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Volume 4, December 2018

"Cover Story"

Nanocomposites Research in Tongji University: Introduction of Prof. Hongbo Gu

Henry A. Colorado*, Qiang Gao*, Subramania Angaiah*, Zhe Wang*, Na Lu*, Ying Li*, Jong Eun Ryu*, Brian J. Edwards* and David P. Young*

Eng. Sci., 2018, 4, 1-3

DOI: 10.30919/es8d624

Recent Advances in Resistive Switching Materials and Devices: From Memories to Memristors

Gang Liu, Yu Chen*, Shuang Gao, Bin Zhang, Run-Wei Li* and Xiaodong Zhuang

Eng. Sci., 2018, 4, 4-43

DOI: 10.30919/es8d779

Abstract：Resistive switching devices have not only been considered as an emerging candidate for the next generation information storage technology, but also demonstrated great potential for in-memory computing systems with greatly enhanced computation capability. This review focuses on the recent advances in resistive materials and devices. We first describe the electric field-induced filamentary conduction model that accounts for the resistive switching behavior observed in inorganic materials, as well as the novel electric field-engineering strategy that is used to optimize the device structure and the memory performance. The alternative ways of using organic and hybrid materials to construct resistive switching devices are then illustrated. By tuning the charge transfer interaction and solid state electrochemical redox properties in small molecules, polymer, metal-organic framework and organic-inorganic hybrid perovskite materials, bistable and multibit memories, as well as the biomimicking memristors have been fabricated. Finally, we discuss the future development of the resistive switching materials and devices, aiming to clarifying the key issues that hinders its practical applications.

Influence of various ionic liquids embedded electrospun polymer membrane electrolytes on the photovoltaic performance of DSSC

Subramania Angaiah*, Vignesh Murugadoss, Subasri Arunachalam, Pratheep Panneerselvam, and Sarathkumar Krishnan

Eng. Sci., 2018, 4, 44-51

DOI: 10.30919/es8d756

Abstract：The influence of various ionic liquids such as 1,3-dimethyl imidazolium iodide (DMImI), 1-propyl-3-methyl imidazolium iodide (PMImI), 1-butyl-3-methyl imidazolium iodide (BMImI) and 1-hexyl-3-methyl imidazolium iodide (HMImI) embedded electrospun PVdF-HFP membrane electrolytes (esPMEs) on the photovoltaic performances of Dye-sensitized solar cells (DSSCs) were investigated. The influence of alkyl chain length of imidazolium and the concentration of ionic liquid electrolytes on the charge diffusion and electron transport kinetics were investigated by electrochemical impedance and Tafel polarization studies. Among the DSSCs fabricated with esPME of various ionic liquids, DSSC with 0.5M BMImI-esPME exhibited highest photoconversion efficiency of 7.08% with excellent long-term stability.

Electrophoretic Deposition and Thermo-Chemical Properties of Al/Fe2O3 Nanothermite Thick Films

Jie Wu, Songbai Xue*, Denzel Bridges, Yongchao Yu, Cary Smith, Kunlun Hong, Curtis Hill, Zhili Zhang, Zhili Feng, and Anming Hu*

Eng. Sci., 2018, 4, 52-64

DOI: 10.30919/es8d751

Abstract：We have successfully fabricated α-Fe₂O₃ oxidizers with different shapes, including nanoparticles (NPs, diameter: ~22.1 nm), nanorods (NRs, length: 385.3 nm) and nanowires (NWs). For the Al/Fe2O3 NPs thermite reaction, as the nominal weight ratio for Al/Fe2O3 (NPs)  reaches 2.5:1, the fastest combustion velocity (2.03 m/s), the largest instant plume propagation speed (10.71 m/s) as well as the maximum heat release (~9.46 kJ/g) can be achieved. However, with the same nominal weight ratio, the average combustion velocity and the instant plume speed of Al/Fe₂O₃ (NRs) and Al/Fe nitrilotriacetic acid precusors NWs (FeNTA,) nanothermite are only about 0.16 m/s and 4.96 2 3 m/s, and 0.098 m/s and 3.28 m/s, respectively. This is probably due to the shape difference that renders different contact configurations between nano-fuel and nano-oxidizer. In addition, an incomplete calcination of FeNTA is also responsible for such a low combustion velocity. The reaction products were further identified by SEM and XRD analysis. Accordingly, the reaction mechanisms for the examined nanothermites were mainly controlled by the oxygen transfer dynamics.

