Examining International Postgraduate Students in Academic Research Writing Competencies

Polymeric dielectrics with high dielectric permittivity (ɛ′) and low loss have momentous applications in energy storage devices. In this study, to concurrently improve the ɛ′ and restrain the loss of original Zn (Zinc)/poly(vinylidene fluoride, PVDF), the core@double‐shell structured Zn@ZnO(zinc oxide)@PS(polystyrene) particles were prepared and composited with the PVDF. The impacts of the dual shells on the dielectric properties and polarization mechanism of composites were explored by fitting the experimental data with a Havriliak–Negami (H–N) equation. The Zn@ZnO@PS/PVDF exhibit remarkably higher ɛ′ in comparison to the raw Zn and Zn@ZnO fillers owing to the induced multiple polarizations originating from the combined contributions of the α relaxation of PVDF, slow interparticle polarization and fast intraparticle polarization. More importantly, the ɛ′ of the composites remarkably increases with the PS shell’ thickness, while the loss is still kept at rather low levels owing to the PS shell’ barrier effect on long‐range charges migration. So, the introduction of the PS shell synchronously promotes both the interparticle and intraparticle polarizations in the Zn@ZnO@PS/PVDF composites toward enhanced dielectric properties. The developed strategy opens a novel path to the design and fabrication of polymer composites with desirable dielectric performances for applications in electronics and electrical industry.

Section: Resultsmentioning

confidence: 99%

Section: Dielectric Propertiesmentioning

confidence: 99%

Engineering of core@double‐shell structured Zn@ZnO@PS particles in poly(vinylidene fluoride) composites towards significantly enhanced dielectric performances

Yao

Zhou

Cao

et al. 2023

“…However, the dielectric constant of PI is very low (

< 4

) 10 . In order to improve the dielectric constant of PI, several methods have been proposed such as the introduction of conductive nano‐fillers or ceramic nano‐fillers 11 . Adding large proportion of ceramic fillers can achieve the high dielectric constant of the nanocomposites, but it will result in poor mechanical property.…”

Section: Introductionmentioning

confidence: 99%

“…10 In order to improve the dielectric constant of PI, several methods have been proposed such as the introduction of conductive nano-fillers or ceramic nano-fillers. 11 Adding large proportion of ceramic fillers can achieve the high dielectric constant of the nanocomposites, but it will result in poor mechanical property. By contrast, the addition of a small amount of conductive filler can significantly improve the dielectric constant due to the formation of micro-capacitors structure and Maxwell-Wagner-Sillars (MWS) interfacial polarization effect.…”

mentioning

confidence: 99%

Cetyltrimethylammonium bromide decorated MXene/polyimide nanocomposites with enhanced dielectric properties, thermostability, and moisture resistance

Cao

Zhao

et al. 2022

Under extreme conditions, the polymer dielectric materials are expected to have good dielectric properties and heat resistance. Polyimide (PI) has high service temperature (>250°C) and low dielectric loss, but its low dielectric constant limits its further application. The addition of MXene can significantly improve the dielectric constant of PI, but the poor compatibility between MXene and weak polar matrix leads to Bénard‐Marangoni (BM) instability in the process of thermal imidization. This issue can be solved by the surface modification of MXene. Therefore, in this work, a new cetyltrimethylammonium bromide (CTAB) decorated MXene/PI nanocomposite film was prepared by in‐situ polymerization. With the addition of 7 wt% MXene@CTAB, the PI nanocomposite shows improved dielectric constant (k = 7.8 at 100 Hz), which is 2.4 times that of pure PI due to the formation of micro‐capacitors structure and Maxwell‐Wagner‐Sillars (MWS) interfacial polarization. Its dielectric loss keeps at an ultra‐low level (0.027 at 100 Hz) while that of 7 wt% MXene/PI nanocomposite is 3.027. It is owing that CTAB inhibits the agglomeration of MXene. In addition, MXene@CTAB/PI composites have excellent thermal stability, good hydrophobicity, and low water absorption. The above properties ensure MXene@CTAB/PI composites wide application in various extreme situations.

“…It is often analyzed by thermogravimetric analysis (TGA). [8][9][10] Although phenolic resins (PF) modified with boron or phosphorus have higher carbon residue and better heat resistance, [11][12][13][14] the boron or phosphorus will react with glass fiber during high temperature pouring when they are used as coating material for casting filter mesh. This will reduce the strength of filter mesh at high temperature.…”

Section: Introductionmentioning

confidence: 99%

Study on the coating material of hexamethylol melamine modified phenolic resin for casting filter

Tang

Huang

Yuan

2022

In this article, hexamethylol melamine (HMM) modified phenolic resin (PF) coating material was prepared by using thermoplastic PF wastewater. Using alcohol soluble PF, the thermoplastic PF wastewater (containing oxalic acid catalyst), methanol and HMM as raw materials, HMM was methyl etherified by oxalic acid and then modified PF was synthesized. By determination of carbon residue, thermogravimetric analysis (TGA) and differential scanning calorimetry, the influences on the heat resistance of modified PF by the composition of wastewater, composition of melamine formaldehyde (MF) resin, and composition of MF resin modified PF were analyzed. The results showed that the phenol content in wastewater had no effect on the heat resistance. The MF resin modified by HMM with the highest molar ratio of formaldehyde and melamine had the highest heat resistance. And the nitrogen content of the highest thermostable modified PF was 5 wt%. Additional curing agent was not required for HMM modified PF. The possible pyrolysis process was discussed. As a filter coating material, the heat resistance of HMM modified PF was better than that of PF cured with traditional urotropine (HMTA).