Toward millimeter thick cellulose nanofiber/epoxy laminates with good transparency and high flexural strength.

While cellulose nanofiber-based bioplastics are of great interest for replacing synthetic polymer and glass materials, the main limitation is their low thickness, which makes them difficult for various applications. In this study, we fabricated millimeter-scale thick bioplastic composites, based on 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers (TEMPO-CNF) and epoxy resin, via sequential lamination processes. The glycerol as softener was added to TEMPO-CNF dispersion to prepare a thick TEMPO-CNF layer without shrinkage. It was discovered that the total thickness of TEMPO-CNF/epoxy laminates can be easily controlled by changing the thickness and number of TEMPO-CNF layers and the total thickness can also be easily increased up to 2.4 mm. Furthermore, these TEMPO-CNF/epoxy laminates have high flexural strength (272 MPa) as well as good transmittance (85% % at 600 nm). We anticipate that our approach will significantly broaden the strategies for fabricating nanocellulose-based bioplastics for use as a replacement for transparent synthetic polymers and glass materials.

Effect of Ag doping on Pd/Ag-CeO2 catalysts for CO and C3H6 oxidation.

To achieve high fuel efficiency and low emission in automobiles, it is necessary to develop highly active diesel oxidation catalysts (DOCs). Pd/CeO2 catalysts have been widely used as active catalysts for CO and C3H6 oxidation reactions. Additionally, Ag has been reported to enhance the oxygen storage capacity (OSC) of CeO2, which contributes to the oxidation ability of Pd/CeO2. In this study, Pd/Ag-CeO2 catalysts were used for CO and C3H6 oxidation reactions. When CeO2 was doped with appropriate amounts of Ag, reducibility and CO desorption rate were increased, which confirmed the high OSCs of Ag-doped catalysts. However, Ag particles were formed and the Ce3+/Ce4+ ratio decreased when CeO2 was doped with excess amounts of Ag. In addition, reduced Pd (Pd0), which is an active species for C3H6 oxidation, was formed and maintained even under oxidative reaction conditions. Since the removal of C3H6 is important for the oxidation of CO and C3H6, the catalyst with the highest Pd0 fraction (Pd/0.1Ag-CeO2 and Pd/0.3Ag-CeO2) presented improved catalytic activity. Consequently, the optimal amount of Ag enhanced the OSC of Pd/Ag-CeO2 catalysts and formed active Pd0 species under oxidative conditions, which resulted in the excellent catalytic activity of Pd/Ag-CeO2 for the CO and C3H6 oxidation reaction.

Double-crosslinked cellulose nanofiber based bioplastic films for practical applications.

While green bioplastic based on carbohydrate polymers have showed considerable promise, the methods typically used to prepare them in a single material have remained a significant challenge. In this study, a simple approach is proposed to fabricate high performance cellulose films composed of chemically and physically dual-crosslinked 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers (DC TEMPO-CNFs). The hydroxyl groups of TEMPO-CNF suspensions were firstly crosslinked chemically with epichlorohydrin (ECH), and subsequently TEMPO-CNF matrices were crosslinked physically via the strong electrostatic interaction between carboxylate and Ca2+ ions. It was found that the optimized DC TEMPO-CNF films exhibit a good transmittance (90 %) and a high tensile strength (303 MPa). Furthermore, these DC TEMPO-CNF films revealed superior thermal stability and excellent water resistance compared to neat TEMPO-CNF films without crosslinked domains. We believe that these results will pave the way to preparing practical polysaccharide bioplastics with simple, environmentally-friendly manufacturing processes.

Effects of La incorporation in catalytic activity of Ag/La-CeO2 catalysts for soot oxidation.

Owing to strengthened regulations toward vehicle emissions, the use of diesel particulate filter technology to reduce particulate matter emissions has attracted significant attention. To achieve low temperature oxidation of particulate matter, numerous studies on Ag/CeO2 catalysts for soot oxidation have been reported. Herein, Ag/La-CeO2 catalysts with different La contents are synthesized and compared to analyze the effect of La. Hydrogen temperature programmed reduction analysis confirms that the reducibility increases with an increase in the La content in La-CeO2. X-ray photoelectron spectroscopy and Raman analysis confirm an increase of oxygen vacancies with La doping. Accordingly, the soot oxidation performances estimated by temperature programmed oxidation experiments increase with La doping. However, the catalytic activity of Ag/La-CeO2 exhibits a volcano trend. When an appropriate amount of La is incorporated in Ag/CeO2, peroxide generation and reducibility improve, thereby enhancing the soot oxidation performance. Conversely, the catalytic activities gradually decrease with excess La-doping. Scanning transmission electron microscopy analysis and density functional theory calculations confirm that excess amounts of La induce the sintering of Ag particles, which lead to the degradation of peroxide generation and reducibility of the catalysts. Consequently, an optimal amount of La incorporation on Ag/La-CeO2 results in the best soot oxidation performance.

