• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.43 no.2
• /
• pp.66-71
• /
• 2011

Biocomposites were fabricated with biodegradable polymers and natural fibers. Biocomposites have benefits of low cost, low density, and biodegradability over inorganic fiber composite, and give comparable strength properties. Hydrophobic polymer used for sizing in paper industry, AKD (Akenyl Keten Dimer), was applied to natural fibers, red algae fibers (RAF) in this study, to make fiber surfaces more compatible to hydrophobic nature of matrix polymers. Composites with RAF, kenaf, glass fibers, and carbon fibers have been fabricated by a compression molding method and their thermo-mechanical properties have been studied. Also, the thermal dimensional stability test was done from at 30 to $100^{\circ}C$. The storage moduli and the thermo-mechanical stabilities of polypropylene and poly lactic acid based biocomposites were improved by reinforcing with the RAF and much more with AKD treated fibers. Dimensional stability of biocomposite was also markedly improved by AKD pretrement on RAF.

• Journal of the Korean Ceramic Society
• /
• v.43 no.8 s.291
• /
• pp.486-491
• /
• 2006

A new $TiN-Ti_5Si_3$ bulk composite was synthesized from preceramic, inorganic polymer (methylpolysilsesquioxane) and $TiH_2$ filler powders via polymer pyrolysis. Using this process, ceramics with high melting points can be produced relatively easily to a near net shape. The $TiN-Ti_5Si_3$ composite oxidized slowly during heating to $1000^{\circ}C$. During heating at the temperatures of at 700 and $800^{\circ}C$, TiN oxidized to Rutile-$TiO_2$ whereas $Ti_5Si_3$ resisted to oxidation. The oxide scale formed consisted primarily of $TiO_2$ containing $Ti_5Si_3$.

• Transactions on Electrical and Electronic Materials
• /
• v.12 no.4
• /
• pp.160-163
• /
• 2011

Polymer nanocomposite has been attracting more attention as a new insulation material because homogeneous dispersion of nano-sized inorganic fillers can improve various properties significantly. In this paper, various kinds of epoxy-based nanocomposites were made, and the AC breakdown strengths of Nano filler and micro-$SiO_2$ filler mixtures of epoxy-based composites were analyzed using sphere-to-sphere electrodes. Moreover, nano- and microfiller combinations were investigated as an approach to practical application of nanocomposite insulation materials. Its composition ratio was 100 (resin):82 (hardener):1.5 (accelerator). AC breakdown tests were performed at room temperature ($25^{\circ}C$), $80^{\circ}C$, and $100^{\circ}C$ in the vicinity of $T_g$ ($90^{\circ}C$). Thermal conductivity was measured using TC-30.

• Elastomers and Composites
• /
• v.45 no.3
• /
• pp.156-164
• /
• 2010

Thermoplastic elastomers (TPEs) exhibit both elastomeric behaviors at used temperature range and melt processibility. Polyamide based thermoplastic elastomers (TPAEs) are segmented block copolymers with hard blocks consisting of polyamide segments, while the soft blocks usually consist of flexible segments having a low glass transition temperature. The TPAE is one of the engineering TPEs possessing high thermal stability, excellent mechanical performances, chemical resistance and excellent processibility. And they showed wide range of physical and functional properties depending upon the structure of each segment and their relative contents and the hybridization with various inorganic particles. In this review, synthesis, properties, and possible applications of TPAEs are summarized.

• Elastomers and Composites
• /
• v.30 no.1
• /
• pp.20-31
• /
• 1995

The purpose of this study is to investigate the reinforcement of inorganic filler silica, treated by MDI about SBR vulcanizate. The characteristics of vulcanization, physical properties, surface properties and dynamic properties were investigated after mixing those silica with SBR and unmodified silica with SBR. In this experiment only the quantity of silica was variable. In the vulcanization characteristics tested by rheometer, S-series showed the fastest scorch $time(t_{10})$ and optimum cure $time(t_{90})$. And in test or tensile characteristics hardness, tensile strength, 100%, 300% modulus and elongation were all appeared in the order of M>S-series. The characteristic bonding of urea between unmodified silica and MDI could be confirmed in IR spectrum. The shapes of silicas treated chemically were observed by SEM. And the dispersion of the filler in the SBR composite was uniform. In the dynamic characteristics by the RDS, the order of elastic modulus G' values was as follows : M>S-series, and also the order of damping values was as follows : M>S-series.

• Journal of the Korean Ceramic Society
• /
• v.35 no.10
• /
• pp.1020-1029
• /
• 1998

The reaction-bonded TiC-Ni/Si/Co composites were prepared by the melt infiltration of Co, Si, and Ni me-tal into the TiC preforms. The miocrostructure reaction composition and mechanical properties were in-vestigated. In the case of the melt infiltrated with Co and Ni TiC grain shape was changed from angular to spherical shape with the average grain size of ∼5$\mu\textrm{m}$. In the case of the melt infiltrated with Co/Si or Ni/Si, Si was reacted with TiC particles and formed SiC particles. The bending strength of both specimens which have atomic ratio of 3 were 710 MPa and 515 MPa respectively. In the case of the melt infiltrated with Ni/Si/Co,. nonstoichiometric TiC was formed and its bending strength decreased to 420 MPa.

