Yasuhiro Hayakawa

Evaluation of the efficiency of deodorants by semiconductor gas sensors

Abstract In order to evaluate the efficiency of deodorants, a method has been proposed in which the concentrations of odours are obtained continuously and quantitatively by SnO2-based semiconductor gas sensors. The SnO2 gas sensors are capable of detecting specified odours simply, rapidly and sensitively. The efficiency of a deodorant based on active carbon for removing ammonia, acetaldehyde, hydrogen sulfide and methyl mercaptan has been determined by measuring a change of the concentrations of the odours in a test chamber. Also, the effective lifetime of four kinds of deodorants for removing ammonia was investigated by continuous supply of ammonia of a constant concentration with dried air to a deodorant. As the proposed method is capable of measuring the amounts of adsorbed and desorbed odours on a deodorant, the efficiency of deodorants can be evaluated quantitatively.

Measurement of hydrogen permeation into steel by using hollow bolt and SnO2 gas sensor

Abstract A method using an SnO2 gas sensor and a specially designed hollow steel bolt was proposed for evaluating hydrogen permeation into steel, which is considered to be responsible for delayed fracture of steel. As measured with the gas sensor, the concentration of hydrogen in the cavity of the hollow bolt after weathering tests increased in different manners depending on the weathering conditions and the kinds of steel. This method was also applied to the dynamic measurement of hydrogen penetration through the steel wall of the hollow bolt by continuously monitoring the hydrogen coming into the cavity. Hydrogen diffusion coefficients estimated from this measurement were well consistent with the hydrogen permeation data in the weathering tests, and showed reasonable dependence on phosphorus, silicon and vanadium contents in steel.

Studies on the Development of Rapid Analytical Methods for Nonmetallic Elements in Iron and Steel Using a Chemical Sensor

The mechanical and metallurgical properties of iron and steel are significantly influenced by the contents and forms of nonmetallic elements. In order to control the chemical composition of steel precisely and rapidly, new analytical methods for nonmetallic elements have been developed. These methods are characterized by the use of a chemical sensor which is capable of detecting the specified gases simply, rapidly and sensitively. An on-line analytical method for hydrogen in molten steel and a method for continuous measurement of hydrogen which can permeate a bolt were developed by using a SnO2 semiconductor gas sensor. A method for simultaneous determination of gas mixtures was also developed using plural semiconductor gas sensors, and was applied to measuring concentrations of coke oven gases. A rapid determination method for phosphorus and sulfur in iron was also developed by using a reflectance photometric sensor with gas detecting tape. These methods are capable of being used at the production sites, and contributing to the precise control of the chemical composition of steel.