A Review on the Application of Cobalt-Based Nanomaterials in Supercapacitors

Among many electrode materials, cobalt-based nanomaterials are widely used in supercapacitors because of their high natural abundance, good electrical conductivity, and high specific capacitance. However, there are still some difficulties to overcome, including poor structural stability and low power density. This paper summarizes the research progress of cobalt-based nanomaterials (cobalt oxide, cobalt hydroxide, cobalt-containing ternary metal oxides, etc.) as electrode materials for supercapacitors in recent years and discusses the preparation methods and properties of the materials. Notably, the focus of this paper is on the strategies to improve the electrochemical properties of these materials. We show that the performance of cobalt-based nanomaterials can be improved by designing their morphologies and, among the many morphologies, the mesoporous structure plays a major role. This is because mesoporous structures can mitigate volume changes and improve the performance of pseudo capacitance. This review is dedicated to the study of several cobalt-based nanomaterials in supercapacitors, and we hope that future scholars will make new breakthroughs in morphology design.

Hydrothermal Synthesis of Binder-Free Metallic NiCo2O4 Nano-Needles Supported on Carbon Cloth as an Advanced Electrode for Supercapacitor Applications

It is of great significance to design electrochemical energy conversion and storage materials with excellent performance to fulfill the growing energy demand. Bimetallic cobalt/nickel-based electrode materials exhibit excellent electrical conductivity compared to mono oxides. However, their potential as electrode materials for high-performance supercapacitors (SCs) is limited because of their poor cycling stability and high-capacity fading. This work demonstrates the synthesis of binder-free bimetallic NiCo₂O₄ nano-needles supported on CC (NCO@CC) via a facile and scalable hydrothermal process. Excellent electrical conductivity and interconnected nanostructure of NCO@CC nano-needles provide the fast transfer of electrons with numerous channels for ion diffusion. Owing to such features, the binder-free NCO@CC electrode for SC discloses excellent specific capacitance (1476 Fg⁻¹ at 1.5 Ag⁻¹) with 94.25% capacitance retention even after 5000 cycles. From these outstanding electrochemical performances, it can be inferred that NCO@CC nano-needle array-structured electrodes may be potential candidates for SC applications.

Study of solvent variation on controlled synthesis of different nanostructured NiCo2O4 thin films for supercapacitive application

The present investigation deals with controlled synthesis of nanostructured NiCo₂O₄ thin films directly on stainless steel substrates by facile and economical chemical bath deposition technique, without adding a surfactant or a binder. The consequences of different compositions of solvents on morphological and electrochemical properties have been studied systematically. We used different solvent composition as Double Distilled Water (DDW), DDW:Ethanol (1:1) and DDW: N, N dimethylformamide (1:1). The films have been named as NCO-W for DDW, NCO-WE for DDW: Ethanol (1:1) solvent and NCO-WD for DDW: N, N dimethylformamide (1:1) solvent. The morphologies of NiCo₂O₄ thin films modify substantially with change in a solvent. NCO-W exhibited the spikes of Crossandra infundibuliformis like nanostructures. The NCO-WE favored the formation of uniformly distributed leaf-like nanostructure whereas NCO-WD showed randomly oriented nanoplates all over the surface area. The Electrochemical performance of these NiCo₂O₄ thin films were studied using cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy techniques. The NCO-W, NCO-WE and NCO-WD electrodes showed specific capacitance values of 271, 553 and 140 F/g respectively at the current density of 0.5 mA/cm² and excellent capacitance retention of 90%, 91% and 80% after 2000 cycles for NCO-W, NCO-WE and NCO-WD samples respectively. This result reveals that NiCo₂O₄ is a prominent electrode material for supercapacitor application.

Construction of high-performance electrode materials of NiCo2O4 nanoparticles encapsulated in ultrathin N-doped carbon nanosheets for supercapacitors

Highly dispersed nitrogen doped carbon (N-C) is decomposed by 2-methylimidazole (C₄H₆N₂) and is used as a composite material with nickel cobaltite (NiCo₂O₄). The N-C and NiCo₂O₄ composites are obtained by a one-step hydrothermal method and subsequent calcination. In addition, N-C is used to control the morphology and structure of NiCo₂O₄ to obtain excellent capacitor materials. The N-C/NiCo₂O₄ electrode shows an excellent specific capacitance of 157.97 mA h g^-1 (1263.75 F g^-1) at 1 A g^-1. Herein, we successfully develop a N-C/NiCo₂O₄//AC asymmetric supercapacitor (ASC), which is prepared using N-C/NiCo₂O₄ as a cathode coupled with activated carbon (AC) as an anode at a voltage of 1.6 V. The prepared N-C/NiCo₂O₄//AC device shows an excellent volumetric energy density of 66.44 mW h kg^-1. The promising performance of N-C/NiCo₂O₄//AC illustrated its potential for portable supercapacitor applications.

