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27 results on '"Zhang, Dongfei"'

4. Investigating the Water-Induced Stiffening Mechanism in a Novel Polyurethane through Simulation and Experimental Analysis

Author

Wang, Ao, Liu, Wenkai, Jin, Xiaohan, Wu, Hecheng, Zhang, Dongfei, Han, Xianglong, Liu, Yang, Li, Zhen, Ding, Mingming, Li, Jiehua, and Tan, Hong

Abstract

Much attention has been drawn to our previously reported polyurethane featuring a hard backbone and dangling poly(ethylene glycol) (PEG) soft segment. It is endowed with a unique self-stiffening property when exposed to water. Yet the mechanism from a molecular perspective is still not quite clear. Herein, coarse-grained (CG) and all-atom (AA) molecular dynamics (MD) simulations, alongside experimental approaches, have been employed to unravel the mechanism behind the phenomenon. It is confirmed that water could induce the polyurethane to achieve a higher degree of phase separation. When being stretched, hard domains of aqueous side chain PEG polyurethane (SPPU) have a stronger tendency to orient in the direction of tensile stress and facilitate the effective transfer of stress. This enhancement effect of water-stiffening cannot be achieved at an insufficient side chain density. The ratio of hydrogen bonds in the SPPU exhibited a higher degree of enhancement with water content, which is in accordance with experimental results. The unique topology of SPPU was considered to be the most important factor to the Young’s modulus determined by the gradient boosting regression (GBR) model. This research helps to advance our comprehension of the interplay between the structure and performance of polyurethane, providing a theoretical foundation for the design of a novel material.

Published
2024
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9. Stiffness Self‐Tuned Shape Memory Hydrogels for Embolization of Aneurysms

Author

Liu, Bo, primary, Xu, Ziyang, additional, Gao, Haijun, additional, Fan, Chuanchuan, additional, Ma, Guangshuo, additional, Zhang, Dongfei, additional, Xiao, Meng, additional, Zhang, Bingjie, additional, Yang, Yang, additional, Cui, Chunyan, additional, Wu, Tengling, additional, Feng, Xuequan, additional, and Liu, Wenguang, additional

Published
2020
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10. Study on the parallel pressure differential type gas laminar flow sensing technique

Author

Zhang Hong-jun, Chen Caolang, Wang Qingqing, Zhang Dongfei, and Li Guozhan

Subjects
Physics, Internal flow, Mass flow, Entrance length, Laminar flow, Mechanics, Flow measurement, Computer Science Applications, Volumetric flow rate, Capillary length, Flow (mathematics), Modeling and Simulation, Electrical and Electronic Engineering, Instrumentation
Abstract

Parallel pressure differential (PPD) type laminar flow sensing technique was invented several years ago to reduce nonlinear effect in a traditional laminar flow element (LFE). In this paper, the internal flow of each branch in a PPD LFE is numerically simulated for gas flow. The results show that the relative deviation of the pressure drops of the two branches in a PPD LFE is within ±0.05% as inlet mass flow being the same, indicating that the flow resistance characteristics of the two branches are consistent, which means that the hypothesis of a same flow rate for the two branches in a real PPD LFE is tenable. There is little difference, ±0.01%, in the local pressure losses of the two upstream capillaries outlet flows, which can be ignored in a real measurement, further verifying that the theoretical analysis of the PPD principle is reliable. Capillary length effect in a PPD LFE is also examined. The bigger capillary length, the higher measurement precision can be achieved for a certain length range. For instance, it is suggested that the length of the short components should not be shorter than the laminar flow dimensionless entrance length defined by Xe (Le/d/Re, where Le is the entrance length) = 0.035, for flow measurement uncertainty within ±1.0%. The simulation and experiment results of gas flow show that the suitable value of Kexp is 1, and in the flow range of (0.0256–5.2985) m3/h measurement error of a PPD LFE is within ±0.8% only with expansion correction, indicating that the PPD laminar flow measurement technique is suitable for the gas flow.

Published
2021
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26. A Fe 3+ -crosslinked pyrogallol-tethered gelatin adhesive hydrogel with antibacterial activity for wound healing.

Author

Han N, Xu Z, Cui C, Li Y, Zhang D, Xiao M, Fan C, Wu T, Yang J, and Liu W

Subjects
Adhesiveness, Animals, Anti-Bacterial Agents chemistry, Benzaldehydes chemistry, Ceramics chemistry, Diabetes Mellitus, Experimental drug therapy, Gelatin chemistry, Glass chemistry, Hydrogels chemistry, Iron administration & dosage, Iron chemistry, Male, Polymethyl Methacrylate chemistry, Pyrogallol chemistry, Rats, Rats, Sprague-Dawley, Rheology, Skin chemistry, Swine, Tissue Adhesives, Wound Healing drug effects, Anti-Bacterial Agents administration & dosage, Benzaldehydes administration & dosage, Gelatin administration & dosage, Hydrogels administration & dosage, Pyrogallol administration & dosage, Staphylococcal Infections drug therapy, Staphylococcus aureus
Abstract

In this work, a tunicate-inspired gelatin-based hydrogel is prepared by simply mixing 2,3,4-trihydroxybenzaldehyde (THB)-tethered gelatin solution with a small amount of Fe 3+ ions via the Schiff-base reaction and simultaneous formation of hexavalent Fe-complexes. The resulting hydrogel (termed GelTHB-Fe) exhibits not only tunable gelation time, rheological properties and self-healing ability by adjusting the composition, but also robust adhesion to a variety of materials, with an average adhesion strength of 136.7 kPa, 147.3 kPa, 153.7 kPa, 92.9 kPa, and 56.5 kPa to PMMA, iron, ceramics, glass and pigskin, respectively. Intriguingly, the pyrogallol moieties impart an antibacterial activity to the GelTHB-Fe hydrogel, which is shown to reduce infection and promote wound healing in a diabetic rat model. This GelTHB-Fe hydrogel holds great potential as a promising tissue adhesive.

Published
2020
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27. The MgB 2 -catalyzed growth of boron nitride nanotubes using B/MgO as a boron containing precursor.

Author

Zhang D, Zhang K, E S, Liu D, Li C, and Yao Y

Abstract

With the development of preparation technology, obtaining boron nitride nanotubes (BNNTs) is no longer difficult, but it is still not easy to balance the quality and purity of the obtained products using existing methods. In this work, we investigated a previously reported MgB 2 catalyst to explore the synthesis of BNNTs at a higher temperature in a conventional chemical vapor deposition (CVD) system from a classic B/MgO precursor. Various characterization methods showed the high activity of MgB 2 at 1400 °C and the superiority of the as-grown BNNTs in terms of purity and quality. Further reference experiments and element characterization measurements were also performed to verify the role of MgB 2 in the growth of the BNNTs, finding that B/MgO/MgB 2 is a simple and efficient precursor., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Published
2020
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