Toshiji Kurobe

Sensing characteristics of tin oxide thick film gas sensor

Thick film gas sensor of tin oxide based materials has been developed by screen printing method, and its sensing characteristics have been examined for some gases. To perform the method, tin oxide fine power with the size about 0.5 μm in diameter was prepared through the fine crystallization in liquid phase, and was mixed with glass frits as a binder and palladium or platinum as a catalyst. This mixed material is used as the paste. With the screen printing method using the paste, the mass production and the sufficient mechanical strength of the sensor can be achieved. The gas sensor of tin oxide incorporated with palladium black as the catalyst shows an excellent selective detection for ethanol and hydrogen gases at the specimen temperature of 250 °C. And the platinum black‐doped tin oxide sensor has also a high sensitivity to both gases at the temperature over 350 °C.

X-Ray Photoelectron Spectroscopy of Fluorocarbon Films Deposited by RF Sputtering

Fluorocarbon films are deposited by rf sputtering of poly(tetrafluoroethylene) targets under conditions of various power and pressure levels in pure argon in order to examine the effect of discharge conditions on the deposition rate and molecular structure of the deposited films. The molecular structures of the films are investigated by means of X-ray photoelectron spectroscopy. The films deposited under conditions favoring high deposition rate, such as higher power at a constant pressure or lower pressure at a constant power, contain higher concentrations of cross-links. Heating the deposited films results in an increase in the component of the C1s spectrum assigned to the cross-linked structure.

Tin oxide gas sensor and countermeasure system against accidental gas leaks

Abstract Gas sensors are used in both domestic and commercial environments. In Japanese apartment buildings, installation of gas sensors is required by law, even though the sensor elements still need improvement. One problem was that sensors could not preferentially detect a specific gas. We have, however, developed three types of tin oxide gas sensors, namely, sintered, tin film and thick film types. The combined use of these three sensors and a microcomputer makes up a gas sensing and countermeasure system. The system preferentially detects leaking gases in ambient atmosphere and stops the gas leak by means of an electromagnetic valve. The kind of gas that is leaking is displayed on a CRT.

Magnetic field-assisted fine finishing

Abstract A field-assisted fine finishing method has been developed which utilizes the electromagnetic behaviour of a magnetic fluid. Finishing experiments indicate that the stock removal rate and the surface roughness can be controlled by varying the current to the electromagnet.

Magnetic field-assisted polishing — application to a curved surface

Abstract Magnetic field-assisted polishing using a magnetic fluid was applied to a curved surface. As a polishing test material, a single crystal of LiNBO3, a hard and brittle material, was examined; it was previously machined to a spherical surface by diamond turning. The results of polishing experiments show that surface roughness of 0.01 μm R max can be easily obtained by this method. It is also clarified that the magnetic field intensity is closely related to the polishing pressure and the removal rate. Therefore, to finish curved surfaces precisely, the magnetic field distribution must be kept uniform.

‘Intelligent’ alarm detector of gas leaks

Abstract Three types of tin oxide gas sensors have been developed and a gas-detecting apparatus using the developed sensors has been manufactured. This apparatus has the ability to identify the type of leaking gas out of isobutane, ethanol, hydrogen and carbon monoxide. It can also be used for accumulating data as the terminal unit of a microcomputer. When city gas or carbon monoxide gas is leaking, a pulse is output from the apparatus to an electromagnetic valve which cuts off the path of the gas. The use of the apparatus and microcomputer composes a countermeasure system against gas leak accidents.

