheres and the MCPA6 matrix. The hollow glass microspheres coated by polyurethane were tightly bonded to the MCPA6 matrix, and the cross-section was rough. The crystallization behaviors of the samples were analyzed using differential scanning calorimetry, the hollow glass microspheres and the hollow glass microspheres coated by polyurethane improved the crystallization temperature and rate of the composites. [ABSTRACT FROM AUTHOR]

Lightweight engineered cementitious composites (LW-ECCs) not only offer comparable mechanical strengths compared with conventional concrete, but also increase the tensile strain of the composite and exhibit strain-hardening behavior, and can be utilized in weight-critical structures such as buildings in seismically active areas. Hollow glass microsphere is a type of ultra-lightweight inorganic non-metallic hollow sphere and it has been deemed as one of the potential sustainable fillers of cement composites. This study aims to investigate the drying shrinkage behavior of LW-ECCs mix designs incorporating different types of hollow glass microspheres (HGMs). Eight types of HGMs with different densities (0.2–0.6 g/cm3) and particle size distributions were incorporated to replace fly ash at 80 and 100 vol% with HGMs. Drying shrinkage was measured from the age of 2 days and up to 91 days. The results demonstrate that all LW-ECCs at 91 days showed greater shrinkage than the control mix, deformation ranged from 1140–1877 µε; 80% replacement ratio of HGMs was regarded as the optimum due to less shrinkage than 100% HGM mixes; the mix incorporating 80% H60 type of HGMs was the relatively most desired mix which had the least shrinkage at 91 days compared to other LW-ECCs, and the strains of the mix using H60 were 1140 and 1385 µε at 91 days for 80% and 100% replacement, respectively. [ABSTRACT FROM AUTHOR]

In order to enhance and toughen the polymer resin with hollow glass microspheres (HGM), polyurethane coating modification was carried out on HGM. The paper aims to explore the conditions and formulas of the physical coating and chemical coating. The physical method is to dissolve thermoplastic polyurethane elastomer in solvent and add HGM to prepare samples. In chemical method, HGM, alcohol component, and isocyanate component are added into solvent, and polymerization reaction is carried out under appropriate conditions to obtain samples. The coating effects and whether there was adhesion between the microspheres were observed through an optical microscope. The results showed that the polyurethane concentration of 4% was suitable for physical method. The reaction temperature of 80 °C is suitable for chemical method. The product synthesized by infrared spectroscopy was polyurethane, and the reaction time was 120 min according to the observation results of optical microscope. The effects of glycerol and toluene-2,4-diisocyanate (TDI) dosage on the thickness of the coating layer were explored through thermogravimetric analysis and optical microscope. This study provides a reference for the preparation of polyurethane-coated HGM 'soft-coated hard' core-shell structure, so that it can be used as a modifier to improve the comprehensive properties of resin. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To investigate the compression properties and failure mechanisms of syntactic foams, two different resin matrices and three types of hollow glass microspheres (HGMs) were used to prepare syntactic foams with different properties. Results showed that the compression strength of syntactic foams increases with the increase in the compression strength of HGMs or resin matrix. Low-strength HGMs will be the first to break down as a source of cracks under stress. When the stress value exceeds the compression strength of the matrix, the matrix will deform and break, leading to the overall destruction of syntactic foam. High-strength HGMs not only act as a lightweight filler but also act as a reinforcing phase to improve the strength of the syntactic foam. The matrix located at the interface will experience initial cracking when subjected to stress, becoming the origin of subsequent cracks. Consequently, the weaker part between the HGMs and the matrix will be the initial point of failure, resulting in the formation of a crack source. The failure of the matrix will ultimately result in the complete destruction of the syntactic foam.

This work presents an alternative to studying and determining the torsion modulus, G, in composites. For this purpose, a measuring system used a rotational motion sensor coupled to a torsion pendulum. The determination of the angular position as a function of time and an equation derived from studies of mechanical spectroscopy, allowed to determine the value of G, so experiments focused on samples of different quantities of hollow glass microspheres (HGMs) in unsaturated polyester resins. The G results show that the addition of HGMs (16.67 %W) reduces the value of torsion modulus by 31% when compared to the unsaturated resin (100 %W). On the other hand, considering the same two samples, there is a material density reduction of approximately 43% with the addition of HGMs, which makes these materials lighter, and of great practical interest. The relationship between G and material density shows that it is possible to change the amount of HGMs for optimal torsion resistance. The advantage of this technique, compared to other dynamic methods, is that it is not necessary to know the Poisson's ratio of the material. [ABSTRACT FROM AUTHOR]

