Surface Of Hollow Glass Microspheres Research Articles

Preparation and characterization of novel form stable phase change materials based on stearic acid (SA)/hollow glass microsphere (HGS) with low supercooling

In this study, the hollow glass microsphere (HGS)/stearic acid (SA) composites were prepared as form stable phase change materials (FSPCMs) for thermal energy storage via directly impregnation. In prepared FSPCMs, SA acted as the phase change substance and the HGS functioned as the supporting materials to prevent the leakage of melted SA. The special structure and large surface of HGS had strong absorption ability for SA. The chemical structure, surface morphology, crystalline properties, phase change properties, thermal reliability and stability of prepared FSPCMs were extensively studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermal cycling test and thermogravimetric analysis (TGA), respectively. FTIR results showed that only physical interaction occurs between HGS and SA, and the SEM images showed the SA is adhered on the surface and internal surface of HGS through physical interaction. The XRD pattern exhibited that the crystalline properties of FSPCMs are not affected by the introduction of HGS. FSPCMs also exhibited good phase change properties with the latent heat in the range of 48.77–133.8 J g−1 and the phase change temperature in the range of 50.20–51.54 °C, and the supercooling degree was lower than 2 °C. The special structure of HGS imparted FSPCMs with good thermal reliability reflected by slightly variation of latent heat and phase change temperature after 100 thermal cycles. TGA results showed the FSPCMs have good thermal stability, which will meet the requirement of application. In conclusion, the prepared FSPCMs had great value in the field of thermal energy storage.

Thermoplastic composites between polybutylene succinate and recycled PET adding hollow glass microspheres

Use of biodegradable polyester-based polymers in various applications has been extensively carried out in the past decades. Blending recycled poly(ethylene terephthalate) (r-PET) would be an alternative way to improve mechanical rigidity, reduce cost of the blends, and integrate recycle route with renewable resource. In this research, we attempted to prepare poly(butylene succinate) (PBS)/recycled PET (PBS/r-PET) blends via melt blending in various blend ratio (90:10, 80:20, and 70:30 wt%) and then melt compounded with hollow glass microspheres (HGM) (3, 5 and 10 wt%) to obtain thermoplastic composites that would be used in electrical or electronic applications. Mechanical properties of blends and their composites were evaluated by means of tensile and notched Izod impact tests. Compatibility and thermal behavior were characterized using DSC and TGA. Morphology of fractured specimens was studied using SEM. It was found that PBS/r-PET blends exhibited higher tensile modulus with respect to r-PET content; however, toughness of the blends was deteriorated from poor interfacial attraction and molecular weight reduction of PBS matrix. Tg of PBS phase was shifted to higher temperature because of transesterification. The composites had higher specific tensile modulus with respect to HGM loading. With the presence of r-PET, HGM surface was wetted implying r-PET acted as compatibilizer between hydrophobic PBS matrix and hydrophilic HGM, and thus, tensile modulus of composites was 10–40% increased depending on HGM loading.

Preparation and characterization of visible light catalyst ZnIn<sub>2</sub>S<sub>4</sub> coated on hollow glass microbeads

