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Xinyu Wang

Bio: Xinyu Wang is an academic researcher from University of Southampton. The author has contributed to research in topics: Nanocomposite & Silane. The author has an hindex of 4, co-authored 13 publications receiving 32 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the effects of filler surface chemistry on the resulting AlN/polypropylene (PP) nanocomposites were examined and compared with an unfilled reference system, and it was observed that different organofunctional groups can provide different nucleating effects and the dispersion states of nanoparticles while the hydrolysable group is not the dominant factor.
Abstract: In nanocomposites, different surface states of nanoparticles can potentially provide different interactions with the base polymer and in turn change the bulk properties. Aluminium nitride (AlN) nanoparticles were surface functionalised with three different silane coupling agents (SCAs) with varying organofunctional and hydrolysable groups. The effects of the filler surface chemistry on the resulting AlN/polypropylene (PP) nanocomposites were examined and compared with an unfilled reference system. It is observed that different organofunctional groups can provide different nucleating effects and the dispersion states of nanoparticles while the hydrolysable group is not the dominant factor. The dielectric spectroscopy results show the hydrolysable group of SCA will also result in a difference of the interphase since the trimethoxy silane treated systems show much higher imaginary permittivity than the triethoxy silane treated systems when the frequency is below 1 Hz. The grafted organofunctional layer on the particle surface can provide a significant improvement of the thermal conductivity of the composite materials, e.g. 15 % improvement in thermal conductivity was observed when adding 10 wt% methacrylate silanes treated nano-AlN into PP, while the untreated counterpart only has 5 % improvement.

15 citations

Journal ArticleDOI
TL;DR: In this article, the influence of adding nanoparticles into epoxy resins and the characteristics of the movement of charges in the materials based on combining analysis on morphology, DC conductivity and space charge measurements is discussed.
Abstract: Nanocomposites those exhibit good insulation properties have already attracted numbers of research and their electrical properties are believed to be related to charge dynamics in bulk of materials. However, it is still unclear on how nanofiller loading ratios, surface treatment and resultant changes in morphology influence the charge dynamics of nanocomposites. In this paper, we have clearly mentioned the influence of adding nanoparticles into epoxy resins and the characteristics of the movement of charges in the materials based on combining analysis on morphology, DC conductivity and space charge measurements. The presence of spherical nanoparticles (SiO2) introduced additional traps in bulk, which impaired the charge injection and reduced the mobility of charge carriers in samples of low filler loading ratios (e.g., 0.5 wt%). However, in silica-based samples of higher filler loadings, more nanoparticles further caused a higher density of traps, which resulted in lower average distance between arbitrary traps/ inter-particle surface distances and thus charge carriers required less energy when moving from one to another by hopping or the quantum tunnelling mechanism. The surface treatment of SiO2 particles introduced deep traps which helped the separation of particles or related traps, and to some extent restricted the transport of charge carriers. In addition, hBN particles seem to act as barriers to charge injection and movement due to the layered structures and large numbers of resultant shallow traps in bulk. In term of moisture effect, the presence of water led to an obvious increase in charge injection and mobility, and resulted in the higher mobility of charge carriers in both base materials and within traps/particles of nanocomposites. The existence of water shells around spherical particles could contribute to a higher probability of the quantum tunnelling process and the formation of conductive percolation channels.

11 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of water immersion and silane treatment on the AC breakdown and complex dielectric response of polypropylene/nano-aluminium nitride composites has been investigated.
Abstract: The influence of water immersion and silane treatment on the AC breakdown and the complex dielectric response of polypropylene/nano-aluminium nitride (PP/nano-AlN) composites has been investigated. The as-received filler was examined to have a nanoscale particle distribution with a hexagonal shape and slight hydrolysation. Grafting the aluminium nitride with an octyl silane reduces the weight increase in samples filled with 10 wt% of aluminium nitride during water immersion by 3, from 0.29 to 0.09%. The results suggest that the AC breakdown strength and complex permittivity of “wet” composite samples are related to the silane treatment of the nanofiller. The AC breakdown strength of octyl silane-treated samples after 9 days of water immersion shows comparable results to the dry samples, while a reduction can be seen on non-treated samples. Although silane-treated samples still show an increased dielectric loss at low frequency after water immersion, a significant reduction in low-frequency dispersion of real and imaginary permittivity can be seen when compared to the non-treated composites. This indicates that significant gains can be obtained for PP/nano-AlN composites by suitable silane treatments.