Nowadays, various types of biocomposites are being developed using different types of natural fibers and polymers to fulfill the requirement for sustainable products. Recently, the addition of fillers in biocomposites has been a useful approach to improve their performance and overwhelm their limitations. The hollow glass microspheres (HGMs) were uniformly distributed into epoxy using a magnetic stirrer and subsequently, a hand lay‐up technique was employed to produce the HGMs/coir/epoxy composites under a static loading condition. In the current study, the effect of varying weight percentages (i.e., 1, 3, and 5) of HGMs on the mechanical, dynamic mechanical, and thermal properties of coir/epoxy composites has been studied. Further, morphological analysis of fractured surfaces of samples was also performed. The results suggested that the addition of HGMs caused a significant improvement in the tensile and impact properties of the composites but could not extensively improve the flexural strength, thermal stability, storage modulus, and loss modulus. There was a significant improvement of 80.5% in tensile strength and 24.7% in impact strength of composites after the addition of 1 wt%. HGMs. Further, tensile and flexural moduli were found to be gradually improved with increased HGMs weight percentages in the composites. Highlights: Development of HGMs/coir/epoxy composites.Addition of HGMs increases tensile and impact strength of coir/epoxy composites.Microstructural analysis of HGMs/coir/epoxy composites. [ABSTRACT FROM AUTHOR]

As an excellent ceramic precursor, polysilazane could be cured at low temperatures, which provided a possibility for the preparation of thermal protective coatings for carbon fibers reinforced polymer (CFRP) composites. Hollow glass microspheres with low thermal conductivity were introduced into coatings. Meanwhile, the thermal protection effect of coatings was further enhanced. The dispersion and stability of hollow glass microspheres in polysilazane resin were improved by alkali treatment and grafting coupling agent. Results showed that the stability could be maintained within 2 h, which was feasible in engineering applications. Static thermal tests and hygrothermal aging tests were designed to evaluate the thermal insulation effect of the coating. After 10 min of heat assessment in air atmosphere, the three-point bending performance of coated samples was better than that of uncoated samples. The protection effect was more obvious when the test temperature was higher than the glass transition temperature of carbon fibers reinforced epoxy composites. The bending strength of the coated sample at 270 °C was 743.9 ± 11.9 MPa, which was higher than that of the uncoated sample at 210 °C (743.4 ± 22.3 MPa). According to the result of 5 cycles hygrothermal aging test, the negative effect of acid environments was greater than that of alkali or water. Dynamic thermomechanical analyzer results showed that the coating effectively prevented the damage of water, alkali, or acid environments on the epoxy resin. The above results indicated that the existence of polysilazane and hollow glass microsphere coating systems could further expand the high-temperature application of CFRP. [ABSTRACT FROM AUTHOR]

The design and preparation of infrared stealth materials that meet the application in complex environments is urgently demanded in military fields. In this paper, composites with low emissivity and thermal insulation are designed to be used for indoor and outdoor infrared stealth. Thereinto, nanoPE-MXene, yttrium oxide coated hollow glass microspheres (HGMs@Y 2 O 3) and polypropylene nonwoven (PPF) were used as low emission, insulation, and antifouling layers, respectively. The sandwich-structured composite reduce the infrared radiation temperature of the 80 °C heat source object to 33.9 °C , and the average infrared emissivity of 3-15 μm is only 0.17. In addition, the infrared stealth performance of the composite is not affected by environmental changes. More importantly, the composite exhibits excellent anti-fouling and ageing resistance performance, which lays the foundation for the practical application of efficient stealth infrared materials. [ABSTRACT FROM AUTHOR]

In this study, hollow glass microsphere/epoxy composites modified with compound coupling agent of titanate (CS201) and silane (KH540) were prepared and characterized. The addition of the compound coupling agent improves the interfacial bonding between the microbeads and the resin matrix. Scanning electron microscopy results indicated that the compound coupling agent can effectively reduce the number of voids between the microbeads and the resin. FTIR and XPS spectra showed that new chemical bonds were formed between the hollow glass microspheres and resin, which enhanced the interfacial bonding between them. By testing the water absorption and mechanical properties of the composites, it found that the addition of the hybrid coupling agent can reduce the water absorption to a minimum level of 1.184%. Due to the improvement of interfacial compatibility, mechanical properties of the composites were enhanced, (with tensile strength of 43.03 MPa, bending strength of 44.56 MPa, bending modulus of 1407 MPa and compressive strength of 81.55 MPa). When the content of the coupling agent was 5% and the volume ratio of CS201 to KH540 was 1:1, the synergistic enhancement effect was the most significant. [ABSTRACT FROM AUTHOR]