Heterogeneous photocatalytic technology based on semiconductors has been considered to be a green technology for environmental remeidation because it can use the solar energy. As a semiconductor visible light catalyst, ZnIn2S4 has attracted a lot of attention because of its narrow bandgap, strong absorption of visible light and unique catalytic properties. However, the disadvantages that the powders ZnIn2S4 are easy to aggregate and hard to separate make its photocatalytic efficiency limited. Besides, micro/nano powders are difficult to recycle, which tends to cause secondary pollution and increase the cost of photocatalysis inevitablely. In order to solve the disadvantages of the powder photocatalysts, floating substrates hollow glass microspheres (HGMs) are used as supporters for the coating of powder photocatalysts. Hollow glass microspheres, which are commonly used as floating-type carrier for photocatalysts due to their favorable properties of high chemical stability, low cost, lightweight mass, low thermal conductivity, hollow spherical morphology, good dispersibility and fluidity, are considered one of the most suitable supporters, and their combination are expected to show higher light utilization and collection efficiencies. In this research, the visible light photocatalyst ZnIn2S4 was coated on HGMs through a hydrothermal method at 160°C, which obtained HGM/ZnIn2S4 composite microspheres. The crystal structure, morphology and optical properties of the obtained composite microspheres were characterized by measurements such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectrum (XPS) and UV-Vis diffuse reflectance spectra (UV-Vis). The optimized conditions of ZnIn2S4 film coated on hollow glass microspheres were investigated by different pretreatment methods.such as alkali pretreatment, H2O2 activation and silane coupling modification. The results revealed that the activation of the HGMs through H2O2 and silane coupler angent KH550 showed better morphology of HGM/ZnIn2S4 composite microspheres with a nano-layered petal-like structure on the HGMs. Besides, HGM/ZnIn2S4 composite microspheres pretreated by silane coupling agent KH550 exhibited a higher hexagonal phase crystal structure compared with the H2O2 pretreated samples,and its band gap was estimated to be 2.37 eV from UV-vis absorbance spectrum,which showed that HGM/ZnIn2S4 composite microspheres exhibited good photocatalytic performance in the visible range. The HGM/ZnIn2S4 composite microspheres can not only maintain the high photocatalytic activity, but also overcome the disadvantages that nanoparticles powder are inclined to agglomeration in water.Furthermore, the degradation effect of Rhodamine B (RhB) under visble light were investigated through the as-prepared HGM/ZnIn2S4 composite microspheres. The results showed that the composite microspheres have good photocatalytic degradation effect on RhB, and the degradation of substrate RhB can reach 99.7 within 2 h. Finally, we proposed the possible growth mechanism of ZnIn2S4 film on HGMs and the formation of HGM/ZnIn2S4 composite microspheres. The precursor of ZnIn2S4 was firstly adsorbed on the surface of hollow glass microspheres by electrostatic adsorption. As the temperature of the reaction system was gradually increased, Zn(TAA) n 2+ and In(TAA) n 3+ generated at the same time can further combine in situ to yield numerous ZnIn2S4 nuclei. When the micronucleus of ZnIn2S4 was formed, the ZnIn2S4 nano-nucleus gradually deposited to form a layered petal structure, and then the HGM/ZnIn2S4 composite microspheres were prepared. The study showed a simple and reliable preparation condition and processe for ZnIn2S4 coated on hollow glass microspheres, which provides a promising application on photocatalytic field of the as prepared floating HGM/ZnIn2S4 composite microspheres, and it will be beneficial to explore the coating mechanism of ZnIn2S4 on glass-based carrier material.

Enhanced capture and release of circulating tumor cells using hollow glass microspheres with a nanostructured surface.

Self-floating hollow glass microspheres (HGMS) modified with tumor-specific antibodies have been developed for the capture of circulating tumor cells (CTCs), and have demonstrated effective cell isolation and good viability of isolated cancer cells. However, the capture efficiency decreases dramatically if the spiked cell concentration is low, possibly due to insufficient interactions between cancer cells and the HGMS surface. In order to apply HGMS-based CTC isolation to clinically relevant samples, it is desirable to create nanostructures on the surface of HGMS to enhance cell-surface interactions. Nevertheless, current microfabrication methods cannot generate nanostructured-surfaces on microspheres. The authors have developed a new HGMS with a controlled nanotopographical surface structure (NSHGMS), and demonstrated isolation and recovery of rare cancer cells. NSHGMS are achieved by applying layer-by-layer (LbL) assembly of negatively charged SiO2 nanoparticles and positively charged poly-l-arginine molecules, then sheathing the surface with an enzymatically degradable LbL film made from biotinylated alginate and poly-l-arginine, and capping with anti-EpCAM antibodies and anti-fouling PEG molecules. Compared to smooth-surfaced HGMS, NSHGMS showed shorter isolation time (20 min), enhanced capture efficiency (93.6 ± 4.9%) and lower detection limit (30 cells per mL) for commonly used cancer cell lines (MCF7, SK-BR-3, PC-3, A549 and CCRF-CEM). This NSHGMS-based CTC isolation method does not require specialized lab equipment or an external power source, and thus, can be used for the separation of targeted cells from blood or other body fluids in a resource-limited environment.