10 citations

Proceedings ArticleDOI
01 Jul 2018
TL;DR: In this article, the effect of different particle surfaces and polymer-particle interphases on the dielectric properties of isotactic polypropylene has been studied and the results show that it can not only affect the dispersion state of nanoparticles but will provide different impacts on the bulk material.
Abstract: Polymer nanocomposites can potentially provide many advantages and the interaction region between polymer and nanoparticles—the so-called interphase is usually considered to be responsible for the change of properties. In this work, nano-aluminium nitride powders with various surface states obtained by three different silane coupling agents (SCA) and an untreated powder, were blended with isotactic polypropylene. AC breakdown strength and dielectric spectroscopy were used to study the effect of different particle surfaces and polymer-particle interphases. The nano-aluminium nitride powder grafted with different organofunctional groups can provide a number of potential interactions with the matrix polymer. The results show that it can not only affect the dispersion state of nanoparticles but will provide different impacts on the dielectric properties of the bulk material. The hydrolysable groups of SCA, notably, can also influence the dielectric properties through altering the surface chemistry of nanoparticles.

8 citations

Journal ArticleDOI
TL;DR: In this article, the role played by the interface and bulk volume of the nanofiller about affecting the electrical properties of a nanocomposite material is discussed, and the effect of the ZnS interface and as contrast to the core material is highlighted.
Abstract: This paper deals with the role played by the interface and bulk volume of the nanofiller about affecting the electrical properties of a nanocomposite material. For this purpose, a simple and completely amorphous matrix, polystyrene (PS), is used as base material, and core-shell quantum dots are exploited for simulating the structure of nanocomposites: CdSe core and CdSe-ZnS core-shell semiconductor quantum dots (QDs) are added into a PS matrix. The latter is to highlight the effect of the ZnS interface and as contrast to the core material. Dispersion and distribution of QDs are first microscopically observed and optimized by including isopropyl alcohol in the manufacturing phase as an additional solvent. Among electrical properties the focus is on space charge accumulation, tested by means of the pulsed electroacoustic technique at 10 kV/mm and 50 kV/mm on CdSe and CdSe-ZnS doped PS composites. Results are then compared with a reference PS without QDs. Trap depth and density are also obtained by space charge measurement results. When CdSe QDs are added to PS, the trap density increases with respect to the baseline values measured on the unfilled polymer. In contrast, the ZnS shell around the CdSe core creates an additional trap level with lower trap depth, which increases charge mobility, thus turning homocharge into heterocharge accumulation. Therefore, the surface shell-structure of QD nanocrystals appears to significantly influence the space charge behavior of the nanocomposite, independently of the polymer.

4 citations


Cited by
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Journal ArticleDOI
01 Aug 2020
TL;DR: In this paper, the effect of different coupling agents on the dielectric properties of polyethylene (PE) with varying filling contents of nano-alumina particles was studied.
Abstract: Generally, the electrical properties of nanocomposite are affected by the type, size, filling concentration and surface treatment process of the nanoparticle. In this study, nanocomposites of polyethylene (PE) with varying filling contents of nano-alumina particles were prepared by the melting blending method and three different kinds of coupling agents were applied for surface modification properties of the nanoparticles. Two of them were silane based and the other was titanate based. The effect of different coupling agents on the dielectric properties was studied. Fourier-transform infrared spectroscopy and thermo-gravimetric analysis were used to verify their compositions. Scanning electron microscope and polarised optical microscopy were used for morphology study. Dielectric permittivity, direct current (DC) volume resistivity and DC breakdown strength characterised their improved insulation performance with nano-alumina as filler. Thermal stimulated current results revealed that adding nano-alumina particles into low-density PE could provide more deep traps and increase DC resistivity.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of filler surface chemistry on the resulting AlN/polypropylene (PP) nanocomposites were examined and compared with an unfilled reference system, and it was observed that different organofunctional groups can provide different nucleating effects and the dispersion states of nanoparticles while the hydrolysable group is not the dominant factor.
Abstract: In nanocomposites, different surface states of nanoparticles can potentially provide different interactions with the base polymer and in turn change the bulk properties. Aluminium nitride (AlN) nanoparticles were surface functionalised with three different silane coupling agents (SCAs) with varying organofunctional and hydrolysable groups. The effects of the filler surface chemistry on the resulting AlN/polypropylene (PP) nanocomposites were examined and compared with an unfilled reference system. It is observed that different organofunctional groups can provide different nucleating effects and the dispersion states of nanoparticles while the hydrolysable group is not the dominant factor. The dielectric spectroscopy results show the hydrolysable group of SCA will also result in a difference of the interphase since the trimethoxy silane treated systems show much higher imaginary permittivity than the triethoxy silane treated systems when the frequency is below 1 Hz. The grafted organofunctional layer on the particle surface can provide a significant improvement of the thermal conductivity of the composite materials, e.g. 15 % improvement in thermal conductivity was observed when adding 10 wt% methacrylate silanes treated nano-AlN into PP, while the untreated counterpart only has 5 % improvement.