• Korean Journal of Materials Research
• /
• v.22 no.10
• /
• pp.526-530
• /
• 2012

Silica-based ceramic-matrix composites have shown promise as advanced materials for many applications such as chemical catalysts, ceramics, pharmaceuticals, and electronics. $SiO_2$-CuO-$CeO_2$ multi-component powders and their thin film, using an oxalic acid template as a chelating agent, have larger surface areas and more uniform pore size distribution than those of inorganic acid catalysts. $SiO_2$-CuO-$CeO_2$ composite powders were synthesized using tetraethylorthosilicate, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate with oxalic acid as template or pore-forming agent. The process of thermal evolution, the phase composition, and the surface morphology of these powders were monitored by thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrometry (EDXS). The mesoporous property of the powders was observed by Brunner-Emmett-Teller surface (BET) analysis. The improved surface area of this powder template with oxalic acid was $371.4m^2/g$. This multi-component thin film on stainless-steel was prepared by sol-gel dip coating with no cracks.

• Elastomers and Composites
• /
• v.56 no.3
• /
• pp.172-178
• /
• 2021

The wear behavior of styrene-butadiene rubber (SBR) and butadiene rubber (BR) was investigated using a blade-type abrader with a steel blade (SB), Ti-coated tungsten carbide blade (TiB), or zirconia blade (ZB). The wear rate of SBR against SB and TiB decreased with increasing number of revolutions because of the blunting of the blades during wear. However, the wear rate of SBR against ZB remained nearly constant with little blade blunting. Generally, the wear rate of BR was largely unaffected by the blade material used for abrasion. The wear rate and frictional coefficient of SBR were found to be higher than those of BR at similar levels of frictional energy input. A power-law relationship was found between the wear rate and frictional energy input during abrasion. A well-known Schallamach pattern was observed for SBR, while a much finer pattern was observed for BR. The blade material affects the wear rate of the rubbers because the macromolecular free radicals and blade tend to undergo mechano-chemical reactions. The inorganic ZB was found to be the most inert for such a mechanism.

• Applied Chemistry for Engineering
• /
• v.33 no.4
• /
• pp.352-366
• /
• 2022

Nuclear power plant operations for electricity generation, rare-earth mining, nuclear medical research, and nuclear weapons reprocessing considerably increase radioactive waste, necessitating massive efforts to eradicate radioactive waste from aquatic environments. Cobalt (⁵⁸Co) and strontium (⁹⁰Sr) radioactive elements have been extensively employed in energy generation, nuclear weapon testing, and the manufacture of healthcare products. The erroneous discharge of these elements as pollutants into the aquatic system, radiation emissions, and long-term disposal is extremely detrimental to humans and aquatic biota. Numerous methods for treating radioactive waste-contaminated water have emerged, among which the adsorption process has been promoted for its efficacy in eliminating radioactive waste from aquatic habitats. The current review discusses the adsorptive removal of radioactive waste from aqueous solutions using low-cost adsorbents, such as graphene oxide, metal-organic frameworks, and inorganic metal oxides, as well as their composites. The chemical modification of adsorbents to increase their removal efficiency is also discussed. Finally, the current state of ⁵⁸Co and ⁹⁰Sr removal performances is summarized and the efficiencies of various adsorbents are compared.

• Elastomers and Composites
• /
• v.55 no.4
• /
• pp.306-313
• /
• 2020

To investigate the reinforcing effects of functional fillers in nitrile rubber (NBR) materials, high-structure carbon black (HS45), coated calcium carbonate (C-CaCO3), silica (200MP), and multi-walled carbon nanotubes (MWCNTs) were used as functional filler, and carbon black (SRF) as a common filler were used for oil-resistant rubber. The curing and mechanical properties of HS45-, 200MP-, and MWCNT-filled NBR compounds were improved compared to those of the SRF-filled NBR compound. The reinforcing effect also increased with a decrease in the particle size of the fillers. The C-CaCO3-filled NBR compound exhibited no reinforcing effect with increasing filler concentration because of their large primary particle size (2 ㎛). The reinforcing behavior based on 100% modulus of the functional filler based NBR compounds was compared by using several predictive equation models. The reinforcing behavior of the C-CaCO3-filled NBR compound was in accordance with the Smallwood-Einstein equation whereas the 200MP- and MWCNT-filled NBR compounds fitted well with the modified Guth-Gold (m-Guth-Gold) equation. The SRF- and HS45-filled NBR compounds exhibited reinforcing behavior in accordance with the Guth-Gold and m-Guth-Gold equations, respectively, at a low filler content. However, the values of reinforcement parameter (100Mf/100Mu) of the SRF- and HS45-filled NBR compounds were higher than those determined by the predictive equation model at a high filler content. Because the chains of SRF composed of spherical filler particles are similarly changed to rod-like filler particles embedded in a rubber matrix and the reinforcement parameter rapidly increased with a high content of HS45, the higher-structured filler. The reinforcing effectiveness of the functional fillers was numerically evaluated on the basis of the effectiveness index (��SRF/��f) determined by the ratio of the volume fraction of the functional filler (��f) to that of the SRF filler (��SRF) at three unit of reinforcing parameter (100Mf/100Mu). On the basis of their effectiveness index, MWCNT-, 200MP-, and HS45-filled compounds showed higher reinforcing effectiveness of 420%, 70%, and 20% than that of SRF-filled compound, respectively whereas C-CaCO3-filled compound exhibited lower reinforcing effectiveness of -50% than that of SRF-filled compound.