In Situ Growth of 2D Ultrathin NiCo2 O4 Nanosheet Arrays on Ni Foam for High Performance and Flexible Solid-State Supercapacitors

In order to further overcome the shortage of electrodes with additive/binder and modulate the structure of NiCo₂ O₄ for supercapacitors, ultrathin NiCo₂ O₄ nanosheet arrays have been in situ grown on Ni foam by optimizing hydrothermal reactions based on crystal growth dynamics. The structure of ultrathin NiCo₂ O₄ nanosheet arrays can expose more active sites, provide abundant diffusion channels and buffer the stress caused by phase transition during charge-discharge process of supercapacitors. The optimized hydrothermal reactions can provide more ordered crystal orientations by keeping nanosheets on Ni foam completely coming from in situ growth, which will decrease the inner resistance of ultrathin NiCo₂ O₄ nanosheets and improve the efficiency and kinetics of electrons transfer. By the virtue of such remarkable features, the electrochemical results confirm the rationality of structural modulation and crystal orientations optimization with a drastically enhanced specific capacitance of 2017.8 F g^-1 , admirable rate performance of 93.2% and outstanding stability retention of 90.9% after cycling 5000 times. More impressively, the assembled flexible solid-state asymmetric supercapacitor (ASC) shows superior energy density, power density, and high stability. The modification strategy in this paper may throw light on the rational design of new generation advanced electrode materials for high-performance flexible supercapacitors.

NiCo2O4 Nano-/Microstructures as High-Performance Biosensors: A Review

Non-enzymatic biosensors based on mixed transition metal oxides are deemed as the most promising devices due to their high sensitivity, selectivity, wide concentration range, low detection limits, and excellent recyclability. Spinel NiCo2O4 mixed oxides have drawn considerable attention recently due to their outstanding advantages including large specific surface area, high permeability, short electron, and ion diffusion pathways. Because of the rapid development of non-enzyme biosensors, the current state of methods for synthesis of pure and composite/hybrid NiCo2O4 materials and their subsequent electrochemical biosensing applications are systematically and comprehensively reviewed herein. Comparative analysis reveals better electrochemical sensing of bioanalytes by one-dimensional and two-dimensional NiCo2O4 nano-/microstructures than other morphologies. Better biosensing efficiency of NiCo2O4 as compared to corresponding individual metal oxides, viz. NiO and Co3O4, is attributed to the close intrinsic-state redox couples of Ni3+/Ni2+ (0.58 V/0.49 V) and Co3+/Co2+ (0.53 V/0.51 V). Biosensing performance of NiCo2O4 is also significantly improved by making the composites of NiCo2O4 with conducting carbonaceous materials like graphene, reduced graphene oxide, carbon nanotubes (single and multi-walled), carbon nanofibers; conducting polymers like polypyrrole (PPy), polyaniline (PANI); metal oxides NiO, Co3O4, SnO2, MnO2; and metals like Au, Pd, etc. Various factors affecting the morphologies and biosensing parameters of the nano-/micro-structured NiCo2O4 are also highlighted. Finally, some drawbacks and future perspectives related to this promising field are outlined.

Facile Solvothermal Synthesis of Hollow BiOBr Submicrospheres with Enhanced Visible-Light-Responsive Photocatalytic Performance

In this work, hierarchical hollow BiOBr submicrospheres (HBSMs) were successfully prepared via a facile yet efficient solvothermal strategy. Remarkable effects of solvents upon the crystallinities, morphologies, and microstructures of the BiOBr products were systematically investigated, which revealed that the glycerol/isopropanol volumetric ratio played a significant role in the formation of hollow architecture. Accordingly, the underlying formation mechanism of the hollow submicrospheres was tentatively put forward here. Furthermore, the photocatalytic activities of the resulting HBSMs were evaluated in detail with photocatalytic degradation of the organic methyl orange under visible light irradiation. Encouragingly, the as-obtained HBSMs with striking recyclability demonstrated excellent visible-light-responsive photocatalytic performance, which benefits from their large surface area, effective visible light absorption, and unique hollow feature, highlighting their promising commercial application in waste water treatment.

