Material Structure Designing Laboratory

Material Structure Designing Laboratory

(Japanese is here.)

Introduction

One of the key targets in the study of inorganic materials is to realize a multiple of functions in a material. The material structure designing laboratory is doing various studies on processes to generate new functions by applying external energy to an inorganic material, in which reactions on the surface or interface of the material are enhanced and micro-structure is controlled. Our goal is to merge material science and surface chemistry. The target processes at our laboratory can be classified into three groups depending on the kinds of applying external energy:

　(A) chemical and kinetic fields by irradiating intense ultrasound,
　(B) electrochemical reactions, and
　(C) mechanical energy such as grinding and kneading.

Research Projects

 1. Utilization of extreme environment generated by irradiation of ultrasound.
 2. Manipulation of particles by acoustic radiation pressure of ulrasound.
 3. Purification system of exhaust gas using electrochemical reactions in solid
    electrolytes.
 4. Novel solid oxide fuel cell system using solid electrolytes.
 5. Structure control technique for inorganic solid particles.

Staff

Chief	MITOME, Hideto	mitome@nirin.go.jp
	HATA, Takayoshi	thata@nirin.go.jp
	SUZUKI, Kazuo	suzuki@nirin.go.jp
	HIBINO, Takashi	thibino@nirin.go.jp
	KOZUKA, Teruyuki	kozuka@nirin.go.jp
	TUZIUTI, Toru	tuziuti@nirin.go.jp
	YASUI, Kyuuichi

Recent research activities

A. Utilization of chemical and kinetic fields generated by irradiation of intense ultrasound

Usually there are many tiny nuclei of bubbles in a liquid. When ultrasound is applied, these bubbles grow and finally burst. This abrupt collapse generates temperatures as high as 5000 K and pressure as high as 1700 atm, and this happens within 100 ns. Although the experimental conditions are ordinary temperature and ordinary pressure macroscopically, extreme environment is generated microscopically without any difficulty. A fundamental study is carried out to apply this phenomena to chemical reaction fields from the viewpoint of ultrasonic engineering.

Ultrasound exerts force on an object placed in a sound field, which is known as acoustic radiation pressure. Since this force comes from propagation of ultrasound, non-contact manipulation is possible. This technique is expected to be applied in manipulation of biomaterial as one of the techniques in micro machine study. The magnitude of acoustic radiation pressure depends on the size, shape and characteristics of the material. This fact suggests utilization of this force to separate and to discriminate inorganic particles.

B. Utilization of electrochemical reactions in a solid electrolyte

New electrochemical devices based on solid electrolytes are under study. The key technique here is to attach two kinds of electrodes with different catalytic activities to opposite surfaces of a solid electrolyte. This enables one to construct a novel solid oxide fuel cell which requires neither the gas separator nor the gas seal. Methane gas is premixed with oxygen gas, and the mixture is supplied into the cell at an operating temperature of 1223 K. Then, there appears an oxygen concentration cell, because of the difference in the catalytic activity for the methane oxidation between the two electrodes. Electric powers above 0.15 Wcm^-2 are generated from the cell. Another key technique is to electrochemically pump oxygen gas from the cathode to the anode by applying the potential from the external electric source. This enables one to purify NOx and HC in exhaust gases from lean-burn engines. The electrochemical oxygen pump brings about a significantly reductive and oxidative atmosphere at the cathode and the anode, respectively, regardless of surrounding gases. As a result, NOx gas is reduced to nitrogen gas at the cathode, and HC gas is oxidized to carbon dioxide at the anode. In addition, the combination of these two techniques makes it possible to develop HC and NOx sensors operating in combustion gases.

Last Modified: 1999/4/1