Mechanical and Interfacial Properties of Flax Fiber-reinforced Plastic Composites Based on a Chemical Modification Method

Hongguang Wang,HAO WU,Lanjie Yang,Guanglong Yu 한국섬유공학회 2020 Fibers and polymers Vol.21 No.7

Due to growing interest in environmental protection, eco-friendly fibers with high specific strength and low costare widely used to reinforce matrix materials. Flax fiber is a natural renewable plant fiber that originates from the phloem offlax. Flax fibers not only have the characteristics of other natural fibers but also have the outstanding mechanical properties ofnatural fibers. However, due to the large amount of hydrophilic hydroxyl groups on the surface, the hydrophilic absorption offlax fibers is large, and the wet-heat durability of the composite is poor, which limits the use of flax fiber as a reinforcementmaterial in civil engineering applications. In this study, based on the research results of flax fiber, a flax fiber sheet wasgrafted with multiwalled carbon nanotubes, a silane coupling agent and nano-TiO2 particles. The effect of different treatmentmethods and process parameters on the mechanical and interfacial properties of flax fiber-reinforced plastic (FFRP)composites materials was studied. The results show that the FFRP composites grafted with multiwalled carbon nanotubeshave higher tensile strength and interlaminar shear strength than those grafted with the same content of nano-TiO2 particles. Flax fiber composites with improved interfacial properties can be obtained by grafting flax fiber sheets, but the content ofparticles on the flax fiber surface should not exceed 2.0 wt.% of nano-TiO2 and multiwalled carbon nanotubes. Under thistreatment, the FFRP composites have improved properties, such as tensile strength, interlaminar shear strength and glasstransition temperature.

Mechanical and Thermodynamic Properties of Unidirectional Flax Fiber Reinforced CNT Modified Epoxy Composites

Hongguang Wang,Lanjie Yang,Huajie Guo,Yagebai Zhao,Jianing Zhao 한국섬유공학회 2019 Fibers and polymers Vol.20 No.6

In this paper, the mechanical and thermodynamic properties of diglycidyl ether of bisphenol-F (DGEBF) epoxyresin and flax fiber FRP composites, which was modified with multi-walled carbon nanotubes (MWCNTs) were studied. Themechanical property tests show significant improvements in the tensile strength (48.7 %), tensile modulus (25.2 %) at1.0 wt.% of MWCNTs. DMTA test reveals that mixture of 1.0 wt.% MWCNTs into the epoxy resin increases 10.68 K of Tg,which is in accordance to the simulated results from molecular dynamics. These improvements in mechanical andthermodynamic properties are attributed to the balanced effect of stress concentration and radiation. The mechanical andthermodynamic properties of flax fiber FRP composites are improved with the addition of MWCNTs. This study is expectedto provide an opportunity to develop high performance of natural fiber FRP composites.

Relevance and L2 Learners' Interpretation of Reflexive Anaphora in VP-Ellipsis: An Exploration of the Relationship between Relevance Theory and Typological Universals

Hongguang Ying 세종대학교 언어연구소 2005 Journal of Universal Language Vol.6 No.1

Twenty-eight intermediate and twenty-two advanced L2 learners (the experimental groups) and twenty native speakers of English (the control group) participated in a study that investigated second language learners interpretation of reflexives in the VP-elliptical sentences. 17 experimental sentences in a null context, 17 experimental sentences followed by a referential context favoring the strict reading interpretation, 17 experimental sentences followed by a non-referential context not favoring the strict reading interpretation, and 51 filler items were presented to the participants using a judgment task in which each sentence is followed by two alternative interpretations (Frazier & Cliffton, 2000). The results indicate that adult L2 learners interpretation of such construction in English was constrained by the minimal processing cost and contextual effects of RT. They interpreted the 160 Relevance and L2 Learners Interpretation of Reflexive Anaphora in∼ reflexive in a null context sloppily, indicating the constraints of the minimal processing cost of RT. The contextual effects of RT were shown in their strict reading of the reflexive in a referential context. The relationship of relevance theory and typological universals in terms of context, constraints, economy and cognitive considerations is also discussed.