Supercapacitor and non-enzymatic biosensor application of an Mn2O3/NiCo2O4 composite material

Energy storage mechanism and catalytic performance of the Mn₂O₃/NiCo₂O₄ composite material.

Fe substitution in urchin-like NiCo2O4 for energy storage devices

A composite of NiCo_2−xFe_xO₄ was designed to investigate the effects of Fe substitution on its energy storage performance. Urchin-like products composed of nanowires were successfully synthesized through the hydrothermal method and calcinations. Scanning electron microscopy (SEM) images revealed that Fe substitution could reduce the diameter of the nanowires and hinder the urchin-like sphere construction. X-ray diffraction (XRD), energy dispersive X-ray mapping (EDS-mapping) and X-ray photoelectron spectroscopy (XPS) revealed the successful Fe substitution for Co. More importantly, the specific capacity could be largely improved from 359 C g⁻¹ (826 F g⁻¹) for x = 0 to 523 C g⁻¹ (1188 F g⁻¹) for x = 0.3 at 1 A g⁻¹. Moreover, with x = 0.3, a specific capacity of 788 F g⁻¹ could be maintained as the current density was increased to 20 A g⁻¹. Asymmetric supercapacitors based on this compound exhibited an energy density of 26.6 W h kg⁻¹ at a power density of 370 W kg⁻¹.

A composite of NiCo_2−xFe_xO₄ was designed to investigate the effects of Fe substitution on its energy storage performance.

Design and Mechanisms of Asymmetric Supercapacitors

Ongoing technological advances in diverse fields including portable electronics, transportation, and green energy are often hindered by the insufficient capability of energy-storage devices. By taking advantage of two different electrode materials, asymmetric supercapacitors can extend their operating voltage window beyond the thermodynamic decomposition voltage of electrolytes while enabling a solution to the energy storage limitations of symmetric supercapacitors. This review provides comprehensive knowledge to this field. We first look at the essential energy-storage mechanisms and performance evaluation criteria for asymmetric supercapacitors to understand the wide-ranging research conducted in this area. Then we move to the recent progress made for the design and fabrication of electrode materials and the overall structure of asymmetric supercapacitors in different categories. We also highlight several key scientific challenges and present our perspectives on enhancing the electrochemical performance of future asymmetric supercapacitors.

Bubble-assisted fabrication of hollow CoMoO4 spheres for energy storage

Herein, gas bubbles generated in situ from precursors assist the rapid construction of hollow sycamore fruit-like CoMoO4 spheres (HSCSs). This bubble-assisted fabrication strategy is easy to operate, ultra-fast, low cost and post-treatment-free, showing great potential for the large-scale production of HSCSs. The growth mechanism of HSCSs is discussed to reveal the evolution process, which may be generalized to the construction of a series of hollow ternary Mo-based oxides. The obtained HSCSs exhibit a superior specific capacitance and outstanding cyclic stability when applied in supercapacitors.

Hierarchical porous NiCo2O4/CeO2 hybrid materials for high performance supercapacitors

Hierarchical porous NiCo₂O₄/CeO₂ hybrid materials are successfully synthesized via a simple solvothermal method and subsequent heat treatment and exhibit remarkable electrochemical performances in supercapacitors.

Toward Aerogel Electrodes of Superior Rate Performance in Supercapacitors through Engineered Hollow Nanoparticles of NiCo2O4

A biomass-templated pathway is developed for scalable synthesis of NiCo2O4@carbon aerogel electrodes for supercapacitors, where NiCo2O4 hollow nanoparticles with an average outer diameter of 30-40 nm are conjoined by graphitic carbon forming a 3D aerogel structure. This kind of NiCo2O4 aerogel structure shows large specific surface area (167.8 m2 g-1), high specific capacitance (903.2 F g-1 at a current density of 1 A g-1), outstanding rate performance (96.2% capacity retention from 1 to 10 A g-1), and excellent cycling stability (nearly without capacitance loss after 3000 cycles at 10 A g-1). The unique structure of the 3D hollow aerogel synergistically contributes to the high performance. For instance, the 3D interconnected porous structure of the aerogel is beneficial for electrolyte ion diffusion and for shortening the electron transport pathways, and thus can improve the rate performance. The conductive carbon joint greatly enhances the specific capacity, and the hollow structure prohibits the volume changes during the charge-discharge process to significantly improve the cycling stability. This work represents a giant step toward the preparation of high-performance commercial supercapacitors.

