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Urea-formaldehyde resin penetration into Pinus radiata tracheid walls assessed by TEM-EDXS
Singh, Adya P.,Nuryawan, Arif,Park, Byung-Dae,Lee, Kwang Ho Walter de Gruyter GmbH 2015 Holzforschung Vol.69 No.3
<B>Abstract</B><P>This paper reports a new method of detecting urea-formaldehyde (UF) resin penetration into the cell walls of radiata pine (<I>Pinus radiata</I> D. Don) by means of transmission electron microscopy (TEM) in combination with energy-dispersive X-ray spectroscopy (EDXS). The quantifications of penetrated UF resin in the ultrathin cuts of cell walls were realized by detecting nitrogen (N) element by TEM-EDXS. Both line scan and area mapping revealed N in cell walls in contact with resin-filled lumens but not in those in contact with empty lumens. Thus, UF resin had penetrated the cell walls from the lumen side.</P>
Tensile Properties and Thermal Stability of Cellulose Nanofibril/Clay Nanocomposites
Park, Byung-Dae,Singh, Adya P.,Um, In Chul Institute of Agricultural Science and Technology 2013 慶北大農學誌 Vol.31 No.1
This work attempted to fabricate organic/inorganic nanocomposite by combining organic cellulose nanofibrils (CNFs), isolated by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation of native cellulose with inorganic nanoclay. The morphology and dimension of CNFs, and tensile properties and thermal stability of CNF/clay nanocomposites were characterized by transmission electron microscope (TEM), tensile test, and thermogravimetry (TG), respectively. TEM observation showed that CNFs were fibrillated structure with a diameter of about $4.86{\pm}1.341nm$. Tensile strength and modulus of the hybrid nanocomposite decreased as the clay content of the nanocomposite increased, indicating a poor dispersion of CNFs or inefficient stress transfer between the CNFs and clay. The elongation at break increased at 1% clay level and then continuously decreased as the clay content increased, suggesting increased brittleness. Analysis of TG and derivative thermogravimetry (DTG) curves of the nanocomposites identified two thermal degradation peak temperatures ($T_{p1}$ and $T_{p2}$), which suggested thermal decomposition of the nanocomposites to be a two steps-process. We think that $T_{p1}$ values from $219.6^{\circ}C$ to $235^{\circ}C$ resulted from the sodium carboxylate groups in the CNFs, and that $T_{p2}$ values from $267^{\circ}C$ to $273.5^{\circ}C$ were mainly responsible for the thermal decomposition of crystalline cellulose in the nanocomposite. An increase in the clay level of the CNF/clay nanocomposite predominately affected $T_{p2}$ values, which continuously increased as the clay content increased. These results indicate that the addition of clay improved thermal stability of the CNF/clay nanocomposite but at the expense of nanocomposite's tensile properties.
Nuryawan, Arif,Singh, Adya P.,Park, Byung-Dae,Causin, Valerio Taylor Francis 2016 The Journal of adhesion Vol.92 No.2
<P>This work examined micro-morphological features responsible for the crystallinity of cured urea-formaldehyde (UF) adhesives, using transmission electron microscopy (TEM) to identify and characterize distinctive crystalline structures in resins obtained with different formaldehyde to urea (F/U) mole ratios and hardener levels. The TEM examination of cured UF resin adhesives impregnated into wood cell lumen revealed the presence of spherical particles with variable diameter and number per unit area. The diameter and number/area of the spherical particles increase for decreasing F/U mole ratio and decrease with an increase in the hardener levels, an effect which is closely related to their crystallinity. Therefore, the present findings suggest that the spherical particles are responsible for the crystallinity of cured UF resin adhesives. The results also indicate that crystalline structures represent an inherent feature of cured UF resin adhesives, particularly for low F/U mole ratios, even though these resins are usually classified as amorphous and cross-linked thermosetting polymers.</P>
Light and Electron Microscopic Characterization of Husk from Korean Rice
Adya P,Singh,Park,Byung-Dae,Wi,Seung-Gon,Lee,Kwang-Ho,Yoon,Tae-Ho,Kim,Yoon-Soo 한국자원식물학회 2002 Plant Resources Vol.5 No.2
Microscopic techniques were used to observe the microstructure of rice husk. Microscopic examination showed that two main components of husk, lemma and palea consisted of outer epidermis, layers of fibers, vascular bundles, parenchyma cells, and inner epidermis, in sequence from the outer to the inner surface. The outer epidermal walls were extremely thick, highly convoluted and lignified. The underlying fibers were also thick-walled and lignified. Parenchyma cells were thin-walled and unlignified. Inner epidermal cells were also unlignified. The outer surface of both lemma and palea were conspicuously ridged, but the lower surface had a flat appearance. As part of a detailed study to characterize rice husk using microscopic and micro-analytical techniques, distribution of silica was also examined, and is presented elsewhere. Rice husk can potentially be used as a raw material for making composite products and the observations presented here form valuable background information for our future work related to product development.
DSTATCOM APPLICATION FOR POWER QUALITY IMPROVEMENT IN DISTRIBUTION SYSTEM
J.R.P.Gupta,Alka Adya,Bhim Singh,A.P.Mitta 전력전자학회 2004 ICPE(ISPE)논문집 Vol.- No.-
Good quality power supply is a prerequisite for industrial growth. Power quality and reliability cost the industry large amounts each year. Hence, a major challenge for engineers these days is to use the advances in Power Electronic devices and technology to control power flow and provide adaptable, fastacting reactive power correction to changing electrical loads. FACTS (Flexible AC Transmission System) controllers have revolutionized the world in the area of generation, transmission and distribution of power. This paper focuses on DSTATCOM (Distribution Static Synchronous Compensator) which is gaining popularity along with other custom power devices like DVR (Dynamic Voltage Restorer) and UPQC (Unified Power Quality Compensator). This paper deals with various aspects like design, modeling and simulation of DSTATCOM for the power quality improvements.
Tensile Properties and Thermal Stability of Cellulose Nanofibril/Clay Nanocomposites
Byung-Dae Park,Adya P. Singh,In Chul Um 경북대학교 농업생명과학대학 2013 Current Research on Agriculture and Life Sciences Vol.31 No.1
This work attempted to fabricate organic/inorganic nanocomposite by combining organic cellulose nanofibrils (CNFs), isolated by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation of native cellulose with inorganic nanoclay. The morphology and dimension of CNFs, and tensile properties and thermal stability of CNF/clay nanocomposites were characterized by transmission electron microscope (TEM), tensile test, and thermogravimetry (TG), respectively. TEM observation showed that CNFs were fibrillated structure with a diameter of about 4.86±1.341 nm. Tensile strength and modulus of the hybrid nanocomposite decreased as the clay content of the nanocomposite increased, indicating a poor dispersion of CNFs or inefficient stress transfer between the CNFs and clay. The elongation at break increased at 1% clay level and then continuously decreased as the clay content increased, suggesting increased brittleness. Analysis of TG and derivative thermogravimetry (DTG) curves of the nanocomposites identified two thermal degradation peak temperatures (Tp1 and Tp2), which suggested thermal decomposition of the nanocomposites to be a two steps-process. We think that Tp1 values from 219.6℃ to 235℃ resulted from the sodium carboxylate groups in the CNFs, and that Tp2 values from 267℃ to 273.5℃ were mainly responsible for the thermal decomposition of crystalline cellulose in the nanocomposite. An increase in the clay level of the CNF/clay nanocomposite predominately affected Tp2 values, which continuously increased as the clay content increased. These results indicate that the addition of clay improved thermal stability of the CNF/clay nanocomposite but at the expense of nanocomposite’s tensile properties.