Application of Terahertz Spectroscopy in Porosity Detection of Polyolefin Films

Qing Li; Mingxia He

doi:10.3788/LOP221114

Journals >Laser & Optoelectronics Progress >Volume 60 >Issue 9 >Page 0930003 > Article

Laser & Optoelectronics Progress
Vol. 60, Issue 9, 0930003 (2023)

Application of Terahertz Spectroscopy in Porosity Detection of Polyolefin Films

Qing Li^1、2 and Mingxia He^1、2、*

Author Affiliations

¹State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China

²Center for Terahertz Waves, Tianjin University, Tianjin 300072, China

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DOI: 10.3788/LOP221114 Cite this Article Set citation alerts

Qing Li, Mingxia He. Application of Terahertz Spectroscopy in Porosity Detection of Polyolefin Films[J]. Laser & Optoelectronics Progress, 2023, 60(9): 0930003 Copy Citation Text

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Fig. 1. Composition diagram of mixture sample prepared for THz-TDS system^［10］

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Fig. 2. Wiener bounds model^［12］

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Fig. 3. Thin film thickness extraction of cathode coating for lithium battery. (a) THz-TDS signal and EEMD fitting results; (b) dual time-domain signal after decomposition

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Fig. 4. Relationship between porosity and permittivity using common effective medium models

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Fig. 5. Simulation results of effective medium model. (a) Fitting with permittivity detection results; (b) absolute error value

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No.	Porosity （theoretical value）	Porosity （experimental value）	Relative error /%
1	40	37.78	5.54
2	45	42.46	5.63
3	50	48.19	3.61
4	55	48.93	11.00
5	60	55.19	8.01

Table 1. Theoretical and experimental porosity values of PP/PE/PP separator (LLL model)

No.	Porosity （theoretical value）	Porosity （experimental value）	Relative error /%
1	40	39.87	0.32
2	45	45.53	1.17
3	50	52.73	5.46
4	55	53.69	2.39
5	60	61.99	3.33

Table 2. Theoretical and experimental porosity values of PP/PE/PP separator (AB-EMA model)

No.	Porosity （theoretical value）	Porosity （experimental value）	Relative error /%
1	40	44.33	10.83
2	45	49.24	9.42
3	50	55.08	10.16
4	55	55.82	1.49
5	60	61.97	3.29

Table 3. Theoretical and experimental porosity values of PP/PE/PP separator (Winer upper bound model)

Model	Average value	Max	Min	Variance
LLL	2.2848	2.2967	2.2609	0.0021
AB-EMA	2.3066	2.3143	2.2877	0.0002
Wiener upper bound	2.2748	2.3102	2.2304	0.0037

Table 4. Intrinsic permittivity of PP separator and PP/PE/PP separator

n	$θ = 1 °$ /%	$θ = 2 °$ /%	$θ = 3 °$ /%	$θ = 4 °$ /%	$θ = 5 °$ /%
1.5	0.036	0.144	0.326	0.581	0.905
1.7	0.027	0.108	0.249	0.438	0.689
2.0	0.019	0.076	0.173	0.306	0.481

Table 5. Measurement errors

Pore size /μm	d /μm	$ε_{e f f}$	Porosity /%
0.45	221	1.27	76
2	186	1.31	81
3	192	1.31	82
5	205	1.29	78

Table 6. Thickness, permittivity, and porosity of microporous membranes with different pore sizes

Qing Li, Mingxia He. Application of Terahertz Spectroscopy in Porosity Detection of Polyolefin Films[J]. Laser & Optoelectronics Progress, 2023, 60(9): 0930003

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