Pseudocapacitance of Mesoporous Spinel-Type MCo2O4 (M = Co, Zn, and Ni) Rods Fabricated by a Facile Solvothermal Route

We present the structural properties and electrochemical capacitance of mesoporous MCo₂O₄ (M = Co, Zn, and Ni) rods synthesized by a facile solvothermal route without necessity to use templates. The Brunauer-Emmett-Teller specific surface areas of these mesoporous rods are found to be about 24, 54, and 62 m² g^-1 with major pore diameters of about 31, 15, and 9 nm for MCo₂O₄, M = Co, Zn, and Ni, respectively. X-ray photoelectron spectroscopy and X-ray diffraction studies reveal the phase purity of the samples with a predominant spinel-type crystal structure. The spinel crystal structure with lattice parameters of 8.118, 8.106, and 8.125 Å is obtained for MCo₂O₄, M = Co, Zn, and Ni, respectively. The transmission electron microscopy study reveals that the mesoporous rods are built by self-assembled aggregates of nanoparticles which are well-interconnected to form stable mesoporous rods. The electrochemical capacitor performance was investigated by means of cyclic voltammetry, galvanostatic charge/discharge cycling, and impedance spectroscopy in a three-electrode configuration. As a result, the spinel-type MCo₂O₄ rods exhibit high specific capacitances of 1846 F g^-1 (CoCo₂O₄), 1983 F g^-1 (ZnCo₂O₄), and 2118 F g^-1 (NiCo₂O₄) at a scan rate of 2 mV/s. Furthermore, the mesoporous spinel-type metal oxides show desirable stability in alkaline electrolyte during long-term cycling with excellent cycling efficiency.

NiCo2 S4 Materials for Supercapacitor Applications

Cobalt-nickel sulfide (NiCo₂ S₄ ) shows extensive potential for innovative photoelectronic and energetic materials owing to distinctive physical and chemical properties. In this review, representative strategies for the fabrication and application of NiCo₂ S₄ and composite nanostructures are outlined for supercapacitors, with the aim of promoting the development of NiCo₂ S₄ and their composites in the supercapacitor field through an analysis and comparison of diverse nanostructures. A brief introduction into the structures, properties, and morphologies are presented. Further prospects and promising developments of the materials in the supercapacitor field are also proposed.

Assembly of flexible CoMoO4@NiMoO4·xH2O and Fe2O3 electrodes for solid-state asymmetric supercapacitors

In this work, CoMoO₄@NiMoO₄·xH₂O core-shell heterostructure electrode is directly grown on carbon fabric (CF) via a feasible hydrothermal procedure with CoMoO₄ nanowires (NWs) as the core and NiMoO₄ nanosheets (NSs) as the shell. This core-shell heterostructure could provide fast ion and electron transfer, a large number of active sites, and good strain accommodation. As a result, the CoMoO₄@NiMoO₄·xH₂O electrode yields high-capacitance performance with a high specific capacitance of 1582 F g^-1, good cycling stability with the capacitance retention of 97.1% after 3000 cycles and good rate capability. The electrode also shows excellent mechanical flexibility. Also, a flexible Fe₂O₃ nanorods/CF electrode with enhanced electrochemical performance was prepared. A solid-state asymmetric supercapacitor device is successfully fabricated by using flexible CoMoO₄@NiMoO₄·xH₂O as the positive electrode and Fe₂O₃ as the negative electrode. The asymmetric supercapacitor with a maximum voltage of 1.6 V demonstrates high specific energy (41.8 Wh kg^-1 at 700 W kg^-1), high power density (12000 W kg^-1 at 26.7 Wh kg^-1), and excellent cycle ability with the capacitance retention of 89.3% after 5000 cycles (at the current density of 3A g^-1).

Pseudocapacitive behaviors of mesoporous nickel–cobalt oxide nanoplate electrodes in different electrolyte systems

A freestanding mesoporous NiCo₂O₄ nanoplate electrode exhibits superior pseudocapacitive performance and long-life stability.