Indium Recovery from Waste Liquid Crystal Display via Chloride Volatilization Process: Thermodynamic Computation

Yaoguang Guo, Qichao Zhang, Xiaoyi Lou, Huili Liu, Jiangbin Wang, Jie Guan, Xin Xu, Xiaojiao Zhang, Yaguang Li, Yingshun Li and Zhanhu Guo*

Eng. Sci., 2018, 4, 65-69

DOI: 10.30919/es8d752

Abstract:With the increase of the scrap liquid crystal displays (LCDs), recycling indium from waste LCDs has captured an international attention. Chloride metallurgy is a promising method for indium recovery from LCD panels, due to the lower boiling point of indium chloride. In the present study, thermodynamic analyses of indium recovery from waste LCDs via chloride volatilization process by the HSC Chemistry software was carried out to understand the reaction mechanism between chlorinating agent and LCDs to avoid adverse factors, and simultaneously obtain the optimal conditions for the extraction of indium. The results show that the recovered indium from LCDs with HCl as the chlorinating agent from the PVC pyrolysis is feasible, with the chlorination temperature controlled between 134.49 and 554.25℃, and the evaporation temperature higher than 490℃, and simultaneously, the oxygen partial pressure controlled or under anaerobic conditions. As such, the influences of SiO₂, Al₂O₃ and Fe₃O₂, contained in LCDs, can be ignored or avoided, and only CaO, K₂O and Na2O would consume partial pressure of HCl gas, reducing the indium recovery reaction rate. The present study might provide important inspiration for indium recovery from waste LCDs via chloride volatilization process.

High-performance Engineered Conducting Polymer Film towards Antimicrobial/Anticorrosion Applications

Amit Nautiyal, Mingyu Qiao, Tian Ren, Tung-Shi Huang*, Xinyu Zhang*, Jonathan Cook, Michael J. Bozack and Ramsis Farag

Eng. Sci., 2018, 4, 70-78

DOI: 10.30919/es8d776

Abstract:The goal of this study was to develop a multifunctional coating material that possessed both electrical and antimicrobial properties. Polypyrrole (PPy) has proved to be transformed into N-halamine after its treatment with chlorine bleach. This PPy based N-halamine was tested to have superior antimicrobial efficacy. Its coating inactivated more than 6 log CFU of both Staphylococcus aureus and Escherichia coli O157:H7 within one min of contact time. The stability of PPy based N-halamine was excellent, maintaining 50% of functional groups after a week storage under fluorescent light. PPy N-halamine coating was successfully synthesized by chlorination of electrodeposited PPy coating on the surface of stainless steel. This PPy N-halamine coating on stainless steel inactivated 6 log CFU of S. aureus within 60s of contact and the antimicrobial activity remained unchanged after a “recharge” cycle. In addition, the PPy N-halamine coating significantly enhanced its the anticorrosion functionality by anodically shifting the corrosion potential. This method of preparing antimicrobial/anticorrosion coating is facile, green and highly effective. The produced PPy N-halamine showed great potential to be applied as multifunctional coating for protecting steels in harsh environments.

Enhancing Dielectric Performance of Poly(vinylidene fluoride) Nanocomposites via Controlled Distribution of Carbon Nanotubes and Barium Titanate Nanoparticles

Jing Wang, Zhicheng Shi*, Xin Wang, Xianmin Mai, Runhua Fan, Hu Liu, Xiaojing Wang and Zhanhu Guo*

Eng. Sci., 2018, 4, 79-86

DOI: 10.30919/es8d759

Abstract:Polymer-based dielectric materials have attracted increasing attention owing to their huge potential applications in modern electronic devices. The dielectric behaviors of polymer composites are greatly determined by the distribution of fillers, thus the clarification of the relationship between the dielectric properties of the composites and the spatial distribution of fillers would be highly favorable for designing novel high-performance dielectrics. Herein, the dielectric performances of ternary composites consisting of barium titanate (BT), carbon nanotube (CNT) and poly(vinylidene fluoride) (PVDF) were investigated. For comparison, the dielectric properties of trilayer 3 composites were also studied. The ternary composites exhibited an ultra-high dielectric constant of 7×10 @10 kHz, but a high loss tangent of 25 @10 kHz. For the trilayer composites, the BT/PVDF outer layers could restrain the development of leakage current, leading to low loss tangent (0.03 @10 kHz) and high breakdown strength. Meanwhile, the trilayer composites also achieved a high dielectric constant of 95 @10 kHz owing to the considerably enhanced polarizations at the filler/matrix and layer/layer interfaces. This research provides important sights into the relationship between the dielectric properties of the composites and the spatial distributions of fillers, which will strongly boost the exploration of high-performance dielectrics.

