Investigation of hydroxylation-induced reconstruction on WO3 surface and the modification mechanism of transformer oil

doi:10.11949/0438-1157.20241250

Abstract

Abstract:

Metal oxide nanoparticles modified transformer oil frequently suffer from the phenomenon of reduced insulation performance due to poor stability. The mechanism of the effect of surface hydroxylation on the insulation performance of nano-modified transformer oil is still controversial. Nano-WO₃ modified transformer oil (WMO) was prepared by sol-gel and two-step methods. X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) revealed the hydroxylation interaction between water molecules and the surface of WO₃ NPs. Besides, the integration of differential charge density analysis and Bader charge calculations validated that this mechanism enables precise modulation of surface-localized electronic configurations, which positively impacts the insulation performance of the nanoparticle-modified transformer oil, as evidenced by the breakdown voltage of up to 68.50 kV. Additionally, the trapping of free electrons on the surface of WO₃ NPs and the formation of electric double layer (EDL) further elucidate the mechanism by which extended relaxation time optimizes the electrical properties of WMO. Thermal conductivity tests and infrared thermography analyses were uncovered phonon-mediated heat transfer phenomena between solid-phase nanoparticles within the oil, elucidating the mechanism of doped WO₃ NPs to enhance the thermal conductivity of WMO. This study confirms the impact of hydroxylation on the electronic configuration and reconstruction behavior of NPs surfaces in transformer oil at the molecular level, providing crucial support for understanding the microscopic mechanisms of nanoparticle-modified transformer oils.

Key words: nano-modified transformer oil, electronic states, surface hydroxylation, infrared thermography

摘要：

金属氧化物纳米颗粒改性变压器油因稳定性欠佳，频繁出现绝缘性能下降的现象，表面羟基化对纳米改性变压器油绝缘性能的影响机制仍存在争议。通过溶胶-凝胶法和两步法制备三氧化钨（WO₃）纳米改性变压器油。借助X射线光电子能谱（XPS）和傅里叶变换红外光谱（FTIR）等表征分析，证实油中水分子与WO₃纳米颗粒表面存在羟基化作用，结合差分电荷密度与Bader电荷计算结果验证了该过程可调控其表面局域电子态结构，优化纳米改性变压器油的绝缘性能（击穿电压可达68.50 kV）。此外，WO₃纳米颗粒表面“捕获”电子以及双电层的形成进一步阐释延长弛豫时间对纳米改性变压器油电气性能的优化机理。开展热导率测试并辅以红外热成像分析，揭示了油液中固相纳米颗粒间声子热传导现象，阐明了掺杂WO₃纳米颗粒提升体系导热性能的作用机制。本项工作从分子尺度上证实了变压器油体系中羟基化作用对纳米颗粒表面电子排布和重构行为的影响，可为研究纳米改性变压器油的微观机理提供参考。

关键词: 改性变压器油, 电子态, 表面羟基化, 红外热成像

CLC Number:

TM 40

Haifeng ZHANG, Jingyi YAN, Yuxue YUE, Zilong ZHANG, Bolin WANG, Xiaonian LI. Investigation of hydroxylation-induced reconstruction on WO₃ surface and the modification mechanism of transformer oil[J]. CIESC Journal, 2025, 76(7): 3696-3709.

张海丰, 闫静怡, 岳玉学, 张子龙, 王柏林, 李小年. WO₃纳米颗粒定性表面羟基化重构及其改性变压器油机制研究[J]. 化工学报, 2025, 76(7): 3696-3709.

Figures/Tables 16

Fig.1 Schematic illustrating the preparation of materials

Fig.2 XRD patterns of WO3 NPs and WO3/MO NPs

Fig.3 TEM images of WO3 NPs (a) and WO3/MO NPs (b); Size distribution of WO3 NPs (c) and WO3/MO NPs (d)

Fig.4 Size distribution (a) and PDI and Z-average (b) of WO3 NFs at different concentration

Fig.5 XPS spectra of WO3 NPs and WO3/MO NPs

Fig.6 FTIR spectra of WO3 NPs, WO3/MO NPs, MO and WO3 NFs

Fig.7 Differential charge density maps of hydroxylation reconstruction on WO3 NPs surface

Table 1 Bader charge of hydroxylation reconstruction on WO3 NPs surface

Structure	Element	Bader charge/e
H—O_α	W	+2.640
	O	-1.172
	H	+0.604
W—O—H	W	+2.625
	O	-1.363
	H	+0.998

Fig.8 AC BDV (a) and Weibull statistic (b) of base oil and WO3 NFs

Table 2 AC breakdown voltage at different breakdown probabilities of nanofluids

NFs	BDV at 1%/ kV	BDV at 50%/ kV	BDV at 90%/ kV
MO	50.49	50.52	50.55
1.0WMO	57.28	57.31	57.34
2.5WMO	65.19	65.22	65.25
3.0WMO	60.29	60.33	60.36
5.0WMO	54.47	54.50	54.53
10.0WMO	45.34	45.37	45.40

Fig.9 Schematic of NPs to improve the breakdown voltage

Fig.10 The dissipation factor and resistivity (a) and variation rate of physicochemical properties (b) in WO3 NFs

Fig.11 Absolute Zeta potential of WO3 NFs

Fig.12 UV-Vis absorbance spectrum (a) and absorbance change trend within 45 d (b) of WO3 NFs

Fig.13 Thermal conductivity of 2.5 mg/L WO3 NFs

Fig.14 Surface temperature changes of transformer oil and WO3 NFs

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Investigation of hydroxylation-induced reconstruction on WO₃ surface and the modification mechanism of transformer oil

WO₃纳米颗粒定性表面羟基化重构及其改性变压器油机制研究

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