Nanorod-assembled NiCo2O4 hollow microspheres assisted by an ionic liquid as advanced electrode materials for supercapacitors

In this work, nanorod-assembled NiCo₂O₄ hollow microspheres have been successfully prepared by an ionic liquid-assisted hydrothermal method for the first time.

Study on preparation of SnO2-TiO2/Nano-graphite composite anode and electro-catalytic degradation of ceftriaxone sodium

In order to improve the electro-catalytic activity and catalytic reaction rate of graphite-like material, Tin dioxide-Titanium dioxide/Nano-graphite (SnO₂-TiO₂/Nano-G) composite was synthesized by a sol-gel method and SnO₂-TiO₂/Nano-G electrode was prepared in hot-press approach. The composite was characterized by X-ray photoelectron spectroscopy, fourier transform infrared, Raman, N₂ adsorption-desorption, scanning electrons microscopy, transmission electron microscopy and X-ray diffraction. The electrochemical performance of the SnO₂-TiO₂/Nano-G anode electrode was investigated via cyclic voltammetry and electrochemical impedance spectroscopy. The electro-catalytic performance was evaluated by the degradation of ceftriaxone sodium and the yield of ·OH radicals in the reaction system. The results demonstrated that TiO₂, SnO₂ and Nano-G were composited successfully, and TiO₂ and SnO₂ particles dispersed on the surface and interlamination of the Nano-G uniformly. The specific surface area of SnO₂ modified anode was higher than that of TiO₂/Nano-G anode and the degradation rate of ceftriaxone sodium within 120 min on SnO₂-TiO₂/Nano-G electrode was 98.7% at applied bias of 2.0 V. The highly efficient electro-chemical property of SnO₂-TiO₂/Nano-G electrode was attributed to the admirable conductive property of the Nano-G and SnO₂-TiO₂/Nano-G electrode. Moreover, the contribution of reactive species ·OH was detected, indicating the considerable electro-catalytic activity of SnO₂-TiO₂/Nano-G electrode.

Hierarchical mesoporous NiCo2O4 hollow nanocubes for supercapacitors

In the present work, mesoporous NiCo₂O₄ hollow nanocubes are synthesized using a “coordinating etching & precipitating” (CEP) route.

Template-free synthesis of 3D hierarchical nanostructured NiCo2O4 mesoporous ultrathin nanosheet hollow microspheres for excellent methanol electrooxidation and supercapacitors

Novel 3D hierarchical NiCo₂O₄ mesoporous ultrathin nanosheets hollow microspheres upon a facile template-free solvothermal method followed air-annealing shows excellent methanol electrooxidation and supercapacitors performance.

Nanostructured Si@C/NiCo2O4 heterostructures for a high performance supercapacitor

As the second most abundant element on the earth, silicon exhibits excellent properties in many fields.

Facile preparation of NiCo2O4@rGO composites for the removal of uranium ions from aqueous solutions

A hierarchical structure of NiCo₂O₄@rGO composite has been fabricated, with its structure and morphology well characterized by XRD, TEM, XPS and BET.

Mesoporous hybrid NiOx–MnOx nanoprisms for flexible solid-state asymmetric supercapacitors

Mesoporous hybrid NiO_x–MnO_x nanoprisms exhibit good performance as electrode materials for flexible solid-state symmetric supercapacitors.

Mesoporous Transition Metal Oxides for Supercapacitors

Recently, transition metal oxides, such as ruthenium oxide (RuO₂), manganese dioxide (MnO₂), nickel oxides (NiO) and cobalt oxide (Co₃O₄), have been widely investigated as electrode materials for pseudo-capacitors. In particular, these metal oxides with mesoporous structures have become very hot nanomaterials in the field of supercapacitors owing to their large specific surface areas and suitable pore size distributions. The high specific capacities of these mesoporous metal oxides are resulted from the effective contacts between electrode materials and electrolytes as well as fast transportation of ions and electrons in the bulk of electrode and at the interface of electrode and electrolyte. During the past decade, many achievements on mesoporous transition metal oxides have been made. In this mini-review, we select several typical nanomaterials, such as RuO₂, MnO₂, NiO, Co₃O₄ and nickel cobaltite (NiCo₂O₄), and briefly summarize the recent research progress of these mesoporous transition metal oxides-based electrodes in the field of supercapacitors.

