A Study of the Solid Reaction Between Zinc Oxide and Ferric Oxide by the Use of Fission Product Rare Gas

169 A Study of the Solid Reaction between Zinc Oxide and Ferric Oxide by the Use of Fission Product Rare Gas Sumio Ichiba SYNOPSIS In order to study the solid reaction between zinc oxide and ferric oxide over a wide temperature range the fission gas emanation method was applied. It was found that the reaction occurs in two processes, the first which occurs at temperature below about 900•Ž is due to the structure sensitive properties of ferric oxide and the second is attributed to the lattice loosening of the zinc oxide. The reaction process could be investigated more sensitively by the fission gas emanation method than by the radon emanation method. (Received July 12, 1962) I Introduction In the preceding papers it was reported by the author that the solid reactions of fine powder, such as crystal structure change, dehydration, decomposition, oxidation and reduction reactions can be observed by the heating curves of emanating radioactive xenon which was previously incorporated into fine powders by fission recoiling. It was further pointed outs' that the heating curves of fine powders like graphite in which no phase change occurs may represent the characteristic properties involved in particle size distribution, imperfections, surface area, pretreatment, etc. The radioactive xenon captured by imperfections of the crystalline powder will be released successively as the imperfections disppear with rising temperature. Since the heating curve of emanating xenon represent the characteristic property of fine powder, the reaction process between solid powders will be observed continuously. In the present experiment, the process of solid state reaction between zinc oxide and ferric oxide was studied by the fission gas emanation method. The solid reaction between zinc oxide and ferric oxide has been studied by many workers". Especially, W. SchrSder" studied extensively the reaction process by Hahn's emanation method, which uses radon as tracer. By the author's method in which xenon is used as tracer, the reaction process can be studied more sensitively, and the relation between the reactivity and the powder property of the reactants could be made clear. II Sample Zinc carbonate of G. R. grade of Kanto Kagaku K. K. was used in the present work. The zinc oxide, samples fo Nos. I and 2, was prepared by thermal decomposition of zinc carbonate by heating at 300•Ž and 1000•Ž, respectively, for 30 min. In all cases, zinc carbonate and zinc oxide powders were ground in a agar mortar and filtered through a 250 mesh sieve. The preparation methods of ferric oxide samples are shown in Table 1. The ferric oxide samples were also ground in a agar mortar and filtered through a 250 mesh sieve. * Presented at the Annual Meeting of Japan Society of Powder Metallurgy, Tokyo, May, 1962. ** Chemistry Division, Japan Atomic Energy Resarch Institute. 昭和37年10月 (7) 170 A Study of the Solid Reaction between Zinc Oxide and Ferric Oxide by the Use of Fission Product Rare Gas Table 1 The preparation methods of the ferric oxide samples The sample powder was mixed with formvar films containing uranium dioxide powder of small size, then irradiated with thermal neutrons of about 5•~10 15 per cm2 in a pneumatic tube of JRR-1 or JRR-2 and cooled for a day. Ethyl alcohol was added to the irradiated sample. The sample powder was separated from the films, after irradiation ; the whole procedure consists of the procedures of passing through a wire gauze, a filtration by filter paper and subsquent drying. In order to prepare the mixture for the solid reaction, another nonactive reactant powder was added to the specimen previously incorporated with the fission product rare gas, which was suspended in the ethyl alcohol. The resultant mixture was separated by pouring on a wire gauze with hard stirring. III Apparatus and Measurements The apparatus used in the experiment was the same as that for the previous experiment. In order to obtain the heating curves, the sample incorporated with the fission rare gas was placed in the heating tube surrounded by an electric furnace, then the tube was evacuated with a vacuum pump. The tube was filled with purified argon and then argon was flowed at a constant rate of 50ml/min. The temperature of the furnace was raised at a constant rate of 5•Ž/min. up to 1150•Ž. The radioactivity of the released xenon, which was carried by the flowing argon, was continuously measured by passing the stream through the counting cell inserted in a well of Nal scintillation crystal. Thus the heating curve could be obtained by plotting the released xenon activities against temperatures. IV Results and