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1.
J Chromatogr A ; 1710: 464404, 2023 Nov 08.
Artículo en Inglés | MEDLINE | ID: mdl-37769425

RESUMEN

This paper presents a multiple headspace extraction (MHE) analysis technique to determine the water vapor transmission rate of cellulose-based papers. The water vapor passing through the sample in a closed headspace vial is determined by MHE-gas chromatography. The results show that the employed method offers good precision (the relative standard deviation < 3.49 %) and good accuracy. The method is rapid and accurate, and is promising for the determination of the water vapor transmission rate of cellulose-based papers in future studies.

2.
Nanotechnology ; 31(26): 265601, 2020 Apr 09.
Artículo en Inglés | MEDLINE | ID: mdl-32163939

RESUMEN

High quality and high quantity few-layer graphene was successfully prepared using a new impinging jet method. Natural graphite flakes were first agitated in N-methyl pyrrolidone (NMP) with the assistance of supercritical CO2, then the half-exfoliated graphite was further stripped using the shear stress derived from the impinging jets. After the energy conversion and stress analysis of the graphite particles during the whole exfoliation process, it was revealed that the size of the target mesh, the distance between the nozzle and the target, the decompression rate, and the size of the raw materials had a significant influence on the exfoliation process. Additionally, a microscopic view of the exfoliation and dispersion mechanism of graphene in the CO2-NMP system was investigated using molecular dynamics simulation, and CO2 was found to be beneficial for the penetration of NMP into the graphite sheets. Finally, the concentration and quality characteristics of the prepared graphene were characterized using ultraviolet-visible spectroscopy, transmission electron microscopy, Raman spectroscopy, and atomic force microscopy. The maximum concentration was as high as 0.689 mg ml-1, the thickness of 68% of the product was less than 2.5 nm, and the lateral dimension was from 0.5 to 3.0 µm. These results indicate that this impinging jet method is promising for large-scale industrial production.

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