Increase in the number of acid sites of a H-ZSM5 zeolite during the dehydration of ethanol

The activity of a H-ZSM5-90 for the dehydration of ethanol at 473 K increased with an increase in time on stream. The results of NH₃-TPD and Ar adsorption showed that the number of acid sites of the H-ZSM5-90 increased during the dehydration. On the other hand, the activity and the number of acid sites of H-mordenite-90 were almost unchanged during the dehydration. Since the pre-treatment of the H-ZSM5-90 with ethylene at 473 K largely increased its activity for the dehydration of ethanol, it is suggested that a large number of new acid sites could be formed inside the pores of H-ZSM5-90 via the polymerization of ethylene produced by the dehydration of ethanol.     

Preparation and properties of optical notch filters of cholesteric liquid crystals

We investigated the influence of preparative conditions of cholesteric-liquid-crystal (CLC) solid films on their cholesteric structures. They are made of poly[γ-butyl- (or )-glutamate] (PBuL(D)G and triethylene glycol dimethacrylate (TGDM), and have the ability to reflect the light in a specified wavelength region. When these films were combined with conventional colour filters, the colour reproduction region was enlarged by about 25% in the area of the CIE chromaticity diagram.     

Grafting onto carbon black by the reaction of reactive carbon black having acyl chloride group with several polymers

Summary Acyl chloride group introduced onto carbon black rapidly lost its activity by the moisture in air. However, the decrease of acyl chloride group content in vacuum was negligibly small. By the reaction of the acyl chloride group with several polymers having hydroxyl or amino group, such as polyethylene glycol (PEG), poly(vinyl alcohol)(PVA), and polyethyleneimine (PEI), these polymers were found to be effectively grafted onto carbon black; for instance, the grafting ratio of PEG (Mn=8.2×10³), PVA (Mn=2.2×10⁴), and PEI (Mn=2.0×10⁴) was 18.5%, 32.9%, and 45.8%, respectively. The number of polymer grafted onto carbon black decreased with an increase of its molecular weight.     

Fabrication of Silicon Carbide-Mullite Composite by Melt Infiltration

The melt infiltration method was used to fabricate a SiC-mullite composite at high temperature. Mullite was successfully obtained from a SiO₂ and Al₂O₃ powder mixture by melting above 1830°C in a BN crucible with a lid. When infiltrated into a porous SiC preform, the mullite significantly reacted with SiC to form gaseous SiO and CO, even at the lowest investigated temperature of 1830°C, consuming SiO₂ and leaving Al₂O₃ and silicon phases in the sample. The relevant reactions were studied in detail. A closed system was adopted to suppress the reaction, and a dense composite was successfully obtained.     

A framework for ICAI systems based on inductive inference and logic programming

The main components of an Intelligent Computer-Assisted Instruction (ICAI) system are the expertise, the student model and tutoring strategies. The student model manages what the student dose and dose not understand, and the performance of an ICAI system depends largely on how well the student model approximates the human student. We propose a new framework for ICAI systems which uses the inductive inference for constructing the student model from the student’s behavior. In the framework, both the expertise and the student model are represented as Prolog programs, which enables to express the meta-knowledge that is the knowledge of how to use the knowledge. Since the construction of the student models is performed independently of the expertise, the framework is domain-independent. Therefore, an ICAI system for any subject area can be built with the framework. As an example, the ICAI system teaching chemical reaction is presented together with a sample performance. The authors believe that the new framework for ICAI systems based on logic programming and inductive inference could be a breakthrough of the future ICAI systems.     

Wear properties of two-phase Al2O3/ZrO2 (Y2O3) ceramics at temperatures from 296 to 1073 K

Reciprocating sliding friction experiments were conducted with various two-phase, directionally solidified Al₂O₃/ZrO₂ (Y₂O₃) pins sliding on B₄C flats in air at temperatures of 296, 873, and 1073 K under dry sliding conditions. Results indicate that all the Al₂O₃/ZrO₂ (Y₂O₃) ceramics, from highly Al₂O₃-rich to ZrO₂-rich, exceed the main wear criterion requirement of 10⁻⁶ mm³ N⁻¹ m⁻¹ or lower for effective wear-resistant applications. Particularly, the eutectics and Al₂O₃-rich ceramics showed superior wear properties. The composition and microstructure of Al₂O₃/ZrO₂ (Y₂O₃) ceramics played a dominant role in controlling the wear and friction properties. The controlling mechanism of the ceramic wear, friction, and hardness was an intrinsic effect involving the resistance to shear fracture of heterophase bonding and cohesive bonding and the interlocking microstructures at different scales in the ceramics.     

Assessment of Erosion Resistance of Coated Polymer Matrix Composites for Propulsion Applications

The erosion behavior of tungsten carbide-cobalt (WC-Co) coated and uncoated polymer matrix composites (PMCs) was examined with solid particle impingement using air jets. Erosion tests were conducted with Arizona Road Dust impinging at 20°, 60°, and 90° angles at a velocity of 229 m s^–1 at both 294 and 366 K. Noncontact optical profilometry was used to measure the wear volume loss. Results indicate that the WC-Co coating enhanced erosion resistance and reduced erosion wear volume loss by a factor of nearly 2. This should contribute to longer wear lives, reduced related breakdowns, decreased maintenance costs, and increased product reliability.     

Adhesion and friction of transition metals in contact with non-metallic hard materials

An investigation was conducted to examine the adhesion and friction behavior of transition metals in contact with various non-metallic hard materials and the nature of the metal transfer to the hard materials. Sliding friction experiments were conducted with the metals yttrium, titanium, tantalum, zirconium, vanadium, neodymium, iron, cobalt, nickel, tungsten, platinum, rhenium, ruthenium and rhodium in sliding contact with singlecrystal diamond, silicon carbide, pyrolytic boron nitride and ferrite. All experiments were conducted under the following conditions: loads, 0.05 –0.3 N; sliding velocities, 3 × 10^?3 and 0.7 × 10^?3 m min^?1; in a vacuum of 10^?8 Pa; at room temperature. Auger electron spectroscopy analysis was conducted with the metals and non-metals to determine the surface chemistry and the degree of surface cleanness. The results of the investigation indicate the adhesion and friction of the transition metals in contact with diamond, silicon carbide, boron nitride and ferrite are related to the relative chemical activity of the metals. The more chemically active the metal, the higher the coefficient of friction and the greater the amount of transfer to the non-metals.     

Quantitative current measurements using scanning magnetoresistance microscopy

We have demonstrated the capability of scanning magnetoresistance microscope (SMRM) to be used for quantitative current measurements. The SMRM is a magnetic microscope that is based on an atomic force microscope (AFM) and simultaneously measures the localized surface magnetic field distribution and surface topography. The proposed SMRM employs an in-house built AFM cantilever equipped with a miniaturized magnetoresistive (MR) sensor as a magnetic field sensor. In this study, a spin-valve type MR sensor with a width of 1 microm was used to measure the magnetic field distribution induced by a current carrying wire with a width of 5 microm and a spacing of 1.6 microm at room temperature and under ambient conditions. Simultaneous imaging of the magnetic field distribution and the topography was successfully performed in the DC current ranging from 500 microA to 8 mA. The characterized SV sensor, which has a linear response to magnetic fields, offers the quantitative analysis of a magnetic field and current. The measured magnetic field strength was in good agreement with the result simulated using Biot-Savart's law.     

Fretting wear of Ti-48Al-2Cr-2Nb

An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296–823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473–823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals.