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Kafy, Abdullahil,Sadasivuni, Kishor Kumar,Kim, Hyun-Chan,Akther, Asma,Kim, Jaehwan The Royal Society of Chemistry 2015 Physical chemistry chemical physics Vol.17 No.8
<P>The demand for flexible energy storage devices is ever increasing, and several polymer nanocomposites are widely used to fabricate them. Here, we present a cellulose based nanocomposite by incorporating graphene oxide (GO) nanoplatelets modified with hexamethylene diisocyanate grafting agent useful for such versatile applications. The simple method of casting/solvent evaporation is applied to prepare the nanocomposites and GO dispersion in the cellulose matrix was analyzed by Fourier transform infrared spectroscopy, X-ray diffraction studies and scanning electron microscopy. The dielectric and ferroelectric properties of the eco-friendly samples were checked with temperature and voltage variations, which can attribute to flexible energy and memory storage properties. Thus, the cellulose modified GO nanocomposite has turned to be environmentally stable and excellent next generation material for energy storage and electronic devices.</P> <P>Graphic Abstract</P><P>The demand for flexible energy storage devices is ever increasing, and several polymer nanocomposites are widely used to fabricate them. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp05921b'> </P>
Akther, Asma,Kafy, Abdullahil,Zhai, Lindong,Kim, Hyun Chan,Shishir, MD Imrul Reza,Kim, Jaehwan IOP 2016 Smart materials & structures Vol.25 No.11
<P>This study deals with ultrasonic wave propagation on a piezoelectric polymer substrate for tactile actuator. On the piezoelectric polymer substrate, a pair of interdigital transductor (IDT) electrodes is patterned by lift-off process and a resonator is made by exciting the IDTs. A standing wave is generated between the pair of IDT electrodes, of which the wavelength matches with the distance between two IDTs. The standing ultrasonic waves can give different textures to the users. The wave propagation in this periodic structure on the polymer substrate is studied by harmonic and transient analysis. Vertical displacement and induced voltage at the output IDT electrode are calculated and the ultrasonic wave generation is experimentally verified. The proposed concept of tactile actuator based on ultrasonic wave is explained.</P>
Calcinated tea and cellulose composite films and its dielectric and lead adsorption properties
Jayaramudu, Tippabattini,Varaprasad, Kokkarachedu,Kim, Hyun Chan,Kafy, Abdullahil,Kim, Jung Woong,Kim, Jaehwan Applied Science Publishers 2017 Carbohydrate polymers Vol.171 No.-
<P><B>Abstract</B></P> <P>In this paper, calcinated tea and cellulose composite (CTCC) films were fabricated via solution casting method. Chemical structure, morphology, crystallinity and thermal stability of the fabricated films were characterized by using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. The effect of calcinated tea loading on the properties of the prepared CTCC films was studied. The results suggest that the prepared CTCC films show higher mechanical properties, thermal stability and dielectric constant than the neat cellulose film. In addition, the CTCC films adsorb Pb<SUP>2+</SUP> ions and its adsorption performance depends on the calcinated tea content and pH level. The CTCC films are useful for sensors, flexible capacitor as well as lead adsorption applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Calcinated tea based cellulose composite (CTCC) film was prepared by blending method. </LI> <LI> The CTCC film shows 4 times higher dielectric constant than the pure cellulose. </LI> <LI> The CTCC film demonstrates lead adsorption, depending on the CT content and pH. </LI> <LI> The CTCC film is useful for sensor, flexible capacitor and metal adsorption. </LI> </UL> </P>
Joel Renaud Ngouanom Gnidakouong,Xiaoyuan Gao,Abdullahil Kafy,Jaehwan Kim,Joo‑Hyung Kim 한국탄소학회 2019 Carbon Letters Vol.29 No.2
Low cost and scalable manufacturing of highly doped cellulose for enhanced multifunctional applications is still an issue. In this work, eco-friendly nanocomposites were fabricated by incorporating regenerated cellulose (RC) of 10, 30, and 50 wt% into an exfoliated graphene nanoplatelets (GNPs), resulting in the intercalation of GnPs. The thermal and electrical properties of hybrid nanocomposites were investigated. The structural property was conducted through scanning electron microscope and X-ray diffraction analyses. Strong frequency-dependent dielectric response was found due to the change of the permittivity and the loss tangent of nanocomposites by different content of RC, which is associated with the polarizations behavior. Non-elastic relaxation at the GNPs–RC chains interfacial areas in an alternating field was identified as the main cause of polarization losses among others. Detailed ferroelectric measurements provided the evidence of the ideal resistive behavior of the nanocomposites, which are confirmed by the resistivity measurements along the out-of-plane direction of the nanocomposite sheets.
Kim, Hyun Chan,Mun, Seongcheol,Ko, Hyun-U,Zhai, Lindong,Kafy, Abdullahil,Kim, Jaehwan IOP 2016 Smart materials & structures Vol.25 No.7
<P>The use of renewable materials is essential in future technologies to harmonize with our living environment. Renewable materials can maintain our resources from the environment so as to overcome degradation of natural environmental services and diminished productivity. This paper reviews recent advancement of renewable materials for smart material applications, including wood, cellulose, chitin, lignin, and their sensors, actuators and energy storage applications. To further improve functionality of renewable materials, hybrid composites of inorganic functional materials are introduced by incorporating carbon nanotubes, titanium dioxide and tin oxide conducting polymers and ionic liquids. Since renewable materials have many advantages of biocompatible, sustainable, biodegradable, high mechanical strength and versatile modification behaviors, more research efforts need to be focused on the development of renewable smart materials.</P>