High Speed Slurry Flow Finishing of the Inner Wall of a Stainless Steel Pipe

Recently, a high speed slurry flow finishing method has been developed for capillary with very fine holes of less than 1 mm inner diameter in our laboratory. In the present work, this finishing method has been tested to finish the inner walls of pipes. The hole diameter is only several millimeters larger than that of the capillaries. In the experiment, a stainless steel mandrel is inserted into the pipe. Such a setup makes it possible for the slurry to flow at high flow rates through the narrow clearance between the inner wall of the pipe and the mandrel under a relatively low slurry injection pressure. It is found that the surface roughness of the inner wall decreases with an increasing number of slurry passes, which proves that by such a modification of the setup, the inner wall of the pipe having a relatively large hole can be finished. The raising of the flow pressure exhibits a rapid decrease in surface roughness in the early stage and a low roughness level. Introduction There are many engineering parts having holes, such as capillaries, pipes, ferrule and so on. In the case of fine holes, it is difficult to finish the inner wall of the hole by ordinary polishing method. In our previous reports [1,2], a new polishing method for inner wall of a fine hole, in which polishing is performed by the high speed slurry flowing through the hole has been developed. In the present study, the high speed slurry flow finishing method is applied to the finishing of the inner wall of pipes having a hole in relatively large diameter. Experimental Tests Polishing apparatus. An schematic view of a slurry flow finishing machine is shown in Fig.1. It has a symmetrical structure composed of an air compressor, a set of plungers, cartridges A and cartridges B. The cartridges A and B are filled with ion exchanged distilled water, where abrasive grains have settled in advance on the bottom of one of the cartridges A. In the present work, because hole diameter is 4.35 mm, that is about ten times larger than that of capillary, slurry injection pressure should be raised to get the high flow rate of the slurry. Raising the slurry injection pressure demands the reconstruction of the apparatus, that is, reinforcing the flow line and the sealing of the connecting parts. In avoiding such a substantial reconstruction, a device was made in setting the pipe on the machine. A pipe is installed into a work holder with fixing ferrules as shown in Fig.1. In addition, a stainless steel mandrel whose diameter and length are 4mm and 200mm respectively, is inserted into the pipe and their ends were fixed with the support tools. Such a setup makes it possible that slurry flows at high flow rate through the narrow clearance between the inner wall of the pipe and the mandrel without raising the slurry injection pressure. Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 345-348 doi:10.4028/www.scientific.net/KEM.238-239.345

Development of high speed slurry flow finishing of the inner wall of stainless steel capillary: Polishing and gas flow characteristics of various size of capillaries

Abstract A new finishing method for inner wall of capillaries has been developed, in which the polishing is performed by letting the slurry flow through the capillary at high speed. With the increasing number of slurry passes, the surface roughness of as-received capillaries decreases rapidly in the early stage of the low number of slurry passes, and then tends to saturate to a certain level depending on the diameter of the capillaries. It is also found that the decreasing surface roughness of the inner wall results in the increasing conductance of gas flow through the capillary. Accounting for the effect of the capillary diameter D on the differential pressure which is measured in nitrogen gas flow through the capillary at a constant flow rate, an empirical equation is found between the differential pressure P and the surface roughness Ra, logP · D4 = 0.362 + logRa1/6.

Application of high speed slurry flow finishing method for finishing of inner wall of fine hole die: Effects of the hardness of die material on the polishing characteristics

In order to warrant the quality of drawn metal wires, the inner wall of the hole die which has been used in the drawing of metal wire, has been usually finished by hand work for a long time using a bar daubed the kneaded paste containing diamond powder. High speed slurry flow finishing method which has been recently developed for the finishing of inner wall of capillary has been applied to the finishing of the hole die. It is found that the surface roughness of inner wall of the hole decreases with the increasing number of slurry flow pass in a relatively short finishing time, and that surface roughness reduction rate depends on the hardness of die materials. Experiments show that the bell mouth shape is spontaneously formed in the high speed slurry flow finishing.

Ultra High Speed Grinding of the Glass with a Single Point Diamond

Shear mode grinding has recently much attention for the machining of brittle material such as a glass, ceramics and silicon. This study presents the effects of a newly developed ultra high speed grinder, which can achieve speeds five times greater than conventional grinders. Scratching modes on a surface of glass ground with a single point diamond were observed in detail by scanning tunnel microscopy. It was found from the experiments that the grinding mode depends exceedingly upon the circulating speed of the disc. The depth of cut observed with STM was about 20-30% smaller than calculated one. Grinding mode changes due to the shape of stylus tip and the cut of depth is influenced by crossing of the scratches.