在强还原剂条件下，以相关的金属氧化物为原材料，采用粉末冶金法成功合成具有不同含量NbB、NbB2和Nb3B4相的硼化铌粉末和单相NbB粉末。在室温下使用高能球磨机球磨Nb2O5、B2O3和 Mg混合粉末。随后，利用HCl浸出除去球磨粉末中无用的MgO相，合成最终产物NbB?NbB2?Nb3B4，产物在1500°C下退火4 h，以便观察硼化物之间的转换。采用XRD、DSC、PSA、SEM/EDX、TEM和 VSM表征该产物。研究球磨时间(达9 h)对产物形成、显微组织和热行为的影响。化学计量混合粉末经2 h球磨后，发生了还原反应。在不存在任何二次相和杂质时，通过机械化学法，球磨5 h并采用4 mol/L HCl浸出，得到高纯纳米尺寸NbB?NbB2?Nb3B4粉末。经退火处理后，纯的纳米尺寸NbB?NbB2?Nb3B4粉末转变为单相NbB，不存在NbB2和Nb3B4相。
Niobium boride powders having NbB, NbB2 and Nb3B4 phases in various amounts and single phase NbB powders were successfully synthesized by using powder metallurgy methods from related metal oxide raw materials in the presence of a strong reducing agent. Nb2O5, B2O3 and Mg powder blends were milled at room temperature by a high-energy ball mill for different time. Subsequently, undesired MgO phase was removed from the milled powders by HCl leaching to constitute NbB?NbB2?Nb3B4 as final products and they were subjected to an annealing process at 1500 °C for 4 h to observe probable boride transformation. Characterization was carried out by XRD, DSC, PSA, SEM/EDX, TEM and VSM. The effects of milling time (up to 9 h) on the formation, microstructure and thermal behavior of the final products were investigated. Reduction reaction took place after milling stoichiometric powder blends for 2 h. Nano-sized NbB?NbB2?Nb3B4 powders in high purity were obtained in the absence of any secondary phase and any impurity via mechanochemistry by milling for 5 h and leaching with 4 mol/L HCl. After annealing, pure and nano-sized NbB?NbB2?Nb3B4 powders transformed to a single NbB phase without leaving behind NbB2 and Nb3B4 phases.
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