Discussion The heating curves of zinc carbonate and zinc oxides mixture are shown in Fig. 1. The peak at 235•Ž of curve (a) shows the decomposition of the zinc carbonate. The peaks of curve (b) represent the peak due to the imperfections in zinc oxide crystalline powder of sample No. 1 but the peaks disappeared in curve (c) of sample No. 2 of zinc oxide because of its high decomposition temperature of 1000•Ž. The rise of curve (c) in the high temperature range may be attributed to the lattice loosening which occurs at higher temperature than "Tamman temperature". The X-ray diffraction diagrams of the zinc oxide samples show that the crystal- lization was completed in sample No. 2 (Fig. 2). The heating curves of ferric oxides are shown in Fig. 3. All the ferric oxides were iden- tified as et-Fe2O3 by X-ray analysis, but their heating curves differ as shown in Fig. 3. Three peaks appeared in curve (a) of sampe No. 1 ; these may also correspond to the imperfections existing in ferric oxide crystalline, as in the case of zinc oxide of sample No. 1. In curve (b) of sample No. 2, however, those peaks appearing on the lower temperature side in curve (a) disappeared, and only a single high peak remained. In sample No. 3 (curve (c)) * Japan Resarch Reactor-1, water boiler type, operated at 50KW thermal out-put. ** Japan Resarch Reactor-2 , CP-5 type, operated at 3000KW thermal out-put. (8) •u•²‘Ì‚¨‚æ‚Ñ•²–––è‹à•v‘æ9Šª‘æ5•† Sumio Ichiba 171 Fig. I Heating curves of zinc carbonate and zinc oxide samples. (a) : ZnCO3, (b):ZnO (No.1), and (c):ZnO (No.2). Fig. 2 X-ray diffraction diagrams of oxide samples.(a):ZnO sample of No. 1 and (b) : ZnO sample of No, 2. the same peak shifted to higher temperature, due to the longer duration of heating at the decomposition temperature. Furthermore, in samples Nos. 4 and 5 (curves (d) and (e)), the peak shifted to higher temperatures correspording to the respective decomposition temperatures. 昭和37年10月 (9) 172 A Study of the Solid Reaction Between Zinc Oxide and Ferric Oxide by the Use of Fission Product Rare Gas Fig. 3 Heating curves of xenon release of ferric oxide samples. The peak height of these curves will vary with thermal neutron dosage ; the numbers of imperfections formed in different samples cannot be compared with one another by the comparison of peak height. In the single curve, however, the relative aboundances of imperfections corresponding to each peak may be estimated from the peak height. To investigate the solid reaction between ferric oxide and zinc oxide the radioactive xenon must be retained in zinc oxide powder up to high temperatures. Therefore , the zinc oxide of sample No. 2 incorporated with radioactive xenon was used as one reactant and the ferric oxide samples as the other reactants. The heating curves of the several mixtures are shown in Fig. 4. In the mixture with sample No.1 (curve (a)), a peak appeared at 590•Ž . The X-ray diffraction diagrams (Fig. 5) of the same mixtures which were heated up to 400•K 630•‹and 800•Ž, corresponding to the changing points on the curve (a), showed that the reaction occurred at 400°C and was completed at 800°C. However, in the cases of (b) , (c), (d) and (e), two peaks appeared in each curve, and it was ascertained by X-ray diffraction that the reaction proceeds through two processes. The X-ray diffraction diagrams of the mixtures of ferric oxide of sample No. 3 and zinc oxide which were heated up to the changing (10) 「粉体および粉末冶金」第9巻第5号 Sumio Tchiha 173 Fig. 4 Heating curves of the mixtures of Fe2O3 samples and labelled ZnO of sample No.2. points of curve (c) are shown in Fig. 6. The spinel pattern of zinc ferrite appeared at the the reaction temperature corresponding to the first peak of curve (c) of Fig. 4 ; it does not grow remarkably at the temperature range near to the first peak, but grows rapidly at the temperature of the second peak. The diffraction patterns of the starting materials can still be observed at the ascending part of the peak, and disappear at the temperatures beyond the peak and the spinel formation is completed. The relation between reactivity of ferric oxide and structure sensitivity may be seen in Fig. 3 and 4. That is, the first peak is predominant when ferric oxides were prepared by thermal decomposition at lower temperatures or for shorter heating period; the height decreases, as compared with the second peak, with increasing decomposition temperature and duration, and the situation is reversed in curve (e). The ferric oxide sample of No. 5 incorporated with fission rare gas was used as one reactant and zinc carbonate and zinc oxides samples as the other reactants. In this case, the curves do not differ remarkably from one another, as shown in Fig.

Load more