THERMAL CONDUCTIVITY and TENSILE PROPERTIES OF HOLLOW GLASS MICROSPHERE / POLYPROPYLENE COMPOSITES

In this study, hollow glass microspheres (HGM) filled polypropylene (PP) composites were prepared by melt extrusion method. In order to understand the effect of structure and physical properties on the performance of composites, the morphologies, tensile properties and thermal conductivities of composites were investigated. The surface of HGMs were modified with 3-(Trimethoxysilyl) propyl methacrylate ( TMSM ) silane coupling agent to improve the compatibility between PP matrix and HGMs. The physical properties of silane modified and unmodified HGMs were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope (SEM). The effect of HGM content and surface modification of HGM on morphological, mechanical and thermal conductivity properties of composites were evaluated. The results indicated that the surface modification of HGM enhance the interfacial region between HGM and polymer matrix. When 20 wt % modified HGM was added to neat PP, the modulus of the composite obtained was 1057 MPa, increasing by 15.1% compared with that of the PP/unmodified HGM composite. However, any positive or consistent effect of surface modification and HGM addition on thermal conductivity of samples can not be observed.

Fabrication and mechanical properties of a novel epoxy-hollow glass microsphere composite

According to the demand of deep-sea buoyancy material with high compression strength and low density, a novel epoxy-hollow glass microsphere composite was manufactured and characterized. Firstly, the epoxy resin is modified by chemical modification methods using poly(methyltriethoxysilane) to improve the toughness of epoxy resin. Then, the ammonium bicarbonate is used as the foaming agent to add into the epoxy resin to produce the bubbles. After mixing with a small amount of hollow glass microsphere, the modified epoxy-hollow glass microsphere composite with foams is fabricated. IR spectrum indicates that the silicone has been successfully grafted on the epoxy resin chain, which benefits the toughness of the resin. It can be found that a lot of smaller bubbles exist on the surface of hollow glass microsphere by SEM, which further reduces the density of the modified epoxy-hollow glass microsphere composite. The compression strength has been significantly improved since the bubbles on the surface of glass beads play the role of a buffer balloon and there are few air bubbles in the resin matrix. The coefficient of water absorption for the modified epoxy-hollow glass microsphere composite also increased. The flexural strength of the modified epoxy-hollow glass microsphere composite was slightly reduced at the same time. The results here confirm a promising method for buoyancy materials to promote the compression strength and reduce the density.

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method.

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 and a superhydrophobic agent were coated on the HGM surface in one step. TBT and PFOTES were selected as the Ti source and the superhydrophobic agent, respectively. They were both coated on the HGM, and after the hydrothermal process, the TBT turned to anatase TiO2. In this way, a PFOTES/TiO2-coated HGM (MCHGM) was prepared. For comparison, PFOTES single-coated HGM (F-SCHGM) and TiO2 single-coated HGM (Ti-SCHGM) were synthesized as well. The PFOTES and TiO2 coatings on the HGM surface were demonstrated through X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive detector (EDS) characterizations. The MCHGM showed a higher contact angle (153°) but a lower sliding angle (16°) than F-SCHGM, with a contact angle of 141.2° and a sliding angle of 67°. In addition, both Ti-SCHGM and MCHGM displayed similar IR reflectivity values, which were about 5.8% higher than the original HGM and F-SCHGM. Also, the PFOTES coating barely changed the thermal conductivity. Therefore, F-SCHGM, with a thermal conductivity of 0.0479 W/(m·K), was quite like the original HGM, which was 0.0475 W/(m·K). MCHGM and Ti-SCHGM were also similar. Their thermal conductivity values were 0.0543 W/(m·K) and 0.0543 W/(m·K), respectively. The TiO2 coating slightly increased the thermal conductivity, but with the increase in reflectivity, the overall heat-insulation property was enhanced. Finally, since the IR-reflecting property is provided by the HGM coating, if the coating is fouled, the reflectivity decreases. Therefore, with the superhydrophobic coating, the surface is protected from fouling, and its lifetime is also prolonged.

ZnO nanostructures decorated hollow glass microspheres as near infrared reflective pigment

Abstract Hollow glass microsphere/ZnO composite pigments were successfully prepared by a facile sol-gel method. ZnO coating layers composed of nanosheets, nanoplates, or nanoparticles were anchored at the surface of hollow glass microspheres by formation of Zn-O-Si bond. A reasonable growth mechanism for elucidating the formation of ZnO nanocoating was proposed. The results indicated that the near-infrared reflectance property of the composite pigments was strongly affected by the morphology of ZnO nanostructures. The nanoparticles structures exhibited higher near-infrared reflectance than that of nanosheets and nanoplates structures. The near-infrared solar reflectance of hollow glass microsphere/ZnO composite pigments was 95.7%, while the total solar reflectance of the composite pigment was as high as 97.2%. An approximately 11.1 °C decrease in outer surface temperature was obtained for the heat box coated with composite pigments. Therefore, hollow glass microsphere/ZnO composites are excellent near infrared reflective pigments for efficient solar reflective coatings designed for building facades and roofs.