15 citations

Journal ArticleDOI
Yan Mi1, Gou Jiaxi1, Liu Lulu1, Xin Ge1, Hui Wan1, Quan Liu1 
TL;DR: The plasma hydroxylation modification method used in this paper can provide a basis for the preparation of high thermal conductivity insulating materials.
Abstract: Filling epoxy resin (EP) with boron nitride (BN) nanosheets (BNNSs) can effectively improve the thermal conductivity of BN/EP nanocomposites. However, due to the few hydroxyl groups on the surface of BNNSs, silane coupling agent (SCA) cannot effectively modify BNNSs. The agglomeration of BNNSs is severe, which significantly reduces the AC breakdown strength of the composites. Therefore, this paper uses atmospheric pressure bipolar nanosecond pulse dielectric barrier discharge (DBD) Ar+H2O low temperature plasma to hydroxylate BNNSs to improve the AC breakdown strength and thermal conductivity of the composites. X-ray photoelectron spectroscopy (XPS) shows that the hydroxyl content of the BNNSs surface increases nearly two fold after plasma modification. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) show that plasma modification enhances the dehydration condensation reaction of BNNSs with SCA, and the coating amount of SCA on the BNNSs surface increases by 45%. The breakdown test shows that the AC breakdown strength of the composites after plasma modification is improved under different filling contents. With the filling content of BNNSs increasing from 10% to 20%, the composites can maintain a certain insulation strength. Meanwhile, the thermal conductivity of the composites increases by 67% as the filling content increases from 10% (SCA treated) to 20% (plasma and SCA treated). Therefore, the plasma hydroxylation modification method used in this paper can provide a basis for the preparation of high thermal conductivity insulating materials.

14 citations

Journal ArticleDOI
01 Apr 2020
TL;DR: In this paper, the performance of epoxy nano-micro composite specimens with micro silica and ion trapping nanoparticle, by shear mixing process, was exposed to gamma radiation and its performance for space charge and charge trap characteristics were analyzed.
Abstract: Epoxy nano–micro composite specimen prepared with micro silica and ion trapping nanoparticle, by shear mixing process, was exposed to gamma radiation and its performance for space charge and charge trap characteristics were analysed. The threshold for space charge accumulation of epoxy nanocomposites reduces and rate of space charge accumulation increases with an increase in dosage of gamma irradiation. The average growth of space charge density during poling and charge decay rate during depoling are relatively higher for gamma-irradiated specimens than the virgin specimen. The initial surface potential has a marginal reduction with increase in the dosage of gamma radiation, but the surface potential decay rate has increased significantly. Trap distribution characteristics indicate more number of shallow traps and increase in charge mobility after irradiation. The relative permittivity and loss tangent of the specimens have high impact due to gamma irradiation. The activation energy calculated from DC conductivity by Arrhenius law reduces with increment in radiation dose. Laser-induced breakdown spectroscopy reflected no change in elemental composition with gamma-irradiated specimen. The variation in plasma temperature and ion line to atomic line intensity ratio with dosage of gamma radiation have direct correlation to the Vickers hardness number of the specimens.

14 citations