Direct atomization of a free-flowing glass melt was carried out using a high-speed flame with the aim of producing tiny, self-expanding glass melt droplets to form hollow glass microspheres. Atomization experiments were carried out using a specially adapted free-fall atomizer in combination with a high-power gas burner to achieve sufficient temperatures to atomize the melt droplets and to directly expand them into hollow glass spheres. In addition, numerical simulations were carried out to investigate non-measurable parameters such as hot gas velocities and temperatures in the flame region by the finite volume-based software Star CCM+® (v. 2022.1.1), using the Reynolds-Averaged Navier–Stokes (RANS) turbulence and the segregated flow model. To calculate the combustion process, the laminar flamelet method was used. The experiments and simulations indicated that a maximum gas velocity of about 170 m/s was achieved at the point of atomization in the flame. The particle size distribution of the atomized glass droplets, either solid or hollow, ranged from 2 µm to 4 mm. Mean particle sizes in the range of 370 µm to 650 µm were highly dependent on process parameters such as gas velocity. They were in good agreement with theoretically calculated median diameters. The formation of hollow glass microspheres with the proposed concept could be demonstrated. However, only a small fraction of hollow glass spheres was found to be formed. These hollow spheres had diameters up to 50 µm and, as expected, a thin wall thickness. [ABSTRACT FROM AUTHOR]

Foam composite panels made from hybrid fillers are materials developed to have low density with high mechanical properties. This work focuses on improving the mechanical properties of epoxy‐based foam composite panels with hybridized fillers by combining hollow glass microspheres (HGM) and nanoclay. The HGM content was varied from 1 wt.% to 3 wt.% in foam composites panel, while nanoclay content was varied from 1 wt.% to 5 wt.% in each of the HGM‐filled series of foam composites panel, these foam composite panels were fabricated using a conventional resin casting method. The mechanical properties such as tensile strength, impact strength, hardness, flexural strength of the prepared hybrid‐filled foam composite panels were determined and compared with the neat epoxy. It was found that the hybrid‐filled foam composite panels exhibited improved mechanical properties than the neat epoxy. These improved properties were because of excellent interfacial adhesion between the hybrid fillers and the matrix. The improved mechanical properties could suggest that this material may be suitable for application in industries where lightweight materials with good mechanical properties are required. This study showed a new area of synthetic foam development research by enhancing mechanical properties using hybrid‐filled. [ABSTRACT FROM AUTHOR]

Hollow glass microspheres (HGMs), as a reinforcing material to prepare lightweight high-performance composites, have excellent mechanical properties. However, the composites prepared by simply mixing hollow glass microspheres with polymer resin have poor performance. In this study, compound coupling agent-modified HGM/EP composites were prepared by casting process with two silane coupling agents as compound coupling agents. Scanning electron microscopy and infrared (IR) spectroscopy were used to characterize the treated HGM. Meanwhile density, water absorption behavior, and mechanical properties of the modified HGM-filled epoxy composites were examined. It is found that the compound coupling agent could effectively improve the interfacial bonding between HGM and the matrix resin. A new chemical bond was formed between HGM and EP, which was confirmed by IR spectroscopy. Compared with their untreated counterparts, the composites treated with the complex coupling agent exhibited excellent mechanical properties, along with lower density and lower water absorption. The composites prepared by treating hollow glass microspheres with mixed coupling agents showed improved properties in all the cases. The mechanical properties of the composites prepared using No. HGM-1 reached the maximum with tensile strength of 36.38 MPa, tensile modulus of 2.383 GPa, flexural strength of 49.82 MPa, flexural modulus of 1.558 GPa, and compressive strength of 98.14 MPa. Our strategy opens a new way to fabricate composites with enhanced mechanical performances. [ABSTRACT FROM AUTHOR]