Investigating the effect of cobalt loading on thermal conductivity and hydrogen storage capacity of hollow glass microspheres (HGMs)

In present study, cobalt loaded hollow glass microspheres (HGMs) were fabricated from amber colored glass powder blended with cobalt nitrate hexahydrate salt, by flame spheroidisation method. The morphology of the samples was observed using field emission-scanning electron microscope (FE-SEM), environmental SEM (ESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy and X-ray diffraction (XRD) techniques. The results showed that HGMs with surface coating of cobalt oxide can be successfully synthesized using this single step process. Effect of cobalt loading percentage (0-10%) in the glass feed on the formation of cobalt loaded HGMs were studied. A continuous thin coating of cobalt oxide on the HGMs surface was obtained when the cobalt content in the feed glass powder was up to 2%. Further increase of the cobalt in the feed glass led to uneven coating on the surface of HGMs. A clear cut diffraction pattern for crystalline CoO was observed at the thick patches observed on the HGMs samples with 10% loading of cobalt. The thermal conductivity of HGMs increased when the cobalt loading increased from 0 to 10 wt.%. The hydrogen storage experiments done on all the prepared samples at 200 °C and 10-bar pressure showed that the hydrogen storage capacity increased when the Co percentage in the sample increased from 0 to 2%. The percentage of cobalt was increased beyond 2 wt.% showed a decline in the hydrogen storage capacity.

Surface modification of hollow glass microsphere with different coupling agents for potential applications in phenolic syntactic foams

ABSTRACTModified hollow glass microsphere (HGM) particles have been prepared by surface treatment. Coupling agents such as γ‐aminopropyltriethoxysilane (APTES), di(dioctylpyrophosphato) ethylene titanate (NDZ‐311), and glutaraldehyde (GA) were used as modifiers to improve the hydrophobicity of HGM. Compared with pristine HGM, the modified HGM, especially the particles coupled with APTES‐GA, show better properties on flexural strength, fracture toughness, and dynamic mechanical properties of phenolic syntactic foams. It is revealed that the coupling agent coating layer grafted onto the surface of HGM reduces the polarity of particles, avoiding agglomeration of HGM in phenolic matrix and exhibiting good interfacial interaction between HGM and phenolic matrix. The remarkable improvement of interfacial adhesion between APTES‐GA modified HGM and phenolic matrix is mainly due to the covalent linkage with phenolic resin while the physical entanglement of molecular chains dominates the linkage between other modified HGM and phenolic matrix. APTES‐GA treatment is a more appropriate surface modification method for inorganic particle reinforced phenolic matrix composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44415.

A Polypyrrole/CoFe2O4/Hollow Glass Microspheres three-layer sandwich structure microwave absorbing material with wide absorbing bandwidth and strong absorbing capacity

A new PPy/CoFe2O4/HGMs microwave absorbing composite particle with three-layer sandwich structure, comprising cobalt ferrite (CoFe2O4) and polypyrrole (PPy) coating on the surface of hollow glass microspheres (HGMs), was synthesized by the method of co-precipitation and in situ polymerization. The surface morphology, phase structure and chemical component of the composite had been characterized by scanning electron microscope and X-ray diffractometer. The results indicated HGMs were coated by CoFe2O4 completely and the obtained CoFe2O4/HGMs composites were warped by PPy. The conductivity and the saturation magnetization Ms of the resulting PPy/CoFe2O4/HGMs composites are 0.09 S/cm and 46 emu/g, respectively. The vector network analyzer showed the composite performed better microwave absorption ability than that of PPy and PPy/HGMs. The reflection loss of the composite with 2.58 mm thickness is more than−10 dB which means over 90 % microwave is absorbed in X-band (8.38–12.4 GHz). The ternary composite that has light weight, wide absorbing bandwidth, strong absorbing capacity and conductivity can be an attractive candidate in the field of microwave absorption.