2S-Soy Protein-Based Biopolymer as a Non-Covalent Surfactant and Its Effects on Electrical Conduction and Dielectric Relaxation of Polymer Nanocomposites

Zhuoyuan Zheng, Olaseeni Olayinka and Bin Li*

Eng. Sci., 2018, 4, 87-99

DOI: 10.30919/es8d766

Abstract:2S-soy protein, a biopolymer extracted from soy protein isolate (2S-SPI), was studied as a non-covalent surfactant for polymer nanocomposites. This study showed that 2S-SPI effectively improved carbon nanofibers (CNFs) dispersion in poly(vinylidene fluoride). 2S-SPI surfactant had remarkable impact on both electrical conduction and dielectric relaxation of the nanocomposites, particularly, at high temperatures. 2S-SPI modified CNFs caused coupling of conductivity relaxation and structural relaxations of the nanocomposites, in contrast to pristine CNFs. Both Maxwell–Wagner–Sillars and conductivity relaxations were enhanced at high temperatures by 2S-SPI, which made different contributions to electrical conduction of the nanocomposites with or without surface modification.

Modulatory Effects of the Composition and Structure on the Osteogenic Enhancement for Superparamagnetic Scaffolds

Suisui Hao, Yaoyi Shen, Haoan Wu, Jie Meng, Lifei Xie, Tao Wen, Ning Gu, Jian Liu*, Yu Zhang* and Haiyan Xu*

Eng. Sci., 2018, 4, 100-110

DOI: 10.30919/es8d782

Abstract:Increasing evidence shows that superparamagnetic scaffolds can enhance the osteogenesis under magnetic fields. The aim of this work is to compare the magnetization and the osteogenic enhancement of superparamagnetic scaffolds composed of different compositions with different microstructures. Herein 9 kinds of superparamagnetic scaffolds of PLA, polyurethane and gelatin were fabricated by incorporating iron oxide nanoparticles in polymeric matrices, and using the process of electrospinning, salt-leaching, and solution casting to obtain microstructure of nanofibrous, porous and smooth respectively, while hydroxyapatite nanoparticles were incorporated in all the scaffolds with the same percentage. It was showed that the magnetization behavior of the scaffolds was associated with the composition and microstructure as well as with the osteogenic enhancement of the scaffolds. The nanofibrous scaffold composed of PLA, nHA and MNPs possessed the strongest magnetization, and significantly promoted the osteogenic differentiation of pre-osteoblasts and bone marrow derived mesenchymal stem cells (bMSCs) under magnetic fields, evidenced by the upregulated gene expression of Runx2 and BMP2, the increased ALP activity, OPN and OCN of the cells. The optimal scaffold recruited more bMSCs and enhanced the osteogenic differentiation and the cross talk among the bMSCs, macrophages and fibroblasts under the magnetic field.

Long-Lived Room-Temperature Phosphorescent Nitrogen-Doped CQDs/PVA Composites: Fabrication, Characterization and Application

Xueyun Wu, Wei Li*, Peng Wu, Chunhui Ma, Yushan Liu, Mingcong Xu and Shouxin Liu*

Eng. Sci., 2018, 4, 111-118

DOI: 10.30919/es8d785

Abstract:Room-temperature phosphorescent (RTP) materials have attracted significant attention because of their potential applications in anticounterfeiting and optical imaging. However, most RTP materials developed to date have short-lived lifetimes, because the triplet excited states are easily quenched by atmospheric oxygen, thus limiting their full potential. Herein, nitrogen-doped carbon quantum dots (NCQDs), prepared by hydrothermal method, are dispersed into a poly(vinyl alcohol) matrix to fabricate phosphorescent materials with ultralong lifetimes at ambient temperature and atmosphere. The N-CQDs/PVA composites, which are 3D aerogel and thin film respectively, display a long lifetime of 442 ms and an average lifetime of 416 ms at ambient conditions. The efficient room-temperature phosphorescence phenomenon can be attributed to the small energy gaps between the singlet and triplet states (ΔE ) of 0.246 eV and 0.23 S,T eV of the RTP materials (aerogel and thin film, respectively), thus facilitating state population through intersystem crossing. In addition, PVA molecule is able to inhibit quenching of the triplet excited state by oxygen, consequently promoting phosphorescence production at ambient conditions. Furthermore, the N-CQDs/PVA composites can be prepared in different physical forms, i.e., as solution, film, or aerogel as per the requirements of varied potential applications in optical imaging, writing, anti-counterfeiting, or sensors.