Tunable exchange bias in La1.5Sr0.5CoMnO6 double perovskite doped with nonmagnetic Ga ions

Zhang Hongguang,Chen Wei,Xie Liang,Zhao HuiHui,Li Qi 한국물리학회 2022 Current Applied Physics Vol.35 No.-

The crystal structure, electronic structure, and magnetic behaviors of nonmagnetic Ga ions doped double perovskite La1.5Sr0.5CoMnO6 single phase crystals have been investigated. Different from the traditional magnetic dilution effect of nonmagnetic doping, Ga doping in La1.5Sr0.5CoMnO6 enhances the ferromagnetic (FM) exchange interaction of Co3+-O-Mn3+. Moreover, both conventional and spontaneous exchange bias (EB) effects can be tuned by modulating the Ga doping content, which is accompanied by the variation of the Co3+/4+ and Mn3+/4+ and the effective magnetic moment. The EB field and magnetization can be improved by nonmagnetic Ga3+ doping with content lower than 0.2. The evolution of conventional and spontaneous EB effects in La1.5Sr0.5Co1-xGaxMnO6 can be understood in terms of the unidirectional interface anisotropic coupling between FM/anti-FM, and/or FM/spin glass, which is affected by antisite disorder, spin glass, and the uncompensated coupling between Co and Mn.

Electric field assisted oxygen removal from the basal plane of the graphitic material

Liu, Hongguang,Lee, Jin Yong Wiley Subscription Services, Inc., A Wiley Company 2013 Journal of computational chemistry Vol.34 No.4

<P><B>Abstract</B></P><P>We provide a novel strategy to eliminate the epoxy group from the basal plane of graphene platelets. Given that the current reduction methods are unsatisfactory to clean the epoxides or sometimes cause undesirable structure deformations, the proposed strategy restores the original hexagonal carbon network without creating other new defects. To the best of our knowledge, the electric field mediated graphene oxide (GO) reduction has not yet been systematically investigated. The capability would permit the improvement of existing GO reduction methods and assist in the fabrication of high‐quality graphitic materials. © 2012 Wiley Periodicals, Inc.</P>

Hidden Role of a Hydroxyl Group in Mediating the Oxygen Line Defect on a Graphene Surface

Liu, Hongguang,Kang, Baotao,Lee, Jin Yong American Chemical Society 2013 The Journal of Physical Chemistry Part C Vol.117 No.34

<P>Atomic fault lines stemming from the linear assembly of epoxy groups are recently proposed to be responsible for the decrease of bulk size of graphitic materials. Yet, the formation of such a line by either the hopping of existing epoxides or the binding with environmental atomic oxygens seems to be infeasible. By employing both finite and periodic graphene models, we uncovered the role of hydroxyl, which is essentially ignored in previous reports, in mediating the epoxy line. It is noteworthy that the intercalation of OH impedes the unzipping of underlying carbons and induces a smoother surface buckling along the epoxy line. The fault line formation would be ascribed to the creation of vacancies when the system temperature elevates.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-34/jp4052159/production/images/medium/jp-2013-052159_0010.gif'></P>

Electronic Structures and Charge Transport of Stacked Annelated β-Trithiophenes

Liu, Hongguang,Kang, Sunwoo,Lee, Jin Yong American Chemical Society 2011 The Journal of physical chemistry B Vol.115 No.18

<P>Density functional theory (DFT) calculations were performed using a MPWB1K functional to interpret the charge transport (CT) properties of stacked annelated β-trithiophene molecules. The goal was to help understand how the chemical composition, face-to-face stacking, intra- and intermolecular correlations, and the applied electric field affect the CT properties of this organic semiconductor compared with those of the edge-to-face “herringbone” motif. The variations in the frontier molecular orbitals, energy gap, nonadiabatic electron attachment energies (EAE), and vertical detachment energies (VDE) were investigated under an external electric field as a function of the number of stacked layers (<I>n</I>). Two possible CT pathways, monomer-to-monomer (MM) and dimer-to-dimer (DD) transports, were postulated to determine the charge carrier conductivities of these molecules. The results highlight that the intermolecular electronic couplings and electrostatic interactions can significantly affect the stacking geometry, even in more extended structures; displaced stacks with smaller interlayer spacing resulted in more compact stacking and, thus, higher CT efficiency; face-to-face stacking geometries can help to reduce the energy gap and VDE. Despite the fact that common thiophene-based oligomers adopting edge-to-face herringbone motifs exhibited p-type (hole-transporting) characters, the face-to-face stacked models based on annelated β-trithiophenes exhibited remarkably increased n-type (electron-transporting) performances. The electric field in the <I>z</I>-direction produced a small influence on the DD charge transport, whereas both electron and hole mobilities decreased dramatically in the MM case. More importantly, in MM charge transport, the electric field increases the hole mobility so that it is higher than that of the electron.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2011/jpcbfk.2011.115.issue-18/jp1045595/production/images/medium/jp-2010-045595_0008.gif'></P>