Cu-plated hollow glass microspheres for hydrogen production and degradation

Cu nanoparticles (CuNPs) were loaded on the surface of hollow glass microspheres (HGMs) by electroless plating technique. The surface morphology and composition of the plated HGMs were characterized by XRD, XPS and SEM. The results show that the size and distribution of the CuNPs varied with the different copper sulfate concentrations and played an important part in photocatalytic hydrogen production. When the concentration was 2 g/L, the hydrogen production reached 3845 μmol/g h with lactic acid as a sacrificial agent and exhibited great stability for at least 20 h, which is better than the freshly synthesized alone CuNPs (1500 μmol/g h). What’s more, the photocatalytic degradation rate of methyl orange reached up to 95.75 % after 2 h under light irradiation and the photocatalysts can be recycled for further use.

Oleophobic Modification of Hollow Glass Microspheres and Its Effect on the Foaming Capacity and Stability of Foam Extinguishing Agent

We utilized tridecafluorooctyltriethoxysilane (F8261) for the surface modification of hollow glass microspheres (HGM). We then measured the contact angles and the residing time of oil droplets on the HGM surface under different conditions and investigated the effects of the modifier concentration, reaction time and reaction temperature, and other factors on the outcomes of the modification reaction. We also compared the effects of HGM on the expansion ratio and 25% drainage time of protein foam liquid before and after the modification treatment and investigated the effects of HGM surface oleophobic modification on the foaming capacity and stability of foam extinguishing agent. The results showed that when the F8261 concentration was 1.0%, the temperature was 60°C, and the ultrasound treatment time was 2.0 h, the contact angle was up to 132.5°, the oleophobic property of HGM could be significantly enhanced, and the foaming capacity and the oil surface stability were significantly improved by the oleophobic modification.

A study on the preparation of floating photocatalyst supported by hollow TiO2 and its performance

This research used hollow glass microspheres (HGMS) as carrier and polystyrene (PSt) as template. PSt was loaded on HGMS surface through the modification by silane coupler. Next, amorphous titanium dioxide (TiO2) produced through tetrabutyl titanate (TBT) hydrolysis precipitated on PSt surface, forming HGMS/PSt/TiO2 particles. Lastly, using the calcinations method, this research obtained anatase TiO2, eliminated PSt, and ultimately acquired composite particles with hollow TiO2 loaded on HGMS surface (HGMSHT). SEM results presented that hollow TiO2 was compact on HGMS surface and a multilayer network structure was formed. The specific surface area of HGMSHT particles was 26m2/g, which was much larger than that of HGMS/TiO2 (HGMST) composite particles (5.6m2/g) through direct TBT hydrolysis. Results of catalytic degradation experiment with Rhodamine B and phenol under UV light and sunlight demonstrated that due to larger TiO2 load capacity and specific surface area, the catalytic activity of HGMSHT composite particles was significantly more desirable than that of HGMST, and the catalyst presented satisfactory stability.

Preparation and microwave absorbing properties of hollow glass microspheres/Fe3O4/Ag composites with core–shell structure

The low-density, conductive and magnetic hollow glass microspheres (HGM)/Fe3O4/Ag composites have been successfully synthesized via co-precipitation and chemical plating method. The morphology, composition, microstructure, magnetic and microwave absorbing properties of the composites were investigated based on the analyses of the results using scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction, vibrating sample magnetometer and vector network analyzer. The results showed that the HGM/Fe3O4 composites were successfully prepared, and the coating layers on the surface of HGM are compact and continuous. Moreover, the final composites were completely covered with Ag nanoparticles. With the addition of Ag nanoparticles, the saturation magnetization of the HGM/Fe3O4 composites reduces from 32.08 to 14.77 emu/g, whereas its conductivity increases to 0.48 S/cm. The reflection loss (R) of HGM/Fe3O4/Ag composites is lower than −10 dB at 8.2–8.7, 9.6–10.8 and 11.4–11.9 GHz, and the minimum loss value is −19.1 dB at 9.9 GHz.

Optimization and modeling of preparation conditions of TiO2 nanoparticles coated on hollow glass microspheres using response surface methodology

Response surface methodology was used to find and optimize the effect of the variables on the preparation, morphology and catalytic activity of nano-crystalline TiO2 thin films coated on hollow glass microspheres (HGMs) by sol–gel method. Three experimental parameters were chosen as independent variables: the calcination temperature, the amount of titanium butoxide and template F127. Morphology analysis showed that structure of TiO2–HGMs prepared was core shell, and the surface of HGMs was coated by TiO2 thin films with an average layer thickness of 728±12nm. A quadratic model was established as a functional relationship between three independent variables and the degradation efficiency of methyl orange (MO). The results of model fitting and statistical analysis demonstrated that the amount of titanium butoxide and F127 played a key role in discoloration for MO. The optimum conditions for maximum MO degradation efficiency (98.6%) were titanium butoxide of 18.64g, F127 of 3.12g and calcination temperature of 501.89°C.

