Preparation of a multilayer and a compositional gradient layer composite by the aerosol filtration method
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A multilayer composite of an oxide superconductor and a compositional gradient layer composite of a ferrite chip component was prepared by the aerosol filtration method. Homogeneous, minute, and arbitrary control of the composition profile was possible for the multilayer composite of the Bi system superconductor. High controllability for designing the composition profile of the compositional gradient layer of nickel zinc ferrite was confirmed by EPMA analysis.
I. INTRODUCTION Recently, various processes for designing a multilayer composite and a compositional gradient layer have been attempted by many investigators. Herein, a multilayer composite means the material structured with two components alternately placed one onto the other, and the compositional gradient layer expresses the layer composite with a gradually changing profile of the ratio of components toward the layer direction. The powder metallurgical process,1 the powder spray forming,1 and the chemical vapor deposition (CVD) 2 are mainly proposed for powder processing techniques in designing the layer composites. However, these all have problems: the powder metallurgical process, in controlling the composition profile; spray forming, in stabilizing the spray condition; and the CVD method, in increasing reproducibility and productivity. The mist pyrolysis method becomes a useful technique to easily produce fine particles with homogeneous chemical compositions.3'4 Furthermore, the particle produced by the mist pyrolysis method is continuously formed in the gas phase. Thus, the use of a mist pyrolyzed particle enables one to design the multilayer and the compositional gradient layer of which the composition profile is homogeneous, minute, and arbitrary with a high deposition rate. This paper is concerned with the multilayer composite of an oxide superconductor and a nickel zinc ferrite chip component for the compositional gradient layer composite. The composites were prepared by an aerosol filtration method using a mist pyrolyzed particle. Controllability of the composition profile of those layer composites is discussed in particular.
particle flow, and a filtration system to form the layer composite, as shown in Fig. 1. Starting solutions were prepared by dissolving the corresponding compounds into distilled water containing nitric and/or hydrochloric acid. These solutions were nebulized by an ultrasonic vibrator operated at 1.7 MHz. An atomized droplet of the starting solution was carried by an oxygen carrier gas to a reaction zone that was held at a setting reaction temperature. Each reaction zone used a quartz tube measuring 350 mm in length and 30 mm in inner diameter. The homogeneous particle, submicron size in diameter, was produced in short residence times. The supply of produced particles was regulated by opening and closing the control valves. The sequences and intervals of the valve operation were controlled at corresponding schedules for designing the multilayer or the compositional gradient layer, as detailed in each section hereinafter. Eac
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