Copper oxides obtained by CO 2 laser irradiation of copper salts
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Rodica Alexandrescu, I. Voicu, and I. Morjan Central Institute of Physics, Bucharest-Magurele, Romania
Monica Popescu and V. Jianu Chimopar Research Center for Reactive, Bd. Th. Pallady 50, Bucharest, Romania (Received 26 May 1993; accepted 4 January 1994)
Various copper salts have been irradiated with the help of a continuous wave CO 2 laser. In other experiments the same salts have been decomposed under a controlled heating rate, in a thermal balance, and copper oxide crystallites have been detected as the final product of both types of experiment. The measurements of crystallites performed with the help of x-ray diffraction exhibited differences between the two types of oxides: those obtained by laser irradiation as compared with the oxides obtained by thermal heating. The magnitude of this difference seems to depend on the laser quanta absorptivity of the initial salts. The results are consistent with those obtained previously on nickel oxides.
I. INTRODUCTION
II. EXPERIMENTAL
The interaction of high-power laser irradiation with solid systems is often investigated using a thermochemical approach, in which the strong localized action of the laser beam imposes the characteristics of the process.1 In earlier works 23 we have shown that the decomposition of inorganic salts exposed to IR laser radiation takes place in unusual heating conditions, characterized by high heating rates developed within the impact region of the laser beam. When compared with the reaction products obtained in classical thermal decomposition, the oxides produced in laser processes exhibited peculiarities concerning their structure and morphology. A correlation was found between these features and the absorptivity of the initial salts to the wavelength of laser radiation. In this work we aim to present some results on the laser decomposition of various copper salts. The similarities of their behavior and that of nickel salts under the same conditions3 are evidenced. The salts were also decomposed under controlled heating. Crystallographic investigations of the produced oxides revealed differences in the size and isotropy of crystallites produced from laser experiments as compared to those obtained by thermal heating. The high heating rates that characterize the laser processes together with the substance absorptivity to the laser wavelength should both be involved in the kinetics of the reactions.
Various copper salts of analytical purity grade have been used. Their IR spectral characteristics within the range of CO 2 laser emission (10.6 yu,m) have been investigated and the results are given in Table I. The experimental arrangement for laser experiments was presented elsewhere.3'4 The salts, in powdered form, were evenly distributed as a thin layer of 2 mm thickness in a metal reaction cell, which was driven perpendicular to a laser beam of 400-600 W/cm 2 intensity, at speeds ranging from 0.18 to 0.53 mm/s. After each passage through the laser beam, the samples were weighed (accuracy of 5 • 10~5) until constant weight was achieved. Th
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