Carbon black is treated with each of three different oxidizing agents (nitric acid, air, and ozone) to introduce oxygencontaining functional groups (OFGs) and the resulting oxidized carbon blacks are used as model catalysts for the hydrolysis of cellulose. At the same time, they are thoroughly characterized by many techniques, especially in terms of surface chemistry, including the type/number of OFGs and the site where OFGs are formed in a carbon structure. Then, by correlating the catalytic activities toward the cellulose hydrolysis with the characterization results, key factors governing the catalysis are elucidated. As a result, this study reveals that two types of acidic OFGs, carboxyl groups (including those derived from the hydrolysis of acid anhydride and lactone groups in the reaction) and phenol groups (including those from lactone groups), act as catalytic sites with almost equal activity, as long as they are present on the external surface and thereby accessible to cellulose molecules.

A novel oxygen sensor using hot spot on ceramic rod of high-T c superconductor RBa2Cu3OT_ ~ (R: rare earth element) has been developed. The hot spot appears by the self-heating of the local part on the RBa2Cu3OT_ ~ ceramic rod when a voltage above threshold is applied at room temperature. This sensor operates without any separate heater by taking advantage of the high temperature of the hot spot wherein oxide ions can diffuse easily. The oxygen concentration is determined from the value of the current flowing through the rod by utilizing the change in the resistivity of the hot spot depending on oxygen partial pressure in atmosphere. Oxygen concentration of 0 ~ 100% can be detected with high sensitivity and the response time is several seconds. The response performance of this oxygen sensor is almost the same as that of limiting-current-type zirconia sensor operating at 500°C.

Porous piezoelectric ceramics of Pb(Zr, Ti)O3, (P-PZT), have been newly developed to apply to transducers in an echo sounder. The P-PZT was prepared from a mixture of PZT and poly-methyl-methacrylate (PMMA) powders. The piezoelectric characteristics of the P-PZT such as the dielectric constant (ε), voltage output constant (g constant), acoustic impedance (Z c) and Q were evaluated. The P-PZT was employed in an echo sounder of 200 kHz, and its transmitting and receiving properties were measured in water. In these measurements, the P-PZT showed suitable characteristics for the echo sounder, which required high sensitivity, wide frequency bandwidth and high resolution. High sensitivity was realized by the large g constant and low Z c of P-PZT which made the impedance matching with water much easier. In the acoustic response to the burst wave, the rise and fall time were shortened to 1/3 that of the conventional PZT transducer.

The experimental evaluation of cylindrical ceramic tubes composed of porous PZT ceramics is reported. They exhibit 5.5 dB higher electroacoustic sensitivity and 20% lower resonant frequency than those composed of conventional PZT ceramics.

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