We investigated the conditions for low-temperature synthesis of ZrC fine powder from Zr0,-Mg-CH,. The synthesis utilizes a thermite-type reaction, with Mg as the reducing agent, and a reaction between Mg and CH, gas as a carbon source. The Mg/ZrO, molar ratio as well as the heating rate were varied. Because C can be continuously fed into the reaction group by the cyclic reaction of Mg through the formation and decomposition of Mg,C, (2Mg + 3CH, + Mg,C, + 6H, + 2Mg + 3C), a molar ratio of 2.2 for Mg/ ZrO, was sufficient for the synthesis of single-phase ZrC. ZrC powders were synthesized under the following conditions: Mg/ZrO, molar ratio = 2.2, heating rate = 20"C/ min, and temperature maintained at 750°C for 30 min. The amount of reaction heat produced in the reduction reaction of ZrO, by Mg depended on the Mg/ZrO, molar ratio, specifically, the amount of ZrO, contained. Moreover, the cyclic reaction of Mg-Mg,C,-Mg was influenced by the amount of reaction heat described above and by the heating rate. The ZrC fine powder showed little aggregation and high dispersibility.

Cement manufacturers today use various waste materials and by-products as raw materials or fuels in cement manufacturing. Waste materials and by-products, however, often have certain chemical properties that differ from conventional raw materials and fuels. Thus, we have researched the overall influence of several minor elements in clinker on the properties of clinker and cement, and we suggest practical measures for Japanese cement manufacturers to take against the unfavorable influence of each minor element. This article introduces our approach and provides representative results and an example of commercialization. We also discuss further challenges in this field as it moves toward rational cement manufacturing.

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