Browsing by Author "Zhao, Yifan"

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The effect mechanism and properties of poplar wood cross-linking modified with polyols and polycarboxylic acid
(2023) Dong, Youming; Gao, Silong; Wang, Kaili; Zhan, Xianxu; Li, Zhiwen; Zhao, Yifan; Wu, Miao; Hughes, Mark
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Although cross-linking modification by polycarboxylic acid greatly improves dimensional stability and decay resistance, it causes severe brittleness and rigidity in wood. Introducing polyols into the cross-linking network could improve the flexibility of the modified wood, however, the related research is limited, especially the relationship between the strength and the reaction. In this study, poplar wood was modified by cross-linking with 1,2,3,4-butanetetracarboxylic acid (BTCA). D-sorbitol (SO) and sucrose (SU) used as the polyols were introduced to the modification system to esterify with BTCA. The physical and mechanical properties of the resulting wood were investigated. The effect mechanism and microstructure of the wood were also examined. The findings demonstrated that a cross-linked structure was formed in wood with increased ester bonds and ample polymer filling in the lumens. SU has lower leachability than SO. Although the incorporation of polyols has lowered anti-swelling efficiency, the reduction of modulus of rupture caused by BTCA treatment could be redeemed by reducing the degree of cross-linking between BTCA and wood components, especially SO-BTCA treatment. The addition of polyols has slight impact on the modulus of elasticity of BTCA treated wood.
Monolithic Saturable Absorber with Gallium Arsenide Nanowires Integrated on the Flexible Substrate for Optical Pulse Generation
(2023-09) Zhao, Yifan; Yang, He; Khayrudinov, Vladislav; Lipsanen, Harri; Su, Xinyang; Qi, Mei; Lu, Baole; Song, Ningfang
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this work, we demonstrated a kind of flexibly monolithic saturable absorber (SA) with GaAs nanowires (NWs) on polyimide (PI) plastic substrate for broadband optical modulation at 1.0 and 1.5 µm, separately. The monolithic SA sample was prepared by the metalorganic vapor phase epitaxy (MOVPE) method. The crystal structure and element analysis were examined carefully by high-resolution scanning transmission electron microscopy (HRSTEM) and energy-dispersive X-ray spectroscopy (EDX). We observed a high-density distribution of NWs on the flexible substrate by scanning electron microscopy (SEM). In addition, linear and nonlinear optical properties of the sample were examined by testing the photoluminescence and absorption properties, which showed its potential application as an optical switch due to the pure semiconducting properties. After the characterizations, we experimentally demonstrated this monolithic SA for laser modulation at 1.0 and 1.5 µm, which yielded the minimum optical pulse widths of 1.531 and 6.232 µs, respectively. Our work demonstrated such a kind of monolithic flexible NW substrate-integrated device used for broadband optical modulation, which not only eased the integration process of NWs onto the fiber endface, but also proved the potential of easily integrating with more semiconducting nanomaterials (e.g., graphene, MoS2, …) to realize monolithic active flexible photonic systems, such as a microscale phase modulator, delay-line, and so on, paving an easy avenue for the development of both active and flexible photonic devices.