Synthesis and electrical discharge machining of advanced ceramics containing zirconium diboride /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1994.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy ProQuest, Abstract |
| Abstract: | The objectives of this research are to synthesize composites containing zirconium diboride under a variety of conditions, to fabricate ZrB$ sb2$-based materials using wire-cutting and die-sinking electrical discharge machines, and to verify the modeling of electrical discharge machining using experimental results. Composites with different compositions were prepared from ZrB$ sb2$ and Mo. It was found that there is an optimum composition for obtaining the highest relative density at around 15 wt% of molybdenum. Based on the results of X-ray diffraction analysis, energy dispersive spectrum analysis, and elemental mapping, it was concluded that the composites contained ZrB$ sb2$, MoB and ZrC due to the reactions between ZrB$ sb2$, Mo and some C present as an impurity. The effects of composition, firing temperature, and holding time on the firing of ZrB$ sb2$-Cu were studied. The relative densities of green bodies and fired composites increase with increasing amounts of copper. For the composites containing 25 vol% copper, the relative densities increase first with increasing firing temperature, and then decrease at higher firing temperatures due to the loss of boron during firing, which was confirmed by elemental mapping. Holding time is not as significant as firing temperature with respect to the final relative densities of composites. Based on experimental and simulation results, spalling is the predominant machining mechanism for pure ZrB$ sb2$. The higher the energy input, the higher will be the material removal rate. Moreover, the experimental results and simulation results show good consistency considering the similarity between the characteristic dimension of debris and the spalling depth. On the other hand, ZrB$ sb2$-Cu, ZrB$ sb2$-Mo and ZrB$ sb2$-Si are machined through a melting mechanism. The material removal rate increased with increasing currents, frequencies and longer pulse durations as a result of higher energy input. ZrB$ sb2$-Cu was difficult to machine due to partial oxidation. |
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| Item Description: | "Major subject: Chemical Engineering." Vita. |
| Physical Description: | xiv, 131 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |