No abstract

MFI-type zeolites containing Ce species were prepared by a mechanochemically assisted two-step method, where first an amorphous Si–Ce–O composite was produced via a mechanochemical reaction of SiO2 and CeO2 and then transformed into an MFI-type zeolite under hydrothermal conditions. The Ce species in this sample were more highly dispersed than those in the two control materials: a Ce-containing MFI-type zeolite synthesized via the conventional one-pot hydrothermal approach and Ce species simply deposited on silicalite-1. The highly dispersed and small Ce species in the zeolite exhibited a unique catalytic performance for the oxidative conversion of methane after the impregnation of Pd species, and the combination of Pd and Ce species produced ethane even at reaction temperatures as low as 100–300 °C.

Substitution of Al atoms in a zeolite framework by catalytic metal atoms has attracted considerable attention because the catalytic behavior can be tuned by the substituted atoms. In the present study, Sn-substituted MFI-type silicates were synthesized using a hydrothermal reaction of an amorphous Si-O-Sn precursor prepared by mechanochemical grinding of SiO2 and Sn(OH)4. The mechanochemical treatment was found to be a key technique for obtaining the amorphous Si-O-Sn precursor, where tetrahedral Sn4+ species were incorporated into the amorphous matrix. The Sn content in the framework of the MFI-type silicates was successfully controlled by the initial HCl/Si molar ratio of the hydrothermal procedures. Optical reflectance measurements revealed that the Sn4+ ions were dispersedly incorporated into the silicate framework while preserving the initial tetrahedrally coordinated species. Infrared results imply that the resulting Sn-substituted MFI-type silicate has Brønsted acid character. Precise control of the Brønsted and Lewis acid properties by Sn doping is a promising approach to the development of novel types of zeolite-based catalytic materials.

Since human body joints have a gel-like structure with low friction that persists for several decades, hydrogels have attracted much interest for developing low-friction materials. However, such advantages can hardly be realized in industrial usage because water in the gel evaporates easily and the gel deswells. The substitution of water with an ionic liquid (IL) is one of the effective ways to overcome this problem. In this study, we substituted water in a double network (DN) hydrogel with 3-ethyl-1-methyl-imidazolium ethylsulfate (EMI-EtSulf), a hydrophilic IL, via a simple solvent exchange method to obtain a DN ion gel. A compressive test and thermogravimetric analysis showed that the DN ion gel has a high compression fracture stress and improved thermal properties, with the difference in 10% loss of temperature being ΔT10 = 234 °C. A friction test conducted using a reciprocating tribometer showed that the friction of a glass ball/DN ion gel was relatively higher than that of a glass ball/DN hydrogel. Because the minimum coefficient of friction (COF) value increased after substitution, the increase in polymer adhesion caused by the electrostatic shielding of the surface moieties of glass and poly 2-acrylamidomethylpropanesulfonic acid (PAMPS) was considered the main contributor to the high friction. As the COF value decreased with increasing temperature, the DN ion gel can achieve low friction via the restriction of polymer adhesion at high temperatures, which is difficult in the DN hydrogel owing to drying.

Currently, the demand for carbon fiber reinforced plastic (CFRP) has increased in various fields. However, there have been few studies investigating the machined surface quality, degradation in CFRP mechanical properties with machining temperature, or machining tool cost. In particular, the machining temperature is considered to affect the machined quality because the CFRP matrix is a resin. In this study, a cubic boron nitride (cBN) electroplated end mill was developed; this novel tool can switch between cutting and grinding without needing to change the tool. To observe the relationship between the amount of abrasive grain in contact with the CFRP and the occurrence of burrs, a grinding test was conducted with different clearance angles of the end mill and different abrasive grain sizes. The temperature during the grinding processes was measured, and the burrs were estimated after the grinding processes. From these results, the contact amount of the abrasive grit suitable for grinding was derived.