The exchange bias effect and Griffiths phase in La1.5Sr0.5Co1-Ni MnO6: The impact of the divalent Ni

Zhang Hongguang,Wang Sen,Chen Wei,Wang Mingjun,Li Yongtao,Xie Liang 한국물리학회 2023 Current Applied Physics Vol.53 No.-

The effects of Co-site doping of Ni2+ ions on the crystal structure, electronic structure, and magnetic properties of La1.5Sr0.5CoMnO6 are investigated. The doping causes an increase in the anti-site disorder and a change in the content of Co2+/3+ and Mn3+/4+, as well as a change in the spin state of Co ions. Ni doping introduces Ni2+-O2-- Mn4+ ferromagnetic interactions to increase the ferromagnetic transition temperature. Samples display different dominant clusters, and field cooling promotes the presence of ferromagnetic clusters, allowing an increase in the Griffiths phase. Interestingly, Ni doping enables tuning the conventional and spontaneous exchange bias (EB) effects, increasing the EB field for intermediate concentrations. Moreover, the maxima of both EB fields do not occur in the same sample, which leads to a new understanding of the relationship between these two effects. The possible mechanisms related to the uncompensated spin and competition between ferromagnetic and antiferromagnetic clusters are discussed, respectively.

Electric Field Effectson the Adsorption of CO ona Graphene Nanodot and the Healing Mechanism of a Vacancy in a GrapheneNanodot

Liu, Hongguang,Lee, Jin Yong AmericanChemical Society 2012 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.116 No.4

<P>It is well known that the external electric field caneffectivelymodify the electronic structures and transport properties of low-dimensionalsystems. However, to our knowledge, the corresponding atomic structureand adsorption property changes of a graphene carbon network underdifferent applied electric fields have not been investigated. Herein,using first-principles DFT calculations, we have systematically exploredthe CO adsorption on the pristine graphene nanodot and the defectiveone by taking the external electric field into account. It is foundthat the electric field can increase the CO adsorption energy andthere is a barrier for CO–vacancy recombination that is mostlybelieved to remerge instantaneously when they come close to each other.Also, we proposed a mechanism for the subsequent healing of a monovacancyon a graphene nanodot by interaction with CO molecules, leading tothe restoration of a pristine hexagonal carbon network.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-4/jp210719r/production/images/medium/jp-2011-10719r_0008.gif'></P>

Oxygen adsorption on single layer graphyne: a DFT study

Kang, Baotao,Liu, Hongguang,Lee, Jin Yong The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.3

<P>Graphyne is a rising two-dimensional (2D) carbon allotrope with excellent electronic properties. In this paper, theoretical calculations were performed to study the corresponding electronic properties of the oxygenated graphyne. Atomic oxygen when bound to the carbon atom of graphyne forms a stable oxide, with a much larger binding energy compared to that on graphene. Owing to the oxygen adsorption, the α- and β-graphyne change from a zero-band-gap material to a semiconductor as indicated in the band structure calculations. Moreover, spin splitting was observed from the band structure of the oxygenated γ-graphyne. These electronic properties are tunable by altering the oxygen coverage through changing the supercell size. Our results based on the first-principles calculations imply that oxygenation is a promising method to functionalize graphyne to achieve designated properties.</P> <P>Graphic Abstract</P><P>In this paper, theoretical calculations were performed to study the corresponding electronic properties of oxygenated graphyne. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp53237b'> </P>