Casing shear deformation caused by fault slip is a serious problem that restricts shale gas development. As yet, there is no effective method for controlling casing shear deformation. In this study, a cement sheath with hollow glass microspheres was used to prevent and mitigate casing deformation caused by a fault slip. An equivalent outer-diameter model was established. This model analyzes the mechanism by which casing shear deformation is controlled by a cement sheath with hollow glass microspheres under the condition of fault slip. The hollow glass microspheres in the cement sheath were broken owing to the strong shear forces of the fault slip. The internal volume of the hollow glass microspheres was released, which reduced the distance of the fault slip across the casing. The casing deformation was prevented or slowed down. A 3D assembly numerical model was established to evaluate the control effect of the hollow glass microspheres on casing shear deformation. Furthermore, the influences of slip distance, casing thickness, mechanical parameters of formation, mechanical parameters of the cement sheath, and crustal stress difference were analyzed. The mathematical calculation results showed that casing deformation increased with an increase in the fault slip distance, an increase in the stratum elastic modulus, and a decrease in the in situ stress difference. Therefore, the mass content of the hollow glass microspheres in the cement sheath also needs to be increased to ensure that the casing does not deform. The numerical analysis results showed that the change in casing thickness, Poisson’s ratio of formation, and mechanical parameters of the cement sheath had little effect on the mass content of hollow glass microspheres. Finally, the model was used to analyze the test wells in the Weirong Block, Sichuan, China. The calculation results showed that under the same condition of casing deformation of 8.23 mm in adjacent wells, casing shear deformation could be avoided by using a cement sheath with 11.9% hollow glass microspheres in the test well. This study provides a theoretical basis and reference for controlling the casing shear deformation caused by fault slip in shale gas wells.

Hollow glass microspheres were obtained from soda-borosilicate glass by a high-temperature method, weight content, %: 10 Na2O; 8 CaO; 0.3 MgO; 0.2 Al2O3 ; 9 B2O3 ; 0.5 SO3 ; 72 SiO2. It was ascertained that the maximum yield of microspheres, up to 87%, is observed on use of a propane–air torch with the following characteristics: air/propane ratio 1.3; maximum temperature on the flame axis 1900°C; opening angle about 15°; and, flow rate of carrier gas 0.2 g/sec. The hollow glass microspheres obtained in this regime are characterized by median diameter 60 μm, average wall thickness 1.3 μm, bulk density 260 kg/m3, and calculated strength 50 MPa. [ABSTRACT FROM AUTHOR]

The present review introduces the analysis and gathering modern ideas about the novel polymer composites, namely polymer syntactic foams, known as extremely widely used multifunctional materials with unique properties that meet the requirements of advanced high-tech industries. The main classifications, methods of synthesis and characteristization of various types of polymer foams were summarized. Special attention has been paid to structural features and properties of polymer syntactic foams. The main types of polymer matrices and fillers used for synthesis of thermosetting syntactic foams were characterized in details. The influence of initial composition and fabrication techniques applied on morphology, physical-chemical properties and application of composite materials comprising polymer syntactic foams in high-tech industries such as marine and underwater, aerospace, defense and transport has been also established. The review also highlights the analysis of world markets, trends and forecasting the further development of syntactic foams, especially high-performanced ones, disclosing their advantages and disadvantages. Presumable ways of modification of the existing types of polymer syntactic foams as well as perspectiveness of further progress in this research area to obtain the improved high-performance materials are also outlined. [ABSTRACT FROM AUTHOR]

With the increase in drilling fluid density requirements in low-pressure coefficient formations, traditional hollow bead drilling fluids and foam drilling fluids each have different degrees of deficiencies. Through extensive indoor experiments, an amphoteric surfactant (cocoamidopropyl betaine) with better foaming performance was selected to formulate an ultra-low-density drilling fluid that combines a foaming agent and hollow glass microbeads to reduce the density of the fluid, with the following specific formulation: 3% bentonite slurry + 0.3% xanthan gum + 0.5% carboxymethyl cellulose + 0.5% starch + 2% lignite resin + 2% blocking agent + 4% hollow glass microspheres + 0.5% foaming agent + 2% nano blocking agent. The performance of the system was evaluated, and the results showed that: the density of the ultra-low-density drilling fluid did not change much before and after aging at 80 °C and was relatively stable; the filter loss amount of the drilling fluid (tested by API) reached 4.6 mL, which meets the requirements for filter loss of drilling fluid; it can bear the pressure of 12 MPa under a 60–90-mesh sand bed and has better pressure sealing capability than hollow glass microbead drilling fluid. [ABSTRACT FROM AUTHOR]

With the continuous use of fossil fuels, the emission of CO2 increases significantly, which seriously affects nowadays’ ecology. In order to reduce the emission of CO2, it’s urgent to use clean energy to replace fossil fuels. Hydrogen energy has advantages of high heat value and zero CO2 emission, making it a good substitute of fossil fuels. However, its small density and low boiling point make it difficult to storage, which limits its large-scale application. At present, hydrogen energy is stored in high-pressure tanks, which have disadvantages of low hydrogen capacity, high cost of transportation and hydrogen embrittlement. The key point of large-scale commercial application of hydrogen is developing new kind of hydrogen storage materials and technologies. Hollow glass microspheres (HGMs) as a kind of hollow, small size and pressure-resistant material, have advantages of good stability, high hydrogen capacity, low cost and no hydrogen embrittlement, which make them have great potential in hydrogen storage. This paper reviews the development of hydrogen storage in HGMs, introduces the mechanism and influencing factors of hydrogen storage in HGMs and further introduces the research of hydrogen release rate and response time. [ABSTRACT FROM AUTHOR]

