The thermodynamics of the titanium + oxygen system: an isothermal gravimetric study of the composition range Ti3O5 to TiO2 at 1304 K
The thermodynamics of the titanium + oxygen system: an isothermal gravimetric study of the composition range Ti3O5 to TiO2 at 1304 K
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DOI：
10.1098/rsta.1973.0078
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发表时间：
1973-08
期刊：
影响因子：
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通讯作者：
R. Merritt;B. Hyde;L. Bursill;D. K. Philp
中科院分区：
文献类型：
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作者：
R. Merritt;B. Hyde;L. Bursill;D. K. Philp
在1304 K下，通过尽可能地用各种组成的（H_2 + H_2O）气体缓冲混合物平衡它们，研究了氧化钛样品的组成。测定质量和样品组成的高精度表明，即使在恒定的环境中几天后，也很少达到完全平衡：在大多数组成中，存在明显的滞后。在（121）和（132）晶体学剪切结构族所占据的区域存在两个复合磁滞回线。在这些环之间，氧化和还原路径几乎是一致的：在这个区域中，仅通过改变取向而不是晶体学剪切面的数量就可以适应成分的变化。第三个磁滞回线被认为存在于（132）回线和轻微还原的金红石组成之间。一个合理的解释的行为。所有的意见似乎是一致的，从平行的电子显微镜研究减少“金红石”。成核的产品相似乎是最重要的因素影响的行为在区域Ti 30 5到Ti 40 7，从它们的结构的考虑将是预期的。我们观察到的行为与其他工作者报告的行为之间的差异被认为是显而易见的：这是由于（a）我们的测量精度更高，以及（B）我们获得的数据点的密度和数量要高得多。各种热力学数据计算为许多更高的钛氧化物的基础上，一个合理的假设推导出近似平衡氧势的观察值。其中大多数以前没有。通过结合Zador（1967）关于Ti 0 199至Ti 0 1999的数据，我们推导出^Ti 30 5+ i 0 2 = TiO a（金红石），AG®（1304 K）= - 78.3 kj mol-1，而JANAF表中为- 79.4 kj mol-1。发现Tiw 0 2w_1相相对于（n- 1）和（w+1）相邻相的混合物的稳定性非常小（~ 104 J/mol Ti 70 13，即~ 5.2 J/mol原子），并且随着n的增加而降低。1
The compositions of titanium oxide samples at 1304 K have been studied by, as far as possible, equilibrating them with (H2 + H aO) gas buffer mixtures of various compositions. The high precision with which the mass, and therefore the sample’s composition, was determined reveals that complete equilibrium is rarely attained, even after several days in a constant ambient: at most compositions there is gross hysteresis. Two composite hysteresis loops exist in the regions occupied by the (121) and (132) crystallographic shear structure families. Between these loops the oxidation and reduction paths are very nearly coincident: this is the region in which a change in composition can be accommodated by varying only the orientation and not the number of crystallographic shear planes. A third hysteresis loop is believed to exist between the (132) loop and the composition of slightly reduced rutile. A plausible explanation of the behaviour is developed. All the observations appear to be consistent with those from parallel electron microscope studies of reduced ‘rutile’. Nucleation of the product phase appears to be the most important factor affecting the behaviour in the region Ti30 5 to Ti40 7, as would be expected from a consideration of their structures. The differences between the behaviour observed by us and that reported by other workers is believed to be only apparent: it results from (a) the higher precision of our measurements, and (b) the much higher density and number of data points we have acquired. Various thermodynamic data are calculated for the many higher titanium oxides on the basis of a reasonable assumption for deducing approximate equilibrium oxygen potentials from the observed values. Most of these have not previously been available. By incorporating Zador’s (1967) data for T i0 199 to T i0 1999 we deduce for ^Ti30 5+ i 0 2 = TiOa (rutile), AG® (1304 K) = — 78.3 kj mol-1 compared with — 79.4 kj mol-1 in the JANAF tables. The stabilities of the Tiw0 2w_1 phases with respect to mixtures of the (n— 1) and (w+1) neighbours are seen to be extremely small ( —104 J/mol of Ti70 13, i.e. — 5.2 J/mol of atoms), and to decrease with increasing n. 1