Synthesis of nanocrystalline manganese oxide powders: Influence of hydrogen peroxide on particle characteristics
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Synthesis of nanocrystalline manganese oxide powders: Influence of hydrogen peroxide on particle characteristics Jooho Moon, Masanobu Awano, Hiroyoshi Takagi, and Yoshinobu Fujishiro National Industrial Research Institute of Nagoya, Nagoya 462, Japan (Received 14 August 1999; accepted 2 September 1999)
Nanocrystalline manganese oxide powders have been prepared at 25 °C by precipitation from Mn(NO3)2 aqueous solution. The presence and addition sequence of H2O2 significantly influence particle characteristics of the resulting manganese oxides, including crystal structure, particle size and morphology, and surface area, depending upon molar ratio of H2O2 with respect to Mn. The precipitation from preoxidized manganese solution by H2O2 results in flakelike-shaped amorphous hydrous manganese oxide (MnO2 ⭈ xH2O). In the absence of H2O2, on the other hand, amorphous Mn(OH)2 is obtained, and a part of Mn(OH)2 subsequently transforms into crystalline Mn3O4 by oxidation in air. Relative population of amorphous Mn(OH)2 decreases by dissolution when post-treated with H2O2. At Mn:H2O2 ⳱ 1:4, the well-defined 16-nm-sized nanocrystalline Mn3O4 with homogenous particle morphology is prepared. The treatment with excess H2O2, however, destroys crystalline Mn3O4 and leads to further oxidation of the aqueous manganese species. Under these conditions, a mixture of needlelike Mn2O3 and cubelike Mn3O4, including amorphous MnO2 ⭈ xH2O, is obtained.
I. INTRODUCTION
Manganese oxides are technologically important materials with a variety of applications. They have been used as oxidative catalysts, electrode materials for rechargeable lithium batteries, starting materials in ferrite production, and colorants and corrosion inhibiting agents for paints.1–4 Recent research also demonstrated that ultrafine manganese oxides can be utilized as an abrasive in chemical mechanical polishing (CMP).5,6 Hanawa et al. reported that the manganese oxides behave similarly as CeO2 in the CMP process of Si and SiO2.7 Even for metals such as W or Cu, the enhanced polishing effect was observed owing to oxidation capability of the manganese oxides. Another advantage of the manganese oxide in the CMP process is its ease for cleaning. In general, various foreign contaminants including abrasives, metals, and chemicals are introduced to a wafer to aid rapid polishing during the CMP processing. Post-CMP cleaning of these contaminants is thus a key step in successful CMP processing. The typical method involves a combination of chemical cleaning, ultrasonic cleaning, and mechanical brush scrubbing.8 However, the particles adhere to polished surfaces by strong intermolecular forces such as van der Waals force and electrostatic double layer interaction. The removal of such particulate materials often poses a significant challenge in both practical and technological aspects. In contrast, the manganese oxides are 4594
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J. Mater. Res., Vol. 14, No. 12, Dec 1999 Downloaded: 28 May 2014
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