With the development of the integrated circuit and chip industry, electronic products and their components are becoming increasingly miniaturized, high-frequency, and low-loss. These demand higher requirements for the dielectric properties and other aspects of epoxy resins to develop a novel epoxy resin system that meets the needs of current development. This paper employs ethyl phenylacetate cured dicyclopentadiene phenol (DCPD) epoxy resin as the matrix and incorporates KH550 coupling-agent-treated SiO2 hollow glass microspheres to produce composite materials with low dielectric, high heat resistance, and high modulus. These materials are applied as insulation films for high density interconnect (HDI) and substrate-like printed circuit board (SLP) boards. The Fourier transform infrared spectroscopy (FTIR) technique was used to characterize the reaction between the coupling agent and HGM, as well as the curing reaction between the epoxy resin and ethyl phenylacetate. The curing process of the DCPD epoxy resin system was determined using differential scanning calorimetry (DSC). The various properties of the composite material with different HGM contents were tested, and the mechanism of the impact of HGM on the properties of the composite material was discussed. The results indicate that the prepared epoxy resin composite material exhibits good comprehensive performance when the HGM content is 10 wt.%. The dielectric constant at 10 MHz is 2.39, with a dielectric loss of 0.018. The thermal conductivity is 0.1872 Wm−1 k−1, the coefficient of thermal expansion is 64.31 ppm/K, the glass transition temperature is 172 °C, and the elastic modulus is 1221.13 MPa. [ABSTRACT FROM AUTHOR]

Lightweight engineered cementitious composites (LW-ECCs) not only offer comparable mechanical strengths compared with conventional concrete, but also increase the tensile strain of the composite and exhibit strain-hardening behavior, and can be utilized in weight-critical structures such as buildings in seismically active areas. Hollow glass microsphere is a type of ultra-lightweight inorganic non-metallic hollow sphere and it has been deemed as one of the potential sustainable fillers of cement composites. This study aims to investigate the drying shrinkage behavior of LW-ECCs mix designs incorporating different types of hollow glass microspheres (HGMs). Eight types of HGMs with different densities (0.2–0.6 g/cm3) and particle size distributions were incorporated to replace fly ash at 80 and 100 vol% with HGMs. Drying shrinkage was measured from the age of 2 days and up to 91 days. The results demonstrate that all LW-ECCs at 91 days showed greater shrinkage than the control mix, deformation ranged from 1140–1877 µε; 80% replacement ratio of HGMs was regarded as the optimum due to less shrinkage than 100% HGM mixes; the mix incorporating 80% H60 type of HGMs was the relatively most desired mix which had the least shrinkage at 91 days compared to other LW-ECCs, and the strains of the mix using H60 were 1140 and 1385 µε at 91 days for 80% and 100% replacement, respectively.

Thermostable heat-insulating composite materials based on solid magnesium phosphate and calcium phosphate binders, fly-ash and glass hollow microspheres have been developed and proposed. Thermal and phase transformations have been studied as well as strength characteristics of the initial composites and products of their thermal treatment up to 1000 °C have been determined. It is shown that the prepared phosphate composites are thermally stable in the temperature range of 20 –1000 °С, have a density 0.4 – 0.6 g/cm3 , thermal conductivity 0.11– 0.19 W/(m ⋅ K) and show sufficiently high strength properties (compressive strength 1.4 –3.2 MPa).

This study aims to assess the effect of hollow glass microspheres of different sizes derived from glass industry waste on the durability and thermal behavior of waterborne paint. The coatings were characterized by electron microscopy to investigate the distribution of the spheres and their influence on the layer morphology. The impact of the various glassy spheres on the mechanical feature of the coatings was assessed using the Buchholz hardness test and the Scrub abrasion test. The role of the spheres in altering the durability of the samples was analyzed by the salt spray exposure test and the electrochemical impedance spectroscopy measurements. Finally, a specific accelerated degradation test was carried out to explore the evolution of the thermal behavior of the composite coatings. Ultimately, this work revealed the pros and cons of using hollow glass spheres as a multifunctional paint filler, highlighting the size of the spheres as a key parameter. For example, spheres with adequate size (25–44 µm), totally embedded in the polymeric matrix, are able to reduce the thermal conductivity of the coating avoiding local heat accumulation phenomena. [ABSTRACT FROM AUTHOR]