Facile method to synthesize silver nanoparticles on the surface of hollow glass microspheres and their microwave shielding properties

In this paper, a facile method for the fabrication of hollow glass microspheres–Ag composite particles with core–shell structures is investigated.

Preparation and Characterization of Zinc Loaded Hollow Glass Microspheres (HGMs) from Amber Coloured Glass Frits

Hollow glass microspheres loaded with ZnO nanoparticles were fabricated from amber colored glass powder blended with zinc acetate salt, by flame spheroidisation method. The morphology and the microstructure of the samples were observed using SEM, TEM, FTIR and XRD techniques, whereas the composition of the feed glass and product HGMs were determined using EDX and ICP. The results showed that HGMs with surface coating of zinc oxide nanoparticles can be successfully synthesized using this single step process. Effect of zinc acetate percentage (0-10%) in the glass feed on the formation of zinc oxide coated HGMs and the nature of the ZnO coating were studied. A continuous thin coating of ZnO nanoparticles on the HGMs surface were obtained when the zinc acetate content in the feed glass powder was 2-5%. Further increase of the zinc acetate in the feed glass led to uneven coating on the surface of HGMs. A clear cut diffraction pattern for crystalline ZnO was observed at the thick patches observed on the HGMs samples with 10% loading of zinc. The thickness of the ZnO coating increased from 10 nm to 500 nm when the zinc content in the feed glass increased from 2 to 10%.

Tailoring of thermal and dielectric properties of LDPE-matrix composites by the volume fraction, density, and surface modification of hollow glass microsphere filler

Hollow glass microsphere (HGM) filled low-density polyethylene (LDPE) composites were prepared, and the effects of density, content, and surface modification of HGM on the thermal and dielectric properties of the composites were investigated. It is found that the thermal conductivity of the composites decreases with increasing HGM content or decreasing HGM density. At the same HGM content and density, the composites filled with suitable amount of silane coupling agent (KH570) modified HGM exhibit higher thermal conductivity than unmodified-HGM filled composites. The dielectric constant at 1MHz of the composites also decreases with increasing HGM content or decreasing HGM density, but their dielectric loss increases with increasing HGM content or increasing HGM density. By modifying the surface of HGM with suitable amount of KH570, the dielectric constant and loss at 1MHz of the composites can be decreased at the same time. The results of microwave dielectric properties of the composites indicate that the dielectric constant decreases with increasing HGM content or decreasing HGM density, the quality factor (Q×f) decreases with increasing HGM content or increasing HGM density, but both dielectric constant and quality factor are slightly affected by the surface modification of HGM. Due to lower intrinsic thermal conductivity and dielectric constant but higher dielectric loss of HGM than LDPE, the thermal conductivity and dielectric properties of the composites can be controlled with adding HGM and varying its volume fraction. The surface modification of HGM improves the interface contact between HGM and LDPE in the composites, which is confirmed by the SEM observation, and thus the heat conduction and dielectric properties at low frequency are improved. Based on calculated thermal conductivity and dielectric constant of HGM, the experimental trends of thermal conductivity and dielectric constant at 1MHz of the composites are analyzed by using different models, including typical models for particles-filled composites and special models developed for hollow microsphere filled composites. The results from suitable models show close correlation with the experimental values.

Preparation and characterisation of ZnO nanorod array-coated hollow glass microsphere composites

Uniform and oriented ZnO nanorod arrays on the surface of hollow glass microspheres (HGMs) were fabricated by using a seed growth process in aqueous solution of zinc nitrate and hexamethylenetetramine at low temperature. The structure and morphology of as-obtained ZnO nanorod array-coated hollow glass microsphere (HGM/ZnO) composites were analysed by using X-ray diffraction and scanning electron microscopy. The results showed that all the HGMs were coated with a well-aligned layer of ZnO nanorod arrays and the ZnO nanorods possessed relatively uniform hexagonal rod structures and stood perpendicular. Moreover, the ZnO nanorod arrays were affected by a variety of growth conditions such as the growth solution concentration and the solution temperature.