Hardness Modulated Thermoplastic Poly(ether Ester) Elastomers for the Automobile Weather-strip Application.

As a means of developing new material for automobile weather-stripping and seal parts replacing the conventional ethylene propylene diene monomer rubber/polypropylene vulcanizate, a series of poly(ether ester) elastomers are synthesized. The hardness is modulated by controlling chain extender composition after fixing the hard segment to soft segment ratio. Targeted hardness is achieved by partly substituting conventional chain extender 1,4-butandiol for soybean oil-originated fatty acid amide diol that bears a long chain branch. The crystallinity and phase separation behavior resultant elastomer are also tunable simply by modulating chain extender composition and hard to soft segment ratio.

Roles of noble metals (M = Ag, Au, Pd, Pt and Rh) on CeO2 in enhancing activity toward soot oxidation: Active oxygen species and DFT calculations.

The effects of noble metal (M = Ag, Au, Pd, Pt, and Rh) on CeO2 in enhancing the activity toward soot oxidation were studied through experimental methods and density functional theory (DFT) calculations. Each noble metal (3 mol.%) was supported on CeO2 (M/CeO2) and the properties of the catalysts were verified by XRD, HRTEM, N2 physisorption, CO chemisorption, XPS, and H2-TPR results. The noble metal was highly dispersed over CeO2, except for Au due to the sintering of Au, and the reducibility of the catalysts was greatly improved according to degree of the interaction between each noble metal and CeO2. The activities of M/CeO2 catalysts for soot oxidation were better than that of CeO2, and followed the order Rh/CeO2 > Ag/CeO2 > Pt/CeO2 > Au/CeO2 > Pd/CeO2 > CeO2. Moreover, our DFT calculations showed that vacancy formation energy was gradually lowered in the following order: CeO2 > Pd4/CeO2 > Pt4/CeO2 > Au4/CeO2 = Ag4/CeO2 > Rh4/CeO2, which was similar order with experimental activity. In addition, the electronic states of the p and f orbitals of CeO2 were studied to compare with the occupied Ce 4f electrons, which affect the redox property. Rh/CeO2 and Ag/CeO2 showed the improved soot oxidation activity, with an enhanced ability to generate oxygen vacancy formation and oxygen adsorption and increased electron transfer. Consequently, the experimental and DFT calculation results revealed the roles of noble metals on ceria with respect to catalytic activity.

CeO2 promoted Ag/TiO2 catalyst for soot oxidation with improved active oxygen generation and delivery abilities.

To evaluate the usability of TiO2 support for silver in soot oxidation, Ag/TiO2 and Ag/CeO2 catalysts were prepared and soot oxidation experiment was performed. The catalytic activity of silver was more enhanced on P25 and rutile than on anatase and CeO2 in tight contact, as evidenced from comparing the activities of supports and silver impregnated catalysts. The reasons for the difference in active metal enhancement were elucidated by various characterization methods (TEM, H2 TPR, and XPS), and it is verified that it resulted not from dispersion of silver but from oxidation ability. On the other hand, Ag/P25 showed poor activity in loose contact because of low contact between silver and soot. To improve the loose contact activity of the Ag/P25 catalyst, CeO2 was introduced for active oxygen delivery. The synthesized CeO2-Ag/P25 catalyst showed enhanced loose contact activity when compared with Ag/P25 and Ag/CeO2 due to synergistic effects from the active oxygen supply ability of silver on P25 and the oxygen transfer ability of loaded CeO2. Thermal stability of the catalyst was identified by recycling test to 800℃, and the maintained T20 and T50 demonstrated its durability for practical use in automobile exhaust removal.

A combinatorial chemistry method for fast screening of perovskite-based NO oxidation catalyst.

A fast parallel screening method based on combinatorial chemistry (combichem) has been developed and applied in the screening tests of perovskite-based oxide (PBO) catalysts for NO oxidation to hit a promising PBO formulation for the oxidation of NO to NO2. This new method involves three consecutive steps: oxidation of NO to NO2 over a PBO catalyst, adsorption of NOx onto the PBO and K2O/Al2O3, and colorimetric assay of the NOx adsorbed thereon. The combichem experimental data have been used for determining the oxidation activity of NO over PBO catalysts as well as three critical parameters, such as the adsorption efficiency of K2O/Al2O3 for NO2 (α) and NO (ß), and the time-average fraction of NO included in the NOx feed stream (ξ). The results demonstrated that the amounts of NO2 produced over PBO catalysts by the combichem method under transient conditions correlate well with those from a conventional packed-bed reactor under steady-state conditions. Among the PBO formulations examined, La0.5Ag0.5MnO3 has been identified as the best chemical formulation for oxidation of NO to NO2 by the present combichem method and also confirmed by the conventional packed-bed reactor tests. The superior efficiency of the combichem method for high-throughput catalyst screening test validated in this study is particularly suitable for saving the time and resources required in developing a new formulation of PBO catalyst whose chemical composition may have an enormous number of possible variations.