Nickel Cobaltite Nanostructures for Photoelectric and Catalytic Applications

Bimetallic oxide nickel cobaltite (NiCo2 O4 ) shows extensive potential for innovative photoelectronic and energetic materials owing to their distinctive physical and chemical properties. In this review, representative fabrications and applications of NiCo2 O4 nanostructures are outlined for photoelectronic conversion, catalysis, and energy storage, aiming to promote the development of NiCo2 O4 nanomaterials in these fields through an analysis and comparison of their diverse nanostructures. Firstly, a brief introduction of the spinel structures, properties, and morphologies of NiCo2 O4 nanomaterials are presented. Then, the advanced progress of NiCo2 O4 nanomaterials for both photoelectronic conversion and energy fields is summarized including such examples as solar cells, electrocatalysis, and lithium ion batteries. Finally, further prospects and promising developments of NiCo2 O4 nanomaterials in these significant fields are proposed.

Two-Dimensional, Porous Nickel-Cobalt Sulfide for High-Performance Asymmetric Supercapacitors

High specific surface area, high electrical conductivity, and abundant channels have been recognized to favor pseudocapacitors, but their realization at the same time is still a great challenge. Here, we report on nickel-cobalt sulfide nanosheets (NSs) with both ultrathin thickness and nanoscale pores for supercapacitors. The porous Ni-Co sulfide NSs were facilely synthesized through micelle-confined growth and subsequent sulfuration. The NSs are as thin as several nanometers and have a large number of pores with a mean size of ∼7 nm, resulting in ultrahigh atom ratio at surface with unique chemical and electronic structure. Therefore, fast diffusion of ions, facile transportation of electrons and high activity make great synergistic contributions to the surface-dependent reversible redox reactions. In the resulted supercapacitors, a specific capacitance of 1304 F g(-1) is achieved at a current density of 2 A g(-1) with excellent rate capability that 85.6% of the original capacitance is remained at 20 A g(-1). The effects of crystallinity and self-doping are optimized so that 93.5% of the original capacitance is obtained after 6000 cycles at a high current density of 8 A g(-1). Finally, asymmetric supercapacitors with a high energy density of 41.4 Wh/kg are achieved at a power density of 414 W/kg.

Heterostructured core-shell ZnMn₂O₄ nanosheets@carbon nanotubes' coaxial nanocables: a competitive anode towards high-performance Li-ion batteries

In this study, we rationally designed a rapid, low-temperature yet general synthetic methodology for the first time, involving in situ growth of two-dimensional (2D) birnessite-type MnO2 nanosheets (NSs) upon each carbon nanotube (CNT), and we designed the subsequent phase transformation into untrathin mesoporous ZnMn2O4 NSs with a thickness of ∼2-3 nm at room temperature to efficiently fabricate heterostructured core-shell ZnMn2O4 NSs@CNT coaxial nanocables with well-dispersed and tunable ZnMn2O4 loading. The underlying insights into the low-temperature formation mechanism of the unique core-shell hybrid nanoarchitectures were tentatively proposed here. When utilized as a high-performance anode for advanced LIBs, the resultant core-shell ZnMn2O4@CNTs' coaxial nanocables (∼84.5 wt.% loading) exhibited large specific discharge capacity (∼1033 mAh g(-1)), good rate capability (∼528 mAh g(-1)) and excellent cycling stability (average capacity degradation of only ∼5.2% per cycle) at a high current rate of 1224 mA g(-1), originating from the distinct core-shell synergetic effect of fast electronic delivery and from the large electrode/electrolyte contacting surfaces/interfaces provided by three-dimensional entangling coaxial CNT-based nanonetwork topology.

Rattle-type NiCo2O4–carbon composite microspheres as electrode materials for high-performance supercapacitors

Rattle-type NiCo₂O₄–carbon composite microspheres with a self-assembled shell were synthesized by a template method, which exhibited superior capacitive performances.

A “rolling ball method” to make glass fiber reinforced hollow epoxy macrospheres used for a three phase epoxy syntactic foam

Glass fiber reinforced hollow epoxy macrospheres (GFR-HEMS) were prepared by a “rolling ball method” and embedded into a mixture of epoxy–hardener and 33.3 wt% HGMS to make a three phase epoxy syntactic foam.